Rationale: The recent emergence of hydrogen sulfide (H 2 S) as a potent cardioprotective signaling molecule necessitates the elucidation of its cytoprotective mechanisms. Objective: The present study evaluated potential mechanisms of H 2 S-mediated cardioprotection using an in vivo model of pharmacological preconditioning. Methods and Results: H 2 S (100 g/kg) or vehicle was administered to mice via an intravenous injection 24 hours before myocardial ischemia. Treated and untreated mice were then subjected to 45 minutes of myocardial ischemia followed by reperfusion for up to 24 hours, during which time the extent of myocardial infarction was evaluated, circulating troponin I levels were measured, and the degree of oxidative stress was evaluated. In separate studies, myocardial tissue was collected from treated and untreated mice during the early (30 minutes and 2 hours) and late (24 hours) preconditioning periods to evaluate potential cellular targets of H 2 S. Initial studies revealed that H 2 S provided profound protection against ischemic injury as evidenced by significant decreases in infarct size, circulating troponin I levels, and oxidative stress. During the early preconditioning period, H 2 S increased the nuclear localization of Nrf2, a transcription factor that regulates the gene expression of a number of antioxidants and increased the phosphorylation of protein kinase C and STAT-3. During the late preconditioning period, H 2 S increased the expression of antioxidants (heme oxygenase-1 and thioredoxin 1), increased the expression of heat shock protein 90, heat shock protein 70, Bcl-2, Bcl-xL, and cyclooxygenase-2 and also inactivated the proapoptogen Bad. Key Words: hydrogen sulfide Ⅲ cardioprotection Ⅲ antioxidant signaling Ⅲ myocardial infarction Ⅲ Nrf2 H ydrogen sulfide (H 2 S) is an endogenously produced gaseous signaling molecule with a diverse physiological profile. Its production in mammalian systems has been attributed to 2 key enzymes in the cysteine biosynthesis pathway, cystathionine ␤-synthase (CBS) and cystathionine ␥-lyase (CGL). The rate of H 2 S production in tissue homogenates is in the range of 1 to 10 pmol per second per milligram of protein, resulting in low micromolar extracellular concentrations. 1,2 It is at these physiological concentrations that H 2 S is cytoprotective in various models of cellular injury. 3,4 The reported cytoprotective effects of H 2 S are partially related to its ability to neutralize reactive oxygen species (ROS), to inhibit leukocyte-endothelial cell interactions, to promote vascular smooth muscle relaxation, to reduce apoptotic signaling, and to reversibly modulate mitochondrial respiration. 5 Pretreatment with NaHS has been reported to reduce the number and duration of arrhythmias in isolated hearts subjected to global ischemia/reperfusion (I/R) 6 and to enhanced the viability of isolated rat ventricular myocytes exposed to glucose deprivation and 2-deoxyglucose. 4 Recently, Elrod et al 7 reported that the administration of H 2 S at the time of reperfu...

The gasotransmitter hydrogen sulfide is known to regulate multiple cellular functions during normal and pathophysiological states. However, a paucity of concise information exists regarding quantitative amounts of hydrogen sulfide involved in physiological and pathological responses. This is primarily due to disagreement among various methods employed to measure free hydrogen sulfide. In this article, we describe a very sensitive method of measuring the presence of H2S in plasma down to nanomolar levels, using monobromobimane (MBB). The current standard assay using methylene blue provides erroneous results that do not actually measure H2S. The method presented herein involves derivatization of sulfide with excess MBB in 100 mM Tris–HCl buffer (pH 9.5, 0.1 mM DTPA) for 30 min in 1% oxygen at room temperature. The fluorescent product sulfide-dibimane (SDB) is analyzed by RP-HPLC using an eclipse XDB-C18 (4.6×250 mm) column with gradient elution by 0.1% (v/v) trifluoroacetic acid in acetonitrile. The limit of detection for sulfide-dibimane is 2 nM and the SDB product is very stable over time, allowing batch storage and analysis. In summary, our MBB method is suitable for sensitive quantitative measurement of free hydrogen sulfide in multiple biological samples such as plasma, tissue and cell culture lysates, or media.

Chronic tissue ischemia due to defective vascular perfusion is a hallmark feature of peripheral artery disease for which minimal therapeutic options exist. We have reported that sodium nitrite therapy exerts cytoprotective effects against acute ischemia/reperfusion injury in both heart and liver, consistent with the model of bioactive NO formation from nitrite during ischemic stress. Here, we test the hypothesis that chronic sodium nitrite therapy can selectively augment angiogenic activity and tissue perfusion in the murine hind-limb ischemia model. Various therapeutic doses (8.25-3,300 g/kg) of sodium nitrite or PBS were administered. Sodium nitrite significantly restored ischemic hind-limb blood flow in a timedependent manner, with low-dose sodium nitrite being most effective. Nitrite therapy significantly increased ischemic limb vascular density and stimulated endothelial cell proliferation. Remarkably, the effects of sodium nitrite therapy were evident within 3 days of the ischemic insult demonstrating the potency and efficacy of chronic sodium nitrite therapy. Sodium nitrite therapy also increased ischemic tissue nitrite and NO metabolites compared to nonischemic limbs. Use of the NO scavenger carboxy PTIO completely abolished sodium nitrite-dependent ischemic tissue blood flow and angiogenic activity consistent with nitrite reduction to NO being the proangiogenic mechanism. These data demonstrate that chronic sodium nitrite therapy is a recently discovered therapeutic treatment for peripheral artery disease and critical limb ischemia.wound healing ͉ endothelial cell ͉ nitric oxide ͉ peripheral artery disease ͉ tissue perfusion