scholarly journals Regulation of Kidney Mitochondrial Function by Caloric Restriction

2021 ◽  
Author(s):  
Julian DC Serna ◽  
Andressa G Amaral ◽  
Camille C Caldeira da Silva ◽  
Ana C Bonassa ◽  
Sergio L Menezes ◽  
...  
Keyword(s):  
Caloric Restriction ◽  
Calcium Homeostasis ◽  
Mitochondrial Function ◽  
Calcium Uptake ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Permeability Transition ◽  
Mitochondrial Calcium ◽  
Mitochondrial Permeability ◽  
Uptake Rates

Caloric restriction (CR) prevents obesity, promotes healthy aging, and increases resilience against several pathological stimuli in laboratory rodents. At the mitochondrial level, protection promoted by CR in the brain and liver is related to higher calcium uptake rates and capacities, avoiding Ca2+-induced mitochondrial permeability transition. Dietary restriction has also been shown to increase kidney resistance against damaging stimuli such as ischemia/reperfusion, but if these effects are related to similar mitochondrial adaptations had not yet been uncovered. Here, we characterized changes in mitochondrial function in response to six months of CR in rats, measuring bioenergetic parameters, redox balance and calcium homeostasis. CR promoted an increase in mitochondrial oxygen consumption rates under non-phosphorylating and uncoupled conditions. While CR prevents mitochondrial reactive oxygen species production in many tissues, in kidney we found that mitochondrial H2O2 release was enhanced, although levels of carbonylated proteins and methionine sulfoxide were unchanged. Surprisingly, and opposite to the effects observed in brain and liver, mitochondria from CR animals are more prone to Ca2+-induced mitochondrial permeability transition. CR mitochondria also displayed higher calcium uptake rates, which were not accompanied by changes in calcium efflux rates, nor related to altered inner mitochondrial membrane potentials or the amounts of the mitochondrial calcium uniporter (MCU). Instead, increased mitochondrial calcium uptake rates in CR kidneys correlate with a loss of MICU2, an MCU modulator. Interestingly, MICU2 is also modulated by CR in liver, suggesting it has a broader diet-sensitive regulatory role controlling mitochondrial calcium homeostasis. Together, our results highlight the organ-specific bioenergetic, redox, and ionic transport effects of CR. Specifically, we describe the regulation of the expression of MICU2 and its effects on mitochondrial calcium transport as a novel and interesting aspect of the metabolic responses to dietary interventions.

Abstract MP124: De-palmitoylation of Cysteine 202 of Cyclophilin-D by Calcium is Important for the Activation of the Permeability Transition Pore

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Georgios Amanakis ◽  
Junhui Sun ◽  
Maria Fergusson ◽  
Chengyu Liu ◽  
Jeff D Molkentin ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Cyclophilin D ◽  
Perfused Heart ◽  
Knock Out

Cyclophilin-D (CypD) is a well-known regulator of the mitochondrial permeability transition pore (PTP), the main effector of cardiac ischemia/reperfusion (I/R) injury characterized by oxidative stress and calcium overload. However, the mechanism by which CypD activates PTP is poorly understood. Cysteine 202 of CypD (C202) is highly conserved across species and can undergo redox-sensitive post-translational modifications, such as S-nitrosylation and oxidation. To study the importance of C202, we developed a knock-in mouse model using CRISPR where CypD-C202 was mutated to a serine (C202S). Hearts from these mice are protected against I/R injury. We found C202 to be abundantly S-palmitoylated under baseline conditions while C202 was de-palmitoylated during ischemia in WT hearts. To further investigate the mechanism of de-palmitoylation during ischemia, we considered the increase of matrix calcium, oxidative stress and uncoupling of ATP synthesis from the electron transport chain. We tested the effects of these conditions on the palmitoylation of CypD in isolated cardiac mitochondria. The palmitoylation of CypD was assessed using a resin-assisted capture (Acyl-RAC). We report that oxidative stress (phenylarsenide) and uncoupling (CCCP) had no effect on CypD palmitoylation (p>0.05, n=3 and n=7 respectively). However, calcium overload led to de-palmitoylation of CypD to the level observed at the end ischemia (1±0.10 vs 0.63±0.09, p=0.012, n=9). To further test the hypothesis that calcium regulates S-palmitoylation of CypD we measured S-palmitoylation of CypD in non-perfused heart lysates from global germline mitochondrial calcium uniporter knock-out mice (MCU-KO), which have reduced mitochondrial calcium and we found an increase in S-palmitoylation of CypD (WT 1±0.04 vs MCU-KO 1.603±0.11, p<0.001, n=6). The data are consistent with the hypothesis that C202 is important for the CypD mediated activation of PTP. Ischemia leads to increased matrix calcium which in turn promotes the de-palmitoylation of CypD on C202. The now free C202 can further be oxidized during reperfusion leading to the activation of PTP. Thus, S-palmitoylation and oxidation of CypD-C202 possibly target CypD to the PTP, making them potent regulators of cardiac I/R injury.

Silencing of cardiac mitochondrial NHE1 prevents mitochondrial permeability transition pore opening

2011 ◽  
Vol 300 (4) ◽  
pp. H1237-H1251 ◽  
Author(s):  
María C. Villa-Abrille ◽  
Eugenio Cingolani ◽  
Horacio E. Cingolani ◽  
Bernardo V. Alvarez
Keyword(s):  
Mitochondrial Permeability Transition Pore ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Mitochondrial Swelling ◽  
Heart Mitochondria ◽  
Rat Cardiomyocytes ◽  
Mitochondrial Permeability ◽  
Mptp Opening

Inhibition of Na+/H+ exchanger 1 (NHE1) reduces cardiac ischemia-reperfusion (I/R) injury and also cardiac hypertrophy and failure. Although the mechanisms underlying these NHE1-mediated effects suggest delay of mitochondrial permeability transition pore (MPTP) opening, and reduction of mitochondrial-derived superoxide production, the possibility of NHE1 blockade targeting mitochondria has been incompletely explored. A short-hairpin RNA sequence mediating specific knock down of NHE1 expression was incorporated into a lentiviral vector (shRNA-NHE1) and transduced in the rat myocardium. NHE1 expression of mitochondrial lysates revealed that shRNA-NHE1 transductions reduced mitochondrial NHE1 (mNHE1) by ∼60%, supporting the expression of NHE1 in mitochondria membranes. Electron microscopy studies corroborate the presence of NHE1 in heart mitochondria. Immunostaining of rat cardiomyocytes also suggests colocalization of NHE1 with the mitochondrial marker cytochrome c oxidase. To examine the functional role of mNHE1, mitochondrial suspensions were exposed to increasing concentrations of CaCl2 to induce MPTP opening and consequently mitochondrial swelling. shRNA-NHE1 transduction reduced CaCl2-induced mitochondrial swelling by 64 ± 4%. Whereas the NHE1 inhibitor HOE-642 (10 μM) decreased mitochondrial Ca2+-induced swelling in rats transduced with nonsilencing RNAi (37 ± 6%), no additional HOE-642 effects were detected in mitochondria from rats transduced with shRNA-NHE1. We have characterized the expression and function of NHE1 in rat heart mitochondria. Because mitochondria from rats injected with shRNA-NHE1 present a high threshold for MPTP formation, the beneficial effects of NHE1 inhibition in I/R resulting from mitochondrial targeting should be considered.

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