Effect of cigarette smoke on esophageal epithelium of the rabbit

Inhibition of NHE-1 Increases Smoke-Induced Proliferative Activity of Barrett's Esophageal Cell Line

Several clinical studies indicate that smoking predisposes its consumers to esophageal inflammatory and malignant diseases, but the cellular mechanism is not clear. Ion transporters protect esophageal epithelial cells by maintaining intracellular pH at normal levels. In this study, we hypothesized that smoking affects the function of ion transporters, thus playing a role in the development of smoking-induced esophageal diseases. Esophageal cell lines were treated with cigarettesmoke extract (CSE), and the viability and proliferation of the cells, as well as the activity, mRNA and protein expression of the Na+/H+ exchanger-1 (NHE-1), were studied. NHE-1 expression was also investigated in human samples. For chronic treatment, guinea pigs were exposed to tobacco smoke, and NHE-1 activity was measured. Silencing of NHE-1 was performed by using specific siRNA. CSE treatment increased the activity and protein expression of NHE-1 in the metaplastic cells and decreased the rate of proliferation in a NHE-1-dependent manner. In contrast, CSE increased the proliferation of dysplastic cells independently of NHE-1. In the normal cells, the expression and activity of NHE-1 decreased due to in vitro and in vivo smoke exposure. Smoking enhances the function of NHE-1 in Barrett's esophagus, and this is presumably a compensatory mechanism against this toxic agent.

Pathophysiology of gastro-esophageal reflux disease: a role for mucosa integrity?

BACKGROUND

Gastro-esophageal reflux disease (GERD) is very prevalent and has a high burden on health security system costs. Nevertheless, pathophysiology is complex and not well-understood. Several mechanisms have been proposed: decreased salivation, impaired esophageal clearance, decreased lower esophageal sphincter pressure resting tone, presence of hiatal hernia, increased number of transient lower esophageal sphincter relaxations (TLESRs), increased acid, and pepsin secretion, pyloric incompetence provoking duodeno-gastro-esophageal reflux of bile acids and trypsin. Independent of the relevance of each mechanism, the ultimate phenomenon is that mucosal epithelium is exposed for a longer time to agents as acid and pepsin or is in contact to luminal agents not commonly present in gastric refluxate as trypsin or bile acids. This leads to a visible damage of the epithelium (erosive esophagitis -EE) or impairing mucosal integrity without any sign of macroscopic alteration as occurs in non-erosive reflux disease (NERD). Luminal factors are not the only responsible for such impairment; more recent data indicate that endogenous factors may also play a role.

PURPOSE

This review will update the most recent findings on the putative pathophysiological mechanisms and specially will focus on the role of esophageal mucosal integrity in GERD. Methodologies used for the evaluation of mucosal integrity, its relevance in EE and NERD, its involvement in symptoms perception and the effect of luminal and endogenous factors will be discussed.

Approach to the patient with presumed extraoesophageal GERD

Reflux related cough, asthma and laryngitis are frequently encountered and are considered part of extraoesophageal syndromes. The diagnosis of extraoesophageal reflux is difficult due to the lack of gold standard diagnostic criteria. Esophagogastroduodenoscopy and esophageal pH monitoring are inadequate diagnostic tools for due to poor sensitivity and specificity. For this reason, empirical PPI therapy is recommended as an initial approach to diagnose and treat the potential underlying cause of these symptoms in patients without alarm symptoms. Diagnostic testing with esophageal pH and/or impedance monitoring and esophageal motility testing is usually reserved for those who continue to be symptomatic despite a trial of therapy with PPIs. Recent developments have increased our understanding of this difficult to treat group of patients but more research into reflux related extraoesophageal symptoms are needed to better diagnose and treat this group.

Protective role of aerodigestive reflexes against aspiration: study on subjects with impaired and preserved reflexes

BACKGROUND & AIMS

Direct evidence to support the airway protective function of aerodigestive reflexes triggered by pharyngeal stimulation was previously demonstrated by abolishing these reflexes by topical pharyngeal anesthesia in normal subjects. Studies have also shown that these reflexes deteriorate in cigarette smokers. Aim of this study was to determine the influence of defective pharyngeal aerodigestive reflexes on airway protection in cigarette smokers.

METHODS

Pharyngoglottal Closure reflex; PGCR, Pharyngo-UES Contractile reflex; PUCR, and Reflexive Pharyngeal Swallow; RPS were studied in 15 healthy non-smokers (24.2±3.3 SD y, 7 males) and 15 healthy chronic smokers (27.3±8.1, 7 males). To elicit these reflexes and to evaluate aspiration, colored water was perfused into the hypopharynx at the rate of 1 mL/min. Maximum volume of water that can safely dwell in the hypopharynx before spilling into the larynx (Hypopharyngeal Safe Volume; HPSV) and the threshold volume to elicit PGCR, PUCR, and RPS were determined in smokers and results compared with non-smokers.

RESULTS

At baseline, RPS was elicited in all non-smokers (100%) and in only 3 of 15 smokers (20%; P<.001). None of the non-smokers showed evidence of laryngeal spillage of water, whereas 12 of 15 smokers with absent RPS had laryngeal spillage. Pharyngeal anesthesia abolished RPS reflex in all non-smokers resulting in laryngeal spillage. The HPSV was 0.61±0.06 mL and 0.76±0.06 mL in non-smokers and smokers respectively (P=.1).

CONCLUSIONS

Deteriorated reflexive pharyngeal swallow in chronic cigarette smokers predispose them to risks of aspiration and similarly, abolishing this reflex in non-smokers also results in laryngeal spillage. These observations directly demonstrate the airway protective function of RPS.

Effects of ethanol and extract of cigarette smoke on the rabbit buccal mucosa

AIM

The combination of smoking and drinking alcohol has a high association with diseases of squamous epithelium within the human oral cavity. Therefore, a study was done to assess the impact of these agents alone or in combination on the squamous epithelium using as model the buccal epithelium from rabbit oral cavity.

METHODS

Buccal epithelium was mounted in Ussing chambers to monitor electrical parameters during exposure to ethanol (5-40%) or to Ringer extract of cigarette smoke (EOCS) from one to six cigarettes dissolved in 10 ml Ringer either alone or with combination.

RESULTS

Exposure to EOCS reduced in a dose dependent manner above 2 cigarettes/10 ml transmural electrical potential difference (PD), short-circuit current (I(sc)), increased transmural electrical resistance (R). Morphology showed from generalize tissue edema to patchy necrosis with the increasing concentrations. Ethanol alone raised PD, I(sc) and R at lower concentrations (5%) and lowered PD, I(sc) and R at higher concentrations (40%). The combination of 5% ethanol, EOCS-1cigarette/10 ml reduced PD, I(sc) by 58% and increased R by 29%. Unlike exposure to 5% EtOH and EOCS-1, 10% EtOH combined with EOCS-1 produces a harmful effect by dropping PD and I(sc).

CONCLUSION

Both, simultaneous, and sequential, use of these agents enhanced their negative impact on these parameters. The enhancement of these effects are not due to solubulization of additional tobacco products by EtOH or by or by EtOH enhancing smoking noxious effect. Histopathologic damage needs higher concentrations of ethanol and EOCS combination and changes were more profound compared to the sum of the isolated effects of both agents.

Effect of systemic alcohol and nicotine on airway protective reflexes

OBJECTIVES

Injection of water into the pharynx induces contraction of the upper esophageal sphincter (UES), triggers the pharyngo-UES contractile reflex (PUCR), and at a higher volume, triggers an irrepressible swallow, the reflexive pharyngeal swallow (RPS). These aerodigestive reflexes have been proposed to reduce the risks of aspiration. Alcohol ingestion can predispose to aspiration and previous studies have shown that cigarette smoking can adversely affect these reflexes. It is not known whether this is a local effect of smoking on the pharynx or a systemic effect of nicotine. The aim of this study was to elucidate the effect of systemic alcohol and nicotine on PUCR and RPS.

METHODS

Ten healthy non-smoking subjects (8 men, 2 women; mean age: 32+/-3 s.d. years) and 10 healthy chronic smokers (7 men, 3 women; 34+/-8 years) with no history of alcohol abuse were studied. Using previously described techniques, the above reflexes were elicited by rapid and slow water injections into the pharynx, before and after an intravenous injection of 5% alcohol (breath alcohol level of 0.1%), before and after smoking, and before and after a nicotine patch was applied. Blood nicotine levels were measured.

RESULTS

During rapid and slow water injections, alcohol significantly increased the threshold volume (ml) to trigger PUCR and RPS (rapid: PUCR: baseline 0.2+/-0.05, alcohol 0.4+/-0.09; P=0.022; RPS: baseline 0.5+/-0.17, alcohol 0.8+/-0.19; P=0.01, slow: PUCR: baseline 0.2+/-0.03, alcohol 0.4+/-0.08; P=0.012; RPS: baseline 3.0+/-0.3, alcohol 4.6+/-0.5; P=0.028). During rapid water injections, acute smoking increased the threshold volume to trigger PUCR and RPS (PUCR: baseline 0.4+/-0.06, smoking 0.67+/-0.09; P=0.03; RPS: baseline 0.7+/-0.03, smoking 1.1+/-0.1; P=0.001). No similar increases were noted after a nicotine patch was applied.

CONCLUSIONS

Acute systemic alcohol exposure inhibits the elicitation PUCR and RPS. Unlike cigarette smoking, systemic nicotine does not alter the elicitation of these reflexes.

The additive effect of ethanol and extract of cigarette smoke on rabbit esophagus epithelium

AIM

The combination of alcohol and smoking takes a place in the epidemiology and pathogenesis of gastroesophageal reflux disease and squamous cancers of the esophagus. Therefore, a study was designed to assess the impact of these agents alone or in combination on the structure and function of squamous epithelium of rabbit esophagus.

METHODS

Rabbit esophageal epithelium was mounted in Ussing Chambers, exposed luminally for ethanol (1-10%), extract of cigarette smoke (EOCS) and combinations or sequential application of these agents. An in-vivo model was also used to mimic conditions more representative of human alcohol consumption.

RESULTS

Ethanol (1-10%) dose dependently decreased tissue resistance. Extract of cigarette smoke caused a reduction on transepithelial potential difference (PD), short circuit current. Combinations of EOCS, ethanol (5-10% EtOH and EOCS 1-2) showed a more pronounced decrease than agents alone, mainly the result of EOCS. In vivo studies showed that EOCS administration dropped PD dose dependently. In-vivo 10% EtOH, EOCS-2 dropped PD (55%) similar to in-vitro 5% EtOH, EOCS-1. The effect was clearly additive; boluses of 10% ethanol (36%) and EOCS-2 (17%) decreased PD and combination of agents resulted in a 55% drop on PD which is a very similar decrease compared to the sum of the separate effects of agents (53%).

CONCLUSION

Ethanol affected the barrier and cigarette smoke altered ion transport on rabbit esophageal epithelium under conditions reflecting human consumption. Results were consistent with in vivo and in vitro conditions except higher concentrations were needed in vivo. When applied, these agents showed an additive effect. Ethanol predisposed the tissue to the effect of EOCS.

Electrical parameters and ion species for active transport in human esophageal stratified squamous epithelium and Barrett's specialized columnar epithelium

The human esophagus is lined by stratified squamous epithelium (ESSE), and in some subjects with reflux disease the distal esophagus becomes lined by Barrett's specialized columnar epithelium (BSCE). ESSE and BSCE differ both histologically and functionally, the latter evident by differences in their in vivo transmural electrical potential difference (PD), ESSE averaging -15 mV and BSCE being greater than -25 mV. In this report we examine the basis for this difference in PD. This is done by mounting endoscopic biopsies of ESSE from 25 subjects without esophageal disease and BSCE from 19 with Barrett's esophagus in mini-Ussing chambers for electrical recordings basally and after bathing solution ion replacement. The results show that the PD of human ESSE reflects a low level of active ion transport (5.1 +/- 0.8 muA/cm(2)) combined with a high level of tissue (electrical) resistance (344 +/- 34 Omega.cm(2)) and that of BSCE reflects a high level of active transport (43.6 +/- 11.6 muA/cm(2)) combined with a low level of resistance (69 +/- 8 Omega.cm(2)). Furthermore, active transport in ESSE was principally due to sodium absorption whereas in BSCE it was equally divided between sodium absorption and anion (chloride/bicarbonate) secretion, the latter through an apical membrane, 4-acetamido4'-isothiocyano-2,2'-stilbenedisulfonic acid-sensitive anion channel. As an anion-secreting tissue with bicarbonate secretory capacity more than fivefold greater than ESSE, BSCE is better suited than ESSE for defense of the esophagus against reflux disease.

Reflux, Dyspepsia, and Disorders of the Foregut

Disorders of the foregut are an increasingly common cause of symptoms in Western populations. This review summarizes recent advances in the understanding and treatment of gastroesophageal reflux disease, dyspepsia and celiac disease.

Pathogenesis of reflux esophagitis and Barrett's esophagus

An understanding of the pathogenesis of reflux esophagitis and Barrett's esophagus requires knowledge of the noxious elements in gastric juice and the three major esophageal defenses designed to protect against them. When the esophageal epithelium cannot prevent gastric acid from acidifying the intercellular spaces, the foundation is set for the development of the major symptoms, signs, and complications of reflux esophagitis. Inadequate defense by the epithelium can occur by exposure to the acidic refluxate for a prolonged period of time, because of defects in the antireflux or luminal clearance mechanisms, or by exposure to ingested products that directly impair the epithelium's intrinsic defenses, rendering it vulnerable to injury from even physiologic levels of acid reflux.

Review article: the pathophysiology of gastro-oesophageal reflux disease - oesophageal manifestations

The pathogenesis of gastro-oesophageal reflux disease (GERD) is multifactorial, involving transient lower oesophageal sphincter relaxations (TLESRs) as well as other lower oesophageal sphincter (LES) pressure abnormalities. GERD is associated with a decrease in LES pressure, which can be provoked by factors such as foods (fat, chocolate, etc.), alcohol, smoking and medications. These factors have also been shown to increase TLESRs. As a result, reflux of acid, bile, pepsin and pancreatic enzymes occurs, leading to oesophageal mucosal injury, which can potentially progress to oesophageal adenocarcinoma in a minority of patients with Barrett's metaplasia. In addition, duodenogastric contents can also contribute to oesophageal injury. Other factors contributing to the pathophysiology of GERD include hiatal hernia, poor oesophageal clearance, delayed gastric emptying and impaired mucosal defensive factors. Hiatal hernia has a permissive role in the pathogenesis of reflux oesophagitis by promoting LES dysfunction. Delayed gastric emptying, resulting in gastric distension, can significantly increase the rate of TLESRs, contributing to postprandial GER. The mucosal defensive factors have an important role in GERD. When excessive acid causes a breakdown in oesophageal epithelial defenses, epithelial resistance may be reduced. Nocturnal GERD is associated with prolonged acid exposure and proximal extent of acid contact, which elevates the risk for oesophageal damage and GERD-related complications. In sum, GERD is a complex problem caused by many factors that are exacerbated when the patient is in the supine position.

Pathogenesis of Gastroesophageal Reflux Disease

The pathophysiology of reflux esophagitis involves contact of the esophageal epithelium with acid-pepsin in the refluxate. For this contact to occur with sufficient duration, there must either be a combination of defects in antireflux and luminal clearance mechanisms for acid-pepsin to overwhelm a previously healthy epithelium or primary defects within the epithelium develop that subsequently enable 'normal' acid contact times to become damaging to the epithelium. This report examines these 2 pathways to reflux esophagitis and questions the causative role attributed to some phenomena. In either case, the final common pathway for the clinical expression of reflux esophagitis is by damage to the esophageal epithelium that is responsible for the development of heartburn and/or esophageal necrosis and inflammation.

Pathogenesis of gastroesophageal reflux disease

The pathophysiology of GERD involves contact of the esophageal epithelium with acid/pepsin in the refluxate. For this contact to occur with sufficient duration, there must be a combination of defects in antireflux and luminal clearance mechanisms for acid/pepsin to overwhelm an intact epithelium, or defects within the epithelium develop that subsequently enable normal acid contact times to become damaging to the epithelium. In either case, the final common pathway is damage to the esophageal epithelium--damage that is reflected in the development of heartburn, esophageal necrosis and inflammation, or both.

Choline acetyltransferase, acetylcholinesterase, and nicotinic acetylcholine receptors of human gingival and esophageal epithelia

A non-neuronal cholinergic system that includes neuronal-like nicotinic acetylcholine receptors (nAChRs) has recently been described in epithelial cells that line the skin and the upper respiratory tract. Since the use of nicotine-containing products is associated with morbidity in the upper digestive tract, and since nicotine may alter cellular functions directly via nAChRs, we sought to identify and characterize a non-neuronal cholinergic system in the gingival and esophageal epithelia. mRNA transcripts for alpha3, alpha5, alpha7, and beta2 nAChR subunits, choline acetyltransferase, and the asymmetric and globular forms of acetylcholinesterase were amplified from gingival keratinocytes (KC) by means of polymerase chain-reactions. These proteins were visualized in the gingival and esophageal epithelia by means of specific antibodies. Variations in distribution and intensity of immunostaining were found, indicating that the repertoire of cholinergic enzymes and receptors expressed by the cells changes during epithelial maturation, and that an upward concentration gradient of free acetylcholine exists. Blocking of the nAChRs with mecamylamine resulted in reversible loss of cell-to-cell adhesion, and shrinking and rounding of cultured gingival KC. Activation of the receptors with acetylcholine or carbachol caused stretching and peripheral ruffling of the cytoplasmic aprons, and formation of new intercellular contacts. These results demonstrate that both the keratinizing epithelium of attached gingiva and the non-keratinizing epithelium lining the upper two-thirds of the esophageal mucosa possess a non-neuronal cholinergic system. The nAChRs expressed by these epithelia are coupled to regulation of cell adhesion and motility, and may provide a target for the deleterious effects of nicotine.

Effects of transdermal nicotine on lower esophageal sphincter and esophageal motility

Cigarette smoking has been shown to decrease lower esophageal sphincter pressure (LESP) by 19-42%. This decrease in LESP may be due to nicotine in the cigarette smoke or substances other than nicotine. The aim of this study was to evaluate the effects of a nicotine patch on esophageal motility since nicotine patches are devoid of all toxins present in the cigarette smoke except the nicotine. Ten healthy nonsmoking volunteers underwent baseline esophageal manometry. Esophageal manometry was repeated after placing a nicotine transdermal patch (Nicotrol) designed to deliver 15 mg of nicotine per day. The parameters that were compared included LESP by rapid pull-through (LESP-RPT) and station pull-through (LESP-SPT), LES relaxation, and velocity, amplitude, and duration of esophageal contractions. Plasma nicotine and cotinine levels were measured prior to baseline manometry and after 12 hr of placing the nicotine patch, the LESP-RPT decreased by 31% from 17.4 +/- 6.1 to 12.1 +/- 3.3 (P = 0.013) and the LESP-SPT by 27% from 13.4 +/- 5.4 to 9.8 +/- 4.8 (P = 0.029) after the nicotine patch. LES relaxation was present in 100% before and after nicotine patch. There were no significant differences in velocity, duration, and amplitude of esophageal contractions after the nicotine patch. Plasma nicotine and cotinine was absent in all subjects at baseline but was significantly elevated after 12 hr of nicotine patch. Transdermal delivery of nicotine results in a significant reduction in LESP in healthy subjects without effecting LES relaxation or esophageal body motility.

Mechanisms of sodium and chloride transport across isolated sheep reticulum

1. 22Na+ and 36Cl- fluxes across isolated reticular epithelium of sheep were measured by using the Ussing-chamber technique. 2. Net NaCl absorption driven by Na(+)-K(+)-ATPase was observed under short-circuit conditions. 3. Evaluation of fluxes measured under voltage-clamp conditions indicated that Na+ absorption is mainly electroneutral. 4. Mucosal application of bumetanide, hydrochlorothiazide, or low dose amiloride (10(-4) M) produced no changes in Na+ transport whereas addition of higher doses of amiloride (> or = 10(-3) M) led to a reduction in net Na+ transport. Short chain fatty acids (SCFA) enhanced the amiloride-sensitive Na+ transport. 5. Alterations of JmsNa induced by inhibitors or by SCFA were always accompanied by qualitatively similar changes of JsmNa. Amiloride-sensitive JsmNa was also decreased at low mucosal Na+ concentration. 6. DIDS, SITS, and nitrate reduced both JmsCl and JsmCl. SCFA did not influence chloride transport. 7. It is concluded that Na+ transport is mediated by Na(+)-H+ exchange and by transport processes operating as Na+ self-exchange. Mucosal-to-serosal chloride transport seems partly to depend on anion exchange systems.

The acute effects of smokeless tobacco on transport and barrier function of buccal mucosa

The acute effects of smokeless tobacco (ST) on buccal mucosal transport and barrier function were studied by means of in vivo and in vitro techniques. In humans, in vivo exposure to 0.5 g ST transiently increased the transmural electrical potential difference (PD). However, despite continued exposure, PD returned to baseline within 20 min. The mechanisms for these changes were explored by use of dog buccal mucosa mounted in Ussing chambers. Luminal exposure to a Ringer-extract of ST (EOST) increased PD and short-circuit current (Isc) and decreased electrical resistance (R), with changes reversible upon removal of EOST from the bath. Further, radioisotopic fluxes showed that the increase in Isc in EOST-exposed tissues was accompanied by increased absorption of electrolytes (Na, Cl, and other ions), and the decrease in R was accompanied by increased permeability to mannitol. Light microscopy of tissues exposed to EOST showed no morphological changes after exposure to 0.5 g of ST, but after exposure to 1.5-2.5 g of ST, dilated intercellular spaces were identified. Contact of aqueous media with ST led to the release of electrolytes and other soluble compounds into solution. To determine the effect of electrolyte release on buccal function, we exposed mucosae luminally to a solution with ion composition and/or osmolality similar to EOST or to one with an EOST previously dialyzed against Ringer. Solutions with similar ion composition and/or osmolarity changed PD, Isc, and R in a manner similar to EOST, while dialyzed-EOST had no effect. In addition, luminal nicotine produced effects different from EOST, decreasing PD and Isc and increasing R.(ABSTRACT TRUNCATED AT 250 WORDS)