Protective effect of p38 mitogen-activated protein kinase inhibitors on zebrafish larvae brain after hypoxia/reoxygenation injury

Abstract

Objective To examine the effects of p38 mitogen-activated protein kinase (MAPK) inhibitor on the behavioral response to zebrafish larvae after hypoxia/reoxygenation brain injury and to identify whether the protective effect is mediated by inhibiting apoptosis and protein, and mRNA related to apoptosis. Methods The 5-day post-fertilization zebrafish larvae were randomly assigned to 3 groups: control group, model group and intervention group.Fishes in the intervention group were separated into 3 subgroups according to p38 MAPK inhibitor concentration (5, 10, 20 μmol/L). The activity levels of the larvae were analyzed by using quantization mode of ZebraLab software, swimming distance and moving speed were recorded.Terminal transferase dUTP nick end labeling (TUNEL) assays of brain assays were performed.The protein levels of phosphorylation of p38 MAPK, apoptosis related proteins of B-cell lymphoma-2(Bcl-2), Bcl-2 associated X protein(Bax) and Caspase-3 were determined by Western blot.The mRNA expressions of Bcl-2, Bax, and caspase-3 were also analyzed by reverse transcription-quantitative PCR (RT-qPCR). Results The activity movement analysis of the intervention group 2 and 3 demonstrated a significantly increase in the swimming distance compared with the model group(P<0.05). After irradiation under strong light, all groups showed dramatically increasing in the moving speed.After removal of strong light, a significant decrease in moving speed was found in the control group and intervention group 2 and intervention group 3.The TUNEL assay showed that apoptosis index decreased in the intervention group (21.7±2.0, 12.8±1.9, 17.7±2.6) compared with model group (46.8±5.3) (all P<0.01). Western blot assays demonstrated a significant increase protein level of phosphorylation of p38 MAPK after hypoxia and reoxygenation, and the inhibitor reduced the p-p38 MAPK expression.Compared with the model group, p38 MAPK inhi-bitor increased the protein and mRNA expression level of Bcl-2, whereas reduced the Bax and caspase-3 expression in the brain. Conclusions Under the influences of p38 MAPK inhibitor, zebrafish larvae improved the behavioral changes after hypoxia-induced brain injury.The inhibitor (10 μmol/L) optimally reduces hypoxia-induced apoptosis in brain by up-regulating Bcl-2, down-regulating Bax/caspase-3 protein and their mRNA level. Key words: Hypoxia-ischemia; Mitogen-activated protein kinase; Apoptosis