TY - JOUR AB - The effect of diuretics can be limited by stimulation of counter-regulatory mechanisms, eventually leading to diuretic resistance. It is thought that the mineralocorticoid aldosterone might contribute to the development of diuretic resistance. To test this, we challenged genetically modified mice with or without a deletion of the gene coding for the aldosterone synthase (AS) with furosemide, hydrochlorothiazide (HCT) and triamterene. Urinary excretion was studied in metabolic cages; kidneys were studied for expression of sodium transporters. In both genotypes, a 4-day treatment with HCT via drinking water (400 mg/l) induced a similar natriuresis and modest loss of body weight < 10%. In contrast, furosemide (125 mg/l) and triamterene (200 mg/l) via drinking water stimulated a significantly higher natriuresis and body weight loss in AS-/- mice and in addition, triamterene caused massive hyperkalemia > 9 mM and acidosis (pH < 7.0). In AS+/+ mice, plasma aldosterone concentration tended to increase under furosemide and HCT administration, while triamterene induced a robust ~ sixfold increase. In the kidney, apical targeting and proteolytic activation of the epithelial sodium channel ENaC were stimulated in AS+/+ mice under triamterene treatment, an effect that was diminished in AS-/- mice. In conclusion, aldosterone is essentially involved in the development of diuretic resistance to ENaC blockade by triamterene and to a lesser extent to furosemide. In contrast, resistance to HCT was independent of aldosterone. AU - Essigke, D. AU - Kalo, M.Z.* AU - Janessa, A.* AU - Bohnert, B.N. AU - Li, X.* AU - Birkenfeld, A.L. AU - Artunc, F. C1 - 74075 C2 - 57327 CY - Tiergartenstrasse 17, D-69121 Heidelberg, Germany SP - 827-840 TI - Impact of aldosterone deficiency on the development of diuretic resistance in mice. JO - Pflugers Arch. VL - 477 IS - 6 PB - Springer Heidelberg PY - 2025 SN - 0031-6768 ER - TY - JOUR AB - The Calcium-sensing receptor (CaSR) senses extracellular calcium, regulates parathyroid hormone (PTH) secretion, and has additional functions in various organs related to systemic and local calcium and mineral homeostasis. Familial hypocalciuric hypercalcemia type I (FHH1) is caused by heterozygous loss-of-function mutations in the CaSR gene, and is characterized by the combination of hypercalcemia, hypocalciuria, normal to elevated PTH, and facultatively hypermagnesemia and mild bone mineralization defects. To date, only heterozygous Casr null mice have been available as model for FHH1. Here we present a novel mouse FHH1 model identified in a large ENU-screen that carries an c.2579 T > A (p.Ile859Asn) variant in the Casr gene (CasrBCH002 mice). In order to dissect direct effects of the genetic variant from PTH-dependent effects, we crossed CasrBCH002 mice with PTH deficient mice. Heterozygous CasrBCH002 mice were fertile, had normal growth and body weight, were hypercalcemic and hypermagnesemic with inappropriately normal PTH levels and urinary calcium excretion replicating some features of FHH1. Hypercalcemia and hypermagnesemia were independent from PTH and correlated with higher expression of claudin 16 and 19 in kidneys. Likewise, reduced expression of the renal TRPM6 channel in CasrBCH002 mice was not dependent on PTH. In bone, mutations in Casr rescued the bone phenotype observed in Pth null mice by increasing osteoclast numbers and improving the columnar pattern of chondrocytes in the growth zone. In summary, CasrBCH002 mice represent a new model to study FHH1 and our results indicate that only a part of the phenotype is driven by PTH. AU - Küng, C.J.* AU - Daryadel, A.* AU - Fuente, R.* AU - Haykir, B.* AU - Hrabě de Angelis, M. AU - Hernando, N.* AU - Rubio-Aliaga, I.* AU - Wagner, C.A.* C1 - 70045 C2 - 55379 CY - Tiergartenstrasse 17, D-69121 Heidelberg, Germany SP - 833-845 TI - A novel mouse model for familial hypocalciuric hypercalcemia (FHH1) reveals PTH-dependent and independent CaSR defects. JO - Pflugers Arch. VL - 476 IS - 5 PB - Springer Heidelberg PY - 2024 SN - 0031-6768 ER - TY - JOUR AB - Hibernation enables many species of the mammalian kingdom to overcome periods of harsh environmental conditions. During this physically inactive state metabolic rate and body temperature are drastically downregulated, thereby reducing energy requirements (torpor) also over shorter time periods. Since blood cells reflect the organism´s current condition, it was suggested that transcriptomic alterations in blood cells mirror the torpor-associated physiological state. Transcriptomics on blood cells of torpid and non-torpid Djungarian hamsters and QIAGEN Ingenuity Pathway Analysis (IPA) revealed key target molecules (TMIPA), which were subjected to a comparative literature analysis on transcriptomic alterations during torpor/hibernation in other mammals. Gene expression similarities were identified in 148 TMIPA during torpor nadir among various organs and phylogenetically different mammalian species. Based on TMIPA, IPA network analyses corresponded with described inhibitions of basic cellular mechanisms and immune system-associated processes in torpid mammals. Moreover, protection against damage to the heart, kidney, and liver was deduced from this gene expression pattern in blood cells. This study shows that blood cell transcriptomics can reflect the general physiological state during torpor nadir. Furthermore, the understanding of molecular processes for torpor initiation and organ preservation may have beneficial implications for humans in extremely challenging environments, such as in medical intensive care units and in space. AU - Cuyutupa, V.R.* AU - Moser, D.* AU - Diedrich, V.* AU - Cheng, Y. AU - Billaud, J.N.* AU - Haugg, E.* AU - Singer, D.* AU - Bereiter-Hahn, J.* AU - Herwig, A.* AU - Choukér, A.* C1 - 68032 C2 - 54510 CY - Tiergartenstrasse 17, D-69121 Heidelberg, Germany SP - 1149-1160 TI - Blood transcriptomics mirror regulatory mechanisms during hibernation-a comparative analysis of the Djungarian hamster with other mammalian species. JO - Pflugers Arch. VL - 475 IS - 10 PB - Springer Heidelberg PY - 2023 SN - 0031-6768 ER - TY - JOUR AB - Proteolytic activation of the epithelial sodium channel (ENaC) by aberrantly filtered serine proteases is thought to contribute to renal sodium retention in nephrotic syndrome. However, the identity of the responsible proteases remains elusive. This study evaluated factor VII activating protease (FSAP) as a candidate in this context. We analyzed FSAP in the urine of patients with nephrotic syndrome and nephrotic mice and investigated its ability to activate human ENaC expressed in Xenopus laevis oocytes. Moreover, we studied sodium retention in FSAP-deficient mice (Habp2-/-) with experimental nephrotic syndrome induced by doxorubicin. In urine samples from nephrotic humans, high concentrations of FSAP were detected both as zymogen and in its active state. Recombinant serine protease domain of FSAP stimulated ENaC-mediated whole-cell currents in a time- and concentration-dependent manner. Mutating the putative prostasin cleavage site in γ-ENaC (γRKRK178AAAA) prevented channel stimulation by the serine protease domain of FSAP. In a mouse model for nephrotic syndrome, active FSAP was present in nephrotic urine of Habp2+/+ but not of Habp2-/- mice. However, Habp2-/- mice were not protected from sodium retention compared to nephrotic Habp2+/+ mice. Western blot analysis revealed that in nephrotic Habp2-/- mice, proteolytic cleavage of α- and γ-ENaC was similar to that in nephrotic Habp2+/+ animals. In conclusion, active FSAP is excreted in the urine of nephrotic patients and mice and activates ENaC in vitro involving the putative prostasin cleavage site of γ-ENaC. However, endogenous FSAP is not essential for sodium retention in nephrotic mice. AU - Artunc, F. AU - Bohnert, B.N. AU - Schneider, J.C.* AU - Staudner, T.* AU - Sure, F.* AU - Ilyaskin, A.V.* AU - Wörn, M.* AU - Essigke, D. AU - Janessa, A.* AU - Nielsen, N.V.* AU - Birkenfeld, A.L. AU - Etscheid, M.* AU - Haerteis, S.* AU - Korbmacher, C.* AU - Kanse, S.M.* C1 - 63710 C2 - 51745 CY - Tiergartenstrasse 17, D-69121 Heidelberg, Germany SP - 217-229 TI - Proteolytic activation of the epithelial sodium channel (ENaC) by factor VII activating protease (FSAP) and its relevance for sodium retention in nephrotic mice. JO - Pflugers Arch. VL - 474 IS - 2 PB - Springer Heidelberg PY - 2022 SN - 0031-6768 ER - TY - JOUR AB - Experimental nephrotic syndrome leads to activation of the epithelial sodium channel (ENaC) by proteolysis and promotes renal sodium retention. The membrane-anchored serine protease prostasin (CAP1/PRSS8) is expressed in the distal nephron and participates in proteolytic ENaC regulation by serving as a scaffold for other serine proteases. However, it is unknown whether prostasin is also involved in ENaC-mediated sodium retention of experimental nephrotic syndrome. In this study, we used genetically modified knock-in mice with Prss8 mutations abolishing its proteolytic activity (Prss8-S238A) or prostasin activation (Prss8-R44Q) to investigate the development of sodium retention in doxorubicin-induced nephrotic syndrome. Healthy Prss8-S238A and Prss8-R44Q mice had normal ENaC activity as reflected by the natriuretic response to the ENaC blocker triamterene. After doxorubicin injection, all genotypes developed similar proteinuria. In all genotypes, urinary prostasin excretion increased while renal expression was not altered. In nephrotic mice of all genotypes, triamterene response was similarly increased, consistent with ENaC activation. As a consequence, urinary sodium excretion dropped in all genotypes and mice similarly gained body weight by + 25 ± 3% in Prss8-wt, + 20 ± 2% in Prss8-S238A and + 28 ± 3% in Prss8-R44Q mice (p = 0.16). In Western blots, expression of fully cleaved α- and γ-ENaC was similarly increased in nephrotic mice of all genotypes. In conclusion, proteolytic ENaC activation and sodium retention in experimental nephrotic syndrome are independent of the activation of prostasin and its enzymatic activity and are consistent with the action of aberrantly filtered serine proteases or proteasuria. AU - Essigke, D. AU - Bohnert, B.N. AU - Janessa, A.* AU - Wörn, M.* AU - Omage, K.* AU - Kalbacher, H.* AU - Birkenfeld, A.L. AU - Bugge, T.H.* AU - Szabo, R.* AU - Artunc, F. C1 - 64622 C2 - 52349 SP - 613-624 TI - Sodium retention in nephrotic syndrome is independent of the activation of the membrane-anchored serine protease prostasin (CAP1/PRSS8) and its enzymatic activity. JO - Pflugers Arch. VL - 474 IS - 6 PY - 2022 SN - 0031-6768 ER - TY - JOUR AU - Worthmann, A.* AU - Bartelt, A. C1 - 63860 C2 - 51822 CY - Tiergartenstrasse 17, D-69121 Heidelberg, Germany SP - 185-186 TI - MALDI MSI for a fresh view on atherosclerotic plaque lipids. JO - Pflugers Arch. VL - 474 PB - Springer Heidelberg PY - 2022 SN - 0031-6768 ER - TY - JOUR AB - Transient receptor potential A1 (TRPA1) channels were originally characterized in neuronal tissues but also identified in lung epithelium by staining with fluorescently coupled TRPA1 antibodies. Its exact function in non-neuronal tissues, however, is elusive. TRPA1 is activated in vitro by hypoxia and hyperoxia and is therefore a promising TRP candidate for sensing hyperoxia in pulmonary epithelial cells and for inducing alveolar epithelial hyperplasia. Here, we isolated tracheal, bronchial, and alveolar epithelial cells and show low but detectable TRPA1 mRNA levels in all these cells as well as TRPA1 protein by Western blotting in alveolar type II (AT II) cells. We quantified changes in intracellular Ca ([Ca]) levels induced by application of hyperoxic solutions in primary tracheal epithelial, bronchial epithelial, and AT II cells isolated from wild-type (WT) and TRPA1-deficient (TRPA1-/-) mouse lungs. In all cell types, we detected hyperoxia-induced rises in [Ca] levels, which were not significantly different in TRPA1-deficient cells compared to WT cells. We also tested TRPA1 function in a mouse model for hyperoxia-induced alveolar epithelial hyperplasia. A characteristic significant increase in thickening of alveolar tissues was detected in mouse lungs after exposure to hyperoxia, but not in normoxic WT and TRPA1-/- controls. Quantification of changes in lung morphology in hyperoxic WT and TRPA1-/- mice, however, again revealed no significant changes. Therefore, TRPA1 expression does neither appear to be a key player for hyperoxia-induced changes in [Ca] levels in primary lung epithelial cells, nor being essential for the development of hyperoxia-induced alveolar epithelial hyperplasia. AU - Kannler, M.* AU - Lüling, R.* AU - Yildirim, A.Ö. AU - Gudermann, T.* AU - Steinritz, D.* AU - Dietrich, A.* C1 - 53518 C2 - 44896 SP - 1231–1241 TI - TRPA1 channels: Expression in non-neuronal murine lung tissues and dispensability for hyperoxia-induced alveolar epithelial hyperplasia. JO - Pflugers Arch. VL - 47 PY - 2018 SN - 0031-6768 ER - TY - JOUR AB - Regular physical activity not only improves the exercise capacity of the skeletal muscle performing the contractions, butit is beneficial for the whole body. An extensive search for exercise factors mediating these beneficial effects has been going on for decades. Particularly skeletal muscle tissue has been investigated as a source of circulating exercise factors, and several myokines have been identified. However, exercise also has an impact on other tissues. The liver is interposed between energy storing and energy utilising tissues and is highly active during exercise, maintaining energy homeostasis. Recently, a novel group of exercise factorstermed hepatokineshas emerged. These proteins (fibroblast growth factor 21, follistatin, angiopoietin-like protein 4, heat shock protein 72, insulin-like growth factor binding protein 1) are released from the liver and increased in the bloodstream during or in the recovery after an exercise bout. In this narrative review, we evaluate this new group of exercise factors focusing on the regulation and potential function in exercise metabolism and adaptations. These hepatokines may convey some of the beneficial whole-body effects of exercise that could ameliorate metabolic diseases, such as obesity or type 2 diabetes. AU - Weigert, C. AU - Hoene, M.* AU - Plomgaard, P.* C1 - 54645 C2 - 45715 CY - Tiergartenstrasse 17, D-69121 Heidelberg, Germany SP - 383-396 TI - Hepatokinesa novel group of exercise factors. JO - Pflugers Arch. VL - 471 IS - 3 PB - Springer Heidelberg PY - 2018 SN - 0031-6768 ER - TY - JOUR AB - SCN5A encodes for the α-subunit of the cardiac voltage-gated sodium channel Nav1.5. Gain-of-function mutations in SCN5A are related to congenital long QT syndrome (LQTS3) characterized by delayed cardiac repolarization, leading to a prolonged QT interval in the ECG. Loss-of-function mutations in SCN5A are related to Brugada syndrome (BrS), characterized by an ST-segment elevation in the right precordial leads (V1-V3). The aim of this study was the characterization of a large set of novel SCN5A variants found in patients with different cardiac phenotypes, mainly LQTS and BrS. SCN5A variants of 13 families were functionally characterized in Xenopus laevis oocytes using the two-electrode voltage-clamp technique. We found in most of the cases, but not all, that the electrophysiology of the variants correlated with the clinically diagnosed phenotype. A susceptibility to develop LQTS can be suggested in patients carrying the variants S216L, K480N, A572D, F816Y, and G983D. However, taking the phenotype into account, the presence of the variants in genomic data bases, the mutational segregation, combined with our in vitro and in silico experiments, the variants S216L, S262G, K480N, A572D, F816Y, G983D, and T1526P remain as variants of unknown significance. However, the SCN5A variants R568H and A993T can be classified as pathogenic LQTS3 causing mutations, while R222stop and R2012H are novel BrS causing mutations. AU - Ortiz-Bonnin, B.* AU - Rinné, S.* AU - Moss, R.* AU - Streit, A.K.* AU - Scharf, M.* AU - Richter, K.* AU - Stöber, A.* AU - Pfeufer, A. AU - Seemann, G.* AU - Kääb, S.* AU - Beckmann, B.M.* AU - Decher, N.* C1 - 48795 C2 - 41332 CY - New York SP - 1375-1387 TI - Electrophysiological characterization of a large set of novel variants in the SCN5A-gene: Identification of novel LQTS3 and BrS mutations. JO - Pflugers Arch. VL - 468 IS - 8 PB - Springer PY - 2016 SN - 0031-6768 ER - TY - JOUR AB - The purpose of our investigation was to identify the transcriptional basis for ultrastructural and functional specialization of human atria and ventricles. Using exploratory microarray analysis (Affymetrix U133A+B),. we detected 11,740 transcripts expressed in human heart, representing the most comprehensive report of the human myocardial transcriptome to date. Variation in gene expression between atria and ventricles accounted for the largest differences in this data set, as 3.300 and 2.974 transcripts showed higher expression in atria and ventricles, respectively. Functional classification based on Gene Ontology identified chamber-specific patterns of gene expression and provided molecular insights into the regional specialization of cardiomyocytes, correlating important functional pathways to transcriptional activity: Ventricular myocytes preferentially express genes satisfying contractile and energetic requirements, while atrial myocytes exhibit specific transcriptional activities related to neurohumoral function. In addition, several pro-fibrotic and apoptotic pathways were concentrated in atrial myocardium, substantiating the higher susceptibility of atria to programmed cell death and extracellular matrix remodelling observed in human and experimental animal models of heart failure. Differences in transcriptional profiles of atrial and ventricular myocardium thus provide molecular insights into myocardial cell diversity and distinct region-specific adaptations to physiological and pathophysiological conditions. Moreover, as major functional classes of atrial- and ventricular-specific transcripts were common to human and murine myocardium, an evolutionarily conserved chamber-specific expression pattern in mammalian myocardium is suggested. AU - Barth, A.S.* AU - Merk, S.* AU - Arnoldi, E.* AU - Zwermann, L.* AU - Kloos, P.* AU - Gebauer, M.* AU - Steinmeyer, K.* AU - Bleich, M.* AU - Kääb, S.* AU - Pfeufer, A. AU - Überfuhr, P.* AU - Dugas, M.* AU - Steinbeck, G.* AU - Näbauer, M.* C1 - 23545 C2 - 31363 SP - 201-208 TI - Functional profiling of human atrial and ventricular gene expression. JO - Pflugers Arch. VL - 450 IS - 4 PB - Springer PY - 2005 SN - 0031-6768 ER - TY - JOUR AB - The flow of RBC suspensions (Hct 25 and 30%) in a constricted section (of length 35 mm and diameter 0.20 mm) in a glass tube was photographed under dark field illumination. The wall shear stress ranged from 0 to 150 dynes/cm2. The following supensions were investigated: normal RBC in plasma (highly deformable); osmotically crenated RBC in hypertonic plasma (hardly deformable); RBC in a 4:1 mixture of plasma and Rheomacrodex (non aggregating). The thickness δ of the cell free medium at the wall was plotted as function of wall shear stress E(w). It was observed that: on increasing E(w) from zero, δ increases to a maximum for values of E(w) between 1.5 and 5.0 dynes/cm2 (maximum axial concentration), then decreases to zero at very high E(w) (no axial concentration); osmotic crenation as well as inhibition of aggregation result in decreased axial concentration for all E(w). AU - Devendran, T. AU - Schmid-Schöenbein, H.J. C1 - 41000 C2 - 35751 SP - 40 TI - Axial concentration in narrow tube flow for various RBC suspensions as function of wall shear stress. JO - Pflugers Arch. VL - 355 PY - 1975 SN - 0031-6768 ER -