Effect of E-cadherin expression on hormone production in rat anterior pituitary lactotrophs in vitro.

Cadherins are a family of transmembrane glycoproteins that mediate cell-to-cell adhesion. A change in cadherin type in cells, i.e., cadherin switching, induces changes in the character of the cell. Recent studies of the developing rat adenohypophysis found that primordial cells co-expressed E- and N-cadherins, but that hormone-producing cells lost E-cadherin and ultimately possessed only N-cadherin. In the present study, we examined the roles of cadherin switching in cytogenesis of anterior pituitary cells by observing prolactin mRNA and protein expression in lactotrophs that were transformed with an E-cadherin expression vector. In hormone-producing cells that were transfected with a pIRES2-ZsGreen1 plasmid with a full-length E-cadherin cDNA (rE-cad-IZ) insert in primary culture, we detected E- and N-cadherins on plasma membrane and E-cadherin in cytoplasm. In these rE-cad-IZ-transfected cells, in situ hybridization revealed prolactin mRNA signals that were at a level identical to that in control cells, while prolactin protein was barely detectable using immunocytochemistry. The mean signal intensity of prolactin protein in rE-cad-IZ-transfected cells was approximately one fourth that in intact cells and in null-IZ-transfected cells (P<0.01). These results suggest that the expression of E-cadherin does not affect prolactin mRNA transcription; rather, it reduces prolactin protein content, presumably by affecting trafficking of secretory granules.

Estrogen receptor alpha regulates retinaldehyde dehydrogenase 1 expression in rat anterior pituitary cells.

Retinoic acid (RA) plays a critical role in embryonic development, growth, and reproduction. RA is synthesized from retinoids via oxidation processes, and the oxidation of retinal to RA is catalyzed by the retinaldehyde dehydrogenases (RALDHs). We previously reported that RALDH1 mRNA was expressed in the anterior pituitary glands of adult rats and suppressed by administration of 17beta-estradiol in vivo. However, little is known about the mechanism regulating pituitary RALDH1 expression. In order to characterize the mechanism of estrogen-induced RALDH1 reduction, we examined the effect of 17beta-estradiol on the regulation of pituitary RALDH1 gene expression and protein production both in vivo and in vitro. Using quantitative real-time PCR and immunoblot analysis, we found that levels of RALDH1 gene expression and protein production markedly decreased after 1-week treatment with 17beta-estradiol in male rats. In immunohistochemical analysis, RALDH1-immunoreaction was observed in prolactin cells and folliculo-stellate cells. In 17beta-estradiol-treated rats, RALDH1-immunoreactivity was lower in prolactin cells, but not in folliculo-stellate cells. Treatment of isolated anterior pituitary cells with 17beta-estradiol (10(-14) - 10(-8) M) decreased expression of RALDH1 mRNA in a dose-dependent manner. Estradiol-induced suppression of RALDH1 expression was completely blocked by the estrogen receptor (ER) antagonist ICI 182, 780. The ERalpha-selective agonist propylpyrazole triol (10(-8) M) mimicked the effect of 17beta-estradiol on RALDH1 expression, but the ERbeta-selective agonist diarylpropionitrile (10(-8) M) did not. These results strongly suggest that RALDH1 mRNA expression is suppressed by 17beta-estradiol through ERalpha, and that estrogen regulates the expression of RALDH1 and production of RA in the anterior pituitary gland.

[Paraneoplastic cerebellar degeneration with bladder cancer confirmed the existence of an anti-neural antibody: a case report].

A 66-year-old man was diagnosed with bladder cancer at our urology department. Three months later, he developed subacute progressive cerebellar limb ataxia and truncal oscillation. Analysis of cerebrospinal fluid showed pleocytosis and increased concentrations of protein, while brain magnetic resonance imaging revealed no abnormalities. Based on the presence of the bladder cancer, the etiology of subacute cerebellar ataxia could be a paraneoplastic neurological syndrome. Four months later, the patient underwent transurethral resection of the bladder tumor, which was identified as urothelial cancer on the basis of pathological examinations. However, this procedure failed to improve his neurological symptoms. Serum paraneoplastic markers such as anti-Yo, anti-Hu, anti-Tr, and other antibodies were not detected. Immunohistochemical staining of mouse cerebellum using the patient's serum revealed coarse granular staining in the cytoplasm of Purkinje cells and diffuse staining in the neuropil of the molecular layer, suggesting the presence of an unknown antibody. Subsequently, one-dimensional electrophoresis western blotting using the patient's serum revealed several bands including a strong positive band of approximately 45 kDa in mouse cerebellum lysates but not in liver lysates. These bands have never been detected in sera derived from healthy donors. These results suggested the presence of a novel antibody in the patient's serum that might recognize the approximately 45 kDa protein related to paraneoplastic cerebellar degeneration. Cases of paraneoplastic neurological syndrome associated with bladder cancer have rarely been reported. We concluded that the present case may be categorized as paraneoplastic neurological syndrome caused by an unknown antibody.

Living-cell imaging of transgenic rat anterior pituitary cells in primary culture reveals novel characteristics of folliculo-stellate cells.

Folliculo-stellate (FS) cells in the anterior pituitary gland appear to possess multifunctional properties. Recently, the development of transgenic rats (S100b-green fluorescent protein (GFP) rats) that express GFP specifically in FS cells in the anterior pituitary gland has allowed us to distinguish and observe living FS cells in other kinds of pituitary cells. We used S100b-GFP rats to investigate the topographic affinity of FS cells for other pituitary cells. We observed living FS cells in enzymatically dispersed anterior pituitary cells of S100b-GFP rats under a fluorescent microscope, and noted that FS cells markedly extended and contracted cytoplasmic processes and formed interconnections with neighboring FS cells. In addition, FS cells adhered to small clusters of GFP-negative cells, which were primarily hormone-producing cells, and these clusters further aggregated during the course of cytoplasmic contraction. In the presence of laminin, fibronectin, and varying types of collagen, FS cells showed marked changes in shape and specific proliferative activity; however, GFP-negative cells did not. On reverse transcription-PCR analysis and immunohistochemistry, FS cells were shown to express integrin subunits, which are the cell surface receptors for extracellular matrix (ECM). In the anterior pituitary gland, FS cells and the various types of hormone-producing cells generate a unique topography in the presence of basement membrane components and interstitial collagens. The novel characteristics of FS cells observed in the present study suggest that in the anterior pituitary gland, FS cells play important roles in determining and/or maintaining local cellular arrangement in the presence of ECM components.