[The effect of captopril and losartan on paraquat-induced pulmonary fibrosis and PlGF expression in the lungs of rats].

Objective To investigate the dynamic expression of placenta growth factor (PlGF) in the lungs and its role in paraquat-induced pulmonary fibrosis and to evaluate the effect of ACEI captopril and AT (1) -receptor blocker losartan on paraquat-induced pulmonary fibrosis. Methods 84 adult healthy female Sprague-Dawley (SD) rats were randomly divided into four groups of different treatments designated as: Control, PQ alone (PQ) , captopril treatment, losartan treatment. Each group was divided into three subgroups of seven animals each. The animals were killed at either 7, 14 or 28 days after PQ administration. The rats in PQ group, treatment group were treated intragastrically (ig) with PQ (40 mg/kg) and the rats in control group were treated with the same dose of saline at the beginning of the experiment. The treatment group received Captopril (60 mg/kg; ig) or Losartan (10 mg/kg; ig) once a day respectively after PQ administration and the other two groups received saline. At the given timepoint, animals were sacrificed and lungs were harvested. A semiquantitative assay of histological examination, hydroxyproline in lung tissues were used to determine the severity of alveolitis and fibrosis. RT-PCR and immunohistochemistry were used to detect the mRNA and protein expression of PlGF. Results Inflammatory cell infiltration and fibrotic scores were more prominent in the model group, hydroxyproline contents in lung tissue were significantly increased after PQ administration compared to the control group. Captopril, losartan apparently attenuated the degree of lung injury and pulmonary fibrosis. On 7th, 14th days, the levels of alveolitis in the intervention groups were significantly alleviated as compared with the model group (P<0.05) . On 28th days, the levels of pulmonary fibrosis in the intervention groups were significantly alleviated as compared with model group (P<0.05) . The hydroxyproline contents in the intervention groups were significantly decreased as compared with model group (P<0.01) . PlGF mRNA on day 7, 14, 28 (1.28±0.29vs0.10±0.01、0.80±0.07vs0.10±0.01、0.65±0.13vs0.10±0.01) in the PQ group were all upregulated as compared with that of the control group. PlGF mRNA on day 7, 14, 28 in the captopril and Losartan intervention groups were significantly decreased (0.94±0.04、0.71±0.09、0.52±0.24 and 0.80±0.12、0.66±0.11、0.51±0.03) . PlGF positive expression index on day 7, 14, 28 (2.27±0.34 vs0.13±0.01、1.78±0.41 vs0.14±0.03、1.25±0.69 vs0.13±0.01) in the PQ group were all upregulated as compared with that of the control group. PlGF positive expression index on day 7, 14, 28 in the captopril and Losartan treatment groups were significantly decreased (1.53±0.78、1.17±0.79、0.97±0.61 and 1.36±0.63、1.24±0.80、0.83±0.47) . PlGF positive expression index on day 7 in the two intervention groups were significantly decreased, as compared with PQ group (P<0.05) . Conclusion PlGF may plays an important role in the development of pulmonary fibrosis following paraquat-induced lung injury in rats. Captopril and losartan had an inhibitory effect on paraquat-induced pulmonary fibrosis, and the effect may be due to inhibition of angiotensin II and, in part, be associated with reduction in PlGF. Key words: Paraquat; Rat; Pulmonary fibrosis; Placenta growth factor