Hydrophilic but not hydrophobic bile acids prevent gallbladder muscle dysfunction in acute cholecystitis

Discovery of betulinic acid derivatives as gut-restricted TGR5 agonists: Balancing the potency and physicochemical properties

The pleiotropic effects of TGR5 make it an appealing target for intervention of metabolic and inflammatory disorders, but systemic activation of TGR5 faces challenges of on-target side effects, especially gallbladder filling. Gut-restricted agonists were proved to be sufficient to circumvent these side effects, but extremely low systemic exposure may not be effective in activating TGR5 since it is located on the basolateral membrane. Herein, to balance potency and physicochemical properties, a series of gut-restricted TGR5 agonists with diversified kinetophores had been designed and synthesized. Compound 22-Na exhibited significant antidiabetic effect, and showed favorable gallbladder safety after 7 days of oral administration in humanized TGR5H88Y mice, confirming that gut-restricted agonism of TGR5 is a viable strategy to alleviate systemic target-related effects.

A Dual Coverage Monitoring of the Bile Acids Profile in the Liver-Gut Axis throughout the Whole Inflammation-Cancer Transformation Progressive: Reveal Hepatocellular Carcinoma Pathogenesis

Hepatocellular carcinoma (HCC) is the terminal phase of multiple chronic liver diseases, and evidence supports chronic uncontrollable inflammation being one of the potential mechanisms leading to HCC formation. The dysregulation of bile acid homeostasis in the enterohepatic circulation has become a hot research issue concerning revealing the pathogenesis of the inflammatory-cancerous transformation process. We reproduced the development of HCC through an N-nitrosodiethylamine (DEN)-induced rat model in 20 weeks. We achieved the monitoring of the bile acid profile in the plasma, liver, and intestine during the evolution of "hepatitis-cirrhosis-HCC" by using an ultra-performance liquid chromatography-tandem mass spectrometer for absolute quantification of bile acids. We observed differences in the level of primary and secondary bile acids both in plasma, liver, and intestine when compared to controls, particularly a sustained reduction of intestine taurine-conjugated bile acid level. Moreover, we identified chenodeoxycholic acid, lithocholic acid, ursodeoxycholic acid, and glycolithocholic acid in plasma as biomarkers for early diagnosis of HCC. We also identified bile acid-CoA:amino acid N-acyltransferase (BAAT) by gene set enrichment analysis, which dominates the final step in the synthesis of conjugated bile acids associated with the inflammatory-cancer transformation process. In conclusion, our study provided comprehensive bile acid metabolic fingerprinting in the liver-gut axis during the inflammation-cancer transformation process, laying the foundation for providing a new perspective for the diagnosis, prevention, and treatment of HCC.

Canine extrahepatic biliary disease: what have we learned?

Extrahepatic biliary disease in dogs is commonly encountered in clinical practice worldwide. Diseases in this segment of the biliary tract are diverse and can manifest with mild clinical signs or can be life-threatening. In the last decade there have been advances in diagnostic tests, imaging modalities and therapeutic interventions as well as the identification of novel prognostic variables that could improve outcomes in dogs with extrahepatic biliary disease. Therefore, the objective of this review was to summarise clinically relevant updates of extrahepatic biliary disease in dogs.

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.

Serum 25-hydroxyvitamin D concentrations in dogs with gallbladder mucocele

Gallbladder mucocele (GBM) is a common biliary disorder in dogs. Gallbladder hypokinesia has been proposed to contribute to its formation and progression. The specific cause of gallbladder stasis in dogs with GBM as well as viable treatment options to resolve dysmotility remains unknown. Vitamin D deficiency is one of the many potential causes of gallbladder hypokinesia in humans and repletion results in complete resolution of stasis. Improving our understanding of the relationship between serum vitamin D and GBM could help identify dogs as a model for humans with gallbladder hypokinesia. Furthermore, this relationship could provide insight into the pathogenesis of GBM and support the need for future studies to investigate vitamin D as a novel treatment target. Therefore, goals of this study were i) to determine if serum 25-hydroxyvitamin(OH)D concentrations were decreased in dogs with GBM, ii) if serum 25(OH)D concentrations were different in clinical versus dogs subclinical for GBM, and iii) to determine if serum 25(OH)D concentrations could predict the ultrasonographic type of GBM. Sixty-two dogs (clinical, n = 26; subclinical, n = 36) with GBM and 20 healthy control dogs were included in this prospective observational study. Serum 25(OH)D concentrations were measured with a competitive chemiluminescence immunoassay. Overall, dogs with GBM had lower serum 25(OH)D concentrations than control dogs (P = 0.004). Subsequent subgroup analysis indicated that this difference was only significant in the subclinical group compared to the control dogs (P = 0.008), and serum 25(OH)D concentrations did not significantly differ between dogs clinical for GBM versus subclinical or control dogs, indicating that inflammatory state in clinical dogs was not the major constituent of the observed findings. Decreasing serum 25(OH)D concentrations, but not clinical status, was associated with a more advanced developmental stage of GBM type determined by ultrasonography. Our results indicate that vitamin D has a role in dogs with GBM. Additional studies are needed to assess if reduced vitamin D in dogs with GBM is a cause or effect of their biliary disease and to investigate if vitamin D supplementation could be beneficial for dogs with GBM.

An Update on the Lithogenic Mechanisms of Cholecystokinin a Receptor (CCKAR), an Important Gallstone Gene for Lith13

The cholecystokinin A receptor (CCKAR) is expressed predominantly in the gallbladder and small intestine in the digestive system, where it is responsible for CCK's regulation of gallbladder and small intestinal motility. The effect of CCKAR on small intestinal transit is a physiological response for regulating intestinal cholesterol absorption. The Cckar gene has been identified to be an important gallstone gene, Lith13, in inbred mice by a powerful quantitative trait locus analysis. Knockout of the Cckar gene in mice enhances cholesterol cholelithogenesis by impairing gallbladder contraction and emptying, promoting cholesterol crystallization and crystal growth, and increasing intestinal cholesterol absorption. Clinical and epidemiological studies have demonstrated that several variants in the CCKAR gene are associated with increased prevalence of cholesterol cholelithiasis in humans. Dysfunctional gallbladder emptying in response to exogenously administered CCK-8 is often found in patients with cholesterol gallstones, and patients with pigment gallstones display an intermediate degree of gallbladder motility defect. Gallbladder hypomotility is also revealed in some subjects without gallstones under several conditions: pregnancy, total parenteral nutrition, celiac disease, oral contraceptives and conjugated estrogens, obesity, diabetes, the metabolic syndrome, and administration of CCKAR antagonists. The physical-chemical, genetic, and molecular studies of Lith13 show that dysfunctional CCKAR enhances susceptibility to cholesterol gallstones through two primary mechanisms: impaired gallbladder emptying is a key risk factor for the development of gallbladder hypomotility, biliary sludge (the precursor of gallstones), and microlithiasis, as well as delayed small intestinal transit augments cholesterol absorption as a major source for the hepatic hypersecretion of biliary cholesterol and for the accumulation of excess cholesterol in the gallbladder wall that further worsens impaired gallbladder motor function. If these two defects in the gallbladder and small intestine could be prevented by the potent CCKAR agonists, the risk of developing cholesterol gallstones could be dramatically reduced.

[Comparative effectiveness of ursodeoxycholic acid preparations in the treatment of biliary sludge]

In the clinical classification of cholelithiasis, biliary sludge (BS) is distinguished as the pre-stone stage. Ursodeoxycholic acid (UDCA) is a drug with an evidence base for effective and safe effects on BS. The therapeutic equivalence of various UDCA drugs remains an important issue for clinical practice.

AIM

To conduct a comparative analysis of the effectiveness of the use of UDCA: Ursofalk with other UDCA drugs for the treatment of BS in a fixed dose of 10 mg/kg of body weight.

MATERIAL AND METHODS

The observation group consisted of 225 patients with various types of BS. In randomized groups, the comparison of the effectiveness of UDCA drugs in the dissolution of BS was determined by the data of ultrasound of the gallbladder. Dynamic ultrasound cholecystography using a standardized technique was performed to study the effect of the compared drugs on the contractile function of the liver. When analyzing the impact of ursotherapy on the clinical manifestations of BS, the dynamics of biliary pain syndrome and dyspeptic disorders were evaluated.

RESULTS

A comparative analysis of the effectiveness of UDCA drugs for BS lysis with a high degree of confidence established the advantage of Ursofalk: after 3 months in 80%, and after 6 months of therapy in 95.65% of patients, a regression of BS was detected. In the group of patients who took other UDCA, the corresponding indicators were 46.36% and 67.27%. The greatest effectiveness of ursotherapy was demonstrated in the BS variant by the type of suspension of hyperechogenic particles, the lowest in the variant by the type of putty-like bile in the form of mobile or fixed clots. In the last variant of BS, the relationship between the success of lysis with the extension of the UDCA intake period to 6 months and the preferred choice of Ursofalk was traced. Normalization of the contractile function of the gallbladder was noted in patients who took Ursofalk.

CONCLUSION

From the standpoint of therapeutic effectiveness, the drug of choice for the treatment of BS, regardless of its type, is Ursofalk, which has proven the best dynamics of BS litolysis, recovery of the contractile function of the gastrointestinal tract, and relief of clinical symptoms.

lncRNA-PDPK2P promotes hepatocellular carcinoma progression through the PDK1/AKT/Caspase 3 pathway

Hepatocellular carcinoma (HCC) is a malignancy with one of the worst prognoses. Long noncoding RNA (lncRNA) are emerging as an important regulator of gene expression and function, leading to the development of cancer. The aim of this study was to determine the relationship between lncRNA and HCC and to further guide clinical therapy. lncRNA in HCC and adjacent tissues were screened, and the correlation between lncRNA-PDPK2P expression in liver tissues and the pathological characteristics and severity of HCC was assessed. The effects of PDPK2P on HCC proliferation, apoptosis, metastasis, and invasion were also systematically investigated via CCK-8 assay, flow cytometry, scratch wound healing, and transwell assay, respectively. The relationship between PDPK2P and PDK1 was verified by RNA pull-down, rescue experiments and western blot. lncRNA-PDPK2P was highly expressed in HCC tissues with a distinct positive correlation between PDPK2P and PDK1, and the upregulation was clinically associated with a larger tumor embolus, low differentiation, and poor survival. Mechanistically, lncRNA-PDPK2P interacted with PDK1 and promoted HCC progression through the PDK1/AKT/caspase 3 signaling pathway. lncRNA-PDPK2P can promote HCC progression, suggesting it may be a clinically valuable biomarker and serve as a molecular target for the diagnosis, prognosis, and therapy of hepatocellular carcinoma.

Effect of emodin on mobility signal transduction system of gallbladder smooth muscle in Guinea pig with cholelithiasis

OBJECTIVE

To study the effect of emodin on protein and gene expressions of the massagers in mobility signal transduction system of cholecyst smooth muscle cells in guinea pig with cholesterol calculus.

METHODS

The guinea pigs were randomly divided into 4 groups, such as control group, gall-stone (GS) group, emodin group and ursodeoxycholic acid (UA) group. Cholesterol calculus models were induced in guinea pigs of GS, emodin and UA groups by lithogenic diet, while emodin or UA were given to the corresponding group for 7 weeks. The histomorphological and ultrastructure change of gallbladder were detected by microscope and electron microscope, the content of plasma cholecystokinin (CCK) and [Ca²⁺]_i were analyzed successively by radioimmunoassay and flow cytometry. The protein and mRNA of Gsα, Giα and Cap in cholecyst cells were determined by western blotting and real time polymerase chain reaction (RT-PCR).

RESULTS

Emodin or UA can relieve pathogenic changes in epithelial cells and muscle cells in gallbladder of guinea pig with cholesterol calculus by microscope and transmission electron microscope. In the cholecyst cells of GS group, CCK levels in plasma and [Ca²⁺]_i decreased, the protein and mRNA of GS were down-regulated, the protein and mRNA of Gi and Cap were up-regulated. Emodin significantly decreased the formative rate of gallstone, improved the pathogenic change in epithelial cells and muscle cells, increased CCK levels in plasma and [Ca²⁺]_i in cholecyst cells, enhanced the protein and mRNA of Gs in cholecyst cells, reduced the protein and mRNA of Gi and Cap in cholecyst cells in guinea pig with cholesterol calculus.

CONCLUSION

The dysfunction of gallbladder contraction gives rise to the disorders of mobility signal transduction system in cholecyst smooth muscle cells, including low content of plasma CCK and [Ca²⁺]_i in cholecyst cells, abnormal protein and mRNA of Gs, Gi and Cap. Emodin can enhance the contractibility of gallbladder and alleviate cholestasis by regulating plasma CCK levels, [Ca²⁺]_i in cholecyst cells and the protein and mRNA of Gs, Gi and Cap.

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.

Impact of ursodeoxycholic acid on a CCK1R cholesterol-binding site may contribute to its positive effects in digestive function

Dysfunction of the type 1 cholecystokinin (CCK) receptor (CCK1R) as a result of increased gallbladder muscularis membrane cholesterol has been implicated in the pathogenesis of cholesterol gallstones. Administration of ursodeoxycholic acid, which is structurally related to cholesterol, has been shown to have beneficial effects on gallstone formation. Our aims were to explore the possible direct effects and mechanism of action of bile acids on CCK receptor function. We studied the effects of structurally related hydrophobic chenodeoxycholic acid and hydrophilic ursodeoxycholic acid in vitro on CCK receptor function in the setting of normal and elevated membrane cholesterol. We also examined their effects on a cholesterol-insensitive CCK1R mutant (Y140A) disrupting a key site of cholesterol action. The results show that, similar to the impact of cholesterol on CCK receptors, bile acid effects were limited to CCK1R, with no effects on CCK2R. Chenodeoxycholic acid had a negative impact on CCK1R function, while ursodeoxycholic acid had no effect on CCK1R function in normal membranes but was protective against the negative impact of elevated cholesterol on this receptor. The cholesterol-insensitive CCK1R mutant Y140A was resistant to effects of both bile acids. These data suggest that bile acids compete with the action of cholesterol on CCK1R, probably by interacting at the same site, although the conformational impact of each bile acid appears to be different, with ursodeoxycholic acid capable of correcting the abnormal conformation of CCK1R in a high-cholesterol environment. This mechanism may contribute to the beneficial effect of ursodeoxycholic acid in reducing cholesterol gallstone formation.

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.

Physiology and Pathophysiology of the Biliary Tract: The Gallbladder and Sphincter of Oddi—A Review

The biliary tract collects, stores, concentrates, and delivers bile secreted by the liver. Its motility is controlled by neurohormonal mechanisms with the vagus and splanchnic nerves and the hormone cholecystokinin playing key roles. These neurohormonal mechanisms integrate the motility of the gallbladder and sphincter of Oddi (SO) with the gastrointestinal tract in the fasting and digestive phases. During fasting most of the hepatic bile is diverted toward the gallbladder by the resistance of the SO. The gallbladder allows the gradual entry of bile relaxing by passive and active mechanisms. During the digestive phase the gallbladder contracts, and the SO relaxes allowing bile to be released into the duodenum for the digestion and absorption of fats. Pathological processes manifested by recurrent episodes of upper abdominal pain affect both the gallbladder and SO. The gallbladder motility and cytoprotective functions are impaired by lithogenic hepatic bile with excess cholesterol allowing the hydrophobic bile salts to induce chronic cholecystitis. Laparoscopic cholecystectomy is the standard treatment. Three types of SO dyskinesia also cause biliary pain. Their pathophysiology is not completely known. The pain of types I and II usually respond to sphincterotomy, but the pain due to type III usually does not.

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.

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.

ATP induces guinea pig gallbladder smooth muscle excitability via the P2Y4 receptor and COX-1 activity

The purpose of this study was to elucidate the mechanisms by which ATP increases guinea pig gallbladder smooth muscle (GBSM) excitability. We evaluated changes in membrane potential and action potential (AP) frequency in GBSM by use of intracellular recording. Application of ATP (100 microM) caused membrane depolarization and a significant increase in AP frequency that were not sensitive to block by tetrodotoxin (0.5 microM). The nonselective P2 antagonist, suramin (100 microM), blocked the excitatory response, resulting in decreased AP frequency in the presence of ATP. The excitatory response to ATP was not altered by pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid (30 microM), a nonselective P2X antagonist. UTP also caused membrane depolarization and increased AP frequency, with a similar dose-response relationship as ATP. RT-PCR demonstrated that the P2Y(4), but not P2Y(2), receptor subtype is expressed in guinea pig gallbladder muscularis. ATP induced excitation was blocked by indomethacin (10 microM) and the cyclooxygenase (COX)-1 inhibitor SC-560 (300 nM), but not the COX-2 inhibitor nimesulide (500 nM). These data suggest that ATP stimulates P2Y(4) receptors within the gallbladder muscularis and, in turn, stimulate prostanoid production via COX-1 leading to increased excitability of GBSM.

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.

Effects of long term hydrophilic bile acid therapy on in vitro contraction of gallbladder muscle strips in patients with cholesterol gallstones

AIM: To evaluate ursodeoxycholic acid (UDCA) therapy on the in vitro contraction of gallbladder smooth muscle strips from cholesterol gallstone patients.

METHODS: The contraction forces of gallbladder smooth muscle strips from 28 patients with cholesterol gallstones treated with UDCA were compared with contraction forces from 14 untreated patients. The strips were stimulated with increasing concentrations of cholecystokinin-8 (CCK-8).

RESULTS: Although the contraction forces that developed in response to CCK-8 were higher in strips from specimens of UDCA treated patients compared to untreated patients, longer treatment periods (6-wk) caused more contraction responses than the short treatment period of 3-wk (F = 19.297, 1.85 ± 0.22 g vs 1.70 ± 0.10 g, P < 0.01). Contraction forces developed with maximal stimulation with KCl in the 6-wk treatment group were also higher than contraction forces in the untreated group (F = 4.274, 3.77 ± 0.45 g vs 3.30 ± 0.30 g, P < 0.05).

CONCLUSION: Six-week UDCA treatment caused an increase in contractions of muscle strips from patients with cholesterol gallstones when compared to shorter treatment administration or controls. We suggest that extending UDCA treatment periods may cause more effective contractions in the gallbladder, and thereby increase the rate of response to treatment.

Prostaglandins mediate tonic contraction of the guinea pig and human gallbladder

The gallbladder (GB) maintains tonic contraction modulated by neurohormonal inputs but generated by myogenic mechanisms. The aim of these studies was to examine the role of prostaglandins in the genesis of GB myogenic tension. Muscle strips and cells were treated with prostaglandin agonists, antagonists, cyclooxygenase (COX) inhibitors, and small interference RNA (siRNA). The results show that PGE2, thromboxane A2 (TxA2), and PGF(2alpha) cause a dose-dependent contraction of muscle strips and cells. However, only TxA2 and PGE2 (E prostanoid 1 receptor type) antagonists induced a dose-dependent decrease in tonic tension. A COX-1 inhibitor decreased partially the tonic contraction and TxB2 (TxA2 stable metabolite) levels; a COX-2 inhibitor lowered the tonic contraction partially and reduced PGE2 levels. Both inhibitors and the nonselective COX inhibitor indomethacin abolished the tonic contraction. Transfection of human GB muscle strips with COX-1 siRNA partially lowered the tonic contraction and reduced COX-1 protein expression and TxB2 levels; COX-2 siRNA also partially reduced the tonic contraction, the protein expression of COX-2, and PGE2. Stretching muscle strips by 1, 2, 3, and 4 g increased the active tension, TxB2, and PGE2 levels; a COX-1 inhibitor prevented the increase in tension and TxB2; and a COX-2 inhibitor inhibited the expected rise in tonic contraction and PGE2. Indomethacin blocked the rise in tension and TxB2 and PGE2 levels. We conclude that PGE2 generated by COX-2 and TxA2 generated by COX-1 contributes to the maintenance of GB tonic contraction and that variations in tonic contraction are associated with concomitant changes in PGE2 and TxA2 levels.

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.

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.

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.