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

Abstract

BACKGROUND:

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.

METHODS:

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.

RESULTS:

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.

CONCLUSION:

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.

• Authors: John Sieh Dumbuya, Lu Chen, Si Yun Shu, Lin Ma, Wei Luo, Fei Li, Jang-Yen Wu, Bin Wang
• Journal: Brain research (Brain Res) Vol. 1739 Pg. 146817 (07 15 2020) ISSN: 1872-6240 [Electronic] Netherlands
• PMID: 32246916 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2020. Published by Elsevier B.V.

Chemical References

• Neuroprotective Agents
• Granulocyte Colony-Stimulating Factor
• mTOR protein, rat
• Ribosomal Protein S6 Kinases, 70-kDa
• TOR Serine-Threonine Kinases
• ribosomal protein S6 kinase, 70kD, polypeptide 2

Topics

• Animals
• Animals, Newborn
• Apoptosis (drug effects)
• Brain (metabolism)
• Disease Models, Animal
• Female
• Granulocyte Colony-Stimulating Factor (metabolism, physiology)
• Hypoxia-Ischemia, Brain (metabolism)
• Ischemia (metabolism)
• Male
• Neuroimmunomodulation (drug effects)
• Neurons (metabolism)
• Neuroprotective Agents
• Rats
• Rats, Sprague-Dawley
• Ribosomal Protein S6 Kinases, 70-kDa (metabolism, pharmacology)
• Signal Transduction (drug effects)
• TOR Serine-Threonine Kinases (metabolism)