Role of p53 in the Progression from Ochratoxin A-Induced DNA Damage to Gene Mutations in the Kidneys of Mice

Abstract

Carcinogenic doses of ochratoxin A (OTA) cause increases of mutant frequencies (MFs) of the red/gam gene (Spi(-)) in the kidneys of p53-deficient gpt delta mice, but not in p53-proficient mice. Here, we investigated the role of p53 in the progression from OTA-induced DNA damage to gene mutations. To this end, p53-proficient and -deficient mice were administered 5 mg/kg OTA for 3 days or 4 weeks by gavage. After 3 days of administration, comet assays were performed and there were no differences in the degrees of OTA-induced DNA damage between p53-proficient and -deficient mice. However, the frequencies of γ-H2AX-positive tubular epithelial cells in p53-deficient mice were significantly higher than those in p53-proficient mice, implying that p53 inhibited the progression from DNA damage to DNA double-strand breaks (DSBs). Evaluation of global gene expression and relevant mRNA/protein expression levels demonstrated that OTA increased the expression of Cdkn1a, which encodes the p21 protein, in p53-proficient mice, but not in p53-deficient mice. Moreover, in p53-deficient mice, mRNA levels of cell cycle progression and DSB repair (homologous recombination repair [HR])-related genes were significantly increased. Thus, G1/S arrest due to activation of the p53/p21 pathway may contribute to the prevention of DSBs in p53-proficient mice. In addition, single base deletions/insertions/substitutions were predominant, possibly due to HR. Overall, these results suggested that OTA induced DSBs at the carcinogenic target site in mice and that p53/p21-mediated cell cycle control prevented an increase in the formation of DSBs, leading to gene mutations.

Ochratoxin A induces DNA damage and G2 phase arrest in human esophageal epithelium Het-1A cells <i>in vitro </i>

“…Several studies also reported that OTA induced DNA strand breaks in cultured primary kidney cells from human, rat and Chinese hamster ovary fibroblast cell line AA8 (Robbiano et al, 2004;Kamp et al, 2005b;Cosimi et al, 2009). Recently, Kuroda found that OTA induced DNA strand breaks, deletion mutations, G2/M arrest and apoptosis in the kidney in rats and mice (Kuroda et al, 2014;Kuroda et al, 2015). Thus, it is reasonable to suggest that OTA may induce DNA damage in Het-1A cells.…”

Precision toxicology shows that troxerutin alleviates ochratoxin A–induced renal lipotoxicity

“…Each day, the troxerutin group (OTA+T group) received 1 mg/kg OTA and then 150 mg/kg troxerutin (purity .98%; Haoyuan Biotech, Xian, China) by gavage. The intertrial interval was more than 1 h. The doses of OTA (36)(37)(38) and troxerutin (39)(40)(41) were selected based on previous studies. Body weights were recorded weekly.…”

Dietary mycotoxins, co-exposure, and carcinogenesis in humans: Short review

“…Consequently, OTA is classified as a possible human carcinogen by IARC, citing sufficient evidence of carcinogenicity in animal models, but insufficient evidence from human studies (World Health Organization & International Agency for Research on Cancer 2002). A recent in vivo study using mice reported that p53 tumour suppressor protein was upregulated during OTA treatment, and investigated the extent to which the p53 protein inhibits progression of OTA-induced DNA damage (Kuroda et al 2015).…”