Ligand-induced changes in Oestrogen and thyroid hormone receptor expression in the developing rat cerebellum: A comparative quantitative PCR and Western blot study

Abstract

Oestrogen (E2) and thyroid hormones (THs) are key regulators of cerebellar development. Recent reports implicate a complex mechanism through which E2 and THs influence the expression levels of each other's receptors (ERs and TRs) to precisely mediate developmental signals and modulate signal strength. We examined the modulating effects of E2 and THs on the expression levels of their receptor mRNAs and proteins in cultured cerebellar cells obtained from 7-day-old rat pups. Cerebellar granule cell cultures were treated with either E2, THs or a combination of these hormones, and resulting receptor expression levels were determined by quantitative PCR and Western blot techniques. The results were compared to non-treated controls and to samples obtained from 14-day-old in situ cerebella. Additionally, we determined the glial effects on the regulation of ER-TR expression levels. The results show that (i) ER and TR expression depends on the combined presence of E2 and THs; (ii) glial cells mediate the hormonal regulation of neuronal ER-TR expression and (iii) loss of tissue integrity results in characteristic changes in ER-TR expression levels. These observations suggest that both E2 and THs, in adequate amounts, are required for the precise orchestration of cerebellar development and that alterations in the ratio of E2/THs may influence signalling mechanisms involved in neurodevelopment. Comparison of data from in vitro and in situ samples revealed a shift in receptor expression levels after loss of tissue integrity, suggesting that such adjusting/regenerative mechanisms may function after cerebellar tissue injury as well.

Bisphenol A influences oestrogen- and thyroid hormone-regulated thyroid hormone receptor expression in rat cerebellar cell culture

“…The results of hormone treatments were concordant with those we previously described (Scalise et al, 2012), so they will not be the major focus of this report; rather, these non-BPA-results are used as the reference base for the comparison between the effects of BPA alone and in combination with either E 2 and/or THs.…”

“…Cerebella of rat pups were seeded into separate culture dishes (i.e., 6 dishes per treatment, n = 6). Astroglia in the cultures was identified by immunohistochemical labelling for the specific astroglia marker glial fibrillary acidic protein (GFAP), as we previously described and illustrated (Scalise et al, 2012).…”

“…In contrast, no AraC was added to the media for analysis of neurones grown in a glia-containing environment (Glia+ cultures). The presence or absence of glia in the cultures was verified and illustrated as shown earlier (Scalise et al, 2012). Cultures were treated with either of the following hormones (at physiologically relevant concentrations, as described below) and/or bisphenol A, 7 days after seeding and 6 h (for qPCR) or 18 h (for Western blot) before harvesting: 17β-oestradiol (E 2 , 1.16x10 -10 M, Sigma Aldrich Ltd., Hungary, Cat.…”

Comparative approaches to understanding thyroid hormone regulation of neurogenesis

“…Besides, EE2 exposure during adulthood has been shown to disrupt cell proliferation in neurogenic niches of mice (Brock et al, 2010;Ormerod et al, 2003) and zebrafish (Diotel et al, 2013). Since cross-talks exist between estrogens and TH pathways at multiple levels, especially through co-regulations of TR and estrogen receptor expression, the implication of TH signaling in EE2-mediated disruption is highly probable (Scalise et al, 2012;Zane et al, 2014). Thus, it appears that EDCs can impact neurogenesis at all stages of life, and even in the ageing brain (Weiss, 2007).…”

Endocrine Disruptors Induced Distinct Expression of Thyroid and Estrogen Receptors in Rat versus Mouse Primary Cerebellar Cell Cultures

“…Available data suggest that estrogens-estrone (E1), 17β-estradiol (E2), and estriol (E3)-and thyroid hormones (THs)-triiodothyronine (T3) and thyroxine (T4)-are equally important regulators of CNS development [31,32]. In the developing cerebellum and possibly in any other brain area, a complex, interconnected effect can be seen between the respective hormones of TRs and ERs, maintaining the physiological levels of these specified receptors [33,34].…”