RESUMO
Ginkgo biloba extract (GBE) is used in traditional Chinese medicine as a herbal supplement for improving memory. Exposure of B6C3F1/N mice to GBE in a 2-year National Toxicology Program (NTP) bioassay resulted in a dose-dependent increase in hepatocellular carcinomas (HCC). To identify key microRNAs that modulate GBE-induced hepatocarcinogenesis, we compared the global miRNA expression profiles in GBE-exposed HCC (GBE-HCC) and spontaneous HCC (SPNT-HCC) with age-matched vehicle control normal livers (CNTL) from B6C3F1/N mice. The number of differentially altered miRNAs in GBE-HCC and SPNT-HCC was 74 (52 up and 22 down) and 33 (15 up and 18 down), respectively. Among the uniquely differentially altered miRNAs in GBE-HCC, miR-31 and one of its predicted targets, Cdk1 were selected for functional validation. A potential miRNA response element (MRE) in the 3'-untranslated regions (3'-UTR) of Cdk1 mRNA was revealed by in silico analysis and confirmed by luciferase assays. In mouse hepatoma cell line HEPA-1 cells, we demonstrated an inverse correlation between miR-31 and CDK1 protein levels, but no change in Cdk1 mRNA levels, suggesting a post-transcriptional effect. Additionally, a set of miRNAs (miRs-411, 300, 127, 134, 409-3p, and 433-3p) that were altered in the GBE-HCCs were also altered in non-tumor liver samples from the 90-day GBE-exposed group compared to the vehicle control group, suggesting that some of these miRNAs could serve as potential biomarkers for GBE exposure or hepatocellular carcinogenesis. These data increase our understanding of miRNA-mediated epigenetic regulation of GBE-mediated hepatocellular carcinogenesis in B6C3F1/N mice.
Assuntos
Biomarcadores Tumorais/genética , Carcinoma Hepatocelular/genética , Transformação Celular Neoplásica/genética , Neoplasias Hepáticas/genética , MicroRNAs/genética , Extratos Vegetais/toxicidade , Transcriptoma , Regiões 3' não Traduzidas , Animais , Biomarcadores Tumorais/metabolismo , Proteína Quinase CDC2/genética , Proteína Quinase CDC2/metabolismo , Carcinoma Hepatocelular/induzido quimicamente , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Transformação Celular Neoplásica/induzido quimicamente , Transformação Celular Neoplásica/metabolismo , Epigênese Genética , Feminino , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Ginkgo biloba , Neoplasias Hepáticas/induzido quimicamente , Neoplasias Hepáticas/metabolismo , Masculino , Camundongos , MicroRNAs/metabolismo , Fatores de TempoRESUMO
There was a significant increase in the incidence of retinal degeneration in F344/N rats chronically exposed to Kava kava extract (KKE) in National Toxicology Program (NTP) bioassay. A retrospective evaluation of these rat retinas indicated a similar spatial and morphological alteration as seen in light-induced retinal degeneration in albino rats. Therefore, it was hypothesized that KKE has a potential to exacerbate the light-induced retinal degeneration. To investigate the early mechanism of retinal degeneration, we conducted a 90-day F344/N rat KKE gavage study at doses of 0 and 1.0 g/kg (dose which induced retinal degeneration in the 2-year NTP rat KKE bioassay). The morphological evaluation indicated reduced number of phagosomes in the retinal pigment epithelium (RPE) of the superior retina. Transcriptomic alterations related to retinal epithelial homeostasis and melatoninergic signaling were observed in microarray analysis. Phagocytosis of photoreceptor outer segment by the underlying RPE is essential to maintain the homeostasis of the photoreceptor layer and is regulated by melatonin signaling. Therefore, reduced photoreceptor outer segment disc shedding and subsequent lower number of phagosomes in the RPE and alterations in the melatonin pathway may have contributed to the increased incidences of retinal degeneration observed in F344/N rats in the 2-year KKE bioassay.
Assuntos
Kava/química , Fagocitose/efeitos dos fármacos , Fagossomos/efeitos dos fármacos , Extratos Vegetais/toxicidade , Degeneração Retiniana/induzido quimicamente , Pigmentos da Retina/metabolismo , Animais , Masculino , Fagossomos/ultraestrutura , Extratos Vegetais/isolamento & purificação , Ratos Endogâmicos F344 , Degeneração Retiniana/metabolismo , Degeneração Retiniana/patologia , Epitélio Pigmentado da Retina/efeitos dos fármacos , Epitélio Pigmentado da Retina/ultraestrutura , Transcriptoma/efeitos dos fármacosRESUMO
Retinal degeneration due to chronic ambient light exposure is a common spontaneous age-related finding in albino rats, but it can also be related to exposures associated with environmental chemicals and drugs. Typically, light-induced retinal degeneration has a central/hemispherical localization whereas chemical-induced retinal degeneration has a diffuse localization. This study was conducted to identify and characterize treatment-related retinal degeneration in National Toxicology Program rodent bioassays. A total of 3 chronic bioassays in F344/N rats (but not in B6C3F1/N mice) were identified that had treatment-related increases in retinal degeneration (kava kava extract, acrylamide, and leucomalachite green). A retrospective light microscopic evaluation of the retinas from rats in these 3 studies showed a dose-related increase in the frequencies of retinal degeneration, beginning with the loss of photoreceptor cells, followed by the inner nuclear layer cells. These dose-related increased frequencies of degenerative retinal lesions localized within the central/hemispherical region are suggestive of exacerbation of light-induced retinal degeneration.