Figure 10. Hemin and HO-1 differentially regulate p38 MAPK isoforms.

A, Hemin differentially regulates p38 MAPK isoforms. Quiescent EC were treated with hemin (10 µM for 24 h), and analyzed for total p38 MAPK and p38 isoforms by Western blotting. B, The autoradiographic signals in panel A were semiquantified by videoimage analysis, and presented as a ratio of p38 MAPK isoforms to that of total p38 MAPK from three independent experiments. C, Ectopic expression of HO-1 reverses IL-18 mediated suppression in p38β MAPK levels. EC transduced with Ad-HO-1 or Ad.GFP for 24 h were treated with IL-18. One hour later, cleared cell lysates were analyzed for total p38 and p38 isoforms by Western blotting. D, The autoradiographic signals in panel C were semiquantified by videoimage analysis, and results are presented as a ratio of p38 MAPK isoforms to that of total p38 MAPK from three independent experiments. E, Knockdown of p38β isoform potentiates IL-18-mediated EC death. EC were treated with p38 MAPK isoform-specific siRNA (100 nM for 48 h) and then treated with IL-18. After 24 h, cell death was analyzed by Annexin V-FITC/PI staining and flow cytometry (n=6). F, Knockdown of p38 MAPK isoforms was confirmed by Western blotting (n=3). αTubulin served as a control. B, *p<0.05 Vs. respective Untreated or solvent, **p<0.001 Vs. Untreated; D, *p<0.01 Vs. respective Untreated, †p<0.001 Vs. IL-18-treated GFP; E, *p<0.001 Vs. Untreated, †p<0.01 Vs. IL-18, §p<0.05 Vs. IL-18.