Anti-Apoptotic and Antioxidant Activities of the Mitochondrial Estrogen Receptor Beta in N2A Neuroblastoma Cells.

Ioannis Tsialtas,Achilleas Georgantopoulos,Aikaterini G Karra,Foteini D Kalousi,Anna-Maria G Psarra,Demetrios D Leonidas,Maria E Karipidou

doi:10.3390/ijms22147620

Ioannis Tsialtas, Achilleas Georgantopoulos + Show 5 more

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https://doi.org/10.3390/ijms22147620

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Abstract

Estrogens are steroid hormones that play a crucial role in the regulation of the reproductive and non-reproductive system physiology. Among non-reproductive systems, the nervous system is mainly affected by estrogens due to their antioxidant, anti-apoptotic, and anti-inflammatory activities, which are mediated by membranous and nuclear estrogen receptors, and also by non-estrogen receptor-associated estrogen actions. Neuronal viability and functionality are also associated with the maintenance of mitochondrial functions. Recently, the localization of estrogen receptors, especially estrogen receptor beta, in the mitochondria of many types of neuronal cells is documented, indicating the direct involvement of the mitochondrial estrogen receptor beta (mtERβ) in the maintenance of neuronal physiology. In this study, cell lines of N2A cells stably overexpressing a mitochondrial-targeted estrogen receptor beta were generated and further analyzed to study the direct involvement of mtERβ in estrogen neuroprotective antioxidant and anti-apoptotic actions. Results from this study revealed that the presence of estrogen receptor beta in mitochondria render N2A cells more resistant to staurosporine- and H2O2-induced apoptotic stimuli, as indicated by the reduced activation of caspase-9 and -3, the increased cell viability, the increased ATP production, and the increased resistance to mitochondrial impairment in the presence or absence of 17-β estradiol (E2). Thus, the direct involvement of mtERβ in antioxidant and anti-apoptotic activities is documented, rendering mtERβ a promising therapeutic target for mitochondrial dysfunction-associated degenerative diseases.

Highlights

Estrogens play a central role in the regulation of the biochemical processes related to female reproduction [1] and non-reproductive tissue physiology [2], but they act on male reproductive tissue [3]
The classical mechanism of estrogen actions is mainly mediated by the nuclear estrogen receptors (ERs), estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), which function as ligand-dependent transcription factors, regulating the transcription of target genes containing the consensus estrogen response element (ERE) in their promoter regions
To explore whether mitochondrial estrogen receptor beta is directly involved in neuroprotection against apoptotic and oxidative stress stimuli, neuroblastoma N2A cells stably overexpressing a mitochondrial targeted ERβ fused with the green fluorescence protein were generated (N2AmtGFPERβ)

Summary

Introduction

Estrogens play a central role in the regulation of the biochemical processes related to female reproduction [1] and non-reproductive tissue physiology [2], but they act on male reproductive tissue [3]. A wide variety of biological actions, including differentiation, cell proliferation, apoptosis, antioxidant defense, and inflammation, are regulated by the main estrogenic hormone 17-β estradiol (E2) [4]. The classical mechanism of estrogen actions is mainly mediated by the nuclear estrogen receptors (ERs), estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), which function as ligand-dependent transcription factors, regulating the transcription of target genes containing the consensus estrogen response element (ERE) in their promoter regions. Estrogen-activated nuclear ERs can regulate non-ERE dependent transcription via interactions with other transcription factors, such as AP-1, affecting positively or negatively the expression of their target genes. In addition to the classical nuclear actions of estrogen, rapid membrane-initiated actions could take place, which are mediated via plasma membrane-associated mERα, mERβ and G-protein coupled ERs (GPER, GPER1) [7,8,9]. The biochemical mechanisms of the direct actions of estrogen in mitochondria, via their cognate receptors, is under investigation and many aspects of these actions remain to be verified and further explored

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