Triphenyl Phosphate Triggers Zebrafish Muscle Damage With Altered Expression of Genes Involved in Nrf2‐Keap1‐ARE Pathway‐Mediated Oxidative Stress and Apoptosis

Triphenyl phosphate (TPhP), a typical kind of organophosphate ester, is a potential threat to the environment and human health. Although it can be absorbed and accumulates in zebrafish muscle tissue, the potential effects on muscle tissue are still far from being studied. Thus, this study investigated the potential mechanism of TPhP-induced muscle damage in zebrafish, focusing on oxidative stress and apoptosis. Elevated TPhP exposure concentration caused muscle tissue damage. TPhP could increase the activities of enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and glutathione S-transferase (GST) involved in antioxidant effects in muscle tissue. Accordingly, oxidative stress caused by TPhP exposure also increased the levels of malondialdehyde (MDA), protein carbonyls, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in zebrafish muscle tissue, indicating that TPhP caused lipid peroxidation, protein oxidation, and DNA damage. In addition, TPhP exposure transcriptionally upregulated the nuclear factor E2-related factor 2 (nrf2)--Kelch-like ECH-associated protein 1 (keap1)--antioxidant response element (ARE) (Nrf2-Keap1-ARE) signaling pathway, as evidenced by increased mRNA levels of downstream genes including nrf2, nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) quinone oxidoreductase 1 (nqo1), heme oxygenase 1 (ho1), glutamate-cysteine ligase catalyst subunit (gclc), and modifier subunit (gclm). Concurrent transcriptional changes were also observed in apoptosis-related genes such as tumor protein p53 (tp53), bcl2-associated X protein (bax), B-cell lymphoma 2 (bcl2), casp3, and casp9, suggesting a potential link to apoptotic responses. Moreover, high-concentration TPhP exposure increased uncoupling protein 2 (ucp2) gene expression, revealing a regulatory role for ucp2 in regulating oxidative stress. These findings not only provide histological and molecular evidence for the toxic effects of TPhP on zebrafish muscle tissue but also emphasize the urgency of conducting a comprehensive environmental risk assessment of TPhP to inform safety standards and risk management measures.