Altered energy metabolism and oxidative injury following endotoxemia in rats with normal or cirrhotic livers

Endotoxin increases oxidative injury to proteins in guinea pig liver: protection by dietary vitamin C

Current information suggests that oxidative damage plays a key role in septic shock induced by endotoxin. This raises the possibility that dietary antioxidant vitamins could protect against endotoxin damage. In this study, the effects of endotoxin administration on protein and lipid oxidative damage and endogenous antioxidants were studied in the liver of guinea pigs previously supplemented with marginal or optimum levels of dietary vitamin C, vitamin E or both. Vitamins C and E inhibited in vitro lipid peroxidation in endotoxin-treated animals. Endotoxin significantly increased oxidative damage to liver proteins in animals receiving low doses of both vitamins, a result described here for the first time. This increase was totally prevented in guinea pigs supplemented with vitamin C alone or in combination with vitamin E, a treatment which strongly increased liver ascorbate. Vitamin C caused small significant increases in superoxide dismutase and glutathione, increased uric acid, and synergically increased alpha-tocopherol levels in vitamin E-supplemented animals treated with endotoxin. The results show that dietary vitamin C protects against endotoxin-induced oxidative damage to proteins in the guinea pig liver. This seems mainly due to a direct protective effect of the increased hepatic ascorbate levels present in vitamin C-supplemented animals.

Endotoxin depletes ascorbate in the guinea pig heart. Protective effects of vitamins C and E against oxidative stress

The effect of acute endotoxin-induced septic shock on myocardium oxidative stress after low or high vitamin C and/or E dietary supplementation was studied in guinea pigs, laboratory animals which, like human, do not have capacity for ascorbate synthesis. Neither the antioxidant enzymes or GSH were modified by endotoxin and vitamin treatments. Vitamin E showed a strong capacity to protect the myocardium against both enzymatic and non-enzymatic lipid peroxidation even in the presence of endotoxin. Vitamin C supplementation increased heart ascorbate whereas endotoxic shock totally depleted the heart ascorbate of vitamin C supplemented animals without changing vitamin E. Endotoxin significantly increased myocardium uric acid, a marker of ischemia induced oxidative stress, in animals fed with low vitamin C levels. This increase was totally prevented in vitamin C supplemented, but not in vitamin E supplemented animals. Strongly depressed levels of plasma vitamin C have been recently described in sepsis in human patients. The results suggest that ascorbate is a primary antioxidant target in the heart of endotoxin treated mammals lacking the capacity to synthesize ascorbate and that ascorbate can have a protective value against endotoxin-induced free radical damage in the myocardium. Implications of these results for the possible preventive role of vitamin C in humans during sepsis are discussed.