Recombinant adiponectin peptide promotes neuronal survival after intracerebral haemorrhage by suppressing mitochondrial and ATF4-CHOP apoptosis pathways in diabetic mice via Smad3 signalling inhibition.

Xun Wu,Kang Guo,Hao Bai,Wenxing Cui,Wei Guo,Lei Zhao,Haixiao Liu,Jianing Luo,Hao Guo,Yan Qu,Dayun Feng

doi:10.1111/cpr.12759

Abstract

ObjectiveLow levels of adiponectin (APN), a biomarker of diabetes mellitus, have been implicated in the poor outcome of intracerebral haemorrhage (ICH). Herein, we aimed to demonstrate the neuroprotective effects of a blood‐brain barrier‐permeable APN peptide (APNp) on ICH injury in diabetic mice and explore the underlying mechanisms.Materials and methodsRecombinant APNp was administrated intraperitoneally to mice with collagenase‐induced ICH. Neurological deficits, brain water content and neural apoptosis were assessed. Western blotting, immunofluorescence staining, quantitative RT‐PCR and transmission electron microscopy were used to determine the signalling pathways affected by APNp.ResultsAdiponectin peptide significantly alleviated neural apoptosis, neurological deficits and brain oedema following ICH in diabetic mice. Mechanistically, APNp promoted the restoration of peroxisome proliferator‐activated receptor gamma coactivator (PGC)‐1α related mitochondrial function and suppressed activating transcription factor 4 (ATF4)‐CCAAT‐enhancer‐binding protein homologous protein (CHOP)‐induced neural apoptosis. Furthermore, Smad3 signalling was found to play a regulatory role in this process by transcriptionally regulating the expression of PGC‐1α and ATF4. APNp significantly suppressed the elevated phosphorylation and nuclear translocation of Smad3 after ICH in diabetic mice, while the protective effects of APNp on mitochondrial and ATF4‐CHOP apoptosis pathways were counteracted when Smad3 was activated by exogenous transforming growth factor (TGF)‐β1 treatment.ConclusionsOur study provided the first evidence that APNp promoted neural survival following ICH injury in the diabetic setting and revealed a novel mechanism by which APNp suppressed mitochondrial and ATF4‐CHOP apoptosis pathways in a Smad3 dependent manner.

Highlights

Intracerebral haemorrhage (ICH) is an acute subtype of cerebral stroke with high death rates and severe neurological deficits
The major findings of the present experiments can be summarized as follows: (a) compared with nondiabetic mice, db/db mice presented some confounding pathological features of ICH, including more severe brain oedema and neurological deficits, aggravated mitochondrial and activating transcription factor 4 (ATF4)-CCAAT-enhancer-binding protein homologous protein (CHOP) apoptosis injuries, and exacerbated activation of Smad[3] signalling. (b) APN peptide (APNp) treatment might be a novel therapeutic strategy for brain injury following ICH complicated with type 2 diabetes. (c) APNp treatment remarkably alleviated mitochondrial dysfunction and ATF4-CHOP axis induced apoptosis after ICH in diabetic mice, and (d) mechanistically, this alleviation was in a Smad3-dependent manner
Reduced APN function has been demonstrated to be a major contributor in the pathogenic process of type 2 Diabetes mellitus (DM); clinical trials showed that the level of serum APN was negatively correlated with acute death and functional impairment after cerebral stroke.[9-11]

Summary

| INTRODUCTION

Intracerebral haemorrhage (ICH) is an acute subtype of cerebral stroke with high death rates and severe neurological deficits. Exploring the protective effects of APNp on mitochondrial and ATF4-CHOP apoptosis pathways after ICH in db/db mice was one of the aims of our study. Previous research used sequence analysis to reveal the presence of SBEs in the promoters of PGC-1α and ATF4 and found that activated Smad[3] signalling could transcriptionally decrease PGC-1α levels[37] and increase ATF4 levels[38] in adipose tissue This led us to question whether Smad[3] played a distinctive role in regulating the mitochondrial and ATF4-CHOP apoptosis pathways in diabetic mice that contribute to aggravated neural apoptosis following ICH. We aimed to investigate the neuroprotective effects of APNp treatment on neural survival following ICH injury in a mouse model of type 2 diabetes and to investigate the mechanisms by which APNp suppresses mitochondrial and ATF4-CHOP apoptosis pathways in a Smad3-dependent manner

| MATERIALS AND METHODS

Findings

| DISCUSSION