RESUMO
Skeletal muscle regeneration involves a signaling network that regulates the proliferation, differentiation, and fusion of muscle precursor cells to injured myofibers. IRE1α, one of the arms of the unfolded protein response, regulates cellular proteostasis in response to ER stress. Here, we demonstrate that inducible deletion of IRE1α in satellite cells of mice impairs skeletal muscle regeneration through inhibiting myoblast fusion. Knockdown of IRE1α or its downstream target, X-box protein 1 (XBP1), also inhibits myoblast fusion during myogenesis. Transcriptome analysis revealed that knockdown of IRE1α or XBP1 dysregulates the gene expression of molecules involved in myoblast fusion. The IRE1α-XBP1 axis mediates the gene expression of multiple profusion molecules, including myomaker (Mymk). Spliced XBP1 (sXBP1) transcription factor binds to the promoter of Mymk gene during myogenesis. Overexpression of myomaker in IRE1α-knockdown cultures rescues fusion defects. Inducible deletion of IRE1α in satellite cells also inhibits myoblast fusion and myofiber hypertrophy in response to functional overload. Collectively, our study demonstrates that IRE1α promotes myoblast fusion through sXBP1-mediated up-regulation of the gene expression of multiple profusion molecules, including myomaker.
Assuntos
Fusão Celular , Endorribonucleases , Desenvolvimento Muscular , Músculo Esquelético , Mioblastos , Proteínas Serina-Treonina Quinases , Transdução de Sinais , Proteína 1 de Ligação a X-Box , Animais , Proteína 1 de Ligação a X-Box/metabolismo , Proteína 1 de Ligação a X-Box/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Camundongos , Mioblastos/metabolismo , Mioblastos/citologia , Músculo Esquelético/metabolismo , Músculo Esquelético/citologia , Desenvolvimento Muscular/genética , Endorribonucleases/metabolismo , Endorribonucleases/genética , Células Satélites de Músculo Esquelético/metabolismo , Regeneração/genética , Diferenciação Celular/genética , Regulação da Expressão Gênica , Proteínas de Membrana , Proteínas MuscularesRESUMO
Polymyxins are a last-resort treatment option for multidrug-resistant gram-negative bacterial infections, but they are associated with nephrotoxicity. Gelofusine was previously shown to reduce polymyxin-associated kidney injury in an animal model. However, the mechanism(s) of renal protection has not been fully elucidated. Here, we report the use of a cell culture model to provide insights into the mechanisms of renal protection. Murine epithelial proximal tubular cells were exposed to polymyxin B. Cell viability, lactate dehydrogenase (LDH) release, polymyxin B uptake, mitochondrial superoxide production, nuclear morphology, and apoptosis activation were evaluated with or without concomitant gelofusine. A megalin knockout cell line was used as an uptake inhibition control. Methionine was included in selected experiments as an antioxidant control. A polymyxin B concentration-dependent reduction in cell viability was observed. Increased viability was observed in megalin knockout cells following comparable polymyxin B exposures. Compared with polymyxin B exposure alone, concomitant gelofusine significantly increased cell viability as well as reduced LDH release, polymyxin B uptake, mitochondrial superoxide, and apoptosis. Gelofusine and methionine were more effective at reducing renal cell injury in combination than either agent alone. In conclusion, the mechanisms of renal protection by gelofusine involve decreasing cellular drug uptake, reducing subsequent oxidative stress and apoptosis activation. These findings would be valuable for translational research into clinical strategies to attenuate drug-associated acute kidney injury.NEW & NOTEWORTHY Gelofusine is a gelatinous saline solution with the potential to attenuate polymyxin-associated nephrotoxicity. We demonstrated that the mechanisms of gelofusine renal protection involve reducing polymyxin B uptake by proximal tubule cells, limiting subsequent oxidative stress and apoptosis activation. In addition, gelofusine was more effective at reducing cellular injury than a known antioxidant control, methionine, and a megalin knockout cell line, indicating that gelofusine likely has additional pharmacological properties besides only megalin inhibition.
Assuntos
Antibacterianos , Apoptose , Polimixina B , Animais , Polimixina B/farmacologia , Camundongos , Apoptose/efeitos dos fármacos , Antibacterianos/farmacologia , Antibacterianos/toxicidade , Sobrevivência Celular/efeitos dos fármacos , Túbulos Renais Proximais/metabolismo , Túbulos Renais Proximais/efeitos dos fármacos , Túbulos Renais Proximais/patologia , Linhagem Celular , Proteína-2 Relacionada a Receptor de Lipoproteína de Baixa Densidade/metabolismo , Proteína-2 Relacionada a Receptor de Lipoproteína de Baixa Densidade/genética , Injúria Renal Aguda/metabolismo , Injúria Renal Aguda/patologia , Injúria Renal Aguda/prevenção & controle , Injúria Renal Aguda/induzido quimicamente , Estresse Oxidativo/efeitos dos fármacos , L-Lactato Desidrogenase/metabolismoRESUMO
Selenoprotein N-related myopathy (SEPN1-RM) is a genetic disease that causes muscle weakness and respiratory failure. Germani et al.1 demonstrate that diaphragm weakness in SEPN1-RM is prevented by the inhibition of ER stress or ERO1 oxidoreductase regulated by transcription factor CHOP.