Ischemia In Vivo Induces Cardiolipin Oxidation in Rat Kidney Mitochondria

In Vitro Hypoxia/Reoxygenation Induces Mitochondrial Cardiolipin Remodeling in Human Kidney Cells

Renal ischemia/reperfusion is a serious condition that not only causes acute kidney injury, a severe clinical syndrome with high mortality, but is also an inevitable part of kidney transplantation or other kidney surgeries. Alterations of oxygen levels during ischemia/reperfusion, namely hypoxia/reoxygenation, disrupt mitochondrial metabolism and induce structural changes that lead to cell death. A signature mitochondrial phospholipid, cardiolipin, with many vital roles in mitochondrial homeostasis, is one of the key players in hypoxia/reoxygenation-induced mitochondrial damage. In this study, we analyze the effect of hypoxia/reoxygenation on human renal proximal tubule epithelial cell (RPTEC) cardiolipins, as well as their metabolism and mitochondrial functions. RPTEC cells were placed in a hypoxic chamber with a 2% oxygen atmosphere for 24 h to induce hypoxia; then, they were replaced back into regular growth conditions for 24 h of reoxygenation. Surprisingly, after 24 h, hypoxia cardiolipin levels substantially increased and remained higher than control levels after 24 h of reoxygenation. This was explained by significantly elevated levels of cardiolipin synthase and lysocardiolipin acyltransferase 1 (LCLAT1) gene expression and protein levels. Meanwhile, hypoxia/reoxygenation decreased ADP-dependent mitochondrial respiration rates and oxidative phosphorylation capacity and increased reactive oxygen species generation. Our findings suggest that hypoxia/reoxygenation induces cardiolipin remodeling in response to reduced mitochondrial oxidative phosphorylation in a way that protects mitochondrial function.

Cyclohexylalanine-Containing α-Helical Amphipathic Peptide Targets Cardiolipin, Rescuing Mitochondrial Dysfunction in Kidney Injury

Mitochondrial dysfunction is linked to degenerative diseases, resulting from cardiolipin (CL)-induced disruption of cristae structure in the inner mitochondrial membrane (IMM); therefore, preserving cristae and preventing CL remodeling offer effective strategies to maintain mitochondrial function. To identify reactive oxygen species (ROS)-blocking agents against mitochondrial dysfunction, a library of cyclohexylamine-containing cell-penetrating α-helical amphipathic "bundle" peptides were screened. Among these, CMP3013 is selectively bound to abnormal mitochondria, preserving the cristae structure impaired by mitochondria-damaging agents. With a stronger affinity for CL compared with other IMM lipid components, CMP3013 exhibited high selectivity. Consequently, it protected cristae, reduced ROS production, and enhanced adenosine triphosphate (ATP) generation. In mouse models of acute kidney injury, a 1 mg/kg dose of CMP3013 demonstrated remarkable efficacy, highlighting its potential as a therapeutic agent for mitochondrial dysfunction-related disorders. Overall, CMP3013 represents a promising agent for mitigating mitochondrial dysfunction and associated diseases.

Mitochondrial modulation of amplified preconditioning influences of remote ischemia plus erythropoietin against skeletal muscle ischemia/reperfusion injury in rats

AIMS

Skeletal muscle ischemia and reperfusion (S-I/R) injury is relieved by interventions like remote ischemic preconditioning (RIPC). Here, we tested the hypothesis that simultaneous exposure to a minimal dose of erythropoietin (EPO) boosts the protection conferred by RIPC against S-I/R injury and concomitant mitochondrial oxidative and apoptotic defects.

MAIN METHODS

S-I/R injury was induced in rats by 3-h right hindlimb ischemia followed by 3-h of reperfusion, whereas RIPC involved 3 brief consecutive I/R cycles of the contralateral hindlimb.

KEY FINDINGS

S-I/R injury caused (i) rises in serum lactate dehydrogenase and creatine kinase and falls in serum pyruvate, (ii) structural deformities like sarcoplasm vacuolations, segmental necrosis, and inflammatory cells infiltration, and (iii) decreased amplitude and increased duration of electromyography action potentials. These defects were partially ameliorated by RIPC and dose-dependently by EPO (500 or 5000 IU/kg). Further, greater repairs of S-I/R-evoked damages were seen after prior exposure to the combined RIPC/EPO-500 intervention. The latter also caused more effective (i) preservation of mitochondrial number (confocal microscopy assessed Mitotracker red staining) and function (citrate synthase activity), (ii) suppression of mitochondrial DNA damage and indices of oxidative stress and apoptosis (succinate dehydrogenase, myeloperoxidase, cardiolipin, and cytochrome c), (iii) preventing calcium and nitric oxide metabolites (NOx) accumulation and glycogen consumption, and (iv) upregulating EPO receptors (EPO-R) gene expression.

SIGNIFICANCE

dual RIPC/EPO conditioning exceptionally mends structural, functional, and neuronal deficits caused by I/R injury and interrelated mitochondrial oxidative and apoptotic damage. Clinically, the utilization of relatively low EPO doses could minimize the hormone-related adverse effects.

Mn(III) Porphyrin, MnTnBuOE-2-PyP5+, Commonly Known as a Mimic of Superoxide Dismutase Enzyme, Protects Cardiomyocytes from Hypoxia/Reoxygenation Induced Injury via Reducing Oxidative Stress

Myocardial ischemia-reperfusion injury (I/R) causes damage to cardiomyocytes through oxidative stress and apoptosis. We investigated the cardioprotective effects of MnTnBuOE-2-PyP5+ (BMX-001), a superoxide dismutase mimic, in an in vitro model of I/R injury in H9c2 cardiomyocytes. We found that BMX-001 protected against hypoxia/reoxygenation (H/R)-induced oxidative stress, as evident by a significant reduction in intracellular and mitochondrial superoxide levels. BMX-001 pre-treatment also reduced H/R-induced cardiomyocyte apoptosis, as marked by a reduction in TUNEL-positive cells. We further demonstrated that BMX-001 pre-treatment significantly improved mitochondrial function, particularly O2 consumption, in mouse adult cardiomyocytes subjected to H/R. BMX-001 treatment also attenuated cardiolipin peroxidation, 4-hydroxynonenal (4-HNE) level, and 4-HNE adducted proteins following H/R injury. Finally, the pre-treatment with BMX-001 improved cell viability and lactate dehydrogenase (LDH) activity in H9c2 cells following H/R injury. Our findings suggest that BMX-001 has therapeutic potential as a cardioprotective agent against oxidative stress-induced H/R damage in H9c2 cardiomyocytes.