High-salt Group Research Articles

The genome and comparative transcriptome of the euryhaline model ciliate Paramecium duboscqui reveal adaptations to environmental salinity

BackgroundAs a potential model organism for studies of environmental and cell biology, Paramecium duboscqui is a special euryhaline species of Paramecium that can be found in fresh, brackish, or marine water in natural salinity ranges between 0‰ and 33‰. However, the genome information as well as molecular mechanisms that account for its remarkable halotolerant traits remain extremely unknown. To characterize its genome feature, we combined PacBio and Illumina sequencing to assemble the first high-quality and near-complete macronuclear genome of P. duboscqui. Meanwhile, comparative transcriptomic profiles under different salinities gave underlying insight into the molecular mechanism of its adaptations to environmental salinity.ResultsThe results showed that the MAC genome of P. duboscqui comprises 160 contigs, with 113 of them possessing telomere (~ 28.82 Mb haploid genome size). Through comparative genomic analyses with the other ciliate, we found that gene families encoding transmembrane transporter proteins have been expanded in P. duboscqui, showing enormous potential in salinity adaptation. Like other Paramecium, P. duboscqui utilizes TGA as its only termination codon and has reassigned TAA and TAG to encode glutamine. P. duboscqui showed different growth rates under different salinities, with an optimum growth rate in 5‰ salinity. A comparison of the transcriptomic profiles among P. duboscqui grown under different concentrations showed that genes involved in protein folding, oxygen respiration, and glutathione-dependent detoxification were upregulated in the high-salt group, whereas genes encoding DNA-binding proteins and transcription factors were upregulated in the low-salt group, suggesting distinct mechanisms for responding to low and high salinity. Weighted gene coexpression network analysis (WGCNA) linked the hub genes expressed at 30‰ salinity to cysteine-type peptidase activity, lipid transfer, sodium hydrogen exchange, and cell division, with the hub genes expressed at 0‰ salinity involved in transmembrane transport and protein localization.ConclusionsThis study characterizes a new euryhaline model Paramecium, provides novel insights into Paramecium evolution, and describes the molecular mechanisms that have allow P. duboscqui to adapt to different osmotic environments.

The Impact of Hydrogen Sulfide in the Paraventricular Nucleus on the MAPK Pathway in High Salt-Induced Hypertension.

The hypothalamic paraventricular nucleus (PVN) plays a central role in regulating cardiovascular activity and blood pressure. We administered hydroxylamine hydrochloride (HA), a cystathionine-β-synthase inhibitor, into the PVN to suppress endogenous hydrogen sulfide and investigate its effects on the mitogen-activated protein kinase (MAPK) pathway in high salt (HS)-induced hypertension. We randomly divided 40 male Dahl salt-sensitive rats into 4 groups: the normal salt (NS) + PVN vehicle group, the NS + PVN HA group, the HS + PVN vehicle group, and the HS + PVN HA group, with 10 rats in each group. The rats in the NS groups were fed a NS diet containing 0.3% NaCl, while the HS groups were fed a HS diet containing 8% NaCl. The mean arterial pressure was calculated after noninvasive measurement using an automatic sphygmomanometer to occlude the tail cuff once a week. HA or vehicle was infused into the bilateral PVN using Alzet osmotic mini pumps for 6 weeks after the hypertension model was successfully established. We measured the levels of H 2 S in the PVN and plasma norepinephrine using enzyme linked immunosorbent assay. In addition, we assessed the parameters of the MAPK pathway, inflammation, and oxidative stress through western blotting, immunohistochemical analysis, or real-time polymerase chain reaction. In this study, we discovered that decreased levels of endogenous hydrogen sulfide in the PVN contributed to the onset of HS-induced hypertension. This was linked to the activation of the MAPK signaling pathway, proinflammatory cytokines, and oxidative stress in the PVN, as well as the activation of the sympathetic nervous system.

Abstract 30: Acute Effects Of Sodium Chloride Or Its Substitute Potassium Chloride On Microvascular Function In Healthy Volunteers

Dietary high sodium intake is a modifiable risk factors for cardiovascular (CV) diseases including vascular dysfunction and subsequently arteriosclerosis. A partial sodium substitution by potassium is associated with a lower risk of CV events and death. Our aim was to investigate the acute impact of sodium and potassium on retinal microvascular function, an established biomarker for systemic CV risk stratification. Eighteen male and 27 female healthy individuals (mean age 31years) were randomized to eat a salty soup containing either 9g sodium chloride (high salt group), 6g sodium chloride (intermediate salt group) or 6g sodium chloride plus 3g potassium chloride (substitution group). Microvascular measurements were performed before (t0) as well as four (t4) and 24 hours (t24) after soup intake. Microvascular health was measured by investigating retinal vessel diameters. A higher arteriolar-to-venular diameter ratio (AVR) is associated with improved vascular health. Microvascular endothelial function was quantified by flickerlight-induced retinal arteriolar dilation. The 9g (139±2mmol/l vs. 141±2mmol/l, p<0.001) and 6g salt group (140±1mmol/l vs. 141±2 mmol/l, p=0.028) had higher serum sodium concentrations at t4 compared to baseline. Serum sodium concentrations of the substitution group showed no significant difference between time points, but a significant increase in serum potassium (3.7±0.3mmol/l vs. 3.9±0.2mmol/l, p=0.019). Microvascular endothelial function was significantly decreased in the high salt group from baseline to t4 (4.5±2.2% vs. 3.7±2.2%, p=0.041), without significant changes in the other groups. In the sodium groups, there was a strong correlation between the increase in serum sodium concentration from t0 to t4 and an impaired endothelial function after t4 (R 2 =0,255, p=0,005). The substitution group showed improved microvascular health, quantified by higher AVR at t4 compared to t0 (0,83±0,07 vs. 0,86±0,07, p<0,001). An increase in serum sodium was negatively associated with AVR (R 2 =0,14, p=0,013) whereas an increase in serum potassium was positively correlated with AVR (R 2 =0,19, p=0,003). An acute increase in serum sodium is associated with impaired microvascular endothelial function. Replacement of sodium by potassium seems to improve microvascular function already after a single potassium intake. These results might explain the beneficial effects of potassium on CV outcomes as well as the harmful effects of sodium on vascular function.

Effects of salt and rice flour concentration on microbial diversity and the quality of sour meat, a Chinese traditional meat

This study investigated the effects of salt (3 % and 6 %, m/m) and rice flour (10 % and 20 %, m/m) addition in sour meat, a traditional Chinese fermented meat. It was found that salt has greater effect than rice flour addition in spontaneous fermentation. Low-salt groups had lower pH and higher titratable total acid. In the low-salt groups, the dominant genera were Lactobacillus and Lactococcus, whereas Staphylococcus, Weissella, and Tetragenococcus were dominant in the high-salt groups. Higher total free amino acids and essential amino acids, organic acids, hexanoic acid ethyl ester and octanoic acid ethyl ester were found in the low-salt groups. The RDA analysis revealed that Lactococcus was closely related to product quality, with the S3F10 (3 % salt and 10 % rice flour) group outperforming the others in the sensory evaluation. Therefore, 3 % salt and 10 % rice flour were considered more appropriate for the production of healthy and tasty fermented sour meats.

Bile Acid Metabolism Analysis Provides Insights into Vascular Endothelial Injury in Salt-Sensitive Hypertensive Rats.

As an unhealthy dietary habit, a high-salt diet can affect the body's endocrine system and metabolic processes. As one of the most important metabolites, bile acids can prevent atherosclerosis and reduce the risk of developing cardiovascular diseases. Therefore, in the present study, we aimed to reveal the bile acid metabolism changes in salt-sensitive hypertension-induced vascular endothelial injury. The model was established using a high-salt diet, and the success of this procedure was confirmed by detecting the levels of the blood pressure, vascular regulatory factors, and inflammatory factors. An evaluation of the histological sections of arterial blood vessels and kidneys confirmed the pathological processes in these tissues of experimental rats. Bile acid metabolism analysis was performed to identify differential bile acids between the low-salt diet group and the high-salt diet group. The results indicated that the high-salt diet led to a significant increase in blood pressure and the levels of endothelin-1 (ET-1) and tumor necrosis factor-α (TNF-α). The high-salt diet causes disorders in bile acid metabolism. The levels of four differential bile acids (glycocholic acid, taurolithocholic acid, tauroursodeoxycholic acid, and glycolithocholic acid) significantly increased in the high-salt group. Further correlation analysis indicated that the levels of ET-1 and TNF-α were positively correlated with these differential bile acid levels. This study provides new evidence for salt-sensitive cardiovascular diseases and metabolic changes caused by a high-salt diet in rats.

The Effect of High-Salt Diet on Oxidative Stress Production and Vascular Function in Tff3−/−/C57BL/6N Knockout and Wild Type (C57BL/6N) Mice

Introduction: It is well documented that high-salt (HS) diet increases systemic and vascular oxidative stress in various animal models and in humans, leading to impairment of vascular reactivity. The present study examined the interaction of genotype and HS diet intake and the potential effects of oxidative stress – antioxidative system balance on the flow-induced dilation (FID) in pressurized carotid arteries of normotensive Tff3−/−/C57BL/6N knockout mice and their wild-type (WT) controls. Methods: Male, ten-week-old transgenic Tff3−/−/C57BL/6N (Tff3−/−) knockout mice and WT/C57BL/6N (WT) (parental strain) healthy mice were divided in LS (0.4% NaCl in rodent chow) and HS (4% NaCl in rodent chow fed for 1 week) groups. Additionally, LS and HS groups were treated with 1 mmol/L 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL) dissolved in the drinking water. After anesthesia with ketamine chloride (100 mg/kg) and midazolam (5 mg/kg), blood pressure was measured, carotid arteries and aortas were isolated, and blood samples were collected. Results: FID was decreased in WT_HS mice and restored by superoxide scavenger TEMPOL in vivo. On the other hand, attenuated FID of Tff3−/− mice was not further affected by HS diet or TEMPOL in vivo treatment. Vascular superoxide/reactive oxygen species levels were increased with HS diet in both strains and restored by TEMPOL. HS upregulated glutathione peroxidase 1 (GPx1) gene expression in WT_HS and Tff3−/−_HS mice, while GPx activity was significantly decreased only in WT_HS group. Systemic (serum) markers of oxidative stress (oxLDL and AOPP) and arterial blood pressure were similar among groups. Conclusion: HS diet increases vascular oxidative stress and impairs vasodilation in WT mice. Tff3 gene deficiency attenuates vasodilation per se, without further effects of HS intake. This can be attributed to vascular upregulation of antioxidative enzyme GPx1 in Tff3−/−/C57BL/6N mice conferring protection from oxidative stress.

The Participation of Ferroptosis in Fibrosis of the Heart and Kidney Tissues in Dahl Salt-Sensitive Hypertensive Rats.

Salt-sensitive hypertension is often more prone to induce damage to target organs such as the heart and kidneys. Abundant recent studies have demonstrated a close association between ferroptosis and cardiovascular diseases. Therefore, we hypothesize that ferroptosis may be closely associated with organ damage in salt-sensitive hypertension. This study aimed to investigate whether ferroptosis is involved in the occurrence and development of myocardial fibrosis and renal fibrosis in salt-sensitive hypertensive rats. Ten 7-week-old male Dahl salt-sensitive (Dahl-SS) rats were adaptively fed for 1 week, then randomly divided into two groups and fed either a normal diet (0.3% NaCl, normal diet group) or a high-salt diet (8% NaCl, high-salt diet group) for 8 weeks. Blood pressure of the rats was observed, and analysis of the hearts and kidneys of Dahl-SS rats was conducted via hematoxylin-eosin (HE) staining, Masson staining, Prussian blue staining, transmission electron microscopy, tissue iron content detection, malondialdehyde content detection, immunofluorescence, and Western blot. Compared to the normal diet group, rats in the high-salt diet group had increases in systolic blood pressure and diastolic blood pressure (P < 0.05); collagen fiber accumulation was observed in the heart and kidney tissues (P < 0.01), accompanied by alterations in mitochondrial ultrastructure, reduced mitochondrial volume, and increased density of the mitochondrial double membrane. Additionally, there were significant increases in both iron content and malondialdehyde levels (P < 0.05). Immunofluorescence and Western blot results both indicated significant downregulation (P < 0.05) of xCT and GPX4 proteins associated with ferroptosis in the high-salt diet group. Ferroptosis is involved in the damage and fibrosis of the heart and kidney tissues in salt-sensitive hypertensive rats.

Dietary Cinnamaldehyde Activation of TRPA1 Antagonizes High-Salt-Induced Hypertension Through Restoring Renal Tubular Mitochondrial Dysfunction.

The renal proximal tubule (RPT) plays a pivotal role in regulating sodium reabsorption and thus blood pressure (BP). Transient receptor potential ankyrin 1 (TRPA1) has been reported to protect against renal injury by modulating mitochondrial function. We hypothesize that the activation of TRPA1 by its agonist cinnamaldehyde may mitigate high-salt intake-induced hypertension by inhibiting urinary sodium reabsorption through restoration of renal tubular epithelial mitochondrial function. Trpa1-deficient (Trpa1-/-) mice and wild-type (WT) mice were fed standard laboratory chow [normal diet (ND) group, 0.4% salt], standard laboratory chow with 8% salt [high-salt diet (HS) group], or standard laboratory chow with 8% salt plus 0.015% cinnamaldehyde [high-salt plus cinnamaldehyde diet (HSC) group] for 6 months. Urinary sodium excretion, reactive oxygen species (ROS) production, mitochondrial function, and the expression of sodium hydrogen exchanger isoform 3 (NHE3) and Na+/K+-ATPase of RPTs were determined. Chronic dietary cinnamaldehyde supplementation reduced tail systolic BP and 24-hour ambulatory arterial pressure in HS-fed WT mice. Compared with the mice fed HS, cinnamaldehyde supplementation significantly increased urinary sodium excretion, inhibited excess ROS production, and alleviated mitochondrial dysfunction of RPTs in WT mice. However, these effects of cinnamaldehyde were absent in Trpa1-/- mice. Furthermore, chronic dietary cinnamaldehyde supplementation blunted HS-induced upregulation of NHE3 and Na+/K+-ATPase in WT mice but not Trpa1-/- mice. The present study demonstrated that chronic activation of Trpa1 attenuates HS-induced hypertension by inhibiting urinary sodium reabsorption through restoring renal tubular epithelial mitochondrial function. Renal TRPA1 may be a potential target for the management of excessive dietary salt intake-associated hypertension.

#1755 Cardio-protective effect of soy proteins during long-term consumption of Cynomolgus Monkeys high-saline diet

Abstract Background and Aims High salt intake is accompanied by the development of cardiovascular disorders, not always associated with an increase in blood pressure (BP). Recently, it has been found that the introduction of soy protein into the diet can have some nephroprotective and cardioprotective effects in chronic kidney disease. Considering the cardioprotective effect of soy proteins in chronic kidney disease, the question arose about the possibility of using soy proteins to neutralize the damaging effect of a high-salt diet on the cardiovascular system. This work aims to study the effect of long-term use of a diet high in NaCl and soy protein on myocardial remodeling in monkeys. Method The study was performed on male Macaca fascicularis. The animals were divided into three groups (6 animals each), comparable in weight and age (6-8 years, body weight - 5.15-9.7 kg). The control group received a standard diet (2 g NaCl/kg feed). The second was a high salt diet (8 g NaCl/kg feed), and the third was a high salt diet and SUPRO760 soy protein (200 g/kg feed). Echocardiography (EchoCG), registration of BP and heart rate were performed at baseline, after 4 and 12 months. EchoCG was performed with a sector transducer with a frequency of 3–5 MHz on the Chison SonoTouch 60 ultrasound system (China). EchoCG was performed in B_mode (two-dimensional scanning), M_mode (one-dimensional scanning), as well as in pulse and tissue Doppler modes. Statistical analysis was performed using parametric statistics: mixed ANOVA in comparing data from 3 study groups (with post hoc analysis using Tukey criterion) and single factor variance analysis for related samples in studying the dynamics of one or another index in each group during the 12-month follow-up. Differences were considered significant at p &amp;lt; 0.05. Results In animals of all three groups for 12 months, blood pressure (BPsis-109±10.09, BPdias – 60 ± 7.42 mm Hg) and heart rate (77 ± 12.61 min-1) did not change significantly (p&amp;gt;0. 05). However, in macaques on a high-salt diet, deterioration in left ventricular (LV) systolic and diastolic function was noted by the end of the study. Macaques of this group had a decrease in the LV shortening fraction (27.9±2.69%) and an increase in the thickness of the posterior wall of the LV in systole (0.69±0.039 cm), LV mass (19.60±2.83 g), compared with animals additionally receiving soy proteins (34.9±6.57%; 0.57 0.0559 cm; 14.86±2.94 g, respectively; all p &amp;lt; 0.05). In addition, the monkeys receiving soy isolate did not differ from the control in these parameters. By the time the study was completed, the animals in this group had significantly increased the magnitude of systolic excursion of the mitral annulus plane, and signs of improvement in LV diastolic function appeared in the form of an increase in the maximum rate of excursion of the mitral valve fibrous annulus in early diastole, as well as a decrease in the E/e' ratio. The thickness of the interventricular septum also decreased (0.42±0.04 cm; in the high-salt group - 0.51±0.08 cm), which can be interpreted as a sign of positive myocardial remodeling. Conclusion Thus, high salt intake leads to adverse structural and functional disorders of the heart in cynomolgus monkeys, not associated with an increase in blood pressure. The inclusion of soy isolate in the diet reduces the negative effects of a high-salt diet on the cardiovascular system.

ACUTE EFFECTS OF SODIUM CHLORIDE OR ITS SUBSTITUTE POTASSIUM CHLORIDE ON VASCULAR FUNCTION IN HEALTHY VOLUNTEERS

Objective: High blood pressure, one of the most important risk factors for cardiovascular mortality, leads to vascular dysfunction and subsequently to arteriosclerosis, stroke, kidney and heart failure. High salt intake and low potassium intake are associated with high blood pressure and an increased risk of cardiovascular disease and mortality. Partial replacement of sodium with potassium led to a lower risk of cardiovascular events and death in a long-term follow-up study. However, the exact mechanism remains unclear. Our aim was to investigate the acute effects of sodium or potassium intake on vascular health to unravel the underlying mechanisms leading to vascular adaptations. Design and method: Six male and nine female healthy individuals (mean age 31 years) were randomized to either 9g of sodium chloride (high salt group), 6g of sodium chloride (regular salt group) or 6 g of sodium chloride plus 3g of potassium chloride group (substitution group). Individuals received a salty soup with the corresponding sodium or potassium load. Blood analyses, blood pressure, body composition and macro- as well as microvascular measurements were performed before as well as four (t4) and 24 hours (t24) after soup intake. To investigate macrovascular health, carotid-to-femoral pulse wave velocity was analyzed. Microvascular health was measured by investigating retinal vessel diameters. Results: The high (139±2mmol/l vs. 143±2mmol/l p=0,003) and regular salt group (140±2mmol/l vs. 141±0,6 mmol/l p=0,029) showed both higher serum sodium concentrations at t4 compared to baseline. These higher values were normalized at t24. The serum sodium concentration of the substitution group showed no statistically significant difference between timepoints. The substitution group showed improved microvascular health, quantified by higher arteriolar-to-venular diameter ratio from baseline to t4 (0,86±0,09 vs. 0,89±0,08 p=0,005). These improvements were regressive at t24 (0,88±0,09). No statistically significant changes were found on pulse wave velocity. The high and regular salt group showed no statistically significant differences at any timepoint on micro- or macrovascular health parameters. Conclusions: Replacement of sodium by potassium seems to improve microvascular function directly after potassium intake. These results might explain the long-term beneficial effects of potassium on cardiovascular outcomes.

Effect of Fasting During Time Restricted Feeding on Mitochondrial Beta-Oxidation Enzyme Expression in the Kidney Cortex of Adult Male Salt-Sensitive Dahl Rats

The Dahl salt-sensitive (SS) rat is a well-characterized model of SS hypertension and renal disease that exhibits enhanced Na+ reabsorption in the kidney. Prior research has shown that SS rats experience a reduction in fatty acid beta oxidation (FAO) in the kidney cortex when placed on a high salt (HS) diet. Time restricted feeding (TRF), a type of intermittent fasting in which food consumption is restricted to &lt;10 hrs/day, has been shown to activate FAO. Since the proximal tubule is responsible for the highest amount of Na+ reabsorption, we are interested in understanding if intermittent salt intake via TRF can mitigate dysfunctional cortical metabolism and slow progression of renal damage. We hypothesized that fasting during TRF would activate FAO throughout the body, as well as in the kidney cortex. To study this, 10-week-old male SS rats were provided ad libitum access to 4.0% NaCl (high salt; HS) or 0.4% (low salt; LS) diet for one week. Rats were then placed into a Promethion Core system (Sable Systems International) for metabolic phenotyping, where some continued ad libitum feeding, and others began time restricted feeding (TRF) for an additional week (n=7-9/group). During TRF, food was provided for 8 hours during the active cycle (2200hrs-0600hrs). Rats were euthanized in the last two hours of the final fasting period. We found that during the last hour of the fasting period, when compared to ad libitum rats, both the LS TRF (0.824 ± 0.01 vs 0.986 ± 0.008) and HS TRF (0.830 ± 0.01 vs 0.980 ± 0.006) rats had a significant reduction in their respiratory exchange ratio (2-way ANOVA with Tukey multiple comparisons, p&lt;0.05, mean ± SEM). This suggests that the TRF protocol induced a net whole-body shift in fuel utilization from primarily carbohydrates to a mix of fuel sources by the end of the 16-hour fasting period, regardless of diet. To investigate the effect of fasting during TRF on the kidney cortex, we performed western blot analysis of acyl-CoA dehydrogenase long chain (ACADL) and acetyl-CoA acyltransferase 2 (ACAA2), enzymes involved in initial and final steps of mitochondrial beta-oxidation, respectively. We found that HS rats had lower ACADL and ACAA2 expression than the LS rats (2-way ANOVA; main effect of HS, p&lt;0.05), and there was no difference between ad libitum and TRF groups within LS or HS groups (2-way ANOVA; main effect of TRF, p&gt;0.05). This data suggests that, even though whole-body FAO may be stimulated by TRF fasting, HS-induced suppression of mitochondrial FAO proteins ACADL and ACAA2 was not restored by TRF. Future studies will investigate the effects of the shift in fuel utilization on other metabolic pathways in the cortex and proximal tubules. Supported by the Advancing a Healthier Wisconsin Endowment, the Medical College of Wisconsin, and NIH 5T32HL007852-25. 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.

Beneficial Effects of Mild Hyperuricemia in Salt-Sensitive Hypertension

Hyperuricemia (HrU) or increased plasma uric acid (UA) is associated with worsening hypertension (HTN) and kidney damage. Paradoxically, UA is also known to be an endogenous antioxidant. Some studies suggest that only HrU with crystals, but not asymptomatic HrU promotes the progression of these diseases. We hypothesized that mild asymptomatic HrU is beneficial in controlling the progression of salt-sensitive (SS) HTN. Due to sex differences in urate handling and SS HTN, we used both male and female Dahl SS rats in this study. Radiotelemetry was used to measure blood pressure and various approaches, including RNA-Seq, were employed to assess kidney injury and identify potential molecular mechanisms. Mild HrU was induced using 2% oxonic acid in the diet, a uricase inhibitor that prevents the breakdown of UA further into more soluble allantoin. Groups: 1-2) male and female 4% NaCl high salt (HS) diet; 3-4) male and female HS + 2% oxonic acid (HS/oxo) diet. After 3 weeks, in response to oxonic acid supplementation, both sexes showed a significant increase of UA in plasma compared to their respective HS-only controls (Males: 0.63 ±0.07 vs. 2.17 ±0.34; Females 0.78 ±0.15 vs. 2.04 ±0.35 mg/dl, HS vs. HS/oxo). Interestingly, only male HS/oxo rats showed a significant increase in uricosuria (Males: 0.23 ±0.03 vs. 0.45 ±0.06; Femaels: 0.26 ±0.06 vs. 0.26 ±0.001 UA/Cre, HS vs. HS/oxo). Moreover, the mild HrU was associated with a significant attenuation of the progression and magnitude of the mean arterial pressure in male but not female rats (Males: 157 ±3 vs. 136 ±3; Females: 155 ±6 vs. 154 ±5 mmHg, HS vs. HS/oxo). Xanthine oxidase (XO) is one of the enzymes that produce UA, and its activity has been shown to affect HTN as well. Therefore, we examined the level of XO activity in the plasma after the treatment. While there was no difference in the activity based on the diet within each sex, females had significantly lower levels of XO activity compared to males in each of the diets. To further investigate the beneficial phenotype seen in male rats, we evaluate changes in the progression of renal pathology. The HS/oxo group compared to the HS group had a lower kidney weight/body weight ratio and lower protein cast accumulation, indicating lower kidney damage. RNA-Seq analysis showed that the attenuated HTN phenotype was associated with an increased expression in Mas1 (MAS receptor), Klk-1 (Kallikrein-1), and Pcsk6 (PCSK6 enzyme) which can all lead to the activation of different vasodilatory pathways. Our study showed that in male but not female Dahl SS rats, asymptomatic mild HrU accompanied by hyperuricosuria ameliorates the progression of SS HTN and protects kidneys from further damage. This work is supported by the American Society of Nephrology Ben J. Lipps Research Fellowship Program (Dimitrios G. Oreopoulos Research Fellowship Award to L.V.D.). 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.

Assessing the effects of tempol on renal fibrosis, inflammation, and oxidative stress in a high-salt diet combined with 5/6 nephrectomy rat model: utilizing oxidized albumin as a biomarker

BackgroundOxidative stress has been implicated in the pathogenesis of chronic kidney disease (CKD), prompting the exploration of antioxidants as a potential therapeutic avenue for mitigating disease progression. This study aims to investigate the beneficial impact of Tempol on the progression of CKD in a rat model utilizing oxidized albumin as a biomarker.MethodsAfter four weeks of treatment, metabolic parameters, including body weight, left ventricle residual weight, kidney weight, urine volume, and water and food intake, were measured. Systolic blood pressure, urinary protein, oxidized albumin level, serum creatinine (Scr), blood urea nitrogen (BUN), 8-OHdG, TGF-β1, and micro-albumin were also assessed. Renal fibrosis was evaluated through histological and biochemical assays. P65-NF-κB was quantified using an immunofluorescence test, while Smad3, P65-NF-κB, and Collagen I were measured using western blot. TNF-α, IL-6, MCP-1, TGF-β1, Smad3, and P65-NF-κB were analyzed by RT-qPCR.ResultsRats in the high-salt diet group exhibited impaired renal function, characterized by elevated levels of blood urea nitrogen, serum creatinine, 8-OHdG, urine albumin, and tubulointerstitial damage, along with reduced body weight. However, these effects were significantly ameliorated by Tempol administration. In the high-salt diet group, blood pressure, urinary protein, and oxidized albumin levels were notably higher compared to the normal diet group, but Tempol administration in the treatment group reversed these effects. Rats in the high-salt diet group also displayed increased levels of proinflammatory factors (TNF-α, IL-6, MCP1) and profibrotic factors (NF-κB activation, Collagen I), elevated expression of NADPH oxidation-related subunits (P65), and activation of the TGF-β1/Smad3 signaling pathway. Tempol treatment inhibited NF-κB-mediated inflammation and TGF-β1/Smad3-induced renal fibrosis signaling pathway activation.ConclusionThese findings suggest that Tempol may hold therapeutic potential for preventing and treating rats undergoing 5/6 nephrectomy. Further research is warranted to elucidate the mechanisms underlying Tempol’s protective effects and its potential clinical applications. Besides, there is a discernible positive relationship between oxidized albumin and other biomarkers, such as 8-OHG, urinary protein levels, mALB, Scr, BUN, and TGF-β1 in a High-salt diet combined with 5/6 nephrectomy rat model. These findings suggest the potential utility of oxidized albumin as a sensitive indicator for oxidative stress assessment.

Comparative transcriptome analysis reveals the adaptive mechanisms of halophyte Suaeda dendroides encountering high saline environment.

Suaeda dendroides, a succulent euhalophyte of the Chenopodiaceae family, intermittently spread around northern Xinjiang, China, has the ability to grow and develop in saline and alkali environments. The objective of this study was therefore to investigate the underlying molecular mechanisms of S. dendroides response to high salt conditions. 27 sequencing libraries prepared from low salt (200 mM NaCl) and high salt (800 mM NaCl) treated plants at 5 different stages were sequenced using Illumina Hiseq 2000. A total of 133,107 unigenes were obtained, of which 4,758 were DEGs. The number of DEGs in the high salt group (3,189) was more than the low salt treatment group (733) compared with the control. GO and KEGG analysis of the DEGs at different time points of the high salt treatment group showed that the genes related to cell wall biosynthesis and modification, plant hormone signal transduction, ion homeostasis, organic osmolyte accumulation, and reactive oxygen species (ROS) detoxification were significantly expressed, which indicated that these could be the main mechanisms of S. dendroides acclimate to high salt stress. The study provides a new perspective for understanding the molecular mechanisms of halophytes adapting to high salinity. It also provides a basis for future investigations of key salt-responsive genes in S. dendroides.

High dietary salt intake attenuates nitric oxide mediated endothelium-dependent vasodilation and increases oxidative stress in pregnancy.

This study aimed to investigate the impact of dietary salt intake during normal pregnancy on maternal microvascular and macrovascular endothelium-dependent reactivity and oxidative stress level. In this cross-sectional study, based on their 24-h urinary sodium excretion, pregnant women (37-40 weeks of gestation) were divided into three groups: normal salt (<5.75 g/day, N = 12), high salt (5.75-10.25 g/day, N = 36), and very high salt (VHS;>10.25 g/day, N = 17). Forearm skin microvascular reactivity in response to vascular occlusion, local heating (LTH) and iontophoresis of acetylcholine (AChID), as well as brachial artery flow mediated dilation (FMD) were measured. Serum nitric oxide, endocan, 8-iso-prostaglandin F2α (8-iso-PGF2α), thiobarbituric acid reactive substances (TBARS), and ferric-reducing ability of plasma assay were measured as biomarkers of endothelial function/activation and oxidative stress. Brachial artery FMD, microvascular AChID, and LTH were significantly decreased in VHS compared with NS group, while LTH was also decreased in normal salt compared with high salt group. Nitric oxide was significantly decreased in both high salt and VHS groups compared with normal salt. Endocan, 8-iso-PGF2α, and TBARS were significantly increased in VHS compared with the normal salt group. High dietary salt intake is associated with decreased nitric oxide mediated endothelium-dependent vasodilation in peripheral microcirculation and macrocirculation of healthy pregnant women due to increased oxidative stress.

Long-term safety of dietary salt: A 5-year ProspEctive rAndomized bliNded and controlled stUdy in healThy aged cats (PEANUT study).

High-salt diets promote urine dilution and decrease urolithiasis risk. Prospectively evaluate the safety of chronic high dietary salt intake (randomized controlled trial). Twenty research colony neutered, healthy aged cats (11.5 years [10.0-11.6], median [interquartile range]). Healthy cats were randomized to control or high-salt dry diets (sodium: 1.02 ± 0.16 [mean, SD] and 3.26 ± 0.30 g/Mcal metabolizable energy [ME], respectively; chloride: 2.26 ± 0.33 and 5.71 ± 0.28 g/Mcal ME, respectively), fed for up to 60 months. Assessments included CBC, plasma biochemistry, urinalysis, glomerular filtration rate (GFR), blood pressure, renal and cardiac (conventional Doppler and 2-dimensional color tissue Doppler) imaging, annually. Cats that died or were euthanized underwent necropsy. Diet effects over time were evaluated with linear mixed models. Follow-up duration (median [Interquartile range]) was similar between the control (38.7 months [28.6-48.2]) and high-salt group (51.4 months [45.7-59.0]). Diet had no significant effect on changes in GFR, blood pressure, plasma creatinine concentration, end-diastolic left ventricular (LV) wall thicknesses, LV internal diameters, LV systolic function, left atrial size, or systolic and diastolic Doppler variables. One control cat developed hypertension. One high-salt group cat developed persistent azotemia. Serial plasma biochemistry and urine specific gravity suggested early chronic kidney disease in 4 nonazotemic cats (2 per group), consistent with necropsy findings. In healthy aged cats, a commercial veterinary diet containing 3.26 ± 0.30 g/Mcal ME sodium was safe with regard to renal and cardiac function for up to 5 years.

Roles of aldosterone on ventricular arrhythmias, and associated gap junction and ion channel remodeling in hypertrophic heart

Abstract Background Ventricular arrhythmias are critical causes of death in patients with chronic heart failure (CHF). Aldosterone (Ald) is an exacerbating factor of CHF and mineral corticoid receptor antagonist (MRA) is usual drug for the management of CHF. MRA also suppressed sudden cardiac death, however, mechanisms of these effects remain unknown. We investigated the effects of MRA on ventricular arrhythmias and arrhythmogenic factors using Dahl Salt sensitive (DS) rats. Methods (in vivo) DS rats were divided into three groups; low salt group (LS), high salt group (HS), and eplerenone-, an MRA, treated high salt group (HS+EPL). Low salt (0.3% NaCl) or high salt (8% NaCl) were administrated for 8 weeks and EPL was administrated in the last 4 weeks. Cardiac geometry and function were assessed by echocardiography. Susceptibility of ventricular arrhythmias were assessed using programmed stimulation. Myocyte hypertrophy and cardiac fibrosis were examined by Masson’s trichrome staining. Expression and distribution of connexin43 (Cx43) were examined by immunostaining and western blotting. mRNA expression of Ca transient-related factors, such as phospholamban, SERCA2a, and ryanosin 2, and potassium ion channel-related factors, such as KCNE1 and KCNQ1, was examined by RT-PCR. (in vitro) Ald (1-100 nM) was administrated to cultured rat neonatal cardiomyocytes. Expression of Cx43, Ca transient-related, and potassium ion channel-related factors are also examined as mentioned above. Effects of Src tyrosin kinase inhibitor, PP2, and ERK inhibitor, PD98059, on Ald-induced Cx43 reduction were examined by RT-PCR and immunostaining. Results Systolic blood pressure and Ald concentrations in cardiac tissue were higher in HS group than LS group, and EPL did not affect them. In HS group left ventricular hypertrophy, dilatation and systolic dysfunction were observed in association with myocyte hypertrophy and interstitial fibrosis. EPL significantly recovered cardiac function and histological impairments. In addition, elongation of QTc in ECG and susceptibility of ventricular tachycardia were remarkable in HS group rather than LS and EPL attenuated them. Distribution of Cx43 was scattered in HS group, and EPL attenuated these changes. Decrease in SERCA2a and increase in KCNE1/KCNQ1 mRNA expression were found in HS group, and these changes were attenuated by EPL. In cultured myocytes, Ald decreased Cx43 mRNA and protein expression in a dose dependent fashion. Ald-induced Cx43 reduction was inhibited by PP2 and PD98059. In addition, Ald (100 nM) also decreased SERCA2a and increased KCNE1/KCNQ1 mRNA expression. Conclusion These results indicate that Ald reduced and dispersed the Cx43 expression reduction and dispersion through Src tyrosin kinase and ERK signaling pathways, and also mediated SRECA2A and KCNE1/KCNQ1 expression, which induced QTc prolongation and susceptibility of lethal ventricular arrhythmias in hypertensive cardiac hypertrophy.

Abstract 14993: Empagliflozin Exerts a Sympathoinhibitory Effect and Ameliorates Cardiorenal Injuries in a Rat Model of Hypertensive Heart Failure

Background: SGLT2 inhibitors may have protective effects on cardiac and renal injuries; however, their mechanisms remain unclear. Sympathetic activation has a crucial role in cardio/renal injuries. This study aimed to investigate whether empagliflozin can inhibit cardio/renal injuries through sympathoinhibition in a rat model of hypertensive heart failure. Methods: Male Dahl salt-sensitive rats were divided into low-salt (LS) and high-salt (HS) diet groups from 6 weeks of age. The rats in HS group were assigned to vehicle (HS-VEH) or empagliflozin (HS-EMPA) treatment group at 8 weeks. The effect of empagliflozin on central sympathetic regulation and cardio/renal injuries was assessed at 12 weeks (pre-heart failure phase), while its protective effect on heart failure was evaluated at 15 weeks in another cohort. Results: At 12 weeks , systolic blood pressure was similarly elevated in HS-VEH and HS-EMPA. Plasma norepinephrine levels were increased in HS-VEH compared to LS, and were suppressed in HS-EMPA, which was consistent with the neuronal activity of pre-sympathetic neurons in the brain. Increased left ventricular (LV) weight/body weight, plasma creatinine levels, renal fibrosis, and glomerular sclerosis in HS-VEH were attenuated in HS-EMPA. At 15 weeks , the high salt-induced blood pressure elevation was similar between HS-VEH and HS-EMPA. Although LV hypertrophy did not significantly differ, both decreased echocardiographic LV fractional shortening and increased lung weight observed in HS-VEH were attenuated in HS-EMPA. Elevated plasma creatinine and norepinephrine levels in HS-VEH were also attenuated in HS-EMPA. Conclusion: Empagliflozin inhibits sympathoexcitation and ameliorates cardio/renal injuries without lowering blood pressure in the hypertensive heart failure model. This sympathoinhibitory effect of empagliflozin observed in the pre-heart failure phase might contribute to the attenuation of heart failure progression.

A Serine Protease Inhibitor, Camostat Mesilate, Suppresses Urinary Plasmin Activity and Alleviates Hypertension and Podocyte Injury in Dahl Salt-Sensitive Rats.

In proteinuric renal diseases, the serine protease (SP) plasmin activates the epithelial sodium channel (ENaC) by cleaving its γ subunit. We previously demonstrated that a high-salt (HS) diet provoked hypertension and proteinuria in Dahl salt-sensitive (DS) rats, accompanied by γENaC activation, which were attenuated by camostat mesilate (CM), an SP inhibitor. However, the effects of CM on plasmin activity in DS rats remain unclear. In this study, we investigated the effects of CM on plasmin activity, ENaC activation, and podocyte injury in DS rats. The DS rats were divided into the control diet, HS diet (8.0% NaCl), and HS+CM diet (0.1% CM) groups. After weekly blood pressure measurement and 24-h urine collection, the rats were sacrificed at 5 weeks. The HS group exhibited hypertension, massive proteinuria, increased urinary plasmin, and γENaC activation; CM treatment suppressed these changes. CM prevented plasmin(ogen) attachment to podocytes and mitigated podocyte injury by reducing the number of apoptotic glomerular cells, inhibiting protease-activated receptor-1 activation, and suppressing inflammatory and fibrotic cytokine expression. Our findings highlight the detrimental role of urinary plasmin in the pathogenesis of salt-sensitive hypertension and glomerular injury. Targeting plasmin with SP inhibitors, such as CM, may be a promising therapeutic approach for these conditions.

Effects of Exercise Training on Mitochondrial Fatty Acid β-Oxidation in the Kidneys of Dahl Salt-Sensitive Rats

Exercise training (Ex) has anti-hypertensive and renal protective effects. In this study, we investigate the effects of Ex on mitochondrial fatty acid metabolism in the kidneys of Dahl salt-sensitive (Dahl-S) rats fed a high-salt (HS) diet. Eight-week-old, male Dahl-S rats were divided into three groups: (1) normal-salt diet, sedentary (NS-Sed), (2) HS diet, sedentary (HS-Sed), and (3) HS-Ex. The NS and HS groups were fed a diet containing 0.6% and 8% NaCl, respectively. The HS-Ex group performed treadmill running for 8 weeks (5 days/week; 60 min/day at 16–20 m/min, 0% gradient). Renal function and the expression of enzymes and regulators of β-oxidation and electron transport chain (ETC) complexes were assessed. HS increased systolic blood pressure and proteinuria, and Ex ameliorated these defects. HS also reduced creatinine clearance, and Ex ameliorated it. HS reduced the renal expression of enzymes of β-oxidation (carnitine palmitoyltransferase type I (CPTI) and acyl-CoA dehydrogenases (CADs)) and the related transcription factors peroxisome proliferator-activated receptor α (PPARα) and PPARγ-coactivator-1α (PGC-1α), and Ex restored this. HS also reduced the renal expression of enzymes in ETC complexes, and Ex restored this expression. Ex ameliorates HS-induced renal damage by upregulating enzymes involved in fatty acid β-oxidation and ETC complexes via increases in PPAR-α and PGC-1α expressions in the kidneys of Dahl-S rats. These results suggest that Ex may have beneficial effects on HS-induced mitochondrial dysfunction in the kidney.