[The protective effect of regulation of paraoxonase 1 gene on liver oxidative stress injury induced by dichlorvos poisoning in mice].

OBJECTIVE: To investigate the protective effect of paraoxonase 1 (PON1) gene against liver oxidative stress injury in mice due to dichlorvos poisoning.

METHODS: Experiment 1: 12 male Balb/c mice were randomly divided into three groups, with 4 mice in each group: control group, green fluorescent protein lentivirus control group (Lv-GFP group), and recombinant PON1 lentivirus group (Lv-PON1 group). 2 × 10⁷ TU of Lv-GFP or Lv-PON1 was transfected via tail vein, while normal saline was given to those in control group. Blood was collected on 0, 1, 3, 5, 7, 9 days via fundus venous plexus for the assay of serum PON1 activity. PON1 mRNA and protein expression levels were respectively determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western Blot on the 3rd post-lentivirus transfection day. Experiment 2: according to the random number table method, another 96 male Balb/c mice were divided into four groups of 24 mice in each control group, dichlorvos group, Lv-GFP intervention group, and Lv-PON1 intervention group. Lv-GFP or Lv-PON1 was transfected via tail vein followed by intraperitoneal injection of dichlorvos 9 mg/kg, while those in control group were given normal saline. Six mice in each group were sacrificed respectively at 6, 12, 24, 48 hours, and liver tissue was collected. PON1 mRNA and nuclear factor E2-related factor 2 (Nrf2) mRNA expression levels were determined by RT-PCR, and PON1 protein level was determined by Western Blot. The content of malondialdehyde (MDA) and glutathione (GSH) in the liver tissue were determined by chemical colorimetry. The activity of superoxide dismutase (SOD) and catalase (CAT) were measured by double antibody sandwich enzyme linked immunosorbent assay (ELISA).

RESULTS: Experiment 1: after Lv-PON1 was transfected to normal mice, PON1 activity in serum gradually increased and maintained a high level on 3rd day, while that of the control group and Lv-GFP group showed a normal low level. On the 3rd post-lentivirus transfection day, PON1 mRNA and PON1 protein expressions in liver were significantly higher than those of control group and Lv-GFP group. Experiment 2: compared with control group, the mice in dichlorvos group showed significant decreases in PON1 mRNA, PON1 protein, Nrf2 mRNA as well as GSH, SOD, CAT levels at 6 hours [PON1 mRNA (gray value): 0.237 ± 0.075 vs. 0.674 ± 0.011, PON1 protein (gray value): 0.602 ± 0.086 vs. 0.998 ± 0.124, Nrf2 mRNA (gray value): 0.089 ± 0.012 vs. 0.126 ± 0.010, GSH (mg/g): 3.84 ± 0.33 vs. 5.52 ± 0.40, SOD (μg/g): 0.383 ± 0.040 vs. 0.564 ± 0.052, CAT (ng/g): 7.32 ± 1.28 vs. 12.46 ± 1.54, all P < 0.05 ], and remarkable increase in MDA content (nmol/g: 7.78 ± 0.41 vs. 2.34 ± 0.25, P < 0.05). With the extension of time, PON1 mRNA, PON1 protein, Nrf2 mRNA and GSH, SOD, CAT levels gradually increased, MDA content gradually decreased, Nrf2 mRNA expression level had risen to the level of control group at 24 hours (0.133 ± 0.019 vs. 0.126 ± 0.009, P > 0.05), and it was higher than that of the control group at 48 hours ( 0.206 ± 0.028 vs. 0.124 ± 0.010, P < 0.05). Compared with that of the dichlorvos group, Lv-PON1 intervention group showed a significant increase in PON1 mRNA, PON1 protein, Nrf2 mRNA and GSH, SOD, CAT levels [PON1 mRNA (gray value): 0.726 ± 0.021 vs. 0.237 ± 0.075, PON1 protein (gray value): 0.739 ± 0.050 vs. 0.602 ± 0.086, Nrf2 mRNA (gray value): 0.158 ± 0.007 vs. 0.089 ± 0.012, GSH (mg/g): 4.30 ± 0.22 vs. 3.84 ± 0.33, SOD ( μg/g): 0.454 ± 0.062 vs. 0.383 ± 0.040, CAT (ng/g): 8.98 ± 1.02 vs. 7.32 ± 1.28, all P < 0.05 ], and a decrease in MDA content (nmol/g: 6.56 ± 0.44 vs. 7.78 ± 0.41, P < 0.05).

CONCLUSIONS: Regulation of PON1 gene can reduce MDA content, enhance SOD and CAT activities, increase GSH content, and it may also up-regulate Nrf2 mRNA expression to play a protective effect against oxidative stress of liver injury induced by dichlorvos poisoning.