The Effect Of Cigarette Smoke And Intermittent Hypoxia On Small Intestine Epithelium Of Rats

Chronic obstructive lung disease(COPD)and Obstructive sleep apnea(OSA)are common diseases,which are not only involved in pulmonary system but also many systems including cardiovascular system,cerebrovascular system,endocrine system and skeletal muscle.COPD is accepted to be a multicomponent disease with various comorbidities.Intestinal integrity is disturbed in COPD patients.Intestinal hyperpermeability is observed at rest and intensifies after performing standardized household activities,with concomitant enhanced enterocyte loss.COPD is recognized as a chronic systemic low-grade inflammatory disease.However,the occurrence of systemic inflammation is highly heterogeneous,ranging from no evidence of systemic inflammation to persistent systemic inflammation.Sleep apnea is a common disorder characterized by cessation of breathing during sleep,which is mostly attributed to repetitive pharyngeal airway collapse(ie,obstructive sleep apnea).Obstructive sleep apnea is associated with a variety of diseases,most notable of which are cardiovascular diseases,such as hypertension,atherosclerosis,and arrhythmia.The resultant insults,including intermittent hypoxia,systemic inflammation,oxidative stress,and sympathetic activation after episodes of apnea.However,the impact of these noxious insults may be more widespread than we would expect,not exclusively limited to the cardiovascular system.Problems or comorbidities of the gastrointestinal system,which are likely to be affected as well,are less frequently although gastroesophageal reflux,fatty liver disease,and liver injury have received more attention.Patients with sleep apnea experienced a 2.4-fold higher risk for incident peptic ulcer bleeding.A critical cell type in the maintenance of intestinal homeostasis is the epithelial cell.This dynamic barrier is maintained primarily by the existence of regulated intercellular tight junctions.Importantly,both the barrier and absorptive functions of the intestinal epithelium can be physiologically regulated by oxygen.Basic and translational researchs have provided important discoveries concerning these interactions in COPD and OSA,resulting in the development of biomarkers reflecting oxidative stress,inflammation,and apoptosis.However,there are various main mechanism in organs.The mechanism of structural change of intestines in COPD and OSA had not been reported in literature.Objective:To set and evaluate rat model of COPD induced by cigarette smoke and rat model of OSA induced by intermittent hypoxia and observe the changes of the small intestine.To observe mRNA expression of NADPH,SOD,Bax,bcl-2,NF-κB in smoke-exposed and intermittent hypoxia exposed rats.To observe mRNA expression of HIF-1α,c-fos,ZO-1,claudin-1,claudin-2,claudin-3 and claudin-4 in smoke-exposed and intermittent hypoxia exposed rats.Methods:1.Establishment of emphsema and intermittent hypoxia model in rats.45 Wistar male rats were divided randomly into 3 groups,fifteen rats per group(n=15).Control group:sham-smoking and sham-intermittent hypoxia;Cigarette smoking(CS)group:smoke exposed and sham-intermittent hypoxia,Intermittent hypoxia(IH)group:intermittent hypoxia and sham-smoking.2.The morphology manifests of lung tissues were evaluated and quantitative morphological analysis was made.3.The histopathological changes of the small intestine epithelium were observed.4.The changes of goblet cells and endocrine cells were observed.5.Changes on the expression of intenstine cells line were detected6.Rat models were evaluated by analyzing small intestinal tight junction using quantitative reverse transcription polymerase chain reaction.Results:Morphology detection of lung tissues showed significant larged air space,disruption of alveolar septum and formation of emphysema in CS group.Compared to the control group,there was a significant increase in lung pathological score,mean alveolar septal thicknes and mean linear intercept.There were less alveolus in CS group than the control group.The blood gas analysis showed that the intermittent hypoxia occurred in the IH group.Morphology detection of intestinal tissues showed the mucous membrane of the small intestine epithelium was deleted and disrupted in IH group and CS group.The number of endocrine cells in the instistine was not different among the three groups.The number of goblet cell was dreased in CS group.The expressions of MUC2 mRNA,ChgA mRNA,Lyszyme mRNA and β-catenin mRNA were increased in CS ang IH groups.Lyszyme mRNA was increased more in CS group than in IH group.Compared to the control group,there was a significant increase in the expression of the nicotinamide adenine dinucleotide phosphate(NADPH)oxidase subunits nox2(p<0.05)and p22phox(p<0.01)in the CS group and IH group.However,antioxidant enzyme superoxide dismutase(SOD)was reduced in CS group and IH group(p<0.05).The bax mRNA expression was greater in the CS group and IH group(p<0.01).In addition,bcl-2 expression was significantly reduced in the CS group and IH group(p<0.01).NF-κB expression was higher in the CS group and IH group,but this change was not significant(p=0.09).The inflammatory cytokine tumor necrosis factor alpha(TNF-α)showed no significant difference in CS group although reduced in IH group.Compared to the control group,there was a significant increase in the expression of HIF-1α in the CS rats and IH rats(p<0.05).The CS group experienced a significantly reduced claudin-1 expression(p<0.01)and increased claudin-2 expression(p<0.01).There were no significant changes were found in claudin-4,occludin,and zo-1 expressions.qRT-PCR demonstrated that the mRNA expression of claudin-1(p<0.01)and claudin-4(p<0.05)were markedly reduced in IH group than the control group.Conclusions:The characters of the COPD animal model induced by cigarette smoke and OSA model induced by intermittent hypoxia were similar with that of the human.The pathological changes were observed in the small intestine in COPD and OSA models.These data suggest that during the development of COPD,the disruption of the small intestine is associated with increased oxidative stress and apoptosis.OSA can cause disruption of duodenum,The mechanism is ascribed to oxidative stress and activated transcription factors.During the development of COPD,HIF-1α expression is altered by the increased oxidative stress and inflammation in the small intestine,eventually resulting in disruption of the intestinal tight junctions.OSA can cause disruption of duodenum.The mechanism is ascribed to increased oxidative stress induced by hypoxia,subsequently induced compromise of intestinal TJs,and ultimately resulted in intestinal injury.