MiR-6918-5p prevents renal tubular cell apoptosis by targeting MBD2 in ischemia/reperfusion-induced AKI.

AIMS: Although previous studies reported that miRNAs are involved in the progression of acute kidney injury (AKI), their exact function and mechanism in ischemic AKI remains largely unknown. This study aims to define the role of miR-6918-5p in ischemia-reperfusion AKI. Materials and methods The renal arteries of C57BL/6J mice were clamped to establish a model of ischemia-reperfusion renal injury. BUMPT cells were added with Antimycin A and calcium ionophore to establish a model of ATP depletion in vitro. Cell apoptosis was detected by CCK8, flow cytometry and western blot, while HE staining and TUNEL staining were used to assess the degree of kidney damage. KEY FINDINGS: We suppressed mmu_miR-6918-5p by ischemic injury in vitro and in vivo. We found that ischemia-reperfusion (I/R)-induced renal tubular cell apoptosis and the expression of cleaved caspase3 were enhanced by the inhibitor of mmu_miR-6918-5p; this effect was attenuated by an mmu_miR-6918-5p mimic. Mechanistically, mmu_miR-6918-5p binds to the 3' UTR region of MBD2 and represses its expression. The mmu_miR-6918-5p mimic alleviated the ischemic AKI by targeting MBD2. Conversely, the inhibitor of mmu_miR-6918-5p enhanced the ischemic AKI; this was diminished by MBD2-KO. SIGNIFICANCE: Mmu_miR-6918-5p protected against the development of ischemic AKI by targeting MBD2.

Eixo XPC-P53-H202 e disfunção mitocondrial: qual é o fator central? / XPC-p53-H2O2 axis and mitochondrial disfunction: Which is the key player

A ausência de XPC, uma proteína canonicamente envolvida em reparo de DNA por excisão de nucleotídeos, está associada a vários fenótipos característicos de disfunção mitocondrial como o desequilíbrio entre os complexos da cadeia transportadora de elétrons (CTE), redução no consumo de oxigênio, maior produção de peróxido de hidrogênio, e maior sensibilidade a agentes que causam estresse mitocondrial. Contudo, uma descrição mecanística da relação entre deficiência de XPC e disfunção mitocondrial ainda não está bem estabelecida. Aqui mostramos que a deficiência de XPC está associada ao aumento na expressão do supressor de tumor p53. Essa alteração é acompanhada pelo aumento da expressão de diversas proteínas que participam em importantes funções mitocondriais. A inibição de p53 reverte a superexpressão de algumas dessas proteínas. O tratamento com o inibidor do Complexo III da CTE antimicina A induz aumento da expressão de p53 de forma mais acentuada na linhagem Xpc-/-, enquanto o tratamento com o antioxidante N-acetilcisteína diminue a produção basal de H2O2, expressão de p53 e sensibilidade aumentada ao tratamento com antimicina A. Em conjunto, nossos resultados suportam a hipótese de que o aumento da produção de H2O2 em células Xpc-/- tem um papel causal na regulação da expressão de p53 e na disfunção mitocondrial

Although XPC has been initially implicated in the nucleotide excision DNA repair pathway, its deficiency is associated with mitochondrial dysfunction, including unbalanced electron transport chain (ETC) activity, lower oxygen consumption, increased hydrogen peroxide production, and greater sensitivity to mitochondrial stress. However, a mechanistic understanding of the role of XPC in regulating mitochondrial function is still not well established. Here we show that XPC deficiency is associated with increased expression of the tumor suppressor p53, which is accompanied by increased expression of several proteins that participate in important mitochondrial functions. Inhibition of p53 reverses the overexpression of some of these proteins. In addition, treatment with the ETC inhibitor antimycin A induces p53 expression more robustly in the Xpc-/- cells, while treatment with the antioxidant N-acetylcysteine decreases basal H2O2 production, p53 expression and sensitivity to antimycin A treatment. Together, our results support a model in which increased H2O2 production in Xpc-/- causes upregulation of p53 expression and mitochondrial dysfunction

Paeoniflorin isolated from Paeonia lactiflora attenuates osteoblast cytotoxicity induced by antimycin A.

The protective effects of paeoniflorin isolated from Paeonia lactiflora against pharmacological inhibition of the respiratory chain were studied using osteoblastic MC3T3-E1 cells. Here we show that paeoniflorin decreases cell death induced by antimycin A, an inhibitor of mitochondrial complex III. Paeoniflorin restored antimycin A-induced inactivation of phosphoinositide 3-kinase (PI3K) and thioredoxin reductase, suggesting that PI3K and thioredoxin reductase may be involved in paeoniflorin-induced cytoprotective responses. We also examined the effect of paeoniflorin on mitochondrial dysfunction and oxidative stress induced by antimycin A. Paeoniflorin inhibited mitochondrial membrane potential dissipation, ATP loss, inactivation of complexes I and IV, cytochrome c release, and cardiolipin oxidation induced by antimycin A. In addition, paeoniflorin prevented antimycin A-induced ROS release and nitrotyrosine increase. These results imply that paeoniflorin protects osteoblasts from antimycin A-induced cell death via improved mitochondrial function.

The effects of dehydrocostus lactone on osteoblastic MC3T3-E1 cells in redox changes and PI3K/Akt/CREB.

Antimycin A (AMA) inhibits mitochondrial electron transport chain between cytochrome b and c. In the present study, we investigated the effects of dehydrocostus lactone on osteoblastic MC3T3-E1 cells in the presence of AMA with a focus on redox changes and PI3K/Akt/CREB signaling. AMA increased nitrotyrosin level and decreased NADPH level, activities of thioredoxin reductase, phosphoinositide 3-kinase (PI3K), and Akt (protein kinase B [PKB]), and phosphorylated cAMP-response element-binding protein (CREB). Pretreatment with dehydrocostus lactone prior to AMA exposure significantly prevented the loss of NADPH, production of nitrotyrosine, and thioredoxin reductase inactivation induced by AMA. Moreover, dehydrocostus lactone increased activities of PI3K and Akt, and CREB phosphorylation inhibited by AMA. These results suggest that antioxidant activity and PI3K/Akt/CREB activation are related to the protective effect of dehydrocostus lactone against osteoblast damage induced by AMA.

Honokiol protects osteoblastic MC3T3-E1 cells against antimycin A-induced cytotoxicity.

OBJECTIVE: Honokiol is a phenolic compound isolated from the bark of Magnolia officinalis, a plant widely used in traditional medicine. Antimycin A, which inhibits complex III of the electron transport system, has been used as a reactive oxygen species generator in biological systems. In the present study, we investigated the protective effects of honokiol on antimycin A-induced dysfunction in osteoblastic MC3T3-E1 cells. MATERIALS AND METHODS: Osteoblastic MC3T3-E1 cells were pre-incubated with honokiol before treatment with antimycin A, and markers of mitochondrial function and oxidative damage were examined. In addition, the effects of honokiol on the activation of PI3K (phosphoinositide 3-kinase) and CREB (cAMP-responsive element-binding protein) were examined in MC3T3-E1 cells. RESULTS: Honokiol significantly (P < 0.05) increased cell viability and calcium deposition and decreased the production of ROS in the presence of antimycin A. Moreover, pretreatment with honokiol prior to antimycin A exposure significantly reduced antimycin A-induced mitochondrial membrane potential (MMP) dissipation, complex IV inactivation, nitrotyrosine formation, and thioredoxin reductase inactivation. Honokiol also induced the activation of PI3K and CREB inhibited by antimycin A, which demonstrates that honokiol utilizes the PI3K and CREB pathway to augment metabolic activity inhibited by antimycin A. CONCLUSION: Honokiol may reduce or prevent osteoblast degeneration in osteoporosis or other degenerative disorders.

[Alpha-tocopherol prevents thymocyte death induced by antimycin A and oligomycin in rats].

The influence of a-tocopherol, its structure analogues--alpha-tocopheryl acetate and a-tocopheryl quinone, ubiquinone (Q10), and also antioxidants quercetin and N-acetyl-L-cysteine on rat thymocytes apoptosis and necrosis induced by antimycin A and oligomyci, accordingly, was investigated. It was established that alpha-tocopherol completely restored the thymocytes survival independent of production of reactive oxygen species (ROS) by them. The degree of inhibition of ROS generation by the antioxidants having different antiradical activity did not correlate with their influence on thymocytes survival. Quercetin and N-acetyl-L-cysteine reducing, to the greatest degree, the ROS level rendered the least effect on cell survival. Taken together, these results demonstrate that the ability of alpha-tocopherol to effectively prevent the rat thymocytes antimycin A- and oligomycin-induced death is not determined by its antioxidant activity, but is possibly conditioned by prevention of mitochondrial dysfunction by stabilisation of mitochondrial membranes and modulation ofbioenergetic processes.

Increased production of mitochondrial superoxide in the spinal cord induces pain behaviors in mice: the effect of mitochondrial electron transport complex inhibitors.

Scavengers of reactive oxygen species (ROS) have been shown to produce a strong antinociceptive effect on persistent pain, and mitochondria are suggested to be the main source of ROS in the spinal dorsal horn. To explore whether excessive generation of mitochondrial superoxide alone can induce pain, the effect of mitochondrial electron transport complex inhibitors on the development of mechanical hyperalgesia was examined in mice. Intrathecal injection of an electron transport complex inhibitor, antimycin A or rotenone, in normal mice resulted in a slowly developing but long-lasting and dose-dependent mechanical hyperalgesia. The levels of mechanical hyperalgesia after antimycin A, a complex III inhibitor, were higher than that with rotenone, a complex I inhibitor. A large increase of mitochondrial superoxide in the spinal dorsal horn and a strong antinociceptive effect of ROS scavengers, phenyl-N-tert-butylnitrone (PBN) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) were observed in antimycin A-treated mice. The study indicates that the enhanced production of spinal mitochondrial superoxide alone without nerve injury can produce mechanical hyperalgesia.

Oxidant regulation of gene expression and neural tube development: Insights gained from diabetic pregnancy on molecular causes of neural tube defects.

AIMS/HYPOTHESIS: Maternal diabetes increases oxidative stress in embryos. Maternal diabetes also inhibits expression of embryonic genes, most notably, Pax-3, which is required for neural tube closure. Here we tested the hypothesis that oxidative stress inhibits expression of Pax-3, thereby providing a molecular basis for neural tube defects induced by diabetic pregnancy. METHODS: Maternal diabetes-induced oxidative stress was blocked with alpha-tocopherol (vitamin E), and oxidative stress was induced with the complex III electron transport inhibitor, antimycin A, using pregnant diabetic or non-diabetic mice, primary cultures of neurulating mouse embryo tissues, or differentiating P19 embryonal carcinoma cells. Pax-3 expression was assayed by quantitative RT-PCR, and neural tube defects were scored by visual inspection. Oxidation-induced DNA fragmentation in P19 cells was assayed by electrophoretic analysis. RESULTS: Maternal diabetes inhibited Pax-3 expression and increased neural tube defects, and alpha-tocopherol blocked these effects. In addition, induction of oxidative stress with antimycin A inhibited Pax-3 expression and increased neural tube defects. In cultured embryo tissues, high glucose-inhibited Pax-3 expression, and this effect was blocked by alpha-tocopherol and GSH-ethyl ester, and Pax-3 expression was inhibited by culture with antimycin A. In differentiating P19 cells, antimycin A inhibited Pax-3 induction but did not induce DNA strand breaks. CONCLUSION/INTERPRETATION: Oxidative stress inhibits expression of Pax-3, a gene that is essential for neural tube closure. Impaired expression of essential developmental control genes could be the central mechanism by which neural tube defects occur during diabetic pregnancy, as well as other sources of oxidative stress.

Grape seed proanthocyanidin extract attenuates oxidant injury in cardiomyocytes.

This study sought to test whether grape seed proanthocyanidin extract (GSPE) attenuates exogenous and endogenous oxidant stress induced in chick cardiomyocytes and whether this cytoprotection is mediated by PKC activation, mito K(ATP) channel opening, NO production, oxidant scavenging, or iron chelating effects. Cells were exposed to hydrogen peroxide (H(2)O(2)) (exogenous oxidant stress, 0.5mM) or antimycin A (endogenous oxidant stress, 100 micro M) for 2h following pretreatment with GSPE at various concentrations for 2h. Cells were also pretreated with GSPE or with inhibitors of PKC (chelerytherine), mito K(ATP) channel (5-hydroxydecanoate), nitric oxide synthase (nitro-L-arginine methyl ester) for 2h. Oxidant stress was measured by 2',7'-dichlorofluorescin diacetate and cell viability was assessed using propidium iodide. Free radical scavenging and iron chelating ability was tested in vitro. GSPE dose-dependently attenuated oxidant formation and significantly improved cell survival and contractile function. However, inhibitors of PKC, mito K(ATP) channel or NO synthase failed to abolish the protective action of GSPE during H(2)O(2) or antimycin A exposure. In vitro studies suggested that GSPE scavenges H(2)O(2), hydroxyl radical and superoxide, and may chelate iron. These results indicate that GSPE confers cardioprotection against exogenous H(2)O(2)- or antimycin A-induced oxidant injury. Its effect does not require PKC, mito K(ATP) channel, or NO synthase, presumably because it acts by reactive oxygen species scavenging and iron chelating directly.