Abstract 1124: CD40L Induces Inflammation in Adipose Tissue - a Potential Link Between the Metabolic Syndrome and Atherosclerosis
Background: CD40L figures prominently as marker and mediator of atherosclerosis and its clinical complications. Recent data also demonstrate an association between CD40L and the metabolic syndrome. In the light of these data we hypothesized a functional pro-inflammatory role of CD40L in adipose tissue that provokes systemic pro-inflammatory responses and potentially mediates some of the high cardiovascular risk associated with the metabolic syndrome.
Methods and Results: Adipocytes and preadipocytes isolated from adipose tissue obtained from bariatic surgery did not express CD40L but its receptor CD40 as assessed by PCR and immunohistochemistry. Furthermore, sections of human adipose tissue from obese donors contained more macrophages and T cells colocalizing with CD40L than those from lean controls. Stimulation of both adipocytes and preadipocytes with recombinant CD40L resulted in a concentration- and time-dependent release of the pro-inflammatory cytokine IL-6, the chemokines MCP -1 and IL-8 as well as the inhibitor of fibrinolysis PAI-1 into the supernatant as quantified by ELISA. Membranes isolated from a Murine cell line overexpressing human CD40L reproduced these pro-inflammatory effects compared to respective controls. Interestingly, fenofibrate but neither rosiglitazone, metformin, nor atorvastatin attenuated the CD40L-inducible expression of these pro-atherogenic mediators. Finally, supernatants from adipocytes and preadipocytes stimulated with CD40L activated endothelial cells and macrophages, typical cell types resident in atherosclerotic lesions, as assessed by FACS for tissue factor, Mac-1, and ICAM-1, respectively.
Conclusions: Our data suggest that CD40L induces inflammatory cytokine production in adipose tissue resulting in activation of endothelial cells and macrophages. This new mechanism may contribute to the high cardiovascular risk of patients suffering from the metabolic syndrome.