Inhibition of peptidyl-arginine deiminases reverses protein-hypercitrullination and disease in mouse models of multiple sclerosis

Mario A Moscarello,Cameron Ackerley,Helena Lei,Reinout Raijmakers,Fabrizio G Mastronardi,Hubert Tsui,Shawn Winer,D Denise Wood,Li Zhang,Zhen Li

doi:10.1242/dmm.010520

Abstract

SUMMARYMultiple sclerosis (MS) is the most common CNS-demyelinating disease of humans, showing clinical and pathological heterogeneity and a general resistance to therapy. We first discovered that abnormal myelin hypercitrullination, even in normal-appearing white matter, by peptidylarginine deiminases (PADs) correlates strongly with disease severity and might have an important role in MS progression. Hypercitrullination is known to promote focal demyelination through reduced myelin compaction. Here we report that 2-chloroacetamidine (2CA), a small-molecule, PAD active-site inhibitor, dramatically attenuates disease at any stage in independent neurodegenerative as well as autoimmune MS mouse models. 2CA reduced PAD activity and protein citrullination to pre-disease status. In the autoimmune models, disease induction uniformly induced spontaneous hypercitrullination with citrulline+ epitopes targeted frequently. 2CA rapidly suppressed T cell autoreactivity, clearing brain and spinal cord infiltrates, through selective removal of newly activated T cells. 2CA essentially prevented disease when administered before disease onset or before autoimmune induction, making hypercitrullination, and specifically PAD enzymes, a therapeutic target in MS models and thus possibly in MS.

Highlights

Multiple sclerosis (MS) is the most common demyelinating disease of human adults
Most currently available therapies are immune modulatory and, they can improve relapse rates, they do not affect disease progression. Previous work by this group showed that myelin basic protein (MBP), a major protein in myelin, is hypercitrullinated in MS, and that the enzymes responsible for converting arginine in proteins to citrulline – the peptidylarginine deiminases (PADs) – are increased in white matter from MS brains
We identified a tryptic peptide in 2CA-reacted PAD2 with a mass of 1386.68 Da, whereas the corresponding unreacted peptide had a mass of only 1330.45 Da

Summary

Introduction

Multiple sclerosis (MS) is the most common demyelinating disease of human adults. Disease heterogeneity provides evidence for non-autoimmune, biochemical and epigenetic MS abnormalities, whose role in the complex hierarchy of pathogenesis remains unclear. In a study of 286 MS cases (mostly biopsies) (Lucchinetti et al, 2000), MS has been categorized into four different patterns of pathogenesis, which we have recognized in our animal models, which combined show most of the features of MS. In early studies we showed that myelin basic protein (MBP) isolated from normal human brain contained about 20% of the citrullinated MBP (Moscarello et al, 1994). In chronic MS white matter, the citrullinated protein was 45% and in Received 13 July 2012; Accepted 29 October 2012

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