Inhibition of 11beta-hydroxysteroid dehydrogenase eliminates impaired glucocorticoid suppression and induces apoptosis in corticotroph tumor cells.

Cushing's disease is characterized by persistent ACTH secretion under hypercortisolemia. In an attempt to clarify the molecular mechanism, we examined the effect of 11beta-hydroxysteroid dehydrogenase (HSD) inhibition on glucocorticoid suppression of ACTH release using murine corticotroph tumor cells. We found that 11beta-HSD2, as well as -HSD1, was expressed in the cells and that its inhibition by carbenoxolone significantly improved the negative feedback effect of glucocorticoid.

Calcium/calmodulin kinase IV pathway is involved in the transcriptional regulation of the corticotropin-releasing hormone gene promoter in neuronal cells.

Although corticotropin-releasing hormone (CRH) plays a pivotal role in the regulation of the hypothalamo-pituitary-adrenal axis, the mechanism of CRH gene expression in the neuronal cell is not completely understood. In this study, we examined the transcriptional regulation of human CRH gene 5'-promoter, using a human BE(2)C neuroblastoma cell line expressing intrinsic CRH. In particular, we focused on the involvement of calmodulin kinases (CaMKs), which are known to play an important role in excitation-induced gene expression through the rise in intracellular calcium in the central nervous system.

Nilvadipine inhibits nuclear factor-kappaB-dependent transcription in hepatic cells.

Background: Recent findings suggest that some dihydropyridine-type calcium channel blockers, widely used as anti-hypertensive drugs, have direct anti-atherogenic action through their antioxidant properties.

Methods: We examined the effect of nilvadipine on the activity of a representative radical-sensitive transcription factor, nuclear factor kappa-B (NF-kappaB), in the human hepatocyte cell line HuH7 in vitro.

Results: Nilvadipine potently inhibited NF-kappaB-dependent transcription in a dose- and time-dependent manner, with a minimal effective concentration of 50 nmol/l.

Effects of hormones targeting nuclear receptors on transcriptional regulation of the growth hormone gene in the MtT/S rat somatotrope cell line.

We have examined the effects of nuclear receptor hormones such as glucocorticoid, gonadal steroid hormones, thyroid hormone and retinoids on the transcriptional regulation of the 5'-promoter activity of growth hormone (GH) gene using the MtT/S rat pure somatotrope cell line or MtT/SGL, a subclone of MtT/S in which the rat GH gene 5'-promoter (1.7 Kb)-luciferase fusion gene was stably incorporated. RT-PCR analyses revealed that receptors for all the hormones except androgen receptor were expressed in the cell line.

The effects of GH-releasing hormone/somatostatin on the 5'-promoter activity of the GH gene in vitro.

The two hypothalamic hormones, GH-releasing hormone (GHRH) and somatostatin (SRIF), are known to regulate GH secretion. However, the effects of these hormones on GH gene expression are not completely clear, partly because of the lack of appropriate host cells maintaining the original characteristics of the somatotroph. Since MtT/S, a pure somatotroph cell line, has become available, the effects of GHRH and SRIF on GH gene transcription have been studied using a subclone of MtT/S (MtT/SGL), in which the GH gene 5'-promoter-luciferase fusion gene was stably incorporated.

Sodium bicarbonate infusion test: a new method for evaluating parathyroid function.

We have developed a new test for estimating the secretory capacity of parathyroid hormone (PTH) from the parathyroid gland. Sodium bicarbonate solution [8.4% (w/v); 35 ml/m(2) body surface area] was infused for 2 min, and blood samples for the determination of plasma ionized calcium, plasma PTH (intact, midregion, carboxy-terminus) and related parameters were serially obtained.

Possible involvement of ryanodine receptor-mediated intracellular calcium release in the effect of corticotropin-releasing factor on adrenocorticotropin secretion.

We examined the role of intracellular calcium release in the regulation of CRH-induced ACTH secretion using the AtT20 corticotroph cell line. We found that ruthenium red, an inhibitor of ryanodine receptor, substantially diminished the secretory response, whereas Xestospongin C, an inositol 1,4,5-triphosphate receptor antagonist, had no effect. Expression of two ryanodine receptor subtypes (RyR1 and RyR3) was confirmed by RT-PCR.

Attenuation by reactive oxygen species of glucocorticoid suppression on proopiomelanocortin gene expression in pituitary corticotroph cells.

Up-regulation of hypothalamo-pituitary-adrenal axis is maintained during acute inflammation and/or infection, in the face of sustained elevation of plasma glucocorticoid hormone. Inflammatory stress is usually associated with high plasma cytokine levels and increased generation of reactive oxygen species (ROS) as well. In this study, we examined the effect of ROS on the negative feedback regulation of glucocorticoid in hypothalamo-pituitary-adrenal axis using AtT20 corticotroph cells in vitro.

Gene therapy for central diabetes insipidus: effective antidiuresis by muscle-targeted gene transfer.

Central diabetes insipidus, characterized by severe polyuria and polydipsia, is a disorder resulting from deficient secretion of the small neuropeptide hormone vasopressin in the neurohypophysis. The standard therapy is daily and life-long administration of vasopressin analog (desmopressin acetate), but gene therapy is potentially alternative to the conventional replacement therapy. To obtain the therapeutic neuropeptide more feasibly, we tried to express vasopressin in nonneuronal tissues using nonviral gene transfer techniques.