Dual effects of TGF-β inhibitor in ALS - inhibit contracture and neurodegeneration

Abstract

As persistent elevation of transforming growth factor-β (TGF-β) promotes fibrosis of muscles and joints and accelerates disease progression in amyotrophic lateral sclerosis (ALS), we investigated whether inhibition of TGF-β would be effective against both exacerbations. The effects of TGF-β and its inhibitor on myoblasts and fibroblasts were tested in vitro and confirmed in vivo, and the dual action of a TGF-β inhibitor in ameliorating the pathogenic role of TGF-β in ALS mice was identified. In the peripheral neuromuscular system, fibrosis in the muscles and joint cavities induced by excessive TGF-β causes joint contracture and muscular degeneration, which leads to motor dysfunction. In an ALS mouse model, an increase in TGF-β in the central nervous system (CNS), consistent with astrocyte activity, was associated with M1 microglial activity and pro-inflammatory conditions, as well as with neuronal cell death. Treatment with the TGF-β inhibitor halofuginone could prevent musculoskeletal fibrosis, resulting in the alleviation of joint contracture and delay of motor deterioration in ALS mice. Halofuginone could also reduce glial cell-induced neuroinflammation and neuronal apoptosis. These dual therapeutic effects on both the neuromuscular system and the CNS were observed from the beginning to the end stages of ALS; as a result, treatment with a TGF-β inhibitor from the early stage of disease delayed the time of symptom exacerbation in ALS mice, which led to prolonged survival.

Keywords: ALS; TGF‐β inhibitor; halofuginone; joint contracture; neurodegeneration.