NF-κB Inhibits Sodium Transport via Down-regulation of SGK1 in Renal Collecting Duct Principal Cells

Tubulointerstitial inflammation is a common feature of renal diseases. We have investigated the relationship between inflammation and Na+ transport in the collecting duct (CD) using the mCCDcl1 and mpkCDDcl4 principal cell models. Lipopolysaccharide (LPS) decreased basal and aldosterone-stimulated amiloride-sensitive transepithelial current in a time-dependent manner. This effect was associated with a decrease in serum and gucocorticoid-regulated kinase 1 (SGK1) mRNA and protein levels followed by a decrease in epithelial sodium channel (ENaC) α-subunit mRNA levels. The LPS-induced decrease in SGK1 expression was confirmed in isolated rat CD. This decreased expression of either SGK1 or the ENaC α-subunit was not due to enhanced degradation of mRNA. In contrast, LPS inhibited transcriptional activity of the SGK1 promoter measured by luciferase-reporter gene assay. The effect of LPS was not mediated by inhibition of mineralocorticoid or glucocorticoid receptor, because expression of both receptors was unchanged and blockade of either receptor by spironolactone or RU486, respectively, did not prevent the down-regulation of SGK1. The effect of LPS was mediated by the canonical NF-κB pathway, as overexpression of a constitutively active mutant, IKKβ (inhibitor of nuclear factor κB kinase-β) decreased SGK1 mRNA levels, and knockdown of p65 NF-κB subunit by small interfering RNA increased SGK1 mRNA levels. Chromatin immunoprecipitation showed that LPS increased p65 binding to two NF-κB sites along the SGK1 promoter. In conclusion, we show that activation of the NF-κB pathway down-regulates SGK1 expression, which might lead to decreased ENaC α-subunit expression, ultimately resulting in decreased Na+ transport. Tubulointerstitial inflammation is a common feature of renal diseases. We have investigated the relationship between inflammation and Na+ transport in the collecting duct (CD) using the mCCDcl1 and mpkCDDcl4 principal cell models. Lipopolysaccharide (LPS) decreased basal and aldosterone-stimulated amiloride-sensitive transepithelial current in a time-dependent manner. This effect was associated with a decrease in serum and gucocorticoid-regulated kinase 1 (SGK1) mRNA and protein levels followed by a decrease in epithelial sodium channel (ENaC) α-subunit mRNA levels. The LPS-induced decrease in SGK1 expression was confirmed in isolated rat CD. This decreased expression of either SGK1 or the ENaC α-subunit was not due to enhanced degradation of mRNA. In contrast, LPS inhibited transcriptional activity of the SGK1 promoter measured by luciferase-reporter gene assay. The effect of LPS was not mediated by inhibition of mineralocorticoid or glucocorticoid receptor, because expression of both receptors was unchanged and blockade of either receptor by spironolactone or RU486, respectively, did not prevent the down-regulation of SGK1. The effect of LPS was mediated by the canonical NF-κB pathway, as overexpression of a constitutively active mutant, IKKβ (inhibitor of nuclear factor κB kinase-β) decreased SGK1 mRNA levels, and knockdown of p65 NF-κB subunit by small interfering RNA increased SGK1 mRNA levels. Chromatin immunoprecipitation showed that LPS increased p65 binding to two NF-κB sites along the SGK1 promoter. In conclusion, we show that activation of the NF-κB pathway down-regulates SGK1 expression, which might lead to decreased ENaC α-subunit expression, ultimately resulting in decreased Na+ transport. Critical regulation of Na+ and water reabsorption occurring in the collecting duct (CD) 2The abbreviations used are: CDcollecting ductCCDcortical collecting ductmCCDmouse CCDMRmineralocorticoid receptorGRglucocorticoid receptorSGK1serum and gucocorticoid-regulated kinase 1GILZglucocorticoid-induced leucine zipperENaCepithelial sodium channelLPSlipopolysaccharideIKKβinhibitor of nuclear factor κB kinase-βRNAiRNA interferenceTNFtumor necrosis factorIL1βinterleukin-1βMAPKmitogen-activated protein kinaseChIPchromatin immunoprecipitation. 2The abbreviations used are: CDcollecting ductCCDcortical collecting ductmCCDmouse CCDMRmineralocorticoid receptorGRglucocorticoid receptorSGK1serum and gucocorticoid-regulated kinase 1GILZglucocorticoid-induced leucine zipperENaCepithelial sodium channelLPSlipopolysaccharideIKKβinhibitor of nuclear factor κB kinase-βRNAiRNA interferenceTNFtumor necrosis factorIL1βinterleukin-1βMAPKmitogen-activated protein kinaseChIPchromatin immunoprecipitation. is handled mainly by systemic hormones such as aldosterone and vasopressin, aldosterone being the major regulator of sodium (Na+) transport in this segment (1Gross J.B. Imai M. Kokko J.P. J. Clin. Investig. 1975; 55: 1284-1294Crossref PubMed Scopus (105) Google Scholar, 2Reif M.C. Troutman S.L. Schafer J.A. J. Clin. Investig. 1986; 77: 1291-1298Crossref PubMed Scopus (177) Google Scholar, 3Tomita K. Pisano J.J. Knepper M.A. J. Clin. Investig. 1985; 76: 132-136Crossref PubMed Scopus (255) Google Scholar). Depending on its concentration, aldosterone either binds to the mineralocorticoid receptor (MR) alone or to both the MR and glucocorticoid receptors (GR) (4Gaeggeler H.P. Gonzalez-Rodriguez E. Jaeger N.F. Loffing-Cueni D. Norregaard R. Loffing J. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 2005; 16: 878-891Crossref PubMed Scopus (168) Google Scholar). Activated receptors translocate into the nucleus and bind to specific promoter sequences leading to increased transcription of early aldosterone-regulated genes, such as serum and glucocorticoid-regulated kinase 1 (SGK1) (5Chen S.Y. Bhargava A. Mastroberardino L. Meijer O.C. Wang J. Buse P. Firestone G.L. Verrey F. Pearce D. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 2514-2519Crossref PubMed Scopus (639) Google Scholar) and glucocorticoid-induced leucine zipper (GILZ) (6Bhalla V. Soundararajan R. Pao A.C. Li H. Pearce D. Am. J. Physiol. 2006; 291: F714-F721Crossref PubMed Scopus (86) Google Scholar). Protein kinase SGK1 is a key player in regulating Na+ transport in the CD. It increases apical plasma membrane expression and activity of the apical epithelial sodium channel (ENaC) by reducing NEDD4 ubiquitin ligase-dependent internalization (7Debonneville C. Flores S.Y. Kamynina E. Plant P.J. Tauxe C. Thomas M.A. Munster C. Chraibi A. Pratt J.H. Horisberger J.D. Pearce D. Loffing J. Staub O. EMBO J. 2001; 20: 7052-7059Crossref PubMed Scopus (579) Google Scholar). SGK1 additionally activates the basolateral Na, K-ATPase (8Henke G. Setiawan I. Bohmer C. Lang F. Kidney Blood Press. Res. 2002; 25: 370-374Crossref PubMed Scopus (59) Google Scholar, 9Summa V. Mordasini D. Roger F. Bens M. Martin P.Y. Vandewalle A. Verrey F. Feraille E. J. Biol. Chem. 2001; 276: 47087-47093Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar, 10Zecevic M. Heitzmann D. Camargo S.M. Verrey F. Pfluegers Arch. Eur. J. Physiol. 2004; 448: 29-35Crossref PubMed Scopus (67) Google Scholar) with a resulting increase of vectorial Na+ transport. In addition to these short term effects, SGK1 exerts long term effects illustrated by the recently demonstrated relief of transcriptional inhibition of the ENaC α-subunit (11Zhang W. Xia X. Reisenauer M.R. Rieg T. Lang F. Kuhl D. Vallon V. Kone B.C. J. Clin. Investig. 2007; 117: 773-783Crossref PubMed Scopus (134) Google Scholar). GILZ is another regulatory protein that has been proposed to activate ENaC in the CD (6Bhalla V. Soundararajan R. Pao A.C. Li H. Pearce D. Am. J. Physiol. 2006; 291: F714-F721Crossref PubMed Scopus (86) Google Scholar). Finally, MR and GR, both of which bind to glucocorticoid-responsive elements, directly stimulate transcription of Na+ transporter subunits such as ENaC (12May A. Puoti A. Gaeggeler H.P. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 1997; 8: 1813-1822Crossref PubMed Google Scholar) and Na, K-ATPase (13Verrey F. Schaerer E. Zoerkler P. Paccolat M.P. Geering K. Kraehen-buhl J.P. Rossier B.C. J. Cell Biol. 1987; 104: 1231-1237Crossref PubMed Scopus (118) Google Scholar) α-subunits. collecting duct cortical collecting duct mouse CCD mineralocorticoid receptor glucocorticoid receptor serum and gucocorticoid-regulated kinase 1 glucocorticoid-induced leucine zipper epithelial sodium channel lipopolysaccharide inhibitor of nuclear factor κB kinase-β RNA interference tumor necrosis factor interleukin-1β mitogen-activated protein kinase chromatin immunoprecipitation. collecting duct cortical collecting duct mouse CCD mineralocorticoid receptor glucocorticoid receptor serum and gucocorticoid-regulated kinase 1 glucocorticoid-induced leucine zipper epithelial sodium channel lipopolysaccharide inhibitor of nuclear factor κB kinase-β RNA interference tumor necrosis factor interleukin-1β mitogen-activated protein kinase chromatin immunoprecipitation. Tubulointerstitial inflammation is frequently observed in renal diseases and can be associated with clinical alterations of Na+ handling by the CD. For example, ENaC expression is decreased in CD of septic and post-obstructive kidney experimental models (14Li C. Wang W. Norregaard R. Knepper M.A. Nielsen S. Frokiaer J. Am. J. Physiol. 2007; 293: F333-F341Google Scholar, 15Schmidt C. Hocherl K. Schweda F. Kurtz A. Bucher M. J. Am. Soc. Nephrol. 2007; 18: 1072-1083Crossref PubMed Scopus (129) Google Scholar). Furthermore, inappropriate salt loss is a hallmark of acute or chronic interstitial nephritis. The NF-κB pathway (reviewed in Refs. 16Baldwin Jr., A.S. Annu. PubMed Scopus Google and Cell Biol. 2007; 8: PubMed Scopus Google a major pathway, is in a of renal diseases V. O. M. S. J. M. T. J. M. J. Am. Soc. Nephrol. 2004; PubMed Scopus Google Scholar, O. J. A. A. T. M. T. Kidney Full Text Full Text PDF PubMed Scopus Google Scholar). It can be into two major the canonical and The canonical pathway is the major NF-κB pathway in and is by and such as lipopolysaccharide This pathway is on the nuclear factor κB kinase-β which protein and its degradation by the leading to the of NF-κB translocate into the nucleus and of p65 and increase or gene The NF-κB pathway is by such as and and is on protein kinase leading to of NF-κB subunit and of NF-κB This pathway is mainly in the and of In addition to these two NF-κB such as and or and NF-κB a and as transcriptional in the of the (reviewed in Refs. 16Baldwin Jr., A.S. Annu. PubMed Scopus Google and Cell Biol. 2007; 8: PubMed Scopus Google Scholar). between transport and the NF-κB pathway has recently been in addition to its major in transport has been to with the canonical NF-κB SGK1 with IKKβ leading to activation of the NF-κB pathway in L. R. X. J. Res. 2005; Google Scholar). GILZ as the NF-κB pathway E. G. S. C. O. L. F. C. 2001; PubMed Scopus Google Scholar, D. S. A. G. L. M.C. A. J. P. M. C. D. PubMed Scopus Google Scholar). Finally, a between the and the NF-κB pathway has been J.A. PubMed Scopus Google Scholar). This to that a between the NF-κB pathway and Na+ transport. was to the that activation of the NF-κB pathway Na+ transport in CD principal and to the pathway in this For this we used both mCCDcl1 and which major and regulatory of CD principal and to and (4Gaeggeler H.P. Gonzalez-Rodriguez E. Jaeger N.F. Loffing-Cueni D. Norregaard R. Loffing J. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 2005; 16: 878-891Crossref PubMed Scopus (168) Google Scholar, M. V. F. L. A. Rossier B.C. Vandewalle A. J. Am. Soc. Nephrol. 1999; PubMed Google Scholar). In this we basal and aldosterone-stimulated amiloride-sensitive transport and SGK1 expression decreased by of MR or and the canonical NF-κB pathway directly down-regulates SGK1 expression, which in reducing ENaC α-subunit expression, leading to a decrease in sodium transport. LPS was as a in water and and as in or and Cell and on to in with serum (4Gaeggeler H.P. Gonzalez-Rodriguez E. Jaeger N.F. Loffing-Cueni D. Norregaard R. Loffing J. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 2005; 16: 878-891Crossref PubMed Scopus (168) Google and in and Kidney with and the kidney was with 1 1 1 and serum of to interstitial the kidney was into small and in and of cortical collecting isolated by in and in experimental was by of the V. Mordasini D. Roger F. Bens M. Martin P.Y. Vandewalle A. Verrey F. Feraille E. J. Biol. Chem. 2001; 276: 47087-47093Abstract Full Text Full Text PDF PubMed Scopus (64) Google the current was to the of transepithelial and measured with a not in because the of the be measured expression of the and the of small interfering RNA was by as M. U. V. M. Mordasini D. M. Martin P.Y. Feraille E. J. Am. Soc. Nephrol. PubMed Scopus Google Scholar). to along with of with serum and of RNA interference or of enhanced constitutively active or using a a that and to in in another or using and and and and active by and to F. H. A. Li J. M. M. A. A. 1997; PubMed Scopus Google was a S. of and and of and as M. U. V. M. Mordasini D. M. Martin P.Y. Feraille E. J. Am. Soc. Nephrol. PubMed Scopus Google Scholar). used of mouse and rat and mouse and mouse Na, K-ATPase and mouse and rat and mouse and and and mouse and mouse and mouse and mouse and and and For of a in a that a was was to a of The the was with the of and the of this was between and that the was by a factor of using and was used as The in was using the and the of to the of experimental and and by and to a membrane as Feraille E. H. Am. J. Physiol. PubMed Google Scholar). SGK1 was using E. Gaeggeler H.P. Rossier B.C. Kidney 2007; Full Text Full Text PDF PubMed Scopus Google MR was with C. of of and subunit by and and and p65 by or The by enhanced using and Chromatin was as S. T. S. I. W. J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). in cell 1 1 1 1 1 and of by 1 1 1 1 1 and chromatin was 1 by For chromatin 1 with protein and in sodium 1 and with with protein of was by with and was with and with with sodium and of in a of was as the NF-κB of the SGK1 promoter and and the NF-κB and as of either or used the Thomas Am. J. Physiol. 2002; PubMed Scopus Google Scholar) of the of of 1 of the of P. of and the of a constitutively active promoter with both and activity was measured using the to the The was measured using a The of activity was to with to the of as the was on the as between two by not using and and SGK1 in CD the effect of a of the NF-κB pathway, on transport in mCCDcl1 and a mouse CD principal cell M. V. F. L. A. Rossier B.C. Vandewalle A. J. Am. Soc. Nephrol. 1999; PubMed Google Scholar). mCCDcl1 or not with LPS in the or of aldosterone The show that LPS decreased the transepithelial current both in the and of It be that the current by aldosterone in the of The addition of to the apical the transepithelial that vectorial Na+ transport the apical to the basolateral the measured current not that LPS a time-dependent inhibition of sodium transport in The decrease in transepithelial current was with increase of transepithelial in both cell not the of cell or of This increase in transepithelial was because of decreased sodium LPS vectorial Na+ transport both basal and aldosterone-stimulated in of CD principal In CD to both and CD of the MR and of sodium transport by of the NF-κB pathway has recently been demonstrated to decrease expression J. 2005; PubMed Scopus Google Scholar) leading to MR by and of sodium transport. We confirmed the decrease in mRNA levels in mCCDcl1 with LPS of We the effect of of and on sodium transport by mCCDcl1 In the of and LPS the increase in current in mCCDcl1 show that the LPS CD transepithelial sodium transport. LPS the amiloride-sensitive transepithelial current not of Na+ transport (4Gaeggeler H.P. Gonzalez-Rodriguez E. Jaeger N.F. Loffing-Cueni D. Norregaard R. Loffing J. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 2005; 16: 878-891Crossref PubMed Scopus (168) Google we mRNA expression levels of of CD Na+ transport early such as SGK1 and that SGK1 expression levels decreased by of in with LPS In the of LPS a of the increase of SGK1 mRNA of In contrast, basal and and R. Wang J. Pearce D. J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar) mRNA levels not by LPS It is that aldosterone increases the expression levels of ENaC and Na, K-ATPase mRNA in the CD S. C. J.B. Knepper M.A. J. Clin. Investig. 1999; 104: PubMed Scopus Google Scholar, M. M. G. J. Biol. Chem. Full Text PDF PubMed Google Scholar). show that mRNA expression levels of the ENaC α-subunit was decreased of to LPS basal of aldosterone-stimulated LPS the increase in ENaC α-subunit mRNA that expression of the Na, K-ATPase α-subunit decreased in the of aldosterone effects not Finally, we observed a increase of mRNA expression in to LPS not that LPS activates the canonical NF-κB pathway in CD principal that LPS the expression levels of not the effect of LPS on SGK1 expression, we a that in mCCDcl1 with the addition of LPS a effect with a observed 1 and a effect the of SGK1 we measured the expression levels of SGK1 of with LPS or with of the NF-κB pathway, and SGK1 mRNA expression with a to that observed in with or both in the and the of aldosterone that of the canonical NF-κB pathway have effects on SGK1 Finally, we observed SGK1 expression by LPS in both and isolated rat with a of SGK1 expression by the canonical NF-κB SGK1 by a in ENaC and of mRNA in to the regulation of SGK1 and ENaC α-subunit mRNA by we SGK1 mRNA expression was by a decrease in SGK1 mRNA levels was observed In contrast, ENaC α-subunit mRNA expression was decreased that SGK1 is early of ENaC α-subunit expression is We degradation of both mRNA was enhanced by LPS We with aldosterone with or LPS (SGK1) or to transcription of both the addition of to The show that LPS did not increase the of SGK1 or ENaC α-subunit mRNA the of mRNA was not SGK1 or that LPS not SGK1 or ENaC α-subunit mRNA degradation decrease transcriptional activity of both we that SGK1 transcription is decreased by we the effect of LPS on activity of a of the SGK1 promoter Thomas Am. J. Physiol. 2002; PubMed Scopus Google Scholar). The gene showed that the SGK1 promoter is constitutively active in mCCDcl1 SGK1 promoter activity was inhibited by by LPS either or in the of In the of aldosterone the decrease in activity was not due to not that LPS SGK1 gene the early effect of LPS on SGK1 we that SGK1 down-regulation in ENaC α-subunit this ENaC α-subunit mRNA levels measured SGK1 knockdown by in mCCDcl1 with aldosterone to levels of SGK1 of mCCDcl1 with SGK1 decreased its mRNA expression to of levels observed in with showed a decrease of SGK1 protein expression in to SGK1 knockdown in decreased ENaC α-subunit mRNA expression, which was of that SGK1 mRNA is a of LPS and that decreased SGK1 expression in in reducing ENaC α-subunit mRNA levels. LPS-induced of SGK1 by MR and aldosterone the effect of LPS on SGK1 expression, we the effect of addition of LPS in the of of We observed that SGK1 mRNA expression was decreased the of aldosterone used SGK1 protein expression decreased to of the of aldosterone used and down-regulation of SGK1 protein expression by LPS was observed in with and aldosterone not CD principal mCCDcl1 both MR and GR, and either or both receptors can be on aldosterone (4Gaeggeler H.P. Gonzalez-Rodriguez E. Jaeger N.F. Loffing-Cueni D. Norregaard R. Loffing J. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 2005; 16: 878-891Crossref PubMed Scopus (168) Google Scholar). We investigated which pathway the down-regulation of SGK1 in the of We LPS directly MR or activity leading to in gene We protein expression of both receptors in mCCDcl1 or not with The show that MR and and protein expression was decreased of LPS a of receptor activity unchanged expression, specific a MR was to the effect by of aldosterone a was to the effect by of aldosterone as in mCCDcl1 (4Gaeggeler H.P. Gonzalez-Rodriguez E. Jaeger N.F. Loffing-Cueni D. Norregaard R. Loffing J. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 2005; 16: 878-891Crossref PubMed Scopus (168) Google Scholar). spironolactone mainly the increase of SGK1 expression by aldosterone of in the of the effect by aldosterone SGK1 mRNA in to either or aldosterone was by LPS to a in the or of spironolactone mainly inhibited the effect of aldosterone of with did not the effect of aldosterone that blockade by RU486, LPS the SGK1 that the effect of LPS on SGK1 expression be by alterations of MR and activity of the NF-κB the of LPS on SGK1 mRNA the regulation of SGK1 by specific NF-κB pathway we used mCCDcl1 with a constitutively active IKKβ Cell in a increase of IKKβ mRNA expression mRNA expression, as a of IKKβ increased by in with constitutively active IKKβ as with The in that expression of constitutively active IKKβ alone SGK1 mRNA expression in the of LPS or activation of IKKβ alone SGK1 expression observed in to LPS and and MR and did not to be this we a pathway of NF-κB in SGK1 expression in mCCDcl1 LPS nuclear of and NF-κB subunits in mCCDcl1 we knockdown of and by to these subunits in the observed regulation of SGK1 decreased p65 mRNA levels by in the of LPS and by in The of p65 knockdown was by and the showed that p65 protein expression was by p65 increased SGK1 mRNA expression in the or of This that the p65 subunit exerts effect on SGK1 mRNA of by decreased both mRNA of and protein expression by of effect on SGK1 mRNA levels, of resulting in decreased and protein expression did not SGK1 mRNA expression either not that the p65 NF-κB subunit in LPS-induced SGK1 expression, by with as a In addition to the NF-κB subunit can in to as transcriptional as demonstrated in to J. 2005; PubMed Scopus Google Scholar). the that in the effect of LPS and on SGK1 expression, we with either of NF-κB which or a directly Cell in mRNA and protein and SGK1 mRNA was not by the of levels of is that the observed effects of on SGK1 expression mediated by as being the factor and p65 as the This to a regulation of SGK1 expression by NF-κB of the mouse SGK1 promoter two binding sites Jr., A.S. Annu. PubMed Scopus Google and of the in addition to the glucocorticoid-responsive sites along the rat and SGK1 a between G.L. Cell Physiol. PubMed Scopus Google Scholar). that p65 binds to either or both NF-κB binding we a using a increase in the mCCDcl1 NF-κB binding that as with and NF-κB p65 subunit did not to bind to either NF-κB binding basal that the SGK1 mouse promoter two NF-κB binding sites that by p65 in to LPS to be in to and in SGK1 expression S. J.A. K. Wang J. Pearce D. 2004; PubMed Scopus Google Scholar). We the effect of specific inhibition on SGK1 mRNA expression by mCCDcl1 1 or with kinase a kinase inhibitor or a kinase to LPS of these in SGK1 expression in to LPS not The of the that and LPS Na+ transport inhibition of SGK1 This in in the regulation of ENaC activity as as its In the cell (4Gaeggeler H.P. Gonzalez-Rodriguez E. Jaeger N.F. Loffing-Cueni D. Norregaard R. Loffing J. Horisberger J.D. Rossier B.C. J. Am. Soc. Nephrol. 2005; 16: 878-891Crossref PubMed Scopus (168) Google as as in decreased basal as as and Na+ transport. This the major by that in with systemic hormones in the regulation of transport in the CD. the observed inhibition of vectorial Na+ transport lead to renal Na+ loss because the CD is the of of Na+ handling to the of Na+ This have In renal epithelial Na, of Na+ of E. A. Physiol. 2001; PubMed Scopus Google Scholar). a of transport activity a of which cell of as aldosterone has been recently to activate the NF-κB pathway in collecting duct J. S. J.P. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google the observed effect of NF-κB activation a of aldosterone activity on Na+ transport. Finally, as a of activation of the NF-κB pathway in the renal is to a systemic of aldosterone the of Na+ transport activity along the CD. The of the inhibition of Na+ transport by to on the down-regulation of a major of Na+ transport in CD principal the transcriptional SGK1 mRNA expression was decreased to a by LPS and of the NF-κB pathway such as and Protein expression of SGK1 was This is to decrease Na+ as SGK1 is a of ENaC and Na, K-ATPase activity in of cell expression S.Y. Loffing-Cueni D. Kamynina E. D. C. S. J. Loffing J. Staub O. J. Am. Soc. Nephrol. 2005; 16: PubMed Scopus Google Scholar, I. G. Bohmer C. W. Lang F. Pfluegers Arch. Eur. J. Physiol. 2002; PubMed Scopus Google Scholar). In addition to these effects, experimental that SGK1 a in the long term of Na+ transport by transcriptional of the ENaC α-subunit gene by the (11Zhang W. Xia X. Reisenauer M.R. Rieg T. Lang F. Kuhl D. Vallon V. Kone B.C. J. Clin. Investig. 2007; 117: 773-783Crossref PubMed Scopus (134) Google Scholar). The of the that inhibition of SGK1 transcription in decreased ENaC α-subunit mRNA levels in to NF-κB inhibition of SGK1 mRNA the decrease in ENaC α-subunit mRNA expression, and of SGK1 in decreased expression of ENaC α-subunit mRNA. the of SGK1 transcriptional inhibition by we in which directly on the ENaC α-subunit promoter. SGK1 expression to be by We that decreased SGK1 mRNA levels not due to enhanced The of gene that inhibition of SGK1 gene transcription is the to the observed LPS-induced down-regulation of this down-regulation be observed in mouse and rat as as in a SGK1 promoter. the between the and the NF-κB pathway J.A. PubMed Scopus Google was to that NF-κB activation SGK1 expression inhibition of This not by experimental the of regulation of MR and expression and activity by active pathway between the NF-κB and SGK1 regulation as expression of a constitutively active IKKβ mutant, the protein kinase that activates the canonical NF-κB pathway of and p65 NF-κB inhibited both basal and SGK1 of p65 increased SGK1 mRNA The that of p65 did not the effect by LPS is to the activation and of p65 subunits by Finally, LPS the NF-κB p65 subunit to bind to the SGK1 promoter as demonstrated by decreased transcriptional activity by binding of the NF-κB p65 subunit to a gene promoter has recently been K. P. 2005; Full Text Full Text PDF PubMed Scopus (64) Google Scholar, R. P. A.S. EMBO J. 2005; PubMed Scopus Google Scholar). IKKβ has been demonstrated to with the of and overexpression of IKKβ increased ENaC current in the expression J. S. J.P. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). we that a constitutively active IKKβ SGK1 which not the that IKKβ directly ENaC activity of NF-κB activation Cell Biol. 2007; 8: PubMed Scopus Google Scholar). In of ENaC activity and inhibition of SGK1 transcription as we have that NF-κB activation by amiloride-sensitive current M. U. Mordasini D. M. M. E. Vandewalle A. Martin P.Y. Feraille E. J. Am. Soc. Nephrol. 2005; 16: PubMed Scopus Google Scholar) in LPS the amiloride-sensitive current in mCCDcl1 as In conclusion, we have demonstrated that the NF-κB pathway Na+ transport in CD principal This effect is due to inhibition of SGK1 gene transcription binding of p65 NF-κB subunit to specific sites of the SGK1 that and Na, K-ATPase α-subunit activity and that in regulating The effect of Na+ transport in salt observed in the of inflammation of the and systemic aldosterone levels. the of SGK1 the expression of NF-κB by SGK1 a in cell as as in of