Salt-sensitive Hypertension Research Articles

Association between salt sensitivity of blood pressure and dietary habits in survey population: A case-control study

Salt sensitivity of blood pressure (SSBP) is an independent risk factor for cardiovascular diseases (CVDs) and links dietary salt with blood pressure. However, the study on the relationship between SSBP and dietary habits is rare. This study investigated the relationship between diet and SSBP in different blood pressure statues. 1459 subjects were assigned into four groups based on a case (hypertension)-control (normotension) study of SSBP and hypertension: 561 Salt-sensitive hypertension (SSH) and 235 non-salt-sensitive hypertension (NSSH) and 424 salt-sensitive normotension (SSN) and 239 non-salt-sensitive normotension (NSSN). Foods information of weekly or daily intakes were recalled. SSBP was tested with the modified salt stress test and was diagnosed with the Sullivan criteria. Compared with the NSSH and SSN groups, SSH group have lower intake of fresh fruits (both P<0.05). Furthermore, NSSN group have the lowest intake of red meat, and bacon (P<0.05). SSH group have the lowest intake of fresh vegetables (P<0.05). SSN group have the highest intake of eggs, dairy products, white meat (all P<0.05). In hypertensive patients, staple food (OR=0.37, 95%CI: 0.10-0.64) was associated with decreased risk of salt sensitivity. In normotensive subjects, white meat (OR=0.28, 95%CI: 0.14-0.43) was associated with reduced risk of salt sensitivity, bacon (OR=5.39, 95%CI: 2.11-8.67) and dairy products (OR=4.22, 95%CI: 1.82-6.56) and red meat (OR=2.95, 95%CI: 1.15-4.84) were associated with elevated risk of salt sensitivity. Dietary habits play an important role in SSBP and the role varies with blood pressure especially among population.

The FSGS protein actinin-4 (ACTN4) interacts with NKCC2 to regulate Thick Ascending Limb (TAL) NaCl reabsorption.

In the kidney, the thick Ascending Limb (TAL) of the loop of Henle is crucial for NaCl homeostasis and blood pressure regulation. In animal models of salt-sensitive hypertension, NaCl reabsorption via the apical Na+/K+/2Cl cotransporter (NKCC2) is abnormally increased in the TAL. We showed that NaCl reabsorption is controlled by the presence of NKCC2 at the apical surface of TALs. However, the molecular mechanisms that maintain the steady-state levels of NKCC2 at the apical surface are not clearly understood. Here, we report that NKCC2 interacts with the F-actin cross-linking protein actinin-4 (ACTN4). We find that ACTN4 is expressed in TALs by Western blot and immunofluorescence microscopy. ACTN4 immunoprecipitated with NKCC2 and recombinant GST-ACTN4 pulled down NKCC2 from TAL lysates. ACTN4 is involved in endocytosis in other cells. Therefore, we hypothesized that ACTN4 binds apical NKCC2 and regulates its trafficking. To study this, we silenced ACTN4 in vivo via shRNA or CRISPR/Cas9 system to decrease ACTN4 expression in TALs. We observed that silencing ACTN4 in vivo via shRNA or CRISPR/Cas9 system increased the amount NKCC2 at the apical surface of TALs. Bumetanide-induced diuresis and natriuresis were enhanced by 35% after silencing of ACTN4 in vivo (AV-NKCC2-Cas9: 3841±709 vs AAV-gRNA-ACTN4: 5546±622 µmols Na/8h, n=5, p<0.05). We conclude that ACTN4, binds NKCC2 to regulate its surface expression. Selective depletion of ACTN4 in TALs using shRNA or CRISPR/Cas9 enhances surface NKCC2 and TAL NaCl reabsorption, indicating that regulation of the ACTN4-NKCC2 interaction is important for renal NaCl reabsorption and could be related to hypertension.

Salt Responsive Gut Microbiota Induces Sex Specific Blood Pressure Changes.

Tryptophan metabolism is important in blood pressure regulation. The tryptophan-indole pathway is exclusively mediated by the gut microbiota. ACE2 (angiotensin-converting enzyme 2) participates in tryptophan absorption, and a lack of ACE2 leads to changes in the gut microbiota. The gut microbiota has been recognized as a regulator of blood pressure. Furthermore, there is ample evidence for sex differences in the gut microbiota. However, it is unclear whether such sex differences impact blood pressure differentially through the tryptophan-indole pathway. To study the sex-specific mechanisms of gut microbiota-mediated tryptophan-indole pathway in hypertension, we generated a novel rat model with Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats-associated protein 9)-targeted deletion of Ace2 in the Dahl salt-sensitive rat. Cecal microbiota transfers from donors of both sexes to female S recipients were performed. Also, Dahl salt-sensitive rats of both sexes were orally gavaged with indole to investigate blood pressure response. The female gut microbiota and its tryptophan-indole pathway exhibited greater buffering capacity when exposed to tryptophan, due to Ace2 deficiency, and salt. In contrast, the male gut microbiota and its tryptophan-indole pathway were more vulnerable. Female rats with male cecal microbiota responded to salt with a higher blood pressure increase. Indole, a tryptophan-derived metabolite produced by gut bacteria, increased blood pressure in male but not in female rats. Moreover, salt altered host-mediated tryptophan metabolism, characterized by reduced serum serotonin of both sexes and higher levels of kynurenine derivatives in the females. We uncovered a novel sex-specific mechanism in the gut microbiota-mediated tryptophan-indole pathway in blood pressure regulation. Salt tipped the tryptophan metabolism between the host and gut microbiota in a sex-dependent manner. Our study provides evidence for a novel concept that gut microbiota and its metabolism play sex-specific roles in the development of salt-sensitive hypertension.

Exacerbating orthodontic tooth movement in mice with salt-sensitive hypertension

Background/purposeOrthodontic tooth movement (OTM) is a critical aspect of dental treatment that requires the precise control of bone remodeling processes. Hypertension (HTN) can affect the effectiveness of OTM. Salt-sensitive hypertension (SSHTN) is of particular concern due to its detrimental effects on bone health, potentially altering orthodontic outcomes. This study aimed to investigate the effects of SSHTN on OTM using a mouse model. Materials and methodsMale mice were divided into a normal and an SSHTN group. The SSHTN model was generated by administering N(ω)-nitro-l-arginine methyl ester (l-NAME) followed by a high-salt diet. The OTM was performed using a nickel-titanium (Ni-Ti) closed-coil spring, and the tooth movement was measured after 12 days. Silicone imprinting was used to estimate the OTM distance. Osteoclast activity was assessed using tartrate-resistant acid phosphatase (TRAP) staining of decalcified maxillary sections. ResultsSSHTN mice exhibited significantly increased tooth movement compared to normal mice. This enhanced movement was associated with more osteoclasts in the SSHTN group than in the control group. These findings suggest that SSHTN increases OTM levels by promoting bone resorption. ConclusionSSHTN significantly affected OTM by enhancing osteoclast activity and increasing tooth movement. These results underscore the importance of considering hypertensive conditions in orthodontic treatment planning as they may require adjustments in force application to prevent potential adverse effects.

Regulating distal nephron functions and salt sensitivity.

This review highlights the molecular basis of salt sensitivity in hypertension, with a focus on the regulation of sodium transport in the distal nephron. Sodium reabsorption in this region is often linked to the actions of aldosterone, although in recent years numerous findings have been reported on the aldosterone-independent pathway of acquiring salt sensitivity by potassium deficiency or potassium loading. The key to this discussion is the interplay, through extracellular potassium concentration, between the first part of the tubules expressing the Na+-Cl- cotransporter (NCC) and the second part expressing the epithelial Na+ channel (ENaC). The molecular pathways such as with-no-lysine 1 (WNK)-STE20/SPS1-related proline-alanine-rich kinase (SPAK)/oxidative stress-responsive kinase 1 (OSR1) signaling, Kelch-like family member 3 (KLHL3)-cullin 3 (CUL3) complex, protein phosphatases, and mechanistic target of rapamycin complex 2 (mTORC2)-Nedd4L pathway are described as the mechanism by which salt sensitivity on blood pressure is acquired in response to changes in physiological conditions including potassium depletion or loading. This review highlights the potential for targeting these molecular pathways to develop novel therapeutic strategies for the treatment of salt-sensitive hypertension, the mechanism of which remains to be elucidated.

Mild Hyperuricemia Is Beneficial for Males with Salt-Sensitive Hypertension and Associated Kidney Damage

Mild Hyperuricemia Is Beneficial for Males with Salt-Sensitive Hypertension and Associated Kidney Damage

Aberrant Trafficking of Intestinal Immune Cells in Salt-Sensitive Hypertension

Aberrant Trafficking of Intestinal Immune Cells in Salt-Sensitive Hypertension

Renal ACE 2, Inflammation, and Oxidative Stress Cross-Talk in Diet-Induced, Salt-Sensitive Hypertension in Mice with Obesity

Renal ACE 2, Inflammation, and Oxidative Stress Cross-Talk in Diet-Induced, Salt-Sensitive Hypertension in Mice with Obesity

Endoplasmic Reticulum Stress Immediate Early Response 3 Gene Mediates Myeloid-Specific Salt-Sensitive Hypertension in Humans

Endoplasmic Reticulum Stress Immediate Early Response 3 Gene Mediates Myeloid-Specific Salt-Sensitive Hypertension in Humans

Irisin mitigates salt-sensitive hypertension via regulating renal AMPK-Rac1 pathway

ABSTRACT Background Irisin, as a myokine, plays a protective role against cardiovascular disease, including myocardial infarction, atherosclerosis and hypertension. However, whether irisin attenuates salt-sensitive hypertension and the related underlying mechanisms is unknown. Methods Male Dahl salt-resistant (DSR) and Dahl salt-sensitive (DSS) (12 weeks) rats were fed a high salt diet (8% NaCl) with or without irisin treatment by intraperitoneal injection for 8 weeks. Results Compared with DSR rats, DSS rats showed higher systolic blood pressure (SBP), impaired natriuresis and diuresis and renal dysfunction. In addition, it was accompanied by downregulation of renal p-AMPKα and upregulation of renal RAC1 and nuclear mineralocorticoid receptor (MR). Irisin intervention could significantly up-regulated renal p-AMPKα level and down-regulated renal RAC1-MR signal, thereby improving renal sodium excretion and renal function, and ultimately reducing blood pressure in DSS rats. Ex vivo treatment with irisin reduced the expression of RAC1 and nuclear MR in primary renal distal convoluted tubule cells from DSS rats and the effects of irisin were abolished by cotreatment of compound C (AMPK inhibitor), indicating that the regulation of RAC1-MR signals by irisin depended on the activation of AMPK. Conclusions Irisin administration lowered salt-sensitive hypertension through regulating RAC1-MR signaling via activation of AMPK, which may be a promising therapeutic approach for salt-sensitive hypertension.

AGTR1 variant rs2638355 is associated with increased salt sensitivity of blood pressure: a female-specific effect in individuals from the HyperPath cohort.

Salt-sensitive hypertension (SSH) affects approximately half of the hypertensive population, increasing the risk of vascular complications. The underlying pathophysiological mechanisms of SSH remain complex and need to be fully elucidated. Our prior research has identified genetic factors contributing to the salt sensitivity of blood pressure (SSBP), particularly involving genes regulating volume and blood pressure. We also observed enhanced peripheral vascular response to angiotensin II in humans with salt-sensitive hypertension. Given the pivotal role of the angiotensin II receptor type-1 (AT1R or AGTR1) in blood pressure and intravascular volume regulation, we hypothesized a genetic association between AGTR1 and SSBP. Our study involved 240 individuals of European ancestry from the HyperPATH cohort, examined under restricted and high dietary salt conditions. We employed a tagging single nucleotide variant approach to genotype participants at AGTR1. Our regression model revealed a significant association between the rs2638355 (A/G) variant and salt-sensitive systolic blood pressure (SS-SBP), and rs2638355 increased AGTR1 gene expression. Notably, carriers of the risk-allele of the noncoding regulatory variant rs2638355 exhibited higher systolic blood pressure under high salt diet conditions than nonrisk allele individuals. A sex-stratified analysis showed this salt-driven effect on systolic blood pressure was significant only in females, underscoring the role of dietary salt in modulating genetic effects in this group. Furthermore, a restricted salt diet in these individuals diminished blood pressure and negated the blood pressure phenotype-genotype association. Overall, our findings could aid in pinpointing individuals with salt-sensitive blood pressure among hypertensive patients, especially considering dietary and sex-specific factors.

Effects of zinc in podocytes and cortical collecting duct in vitro and Dahl salt-sensitive rats in vivo

Zinc is one of the essential divalent cations in the human body and a fundamental microelement involved in the regulation of many cellular and subcellular functions. Experimental studies reported that zinc deficiency is associated with renal damage and could increase blood pressure. It was proposed that zinc dietary supplementation plays a renoprotective role. Our study aimed to investigate the effects of zinc on intracellular signaling in renal cells and explore the correlation between dietary zinc and the progression of salt-induced hypertension. The impact of extracellular zinc concentrations on two different kidney epithelial cell types - podocytes and principal cells of the cortical collecting duct (CCD), was tested. In podocytes, a rise in extracellular zinc promotes TRPC6 channel-mediated calcium entry but not altered intracellular zinc levels. However, we observe the opposite effect in CCD cells with no alteration in calcium levels and steady-state elevation in intracellular zinc. Moreover, prolonged extracellular zinc exposure leads to cytotoxic insults in CCD cells but not in podocytes, characterized by increased cell death and disrupted cytoskeletal organization. Next, we tested if dietary zinc plays a role in the development of hypertension in Dahl salt-sensitive rats. Neither zinc-rich nor deficient diets impact the regular development of salt-sensitive hypertension. These results suggest specialized roles for zinc in renal function, implicating its involvement in proliferation and apoptosis in CCD cells and calcium signaling and cytoskeletal dynamics modulation in podocytes. Further research is required to elucidate the detailed mechanisms of zinc action and its implications in renal health and disease.

Salt-sensitive hypertension in GR mutant rats is associated with altered plasma polyunsaturated fatty acid levels and aortic vascular reactivity.

In humans, glucocorticoid resistance is attributed to mutations in the glucocorticoid receptor (GR). Most of these mutations result in decreased ligand binding, transactivation, and/or translocation, albeit with normal protein abundances. However, there is no clear genotype‒phenotype relationship between the severity or age at disease presentation and the degree of functional loss of the receptor. Previously, we documented that a GR+/- rat line developed clinical features of glucocorticoid resistance, namely, hypercortisolemia, adrenal hyperplasia, and salt-sensitive hypertension. In this study, we analyzed the GR+/em4 rat model heterozygously mutant for the deletion of exon 3, which encompasses the second zinc finger, including the domains of DNA binding, dimerization, and nuclear localization signals. On a standard diet, mutant rats exhibited a trend toward increased corticosterone levels and a normal systolic blood pressure and heart rate but presented with adrenal hyperplasia. They exhibited increased adrenal soluble epoxide hydroxylase (sEH), favoring an increase in less active polyunsaturated fatty acids. Indeed, a significant increase in nonactive omega-3 and omega-6 polyunsaturated fatty acids, such as 5(6)-DiHETrE or 9(10)-DiHOME, was observed with advanced age (10 versus 5weeks old) and following a switch to a high-salt diet accompanied by salt-sensitive hypertension. In thoracic aortas, a reduced soluble epoxide hydrolase (sEH) protein abundance resulted in altered vascular reactivity upon a standard diet, which was blunted upon a high-salt diet. In conclusion, mutations in the GR affecting the ligand-binding domain as well as the dimerization domain resulted in deregulated GR signaling, favoring salt-sensitive hypertension in the absence of obvious mineralocorticoid excess.

Abstract 33: CD4+ T Cell-Induced Renal Damage and Salt-Sensitive Hypertension is Not Modified by CD8+ T Cells

Salt-Sensitive (SS) hypertension and renal damage in the Dahl SS rat mirrors human disease with T cell infiltration in the kidney accompanying the development of SS hypertension and renal damage. Deletion of T cells on the Dahl SS genetic background (SS CD247-/- ) attenuates hypertension and renal damage, and subsequent replacement of CD4+ T cells alone restores the disease phenotype while the transfer of only CD8+ T cells had no significant effect on the disease phenotype. The present study tested the hypothesis that CD4+ and CD8+ T cells will synergistically act to enhance salt-sensitive hypertension and renal damage in the Dahl SS compared to the injection of only CD4+ T cells. This hypothesis was tested by adoptive transferring purified CD4+ T cells from Dahl SS (~5 million, CD4+ SS→), a combination of ~5 million CD4+ T cells with ~5 million CD8+ T cells from Dahl SS (CD4+CD8+ SS→) or PBS vehicle (PBS→) into the SS CD247-/- rat on postnatal day 5. Animals were instrumented with radiotelemeters at 8 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→, CD4+CD8+ SS→, or PBS→ groups (121±2, 122±2, 119±1 mmHg; n=9, 10, 6, respectively). After three weeks of HS, both CD4+ SS→ and CD4+CD8+ SS→ rats demonstrated an equivalent amplification of SS hypertension (176±6 and 179±5 mmHg) and albuminuria (261±53 and 285±37 mg/day, respectively) which was significantly greater than the MAP (159±5 mmHg) and albuminuria (169±29 mg/day) in PBS→. Finally, a flow cytometric analysis at the end of the experiment confirmed the absence of CD3+ T cells in the PBS→ and documented the reconstitution of equal numbers of CD4+ cells in the blood and kidney of the rats receiving CD4+ cells or the combined CD4+ CD8+ cell transfer. We also confirmed the CD4+CD8+ was the only group that had reconstituted CD8+ T cells. These studies demonstrated that CD4+ T cells amplify salt-sensitive hypertension and renal damage in the Dahl SS independently from CD8+ T cells.

Abstract P426: Reduced Nfatc1 Expression Results in Enhanced Pressure Natriuresis and Resistance to Salt-Sensitive Hypertension

Background: Nuclear factor of activated T cells-cytoplasmic 1 (NFATc1) has recently been shown to have a non-canonical role in chronic kidney disease in humans by a trans-ethnic meta-analysis of genome-wide associate studies (GWAS). Follow-up studies in a salt-sensitive mouse model showed that Nfatc1 mRNA expression was suppressed in the kidneys when animals were fed a high-salt diet. Here, we further explore the link between NFATc1 and salt-sensitive (SS) hypertension. Methods: Adult male wild-type (WT) and heterozygous Nfatc1 knockout (Het) mice (2-5 months of age) on the SS 129S6 background were started on standard chow (0.8% NaCl, NSD) and then switched to a high-salt diet (6% NaCl, HSD). Systolic blood pressure (SBP) was measured by either tail cuff manometry with at least 2 weeks of training or implantable radiotelemetry transmitters with at least 2 weeks of post-surgical recovery. Immediately before and for 2-3 days after the change in diet, 24 h urine was collected using metabolic cages, and urinary sodium was measured by flame photometry. Sigmoid pressure-natriuresis curves were generated and the Hill slope was compared between genotypes. Results: WT mice showed a significant increase in SBP between NSD and after 3 weeks on HSD (127.8±9.9 vs 143.4±8.9, p = 0.0089, n = 9). In contrast, Het mice had no change in SBP (125.8±8.7 mmHg vs. 125.7±10.6 mmHg, p = 1.0, n = 9). During the initial switch to the HSD, SBP was not significantly different between WT and Het mice (133.2±2.9 vs. 134.4±3.0, p = 0.45, n = 7/group). However, WT mice had a shallower pressure-natriuresis curve (Hill slope of 0.58 vs. 0.93, 7 mice/group, 25/26 data points). Conclusion: Our data illustrates that decreasing Nfatc1 expression in a mouse model is protective against SS hypertension. While acute increases in SBP in response to HSD remained in Het mice, sodium excretion was increased and SBP remained unchanged after 3 weeks, indicating that NFATc1 has the potential to be a therapeutic target against SS hypertension.

Abstract P456: Loss of Renal Resident Tissue Macrophages Reduces Nitric Oxide-Mediated Relaxation during Salt-Sensitive Hypertension

Salt-sensitive hypertension (SS-HTN) associates with increased renal sodium reabsorption, arterial dysfunction, and heightened pro-inflammatory cytokines such as interleukin 6 (IL-6). Renal resident tissue macrophages (rRTMs) function to both maintain tissue homeostasis and once activated, can secrete IL-6. We reported that loss of the rRTM population prevents SS-HTN but their influence on arterial reactivity has not been tested. We hypothesize that rRTM-induced IL-6 production impairs endothelial function. Wild-type (Wt) or rRTM-depleted (CX 3 CR 1 - EGFP+/+ ) male mice (12wks) were used. Mice were given the nitric oxide synthase (NOS) inhibitor, L-NAME (0.5mg/mL, in drinking water, 2wks) and allowed to washout (1-2wks) before fed normal chow (NC), high salt (HS) chow (4%) for 2 days (early salt-sensitive, eSS) or for 3wks HS (SS-HTN). eSS mice were salt-sensitive, but not yet hypertensive. Mice were also given HS chow alone (3wks). Serum was collected for systemic cytokines (Meso-Scale Discovery; n=4-15) and second-order mesenteric resistance arteries (MRAs) were obtained (n=3-5). Concentration response curves (CRCs) to phenylephrine (Phe) and acetylcholine (ACh) were performed in the presence or absence of potassium chloride (KCl) or L-NMMA. Serum IL-6 levels were not increased following HS diet alone, but concentrations trended higher during SS-HTN (1.46 ± 0.2 pg/mL vs. 1.07 ± 0.2 pg/mL NC). The nadir was observed in eSS mice, before the development of SS-HTN, and was prevented in rRTM-depleted mice (1.81 ± 0.3 pg/mL vs. 0.58 ± 0.17, **p&lt;0.001, grouped ANOVA). No differences were observed between NC-fed Wt and rRTM-depleted MRAs, but the development of SS-HTN did impair relaxation responses. Overall, ACh-mediated relaxation responses were generally lower in MRAs from rRTM-depleted mice compared to Wt. Interestingly, rRTM-depleted MRAs from SS-HTN animals exhibited a near complete inhibition of all relaxation responses with NOS inhibition (R max 6.20% ± 8 rRTM SS-HTN vs. 63.0% ± 10 Wt SS-HTN, *p&lt;0.05), suggesting greater dependence on NO-mediated relaxation. Together, these data suggest that rRTMs contribute to an early, hypertension-independent spike in IL-6 which may reduce endothelial function later during SS-HTN. We also show that rRTM-depletion affects the function of the resistance vasculature, including loss of non-NO-mediated relaxation during SS-HTN. These data suggest that renal-derived cytokines, via rRTMs, may influence endothelial function.

Abstract P179: The Role of Sodium Induced-RGMa in Salt-Sensitive Hypertension

Salt sensitivity of blood pressure, characterized by blood pressure fluctuations that mirror dietary sodium (Na) intake, is an independent risk factor for cardiovascular morbidity and mortality in people with and without hypertension. We previously found that elevated Na uptake via the amiloride-sensitive epithelial sodium channel (ENaC) in antigen-presenting cells leads to the upregulation of isolevuglandins and proinflammatory cytokines ultimately leading to T cell activation and salt-sensitive hypertension. In addition, we also showed that SMAD3 activation plays a role in inflammation and salt-sensitive hypertension. In previous studies, RGMa has been shown to be upstream of SMAD3. Furthermore, previous studies have also shown that knockdown of RGMa leads to reduced levels of TGFβ1-induced SMAD3 phosphorylation. The exact mechanism by which elevated extracellular Na leads to increased blood pressure remains unknown. We hypothesized that RGMa complexes with TGFβ1R1 to promote SMAD3 phosphorylation ultimately contributing to inflammation in salt-sensitive hypertension. To test our hypothesis, we isolated monocytes from human participants (N =11) and treated them with either high (190 mMol/L) or normal (150 mMol/L) Na in vitro for 72 hours and subsequently performed bulk RNA sequencing. In additional experiments, we performed an in vivo high Na treatment by utilizing a rigorous salt-loading/depletion protocol on human participants (N = 9) and conducted single-cell transcriptomic analyses. Our bulk RNA sequencing analyses revealed there was no difference in expression of TGFβ1R1 (8837 ± 780.9 vs. 9688 ± 942.5, p =0.350) and TGFβ1R2 (7012 ± 717.0 vs. 7176 ± 633.9, p = 0.059). Interestingly, RGMa (2253 ± 441.0 vs. 516 ± 84.1, p &lt;0.001) and TGFβ1 (5118 ± 353.9 vs. 9067 ± 826.4, p = 0.073) were significantly upregulated in human monocytes after high Na treatment compared to normal salt. However, single-cell transcriptomic analyses found no correlation between the changes in pulse pressure and RGMa (r = 0.5154, p = 0.1911). Our data suggest that RGMa mediates Na-induced inflammation but may not play a role in salt-sensitive hypertension.

Abstract 04: Renal- and TAL-Specific Inhibition of Traf2 and NCK Interacting Kinase (TNIK) Decreases NKKC2 Phosphorylation and Blunts Salt-Sensitive Hypertension in Dahl Salt-Sensitive Rats

Up to 50% of hypertensive patients are salt-sensitive. Abnormally enhanced NaCl reabsorption by the thick ascending limb of the loop of Henle (TAL) in the kidney contributes to the development of salt-sensitivity. NaCl reabsorption in the TAL is entirely mediated by the apical Na/K/2Cl cotransporter NKCC2. We showed that NKCC2 phosphorylation at Thr-96,101 is increased in TALs from Dahl salt-sensitive (DSS) rats. We discovered a new kinase, TNIK (Traf2-and-NCK-interacting kinase), that binds the amino-terminus of NKCC2 and phosphorylates NKCC2 at Thr-96,101. TNIK is abundantly expressed in TALs and other nephron segments. We hypothesized that TNIK contributes to salt-sensitive hypertension by increasing NKCC2 phosphorylation in TALs from DSS rats. First, we measured TNIK expression in isolated TALs. TNIK expression was 8±4-fold higher in TALs from DSS compared to SD rats (n=5, p&lt;0.05). Then, we used a pharmacological specific inhibitor of TNIK, NCB-0846. We implanted renal medullary catheters connected to minipumps to directly infuse NCB-0846 or vehicle into the left kidney of uninephrectomized DSS rats. After recovery rats were fed 4% NaCl diet and measured systolic blood pressure (SBP) via tail-cuff. NCB-0846 decreased SBP by 21±6 mmHg within four days compared to the vehicle-infused group, and BP remained lower for 7 days (n=5, p&lt;0.03 vs vehicle). To specifically decrease TNIK gene expression in medullary TALs, we used Cas9-mediated gene editing. We injected the renal medulla of the left kidney with AAV-gRNA-TNIK simultaneously with AV-NKCC2promoter-Cas9 (drives Cas9 expression in TALs) or AV-NKCC2promoter-Cas9 alone (AV-control) in DSS rats. After 10 days, rats were fed a 4% NaCl diet and SBP was measured. Rats transduced with AAV-gRNA-TNIK had a 18±5 mmHg lower BP compared to AV-control group (AV-control:147 ± 4.7 vs AAV-gRNA-TNIK:129 ± 5.6 mmHg n=5, p&lt;0.03 vs control) which remained lower after 14 days (AV-control:163 ± 4.8 vs AAV-gRNA-TNIK:140 ± 4.9 mmHg, n=5, p&lt;0.01). After 14 days on high salt, TNIK expression was decreased by 30 ± 4% (n=4, p&lt;0.05), and pThr-96,101-NKCC2 decreased by 43 ± 11% in AAV-gRNA-TNIK transduced TALs compared to AV-control transduced TALs (n=4, p&lt;0.02). We conclude that hypertension and enhanced NKCC2 phosphorylation in the DSS rat is partly due to higher TNIK expression in TALs and that inhibition of this novel kinase could be a target for salt-sensitive hypertension.

P097 SEXUAL DIMORPHISM IN A HYPERTENSIVE MODEL OF FRUCTOSE PLUS HIGH SALT DIET

High salt diet (HSD) and fructose are both consumed in excess and contributes to hypertension (HTN). Fructose is commonly used to sweeten soft drinks, and studies have linked soft drink consumption to salt-sensitive HTN. However, full mechanisms aren’t understood. Previous data indicates that an acute fructose-enriched diet (FED) increases Na/K/2Cl cotransporter (NKCC2) activity, promoting salt-sensitive HTN in rats; however, there is no research on long-term consumption. Here, our goal was to evaluate whether a FED, coupled to HSD, can induce HTN. Given the known sex-dependent differences in salt-sensitive HTN, we also hypothesized differences between male and female mice. Male and female C57BI/6 mice (10 weeks old, n=4-6) were treated with vehicle or fructose (10% in drinking water) plus HSD (4% in food) for 28 days. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography, and cardiac hypertrophy (morphometry). We performed an acute diuresis test using furosemide to inhibit NKCC2 (20 mg/kg bw, ip) at day 26, and then measured natriuresis (metabolic cages) for 2-hrs. All data are presented by mean standard deviation. Fructose+HSD increased SBP in male mice after 28 days (Veh=110.5±4.6 vs. Frucose+HSD=130.2±5.6 mmHg; p&lt;0.01); in contrast, HTN was completely prevented in female mice (Veh=109.8±6.8 vs. Fructose+HSD=114.0±11.0 mmHg; ns). We did not observe changes in cardiac hypertrophy in either sex. We observed a significant decrease in natriuresis (∼20%) after furosemide injection in male mice (Veh=5.9±1.1 vs. Fructose+HSD=4.7±0.8 μEq/2 h/g bw; ns). Surprisingly, we observed an increase in natriuresis following furosemide injection in female mice (Veh=3.8±5.0 vs. Fructose+HSD= 7.7±2.7 μEq/2 h/g bw; p&lt;0.01). We observed HTN in males following a FED combined with HSD, which was not associated with increased NKCC2 activation. In contrast, female mice showed a resistance to HTN, and yet an apparent increase in NKCC2 activity. This probably suggests a dysregulation of other transporters not evaluated in this work. Finally, we demonstrate that long-term FED, with HSD, induces HTN with a sexual dimorphic effect, apparently through differential renal sodium handling.

Abstract P200: Immune memory contributes to chronic hypertension recurrence

Keeping blood pressure under control is a challenge in hypertension treatment because high blood pressure quickly returns with a momentary lapse in treatment or a high-salt diet. We have previously reported the CD8+ T cells (CD8Ts) in the kidney can drive aberrant sodium handling to aggravate blood pressure. Recently, our new findings suggest that these CD8Ts remain long-term within the kidney. Here, we propose these CD8Ts have developed into a resident memory (Trm) population with the aid of TGFβ signaling, and this residency continually aggravates and leads to the recurrence of hypertension . To explore this hypothesis, we utilized two mouse models of hypertension, including a classic DOCA-salt model and a novel Angiotensin II (Ang II) induced salt memory model, with continuous blood pressure monitored by radiotelemetry. In the Ang II-induced salt memory model, the mice were administered Ang II and high salt for a week before a resting period to restore normal blood pressure. Thereafter, the mice were given a second high salt challenge to model the high salt-driven recurrence of hypertension. Mouse strains include both wild-type (WT) and a T-cell specific TGFβRII KO (Tsp-TGFβR KO), which has T cells unable to develop into Trm due to the reliance of Trm on TGFβ signaling. T cells were analyzed with flow cytometry. In the DOCA-salt model, WT mice developed a significant CD8Trm population within the kidney. In contrast, TSP-TGFβR KO mice, which lack the ability to develop Trm, had an attenuated development of hypertension with DOCA-salt treatment. Testing the capability for hypertension to recur, both WT and Tsp-TGFβR KO mice experienced a similar degree of hypertension with Ang II-salt treatment. However, only the WT had a significant expansion of Trm and demonstrated the clinical manifestation of recurring hypertension with the rapid increase of blood pressure with a high salt challenge. Isolating the T cells from the kidneys confirmed that the significant CD8Trm population development in the WT was not present in the Tsp-TGFβR KO. In summary, our findings suggest that the memory T cell population developed in the kidney during hypertension instills a perpetual memory for salt sensitivity in hypertension. Without the ability to develop this memory population, mice are protected against this recurrence of high-salt-induced hypertension.