Primary dual defect of cholesterol and bile acid metabolism in liver of patients with intrahepatic calculi

Genetic Analysis of ABCB4 Mutations and Variants Related to the Pathogenesis and Pathophysiology of Low Phospholipid-Associated Cholelithiasis

Clinical studies have revealed that the ABCB4 gene encodes the phospholipid transporter on the canalicular membrane of hepatocytes, and its mutations and variants are the genetic basis of low phospholipid-associated cholelithiasis (LPAC), a rare type of gallstone disease caused by a single-gene mutation or variation. The main features of LPAC include a reduction or deficiency of phospholipids in bile, symptomatic cholelithiasis at <40 years of age, intrahepatic sludge and microlithiasis, mild chronic cholestasis, a high cholesterol/phospholipid ratio in bile, and recurrence of biliary symptoms after cholecystectomy. Needle-like cholesterol crystals, putatively “anhydrous” cholesterol crystallization at low phospholipid concentrations in model and native bile, are characterized in ABCB4 knockout mice, a unique animal model for LPAC. Gallbladder bile with only trace amounts of phospholipids in these mice is supersaturated with cholesterol, with lipid composition plotting in the left two-phase zone of the ternary phase diagram, consistent with “anhydrous” cholesterol crystallization. In this review, we summarize the molecular biology and physiological functions of ABCB4 and comprehensively discuss the latest advances in the genetic analysis of ABCB4 mutations and variations and their roles in the pathogenesis and pathophysiology of LPAC in humans, based on the results from clinical studies and mouse experiments. To date, approximately 158 distinct LPAC-causing ABCB4 mutations and variants in humans have been reported in the literature, indicating that it is a monogenic risk factor for LPAC. The elucidation of the ABCB4 function in the liver, the identification of ABCB4 mutations and variants in LPAC patients, and the exploration of gene therapy for ABCB4 deficiency in animal models can help us to better understand the cellular, molecular, and genetic mechanisms underlying the onset of the disease, and will pave the way for early diagnosis and prevention of susceptible subjects and effective intervention for LPAC in patients.

Etiology and pathogenesis of hepatolithiasis

Hepatolithiasis is a relatively common disease frequently encountered in department of hepatobiliary surgery. Intrahepatic stones are a major cause of mortality in patients with non-neoplastic diseases of the biliary tract. Environmental factors, nutritional status, bile duct inflammation, biliary stasis, virus infection, parasites, and anatomic variation of the bile duct are involved in the pathogenesis of hepatolithiasis. Surgery is the main treatment for hepatolithiasis but is associated with many serious postoperative complications and relapse. Thus, it is important to fully understand the etiology of hepatolithiasis to take effective measures to prevent the disease.

Primary cholesterol hepatolithiasis associated with cholangiocellular carcinoma: a case report and literature review

Hepatolithiasis associated with cholangiocellular carcinoma is occasionally a calcium bilirubinate stone. Primary cholesterol hepatolithiasis associated with cholangiocellular carcinoma is rare; only 6 cases have been reported in the literature. A 55-year-old man was admitted to our hospital because of an elevated level of carbohydrate antigen 19-9. Various imaging studies demonstrated a mass in the segment VII of the liver. The patient underwent a curative surgical operation. Histopathological examination revealed that it was cholangiocellular carcinoma located in the periphery of the liver. A cholesterol stone was present, encircled by the cholangiocellular carcinoma. Minor inflammatory changes were observed around the stone.

[Effects of Shengqing Capsules on cholelithiasis-related genes in guinea pigs]

OBJECTIVE

To explore the molecular mechanisms of Shengqing Capsules in treating cholelithiasis.

METHODS

Sixty female guinea pigs were randomized into 3 groups: group I (fed with normal diet), group II (fed with low-protein diet) and group III (fed with low-protein diet and Shengqing Capsules). After six-week feeding, the gallstone formation and the expressions of bilirubin UDP-glucuronosyltransferase (B-UGT) mRNA and cholesterol 7alpha-hydroxylase (CYP7A1) mRNA were observed.

RESULTS

The proportions of stone-formed in groups I, II and III were 2/14, 9/12 and 4/14, respectively. There were significant differences among the three groups (P<0.05). The expressions of B-UGT and CYP7A1 mRNAs were higher in both group I and group III as compared with those in the group II (P<0.05).

CONCLUSION

Shengqing Capsules can reduce the rate of stone-formation, which may be due to its interference of metabolism of bilirubin and cholesterol and up-regulation of the expressions of B-UGT and CYP7A1 mRNAs.

Prostaglandin E receptors in bile ducts of hepatolithiasis patients and the pathobiological significance for cholangitis

BACKGROUND & AIMS

In hepatolithiasis, chronic proliferative cholangitis may influence the progression of the disease. Prostaglandin (PG) E(2) experimentally causes morphologic changes to intrahepatic bile ducts, analogous to the changes found in cholangitis. This study was designed to gain an understanding of the involvement of PGE(2) and PGE receptor (EP) subtypes in the development of cholangitis.

METHODS

The expression levels of secretory-type group IIA phospholipase A(2) (sPLA(2)-IIA) and cyclooxygenase (COX)-2 as well as EP subtypes were determined in the bile ducts with change of cholangitis. In in vitro experiments, growth promotion and mucin secretagogue properties of biliary epithelial cells in response to EP-selective agonists or antagonists were studied.

RESULTS

The messenger RNA (mRNA) level of sPLA(2)-IIA and the protein and mRNA levels of COX-2 were significantly increased in the bile ducts of patients with hepatolithiasis compared with the levels of the bile ducts of control subjects. These changes were associated with a concomitant increase in PGE(2) and total mucin concentrations in the bile. The mRNAs of EP subtypes EP(2), EP(3), and EP(4) but not EP(1) were amplified in the bile ducts. Treatment with an EP(4)-selective agonist (ONO-AE1-329) caused a dose-dependent increase in DNA synthesis, colony number, and mucin secretion in the cells. Conversely, treatment with an EP(4)-selective antagonist (ONO-AE3-208) abolished the biological effects of PGE(2) on the cells.

CONCLUSIONS

In hepatolithiasis, an enhanced synthesis of sPLA(2)-/COX-2-derived PGE(2) and its actions mediated via the EP(4) receptor in the bile ducts may be of pathobiological significance for chronic proliferative cholangitis.

Hemorrhagic gastric carcinoma in an acromegalic patient

A rare case of hemorrhagic gastric carcinoma in an acromegalic patient is reported. A 79-year-old Japanese man was referred to our hospital with diagnoses of upper gastrointestinal hemorrhage and angina pectoris. This patient showed typical clinical features of acromegaly, with increased serum growth hormone (GH) and insulin-like growth factor I (IGF-I) level. A high titer of serum anti-Helicobacter pylori (H. pylori) IgG was also observed. After percutaneous transluminal coronary angioplasty treatment for stenosis of the right coronary artery, the patient underwent distal gastrectomy. Gastric cancer was Type 2 macroscopically and was diagnosed histologically as a papillary and well to moderately differentiated tubular adenocarcinoma. Reverse transcription-polymerase chain reaction analysis estimated that the amount of IGF-I receptor mRNA expression in the gastric cancer tissue was 1.6 times higher than that in the adjacent atrophic mucosa, whereas the amount of IGF-I mRNA expression in the cancer tissue was only half that in the atrophic mucosa. Both the stimulatory effects of GH and/or IGF-I on cell proliferation and H. pylori infection in gastric tumorigenesis may have been responsible for the development and growth of gastric carcinoma in this patient.

Secretory low-molecular-weight phospholipases A2 and their specific receptor in bile ducts of patients with intrahepatic calculi: factors of chronic proliferative cholangitis

Intrahepatic calculi is characterized by an intractable course and frequent recurrences, requiring multiple operative interventions. Chronic proliferative cholangitis, an active and long-standing inflammation of the stone-containing bile ducts with the hyperplasia of epithelia and the proliferation of the duct-associated mucus glands, may underlie the complex nature of the disease. In terms of the pathophysiology, interest has been focused on the role of secretory low-molecular-weight phospholipases A2 (sPLA2s) as inflammatory mediators or factors modulating cell functions via their specific sPLA2-receptor, and also on the production and secretion of altered mucin molecules from the inflamed bile ducts. In search of factors involving chronic proliferative cholangitis, the sPLA2 isoforms in the bile such as the pancreatic-type sPLA2 (group IB sPLA2) and the arthritic-type sPLA2 (group IIA sPLA2), were assayed to correlate protein masses of the sPLA2s with alterations in biliary composition. Furthermore, the steady-state messenger RNA (mRNA) levels of the sPLA2s, the membrane-bound sPLA2-receptor, cystic fibrosis transmembrane conductance regulator (CFTR), and mucin core polypeptide (MUC) genes in the bile ducts were assayed by reverse- transcriptase polymerase chain reaction (RT-PCR). Immunoreactive sPLA2-IB and sPLA2-IIA levels were significantly higher in the bile from the stone-containing hepatic ducts (2315 +/- 677 for sPLA2-IB; 281 +/- 42 for sPLA2-IIA ng/dL, mean +/- SEM; n = 20) than in the ductal bile from gallbladder stone patients (609 +/- 92, P <.01; 22 +/- 2, P <.01; n = 24). The increased sPLA2 levels were associated with a concomitant increase in lysophosphatidylcholine, prostaglandin E2 (PGE2), and total mucin concentrations. The affected bile ducts showed an increased mRNA level of sPLA2-IB and sPLA2-IIA compared with the ducts from control subjects, in whom the mRNAs of the sPLA2-receptor and other sPLA2 isoforms, such as groups V and X sPLA2s, were coincidently expressed. Reflecting the increased amounts of total biliary mucins, the affected ducts showed an increase in mRNA levels of CFTR as well as MUC2, MUC3, MUC5AC, MUC5B, and MUC6 compared with the ducts from control subjects. In intrahepatic calculi, an enhanced expression of the sPLA2s and their possible cross-talk via sPLA2-receptor may be of pathophysiological significance for the chronic proliferative cholangitis, in association with the enhanced CFTR expression and the alterations in mucin gene expression in the bile ducts, probably through potentiating arachidonate metabolism with associated biliary alterations favoring growth of preexisting stones and even further progressions.

Physical and metabolic factors in gallstone pathogenesis

Gallstones form when the tenuous balance of solubility of biliary lipids tips in favor of precipitation of cholesterol, unconjugated bilirubin, or bacterial degradation products of biliary lipids. For cholesterol gallstones, metabolic alterations in hepatic cholesterol secretion combine with changes in gallbladder motility and intestinal bacterial degradation of bile salts to destabilize cholesterol carriers in bile and produce cholesterol crystals. For black pigment gallstones, changes in heme metabolism or bilirubin absorption lead to increased bilirubin concentrations and precipitation of calcium bilirubinate. In contrast, mechanical obstruction of the biliary tract is the major factor leading to bacterial degradation and precipitation of biliary lipids in brown pigment stones. Further understanding of the physical and metabolic factors of cholesterol and black pigment formation is likely to provide interventions to interrupt the earliest stages of gallstone formation.

Analysis of human CYP7A1 mRNA decay in HepG2 cells by reverse transcription-polymerase chain reaction

The conversion of cholesterol to bile acids is the major pathway through which cholesterol is removed from the body. The initial and rate-limiting step in this catabolic pathway is catalyzed by the liver-specific enzyme cholesterol 7alpha-hydroxylase (CYP7A1). The HepG2 cell line has been used as a model to study human CYP7A1. The levels of CYP7A1 mRNA, however, are quite low in this cell line and require the use of poly(A)+ mRNA for detection using standard Northern analysis. As an alternative, we established a reverse transcription-polymerase chain reaction (RT-PCR) assay that can be used to study CYP7A1 mRNA in HepG2 cells. Using RT-PCR, we analyzed the influence of cell culture conditions on CYP7A1 mRNA levels. We observed an increase in CYP7A1 mRNA levels as the density of the cell culture increased. This rise in CYP7A1 was accompanied by a reciprocal drop in the levels of the proto-oncogene c-myc. Since c-myc expression is strongly associated with cell growth status, this inverse relationship suggests that conditions that favor reduced cell proliferation result in higher levels of CYP7A1 expression. We also established the validity of using RT-PCR for the measurement of mRNA decay rates using c-myc and glyceraldehyde-3-phosphate dehydrogenase mRNAs as a model: The same half-life value was obtained for the c-myc mRNA using either Northern analysis or RT-PCR. Using our RT-PCR method we determined that human CYP7A1 mRNA decays with a half-life of 4.6 +/- 0.9 h (n = 8) in HepG2 cells. We show that the protein synthesis inhibitor cycloheximide prolonged the CYP7A1 mRNA half-life, suggesting that translation is required for mRNA decay. Dexamethasone treatment, however, did not alter CYP7A1 mRNA decay rate but it increased CYP7A1 steady-state mRNA levels, suggesting that the effect of this glucocorticoid in HepG2 cells may be transcriptional.

Effects of long-term ursodeoxycholate administration on expression levels of secretory low-molecular-weight phospholipases A2 and mucin genes in gallbladders and biliary composition in patients with multiple cholesterol stones

Group IIA phospholipase A2 (PLA2), a secretory low-molecular-weight PLA2, may play a critical role in the process of gallbladder mucosal inflammation in multiple cholesterol stones, which in turn may produce biliary pronucleating proteins as well as mucin. On the other hand, ursodeoxycholate (UDC) decreases biliary levels of various pronucleating proteins, possibly because of its membrane-protective effects on the inflamed gallbladder mucosa. To elucidate that beneficial effect of UDC, the expression levels of low-molecular-weight PLA2s, group IIA PLA2 (PLA2-IIA), and group V PLA2 (PLA2-V), and mucin core polypeptide genes in the gallbladders were studied for UDC-treated patients and untreated patients with multiple cholesterol stones. Furthermore, the results were correlated with alterations in biliary composition. With long-term administration of UDC, the PLA2-IIA protein mass (2.7 +/- 0.5 vs. 5.0 +/- 0.4 ng/mg x protein [mean +/- SEM]; P < .01) and steady-state mRNA level, as well as the PLA2-V mRNA level, were significantly decreased in the gallbladders, where the prostaglandin E2 (PGE2) level was concomitantly decreased (190.7 +/- 27.9 vs. 393.6 +/- 55.3 pg/mg x protein; P < .01). In the gallbladder bile, the immunoradiometrically determined PLA2-IIA levels were significantly decreased in the UDC-treated patients (43 +/- 4 ng/dL; P < .01) in comparison with untreated patients (78 +/- 6 ng/dL). Significant decreases were similarly found for total protein, mucin, and free arachidonate concentrations, as well as nucleation activity in the bile. The degree of the changes was found to be rather small in solitary stones. In contrast to the decreased mucin concentration, however, there were no significant changes in the expression levels of mucin core polypeptide genes (MUC1-MUC6) between the UDC-treated and untreated patients. Long-term UDC administration was observed to lower the increased PLA2-IIA protein mass and mRNA level, as well as the PLA2-V mRNA level, in the gallbladders of patients with multiple cholesterol stones, which in turn may be of therapeutic importance in improving the gallbladder mucosal inflammation. Effects of UDC on secretory low-molecular-weight PLA2s as inflammatory mediators may relate to the reported efficacy of UDC treatment in cholesterol gallstone disease.

Abnormal duodenal bile composition in patients with acalculous chronic cholecystitis

OBJECTIVE

Our goal was to characterize biliary lipid composition in patients with the syndrome of chronic biliary pain, absence of gallstones, and inflammation of the gallbladder mucosa (acalculous chronic cholecystitis).

METHODS

Duodenal bile, obtained from 27 patients with a history of right upper quadrant pain and with negative imaging studies of the biliary tract, was analyzed enzymatically for bile acids, phospholipids, and cholesterol. Fifteen patients were found to have inflammation and/or fibrosis of the gallbladder at cholecystectomy.

RESULTS

The 15 patients with abnormal gallbladder histology had more dilute duodenal bile, as indicated by a low bile acid concentration and a lower proportion of phospholipids (p < 0.01) when values were compared with those of duodenal bile samples from postmenopausal women without gallbladder disease or from radiolucent gallstone subjects participating in the National Cooperative Gallstone Study. Cholecystectomy relieved pain in 9 of 14 patients.

CONCLUSIONS

Some patients with acalculous chronic cholecystitis have duodenal bile samples characterized by a decreased bile acid concentration and a decreased proportion of biliary phospholipids. The low biliary bile acid concentration may result from impaired gallbladder contraction and/or secretion by the biliary tract epithelium. The low proportion of phospholipid may result from posthepatic hydrolysis of luminal phosphatidylcholine followed by absorption of the hydrolysis products. The latter process could be caused by and/or contribute to mucosal inflammation and would also elevate the cholesterol saturation of bile, increasing the risk for cholesterol gallstone formation.

Hepatolithiasis and biliary parasites

Hepatolithiasis, or the presence of intrahepatic stones, is prevalent in East Asia and is characterized by the finding of stones within the intrahepatic bile ducts proximal to the confluence of the right and left hepatic ducts. Bile stasis and bacterial infection have been incriminated as the major aetiopathogenic factors. Clinical features include recurrent pyogenic cholangitis, multiple liver abscesses, secondary biliary cirrhosis and cholangiocarcinoma. The goals of management include accurate localization of pathologies, control of biliary sepsis and the elimination of stones and stasis. Ultrasonography, computed tomography and direct cholangiography complement each other in defining the stones, strictures and degree of liver damage. Non-operative biliary decompression by endoscopy and interventional radiology is effective in controlling the infection, but surgery remains the mainstay for the treatment of stones and strictures. Intra-operative ultrasound and flexible choledochoscopy, combined with percutaneous transhepatic cholangioscopy and intraductal lithotripsy, facilitate stone removal. Balloon dilatation and biliary stenting serve to open the bile duct strictures. The creation of a hepaticocutaneous jejunostomy after conventional surgery allows atraumatic access to the biliary system for the removal of recurrent stones. The management of biliary parasites begins with conservative measures, including analgesics and anti-helminthic therapy. In refractory cases or patients with acute cholangitis, endoscopic biliary drainage and the extraction of worms may be necessary. Improvement in sanitation plays a crucial role in the epidemiological control of these biliary diseases.

Structure and composition of primary intrahepatic stones in Korean patients

We have analyzed the chemical composition of primary intrahepatic stones from 72 Korean patients. Two types of concretions have been identified: brown pigment (calcium bilirubinate) stones and black-colored mixed stones. Brown pigment stones were found in 68% of all cases and the remainder (32%) consisted of mixed stones. Intrahepatic mixed stones had mean cholesterol and bilirubin contents of 46.6% and 25.9%, respectively, whereas calcium bilirubinate stones had mean cholesterol and bilirubin contents of 14.1% and 43.6%, respectively. Intrahepatic mixed stones had a smooth black-colored surface and on cross section, exhibited a distinct outer shell surrounding an inner yellow, cholesterol-rich body. The finding of intrahepatic mixed stones with high cholesterol content suggests that primary hepatolithiasis may result from at least two different conditions or disorders and points to different approaches to their treatment.