Dose-dependent enhancing effects of quinacrine on induction of preneoplastic glutathione S-transferase placental form positive liver cell foci in male F344 rats

A brain aggregate model gives new insights into the pathobiology and treatment of prion diseases

Brain aggregates (BrnAggs) derived from fetal mouse brains contain mature neurons and glial cells. We determined that BrnAggs are consistently infected with Rocky Mountain Laboratory scrapie strain prions and produce increasing levels of the pathogenic form of the prion protein (PrP). Their abundant dendrites undergo degeneration shortly after prion infection. Treatment of prion-infected BrnAggs with drugs, such as a γ-secretase inhibitors and quinacrine (Qa), which stop PrP formation and dendritic degeneration, mirrors the results from rodent studies. Because PrP is trafficked into lysosomes by endocytosis and autophagosomes by phagocytosis in neurons of prion strain-infected BrnAggs, we studied the effects of drugs that modulate subcellular trafficking. Rapamycin (Rap), which activates autophagy, markedly increased light-chain 3-II (LC3-II)-positive autophagosomes and cathepsin D-positive lysosomes in BrnAggs but could not eliminate the intracellular PrP within them. Adding Qa to Rap markedly reduced the number of LC3-II-positive autolysosomes. Rap + Qa created a competition between Rap increasing and Qa decreasing LC3-II. Rapamycin + Qa decreased total PrP by 56% compared with that of Qa alone, which reduced PrP by 37% relative to Rap alone. We conclude that the decrease was dominated by the ability of Qa to decrease the formation of PrP. Therefore, BrnAggs provide an efficient in vitro tool for screening drug therapies and studying the complex biology of prions.

Enhancing effects of quinacrine on development of hepatopancreatic lesions in N-nitrosobis(2-oxopropyl)amine-initiated hamsters

The modifying effects of quinacrine administration during the post-initiation phase of carcinogenesis were investigated in hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Female Syrian hamsters were given three weekly s.c. injections of BOP at a dose of 10 mg/kg and then 300 or 100 ppm quinacrine in their diet for 37 weeks. Additional groups of animals received the BOP injection alone, or only the 300 ppm quinacrine treatment as BOP-negative controls. At week 40 of the experiment, all surviving animals were killed and development of proliferative lesions was assessed histopathologically. The multiplicity of pancreatic adenocarcinomas and dysplastic lesions per hamster was significantly higher (P<0.01 and P<0.05) in the BOP/Q100 group (1.92 and 1.78) than in the BOP-alone group (1.07 and 0.79). The incidence of hepatocellular adenomas plus carcinomas was also significantly elevated (P<0.05) in the BOP/Q300 and BOP/Q100 groups. In contrast, the multiplicity of lung adenomas plus adenocarcinomas was significantly decreased (P<0.05) by the Q300 treatment. Neither the incidence nor the multiplicity of renal cell tumors (adenomas and carcinomas) or nephroblastomas significantly differed between the BOP-treated groups. Electron microscopic examination revealed an abundance of myeloid lamellar bodies filling the cytoplasm of hepatocytes and pancreatic ductular and acinar cells, and epithelial cells of the gallbladder in the quinacrine-treated animals, the degree being dose-dependent. Our results indicate that quinacrine enhances pancreatic and hepatic carcinogenesis in hamsters induced by BOP.

22-Oxa-1,25(OH)2vitamin D3, a synthetic analogue of vitamin D3, has no promoting activity in a rat liver medium-term bioassay

Modifying effects of 22-oxa-1,25(OH)2vitamin D3(OCT), a synthetic analogue of vitamin D3, were evaluated in a liver medium-term bioassay using glutathione S-transferase placental form (GST-P)-positive foci and 5-bromo-2'-deoxyuridine (BrdU) labeling to give an index of DNA synthesis. F344 rats were given a single intraperitoneal injection of diethylnitrosamine (200 mg/kg body wt.) and subjected to two-thirds partial hepatectomy at week 3. Commencing 2 weeks from the start, 500 p.p.m. phenobarbital sodium and/or basal diet were fed to the rats for 6 weeks, at the same time as OCT and/or propylene glycol as the vehicle injected intraperitoneally 5 times a week. OCT demonstrated no promoting activity for rat hepatocarcinogenesis, and, in fact, showed a tendency to decrease the area per unit area of (GST-P)-positive foci in the livers of rats fed 500 p.p.m. phenobarbital sodium. However, intergroup differences in areas and numbers per unit area as well as in BrdU labeling indices were not statistically significant.