[Early acute liver injury in paraquat poisoning rats]

To observe hepatocellular apoptosis and inflammatory cytokines expression and their mechanisms after paraquat poisoning in rat.

Forty Wistar rats were divided into control group (n=8) and model group (n=32) by random number table. Rats in model group were intraperitoneally injected with 30 mg/kg 20% paraquat concentrate, while those in control group were injected with normal saline. 0.5, 1, 3, 7 days after reproduction of the model, 8 rats were sacrificed, and blood was collected from inferior vena cava and hepatic tissue was harvested. The serum levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were determined by enzyme-linked immunosorbent assay (ELISA). The mRNA expressions of IL-1β, TNF-α, inducible nitric oxide synthase (iNOS) and p53 were determined by reverse transcription-polymerase chain reaction (RT-PCR). Cysteine-containing aspartate-specific proteases (caspase-3, -8, -9, -12) activity in hepatic tissue was determined on the 3rd day with chromogenic substrate method. The liver histopathological changes were observed after hematoxylin-eosin (HE) staining.

In model group, hepatic tissue showed extensive necrosis with inflammatory cell infiltration in time dependant manner. Serum IL-1β and TNF-α levels were significantly higher in model group half a day after reproduction than those in control group (IL-1β: 220.13 ± 69.74 ng/L vs. 0.14 ± 0.03 ng/L, TNF-α: 102.66 ± 26.43 ng/L vs. 0.16 ± 0.02 ng/L, P<0.01 and P<0.05), and peaked on the 3rd day and 1st day (IL-1β: 423.72 ± 153.11 ng/L, TNF-α: 690.35 ± 229.64 ng/L). They then decreased gradually, but were still significantly higher than those in control group on the 7th day (IL-1β: 357.47 ± 87.28 ng/L, TNF-α: 12.39 ± 5.06 ng/L, both P<0.05). The contents of IL-1β, TNF-α and iNOS mRNA expressions in hepatic tissue were significantly higher than those in control group, and the highest values were seen on the 1st day, the 1st day, and the 3rd day [IL-1β mRNA (gray value): 1.569 ± 0.057 vs. 0.123 ± 0.016, TNF-α mRNA (gray value): 0.683 ± 0.077 vs. 0.261 ± 0.025, iNOS mRNA (gray value): 3.259 ± 0.135 vs. 0.002±0.001, P<0.05 or P<0.01]. There was no difference in p53 mRNA expression between model group and control group at early stage, and both of them showed low expression, and p53 mRNA expression was significantly higher in model group on the 7th day (gray value: 2.959±0.086 vs. 0.263±0.032, P<0.01). In model group, caspase activity in liver tissue were significantly higher on the 3rd day than those in control group (caspase-3: 857.25±309.26 pmol/mg vs. 169.73±48.21 pmol/mg, caspase-8: 199.18±61.41 pmol/mg vs. 32.26±11.09 pmol/mg, caspase-9: 321.62±80.73 pmol/mg vs. 90.38±29.76 pmol/mg, caspase-12: 413.13±89.77 pmol/mg vs. 26.73±9.86 pmol/mg, all P<0.01).

Paraquat can cause acute liver injury in rats, with caspase-3, -8, -9, -12 activities markedly enhanced, and liver injury may be associated with an early high expression of TNF-α, iNOS and p53 gene.