The Involvement of the CD40-CD40L Pathway in Activated Platelet-Induced Changes in HUVEC COX-2 and PPARα Expression

We aim to determine the extent of the CD40-CD40L pathway involvement in activated platelet-induced changes in human umbilical endothelial cells (HUVECs). Activated platelets were co-incubated with HUVECs in the presence or absence of CD40LmAb. HUVECs were also directly stimulated with rhCD40L. HUVEC endothelial cyclooxygenase 2 (COX-2) and peroxisome proliferator-activated receptor alpha (PPAR alpha) expression was then assessed. To estimate COX-2 activity, PGE2 concentration was determined. PPAR alpha activity was assessed using a nuclear factor activity kit. Co-incubation with activated platelets increased HUVEC COX-2 and PPAR alpha mRNA expression (P < 0.01). The addition of CD40L mAb significantly attenuated these increases in mRNA and protein (both P < 0.01). Direct stimulation by rhCD40L increased HUVEC COX-2 mRNA and protein (P < 0.05) but did not significantly change the expression of PPAR alpha mRNA and protein. CD40LmAb significantly decreased (P < 0.05) and rhCD40L significantly (P < 0.01) increased COX-2 enzymatic activity, but had almost no effects on PPAR alpha binding activity. Activated platelets may increase HUVEC COX-2 expression and activity partly through the CD40-CD40L pathway.