Novel Role of Rac1/WAVE Signaling Mechanism in Regulation of the Epithelial Na
            <sup>+</sup>
            Channel

Karpushev, Alexey V.; Levchenko, Vladislav; Ilatovskaya, Daria V.; Pavlov, Tengis S.; Staruschenko, Alexander

doi:10.1161/hypertensionaha.110.157784

Cited by 35 publications

(29 citation statements)

References 39 publications

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“…48 Our recent findings show that Rac1 increases ENaC activity. 49,50 We hypothesize that the low EGF level in SS rats on a HS diet leads to high Rac1 and, consequently, increased ENaC activity that contributes to inappropriate salt retention and hypertension. This theory might explain the mechanism of beneficial effects of MR blockade on BP and renal and vascular damage.…”

Section: Discussionmentioning

confidence: 99%

“…7,49 The rats were euthanized with sodium pentobarbital (50 mg/kg, intraperitoneally); the kidneys were then removed and placed into zinc formalin. The kidney sections were cut at 4-mm slices, dried, and deparaffinized for subsequent streptavidin-biotin immunohistochemistry.…”

Section: Histologic and Immunohistochemical Analysesmentioning

confidence: 99%

“…CCDs were isolated from SS rats as previously described. 35,49,50 Kidneys were cut into thin slices (,1 mm) and then placed into ice-cold physiologic salt solution (pH 7.4). Collecting ducts were mechanically isolated from slices by microdissection using forceps under a stereomicroscope.…”

Section: Isolation Of Ccdsmentioning

confidence: 99%

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Deficiency of Renal Cortical EGF Increases ENaC Activity and Contributes to Salt-Sensitive Hypertension

Pavlov¹,

Levchenko²,

O’Connor³

et al. 2013

Journal of the American Society of Nephrology

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Various stimuli, including hormones and growth factors, modulate epithelial sodium channels (ENaCs), which fine-tune Na + absorption in the kidney. Members of the EGF family are important for maintaining transepithelial Na + transport, but whether EGF influences ENaC, perhaps mediating salt-sensitive hypertension, is not well understood. Here, the ENaC inhibitor benzamil attenuated the development of hypertension in Dahl salt-sensitive rats. Feeding these salt-sensitive rats a high-salt diet led to lower levels of EGF in the kidney cortex and enhanced the expression and activity of ENaC compared with feeding a lowsalt diet. To directly evaluate the role of EGF in the development of hypertension and its effect on ENaC activity, we infused EGF intravenously while continuously monitoring BP of the salt-sensitive rats. Infusion of EGF decreased ENaC activity, prevented the development of hypertension, and attenuated glomerular and renal tubular damage. Taken together, these findings indicate that cortical EGF levels decrease with a high-salt diet in salt-sensitive rats, promoting ENaC-mediated Na + reabsorption in the collecting duct and the development of hypertension. More than 76 million American adults have high BP 1 and the likelihood of developing hypertension significantly increases with age. Nearly 40% of African Americans aged .20 years exhibit hypertension and nearly 70% of these individuals have a form of hypertension that is highly sensitive to salt intake. A reduced ability to maintain sodium homeostasis and normal levels of arterial pressure is a hallmark of all forms of hypertension. 2 In the kidney, discretionary Na + reabsorption in response to endocrine input to the aldosterone-sensitive distal nephron (ASDN) is a determinant of the pressurenatriuresis relationship, which is of fundamental importance in the long-term control of arterial pressure. 2,3 Although sodium transport in ASDN accounts for a small proportion of renal sodium transport (,10%), ENaC activity is the rate-limiting step for this discretionary Na + reabsorption. 4 The Dahl salt-sensitive (SS) rat strain used in this study is a genetic animal model of hypertension and kidney disease that reveals disease traits similar to those observed in humans. This inbred strain exhibits a low-renin, sodium-sensitive form of hypertension that is associated with severe and progressive proteinuria, glomerulosclerosis, and renal interstitial fibrosis. [5][6][7] The EGF and related hormones are multipotent agents [8][9][10][11] involved in regulation of various renal

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Section: Discussionmentioning

confidence: 99%

Section: Histologic and Immunohistochemical Analysesmentioning

confidence: 99%

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Deficiency of Renal Cortical EGF Increases ENaC Activity and Contributes to Salt-Sensitive Hypertension

Pavlov¹,

Levchenko²,

O’Connor³

et al. 2013

Journal of the American Society of Nephrology

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“…A Millicel Electrical Resistance System (Millipore, Billerica, MA) was used to measure voltage and resistance across the mpkCCD c14 cell monolayers grown on permeable supports as described previously (18,20,32). Equivalent transepithelial Na ϩ currents were calculated as the quotient of transepithelial voltage to transepithelial resistance under short-circuit conditions.…”

Section: Methodsmentioning

confidence: 99%

Effects of cytochromeP-450 metabolites of arachidonic acid on the epithelial sodium channel (ENaC)

Pavlov¹,

Ilatovskaya

Levchenko³

et al. 2011

American Journal of Physiology-Renal Physiology

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Previous studies have indicated that arachidonic acid (AA) and its metabolite 11,12-EET but not other regioisomers of EETs inhibit ENaC activity in the collecting duct. The goal of this study was to investigate the endogenous metabolism of AA in cultured mpkCCD c14 principal cells and the effects of these metabolites on ENaC activity. Liquid chromatography/mass spectrometry analysis of the mpkCCD c14 cells indicated that these cells produce prostaglandins, 8,9-EET, 11,12-EET, 14,15-EET, 5-HETE, 12/8-HETE, and 15-HETE, but not 20-HETE. Single-channel patch-clamp experiments revealed that 8,9-EET, 14,15-EET, and 11,12-EET all decrease ENaC activity. Neither 5-, 12-, nor 15-HETE had any effect on ENaC activity. Diclofenac and ibuprofen, inhibitors of cyclooxygenase, decreased transepithelial Na ϩ transport in the mpkCCDc14 cells. Inhibition of cytochrome P-450 (CYP450) with MS-PPOH activated ENaC-mediated sodium transport when cells were pretreated with AA and diclofenac. Coexpression of CYP2C8, but not CYP4A10, with ENaC in Chinese hamster ovary cells significantly decreased ENaC activity in whole-cell experiments, whereas 11,12-EET mimicked this effect. Thus both endogenously formed EETs and their exogenous application decrease ENaC activity. Downregulation of ENaC activity by overexpression of CYP2C8 was PKA dependent and was prevented by myristoylated PKI treatment. Biotinylation experiments and single-channel analysis revealed that long-term treatment with 11,12-EET and overexpression of CYP2C8 decreased the number of channels in the membrane. In contrast, the acute inhibitory effects are mediated by a decrease in the open probability of the ENaC. We conclude that 11,12-EET, 8,9-EET, and 14,15-EET are endogenously formed eicosanoids that modulate ENaC activity in the collecting duct. aldosterone; eicosanoids; 11,12-EET; 8,9-EET; 14,15-EET; 20-HETE; prostaglandins THE EPITHELIAL SODIUM CHANNEL (ENaC) is thought to represent the rate-limiting step for sodium absorption in the renal collecting duct. Consequently, ENaC is a central effector that impacts blood volume and systemic arterial pressure regulation. ENaC is localized to the luminal plasma membrane of epithelial cells and is involved in Na ϩ homeostasis. Multiple factors regulate the renal handling of sodium, including the renin-angiotensin-aldosterone system, nitric oxide, arachidonic acid (AA), and its metabolites. AA is primarily metabolized by cytochrome P-450 enzymes to 19-and 20-HETE and EETs (5,6-, 8,9-, 11,12-, and 14,15-EET) in the renal cortex, and these compounds have been shown to play critical roles in the regulation of renal tubular and vascular function (34). Cytochrome P-450 members of the CYP2C and CYP4A families are the predominant epoxygenases and -hydroxylase enzymes expressed in the kidney (5). The cyp4A isoform has been reported to be expressed in the cortical collecting ducts (CCD) (15). Knockdown of the Cyp4a10 gene in mice produces a salt-sensitive form of hypertension that is associated with alterations in the activity of ENaC (28...

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“…The role of actin microfilaments in the regulation of ENaC activity is well-documented. [40][41][42] More recently, Karpushev et al 43 reported that WASP proteins increased ENaC activity when coexpressed in Chinese hamster ovary cells. The role of Fnbp1 in cytoskeleton-and WASP-mediated regulation of ENaC activity and involvement of aldosterone-independent regulation by vasopressin 17 are currently investigated in our laboratory.…”

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confidence: 99%

Increased Renal Epithelial Na Channel Expression and Activity Correlate With Elevation of Blood Pressure in Spontaneously Hypertensive Rats

et al. 2013

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N umerous quantitative trait loci for blood pressure (BP) elevation have been identified in essential hypertension in the last decade, followed by genome-wide association studies. [1][2][3][4][5] The high heritability of gene expression variation indicates that it may serve as an intermediate phenotype for the identification of genomic determinants of complex traits, such as essential hypertension. We initiated this approach by exploring the pleiotropic regulation of heat stress genes mapping the mRNA accumulation after heat stress and using recombinant inbred strains (RIS) developed by inbreeding the F 2 generation of normotensive Brown-Norway (BN-Lx) and spontaneously hypertensive rats (SHR). 6 We discovered a common regulator of heat stress genes, the rat heat stress transcription factor. 7 Subsequently, Hubner et al 8 undertook integrated gene expression profiling in the adipose tissue and kidneys of 6-week-old male animals from the same RIS. Dmitrieva et al 9 adopted this strategy for comparative analysis of common differentially-expressed genes in the kidneys of 4-, 8-, 12-, and 18-week-old males of 3 distinct SHR lines versus normotensive Wistar-Kyoto (WKY) rats. The renal transcriptomes of 2-week-old SHR and WKY females 10 and 9-week-old rats of both sexes 11 were compared by other research teams. However, results generated by these studies cannot serve to identify genes involved in the age-dependent development of hypertension. In the present investigation, we compared whole genome expression profiles in kidneys isolated from 12-, 40-, and 80-week-old male and female SHR and 4 RIS (HXB3, 13, 17, and 23) with different temporal patterns of hypertension development. Among the genes significantly correlating with increasing mean systolic and diastolic blood pressures, we noted the augmented mRNAs levels of Scnn1b and Scnn1g genes encoding β-and γ-epithelial Na channel (ENaC) subunits. The present study is thus focusing on the expression and activity of these genes in relation to age-dependent increase of blood pressure.Abstract-Elevation of blood pressure with age is one of the hallmarks of hypertension in both males and females. This study examined transcriptomic profiles in the kidney of 12-, 40-, and 80-week-old spontaneously hypertensive rats and 4 recombinant inbred strains in search for functional genetic elements supporting temporal dynamics of blood pressure elevation. We found that both in males and females of spontaneously hypertensive rats and hypertensive recombinant inbred strains age-dependent blood pressure increment was accompanied by 50% heightened expression of epithelial sodium channel β-and γ-subunits. Epithelial sodium channel subunit expression correlated positively with blood pressure but correlated negatively with renin expression. Increased epithelial sodium channel activity was observed in cultured epithelial cells isolated from the kidney medulla of 80-week-old spontaneously hypertensive rats but not in agematched normotensive Wistar Kyoto. This difference remained evident after ...

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Novel Role of Rac1/WAVE Signaling Mechanism in Regulation of the Epithelial Na ⁺ Channel

Cited by 35 publications

References 39 publications

Deficiency of Renal Cortical EGF Increases ENaC Activity and Contributes to Salt-Sensitive Hypertension

Deficiency of Renal Cortical EGF Increases ENaC Activity and Contributes to Salt-Sensitive Hypertension

Effects of cytochromeP-450 metabolites of arachidonic acid on the epithelial sodium channel (ENaC)

Increased Renal Epithelial Na Channel Expression and Activity Correlate With Elevation of Blood Pressure in Spontaneously Hypertensive Rats

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Novel Role of Rac1/WAVE Signaling Mechanism in Regulation of the Epithelial Na + Channel

Cited by 35 publications

References 39 publications

Deficiency of Renal Cortical EGF Increases ENaC Activity and Contributes to Salt-Sensitive Hypertension

Deficiency of Renal Cortical EGF Increases ENaC Activity and Contributes to Salt-Sensitive Hypertension

Effects of cytochromeP-450 metabolites of arachidonic acid on the epithelial sodium channel (ENaC)

Increased Renal Epithelial Na Channel Expression and Activity Correlate With Elevation of Blood Pressure in Spontaneously Hypertensive Rats

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Novel Role of Rac1/WAVE Signaling Mechanism in Regulation of the Epithelial Na ⁺ Channel