Comparative genomic analysis of Fischer F344 rat livers exposed for 90 days to 3-methylfuran or its parental compound furan.

Furan is a naturally forming compound found in heat-processed foods such as coffee, canned meats, and jarred baby food. It is concurrently found with analogues including 2-methylfuran (2-MF) and 3-methylfuran (3-MF), and toxicity studies demonstrate all are potent liver toxins. Toxicity studies found 3-MF is more toxic than either furan, or 2-MF. The present analysis assesses the transcriptional response in liver samples taken from male Fischer (F344) rats exposed to furan or 3-MF from 0 to 2.0 and 0-1.0 mg/kg bw/day, respectively, for 90 days. Transcriptional analyses found decreased liver function and fatty acid metabolism are common responses to both furan and 3-MF exposure. Furan liver injury promotes a ductular reaction through Hippo and TGFB signalling, which combined with increased immune response results in ameliorating perturbed bile acid homeostasis in treated rats. Failure to activate these pathways in 3-MF exposed rats and decreased p53 activity leads to cholestasis, and increased toxicity. Finally, BMD analysis indicate many of the most sensitive pathways affected by furan and 3-MF exposure relate to metabolism - malate dehydrogenase and glucose metabolism with BMDLs of 0.03 and 0.01 mg/kg bw/day for furan and 3-MF exposure, respectively, which agrees with BMDLs previously reported for apical and microarray data.

Genomic analysis of Fisher F344 rat kidneys from a reproductive study following dietary ochratoxin A exposure.

Ochratoxin A (OTA) is a mycotoxin produced by species of Penicillium and Aspergillus, and is found in many commodities including cereal grains, nuts, and coffee. OTA is a renal carcinogen and nephrotoxin at high concentrations, targeting the proximal tubules. This study uses transcriptomics and the previously reported apical data (Bondy et al., 2021) to infer mode-of-action of OTA toxicity in male and female rats exposed to low doses of OTA in utero and throughout development. Our findings support a male-specific activation of the innate and adaptive immune responses in F1 pups to OTA exposure. This was not found in the female F1 pups, and may be due to female-specific increased p38 activity and VDR signaling. Differentially expressed genes related to karyomegaly, MAPK activity, and immune activation appears to develop from in utero exposure to OTA whereas those related to decreased kidney and liver function, and changes to reproductive pathways occur in both rat generations. Together, these transcriptional results confirm that dietary exposure to OTA causes renal toxicity as well as alterations to hepatic and reproductive pathways in rats. In utero exposure of rats to OTA results in sex-specific alterations in immune response pathways, VDR signaling, and p38 activity.

A 13-week subchronic toxicity study of 2-(l-menthoxy)ethanol in F344 rats.

2-(l-Menthoxy)ethanol has been frequently employed as a flavoring agent; however, data regarding 2-(l-menthoxy)ethanol toxicity remain limited. We performed a 13-week subchronic toxicity study of 2-(l-menthoxy)ethanol in male and female F344 rats, with doses of 0, 15, 60, or 250 mg/kg body weight (BW)/day orally administered by gavage using corn oil as the vehicle. No significant toxicological changes in general condition, body weight, or food intake were observed in any groups. The hematological assessment showed decreased hemoglobin, hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin and increased platelet count in the male 250 mg/kg group. Serum biochemistry revealed elevated total cholesterol in the 250 mg/kg group of male and female rats, reduced triglyceride in the female 250 mg/kg group, and increased total protein in the male 250 mg/kg group, indicating effects on lipid metabolism and protein synthesis. For organ weights, absolute and relative weights of the liver and adrenal glands were increased in the 250 mg/kg group of both sexes and the male 250 mg/kg group, respectively. Histopathological analysis showed chronic nephropathy in the male 15 mg/kg or higher groups, with increased absolute and relative kidney weights, as well as elevated serum creatinine, in the male 60 and 250 mg/kg groups. However, eosinophilic granules containing α2u-globulin were identified in proximal tubules, suggesting α2u-globulin nephropathy specific to male rats and without toxicological significance. These results indicated that the no-observed-adverse-effect level of 2-(l-menthoxy)ethanol was 60 mg/kg BW/day for both sexes.

A one-generation reproductive toxicity study of the mycotoxin ochratoxin A in Fischer rats.

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium molds. Grain-based foods account for most human dietary exposures to OTA. OTA is a teratogen, but its reproductive and developmental effects are poorly understood. A one-generation reproductive toxicity study was conducted with groups of 16 male and 16 female Fischer rats exposed to 0, 0.026, 0.064, 0.16, 0.4 or 1.0 mg OTA/kg in diet. Dams exposed to 1.0 mg OTA/kg diet had statistically significant F1 pup losses between implantation and postnatal day (PND 4). Delays in preputial separation (PPS) and vaginal opening (VO) were indicative of delayed puberty in F1 rats. Mild renal lesions in nursing pups indicated that exposure prior to weaning impacted the kidneys. The developing kidney was more susceptible to OTA than the adult kidney. Significant increases in multi-oocyte follicles (MOFs) and proportional changes in resting and growing follicles were observed in F1 female ovaries. Plasma testosterone was reduced in F0 males, and there were negative effects on sperm quality in F0 and F1 male rats. The results confirm that continuous dietary exposure to OTA causes post-implantation fetotoxicity in dams, and renal and reproductive toxicity in their male and female offspring.

Neuromuscular and vascular hamartoma of the small intestine in an F344 rat.

An intestinal mass was found in the border area of the jejunum and ileum of a 110-week-old male F344 rat. Histopathologically, the mass protruded into the lumen and was covered with intestinal epithelium, exhibiting a normal architecture. The lesion was located in the submucosa and consisted of loose connective tissue, smooth muscle, scattered ganglion cells, and blood vessels of various sizes. Although these components showed an irregular and disordered structure, no cellular atypia, increased proliferation activity, or invasive growth to adjacent tissues were detected. Immunohistochemical analyses revealed that smooth muscle, ganglion, and endothelial cells were positive for α-smooth muscle actin and vimentin, S-100, and CD34 and von Willebrand factor, respectively, indicating maturation of these cells. Thus, the mass was diagnosed as a neuromuscular and vascular hamartoma of the small intestine. To the best of our knowledge, this is the first report of this type of lesion in rodents.

Spontaneous malignant myoid thymoma in an aged female Fischer 344 rat.

A whitish mass approximately 30 mm in diameter was noted in the anterior mediastinum of a 67-week-old female Fischer 344 rat. Histopathologically, two types of tumor cells were identified on the basis of morphologic features: epithelial tumor cells with a tubular or cord-like growth pattern and rhabdomyosarcomatous tumor cells characterized by the presence of cross-striations. Immunohistochemically, the epithelial tumor cells reacted positively for cytokeratin AE1/AE3, and some reacted positively for p63, which is expressed in normal thymic epithelial cells. The rhabdomyosarcomatous tumor cells stained positively for desmin, sarcomeric actin, and S-100 protein, which coincides with the stainability of normal thymic myoid cells. Since the tumor was also found to have malignant features such as high proliferative activity, cytologic atypia, and necrotic behavior, it was diagnosed as a malignant myoid thymoma. We believe that this is the first case report of such a tumor in a rodent.

Metabolic, stress, and inflammatory biomarker responses to glucose administration in Fischer-344 rats: intraperitoneal vs. oral delivery.

INTRODUCTION: Metabolic effects of anthropogenic chemicals are a focus of environmental health research due to the significant public health implications. Conventional glucose tolerance tests (GTTs) do not generally examine multiple metabolic, inflammatory, and endocrine factors; however, responses to exogenous glucose can provide insight into mode-of-action and disease processes, and warrant consideration in developing models for toxicological assessment. METHODS: GTTs were conducted on male Fischer-344 rats to 1) assess the feasibility of measuring multiple analytes in small sample volumes; 2) monitor analyte response; and 3) determine whether route of glucose delivery (oral, OGTT vs. intraperitoneal, IPGTT, 2g/kg) modified responses. Plasma samples (0, 30, 60, 90, 120min post-glucose administration) were analyzed for triglycerides; hormones involved in glucose regulation (insulin, glucagon, glucagon-like peptide (GLP)-1)), energy homeostasis (ghrelin, leptin), and stress response (corticosterone); cytokines (TNF, IL-6); and markers of endothelial dysfunction (VEGF, PAI-1). RESULTS: Glucose peaked at 30min during the IPGTT but not the OGTT (p<0.001), a trend paralleled by insulin, while triglycerides decreased following the IPGTT (transient) and the OGTT (sustained). GLP-1 was transiently decreased while ghrelin and leptin levels increased progressively during the IPGTT alone. Corticosterone was increased during both the IPGTT (sustained) and OGTT (transient). TNF and VEGF were unchanged, while PAI-1 and IL-6 were not detected. Increasing the oral glucose dose to 3g/kg did not significantly alter profiles. DISCUSSION: Results confirm the feasibility of measuring multiple analytes during a GTT, and indicate that administration of glucose can impact metabolic and endocrine profiles in a route-dependent manner.