Altered expression, intracellular distribution and activity of lymphocyte calpain II in Duchenne muscular dystrophy

LED therapy plus idebenone treatment targeting calcium and mitochondrial signaling pathways in dystrophic muscle cells

Intracellular calcium dysregulation, oxidative stress, and mitochondrial dysfunction are some of the main pathway contributors towards disease progression in Duchenne muscular dystrophy (DMD). This study is aimed at investigating the effects of light emitting diode therapy (LEDT) and idebenone antioxidant treatment, applied alone or together in dystrophic primary muscle cells from mdx mice, the experimental model of DMD. Mdx primary muscle cells were submitted to LEDT and idebenone treatment and evaluated for cytotoxic effects and calcium and mitochondrial signaling pathways. LEDT and idebenone treatment showed no cytotoxic effects on the dystrophic muscle cells. Regarding the calcium pathways, after LEDT and idebenone treatment, a significant reduction in intracellular calcium content, calpain-1, calsequestrin, and sarcolipin levels, was observed. In addition, a significant reduction in oxidative stress level markers, such as H2O2, and 4-HNE levels, was observed. Regarding mitochondrial signaling pathways, a significant increase in oxidative capacity (by OCR and OXPHOS levels) was observed. In addition, the PGC-1α, SIRT-1, and PPARδ levels were significantly higher in the LEDT plus idebenone treated-dystrophic muscle cells. Together, the findings suggest that LEDT and idebenone treatment, alone or in conjunction, can modulate the calcium and mitochondrial signaling pathways, such as SLN, SERCA 1, and PGC-1α, contributing towards the improvement of the dystrophic phenotype in mdx muscle cells. In addition, data from the LEDT plus idebenone treatment showed slightly better results than those of each separate treatment in terms of SLN, OXPHOS, and SIRT-1.

Abnormal Calcium Handling in Duchenne Muscular Dystrophy: Mechanisms and Potential Therapies

Duchenne muscular dystrophy (DMD) is an X-linked muscle-wasting disease caused by the loss of dystrophin. DMD is associated with muscle degeneration, necrosis, inflammation, fatty replacement, and fibrosis, resulting in muscle weakness, respiratory and cardiac failure, and premature death. There is no curative treatment. Investigations on disease-causing mechanisms offer an opportunity to identify new therapeutic targets to treat DMD. An abnormal elevation of the intracellular calcium (Cai2+) concentration in the dystrophin-deficient muscle is a major secondary event, which contributes to disease progression in DMD. Emerging studies have suggested that targeting Ca²⁺-handling proteins and/or mechanisms could be a promising therapeutic strategy for DMD. Here, we provide an updated overview of the mechanistic roles the sarcolemma, sarcoplasmic/endoplasmic reticulum, and mitochondria play in the abnormal and sustained elevation of Cai2+ levels and their involvement in DMD pathogenesis. We also discuss current approaches aimed at restoring Ca²⁺ homeostasis as potential therapies for DMD.

Peptidyl alpha-ketoamides with nucleobases, methylpiperazine, and dimethylaminoalkyl substituents as calpain inhibitors

A series of peptidyl alpha-ketoamides with the general structure Cbz-L-Leu-D,L-AA-CONH-R were synthesized and evaluated as inhibitors for the cysteine proteases calpain I, calpain II, and cathepsin B. Nucleobases, methylpiperazine, and dimethylaminoalkyl groups were incorporated into the primed region of the inhibitors to generate compounds that potentially cross the blood-brain barrier. Two of these compounds (Cbz-Leu-D,L-Abu-CONH-(CH(2))(3)-adenin-9-yl and Cbz-Leu-D,L-Abu-CONH-(CH(2))(3)-(4-methylpiperazin-1-yl) have been shown to have useful concentrations in the brain in animals. The best inhibitor for calpain I was Cbz-Leu-D,L-Abu-CONH-(CH(2))(3)-2-methoxyadenin-9-yl (K(i) = 23 nM), and the best inhibitor for calpain II was Cbz-Leu-D,L-Phe-CONH-(CH(2))(3)-adenin-9-yl (K(i) = 68 nM). On the basis of the crystal structure obtained with heterocyclic peptidyl alpha-ketoamides, we have improved inhibitor potency by introducing a small hydrophobic group on the adenine ring. These inhibitors have good potential to be used in the treatment of neurodegenerative diseases.

Characterization of the calpain/calpastatin system in human hemopoietic cell lines

As previously suggested by PCR analysis [R. DeTullio, R. Stifanese, F. Salamino, S. Pontremoli, E. Melloni, Characterization of a new p94-like calpain form in human lymphocytes, Biochem. J. 375 (2003) 689-696], a p94-like calpain was now established to be present in six different human cells resembling the various peripheral blood cell types. This protease resulted to be the predominant calpain isoforms whereas the conventional mu- and m-calpains are also expressed although at lower or almost undetectable amounts. The p94-like calpain has been identified by a specific mAb and displays unique features such as: Ca2+ requirement for half maximum activity around 30 microM; no autolytic conversion to a low Ca2+ requiring form and lower sensitivity to calpastatin inhibition. Following cell stimulation, the p94-like calpain undergoes inactivation, a process indicating that the protease is activated and participates in the cell responses to stimuli. The involvement of this protease isoform in immunocompetent cell activation is further supported by its partial recruitment on plasma membranes, the site of action of the conventional calpain forms. The amount of calpain translocated to the membranes correlates to the level of calpastatin which has been shown to control this process through the formation of a complex with calpain, which maintains the protease in the cytosol. These results provide new information on the calpain/calpastatin system expressed in immunocompetent cells and on the functional relationship between the p94-like calpain and the biological function of these cells.