The mitochondrial NO‐synthase/guanylate cyclase/protein kinase G signaling system underpins the dual effects of nitric oxide on mitochondrial respiration and opening of the permeability transition pore

Abstract

Keywords mitochondrial nitric oxide synthase; mitochondrial respiration; nitric oxide; permeability transition pore; protein kinase G CorrespondenceThe available data on the involvement of nitric oxide (NO) and mitochondrial calcium-dependent NO synthase (mtNOS) in the control of mitochondrial respiration and the permeability transition pore (mPTP) are contradictory. We have proposed that the mitochondrial mtNOS/guanylate cyclase/protein kinase G signaling system (mtNOS-SS) is also implicated in the control of respiration and mPTP, providing the interplay between NO and mtNOS-SS, which, in turn, may result in inconsistent effects of NO. Therefore, using rat liver mitochondria, we applied specific inhibitors of the enzymes of this signaling system to evaluate its role in the control of respiration and mPTP opening. Steady-state respiration was supported by pyruvate, glutamate, or succinate in the presence of hexokinase, glucose, and ADP. When applied at low concentrations, L-arginine (to 500 µM) and NO donors (to 50 µM) activated the respiration and increased the threshold concentrations of calcium and D,L-palmitoylcarnitine required for the dissipation of the mitochondrial membrane potential and pore opening. Both effects were eliminated by the inhibitors of NO synthase, guanylate cyclase, and kinase G, which denotes the involvement of mtNOS-SS in the activation of respiration and deceleration of mPTP opening. At high concentrations, L-arginine and NO donors inhibited the respiration and promoted pore opening, indicating that adverse effects induced by an NO excess dominate over the protection provided by mtNOS-SS. Thus, these results demonstrate the opposite impact of NO and mtNOS-SS on the respiration and mPTP control, which can explain the dual effects of NO. 1526The FEBS Journal 287 (2020) 1525-1536 ª 2019 Federation of European Biochemical Societies Nitric oxide, respiration, and mPTP opening V. V. Dynnik et al.

Dissecting Cellular Mechanisms of Long-Chain Acylcarnitines-Driven Cardiotoxicity: Disturbance of Calcium Homeostasis, Activation of Ca2+-Dependent Phospholipases, and Mitochondrial Energetics Collapse

“…Furthermore, vice versa, in the presence 20 µM Ca 2+ average threshold concentration of PC* diminished by 35% (green bars, panel F). Similar synergistic action of Ca 2+ and PC on mPTP was demonstrated earlier on liver mitochondria [ 16 ]. This result may help to explain the discrepancy between the minimal concentration of PC required for Ca 2+ overload in CM (20 µM, Figure 1 C) and critical PC* value inducing mPTP opening in isolated mitochondria preincubated in Ca 2+ -free medium (40 µM, panel B).…”

“…Glutamate plus pyruvate or malate plus α-ketoglutarate were used as substrates. Initial steady state respiration was preset by ADP that, in the presence of glucose and hexokinase in the medium, provided a high rate of respiration close to State 3 respiration rate (80–90% of VO 2max ) [ 16 ]. Current values of the respiration rate may be evaluated by the slope of polarographic tracks ( Figure 5 , blue tracks, [O 2 ]).…”

“…Added FCCP cannot induce further dissipation of ΔΨ m , indicating irreversible effect of PC based on mPTP (panel B). Recently, it was shown that PC excess induced irreversible mitochondrial depolarization, mitochondrial Ca 2+ loss and swelling, collectively indicating mPTP opening [ 16 ].…”

“…However, existing data on the protective effect of CsA are inconsistent. In the experiments on liver mitochondria, CsA prevented swelling and mPTP opening when the concentration of PC by not far exceeded some critical level [ 16 ]. However, in cardiac mitochondria added CsA was ineffective to abrogate mitochondrial Ca 2+ efflux and restore the respiration at PC excess [ 15 ].…”

“…At 10 µM, PC has been shown to induce the dissipation of mitochondrial potential (ΔΨ m ) and mPTP opening [ 10 ]. Recent studies have suggested that PC and Ca 2+ can be used as mPTP inducers in liver mitochondria, and could act synergistically by reinforcing the effects of each other [ 16 ].…”