OBJECTIVETo explore the neuroprotective effect and mechanism of picroside II on extracellular regulated protein kinases1/2 (ERK1/2) signal transduction pathway in cerebral ischemia injuryrats. METHODS The middle cerebral artery occlusion (MCAO) model was established by inserting a monofilament into middle cerebral artery. Totally 96 successfully modeled Wistar rats were divided into the modelgroup, the treatment (picroside II) group, the Lipopolysachcaride (LPS) group, and the U0126 group according to random digit table. Each group was further divided into 3 subgroups, i.e. 6, 12, and 24 h sub-groups. Picroside II (20 mg/kg) was peritoneally injected to rats in the treatment group 2 h after ischemia.LPS (20 mg/kg) and Picroside II (20 mg/kg) were peritoneally injected to rats in the LPS group 2 h after ischemia. U0126-EtOH (20 mg/kg)and Picroside II (20 mg/kg) were peritoneally injected to rats in the U0126group 2 h after ischemia. Equal volume of normal saline was peritoneally injected to rats in the control groupand the model group. The neurobehavioral function was evaluated by modified neurological severity score(mNSS) test. The structure of neurons was observed using hematoxylin-eosinstaining (HE) staining. Theapoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The expression of phosphorylated extracellular signal-regulated protein kinase1,2 (pERK1,2) in cortex was detected using immunohistochemistry (IHC) and Western blot.

RESULTSAfter cerebral ischemia injury neurological impairment score increased, the damage of neuron in the cortical area was aggravated, apoptotic cells increased in the model group as time went by. The expression of pERK1/2 increased more significantly in the model group than in the control group (P <0.05). The damage of neuron in the cortical area was milder, while apoptotic cells decreased, the expression of pERK1f2 obviously decreased more in the treatment group and the U0126 group (P < 0.05). The early damage of neuron in the cortical area was more severe, apoptotic cells and the expression of pERK12 were comparatively higher in early stage of the LPS group, but the expression of pERK1/2 was somewhat decreased in late stage.

CONCLUSIONSActivating ERK12 pathway could mediate apoptosis and inflammatory reactions of neurons after cerebral ischemia injury. Picroside II could protect the nerve system possibly through reducing activation of ERKI2 pathway, inhibiting apoptosis of neurons and inflammation reaction.