Cigarette smoke induces molecular responses in respiratory tissues of ApoE(-/-) mice that are progressively deactivated upon cessation.

Cigarette smoking is the primary etiology of chronic obstructive pulmonary disease (COPD) and a risk factor for both lung and cardiovascular (CV) diseases, which are rarely investigated concomitantly. Although smoking cessation shows clear CV risk benefit, lung-related disease risk remains higher in former smokers than in never smokers. We sought to determine the differential molecular responses of murine respiratory tissues to better understand the toxicity pathways involved in smoking-related disease risk and those related to the benefits of smoking cessation. ApoE(-/-) mice were exposed to mainstream cigarette smoke (CS) or a smoking cessation-mimicking protocol for up to 6 months and transcriptomics analysis of nasal epithelium and lung parenchyma performed. We supported our gene expression profiling approach with standard lung histopathology and bronchoalveolar lavage fluid (BALF) analysis. Many BALF analytes involved in functions ranging from inflammation to cell proliferation and tissue remodeling were found elevated in BALF. Gene expression levels of these molecules were also increased in lung tissue, suggesting that the inflammatory response was the result of local tissue activation and the contribution of recruited inflammatory cells. Gene set enrichment analysis (GSEA) of expression data from murine lungs and nasal epithelium showed distinct activation patterns of inflammation, complement, and xenobiotic metabolism pathways during CS exposure that were deactivated upon smoking cessation. Pathways involved in cell proliferation and tissue remodeling were activated by CS and progressively deactivated upon smoke exposure cessation. Differential CS-mediated responses of pulmonary and nasal tissues reflect common mechanisms but also the varying degrees of epithelial functional specialization and exposure along the respiratory tract.

Cigarette-smoke-induced atherogenic lipid profiles in plasma and vascular tissue of apolipoprotein E-deficient mice are attenuated by smoking cessation.

Tobacco smoke exerts perturbations on lipid metabolism and arterial cell function that accelerate atherosclerosis. Lipidomics has emerged as a key technology in helping to elucidate the lipid-related mechanisms of atherosclerosis. In this study, we investigated the effects of smoking cessation on plaque development and aortic arch content of various lipid molecular classes and species. Apolipoprotein E-deficient mice were exposed to fresh air (sham) or to mainstream cigarette smoke (CS) for 6 months, or to CS for 3 months followed by sham for 3 months (cessation group). Lipids from plasma and aortic arches, plasma lipoprotein profiles and plaque morphometry measurements were analyzed. We already showed that CS exposure accelerated plaque size and total cholesterol content of the aortic arch at 3 and 6 months. Marked increases were seen in the relative enrichment of cholesteryl esters, phospholipids, sphingomyelins, and glycosphingolipids. Smoking cessation slowed plaque progression and resulted in lower levels of many lipid species in plasma and aortic arch. While CS exposure promoted rapid lipid accumulation in mouse aorta, smoking cessation translated into a slow removal of lipids from the vessel wall. Despite the smoking cessation-dependent metabolic changes leading to increased animal body weight, accumulation of proatherogenic lipids in the vessel was halted after exposure cessation, indicating that the clinical benefits of smoking cessation translate directly to the vessel wall and its lipid makeup.

Cigarette smoke and LDL cooperate in reducing nitric oxide bioavailability in endothelial cells via effects on both eNOS and NADPH oxidase.

The ubiquitous free radical nitric oxide (NO) plays an important role in many biological processes, including the regulation of both vascular tone and inflammatory response; however, its role in the effects of cigarette smoke exposure on atherosclerosis remains unclear. Our aim was to study the mechanisms of NO regulation in endothelial cells in response to cigarette smoke exposure in vitro. Using human umbilical vein endothelial cells (HUVEC), we have demonstrated that combining non-toxic concentrations of cigarette smoke bubbled through PBS (smoke-bubbled PBS [sbPBS]) with native LDL (nLDL) significantly reduces the amount of bioavailable NO. The effect is comparable to that seen with oxidized LDL (oxLDL), but has not been seen with sbPBS or nLDL alone. Mechanistic investigations showed that the combination of sbPBS+nLDL did not reduce the amount of endothelial nitric oxide synthase (eNOS), but did inhibit its enzymatic activity. Concomitantly, both sbPBS+nLDL and oxLDL significantly increased the production of reactive oxygen species (ROS) in the form of superoxide anions ((·)O(2)(-)) and peroxynitrite (ONOO(-)) in HUVEC. Selective inhibition of NADPH oxidase prevented this response. Incubation of sbPBS+nLDL revealed the formation of 7-ketocholesterol (7-KC) and 7-hydroxycholesterol, which are indicators for oxidative modification of LDL. This could explain the reported increase in circulatory levels of oxLDL in smokers. Our results suggest that reduction of functional NO in response to a combination of sbPBS+nLDL is secondary to both reduction of eNOS activity and stimulation of NADPH oxidase activity. Because sbPBS alone showed no effect on eNOS activity or ROS formation, nLDL should be included in cigarette-smoke-related mechanistic in vitro experiments on endothelial cells to be more reflective of the clinical situation.