Silencing the fibronectin gene (FN1) improves NaCl-induced cardiac fibrosis via ferritinophagy-mediated ferroptosis in a nuclear receptor coactivator 4 (NCOA4)-dependent manner.

Background and purpose: High-salt diet (HSD) induces heart damage, including cardiac fibrosis, independent of blood pressure. Exploring the underlying molecular mechanisms is of significant clinical value.

Experimental approach: Male rats or neonatal rat cardiac fibroblasts (NRCFs) were treated with HSD or sodium chloride (NaCl) to induce cardiac fibrosis in vivo and in vitro, respectively. Exosome high-throughput sequencing was performed from exosomes isolated from culture supernatants of NRCFs treated with/without NaCl.

Key results: First, HSD and NaCl induced myocardial fibrosis and ferroptosis in vivo and in vitro, respectively. The results of exosome high-throughput sequencing, along with validation experiments, showed that NaCl increased fibronectin gene (Fn1) expression via post-transcriptional regulation in NRCFs. Cardiac-specific silencing of Fn1attenuated HSD-induced cardiac fibrosis and ferroptosis, while Fn1 overexpression counteracted these effects. Also, GW4869-mediated exosome depletion reduced extracellular FN-1 but did not rescue NaCl-induced cardiac fibrosis. Moreover, silencing Fn1 inhibited NaCl-induced increase of nuclear receptor coactivator 4 (NCOA4). Fn1 loss exacerbated NCOA4 degradation. Next, inhibition of NOCA4-mediated ferritinophagy improved HSD-induced cardiac fibrosis, whereas NCOA4 overexpression hampered the antifibrotic effects of silencing Fn1in NaCl-induced NRCFs. Besides, autophagy inhibitor 3-MA ameliorated NaCl-induced cardiac fibrosis and ferroptosis, indicating that autophagy was essential for NCOA4-mediated ferroptosis.

Conclusion and implications: Overall, our finding identified that silencing Fn1 possessed beneficial effects against NaCl-induced cardiac fibrosis through downregulating the ferroptosis of NRCFs, which was attributed to the inhibition of NOCA4-mediated ferritinophagy.