title: 1,25-Dihydroxyvitamin D3-3-bromoacetate, a novel vitamin D analog induces immunosuppression through PI3K/Akt/mTOR signaling cascade.
abstract: OBJECTIVE
  The molecular mechanism responsible for the immunomodulatory effect of 1,25-dihydroxyvitamin D3 (Vit-D) is still not well elucidated. Unavoidable systemic toxicity of Vit-D has encouraged to develop more potent and less toxic Vit-D analogs, such as 1,25-dihydroxyvitamin D3-3-bromoacetate (BE). Our aim was to explore the immunosuppressive effect of BE and its molecular mechanism in autoimmune diseases.
  
  
  METHODS
  Magnetically sorted CD3(+) T cells (T cells) from PBMCs of psoriasis and autoimmune arthritis patients were cultured with/without BE and Vit-D followed by proliferation (MTT, CFSE dilution assays) and apoptosis assays (annexin V). Immunoblot was performed to determine the signaling cascade responsible for the antiproliferative effect.
  
  
  RESULTS
  In MTT assay, BE (OD: 0.64±0.08) markedly inhibited the anti-CD3/CD28 stimulated proliferation of T cells (OD: 1.8±0.30, p<0.001) and at equivalent doses, the inhibitory effect was more than that of Vit-D (OD: 0.91±0.11, p<0.05). The antiproliferative effect of BE was extended to activated CD4(+) and CD8(+) memory T cells (CD45RA(-)CD11a(+)) without much effect on the naïve T cells. BE induced more apoptosis of T cells (45.01±4.27%, p<0.01) compared to untreated cells (3.45±1.8%), and the proapoptotic effect was markedly more than that of Vit-D (26.1±2.05%, p<0.05). BE effectively inhibited the anti-CD3/CD28-induced phosphorylation of Akt and mTOR and in both, BE showed more potency than Vit-D (p<0.05).
  
  
  CONCLUSIONS
  Topical Vit-D is being used successfully in psoriasis for years. However, its potency is less compared to topical corticosteroids. The de novo BE showed significantly more immunosuppression than conventional Vit-D and the immunosuppressive effect is PI3K/Akt/mTOR dependent. Our results indicate that BE could be an effective therapeutic agent for psoriasis and other T-cell-mediated autoimmune diseases.
authors.affiliation: Department of Internal Medicine/Rheumatology, Allergy and Clinical Immunology, School of Medicine, University of California Davis, Davis, CA 95616, USA; VA Medical Centre Sacramento, Mather, CA 95655, USA.
authors.forename: Ananya
authors.initials: A
authors.lastname: Datta-Mitra
authors.forename: Anupam
authors.initials: A
authors.lastname: Mitra
authors.forename: Rahul
authors.initials: R
authors.lastname: Ray
authors.forename: Siba P
authors.initials: SP
authors.lastname: Raychaudhuri
authors.forename: Smriti
authors.initials: S
authors.lastname: Kundu-Raychaudhuri
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001172:Arthritis, Rheumatoid / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D007165:Immunosuppression Therapy; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007963:Leukocytes, Mononuclear / Q000166:cytology; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology; D051057:Proto-Oncogene Proteins c-akt / Q000276:immunology; D011565:Psoriasis / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D058570:TOR Serine-Threonine Kinases / Q000276:immunology
chemical_list: D017252:CD3 Complex; D002117:Calcitriol; D007166:Immunosuppressive Agents; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C104313:1,25-dihydroxyvitamin D3-3-bromoacetate; C546842:MTOR protein, human
keywords: 1α,25-dihydroxyvitamin D3-3-bromoacetate; Akt/mTOR; Proliferation; T cells