Lipid from electronic cigarette smoke both with and without nicotine induced pro- inflammatory macrophage polarization and disrupted phagocytosis

Abstract

Clinical cases and experimental evidence show that electronic cigarette (ECIG) induce serious adverse health effects but underlying mechanisms much remain to be uncovered. Based on recent exploratory evidence, investigating the effects of ECIG on macrophages can broadly define potential mechanisms by focusing on the effect of ECIG exposure with or without nicotine. Here we investigated the effect of ECIG-smoke exposure on macrophages (MQ) phenotype, inflammatory response, and function of macrophages. MQ were cultured at air liquid interface and exposed to ECIG smoke. Oxidative stress was determined by reactive oxygen species (ROS), heat shock protein 60 (HSP60), glutathione peroxidase (GPx) and heme oxygenase1 (HMOX1). Lipid accumulation was ensured by lipid staining and lipid peroxidation was measured by level of malondialdehyde (MDA). MQ polarization was identified by surface expression markers CD86, CD11C and CD206 as well as pro-inflammatory and anti-inflammatory cytokines in gene and protein level. Phagocytosis of E. coli by MQ were investigated by fluorescence-based phagocytosis assay. ECIG smoke exposure in presence or absence of nicotine induced oxidative stress as ROS, HSP60, GPx, GPx4 and HMOX1 was upregulated in MQ. ECIG exposure induced accumulation lipids and the lipid peroxidation product MDA in MQ. Pro-inflammatory MQ (M1) markers CD86 and CD11C but not anti-inflammatory MQ (M2) marker CD206 were upregulated in response to ECIG exposure. In addition, ECIG induced pro-inflammatory cytokines IL-1beta and IL-8 in gene level and IL-6, IL-8, and IL-1beta in protein level whereas ECIG exposure downregulated anti-inflammatory cytokine IL-10 in protein level. Phagocytosis activity of MQ was downregulated by ECIG exposure. shRNA mediated lipid scavenger receptor CD36 silencing inhibited ECIG-induced pro-inflammatory MQ polarization and recovered phagocytic activity of MQ. ECIG exposure alter lung lipid homeostasis and thus induced inflammation by inducing M1 type MQ and impair phagocytic function, which could be a potential cause of ECIG-induced lung inflammation in healthy and inflammatory exacerbation in disease condition.