Roles of Bone Morphogenetic Protein-6 in Aldosterone Regulation by Adrenocortical Cells

Aldosterone production occurs in the adrenal cortex, and is regulated primarily by angiotensin II (Ang II), potassium and adrenocorticotropin (ACTH). In the presence of the aldosterone stimulators, steroidogenesis is further governed by local autocrine and/or paracrine factors in the adrenal cortex. We reported the presence of functional bone morphogenetic protein (BMP) system in the adrenal cortex and also demonstrated that BMP-6 increases Ang II-induced aldosterone production, which could be involved in the "aldosterone breakthrough" phenomenon. Aldosterone breakthrough is the phenomenon by which circulating aldosterone concentrations increase above pre-treatment levels after long-term therapy with ACE inhibitors or Ang II type 1 receptor antagonists (ARB). This phenomenon may lead to important clinical consequences since increased aldosterone in a high-salt state facilitates cardiovascular and renal damage in hypertensive patients. We found that long-term ARB treatment reverses the reduction of aldosterone synthesis by adrenocortical cells, thereby causing "cellular aldosterone breakthrough". The availability of BMP-6 in the adrenal cortex may be at least partly involved in the occurrence of cellular escape from aldosterone suppression under chronic treatment with ARB

Activities of bone morphogenetic proteins in prolactin regulation by somatostatin analogs in rat pituitary GH3 cells

Involvement of the pituitary BMP system in the modulation of prolactin (PRL) secretion regulated by somatostatin analogs, including octreotide (OCT) and pasireotide (SOM230), and a dopamine agonist, bromocriptine (BRC), was examined in GH3 cells. GH3 cells are rat pituitary somato-lactotrope tumor cells that express somatostatin receptors (SSTRs) and BMP system molecules including BMP-4 and -6. Treatment with BMP-4 and -6 increased PRL and cAMP secretion by GH3 cells. The BMP-4 effects were neutralized by adding a BMP-binding protein Noggin. These findings suggest the activity of endogenous BMPs in augmenting PRL secretion by GH3 cells. BRC and SOM230 reduced PRL secretion, but OCT failed to reduce the PRL level. In GH3 cells activated by forskolin, BRC suppressed forskolin-induced PRL secretion with reduction in cAMP levels. OCT did not affect forskolin-induced PRL level, while SOM230 reduced PRL secretion and PRL mRNA expression induced by forskolin. BMP-4 treatment enhanced the reducing effect of SOM230 on forskolin-induced PRL level while BMP-4 did not affect the effects of OCT or BRC. Noggin treatment had no significant effect on the BRC actions reducing PRL levels by GH3 cells. However, in the presence of Noggin, OCT elicited an inhibitory effect on forskolin-induced PRL secretion and PRL mRNA expression, whereas the SOM230 effect on PRL reduction was in turn impaired. It was further found that BMP-4 and -6 suppressed SSTR-2 but increased SSTR-5 mRNA expression of GH3 cells. These findings indicate that Noggin rescues SSTR-2 but downregulates SSTR-5 by neutralizing endogenous BMP actions, leading to an increase in OCT sensitivity and a decrease in SOM230 sensitivity of GH3 cells. In addition, BMP signaling was facilitated in GH3 cells treated with forskolin. Collectively, these findings suggest that BMPs elicit differential actions in the regulation of PRL release dependent on cellular cAMP-PKA activity. BMPs may play a key role in the modulation of SSTR sensitivity of somato-lactotrope cells in an autocrine/paracrine manner

Induction of tumour necrosis factor receptor-expressing macrophages by interleukin-10 and macrophage colony-stimulating factor in rheumatoid arthritis

Despite its potent ability to inhibit proinflammatory cytokine synthesis, interleukin (IL)-10 has a marginal clinical effect in rheumatoid arthritis (RA) patients. Recent evidence suggests that IL-10 induces monocyte/macrophage maturation in cooperation with macrophage-colony stimulating factor (M-CSF). In the present study, we found that the inducible subunit of the IL-10 receptor (IL-10R), type 1 IL-10R (IL-10R1), was expressed at higher levels on monocytes in RA than in healthy controls, in association with disease activity, while their expression of both type 1 and 2 tumour necrosis factor receptors (TNFR1/2) was not increased. The expression of IL-10R1 but not IL-10R2 was augmented on monocytes cultured in the presence of RA synovial tissue (ST) cell culture supernatants. Cell surface expression of TNFR1/2 expression on monocytes was induced by IL-10, and more efficiently in combination with M-CSF. Two-color immunofluorescence labeling of RA ST samples showed an intensive coexpression of IL-10R1, TNFR1/2, and M-CSF receptor in CD68(+ )lining macrophages. Adhered monocytes, after 3-day preincubation with IL-10 and M-CSF, could produce more IL-1β and IL-6 in response to TNF-α in the presence of dibutyryl cAMP, as compared with the cells preincubated with or without IL-10 or M-CSF alone. Microarray analysis of gene expression revealed that IL-10 activated various genes essential for macrophage functions, including other members of the TNFR superfamily, receptors for chemokines and growth factors, Toll-like receptors, and TNFR-associated signaling molecules. These results suggest that IL-10 may contribute to the inflammatory process by facilitating monocyte differentiation into TNF-α-responsive macrophages in the presence of M-CSF in RA

Risk Factors for Infection in Patients with Remitted Rheumatic Diseases Treated with Glucocorticoids

It is well known that infection is one of the major causes of morbidity and mortality in rheumatic disease patients treated with high-dose glucocorticoids, especially in the early phase after achievement of disease remission. The aim of this study was to identify the risk factors for infection, with a focus on the dose of glucocorticoids administered, following the achievement of disease remission in rheumatic diseases patients. We retrospectively analyzed the medical records of rheumatic disease patients who had been treated with glucocorticoids. The primary endpoint was the incidence rate of infection during a period from 1 to 2 months after the commencement of treatment. From April 2006 to March 2010, 19 of 92 patients suffered from infection during the observation period. Age≧65 yrs, presence of interstitial pneumonia, diagnosis of systemic vasculitis and serum creatinine level≧2.0mg/dl were found to be univariate predictors for infection. However, only the presence of interstitial pneumonia was an independent risk factor for infection (HR＝4.50, 95%CI＝1.65 to 14.44) by the Cox proportional hazard model. Even after achievement of clinical remission, careful observation is needed for patients with interstitial pneumonia, more so than for those receiving high-dose glucocorticoids

Mutual interaction of kisspeptin, estrogen and bone morphogenetic protein-4 activity in GnRH regulation by GT1-7 cells

Reproduction is integrated by interaction of neural and hormonal signals converging on hypothalamic neurons for controlling gonadotropin-releasing hormone (GnRH). Kisspeptin, the peptide product of the kiss1 gene and the endogenous agonist for the GRP54 receptor, plays a key role in the regulation of GnRH secretion. In the present study, we investigated the interaction between kisspeptin, estrogen and BMPs in the regulation of GnRH production by using mouse hypothalamic GT1-7 cells. Treatment with kisspeptin increased GnRH mRNA expression and GnRH protein production in a concentration-dependent manner. The expression levels of kiss1 and GPR54 were not changed by kisspeptin stimulation. Kisspeptin induction of GnRH was suppressed by co-treatment with BMPs, with BMP-4 action being the most potent for suppressing the kisspeptin effect. The expression of kisspeptin receptor, GPR54, was suppressed by BMPs, and this effect was reversed in the presence of kisspeptin. It was also revealed that BMP-induced Smad1/5/8 phosphorylation and Id-1 expression were suppressed and inhibitory Smad6/7 was induced by kisspeptin. In addition, estrogen induced GPR54 expression, while kisspeptin increased the expression levels of ER alpha. and ER beta, suggesting that the actions of estrogen and kisspeptin are mutually enhanced in GT1-7 cells. Moreover, kisspeptin stimulated MAPKs and AKT signaling, and ERK signaling was functionally involved in the kisspeptin-induced GnRH expression. BMP-4 was found to suppress kisspeptin-induced GnRH expression by reducing ERK signaling activity. Collectively, the results indicate that the axis of kisspeptin-induced GnRH production is bi-directionally controlled, being augmented by an interaction between ER alpha/beta and GPR54 signaling and suppressed by BMP-4 action in GT1-7 neuron cells

Peroxisome proliferator-activated receptor activity is involved in the osteoblastic differentiation regulated by bone morphogenetic proteins and tumor necrosis factor-α.

Recent studies have suggested possible adverse effects of thiazolidinediones on bone metabolism. However, the detailed mechanism by which the activity of PPAR affects bone formation has not been elucidated. Impaired osteoblastic function due to cytokines is critical for the progression of inflammatory bone diseases. In the present study, we investigated the cellular mechanism by which PPAR actions interact with osteoblast differentiation regulated by BMP and TNF-alpha using mouse myoblastic C2C12 cells. BMP-2 and -4 potently induced the expression of various bone differentiation markers including Runx2, osteocalcin, type-1 collagen and alkaline phosphatase (ALP) in C2C12 cells. When administered in combination with a PPAR alpha agonist (fenofibric acid) but not with a PPAR gamma agonist (pioglitazone), BMP-4 enhanced osteoblast differentiation through the activity of PPAR alpha. The osteoblastic changes induced by BMP-4 were readily suppressed by treatment with TNF-alpha. Interestingly, the activities of PPAR alpha and PPAR gamma agonists reversed the suppression by TNF-alpha of osteoblast differentiation induced by BMP-4. Furthermore, TNF-alpha-induced phosphorylation of MAPKs, NF kappa B, I kappa B and Stat pathways was inhibited in the presence of PPAR alpha and PPAR gamma agonists with reducing TNF-alpha receptor expression. In view of the finding that inhibition of SAPK/JNK. Stat and NF kappa B pathways reversed the TNF-alpha suppression of osteoblast differentiation, we conclude that these cascades are functionally involved in the actions of PPARs that antagonize TNF-alpha-induced suppression of osteoblast differentiation. It was further discovered that the PPAR alpha agonist enhanced BMP-4-induced Smad1/5/8 signaling through downregulation of inhibitory Smad6/7 expression, whereas the PPAR gamma agonist impaired this activity by suppressing BMPRII expression. On the other hand, BMPs increased the expression levels of PPAR alpha and PPAR gamma in the process of osteoblast differentiation. Thus, PPAR alpha actions promote BMP-induced osteoblast differentiation, while both activities of PPAR alpha and PPAR gamma suppress TNF-alpha actions. Collectively, our present data establishes that PPAR activities are functionally involved in modulating the interaction between the BMP system and TNF-alpha receptor signaling that is crucial for bone metabolism