The prolyl hydroxylase inhibitor GSK1120360A reduces early brain injury, but protection is not maintained in a neonatal rat model of hypoxic ischaemic encephalopathy

Abstract

Hypoxic–ischemic encephalopathy (HIE) in newborns is associated with high morbidity and mortality, with many babies suffering long-term neurological deficits. Currently, treatment options are limited to therapeutic hypothermia, which is not appropriate for use in all babies. Previous studies have shown protective effects of increasing the transcription factor—hypoxia-inducible factor-1 (HIF-1) in animal models, by using mild hypoxia or compounds that act as prolyl hydroxylase inhibitors (PHIs). Here, we aimed to examine the neuroprotective actions of an orally active, small molecule PHI, GSK1120360A in a neonatal rat model of hypoxia-ischemia (HI) compared to another PHI, desferrioxamine (DFX). Sprague–Dawley rats underwent HI surgery on postnatal day 7 (P7), where unilateral carotid artery occlusion was performed followed by hypoxia (8% oxygen, 3 h). Initial testing showed that GSK1120360A and erythropoietin levels were detectable in plasma at 6 h following oral exposure to GSK1120360A. For the short-term neuroprotection study, pups were assigned to receive either saline (s.c), desferrioxamine (DFX—200 mg/kg, s.c), methylcellulose (1%, oral) or GSK1120360A (30 mg/kg, oral) immediately after HI. Histological analysis showed that GSK1120360A in this setting reduced brain injury size 7 days after HI, compared to the methylcellulose vehicle control group. DFX had no significant effect on injury size compared to saline group at the same 7 day timepoint. In the long-term neuroprotection study, pups were randomly assigned to be administered methylcellulose (1%, oral) or GSK1120360A (30 mg/kg, oral) immediately after HI. On P42, rats underwent behavioural testing using the forelimb grip strength, grid walking and novel object recognition tasks, and brains were collected for histological analysis. Long-term behavioural deficits were observed in grid walking, grip strength and novel object recognition tests after HI which were not improved in the GSK1120360A treatment group compared to the methylcellulose group. Similarly, there was no improvement in injury size on P42 in the GSK1120360A study group compared to the methylcellulose group. Here, we have shown that GSK1120360A can reduce brain injury at 7 days but that this neuroprotective benefit is not maintained when examined at 5 weeks after HI.