Leupeptin-based inhibitors do not improve the mdx phenotype.
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.
Selsby
Joshua
J
Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Pendrak
Klara
K
Zadel
Monica
M
Tian
Zuozhen
Z
Pham
Jennifer
J
Carver
Ted
T
Acosta
Pedro
P
Barton
Elisabeth
E
Sweeney
H Lee
HL
D000818:Animals; D015415:Biomarkers / Q000097:blood; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000378:metabolism; D003402:Creatine Kinase / Q000097:blood; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005838:Genotype; D007976:Leupeptins / Q000494:pharmacology*; D051379:Mice; D018101:Mice, Inbred mdx; D009119:Muscle Contraction / Q000187:drug effects; D053580:Muscle Strength / Q000187:drug effects; D020388:Muscular Dystrophy, Duchenne / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D009336:Necrosis; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D013997:Time Factors
D015415:Biomarkers; D002135:Calcium-Binding Proteins; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; C033668:calpastatin; D003402:Creatine Kinase; D002154:Calpain; D046988:Proteasome Endopeptidase Complex; C032854:leupeptin