The role of the interleukin-23/Th17 pathway in cardiometabolic comorbidity associated with psoriasis

Abstract

Alterations in the innate and adaptive immunity underpin psoriasis pathophysiology, with the Th17 cells subset now recognized as the fundamental cells in the key controlling pathway involved in its pathogenesis. Since psoriasis is a systemic disease with important comorbidity, further knowledge on the interleukin (IL)-23/Th17 axis led to the hypothesis that there may be shared pathogenic pathways between primary skin disease and comorbidity. Psoriasis has been identified as a risk factor for cardiovascular and metabolic disease, and increasing evidence gives support to this epidemiological observation from the clinical-pathologically field. As an example, increased levels of IL-23 and IL-23R have been found in human atherosclerotic plaque, and levels correlated with symptom duration and mortality. Also, upregulation of IL-23/IL-17 seems to play an important role in both myocardial damage and stroke, with interesting reports on deleterious effect neutralization after administration of related anti-bodies in both associated conditions. In diabetic patients, increased levels of IL-23/IL-17 have also been observed and available data support a synergistic role of IL-23/IL-17 in β-cells damage. In obesity, signs of an expansion of Th17 subset in adipose tissue have been reported, as well as elevated concentrations of IL-23 in obese patients. In non-alcoholic fatty liver disease, closely related to metabolic syndrome, but also in other mentioned cardiometabolic disorders, a predominance of IL-23 and other related pro-inflammatory factors has been identified as participating in their pathogenesis. Thus, the involvement of the IL-23/Th17 axis in these shared psoriasis-cardiometabolic pathogenic mechanisms is reviewed and discussed in the light of the existing preclinical and clinical evidence, including that from comorbid psoriasis patients.

Figure 1

Schematic representation of Th17 cells developmental mechanism, regulators involved and effector functions.

Figure 2

Schematic representation of Treg and Th17 cells regulation, stimulator and inhibitor molecules involved in development and ultimate effector action of each pathway.

Figure 3

Scheme of involvement of Th17/IL‐23 axis in psoriasis and cardiometabolic diseases. CAD, coronary artery disease; CV, cardiovascular; CVR, cardiovascular risk; NAFLD, non‐alcoholic fatty liver disease; NGF, nerve growth factor; PAD, peripheral artery disease; PAI‐1, plasminogen activator inhibitor‐1; TIA, transient ischaemic attack; VEGF, vascular endothelial growth factor.. Yellow: CV diseases. Green: Metabolic diseases.