Mitofilin Preservation Mitigates Cardiac Injury in Donation-After-Circulatory-Death Hearts

Donation after circulatory death (DCD) involves unavoidable ischemia–reperfusion injury (IRI). Mitochondrial permeability transition pore (MPTP) opening plays a critical role in DCD heart injury. Activation of ubiquitous calpains, including calpain-1 and calpain-2 (CPN1/2), increases MPTP opening in DCD hearts. Mitofilin, a mitochondrial inner membrane protein that regulates cristae morphology, is also involved in MPTP opening during ischemia–reperfusion. However, it remains unclear whether CPN1/2 activation contributes to mitofilin-mediated IRI in DCD hearts. We first incubated a mitofilin peptide with exogenous CPN1 in vitro to investigate the link between CPN1 activation and mitofilin degradation. Next, we tested whether CPN1/2 inhibition reduces cardiac injury in DCD hearts by preserving mitofilin and limiting MPTP opening. Sprague-Dawley (SD) rat hearts were subjected to 25 min of in vivo ischemia followed by ex vivo perfusion with or without the CPN1/2 inhibitor MDL-28170 (10 µM). In vitro incubation with CPN1 led to mitofilin degradation, confirming mitofilin as a CPN1 substrate. CPN1/2 inhibition significantly reduced infarct size compared with untreated DCD hearts, preserved mitofilin expression, and decreased MPTP opening. These findings indicate that CPN1/2 activation promotes MPTP opening in DCD hearts through mitofilin degradation. Timely inhibition of CPN1/2 represents a promising strategy to reduce cardiac injury and improve DCD heart function.