Klotho Deficiency Induces Arteriolar Hyalinosis in a Trade-Off with Vascular Calcification.

Hyalinosis is a vascular lesion affecting the renal vasculature and contributing to aging-related renal function decline. We assessed whether arteriolar hyalinosis is caused by Klotho deficiency, a state known to induce both renal and vascular phenotypes associated with aging. Histochemistry was used to assess hyalinosis in Klotho-/- kidneys, compared with Klotho+/- and wild-type littermates. Immunohistochemistry was used to investigate vascular lesion composition and the different layers of the vascular wall. Finally, spironolactone was used to inhibit calcification in kl/kl mice, and vascular lesions were characterized in the kidney. Arteriolar hyalinosis was detected in Klotho-/- mice, which was present up to the afferent arterioles. Hyalinosis was accompanied by loss of α-smooth muscle actin expression, whereas the endothelial lining was mostly intact. Hyalinous lesions were positive for IgM and iC3b/c/d, indicating subendothelial leakage of plasma proteins. The presence of extracellular matrix proteins suggested increased production by smooth muscle cells (SMCs). Finally, in Klotho-/- mice with marked vascular calcification, treatment with spironolactone allowed for replacement of calcification by hyalinosis. Klotho deficiency potentiates both endothelial hyperpermeability and SMC dedifferentiation. In the absence of a calcification-inducing stimulus, SMCs assume a synthetic phenotype in response to subendothelial leakage of plasma proteins. In the kidney, this results in arteriolar hyalinosis, which contributes to the decline in renal function. Klotho may play a role in preventing aging-related arteriolar hyalinosis.

Comparative efficacy of Gum Arabic (Acacia senegal) and Tribulus terrestris on male fertility.

In this study the effect of Gum arabic (Acacia Senegal) was systemically targeted at male fertility with two experiments, the first comparing the effectiveness of Gum arabic (GA) and Tribulus terrestris (TT). For the first experiment, 27 adult mice Balb / c (18 females, 9 males) were divided into 3 in each group, one male and two females, group one had the usual tap water as power, group two had 5% (w / v) GA and group three had 5% (w / v) of TT for 21 days. The results showed, the number of offspring was more with GA treated when compared to TT treated. Blood measurements of testosterone showed significant increase in the GA group as compared to other groups, also Histopathological analysis showed the dose dependent 5% GA had normal seminiferous tubules with increase spermatogenesis. In this study the enhanced fertility in GA-treated mice Balb/c was observed and the experimental studies also show that GA fertility was increased.

Genetic deficiency of the tumor suppressor protein p53 influences erythrocyte survival.

The transcription factor p53 suppresses tumor growth by inducing nucleated cell apoptosis and cycle arrest. Because of its influence on primitive erythroid cell differentiation and survival, p53 is an important determinant of erythropoiesis. However, the impact of p53 on the fate of erythrocytes, cells lacking nucleus and mitochondria, during their post-maturation phase in the circulation remained elusive. Erythrocyte survival may be compromised by suicidal erythrocyte death or eryptosis, which is hallmarked by phosphatidylserine translocation and stimulated by increase of cytosolic Ca2+ concentration. Here, we comparatively examined erythrocyte homeostasis in p53-mutant mice (Trp53tm1Tyj/J) and in corresponding WT mice (C57BL/6J) by analyzing eryptosis and erythropoiesis. To this end, spontaneous cell membrane phosphatidylserine exposure and cytosolic Ca2+ concentration were higher in erythrocytes drawn from Trp53tm1Tyj/J mice than from WT mice. Eryptosis induced by glucose deprivation, a pathophysiological cell stressor, was slightly, but significantly more prominent in erythrocytes drawn from Trp53tm1Tyj/J mice as compared to WT mice. The loss of erythrocytes by eryptosis was fully compensated by enhanced erythropoiesis in Trp53tm1Tyj/J mice, as reflected by increased reticulocytosis and abundance of erythroid precursor cells in the bone marrow. Accordingly, erythrocyte number, packed cell volume and hemoglobin were similar in Trp53tm1Tyj/J and WT mice. Taken together, functional p53 deficiency enhances the turnover of circulating erythrocytes by parallel increase of eryptosis and stimulated compensatory erythropoiesis.

Inhibition of Collagen Related Peptide Induced Platelet Activation and Apoptosis by Ceritinib.

BACKGROUND/AIMS: The anaplastic lymphoma (tyrosine) kinase (ALK) inhibitor ceritinib triggers apoptosis of tumor cells and eryptosis of erythrocytes. Blood platelets may similarly enter a state resembling apoptosis, which could be triggered by activation with collagen related peptide (CRP). CRP-induced platelet apoptosis is characterized by cell membrane scrambling with phosphatidylserine exposure to the platelet surface and cell shrinkage, preceded by externalization of Ca2+ channel Orai1, increase of cytosolic Ca2+-activity ([Ca2+]i), formation of reactive oxygen species (ROS), and caspase activation. The present study explored whether ceritinib triggers platelet apoptosis and/or modifies the CRP induced apoptosis. METHODS: Platelets isolated from wild-type mice were exposed for 30 minutes to ceritinib (1.5 µg/ml) without or with 2.5 - 15 min pretreatment with CRP (2 µg/ml or 5 µg/ml). Flow cytometry was employed to estimate cytosolic Ca2+-activity ([Ca2+]i) from Fluo-3 fluorescence, ROS abundance from 2',7'-dichlorodihydrofluorescein diacetate fluorescence, platelet degranulation from P-selectin abundance, integrin activation from αIIbß3 integrin abundance, caspase activity utilizing an Active Caspase-3 Staining kit, phosphatidylserine abundance from annexin-V-binding, platelet volume from forward scatter and aggregation utilizing staining with CD9-APC and CD9-PE. RESULTS: In the absence of CRP, ceritinib slightly, but significantly decreased [Ca2+]i without significantly modifying the other measured parameters. CRP significantly increased [Ca2+]i, ROS abundance, P-selectin abundance, activated αIIbß3 integrin, annexin-V-binding, caspase activity as well as aggregation and decreased cell volume, all effects significantly blunted in the presence of ceritinib. CONCLUSIONS: The present observations uncover a novel, unexpected effect of ceritinib, i.e. inhibition of CRP-induced platelet activation and apoptosis.

Alkaline Cytosolic pH and High Sodium Hydrogen Exchanger 1 (NHE1) Activity in Th9 Cells.

CD4+ T helper 9 (Th9) cells are a newly discovered Th cell subset that produce the pleiotropic cytokine IL-9. Th9 cells can protect against tumors and provide resistance against helminth infections. Given their pivotal role in the adaptive immune system, understanding Th9 cell development and the regulation of IL-9 production could open novel immunotherapeutic opportunities. The Na+/H+ exchanger 1 (NHE1; gene name Slc9α1)) is critically important for regulating intracellular pH (pHi), cell volume, migration, and cell survival. The pHi influences cytokine secretion, activities of membrane-associated enzymes, ion transport, and other effector signaling molecules such as ATP and Ca2+ levels. However, whether NHE1 regulates Th9 cell development or IL-9 secretion has not yet been defined. The present study explored the role of NHE1 in Th9 cell development and function. Th cell subsets were characterized by flow cytometry and pHi was measured using 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein-acetoxymethyl ester (BCECF-AM) dye. NHE1 functional activity was estimated from the rate of realkalinization following an ammonium pulse. Surprisingly, in Th9 cells pHi and NHE1 activity were significantly higher than in all other Th cell subsets (Th1/Th2/Th17 and induced regulatory T cells (iTregs)). NHE1 transcript levels and protein abundance were significantly higher in Th9 cells than in other Th cell subsets. Inhibition of NHE1 by siRNA-NHE1 or with cariporide in Th9 cells down-regulated IL-9 and ATP production. NHE1 activity, Th9 cell development, and IL-9 production were further blunted by pharmacological inhibition of protein kinase Akt1/Akt2. Our findings reveal that Akt1/Akt2 control of NHE1 could be an important physiological regulator of Th9 cell differentiation, IL-9 secretion, and ATP production.

Temsirolimus Sensitive Stimulation of Platelet Activity, Apoptosis and Aggregation by Collagen Related Peptide.

BACKGROUND/AIMS: The mammalian target of rapamycin (mTOR) inhibitor temsirolimus stimulates apoptosis of tumor cells and is thus therapeutically used for the treatment of diverse malignancies. On the other hand, temsirolimus has been shown to protect against apoptosis of hippocampal neurons. Similar to nucleated cells, blood platelets may enter suicidal death characterized by cell shrinkage and cell membrane scrambling. Platelet apoptosis is frequently preceded by Ca2+ entry, degranulation, integrin activation and stimulation of caspases. Those events could be triggered by collagen related peptide (CRP). The present study explored whether treatment of platelets with temsirolimus modifies platelet activation, caspase activity, platelet shrinkage, and phosphatidylserine abundance. METHODS: Platelets isolated from wild-type mice were exposed for 30 minutes to temsirolimus (40 µg/ml) without or with additional CRP (2 µg/ ml or 5 µg/ml) treatment. Flow cytometry was employed to estimate cytosolic Ca2+-activity ([Ca2+]i) from Fluo-3 fuorescence, platelet degranulation from P-selectin abundance, integrin activation from αIIbß3 integrin abundance, caspase activity utilizing an Active Caspase-3 Staining kit, phosphatidylserine abundance from annexin-V-binding and relative platelet volume from forward scatter. RESULTS: In the absence of CRP, the administration of temsirolimus (40 µg/ml) significantly decreased [Ca2+]i, but did not significantly modify P-selectin abundance, activated αIIbß3 integrin, annexin-V-binding, cell volume, caspase activity and aggregation. Exposure of platelets to CRP was followed by significant increase of [Ca2+]i, P-selectin abundance, αIIbß3 integrin activity, annexin-V-binding, ROS, caspase activity and aggregation, effects significantly blunted in the presence of temsirolimus. CRP further decreased forward scatter, an effect again significantly blunted by temsirolimus. CONCLUSIONS: Temsirolimus is a powerful inhibitor of platelet activation and suicidal platelet death.

Effect of Bexarotene on Platelet Activation and Apoptosis.

BACKGROUND/AIMS: The retinoid X receptor (RXRs) stimulator Bexarotene ((4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)ethynyl] benzoic acid) is used for the treatment of several malignancies. Bexarotene is at least in part effective by stimulation of apoptosis of tumor cells. Moreover, Bexarotene triggers eryptosis, the suicidal death of erythrocytes. Similar to erythrocytes, blood platelets lack nuclei but are nevertheless able to enter an apoptosis-like phenotype, characterized by caspase activation, cell shrinkage and cell membrane scrambling with phospha-tidylserine translocation to the cell surface. Platelet apoptosis is triggered by increase of cytosolic Ca2+-activity ([Ca2+]i), which further leads to degranulation and integrin activation. Platelet activation and apoptosis could be elicited by thrombin or collagen related peptide (CRP). The present study explored whether treatment of platelets with bexarotene modifies platelet activation and apoptosis following exposure to thrombin or CRP. METHODS: Platelets isolated from wild-type mice were exposed for 30 minutes to bexarotene (6 µg/ml) without or with an additional treatment with thrombin (0.01 U/ml) or CRP (2 µg/ml or 5 µg/ml). Flow cytometry was employed to estimate cytosolic Ca2+-activity ([Ca2+]i) from Fluo-3 fluorescence, platelet degranulation from P-selectin abundance, integrin activation from αIIbß3 integrin abundance, caspase activity utilizing an Active Caspase-3 Staining kit, phosphatidylserine abundance from annexin-V-binding, and relative platelet volume from forward scatter. RESULTS: In the absence of thrombin or CRP, the administration of bexarotene slightly but significantly increased [Ca2+]i, but did not significantly modify P-selectin abundance, activated αIIbß3 integrin, annexin-V-binding, cell volume, or caspase activity. Exposure of platelets to thrombin or CRP was followed by significant increase of [Ca2+]i, P-selectin abundance, active αIIbß3 integrin, annexin-V-binding, and caspase activity. The effects of thrombin on [Ca2+]i, annexin-V-binding, cell volume, and caspase activity as well as the effects of CRP on [Ca2+]i, P-selectin abundance, activated αIIbß3 integrin, annexin-V-binding, cell volume, and caspase activity were significantly augmented in the presence of bexarotene. CONCLUSIONS: Bexarotene sensitizes blood platelets for thrombin and/or CRP induced activation and apoptosis.

Effects of Antimalarial Tafenoquine on Blood Platelet Activity and Survival.

BACKGROUND/AIMS: The 8-aminoquinoline tafenoquine has been shown to be effective against Plasmodia, Leishmania and Trypanosoma. The substance is at least in part effective by triggering apoptosis of the parasites. Moreover, tafenoquine has been shown to trigger eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. The effect of tafenoquine on eryptosis is in part due to stimulation of Ca2+ entry and oxidative stress. Ca2+ entry is a critical event in the activation of blood platelets by thrombin and collagen related peptide (CRP). The present study explored, whether tafenoquine influences Ca2+ entry, activation and apoptosis of blood platelets. METHODS: Platelets isolated from wild-type mice were exposed for 30 minutes to tafenoquine (2.5 µg/ml) without or with an additional treatment with thrombin (0.01 U/ml) or CRP (2 µg/ml or 5 µg/ml). Flow cytometry was employed to estimate cytosolic Ca2+-activity ([Ca2+]i) from Fluo-3 fluorescence, platelet degranulation from P-selectin abundance, integrin activation from αIIbß3 integrin abundance, phosphatidylserine abundance from annexin-V-binding, relative platelet volume from forward scatter, reactive oxygen species (ROS) from DCF fluorescence, caspase 3 activity with an active caspase-3 Staining kit, and aggregation utilizing staining with CD9-APC and CD9-PE. RESULTS: Both, thrombin (0.01 U/ml) and CRP (2 µg/ml or 5 µg/ml), significantly increased [Ca2+]i, P-selectin abundance, active αIIbß3 integrin, and annexin-V-binding, and both significantly decreased platelet volume, activated caspase 3 and stimulated aggregation. Administration of tafenoquine (2.5 µg/ml, 30 min) significantly decreased [Ca2+]i both, in the absence and presence of thrombin and CRP. Tafenoquine significantly blunted the effect of thrombin and CRP on [Ca2+]i, P-selectin abundance, and active αIIbß3 integrin, but significantly increased ROS and annexin-V-binding, significantly augmented the effect of thrombin on caspase 3 activity and platelet volume and significantly enhanced platelet aggregation. CONCLUSIONS: Tafenoquine counteracts thrombin and CRP induced increase of cytosolic Ca2+ activity and platelet activation, but enhances platelet apoptosis and platelet aggregation.

Inhibitory Effect of Afatinib on Platelet Activation and Apoptosis.

BACKGROUND/AIMS: The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor afatinib is used for the treatment of several malignancies. Afatinib is at least partially effective by triggering apoptosis of tumor cells. Platelets may similarly undergo apoptosis, which is characterized by caspase 3 activation, cell shrinkage and phosphatidylserine translocation. However, an effect of afatinib on platelets has never been reported. The present study explored whether treatment of platelets with afatinib modifies platelet activation and apoptosis in the absence and presence of platelet activators thrombin or collagen related peptide (CRP). METHODS: Platelets isolated from wild-type mice were exposed for 30 minutes to afatinib (18 µg/ml) without or with subsequent treatment with thrombin (0.005 U/ml or 0.01 U/ml) or CRP (2 µg/ml or 5 µg/ml). Flow cytometry was employed to estimate Orai1 abundance at the platelet surface with specific antibodies, cytosolic Ca2+-activity ([Ca2+]i) from Fluo-3 fluorescence, platelet degranulation from P-selectin abundance, integrin activation from αIIbß3 integrin abundance, caspase activity utilizing an Active Caspase-3 Staining kit, phosphatidylserine abundance from annexin-V-binding, platelet volume from forward scatter and aggregation utilizing staining with CD9-APC and CD9-PE. RESULTS: In the absence of thrombin and CRP, the administration of afatinib (18 µg/ml) slightly, but significantly, increased [Ca2+]i and annexin-V-binding, but did not significantly modify Orai1 abundance, P-selectin abundance, activated αIIbß3 integrin, cell volume, caspase activity and aggregation. Exposure of platelets to 0.005 U/ml or 0.01 U/ml thrombin or 2 µg/ml or 5 µg/ ml CRP was followed by a significant increase of Orai1 abundance, increase of [Ca2+]i, P-selectin abundance, αIIbß3 integrin activity, annexin-V-binding, caspase activity, and aggregation, as well as a significant decrease of forward scatter, all effects significantly blunted (thrombin) or virtually abolished (CRP) by afatinib. CONCLUSIONS: Afatinib is a powerful inhibitor of platelet activation, platelet apoptosis and platelet aggregation.

Enhanced FGF23 production in mice expressing PI3K-insensitive GSK3 is normalized by ß-blocker treatment.

Glycogen synthase kinase (GSK)-3 is a ubiquitously expressed kinase inhibited by insulin-dependent Akt/PKB/SGK. Mice expressing Akt/PKB/SGK-resistant GSK3α/GSK3ß (gsk3(KI)) exhibit enhanced sympathetic nervous activity and phosphaturia with decreased bone density. Hormones participating in phosphate homeostasis include fibroblast growth factor (FGF)-23, a bone-derived hormone that inhibits 1,25-dihydroxyvitamin D3 (1,25(OH)2D3; calcitriol) formation and phosphate reabsorption in the kidney and counteracts vascular calcification and aging. FGF23 secretion is stimulated by the sympathetic nervous system. We studied the role of GSK3-controlled sympathetic activity in FGF23 production and phosphate metabolism. Serum FGF23, 1,25(OH)2D3, and urinary vanillylmandelic acid (VMA) were measured by ELISA, and serum and urinary phosphate and calcium were measured by photometry in gsk3(KI) and gsk3(WT) mice, before and after 1 wk of oral treatment with the ß-blocker propranolol. Urinary VMA excretion, serum FGF23, and renal phosphate and calcium excretion were significantly higher, and serum 1,25(OH)2D3 and phosphate concentrations were lower in gsk3(KI) mice than in gsk3(WT) mice. Propranolol treatment decreased serum FGF23 and loss of renal calcium and phosphate and increased serum phosphate concentration in gsk3(KI) mice. We conclude that Akt/PKB/SGK-sensitive GSK3 inhibition participates in the regulation of FGF23 release, 1,25(OH)2D3 formation, and thus mineral metabolism, by controlling the activity of the sympathetic nervous system.

Effect of Lysosomotropic Polyamineoxidase Inhibitor MDL-72527 on Platelet Activation.

BACKGROUND/AIMS: The polyamine oxidase inhibitor MDL-72527 (N1,N4-bis(2,3-butadienyl)-1,4-butanediamine) were expected to increase the abundance of spermine, a powerful inhibitor of platelet activation. Nothing is known, however, on the sensitivity of platelet function and survival to MDL-72527 exposure. The present study thus explored whether MDL-72527 modifies function and survival of platelets without and with platelet activation by collagen related peptide (CRP). METHODS: Platelets isolated from wild-type mice were exposed for 30 minutes to MDL-72527 (100 µM) with or without subsequent activation with CRP (2-5 µg/ml). Flow cytometry was employed to estimate cytosolic Ca2+-activity ([Ca2+]i) from Fluo-3 fluorescence, platelet degranulation from P-selectin abundance, integrin activation from αIIbß3 integrin abundance, generation of reactive oxygen species (ROS) from DCFDA fluorescence, phospholipid scrambling of the cell membrane from annexin-V-binding, platelet volume from forward scatter and aggregation utilizing staining with CD9-APC and CD9-PE. RESULTS: In the absence of CRP, exposure of platelets to MDL-72527 did not significantly modify [Ca2+]i, P-selectin abundance, αIIbß3 integrin abundance, ROS, annexin-V-binding, and forward scatter. The addition of 2-5 µg/ml CRP was followed by significant increase of [Ca2+]i, P-selectin abundance, αIIbß3 integrin activation, ROS abundance, annexin-V-binding, and aggregation as well as a significant decrease of forward scatter, all effects significantly blunted or virtually abolished in the presence of MDL-72527. CONCLUSIONS: MDL-72527 is a powerful inhibitor of platelet activation, apoptosis and aggregation.

Influence of γ-Secretase Inhibitor 24-Diamino-5-Phenylthiazole DAPT on Platelet Activation.

BACKGROUND/AIMS: DAPT (24-diamino-5-phenylthiazole) inhibits γ-secretase, which cleaves the signaling molecule CD44, a negative regulator of platelet activation and apoptosis. CD44 is a co-receptor for macrophage migration inhibitory factor (MIF) an anti-apoptotic pro-inflammatory cytokine expressed and released from blood platelets. Whether DAPT influences platelet function, remained, however, elusive. Activators of platelets include collagen related peptide (CRP). The present study thus explored whether DAPT modifies the stimulating effect of CRP on platelet function. METHODS: Platelets isolated from wild-type mice were exposed for 30 minutes to DAPT (10 µM). Flow cytometry was employed to estimate Orai1 abundance with specific antibodies, cytosolic Ca(2+)-activity ([Ca2+]i) from Fluo-3 fluorescence, platelet degranulation from P-selectin abundance, integrin activation from α(IIb)ß3 integrin abundance, generation of reactive oxygen species (ROS) from DCFDA fluorescence, mitochondrial transmembrane potential from TMRE fluorescence, phospholipid scrambling of the cell membrane from annexin-V-binding, relative platelet volume from forward scatter and aggregation utilizing staining with CD9-APC and CD9-PE. RESULTS: Exposure of platelets to 2-5 µg/ml CRP was followed by significant increase of Orai1 abundance, [Ca2+]i, and P-selectin abundance, as well as by α(IIb)ß3 integrin activation, ROS generation, mitochondrial depolarization, enhanced annexin-V-binding, decreased cell volume, and aggregation. All CRP induced effects were significantly blunted in the presence of DAPT. CONCLUSIONS: The γ-secretase inhibitor DAPT counteracts agonist induced platelet activation, apoptosis and aggregation.

LEFTYA Activates the Epithelial Na+ Channel (ENaC) in Endometrial Cells via Serum and Glucocorticoid Inducible Kinase SGK1.

BACKGROUND: Serum & glucocorticoid inducible kinase (SGK1) regulates several ion channels, including amiloride sensitive epithelial Na+ channel (ENaC). SGK1 and ENaC in the luminal endometrium epithelium, are critically involved in embryo implantation, although little is known about their regulation. The present study explored whether SGK1 and ENaC are modulated by LEFTYA, a negative regulator of uterine receptivity. METHODS: Expression levels were determined by qRT-PCR and Western blotting, ENaC channel activity by whole cell patch clamp and transepithelial current by Ussing chamber experiments. RESULTS: Treatment of Ishikawa cells, an endometrial adenocarcinoma model cell line of endometrial epithelial cells, with LEFTYA rapidly up-regulated SGK1 and ENaC transcript and protein levels. Induction of ENaC in response to LEFTYA was blunted upon co-treatment with the SGK1 inhibitor EMD638683. ENaC levels also significantly upregulated upon expression of a constitutively active, but not a kinase dead, SGK1 mutant in Ishikawa cells. LEFTYA increased amiloride sensitive Na+-currents in Ishikawa cells and amiloride sensitive transepithelial current across the murine endometrium. Furthermore, LEFTYA induced the expression of ENaC in the endometrium of wild-type but not of Sgk1-deficient mice. CONCLUSIONS: LEFTYA regulates the expression and activity of ENaC in endometrial epithelial cells via SGK1. Aberrant regulation of SGK1 and ENaC by LEFTYA could contribute to the pathogenesis of unexplained infertility.

Up-regulation of FGF23 release by aldosterone.

The fibroblast growth factor (FGF23) plasma level is high in cardiac and renal failure and is associated with poor clinical prognosis of these disorders. Both diseases are paralleled by hyperaldosteronism. Excessive FGF23 levels and hyperaldosteronism are further observed in Klotho-deficient mice. The present study explored a putative aldosterone sensitivity of Fgf23 transcription and secretion the putative involvement of the aldosterone sensitive serum & glucocorticoid inducible kinase SGK1, SGK1 sensitive transcription factor NFκB and store operated Ca(2+) entry (SOCE). Serum FGF23 levels were determined by ELISA in mice following sham treatment or exposure to deoxycorticosterone acetate (DOCA) or salt depletion. In osteoblastic UMR106 cells transcript levels were quantified by qRT-PCR, cytosolic Ca(2+) concentration utilizing Fura-2-fluorescence, and SOCE from Ca(2+) entry following store depletion by thapsigargin. As a result, DOCA treatment and salt depletion of mice elevated the serum C-terminal FGF23 concentration. In UMR106 cells aldosterone enhanced and spironolactone decreased SOCE. Aldosterone further increased Fgf23 transcript levels in UMR106 cells, an effect reversed by mineralocorticoid receptor blockers spironolactone and eplerenone, SGK1 inhibitor EMD638683, NFκB-inhibitor withaferin A, and Ca(2+) channel blocker YM58483. In conclusion, Fgf23 expression is up-regulated by aldosterone, an effect sensitive to SGK1, NFκB and store-operated Ca(2+) entry.

Impact of Annexin A 7 Deficiency on FGF23 Plasma Concentrations.

BACKGROUND/AIMS: The release of fibroblast growth factor FGF23, a powerful regulator of 1,25(OH)2D3 formation and mineral metabolism, is stimulated by store-operated Ca2+ entry (SOCE), which is accomplished by the pore forming Ca2+ release activated channel protein Orai1. Regulators of Orai1 and thus FGF23 release include serum & glucocorticoid inducible kinase SGK1, a kinase up-regulated by glucocorticosteroids. Some effects of glucocorticoids require the presence of annexin A7, such as suppression of prostaglandin E2 in gastric glands. The present study thus explored whether annexin A7 impacts on FGF23 plasma levels. METHODS: Comparisons were made between gene targeted mice lacking functional annexin A7 (Anx7-/-) and their wild type littermates (Anx7+/+). Serum C-terminal-FGF23, intact FGF23, 1,25(OH)2D3 and PTH concentrations were measured by ELISA or EIA. The serum and urinary phosphate concentrations were measured by colorimetry, the serum Ca2+ concentration and the urinary Ca2+ concentration by flame photometry. RESULTS: Serum C-terminal FGF23 levels and corticosterone levels were significantly higher and serum 1,25(OH)2 D3 and PTH levels were significantly lower in Anx7-/- than in Anx7+/+ mice. Water intake was slightly but significantly higher in Anx7-/- mice than in Anx7+/+ mice. No significant difference was observed between Anx7-/- and Anx7+/+ mice in urinary fluid excretion, plasma Ca2+ concentration, plasma phosphate concentration and urinary Ca2+ output. The urinary phosphate output was significantly lower in Anx7-/- mice than in Anx7+/+ mice. CONCLUSION: Annexin A7 deficiency upregulates FGF23 plasma levels, an effect paralleled by increased corticosterone plasma levels, as well as decreased 1,25(OH)2 D3 and PTH plasma levels.

Influence of annexin A7 on insulin sensitivity of cellular glucose uptake.

Insulin sensitivity is decreased by prostaglandin E2 (PGE2), a major product of cyclooxygenase (COX). As shown in erythrocytes, PGE2 formation is inhibited by annexin A7. The present study defined the role of annexin A7 in glucose metabolism. Gene-targeted mice lacking annexin A7 (annexin7 (-/-)) were compared to wild-type mice (annexin7 (+/+)). The serum 6-Keto-prostaglandin-F1α (6-Keto-PGF1α) concentration was measured by ELISA and hepatic COX activity determined by an enzyme assay. Expression of COX-1, COX-2, prostaglandin E synthase, GLUT-4, and insulin receptor was determined by Western blotting. Glucose and insulin serum concentrations were analyzed following an intraperitoneal glucose load and glucose serum levels after intraperitoneal injection of insulin. Experiments were done without and with pretreatment of the mice with COX-inhibitor aspirin. The serum 6-Keto-PGF1α level and hepatic COX activity were significantly higher in annexin7 (-/-) than in annexin7 (+/+) mice. Hepatic COX-1 expression was higher in annexin7 (-/-) mice. Glucose tolerance was decreased in annexin7 (-/-) mice. Intraperitoneal insulin injection decreased the serum glucose level in both genotypes, an effect significantly less pronounced in annexin7 (-/-) mice. Glucose-induced insulin secretion was higher in annexin7 (-/-) mice. GLUT-4 expression in skeletal muscle from annexin7 (-/-) mice was reduced. Aspirin pretreatment lowered the increase in insulin concentration following glucose injection in both genotypes and virtually abrogated the differences in serum insulin between the genotypes. Aspirin pretreatment improved glucose tolerance in annexin7 (-/-) mice. In conclusion, annexin A7 influences insulin sensitivity of cellular glucose uptake and thus glucose tolerance. These effects depend on COX activity.

Janus kinase 3 regulates renal 25-hydroxyvitamin D 1α-hydroxylase expression, calcitriol formation, and phosphate metabolism.

Calcitriol, a powerful regulator of phosphate metabolism and immune response, is generated by 25-hydroxyvitamin D 1α-hydroxylase in the kidney and macrophages. Renal 1α-hydroxylase expression is suppressed by Klotho and FGF23, the expression of which is stimulated by calcitriol. Interferon γ (INFγ) regulates 1α-hydroxylase expression in macrophages through transcription factor interferon regulatory factor-1. INFγ-signaling includes Janus kinase 3 (JAK3) but a role of JAK3 in the regulation of 1α-hydroxylase expression and mineral metabolism has not been shown. Thus, the impact of JAK3 deficiency on calcitriol formation and phosphate metabolism was measured. Renal interferon regulatory factor-1 and 1α-hydroxylase transcript levels, serum calcitriol and FGF23 levels, intestinal phosphate absorption as well as absolute and fractional renal phosphate excretion were significantly higher in jak3 knockout than in wild-type mice. Coexpression of JAK3 increased the phosphate-induced current in renal sodium-phosphate cotransporter-expressing Xenopus oocytes. Thus, JAK3 is a powerful regulator of 1α-hydroxylase expression and phosphate transport. Its deficiency leads to marked derangement of phosphate metabolism.

Rapid Upregulation of Orai1 Abundance in the Plasma Membrane of Platelets Following Activation with Thrombin and Collagen Related Peptide.

BACKGROUND: Blood platelets accomplish primary hemostasis following vascular injury and contribute to the orchestration of occlusive vascular disease. Platelets are activated by an increase of cytosolic Ca2+-activity ([Ca2+]i), which is accomplished by Ca2+-release from intracellular stores and subsequent store operated Ca2+ entry (SOCE) through Ca2+ release activated Ca2+ channel moiety Orai1. Powerful activators of platelets include thrombin and collagen related peptide (CRP), which are in part effective by activation of small G- protein Rac1. The present study explored the influence of thrombin and CRP on Orai1 protein abundance and cytosolic Ca2+-activity ([Ca2+]i) in platelets drawn from wild type mice. METHODS: Orai1 protein surface abundance was quantified utilizing CF™488A conjugated antibodies, and [Ca2+]i was determined with Fluo3-fluorescence. RESULTS: In resting platelets, Orai1 protein abundance and [Ca2+]i were low. Thrombin (0.02 U/ml) and CRP (5ug/ml) within 2 min increased [Ca2+]i and Orai1 protein abundance at the platelet surface. [Ca2+]i was further increased by Ca2+ ionophore ionomycin (1 µM) and by store depletion with the sarcoendoplasmatic Ca2+ ATPase inhibitor thapsigargin (1 µM). However, Orai1 protein abundance at the platelet surface was not significantly affected by ionomycin and only slightly increased by thapsigargin. The effect of thrombin and CRP on Orai1 abundance and [Ca2+]i was significantly blunted by Rac1 inhibitor NSC23766 (50 µM). CONCLUSION: The increase of [Ca2+]i following stimulation of platelets with thrombin and collagen related peptide is potentiated by ultrarapid Rac1 sensitive translocation of Orai1 into the cell membrane.

The Role of Janus Kinase 3 in the Regulation of Na⁺/K⁺ ATPase under Energy Depletion.

BACKGROUND/AIMS: Janus kinase-3 (JAK3) is activated during energy depletion. Energy-consuming pumps include the Na(+)/K(+)-ATPase. The present study explored whether JAK3 regulates Na(+)/K(+)-ATPase in dendritic cells (DCs). METHODS: Ouabain (100 µM)-sensitive (Iouabain) and K(+)-induced (Ipump) outward currents were determined by utilizing whole cell patch-clamp, Na(+)/K(+)-ATPase α1-subunit mRNA levels by RT-PCR, Na(+)/K(+)-ATPase protein abundance by flow cytometry or immunofluorescence, and cellular ATP by luciferase-assay in DCs from bone marrow of JAK3-knockout (jak3(-/-)) or wild-type mice (jak3(+/+)). Ipump was further determined by voltage clamp in Xenopus oocytes expressing JAK3, active (A568V)JAK3 or inactive (K851A)JAK3. RESULTS: Na(+)/K(+)-ATPase α1-subunit mRNA and protein levels, as well as Ipump and Iouabain were significantly higher in jak3(-/-)DCs than in jak3(+/+)DCs. Energy depletion by 4h pre-treatment with 2,4-dinitro-phenol significantly decreased Ipump in jak3(+/+) DCs but not in jak3(-/-)DCs. Cellular ATP was significantly lower in jak3(-/-)DCs than in jak3(+/+)DCs and decreased in both genotypes by 2,4-dinitro-phenol, an effect significantly more pronounced in jak3(-/-)DCs than in jak3(+/+)DCs and strongly blunted by ouabain in both jak3(+/+) and jak3(-/-)DCs. Ipump and Iouabain in oocytes were decreased by expression of JAK3 and of (A568V)JAK3 but not of (K851A)JAK3. JAK3 inhibitor WHI-P154 (4-[(3'-bromo-4'-hydroxyphenyl)amino]-6,7-dimethoxyquinazoline, 22 µM) enhanced Ipump and Iouabain in JAK3 expressing oocytes. The difference between (A568V)JAK3 and (K851A)JAK3 expressing oocytes was virtually abrogated by actinomycin D (50 nM). CONCLUSIONS: JAK3 down-regulates Na(+)/K(+)-ATPase activity, an effect involving gene expression and profoundly curtailing ATP consumption.

SPAK Sensitive Regulation of the Epithelial Na Channel ENaC.

BACKGROUND/AIMS: The WNK-dependent STE20/SPS1-related proline/alanine-rich kinase SPAK participates in the regulation of NaCl and Na(+),K(+),2Cl(-) cotransport and thus renal salt excretion. The present study explored whether SPAK has similarly the potential to regulate the epithelial Na(+) channel (ENaC). METHODS: ENaC was expressed in Xenopus oocytes with or without additional expression of wild type SPAK, constitutively active (T233E)SPAK, WNK insensitive (T233A)SPAK or catalytically inactive (D212A)SPAK, and ENaC activity estimated from amiloride (50 µM) sensitive current (Iamil) in dual electrode voltage clamp experiments. Moreover, Ussing chamber was employed to determine Iamil in colonic tissue from wild type mice (spak(wt/wt)) and from gene targeted mice carrying WNK insensitive SPAK (spak(tg/tg)). RESULTS: Iamil was observed in ENaC-expressing oocytes, but not in water-injected oocytes. In ENaC expressing oocytes Iamil was significantly increased following coexpression of wild-type SPAK and (T233E)SPAK, but not following coexpression of (T233A)SPAK or (D212A)SPAK. Colonic Iamil was significantly higher in spak(wt/wt) than in spak(tg/tg) mice. CONCLUSION: SPAK has the potential to up-regulate ENaC.