[Heat shock response in a rat model of septic multiple organ dysfunction syndrome]

Severe sepsis is known to result in multiple organ dysfunction syndrome (MODS), which is thought to be mediated by oxidative stress, as a result of excessive systemic inflammation. Heme Oxygenase-1 (HO-1), the rate limiting enzyme in heme catabolism, is also known as HSP32. HO-1 is induced not only by its substrate heme but also by oxidative stress. We investigated gene expression of HO-1 and physiological significance of HO-1 induction in a rat model of septic MODS induced by intraperitoneal injection of bacterial lipopolysaccharide (LPS). Following administration of LPS, HO-1 mRNA was significantly induced in the liver, lung and kidney in an organ-specific manner. Hepatic HO-1 induction appears to be mediated by an increase in hepatic free heme concentration. Inhibition of HO activity by tin mesoporphyrin significantly exacerbated lung injury. These results suggest that HO-1 induction may play an important role in conferring protection on cells from oxidative damage not only by catalyzing heme, a pro-oxidant, but also by producing bilirubin, an anti-oxidant. Furthermore, HO-1 mRNA is induced markedly in the buffy coat of the blood at 3 h after LPS administration, coinciding with the increase in serum IL-6 level, suggesting that HO-1 may be one of the key markers of septic MODS.