Mineralocorticoid receptor antagonists and glucocorticoids differentially affect skeletal muscle inflammation and pathology in muscular dystrophy

Mineralocorticoid receptor antagonists (MRAs) slow cardiomyopathy in patients with Duchenne muscular dystrophy (DMD) and improve skeletal muscle pathology and function in dystrophic mice. However, glucocorticoids, known antiinflammatory drugs, remain a standard of care for DMD, despite substantial side effects. Exact mechanisms underlying mineralocorticoid receptor (MR) signaling contribution to dystrophy are unknown. Whether MRAs affect inflammation in dystrophic muscles and how they compare with glucocorticoids is unclear. The MRA spironolactone and glucocorticoid prednisolone were each administered for 1 week to dystrophic mdx mice during peak skeletal muscle necrosis to compare effects on inflammation. Both drugs reduced cytokine levels in mdx quadriceps, but prednisolone elevated diaphragm cytokines. Spironolactone did not alter myeloid populations in mdx quadriceps or diaphragms, but prednisolone increased F4/80hi macrophages. Both spironolactone and prednisolone reduced inflammatory gene expression in myeloid cells sorted from mdx quadriceps, while prednisolone additionally perturbed cell cycle genes. Spironolactone also repressed myeloid expression of the gene encoding fibronectin, while prednisolone increased its expression. Overall, spironolactone exhibits antiinflammatory properties without altering leukocyte distribution within skeletal muscles, while prednisolone suppresses quadriceps cytokines but increases diaphragm cytokines and pathology. Antiinflammatory properties of MRAs and different limb and respiratory muscle responses to glucocorticoids should be considered when optimizing treatments for patients with DMD.