Abstract Body: Background: Mitochondrial dysfunction is a key hallmark contributing to heart disease in the aging population. The mitochondrial chaperonin CLPB is known to regulate protein quality control within the mitochondrial inter-membrane space and plays a critical role in protein refolding and degradation under stress conditions. The study aims to investigate the role of CLPB in regulating age-induced mitochondrial and cardiac dysfunction.
Methods: The study was conducted using an aging mouse model, the senescence-accelerated prone 8 (SAMP8) mouse, and control mice, the senescence-accelerated mouse resistant 1 (SAMR1). Both groups were administered AAV9-cTNT-CLPB (overexpression model) and AAV9-sh-CLPB (knockdown model). Cardiac phenotypes were assessed through echocardiography at 3, 6, and 9 months of age. Mitochondrial respiration in cardiac tissue was evaluated using the Oroboros O2K instrument, while the calcium retention capacity of isolated mitochondria was measured using the spectrofluorometer. Additionally, in vitro studies were conducted on the mouse cardiac cell line (HL-1) with doxorubicin-induced cell senescence. The expression levels of cell senescence marker proteins were analyzed via immunoblotting, and mitochondrial function was assessed by measuring ROS levels, membrane potential, calcium retention capacity (CRC), and oxygen consumption rate (OCR). Results: Our findings indicate that CLPB expression exhibited an age-dependent decline in the hearts of SAMP8 mice and in doxorubicin-treated HL-1 cells. Loss of CLPB protected HL-1 cells from doxorubicin-induced cell senescence and restored mitochondrial function by reducing ROS levels and preserving mitochondrial membrane potential. Similarly, loss of CLPB improved mitochondrial respiration in aging SAMP8 mice and regulated OCR in doxorubicin-treated HL-1 cells. Furthermore, calcium retention capacity was enhanced in doxorubicin-treated CLPB KO HL-1 cells as well as in the hearts of CLPB KO SAMP8 mice compared to SAMP8-GFP mice. Echocardiographic analysis revealed that CLPB KO mice exhibited improved cardiac function, including enhanced ejection fraction and fractional shortening, compared to control mice. Overall, both in vitro and in vivo aging model analyses indicate that loss of CLPB mitigates age-induced mitochondrial and cardiac dysfunction. Conclusion: Our findings highlight the critical role of mitochondrial chaperonin CLPB in the regulation of age-induced mitochondrial and cardiac dysfunction.