scholarly journals Coupling of epithelial Na+ and Cl− channels by direct and indirect activation by serine proteases

2012 ◽  
Vol 303 (9) ◽  
pp. C936-C946 ◽  
Author(s):  
Veronika Gondzik ◽  
Wolf Michael Weber ◽  
Mouhamed S. Awayda
Keyword(s):  
Serine Proteases ◽  
Collecting Duct ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Epithelial Cell Line ◽  
Extracellular Proteases ◽  
Direct Role ◽  
Renal Epithelial Cell ◽  
Transport Pathways

The mammalian collecting duct (CD) is continuously exposed to urinary proteases. The CD expresses an epithelial Na+ channel (ENaC) that is activated after cleavage by serine proteases. ENaC also exists at the plasma membrane in the uncleaved form, rendering activation by extracellular proteases an important mechanism for regulating Na+ transport. Many exogenous and a small number of endogenous extracellular serine proteases have been shown to activate the channel. Recently, kallikrein 1 (KLK1) was shown to increase γENaC cleavage in the native CD indicating a possible direct role of this endogenous protease in Na+ homeostasis. To explore this process, we examined the coordinated effect of this protease on Na+ and Cl− transport in a polarized renal epithelial cell line (Madin-Darby canine kidney). We also examined the role of native urinary proteases in this process. Short-circuit current ( Isc) was used to measure transport of these ions. The Isc exhibited an ENaC-dependent Na+ component that was amiloride blockable and a cystic fibrosis transmembrane conductance regulator (CFTR)-dependent Cl− component that was blocked by inhibitor 172. Apical application of trypsin, an exogenous S1 serine protease, activated IENaC but was without effects on ICFTR. Subtilisin an exogenous S8 protease that mimics endogenous furin-type proteases activated both currents. A similar activation was also observed with KLK1 and native rat urinary proteases. Activation with urinary proteases occurred within minutes and at protease concentrations similar to those in the CD indicating physiological significance of this process. ENaC activation was irreversible and mediated by enhanced cleavage of γENaC. The activation of CFTR was indirect and likely dependent on activation of an endogenous apical membrane protease receptor. Collectively, these data demonstrate coordinated stimulation of separate Na+ and Cl− transport pathways in renal epithelia by extracellular luminal proteases. They also indicate that baseline urinary proteolytic activity is sufficient to modify Na+ and Cl− transport in these epithelia.

Amiloride-sensitive and HCO3(-)-dependent ion transport activated by aldosterone and vasotocin in A6 cells

1995 ◽  
Vol 268 (3) ◽  
pp. C762-C770 ◽  
Author(s):  
Y. Doi ◽  
Y. Marunaka
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Arginine Vasotocin ◽  
Transient Increase ◽  
Epithelial Cell Line ◽  
Bathing Solution ◽  
Renal Epithelial Cell ◽  
Sustained Increase ◽  
In Cells

We studied the effects of aldosterone (Aldo) and arginine vasotocin (AVT) on ion transport of renal epithelial cell line (A6) by measuring short-circuit current (Isc). AVT induced a rapid, transient increase in Isc, followed by a decrease toward the baseline in cells untreated with Aldo. In cells treated with Aldo, Isc showed a biphasic response to AVT, i.e., both transient and sustained increases over 40 min after addition of AVT. The transient increase was composed only of amiloride-insensitive Isc regardless of Aldo treatment, whereas the sustained increase contained both amiloride-sensitive and amiloride-insensitive components. The main part of the amiloride-insensitive, sustained Isc depended on HCO3(-). In cells treated with Aldo for 1 day, removal of HCO3(-) in the bathing solution enhanced the amiloride-sensitive component and decreased the amiloride-insensitive one. These data suggest that 1) Aldo treatment is necessary for an AVT-induced sustained increase of Isc and 2) a HCO3(-)-dependent Isc mainly contributes to the sustained increase in amiloride-insensitive Isc.

Abstract P229: Site-1 Protease-derived Soluble (pro) Renin Receptor Mediates Aldosterone-induced Enac Activation In The Collecting Duct

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Fei Wang ◽  
Renfei Luo ◽  
KEXIN PENG ◽  
Peng Wu ◽  
Xiyang Liu ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Fold Increase ◽  
Short Circuit Current ◽  
Vehicle Group ◽  
Α Subunit ◽  
Collecting Duct Cells

We have previously shown that activation of (pro)renin receptor (PRR) induces epithelial Na + channel (ENaC) activity in cultured collecting duct cells. Here, we examined the role of soluble PRR (sPRR), generated by site-1 protease (S1P), a newly identified PRR cleavage protease, in ENaC regulation, and further tested its relevance to Aldo signaling. In cultured mpkCCD cells, administration of recombinant histidine-tagged sPRR (sPRR-His) at 10 nM for 24 h induced a significant increase in the amiloride-sensitive short-circuit current as assessed using the Ussing chamber technique ( I eq : 7.5 ± 0.7 μA/cm 2 in sPRR group vs. 3.5 ± 0.5 μA/cm 2 in vehicle group, n = 6, p < 0.01) . In primary cultured rat IMCD cells, the same sPRR-His treatment induced a 1.7 fold increase in protein expression of the α-subunit but not β- or γ-subunit of ENaC, in parallel with upregulation of mRNA expression as well as promoter activity of the α-subunit. The upregulation of α-ENaC transcription depended on β-catenin signaling. Consistent results obtained by epithelial volt ohmmeter measurement of equivalent current and Using chamber determination of short-circuit current showed that Aldo-induced ENaC activity was almost completely abolished by PF-429242 (PF), a S1P inhibitor, and the response was restored by supplement of sPRR-His ( I eq : 7.2 ± 0.7 μA/cm 2 in Aldo group vs. 5.0 ± 0.3 μA/cm 2 in Aldo/PF group vs. 6.8 ± 0.3 μA/cm 2 in Aldo/PF/sPRR-His group, n = 5, p < 0.05). Medium sPRR was elevated by Aldo and inhibited by PF. Male C57BL/6 mice were pretreated with PF (30 mg/kg/day) or vehicle via minipump, followed by 3 days of aldosterone (0.2 mg/kg/day via a second minipump). Amiloride-sensitive Na+ current in freshly isolated CCD as measured by using patch clamp lower in Aldo + PF group than in Aldo group. Together, these results support an essential role of S1P-derived sPRR in mediating Aldo-induced ENaC activation.

scholarly journals Activation of the Amiloride-Sensitive Epithelial Sodium Channel by the Serine Protease mCAP1 Expressed in a Mouse Cortical Collecting Duct Cell Line

2000 ◽  
Vol 11 (5) ◽  
pp. 828-834
Author(s):  
GRÉGOIRE VUAGNIAUX ◽  
VÉRONIQUE VALLET ◽  
NICOLE FOWLER JAEGER ◽  
CORINNE PFISTER ◽  
MARCELLE BENS ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Cell Line ◽  
Serine Protease ◽  
Sodium Transport ◽  
Serine Proteases ◽  
Collecting Duct ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Duct Cell ◽  
Cortical Collecting Duct

Abstract. This study examines whether serine proteases can activate the amiloride-sensitive sodium channel (ENaC) in mammalian kidney epithelial cells. The transepithelial sodium transport assessed by amiloride-sensitive short-circuit current appears to be sensitive to aprotinin, a protease inhibitor in a mouse cortical collecting duct cell line (mpkCCDc14). This result indicated that serine proteases may be implicated in the regulation of ENaC-mediated sodium transport. Using degenerated oligonucleotides to a previously isolated serine protease from Xenopus, xCAP1 (channel activating protease), a novel full-length serine protease (mCAP1), has been isolated and characterized. RNA analysis showed a broad pattern of expression in tissues (kidney, lung, colon, and salivary glands) expressing ENaC. Reverse transcription-PCR experiments also showed that mCAP1 was abundantly expressed in proximal tubule cells and was also expressed in intact and cultured collecting duct cells. Coexpression of the Xenopus, rat, or human α-, β-, and γ-ENaC subunits in Xenopus oocytes also showed that mCAP1 induces a significant increase in ENaC-mediated current accompanied by a decrease of channel molecules at the cell surface. It is proposed that this novel mouse channel activating protease may act as a regulator of ENaC within the kidney.

Enhancement of the performance of CdS/CdTe heterojunction solar cell using TiO2/ZnO bi-layer ARC and V2O5 BSF layers: A simulation approach

2020 ◽  
Vol 92 (2) ◽  
pp. 20901
Author(s):  
Abdul Kuddus ◽  
Md. Ferdous Rahman ◽  
Jaker Hossain ◽  
Abu Bakar Md. Ismail
Keyword(s):  
Solar Cell ◽  
Short Circuit ◽  
Photovoltaic Performance ◽  
Short Circuit Current ◽  
Short Circuit Current Density ◽  
Open Circuit ◽  
Heterojunction Solar Cell ◽  
Back Surface ◽  
Heterojunction Solar Cells

This article presents the role of Bi-layer anti-reflection coating (ARC) of TiO2/ZnO and back surface field (BSF) of V2O5 for improving the photovoltaic performance of Cadmium Sulfide (CdS) and Cadmium Telluride (CdTe) based heterojunction solar cells (HJSCs). The simulation was performed at different concentrations, thickness, defect densities of each active materials and working temperatures to optimize the most excellent structure and working conditions for achieving the highest cell performance using obtained optical and electrical parameters value from the experimental investigation on spin-coated CdS, CdTe, ZnO, TiO2 and V2O5 thin films deposited on the glass substrate. The simulation results reveal that the designed CdS/CdTe based heterojunction cell offers the highest efficiency, η of ∼25% with an enhanced open-circuit voltage, Voc of 0.811 V, short circuit current density, Jsc of 38.51 mA cm−2, fill factor, FF of 80% with bi-layer ARC and BSF. Moreover, it appears that the TiO2/ZnO bi-layer ARC, as well as ETL and V2O5 as BSF, could be highly promising materials of choice for CdS/CdTe based heterojunction solar cell.

Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro

2004 ◽  
Vol 286 (5) ◽  
pp. G814-G821 ◽  
Author(s):  
Bi-Guang Tuo ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett ◽  
Jon I. Isenberg
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Duodenal Mucosa ◽  
Bicarbonate Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers ◽  
Duodenal Bicarbonate Secretion

PKC has been shown to regulate epithelial Cl- secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc ( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Isc in a concentration-dependent manner (from 10-8 to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.

Histamine augments colonic secretion in guinea pig distal colon

1990 ◽  
Vol 258 (3) ◽  
pp. G432-G439 ◽  
Author(s):  
Y. Z. Wang ◽  
H. J. Cooke ◽  
H. C. Su ◽  
R. Fertel
Keyword(s):  
Short Circuit ◽  
Nordihydroguaiaretic Acid ◽  
Short Circuit Current ◽  
Intestinal Secretion ◽  
Distal Colon ◽  
H2 Antagonist ◽  
Colonic Secretion ◽  
Set Up ◽  
Colonic Transport

We tested the hypothesis that the role of histamine in the control of intestinal secretion is mediated by prostaglandins (PGs). The effects of histamine on ion transport were examined in muscle-stripped sheets of mucosa/submucosa set up in flux chambers. Histamine evoked a transient concentration-dependent increase in short-circuit current (Isc) that was reduced by the Cl- transport inhibitor bumetanide. Histamine also caused the release of PGE2. The Isc response to histamine was reduced by indomethacin and piroxicam, which block PG formation, but not by nordihydroguaiaretic acid, which prevents production of lipoxygenase products. 2-Methylhistamine, but not dimaprit, evoked a concentration-dependent increase in Isc. The Isc response to histamine was reduced by the H1-blocker pyrilamine, but not by the H2-antagonist cimetidine. In addition to its direct effect, histamine augmented the responses of endogenously released neurotransmitters with and without indomethacin and hexamethonium. Tetrodotoxin (TTX) reduced the Isc response to 10(-3) M histamine. In the presence of TTX, exogenous histamine amplified the responses to PGs, vasoactive intestinal polypeptide, 2-chloroadenosine, bethanechol, and carbachol. These results suggest that histamine acts at H1-receptors on cells within the gut to mediate intestinal Cl- secretion in part by releasing PGs and by augmenting the actions of endogenously released neurotransmitters. Our results indicate that histamine has a role in the regulation of colonic transport function.

Activation of KCNQ (KV7) K+ channels in enteric neurons inhibits epithelial Cl- secretion in mouse distal colon

2021 ◽  
Author(s):  
Andrew J. Nickerson ◽  
Trey S. Rottgen ◽  
Vazhaikkurichi M. Rajendran
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Therapeutic Benefit ◽  
Enteric Neurons ◽  
Intestinal Epithelial ◽  
Cell Monolayers ◽  
Neuronal Populations ◽  
Irritable Bowel

KV7 (KCNQ) K+ channels are expressed in many neuronal populations, and play an important role in regulating membrane potential by generating a hyper-polarizing K+ current and decreasing cell excitability. However, the role of KV7 channels in the neural regulation of intestinal epithelial Cl- secretion is not known. Cl- secretion in mouse distal colon was measured as a function of short circuit current (ISC), while pharmacological approaches were used to test the hypothesis that activation of KV7 channels in enteric neurons would inhibit epithelial Cl- secretion. Flupirtine, a non-selective KV7 activator, inhibited basal Cl- secretion in mouse distal colon and abolished or attenuated the effects of drugs that target various components of enteric neurotransmission, including tetrodotoxin (NaV channel blocker), Veratridine (NaV channel activator), Nicotine (nicotinic acetylcholine receptor agonist) and Hexamethonium (nicotinic antagonist). In contrast, flupritine did not block the response to epithelium-targeted agents VIP (endogenous VPAC receptor ligand) or carbachol (non-selective cholinergic agonist). Flupirtine inhibited Cl- secretion in both full-thickness and seromuscular-stripped distal colon (containing the submucosal, but not myenteric plexus), but generated no response in epithelial T84 cell monolayers. KV7.2 and KV7.3 channel proteins were detected by immunofluorescence in whole-mount preparations of the submucosa from mouse distal colon. ICA 110381 (KV7.2/7.3 specific activator) inhibited Cl- secretion comparably to flupirtine. We conclude that KV7 channel activators inhibit neurally-driven Cl- secretion in the colonic epithelium, and may therefore have therapeutic benefit in treating pathologies associated with hyper-excitable enteric nervous system, such as irritable bowel syndrome with diarrhea (IBS-D).

scholarly journals Site-1 Protease-Derived Soluble (Pro)Renin Receptor Contributes to Angiotensin II–Induced Hypertension in Mice

Hypertension ◽  
2020 ◽  
Author(s):  
Ye Feng ◽  
Kexin Peng ◽  
Renfei Luo ◽  
Fei Wang ◽  
Tianxin Yang
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Collecting Duct ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Duct Cell ◽  
Ang Ii ◽  
Cortical Collecting Duct ◽  
Induced Hypertension

Activation of PRR ([pro]renin receptor) contributes to enhancement of intrarenal RAS and renal medullary α-ENaC and thus elevated blood pressure during Ang II (angiotensin II) infusion. The goal of the present study was to test whether such action of PRR was mediated by sPRR (soluble PRR), generated by S1P (site-1 protease), a newly identified PRR cleavage protease. F1 B6129SF1/J mice were infused for 6 days with control or Ang II at 300 ng/kg per day alone or in combination with S1P inhibitor PF-429242 (PF), and blood pressure was monitored by radiotelemetry. S1P inhibition significantly attenuated Ang II–induced hypertension accompanied with suppressed urinary and renal medullary renin levels and expression of renal medullary but not renal cortical α-ENaC expression. The effects of S1P inhibition were all reversed by supplement with histidine-tagged sPRR termed as sPRR-His. Ussing chamber technique was performed to determine amiloride-sensitive short-circuit current, an index of ENaC activity in confluent mouse cortical collecting duct cell line cells exposed for 24 hours to Ang II, Ang II + PF, or Ang II + PF + sPRR-His. Ang II–induced ENaC activity was blocked by PF, which was reversed by sPRR-His. Together, these results support that S1P-derived sPRR mediates Ang II–induced hypertension through enhancement of intrarenal renin level and activation of ENaC.

Effects of bile acids on dog pancreatic duct epithelial cell secretion and monolayer resistance

2002 ◽  
Vol 283 (5) ◽  
pp. G1042-G1050 ◽  
Author(s):  
Charles Okolo ◽  
Thomas Wong ◽  
Mark W. Moody ◽  
Toan D. Nguyen
Keyword(s):  
Pancreatic Duct ◽  
Bile Acids ◽  
Short Circuit ◽  
Bile Reflux ◽  
Short Circuit Current ◽  
Cell Secretion ◽  
Luminal A ◽  
Transport Pathways ◽  
Ussing Chambers ◽  
Lactate Dehydrogenase Release

Pancreatic duct epithelial cells (PDEC) mediate the secretion of fluid and electrolytes and are exposed to refluxed bile. In nontransformed cultured dog PDEC, which express many ion transport pathways of PDEC, 1 mM taurodeoxycholic acid (TDCA) stimulated an125I−efflux inhibited by DIDS and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and a86Rb+efflux inhibited by charybdotoxin. Inhibition by 1,2-bis(2-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid (BAPTA)-AM suggests mediation via increased intracellular Ca2+concentration, whereas the absence of lactate dehydrogenase release excludes cellular toxicity. At 1 mM, TDCA stimulated a larger125I−efflux than glycodeoxycholate; two dihydroxy bile acids, taurochenodeoxycholate and TDCA, were similarly effective, whereas a trihydroxy bile acid, taurocholate, was ineffective. In Ussing chambers, 1 mM serosal or 2 mM luminal TDCA stimulated an Iscincrease from confluent PDEC monolayers. TDCA also stimulated 1) a short-circuit current ( Isc) increase from basolaterally permeabilized PDEC subject to a serosal-to-luminal Cl−gradient that was inhibited by BAPTA-AM, DIDS, and NPPB and 2) an Iscincrease from apically permeabilized PDEC subject to a luminal-to-serosal K+gradient inhibited by BAPTA-AM and charybdotoxin. Along with the efflux studies, these findings suggest that TDCA interacts directly with PDEC to stimulate Ca2+-activated apical Cl−channels and basolateral K+channels. Monolayer transepithelial resistance was only minimally affected by 1 mM serosal and 2 mM luminal TDCA but decreased after exposure to higher TDCA concentrations (2 mM serosal and 4 mM luminal). A secretory role for bile acids should be considered in pancreatic diseases associated with bile reflux.

Role of nutrient HCO3(-) in protection of amphibian gastric mucosa

1980 ◽  
Vol 239 (6) ◽  
pp. G536-G542
Author(s):  
R. Schiessel ◽  
A. Merhav ◽  
J. B. Matthews ◽  
L. A. Fleischer ◽  
A. Barzilai ◽  
...  
Keyword(s):  
Gastric Mucosa ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Experimental Conditions ◽  
Slow Decline ◽  
Alkaline Tide ◽  
Artificial Gastric Juice ◽  
Rapid Drop

In in vitro bullfrog fundic mucosa inhibited with 10(-3) M metiamide and exposed to a luminal pH of 2 a progressive slow decline in potential difference (PD) and short-circuit current (Isc) and a rise in resistance (R) were observed when the nutrient solution (N) contained 18 mM HCO3(-), but these changes were restored by an N containing 50 mM HCO3(-). Substitution of PO4(3-) or N-tris(hydroxymethyl)-methyl-2-aminoethanesulfonic acid for NHO3(-) in N caused a rapid drop in PD and Isc in inhibited tissues, changes that could be prevented by 10(-4) M histamine. Ulceration occurred more frequently in metiamide-inhibited gastric sacs exposed to artificial gastric juice with an N of 18 mMHCO3(-) than with 50 mM HCO3(-), but histamine prevented ulceration in the 18 mM HCO3(-) solution. JnetCl approximated Isc under most experimental conditions in inhibited mucosa and was reduced dramatically as were both Jn leads to sCl and Js leads to nCl when HCO3(-) was removed from N. In histamine-stimulated tissues, removal of nutrient HCO3(-) did not influence Cl- transport. Our results are consistent with the proposal that HCO3(-) in N supports normal Cl- flux and that the alkaline tide of actively secreting oxyntic cells can do the same in the absence of ambient HCO3(-).

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