Gene regulation by NMDA receptor activation in the SDN-POA neurons of male rats during sexual development

Abstract

The present study was designed to identify possible signaling pathways, which may play a role in prevention of neuronal apoptosis in the sexually dimorphic nucleus of the preoptic area (SDN-POA) after physiological activation of the N-methyl-D-aspartate (NMDA) receptor. Gene response to the blockage of the NMDA receptor by an antagonist (dizocilpine hydrogen maleate; MK-801) was screened after suppression subtractive hybridization (SSH). The results showed that dfferential screening after SSH detected the presence of some neurotrophic genes (RNA binding motif protein 3 (RBM3), -tubulin) as well as apoptosis-related genes (Bcl-2, cytochrome oxidase subunit II, cytochrome oxidase subunit III) in the SDN-POA of male rats, which were down-regulated by blocking the NMDA receptor. The RT-PCR products of the aforementioned genes in MK-801-treated males were significantly less than that in untreated males. In particular, the expression of Bcl-2 mRNA, including Bcl-2 protein, in male rats were significantly suppressed by MK-801 treatment. Moreover, the binding activity of nuclear factor B (NF B) was significantly higher in male rats than in females, but significantly diminished by blocking the NMDA receptor with MK-801 in male rats. No significant difference in cAMP response element-binding protein (CREB) binding activity was observed among untreated male, MK-801-treated male, untreated female and MK-801-treated female groups. These results suggest that genes regulated by NMDA receptor activation might participate in neuronal growth and/or anti-apoptosis, and support an important signaling pathway of NF B activation and its target gene, Bcl-2, in preventing neuronal apoptosis in the SDN-POA of male rats during sexual development.

Developmental programming and endocrine disruptor effects on reproductive neuroendocrine systems

“…For example, bcl-2 (an anti-apoptotic protein) expression is higher in male than female rats on postnatal day 8, consistent with the overall larger POA size of male rats [78]. A subsequent study from the Hsu group also showed specificity of this phenomenon to the SDN-POA, for which bcl-2 expression was higher in neonatal (postnatal day 2) males than females [79]. Davis et al found that the number of apoptotic cells in the SDN-POA exhibited differential developmental profiles between the sexes, peaking at postnatal day 6 in males and later (between days 7-10) in the females [40].…”

The molecular events occur during MK-801-induced cytochrome oxidase subunit II down-regulation in GT1-7 cells

“…Previously, we have demonstrated that the apoptotic incidence of neurons in SDN-POA of male rats is significantly increased when NMDA receptor is blocked by MK-801 (Hsu et al 2001) and the physiological activation of NMDA receptor may protect against neuronal death by transcriptional increase of some survival-related genes, including COII, in SDN-POA during sexual development (Hsu et al 2005). In this study, we attempted to map the signaling pathway of NMDA receptor-mediated neuronal survival in the GT1-7 cell lines, which were derived from hypothalamic GnRH neurons and expressed NMDA receptor as well as mitochondrial COII genes, by comparing the time course of intracellular events, which have been suggested to be involved in the neuronal apoptosis, induced by blocking the activation of NMDA receptor.…”

“…The apoptotic incidence of neurons in the sexually dimorphic nucleus of the preoptic area (SDN-POA) of male rats is significantly increased when the NMDA receptor is blocked by MK-801 (Hsu et al 2001). Recently, we reported that some neurotropic genes (RNA binding motif protein 3 (RBM3), cytosolic phosphoprotein (P19), cytoskeletal gactin, and a-tubulin) as well as survival-related genes (Bcl-2, cytochrome oxidase subunits II, III (COII), (COIII), and cytochrome b) in SDN-POA of neonatal male rats were significantly down-regulated when the NMDA receptor was blocked (Hsu et al 2005).…”

Microarray analysis of neonatal rat anteroventral periventricular transcriptomes identifies the proapoptotic Cugbp2 gene as sex-specific and regulated by estradiol

“…In addition, Cugbp2 regulates splicing, stabilization or translation of NMDA receptor subunit 1 (Nr1) (Dembowski and Grabowski, 2009), cyclooxygenase 2 (Cox2) (Mukhopadhyay et al, 2003a;Ramalingam et al, 2012) and AR (Miyazaki et al, 2012a). These mRNAs have been previously linked to sexual differentiation of the POA (Hsu et al, 2001(Hsu et al, , 2005McCarthy, 2002, 2004;Zuloaga et al, 2008). Therefore, we performed follow-up studies on Cugbp2 mRNA.…”

“…NMDA R1 splice variants produce NMDA receptors with different characteristics (Durand et al, 1993;Tingley et al, 1993). Although not studied in the AVPV, post-transcriptional (Hsu et al, 2001(Hsu et al, , 2005 regulation of Nr1 appears to mediate protective effects of E 2 in the developing SDN-POA (Hsu et al, 2001). Interestingly, a-actinin two, a protein that directly anchors NMDA receptors in the post-synaptic density (Wyszynski et al, 1997(Wyszynski et al, , 1998, was also upregulated in the male and Cugbp2 regulates splicing of a-actinin (Gromak et al, 2003).…”