The mitochondria-targeted antioxidant MitoQ ameliorated tubular injury mediated by mitophagy in diabetic kidney disease via Nrf2/PINK1
TL;DR: It is suggested that mitoQ exerts beneficial effects on tubular injury in DKD via mitophagy and that mitochondrial quality control is mediated by Nrf2/PINK.
Abstract: Mitochondria play a crucial role in tubular injury in diabetic kidney disease (DKD). MitoQ is a mitochondria-targeted antioxidant that exerts protective effects in diabetic mice, but the mechanism underlying these effects is not clear. We demonstrated that mitochondrial abnormalities, such as defective mitophagy, mitochondrial reactive oxygen species (ROS) overexpression and mitochondrial fragmentation, occurred in the tubular cells of db/db mice, accompanied by reduced PINK and Parkin expression and increased apoptosis. These changes were partially reversed following an intraperitoneal injection of mitoQ. High glucose (HG) also induces deficient mitophagy, mitochondrial dysfunction and apoptosis in HK-2 cells, changes that were reversed by mitoQ. Moreover, mitoQ restored the expression, activity and translocation of HG-induced NF-E2-related factor 2 (Nrf2) and inhibited the expression of Kelch-like ECH-associated protein (Keap1), as well as the interaction between Nrf2 and Keap1. The reduced PINK and Parkin expression noted in HK-2 cells subjected to HG exposure was partially restored by mitoQ. This effect was abolished by Nrf2 siRNA and augmented by Keap1 siRNA. Transfection with Nrf2 siRNA or PINK siRNA in HK-2 cells exposed to HG conditions partially blocked the effects of mitoQ on mitophagy and tubular damage. These results suggest that mitoQ exerts beneficial effects on tubular injury in DKD via mitophagy and that mitochondrial quality control is mediated by Nrf2/PINK.
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TL;DR: The results of this 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.
Abstract: 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 (DUSP1TG 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.
307 citations
Cites background from "The mitochondria-targeted antioxida..."
...The mitochondrial quantity is maintained via mitochondrial dynamics and/or the selective clearance of damaged organelles [49]....
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TL;DR: It is postulate that the diabetic milieu and inherited factors that underlie abnormalities in mitochondrial function synergistically drive the development and progression of DKD.
Abstract: 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.
285 citations
TL;DR: It is demonstrated that PINK1-Parkin–mediated mitophagy played a protective role in CI-AKI by reducing NLRP3 inflammasome activation and preventing RTEC apoptosis, tissue damage, mitochondrial damage, and renal injury under contrast exposure were more severe in Pink1- or PARK2-deficient cells and mice than in wild-type groups.
Abstract: Contrast-induced acute kidney injury (CI-AKI) occurs in more than 30% of patients after intravenous iodinated contrast media and causes serious complications, including renal failure and mortality. Recent research has demonstrated that routine antioxidant and alkaline therapy failed to show benefits in CI-AKI patients with high risk for renal complications. Mitophagy is a mechanism of selective autophagy, which controls mitochondrial quality and mitochondrial reactive oxygen species (ROS) through degradation of damaged mitochondria. The role of mitophagy and its regulation of apoptosis in CI-AKI are poorly understood. In this study, we demonstrated that mitophagy was induced in renal tubular epithelial cells (RTECs) during CI-AKI, both in vivo and in vitro. Meanwhile, contrast media-induced mitophagy was abolished when silencing PINK1 or PARK2 (Parkin), indicating a dominant role of the PINK1-Parkin pathway in mitophagy. Moreover, mitochondrial damage, mitochondrial ROS, RTEC apoptosis, and renal injury under contrast exposure were more severe in PINK1- or PARK2-deficient cells and mice than in wild-type groups. Functionally, PINK1-Parkin-mediated mitophagy prevented RTEC apoptosis and tissue damage in CI-AKI through reducing mitochondrial ROS and subsequent NLRP3 inflammasome activation. These results demonstrated that PINK1-Parkin-mediated mitophagy played a protective role in CI-AKI by reducing NLRP3 inflammasome activation.
270 citations
TL;DR: The 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.
Abstract: 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.
230 citations
Cites background or methods from "The mitochondria-targeted antioxida..."
...The mice were sacrificed at 24 weeks of age, and the kidneys were harvested as discussed previously [22]....
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...Moreover, previous studies by our laboratory and others have shown that mitochondrial ROS production plays a key role in the development of DN [22,26,41]....
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...HK-2 cells were pre-transfected with TXNIP or TRX siRNA using Lipofectamine 2000 (Life Technologies, USA), as previously described [22]....
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...MitoQ protects against a range of oxidation-related diseases, including cardiovascular disease [19], metabolic syndrome [20], Alzheimer's disease [21] and DN [22]....
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...Kidney tissue sections from humans or mice were prepared for IHC, as described in ref [22]....
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TL;DR: The data show that high-fat-mediated liver damage is associated with Sirt3 downregulation, which is followed by ERK-CREB pathway inactivation and Bnip3-mediated inhibition of mitophagy, causing hepatocytes to undergo mitochondria-dependent cell death.
Abstract: Increased mitochondrial damage is related to the progression of a diet-induced nonalcoholic fatty liver disease. The aim of our study is to investigate the role of Sirtuin 3 (Sirt3) in treating nonalcoholic fatty liver disease with a focus on mitophagy and the ERK-CREB pathway. Our data indicated that Sirt3 was downregulated in liver tissue in response to chronic HFD treatment. Interestingly, re-introduction of Sirt3 protected hepatic function, attenuated liver fibrosis, alleviated the inflammatory response, and prevented hepatocyte apoptosis. Molecular investigations demonstrated that lipotoxicity was associated with an increase in mitochondrial apoptosis as evidenced by reduced mitochondrial potential, augmented ROS production, increased cyt-c leakage into the nucleus, and activated caspase-9 apoptotic signalling. Additionally, Sirt3 overexpression protected hepatocytes against mitochondrial apoptosis via promoting Bnip3-required mitophagy. Functional studies showed that Sirt3 reversed Bnip3 expression and mitophagy activity via the ERK-CREB signalling pathway. Blockade of the ERK-CREB axis repressed the promotive effects of Sirt3 on Bnip3 activation and mitophagy augmentation, finally negating the anti-apoptotic influences of Sirt3 on hepatocytes in the setting of high-fat-stress. Collectively, our data show that high-fat-mediated liver damage is associated with Sirt3 downregulation, which is followed by ERK-CREB pathway inactivation and Bnip3-mediated inhibition of mitophagy, causing hepatocytes to undergo mitochondria-dependent cell death. Based on this, strategies for enhancing Sirt3 activity and activating the ERK-CREB-Bnip3-mitophagy pathways could be used to treat nonalcoholic fatty liver disease.
211 citations
Cites background from "The mitochondria-targeted antioxida..."
...In liver ischaemia-reperfusion injury, Sirt3 is unfortunately downregulated, whereas exogenous administration of Sirt3 attenuates reperfusion-mediated liver damage via maintaining mitochondrial calcium homeostasis and energetic balance [22,23]....
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References
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TL;DR: Inhibition of mitochondria ATPase likely accounts for the cytotoxicity of Rhodamine 123, a sensitive and specific probe of delta psi in isolated mitochondria at concentrations which do not inhibit mitochondrial function.
780 citations
"The mitochondria-targeted antioxida..." refers methods in this paper
...[27] Nrf2-antioxidant response element (ARE) binding was measured using a TransAM Nrf2 Kit (active motif), as previously described....
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TL;DR: In vivo and in vitro models of ischemia-reperfusion demonstrated autophagy induction during hypoxic and ischemic renal injury and suggested that under these pathological conditions,autophagy may provide a protective mechanism for cell survival.
Abstract: Autophagy mediates bulk degradation and recycling of cytoplasmic constituents to maintain cellular homeostasis. In response to stress, autophagy is induced and may either contribute to cell death or serve as a cell survival mechanism. Very little is known about autophagy in renal pathophysiology. This study examined autophagy and its pathological role in renal cell injury using in vitro and in vivo models of ischemia−reperfusion. We found that hypoxia (1% O2) induced autophagy in cultured renal proximal tubular cells. Blockade of autophagy by 3-methyladenine or small-interfering RNA knockdown of Beclin-1 and ATG5 (two key autophagic genes) sensitized the tubular cells to hypoxia-induced apoptosis. In an in vitro model of ischemia−reperfusion, autophagy was not induced by anoxic (0% O2) incubation in glucose-free buffer, but was induced during subsequent recovery/reperfusion period. In this model, suppression of autophagy also enhanced apoptosis. In vivo, autophagy was induced in kidney tissues during renal ischemia−reperfusion in mice. Autophagy was not obvious during the ischemia period, but was significantly enhanced during reperfusion. Inhibition of autophagy by chloroquine and 3-methyladenine worsened renal ischemia/reperfusion injury, as indicated by renal function, histology, and tubular apoptosis. Together, the results demonstrated autophagy induction during hypoxic and ischemic renal injury. Under these pathological conditions, autophagy may provide a protective mechanism for cell survival.
347 citations
"The mitochondria-targeted antioxida..." refers methods in this paper
...[3,26] Briefly, we fixed dissected renal cortices with 2....
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TL;DR: Administration of the mitochondria-targeted antioxidant MitoQ10 protects against the development of hypertension, improves endothelial function, and reduces cardiac hypertrophy in young stroke-prone spontaneously hypertensive rats and provides a novel approach to attenuate mitochondrial-specific oxidative damage.
Abstract: Mitochondria are a major site of reactive oxygen species production, which may contribute to the development of cardiovascular disease. Protecting mitochondria from oxidative damage should be an effective therapeutic strategy; however, conventional antioxidants are ineffective, because they cannot penetrate the mitochondria. This study investigated the role of mitochondrial oxidative stress during development of hypertension in the stroke-prone spontaneously hypertensive rat, using the mitochondria-targeted antioxidant, MitoQ(10). Eight-week-old male stroke-prone spontaneously hypertensive rats were treated with MitoQ(10) (500 mumol/L; n=16), control compound decyltriphenylphosphonium (decylTPP; 500 mumol/L; n=8), or vehicle (n=9) in drinking water for 8 weeks. Systolic blood pressure was significantly reduced by approximately 25 mm Hg over the 8-week MitoQ(10) treatment period compared with decylTPP (F=5.94; P=0.029) or untreated controls (F=65.6; P=0.0001). MitoQ(10) treatment significantly improved thoracic aorta NO bioavailability (1.16+/-0.03 g/g; P=0.002, area under the curve) compared with both untreated controls (0.68+/-0.02 g/g) and decylTPP-treated rats (0.60+/-0.06 g/g). Cardiac hypertrophy was significantly reduced by MitoQ(10) treatment compared with untreated control and decylTPP treatment (MitoQ(10): 4.01+/-0.05 mg/g; control: 4.42+/-0.11 mg/g; and decylTPP: 4.40+/-0.09 mg/g; ANOVA P=0.002). Total MitoQ(10) content was measured in liver, heart, carotid artery, and kidney harvested from MitoQ(10)-treated rats by liquid chromatography-tandem mass spectrometry. All of the organs analyzed demonstrated detectable levels of MitoQ(10), with comparable accumulation in vascular and cardiac tissues. Administration of the mitochondria-targeted antioxidant MitoQ(10) protects against the development of hypertension, improves endothelial function, and reduces cardiac hypertrophy in young stroke-prone spontaneously hypertensive rats. MitoQ(10) provides a novel approach to attenuate mitochondrial-specific oxidative damage with the potential to become a new therapeutic intervention in human cardiovascular disease.
322 citations
TL;DR: The mitochondria‐targeted anti‐oxidant mitoquinone combines a potent anti‐ oxidant with a lipophilic cation that causes it to accumulate several‐hundred fold within mitochondria in vivo.
Abstract: Background: Increased oxidative stress and subsequent mitochondrial damage are important pathways for liver damage in chronic hepatitis C virus (HCV) infection; consequently, therapies that decrease mitochondrial oxidative damage may improve outcome. The mitochondria-targeted anti-oxidant mitoquinone combines a potent anti-oxidant with a lipophilic cation that causes it to accumulate several-hundred fold within mitochondria in vivo.
Aims: In this phase II study, we investigated the effect of oral mitoquinone on serum aminotransferases and HCV RNA levels in HCV-infected patients.
Methods: Thirty HCV patients who were either non-responders or unsuitable candidates for standard-of-care (pegylated interferon plus ribavirin) were randomized to receive mitoquinone (40 or 80 mg) or placebo once daily for 28 days, and serum aminotransferases and HCV RNA levels were measured.
Results: Both treatment groups showed significant decreases in absolute and percentage changes in serum alanine transaminase (ALT) from baseline to treatment day 28 (P 0.05). There was no change in HCV load on mitoquinone treatment.
Conclusions: Administration of the mitochondria-targeted anti-oxidant mitoquinone significantly decreased plasma ALT and aspartate aminotransferase in patients with chronic HCV infection, and this suggests that mitoquinone may decrease necroinflammation in the liver in these patients. As mitochondrial oxidative damage contributes to many other chronic liver diseases, such as steatohepatitis, further studies using mitochondria-targeted anti-oxidants in HCV and other liver diseases are warranted.
312 citations
"The mitochondria-targeted antioxida..." refers background in this paper
...[19] Emerging data indicate that mitoQ may exert beneficial effects on tubular injury under various conditions....
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TL;DR: A literature review summarizes the current knowledge on mitochondria-targeted antioxidants and their contribution to the body's antioxidant defense system, including promising therapeutic agents and new strategic approaches.
Abstract: Redox homeostasis is maintained by the antioxidant defense system, which is responsible for eliminating a wide range of oxidants, including reactive oxygen species (ROS), lipid peroxides, and metals. Mitochondria-localized antioxidants are widely studied because the mitochondria, the major producers of intracellular ROS, have been linked to the cause of aging and other chronic diseases. Mitochondria-targeted antioxidants have shown great potential because they cross the mitochondrial phospholipid bilayer and eliminate ROS at the heart of the source. Growing evidence has identified mitochondria-targeted antioxidants, such as MitoQ and tiron, as potentially effective antioxidant therapies against the damage caused by enhanced ROS generation. This literature review summarizes the current knowledge on mitochondria-targeted antioxidants and their contribution to the body's antioxidant defense system. In addition to addressing the concerns surrounding current antioxidant strategies, including difficulties in targeting antioxidant treatment to sites of pathologic oxidative damage, we discuss promising therapeutic agents and new strategic approaches.
285 citations