3H-1,2-Dithiole-3-thione Targets Nuclear Factor B to Block Expression of Inducible Nitric-Oxide Synthase, Prevents Hypotension, and Improves Survival in Endotoxemic Rats

Septicemia is a major cause of death associated with noncoronary intensive care. Systemic production of nitric oxide (NO) by inducible nitric-oxide synthase (iNOS) is a major cause of hypotension and poor organ perfusion seen in septic shock. Here, we show that pretreatment of F344 rats with the cancer chemoprotective agent 3H-1,2-dithiole-3-thione (D3T) blocks lipopolysaccharide (LPS)-mediated induction of hepatic iNOS and significantly reduces the associated serum levels of NO metabolites and enzyme markers of toxicity provoked by treatment with LPS. Immunohistochemical analysis shows that this protective effect is largely due to suppression of iNOS expression in hepatocytes. Importantly, pretreatment of animals with D3T blunts LPS-mediated hypotension and dramatically increases their survival. Inasmuch as iNOS expression can be regulated by nuclear factor (NF) B, mechanistic studies show that D3T blocks NF B nuclear translocation and DNA binding and that these effects are accompanied by changes in the levels of phospho-inhibitor of NF B. In conclusion, this study identifies new drug classes and targets that may improve the prevention and treatment of septic shock, as well as chronic diseases associated with the NF B and iNOS pathways. Systemic production of nitric oxide (NO) by inducible nitric-oxide synthase (iNOS) is a major cause of the hypotension and poor organ perfusion that is seen in septic shock (Julou-Schaeffer et al., 1990; Thiemermann and Vane, 1990). Studies of iNOS null mutant mice have shown such mice to be resistant to the hypotension and death caused by lipopolysaccharide (LPS) (MacMicking et al., 1995; Wei et al., 1995). Inhibition of nitric-oxide synthase activity with selective inhibitors of iNOS have been shown to have beneficial effects in rodent models of septic shock, whereas inhibition of endothelial nitric-oxide synthase (eNOS) may lead to adverse effects including enhanced organ damage and excessive vasoconstriction (Thiemermann, 1997; Vos et al., 1997). Treatments such as dexamethasone that act to block the expression of iNOS protein decrease circulatory and organ failure, although such agents must be administered prior to endotoxin to achieve these beneficial outcomes (for review, see Thiemer-