OBJECTIVETo investigate the effects of phosphorylated mitogen-activated protein kinases (MAPK), including the phosphorylated extracellular signal-regulated protein kinase 1/2 (p-ERK1/2), the phosphorylated protein p38 (p-p38), the phosphorylated c-Jun N-terminal kinase (p-JNK), on phosgene inhalation-induced lung injury and its relationship with matrix metalloproteinase 9 (MMP-9).

METHODSAccording to the random number table, 30 male Wistar rats were divided into air control group (C), phosgene inhalation group (P), PD98059 (specific inhibitor of ERK1/2) group, SB203580 (specific inhibitor of p38) group, and SP600125 (specific inhibitor of JNK) group, with 6 rats in each group. The number of neutrophils in the bronchoalveolar lavage fluid (BALF) was counted and the lung wet-dry ratio (W/D) was examined. The serum levels of inflammatory factors TNF-α, IL-1β, IL-6, and IL-8 were determined with ELISA. The protein expressions of p-ERK1/2, p-p38, p-JNK, and MMP-9 in lung tissue were detected with Western blotting. The mRNA level of MMP-9 in lung tissue was detected with real-time fluorescence quantitative PCR. Data were processed with one-way analysis of variance (among groups) and SNK method (paired comparison).

RESULTSCompared with those of group C [respectively (2.0 ± 0.7)×10(4) /mL and 3.7 ± 0.6], the number of neutrophils and W/D of group P [respectively (10.7 ± 1.4)×10(4) /mL and 7.6 ± 0.4] were increased. The number of neutrophils in group SB203580 and group SP600125 was respectively (8.3 ± 1.1)×10(4), (7.9 ± 1.3)×10(4)/mL, with W/D respectively 6.1 ± 1.4, 6.1 ± 0.9, all of which decreased as compared with those of group P (with P values all below 0.01). Compared with those of group C, the levels of TNF-a, IL-1β, IL-6, and IL-8 of group P were increased, but decreased in group SB203580 and group SP600125 compared with that of group P, though still higher than those of group C, and the differences were statistically significant (P < 0.05 or P<0.01). Protein quantities of p-p38 and p-JNK were higher in group P (respectively 1.19 ± 0.22 and 1.43 ± 0.14) than in group C (respectively 0.76 ± 0.06 and 0.74 ± 0.05). Compared with those of group P, the protein levels of p-ERK1/2 (0.47 ± 0.05) in group PD98059, p-p38 (0.88 ± 0.07) in group SB203580, and p-JNK (0.91 ± 0.07) in group SP600125 were significantly reduced (P < 0.05 or P < 0.01). The protein and mRNA levels of MMP-9 were higher in group P (respectively 2.23 ± 0.18 and 4.93 ± 0.12) than in group C (respectively 1.26 ± 0.14 and 1.80 ± 0.03). The protein and mRNA levels of MMP-9 in group SB203580 (respectively 1.58 ± 0.14 and 2.96 ± 0.09) and group SP600125 (respectively 1.55 ± 0.30 and 3.00 ± 0.13) were lower than those in group P (P < 0.05 or P < 0.01).

CONCLUSIONSThe phosgene inhalation can activate the MAPK signaling protein pathway by increasing expressions of p-p38 and p-JNK, which lead to an up-regulation of MMP-9, and this may contribute to the phosgene inhalation-induced lung injury.