Bile Pigment Bilirubin Research Articles

Bile acids, bile pigments and colorectal cancer risk.

The gut microbial co-metabolism of bile-derived compounds (e.g. bile acids and bile pigments) affects colorectal cancer (CRC) risk. Here, we review recent findings with focus on selected novel aspects of bile-associated effects with interesting but unclear implications on CRC risk. Numerous studies demonstrated novel biotransformation of bile acids by gut bacteria (e.g. microbial conjugation of bile acids), resulting in diverse bile acid compounds that show complex interactions with host receptors (e.g. FXR, TGR5). In addition, YAP-associated signalling in intestinal epithelial cells is modulated via bile acid receptor TGR5 and contributes to colonic tumorigenesis. Finally, studies indicate that serum levels of the bile pigment bilirubin are inversely associated with CRC risk or intestinal inflammation and that bilirubin affects gut microbiota composition. Bile acids and bile pigments have multiple effects on intestinal microbe-host interactions, which may collectively modulate long-term CRC risk of the host.

Impact of higher-order heme degradation products on hepatic function and hemodynamics

Biliverdin and bilirubin were previously considered end products of heme catabolism; now, however, there is evidence for further degradation to diverse bioactive products. Z-BOX A and Z-BOX B arise upon oxidation with unknown implications for hepatocellular function and integrity. We studied the impact of Z-BOX A and B on hepatic functions and explored their alterations in health and cholestatic conditions. Functional implications and mechanisms were investigated in rats, hepatocytic HepG2 and HepaRG cells, human immortalized hepatocytes, and isolated perfused livers. Z-BOX A and B were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in acute and acute-on-chronic liver failure and hereditary unconjugated hyperbilirubinemia. Z-BOX A and B are found in similar amounts in humans and rodents under physiological conditions. Serum concentrations increased ∼20-fold during cholestatic liver failure in humans (p<0.001) and in hereditary deficiency of bilirubin glucuronidation in rats (p<0.001). Pharmacokinetic studies revealed shorter serum half-life of Z-BOX A compared to its regio-isomer Z-BOX B (p=0.035). While both compounds were taken up by hepatocytes, Z-BOX A was enriched ∼100-fold and excreted in bile. Despite their reported vasoconstrictive properties in the brain vasculature, BOXes did not affect portal hemodynamics. Both Z-BOX A and B showed dose-dependent cytotoxicity, affected the glutathione redox state, and differentially modulated activity of Rev-erbα and Rev-erbβ. Moreover, BOXes-triggered remodeling of the hepatocellular cytoskeleton. Our data provide evidence that higher-order heme degradation products, namely Z-BOX A and B, impair hepatocellular integrity and might mediate intra- and extrahepatic cytotoxic effects previously attributed to hyperbilirubinemia. Degradation of the blood pigment heme yields the bile pigment bilirubin and the oxidation products Z-BOX A and Z-BOX B. Serum concentrations of these bioactive molecules increase in jaundice and can impair liver function and integrity. Amounts of Z-BOX A and Z-BOX B that are observed during liver failure in humans have profound effects on hepatic function when added to cultured liver cells or infused into healthy rats.

Therapeutic uses of animal biles in traditional Chinese medicine: an ethnopharmacological, biophysical chemical and medicinal review.

Forty-four different animal biles obtained from both invertebrates and vertebrates (including human bile) have been used for centuries for a host of maladies in traditional Chinese medicine (TCM) beginning with dog, ox and common carp biles approximately in the Zhou dynasty (c. 1046-256 BCE). Overall, different animal biles were prescribed principally for the treatment of liver, biliary, skin (including burns), gynecological and heart diseases, as well as diseases of the eyes, ears, nose, mouth and throat. We present an informed opinion of the clinical efficacy of the medicinal uses of the different animal biles based on their presently known principal chemical components which are mostly steroidal detergent-like molecules and the membrane lipids such as unesterified cholesterol and mixed phosphatidylcholines and sometimes sphingomyelin, as well as containing lipopigments derived from heme principally bilirubin glucuronides. All of the available information on the ethnopharmacological uses of biles in TCM were collated from the rich collection of ancient Chinese books on materia medica held in libraries in China and United States and the composition of various animal biles was based on rigorous separatory and advanced chemical identification techniques published since the mid-20(th) century collected via library (Harvard's Countway Library) and electronic searches (PubMed and Google Scholar). Our analysis of ethnomedical data and information on biliary chemistry shows that specific bile salts, as well as the common bile pigment bilirubin and its glucuronides plus the minor components of bile such as vitamins A, D, E, K, as well as melatonin (N-acetyl-5-methoxytryptamine) are salutary in improving liver function, dissolving gallstones, inhibiting bacterial and viral multiplication, promoting cardiac chronotropsim, as well as exhibiting anti-inflammatory, anti-pyretic, anti-oxidant, sedative, anti-convulsive, anti-allergic, anti-congestive, anti-diabetic and anti-spasmodic effects. Pig, wild boar and human biles diluted with alcohol were shown to form an artificial skin for burns and wounds one thousand years ago in the Tang dynasty (618-907 CE). Although various animal biles exhibit several generic effects in common, a number of biles appear to be advantageous for specific therapeutic indications. We attempt to understand these effects based on the pharmacology of individual components of bile as well as attempting to identify a variety of future research needs.

Anti-Genotoxic Potential of Bilirubin In Vivo: Damage to DNA in Hyperbilirubinemic Human and Animal Models

The bile pigment bilirubin is a known antioxidant and is associated with protection from cancer and cardiovascular disease (CVD) when present in too strong concentrations. Unconjugated bilirubin (UCB) might also possess anti-genotoxic potential by preventing oxidative damage to DNA. Moderately elevated bilirubin levels are found in individuals with Gilbert syndrome and more severe in the hyperbilirubinemic Gunn rat model. This study was therefore aimed to assess the levels of oxidative damage to DNA in Gilbert syndrome subjects and Gunn rats compared to matched controls. Seventy-six individuals (age- and sex-matched) were allocated into Gilbert syndrome (UCB ≥17.1 μmol/L; n = 38) or control groups (UCB < 17.1 μmol/L; n = 38). In addition, 40 Gunn rats were used to support the results of the human trial. Single-cell gel electrophoresis (SCGE) assay measuring standard conditions (strand breaks, apurinic/apyrimidinic sites) and formamidopyrimidine glycosylase (FPG)-sensitive sites was conducted in human peripheral blood mononuclear cells (PBMC) and rat PBMCs, colon, and hepatocytes. Furthermore, urinary 8-oxo-2'-deoxyguanosine (8oxodGuo, DNA oxidation) and 8-oxo-guanosine (8oxoGuo, RNA oxidation) were measured in humans. The Gilbert syndrome and Gunn rat groups had significantly higher UCB levels (P < 0.001) than the corresponding controls. No further differences in damage to DNA or RNA were detected between the two groups, except higher strand breaks (PBMCs) in Gunn rats when compared with controls. However, when demographic effects were analyzed, lower 8oxodGuo concentrations were detected in the human group with a BMI ≥25 kg/m(2) (1.70 ± 0.67 vs. 1.38 ± 0.43 nmol/mmol creatinine, P < 0.05), although this group showed lower UCB levels than normal weight subjects. This study suggests that the disease preventative effect of UCB is unrelated to DNA oxidation/strand breaks in human and animal models of hyperbilirubinaemia.

Promotive Effects of the Dietary Organic Germanium Poly-trans-[(2-carboxyethyl) germasesquioxane] (Ge-132) on the Secretion and Antioxidative Activity of Bile in Rodents

Poly-trans-[(2-carboxyethyl) germasesquioxane] (Ge-132) is the most common organic germanium compound. This compound has many physiological effects, which are mediated via the modulation of immune-system activation. The intake of dietary Ge-132 causes fecal color changes in humans, and we studied the mechanism of this in a rodent model. Male Wistar rats were given a diet containing 0.05% Ge-132 for two weeks and were compared with rats given a germanium free diet. The color of their feces and cecal contents changed from grayish-green to yellow in rats fed with Ge-132. The concentrations of stercobilin, a major fecal pigment, and total bile acids in cecal contents, were significantly increased by dietary Ge-132. Stercobilin is a metabolite of the bile pigment bilirubin. These results were produced by increases in bile components, such as bilirubin and bile acids, and showed that dietary Ge-132 promotes bile secretion into the intestine. Next, we administered Ge-132 (per os) to male rats at 50 mg/kg body weight per day for four days to reveal its effect on bile (and particularly on bilirubin). Bile juice samples were collected, and their bilirubin content and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were analyzed. The bilirubin level in the bile was significantly increased by the administration of Ge-132, and the DPPH radical scavenging activity of bile was also significantly increased. As the increases in these two factors were correlated, we supposed that the anti-oxidative properties of the bile of rats fed with Ge-132 were due to bilirubin glucuronides. Oral intake of Ge-132 also increased the mRNA expression of uridine diphosphate glucuronosyltransferase 1a1 (Ugt1a1) and bile acid coenzyme A: amino acid N-acyltransferase (Baat), which encode bile component conjugating enzymes for secretion. The acceleration of bile pigment secretion into the intestine as well as increases in the anti-oxidant activity of bilirubin was induced by oral intake of dietary Ge-132. It is suggested that the antioxidative effect of bile against oxidative stress occurs through radical trapping.

Bioenergetics of mitochondria of the liver with biliary atresia during prolonged starvation

L.),a representative of the class Cyclostomata, is a uniqueobject for studying the bioenergetics of liver mitochon-dria not only in the theoretical aspect but also in termsof clinical studies for the following reasons. Duringanadromous migrations in rivers (in our case, in theNeva River), lampreys switch off exogenous nutrition.This period, called synchrony, continues from Septem-ber to May. In May–June, lampreys as monocyclic ani-mals spawn and then die. Thus, cyclostomes provide arare opportunity to study the physiology and biochem-istry of the liver during multi-month starvation. In addi-tion, the liver of an adult lamprey lacks the gallbladderand bile ducts; as a result of biliary atresia (a fatal dis-ease of newborns), lamprey hepatocytes accumulatebile acids and bile pigments (bilirubin, biliverdin, andhemosiderin) [1]. It is known that cholestasis in humansis provoked by many drugs and is the result of manyliver pathologies [2]. In addition, during winter starva-tion, hepatocytes of lampreys (especially those ofmales) are filled with lipid drops [3]. The combinationof hepatic steatosis and cholestasis (steatocholestasis isa genetic metabolic liver disease widespread amongchildren [4]) makes lamprey liver an ideal naturalmodel for studying the bioenergetic of mitochondria inthese conditions, which are severe pathologies inhumans and a quite natural phase of the life cycle ofcyclostomes. During anadromous migration, lamprey liver almostdoes not contain glycogen, liver metabolism at this timeis solely anaerobic and is based on fatty acid oxidation[5]. Earlier, we showed that, after three- to four-monthstarvation in winter, the hepatocyte respiration of lam-preys reduces several times compared to the level char-acteristic of early migrants in autumn and in theprespawning period in spring [6]. The content of ade-nine nucleotides (in particular, ATP) in winter drasti-cally decreases, precisely corresponding to the respira-tory activity of hepatocytes. In approximately 25% ofexamined lampreys, the Atkinson energy charge (EC,[ATP] + 1/2 [ADP]/[ATP + ADP + AMP]) drops to crit-ically low values (0.2–0.3), which is characteristic ofcells in anabiosis, which was first described by us forhepatocytes of a vertebrate animal [7]. In the majorityof cells, EC was 0.5–0.6. At this potential value, cellscould survive but were incapable of growth and repro-duction. The goal of this work was to study the bioen-ergetic of isolated mitochondrial fractions of the lam-prey in winter during metabolic depression.Mitochondrial fractions were isolated in sucrose bythe conventional procedure [3]. In some cases, the iso-lation and incubation media were supplemented withbovine serum albumin (BSA). The mitochondrial respi-ration rates were measured with an LP-7 polarographequipped with a Clark electrode. The potential on theinner mitochondrial membrane was assessed bychanges in the fluorescence intensity (arb. units) of saf-ranine in a mitochondrial suspension with a ShimadzuRF-1501 spectrofluorometer (Shimadzu, Japan) at anexcitation wavelength of 485 nm and an emissionwavelength of 590 nm (Fig. 1). Mitochondria (0.5 mgprotein/ml) were added to a quartz cell filled an incuba-tion medium (3 ml) containing 250 mM sucrose, 3 mMTris-HCl (pH 7.3), 3 mM MgCl

Protective Response of the Ah Receptor to ANIT-Induced Biliary Epithelial Cell Toxicity in See-Through Medaka

The adaptive role of the aryl hydrocarbon receptor (Ah receptor or AHR) in protecting against disease-related conditions remains unclear in nonmammalian models, particularly teleosts. Therefore, this study focused on the potential role of AHR in response to biliary epithelial cell toxicity and hepatobiliary alteration in medaka. See-through medaka (STII strain) were exposed for 96 h using the biliary toxicant alpha-naphthylisothiocyanate (ANIT) as a reagent, and fish were evaluated daily using histological and ultrastructural analysis, and by imaging directly through the body wall of living fish. Brightfield and transmission electron microscopy showed that a single ANIT dose (40 mg/kg) specifically induced swelling and apoptosis of bile preductular epithelial cells (BPDECs) as early as 6 h after initial exposure. Following ANIT-induced BPDEC toxicity, in vivo imaging of STII medaka showed significant gallbladder discoloration from 48-72 h. Collectively, these pathologic data suggested that ANIT exposure resulted in acute hepatobiliary changes, lasting < 96 h following initial exposure. We then tested the potential role of AHR in response to ANIT-induced hepatobiliary alteration. Overall, we demonstrated that (1) transient AHR activation and cytochrome P450 1A (CYP1A) induction in livers occurred during ANIT-induced hepatobiliary impairment, (2) pretreatment with an AHR agonist partially protected against acute hepatobiliary alteration, and (3) using a luciferase-based reporter assay, the bile pigment bilirubin weakly activated mouse AHR and binding to medaka-specific CYP1A promoter, resulting in AHR element-driven transcription. Given that bile acids and pigments are present in mammalian and fish liver, these studies collectively suggest that bile-induced AHR activation may be conserved between teleosts and rodents.

Induction of Heme Oxygenase-1 In Vivo Suppresses NADPH Oxidase–Derived Oxidative Stress

Our previous studies suggest that heme oxygenase (HO)-1 induction and/or subsequent bilirubin generation in endothelial cells may suppress superoxide generation of from reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase. In this study, we examined the consequence of HO-1 induction in vivo on NADPH oxidase activity. Three doses of hemin (25 mg x kg(-1), IP, every 48 hours), with or without cotreatment with the HO inhibitor tin protoporphyrin-IX (15 mg x kg(-1), IP), were given to apolipoprotein E-deficient mice, which display vascular oxidative stress. Hemin treatment increased HO-1 expression and activity in aorta (undetectable at baseline) and kidney (by 3-fold) and significantly reduced both NADPH oxidase activity (by approximately 25% to 50%) and superoxide generation in situ. The increase in HO-1 activity and inhibition of NADPH oxidase activity by hemin were reversed by tin protoporphyrin-IX and were not associated with changes in Nox2 or Nox4 protein levels. Hemin also reduced plasma F(2)-isoprostane levels by 23%. The inhibition of NADPH oxidase activity by hemin in the aorta was mimicked by bilirubin in vitro (0.01 to 1 micromol/L). Bilirubin also concentration-dependently reduced NADPH oxidase-dependent superoxide production stimulated by angiotensin II in rat vascular smooth muscle cells and by phorbol 12-myristate 13-acetate in human neutrophil-like HL-60 cells. HO-1 overexpression by plasmid-mediated gene transfer in rat vascular smooth muscle cells decreased NADPH-stimulated superoxide production. Thus, systemic expression of HO-1 suppresses NADPH oxidase activity by mechanisms at least partly mediated by the bile pigment bilirubin, thereby reducing oxidative stress.

Interaction between bilirubin and sodium deoxycholate and their adsorption from mixed solutions on the surface of silica sorbents

The interaction between the bile pigment bilirubin and sodium deoxycholate is studied in aqueous buffer solutions at pH 7.4. It is established that bilirubin forms strong complexes with deoxycholate trimers. The complexation constant is determined by spectrophotometry. The adsorption of bilirubin and sodium deoxycholate from their mixed solutions on the surface of a hydrophilic and two hydrophobic silica sorbents is investigated. It is shown that bilirubin is adsorbed on the surface of all these sorbents only in the free state. Sodium deoxycholate is adsorbed in the forms of monomers and trimers. The affinity of all adsorbed particles is higher for hydrophobic silica sorbents. The binding constants of bilirubin, as well as monomers and trimers of deoxycholate, with the surfaces of all examined sorbents are determined.

Electronic absorption spectra and acid-base and ligand properties of alkyl-substituted biladiene-a,c

The influence of the nature of a solvating medium on the chromophore properties and stability of alkyl-substituted biladiene-a,c dihydrobromide, a synthetic analogue of a bile pigment bilirubin, was analyzed. The results of the spectrophotometric study of the protonation of a tetrapyrrol ligand and of the complex formation with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) acetates in DMF at 298.15 K were considered. Depending on the nature of a complex-forming cation and concentrations of reagents in solution the formation of complexes of three various types is possible: porphyrin-like (1:1), binuclear with different ligands (2:1), and binuclear biligand (2:2). The nature of metal cation renders essential influence on the formation of coordination polyhedra of the metal chelates with various structure.

BILIRUBIN SUPPRESSES NEOINTIMA FORMATION BY INTERACTING WITH THE RETINOBLASTOMA TUMOR SUPPRESSOR PROTEIN PATHWAY

O386* Aims: Induction of heme oxygenase 1 (HO-1) ameliorates the development of chronic allograft arteriosclerosis, which normally involves oxidative stress and vascular smooth muscle cell (VSMC) proliferation. Bilirubin and biliverdin, generated during heme catabolism by HO-1, are potent antioxidants that play a role in maintenance of homeostasis. Based on the clinical observation that healthy individuals with higher levels of bilirubin develop less arteriosclerosis, we hypothesized that the bile pigments would inhibit VSMC proliferation in vitro and neointima formation in vivo. We used balloon injury (BI) as a model of the neointimal proliferation seen in transplant arteriosclerosis. Methods: BI was performed in the left common carotid artery of congenitally hyperbilirubinemic Gunn rats and congenic wild-type Wistar rats. The artery was harvested two weeks after BI, and neointima formation was assessed by quantifying intima/media ratio and luminal cross-sectional area narrowing (LCAN). In vitro, proliferation of primary vascular smooth muscle cells (VSMC) was measured by 3H-thymidine incorporation in the presence or absence of bilirubin/ biliverdin. Cell cycle progression was monitored by DNA content analysis; apoptosis by the Annexin V binding assay. Protein levels were detected by western blot. Immuncytochemistry was performed using antibody directed against the retinoblastoma tumor suppressor protein (pRb). Results: BI mediated neointima formation was significantly reduced in hyperbilirubinemic Gunn rats (serum bilirubin levels: 12.0 ± 2.5 mg/dl) as compared to control Wistar rats (LCAN 0.18 vs. 0.44; p < 0.05). Systemic administration of biliverdin, the precursor of bilirubin, to normal rats also suppressed neointima proliferation (LCAN 0.29 vs. 0.43; p < 0.05). In vitro, bilirubin inhibited VSMC proliferation in a dose-dependent manner. Bilirubin (200 μM) arrested VSMC cell cycle progression at the G0/G1 phase, while it did not increase apoptosis (p=0.2816). Inhibition of cell cycle progression was mediated by reduced phosphorylation of p38 MAPK and c-Jun NH2-terminal kinase 1/2 (JNK 1/2), down-regulation of cdk2, cyclins D1, E and A, and the resulting decreased phosphorylation of pRb. In nuclear extracts, lower total levels of pRb were found in bilirubin treated VSMCs, consistent with the findings that a significant portion of pRb was kept in the cytosol after bilirubin treatment as assessed by immunocytochemistry. Further, bilirubin treatment reduced expression levels of the transcription factor YY1, a zinc finger DNA-binding transcription factor known to regulate the expression of genes with important functions during cell growth and differentiation. The effects of bilirubin were independent of HO-1 expression, as demonstrated in HO-1−/− VSMCs. Conclusions: Biliverdin and bilirubin suppress both BI induced neointima formation in vivo and VSMC proliferation in vitro. Our data suggest that bilirubin treatment inhibits VSMC growth by impaired activation of p38 and JNK 1/2, resulting in two events. Firstly, the inhibition of pRb phosphorylation impedes the release of transcription factors such as YY1 that are important for VSMC growth. Secondly, there is reduced expression of the transcription factor YY1 itself, resulting in a suppressed capacity to induce DNA synthesis and transcriptional activity. Thus, administration of the bile pigments bilirubin and biliverdin may have a beneficial effect on VSMC proliferation in chronic allograft arteriopathy and may become a potent strategy for the treatment of chronic rejection.

Is Low Serum Bilirubin an Independent Risk Factor for Coronary Artery Disease in Men but Not in Women?

For many years, the bile pigment bilirubin was considered to be only a toxic waste product formed during heme catabolism. Recent evidence, however, suggests that bilirubin acts as a potent physiologic antioxidant that may provide important protection against arteriosclerosis, coronary artery disease (CAD), and inflammation (1)(2)(3). The antioxidant capacity of bilirubin and its potent ability to scavenge peroxyl radicals have led to the concept that mildly increased circulatory bilirubin may have a physiologic function to protect against disease processes that involve oxygen and peroxyl radicals (4). Indeed, inverse correlations between the presence of CAD and total bilirubin concentrations in the circulation were reported recently in several independent studies (5)(6). Additionally, plasma bilirubin correlates inversely with several established risk factors for CAD, including smoking, increased LDL-cholesterol, diabetes, and obesity, but is directly proportional to the protective factor HDL-cholesterol (5)(7). The effect of bilirubin on the risk of cardiovascular disease is apparent in men (8) but is less clear in women (6)(9)(10). In the present study, we therefore examined the influence of gender on total bilirubin concentrations. All patients referred to the Department of Cardiology, University of Vienna, between August 1999 and September 2001 for whom clinical data were available were included in our study. Patients were divided in a CAD and a non-CAD group. The CAD group consisted of 544 patients (157 females and 387 males) with clinically relevant CAD. Clinically relevant CAD was defined as an exercise-induced ischemic ST-segment depression >0.1 mV (12%) (11) and/or a history of myocardial infarction (53%) or coronary intervention [coronary artery bypass (8%) or percutaneous transluminal coronary angioplasty (27%)]. In the non-CAD group (359 patients; 186 females and 173 males), the presence of CAD …

Detection of Biliverdin Reductase Activity

The conversion of biliverdin to the bile pigment bilirubin is catalyzed by biliverdin reductase, a cytosolic enzyme with two pH optima with different cofactors. The enzyme is assayed at pH 8.7 with NADPH as a cofactor and at 6.75 with NADH. The production of bilirubin is detected as described in this unit with a spectrophotometric assay. The enzyme can be qualitatively assayed by immunoblotting and changes in reductase isoform expression can be detected by two-dimensional electrophoresis.

Effects of pH on the absorption, emission and light scattering spectroscopy of bilirubin and xanthobilirubic acid in sodium taurocholate solution

Electronic absorption, differential absorption and emission spectra, as well as light scattering intensities, have been obtained for solutions of the bile pigment bilirubin in the presence of the bile salt sodium taurocholate over the pH range 5.0–8.0. Similar measurements were performed on the dipyrrinone analog compound xanthobilirubic acid. The results are interpreted in terms of hydrophobic solubilization of monomeric bilirubin at alkaline pH, and formation of hydrophobic mixed aggregates of pigment and bile salt at lower pH, with the size of the bilirubin aggregates increasing as the pH decreases. The data are consistent with a model of co-micellization of pigment and bile salt, and also suggest that the chemistry of these complexes is determined mainly by the structural properties of the tetrapyrrole.

Bilirubin sensitized photooxidation of human plasma low density lipoprotein

Previous investigations have shown that the bile pigment bilirubin can act as peroxyl radicals scavenger and transition metals trap, but also as a prooxidant, to erythrocyte ghost membranes through 102driven photooxidation. In the present study we examined the changes occurring in the lipoprotein particle following bilirubin-sensitized photooxidation of isolated plasma LDL. The oxidative stress resulted in increased TBA reactivity, diene formation, free cholesterol oxidation, apo B fragmentation and enhanced uptake of the modified particle by the mouse macrophage scavenger receptors as well as the decrease binding to the native B, E-receptor on fibroblasts. The marked increase in TBARS production in D20-enriched medium and the inhibition of lipid peroxidation of azide is consistent with singlet oxygen involvement in the oxidation process. The apo B-bound Cu2+ appears to become redox active during photooxidation since the presence of EDTA in the reaction mixture greatly reduced protein fragmentation. It was also found that BHT inhibited almost completely the lipid peroxidation, as determined by the TBA reaction but could not totally abolish the formation of 5 a-hydroxycholesterol, which is the main product formed by the direct attack of 102 on cholesterol. The results of this work strongly suggest that, through photooxidation by light-activated bilirubin, the lipoprotein particle may be modified in the blood stream as well, besides being modified in the well known oxidation site within the arterial wall. Our findings provide the rationale for extending these studies to clinical investigations, which aim at developing strategies for minimizing damage to arterial tissue following phototherapy of hyperbilirubinemic newborns or cancer patients after systemic administration of photosensitizers.

Bile Pigment Composition and Bilirubin Esterification in the Developing Chick

Bile Pigment Composition and Bilirubin Esterification in the Developing Chick

Azachlorins: Synthesis of a novel type of hydroporphyrins from the bile pigment bilirubin

AbstractAzachlorins rac‐10a,b, rac‐11, and rac‐16, a novel type of hydroporphinoid compounds, were synthesized from azaporphyrins 8 and 13 by regioselective cycloaddition of singlet oxygen and further transformation by amide acetal Claisen rearrangement. The azaporphyrins are readily accessible from the naturally occurring bile pigment bilirubin (5). The photophysical properties of the azachlorins recommend these chlorin derivatives as potential photosensitizers for Photodynamic Therapy (PDT).

Chromosomal Localization of the Human Heme Oxygenase Genes: Heme Oxygenase-1 (HMOX1) Maps to Chromosome 22q12 and Heme Oxygenase-2 (HMOX2) Maps to Chromosome 16p13.3

Heme oxygenase catalyzes the oxidation of heme to biliverdin, the precursor of the bile pigment bilirubin, and carbon monoxide, a putative neurotransmitter. We have employed polymerase chain reaction and fluorescence in situ hybridization to determine the chromosome localization of the genes coding for the two known heme oxygenase isozymes. Heme oxygenase-1 (HMOX1), the inducible form, was localized to human chromosome 22q12, while heme oxygenase-2 (HMOX2), the constitutive form, was localized to chromosome 16p13.3.

Synergistic interaction between vitamin E and the bile pigments bilirubin and biliverdin

The oxidation of soybean phosphatidylcholine (PC) liposomes initiated with a lipid-soluble azo compound within the liposomal membranes has been studied in the absence and presence of membrane-bound vitamin E and water-soluble bile pigments. In the absence of vitamin E, lipid peroxidation proceeded linearly and without delay. Low micromolar amounts of bilirubin ditaurine (BR-DT, a model compound of conjugated bilirubin) or biliverdin (BV) inhibited the oxidation of PC significantly and in a concentration-dependent way. In contrast, neither taurine, ascorbic acid nor reduced glutathione inhibited significantly under these conditions. Both bile pigments were consumed during their protective action. Vitamin E incorporated into the liposomal membranes suppressed the oxidation initially almost completely, thereby producing an induction period. In the combined presence of vitamin E and either of the two bile pigments at 10 μM each, this induction period was increased by at least 200%. In contrast, when 10 μM vitamin E was combined with an equimolar concentration of reduced glutathione, the induction period increased by only about 30%. BR-DT and BV both spared the consumption of vitamin E during the oxidation of PC liposomes. These results demonstrate that conjugated bilirubin and BV located in the aqueous phase can directly scavenge lipid radicals to some extent. Furthermore, both bile pigments can act synergistically with membrane-bound vitamin E to prevent lipid peroxidation initiated in the lipid phase, most likely through regeneration of the vitamin from its chromanoxyl radical.

Epidermal pigmentation and liver coloration in the southern hemisphere lamprey,Geotria austral isGray

Abstract During metamorphosis from ammocoete to macrophthalmia in the southern hemisphere lamprey, Geotria australis Gray, 2 blue‐green dorso‐lateral stripes develop along the length of the body. These stripes are retained during the marine parasitic feeding stage and are conspicuous when the adults enter fresh water at the beginning of the spawning migration. They disappear as the upstream migration progresses. The blue‐green coloration is present in the epidermal mucous layer and results from the deposition of biliverdin, a bile pigment produced as a breakdown product of haemoglobin. Liver colour changes during the upstream spawning migration. At the beginning of the migration liver colour is predominantly brown or brick‐red, and livers contain the bile pigment bilirubin. Lampreys collected 50 km from the sea had predominantly green livers owing to the presence of the bile pigment biliverdin, and gonad development had not increased from that observed at the beginning of the spawning migration. Pouched males contained dark green livers with biliverdin as the predominant pigment.