RESUMO
Limb-girdle muscular dystrophy R12 (LGMD-R12) is caused by recessive mutations in the Anoctamin-5 gene (ANO5, TMEM16E). Although ANO5 myopathy is not X-chromosome linked, we performed a meta-analysis of the research literature and found that three-quarters of patients with LGMD-R12 are males. Females are less likely to present with moderate to severe skeletal muscle and/or cardiac pathology. Because these sex differences could be explained in several ways, we compared males and females in a mouse model of LGMD-R12. This model recapitulates the sex differences in human LGMD-R12. Only male Ano5-/- mice had elevated serum creatine kinase after exercise and exhibited defective membrane repair after laser injury. In contrast, by these measures, female Ano5-/- mice were indistinguishable from wild type. Despite these differences, both male and female Ano5-/- mice exhibited exercise intolerance. Although exercise intolerance of male mice can be explained by skeletal muscle dysfunction, echocardiography revealed that Ano5-/- female mice had features of cardiomyopathy that may be responsible for their exercise intolerance. These findings heighten concerns that mutations of ANO5 in humans may be linked to cardiac disease.
Assuntos
Anoctaminas/deficiência , Cardiomiopatias/metabolismo , Músculo Esquelético/metabolismo , Distrofia Muscular do Cíngulo dos Membros/metabolismo , Miocárdio/metabolismo , Animais , Anoctaminas/genética , Cardiomiopatias/genética , Cardiomiopatias/patologia , Cardiomiopatias/fisiopatologia , Creatina Quinase/sangue , Tolerância ao Exercício , Feminino , Humanos , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Contração Muscular , Músculo Esquelético/patologia , Músculo Esquelético/fisiopatologia , Distrofia Muscular do Cíngulo dos Membros/genética , Distrofia Muscular do Cíngulo dos Membros/patologia , Distrofia Muscular do Cíngulo dos Membros/fisiopatologia , Miocárdio/patologia , Caracteres Sexuais , Fatores SexuaisRESUMO
RATIONALE: Mitochondrial Ca2+ loading augments oxidative metabolism to match functional demands during times of increased work or injury. However, mitochondrial Ca2+ overload also directly causes mitochondrial rupture and cardiomyocyte death during ischemia-reperfusion injury by inducing mitochondrial permeability transition pore opening. The MCU (mitochondrial Ca2+ uniporter) mediates mitochondrial Ca2+ influx, and its activity is modulated by partner proteins in its molecular complex, including the MCUb subunit. OBJECTIVE: Here, we sought to examine the function of the MCUb subunit of the MCU-complex in regulating mitochondria Ca2+ influx dynamics, acute cardiac injury, and long-term adaptation after ischemic injury. METHODS AND RESULTS: Cardiomyocyte-specific MCUb overexpressing transgenic mice and Mcub gene-deleted (Mcub-/-) mice were generated to dissect the molecular function of this protein in the heart. We observed that MCUb protein is undetectable in the adult mouse heart at baseline, but mRNA and protein are induced after ischemia-reperfusion injury. MCUb overexpressing mice demonstrated inhibited mitochondrial Ca2+ uptake in cardiomyocytes and partial protection from ischemia-reperfusion injury by reducing mitochondrial permeability transition pore opening. Antithetically, deletion of the Mcub gene exacerbated pathological cardiac remodeling and infarct expansion after ischemic injury in association with greater mitochondrial Ca2+ uptake. Furthermore, hindlimb remote ischemic preconditioning induced MCUb expression in the heart, which was associated with decreased mitochondrial Ca2+ uptake, collectively suggesting that induction of MCUb protein in the heart is protective. Similarly, mouse embryonic fibroblasts from Mcub-/- mice were more sensitive to Ca2+ overload. CONCLUSIONS: Our studies suggest that Mcub is a protective cardiac inducible gene that reduces mitochondrial Ca2+ influx and permeability transition pore opening after ischemic injury to reduce ongoing pathological remodeling.
Assuntos
Cálcio/metabolismo , Membro Posterior/irrigação sanguínea , Proteínas de Membrana/metabolismo , Mitocôndrias Cardíacas/metabolismo , Proteínas Mitocondriais/metabolismo , Infarto do Miocárdio/metabolismo , Traumatismo por Reperfusão Miocárdica/metabolismo , Miócitos Cardíacos/metabolismo , Remodelação Ventricular , Animais , Sinalização do Cálcio , Morte Celular , Linhagem Celular , Modelos Animais de Doenças , Feminino , Fibroblastos/metabolismo , Fibroblastos/patologia , Precondicionamento Isquêmico , Masculino , Proteínas de Membrana/genética , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias Cardíacas/patologia , Poro de Transição de Permeabilidade Mitocondrial/metabolismo , Proteínas Mitocondriais/genética , Infarto do Miocárdio/patologia , Infarto do Miocárdio/fisiopatologia , Infarto do Miocárdio/prevenção & controle , Traumatismo por Reperfusão Miocárdica/patologia , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Miócitos Cardíacos/patologiaRESUMO
OBJECTIVE: Aloe vera is a cost-effective, accessible wound care adjunct with a minimal risk profile. Despite its centuries-long history being used to treat varying wound types, published reports remain inconclusive on its efficacy. In this article, the authors report the results of a systematic review assessing the efficacy of topical aloe vera products in wound care applications, as well as a meta-analysis of its utility in burn healing where data are most robust. DATA SOURCES: In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, the authors searched PubMed, EMBASE, and Cochrane CENTRAL for randomized controlled trials assessing the use of aloe vera in healing various wound types. STUDY SELECTION: The database search identified 91 articles. After duplicates were removed, 74 articles were screened, and of those, 47 were assessed for eligibility. Ultimately, 28 articles were included in the qualitative synthesis, and 4 studies assessing second-degree burns were included in the meta-analysis. DATA EXTRACTION: The following data points were collected from each study: number of participants/wounds, treatment type, adjunctive therapy (if any), and primary outcomes. DATA SYNTHESIS: Risk-of-bias analysis was conducted on included articles, and results were compiled. A meta-analysis was undertaken for studies focusing on the treatment of burns. Cumulatively, these studies had a total of 133 patients with 163 wounds being assessed. Analysis revealed a statistically significant mean difference in time to healing of 4.44 days in favor of aloe vera treatment (P = .004). CONCLUSIONS: Topical aloe vera usage for second-degree burn wound healing demonstrated significantly faster time to healing compared with other treatments.
Assuntos
Aloe , Queimaduras , Lesões dos Tecidos Moles , Humanos , Fitoterapia/métodos , Queimaduras/tratamento farmacológico , CicatrizaçãoRESUMO
The nuclear genome-encoded mitochondrial DNA (mtDNA) transcription factor A (TFAM) is indispensable for mitochondrial energy production in the developing and postnatal heart; a similar role for TFAM is inferred in adult heart. Here, we provide evidence that challenges this long-standing paradigm. Unexpectedly, conditional Tfam ablation in vivo in adult mouse cardiomyocytes resulted in a prolonged period of functional resilience characterized by preserved mtDNA content, mitochondrial function, and cardiac function, despite mitochondrial structural alterations and decreased transcript abundance. Remarkably, TFAM protein levels did not directly dictate mtDNA content in the adult heart, and mitochondrial translation was preserved with acute TFAM inactivation, suggesting maintenance of respiratory chain assembly/function. Long-term Tfam inactivation, however, downregulated the core mtDNA transcription and replication machinery, leading to mitochondrial dysfunction and cardiomyopathy. Collectively, in contrast to the developing heart, these data reveal a striking resilience of the differentiated adult heart to acute insults to mtDNA regulation.
Assuntos
Proteínas de Ligação a DNA/genética , Coração/fisiologia , Proteínas de Grupo de Alta Mobilidade/genética , Mitocôndrias/genética , Miócitos Cardíacos/metabolismo , Animais , Replicação do DNA/genética , DNA Mitocondrial/genética , Regulação para Baixo/genética , Transporte de Elétrons/genética , Feminino , Regulação da Expressão Gênica/genética , Masculino , Camundongos , Proteínas Mitocondriais/genética , Fatores de Transcrição/genética , Transcrição Gênica/genéticaRESUMO
Mitochondria are recognized as signaling organelles, because under stress, mitochondria can trigger various signaling pathways to coordinate the cell's response. The specific pathway(s) engaged by mitochondria in response to mitochondrial energy defects in vivo and in high-energy tissues like the heart are not fully understood. Here, we investigated cardiac pathways activated in response to mitochondrial energy dysfunction by studying mice with cardiomyocyte-specific loss of the mitochondrial phosphate carrier (SLC25A3), an established model that develops cardiomyopathy as a result of defective mitochondrial ATP synthesis. Mitochondrial energy dysfunction induced a striking pattern of acylome remodeling, with significantly increased posttranslational acetylation and malonylation. Mass spectrometry-based proteomics further revealed that energy dysfunction-induced remodeling of the acetylome and malonylome preferentially impacts mitochondrial proteins. Acetylation and malonylation modified a highly interconnected interactome of mitochondrial proteins, and both modifications were present on the enzyme isocitrate dehydrogenase 2 (IDH2). Intriguingly, IDH2 activity was enhanced in SLC25A3-deleted mitochondria, and further study of IDH2 sites targeted by both acetylation and malonylation revealed that these modifications can have site-specific and distinct functional effects. Finally, we uncovered a novel cross talk between the two modifications, whereby mitochondrial energy dysfunction-induced acetylation of sirtuin 5 (SIRT5), inhibited its function. Because SIRT5 is a mitochondrial deacylase with demalonylase activity, this finding suggests that acetylation can modulate the malonylome. Together, our results position acylations as an arm of the mitochondrial response to energy dysfunction and suggest a mechanism by which focal disruption to the energy production machinery can have an expanded impact on global mitochondrial function.
Assuntos
Cardiomiopatias/genética , Proteínas de Transporte de Cátions/genética , Isocitrato Desidrogenase/genética , Mitocôndrias Cardíacas/metabolismo , Proteínas Mitocondriais/genética , Miócitos Cardíacos/metabolismo , Proteínas de Transporte de Fosfato/genética , Processamento de Proteína Pós-Traducional , Proteínas Carreadoras de Solutos/genética , Acetilação , Animais , Transporte Biológico , Cardiomiopatias/metabolismo , Cardiomiopatias/patologia , Proteínas de Transporte de Cátions/deficiência , Metabolismo Energético , Feminino , Redes Reguladoras de Genes , Isocitrato Desidrogenase/metabolismo , Masculino , Malonatos/metabolismo , Camundongos , Camundongos Knockout , Mitocôndrias Cardíacas/genética , Mitocôndrias Cardíacas/patologia , Proteínas Mitocondriais/deficiência , Modelos Moleculares , Miocárdio/metabolismo , Miocárdio/patologia , Miócitos Cardíacos/patologia , Proteínas de Transporte de Fosfato/deficiência , Fosfatos , Conformação Proteica , Mapeamento de Interação de Proteínas , Transdução de Sinais , Sirtuínas/genética , Sirtuínas/metabolismo , Proteínas Carreadoras de Solutos/deficiênciaRESUMO
BACKGROUND: Cutaneous wounds in patients with diabetes exhibit impaired healing due to physiological impediments and conventional care options are severely limited. Multipotent stromal cells (MSCs) have been touted as a powerful new therapy for diabetic tissue repair owing to their trophic activity and low immunogenicity. However, variations in sources and access are limiting factors for broader adaptation and study of MSC-based therapies. Amniotic fluid presents a relatively unexplored source of MSCs and one with wide availability. Here, we investigate the potential of amniotic fluid-derived multipotent stromal cells (AFMSCs) to restore molecular integrity to diabetic wounds, amend pathology and promote wound healing. METHOD: We obtained third trimester amniotic fluid from term cesarean delivery and isolated and expanded MSCs in vitro. We then generated 10 mm wounds in Leprdb/db diabetic mouse skin, and splinted them open to allow for humanized wound modeling. Immediately after wounding, we applied AFMSCs topically to the sites of injuries on diabetic mice, while media application only, defined as vehicle, served as controls. Post-treatment, we compared healing time and molecular and cellular events of AFMSC-treated, vehicle-treated, untreated diabetic, and non-diabetic wounds. A priori statistical analyses measures determined significance of the data. RESULT: Average time to wound closure was approximately 19 days in AFMSC-treated diabetic wounds. This was significantly lower than the vehicle-treated diabetic wounds, which required on average 27.5 days to heal (p < 0.01), and most similar to time of closure in wild type untreated wounds (an average of around 18 days). In addition, AFMSC treatment induced changes in the profiles of macrophage polarizing cytokines, resulting in a change in macrophage composition in the diabetic wound bed. We found no evidence of AFMSC engraftment or biotherapy induced immune response. CONCLUSION: Treatment of diabetic wounds using amniotic fluid-derived MSCs encourages cutaneous tissue repair through affecting inflammatory cell behavior in the wound site. Since vehicle-treated diabetic wounds did not demonstrate accelerated healing, we determined that AFMSCs were therapeutic through their paracrine activities. Future studies should be aimed towards validating our observations through further examination of the paracrine potential of AFMSCs. In addition, investigations concerning safety and efficacy of this therapy in clinical trials should be pursued.
Assuntos
Líquido Amniótico , Diabetes Mellitus Experimental , Animais , Diabetes Mellitus Experimental/terapia , Feminino , Humanos , Macrófagos , Camundongos , Gravidez , Pele , Células Estromais , CicatrizaçãoRESUMO
Neurodevelopmental disorders offer insight into synaptic mechanisms. To unbiasedly uncover these mechanisms, we studied the 22q11.2 syndrome, a recurrent copy number variant, which is the highest schizophrenia genetic risk factor. We quantified the proteomes of 22q11.2 mutant human fibroblasts from both sexes and mouse brains carrying a 22q11.2-like defect, Df(16)A+/- Molecular ontologies defined mitochondrial compartments and pathways as some of top ranked categories. In particular, we identified perturbations in the SLC25A1-SLC25A4 mitochondrial transporter interactome as associated with the 22q11.2 genetic defect. Expression of SLC25A1-SLC25A4 interactome components was affected in neuronal cells from schizophrenia patients. Furthermore, hemideficiency of the Drosophila SLC25A1 or SLC25A4 orthologues, dSLC25A1-sea and dSLC25A4-sesB, affected synapse morphology, neurotransmission, plasticity, and sleep patterns. Our findings indicate that synapses are sensitive to partial loss of function of mitochondrial solute transporters. We propose that mitoproteomes regulate synapse development and function in normal and pathological conditions in a cell-specific manner.SIGNIFICANCE STATEMENT We address the central question of how to comprehensively define molecular mechanisms of the most prevalent and penetrant microdeletion associated with neurodevelopmental disorders, the 22q11.2 microdeletion syndrome. This complex mutation reduces gene dosage of â¼63 genes in humans. We describe a disruption of the mitoproteome in 22q11.2 patients and brains of a 22q11.2 mouse model. In particular, we identify a network of inner mitochondrial membrane transporters as a hub required for synapse function. Our findings suggest that mitochondrial composition and function modulate the risk of neurodevelopmental disorders, such as schizophrenia.
Assuntos
Síndrome da Deleção 22q11/metabolismo , Encéfalo/metabolismo , Mitocôndrias/metabolismo , Neurônios/metabolismo , Sinapses/metabolismo , Translocador 1 do Nucleotídeo Adenina/metabolismo , Animais , Comportamento Animal , Linhagem Celular , Deleção Cromossômica , Cromossomos Humanos Par 22/metabolismo , Drosophila , Feminino , Fibroblastos/metabolismo , Humanos , Masculino , Proteínas Mitocondriais/metabolismo , Transportadores de Ânions Orgânicos/metabolismo , Proteoma , Esquizofrenia/metabolismoRESUMO
The mitochondrial calcium uniporter (MCU) relays cytosolic Ca2+ transients to the mitochondria. We examined whether energy metabolism was compromised in hearts from mice with a cardiac-specific deficiency of MCU subjected to an isoproterenol (ISO) challenge. Surprisingly, isolated working hearts from cardiac MCU-deficient mice showed higher cardiac work, both in the presence or absence of ISO. These hearts were not energy-starved, with ISO inducing a similar increase in glucose oxidation rates compared to control hearts, but a greater increase in fatty acid oxidation rates. This correlated with lower levels of the fatty acid oxidation inhibitor malonyl CoA, and to an increased stimulatory acetylation of its degrading enzyme malonyl CoA decarboxylase and of the fatty acid ß-oxidation enzyme ß-hydroxyacyl CoA dehydrogenase. We conclude that impaired mitochondrial Ca2+ uptake does not compromise cardiac energetics due to a compensatory stimulation of fatty acid oxidation that provides a higher energy reserve during acute adrenergic stress.
Assuntos
Canais de Cálcio/deficiência , Ácidos Graxos/metabolismo , Miocárdio/metabolismo , Acetilação , Animais , Canais de Cálcio/metabolismo , Metabolismo Energético/efeitos dos fármacos , Testes de Função Cardíaca , Frequência Cardíaca/efeitos dos fármacos , Isoproterenol/farmacologia , Camundongos , Especificidade de Órgãos , Oxirredução , Fosforilação/efeitos dos fármacosRESUMO
Copper is required for the activity of cytochrome c oxidase (COX), the terminal electron-accepting complex of the mitochondrial respiratory chain. The likely source of copper used for COX biogenesis is a labile pool found in the mitochondrial matrix. In mammals, the proteins that transport copper across the inner mitochondrial membrane remain unknown. We previously reported that the mitochondrial carrier family protein Pic2 in budding yeast is a copper importer. The closest Pic2 ortholog in mammalian cells is the mitochondrial phosphate carrier SLC25A3. Here, to investigate whether SLC25A3 also transports copper, we manipulated its expression in several murine and human cell lines. SLC25A3 knockdown or deletion consistently resulted in an isolated COX deficiency in these cells, and copper addition to the culture medium suppressed these biochemical defects. Consistent with a conserved role for SLC25A3 in copper transport, its heterologous expression in yeast complemented copper-specific defects observed upon deletion of PIC2 Additionally, assays in Lactococcus lactis and in reconstituted liposomes directly demonstrated that SLC25A3 functions as a copper transporter. Taken together, these data indicate that SLC25A3 can transport copper both in vitro and in vivo.
Assuntos
Proteínas de Transporte de Cátions/metabolismo , Cobre/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas de Transporte de Fosfato/metabolismo , Proteínas Carreadoras de Solutos/metabolismo , Animais , Transporte Biológico , Proteínas de Transporte de Cátions/genética , Complexo IV da Cadeia de Transporte de Elétrons/genética , Humanos , Camundongos , Mitocôndrias/genética , Mitocôndrias/metabolismo , Proteínas Mitocondriais/genética , Proteínas de Transporte de Fosfato/genética , Proteínas Carreadoras de Solutos/genéticaRESUMO
RATIONALE: Mitochondria produce ATP, especially critical for survival of highly aerobic cells, such as cardiac myocytes. Conversely, opening of mitochondrial high-conductance and long-lasting permeability transition pores (mPTP) causes respiratory uncoupling, mitochondrial injury, and cell death. However, low conductance and transient mPTP openings (tPTP) might limit mitochondrial Ca(2+) load and be cardioprotective, but direct evidence for tPTP in cells is limited. OBJECTIVE: To directly characterize tPTP occurrence during sarcoplasmic reticulum Ca(2+) release in adult cardiac myocytes. METHODS AND RESULTS: Here, we measured tPTP directly as transient drops in mitochondrial [Ca(2+)] ([Ca(2+)]mito) and membrane potential (ΔΨm) in adult cardiac myocytes during cyclic sarcoplasmic reticulum Ca release, by simultaneous live imaging of 500 to 1000 individual mitochondria. The frequency of tPTPs rose at higher [Ca(2+)]mito, [Ca(2+)]i, with 1 µmol/L peroxide exposure and in myocyte from failing hearts. The tPTPs were suppressed by preventing mitochondrial Ca(2+) influx, by mPTP inhibitor cyclosporine A, sanglifehrin, and in cyclophilin D knockout mice. These tPTP events were 57±5 s in duration, but were rare (occurring in <0.1% of myocyte mitochondria at any moment) such that the overall energetic cost to the cell is minimal. The tPTP pore size is much smaller than for permanent mPTP, as neither Rhod-2 nor calcein (600 Da) were lost. Thus, proteins and even molecules the size of NADH (663 Da) will be retained during these tPTP. CONCLUSIONS: We conclude that tPTP openings (MitoWinks) may be molecularly related to pathological mPTP, but are likely to be normal physiological manifestation that benefits mitochondrial (and cell) survival by allowing individual mitochondria to reset themselves with little overall energetic cost.
Assuntos
Mitocôndrias Cardíacas/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Miócitos Cardíacos/metabolismo , Animais , Células Cultivadas , Camundongos , Camundongos Endogâmicos C57BL , PermeabilidadeRESUMO
Ca2+ and mitochondria are inextricably linked to cardiac function and dysfunction. Ca2+ is central to cardiac excitation-contraction coupling and stimulates mitochondrial energy production to fuel contraction. Under pathological conditions of dysregulated Ca2+ cycling, mitochondrial Ca2+ overload activates cellular death pathways. Thus, in the cardiomyocyte, the mitochondrial Ca2+ microdomain is where contraction, energy and death collide. A key component of mitochondrial Ca2+ signalling is the mitochondrial Ca2+ uniporter complex (uniplex), an inner membrane Ca2+ transporter and major pathway of mitochondrial Ca2+ entry. Once known only as the unidentified target for ruthenium red and related compounds, in recent years, the uniplex has evolved into a complex multiprotein assembly. The identification of the molecular constituents of the uniplex has made possible the generation of targeted genetic models to interrogate uniplex function in vivo. This review will summarize our current understanding of the molecular structure of the uniplex, its impact on mitochondrial energetics and cardiac physiology, its contribution to cardiomyocyte death, and its expanding roles in cardiac biology.
Assuntos
Canais de Cálcio/metabolismo , Sinalização do Cálcio/fisiologia , Cálcio/metabolismo , Mitocôndrias Cardíacas/metabolismo , Animais , Morte Celular/fisiologia , Acoplamento Excitação-Contração/fisiologia , Humanos , Membranas Mitocondriais/metabolismo , Miócitos Cardíacos/metabolismo , Rutênio Vermelho/metabolismoRESUMO
Muscular dystrophies are a group of genetic diseases that lead to muscle wasting and, in most cases, premature death. Cytokines and inflammatory factors are released during the disease process where they promote deleterious signaling events that directly participate in myofiber death. Here, we show that p38α, a kinase in the greater mitogen-activated protein kinase (MAPK)-signaling network, serves as a nodal regulator of disease signaling in dystrophic muscle. Deletion of Mapk14 (p38α-encoding gene) in the skeletal muscle of mdx- (lacking dystrophin) or sgcd- (δ-sarcoglycan-encoding gene) null mice resulted in a significant reduction in pathology up to 6 months of age. We also generated MAPK kinase 6 (MKK6) muscle-specific transgenic mice to model heightened p38α disease signaling that occurs in dystrophic muscle, which resulted in severe myofiber necrosis and many hallmarks of muscular dystrophy. Mechanistically, we show that p38α directly induces myofiber death through a mitochondrial-dependent pathway involving direct phosphorylation and activation of the pro-death Bcl-2 family member Bax. Indeed, muscle-specific deletion of Bax, but not the apoptosis regulatory gene Tp53 (encoding p53), significantly reduced dystrophic pathology in the muscles of MKK6 transgenic mice. Moreover, use of a p38 MAPK pharmacologic inhibitor reduced dystrophic disease in Sgcd(-/-) mice suggesting a future therapeutic approach to delay disease.
Assuntos
Proteína Quinase 14 Ativada por Mitógeno/genética , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Músculo Esquelético/patologia , Distrofias Musculares/patologia , Proteína X Associada a bcl-2/metabolismo , Animais , Modelos Animais de Doenças , Distrofina/genética , Regulação da Expressão Gênica , Humanos , Camundongos , Camundongos Endogâmicos mdx , Camundongos Transgênicos , Mitocôndrias/metabolismo , Músculo Esquelético/metabolismo , Distrofias Musculares/metabolismo , Sarcoglicanas/genética , Transdução de Sinais , Proteína X Associada a bcl-2/genéticaRESUMO
Muscular dystrophy is a progressive muscle wasting disease that is thought to be initiated by unregulated Ca(2+) influx into myofibers leading to their death. Store-operated Ca(2+) entry (SOCE) through sarcolemmal Ca(2+) selective Orai1 channels in complex with STIM1 in the sarcoplasmic reticulum is one such potential disease mechanism for pathologic Ca(2+) entry. Here, we generated a mouse model of STIM1 overexpression in skeletal muscle to determine whether this type of Ca(2+) entry could induce muscular dystrophy. Myofibers from muscle-specific STIM1 transgenic mice showed a significant increase in SOCE in skeletal muscle, modeling an observed increase in the same current in dystrophic myofibers. Histological and biochemical analysis of STIM1 transgenic mice showed fulminant muscle disease characterized by myofiber necrosis, swollen mitochondria, infiltration of inflammatory cells, enhanced interstitial fibrosis and elevated serum creatine kinase levels. This dystrophic-like disease in STIM1 transgenic mice was abrogated by crossing in a transgene expressing a dominant-negative Orai1 (dnOrai1) mutant. The dnOrai1 transgene also significantly reduced the severity of muscular dystrophy in both mdx (dystrophin mutant mice) and δ-sarcoglycan-deficient (Sgcd(-/-)) mouse models of disease. Hence, Ca(2+) influx across an unstable sarcolemma due to increased activity of a STIM1-Orai1 complex is a disease determinant in muscular dystrophy, and hence, SOCE represents a potential therapeutic target.
Assuntos
Canais de Cálcio/metabolismo , Cálcio/metabolismo , Proteínas de Membrana/metabolismo , Distrofias Musculares/patologia , Proteínas de Neoplasias/metabolismo , Animais , Regulação da Expressão Gênica , Humanos , Camundongos , Camundongos Transgênicos , Mitocôndrias/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Distrofias Musculares/metabolismo , Distrofia Muscular Animal , Proteína ORAI1 , Molécula 1 de Interação EstromalRESUMO
A T-->G transversion at nt 8993 in mitochondrial DNA of MTATP6 (encoding ATPase 6 of complex V of the respiratory chain) causes impaired mitochondrial ATP synthesis in two related mitochondrial disorders: neuropathy, ataxia and retinitis pigmentosa and maternally inherited Leigh syndrome. To overcome the biochemical defect, we expressed wildtype ATPase 6 protein allotopically from nucleus-transfected constructs encoding an amino-terminal mitochondrial targeting signal appended to a recoded ATPase 6 gene (made compatible with the universal genetic code) that also contained a carboxy-terminal FLAG epitope tag. After transfection of human cells, the precursor polypeptide was expressed, imported into and processed within mitochondria, and incorporated into complex V. Allotopic expression of stably transfected constructs in cytoplasmic hybrids (cybrids) homoplasmic with respect to the 8993T-->G mutation showed a significantly improved recovery after growth in selective medium as well as a significant increase in ATP synthesis. This is the first successful demonstration of allotopic expression of an mtDNA-encoded polypeptide in mammalian cells and could form the basis of a genetic approach to treat a number of human mitochondrial disorders.
Assuntos
Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/biossíntese , Núcleo Celular/metabolismo , DNA Mitocondrial/genética , Trifosfato de Adenosina/metabolismo , Alelos , Sequência de Aminoácidos , Animais , Western Blotting , Linhagem Celular , Mapeamento Cromossômico , Códon , Citosol/enzimologia , DNA Mitocondrial/metabolismo , Epitopos , Humanos , Imuno-Histoquímica , Microscopia de Fluorescência , Mitocôndrias/metabolismo , ATPases Mitocondriais Próton-Translocadoras , Modelos Genéticos , Dados de Sequência Molecular , Mutação , Peptídeos/química , Fenótipo , Plasmídeos/metabolismo , Polimorfismo de Fragmento de Restrição , Biossíntese de Proteínas , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Tempo , Transcrição Gênica , TransfecçãoRESUMO
The developing mammalian heart undergoes an important metabolic shift from glycolysis toward mitochondrial oxidation, such that oxidative phosphorylation defects may present with cardiac abnormalities. Here, we describe a new mechanistic link between mitochondria and cardiac morphogenesis, uncovered by studying mice with systemic loss of the mitochondrial citrate carrier SLC25A1. Slc25a1 null embryos displayed impaired growth, cardiac malformations, and aberrant mitochondrial function. Importantly, Slc25a1 haploinsufficient embryos, which are overtly indistinguishable from wild type, exhibited an increased frequency of these defects, suggesting Slc25a1 dose-dependent effects. Supporting clinical relevance, we found a near-significant association between ultrarare human pathogenic SLC25A1 variants and pediatric congenital heart disease. Mechanistically, SLC25A1 may link mitochondria to transcriptional regulation of metabolism through epigenetic control of PPARγ to promote metabolic remodeling in the developing heart. Collectively, this work positions SLC25A1 as a novel mitochondrial regulator of ventricular morphogenesis and cardiac metabolic maturation and suggests a role in congenital heart disease.
RESUMO
Mitochondrial composition varies by organ and their constituent cell types. This mitochondrial diversity likely determines variations in mitochondrial function. However, the heterogeneity of mitochondria in the brain remains underexplored despite the large diversity of cell types in neuronal tissue. Here, we used molecular systems biology tools to address whether mitochondrial composition varies by brain region and neuronal cell type in mice. We reasoned that proteomics and transcriptomics of microdissected brain regions combined with analysis of single-cell mRNA sequencing (scRNAseq) could reveal the extent of mitochondrial compositional diversity. We selected nuclear encoded gene products forming complexes of fixed stoichiometry, such as the respiratory chain complexes and the mitochondrial ribosome, as well as molecules likely to perform their function as monomers, such as the family of SLC25 transporters. We found that the proteome encompassing these nuclear-encoded mitochondrial genes and obtained from microdissected brain tissue segregated the hippocampus, striatum, and cortex from each other. Nuclear-encoded mitochondrial transcripts could only segregate cell types and brain regions when the analysis was performed at the single-cell level. In fact, single-cell mitochondrial transcriptomes were able to distinguish glutamatergic and distinct types of GABAergic neurons from one another. Within these cell categories, unique SLC25A transporters were able to identify distinct cell subpopulations. Our results demonstrate heterogeneous mitochondrial composition across brain regions and cell types. We postulate that mitochondrial heterogeneity influences regional and cell type-specific mechanisms in health and disease.
Assuntos
Genes Mitocondriais , Neurônios , Animais , Núcleo Celular , Hipocampo , Camundongos , Mitocôndrias/genética , Neurônios/metabolismoRESUMO
Chronic venous insufficiency (CVI) stems from venous hypertension, extravasation of blood, and iron-rich skin deposits. The latter is central to ulcer development through generating reactive oxygen species (ROS) that drive persistent local inflammation and the development of lipodermatosclerosis. The ability to study CVI cutaneous inflammation is fundamental to advancing therapies. To address this end, a novel protocol was adapted to investigate cutaneous wound healing in iron-induced inflammation. METHODS: Mice were injected subcutaneously or intraperitoneally with iron-dextran, and excisional wounding was performed. Histologic and biomolecular analysis was performed. RESULTS: Iron loading was associated with dense iron deposits similar to those in chronic venous stasis. Subcutaneous but not intraperitoneal loading resulted in dermal collagen expansion. Iron overload was associated with atypical antioxidant expression as compared to vehicle controls (p < 0.0001) as well as delayed wound healing by 3-4 days. A potent activator of Nuclear factor erythroid 2-related factor 2 (Nrf2), a major transcriptional regulator of redox status, was applied to establish therapeutic efficacy. Nrf2 activation in the wound resulted in significant reduction of closure times across all experimental arms. Antioxidant expression following topical treatment was significantly increased for intraperitoneally iron-loaded mice (p < 0.0001) but did not achieve significance for the subcutaneously-loaded animals. CONCLUSIONS: We have characterized a novel model of cutaneous iron-overload designed to advance our understanding of dysfunctional wound healing in CVI. Cutaneous changes of iron overload coincide with redox imbalance and delayed wound healing. By activating Nrf2, we demonstrate the regenerative potential of pro-antioxidant mediators in treating CVI related wound complications.
RESUMO
Unveiling the molecular mechanisms underlying tissue regeneration provides new opportunities to develop treatments for diabetic ulcers and other chronic skin lesions. Here, we show that Ccl2 secretion by epidermal keratinocytes is directly orchestrated by Nrf2, a prominent transcriptional regulator of tissue regeneration that is activated early after cutaneous injury. Through a unique feedback mechanism, we find that Ccl2 from epidermal keratinocytes not only drives chemotaxis of macrophages into the wound but also triggers macrophage expression of EGF, which in turn activates basal epidermal keratinocyte proliferation. Notably, we find dysfunctional activation of Nrf2 in epidermal keratinocytes of diabetic mice after wounding, which partly explains regenerative impairments associated with diabetes. These findings provide mechanistic insight into the critical relationship between keratinocyte and macrophage signaling during tissue repair, providing the basis for continued investigation of the therapeutic value of Nrf2.
Assuntos
Diabetes Mellitus Experimental/fisiopatologia , Fator de Crescimento Epidérmico/metabolismo , Queratinócitos/metabolismo , Macrófagos/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Engenharia Tecidual/métodos , Animais , Humanos , Camundongos , Transdução de SinaisRESUMO
Beyond their role as a cellular powerhouse, mitochondria are emerging as integral players in molecular signaling and cell fate determination through reactive oxygen species (ROS). While ROS production has historically been portrayed as an unregulated process driving oxidative stress and disease pathology, contemporary studies reveal that ROS also facilitate normal physiology. Mitochondria are especially abundant in cardiac tissue; hence, mitochondrial dysregulation and ROS production are thought to contribute significantly to cardiac pathology. Moreover, there is growing appreciation that medical therapies designed to mediate mitochondrial ROS production can be important strategies to ameliorate cardiac disease. In this review, we highlight evidence from animal models that illustrates the strong connections between mitochondrial ROS and cardiac disease, discuss advancements in the development of mitochondria-targeted antioxidant therapies, and identify challenges faced in bringing such therapies into the clinic.
Assuntos
Cardiopatias/metabolismo , Mitocôndrias/metabolismo , Doenças Mitocondriais/metabolismo , Estresse Oxidativo/fisiologia , Animais , Cardiomiopatias/metabolismo , Humanos , Espécies Reativas de Oxigênio/metabolismo , Transdução de SinaisRESUMO
Ca2+ handling by mitochondria is a critical function regulating both physiological and pathophysiological processes in a broad spectrum of cells. The ability to accurately measure the influx and efflux of Ca2+ from mitochondria is important for determining the role of mitochondrial Ca2+ handling in these processes. In this report, we present two methods for the measurement of mitochondrial Ca2+ handling in both isolated mitochondria and cultured cells. We first detail a plate reader-based platform for measuring mitochondrial Ca2+ uptake using the Ca2+ sensitive dye calcium green-5N. The plate reader-based format circumvents the need for specialized equipment, and the calcium green-5N dye is ideally suited for measuring Ca2+ from isolated tissue mitochondria. For our application, we describe the measurement of mitochondrial Ca2+ uptake in mitochondria isolated from mouse heart tissue; however, this procedure can be applied to measure mitochondrial Ca2+ uptake in mitochondria isolated from other tissues such as liver, skeletal muscle, and brain. Secondly, we describe a confocal microscopy-based assay for measurement of mitochondrial Ca2+ in permeabilized cells using the Ca2+ sensitive dye Rhod-2/AM and imaging using 2-dimensional laser-scanning microscopy. This permeabilization protocol eliminates cytosolic dye contamination, allowing for specific recording of changes in mitochondrial Ca2+. Moreover, laser-scanning microscopy allows for high frame rates to capture rapid changes in mitochondrial Ca2+ in response to various drugs or reagents applied in the external solution. This protocol can be applied to measure mitochondrial Ca2+ uptake in many cell types including primary cells such as cardiac myocytes and neurons, and immortalized cell lines.