Objective: Interferon gamma (IFN-gamma) was shown to induce CD40 and CD40L expression on endothelial cells (ECs) and consequently to promote neutrophil adhesion. The pro- and anti-inflammatory effects of estrogens are well recognized but their role on the regulation of CD40 and CD40L expression on ECs remains undefined.
Methods and results: Treatment of porcine aortic endothelial cells (PAEC) with IFN-gamma for 24 h enhanced CD40 and CD40L expression by 97% and 78%, respectively. Pretreatment of PAEC with 17-beta-estradiol (17betaE) for 24 h prevented the latter expression of CD40/CD40L. Treatment of PAEC with antisense oligomers targeting ERalpha mRNA attenuated the ability of 17betaE to inhibit the IFN-gamma-induced CD40 and CD40L protein expression. The IFN-gamma activation pathway of CD40 is known to involve the phosphorylation of the Janus activated kinase (JAK) and the signal transducer and activator of transcription 1 (Stat1). 17betaE, acting via the estrogen receptor alpha (ERalpha), abrogated IFN-gamma-mediated effects on Stat1 but failed to inhibit Jak1 and Jak2 phosphorylation. Furthermore, 17betaE prevented neutrophil adhesion induced by IFN-gamma.
Conclusion: In summary, 17betaE binding to ERalpha blocked IFN-gamma-induced Stat1 phosphorylation, CD40 and CD40L protein expression, and neutrophil adhesion onto ECs.