Voltage gated proton channels modulate mitochondrial reactive oxygen species production by complex I in renal medullary thick ascending limb

Abstract

Hv1 is a voltage-gated proton channel highly expressed in immune cells where, it acts to maintain NAD(P)H oxidase activity during the respiratory burst. We have recently reported that Hv1 is expressed in cells of the medullary thick ascending limb (mTAL) of the kidney and is critical to augment reactive oxygen species (ROS) production by this segment. While Hv1 is associated with NOX2 mediated ROS production in immune cells, the source of the Hv1 dependent ROS in mTAL remains unknown. In the current study, the rate of ROS formation was quantified in freshly isolated mTAL using dihydroethidium and ethidium fluorescence. Hv1 dependent ROS production was stimulated by increasing bath osmolality and ammonium chloride (NH4Cl) loading. Loss of either p67phox or NOX4 did not abolish the formation of ROS in mTAL. Hv1 was localized to mitochondria within mTAL, and the mitochondrial superoxide scavenger mitoTEMPOL reduced ROS formation. Rotenone significantly increased ROS formation and decreased mitochondrial membrane potential in mTAL from wild-type rats, while treatment with this inhibitor decreased ROS formation and increased mitochondrial membrane potential in mTAL from Hv1−/− mutant rats. These data indicate that NADPH oxidase is not the primary source of Hv1 dependent ROS production in mTAL. Rather Hv1 localizes to the mitochondria in mTAL and modulates the formation of ROS by complex I. These data provide a potential explanation for the effects of Hv1 on ROS production in cells independent of its contribution to maintenance of cell membrane potential and intracellular pH.

Contribution of ROS and metabolic status to neonatal and adult CD8+ T cell activation

“…This channel expels the excess protons generated by the action of NADPH-oxidase. Recent evidence suggests that this channel is also located in the internal mitochondrial membrane, contributing to the production and modulation of mROS [40]. This suggest that neonatal cells cannot use the high levels of NADH produced by glycolysis.…”

An altered metabolism could contribute to the low activation of neonatal CD8+T cells

“…This channel expels the excess protons generated by the action of the NADPH-oxidase enzyme. Recent evidence suggests that this channel is also located in the internal mitochondrial membrane, contributing to the production and modulation of mROS (Patel et al, 2019). This suggest that neonatal cells cannot modulate the high levels of reducing power produced by glycolysis.…”

TI: NLRP3 Inflammasome-Dependent Pyroptosis in CNS Trauma: A Potential Therapeutic Target

“…In the injured spinal cord segment of TLR4 −/−mice, the protein and mRNA expression levels of NLRP3 were sharply reduced 3 days post-injury, as well as in BV2 microglial cells treated with the TLR4 inhibitor TAK242 compared to the wild-type (WT) sham-operated group (Xu et al, 2020). As mentioned earlier, the increase in ROS levels is a common event that activates NLRP3 inflammasomes and is regulated by the voltage-gated proton channel (Hv1) (Patel et al, 2019). The latest research shows that Hv1 in spinal microglia increases significantly after spinal nerve transection and contributes to the production of ROS.…”