SLC31A1 loss depletes mitochondrial copper and promotes cardiac fibrosis

Abstract

Background and aims: Metals serve as co-factors for a host of metalloenzymes involved in mitochondrial metabolic reprogramming. Modifications in metal homeostasis are linked to epigenetic mechanisms. However, the epigenetic mechanisms through which metal affects cardiac fibrosis (CF) remain poorly understood.

Methods: The metal content of mouse heart samples was measured using inductively coupled plasma mass spectrometry. Cardiac fibroblast-specific MeCP2-deficient mice and control mice were treated with isoprenaline/angiotensin II to induce CF. AAV9 carrying POSTN promoter-driven small hairpin RNA targeting MeCP2, YTHDF1, or SLC31A1 and the copper-chelating agent tetrathiomolybdate were administered to investigate their vital roles in CF. Histological and biochemical analyses were performed to determine how YTHDF1/MeCP2 regulated SLC31A1 expression in CF. The reconstitution of SLC31A1 in YTHDF1/MeCP2-deficient cardiac fibroblasts and mouse hearts was performed to study its effect on mitochondrial copper depletion and fibrosis. Human heart tissues from atrial fibrillation patients were used to validate the findings.

Results: Lower copper concentrations are accompanied by SLC31A1 down-regulation and mitochondrial copper depletion in CF. Fibroblast-specific SLC31A1 deficiency enhances mitochondrial copper depletion, augments glycolysis, promotes fibroblast proliferation and triggers CF. SLC31A1 inhibition due to increased MeCP2-recognized methylating CpG islands of SLC31A1 in the promoter region restrains its transcription. Conversely, MeCP2 knockdown rescued SLC31A1 expression, resulting in contradictory effects. MeCP2 up-regulation is associated with elevated m6A mRNA levels. Mechanistically, YTHDF1 recognizes target MeCP2 mRNA and induces its translation. In human heart tissues from atrial fibrillation patients, reduced copper concentrations and SLC31A1 expression, along with elevated levels of YTHDF1 and MeCP2, were observed. These changes were associated with mitochondrial copper depletion, enhanced glycolysis, and CF.

Conclusions: A novel epigenetic mechanism was demonstrated through which copper deficiency increases mitochondrial copper depletion and impairs CF. Findings provide new insights for the development of preventive measures for CF.

Keywords: Atrial fibrillation; Cardiac fibrosis; DNA methylation; Mitochondrial copper depletion; RNA methylation.