bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suramin Protects From Cisplatin‐Induced Acute Kidney Injury
Authors: Dupre Tess , Doll Mark , Shah Parag , Sharp Cierra , Kiefer Alex , Scherzer Michael , Saurabh Kumar , Safaro Doug , Siow Deanna , Casson Lavona , Arteel Gavin , Jenson Alfred Bennett , Megyesi Judit , Schnellmann Rick , Beverly Levi , Siskind Leah 
Published: November 2023

Cisplatin, a commonly used cancer chemotherapeutic, has a dose limiting side effect of nephrotoxicity. According to the Risk, Injury, Failure, Loss of Function, and End Stage Renal Disease (RIFLE) criteria of kidney injury, approximately 30% of patients administered cisplatin suffer from kidney injury and there is currently no treatment for cisplatin‐induced kidney injury other than palliative care. Suramin, FDA‐approved for the treatment of trypanosomiasis, improves kidney function following various forms of kidney injury in rodent models. We hypothesized that suramin would attenuate cisplatin‐induced kidney injury. Suramin treatment prior to cisplatin administration reduced cisplatin‐induced decreases in kidney function and injury. Furthermore, suramin attenuated cisplatin‐induced expression of inflammatory cytokines and chemokines, endoplasmic reticulum stress, and apoptosis in the kidney cortex. Treatment of mice with suramin 24 hours after cisplatin improved kidney function, suggesting that the mechanism of protection is neither via inhibiting tubular cisplatin uptake nor its metabolism to nephrotoxic species. If suramin is to be utilized in the context of cancer, then suramin cannot prevent cisplatin‐induced cytotoxicity within tumors. Mice harboring lung adenocarcinomas were pretreated with suramin and then administered cisplatin. Lung histology and markers of kidney function indicated that suramin protected mice from cisplatin‐induced acute kidney injury, but did not inhibit cisplatin induced cytotoxic effects within the tumor. These results provide evidence that suramin has great potential as a renoprotective agent for the treatment/prevention of cisplatin‐induced acute kidney injury.Support or Funding InformationSupport for these studies was provided by the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases [Grant R01‐ DK093462, to L.J.S]. This work was also supported by the National Institutes of Health National Institute of General Medical Sciences [Grant R01‐GM084147 to R.G.S.]; the National Institutes of Health National Center for Research Resources [Grant UL1‐RR029882 to R.G.S.]; the Biomedical Laboratory Research and Development Program of the Department of Veterans Affairs [1BX000851 to R.G.S.]; the South Carolina Clinical and Translational Research Institute, with an academic home at the Medical University of South Carolina (to R.G.S.); and the National Institute of Environmental Health and Sciences (SBIR/STTR ES023767 to R.G.S.).
The Role of Par‐1a/b Polarity Proteins in Acute Kidney Injury
Authors: Kazi Ananna N , Pal Abhijeet , Du Zhongfang , Reidy Kimberly J 
Published: November 2023

Acute Kidney Injury (AKI) is defined as the rapid loss of kidney function. Patients with acute kidney injury are unable to filter waste products from their body. The integrity of renal epithelial apico‐basal polarity is critical for many aspects of kidney function, including reabsorption of solutes. Loss of epithelial cell polarity occurs in several kidney disorders, including acute kidney injury. Partitioning defective 1 (Par‐1) is a member of the Par polarity protein family that localizes to the basolateral aspect of cells. Studies of Par‐1a+/−:Par‐1b−/− and Par‐1a−/−:Par‐1b+/− newborn mice determined that Par‐1 contributes to proximal tubular development. Complete loss of Par‐1a/b (Par‐1a−/−: Par‐1b−/−) leads to death early in fetal development of mice. Par‐1a and Par‐1b are expressed in developing nephrons and their expression decreases in adult nephrons. Tubular injury in mice correlates with increased expression of Par‐1a and Par‐1b. In our research, we hypothesized that Par‐1a/b polarity proteins are protective in the setting of acute kidney injury. In order to test this, cisplatin was injected intraperitoneal into Par‐1a/b global knockout mice at 5 weeks and they were sacrificed 3 days after injection. Cisplatin is one of the most widely used chemotherapy drugs that has been recently found to contribute to nephrotoxicity, especially on the signaling pathways leading to renal tubular cell death and inflammation. Hematoxylin and Eosin (H&E) staining was performed to assess tubular injury. Controls were non‐injected Par‐1a−/− and Par‐1b−/− mutants and injected wild type littermates. Ki‐67 staining was performed to identify cell proliferation. The level of tubular injury and cellular proliferation was examined by light microscopy. Our data showed that Par‐1b knockout mice were more susceptible to renal tubular injury than controls. Par‐1b knockout mice also had decreased cellular proliferation after cisplatin injury. Our ongoing experiment is testing the role of Par‐1a in AKI. In conclusion, Par‐1b polarity proteins contribute to renal tubular epithelial response to injury. Either decreased or delayed cellular proliferation may contribute to the increased tubular injury in Par‐1b−/− mice.Support or Funding InformationThis research was supported by American Physiological Society (APS) Short‐Term Research Experience for Underrepresented Persons (STEP‐UP) program, NIH NIDDK K08 5K08DK091507, R03 DK105242, and T32 DK007110. Thank you to Dr. Piwnica‐Worms for the Par‐1b+/− mice.
Zinc Deficiency Stimulates NADPH Oxidase‐2 Upregulation in Mouse Kidneys
Authors: Li Mirandy S , Gooch Jennifer L , Hoover Robert S , Williams Clintoria R 
Published: November 2023

BackgroundZn2+ deficiency (ZnD) is common in chronic kidney disease, including diabetic nephropathy. Experimental studies show that ZnD worsens diabetic kidney complications. Oxidative stress caused by increased reactive oxygen species (ROS) plays a role in the harmful effects of ZnD. However, the sources of oxidative stress continue to be identified. In the kidney, NADPH oxidases (Nox) are the predominant enzymes that promote oxidative stress.HypothesisThe objective of this study is to determine the role of Nox in ZnD‐induced oxidative stress. We hypothesize that ZnD upregulates Nox, resulting in sustained ROS levels and kidney damage (see proposed schema).MethodsWT mice were pair‐fed a ZnD or control diet for 6 weeks. After collecting kidneys and urine, kidney damage (urinary albumin:creatinine ratios), ROS levels (Amplex Red and 2′,7′‐dichlorofluorescein diacetate) and Nox expression (qRT‐PCR and Western blot) were examined. To further investigate the effects of Zn2+ bioavailability on Nox, mouse distal convoluted tubular (mDCT) cells were exposed to the Zn2+ chelator N,N,N′,N′‐Tetrakis(2‐pyridylmethyl)ethylenediamine (TPEN) or vehicle (DMSO) for 24 hours ± Zn2+ supplementation for an additional 24 hours.ResultsMice fed a Zn2+‐restricted diet develop microalbuminuria that is accompanied by elevated renal Nox2 expression and ROS levels compared to control‐diet fed mice. In mDCT cells, intracellular Zn2+ depletion with TPEN increases Nox2 expression and ROS levels compared to vehicle‐treated cells. Nox inhibition with diphenyleneiodonium (DPI) prevents TPEN‐induced ROS increases. Furthermore, intracellular Zn2+ repletion reverses Nox2 upregulation induced in TPEN‐exposed mDCT cells.ConclusionsTaken together, these findings identify Nox2 as a possible mediator of ZnD‐induced oxidative stress and kidney damage.SignificanceUnderstanding the mechanisms by which ZnD contributes to kidney injury may have important impact on the treatment of diabetic kidney disease.Support or Funding InformationR25DK101390 (MSL), VA‐MERIT (JLG), R01DK085097 (RSH), T32‐DK00756 (CRW)
Aldosterone Blockade Reduces Low Salt‐induced Renal Oxygen Consumption
Authors: Patinha Daniela , Pihl Liselotte , Fasching Angelica , Palm Fredrik 
Published: November 2023

Low salt (LS) diet activates the renin‐angiotensin system, in order to maintain volume homeostasis, which increases active electrolyte transport and thus kidney oxygen consumption (QO2). However, the role of aldosterone in low salt‐induced QO2 and tissue hypoxia is presently unknown.Male Sprague Dawley rats were fed normal (NS, 0.4%) or low (LS, 0.01%) salt diet during two weeks. Thereafter, catheters were placed in the carotid artery and femoral vein for blood pressure measurement and infusion of 3H‐inulinin thiobutabarbital‐anesthetized animals. The left kidney was immobilized. Measurements were obtained before and after intravenous administration of the aldosterone antagonist canrenoic acid (20 mg/kg). QO2 was estimated from the arterio‐venous difference in oxygen content multiplied by renal blood flow (RBF; Transonic flow probe). Renal cortical and medullary partial pressures of oxygen (PO2) were measured using Clark‐type electrodes.Mean arterial blood pressure, glomerular filtration rate and RBF were similar in both groups. LS rats had lower fractional excretion of Na+ (FENa) and less efficient Na+ transport (TNa), defined as TNa/QO2 together with increased QO2 and markers of oxidative stress compared to NS. LS intake also reduced cortical PO2 and increased medullary PO2. Acute aldosterone inhibition doubled FENa, normalized QO2 and reduced oxidative stress only in LS.In conclusion, LS‐induced QO2 and oxidative stress are caused by increased intrarenal aldosterone signaling. However, if the beneficial effects of aldosterone blockade for long‐term kidney function in chronic kidney disease are due to normalized oxygen metabolism remains to be determined.Support or Funding InformationThis work was supported by the Swedish Heart and Lung Foundation and the Swedish Research Council.
Increased Susceptibility to Cisplatin‐Induced Acute Kidney Injury in the Kidneys of Na‐H Exchanger Regulatory Factor Isoform 1 (NHERF1) Deficient Mice
Authors: Sherwood Amanda Renee , Khundmiri Syed Jalal , Conklin Caryl Anne , Siskind Leah Renee , Bushau Adrienne , Dupre Tess , Barati Michelle , Merchant Michael , Lederer Eleanor DeLand 
Published: November 2023

NHERF1 is a PDZ binding protein that plays a critical role in defining both the renal proximal tubule brush border membrane (BBM) composition and regulating ion transport through modulation of trafficking and anchoring functions. In a NHERF1‐deficient opossum kidney (OK) cell line, we have observed slower cell growth, a decrease in total mRNA expression, diminished BBM protein glycosylation, and higher levels of phosphorylated PERK, a marker of ER stress. We hypothesized that kidneys from NHERF1 deficient mice were more susceptible to acute kidney injury as a result of increased ER stress. To test this hypothesis, we treated 2 month old WT and NHERF1 deficient mice with 20 mg/kg IP cisplatin for 72 hours. Hemotoxylin and eosin staining of the kidney cortex of NHERF1 deficient mice showed greater injury manifested by BBM sloughing, tubular cell detachment and vacuolization, and intratubular proteinaceous debris. NHERF1 KO mice treated with cisplatin also demonstrated decreased expression of GRP78, a prosurvival ER chaperone that is upregulated during ER stress. Using ID‐RP (C18) nanoflow ultra high performance liquid chromatography and nanoelectrospray‐mass spectrometry (MS), we examined the composition of the BBM of proximal tubule cells from 4 month old NHERF1 KO mice. Compared to WT mice, NHERF1 KO mice demonstrated decreased abundance of several proteins involved in cell survival including ACADS, CDK18, and PRKAR2A in the BBM, while the abundance of proteins specific to renal cell proliferation and survival such as FGFR2, GRN, and NOS3 were decreased 3 to 25 fold. Interestingly, proteins such as DAPK1, a positive mediator of gamma interferon‐induced programmed cell death, and GAK, a direct transcriptional target of p53 that is itself a stress‐induced protein involved in cell cycle arrest and apoptosis, were increased 2 and 19 fold in the NHERF1 KO BBM. We conclude that NHERF1 deficiency increases susceptibility to cisplatin‐induced AKI due to the presence of underlying ER stress and reduced expression of signaling pathways that promote cell survival.Support or Funding InformationUniversity of Louisville, NIH‐NIA Grant # 5R21 AG047474‐02
Proximal‐tubule‐select dual knockout of insulin and insulin‐like‐growth factor (type I) receptors in mice alters responses to dietary fructose
Authors: Ecelbarger Carolyn M. , Doh Kwame , Lee Hwal , Tiwari Swasti , Li Lijun 
Published: November 2023

The monosaccharide, fructose is a common dietary constituent, but metabolized quite differently from glucose. One site of fructose metabolism is the renal proximal tubule (PT). How and whether insulin or the related hormone, insulin‐like‐growth‐factor, type 1 (IGF1), modulate fructose metabolism at this site is not known. To address this, we bred mice with dual knockout (KO) of the insulin receptor (IR) and the IGF1 receptor (IGF1R) from PT by Cre‐lox recombination using a γ‐glutamyltransferase promoter. Male (M) and female (F) wild‐type (WT) and KO mice were fed control (C) or high fructose (Fr) diet (60%) for 4 weeks (n = 10–12/group). KO mice had marginally lower body and/or kidney weights. Fructose feeding did not affect final body weight. Glucose tolerance was significantly impaired by fructose feeding, but only in the WT mice. KO mice also had a phenotype suggesting renal tubular acidosis, i.e., with significantly elevated blood chloride levels, and decreased blood total CO2 levels. Plasma sodium was also reduced in male KO by fructose, but not in the WT or females. Western blotting of cortex homogenates revealed significantly reduced (2‐way ANOVA) band densities for IR, IGF1R, and NaPi‐2 (sodium phosphate cotransporter) in the KO mice. However, no genotype differences were found for band densities of the fructose transporter (GLUT5) and ketohexokinase (KHK), the first enzyme in fructose metabolism, although the abundances of these two proteins were significantly increased in males and in fructose‐fed animals. The sodium bicarbonate cotransporter (NBC) was reduced in KO, but not WT males by fructose‐feeding. Females, overall, had significantly lower levels of NBC. Overall, genotype differences in the metabolic responses to fructose suggest a role for PT IR/IGF1R expression as a modulator of PT metabolism and/or acid‐base homeostasis.Support or Funding InformationMarriott Cardiovascular Fellowship and Georgetown Internal funding
Functional Dynamics of Cysteines in the Epithelial Na+ Channel Finger Domains
Authors: Blobner Brandon Michael , Kashlan Ossama B 
Published: November 2023

The epithelial Na+ channel (ENaC) is a member of the ENaC/Degenerin family of ion channels. The structure of one member of this protein family, acid sensing ion channel 1 (ASIC1), has been resolved. ASIC1 shares high sequence homology with ENaC. ENaC has a set of cysteines in the extracellular domains of each subunit that form disulphide bonds, as is characteristic of this protein family. ENaC subunits contain an additional pair of cysteines in the poorly conserved extracellular finger domains that are not present in ASIC1. The disposition of these cysteines is unclear. Using bifunctional methanethiosulfonate (MTS) crosslinkers and the oxidizing agent copper phenanthroline, we probed the region surrounding the finger domain cysteines. Our data shows that the finger domain cysteines of both the alpha and gamma subunits are positioned in close proximity to the finger‐thumb domain interface of the respective subunits. Crosslinking to these cysteines affected ENaC currents, suggesting mechanical linkage between this peripheral site and the channel gate. Our data also shows that removal of either gamma finger domain cysteine results in the loss of irreversible ENaC inhibition by MTS reagents, an affect that we previously reported. Our data suggests that ENaC finger domain cysteines may be experimentally modified in a manner that regulates ENaC activity.Support or Funding InformationThis work is supported by NIH grants DK098204 and DK061296‐12.
Ankyrin G Alters ENaC Membrane Delivery to Increase Na+ Transport in the Distal Kidney Nephron
Authors: Klemens Christine Anne , Kightlinger Lindsay , Liu Xiaoning , Edinger Robert , Butterworth Michael Bruce 
Published: November 2023

The heterotrimeric epithelial sodium channel (ENaC) comprised of α, β, and γ subunits, is the predominant aldosterone regulated sodium (Na+) channel in the kidney distal nephron, and plays an essential role in fine‐tuning Na+ reabsorption into the blood. Stimulation by aldosterone induces a number of changes to increase urinary Na+ reabsorption, including increasing ENaC subunit translation and modifying key regulators that alter ENaC function and/or membrane density. We identified ankyrin G (AnkG) to be a novel, aldosterone stimulated, ENaC regulator. Knock down of AnkG expression reduces the endogenous amiloride sensitive (ENaC) current by 69%±1.57% (n=15, p<0.0001), while over expression of AnkG increases ENaC current by 67%±11% (n=12, p=0.0001) in mouse cortical collecting duct (mCCD) cells. Membrane permeabilization verified that this alteration of Na+ transport was through ENaC and not a secondary effect of intracellular driving force via altered Na+K+ATPase. The aim of this study was to determine the mechanism behind AnkG's regulation of ENaC activity, whether through increased surface delivery, altered channel open probability, increased membrane dwell time, increased intracellular recycling, or blunted internalization and degradation. We propose that AnkG expression modulates Na+ reabsorption in collecting duct cells by increasing ENaC delivery to the surface, thereby increasing the number of channels present at the apical membrane.Biotinylation of surface βENaC determined that AnkG over expression increases the number of channels at the surface 71%±26% (n=4, p‐value=0.02). Using a combination of electrical and biochemical pulse‐chase assays, we found that AnkG expression does not alter ENaC internalization rates or ENaC recycling; however, mCCD cells with reduced AnkG had significantly slower apical delivery rates (k=0.1361 min−1 ±0.0081vs k=0.1867 min−1±0.0045, n=12, p<0.0001), while AnkG over expression in mCCDs accelerated ENaC delivery (k=0.1724 min−1 ±.0020vs k=0.1298 min−1±.0035, n=9, p<0.0001). Neither AnkG knock down or over expression altered the total amount of ENaC protein in the mCCD cells, suggesting AnkG is impacting ENaC delivery rates, rather than the quantity of ENaC delivered to the surface.These findings highlight the role of AnkG as an aldosterone induced protein and novel regulator of ENaC that could alter Na+ reabsorption in the distal nephron. Ongoing studies aim to fully characterize the molecular mechanisms underlying this dynamic interaction.Support or Funding Information15PRE25680068, DK079307, UPMC Cell Biology Teaching Fellowship
The Role Of Several Prominent Claudin Tight Junction Proteins In Teleost Fish Gill Epithelium Paracellular Permeability
Authors: Kolosov Dennis , Donini Andrew , Kelly Scott P. 
Published: November 2023

Because the internal fluids of freshwater (FW) teleost fishes are hyperosmotic relative to their surroundings, these organisms experience obligatory ion loss across epithelia that directly interface with water (e.g. the gill epithelium). In FW fishes, the tight junction (TJ) complex is broadly acknowledged to limit paracellular ion loss across the gill epithelium as it occludes the paracellular cleft and therefore acts as a barrier to impede paracellular solute movement. The vertebrate TJ complex is composed of numerous TJ proteins and the major proportion of these belong to the claudin (Cldn) superfamily. Cldn TJ proteins are not only implicated in regulating general permeability but also ion‐specific permselectivity of various vertebrate epithelia. Several Cldns seem to be particularly important for the establishment and maintenance of the barrier properties of the fish gill epithelium. Additionally several important ionoregulatory hormones in teleost fishes (e.g. cortisol), have been implicated in the regulation of paracellular permeability of FW teleost fish gill epithelia by exerting their actions on specific Cldns and other TJ proteins. Nevertheless, a clear picture of how paracellular movement of specific ions is regulated by the complex molecular architecture of TJs in an architecturally complex epithelium is only beginning to emerge. This has been achieved in part, by using primary cultured ‘reconstructed’ gill epithelia composed of different gill cell types. These architecturally simple models permit endpoints of transepithelial and paracellular permeability to be measured across a tissue that otherwise exhibits a restrictive morphology and problematic cellular heterogeneity. This can be done in the presence of ionoregulatory hormones and measurements of permeability can then be coupled with manipulations of TJ architecture via transcriptional knockdown of TJ proteins using dsRNA. This study will present an examination of the contribution of several Cldns to gill epithelium permeability as well as endocrine mechanisms regulating TJ protein abundance in the gill epithelium. Particular attention has been paid to the compensatory response caused by transcriptional knockdown of specific Cldns in the gill epithelium of fish as this area has been entirely overlooked, despite the fact that the teleost genome is well known to possess a particularly large number of Cldn genes due to teleost‐specific genome duplication events.Support or Funding InformationThis work was funded by National Science and Engineering Research Council of Canada
Heterogeneity of Signal Transduction by Na/K‐ATPase α‐Isoforms: Role of Src Interaction
Authors: Yu Hui , Cui Xiaoyu , Xie ZiJian 
Published: November 2023

Among the four α isoforms expressed in mammalian cells, we have shown that the ubiquitous α1 Na/K‐ATPase possesses both ion‐pumping and Src‐dependent signaling functions. In contrast, we have reported that α2 Na/K‐ATPase pumps but does not conduct Src‐dependent signal transduction, which represents a major functional difference between α isoforms. We have identified two putative pairs of domain interactions between α1 Na/K‐ATPase and Src, but others have challenged the concept of a direct interaction between Na/K‐ATPase and Src. In support of our model, a sequence comparison revealed major differences between α1 and α2 in these two putative Src‐interacting domains, in contrast to the overall high (~80%) level of homology between the α1 and α2 polypeptides. In this study, we tested whether targeted point mutations in the two putative Src‐interacting domains could confer “α1‐like” Src‐regulating properties to α2.To this end, we generated stable mammalian cell lines that express almost exclusively a α2 polypeptide mutated to mimic α1 sequence in the putative Src‐interacting domains. Functional analyses of α2 and α2 mutant cell lines reveal the following. First, the mutant α2 was fully functional as an ion pump. Second, unlike α2, the mutated α2 gained α1‐like signaling function, was capable of Src regulation, and restored caveolin‐1 expression. Because these mutated sequences of α2 are highly conserved across different species, the lack of Src‐regulation by α2 appears to be a conserved property of this isoform, most likely to provide α2‐specific and physiologically important functions that Src interaction could alter. Third, as expected, ouabain activated Src/ERK in the α2 mutant, but not in α2‐expressing cells. Finally, the mutant α2 cells exhibited a growth phenotype comparable to that of α1, which was much faster than that of α2 cells. Taken together, these new findings not only reveal the structural requirements for the Na/K‐ATPase to function as a Src‐dependent receptor, but also provide strong evidence of isoform‐specific Src interaction involving the identified key amino acids.