PS-BPB09-3: CIGARETTE SMOKE EXTRACT INDUCES DNA DAMAGE AND TRIGGERS AN INNATE IMMUNE RESPONSE

Abstract

Objective: Elevated blood pressure and tobacco smoking are causes of preventable mortality. The effects of tobacco smoking on blood pressure are complex and chronic effects are inconsistent. We have previously reported increased DNA damage in peripheral mononuclear cells of smokers compared to nonsmokers. In this study, we investigated the effects of cigarette smoke extract (CSE) on DNA damage and the physiological influence of DNA damage in endothelial cells. Design and method: The effect of CSE extracted from tobacco smoke was examined in human umbilical vein endothelial cells (HUVECs). CSE was added to HUVECs and the formation of DNA damage was quantified by fluorescent immunostaining. The mRNA expression of inflammatory cytokines was quantified by real-time RT PCR. Results: CSE increased double-strand breaks in HUVEC by 72 hours. CSE also increased oxidative DNA damage both in the nucleus and mitochondria, and decreased mitochondria membrane potential. Mitochondrial dysfunction partially induced mitochondrial outer membrane permeabilization, resulting in the partial activation of caspase-3 and nuclear translocation of caspase-activated deoxyribonuclease, which fragments DNA in the nucleus. It was suggested that this is one of the mechanisms of nuclear DNA double-strand breaks. CSE induced the accumulation of nuclear and mitochondrial DNA in the cytosol. We further examined whether accumulated cytosolic DNA activated cytosolic DNA-sensing pathways. The production of cGAMP, a second messenger in cGAS (a DNA-sensing receptor) signaling, was increased by CSE, followed by nuclear translocation of NF-kB and increased mRNA expression of IL-6. The increase in IL-6 expression was suppressed by si-cGAS. Conclusions: Our study revealed that continuous exposure to CSE induces DNA damages not only in the nucleus but also in the mitochondria, which leads to cytosolic DNA accumulation, and evokes chronic inflammation via the cGAS pathway.