Hspa1b attenuates hypoxia/reoxygenation-induced cardiomyocyte injury through dual suppression of P53-driven apoptotic...

While the cardioprotective role of heat shock proteins (HSPs) in cardiovascular diseases is well established, the isoform-specific functions of HSP70 members in ischemia-reperfusion (I/R) injury remain unclear. This study investigates the role of Hspa1b, a stress-inducible HSP70 isoform, in cardiac I/R injury and elucidates its underlying mechanisms. In vivo, male C57BL/6 J mice were subjected to myocardial I/R surgery. In vitro, H9C2 cardiomyocytes were transfected with siRNA targeting Hspa1b or p53 and subjected to a hypoxia/reoxygenation (H/R) model. Cellular injury was quantified via lactate dehydrogenase (LDH) release, while viability was assessed using the CCK-8 assay. Apoptotic (Bax, Bcl2, and cleaved Caspase3) and ferroptotic (GPX4, XCT/SLC7A11) markers were analyzed by Western blotting. We found that I/R injury in mouse hearts upregulated Hspa1b and p53 protein levels, accompanied by increased infarct size and elevated plasma CK-MB levels. Similarly, H/R treatment in H9C2 cells increased Hspa1b and p53, which coincided with increased apoptosis and ferroptosis. Knockdown of Hspa1b exacerbated H/R-induced cellular injury, as evidenced by further increases in LDH release and reductions in cell viability, and amplified the changes in apoptotic and ferroptotic markers. Crucially, co-silencing Hspa1b and p53 partially rescued these effects, restoring cell viability and suppressing death pathways. Hspa1b confers cardioprotection against H/R injury by suppressing p53-mediated apoptosis and ferroptosis. These findings identify Hspa1b as a key protective regulator that mitigates I/R injury through dual regulation of cell death pathways.