OBJECTIVETo explore the role of p38 signal pathway in regulating matrix metalloproteinase-9 (MMP-9) expression and brain edema formation in a rat model of traumatic brain injury (TBI).

METHODSA total of 130 adult male Sprague Dawley rats were randomly divided into 4 groups, namely the normal group (n=10), sham-operated group (n=40), TBI (induced by Feeney free falling methods) group (n=40), and SB group with intraperitoneal SB203580 treatment (10 µmol/L) 15 min before TBI (n=40). The rats were sacrificed 2 h and 2 days after TBI. The expressions of p38, p-p38, and MMP-9 mRNA and protein were detected by RT-PCR and Western blotting. The blood brain barrier permeability was detected by Evans Blue (EB) test, and the brain water content (BWC) was determined using a gravimetric technique.

RESULTSThe expression of p-p38 protein increased markedly 2 h after TBI (P<0.05), and was suppressed by SB203580 treatment (P<0.05). MMP-9 mRNA and protein showed no obvious increase at 2 h after TBI, but significantly increased at 2 days as compared with those in the sham-operated group (P<0.05). MMP-9 mRNA and protein were much lower in SB group than in TBI group 2 days after TBI (P<0.05). The blood brain barrier permeability significantly increased 2 h after TBI (P<0.05) and kept increasing until 2 days (P<0.05), but was reduced significantly by SB203580 (P<0.05). BWC increased obviously 2 days after TBI (P<0.05) and was lessened by SB203580 (P<0.05).

CONCLUSIONBlocking p38 signal pathway can attenuate MMP-9 upregulation and brain edema after TBI, suggesting the important role of p38 in regulating MMP-9 expression to affect traumatic brain edema.