The Research Of The Role Of The P38MAPK In The Acute Lung Injury Induced By PQ In Rats

Background Paraquat (PQ), a high efficiency vegetative herbicide, has been widely used around the word.Cases of suicidal or accidental ingestion of PQ have occupied a large proportion of heibicide poison incidents in clinical.Due to the strong toxity and lacking of effective treatments PQ has a high fatality rate.After absorption into the body, PQ can mediate multiple organ dysfunction,especially in the lung,which mainly shows the early acute lung injury(ALI) and subsequent development of pulmonary fibrosis.Related meta-analysis shows that present treatments do not change the high mortality clinical results for PQ poisioning patients. Since the mechanism of PQ poisioning has not been fully eclucidated,further perfecting the mechanism of PQ poisioning and to find new therapeutic is imminent.The oxodative stress reaction caused by PQ can mediate the lung tissue and the whole body produces a large number of inflammatory cytokines,especially the rise of tumor necrosis factor?(c)and interleukin-1?(IL-1?) expression,which futher aggravating the acute lung injury.So blocking or alleviating the early lung tissue inflammation may inhibit the fibrosis in the late progress and improve the prognosis of patients.P38MAPK which belongs the MAPKs family has become the research hotspot and difficulty.Alarge number of studies have confirmed that p38MAPK plays an important role in inflammatory response and apotosis of acute lung injury.p38MAPK can mediate the downstream inflammation to increase the cytokines expression for example TNFaand IL-1?,through regulating the gene level or transcriptional level protein changes. TNFaand IL-1?,which are the key factors of the inflammatory,in turn,activate p38MAPK again.This progress forms a vicious cycle.Inhibition of p38MAPK has been reported to decrease the release of TNFaand IL-1?and reduce the lung injury in models of trauma and endotoxemia.However,it is surprising to note that the detailed change in p38 kinase activity in PQ-induced acute lung injury has been rarely reported.Therefore we investgated the role of p38MAPK in the PQ induced acute lung injury,otherwise,we use the specific inhibitor SB203580 to further clarify the potential clinical significance in the treatment of PQ poisioning.Objective TO investigate the role of p38MAPK in acute lung injury induced by paraquat,to further improve the mechanism of PQ poisioning and provide new targets for clinical treatment.Method 96 healthy Adult Sprague-Dawley rats weighing 250-300g were divided randomly into the following four groups(each group n=24):(1) Sham group, rats were only received normal saline (18mg/kg, i.p.) as a control group; (2) PQ group, rats were poisoned with PQ (18mg/kg, i.p.); (3) PQ+SB group, rats were injected with SB203580(10mg/kg, i.p.) 30 min before PQ (18mg/kg, i.p.) treatment; (4) SB group, rats were only received SB203580(10mg/kg, i.p.). The doses of these drugs we chose were on the basis of previous studies and our preliminary experiments. In each group, rats were sacrificed on 1d,3d,5d and 7d after paraquat intoxication for collecting bronchoalveolar lavage fluid (BALF) and lung sample. The superior lobe of the right lung was frozen in liquid nitrogen for determination of TNF-a and IL-1? protein expression by ELISA. The superior lobe of the left lung was kept in 10% formaldehyde for histology under the light microscope. The remaining lung was used for p38 and p-p38MAPK protein quantification.Results1) Lung wet/dry weight ratio The lung wet/dry ratios were significantly higher at 3d, 5d and 7d in the PQ group compared with the control group(P<0.05). SB203580 administration significantly decreased the lung edema at 3d,5d and 7d after paraquat intoxication. No difference can be found between the two treated groups at 1d and the control group.2) Measurement of TNF-a and IL-1? in lung and BALF The TNF-a and IL-1? in rat lung tissue and BALF were measured by ELISA. Paraquat intoxication led to a peak in the contents of TNF-a and IL-1? in both lung and BALF on day 1 following a time-dependent reduction (P<0.05). The treatment of SB203580 significantly reduced the levels of TNF-a and IL-1? at each times (P<0.05) except the TNF-a levels in BALF on 5 days and 7 days after administration. No statistically difference in each pionts of the two pro-inflammation levels was observed between NS group and SB group.3) Pulmonary histology The pulmonary histologic scores were significantly elevated in the PQ group in comparison with NS group after the administration of paraquat, which could be significantly alleviated by SB203580 pretreatment.4) Expressions of p38 MAP kinase and phosphorylated p38 MAP kinase in lung tissue The total p38 density of the bands of each group seemed similar. Phosphorylated p38 MAP kinase was evidently augmented in PQ group compared with NS group (P<0.05), whereas its expression was markedly attenuated in SB203580 treatment group (P<0.05). The mean density ratio of the bands for phosphorylated p38 MAP kinase in the four (NG, SB, PQ, PQ+SB) groups was 1:0.8:5.3:3.4.Conclusion1) p38MAPK signaling pathway plays a critical role in the expression of TNF-aand IL-1 P in the PQ-induced acute lung injury.2) Inhibition of p38MAPK activity by administration of SB203580 can alleviate the lung injury induced by PQ.