Sphingosine-1-Phosphate Reduces CD4+ T-Cell Activation in Type 1 Diabetes Through Regulation of Hypoxia-Inducible Factor Short Isoform I.1 and CD69

  1. Suseela Srinivasan1,
  2. David T. Bolick1,
  3. Dmitriy Lukashev2,
  4. Courtney Lappas3,
  5. Michail Sitkovsky2,
  6. Kevin R. Lynch3 and
  7. Catherine C. Hedrick13
  1. 1Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia
  2. 2New England Inflammation and Tissue Protection Institute, Northeastern University, Boston, Massachusetts
  3. 3Department of Pharmacology, University of Virginia, Charlottesville, Virginia
  1. Address correspondence and reprint requests to Catherine C. Hedrick, PhD, Cardiovascular Research Center, University of Virginia, P.O. Box 801394, 415 Lane Rd., MR5, Rm. G123, Charlottesville, VA 22908. E-mail: cch6n{at}virginia.edu

Abstract

OBJECTIVES—Non-obese diabetic (NOD) mice develop spontaneous type 1 diabetes. We have shown that sphingosine-1-phosphate (S1P) reduces activation of NOD diabetic endothelium via the S1P1 receptor. In the current study, we tested the hypothesis that S1P could inhibit CD4+ T-cell activation, further reducing inflammatory events associated with diabetes.

RESEARCH DESIGN AND METHODS—CD4+ T-cells were isolated from diabetic and nondiabetic NOD mouse splenocytes and treated in the absence or presence of S1P or the S1P1 receptor-specific agonist, SEW2871. Lymphocyte activation was examined using flow cytometry, cytokine bead assays, and a lymphocyte:endothelial adhesion assay.

RESULTS—Diabetic T-cells secreted twofold more γ-interferon (IFN-γ) and interleukin-17 than nondiabetic lymphocytes. Pretreatment with either S1P or SEW2871 significantly reduced cytokine secretion by ∼50%. Flow cytometry analysis showed increased expression of CD69, a marker of lymphocyte activation, on diabetic T-cells. Both S1P and SEW2871 prevented upregulation of CD69 on CD4+ cells. Quantitative RT-PCR showed that lymphocytes from diabetic NOD mice had 2.5-fold lower hypoxia-inducible factor (HIF)-1α short isoform I.1 (HIF1αI.1) mRNA levels than control. HIF1αI.1 is a negative regulator of lymphocyte activation. S1P significantly increased HIF1α I.1 mRNA levels in both control and diabetic groups. IFN-γ production and surface CD69 expression was significantly increased in lymphocytes of HIF1αI.1-deficient mice. S1P did not reduce either CD69 or IFN-γ expression in lymphocytes from HIF1αI.1-deficient mice.

CONCLUSIONS—S1P acts through the S1P1 receptor and HIF1α I.1 to negatively regulate T-cell activation, providing a potential therapeutic target for prevention of diabetes and its vascular complications.

Footnotes

  • Published ahead of print at http://diabetes.diabetesjournals.org on 14 November 2007. DOI: 10.2337/db07-0855.

    The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Accepted October 31, 2007.
    • Received June 23, 2007.
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  1. Diabetes vol. 57 no. 2 484-493
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