Abstract 886: Mitochondrial Stress Response by Lonp1 in Cardiac Function and Protection

Abstract

LonP1 is a mitochondrial protease that is crucial for maintaining cardiac mitochondrial homeostasis. We recently showed that LonP1 mediates cardioprotection during cardiac ischemia-reperfusion (I/R) by reducing oxidative stress and infarct size. We hypothesize that LonP1 promotes mitochondrial biogenesis during cardiac differentiation and development and protects the heart from oxidative injury by recalibrating bioenergetics. Here, we employ human induced pluripotent stem cells differentiated into cardiomyocytes (iPSC-CMs), rat neonatal ventricular myocytes (rNVMs), and mouse models with cardiac-specific LonP1 overexpression (LonTg) and heterozygous LonP1 knockout ( LONP1 +/- ). In iPSC-CMs, LonP1 is induced 4.8-fold at 39 vs. 12 days after differentiation. During the maturation of murine hearts, LonP1 is increased 4.6-fold at 3 months vs. during 1 day. Upregulation was also observed in rNVMs in which LonP1 is induced 5- fold after 5 days culturing, compared to 0 days. LonP1 induction in rNVMs is accompanied by substantial 2-fold upregulation of mitochondrial transcripts, MT-CYB and MT-COI. However, the levels of another mitochondrial matrix protease ClpP was not altered, suggesting that LonP1 specifically may play an important role during mitochondrial biogenesis and proteostasis in the heart. In vivo, LonTg protected the myocardium against ischemia-reperfusion (I/R) injury by preventing oxidative damage. In LonTg hearts, basal complex I activity was significantly (p<0.05) reduced (Ntg-0.01 ± 0.001 vs. LonTg-0.0078 ± 0.001 mOD/min), as well as during I/R (Ntg-0.0139 ± 0.0005 vs LonTg-0.0102 ± 0.001 mOD/min) (n=3 each). However, no difference was observed in the complex I activity in LONP1 +/+ (0.0118 ± 0.0 mOD/min) and LONP1 +/- (0.0121 ± 0.0 mOD/min) mice (n=3 each). In addition, our preliminary native gel data of LonTg hearts shows a 40% reduction (n=1) in the levels of mitochondrial supercomplexes, compared to NTg hearts (n=4). Further studies are underway to explore the role of LonP1 during differentiation, and in response to mitochondrial cardiac stress. Together, our findings show a novel role of LonP1 in regulating cardiac function during mitochondrial biogenesis and in mitigating cardiac stress-induced injury.