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Updated: Jun 8, 2026
Assessing Functional Performance in the Mdx Mouse Model
Published on: March 27, 2014
Leupeptin-based inhibitors do not improve the mdx phenotype
Joshua Selsby1, Klara Pendrak, Monica Zadel
1Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Abstract:
Calpain activation has been implicated in the disease pathology of Duchenne muscular dystrophy. Inhibition of calpain has been proposed as a promising therapeutic target, which could lessen the protein degradation and prevent progressive fibrosis. At the same time, there are conflicting reports as to whether elevation of calpastatin, an endogenous calpain inhibitor, alters pathology. We compared the effects of pharmacological calpain inhibition in the mdx mouse using leupeptin and a proprietary compound (C101) that linked the inhibitory portion of leupeptin to carnitine (to increase uptake into muscle). Administration of C101 for 4 wk did not improve muscle histology, function, or serum creatine kinase levels in mdx mice. Mdx mice injected daily with leupeptin (36 mg/kg) for 6 mo also failed to show improved muscle function, histology, or creatine kinase levels. Biochemical analysis revealed that leupeptin administration caused an increase in m-calpain autolysis and proteasome activity, yet calpastatin levels were similar between treated and untreated mdx mice. These data demonstrate that pharmacological inhibition of calpain is not a promising intervention for the treatment of Duchenne muscular dystrophy due to the ability of skeletal muscle to counter calpain inhibitors by increasing multiple degradative pathways.
Insights
Pharmacological calpain inhibition did not improve outcomes in Duchenne muscular dystrophy models. Skeletal muscle countered these inhibitors by increasing degradative pathways, suggesting this approach is not a viable therapeutic strategy.
Area of Science:
- Biochemistry
- Molecular Biology
- Muscle Physiology
Background:
- Calpain activation is linked to Duchenne muscular dystrophy (DMD) pathology.
- Calpain inhibition is a potential therapeutic strategy for DMD, aiming to reduce protein degradation and fibrosis.
- Conflicting reports exist regarding the role of calpastatin, an endogenous calpain inhibitor, in DMD.
Purpose of the Study:
- To investigate the efficacy of pharmacological calpain inhibition in the mdx mouse model of DMD.
- To compare the effects of leupeptin and a novel compound (C101) on muscle pathology, function, and biochemical markers in mdx mice.
Main Methods:
- Administration of leupeptin and C101 to mdx mice.
- Assessment of muscle histology, function, and serum creatine kinase levels.
- Biochemical analysis of calpain activity, autolysis, proteasome activity, and calpastatin levels.
Main Results:
- Neither C101 (4 weeks) nor leupeptin (6 months) improved muscle histology, function, or creatine kinase levels in mdx mice.
- Leupeptin administration increased m-calpain autolysis and proteasome activity.
- Calpastatin levels remained unchanged in treated versus untreated mdx mice.
Conclusions:
- Pharmacological calpain inhibition is not a promising therapeutic intervention for Duchenne muscular dystrophy.
- Skeletal muscle can counteract calpain inhibitors by upregulating alternative degradative pathways, limiting therapeutic efficacy.
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