Inhibition of endogenous hydrogen sulfide formation reduces the organ injury caused by endotoxemia

Abstract

Hydrogen sulfide (H2S) is a naturally occurring gaseous transmitter, which may play important roles in normal physiology and disease. Here, we investigated the role of H2S in the organ injury caused by severe endotoxemia in the rat. Male Wistar rats were subjected to acute endotoxemia (Escherichia coli lipopolysaccharide (LPS) 6 mg kg(-1) intravenously (i.v.) for 6 h) and treated with vehicle (saline, 1 ml kg(-1) i.v.) or DL-propargylglycine (PAG, 10-100 mg kg(-1) i.v.), an inhibitor of the H2S-synthesizing enzyme cystathionine-gamma-lyase (CSE). PAG was administered either 30 min prior to or 60 min after the induction of endotoxemia. Endotoxemia resulted in circulatory failure (hypotension and tachycardia) and an increase in serum levels of alanine aminotransferase and aspartate aminotransferase (markers for hepatic injury), lipase (indicator of pancreatic injury) and creatine kinase (indicator of neuromuscular injury). In the liver, endotoxemia induced a significant increase in the myeloperoxidase (MPO) activity, and in the expression and activity of the H2S-synthesizing enzymes CSE and cystathionine-beta-synthase. Administration of PAG either prior to or after the injection of LPS dose-dependently reduced the hepatocellular, pancreatic and neuromuscular injury caused by endotoxemia, but not the circulatory failure. Pretreatment of rats with PAG abolished the LPS-induced increase in the MPO activity and in the formation of H2S and in the liver. These findings support the view that an enhanced formation of H2S contributes to the pathophysiology of the organ injury in endotoxemia. We propose that inhibition of H2S synthesis may be a useful therapeutic strategy against the organ injury associated with sepsis and shock.

Figure 1

Alterations in (a) mean arterial blood pressure (MAP) and (b) heart rate (HR) in rats subjected to the surgical procedure and pretreated with either saline (Sham Control, n=9) or DL-propargylglycine (Sham PAG, n=6). Rats subjected to endotoxemia (LPS 6 mg kg⁻¹ i.v.) were pretreated with either saline (LPS Control, n=9) or PAG. PAG was administered either 30 min prior to the induction of endotoxemia at 10 mg kg⁻¹ (LPS PAG 10 Pre, n=8) or 50 mg kg⁻¹ (LPS PAG 50 Pre, n=9), or 60 min after the induction of endotoxemia at 50 mg kg⁻¹ (LPS PAG 50 Post, n=9). ^*P<0.05 when compared with LPS Control.

Figure 2

Alterations in the serum levels of (a) alanine aminotransferase (ALT) and (b) aspartate aminotransferase (AST), (c) creatine kinase (CK) and (d) lipase in rats subjected to the surgical procedure and pretreated with either saline (Sham Control, n=9) or DL-propargylglycine (Sham PAG, n=6). Rats subjected to endotoxemia (LPS 6 mg kg⁻¹ i.v.) were treated with either saline (LPS Control, n=9) or PAG. PAG was administered either 30 min prior to the induction of endotoxemia at 10 mg kg⁻¹ (LPS PAG 10 Pre, n=8) or 50 mg kg⁻¹ (LPS PAG 50 Pre, n=9), or 60 min after the induction of endotoxemia at 50 mg kg⁻¹ (LPS PAG 50 Post, n=9). ^*P<0.05 when compared with LPS Control, ^#P<0.05 when compared with Sham Control, ^$P<0.05 when compared with LPS PAG 10 Pre.

Figure 3

Myeloperoxidase (MPO) activity in the liver of rats subjected to the surgical procedure and pretreated with either saline (Sham Control) or DL-propargylglycine (Sham PAG). Rats subjected to endotoxemia (LPS 6 mg kg⁻¹ i.v.) were pretreated with either saline (LPS Control) or PAG 30 min prior to (LPS PAG Pre) the induction of endotoxemia. N=6 for each group. ^*P<0.05 when compared with LPS Control.

Figure 4

CSE and CBS mRNA expression in the liver of rats subjected to the surgical procedure only (Sham) or endotoxemia (LPS). N=6 for each group. ^*P<0.05 when compared with respective Sham.

Figure 5

H₂S formation in the liver of rats subjected to the surgical procedure and pretreated with either saline (Sham Control) or DL-propargylglycine (Sham PAG). Rats subjected to endotoxemia (LPS 6 mg kg⁻¹ i.v.) were pretreated with either saline (LPS Control) or PAG 30 min prior to (LPS PAG Pre) the induction of endotoxemia. N=6 for each group. ^*P<0.05 when compared with LPS Control, ^#P<0.05 when compared with Sham Control.