Effect of exogenous hydrogen sulfide on mitochondrion-dependent apoptosis in lung tissues of rats with endotoxemia

Abstract

Objective To evaluate the effect of exogenous hydrogen sulfide (H2S) on mitochondrion-dependent apoptosis in lung tissues of rats with endotoxemia. Methods Forty healthy male Sprague-Dawley rats, aged 2-3 months, weighing 250-310 g, were divided into 5 groups (n=8 each) using a random number table: control group (group C), lipopolysaccharide (LPS) group, low dose sodium hydrosulphide (NaHS) group (group L-NaHS), moderate dose NaHS group (group M-NaHS) and high dose NaHS group (group H-NaHS). Endotoxemia was induced by IV LPS 5 mg/kg in chloral hydrate-anesthetized rats.The equal volume of 0.9% sodium chloride solution was intravenously injected in group C. NaHS (an exogenous donor of H2S) 0.78, 1.56 and 3.12 mg/kg were intraperitoneally injected at 3 h after LPS injection in L-NaHS, M-NaHS and H-NaHS groups, respectively.The rats were sacrificed at 6 h after injection of LPS or 0.9% sodium chloride solution, and lungs were removed for examination of the mitochondrial ultrastructure of lung tissues and for determination of apoptosis in lung cells (by flow cytometry) and expression of caspase-3, caspase-9, Bcl-2 and Bax protein and mRNA in lung tissues (by Western blot or real-time polymerase chain reaction). The apoptosis rate and ratio of Bcl-2 expression to Bax expression (Bcl-2/Bax ratio) were calculated.The expression of cytochrome c (Cyt c) in cytoplasm and mitochondria of lung tissues was detected by Western blot. Results The apoptosis rate was significantly increased, the expression of caspase-3, caspase-9, Bcl-2 and Bax protein and mRNA was up-regulated, Bcl-2/Bax ratio was decreased, the expression of Cyt c in cytoplasm was up-regulated, and the expression of Cyt c in mitochondria was down-regulated in group LPS (P 0.05), and the damage to mitochondrial ultrastructure was significantly mitigated in M-NaHS and H-NaHS groups. Conclusion The mechanism by which exogenous H2S inhibits cell apoptosis in lung tissues may be related to inhibition of mitochondrion-dependent apoptosis in rats with endotoxemia. Key words: Hydrogen sulfide; Endotoxemia; Lung; Apoptosis; Mitochondria