Sundararajan Venkatesh1, Min Li2, Toshiro Saito3, Mingming Tong3, Eman Rashed2, Satvik Mareedu2, Peiyong Zhai3, Clea Bárcena4, Carlos López-Otín4, Ghassan Yehia5, Junichi Sadoshima3, Carolyn K Suzuki6. 1. Department of Microbiology, Biochemistry & Molecular Genetics, New Jersey Medical School- Rutgers, The State University of New Jersey, Newark, NJ, USA. Electronic address: sundarve@njms.rutgers.edu. 2. Department of Microbiology, Biochemistry & Molecular Genetics, New Jersey Medical School- Rutgers, The State University of New Jersey, Newark, NJ, USA. 3. Department of Cell Biology & Molecular Medicine, New Jersey Medical School- Rutgers, The State University of New Jersey, Newark, NJ, USA. 4. Dpto. de Bioquímica y Biología Molecular, Instituto Universitario de Oncología (IUOPA), Universidad de Oviedo, Oviedo, Spain. 5. Genome Editing Core Facility, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA. 6. Department of Microbiology, Biochemistry & Molecular Genetics, New Jersey Medical School- Rutgers, The State University of New Jersey, Newark, NJ, USA. Electronic address: suzukick@njms.rutgers.edu.
Abstract
RATIONALE: LonP1 is an essential mitochondrial protease, which is crucial for maintaining mitochondrial proteostasis and mitigating cell stress. However, the importance of LonP1 during cardiac stress is largely unknown. OBJECTIVE: To determine the functions of LonP1 during ischemia/reperfusion (I/R) injury in vivo, and hypoxia-reoxygenation (H/R) stress in vitro. METHODS AND RESULTS: LonP1 was induced 2-fold in wild-type mice during cardiac ischemic preconditioning (IPC), which protected the heart against ischemia-reperfusion (I/R) injury. In contrast, haploinsufficiency of LonP1 (LONP1+/-) abrogated IPC-mediated cardioprotection. Furthermore, LONP1+/- mice showed significantly increased infarct size after I/R injury, whereas mice with 3-4 fold cardiac-specific overexpression of LonP1 (LonTg) had substantially smaller infarct size and reduced apoptosis compared to wild-type controls. To investigate the mechanisms underlying cardioprotection, LonTg mice were subjected to ischemia (45 min) followed by short intervals of reperfusion (10, 30, 120 min). During early reperfusion, the left ventricles of LonTg mice showed substantially reduced oxidative protein damage, maintained mitochondrial redox homeostasis, and showed a marked downregulation of both Complex I protein level and activity in contrast to NTg mice. Conversely, when LonP1 was knocked down in isolated neonatal rat ventricular myocytes (NRVMs), an up-regulation of Complex I subunits and electron transport chain (ETC) activities was observed, which was associated with increased superoxide production and reduced respiratory efficiency. The knockdown of LonP1 in NRVMs caused a striking dysmorphology of the mitochondrial inner membrane, mitochondrial hyperpolarization and increased hypoxia-reoxygenation (H/R)-activated apoptosis. Whereas, LonP1 overexpression blocked H/R-induced cell death. CONCLUSIONS: LonP1 is an endogenous mediator of cardioprotection. Our findings show that upregulation of LonP1 mitigates cardiac injury by preventing oxidative damage of proteins and lipids, preserving mitochondrial redox balance and reprogramming bioenergetics by reducing Complex I content and activity. Mechanisms that promote the upregulation of LonP1 could be beneficial in protecting the myocardium from cardiac stress and limiting I/R injury.
RATIONALE: LonP1 is an essential mitochondrial protease, which is crucial for maintaining mitochondrial proteostasis and mitigating cell stress. However, the importance of LonP1 during cardiac stress is largely unknown. OBJECTIVE: To determine the functions of LonP1 during ischemia/reperfusion (I/R) injury in vivo, and hypoxia-reoxygenation (H/R) stress in vitro. METHODS AND RESULTS:LonP1 was induced 2-fold in wild-type mice during cardiac ischemic preconditioning (IPC), which protected the heart against ischemia-reperfusion (I/R) injury. In contrast, haploinsufficiency of LonP1 (LONP1+/-) abrogated IPC-mediated cardioprotection. Furthermore, LONP1+/- mice showed significantly increased infarct size after I/R injury, whereas mice with 3-4 fold cardiac-specific overexpression of LonP1 (LonTg) had substantially smaller infarct size and reduced apoptosis compared to wild-type controls. To investigate the mechanisms underlying cardioprotection, LonTgmice were subjected to ischemia (45 min) followed by short intervals of reperfusion (10, 30, 120 min). During early reperfusion, the left ventricles of LonTgmice showed substantially reduced oxidative protein damage, maintained mitochondrial redox homeostasis, and showed a marked downregulation of both Complex I protein level and activity in contrast to NTgmice. Conversely, when LonP1 was knocked down in isolated neonatal rat ventricular myocytes (NRVMs), an up-regulation of Complex I subunits and electron transport chain (ETC) activities was observed, which was associated with increased superoxide production and reduced respiratory efficiency. The knockdown of LonP1 in NRVMs caused a striking dysmorphology of the mitochondrial inner membrane, mitochondrial hyperpolarization and increased hypoxia-reoxygenation (H/R)-activated apoptosis. Whereas, LonP1 overexpression blocked H/R-induced cell death. CONCLUSIONS:LonP1 is an endogenous mediator of cardioprotection. Our findings show that upregulation of LonP1 mitigates cardiac injury by preventing oxidative damage of proteins and lipids, preserving mitochondrial redox balance and reprogramming bioenergetics by reducing Complex I content and activity. Mechanisms that promote the upregulation of LonP1 could be beneficial in protecting the myocardium from cardiac stress and limiting I/R injury.
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