title: Vitamin D, steroid hormones, and autoimmunity.
abstract: The endogenous serum metabolite of vitamin D (calcitriol, 1,25(OH)2 D3 ) is considered a true steroid hormone (D hormone), and like glucocorticoids (GCs) and gonadal hormones, may exert several immunomodulatory activities. Serum vitamin D deficiency (25(OH) D), and therefore reduced 1,25(OH)2 D3 availability, is considered a risk factor for several chronic/inflammatory or autoimmune conditions, including infectious diseases, type 1 diabetes, multiple sclerosis, and especially autoimmune rheumatic diseases (ARD). In ARD in particular, 1,25(OH)2 D3 regulates both innate and adaptive immunity, potentiating the innate response (antimicrobial activity) but reducing adaptive immunity (antigen presentation, T and B cell activities). Regarding a possible synergism between vitamin D and GCs, several studies show that 1,25(OH)2 D3 has significant additive effects on dexamethasone-mediated inhibition of human lymphocyte and monocyte proliferation. Conversely, vitamin D deficiency seems to play a role in increasing autoantibody production by B cells, and seasonal vitamin D declines may trigger flares in ARD, as recently shown. Finally, 1,25(OH)2 D3 seems to reduce aromatase activity and limit the negative effects related to increased peripheral estrogen metabolism (cell proliferation, B cell overactivity).
authors.affiliation: Research Laboratories and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Genova, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Cutolo
authors.forename: Sabrina
authors.initials: S
authors.lastname: Paolino
authors.forename: Alberto
authors.initials: A
authors.lastname: Sulli
authors.forename: Vanessa
authors.initials: V
authors.lastname: Smith
authors.forename: Carmen
authors.initials: C
authors.lastname: Pizzorni
authors.forename: Bruno
authors.initials: B
authors.lastname: Seriolo
mesh_terms: D001172:Arthritis, Rheumatoid / Q000276:immunology*; D015551:Autoimmunity; D002117:Calcitriol / Q000502:physiology*; D005938:Glucocorticoids / Q000502:physiology*; D042341:Gonadal Hormones / Q000502:physiology*; D006801:Humans; D007155:Immunologic Factors / Q000502:physiology; D012306:Risk; D013472:Sunlight; D014807:Vitamin D / Q000502:physiology; D014808:Vitamin D Deficiency / Q000276:immunology
chemical_list: D005938:Glucocorticoids; D042341:Gonadal Hormones; D007155:Immunologic Factors; D014807:Vitamin D; D002117:Calcitriol
keywords: autoimmune rheumatic diseases; autoimmunity; estrogens; glucocorticoids; rheumatoid arthritis; solar light; vitamin D