Role of bone morphogenetic proteins in adrenal physiology and disease.

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta superfamily of ligands that impact on a multitude of biological processes including cell type specification, differentiation and organogenesis. Furthermore, a large body of evidence points towards important BMP-dependent mechanisms in tumorigenesis. In accordance with their diverse actions, BMPs have been demonstrated to serve as auto-, para- and endocrine modulators also in a number of hormonal systems. In this review, we highlight novel aspects of BMP-dependent regulatory networks that pertain to adrenal physiology and disease, which have been uncovered during recent years. These aspects include the role of BMP-dependent mechanism during adrenal development, modulating effects on catecholamine synthesis and steroidogenesis and dysregulation of BMP signalling in adrenal tumorigenesis. Furthermore, we summarize potential therapeutic approaches that are based on reconstitution of BMP signalling in adrenocortical tumour cells.

Bone morphogenetic proteins 2 and 5 are down-regulated in adrenocortical carcinoma and modulate adrenal cell proliferation and steroidogenesis.

Bone morphogenetic proteins (BMP) have been shown to affect tumorigenesis in a variety of tumors. Quantitative PCR analysis revealed down-regulation of BMP2 and BMP5 in tissue samples from adrenocortical carcinoma and adrenocortical tumor cell lines compared with normal adrenal glands. Integrity of BMP-dependent pathways in these cell lines could be shown by activation of the Smad1/5/8 pathway with subsequent increase of ID protein expression upon incubation with BMP2 or BMP5. On a functional level, BMP treatment resulted in inhibition of cell proliferation and viability in a dose- and time-dependent manner. This growth inhibitory effect was associated with BMP-dependent reduction of AKT phosphorylation under baseline conditions and under insulin-like growth factor costimulation. Furthermore, steroidogenic function, including melanocortin-2 receptor and steroidogenic enzyme expressions, was profoundly reduced. In vitro demethylation treatment and overexpression of GATA6 resulted in reactivation of BMP-dependent pathways with concomitant modulation of steroidogenesis. Taken together, we show that loss of expression of members of the BMP family of ligands is a common finding in adrenocortical tumors and we provide evidence that BMP-dependent pathways are likely to be involved in the modulation of the malignant and functional phenotype of adrenocortical cancer cells.

Chronic growth hormone excess is associated with increased aldosterone: a study in patients with acromegaly and in growth hormone transgenic mice.

Acromegaly is a disease characterized by chronic growth hormone (GH) excess. Since hypertension is a common finding in patients with acromegaly, interactions between GH and the renin-angiotensin-aldosterone system (RAAS) are under controversial debate. We examined GH, IGF-I, aldosterone, and renin in a well-defined group of acromegalic patients before and after cure by surgery. In addition, we analyzed the impact of chronic GH excess on the RAAS in mouse models over-expressing GH alone (G) or in combination with insulin-like growth factor-binding protein-2 (IGFBP-2; GB). Normalization of GH secretion after cure by surgery was accompanied by significant decreases of serum aldosterone in acromegalic patients (pre-op: 96.5 +/- 37.1 pg/mL, post-op: 41.3 +/- 28.2 pg/ mL; P < 0.001; n = 13), but renin concentrations were unaffected. In addition, aldosterone concentrations were positively correlated to GH levels (Spearman r = 0.39; P = 0.025; n = 26). To further study this association, we analysed two transgenic mouse models and found a similar relationship between GH and aldosterone in G mice, which showed about 3-fold elevated serum aldosterone levels in comparison to non-transgenic controls (males: 442 +/- 331 pg/mL vs. 151 +/- 84 pg/mL; P = 0.002; n > or = 12; females: 488 +/- 161 pg/mL vs. 108 +/- 125 pg/mL; P = 0.05; n > or = 4). Expression of aldosterone synthase was similar in adrenal glands of C and G mice. Aldosterone levels in G and GB mice of both genders were not different, indicating that the elevated aldosterone was due to GH excess and not caused by elevated IGF-I, which is known to be blocked by IGFBP-2 overexpression. Also in the mouse models, changes in aldosterone were independent from renin. In summary, we show that chronic GH excess is associated with increased aldosterone in humans and mice. GH-induced increases of aldosterone potentially contribute to the increased cardiovascular risk in acromegalic patients. The underlying mechanism is likely to be independent of renin, excess IGF-I, or adrenal aldosterone synthase expression.

Decreased p44/42 mitogen-activated protein kinase phosphorylation in gender- or hormone-related but not during age-related adrenal gland growth in mice.

Postnatal growth of the mouse adrenal gland shows a characteristic gender-dependent pattern, resulting in an almost 2-fold higher adrenal weight in 11-wk-old female vs. male mice. We demonstrated that the higher weight of the adrenal glands in female mice is due to a significantly (P < 0.05) increased growth rate in female mice and a shorter growth phase of the adrenal glands in male mice (P < 0.05). To address the signaling mechanisms underlying these differential growth patterns, we evaluated the phosphorylation levels of p44/42 and p38 MAPK. In female mice, age-dependent reductions of p38 MAPK phosphorylation were found between wk 3 and 9 (47% reduction; P < 0.05). At the age of 11 wk, the p38 MAPK phosphorylation level in female adrenal glands was about 60% lower than in the male counterparts (P < 0.01). Similarly, the phosphorylation level of p44/42 MAPK was 50% lower in female adrenal glands (P < 0.001). Reduced activation of p44/42 MAPK was also observed after growth stimulation of the adrenal glands in male mice after ACTH treatment (-36%; P < 0.001) or by expression of a GH transgene (-34%; P < 0.001), whereas p38 MAPK, JNK, or PDK1 activation was unaffected. From our findings in three independent mouse models where partial deactivation of p44/42 MAPK was observed under conditions of elevated growth, we suggest a function of p44/42 MAPK for adrenal growth and a role of p44/42 MAPK for the integration of different endocrine stimuli.

Gonadectomy in mice of the inbred strain CE/J induces proliferation of sub-capsular adrenal cells expressing gonadal marker genes.

Mouse models of adrenal tumorigenesis have the potential to give insights in the dysregulation of adrenal growth and differentiation. The inbred mouse strain CE/J has been reported to develop adrenal tumors upon gonadectomy (GDX) similar to mice with targeted deletions of the inhibin alpha subunit (Inh-/-). We performed a detailed morphological and molecular characterization of adrenal glands from CE/J mice 8-50 weeks of age to define the cellular origin of these tumors as well as the spatial and temporal expression of marker genes associated with tumor growth. In contrast to the induction of x-zone growth upon GDX in Inh-/- mice, GDX in CE/J mice induced the appearance of sub-capsular nests of densely packed cells that progress into adrenal tumors. Staining for proliferative cell nuclear antigen confirms a substantial increased in cellular proliferation within this sub-capsular compartment and lack of apoptosis upon GDX. Induction of adrenal tumor growth was accompanied by transcriptional changes that otherwise define gonadal endocrine cells. These regulated genes included transcription factors such as GATA-4, WT-1, FOG-1, and steroidogenic factor-1 (SF-1), peptide hormones such as Mullerian-inhibiting substance (MIS), hormone receptors including luteinizing hormone and MIS receptor, and steroidogenic enzymes such as P450c17 and P450 aromatase. The functional significance of steroid enzyme expression was demonstrated by a gradual increase of adrenal androgens after GDX. Taken together these data suggest that adrenal tumors in gonad-ectomized CE/J mice are direct derivatives from cells of the proposed sub-capsular stem cell zone. The distinct expression pattern of this cell population is consistent with a defect in the differentiation of these cells into a cell population with functional properties that otherwise define a gonadal endocrine phenotype.

The genus Hypericum--a valuable resource of anti-Staphylococcal leads.

In the present study, extracts of 34 species and varieties of the genus Hypericum were screened for activity against a clinical isolate of methicillin-resistant Staphylococcus aureus, which in addition possessed a multidrug efflux mechanism conferring a high level of resistance to therapeutically useful antibiotics. Thirty-three of the 34 chloroform extracts showed significant activity in a disk diffusion assay, and five extracts had minimum inhibitory concentrations of 64 microg/ml, indicating that this genus has great potential to yield compounds with potent activity against multidrug-resistant bacteria.