Diethylstilbestrol-induced jaundice in the Chinese and Armenian hamster

Human UDP-Glucuronosyltransferases 1A1, 1A3, 1A9, 2B4 and 2B7 are Inhibited by Diethylstilbestrol

Inhibition of UDP-glucuronosyltransferases (UGTs) can result in many undesired side effects. Diethylstilbestrol (DES), a synthetic oestrogen famous for its multiple toxicities, was once widely administered to women in high dosages and now still gains application in clinics. This study investigated in vitro inhibitory effects of DES on catalytic activities of human UGTs, aiming at disclosing new potential toxic mechanisms on the basis of interactions between DES and metabolizing enzymes. DES (10 μM) could decrease activities of UGT1A1, 1A3, 1A9, 2B4 and 2B7 in catalysing 4-methylumbelliferone (4-Mu) glucuronidation. Further kinetic analyses showed that inhibition of these UGTs followed competitive (UGT1A1 and 1A9), mixed (UGT1A3 and 2B4) and non-competitive (UGT2B7) mechanisms, with K_i values ranging from 0.91 to 4.1 μM. The inhibition potentials of UGT1A9 and 2B7 in human liver microsomes (HLM) were further tested by employing propofol and zidovudine as probe substrates, respectively. The inhibition of human liver microsomal UGT1A9 followed mixed mechanism, with the K_i value of 3.5 μM and α of 4.1. On the other hand, DES displayed non-competitive inhibition against UGT2B7 in HLM, with the K_i value of 9.8 μM. The risks of in vivo inhibition of human UGTs were also predicted by calculation of plasma C/K_i values. Results suggest that DES can trigger in vivo inhibition of UGT1A1, 1A3, 1A9, 2B4 and 2B7 after the intravenous administration in high doses.

Drug-induced steatohepatitis

Drugs rarely cause steatohepatitis, but amiodarone, perhexiline, and DH, have unequivocally been found to independently induce the histologic picture of alcoholic liver disease or NASH. All three agents have similar pathogenetic mechanisms of hepatotoxicity, targeting mitochondrial ATP production and fatty acid catabolism. Other drugs that occasionally cause steatohepatitis, most importantly steroid hormones, likely exacerbate the pathogenetic mechanisms leading to NASH. Similar to NASH, lipid peroxidation resulting from mitochondrial injury may account for all of the histologic findings in drug-induced steatohepatitis. Further research should determine the mechanisms by which drug-induced steatosis, a benign lesion, evolves to steatohepatitis and progressive fibrosis.

Estrogen induces cytokeratin aggregation in primary cultures of Armenian hamster hepatocytes

The effect of estrogen administration to cultured Armenian hamster was studied. Isolated Armenian hamster hepatocytes were cultured in RPMI medium supplemented with beta-estradiol (E2). Beta-estradiol treatment for 24-48 hr induced cytoplasmic inclusion bodies which by immunocytochemistry were positive for cytokeratin (CK) 8, CK 18, and ubiquitin but negative for CK 7 and CK 19. These inclusion bodies appeared as filamentous tangles or amorphous aggregates when observed by electron microscopy. F-actin, tubulin, and desmosomes were not influenced by the presence of the inclusion bodies. Addition of ethanol to culture medium increased the incidence of the inclusion formation. In combination with 0.5% ethanol 1 microM of E2 induced five to six times more inclusion bodies, while the number of inclusion bodies decreased when epidermal growth factor (EGF) was added to the medium in combination with E2. This reduction effect was nullified by treatment with anti-EGF receptor antibody. These findings suggest that E2 treatment to Armenian hamster hepatocytes in vitro induces Mallory body-like inclusions whose incidence can be influenced by addition of ethanol or EGF to the culture medium.

Estrogen-induced hepatic toxicity and hepatic cancer: differences between two closely related hamster species

AIMS/BACKGROUND

Estrogen is known to affect hepatobiliary function; however, it is unusual for high serum levels of estrogen to actually result in clinically detectable hyperbilirubinemia. Women affected by cholestatic jaundice during pregnancy share this genetic susceptibility with two Cricetulus hamsters, the Armenian hamster (Cricetulus migratorius) and the Chinese hamster (Cricetulus griseus). Nevertheless, the pathophysiologic process responsible for this estrogen induced icterus may be different in women and hamsters. The present study compares various facets of estrogen-induced icterus in these two closely related hamsters.

METHODS

Hamsters were injected with various estrogens and the acute and chronic effects on liver were monitored by measuring changes in serum constituents and by observing changes in hepatic structure as seen grossly and by light and electron microscopy.

RESULTS

In previous studies, hepatic tumors developed in most Armenian hamsters after chronic estrogen treatment, but in the present study, the livers of Chinese hamsters were remarkably free of neoplastic change under similar conditions. Also, when compared with the responses in the Armenian hamsters, signs of hepatic destruction and regeneration were less prevalent in estrogen-treated Chinese hamsters, and they were less susceptible to the effects of estrogen (because larger doses of estrogen were required to produce icterus and the bilirubin levels were lower and of shorter duration). In contrast to the findings in Armenian hamsters, bile canaliculi were severely affected in livers of estrogen-treated Chinese hamsters, and hepatic microvesicular steatosis, indicative of an unusual lipodystrophy caused by estrogen, was prominent. An additional lesion peculiar to the Chinese hamster was striking sinusoidal dilatation, which may be analogous to the oral contraceptive-induced sinusoidal dilatation in humans.

CONCLUSIONS

Although these two hamster species are genetically similar, the genes activated by the estrogen receptor show remarkable heterogeneity when their respective livers are examined. Comparisons within these species may provide information about the specific gene activation responsible for particular pathologic events.

The Mallory body: morphological, clinical and experimental studies (Part 1 of a literature survey)

To aid understanding of markers of disease and predictors of outcome in alcohol-exposed systems, we undertook a literature survey of more than 700 articles to view the morphological characteristics and the clinical and experimental epidemiology of the Mallory body. Mallory bodies are filaments of intermediate diameter that contain intermediate filament components (e.g., cytokeratins) observable by conventional light microscopy or immunohistochemical methods, identical in structure regardless of initiating factors or putative pathogenesis. Although three morphological types can be identified under electron microscopy (with fibrillar structure parallel, random or absent), they remain stereotypical manifestations of hepatocyte injury. A summary of the conditions associated with Mallory bodies in the literature and their validity and potential etiological relationships is presented and discussed, including estimates on the combined light microscopic and immunohistochemical prevalences and kinetics. Emphasis is placed on proper confounder control (in particular, alcohol history), which is highly essential but often inadequate. These conditions include (mean prevalence of Mallory bodies in parentheses): Indian childhood cirrhosis (73%), alcoholic hepatitis (65%), alcoholic cirrhosis (51%), Wilson's disease (25%), primary biliary cirrhosis (24%), nonalcoholic cirrhosis (24%), hepatocellular carcinoma (23%), morbid obesity (8%) and intestinal bypass surgery (6%). Studies in alcoholic hepatitis strongly suggest a hit-and-run effect of alcohol, whereas other chronic liver diseases show evidence of gradual increase in prevalence of Mallory bodies with severity of hepatic pathology. Mallory bodies in cirrhosis do not imply alcoholic pathogenesis. Obesity, however, is associated with alcoholism and diabetes, and Mallory bodies are only present in diabetic patients if alcoholism or obesity complicates the condition. In addition, case studies on diseases in which Mallory bodies have been identified, along with pharmacological side effects and experimental induction of Mallory bodies by various antimitotic and oncogenic chemicals, are presented. Mallory bodies occur only sporadically in abetalipoproteinemia, von Gierke's disease and focal nodular hyperplasia and during hepatitis due to calcium antagonists or perhexiline maleate. Other conditions and clinical drug side effects are still putative. Finally, a variety of experimental drugs have been developed that cause Mallory body formation, but markedly different cell dynamics and metabolic pathways may raise questions about the relevance of such animal models for human Mallory body formation. In conclusion, the Mallory body is indicative but not pathognomonic of alcohol involvement. A discussion on theories of development and pathological significance transcending the clinical frameworks will be presented in a future paper.

Serum amyloid-P component of the Armenian hamster: gene structure and comparison with structure and expression of the SAP gene from Syrian hamster

Serum amyloid P (SAP), a phylogenetically conserved pentraxin, is an integral component of all amyloid deposits. Regulation of expression of SAP gene expression is quite different in two related hamster species. In Syrian hamsters, the resting serum levels of SAP are determined by gender, and the direction of alteration following inflammation is divergent. In Armenian hamsters, SAP is not a prominent acute-phase reactant and there is no gender dimorphism of expression. The structure and expression of the SAP gene of the Armenian hamsters was investigated by isolation of genomic clones, nucleotide sequence analysis, and RNA studies. The gene structure of Armenian hamster SAP is similar to the genes of all other pentraxins studied. While the upstream regions of the SAP genes of Syrian and Armenian hamsters are quite similar, important differences in potential enhancer sites have been recognized by comparing the corresponding sequences of SAP genes from both species. Little alteration in hepatic levels of transcripts encoding SAP or CRP, the other pentraxin, were noted following administration of lipopolysaccharide to Armenian hamsters. This relative lack of response occurred despite a marked acute phase reaction documented for serum amyloid A mRNA levels.

Tamoxifen prevents induction of hepatic neoplasia by zeranol, an estrogenic food contaminant

Zeranol (alpha-zearalanol) is a beta-resorcylic acid lactone (RAL) that has estrogen activity. It is synthesized by molds and is difficult to avoid in human food products. We tested the ability of this mycoestrogen to damage the liver of the Armenian hamster, a rodent that is especially sensitive to hepatotoxic effects of exogenous estrogens. Zeranol induced acute hepatotoxicity and, subsequently, hepatic carcinogenesis; both effects were blocked by tamoxifen, suggesting estrogen receptor mediation. Because zeranol is acting alone as a primary initiator of hepatic neoplasms, this model provides an unusual opportunity to study the pathogenesis of estrogen-initiated tumorigenesis.

Alcoholic liver disease: pathologic, pathogenetic and clinical aspects

Alcoholic liver disease includes steatosis, alcoholic hepatitis and cirrhosis. Other liver diseases of genetic origin, but with a curious association with alcohol intake, are hemochromatosis and porphyria cutanea tarda. The attribution of chronic hepatitis to alcohol intake remains speculative, and the association may reflect hepatitis C infection. Hepatic injury attributed to alcohol includes the changes reported in the fetal alcohol syndrome. Steatosis, the characteristic consequence of excess alcohol intake, is usually macrovesicular and rarely microvesicular. Acute intrahepatic cholestasis, which in rare instances accompanies steatosis, must be distinguished from other causes of intrahepatic cholestasis (e.g., drug-induced) and from mechanical obstruction of the intrahepatic bile ducts (e.g., pancreatitis, choledocholithiasis) before being accepted. Alcoholic hepatitis (steatonecrosis) is characterized by a constellation of lesions: steatosis, Mallory bodies (with or without a neutrophilic inflammatory response), megamitochondria, occlusive lesions of terminal hepatic venules, and a lattice-like pattern of pericellular fibrosis. All these lesions mainly affect zone 3 of the hepatic acinus. Other changes, observed at the ultrastructural level, are of importance in progression of the disease. They include widespread cytoplasmic shedding, and capillarization and defenestration of sinusoids. Progressive fibrosis complicating alcoholic hepatitis eventually leads to cirrhosis that is typically micronodular but can evolve to a mixed or macronodular pattern. Hepatocellular carcinoma occurs in 5 to 15% of patients with alcoholic liver disease. The clinical syndrome of alcoholic liver disease is the result of three factors--parenchymal insufficiency, portal hypertension and the clinical consequences of extrahepatic damage produced by alcohol. At the several phases of the life history of alcoholic liver disease, the individual factors play a different role. The clinical manifestations of alcoholic steatosis are mainly extrahepatic in origin. Those of alcoholic hepatitis reflect mainly parenchymal insufficiency and those of cirrhosis are mainly those of portal hypertension. Alcoholic liver injury appears to be generated by the effects of ethanol metabolism and the toxic effects of acetaldehyde, perhaps the immune responses to alcohol- or acetaldehyde-altered proteins, and questionably enhanced by viral hepatitis. Alcoholic hepatitis may be mimicked histologically, and to a varying degree clinically, by a number of conditions (obesity, diabetes, several drug-induced injuries, jejunoileal bypass, and related "shortcircuiting" of the bowel). Perhaps the most important facet of the hepatotoxicity of alcohol is its enhancement of the effects of a number of other hepatotoxic agents, among which acetaminophen is the prime example.

Estrogen induction of hepatocellular carcinomas in Armenian hamsters

Liver tumors were found in most Armenian hamsters (Cricetulus migratorius) injected with on 15-mg pellet of diethylstilbestrol. The tumors were detectable as early as 1 1/2 mo after diethylstilbestrol administration and were usually present as multiple nodules that progressively increased in size. Histologically, the multicentric neoplasms were all hepatocellular carcinomas of varied degrees of differentiation and frequently (42.8%) contained Mallory bodies; preneoplastic lesions were not observed. This hepatocellular carcinoma hamster model is unique because estrogen alone without any other known mutagen is responsible for induction of hepatocellular carcinoma.

Biotransformation, estrogenicity, and steroid structure as determinants of dysmorphogenic and generalized embryotoxic effects of steroidal and nonsteroidal estrogens

A series of nine chemicals of varying structure and estrogenicity was investigated for biochemical determinants of their relative capacities to alter normal embryonic growth and developmental patterns during organogenesis in rats. In order to circumvent the potentially confounding influences of maternal factors, the direct effects of steroidal and nonsteroidal estrogens on cultured whole embryos were compared at concentrations producing readily measurable embryotoxicity but low embryolethality (2-20%). Nonsteroidal estrogens included were diethylstilbestrol (DES), hexestrol (HES), E,E-dienestrol (alpha-DIES), and tamoxifen (TAM). Steroidal estrogens were estradiol 17 beta (E2), estrone (E1), and 17 alpha-ethinylestradiol 17 beta (EE). For comparative purposes, the effects of two essentially nonestrogenic phenols, Z,Z-dienestrol (beta-DIES) and phenol, were also studied. TAM, a weak estrogen which also exhibits antiestrogenic properties, was studied for possible interactive effects with potent estrogens. Prosencephalic hypoplasia was the abnormality most consistently observed and was elicited by each of the chemicals investigated. Embryotoxicity was neither attenuated by TAM nor related to estrogenic potency or steroidal structure, but was strongly and unpredictably influenced by biotransformational determinants. Presence of a cytochrome P450-dependent oxidizing system in the culture medium resulted in marked increases in embryotoxicity of E1, E2, and phenol, only minor increases for beta-DIES and alpha-DIES, but in strikingly decreased effects of EE, TAM, and HES. It produced no statistically significant differences in effects of DES. The results obtained were compatible with the concept that effects of these agents on growth and development during the earlier stages of organogenesis are independent of steroid structure or estrogenic activity but strongly dependent upon pathways and rates of biotransformation of some (but not all) of the parent chemicals.

Alcohollike liver disease in nonalcoholics. A clinical and histologic comparison with alcohol-induced liver injury

Individuals who deny alcohol consumption may develop liver injury that histologically resembles the liver injury found in alcoholic patients. To determine whether any clinical or histologic features distinguish alcoholic and nonalcoholic subjects with "alcohollike" liver injury, the clinical records and liver biopsy specimens of 68 alcoholic and 39 nonalcoholic patients with alcohollike injury on liver biopsy were compared. The clinical and biochemical features of the two groups differed significantly. Alcoholism was associated with more severe clinical and biochemical manifestations of liver disease. However, there was considerable overlap among histologic features of the two clinically defined groups. Based on histology alone, alcoholic and nonalcoholic patients were often indistinguishable. The observations suggest that the clinical differences between the alcoholic and non-alcoholic patients cannot be attributed to qualitative or quantitative differences in liver histology. On the other hand, histologic similarities between the two groups raise the possibility that a shared condition, perhaps nutritional or hormonal, is responsible for the histologic expression of alcohollike injury in both groups.

Drug-induced cholestasis

Intrahepatic cholestasis, defined as arrested bile flow, mimics extrahepatic obstruction in its biochemical, clinical and morphological features. It may be due to hepatocyte lesions of which there are three types, termed canalicular, hepatocanalicular and hepatocellular, respectively; or it may be due to ductal lesions at the level of the cholangiole or portal or septal ducts. Defective bile flow due to hepatic lesions reflects abnormal modification of the ductular bile. Defective formation of canalicular bile may involve bile acid-dependent or independent flow. It appears to result most importantly from defective secretion of bile acid-dependent flow secondary to defective uptake from sinusoidal blood, defective transcellular transport and defective secretion; or from regurgitation of secreted bile via leaky tight junctions. An independent defect in bile acid-independent flow is less clear. Defective flow of bile along the canaliculus may reflect increased viscosity and impaired canalicular contractility secondary to injury of the pericanalicular microfibrillar network. Impaired flow beyond the canaliculus may result from ductal injury. Sites of lesions that contribute to cholestasis include the sinusoidal and canalicular plasma membrane, the pericanalicular network and the tight junction and, less certainly, microtubules and microfilaments and Golgi apparatus. A number of drugs that lead to cholestasis have been found to lead to injury at one or more of these sites. Other agents (alpha-naphthylisothiocyanate, methylenedianiline, contaminated rapeseed oil, paraquat) lead to ductal injury resulting in cholestasis. Reports of inspissated casts in ductules (benoxaprofen jaundice) and injury to the major excretory tree (5-fluorouridine after hepatic artery infusion) have led to other forms of ductal cholestasis. Most instances of drug-induced cholestasis present as acute, transient illness, although important chronic forms also occur. The clinical features include the reflection of the cholestasis (pruritus, jaundice), systemic manifestations and extrahepatic organ involvement. While nearly all classes of medicinal agents include some that can lead to cholestasis, there are differences among the various categories. Phenothiazines and related antipsychotic and 'tranquillizer' drugs characteristically lead to cholestatic hepatic injury. The tricyclic antidepressants may lead to cholestatic or hepatocellular injury.(ABSTRACT TRUNCATED AT 400 WORDS)