Inhibition of HDAC4 Attenuated JNK/c-Jun-Dependent Neuronal Apoptosis and Early Brain Injury Following Subarachnoid Hemorrhage by Transcriptionally Suppressing MKK7.

Liqiang Wu,Shanshan Ma,Sisi Liu,Cheng Zhi,Shulian Zeng,Huaidong Peng,Ziyan Huang,Yali Cao,Zhongmin Yuan,Kunhua Hu

doi:10.3389/fncel.2019.00468

Abstract

The c-Jun N-terminal kinase (JNK)/c-Jun cascade-dependent neuronal apoptosis has been identified as a central element for early brain injury (EBI) following subarachnoid hemorrhage (SAH), but the molecular mechanisms underlying this process are still thoroughly undefined to date. In this study, we found that pan-histone deacetylase (HDAC) inhibition by TSA, SAHA, VPA, and M344 led to a remarkable decrease in the phosphorylation of JNK and c-Jun, concomitant with a significant abrogation of apoptosis caused by potassium deprivation in cultured cerebellar granule neurons (CGNs). Further investigation showed that these effects resulted from HDAC inhibition-induced transcriptional suppression of MKK7, a well-known upstream kinase of JNK. Using small interference RNAs (siRNAs) to silence the respective HDAC members, HDAC4 was screened to be required for MKK7 transcription and JNK/c-Jun activation. LMK235, a specific HDAC4 inhibitor, dose-dependently suppressed MKK7 transcription and JNK/c-Jun activity. Functionally, HDAC4 inhibition via knockdown or LMK235 significantly rescued CGN apoptosis induced by potassium deprivation. Moreover, administration of LMK235 remarkably ameliorated the EBI process in SAH rats, associated with an obvious reduction in MKK7 transcription, JNK/c-Jun activity, and neuronal apoptosis. Collectively, the findings provide new insights into the molecular mechanism of neuronal apoptosis regarding HDAC4 in the selective regulation of MKK7 transcription and JNK/c-Jun activity. HDAC4 inhibition could be a potential alternative to prevent MKK7/JNK/c-Jun axis-mediated nervous disorders, including SAH-caused EBI.

Highlights

Subarachnoid hemorrhage (SAH) is a severe and devastating cerebrovascular disease with high mortality and disability rates greater than 50% (Sekerdag et al, 2018)
To identify the specific histone deacetylase (HDAC) member that is involved in the regulation of MKK7 transcription, the MKK7 mRNA levels were determined following the utility of specific small interference RNAs (siRNAs) to silence the respective member of Class I HDAC (HDAC1, 2, 3, and 8) and Class II HDAC (HDAC4, 5, 6, 7, and 9)
To examine whether Jun N-terminal kinase (JNK)/c-Jun activation and neuronal apoptosis occur in the early brain injury (EBI) following SAH, the rat SAH model was established by using the endovascular perforation method

Summary

Introduction

Subarachnoid hemorrhage (SAH) is a severe and devastating cerebrovascular disease with high mortality and disability rates greater than 50% (Sekerdag et al, 2018). The prevalence of neuronal apoptosis after SAH has been confirmed to be an important contributor to the EBI process (Serrone et al, 2015). The c-Jun N-terminal kinase (JNK; referred to as the stress-activated protein kinase) cascade is one apoptotic pathway that appears to be important in neurons (Coffey, 2014). JNK/c-Jun-dependent neuronal apoptosis has been implicated in EBI after SAH, and the upstream kinases mixed lineage kinase 3 (MLK3)-MKK7 were evidenced to be required for JNK activation (Yin et al, 2016; Okada et al, 2019). The identification of new ways to target the MLK3-MKK7-JNK-cJun cascade would be a promising strategy for the treatment of SAH

Methods

Results

Conclusion