G-CSF attenuates neuroinflammation and neuronal apoptosis via the mTOR/p70SK6 signaling pathway in neonatal Hypoxia-Ischemia rat model

• Published in: Brain research Vol. 1739; p. 146817
• Main Authors: Dumbuya, John Sieh, Chen, Lu, Shu, Si Yun, Ma, Lin, Luo, Wei, Li, Fei, Wu, Jang-Yen, Wang, Bin
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.07.2020
• Subjects: Apoptosis; Granulocyte-colony stimulating factor; Hypoxic-ischemic encephalopathy; Inflammatory cytokines; mTOR; Neonatal; Neuro-inflammation; RAP; Bcl-2; HI; TTC; Neonatal; BBB; DMSO; CNS; CC3; TUNEL; NMDA; mTOR; TBI; Hypoxic-ischemic encephalopathy; Neuro-inflammation; Inflammatory cytokines; HIE; P7; P9; PICs; IL-1β; G-CSF; PVDF; IL-10; TNF-α; ROS; Bax; Granulocyte-colony stimulating factor; mTOR/p70S6K; GAPDH; Apoptosis
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2020.146817

•G-CSF greatly reduces hypoxic-ischemic encephalopathy (HIE) induced brain injury.•G-CSF reduces neuroinflammation and neuronal apoptosis.•The mode of action of G-CSF involved the mTOR/p70S6K signalling pathway. Hypoxic-ischemic encephalopathy (HIE) is an important cause of permanent damage to the central nervous system, associated with long-lasting neurological disabilities and neurodevelopmental impairment in neonates. Granulocyte-colony stimulating factor (G-CSF) has been shown to have neuroprotective activity in a variety of experimental brain injury models and G-CSF is a standard treatment in chemotherapeutic-induced neutropenia. The underlying mechanisms are still unclear. The mTOR (mammalian target of rapamycin) signaling pathway is a master regulator of cell growth and proliferation in the nervous system. However, the effects of G-CSF treatment on the mTOR signaling pathway have not been elucidated in neonates with hypoxic-ischemic (HI) brain injury. Our study investigated the neuroprotective effect of G-CSF on neonates with hypoxic-ischemic (HI) brain injury and the possible mechanism involving the mTOR/p70S6K pathway. Sprague-Dawley rat pups at postnatal day 7 (P7) were subjected to right unilateral carotid artery ligation followed by hypoxic (8% oxygen and balanced nitrogen) exposure for 2.5 h or sham surgery. Pups received normal saline, G-CSF, G-CSF combined with rapamycin or ethanol (vehicle for rapamycin) intraperitoneally. On postnatal day 9 (P9), TTC staining for infarct volume, and Nissl and TUNEL staining for neuronal cell injury were conducted. Activation of mTOR/p70S6K pathway, cleaved caspase-3 (CC3), Bax and Bcl-2 and cytokine expression levels were determined by western blotting. The G-CSF treated group was associated with significantly reduced infarction volume and decreased TUNEL positive neuronal cells compared to the HI group treated with saline. The expression levels of TNF-α and IL-1ß were significantly decreased in the G-CSF treated group, while IL-10 expression level was increased. The relative immunoreactivity of p-mTOR and p-p70S6K was significantly reduced in the HI group compared to sham. The HI group treated with G-CSF showed significant upregulated protein expression for p-mTOR and p-p70S6K levels compared to the HI group treated with saline. Furthermore, G-CSF treatment increased Bcl-2 expression levels and decreased CC3 and Bax expression levels in the ipsilateral hemispheres of the HI brain. The effects induced by G-CSF were all reversed by rapamycin. Treatment with G-CSF decreases inflammatory mediators and apoptotic factors, attenuating neuroinflammation and neuronal apoptosis via the mTOR/p70S6K signalling pathway, which represents a potential target for treating HI induced brain damage in neonatal HIE.