The role of p38 MAPK in acute paraquat-induced lung injury in rats.

Context: Paraquat (PQ; 1,1'-dimethyl-4,4'-bipyridinium dichloride) is highly toxic and accounts for a large proportion of the herbicide poisonings seen in clinic. The major cause of mortality is respiratory failure. The p38 mitogen-activated protein kinase (MAPK) signal transduction pathway coordinates various cellular stress responses that have been shown to participate in the pathogenesis of PQ-induced lung injury.

Objective: To evaluate the effect of the specific p38 MAPK inhibitor SB203580 on PQ-induced lung injury and cytokine secretion.

Methods: In groups of 24, rats were treated with PQ, PQ and SB203580 (SB + PQ), SB203580 alone (SB) or normal saline (control group). Six rats from each group were euthanized at 1, 3, 5 or 7 d. Pathology of lung specimens was scored through hematoxylin and eosin staining. Edema in the lung was quantified from wet-to-dry weight ratios. p38 and p-p38MAPK proteins were measured via electrochemiluminescent Western blots. tumor necrosis factor (TNF)-alpha and interleukin-1 beta (IL-1β) concentrations in lung specimens and bronchoalveolar lavage fluid (BALF) were quantified via enzyme-linked immunosorbent assay.

Results: The mortality rate of the SB + PQ group (16.7%) was significantly lower than that of the PQ group (33.3%; p < 0.05). The PQ group had significantly higher pulmonary histology scores, wet-to-dry weight ratios and phosphorylated p-p38 MAPK levels, as well as higher IL-1β and TNF-alpha levels in BALF and lung tissues, that did the SB + PQ and control groups (p < 0.05, all).

Conclusion: The data suggest that the p38 MAPK signaling pathway has an important role in regulating the production of IL-1β and TNF-alpha in PQ-induced lung injury in rats.