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Background: Hypertensive disorders of pregnancy are associated with increased risk for cardiovascular disease, renal disease, and mortality. While the exact mechanisms remain unclear, T cells and reactive oxygen species have been implicated in its pathogenesis. We utilized Dahl salt-sensitive (SS), SS CD247-/- (Dahl SS CD247 knockout rat; lacking T cells), and SS p67phox-/- (Dahl SS p67 phox [NOX2 (NADPH [nitcotinamide adenine dinucleotide phosphate] oxidase 2)] knockout rat; lacking NOX2) rats to investigate these mechanisms in primigravida and multigravida states., Methods: We assessed blood pressure and renal damage phenotypes in SS, SS CD247-/- , and SS p67phox-/- rats during primigravida and multigravida states. To investigate the contribution of NOX2 in T cells, we performed adoptive transfers of splenocytes or cluster of differentiation (CD)4 + T cells from either SS or SS p67phox-/- donors into SS CD247-/- recipients to determine pregnancy-specific alterations in phenotype., Results: Multigravida SS rats developed significant pregnancy-induced renal damage and renal functional impairment associated with elevated maternal mortality rates, whereas deletion of T cells or NOX2 garnered protection. During primigravida states, this attenuation in renal damage was observed, with the greatest protection in the SS p67phox-/- rat. To demonstrate that NOX2 in T cells contributes to adverse pregnancy phenotypes, adoptive transfer of SS splenocytes into SS CD247-/- rats resulted in significant pregnancy-induced renal damage, whereas transfer of SS p67phox-/- splenocytes garnered protection. Specifically, the transfer of SS CD4 + T cells resulted in pregnancy-induced proteinuria and increases in uterine artery resistance index, an effect not seen with the transfer of SS p67phox-/- CD4 + T cells., Conclusions: T cells and NOX2-derived reactive oxygen species, thus, contribute to end-organ damage in both primigravida and multigravida pregnancies in the SS rat leading to increases in maternal mortality., Competing Interests: None.

Background: It is established that the immune system, namely T cells, plays a role in the development of hypertension and renal damage in male Dahl salt-sensitive (SS) rats, but far less is known about this relationship in females. Rats with genetically deleted T cells via CD247 gene mutation on the Dahl SS background (SS CD247-/- ) were utilized to interrogate the effect of sex and T cells on salt sensitivity., Methods: We assessed the hypertensive and kidney injury phenotypes in male versus female SS and SS CD247-/- rats challenged with 3 weeks of high salt (4.0% NaCl). Differences in T cell activation genes were examined in renal T cells from male and female SS rats, and a sex-specific adoptive transfer was performed by injecting male or female splenocytes into either male or female SS CD247-/- recipients to determine the potential contribution of T cell sex., Results: The lack of functional T cells in SS CD247-/- rats significantly reduced salt-induced hypertension and proteinuria in both sexes, although SS CD247-/- females exhibited greater protection from kidney damage. Adoptive transfer of either Dahl SS male or female splenocytes into SS CD247-/- male recipients exacerbated hypertension and proteinuria compared with controls, while in SS CD247-/- female recipients, exacerbation of disease occurred only upon transfer of male, but not female, SS splenocytes., Conclusions: The absence of T cells in the SS CD247-/- normalized sex differences in blood pressure, though sex differences in renal damage persisted. Splenocyte transfer experiments demonstrated that salt sensitivity is amplified if the sex of the T cell or the recipient is male., Competing Interests: Disclosures None.

Purpose of Review: In this article, we summarize the current literature supporting metabolic and redox signaling pathways as important mechanisms underlying T cell activation in the context of hypertension., Recent Findings: T cell immunometabolism undergoes dramatic remodeling in order to meet the demands of T cell activation, differentiation, and proliferation. Recent evidence demonstrates that the T cell oxidation-reduction (redox) system also undergoes significant changes upon activation, which can itself modulate metabolic processes and T cell function. Dysregulation of these signaling pathways can lead to aberrant T cell activation and inappropriate ROS production, both of which are linked to pathological conditions like hypertension. While the contribution of T cells to the progression of hypertension has been thoroughly investigated, how T cell metabolism and redox signaling changes, both separately and together, is an area of study that remains largely untouched. This review presents evidence from our own laboratory as well as others to highlight the importance of these two mechanisms in the study of hypertension., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

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The SS (Dahl salt sensitive) rat is an established model of hypertension and renal damage that is accompanied with immune system activation in response to a high-salt diet. Investigations into the effects of sodium-independent and dependent components of the diet were shown to affect the disease phenotype with SS/MCW (JrHsdMcwi) rats maintained on a purified diet (AIN-76A) presenting with a more severe phenotype relative to grain-fed SS/CRL (JrHsdMcwiCrl) rats. Since contributions of the immune system, environment, and diet are documented to alter this phenotype, this present study examined the epigenetic profile of T cells isolated from the periphery and the kidney from these colonies. T cells isolated from kidneys of the 2 colonies revealed that transcriptomic and functional differences may contribute to the susceptibility of hypertension and renal damage. In response to high-salt challenge, the methylome of T cells isolated from the kidney of SS/MCW exhibit a significant increase in differentially methylated regions with a preference for hypermethylation compared with the SS/CRL kidney T cells. Circulating T cells exhibited similar methylation profiles between colonies. Utilizing transcriptomic data from T cells isolated from the same animals upon which the DNA methylation analysis was performed, a predominant negative correlation was observed between gene expression and DNA methylation in all groups. Lastly, inhibition of DNA methyltransferases blunted salt-induced hypertension and renal damage in the SS/MCW rats providing a functional role for methylation. This study demonstrated the influence of epigenetic modifications to immune cell function, highlighting the need for further investigations.

The Dahl salt-sensitive (SS) rat is an established model of SS hypertension and renal damage. In addition to salt, other dietary components were shown to be important determinants of hypertension in SS rats. With previous work eliminating the involvement of genetic differences, grain-fed SS rats from Charles River Laboratories (SS/CRL; 5L2F/5L79) were less susceptible to salt-induced hypertension and renal damage compared with purified diet-fed SS rats bred at the Medical College of Wisconsin (SS/MCW; 0.4% NaCl, AIN-76A). With the known role of immunity in hypertension, the present study characterized the immune cells infiltrating SS/MCW and SS/CRL kidneys via flow cytometry and RNA sequencing in T-cells isolated from the blood and kidneys of rats maintained on their respective parental diet or on 3 weeks of high salt (4.0% NaCl, AIN-76A). SS/CRL rats were protected from salt-induced hypertension (116.5±1.2 versus 141.9±14.4 mm Hg), albuminuria (21.7±3.5 versus 162.9±22.2 mg/d), and renal immune cell infiltration compared with SS/MCW. RNA-seq revealed >50% of all annotated genes in the entire transcriptome to be significantly differentially expressed in T-cells isolated from blood versus kidney, regardless of colony or chow. Pathway analysis of significantly differentially expressed genes between low and high salt conditions demonstrated changes related to inflammation in SS/MCW renal T-cells compared with metabolism-related pathways in SS/CRL renal T-cells. These functional and transcriptomic T-cell differences between SS/MCW and SS/CRL show that dietary components in addition to salt may influence immunity and the infiltration of immune cells into the kidney, ultimately impacting susceptibility to salt-induced hypertension and renal damage.

The present study, performed in Dahl salt-sensitive (SS) and SS- Rag1 -/- rats lacking T and B lymphocytes, tested the hypothesis that immune cells amplify salt-sensitive hypertension and kidney damage in response to a high-protein diet. After being weaned, SS and SS- Rag1 -/- rats were placed on an isocaloric, 0.4% NaCl diet containing normal (18%) or high (30%) protein. At 9 wk of age, rats were switched to a 4.0% NaCl diet containing the same amount of dietary protein and maintained on the high-salt diet for 3 wk. After being fed the high-salt diet, SS rats fed high protein had amplified hypertension and albumin excretion (158.7 ± 2.6 mmHg and 140.8 ± 16.0 mg/day, respectively, means ± SE) compared with SS rats fed normal protein (139.4 ± 3.6 mmHg and 69.4 ± 11.3 mg/day). When compared with the SS rats, SS- Rag1 -/- rats fed high protein were protected from exacerbated hypertension and albuminuria (142.9 ± 5.8 mmHg and 66.2 ± 10.8 mg/day). After 3 wk of the high-salt diet, there was a corresponding increase in total leukocyte infiltration (CD45 + ) in the kidneys of both strains fed high-protein diet. The SS- Rag1 -/- rats fed high-protein diet had 74-86% fewer CD3 + T lymphocytes and CD45R + B lymphocytes infiltrating the kidney versus SS rats, but there was no difference in the infiltration of CD11b/c + monocytes and macrophages, suggesting that the protective effects observed in the SS- Rag1 -/- rats are specific to the reduction of lymphocytes. With the SS- Rag1 -/- rats utilized as a novel tool to explore the effects of lymphocyte deficiency, these results provide evidence that adaptive immune mechanisms contribute to the exacerbation of salt-induced hypertension and renal injury mediated by increased dietary protein intake.

The present study assessed the importance of immunity in angiotensin (ANG) II (5 ng·kg -1 ·min -1 iv)-mediated hypertension in Dahl salt-sensitive (SS) rats and SS rats deficient in T and B lymphocytes (SS Rag1-/- ) fed a 0.4% NaCl diet. Baseline mean arterial blood pressure (MAP) was not different between groups. ANG II infusion significantly increased MAP in both groups, although MAP increased more rapidly in SS rats, and the maximal MAP achieved was significantly greater in SS than SS Rag1-/- rats (190 ± 3 vs. 177 ± 3 mmHg) after 12 days. Renal damage, as assessed by albumin excretion rate, was significantly increased after 12 days of ANG lI infusion in SS (from 32 ± 4 to 81 ± 9 mg/day) and SS Rag1-/- (from 12 ± 2 to 51 ± 8 mg/day) rats; albumin excretion rate was significantly different between SS and SS Rag1-/- rats at all points measured. After 9 days of recovery from ANG II, MAP was decreased to a greater extent in SS Rag1-/- than SS rats (143 ± 5 vs. 157 ± 8 mmHg) compared with the peak MAP during ANG II infusion. At this same time point, albumin excretion rate was significantly lower in SS Rag1-/- than SS rats (42 ± 8 vs. 66 ± 7 mg/day). Further studies demonstrated an increase in CD45 + total leukocytes, CD11b/c + macrophages/monocytes, and CD3 + T cells in kidneys of ANG II- compared with vehicle-treated SS rats. The present data suggest that infiltrating T cells in the kidney exacerbate renal damage in ANG II-induced hypertension in SS rats maintained on a 0.4% NaCl diet, similar to results observed with a salt stimulus in SS rats.

Renal T-cell infiltration is a key component of salt-sensitive hypertension in Dahl salt-sensitive (SS) rats. Here, we use an electronic servo-control technique to determine the contribution of renal perfusion pressure to T-cell infiltration in the SS rat kidney. An aortic balloon occluder placed around the aorta between the renal arteries was used to maintain perfusion pressure to the left kidney at control levels, ≈128 mm Hg, during 7 days of salt-induced hypertension, whereas the right kidney was exposed to increased renal perfusion pressure that averaged 157±4 mm Hg by day 7 of high-salt diet. The number of infiltrating T cells was compared between the 2 kidneys. Renal T-cell infiltration was significantly blunted in the left servo-controlled kidney compared with the right uncontrolled kidney. The number of CD3 + , CD3 + CD4 + , and CD3 + CD8 + T cells were all significantly lower in the left servo-controlled kidney. This effect was not specific to T cells because CD45R + (B cells) and CD11b/c + (monocytes and macrophages) cell infiltrations were all exacerbated in the hypertensive kidneys. Increased renal perfusion pressure was also associated with augmented renal injury, with increased protein casts and glomerular damage in the hypertensive kidney. Levels of norepinephrine were comparable between the 2 kidneys, suggestive of equivalent sympathetic innervation. Renal infiltration of T cells was not reversed by the return of renal perfusion pressure to control levels after 7 days of salt-sensitive hypertension. We conclude that increased pressure contributes to the initiation of renal T-cell infiltration during the progression of salt-sensitive hypertension in SS rats., (© 2017 American Heart Association, Inc.)

Purpose of Review: Immune mechanisms exacerbate the severity of hypertension in humans and animal models of disease. This review summarizes recent mechanistic studies exploring the pathways whereby immunity influences salt-sensitive hypertension and renal disease., Recent Findings: Emphasis is placed on the role of T cell subtypes, the mechanisms of T-cell activation, and the identification of potential antigens or neoantigens., Summary: Significant advancements have occurred in the search for pathways which activate the adaptive immune response. An enhanced understanding of the factors contributing to hypertension can lead to better therapies.

Purpose of Review: The role of immune mechanisms to amplify hypertension in patients and animal models has been appreciated for decades. This review briefly summarizes recent studies exploring the mechanistic pathways, whereby the immune system participates in hypertension and renal disease., Recent Findings: Emphasis in this review is placed upon recent studies exploring the role of T cell subtypes, newly described mechanisms of T cell activation, the identification of potential neoantigens, and environmental influences on immune cell activation., Summary: Significant advancements have been made in the search for antigens and pathways responsible for activation of the adaptive immune response, furthering our understanding of the factors contributing to hypertension and potentially leading to the development of new and more effective therapies.

Research studying the role of inflammation in hypertension and cardiovascular disease has flourished in recent years; however, the exact mechanisms by which the activated immune cells lead to the development and maintenance of hypertension remain to be elucidated. The objectives of this brief review are to summarize and discuss the most recent findings in the field, with special emphasis on potential therapeutics to treat or prevent hypertension. This review will cover novel immune cell subtypes recently associated to the disease including the novel role of cytokines, toll-like receptors, and inflammasomes in hypertension.

The importance of the immune system in hypertension, vascular disease, and renal disease has been appreciated for over 50 years. Recent experimental advances have led to a greater appreciation of the mechanisms whereby inflammation and immunity participate in cardiovascular disease. In addition to the experimental data, multiple studies in patients have demonstrated a strong correlation between the observations made in animals and humans. Of great interest is the development of salt-sensitive hypertension in humans with the concurrent increase in albumin excretion rate. Experiments in our laboratory have demonstrated that feeding a high-NaCl diet to Dahl salt-sensitive (SS) rats results in a significant infiltration of T lymphocytes into the kidney that is accompanied by the development of hypertension and renal disease. The development of disease in the Dahl SS closely resembles observations made in patients; studies were therefore performed to investigate the pathological role of infiltrating immune cells in the kidney in hypertension and renal disease. Pharmacological and genetic studies indicate that immune cell infiltration into the kidney amplifies the disease process. Further experiments demonstrated that infiltrating T cells may accentuate the Dahl SS phenotype by increasing intrarenal ANG II and oxidative stress. From these and other data, we hypothesize that infiltrating immune cells, which surround the blood vessels and tubules, can serve as a local source of bioactive molecules which mediate vascular constriction, increase tubular sodium reabsorption, and mediate the retention of sodium and water to amplify sodium-sensitive hypertension. Multiple experiments remain to be performed to refine and clarify this hypothesis., (Copyright © 2014 the American Physiological Society.)

The CD3 ζ chain (CD247), a gene involved in T-cell signaling, has been shown to associate with blood pressure in human genetic studies. To test the functional role of CD247 in hypertension and renal disease, zinc-finger nucleases targeting CD247 were injected into Dahl salt-sensitive (SS/JrHsdMcwi) embryos. The resulting 11-bp frameshift deletion in exon 1 of CD247 led to a predicted premature stop codon. Western blotting confirmed the absence of CD247 protein in the thymus, and flow cytometry (n=5-9 per group) demonstrated that the mutant rats (CD247(-/-)) have a >99% reduction in circulating CD3(+) T cells compared with littermate controls (CD247(+/+)). Studies were performed on age-matched, littermate male, CD247(+/+) and CD247(-/-) rats fed a 4.0% NaCl diet for 3 weeks. The infiltration of CD3(+) T cells into the kidney after high salt was significantly blunted in CD247(-/-) (1.4±0.4×10(5) cells per kidney) when compared with that in the CD247(+/+) (8.7±2.0×10(5) cells per kidney). Accompanying the reduced infiltration of T cells, mean arterial blood pressure was significantly lower in CD247(-/-) than in CD247(+/+) (134±1 versus 151±2 mm Hg). As an index of kidney disease, urinary albumin and protein excretion rates were significantly reduced in CD247(-/-) (17±1 and 62±2 mg/d, respectively) when compared with that in CD247(+/+) (49±3 and 121±5 mg/d, respectively). Glomerular and renal tubular damage were also attenuated in the CD247(-/-). These studies demonstrate that functional T cells are required for the full development of Dahl salt-sensitive hypertension and indicate that the association between CD247 and hypertension in humans may be related to altered immune cell function.

The present studies examined the role and mechanism of action of infiltrating T lymphocytes in the kidney during salt-sensitive hypertension. Infiltrating T lymphocytes in the Dahl salt-sensitive (SS) kidney significantly increased from 7.2 ± 1.8 × 10(5) cells/2 kidneys to 18.2 ± 3.9 × 10(5) cells/2 kidneys (n = 6/group) when dietary NaCl was increased from 0.4 to 4.0%. Furthermore, the expression of immunoreactive p67(phox), gp91(phox), and p47(phox) subunits of NADPH oxidase was increased in T cells isolated from the kidneys of rats fed 4.0% NaCl. The urinary excretion of thiobarbituric acid-reactive substances (TBARS; an index of oxidative stress) also increased from 367 ± 49 to 688 ± 92 nmol/day (n = 8/group) when NaCl intake was increased in Dahl SS rats. Studies were then performed on rats treated with a daily injection of vehicle (5% dextrose) or tacrolimus (0.25 mg·kg(-1)·day(-1) ip), a calcineurin inhibitor that suppresses immune function, during the period of high-NaCl intake (n = 5/group). In contrast to the immune cell infiltration, increased NADPH oxidase expression, and elevated urine TBARS excretion in vehicle-treated Dahl SS fed high salt, these parameters were unaltered as NaCl intake was increased in Dahl SS rats administered tacrolimus. Moreover, tacrolimus treatment blunted high-salt mean arterial blood pressure and albumin excretion rate (152 ± 3 mmHg and 20 ± 9 mg/day, respectively) compared with values in dextrose-treated Dahl SS rats (171 ± 8 mmHg and 74 ± 28 mg/day). These experiments indicate that blockade of infiltrating immune cells is associated with decreased oxidative stress, an attenuation of hypertension, and a reduction of renal damage in Dahl SS rats fed high salt.

This study examined mechanisms by which immune cells participate in the development of hypertension and renal disease in Dahl salt-sensitive (SS) rats. Increasing dietary salt from 0.4% to 4.0% NaCl significantly increased renal infiltration of T lymphocytes from 8.8 +/- 1.2 x 10(5) to 14.4 +/- 2.0 x 10(5) cells/2 kidneys, increased arterial blood pressure from 131 +/- 2 to 165 +/- 6 mmHg, increased albumin excretion rate from 17 +/- 3 to 129 +/- 20 mg/day, and resulted in renal glomerular and tubular damage. Furthermore, renal tissue ANG II was not suppressed in the kidneys of SS rats fed 4.0% NaCl. Administration of the immunosuppressive agent mycophenolate mofetil (MMF; 20 mg.kg(-1).day(-1)) prevented the infiltration of T lymphocytes and attenuated Dahl SS hypertension and renal disease. In contrast to vehicle-treated rats, Dahl SS rats administered MMF demonstrated a suppression of renal tissue ANG II from 163 +/- 26 to 88 +/- 9 pg/g of tissue when fed high salt. Finally, it was demonstrated that the T lymphocytes isolated from the kidney possess renin and angiotensin-converting enzyme activity. These data indicate that infiltrating T cells are capable of participating in the production of ANG II and are associated with increased intrarenal ANG II, hypertension, and renal disease. The suppression of T-cell infiltration decreased intrarenal ANG II and prevented Dahl SS hypertension and kidney damage. As such, infiltrating cells are capable of participating in the established phase of Dahl SS hypertension.