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Ratko M, Habek N, Radmilović MD, Škokić S, Justić H, Barić A, Dugandžić A. Role of uroguanylin's signaling pathway in the development of ischemic stroke. Eur J Neurosci 2022; 56:3720-3737. [PMID: 35445449 PMCID: PMC9542124 DOI: 10.1111/ejn.15674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 03/30/2022] [Accepted: 04/17/2022] [Indexed: 11/28/2022]
Abstract
Stroke is one of the leading causes of mortality and disability worldwide. By affecting bradykinin function, activation of guanylate cyclase (GC)‐A has been shown to have a neuroprotective effect after ischaemic stroke, whereas the same has not been confirmed for GC‐B; therefore, we aimed to determine the possible role of GC‐C and its agonist, uroguanylin (UGN), in the development of stroke. In this study, middle cerebral artery occlusion (MCAO) was performed on wild‐type (WT), GC‐C KO and UGN KO mice. MR images were acquired before and 24 h after MCAO. On brain slices 48 h after MCAO, the Ca2+ response to UGN stimulation was recorded. Our results showed that the absence of GC‐C in GC‐C KO mice resulted in the development of smaller ischaemic lesions compared with WT littermates, which is an opposite effect compared with the effects of GC‐A agonists on brain lesions. WT and UGN KO animals showed a stronger Ca2+ response upon UGN stimulation in astrocytes of the peri‐ischaemic cerebral cortex compared with the same cortical region of the unaffected contralateral hemisphere. This stronger activation was not observed in GC‐C KO animals, which may be the reason for smaller lesion development in GC‐C KO mice. The reason why GC‐C might affect Ca2+ signalling in peri‐ischaemic astrocytes is that GC‐C is expressed in these cells after MCAO, whereas under normoxic conditions, it is expressed mainly in cortical neurons. Stronger activation of the Ca2+‐dependent signalling pathway could lead to the stronger activation of the Na+/H+ exchanger, tissue acidification and neuronal death.
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Affiliation(s)
- Martina Ratko
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.,Centre of Excellence for Basic, Clinical and Translational Neuroscience, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Nikola Habek
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
| | | | - Siniša Škokić
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Helena Justić
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Anja Barić
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Aleksandra Dugandžić
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.,Centre of Excellence for Basic, Clinical and Translational Neuroscience, School of Medicine, University of Zagreb, Zagreb, Croatia.,Department of Physiology, School of Medicine, University of Zagreb, Zagreb, Croatia
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2
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Activation of brown adipose tissue in diet-induced thermogenesis is GC-C dependent. Pflugers Arch 2020; 472:405-417. [PMID: 31940065 DOI: 10.1007/s00424-020-02347-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 12/09/2019] [Accepted: 01/02/2020] [Indexed: 10/25/2022]
Abstract
Uroguanylin (UGN) is released from the intestine after a meal. When applied in brain ventricles, UGN increases expression of markers of thermogenesis in brown adipose tissue (BAT). Therefore, we determine the effects of its receptor, guanylate cyclase C (GC-C), on mouse interscapular BAT (iBAT) activity during diet-induced thermogenesis (DIT). The activation of iBAT after a meal is diminished in GC-C KO mice, decreased in female wild type (WT) mice, and abolished in old WT animals. The activation of iBAT after a meal is the highest in male WT animals which leads to an increase in GC-C expression in the hypothalamus, an increase in iBAT volume by aging, and induction of iBAT markers of thermogenesis. In contrast to iBAT activation after a meal, iBAT activation after a cold exposure could still exist in GC-C KO mice and it is significantly higher in female WT mice. The expression of GC-C in the proopiomelanocortin neurons of the arcuate nucleus of the hypothalamus but not in iBAT suggests central regulation of iBAT function. The iBAT activity during DIT has significantly reduced in old mice but an intranasal application of UGN leads to an increase in iBAT activity in a dose-dependent manner which is in strong negative correlation to glucose concentration in blood. This activation was not present in GC-C KO mice. Our results suggest the physiological role of GC-C on the BAT regulation and its importance in the regulation of glucose homeostasis and the development of new therapy for obesity and insulin resistance.
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Freire EG, Albuquerque JCS, Leal IP, Sousa NA, Graça JRVD. EFFECT OF CHRONIC RENAL DYSFUNCTION ON THE PERMEABILITY OF THE COLON TO WATER AND ELECTROLYTES: EXPERIMENTAL STUDY IN RATS. ACTA ACUST UNITED AC 2019; 32:e1472. [PMID: 31859925 PMCID: PMC6918759 DOI: 10.1590/0102-672020190001e1472] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 07/02/2019] [Indexed: 01/18/2023]
Abstract
Background: Renal insufficiency is a disease that affects several organs by provoking hypervolemia and uremia. The disease reaches more than 500 million people worldwide and few studies bring their influence on the gastrointestinal tract. Aim: To evaluate the influence of 5/6 nephrectomy-induced hypervolemia on colonic permeability to water and electrolytes. Method: Sixty male Wistar rats weighing between 280-300 g were divided into three groups: 3, 7 and 14 days after nephrectomy, each one having a false-operated/control and partially nephrectomized. For colonic permeability they were submitted to colonic perfusion with a solution of Tyroad containing phenolphthalein. Differences among the concentrations of Na+, K+ and Cl- were used to calculate the rate of colonic permeability for the electrolytes. Phenolphthalein concentrations were used to evaluate the rate of secretion and water absorption. Results: The colonic secretion of water and electrolytes occurred expressively in the group seven days after nephrectomy. Hemodynamic and biochemical assessments determined the progression of renal failure in all three groups and polyethylene glycol was shown to be effective in reversing the secretory capacity of the colon. Conclusion: Hypervolemia established after 7 days post-nephrectomy 5/6 caused marked colonic secretion for water and electrolytes. The organism presents progressive colonic secretion as the blood volume increases; on the other hand, polyethylene glycol was able to revert this secretory framework of the colon to water and electrolytes by reversing the hypervolemia.
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Affiliation(s)
- Elionai Gomes Freire
- Physiology and Neuroscience Laboratory of the Biotechnology Graduate Program, School of Medicine, Sobral, CE, Brazil
| | | | - Israel Pinto Leal
- Physiology and Neuroscience Laboratory of the Biotechnology Graduate Program, School of Medicine, Sobral, CE, Brazil
| | - Nayara Alves Sousa
- Pharmacology Laboratory of the Federal University of Ceará, Sobral, CE, Brazil
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Begg DP, Steinbrecher KA, Mul JD, Chambers AP, Kohli R, Haller A, Cohen MB, Woods SC, Seeley RJ. Effect of guanylate cyclase-C activity on energy and glucose homeostasis. Diabetes 2014; 63:3798-804. [PMID: 24898144 PMCID: PMC4207398 DOI: 10.2337/db14-0160] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Uroguanylin is a gastrointestinal hormone primarily involved in fluid and electrolyte handling. It has recently been reported that prouroguanylin, secreted postprandially, is converted to uroguanylin in the brain and activates the receptor guanylate cyclase-C (GC-C) to reduce food intake and prevent obesity. We tested central nervous system administration of two GC-C agonists and found no significant reduction of food intake. We also carefully phenotyped mice lacking the GC-C receptor and found them to have normal body weight, adiposity, and glucose tolerance. Interestingly, uroguanylin knockout mice had a small but significant increase in body weight and adiposity that was accompanied by glucose intolerance. Our data indicate that the modest effects of uroguanylin on energy and glucose homeostasis are not mediated by central GC-C receptors.
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Affiliation(s)
- Denovan P Begg
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, OH School of Psychology, University of New South Wales, Sydney, New South Wales, Australia
| | - Kris A Steinbrecher
- Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - Joram D Mul
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, OH
| | - Adam P Chambers
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, OH
| | - Rohit Kohli
- Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - April Haller
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, OH
| | - Mitchell B Cohen
- Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - Stephen C Woods
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, OH
| | - Randy J Seeley
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, OH
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da Silva Lima V, Crajoinas RO, Carraro-Lacroix LR, Godinho AN, Dias JLG, Dariolli R, Girardi ACC, Fonteles MC, Malnic G, Lessa LMA. Uroguanylin inhibits H-ATPase activity and surface expression in renal distal tubules by a PKG-dependent pathway. Am J Physiol Cell Physiol 2014; 307:C532-41. [PMID: 25031022 DOI: 10.1152/ajpcell.00392.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cumulative evidence suggests that guanylin peptides play an important role on electrolyte homeostasis. We have previously reported that uroguanylin (UGN) inhibits bicarbonate reabsorption in a renal distal tubule. In the present study, we tested the hypothesis that the bicarbonaturic effect of UGN is at least in part attributable to inhibition of H(+)-ATPase-mediated hydrogen secretion in the distal nephron. By in vivo stationary microperfusion experiments, we were able to show that UGN inhibits H(+)-ATPase activity by a PKG-dependent pathway because KT5823 (PKG inhibitor) abolished the UGN effect on distal bicarbonate reabsorption and H89 (PKA inhibitor) was unable to prevent it. The in vivo results were confirmed by the in vitro experiments, where we used fluorescence microscopy to measure intracellular pH (pHi) recovery after an acid pulse with NH4Cl. By this technique, we observed that UGN and 8 bromoguanosine-cGMP (8Br-cGMP) inhibited H(+)-ATPase-dependent pHi recovery and that the UGN inhibitory effect was abolished in the presence of the PKG inhibitor. In addition, by using RT-PCR technique, we verified that Madin-Darby canine kidney (MDCK)-C11 cells express guanylate cyclase-C. Besides, UGN stimulated an increase of both cGMP content and PKG activity but was unable to increase the production of cellular cAMP content and PKA activity. Furthermore, we found that UGN reduced cell surface abundance of H+-ATPase B1 subunit in MDCK-C11 and that this effect was abolished by the PKG inhibitor. Taken together, our data suggest that UGN inhibits H(+)-ATPase activity and surface expression in renal distal cells by a cGMP/PKG-dependent pathway.
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Affiliation(s)
- Vanessa da Silva Lima
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil
| | | | - Luciene R Carraro-Lacroix
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, São Paulo, Brazil
| | - Alana N Godinho
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil
| | - João L G Dias
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil
| | | | | | - Manassés C Fonteles
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil; Mackenzie University, São Paulo, São Paulo, Brazil
| | - Gerhard Malnic
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, São Paulo, Brazil
| | - Lucília M A Lessa
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil;
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6
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Rozenfeld J, Tal O, Kladnitsky O, Adler L, Efrati E, Carrithers SL, Alper SL, Zelikovic I. Pendrin, a novel transcriptional target of the uroguanylin system. Cell Physiol Biochem 2013; 32:221-37. [PMID: 24429828 DOI: 10.1159/000356641] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2013] [Indexed: 12/22/2022] Open
Abstract
Guanylin (GN) and uroguanylin (UGN) are low-molecular-weight peptide hormones produced mainly in the intestinal mucosa in response to oral salt load. GN and UGN (guanylin peptides) induce secretion of electrolytes and water in both intestine and kidney. Thought to act as "intestinal natriuretic factors", GN and UGN modulate renal salt secretion by both endocrine mechanisms (linking the digestive system and kidney) and paracrine/autocrine (intrarenal) mechanisms. The cellular function of GN and UGN in intestine and proximal tubule is mediated by guanylyl cyclase C (GC-C)-, cGMP-, and G protein-dependent pathways, whereas, in principal cells of the cortical collecting duct (CCD), these peptide hormones act via GC-C-independent signaling through phospholipase A2 (PLA2). The Cl(-)/HCO(-)3 exchanger pendrin (SLC26A4), encoded by the PDS gene, is expressed in non-α intercalated cells of the CCD. Pendrin is essential for CCD bicarbonate secretion and is also involved in NaCl balance and blood pressure regulation. Our recent studies have provided evidence that pendrin-mediated anion exchange in the CCD is regulated at the transcriptional level by UGN. UGN exerts an inhibitory effect on the pendrin gene promoter likely via heat shock factor 1 (HSF1) action at a defined heat shock element (HSE) site. Recent studies have unraveled novel roles for guanylin peptides in several organ systems including involvement in appetite regulation, olfactory function, cell proliferation and differentiation, inflammation, and reproductive function. Both the guanylin system and pendrin have also been implicated in airway function. Future molecular research into the receptors and signal transduction pathways involved in the action of guanylin peptides and the pendrin anion exchanger in the kidney and other organs, and into the links between them, may facilitate discovery of new therapies for hypertension, heart failure, hepatic failure and other fluid retention syndromes, as well as for diverse diseases such as obesity, asthma, and cancer.
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Affiliation(s)
- Julia Rozenfeld
- Laboratory of Developmental Nephrology, Department of Physiology and Biophysics, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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7
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Teixeira MDA, Nascimento NRF, Fonteles MC, Vale OC. Uroguanylin induces electroencephalographic spikes in rats. BRAZ J BIOL 2013; 73:623-7. [PMID: 24212704 DOI: 10.1590/s1519-69842013000300021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 03/21/2013] [Indexed: 11/21/2022] Open
Abstract
Uroguanylin (UGN) is an endogenous peptide that acts on membrane-bound guanylate cyclase receptors of intestinal and renal cells increasing cGMP production and regulating electrolyte and water epithelial transport. Recent research works demonstrate the expression of this peptide and its receptor in the central nervous system. The current work was undertaken in order to evaluate modifications of electroencephalographic spectra (EEG) in anesthetized Wistar rats, submitted to intracisternal infusion of uroguanylin (0.0125 nmoles/min or 0.04 nmoles/min). The current observations demonstrate that 0.0125 nmoles/min and 0.04 nmoles/min intracisternal infusion of UGN significantly enhances amplitude and frequency of sharp waves and evoked spikes (p = 0.03). No statistical significance was observed on absolute alpha and theta spectra amplitude. The present data suggest that UGN acts on bioelectrogenesis of cortical cells by inducing hypersynchronic firing of neurons. This effect is blocked by nedocromil, suggesting that UGN acts by increasing the activity of chloride channels.
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Affiliation(s)
- M D A Teixeira
- Pharmacology and Physiology Department, Biomedicine Institute, Clinical Research Unit, Federal University of Ceará, FortalezaCE, Brazil
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8
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Sindic A. Current understanding of guanylin peptides actions. ISRN NEPHROLOGY 2013; 2013:813648. [PMID: 24967239 PMCID: PMC4045495 DOI: 10.5402/2013/813648] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 02/26/2013] [Indexed: 01/12/2023]
Abstract
Guanylin peptides (GPs) family includes guanylin (GN), uroguanylin (UGN), lymphoguanylin, and recently discovered renoguanylin. This growing family is proposed to be intestinal natriuretic peptides. After ingestion of a salty meal, GN and UGN are secreted into the intestinal lumen, where they inhibit sodium absorption and induce anion and water secretion. At the same conditions, those hormones stimulate renal electrolyte excretion by inducing natriuresis, kaliuresis, and diuresis and therefore prevent hypernatremia and hypervolemia after salty meals.
In the intestine, a well-known receptor for GPs is guanylate cyclase C (GC-C) whose activation increases intracellular concentration of cGMP. However, in the kidney of GC-C-deficient mice, effects of GPs are unaltered, which could be by new cGMP-independent signaling pathway (G-protein-coupled receptor). This is not unusual as atrial natriuretic peptide also activates two different types of receptors: guanylate cylcase A and clearance receptor which is also G-protein coupled receptor. Physiological role of GPs in other organs (liver, pancreas, lung, sweat glands, and male reproductive system) needs to be discovered. However, it is known that they are involved in pathological conditions like cystic fibrosis, asthma, intestinal tumors, kidney and heart failure, obesity, and metabolic syndrome.
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Affiliation(s)
- Aleksandra Sindic
- Department of Physiology, School of Medicine, University of Zagreb, Salata 3, 10000 Zagreb, Croatia
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9
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Sodium challenge does not support an acute gastrointestinal–renal natriuretic signaling axis in humans. Kidney Int 2012; 82:1313-20. [DOI: 10.1038/ki.2012.269] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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10
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Abstract
The uroguanylin system is a newly discovered endocrine/paracrine system that may have a role in the regulation of salt balance, appetite and gut health. The precursor pro-uroguanylin is predominantly synthesized in the gut, although there may be other sites of synthesis, including the kidney tubules. Products from pro-uroguanylin may mediate natriuresis following oral consumption of a salt load through both GC-C (guanylate cyclase C)-dependent and -independent mechanisms, and recent evidence suggests a role in appetite regulation. Local paracrine effects in the gut through GC-C stimulation may have tumour-suppressing actions through the regulation of cell proliferation and metabolism. Although most information on this system has been derived from knockout models, recent human studies have indicated possible roles in heart failure and renal failure. An improved understanding of the nature of its natriuretic, appetite and tumour-suppressing actions may facilitate the discovery of new therapies for heart failure, obesity and cancer prophylaxis.
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Lessa LMA, Carraro-Lacroix LR, Crajoinas RO, Bezerra CN, Dariolli R, Girardi ACC, Fonteles MC, Malnic G. Mechanisms underlying the inhibitory effects of uroguanylin on NHE3 transport activity in renal proximal tubule. Am J Physiol Renal Physiol 2012; 303:F1399-408. [PMID: 22952280 DOI: 10.1152/ajprenal.00385.2011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We previously demonstrated that uroguanylin (UGN) significantly inhibits Na(+)/H(+) exchanger (NHE)3-mediated bicarbonate reabsorption. In the present study, we aimed to elucidate the molecular mechanisms underlying the action of UGN on NHE3 in rat renal proximal tubules and in a proximal tubule cell line (LLC-PK(1)). The in vivo studies were performed by the stationary microperfusion technique, in which we measured H(+) secretion in rat renal proximal segments, through a H(+)-sensitive microelectrode. UGN (1 μM) significantly inhibited the net of proximal bicarbonate reabsorption. The inhibitory effect of UGN was completely abolished by either the protein kinase G (PKG) inhibitor KT5823 or by the protein kinase A (PKA) inhibitor H-89. The effects of UGN in vitro were found to be similar to those obtained by microperfusion. Indeed, we observed that incubation of LLC-PK(1) cells with UGN induced an increase in the intracellular levels of cAMP and cGMP, as well as activation of both PKA and PKG. Furthermore, we found that UGN can increase the levels of NHE3 phosphorylation at the PKA consensus sites 552 and 605 in LLC-PK(1) cells. Finally, treatment of LLC-PK(1) cells with UGN reduced the amount of NHE3 at the cell surface. Overall, our data suggest that the inhibitory effect of UGN on NHE3 transport activity in proximal tubule is mediated by activation of both cGMP/PKG and cAMP/PKA signaling pathways which in turn leads to NHE3 phosphorylation and reduced NHE3 surface expression. Moreover, this study sheds light on mechanisms by which guanylin peptides are intricately involved in the maintenance of salt and water homeostasis.
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Affiliation(s)
- Lucília M A Lessa
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo/SP, Brazil.
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12
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Rozenfeld J, Tal O, Kladnitsky O, Adler L, Efrati E, Carrithers SL, Alper SL, Zelikovic I. The pendrin anion exchanger gene is transcriptionally regulated by uroguanylin: a novel enterorenal link. Am J Physiol Renal Physiol 2011; 302:F614-24. [PMID: 22129966 DOI: 10.1152/ajprenal.00189.2011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The pendrin/SLC26A4 Cl(-)/HCO(3)(-) exchanger, encoded by the PDS gene, is expressed in cortical collecting duct (CCD) non-A intercalated cells. Pendrin is essential for CCD bicarbonate secretion and is also involved in NaCl balance and blood pressure regulation. The intestinal peptide uroguanylin (UGN) is produced in response to oral salt load and can function as an "intestinal natriuretic hormone." We aimed to investigate whether UGN modulates pendrin activity and to explore the molecular mechanisms responsible for this modulation. Injection of UGN into mice resulted in decreased pendrin mRNA and protein expression in the kidney. UGN decreased endogenous pendrin mRNA levels in HEK293 cells. A 4.2-kb human PDS (hPDS) promoter sequence and consecutive 5' deletion products were cloned into luciferase reporter vectors and transiently transfected into HEK293 cells. Exposure of transfected cells to UGN decreased hPDS promoter activity. This UGN-induced effect on the hPDS promoter occurred within a 52-bp region encompassing a single heat shock element (HSE). The effect of UGN on the promoter was abolished when the HSE located between nt -1119 and -1115 was absent or was mutated. Furthermore, treatment of HEK293 cells with heat shock factor 1 (HSF1) small interfering RNA (siRNA) reversed the UGN-induced decrease in endogenous PDS mRNA level. In conclusion, pendrin-mediated Cl(-)/HCO(3)(-) exchange in the renal tubule may be regulated transcriptionally by the peptide hormone UGN. UGN exerts its inhibitory activity on the hPDS promoter likely via HSF1 action at a defined HSE site. These data define a novel signaling pathway involved in the enterorenal axis controlling electrolyte and water homeostasis.
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Affiliation(s)
- Julia Rozenfeld
- Laboratory of Developmental Nephrology, Department of Physiology and Biophysics, Haifa, Israel
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13
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Valentino MA, Lin JE, Snook AE, Li P, Kim GW, Marszalowicz G, Magee MS, Hyslop T, Schulz S, Waldman SA. A uroguanylin-GUCY2C endocrine axis regulates feeding in mice. J Clin Invest 2011; 121:3578-88. [PMID: 21865642 DOI: 10.1172/jci57925] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 06/29/2011] [Indexed: 12/16/2022] Open
Abstract
Intestinal enteroendocrine cells are critical to central regulation of caloric consumption, since they activate hypothalamic circuits that decrease appetite and thereby restrict meal size by secreting hormones in response to nutrients in the gut. Although guanylyl cyclase and downstream cGMP are essential regulators of centrally regulated feeding behavior in invertebrates, the role of this primordial signaling mechanism in mammalian appetite regulation has eluded definition. In intestinal epithelial cells, guanylyl cyclase 2C (GUCY2C) is a transmembrane receptor that makes cGMP in response to the paracrine hormones guanylin and uroguanylin, which regulate epithelial cell dynamics along the crypt-villus axis. Here, we show that silencing of GUCY2C in mice disrupts satiation, resulting in hyperphagia and subsequent obesity and metabolic syndrome. This defined an appetite-regulating uroguanylin-GUCY2C endocrine axis, which we confirmed by showing that nutrient intake induces intestinal prouroguanylin secretion into the circulation. The prohormone signal is selectively decoded in the hypothalamus by proteolytic liberation of uroguanylin, inducing GUCY2C signaling and consequent activation of downstream anorexigenic pathways. Thus, evolutionary diversification of primitive guanylyl cyclase signaling pathways allows GUCY2C to coordinate endocrine regulation of central food acquisition pathways with paracrine control of intestinal homeostasis. Moreover, the uroguanylin-GUCY2C endocrine axis may provide a therapeutic target to control appetite, obesity, and metabolic syndrome.
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Affiliation(s)
- Michael A Valentino
- Department of Pharmacology and Experimental Therapeutics, Division of Clinical Pharmacology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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14
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Fonteles MC, do Nascimento NRF. Guanylin peptide family: history, interactions with ANP, and new pharmacological perspectives. Can J Physiol Pharmacol 2011; 89:575-85. [PMID: 21815750 DOI: 10.1139/y11-050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The guanylin family of peptides has 3 subclasses of peptides containing either 3 intramolecular disulfide bonds found in bacterial heat-stable enterotoxins (ST), or 2 disulfides observed in guanylin and uroguanylin, or a single disulfide exemplified by lymphoguanylin. These peptides bind to and activate cell-surface receptors that have intrinsic guanylate cyclase (GC) activity. These hormones are synthesized in the intestine and released both luminally and into the circulation, and are also produced within the kidney. Stimulation of renal target cells by guanylin peptides in vivo or ex vivo elicits a long-lived diuresis, natriuresis, and kaliuresis by both cGMP-dependent and independent mechanisms. Uroguanylin may act as a hormone in a novel endocrine axis linking the digestive system and kidney as well as a paracrine system intrarenally to increase sodium excretion in the postprandial period. This highly integrated and redundant mechanism allows the organism to maintain sodium balance by eliminating excess sodium in the urine. In addition, small concentrations of the atrial natriuretic peptide (ANP) can synergize with low concentrations of both guanylin or uroguanylin, which do not induce natriuresis per se, to promote significant natriuresis. Interestingly, the activation of the particulate guanylate cyclase receptors by natriuretic peptides can promote relaxation of animal and human penile erectile tissue and increase intracavernosal pressure to induce penile erection. These peptides can be prototypes for new drugs to treat erectile dysfunction, especially in patients with endothelial and nitrergic dysfunction, such as in diabetes.
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Affiliation(s)
- Manassés Claudino Fonteles
- Instituto Superior de Ciências Biomédicas (ISCB), Laboratório de Farmacologia - Universidade Estadual do Ceará (UECE), Avenida Paranjana 1700, Campus do Itaperi, CEP 60740-000, Fortaleza-CE, Brazil.
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15
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Sopjani M, Alesutan I, Dërmaku-Sopjani M, Gu S, Zelenak C, Munoz C, Velic A, Föller M, Rosenblatt KP, Kuro-o M, Lang F. Regulation of the Na+
/K+
ATPase by Klotho. FEBS Lett 2011; 585:1759-64. [DOI: 10.1016/j.febslet.2011.05.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 05/03/2011] [Accepted: 05/04/2011] [Indexed: 11/29/2022]
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Sousa CM, Havt A, Santos CF, Arnaud-Batista FJ, Cunha KMA, Cerqueira JBG, Fonteles MC, Nascimento NRF. The relaxation induced by uroguanylin and the expression of natriuretic peptide receptors in human corpora cavernosa. J Sex Med 2011; 7:3610-9. [PMID: 20102442 DOI: 10.1111/j.1743-6109.2009.01672.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
INTRODUCTION Receptors for natriuretic peptides have been demonstrated as potential targets for the treatment of male erectile dysfunction. AIM This study investigates the relaxant effects of the atrial natriuretic peptide (ANP) and uroguanylin (UGN), and expression of natriuretic peptide receptors on strips of human corpora cavernosa (HCC). MAIN OUTCOME MEASURES Quantitative analysis of natriuretic receptor expression and relaxation of precontracted strips were used to assess the membrane-bound guanylate cyclase-cyclic guanosine monophosphate (cGMP) pathway in HCC strips. METHODS HCC was obtained from a cadaver donor at the time of collection of organs for transplantation (14-47 years) and strips were mounted in organ baths for isometric studies. RESULTS ANP and UGN both induced concentration-dependent relaxation on HCC strips with a maximal response attained at 300 nM, corresponding to 45.4±4.0% and 49±4.8%, respectively. The relaxation is not affected by 30 µM 1H-[1,2,4]oxaolodiazolo[4,3-a]quinoxalin-1-one (ODQ) (a soluble guanylate cyclase inhibitor), but it is significantly blocked by 10 µM isatin, a nonspecific particulate guanylate cyclase (pGC) inhibitor. UGN was unable to potentiate electrical field stimulation (EFS) or acetylcholine-induced relaxations. The potential role of pGC activation and cGMP generation in this effect is reinforced by the potentiation of this effect by phosphodiesterase-5 inhibitor vardenafil (55.0±7.5-UGN vs. 98.6±1.4%-UGN+vardenafil; P<0.05). The relaxant effect was also partially (37.6%) blocked by the combination iberitoxin-apamin but was insensitive to glybenclamide. The expression of guanylate cyclase receptors (GC-A, GC-B, GC-C) and the expression of the natriuretic peptide "clearance" receptor (NPR-C) were confirmed by real-time polymerase chain reaction. The exposure of HCC strips to ANP (1 µM) and UGN (10 µM) significantly increased cGMP, but not cyclic adenosine monophosphate (cAMP) levels. CONCLUSIONS UGN relaxes HCC strips by a guanylate cyclase and K(ca)-channel-dependent mechanism. These findings obtained in HCC reveal that the natriuretic peptide receptors are potential targets for the development of new drugs for the treatment of erectile dysfunction.
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Affiliation(s)
- Clauber M Sousa
- Superior Institute of Biomedical Sciences, Ceara State University, Fortaleza, Ceara, Brazil
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17
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Qian X, Moss NG, Fellner RC, Taylor-Blake B, Goy MF. The rat kidney contains high levels of prouroguanylin (the uroguanylin precursor) but does not express GC-C (the enteric uroguanylin receptor). Am J Physiol Renal Physiol 2011; 300:F561-73. [PMID: 21106860 PMCID: PMC3280727 DOI: 10.1152/ajprenal.00282.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Accepted: 11/18/2010] [Indexed: 01/13/2023] Open
Abstract
The peptide uroguanylin (Ugn) regulates enteric and renal electrolyte transport. Previous studies have shown that Ugn and its receptor GC-C (a ligand-activated guanylate cyclase) are abundant in the intestine. Less is known about Ugn and GC-C expression in the kidney. Here, we identify a 9.4-kDa polypeptide in rat kidney extracts that appears, based on its biochemical and immunological properties, to be authentic prouroguanylin (proUgn). This propeptide is relatively plentiful in the kidney (~16% of intestinal levels), whereas its mRNA is marginally present (<1% of intestinal levels), and free Ugn peptide levels are below detection limits (<0.4% of renal proUgn levels). The paucity of preproUgn-encoding mRNA and free Ugn peptide raises the possibility that the kidney might absorb intact proUgn from plasma, where the concentration of propeptide greatly exceeds that of Ugn. However, immunocytochemical analysis reveals that renal proUgn is found exclusively in distal tubular segments, sites previously shown not to accumulate radiolabeled proUgn after intravascular infusions. Thus proUgn appears to be synthesized within the kidney, but the factors that determine its abundance (rates of transcription, translation, processing, and secretion) must be balanced quite differently than in the gut. Surprisingly, we also find negligible expression of GC-C in the rat kidney, a result confirmed both by RT-PCR and by functional assays that measure Ugn-activated cGMP synthesis. Taken together, these data provide evidence for an intrarenal Ugn system that differs from the well-described intestinal system in its regulatory mechanisms and in the receptor targeted by the peptide.
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Affiliation(s)
- Xun Qian
- Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, NC 27599-7545, USA
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18
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Moss NG, Riguera DA, Fellner RC, Cazzolla C, Goy MF. Natriuretic and antikaliuretic effects of uroguanylin and prouroguanylin in the rat. Am J Physiol Renal Physiol 2010; 299:F1433-42. [PMID: 20861080 DOI: 10.1152/ajprenal.00281.2010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The peptide uroguanylin (Ugn) is stored and released as a propeptide (proUgn) by enterochromaffin cells in the intestine, and converted to Ugn and other metabolites in the renal tubules. Both proUgn and Ugn are natriuretic, although the response to proUgn is thought to depend on its conversion to Ugn within nephrons. To assess the efficiency of intrarenal conversion of proUgn to Ugn, we measured urinary Ugn excretion in rats following intravenous infusions of proUgn or Ugn. Infusion of 2 and 10 nmol proUgn/kg body wt increased plasma proUgn concentration from 2.2 ± 0.3 to 5.6 ± 1.3 pmol/ml and to 37 ± 9.6 pmol/ml, respectively. No proUgn was detected in urine before, during, or after proUgn infusions. These two proUgn infusion doses resulted in total Ugn recovery in urine of 162 ± 64 and 206 ± 39 pmol/kg body wt (9 and 2% of the infused amount, respectively). By contrast, the same molar amounts of Ugn resulted in 1,009 ± 477 and 5,352 ± 2,133 pmol/kg body wt of Ugn in urine (recoveries of ∼50%). Unexpectedly, comparisons of natriuretic dose-response curves for each peptide showed proUgn to be about five times more potent than Ugn, despite the relatively modest amount of Ugn generated from infused proUgn. In addition, both peptides were antikaliuretic at low doses, but in this case Ugn showed greater potency than proUgn. These data do not support Ugn as the primary active principle of proUgn for regulation of renal sodium excretion. Instead, an alternative peptide fragment produced from proUgn may be responsible for natriuretic activity in the kidney, whereas Ugn itself may play an antikaliuretic role.
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Affiliation(s)
- Nicholas G Moss
- Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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19
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Youn JH, McDonough AA. Recent advances in understanding integrative control of potassium homeostasis. Annu Rev Physiol 2009; 71:381-401. [PMID: 18759636 DOI: 10.1146/annurev.physiol.010908.163241] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The potassium homeostatic system is very tightly regulated. Recent studies have shed light on the sensing and molecular mechanisms responsible for this tight control. In addition to classic feedback regulation mediated by a rise in extracellular fluid (ECF) [K(+)], there is evidence for a feedforward mechanism: Dietary K(+) intake is sensed in the gut, and an unidentified gut factor is activated to stimulate renal K(+) excretion. This pathway may explain renal and extrarenal responses to altered K(+) intake that occur independently of changes in ECF [K(+)]. Mechanisms for conserving ECF K(+) during fasting or K(+) deprivation have been described: Kidney NADPH oxidase activation initiates a cascade that provokes the retraction of K(+) channels from the cell membrane, and muscle becomes resistant to insulin stimulation of cellular K(+) uptake. How these mechanisms are triggered by K(+) deprivation remains unclear. Cellular AMP kinase-dependent protein kinase activity provokes the acute transfer of K(+) from the ECF to the ICF, which may be important in exercise or ischemia. These recent advances may shed light on the beneficial effects of a high-K(+) diet for the cardiovascular system.
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Affiliation(s)
- Jang H Youn
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9142, USA.
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20
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Klokkers J, Langehanenberg P, Kemper B, Kosmeier S, von Bally G, Riethmüller C, Wunder F, Sindic A, Pavenstädt H, Schlatter E, Edemir B. Atrial natriuretic peptide and nitric oxide signaling antagonizes vasopressin-mediated water permeability in inner medullary collecting duct cells. Am J Physiol Renal Physiol 2009; 297:F693-703. [PMID: 19570884 DOI: 10.1152/ajprenal.00136.2009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
AVP and atrial natriuretic peptide (ANP) have opposite effects in the kidney. AVP induces antidiuresis by insertion of aquaporin-2 (AQP2) water channels into the plasma membrane of collecting duct principal cells. ANP acts as a diuretic factor. An ANP- and nitric oxide (NO)/soluble guanylate cyclase (sGC)-induced insertion of AQP2 into the plasma membrane is reported from different models. However, functional data on the insertion of AQP2 is missing. We used primary cultured inner medullary collecting duct (IMCD) cells and digital holographic microscopy, calcein-quenching measurements, and immunofluorescence and Western blotting to analyze the effects of ANP and NO donors on AQP2 phosphorylation, membrane expression, and water permeability. While AVP led to acceleration in osmotically induced swelling, ANP had no effect. However, in AVP-pretreated cells ANP significantly decreased the kinetics of cell swelling. This effect was mimicked by 8-bromo-cGMP and blunted by PKG inhibition. Stimulation of the NO/sGC pathway or direct activation of sGC with BAY 58-2667 had similar effects to ANP. In cells treated with AVP, AQP2 was predominantly localized in the plasma membrane, and after additional incubation with ANP AQP2 was mostly localized in the cytosol, indicating an increased retrieval of AQP2 from the plasma membrane by ANP. Western blot analysis showed that ANP was able to reduce AVP-induced phosphorylation of AQP2 at position S256. In conclusion, we show that the diuretic action of ANP or NO in the IMCD involves a decreased localization of AQP2 in the plasma membrane which is mediated by cGMP and PKG.
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Affiliation(s)
- Jens Klokkers
- Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Universitätsklinikum Münster, Münster, Germany
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21
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Lessa LMA, Amorim JBO, Fonteles MC, Malnic G. Effect of renoguanylin on hydrogen/bicarbonate ion transport in rat renal tubules. ACTA ACUST UNITED AC 2009; 157:37-43. [PMID: 19540271 DOI: 10.1016/j.regpep.2009.06.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 03/26/2009] [Accepted: 06/03/2009] [Indexed: 12/28/2022]
Abstract
Renoguanylin (REN) is a recently described member of the guanylin family, which was first isolated from eels and is expressed in intestinal and specially kidney tissues. In the present work we evaluate the effects of REN on the mechanisms of hydrogen transport in rat renal tubules by the stationary microperfusion method. We evaluated the effect of 1 muM and 10 muM of renoguanylin (REN) on the reabsorption of bicarbonate in proximal and distal segments and found that there was a significant reduction in bicarbonate reabsorption. In proximal segments, REN promoted a significant effect at both 1 and 10 muM concentrations. Comparing control and REN concentration of 1 muM, JHCO(3)(-), nmol cm(-2) s(-1)-1,76+/-0,11(control)x1,29+/-0,08(REN 10 muM); P<0.05, was obtained. In distal segments the effect of both concentrations of REN was also effective, being significant e.g. at a concentration of 1 muM (JHCO(3)(-), nmol cm(-2) s(-)1-0.80+/-0.07(control)x0.60+/-0.06(REN 1 muM); P<0.05), although at a lower level than in the proximal tubule. Our results suggest that the action of REN on hydrogen transport involves the inhibition of Na(+)/H(+)exchanger and H(+)-ATPase in the luminal membrane of the perfused tubules by a PKG dependent pathway.
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Affiliation(s)
- L M A Lessa
- Dept. Physiology and Biophysics, Inst. of Biomedical Sciences, Univ. São Paulo, Av. Prof. Lineu Prestes 1524, 05508-900 São Paulo, Brazil
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22
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Wang WH, Giebisch G. Regulation of potassium (K) handling in the renal collecting duct. Pflugers Arch 2009; 458:157-68. [PMID: 18839206 PMCID: PMC2730119 DOI: 10.1007/s00424-008-0593-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 09/20/2008] [Indexed: 12/13/2022]
Abstract
This review provides an overview of the molecular mechanisms of K transport in the mammalian connecting tubule (CNT) and cortical collecting duct (CCD), both nephron segments responsible for the regulation of renal K secretion. Aldosterone and dietary K intake are two of the most important factors regulating K secretion in the CNT and CCD. Recently, angiotensin II (AngII) has also been shown to play a role in the regulation of K secretion. In addition, genetic and molecular biological approaches have further identified new mechanisms by which aldosterone and dietary K intake regulate K transport. Thus, the interaction between serum-glucocorticoid-induced kinase 1 (SGK1) and with-no-lysine kinase 4 (WNK4) plays a significant role in mediating the effect of aldosterone on ROMK (Kir1.1), an important apical K channel modulating K secretion. Recent evidence suggests that WNK1, mitogen-activated protein kinases such as P38, ERK, and Src family protein tyrosine kinase are involved in mediating the effect of low K intake on apical K secretory channels.
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Affiliation(s)
- Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, 10595, USA.
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23
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Moss NG, Riguera DA, Solinga RM, Kessler MM, Zimmer DP, Arendshorst WJ, Currie MG, Goy MF. The natriuretic peptide uroguanylin elicits physiologic actions through 2 distinct topoisomers. Hypertension 2009; 53:867-76. [PMID: 19289652 DOI: 10.1161/hypertensionaha.108.128264] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The peptide uroguanylin regulates electrolyte transport in the intestine and kidney. Human uroguanylin has 2 conformations that can be stably isolated because of their slow interconversion rate. The A isomer potently activates the guanylate cyclase C receptor found primarily in the intestine. The B isomer, by contrast, is a very weak agonist of this receptor, leading to a widely held assumption that it is physiologically irrelevant. We show here, however, that human uroguanylin B has potent natriuretic activity in the kidney. Interestingly, uroguanylin A and B both induce saluretic responses, but the activity profiles for the 2 peptides differ markedly. The uroguanylin B dose-response curve is sigmoidal with a threshold dose of approximately 10 nmol/kg of body weight, whereas uroguanylin A has a comparable threshold but a bell-shaped dose-response curve. In addition, our study indicates a unique interplay between the A and B isoforms, such that the A form at high concentrations antagonizes the natriuretic action of the B form. These data show that the kidney contains a uroguanylin receptor of which the pharmacological profile does not match that of the well-defined intestinal uroguanylin receptor (guanylate cyclase C), an observation consistent with previous studies showing that the kidney of the guanylate cyclase C knockout mouse remains responsive to uroguanylin. The results presented here also support the unconventional notion that distinct conformations of a single endocrine peptide can elicit different responses in different tissues.
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Affiliation(s)
- Nicholas G Moss
- University of North Carolina at Chapel Hill, Department of Cell and Molecular Physiology, 111 Mason Farm Rd, Chapel Hill, NC 27599, USA
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24
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Kuhn M. Function and dysfunction of mammalian membrane guanylyl cyclase receptors: lessons from genetic mouse models and implications for human diseases. Handb Exp Pharmacol 2009:47-69. [PMID: 19089325 DOI: 10.1007/978-3-540-68964-5_4] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Besides soluble guanylyl cyclase (GC), the receptor for NO, there are seven plasma membrane forms of guanylyl cyclase (GC) receptors, enzymes that synthesize the second-messenger cyclic GMP (cGMP). All membrane GCs (GC-A to GC-G) share a basic topology, which consists of an extracellular ligand binding domain, a short transmembrane region, and an intracellular domain that contains the catalytic (GC) region. Although the presence of the extracellular domain suggests that all these enzymes function as receptors, specific ligands have been identified for only four of them (GC-A through GC-D). GC-A mediates the endocrine effects of atrial and B-type natriuretic peptides regulating arterial blood pressure and volume homeostasis and also local antihypertrophic and antifibrotic actions in the heart. GC-B, the specific receptor for C-type natriuretic peptide, has a critical role in endochondral ossification. GC-C mediates the effects of guanylin and uroguanylin on intestinal electrolyte and water transport and epithelial cell growth and differentiation. GC-E and GC-F are colocalized within the same photoreceptor cells of the retina and have an important role in phototransduction. Finally, GC-D and GC-G appear to be pseudogenes in the human. In rodents, GC-D is exclusively expressed in the olfactory neuroepithelium, with chemosensory functions. GC-G is the last member of the membrane GC form to be identified. No other mammalian transmembrane GCs are predicted on the basis of gene sequence repositories. In contrast to the other orphan receptor GCs, GC-G has a broad tissue distribution in rodents, including the lung, intestine, kidney, skeletal muscle, and sperm, raising the possibility that there is another yet to be discovered family of cGMP-generating ligands. This chapter reviews the structure and functions of membrane GCs, with special focus on the insights gained to date from genetically modified mice and the role of alterations of these ligand/receptor systems in human diseases.
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Affiliation(s)
- Michaela Kuhn
- Institut für Physiologie, Universität Würzburg, Röntgenring 9, Würzburg, 97070, Germany.
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Baba A, Fujimoto S, Kikuchi M, Kita T, Kitamura K. Effects of uroguanylin on natriuresis in experimental nephrotic rats. Nephrology (Carlton) 2008; 14:80-5. [PMID: 19054333 DOI: 10.1111/j.1440-1797.2008.01006.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM Uroguanylin, isolated from human and opossum urine, is a candidate intestinal natriuretic hormone that controls the sodium and water balance between the intestine and the kidneys. Levels of immunoreactive (ir)-uroguanylin in the plasma and urine are increased in rats and humans with nephrotic syndrome, which is physiologically characterized by sodium retention with massive proteinuria. The present study evaluates the effect of natriuresis induced by uroguanylin on nephrotic rats. METHODS Normal rats and rats rendered nephrotic by injections of puromycin aminonucleoside (PAN) were treated with uroguanylin (0.5 nmol/h, delivered by an osmotic pump) or with vehicle during the sodium retention phase. All rats consumed the same quantity of sodium. RESULTS Uroguanylin did not increase urinary excretion of sodium and water in normal rats, but significantly increased urinary sodium excretion during the sodium retention phase in nephrotic rats (untreated vs uroguanylin-treated nephrotic rats in mmol/mmol creatinine; 2.92 +/- 0.65 vs 8.93 +/- 2.53 on day 6, P < 0.05; 3.55 +/- 0.47 vs 10.37 +/- 1.73 on day 7, P < 0.01; 14.88 +/- 2.32 vs 24.47 +/- 2.86 on day 8, P < 0.05). Plasma levels of ir-uroguanylin in uroguanylin-treated nephrotic rats on day 6 were significantly increased compared with those in uroguanylin-treated control and untreated nephrotic rats. CONCLUSION Uroguanylin increased urinary sodium excretion in rats with PAN-induced nephrosis, and might be useful for treating sodium retention in patients with nephrotic syndrome.
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Affiliation(s)
- Akiko Baba
- Department of Internal Medicine, University of Miyazaki, Japan.
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26
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Qian X, Moss NG, Fellner RC, Goy MF. Circulating prouroguanylin is processed to its active natriuretic form exclusively within the renal tubules. Endocrinology 2008; 149:4499-509. [PMID: 18499761 PMCID: PMC2553375 DOI: 10.1210/en.2007-1724] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The intestine and kidney are linked by a mechanism that increases salt excretion in response to salt intake. The peptide uroguanylin (UGn) is thought to mediate this signaling axis. Therefore, it was surprising to find (as reported in a companion publication) that UGn is stored in the intestine and circulates in the plasma almost exclusively in the form of its biologically inactive propeptide precursor, prouroguanylin (proUGn), and, furthermore, that infused proUGn leads to natriuretic activity. Here, we investigate the fate of circulating proUGn. Kinetic studies show rapid renal clearance of radiolabeled propeptide. Radiolabel accumulates at high specific activity in kidney (relative to other organs) and urine (relative to plasma). The principal metabolites found in kidney homogenates are free cysteine and methionine. In contrast, urine contains cysteine, methionine, and three other radioactive peaks, one comigrating with authentic rat UGn15. Interestingly, proUGn is not converted to these or other metabolites in plasma, indicating that circulating proUGn is not processed before entering the kidney. Therefore, our findings suggest that proUGn is the true endocrine agent released in response to salt intake and that the response of the kidney is dependent on conversion of the propeptide to an active form after it reaches the renal tubules. Furthermore, proUGn metabolites (other than small amounts of cysteine and methionine) are not returned to the circulation from the kidney or any other organ. Thus, to respond to proUGn released from the gut, any target organ must use a local mechanism for production of active peptide.
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Affiliation(s)
- Xun Qian
- Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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27
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Sellers ZM, Mann E, Smith A, Ko KH, Giannella R, Cohen MB, Barrett KE, Dong H. Heat-stable enterotoxin of Escherichia coli (STa) can stimulate duodenal HCO3(-) secretion via a novel GC-C- and CFTR-independent pathway. FASEB J 2007; 22:1306-16. [PMID: 18096816 DOI: 10.1096/fj.06-7540com] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The heat-stable enterotoxin of Escherichia coli (STa) is a potent stimulant of intestinal chloride and bicarbonate secretion. Guanylyl cyclase C (GC-C) has been shown to be the primary receptor involved in mediating this response. However, numerous studies have suggested the existence of an alternative STa-binding receptor. The aims of this study were to determine whether a non-GC-C receptor exists for STa and what is the functional relevance of this for intestinal bicarbonate secretion in mice. (125)I-STa-binding experiments were performed with intestinal mucosae from GC-C knockout (KO) and wild type (WT) mice. Subsequently, the functional relevance of an alternative STa-binding receptor was explored by examining STa-, uroguanylin-, and guanylin-stimulated duodenal bicarbonate secretion (DBS) in GC-C KO mice in vitro and in vivo. Significant (125)I-STa-binding occurred in the proximal small intestines of GC-C KO and WT mice. Analysis of binding coefficients and pH dependence showed that (125)I-STa-binding in GC-C KO mice involved a receptor distinct from that of WT mice. Functionally, STa, uroguanylin, and guanylin all stimulated a significant increase in DBS in GC-C KO mice. Uroguanylin- and guanylin-stimulated DBS were significantly inhibited by glibenclamide, but not by 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS). However, STa-stimulated DBS was unaffected by glibenclamide but inhibited by DIDS. Taken together, our results suggest that alternative, non-GC-C, receptors likely exist for STa, uroguanylin, and guanylin in the intestines of mice. While uroguanylin- and guanylin-stimulated DBS are cystic fibrosis transmembrane conductance regulator (CFTR) dependent, STa-stimulated DBS is CFTR independent. Further understanding of this alternative receptor and its signaling pathway may provide important insights into rectification of intestinal bicarbonate secretion in cystic fibrosis.
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Affiliation(s)
- Zachary M Sellers
- Department of Medicine, Division of Gastroenterology, University of California, San Diego, La Jolla, California, USA
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Li P, Lin JE, Chervoneva I, Schulz S, Waldman SA, Pitari GM. Homeostatic control of the crypt-villus axis by the bacterial enterotoxin receptor guanylyl cyclase C restricts the proliferating compartment in intestine. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 171:1847-58. [PMID: 17974601 DOI: 10.2353/ajpath.2007.070198] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Guanylyl cyclase C (GC-C), the receptor for diarrheagenic enterotoxins and the paracrine ligands guanylin and uroguanylin, regulates intestinal secretion. Beyond volume homeostasis, its importance in modulating cancer cell proliferation and its uniform dysregulation early in colon carcinogenesis, reflecting loss of ligand expression, suggests a role for GC-C in organizing the crypt-villus axis. Here, eliminating GC-C expression in mice increased crypt length along a decreasing rostral-caudal gradient by disrupting component homeostatic processes. Crypt expansion reflected hyperplasia of the proliferating compartment with reciprocal increases in rapidly cycling progenitor cells and reductions in differentiated cells of the secretory lineage, including Paneth and goblet cells, but not enteroendocrine cells. GC-C signaling regulated proliferation by restricting the cell cycle at the G(1)/S transition. Moreover, crypt expansion in GC-C(-/-) mice was associated with adaptive increases in cell migration and apoptosis. Reciprocal alterations in proliferation and differentiation resulting in expansion associated with adaptive responses in migration and apoptosis suggest that GC-C coordinates component processes maintaining homeostasis of the crypt progenitor compartment. In the context of uniform loss of GC-C signaling during tumorigenesis, dysregulation of those homeostatic processes may contribute to mechanisms underlying colon cancer.
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Affiliation(s)
- Peng Li
- Division of Clinical Pharmacology, Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, 1100 Walnut St./MOB 810, Philadelphia, PA 19107, USA
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YOSHIKAWA Y, NAKAYAMA T, SAITO K, HUI P, MORITA A, SATO N, TAKAHASHI T, TAMURA M, SATO I, AOI N, DOBA N, HINOHARA S, SOMA M, USAMI R. Haplotype-Based Case-Control Study of the Association between the Guanylate Cyclase Activator 2B (GUCA2B, Uroguanylin) Gene and Essential Hypertension. Hypertens Res 2007; 30:789-96. [DOI: 10.1291/hypres.30.789] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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30
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Current World Literature. Curr Opin Nephrol Hypertens 2007; 16:52-7. [PMID: 17143072 DOI: 10.1097/mnh.0b013e32801271d6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
PURPOSE OF REVIEW Guanylin peptides are secreted from the intestine and influence electrolyte and water transport in intestine and kidney, suggesting that these peptides act as intestinal natriuretic peptides. This review presents recent research on renal guanylin and uroguanylin effects. RECENT FINDINGS After salty meals guanylin peptides are produced in the intestine activating anion secretion and inhibiting sodium absorption. In the kidney guanylin peptides induce saluresis and diuresis. The signaling of guanylin peptides in the intestine is well known, involving guanylate cyclase C and increases in cellular cGMP concentrations. As in the intestine in proximal tubule cells a cGMP and guanylate cyclase C-dependent signaling pathway exists. In guanylate cyclase C-deficient mice, renal effects are unaltered, which could be by explained by recently described new cGMP-independent signaling pathways. In proximal tubules, Uroguanylin activates a pertussis toxin-sensitive receptor. Another cGMP-independent signaling pathway of guanylin peptides involving phospholipase A2 and arachidonic acid is shown for principal cells of human and mouse cortical collecting ducts. SUMMARY Mechanisms and sites of renal actions of guanylin peptides are still not completely understood. Renal receptors for guanylin peptides are probably G-protein-coupled. The influences of guanylin peptides on natriuresis, kaliuresis, and diuresis are complex and only further detailed studies will allow a complete understanding of the function of these peptides.
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Affiliation(s)
- Aleksandra Sindić
- Department of Internal Medicine D, Experimental Nephrology, University Hospital Münster, Germany
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32
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Abstract
Ingestion of a salty meal induces secretion of guanylin (GN) and uroguanylin (UGN) into the intestinal lumen, where they inhibit Na+ absorption and induce Cl-, HCO3-, and water secretion. Simultaneously, these hormones stimulate renal electrolyte excretion by inducing natriuresis, kaliuresis, and diuresis. GN and UGN therefore participate in the prevention of hypernatremia and hypervolemia after salty meals. The signaling pathway of GN and UGN in the intestine is well known. They activate enterocytes via guanylate cyclase C (GC-C), which leads to cGMP-dependent inhibition of Na+/H+ exchange and activation of the cystic fibrosis transmembrane regulator. In GC-C-deficient mice, GN and UGN still produce renal natriuresis, kaliuresis, and diuresis, suggesting different signaling pathways in the kidney compared with the intestine. Signaling pathways for GN and UGN in the kidney differ along the various nephron segments. In proximal tubule cells, a cGMP- and GC-C-dependent signaling was demonstrated for both peptides. In addition, UGN activates a pertussis toxin-sensitive G-protein-coupled receptor. A similar dual signaling pathway is also known for atrial natriuretic peptide. Recently, a cGMP-independent signaling pathway for GN and UGN was also shown in principal cells of the human and mouse cortical collecting duct. Because GN and UGN activate different signaling pathways in specific organs and even within the kidney, this review focuses on more recent findings on cellular effects and signaling mechanisms of these peptides and their pathophysiologic implications in the intestine and the kidney.
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Affiliation(s)
- Aleksandra Sindić
- Universitätsklinikum Münster, Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Domagkstrasse 3a, Münster 48149, Germany
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