Relationship between bilirubin free radical and formation of pigment gallstone

Quantitative phase analysis and molecular structure of human gallstones using synchrotron radiation X-ray diffraction and FTIR spectroscopy

Human gallstones are the most common disorder in the biliary system, affecting up to 20 % of the adult population. The formation of gallstones is primarily due to the supersaturating of cholesterol in bile. In order to comprehend gallstone disease in detail, it is necessary to have accurate information about phase identification and molecular structure. Different types of gallstone samples were collected from the Middle East area after surgical operations including; cholesterol, pigment, and mixed gallstones. To estimate the basic information about the stone formation and the pathophysiology of cholelithiasis as well as to classify the collected human gallstones, attenuated total reflection Fourier transform Infrared spectrometry (ATR-FTIR) was used to analyze the different gallstone structures in the wavenumber range from 400 to 4000 cm-1. Calcium bilirubinate was specified by the bands at 1662 cm-1, 1626 cm-1, and 1572 cm-1, while cholesterol rings were designated by the bands at 1464, 1438, 1055, and 1022 cm-1. It can be assumed that all samples consist of mixed gallstones based on the doublets at 1375 cm-1 and 1365 cm-1. The levels of calcium bilirubin and various minerals varied among the analyzed samples, indicating the heterogeneity in their composition and suggesting potential implications for gallstone formation. Based on the quantitative phase analysis using synchrotron radiation X-ray diffraction (SR-XRD), two phases of anhydrous cholesterol as a major content and one phase of monohydrate cholesterols as trace content represent the main components of most of the gallstones. Additional phases of calcium carbonate in the form of calcite, vaterite, aragonite, and bilirubinate were also quantified. According to the outcomes of the FTIR and the SR-XRD measurements, there exists a statistical correlation between the different types of chemical constituents of the gallstones.

Features of Metabolite Changes in Disease Evolution in Cholecystolithiasis

BACKGROUND

Cholecystolithiasis is defined as a disease caused by complex and changeable factors. Advanced age, female sex, and a hypercaloric diet rich in carbohydrates and poor in fiber, together with obesity and genetic factors, are the main factors that may predispose people to choledocholithiasis. However, serum biomarkers for the rapid diagnosis of choledocholithiasis remain unclear.

AIMS

This study was designed to explore the pathogenesis of cholecystolithiasis and identify the possible metabolic and lipidomic biomarkers for the diagnosis of the disease.

METHODS

Using UHPLC-MS/MS and GC-MS, we detected the serum of 28 cholecystolithiasis patients and 19 controls. Statistical analysis of multiple variables included Principal Component Analysis (PCA). Visualization of differential metabolites was performed using volcano plots. The screened differential metabolites were further analyzed using clustering heatmaps. The quality of the model was assessed using random forests.

RESULTS

In this study, dramatically altered lipid homeostasis was detected in cholecystolithiasis group. In addition, the levels of short-chain fatty acids and amino acids were noticeably changed in patients with cholecystolithiasis. They detected higher levels of FFA.18.1, FFA.20.1, LPC16.0, and LPC20.1, but lower levels of 1-Methyl-L-histidine and 4-Hydroxyproline. In addition, glycine and L-Tyrosine were higher in choledocholithiasis group. Analyses of metabolic serum in affected patients have the potential to develop an integrated metabolite-based biomarker model that can facilitate the early diagnosis and treatment of the disease.

CONCLUSION

Our results highlight the value of integrating lipid, amino acid, and short-chain fatty acid to explore the pathophysiology of cholecystolithiasis disease, and consequently, improve clinical decision-making.

Role of osteopontin in diet-induced brown gallstone formation in rats

Background:

Although osteopontin (OPN) is expressed in the liver and pigment gallstones of patients with hepatolithiasis, its role in pigment gallstone formation remains unclear. This study aimed to explore the function of OPN in pigment gallstone formation.

Methods:

Rats were fed a chow diet (CD) or lithogenic diet (LD) for 10 consecutive weeks; blocking tests were then performed using an OPN antibody (OPN-Ab). Incidence of gallstones and levels of several bile components, OPN, tumor necrosis factor alpha (TNF-α), and cholesterol 7 alpha-hydroxylase (CYP7A1) were analyzed. To determine TNF-α expression in hepatic macrophages and both CYP7A1 and bile acid (BA) expression in liver cells, recombinant rat OPN and recombinant rat TNF-α were used to treat rat hepatic macrophages and rat liver cells, respectively. Chi-square or Fisher exact tests were used to analyze qualitative data, Student t-test or one-way analysis of variance were used to analyze qualitative data.

Results:

Incidence of gallstones was higher in LD-fed rats than in CD-fed rats (80% vs. 10%, P < 0.05). BA content significantly decreased in bile (t = −36.08, P < 0.01) and liver tissue (t = −16.16, P < 0.01) of LD-fed rats. Both hepatic OPN protein expression (t = 9.78, P < 0.01) and TNF-α level (t = 8.83, P < 0.01) distinctly increased in the LD group; what's more, CYP7A1 mRNA and protein levels (t = −12.35, P < 0.01) were markedly down-regulated in the LD group. Following OPN-Ab pretreatment, gallstone formation decreased (85% vs. 25%, χ² = 14.55, P < 0.01), liver TNF-α expression (F = 20.36, P < 0.01) was down-regulated in the LD group, and CYP7A1 expression (F = 17.51, P < 0.01) was up-regulated. Through CD44 and integrin receptors, OPN promoted TNF-α production in macrophage (F = 1041, P < 0.01), which suppressed CYP7A1 expression (F = 48.08, P < 0.01) and reduced liver BA synthesis (F = 119.4, P < 0.01).

Conclusions:

We provide novel evidence of OPN involvement in pigmented gallstone pathogenesis in rats.

Classification of gallstones using Fourier-transform infrared spectroscopy and photography

Background

Gallstones have conventionally been classified by gross inspection into 4 categories: cholesterol gallstones, black pigment (calcium bilirubinate) gallstones, brown gallstones, and mixed gallstones that contain both cholesterol and calcium bilirubinate. Classification using Fourier-transform infrared (FT-IR) spectroscopy supplements gross inspection; however, the issue of ambiguity in gallstone classification has not been fully addressed to date.

Methods

Twenty-six gallstones obtained after surgical gallbladder removal were examined using FT-IR spectroscopy and digital photography, and classified into 6 gallstone groups according to characteristic FT-IR absorption bands.

Results

FT-IR spectra of nine gallstones matched well with that of pure cholesterol, and the gallstones were thus classified as cholesterol stones. Twelve gallstones were classified as calcium bilirubinate stones as they showed characteristic absorption bands of calcium bilirubinate. However, the FT-IR spectra of these gallstones always showed a broad absorption band of bound water at 3600–2400 cm^− 1. The other five gallstones were classified as mixed stones with combinations of cholesterol, calcium bilirubinate, and calcium carbonate.

Conclusion

FT-IR spectroscopy is a powerful and convenient method for gallstone classification. Nevertheless, one should take serious note of the superposition of FT-IR absorption bands of different chemical components of gallstones including that of bound water.

Hepatic Parenchymal Injury in Crigler-Najjar Type I

BACKGROUND

Crigler-Najjar syndrome type I (CNI) arises from biallelic variants of UGT1A1 that abrogate uridine diphosphate glucuronosyltransferase (UGT1A1) activity resulting in unconjugated hyperbilirubinemia. Historically, liver parenchyma in CNI was considered structurally and histologically normal. Recent review of CNI liver explants revealed fibrosis. Our aim was to investigate the association between hepatic histology and disease phenotype in CNI.

METHODS

We extracted data from the medical record at the time of liver transplant from 22 patients with CNI at the Children's Hospital of Pittsburgh, and reviewed explant histology. Continuous data were normally distributed, are presented as mean (±1 SD), and analyzed using two-tailed Student t-test. Categorical data were analyzed using the Chi-square test.

RESULTS

Both alanine transaminase (ALT; mean 87.4 IU/L) and aspartate transaminase (AST; mean 54.6 IU/L) were elevated. Nine (41%) of 22 explants had significant fibrosis. Pericentral (n = 5), periportal (n = 2), and mixed (n = 2) patterns of fibrosis occurred. A significant difference in mean age of subjects with fibrotic versus non-fibrotic livers (16.1 years vs 10.5 years; P = 0.02) was seen. There were no indices of synthetic liver dysfunction or portal hypertension. Neither a history of gallstone disease nor excess weight appeared to contribute to the development of fibrosis.

CONCLUSIONS

For the first time, we report a 41% prevalence of clinically silent, yet histologically significant fibrosis among subjects with Crigler-Najjar type 1. Risk for fibrosis appears to accrue with time, indicating that earlier intervention may be prudent whenever considering alternative treatments such as hepatocyte transplant, auxiliary liver transplant, or viral gene therapy.

Role of the Free Radicals in Mechanisms of Gallstone Formation: An EPR Study

The mechanism of gallstone formation is not well understood. Abnormal regulation of hepatic cholesterol, bile acid synthesis or esterification, deposition of cholesterol monohydrate crystals and gall bladder dysfunction are thought to be the principal metabolic aberrations that may cause gallstone formation. One plausible mechanism leading to these abnormalities is the role of free radicals, whose presence can be investigated using Electron Paramagnetic Resonance (EPR). Surgically removed gall bladder stones were used to obtain purified bilirubin, which was irradiated in vitro with visible light and measured with EPR in the presence of and without oxygen. EPR detected oxidized bilirubin free radical (BFR) (g = 2.003, ΔH = 1.0 mTl) in the gallstones. In vitro exposure of bilirubin to visible light in the presence of oxygen induced BFR formation; its intensity was radiation time dependent and decreased under the influence of β-carotene; irradiation in a vacuum did not generate BFRs. These results indicate the important role of oxidative processes (oxidation of bilirubin) in the gallstone formation. In oxidative stress, bilirubin acting as a second type photosensitizer undergoes rapid oxidation and free radical polymerization that plays an important role in the nucleation and deposition of gallstones.

New Evidences of Key Factors Involved in "Silent Stones" Etiopathogenesis and Trace Elements: Microscopic, Spectroscopic, and Biochemical Approach

The knowledge of the key factors involved in etiopathogenesis of the gallstone disease requires chemical, structural, and elemental composition analysis. The application of different complementary analytical techniques, both microscopic and spectroscopic, are aimed to provide a more comprehensive determination of the gallbladder calculi ultrastructure and trace element identification. High sensitivity techniques such as electron microscopy (SEM), Fourier transform infrared (FTIR), electron paramagnetic resonance (EPR) spectroscopy, and X-ray diffraction (XRD) along with biochemical analysis are used in a new attempt to investigate various factors which play a regulatory role in the pathogenesis of gallstones. The microstructure of different types of gallbladder stones has specific characteristics which are related to the elemental composition. The binding of metal ions with bile salts and bilirubin plays important roles in gallstone formation as revealed by FTIR spectrum of calcium bilirubinate complex in pigment gallstones. The EPR results demonstrated the generation of bilirubin free radicals and variation of its electronic structure and conjugation system in the skeleton of bilirubin molecule during complex formation. EPR spectra of pigment gallstones demonstrate the coexistence of four paramagnetic centers including stable bilirubin free radical, Mn2+, Cu2+, and Fe3+ with distinct magnetic parameters and well-resolved hyperfine structure in the case of Mn2+ ions. The result confirms a macromolecular network structure with proteins and the formation of bilirubin-coordinated polymer. Bilirubin and bilirubinate free radical complexes may play an important role in pigment gallstone formation.

The 42.1 and 53.7 kDa bands in SDS-PAGE of R-phycoerythrin from Polysiphonia urceolata

In SDS-PAGE gels of three purified R-phycoerythrins (R-PEs) isolated from three species of red algae, two bands whose molecular weights were about 40 kDa and 50 kDa can stably be found when the sample loading amount was enough. It is important for structure study of R-PE to clarify what these bands represent and how they are formed. According to results of the second SDS-PAGE, as well as molecular weights, fluorescences under UV and abundance, the 42.1 kDa and 53.7 kDa bands in SDS-PAGE gels of R-PE from Polysiphonia urceolata were believed to be complexes of αβ and βγ1, respectively. Formation of these bands may be related to light and phycourobilins (PUB) in subunits; and appearance of these two bands provided some proofs on position of chromophores and directions of energy transfer in R-PE. R-PE containing γ1 subunit was obviously more stable than R-PE containing γ2 subunit when they were exposed to protein denaturants, so γ subunits of R-PE may play important roles in structural stability of R-PE aggregates and the main forces that maintain the stability of R-PE may be interactions between γ subunit and β subunits.

New pathophysiological concepts underlying pathogenesis of pigment gallstones

Pigment gallstones, which are much less frequent than cholesterol stones, are classified descriptively as "black" or "brown". They are composed mostly of calcium hydrogen bilirubinate, Ca(HUCB)(2), which is polymerized and oxidized in "black" stones but remains unpolymerized in "brown" stones. Black stones form in sterile gallbladder bile but brown stones form secondary to stasis and anaerobic bacterial infection in any part of the biliary tree, including the gallbladder. Other calcium salts coprecipitate in both stone types; crystalline calcium phosphate and/or carbonate in the case of "black" stones and amorphous calcium salts of long chain saturated fatty acids ("soaps") in the case of "brown" stones. Cholesterol is present in variable proportions in "brown" more than "black" stones and in the latter, the bile sterol may be totally absent. The "scaffolding" of both stone types is a mixed mucin glycoprotein matrix secreted by epithelial cells lining the biliary tree. The critical pathophysiological prerequisite for "black" stone formation is "hyperbilirubinbilia" (biliary hypersecretion of bilirubin conjugates). It is due principally to hemolysis, ineffective erythropoiesis, or pathologic enterohepatic cycling of unconjugated bilirubin. Endogenous biliary β-glucuronidase hydrolysis of bilirubin conjugates in gallbladder bile provides HUCB(-) molecules that precipitate as insoluble salts with ionized Ca. Putatively, reactive oxygen species secreted by an inflamed gallbladder mucosa are responsible for transforming the initial soft yellow precipitates into hard black [Ca(HUCB)(2)](n) polymers. Despite "brown" gallstones being soft and amenable to mechanical removal, chronic anaerobic infection of the biliary tree is often markedly resistant to eradication.

Pathophysiological conditions in cholelithiasis formation in North Indian population: spectroscopic, biophysical, and biochemical study

Knowledge of the chemical, structural, and elemental composition of gallstones is essential for etiopathogenesis of gallstone disease. To identify the predisposing factors for gallstone formation, X-ray diffraction powder analysis, atomic absorption spectroscopy, and various biochemical estimations were carried out. In the present study, trace elemental analysis revealed calcium as the major constituent element in addition to the iron, magnesium, and zinc in the majority of the gallstones. Patients with gallstones exhibited increased serum total bilirubin and conjugated bilirubin levels and liver function parameters (serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase, and alkaline phosphatase). In patients with gallstones, higher concentrations of malondialdehyde, significantly higher glutathione disulfide/glutathione (GSH) ratio, reduced total GSH levels, and significantly decreased antioxidant enzymes activities (superoxide dismutase, catalase, and glutathione peroxidase) were found than in patients without gallstones. Further studies are needed to establish whether the observed differences are a cause or an effect of gallstone formation. Such studies could ultimately result in the development of new strategies for the treatment of gallstones and might provide clues for prevention of gallstones formation.

Influence of duodenal-biliary reflux on formation of bile duct pigment gallstone

AIM: To investigate the possible action and mechanism of duodenal-biliary reflux in the pathogenesis of bile duct pigment gallstone.

METHODS: Forty-eight patients were divided into three groups: polyp of gallbladder (PG, n = 10), cholecystolithiasis (CH, n = 27) and calculus of bile duct (CBD, n = 11). Bile samples were collected during operation for bacterial culture and endotoxin examination. Forty-one patients received T tube drainage after cholecystectomy and choledochotomy were divided into reflux (n = 16) and non-reflux group (n = 25) according to radionuclide examination. The activity of biliary amylase, lipase and β-glucuronidase were detected in 26 of the 41 patients.

RESULTS: The positive rate of bacterial culture was 0% in PG group, 0% in CH group and 81.8% in CBD group, and the level of endotoxin in bile was (0.003 ± 0.004) × 10^-6, (0.01 ± 0.02) × 10^-6, and (10.12 ± 4.49) × 10^-6 EU/L the above corresponding group, respectively. Compared with those in the former two groups, the positive rate and endotoxin level were higher in the latter CBD group (P < 0.01). Sixteen patients showed duodenal-biliary reflux (39.02%) among 41 patients. The activities of biliary amylase, lipase and exogenous β-glucuronidase in reflux group was significantly higher than those in non-reflux group (amylase: 79 891 ± 91 152 nkat/L vs 582 ± 928 nkat/L, P < 0.01; lipase: 86 110 ± 58 255 nkat/L vs 6 124 ± 7 500 nkat/L, P < 0.01; β-glucuronidase: 27 789 ± 13 849 nkat/L vs 15 369 ± 7 533 nkat/L, P < 0.01).

CONCLUSION: Duodenal-biliary reflux can promote the formation of pigment gallstone through bacteria, endotoxin, amylase, lipase and exogenous β-glucuronidase.