TRPA1-mediated effects on the functional activity of macrophages under the exposure with cigarette smoke and cinnamaldehyde

Abstract

Introduction. Being the leading cause of COPD, smoking represents a major health problem. Upon entering the respiratory tract, cigarette smoke comes into contact with various cells, including macrophages expressing on their surface TRPA1 receptors, which are sensitive to the main pathogenic compounds formed during tobacco combustion.Aim. To study the functional activity of TRPA1 channels on macrophages in terms of cell responses to cigarette smoke and the TRPA1 agonist cinnamaldehyde (CA). Materials and methods. The experimental conditions included exposure of monocyte-derived macrophages to CA (100 μM), 4% cigarette smoke extract (CSE) and 4% CSE after pretreatment with TRPA1 selective antagonist (HC-030031 100 μM). The concentration of cytokines in the culture medium, the expression of TRPA1 on the cell surface, as well as the phagocytic activity of macrophages were analyzed by flow cytometry.Results. We found that 60.2 (49.6; 71.8)% of cells expressed TRPA1 and their number increased after exposure with CA. CSE significantly inhibited CXCL10 production from 1121.3 (295.7; 3154.6) pg/ml to 187.9 (113.8; 398.3) pg/ml (p=0.04), which was partially prevented by blocking TRPA1 (692.4 [428.6; 2916.6] pg/ml, p=0.04). Similar to CSE, CA also caused a decrease in CXCL10 concentration (189.2 [111.7; 311.3] pg/ml, p=0.03). Among other observations, there was an increase in the concentration of IL-1β after the exposition with HC-030031, as well as a decrease in TNF-α, IFN-γ and IL-12p70 after the treatment with CA. CSE caused a minor inhibition in phagocytic cells number, which was not prevented by TRPA1 blocking. CA, on the contrary, increased the phagocytic activity of macrophages. The initial expression of TRPA1 had a negative correlation with the dynamics of CXCL10 in response to CSE and CA but a positive correlation with the number of phagocytic cells after exposition with CA (ρ=0.81, p=0.005). Conclusions. TRPA1 expressed on macrophages apparently mediate an anti-inflammatory effect in terms of produced cytokines but increase phagocytic activity of the cells. TRPA1 are also major receptors involved in the diminished CXCL10 production by macrophage under exposition with cigarette smoke