Cholic Acid Protects In Vitro Neurovascular Units against Oxygen and Glucose Deprivation-Induced Injury through the BDNF-TrkB Signaling Pathway.

Changxiang Li,Congai Chen,Juntang Yan,Xiaona Ma,Wei Wang,Fafeng Cheng,Xueqian Wang,Qingguo Wang,Robert Ostrowski

doi:10.1155/2020/1201624

Abstract

Ischemic stroke (IS) can disrupt various types of brain cells in the neurovascular unit (NVU) at both the structural and functional levels. Therefore, NVU is considered to be a more comprehensive target for the treatment of IS. It is necessary to develop drugs which targeted multiple mechanisms and cell types on NVU against IS. As a component of bile acid, cholic acid has been reported to be able to diffuse across phospholipid bilayers and further cross the blood-brain barrier (BBB). However, the effects exerted by cholic acid (CA) on the NVU after stroke remain unclear. Based on our previous research, we established and further supplemented the characteristics of the functional in vitro NVU model and its oxygen-glucose deprivation and reoxygenation (OGD/R) model. Then, we investigated the effect of CA on the maintenance of the in vitro NVU after OGD/R and further discussed the specific molecular targets that CA played a role in. For the first time, we found that CA significantly maintained BBB integrity, downregulated apoptosis, and mitigated oxidative stress and inflammation damage after OGD/R. Meanwhile, CA obviously increased the levels of brain-derived neurotrophic factor (BDNF), which were mainly secreted from astrocytes, in the coculture system after OGD/R. The results demonstrated that CA significantly increased the expression of TrkB, PI3K/Akt, MAPK/Erk, and CREB in neurons. These positive effects on the downstream proteins of BDNF were suppressed by treatment with ANA12 which is an inhibitor of TrkB. In conclusion, the present study demonstrates that CA exerted multiple protective effects on the NVU, mediated by increasing the release of BDNF and further stimulating the BDNF-TrkB-PI3K/Akt and BDNF-TrkB-MAPK/Erk signaling pathways in the context of OGD/R-induced injury. These findings indicate that CA possesses the effect of antagonizing multiple mechanisms of IS and protecting multiple cell types in NVU and may be useful as a treatment for IS.

Highlights

Stroke remains one of the leading causes of death and disability worldwide; Ischemic stroke (IS) accounts for over 80% of strokes [1]
Immunofluorescence and western blotting results revealed that tight junction proteins were expressed when cultured with neurons and astrocytes at 120 h compared to single brain microvascular endothelial cells (BMECs), and the expression was most abundant in the presence of astrocytes and neurons (Figures 2(e) and 2(f))
Western Blot (WB) results showed that the MAP2 level was significantly higher in the in vitro neurovascular unit (NVU) model than in the monoculture, cocultured with BMECs or astrocytes (Figure 2(i))

Summary

Introduction

Stroke remains one of the leading causes of death and disability worldwide; IS accounts for over 80% of strokes [1]. The thrombolytic approach was the FDA-approved therapy for cerebral ischemia; only approximately 5% of patients benefit from this treatment [2]. Many studies have been devoted to demonstrating that neuroprotective and neurorestorative therapies limit ischemic injury after stroke by promoting structural and functional recovery [3]. A majority of agents targeted a single event in the ischemic cascade and targeted the single neural element; the overspecifications may in part explain failure in the clinical setting [4]. It is strongly suggested that stroke be approached with multiple, multifaceted neuroprotective and neurorestorative methods. The establishment of structural and functional units of organs in vitro is necessary to further understand brain functions and facilitate new treating approaches to enable cost-effective and more accurate predictions of drug efficacy [4]

Methods

Results

Discussion

Conclusion