Beneficial effect of HCL-31D in murine models of endotoxaemia

We evaluated the effect of HCL-31D. a novel cAMP-specific phosphodiesterase inhibitor, on the induction of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma)-treated rat aortic smooth muscle cells (RASMC) and on survival in a murine model of severe endotoxaemia. Treatment of cultured RASMC with LPS and IFN-gamma resulted in an increase of nitrite, tumour necrosis factor (TNF-alpha) production and induction of iNOS mRNA. However, incubation with HCL-31 D (1 similar to 50 muM) for 24 It caused significant attenuation of nitrite and TNF-alpha formation as well as iNOS mRNA induction in a dose-dependent manner but no effect on iNOS activity in RASMC. In addition, administration of HCL-31D (5 mg/kg, i.p.) resulted in that the increase of both plasma nitrate and TNF-alpha levels induced by LPS in vivo was significantly reduced in LPS-treated rats. Treatment of conscious mice with a high dose of LPS (60 mg/kg, i.P.) to ICR mice resulted in a 24-h survival rate of only 10%. However, administration of HCL-31D (5 mg/kg, i.p. at 0 h and 6 h after LPS) improved the 24-h survival to 50%. indicating that HCL-3 I D has a beneficial effect in murine model endotoxaemia. These effects may be mainly due to inhibition of TNF-alpha formation and of the induction of iNOS. We proposed that the elevation of cAMP levels by HCL-31D may be involved in the prevention of TNF-alpha. formation and iNOS induction.