Tobacco Smoke Exposure and Oxidative Stress: The Role of Circulating Lipopolysaccharides in Heated and Conventional Products

Abstract

Background: Exposure to tobacco smoke, from conventional tobacco cigarettes (CTC) or heated tobacco products (HTPs), increases oxidative stress, causing endothelial dysfunction and higher cardiovascular risk. It is unclear whether smoke exposure also promotes low-grade endotoxemia, potentially activating NADPH oxidase and further impairing endothelial function. This study assessed serum lipopolysaccharide (LPS) levels in children and adults actively or passively exposed to conventional cigarette smoke or HTPs, compared with non-exposed controls. Methods: We conducted a cross-sectional study comprising 26 children passively exposed to HTPs, 26 children exposed to CTC, and 26 unexposed controls, as well as 20 adult chronic HTP users, 20 chronic CTC, and 20 non-smoking adults. Circulating LPS was measured alongside oxidative stress markers (NOX2, H₂O₂), endothelial function, intestinal permeability (zonulin), and nicotine exposure (serum cotinine). Results: Exposed children had higher cotinine, LPS, and zonulin than controls, with no differences between HTP and CTC groups. Multiple linear regression analysis identified cotinine (β = 0.343; p = 0.005) and zonulin (β = 0.441; p < 0.001) as independent LPS predictors. In adults, LPS and zonulin were higher in both smoker groups versus controls; zonulin (β = 0.477; p < 0.001) and nitric oxide bioavailability (β = -0.307; p = 0.007) independently predicted LPS. Conclusions: Passive and active exposure to CTC or HTPs increases low-grade endotoxemia and zonulin, potentially driving NOX2-mediated oxidative stress.

Keywords: LPS; NADPH-oxidase 2; NOX-2; atherosclerosis; cigarettes; endothelial dysfunction; flow-mediated dilation; heated tobacco products; lipopolysaccharides; smoking.

Figure 1

Box–and–whisker plots showing data from children divided into three groups: controls, those exposed to traditional tobacco cigarette smoke (TT), and those exposed to heated tobacco product emissions (HTPs). Panel A displays circulating lipopolysaccharide (LPS) levels, while Panel B shows circulating zonulin levels. The boxes represent the interquartile range (IQR; 25th–75th percentile), with the horizontal line indicating the median. Whiskers extend to values from the box to the minimum and maximum values. Panel (A): * p < 0.001; ° p < 0.001. Panel (B): * p = 0.006; ° p = 0.003.

Figure 2

Box-and-whisker plots illustrating data from adults across three groups: healthy controls, chronic smokers of conventional tobacco cigarettes (TT), and users of heated tobacco products (HTPs). Panel A shows circulating levels of LPS, while Panel B reports circulating levels of zonulin. Panel (A): * p < 0.001; ° p = 0.001. Panel (B): * p = 0.002; ° p < 0.001.

Figure 3

Following exposure to first-, second-, or third-hand smoke—whether derived from heated tobacco products or from conventional combustible cigarettes—there is an increase in circulating levels of lipopolysaccharides (LPS), most likely as a consequence of enhanced intestinal epithelial permeability. Elevated concentrations of even low-grade LPS promote the activation of the enzyme NADPH oxidase 2 (NOX2), which in turn drives excessive production of reactive oxygen species (ROS). This oxidative imbalance contributes to endothelial dysfunction and enhances platelet activation, two interrelated processes that are widely recognized as pivotal mechanisms in the development and progression of cardiovascular risk.