Influence of pentoxifylline on fevers induced by bacterial lipopolysaccharide and tumor necrosis factor-alpha in guinea pigs

In guinea pigs intraperitoneal (i.p.) injections of 50 mg/kg pentoxifylline had no influence on abdominal temperature while higher doses of pentoxifylline caused a hypothermic response lasting for 2-3 h. Administration of 50 mg/kg pentoxifylline 1 h before intramuscular (i.m.) injections of 20 mu g/kg bacterial lipopolysaccharide reduced the lipopolysaccharide-induced production of endogenous tumor necrosis factor-alpha (TNF-alpha) by 68%. The second phase of lipopolysaccharide-induced fever was significantly attenuated by pretreatment with 50 mg/kg pentoxifylline, a dose which had, per se, no influence on core temperature of guinea pigs. The thermal response of guinea pigs to administration of exogenous TNF-alpha was not modulated by pretreatment with pentoxifylline. Intra-arterial infusions with 5 mu g/kg TNF-alpha, a dose which yielded the same circulating TNF bioactivity as i.m. injections of 20 mu g/kg lipopolysaccharide, induced a biphasic febrile response. The magnitude and duration of TNF-induced fever were the same whether guinea pigs were pretreated with pentoxifylline or with 0.9% saline. The results indicate that endogenous formation of TNF-alpha may contribute to the development of fever induced by lipopolysaccharide, but is not its only mediator, since the first phase of lipopolysaccharide-induced fever was not altered by the blockade of TNF production.