Low and High Molecular Weight FGF-2 Have Differential Effects on Astrocyte Proliferation, but Are Both Protective Against Aβ-Induced Cytotoxicity.

Xi Chen,Y Peng Loh,Elissavet Kardami,Zhaojin Li,Yong Cheng

doi:10.3389/fnmol.2019.00328

Abstract

Astrocytes are the most abundant type of glial cells in the brain, and they play a key role in Alzheimer’s disease (AD). Fibroblast Growth Factor-2 (FGF-2) has been implicated as a potential therapeutic agent for treating AD. In the present study, we investigated the protective effects of low molecular weight (LMW; 17 KDa) and high molecular weight (HMW; 23 KDa) forms of FGF-2 on Aβ1–42-induced toxicity, and proliferation in astrocytes. We show that both isoforms of FGF-2 have similar protective effects against Aβ1–42-induced cytotoxicity in primary cultured cortical astrocytes as measured by Lactate Dehydrogenase (LDH) release assay. Additionally, 17 KDa FGF-2 significantly promoted astrocyte proliferation as measured by Trypan Blue, DRAQ5 and 5-ethynyl-2’-deoxyuridine (EdU) staining, but not 23 kDa FGF-2. Furthermore, our results demonstrated that AKT signaling pathway was required for the protective and proliferative effects of FGF-2. Downstream effector studies indicated that 17 kDa FGF-2 promoted astrocyte proliferation by enhanced expression of c-Myc, Cyclin D1, Cyclin E. Furthermore, our data suggested that Cyclin D1 was required for the proliferative effect of LMW FGF2 in astrocytes. Taken together, our findings provide important information for the similarities and differences between 23 kDa and17 kDa isoforms of FGF-2 on astrocyte survival and proliferation.

Highlights

Alzheimer’s disease (AD) is the most prevalent type of dementia and is characterized by the progressive decline, and loss of multiple cognitive functions (Ai et al, 2019; Das et al, 2019)
To determine whether Fibroblast Growth Factor-2 (FGF-2) (Figure 1A) protects astrocytes against Aβ1–42 toxicity, 20 μM Aβ1–42 with or without 10 ng/ml low molecular weight (LMW) and high molecular weight (HMW) Fibroblast growth factors (FGFs)-2 was added to the media of the cultured astrocytes and incubated for 24 h, and the purity of cultured astrocytes was above 95% (Figures 1B,C)
This protective effect was further investigated by adding both isoforms of FGF-2 to astrocytes subjected to oxidative stress induced by 200 μM H2O2 treatment

Summary

Introduction

Alzheimer’s disease (AD) is the most prevalent type of dementia and is characterized by the progressive decline, and loss of multiple cognitive functions (Ai et al, 2019; Das et al, 2019). The characteristic pathologic hallmarks, including neuritic plaques, synaptic loss (Katsouri et al, 2015), neurofibrillary tangles, and deposits of Aβ have been observed in the brain of AD patients (Granadillo et al, 2017). Aβ is believed to be a pivotal mediator of neuronal degeneration, leading to impaired cognitive function (Mattson, 2004; Hardy, 2006). It is, imperative to search for drugs that target Aβ toxicity. Aβ is a peptide of 39–43 amino acids and has been shown to have a wide range of toxic effects in vitro and in vivo, including excitotoxicity, mitochondrial alterations, synaptic dysfunction, altered calcium homeostasis and oxidative stress (Carrillo-Mora et al, 2014). Most researchers have focused on the Aβ1−42 form which has been found to be more aggregation-prone (Finder et al, 2010; Hubin et al, 2014) and is considered to be more closely linked with AD pathogenesis than the Aβ1−40 form (Harasta and Ittner, 2017)

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Conclusion