A preliminar analysis of the influence of Resistin on immunological cells in nonalcoholic fatty liver disease

Abstract

Background: Resistin (RES) is a cytokine highly expressed in plasma of nonalcoholic fatty liver disease (NAFLD) patients which promotes insulin resistance. It has a pro-inflammatory role through simulation of liver/adipose infiltrating monocytes/macrophages. As these cells are the main source of RES, a pro-inflammatory loop is created due to its role as chemokine for T cells. RES binding to adenylyl cyclase-associated protein 1 (CAP1), which expression was only reported in monocytes, activates nuclear factor kappa B (NF-kB). NF-kB is also activated via TCR to modulate CD69 expression in immunological cells. Aims: to evaluate CAP1 expression in peripheral blood mononuclear cells (PBMC) from patients and controls (Co), and RES-mediated modulation of CD69. Methods: PBMC were obtained by density gradient from whole blood of NAFLD patients (n= 8) and Co (n= 10). All patients provided written informed consent. CAP1 expression was studied by flow cytometry (FC) in PBMC stained with anti-CD3, -CD4, -CD14 and -CD56 antibodies. For functional approach, PBMC from Co were stimulated with coated anti-CD3 (3ug/ml) +/- RES (500 ng/ml) for 24 h, stained with anti-CD3, -CD4 and -CD56 and evaluated for CD69 expression by FC. Mann-Whitney test was used. Results: CAP1 expression is decreased in monocytes (p=0.018), CD3+CD4+ (p=0.016) and CD3+ CD4- (p=0.018) cells in patients with NAFLD (vs. Co). RES alone did not activate PBMC. Costimulation with anti-CD3+RES decreased CD69 mean fluorescence intensity (MFI) in CD3+CD4+ and CD3+CD4-, natural killer T (NKT) and NK CD56 bright cells (p=0.0043, p=0.021, p=0.044 and p=0.035 respectively; anti-CD3+RES vs. anti-CD3). Conclusion: CAP1 is a functional receptor in healthy donors able to regulate RES influence on immunological cells. Even though RES does not induce CD69 expression per se, it can modulate the activation of immunological cells. Thus, an overall decrease in CAP1 expression might modulate the stimulus induced by RES in the context of NAFLD. This potential regulatory circuit deserves further investigation.