Contractile force is enhanced in Aortas from pendrin null mice due to stimulation of angiotensin II-dependent signaling.

Pendrin is a Cl-/HCO3- exchanger expressed in the apical regions of renal intercalated cells. Following pendrin gene ablation, blood pressure falls, in part, from reduced renal NaCl absorption. We asked if pendrin is expressed in vascular tissue and if the lower blood pressure observed in pendrin null mice is accompanied by reduced vascular reactivity. Thus, the contractile responses to KCl and phenylephrine (PE) were examined in isometrically mounted thoracic aortas from wild-type and pendrin null mice. Although pendrin expression was not detected in the aorta, pendrin gene ablation changed contractile protein abundance and increased the maximal contractile response to PE when normalized to cross sectional area (CSA). However, the contractile sensitivity to this agent was unchanged. The increase in contractile force/cross sectional area observed in pendrin null mice was due to reduced cross sectional area of the aorta and not from increased contractile force per vessel. The pendrin-dependent increase in maximal contractile response was endothelium- and nitric oxide-independent and did not occur from changes in Ca2+ sensitivity or chronic changes in catecholamine production. However, application of 100 nM angiotensin II increased force/CSA more in aortas from pendrin null than from wild type mice. Moreover, angiotensin type 1 receptor inhibitor (candesartan) treatment in vivo eliminated the pendrin-dependent changes contractile protein abundance and changes in the contractile force/cross sectional area in response to PE. In conclusion, pendrin gene ablation increases aorta contractile force per cross sectional area in response to angiotensin II and PE due to stimulation of angiotensin type 1 receptor-dependent signaling. The angiotensin type 1 receptor-dependent increase in vascular reactivity may mitigate the fall in blood pressure observed with pendrin gene ablation

Glycosylation in the thyroid gland : vital aspects of glycoprotein function in thyrocyte physiology and thyroid disorders

The key proteins responsible for hormone synthesis in the thyroid are glycosylated. Oligosaccharides strongly affect the function of glycosylated proteins. Both thyroid-stimulating hormone (TSH) secreted by the pituitary gland and TSH receptors on the surface of thyrocytes contain N-glycans, which are crucial to their proper activity. Thyroglobulin (Tg), the protein backbone for synthesis of thyroid hormones, is a heavily N-glycosylated protein, containing 20 putative N-glycosylated sites. N-oligosaccharides play a role in Tg transport into the follicular lumen, where thyroid hormones are produced, and into thyrocytes, where hyposialylated Tg is degraded. N-glycans of the cell membrane transporters sodium/iodide symporter and pendrin are necessary for iodide transport. Some changes in glycosylation result in abnormal activity of the thyroid and alteration of the metabolic clearance rate of hormones. Alteration of glycan structures is a pathological process related to the progression of chronic diseases such as thyroid cancers and autoimmunity. Thyroid carcinogenesis is accompanied by changes in sialylation and fucosylation, β1,6-branching of glycans, the content and structure of poly-LacNAc chains, as well as O-GlcNAcylation, while in thyroid autoimmunity the main processes affected are sialylation and fucosylation. The glycobiology of the thyroid gland is an intensively studied field of research, providing new data helpful in understanding the role of the sugar component in thyroid protein biology and disorders

Versatility of NaCl transport mechanisms in the cortical collecting duct

Versatility of NaCl transport mechanisms in the cortical collecting duct. Am J Physiol Renal Physiol 313: F1254 –F1263, 2017. First published September 6, 2017; doi:10.1152/ajprenal.00369.2017.—The cortical collecting duct (CCD) forms part of the aldosterone-sensitive distal nephron and plays an essential role in maintaining the NaCl balance and acid-base status. The CCD epithelium comprises principal cells as well as different types of intercalated cells. Until recently, transcellular Na transport was thought to be restricted to principal cells, whereas (acid-secreting) type A and (bicarbonate-secreting) type B intercalated cells were associated with the regulation of acid-base homeostasis. This review describes how this traditional view has been upended by several discoveries in the past decade. A series of studies has shown that type B intercalated cells can mediate electroneutral NaCl reabsorption by a mechanism involving Na-dependent and Na-independent Cl/HCO3 exchange, and that is energetically driven by basolateral vacuolar H-ATPase pumps. Other research indicates that type A intercalated cells can mediate NaCl secretion, through a bumetanide-sensitive pathway that is energized by apical H,K-ATPase type 2 pumps operating as Na/K exchangers. We also review recent findings on the contribution of the paracellular route to NaCl transport in the CCD. Last, we describe cross-talk processes, by which one CCD cell type impacts Na/Cl transport in another cell type. The mechanisms that have been identified to date demonstrate clearly the interdependence of NaCl and acid-base transport systems in the CCD. They also highlight the remarkable versatility of this nephron segment.This work was supported in part by recurring grants from the Institut National de la Sante et de la Recherche Medicale (INSERM), the Centre National de la Recherche Scientifique (CNRS), and the University Pierre et Marie Curie (UPMC). (Institut National de la Sante et de la Recherche Medicale (INSERM); Centre National de la Recherche Scientifique (CNRS); University Pierre et Marie Curie (UPMC))Accepted manuscrip

Functional characterization of human thyroid tissue with immunohistochemistry

Immunohistochemistry provides insights in the expression of functional proteins and of their localization in normal thyroid tissue and in thyroid diseases. In hyperfunctional thyroid tissues, staining for sodium/iodide symporter (NIS), pendrin, thyroid peroxidase (TPO), and thyroglobulin (Tg) is increased. In hypofunctioning thyroid tissues, NIS staining is markedly decreased; in benign hypofunctioning adenomas, the expression of the other functional proteins is unmodified or slightly decreased, whereas their expression is profoundly decreased or absent in differentiated thyroid carcinoma

Electrogenic transport and K(+) ion channel expression by the human endolymphatic sac epithelium.

The endolymphatic sac (ES) is a cystic organ that is a part of the inner ear and is connected to the cochlea and vestibule. The ES is thought to be involved in inner ear ion homeostasis and fluid volume regulation for the maintenance of hearing and balance function. Many ion channels, transporters, and exchangers have been identified in the ES luminal epithelium, mainly in animal studies, but there has been no functional study investigating ion transport using human ES tissue. We designed the first functional experiments on electrogenic transport in human ES and investigated the contribution of K(+) channels in the electrogenic transport, which has been rarely identified, even in animal studies, using electrophysiological/pharmacological and molecular biological methods. As a result, we identified functional and molecular evidence for the essential participation of K(+) channels in the electrogenic transport of human ES epithelium. The identified K(+) channels involved in the electrogenic transport were KCNN2, KCNJ14, KCNK2, and KCNK6, and the K(+) transports via those channels are thought to play an important role in the maintenance of the unique ionic milieu of the inner ear fluid

IL-17A induces Pendrin expression and chloride-bicarbonate exchange in human bronchial epithelial cells

The epithelium plays an active role in the response to inhaled pathogens in part by responding to signals from the immune system. Epithelial responses may include changes in chemokine expression, increased mucin production and antimicrobial peptide secretion, and changes in ion transport. We previously demonstrated that interleukin-17A (IL-17A), which is critical for lung host defense against extracellular bacteria, significantly raised airway surface pH in vitro, a finding that is common to a number of inflammatory diseases. Using microarray analysis of normal human bronchial epithelial (HBE) cells treated with IL-17A, we identified the electroneutral chloride-bicarbonate exchanger Pendrin (SLC26A4) as a potential mediator of this effect. These data were verified by real-time, quantitative PCR that demonstrated a time-dependent increase in Pendrin mRNA expression in HBE cells treated with IL-17A up to 48 h. Using immunoblotting and immunofluorescence, we confirmed that Pendrin protein expression is increased in IL-17 treated HBE cells and that it is primarily localized to the mucosal surface of the cells. Functional studies using live-cell fluorescence to measure intracellular pH demonstrated that IL-17A induced chloride-bicarbonate exchange in HBE cells that was not present in the absence of IL-17A. Furthermore, HBE cells treated with short interfering RNA against Pendrin showed substantially reduced chloride-bicarbonate exchange. These data suggest that Pendrin is part of IL-17A-dependent epithelial changes and that Pendrin may therefore be a therapeutic target in IL-17A-dependent lung disease. © 2014 Adams et al

Genetic Factors That Might Lead to Different Responses in Individuals Exposed to Perchlorate

Perchlorate has been detected in groundwater in many parts of the United States, and recent detection in vegetable and dairy food products indicates that contamination by perchlorate is more widespread than previously thought. Perchlorate is a competitive inhibitor of the sodium iodide symporter, the thyroid cell–surface protein responsible for transporting iodide from the plasma into the thyroid. An estimated 4.3% of the U.S. population is subclinically hypothyroid, and 6.9% of pregnant women may have low iodine intake. Congenital hypothyroidism affects 1 in 3,000 to 1 in 4,000 infants, and 15% of these cases have been attributed to genetic defects. Our objective in this review is to identify genetic biomarkers that would help define subpopulations sensitive to environmental perchlorate exposure. We review the literature to identify genetic defects involved in the iodination process of the thyroid hormone synthesis, particularly defects in iodide transport from circulation into the thyroid cell, defects in iodide transport from the thyroid cell to the follicular lumen (Pendred syndrome), and defects of iodide organification. Furthermore, we summarize relevant studies of perchlorate in humans. Because of perchlorate inhibition of iodide uptake, it is biologically plausible that chronic ingestion of perchlorate through contaminated sources may cause some degree of iodine discharge in populations that are genetically susceptible to defects in the iodination process of the thyroid hormone synthesis, thus deteriorating their conditions. We conclude that future studies linking human disease and environmental perchlorate exposure should consider the genetic makeup of the participants, actual perchlorate exposure levels, and individual iodine intake/excretion levels

Novel roles for chloride channels, exchangers, and regulators in chronic inflammatory airway diseases

Chloride transport proteins play critical roles in inflammatory airway diseases, contributing to the detrimental aspects of mucus overproduction, mucus secretion, and airway constriction. However, they also play crucial roles in contributing to the innate immune properties of mucus and mucociliary clearance. In this review, we focus on the emerging novel roles for a chloride channel regulator (CLCA1), a calcium-activated chloride channel (TMEM16A), and two chloride exchangers (SLC26A4/pendrin and SLC26A9) in chronic inflammatory airway diseases

Postnatal expression of transport proteins involved in acid-base transport in mouse kidney

The kidney plays a major role in maintaining and controlling systemic acid-base homeostasis by reabsorbing bicarbonate and secreting protons and acid-equivalents, respectively. During postnatal kidney development and adaptation to changing diets, plasma bicarbonate levels are increasing, the capacity for urinary acidification maturates, and the final morphology and distribution of intercalated cells is achieved. In adult kidney, at least two types of intercalated cells (IC) are found along the collecting duct characterised either by the expression of AE1 (type A IC) or pendrin (non-type A IC) where non-type A IC are found only in the convoluted distal tubule, connecting tubule and cortical collecting duct. Here we investigated in mouse kidney the relative mRNA abundance, protein expression levels and distribution of several proteins involved in renal acid-base transport, namely, the Na+/HCO3 − cotransporter NBC1 (SLC4A4), the Na+/H+-exchanger NHE3 (SLC9A3), two subunits of the vacuolar H+-ATPase [ATP6V0A4 (a4), ATP6V1B1 (B1)], the Cl−/HCO3 − exchangers AE1 (SLC4A1) and pendrin (SLC26A4). Relative mRNA abundance of all transport proteins was lowest at day3 after birth and increased thereafter in parallel with protein levels. The numbers of type A and non-type A IC in the cortical collecting duct (CCD) increased from day3 to days18 and 24, whereas the number of IC in the CCD with apical staining for the vacuolar H+-ATPase subunits a4 and B1 decreased from day3 to days18 and 24, respectively. In addition, cells with characteristics of non-type A IC (pendrin expression, basolateral expression of vacuolar H+-ATPase subunits) were found in the inner and outer medulla 3days after birth but were absent from the medulla of 24-day-old mice. Taken together, these results demonstrate massive changes in mRNA and protein expression levels of several acid-base transporters during postnatal kidney maturation and also show changes in intercalated cell phenotype in the medulla during these processe

Measurements of endolymphatic K⁺ concentrations in the utricle of pre- and postnatal Slc26a4 Δ/+ and Slc26a4 Δ/Δ mice

Master of ScienceDepartment of Anatomy and PhysiologyA. Philine WangemannSLC26A4 and its murine ortholog Slc26a4 code for pendrin, an anion-exchanger that is expressed in the inner ear. Patients with mutations in SLC26A4 have syndromic or nonsyndromic hearing loss that is associated with a prenatal enlargement of the membranous labyrinth. The mouse model Slc26a4[superscript]Δ/Δ recapitulates the enlargement, develops an enlargement of the inner ear and fails to acquire hearing. The vestibular labyrinth secretes fluid, accounting for enlargement of the membranous labyrinth. The objective of the current study was to measure K⁺ concentrations in the utricular endolymph of Slc26a4[superscript]Δ/+ and Slc26a4[superscript]Δ/Δ mice as a first step toward a mechanistic understanding of fluid secretion during perinatal development. Doublebarreled K⁺-selective electrodes were used to measure K⁺ concentrations of the utricular endolymph in vitro. Potassium concentrations were ~10 mM in both genotypes at embryonic (E) day 16.5. The K⁺ concentrations started to rise at E17.5 in Slc26a4[superscript]Δ/+ mice. There was a 1-day delay in Slc26a4[superscript]Δ/Δ mice. This delay may be the consequence of a larger fluid volume. K⁺ concentrations rose to 150 mM and 132 mM in Slc26a4[superscript]Δ/+ and Slc26a4[superscript]Δ/Δ adult mice, respectively. Consistently, expression of KCNQ1 and the Na⁺/2Cl⁻/K⁺ cotransporter SLC12A2 was found in the utricle at E19.5 in Slc26a4[superscript]Δ/+ and Slc26a4[superscript]Δ/Δ mice. In conclusion, the data suggest that K⁺ secretion is not the major driving force of fluid secretion in the utricle of the developing mouse inner ear