Effect of potential-dependent potassium uptake on production of reactive oxygen species in rat brain mitochondria

Abstract

The effect of potential-dependent potassium uptake on reactive oxygen species (ROS) generation in mitochondria of rat brain was studied. It was found that the effect of K+ uptake on ROS production in the brain mitochondria under steady-state conditions (state 4) was determined by potassium-dependent changes in the membrane potential of the mitochondria (ΔΨm). At K+ concentrations within the range of 0-120 mM, an increase in the initial rate of K(+)-uptake into the matrix resulted in a decrease in the steady-state rate of ROS generation due to the K(+)-induced depolarization of the mitochondrial membrane. The selective blockage of the ATP-dependent potassium channel (K(ATP)(+)-channel) by glibenclamide and 5-hydroxydecanoate resulted in an increase in ROS production due to the membrane repolarization caused by partial inhibition of the potential-dependent K+ uptake. The ATP-dependent transport of K+ was shown to be ~40% of the potential-dependent K+ uptake in the brain mitochondria. Based on the findings of the experiments, the potential-dependent transport of K+ was concluded to be a physiologically important regulator of ROS generation in the brain mitochondria and that the functional activity of the native K(ATP)(+)-channel in these organelles under physiological conditions can be an effective tool for preventing ROS overproduction in brain neurons.

Direct and Off-Target Effects of ATP-Sensitive Potassium Channels Opener Diazoxide

“…Using indirect methods (polarography and light absorbance to monitor the oxygen consumption and mitochondrial volume changes), we have shown full activation of native liver mK ATP channel elicited by ≤500 nM of DZ [55]. Likewise, with the same methods we observed that channel blockage by glibenclamide and 5-HD did not require the presence of Mg·ATP in isolated liver and brain mitochondria [55,56].…”

“…Thus we obtained a reliable appraisal of the share of mK ATP channel in potassium transport and mitochondrial uncoupling by DZ in liver mitochondria [55]. Using DZ as pharmacological tool, we also established the share of mK ATP channel in membrane depolarization and suppression of potential-dependent ROS production in brain mitochondria, which was confirmed independently by using K ATP channel blockers, glibenclamide and 5-HD [56].…”

“…Because mitochondrial membrane potential and the uncoupling of the respiratory chain (assessed as RCR ratio) were both dependent on the state 4 oxygen consumption, this allowed us to estimate the share of mK ATP channel in bioenergetic effects of DZ and total potassium transport regardless of the presence of ATP-insensitive component [55,56]. Thus we obtained a reliable appraisal of the share of mK ATP channel in potassium transport and mitochondrial uncoupling by DZ in liver mitochondria [55].…”

“…Besides, increase in oxygen consumption and the waste of free energy generated by the respiratory chain on potassium cycle diminishes a redox-potential of the sites being a primary source of ROS in the respiratory chain within the Complexes I, II and III [17,71], thereby diminishing ROS production. While the effects of mK ATP channels opening on ROS production known thus far were rather ambiguous, in several works including our own, decrease of ROS production ensuing of mK ATP opening and mild mitochondrial uncoupling was observed [8,17,20,56].…”

Toxicity assessment of nanoparticles in various systems and organs

“…Peripheral electrical stimulus is one common method used in neurophysiology study, in which caudal sensory nerve action potentials [92] (caudal SNAPs) are recorded centrally from the tail. As the high oxidative metabolism in the brain, the function of brain mitochondria, which is easily isolated by differential centrifugation, is a good index to evaluate brain nerve injury [93,94]. The respiratory chain [95] of the mitochondria provides opportunities for potential mechanism study.…”