Effects of thymoquinone on alpha-amanitin induced hepatotoxicity in human C3A hepatocytes

Abstract Thymoquinone (TQ) has shown hepatoprotective effects in various experimental studies. We aimed to investigate the possible beneficial effects of TQ regarding its prevention of alpha-amanitin induced hepatotoxicity in human C3A hepatocytes. After administering alpha-amanitin in a concentrations of 1 and 10µg/mL on the cells in a hepatocyte cell line, TQ was administered in various concentrations (10, 5, 1, 0.5, 0.1, 0.05, 0.01, 0.005 µg/mL). The MTT test was used to determine cell viability. For the groups given only TQ at various concentrations, the cell viability rates at 48 hours post-administration were found at 82.6, 98.3, 102.1, 102.5, 99.4, 99.4, 101.9 and 106.3%, respectively. For the group with 1μg/mL alpha-amanitin and various TQ concentrations, the cell viability rates were found at 74.6, 88.5, 87.4, 88.7, 85.7, 86.8, 88.4, and 92.9%, respectively. For the group with 10μg/mL alpha-amanitin and various TQ concentrations, the cell viability rates for each TQ subgroup were found at 65.2, 79.2, 81.4, 81.1, 81.8, 81.8, 82.2 and 91.9%, respectively. Our study is the first in vitro study that investigates TQ's effects on alpha-amanitin induced hepatotoxicity. Although TQ had beneficial effect in low doses did not significantly increase cell viability in liver damage due to alpha-amanitin toxicity.

Evaluation of the genotoxicity of alpha-amanitin in mice bone marrow cells.

Alpha-amanitin is a known cytotoxic substance found in some mushroom species including Amanita phalloides. Its main mechanism of action is to block the transcription, which can lead to cell death. Lack of reports on the genotoxicity of this toxin was an inspiration for undertaking this experiment. Genotoxic effect of α-amanitin on balb/c mice bone marrow cells was tested using: comet assay and chromosomal aberration test. The tested substance was given once by intraperitoneal administration to animals at doses: 0.1 mg/kg, 0.15 mg/kg and 0.25 mg/kg (LD50) body weight with 48 h exposure. The comet assay demonstrated a statistically significant increase in DNA damage for all the investigated α-amanitin doses compared to the negative control (p < 0.0001). The exposure to 0.15 and 0.25 mg/kg doses of α-amanitin also generated a statistically significant increase in the frequency of chromosomal aberrations in bone marrow cells of mice compared to the negative control (p < 0.05). The genotoxic effect induced by α-amanitin in mammalian cells can result in genome instability and its functional consequences.

α-Amanitin Restrains Cancer Relapse from Drug-Tolerant Cell Subpopulations via TAF15.

Cancer relapse occurs with substantial frequency even after treatment with curative intent. Here we studied drug-tolerant colonies (DTCs), which are subpopulations of cancer cells that survive in the presence of drugs. Proteomic characterization of DTCs identified stemness- and epithelial-dominant subpopulations, but functional screening suggested that DTC formation was regulated at the transcriptional level independent from protein expression patterns. We consistently found that α-amanitin, an RNA polymerase II (RNAPII) inhibitor, effectively inhibited DTCs by suppressing TAF15 expression, which binds to RNA to modulate transcription and RNA processing. Sequential administration of α-amanitin and cisplatin extended overall survival in a cancer-relapse mouse model, namely peritonitis carcinomatosa. Therefore, post-treatment cancer relapse may occur through non-distinct subpopulations and may be effectively prevented by α-amanitin to disrupt transcriptional machinery, including TAF15.

Early morphological and functional alterations in canine hepatocytes due to alpha-amanitin, a major toxin of Amanita phalloides.

The toadstool death cap (Amanita phalloides) and its subspecies, destroying angel (A. virosa) and death angel (A. verna) are responsible for nearly 95% of all fatal mushroom poisonings. High mortality rate in A. phalloides intoxications is principally a result of the acute liver failure following significant hepatocyte damage due to hepatocellular uptake of amanitins, the major toxins of this mushroom. This study evaluated early morphological and functional alterations in hepatocytes exposed to different concentrations of alpha-amanitin (alpha-AMA). All experiments were performed on cultured canine hepatocytes since intoxicated with A. phalloides dogs have clinical course and pathological findings similar to those seen in humans. The overall functional integrity and viability of cultured hepatocytes were assessed using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and by measurements of lactate dehydrogenase (LDH), total protein, and urea levels. Our results showed that the course of alpha-AMA toxicity in cultured dog hepatocytes is divided into two phases. The first phase comprises functional cell impairments expressed by significant increase of LDH activity and inhibition of protein and urea synthesis when compared with the control group. This is followed by discrete changes in hepatocyte ultrastructure, including marginalization and condensation of nuclear chromatin, as well as formation of the foamlike cytoplasm. The second stage is lethal and is characterized by ongoing necrosis, and/or apoptosis. This may be related to dose of toxin and time of exposure.