scholarly journals Cyp2c44 epoxygenase in the collecting duct is essential for the high K+ intake-induced antihypertensive effect

2014 ◽  
Vol 307 (4) ◽  
pp. F453-F460 ◽  
Author(s):  
Wen-Hui Wang ◽  
Chengbiao Zhang ◽  
Dao-Hong Lin ◽  
Lijun Wang ◽  
Joan P. Graves ◽  
...  
Keyword(s):  
Salt Intake ◽  
Collecting Duct ◽  
Proximal Convoluted Tubule ◽  
High Salt ◽  
Conditional Knockout ◽  
Thick Ascending Limb ◽  
Real Time Quantitative Pcr ◽  
High K ◽  
High Salt Intake ◽  
Cytochrome P 450

Cytochrome P-450, family 2, subfamily c, polypeptide 44 (Cyp2c44) epoxygenase metabolizes arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) in kidney and vascular tissues. In the present study, we used real-time quantitative PCR techniques to examine the effect of high salt or high K+ (HK) intake on the expression of Cyp2c44, a major Cyp2c epoxygenase in the mouse kidney. We detected Cyp2c44 in the proximal convoluted tubule, thick ascending limb, distal convoluted tubule (DCT)/connecting tubule (CNT), and collecting duct (CD). A high-salt diet increased the expression of Cyp2c44 in the thick ascending limb and DCT/CNT but not in the proximal convoluted tubule and CD. In contrast, an increase in dietary K+ intake augmented Cyp2c44 expression only in the DCT/CNT and CD. Neither high salt nor HK intake had a significant effect on the blood pressure (BP) of wild-type mice. However, HK but not high salt intake increased BP in CD-specific, Cyp2c44 conditional knockout (KO) mice. Amiloride, an epithelial Na+ channel (ENaC) inhibitor, normalized the BP of KO mice fed HK diets, suggesting that lack of Cyp2c44 in the CD enhances ENaC activity and increases Na+ absorption in KO mice fed HK diets. This notion was supported by metabolic cage experiments demonstrating that renal Na+ excretion was compromised in KO mice fed HK diets. Also, patch-clamp experiments demonstrated that 11,12-EET, a major Cyp2c44 product, but not AA inhibited ENaC activity in the cortical CD of KO mice. We conclude that Cyp2c44 in the CD is required for preventing the excessive Na+ absorption induced by HK intake by inhibition of ENaC and facilitating renal Na+ excretion.

Abstract 040: Upregulation Of Cyp Epoxygenase In The Connecting Tubule(cnt)/cortical Collecting Duct (ccd) Is Essential For High Potassium (k) Intake-induced Antihypertensive Effect

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Daohong Lin ◽  
Chengbiao Zhang ◽  
Lijun Wang ◽  
Wenhui Wang
Keyword(s):  
Antihypertensive Effect ◽  
Salt Intake ◽  
Collecting Duct ◽  
Smooth Muscles ◽  
High Salt ◽  
Conditional Knockout ◽  
Na Channel ◽  
Thick Ascending Limb ◽  
High K ◽  
High Salt Intake

Cyp epoxygenase is responsible for metabolizing arachidonic acid to epoxyeicosatrienoic acid (EET) in the kidney and vascular tissues. EET has been shown to cause vasodilation by stimulating Ca 2+ -activated K channels in vascular smooth muscles and to have natriuretic effect by inhibiting the epithelial Na channel (ENaC) in the kidney. In the present study we used real time PCR technique to examine the effect of high salt intake or high K intake on Cyp2c44 (a major type of Cyp epoxygenase in the mouse kidney) in the proximal tubule (PxT), thick ascending limb (TAL), distal convoluted tubule (DCT) and the CNT/CCD. An increase in dietary Na content stimulates the expression of Cyp2c4 in TAL, DCT and CNT/CCD but not in PxT while an increase in dietary K intake augments the expression of Cyp2c44 only in DCT and CNT/CCD. Neither high salt intake nor high K intake has a significant effect on the blood pressure (BP) in wt mice. However, high K intake increased BP in CNT/CCD specific conditional knockout (KO) mice. In contrast, the high Na intake did not significantly increase the BP in those KO mice. This suggests that Cyp2c44 in the CNT/CCD plays a key role in preventing hypertension induced by increasing dietary K intake. Administration of amiloride (a ENaC inhibitor) restored the normal BP in KO mice fed high K diet, suggesting that down-regulation of Cyp2c44 may enhance the Na absorption in the CNT/CCD. This notion was also supported by metabolic cage study demonstrating that renal Na excretion was compromised in KO mice. We conclude that Cyp2c44 plays a key role in stimulating renal Na excretion during increasing dietary K intake and that Cyp-epoxygenase is required for antihypertensive effect induced by high K intake.

scholarly journals Conditional knockout of collecting duct bradykinin B2 receptors exacerbates angiotensin II-induced hypertension during high salt intake

2015 ◽  
Vol 38 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Libor Kopkan ◽  
Zuzana Husková ◽  
Šárka Jíchová ◽  
Lenka Červenková ◽  
Luděk Červenka ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Salt Intake ◽  
Collecting Duct ◽  
High Salt ◽  
Conditional Knockout ◽  
High Salt Intake ◽  
Induced Hypertension ◽  
B2 Receptors

scholarly journals The Sodium‐Activated Sodium Channel (Nax) present in kidney thick ascending limb and collecting duct cells is augmented during high salt intake

2011 ◽  
Vol 25 (S1) ◽  
Author(s):  
Lucienne S. Lara ◽  
Alexis A. Gonzalez ◽  
Camille Bourgeois ◽  
Andrea Zsombok ◽  
Minolfa C. Prieto ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Salt Intake ◽  
Collecting Duct ◽  
High Salt ◽  
Thick Ascending Limb ◽  
Duct Cells ◽  
High Salt Intake ◽  
Collecting Duct Cells

scholarly journals The sodium-activated sodium channel is expressed in the rat kidney thick ascending limb and collecting duct cells and is upregulated during high salt intake

2012 ◽  
Vol 303 (1) ◽  
pp. F105-F109 ◽  
Author(s):  
Lucienne S. Lara ◽  
Ryousuke Satou ◽  
Camille R. T. Bourgeois ◽  
Alexis A. Gonzalez ◽  
Andrea Zsombok ◽  
...  
Keyword(s):  
Gene Expression ◽  
Epithelial Cells ◽  
Salt Intake ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Extracellular Fluid ◽  
High Salt ◽  
Thick Ascending Limb ◽  
Principal Cells ◽  
High Salt Intake

Increased dietary salt triggers oxidative stress and kidney injury in salt-sensitive hypertension; however, the mechanism for sensing increased extracellular Na+ concentration ([Na+]) remains unclear. A Na+-activated Na+ channel (Na sensor) described in the brain operates as a sensor of extracellular fluid [Na+]; nonetheless, its presence in the kidney has not been established. In the present study, we demonstrated the gene expression of the Na sensor by RT-PCR and Western blotting in the Sprague-Dawley rat kidney. Using immunofluorescence, the Na sensor was localized to the luminal side in tubular epithelial cells of collecting ducts colocalizing with aquaporin-2, a marker of principal cells, and in thick ascending limb, colocalizing with the glycoprotein Tamm-Horsfall. To determine the effect of a high-salt diet (HSD) on Na sensor gene expression, we quantified its transcript and protein levels primarily in renal medullas from control rats and rats subjected to 8% NaCl for 7 days ( n = 5). HSD increased Na sensor expression levels (mRNA: from 1.2 ± 0.2 to 5.1 ± 1.3 au; protein: from 0.98 ± 0.15 to 1.74 ± 0.28 au P < 0.05) in the kidney medulla, but not in the cortex. These data indicate that rat kidney epithelial cells of the thick ascending limb and principal cells of the collecting duct possess a Na sensor that is upregulated by HSD, suggesting an important role in monitoring changes in tubular fluid [Na+].

Abstract 142: A Fructose-but Not a Glucose-enriched Diet, Induces a Salt-dependent Increase in Blood Pressure and Enhances NKCC2 Phosphorylation in Normal Rats

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Keyona N King-Medina ◽  
Emily Henson ◽  
Pablo Ortiz
Keyword(s):  
Blood Pressure ◽  
Drinking Water ◽  
Salt Intake ◽  
Caloric Intake ◽  
High Salt ◽  
Human Consumption ◽  
Thick Ascending Limb ◽  
Sprague Dawley ◽  
High Fructose ◽  
High Salt Intake

Human consumption of fructose as a sweetener has increased in the past 30 years. High fructose intake has been implicated in the development of hypertension, diabetes, and obesity. In the US, the upper 10th percentile of the population consumes up to 40% of their caloric intake from added sugars, in which fructose represents half of these. Fructose metabolism is strikingly different from that of glucose. Yet, the effect of a fructose or glucose-enriched diet in salt handling by the kidney, affecting blood pressure, and its interaction with high salt intake has been poorly studied. In genetic models of salt-sensitive hypertension, the activity of the Na + /K + /2Cl - cotransporter (NKCC2) in the thick ascending limb (TAL) is abnormally enhanced. We hypothesized that chronic fructose in drinking water induces a salt-dependent increase in blood pressure and stimulates NKCC2 during high salt intake in normal rats. Sprague-Dawley rats were given 20% fructose or 20% glucose in drinking water for 1 week after which a high salt (HS) diet (4% Na + in chow) was started for 3 weeks. When we measured systolic blood pressure (SBP) by tail cuff plethysmography in fructose-fed and glucose-fed rats on a HS diet, only the fructose-fed rats had an increased SBP from 120±10 to 132±6 mmHg on day 7 of HS (p<0.01). SBP continued to increase up to 144±18 mmHg after 3 weeks (p<0.01 vs glucose). Fructose or glucose alone did not increase SBP after 4 weeks. We then repeated the protocol using radiotelemetry to monitor the blood pressure (BP). In rats fed fructose, by day 5 of HS the SBP increased by 12±3 mmHg (p<0.02) and SBP remained elevated for 3 weeks (delta: 10±2.5 mmHg, n=3). In rats fed glucose, a HS diet did not significantly change SBP for 3 weeks (n=5). Moreover, NKCC2 activity in the TAL is enhanced by phosphorylation at Thr96, 101. We found that NKCC2 phosphorylation was higher in rats fed fructose plus HS (p<0.02) but not in rats fed glucose plus HS for 3 weeks (HS: 100, fructose+HS: 250±40%, glucose+HS: 95±10%). Therefore, we conclude that a high fructose (but not a glucose) diet in normal rats induces a salt-dependent increase in BP independently from caloric intake. Thus, the increase in BP may in part be due to the stimulation of NKCC2 phosphorylation in the TAL by fructose.

scholarly journals The Relationship Between Urine Uromodulin and Blood Pressure Changes: The DASH-Sodium Trial

2020 ◽  
Author(s):  
Christine Y Bakhoum ◽  
Cheryl A M Anderson ◽  
Stephen P Juraschek ◽  
Casey M Rebholz ◽  
Lawrence J Appel ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Salt Intake ◽  
Control Diet ◽  
Random Order ◽  
High Salt ◽  
Thick Ascending Limb ◽  
Feeding Period ◽  
High Sodium ◽  
Sodium Diet ◽  
High Salt Intake

Abstract BACKGROUND Uromodulin modulates the sodium-potassium-two-chloride transporter in the thick ascending limb of the loop of Henle, and its overexpression in murine models leads to salt-induced hypertension. We hypothesized that individuals with higher baseline levels of urine uromodulin would have a greater increase in systolic blood pressure (SBP) for the same increase in sodium compared with those with lower uromodulin levels. METHODS We used data from 157 subjects randomized to the control diet of the Dietary Approaches to Stop Hypertension (DASH)-Sodium trial who were assigned to 30 days of low (1,500 mg/d), medium (2,400 mg/d), and high salt (3,300 mg/d) diets in random order. Blood pressure was measured prerandomization and then weekly during each feeding period. We evaluated the association of prerandomization urine uromodulin with change in SBP between diets, as measured at the end of each feeding period, using multivariable linear regression. RESULTS Baseline urine uromodulin stratified by tertiles was ≤17.64, 17.65–31.97, and ≥31.98 µg/ml. Across the tertiles, there were no significant differences in SBP at baseline, nor was there a differential effect of sodium diet on SBP across tertiles (low to high, P = 0.81). After adjusting for age, sex, body mass index, and race, uromodulin levels were not significantly associated with SBP change from low to high sodium diet (P = 0.42). CONCLUSIONS In a randomized trial of different levels of salt intake, higher urine uromodulin levels were not associated with a greater increase in blood pressure in response to high salt intake.

scholarly journals Salt-sensitive splice variant of nNOS expressed in the macula densa cells

2010 ◽  
Vol 298 (6) ◽  
pp. F1465-F1471 ◽  
Author(s):  
Deyin Lu ◽  
Yiling Fu ◽  
Arnaldo Lopez-Ruiz ◽  
Rui Zhang ◽  
Ramiro Juncos ◽  
...  
Keyword(s):  
Salt Intake ◽  
Splice Variants ◽  
Macula Densa ◽  
High Salt ◽  
Tubuloglomerular Feedback ◽  
No Production ◽  
Thick Ascending Limb ◽  
High Salt Diet ◽  
Salt Diet ◽  
High Salt Intake

Neuronal nitric oxide synthase (nNOS), which is abundantly expressed in the macula densa cells, attenuates tubuloglomerular feedback (TGF). We hypothesize that splice variants of nNOS are expressed in the macula densa, and nNOS-β is a salt-sensitive isoform that modulates TGF. Sprague-Dawley rats received a low-, normal-, or high-salt diet for 10 days and levels of the nNOS-α, nNOS-β, and nNOS-γ were measured in the macula densa cells isolated with laser capture microdissection. Three splice variants of nNOS, α-, β-, and γ-mRNAs, were detected in the macula densa cells. After 10 days of high-salt intake, nNOS-α decreased markedly, whereas nNOS-β increased two- to threefold in the macula densa measured with real-time PCR and in the renal cortex measured with Western blot. NO production in the macula densa was measured in the perfused thick ascending limb with an intact macula densa plaque with a fluorescent dye DAF-FM. When the tubular perfusate was switched from 10 to 80 mM NaCl, a maneuver to induce TGF, NO production by the macula densa was increased by 38 ± 3% in normal-salt rats and 52 ± 6% ( P < 0.05) in the high-salt group. We found 1) macula densa cells express nNOS-α, nNOS-β, and nNOS-γ, 2) a high-salt diet enhances nNOS-β, and 3) TGF-induced NO generation from macula densa is enhanced in high-salt diet possibly from nNOS-β. In conclusion, we found that the splice variants of nNOS expressed in macula densa cells were α-, β-, and γ-isoforms and propose that enhanced level of nNOS-β during high-salt intake may contribute to macula densa NO production and help attenuate TGF.

Connexin 37 is localized in renal epithelia and responds to changes in dietary salt intake

2010 ◽  
Vol 298 (1) ◽  
pp. F216-F223 ◽  
Author(s):  
Adelina Stoessel ◽  
Nina Himmerkus ◽  
Markus Bleich ◽  
Sebastian Bachmann ◽  
Franziska Theilig
Keyword(s):  
Gap Junctions ◽  
Epithelial Transport ◽  
Salt Intake ◽  
Collecting Duct ◽  
Mrna Level ◽  
High Salt ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Renal Epithelia ◽  
Basolateral Side

Connexins are the main components of gap junction channels, which are important for intercellular communication. In the kidney, several members of the connexin (Cx) family have been identified. Renal vascular expression and hemodynamic impacts have so far been shown for Cx37, Cx40, and Cx43. Additionally, Cx30, Cx30.3, and Cx43 have been identified to be part of tubular epithelial gap junctions and/or hemichannels. However, the localization and role of other Cx family members in renal epithelial structures remain undetermined. We aimed to localize Cx37 in the kidney to obtain information on its epithelial expression and potential functions. Immunohistochemistry in rodent kidney showed characteristic punctate patterns in the vasculature and along the nephron. Strong basolateral expression was found in the thick ascending limb and distal convoluted tubule. Weaker abundances were found in the proximal tubule and the collecting duct also at the basolateral side. In situ hybridization and real-time PCR of isolated nephron segments confirmed this distribution at the mRNA level. Ultrastructurally, Cx37 immunostaining was confined to basolateral cell interdigitations and infoldings. As a functional approach, rats were fed low- or high-salt diets. Compared with control and high-salt diets, rats treated with low-salt diet showed significantly increased Cx37 mRNA and protein levels. This may be indicative of an adaptive tubular response to changes in sodium reabsorption. In summary, renal epithelia express Cx37 in their basolateral membranes. Here, the formation of Cx37 gap junctions may be involved in cellular communication and adjustments of vectorial epithelial transport.

Abstract P332: Urine Uromodulin Does Not Alter the Relationship Between Salt Intake and Blood Pressure: The DASH-Sodium Trial

Circulation ◽  
2020 ◽  
Vol 141 (Suppl_1) ◽  
Author(s):  
Christine Bakhoum ◽  
Cheryl A Anderson ◽  
Stephen Juraschek ◽  
Casey M Rebholz ◽  
Lawrence J Appel ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Salt Intake ◽  
Association Studies ◽  
High Salt ◽  
Thick Ascending Limb ◽  
Genome Wide Association Studies ◽  
Feeding Period ◽  
Sodium Diet ◽  
High Salt Intake

Introduction: Genome-wide association studies have revealed susceptibility variants for hypertension in the UMOD gene. The encoded protein, uromodulin, modulates NKCC2 transporter in the thick ascending limb of the loop of Henle, and its overexpression in murine models leads to salt-induced hypertension. Hypothesis: Individuals with higher levels of urine uromodulin will have a greater increase in systolic blood pressure compared to those with lower uromodulin levels. Methods: We used data from 157 subjects in the control diet of the DASH-Sodium trial assigned to 30 days of low (1500 mg/d), medium (2400 mg/d), and high salt (3300 mg/d) diets in random order. Blood pressure was measured at baseline and at 5 visits during the last 9 days of each feeding period. We evaluated the association of urine uromodulin with change in systolic blood pressure between diets, as measured by the average at the end of each feeding period, using multivariable linear regression. Results: Baseline urine uromodulin stratified by tertiles was less than or equal to 17.64, 17.65 - 31.97, and greater than or equal to 31.98 μg/mL (overall mean 30.0 μg/mL, SEM 1.85 μg/mL). Across the tertiles, there were no significant differences in systolic blood pressure (SBP) at baseline, nor was there a differential effect of sodium diet on SBP across tertiles (low to high p = 0.81, Figure). After adjusting for age, sex, BMI, and race, uromodulin levels were not significantly associated with SBP change from low to high sodium diet (β = -0.68 per 10 μg/mL increase in urine uromodulin, p = 0.28). Conclusion: In a randomized trial of different levels of salt intake, higher urine uromodulin levels were not associated with a greater increase in blood pressure in response to high salt intake. Further human studies are needed to evaluate the findings seen in animal models, where the expression of higher levels of urine uromodulin has been associated with salt sensitive hypertension.

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