Abstract 1913: CaMKII Regulates Ang-II Induced Vascular Smooth Muscle Cell Hypertrophy by a Pathway Involving HDAC4/MEF2
Introduction: The calcium/calmodulin-dependent kinase II (CaMKII) is activated by angiotensin-II, a strong inducer of vascular smooth muscle cell (VSM) hypertrophy. CaMKII activates HDAC4/MEF-2 dependent gene transcription by phosphorylation of HDAC4 S467 and 632. Here, we demonstrate that CaMKII mediates Ang-II-induced VSM hypertrophy in vitro and in vivo by activation of the HDAC4/MEF-2 signal transduction pathway.
Methods and Results: Medial hypertrophy by Ang-II infusion at pressor dose over 10 days was significantly reduced in C57Bl/6 mice when the CaMKII inhibitor KN93 was given daily i.p. (0.070 mm2 vs 0.052 mm2, p<0.05). In vitro, Ang-II increased the 3H-Leucine/3H-Thymidine uptake in control aortic VSM cells by 50% after 24 hr, whereas overexpression of the CaMKII peptide inhibitor CaMKIIN resulted only in 14 % increase (p<0.05). Ang-II induced phosphorylation of HDAC4 that was further increased under overexpression of CaMKIIδ2. CaMKII overexpression resulted in increased nucleoprotein complex formation in MEF2-electrophoretic mobility shift assays in response to Ang-II. CaMKII blockade by CaMKIIN significantly decreased the response to Ang-II in MEF2-promoter assays (1.2-fold increase vs 2.6-fold in controls, p<0.05). Overexpression of dominant-negative HDAC4 S467,632A mutant that cannot be phosphorylated by CaMKII significantly reduced MEF2-promoter activity and VSM hypertrophy in response to Ang-II (p<0.05). Ang-II induced MEF2-dependent transcription in vivo in MEF2-reporter mice that were infused with Ang-II at pressor dose for 14 days. The administration of the CaMKII inhibitor KN93 abolished MEF2 activation by Ang-II in these mice.
Conclusion: CaMKII mediates Ang-II induced VSM hypertrophy by regulating the pro-hypertrophic transcription pathway HDAC4/MEF2 in the aortic media and VSM cells.
This research has received full or partial funding support from the American Heart Association, National Center.