Protection of granulocyte-colony stimulating factor to hemorrhagic brain injuries and its involved mechanisms: Effects of vascular endothelial growth factor and aquaporin-4

- G-CSF can up-regulate perihematomal VEGF and AQP4 expression after ICH.
- G-CSF activates STAT3 and ERK pathways to up-regulate VEGF and AQP4 respectively.
- G-CSF has protective effects on perihematomal tissue injuries following ICH.
- The above effects of G-CSF on ICH were VEGF and AQP4 dependent.

Granulocyte-colony stimulating factor (G-CSF) has protective effects on many neurological diseases. Here, we aimed to test G-CSF's effects on perihematomal tissue injuries following intracerebral hemorrhage (ICH) and examine whether the effects were functionally dependent on vascular endothelial growth factor (VEGF) and aquaporin-4 (AQP4). We detected the expression of perihematomal VEGF, VEGF receptors (VEGFRs) and AQP4 at 1, 3 and 7 days after ICH. Also, we examined the effects of G-CSF on tissue injuries by ICH in wild type mice, and tested whether such effects were VEGF and AQP4 dependent by using VEGFR inhibitor - SU5416 and AQP4 knock-out (AQP4−/−) mice. Furthermore, we assessed the related signal transduction pathways via astrocyte cultures. We found G-CSF highly increased perihematomal VEGF, VEGFR-2 and AQP4. Importantly, G-CSF led to neurological functional improvement in both types of mice by associating with reduction of brain edema, blood-brain barrier (BBB) permeability and neuronal death and apoptosis and statistical analysis suggested AQP4 was required for these effects. Besides, except BBB leakage alleviation, the above effects were attenuated but not counteracted by SU5416, suggesting involvement of VEGF. G-CSF up-regulated phosphorylation of extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription 3 (STAT3) as well as VEGF and AQP4 proteins in cultured astrocytes. The latter was inhibited by ERK and STAT3 inhibitors respectively. Our data suggest the protective effects of G-CSF on perihematomal tissue injuries after ICH are highly associated with the increased levels of VEGF and AQP4, possibly act through C-Jun amino-terminal kinase and ERK pathways respectively.