Impact of salt and the osmoprotective transcription factor NFAT-5 on macrophages during mechanical strain.

Myeloid cells regulate bone density in response to increased salt (NaCl) intake via the osmoprotective transcription factor, nuclear factor of activated T cells-5 (NFAT-5). Because orthodontic tooth movement (OTM) is a pseudoinflammatory immunological process, we investigated the influence of NaCl and NFAT-5 on the expression pattern of macrophages in a model of simulated OTM. RAW264.

Osteoprotective action of low-salt diet requires myeloid cell-derived NFAT5.

Dietary salt consumption leads to cutaneous Na+ storage and is associated with various disorders, including osteopenia. Here, we explore the impact of Na+ and the osmoprotective transcription factor nuclear factor of activated T cell 5 (NFAT5) on bone density and osteoclastogenesis. Compared with treatment of mice with high-salt diet, low-salt diet (LSD) increased bone density, decreased osteoclast numbers, and elevated Na+ content and Nfat5 levels in the BM.

Genetic ablation of NFAT5/TonEBP in smooth muscle cells impairs flow- and pressure-induced arterial remodeling in mice.

The arterial wall adapts to alterations in blood flow and pressure by remodeling the cellular and extracellular architecture. Biomechanical stress of vascular smooth muscle cells (VSMCs) in the media is thought to precede this process and promote their activation and subsequent proliferation. However, molecular determinants orchestrating the transcriptional phenotype under these conditions have been insufficiently studied.

Renal Sodium Gradient Orchestrates a Dynamic Antibacterial Defense Zone.

Lower urinary tract infections are among the most common human bacterial infections, but extension to the kidneys is rare. This has been attributed to mechanical forces, such as urine flow, that prevent the ascent of bladder microbes. Here, we show that the regional hypersalinity, required for the kidney's urine-concentrating function, instructs epithelial cells to produce chemokines that localize monocyte-derived mononuclear phagocytes (MNPs) to the medulla.

Autocrine MCP-1/CCR2 signaling stimulates proliferation and migration of renal carcinoma cells.

The chemokine monocyte chemoattractant protein-1 [MCP-1; also known as chemokine (C-C motif) ligand 2] is an important mediator of monocyte recruitment during inflammatory processes. Pathologically high expression levels of MCP-1 by tumor cells have been observed in a variety of cancer types. In the majority of cases, high MCP-1 expression is associated with a poor prognosis, as infiltration of the tumor with inflammatory monocytes promotes tumor progression and metastasis.

LPS-induced NFκB enhanceosome requires TonEBP/NFAT5 without DNA binding.

NFκB is a central mediator of inflammation. Present inhibitors of NFκB are mostly based on inhibition of essential machinery such as proteasome and protein kinases, or activation of nuclear receptors; as such, they are of limited therapeutic use due to severe toxicity. Here we report an LPS-induced NFκB enhanceosome in which TonEBP is required for the recruitment of p300.

High salt reduces the activation of IL-4- and IL-13-stimulated macrophages.

A high intake of dietary salt (NaCl) has been implicated in the development of hypertension, chronic inflammation, and autoimmune diseases. We have recently shown that salt has a proinflammatory effect and boosts the activation of Th17 cells and the activation of classical, LPS-induced macrophages (M1). Here, we examined how the activation of alternative (M2) macrophages is affected by salt.

Dual effect of lithium on NFAT5 activity in kidney cells.

Lithium salts are used widely for treatment of bipolar and other mental disorders. Lithium therapy is accompanied frequently by renal side effects, such as nephrogenic diabetes insipidus or chronic kidney disease (CKD), but the molecular mechanisms underlying these effects are still poorly understood. In the present study we examined the effect of lithium on the activity of the osmosensitive transcriptional activator nuclear factor of activated T cells 5 (NFAT5, also known as TonEBP), which plays a key role in renal cellular osmoprotection and urinary concentrating ability.

Cutaneous Na+ storage strengthens the antimicrobial barrier function of the skin and boosts macrophage-driven host defense.

Immune cells regulate a hypertonic microenvironment in the skin; however, the biological advantage of increased skin Na(+) concentrations is unknown. We found that Na(+) accumulated at the site of bacterial skin infections in humans and in mice. We used the protozoan parasite Leishmania major as a model of skin-prone macrophage infection to test the hypothesis that skin-Na(+) storage facilitates antimicrobial host defense.

Generation of a conditional knockout allele for the NFAT5 gene in mice.

The osmosensitive transcription factor nuclear factor of activated T-cells 5 (NFAT5), also known as tonicity enhancer element binding protein (TonEBP) plays a crucial role in protection of renal medullary cells against hyperosmotic stress, urinary concentration, the adaptive immune response, and other physiological systems. Since it is also important for development, conventional homozygous-null mutations result in perinatal death, which hinders the analysis of NFAT5 function in specific tissues in vivo. Here we describe the generation of mice with a conditional-null allele, in which loxP sites are inserted around exon 4.

NFAT5-mediated expression of S100A4 contributes to proliferation and migration of renal carcinoma cells.

The osmosensitive transcription factor nuclear factor of activated T-cells (NFAT) 5, also known as tonicity enhancer binding protein (TonEBP), has been associated with the development of a variety of tumor entities, among them breast cancer, colon carcinoma, and melanoma. The aim of the present study was to determine whether NFAT5 is also involved in the development of renal cell carcinoma (RCC). The most common type of RCC, the clear cell RCC, originates from the proximal convoluted tubule.

Focal adhesion kinase regulates the activity of the osmosensitive transcription factor TonEBP/NFAT5 under hypertonic conditions.

TonEBP/NFAT5 is a major regulator of the urinary concentrating process and is essential for the osmoadaptation of renal medullary cells. Focal adhesion kinase (FAK) is a mechanosensitive non-receptor protein tyrosine kinase expressed abundantly in the renal medulla. Since osmotic stress causes cell shrinkage, the present study investigated the contribution of FAK on TonEBP/NFAT5 activation.

Immune cells control skin lymphatic electrolyte homeostasis and blood pressure.

The skin interstitium sequesters excess Na+ and Cl- in salt-sensitive hypertension. Mononuclear phagocyte system (MPS) cells are recruited to the skin, sense the hypertonic electrolyte accumulation in skin, and activate the tonicity-responsive enhancer-binding protein (TONEBP, also known as NFAT5) to initiate expression and secretion of VEGFC, which enhances electrolyte clearance via cutaneous lymph vessels and increases eNOS expression in blood vessels. It is unclear whether this local MPS response to osmotic stress is important to systemic blood pressure control.

NFAT5 contributes to osmolality-induced MCP-1 expression in mesothelial cells.

Increased expression of the C-C chemokine monocyte chemoattractant protein-1 (MCP-1) in mesothelial cells in response to high glucose concentrations and/or high osmolality plays a crucial role in the development of peritoneal fibrosis during continuous ambulatory peritoneal dialysis (CAPD). Recent studies suggest that in kidney cells osmolality-induced MCP-1 upregulation is mediated by the osmosensitive transcription factor, nuclear factor of activated T cells 5 (NFAT5). The present study addressed the question of whether activation of NFAT5 by hyperosmolality, as present in PD fluids, contributes to MCP-1 expression in the mesothelial cell line Met5A.

Sepsis-induced urinary concentration defect is related to nitric oxide-dependent inactivation of TonEBP/NFAT5, which downregulates renal medullary solute transport proteins and aquaporin-2.

Objective: Acute kidney injury associated with reduced urinary concentration is a frequent and severe complication during sepsis. The present study addressed the effect of endotoxemia on the functional and molecular mechanisms that determine urinary concentrating ability. Efficient urinary concentration depends on, amongst other factors, the expression of the Cl channel kidney-specific chloride channel 1 and its subunit Barttin, the urea transporter-A1, and the water channel aquaporin 2, all of which are regulated by the transcription factor TonEBP/NFAT5.

Toll-like receptor 4 activates NF-κB and MAP kinase pathways to regulate expression of proinflammatory COX-2 in renal medullary collecting duct cells.

Binding of bacterial LPS to the Toll-like receptor 4 (TLR4) complex of inner medullary collecting duct (IMCD) cells plays a central role in recognition of ascending bacterial infections and activation of proinflammatory responses. Since proinflammatory cyclooxygenase (COX)-2 is induced in IMCD cells upon LPS exposure, the present study addressed the question of whether TLR4 mediates COX-2 induction in IMCD cells and characterized the underlying signaling mechanisms. Enhanced COX-2 expression and activity in the presence of LPS was diminished by TLR4 inhibition.

Cyclooxygenase-2-dependent phosphorylation of the pro-apoptotic protein Bad inhibits tonicity-induced apoptosis in renal medullary cells.

During antidiuresis, cell survival in the renal medulla requires cyclooxygenase-2 (COX-2) activity. We have recently found that prostaglandin E2 (PGE2) promotes cell survival by phosphorylation and, hence, inactivation of the pro-apoptotic protein Bad during hypertonic stress in Madin-Darby canine kidney (MDCK) cells in vitro. Here we determine the role of COX-2-derived PGE(2) on phosphorylation of Bad and medullary apoptosis in vivo using COX-2-deficient mice.

Role of NFAT5 in inflammatory disorders associated with osmotic stress.

Nuclear factor of activated T cells 5 (NFAT5) is the most recently described member of the Rel family of transcription factors, including NF-κB and NFAT1-4, which play central roles in inducible gene expression during the immune response. NFAT5 was initially described to drive osmoprotective gene expression in renal medullary cells, which are routinely faced by high extracellular osmolalities. Recent data however indicate profound biological importance of the mammalian osmotic stress response in view of NFAT5 dependent gene regulation in non-renal tissues.

Macrophages regulate salt-dependent volume and blood pressure by a vascular endothelial growth factor-C-dependent buffering mechanism.

In salt-sensitive hypertension, the accumulation of Na(+) in tissue has been presumed to be accompanied by a commensurate retention of water to maintain the isotonicity of body fluids. We show here that a high-salt diet (HSD) in rats leads to interstitial hypertonic Na(+) accumulation in skin, resulting in increased density and hyperplasia of the lymphcapillary network. The mechanisms underlying these effects on lymphatics involve activation of tonicity-responsive enhancer binding protein (TonEBP) in mononuclear phagocyte system (MPS) cells infiltrating the interstitium of the skin.

EGF receptor signaling is involved in expression of osmoprotective TonEBP target gene aldose reductase under hypertonic conditions.

Renal medullary cells adapt to their hyperosmotic environment by enhanced expression of various osmoprotective genes. Although it is clearly established that TonEBP contributes to the expression of these genes, neither the precise signaling mechanism by which hypertonicity activates TonEBP is completely understood, nor is it known whether a membrane-bound osmosenser, corresponding to yeast and bacteria, is present in mammalian cells. We found evidence that metalloproteinase (MMP)-dependent activation of the epidermal growth factor receptor (EGFR) signals to TonEBP and stimulates the expression of the TonEBP target gene aldose reductase (AR) under hypertonic conditions.

PGE2 potentiates tonicity-induced COX-2 expression in renal medullary cells in a positive feedback loop involving EP2-cAMP-PKA signaling.

Cyooxygenase-2 (COX-2)-derived PGE2 is critical for the integrity and function of renal medullary cells during antidiuresis. The present study extended our previous finding that tonicity-induced COX-2 expression is further stimulated by the major COX-2 product PGE2 and investigated the underlying signaling pathways and the functional relevance of this phenomenon. Hyperosmolality stimulated COX-2 expression and activity in Madin-Darby canine kidney (MDCK) cells, a response that was further increased by PGE2-cAMP signaling, suggesting the existence of a positive feedback loop.

Osmoadaptation of Mammalian cells - an orchestrated network of protective genes.

In mammals, the cells of the renal medulla are physiologically exposed to interstitial osmolalities several-fold higher that found in any other tissue. Nevertheless, these cells not only have the ability to survive in this harsh environment, but also to function normally, which is critical for maintenance of systemic electrolyte and fluid homeostasis. Over the last two decades, a substantial body of evidence has accumulated, indicating that sequential and well orchestrated genomic responses are required to provide tolerance to osmotic stress.

Method for diagnosis of a disease involving an anti-endothelin receptor antibody.

Background: Endothelin (ET) is a potent vasoconstrictor peptide with profibrotic, promitotic, and proinflammatory effects. Elevated levels of ET or inappropriate activation of ET receptors are believed to contribute to the pathogenesis of various disorders, including cardiovascular and autoimmune diseases and allograft rejection.

Objective: The pathogenetic significance of activating anti-ET receptor autoantibodies and their diagnostic usefulness are addressed.