Dahl Salt-sensitive Research Articles

Effects of Hyperuricemia on the Progression of Salt-Sensitive (SS) Hypertension in Dahl SS Rats

Effects of Hyperuricemia on the Progression of Salt-Sensitive (SS) Hypertension in Dahl SS Rats

Benincasa hispida extracts positively regulated high salt-induced hypertension in Dahl salt-sensitive rats: Impact on biochemical profile and metabolic patterns.

Salt-induced hypertension is one of the major issues worldwide and one of the main factors involved in heart and kidney failure. The objective of this study was to investigate the potential role of Benincasa hispida extracts on high salt-induced hypertension in Dahl-salt sensitive (D-SS) rats and to find out the metabolic and biochemical pattern involved in the reduction of hypertension. Twenty-six Dahl salt-sensitive (D-SS) rats were selected and divided into four groups. The metabolic strategy was applied to test the extracts on salt-sensitive hypertension in kidney. Gas Chromatography-Mass spectrometry (GC-MS) was used to identify the potent biochemical profile in renal medulla and cortex of rat kidneys. The differential metabolites of cortex and medulla, enrichment analysis and pathway analysis were performed using metabolomics data. The GC-MS data revealed that 24 different antihypertensive metabolites was detected in renal cortex, while 16 were detected in renal medulla between different groups. The significantly metabolic pathways namely citrate cycle, glutathione metabolism, glycine, serine, and threonine metabolism, glyoxylate and dicarboxylate metabolism, glycerolipid metabolism, alanine, aspartate and glutamate metabolism in renal cortex and glycerolipid metabolism, pentose phosphate pathway, citrate cycle, glycolysis, glycerophospholipid metabolism, phenylalanine, tyrosine and tryptophan biosynthesis in renal medulla were involved in the process of Hypertension. The results suggest that the extract mainly alter the metabolic pathways of amino acid in Dahl salt-sensitive rats and its antioxidant potential reduced the hypertension patterns of Salt-sensitive rat. The antihypertensive components malic acid, aspartic acid, and glycine of extract can be used as therapeutic drugs to protect kidneys from salt-induced hypertension. PRACTICAL APPLICATIONS: Hypertension is a multifactorial disease and one of the risk factors for heart and kidney failure. Benincasa hispida is a widely used vegetable in China, which belongs to the Cucurbitaceae family. Benincasa hispida (wax gourd) has been used in traditional Chinese medicine for the treatment of inflammation and hypertension. The Benincasa hispida contains many compounds such as amino acids, carbohydrates, volatile compounds, vitamins, and minerals. The amino acid present in the pulp of Benincasa hispida are ornithine, threonine, aspartate, glutamate, serine, glycine, proline, alanine, valine, cysteine, isoleucine, tyrosine, leucine, lysine, phenylalanine, histidine, arginine, and γ-aminobutyric acid. Our results showed that Benincasa hispida is one of the potent natural antioxidants and can maintain normal blood pressure in Dahl salt-sensitive rats (D-SS). In conclusion, the current results provide good theoretical basis for the development and research using Benincasa hispida as an effective natural antioxidant for hypertension.

The serine protease plasmin plays detrimental roles in epithelial sodium channel activation and podocyte injury in Dahl salt-sensitive rats.

Salt-sensitive hypertension is associated with poor clinical outcomes. The epithelial sodium channel (ENaC) in the kidney plays pivotal roles in sodium reabsorption and blood pressure regulation, in which its γ subunit is activated by extracellular serine proteases. In proteinuric nephropathies, plasmin filtered through injured glomeruli reportedly activates γENaC in the distal nephron and causes podocyte injury. We previously reported that Dahl salt-sensitive (DS) rats fed a high-salt (HS) diet developed hypertension and proteinuria along with γENaC activation and that a synthetic serine protease inhibitor, camostat mesilate, mitigated these changes. However, the role of plasmin in DS rats remained unclear. In this study, we evaluated the relationship between plasmin and hypertension as well as podocyte injury and the effects of plasmin inhibitors in DS rats. Five-week-old DS rats were divided into normal-salt diet, HS diet, and HS+plasmin inhibitor (either tranexamic acid [TA] or synthetic plasmin inhibitor YO-2) groups. After blood pressure measurement and 24 h urine collection over 5 weeks, rats were sacrificed for biochemical analyses. The HS group displayed severe hypertension and proteinuria together with activation of plasmin in urine and γENaC in the kidney, which was significantly attenuated by YO-2 but not TA. YO-2 inhibited the attachment of plasmin(ogen) to podocytes and alleviated podocyte injury by inhibiting apoptosis and inflammatory/profibrotic cytokines. YO-2 also suppressed upregulation of protease-activated receptor-1 and phosphorylated ERK1/2. These results indicate an important role of plasmin in the development of salt-sensitive hypertension and related podocyte injury, suggesting plasmin inhibition as a potential therapeutic strategy.

Abstract P343: Adaptive Immune Mechanisms Exacerbate Cholinergic Activation-mediated Hypertension In Dahl Salt-sensitive Rats

Hypertension affects over one billion people worldwide and significantly contributes to the pathogenesis of cardiovascular and renal disease. Activation of nicotinic acetylcholine receptors (nAChR) in immune cells regulates immune responses. We have shown earlier that the development of hypertension in a genetic model of human essential hypertension, the Spontaneously Hypertensive Rats (SHR), is dependent on nAChR-mediated renal inflammation. Broadening the application of this mechanism, in the present study we hypothesized that nAChR activation plays a role in inflammation and the development of hypertension in a salt-sensitive model of hypertension, the Dahl salt-sensitive (DSS) rat. To test the hypothesis, we infused 4 weeks old DSS (n=12) and Dahl salt resistant (DSR, n=12) rats with either saline (n=6) or nicotine (15mg/kg/day, n=6) for 4 weeks. Animals were fed a 4% NaCl diet for the entire duration and moved into metabolic cages 3 days prior to euthanasia. Systolic blood pressure (SBP) measured by tail cuff method remained unaltered in DSR. However, SBP was significantly elevated in DSS rats that received nicotine as compared to saline (196.33±7.8 vs. 168±5.2 mmHg, p<0.05). SBP changes in nicotine infused DSS were not accompanied by differences in albuminuria or urinary sodium excretion compared to saline controls. RT-PCR revealed significantly increased CD3e mRNA expression (a marker of T-cell, P=0.04) in the immune cells derived from nicotine infused DSS as compared to saline controls. Increased CD3e mRNA expression in the kidney of nicotine infused DSS compared to saline was observed. Nicotine infusion did not change mRNA expression of nAChR subunits in DSR immune cells. In contrast, there was a ≥50% decrease in mRNA expression of α1-α7, α9, α10, β2, and β3 nAChR in immune cells derived from nicotine infused DSS compared to saline controls. There was a small yet significant increase in the mRNA expression of the β1-nAChR subunit in the immune cells of nicotine infused DSS compared to saline controls. We conclude that nAChR activation potentiates hypertension in the DSS independent of sodium retention or renal function. Our preliminary data suggests a possible role for nAChR mediated adaptive immune mechanisms in salt-sensitive hypertension.

Abstract 107: Adoptive Transfer Reveals That T Cell-Derived Reactive Oxygen Species Contributes To Pregnancy-Induced Renal Damage In The Dahl SS Rat

Previous work from our lab demonstrated that Dahl SS rats develop a pregnancy-specific increase in blood pressure and proteinuria, also known as maternal syndrome (MS). Both T cells and reactive oxygen species (ROS) have been implicated in MS, and genetic deletion of either resulted in protection from MS in the Dahl SS rat. Therefore, we tested the hypothesis that ROS produced from T cells contributes to the development of MS in the Dahl SS. An adoptive transfer of splenocytes was utilized to reconstitute T cells from wild type Dahl SS (SS→CD247) or SS p67phox-/- (p67phox→CD247), which lack the ability to generate NOX2-derived ROS, into SS CD247-/- rats by intraperitoneal injection at postnatal day 5 to investigate the oxidative capacity of T cells. Injected SS CD247-/- rats were mated at 9-11 weeks of age with naïve littermate males, and virgin controls were run in parallel. Baseline protein excretion rates were comparable between mated groups (72±12 vs 66±9 mg/day, p> 0.05, n=10/group, SS→CD247 vs p67phox→CD247, respectively), yet the SS→CD247 develop an increase in proteinuria throughout pregnancy that is significantly elevated relative to p67phox→CD247 rats (217±65 vs 114±14 mg/day, p< 0.05). There was a trending decrease in creatinine clearance in the SS→CD247 vs p67phox→CD247 at the end of the study (0.37±0.03 vs 0.46±0.06, p =0.1), but MAP did not differ between groups. There was however, an increase in uterine artery resistance index as assessed by Doppler ultrasound at GD20 in the SS→CD247 relative p67phox→CD247 (0.72±0.03 vs 0.61±0.02, p <0.01) indicating an impairment in blood flow leading to the placenta. While, there was no difference observed in the number of infiltrating leukocytes into the kidneys between SS→CD247 vs p67phox→CD247, a significant correlation was observed between the number of infiltrating CD4+ T cells and the late pregnancy proteinuria levels (R 2 =0.7973) in the SS→CD247 mated group while no correlation was observed in the p67phox→CD247 (R 2 =0.0472). Taken together, adoptive transfer of T cells lacking NOX2 into SS CD247-/- rats fails to induce pregnancy associated renal damage and uterine artery blood flow impairment indicating a potential role for ROS in MS.

Abstract 028: Toll-Like Receptor 4 Promotes Renal Immune Cell Infiltration And The Development Of Renal Damage During Dahl Salt-Sensitive Hypertension

Previous work in our laboratory has implicated a significant role for the immune system in potentiating the hypertensive and kidney damage phenotypes which occur in the Dahl Salt-Sensitive (SS) rat. Toll-like receptors (TLRs), usually expressed on macrophages, play a key role in the innate immune system. A number of TLRs have been implicated in cardiovascular disease and chronic kidney disease with particular interest in TLR4, which specifically binds gram-negative lipopolysaccharide or endogenous molecules produced as a result of tissue injury. We previously performed a transcriptomic analysis which demonstrated TLR4 upregulation in renal medullary tissue of Dahl SS rats fed a high salt (4.0% NaCl) diet. The present study tests the hypothesis that TLR4 influences high salt diet-induced hypertension and renal damage in the Dahl SS rat. Using CRISPR/Cas9 technology, a mutation was generated in the TLR4 gene on the Dahl SS background, creating a 1-bp frameshift deletion resulting in a premature stop codon. SS TLR4-/- males and parental Dahl SS males (SS TLR4+/+ ), maintained on a 0.4% NaCl chow, underwent carotid artery telemetry implantation at 7 weeks of age. After recovery and baseline mean arterial pressure (MAP) recordings (day 0: 125.6 ± 0.5 vs 124.2 ± 2 mmHg), animals were switched to a 4.0% NaCl chow for 3 weeks. Overnight urine collections occurred once during the low salt period and weekly throughout the high salt challenge. Kidneys were flushed prior to euthanasia. Although SS TLR4-/- MAP was not different from SS TLR4+/+ during the high salt challenge (day 21: 176.8 ± 14 mmHg, n=2 vs 172.3 ± 18 mmHg, n=4), high salt day 21 urinary albumin excretion was significantly reduced in SS TLR4-/- (272.7 ± 65 mg/day, n=5, p<0.01) compared to SS TLR4+/+ (427.5 ± 67 mg/day, n=7), indicating reduced renal damage in TLR4 absence. Furthermore, flow cytometric analysis of isolated renal immune cells indicated a 33% reduction in CD45+ total leukocytes (5.0 ± 1.2 vs 3.4 ± 0.9 x10 6 cells) and a 31% reduction in CD11bc+ monocytes/macrophages (3.9 ± 0.9 vs 2.6 ± 0.7 x10 6 cells) in SS TLR4-/- (n=5) vs SS TLR4+/+ (n=7) kidneys. Together, these data indicate that TLR4 may drive the immune response during the induction and progression of salt-sensitive hypertension and renal disease.

Abstract P075: Functional NOX2 In T Cells Amplifies Salt-Sensitive Hypertension And Associated Renal Damage

Infiltrating T cells in the kidney amplify salt-sensitive (SS) hypertension and renal damage, but the mechanisms are not known. Genetic deletion of T cells (SS CD247-/- ) or the p67phox subunit of NOX2 (SS p67phox-/- ) attenuates salt-sensitive hypertension in the Dahl SS rat. We hypothesized that reactive oxygen species (ROS) produced by NOX2 in T cells drive the SS phenotype and renal damage. T cells were reconstituted by adoptively transferring ~10 million splenocytes from the Dahl SS (SS→CD247, n=14), the SS p67phox-/- (p67phox→CD247, n=19), or PBS only (PBS→CD247, n=8), into the peritoneum of SS CD247-/- rats on postnatal day 5. Animals were instrumented with radiotelemeters at 8 weeks of age. After a week of recovery, blood pressure and albumin excretion were measured while rats were fed a low salt (LS, 0.4% NaCl) diet. Rats were then switched to a high salt (HS, 4.0% NaCl) diet for 21 days, with continuous blood pressure measurements and urine collections every 7 days. On day 22, the rats were euthanized, and their kidneys were perfused and collected for histology and renal immune cell characterization by flow cytometry. At baseline there was no detectable difference in mean arterial pressure (MAP) between groups (124±2 vs 123±2 vs 116±2 mmHg; SS→CD247 vs p67phox→CD247 vs PBS→CD247, respectively). After 21 days of HS, MAP was significantly greater in the SS→CD247 compared to the p67phox→CD247 rats (155±3 vs 144±2 mmHg; p<0.001) and the PBS→CD247 rats (155±3 vs 141±3 mmHg; p<0.001). Indices of renal damage identified no difference in albuminuria between SS→CD247 and p67phox→CD247 on LS (25.8±4.7 vs 23.2±3.2 mg/day). After 21 days of HS, albuminuria was significantly greater in the SS→CD247 (242.8±30.3 mg/day) compared to the p67phox→CD247 (175.5 ± 14.3 mg/day, p<0.03) and PBS→CD247 (135.9±27.8 mg/day, p<0.005). There was no difference between p67phox→CD247 and PBS→CD247 in albuminuria or MAP during LS or HS. The lack of CD3+ cells in the PBS→CD247 but presence of CD3+ cells in rats receiving the T cell transfer demonstrated the effectiveness of the adoptive transfer. These results indicate that ROS production by T cells participates in the amplification of salt-sensitive hypertension and renal damage.

Abstract 025: RNAseq And Bioinformatics Identify New Pathways In The Thick Ascending Limb (TAL) Involved In Fructose Induced Salt Sensitive Hypertension

Elevated fructose consumption is associated with hypertension in humans. In normal Sprague Dawley rats, a high fructose intake (20% fructose drinking water) induced salt sensitive hypertension. We found that fructose directly stimulates the apical Na/K/2Cl cotransporter NKCC2 in the thick ascending limb (TAL), and when consumed for more than 7 days, increases NKCC2 phosphorylation at Thre 96,101. SPAK and OSR1 kinases are known to phosphorylate NKCC2, but it is not known how fructose activates SPAK or OSR1. We hypothesized that fructose intake activates several signaling cascades in TALs that selectively stimulate SPAK. Using an antibody that recognizes activated SPAK and OSR1 (P-Ser 373 SPAK; Ser325 in OSR1), we found that 20% fructose (14 d) enhanced SPAK/OSR1 phosphorylation by 179±32% (p<0.05). This effect was specific for SPAK because phosphorylation of OSR1, immunoprecipitated from TALs, was not increased by fructose. To study the mechanism of SPAK activation, we isolated TALs from rats on control or 20% fructose diet for (14 d, n=6) and performed RNAseq. Over 12,000 genes were statistically compared and 500 were significantly different (p<0.05). Expression of some of the most highly upregulated genes (PRKRIP1 and SOCS3) was confirmed by Western blot in TALs. However, expression of upstream SPAK activators was unchanged by fructose (WNK1/3/4). We developed a targeted bioinformatics approach that included angiotensin signaling, nitric oxide and lipid metabolism, plus protein-protein interaction networks for SPAK. We identified PRKCQ (PKC Theta), a kinase upstream of SPAK, that was upregulated in TALs by fructose. In fructose fed rats, PRKCQ expression was 31±11% higher than control, as was Phospho-PRKCQ (223±45% increase, p<0.05). We then measured systolic BP (SBP) by telemetry in Dahl SS rats with genetic deletion of SPAK (SPAK KO). In WT Dahl SS rats, 4 weeks of fructose intake increased SBP by 25±4 mmHg (p<0.05), whereas in SPAK KO the increase in SBP was reduced (11±4 mmHg, p<0.05). We concluded that high fructose intake induces several prohypertensive signaling pathways in the TAL that lead to SPAK and NKCC2 activation. We identified PRKCQ as a potential activator of SPAK. Fructose induced hypertension in Dahl SS rats was in part mediated by SPAK.

Abstract P003: Chemerin Supports Basal Blood Pressure In Both Male And Female Dahl SS Rats

Evidence supports that Antisense oligonucleotides (ASO) against the adipokine chemerin reduce the blood pressure of the normal male Sprague Dawley rat and, to a greater magnitude, the hypertensive Dahl SS rat fed a high fat diet. In the Dahl SS rat, chemerin protein concentration in white adipose tissue [mesenteric perivascular adipose tissue (Mes PVAT)] was significantly higher in females vs males. We hypothesized that female Dahl SS rats would be more dependent on chemerin for blood pressure maintenance than males because of the Mes PVAT’s proximity to blood vessels that control total peripheral resistance. Age-matched male and female Dahl SS rats on a standard chow (0.2% NaCl, 6.2% fat) diet were used. Radiotelemeters were implanted to measure blood pressure (MAP) and heart rate (bpm). Following a two-week recovery period after implantation, one week of baseline measures were collected. Knockdown of whole body chemerin was achieved by subcutaneous injections of scrambled control ASO or whole-body ASO against chemerin (both 25 mg/kg) on days 0, 7, 14, and 21. On day 23, the rats were euthanized, and samples were collected for western blot and qPCR of the chemerin gene Rarres2 . Plasma chemerin was abolished in both male and female rats given the ASO against chemerin vs that of rats receiving the control ASO. In males and females, respectively, chemerin mRNA expression (2 -ΔCT ) was reduced from 0.53 to 0.001 ± 0.002 and 0.23 to 0.001 ± 0.02 in liver, 0.05 to 0.01 ± 0.005 and 0.07 to 0.005 ± 0.02 in RP fat, and 0.09 to 0.01 ± 0.003 and 0.05 to 0.001 ± 0.02 in epididymal/uterine fat. MAP in control ASO rats showed no significant change from baseline measurements (M:137.4 ± 3.0 /F: 130.6 ± 1.5 mmHg), while males and females treated with whole-body ASO dropped by 10.7 ± 1.6 and 10.9 ± 2.1 mmHg respectively after four injections, with no significant change in heart rate. Pulse pressure also decreased by 5.6 ± 1.3 and 6.8 ± 1.3 mmHg in whole-body ASO males and females, respectively, with no significant changes from baseline in the control animals. These data suggest, contrary to our hypothesis, that chemerin plays a similar role in basal blood pressure regulation in males and females. This indicates that males and females may be equally dependent on chemerin for high fat diet-induced hypertension.

Abstract P227: A High Fat Diet Does Not Enhance Blood Pressure Dependence On Chemerin In Normotensive Rats

Various humoral factors produced by adipose tissue are suggested to contribute to obesity associated hypertension and cardiovascular pathology. The adipokine chemerin is a frontrunner candidate. Male Dahl SS rats fed a high fat (HF; 60% kCal) diet from weaning develop severe hypertension that is profoundly reduced by weekly treatment with an antisense oligonucleotide (ASO) that disables chemerin mRNA. Here we hypothesized that feeding a HF diet from weaning to male Sprague Dawley (SD) rats would similarly increase the dependence of blood pressure (BP) regulation on chemerin. Over 17 weeks of feeding, HF fed SD rats gained significantly more weight and body fat than those fed control (10% kCal) diet. Radiotelemeters were implanted at 17 weeks of age to measure BP. Two weeks of basal BP was collected, and as we and others have shown previously, the HF diet did not increase BP in SD rats (control = 117±2.5 mm Hg; HF = 122±2.2 mm Hg). Vehicle or Gen 2.5 ASO chemerin (25 mg/kg, sc) were then given once a week for four weeks. Gen 2.5 ASO chemerin caused a slowly developing but significant reduction in BP in control rats (-14.0±2.7 mm Hg) that was not significantly different from the BP fall in HF rats (-12.4±2.3 mm Hg). RT-PCR analyses validated complete loss of chemerin mRNA in the liver and fat (primary producers of chemerin) from rats given the Gen 2.5 ASO chemerin vs control. These data show that in normal, normotensive rats a HF diet alone is insufficient to increase BP dependence on chemerin

Association of Antihypertensive Effects of Esaxerenone with the Internal Sodium Balance in Dahl Salt-Sensitive Hypertensive Rats.

Background: The nonsteroidal mineralocorticoid receptor blocker esaxerenone is effective in reducing blood pressure (BP). Objective: In this study, we investigated esaxerenone-driven sodium homeostasis and its association with changes in BP in Dahl salt-sensitive (DSS) hypertensive rats. Methods: In the different experimental setups, we evaluated BP by a radiotelemetry system, and sodium homeostasis was determined by an approach of sodium intake (food intake) and excretion (urinary excretion) in DSS rats with a low-salt diet (0.3% NaCl), high-salt diet (HSD, 8% NaCl), HSD plus 0.001% esaxerenone (w/w), and HSD plus 0.05% furosemide. Results: HSD-fed DSS rats showed a dramatic increase in BP with a non-dipper pattern, while esaxerenone treatment, but not furosemide, significantly reduced BP with a dipper pattern. The cumulative sodium excretion in the active period was significantly elevated in esaxerenone- and furosemide-treated rats compared with their HSD-fed counterparts. Sodium content in the skin, skinned carcass, and total body tended to be lower in esaxerenone-treated rats than in their HSD-fed counterparts, while these values were unchanged in furosemide-treated rats. Consistently, sodium balance tended to be reduced in esaxerenone-treated rats during the active period. Histological evaluation showed that esaxerenone, but not furosemide, treatment attenuated glomerulosclerosis, tubulointerstitial fibrosis, and urinary protein excretion induced by high salt loading. Conclusions: Collectively, these findings suggest that an esaxerenone treatment-induced reduction in BP and renoprotection are associated with body sodium homeostasis in salt-loaded DSS rats.

Modulation of blood pressure regulatory genes in the Agtrap-Plod1 locus associated with a deletion in Clcn6.

The AGTRAP‐PLOD1 locus is a conserved gene cluster containing several blood pressure regulatory genes, including CLCN6, MTHFR, NPPA, and NPPB. Previous work revealed that knockout of Clcn6 on the Dahl Salt‐Sensitive (SS) rat background (SS‐Clcn6) resulted in lower diastolic blood pressure compared to SS‐WT rats. Additionally, a recent study found sickle cell anemia patients with mutations in CLCN6 had improved survival and reduced stroke risk. We investigated whether loss of Clcn6 would delay the mortality of Dahl SS rats on an 8% NaCl (HS) diet. No significant difference in survival was found. The ability of Clcn6 to affect mRNA expression of nearby Mthfr, Nppa, and Nppb genes was also tested. On normal salt (0.4% NaCl, NS) diets, renal Mthfr mRNA and protein expression were significantly increased in the SS‐Clcn6 rats. MTHFR reduces homocysteine to methionine, but no differences in circulating homocysteine levels were detected. Nppa mRNA levels in cardiac tissue from SS‐Clcn6 rat in both normotensive and hypertensive conditions were significantly reduced compared to SS‐WT. Nppb mRNA expression in SS‐Clcn6 rats on a NS diet was also substantially decreased. Heightened Mthfr expression would be predicted to be protective; however, diminished Nppa and Nppb expression could be deleterious and by preventing or blunting vasodilation, natriuresis, and diuresis that ought to normally occur to offset blood pressure increases. The conserved nature of this genetic locus in humans and rats suggests more studies are warranted to understand how mutations in and around these genes may be influencing the expression of their neighbors.

Divergence of Chemerin Reduction by an ATS9R Nanoparticle Targeting Adipose Tissue In Vitro vs. In Vivo in the Rat.

Nanoparticles (NPs) can enable delivery of a drug to a targeted tissue. Previous studies have shown that an NP utilizing an adipose targeting sequence (ATS) peptide in conjunction with a drug can selectively deliver the drug to mouse adipose tissues, using the prohibitin protein expressed in adipose tissue as the target of the ATS. Adipose tissue is a major source of the adipokine chemerin, a prohypertensive protein. Liver-derived chemerin, the largest source of circulating chemerin, is biologically inactive in blood pressure regulation. Our goal is to understand if chemerin produced in adipose tissue contributes to blood pressure/hypertension. We hypothesize the ATS drug delivery system could be used specifically to reduce the levels of adipose tissue-derived chemerin. We created an NP consisting of an antisense oligonucleotide (ASO) against chemerin and a FITC-labeled ATS with a nine arginine sequence (ATS9R). In vitro studies showed that the ASO is functional when incorporated into an NP with ATS9R as it reduced chemerin mRNA expression in isolated epidydimal (Epi) and retroperitoneal (RP) fat adipocytes from Dahl SS rats. This same NP reduced chemerin in isolated whole fats. However, this NP was unable to selectively deliver the ASO to adipose tissue in vivo; liver delivery was dominant. Varying NP doses, administration route, and the concentration of components constituting the NP showed no improvement in ASO delivery to fats vs. the liver. Further studies are therefore needed to develop the ATS9R system to deliver an ASO to adipose beds in rats.

Momordica charantiaExtract Confers Protection Against Hypertension in Dahl Salt-Sensitive Rats.

Hypertension is one of the main factors of cardiovascular disease worldwide and is strongly related to the overall mortality. High salt intake is a major risk factors for hypertension. Identifying functional foods that can help prevent mechanistic abnormalities mediating salt-induced hypertension is an issue of considerable nutraceutical and scientific interest. Dietary Momordica charantia may be an alternative approach to avoid salt-induced hypertension. Dahl salt-sensitive (DSS) rats were used to determine whether Momordica charantia water extracts (ME) exerts anti-hypertensive effects in the present study. ME gavage could significantly prevented the increase of blood pressure, blood urea nitrogen, creatinine, and urine protein-to-creatinine ratio of DSS rats. Metabolomics analysis indicated that high-salt diet induced abnormal amino acid metabolism was related to nitric oxide (NO) deficiency, but ME gavage could upregulate the activities of nitric oxide synthase, aspartate aminotransferase, argininosuccinate lyase, argininosuccinate synthase and restore endogenous synthesis of arginine and NO. Meanwhile, renal function was improved after ME gavage. Citrulline, as one of the important component in ME, could attenuate salt-induced hypertension by increasing endogenous synthesis of arginine and NO. Antioxidants in ME, such as phenolic compound, may avoid high-salt induced oxidative stress in DSS rats, which may be another mechanism by which ME prevented blood pressure increase. Thus, the present study indicated that feeding Momordica charantia could avoid high-salt-induced hypertension in DSS rats.

First Author Spotlight

AnnouncementFirst Author SpotlightPublished Online:07 Jun 2022https://doi.org/10.1152/ajprenal.2022.322.6.AUMoreSectionsPDF (247 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat MADELINE GAUTHIERDepartment of Physiology, University of Arizona Health Sciences Center, Tucson, ArizonaFigure 1.Madeline GauthierDownload figureDownload PowerPointMadeline Gauthier is an MD student and PhD candidate, conducting a PhD while on a leave of absence from medical school at Loyola University Chicago. She is currently completing her PhD in the Physiological Sciences Graduate Interdisciplinary Program at the University of Arizona [Photo: Fig. 1].https://doi.org/10.1152/ajprenal.00009.2022OLHA KRAVTSOVADepartment of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FloridaFigure 2.Olha KravtsovaDownload figureDownload PowerPointOlha Kravtsova is a postdoctoral fellow in Dr. Alexander Staruschenko’s laboratory at the University of South Florida in the Department of Molecular Pharmacology and Physiology. She earned her PhD degree at the Institute of Hydrobiology, Kyiv, Ukraine. Her current research focuses on renal transporters, specifically in the proximal tubule. Outside of work, she enjoys workouts, traveling, and hiking [Photo: Fig. 2].https://doi.org/10.1152/ajprenal.00053.2022This article has no references to display. Download PDF Back to Top Next FiguresReferencesRelatedInformation Collections Related ArticlesSGLT2 inhibition effect on salt-induced hypertension, RAAS, and Na+ transport in Dahl SS rats 16 May 2022American Journal of Physiology-Renal PhysiologyContributions of afferent and sympathetic renal nerves to cystogenesis and arterial pressure regulation in a preclinical model of autosomal recessive polycystic kidney disease 16 May 2022American Journal of Physiology-Renal Physiology More from this issue > Volume 322Issue 6June 2022Pages i-i Crossmark Copyright & PermissionsCopyright © 2022 the American Physiological Society.https://doi.org/10.1152/ajprenal.2022.322.6.AUHistory Received 2 November 2021 Accepted 30 March 2022 Published online 7 June 2022 Published in print 1 June 2022 Metrics

Effects of elevation of ANP and its deficiency on cardiorenal function.

Atrial natriuretic peptide (ANP), encoded by Nppa, is a vasodilatory hormone that promotes salt excretion. Genome-wide association studies identified Nppa as a causative factor of blood pressure development, and in humans, ANP levels were suggested as an indicator of salt sensitivity. This study aimed to provide insights into the effects of ANP on cardiorenal function in salt-sensitive hypertension. To address this question, hypertension was induced in SSNPPA–/– (KO of Nppa in the Dahl salt-sensitive [SS] rat background) or SSWT (WT Dahl SS) rats by a high-salt (HS) diet challenge (4% NaCl for 21 days). Chronic infusion of ANP in SSWT rats attenuated the increase in blood pressure and cardiorenal damage. Overall, the SSNPPA–/– strain demonstrated higher blood pressure and intensified cardiac fibrosis (with no changes in ejection fraction) compared with SSWT rats. Furthermore, SSNPPA–/– rats exhibited kidney hypertrophy and higher glomerular injury scores, reduced diuresis, and lower sodium and chloride excretion than SSWT when fed a HS diet. Additionally, the activity of epithelial Na+ channel (ENaC) was found to be increased in the collecting ducts of the SSNPPA–/– rats. Taken together, these data show promise for the therapeutic benefits of ANP and ANP-increasing drugs for treating salt-sensitive hypertension.

Btg2 mutation induces renal injury and impairs blood pressure control in female rats.

Hypertension (HTN) is a complex disease influenced by heritable genetic elements and environmental interactions. Dietary salt is among the most influential modifiable factors contributing to increased blood pressure (BP). It is well established that men and women develop BP impairment in different patterns and a recent emphasis has been placed on identifying mechanisms leading to the differences observed between the sexes in HTN development. The current work reported here builds on an extensive genetic mapping experiment that sought to identify genetic determinants of salt-sensitive (SS) HTN using the Dahl SS rat. BTG antiproliferation factor 2 (Btg2) was previously identified by our group as a candidate gene contributing to SS HTN in female rats. In the current study, Btg2 was mutated using transcription activator-like effector nuclease (TALEN)-targeted gene disruption on the SSBN congenic rat background. The Btg2 mutated rats exhibited impaired BP and proteinuria responses to a high-salt diet compared with wild-type rats. Differences in body weight, mutant pup viability, skeletal morphology, and adult nephron density suggest a potential role for Btg2 in developmental signaling pathways. Subsequent cell cycle gene expression assessment provides several additional signaling pathways that Btg2 may function through during salt handling in the kidney. The expression analysis also identified several potential upstream targets that can be explored to further isolate therapeutic approaches for SS HTN.

SPAK‐Independent NKCC2 Phosphorylation in Dahl SS Rats: A Role for TNIK in NKCC2 Hyperphosphorylation

Increased NaCl reabsorption in the Thick Ascending Limb (TAL) is implicated in salt sensitive hypertension. NaCl reabsorption by the TAL is mediated by the apical Na/K/2Cl cotransporter NKCC2. We reported that NKCC2 phosphorylation at Tre 96,101 and surface expression are enhanced in Dahl Salt sensitive rats (Dahl SS) on normal or high salt diets. The phosphorylation of SPS1‐related proline/alanine‐rich kinase (SPAK), an upstream kinase for Thre 96,101 in NKCC2, was found to be higher in Dahl SS TALs. Deletion of SPAK in Dahl SS, lowers NKCC2 phosphorylation and expression and blunts salt‐sensitive hypertension, but does not completely prevent this. Other kinases may be involved in NKCC2 phosphorylation. Using a targeted proteomics approach, we identified TNIK (Traf2 and NCK interacting kinase) as a kinase that binds and phosphorylates Thre 96,101 in NKCC2. We hypothesize that TNIK is in part responsible for enhanced NKCC2 phosphorylation in Dahl SS rats. We first measured total expression of SPAK, OSR1 and TNIK by Western blot in TALs isolated form Dahl SS and control rats. SPAK and OSR1 expression (normalized to GAPDH) was similar between strains whereas TNIK expression was 3‐fold higher in Dahl SS TALs (control: 100, Dahl SS: 396±80%, n =5, p<.025). We then tested whether a novel TNIK inhibitor (KY‐05009) decreased NKCC2 phosphorylation in Dahl SS rats. Treating TALs from Dahl SS with KY‐05009 (1 µM) for 25 min decreased NKCC2 Thre 96,101 phosphorylation by 40±4% (p<0.05, n=5). To study whether NKCC2 phosphorylation can be stimulated in the absence of SPAK, we used SPAK knockout Dahl SS rats. Baseline NKCC2 expression and phosphorylation in TALs was 50% lower in Dahl SS‐SPAK KO TALs, however, stimulation of Beta‐adrenergic receptors with Isoproterenol increased NKCC2 phosphorylation by 192±49% (p<0.01, n =4) in SPAK‐KO. Similarly, the cAMP analogue db‐cAMP (500 µM) increased NKCC2 phosphorylation by 939±183% in SPAK KO (p<0.01 n=4) and by 497±105% (p<0.01 n=4) in control rat TALs, indicating that a kinase other than SPAK is essential for baseline and cAMP‐stimulated NKCC2 phosphorylation in Dahl SS rats. We conclude that enhanced NKCC2 phosphorylation at baseline in Dahl SS TALs is in part caused by TNIK, which show 3‐fold higher expression in this strain. SPAK also contributes to higher baseline NKCC2 phosphorylation, whereas a kinase other than SPAK (either TNIK or OSR1) is involved in cAMP‐stimulated NKCC2 Thre 96,101 phosphorylation in Dahl SS TALs.

Corn Bedding Mediates Protection from the Dahl Salt‐Sensitive Hypertensive and Renal Damage Phenotype

The Dahl Salt‐Sensitive (SS) rat is a well‐established translational model of human salt sensitive hypertension. When challenged with a high salt (4.0% NaCl) diet, Dahl SS develop an increase in mean arterial pressure (MAP) and renal damage, as assessed by an increase in albumin excretion and infiltration of immune cells in the kidneys. Our colony of Dahl SS recently moved to a new animal facility, and we observed that the SS rats challenged on a high salt diet showed an attenuation of the high salt‐induced increase in MAP and albumin excretion. Upon further investigation, differences in the animal bedding were noted between the locations. In the present study, the salt‐sensitive disease phenotype was examined in age‐matched, genetically‐identical male Dahl SS rats fed the same diets (AIN‐76A with 0.4% or 4.0% NaCl) maintained on either an aspen‐based wood bedding or a corn‐cob based bedding. Based upon the known protective effects of a plant‐based diet and observations that the rats were eating the corn‐cob bedding, we hypothesized that the change in bedding from wood to corn was providing a protective phenotype to the SS rats. We tested this hypothesis by comparing the disease phenotypes in Dahl SS maintained on the corn‐cob or wood bedding from birth until the end of the study. SS rats were instrumented at 7 weeks of age with radiotelemeters for continuous blood pressure monitoring and were allowed about a week to recover. While the rats were maintained on a low salt (0.4% NaCl) diet, there were no significant differences in MAP (123.2±1.1 vs 126.8±0.8 mmHg, n=13, 16) or albumin excretion rate (7.5±1.8 vs 18.8±3.5 mg/day, n=10, 17) in Dahl SS maintained on the corn‐cob vs the wood bedding, respectively. While MAP and albumin excretion significantly increased in all Dahl SS following a 21‐day high salt challenge, there was significantly reduced albumin excretion in the corn‐cob bedding rats (128±27 mg/day, n=10) when compared to the wood bedding rats (332±50 mg/day, n=17, p˂0.005). The SS rats maintained on the corn‐cob bedding also had significantly attenuated MAP at the end of the 21 day challenge when compared to the rats on the wood bedding (corn‐cob bedding: 141.1±4.2 mmHg vs wood bedding: 159.5±3.6 mmHg, p˂0.0001, n=12, 16 respectively). This was further characterized with a significant reduction in CD45+ leukocytes infiltrating in the SS rat kidneys on corn‐cob bedding by ~48% (p<0.003). That occurred by a significant reduction observed in the CD11b/c+ macrophages/monocytes by ~49% (p<0.003) and in CD45R+ B‐cells by ~64% (p<0.004). There was no difference between the body weights of the rats between the different beddings (corn‐cob bedding: 336±6 g vs wood bedding: 339±5 g, n=13, 17) respectively but kidney weight was a significantly reduced by ~17% (p<0.0001) in corn‐cob bedding compared to the SS rats on the wood bedding. This attenuated phenotype was also mirrored in female Dahl SS rats when maintained on the corn‐cob bedding compared to age‐matched females on the wood bedding. These data suggest that the change in bedding from wood to corn had a significant protective effect in the Dahl SS rat. Further work will need to be performed to determine the exact cause in the reduction of the salt‐sensitive phenotype when on a corn‐cob bedding. These data highlight the importance of controlling all environmental parameters in experimental work, and to consider environmental effects that may influence other disease phenotypes.

CD14 Deletion Amplifies Dahl Salt‐Sensitive Hypertension and Renal Damage through a NOX2‐dependent Mechanism

Previous work has implicated the immune system in potentiating salt‐sensitive (SS) hypertension. The innate immunity protein Cluster of Differentiation 14 (CD14), a co‐receptor with Toll‐like Receptor 4 in the inflammasome pathway of macrophages, has been associated with cardiovascular disease in humans. Interestingly, genetic deletion of CD14 in the Dahl SS rat (SSCD14‐/‐) confers a significant exacerbation of salt‐induced hypertension and associated renal disease that is specific to females. We speculated that CD14 may modulate the production of reaction oxygen species (ROS), since our previous findings implicate NADPH oxidase 2 (NOX2) derived ROS in immune cells in the pathogenesis of salt‐sensitive hypertension. In initial in vitro studies (n>4), peritoneal macrophages from Dahl SS, SSCD14‐/‐, and SSp67phox‐/‐ (a strain lacking the critical p67phox subunit of NOX2) rats were stimulated with phorbol 12‐myristate 13‐acetate, and the production of superoxide was assessed by chemiluminescence via luminol derivative L‐012. Specificity was determined using superoxide dismutase which diminished all detected signal. Superoxide release was 2.4x greater from peritoneal macrophages from female SSCD14‐/‐ when compared to SS macrophages. The SSp67phox‐/‐, lacking NOX2 activity, served as a negative control. The present study tests the hypothesis that the amplification of salt‐sensitive hypertension and renal damage in Dahl SS females lacking CD14 is mediated by NOX2. A double knockout Dahl SS rat was bred to lack both CD14 and functional NOX2 (SSCD14‐/‐p67phox‐/‐ (DKO)) to investigate a potential link between CD14 and oxidative stress. The hypertensive and kidney injury phenotype in response to a 3 week high salt challenge (HS, 4.0% NaCl, AIN‐76A) was examined in DKO females compared to SSCD14‐/‐ and SSp67phox‐/‐ females. After 3 weeks of HS, DKOrats had a significantly blunted change in mean arterial pressure (MAP) from baseline (0.4%) to HS day 21 compared to SSCD14‐/‐ rats (15 mmHg, n=3 versus 38 mmHg, n=7, p=0.01). Importantly, HS MAP in the DKO was not different than that of the SSp67phox‐/‐ (121 ± 4 mmHg versus 120 ± 2 mmHg, n=3, p>0.05), indicating that ROS production from NOX2 is likely mediating the amplified elevation of MAP following CD14 deletion. As an index of renal damage, albuminuria was significantly reduced in the DKO (11.8 ± 1.7 mg/day, n=9, p=0.004) compared to the SSCD14‐/‐ (101.8 ± 17.5 mg/day, n=12) at HS day 21. There was no difference in albuminuria between the DKO and SSp67phox‐/‐(11.7 ± 2.9 mg/day, n=7, p>0.05). Flow cytometric analysis of immune cells isolated from the kidneys of these rats indicated a reduction in renal inflammation in the DKO compared to the SSCD14‐/‐. There were fewer CD45+ total leukocytes (46% reduction), CD3+ T cells (45%), CD45R+ B cells (60%), and CD11b/c+ monocytes/macrophages (46%) in DKO (n=7) versus SSCD14‐/‐ kidneys (n=7). Together, these data suggest a role of CD14 in reducing the pathogenesis of salt‐sensitive hypertension and renal damage in a process dependent upon NOX2‐mediated oxidative stress. Here we highlight a novel renoprotective role of CD14.