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Smooth muscle-specific HuR knockout induces defective autophagy and atherosclerosis.

ABSTRACT: Human antigen R (HuR) is a widespread RNA-binding protein involved in homeostatic regulation and pathological processes in many diseases. Atherosclerosis is the leading cause of cardiovascular disease and acute cardiovascular events. However, the role of HuR in atherosclerosis remains unknown. In this study, mice with smooth muscle-specific HuR knockout (HuR^SMKO) were generated to investigate the role of HuR in atherosclerosis. HuR expression was reduced in atherosclerotic plaques. As compared with controls, HuR^SMKO mice showed increased plaque burden in the atherosclerotic model. Mechanically, HuR could bind to the mRNAs of adenosine 5'-monophosphate-activated protein kinase (AMPK) α1 and AMPKα2, thus increasing their stability and translation. HuR deficiency reduced p-AMPK and LC3II levels and increased p62 level, thereby resulting in defective autophagy. Finally, pharmacological AMPK activation induced autophagy and suppressed atherosclerosis in HuR^SMKO mice. Our findings suggest that smooth muscle HuR has a protective effect against atherosclerosis by increasing AMPK-mediated autophagy.

SUBMITTER: Liu S

PROVIDER: S-EPMC8035143 | biostudies-literature | 2021 Apr

REPOSITORIES: biostudies-literature

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Smooth muscle-specific HuR knockout induces defective autophagy and atherosclerosis.

Liu Shanshan S Jiang Xiuxin X Cui Xiuru X Wang Jingjing J Liu Shangming S Li Hongxuan H Yang Jianmin J Zhang Cheng C Zhang Wencheng W

Cell death & disease 20210409 4

Human antigen R (HuR) is a widespread RNA-binding protein involved in homeostatic regulation and pathological processes in many diseases. Atherosclerosis is the leading cause of cardiovascular disease and acute cardiovascular events. However, the role of HuR in atherosclerosis remains unknown. In this study, mice with smooth muscle-specific HuR knockout (HuR<sup>SMKO</sup>) were generated to investigate the role of HuR in atherosclerosis. HuR expression was reduced in atherosclerotic plaques. As ...[more]

PMID: 33837179

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Project description:BACKGROUND:Atherosclerotic plaques demonstrate extensive accumulation of oxidative DNA damage, predominantly as 8-oxoguanine (8oxoG) lesions. 8oxoG is repaired by base excision repair enzymes; however, the mechanisms regulating 8oxoG accumulation in vascular smooth muscle cells (VSMCs) and its effects on their function and in atherosclerosis are unknown. METHODS:We studied levels of 8oxoG and its regulatory enzymes in human atherosclerosis, the mechanisms regulating 8oxoG repair and the base excision repair enzyme 8oxoG DNA glycosylase I (OGG1) in VSMCs in vitro, and the effects of reducing 8oxoG in VSMCs in atherosclerosis in ApoE-/- mice. RESULTS:Human plaque VSMCs showed defective nuclear 8oxoG repair, associated with reduced acetylation of OGG1. OGG1 was a key regulatory enzyme of 8oxoG repair in VSMCs, and its acetylation was crucial to its repair function through regulation of protein stability and expression. p300 and sirtuin 1 were identified as the OGG1 acetyltransferase and deacetylase regulators, respectively, and both proteins interacted with OGG1 and regulated OGG1 acetylation at endogenous levels. However, p300 levels were decreased in human plaque VSMCs and in response to oxidative stress, suggesting that reactive oxygen species-induced regulation of OGG1 acetylation could be caused by reactive oxygen species-induced decrease in p300 expression. We generated mice that express VSMC-restricted OGG1 or an acetylation defective version (SM22?-OGG1 and SM22?-OGG1K-R mice) and crossed them with ApoE-/- mice. We also studied ApoE-/- mice deficient in OGG1 (OGG1-/-). OGG1-/- mice showed increased 8oxoG in vivo and increased atherosclerosis, whereas mice expressing VSMC-specific OGG1 but not the acetylation mutant OGG1K-R showed markedly reduced intracellular 8oxoG and reduced atherosclerosis. VSMC OGG1 reduced telomere 8oxoG accumulation, DNA strand breaks, cell death and senescence after oxidant stress, and activation of proinflammatory pathways. CONCLUSIONS:We identify defective 8oxoG base excision repair in human atherosclerotic plaque VSMCs, OGG1 as a major 8oxoG repair enzyme in VSMCs, and p300/sirtuin 1 as major regulators of OGG1 through acetylation/deacetylation. Reducing oxidative damage by rescuing OGG1 activity reduces plaque development, indicating the detrimental effects of 8oxoG on VSMC function.

Project description:AimsVascular smooth muscle cells (SMCs) and their derivatives are key contributors to the development of atherosclerosis. However, studying changes in SMC gene expression in heterogeneous vascular tissues is challenging due to the technical limitations and high cost associated with current approaches. In this paper, we apply translating ribosome affinity purification sequencing to profile SMC-specific gene expression directly from tissue.Methods and resultsTo facilitate SMC-specific translatome analysis, we generated SMCTRAP mice, a transgenic mouse line expressing enhanced green fluorescent protein (EGFP)-tagged ribosomal protein L10a (EGFP-L10a) under the control of the SMC-specific αSMA promoter. These mice were further crossed with the atherosclerosis model Ldlr-/-, ApoB100/100 to generate SMCTRAP-AS mice and used to profile atherosclerosis-associated SMCs in thoracic aorta samples of 15-month-old SMCTRAP and SMCTRAP-AS mice. Our analysis of SMCTRAP-AS mice showed that EGFP-L10a expression was localized to SMCs in various tissues, including the aortic wall and plaque. The TRAP fraction demonstrated high enrichment of known SMC-specific genes, confirming the specificity of our approach. We identified several genes, including Cemip, Lum, Mfge8, Spp1, and Serpina3, which are known to be involved in atherosclerosis-induced gene expression. Moreover, we identified several novel genes not previously linked to SMCs in atherosclerosis, such as Anxa4, Cd276, inter-alpha-trypsin inhibitor-4 (Itih4), Myof, Pcdh11x, Rab31, Serpinb6b, Slc35e4, Slc8a3, and Spink5. Among them, we confirmed the SMC-specific expression of Itih4 in atherosclerotic lesions using immunofluorescence staining of mouse aortic roots and spatial transcriptomics of human carotid arteries. Furthermore, our more detailed analysis of Itih4 showed its link to coronary artery disease through the colocalization of genome-wide association studies, splice quantitative trait loci (QTL), and protein QTL signals.ConclusionWe generated a SMC-specific TRAP mouse line to study atherosclerosis and identified Itih4 as a novel SMC-expressed gene in atherosclerotic plaques, warranting further investigation of its putative function in extracellular matrix stability and genetic evidence of causality.

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Smooth muscle-specific HuR knockout induces defective autophagy and atherosclerosis.

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Smooth muscle-specific HuR knockout induces defective autophagy and atherosclerosis.

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