ALKBH5 induces fibroblast-to-myofibroblast transformation during hypoxia to protect against cardiac rupture after myocardial infarction

Sep 9, 2023Journal of advanced research

ALKBH5 helps transform heart support cells during low oxygen to protect the heart after a heart attack

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Abstract

Global ALKBH5 knockin reduced infarct size and improved cardiac function after myocardial infarction.

ALKBH5 expression significantly changed during the early stages post-myocardial infarction and in hypoxic fibroblasts.
Mice lacking ALKBH5 showed low survival rates, poor collagen repair, and cardiac rupture.
Loss of ALKBH5 in both in vivo and in vitro settings led to impaired fibroblast activation and reduced collagen deposition.
Hypoxia increased ALKBH5 expression in myofibroblasts through HIF-1α-dependent regulation, while TGF-β1 and Ang II did not.
ALKBH5's role includes promoting the stability of ErbB4 mRNA and degrading ST14 mRNA through m6A demethylation.

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INTRODUCTION: N6-methyladenosine (m6A) methylation produces a marked effect on cardiovascular diseases. The m6A demethylase AlkB homolog 5 (ALKBH5), as an m6A "eraser", is responsible for decreased m6A modification. However, its role in cardiac fibroblasts during the post-myocardial infarction (MI) healing process remains elusive.

OBJECTIVES: To investigate the effect of ALKBH5 in cardiac fibroblasts during infarct repair.

METHODS: MI was mimicked by permanent left anterior descending artery ligation in global ALKBH5-knockout, ALKBH5-knockin, and fibroblast-specific ALKBH5-knockout mice to study the function of ALKBH5 during post-MI collagen repair. Methylated RNA immunoprecipitation sequencing was performed to explore potential ALKBH5 targets.

RESULTS: Dramatic alterations in ALKBH5 expression were observed during the early stages post-MI and in hypoxic fibroblasts. Global ALKBH5 knockin reduced infarct size and ameliorated cardiac function after MI. The global and fibroblast-specific ALKBH5-knockout mice both exhibited low survival rates along with poor collagen repair, impaired cardiac function, and cardiac rupture. Both in vivo and in vitro ALKBH5 loss resulted in impaired fibroblast activation and decreased collagen deposition. Additionally, hypoxia, but not TGF-β1 or Ang II, upregulated ALKBH5 expression in myofibroblasts by HIF-1α-dependent transcriptional regulation. Mechanistically, ALKBH5 promoted the stability of ErbB4 mRNA and the degradation of ST14 mRNA via m6A demethylation. Fibroblast-specific ErbB4 overexpression ameliorated the impaired fibroblast-to-myofibroblast transformation and poor post-MI repair due to ALKBH5 knockout.

CONCLUSION: Fibroblast ALKBH5 positively regulates post-MI healing by stabilization of ErbB4 mRNA in an m6A-dependent manner. ALKBH5/ErbB4 might be potential therapeutic targets for post-MI cardiac rupture.

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ALKBH5 induces fibroblast-to-myofibroblast transformation during hypoxia to protect against cardiac rupture after myocardial infarction

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