Mitochondrial defects in motor neurons are pathological hallmarks of ALS, a neuromuscular disease with no effective treatment. Studies have shown that butyrate, a natural gut-bacteria product, alleviates the disease progression of ALS mice overexpressing a human ALS-associated mutation, hSOD1G93A. In the current study, we examined the potential molecular mechanisms underlying the effect of butyrate on mitochondrial function in cultured motor-neuron-like NSC34 with overexpression of hSOD1G93A (NSC34-G93A). The live cell confocal imaging study demonstrated that 1mM butyrate in the culture medium improved the mitochondrial network with reduced fragmentation in NSC34-G93A cells. Seahorse analysis revealed that NSC34-G93A cells treated with butyrate showed an increase of ~5-fold in mitochondrial Spare Respiratory Capacity with elevated Maximal Respiration. The time-dependent changes in the mRNA level of PGC1α, a master regulator of mitochondrial biogenesis, revealed a burst induction with an early increase (~5-fold) at 4 h, a peak at 24 h (~19-fold), and maintenance at 48 h (8-fold) post-treatment. In line with the transcriptional induction of PGC1α, both the mRNA and protein levels of the key molecules (MTCO1, MTCO2, and COX4) related to the mitochondrial electron transport chain were increased following the butyrate treatment. Our data indicate that activation of the PGC1α signaling axis could be one of the molecular mechanisms underlying the beneficial effects of butyrate treatment in improving mitochondrial bioenergetics in NSC34-G93A cells.
Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disease that affects all voluntary muscles in the body, leading to paralysis and respiratory failure, while the extraocular muscles (EOMs) are largely spared even at the end-stage of ALS. Through whole-mount muscle imaging, we detected severe denervation along with depletion of Pax7+ satellite cells (SCs) peri-neuromuscular junction (NMJ) in hindlimb and diaphragm muscles of end-stage SOD1G93A mice (a familial ALS mouse model), but not in EOMs. Upon isolating SCs from different muscles using fluorescence activated cell sorting (FACS), the FACS profiles of hindlimb and diaphragm SCs of G93A mice exhibited activation and depletion phenotypes but not in wildtype controls. Importantly, both wildtype and G93A EOM SCs exhibited spontaneous activation behavior without significant differences in abundance. Examination of Pax7+ and Ki67+ cell ratios and RNA-Seq of SCs cultured in growth and differentiation medium revealed that EOM SCs maintained renewability and stemness better than diaphragm and hindlimb counterparts, especially in differentiation-favoring environments. Comparative functional annotation analyses indicate enrichment of axon guidance molecules, such as Cxcl12, in cultured EOM SCs. In neuromuscular coculture experiments, overexpressing Cxcl12 in G93A hindlimb SC-derived myotubes enhanced motor neuron axon extension and improved innervation, partially replicating the multi-innervation property of EOM SC-derived myotubes. The unique SC homeostasis regulation and the production of axon guidance molecules including Cxcl12 may explain the ALS resistant nature of EOMs. Intriguingly, feeding G93A mice with sodium butyrate extended the life span of G93A mice, alleviated NMJ denervation and SCs depletion. Butyrate treatment promoted renewability and stemness of cultured G93A hindlimb and diaphragm SCs, as well as Cxcl12 expression. Thus, butyrate-induced EOM SC-like transcriptomic patterns may contribute to its beneficiary effects observed in G93A mice.
The plasma membrane (sarcolemma) of skeletal muscle myofibers is susceptible to injury caused by physical and chemical stresses during normal daily movement and/or under disease conditions. These acute plasma membrane disruptions are normally compensated by an intrinsic membrane resealing process involving interactions of multiple intracellular proteins including dysferlin, annexin, caveolin, and Mitsugumin 53 (MG53)/TRIM72. There is new evidence for compromised muscle sarcolemma repair mechanisms in Amyotrophic Lateral Sclerosis (ALS). Mitochondrial dysfunction in proximity to neuromuscular junctions (NMJs) increases oxidative stress, triggering MG53 aggregation and loss of its function. Compromised membrane repair further worsens sarcolemma fragility and amplifies oxidative stress in a vicious cycle. This article is to review existing literature supporting the concept that ALS is a disease of oxidative-stress induced disruption of muscle membrane repair that compromise the integrity of the NMJs and hence augmenting muscle membrane repair mechanisms could represent a viable therapeutic strategy for ALS.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.