Table_1_Oxidative Stress Causes Masculinization of Genetically Female Medaka Without Elevating Cortisol.docx

Medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system. Sex reversal from female-to-male (masculinization of XX fish) can be induced through cortisol elevation from exposure to environmental stress such as high temperature during sexual differentiation. However, the effects of oxidative stress, generated via metabolic reactions and biological defense mechanisms, on the sexual differentiation of medaka are unclear. Here, we investigated the effect of oxidative stress on medaka sexual differentiation using hydrogen peroxide (H2O2), which induces oxidative stress in vertebrates. H2O2 treatment from 0 to 5 days post-hatching induced masculinization of wild-type XX medaka, but not of gonadal soma-derived growth factor (gsdf) or peroxisome proliferator-activated receptor alpha-a (pparaa) knockout XX fish. Co-treatment with an oxidative stress inhibitor caused masculinization recovery but co-treatment with a cortisol synthesis inhibitor did not. H2O2 treatment significantly upregulated gsdf and pparaa expression in XX medaka. However, H2O2 did not elevate cortisol levels in medaka larvae during sexual differentiation. These results strongly indicate that oxidative stress induces masculinization of XX medaka without causing elevation of cortisol.

Medaka（Oryzias latipes）是一种具有XX/XY性别决定系统的辐鳍鱼类。通过暴露于环境压力，如性分化期间的高温，可诱导雌性至雄性的性别逆转（XX鱼类的雄性化）。然而，氧化应激（通过代谢反应和生物防御机制产生）对Medaka性别分化的影响尚不明确。在本研究中，我们采用过氧化氢（H2O2）诱导的氧化应激，以研究其对Medaka性别分化的影响，因为过氧化氢能够诱导脊椎动物产生氧化应激。孵化后0至5天内的H2O2处理可诱导野生型XX Medaka的雄性化，但并未对来自性腺体细胞来源的生长因子（gsdf）或过氧化物酶体增殖物激活受体α-a（pparaa）敲除的XX鱼产生影响。与氧化应激抑制剂合用可导致雄性化恢复，而与皮质醇合成抑制剂合用则不能。H2O2处理显著上调了XX Medaka中gsdf和pparaa的表达。然而，H2O2并未在性分化期间的Medaka幼虫中提高皮质醇水平。这些结果强烈表明，氧化应激可以诱导XX Medaka的雄性化，而不会导致皮质醇水平的升高。