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Induction of nitric oxide synthase by bacterial endotoxin in vivo can be mimicked by treating cultured hepatocytes with a combination of lipopolysaccharide and cytokines (LPS/cytokines), but the role of LPS/cytokine-induced nitric oxide in hepatocyte glucose metabolism is ambiguous. In this study, intermediary metabolite effects on LPS/cytokine-induced hepatocyte nitric oxide synthesis were examined. Pyruvate, lactate, oxaloacetate, and fumarate all showed some inhibitory effects on hepatocyte nitric oxide synthesis. However, these metabolic intermediates could not improve the mitochondrial respiration of LPS/cytokine-treated hepatocytes. Phosphoenolpyruvate carboxykinase activity (or flux) relating factors, glucocorticoids and cAMP, also blocked LPS/cytokine-induced nitric oxide synthesis. Insulin was much less potent than cAMP and glucocorticoids, and phorbol ester did not show any effect on hepatocyte nitric oxide synthesis. These results suggest that LPS/cytokine-induced nitric oxide synthesis is related, at least partly, to phosphoenolpyruvate carboxykinase activity (or flux) in hepatocytes.

Widespread clinical applications of peptide drugs have been hindered by their low stability and selectivity. Peptides can be easily digested by various enzymes in the blood and thus show a short life-span. Meanwhile, peptide drugs can cause severe normal tissue damage due to their low selectivity. Therefore, for effective therapy, a high dosage of peptide is required which is usually in excess of the clinically and economically acceptable level. In this study, we have tried to design new lytic peptides which can self-assemble into peptide fibrils with defined nanostructures as observed under atomic force microscopy. Lytic peptides in self-assembled peptide fibrils will lose their cell lysis activity but become resistant to enzyme degradation. Such lytic peptide self-assembly has proven to be a reversible process which is controlled by surrounded environments. A concentration controlled sustained release of free and active lytic peptide from self-assembled peptide fibrils has been achieved. Self-assembled lytic peptides with enzyme resistance, sustained release, and prodrug feature may have great clinical application potentials.

Cell-penetrating peptide (CPP) was linked to insulin to form insulin-CPP hybrids. The intestinal absorption efficiency of CPP hybridized insulin was 6-8 times increased compared to normal insulin as tested on Caco-2 cell monolayer, a widely used in vitro model for intestinal absorption. Insulin-CPP hybrid transportation seemed to be through an active and transcytosis-like mechanism. Importantly, insulin in hybrids kept intact after they passed through the Caco-2 cell monolayer. This study provides a new clue for oral insulin development.

Nitric oxide (NO) from artificial NO donors induces cell death through complete inhibition of mitochondrial respiration of hepatocytes. Treatment of hepatocytes with lipopolysaccharide (LPS) and cytokine mixture (interferon gamma and tumor necrosis factor alpha) not only results in NO production but also causes cellular respiration suppression and cell death in hepatocytes. NG-monomethyl-L-arginine, a specific inhibitor of nitric oxide synthase, inhibits hepatocyte NO synthesis but cannot prevent hepatocytes from LPS and cytokine mixture-induced cellular injuries. Similarly, some metabolic intermediates capable of inhibiting hepatocyte NO synthesis cannot block LPS and cytokine mixture-mediated cellular injuries in hepatocytes. These results imply that lipopolysaccharide and cytokine mixture-induced cellular injuries and NO syntheses are parallel events, NO is not involved in LPS and cytokine mixture-induced cell damage.