Activation of Ubiquitous Calpains Increases Cardiac Injury in Donation After Circulatory Death Donor Hearts by Degrading Mitofilin

Donation after circulatory death (DCD) donors serve as an alternative source for heart donors for transplantation. However, the DCD process involves unavoidable ischemia-reperfusion injuries, leading to mitochondrial dysfunction and myocardial damage. Activation of calpain-1 and calpain-2 (CPN1/2) exacerbates mitochondrial damage during ischemia-reperfusion. We investigated the role of CPN1/2 activation in mitochondrial and cardiac injury in DCD hearts. In this study, rat hearts were divided into three groups: (1) control beating-heart donor (CBD) hearts, which were procured without in vivo ischemia and subsequently underwent ex vivo perfusion; (2) DCD hearts, which underwent 25 minutes of in vivo ischemia followed by ex vivo perfusion; and (3) DCD hearts treated with a CPN1/2 inhibitor (MDL-28170, 10 μM) during ex vivo perfusion. MDL treatment significantly reduced infarct size in DCD hearts, supporting the notion that CPN1/2 activation exacerbates cardiac injury. Additionally, MDL treatment reduced mitochondrial permeability transition pore (MPTP) opening in DCD hearts and prevented the degradation of mitofilin, a protein that interacts with cyclophilin D to regulate MPTP opening. Notably, the content of cyclophilin D remained unchanged in DCD hearts. Our study suggests that CPN1/2-mediated mitofilin degradation contributes to increased MPTP opening in DCD hearts. Administering a CPN1/2 inhibitor during early reperfusion is a promising strategy to mitigate cardiac injury in DCD hearts by preserving mitofilin and reducing MPTP opening.