Effects of sCD40L on eNOS protein levels and NO production in HCAECs. (A) Western blot analysis. HCAECs were treated with sCD40L for 24 hours and eNOS protein levels were determined by Western blot. (B) eNOS enzyme activity. HCAECs were treated with sCD50L for 24 hours. The eNOS enzyme activity was determined by a commercial eNOS fluorimetric assay kit. (C) Cellular NO levels. HCAECs were treated with sCD40L for 24 hours and cellular NO levels were determined by DAF-FM DA staining and flow cytometric analysis. (D) Effect of sCD40L trimer on eNOS mRNA and (E) protein levels. HCAECs were treated with sCD40L monomer form or sCD40L trimer form for 24 hours, and eNOS mRNA and protein levels were determined by real-time PCR analysis and Western blot, respectively. *P < .05 and **P < .01, compared with the control. n = 3. Data are means and SE of multiple experiments (n).