Poly-arginine peptides reduce infarct volume in a permanent middle cerebral artery rat stroke model

Diego Milani,Jane L Cross,Ryan S Anderton,Vince W Clark,Neville W Knuckey,Bruno P Meloni

doi:10.1186/s12868-016-0253-z

Abstract

BackgroundWe recently reported that poly-arginine peptides have neuroprotective properties both in vitro and in vivo. In cultured cortical neurons exposed to glutamic acid excitotoxicity, we demonstrated that neuroprotective potency increases with polymer length plateauing at R15 to R18 (R = arginine resides). In an in vivo study in rats, we also demonstrated that R9D (R9 peptide synthesised with D-isoform amino acids) administered intravenously at a dose of 1000 nmol/kg 30 min after permanent middle cerebral artery occlusion (MCAO) reduces infarct volume. Based on these positive in vitro and in vivo findings, we decided to examine the neuroprotective efficacy of the L-isoform poly-arginine peptides, R12, R15 and R18 when administered at a dose of 1000 nmol/kg 30 min after permanent MCAO in the rat.ResultsAt 24 h post-MCAO, there was reduced total infarct volume for R12 (12.8 % reduction) and R18 (20.5 % reduction), but this reduction only reached statistical significance for R18. Brain slice analysis revealed significantly reduced injury in coronal slices 4 and 5 for R18, and slice 5 for R12. The R15 peptide had no effect on infarct volume. Peptide treatment did not reveal any statistical significant improvement in functional outcomes.ConclusionWhile these findings confirm the in vivo neuroprotective properties of poly-arginine peptides, additional dose studies are required particularly in less severe transient MCAO models so as to further assess the potential of these agents as a stroke therapy.

Highlights

We recently reported that poly-arginine peptides have neuroprotective properties both in vitro and in vivo
As evidence of their clinical applicability, we have demonstrated that the poly-arginine R9D significantly reduces infarct volume in vivo following permanent middle cerebral artery occlusion (MCAO) in the rat [6]
These results show that the R18 peptide significantly reduced infarct volume (20.5 % reduction; P = 0.014)

Summary

Introduction

We recently reported that poly-arginine peptides have neuroprotective properties both in vitro and in vivo. In an in vivo study in rats, we demonstrated that R9D (R9 peptide synthesised with D-isoform amino acids) administered intravenously at a dose of 1000 nmol/kg 30 min after permanent middle cerebral artery occlusion (MCAO) reduces infarct volume. Against the backdrop of the limited nature of current therapies, we have recently demonstrated that poly-arginine (and arginine-rich) peptides have potent neuroprotective properties in in vitro injury models that mimic the effects of stroke [5,6,7]. Our in vitro data show that neuroprotective potency is enhanced with increasing arginine content (e.g. polymer length) [6] As evidence of their clinical applicability, we have demonstrated that the poly-arginine R9D significantly reduces infarct volume in vivo following permanent middle cerebral artery occlusion (MCAO) in the rat [6]. A recent report [8] has demonstrated that poly-arginine 7 (R7) containing peptides are neuroprotective in an in vivo retinal ganglion NMDA excitotoxicity model

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