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The proteasome inhibitor MG132 reduces immobilization-induced skeletal muscle atrophy in mice
Annabelle Z Caron1, Sonia Haroun, Elisabeth Leblanc
1Centre de Recherche Clinique Étienne-Lebel, 3001-12th Avenue North, Sherbrooke, QC J1H5N4, Canada.
Background:
Skeletal muscle atrophy is a serious concern for the rehabilitation of patients afflicted by prolonged limb restriction. This debilitating condition is associated with a marked activation of NFκB activity. The ubiquitin-proteasome pathway degrades the NFκB inhibitor IκBα, enabling NFκB to translocate to the nucleus and bind to the target genes that promote muscle atrophy. Although several studies showed that proteasome inhibitors are efficient to reduce atrophy, no studies have demonstrated the ability of these inhibitors to preserve muscle function under catabolic condition.
Methods:
We recently developed a new hindlimb immobilization procedure that induces significant skeletal muscle atrophy and used it to show that an inflammatory process characterized by the up-regulation of TNFα, a known activator of the canonical NFκB pathway, is associated with the atrophy. Here, we used this model to investigate the effect of in vivo proteasome inhibition on the muscle integrity by histological approach. TNFα, IL-1, IL-6, MuRF-1 and Atrogin/MAFbx mRNA level were determined by qPCR. Also, a functional measurement of locomotors activity was performed to determine if the treatment can shorten the rehabilitation period following immobilization.
Results:
In the present study, we showed that the proteasome inhibitor MG132 significantly inhibited IκBα degradation thus preventing NFκB activation in vitro. MG132 preserved muscle and myofiber cross-sectional area by downregulating the muscle-specific ubiquitin ligases atrogin-1/MAFbx and MuRF-1 mRNA in vivo. This effect resulted in a diminished rehabilitation period.
Conclusion:
These finding demonstrate that proteasome inhibitors show potential for the development of pharmacological therapies to prevent muscle atrophy and thus favor muscle rehabilitation.
Insights
Proteasome inhibitors like MG132 prevent skeletal muscle atrophy by inhibiting NFκB activation. This preserves muscle function and shortens rehabilitation periods after immobilization.
Area of Science:
- Muscle physiology and molecular biology
- Pharmacology and drug development
- Rehabilitation medicine
Background:
- Skeletal muscle atrophy is a significant issue in patient rehabilitation following prolonged limb restriction.
- Atrophy is linked to Nuclear Factor kappa B (NFκB) activation, mediated by the ubiquitin-proteasome pathway degrading the NFκB inhibitor IκBα.
- While proteasome inhibitors show promise, their ability to preserve muscle function during catabolic conditions remains understudied.
Purpose of the Study:
- To investigate the efficacy of in vivo proteasome inhibition in preserving muscle integrity and function.
- To evaluate the impact of proteasome inhibition on key molecular markers of muscle atrophy.
- To determine if proteasome inhibition can accelerate the rehabilitation period post-immobilization.
Main Methods:
- Utilized a hindlimb immobilization model to induce skeletal muscle atrophy.
- Administered the proteasome inhibitor MG132 in vivo.
- Assessed muscle integrity via histology, measured mRNA levels of TNFα, IL-1, IL-6, MuRF-1, and Atrogin/MAFbx using qPCR, and evaluated locomotor activity.
Main Results:
- MG132 effectively inhibited IκBα degradation, preventing NFκB activation.
- Proteasome inhibition preserved muscle and myofiber cross-sectional area.
- MG132 treatment downregulated atrogin-1/MAFbx and MuRF-1 mRNA, leading to a reduced rehabilitation period.
Conclusions:
- Proteasome inhibitors demonstrate potential as therapeutic agents to prevent muscle atrophy.
- Pharmacological inhibition of the proteasome pathway can aid in muscle rehabilitation.
- These findings support the development of proteasome inhibitor-based therapies for muscle-wasting conditions.
