WP5356 - Affected pathways in Duchenne muscular dystrophy - Homo sapiens

DMD (Duchenne Muscular Dystrophy) is a genetic disorder that primarily affects muscles in the body, causing progressive muscle weakness and wasting. It is caused by mutations in the DMD gene, which results in a deficiency or absence of the protein dystrophin, leading to muscle degeneration.

DMD is characterized by abnormal calcium levels resulting from dysfunction in the muscle cell membrane. This leads to the uncontrolled opening of the mitochondrial permeability transition pore (mPTP) which inhibits ATP synthesis and thus, drives the cell into apoptosis. This influx activates a cascade of harmful events, including increased production of reactive oxygen species (ROS) and activation of proteases that can damage the cell structure of muscle fibers.
The lack of the dystrophin protein affects essential components for muscle contraction namely the Disassembled Dystrophin-associated glycoprotein complex (DAPC) which disturbs the normal contraction-relaxation process of the muscle in DMD. Sustained contractions occur due to the high calcium influx causing muscle stiffness and fibrosis, which are known characteristics of DMD.

Indeed, fibrosis is commonly stimulated in dystrophic muscle cells as a result of the upregulation of several pro-fibrotic transcription factors such as SERPINE1, SCX and GL1. Hence, excessive amounts of collagen and fibronectin are produced, enhancing fibrosis.

All these events cause chronic inflammation in the muscle cell, attracting pro-inflammatory cytokines, chemokines and other inflammatory mediators. The chronic inflammation in DMD can further perpetuate muscle degeneration, fibrosis, and impaired muscle function.

Acknowledgments: Bria Jackson, Amaia Alvarez van Schie, Otto Rämö, Tuneille Adelaar