Niclosamide Targets Inflammatory and Profibrotic Pathways in Amyotrophic Lateral Sclerosis

Abstract BackgroundAn increasing number of studies evidence that amyotrophic lateral sclerosis (ALS) is characterized by extensive alterations in different cell types and in different regions besides the CNS. We previously reported the up-regulation in ALS models of a gene called fibroblast-specific protein (FSP)-1 or S100A4, generally recognized as a pro-inflammatory and profibrotic factor. Since inflammation and fibrosis are often mutual-sustaining events that contribute to establish a hostile environment for organ functioning, the comprehension of the elements responsible for these interconnected pathways is crucial to disclose novel aspects involved in ALS pathology.MethodsHere we employed fibroblasts derived from ALS patients harboring the C9orf72 hexanucleotide repeat expansion and sporadic ALS patients with no mutations in known ALS-associated genes and we downregulated S100A4 using siRNA or the S100A4 transcriptional inhibitor niclosamide. Mice overexpressing human FUS were adopted to assess the effects of niclosamide in vivo on ALS pathology.ResultsWe demonstrated that S100A4 underlies impaired autophagy and a profibrotic phenotype, which characterize ALS fibroblasts. Indeed, its inhibition reduces inflammatory, autophagic and profibrotic pathways in ALS fibroblasts, and to interfere with different markers known as pathogenic in the disease, such as mTOR, SQSTM1/p62, STAT3, α-SMA and NF-κB. Importantly, niclosamide in vivo treatment of ALS-FUS mice reduces the expression of S100A4, α-SMA and PDGFRβ in the spinal cord, as well as gliosis in central and peripheral nervous tissues, together with axonal impairment and displays beneficial effects on muscle atrophy, by promoting muscle regeneration and reducing fibrosis.ConclusionOur findings show that S100A4 has a role in ALS-related mechanisms, and that drugs such as niclosamide that are able to target inflammatory and fibrotic pathways could represent promising pharmacological tools for ALS.