Hsp32-mediated rescue of HMC-1 cells from the effects of PKC412. (A) HMC-1.2 cells were cultured in control medium or hemin (10 μM) at 37°C and then were exposed to PKC412 at 1 μM (left panel) or 5 μM (right panel) for 48 hours. Thereafter, the number of apoptotic cells were determined by light microscopy. Results show the percentage of apoptotic cells and represent the mean (± SD) of 3 independent experiments. *P <.05. In the absence of PKC412, the percentage of apoptotic cells ranged between 1% and 3% (not shown). (B) Doxycycline-induced expression of Hsp32/HO-1 in HMC-1.2.K-HO-1 cells. HMC-1.2.K-HO-1 cells were incubated in the absence or presence of doxycycline (1 μg/mL) at 37°C for 24 hours. When added, PKC412 (1 μM, 24 hours) was found to down-regulate the expression of Hsp32 to trace amounts in the absence of doxycycline, whereas the doxycycline-induced expression of Hsp32 in these cells could not be completely abrogated by PKC412. (C) HMC-1.2.K-HO-1 cells were incubated in the absence or presence of doxycycline (1 μg/mL) at 37°C for 24 hours. Then, cells were exposed to control medium or PKC412 (0.5 μM) at 37°C for 24 hours. Thereafter, the numbers of apoptotic cells were assessed by light microscopy. Results represent the mean (± SD) of 3 independent experiments. *P < .05.