Br J Pharmacol. 2025 Nov 14. doi: 10.1111/bph.70249. Online ahead of print.
ABSTRACT
BACKGROUND AND PURPOSE: Communication between various cardiac cells by paracrine factors and exosomes has an important role in myocardial ischaemia/reperfusion (I/R) injury. It remains unclear whether exosomes derived from healthy cardiac fibroblasts affect I/R injury and, if so, what are the underlying mechanisms?
EXPERIMENTAL APPROACH: Cardiac fibroblasts were isolated from neonatal rats, adult rats and adult rats subjected to I/R. Their exosomes were designated as follows: neonatal cardiac fibroblasts (N-Exo), adult rat cardiac fibroblasts (A-Exo) and cardiac fibroblasts in a remote non-ischaemic area (R-Exo). Apoptosis of cardiomyocytes and the role of a cluster of microRNAs from exosomes in I/R injury were investigated.
KEY RESULTS: N-Exo, A-Exo and R-Exo were taken up by ischaemic cardiomyocytes through clathrin heavy chain (Cltc)-mediated endocytosis, enhancing cardiomyocyte apoptosis and increasing myocardial infarct size in rats and mice. Inhibiting Cltc-mediated endocytosis with chlorpromazine reduced the pro-apoptotic effects of N-Exo in neonatal rat cardiomyocytes under anoxia/reoxygenation. A functional cluster of miRNAs (miR-9a-5p, miR-92b-3p, miR-181a-5p, miR-494-3p and miR-708-5p) from exosomes was identified and promoted cardiomyocyte apoptosis via a common gene, Rap1b. R-Exo downregulated cardiac Rap1b and Bcl2 in I/R rats. Mimics of these miRNAs reduced luciferase activity of the Rap1b gene and were blocked by site-directed mutagenesis of the Rap1b gene at miRNAs binding sites. Co-immunoprecipitation demonstrated that Rap1b protein bound to ERK1/2 and Cltc.
CONCLUSIONS AND IMPLICATIONS: Exosomes from non-ischaemic fibroblasts worsen I/R injury by promoting apoptosis of ischaemic cardiomyocytes through a cluster of miRNAs targeting the Rap1b/ERK1/2 pathway, highlighting Rap1b restoration as a potential therapeutic strategy.
PMID:41236828 | DOI:10.1111/bph.70249
