Anti-neutrophil antibody enhances the neuroprotective effects of G-CSF by decreasing number of neutrophils in hypoxic ischemic neonatal rat model

- G-CSF + Ab treatment was more effective than G-CSF alone treatment after HI.
- G-CSF + Ab reduced infarct volume.
- G-CSF + Ab prevented brain atrophy and significantly improved neurological function.
- Ab enhanced G-CSF's neuroprotection by reducing blood neutrophil counts post HI.

ObjectivesNeonatal hypoxia ischemia (HI) is an injury that can lead to neurological impairments such as behavioral and learning disabilities. Granulocyte-colony stimulating factor (G-CSF) has been demonstrated to be neuroprotective in ischemic stroke however it has also been shown to induce neutrophilia, ultimately exacerbating neuronal injury. Our hypothesis is that coadministration of anti-neutrophil antibody (Ab) with G-CSF will decrease blood neutrophil counts thereby reducing infarct volume and improving neurological function post HI brain injury.MethodsRat pups were subjected to unilateral carotid artery ligation followed by 2.5 h of hypoxia. Animals were randomly assigned to five groups: Sham (n = 15), vehicle (HI, n = 15), HI with G-CSF treatment (n = 15), HI with G-CSF + Ab treatment (n = 15), and HI with Ab treatment (n = 15). Ab (325 μg/kg) was administered intraperitoneally while G-CSF (50 μg/kg) was administered subcutaneously 1 h post HI followed by daily injections for 3 consecutive days. Animals were euthanized at 96 h post HI for blood neutrophil counts and brain infarct volume measurements as well as at 5 weeks for neurological function testing and brain weight measurements. Lung and spleen weights at both time points were further analyzed.ResultsThe G-CSF treatment group showed tendencies to reduce infarct volume and improve neurological function while significantly increasing neutrophil counts. On the other hand, the G-CSF + Ab group significantly reduced infarct volume, improved neurological function and decreased neutrophil counts. The Ab alone group showed reversal of the neuroprotective effects of the G-CSF + Ab group. No significant differences were found in peripheral organ weights between groups.ConclusionOur data suggest that coadministration of G-CSF with Ab not only prevented brain atrophy but also significantly improved neurological function by decreasing blood neutrophil counts. Hence the neuroprotective effects of G-CSF may be further enhanced if neutrophilia is avoided.