Calcium and the damage pathways in muscular dystrophy

Area of Science:

• Muscle physiology
• Cellular biology
• Biochemistry

Background:

• Duchenne muscular dystrophy (DMD) results from dystrophin absence, leading to muscle fragility.
• MDX mouse models show heightened susceptibility to stretch-induced muscle injury.
• Elevated intracellular calcium ([Ca2+]i) is observed in damaged mdx muscle fibers.

Purpose of the Study:

• To review evidence linking stretch-induced muscle damage in DMD to calcium channel activity.
• To explore the role of TRPC1, reactive oxygen species (ROS), and src kinase in this process.
• To elucidate the molecular pathway responsible for calcium ([Ca2+]i) influx in DMD.

Main Methods:

• Review of experimental data on mdx mouse muscle fibers.
• Analysis of calcium ([Ca2+]i) concentration changes following stretched contractions.
• Investigation of TRPC1 gene expression and protein localization in muscle cells.
• Assessment of the effects of ROS and src kinase inhibition on calcium ([Ca2+]i) influx.

Main Results:

• Stretched contractions in mdx muscle fibers cause sustained increases in intracellular calcium ([Ca2+]i).
• Calcium ([Ca2+]i) influx occurs via stretch-activated channels (SACNSC), with TRPC1 as a candidate.
• Stretch-induced reactive oxygen species (ROS) production activates SACNSC, involving src kinase.
• TRPC1 membrane expression requires coexpression with caveolin-3 for ROS-mediated activation.

Conclusions:

• A pathway involving stretch-induced ROS production, src kinase activation, and subsequent SACNSC opening leads to calcium ([Ca2+]i) entry.
• This mechanism contributes significantly to muscle damage in Duchenne muscular dystrophy (DMD).
• Targeting this pathway may offer therapeutic strategies for DMD.