Kidney tubular transcription co-activator, Yes-associated protein 1 (YAP), controls the expression of collecting duct aquaporins and water homeostasis.
Kidney international
Final urine volume and concentration are defined by water reabsorption through the water channel proteins aquaporin (AQP)-2, -3 and -4 in the collecting duct. However, the transcriptional regulation of these AQPs is not well understood. The Hippo/Yes-associated protein 1 (YAP) pathway plays an important role in organ size control and tissue homeostasis. When the Hippo pathway including the Mst1/Mst2 kinases is inhibited, YAP is activated and functions as a transcription co-activator. Our previous work revealed a pathological role of tubular YAP activation in chronic kidney disease, but the physiological role of YAP in the kidney remains to be established. Here, we found that tubule-specific Yap knockout mice showed increased urine output and decreased urinary osmolality. Decreases in Aqp2, -3 and -4 mRNA and protein abundance in the kidney were evident in Yap knockout mice. Analysis of Mst1/Mst2 double knockout and Mst1/Mst2/Yap triple knockout mice showed that expression of Aqp2 and Aqp4 but not Aqp3 was dependent on YAP. Furthermore, YAP was recruited to the promoters of the Aqp2 and Aqp4 genes and stimulated their transcription. Interestingly, YAP was found to interact with transcription factors GATA2, GATA3 and NFATc1. These three factors promoted Aqp2 transcription in a YAP dependent manner in collecting duct cells. These three factors also promoted Aqp4 transcription whereas only GATA2 and GATA3 enhanced Aqp3 transcription. Thus, our results suggest that YAP promotes Aqp2 and Aqp4 transcription, interacts with GATA2, GATA3 and NFATc1 to control Aqp2 expression, while Aqp-2, -3 and -4 exploit overlapping mechanisms for their baseline transcriptional regulation.
10.1016/j.kint.2022.10.007
Changes in Oxygen Consumption and Metabolomic Profiles in the Kidney of Sprague-Dawley Rat fed a High-Salt Diet.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology
The metabolism of oxygen and substrates in the kidney under normal conditions and in salt-sensitive hypertension is still not well understood. A novel method was developed to collect renal arteriovenous blood and urine from conscious freely moving rats, while measuring renal blood flow (RBF) and blood pressure (BP). As such, global renal O consumption and metabolic profiles can be studied in response to various stimuli such as changes in salt diet. We report here changes observed in male Sprague-Dawley rats (SD; 10 wk age) before and after 21 days switching from a 0.4% NaCl (LS) diet to a 4.0% NaCl diet (HS). Rats were surgically instrumented with a renal ultrasonic artery flow probe (Transonic), a femoral arterial catheter, and a renal venous catheter and placed in a movement response caging system. After 7 days recovery, control levels of RBF and BP (24 hr/day) were obtained, and arterial and renal venous blood were sampled. Rats were then switched to the HS diet and blood sampled at days 7, 14 and 21 while RBF and BP were recorded continuously throughout the study. Blood O content was measured by radiometer immediately after blood collection and plasma samples frozen for global metabolomic analysis by the Jackson laboratory. The metabolomic analysis (Thermo Q-Exactive Orbitrap coupled to a Vanquich UPLC system) was performed in 4 modes (C18 positive, C18 negative, HILIC positive and HILIC negative). Average 24 hr mean arterial pressure (MAP) of the SD rats increased slightly over the 21 days of the HS diet from 111 ± 2 to 119 ± 5 mmHg (p<0.05; n=7). Average 24 hr RBF rose from 9.2 ± 0.6 to 11.7 + 0.6 ml/min (p<0.05). O consumption increased significantly from 0.17 ± 0.03 to 0.26 ± 0.03 ml/min (p<0.05) as did O extraction which increased from 10.8 ± 1.1 % to 15.0 ± 1.2 % by Day 21 of HS diet. Of a total 1205 named metabolites detected, we present here those that differed between arterial and renal venous blood by more than 2-fold and significantly (p<0.05; Benjamini-Hochberg corrected). At the time of this report, in rats fed the LS diet, 33 compounds were found more abundant in arterial blood than in venous blood. 10 compounds were found more abundant in venous blood. The HS diet increased the arterial / venous ratio of some compounds progressively throughout the 21 days while others decreased. No evidence of anaerobic respiration was obtained with lactate, pyruvate, glutamate and TCA cycle related metabolites remaining unchanged throughout the study. Interestingly, some gut microbiome generated compounds were found to differentially altered by the HS diet. Despite no changes in arterial concentrations, a progressive reduction was observed in Triethylamine in the renal venous blood at each time point, while a progressive elevation was observed in Hexanoic acid. Venous levels of Cis-4-Decenedioic acid and Succinylacetone, known to be altered in some metabolic diseases were significantly increased by the HS diet. Urine measurements and cortical and outer medullary tissue measurements are currently under way which together with the RBF will enable calculation of metabolic fluxes of these various metabolites. We conclude that a high-salt diet increases oxygen consumption and alters the metabolomic profiles of the kidney.
10.1096/fasebj.2022.36.S1.R2605
Multi-Effects of Acute Salinity Stress on Osmoregulation, Physiological Metabolism, Antioxidant Capacity, Immunity, and Apoptosis in .
Antioxidants (Basel, Switzerland)
Salinity stress can trigger a series of physiological changes. However, the mechanism underlying the response to acute salinity stress in remains poorly understood. In this study, osmoregulation, physiological metabolism, antioxidant capacity, and apoptosis were examined over 96 h of acute salinity stress. Hemolymph osmolality increased with increasing salinity. After 48 h of salinity exposure, the glucose, triglycerides, total protein, and total cholesterol contents in two salinity stress groups (13 and 26‱ salinity) were significantly lower than those in the 0‱ salinity group. The highest levels of these parameters were detected at 6 h; however, superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) were the lowest at 96 h in the 13‱ salinity group. The activity of immunity-related enzyme alkaline phosphatase (AKP) showed a decreasing trend with increasing salinity and remained at a low level in the 26‱ salinity group throughout the experiment. No significant differences were observed in aspartate aminotransferase (AST), alanine aminotransferase (ALT), or lysozyme (LZM) among the three treatments at 96 h. After 96 h of salinity treatments, the gill filament diameter significantly decreased, and a more pronounced terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive signal was detected in the 13‱ and 26‱ groups compared to that in the 0‱ group. Expression levels of apoptosis-related genes, including Cysteine-aspartic acid protease 3 (), Cysteine-aspartic acid protease 8 (), Cytochrome c (), tumor suppressor gene (), Nuclear factor kappa-B (), and B cell lymphoma 2 ovarian killer () were significantly higher in the 26‱ salinity group than in the other groups at 24 h, but lower than those in the 0‱ salinity group at 96 h. and levels exhibited a significantly positive relationship with MDA, AST, and LZM activity during salinity stress. In the 13‱ salinity group, expression was significantly correlated with SOD, T-AOC, AKP, acid phosphatase, and LZM activity, whereas in the 26‱ group, the AST content was positively correlated with , , and expression. A significant negative relationship was observed between expression and catalase (CAT) activity. These findings provide insight into the mechanisms underlying the response to acute salinity stress and will contribute to improving aquaculture and management practices.
10.3390/antiox12101836
Na delivery and ENaC mediate flow regulation of collecting duct endothelin-1 production.
American journal of physiology. Renal physiology
Collecting duct (CD) endothelin-1 (ET-1) is an important autocrine inhibitor of Na and water transport. CD ET-1 production is stimulated by extracellular fluid volume expansion and tubule fluid flow, suggesting a mechanism coupling CD Na delivery and ET-1 synthesis. A mouse cortical CD cell line, mpkCCDc14, was subjected to static or flow conditions for 2 h at 2 dyn/cm(2), followed by determination of ET-1 mRNA content. Flow with 300 mosmol/l NaCl increased ET-1 mRNA to 65% above that observed under static conditions. Increasing perfusate osmolarity to 450 mosmol/l with NaCl or Na acetate increased ET-1 mRNA to ∼184% compared with no flow, which was not observed when osmolarity was increased using mannitol or urea. Reducing Na concentration to 150 mosmol/l while maintaining total osmolarity at 300 mosmol/l with urea or mannitol decreased the flow response. Inhibition of epithelial Na channel (ENaC) with amiloride or benzamil abolished the flow response, suggesting involvement of ENaC in flow-regulated ET-1 synthesis. Aldosterone almost doubled the flow response. Since Ca(2+) enhances CD ET-1 production, the involvement of plasma membrane and mitochondrial Na/Ca(2+) exchangers (NCX) was assessed. SEA0400 and KB-R7943, plasma membrane NCX inhibitors, did not affect the flow response. However, CGP37157, a mitochondrial NCX inhibitor, abolished the response. In summary, the current study indicates that increased Na delivery, leading to ENaC-mediated Na entry and mitochondrial NCX activity, is involved in flow-stimulated CD ET-1 synthesis. This constitutes the first report of either ENaC or mitochondrial NCX regulation of an autocrine factor in any biologic system.
10.1152/ajprenal.00034.2012
Mitochondrial dysfunction causing cardiac sodium channel downregulation in cardiomyopathy.
Journal of molecular and cellular cardiology
Cardiomyopathy is associated with cardiac Na(+) channel downregulation that may contribute to arrhythmias. Previously, we have shown that elevated intracellular NADH causes a decrease in cardiac Na(+) current (I(Na)) signaled by an increase in mitochondrial reactive oxygen species (ROS). In this study, we tested whether the NADH-mitochondria ROS pathway was involved in the reduction of I(Na) in a nonischemic cardiomyopathic model and correlated the findings with myopathic human hearts. Nonischemic cardiomyopathy was induced in C57BL/6 mice by hypertension after unilateral nephrectomy, deoxycorticosterone acetate (DOCA) pellet implantation, and salt water substitution. Sham operated mice were used as controls. After six weeks, heart tissue and ventricular myocytes isolated from mice were utilized for whole cell patch clamp recording, NADH/NAD(+) level measurements, and mitochondrial ROS monitoring with confocal microscopy. Human explanted hearts were studied using optical mapping. Compared to the sham mice, the arterial blood pressure was higher, the left ventricular volume was significantly enlarged (104.7±3.9 vs. 87.9±6.1 μL, P<0.05), and the ejection fraction was reduced (37.1±1.8% vs. 49.4±3.7%, P<0.05) in DOCA mice. Both the whole cell and cytosolic NADH level were increased (279±70% and 123±2% of sham, respectively, P<0.01), I(Na) was decreased (60±10% of sham, P<0.01), and mitochondrial ROS overproduction was observed (2.9±0.3-fold of sham, P<0.01) in heart tissue and myocytes of myopathic mice vs. sham. Treatment of myocytes with NAD(+) (500 μM), mitoTEMPO (10 μM), chelerythrine (50 μM), or forskolin (5 μM) restored I(Na) back to the level of sham. Injection of NAD(+) (100mg/kg) or mitoTEMPO (0.7 mg/kg) twice (at 24h and 1h before myocyte isolation) to animals also restored I(Na). All treatments simultaneously reduced mitochondrial ROS levels to that of controls. CD38 was found to transduce the extracellular NAD(+) signal. Correlating with the mouse model, failing human hearts showed a reduction in conduction velocity that improved with NAD(+). Nonischemic cardiomyopathy was associated with elevated NADH level, PKC activation, mitochondrial ROS overproduction, and a concomitant decrease in I(Na). Reducing mitochondrial ROS by application of NAD(+), mitoTEMPO, PKC inhibitors, or PKA activators, restored I(Na). NAD(+) improved conduction velocity in human myopathic hearts.
10.1016/j.yjmcc.2012.10.011
Regulation of Vascular and Renal Function by Metabolite Receptors.
Peti-Peterdi János,Kishore Bellamkonda K,Pluznick Jennifer L
Annual review of physiology
To maintain metabolic homeostasis, the body must be able to monitor the concentration of a large number of substances, including metabolites, in real time and to use that information to regulate the activities of different metabolic pathways. Such regulation is achieved by the presence of sensors, termed metabolite receptors, in various tissues and cells of the body, which in turn convey the information to appropriate regulatory or positive or negative feedback systems. In this review, we cover the unique roles of metabolite receptors in renal and vascular function. These receptors play a wide variety of important roles in maintaining various aspects of homeostasis-from salt and water balance to metabolism-by sensing metabolites from a wide variety of sources. We discuss the role of metabolite sensors in sensing metabolites generated locally, metabolites generated at distant tissues or organs, or even metabolites generated by resident microbes. Metabolite receptors are also involved in various pathophysiological conditions and are being recognized as potential targets for new drugs. By highlighting three receptor families-(a) citric acid cycle intermediate receptors, (b) purinergic receptors, and
10.1146/annurev-physiol-021115-105403
Renal Dopamine Oxidation and Inflammation in High Salt Fed Rats.
Banday Anees A,Lokhandwala Mustafa F
Journal of the American Heart Association
Background Oxidative stress and high salt intake could be independent or intertwined risk factors in the origin of hypertension. Kidneys are the major organ to regulate sodium homeostasis and blood pressure and the renal dopamine system plays a pivotal role in sodium regulation during sodium replete conditions. Oxidative stress has been implicated in renal dopamine dysfunction and development of hypertension, especially in salt-sensitive animal models. Here we show the nexus between high salt intake and oxidative stress causing renal tubular dopamine oxidation, which leads to mitochondrial and lysosomal dysfunction and subsequently causes renal inflammation and hypertension. Methods and Results Male Sprague Dawley rats were divided into the following groups, vehicle (V)-tap water, high salt (HS)-1% NaCl, L-buthionine-sulfoximine (BSO), a prooxidant, and HS plus BSO without and with antioxidant resveratrol (R) for 6 weeks. Oxidative stress was significantly higher in BSO and HS+BSO-treated rat compared with vehicle; however, blood pressure was markedly higher in the HS+BSO group whereas an increase in blood pressure in the BSO group was modest. HS+BSO-treated rats had significant renal dopamine oxidation, lysosomal and mitochondrial dysfunction, and increased renal inflammation; however, HS alone had no impact on organelle function or inflammation. Resveratrol prevented oxidative stress, dopamine oxidation, organelle dysfunction, inflammation, and hypertension in BSO and HS+BSO rats. Conclusions These data suggest that dopamine oxidation, especially during increased sodium intake and oxidative milieu, leads to lysosomal and mitochondrial dysfunction and renal inflammation with subsequent increase in blood pressure. Resveratrol, while preventing oxidative stress, protects renal function and mitigates hypertension.
10.1161/JAHA.119.014977
Sugar, salt, immunity and the cause of primary hypertension.
Clinical kidney journal
Despite its discovery more than 150 years ago, the cause of primary hypertension remains unknown. Most studies suggest that hypertension involves genetic, congenital or acquired risk factors that result in a relative inability of the kidney to excrete salt (sodium chloride) in the kidneys. Here we review recent studies that suggest there may be two phases, with an initial phase driven by renal vasoconstriction that causes low-grade ischemia to the kidney, followed by the infiltration of immune cells that leads to a local autoimmune reaction that maintains the renal vasoconstriction. Evidence suggests that multiple mechanisms could trigger the initial renal vasoconstriction, but one way may involve fructose that is provided in the diet (such as from table sugar or high fructose corn syrup) or produced endogenously. The fructose metabolism increases intracellular uric acid, which recruits NADPH oxidase to the mitochondria while inhibiting AMP-activated protein kinase. A drop in intracellular ATP level occurs, triggering a survival response. Leptin levels rise, triggering activation of the sympathetic central nervous system, while vasopressin levels rise, causing vasoconstriction in its own right and stimulating aldosterone production via the vasopressin 1b receptor. Low-grade renal injury and autoimmune-mediated inflammation occur. High-salt diets can amplify this process by raising osmolality and triggering more fructose production. Thus, primary hypertension may result from the overactivation of a survival response triggered by fructose metabolism. Restricting salt and sugar and hydrating with ample water may be helpful in the prevention of primary hypertension.
10.1093/ckj/sfad058
Self-maintaining macrophages within the kidney contribute to salt and water balance by modulating kidney sympathetic nerve activity.
Kidney international
The kidney is critical in controlling salt and water balance, with the interstitium involved with a variety of components including immune cells in steady state. However, the roles of resident immune cells in kidney physiology are largely unknown. To help unravel some of these unknowns, we employed cell fate mapping, and identified a population of embryo-derived self-maintaining macrophages (SM-MØ) that were independent of the bone marrow in adult mouse kidneys. This kidney-specific SM-MØ population was distinctive from the kidney monocyte-derived macrophages in transcriptome and in their distribution. Specifically, the SM-MØ highly expressed nerve-associated genes; high-resolution confocal microscopy revealed that the SM-MØ in the cortex were in close association with sympathetic nerves and there was a dynamical interaction between macrophages and sympathetic nerves when live kidney sections were monitored. Kidney-specific depletion of the SM-MØ resulted in reduced sympathetic distribution and tone, leading to reduced renin secretion, increased glomerular filtration rate and solute diuresis, which caused salt decompensation and significant weight loss under a low-salt diet challenge. Supplementation of L-3,4-dihydroxyphenylserine which is converted to norepinephrine in vivo rescued the phenotype of SM-MØ-depleted mice. Thus, our findings provide insights in kidney macrophage heterogeneity and address a non-canonical role of macrophages in kidney physiology. In contrast to the well-appreciated way of central regulation, local regulation of sympathetic nerve distribution and activities in the kidney was uncovered.
10.1016/j.kint.2023.04.023