Abstract-Atherosclerosis is a chronic inflammatory arterial disease driven by both innate and adaptive immune responses to modified lipoproteins and components of the injured vascular wall. Specific T lymphocyte responses driven by T helper-1 or T regulatory cells play distinct and opposing roles in atherosclerosis. More recently, T helper-17 cells, which produce the prototype cytokine interleukin-17, have been characterized and shown to be critical in mucosal host defense against microbial and fungal pathogens. Sustained production of interleukin-17 in an inflammatory context has been linked to the pathology of several autoimmune and inflammatory diseases. However, regulatory and protective roles have also been reported in selective disease settings. Studies in atherosclerosis led to conflicting results on the roles of interleukin-17 and T helper-17 cells in disease development and plaque stability. The present review provides a summary of the available evidence and putative mechanisms linking this pathway to atherosclerosis, as well as a perspective on the risks and benefits of interleukin-17-targeted cytokine therapy in patients at high cardiovascular risk.
ATVB in Focus Modulation of Atherosclerotic Lesions by Circulating Cells:The Translational Spectrum
Taleb et al Th17 Cells and Atherosclerosis 259but is also expressed at high levels in Th17 cells and may act in an autocrine manner to maintain Th17 cells in vivo. 12 Still the absolute requirement of TGF-β for in vivo Th17 differentiation in mice has been questioned. Indeed, Th17 cells are present in the gut of TGF-β signaling-deficient mice. 13,14 Furthermore, IL-6 and IL-23 in combination with IL-1β were able to induce IL-17 production in the absence of TGF-β signaling, 14 suggesting an alternative mode for Th17 cell differentiation. In humans, initial claim that TGF-β was dispensable for human Th17 differentiation 15 was subsequently challenged by several investigators who provided convincing evidence for the importance of this factor in the human setting. [16][17][18] Additional key regulators that are involved in vascular remodeling and thus associated to cardiovascular disease have been recently identified as key regulators of Th17 differentiation. For example, nitric oxide mediates nitration of tyrosine residues in RORγt, leading to the suppression of RORγt-induced IL-17 promoter activation, which highlights a negative role for nitric oxide in Th17 differentiation.19 Salt (sodium chloride) concentrations found locally under physiological conditions in vivo markedly boost the induction of murine and human Th17 cells.
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IL-17 SignalingIL-17 receptor (IL-17R) family consists of 5 subunits. IL-17 binds to the heterodimeric receptor, IL-17RA and IL-17RC, and stimulates its signaling pathway. IL17RA is ubiquitously expressed throughout the body, resulting in pleiotropic actions of IL-17 on a wide range of cell types (for review, see Ref. 21). IL-17 binds to the receptor in homodimers (IL-17A/ IL-17A or IL-17F/IL-17F) or heterodimers (IL-17A/IL-17F) conf...