Low doses of 3-nitropropionic acid in vivo induce damage in mouse skeletal muscle

Mitochondrial alterations are believed to play a critical role in the pathophysiology of neurodegenerative diseases and in some well-described myopathies. In the present study, we evaluated muscle changes in vivo after blocking the mitochondrial complex II of the respiratory chain by using 3-nitropropionic acid (3-NP). This neurotoxin has been used as a pharmacological tool in animal models to address some of the metabolic modifications that might underlie central neurodegeneration; however, changes in peripheral musculature have not been documented. We believe that skeletal muscles must be affected because their integrity highly depends on oxidative metabolism. Therefore, histochemical, ultrastructural, and biochemical changes were studied in the muscles of mice treated with low doses of 3-NP (15 mg/kg, i.p., for 5 days). 3-NP-treated mice displayed changes in alkaline phosphatase (APase), succinic dehydrogenase (SDH), and cytochrome c oxidase (COX) levels in the gracilis and gastrocnemius muscles. These changes were statistically significant for APase and SDH in both muscles and for COX only in the gastrocnemius. No significant alterations in acetylcholinesterase (AChE) expression were observed in either muscle. Analysis of the muscle ultrastructure revealed mitochondrial atrophy as well as sarcomere and nuclei disorganization. At the biochemical level, nitric oxide (NO) and lipid peroxidation (LPO) changed in the muscles of 3-NP-treated mice, suggesting metabolic alterations due to oxidative stress. Early damage in the striatal tissue and behavioral modifications are also documented.