Ethanol inhibits contractility of esophageal smooth muscle strips

Review article: Oesophageal disorders in chronic liver disease

BACKGROUND

Oesophageal disorders and chronic liver disease are common worldwide and significantly impact quality of life. The intricate link between these conditions, including how oesophageal disorders like GERD, Barrett's oesophagus and oesophageal cancer affect and are affected by chronic liver disease, remains poorly understood.

AIMS

To review the relationship between oesophageal disorders and chronic liver disease, evaluating epidemiology, pathophysiology and therapeutic factors.

METHODS

We reviewed the literature on the relationship between oesophageal disorders and chronic liver disease, including cirrhosis, using the PubMed database RESULTS: Oesophageal disorders such as gastroesophageal reflux disease, Barrett's oesophagus, oesophageal cancer, oesophageal motor disorders and oesophageal candidiasis are prevalent among individuals with cirrhosis, exacerbating the burden of liver disease. These diseases have a multifaceted symptomatology and pathogenic basis, posing a significant challenge in cirrhotic patients that necessitates careful diagnosis and management. Additionally, therapies frequently used for these diseases, such as proton pump inhibitors, require careful consideration in cirrhotic patients due to potential adverse effects and altered pharmacokinetics. Managing oesophageal disorders in cirrhotic patients requires a cautious approach due to possible interactions with medications and the risk of adverse effects. Furthermore, symptoms associated with these conditions are often exacerbated by common interventions in patients with cirrhosis, such as band ligation for oesophageal varices.

CONCLUSIONS

Oesophageal disorders are common in cirrhosis and increase the disease burden. These conditions require careful management due to complex symptoms and treatment risks. Proton pump inhibitors and other therapies must be used cautiously, as cirrhosis interventions can worsen symptoms.

Spectrum of esophageal motility disorders in patients with liver cirrhosis

Disorders of esophageal motility have been described in patients with cirrhosis in a small number of studies. In this review, we aim to provide an overview of the available evidence on esophageal motility disorders in cirrhosis and their clinical implications. This review delves into the following concepts: (1) Gastroesophageal reflux disease is common in liver cirrhosis due to many mechanisms; however, when symptomatic it is usually nocturnal and has an atypical presentation; (2) Endoscopic band ligation is better than sclerotherapy in terms of its effect on esophageal motility and seems to correct dysmotilities resulting from the mechanical effect of esophageal varices; (3) Chronic alcoholism has no major effects on esophageal motility activity other than lower esophageal sphincter hypertension among those with alcoholic autonomic neuropathy; (4) An association between primary biliary cholangitis and scleroderma can be present and esophageal hypomotility is not uncommon in this scenario; and (5) Cyclosporin-based immunosuppression in liver transplant patients can have a neurotoxic effect on the esophageal myenteric plexus leading to reversible achalasia-like manifestations.

Alcoholic disease: liver and beyond

The harmful use of alcohol is a worldwide problem. It has been estimated that alcohol abuse represents the world's third largest risk factor for disease and disability; it is a causal factor of 60 types of diseases and injuries and a concurrent cause of at least 200 others. Liver is the main organ responsible for metabolizing ethanol, thus it has been considered for long time the major victim of the harmful use of alcohol. Ethanol and its bioactive products, acetaldehyde-acetate, fatty acid ethanol esters, ethanol-protein adducts, have been regarded as hepatotoxins that directly and indirectly exert their toxic effect on the liver. A similar mechanism has been postulated for the alcohol-related pancreatic damage. Alcohol and its metabolites directly injure acinar cells and elicit stellate cells to produce and deposit extracellular matrix thus triggering the "necrosis-fibrosis" sequence that finally leads to atrophy and fibrosis, morphological hallmarks of alcoholic chronic pancreatitis. Even if less attention has been paid to the upper and lower gastrointestinal tract, ethanol produces harmful effects by inducing: (1) direct damaging of the mucosa of the esophagus and stomach; (2) modification of the sphincterial pressure and impairment of motility; and (3) alteration of gastric acid output. In the intestine, ethanol can damage the intestinal mucosa directly or indirectly by altering the resident microflora and impairing the mucosal immune system. Notably, disruption of the intestinal mucosal barrier of the small and large intestine contribute to liver damage. This review summarizes the most clinically relevant alcohol-related diseases of the digestive tract focusing on the pathogenic mechanisms by which ethanol damages liver, pancreas and gastrointestinal tract.

Effects of chronic ethanol consumption on rat upper gastrointestinal system: functional and histologic findings

The purpose of the present study was to determine the effect of chronic alcohol consumption on reactivity of esophageal tunica muscularis mucosae (TMM) and lower esophageal sphincter (LES) smooth muscle. Six male rats in alcohol-fed group received ethanol (7.2% v/v) in a modified liquid diet for 4 weeks. Two control groups were used; six rats in the standard diet-fed group received rat chow and water for 4 weeks. Six rats in sucrose-fed group were given sucrose and received a liquid diet. The smooth muscle reactivity of TMM and LES strips from ethanol-fed and control animals was evaluated in organ chambers. Also histologic study was undertaken to show effects of chronic alcohol consumption. Maximum contractile responses of TMM to KCl and carbachol were decreased in the ethanol-fed group compared to the control groups. Relaxant responses to serotonin were decreased in the ethanol-fed group compared to the control groups. In TMM, isoproterenol- and papaverine-induced relaxant responses were similar in the ethanol-fed and control groups. In LES smooth muscle, relaxant responses to papaverine or isoproterenol were similar in the control groups and the ethanol-fed group. There was no change in agonist potency among the groups. The relaxation response elicited by nicotine and sodium nitroprusside (SNP) or contractile response elicited by carbachol and 80 mM KCl was decreased with maximum responses and pD(2) values, in the ethanol-fed group compared to that of the control groups in LES. Decreased nNOS immunoreactivity in myenteric plexus was found in alcohol-exposed group compared to control groups. Our findings suggest that chronic alcohol consumption impairs relaxant and contractile responses of both TMM and LES smooth muscle and it may contribute to gastroesophageal reflux commonly seen after alcohol binges.

Is alcohol consumption associated with gastroesophageal reflux disease?

Gastroesophageal reflux disease (GERD) is one of the most common disorders with an increasing incidence and prevalence. Alcohol consumption may be a risk factor for GERD; however, the relationship remains to be fully elucidated. The results of different studies are diverse and contradictory. Systematic investigations concerning this matter are inappropriate and further well-designed prospective studies are needed to clarify the effect of alcohol on GERD.

Animal models and their results in gastrointestinal alcohol research

Alcohol-induced diseases of the gastrointestinal tract play an important role in clinical gastroenterology. However, the precise pathophysiological mechanisms are still largely unknown. Alcohol research depends essentially on animal models due to the fact that controlled experimental studies of ethanol-induced diseases in humans are unethical. Animal models have already been successfully applied to disclose and analyze molecular mechanisms in alcohol-induced diseases, partially by using knockout technology. Because of a lack of transferability of some animal models to the human condition, results have to be interpreted cautiously. For some alcohol-related diseases like chronic alcoholic pancreatitis, the ideal animal model does not yet exist. Here we provide an overview of the most commonly used animal models in gastrointestinal alcohol research. We will also briefly discuss the findings based on animal models as well as the current concepts of pathophysiological mechanisms involved in acute and chronic alcoholic damage of the esophagus, stomach, small and large intestine, pancreas and liver.

Animal models in gastrointestinal alcohol research-a short appraisal of the different models and their results

Alcohol-related diseases of the gastrointestinal tract play an important role in clinical gastroenterology. However, the mechanisms and pathophysiology underlying the effects of ethanol on the organs of the digestive tract are not yet completely understood. Animal models represent an essential tool for investigating alcohol-related diseases because they give researchers the opportunity to use methods that cannot be used in humans, such as knockout technology. However, there is still a need for new animal models resembling the human condition, since for some alcohol-related diseases such as chronic alcoholic pancreatitis, the ideal animal model does not yet exist. In this chapter, we provide an overview of the most commonly used animal models in gastrointestinal alcohol research. We will also briefly discuss the current concepts of the pathophysiological mechanisms involved in acute and chronic alcoholic damage of the oesophagus, stomach, small and large intestine, pancreas and liver.

Esophageal pharmacology and treatment of primary motility disorders

Swallowing is a complex mechanism based on the coordinated collaboration of tongue, pharynx and esophagus. Disturbances of this interplay or disorders of one or several of these components lead to dysphagia, non-cardiac chest pain or regurgitation. The major primary esophageal motility disorders--achalasia, diffuse esophageal spasm, hypercontractile esophagus ('nutcracker esophagus') and non-specific motility disorder--are of unknown etiology. Other esophageal diseases, such as cervical diverticula or gastroesophageal reflux disease, might also be caused by a primary esophageal motility disorder. Medical treatment of esophageal disorders with esophageal hyper- or dysmotility requires agents that reduce esophageal contractile force (anticholinergic agents, nitrates, calcium antagonists). Despite the beneficial effect of the various drugs on esophageal motility parameters, the clinical benefit of medical treatment of esophageal motility disorders is rather disappointing. Calcium channel antagonist, alone or in combination with anticholinergics or nitrates, can be used as a medical trial, especially in mild achalasia. However, medical therapy is clearly inferior to pneumatic balloon dilation therapy. Recently, botulinum toxin injection was suggested as a therapeutic option in achalasia patients with good results on lower esophageal sphincter pressure (LESP) and symptom scores that were similar to the results achieved by pneumatic balloon dilation. Hypercontractile esophagus shows a good manometric response to calcium channel antagonists, but only little clinical effect in terms of improvement of symptoms. Diffuse esophageal spasm is a relatively rare disease and few clinical studies are available. The use of calcium channel antagonists can be beneficial, at least in some patients with diffuse esophageal spasm. From clinical and epidemiological studies, there is some evidence of a 'psychological' component in the pathogenesis or perception of esophageal symptoms. There is some clinical benefit from centrally acting drugs such as benzodiazepines or antidepressants. With the exception of botulinum toxin for achalasia, medical therapy of primary esophageal motility disorders is rather limited and the clinical results are poor. Further understanding of esophageal pathophysiology as well as development of new receptor-selective drugs might increase our chances of a successful treatment of primary esophageal motility disorders.

Are dipyridamole (sensitive) calcium channels present in esophageal smooth muscle?

Calcium (Ca2+) entry from the extra-cellular space into the cytoplasm through voltage-dependent Ca2+ channels, specifically dipyridamole (DHP) sensitive ones (L-type), control a variety of biological processes, including excitation-contraction coupling in vascular and GI muscle cells. It has also been proposed that these channels may control esophageal contractility. However, DHP-sensitive Ca2+ channels in esophagus have not been well characterized biochemically. Thus, it is not known if these channels are similar in number or affinity to those in vascular or neural tissues--organs for which clinical use of calcium channel blockers has been successful. Thus, the purpose of this study was to identify and characterize DHP-sensitive calcium channels in esophagus and compare them to vascular, neural, and other GI tissues.

METHODS

We carried out in vitro receptor binding assays on lower esophageal muscle homogenates, gastric and intestinal and colonic homogenates, and aortic muscle homogenates from ca; and on brain homogenates from rat. We used a radio-labeled dihydropyridine derivative [3H]nitrendipine, to label these sites and co-administration of unlabeled nimodipine to define specific binding.

RESULTS

As expected, ligand binding to L-type Ca2+ channels in aortic vascular smooth muscle and brain was readily detectable: brain, Bmax=252 fmol/mg protein, Kd=0.88 nM; aorta, Bmax=326 fmol/mg protein, Kd=0.84 nM. For esophagus (Bmax=97; Kd=0.73) and for other GI tissues, using the same assay conditions, we detected a smaller signal, suggesting that L-type Ca2+ channels are present in lower quantities.

CONCLUSION

L-type Ca2+ channel are present in esophagus and in other GI muscles, their affinity is similar, but their density is relatively sparse. These findings are consistent with the relatively limited success that has been experienced clinically in the use of calcium channel blockers for treatment of esophageal dysmotility.