Interaction of Agaric Acid with the Adenine Nucleotide Translocase Induces Mitochondrial Oxidative Stress.

Mitochondrial permeability transition is characterized by the opening of a transmembranal pore that switches membrane permeability from specific to nonspecific. This structure allows the free traffic of ions, metabolites, and water across the mitochondrial inner membrane. The opening of the permeability transition pore is triggered by oxidative stress along with calcium overload. In this work, we explored if oxidative stress is a consequence, rather than an effector of the pore opening, by evaluating the interaction of agaric acid with the adenine nucleotide translocase, a structural component of the permeability transition pore. We found that agaric acid induces transition pore opening, increases the generation of oxygen-derived reactive species, augments the oxidation of unsaturated fatty acids in the membrane, and promotes the detachment of cytochrome c from the inner membrane. The effect of agaric acid was inhibited by the antioxidant tamoxifen in association with decreased binding of the thiol reagent eosin-3 maleimide to the adenine nucleotide translocase. We conclude that agaric acid promotes the opening of the pore, increasing ROS production that exerts oxidative modification of critical thiols in the adenine nucleotide translocase.

Redox signaling in ischemic postconditioning protection involves PKCε and Erk1/2 pathways and converges indirectly in Nrf2 activation.

Ischemic-postconditioning (iPostC) exerts cardioprotection by preserving redox homeostasis in the reperfused heart. This protective effect has been associated with the activation of endogenous antioxidant response driven by transcription factor Nrf2 and with the activation of 'reperfusion injury salvage kinases' (RISK) as PI3K, PKC and Erk1/2. Redox homeostasis is essential for normal cell physiology since reactive oxygen species (ROS) are crucial for processes that involve protein signaling. Thus, it has become clear that not only the perturbation of redox balance to oxidative state is deleterious but also towards a reductive state contributing to pathogenesis of diseases. However, there is still a scarce knowledge about the role of ROS in the cardioprotective signals mediated by RISK in postconditioned hearts. Therefore, we studied the role of ROS as initiator of RISK signaling molecules in iPostC-conferred cardioprotection. With the aim to study the relationship between redox-dependent RISK activation and the downstream activation of the transcription factor Nrf2, we evaluated the effect of redox signaling disruption by the effect of ascorbic acid in iPostC hearts. Our results showed that PKCε and Erk1/2 activation is redox-dependent and that concurs downstream with Nrf2 deficient activation. Besides, using inhibitors we found that neither PI3K nor Erk1/2 are directly related with Nrf2 activation, indicating that these kinases have other targets. We conclude that redox signaling participates in cardioprotection triggered by iPostC through the action of kinase-dependent and -independent mechanisms and concurred with the downstream regulation of Nrf2-mediated antioxidant response to prolonged redox balance during long reperfusion.

On the oxidative damage by cadmium to kidney mitochondrial functions.

In the kidney, the accumulation of heavy metals such as Cd2+ produces mitochondrial dysfunctions, i.e., uncoupling of the oxidative phosphorylation, inhibition of the electron transport through the respiratory chain, and collapse of the transmembrane electrical gradient. This derangement may be due to the fact that Cd2+ induces the transition of membrane permeability from selective to nonselective via the opening of a transmembrane pore. In fact, Cd2+ produces this injury through the stimulation of oxygen-derived radical generation, inducing oxidative stress. Several molecules have been used to avoid or even reverse Cd2+-induced mitochondrial injury, for instance, cyclosporin A, resveratrol, dithiocarbamates, and even EDTA. The aim of this study was to explore the possibility that the antioxidant tamoxifen could protect mitochondria from the deleterious effects of Cd2+. Our results indicate that the addition of 1 µmol/L Cd2+ to mitochondria collapsed the transmembrane electrical gradient, induced the release of cytochrome c, and increased both the generation of H2O2 and the oxidative damage to mitochondrial DNA (among other measured parameters). Of interest, these mitochondrial dysfunctions were ameliorated after the addition of tamoxifen.

Cytidine-5'-Diphosphocholine Protects the Liver From Ischemia/Reperfusion Injury Preserving Mitochondrial Function and Reducing Oxidative Stress.

Cytidine-5'-diphosphocholine (CDP-choline) participates as an intermediary in the synthesis of phosphatidylcholine, an essential component of cellular membranes. Citicoline treatment has shown beneficial effects in cerebral ischemia, but its potential to diminish reperfusion damage in liver has not been explored. In this work, we evaluated the hepatoprotective effect of citicoline and its possible association with inflammatory/oxidative stress and mitochondrial function because they are the main cellular features of reperfusion damage. Ischemia/reperfusion (I/R) in rat livers was performed with the Pringle's maneuver, clamping the 3 elements of the pedicle (hepatic artery, portal vein, and biliary tract) for 30 minutes and then removing the clamp to allow hepatic reperfusion for 60 minutes. The I/R + citicoline group received the compound before I/R. Liver injury was evaluated by measuring aspartate aminotransferase and alanine aminotransferase as well as lactic acid levels in serum; proinflammatory cytokines, proresolving lipid mediators, and nuclear factor kappa B content were determined as indicators of the inflammatory response. Antioxidant effects were evaluated by measuring markers of oxidative stress and antioxidant molecules. Oxygen consumption and the activities of the respiratory chain were used to monitor mitochondrial function. CDP-choline reduced aspartate aminotransferase (AST), alanine aminotransferase (ALT), as well as lactic acid levels in blood samples from reperfused rats. Diminution in tumor necrosis factor alpha (TNF-α) and increase in the proresolving lipid mediator resolvin D1 were also observed in the I/R+citicoline group, in comparison with the I/R group. Oxidative/nitroxidative stress in hepatic mitochondria concurred with deregulation of oxidative phosphorylation, which was associated with the loss of complex III and complex IV activities. In conclusion, CDP-choline attenuates liver damage caused by ischemia and reperfusion by reducing oxidative stress and maintaining mitochondrial function. Liver Transplantation XX XX-XX 2018 AASLD.