title: Citrullination and autoimmunity.
abstract: Autoimmune diseases are characterized by the body's own immune system attack to the self-tissues, a condition enabled, in predisposed subjects, by the reduction of self-tolerance. A central role has been recently recognized to post-translational modifications, since they can promote generation of neo-(auto)antigens and in turn an autoimmune response. During the last years great attention has been paid to citrullination, because of its role in inducing anti-citrullinated proteins/peptide antibodies (ACPA), a class of autoantibodies with diagnostic, predictive and prognostic value for Rheumatoid Arthritis (RA). Nonetheless, citrullination has been reported to be a process present in a wide range of inflammatory tissues. Indeed, citrullinated proteins have been detected also in other inflammatory arthritides and in inflammatory conditions other than arthritides (polymyositis, inflammatory bowel disease and chronic tonsillitis). Moreover, environmental exposure to cigarette smoke and nanomaterials of air pollution may be able to induce citrullination in lung cells prior to any detectable onset of inflammatory responses, suggesting that protein citrullination could be considered as a sign of early cellular damage. Accordingly, citrullination seems to be implicated in all those para-physiological processes, such as cells death pathways, in which intracellular calcium concentration raises to higher levels than in physiologic conditions: hence, peptidylarginine deiminases enzymes are activated during apoptosis, autophagy and NETosis, processes which are well-known to be implicated in autoimmunity. Taken together, these data support the hypothesis that rather than being a disease-dependent process, citrullination is an inflammatory-dependent condition that plays a central role in autoimmune diseases.
authors: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia - Sapienza Università di Roma, Rome, Italy. Electronic address: guido.valesini@uniroma1.it.
authors: Guido
authors: G
authors: Valesini
authors: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia - Sapienza Università di Roma, Rome, Italy.
authors: Maria C
authors: MC
authors: Gerardi
authors: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia - Sapienza Università di Roma, Rome, Italy.
authors: Cristina
authors: C
authors: Iannuccelli
authors: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia - Sapienza Università di Roma, Rome, Italy.
authors: Viviana A
authors: VA
authors: Pacucci
authors: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia - Sapienza Università di Roma, Rome, Italy.
authors: Monica
authors: M
authors: Pendolino
authors: The Zabludowicz Center for Autoimmune Diseases, Sheba Medical Center, Tel Hashomer, Israel; Sackler Faculty of Medicine, Incumbent of the Laura Schwarz-Kipp Chair for Research of Autoimmune Diseases, Tel-Aviv University, Israel.
authors: Yehuda
authors: Y
authors: Shoenfeld
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology; D015551:Autoimmunity; D016923:Cell Death; D002956:Citrulline / Q000276:immunology*; D006801:Humans; D011499:Protein Processing, Post-Translational
chemical_list: D001323:Autoantibodies; D002956:Citrulline
keywords: Apoptosis; Autoimmunity; Autophagy; Citrullination; Inflammation; NETosis