CORM-3-induced HO-1 protein expression is mediated via protein kinase C (PKCα). (A) RBA-1 cells were pretreated with various concentrations of Ro31-8220, Gö6976, or Gö6983 for 1 h, and then incubated with 30 μM CORM-3 for 6 h. The levels of HO-1 and GAPDH (as an internal control) protein expression were determined by Western blot. (B) RBA-1 cells were pretreated with 3 μM Gö6976, 3 μM Gö6983, or 3 μM Ro31-8220 for 1 h and then incubated with 30 μM CORM-3 for 4 h. The levels of HO-1 mRNA were determined by real-time PCR (Open bars). Cells were transiently transfected with HO-1 report gene together a β-galactosidase plasmid, pretreated with 3 μM Gö6976, 3 μM Gö6983, or 3 μM Ro31-8220 for 1 h, and then incubated with 30 μM CORM-3 for 1 h. Promoter activity was determined in the cell lysates (Gray bars). (C) RBA-1 cells were transfected with PKCα siRNA and then incubated with 30 μM CORM-3 for 6 h. The cell lysates were subjected to western blot using an anti-HO-1, anti-PKCα, or anti-GAPDH (as internal control). The densitometric quantifications are indicated on the panels. (D) RBA-1 cells were pretreated with 3 μM Ro31-8220, 3 μM Gö6983, 3 μM Gö6976, 10 μM SU6656, or 10 μM PF431396 for 1 h, and stimulated with 30 μM CORM-3 for the indicated time intervals. Phosphorylation of PKCα/βII was determined by Western blot using an anti-phospho-PKCα/βII or anti-PKCα antibody. Data are expressed as the mean ± SEM of three independent experiments ( n = 3). * p