CSA AND FK506 UP-REGULATE ENOS EXPRESSION - ROLE OF REACTIVE OXYGEN SPECIES AND AP-1

Cyclosporine A (CsA) and FK506 increase endothelial nitric oxide synth ase (eNOS) mRNA expression in cultured bovine aortic endothelial cells (BAEC). CsA appears to increase eNOS mRNA levels mainly by increasing the rate of transcription, although a small contribution of mRNA stab ilization could not be ruled out. CsA and FK506 induced an increase of ROS synthesis with the fluorescent probe used, DHR123. The ROS genera ting system glucose oxidase (GO) increased the expression of eNOS mRNA in BAEC. This upregulation of eNOS mRNA by CsA or GO was abrogated by catalase. As AP-1 is a redox-sensitive transcription factor and the b ovine eNOS promoter has an AP-1 consensus sequence, a role of this fac tor in the up-regulation of eNOS mRNA was studied. Electrophoretic mob ility shift assays were consistent with an increase in AP-1 DNA-bindin g activity in BAEC treated with CsA or glucose oxidase. The potential participation of ROS and the transcription factor AP-1 in the regulati on of eNOS gene expression is suggested.