Early applications of granulocyte colony-stimulating factor (G-CSF) can stabilize the blood-optic nerve barrier and further ameliorate optic nerve inflammation in a rat model of anterior ischemic optic neuropathy (rAION)

Abstract

Granulocyte colony-stimulating factor (G-CSF) was reported to have a neuroprotective effect in a rat model of anterior ischemic optic neuropathy (rAION model). However, the therapeutic window and anti-inflammatory effects of G-CSF in a rAION model have yet to be elucidated. Thus, this study aimed to determine the therapeutic window of G-CSF and investigate the mechanisms of G-CSF via regulation of optic nerve (ON) inflammation in a rAION model. Rats were treated with G-CSF on day 0, 1, 2 or 7 post-rAION induction for 5 consecutive days, and a control group were treated with phosphate-buffered saline (PBS). Visual function was assessed by flash visual evoked potentials at 4 weeks post-rAION induction. The survival rate and apoptosis of retinal ganglion cells were determined by FluoroGold labeling and TUNEL assay, respectively. ON inflammation was evaluated by staining of ED1 and Iba1, and ON vascular permeability was determined by Evans Blue extravasation. The type of macrophage polarization was evaluated using quantitative real-time PCR (qRT-PCR). The protein levels of TNF-α and IL-1β were analyzed by western blotting. A therapeutic window during which G-CSF could rescue visual function and retinal ganglion cell survival was demonstrated at day 0 and day 1 post-infarct. Macrophage infiltration was reduced by 3.1- and 1.6-fold by G-CSF treatment starting on day 0 and 1 post-rAION induction, respectively, compared with the PBS-treated group (P<0.05). This was compatible with 3.3- and 1.7-fold reductions in ON vascular permeability after G-CSF treatment compared with PBS treatment (P<0.05). Microglial activation was increased by 3.8- and 3.2-fold in the early (beginning treatment at day 0 or 1) G-CSF-treated group compared with the PBS-treated group (P<0.05). Immediate (within 30 mins of infarct) treatment with G-CSF also induced M2 microglia/macrophage activation. The cytokine levels were lower in the group that received immediate G-CSF treatment compared to those in the later G-CSF treatment group (P<0.05). Early treatment with G-CSF stabilized the blood–ON barrier to reduce macrophage infiltration and induced M2 microglia/macrophage polarization to decrease the expressions of pro-inflammatory cytokines in this rAION model.

Haematococcus pluvialis-Derived Astaxanthin Is a Potential Neuroprotective Agent against Optic Nerve Ischemia

“…Neuroinflammation has been shown to play a vital role after optic nerve ischemia [28][29][30][31]. In our observations, treatment with astaxanthin decreased the levels of IL-1β and TNFα in the retina and reduced ED1-positive macrophage infiltration in the optic nerve after rAION induction.…”

Early Methylprednisolone Treatment Can Stabilize the Blood-Optic Nerve Barrier in a Rat Model of Anterior Ischemic Optic Neuropathy (rAION)

“…[9][10][11][12] After the induction of ON ischemia, the breakdown of the blood-optic nerve barrier (BOB) occurs within hours, 8,13 and the recruitment of extrinsic macrophages and the activation of resident microglia at the ischemic core are identified as early as 3 days after the insult. [14][15][16][17] Functional changes such as in the amplitude of visual-evoked potentials (VEPs) were also mitigated early before the permanent degradation following rAION induction. 18 There is evidence suggesting that the administration of corticosteroids can effectively decrease tissue edema by increasing the expression levels of the occludin and claudin-5 genes and stabilizing the blood-brain barrier (BBB) in models of brain osmotic insult, as well as models of retinal diseases.…”

“…The laser settings were the same as that reported in our previous paper. 14,27,28 Flash Visual-Evoked Potentials (FVEP)…”

“…29,30 The details of the vascular permeability test have been described in our previous report. 14 The summary of the animal numbers used in the vascular permeability study is illustrated in Figure 1. After the rats were anesthetized, 2% EB (Sigma-Aldrich Corp., sonicated and filtered) was injected into the tail vein (final dosage: 4 mL/ kg).…”

A RATional choice for translational research?

“…In the second study, Rong-Kung Tsai and co-authors aimed to determine the therapeutic window and anti-inflammatory mechanism for the neuroprotective effect of granulocyte colony-stimulating factor (G-CSF), using an established rat model of acute ischemic optic neuropathy. They showed that early treatment with G-CSF rescued visual function and retinal ganglion cell survival, most likely through stabilising the blood–brain barrier and reducing macrophage infiltration (Wen et al, 2016). …”