PAF effects on MCP-1 and IL-6 secretion in U-937 monocytes in comparison with OxLDL and IL-1β effects

Abstract

ObjectiveTo study the effects of PAF, in comparison with OxLDL and IL-1β on MCP-1 and IL-6 secretion from U-937 monocytes and to investigate the mechanism of its action. MethodsU-937 cell line was cultured in the presence or absence of PAF or OxLDL or IL-1β. Secretion of IL-6 and MCP-1 was measured by ELISA method, mRNA levels of MCP-1 and PAFR was measured using real-time PCR. In order to investigate the mechanism of mediator's action signal transduction appropriate inhibitors was used and oxidant status of cells by measurement the total cellular thiols content and glutathione was determined. Results and conclusionNone of the tested mediators induced the secretion of IL-6. On the other hand PAF and OxLDL caused a short-term while IL-1β caused a long-term secretion and expression of MCP-1. Reduced total thiol levels and GSH/GSSG ratio indicate that the above mediators induce oxidative stress. The signal transduction of all mediators is mediated through G-proteins, protein kinases (PKC, serine–threonine kinase and tyrosine kinase) and NF-κB activation. In addition, PAF, OxLDL, IL-1β activates monocytes leading to increased PAF receptor mRNA levels. These results indicate that PAF and OxLDL, in a different pattern from that of IL-1β, regulate MCP-1 expression via pathways that involve changes in cell redox status.