17β-estradiol modulates mitochondrial Ca²⁺ flux in rat caudate nucleus and brain stem

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

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.

Effect of 17β-estradiol on striatal dopaminergic transmission induced by permethrin in early childhood rats

A positive effect of estrogen treatment has been observed in neurodegenerative diseases such as Parkinson's disease. Since 17β-estradiol can modulate positively dopaminergic system, here we sought to evaluate the effect of 17β-estradiol supplementation on an animal model developing dopaminergic alterations on nucleus of striatum after neonatal exposure to permethrin pesticide. The goal of the study was to verify if the co-treatment with 17β-estradiol could protect against the damage induced by pesticide exposure in early life. Permethrin treated rats showed a decrease of dopamine and Nurr1 gene expression in striatum, while a more pronounced decrease of dopamine was observed in rats co-administered with permethrin+17β-estradiol. No difference between control and permethrin treated rats was observed in both mRNA of ERα and ERβ, whereas the rats co-administered with permethrin+17β-estradiol showed a down-regulation of ERα expression. The in vitro studies showed that permethrin, at high concentration may have an antagonist effect on ERα and even more pronounced in ERβ, thus suggesting that permethrin may block the estrogen neuroprotective effects. In conclusion, in male rats, the administration of estrogen further enhanced the impairment of dopaminergic transmission due to exposure to permethrin.