title: Role of muscarinic-3 receptor antibody in systemic sclerosis: correlation with disease duration and effects of IVIG.
abstract: Gastrointestinal dysmotility in systemic sclerosis (SSc) is associated with autoantibodies against muscarinic-3 receptor (M3-R). We investigated the temporal course of the site of action of these autoantibodies at the myenteric neurons (MN) vs. the smooth muscle (SM) M3-R in relation to disease duration, and determined the role of intravenous immunoglobulin (IVIG) in reversing these changes. Immunoglobulins purified from SSc patients (SScIgG) were used to assess their differential binding to MN and SM (from rat colon) employing immunohistochemistry (IHC). Effect of SScIgG on neural and direct muscle contraction was determined by cholinergic nerve stimulation and bethanechol-induced SM contraction. Effects of IVIG and its antigen-binding fragment F(ab')2 on SScIgG binding were studied by enzyme-linked immunosorbent assay (ELISA) of rat colonic longitudinal SM myenteric plexus (LSMMP) lysate and to second extracellular loop peptide of M3-R (M3-RL2). SScIgG from all patients demonstrated significantly higher binding to MN than to SM. With progression of SSc duration, binding at MN and SM increased in a linear fashion with a correlation coefficient of 0.696 and 0.726, respectively (P < 0.05). SScIgG-mediated attenuation of neural and direct SM contraction also increased with disease duration. ELISA analysis revealed that IVIG and F(ab')2 significantly reduced SScIgG binding to LSMMP lysate and M3-RL2. Dysmotility in SSc occurs sequentially, beginning with SScIgG-induced blockage of cholinergic neurotransmission (neuropathy), which progresses to inhibition of acetylcholine action at the SM cell (myopathy). IVIG reverses this cholinergic dysfunction at the neural and myogenic receptors by anti-idiotypic neutralization of SScIgG.
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania;
authors.forename: Sumit
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania;
authors.forename: Jagmohan
authors.initials: J
authors.lastname: Singh
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania;
authors.forename: Ramalinga
authors.initials: R
authors.lastname: Kedika
authors.affiliation: Division of Rheumatology, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania;
authors.forename: Fabian
authors.initials: F
authors.lastname: Mendoza
authors.affiliation: Jefferson Institute of Molecular Medicine and Scleroderma Center, Thomas Jefferson University, Philadelphia, Pennsylvania; and.
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Jimenez
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania.
authors.forename: Erik S
authors.initials: ES
authors.lastname: Blomain
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania;
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: DiMarino
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania;
authors.forename: Sidney
authors.initials: S
authors.lastname: Cohen
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Thomas Jefferson University, Sidney Kimmel Medical College, Philadelphia, Pennsylvania; satish.rattan@jefferson.edu.
authors.forename: Satish
authors.initials: S
authors.lastname: Rattan
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D005260:Female; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000276:immunology / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000378:metabolism / Q000502:physiology; D009197:Myenteric Plexus / Q000166:cytology; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D043587:Receptor, Muscarinic M3 / Q000276:immunology*; D012595:Scleroderma, Systemic / Q000276:immunology* / Q000628:therapy
chemical_list: D016756:Immunoglobulins, Intravenous; D043587:Receptor, Muscarinic M3
keywords: muscarinic receptor; myenteric neuron; scleroderma autoantibodies; smooth muscle