Salvage of Enteric Tissue after a Period of Critical Ischemia: Diminution of Oxidative Stress via Treatment with Hydrogen Sulfide
Allie M. Sohn, BS, Peter W. Henderson, MD MBA, Andrew L. Weinstein, BS, Alice Harper, BA, Jason A. Spector, MD FACS.
Weill Cornell Medical College, New York, NY, USA.
BACKGROUND: Our lab has previously demonstrated that hydrogen sulfide (HS) protects intestinal tissue against ischemia-reperfusion injury (IRI) when delivered prior to the ischemic event. While the obligatory ischemic interval for patients undergoing free tissue transfer can be anticipated, an unanticipated ischemic event in the post-operative period can be a source of additional IRI-induced morbidity for these patients. We investigated whether HS is also capable of attenuating the degree of IRI seen in enteric tissue even when delivered after the onset of ischemia.
METHODS: Rat intestinal epithelial (IEC-6) cells were exposed to hypoxia (1% O2) for 1 hour or 2 hours, and were bathed in media containing 0-100µM NaHS for the final 20 minutes of the hypoxic period. They were then moved to a standard incubator (21% O2) for 3 hours of normoxia. A TUNEL assay determined the apoptotic index (AI) for each group. Additionally, 27 Sprague-Dawley rats underwent 1 hour or 2 hours of jejunal ischemia. Twenty minutes prior to 3 hours of reperfusion, intravenous NaHS sufficient to raise bloodstream concentrations to [0µM], [10µM], or [100µM] was injected. After reperfusion, the ischemic-reperfused segment and non-ischemic control were harvested, and villus height was measured. Values are reported as mean percent of non-ischemic control ± standard error of the mean.
RESULTS: In vitro, a significant decrease in AI (p<0.05) was seen at both time points after treatment with 10µM, and at 2 hours after treatment with 100µM (Figure 1). In vivo, treatment with [10µM] or [100µM] resulted in preservation of villus height at both time points (Figure 2). After 1 hour of ischemia, the villus height of the 0 HS group was 42% ± 12%, 10μM was 65% ± 7% (p<0.01), and 100μM was 55% ± 5% (p=<0.01). After 2 hours of ischemia, the 0μM was 22% ± 4%, 10μM was 51% ± 7% (p<0.01), and 100μM was 38% ± 8% (p<0.01). There was no toxicity in non-ischemic HS-treated groups.
CONCLUSIONS: These data demonstrate that HS is non-toxic at micromolar range doses, and that pharmacologic post-conditioning with this molecule provides significant protection against IRI. Therefore, HS has tremendous potential to be beneficial not only in situations of anticipated ischemia (when it can be given prior to the ischemic event), but also in situations of unexpected ischemia, when it can be given as an adjunct to operative revision. Such treatment may prove especially useful in the salvage of enteric tissue, which is known to be exquisitely sensitive to even brief periods of ischemia and reperfusion.
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