Impaired Sodium Excretion Research Articles

Effects of Patiromer and Sodium Zirconium Cyclosilicate on Blood Pressure in Rats with Chronic Kidney Disease.

Potassium-binders patiromer and sodium zirconium cyclosilicate (SZC) are approved to treat hyperkalaemia, which is frequently observed in chronic kidney disease (CKD). Elevated blood pressure (BP) is common in CKD, due in part to impaired sodium excretion. The effect of patiromer, which exchanges calcium for potassium and SZC, which exchanges sodium or hydrogen for potassium, on BP was assessed in a CKD rat model. Thirty-six Sprague Dawley rats with 5/6 nephrectomy were randomised to three groups (n = 12/group) to receive 4 g/kg/day patiromer or SZC, or vehicle treatment, for 8 weeks. BP was determined by radiotelemetry and urinary protein and electrolytes were measured. At Week 8, systolic BP (sBP) increased in all groups; however, patiromer led to a lower mean (standard deviation) sBP than vehicle or SZC (141 [2.9] vs 158 [5.2] or 162 [6.1] mm Hg, respectively, both p < 0.001), with no difference in sBP between vehicle and SZC (p = 0.08). Similar results were observed for diastolic BP. Serum potassium levels fell with SZC (p < 0.02), but not vehicle or patiromer. Urine potassium decreased with both patiromer and SZC versus vehicle (p < 0.01); urine sodium increased with SZC (p < 0.01); and urine calcium increased with patiromer (p < 0.01). Urine phosphorus decreased with patiromer (p < 0.01) but increased with SZC (p < 0.01). Patiromer resulted in less proteinuria than vehicle or SZC (both p < 0.017). After 8 weeks, treatment with patiromer resulted in lower BP in rats than vehicle or SZC. Further studies are needed to determine the mechanism of the differential effect of potassium binders on rat BP.

The role of glycosaminoglycans in blood pressure regulation.

Essential hypertension (HT) is the global health problem and is a major risk factor for the development of cardiovascular and kidney disease. High salt intake has been associated with HT and impaired kidney sodium excretion is considered to be a major mechanism for the development of HT. Although kidney has a very important role in regulation of BP, this traditional view of BP regulation was challenged by recent findings suggesting that nonosmotic tissue sodium deposition is very important for BP regulation. This new paradigm indicates that sodium can be stored and deposited nonosmotically in the interstitium without water retention and without increased BP. One of the major determinants of this deposition is glycosaminoglycans (GAGs). By binding to GAGs found in the endothelial surface layer (ESL) which contains glycocalyx, sodium is osmotically inactivated and not induce concurrent water retention. Thus, GAGs has important function for homeostatic BP and sodium regulation. In the current review, we summarized the role of GAGs in ESL and BP regulation.

Circadian Urinary Excretion of Water, and Not Salt, Is Affected by the White Coat Effect.

Hypertension is an important morbidity factor. The prognostic consequences of the white-coat effect have been studied extensively. The repercussion on the circadian rhythm of urinary water and salt excretion in the same subgroup remain, conversely, among the open topics. Postulating an impaired diurnal sodium and volume excretion we decided to investigate both, in subjects with or without a white-coat effect, in the general population. A sample of 1023 subjects, has been considered. We collected 24-h urine samples, divided in day and night, and we measured the blood pressure with an Ambulatory Blood Pressure Monitoring (ABPM). ABPM values were then compared with physician collected in-office values to assign subjects to the group with or without the white-coat effect. Concerning the circadian pattern of urinary sodium excretion, we found no significant differences between the groups. There was instead in the white-coat effect group a higher night/day ratio of urinary water excretion. The white-coat effect, has been considered a potential hypertension precursor, and its consequent handling could be prospectively relevant in hypertension prevention. The absence of repercussions on the urinary circadian sodium excretion pattern and on the potentially related risk factors in subjects with a white coat effect is reassuring. The clinical significance of the impact on the night/day ratio of water excretion needs to be further investigated.

Salt-sensitive hypertension after reversal of unilateral ureteral obstruction

The incidence of ureter obstruction is increasing and patients recovering from this kidney injury often progress to chronic kidney injury. There is evidence that a long-term consequence of recovery from ureter obstruction is an increased risk for salt-sensitive hypertension. A reversal unilateral ureteral obstruction (RUUO) model was used to study long-term kidney injury and salt-sensitive hypertension. In this model, we removed the ureteral obstruction at day 10 in mice. Mice were divided into four groups: (1) normal salt diet, (2) high salt diet, (3) RUUO normal salt diet, and (4) RUUO high salt diet. At day 10, the mice were fed a normal or high salt diet for 4 weeks. Blood pressure was measured, and urine and kidney tissue collected. There was a progressive increase in blood pressure in the RUUO high salt diet group. RUUO high salt group had decreased sodium excretion and glomerular injury. Renal epithelial cell injury was evident in RUUO normal and high salt mice as assessed by neutrophil gelatinase-associated lipocalin (NGAL). Kidney inflammation in the RUUO high salt group involved an increase in F4/80 positive macrophages; however, CD3+ positive T cells were not changed. Importantly, RUUO normal and high salt mice had decreased vascular density. RUUO was also associated with renal fibrosis that was further elevated in RUUO mice fed a high salt diet. Overall, these findings demonstrate long-term renal tubular injury, inflammation, decreased vascular density, and renal fibrosis following reversal of unilateral ureter obstruction that could contribute to impaired sodium excretion and salt-sensitive hypertension.

Activation of TRPV1 improves natriuresis and salt sensitivity in high-fat diet fed mice

Western diet (WD) intake increases morbidity of obesity and salt-sensitive hypertension albeit mechanisms are largely unknown. We investigated the role of transient receptor potential vanilloid 1 (TRPV1) in WD intake-induced hypertension. TRPV1−/− and wild-type (WT) mice were fed a normal (CON) or Western diet (WD) for 16–18 weeks. Mean arterial pressure (MAP) after normal sodium glucose (NSG) loading with or without L-NAME (a NO synthase inhibitor) or N-oleoyldopamine (OLDA, a TRPV1agonist) was not different between the two strains on CON.WT or TRPV1−/− mice fed WD had increased MAP after NSG, with a greater magnitude in TRPV1−/− mice. OLDA decreased while L-NAME increased MAP in WT-WD but not in TRPV1−/−-WD mice. The urinary nitrates plus nitrites excretion (UNOx), an indicator of renal NO production, was increased in both strains on CON after NSG. TRPV1 ablation with WD intake abolished NSG-induced increment in UNOx. OLDA further increased while L-NAME prevented NSG-induced increment in UNOx in WT-WD mice. Urinary sodium excretion was increased in both strains on CON and in WT-WD mice but not in TRPV1−/−-WD mice after NSG. OLDA further increased while L-NAME prevented NSG-induced increases in sodium excretion in WT-WD but not in TRPV1−/−-WD mice. Thus, TRPV1 ablation increases salt sensitivity during WD intake possibly via impaired renal NO production and sodium excretion. Activation of TRPV1 enhances renal NO production and sodium excretion, resulting in prevention of increased salt sensitivity during WD intake.

The Dropsy of Popes (1555–1978): A Bad Prognostic Sign Foreboding of Death

The purpose of this study is to explore the historical background of edema as a prognostic sign in popes, a special category of medical subjects whose health status was closely monitored and chronicled because of their unique important status in the events of their times. Nine out of 51 popes, who reigned in the years 1555–1978, died edematous at a mean age of 75.5 years of age. The cause of edema was: heart failure for John Paul I, liver disease, obstructive nephropathy associated with anemia for Paul IV, who also suffered from deep vein thrombosis, and malnutrition for Innocent XIII. Chronic kidney disease due to renal stones of gouty origin caused edema in Clement VIII, Clement X, Clement XI, and Benedict XIV. Obstructive nephropathy due to renal stones of non-gouty origin caused edema in Clement XIII, whereas toxic nephropathy due to the use of mercurials caused edema in Clement XIV. Innocent XI, Benedict XIV, and Clement XIV were bled before death because of impending pulmonary edema. It is not surprising that chronic kidney disease was a significant cause of edema in popes with chronic kidney disease which is associated with impaired sodium excretion. The edema was likely aggravated by the excessive dietary salt intake of the period when the importance of sodium chloride restriction was still not discovered and effective diuretic agents were not available.

Chronic Circadian Disruption Contributes to Excess Aldosterone Production and Loss of Diurnal Electrolyte Excretion

Disruptions in circadian rhythms contribute to a number of cardiometabolic health risks, including kidney disease. While chronic circadian disruption (CCD) has been recognized as a health risk in a number of other organ systems, we do not understand the effects of CCD on kidney function and sodium handling factors. Individuals with CCDs such as rotating shift workers, have an increased incidence of kidney and cardiovascular disease including impaired sodium excretion patterns. We hypothesized that this impaired sodium excretion is due in part to increased activation of the renin‐aldosterone‐angiotensin system (RAAS). We recently observed that CCD interrupts blood pressure, heart rate, and activity rhythms. Male 8‐week‐old C57BL/6J mice were placed under either a normal 12:12 light/dark cycle (control) protocol or a 10:10 light/dark cycle (CCD, T20) protocol, each with ad libitum food and water for 12 weeks. Previous experiments with this model have demonstrated that after 10 weeks the T20 mice did not exhibit a significant difference in mean arterial pressure (MAP) between the light and dark cycles (114±13mmHg during dark cycle, 113±12mmHg during light cycle, p=0.86) as opposed to control animals, who did display a typical circadian pattern in MAP averaging 119±3 mmHg during the dark cycle and 101±2 mmHg during the light cycle (p&gt;0.001). The same pattern persisted in the heart rate (HR) of these animals, with the T20 animals lacking a diurnal variation in HR (537±14 BPM during dark cycle, 526±5 BPM during light cycle, p=0.48), and the control animals maintaining a dark/light period difference (584±11 BPM during dark cycle, 511±4 BPM during light cycle, p=0.001). Prior studies indicate that the circadian timing system controls sodium reabsorption throughout the nephron by effecting aldosterone effects on collecting duct sodium transport systems via the molecular clock. Therefore, aldosterone excretion was assayed in urine from control(n=6) and T20 mice (n=4). Interestingly, T20 animals excreted an order of magnitude more aldosterone than control animals (p&lt;0.015 2‐way ANOVA) and lacked a diurnal variation in aldosterone excretion (115.1±51.5 µg/hr during the dark cycle, 64.1±13.1 µg/hr during the light cycle, p=0.17 dark v. light) and during both dark and light phases (0.080±0.014 µg/hr and 0.012±0.003 µg/hr, respectively, p=0.02 dark v. light). T20 mice also lacked a diurnal variation in sodium (UNaV) and potassium (UKV) excretion as compared to control mice. These results suggest that CCD disrupts diurnal sodium handling, at least in part, by disruptions in the RAAS. We further propose that the loss of blood pressure rhythms may be due to hyperaldosteronism in CCD mice.

Paternal long-term PM2.5 exposure causes hypertension via increased renal AT1R expression and function in male offspring.

Maternal exposure to fine particulate matter (PM2.5) causes hypertension in offspring. However, paternal contribution of PM2.5 exposure to hypertension in offspring remains unknown. In the present study, male Sprague-Dawley rats were treated with PM2.5 suspension (10 mg/ml) for 12 weeks and/or fed with tap water containing an antioxidant tempol (1 mM/L) for 16 weeks. The blood pressure, 24 h-urine volume and sodium excretion were determined in male offspring. The offspring were also administrated with losartan (20 mg/kg/d) for 4 weeks. The expressions of angiotensin II type 1 receptor (AT1R) and G-protein–coupled receptor kinase type 4 (GRK4) were determined by qRT-PCR and immunoblotting. We found that long-term PM2.5 exposure to paternal rats caused hypertension and impaired urine volume and sodium excretion in male offspring. Both the mRNA and protein expression of GRK4 and its downstream target AT1R were increased in offspring of PM2.5-exposed paternal rats, which was reflected in its function because treatment with losartan, an AT1R antagonist, decreased the blood pressure and increased urine volume and sodium excretion. In addition, the oxidative stress level was increased in PM2.5-treated paternal rats. Administration with tempol in paternal rats restored the increased blood pressure and decreased urine volume and sodium excretion in the offspring of PM2.5-exposed paternal rats. Treatment with tempol in paternal rats also reversed the increased expressions of AT1R and GRK4 in the kidney of their offspring. We suggest that paternal PM2.5 exposure causes hypertension in offspring. The mechanism may be involved that paternal PM2.5 exposure-associated oxidative stress induces the elevated renal GRK4 level, leading to the enhanced AT1R expression and its-mediated sodium retention, consequently causes hypertension in male offspring.

ANGIOTENSIN II MODULATES MONOCYTE-TO-MACROPHAGE DIFFERENTIATION: EFFECT ON THP-1-LIKE MACROPHAGE CELL PHENOTYPE, POLARIZATION AND REACTIVE OXYGEN SPECIES GENERATION

Objective: Circulating monocytes and tissue macrophages play complex roles in the pathogenesis of hypertension, a highly prevalent cardiovascular(CV) risk factor associated with increased CV morbidity and mortality. One of the main effector cells in innate immune response are macrophages and several studies have reported their implication in pathophysiology of hypertension. In the vasculature and kidney, macrophage-derived reactive oxygen species (ROS) and inflammatory cytokines cause endothelial dysfunction, resulting in vascular oxidative stress and impairment of sodium excretion. Furthermore, angiotensin (Ang) II infusion is known to induce hypertension and vascular damage, particularly endothelial dysfunction, inflammation and oxidative stress. Renin angiotensin system (RAS) stimulation triggers monocyte activation and migration. ROS and cytokines secreted by macrophages can modulate blood pressure(BP) by triggering vascular endothelial dysfunction. Angiotensin II receptors are expressed in immune cells like T cells and monocytes. The aim of our study was to explore the effect of angiotensin II on THP-1-like macrophage cell phenotype, polarization and ROS generation. Design and method: THP-1-like macrophage cells were incubated with Ang II (100 nM) for 48 h. Cell phenotype analysis was performed using flow cytometry after intracellular and extracellular staining with CD11c, CD64, CD206, HLA-DR, CD116 and TNFa. We determined the effect of Ang II stimulation on ROS generation by macrophages using Cell Rox kit; viability and apoptosis using immunofluorescence and cell phenotyping using flow cytometry. Results: There was a significant increase in ROS generation in cells incubated with Ang II compared with control. Ang II induces THP-1-like macrophage polarization by increasing HLA-DR, CD11c and TNFa and decreasing CD206 markers. Ang II significantly increases apoptosis in a time-dependent fashion from 24 to 72-h and changed cell CD inflammatory markers after 24-h incubation. Conclusions: Differences in ROS generation, phenotype and polarization of THP-1-like macrophage cells in presence of Ang-II may underlie the role of monocyte/macrophages in vascular inflammation. The downstream pathways may be a potential therapeutic target for ang-II induced inflammation and vascular damage in hypertension.

Role of Rho in Salt-Sensitive Hypertension.

A high amount of salt in the diet increases blood pressure (BP) and leads to salt-sensitive hypertension in individuals with impaired renal sodium excretion. Small guanosine triphosphatase (GTP)ase Rho and Rac, activated by salt intake, play important roles in the pathogenesis of salt-sensitive hypertension as key switches of intracellular signaling. Focusing on Rho, high salt intake in the central nervous system increases sodium concentrations of cerebrospinal fluid in salt-sensitive subjects via Rho/Rho kinase and renin-angiotensin system activation and causes increased brain salt sensitivity and sympathetic nerve outflow in BP control centers. In vascular smooth muscle cells, Rho-guanine nucleotide exchange factors and Rho determine sensitivity to vasoconstrictors such as angiotensin II (Ang II), and facilitate vasoconstriction via G-protein and Wnt pathways, leading to increased vascular resistance, including in the renal arteries, in salt-sensitive subjects with high salt intake. In the vascular endothelium, Rho/Rho kinase inhibits nitric oxide (NO) production and function, and high salt amounts further augment Rho activity via asymmetric dimethylarginine, an endogenous inhibitor of NO synthetase, causing aberrant relaxation and increased vascular tone. Rho-associated mechanisms are deeply involved in the development of salt-sensitive hypertension, and their further elucidation can help in developing effective protection and new therapies.

Abstract 13013: Grk4-mediated Adiponectin Receptor-1 Phosphorylative Desensitization as a Novel Mechanism of Reduced Renal Sodium Excretion in Hypertension

Introduction: Hypertensive patients have impaired sodium excretion. However, the mechanisms are incompletely understood. There is interaction between kidney and adipose tissue. Whether and how adiponectin, one of adipokines, contributes to impaired sodium excretion in hypertension has not been previously investigated. Hypothesis: Adiponectin promotes natriuresis and diuresis and their impairment is involved in hypertension. Methods: We used Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHRs), GRK4g142A&gt;V transgenic mice to test the natriuresis-effect of adiponectin through intrarenal arterial infusion. Renal proximal tubule (RPT) cells, adiponectin knock out (Adipo-/-) mice, mutant plasmid were used. Results: We demonstrate that sodium excretion was reduced in Adipo-/- mice. The intrarenal arterial infusion of adiponectin induced natriuresis and diuresis in WKY rats, which was impaired in SHRs. Adiponectin inhibited Na+-K+-ATPase activity in RPT cells from WKY rats but not from SHRs. Increased adiponectin receptor phosphorylation and subsequent uncoupling from Gai, rather than altered adiponectin receptor expression, were responsible for the loss of adiponectin-mediated inhibition of RPT Na+-K+-ATPase activity, impaired natriuresis and diuresis in SHRs. Mutation of the AdipoR1 phosphorylation site restored its linkage to Gai and the adiponectin-mediated inhibition of Na+-K+-ATPase activity in RPT cells from SHRs. Finally, we identified G protein-coupled receptor kinase 4 (GRK4) as the cause of adiponectin receptor hyper-phosphorylation. GRK4g142A&gt;V transgenic mice replicated the abnormal adiponectin function in SHRs, whereas down-regulation of GRK4 by renal-ultrasound directed siRNA restored the adiponectin-mediated sodium excretion and reduced the blood pressure in SHRs. Conclusions: The stimulatory effect of adiponectin on sodium excretion is impaired in hypertension, which is attributable to increased renal GRK4 expression and subsequent adiponectin receptor hyper-phosphorylation. Targeting GRK4/adiponectin receptor/Gai may restore the impaired adiponectin-mediated sodium excretion in hypertension, thus representing a novel strategy against hypertension.

GRK4-mediated adiponectin receptor-1 phosphorylative desensitization as a novel mechanism of reduced renal sodium excretion in hypertension

Hypertensive patients have impaired sodium excretion. However, the mechanisms are incompletely understood. Despite the established association between obesity/excess adiposity and hypertension, whether and how adiponectin, one of the adipokines, contributes to impaired sodium excretion in hypertension has not been previously investigated. The current study tested the hypothesis that adiponectin promotes natriuresis and diuresis in the normotensive state. However, impaired adiponectin-mediated natriuresis and diuresis are involved in pathogenesis of hypertension. We found that sodium excretion was reduced in adiponectin knockout (Adipo-/-) mice; intrarenal arterial infusion of adiponectin-induced natriuresis and diuresis in Wistar-Kyoto (WKY) rats. However, the natriuretic and diuretic effects of adiponectin were impaired in spontaneously hypertensive rats (SHRs), which were ascribed to the hyperphosphorylation of adiponectin receptor and subsequent uncoupling from Gαi. Inhibition of adiponectin receptor phosphorylation by a specific point mutation restored its coupling with Gαi and the adiponectin-mediated inhibition of Na+-K+-ATPase activity in renal proximal tubule (RPT) cells from SHRs. Finally, we identified G protein-coupled receptor kinase 4 (GRK4) as a mediator of adiponectin receptor hyperphosphorylation; mice transgenic for a hyperphosphorylating variant of GRK4 replicated the abnormal adiponectin function observed in SHRs, whereas down-regulation of GRK4 by renal ultrasound-directed small interfering RNA (siRNA) restored the adiponectin-mediated sodium excretion and reduced the blood pressure in SHRs. We conclude that the stimulatory effect of adiponectin on sodium excretion is impaired in hypertension, which is ascribed to the increased renal GRK4 expression and activity. Targeting GRK4 restores impaired adiponectin-mediated sodium excretion in hypertension, thus representing a novel strategy against hypertension.

Impaired Daytime Urinary Sodium Excretion Impacts Nighttime Blood Pressure and Nocturnal Dipping at Older Ages in the General Population.

The circadian rhythm of urinary sodium excretion is related to the diurnal blood pressure regulation (BP) and the nocturnal dipping pattern. The renal sodium excretion expressed as daytime/nighttime ratio impacts BP, but a limited number of studies have investigated this topic to date. In this cross-sectional study, we aimed to investigate the impact of different daily patterns of sodium excretion (comparing low with high ratios) on BP and nocturnal dipping and to explore the relationship with age. Twenty-four-hour ambulatory BP monitoring and daytime and nighttime urinary sodium collections were used to assess 1062 subjects in Switzerland. Analyses were performed according to the day/night urinary sodium excretion ratio quartiles (Q1–Q4) and by age group (≤50 and ≥50 years). Subjects in Q1 can be considered low excretors of sodium during the daytime since the rate of sodium excretion during the daytime was 40% lower than that of subjects in Q4. Quartiles of the day/night urinary sodium excretion ratio showed that subjects in Q1 were 7 years older and had respectively 6 and 5 mmHg higher nighttime systolic and diastolic BP and a higher nocturnal dipping compared with subjects in Q4 (p-value ≤0.001). Associations found were significant only for subjects older than 50 years (all p < 0.05). The present results suggest that a decreased capacity to excrete sodium during daytime is more prevalent as age increases and that it impacts nighttime blood pressure and nocturnal dipping in older subjects.

Role of the renin-angiotensin system in kidney development and programming of adult blood pressure.

Adverse events during fetal life such as insufficient protein intake or elevated transfer of glucocorticoid to the fetus may impact cardiovascular and metabolic health later in adult life and are associated with increased incidence of type 2 diabetes, ischemic heart disease and hypertension. Several adverse factors converge and suppress the fetal renin-angiotensin-aldosterone system (RAAS). The aim of this review is to summarize data on the significance of RAAS for kidney development and adult hypertension. Genetic inactivation of RAAS in rodents at any step from angiotensinogen to angiotensin II (ANGII) type 1 receptor (AT1) receptors or pharmacologic inhibition leads to complex developmental injury to the kidneys that has also been observed in human case reports. Deletion of the 'protective' arm of RAAS, angiotensin converting enzyme (ACE) 2 (ACE-2) and G-protein coupled receptor for Angiotensin 1-7 (Mas) receptor does not reproduce the AT1 phenotype. The changes comprise fewer glomeruli, thinner cortex, dilated tubules, thicker arterioles and arteries, lack of vascular bundles, papillary atrophy, shorter capillary length and volume in cortex and medulla. Altered activity of systemic and local regulators of fetal-perinatal RAAS such as vitamin D and cyclooxygenase (COX)/prostaglandins are associated with similar injuries. ANGII-AT1 interaction drives podocyte and epithelial cell formation of vascular growth factors, notably vascular endothelial growth factor (VEGF) and angiopoietins (Angpts), which support late stages of glomerular and cortical capillary growth and medullary vascular bundle formation and patterning. RAAS-induced injury is associated with lower glomerular filtration rate (GFR), lower renal plasma flow, kidney fibrosis, up-regulation of sodium transporters, impaired sodium excretion and salt-sensitive hypertension. The renal component and salt sensitivity of programmed hypertension may impact dietary counseling and choice of pharmacological intervention to treat hypertension.

Is urinary excretion of plasminogen associated with development of pre-eclampsia? An observational, explorative case–control study

ObjectivesPre-eclampsia (PE) is characterised by renal glomerular endotheliosis and injury to the glomerular filtration barrier with proteinuria. Patients with PE display aberrant filtration of the plasma proenzyme plasminogen which is...

Role of Thioredoxin 1 in Impaired Renal Sodium Excretion of hD 5 R F173L Transgenic Mice.

BackgroundDopamine D5 receptor (D5R) plays an important role in the maintenance of blood pressure by regulating renal sodium transport. Our previous study found that human D5R mutant F173L transgenic (hD 5 R F173L‐TG) mice are hypertensive. In the present study, we aimed to investigate the mechanisms causing this renal D5R dysfunction in hD 5 R F173L‐TG mice.Methods and ResultsCompared with wild‐type D5R‐TG (hD 5 R WT‐TG) mice, hD 5 R F173L‐TG mice have higher blood pressure, lower basal urine flow and sodium excretion, and impaired agonist‐mediated natriuresis and diuresis. Enhanced reactive oxygen species production in hD 5 R F173L‐TG mice is caused, in part, by decreased expression of antioxidant enzymes, including thioredoxin 1 (Trx1). Na+‐K+‐ATPase activity is increased in mouse renal proximal tubule cells transfected with hD 5 R F173L, but is normalized by treatment with exogenous recombinant human Trx1 protein. Regulation of Trx1 by D5R occurs by the phospholipase C/ protein kinase C (PKC) pathway because upregulation of Trx1 expression by D5R does not occur in renal proximal tubule cells from D1R knockout mice in the presence of a phospholipase C or PKC inhibitor. Fenoldopam, a D1R and D5R agonist, stimulates PKC activity in primary renal proximal tubule cells of hD5R WT ‐TG mice, but not in those of hD 5 R F173L‐TG mice. Hyperphosphorylation of hD5RF173L and its dissociation from Gαs and Gαq are associated with impairment of D5R‐mediated inhibition of Na+‐K+‐ATPase activity in hD 5 R F173L‐TG mice.ConclusionsThese suggest that hD 5 R F173L increases blood pressure, in part, by decreasing renal Trx1 expression and increasing reactive oxygen species production. Hyperphosphorylation of hD5RF173L, with its dissociation from Gαs and Gαq, is the key factor in impaired D5R function of hD 5 R F173L‐TG mice.

Sex‐specific Impairment of Diurnal Renal Na+ Excretion in Obese Sprague‐Dawley Rats

The role of the renal endothelin system in obesity is poorly understood despite playing a key role in excreting a high salt diet. Sodium excretion follows a diurnal rhythm that is controlled by central and peripheral clock genes. The aim of this study was to determine whether the renal endothelin system is disrupted in obesity and interferes with the diurnal rhythm of Na+ excretion. Our overarching hypothesis is that diet‐induced obesity impairs salt handling in a time of day‐dependent manner through renal endothelin dysfunction. Male and female Sprague‐Dawley rats were put on either 45 Kcal% fat (high fat, HF) or control 10 Kcal% fat (normal fat, NF) diet starting at 6 weeks of age. After 8 weeks, rats were put in metabolic cages for 2 days of acclimation, followed by 12‐hour collections of baseline urine output, food and water intake for an additional 2 days. On day 5, rats were given an acute salt load of (900 mEq NaCl in 1ml H2O, i.p.) either at the beginning of their inactive period (Zeitgeber time 0, ZT0) or active period (Zeitgeber time 12, ZT12). Urine was collected over the following 24 hours in 12‐hour intervals. Both male and female rats on HF diet showed significantly greater body weights (414 ± 6 vs 386 ± 6 gm in males, n= 12 and 303 ± 9 vs 266 ± 7 gm in females, n= 8) and total body fat measured by QMR (10.8 ± 0.5 vs 6.7 ± 0.4% in males, n= 12 and 15.3 ± 0.9 vs 9.8 ± 0.5% in females, n= 8) compared to NF controls. Male rats on HF given salt load at ZT0 showed similar urine and Na+ excretion (UNaV) rates compared to lean controls (DUNaV was 395 ± 46 vs 496 ± 71 μEq/12 hrs in the first 12 hours post‐load, n= 12). However, HF rats showed significantly delayed natriuresis in response to ZT12 salt load (DUNaV was 605 ± 98 vs 960 ± 59 μEq/12 hrs in the first 12 hours post‐load, n= 8). On the other hand, obese female rats showed an intact natriuretic response at both ZT0 (772 ± 32 vs 673 ± 84 μEq/12 hrs in the first 12 hours post‐load, n= 8) and ZT12 (671 ± 153 vs 801. ± 106 μEq/12 hrs in the first 12 hours post‐load, n=8) compared to NF. Assessment of urinary endothelin‐1 (ET1) showed significantly decreased active period ET1 excretion rates in obese males (0.3 ± 0.04 vs 0.3 ± 0.04 pg/12 hrs inactive and 0.8 ± 0.1 vs 1.5 ± 0.1 pg/12 hrs active period, n=11) and following salt challenge (0.9 ± 0.1 vs 1.7 ± 0.2 pg/12 hrs in the second 12 hrs of ZT0 salt load and 1.5 ± 0.1 vs 2.7 ± 0.1 pg/12 hrs in the first 12 hrs of ZT12 salt load, n=11). The reduced ET1 in the HF group was evident during their active period, while inactive period ET1 was similar among groups. Obese female rats, on the other hand, showed comparable urine ET1 values to their lean control, at both baseline (0.5 ± 0.2 vs 0.3 ± 0.1 pg/12 hrs at inactive and 1.1 ± 0.2 vs 1.4 ± 0.2 pg/12 hrs at active period, n=5) and following the acute salt load regardless of time of day (0.8 ± 0.1 vs 0.7 ± 0.1 pg/12 hrs at ZT0 and 1.3 ± 0.3 vs 1.6 ± 0.1 pg/12 hrs at ZT12). In conclusion, our study shows that impairment of sodium excretion in obesity is time‐of‐day and sex‐dependent. It also shows a strong correlation between renal endothelin‐1 dysfunction and impaired Na+ excretion in obese male Sprague‐Dawley ratsSupport or Funding InformationP01 HL136267 to DMPThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Increased sodium transporters in distal nephron segments are associated with clozapineinduced hypertension

Dopamine receptor subtype 4 (D4R) antagonists, such as clozapine, are used in the treatment of schizophrenia. A common side effect of clozapine is hypertension but the mechanism of the clozapine‐induced hypertension is unknown. D4R plays an important role in blood pressure (BP) regulation; deletion of the D4R gene in mice causes hypertension. To determine if renal mechanisms are involved in clozapine‐induced hypertension, we characterized the distribution of D4R in mouse kidney and measured BP, water and sodium balance, and renal protein expression of sodium transporters in clozapine‐ and vehicle‐treated mice. D4R (immunocytochemistry) was mainly located in thick ascending limb, distal convoluted tubule and cortical and medullary collecting ducts; there is slight staining of D4R in the proximal convoluted but not straight tubule. Clozapine (20mg/kg/day) or vehicle was delivered subcutaneously to adult male C57BL/6J mice for seven days via osmotic mini‐pump (n=5/group). In clozapine‐treated mice, systolic (110±0.5, mm Hg, under anesthesia) and diastolic BPs (76.6±1),) were elevated, relative to vehicle‐treated mice (SBP=97.6±1.6, DBP=69.5±2.3). Food and water intake, body weight, serum electrolytes and creatinine, urine volume, and creatinine clearance were similar in the two groups. The sodium excretion tended to decrease while sodium excretion and blood pressure plot in clozapine‐treated mice was shifted to the right of the vehicle‐treated mice. Renal protein expressions (immunoblotting) of sodium hydrogen exchanger 3 and sodium phosphate cotransporter 2 were similar in clozapine‐ and vehicle‐treated mice. However, the renal protein expressions of sodium potassium 2 chloride cotransporter (180±21, % of control) and sodium chloride cotransporter (171±22% ), and the three subunits of epithelial sodium channel, α (140±7%), β (166±21%) and γ (55 kDa=130±7%, 85kDa=114±10% ), were greater in clozapine‐than vehicle‐treated mice. Renal protein expression of a‐sodium potassium ATPase was also slightly increased (118±4%) in clozapine‐treated mice. These findings suggest that inhibition of D4R by clozapine increases sodium transporters in distal nephron segments. Furthermore, a similar increase in the protein expression of sodium chloride cotransporter was also found in the immortalized mouse renal distal convoluted tubule cells in vitro with inhibition of D4R with its siRNA and antagonists. Thus, inhibition of renal D4R may cause the impaired sodium excretion that may be responsible for the increased blood pressure in clozap‐inetreated mice.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Role of endocannabinoid system in pressure natriuresis, in mice with and without fatty acid amide hydrolase

Kidney is the major organ responsible for long term regulation of blood pressure. Impaired renal sodium excretion and perfusion pressure is main driver of hypertension. This perfusion pressure and renal sodium excretion is called as acute pressure natriuresis (PN). It was surprising to know that none of the study explained the role of endocannabinoids (ECs) in PN and importance of EC hydrolyzing enzymes in the modulation of PN mechanism. This study set out with the primary objective that after acute increase in mean arterial pressure (MAP) either anandamide (AEA) or 2‐arachidonoyl glycerol (2‐AG) is released in the kidney which modulate PN by lowering MAP, natriuretic and diuretic activities. Secondly, effect of genetic and pharmacological ablation of fatty acid amide hydrolase (FAAH) genes in mice modulate the PN relationship. Mice were anesthetized and cannulation was done in trachea, jugular vein, carotid artery and bladder. PN model was established in animals by ligations of celiac and superior mesenteric arteries (CML) and abdominal aorta (AL) while MAP and UV were observed at 10 minutes intervals in FAAH wild type and its knock out littermate. Ligation of celiac and mesenteric arteries resulted in increase in MAP (from baseline to CML‐1 phase) 91 to 121 (mmHg) with corresponding increase in UV from 9 to 17 (ul/min/g kwt) and urinary sodium (UNa) from 1.3 to 3.0 (umol/min/g kwt). MAP and UV reported at CML‐2 ligation was 113 mmHg and 17 ul/min/g kwt. MAP at AL‐1 and AL‐2 was noted as 119 and 104 (mmHg) with corresponding increase in UV 21 and 26 (ul/min/g kwt) while UNa was noted as 3.4 umol/min/g kwt. Pretreatment with selective FAAH inhibitor in the medulla of the kidney resulted in increase in MAP from baseline 88 to 131 and 109 mmHg at CML‐1, CML‐2 respectively while MAP was also observed 119 and 123 mmHg at AL‐1 and AL‐2 phase. There was significant increase (p&lt;0.05) in UV after pretreatment with FAAH inhibitor which was noted 26 and 28 (ul/min/g kwt) at CML‐1 and CML‐2 while 49 and 48 (ul/min/g kwt) at AL‐1 and AL‐2 respectively. FAAH KO animals shifted MAP and UV curves of PN study towards right when compared to FAAH WT group. Analytical data showed significant increase (P&lt;0.05) in 2‐AG levels in the kidney and plasma samples of FAAH WT animals underwent through PN when compared to control FAAH WT while AEA levels was significantly higher (p&lt;0.05) in the kidney of FAAH KO animals with PN as compared to respective control group. It can be concluded that endocannabinoids are released in response to acute increase in MAP and results in diuretic and natriuretic activities which lowers the MAP and keep PN relationship intact. Lastly, regional blocking of FAAH in the kidney shift the MAP and UV curves of the PN models towards left and positively modulate the PN relationship.Support or Funding InformationThis work was supported by National Institute of Diabetes and Digestive and Kidney Disorders grant, DK102539This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Collagen type IV remodelling gender-specifically predicts mortality in decompensated cirrhosis.

Background & AimsRemodelling of extracellular matrix is crucial in progressive liver fibrosis. Collagen type III desposition has been shown in acute decompensation. Extratracellular matrix is compiled of deposition of various components. The role of basement membrane collagen type IV in advanced cirrhosis and acute decompensation is unclear and investigated in this study.MethodsPatients with decompensated cirrhosis from the prospective NEPTUN cohort (ClinicalTrials.gov Identifier: NCT03628807), who underwent transjugular intrahepatic portosystemic shunt procedure were included. Clinical and laboratory parameters, PRO‐C4 and C4M levels were measured in blood samples from portal and hepatic veins just before transjugular intrahepatic portosystemic shunt placement.ResultsLevels of C4M and PRO‐C4 are significantly lower in patients with massive ascites and impaired renal sodium excretion. C4M and PRO‐C4 show gender‐specific profiles with significantly lower levels in females compared to males. Females with higher C4M levels show higher mortality. By contrast, males with higher C4M levels show lower mortality. In multivariate Cox regression analysis, C4M is an independent predictor of survival in female patients.ConclusionThis study shows that markers of collagen type IV remodelling do not accumulate in severe renal dysfunction. Although collagen type IV degradation markers derive from the liver, portal venous C4M levels are relevant for survival. Moreover, it demonstrates that circulating C4M shows gender‐specific profiles, which can independently predict survival in female patients with decompensated cirrhosis.