Mechanistic study of adverse actions of cigarette smoke exposure on acetic acid-induced gastric ulceration in rats

Ameliorative effect of chronic moderate exercise in smoke exposed or nicotine applied rats from acute stress

INTRODUCTION

Physical activity has been found to be related with many health benefits. Our aim was to investigate the effect of chronic moderate exercise from acute stress on nicotine and cigarette smoke exposed rats.

METHODS

Male Sprague Dawley rats (200-250g, n = 48) were divided into 6 groups as non-exercised, exercised, smoke exposed, smoke exposed and exercised, nicotine applied, and nicotine applied and exercised. Nicotine bitartarate was applied intraperitoneally (0.1mg/kg/day) for 5 weeks, and cigarette smoke was exposed in a ventilated chamber. After 1 week of nicotine application or smoke exposure, moderate exercise training protocol was applied to exercise groups. At the end of the experiments, acute stress induction was made to all groups by electric foot shock. Holeboard tests were performed before and after the experiments. Biochemical and histological analyses were performed in lung, liver, colon, stomach, and gastrocnemius tissues.

RESULTS

Malondialdehyde levels were increased in all tissues of smoke exposed group (p < .05-.01) except gastrocnemius tissue compared to non-exercised group and were decreased with exercise (p < .05-.001). Myeloperoxidase levels were increased in lung, liver and colon tissues of smoke exposed group (p < .05-.001) and liver and colon tissues of nicotine applied rats (p < .01-.001) and decrease with exercise in liver and colon tissues of both smoke exposed or nicotine applied groups (p < .05-.01). In all tissue samples, increased histological injury scores (p < .05-.001) decreased significantly with exercise (p < .01-.001).

CONCLUSION

Biochemical parameters and histological scoring indicated increased tissue injury due to nicotine application and cigarette smoke exposure and exercise training ameliorated these effects in most of the tissues of acute stress induced rats.

Xanthine oxidoreductase is a critical mediator of cigarette smoke-induced endothelial cell DNA damage and apoptosis

Cigarette smoke (CS) exposure is unquestionably the most frequent cause of emphysema in the United States. Accelerated pulmonary endothelial cell (EC) apoptosis is an early determinant of lung destruction in emphysema. One of the pathogenic causes of emphysema is an alveolar oxidant and antioxidant imbalance. The enzyme xanthine oxidoreductase (XOR) has been shown to be a source of reactive oxygen species (ROS) in a multitude of diseases (S. Sakao et al., FASEB J.21, 3640-3652; 2007). The contribution of XOR to CS-induced apoptosis is not well defined. Here we demonstrate that C57/bl6 mice exposed to CS have increased pulmonary XOR activity and protein levels compared to filtered-air-exposed controls. In addition, we demonstrate that primary pulmonary human lung microvascular endothelial cells exposed to cigarette smoke extract undergo increased rates of caspase-dependent apoptosis that are reliant on XOR activity, ROS production, and p53 function/expression. We also demonstrate that exogenous XOR is sufficient to increase p53 expression and induce apoptosis, suggesting that XOR is an upstream mediator of p53 in CS-induced EC apoptosis. Furthermore, we show that XOR activation results in DNA double-strand breaks that activate the enzyme ataxia telangiectasia mutated, which phosphorylates histone H2AX and upregulates p53. In conclusion, CS increases XOR expression, and the enzyme is both sufficient and necessary for p53 induction and CS-induced EC apoptosis.

Dysregulation of gastric H,K-ATPase by cigarette smoke extract

AIM

To test whether the expression and activity of H,K-ATPase in parietal cells would be affected by cigarette smoke extract.

METHODS

Extracts of cigarette smoke were administered into mice by gastric gavage (5 mg/kg body weight/day) for 3 d or in drinking water for 7 or 14 d. For the latter, each day a mouse consumed 5 mL water containing extracts of two cigarettes, on average. Control littermate mice received only vehicle. To compare the amount of H,K-ATPase in control and smoke-treated mice, the stomach was processed for Western blotting and immunohistochemical analysis using monoclonal antibodies specific for alpha- or beta-subunits of H,K-ATPase. The p-nitrophenylphosphatase activity assay was used as a measurement for K-dependent H,K-ATPase activity.

RESULTS

Probed transblots showed an increase in the amount of H,K-ATPase in smoke-treated mice which was confirmed by immunohistochemistry and was found to be due to increased amounts of protein per parietal cell rather than an increased parietal cell number. The increase in the amount of H,K-ATPase was associated with an enhancement of its enzymatic activity. K-dependent activity in control and smoke-treated mice was significantly different (respectively, 0.12 micromol/mg vs 0.27 micromol/mg per minute, P < 0.05).

CONCLUSION

Administration of cigarette smoke extract is associated with an increase in the amount and activity of H,K-ATPase and hence, smokers are susceptible to development of peptic ulcer.

Risk factors for gastrointestinal complications in aspirin users: review of clinical and experimental data

This paper reviews recent clinical evidence that suggests that aspirin prophylaxis against cardiac and cerebral vascular ischemia is associated with significant gastrointestinal complications. The clinical and experimental evidence to confirm the role of risk factors of concomitant use of nonsteroidal anti-inflammatory drugs (NSAID), tobacco cigarette smoking, and alcohol consumption are discussed. The limitations of long-term acid suppression treatment for the prevention of these complications are considered. Future experimental studies to guide the clinical approach to develop novel and potentially cost-effective management strategies are discussed.

Predictors of endoscopic findings after Roux-en-Y gastric bypass

OBJECTIVES

To evaluate predictors of endoscopic findings in symptomatic patients after Roux-en-Y gastric bypass (RYGBP) for obesity.

METHODS

A retrospective chart review of 1,001 RYGBP procedures was performed. Two hundred twenty-six (23%) patients were identified as having endoscopy to evaluate upper gastrointestinal symptoms following surgery. Polychotomous logistic regression analysis was used to assess predictors of normal endoscopy, marginal ulcers, stomal stenosis, and staple-line dehiscence.

RESULTS

The most common endoscopic findings were 99 (44%) normal postsurgical anatomy, 81 (36%) marginal ulcer, 29 (13%) stomal stenosis, and 8 (4%) staple-line dehiscence. Factors that significantly increase the risk of marginal ulcers following surgery include smoking (AOR = 30.6, 95% CI 6.4-146) and NSAID use (AOR = 11.5, 95% CI 4.8-28). PPI therapy following surgery was protective against marginal ulcers (AOR = 0.33, 95% CI 0.11-0.97). Median time for diagnosis of marginal ulcers following surgery was 2 months, and 77 of 81 (95%) presented within 12 months.

CONCLUSIONS

Following RYGBP surgery for obesity, smoking and NSAID use significantly increase the risk of marginal ulceration, and PPI therapy is protective. Because a significant majority of marginal ulcers present within 12 months of surgery, it may be reasonable to consider prophylactic PPI therapy during this time period, especially for high risk patients.

Impact of sidestream whole smoke solutions on the outcome of wound repair and related angiogenesis

Wound angiogenesis is essential to support the regenerating tissue and any setback in angiogenesis may result in retarded wound repair. Cigarette smoking causes numerous adverse effects, some of which are associated with poor healing. The current experiment was carried out to elucidate the possible detrimental effects of sidestream whole smoke solutions (SSWSS) on wound healing and related angiogenesis, using a well-defined chicken dorsum excision wound assay. Gross, histopathologic, SEM and computer based 3D image-probing modalities were utilized to quantify different detrimental effects of SSWSS on the fundamental processes of wound healing. A total of 160 chicks, aged 1 week, divided in eight groups were topically exposed for 8 days to SSWSS with different nicotine concentrations. At day 6 and day 8 post-wounding, very highly significant reduction (P<0.001) in wound closure was observed among all SSWSS treated groups. Histological and SEM evaluation of SSWSS treated wounds unveiled deteriorated dermal matrix, delayed re-epithelialization and retarded neovascularization. Moreover, image-probing exploration of SSWSS treated wounds also divulge a very highly significant decrease (P<0.001) in angular spectrum, Sa, Sy and Sci, at day 6 post-wounding. Our study suggests that the cumulative effect of different components of SSWSS has a negative impact on wound healing and related angiogenesis. Furthermore, our study demonstrates the effects that can contribute to abnormal healing and may explain why people who are consistently exposed to sidestream smoke suffer from slow healing and excessive scarring of wounds, much like the smokers themselves.

Impaired wound healing by exposure of different mainstream whole smoke solutions of commercial cigarettes

Cigarette smoke has been shown to potentiate wound damage and delayed ulcer healing. The chicken dorsum excisional wound assay was used to elucidate the deleterious effects of different mainstream whole smoke solutions (MSWSS) on the fundamental processes of wound healing. Gross, histopathology, SEM and computer based 3D image probing techniques were utilized to quantify different toxic effects of MSWSS on wound healing. A total of 160 chicks, aged 1 week, divided in eight groups were exposed to MSWSS with different nicotine concentration; 0.2mg (group A), 0.3mg (group B), 0.5mg (group C), 0.6mg (group D), 0.7mg (group E) and 1mg (group F). A very highly significant reduction (P<0.001) in wound closure was observed among all MSWSS treated groups at day 8 post-wounding. Histological investigations revealed a significant impede outcome in the re-epithelialization of all MSWSS exposed wounds. Delayed dermal matrix regeneration and maturation of collagen bundles were observed among all MSWSS treated wounds. Similar results were achieved through SEM of treated wounds. Histological and image probing analysis unveiled the scanty neovascularization among MSWSS treated wounds. Abbot curve, angular spectrum and different other parameters of 3D surface topographies of wounds revealed a very highly significant reduction (P<0.001) in angiogenesis among all MSWSS treated groups. These annotations validate the damaging effects of MSWSS on the healing of wounds.

Smoking and the pathogenesis of gastroduodenal ulcer--recent mechanistic update

Peptic ulcer is a common disorder of gastrointestinal system and its pathogenesis is multifactorial, where smoking and nicotine have significant adverse effects. Smoking and chronic nicotine treatment stimulate basal acid output which is more pronounced in the smokers having duodenal ulcer. This increased gastric acid secretion is mediated through the stimulation of H2-receptor by histamine released after mast cell degranulation and due to the increase of the functional parietal cell volume or secretory capacity in smokers. Smoking and nicotine stimulate pepsinogen secretion also by increasing chief cell number or with an enhancement of their secretory capacity. Long-term nicotine treatment in rats also significantly decreases total mucus neck cell population and neck-cell mucus volume. Smoking also increases bile salt reflux rate and gastric bile salt concentration thereby increasing duodenogastric reflux that raises the risk of gastric ulcer in smokers. Smoking and nicotine not only induce ulceration, but they also potentiate ulceration caused by H. pylori, alcohol, nonsteroidal anti-inflammatory drugs or cold restrain stress. Polymorphonuclear neutrophils (PMN) play an important role in ulcerogenesis through oxidative damage of the mucosa by increasing the generation of reactive oxygen intermediates (ROI), which is potentiated by nicotine and smoking. Nicotine by a cAMP-protein kinase A signaling system elevates the endogenous vasopressin level, which plays an aggressive role in the development of gastroduodenal lesions. Smoking increases production of platelet activating factor (PAF) and endothelin, which are potent gastric ulcerogens. Cigarette smoking and nicotine reduce the level of circulating epidermal growth factor (EGF) and decrease the secretion of EGF from the salivary gland, which are necessary for gastric mucosal cell renewal. Nicotine also decreases prostaglandin generation in the gastric mucosa of smokers, thereby making the mucosa susceptible to ulceration. ROI generation and ROI-mediated gastric mucosal cell apoptosis are also considered to be important mechanism for aggravation of ulcer by cigarette smoke or nicotine. Both smoking and nicotine reduce angiogenesis in the gastric mucosa through inhibition of nitric oxide synthesis thereby arresting cell renewal process. Smoking or smoke extract impairs both spontaneous and drug-induced healing of ulcer. Smoke extract also inhibits gastric mucosal cell proliferation by reducing ornithine decarboxylase activity, which synthesises growth-promoting polyamines. It is concluded that gastric mucosal integrity is maintained by an interplay of some aggressive and defensive factors controlling apoptotic cell death and cell proliferation and smoking potentiates ulcer by disturbing this balance.

[An overview of acetic acid ulcer models and their utility for drug screening]

Since Takagi et al. reported an experimental chronic gastric ulcer model [acetic acid ulcers induced by submucosal injection of acetic acid (Type 1)], we further modified the methodology and subsequently devised three more models. The second model involves inducing ulcers by serosal application of an acetic acid solution (Type 2) and the third model achieves ulcer induction by intragastric application of an acetic acid solution (Type 3). The forth model was modification of the third model by giving the acetic acid solution and the same volume of air to make one ulcer in the stomach (Type 4). In general, animals accepted the procedures without problems and no undesirable effects were noticed. More importantly, this experimental animal model allows production of ulcers that highly resemble human ulcers in terms of both pathology and healing. Indeed, relapse is even endoscopically observed for 360 days after ulceration. The ulcers produced not only respond well to various anti-ulcer medications, such as antisecretory and mucosal protective drugs and growth factors, but also demonstrate appropriate responses to ulcerogenic agents such as NSAIDs. In addition, we have recently demonstrated that H. pylori infection resulted in delayed ulcer healing and recurrence of healed acetic acid ulcers induced in Mongolian gerbils. The present article gives a brief summary of the ulcer history before establishment of acetic acid ulcers and characteristic features of acetic acid ulcer, including both their merits and shortcomings.

Upregulation of xanthine oxidase by tobacco smoke condensate in pulmonary endothelial cells

Tobacco smoking has been causally linked to the development of chronic obstructive pulmonary disease. It has been reported that the reactive oxygen species (ROS)- generating enzyme xanthine dehydrogenase/oxidase (XO) is increased in smoking-related stomach ulcers and that gastric mucosal damage caused by tobacco smoke can be blocked by the XO inhibitor allopurinol. In order to test the hypothesis that tobacco may cause the upregulation of XO in the lung, cultured rat pulmonary microvascular endothelial cells were exposed to tobacco smoke condensate (TSC). TSC at a concentration of 20 microg/mL significantly upregulated XO activity after 24 h of exposure. Longer exposure (1 week) to a lower concentration of TSC (2 microg/mL) also caused an increase in XO activity. Unlike hypoxia, TSC treatment did not alter the phosphorylation of XO. However, TSC treatment increased XO mRNA expression and the XO gene promoter activity. Furthermore, actinomycin D blocked the activation of XO by TSC. In conclusion, our results indicate that tobacco smoke condensate causes upregulation of XO transcription and activity.

Involvement of bcl-2 and caspase-3 in apoptosis induced by cigarette smoke extract in the gastric epithelial cell

Previous studies have shown that short-term passive cigarette smoking can increase apoptosis in rat gastric mucosa. However, the mechanism is not yet defined. Chloroform and ethanol extracts were used to investigate whether cigarette smoke could induce apoptosis in a human gastric epithelial cell line (AGS) as well as the roles of bcl-2, caspase-3, and cytochrome c in this process. AGS cell lines were treated with either chloroform extract (CE) or ethanol extract (EE) for 5 hours, and the level of bcl-2, the activity of caspase-3, and the level of cytosolic cytochrome c in these cells were determined. Time course studies on the effects of cigarette smoke extracts (CSEs) on DNA fragmentation and cytochrome c relocalization were also performed. Data showed that only CE induced apoptosis in a dose- and time-dependent manner in AGS cells, along with a decrease of bcl-2 and an increase of caspase-3 activity. Pretreatment with Z-DEVD-FMK (specific inhibitor of caspase-3) dose-dependently blocked the DNA fragmentation induced by the CE. Moreover, CE could time- and dose-dependently increase the level of cytochrome c in the cytoplasm, which might activate caspase-3. In conclusion, CSE triggers apoptosis in AGS cells through the inhibition of bcl-2 and the activation of a mitochondria-related pathway.

Cigarette smoke extracts delay wound healing in the stomach: involvement of polyamine synthesis

The association between cigarette smoking and peptic ulcer diseases has been well established. Ornithine decarboxylase (ODC) is crucial for the gastroprotective and mucosal growth promoting effects in gastric ulcer healing. The aim of this study is to elucidate the possible mechanism of how inhibition of ODC activity is involved in the delay of ulcer healing, if any, by cigarette smoke extracts (CSE). CSE were fractionated into chloroform extract (CE) and ethanol extract (EE). In in vivo study, rats with acetic acid-induced ulcers were given CE or EE intragastrically (2.5 or 5 mg/kg) once daily for 3 days. Ulcer sizes were significantly larger after CE or EE administration, followed by an increase in myeloperoxidase activity and a reduction in cell proliferation. However, both CSE stimulated the number of microvessels following the increase of basic fibroblast growth factor. In in vitro studies, the effect of CE or EE (10, 40, or 100 microg/ml) on cell migration and cell proliferation were measured using an in vitro wound model and [(3)H]-thymidine incorporation assay, respectively. Both CSE delayed cell migration and decreased cell proliferation, which were accompanied with a reduction in ODC activity. Exogenous spermidine (5 or 10 microM) could reverse the inhibitory action on cell proliferation and ODC activity induced by CSE. In conclusion, both CSE significantly delayed ulcer healing as a result of reduction in cell proliferation and cell migration. All these effects are, in part, related to the reduction of polyamine synthesis.

Cigarette smoke and its extract delays ulcer healing and reduces nitric oxide synthase activity and angiogenesis in rat stomach

1. The purpose of the present study was to examine whether cigarette smoke and its extract could affect ulcer healing, angiogenesis and nitric oxide synthase (NOS) activity in the gastric mucosa. 2. Ulcerated rats were either exposed to cigarette smoke or given smoke extract once daily for 3 days. Rats were killed and stomachs were removed for the measurement of ulcer size, angiogenesis and NOS activity. 3. Angiogenesis and constitutive NOS activity were concomitantly and dose-dependently reduced by cigarette smoke or its extract. The same treatments also delayed ulcer healing. 4. These results indicate that cigarette smoke and its extract repress the processes of new blood vessel formation and NOS activity during tissue repair in the gastric mucosa. These could, in turn, retard the healing process in the gastric mucosa.

Cigarette smoking delays ulcer healing: role of constitutive nitric oxide synthase in rat stomach

Epidemiological studies have shown that cigarette smoking is associated with peptic ulceration. This study aims to investigate the mechanisms by which cigarette smoking delays ulcer healing in rats. Gastric ulcers were induced by applying acetic acid to the luminal surfaces in rats. Twenty-four hours later, rats were exposed to different concentrations of cigarette smoke (0, 2, or 4%) for a 1-h period once daily for 3 or 6 days. Cigarette smoke exposure delayed ulcer healing and decreased gastric blood flow and angiogenesis at the ulcer margin. These changes were accompanied by a significant reduction of constitutive nitric oxide synthase (cNOS) activity but not PGE2 production and vascular endothelial growth factor levels. Administration of L-arginine (10 mg/kg iv) completely reversed the adverse actions on ulcer healing, gastric blood flow, and angiogenesis in the mucosa at the ulcer margin but partially restored angiogenesis in granulation tissues. In conclusion, cigarette smoke exposure delays ulcer healing through depression of gastric blood flow and angiogenesis at the ulcer margin. Reduction of cNOS expression and activity is suggested to be involved in these ulcerogenic processes.

Cigarette smoking: Effects on P selectin expression and subsequent inflammatory responses in ethanol-induced gastric mucosal damage

Experimental evidence has shown that cigarette smoking potentiates ulcer formation and delays ulcer healing. The exact mechanisms are still not completely defined. We investigated the effects of cigarette smoking on P selectin expression and its actions on neutrophil infiltration and nitric oxide formation in ethanol-induced gastric mucosal damage. In the present study, rats were exposed to cigarette smoke for three 1 h periods. Cigarette smoke exposure significantly up-regulated P selectin expression in the gastric mucosa. Cigarette smoke exposure following ethanol challenge substantially potentiated the mucosal damage, which was accompanied with an increase in myeloperoxidase and inducible nitric oxide synthase activities. Anti-neutrophil serum completely abolished these changes, whereas aminoguanidine produced similar effects without affecting myeloperoxidase activity. Taken together, cigarette smoke exposure can up-regulate P selectin expression, which facilitates neutrophil rolling, margination and infiltration when challenged with ethanol. These actions activate inducible nitric oxide synthase activity, which may contribute to the potentiating effect of cigarette smoking on ethanol-induced gastric ulceration in rats.