The dual role of mTOR in multiple sclerosis pathophysiology: a systematic review

Multiple sclerosis (MS) is a chronic autoimmune disease characterized by demyelination, neuroinflammation, and progressive neurodegeneration. The mechanistic target of rapamycin (mTOR) pathway plays a key role in regulating immune responses, cell metabolism, autophagy, and repair processes. Although the role of mTOR in neurodegeneration has been explored in previous reviews, a systematic assessment of its function in MS across different models is still lacking. This systematic review aimed to examine the role of mTOR signaling in the pathophysiology of MS. Following Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines, we screened preclinical and clinical studies using two databases and assessed the risk of bias specific to the study types. A total of 189 records were identified, of which 90 met the inclusion criteria for qualitative analysis. Studies using in vitro and in vivo (mainly rodent models, both sexes) models of MS, as well as MS patient tissue or data, consistently demonstrated that mTOR is involved in the MS-related processes neuroinflammation, myelination, autophagy, gliosis, mitochondrial dysfunction, and oxidative stress. mTOR inhibition reduces pro-inflammatory signaling and may enhance autophagy, offering neuroprotection. In contrast, activation of mTOR promotes remyelination by enhancing oligodendrocyte differentiation and maturation. These remyelinating effects may be masked in inflammatory environments, because activation of mTOR supports immune cell expansion and glial reactivity, inducing inflammation and oxidative stress. Overall, our findings underscore a dual role of mTOR in MS pathology, with important implications for disease stage and timing of intervention. Although mTOR is mechanistically important in MS, its therapeutic modulation is unlikely to be readily clinically translatable without a substantial risk of unintended and context-dependent effects.