STAT4 Regulates the CD8 + Regulatory T Cell/T Follicular Helper Cell Axis and Promotes Atherogenesis in Insulin-Resistant Ldlr -/- Mice

J Immunol. 2017 Nov 15;199(10):3453-3465. doi: 10.4049/jimmunol.1601429. Epub 2017 Oct 20.

Abstract

The metabolic syndrome and diabetic conditions support atherosclerosis, but the exact mechanisms for accelerated atherogenesis remain unclear. Although the proinflammatory role of STAT4 in atherosclerosis and diet-induced insulin resistance (IR) was recently established, the impact of STAT4 on atherogenesis in conditions of IR is not known. In this study, we generated Stat4-/-Ldlr-/- mice that were fed a diabetogenic diet with added cholesterol (DDC). DDC-fed Stat4-/-Ldlr-/- mice demonstrated improved glucose tolerance, insulin sensitivity, and a 36% reduction in atherosclerosis compared with Ldlr-/- controls. Interestingly, we detected a reduction in T follicular helper (Tfh) cells and plasma B cells but a sharp elevation in CD8+ regulatory T cells (Tregs) in spleens and aortas of Stat4-/-Ldlr-/- mice compared with Ldlr-/- mice. Similarly, STAT4 deficiency supported CD8+ Treg differentiation in vitro. STAT4-deficient CD8+ Tregs suppressed Tfh cell and germinal center B cell development upon immunization with keyhole limpet hemocyanin, indicating an important role for STAT4 in CD8+ Treg functions in vivo. Furthermore, adoptive transfer of Stat4-/-Ldlr-/- CD8+ Tregs versus Ldlr-/- CD8+ Tregs resulted in a significant reduction in plaque burden and suppression of Tfh cell and germinal center B cells in DDC-fed Ldlr-/- recipients. STAT4 expression in macrophages (MΦs) also affected the Tfh/CD8+ Treg axis, because conditioned media from Stat4-/-Ldlr-/- MΦs supported CD8+ Treg differentiation, but not Tfh cell differentiation, in a TGF-β-dependent manner. These findings suggest a novel mechanism by which STAT4 supports atherosclerosis in IR Ldlr-/- mice via STAT4-dependent MΦs, as well as cell-intrinsic suppression of CD8+ Treg generation and functions and maintenance of Tfh cell generation and the accompanying humoral immune response.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Atherosclerosis / immunology*
  • CD8 Antigens / metabolism
  • Cells, Cultured
  • Cholesterol / metabolism
  • Diet, Atherogenic
  • Germinal Center / immunology
  • Humans
  • Insulin Resistance
  • Lymphocyte Activation
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Receptors, LDL / genetics
  • Receptors, LDL / metabolism*
  • STAT4 Transcription Factor / genetics
  • STAT4 Transcription Factor / metabolism*
  • T-Lymphocytes, Helper-Inducer / immunology*
  • T-Lymphocytes, Regulatory / immunology*

Substances

  • CD8 Antigens
  • Receptors, LDL
  • STAT4 Transcription Factor
  • Stat4 protein, mouse
  • Cholesterol