Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review.

Pyrrolizidine alkaloids (PAs) are naturally occurring secondary metabolites of plants. To date, more than 660 types of PAs have been identified from an estimated 6000 plants, and approximately 120 of these PAs are hepatotoxic. As a result of PAs being found in spices, herbal teas, honey, and milk, PAs are considered contaminants in foods, posing a potential risk to human health. Here, we summarize the chemical structure, toxic effects, levels, and regulation of PAs in different countries to provide a better understanding of their toxicity and risk assessment. With recent research on the risk assessment of PAs, this review also discusses the challenges facing this field, aiming to provide a scientific basis for PA toxicity research and safety assessment.

Quizalofop-P-ethyl exposure increases estrogen axis activity in male and slightly decreases estrogen axis activity in female zebrafish (Danio rerio).

The herbicide Quizalofop-P-ethyl (QpE) exerts toxic effects in fish, but limited information is currently available on its effects on the endocrine system. In the current study, adult zebrafish (Danio rerio) were exposed to different concentrations (0, 2, 20, 200µg/L) of QpE for 30days. In males, QpE exposure significantly increased plasma estradiol (E2) and vitellogenin (VTG) levels, concomitant with up-regulation of hepatic esr1 and vtg gene expression. In females, plasma sex hormone levels and VTG concentrations were not altered significantly, but an increased expression of hepatic esr1 in addition to decreased expression of hepatic vtg, esr2a and esr2b was observed. Marked histological lesions were also observed in the gonads of both males and females. Moreover, QpE exposure significantly increased transcriptional profiles of some genes in the HPG axis and liver in males, while the majority of these genes were down-regulated in females. Docking studies showed QpE forming stable interactions with the ligand-binding domain (LBD) of zebrafish ESR1 and ESR2a, suggesting QpE may bind to estrogen receptors (ESRs). This study for the first time reveals QpE as an endocrine-disrupting chemical (EDC) disrupting the zebrafish endocrine system in a sex-specific manner, whereby it increases estrogen axis activity in males and slightly decreases estrogen axis activity in females, which may be accounted for by QpE regulating steroidogenesis and/or activating ESR(s).

Toxicity of multi-walled carbon nanotubes, graphene oxide, and reduced graphene oxide to zebrafish embryos.

OBJECTIVE: This study was aimed to investigate the toxic effects of 3 nanomaterials, i.e. multi-walled carbon nanotubes (MWCNTs), graphene oxide (GO), and reduced graphene oxide (RGO), on zebrafish embryos. METHODS: The 2-h post-fertilization (hpf) zebrafish embryos were exposed to MWCNTs, GO, and RGO at different concentrations (1, 5, 10, 50, 100 mg/L) for 96 h. Afterwards, the effects of the 3 nanomateria on spontaneous movement, heart rate, hatching rate, length of larvae, mortality, and malformations ls were evaluated. RESULTS: Statistical analysis indicated that RGO significantly inhibited the hatching of zebrafish embryos. Furthermore, RGO and MWCNTs decreased the length of the hatched larvae at 96 hpf. No obvious morphological malformation or mortality was observed in the zebrafish embryos after exposure to the three nanomaterials. CONCLUSION: MWCNTs, GO, and RGO were all toxic to zebrafish embryos to influence embryos hatching and larvae length. Although no obvious morphological malformation and mortality were observed in exposed zebrafish embryos, further studies on the toxicity of the three nanomaterials are still needed.