Soy-Derived Equol Induces Antioxidant Activity in Zebrafish in an Nrf2-Independent Manner

Abstract

Antioxidant effects of soy-derived isoflavones are predicted to be mediated by the Keap1-Nrf2 pathway. Recently, we constructed an assay system to evaluate the antioxidant effects of dietary phytochemicals in zebrafish and revealed a relationship between these effects and the Keap1-Nrf2 pathway. In this study, we used this system to examine the antioxidant effects of seven isoflavones. Among those seven, equol showed strong antioxidant effects when arsenite was used as an oxidative stressor. The antioxidant effect of equol was also shown in Nrf2-mutant zebrafish nfe2l2afh318, suggesting that this effect was not mediated by the Keap1-Nrf2 pathway. To elucidate this unidentified mechanism, the gene expression profiles of equol-treated larvae were analyzed using RNA-seq and qRT-PCR, while no noticeable changes were detected in the expression of genes related to antioxidant effects, except weak induction of Nrf2 target genes. Because nfe2l2afh318 is an amino acid-substitution mutant (Arg485Lue), we considered that the antioxidant effect of equol in this mutant might be due to residual Nrf2 activity. To examine this possibility, we generated an Nrf2-knockout zebrafish nfe2l2ait321 using CRISPR-Cas9 and analyzed the antioxidant effect of equol. As a result, equol showed strong antioxidant effects even in Nrf2-knockout larvae, suggesting that equol indeed upregulates antioxidant activity in zebrafish in an Nrf2-independent manner.

In Search of a Target Gene for a Desirable Phenotype in Aquaculture: Genome Editing of Cyprinidae and Salmonidae Species

“…The targets of studies include lysosomes [ 170 , 171 ], endoplasmic reticulum [ 172 ], membranes [ 173 ], membrane channels [ 174 ], cytoskeleton [ 175 ], recombination processes [ 176 ], aneuploidy [ 177 ], expression regulation [ 178 ], and signaling [ 179 ]. There is research on the genetic basis of the organism’s response to oxidative stress [ 180 , 181 , 182 , 183 , 184 ], hypoxia [ 185 , 186 , 187 ], sodium ion uptake from the surrounding aquatic environment and ammonia excretion [ 188 , 189 , 190 ], inflammation processes [ 191 , 192 ], immunity [ 193 , 194 , 195 , 196 ] and disease resistance [ 197 , 198 , 199 , 200 , 201 ].…”

Keap1/Nrf2-independent antioxidative activity of Phyllanthus amarus extract in zebrafish

“…The zebrafish is commonly used as a model for toxicological and human disease research (Zhang et al, 2003;Xu, Zon 2010;Fuse, Kobayashi 2017). A recent study employed zebrafish to assess the protective effects of phytochemicals on acute H2O2 and NaAsO2 toxicity (Endo et al, 2020;Nguyen et al, 2020;Watanabe et al, 2022). This study provides evidence of the protective effects of PAE against oxidative stress induced by H2O2 and NaAsO2.…”