Friday, April 26, 2024
4/26/2024
VSMCs dedifferentiate into a proliferative state upon vessel injury or transdifferentiate into macrophage-like cells (MLCs) during atherosclerosis progression. VSMC phenotypic switching are driven by multiple transcriptional and epigenetic changes that lead to increased proliferation with reduced contractile gene expression and increased matrix production, which is detrimental to atherosclerotic lesions, direct interventional studies that target this process have been lacking. Increased matrix and growth factors alter integrin signaling and leads to aberrant focal adhesion kinase (FAK) activation, which may promote VSMC phenotypic switching. We demonstrated that FAK is inactive and primarily localized in the nuclei of VSMCs of healthy arteries. However, vessel injury promoted FAK activation and cytoplasmic relocalization, which increased cyclin D1 transcription and cell cycling. While we found that inhibition of FAK activity in VSMCs induced nuclear localization of FAK and increased contractile gene transcription, the underlying mechanism by which FAK regulates the contractile genes is not known. We have identified DNA methyltransferase 3A (DNMT3A) and the nucleosome remodeling and deacetylase (NuRD) complex, two key epigenetic repression machineries, as nuclear FAK-interacting partners in VSMCs. FAK inhibition decreased DNMT3A and NuRD component expression, which was associated with decreased DNA methylation and increased active histone marks within contractile gene promoters. Using genetic FAK cytoplasmic (Cyto) restricted VSMCs, we found that nuclear FAK is required for reducing DNMT3A/NuRD and for increasing contractile gene expression. Additionally, ApoE-/-;FAK-Cyto mice showed increased atherosclerosis compared to WT mice, suggesting that active cytoplasmic FAK exacerbates atherosclerosis. Further, FAK showed increased cytoplasmic localization and activity within human atherosclerotic lesions compared to healthy specimens. Importantly, FAK inhibitor reduced advanced atherosclerotic lesions in ApoE-/- mice, which was associated with reduced DNMT3A and NuRD component expression with increased ACTA2+ cells in the fibrous cap. Our hypothesis is that FAK catalytic inhibition forces FAK nuclear localization and promotes VSMC differentiation via reduced expression of epigenetic regulators DNMT3A and NuRD complex. Aim 1 will elucidate the molecular mechanism of nuclear FAK-mediated VSMC phenotypic switching via epigenetic modulation of DNA methylation, chromatin remodeling, and histone modification. Aim 2 will investigate the role of DNMT3A and the NuRD complex in VSMC dedifferentiation upon vascular injury using both DNMT3A and NuRD genetic models. Aim 3 will evaluate the effect of FAK inhibition on blocking VSMC transdifferentiation and promoting plaque stability in early and advanced atherosclerosis. This study will provide new insights into VSMC phenotype switching via FAK-mediated epigenetic control through DNMT3A and NuRD complex stability. The therapeutic potential of FAK inhibitors in alleviating intimal thickening in vascular injury and atherosclerosis will also be assessed.
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