Effect of ethanol on the structure and function of rabbit esophageal epithelium

Squamous Cell Carcinoma of the Esophagus

Esophageal squamous cell carcinoma (ESCC) is common in the developing world with decreasing incidence in developed countries and carries significant morbidity and mortality. Major risk factors for ESCC development include significant use of alcohol and tobacco. Screening for ESCC can be recommended in high-risk populations living in highly endemic regions. The treatment of ESCC ranges from endoscopic resection therapy or surgery in localized disease to chemoradiotherapy in metastatic disease, and prognosis is directly related to the stage at diagnosis. New immunotherapies and molecular targeted therapies may improve the dismal survival outcomes in patients with metastatic ESCC.

Establishment of a Simple and Versatile Evaporation Compensation Model for in vitro Chronic Ethanol Treatment: Impact on Neuronal Viability

Alcohol overconsumption is a major cause of preventable mental disorders and death in the United States and around the world. The pathogenesis of alcohol dependence, abuse, and toxicity to the central nervous system remains incompletely understood. In vitro and cell culture-based models have been highly valuable in studying the molecular and cellular mechanisms underlying the contribution of individual CNS cell types to ethanol's effects on the brain. However, conventional cell culture model systems carry the inherent disadvantage of rapid loss of ethanol due to evaporation following a bolus addition at the start of the treatment. We have established a multi-well cell culture plate-based ethanol evaporation compensation model that utilizes the inter-well space as a reservoir to compensate for the evaporative loss of ethanol in the cell treatment wells. Following a single bolus addition at the start of the treatment, ethanol concentration rapidly decreased over time. Through compensation using the multi-well plate platform, maintenance of ethanol concentrations ranging from 10-100 mM was achieved for up to 72 hours in a cell-free system. Greater effects in ethanol-induced decrease in neuronal cell viability were observed with than without compensation. Our method effectively compensates for the evaporative loss of ethanol typically observed in the traditional method. This method provides an economic, simple and effective in vitro model system for ethanol treatment over an extended timeframe where maintenance of a relatively constant concentration of ethanol is desired.

Laboratory models available to study alcohol-induced organ damage and immune variations: choosing the appropriate model

The morbidity and mortality resulting from alcohol-related diseases globally impose a substantive cost to society. To minimize the financial burden on society and improve the quality of life for individuals suffering from the ill effects of alcohol abuse, substantial research in the alcohol field is focused on understanding the mechanisms by which alcohol-related diseases develop and progress. Since ethical concerns and inherent difficulties limit the amount of alcohol abuse research that can be performed in humans, most studies are performed in laboratory animals. This article summarizes the various laboratory models of alcohol abuse that are currently available and are used to study the mechanisms by which alcohol abuse induces organ damage and immune defects. The strengths and weaknesses of each of the models are discussed. Integrated into the review are the presentations that were made in the symposium "Methods of Ethanol Application in Alcohol Model-How Long is Long Enough" at the joint 2008 Research Society on Alcoholism (RSA) and International Society for Biomedical Research on Alcoholism (ISBRA) meeting, Washington, DC, emphasizing the importance not only of selecting the most appropriate laboratory alcohol model to address the specific goals of a project but also of ensuring that the findings can be extrapolated to alcohol-induced diseases in humans.

Dilated intercellular spaces as a marker of GERD

Gastroesophageal reflux disease (GERD) is typically heralded by the substernal burning pain of heartburn. On endoscopic examination, about one third of GERD subjects with heartburn have erosive disease, and the remainder have nonerosive reflux disease (NERD). Unlike patients with erosive disease, those with NERD (approximately 50%) often do not respond to therapy with proton pump inhibitors (PPIs), raising the question of whether they have NERD and, if they do, whether the cause of their symptoms is similar to those who respond to PPIs. Recently, biopsies established that subjects with heartburn and PPI-responsive NERD, like those with erosive esophagitis, have lesions within the esophageal epithelium known as dilated intercellular space (DIS). In this article, we discuss the physicochemical basis for DIS in acid-injured esophageal epithelium and its significance in GERD. Although DIS is not pathognomic of GERD, it is a marker of a break in the epithelial (junctional) barrier reflecting an increase in paracellular permeability.

In vitro and in vivo models of acute alcohol exposure

Alcohol abuse is a global problem due to the financial burden on society and the healthcare system. While the harmful health effects of chronic alcohol abuse are well established, more recent data suggest that acute alcohol consumption also affects human wellbeing. Thus, there is a need for research models in order to fully understand the effect of acute alcohol abuse on different body systems and organs. The present manuscript summarizes the interdisciplinary advantages and disadvantages of currently available human and non-human models of acute alcohol abuse, and identifies their suitability for biomedical research.

Ethanol increases the paracellular permeability of monolayers of CAPAN-1 pancreatic duct cells

When grown on permeable supports, pancreatic duct adenocarcinoma CAPAN-1 cells establish very high values of transepithelial resistance (TER). The addition of ethanol produced a dose-related, reversible drop in the TER of these cells, ranging from 15% (with 1% ethanol) to 65% (with 10% ethanol). The ethanol effect was rapid and reversible. The resistance decrease was associated with an increase in monolayer permeability to mannitol. No significant decrease in cell ATP was detected for ethanol concentrations lower than 7%. Confocal vertical sections of calcein-loaded monolayers of CAPAN-1 cells, grown on plasticware, showed a progressive deflation of domes detectable after 5 min of treatment with 2% ethanol. Incubation in an ethanol-free medium caused a progressive dome restoration. Immunocytochemical analysis of ethanol-treated cells indicated that ZO-1 and occludin exhibited clear cut distribution changes while the perijunctional actin pattern was slightly modified. Electron microscopy showed that a discrete intercellular space was detectable between adjacent ethanol-treated cells but not between control cells. These data indicate that ethanol is a tight junction barrier opener in pancreatic duct cells.

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.

Calcium-switch technique and junctional permeability in native rabbit esophageal epithelium

The Ca(2+)-switch technique was used to investigate the nature of the barrier governing (paracellular) permeability across the junctions of "native" rabbit esophageal epithelium. This was done by mounting esophageal epithelium in Ussing chambers to monitor transepithelial electrical resistance (R(T)), a marker of junctional permeability. When exposed to Ca(2+)-free Ringer solutions containing EDTA, R(T) declined approximately 35% below baseline over 2 h, and this decline reversed within 2 h by restoration of (1.2 mM) Ca(2+)-containing, normal Ringer solution ("Ca(2+)-switch technique"). Junctional resealing, i.e., increased R(T) on Ca(2+) replacement, was assessed by the Ca(2+)-switch technique and shown to be 1) specific for Ca(2+), with only Mn(2+) among substituted divalent cations yielding partial resealing; 2) a function of extracellular Ca(2+) levels because maneuvers (BAPTA/AM or A23187 exposure) to alter intracellular Ca(2+) had no effect; 3) dose dependent, requiring as a minimum > or =0.5 mM Ca(2+) and 1.2 mM Ca(2+) for optimization; and 4) independent of protein synthesis because it was not inhibited by cycloheximide. Resealing was also inhibited by luminal antibodies or synthetic peptides to the extracellular domain of E-cadherin. Immunohistochemistry revealed E-cadherin within all layers of stratum corneum in Ca(2+)-free but not Ca(2+)-containing solution. The present investigation documents, using the Ca(2+)-switch technique, that esophageal epithelial junctions contain a major Ca(2+)-dependent component and that this component reflects adhesion between the extracellular domains of E-cadherin containing a histidine-alanine-valine recognition sequence.

Esophageal exposure to ethanol increases risk of acid damage in rabbit esophagus

Heavy alcohol consumption is associated with the development of reflux esophagitis. Among the reasons for this are impairment of the antireflux barrier, stimulation of acid secretion, and altered tissue resistance. To explore the contribution of altered tissue resistance to the development of esophagitis, sections of rabbit esophageal epithelium were mounted in Ussing chambers and exposed luminally to 10% ethanol, acid (HCl, pH 2), or combinations of both. Tissue injury was assessed by measurements of potential difference (PD), short circuit current (Isc) and electrical resistance (R) and by histology. Tissues exposed luminally to HCl for 1 hr exhibited little or no change electrically or morphologically compared to Ringer controls, while luminal exposure to 10% ethanol for 1 hr lowered PD (53 +/- 4%), Isc (30 +/- 1%), and R (31 +/- 5%) and produced cellular edema in the upper layers. Simultaneous exposure to ethanol and acid resulted in significantly greater declines in PD (81 +/- 1%) and Isc (70 +/- 2%), but not R (40 +/- 4%), and greater morphologic damage. Moreover, this vulnerability of ethanol-exposed tissues to acid was demonstrable at generally innocuous levels of acidity (pH 2-4), after only short periods of ethanol exposure (10 min) and with delays for acid exposures of up to 1 hr following ethanol removal from the bathing solution. In conclusion, ethanol has a direct noxious effect on esophageal epithelium, which predisposes the tissue to acid injury. Tissue vulnerability develops with even short exposures to clinically relevant concentrations of ethanol, lasts for at least 1 hr after ethanol clearance, and transforms relatively innocuous concentrations of acid into damaging agents. These results support the likelihood that ethanol's ability to alter tissue resistance plays an important role in the development of reflux esophagitis in humans.