Peptidylarginine deiminases: novel drug targets for prevention of neuronal damage following hypoxic ischemic insult (HI) in neonates.

Sigrun Lange,Donald Peebles,Mariya Hristova,Venkataraman Subramanian,Eridan Rocha‐Ferreira,Priyanka Mawjee,Paul R Thompson,Laura Thei,Gennadij Raivich,Anthony P Nicholas,Kate Bennett

doi:10.1111/jnc.12744

Abstract

Neonatal hypoxic ischaemic (HI) injury frequently causes neural impairment in surviving infants. Our knowledge of the underlying molecular mechanisms is still limited. Protein deimination is a post-translational modification caused by Ca+2-regulated peptidylarginine deiminases (PADs), a group of five isozymes that display tissue-specific expression and different preference for target proteins. Protein deimination results in altered protein conformation and function of target proteins, and is associated with neurodegenerative diseases, gene regulation and autoimmunity. In this study, we used the neonatal HI and HI/infection [lipopolysaccharide (LPS) stimulation] murine models to investigate changes in protein deimination. Brains showed increases in deiminated proteins, cell death, activated microglia and neuronal loss in affected brain areas at 48 h after hypoxic ischaemic insult. Upon treatment with the pan-PAD inhibitor Cl-amidine, a significant reduction was seen in microglial activation, cell death and infarct size compared with control saline or LPS-treated animals. Deimination of histone 3, a target protein of the PAD4 isozyme, was increased in hippocampus and cortex specifically upon LPS stimulation and markedly reduced following Cl-amidine treatment. Here, we demonstrate a novel role for PAD enzymes in neural impairment in neonatal HI Encephalopathy, highlighting their role as promising new candidates for drug-directed intervention in neurotrauma.Hypoxic Ischaemic Insult (HI) results in activation of peptidylarginine deiminases (PADs) because of calcium dysregulation. Target proteins undergo irreversible changes of protein bound arginine to citrulline, resulting in protein misfolding. Infection in synergy with HI causes up-regulation of TNFα, nuclear translocation of PAD4 and change in gene regulation as a result of histone deimination. Pharmacological PAD inhibition significantly reduced HI brain damage.

Highlights

Address correspondence and reprint requests to Sigrun Lange, UCL Institute for Women’s Health, Maternal & Fetal Medicine, Perinatal Brain Repair Group, London WC1E 6HX, UK
Lange et al (2011) demonstrated a novel functional role in spinal cord injury by using pharmacological inhibition of protein deimination with the pan-peptidylarginine deiminases (PADs) inhibitor Cl-amidine. This resulted in significantly reduced cavity size, neuronal damage and apoptosis in the injured spinal cord. As this was the first, and so far sole study to show a role for PADs in neuronal injury, and protein deimination has not been described in brain injury before, our question was if the protective effect of PAD inhibition would be translatable to other models of neuronal damage
As in the spinal cord, histone deimination suggested a role for epigenetic regulation in response to injury, while changes in deimination of cytoskeletal components could affect apoptosis, cell motility and the ability of injured neurons to regrow axons (Lange et al 2011), we focused on detecting changes in total protein deimination, and deiminated histones, in response to PAD inhibition in the HI Encephalopathy (HIE) model

Summary

Introduction

Lange et al (2011) demonstrated a novel functional role in spinal cord injury by using pharmacological inhibition of protein deimination with the pan-PAD inhibitor Cl-amidine. This resulted in significantly reduced cavity size, neuronal damage and apoptosis in the injured spinal cord. As this was the first, and so far sole study to show a role for PADs in neuronal injury, and protein deimination has not been described in brain injury before, our question was if the protective effect of PAD inhibition would be translatable to other models of neuronal damage. The identification of target molecules for drug-directed early intervention in response to hypoxic insult is of great importance in relation to the prevention of long-term damage caused by oxygen deprivation and infections in neonates

Methods

Results

Conclusion