Biology subjects

Cooper, R. G.

Publications and source records attributed to Cooper, R. G..

3 recordsLinked to original sources

bioRxiv2022

Major Histocompatibility Complex (MHC) I-induced Endoplasmic Reticulum (ER) Stress mediates the secretion of pro-inflammatory muscle-derived cytokines

Major histocompatibility complex (MHC) I is an important component of intracellular antigen presentation. However, improper expression of MHC I upon the cell surface has been associated with several autoimmune diseases. Myositis is a rare acquired autoimmune diseases which targets skeletal muscle, and MHC I overexpression on the surface of muscle fibres and immune cell infiltration are clinical hallmarks. MHC I overexpression may have an important pathogenic role, mediated by the activation of the endoplasmic reticulum (ER) stress response. Given the evidence that muscle is a diverse source of cytokines, we aimed to investigate whether MHC I overexpression can modify the profile of muscle-derived cytokines and what role the ER stress pathway may play. Using C2C12 myoblasts we overexpressed MHC I with a H-2kb vector in the presence or absence of salubrinal an ER stress pathway modifying compound. MHC I overexpression induced ER stress pathway activation and elevated cytokine gene expression. MHC I overexpression caused significant release of cytokines and chemokines, which was attenuated in the presence of salubrinal. Conditioned media from MHC I overexpressing cells induced in vitro T-cell chemotaxis, atrophy of healthy myotubes and modified mitochondrial function, features which were attenuated in the presence of salubrinal. Collectively, these data suggest that MHC I overexpression can induce pro-inflammatory cytokine/chemokine release from C2C12 myoblasts, a process which appears to be mediated in-part by the ER stress pathway.

cell biology↗

bioRxiv2020

Eukarion-134 attenuates endoplasmic reticulum stress-induced mitochondrial dysfunction in human skeletal muscle cells

ABSTRACTMaladaptive endoplasmic reticulum (ER) stress is associated with modified reactive oxygen species (ROS) generation, altered mitochondrial bioenergetics, and oxidative damage; and is postulated as a potential mechanism involved in the underlying muscle weakness experienced by patients with myositis, an acquired autoimmune neuromuscular disease. In this study, we investigate the impact of ROS generation in an in vitro model of ER stress in skeletal muscle, using the ER stress inducer tunicamycin (24 hours) in presence or absence of a superoxide dismutase/catalase mimetic Eukarion (EUK)-134. ER stress activation, ROS generation, mitochondrial function, biogenesis, morphology and dynamics (fusion/fission) were examined. Tunicamycin induced maladaptive ER stress, validated by stimulation of GRP94, GRP78, CHOP, XBP-1, ERDJ4, and GADD34, which were mostly mitigated by EUK-134 at transcriptional level. ER stress triggered mitochondrial unfolded protein response and promoted mitochondrial dysfunction, described by substantial loss of mitochondrial membrane potential, as well as reduction of respiratory control ratio, reserve capacity, phosphorylating respiration, and coupling efficiency, which was ameliorated by EUK-134. ROS-mediated biogenesis and fusion of mitochondria was evident in presence of tunicamycin, which however, had high propensity of fragmentation, accompanied by upregulated mRNA levels of fission-related markers. Increased cellular ROS generation oxidative stress was observed in response to ER stress that was ameliorated in the presence of EUK-134, even though no changes in mitochondrial superoxide were noticeable. These findings suggest that targeting ROS generation using the superoxide dismutase/catalase mimetic EUK-134 can amend aspects of ER stress-induced changes in mitochondrial dynamics and function. Overall, this study suggests that in instances of chronic ER stress, such as in myositis, quenching ROS generation may be a promising therapy for muscle weakness and dysfunction.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2018

17-(Allylamino)-17demethoxygeldanamycin reduces Endoplasmic Reticulum (ER) stress-induced mitochondrial dysfunction in C2C12 myotubes

In patients with myositis, persistent skeletal muscle weakness in the absence of significant inflammatory cell infiltrates is a well-recognised, but poorly understood, cause of morbidity. This has led researchers to investigate cellular mechanisms independent of immune cells, which may contribute to this underlying muscle weakness. Chronic ER stress pathway activation is evident in the muscle of myositis patients, and is now a potential mediator of muscle weakness in the absence of inflammation. Abnormal ER stress pathway activation is associated with mitochondrial dysfunction, resulting in bioenergetic deficits and reactive oxygen species (ROS) generation, which in this context may potentially damage muscle proteins and thus impair contractile performance. This study examined whether treatment with the HSP90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17AAG) could mitigate these ER stress-induced changes. C2C12 myotubes were treated with the ER stress-inducing compound Tunicamycin, in the presence or absence of 17AAG. Myotubes were examined for changes relating to ER stress pathway activation, mitochondrial function, markers of oxidative damage and in myotubular dimensions. ER stress pathway activation caused mitochondrial dysfunction, as evidenced by reduced oxygen consumption and ATP generation and by increased gene expression levels of the bio-energetic regulator, uncoupling protein 3 (UCP-3), the latter indicative of electron transport chain uncoupling. ER stress pathway activation also caused increased gene expression of superoxide dismutase (SOD) 2 and peroxiredoxin (PRDX) 3, elevated H2O2 levels, and reduced total thiol pool levels and a significant diminution of myotubular dimensions. Exposure to 17AAG ameliorated these ER stress-induced changes. These findings, which suggest that 17AAG can reduce ER stress-induced mitochondrial dysfunction, oxidative damage and myotubular atrophy, have potential implications in the context of human myositis.

cell biology↗