Effects of bile acids on the muscle functions of guinea pig gallbladder

Acalculous Cholecystitis in COVID-19 Patients: A Narrative Review

Acute acalculous cholecystitis (AAC) represents cholecystitis without gallstones, occurring in approximately 5-10% of all cases of acute cholecystitis in adults. Several risk factors have been recognized, while infectious diseases can be a cause of cholecystitis in otherwise healthy people. Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has spread worldwide, leading to an unprecedented pandemic. The virus enters cells through the binding of the spike protein to angiotensin-converting enzyme 2 (ACE2) receptors expressed in many human tissues, including the epithelial cells of the gastrointestinal (GI) tract, and this explains the symptoms emanating from the digestive system. Acute cholecystitis has been reported in patients with COVID-19. The purpose of this review is to provide a detailed analysis of the current literature on the pathogenesis, diagnosis, management, and outcomes of AAC in patients with COVID-19.

Glycocholic acid supplementation improved growth performance and alleviated tissue damage in the liver and intestine in Pelteobagrus fulvidraco fed a high-pectin diet

In a study on the anti-nutritional effect of dietary fiber, it was noticed that a high-pectin diet (PEC diet) caused growth retardation, hepatic cholestasis, steatosis, fibrosis, and enteritis accompanied by decreased glycocholic acid (GCA) in Pelteobagrus fulvidraco. This study was conducted to investigate the potential alleviating effects of supplementation with GCA. A PEC diet and a diet supplemented with 0.6 g kg-1 GCA based on the PEC diet (named the GCA diet) were formulated and randomly fed to juvenile Pelteobagrus fulvidraco. Compared to fish that were fed the PEC diet for 7 days, the GCA content in liver increased significantly in fish fed the GCA diet, the incidence of abnormal liver color, gallbladder somatic index (GBSI), total bile acid concentration in serum and liver, and the expression of arnesoid X receptor gene (fxr) upregulated and genes involved in bile acid (BA) synthesis and uptake in liver decreased significantly. After 56 days, the SGR, the expression of fxr and genes involved in BA synthesis and transportation in the liver, the serum content of total bilirubin, total protein, and globulin were significantly higher, while the hepatosomatic index, GBSI, liver lipid and collagen content, and the incidence of distal intestine tissue damage were lower in fish fed the GCA diet than in those fed the PEC diet. These results suggested that GCA improved growth performance and alleviated hepatic cholestasis and tissue damage to the liver and intestine induced by a high-pectin diet, which might occur through activating FXR.

The interaction of bile acids and gut inflammation influences the pathogenesis of inflammatory bowel disease

Bile acids (BA) are amphipathic molecules originating from cholesterol in the liver and from microbiota-driven biotransformation in the colon. In the gut, BA play a key role in fat digestion and absorption and act as potent signaling molecules on the nuclear farnesoid X receptor (FXR) and membrane-associated G protein-coupled BA receptor-1 (GPBAR-1). BA are, therefore, involved in the maintenance of gut barrier integrity, gene expression, metabolic homeostasis, and microbiota profile and function. Disturbed BA homeostasis can activate pro-inflammatory pathways in the gut, while inflammatory bowel diseases (IBD) can induce gut dysbiosis and qualitative and/or quantitative changes of the BA pool. These factors contribute to impaired repair capacity of the mucosal barrier, due to chronic inflammation. A better understanding of BA-dependent mechanisms paves the way to innovative therapeutic tools by administering hydrophilic BA and FXR agonists and manipulating gut microbiota with probiotics and prebiotics. We discuss the translational value of pathophysiological and therapeutic evidence linking BA homeostasis to gut inflammation in IBD.

Influence of poly-L-ornithine-bile acid nano hydrogels on cellular bioactivity and potential pharmacological applications

Aim: Cellular bioactivity and pathophysiological changes associated with chronic disorders are considered pivotal detrimental factors when developing novel formulations for biomedical applications. Methods: This paper investigates the use of bile acids and synthetic polypeptide poly-L-ornithine (PLO) in formulations and their impacts on a variety of cell lines, with a particular focus on their cellular bioactivity. Results: The hepatic cell line was the most negatively affected by the presence of PLO, while the muscle and beta-pancreatic cell lines did not show as profound of a negative impact of PLO on cellular viability. PLO was the least disruptive regarding mitochondrial function for muscle and beta cells. Conclusion: The addition of bile acids generally decreased mitochondrial respiration and altered bioenergetic parameters in all cell lines.

Concomitant gallstone disease was not associated with long-term outcomes in ursodeoxycholic acid-treated patients with primary biliary cholangitis

OBJECTIVES

Primary biliary cholangitis (PBC) is a rare disease characterized by intrahepatic cholestasis, whereas gallstone disease (GD) is common. In this study, we aimed to investigate the prevalence and impact of GD on the prognosis of PBC in China.

METHODS

Medical records of the PBC patients were retrospectively reviewed and their follow-up data were obtained via regular structured, standardized telephone interviews. GD was defined as gallstones on ultrasonography or a history of cholecystectomy for gallstones. Propensity score matching (PSM) and Cox regression analysis were performed. The primary end-point was liver-related death and/or liver transplantation.

RESULTS

A total of 985 ursodeoxycholic acid (UDCA)-treated PBC patients were enrolled with a median follow-up duration of 5.3 years (range 1.0-20.9 years). Among them, 258 (26.2%) had GD, including 157 (22.9%) of non-cirrhotic and 101 (33.8%) of cirrhotic patients. Compared with PBC without GD, those with GD were older, more often had type 2 diabetes mellitus, and had a more severe liver disease at baseline. After PSM (1:2), 229 PBC patients with GD were matched with 458 PBC patients without GD based on age, sex, cirrhosis, and total bilirubin level. The transplant-free survival and incidence of hepatic events were similar between the two groups. Furthermore, multivariate Cox regression analysis showed that concomitant GD was not independently associated with a worse prognosis for PBC patients.

CONCLUSION

Concomitant GD was common but was not associated with long-term outcomes in patients with UDCA-treated PBC.

Advances in the Study of Acute Acalculous Cholecystitis: A Comprehensive Review

BACKGROUND

Acute acalculous cholecystitis (AAC) is characterized by acute necrotizing inflammation with no calculi and is diagnosed based on imaging, intraoperative, and pathological examinations.

KEY MESSAGE

Although AAC has been studied clinically for a long time, it remains difficult to diagnose and treat. The pathogenesis of AAC is still not fully understood, and it is often regarded as a relatively independent clinical disease that is different from acute calculous cholecystitis (ACC). Pathological studies suggest that AAC is the manifestation of a critical systemic disease, while ACC is a local disease of the gallbladder.

SUMMARY

Concerning the pathogenesis, diagnosis, and treatment of AAC, we reviewed the research progress of AAC, which will enhance the understanding of the early diagnosis and treatment of AAC.

Clinical characteristics and histology of cholecystectomised dogs with nongravity-dependent biliary sludge: 16 cases (2014-2019)

OBJECTIVES

To report the available histology, biochemistry and clinical progression of dogs without classic overt biliary tract signs that underwent cholecystectomy for nongravity-dependent biliary sludge.

MATERIALS AND METHODS

Case series of client-owned dogs for which a cholecystectomy was performed for nongravity-dependent biliary sludge. In six dogs, for which nongravity-dependent biliary sludge filled less than half of gall bladder volume, gall bladder ejection fractions were measured. Available histology, biochemistry, presenting clinical signs and post-surgical clinical progression were reported.

RESULTS

Sixteen dogs were included in this retrospective case series. No dogs met the histological criteria for gall bladder mucocoeles or had histological evidence of primary hepatitis or cholangitis. Biochemistry was normal for 11 dogs. Hypercholesterolaemia was not noted in any dog. Twelve dogs had cholecystitis (11 lymphoplasmacytic, one neutrophilic) and nine dogs had biliary mucosal hyperplasia. Thirteen dogs had enteritis (12 lymphoplasmacytic, one eosinophilic) and nine dogs had reactive hepatitis (eight lymphoplasmacytic, one neutrophilic). All six dogs with nongravity-dependent biliary sludge that filled less than half of gall bladder volume had sub-optimal gall bladder function. Presenting clinical signs, including diurnal inappetence in the morning and exercise intolerance, resolved in 86% (12/14) of dogs after cholecystectomy and clinical improvement was noted in 81% (13/16) of dogs overall.

CLINICAL SIGNIFICANCE

Duodenal inflammation could potentially impact gall bladder dysmotility in dogs with nongravity-dependent biliary sludge. Furthermore, diurnal inappetence in the morning and exercise intolerance could indicate symptomatic gall bladder disease in dogs with NDBS and can potentially precede more obvious systemic clinical signs associated with gall bladder mucocoeles.

Bile acid composition of gallbladder contents in dogs with gallbladder mucocele and biliary sludge

OBJECTIVE To examine bile acid composition of gallbladder contents in dogs with gallbladder mucocele and biliary sludge. ANIMALS 18 dogs with gallbladder mucocele (GBM group), 8 dogs with immobile biliary sludge (i-BS group), 17 dogs with mobile biliary sludge (m-BS group), and 14 healthy dogs (control group). PROCEDURES Samples of gallbladder contents were obtained by use of percutaneous ultrasound-guided cholecystocentesis or during cholecystectomy or necropsy. Concentrations of 15 bile acids were determined by use of highperformance liquid chromatography, and a bile acid compositional ratio was calculated for each group. RESULTS Concentrations of most bile acids in the GBM group were significantly lower than those in the control and m-BS groups. Compositional ratio of taurodeoxycholic acid, which is 1 of 3 major bile acids in dogs, was significantly lower in the GBM and i-BS groups, compared with ratios for the control and m-BS groups. The compositional ratio of taurocholic acid was significantly higher and that of taurochenodeoxycholic acid significantly lower in the i-BS group than in the control group. CONCLUSIONS AND CLINICAL RELEVANCE In this study, concentrations and fractions of bile acids in gallbladder contents were significantly different in dogs with gallbladder mucocele or immobile biliary sludge, compared with results for healthy control dogs. Studies are needed to determine whether changes in bile acid composition are primary or secondary events of gallbladder abnormalities.

Prevention of gallbladder hypomotility via FATP2 inhibition protects from lithogenic diet-induced cholelithiasis

Gallstone disease is a widespread disorder costing billions for annual treatment in the United States. The primary mechanisms underlying gallstone formation are biliary cholesterol supersaturation and gallbladder hypomotility. The relative contribution of these two processes has been difficult to dissect, as experimental lithogenic diets cause both bile supersaturation and alterations in gallbladder motility. Importantly, there is no mechanistic explanation for obesity as a major risk factor for cholelithiasis. We discovered that lithogenic diets induce ectopic triacylglycerol (TAG) accumulation, a major feature of obesity and a known muscle contraction impairing condition. We hypothesized that prevention of TAG accumulation in gallbladder walls may prevent gallbladder contractile dysfunction without impacting biliary cholesterol saturation. We utilized adeno-associated virus-mediated knock down of the long-chain fatty acid transporter 2 (FATP2; Slc27A2), which is highly expressed by gallbladder epithelial cells, to downregulate lithogenic diet-associated TAG accumulation. FATP2-knockdown significantly reduced gallbladder TAG, but did not affect key bile composition parameters. Importantly, measurements with force displacement transducers showed that contractile strength in FATP2-knockdown gallbladders was significantly greater than in control gallbladders following lithogenic diet administration, and the magnitude of this effect was sufficient to prevent the formation of gallstones. FATP2-driven fatty acid uptake and the subsequent TAG accumulation in gallbladder tissue plays a pivotal role in cholelithiasis, and prevention of this process can protect from gallstone formation, even in the context of supersaturated bile cholesterol levels, thus pointing to new treatment approaches and targets.

Cholesterol gallstone disease: focusing on the role of gallbladder

Gallstone disease (GSD) is one of the most common biliary tract diseases worldwide in which both genetic and environmental factors have roles in its pathogenesis. Biliary cholesterol supersaturation from metabolic defects in the liver is traditionally seen as the main pathogenic factor. Recently, there have been renewed investigative interests in the downstream events that occur in gallbladder lithogenesis. This article focuses on the role of the gallbladder in the pathogenesis of cholesterol GSD (CGD). Various conditions affecting the crystallization process are discussed, such as gallbladder motility, concentrating function, lipid transport, and an imbalance between pro-nucleating and nucleation inhibiting proteins.

Human colonic myogenic dysfunction induced by mucosal lipopolysaccharide translocation and oxidative stress

BACKGROUND

Impairment of gastrointestinal motility is frequently observed in patients with severe infection.

AIM

To assess whether exposure of human colonic mucosa to pathogenic lipopolysaccharide affects smooth muscle contractility.

METHODS

Human colonic mucosa and submucosa were sealed between two chambers, with the luminal side facing upwards and covered with Krebs solution, with or without lipopolysaccharide from a pathogenic strain of Escherichia coli (O111:B4; 1,000 ng/mL), and with the submucosal side facing downwards into Krebs. The solution on the submucosal side was collected following 30-min mucosal exposure to Krebs without (N-undernatant) or with lipopolysaccharide (lipopolysaccharide undernatant). Undernatants were tested for lipopolysaccharide and hydrogen peroxide levels and for their effects on smooth muscle cells in the presence of catalase, indomethacin or MG132.

RESULTS

Smooth muscle cells incubated with N-undernatant had a maximal contraction of 32 ± 5% that was reduced by 62.9 ± 12% when exposed to lipopolysaccharide undernatant. Inhibition of contraction was reversed by catalase, indomethacin and MG132. Lipopolysaccharide levels were higher in the lipopolysaccharide undernatant (2.7 ± 0.7 ng/mL) than in N-undernatant (0.45 ± 0.06 ng/mL) as well as hydrogen peroxide levels (133.75 ± 15.9 vs 82 ± 7.5 nM respectively).

CONCLUSIONS

Acute exposure of colonic mucosa to pathogenic lipopolysaccharide impairs muscle cell contractility owing to both lipopolysaccharide mucosal translocation and production of free radicals.

Ursodeoxycholic acid therapy in gallbladder disease, a story not yet completed

Gallstone disease represents an important issue in the healthcare system. The principal non-invasive non-surgical medical treatment for cholesterol gallstones is still represented by oral litholysis with bile acids. The first successful and documented dissolution of cholesterol gallstones was achieved in 1972. Since then a large number of investigators all over the world, have been dedicated in biochemical and clinical studies on ursodeoxycholic acid (UDCA), demonstrating its extreme versatility. This editorial is aimed to provide a brief review of recent developments in UDCA use, current indications for its use and, the more recent advances in understanding its effects in terms of an anti-inflammatory drug.

Roles of cholesterol and bile salts in the pathogenesis of gallbladder hypomotility and inflammation: cholecystitis is not caused by cystic duct obstruction

A large number of human and animal studies have challenged the hypothesis that cystic duct obstruction by gallstones causes cholecystitis. These studies suggest that lithogenic bile that can deliver high cholesterol concentrations to the gallbladder wall causes hypomotility and creates a permissive environment that allows normal concentrations of hydrophobic bile salts to inflame the mucosa and impair muscle function inhibiting gallbladder emptying. High concentrations of cholesterol increase its diffusion rates through the gallbladder wall where they are incorporated into the sarcolemmae of muscle cells by caveolin proteins. High caveolar cholesterol levels inhibit tyrosine-induced phosphorylation of caveolin proteins required to transfer receptor-G protein complexes into recycling endosomes. The sequestration of these receptor-G protein complexes in the caveolae results in fewer receptors recycling to the sarcolemmae to be available for agonist binding. Lower internalization and recycling of CCK-1 and other receptors involved in muscle contraction explain gallbladder hypomotility. PGE2 receptors involved in cytoprotection are similarly affected. Cells with a defective cytoprotection failed to inactivate free radicals induced by normal concentrations of hydrophobic bile salts resulting in chronic inflammation that may lead to acute inflammation. Ursodeoxycholic acid salts (URSO) block these bile salts effects thereby preventing the generation of free radicals in muscle cells in vitro and development of cholecystitis in the ligated common bile duct in guinea pigs in vivo. Treatment with URSO improves muscle contraction and reduces the oxidative stress in patients with symptomatic cholesterol gallstones by lowering cholesterol concentrations and blocking the effects of hydrophobic bile salts on gallbladder tissues.

Disruption of gallbladder smooth muscle function is an early feature in the development of cholesterol gallstone disease

BACKGROUND; Decreased gallbladder smooth muscle (GBSM) contractility is a hallmark of cholesterol gallstone disease, but the interrelationship between lithogenicity, biliary stasis, and inflammation are poorly understood. We studied a mouse model of gallstone disease to evaluate the development of GBSM dysfunction relative to changes in bile composition and the onset of sterile cholecystitis.

METHODS

BALB/cJ mice were fed a lithogenic diet for up to 8 weeks, and tension generated by gallbladder muscle strips was measured. Smooth muscle Ca(2+) transients were imaged in intact gallbladder.

KEY RESULTS

Lipid composition of bile was altered lithogenically as early as 1 week, with increased hydrophobicity and cholesterol saturation indexes; however, inflammation was not detectable until the fourth week. Agonist-induced contractility was reduced from weeks 2 through 8. GBSM normally exhibits rhythmic synchronized Ca(2+) flashes, and their frequency is increased by carbachol (3 μm). After 1 week, lithogenic diet-fed mice exhibited disrupted Ca(2+) flash activity, manifesting as clustered flashes, asynchronous flashes, or prolonged quiescent periods. These changes could lead to a depletion of intracellular Ca(2+) stores, which are required for agonist-induced contraction, and diminished basal tone of the organ. Responsiveness of Ca(2+) transients to carbachol was reduced in mice on the lithogenic diet, particularly after 4-8 weeks, concomitant with appearance of mucosal inflammatory changes.

CONCLUSIONS & INFERENCES

These observations demonstrate that GBSM dysfunction is an early event in the progression of cholesterol gallstone disease and that it precedes mucosal inflammation.

Therapy of gallstone disease: What it was, what it is, what it will be

Cholesterol gallstone disease is a common clinical condition influenced by genetic factors, increasing age, female gender, and metabolic factors. Although laparoscopic cholecystectomy is currently considered the gold standard in treating patients with symptomatic gallstones, new perspectives regarding medical therapy of cholelithiasis are currently under discussion, also taking into account the pathogenesis of gallstones, the natural history of the disease and the analysis of the overall costs of therapy. A careful selection of patients may lead to successful non-surgical therapy in symptomatic subjects with a functioning gallbladder harboring small radiolucent stones. The classical oral litholysis by ursodeoxycholic acid has been recently paralleled by new experimental observations, suggesting that cholesterol-lowering agents which inhibit cholesterol synthesis (statins) or intestinal cholesterol absorption (ezetimibe), or drugs acting on specific nuclear receptors involved in cholesterol and bile acid homeostasis, might be proposed as additional approaches for treating cholesterol gallstones. In this review we discuss old, recent and future perspectives on medical treatment of cholesterol cholelithiasis.

Effect of ursodeoxycholic acid on inflammatory infiltrate in gallbladder muscle of cholesterol gallstone patients

BACKGROUND

Reduced gallbladder (GB) contractility and chronic inflammatory changes in the mucosa have been reported in patients with cholesterol gallstones (GS). Ursodeoxycholic acid (UDCA) restores GB contractility and antagonises liver macrophage activation. In the colon, hydrophobic bile acid, not hydrophilic UDCA, induces mast cell degranulation. We studied the presence of monocyte/macrophage infiltrate, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) expression, the number of total and degranulated mast cells in the GB muscle layer of cholesterol GS patients, and the effect of UDCA administration.

METHODS

Gallbladder tissue was obtained from cholesterol GS patients, either treated or untreated with UDCA (10 mg kg(-1) day(-1)) for 30 days prior to surgery. Gallbladders removed for neoplastic diseases, not involving GB, were evaluated for control purposes. The presence of monocytes/macrophages (CD68 positive), granulocytes, and mast cells, and the COX-2 and iNOS expression, was determined immunohistochemically.

KEY RESULTS

The number of CD68, granulocytes, mast cells, COX-2 and iNOS positive cells was significantly higher in the muscle layer of GS patients than in controls. Compared to untreated patients, those treated with UDCA showed significantly lower levels of CD68, COX-2 positive cells and degranulated mast cells and a lesser number of iNOS positive cells and granulocytes.

CONCLUSIONS & INFERENCES

An inflammatory monocyte/macrophage, mast cell and granulocyte infiltrate is present in the GB muscle layer of GS patients. Ursodeoxycholic acid decreases macrophages, degranulated mast cells and COX-2 expression. These results suggest that monocytes/macrophages and degranulating mast cells contribute to muscle cell dysfunction in cholesterol GS patients and support the anti-inflammatory effect of UDCA.

Targets for current pharmacologic therapy in cholesterol gallstone disease

Gallstone disease is a frequent condition throughout the world and, cholesterol stones are the most frequent form in Western countries. The standard treatment of symptomatic gallstone subjects is laparoscopic cholecystectomy. The selection of patients amenable for nonsurgical, medical therapy is of key importance; a careful analysis should consider the natural history of the disease and the overall costs of therapy. Only patients with mild symptoms and small, uncalcified cholesterol gallstones in a functioning gallbladder with a patent cystic duct are considered for oral litholysis by hydrophilic ursodeoxycholic acid, in the hope of achieving cholesterol desaturation of bile and progressive stone dissolution. Recent studies have raised the possibility that cholesterol-lowering agents that inhibit hepatic cholesterol synthesis (statins) or intestinal cholesterol absorption (ezetimibe), or drugs acting on specific nuclear receptors involved in cholesterol and bile acid homeostasis, may offer, alone or in combination, additional medical therapeutic tools for treating cholesterol gallstones. Recent perspectives on medical treatment of cholesterol gallstone disease are discussed in this article.

Reactive oxygen species and the hypomotility of the gall bladder as targets for the treatment of gallstones with melatonin: a review

Free radical-mediated damage of the gall bladder epithelium predisposes to the development of both gall bladder inflammation and gallstone formation, which often coexist. Melatonin, a pineal and gut secretory product, due to its antioxidant activity along with its effect on the aging gall bladder myocytes, inhibits gallstone formation. Melatonin reduces the biliary levels of cholesterol by inhibiting cholesterol absorption across the intestinal epithelium and by increasing the conversion of cholesterol to bile acids. The incidence of gallstones is increasing and is expected to rise dramatically with the increase in the longevity and the risk factors such as obesity. The change in the prevalence of cholelithiasis is associated with a proportionate rise in the incidence of cholangiocarcinoma. In an attempt to improve the quality of life of the rapidly increasing aging population, this article reviews up-to-date information on the pathophysiology of the gall bladder function and discusses the development of new therapies with potential good patient compliance and lower cost than the current treatments.

Coordinate regulation of gallbladder motor function in the gut-liver axis

Gallstones are one of the most common digestive diseases with an estimated prevalence of 10%-15% in adults living in the western world, where cholesterol-enriched gallstones represent 75%-80% of all gallstones. In cholesterol gallstone disease, the gallbladder becomes the target organ of a complex metabolic disease. Indeed, a fine coordinated hepatobiliary and gastrointestinal function, including gallbladder motility in the fasting and postprandial state, is of crucial importance to prevent crystallization and precipitation of excess cholesterol in gallbladder bile. Also, gallbladder itself plays a physiopathological role in biliary lipid absorption. Here, we present a comprehensive view on the regulation of gallbladder motor function by focusing on recent discoveries in animal and human studies, and we discuss the role of the gallbladder in the pathogenesis of gallstone formation.

Reactive oxygen species are messengers in maintenance of human and guinea pig gallbladder tonic contraction

The tonic contraction of human and guinea pig gallbladder (GB) is dependent on basal levels of PGE(2) and thromboxane A(2) (TxA(2)). The pathway involved in the genesis of these prostaglandins has not been elucidated. We aimed to examine the source of reactive oxygen species (ROS) and whether they contribute to the genesis of GB tonic contraction by generating basal prostaglandin levels. Tonic contraction was studied in human and guinea pig GB muscle strips treated with ROS scavengers (Tiron and catalase), apocynin (an inhibitor of NADPH oxidase), and NOX-1 small interference RNA (siRNA). The subunits of NADPH oxidase and their functional roles were determined with specific antibodies in GB muscle cells. ROS scavengers reduced the GB tonic contraction and H(2)O(2) and PGE(2) levels. Apocynin also inhibited the tonic contraction. Antibodies against subunits of NADPH oxidase present in GB muscle cells lowered H(2)O(2) and PGE(2) levels. NOX-1 siRNA transfection reduced the tonic contraction, NOX-1 expression, and levels of H(2)O(2) and PGE(2). Tiron and apocynin inhibited the expected increase in tension and H(2)O(2) levels induced by stretching of muscle strips. H(2)O(2) increased the levels of PGE(2) and TxA(2) by increasing platelet-activating factor-like lipids that phosphorylate p38 and cPLA(2) sequentially. H(2)O(2) generated by NADPH oxidase participates in a signal transduction pathway that maintains the GB tonic contraction by activating PAF, p38, and cPLA(2) to generate prostaglandins.

T-cell function is critical for murine cholesterol gallstone formation

BACKGROUND & AIMS

The formation of cholesterol gallstones is a complex process involving contributions from genes and environmental factors. Although gallbladder inflammation is believed to be common during cholelithogenesis, the role of immunologic factors is unknown.

METHODS

The role of adaptive immunity in cholesterol cholelithogenesis was analyzed utilizing immunocompetent Helicobacter spp.-infected and -uninfected BALB/c and congenic immunodeficient Rag2(-/-) (Rag) mice. Lymphocyte transfer studies were performed to determine which cellular subset was responsible for cholesterol gallstone formation. Also, gallbladder inflammation was quantified to determine the nature of the inflammatory response associated with cholelilithogenesis.

RESULTS

When fed a lithogenic diet for 8 weeks, wild-type mice developed significantly more cholesterol gallstones (27%-80% prevalence) than Rag mice ( approximately 5%, P < .05). Helicobacter spp.-infected BALB/cJ mice displayed statistically significant increases in cholesterol gallstone prevalence compared with uninfected mice (81% vs. 39%; P < .05). Transfer of splenocytes or T lymphocytes to Rag2(-/-) mice increased stone prevalence markedly (26% and 40% respectively; P < .05), whereas transfer of B cells was not appreciably cholelithogenic (13%). The adaptive immune response increased the expression of gallbladder Muc genes and accumulation of mucin gel. In addition, T cells and cholesterol monohydrate crystals induced proinflammatory gene expression in the gallbladder, which likely contributes to gallbladder dysfunction.

CONCLUSIONS

These studies indicate that T cells are critical in murine cholesterol cholelithogenesis. Furthermore, cholesterol monohydrate crystals induce expression of proinflammatory cytokines in a T-cell-dependent fashion. Acquired immunity and inflammation are likely to be crucial factors in cholesterol gallstone pathogenesis, rather then merely the result of cholelithogenesis.

Role of caveolae in the pathogenesis of cholesterol-induced gallbladder muscle hypomotility

Muscle cells from human gallbladders (GB) with cholesterol stones (ChS) exhibit a defective contraction, excess cholesterol (Ch) in the plasma membrane, and lower binding of CCK-1 receptors. These abnormalities improved after muscle cells were incubated with Ch-free liposomes that remove the excess Ch from the plasma membrane. The present studies were designed to investigate the role of caveolin-3 proteins (Cav-3) in the pathogenesis of these abnormalities. Muscle cells from GB with ChS exhibit higher Ch levels in the plasma membrane that were mostly localized in caveolae and associated with parallel increases in the expression of Cav-3 in the caveolae compared with that in GB with pigment stones (PS). The overall number of CCK-1 receptors in the plasma membrane was not different between muscle cells from GB with ChS and PS, but they were increased in the caveolae in muscle cells from GB with ChS. Treatment of muscle cells from GB with ChS with a Galpha(i3) protein fragment increased the total binding of CCK-1 receptors (from 8.3 to 11.2%) and muscle contraction induced by CCK-8 (from 11.2 to 17.3% shortening). However, Galpha(q/11) protein fragment had no such effect. Moreover, neither fragment had any effect on muscle cells from GB with PS. We conclude that the defective contraction of muscle cells with excessive Ch levels in the plasma membrane is due to an increased expression of Cav-3 that results in the sequestration of CCK-1 receptors in the caveolae, probably by inhibiting the functions of Galpha(i3) proteins.

Ursodeoxycholic acid improves gastrointestinal motility defects in gallstone patients

AIM: To simultaneously evaluate the presence of defects in gallbladder and gastric emptying, as well as in intestinal transit in gallstone patients (GS) and the effect of chronic ursodeoxycholic acid (UDCA) administration on these parameters and on serum bile acids and clinical outcome in GS and controls (CTR).

METHODS: After a standard liquid test meal, gallbla-dder and gastric emptying (by ultrasound), oroileal transit time (OITT) (by an immunoenzymatic technique) and serum bile acids (by HPLC) were evaluated before and after 3 mo of UDCA (12 mg/kg bw/d) or placebo administration in 10 symptomatic GS and 10 matched healthy CTR.

RESULTS: OITT was longer in GS than in CTR (P < 0.0001); UDCA significantly reduced OITT in GS (P < 0.0001), but not in CTR. GS had longer gastric half-emptying time (t_1/2) than CTR (P < 0.0044) at baseline; after UDCA, t_1/2 significantly decreased (P < 0.006) in GS but not in CTR. Placebo administration had no effect on gastric emptying and intestinal transit in both GS and CTR.

CONCLUSION: The gallstone patient has simultaneous multiple impairments of gallbladder and gastric emptying, as well as of intestinal transit. UDCA administration restores these defects in GS, without any effect in CTR. These results confirm the pathogenetic role of gastrointestinal motility in gallstone disease and suggest an additional mechanism of action for UDCA in reducing bile cholesterol supersaturation.

Effects of chenodeoxycholic acid and deoxycholic acid on cholesterol absorption and metabolism in humans

Quantitative and qualitative differences in intralumenal bile acids may affect cholesterol absorption and metabolism. To test this hypothesis, 2 cross-over outpatient studies were conducted in adults with apo-A IV 1/1 or apo-E 3/3 genotypes. Study 1 included 11 subjects 24 to 37 years of age, taking 15 mg/kg/day chenodeoxycholic acid (CDCA) or no bile acid for 20 days while being fed a controlled diet. Study 2 included 9 adults 25 to 38 years of age, taking 15 mg/kg/day deoxycholic acid (DCA) or no bile acid, following the same experimental design and procedures as study 1. CDCA had no effect on plasma lipid concentrations, whereas DCA decreased (P < 0.05) plasma high-density lipoprotein (HDL)-cholesterol and tended to decrease (P = 0.15) low-density lipoprotein (LDL)-cholesterol. CDCA treatment enriched (P < 0.0001) bile with CDCA and increased cholesterol concentration in micelles, whereas meal-stimulated bile acid concentrations were decreased. DCA treatment enriched (P < 0.0001) bile with DCA and tended to increase intralumenal cholesterol solubilized in micelles (P = 0.06). No changes were found in cholesterol absorption, free cholesterol fractional synthetic rate (FSR), or 3-hydroxy-3 methylglutaryl (HMG) CoA reductase and LDL receptor messenger ribonucleic acid (mRNA) levels after CDCA treatment. DCA supplementation tended to decrease cholesterol absorption and reciprocally increase FSR and HMG CoA reductase and LDL receptor mRNA levels. Results of these 2 studies suggest that the solubilization of cholesterol in the intestinal micelles is not a rate-limiting step for its absorption.

Changes in guinea pig gallbladder smooth muscle Ca2+ homeostasis by acute acalculous cholecystitis

Impaired smooth muscle contractility is a hallmark of acute acalculous cholecystitis. Although free cytosolic Ca2+ ([Ca2+]i) is a critical step in smooth muscle contraction, possible alterations in Ca2+ homeostasis by cholecystitis have not been elucidated. Our aim was to elucidate changes in the Ca2+ signaling pathways induced by this gallbladder dysfunction. [Ca2+]i was determined by epifluorescence microscopy in fura 2-loaded isolated gallbladder smooth muscle cells, and isometric tension was recorded from gallbladder muscle strips. F-actin content was quantified by confocal microscopy. Ca2+ responses to the inositol trisphosphate (InsP3) mobilizing agonist CCK and to caffeine, an activator of the ryanodine receptors, were impaired in cholecystitic cells. This impairment was not the result of a decrease in the size of the releasable pool. Inflammation also inhibited Ca2+ influx through L-type Ca2+ channels and capacitative Ca2+ entry induced by depletion of intracellular Ca2+ pools. In addition, the pharmacological phenotype of these channels was altered in cholecystitic cells. Inflammation impaired contractility further than Ca2+ signal attenuation, which could be related to the decrease in F-actin that was detected in cholecystitic smooth muscle cells. These findings indicate that cholecystitis decreases both Ca2+ release and Ca2+ influx in gallbladder smooth muscle, but a loss in the sensitivity of the contractile machinery to Ca2+ may also be responsible for the impairment in gallbladder contractility.

Short-term ursodeoxycholic acid treatment improves gallbladder bile turnover in gallstone patients: a randomized trial

Ursodeoxycholic acid (UDCA) prevents in vitro gallbladder (GB) muscle damage caused by acute cholecystitis and reduces risk of biliary pain and complications in gallstone (GS) patients. These effects could be partially explained by the improved GB bile turnover.

OBJECTIVES

To assess the effect of short-term UDCA treatment on GB motility and bile turnover.

METHODS

Ultrasonographic (US) assessment of GB volumes was performed in 16 GS patients, in the postprandial phase, for 90 min with a time sampling of 1 min, before and after 30 days of UDCA (10 mg kg(-1) die(-1)) or placebo, randomly assigned. US data were analysed with statistical tools and with computer fluido-dynamic (CFD) software Fluent(TM) to simulate GB bile flow.

RESULTS

After therapy, fasting volume (FV) increased from 21.6 +/- 9 to 28.2 +/- 12 mL (p < 0.001) while the ejection fraction (EF) remained unchanged (44.5 +/- 17% vs 45.1 +/- 20%; p: ns). Volumes before and after treatment were poorly correlated (0.02 < r < 0.35), unlike those in placebo patients (r > 0.6). The average GB volume was increased in 7 out of 10 patients following UDCA (range 7-67%). CFD analysis supports the finding of improved bile flow after treatment.

CONCLUSIONS

Unlike results of conventional US parameters of GB motility, CFD analysis shows that UDCA improves GB bile turnover in GS patients.

Impaired cytoprotective function of muscle in human gallbladders with cholesterol stones

Acute cholecystitis develops in gallbladders (GB) with excessive bile cholesterol (Ch). Increased membrane Ch content affects membrane function and may affect PGE(2) receptors involved in the cytoprotection against acute inflammation. This study was aimed at determining whether the cytoprotective response to PGE(2) is affected by lithogenic bile with Ch. Muscle cells from human GB with cholesterol stones (ChS) or pigment stones (PS) were obtained by enzymatic digestion. PGE(2) levels were measured by radioimmunoassay, and activities of superoxide dismutase (SOD) and catalase were assayed by spectrophotometry. The contraction in response to H(2)O(2) in muscle cells from PS was 14 +/- 0.3%, not different from normal controls, and decreased after the cells were incubated with Ch-rich liposomes (P < 0.05), which increase the Ch content in the plasma membranes. In muscle cells from GB with ChS, H(2)O(2)-induced contraction was only 9.2 +/- 1.3% and increased to 14 +/- 0.2% after Ch-free liposome treatment to remove Ch from the plasma membranes (P < 0.01). H(2)O(2) caused a similar increase in the levels of lipid peroxidation and PGE(2) content in muscle cells from GBs with ChS and PS. However, the activities of SOD and catalase were significantly lower in muscle cells from GBs with ChS compared with those with PS. The binding capacity of PGE(2) receptors was also significantly lower in muscle cells from GBs with ChS compared with those with PS. In conclusion, the cytoprotective response to reactive oxygen species is reduced in muscle cells from GBs with ChS despite a normal increase in the cellular levels of PGE(2). This impaired cytoprotective response may be due to a dysfunction of PGE(2) receptors with decreased binding capacity resulting from excessive Ch levels in the plasma membrane.

Deoxycholic acid inhibits pacemaker currents by activating ATP-dependent K+ channels through prostaglandin E2 in interstitial cells of Cajal from the murine small intestine

1. We investigated the role of deoxycholic acid in pacemaker currents using whole-cell patch-clamp techniques at 30 degrees C in cultured interstitial cells of Cajal (ICC) from murine small intestine. 2. The treatment of ICC with deoxycholic acid resulted in a decrease in the frequency and amplitude of pacemaker currents and increases in resting outward currents. Also, under current clamping, deoxycholic acid produced the hyperpolarization of membrane potential and decreased the amplitude of the pacemaker potentials. 3. These observed effects of deoxycholic acid on pacemaker currents and pacemaker potentials were completely suppressed by glibenclamide, an ATP-sensitive K(+) channel blocker. 4. NS-398, a specific cyclooxygenase-2 (COX-2) inhibitor, significantly inhibited the deoxycholic acid-induced effects. The treatment with prostaglandin E(2) (PGE(2)) led to a decrease in the amplitude and frequency of pacemaker currents and to an increase in resting outward currents, and these observed effects of PGE(2) were blocked by glibenclamide. 5. We next examined the role of deoxycholic acid in the production of PGE(2) in ICC, and found that deoxycholic acid increased PGE(2) production through the induction of COX-2 enzyme activity and its gene expression. 6. The results suggest that deoxycholic acid inhibits the pacemaker currents of ICC by activating ATP-sensitive K(+) channels through the production of PGE(2).

Effect of EGF on H2O2-induced inhibition of ?-MG uptake in renal proximal tubule cells: Involvement of MAPK and AA release

Both oxidative stress and epidermal growth factor (EGF) contribute to the initiation and progression of renal proximal tubular dysfunction under pathophysiologic conditions. Thus, this study was performed (1) to examine both the individual, and the combined effects of H2O2 and EGF on alpha-methyl-D-glucopyranoside uptake (alpha-MG uptake) in the primary cultured renal proximal tubule cells (PTCs), and (2) to elucidate the involvement of p44/42 mitogen activated protein kinase (MAPK) and phospholipase A2 in mediating these actions. Both H2O2 and EGF inhibited alpha-MG uptake individually, while the combination of H2O2 and EGF further potentiated the inhibitory effect on alpha-MG uptake, which was elicited by each agent. H2O2 not only caused a rapid increase in the phosphorylation of p44/42 MAPK, but also promoted the translocation of cytosolic phospholipase A2 (cPLA2) from the cytosolic to particulate fraction, and stimulated cellular [3H]-arachidonic acid (AA) release. EGF similarly activates phosphorylation of p44/42 MAPK and stimulates [3H]-AA release. When PTCs were exposed to 100 microM H2O2 and 50 ng/ml EGF simultaneously, a further increase in the phosphorylation of p44/42 MAPK, of [3H]-AA release, and of prostaglandin E2 (PGE2) production was elicited as compared with the effects of each individual agonist alone. Moreover, the additive phosphorylation of p44/42 MAPK, [3H]-AA release, and PGE2 production by H2O2 and EGF was almost completely inhibited by the p44/42 MAPK inhibitor, PD 98059. In conclusion, these results are consistent with the hypothesis that under conditions of oxidative stress, the H2O2-induced inhibition of alpha-MG uptake in the renal proximal tubule is mediated through a modulation of the EGF signaling pathway, promoting further phosphorylation of p44/42 MAPK, activation of PLA2.

Smooth muscle function and dysfunction in gallbladder disease

The gallbladder epithelium and smooth muscle layer are exposed to concentrated biliary solutes, including cholesterol and potentially toxic hydrophobic bile salts, which are able to influence muscle contraction. Physiologically, gallbladder tone is regulated by spontaneous muscle activity, hormones, and neurotransmitters released into the muscle from intrinsic neurons and extrinsic sympathetic nerves. Methods to explore gallbladder smooth muscle function in vitro include cholecystokinin (CCK) receptor-binding studies and contractility studies. In human and animal models, studies have focused on cellular and molecular events in health and disease, and in vitro findings mirror in vivo events. The interplay between contraction and relaxation of the gallbladder muscularis leads in vivo to appropriate gallbladder emptying and refilling during fasting and postprandially. Defective smooth muscle contractility and/or relaxation are found in cholesterol stone-containing gallbladders, featuring a type of gallbladder leiomyopathy; defects of CCKA receptors and signal transduction may coexist with abnormal responses to oxidative stress and inflammatory mediators. Abnormal smooth musculature contractility, impaired gallbladder motility, and increased stasis are key factors in the pathogenesis of cholesterol gallstones.

Role of PGE2 on gallbladder muscle cytoprotection of guinea pigs

H2O2 and taurochenodeoxycholic acid (TCDC) impair the contraction induced by CCK-8, ACh, and KCl without affecting the actions of PGE2 and damage functions of membrane proteins except for PGE2 receptors. The aim of this study was to examine whether the preserved PGE2 actions contribute to cytoprotective mechanisms against reactive oxygen species. Muscle cells from guinea pig gallbladder were obtained by enzymatic digestion. Levels of lipid peroxidation and activities of SOD and catalase were determined by spectrophotometry. Pretreatment with PGE2 prevented the inhibition of H2O2 or TCDC on agonist (CCK-8, ACh, and KCl)-induced contraction and reduced the expected increase in lipid peroxidation and activities of catalase and SOD caused by H2O2 and TCDC. Incubation with CCK-8 for 60 min desensitized CCK-1 receptors up to 30 min, whereas no receptor desensitization was observed after PGE2 pretreatment. Cholesterol-rich liposome treatment enhanced the inhibition of H2O2 and TCDC on agonists-induced contraction, including that of PGE2. Pretreatment with PGE2 before H2O2 and TCDC did not completely block their inhibition on agonist-induced contraction. Cholesterol-rich liposome treatment impaired the expected increase in catalase activities in response to PGE2. We conclude that pretreatment with PGE2 prevents the muscle cell damage caused by H2O2 and TCDC due to the resistance of PGE2 receptors to agonist-induced desensitization. The preservation of PGE2 receptors may be designed to conserve these cytoprotective functions that are, however, impaired by the presence of excess cholesterol in the plasma membrane.

PAF-like lipids- and PAF-induced gallbladder muscle contraction is mediated by different pathways in guinea pigs

H2O2 stimulates gallbladder muscle contraction and scavengers of free radicals through the generation of PGE2. Oxidative stress causes lipid peroxidation and generation of platelet-activating factor (PAF) or PAF-like lipids. The present studies therefore were aimed at determining whether either one induced by H2O2 mediates the increased generation of PGE2. Dissociated muscle cells of guinea pig gallbladder were obtained by enzymatic digestion. Both PAF-like lipids and PAF-induced muscle contraction was blocked by the PAF receptor antagonist CV-3988. This antagonist also blocked the increased PGE2 production caused by PAF-like lipids or PAF. Actions of PAF-like lipids were completely inhibited by indomethacin, but those of PAF were only partially reduced by indomethacin or by nordihydroguaiaretic acid and completely blocked by their combination. PAF-like lipids-induced contraction was inhibited by AACOCF3 (cystolic phospholipase A2 inhibitor), whereas the actions of PAF were blocked by MJ33 (secretory phospholipase A2 inhibitor). Receptor protection studies showed that pretreatment with PAF-like lipids before N-ethylmaleimide protected the contraction induced by a second dose of PAF-like lipids or PGE2 but not by PAF. In contrast, pretreatment with PAF protected the actions of PAF and PGE2 but not that of PAF-like lipids. Both PAF-like lipids and PAF-induced contractions were inhibited by anti-Galphaq/11 antibody and by inhibitors of MAPK and PKC. In conclusion, PAF-like lipids seem to activate a pathway different from that of PAF probably by stimulating a different PAF receptor subtype.

Diabetes and hyperlipidemia correlate with gallbladder contractility in leptin-related murine obesity

Obesity is associated with many comorbid conditions including diabetes, hyperlipidemia, and gallstones. However, the interaction among these modalities remains unclear. We recently demonstrated that both leptin-deficient and leptin-resistant obese mice have impaired biliary motility. These obese mice also are diabetic and hyperlipidemic. Therefore, we tested the hypothesis that serum glucose, insulin, cholesterol, and triglyceride levels would correlate with gallbladder contractility. Thirty-four lean control, 10 lean heterozygous leptin-deficient, 18 obese homozygous leptin-deficient, and 12 obese homozygous leptin-resistant mice were fed a nonlithogenic chow diet while nine lean control and nine obese homozygous leptin-deficient mice were fed a high-cholesterol diet for 4 weeks. In vitro gallbladder responses to cholecystokinin (CCK; 10(-8) mol/L), acetylcholine (ACh; 10(-5) mol/L), and neuropeptide Y (NPY; 10(-6) mol/L) were measured. Serum glucose, insulin, cholesterol, and triglyceride levels were measured from pooled serum from an additional 704 animals. Gallbladder responses were greatest for CCK, intermediate for ACh, and least for NPY. Serum glucose, insulin, cholesterol, and triglyceride levels and body weight all correlated similarly, negatively, and significantly (P<0.001) with gallbladder contractility. Hyperglycemia, insulin-resistance, hyperlipidemia, and body weight in obese mice with leptin dysfunction are associated with poor gallbladder contractility, which in turn may contribute to the association between obesity and gallstone formation.

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Disorders of bile acid metabolism in cholesterol gallstone disease

The aim of the study was to evaluate the metabolism of individual bile acids in patients with cholesterol gallstone disease. Therefore, we determined pool size and turnover of deoxycholic (DCA), cholic (CA), and chenodeoxycholic acid (CDCA) in 23 female gallstone patients classified according to their gallbladder function and in 15 healthy female controls. Gallstone patients had normal hepatic bile acid synthesis, but, depending on gallbladder function, differed with respect to turnover and size of the bile acid pools: Patients with well-emptying gallbladder (group A, n = 9) had enhanced turnover and reduced pools of CA (-46%; P less than 0.01 vs. controls) and CDCA (-24%; P less than 0.05), but normal input and size of the DCA pool. With reduced gallbladder emptying (less than 50% of volume; group B, n = 6), turnover and pools of CA, CDCA, and DCA were similar as in controls. Patients with loss of gallbladder reservoir (group C, n = 8) had increased input (+100%; P less than 0.01) and pool size of DCA (+45%; P = 0.07) caused by rapid conversion of CA to DCA, while the pools of CA (-71%; P less than 0.001 vs. controls) and CDCA (-36%; P less than 0.05) were reduced by enhanced turnover. Thus, in patients with cholesterol gallstones, the pools of primary bile acids are diminished, unless gallbladder emptying is reduced. Furthermore, in a subgroup of gallstone patients, who had completely lost gallbladder function, the CA pool is largely replaced by DCA owing to rapid transfer of CA to the DCA pool. This probably contributes to supersaturation of bile with cholesterol.