Low Na intake suppresses expression of CYP2C23 and arachidonic acid-induced inhibition of ENaC

2006 ◽  
Vol 291 (6) ◽  
pp. F1192-F1200 ◽  
Author(s):  
Peng Sun ◽  
Dao-Hong Lin ◽  
Tong Wang ◽  
Elisa Babilonia ◽  
Zhijian Wang ◽  
...  

We previously demonstrated that arachidonic acid (AA) inhibits epithelial Na channels (ENaC) through the cytochrome P-450 (CYP) epoxygenase-dependent pathway ( 34 ). In the present study, we tested the hypothesis that low Na intake suppresses the expression of CYP2C23, which is mainly responsible for converting AA to epoxyeicosatrienoic acid (EET) in the kidney ( 11 ) and attenuates the AA-induced inhibition of ENaC. Immunostaining showed that CYP2C23 is expressed in the Tamm-Horsfall protein (THP)-positive and aquaporin 2 (AQP2)-positive tubules. This suggests that CYP2C23 is expressed in the thick ascending limb (TAL) and collecting duct (CD). Na restriction significantly suppressed the expression of CYP2C23 in the TAL and CD. Western blot also demonstrated that the expression of CYP2C23 in renal cortex and outer medulla diminished in rats on Na-deficient diet (Na-D) but increased in those on high-Na diet (4%). Moreover, the content of 11,12-epoxyeicosatrienoic acid (EET) decreased in the isolated cortical CD from rats on Na-D compared with those on a normal-Na diet (0.5%). Patch-clamp study showed that application of 15 μM AA inhibited the activity of ENaC by 77% in the CCD of rats on a Na-D for 3 days. However, the inhibitory effect of AA on ENaC was significantly attenuated in rats on Na-D for 14 days. Furthermore, inhibition of CYP epoxygenase with MS-PPOH increased the ENaC activity in the CCD of rats on a control Na diet. We also used microperfusion technique to examine the effect of MS-PPOH on Na transport in the distal nephron. Application of MS-PPOH significantly increased Na absorption in the distal nephron of control rats but had no significant effect on Na absorption in rats on Na-D for 14 days. We conclude that low Na intake downregulates the activity and expression of CYP2C23 and attenuates the inhibitory effect of AA on Na transport.

1993 ◽  
Vol 265 (3) ◽  
pp. F399-F405 ◽  
Author(s):  
T. Satoh ◽  
H. T. Cohen ◽  
A. I. Katz

We recently reported a novel intracellular mechanism of Na-K-adenosinetriphosphatase (Na-K-ATPase) regulation in the cortical collecting duct (CCD) by agents that increase cell adenosine 3',5'-cyclic monophosphate (cAMP), which involves stimulation of protein kinase A (PKA) and phospholipase A2 (PLA2). We now determined whether this mechanism also operates in other nephron segments. In the medullary thick ascending limb (MTAL) dopamine, the DA1 agonist fenoldopam, forskolin, or dibutyryl-cAMP inhibited Na-K-ATPase activity, similar to results in CCD. In both segments this effect was blocked by 20-residue inhibitory peptide (IP20), a peptide inhibitor of PKA, but not by staurosporine, a protein kinase C (PKC) inhibitor. PKC activators phorbol 12-myristate 13-acetate, phorbol 12,13-dibutyrate, and 1,2-myristate 13-acetate, phorbol 12,13-dibutyrate, and 1,2-dioctanoylglycerol had no effect on Na-K pump activity in either CCD or MTAL. In contrast, all three PKC activators inhibited pump activity in the proximal convoluted tubule (PCT), an effect reproduced only by dopamine or by parathyroid hormone [PTH-(1-34)]. In PCT the pump inhibition by dopamine or PTH-(1-34) was abolished by staurosporine but not by IP20. The PLA2 inhibitor mepacrine prevented the effect of all agents, and arachidonic acid produced a dose-dependent pump inhibition in each of the three segments studied. We conclude that intracellular mechanisms of Na-K-ATPase regulation differ along the nephron, as they involve activation of PKA in CCD and MTAL and of PKC in PCT. These two pathways probably share a common mechanism in stimulating PLA2, arachidonic acid release, and production of eicosanoids in both the proximal and distal nephron.


2000 ◽  
Vol 11 (11) ◽  
pp. 1987-1994
Author(s):  
KAYOKO OOKATA ◽  
AKIHIRO TOJO ◽  
YOSHIRO SUZUKI ◽  
NOBUHIRO NAKAMURA ◽  
KENJIRO KIMURA ◽  
...  

Abstract. Inward rectifier potassium channels (Kir) play an important role in the K+ secretion from the kidney. Recently, a new subfamily of Kir, Kir7.1, has been cloned and shown to be present in the kidney as well as in the brain, choroid plexus, thyroid, and intestine. Its cellular and subcellular localization was examined along the renal tubule. Western blot from the kidney cortex showed a single band for Kir7.1 at 52 kD, which was also observed in microdissected segments from the thick ascending limb of Henle, distal convoluted tubule (DCT), connecting tubule, and cortical and medullary collecting ducts. Kir7.1 immunoreactivity was detected predominantly in the DCT, connecting tubule, and cortical collecting duct, with lesser expression in the thick ascending limb of Henle and in the medullary collecting duct. Kir7.1 was detected by electron microscopic immunocytochemistry on the basolateral membrane of the DCT and the principal cells of cortical collecting duct, but neither type A nor type B intercalated cells were stained. The message levels and immunoreactivity were decreased under low-K diet and reversed by low-K diet supplemented with 4% KCl. By the double-labeling immunogold method, both Kir7.1 and Na+, K+-ATPase were independently located on the basolateral membrane. In conclusion, the novel Kir7.1 potassium channel is located predominantly in the basolateral membrane of the distal nephron and collecting duct where it could function together with Na+, K+-ATPase and contribute to cell ion homeostasis and tubular K+ secretion.


2002 ◽  
Vol 283 (3) ◽  
pp. F407-F414 ◽  
Author(s):  
Rui-Min Gu ◽  
Wen-Hui Wang

We have used the patch-clamp technique to study the effect of arachidonic acid (AA) on the basolateral K channels in the medullary thick ascending limb (mTAL) of rat kidney. An inwardly rectifying 50-pS K channel was identified in cell-attached and inside-out patches in the basolateral membrane of the mTAL. The channel open probability ( P o) was 0.51 at the spontaneous cell membrane potential and decreased to 0.25 by 30 mV hyperpolarization. The addition of 5 μM AA decreased channel activity, identified as NP o, from 0.58 to 0.08 in cell-attached patches. The effect of AA on the 50-pS K channel was specific because 10 μM cis-11,14,17-eicosatrienoic acid had no significant effect on channel activity. To determine whether the effect of AA was mediated by AA per se or by its metabolites, we examined the effect of AA on channel activity in the presence of indomethacin, an inhibitor of cyclooxygenase, or N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS), an inhibitor of cytochrome P-450 monooxygenase. Inhibition of cyclooxygenase increased channel activity from 0.54 to 0.9. However, indomethacin did not abolish the inhibitory effect of AA on the 50-pS K channel. In contrast, inhibition of cytochrome P-450 metabolism not only increased channel activity from 0.49 to 0.83 but also completely abolished the effect of AA. Moreover, addition of DDMS can reverse the inhibitory effect of AA on channel activity. The notion that the effect of AA was mediated by cytochrome P-450-dependent metabolites of AA is also supported by the observation that addition of 100 nM of 20-hydroxyeicosatetraenoic acid, a main metabolite of AA in the mTAL, can mimic the effect of AA. We conclude that AA inhibits the 50-pS K channel in the basolateral membrane of the mTAL and that the effect of AA is mainly mediated by cytochrome P-450-dependent metabolites of AA.


2015 ◽  
Vol 309 (4) ◽  
pp. F280-F299 ◽  
Author(s):  
M. L. A. Kortenoeven ◽  
N. B. Pedersen ◽  
L. L. Rosenbaek ◽  
R. A. Fenton

Arginine vasopressin (AVP) is released from the posterior pituitary gland during states of hyperosmolality or hypovolemia. AVP is a peptide hormone, with antidiuretic and antinatriuretic properties. It allows the kidneys to increase body water retention predominantly by increasing the cell surface expression of aquaporin water channels in the collecting duct alongside increasing the osmotic driving forces for water reabsorption. The antinatriuretic effects of AVP are mediated by the regulation of sodium transport throughout the distal nephron, from the thick ascending limb through to the collecting duct, which in turn partially facilitates osmotic movement of water. In this review, we will discuss the regulatory role of AVP in sodium transport and summarize the effects of AVP on various molecular targets, including the sodium-potassium-chloride cotransporter NKCC2, the thiazide-sensitive sodium-chloride cotransporter NCC, and the epithelial sodium channel ENaC.


2004 ◽  
Vol 124 (6) ◽  
pp. 719-727 ◽  
Author(s):  
Yuan Wei ◽  
Dao-Hong Lin ◽  
Rowena Kemp ◽  
Ganesh S.S. Yaddanapudi ◽  
Alberto Nasjletti ◽  
...  

We used the patch-clamp technique to study the effect of arachidonic acid (AA) on epithelial Na channels (ENaC) in the rat cortical collecting duct (CCD). Application of 10 μM AA decreased the ENaC activity defined by NPo from 1.0 to 0.1. The dose–response curve of the AA effect on ENaC shows that 2 μM AA inhibited the ENaC activity by 50%. The effect of AA on ENaC is specific because neither 5,8,11,14-eicosatetraynoic acid (ETYA), a nonmetabolized analogue of AA, nor 11,14,17-eicosatrienoic acid mimicked the inhibitory effect of AA on ENaC. Moreover, inhibition of either cyclooxygenase (COX) with indomethacin or cytochrome P450 (CYP) ω-hydroxylation with N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS) failed to abolish the effect of AA on ENaC. In contrast, the inhibitory effect of AA on ENaC was absent in the presence of N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide (MS-PPOH), an agent that inhibits CYP-epoxygenase activity. The notion that the inhibitory effect of AA is mediated by CYP-epoxygenase–dependent metabolites is also supported by the observation that application of 200 nM 11,12-epoxyeicosatrienoic acid (EET) inhibited ENaC in the CCD. In contrast, addition of 5,6-, 8,9-, or 14,15-EET failed to decrease ENaC activity. Also, application of 11,12-EET can still reduce ENaC activity in the presence of MS-PPOH, suggesting that 11,12-EET is a mediator for the AA-induced inhibition of ENaC. Furthermore, gas chromatography mass spectrometry analysis detected the presence of 11,12-EET in the CCD and CYP2C23 is expressed in the principal cells of the CCD. We conclude that AA inhibits ENaC activity in the CCD and that the effect of AA is mediated by a CYP-epoxygenase–dependent metabolite, 11,12-EET.


1996 ◽  
Vol 271 (4) ◽  
pp. C1303-C1315 ◽  
Author(s):  
F. Ciampolillo ◽  
D. E. McCoy ◽  
R. B. Green ◽  
K. H. Karlson ◽  
A. Dagenais ◽  
...  

Amiloride-sensitive, electrogenic Na+ absorption across the distal nephron plays a vital role in regulating extracellular fluid volume and blood pressure. Recently, two amiloride-sensitive, Na(+)-conducting ion channel cDNAs were cloned. One, an epithelial Na(+)-selective channel (ENaC), is responsible for Na+ absorption throughout the distal nephron. The second, a guanosine 3',5'-cyclic monophosphate (cGMP)-inhibitable cation channel, is conductive to Na+ and Ca2+ and contributes to Na+ absorption across the inner medullary collecting duct (IMCD). As a first step toward understanding the segment-specific contributions(s) of cGMP-gated cation channels and ENaC to Na+ and Ca2+ uptake along the nephron, we used in situ reverse transcription-polymerase chain reaction (RT-PCR) hybridization, solution-phase RT-PCR, and Western blot analysis to examine the nephron and cell-specific expression of these channels in mouse kidney cell lines and/or dissected nephron segments. cGMP-gated cation channel mRNA was detected in proximal tubule, medullary thick ascending limb (mTAL), distal convoluted tubule (DCT), cortical collecting duct (CCD), outer medullary collecting duct (OMCD), and IMCD. cGMP-gated cation channel protein was detected in DCT, CCD, and IMCD cell lines. These observations suggest that hormones that modulate intracellular cGMP levels may regulate Na+, and perhaps Ca2+, uptake throughout the nephron. mRNA for alpha-mENaC, a subunit of the mouse ENaC, was detected in mTAL, DCT, CCD, OMCD, and IMCD. Coexpression of alpha-mENaC and cGMP-gated cation channel mRNAs in mTAL, DCT, CCD, OMCD, and IMCD suggests that both channels may contribute to Na+ absorption in these nephron segments.


1996 ◽  
Vol 271 (3) ◽  
pp. F588-F594 ◽  
Author(s):  
C. M. Macica ◽  
Y. Yang ◽  
S. C. Hebert ◽  
W. H. Wang

Arachidonic acid (AA) has been shown to inhibit the activity of the low-conductance ATP-sensitive K+ channel in the apical membrane of the cortical collecting duct [W. Wang, A. Cassola, and G. Giebisch. Am. J. Physiol. 262 (Renal Fluid Electrolyte Physiol. 31): F554-F559, 1992]. ROMK1, a K+ channel derived from the rat renal outer medulla, shares many biophysical properties of the native low-conductance K+ channel, which is localized to the apical membranes of the cortical collecting duct and thick ascending limb. This study was designed to determine whether the ROMK channel maintains the property of AA sensitivity of the native low-conductance K+ channel. Experiments were conducted in Xenopus oocytes injected with cRNA encoding the ROMK1 channel by use of patch-clamp techniques. We have confirmed previous reports that the cloned ROMK1 has similar channel kinetics, high open probability, and inward slope conductance as the native low-conductance K+ channel, respectively. Addition of 5 microM AA to an inside-out patch resulted in reversible inhibition of channel activity at a concentration similar to the inhibitor constant for AA on the native K+ channel. The effect of AA on channel activity was preserved in the presence of 10 microM indomethacin, a cyclooxygenase inhibitor, 4 microM cinnamyl-3,4-dihydroxycyanocinnamate, a lipoxygenase inhibitor, and 4 microM 17-octadecynoic acid, an inhibitor of cytochrome P-450 monooxygenases, thus indicating that the effect of AA was not mediated by metabolites of AA. The effect did not appear to be the result of changes in membrane fluidity, since 5 microM eicosatetraynoic acid, an AA analogue that is a potent modulator of membrane fluidity, had no effect. Furthermore, the addition of AA to the outside of the patch also had no effect on channel activity. These results indicate that, like the native low-conductance channel, AA is able to directly inhibit ROMK1 channel activity.


2008 ◽  
Vol 294 (6) ◽  
pp. F1441-F1447 ◽  
Author(s):  
ZhiJian Wang ◽  
Yuan Wei ◽  
John R. Falck ◽  
Krishnam Raju Atcha ◽  
Wen-Hui Wang

We used the patch-clamp technique to study the effect of arachidonic acid (AA) on basolateral 18-pS K channels in the principal cell of the cortical collecting duct (CCD) of the rat kidney. Application of AA inhibited the 18-pS K channels in a dose-dependent manner and 10 μM AA caused a maximal inhibition. The effect of AA on the 18-pS K channel was specific because application of 11,14,17-eicosatrienoic acid had no effect on channel activity. Also, the inhibitory effect of AA on the 18-pS K channels was abolished by blocking cytochrome P-450 (CYP) epoxygenase with N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide (MS-PPOH) but was not affected by inhibiting CYP ω-hydroxylase or cyclooxygenase. The notion that the inhibitory effect of AA was mediated by CYP epoxygenase-dependent metabolites was further supported by the observation that application of 100 nM 11,12-epoxyeicosatrienoic acid (EET) mimicked the effect of AA and inhibited the basolateral 18-pS K channels. In contrast, addition of either 5,6-, 8,9-, or 14,15-EET failed to inhibit the 18-pS K channels. Moreover, application of 11,12-EET was still able to inhibit the 18-pS K channels in the presence of MS-PPOH. This suggests that 11,12-EET is a mediator for the AA-induced inhibition of the 18-pS K channels. We conclude that AA inhibits basolateral 18-pS K channels by a CYP epoxygenase-dependent pathway and that 11,12-EET is a mediator for the effect of AA on basolateral K channels in the CCD.


2003 ◽  
Vol 228 (7) ◽  
pp. 786-794 ◽  
Author(s):  
Wieslaw Kozak ◽  
David M. Aronoff ◽  
Olivier Boutaud ◽  
Anna Kozak

Cytochrome P-450 monooxygenase (epoxygenase)-derived arachidonic acid (AA) metabolites, including 11,12-epoxyeicosatrienoic acid (11,12-EET), possess anti-inflammatory and antipyretic properties. Prostaglandin E2 (PGE2), a cyclooxygenase (COX)-derived metabolite of AA, is a well-defined mediator of fever and inflammation. We have tested the hypothesis that 11,12-EET attenuates synthesis of PGE2 in monocytes, which are the cells that are indispensable for induction of fever and initiation of inflammation. Monocytes isolated from freshly collected rat blood were stimulated with lipopolysaccharide (LPS; 100 ng/2 × 105 cells) to induce COX-2 and stimulate generation of PGE2. SKF-525A, an inhibitor of epoxygenases, significantly augmented the lipopolysaccharide-provoked synthesis of PGE2 in cell culture in a concentration-dependent manner. It did not affect, however, elevation of the expression of COX-2 protein in monocytes stimulated with LPS. 11,12-EET also did not affect the induction of COX-2 in monocytes incubated with lipopolysaccharide. However, 11,12-EET suppressed, in a concentration-dependent fashion, the generation of PGE2 in incubates. Preincubation of a murine COX-2 preparation for 0–5 min with three concentrations of 11,12-EET (1, 5, and 10 μM) inhibited the oxygenation of [14C]-labeled AA by the enzyme. The inhibitory effect of 11,12-EET on COX-2 was time-and-concentration-dependent, suggesting a mechanism-based inhibition. Based on these data, we conclude that 11,12-EET suppresses generation of PGE2 in monocytes via modulating the activity of COX-2. These data support the hypothesis that epoxygenasederived AA metabolites constitute a negative feedback on the enhanced synthesis of prostaglandins upon inflammation.


2007 ◽  
Vol 292 (1) ◽  
pp. F456-F466 ◽  
Author(s):  
Wencui Zheng ◽  
Jill W. Verlander ◽  
I. Jeanette Lynch ◽  
Melanie Cash ◽  
Jiahong Shao ◽  
...  

Mechanisms of K+ secretion and absorption along the collecting duct are not understood fully. Because KCNQ1 participates in K+ secretion within the inner ear and stomach, distribution of KCNQ1 in mouse kidney was studied using Northern and Western analyses, RT-PCR of isolated tubules, and immunohistochemistry. Northern blots demonstrated KCNQ1 transcripts in whole kidney. RT-PCR showed KCNQ1 mRNA in isolated distal convoluted tubule (DCT), connecting segment (CNT), collecting ducts (CD), and glomeruli. Immunoblots of kidney and stomach revealed a ∼75-kDa protein, the expected mobility for KCNQ1. KCNQ1 was detected by immunohistochemistry throughout the distal nephron and CD. Thick ascending limbs exhibited weak basolateral immunolabel. In DCT and CNT cells, immunolabel was intense and basolateral, although KCNQ1 label was stronger in late than in early DCT. Initial collecting tubule and cortical CD KCNQ1 immunolabel was predominantly diffuse, but many cells exhibited discrete apical label. Double-labeling experiments demonstrated that principal cells, type B intercalated cells, and a few type A intercalated cells exhibited distinct apical KCNQ1 immunolabel. In inner medullary CD, principal cells exhibited distinct basolateral KCNQ1 immunolabel, whereas intercalated cells showed diffuse cytoplasmic staining. Thus KCNQ1 protein is widely distributed in mouse distal nephron and CD, with significant axial and cellular heterogeneity in location and intensity. These findings suggest that KCNQ1 has cell-specific roles in renal ion transport and may participate in K+ secretion and/or absorption along the thick ascending limb, DCT, connecting tubule, and CD.


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