Sex- and Age-Specific Impact of ERK Loss Within the Pituitary Gonadotrope in Mice.

Extracellular signal-regulated kinase (ERK) signaling regulates hormone action in the reproductive axis, but specific mechanisms have yet to be completely elucidated. In the current study, ERK1 null and ERK2 floxed mice were combined with a gonadotropin-releasing hormone receptor (GnRHR)-internal ribosomal entry site-Cre (GRIC) driver. Female ERK double-knockout (ERKdko) animals were hypogonadotropic, resulting in anovulation and complete infertility. Transcript levels of four gonadotrope-specific genes (GnRHR and the three gonadotropin subunits) were reduced in pituitaries at estrus in ERKdko females, and the postcastration response to endogenous GnRH hyperstimulation was blunted. As females aged, they exhibited abnormal ovarian histology, as well as increased body weight. ERKdko males were initially less affected, showing moderate subfertility, up to 6 months of age. Male ERKdko mice also displayed a blunted response to endogenous GnRH following castration. By 12 months of age, ERKdko males had reduced testicular weights and sperm production. By 18 months of age, the ERKdko males displayed reduced testis and seminal vesicle weights, marked seminiferous tubule degeneration, and a 77% reduction in sperm production relative to controls. As the GRIC is also active in the male germ line, we examined the specific role of ERK loss in the testes using the stimulated by retinoic acid 8 (Stra8)-Cre driver. Whereas ERK loss in GRIC and Stra8 males resulted in comparable losses in sperm production, seminiferous tubule histological degeneration was only observed in the GRIC-ERKdko animals. Our data suggest that loss of ERK signaling and hypogonadotropism within the reproductive axis impacts fertility and gonadal aging.

Inhibitory action of tongue sole LPXRFa, the piscine ortholog of gonadotropin-inhibitory hormone, on the signaling pathway induced by tongue sole kisspeptin in COS-7 cells transfected with their cognate receptors.

Kisspeptin (Kiss) acts as a positive regulator of reproduction by acting on gonadotropes and gonadotropin-releasing hormone (GnRH) neurons. Despite its functional significance, the intricate web of intracellular signal transduction pathways in response to Kiss is still far from being fully understood in teleosts. Accordingly, we investigated the molecular mechanism of Kiss action and its possible interaction with LPXRFa signaling in this study. In vitro functional analysis revealed that synthetic tongue sole Kiss2 decapeptide increased the cAMP responsive element-dependent luciferase (CRE-luc) activity in COS-7 cells transfected with its cognate receptor, while this stimulatory effect was markedly reduced by two inhibitors of the adenylate cyclase (AC)/protein kinase A (PKA) pathway. Similarly, Kiss2 also significantly stimulated serum responsive element-dependent luciferase (SRE-luc) activity, whereas this stimulatory effect was evidently attenuated by two inhibitors of the phospholipase C (PLC)/protein kinase C (PKC) pathway. In addition, LPXRFa-2 suppressed Kiss2-elicited CRE-luc activity in a dose-dependent manner. Taken together, Kiss2 utilizes both AC/PKA and PLC/PKC pathways to exert its functions via its cognate receptor and LPXRFa may antagonize the action of Kiss2 by inhibiting kisspeptin signaling. As far as we know, this study is the first to characterize the half-smooth tongue sole kisspeptin and LPXRFa signaling pathway in COS-7 cells transfected with their cognate receptors and provides novel information on the interaction between LPXRFa system and kisspeptin system in teleosts.

Giant pituitary adenomas: pathologic-radiographic correlations and lack of role for p53 and MIB-1 labeling.

Giant pituitary adenomas, with diameter ≥4 cm, were formerly considered rare and not surgically approachable. Few United States-based series exist. We reviewed our 10-year experience with these tumors and identified 17 patients, 11 male and 6 female, aged 27 to 65 years. Twelve of 17 cases were either gonadotroph or null cell adenomas and 5 were giant prolactinomas. By neuroimaging, all invaded the cavernous sinus(es) and tumors in 13 patients invaded the skull base. Despite massive size, only 5 showed apoplectic clinical and neuroimaging features. When present, this feature occasionally prompted preoperative consideration of craniopharyngioma. Transsphenoidal surgical excision was possible in all patients, with 3 undergoing planned second-stage reoperations and 2 requiring a second surgery for recurrence (both at 6-year intervals). Despite the aggressive features of massive size and cavernous sinus invasion, mitotic rates and immunohistochemistry (IHC) labeling for p53 and MIB-1, features alleged to be associated with atypical adenomas, were minimally increased. Absence of a role for TP53 and cell cycle markers was further verified on a subset of our cases by microarray and quantitative reverse transcription polymerase chain reaction analyses. Five giant gonadotroph adenomas were compared with 7 nonaggressive, nongiant gonadotroph cell adenomas, and no statistically significant changes in transcript levels of MIB-1 (MKI67) or TP53 were observed. A number of other genes, however, did show differential gene expression. In conclusion, most giant pituitary adenomas are gonadotroph cell adenomas or giant prolactinomas in men. Microarray profiling validates the IHC impression that MIB-1 and p53 IHC do not correlate with aggressive features in the most common type of giant adenoma.

Influence of gonadal hormones on endocrine activity of gonadotroph cells in the adenohypophysis of male lambs during the postnatal transition to puberty.

Using histomorphological and functional criteria we describe the feedback mechanisms which could play a role in the regulation of the gonadotrophic axis during the postnatal transition to puberty in male lambs. The working hypothesis was that the testicular factors change the peripheral levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by influencing the synthesis rate and storage of LH and FSH in adenohypophyseal gonadotroph cells of weanling and weaned pubertal lambs. The examination was made in (i) 9-week-old infantiles, suckling lambs undergoing weaning, testis-intact (TEI) and orchidectomised (ORCHX) at the 6th week of age, and (ii) 16-week-old pubertal lambs TEI and ORCHX at the 12th week of age (n=5 per group). Changes in gonadotrophs were assayed with hybridohistochemistry, immunohistochemistry and radioimmunoassay. The percentage of the adenohypophyseal area (PA) occupied by cells containing LHß-mRNA and FSHß-mRNA and peripheral levels of both gonadotrophins were lower (P<0.01) in the 16-week-old TEI lambs in comparison with the 9-week-old ones. The PA occupied by cells immunoreactive for LHß was lower (P<0.01), whereas in the case of FSH was greater (P<0.001) in the 16-week-old lambs. After orchidectomy the PA occupied by gonadotrophs stained for LHß-mRNA was greater (P<0.01) in 16-week-old lambs. The PA occupied by LHß-labelled cells was lower (P<0.05) in the 9-week-old ORCHX lambs, whereas in 16-week-old ones was higher (P<0.05) in comparison with the TEI lambs. The circulating LH was greater (P<0.01) in the ORCHX 9- and 16-week-old lambs compared to the TEI ones. The PA occupied by cells containing FSHß-mRNA and the plasma FSH concentration were greater (P<0.001) after orchidectomy in lambs from both age stages. The PA occupied by FSHß-labelled cells was greater (P<0.01) in the 9-week-old ORCHX lambs, whereas in 16-week-old ones was lower (P<0.05) compared to the lambs from TEI groups. In conclusion, in infantile lambs testicular factors may play inhibitory role in regulating FSH synthesis rate, storage and release in contrast to the stimulatory role in regulating LH storage reflected by the inhibitory role in regulating LH release. In lambs at the beginning of puberty, testicular factors may play inhibitory role in regulating LH synthesis rate, storage and release in contrast to the stimulatory role in regulating FSH storage reflected by the inhibitory role in regulating FSH synthesis rate and release. The effects of testicular hormones on the gonadotrophin storage, i.e. releasable pools in adenohypophyseal cells, are specific for both LH and FSH in lambs during the postnatal transition to puberty. Thus, the initiation of puberty in male sheep is a function of change of the inhibitory role of gonadal factors in regulating FSH storage to the stimulatory one and the stimulatory role of gonadal factors in regulating LH storage to the inhibitory one.

Ovarian stimulation with FSH reduces phosphorylation of gonadotrope progesterone receptor and LH secretion in the rat.

Administration of human FSH (hFSH) to cyclic rats during the dioestrous phase attenuates progesterone receptor (PR)-dependent events of the preovulatory LH surge in pro-oestrus. The increased bioactivity of the putative ovarian gonadotropin surge inhibiting/attenuating factor induced by hFSH treatment is not associated with a decrease in PR protein expression, and the possibility of its association at a PR posttranslational effect has been raised. The present experiments aimed to analyse PR phosphorylation status in the gonadotrope of rats with impaired LH secretion induced by in vivo hFSH injection. Two experimental approaches were used. First, incubated pro-oestrous pituitaries from hFSH-injected cycling and oestrogen-treated ovariectomized (OVX) rats were used to analyze the effect of calyculin, an inhibitor of intracellular phosphatases, on PR-dependent LH release, which was measured in the incubation medium by RIA. Second, pituitaries taken from hFSH-injected intact cycling and OVX rats and later incubated with P or GNRH1 were used to assess the phosphorylation rate of gonadotrope. The latter was analysed in formalin-fixed, paraffin-embedded tissue sections by immunohistochemistry using a MAB that recognizes the phosphorylated (p) form of PR at Ser294. Calyculin reduced the ovary-mediated inhibition of hFSH in GNRH1-stimulated LH secretion. In addition, the immunohistochemical expression of pSer294 PR was significantly reduced after ovarian stimulation with hFSH in pituitaries from pro-oestrous rats incubated with P or GNRH1. Altogether, these results suggested that the ovarian-dependent inhibitory effect of FSH injection on the preovulatory LH secretion in the rat may involve an increase in dephosphorylation of PR.

A proteomic comparison of immature and mature mouse gonadotrophs reveals novel differentially expressed nuclear proteins that regulate gonadotropin gene transcription and RNA splicing.

The alphaT3-1 and LbetaT2 gonadotroph cell lines contain all the known factors required for expression of gonadotropin genes, yet only the LbetaT2 cells express the beta subunits. We hypothesized that comparison of their nuclear proteomes would reveal novel proteins and/or modifications that regulate expression of these genes. We identified nine proteins with different expression profiles in the two cell lines, of which several were chosen for further functional studies. Of those found at higher levels in alphaT3-1 nuclei, 1110005A23RIK was found associated with the Fshb gene promoter and repressed its expression. Transgelin 3 overexpression reduced transcript levels of Fshb, and its knockdown elevated Lhb and Cga transcript levels, indicating an ongoing repressive effect on these more highly expressed genes, possibly through altering levels of phosphorylated mitogen-activated protein kinase. Heterogeneous nuclear ribonucleoprotein A2/B1 repressed splicing of the Fshb primary transcript, which it binds in the first intron. Proteins at higher levels in LbetaT2 nuclei included prohibitin, the overexpression of which reduced promoter activity of all three gonadotropin subunits, and appeared to mediate the differential effect of GnRH on proliferation of the two cell lines; its knockdown also altered cell morphology. Two other splicing factors were also found at higher levels in LbetaT2 nuclei: the knockdown of PRPF19 or EIF4A3 decreased splicing of Lhb, or of both beta subunit transcripts, respectively. The levels of Eif4a3 mRNA were increased by activin, and both factors increased Fshb splicing. This study has revealed a number of novel factors that alter gonadotropin expression and gonadotroph function, and likely mediate or moderate effects of the regulatory hormones.

Immunohistochemical distribution of regulatory peptides in the human fetal adenohypophysis.

We have studied here the cellular distribution of several regulatory peptides in hormone-producing cells of the human pituitary during the fetal period. Immunohistochemistry was used to show the expression of several regulatory peptides, namely Angiotensin-II, Neurotensin and Galanin, at successive gestational stages and their co-localization with hormones in the human fetal adenohypophysis. Somatotrophs, gonadotrophs and thyrotrophs were differentiated earliest. At gestational week 9, Angiotensin-II immunoreactivity was co-localized only with growth hormone immunoreactivity in somatotrophs, one of the first hormone-producing cells to differentiate. This co-localization remained until week 37. Neurotensin immunoreactivity was present in gonadotrophs and thyrotrophs in week 23, after FSH and TSH hormone differentiation. Galanin immunoreactivity was present in all hormone-producing cell types except corticotrophs. The different pro-opiomelanocortin-derived peptides were detected at different stages of gestation and adrenocorticotrophic hormone immunoreaction was the last to be detected. Our results show an interesting relationship between regulatory peptides and hormones during human fetal development, which could imply that these peptides play a regulatory role in the development of pituitary function.

Immunohistochemical localization of hormones and peptides in the human pituitary cells in a case of hypercortisolism by ACTH secreting microadenoma.

This study assesses the action of hypercortisolism on the hormone and peptide periadenoma region of removed ACTH-producing microadenoma. Our findings show that cortisol excess affects both ACTH and GH production, with no immunoreaction for these hormones. The remaining pituitary hormones (TSH, FSH and PRL) and POMC-derived peptides (betaEnd, alphaMSH and betaMSH) were not modified. Likewise, we observed pituitary immunoreactive cells for Neurotensin (NT), Intestinal vasoactive peptide (VIP), Substance P (SP) and Angiotensin-II (Ang-II). The colocalization demonstrated that NT was expressed in thyrotrope and gonadotrope cells, VIP in gonadotrope cells and SP in corticotrope cells. The results about Ang-II were inconclusive. On the other hand, immunoreaction for the NPY and Gal peptides were not present. In the adenomatous cells, the peptide NT is present in ACTH cells as well as SP. These results suggest a peptide regulation of pituitary cells in the pathological state that can differ between normal and tumoural cells of the same pituitary.