Differential effects of pentoxifylline and interleukin-10 on production of tumor necrosis factor and inducible nitric oxide synthase by murine macrophages

The abilities of pentoxifylline and recombinant interleukin-10 (rlL-10) to inhibit tumor necrosis factor (TNF) and inducible nitric oxide synthase (iNOS) production in RAW 264.7 murine macrophages were compared. Pentoxifylline consistently inhibited the accumulation of both TNF and iNOS in a dose-dependent manner whether the stimulus was bacterial lipopolysaccharide (LPS), recombinant interferon-gamma (rIFN-gamma), or LPS plus rIFN-gamma. Similarly, rIL-10 consistently reduced TNF production by cells stimulated with LPS, rIFN-gamma, or LPS plus rIFN-gamma. However, rIL-10 weakly inhibited LPS-induced iNOS production but failed to block (and often augmented) rIFN-gamma-induced iNOS production. Combinations of pentoxifylline and rIL-10 led to additive or synergistic inhibition of TNF but not iNOS production; in fact, rIL-10 appeared to interfere with the ability of pentoxifylline to block iNOS accumulation. These data suggest that combinations of antiinflammatory agents may have unanticipated effects on inflammatory mediator production.