Insights into the regulation of TNF-a production in human mononuclear cells: the effects of non-specific phosphodiesterase inhibition

objective: the objective of this study was to determine the effect of nonspecific phosphodiesterase inhibition on transcription factor activation and tumor necrosis factor-alpha (tnf-a) production in lipopolysaccharide (lps)-stimulated human mononuclear cells. introduction: the production of tnf-a following lps stimulation is one of the key steps in bacterial sepsis and inflammation. the mechanism by which phosphodiesterase inhibition alters tnf-a production in the presence of lps remains unclear. methods: human mononuclear cells were stimulated with lps (1 μg/ml), in the presence and absence of pentoxifylline (ptx; 20 mm), a nonspecific phosphodiesterase inhibitor. western blotting of phosphorylated cytoplasmic i-kba, nuclear factor-kb p65 (nf-kb), and nuclear camp-response element binding protein (creb) was performed. dna binding of nf-kb and creb was verified by electrophoretic mobility shift assay. tnf-a levels were determined in the supernatant of stimulated cells in the presence and absence protein kinase a inhibition by an enzyme-linked immunosorbent assay (elisa). results: ptx was demonstrated to significantly reduce cytoplasmic i-kba phosphorylation, nuclear p65 phosphorylation, and the dna binding activity of nf-kb. in contrast, ptx markedly enhanced the phosphorylation and dna binding activity of creb. cells concomitantly treated with ptx and lps secreted similar levels of tnf-a in the presence and absence protein kinase a inhibition. discussion: the increased level of camp that results from phosphodiesterase inhibition affects cytoplasmic and nuclear events, resulting in the attenuation of nf-kb and the activation of creb transcriptional dna binding through pathways that are partially protein kinase a-independent. conclusion: ptx-mediated phosphodiesterase inhibition occurs partially through a protein kinase a-independent pathway and may serve as a useful tool in the attenuation of lps-induced inflammation.