Effects of sCD40L and SeMet on activities of NOX, CAT, and SOD and eNOS mRNA levels in HCAECs. (A) NADPH oxidase (NOX) activity. HCAECs were treated with sCD40L for 24 hours, and NOX activities were determined by lucigenin-enhanced chemiluminescence with the presence of its substrate β-NADPH. O2− scavenger Tiron or flavoprotein inhibitor DPI was included in the assay to confirm the specificity of NOX activity. (B) CAT activity. HCAECs were treated with sCD40L for 24 hours and CAT activity was determined with a commercial kit. Antioxidant SeMet was included. (C) SOD activity. HCAECs were treated with sCD40L for 24 hours and SOD activity was determined with a commercial kit. Antioxidant SeMet was included. (D) eNOS mRNA levels. HCAECs were treated with sCD40L and/or SeMet for 24 hours, and eNOS mRNA levels were determined by real-time PCR analysis. *P < .05 and **P < .01, compared with the control. #P < .05 compared with sCD40L treatment. t test. n = 3. Data are means and SE of multiple experiments (n).