This work was funded by NIH intramural grant to Dr Alan N. Schechter.

NOTE: Blood samples were obtained from NIH blood bank (IRB approved protocol: 99-CC-0168).
1. Blood Sample Preparation
NOTE: To avoid platelet activation, draw blood slowly and mix gently with citrate by inverting the tube several times.
<ol>
	<li>Platelet-rich plasma (PRP) preparation
	<ol>
		<li>Draw 30&#8211;50 mL of blood using a 20 G or larger diameter needle and add into a tube containing sodium citrate (3.8%) in a 1:9 ratio or acid citrate dextrose (ACD) (85 mM trisodium citrate, 66.6 mM citric acid, 111 mM glucose, pH 4.5) in a 1:6 ratio.</li>
		<li>Aliquot 5 mL of freshly collected whole blood into empty 15-mL conical tubes. Centrifuge whole blood at 120 x g for 10 min at room temperature.</li>
		<li>Carefully collect the supernatant containing the platelets (platelet-rich plasma, PRP) from the upper portion by a plastic transfer pipette. 
		NOTE: PRP from Step 1.1.3 is ready for use in experiments or for further processing to prepare washed platelets. The soft pellet obtained after centrifugation (Step 1.1.2) contains red blood cells and white cells and can be further purified to obtain washed red blood cells (RBC) &#8212; see Step 1.3. The experiment needs to be finished within 2 h after drawing blood. When collecting PRP (supernatant), avoid the collection of buffy coat-containing leukocytes accumulated on the PRP/RBC interface.</li>
	</ol>
	</li>
	<li>Washed platelet preparation (optional)
	<ol>
		<li>Centrifuge collected PRP at 400 x g for 10 min at room temperature. Discard the supernatant and keep the platelet pellets.</li>
		<li>Gently wash the pellets by adding 5 mL of CGS buffer (120 mM NaCl, 12.9 mM trisodium citrate and 30 mM glucose, pH 6.5) and centrifuge at 400 x g for 10 min at room temperature.</li>
		<li>Resuspend the platelet pellets with 3 mL of modified Tyrode buffer (134 mM NaCl, 0.34 mM NaH2PO4, 2.9 mM KCl, 12 mM NaHCO3, 20 mM HEPES, 1 mM MgCl2, 2 mM CaCl2, 10 mM glucose pH 7.4).</li>
		<li>Dilute the platelets (1:100 &#8212; as example, 10 &#181;L of platelets in 990 &#181;L of Rees-Ecker solution) with Rees Ecker solution and count by hemocytometer.</li>
		<li>Adjust the density of platelets to 3 x 108 cells/mL by adding Tyrode buffer.</li>
		<li>Incubate the platelet suspension at 37 &#176;C for 1 h before starting the experiment. 
		NOTE: Washed platelets are stable for 5&#8211;8 h at 37 &#176;C.</li>
	</ol>
	</li>
	<li>Preparation of washed red blood cells (RBC)
	<ol>
		<li>After the collection, centrifuge the soft pellet obtained in Step 1.1.3 at 2,500 x g for 10 min at room temperature.</li>
		<li>Discard the supernatant and wash the RBC pellet with 5 mL of PBS by centrifugation at 2,500 x g for 10 min at room temperature. Repeat this step for 3 times.</li>
		<li>Discard the PBS and use washed RBCs for further experiments.</li>
	</ol>
	</li>
</ol>
2. Deoxygenation
<ol>
	<li>Add 1 mL of the mixture of PRP (prepared in Step 1.1.4. or 1.2.4.) and RBCs (prepared in Step 1.3.) at the desired hematocrit into a polypropylene bottle closed with a rubber stopper. For example, at 20% hematocrit, add 200 &#181;L of RBCs to 800 &#181;L of PRP. 
	NOTE: Suggested hematocrits are from 0% up to 40%. Do not use a glass bottle or flask as platelets adhere to glass surface.</li>
	<li>Insert the needle connected to helium gas tank into the closed bottle and make the gas outlet by inserting a 26 G needle (Figure 1).</li>
	<li>Slowly swirl the bottle at room temperature. 
	NOTE: Do not allow He gas to bubble through blood preparation. Slow gas flow is preferable for this procedure, and excessively fast He gas flow leads to increased hemolysis. The most efficient gas flow needs to be determined by trial, as it highly depends on the geometry of the experimental setup.</li>
	<li>Periodically follow the deoxygenation process by measuring the partial oxygen pressure (pO2) using a CO-oximeter. 
	NOTE: In our hands, 10 min of deoxygenation decreases pO2 to 25 mmHg which is required for nitrite reduction by RBCs. Continuing deoxygenation did further reduce pO2 to 10 mmHg; however, it led to increased hemolysis and increases in cell-free hemoglobin (Figure 2).</li>
</ol>
3. Red Blood Cell Nitrite Reduction
<ol>
	<li>Add 1 mL of PBS (pH 7.4) into 0.0345 g of NaNO2 to make 500 mM stock solution of nitrite. Dilute 500 mM NaNO2 to 250 &#181;M NaNO2 (25x) by serial dilution in PBS (pH 7.4).</li>
	<li>Using a microsyringe, inject nitrite (40 &#181;L) through the septum into the deoxygenated sample of PRP and RBCs to achieve final concentrations of 10 &#181;M in total 1 mL of sample. 
	NOTE: In this experiment, the final concentrations of nitrite used is 10 &#181;M.</li>
	<li>Incubate the sample at 37 &#176;C for 10 min or longer. 
	NOTE: Adjust the exact duration of RBC incubation with nitrite needed for maximal nitrite reduction for different type of experiments.</li>
	<li>Remove the stopper and pipette 1 mL of the sample into a microcentrifuge tube.</li>
	<li>Centrifuge at 200 x g for 3 min at room temperature.</li>
	<li>Pipette 300 &#181;L of the platelet suspension from the upper portion of the supernatant and mix with ACD (pH 6.5) in a 1:9 ratio. Discard the RBC pellet.</li>
	<li>Centrifuge the platelet suspension at 500 x g for 4 min at room temperature.</li>
	<li>Add 80 &#181;L of ice-cold lysis buffer (150 mM NaCl, 50 mM Tris, 0.5% NP-40, pH 7.4) containing protease inhibitor cocktail III (1:500) to the platelet pellets.</li>
</ol>
4. Western Blotting of VASP
<ol>
	<li>Load 15 &#181;g of the protein from each sample to 2 separate 10% SDS-PAGE gels. 
	NOTE: Harsh stripping buffer, which contains b-mercaptoethanol, cannot remove P-VASPSer239 and VASP antibodies from the membrane; therefore, P-VASP Ser239 and VASP should be run separately.</li>
	<li>Run the gels at 120 V for 1.30 h and transfer to the nitrocellulose membrane.</li>
	<li>Block non-specific binding with 5% non-fat dry milk.</li>
	<li>Incubate the membrane with P-VASPSer239 (1:500), VASP (1:1,000) and GAPDH (1:1,000) for overnight at 4 &#176;C.</li>
	<li>Incubate horseradish peroxidase (HRP) secondary antibody with the membrane for 45 min at room temperature.</li>
	<li>Expose the membrane with an imager machine and quantify the band density using ImageJ.</li>
</ol>

<ol>
	<li>Huang, K. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+reaction+between+nitrite+and+deoxyhemoglobin.+Reassessment+of+reaction+kinetics+and+stoichiometry.">The reaction between nitrite and deoxyhemoglobin. Reassessment of reaction kinetics and stoichiometry.</a> Journal of Biological Chemistry. 280 (35), 31126-31131 (2005).</li><li>Cosby, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitrite+reduction+to+nitric+oxide+by+deoxyhemoglobin+vasodilates+the+human+circulation.">Nitrite reduction to nitric oxide by deoxyhemoglobin vasodilates the human circulation.</a> Nature Medicine. 9 (12), 1498-1505 (2003).</li><li>Mo, E., Amin, H., Bianco, I. H., Garthwaite, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetics+of+a+cellular+nitric+oxide/cGMP/phosphodiesterase-5+pathway.">Kinetics of a cellular nitric oxide/cGMP/phosphodiesterase-5 pathway.</a> Journal of Biological Chemistry. 279 (5), 26149-26158 (2004).</li><li>Park, J. W., Piknova, B., Nghiem, K., Lozier, J. N., Schechter, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibitory+effect+of+nitrite+on+coagulation+processes+demonstrated+by+thromboelastography.">Inhibitory effect of nitrite on coagulation processes demonstrated by thromboelastography.</a> Nitric oxide. 40, 45-51 (2014).</li><li>Wajih, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+red+blood+cell+S-nitrosation+in+nitrite+bioactivation+and+its+modulation+by+leucine+and+glycose.">The role of red blood cell S-nitrosation in nitrite bioactivation and its modulation by leucine and glycose.</a> Redox Biology. 8, 415-421 (2016).</li><li>Akrawinthawong, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+flow+cytometric+analysis+of+the+inhibition+of+platelet+reactivity+due+to+nitrite+reduction+by+deoxygenated+erythrocytes.">A flow cytometric analysis of the inhibition of platelet reactivity due to nitrite reduction by deoxygenated erythrocytes.</a> PLoS One. 9 (3), e92435 (2014).</li><li>Friebe, A., Koesling, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+nitric+oxide-sensitive+guanylyl+cyclase.">Regulation of nitric oxide-sensitive guanylyl cyclase.</a> Circulation Research. 93 (2), 96-105 (2003).</li><li>Srihirun, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelet+inhibition+by+nitrite+is+dependent+on+erythrocytes+and+deoxygenation.">Platelet inhibition by nitrite is dependent on erythrocytes and deoxygenation.</a> PLoS One. 7 (1), e30380 (2012).</li><li>Smolenski, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+and+regulation+of+vasodilator-stimulated+phosphoprotein+serine+239+phosphorylation+in+vitro+and+in+intact+cells+using+a+phosphospecific+monoclonal+antibody.">Analysis and regulation of vasodilator-stimulated phosphoprotein serine 239 phosphorylation in vitro and in intact cells using a phosphospecific monoclonal antibody.</a> Journal of Biological Chemistry. 273 (32), 20029-20035 (1998).</li><li>Burkhart, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+first+comprehensive+and+quantitative+analysis+of+human+platelet+protein+composition+allows+the+comparative+analysis+of+structural+and+functional+pathways.">The first comprehensive and quantitative analysis of human platelet protein composition allows the comparative analysis of structural and functional pathways.</a> Blood. 120 (15), e73-e82 (2012).</li><li>Parakaw, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelet+inhibition+and+increased+phosphorylated+vasodilator-stimulated+phosphoprotein+following+sodium+nitrite+inhalation.">Platelet inhibition and increased phosphorylated vasodilator-stimulated phosphoprotein following sodium nitrite inhalation.</a> Nitric oxide. 66, 10-16 (2017).</li><li>Srihirun, S., Piknova, B., Sibmooh, N., Schechter, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorylated+vasodilator-stimulated+phosphoprotein+(P-VASPSer239)+in+platelets+is+increased+by+nitrite+and+partially+deoxygenated+erythrocytes.">Phosphorylated vasodilator-stimulated phosphoprotein (P-VASPSer239) in platelets is increased by nitrite and partially deoxygenated erythrocytes.</a> PLoS One. 13 (3), e0193747 (2018).</li><li>Mal Cortese-Krott, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+soluble+guanylate+cyclase+in+RBCs:+preserved+activity+in+patients+with+coronary+artery+disease.">Identification of a soluble guanylate cyclase in RBCs: preserved activity in patients with coronary artery disease.</a> Redox Biology. 14, 328-337 (2018).</li><li>Abel, K., Mieskes, G., Walter, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dephosphorylation+of+the+focal+adhesion+protein+VASP+in+vitro+and+in+intact+human+platelets.">Dephosphorylation of the focal adhesion protein VASP in vitro and in intact human platelets.</a> FEBS letter. 370 (3), 184-188 (1995).</li></ol>

Dr. Alan Schechter is listed as a co-inventor on several patents issued to the National Institutes of Health for the use of nitrite salts for the treatment of cardiovascular diseases. He receives royalties based on NIH licensing of these patents for clinical development but no other compensation.

Since platelets are easily activated, gentle handling of platelet-containing samples is required. Fast pipetting and vigorous shaking should be avoided. Platelet inhibitors such as prostacyclin (PGI2) can be used to prevent platelet activation; however, this may affect some signaling pathways inside the platelets. For the preparation of platelet pellets, we add ACD to the platelet suspensions and use low speed centrifugation.
Freshly prepared platelets in PRP have a limited life span, up to 2 h. To achieve high reproducibility, all experiments should be done only with fresh platelets and within 2 h after blood collection. The presented data were obtained with platelets in PRP, which is considered more physiological than washed platelets. Although the life span and purity increase for washed platelets, repeated centrifugation during preparation of washed platelets can lead to their spontaneous activation and this may result in inconsistent quality of platelet preparations. PRP is preferred over washed platelets since the procedure is faster and further handling could activate platelets. However, in specific cases, when the interference of plasma blood clotting factors could interfere with experimental setup, washing platelets represents solution to avoid these problems.
Oxygen contamination in deoxygenated samples is the most important critical step for this assay. RBCs can be pooled and deoxygenated before being added to the PRP. However, transferring deoxygenated RBCs increases the risk of oxygen contamination. In addition, deoxygenation of concentrated RBCs requires more time than deoxygenation of the full preparation at the desired hematocrit, and longer exposure to He gas leads to increased levels of cell-free hemoglobin. Although cell-free hemoglobin can be washed out of deoxygenated RBCs, the phosphate buffer saline or other buffers used for washing must be carefully deoxygenated to prevent oxygen contamination during the centrifugation. To shorten the preparation process and avoid unnecessary oxygen contamination, each PRP+RBCs sample was prepared at the desired hematocrit first and then deoxygenated before the addition of nitrite.
To quantify P-VASPSer239 by Western blot, RBCs must be separated out of the platelets. VASP is expressed in RBCs13, but the levels are nonsignificant when compared to hemoglobin and much lower than in platelets. Since total protein concentration is used for loading controls in the Western blots, the presence of RBCs in lysate samples interferes with P-VASP and VASP measurement by Western blotting. Due to a slow rate of dephosphorylation by phosphatase enzymes in platelets14, P-VASP is sustained for 10 min (Figure 4) and therefore it is possible to separate RBCs by centrifugation before collecting platelet cell lysates.
The EC50 for VASP phosphorylation is almost an order of magnitude lower than the EC50 for the peak cGMP increase, 0.5 nM and 9 nM, respectively3, which makes VASP phosphorylation one of the most sensitive methods to detect the presence of low amounts of NO. However, the VASP phosphorylation curve in response to NO is bell-shaped; a phosphorylation decrease is observed after peaking at 3-30 nM of NO3. This nonlinear response to increasing NO concentrations makes VASP unsuitable for rigorous NO quantification.
Since platelets in PRP have a short life span, the assay must be done in fresh platelets within 2 h after drawing blood. The inconsistency of pO2 levels after the deoxygenation can be found since the deoxygenation of samples is dependent on the flow rate of helium gas and rate of swirling the bottle. Therefore, the time for deoxygenation needs to be determined by trial. For the measurement of P-VASP by Western blots, the antibody choice is critical, and one needs to use a direct NO donor as a positive control to check the specificity. In addition to NO, P-VASPSer239 in platelets can be phosphorylated by the inhibition of phosphodiesterease enzymes and the activation of protein kinase A pathway.
The measurement of P-VASPSer239 has some advantages over cGMP assay. cGMP in platelets has a very short half-life (less than 10 s) and the measurement of cGMP requires the addition of phosphodiesterase inhibitor3. Also, the cGMP measurement uses a rather expensive ELISA technique. VASP can be simply measured by an in-house Western blot protocol and therefore is more readily available.
Increased P-VASPSer239 in platelets was successfully used as a sensor for NO generation by inhaled nitrite in vivo6. Therefore, we showed that it is possible to use P-VASPSer239 in platelets as a marker of NO generation in vitro and in vivo in the blood and possibly in various other situations. The unusually low EC50 makes this method an excellent candidate for detecting the presence of very low NO concentrations in blood. Therefore, this protocol provides a possibility to study NO generation in blood at various physiological stimuli, such as during blood coagulation cascade, increased sheer stress or increased inflammation.

Platelets are small disc-shaped cell fragments derived from megakaryocytes that are crucial for blood clotting. The clotting cascade is initiated by various bioactive molecules (such as collagen or ADP), released after the injury of vascular wall. The blood clotting process can be modified, among various effectors by nitric oxide (NO). NO, naturally produced by mammalian cells, is one of the most versatile physiological signals. It acts as a potent vasodilator, neurotransmitter and immune modulator, to name a few of its many functions. In the bloodstream, NO also helps to regulate the extent of blood clotting by inhibiting platelet aggregation. One of the most likely sources of NO in the bloodstream is nitrite, an inorganic ion that has been shown to serve as a precursor of NO. Reacting with red blood cells (RBCs), nitrite is reduced to NO and deoxyHb is oxidized to methemoglobin (metHb)1. NO released from RBCs is vasoactive and causes vasorelaxation2. This nitrite reduction pathway is an alternate NO generation pathway, acting together with and complementing the classical NO generation path by endothelial nitric oxide synthase at hypoxic conditions.
Platelets themselves are not able to reduce nitrite into NO but are very sensitive to its presence. In intact platelets, NO in the nanomolar range increases cGMP (EC50 = 10 nM) and phosphorylation of VASP (EC50 = 0.5 nM)3. Therefore, platelets may serve as an excellent sensor of nitrite reduction by RBCs and NO release into blood. There are several methods that can directly measure the extent of platelet activation - such as aggregometry and thromboelastography (TEG)4,5. However, these methods require expensive specialized instrumentation and rather large amounts of material. It is also possible to monitor events downstream, after NO is released from RBCs, using the changes in platelet surface protein expression &#8211; such as P-selectin6. NO is also known to increase the amount of cGMP in the platelets7. Previously, we used cGMP to monitor NO release into blood after nitrite reduction by deoxygenated RBC8. This proved to be a very sensitive method; however, cGMP is a short-lived molecule and its detection involves extensive labor. Another possibility, described in the presented protocol, uses phosphorylation of the vasodilator-stimulated phospho (VASP)-protein to detect the presence of NO in blood. VASP is a substrate of protein kinase G activation, which is phosphorylated upon the interaction with NO through the sGC/cGMP pathway9. Detectable VASP phosphorylation occurs at very low NO concentrations, which could make platelets a very sensitive detector of NO presence in blood. VASP is highly expressed in platelets, but not in other blood cells, which allows to follow selectively the events involving platelets10.
The main goal of this protocol is to describe the method in detail for the detection of NO release in whole blood using its interaction with platelets by monitoring VASP phosphorylation11,12. The described method allows early detection of low NO concentrations - theoretically in the nanomolar range which makes the present protocol more sensitive than cGMP determination, due to the use of standard Western blot techniques achievable in most laboratory settings.

<table>
	<tbody>
		<tr>
			<td>Tri-sodium citrate</td>
			<td>Supply by NIH blood bank</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Citric acid</td>
			<td>Supply by NIH blood bank</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma</td>
			<td>G7528-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl; sodium chloride</td>
			<td>Sigma</td>
			<td>S-7653 1kg</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4; sodium phosphate monobasic, monohydrate</td>
			<td>Mallinckrodt Chemical</td>
			<td>7892-04</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl; potassium chloride</td>
			<td>Mallinckrodt Chemical</td>
			<td>6858</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3; sodium bicarbonate</td>
			<td>Mallinckrodt Chemical</td>
			<td>7412-12</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES; N-[2-Hydroxyethyl]piperazine-N&#39;-[-ethanesulfonic acid]</td>
			<td>Sigma</td>
			<td>H3375-500g</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2 (1 M); magnesium chloride</td>
			<td>Quality Biology</td>
			<td>351-033-721</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2; calcium chloride</td>
			<td>Sigma</td>
			<td>C5080-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Nalgene Narrow-mouth HDPE Economy bottles</td>
			<td>Nalgene</td>
			<td>2089-0001</td>
			<td></td>
		</tr>
		<tr>
			<td>Red septum stopper NO.29</td>
			<td>Fisherbrand</td>
			<td>FB57877</td>
			<td></td>
		</tr>
		<tr>
			<td>NaNO2-; sodium nitrite</td>
			<td>Sigma</td>
			<td>S2252-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>TRIZMA Base; Tris[hydroxymethyl]aminomethane</td>
			<td>Sigma</td>
			<td>T8524-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>NP-40; 4-Nonylphenyl-polyethylene glycol</td>
			<td>Sigma</td>
			<td>74385-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Protease inhibitor cocktail set III</td>
			<td>Calbiochem</td>
			<td>539134</td>
			<td></td>
		</tr>
		<tr>
			<td>Phospho-VASP (Ser239) antibody</td>
			<td>Cell signaling technology</td>
			<td>3114</td>
			<td></td>
		</tr>
		<tr>
			<td>VASP antibody</td>
			<td>Cell signaling technology</td>
			<td>3112</td>
			<td></td>
		</tr>
		<tr>
			<td>GAPDH (14C10) Rabbit mAb</td>
			<td>Cell signaling technology</td>
			<td>2118</td>
			<td></td>
		</tr>
		<tr>
			<td>2-mercaptoethanol</td>
			<td>Sigma</td>
			<td>M-6250-10ml</td>
			<td></td>
		</tr>
		<tr>
			<td>Peroxidase AffiniPure Goat Anti-Rabbit IgG (H+L)</td>
			<td>Jackson Immuno Research Laboratories</td>
			<td>111-035-003</td>
			<td></td>
		</tr>
		<tr>
			<td>Clarity Western ECL Substrate</td>
			<td>BIO-RAD</td>
			<td>1705060-200ml</td>
			<td></td>
		</tr>
		<tr>
			<td>CO-oximeter (ABL 90 flex)</td>
			<td>Radiometer</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

platelet-based detection of nitric oxide in blood by measuring vasp phosphorylation

Platelets are the blood components responsible for proper blood clotting. Their function is highly regulated by various pathways. One of the most potent vasoactive agents, nitric oxide (NO), can also act as a powerful inhibitor of platelet aggregation. Direct NO detection in blood is very challenging due to its high reactivity with cell-free hemoglobin that limits NO half-life to the millisecond range. Currently, NO changes after interventions are only estimated based on measured changes of nitrite and nitrate (members of the nitrate-nitrite-NO metabolic pathway). However precise, these measurements are rather difficult to interpret vis a vis actual NO changes, due to the naturally high baseline nitrite and nitrate levels that are several orders of magnitude higher than expected changes of NO itself. Therefore, the development of direct and simple methods that would allow one to detect NO directly is long overdue. This protocol addresses a potential use of platelets as a highly sensitive NO sensor in blood. It describes initial platelet rich plasma (PRP) and washed platelet preparations and the use of nitrite and deoxygenated red blood cells as NO generators. Phosphorylation of VASP at serine 239 (P-VASPSer239) is used to detect the presence of NO. The fact that VASP protein is highly expressed in platelets and that it is rapidly phosphorylated when NO is present leads to a unique opportunity to use this pathway to directly detect NO presence in blood.

Venous blood samples have pO2 values between 50-80 mmHg. Deoxygenation by helium rapidly decreases pO2 to 25 mmHg within 10 min. Increased deoxygenation time slightly further decreases pO2. However, increased time of deoxygenation also leads to significantly increased levels of cell-free hemoglobin (determined by CO-Oximeter, visually seen on Figure 2 as increasingly red coloration of plasma) (Figure&#160;2A-B). Increased hemolysis is not associated with stirring because stirring without deoxygenation does not induce hemolysis (Figure 2C).
We found that the presence of RBCs in lysed samples decreases P-VASPSer239 and VASP detected by Western blotting (Figure 3). Therefore, we first separate platelets and RBCs before running Western blots to detect P-VASPSer239 in platelets.
To show that there is enough time to separate RBCs out of platelets without affecting VASP phosphorylation, we used a short-lived NO donor. PROLI NONOate (NO donor with half-life of 1.8 s at 37 C pH 7.4), rapidly increased P-VASPSer239 in platelets (within 10 s of incubation). P-VASPSer239 induced by PROLI NONOate is detected for 10 min after the incubation with PRP (Figure 4).
Nitrite increases P-VASPSer239 in platelets in the presence of deoxygenated RBCs (pO2 25 mmHg). Nitrite reductase activity of deoxygenated RBCs depends on hematocrit and the maximum effect is observed at 20% hematocrit (Figure 5).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58647/58647fig1.jpg" /> 
Figure 1: Deoxygenation chamber. Mixture of PRP and RBCs is added into a plastic bottle closed with a rubber septum. The closed bottle is connected to helium (He) line using a needle. Oxygen is flushed out by a small syringe needle (26 G) serving as a gas outlet.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58647/58647fig2.jpg" /> 
Figure 2: Partial oxygen pressure (pO2) and cell-free hemoglobin after deoxygenation. (A) PRP and RBCs samples were deoxygenated for 3, 5, 10, 15, 30 and 50 min. pO2 of samples were measured by blood gas analyzer (n = 3). Error bars are SEM. Representative pictures of supernatant of PRP+RBCs samples stirred with (B) or without helium (C). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58647/58647fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58647/58647fig3.jpg" /> 
Figure 3: Representative VASP Western blot bands in samples of PRP/RBCs prepared at various hematocrit. RBCs were added into PRP to 1, 5, 10, 15, 20, 40% hematocrit.&#160;Mixtures of PRP + RBCs were centrifuged at 500 x g for 5 min and lysed with lysis buffer.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58647/58647fig4.jpg" /> 
Figure 4: Representative Western blot bands of P-VASPSer239 and VASP in PRP after exposure to NO donor PROLI NONOate. PROLI NONOate (10 M) was added into PRP and incubated at 37 &#176;C for 10 and 30 s and 1, 2, 5, 10, 20 and 40 min.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58647/58647fig5.jpg" /> 
Figure 5: VASPSer239 phosphorylation depends on pO2 and hematocrit levels. (A) PRP + RBCs (20% hematocrit) were deoxygenated to two different pO2 levels, 40 and 25 mmHg. P-VASPSer239 and VASP were measured after the incubation of deoxygenated samples with 10 M nitrite at 37 C for 10 min. (B) Nitrite (10 M) was added into deoxygenated PRP + RBCs at 0, 10, 20 and 40% hematocrit (pO2 = 25 mmHg). Fold increased (P-VASPSer239) was calculated relative to control (PRP+RBCs without nitrite) for each hematocrit value. Error bars = SEM. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58647/58647fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Platelet-based Detection of Nitric Oxide in Blood by Measuring VASP Phosphorylation at JoVE.com

Platelet-based Detection of Nitric Oxide in Blood by Measuring VASP Phosphorylation

Here, we present a protocol to address the potential use of platelets as a highly sensitive nitric oxide sensor in blood. It describes initial platelet preparation and the use of nitrite and deoxygenated red blood cells as nitric oxide generators.

Platelets are the blood components responsible for proper blood clotting. Their function is highly regulated by various pathways. One of the most potent ...

platelet-based-detection-nitric-oxide-blood-measuring-vasp

Nanyang Technological University

Research

JoVE Journal

Medicine

7.9K Views.  Mahidol University. Here, we present a protocol to address the potential use of platelets as a highly sensitive nitric oxide sensor in blood. It describes initial platelet preparation and the use of nitrite and deoxygenated red blood cells as nitric oxide generators.

Video: Platelet-based Detection of Nitric Oxide in Blood by Measuring VASP Phosphorylation

Analytical Techniques for Assaying Nitric Oxide Bioactivity

Nitric oxide (NO) is a diatomic free radical that is extremely short lived in biological systems (less than 1 second in circulating blood)1. NO may be considered one of the most important signaling molecules produced in our body, regulating essential functions including but not limited to regulation of blood pressure, immune response and neural communication. Therefore its accurate detection and quantification in biological matrices is critical to understanding the role of NO in health and disease. With such a short physiological half life of NO, alternative strategies for the detection of reaction products of NO biochemistry have been developed. The quantification of relevant NO metabolites in multiple biological compartments provides valuable information with regards to in vivo NO production, bioavailability and metabolism. Simply sampling a single compartment such as blood or plasma may not always provide an accurate assessment of whole body NO status, particularly in tissues. The ability to compare blood with select tissues in experimental animals will help bridge the gap between basic science and clinical medicine as far as diagnostic and prognostic utility of NO biomarkers in health and disease. Therefore, extrapolation of plasma or blood NO status to specific tissues of interest is no longer a valid approach. As a result, methods continue to be developed and validated which allow the detection and quantification of NO and NO-related products/metabolites in multiple compartments of experimental animals in vivo. The established paradigm of NO biochemistry from production by NO synthases to activation of soluble guanylyl cyclase (sGC) to eventual oxidation to nitrite (NO2-) and nitrate (NO3-) may only represent part of NO's effects in vivo. The interaction of NO and NO-derived metabolites with protein thiols, secondary amines, and metals to form S-nitrosothiols (RSNOs), N-nitrosamines (RNNOs), and nitrosyl-heme respectively represent cGMP-independent effects of NO and are likely just as important physiologically as activation of sGC by NO. A true understanding of NO in physiology is derived from in vivo experiments sampling multiple compartments simultaneously. Nitric oxide (NO) methodology is a complex and often confusing science and the focus of many debates and discussion concerning NO biochemistry. The elucidation of new mechanisms and signaling pathways involving NO hinges on our ability to specifically, selectively and sensitively detect and quantify NO and all relevant NO products and metabolites in complex biological matrices. Here, we present a method for the rapid and sensitive analysis of nitrite and nitrate by HPLC as well as detection of free NO in biological samples using in vitro ozone based chemiluminescence with chemical derivitazation to determine molecular source of NO as well as ex vivo with organ bath myography.

The endogenous production of nitric oxide (NO) regulates a wide variety of biological functions. It is becoming increasingly clear that disruption or dysregulation of NO based signaling is involved in many human diseases. Methods to quantify relevant NO metabolites may provide novel diagnostic or prognostic biomarkers for human disease.

Nitric oxide (NO) is a diatomic free radical that is extremely short lived in biological systems (less than 1 second in circulating blood)1. NO may be ...

MicroRNA Detection in Prostate Tumors by Quantitative Real-time PCR (qPCR)

MicroRNAs (miRNAs) are single-stranded, 18&#x2013;24 nucleotide long, non-coding RNA molecules. They are involved in virtually every cellular process including development1, apoptosis2, and cell cycle regulation3. MiRNAs are estimated to regulate the expression of 30% to 90% of human genes4 by binding to their target messenger RNAs (mRNAs)5. Widespread dysregulation of miRNAs has been reported in various diseases and cancer subtypes6. Due to their prevalence and unique structure, these small molecules are likely to be the next generation of biomarkers, therapeutic agents and/or targets.
Methods used to investigate miRNA expression include SYBR green I dye- based as well as Taqman-probe based qPCR. If miRNAs are to be effectively used in the clinical setting, it is imperative that their detection in fresh and/or archived clinical samples be accurate, reproducible, and specific. qPCR has been widely used for validating expression of miRNAs in whole genome analyses such as microarray studies7. The samples used in this protocol were from patients who underwent radical prostatectomy for clinically localized prostate cancer; however other tissues and cell lines can be substituted in. Prostate specimens were snap-frozen in liquid nitrogen after resection. Clinical variables and follow-up information for each patient were collected for subsequent analysis8.
Quantification of miRNA levels in prostate tumor samples. The main steps in qPCR analysis of tumors are: Total RNA extraction, cDNA synthesis, and detection of qPCR products using miRNA-specific primers. Total RNA, which includes mRNA, miRNA, and other small RNAs were extracted from specimens using TRIzol reagent. Qiagen's miScript System was used to synthesize cDNA and perform qPCR (Figure 1). Endogenous miRNAs are not polyadenylated, therefore during the reverse transcription process, a poly(A) polymerase polyadenylates the miRNA. The miRNA is used as a template to synthesize cDNA using oligo-dT and Reverse Transcriptase. A universal tag sequence on the 5' end of oligo-dT primers facilitates the amplification of cDNA in the PCR step. PCR product amplification is detected by the level of fluorescence emitted by SYBR Green, a dye which intercalates into double stranded DNA. Specific miRNA primers, along with a Universal Primer that binds to the universal tag sequence will amplify specific miRNA sequences. 
The miScript Primer Assays are available for over a thousand human-specific miRNAs, and hundreds of murine-specific miRNAs. Relative quantification method was used here to quantify the expression of miRNAs. To correct for variability amongst different samples, expression levels of a target miRNA is normalized to the expression levels of a reference gene. The choice of a gene on which to normalize the expression of targets is critical in relative quantification method of analysis. Examples of reference genes typically used in this capacity are the small RNAs RNU6B, RNU44, and RNU48 as they are considered to be stably expressed across most samples. In this protocol, RNU6B is used as the reference gene.

MicroRNA Detection in Prostate Tumors by Quantitative Real-time PCR qPCR

Quantitative Real Time polymerase chain reaction (qPCR) is a rapid and sensitive method to investigate the expression levels of various microRNA (miRNA) molecules in tumor samples. Using this method expression of hundreds of different miRNA molecules can be amplified, quantified, and analyzed from the same cDNA template.

MicroRNAs (miRNAs) are single-stranded, 18&#x2013;24 nucleotide long, non-coding RNA molecules. They are involved in virtually every cellular process ...

Cerenkov Luminescence Imaging (CLI) for Cancer Therapy Monitoring

In molecular imaging, positron emission tomography (PET) and optical imaging (OI) are two of the most important and thus most widely used modalities1-3. PET is characterized by its excellent sensitivity and quantification ability while OI is notable for non-radiation, relative low cost, short scanning time, high throughput, and wide availability to basic researchers. However, both modalities have their shortcomings as well. PET suffers from poor spatial resolution and high cost, while OI is mostly limited to preclinical applications because of its limited tissue penetration along with prominent scattering optical signals through the thickness of living tissues.
 Recently a bridge between PET and OI has emerged with the discovery of Cerenkov Luminescence Imaging (CLI)4-6. CLI is a new imaging modality that harnesses Cerenkov Radiation (CR) to image radionuclides with OI instruments. Russian Nobel laureate Alekseyevich Cerenkov and his colleagues originally discovered CR in 1934. It is a form of electromagnetic radiation emitted when a charged particle travels at a superluminal speed in a dielectric medium7,8. The charged particle, whether positron or electron, perturbs the electromagnetic field of the medium by displacing the electrons in its atoms. After passing of the disruption photons are emitted as the displaced electrons return to the ground state. For instance, one 18F decay was estimated to produce an average of 3 photons in water5. 
 Since its emergence, CLI has been investigated for its use in a variety of preclinical applications including in vivo tumor imaging, reporter gene imaging, radiotracer development, multimodality imaging, among others4,5,9,10,11. The most important reason why CLI has enjoyed much success so far is that this new technology takes advantage of the low cost and wide availability of OI to image radionuclides, which used to be imaged only by more expensive and less available nuclear imaging modalities such as PET.
 Here, we present the method of using CLI to monitor cancer drug therapy. Our group has recently investigated this new application and validated its feasibility by a proof-of-concept study12. We demonstrated that CLI and PET exhibited excellent correlations across different tumor xenografts and imaging probes. This is consistent with the overarching principle of CR that CLI essentially visualizes the same radionuclides as PET. We selected Bevacizumab (Avastin; Genentech/Roche) as our therapeutic agent because it is a well-known angiogenesis inhibitor13,14. Maturation of this technology in the near future can be envisioned to have a significant impact on preclinical drug development, screening, as well as therapy monitoring of patients receiving treatments.

Cerenkov Luminescence Imaging CLI for Cancer Therapy Monitoring

Use of Cerenkov Luminescence Imaging (CLI) for monitoring preclinical cancer treatment is described here. This method takes advantage of Cerenkov Radiation (CR) and optical imaging (OI) to visualize radiolabeled probes and thus provides an alternative to PET in preclinical therapeutic monitoring and drug screening.

In  molecular imaging, positron emission tomography (PET) and optical imaging (OI)  are two of the most important and thus most widely used modalities1-3. ...

5/6th Nephrectomy in Combination with High Salt Diet and Nitric Oxide Synthase Inhibition to Induce Chronic Kidney Disease in the Lewis Rat

Chronic kidney disease (CKD) is a global problem. Slowing CKD progression is a major health priority. Since CKD is characterized by complex derangements of homeostasis, integrative animal models are necessary to study development and progression of CKD. To study development of CKD and novel therapeutic interventions in CKD, we use the 5/6th nephrectomy ablation model, a well known experimental model of progressive renal disease, resembling several aspects of human CKD. The gross reduction in renal mass causes progressive glomerular and tubulo-interstitial injury, loss of remnant nephrons and development of systemic and glomerular hypertension. It is also associated with progressive intrarenal capillary loss, inflammation and glomerulosclerosis. Risk factors for CKD invariably impact on endothelial function. To mimic this, we combine removal of 5/6th of renal mass with nitric oxide (NO) depletion and a high salt diet. After arrival and acclimatization, animals receive a NO synthase inhibitor (NG-nitro-L-Arginine) (L-NNA) supplemented to drinking water (20 mg/L) for a period of 4 weeks, followed by right sided uninephrectomy. One week later, a subtotal nephrectomy (SNX) is performed on the left side. After SNX, animals are allowed to recover for two days followed by LNNA in drinking water (20 mg/L) for a further period of 4 weeks. A high salt diet (6%), supplemented in ground chow (see time line Figure 1), is continued throughout the experiment. Progression of renal failure is followed over time by measuring plasma urea, systolic blood pressure and proteinuria. By six weeks after SNX, renal failure has developed. Renal function is measured using 'gold standard' inulin and para-amino hippuric acid (PAH) clearance technology. This model of CKD is characterized by a reduction in glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), hypertension (systolic blood pressure&gt;150 mmHg), proteinuria (&gt; 50 mg/24 hr) and mild uremia (&gt;10 mM). Histological features include tubulo-interstitial damage reflected by inflammation, tubular atrophy and fibrosis and focal glomerulosclerosis leading to massive reduction of healthy glomeruli within the remnant population (&lt;10%). Follow-up until 12 weeks after SNX shows further progression of CKD.

A two-stage method to establish chronic kidney disease (CKD) in the Lewis rat by surgically removing 5/6th of renal mass is described. Combination of the surgical procedure, NOS-inhibition and a high-salt diet leads to a model resembling human CKD, allowing study of causal mechanisms and development of novel therapeutic interventions.

Chronic kidney disease (CKD) is a global problem. Slowing CKD progression is a major health priority. Since CKD is characterized by complex derangements ...

Phosphorus-31 Magnetic Resonance Spectroscopy: A Tool for Measuring In Vivo Mitochondrial Oxidative Phosphorylation Capacity in Human Skeletal Muscle

Skeletal muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity, which is critically important in health and disease, can be measured in vivo and noninvasively in humans via phosphorus-31 magnetic resonance spectroscopy (31PMRS). However, the approach has not been widely adopted in translational and clinical research, with variations in methodology and limited guidance from the literature. Increased optimization, standardization, and dissemination of methods for in vivo 31PMRS would facilitate the development of targeted therapies to improve OXPHOS capacity and could ultimately favorably impact cardiovascular health. 31PMRS produces a noninvasive, in vivo measure of OXPHOS capacity in human skeletal muscle, as opposed to alternative measures obtained from explanted and potentially altered mitochondria via muscle biopsy. It relies upon only modest additional instrumentation beyond what is already in place on magnetic resonance scanners available for clinical and translational research at most institutions. In this work, we outline a method to measure in vivo skeletal muscle OXPHOS. The technique is demonstrated using a 1.5 Tesla whole-body MR scanner equipped with the suitable hardware and software for 31PMRS, and we explain a simple and robust protocol for in-magnet resistive exercise to rapidly fatigue the quadriceps muscle. Reproducibility and feasibility are demonstrated in volunteers as well as subjects over a wide range of functional capacities.

Phosphorus-31 Magnetic Resonance Spectroscopy: A Tool for Measuring In Vivo Mitochondrial Oxidative Phosphorylation Capacity in Human Skeletal Muscle

This work demonstrates the feasibility of an in vivo phosphorus-31 magnetic resonance spectroscopy (31PMRS) technique to quantify mitochondrial oxidative phosphorylation (OXPHOS) capacity in human skeletal muscle.

Skeletal muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity, which is critically important in health and disease, can be measured in vivo ...

In Vitro and In Vivo Detection of Mitophagy in Human Cells, C. Elegans, and Mice

Mitochondria are the powerhouses of cells and produce cellular energy in the form of ATP. Mitochondrial dysfunction contributes to biological aging and a wide variety of disorders including metabolic diseases, premature aging syndromes, and neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Maintenance of mitochondrial health depends on mitochondrial biogenesis and the efficient clearance of dysfunctional mitochondria through mitophagy. Experimental methods to accurately detect autophagy/mitophagy, especially in animal models, have been challenging to develop. Recent progress towards the understanding of the molecular mechanisms of mitophagy has enabled the development of novel mitophagy detection techniques. Here, we introduce several versatile techniques to monitor mitophagy in human cells, Caenorhabditis elegans (e.g., Rosella and DCT-1/ LGG-1 strains), and mice (mt-Keima). A combination of these mitophagy detection techniques, including cross-species evaluation, will improve the accuracy of mitophagy measurements and lead to a better understanding of the role of mitophagy in health and disease.

In Vitro and In Vivo Detection of Mitophagy in Human Cells, C. Elegans, and Mice

Mitophagy, the process of clearing damaged mitochondria, is necessary for mitochondrial homeostasis and health maintenance. This article presents some of the latest mitophagy detection methods in human cells, Caenorhabditis elegans, and mice.

Mitochondria are the powerhouses of cells and produce cellular energy in the form of ATP. Mitochondrial dysfunction contributes to biological aging and a ...

Routine Screening Method for Microparticles in Platelet Transfusions

Platelet inventory management based on screening microparticle content in platelet concentrates is a new quality improvement initiative for hospital blood banks. Cells fragment off microparticles (MP) when they are stressed. Blood and blood components may contain cellular fragments from a variety of cells, most notably from activated platelets. When performing their roles as innate immune cells and major players in coagulation and hemostasis, platelets change shape and generate microparticles. With dynamic light scattering (DLS)-based microparticle detection, it is possible to differentiate activated (high microparticle) from non-activated (low microparticle) platelets in transfusions, and optimize the use of this scarce blood product. Previous research suggests that providing non-activated platelets for prophylactic use in hematology-oncology patients could reduce their risk of becoming refractory and improve patient care. The goal of this screening method is to routinely differentiate activated from non-activated platelets. The method described here outlines the steps to be performed for routine platelet inventory management in a hospital blood bank: obtaining a sample from a platelet transfusion, loading the sample into the capillary for DLS measurement, performing the DLS test to identify microparticles, and using the reported microparticle content to identify activated platelets.

Platelet inventory management based on screening microparticle content in platelet concentrates is a new quality improvement initiative in hospital blood banks. The goal is to differentiate activated from non-activated platelets to optimize the use of platelets. Providing non-activated platelets to hematology-oncology patients might reduce their high risk to become refractory.

Platelet inventory management based on screening microparticle content in platelet concentrates is a new quality improvement initiative for hospital blood ...

Synthesis, Characterization, and Application of Superparamagnetic Iron Oxide Nanoprobes for Extrapulmonary Tuberculosis Detection

A molecular imaging probe comprising superparamagnetic iron oxide (SPIO) nanoparticles and Mycobacterium tuberculosis surface antibody (MtbsAb) was synthesized to enhance imaging sensitivity for extrapulmonary tuberculosis (ETB). An SPIO nanoprobe was synthesized and conjugated with MtbsAb. The purified SPIO-MtbsAb nanoprobe was characterized using TEM and NMR. To determine the targeting ability of the probe, SPIO-MtbsAb nanoprobes were incubated with Mtb for in vitro imaging assays and injected into Mtb-inoculated mice for in vivo investigation with magnetic resonance (MR). The contrast enhancement reduction on magnetic resonance imaging (MRI) of Mtb and THP1 cells showed proportional to the SPIO-MtbsAb nanoprobe concentration. After 30 min of intravenous SPIO-MtbsAb nanoprobe injection into Mtb-infected mice, the signal intensity of the granulomatous site was enhanced by 14-fold in the T2-weighted MR images compared with that in mice receiving PBS injection. The MtbsAb nanoprobes can be used as a novel modality for ETB detection.

To improve serological diagnostic tests for Mycobacterium tuberculosis antigens, we developed superparamagnetic iron oxide nanoprobes to detect extrapulmonary tuberculosis.

A molecular imaging probe comprising superparamagnetic iron oxide (SPIO) nanoparticles and Mycobacterium tuberculosis surface antibody (MtbsAb) was ...

Endotoxin Activity Assay for the Detection of Whole Blood Endotoxemia in Critically Ill Patients

Lipopolysaccharide, also known as endotoxin, is a fundamental component of gram-negative bacteria and plays a crucial role in the development of sepsis and septic shock. The early identification of an infectious process that is rapidly evolving to a critical illness might prompt a quicker and more intensive treatment, thereby potentially leading to better patient outcomes. The Endotoxin Activity (EA) assay can be used at the bedside as a reliable biomarker of systemic endotoxemia. The detection of elevated endotoxin activity levels has been repeatedly shown to be associated with an increased disease severity in patients with sepsis and septic shock. The assay is quick and easy to perform. Briefly, after sampling, an aliquot of whole blood is mixed with an anti-endotoxin antibody and with added LPS. Endotoxin activity is measured as the relative oxidative burst of primed neutrophils as detected by chemioluminescence. The assay&#39;s output is expressed on a scale from 0 (absent) to 1 (maximal) and categorized as &#8220;low&#8221; (&#60;0.4 units), &#8220;intermediate&#8221; (0.4&#8211;0.59 units), or &#8220;high&#8221; (&#8805;0.6 units). The detailed methodology and rationale for the implementation of the EA assay are reported in this manuscript.

We hereby present a protocol to measure at the bedside the endotoxin activity of human whole blood samples. The Endotoxin Activity assay is a simple test to perform and may be a useful biomarker in critically ill patients with sepsis.

Lipopolysaccharide, also known as endotoxin, is a fundamental component of gram-negative bacteria and plays a crucial role in the development of sepsis ...

A Novel Inhalation Mask System to Deliver High Concentrations of Nitric Oxide Gas in Spontaneously Breathing Subjects

Nitric Oxide (NO) is administered as gas for inhalation to induce selective pulmonary vasodilation. It is a safe therapy, with few potential risks even if administered at high concentration. Inhaled NO gas is routinely used to increase systemic oxygenation in different disease conditions. The administration of high concentrations of NO also exerts a virucidal effect in vitro. Owing to its favorable pharmacodynamic and safety profiles, the familiarity in its use by critical care providers, and the potential for a direct virucidal effect, NO is clinically used in patients with coronavirus disease-2019 (COVID-19). Nevertheless, no device is currently available to easily administer inhaled NO at concentrations higher than 80 parts per million (ppm) at various inspired oxygen fractions, without the need for dedicated, heavy, and costly equipment. The development of a reliable, safe, inexpensive, lightweight, and ventilator-free solution is crucial, particularly for the early treatment of non-intubated patients outside of the intensive care unit (ICU) and in a limited-resource scenario. To overcome such a barrier, a simple system for the non-invasive NO gas administration up to 250 ppm was developed using standard consumables and a scavenging chamber. The method has been proven safe and reliable in delivering a specified NO concentration while limiting nitrogen dioxide levels. This paper aims to provide clinicians and researchers with the necessary information on how to assemble or adapt such a system for research purposes or clinical use in COVID-19 or other diseases in which NO administration might be beneficial.

This simple and highly adaptable system device for the inhalation of high-concentration nitric oxide (NO) gas does not require mechanical ventilators, positive pressure, or high gas flows. Standard medical consumables and a snug-fitting mask are used to safely deliver NO gas to spontaneously breathing subjects.

Nitric Oxide (NO) is administered as gas for inhalation to induce selective pulmonary vasodilation. It is a safe therapy, with few potential risks even if ...