bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intermittent Hypoxia Exacerbates Decreased GFR and Increased Blood Pressure in Rats with Chronic Kidney Disease
Authors: Riggs Jennifer L. , Pace Carolyn , Danielson Leslie , Fischer Edgar , Ward Heather , Kanagy Nancy 
Published: November 2023

Kidney injury and sleep apnea (SA) are risk factors for hypertension. This study evaluated interactions between simulated sleep apnea and chronic kidney disease. Rats were exposed to intermittent hypoxia (IH) to simulate SA and were given excess adenine in the diet to cause acute renal injury leading to chronic kidney disease (CKD). We hypothesized that exposing CKD rats to IH would accelerate declines in renal function and increase blood pressure. Male Sprague‐Dawley rats were fed a 0.4% adenine diet or a control diet until plasma urea nitrogen was >140 mg/dL in the adenine group. After two weeks of recovery (normal rat chow for all groups), rats were exposed to IH (20 exposures/hr of 5% O2/5% CO2 7 hr/day) or SHAM for 6 weeks. Arterial pressure (AP) was monitored continuously with indwelling telemeters and plasma and urine samples were collected weekly using metabolism cages to calculate glomerular filtration rate (GFR). AP was increased in rats fed the adenine diet compared to rats on the control diet prior to starting IH. IH treatment further increased AP so that after 6 weeks of Sham or IH treatment AP was elevated in both adenine groups and in the IH only group with pressures in Adenine/IH rats > adenine/Sham rats = Control/IH rats > Control/Sham rats. Histological analysis revealed crystalline deposits and damage to the proximal and distal tubules with interstitial fibrosis in the kidneys of all the adenine fed rats. Fibrosis persisted up to 8 weeks post adenine removal and IH did not cause any apparent additional damage. GFR remained impaired in both the adenine groups throughout the six weeks of IH or SHAM exposures with elevated plasma creatinine levels that were not altered by IH treatment. Therefore simulated SA augments increases in blood pressure in rats with pre‐existing CKD without affecting GFR suggesting that treating apnea should help prevent worsening secondary cardiovascular stresses in CKD patients.Support or Funding InformationNHLBI 123301, Dialysis Clinic Inc. Reserve Fund Grant
Differential regulation of large conductance K+ (BK) channel mediated K+ secretion in proximal and distal colon by aldosterone
Authors: Nickerson Andrew J , Galbreath Kyla M , Rajendran Vazhaikkurichi M 
Published: November 2023

Aldosterone (“aldo”) differentially regulates electrolyte transport processes, as it stimulates Na‐H exchanger isoform‐3 (NHE3) mediated electroneutral Na+ absorption, and down‐regulates NHE3 and induces epithelial Na+ channel (ENaC) mediated electrogenic Na+ absorption in proximal and distal segments of rat colon, respectively. Electrogenic active K+ secretion is present in proximal colon, while H+, K+‐ATPase mediated electroneutral K+ absorption is present in distal colon of normal rat colon. Aldo enhances H+, K+‐ATPase expression and electroneutral K+ absorption in distal colon. Mucosal ortho‐vanadate (VO4; p‐type ATPase inhibitor) unmasked the “aldo” induced BK channel mediated K+ secretion in distal colon. It is not known whether “aldo” also stimulates BK channel mediated active K+ secretion in proximal colon. Studies were, therefore, initiated to identify whether “aldo” also activates K+ secretion in proximal colon. Aldo rats were generated by feeding Na‐free diet for 6 – 7 days. 86Rb (K+ surrogate) fluxes were measured in muscularis stripped proximal colon mounted under voltage clamp condition in Ussing chamber. Mucosal to serosal (m‐s) and serosal to mucosal (s‐m) fluxes were measured, while net fluxes were calculated by subtracting s‐m from m‐s. Net positive and negative fluxes represent active absorption and secretion, respectively. Aldo significantly enhanced K+ secretion (−0.25 ± 0.05 vs −0.47 ± 0.12 μEq/h.cm2; p < 0.05). Forskolin (FSK, adenylate kinase activator) stimulated K+ secretion in both normal (0.25 ± 0.05 vs 0.42 ± 0.09 μEq/h.cm2; p < 0.05) and aldo (0.47 ± 0.12 vs 1.30 ± 0.12 μEq/h.cm2). Mucosal iberiotoxin (IbTX, BK channel inhibitor) inhibited FSK‐stimulated K+ secretion in normal, but it did not affect FSK‐stimulated K+ secretion in aldo proximal colon. In contrast to IbTX, mucosal charybdotoxin [CTX; intermediate K+ (IK) channel blocker) completely inhibited the FSK‐stimulated K+ secretion in aldo proximal. We conclude that FKS stimulates active K+ secretion via: 1) both BK and IK channels in normal proximal colon; and 2) entirely through IK channels in proximal colon.Support or Funding InformationThis work was supported by NIH NIDDK Grant 1006856R to VMR.
Regulation of cell junctions by ClCN2 in cystic fibrosis
Authors: Henry Katherine , Lee Seakwoo , Zeitlin Pamela 
Published: November 2023

Cystic Fibrosis (CF) is an autosomal recessive disease, characterized by mutations in the CFTR gene, incorrect protein folding, and impaired chloride secretion. Ultimately, patients with CF exhibit a change in membrane potential regulation and it is possible that some of these changes are the result of impaired cell junctions. Previous data from our lab shows there is a targeted localization of ClCN2 to areas of cell junctions when portions of the c‐terminus are removed (ClCN2‐584). New data shows that this targeted localization is associated with a significant increase in transepithelial resistance in vitro. We hypothesize that this targeted localization and increase in TER suggests a potentially important role for ClCN2 in the regulation of tight junctions during CF, including changes in protein expression, protein interactions and tight junction function.Support or Funding Information5T32HL72748‐11: Ruth L Kirschstein National Research Service Award
A Role For 11‐Deoxycortisol In The Regulation Of Tight Junction Permeability In An Extant Agnathan
Authors: Zimina Anna , Kolosov Dennis , Wilkie Michael P , Kelly Scott P 
Published: November 2023

Corticosteroid hormones are important regulators of paracellular permeability across vertebrate epithelia. In aquatic vertebrates such as teleost fishes, cortisol reduces the paracellular permeability of the gill epithelium, which in a freshwater (FW) environment has been proposed to contribute to reduced passive ion loss under conditions of environmental or systemic perturbation. However, it is not known whether corticosteroids contribute to the regulated movement of solutes across the paracellular pathway in less derived vertebrates, such as agnathans. This gap in knowledge speaks to the difficulty of pinning down the identity of corticosteroid hormones in agnathans. But recent studies have revealed that 11‐deoxycortisol is the only circulating corticosteroid with high affinity and specificity to the sea lamprey corticosteroid receptor. This knowledge now presents us with an opportunity to examine whether 11‐deoxycortisol contributes to the regulation of paracellular ion transport in sea lamprey. Given the strong link between corticosteroids and paracellular solute movement across epithelia of more derived fishes, as well as other vertebrates, it can be hypothesized that 11‐deoxycortisol will play a similar role in the lamprey. Using the stenohaline FW larval form of the sea lamprey, the objectives of this study were to examine the dose‐dependent effects of 11‐deoxycortisol on: (1) endpoints of salt and water balance and (2) the molecular physiology of the larval lamprey TJ complex in iono/osmoregulatory organs such as the gill and kidney. Results indicated that 11‐deoxycortisol treatment of larval sea lamprey dose‐dependently altered endpoints of salt and water balance as well as the abundance of select TJ proteins. Therefore a third objective of this study was to examine whether changes brought about by 11‐deoxycortisol are beneficial to larval lamprey in terms of coping with ionoregulatory disturbance (i.e. abrupt exposure to an ion deficient environment). While data on the molecular physiology of the lamprey TJ complex suggests that the changes produced by 11‐deoxycortisol are useful for ion retention in a hyposmotic or ion‐deficient environment, net flux of Na+ and Cl‐ upon abrupt exposure to ion‐poor water paradoxically suggest that transepithelial solute permeability is greater following 11‐deoxycortisol treatment. Overall, data from these studies provide evidence to support the hypothesis that 11‐deoxycortisol contributes to the regulation of TJ permeability in an extant FW larval agnathan, but this may differ from the role that corticosteroids such as cortisol play in more derived fishes.Support or Funding InformationThis research was supported by Natural Sciences and Engineering Research Council of Canada.
Claudins of the Thick Ascending Limb of Henle's Loop – From Interaction to Function
Authors: Milatz Susanne , Wulfmeyer Vera Christine , Plain Allein , Drewell Hoora , Mutig Kerim , Breiderhoff Timan , Fromm Michael , Hou Jianghui , Bleich Markus , Günzel Dorothee , Himmerkus Nina 
Published: November 2023

The thick ascending limb of Henle's loop (TAL) drives paracellular Na+, Ca2+ and Mg2+ reabsorption via the tight junction (TJ). The TJ is composed of claudins which seal the paracellular cleft or form size‐, charge‐ and water‐specific pores. This is achieved by a concerted interaction of different claudin proteins within the same plasma membrane (cis‐interaction) and of neighboring plasma membranes (trans‐interaction) resulting in the formation of a complex TJ strand meshwork. Claudins consist of four transmembrane segments, a small intracellular loop and two extracellular loops.Single TAL segments were obtained from cortex or medulla and microperfused. Electrophysiological measurements of single tubules were combined with claudin expression analyses by subsequent immunostaining and confocal laser‐scanning microscopy. In order to gain insight into the molecular composition of TAL TJ strands, claudin cis‐and trans‐interaction was examined by means of live cell imaging and Förster/fluorescence resonance energy transfer (FRET) in an overexpression system. A set of TAL claudin protein chimeras was created to reveal determinants of interaction properties.Cortical and medullary TAL differed regarding their paracellular permeability properties and their equipment with claudins 3, 10, 11, 16, and 19. A clear correlation between dominance of specific claudins within the TJ and ion selectivity was observed. Although most of these claudins were co‐expressed within the TJ, some of them failed to interact with each other in cis‐or in trans‐configuration. Interaction analyses of claudin chimeras suggested an involvement of the extracellular loops of TAL claudins in cis‐and trans‐interaction.In conclusion, a specific claudin expression pattern along the TAL corticomedullary axis is revealed. This special composition of claudins can be explained by their particular interaction capabilities. We suggest the existence of at least two spatially distinct types of paracellular pores with different preferences for Na+, Ca2+ and Mg2+ in the TAL.Support or Funding InformationSupported by DFG FOR 721/2; National Institutes of Health Grant R01DK084059
Hyperglycemia‐induced Elevation of NKCC1 Expression in Blood Brain Barrier Endothelial Cells: Greater Effect of Intermittent Versus Sustained Exposures
Authors: Klug Nicholas R , Raposa Jesse T , Riley Michelle A , O'Donnell Martha E 
Published: November 2023

Diabetics with accompanied hyperglycemia (HG) suffer from exacerbated cerebral edema and worsened neurological outcomes following ischemic stroke. We have demonstrated previously that hypoxia and other factors present during cerebral ischemia stimulate cerebral microvascular endothelial cell (CMEC) Na‐K‐Cl (NKCC) cotransport and Na/H exchange (NHE) activities. We also found that inhibition of these blood‐brain barrier (BBB) Na transporters reduces brain Na uptake and edema in the rat middle cerebral artery occlusion (MCAO) model of ischemic stroke. In more recent studies focusing on diabetic stroke, we demonstrated that sustained 6‐hour to 7‐day HG exposures increase expression and activity of CMEC NKCC and NHE, resulting in more pronounced responses to ischemic factor stimulation. Further, we found that inhibition of BBB NKCC and NHE effectively reduces edema and infarct in hyperglycemic rats subjected to MCAO. Diabetics often experience postprandial excursions of blood glucose. Studies have provided evidence that while sustained HG can induce stress/injury responses in endothelial cells, intermittent HG can exaggerate those responses. The present study was conducted to investigate the effects of intermittent HG exposures on BBB Na transporter expression and activity. For this, cultured bovine CMEC were exposed daily over 2 to 5 days to HG medium (DMEM with 30 mM glucose, 320 mOsm) or to osmotic control medium (DMEM with 30 mM mannitol, 320 mOsm) for 6 hours, followed by exposure to normoglycemic medium (DMEM with 5 mM glucose, 295 mOsm) for 18 hours. Quantitative Western blot analysis was then used to assess NKCC1 protein abundance in CMEC lysates. We found that CMEC NKCC1 abundance increased in response to intermittent HG exposures in a graded manner with larger increases observed following greater number of successive exposures. No change in NKCC1 abundance occurred with repeated intermittent exposures to normoglycemic medium. In addition, our results show that 5 days of intermittent HG exposures caused a 124% increase in NKCC1 abundance compared to 40% and 65% increases following sustained 2‐day and 7‐day exposures, respectively. In the present study we also investigated the effects of varying HG levels on CMEC Na transporter abundance. Here, we exposed CMEC for 48 hours to HG media containing 10, 20 and 30 mM glucose, to osmotic control media (with mannitol) or to normoglycemic medium (with 5 mM glucose). We found that NKCC1 and NHE1 protein abundances exhibited a graded response to increasing HG levels. Our findings support the hypothesis that BBB endothelial NKCC1 and NHE1 are highly sensitive to increasing levels of HG and, in particular, that clinically relevant repeated intermittent exposures result in more pronounced BBB Na transporter responses than sustained exposures.Support or Funding InformationSupported by NIH, ADA and AHA
Molecular Basis of Inhibition of Acid Sensing Ion Channels by Diminazene
Authors: Carattino Marcelo D , Krauson Aram J 
Published: November 2023

Acid sensing ion channels (ASICs) are proton‐gated channels that contribute to pain sensation in the peripheral nervous system. We employed site‐directed mutagenesis and electrophysiology to investigate the mechanism of inhibition of ASICs by the aromatic diamidine diminazene. We found that diminazene inhibits mouse ASIC1a and ASIC3 with a half‐maximal inhibitory concentration (IC50) of 2.4 μM and 1.5 μM, respectively. To determine whether diminazene alters ASICs proton sensitivity, we generated dose‐response activation curves for ASIC3 in the absence and presence of diminazene (2 μM). Consistent with a competitive mechanism of action, diminazene shifted the pH of half‐maximal activation of ASIC3 from 6.32 ± 0.06 to 6.00 ± 0.06. To examine whether diminazene binds to a previously identified proton coordination site in the lower palm domain of ASIC1a formed by the residues Glu79 and Glu416, we generated dose‐response inhibition curves with channels bearing Gln substitutions at these positions. E79Q and E416Q ASIC1a channels were inhibited by diminazene with IC50 values of 18 μM (CI 8.2 – 41.8) and 14 μM (CI 5.9 – 32.7), respectively. Likewise, the neutralization of Glu79 (E79Q) on ASIC3 shifted diminazene IC50 from 1.5 μM (CI 1.0 – 2.4) to 5.6 μM (CI 2.6 –12.4). On the contrary, the neutralization of residues in the acidic pocket of ASIC1a, a cluster of negatively charged residues in the extracellular region that serves as binding site for psalmotoxin, did not change apparent diminazene binding affinity. These results strongly indicate that Glu79 and Glu416 in the lower palm domain are part of the diminazene binding site.Support or Funding InformationR01 DK084060 and P30 DK079307 Pittsburgh Center for Kidney Research
Inhibition of ERK phosphorylation decreases post‐stress avoidance in high stress reactive rats
Authors: Whitaker Annie , Gilpin Nicholas 
Published: November 2023

Avoidance is a primary symptom of post‐traumatic stress disorder (PTSD). Our laboratory has established a rodent model of traumatic stress that mimics the avoidance symptom cluster of PTSD. Animals are classified as ‘Avoiders’ or Non‐Avoiders’ post‐stress based on avoidance of predator‐odor paired context. Previously we have demonstrated that Avoiders exhibit differences in neuronal activation patterns associated with re‐exposure to traumatic stress‐related stimuli. The central amygdala (CeA) is a brain region important for mediating emotional responses and fear. Humans with PTSD exhibit amygdalar hyperactivity in response to stimuli associated with their traumatic experiences. The aim of these studies was to examine the effects of traumatic stress on CeA neuronal activation as measured by increases in ERK phosphorylation and the role of ERK phosphorylation in mediating stress‐induced avoidance. Male Wistar rats (275g) were exposed to predator odor (bobcat urine) paired with context and were 1) sacrificed from home cage or re‐exposed to context prior to sacrifice for examination of ERK phosphorylation in the CeA or 2) infused with either vehicle or the ERK inhibitor (U0126; 1ug/0.5ul/side) and re‐tested for avoidance of the predator odor‐paired context. Re‐exposure to the predator‐odor paired context produced an increase in ERK phosphorylation in the CeA of Avoider rats relative to Non‐Avoider rats (2.69±0.76 vs. 1.44±0.46; p=NS). Furthermore, pre‐treatment with U0126 decreased avoidance compared to vehicle treated Avoider rats. These data provide insight into the neural mechanisms mediating stress‐induced avoidance.Support or Funding InformationThis work was supported by NIH grants: AA018400 (NWG), AA023305 (NWG).
High Fat Diet (HFD) Induced Inhibition of Sympathetic Outflow to Brown Adipose Tissue (BAT): Role of the Nucleus Tractus Solitarius (NTS)
Authors: Madden Christopher J , Morrison Shaun F 
Published: November 2023

The lack of radio labeled glucose uptake in BAT in obese humans has been interpreted to suggest that these individuals lack significant depots of active BAT. This seemingly contradicts the observation in rodent models of diet‐induced obesity that BAT (UCP‐1 expression) is upregulated, a state that is typically associated with increased activity of BAT. In the current studies rats made obese by maintenance on a HFD failed to increase BAT sympathetic nerve activity (SNA) in response to cooling. In contrast, mRNA for UCP‐1 was up regulated by a HFD. In addition, activation of the sympathetic premotor neurons in the raphe pallidus with the GABAA receptor antagonist, bicuculline, increased BAT SNA and thermogenesis in both rats maintained on a HFD and those on control diet; suggesting that the sympathetic pathway from the level of the sympathetic premotor neurons to the BAT is not impaired in rats maintained on a HFD. Stimulation of vagal afferent activity or activation of neurons in the NTS (the site of vagal afferent terminals) inhibits cooling‐evoked sympathetic outflow to BAT, therefore this study also sought to test whether glutamatergic activation of neurons in the NTS plays a role in HFD‐induced inhibition of BAT SNA. Blockade of glutamatergic receptors in the NTS reversed the HFD‐induced inhibition of BAT SNA and thermogenesis. Finally, lipid metabolites that may be altered in animals on a high fat diet act on TRPV‐1 receptors in the NTS to enhance glutamatergic neurotransmission. The current study investigated whether activation of TRPV‐1 receptors in the NTS also play a role in the HFD‐induced inhibition of BAT SNA. Blockade of TRPV‐1 receptors in the NTS reversed the HFD‐induced impairment of cooling‐evoked BAT SNA. These data suggest that plasticity in the NTS during maintenance on a HFD may contribute to weight gain by impairing metabolism in adipose tissue.Support or Funding InformationSupported by American Diabetes Association Basic Science grant #1‐13‐BS‐120 and NIH R01 NS091066.
Does Acute Heat Stress Differentially‐Modulate RVLM Gene Expression of Ionotropic Neurotransmitter Receptors in Young and Aged F344 Rats?
Authors: Pawar Hitesh N , Balivada Shivasai , Montgomery Shawnee , Kenney Michael J 
Published: November 2023

The rostral ventrolateral medulla (RVLM) is involved in the regulation of sympathetic nerve discharge (SND) and arterial blood pressure. Acute hyperthermia produces marked activation of visceral SND in young rats, and the functional integrity of this brainstem region is crucial for sustaining visceral sympathoexcitation to increased internal body temperature (Tc). Visceral SND responses to increased Tc are attenuated in aged compared with young F344 rats, and central mechanisms contributing to age‐associated alterations in SND responses to hyperthermia are not well‐established. The balance between excitatory and inhibitory inputs, mediated primarily by glutamate and GABA neural systems, is important for regulating RVLM neuronal activity. In the present study we hypothesized that, in response to acute hyperthermia, the RVLM gene expression of various excitatory and inhibitory ionotropic neurotransmitter receptors would demonstrate age‐related differences. Tc was increased from 38°C to 41.5°C in young (3–4 months) and aged (23–24 months) anesthetized F344 rats. Total RNA was extracted from RVLM‐containing micropunches and gene expression analysis for ionotropic neurotransmitter receptor subunits was performed using TaqMan real time RT‐PCR. Gene expression levels of glutamate, GABA and glycine neurotransmitter binding receptor subunits were compared between age groups. Gene expression analysis revealed an upregulation in some, but not all, major excitatory NMDA and AMPA neurotransmitter receptor subunits in young compared with aged rats. In addition, major subunits of the inhibitory GABA and glycine receptors demonstrated substantial upregulation in aged compared with young rats. These preliminary data suggest that, in response to acute hyperthermia, aging modulates the functional balance of RVLM excitatory and inhibitory neurotransmitter receptor subunits.Support or Funding InformationNIH AG‐041948.