bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Dietary Fructose Rapidly Induces Salt‐Sensitive Hypertension in Rats
Authors: Gordish Kevin L , Ortiz Pablo A , Garvin Jeffrey L , Beierwaltes William H 
Published: November 2023

Fructose consumption is associated with increased sodium reabsorption, increased formation of reactive oxygen species, and the development of hypertension. In normal rats, 20% dietary fructose supplementation induces hypertension within 8–12 weeks. We hypothesized a diet combining 20% fructose supplemented with high salt (4% NaCl) would induce abnormal sodium retention, increased oxidative stress, and accelerate the development of elevated blood pressure. Rats weighing 200–225 g were pre‐trained for 2 weeks for non‐invasive tail cuff blood pressure measurements and then placed in metabolic caging. Rats were pair‐fed for 2 weeks with one of 4 different diets: 1) control group (0.4% NaCl), 2) high salt chow group (4% NaCl), 3) 20% fructose group (in the drinking water), and 4) 20% fructose plus high salt group (n's = 9,5,9,18). Blood pressure, urinary sodium excretion and cumulative sodium balance were measured over 2 weeks and urinary 8‐Isoprostane excretion, as a marker for reactive oxygen species, during the final two days. High salt chow replaced normal chow at the beginning of the second week. By the end of the protocol, systolic blood pressure was unchanged in control group (121±2 to 122±2 mmHg) as well as the high salt group (122±2 to 122±1 mmHg). 20% fructose alone had no effect on blood pressure over the 2 weeks (121±1 to 125±1 mmHg). However, blood pressure significantly increased in the 20% fructose plus high salt group (125 to 140 mmHg p<0.001). The increased blood pressure was concomitant with increased positive cumulative sodium balance. During the final week mean urinary sodium excretion in the high salt and 20% fructose plus high salt groups were 5–6 fold higher than normal salt controls (p<0.001): 1.13±0.07, 7.67±0.31, 1.20±0.10, 5.33±0.21 μmol/24 hrs, respectively. Despite similar consumption, urinary sodium excretion in the 20% fructose plus high salt group was significantly lower than the high salt group (p<0.0001). Urinary 8‐Isoprostane excretion was significantly higher in the high salt, 20% fructose, and 20% fructose plus high salt groups compared to control: 16.4±1.3, 29.5±2.5, 32.2±3.9, 31.2±2.5 ng/24 hrs, (p<0.001). Our results suggests enhanced fructose and salt consumption increases sodium retention and oxidative stress. High salt can induce elevations in blood pressure in 20% fructose‐fed rats within just one week. Increased blood pressure appears to associate with increased sodium retention and positive cumulative sodium balance. Overall, fructose combined with high salt in the diet contributes to the accelerated development of salt‐sensitive hypertension.Support or Funding InformationNational Institutes of Health Grant 5P01HL090550‐05
Hypoxia precedes proteinuria in mice with diabetic nephropathy
Authors: Franzen Stephanie , Pihl Liselotte , Gustafsson Håkan , Palm Fredrik 
Published: November 2023

Kidney hypoxia has been suggested to be a unifying mechanism for the progression of diabetic nephropathy and chronic kidney disease. Though, for hypoxia to be the actual causing mechanism it needs to be present before other functional alterations. Proteinuria is a commonly used biomarker for kidney damage and therefore, we investigated if hypoxia can be seen as early as proteinuria in mice with diabetic nephropathy.Kidney cortex oxygen tensions were analyzed using a minimally invasive electron paramagnetic resonance oximetry technique with implanted oxygen sensing probes. Measurements were made before and up to 15 days after the induction of type‐1 diabetes in male mice and compared to corresponding controls. After 16 days, proteinuria and conscious glomerular filtration rates were analyzed in order to investigate the progressive relationship between kidney hypoxia and disease progression.Diabetic mice developed pronounced intrarenal hypoxia three days after the induction of diabetes, which maintained throughout the study. On day 16, diabetic mice had increased glomerular filtration rate but normal proteinuria.In conclusion, kidney hypoxia precedes proteinuria and could therefore be considered a promising biomarker for the progression if kidney damage.Support or Funding InformationAll experiments was conducted according to the FASEB Statement of Principles. The study was supported and funded by the Swedish Research Council, the Swedish Diabetes Foundation and the Swedish Heart Lung Foundation.
Chronic Renal Hypoxia Leads to Injury and Dysfunction: Role of HIF1alpha
Authors: Welch William J , Araujo Magali , Hosszu Adam , Luo Zaiming , Solis Glenn 
Published: November 2023

Renal hypoxia precedes renal injury and impaired GFR in multiple renal disease models and in hypertension. Further, in imaging studies in humans, renal hypoxia correlates with hypertension and reduced renal function. We propose that renal injury that accompanies hypertension is mediated by events stimulated by hypoxia and responses linked to HIF1a. To test these effects, we developed a pilot study to generate reproducible renal hypoxia in rats by treatment with 2,4‐dinitrophenol (DNP, 30 mg/kg/day). DNP is a mitochondrial uncoupling agent that acts as a proton ionophore, which reduces production of ATP, yet still consumes O2. Renal cortical and medullary pO2 levels were lower in DNP‐treated rats compared to vehicle (Cortex pO2: 34±4 vs 44±4 mmHg; Medulla pO2: 22±3 ve 31±3 mmHg, p<0.001, n=6). Blood pO2 was unchanged by DNP treatment. Expressions of HIF1a and the pro‐oxidant enzyme, NADPH oxidase‐2 (NOX‐2) were increased in DNP‐treated rats. Conversely the antioxidant enzyme, superoxide dismutase‐2 (SOD‐2), was not changed. Further, the renal injury markers TGFb and NGAL were higher in DNP‐treated rats. MAP, basal GFR and RBF were unchanged in response to DNP‐generated renal hypoxia. Separate DNP‐fed rats were treated with direct left renal injections of siRNA directed to HIF1a, 48 hours prior to measuring renal pO2. Expression of HIF1a was reduced by 66±3% in the left kidneys treated with siRNA in DNP‐treated rats and was 32% lower than HIF1a in Veh‐treated rats. Expression of HIF1a in the right kidney was not altered by siRNA injection in the left kidney. Knockdown of HIF1a further reduced pO2 compared to DNP‐treated rats (Cort pO2 = −4±2 mmHg; Med pO2 = −8±1 mmHg, p<0.01), suggesting HIF1a protects the kidney from greater renal hypoxia. Further, expression of renal injury markers was higher in HIF1a reduced kidneys. We conclude that chronic renal hypoxia induces renal injury via oxidant pathways and stimulates HIF1a, which is only partially protective. DNP‐induced renal hypoxia is a viable model to test the long‐term effects of hypertension on renal oxygen metabolism.Support or Funding InformationHL089583; HL068686
Prasugrel Suppresses Development of Lithium‐induced Nephrogenic Diabetes Insipidus in Mice
Authors: Kishore Bellamkonda K , Brandes Anna U , Carlson Noel G , Zhang Yue 
Published: November 2023

Previously we localized ADP‐activated P2Y12 receptor in rodent kidney and showed that its blockade by clopidogrel bisulfate (CLPD) attenuates lithium(Li)‐induced nephrogenic diabetes insipidus (NDI) (Zhang et al, JASN ePub 2015; Zhang et al, Puriner Signal ePub 2015). In order to explore whether such attenuation is possible by the use of other drugs that are known to block P2Y12 receptor, we evaluated the effect of administration of prasugrel (PRSG) on Li‐induced NDI in mice. Similar to CLPD, PRSG belongs to thienopyridine class of ADP receptors inhibitors, and is a prodrug metabolized in the liver into its active form, which irreversibly binds to P2Y12 receptor. Groups of age‐matched adult B6D2 mice (n = 5/group) were fed either regular rodent chow (controls, CNT) or rodent chow with added LiCl (LI; 40 mmol/kg chow) or PRSG in drinking water (PRG; 10 mg/kg bw/day) or a combination of Li and PRSG for 14 days. Twenty‐four hour water consumption and urine output were determined on day 0 and day 14, and the mice were humanely euthanized. Blood and kidney tissues were collected and analyzed. Administration of PRSG completely suppressed Li‐induced NDI as assessed by water intake, urine output and urine osmolality. Semi‐quantitative immunoblotting revealed that administration of PRSG significantly prevented Li‐induced decrease in AQP2 protein abundance in renal cortex (3.4‐fold higher) and medulla (3.2‐fold higher). Serum Li, Na, and K levels and osmolality were not affected by the administration of PRG. Similar to CLPD, PRSG administration had no effect on Li‐induced increase in urinary Na excretion. Taken together, our data suggest that pharmacological inhibition of P2Y12 receptor by thienopyridine group of drugs may potentially offer therapeutic benefits in Li‐induced NDI.Support or Funding InformationDept. of Veterans Affairs
Endothelin‐1 mediates glomerular and tubular injury in sickle cell mice
Authors: Kasztan Malgorzata , Sun Chiao‐Wang , Townes Tim M. , Pollock David M. 
Published: November 2023

Sickle nephropathy (SN) is associated with structural and functional abnormalities in kidneys that lead to albuminuria/proteinuria, a major mortality risk factor in sickle cell disease (SCD). Elevated urinary endothelin‐1 (ET‐1) excretion reported in SCD patients correlates with microalbuminuria, suggesting a pathophysiological link between ET‐1 and development and progression of SN. The aim of the study was to determine whether ET‐1 contributes to glomerular and tubular injury in SCD and if ETA receptors blockade ameliorates these damages. Experiments utilized 14 week old humanized sickle cell mice (HbSS) and genetic controls (HbAA). Ambrisentan (ETA antagonist), A‐182086 (ETA/B antagonist) or vehicle was administrated via drinking water (10mg/kg/day) for 10 (beginning at weaning) or 2 weeks (beginning at 12 week of age). Glomeruli were isolated for direct permeability measurements as a volume response to an oncopressive medium generated by changing concentrations of albumin. Markers of glomerular and tubular injury were measured in 24h urine samples. Administration of ambrisentan for 2 weeks significantly reduced elevated Palb (0.22±0.03 vs. 0.48±0.05), urinary albumin (20.2±3.9 vs. 68.5±20.7μg/24h) as well as markers of tubular injury excretion: KIM‐1(171.3± 13.4 vs. 347±53 pg/24h) and NAG (3.07±1.9 vs. 15.9±1.5 U/L) in HbSS mice. Treatment with the dual ETA/B receptor antagonist had similar effect on Palb, however there was no effect on the excretion of the markers of glomerular and tubular injury. Administration of ambrisentan for 10 weeks significantly reduced elevated Palb (0.14±0.03 vs. 0.52±0.04), markers of glomerular injury: albumin (17.2±4.6 vs. 38.7±5.8μg/24h) and protein (0.74± 0.17 vs. 3.23± 0.4mg/24h), as well as markers of tubular injury excretion: KIM‐1(96.1± 21.6 vs. 373±111.5pg/24h) and NAG (5.8±2.1 vs. 14.5±1.2 U/L) in HbSS mice. Treatment with the dual ETA/B receptor antagonist had similar effect on Palb, however there was no effect on the excretion of the markers of glomerular and tubular injury. Neither antagonist altered any of the measured parameters in HbAA mice. These data support the hypothesis that ET‐1 contributes to the development and progression of sickle cell nephropathy and support the use of chronic ETA antagonism as a prospective treatment for sickle cell nephropathy.Support or Funding InformationThis work was supported by the program project grant on The Role of Endothelin‐1 in Sickle Cell Disease (U01 HL117684).
The ubiquitin ligase Ubr4 controls disassembly and stability of mechanosensitive podocin/MEC‐2 ion channel supercomplexes
Authors: Rinschen Markus M , Benzing Thomas 
Published: November 2023

The kidney expressed PHB‐domain protein podocin maintains the renal filtration barrier. Podocin and its C. elegans orthologue MEC‐2 have emerged as key components of mechanosensitive membrane protein signalling complexes. Whereas podocin resides at a specialized cell junction at the kidney filtration barrier, MEC‐2 is found in neurons required for touch sensitivity. Here we show that the ubiquitin ligase Ubr4 binds to and colocalizes with podocin in kidney podocytes and regulates podocin stability. We also find that this process is conserved in C. elegans and responsible for the degradation of mislocalized MEC‐2 multimers. Surprisingly, degradation depends on Ubr4‐dependent ubiquitylation of very specific lysine residues in the PHB‐domain that are conserved in evolution. Molecular dynamics simulations revealed that ubiquitylation of these sites does not only target podocin/MEC‐2 for proteasomal degradation but may also affect stability and disassembly of the multimeric complex. We suggest that ubiquitylation of specific lysine residues may represent an evolutionarily conserved principle in proteostasis of podocin/MEC‐2 supercomplexes.Support or Funding InformationDFG
Mass spectrometric imaging of metabolites in kidney tissues from rats treated with furosemide
Authors: Choi Hyo‐Jung , Park Eui‐Jung , Kim Dasom , Lee Yu‐Jung , Kwon Tae‐Hwan 
Published: November 2023

In the kidney, metabolic processes are different among the cortex (COR), outer medulla (OM), and inner medulla (IM). Using a novel technology of the matrix‐assisted laser desorption/ionization (MALDI) and imaging mass spectrometry (IMS), we examined the regional differences of the metabolites in the kidneys of furosemide‐infused rats. Osmotic minipumps were implanted in male Sprague‐Dawley rats to deliver 12 mg/d/rat of furosemide. Vehicle‐treated‐ (n = 14) and furosemide‐treated‐ (furosemide rats, n = 15) rats in metabolic cages received a fixed amount of rat chow (15 g/220 g bw/day/rat) with free access to water intake for 6 days. At day 6, higher urine output (32 ± 4 vs. 9 ± 1 ml/day) and lower urine osmolality (546 ± 44 vs. 1,677 ± 104 mOsm/KgH2O) were observed in furosemide rats. Extracts of COR, OM, and IM were analyzed by UPLC/Q‐TOF‐MS, where multivariate analysis revealed significant differences between the two groups. Several metabolites, including acetyl carnitine, betaine, carnitine, choline, and glycerophosphorylcholine (GPC), were significantly changed. The changes of metabolites were further identified by MALDI‐TOF/TOF and IMS. Importantly, their spatial distribution and relative quantitation in the kidneys were analyzed by IMS. Choline compounds were increased in COR and OM, but decreased in IM from furosemide rats. Carnitine compounds were increased in COR and IM, whereas carnitine and acetyl carnitine were decreased in OM. Betaine and GPC were decreased in OM and IM. Taken together, MALDI‐TOF/TOF and IMS successfully provide the spatial distribution and relative quantitation of metabolites in the kidney.Support or Funding InformationThis study was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning, Korea (2013R1A1A2007266, and 2014R1A5A2009242).
High Fructose Concentrations Could Cause Changes in Intracellular Signaling Pathways and transepithelial electrical resistance in Proximal Tubule Cells
Authors: Matsumoto Larissa Emi , Yokota Rodrigo , de Oliveira Leite Ana Paula , Jara Zaira Palomino , Casarini Dulce Elena 
Published: November 2023

In the western lifestyle is observed the excessive consumption of industrialized foods composed with high fructose. This sugar is an important contributor of the Metabolic Syndrome (MS). MS is a set of pathologies that includes cardiovascular and renal diseases, like diabetes, hypertension, and obesity. Recent studies showed that hypertension in MS is induced by high fructose consumption and it is associated with direct changes of Renin‐Angiotensin System (RAS) balance. This system is present locally in several tissues. In the kidney, the proximal tubule (PT) that is the major region of sodium and water re‐absorption expresses all of the RAS components. In high fructose ingestion, inflammation has been observed in this region, but it is unclear how Ang II contributes to fructose inflammatory process, as well as which signaling pathways are involved in this process. We hypothesized that high fructose intake can increase Ang II concentration, which results in activation of proinflammatory second messengers as mitogen‐activated protein kinases, including extracellular‐signal‐regulated kinases (ERK 1/2), as well as modified the transepithelial electrical resistance (TEER) consequently impacting sodium and water transport. To verify the ERK phosphorilation pattern, it was used immortalized rat proximal tubule cells (IRPTC) treated with high fructose concentrations, RAS antagonists (angiotensin II type 1 receptor (AT1R) antagonist: losartan, angiotensin II type 2 receptor (AT2R) antagonist: PD123319, and angiotensin‐(1–7) antagonist: D‐Ala), and angiotensin‐converting enzyme inhibitor. To verified TEER changes it was used IRPTC treated with fructose, fructose + NaCl, and NaCl alone. Our results indicate that the group treated with fructose together with D‐Ala and PD123319 enhanced phosphorilated ERK 1/2 expression. The TEER results showed that voltage in fructose and fructose + NaCl treated cells were significantly decreased compared to the negative (without any treatment) and positive (NaCl) control. In conclusion, the enhanced phosphorilation of ERK via AT2R and MAS antagonism could indicate; first, modulation of angiotensins levels, second that there is anti‐inflammatory response activated; and third, this response could be increase to compensate the inflammatory process fructose‐dependent. The drastic voltage reduction could be involved in modulation of sodium transporter such as NHE3, among others and modulation of AQP‐1, main water channel in the PT.Support or Funding InformationSupported by Capes
Subunit‐Specific Role of the Epithelial Na+ Channel Thumb Domain
Authors: SHENG SHAOHU , CHEN JINGXIN , TOLINO MICHAEL A. , KLEYMAN THOMAS R. 
Published: November 2023

Members of the epithelial Na+ channel/degenerin (ENaC/DEG) family of ion channels have large extracellular domains with common structural features, including a β‐strand central core embraced by helical peripheral domains (referred to as finger, thumb and knuckle). We hypothesized that the peripheral helical domains serve as functional modules that facilitate interactions between ENaC and extracellular regulatory factors. In this study, we examined the properties of channels where the thumb domain was deleted from a specific subunit. We found that channels lacking the γ subunit thumb domain retained activity when expressed in Xenopus oocytes, but channels lacking the α or β subunit thumb domain had greatly reduced activity. Surface expression of channels lacking the thumb domain of any subunit was significantly lower than wild‐type. Channels with a γ subunit thumb domain deletion exhibited a loss of the Na+ self‐inhibition response, suggesting a high channel open probability in the presence of a high extracellular Na+ concentration. We conclude that the presence of the thumb domain in each ENaC subunit is required for optimal surface ENaC expression in oocytes. Furthermore, the presence of the γ thumb domain is required for the inhibitory response to extracellular Na+ (Na+ self‐inhibition).Support or Funding InformationSupported by NIH ES014701, DK051391 and P30 DK079307
Tight Junction Proteins In Adult Rainbow Trout Skin: Regional Distribution, Response To Environmental Salinity, And Potential Regulatory Mechanisms
Authors: Gauberg Julia , Kolosov Dennis , Kelly Scott P. 
Published: November 2023

Freshwater (FW) fishes reside exist in aquatic habitats that are more dilute than their inner fluids. This leads to passive ion loss across tissues that directly interface with the surrounding medium, such as the gill and skin. The barrier properties of adult teleost fish skin in FW are well documented and in most cases, the trunk skin of adult fishes is void of any significant capacity for active ion movement. Therefore, despite its complex structure and extensive contact with the external environment, the skin of adult fishes is classically regarded as a relatively static, passive barrier to diffusional ion loss in FW. Nevertheless, recent observations have revealed the presence of a considerable number of genes encoding tight junction (TJ) proteins in the adult skin of several fish species. In addition, some studies have also shown that select TJ proteins in the skin of fish significantly alter in abundance upon exposure to environments that vary in ionic composition. This suggests that the molecular architecture of the skin TJ complex may play an important role in regulating skin permeability during environmental change. Despite this, almost nothing is known about how the molecular physiology of the TJ complex in this boundary tissue is regulated. Additionally, structural and functional differences are known to exist along the dorsoventral axis of the adult fish skin. However, none of the studies conducted to date, have taken this documented regional heterogeneity into account. This study examined TJ protein response to environmental change (acclimation to ion‐poor water, IPW) in freshwater (FW) rainbow trout (Oncorhynchus mykiss) skin. Changes in TJ protein abundance along the dorsoventral axis of the trout skin taken into consideration, as were possible roles for prolactin and cortisol, hormones involved in salinity‐dependent regulation of TJ/passive permeability. Differences in abundance of cldn‐3a, −5b, −6, −10c, −30, −32a and zo‐1 were detected along the dorsoventral axis of rainbow trout skin and many of these were found to be enriched in the lateral and dorsolateral regions. In addition, cldn mRNA abundance altered in response to IPW acclimation in a region‐specific manner. Osmoregulatory hormones, cortisol and prolactin, and their receptors were implicated in the regulation of Cldn transcript abundance in rainbow trout skin. These data provide a unique look at the region‐specific endocrine regulation of TJ complex components in adult fish skin.Support or Funding InformationThis work was funded by National Science and Engineering Research Council of Canada