Knockout of mitochondrial voltage-dependent anion channel type 3 increases reactive oxygen species (ROS) levels and alters renal sodium transport

Molecular and structural analyses of voltage-dependent anion channel 2 and its anti-apoptotic function in stress and pollutant resistance in Pacific abalone

This study aimed to identify voltage-dependent anion channel 2 (Hdh-VDAC2) and determine its functional role in response to acute thermal stress, H2O2-induced stress, heavy metal toxicity, bacterial and viral infections, and during metamorphosis. Structural analysis confirmed that Hdh-VDAC2 is a pore-forming β-barrel protein. Molecular docking further confirmed the protein-protein interactions of Hdh-VDAC2 with Hdh-BAX, Hdh-caspase 3, and Hdh-BCL2. In the Hdh-VDAC2-inhibited hemocytes (HCY), apoptotic genes (Hdh-caspase-3 and Hdh-BAX) exhibited elevated mRNA expression, while the anti-apoptotic gene (Hdh-BCL2) was downregulated. Further, fluorescent techniques confirmed excessive reactive oxygen species (ROS) production, lower cell viability, elevated caspase 3 activity, and increased DNA fragmentation in Hdh-VDAC2-inhibited HCY, indicating an anti-apoptotic role of Hdh-VDAC2 in Pacific abalone. Transcriptomic analysis revealed differential expression patterns, with upregulation in the digestive gland (DG) and downregulation in the gill (GIL) and HCY when comparing heat-tolerant (HT) versus heat-sensitive (HS) abalone groups. Additionally, both cold and heat stresses induced Hdh-VDAC2 expression. Other environmental factors including H2O2, cadmium, bacteria, and viruses, were also shown to induce Hdh-VDAC2 mRNA expression in the GIL and DG of Pacific abalone. During metamorphosis, the blastula (BLS) stage exhibited higher Hdh-VDAC2 mRNA expression. These findings suggest that Hdh-VDAC2 plays a crucial anti-apoptotic role and may be a biomarker for summer mortality in Pacific abalone.

VDAC in Retinal Health and Disease

The retina, a tissue of the central nervous system, is vital for vision as its photoreceptors capture light and transform it into electrical signals, which are further processed before they are sent to the brain to be interpreted as images. The retina is unique in that it is continuously exposed to light and has the highest metabolic rate and demand for energy amongst all the tissues in the body. Consequently, the retina is very susceptible to oxidative stress. VDAC, a pore in the outer membrane of mitochondria, shuttles metabolites between mitochondria and the cytosol and normally protects cells from oxidative damage, but when a cell's integrity is greatly compromised it initiates cell death. There are three isoforms of VDAC, and existing evidence indicates that all three are expressed in the retina. However, their precise localization and function in each cell type is unknown. It appears that most retinal cells express substantial amounts of VDAC2 and VDAC3, presumably to protect them from oxidative stress. Photoreceptors express VDAC2, HK2, and PKM2-key proteins in the Warburg pathway that also protect these cells. Consistent with its role in initiating cell death, VDAC is overexpressed in the retinal degenerative diseases retinitis pigmentosa, age related macular degeneration (AMD), and glaucoma. Treatment with antioxidants or inhibiting VDAC oligomerization reduced its expression and improved cell survival. Thus, VDAC may be a promising therapeutic candidate for the treatment of these diseases.

Mitochondrial quality control in health and cardiovascular diseases

Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

Role of NLRP3 inflammasome-mediated neuronal pyroptosis and neuroinflammation in neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are a common group of neurological disorders characterized by progressive loss of neuronal structure and function leading to cognitive impairment. Recent studies have shown that neuronal pyroptosis mediated by the NLRP3 inflammasome plays a crucial role in the pathogenesis of neurodegenerative diseases.

OBJECTIVE AND METHOD

The NLRP3 inflammasome is a multiprotein complex that, when activated within cells, triggers an inflammatory response, ultimately leading to pyroptotic cell death of neurons. Pyroptosis is a typical pro-inflammatory programmed cell death process occurring downstream of NLRP3 inflammasome activation, characterized by the formation of pores on the cell membrane by the GSDMD protein, leading to cell lysis and the release of inflammatory factors. It has been found that NLRP3 inflammasome-mediated neuronal pyroptosis is closely associated with the development of various neurodegenerative diseases, such as Alzheimer's disease, traumatic brain injury, and Parkinson's disease. Therefore, inhibiting NLRP3 inflammasome activation and attenuating neuronal pyroptosis could potentially serve as novel strategies for the treatment of neurodegenerative diseases.

RESULTS

The aim of this review is to explore the role of NLRP3 activation-mediated neuronal pyroptosis and neuroinflammation in neurodegenerative diseases. Firstly, we extensively discuss the relationship between NLRP3 inflammasome-mediated neuronal pyroptosis and neuroinflammation in various neurodegenerative diseases. Subsequently, we further explore the mechanisms driving NLRP3 activation and assembly, as well as the post-translational modifications regulating NLRP3 inflammasome activation.

CONCLUSION

Understanding these mechanisms will contribute to a deeper understanding of the link between neuronal pyroptosis and neurodegenerative diseases, and hold significant implications for the treatment and prevention of neurodegenerative diseases.

Novel Strategies in the Early Detection and Treatment of Endothelial Cell-Specific Mitochondrial Dysfunction in Coronary Artery Disease

Although elevated cholesterol and other recognised cardiovascular risk factors are important in the development of coronary artery disease (CAD) and heart attack, the susceptibility of humans to this fatal process is distinct from other animals. Mitochondrial dysfunction of cells in the arterial wall, particularly the endothelium, has been strongly implicated in the pathogenesis of CAD. In this manuscript, we review the established evidence and mechanisms in detail and explore the potential opportunities arising from analysing mitochondrial function in patient-derived cells such as endothelial colony-forming cells easily cultured from venous blood. We discuss how emerging technology and knowledge may allow us to measure mitochondrial dysfunction as a potential biomarker for diagnosis and risk management. We also discuss the "pros and cons" of animal models of atherosclerosis, and how patient-derived cell models may provide opportunities to develop novel therapies relevant for humans. Finally, we review several targets that potentially alleviate mitochondrial dysfunction working both via direct and indirect mechanisms and evaluate the effect of several classes of compounds in the cardiovascular context.

Mitochondrial Ion Channels

Mitochondria are involved in multiple cellular tasks, such as ATP synthesis, metabolism, metabolite and ion transport, regulation of apoptosis, inflammation, signaling, and inheritance of mitochondrial DNA. The majority of the correct functioning of mitochondria is based on the large electrochemical proton gradient, whose component, the inner mitochondrial membrane potential, is strictly controlled by ion transport through mitochondrial membranes. Consequently, mitochondrial function is critically dependent on ion homeostasis, the disturbance of which leads to abnormal cell functions. Therefore, the discovery of mitochondrial ion channels influencing ion permeability through the membrane has defined a new dimension of the function of ion channels in different cell types, mainly linked to the important tasks that mitochondrial ion channels perform in cell life and death. This review summarizes studies on animal mitochondrial ion channels with special focus on their biophysical properties, molecular identity, and regulation. Additionally, the potential of mitochondrial ion channels as therapeutic targets for several diseases is briefly discussed.

Osmoregulatory strategies of estuarine fish Scatophagus argus in response to environmental salinity changes

BACKGROUND

Scatophagus argus, an estuarine inhabitant, can rapidly adapt to different salinity environments. However, the knowledge of the molecular mechanisms underlying its strong salinity tolerance remains unclear. The gill, as the main osmoregulatory organ, plays a vital role in the salinity adaptation of the fish, and thus relative studies are constructive to reveal unique osmoregulatory mechanisms in S. argus.

RESULTS

In the present study, iTRAQ coupled with nanoLC-MS/MS techniques were employed to explore branchial osmoregulatory mechanisms in S. argus acclimated to different salinities. Among 1,604 identified proteins, 796 differentially expressed proteins (DEPs) were detected. To further assess osmoregulatory strategies in the gills under different salinities, DEPs related to osmoregulatory (22), non-directional (18), hypo- (52), and hypersaline (40) stress responses were selected. Functional annotation analysis of these selected DEPs indicated that the cellular ion regulation (e.g. Na⁺-K⁺-ATPase [NKA] and Na⁺-K⁺-2Cl^- cotransporter 1 [NKCC1]) and ATP synthesis were deeply involved in the osmoregulatory process. As an osmoregulatory protein, NKCC1 expression was inhibited under hyposaline stress but showed the opposite trend in hypersaline conditions. The expression levels of NKA α1 and β1 were only increased under hypersaline challenge. However, hyposaline treatments could enhance branchial NKA activity, which was inhibited under hypersaline environments, and correspondingly, reduced ATP content was observed in gill tissues exposed to hyposaline conditions, while its contents were increased in hypersaline groups. In vitro experiments indicated that Na⁺, K⁺, and Cl^- ions were pumped out of branchial cells under hypoosmotic stress, whereas they were absorbed into cells under hyperosmotic conditions. Based on our results, we speculated that NKCC1-mediated Na⁺ influx was inhibited, and proper Na⁺ efflux was maintained by improving NKA activity under hyposaline stress, promoting the rapid adaptation of branchial cells to the hyposaline condition. Meanwhile, branchial cells prevented excessive loss of ions by increasing NKA internalization and reducing ATP synthesis. In contrast, excess ions in cells exposed to the hyperosmotic medium were excreted with sufficient energy supply, and reduced NKA activity and enhanced NKCC1-mediated Na⁺ influx were considered a compensatory regulation.

CONCLUSIONS

S. argus exhibited divergent osmoregulatory strategies in the gills when encountering hypoosmotic and hyperosmotic stresses, facilitating effective adaptabilities to a wide range of environmental salinity fluctuation.

A Redoxable Mn Porphyrin, MnTnBuOE-2-PyP5+, Synergizes with Carboplatin in Treatment of Chemoresistant Ovarian Cell Line

We have employed a redox-active MnP (MnTnBuOE-2-PyP⁵⁺, Mn(III) meso-tetrakis (N-n-butoxyethylpyridinium-2-yl) porphyrin) frequently identified as superoxide dismutase mimic or BMX-001, to explore the redox status of normal ovarian cell in relation to two ovarian cancer cell lines: OV90 human serous ovarian cancer cell and chemotherapy-resistant OV90 cell (OVCD). We identified that OVCD cells are under oxidative stress due to high hydrogen peroxide (H₂O₂) levels and low glutathione peroxidase and thioredoxin 1. Furthermore, OVCD cells have increased glycolysis activity and mitochondrial respiration when compared to immortalized ovarian cells (hTER7) and parental cancer cells (OV90). Our goal was to study how ovarian cell growth depends upon the redox state of the cell; hence, we used MnP (BMX-001), a redox-active MnSOD mimetic, as a molecular tool to alter ovarian cancer redox state. Interestingly, OVCD cells preferentially uptake MnP relative to OV90 cells which led to increased inhibition of cell growth, glycolytic activity, OXPHOS, and ATP, in OVCD cells. These effects were further increased when MnP was combined with carboplatin. The effects were discussed with regard to the elevation in H₂O₂ levels, increased oxidative stress, and reduced Nrf2 levels and its downstream targets when cells were exposed to either MnP or MnP/carboplatin. It is significant to emphasize that MnP protects normal ovarian cell line, hTER7, against carboplatin toxicity. Our data demonstrate that the addition of MnP-based redox-active drugs may be used (via increasing excessively the oxidative stress of serous ovarian cancer cells) to improve cancer patients' chemotherapy outcomes, which develop resistance to platinum-based drugs.

Voltage Dependent Anion Channel 3 (VDAC3) protects mitochondria from oxidative stress

Unraveling the role of VDAC3 within living cells is challenging and still requires a definitive answer. Unlike VDAC1 and VDAC2, the outer mitochondrial membrane porin 3 exhibits unique biophysical features that suggest unknown cellular functions. Electrophysiological studies on VDAC3 carrying selective cysteine mutations and mass spectrometry data about the redox state of such sulfur containing amino acids are consistent with a putative involvement of isoform 3 in mitochondrial ROS homeostasis. Here, we thoroughly examined this issue and provided for the first time direct evidence of the role of VDAC3 in cellular response to oxidative stress. Depletion of isoform 3 but not isoform 1 significantly exacerbated the cytotoxicity of redox cyclers such as menadione and paraquat, and respiratory complex I inhibitors like rotenone, promoting uncontrolled accumulation of mitochondrial free radicals. High-resolution respirometry of transiently transfected HAP1-ΔVDAC3 cells expressing the wild type or the cysteine-null mutant VDAC3 protein, unequivocally confirmed that VDAC3 cysteines are indispensable for protein ability to counteract ROS-induced oxidative stress.

Voltage-Dependent Anion Selective Channel 3: Unraveling Structural and Functional Features of the Least Known Porin Isoform

Voltage-dependent anion-selective channels (VDAC) are pore-forming proteins located in the outer mitochondrial membrane. Three isoforms are encoded by separate genes in mammals (VDAC1-3). These proteins play a crucial role in the cell, forming the primary interface between mitochondrial and cellular metabolisms. Research on the role of VDACs in the cell is a rapidly growing field, but the function of VDAC3 remains elusive. The high-sequence similarity between isoforms suggests a similar pore-forming structure. Electrophysiological analyzes revealed that VDAC3 works as a channel; however, its gating and regulation remain debated. A comparison between VDAC3 and VDAC1-2 underlines the presence of a higher number of cysteines in both isoforms 2 and 3. Recent mass spectrometry data demonstrated that the redox state of VDAC3 cysteines is evolutionarily conserved. Accordingly, these residues were always detected as totally reduced or partially oxidized, thus susceptible to disulfide exchange. The deletion of selected cysteines significantly influences the function of the channel. Some cysteine mutants of VDAC3 exhibited distinct kinetic behavior, conductance values and voltage dependence, suggesting that channel activity can be modulated by cysteine reduction/oxidation. These properties point to VDAC3 as a possible marker of redox signaling in the mitochondrial intermembrane space. Here, we summarize our current knowledge about VDAC3 predicted structure, physiological role and regulation, and possible future directions in this research field.

Tempol Alters Urinary Extracellular Vesicle Lipid Content and Release While Reducing Blood Pressure during the Development of Salt-Sensitive Hypertension

Salt-sensitive hypertension resulting from an increase in blood pressure after high dietary salt intake is associated with an increase in the production of reactive oxygen species (ROS). ROS are known to increase the activity of the epithelial sodium channel (ENaC), and therefore, they have an indirect effect on sodium retention and increasing blood pressure. Extracellular vesicles (EVs) carry various molecules including proteins, microRNAs, and lipids and play a role in intercellular communication and intracellular signaling in health and disease. We investigated changes in EV lipids, urinary electrolytes, osmolality, blood pressure, and expression of renal ENaC and its adaptor protein, MARCKS/MARCKS Like Protein 1 (MLP1) after administration of the antioxidant Tempol in salt-sensitive hypertensive 129Sv mice. Our results show Tempol infusion reduces systolic blood pressure and protein expression of the alpha subunit of ENaC and MARCKS in the kidney cortex of hypertensive 129Sv mice. Our lipidomic data show an enrichment of diacylglycerols and monoacylglycerols and reduction in ceramides, dihydroceramides, and triacylglycerols in urinary EVs from these mice after Tempol treatment. These data will provide insight into our understanding of mechanisms involving strategies aimed to inhibit ROS to alleviate salt-sensitive hypertension.

The regulatory function of mixed lineage kinase 3 in tumor and host immunity

Protein kinases are the second most sought-after G-protein coupled receptors as drug targets because of their overexpression, mutations, and dysregulated catalytic activities in various pathological conditions. Till 2019, 48 protein kinase inhibitors have received FDA approval for the treatment of multiple illnesses, of which the majority of them are indicated for different malignancies. One of the attractive sub-group of protein kinases that has attracted attention for drug development is the family members of MAPKs that are recognized to play significant roles in different cancers. Several inhibitors have been developed against various MAPK members; however, none of them as monotherapy has shown sustainable efficacy. One of the MAPK members, called Mixed Lineage Kinase 3 (MLK3), has attracted considerable attention due to its role in inflammation and neurodegenerative diseases; however, its role in cancer is an emerging area that needs more investigation. Recent advances have shown that MLK3 plays a role in cancer cell survival, migration, drug resistance, cell death, and tumor immunity. This review describes how MLK3 regulates different MAPK pathways, cancer cell growth and survival, apoptosis, and host's immunity. We also discuss how MLK3 inhibitors can potentially be used along with immunotherapy for different malignancies.

Renal metabolism and hypertension

Hypertension is a leading risk factor for disease burden worldwide. The kidneys, which have a high specific metabolic rate, play an essential role in the long-term regulation of arterial blood pressure. In this review, we discuss the emerging role of renal metabolism in the development of hypertension. Renal energy and substrate metabolism is characterized by several important and, in some cases, unique features. Recent advances suggest that alterations of renal metabolism may result from genetic abnormalities or serve initially as a physiological response to environmental stressors to support tubular transport, which may ultimately affect regulatory pathways and lead to unfavorable cellular and pathophysiological consequences that contribute to the development of hypertension.

Metabolic Dysregulation Contributes to the Progression of Alzheimer's Disease

Alzheimer's disease (AD) is an incurable neurodegenerative disease. Numerous studies have demonstrated a critical role for dysregulated glucose metabolism in its pathogenesis. In this review, we summarize metabolic alterations in aging brain and AD-related metabolic deficits associated with glucose metabolism dysregulation, glycolysis dysfunction, tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS) deficits, and pentose phosphate pathway impairment. Additionally, we discuss recent treatment strategies targeting metabolic defects in AD, including their limitations, in an effort to encourage the development of novel therapeutic strategies.

Interaction of TPPP3 with VDAC1 Promotes Endothelial Injury through Activation of Reactive Oxygen Species

Endothelial injury plays a critical role in the pathogenesis of cardiovascular disorders and metabolic-associated vascular complications which are the leading cause of death worldwide. However, the mechanism underlying endothelial dysfunction is not completely understood. The study is aimed at investigating the role of tubulin polymerization-promoting protein family member 3 (TPPP3) in palmitic acid- (PA-) induced endothelial injury. The effect of TPPP3 on human umbilical vein endothelial cells (HUVECs) was determined by evaluating apoptosis, tube formation, and reactive oxygen species (ROS) production. TPPP3 silencing inhibited PA overload-induced apoptosis and production of ROS, along with the alteration of apoptosis-related key proteins such as BCL-2 and Bax. Mechanically, voltage-dependent anion channel 1 (VDAC1) was identified as a novel functional binding partner of TPPP3, and TPPP3 promoted VDAC1 protein stability and its activity. Further studies indicated that TPPP3 could promote apoptosis, ROS production, tube formation, and proapoptotic protein expression and reduce antiapoptotic protein expression through increasing VDAC1 expression under mildly elevated levels of PA. Collectively, these results demonstrated that TPPP3 could promote PA-induced oxidative damage in HUVECs via a VDAC1-dependent pathway, suggesting that TPPP3 might be considered as a potential therapeutic target in vascular disease.

Stimulatory Role of SPAK Signaling in the Regulation of Large Conductance Ca2+-Activated Potassium (BK) Channel Protein Expression in Kidney

SPS1-related proline/alanine-rich kinase (SPAK) plays important roles in regulating the function of numerous ion channels and transporters. With-no-lysine (WNK) kinase phosphorylates SPAK kinase to active the SPAK signaling pathway. Our previous studies indicated that WNK kinases regulate the activity of the large-conductance Ca²⁺-activated K⁺ (BK) channel and its protein expression via the ERK1/2 signaling pathway. It remains largely unknown whether SPAK kinase directly modulates the BK protein expression in kidney. In this study, we investigated the effect of SPAK on renal BK protein expression in both HEK293 cells and mouse kidney. In HEK293 cells, siRNA-mediated knockdown of SPAK expression significantly reduced BK protein expression and increased ERK1/2 phosphorylation, whereas overexpression of SPAK significantly enhanced BK expression and decreased ERK1/2 phosphorylation in a dose-dependent manner. Knockdown of ERK1/2 prevented SPAK siRNA-mediated inhibition of BK expression. Similarly, pretreatment of HEK293 cells with either the lysosomal inhibitor bafilomycin A1 or the proteasomal inhibitor MG132 reversed the inhibitory effects of SPAK knockdown on BK expression. We also found that there is no BK channel activity in PCs of CCD in SPAK KO mice using the isolated split-open tubule single-cell patching. In addition, we found that BK protein abundance in the kidney of SPAK knockout mice was significantly decreased and ERK1/2 phosphorylation was significantly enhanced. A high-potassium diet significantly increased BK protein abundance and SPAK phosphorylation levels, while reducing ERK1/2 phosphorylation levels. These findings suggest that SPAK enhances BK protein expression by reducing ERK1/2 signaling-mediated lysosomal and proteasomal degradations of the BK channel.

Deletion of VDAC1 Hinders Recovery of Mitochondrial and Renal Functions After Acute Kidney Injury

Voltage-dependent anion channels (VDACs) constitute major transporters mediating bidirectional movement of solutes between cytoplasm and mitochondria. We aimed to determine if VDAC1 plays a role in recovery of mitochondrial and kidney functions after ischemia-induced acute kidney injury (AKI). Kidney function decreased after ischemia and recovered in wild-type (WT), but not in VDAC1-deficient mice. Mitochondrial maximum respiration, activities of respiratory complexes and F_oF₁-ATPase, and ATP content in renal cortex decreased after ischemia and recovered in WT mice. VDAC1 deletion reduced respiration and ATP content in non-injured kidneys. Further, VDAC1 deletion blocked return of activities of respiratory complexes and F_oF₁-ATPase, and recovery of respiration and ATP content after ischemia. Deletion of VDAC1 exacerbated ischemia-induced mitochondrial fission, but did not aggravate morphological damage to proximal tubules after ischemia. However, VDAC1 deficiency impaired recovery of kidney morphology and increased renal interstitial collagen accumulation. Thus, our data show a novel role for VDAC1 in regulating renal mitochondrial dynamics and recovery of mitochondrial function and ATP levels after AKI. We conclude that the presence of VDAC1 (1) stimulates capacity of renal mitochondria for respiration and ATP production, (2) reduces mitochondrial fission, (3) promotes recovery of mitochondrial function and dynamics, renal morphology, and kidney functions, and (4) increases survival after AKI.

Renal Hydrogen Peroxide Production Prevents Salt-Sensitive Hypertension

Background The regulation of sodium excretion is important in the pathogenesis of hypertension and salt sensitivity is predictive of cardiovascular events and mortality. C57Bl/6 and BALB/c mice have different blood pressure sensitivities to salt intake. High salt intake increases blood pressure in some C57Bl/6J mouse strains but not in any BALB/c mouse strain. Methods and Results We determined the cause of the difference in salt sensitivity between C57Bl/6 and BALB/c mice. Basal levels of superoxide and H2O2 were higher in renal proximal tubule cells (RPTCs) from BALB/c than C57Bl/6J mice. High salt diet increased H2O2 production in kidneys from BALB/c but C57Bl/6J mice. High sodium concentration (170 mmol/L) in the incubation medium increased H2O2 levels in BALB/c-RPTCs but not in C57Bl/6J-RPTCs. H2O2 (10 μmol/L) treatment decreased sodium transport in RPTCs from BALB/c but not C57Bl/6J mice. Overexpression of catalase in the mouse kidney predisposed BALB/c mice to salt-sensitive hypertension. Conclusions Our data show that the level of salt-induced H2O2 production negatively regulates RPTC sodium transport and determines the state of salt sensitivity in 2 strains of mice. High concentrations of antioxidants could prevent H2O2 production in renal proximal tubules, which would result in sodium retention and increased blood pressure.

Biochemical basis and metabolic interplay of redox regulation

Accumulated evidence strongly indicates that oxidative stress, characterized by an imbalance between reactive oxygen species (ROS) production and antioxidants in favor of oxidants, plays an important role in disease pathogenesis. However, ROS can act as signaling molecules and fulfill essential physiological functions at basal levels. Each ROS would be different in the extent to stimulate and contribute to different pathophysiological effects. Importantly, multiple ROS generators can be activated either concomitantly or sequentially by relevant signaling molecules for redox biological functions. Here, we summarized the current knowledge related to chemical and biochemical features of primary ROS species and corresponding antioxidants. Metabolic pathways of five major ROS generators and five ROS clearance systems were described, including their ROS products, specific ROS enriched tissue, cell and organelle, and relevant functional implications. We provided an overview of ROS generation and induction at different levels of metabolism. We classified 11 ROS species into three types based on their reactivity and target selectivity and presented ROS homeostasis and functional implications in pathological and physiological status. This article intensively reviewed and refined biochemical basis, metabolic signaling and regulation, functional insights, and provided guidance for the identification of novel therapeutic targets.

Genetic polymorphisms associated with reactive oxygen species and blood pressure regulation

Hypertension is the most prevalent cause of cardiovascular disease and kidney failure, but only about 50% of patients achieve adequate blood pressure control, in part, due to inter-individual genetic variations in the response to antihypertensive medication. Significant strides have been made toward the understanding of the role of reactive oxygen species (ROS) in the regulation of the cardiovascular system. However, the role of ROS in human hypertension is still unclear. Polymorphisms of some genes involved in the regulation of ROS production are associated with hypertension, suggesting their potential influence on blood pressure control and response to antihypertensive medication. This review provides an update on the genes associated with the regulation of ROS production in hypertension and discusses the controversies on the use of antioxidants in the treatment of hypertension, including the antioxidant effects of antihypertensive drugs.

Loss of primary cilia increases polycystin-2 and TRPV4 and the appearance of a nonselective cation channel in the mouse cortical collecting duct

Flow-related bending of cilia results in Ca²⁺ influx through a polycystin-1 (Pkd1) and polycystin-2 (Pkd2) complex, both of which are members of the transient receptor potential (TRP) family (TRPP1 and TRPP2, respectively). Deletion of this complex as well as cilia result in polycystic kidney disease. The Ca²⁺ influx pathway has been previously characterized in immortalized collecting duct cells without cilia and found to be a 23-pS channel that was a multimere of TRPP2 and TRPV4. The purpose of the present study was to determine if this TRPP2 and TRPV4 multimere exists in vivo. Apical channel activity was measured using the patch-clamp technique from isolated split-open cortical collecting ducts from adult conditional knockout mice with (Ift88^flox/flox) or without (Ift88^-/-) cilia. Single tubules were isolated for measurements of mRNA for Pkd1, Pkd2, Trpv4, and epithelial Na⁺ channel subunits. The predominant channel activity from Ift88^flox/flox mice was from epithelial Na⁺ channel [5-pS Na⁺-selective channels with long mean open times (475.7 ± 83.26 ms) and open probability > 0.2]. With the loss of cilia, the predominant conductance was a 23-pS nonselective cation channel (reversal potential near 0) with a short mean open time (72 ± 17 ms), open probability < 0.08, and a characteristic flickery opening. Loss of cilia increased mRNA levels for Pkd2 and Trpv4 from single isolated cortical collecting ducts. In conclusion, 23-pS channels exist in vivo, and activity of this channel is elevated with loss of cilia, consistent with previous finding of an elevated-unregulated Ca²⁺-permeable pathway at the apical membrane of collecting duct cells that lack cilia.

Effects of reactive oxygen species on renal tubular transport

Reactive oxygen species (ROS) play a critical role in regulating nephron transport both via transcellular and paracellular pathways under physiological and pathological circumstances. Here, we review the progress made in the past ~10 yr in understanding how ROS regulate solute and water transport in individual nephron segments. Our knowledge in this field is still rudimentary, with basic information lacking. This is most obvious when looking at the reported disparate effects of superoxide ([Formula: see text]) and H₂O₂ on proximal nephron transport, where there are no easy explanations as to how to reconcile the data. Similarly, we know almost nothing about the regulation of transport in thin descending and ascending limbs, information that is likely critical to understanding the urine concentrating mechanism. In the thick ascending limb, there is general agreement that ROS enhance transcellular reabsorption of NaCl, but we know very little about their effects on the paracellular pathway and therefore Ca²⁺ and Mg²⁺ transport. In the distal convoluted tubule, precious little is known. In the collecting duct, there is general agreement that ROS stimulate the epithelial Na⁺ channel.

Voltage-dependent anion channel isoform 3 as a potential male contraceptive drug target

Voltage-dependent anion channel isoform 3 (VDAC3), a channel in the mitochondrial outer membrane, has been suggested to play a role in the regulation of ATP transport and Ca²⁺ homeostasis. These processes are regarded as important for spermatozoa motility. Accordingly, in previous years, mutations in the VDAC3-encoding gene were detected in spermatozoa with low motility from infertile patients. Therefore, it can be assumed that these mutations would cause alteration of the structure and/or charge of the VDAC3 channel. The review is focused on current knowledge about contribution of VDAC3 activity to human spermatozoa motility and morphology. We also discuss the possibility of designing new molecules that could specifically block the VDAC3 channel and consequently act as male contraceptives.

Detection of mitochondria-generated reactive oxygen species in cells using multiple probes and methods: Potentials, pitfalls, and the future

Reactive oxygen and nitrogen species (ROS/RNS) such as superoxide (O₂^̇̄), hydrogen peroxide, lipid hydroperoxides, peroxynitrite, and hypochlorous and hypobromous acids play a key role in many pathophysiological processes. Recent studies have focused on mitochondrial ROS as redox signaling species responsible for promoting cell division, modulating and regulating kinases and phosphatases, and activating transcription factors. Many ROS also stimulate cell death and senescence. The extent to which these processes occur is attributed to ROS levels (low or high) in cells. However, the exact nature of ROS remains unknown. Investigators have used redox-active probes that, upon oxidation by ROS, yield products exhibiting fluorescence, chemiluminescence, or bioluminescence. Mitochondria-targeted probes can be used to detect ROS generated in mitochondria. However, because most of these redox-active probes (untargeted and mitochondria-targeted) are oxidized by several ROS species, attributing redox probe oxidation to specific ROS species is difficult. It is conceivable that redox-active probes are oxidized in common one-electron oxidation pathways, resulting in a radical intermediate that either reacts with another oxidant (including oxygen to produce O₂^̇̄) and forms a stable fluorescent product or reacts with O₂^̇̄ to form a fluorescent marker product. Here, we propose the use of multiple probes and complementary techniques (HPLC, LC-MS, redox blotting, and EPR) and the measurement of intracellular probe uptake and specific marker products to identify specific ROS generated in cells. The low-temperature EPR technique developed to investigate cellular/mitochondrial oxidants can easily be extended to animal and human tissues.