Modulation of inflammatory response by pentoxifylline is independent of heme oxygenase-1 pathway.

OBJECTIVE It was reported that some effects of pentoxifylline (PTX) are mediated by heme oxygenase-1 (HO-1) induction. We investigated the role of HO-1 in anti-inflammatory activity of PTX. METHODS Experiments were performed in human and murine monocytes and endothelial cells and in HO-1 deficient mice. RESULTS PTX dose-dependently decreased expression of HO-1 in cell lines studied. As expected, PTX reduced also production of TNF. This effect was independent of HO-1 activity, as demonstrated in cells treated with HO-1 activators and inhibitors or in cells overexpressing HO-1. Moreover, inhibition of TNF was the same in human endothelial cells of different HO-1 genotypes, showing that PTX is similarly efficient in carriers of more and less active HO-1 promoter variants. In mice, PTX did not influence HO-1 expression, as measured in liver, kidney, spleen, heart, and skin. Accordingly, the response of PTX treated animals to LPS was the same in wild type and HO-1 deficient mice. PTX to a similar extent increased influx of leukocyte into peritoneal cavity, decreased production of TNF and reduced expression of VCAM-1 in vascular intima. CONCLUSION PTX inhibits production of TNF and may decrease inflammatory reaction both in vitro and in vivo, but these effects are independent of HO-1.