Parental Transfer of Microcystin-LR-Induced Innate Immune Dysfunction of Zebrafish: A Cross-Generational Study

Transgenerational effects of microcystin-LR (MC-LR) released by cyanobacterial blooms have become a hot topic. In the present study, adult zebrafish pairs were exposed to 0, 0.4, 2, and 10 mu g/L MC-LR for 60 days and the embryos (F1 generation) were hatched without or with continued MC-LR exposures at the same concentrations until 5 days postfertilization (dpf). The results showed the existence of MC-LR both in F0 gonads and in F1 embryos and indicated that MC-LR could be transferred directly from the FO adult fish to F1 offspring. The adverse effects on sex hormone levels, sexual development, and fecundity in FO generation along with abnormal development in Fl offspring were observed. Furthermore, downregulation of antioxidant genes (cat, mnsod, gpxla) and upregulation of innate immune-related genes (tlr4a, myd88, tnf alpha, il1 beta) as well as increased proinflammation cytokine contents (TNF-alpha, IL-1 beta, IL-6) were noticed in Fl offspring without/with continued MC-LR exposures. In addition, significant differences between the two F1 embryo treatments demonstrated that continuous MC-LR exposure could result in a higher degree of inflammatory response compared to those without MC-LR exposure. Our findings revealed that MC-LR could exert cross-generational effects of immunotoxicity by inhibiting the antioxidant system and activating an inflammatory response.