Loss of MURC/Cavin-4 induces JNK and MMP-9 activity enhancement in vascular smooth muscle cells and exacerbates abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is relatively common in elderly patients with atherosclerosis. MURC (muscle-restricted coiled-coil protein)/Cavin-4 modulating the caveolae function of muscle cells is expressed in cardiomyocytes, skeletal muscle cells and smooth muscle cells. Here, we show a novel functional role of MURC/Cavin-4 in vascular smooth muscle cells (VSMCs) and AAA development. Both wild-type (WT) and MURC/Cavin-4 knockout (MURC−/−) mice subjected to periaortic application of CaCl2 developed AAAs. Six weeks after CaCl2 treatment, internal and external aortic diameters were significantly increased in MURC−/− AAAs compared with WT AAAs, which were accompanied by advanced fibrosis in the tunica media of MURC−/− AAAs. The activity of JNK and matrix metalloproteinase (MMP) −2 and −9 were increased in MURC−/− AAAs compared with WT AAAs at 5 days after CaCl2 treatment. At 6 weeks after CaCl2 treatment, MURC−/− AAAs exhibited attenuated JNK activity compared with WT AAAs. There was no difference in the activity of MMP-2 or -9 between saline and CaCl2 treatments. In MURC/Cavin-4-knockdown VSMCs, TNFα-induced activity of JNK and MMP-9 was enhanced compared with control VSMCs. Furthermore, WT, MURC−/−, apolipoprotein E−/− (ApoE−/−), and MURC/Cavin-4 and ApoE double-knockout (MURC−/−ApoE−/−) mice were subjected to angiotensin II (Ang II) infusion. In both ApoE−/− and MURC−/−ApoE−/− mice infused for 4 weeks with Ang II, AAAs were promoted. The internal aortic diameter was significantly increased in Ang II-infused MURC−/−ApoE−/− mice compared with Ang II-infused ApoE−/− mice. In MURC/Cavin-4-knockdown VSMCs, Ang II-induced activity of JNK and MMP-9 was enhanced compared with control VSMCs. Our results suggest that MURC/Cavin-4 in VSMCs modulates AAA progression at the early stage via the activation of JNK and MMP-9. MURC/Cavin-4 is a potential therapeutic target against AAA progression.