Effect of exposure of rats to cigarette smoke on the metabolism of lipids

Cigarette smoke extract stimulates PCSK9 production in HepG2 cells via ROS/NF‑κB signaling

Cigarette smoke (CS) exposure is a risk factor for dyslipidemia and atherosclerosis. Reduced expression of low-density lipoprotein receptor (LDLR) in hepatocytes may be one of the underlying mechanisms for these disorders. The aim of the present study was to investigate the molecular mechanism underlying the regulatory effect of CS extract (CSE) on proprotein convertase subtilisin/kexin type 9 (PCSK9) and low LDLR expression in HepG2 cells. PCSK9 and LDLR mRNA and protein expression levels in HepG2 cells were evaluated after CSE treatment via reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. In addition, total intracellular reactive oxygen species (ROS) production was determined via 2,7-dichlorofluorescein diacetate fluorescence. CSE significantly increased PCSK9 expression and inhibited LDLR expression in a time- and concentration-dependent manner. Furthermore, CSE significantly induced ROS production and nuclear factor κB (NF-κB) activation. However, pretreatment with a ROS scavenger or an NF-κB inhibitor significantly attenuated the CSE-induced changes in PCSK9 and LDLR expression. In addition, pretreatment with melatonin markedly reduced ROS production, NF-κB activation and PCSK9 expression, and increased LDLR expression in the CSE-treated cells. These data suggest that melatonin inhibits CSE-regulated PCSK9 and LDLR production in HepG2 cells via ROS/NF-κB signaling.

The reduction of DSS-induced colitis severity in mice exposed to cigarette smoke is linked to immune modulation and microbial shifts

Exposure to cigarette smoke (CS) causes detrimental health effects, increasing the risk of cardiovascular, pulmonary diseases and carcinogenesis in exposed individuals. The impact of CS on Inflammatory Bowel Disease (IBD) has been established by a number of epidemiological and clinical studies. In fact, CS is associated with a higher risk of developing Crohn's disease (CD) while inversely correlates with the development, disease risks, and relapse rate of ulcerative colitis (UC). To investigate the effect of CS exposure on experimental colitis, we performed a comprehensive and integrated comparative analysis of colon transcriptome and microbiome in mice exposed to dextran sodium sulfate (DSS) and CS. Colon transcriptome analysis revealed that CS downregulated specific pathways in a concentration-dependent manner, affecting both the inflammatory state and composition of the gut microbiome. Metagenomics analysis demonstrated that CS can modulate DSS-induced dysbiosis of specific bacterial genera, contributing to resolve the inflammation or accelerate recovery. The risks of smoking far outweigh any possible benefit, thus smoking cessation must always be encouraged because of its significant health benefits. However, the inverse association between active smoking and the development of UC cannot be ignored and the present study lays the foundation for investigating potential molecular mechanisms responsible for the attenuation of colitis by certain compounds of tobacco when decoupled from combustion.

Induced Pluripotent Stem Cells-Derived Mesenchymal Stem Cells Attenuate Cigarette Smoke-Induced Cardiac Remodeling and Dysfunction

The strong relationship between cigarette smoking and cardiovascular disease (CVD) has been well-documented, but the mechanisms by which smoking increases CVD risk appear to be multifactorial and incompletely understood. Mesenchymal stem cells (MSCs) are regarded as an important candidate for cell-based therapy in CVD. We hypothesized that MSCs derived from induced pluripotent stem cell (iPSC-MSCs) or bone marrow (BM-MSCs) might alleviate cigarette smoke (CS)-induced cardiac injury. This study aimed to investigate the effects of BM-MSCs or iPSC-MSCs on CS-induced changes in serum and cardiac lipid profiles, oxidative stress and inflammation as well as cardiac function in a rat model of passive smoking. Male Sprague-Dawley rats were randomly selected for exposure to either sham air (SA) as control or 4% CS for 1 h per day for 56 days. On day 29 and 43, human adult BM-MSCs, iPSC-MSCs or PBS were administered intravenously to CS-exposed rats. Results from echocardiography, serum and cardiac lipid profiles, cardiac antioxidant capacity, cardiac pro- and anti-inflammatory cytokines and cardiac morphological changes were evaluated at the end of treatment. iPSC-MSC-treated group showed a greater effect in the improvement of CS-induced cardiac dysfunction over BM-MSCs-treated group as shown by increased percentage left ventricular ejection fraction and percentage fractional shortening, in line with the greater reversal of cardiac lipid abnormality. In addition, iPSC-MSCs administration attenuated CS-induced elevation of cardiac pro-inflammatory cytokines as well as restoration of anti-inflammatory cytokines and anti-oxidative markers, leading to ameliorate cardiac morphological abnormalities. These data suggest that iPSC-MSCs on one hand may restore CS-induced cardiac lipid abnormality and on the other hand may attenuate cardiac oxidative stress and inflammation via inhibition of CS-induced NF-κB activation, leading to improvement of cardiac remodeling and dysfunction. Thus, iPSC-MSCs may be a promising candidate in cell-based therapy to prevent cardiac complications in smokers.

Heavy Cigarette Smokers in a Chinese Population Display a Compromised Permeability Barrier

Cigarette smoking is associated with various cutaneous disorders with defective permeability. Yet, whether cigarette smoking influences epidermal permeability barrier function is largely unknown. Here, we measured skin biophysical properties, including permeability barrier homeostasis, stratum corneum (SC) integrity, SC hydration, skin surface pH, and skin melanin/erythema index, in cigarette smokers. A total of 99 male volunteers were enrolled in this study. Smokers were categorized as light-to-moderate (<20 cigarettes/day) or heavy smokers (≥20 cigarettes/day). An MPA5 was used to measure SC hydration and skin melanin/erythema index on the dorsal hand, forehead, and cheek. Basal transepidermal water loss (TEWL) and barrier recovery rates were assessed on the forearm. A Skin-pH-Meter pH900 was used to measure skin surface pH. Our results showed that heavy cigarette smokers exhibited delayed barrier recovery after acute abrogation (1.02% ± 13.06 versus 16.48% ± 6.07), and barrier recovery rates correlated negatively with the number of daily cigarettes consumption (p = 0.0087). Changes in biophysical parameters in cigarette smokers varied with body sites. In conclusion, heavy cigarette smokers display compromised permeability barrier homeostasis, which could contribute, in part, to the increased prevalence of certain cutaneous disorders characterized by defective permeability. Thus, improving epidermal permeability barrier should be considered for heavy cigarette smokers.

Effects of cigarette smoke, cessation and switching to a candidate modified risk tobacco product on the liver in Apoe -/- mice--a systems toxicology analysis

The liver is one of the most important organs involved in elimination of xenobiotic and potentially toxic substances. Cigarette smoke (CS) contains more than 7000 chemicals, including those that exert biological effects and cause smoking-related diseases. Though CS is not directly hepatotoxic, a growing body of evidence suggests that it may exacerbate pre-existing chronic liver disease. In this study, we integrated toxicological endpoints with molecular measurements and computational analyses to investigate effects of exposures on the livers of Apoe(-/- )mice. Mice were exposed to 3R4F reference CS, to an aerosol from the Tobacco Heating System (THS) 2.2, a candidate modified risk tobacco product (MRTP) or to filtered air (Sham) for up to 8 months. THS2.2 takes advantage of a "heat-not-burn" technology that, by heating tobacco, avoids pyrogenesis and pyrosynthesis. After CS exposure for 2 months, some groups were either switched to the MRTP or filtered air. While no group showed clear signs of hepatotoxicity, integrative analysis of proteomics and transcriptomics data showed a CS-dependent impairment of specific biological networks. These networks included lipid and xenobiotic metabolism and iron homeostasis that likely contributed synergistically to exacerbating oxidative stress. In contrast, most proteomic and transcriptomic changes were lower in mice exposed to THS2.2 and in the cessation and switching groups compared to the CS group. Our findings elucidate the complex biological responses of the liver to CS exposure. Furthermore, they provide evidence that THS2.2 aerosol has reduced biological effects, as compared with CS, on the livers of Apoe(-/- )mice.

Effect of filtration by activated charcoal on the toxicological activity of cigarette mainstream smoke from experimental cigarettes

Activated charcoal (AC) filtration reportedly decreases the yields of smoke vapor phase constituents including some identified as human carcinogens and respiratory irritants. Non-clinical studies including chemical smoke analysis, in vitro cytotoxicity and mutagenicity (bacterial and mammalian cells), and in vivo subchronic rat inhalation studies were carried out using machine smoking at ISO conditions with lit-end research cigarettes containing AC filters. The objective was to assess whether AC filter technology would alter the established toxicity profile of mainstream smoke by increasing or decreasing any known toxicological properties, or elicit new ones. The reduced yield of vapor phase irritants from AC filter cigarettes correlated with markedly decreased in vitro cytotoxicity and in vivo morphology of the nose and lower respiratory tract. Increased yields of particulate phase constituents (e.g. polycyclic aromatic hydrocarbons) in AC filtered smoke were noted in comparison to controls in some studies. The in vitro bacterial mutagenicity of AC filtered smoke particulate preparations was occasionally increased over control levels. Laryngeal epithelial thickness was increased in some rats inhaling AC filtered smoke in comparison to controls, an effect perhaps related to higher inspiratory flow. When tested under more intense Massachusetts Department of Public Health smoking conditions, AC filter associated reductions in vapor phase constituent yields were smaller than those seen with ISO conditions, but the effect on in vitro cytotoxicity remained.

Reduced toxicological activity of cigarette smoke by the addition of ammonia magnesium phosphate to the paper of an electrically heated cigarette: subchronic inhalation toxicology

Cigarette smoke is a complex chemical mixture that causes a variety of diseases, such as lung cancer. With the electrically heated cigarette smoking system (EHCSS), temperatures are applied to the tobacco below those found in conventional cigarettes, resulting in less combustion, reduced yields of some smoke constituents, and decreased activity in some standard toxicological tests. The first generation of electrically heated cigarettes (EHC) also resulted in increased formaldehyde yields; therefore, a second generation of EHC was developed with ammonium magnesium phosphate (AMP) in the cigarette paper in part to address this increase. The toxicological activity of mainstream smoke from these two generations of EHC and of a conventional reference cigarette was investigated in two studies in rats: a standard 90-day inhalation toxicity study and a 35-day inhalation study focusing on lung inflammation. Many of the typical smoke exposure-related changes were found to be less pronounced after exposure to smoke from the second-generation EHC with AMP than to smoke from the first-generation EHC or the conventional reference cigarette, when compared on a particulate matter or nicotine basis. Differences between the EHC without AMP and the conventional reference cigarette were not as prominent. Overall, AMP incorporated in the EHC cigarette paper reduced the inhalation toxicity of the EHCSS more than expected based on the observed reduction in aldehyde yields.

Curcumin Combats Against Cigarette Smoke and Ethanol-Induced Lipid Alterationsin Rat Lung and Liver

BACKGROUND

Human population, in spite of the medical and scientific achievements, still fall as a prey to the evils of habitual smoking and alcohol, thus necessitating safer counteracting measures.

OBJECTIVE

To evaluate the effect of cotreatment of curcumin (Curcuma longa) in rats subjected to acute exposure to cigarette smoke (CS) and ethanol (EtOH).

METHODOLOGY

Of the four groups of experimental rats, a set of rats was subjected to whole body exposure to cigarette smoke along with ethanol administration serving as a model of CS+EtOH injury. Curcumin treatment was given to two sets of rats: (i) one set receiving simultaneous CS+EtOH and (ii) one set of normal rats without any administration. The other group of rats served as control. Blood, liver and lung of rats were selected for assessment of CS+EtOH injury as well as curcumin treatment.

RESULT

Altered lipid, lipoprotein profile and bile acid excretion were observed in CS+EtOH rats along with premalignant pathological state in tissues. In treated rats, the levels were maintained at near-normal levels along with near-normal histology.

CONCLUSION

This biochemical picture on cotreatment with curcumin suggests that curcumin could counteract the injurious effects of combined CS and EtOH and thus might help to reduce the risk of hyperlipidemic disorders which develop due to smoking and drinking.

Toxicological evaluation of an electrically heated cigarette. Part 4: Subchronic inhalation toxicology

The biological activity of mainstream smoke from an electrically heated cigarette (EHC) with controlled combustion and from the University of Kentucky Reference Cigarette 1R4F was determined in Sprague Dawley rats exposed nose-only for 90 days, 6 h a day, 7 days per week. For an equivalent response comparison between the two cigarette types, two doses were chosen for the EHC where the anticipated results were in the dynamic range of the 1R4F dose-response curve (four concentrations) for most end points. The number of cigarettes smoked per m(3) of diluted smoke resulted in total particulate matter concentrations of 40 and 90 microg l (-1) for the EHC and 40-170 microg l (-1) for the 1R4F. Biomonitoring indicated achievement of target doses. Mainstream smoke yields were lower for the EHC, with the exception of formaldehyde. No smoke-related mortality, remarkable in-life observations or abnormal gross pathological findings were observed. Smoke- and dose-related clinical pathology and organ weight changes included: increases in segmented neutrophils, some liver parameters and lung and adrenal weight relative to body weight; and decreases in lymphocytes, glucose concentration and spleen weight. Smoke-related histopathological findings in the respiratory tract included epithelial cell hyperplasia, squamous metaplasia, atrophy and accumulation of pigmented alveolar macrophages; they were mostly dose-dependent, more pronounced in the upper than lower respiratory tract and completely or partially reversed by 6 weeks post-inhalation. Qualitatively, the biological effects seen for the EHC and the 1R4F were comparable and similar to those observed in other mainstream smoke inhalation studies. Quantitatively, the biological activity of the EHC mainstream smoke was, on average, 65% lower than that of the 1R4F mainstream smoke on an equal cigarette basis and equivalent activity on an equal TPM basis.

Nicotine increases hepatic oxygen uptake in the isolated perfused rat liver by inhibiting glycolysis

Nicotine influences energy metabolism, yet mechanisms remain unclear. Since the liver is one of the largest organs and performs many metabolic functions, the goal of this study was to determine whether nicotine would affect respiration and other metabolic functions in the isolated perfused liver. Infusion of 85 microM nicotine caused a rapid 10% increase in oxygen uptake over basal values of 105 +/- 5 micromol/g/h in perfused livers from fed rats, and an increase of 27% was observed with 850 microM nicotine. Concomitantly, rates of glycolysis of 105 +/- 8 micromol/g/h were decreased to 52 +/- 9 micromol/g/h with nicotine, whereas ketone body production was unaffected. Nicotine had no effect on oxygen uptake in glycogen-depleted livers from 24-h fasted rats. Furthermore, addition of glucose to perfused livers from fasted rats partially restored the stimulatory effect of nicotine. Infusion of atractyloside, potassium cyanide, or glucagon blocked the nicotine-induced increase in respiration. Intracellular calcium was increased in isolated hepatocytes by nicotine, a phenomenon prevented by incubation of cells with d-tubocurarine, a nicotinic acetylcholine receptor antagonist. Respiration was also increased approximately 30% in hepatocytes isolated from fed rats by nicotine, whereas hepatocytes isolated from fasted rats showed little response. In the presence of N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), an inhibitor of cyclic AMP-dependent protein kinase A, nicotine failed to stimulate respiration. These data support the hypothesis that inhibition of glycolysis by nicotine increases oxygen uptake due to an ADP-dependent increase in mitochondrial respiration.

Evaluation of the potential effects of ingredients added to cigarettes. Part 4: subchronic inhalation toxicity

Mainstream smoke from blended research cigarettes with (test) and without (control) the addition of ingredients to the tobacco was assayed for inhalation toxicity. In total, 333 ingredients commonly used in cigarette manufacturing were assigned to three different groups. Each group of ingredients was introduced at a low and a high level to the test cigarettes. Male and female Sprague-Dawley rats were exposed nose-only either to fresh air (sham) or diluted mainstream smoke from the test, the control, or the Reference Cigarette 1R4F at a concentration of 150 microg total particulate matter/l for 90 days, 6h/day, 7 days/week. A 42-day post-inhalation period was included to evaluate reversibility of possible findings. There were no remarkable differences in in-life observations or gross pathology between test and control groups. An increase in activity of liver enzymes, known to be due to the high smoke dose, revealed no toxicologically relevant differences between the test and control groups. No toxicological differences were seen between the test and control groups for smoke-related hematological changes, such as a decrease in total leukocyte count. The basic smoke-related histopathological effects, which were more pronounced in the upper respiratory tract than in the lower respiratory tract, were hyperplasia and squamous metaplasia of the respiratory epithelium, squamous metaplasia and atrophy of the olfactory epithelium, and accumulation of pigmented alveolar macrophages. There were no relevant qualitative or quantitative differences in findings in the respiratory tract of the rats exposed to the smoke from the control and test cigarettes. The data indicate that the addition of these 333 commonly used ingredients, added to cigarettes in three groups, did not increase the inhalation toxicity of the smoke, even at the exaggerated levels used.

Effect of smoking on lipid and thrombogenic factors two months after acute myocardial infarction

Cigarette smoking is linked to increased cardiac morbidity and mortality, and has been shown to affect both lipid profiles and thrombotic factors in healthy subjects. However, the influence of smoking on the atherothrombotic environment has not been studied in a large population of patients after acute myocardial infarction (AMI). Blood samples and medical history, including smoking status, were obtained from 1,045 patients at a 2-month visit after AMI. Smokers were asked to refrain 24 hours before the visit, but not all complied. Measurements included total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, apolipoprotein-B, apolipoprotein-A, triglycerides, factor VII, factor VIIa, von Willebrand factor, D-dimer, and plasminogen activator inhibitor. There were 247 current, 443 past, and 349 nonsmokers. After adjustment for clinical variables, current smokers had higher levels of total cholesterol and apolipoprotein-B than past and nonsmokers (p <0.01). High-density lipoprotein cholesterol and apolipoprotein-A levels were similar between groups. Fibrinogen was elevated in current (p = 0.001) and past (p = 0.029) smokers, compared with nonsmokers. Smokers who smoked within 24 hours of blood sampling had higher apolipoprotein-B (p = 0.005), total cholesterol (p = 0.001), and fibrinogen (p = 0.015) levels than those who refrained from smoking. In conclusion, postinfarction patients, who historically have higher levels of atherogenic lipids than healthy subjects, have increased levels of these lipids attributed to active smoking. After smoking cessation, lipid profiles approach nonsmoker levels, but fibrinogen remains elevated. Smoking within 24 hours of blood sampling was associated with further adverse prothrombotic and lipogenic effects.

The biology of the artery wall in atherogenesis

A great deal of progress has been made in the past few years in our understanding of the processes involved in atherogenesis and in mechanisms by which commonly accepted risk factors may affect these processes. These insights have allowed us to understand how various interventions may retard atherogenesis and decrease clinical events by improving plaque stability. The identification of new risk factors, such as lipoprotein(a), and of particular molecules that can be identified in atherosclerotic tissue, such as adhesion molecules, growth factors, cytokines, and proteins that regulate cholesterol uptake and removal, have identified several potential new targets for therapeutic intervention. Advances in molecular biologic techniques, including transgenic techniques, have markedly increased the types of potential interventions available. A major challenge for the future will be to determine which among this plethora of therapeutic possibilities holds the most promise for decreasing the morbidity and mortality associated with this disease.

Changes in the glycosaminoglycans and glycoproteins in the tissues in rats exposed to cigarette smoke

Prolonged exposure of rats to cigarette smoke resulted in significant alteration in the metabolism of glycosaminoglycans (GAG) and glycoproteins (GP). The concentration of many GAG fractions generally decreased in the aorta, liver and heart, but increased in the lungs. Concentration of chondroitin sulphates decreased in all the tissues. The activity of many enzymes concerned with the degradation of GAG (hyaluronidase, beta-glucuronidase and cathepsin-D) showed increase in these tissues. The concentration of the carbohydrate components (total hexose fucose and sialic acid) of aorta, heart and liver showed decrease in the rats exposed to cigarette smoke while there was increase in the lungs. The activity of many glycohydrolases generally showed increase in these tissues. Thus, exposure of rats to cigarette smoke for long periods produced changes in the aortic GAG and GP which are similar to those observed in atherosclerosis. On the other hand there was accumulation of many GAG in the lung tissue.

Effects of cigarette smoking and dietary lipids on rat lipoprotein metabolism

The effects of cigarette smoke inhalation on rat lipoprotein metabolism have been examined. Rats were subjected to cigarette smoke exposure over a 3-week period (two 1-h sessions/day) using a Bat-Mason inhalation machine. Rats exposed to cigarette smoke showed a decrease in total serum triglyceride and an increase in very low density lipoprotein cholesterol (VLDL-C). Administration of cigarette smoke to rats fed a saturated fat and cholesterol enriched diet also led to an increase in VLDL-C and a decrease in total serum triglycerides compared to controls. In addition, cigarette smoke exposure to animals fed the lipid enriched diet caused a decrease in high density lipoprotein cholesterol (HDL-C). Pair-feeding experiments indicated that the increase in VLDL-C and the decrease in HDL-C could not be solely attributed to the reduction in food intake and the small decrease in growth rate observed following cigarette smoke exposure. The changes observed in VLDL-C and HDL-C are at least qualitatively similar to the changes seen in human smokers compared to non-smokers.