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MYC is a highly pleiotropic transcription factor whose deregulation promotes cancer. In contrast, we find that Myc haploinsufficient (Myc(+/-)) mice exhibit increased lifespan. They show resistance to several age-associated pathologies, including osteoporosis, cardiac fibrosis, and immunosenescence. They also appear to be more active, with a higher metabolic rate and healthier lipid metabolism. Transcriptomic analysis reveals a gene expression signature enriched for metabolic and immune processes. The ancestral role of MYC as a regulator of ribosome biogenesis is reflected in reduced protein translation, which is inversely correlated with longevity. We also observe changes in nutrient and energy sensing pathways, including reduced serum IGF-1, increased AMPK activity, and decreased AKT, TOR, and S6K activities. In contrast to observations in other longevity models, Myc(+/-) mice do not show improvements in stress management pathways. Our findings indicate that MYC activity has a significant impact on longevity and multiple aspects of mammalian healthspan.
Assuntos
Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Envelhecimento , Animais , Tamanho Corporal , Feminino , Longevidade , Linfoma/genética , Masculino , Redes e Vias Metabólicas , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , TranscriptomaRESUMO
Invariant NKT (iNKT) cells are a group of innate-like T cells that plays important roles in immune homeostasis and activation. We found that iNKT cells, compared with CD4+ T cells, have significantly higher levels of lipid peroxidation in both mice and humans. Proteomic analysis also demonstrated that iNKT cells express higher levels of phospholipid hydroperoxidase glutathione peroxidase 4 (Gpx4), a major antioxidant enzyme that reduces lipid peroxidation and prevents ferroptosis. T cell-specific deletion of Gpx4 reduces iNKT cell population, most prominently the IFN-γ-producing NKT1 subset. RNA-sequencing analysis revealed that IFN-γ signaling, cell cycle regulation, and mitochondrial function are perturbed by Gpx4 deletion in iNKT cells. Consistently, we detected impaired cytokine production, elevated cell proliferation and cell death, and accumulation of lipid peroxides and mitochondrial reactive oxygen species in Gpx4 knockout iNKT cells. Ferroptosis inhibitors, iron chelators, vitamin E, and vitamin K2 can prevent ferroptosis induced by Gpx4 deficiency in iNKT cells and ameliorate the impaired function of iNKT cells due to Gpx4 inhibition. Last, vitamin E rescues iNKT cell population in Gpx4 knockout mice. Altogether, our findings reveal the critical role of Gpx4 in regulating iNKT cell homeostasis and function, through controlling lipid peroxidation and ferroptosis.
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Cognitive decline is a debilitating aspect of aging and neurodegenerative diseases such as Alzheimer's disease are closely associated with mitochondrial dysfunction, increased reactive oxygen species, neuroinflammation, and astrogliosis. This study investigated the effects of decreased mitochondrial antioxidant response specifically in astrocytes on cognitive performance and neuronal function in C57BL/6J mice using a tamoxifen-inducible astrocyte-specific knockout of manganese superoxide dismutase (aSOD2-KO), a mitochondrial matrix antioxidant that detoxifies superoxide generated during mitochondrial respiration. We reduced astrocyte SOD2 levels in male and female mice at 11-12 months of age and tested in an automated home cage (PhenoTyper) apparatus for diurnal patterns, spatial learning, and memory function at 15 months of age. aSOD2-KO impaired hippocampal-dependent spatial working memory and decreased cognitive flexibility in the reversal phase of the testing paradigm in males. Female aSOD2-KO showed no learning and memory deficits compared with age-matched controls despite significant reduction in hippocampal SOD2 expression. aSOD2-KO males further showed decreased hippocampal long-term potentiation, but paired-pulse facilitation was unaffected. Levels of d-serine, an NMDA receptor coagonist, were also reduced in aSOD2-KO mice, but female knockouts showed a compensatory increase in serine racemase expression. Furthermore, aSOD2-KO mice demonstrated increased density of astrocytes, indicative of astrogliosis, in the hippocampus compared with age-matched controls. These data demonstrate that reduction in mitochondrial antioxidant stress response in astrocytes recapitulates age-related deficits in cognitive function, d-serine availability, and astrogliosis. Therefore, improving astrocyte mitochondrial homeostasis may provide a therapeutic target for intervention for cognitive impairment in aging.SIGNIFICANCE STATEMENT Diminished antioxidant response is associated with increased astrogliosis in aging and in Alzheimer's disease. Manganese superoxide dismutase (SOD2) is an antioxidant in the mitochondrial matrix that detoxifies superoxide and maintains mitochondrial homeostasis. We show that astrocytic ablation of SOD2 impairs hippocampal-dependent plasticity in spatial working memory, reduces long-term potentiation of hippocampal neurons and levels of the neuromodulator d-serine, and increases astrogliosis, consistent with defects in advanced aging and Alzheimer's disease. Our data provide strong evidence for sex-specific effects of astrocytic SOD2 functions in age-related cognitive dysfunction.
Assuntos
Doença de Alzheimer , Astrócitos , Superóxido Dismutase , Doença de Alzheimer/metabolismo , Animais , Antioxidantes/metabolismo , Astrócitos/metabolismo , Cognição/fisiologia , Feminino , Gliose/metabolismo , Hipocampo/metabolismo , Masculino , Memória de Curto Prazo , Camundongos , Camundongos Endogâmicos C57BL , Serina/metabolismo , Fatores Sexuais , Superóxido Dismutase/genética , Superóxidos/metabolismoRESUMO
Our laboratory previously showed lipid hydroperoxides and oxylipin levels are elevated in response to loss of skeletal muscle innervation and are associated with muscle pathologies. To elucidate the pathological impact of lipid hydroperoxides, we overexpressed glutathione peroxidase 4 (GPx4), an enzyme that targets reduction of lipid hydroperoxides in membranes, in adult CuZn superoxide dismutase knockout (Sod1KO) mice that show accelerated muscle atrophy associated with loss of innervation. The gastrocnemius muscle from Sod1KO mice shows reduced mitochondrial respiration and elevated oxidative stress (F2 -isoprostanes and hydroperoxides) compared to wild-type (WT) mice. Overexpression of GPx4 improved mitochondrial respiration and reduced hydroperoxide generation in Sod1KO mice, but did not attenuate the muscle loss that occurs in Sod1KO mice. In contrast, contractile force generation is reduced in EDL muscle in Sod1KO mice relative to WT mice, and overexpression of GPx4 restored force generation to WT levels in Sod1KO mice. GPx4 overexpression also prevented loss of muscle contractility at the single fibre level in fast-twitch fibres from Sod1KO mice. Muscle fibres from Sod1KO mice were less sensitive to both depolarization and calcium at the single fibre level and exhibited a reduced activation by S-glutathionylation. GPx4 overexpression in Sod1KO mice rescued the deficits in both membrane excitability and calcium sensitivity of fast-twitch muscle fibres. Overexpression of GPx4 also restored the sarco/endoplasmic reticulum Ca2+ -ATPase activity in Sod1KO gastrocnemius muscles. These data suggest that GPx4 plays an important role in preserving excitation-contraction coupling function and Ca2+ homeostasis, and in maintaining muscle and mitochondrial function in oxidative stress-induced sarcopenia. KEY POINTS: Knockout of CuZn superoxide dismutase (Sod1KO) induces elevated oxidative stress with accelerated muscle atrophy and weakness. Glutathione peroxidase 4 (GPx4) plays a fundamental role in the reduction of lipid hydroperoxides in membranes, and overexpression of GPx4 improves mitochondrial respiration and reduces hydroperoxide generation in Sod1KO mice. Muscle contractile function deficits in Sod1KO mice are alleviated by the overexpression of GPx4. GPx4 overexpression in Sod1KO mice rescues the impaired muscle membrane excitability of fast-twitch muscle fibres and improves their calcium sensitivity. Sarco/endoplasmic reticulum Ca2+ -ATPase activity in Sod1KO muscles is decreased, and it is restored by the overexpression of GPx4. Our results confirm that GPx4 plays an important role in preserving excitation-contraction coupling function and Ca2+ homeostasis, and maintaining muscle and mitochondrial function in oxidative stress-induced sarcopenia.
Assuntos
Sarcopenia , Animais , Camundongos , Adenosina Trifosfatases/genética , Cálcio , Glutationa , Glutationa Peroxidase/genética , Peróxido de Hidrogênio , Lipídeos , Camundongos Knockout , Músculo Esquelético/fisiologia , Fenótipo , Fosfolipídeo Hidroperóxido Glutationa Peroxidase/genética , Superóxido Dismutase , Superóxido Dismutase-1/genéticaRESUMO
Skeletal muscle suffers atrophy and weakness with aging. Denervation, oxidative stress, and mitochondrial dysfunction are all proposed as contributors to age-associated muscle loss, but connections between these factors have not been established. We examined contractility, mitochondrial function, and intracellular calcium transients (ICTs) in muscles of mice throughout the life span to define their sequential relationships. We performed these same measures and analyzed neuromuscular junction (NMJ) morphology in mice with postnatal deletion of neuronal Sod1 (i-mn-Sod1-/- mice), previously shown to display accelerated age-associated muscle loss and exacerbation of denervation in old age, to test relationships between neuronal redox homeostasis, NMJ degeneration and mitochondrial function. In control mice, the amount and rate of the decrease in mitochondrial NADH during contraction was greater in middle than young age although force was not reduced, suggesting decreased efficiency of NADH utilization prior to the onset of weakness. Declines in both the peak of the ICT and force were observed in old age. Muscles of i-mn-Sod1-/- mice showed degeneration of mitochondrial and calcium handling functions in middle-age and a decline in force generation to a level not different from the old control mice, with maintenance of NMJ morphology. Together, the findings support the conclusion that muscle mitochondrial function decreases during aging and in response to altered neuronal redox status prior to NMJ deterioration or loss of mass and force suggesting mitochondrial defects contribute to sarcopenia independent of denervation.
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Envelhecimento , Cálcio/metabolismo , Mitocôndrias Musculares/patologia , Neurônios/patologia , Estresse Oxidativo , Sarcopenia/patologia , Superóxido Dismutase-1/fisiologia , Animais , Denervação , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias Musculares/metabolismo , Contração Muscular , Neurônios/metabolismo , Oxirredução , Sarcopenia/etiologiaRESUMO
Sarcopenia has a significant negative impact on healthspan in the elderly and effective pharmacologic interventions remain elusive. We have previously demonstrated that sarcopenia is associated with reduced activity of the sarcoplasmic reticulum Ca2+ ATPase (SERCA) pump. We asked whether restoring SERCA activity using pharmacologic activation in aging mice could mitigate the sarcopenia phenotype. We treated 16-month male C57BL/6J mice with vehicle or CDN1163, an allosteric SERCA activator, for 10 months. At 26 months, maximal SERCA activity was reduced 41% in gastrocnemius muscle in vehicle-treated mice but maintained in old CDN1163 treated mice. Reductions in gastrocnemius mass (9%) and in vitro specific force generation in extensor digitorum longus muscle (11%) in 26 versus 16-month-old wild-type mice were also reversed by CDN1163. CDN1163 administered by intra-peritoneal injection also prevented the increase in mitochondrial ROS production in gastrocnemius muscles of aged mice. Transcriptomic analysis revealed that these effects are at least in part mediated by enhanced cellular energetics by activation of PGC1-α, UCP1, HSF1, and APMK and increased regenerative capacity by suppression of MEF2C and p38 MAPK signaling. Together, these exciting findings are the first to support that pharmacological targeting of SERCA can be an effective therapy to counter age-related muscle dysfunction.
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Aminoquinolinas/farmacologia , Benzamidas/farmacologia , Debilidade Muscular/prevenção & controle , Atrofia Muscular/prevenção & controle , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Fatores Etários , Aminoquinolinas/administração & dosagem , Animais , Benzamidas/administração & dosagem , Ativação Enzimática/efeitos dos fármacos , Injeções Intraperitoneais , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Camundongos Endogâmicos C57BL , Mitocôndrias Musculares/efeitos dos fármacos , Mitocôndrias Musculares/metabolismo , Debilidade Muscular/fisiopatologia , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Atrofia Muscular/metabolismo , Atrofia Muscular/fisiopatologia , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Espécies Reativas de Oxigênio/metabolismo , Proteína Desacopladora 1/metabolismoRESUMO
Skeletal muscle ageing is characterised by atrophy, a deficit in specific force generation, increased susceptibility to injury, and incomplete recovery after severe damage. The hypothesis that increased generation of reactive oxygen species (ROS) in vivo plays a key role in the ageing process has been extensively studied, but remains controversial. Skeletal muscle generates ROS at rest and during exercise. ROS can cause oxidative damage particularly to proteins. Indeed, products of oxidative damage accumulate in skeletal muscle during ageing and the ability of muscle cells to respond to increased ROS becomes defective. The aim of this review is to examine the evidence that ROS manipulation in peripheral nerves and/or muscle modifies mechanisms of proteostasis in skeletal muscle and plays a key role in initiating sarcopenia.
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Envelhecimento/fisiologia , Proteínas Musculares/metabolismo , Músculo Esquelético/inervação , Músculo Esquelético/metabolismo , Nervos Periféricos/fisiologia , Proteostase , Espécies Reativas de Oxigênio/metabolismo , Envelhecimento/metabolismo , Animais , Fragilidade/metabolismo , Humanos , Sarcopenia/metabolismoRESUMO
Chronic ethyl alcohol (EtOH) consumption results in reactive oxygen species (ROS) generation in bone and osteopenia due to increased bone resorption and reduced bone formation. In this study, transgenic C57Bl/6J mice overexpressing human catalase (TgCAT) were used to test whether limiting excess hydrogen peroxide would protect against EtOH-mediated bone loss. Micro-computed tomography analysis of the skeletons of 6-week-old female chow-fed TgCAT mice revealed a high bone mass phenotype with increased cortical bone area and thickness as well as significantly increased trabecular bone volume (P < 0.05). Six-week-old wild-type (WT) and TgCAT female mice were chow fed or pair fed (PF) liquid diets with or without EtOH, approximately 30% of calories, for 8 weeks. Pair feeding of WT had no demonstrable effect on the skeleton; however, EtOH feeding of WT mice significantly reduced cortical and trabecular bone parameters along with bone strength compared with PF controls (P < 0.05). In contrast, EtOH feeding of TgCAT mice had no effect on trabecular bone compared with PF controls. At 14 weeks of age, there was significantly less trabecular bone and cortical cross-sectional area in TgCAT mice than WT mice (P < 0.05), suggesting impaired normal bone accrual with age. TgCAT mice expressed less collagen1α and higher sclerostin mRNA (P < 0.05), suggesting decreased bone formation in TgCAT mice. In conclusion, catalase overexpression resulted in greater bone mass than in WT mice at 6 weeks and lower bone mass at 14 weeks. EtOH feeding induced significant reductions in bone architecture and strength in WT mice, but TgCAT mice were partially protected. These data implicate ROS signaling in the regulation of bone turnover in an age-dependent manner, and indicate that excess hydrogen peroxide generation contributes to alcohol-induced osteopenia.
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Envelhecimento/metabolismo , Remodelação Óssea/efeitos dos fármacos , Catalase/metabolismo , Etanol/toxicidade , Espécies Reativas de Oxigênio/metabolismo , Envelhecimento/patologia , Animais , Fenômenos Biomecânicos , Densidade Óssea/efeitos dos fármacos , Catalase/genética , Feminino , Fêmur/efeitos dos fármacos , Fêmur/metabolismo , Fêmur/patologia , Peróxido de Hidrogênio/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Tíbia/efeitos dos fármacos , Tíbia/metabolismo , Tíbia/patologiaRESUMO
Deletion of copper-zinc superoxide dismutase (CuZnSOD) in Sod1(-/-) mice leads to accelerated loss of muscle mass and force during aging, but the losses do not occur with muscle-specific deletion of CuZnSOD. To determine the role of motor neurons in the muscle decline, we generated transgenic Sod1(-/-) mice in which CuZnSOD was expressed under control of the synapsin 1 promoter (SynTgSod1(-/-) mice). SynTgSod1(-/-) mice expressed CuZnSOD in brain, spinal cord, and peripheral nerve, but not in other tissues. Sciatic nerve CuZnSOD content in SynTgSod1(-/-) mice was ~20% that of control mice, but no reduction in muscle mass or isometric force was observed in SynTgSod1(-/-) mice compared with control animals, whereas muscles of age-matched Sod1(-/-) mice displayed 30-40% reductions in mass and force. In addition, increased oxidative damage and adaptations in stress responses observed in muscles of Sod1(-/-) mice were absent in SynTgSod1(-/-) mice, and degeneration of neuromuscular junction (NMJ) structure and function occurred in Sod1(-/-) mice but not in SynTgSod1(-/-) mice. Our data demonstrate that specific CuZnSOD expression in neurons is sufficient to preserve NMJ and skeletal muscle structure and function in Sod1(-/-) mice and suggest that redox homeostasis in motor neurons plays a key role in initiating sarcopenia during aging.
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Neurônios Motores/metabolismo , Músculo Esquelético/metabolismo , Atrofia Muscular/metabolismo , Superóxido Dismutase/metabolismo , Envelhecimento/genética , Envelhecimento/metabolismo , Envelhecimento/fisiologia , Animais , Western Blotting , Eletromiografia , Humanos , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Músculo Esquelético/patologia , Músculo Esquelético/fisiopatologia , Atrofia Muscular/genética , Atrofia Muscular/fisiopatologia , Junção Neuromuscular/metabolismo , Junção Neuromuscular/fisiopatologia , Tamanho do Órgão/genética , Oxirredução , Sarcopenia/genética , Sarcopenia/metabolismo , Sarcopenia/fisiopatologia , Superóxido Dismutase/genética , Superóxido Dismutase-1 , Transmissão Sináptica/genética , Transmissão Sináptica/fisiologiaRESUMO
INTRODUCTION: Histone deacetylases (HDACs) have been implicated in neurogenic muscle atrophy, but the mechanisms by which HDAC inhibitors might have beneficial effects are not defined. METHODS: We used sciatic nerve crush to determine the effect of butyrate on denervation-induced gene expression and oxidative stress. RESULTS: Butyrate treatment initiated 3 weeks before injury and continued 1 week after injury increases histone acetylation and reduces muscle atrophy after nerve crush. Butyrate delivered only after nerve crush similarly prevented muscle atrophy. Butyrate had no effect on the increase in histone deacetylase 4 (HDAC4) protein levels following nerve crush but prevented the increase in expression of myogenin, MuRF1, and atrogin-1. Butyrate did not affect mitochondrial reactive oxygen species production, but it increased antioxidant enzyme activity, reduced proteasome activity, and reduced oxidative damage following nerve injury. CONCLUSIONS: These data suggest that HDAC inhibitors are promising pharmacological agents for treating neurogenic muscle atrophy. Muscle Nerve 52: 859-868, 2015.
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Ácido Butírico/uso terapêutico , Atrofia Muscular/prevenção & controle , Neuropatia Ciática/tratamento farmacológico , Animais , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Atrofia Muscular/etiologia , Atrofia Muscular/metabolismo , Neuropatia Ciática/complicações , Neuropatia Ciática/metabolismoRESUMO
Mutations in SURF1 (surfeit locus protein 1) COX (cytochrome c oxidase) assembly protein are associated with Leigh's syndrome, a human mitochondrial disorder that manifests as severe mitochondrial phenotypes and early lethality. In contrast, mice lacking the SURF1 protein (Surf1-/-) are viable and were previously shown to have enhanced longevity and a greater than 50% reduction in COX activity. We measured mitochondrial function in heart and skeletal muscle, and despite the significant reduction in COX activity, we found little or no difference in ROS (reactive oxygen species) generation, membrane potential, ATP production or respiration in isolated mitochondria from Surf1-/- mice compared with wild-type. However, blood lactate levels were elevated and Surf1-/- mice had reduced running endurance, suggesting compromised mitochondrial energy metabolism in vivo. Decreased COX activity in Surf1-/- mice is associated with increased markers of mitochondrial biogenesis [PGC-1α (peroxisome-proliferator-activated receptor γ co-activator 1α) and VDAC (voltage-dependent anion channel)] in both heart and skeletal muscle. Although mitochondrial biogenesis is a common response in the two tissues, skeletal muscle has an up-regulation of the UPRMT (mitochondrial unfolded protein response) and heart exhibits induction of the Nrf2 (nuclear factor-erythroid 2-related factor 2) antioxidant response pathway. These data are the first to show induction of the UPRMT in a mammalian model of decreased COX activity. In addition, the results of the present study suggest that impaired mitochondrial function can lead to induction of mitochondrial stress pathways to confer protective effects on cellular homoeostasis.
Assuntos
Complexo IV da Cadeia de Transporte de Elétrons/genética , Proteínas de Membrana/genética , Mitocôndrias Musculares/metabolismo , Proteínas Mitocondriais/genética , Trifosfato de Adenosina/biossíntese , Animais , Coração/fisiologia , Peróxido de Hidrogênio/metabolismo , Longevidade , Potenciais da Membrana , Camundongos Knockout , Mitocôndrias Cardíacas/metabolismo , Mitocôndrias Cardíacas/ultraestrutura , Mitocôndrias Musculares/ultraestrutura , Músculo Esquelético/metabolismo , Miocárdio/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Consumo de Oxigênio , Superóxidos/metabolismo , Resposta a Proteínas não DobradasRESUMO
Mice lacking Surf1, a complex IV assembly protein, have â¼50-70% reduction in cytochrome c oxidase activity in all tissues yet a paradoxical increase in lifespan. Here we report that Surf1(-/-) mice have lower body (15%) and fat (20%) mass, in association with reduced lipid storage, smaller adipocytes, and elevated indicators of fatty acid oxidation in white adipose tissue (WAT) compared with control mice. The respiratory quotient in the Surf1(-/-) mice was significantly lower than in the control animals (0.83-0.93 vs. 0.90-0.98), consistent with enhanced fat utilization in Surf1(-/-) mice. Elevated fat utilization was associated with increased insulin sensitivity measured as insulin-stimulated glucose uptake, as well as an increase in insulin receptor levels (â¼2-fold) and glucose transporter type 4 (GLUT4; â¼1.3-fold) levels in WAT in the Surf1(-/-) mice. The expression of peroxisome proliferator-activated receptor γ-coactivator 1-α (PGC-1α) mRNA and protein was up-regulated by 2.5- and 1.9-fold, respectively, in WAT from Surf1(-/-) mice, and the expression of PGC-1α target genes and markers of mitochondrial biogenesis was elevated. Together, these findings point to a novel and unexpected link between reduced mitochondrial complex IV activity, enhanced insulin sensitivity, and increased mitochondrial biogenesis that may contribute to the increased longevity in the Surf1(-/-) mice.
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Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Resistência à Insulina/genética , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Receptor de Insulina/metabolismo , Tecido Adiposo Branco/metabolismo , Animais , Complexo IV da Cadeia de Transporte de Elétrons/genética , Transportador de Glucose Tipo 4/genética , Transportador de Glucose Tipo 4/metabolismo , Insulina/metabolismo , Masculino , Camundongos , Mitocôndrias/genética , Músculo Esquelético/metabolismo , Oxirredução , PPAR gama/metabolismoRESUMO
We have previously shown that deletion of CuZnSOD in mice (Sod1(-/-) mice) leads to accelerated loss of muscle mass and contractile force during aging. To dissect the relative roles of skeletal muscle and motor neurons in this process, we used a Cre-Lox targeted approach to establish a skeletal muscle-specific Sod1-knockout (mKO) mouse to determine whether muscle-specific CuZnSOD deletion is sufficient to cause muscle atrophy. Surprisingly, mKO mice maintain muscle masses at or above those of wild-type control mice up to 18 mo of age. In contrast, maximum isometric specific force measured in gastrocnemius muscle is significantly reduced in the mKO mice. We found no detectable increases in global measures of oxidative stress or ROS production, no reduction in mitochondrial ATP production, and no induction of adaptive stress responses in muscle from mKO mice. However, Akt-mTOR signaling is elevated and the number of muscle fibers with centrally located nuclei is increased in skeletal muscle from mKO mice, which suggests elevated regenerative pathways. Our data demonstrate that lack of CuZnSOD restricted to skeletal muscle does not lead to muscle atrophy but does cause muscle weakness in adult mice and suggest loss of CuZnSOD may potentiate muscle regenerative pathways.
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Contração Muscular/fisiologia , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiopatologia , Atrofia Muscular/enzimologia , Superóxido Dismutase/metabolismo , Animais , Western Blotting , Peroxidação de Lipídeos/genética , Peroxidação de Lipídeos/fisiologia , Camundongos , Camundongos Knockout , Microscopia Eletrônica de Transmissão , Microscopia de Fluorescência , Contração Muscular/genética , Músculo Esquelético/ultraestrutura , Atrofia Muscular/genética , Estresse Oxidativo , Superóxido Dismutase/genética , Superóxido Dismutase-1 , Tirosina/análogos & derivados , Tirosina/metabolismoRESUMO
Oxidative stress is associated with tissue dysfunctions that can lead to reduced health. Prior work has shown that oxidative stress contributes to both muscle atrophy and cellular senescence, which is a hallmark of aging that may drive in muscle atrophy and muscle contractile dysfunction. The purpose of the study was to test the hypothesis that cellular senescence contributes to muscle atrophy or weakness. To increase potential senescence in skeletal muscle, we used a model of oxidative stress-induced muscle frailty, the CuZn superoxide dismutase knockout (Sod1KO) mouse. We treated 6-month-old wildtype (WT) and Sod1KO mice with either vehicle or a senolytic treatment of combined dasatinib (5 mg/kg) + quercetin (50 mg/kg) (D + Q) for 3 consecutive days every 15 days. We continued treatment for 7 months and sacrificed the mice at 13 months of age. Treatment with D + Q did not preserve muscle mass, reduce NMJ fragmentation, or alter muscle protein synthesis in Sod1KO mice when compared to the vehicle-treated group. However, we observed an improvement in muscle-specific force generation in Sod1KO mice treated with D + Q when compared to Sod1KO-vehicle mice. Overall, these data suggest that reducing cellular senescence via D + Q is not sufficient to mitigate loss of muscle mass in a mouse model of oxidative stress-induced muscle frailty but may mitigate some aspects of oxidative stress-induced muscle dysfunction.
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Fragilidade , Senoterapia , Camundongos , Animais , Superóxido Dismutase-1/genética , Superóxido Dismutase-1/metabolismo , Camundongos Knockout , Estresse Oxidativo , Atrofia Muscular/metabolismo , Atrofia Muscular/patologia , Músculo Esquelético/metabolismo , Superóxido Dismutase/metabolismoRESUMO
Despite the universal impact of sarcopenia on compromised health and quality of life in the elderly, promising pharmaceutical approaches that can effectively mitigate loss of muscle and function during aging have been limited. Our group and others have reported impairments in peripheral motor neurons and loss of muscle innervation as initiating factors in sarcopenia, contributing to mitochondrial dysfunction and elevated oxidative stress in muscle. We recently reported a reduction in α motor neuron loss in aging mice in response to the compound OKN-007, a proposed antioxidant and anti-inflammatory agent. In the current study, we asked whether OKN-007 treatment in wildtype male mice for 8-9 months beginning at 16 months of age can also protect muscle mass and function. At 25 months of age, we observed a reduction in the loss of whole-body lean mass, a reduced loss of innervation at the neuromuscular junction and well-preserved neuromuscular junction morphology in OKN-007 treated mice versus age matched wildtype untreated mice. The loss in muscle force generation in aging mice (~ 25%) is significantly improved with OKN-007 treatment. In contrast, OKN-007 treatment provided no protection in loss of muscle mass in aging mice. Mitochondrial function was improved by OKN-007 treatment, consistent with its potential antioxidative properties. Together, these exciting findings are the first to demonstrate that interventions through neuroprotection can be an effective therapy to counter aging-related muscle dysfunction.
Assuntos
Envelhecimento , Debilidade Muscular , Fármacos Neuroprotetores , Sarcopenia , Animais , Masculino , Envelhecimento/efeitos dos fármacos , Envelhecimento/fisiologia , Fármacos Neuroprotetores/farmacologia , Debilidade Muscular/tratamento farmacológico , Camundongos , Sarcopenia/tratamento farmacológico , Sarcopenia/prevenção & controle , Músculo Esquelético/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Junção Neuromuscular/efeitos dos fármacos , Antioxidantes/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Modelos Animais de DoençasRESUMO
In orthopedic research, many studies have applied vitamin E as a protective antioxidant or used tert-butyl hydroperoxide to induce oxidative injury to chondrocytes. These studies often support the hypothesis that joint pathology causes oxidative stress and increased lipid peroxidation that might be prevented with lipid antioxidants to improve cell survival or function and joint health; however, lipid antioxidant supplementation was ineffective against osteoarthritis in clinical trials and animal data have been equivocal. Moreover, increased circulating vitamin E is associated with increased rates of osteoarthritis. This disconnect between benchtop and clinical results led us to hypothesize that oxidative stress-driven paradigms of chondrocyte redox function do not capture the metabolic and physiologic effects of lipid antioxidants and prooxidants on articular chondrocytes. We used ex vivo and in vivo cartilage models to investigate the effect of lipid antioxidants on healthy, primary, articular chondrocytes and applied immuno-spin trapping techniques to provide a broad indicator of high levels of oxidative stress independent of specific reactive oxygen species. Key findings demonstrate lipid antioxidants were pro-mitochondrial while lipid prooxidants decreased mitochondrial measures. In the absence of injury, radical formation was increased by lipid antioxidants; however, in the presence of injury, radical formation was decreased. In unstressed conditions, this relationship between chondrocyte mitochondria and redox regulation was reproduced in vivo with overexpression of glutathione peroxidase 4. In mice aged 18 months or more, overexpression of glutathione peroxidase 4 significantly decreased the presence of pro-mitochondrial peroxisome proliferation activated receptor gamma and deranged the relationship between mitochondria and the redox environment. This complex interaction suggests strategies targeting articular cartilage may benefit from adopting more nuanced paradigms of articular chondrocyte redox metabolism.
Assuntos
Condrócitos , Peroxidação de Lipídeos , Mitocôndrias , Oxirredução , Estresse Oxidativo , Condrócitos/metabolismo , Condrócitos/efeitos dos fármacos , Animais , Mitocôndrias/metabolismo , Mitocôndrias/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Antioxidantes/farmacologia , Antioxidantes/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Cartilagem Articular/metabolismo , Camundongos , Células CultivadasRESUMO
Objectives: Sjögren's disease (SjD) is a common exocrine disorder typified by chronic inflammation and dryness, but also profound fatigue, suggesting a pathological basis in cellular bioenergetics. In healthy states, damaged or dysfunctional mitochondrial components are broken down and recycled by mitophagy, a specialized form of autophagy. In many autoimmune disorders, however, evidence suggests that dysfunctional mitophagy allows poorly functioning mitochondria to persist and contribute to a cellular milieu with elevated reactive oxygen species. We hypothesized that mitophagic processes are dysregulated in SjD and that dysfunctional mitochondria contribute to overall fatigue. We sought to link fatigue with mitochondrial dysfunction directly in SjD, heretofore unexamined, and further sought to assess the pathogenic extent and implications of dysregulated mitophagy in SjD. Methods: We isolated pan T cells via negative selection from the peripheral blood mononuclear cells of 17 SjD and 8 age-matched healthy subjects, all of whom completed fatigue questionnaires prior to phlebotomy. Isolated T cells were analyzed for mitochondrial oxygen consumption rate (OCR) and glycolysis using Seahorse, and linear correlations with fatigue measures were assessed. A mitophagy transcriptional signature in SjD was identified by reanalysis of whole-blood microarray data from 190 SjD and 32 healthy subjects. Differential expression analyses were performed by case/control and subgroup analyses comparing SjD patients by mitophagy transcriptional cluster against healthy subjects followed by bioinformatic interpretation using gene set enrichment analysis. Results: Basal OCR, ATP-linked respiration, maximal respiration, and reserve capacity were significantly lower in SjD compared to healthy subjects with no observed differences in non-mitochondrial respiration, basal glycolysis, or glycolytic stress. SjD lymphocytic mitochondria show structural alterations compared to healthy subjects. Fatigue scores related to pain/discomfort in SjD correlated with the altered OCR. Results from subgroup analyses by mitophagic SjD clusters revealed highly variable inter-cluster differentially expressed genes (DEGs) and expanded the number of SjD-associated gene targets by tenfold within the same dataset. Conclusion: Mitochondrial dysfunction, associated with fatigue, is a significant problem in SjD and warrants further investigation.
RESUMO
Age-related endothelial dysfunction is a pivotal factor in the development of cardiovascular diseases, stemming, at least in part, from mitochondrial dysfunction and a consequential increase in oxidative stress. These alterations are central to the decline in vascular health seen with aging, underscoring the urgent need for interventions capable of restoring endothelial function for preventing cardiovascular diseases. Dietary interventions, notably time-restricted feeding (TRF), have been identified for their anti-aging effects on mitochondria, offering protection against age-associated declines in skeletal muscle and other organs. Motivated by these findings, our study aimed to investigate whether TRF could similarly exert protective effects on endothelial health in the vasculature, enhancing mitochondrial function and reducing oxidative stress. To explore this, 12-month-old C57BL/6 mice were placed on a TRF diet, with food access limited to a 6-h window daily for 12 months. For comparison, we included groups of young mice and age-matched controls with unrestricted feeding. We evaluated the impact of TRF on endothelial function by measuring acetylcholine-induced vasorelaxation of the aorta. Mitochondrial health was assessed using fluororespirometry, and vascular reactive oxygen species (ROS) production was quantified with the redox-sensitive dye dihydroethidium. We also quantified 4-hydroxynonenal (4-HNE) levels, a stable marker of lipid peroxidation, in the aorta using ELISA. Our findings demonstrated that aged mice on a standard diet exhibited significant impairments in aortic endothelial relaxation and mitochondrial function, associated with elevated vascular oxidative stress. Remarkably, the TRF regimen led to substantial improvements in these parameters, indicating enhanced endothelial vasorelaxation, better mitochondrial function, and reduced oxidative stress in the aortas of aged mice. This investigation establishes a vital foundation, paving the way for subsequent clinical research aimed at exploring the cardiovascular protective benefits of intermittent fasting.
Assuntos
Envelhecimento , Aorta , Endotélio Vascular , Mitocôndrias , Estresse Oxidativo , Espécies Reativas de Oxigênio , Vasodilatação , Animais , Camundongos , Mitocôndrias/metabolismo , Endotélio Vascular/metabolismo , Endotélio Vascular/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Aorta/metabolismo , Aorta/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Envelhecimento/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Aldeídos/metabolismo , Aldeídos/farmacologiaRESUMO
The development of insulin resistance is the primary step in the etiology of type 2 diabetes mellitus. There are several risk factors associated with insulin resistance, yet the basic biological mechanisms that promote its development are still unclear. There is growing literature that suggests mitochondrial dysfunction and/or oxidative stress play prominent roles in defects in glucose metabolism. Here, we tested whether increased expression of CuZn-superoxide dismutase (Sod1) or Mn-superoxide dismutase (Sod2) prevented obesity-induced changes in oxidative stress and metabolism. Both Sod1 and Sod2 overexpressing mice were protected from high fat diet-induced glucose intolerance. Lipid oxidation (F2-isoprostanes) was significantly increased in muscle and adipose with high fat feeding. Mice with increased expression of either Sod1 or Sod2 showed a significant reduction in this oxidative damage. Surprisingly, mitochondria from the muscle of high fat diet-fed mice showed no significant alteration in function. Together, our data suggest that targeting reduced oxidative damage in general may be a more applicable therapeutic target to prevent insulin resistance than is improving mitochondrial function.
Assuntos
Gorduras na Dieta/efeitos adversos , Mitocôndrias/metabolismo , Obesidade/enzimologia , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Obesidade/patologia , Superóxido Dismutase/genética , Regulação para Cima/efeitos dos fármacosRESUMO
Comparing biological processes in closely related species with divergent life spans is a powerful approach to study mechanisms of aging. The oxidative stress hypothesis of aging predicts that longer-lived species would have lower reactive oxygen species (ROS) generation and/or an increased antioxidant capacity, resulting in reduced oxidative damage with age than in shorter-lived species. In this study, we measured ROS generation in the young adult animals of the long-lived white-footed mouse, Peromyscus leucopus (maximal life span potential, MLSP = 8 yr) and the common laboratory mouse, Mus musculus (C57BL/6J strain; MLSP = 3.5 yr). Consistent with the hypothesis, our results show that skeletal muscle mitochondria from adult P. leucopus produce less ROS (superoxide and hydrogen peroxide) compared with M. musculus. Additionally, P. leucopus has an increase in the activity of antioxidant enzymes superoxide dismutase 1, catalase, and glutathione peroxidase 1 at young age. P. leucopus compared with M. musculus display low levels of lipid peroxidation (isoprostanes) throughout life; however, P. leucopus although having elevated protein carbonyls at a young age, the accrual of protein oxidation with age is minimal in contrast to the linear increase in M. musculus. Altogether, the results from young animals are in agreement with the predictions of the oxidative stress hypothesis of aging with the exception of protein carbonyls. Nonetheless, the age-dependent increase in protein carbonyls is more pronounced in short-lived M. musculus, which supports enhanced protein homeostasis in long-lived P. leucopus.