Reactive oxygen species are thought to be involved in the pathogenesis of septic
multiple organ dysfunction syndrome (
MODS). It has been reported that
heme oxygenase-1 (HO-1) (EC 1.14.99.3) is induced in septic animal models and is thought to confer protection against oxidative tissue injury. In this study, we examined changes in gene expression of HO-1 and non-specific
delta-aminolevulinate synthase (ALAS-N) (EC 2.3.1.37), the rate-limiting
enzymes in
heme catabolism and
heme synthesis, respectively, after intraperitoneal administration of bacterial
lipopolysaccharide (LPS) to rats. LPS treatment caused the elevation of body temperature, increases in white blood cell counts, and marked elevation of serum
interleukin-6 levels associated with liver, lung, and kidney
injuries, characteristic of septic
MODS. LPS administration significantly induced HO-1
mRNA,
protein, and
enzyme activity in the liver, lung, and kidney. In contrast, ALAS-N
mRNA was decreased rapidly in the liver, followed by an oscillating recovery pattern. Induction of hepatic HO-1
mRNA and rapid suppression of ALAS-N
mRNA were likely the result of a rapid increase in hepatic free
heme concentration as judged by the increase in
heme saturation of
tryptophan pyrrolase. In contrast to that in the liver, the ALAS-N
mRNA level in the lung and kidney was increased significantly after LPS administration, suggesting a novel mechanism of ALAS-N regulation in these tissues. These findings suggest that HO-1 and ALAS-N
mRNA are regulated in a tissue-specific manner in a rat model of septic
MODS.