Dahl Salt-sensitive Rat Model Research Articles

Progesterone Supplementation Improves the Maternal Syndrome of Superimposed Preeclampsia in the Dahl Salt Sensitive Rats

Introduction: Preeclampsia (PE) is characterized by new onset of hypertension after 20 weeks of gestation. It affects 5-7% of all pregnancies in the U.S., and is associated with reduced fetal weight, inflammation and hypertension (HTN). Importantly, 30% of HTN disorders in pregnancy are caused by chronic HTN that is present prior to pregnancy which increases the risk of superimposed PE (SIPE). The mechanisms responsible for the pathogenesis of PE and SIPE are unclear and currently the only treatment is early delivery of the fetus. Progesterone is important for the establishment and maintenance of pregnancy. We have previously shown that progesterone supplementation with 17-hydroxyprogesterone caproate (17-OHPC) improves inflammation, fetal weight and blood pressure in the preclinical RUPP rat model of PE, however the mechanism for this in SIPE is still unknown. Hypothesis: This study was designed to test the hypothesis that 17-OHPC reduces inflammation while improving maternal blood pressure in the preclinical pregnant Dahl Salt Sensitive (DS) rat model of SIPE. Methods: 17-OHPC (3.32mg/kg) or vehicle (Saline) was administrated intraperitoneally on gestation day (GD) 15 to normal pregnant (NP) Sprague-Dawley (SD) and pregnant Dahl Salt Sensitive (DS) rats. On GD 18, Uterine Artery Resistance Index (UARI) was measured by Vevo Doppler Ultrasound and carotid catheters were inserted. On GD 19, mean arterial blood pressure (MAP) and samples were collected. All data are expressed as mean ± standard error means (SEM). Results: MAP was 105±5 mmHg in SD+ Saline rats (n=7) and 105±4 mmHg in SD+17-OHPC rats (n=4), 137±3 mmHg in DS + Saline rats (p<0.05, n=11), which improved to 125±4 mmHg in DS+17-OHPC rats (p<0.05, n=7). Pup and Placenta weights were 2.1± 0.1 g, 0.6 ± 0.1 g in SD + saline rats and significantly reduced to 1.4±0.1 g, 0.5±0.1 g in DS+ Saline rats (p<0.05). Neither placental weight nor pup weight was affected by 17-OHPC. UARI was 0.5 ±0.1 in SD+ Saline rats (n=6) and 0.5 ±0.1 in in SD+17-OHPC (n=4), 0.7±0.1 in DS+Saline rats (n=6, p<0.05), which reduced to 0.5±0.1 in DS+17-OHPC (n=7, p<0.05). TNF-alpha levels were 3.0±1.0 pg/mL in SD+ Saline rats, 11.0±1.2 in DS + Saline rats, which reduced to 4.1±1.6 in DS+17-OHPC (n=4, p<0.05). Importantly, circulating and placental CD4+ T cells were 9.3±3.7 % Gate and 6.4± 1.6 % Gate in SD+ Saline rats (n=4), 38.9 ±2.9 % Gate and 33.1±4.3 % Gate in DS + Saline rats (n=6), which significantly reduced to 26.3 ± 0.1 % Gate and 3.4±1.2 % Gate in DS + 17-OHPC. Conclusion: Collectively, our findings demonstrate that 17-OHPC reduces inflammation and hypertension in the Dahl Salt Sensitive rat model of SIPE. Supported by NIH P20GM121334. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Salt-Sensitive Hypertension and Renal Damage are Amplified by Adoptive Transfer of CD4+ and Not CD8+ T Cells: A Role of NADPH Oxidase 2 (NOX2)

Infiltration of T cells into the kidney of the Dahl Salt Sensitive (SS) rat model of human disease accompanies the development of salt-sensitive hypertension and renal damage. Deletion of T cells on the Dahl SS genetic background (SSCD247−/−) attenuates hypertension and renal damage, and subsequent replacement of T cells by splenocyte transfer restores the disease phenotype. The present studies were performed to assess if the T cell subtype (CD4+ vs CD8+) is important in Dahl SS hypertension and interrogate the mechanism of action. In initial experiments, adoptive transfer of purified CD4+ or CD8+ T cells (~5 million) from splenocytes isolated from the Dahl SS (CD4+ SS→CD247 or CD8+ SS→CD247) or PBS vehicle (PBS→CD247) into the SSCD247−/− rat was performed on postnatal day 5. Animals were recovered and instrumented with radiotelemeters at 7 weeks of age. After a week of recovery, baseline measurements of blood pressure and albumin excretion were obtained 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 21, the rats were euthanized, and their kidneys were perfused and collected for immune cell analysis by flow cytometry. During the LS baseline period there was no significant difference observed in mean arterial pressure (MAP) between the CD4+ SS→CD247, CD8+ SS→CD247, or PBS→CD247 groups (113±1, 115±1, 114±1 mmHg; n=21, 10, 24, respectively). After three weeks of HS, rats receiving CD4+ T cells from the SS (CD4+ SS→CD247) demonstrated an amplified salt-sensitive hypertension (154±3 mmHg) and albuminuria (184±22 mg/day) compared to blood pressure (140±3 and 145±3 mmHg) and albuminuria (82±9 and 85±8 mg/day) in the CD8+ SS→CD247 or PBS→CD247 groups, respectively. Since the deletion of the p67phox subunit of NADPH oxidase 2 (NOX2) in adoptively transferred splenocytes attenuated Dahl SS hypertension and kidney damage, parallel studies examined the influence of deletion of p67phox in CD4+ (n=14) and CD8+ T cells (n=8). The adoptive transfer of either CD4+ or CD8+ T cells lacking functional NOX2 did not alter the LS or HS blood pressure or albuminuria when compared to the PBS control group. Finally, a flow cytometric analysis at the end of the experiment confirmed the absence of CD3+ T cells in the PBS→CD247 and documented the reconstitution of equal numbers of CD4+ cells in the blood and kidney of the rats receiving CD4+ cells with intact or deficient NOX2. Interestingly, no difference was observed in CD8+ T cells in the kidney and blood of rats receiving CD8+ cells with intact or deficient NOX2, but a significant number of CD4+ T cells were also observed in the SSCD247−/− rats receiving the purified CD8+ T cells. In summary, these studies demonstrate that CD4+ T cells amplify salt-sensitive hypertension and renal damage in the Dahl SS via a NOX2-dependent mechanism while CD8+ T cells do not alter disease phenotypes when compared to PBS control. GRANTS: HL161231, HL166458, Georgia Research Alliance. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Dissociation of Hypertension and Renal Damage After Cessation of High-Salt Diet in Dahl Rats.

Every year, thousands of patients with hypertension reduce salt consumption in an effort to control their blood pressure. However, hypertension has a self-sustaining character in a significant part of the population. We hypothesized that chronic hypertension leads to irreversible renal damage that remains after removing the trigger, causing an elevation of the initial blood pressure. Dahl salt-sensitive rat model was used for chronic, continuous observation of blood pressure. Rats were fed a high salt diet to induce hypertension, and then the diet was switched back to normal sodium content. We found that developed hypertension was irreversible by salt cessation: after a short period of reduction, blood pressure grew even higher than in the high-salt phase. Notably, the self-sustaining phase of hypertension was sensitive to benzamil treatment due to sustaining epithelial sodium channel hyperactivity, as shown with patch-clamp analysis. Glomerular damage and proteinuria were also irreversible. In contrast, some mechanisms, contributing to the development of salt-sensitive hypertension, normalized after salt restriction. Thus, flow cytometry demonstrated that dietary salt reduction in hypertensive animals decreased the number of total CD45+, CD3+CD4+, and CD3+CD8+ cells in renal tissues. Also, we found tubular recovery and improvement of glomerular filtration rate in the postsalt period versus a high-salt diet. Based on earlier publications and current data, poor response to salt restriction is due to the differential contribution of the factors recognized in the developmental phase of hypertension. We suggest that proteinuria or electrolyte transport can be prioritized over therapeutic targets of inflammatory response.

Anti-hypertensive effect of a novel angiotensin II receptor neprilysin inhibitor (ARNi) -S086 in DSS rat model.

Angiotensin receptor-neprilysin inhibitor (ARNi), comprised of an angiotensin receptor blocker (ARB) and a neprilysin inhibitor (NEPi), has established itself as a safe and effective intervention for hypertension. S086 is a novel ARNi cocrystal developed by Salubris for the treatment of heart failure and hypertension. Dahl Salt Sensitive (DSS) hypertensive rat model and telemetry system were employed in this study to investigate the anti-hypertensive efficacy of S086 and compare it with the first ARNi-LCZ696. The study showed that oral administration of S086 dose-dependently lowered blood pressure (P < 0.001). The middle dosage of S086 (23 mg/kg) exhibited efficacy comparable to LCZ696 (68 mg/kg), while also demonstrating superiority at specific time points (P < 0.05). Notably, water consumption slightly decreased post-treatment compared to the vehicle group. Furthermore, there were significant increases in natriuresis and diuresis observed on the first day of treatment with 23 mg/kg and 68 mg/kg S086 (P < 0.001). However, over the course of treatment, the effects in all treatment groups gradually diminished. This study demonstrates the anti-hypertensive efficacy of S086 in DSS hypertensive rat model, offering promising avenues for the clinical development of S086 as a hypertension treatment.

Abstract P400: Effects Of Time Restricted Feeding On Blood Pressure And Urine Output

Americans consume ~48% more salt than the recommended daily intake, increasing the sodium load placed on the kidneys. Normally, the kidneys excrete this excess sodium, however salt-sensitive (SS) individuals are unable to do so and develop hypertension. Time-restricted feeding (TRF), in which food is consumed in &lt;10 hours, has been shown to improve various cardiometabolic disorders, however there is limited research on its effect in SS hypertension. The goal of this study was to determine if intermittent salt consumption via TRF can improve SS hypertension in the Dahl SS rat model. Male (n=7-9/group) and female (n=4/group) SS rats were randomly divided into the following groups: low salt ad libitum (LS ad lib), low salt TRF (LS TRF), high salt ad libitum (HS ad lib), or high salt TRF (HS TRF) and underwent a two-week protocol. During the first week, all rats had ad libitum access to their respective diet to establish hypertension in the HS groups. During the second week, some animals began TRF, in which food was provided for 8 hours during the active period (2200-0600 hrs), and metabolic phenotypes were assessed in all rats using the Promethion (Sable Systems). Urine was collected for 8-9 hrs after the feeding period. Prior to endpoint, anesthetized blood pressure was measured at the end of the fasting period. We found that the HS TRF group had reduced systolic blood pressure in both males (138.69 ± 4.29 mmHg vs 143.33 ± 7.43 mmHg; mean ± SEM) and females (129.19 ± 6.29 mmHg vs 135.85 ± 10.88 mmHg; mean ± SEM) compared to the HS ad lib group, however this was not significant. Urine excretion was significantly higher in the HS TRF group compared to the HS ad lib group in both males (8.89 ± 1.06 mL vs 4.06 ± 0.42 mL; mean ± SEM; p&lt;0.05) and females (7.5 ± 0.20 mL vs 4.88 ± 0.43 mL; mean ± SEM; p&lt;0.05). Furthermore, while the rats were in the Promethion, there was a higher amount of water loss (VH 2 O; which can include evaporated urine) in the HS TRF group compared to the HS ad lib group during the fasting period in both males (1.52 ± 0.03 g/hr vs 1.40 ± 0.03 g/hr; mean ± SEM; p&lt;0.05) and females (1.18 ± 0.03 g/hr vs 0.96 ± 0.01 g/hr; mean ± SEM; p&lt;0.05). Overall, these results may suggest that TRF produces a diuretic effect in the Dahl SS rat model, however further studies are required to confirm this.

Cardioprotective Effects of Paraoxanase 3 in a Dahl Salt-Sensitive Rat Model of Chronic Kidney Disease

Objective: Paraoxanases (Pon) are hydrolytic enzymes with three distinct isoforms. Decreased circulating Pon activity is associated with increased oxidant stress and adverse clinical outcomes in the setting of chronic kidney disease (CKD), yet the mechanism of action is unknown. We tested the hypothesis that Pon-3 is cardioprotective in a Dahl salt-sensitive model of hypertensive renal disease.&#x0D; Methods: Ten week old, age-matched, Dahl salt-sensitive wildtype and Pon3 mutant male and female rats were maintained on eight percent high salt diets for eight weeks to initiate the salt-sensitive hypertensive renal disease characteristic of this model. After eight weeks, animals were euthanized and hearts were processed for histology. Echocardiography was performed to measure left ventricular function.&#x0D; Results: By 8 weeks, mortality was observed in 18.2% of male SS-Pon3 KO rats on high salt; no mortality was observed in male SS male rats on high salt. In female rats, by 8 weeks 100% mortality was observed in SS-Pon3 KO rats on high salt diet while no mortality was observed in SS rats on high salt. High salt fed SS-Pon3 KO male rats that survived the echocardiography study demonstrated significantly decreased left ventricular end-systolic diameter and end-diastolic diameter, as well as significant increases in left ventricular relative wall thickness compared to age matched SS rats. Furthermore, SS-Pon3 KO rats demonstrated significantly increased heart-weight-to-body-weight ratio compared to age matched SS rats. &#x0D; Conclusion: These findings suggest a cardioprotective role for PON-3 in the setting of salt-sensitive hypertensive renal disease.

Paraoxanase 1 Regulation of Cardiac Inflammation and Fibrosis in a Dahl Salt-Sensitive Rat Model of Chronic Kidney Disease

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Paraoxanase 1 Deletion Leads to Increased Cardiac Remodeling and Cardiac Fibrosis in a Dahl Salt-Sensitive Rat Model of Chronic Kidney Disease

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Abstract 13724: Development of VS-041 as a Precision Medicine Targeting Cardiac-Relevant Matrix Metalloproteases (MMPs) in Heart Failure With Preserved Ejection Fraction (HFpEF)

Introduction. HFpEF is a heterogeneous syndrome, with several underlying etiologic and pathophysiologic factors. As “one size fits all” therapies are not equally efficacious across various HFpEF comorbidities, a precision medicine approach can offer a disease modifying treatment for HFpEF subpopulation stratified for specific molecular targets. Expression of MMP2, 9, and 13 in heart is elevated in HFpEF patients with hypertension, diabetes or coronary disease, and their levels in plasma correlate with survival, suggesting utility as predictive biomarkers. Genetic ablation of MMP2, 9, and 13 leads to a robust antifibrotic effect in the myocardium. Inhibition of MMP2, 9, and 13 directly regulates of Ca 2+ transients and protects sarcomere function. Hypothesis. We present preclinical profile of VS-041, a novel and narrow-spectrum MMP inhibitor, as a drug candidate for HFpEF patients with elevated levels of MMP2, 9, and 13. Methods and Results. VS-041, optimized with computer-aided drug design methods, shows single-digit IC 50 against MMP2 (1nM), MMP9 (2nM) and MMP13 (1nM), and maintains &gt;300-fold selectivity against MMP1 and TACE. In isolated cardiomyocytes VS-041 reduces contractility deficit due to fast pacing. With high predicted metabolic bioavailability (MF%=90), &gt;80% target occupancy by VS-041 is estimated after 50 mg/kg PO dose in rats. VS-041 demonstrated robust efficacy in Dahl Salt Sensitive rat model of hypertension and HFpEF after dosing at 25 or 50 mg/kg PO for 5 wks in a therapeutic mode (after 1-wk of high salt lead-in). VS-041 had no effect on blood pressure or ejection fraction confirming a direct effect on diastolic function. In Doppler mitral inflow, analysis of the isovolumic relaxation time and the E/A ratio of peak velocity of filling waves revealed 40% improvement in diastolic function. LV fibrosis was dose-proportionally decreased based on PSR morphometry. No adverse effects were observed after 5 weeks of dosing. Conclusions. Preclinical pharmacology and safety profile of VS-041 support its nomination as clinical candidate and initiation of IND-enabling studies. VS-041 has potential to be first-in-class precision medicine treatment for HFPEF patients with elevated levels of cardiac-relevant MMP2, 9 and 13.

LOSARTAN, ANGIOTENSIN II TYPE 1 RECEPTOR BLOCKER, REDUCED AORTIC STIFFNESS AND IMPROVED COGNITIVE FUNCTION IN DAHL SALT SENSITIVE RAT MODEL OF AGE-ASSOCIATED VASCULAR DEMENTIA

Objective: Cardiovascular diseases are the major contributors to the pathogenesis of vascular dementia. The Dahl salt sensitive (Dahl-S) rat model is characterized by the development of central arterial stiffness (CAS), hypertension and cognitive decline with age on a normal salt diet. We hypothesized that treatment with losartan (LOS), angiotensin II type 1 receptor (AT1R) blocker, via reduction of blood pressure (BP) and CAS, will improve cognitive function in aged Dahl-S rats. Design and method: Male Dahl-S rats (n = 30) were kept on a normal salt diet (0.5% NaCl) for the duration of the study. Baseline measurements were taken at 3- and/or 6-mo of age following by the treatment with LOS in drinking water (30 mg/kg/day, n = 14) or control treatment (n = 16) for 6-mo. Measurements were taken every 3 months and included systolic and diastolic BP (SBP, DBP), pulse wave velocity (PWV), a measure of CAS, left ventricular posterior wall thickness in diastole (LVPWd), fractional shortening (FS) and LV mass (by echocardiography). At 12-mo of age the rats were tested in operant chambers using a simple reaction task to assess attention and impulsivity, and in elevated plus maze (EPM) to assess anxiety-like behavior. Statistical analyses were performed using 2-way ANOVA and t-test. Data are presented as mean ± SEM. Results: Prior to the treatment, LOS and control groups did not display differences in any parameter analyzed. Following the treatment, LOS rats had lower SBP, DBP, PWV, thinner LVPWd, higher FS and smaller LV mass at 9- and 12-mo of age vs. control group (Fig.1A-F). In the reaction task, LOS rats demonstrated more correct responses and fewer premature responses. The LOS rats exhibited lower anxiety level, because they spent more time in the open arm of EPM vs. control rats (Fig.1G,H). Conclusions: Beneficial effect of LOS on cognitive function in aged male Dahl-S rats was associated with the improvement of cardiovascular function and remodeling. The CAS stabilizing and BP reduction by LOS treatment was associated with improved attentional performance, lower impulsivity and lower anxiety. The mechanistic basis of these effects of LOS on cognition via cerebrovascular and brain changes will be further investigated.

Changes of gut microbiome composition and metabolites associated with hypertensive heart failure rats

BackgroundThe potential role of the gut microbiome (GM) in heart failure (HF) had recently been revealed. However, the underlying mechanisms of the GM and fecal metabolome in HF have not been characterized. The Dahl salt-sensitive rat model of hypertensive heart failure (H-HF) was used to study the clinical symptoms and characteristics. To elucidate the pathogenesis of HF, we combined 16S rRNA gene sequencing and metabolomics to analyze gut microbial compositions and fecal metabolomic profiles of rats with H-HF.ResultsPCoA of beta diversity shown that the gut microbiome composition profiles among the three groups were separated. Gut microbial composition was significantly altered in H-HF rats, the ratio of Firmicutes to Bacteroidetes(F/B) increased and the abundance of Muribaculaceae, Lachnospiraceae, and Lactobacillaceae decreased. Significantly altered levels of 17 genera and 35 metabolites were identified as the potential biomarker of H-HF. Correlation analysis revealed that specific altered genera were strongly correlated with changed fecal metabolites. The reduction in short-chain fatty acids (SCFA)-producing bacteria and trimethylamine N-oxide (TMAO) might be a notable characteristic for H-HF.ConclusionsThis is the first study to characterize the fecal microbiome of hypertensive heart failure by integrating 16S rRNA gene sequencing and LC–MS-based metabolomics approaches. Collectively, the results suggesting changes of gut microbiome composition and metabolites are associated with hypertensive heart failure rats.

Potential mechanisms of Guizhi decoction against hypertension based on network pharmacology and Dahl salt-sensitive rat model

BackgroundGuizhi decoction (GZD), a classical Chinese herbal formula, has been widely used to treat hypertension, but its underlying mechanisms remain elusive. The present study aimed to explore the potential mechanisms and therapeutic effects of GZD on hypertension by integrating network pharmacology and experimental validation.MethodsThe active ingredients and corresponding targets were collected from the Traditional Chinese Medicine Systems Pharmacology database and Analysis Platform (TCMSP). The targets related to hypertension were identified from the CTD, GeneCards, OMIM and Drugbank databases. Multiple networks were constructed to identify the key compounds, hub targets, and main biological processes and pathways of GZD against hypertension. The Surflex-Dock software was used to validate the binding affinity between key targets and their corresponding active compounds. The Dahl salt-sensitive rat model was used to evaluate the therapeutic effects of GZD against hypertension.ResultsA total of 112 active ingredients, 222 targets of GZD and 341 hypertension-related targets were obtained. Furthermore, 56 overlapping targets were identified, five of which were determined as the hub targets for experimental verification, including interleukin 6 (IL-6), C–C motif chemokine 2 (CCL2), IL-1β, matrix metalloproteinase 2 (MMP-2), and MMP-9. Pathway enrichment analysis results indicated that 56 overlapping targets were mainly enriched in several inflammation pathways such as the tumor necrosis factor (TNF) signaling pathway, Toll-like receptor (TLR) signaling pathway and nuclear factor kappa-B (NF-κB) signaling pathway. Molecular docking confirmed that most active compounds of GZD could bind tightly to the key targets. Experimental studies revealed that the administration of GZD improved blood pressure, reduced the area of cardiac fibrosis, and inhibited the expression of IL-6, CCL2, IL-1β, MMP-2 and MMP-9 in rats.ConclusionThe potential mechanisms and therapeutic effects of GZD on hypertension may be attributed to the regulation of cardiac inflammation and fibrosis.

Gestational gut microbial remodeling is impaired in a rat model of preeclampsia superimposed on chronic hypertension.

Preeclampsia is a progressive hypertensive disorder of pregnancy affecting 2%-8% of pregnancies globally. Preexisting chronic hypertension is a major risk factor associated with developing preeclampsia, and growing evidence suggests a role for the gut microbiome in the development of preeclampsia. However, neither alterations in the gut microbiome associated with preeclampsia nor the mechanisms involved are fully understood. In this study, we tested the hypothesis that normal gestational maternal gut microbiome remodeling is impaired in the Dahl salt-sensitive (Dahl S) rat model of superimposed preeclampsia. Gut microbiome profiles of pregnant Dahl S, normal pregnant Sprague-Dawley (SD), and matched virgin controls were assessed by 16S rRNA gene sequencing at baseline; during early, middle, and late pregnancy; and 1-wk postpartum. Dahl S rats had significantly higher abundance in Proteobacteria, and multiple genera were significantly different from SD rats at baseline. The pregnant SD displayed a significant increase in Proteobacteria and genera such as Helicobacter, but these were not different between pregnant and virgin Dahl S rats. By late pregnancy, Dahl S rats had significantly lower α-diversity and Firmicutes compared with their virgin Dahl S controls. β-diversity was significantly different among groups (P < 0.001). KEGG metabolic pathways including those associated with short-chain fatty acids were different in Dahl S pregnancy but not in SD pregnancy. These results reveal an association between chronic hypertension and gut microbiome dysbiosis which may hinder pregnancy-specific remodeling in the gut microbial composition during superimposed preeclampsia.

Abstract 16835: Targeted Disruption of Paraoxonase 3 in a Dahl Salt-Sensitive Rat Model of Chronic Kidney Disease Increases Renal Cortical Pro-Inflammatory Eicosanoids

Background: Paraoxonase 3 (Pon3), is one of the three isoforms of the paraoxonase gene family. While Pon1 and Pon2 are widely studied, there is a paucity of knowledge regarding Pon3. Pon3 is synthesized in the liver and can circulate bound to high-density lipoproteins. There is significant expression in the kidney also. Pon3 has the ability to metabolize eicosanoids, which can act as signaling molecules and have known roles in the pathophysiology of some renal diseases. Decreased Pon activity is associated with elevated levels of eicosanoid metabolites and adverse clinical outcomes. We tested the hypothesis that targeted disruption of Pon3 results in elevated levels of pro-inflammatory eicosanoids and progression of renal injury. Methods/ Results: Ten week old male Dahl salt-sensitive (SS rats) and Pon3 mutant rats (SS Pon3 KO) were maintained on 8% high salt diet for eight weeks, to initiate salt-sensitive hypertensive renal disease. Previously we observed that SS Pon3 KO rats on eight weeks high salt diet demonstrated significantly increased phenotypic renal injury and mortality. In the current study, we noted that SS Pon3 KO had significantly decreased (p&lt;0.05) glomerular filtration rate compared to SS wild type. Blood pressure (radiotelemetry) as well as plasma angiotensin and aldosterone (LC-MS/MS) were not different between the two groups after high salt diet. We used targeted lipidomic profiling to determine eicosanoid content in renal cortex from SS Pon3 KO and SS wild type rats at the end of eight weeks of high salt diet. We found that hydroxyl fatty acids 5-HEPE and 5-HETE (5-lipoxygenase dependent arachidonic acid metabolites) were significantly (p&lt;0.05) elevated in the renal cortex of SS Pon3 KO compared to SS wild type rats. In addition to being mediators of inflammation, these metabolites are associated with renal cell injury and death. Furthermore, prostaglandin 6-keto-PGF 1α , which has known links to renal inflammation, was significantly (p&lt;0.05) increased in renal cortex of SS- Pon3 KO compared to SS wild type rats. Conclusion: These findings suggest that targeted deletion of Pon3 increases pro-inflammatory eicosanoids (5-HETE and 5-HEPE) and prostaglandins (6-keto-PGF 1α ), as well as increases renal damage independent of blood pressure.

Abstract 16965: Paraoxanase-1 Modulates Cardiotonic Steroid Induced Cardiac Inflammation and Fibrosis in Dahl Salt Sensitive Model of Chronic Kidney Disease

Objective: Cardiotonic steroids (CTS) are known ligands of the Na+/K+-ATPase (NKA) and chronic elevations in volume expanded conditions such as hypertension and chronic kidney disease (CKD) can mediate a pro-inflammatory and pro-fibrotic phenotype. Paraoxonase1 (PON1) is a lactonase enzyme that circulates bound to HDL and possesses antioxidant, anti-inflammatory and anti-atherogenic properties. PON1 can hydrolyze CTS to inactive open-ring forms making them incapable of stimulating NKA and initiating pro-inflammatory signaling cascades. Diminished PON1 activity results in detrimental clinical outcomes in the context of CKD but whether reduced PON1 activity is mechanistically linked to adverse cardiovascular events in CKD remains unknown. We hypothesized that PON-1 can attenuate progression of cardiac inflammation in CKD via modulating the pathogenic pathways induced by CTS signaling using a well characterized Dahl salt-sensitive rat model of hypertensive renal disease and elevated CTS. Methods: Dahl salt-sensitive wild type ( SS-WT ), PON1 knockout ( SS-PON1KO ), and PON1 knockout rats treated with 3E9 anti-CTS antibody (3E9 mAb,50μg/kg i.p. every week for a total of 4 injections) were fed a high salt (8%) diet for five weeks to induce hypertensive renal disease and elevate CTS levels. H&amp;E staining was performed on hearts to analyze immune cell infiltration. Real-time PCR (RT-PCR) analysis was performed for markers of inflammation (IL6, IL1β, and CCL2), hypertrophy (Myh7, NPPA, and Slc8a), and fibrosis (Timp1). Results: RT-PCR analysis revealed significantly increased (≥1.5 fold) expression of cardiac inflammatory (p&lt;0.005), hypertrophy (p&lt;0.0005), and fibrotic markers (p&lt;0.05) in SS-PON1 KO compared to SS-WT rats after high salt feeding. Treatment of SS-PON1 KO rats with 3E9 mAb significantly decreased (≥ 2.5 fold) expression of Timp1, IL6, Ccl2, IL1β, NPPA, Myh7 and Slc8a (all p&lt;0.005). H&amp;E analysis of hearts revealed significantly decreased immune cell infiltration in SS-PON1KO rats treated with 3E9 mAb compared to SS-PON-1 KO rats (3.5±0.5 VS1.813±0.4094,p&lt;0.005). Conclusion: Our findings suggest that PON-1 via its counter-regulatory mechanism of the CTS signaling axis exhibits a cardioprotective role in chronic kidney disease.

Abstract 14390: The Cardiac Myosin Inhibitor, Ck-3772271, Attenuates Cardiac Fibrosis and Diastolic Dysfunction in the Dahl/salt Sensitive Rat Model of Heart Failure With Preserved Ejection Fraction

Introduction: Heart failure with preserved ejection fraction (HFpEF) is characterized by underlying contractile dysfunction and progressive myocardial fibrosis and stiffness. CK-3772271 (CK-271) is a novel small molecule cardiac myosin inhibitor that reduces cardiac myosin ATPase activity and reduces cardiac contractility in unloaded isolated cardiomyocytes in vitro and in healthy rats and dogs in vivo . The effect of chronic CK-271 treatment on cardiac function and morphology was evaluated in the Dahl/Salt Sensitive (DSS) rat hypertension model of HFpEF. Methods: DSS male rats were fed either a control low salt (LS, 0.3% NaCl) or high salt (HS, 4% NaCl) diet to induce a hypertension-driven HFpEF disease phenotype. 6 weeks after HS diet treatment, DSS rats were randomized into two sub-groups: continued HS diet or a HS diet formulated with CK-271 (100 ppm) for an additional 6 weeks. Body mass, systolic blood pressure, and cardiac function were measured longitudinally. After 12 weeks of HS treatment, hearts were collected to assess cardiac fibrosis. Results: HS diet treatment increased systolic blood pressure (LS:132.2 ± 4.7 mm Hg vs. HS: 163.5 ± 4.0 mm Hg, mean ± SEM, p&lt; 0.001) and caused cardiac hypercontractility as evidenced by an increase in the end-systolic pressure-volume relationship (LS: 0.8 ± 0.17 vs. HS: 2.1 ± 0.46 mm Hg/ml). HS diet also increased isovolumic relaxation time (IVRT) (LS: 16.8 ± 0.6 vs. HS: 22.8 ± 0.6 ms, p&lt;0.0001), left atrial area (LS: 30.3 ± 0.8 vs. HS: 42.5 ± 2.2 mm 2 , p&lt;0.0001) and cardiac fibrosis (LS: 3.4 ± 0.4 vs. HS: 5.0 ± 0.6 %). 6 weeks of CK-271 treatment reduced fractional shortening (HS: 53.8 ± 1.4 vs. HS+CK-271: 42.7 ± 1.0 %, p&lt;0.0001) and reduced HS diet-induced diastolic dysfunction, including IVRT (HS: 22.8 ± 0.6 vs. HS+CK-271: 19.5 ± 0.5 ms, p&lt;0.0001) and left atrial area (HS: 42.5 ± 2.2 vs. HS+CK-271: 35.4 ± 0.8 mm 2 , p&lt;0.0001). Furthermore CK-271 reduced the development of cardiac fibrosis (HS: 5.0 ± 0.6 vs. HS+CK-271: 3.5 ± 0.3 %, p&lt;0.05) induced by HS diet. Conclusion: The small molecule cardiac myosin inhibitor, CK-3772271, attenuated the development of cardiac hypercontractility, diastolic dysfunction and fibrosis in the DSS rat model of HFpEF. Cardiac myosin inhibition may be a novel approach to mitigate the development of HFpEF.

Effects of Lisinopril on Arterial Stiffness, Cerebral Blood Flow, Neuronal Viability and Cortical Thickness in Late‐Life Hypertension in Dahl‐S Rats

Effects of Lisinopril on Arterial Stiffness, Cerebral Blood Flow, Neuronal Viability and Cortical Thickness in Late‐Life Hypertension in Dahl‐S Rats

Natural Compound Library Screening Identifies New Molecules for the Treatment of Cardiac Fibrosis and Diastolic Dysfunction.

Myocardial fibrosis is a hallmark of cardiac remodeling and functionally involved in heart failure development, a leading cause of deaths worldwide. Clinically, no therapeutic strategy is available that specifically attenuates maladaptive responses of cardiac fibroblasts, the effector cells of fibrosis in the heart. Therefore, our aim was to develop novel antifibrotic therapeutics based on naturally derived substance library screens for the treatment of cardiac fibrosis. Antifibrotic drug candidates were identified by functional screening of 480 chemically diverse natural compounds in primary human cardiac fibroblasts, subsequent validation, and mechanistic in vitro and in vivo studies. Hits were analyzed for dose-dependent inhibition of proliferation of human cardiac fibroblasts, modulation of apoptosis, and extracellular matrix expression. In vitro findings were confirmed in vivo with an angiotensin II-mediated murine model of cardiac fibrosis in both preventive and therapeutic settings, as well as in the Dahl salt-sensitive rat model. To investigate the mechanism underlying the antifibrotic potential of the lead compounds, treatment-dependent changes in the noncoding RNAome in primary human cardiac fibroblasts were analyzed by RNA deep sequencing. High-throughput natural compound library screening identified 15 substances with antiproliferative effects in human cardiac fibroblasts. Using multiple in vitro fibrosis assays and stringent selection algorithms, we identified the steroid bufalin (from Chinese toad venom) and the alkaloid lycorine (from Amaryllidaceae species) to be effective antifibrotic molecules both in vitro and in vivo, leading to improvement in diastolic function in 2 hypertension-dependent rodent models of cardiac fibrosis. Administration at effective doses did not change plasma damage markers or the morphology of kidney and liver, providing the first toxicological safety data. Using next-generation sequencing, we identified the conserved microRNA 671-5p and downstream the antifibrotic selenoprotein P1 as common effectors of the antifibrotic compounds. We identified the molecules bufalin and lycorine as drug candidates for therapeutic applications in cardiac fibrosis and diastolic dysfunction.

Soluble guanylate cyclase stimulator praliciguat attenuates inflammation, fibrosis, and end-organ damage in the Dahl model of cardiorenal failure.

Reduced nitric oxide (NO) and a decrease in cGMP signaling mediated by soluble guanylate cyclase (sGC) has been linked to the development of several cardiorenal diseases. Stimulation of sGC is a potential means for enhancing cGMP production in conditions of reduced NO bioavailability. The purpose of our studies was to determine the effects of praliciguat, a clinical-stage sGC stimulator, in a model of cardiorenal failure. Dahl salt-sensitive rats fed a high-salt diet to induce hypertension and organ damage were treated with the sGC stimulator praliciguat to determine its effects on hemodynamics, biomarkers of inflammation, fibrosis, tissue function, and organ damage. Praliciguat treatment reduced blood pressure, improved cardiorenal damage, and attenuated the increase in circulating markers of inflammation and fibrosis. Notably, praliciguat affected markers of renal damage at a dose that had minimal effect on blood pressure. In addition, liver fibrosis and circulating markers of tissue damage were attenuated in praliciguat-treated rats. Stimulation of the NO-sGC-cGMP pathway by praliciguat attenuated or normalized indicators of chronic inflammation, fibrosis, and tissue dysfunction in the Dahl salt-sensitive rat model. Stimulation of sGC by praliciguat may present an effective mechanism for treating diseases linked to NO deficiency, particularly those associated with cardiac and renal failure. Praliciguat is currently being evaluated in patients with diabetic nephropathy and heart failure with preserved ejection fraction.

Abstract P164: Sexual Dimorphic Role of CD14 in Dahl SS Hypertension

Previous work has implicated the immune system in potentiating salt-sensitive (SS) hypertension and kidney damage in the Dahl SS rat model. The innate immunity protein Cluster of Differentiation 14 (CD14), normally involved in bacterial responses of macrophages, has been associated with hypertension in humans. The present study tests the hypothesis that CD14 influences the extent of high-salt diet induced renal damage and hypertension in the Dahl SS rat, by modulating activation of the innate immune system. CD14 was mutated in the Dahl SS background using CRISPR-Cas9 technology, leading to the loss of CD14 protein in peritoneal macrophages (pMacs) as evidenced by mass spectrometry-based parallel reaction monitoring. pMac stimulation in vitro demonstrated altered IL-1β production in CD14-/- animals. To monitor SS phenotypes in vivo , male and female CD14+/+ and CD14-/- animals maintained on a 0.4% NaCl diet underwent carotid catheter telemetry implantation at 7 weeks of age (n=12/14). After recovery and baseline recordings, animals were switched to a 4.0% NaCl diet for 21 days. There was no significant difference in the SS increase in blood pressure or albuminuria between genotypes of males. However, female CD14-/- animals demonstrated exacerbated salt-sensitivity of blood pressure (+45mmHg) compared to wild types (+31mmHg). To determine what may mediate this difference, immune cells were isolated from the kidneys of these animals. Accordingly, males showed no difference in immune cell infiltration; whereas, female CD14-/- animals showed an elevation in the infiltration of CD11b/c+ macrophages. To determine whether knockout of CD14 in immune cells specifically was responsible for this phenotypic difference, a lethal dose of total body irradiation (11Gy) of CD14+/+ recipient animals followed by either CD14-/- or CD14+/+ bone marrow transfer experiment was done in female animals (n=6/7). Remarkably, even though all host tissue cells were wildtype, transfer of CD14-/- bone marrow recapitulated the exacerbated SS phenotypes, including increased renal infiltration of macrophages. Together, these data demonstrate that CD14 signaling in hematopoietic cells of females modulates the full extent of the immune response and blunts SS hypertension.