Granulocyte-colony stimulating factor exerts its neuroprotective effects by regulating inflammatory cascades via mTOR/p70SK6 signaling pathway when hypoxia-ischemia occurs in neonatal rats / 中华实用儿科临床杂志

ABSTRACT

Objective@#To investigate the role of granulocyte-colony stimulating factor (G-CSF) on the regulation of inflammatory cytokines in neonatal hypoxic-ischemic brain damage(HIBD) rat model, and to explore the possible mechanism involved in G-CSF neuroprotective effect via the mammalian target of Rapamycin/p70 ribosomal S6 protein kinase (mTOR/p70S6K) signaling pathway.@*Methods@#A group of postnatal day 7 (P7) Sprague-Dawley rat pups (90 cases) were randomly divided into sham-operated group, hypoxia-ischemia(HI) group, G-CSF group, Rapamycin (RAP) group and control group, and the improved Rice method was used to establish a neonatal rat model of HIBD.One hour before HI induction, Rapamycin was administered intraperitoneally with a dose of 250 μg/kg, and the control group was given equal volume of ethanol injected intraperitoneally.One hour after HI, a dose of 50 μg/kg of G-CSF was injected intraperitoneally into the G-CSF group, Rapamycin group and control group.The same volume of normal saline was injected intraperitoneally into HI group and sham-operated group.Forty-eight hours after HI, Western blot was used to detect the protein levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-10, and the mTOR/p70S6K signaling pathway in brain tissue.Neuron injury of the hippocampal CA1 region and the cortex was assessed by Nissl staining, and infarct volume detected by 2, 3, 5-triphenyltetrazolium chloride staining.@*Results@#The G-CSF group and control group were associated with significantly reduced infarction volume compared to the HI group [(12.87±1.54)%, (11.90±1.31)% vs.(24.21±3.28)%], and the differences were statistically significant(P<0.05). There was an increased positive neuron cell number in the ipsilateral hemispheres of the hippocampal CA1 region in the G-CSF group and the control group [(61.00±4.90) cell/field and (61.67±6.40) cell/field] and cortex [(92.67±6.68) cell/field and (90.17±4.45) cell/field] compared with those in HI group [(42.62±4.46) cell/field and (70.83±6.97) cell/field], and the differences were all statistically significant (all P<0.05). The expression levels of TNF-α and IL-1β were significantly decreased in the G-CSF group and the control group, compared with those in HI group(TNF-α 0.67±0.07, 0.55±0.05 vs.0.86±0.05; IL-1β 0.65±0.06, 0.52±0.10 vs.0.86±0.06), and the differences were all statistically significant (all P<0.05). There was increased expression levels of IL-10, p-mTOR/mTOR and p-p70S6K/p70S6K in the G-CSF group and the control group, compared with those in HI group (IL-10 0.68±0.04, 0.62±0.05 vs.0.34±0.02; p-mTOR/mTOR 0.53±0.02, 0.51±0.01 vs.0.26±0.01; p-p70S6K/p70S6K 0.89±0.03, 0.90±0.03 vs.0.55±0.02), and the differences were all statistically significant(all P<0.05). There was an increased infarct volume in Rapamycin group [(25.70±1.50)%], compared with the G-CSF group and the control group, and there were decreased number of positive neuron cell count in the hippocampal CA1 region [(40.67±3.50) cell/field] and cortex [(68.33±8.17) cell/field], increased expression levels of TNF-α and IL-1β (0.97±0.06 and 0.98±0.10, respectively), decreased expression levels of IL-10, p-mTOR/mTOR and p-p70S6K/p70S6K (0.21±0.02, 0.30±0.01 and 0.55±0.01, respectively) in the Rapamycin group, and the differences were all statistically significant (all P<0.05).@*Conclusions@#G-CSF may inhibit inflammatory responses after HIBD by up-regulating the mTOR/p70S6K signaling pathway in neonatal HI encephalopathy.