Long-Term Blocking of Calcium Channels in mdx Mice Results in Differential Effects on Heart and Skeletal Muscle

Abstract

The disease mechanisms underlying dystrophin-deficient muscular dystrophy are complex, involving not only muscle membrane fragility, but also dysregulated calcium homeostasis. Specifically, it has been proposed that calcium channels directly initiate a cascade of pathological events by allowing calcium ions to enter the cell. The objective of this study was to investigate the effect of chronically blocking calcium channels with the aminoglycoside antibiotic streptomycin from onset of disease in the mdx mouse model of Duchenne muscular dystrophy (DMD).Treatment in utero onwards delayed onset of dystrophic symptoms in the limb muscle of young mdx mice, but did not prevent degeneration and regeneration events occurring later in the disease course. Long-term treatment had a positive effect on limb muscle pathology, reduced fibrosis, increased sarcolemmal stability, and promoted muscle regeneration in older mice. However, streptomycin treatment did not show positive effects in diaphragm or heart muscle, and heart pathology was worsened. Thus, blocking calcium channels even before disease onset does not prevent dystrophy, making this an unlikely treatment for DMD. These findings highlight the importance of analyzing several time points throughout the life of the treated mice, as well as analyzing many tissues, to get a complete picture of treatment efficacy.

Sulforaphane Attenuates Muscle Inflammation in Dystrophin-deficient mdx Mice via NF-E2-related Factor 2 (Nrf2)-mediated Inhibition of NF-κB Signaling Pathway

“…Immunohistochemistry/Immunofluorescence-Immunohistochemistry and immunofluorescence of the muscle tissues (TA, TB, and GAS) were performed as described previously (25). 10-m muscle sections were incubated with commercial rabbit polyclonal antibodies against Nrf2, HO-1, NF-B(p65), and CD45 at 1:100 dilution overnight at 4°C.…”

“…6, A and C). CD45, which can detect all lymphocytes and is a specific marker of inflammatory cell infiltration, is frequently used as an indicator of inflammation (25). To further determine whether Nrf2 (activated by SFN)-mediated inhibition of NF-B signaling pathway could result in an attenuation of the inflammation in dystrophic muscle, we also examined the protein expression of CD45 in TA muscles from BL10 and mdx mice with Western blotting and found that protein expression of CD45 was much higher (ϳ2.4-fold) in mdx mice than in BL10 controls (Fig.…”

Na+ Dysregulation Coupled with Ca2+ Entry through NCX1 Promotes Muscular Dystrophy in Mice

“…The diaphragm is specialized to contract rhythmically and hence has more features in common with the heart than with the limb musculature (52)(53)(54)(55). In the heart, NCX1 is known to operate predominantly in forward mode to remove Ca 2ϩ after each contractile cycle, which we suspected could also be the case in the diaphragm.…”

Quantitative Proteomic Analysis Reveals Metabolic Alterations, Calcium Dysregulation, and Increased Expression of Extracellular Matrix Proteins in Laminin α2 Chain–deficient Muscle

“…In line with the hypothesis that calcium dysregulation could be a primary event in the onset of muscular dystrophy, several treatment approaches aimed at normalizing the calcium homeostasis in dystrophic muscle have been evaluated in mice, and in particular in the mdx mouse model for Duchenne muscular dystrophy (63)(64)(65). Notably, it has been demonstrated that overexpression of SERCA1 is beneficial in the mdx mouse, as well as in a mouse model for sarcoglycanopathy (65).…”