INTRODUCTION:Cytokines might play a key role in the pathophysiology of major depressive disorder (MDD). The speed of onset of depressive episodes has been discussed as an important clinical parameter in MDD. The aim of this study was to investigate a potential influence of the speed of onset of the depressive episode on cytokine serum levels. METHOD:Serum level of the cytokines interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor alpha (TNF-α), interferon-gamma (IFN-γ) granulocyte and monocyte colony stimulating factor (GM-CSF) were measured in a total of 92 patients with MDD that did not respond to at least one previous antidepressant treatment. Patients were retrospectively divided in two groups: Faster (≤4 weeks) and slower (>4 weeks) onset of the depressive episode defined as the time passing from the first depressive symptoms to a full-blown depressive episode by using information from a clinical interview. RESULTS:We found significantly lower serum levels of IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ in patients with a faster onset compared to patients with a slower onset of the depressive episodes. Furthermore, lower cytokine serum levels of IL-2, IL-8, IL-10 and IFN-γ were found in patients with a shorter duration (less than 6 months) compared to a longer duration (6-24 months) of the current depressive episode. This effect on cytokines was independent from the effect of the speed of onset of the depressive episode. CONCLUSIONS:Patients with faster onset of the depressive episode might represent a biological subtype of MDD with lower serum levels of IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ.

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.

Embryo implantation requires a hospitable uterine environment. A key metabolic change that occurs during the peri-implantation period, and throughout early pregnancy, is the rise in endometrial glycogen content. Glycogen accumulation requires prior cellular uptake of glucose. Here we show that both human and murine endometrial epithelial cells express the high affinity Na + -coupled glucose carrier SGLT1. Ussing chamber experiments revealed electrogenic glucose transport across the endometrium in wild type ( Slc5a1 +/+ ) but not in SGLT1 deficient ( Slc5a1 −/− ) mice. Endometrial glycogen content, litter size and weight of offspring at birth were significantly lower in Slc5a1 −/− mice. In humans, SLC5A1 expression was upregulated upon decidualization of primary endometrial stromal cells. Endometrial SLC5A1 expression during the implantation window was attenuated in patients with recurrent pregnancy loss when compared with control subjects. Our findings reveal a novel mechanism establishing adequate endometrial glycogen stores for pregnancy. Disruption of this histiotrophic pathway leads to adverse pregnancy outcome.

The transcription factor nuclear factor of activated T cells 5 (NFAT5) is up-regulated in several clinical disorders, including dehydration. NFAT5-sensitive genes include serum and glucocorticoid-inducible kinase 1 (SGK1). The kinase is a powerful regulator of Orai1, a Ca2+ channel accomplishing store-operated Ca2+ entry (SOCE). Orai1 is stimulated after intracellular store depletion by the Ca2+ sensors stromal interaction molecule 1 (STIM1), or STIM2, or both. In the present study, we explored whether nuclear factor of activated T cell (NFAT)-5 influences Ca2+ signaling in megakaryocytes. To this end, human megakaryocytic (MEG-01) cells were transfected with NFAT5 or with siNFAT5. Platelets and megakaryocytes were isolated from wild-type mice with either access to water ad libitum or dehydration by 36 h of water deprivation. Transcript levels were determined with quantitative RT-PCR and protein abundance by Western blot analysis and flow cytometry, cytosolic (intracellular) Ca2+ concentration ([Ca2+]i) by fura-2-fluorescence. SOCE was estimated from the increase of [Ca2+]i following readdition of extracellular Ca2+ after store depletion with thapsigargin (1 µM). Platelet degranulation was estimated from P-selectin abundance and integrin activation from αIIbβ3 integrin abundance determined by flow cytometry. As a result, NFAT5 transfection or exposure to hypertonicity (+40 mM NaCl) of MEG-01 cells increased Orai1, Orai2, STIM1, and STIM2 transcript levels. Orai1 transcript levels were decreased by NFAT5 silencing. NFAT5 transfection and IκB inhibitor BMS 345541 (5 µM) increased SOCE, whereas NFAT5 silencing and SGK1 inhibitor GSK650394 (10 µM) decreased SOCE. In the mice, dehydration increased NFAT5 and Orai1 protein abundance in megakaryocytes and NFAT5, Orai1, and Orai2 abundance in platelets. Dehydration further augmented the degranulation and integrin activation by thrombin and collagen-related peptide. In summary, NFAT5 is a powerful regulator of Orai1-expression and SOCE in megakaryocytes.-Sahu, I., Pelzl, L., Sukkar, B., Fakhri, H., al-Maghout, T., Cao, H., Hauser, S., Gutti, R., Gawaz, M., Lang, F. NFAT5-sensitive Orai1 expression and store-operated Ca2+ entry in megakaryocytes.

Background: The Na+,Cl- coupled creatine transporter CreaT (SLC6A8) is expressed in a variety of tissues including the brain. Genetic defects of CreaT lead to mental retardation with seizures. The present study explored the regulation of CreaT by the ubiquitously expressed glycogen synthase kinase GSK3ß, which contributes to the regulation of neuroexcitation. GSK3ß is phosphorylated and thus inhibited by PKB/Akt. Moreover, GSK3ß is inhibited by the antidepressant lithium. The present study thus further tested for the effects of PKB/Akt and of lithium. Methods: CreaT was expressed in Xenopus laevis oocytes with or without wild-type GSK3ß or inactive K85RGSK3ß. CreaT and GSK3ß were further expressed without and with additional expression of wild type PKB/Akt. Creatine transport in those oocytes was quantified utilizing dual electrode voltage clamp. Results: Electrogenic creatine transport was observed in CreaT expressing oocytes but not in water-injected oocytes. In CreaT expressing oocytes, co-expression of GSK3ß but not of K85RGSK3ß, resulted in a significant decrease of creatine induced current. Kinetic analysis revealed that GSK3ß significantly decreased the maximal creatine transport rate. Exposure of CreaT and GSK3ß expressing oocytes for 24 hours to Lithium was followed by a significant increase of the creatine induced current. The effect of GSK3ß on CreaT was abolished by co-expression of PKB/Akt. Conclusion: GSK3ß down-regulates the creatine transporter CreaT, an effect reversed by treatment with the antidepressant Lithium and by co-expression of PKB/Akt.

Fibroblast growth factor (FGF23) plasma levels are elevated in cardiac and renal failure and correlate with poor clinical prognosis of those disorders. Both disorders are associated with inflammation and activation of the inflammatory transcription factor NFκB. An excessive FGF23 level is further observed in Klotho-deficient mice. The present study explored a putative sensitivity of FGF23 expression to transcription factor NFκB, which is known to upregulate Orai1, the Ca2+ channel accomplishing store-operated Ca2+ entry (SOCE). In osteoblastic cells (UMR106) and immortalized primary periosteal (IPO) cells, protein abundance was determined by Western blotting, and in UMR106 cells, transcript levels were quantified by RT-PCR, cytosolic Ca2+ activity utilizing Fura-2-fluorescence, and SOCE from Ca2+ entry following store depletion by thapsigargin. As a result, UMR106 and IPO cells expressed Ca2+ channel Orai1. SOCE was lowered by NFκB inhibitor wogonin as well as by Orai1 inhibitors 2-APB and YM58483. UMR106 cell Fgf23 transcripts were increased by stimulation of SOCE and Ca2+ ionophore ionomycin and decreased by Orai inhibitors 2-APB, YM58483 and SK&F96365, by Orai1 silencing, as well as by NFκB inhibitors wogonin, withaferin A, and CAS 545380-34-5. In conclusion, Fgf23 expression is upregulated by stimulation of NFκB-sensitive, store-operated Ca2+ entry.

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.

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.

Putative functions of the heterotrimeric G-protein subunit Gαi2-dependent signaling include ion channel regulation, cell differentiation, proliferation and apoptosis. Erythrocytes may, similar to apoptosis of nucleated cells, undergo eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine (PS) exposure. Eryptosis may be triggered by increased cytosolic Ca 2+ activity and ceramide. In the present study, we show that Gαi2 is expressed in both murine and human erythrocytes and further examined the survival of erythrocytes drawn from Gαi2-deficient mice ( Gαi2 −/− ) and corresponding wild-type mice ( Gαi2 +/+ ). Our data show that plasma erythropoietin levels, erythrocyte maturation markers, erythrocyte counts, hematocrit and hemoglobin concentration were similar in Gαi2 −/− and Gαi2 +/+ mice but the mean corpuscular volume was significantly larger in Gαi2 −/− mice. Spontaneous PS exposure of circulating Gαi2 −/− erythrocytes was significantly lower than that of circulating Gαi2 +/+ erythrocytes. PS exposure was significantly lower in Gαi2 −/− than in Gαi2 +/+ erythrocytes following ex vivo exposure to hyperosmotic shock, bacterial sphingomyelinase or C6 ceramide. Erythrocyte Gαi2 deficiency further attenuated hyperosmotic shock-induced increase of cytosolic Ca 2+ activity and cell shrinkage. Moreover, Gαi2 −/− erythrocytes were more resistant to osmosensitive hemolysis as compared to Gαi2 +/+ erythrocytes. In conclusion, Gαi2 deficiency in erythrocytes confers partial protection against suicidal cell death.

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.

To the Editor Depression is a multifaceted disorder with diverse causes and has been associated with the risk to develop severe medical disorders.1 Indeed, depression increases the risk of cardiovascular disease by 1.5-fold to 2-fold, of stroke by 1.8-fold, of Alzheimer disease by 2.1-fold, of diabetes by 60%, and of cancer by 1.3-fold to 1.8-fold.1 Fibroblast growth factors (FGFs) are best known for their regulatory roles in cell growth, differentiation, and morphogenesis in early stages of neural development and have been discussed as switch genes, biomarkers, and treatment targets for affective disorders recently.2,3 However, at least FGF-23 has also been proposed as a cardiovascular risk marker,4 a central player of disordered mineral metabolism,5 and acts to decrease phosphate, 1,25-dihydroxyvitamin D, and parathyroid hormone levels.5 A close, bidirectional relationship exists between depression and cardiovascular disease.1 Indeed, major depression is associated with an increased risk of coronary artery disease, myocardial infarction, congestive heart failure, and isolated systolic hypertension leading to increased mortality and morbidity in patients.1 Moreover, a strong relationship has been described between severe coronary and aortic calcifications, intima thickness, osteoporosis, and depressive disorders.1 Fibroblast growth factor 23 lowers serum levels of 1,25(OH)2D3, which in turn up-regulates renal and intestinal phosphate and calcium transport.6–9 In mice, it was shown recently that lithium treatment up-regulates FGF-23 formation, an effect paralleled by substantial decrease of serum 1,25(OH)2D3 and phosphate concentrations.10 The present study explores the effect of lithium treatment on serum FGF-23, 1,25(OH)2D3, calcium, and phosphate concentrations in depressed patients. A total of 95 acute depressive patients (age 48 ± 14 years) were recruited for this study. Inclusion criteria consist of unipolar depression, age older than 18 years, indication for antidepressant pharmacotherapy, insufficient response to an adequate antidepressant pretreatment and clinical indication for lithium augmentation, hamilton depression rating score greater than 12, and written informed consent. Diagnosis was confirmed on the basis of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders. Fibroblast growth factor 23 serum concentrations were measured first in medicated patients before lithium augmentation and then after 4 weeks of medication with lithium. Detailed clinical data of the patients have already been published.11 All patients reached a lithium serum level of more than 0.4 mmol/L. Serum FGF-23 concentrations were measured by enzyme-linked immunosorbent assay (Immutopics International, California; AVP EIA kit, Phoenix Europe, Karlsruhe, Germany). enzyme-linked immunosorbent assay kits were employed to determine serum concentrations of 1,25(OH)2D3 (IDS, Boldon, United Kingdom). Data are provided as mean ± SEM; n represents the number of independent experiments. All data were tested for significance using unpaired Student t test. Only results with P < 0.05 were considered statistically significant. As illustrated in Figure 1, lithium treatment was followed by a marked increase of serum FGF-23 concentration. As shown in Figure 1, lithium treatment significantly decreased serum 1,25(OH)2D3 concentration. Lithium treatment significantly decreased serum phosphate concentrations (data not shown).FIGURE 1: Serum FGF-23 and 1,25(OH)2D3 levels/concentrations before and after lithium treatment. Arithmetic means ± SEM (n = 95) of serum FGF-23 (A) and 1,25(OH)2D3 levels (B) before (white bars) and after (black bars) lithium treatment. **P < 0.01 indicates significant difference from respective value before treatment.DISCUSSION The present observations reveal that lithium treatment results in a significant increase of serum FGF-23 concentration, a significant decrease of serum 1,25(OH)2D3 concentration, and a significant decrease of serum phosphate concentration. Neuroprotective and procognitive effects of lithium have been evidenced in both experimental research and in clinical studies using brain imaging, suggesting lithium to be effective in the prophylaxis of dementia and in neurodegenerative disorders, such as Huntington disease, Parkinson disease, and amyotrophic lateral sclerosis.12 However, the exact mechanism of lithium’s neuroprotective effect is largely unknown. Interestingly, lithium augmentation leads to a brain-derived neurotrophic factor increase,11 and lithium acts as a GSK3 β inhibitor.13 Fibroblast growth factor 2, IGF-1, and brain-derived neurotrophic factor can stimulate the magnitude of Akt activation.13 At least FGF-2 has been shown to promote the survival of hippocampal neurons significantly more effectively than the 2 other peptides.13 In line with our data, the neuroprotective effect of lithium might be at least partly mediated by an increase of FGF-23. Enhanced serum phosphate concentration predisposes to vascular calcification4–9 and is considered a predictor of early mortality.4–9 Along those lines, FGF-23 deficiency is followed by increase of serum phosphate, calcium, and 1,25(OH)2D3 concentrations with subsequent vascular calcification, decrease of bone density, and reduction of life-span.4–9 Conversely, low-dose lithium uptake in tap water has been shown to promote longevity in humans.14 In conclusion, our observations might partly explain these findings as lithium might decrease phosphate concentrations, decrease vascular calcification, and thereby increase the life-span. At least in theory, the effect of lithium on FGF-23 serum levels may in part be due to polyuria and dehydration.15 Serum FGF-23 levels are enhanced in gene-targeted mice lacking kinases involved in stimulation of renal tubular NaCl transport, and thus required for adequate renal salt and fluid reabsorption as well as hydration.15,16 The increase of FGF-23 serum concentration presumably accounts for the decrease of serum 1,25(OH)2D3 concentrations after lithium treatment, as FGF-23 down-regulates the renal 1α hydroxylase and thus the formation of 1,25(OH)2D3.6,8 1,25(OH)2D3 stimulates both renal and intestinal phosphate transport.17 Beyond its effect on 1,25(OH)2D3 formation, FGF-23 inhibits renal tubular phosphate reabsorption more directly.6,8 The effect of FGF-23 on 1,25(OH)2D3 formation and renal tubular phosphate transport presumably accounts for the observed decrease of serum phosphate concentration. High serum phosphate concentrations foster vascular calcification and eventually lead to early appearance of age-related disorders and decrease of life-span.18,19 Fibroblast growth factor 23 is a powerful inhibitor of aging.19 Lack of FGF-23 leads to premature appearance of a wide variety of age-related disorders, such as osteopenia, osteoporosis, impaired angiogenesis, enhanced erythrocyte turnover, pulmonary emphysema, skin atrophy, infertility, hearing loss, neuron degeneration, Parkinson disease, cognitive impairment, neoplasms, and inflammation.19 In view of the present observations, lithium may counteract at least some of those disorders observed in FGF-23 deficiency. However, the observation of an increased bone mass after treatment with lithium might underlie our observed effect of lithium on FGF-23 concentrations.20 However, our data are preliminary; as in this study, no placebo-treated group was observed, and the effects on FGF-23 and 1,25(OH)2D3 were rather small in magnitude. However, small effects might cause changes when medications are used chronically. In conclusion, lithium treatment might lead to an up-regulation of FGF-23 serum concentration, which in turn might result in decreased serum 1,25(OH)2D3 and phosphate concentrations. Antidepressant mechanisms that may underlie the observed effect of lithium on FGF-23 are the proper formation of synaptic connections in the cerebral cortex, the maturation and survival of catecholamine neurons, and neurogenesis.2 Our data are in line with an observed dysregulation of several FGF system transcripts in the frontal cortical regions of the brains of human subjects with major depressive disorder.21 Fibroblast growth factor is a growth factor essential for the proper formation of synaptic connections in the cerebral cortex, maturation and survival of catecholamine neurons, and neurogenesis.21,22 Moreover, a correlation between antidepressant treatments and FGF expression in the cerebral cortex and hippocampus has been observed.22,23 Our data are in line with previous observations showing that the FGF system might be altered in post-mortem brains of individuals with major depressive disorder22 and can be modulated by antidepressant treatment.22,23 Moreover, a change of the FGF system after acute social defeat has been observed, and FGF showed an antidepressant effect in rat.23 In this context, the stimulation of FGF via lithium might be linked to its known GSK3 β inhibitory action.1,10 In summary, the effects of lithium on FGF-23 serum levels may protect from vascular calcification and the appearance of age-related disorders. Hajar Fakhri, MD Department of Physiology University of Tübingen Tübingen, Germany Roland Ricken, MD Mazda Adli, MD, PhD Department of Psychiatry and Psychotherapy Charité University Medicine Berlin Campus Mitte Berlin, Germany Abul Fajol, MD Department of Physiology University of Tübingen Tübingen, Germany Marc Walter, MD, PhD University Psychiatric Clinics University of Basel Basel, Switzerland Michael Föller, MD, PhD Berlin Research Network of Depression* Florian Lang, MD, PhD Department of Physiology University of Tübingen Tübingen, Germany Undine E. Lang, MD, PhD University Psychiatric Clinics University of Basel Basel, Switzerland [email protected] Claudia Lange, MSc University Psychiatric Clinics University of Basel Basel, Switzerland ACKNOWLEDGMENT H. Fakhri, R. Ricken, and M. Adli share the first authorship. Supported by the Deutsche Forschungsgemeinschaft (LA 2694/1-2). AUTHOR DISCLOSURE INFORMATION The authors declare no conflicts of interest. *Berlin Research Network of Depression: Christoph Richter, MD; Bruno Steinacher, MD, PhD; Tom Bschor, MD, PhD; Sebastian Erbe, MD; Albert Dieffenbacher, MD, PhD; Samuel Elstner, MD; Marcus Gastpar, MD, PhD; Brigitte Schulz-Ratei, MD, PhD; Hubertus Himmerich, MD, PhD; Joachim Zeiler, MD, PhD; Alexandra Lingesleben, MD; Andreas Heinz, MD, PhD; Jürgen Gallinat, MD, PhD; Meryam Schouler-Ocak, MD, PhD; Gernot Deter, MD; Hartmut Dormhagen, MD; Rainer Hellweg, MD, PhD; Phillip Sterzer, MD, PhD; Andreas Str?le, MD, PhD; Thomas Stamm, MD; Mazda Adli, MD, PhD; Roland Ricken, MD; Friedel M. Reischies, MD, PhD; Peter Br?nig, MD, PhD; Ramona Pietsch, MD; Iris Hauth, MD; Frank Godemann, MD, PhD; Peter Neu, MD, PhD.

Lithium, an inhibitor of glycogen synthase kinase 3 (GSK3), is widely used for the treatment of mood disorders. Side effects of lithium include nephrogenic diabetes insipidus, leading to renal water loss. Dehydration has in turn been shown to downregulate Klotho, which is required as co-receptor for the downregulation of 1,25(OH)2D3 formation by fibroblast growth factor 23 (FGF23). FGF23 decreases and 1,25(OH)2D3 stimulates renal tubular phosphate reabsorption. The present study explored whether lithium influences renal Klotho expression, FGF23 serum levels, 1,25(OH)2D3 formation, and renal phosphate excretion. To this end, mice were analyzed after a 14-day period of sham treatment or of treatment with lithium (200 mg/kg/day subcutaneously). Serum antidiuretic hormone (ADH), FGF23, and 1,25(OH)2D3 concentrations were determined by ELISA or EIA, renal Klotho protein abundance and GSK3 phosphorylation were analyzed by Western blotting, and serum phosphate and calcium concentration by photometry. Lithium treatment significantly increased renal GSK3 phosphorylation, enhanced serum ADH and FGF23 concentrations, downregulated renal Klotho expression, stimulated renal calcium and phosphate excretion, and decreased serum 1,25(OH)2D3 and phosphate concentrations. In conclusion, lithium treatment upregulates FGF23 formation, an effect paralleled by substantial decrease of serum 1,25(OH)2D3, and phosphate concentrations and thus possibly affecting tissue calcification.

BACKGROUND:The anion exchanger pendrin (SLC26A4) is required for proper development of the inner ear, and contributes to iodide organification in thyroid glands as well as anion transport in various epithelia, such as airways and renal tubules. SLC26A4 deficiency leads to Pendred syndrome, which is characterized by hearing loss with enlarged vestibular aqueducts and variable hypothyroidism and goiter. Pendrin expression in kidney, heart, lung and thyroid is up-regulated by the mineralocorticoid deoxycorticosterone (DOCA). Platelets express anion exchangers but virtually nothing is known about the molecular identity and regulation of those carriers. Other carriers such as the Na(+)/H(+) exchanger are regulated by the mineralocorticoid-sensitive serum and glucocorticoid inducible kinase SGK1.METHODS:The present study utilized i) quantitative reverse transcription polymerase chain reaction (RT-qPCR) to quantify the transcript levels of Slc26a4 as compared to Gapdh and ii) western blotting to assess Slc26a4 protein abundance in murine platelets from gene-targeted mice lacking Sgk1 (sgk1(-/-)) and respective wild type animals (sgk1(+/+)) treated without or with a subcutaneous injection of 2.5 mg DOCA for 3 h, or in sgk1(+/+) platelets with or without in vitro treatment for 1 h with 10 µg/ml DOCA.RESULTS:Slc26a4 was expressed in platelets, and in vitro DOCA treatment increased Slc26a4 mRNA levels in platelets isolated from sgk1(+/+) mice. Moreover, in vivo DOCA treatment significantly up-regulated Slc26a4 mRNA levels in platelets isolated from sgk1(+/+) but not sgk1(-/-) mice. An increase in Sgk1 mRNA levels paralleled that of Slc26a4 mRNA levels in platelets of sgk1(+/+) mice. In addition, DOCA treatment further increased Slc26a4 protein abundance in platelets isolated from sgk1(+/+) mice.CONCLUSIONS:Pendrin is expressed in platelets and is presumably regulated by SGK1 and mineralocorticoids.

BACKGROUND/AIMS:Pendrin (SLC26A4), a transporter accomplishing anion exchange, is expressed in inner ear, thyroid gland, kidneys, lung, liver and heart. Loss or reduction of function mutations of SLC26A4 underlie Pendred syndrome, a disorder invariably leading to hearing loss with enlarged vestibular aqueducts and in some patients to hypothyroidism and goiter. Renal pendrin expression is up-regulated by mineralocorticoids such as aldosterone or deoxycorticosterone (DOCA). Little is known about the impact of mineralocorticoids on pendrin expression in extrarenal tissues.METHODS:The present study utilized RT-qPCR and Western blotting to quantify the transcript levels and protein abundance of Slc26a4 in murine kidney, thyroid, heart and lung prior to and following subcutaneous administration of 100 mg/kg DOCA.RESULTS:Slc26a4 transcript levels as compared to Gapdh transcript levels were significantly increased by DOCA treatment in kidney, heart, lung and thyroid. Accordingly pendrin protein expression was again significantly increased by DOCA treatment in kidney, heart, lung and thyroid.CONCLUSION:The observations reveal mineralocorticoid sensitivity of pendrin expression in kidney, heart, thyroid and lung.