IL-23 involvement in human carotid atherosclerosis progression

Atherosclerosis is now considered an autoimmune-inflammatory disease associated with lipoprotein metabolism alterations. Atheroma begins with the accumulations of oxidized low-density lipoprotein in the subendothelial matrix and the recruitment of monocytes which then differentiate to different functional phenotypes depending on the surrounding microenvironment. Plaque macrophages represent the majority of leukocytes in the atherosclerotic lesions, and their secretory activity, including proinflammatory cytokines and matrix-degrading proteases, is related to the progression as well as to the fragilization and rupture of the plaque (1). The balance between pro- and anti-inflammatory molecules is a major determinant of disease progression (2). In this connection an important role is played by cytokines secreted by 2 major populations of macrophages: M1 or classically activated and M2 or alternatively activated (3). Advanced plaques contain a majority of pro-inflammatory cells and processes leading to plaque rupture are probably dependent on mediators released by these cells in the close proximity of the fibrous cap. The identification of molecules involved in such a mechanism should provide new target for an effective prevention of main tromboembolic complications. Recently, among the many inflammatory cells and cytokines involved in atherosclerosis, an emerging role has been assigned to Th17 and IL-17 cytokine family. IL-23, a heterodimeric cytokine, member of IL-12 family of cytokines, represents the most important cytokine for maintaining and expanding Th17 cells and contributes to local inflammation. Interestingly, very recent meta-analysis correlated autoimmune diseases with excessive cardiovascular events (4), and previous studies have shown the presence of autoantibodies directed to autoantigens of the plaque in patients with carotid atherosclerosis (5,6). Aim of our study was to localize IL-23- and IL-23 receptor-positive cells within human carotid atherosclerotic plaques and to determine the levels of this cytokine in plaque supernatants and in sera from patients with carotid atherosclerosis. We investigated the presence of IL-23 and IL-23 receptor in human carotid atherosclerotic plaques by immunohistochemistry (30 samples), fluorescent in situ hybridization (FISH) (10 samples) and western blot (11 samples). 53% of the supernatant of cultered carotid plaques (19 samples) as well as 60% of carotid atherosclerosis patient sera (25 samples) have shown to contain discrete amounts of IL-23, as measured by enzyme-linked immunosorbent assay (ELISA). In particular our results demonstrated the presence of CD 68 and IL-23-double positive cells at the border and within the fibrous cap of complicated plaques. Moreover IL-23 receptor was detected at the surface of T lymphocytes distributed within the inflammatory infiltrate of the plaque. Of note, only human M1 pro-inflammatory macrophages obtained in vitro from monocytes induced to differentiate in the presence of granulocyte-macrophage colony stimulating factor were able to release IL-23, in response to toll-like receptor 2 and 4 agonists. In addition 53% of the supernatant of cultured carotid plaques (19 samples) as well as 60% of patient sera (25 samples) contained detectable amounts of IL-23, as measured by ELISA. All these findings suggest a relevant role for IL-23 in the inflammatory processes of atherosclerosis, identifying a new potential therapeutic target for immune modulation of atherosclerosis. 1) Businaro R. J Neuroimmune Pharmacol. 2013;8:15-27. 2) Businaro R. et al. Ann N Y Acad Sci. 2012;1262:134-41. 3) Taghavie-Moghadam et al. Ann N Y Acad Sci. 2014;1319:19-37. 4) Amaya-Amaya et al.Biomed Res Int. 2014;2014:367359. 5) Riganò R. et al. Ann N Y Acad Sci. 2007;1107:1-10 6) Businaro R. et al Atherosclerosis. 2009;207:74-83