Reproductive toxicity and associated mechanism of tricresyl phosphate on Caenorhabditis elegans

Abstract

BackgroundTricresyl phosphate (TCP) is mainly used as a flame retardant. Studies have confirmed that it has cytotoxicity and neurotoxicity, but its reproductive toxicity is not clear.ObjectiveTo investigate the reproductive toxicity and potential mechanism of TCP subacute exposure on Caenorhabditis elegans.MethodsCaenorhabditis elegans were exposed to solvent control and 0.1, 1, 10, 100, and 1000 μg·L−1 TCP respectively for 72 h. Brood size and number of fertilized eggs in the uterus were detected to evaluate reproductive ability. The number of total germline cells and the relative area of gonad arm were measured to evaluate the development of gonads. The body length and body width of Caenorhabditis elegans were detected to evaluate growth and development. The activities of reactive oxygen species (ROS) and superoxide dismutase (SOD) in Caenorhabditis elegans, and the mitochondrial active oxygen metabolism genes (mev-1 and gas-1) of N2 nematodes were detected by real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) to evaluate oxidative stress. WS1433 transgenic nematodes and wild-type nematodes N2 were exposed to solvent control or TCP (0.1, 1, 10, 100, and 1000 μg·L−1) respectively. DNA damage in germ cells of WS1433 transgenic nematodes was detected, the relative expressions of DNA damage-related genes (hus-1, clk-2, cep-1, and egl-1) in N2 nematodes were detected by qRT-PCR to evaluate the effect of TCP exposure on genetic damage.ResultsCompared with the solvent control group (217.00 ± 12.20), the brood size of N2 nematodes in the 100 μg·L−1 and 1000 μg·L−1 TCP groups decreased (170.80 ± 11.51, 169.60 ± 10.52, P < 0.05). Compared with the solvent control group (18.43 ± 1.69), the number of fertilized eggs of N2 nematodes in the 100 μg·L−1 and 1000 μg·L−1 TCP groups decreased (13.47 ± 0.81, 11.95 ± 0.90, P < 0.05). Compared with the solvent control group (312.46 ± 77.4), the number of total germline cells of N2 nematodes in the 100 μg·L−1 and 1000 μg·L−1 TCP groups decreased (281.80 ± 12.98, 273.50 ± 8.53, P < 0.05). Compared with the solvent control group, the relative area of gonads of N2 nematodes in the 100 μg·L−1 and 1000 μg·L−1 TCP groups decreased by 13.83% and 17.25% respectively (P<0.05). Compared with the solvent control group [(1058.10±80.12) μm, (78.21±14.69) μm], the body length and body width of N2 nematodes in the 100 μg·L−1 and 1000 μg·L−1 TCP groups decreased (P<0.05). Compared with the solvent control group, the relative fluorescence intensity of ROS in nematodes in the 10, 100, and 1000 μg·L−1 TCP groups increased significantly (107.60%±1.02%, 105.90%±1.40%, and 106.40%±1.85%, respectively, P<0.05), and the activities of SOD were reduced (by 20.66%, 15.88%, and 16.44%, respectively, P<0.05). Compared with the solvent control group (1.3±1.3), the number of DNA-damaged germ cells of WS1433 nematodes in the 100 and 1000 μg·L−1 TCP groups increased significantly (2.4±0.3, 2.7±0.3, P<0.05); the expressions of mev-1 and gas-1 genes in N2 nematodes in the 10, 100 and 1000 μg·L−1 TCP groups decreased significantly (P<0.05); the expressions of hus-1 in the 0.1-1000 μg·L−1 TCP groups significantly increased (P<0.05); the expressions of clk-2 and egl-1 in the 100 and 1000 μg·L−1 TCP groups increased significantly (P<0.05); the expressions of cep-1 in the 1, 10, and 100 μg·L−1 TCP groups increased significantly (P<0.05).ConclusionTCP may cause reproductive damage to nematodes through oxidative stress and germ cell DNA damage.

Keywords

• organophosphate esters
• caenorhabditis elegans
• reproductive toxicity
• dna damage
• oxidative stress