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Myocardin Attenuates Aortic Aneurysm and Dissection Through the Maintenance of VSMC Homeostasis

ABSTRACT: Myocardin (Myocd) plays an important role in the maintenance and homeostasis of the vasculature. The loss of Myocd results in vascular smooth muscle cell (VSMC) phenotypic transition and thoracic aortic aneurysms and dissections (TAADs) by downregulating VSMC contractile genes. VSMC phenotypic transition plays a key role in the formation of abdominal aortic aneurysms and dissections (AAADs). However, little is known about the role of Myocd in AAAD. The effect of Myocd on AAA formation was proven in an angiotensin II (Ang II)-induced AAD model. Myocd overexpression or knockdown was achieved by the injection of the corresponding adeno-associated virus serotype 9 (AAV9) through the tail vein. The knockdown of Myocd in C57BL/6J mice treated with angiotensin II promoted the formation of AAAD, as demonstrated by increases in the maximal aortic diameter, vascular inflammation and elastin degradation relative to the control group, while Myocd-overexpressing ApoE-/- mice infused with Ang II were less likely to develop AAAD. Mechanistically, Myocd deficiency significantly repressed VSMC marker gene expression. In addition, qPCR results showed that Myocd knockdown promoted the expression of lncRNAs, which showed increased levels in human AAD tissues. Our results indicated the pivotal role of Myocd in protecting against AAAD formation.

ORGANISM(S): Mus musculus

PROVIDER: GSE180990 | GEO | 2024/10/25

REPOSITORIES: GEO

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Project description:The Ca2+/calmodulin-dependent kinase II is expressed in smooth muscle and believed to mediate intracellular calcium handling and calcium-dependent gene transcription. CaMKII is activated by Angiotensin-II. The multifunctional calcium/calmodulin-dependent kinase II (CaMKII) is activated by Angiotensin-II (Ang-II) in vascular smooth muscle cells (VSMC), but its impact on hypertension remains unknown. In our transgenic mice that express the inhibitor peptide CaMKIIN in smooth muscle (TG SM-CaMKIIN), the blood pressure response to chronic Ang-II infusion was significantly reduced as compared to littermate controls. Surprisingly, examination of blood pressure and heart rate under ganglionic blockade revealed a key role for VSMC CaMKII in efferent sympathetic outflow in response to Ang II hypertension. Consistently, the efferent splanchnic nerve activity and plasma phenylephrine concentrations were significantly lower in TG SM-CaMKIIN mice as compared to littermates. Moreover, the aortic depressor nerve activity was reset in hypertensive wild type animals, but not in TG SM-CaMKIIN mice, suggesting that changes in baroreceptor wall activity may be responsible for the blood pressure difference in Ang-II hypertension. The pulse wave velocity, a measure of vascular wall stiffness in vivo, was increased in aortas of hypertensive compared to normotensive WT animals. However, Ang-II infusion did not alter the pulse wave velocity in transgenic mice, suggesting that CaMKII in VSMC controls structural smooth muscle genes. Accordingly, analysis of gene expression changes in aortas from wild type and TG SM-CaMKIIN hypertensive mice demonstrated that CaMKII inhibition mainly altered the expression of muscle contractile proteins. In contrast, TG SM-CaMKIIN aortas were protected from the Ang-II induced upregulation of genes linked to proliferation, suggesting that CaMKII inhibition prevents the Ang-II-induced reprogramming of smooth muscle cell gene expression towards a proliferative phenotype. 5 WT C57Bl/6 and 5 mice that express the Ca2+/calmodulin-dependent kinase II peptide inhibitor CaMKIIN in smooth muscle only (TG SM-CaMKIIN) were infused with 1.25 ug/kg/min Angiotensin-II by osmotic minipump for 14 days. 5 WT and 5 transgenic mice infused with normal saline served as controls. The mice were sacrificed on day 14 and the thoracic aortas isolated. RNA was isolated and pooled for the following groups: WT (wild type), C (TG SM-CaMKIIN), WT-A (WT with Angiotensin-II), C-A (TG SM-CaMKIIN + Angiotensin-II)

Project description:BACKGROUND: Thoracic aortic dissection (TAD) and abdominal aortic aneurysm (AAA) are fatal cardiovascular diseases with a high mortality rate in rupture events, closely related to vascular smooth muscle cell (VSMC) transformation from contractile to synthetic type and extracellular matrix degradation. NFATc3 in macrophages has recently been revealed as an atherosclerosis and foam cell formation negative regulator. However, the role of NFATc3 in aortic aneurysm and dissection (AAD) remains unknown. Therefore, we aimed to investigate the role of VSMC in NFATc3 in developing AAD and establishing NFATc3 as a novel target to treat AAD. METHODS: NFATc3 expression was measured in human and mouse aortic dissection and aneurysm samples. To investigate the role of VSMC-NFATc3 in AAD, we generated VSMC-specific NFATc3 knockout and knockin mice from three different murine AAD models, including proprotein convertase subtilisin/kexin type 9/ AngII (angiotensin II), β-aminopropionitrile (BAPN)/AngII models and BAPN models. The molecular mechanisms underlying NFATc3 function were investigated using RNA-seq analysis, mass spectrometry analysis, gelatin zymography, a luciferase reporter assay ChIP-qPCR, nuclear run-on assay, polyribosome profiling, coimmunoprecipitation, and mammalian 2-hybrid assay. RESULTS: We found that cytoplasmic and nuclear NFATc3 levels are elevated in human and mouse aortic dissection aneurysms. VSMC-specific NFATc3 deletion in mice reduced TAD and AAA progression, whereas VSMC-specific NFATc3 overexpression mice exhibited the opposite phenotype. VSMC-NFATc3 aggravated AAD independently of blood pressure regulation. VSMC-specific NFATc3 deletion reduces extracellular matrix degradation and maintains VSMC contractile phenotype. Mechanistically, nuclear NFATc3 specifically targeted and transcriptionally up-regulated MMP9 and MMP2, promoting extracellular matrix degradation and AAD development. We found that NFATc3 promoted VSMC phenotypic switch by binding to eEF2 and inhibiting its phosphorylation in VSMC cytoplasm, increasing protein synthesis and translational elongation, downregulating VSMC differentiation markers, and eventually exacerbating AAD development. We found that cabamiquine, a novel antimalarial agent that targets eEF2 and inhibits protein synthesis, inhibited AAD development and progression in VSMC-specific NFATc3 overexpression mice. Conclusion: Thus, VSMC-NFATc3 promotes VSMC change from contractile to synthetic type and extracellular matrix degradation, exacerbating AAD development, suggesting that VSMC-NFATc3 is a novel therapeutic target for preventing and treating AAD.

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Myocardin Attenuates Aortic Aneurysm and Dissection Through the Maintenance of VSMC Homeostasis

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