ABSTRACT
AZD7969 is a potent inhibitor of glycogen synthase kinase 3 (GSK3ß), which is a multifunctional serine/threonine kinase that negatively regulates the Wnt/ß-catenin signaling pathway. Treatment of rats and dogs with AZD7969 for periods of up to 4 weeks resulted in a number of changes, the most significant of which was a dose-dependent, and treatment-related, increase in proliferation in a number of tissues that was thought to arise from derepression of Wnt/ß-catenin signaling in the stem cell compartment. Phenotypically, this resulted in hyperplasia that either maintained normal tissue architecture in the gastrointestinal tract, liver, kidney, and adrenals or effaced normal tissue architecture within the bones, incisor teeth, and femorotibial joint. In addition to these changes, we noted a treatment-related increase in iron loading in the liver and proximal small intestines. This off-target effect was robust, potent, and occurred in both dogs and rats suggesting that AZD7969 might be a useful tool compound to study iron storage disorders in the laboratory.
Subject(s)
Enzyme Inhibitors/toxicity , Glycogen Synthase Kinase 3/antagonists & inhibitors , Stem Cells/drug effects , Animals , Blood Cell Count , Body Weight/drug effects , Cell Proliferation/drug effects , Dogs , Dose-Response Relationship, Drug , Eating/drug effects , Female , Intestine, Small/metabolism , Intestine, Small/pathology , Iron/metabolism , Liver/metabolism , Liver/pathology , Male , Rats , Stem Cells/pathologyABSTRACT
Cholangiofibrosis is a structural anomaly that precedes the development of cholangiocarcinoma in some rodent models. In this article, the authors examine the contribution of the epithelial and mesenchymal cells in the pathogenesis of this complex lesion. Furan was administered to rats by gavage in corn oil at 30 mg/kg b.w. (five daily doses per week) and livers were sampled between eight hr to three months. Characteristically the administration of furan caused centrilobular injury, and restoration was accomplished by proliferation of hepatocytes. Some areas of the liver were, however, more severely affected, and here, injury extended into portal and capsular areas, which resulted in a rapid proliferation of ductular cells that extended into the parenchyma accompanied by a subtype of liver fibroblasts. These ductules either differentiated into hepatocytes, with loss of the associated fibroblasts, or progressed to form tortuous ductular structures that replaced much of the parenchyma, leading to cholangiofibrosis. Although it is unclear what determines the difference in the hepatic response, a loss of micro-environmental cues that instigate hepatocyte differentiation and termination of the hepatocyte stem cell repair response may be perturbed by continual furan administration that results in an irreversible expansile lesion that may mimic the features of cholangiocarcinoma.
Subject(s)
Bile Ducts/pathology , Carcinogens/toxicity , Chemical and Drug Induced Liver Injury/pathology , Furans/toxicity , Liver Cirrhosis, Experimental/pathology , Administration, Oral , Animals , Bile Ducts/drug effects , Carcinogens/administration & dosage , Cell Proliferation/drug effects , Disease Progression , Epithelial Cells , Furans/administration & dosage , Hepatocytes/pathology , Immunohistochemistry , Liver/drug effects , Liver/pathology , Liver Cirrhosis, Experimental/chemically induced , Male , Rats , Rats, Sprague-DawleyABSTRACT
Furan is a potent cholangiocarcinogen in rat by an as yet undefined mechanism. The risk to man remains unclear. Using a time-course stop study design, we have investigated the potential of furan to induce oxidative stress and DNA damage associated with inflammatory and regenerative responses in rat liver. Furan was administered via oral gavage (30 mg/kg b.w. 5 daily doses per week), and livers were analyzed at time points between eight hr and three months. A one-month recovery group previously treated for three months was also included. There was a marked association between CYP2E1 expression and DNA oxidation (8-oxo-dG) in areas of centrilobular hepatocyte necrosis seen after a single dose. After one-month recovery from three-month treatment, 8-oxo-dG was still observed in areas of furan-induced cholangiofibrosis. Furan-induced changes in the expression of various genes associated with oxidative stress, DNA damage, and cell cycle control were identified during treatment and recovery. We propose that furan-induced cholangiocarcinomas emerge from areas of cholangiofibrosis as a result of a combination of chronic, persistent indirect damage to DNA through oxygen radicals coupled with persistent proliferative signals, including loss of connexin 32, that act to convert this DNA damage to fixed mutations.
Subject(s)
Carcinogens/toxicity , Cell Proliferation/drug effects , DNA Damage , Furans/toxicity , Gene Expression/drug effects , Liver/drug effects , Oxidative Stress , 8-Hydroxy-2'-Deoxyguanosine , Animals , Bile Ducts/metabolism , Bile Ducts/pathology , Carcinogenicity Tests , Cytochrome P-450 CYP2E1/metabolism , Deoxyguanosine/analogs & derivatives , Deoxyguanosine/metabolism , Dose-Response Relationship, Drug , Hepatocytes/drug effects , Hepatocytes/enzymology , Hepatocytes/metabolism , Liver/metabolism , Liver/pathology , Liver Cirrhosis/chemically induced , Liver Cirrhosis/pathology , Male , Metaplasia/chemically induced , Metaplasia/pathology , RatsABSTRACT
The localisation of IgE to mast cells of rats infested with Nippostrongylus brasiliensis has been studied in an attempt to find a fixation procedure which will best preserve (a) the antigenicity of IgE for immunocytochemical demonstration, and (b) the histochemical staining properties of mast cells. A fixative comprising Carnoy's fluid and picric acid (CPA) best fulfilled these criteria, allowing localisation of IgE to both the plasma membrane and cytoplasm of mucosal mast cells of rat small intestine, but only to the plasma membrane of connective tissue mast cells of rat tongue. Formaldehyde-containing fixatives prevented labelling of IgE in the cytoplasm of mucosal mast cells.
