Poly-arginine R18 and R18D (D-enantiomer) peptides reduce infarct volume and improves behavioural outcomes following perinatal hypoxic-ischaemic encephalopathy in the P7 rat

Adam B Edwards,Ryan S Anderton,Jane L Cross,Neville W Knuckey,Bruno P Meloni

doi:10.1186/s13041-018-0352-0

Abstract

We examined the neuroprotective efficacy of the poly-arginine peptide R18 and its D-enantiomer R18D in a perinatal hypoxic-ischaemic (HI) model in P7 Sprague-Dawley rats. R18 and R18D peptides were administered intraperitoneally at doses of 30, 100, 300 or 1000 nmol/kg immediately after HI (8% O2/92%N2 for 2.5 h). The previously characterised neuroprotective JNKI-1-TATD peptide at a dose of 1000 nmol/kg was used as a control. Infarct volume and behavioural outcomes were measured 48 h after HI. For the R18 and R18D doses examined, total infarct volume was reduced by 25.93% to 43.80% (P = 0.038 to < 0.001). By comparison, the JNKI-1-TATD reduced lesion volume by 25.27% (P = 0.073). Moreover, R18 and R18D treatment resulted in significant improvements in behavioural outcomes, while with JNKI-1-TATD there was a trend towards improvement. As an insight into the likely mechanism underlying the effects of R18, R18D and JNKI-1-TATD, the peptides were added to cortical neuronal cultures exposed to glutamic acid excitotoxicity, resulting in up to 89, 100 and 71% neuroprotection, respectively, and a dose dependent inhibition of neuronal calcium influx. The study further confirms the neuroprotective properties of poly-arginine peptides, and suggests a potential therapeutic role for R18 and R18D in the treatment of HIE.

Highlights

In the human neonate, hypoxic-ischaemic encephalopathy (HIE) remains the leading cause of neonatal mortality and morbidity, with a reported incidence of 1–3 per 1000 live term births [1], [2]
To assess infarct development within 2 mm coronal slices, rostral to caudal topographic analysis of infarcts revealed that R18, R18D and JNKI-1-TATD at all doses significantly reduced brain injury in one or more coronal slices 1 to 6 (Fig. 1c; refer to Additional file 1: Table S1 for descriptive statistics)
Animals treated with JNKI-1-TATD (1000 nmol/kg) showed no a b c d e f g h statistically significant improvement, there was a trend towards improvement (43.87%; P = 0.063)

Summary

Introduction

Hypoxic-ischaemic encephalopathy (HIE) remains the leading cause of neonatal mortality and morbidity, with a reported incidence of 1–3 per 1000 live term births [1], [2]. Due to the need for additional neuroprotective strategies for HIE, research has focused on the development of a pharmacological neuroprotective agent that can be Edwards et al Molecular Brain (2018) 11:8 administered alone and/or in combination with current hypothermia treatment to improve neonatal outcomes in HIE. We and others have recently demonstrated that cationic arginine-rich and poly-arginine peptides (hereafter referred to as CARPs) have potent neuroprotective properties in in vitro excitotoxicity neuronal injury models [5,6,7,8,9,10,11,12,13], as well as in animal stroke models [10, 11, 14,15,16]. We have demonstrated that the polyarginine peptide, R18, is highly neuroprotective in permanent and transient middle cerebral artery occlusion (MCAO) stroke models [11, 14,15,16]

Methods

Results

Conclusion