The mitochondria-targeted antioxidant MitoQ ameliorated tubular injury mediated by mitophagy in diabetic kidney disease via Nrf2/PINK1

PTEN enhances nasal epithelial cell resistance to TNFα‑induced inflammatory injury by limiting mitophagy via repression of the TLR4‑JNK‑Bnip3 pathway

Nasal epithelial cell inflammatory injury is associated with chronic obstructive pulmonary disease development. However, the mechanism by which inflammation triggers nasal epithelial cell damage remains unclear. In the present study, tumor necrosis factor (TNF)α was used to induce an inflammatory injury and explore the underlying pathogenesis for nasal epithelial cell apoptosis in vitro, with a focus on mitochondrial homeostasis. Then, cellular apoptosis was detected via a terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labeling assay and western blotting. Mitochondrial function was evaluated via JC‑1 staining, mPTP opening measurement and western blotting. The results demonstrated that TNFα treatment induced nasal epithelial cell apoptosis, proliferation arrest and migration inhibition via downregulating phosphatase and tensin homolog (PTEN) levels. Increased PTEN expression was associated with reduce Toll‑like receptor (TLR)4‑c‑Jun kinase (JNK)‑Bcl2‑interacting protein 3 (Bnip3) pathway signaling, leading to reductions in mitophagy activity. Excessive mitophagy resulted in ATP deficiencies, mitochondrial dysfunction, caspase‑9 activation and cellular apoptosis. By contrast, PTEN overexpression in nasal epithelial cells alleviated the mitochondrial damage and cellular apoptosis via inhibiting the TLR4‑JNK‑Bnip3 pathway, favoring the survival of nasal epithelial cells under inflammatory injury. Therefore, this data uncovered a potential molecular basis for nasal epithelial cell apoptosis in response to inflammatory injury, and PTEN was identified as the endogenous defender of nasal epithelial cell survival via controlling lethal mitophagy by inhibiting the TLR4‑JNK‑Bnip3 pathway, suggesting that this pathway may be a potential target for clinically treating chronic nasal and sinus inflammatory injury.

NR4A1 contributes to high-fat associated endothelial dysfunction by promoting CaMKII-Parkin-mitophagy pathways

Parkin-related mitophagy is vital for endothelial cell viability and the development of atherosclerosis, although the upstream regulatory factor underlying Parkin-mediated mitophagy in endothelial apoptosis and atherosclerosis progression remains unknown. In the present study, we demonstrated that nuclear receptor subfamily 4 group A member 1 (NR4A1) is actually expressed in aortic endothelial cells (AECs) under oxidized low-density lipoprotein (ox-LDL) treatment in vitro or isolated from high-fat treated mice in vivo. Higher NR4A1 levels were associated with AEC apoptosis, mitochondrial dysfunction, and energy disorder. At the molecular level, ox-LDL stimulation increased NR4A1 expression, which evoked Parkin-mediated mitophagy. Excessive mitophagy overtly consumed mitochondrial mass, leading to an energy shortage and mitochondrial dysfunction. However, loss of NR4A1 protected AECs against ox-LDL induced apoptosis by inhibiting excessive mitophagy. Furthermore, we also identified that NR4A1 regulated Parkin activation via post-transcriptional modification by Ca2+/calmodulin-dependent protein kinase II (CaMKII). Activated CaMKII via NR4A1 induced the phosphorylated activation of Parkin. In summary, our data support the role of NR4A1/CaMKII/Parkin/mitophagy in AEC apoptosis and atherosclerosis formation and provide new insights into treating atherosclerosis with respect to endothelial viability, mitophagy, and NR4A1.

Ameliorating mitochondrial dysfunction restores carbon ion-induced cognitive deficits via co-activation of NRF2 and PINK1 signaling pathway

Carbon ion therapy is a promising modality in radiotherapy to treat tumors, however, a potential risk of induction of late normal tissue damage should still be investigated and protected. The aim of the present study was to explore the long-term cognitive deficits provoked by a high-linear energy transfer (high-LET) carbon ions in mice by targeting to hippocampus which plays a crucial role in memory and learning. Our data showed that, one month after 4 Gy carbon ion exposure, carbon ion irradiation conspicuously resulted in the impaired cognitive performance, neurodegeneration and neuronal cell death, as well as the reduced mitochondrial integrity, the disrupted activities of tricarboxylic acid cycle flux and electron transport chain, and the depressed antioxidant defense system, consequently leading to a decline of ATP production and persistent oxidative damage in the hippocampus region. Mechanistically, we demonstrated the disruptions of mitochondrial homeostasis and redox balance typically characterized by the disordered mitochondrial dynamics, mitophagy and glutathione redox couple, which is closely associated with the inhibitions of PINK1 and NRF2 signaling pathway as the key regulators of molecular responses in the context of neurotoxicity and neurodegenerative disorders. Most importantly, we found that administration with melatonin as a mitochondria-targeted antioxidant promoted the PINK1 accumulation on the mitochondrial membrane, and augmented the NRF2 accumulation and translocation. Moreover, melatonin pronouncedly enhanced the molecular interplay between NRF2 and PINK1. Furthermore, in the mouse hippocampal neuronal cells, overexpression of NRF2/PINK1 strikingly protected the hippocampal neurons from carbon ion-elicited toxic insults. Thus, these data suggest that alleviation of the sustained mitochondrial dysfunction and oxidative stress through co-modulation of NRF2 and PINK1 may be in charge of restoration of the cognitive impairments in a mouse model of high-LET carbon ion irradiation.

Mitochondrial-targeted antioxidant MitoQ provides neuroprotection and reduces neuronal apoptosis in experimental traumatic brain injury possibly via the Nrf2-ARE pathway

Mitoquinone (MitoQ) is a powerful mitochondrial-targeted antioxidant whose neuroprotective effects have been shown in a variety of animal models of neurological diseases. However, its roles in traumatic brain injury (TBI) remain unexplored. The primary objective of this study was to investigate the neuroprotection afforded by MitoQ in a mouse model of TBI, and the involvement of the Nrf2-ARE signaling pathway in the putative neuroprotective mechanism. Mice were randomly divided into four groups: sham group, TBI group, TBI + vehicle group, and TBI + MitoQ group. MitoQ (4 mg/kg, administered intraperitoneally) or an equal volume of vehicle was given at 30 min after TBI. After 24 h, brain samples were harvested for analysis. The results demonstrated that treatment with MitoQ significantly improved neurological deficits, alleviated brain edema and inhibited cortical neuronal apoptosis. Furthermore, MitoQ administration increased the activity of antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxidase (GPx), whereas it decreased the malondialdehyde (MDA) content. In addition, MitoQ treatment reduced Bax protein translocation to mitochondria and cytochrome c release into the cytosol. Moreover, MitoQ greatly accelerated the Nrf2 nuclear translocation and subsequently upregulated the expression of Nrf2 downstream proteins, including heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (Nqo1). In conclusion, the results in the study demonstrate that MitoQ exerts neuroprotective effects in the mouse model of TBI, possibly by activating the Nrf2-ARE pathway.

Protective mechanisms involving enhanced mitochondrial functions and mitophagy against T-2 toxin-induced toxicities in GH3 cells

T-2 toxin is the most toxic member of trichothecene mycotoxin. So far, the mechanism of mitochondrial toxicity and protective mechanism in mammalian cells against T-2 toxin are not fully understood. In this study, we aimed to investigate the cellular and mitochondrial toxicity of T-2 toxin, and the cellular protective mechanisms in rat pituitary GH3 cells. We showed that T-2 toxin significantly increased reactive oxygen species (ROS) and DNA damage and caused apoptosis in GH3 cells. T-2 toxin induced abnormal cell morphology, cytoplasm and nuclear shrinkage, nuclear fragmentation and formation of apoptotic bodies and autophagosomes. The mitochondrial degradative morphologies included local or total cristae collapse and small condensed mitochondria. T-2 toxin decreased the mitochondrial membrane potential. However, T-2 toxin significantly increased the superoxide dismutase (SOD) activity and expression of antioxidant genes glutathione peroxidase 1 (GPx-1), catalase (CAT), mitochondria-specific SOD-2 and mitochondrial uncoupling protein-1, -2 and -3 (UCP-1, 2 and 3). Interestingly, T-2 toxin increased adenosine triphosphate (ATP) levels and mitochondrial complex I activity, and increased the expression of most of mitochondrial electron transport chain subunits tested and critical transcription factors controlling mitochondrial biogenesis and mitochondrial DNA transcription and replication. T-2 toxin increased mitophagic activity by increasing the expression of mitophagy-specific proteins NIP-like protein X (NIX), PTEN-induced putative kinase protein 1 (PINK1) and E3 ubiquitin ligase Parkin. T-2 toxin activated the protective protein kinase A (PKA) signaling pathway, which activated the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/PINK1/Parkin pathway to mediate mitophagy. Taken together, our results suggested that the mammalian cells could increase their resistance against T-2 toxin by increasing the antioxidant activity, mitophagy and mitochondrial function.

Role of p53/miR-155-5p/sirt1 loop in renal tubular injury of diabetic kidney disease

BACKGROUND

Diabetic kidney disease is a renal microvascular disease caused by diabetes, known as one of the most serious and lethal complications of diabetes. Early renal hypertrophy is the main pathological feature, which gradually leads to the deposition of glomerular extracellular matrix and tubulointerstitial fibrosis, eventually developing irreversible structural damage to the kidneys. Autophagy is a cell self-homeostatic mechanism that is activated under stress conditions and may serve as a protective response to the survival of renal fibrogenic cells. MicroRNA (miRNA) network may be involved in the regulation of fibrosis. The purpose of this study is to assess how miRNAs regulate diabetic kidney disease and autophagy and fibrosis in renal proximal tubular cells under high glucose conditions.

METHODS

Human renal proximal tubular (HK-2) cells were exposed to high glucose in vitro. Bioinformatic analysis was used to select the candidate gene for potential target regulation of miR-155, Sirt1. ATG5, ATG7 is the key to autophagosome formation, regulated by Sirt1. p53 regulates miR-155 expression as a transcription factor. MiR-155 overexpression and inhibition were achieved by transfection of miR-155 mimic and inhibit to evaluate its effect on Sirt1 and autophagy and fibrosis markers. Dual luciferase reporter assays were used to confirm the direct interaction of Sirt1 with miR-155. Overexpression and inhibition of Sirt1 gene were achieved by transfection of Sirt1 plasmid and Sirt1 si to observe its effect on P53. Chip assay experiments confirmed the direct regulation of P53 on miR-155.

RESULTS

Under high glucose conditions, miR-155 was detected in HK-2 cells in concentration gradient, increased expression of p53 and down-regulated expression of sirt1 and autophagy-associated proteins LC3II, ATG5 and ATG7. Dual luciferase reporter assays indicate that miR-155 can target its binding to the Sirt1 3'UTR region to reduce its expression. Under high glucose conditions, over expression of miR-155 decreased the expression of LC3-II and ATG5 in HK-2 cells, while inhibition of miR-155 reversed this effect. Using chip assay testing in HK-2 cells, we demonstrated that p53 binds directly to miR-155.

CONCLUSIONS

The signaling axis of p53, miR-155-5p, and sirt1 in autophagic process might be a critical adapting mechanism for diabetic kidney injury.

MitoQ protects dopaminergic neurons in a 6-OHDA induced PD model by enhancing Mfn2-dependent mitochondrial fusion via activation of PGC-1α

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic neurons in the substantia nigra compacta (SNc). Although mitochondrial dysfunction is the critical factor in the pathogenesis of PD, the underlying molecular mechanisms are not well understood, and as a result, effective medical interventions are lacking. Mitochondrial fission and fusion play important roles in the maintenance of mitochondrial function and cell viability. Here, we investigated the effects of MitoQ, a mitochondria-targeted antioxidant, in 6-hydroxydopamine (6-OHDA)-induced in vitro and in vivo PD models. We observed that 6-OHDA enhanced mitochondrial fission by decreasing the expression of Mfn1, Mfn2 and OPA1 as well as by increasing the expression of Drp1 in the dopaminergic (DA) cell line SN4741. Notably, MitoQ treatment particularly upregulated the Mfn2 protein and mRNA levels and promoted mitochondrial fusion in the presence of 6-OHDA in a Mfn2-dependent manner. In addition, MitoQ also stabilized mitochondrial morphology and function in the presence of 6-OHDA, which further suppressed the formation of reactive oxygen species (ROS), as well as ameliorated mitochondrial fragmentation and cellular apoptosis. Moreover, the activation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) was attributed to the upregulation of Mfn2 induced by MitoQ. Consistent with these findings, administration of MitoQ in 6-OHDA-treated mice significantly rescued the decrease of Mfn2 expression and the loss of DA neurons in the SNc. Taken together, our findings suggest that MitoQ protects DA neurons in a 6-OHDA induced PD model by activating PGC-1α to enhance Mfn2-dependent mitochondrial fusion.

Mitochonic acid 5 activates the MAPK-ERK-yap signaling pathways to protect mouse microglial BV-2 cells against TNFα-induced apoptosis via increased Bnip3-related mitophagy

BACKGROUND

The regulation of microglial function via mitochondrial homeostasis is important in the development of neuroinflammation. The underlying mechanism for this regulatory function remains unclear. In this study, we investigated the protective role of mitochonic acid 5 (MA-5) in microglial mitochondrial apoptosis following TNFα-induced inflammatory injury.

METHODS

TNFα was used to induce inflammatory injury in mouse microglial BV-2 cells with and without prior MA-5 treatment. Cellular apoptosis was assessed using the MTT and TUNEL assays. Mitochondrial functions were evaluated via mitochondrial membrane potential JC-1 staining, ROS flow cytometry analysis, mPTP opening assessment, and immunofluorescence of cyt-c. Mitophagy was examined using western blots and immunofluorescence. The pathways analysis was carried out using western blots and immunofluorescence with a pathway blocker.

RESULTS

Our results demonstrated that TNFα induced apoptosis in the microglial BV-2 cell line by activating the caspase-9-dependent mitochondrial apoptotic pathway. Mechanistically, inflammation reduced mitochondrial potential, induced ROS production, and contributed to the leakage of mitochondrial pro-apoptotic factors into the cytoplasm. The inflammatory response reduced cellular energy metabolism and increased oxidative stress. By contrast, treatment with MA-5 reduced mitochondrial apoptosis via upregulation of mitophagy. Increased mitophagy degraded damaged mitochondria, disrupting mitochondrial apoptosis, neutralizing ROS overproduction, and improving cellular energy production. We also identified that MA-5 regulated mitophagy via Bnip3 through the MAPK-ERK-Yap signaling pathway. Inhibiting this signaling pathway or knocking down Bnip3 expression prevented MA-5 from having beneficial effects on mitochondrial homeostasis and increased microglial apoptosis.

CONCLUSIONS

After TNFα-induced inflammatory injury, MA-5 affects microglial mitochondrial homeostasis in a manner mediated via the amplification of protective, Bnip3-related mitophagy, which is mediated via the MAPK-ERK-Yap signaling pathway.

Astaxanthin Promotes Nrf2/ARE Signaling to Inhibit HG-Induced Renal Fibrosis in GMCs

Oxidative stress is the main cause of diabetic nephropathy (DN) progression. Nuclear factor-erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling is a crucial cellular defense system to cope with oxidative stress. Astaxanthin (AST) is a fat-soluble xanthophyll carotenoid with remarkable antioxidative capacity. AST exerted renal protective in diabetic rats. This study aimed to determine whether AST could alleviate the pathological progress of DN by activating Nrf2/ARE signaling and diminishing the excessive oxidative stress and fibronectin (FN) accumulation in glomerular mesangial cells (GMCs) challenged with high glucose (HG). In the current study, we found that AST treatment alleviated the metabolic parameters, renal morphology and extracellular matrix (ECM) accumulation in streptozotocin-induced diabetic rats. Additionally, HG induced the adaptively activated Nrf2/ARE signaling and increased the expression of FN, intercellular adhesion molecule-1 (ICAM-1) and transforming growth factor-β1 (TGF-β1), as well as the intracellular reactive oxygen species (ROS) generation in GMCs. However, AST treatment strongly promoted the nuclear translocation and transcriptional activity of Nrf2 as well as upregulated the expression of superoxide dismutase (SOD1), NAD(P)H: quinone oxidoreductase (NQO1) and heme oxygenase-1 (HO-1), ultimately quenching the higher level of ROS and inhibiting the FN, ICAM-1 and TGF-β1 expression induced by HG. Collectively, our data suggest that the renoprotective effect of AST on DN depends on Nrf2/ARE signaling activation, which could be a potentially therapeutic strategy in the treatment of DN.

Glomerular Endothelial Cell Stress and Cross-Talk With Podocytes in Early [corrected] Diabetic Kidney Disease

Diabetic kidney disease (DKD) is one of the major causes of morbidity and mortality in diabetic patients and also the leading single cause of end-stage renal disease in the United States. A large proportion of diabetic patients develop DKD and others don't, even with comparable blood glucose levels, indicating a significant genetic component of disease susceptibility. The glomerulus is the primary site of diabetic injury in the kidney, glomerular hypertrophy and podocyte depletion are glomerular hallmarks of progressive DKD, and the degree of podocyte loss correlates with severity of the disease. We know that chronic hyperglycemia contributes to both microvascular and macrovascular complications, as well as podocyte injury. We are beginning to understand the role of glomerular endothelial injury, as well as the involvement of reactive oxygen species and mitochondrial stress, which play a direct role in DKD and in other diabetic complications. There is, however, a gap in our knowledge that links genetic susceptibility to early molecular mechanisms and proteinuria in DKD. Emerging research that explores glomerular cell's specific responses to diabetes and cell cross-talk will provide mechanistic clues that underlie DKD and provide novel avenues for therapeutic intervention.

The mitochondrially targeted antioxidant MitoQ protects the intestinal barrier by ameliorating mitochondrial DNA damage via the Nrf2/ARE signaling pathway

Disruption of the mucosal barrier following intestinal ischemia reperfusion (I/R) is life threatening in clinical practice. Mitochondrial dysfunction and oxidative stress significantly contribute to the early phase of I/R injury and amplify the inflammatory response. MitoQ is a mitochondrially targeted antioxidant that exerts protective effects following I/R injury. In the present study, we aimed to determine whether and how MitoQ protects intestinal epithelial cells (IECs) from I/R injury. In both in vivo and in vitro studies, we found that MitoQ pretreatment downregulated I/R-induced oxidative stress and stabilized the intestinal barrier, as evidenced by MitoQ-treated I/R mice exhibiting attenuated intestinal hyperpermeability, inflammatory response, epithelial apoptosis, and tight junction damage compared to controls. Mechanistically, I/R elevated mitochondrial 8-hydroxyguanine content, reduced mitochondrial DNA (mtDNA) copy number and mRNA transcription levels, and induced mitochondrial disruption in IECs. However, MitoQ pretreatment dramatically inhibited these deleterious effects. mtDNA depletion alone was sufficient to induce apoptosis and mitochondrial dysfunction of IECs. Mitochondrial transcription factor A (TFAM), a key activator of mitochondrial transcription, was significantly reduced during I/R injury, a phenomenon that was prevented by MitoQ treatment. Furthermore, we observed that thee protective properties of MitoQ were affected by upregulation of cellular antioxidant genes, including HO-1, NQO-1, and γ-GCLC. Transfection with Nrf2 siRNA in IECs exposed to hypoxia/reperfusion conditions partially blocked the effects of MitoQ on mtDNA damage and mitochondrial oxidative stress. In conclusion, our data suggest that MitoQ exerts protective effect on I/R-induced intestinal barrier dysfunction.

Acute Kidney Injury and Progression of Diabetic Kidney Disease

Diabetic kidney disease, commonly termed diabetic nephropathy (DN), is the most common cause of end-stage kidney disease (ESKD) worldwide. The characteristic histopathology of DN includes glomerular basement membrane thickening, mesangial expansion, nodular glomerular sclerosis, and tubulointerstitial fibrosis. Diabetes is associated with a number of metabolic derangements, such as reactive oxygen species overproduction, hypoxic state, mitochondrial dysfunction, and inflammation. In the past few decades, our knowledge of DN has advanced considerably although much needs to be learned. The traditional paradigm of glomerulus-centered pathophysiology has expanded to the tubule-interstitium, the immune response and inflammation. Biomarkers of proximal tubule injury have been shown to correlate with DN progression, independent of traditional glomerular injury biomarkers such as albuminuria. In this review, we summarize mechanisms of increased susceptibility to acute kidney injury in diabetes mellitus and the roles played by many kidney cell types to facilitate maladaptive responses leading to chronic and end-stage kidney disease.

Mechanisms, pathophysiological roles and methods for analyzing mitophagy - recent insights

In 2012, we briefly summarized the mechanisms, pathophysiological roles and methods for analyzing mitophagy. As then, the mitophagy field has continued to grow rapidly, and many new molecular mechanisms regulating mitophagy and molecular tools for monitoring mitophagy have been discovered and developed. Therefore, the purpose of this review is to update information regarding these advances in mitophagy while focusing on basic molecular mechanisms of mitophagy in different organisms and its pathophysiological roles. We also discuss the advantage and limitations of current methods to monitor and quantify mitophagy in cultured cells and in vivo mouse tissues.

Defective Autophagy in Atherosclerosis: To Die or to Senesce?

Autophagy is a subcellular process that plays an important role in the degradation of proteins and damaged organelles such as mitochondria (a process termed “mitophagy”) via lysosomes. It is crucial for regulating protein and mitochondrial quality control and maintaining cellular homeostasis, whereas dysregulation of autophagy has been implicated in a wide range of diseases including atherosclerosis. Recent evidence has shown that the autophagic process becomes dysfunctional during the progression of atherosclerosis, regardless of whether there are many autophagy-stimulating factors (e.g., reactive oxygen species, oxidized lipids, and cytokines) present within the atherosclerotic plaque. This review highlights the recent insights into the causes and consequences of defective autophagy in atherosclerosis, with a special focus on the role of autophagy and mitophagy in plaque macrophages, vascular smooth muscle cells (VSMCs), and endothelial cells (ECs). It has been shown that defective autophagy can promote apoptosis in macrophages but that it accelerates premature senescence in VSMCs. In the ECs, defective autophagy promotes both apoptosis and senescence. We will discuss the discrepancy between these three cell types in their response to autophagy deficiency and underline the cell type-dependent role of autophagy, which may have important implications for the efficacy of autophagy-targeted treatments for atherosclerosis.

Mitochondrial dysfunction in diabetic kidney disease

Globally, diabetes is the leading cause of chronic kidney disease and end-stage renal disease, which are major risk factors for cardiovascular disease and death. Despite this burden, the factors that precipitate the development and progression of diabetic kidney disease (DKD) remain to be fully elucidated. Mitochondrial dysfunction is associated with kidney disease in nondiabetic contexts, and increasing evidence suggests that dysfunctional renal mitochondria are pathological mediators of DKD. These complex organelles have a broad range of functions, including the generation of ATP. The kidneys are mitochondrially rich, highly metabolic organs that require vast amounts of ATP for their normal function. The delivery of metabolic substrates for ATP production, such as fatty acids and oxygen, is altered by diabetes. Changes in metabolic fuel sources in diabetes to meet ATP demands result in increased oxygen consumption, which contributes to renal hypoxia. Inherited factors including mutations in genes that impact mitochondrial function and/or substrate delivery may also be important risk factors for DKD. Hence, we postulate that the diabetic milieu and inherited factors that underlie abnormalities in mitochondrial function synergistically drive the development and progression of DKD.

Reactive oxygen species promote tubular injury in diabetic nephropathy: The role of the mitochondrial ros-txnip-nlrp3 biological axis

NLRP3/IL-1β activation via thioredoxin (TRX)/thioredoxin-interacting protein (TXNIP) following mitochondria ROS (mtROS) overproduction plays a key role in inflammation. However, the involvement of this process in tubular damage in the kidneys of patients with diabetic nephropathy (DN) is unclear. Here, we demonstrated that mtROS overproduction is accompanied by decreases in TRX expression and TXNIP up-regulation. In addition, we discovered that mtROS overproduction is also associated with increases in NLRP3/IL-1β and TGF-β expression in the kidneys of patients with DN and db/db mice. We reversed these changes in db/db mice by administering a peritoneal injection of MitoQ, an antioxidant targeting mtROS. Similar results were observed in human tubular HK-2 cells subjected to high-glucose (HG) conditions and treated with MitoQ. Treating HK-2 cells with MitoQ suppressed the dissociation of TRX from TXNIP and subsequently blocked the interaction between TXNIP and NLRP3, leading to the inhibition of NLRP3 inflammasome activation and IL-1β maturation. The effects of MitoQ were enhanced by pretreatment with TXNIP siRNA and abolished by pretreatment with monosodium urate (MSU) and TRX siRNA in vitro. These results suggest that mitochondrial ROS-TXNIP/NLRP3/IL-1β axis activation is responsible for tubular oxidative injury, which can be ameliorated by MitoQ via the inhibition of mtROS overproduction.

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Reactive oxygen species promotes renal damage in diabetic nephropathy.

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Mitochondrial ROS- TXNIP-NLRP3 biological axis involved in tubular injury of DN.

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Inhibition of mitochondrial ROS by MitoQ ameliorated the renal tubular injury.

ALA/LA ameliorates glucose toxicity on HK-2 cells by attenuating oxidative stress and apoptosis through the ROS/p38/TGF-β1 pathway

BACKGROUND

Growing evidence indicates that oxidative stress (OS) plays a pivotal role in Diabetic nephropathy (DN). In a previous study we demonstrated that ALA/LA protected HK-2 cells against high glucose-induced cytotoxicity. So we aimed to establish the glucose injury model of HK-2 cells and investigate the beneficial effects of ALA/LA on high glucose-induced excessive production of TGF-β1 and the possible mechanisms mediating the effects.

METHODS

The expression of OS markers in high glucose-induced HK-2 cells treated with ALA/LA., including the antioxidant enzymes and reactive oxygen species (ROS) production, as well as the apoptosis rate were assayed by ELISA and flow cytometry. The p38/transforming growth factor β1 (TGF-β1) signal pathway were measured by real-time RT-PCR and western blot.

RESULTS

The modeling condition of glucose toxicity on HK-2 cells was at the glucose concentration of 40.9 mM. ALA/LA can significantly increase the activities of antioxidant enzymes and decrease ROS production stimulated by high glucose. The study also found that ALA/LA caused a decrease in the apoptosis rate and TGF-β1 level of HK-2 cells under high glucose stress through the ROS/p38 pathway.

CONCLUSIONS

ALA/LA exerts protective effects in vitro through inhibition of ROS generation, down regulation of the activation of the p38MAPK pathway and the expression of TGF-β1 in HK-2 cells.

Mitochondria-targeted ubiquinone (MitoQ) enhances acetaldehyde clearance by reversing alcohol-induced posttranslational modification of aldehyde dehydrogenase 2: A molecular mechanism of protection against alcoholic liver disease

Alcohol metabolism in the liver generates highly toxic acetaldehyde. Breakdown of acetaldehyde by aldehyde dehydrogenase 2 (ALDH2) in the mitochondria consumes NAD⁺ and generates reactive oxygen/nitrogen species, which represents a fundamental mechanism in the pathogenesis of alcoholic liver disease (ALD). A mitochondria-targeted lipophilic ubiquinone (MitoQ) has been shown to confer greater protection against oxidative damage in the mitochondria compared to untargeted antioxidants. The present study aimed to investigate if MitoQ could preserve mitochondrial ALDH2 activity and speed up acetaldehyde clearance, thereby protects against ALD. Male C57BL/6 J mice were exposed to alcohol for 8 weeks with MitoQ supplementation (5 mg/kg/d) for the last 4 weeks. MitoQ ameliorated alcohol-induced oxidative/nitrosative stress and glutathione deficiency. It also reversed alcohol-reduced hepatic ALDH activity and accelerated acetaldehyde clearance through modulating ALDH2 cysteine S-nitrosylation, tyrosine nitration and 4-hydroxynonenol adducts formation. MitoQ ameliorated nitric oxide (NO) donor-mediated ADLH2 S-nitrosylation and nitration in Hepa-1c1c7 cells under glutathion depletion condition. In addition, alcohol-increased circulating acetaldehyde levels were accompanied by reduced intestinal ALDH activity and impaired intestinal barrier. In accordance, MitoQ reversed alcohol-increased plasma endotoxin levels and hepatic toll-like receptor 4 (TLR4)-NF-κB signaling along with subsequent inhibition of inflammatory cell infiltration. MitoQ also reversed alcohol-induced hepatic lipid accumulation through enhancing fatty acid β-oxidation. Alcohol-induced ER stress and apoptotic cell death signaling were reversed by MitoQ. This study demonstrated that speeding up acetaldehyde clearance by preserving ALDH2 activity critically mediates the beneficial effect of MitoQ on alcohol-induced pathogenesis at the gut-liver axis.

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PTMs of ALDH2 participated in the pathogenesis of alcoholic liver disease.

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MitoQ treatment accelerated acetaldehyde detoxification.

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MitoQ ameliorated acetaldehyde-related tight junction disruption.

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MitoQ reversed TLR4-mediated inflammatory response in alcoholic liver disease.

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MitoQ counteracts alcohol-induced ER stress and cell apoptosis.

DUSP1 alleviates cardiac ischemia/reperfusion injury by suppressing the Mff-required mitochondrial fission and Bnip3-related mitophagy via the JNK pathways

Mitochondrial fission and selective mitochondrial autophagy (mitophagy) form an essential axis of mitochondrial quality control that plays a critical role in the development of cardiac ischemia-reperfusion (IR) injury. However, the precise upstream molecular mechanism of fission/mitophagy remains unclear. Dual-specificity protein phosphatase1 (DUSP1) regulates cardiac metabolism, but its physiological contribution in the reperfused heart, particularly its influence on mitochondrial homeostasis, is unknown. Here, we demonstrated that cardiac DUSP1 was downregulated following acute cardiac IR injury. In vivo, compared to wild-type mice, DUSP1 transgenic mice (DUSP1^TG mice) demonstrated a smaller infarcted area and the improved myocardial function. In vitro, the IR-induced DUSP1 deficiency promoted the activation of JNK which upregulated the expression of the mitochondrial fission factor (Mff). A higher expression level of Mff was associated with elevated mitochondrial fission and mitochondrial apoptosis. Additionally, the loss of DUSP1 also amplified the Bnip3 phosphorylated activation via JNK, leading to the activation of mitophagy. Increased mitophagy overtly consumed mitochondrial mass resulting into the mitochondrial metabolism disorder. However, the reintroduction of DUSP1 blunted Mff/Bnip3 activation and therefore alleviated the fatal mitochondrial fission/mitophagy by inactivating the JNK pathway, providing a survival advantage to myocardial tissue following IR stress. The results of our study suggest that DUSP1 and its downstream JNK pathway are therapeutic targets for conferring protection against IR injury by repressing Mff-mediated mitochondrial fission and Bnip3-required mitophagy.

Pharmacologic Approaches to Improve Mitochondrial Function in AKI and CKD

AKI is associated with high morbidity and mortality, and it predisposes to the development and progression of CKD. Novel strategies that minimize AKI and halt the progression of CKD are urgently needed. Normal kidney function involves numerous different cell types, such as tubular epithelial cells, endothelial cells, and podocytes, working in concert. This delicate balance involves many energy-intensive processes. Fatty acids are the preferred energy substrates for the kidney, and defects in fatty acid oxidation and mitochondrial dysfunction are universally involved in diverse causes of AKI and CKD. This review provides an overview of ATP production and energy demands in the kidney and summarizes preclinical and clinical evidence of mitochondrial dysfunction in AKI and CKD. New therapeutic strategies targeting mitochondria protection and cellular bioenergetics are presented, with emphasis on those that have been evaluated in animal models of AKI and CKD. Targeting mitochondrial function and cellular bioenergetics upstream of cellular damage may offer advantages compared with targeting downstream inflammatory and fibrosis processes.

microRNA-383 mediates high glucose-induced oxidative stress and apoptosis in retinal pigment epithelial cells by repressing peroxiredoxin 3

Hyperglycemia-mediated damage to retinal pigment epithelial (RPE) cells plays a central role in the pathogenesis of diabetic retinopathy. Dysregulation of microRNA (miR)-383 modulates pancreatic beta cell survival in diabetes; however, its role in diabetic retinopathy remains unclear. In this study, we examined the expression of miR-383 in ARPE-19 human RPE cell lines after high glucose treatment and investigated its functions in high glucose-induced reactive oxygen species (ROS) generation and apoptotic responses. The downstream target gene that mediated the action of miR-383 was functionally characterized. It was found that high glucose induced a 2.4-fold increase in miR-383 abundance, compared to ARPE-19 cells treated with normal glucose. Overexpression of miR-383 inhibited cell viability and promoted apoptosis and ROS formation in ARPE-19 cells, which was coupled with deregulation of Bcl-2 and Bax. Peroxiredoxin 3 (PRDX3) expression was repressed by miR-383 in ARPE-19 cells. Restoration of PRDX3 counteracted miR-383-induced ROS generation and apoptosis, while silencing of PRDX3 phenocopied the detrimental effects of miR-383 on ARPE-19 cells. Delivery of anti-miR-383 inhibitors led to an increase of PRDX3 expression and prevented high glucose-elicited ROS formation and apoptosis in ARPE-19 cells. Overall, miR-383 upregulation accounts for high glucose-induced oxidative stress and apoptosis in RPE cells by repressing PRDX3 expression. Targeting miR-383 may have therapeutic potential in the treatment of diabetic retinopathy.