Stanniocalcin-1, an inhibitor of macrophage chemotaxis and chemokinesis

Anti-inflammatory and renal protective actions of stanniocalcin-1 in a model of anti-glomerular basement membrane glomerulonephritis

We have previously shown that stanniocalcin-1 (STC1) inhibits the transendothelial migration of macrophages and T cells, suppresses superoxide generation in macrophages, and attenuates macrophage responses to chemoattractants. To study the effects of STC1 on inflammation, in this study we induced a macrophage- and T-cell-mediated model of anti-glomerular basement membrane disease in STC1 transgenic mice, which display elevated serum STC1 levels and preferentially express STC1 in both endothelial cells and macrophages. We examined the following parameters both at baseline and after anti-glomerular basement membrane antibody treatment: blood pressure; C(3a) levels; urine output; proteinuria; blood urea nitrogen; and kidney C(3) deposition, fibrosis, histological changes, cytokine expression, and number of T cells and macrophages. Compared with wild-type mice, after anti-glomerular basement membrane treatment STC1 transgenic mice exhibited: i) diminished infiltration of inflammatory macrophages in the glomeruli; ii) marked reduction in crescent formation and sclerotic glomeruli; iii) decreased interstitial fibrosis; iv) preservation of kidney function and lower blood pressure; v) diminished C(3) deposition in the glomeruli; and vi) reduced expression of macrophage inhibitory protein-2 and transforming growth factor-beta2 in the kidney. Compared with baseline, wild-type mice, but not STC1 transgenic mice, had higher proteinuria and a marked reduction in urine output. STC1 had minimal effects, however, on both T-cell number in the glomeruli and interstitium and on cytokine expression characteristic of either TH1 or TH2 activation. These data suggest that STC1 is a potent anti-inflammatory and renal protective protein.

The murine stanniocalcin 2 gene is a negative regulator of postnatal growth

Stanniocalcin (STC), a secreted glycoprotein, was first studied in fish as a classical hormone with a role in regulating serum calcium levels. There are two closely related proteins in mammals, STC1 and STC2, with functions that are currently unclear. Both proteins are expressed in numerous mammalian tissues rather than being secreted from a specific endocrine gland. No phenotype has been detected yet in Stc1-null mice, and to investigate whether Stc2 could have compensated for the loss of Stc1, we have now generated Stc2(-/-) and Stc1(-/-) Stc2(-/-) mice. Although Stc1 is expressed in the ovary and lactating mouse mammary glands, like the Stc1(-/-) mice, the Stc1(-/-) Stc2(-/-) mice had no detected decrease in fertility, fecundity, or weight gain up until weaning. Serum calcium and phosphate levels were normal in Stc1(-/-) Stc2(-/-) mice, indicating it is unlikely that the mammalian stanniocalcins have a major physiological role in mineral homeostasis. Mice with Stc2 deleted were 10-15% larger and grew at a faster rate than wild-type mice from 4 wk onward, and the Stc1(-/-) Stc2(-/-) mice had a similar growth phenotype. This effect was not mediated through the GH/IGF-I axis. The results are consistent with STC2 being a negative regulator of postnatal growth.

Human stanniocalcin-1 blocks TNF-alpha-induced monolayer permeability in human coronary artery endothelial cells

OBJECTIVE

Our previous studies revealed upregulation of stanniocalcin-1 (STC1) in cardiac vessels in dilated cardiomyopathy. However, the functional significance of STC1 is unknown. The objective of this study was to determine the effects of STC1 on TNF-alpha-induced monolayer permeability of human coronary artery endothelial cells (HCAECs).

METHODS AND RESULTS

Cells were pretreated with STC1 for 30 minutes followed by treatment with TNF-alpha (2 ng/mL) for 24 hours. Monolayer permeability was studied using a transwell system. STC1 pretreatment significantly blocked TNF-alpha-induced monolayer permeability in a concentration- and time-dependent manner. STC1 effectively blocked TNF-alpha-induced downregulation of endothelial tight junction proteins zonula occluden-1 and claudin-1 at both mRNA and protein levels. STC1 also significantly decreased TNF-alpha-induced superoxide anion production. The inhibitory effect of STC1 was specific to TNF-alpha, as it failed to inhibit VEGF-induced endothelial permeability. Furthermore, STC1 partially blocked NF-kappaB and JNK activation in TNF-alpha-treated endothelial cells. JNK inhibitor and antioxidant also effectively blocked TNF-alpha-induced NF-kappaB activation and monolayer permeability in HCAECs.

CONCLUSIONS

STC1 maintains endothelial permeability in TNF-alpha-treated HCAECs through preservation of tight junction protein expression, suppression of superoxide anion production, and inhibition of the activation of NFkappaB and JNK, suggesting an important role for STC1 in regulating endothelial functions during cardiovascular inflammation.

Changes in the transcriptional profile of cardiac myocytes following green fluorescent protein expression

Green fluorescent protein (GFP) and its multiple forms, such as enhanced GFP (EGFP), have been widely used as marker proteins and for tracking purposes in many biological systems, including the heart and cardiac cell systems. Despite some concerns on its toxicity under certain circumstances, GFP remains amongst the most reliable and easy-to-use markers available. Using rat full genome DNA microarrays, we have investigated the broader consequences of adenoviral-driven GFP expression in cardiac myocytes. In our transcriptional profiling analysis, we set a threshold of a twofold change. We removed possible changes resulting from adenoviral infection by comparison with transcriptional profiles of cardiac myocytes with adenoviral-driven expression of an unrelated protein, the kinase MEK. Our analysis revealed changes in the expression of 212 genes. Of these genes, 174 were upregulated and 38 were downregulated following GFP expression. Many of these genes remain unannotated, but an evaluation of those with described functions for their resulting proteins indicated that many were involved in processes, including responses to stimuli/stress and signal transduction. Our analysis thus indicates the broader consequences of GFP expression in altering gene expression profiles in cardiac cells. Care should therefore be taken when using GFP expression as a control in gene expression studies.

Stanniocalcin 1 prevents cytosolic Ca2+ overload and cell hypercontracture in cardiomyocytes

BACKGROUND

The aim of the present study was to examine whether stanniocalcin 1 (STC1) affects cardiomyocytes under physiological or pathophysiological conditions.

METHODS AND RESULTS

Using fresh isolated rat cardiomyocytes, the effects of STC1 on cell hypercontracture, cell shortening and Ca(2+) transients were measured after exposing the cells to ouabain. STC1 alone did not affect cell shortening or the Ca(2+) transient. Exposure to ouabain significantly increased the fraction of hypercontractured cells (40.5+/-1.4% vs 3.5+/-1.7% in the control, p<0.01). However, treatment with STC1 decreased the percentage of cell hypercontracture that was induced by ouabain, in a concentration-dependent manner (17.4+/-2.6% at 2.5 nmol/L STC1, p<0.01). Moreover, STC1 prevented the increase in diastolic intracellular Ca(2+) level that was induced by ouabain (-5.3+/-2.7% vs 7.9+/-3.7% induced by ouabain, p<0.05; -15.3+/-5.1% in the control) in the cardiomyocytes.

CONCLUSIONS

STC1 prevented the increase in diastolic Ca(2+) overload and ouabain-induced cell hypercontracture, which suggests that STC1 could effectively prevent cytosolic Ca(2+) overload and protect cardiomyocytes from pathophysiological conditions such as in the failing heart.

Stanniocalcin-1 regulates endothelial gene expression and modulates transendothelial migration of leukocytes

The mammalian counterpart of the fish calcium-regulating hormone stanniocalcin-1 (STC1) inhibits monocyte chemotactic protein-1- and stromal-derived factor-1alpha (SDF-1alpha)-mediated chemotaxis and diminishes chemokinesis in macrophage-like RAW264.7 and U937 cells in a manner that may involve attenuation of the intracellular calcium signal. STC1 is strongly induced in the kidney following obstructive injury. We hypothesized that STC1 may serve to attenuate the influx of inflammatory cells to the site of tissue injury. In this study, we examined the effect of STC1 on the migration of freshly isolated human macrophages, neutrophils, and T and B lymphocytes through quiescent or IL-1beta-treated human umbilical vein endothelial cell (HUVEC) monolayers. STC1 inhibited transmigration of macrophages and T lymphocytes through quiescent or IL-1beta-activated HUVECs but did not attenuate the transmigration of neutrophils and B lymphocytes. STC1 regulates gene expression in cultured endothelial cells and is detected on the apical surface of endothelial cells in vivo. The data suggest that STC1 plays a critical role in transendothelial migration of inflammatory cells and is involved in the regulation of numerous aspects of endothelial function.

Biological Activities Encoded by the Murine Mesenchymal Stem Cell Transcriptome Provide a Basis for Their Developmental Potential and Broad Therapeutic Efficacy

We used serial analysis of gene expression to catalog the transcriptome of murine mesenchymal stem cells (MSCs) enriched from bone marrow by immunodepletion. Interrogation of this database, results of which are delineated in the appended databases, revealed that immunodepleted murine MSCs (IDmMSCs) highly express transcripts encoding connective tissue proteins and factors modulating T-cell proliferation, inflammation, and bone turnover. Categorizing the transcriptome based on gene ontologies revealed the cells also expressed mRNAs encoding proteins that regulate mesoderm development or that are characteristic of determined mesenchymal cell lineages, thereby reflecting both their stem cell nature and differentiation potential. Additionally, IDmMSCs also expressed transcripts encoding proteins regulating angiogenesis, cell motility and communication, hematopoiesis, immunity and defense as well as neural activities. Immunostaining and fluorescence-activated cell sorting analysis revealed that expression of various regulatory proteins was restricted to distinct subpopulations of IDmMSCs. Moreover, in some cases, these proteins were absent or expressed at reduced levels in other murine MSC preparations or cell lines. Lastly, by comparing their transcriptome to that of 17 other murine cell types, we also identified 43 IDmMSC-specific transcripts, the nature of which reflects their varied functions in bone and marrow. Collectively, these results demonstrate that IDmMSC express a diverse repertoire of regulatory proteins, which likely accounts for their demonstrated efficacy in treating a wide variety of diseases. The restricted expression pattern of these proteins within populations suggests that the cellular composition of marrow stroma and its associated functions are more complex than previously envisioned.

The murine stanniocalcin 1 gene is not essential for growth and development

The stanniocalcin 1 (STC1) gene is expressed in a wide variety of tissues, including the kidney, prostate, thyroid, bone, and ovary. STC1 protein is considered to have roles in many physiological processes, including bone development, reproduction, wound healing, angiogenesis, and modulation of inflammatory response. In fish, STC1 is a hormone that is secreted by the corpuscles of Stannius and is involved in calcium and phosphate homeostasis. To determine the role of STC1 in mammals, we generated Stc1-null mice by gene targeting. The number of Stc1-/- mice obtained was in accordance with Mendelian ratios, and both males and females produced offspring normally. No anatomical or histological abnormalities were detected in any tissues. Our results demonstrated that Stc1 function is not essential for growth or reproduction in the mouse.

Inhibition of store-operated calcium entry-mediated superoxide generation by histamine trifluoromethyltoluide independent of histamine receptors

Store-operated calcium entry (SOCE) plays an important role in shaping the Ca(2+) response of various tissues and cell types. In this report, we show that thapsigargin (TG)-induced SOCE was inhibited by the histamine receptor agonist, histamine-trifluoromethyltoluide (HTMT), in U937 and HL-60 human promyelocytes. Preincubation of HTMT resulted in a significant inhibition of subsequent TG-induced Ca(2+) elevation without affecting Ca(2+) release from intracellular stores. HTMT also inhibited TG-induced Ca(2+) current and Ba(2+)/Mn(2+) influx in a concentration-dependent manner. In contrast with HTMT, other H1 histamine receptor agonists, histamine, 2-methylhistamine and 2-thiazolylethylamine, did not affect TG-induced SOCE. In addition, HTMT also attenuated TG-induced cytosolic superoxide generation. Taken together, our data clearly suggest that the anti-inflammatory effect of HTMT may occur through direct inhibition of SOCE.

Stanniocalcin: no longer just a fish tale

Stanniocalcin was originally described as a hormone with calcitonin-like actions in fish. During the last decade, mammalian forms of stanniocalcin have been identified, and this discovery has led to important advances in our understanding of this enigmatic polypeptide hormone. This review briefly covers some early studies on stanniocalcin in fish and then provides a more in-depth look at some of the more intriguing, new aspects of its functions in mammals. The roles of stanniocalcin in renal function, metabolism, angiogenesis, pregnancy and lactation, bone formation, and neural protection are discussed, along with new information relating to its receptor-mediated sequestration and accumulation in target cell organelles.

Stanniocalcin in terminally differentiated mammalian cells

Stanniocalcin (STC) is a glycoprotein hormone originally found in teleost fish, where it regulates the calcium/phosphate homeostasis, and protects the fish against toxic hypercalcemia. STC was considered an exclusive fish protein, until the cloning of cDNA for human (in 1995) and murine (in 1996) STC. We originally reported a high constitutive content of STC in mammalian brain neurons, and found that the expression of STC occurred concomitantly with terminal differentiation of neural cells. Since then, we have investigated the expression of STC in relation to terminal cell differentiation also in mammalian hematopoietic tissue, and fat tissues. In this review we summarize our findings on STC expression during postmitotic differentiation in three different cell systems; in neural cells, in megakaryocytes and in adipocytes. We also present findings, suggesting that STC plays a role for maintaining the integrity of terminally differentiated mammalian cells.

Stanniocalcin 1 as a pleiotropic factor in mammals

Stanniocalcin (STC)1 is the mammalian homologue of STC which was originally identified as a calcium/phosphate-regulating hormone in bony fishes. STC1 is a homodimeric phosphoglycoprotein with few if any identified unique motifs in its structure with the exception of CAG repeats in the 5'-untranslated region. In contrast to fish STC which is expressed mainly in the corpuscles of Stannius, STC1 is expressed in a wide variety of tissues, but unexpectedly is not detected in the circulation under normal circumstances. Thus, STC1 may play an autocrine/paracrine rather than a classic endocrine role in mammals. Consistent with this, pleiotropic effects of STC1 have been postulated in physiological and measured in pathological situations. There is much current interest in identifying a specific STC1 receptor and putative signaling pathways to which it may be coupled. In this regard, STC1 may regulate intracellular calcium and/or phosphate (Pi) levels. In the skeletal system, for example, Pi uptake in bone-forming osteoblasts via a direct effect of STC1 on expression of the NaPi transporter Pit1 may contribute to bone formation. Here we review current understanding of the role of STC1 and its possible molecular mechanisms in the skeleton and elsewhere.