A salt-sensing kinase in T lymphocytes, SGK1, drives hypertension and hypertensive end-organ damage

High sodium, rather than high blood pressure, induces immune cell activation and renal infiltration in ovariectomized adult Wistar rats

We used an animal model of salt-sensitive hypertension (SSH) in which ovariectomized (oVx) rats developed hypertension with high salt (HS) intake. Hypertension is accompanied by changes in the percentage of CD4+ T lymphocytes, immune CD45+ cell infiltration into renal tissue, and changes in Na+, K+- ATPase (NKA) expression in both renal tissue and peripheral blood mononuclear cells (PBMCs). To determine whether the observed changes resulted from HS intake, high blood pressure, or both, hydralazine (HDZ) was used to lower blood pressure. The oVx HS rats received two HDZ schedules either to prevent or to treat hypertension. NKA was overexpressed in the kidneys of all oVx groups and in PBMCs of oVx HS rats. This pattern was not altered with HDZ treatment. Changes in CD4+ T lymphocytes and renal infiltration of CD45+ cells were not reversed either. High salt, but not high blood pressure, induces immune cell activation and renal infiltration. Overexpressed NKA is the primary event, and HS is the perturbation to the system in this model of SSH, which resembles the postmenopausal state.

Placental growth factor mediates pathological uterine angiogenesis by activating the NFAT5-SGK1 signaling axis in the endometrium: implications for preeclampsia development

After menstruation the uterine spiral arteries are repaired through angiogenesis. This process is tightly regulated by the paracrine communication between endometrial stromal cells (EnSCs) and endothelial cells. Any molecular aberration in these processes can lead to complications in pregnancy including miscarriage or preeclampsia (PE). Placental growth factor (PlGF) is a known contributing factor for pathological angiogenesis but the mechanisms remain poorly understood. In this study, we investigated whether PlGF contributes to pathological uterine angiogenesis by disrupting EnSCs and endothelial paracrine communication. We observed that PlGF mediates a tonicity-independent activation of nuclear factor of activated T cells 5 (NFAT5) in EnSCs. NFAT5 activated downstream targets including SGK1, HIF-1α and VEGF-A. In depth characterization of PlGF - conditioned medium (CM) from EnSCs using mass spectrometry and ELISA methods revealed low VEGF-A and an abundance of extracellular matrix organization associated proteins. Secreted factors in PlGF-CM impeded normal angiogenic cues in endothelial cells (HUVECs) by downregulating Notch-VEGF signaling. Interestingly, PlGF-CM failed to support human placental (BeWo) cell invasion through HUVEC monolayer. Inhibition of SGK1 in EnSCs improved angiogenic effects in HUVECs and promoted BeWo invasion, revealing SGK1 as a key intermediate player modulating PlGF mediated anti-angiogenic signaling. Taken together, perturbed PlGF-NFAT5-SGK1 signaling in the endometrium can contribute to pathological uterine angiogenesis by negatively regulating EnSCs-endothelial crosstalk resulting in poor quality vessels in the uterine microenvironment. Taken together the signaling may impact on normal trophoblast invasion and thus placentation and, may be associated with an increased risk of complications such as PE.

Immunological insights into hypertension: unraveling triggers and potential therapeutic avenues

Hypertension remains the leading cause of morbidity and mortality worldwide. Despite its prevalence, the development of novel antihypertensive therapies has only recently accelerated, with novel agents not yet commercialized, leaving a substantial proportion of individuals resistant to existing treatments. The intricate pathophysiology of hypertension is now understood to involve chronic low-grade inflammation, which places the immune system in the spotlight as a potential target for new therapeutics. This review explores the factors that initiate and sustain an immune response in hypertension, offering insights into potential targets for new treatments. Several factors contribute to immune activation in hypertension, including diet and damage-associated molecular pattern (DAMP) generation. Diets rich in fat or sodium can promote inflammation by inducing intestinal barrier dysfunction and triggering salt-sensitive receptors in T cells and dendritic cells. DAMPs, such as extracellular adenosine triphosphate and heat-shock protein 70, are released during episodes of increased blood pressure, contributing to immune cell activation and inflammation. Unconventional innate-like γδ T cells contribute to initiating and maintaining an immune response through their potential involvement in antigen presentation and regulating cytokine-mediated responses. Immunologic memory, sustained through the formation of effector memory T cells after exposure to hypertensive insults, likely contributes to maintaining an immune response in hypertension. When exposed to hypertensive insults, these memory cells are rapidly activated and contribute to elevated blood pressure and end-organ damage. Evidence from human hypertension, although limited, supports the relevance of distinct immune pathways in hypertension, and highlights the potential of targeted immune interventions in human hypertension. Diet and acute bouts of high blood pressure result in the release of dietary triggers, neoantigens, and damage-associated molecular patterns (DAMPs), which promote immune system activation. Elements such as lipopolysaccharides (LPS), sodium, heat-shock protein (HSP)70, extracellular adenosine triphosphate (eATP), and growth arrest-specific 6 (GAS6) promote activation of innate immune cells such as dendritic cells (DCs) and monocytes (Mo) through their respective receptors (toll-like receptor [TLR]4, amiloride-sensitive epithelial sodium channel [ENaC], TLR2/4, P2X7 receptor [P2RX7], and Axl) leading to costimulatory molecule expression and interleukin (IL)-1β and IL-23 production. The neoantigens HSP70 and isolevuglandins (IsoLGs) are presented to T cells by DCs and possibly γδ T cells, triggering T cell activation, IL-17 and interferon (IFN)-γ production, and the formation of T effector memory (TEM) cells in the kidney, perivascular adipose tissue, bone marrow, and spleen. Exposure of TEM cells to their cognate antigen or previous activating stimuli causes these cells rapid expansion and activation. Cumulatively, this inflammatory state contributes to hypertension and end-organ damage. The figure was created using images from smart.servier.com and is licensed under a Creative Commons Attribution 4.0 license (CC BY 4.0).

Sex-Dependency of T Cell-Induced Salt-Sensitive Hypertension and Kidney Damage

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 (SSCD247-/-) 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 SSCD247-/- 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 SSCD247-/- recipients to determine the potential contribution of T cell sex.

RESULTS

The lack of functional T cells in SSCD247-/- rats significantly reduced salt-induced hypertension and proteinuria in both sexes, although SSCD247-/- females exhibited greater protection from kidney damage. Adoptive transfer of either Dahl SS male or female splenocytes into SSCD247-/- male recipients exacerbated hypertension and proteinuria compared with controls, while in SSCD247-/- female recipients, exacerbation of disease occurred only upon transfer of male, but not female, SS splenocytes.

CONCLUSIONS

The absence of T cells in the SSCD247-/- 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.

Immune and inflammatory mechanisms in hypertension

Hypertension is a global health problem, with >1.3 billion individuals with high blood pressure worldwide. In this Review, we present an inflammatory paradigm for hypertension, emphasizing the crucial roles of immune cells, cytokines and chemokines in disease initiation and progression. T cells, monocytes, macrophages, dendritic cells, B cells and natural killer cells are all implicated in hypertension. Neoantigens, the NLRP3 inflammasome and increased sympathetic outflow, as well as cytokines (including IL-6, IL-7, IL-15, IL-18 and IL-21) and a high-salt environment, can contribute to immune activation in hypertension. The activated immune cells migrate to target organs such as arteries (especially the perivascular fat and adventitia), kidneys, the heart and the brain, where they release effector cytokines that elevate blood pressure and cause vascular remodelling, renal damage, cardiac hypertrophy, cognitive impairment and dementia. IL-17 secreted by CD4+ T helper 17 cells and γδ T cells, and interferon-γ and tumour necrosis factor secreted by immunosenescent CD8+ T cells, exert crucial effector roles in hypertension, whereas IL-10 and regulatory T cells are protective. Effector mediators impair nitric oxide bioavailability, leading to endothelial dysfunction and increased vascular contractility. Inflammatory effector mediators also alter renal sodium and water balance and promote renal fibrosis. These mechanisms link hypertension with obesity, autoimmunity, periodontitis and COVID-19. A comprehensive understanding of the immune and inflammatory mechanisms of hypertension is crucial for safely and effectively translating the findings to clinical practice.

Immunoproteasomal Processing of IsoLG-Adducted Proteins Is Essential for Hypertension

BACKGROUND

Hypertension is characterized by CD8+ (cluster differentiation 8) T cell activation and infiltration into peripheral tissues. CD8+ T cell activation requires proteasomal processing of antigenic proteins. It has become clear that isoLG (isolevuglandin)-adduced peptides are antigenic in hypertension; however, IsoLGs inhibit the constitutive proteasome. We hypothesized that immunoproteasomal processing of isoLG-adducts is essential for CD8+ T cell activation and inflammation in hypertension.

METHODS

IsoLG adduct processing was studied in murine dendritic cells (DCs), endothelial cells (ECs), and B8 fibroblasts. The role of the proteasome and the immunoproteasome in Ang II (angiotensin II)-induced hypertension was studied in C57BL/6 mice treated with bortezomib or the immunoproteasome inhibitor PR-957 and by studying mice lacking 3 critical immunoproteasome subunits (triple knockout mouse). We also examined hypertension in mice lacking the critical immunoproteasome subunit LMP7 (large multifunctional peptidase 7) specifically in either DCs or ECs.

RESULTS

We found that oxidant stress increases the presence of isoLG adducts within MHC-I (class I major histocompatibility complex), and immunoproteasome overexpression augments this. Pharmacological or genetic inhibition of the immunoproteasome attenuated hypertension and tissue inflammation. Conditional deletion of LMP7 in either DCs or ECs attenuated hypertension and vascular inflammation. Finally, we defined the role of the innate immune receptors STING (stimulator of interferon genes) and TLR7/8 (toll-like receptor 7/8) as drivers of LMP7 expression in ECs.

CONCLUSIONS

These studies define a previously unknown role of the immunoproteasome in DCs and ECs in CD8+ T cell activation. The immunoproteasome in DCs and ECs is critical for isoLG-adduct presentation to CD8+ T cells, and in the endothelium, this guides homing and infiltration of T cells to specific tissues.

Adipose c-Jun NH2-terminal kinase promotes angiotensin II-induced and deoxycorticosterone acetate salt-induced hypertension and vascular dysfunction by inhibition of adiponectin production and activation of SGK1 in mice

BACKGROUND

Adipose c-Jun NH2-terminal kinase 1/2 (JNK1/2) is a central mediator involved in the development of obesity and its complications. However, the roles of adipose JNK1/2 in hypertension remain elusive. Here we explored the role of adipose JNK1/2 in hypertension.

METHODS AND RESULTS

The roles of adipose JNK1/2 in hypertension were investigated by evaluating the impact of adipose JNK1/2 inactivation in both angiotensin II (Ang II)-induced and deoxycorticosterone acetate (DOCA) salt-induced hypertensive mice. Specific inactivation of JNK1/2 in adipocytes significantly alleviates Ang II-induced and DOCA salt-induced hypertension and target organ damage in mice. Interestingly, such beneficial effects are also observed in hypertensive mice after oral administration of JNK1/2 inhibitor SP600125. Mechanistically, adipose JNK1/2 acts on adipocytes to reduce the production of adiponectin (APN), then leads to promote serum and glucocorticoid-regulated kinase 1 (SGK1) phosphorylation and increases epithelial Na + channel α-subunit (ENaCα) expression in both renal cells and adipocytes, respectively, finally exacerbates Na + retention. In addition, chronic treatment of recombinant mouse APN significantly augments the beneficial effects of adipose JNK1/2 inactivation in DOCA salt-induced hypertension. By contrast, the blood pressure-lowering effects of adipose JNK1/2 inactivation are abrogated by adenovirus-mediated SGK1 overexpression in Ang II -treated adipose JNK1/2 inactivation mice.

CONCLUSION

Adipose JNK1/2 promotes hypertension and targets organ impairment via fine-tuning the multiorgan crosstalk among adipose tissue, kidney, and blood vessels.

Endothelial cell serum and glucocorticoid regulated kinase 1 (SGK1) mediates vascular stiffening

BACKGROUND

Excessive dietary salt intake increases vascular stiffness in humans, especially in salt-sensitive populations. While we recently suggested that the endothelial sodium channel (EnNaC) contributes to salt-sensitivity related endothelial cell (EC) and arterial stiffening, mechanistic understanding remains incomplete. This study therefore aimed to explore the role of EC-serum and glucocorticoid regulated kinase 1 (SGK1), as a reported regulator of sodium channels, in EC and arterial stiffening.

METHODS AND RESULTS

A mouse model of salt sensitivity-associated vascular stiffening was produced by subcutaneous implantation of slow-release deoxycorticosterone acetate (DOCA) pellets, with salt (1 % NaCl, 0.2 % KCl) administered via drinking water. Preliminary data showed that global SGK1 deletion caused significantly decreased blood pressure (BP), EnNaC activity and aortic endothelium stiffness as compared to control mice following DOCA-salt treatment. To probe EC signaling pathways, selective deletion of EC-SGK1 was performed by cross-breeding cadherin 5-Cre mice with sgk1flox/flox mice. DOCA-salt treated control mice had significantly increased BP, EC and aortic stiffness in vivo and ex vivo, which were attenuated by EC-SGK1 deficiency. To demonstrate relevance to humans, human aortic ECs were cultured in the absence or presence of aldosterone and high salt with or without the SGK1 inhibitor, EMD638683 (10uM or 25uM). Treatment with aldosterone and high salt increased intrinsic stiffness of ECs, which was prevented by SGK1 inhibition. Further, the SGK1 inhibitor prevented aldosterone and high salt induced actin polymerization, a key mechanism in cellular stiffening.

CONCLUSION

EC-SGK1 contributes to salt-sensitivity related EC and aortic stiffening by mechanisms appearing to involve regulation of actin polymerization.

In utero exposure to maternal diabetes exacerbates dietary sodium intake-induced endothelial dysfunction by activating cyclooxygenase 2-derived prostanoids

Prenatal exposure to maternal diabetes has been recognized as a significant cardiovascular risk factor, increasing the susceptibility to the emergence of conditions such as high blood pressure, atherosclerosis, and heart disease in later stages of life. However, it is unclear if offspring exposed to diabetes in utero have worse vascular outcomes on a high-salt (HS) diet. To test the hypothesis that in utero exposure to maternal diabetes predisposes to HS-induced vascular dysfunction, we treated adult male wild-type offspring (DM_Exp, 6 mo old) of diabetic Ins2+/C96Y mice (Akita mice) with HS (8% sodium chloride, 10 days) and analyzed endothelial function via wire myograph and cyclooxygenase (COX)-derived prostanoids pathway by ELISA, quantitative PCR, and immunochemistry. On a regular diet, DM_Exp mice did not manifest any vascular dysfunction, remodeling, or inflammation. However, HS increased aortic contractility to phenylephrine and induced endothelial dysfunction (analyzed by acetylcholine-induced endothelium-dependent relaxation), vascular hydrogen peroxide production, COX2 expression, and prostaglandin E2 (PGE2) overproduction. Interestingly, ex vivo antioxidant treatment (tempol) or COX1/2 (indomethacin) or COX2 (NS398) inhibitors improved or reverted the endothelial dysfunction in DM_Exp mice fed a HS diet. Finally, DM_Exp mice fed with HS exhibited greater circulating cytokines and chemokines accompanied by vascular inflammation. In summary, our findings indicate that prenatal exposure to maternal diabetes predisposes to HS-induced vascular dysfunction, primarily through the induction of oxidative stress and the generation of COX2-derived PGE2. This supports the concept that in utero exposure to maternal diabetes is a cardiovascular risk factor in adulthood.NEW & NOTEWORTHY Using a unique mouse model of prenatal exposure to maternal type 1 diabetes, our study demonstrates the novel observation that prenatal exposure to maternal diabetes results in a predisposition to high-salt (HS) dietary-induced vascular dysfunction and inflammation in adulthood. Mechanistically, we demonstrated that in utero exposure to maternal diabetes and HS intake induces vascular oxidative stress, cyclooxygenase-derived prostaglandin E2, and inflammation.

Dietary High Salt Intake Exacerbates SGK1-Mediated T Cell Pathogenicity in L-NAME/High Salt-Induced Hypertension

Sodium chloride (NaCl) activates Th17 and dendritic cells in hypertension by stimulating serum/glucocorticoid kinase 1 (SGK1), a sodium sensor. Memory T cells also play a role in hypertension by infiltrating target organs and releasing proinflammatory cytokines. We tested the hypothesis that the role of T cell SGK1 extends to memory T cells. We employed mice with a T cell deletion of SGK1, SGK1fl/fl × tgCD4cre mice, and used SGK1fl/fl mice as controls. We treated the mice with L-NAME (0.5 mg/mL) for 2 weeks and allowed a 2-week washout interval, followed by a 3-week high-salt (HS) diet (4% NaCl). L-NAME/HS significantly increased blood pressure and memory T cell accumulation in the kidneys and bone marrow of SGK1fl/fl mice compared to knockout mice on L-NAME/HS or groups on a normal diet (ND). SGK1fl/fl mice exhibited increased albuminuria, renal fibrosis, and interferon-γ levels after L-NAME/HS treatment. Myography demonstrated endothelial dysfunction in the mesenteric arterioles of SGK1fl/fl mice. Bone marrow memory T cells were adoptively transferred from either mouse strain after L-NAME/HS administration to recipient CD45.1 mice fed the HS diet for 3 weeks. Only the mice that received cells from SGK1fl/fl donors exhibited increased blood pressure and renal memory T cell infiltration. Our data suggest a new therapeutic target for decreasing hypertension-specific memory T cells and protecting against hypertension.

CD4+ T-Cell Legumain Deficiency Attenuates Hypertensive Damage via Preservation of TRAF6

BACKGROUND

T cells are central to the immune responses contributing to hypertension. LGMN (legumain) is highly expressed in T cells; however, its role in the pathogenesis of hypertension remains unclear.

METHODS

Peripheral blood samples were collected from patients with hypertension, and cluster of differentiation (CD)4+ T cells were sorted for gene expression and Western blotting analysis. TLGMNKO (T cell-specific LGMN-knockout) mice (Lgmnf/f/CD4Cre), regulatory T cell (Treg)-specific LGMN-knockout mice (Lgmnf/f/Foxp3YFP Cre), and RR-11a (LGMN inhibitor)-treated C57BL/6 mice were infused with Ang II (angiotensin II) or deoxycorticosterone acetate/salt to establish hypertensive animal models. Flow cytometry, 4-dimensional label-free proteomics, coimmunoprecipitation, Treg suppression, and in vivo Treg depletion or adoptive transfer were used to delineate the functional importance of T-cell LGMN in hypertension development.

RESULTS

LGMN mRNA expression was increased in CD4+ T cells isolated from hypertensive patients and mice, was positively correlated with both systolic and diastolic blood pressure, and was negatively correlated with serum IL (interleukin)-10 levels. TLGMNKO mice exhibited reduced Ang II-induced or deoxycorticosterone acetate/salt-induced hypertension and target organ damage relative to wild-type (WT) mice. Genetic and pharmacological inhibition of LGMN blocked Ang II-induced or deoxycorticosterone acetate/salt-induced immunoinhibitory Treg reduction in the kidneys and blood. Anti-CD25 antibody depletion of Tregs abolished the protective effects against Ang II-induced hypertension in TLGMNKO mice, and LGMN deletion in Tregs prevented Ang II-induced hypertension in mice. Mechanistically, endogenous LGMN impaired Treg differentiation and function by directly interacting with and facilitating the degradation of TRAF6 (tumor necrosis factor receptor-associated factor 6) via chaperone-mediated autophagy, thereby inhibiting NF-κB (nuclear factor kappa B) activation. Adoptive transfer of LGMN-deficient Tregs reversed Ang II-induced hypertension, whereas depletion of TRAF6 in LGMN-deficient Tregs blocked the protective effects.

CONCLUSIONS

LGMN deficiency in T cells prevents hypertension and its complications by promoting Treg differentiation and function. Specifically targeting LGMN in Tregs may be an innovative approach for hypertension treatment.

Common salt aggravated pathology of testosterone-induced benign prostatic hyperplasia in adult male Wistar rat

BACKGROUND

Benign prostatic hyperplasia (BPH) is a major health concern associated with lower urinary tract symptoms and sexual dysfunction in men. Recurrent inflammation, decreased apoptotic rate and oxidative stress are some of the theories that explain the pathophysiology of BPH. Common salt, a food additive, is known to cause systemic inflammation and redox imbalance, and may serve as a potential risk factor for BPH development or progression. This study examined the effect of common salt intake on the pathology of testosterone-induced BPH.

METHODS

Forty male Wistar rats were randomly divided into four equal groups of 10: a control and three salt diet groups-low-salt diet (LSD), standard-salt diet (SSD) and high-salt diet (HSD). The rats were castrated, allowed to recuperate and placed on salt-free diet (control), 0.25% salt diet (LSD), 0.5% salt diet (SSD) and 1.25% salt diet (HSD) for 60 days ad libitum. On day 33, BPH was induced in all the rats with daily injections of testosterone propionate-Testost® (3 mg/kg body weight) for 28 days. The rats had overnight fast (12 h) on day 60 and were euthanized the following day in order to collect blood and prostate samples for biochemical, molecular and immunohistochemistry (IHC) analyses. Mean ± SD values were calculated for each group and compared for significant difference with ANOVA followed by post hoc test (Tukey HSD) at p < 0.05.

RESULTS

This study recorded a substantially higher level of IL-6, IL-8 and COX-2 in salt diet groups and moderate IHC staining of COX-2 in HSD group. The prostatic level of IL-17, IL-1β, PGE2, relative prostate weight and serum PSA levels were not statistically different. The concentrations of IGF-1, TGF-β were similar in all the groups but there were multiple fold increase in Bcl-2 expression in salt diet groups-LSD (13.2), SSD (9.5) and HSD (7.9) and multiple fold decrease in VEGF expression in LSD (-6.3), SSD (-5.1) and HSD (-14.1) compared to control. Activity of superoxide dismutase (SOD) and concentration of nitric oxide rose in LSD and SSD groups, and SSD and HSD groups respectively. Activities of glutathione peroxidase and catalase, and concentration of NADPH and hydrogen peroxide were not significantly different. IHC showed positive immunostaining for iNOS expression in all the groups while histopathology revealed moderate to severe prostatic hyperplasia in salt diet groups.

CONCLUSIONS

These findings suggest that low, standard and high salt diets aggravated the pathology of testosterone-induced BPH in Wistar rats by promoting inflammation, oxidative stress, while suppressing apoptosis and angiogenesis.

Role of Female Sex Hormones and Immune Response in Salt-Sensitive Hypertension Development: Evidence from Experimental Models

PURPOSEOF REVIEW

Female sex hormones have systemic effects unrelated to their reproductive function. We describe experiences of different research groups and our own, on aspects related to the importance of female sex hormones on blood pressure (BP) regulation and salt-sensitivity-mediated BP response and salt sensitivity without alterations in BP, as well as renal sodium handling and interactions with the immune system.

RECENT FINDINGS

Changes in sodium intake in normotensive premenopausal women cause more BP variations than in men. After menopause, women often develop arterial hypertension (HT) with a profile of sodium sensitivity. Besides, experimental results have shown that in adult rat models resembling the postmenopausal hormonal state induced by ovariectomy, controlling BP is not enough to avoid renal and other tissue infiltration with immune cells, which does not occur when sodium intake is low or normal. Therefore, excess sodium promotes an inflammatory state with the involvement of immune cells. The evidence of activation of adaptive immunity, besides changes in T cell subpopulations, includes changes in sodium transporters and receptors. More studies are needed to evaluate the particular sodium sensitivity of women and its meaning. Changes in lifestyle and sodium intake reduction are the main therapeutic steps. However, to face the actual burden of salt-sensitive HT in postmenopausal women and its associated inflammatory/immune changes, it seems reasonable to work on immune cell activity by considering the peripheral blood mononuclear cell phenotypes of molecules and transport proteins related to sodium handle, both to screen for and treat cell activation.

A new immune disease: systemic hypertension

Systemic hypertension is the most common medical comorbidity affecting the adult population globally, with multiple associated outcomes including cerebrovascular diseases, cardiovascular diseases, vascular calcification, chronic kidney disease, metabolic syndrome and mortality. Despite advancements in the therapeutic field approximately one in every five adult patients with hypertension is classified as having treatment-resistant hypertension, indicating the need for studies to provide better understanding of the underlying pathophysiology and the need for more therapeutic targets. Recent pre-clinical studies have demonstrated the role of the innate and adaptive immune system including various cell types and cytokines in the pathophysiology of hypertension. Moreover, pre-clinical studies have indicated the potential beneficial effects of immunosuppressant medications in the control of hypertension. Nevertheless, it is unclear whether such pathophysiological mechanisms and therapeutic alternatives are applicable to human subjects, while this area of research is undoubtedly a rapidly growing field.

Vascular smooth muscle cell mechanotransduction through serum and glucocorticoid inducible kinase-1 promotes interleukin-6 production and macrophage accumulation in murine hypertension

Objective

The objective of this investigation was to demonstrate that in vivo induction of hypertension (HTN) and in vitro cyclic stretch of aortic vascular smooth muscle cells (VSMCs) can cause serum and glucocorticoid-inducible kinase (SGK-1)-dependent production of cytokines to promote macrophage accumulation that may promote vascular pathology.

Methods

HTN was induced in C57Bl/6 mice with angiotensin II infusion (1.46 mg/kg/day × 21 days) with or without systemic infusion of EMD638683 (2.5 mg/kg/day × 21 days), a selective SGK-1 inhibitor. Systolic blood pressure was recorded. Abdominal aortas were harvested to quantify SGK-1 activity (pSGK-1/SGK-1) by immunoblot. Flow cytometry quantified the abundance of CD11b+/F480+ cells (macrophages). Plasma interleukin (IL)-6 and monocyte chemoattractant protein-1 (MCP-1) was assessed by enzyme-linked immunosorbent assay. Aortic VSMCs from wild-type mice were subjected to 12% biaxial cyclic stretch (Stretch) for 3 or 12 hours with or without EMD638683 (10 μM) and with or without SGK-1 small interfering RNA with subsequent quantitative polymerase chain reaction for IL-6 and MCP-1 expression. IL-6 and MCP-1 in culture media were analyzed by enzyme-linked immunosorbent assay. Aortic VSMCs from SGK-1flox+/+ mice were transfected with Cre-Adenovirus to knockdown SGK-1 (SGK-1KD VSMCs) and underwent parallel tension experimentation. Computational modeling was used to simulate VSMC signaling. Statistical analysis included analysis of variance with significance at a P value of <.05.

Results

SGK-1 activity, abundance of CD11b+/F4-80+ cells, and plasma IL-6 were increased in the abdominal aorta of mice with HTN and significantly reduced by treatment with EMD638683. This outcome mirrored the increased abundance of IL-6 in media from Stretch C57Bl/6 VSMCs and attenuation of the effect with EMD638683 or SGK-1 small interfering RNA. C57Bl/6 VSMCs also responded to Stretch with increased MCP-1 expression and secretion into the culture media. Further supporting the integral role of mechanical signaling through SGK-1, target gene expression and cytokine secretion was unchanged in SGK-1KD VSMCs with Stretch, and computer modeling confirmed SGK-1 as an intersecting node of signaling owing to mechanical strain and angiotensin II.

Conclusions

Mechanical activation of SGK-1 in aortic VSMCs can promote inflammatory signaling and increased macrophage abundance, therefore this kinase warrants further exploration as a pharmacotherapeutic target to abrogate hypertensive vascular pathology.

SARS-CoV-2 infection and recovery in children: Distinct T cell responses in MIS-C compared to COVID-19

SARS-CoV-2 infection for most children results in mild or minimal symptoms, though in rare cases severe disease can develop, including a multisystem inflammatory syndrome (MIS-C) with myocarditis. Here, we present longitudinal profiling of immune responses during acute disease and following recovery in children who developed MIS-C, relative to children who experienced more typical symptoms of COVID-19. T cells in acute MIS-C exhibited transient signatures of activation, inflammation, and tissue residency which correlated with cardiac disease severity, while T cells in acute COVID-19 upregulated markers of follicular helper T cells for promoting antibody production. The resultant memory immune response in recovery showed increased frequencies of virus-specific memory T cells with pro-inflammatory functions in children with prior MIS-C compared to COVID-19 while both cohorts generated comparable antibody responses. Together our results reveal distinct effector and memory T cell responses in pediatric SARS-CoV-2 infection delineated by clinical syndrome, and a potential role for tissue-derived T cells in the immune pathology of systemic disease.

Immunometabolism at the Heart of Cardiovascular Disease

Immune cell function among the myocardium, now more than ever, is appreciated to regulate cardiac function and pathophysiology. This is the case for both innate immunity, which includes neutrophils, monocytes, dendritic cells, and macrophages, as well as adaptive immunity, which includes T cells and B cells. This function is fueled by cell-intrinsic shifts in metabolism, such as glycolysis and oxidative phosphorylation, as well as metabolite availability, which originates from the surrounding extracellular milieu and varies during ischemia and metabolic syndrome. Immune cell crosstalk with cardiac parenchymal cells, such as cardiomyocytes and fibroblasts, is also regulated by complex cellular metabolic circuits. Although our understanding of immunometabolism has advanced rapidly over the past decade, in part through valuable insights made in cultured cells, there remains much to learn about contributions of in vivo immunometabolism and directly within the myocardium. Insight into such fundamental cell and molecular mechanisms holds potential to inform interventions that shift the balance of immunometabolism from maladaptive to cardioprotective and potentially even regenerative. Herein, we review our current working understanding of immunometabolism, specifically in the settings of sterile ischemic cardiac injury or cardiometabolic disease, both of which contribute to the onset of heart failure. We also discuss current gaps in knowledge in this context and therapeutic implications.

Immunoproteasomal Processing of Isolevuglandin Adducts in Hypertension

Isolevuglandins (isoLGs) are lipid aldehydes that form in the presence of reactive oxygen species (ROS) and drive immune activation. We found that isoLG-adducts are presented within the context of major histocompatibility complexes (MHC-I) by an immunoproteasome dependent mechanism. Pharmacologic inhibition of LMP7, the chymotrypsin subunit of the immunoproteasome, attenuates hypertension and tissue inflammation in the angiotensin II (Ang II) model of hypertension. Genetic loss of function of all immunoproteasome subunits or conditional deletion of LMP7 in dendritic cell (DCs) or endothelial cells (ECs) attenuated hypertension, reduced aortic T cell infiltration, and reduced isoLG-adduct MHC-I interaction. Furthermore, isoLG adducts structurally resemble double-stranded DNA and contribute to the activation of STING in ECs. These studies define a critical role of the immunoproteasome in the processing and presentation of isoLG-adducts. Moreover they define a role of LMP7 as a regulator of T cell activation and tissue infiltration in hypertension.

Modulating T Cell Phenotype and Function to Treat Hypertension

Hypertension is the leading modifiable risk factor of worldwide morbidity and mortality because of its effects on cardiovascular and renal end-organ damage. Unfortunately, BP control is not sufficient to fully reduce the risks of hypertension, underscoring the need for novel therapies that address end-organ damage in hypertension. Over the past several decades, the link between immune activation and hypertension has been well established, but there are still no therapies for hypertension that specifically target the immune system. In this review, we describe the critical role played by T cells in hypertension and hypertensive end-organ damage and outline potential therapeutic targets to modulate T-cell phenotype and function in hypertension without causing global immunosuppression.

Role of IL-17A in different stages of ischemic stroke

Interleukin-17A (IL-17A) plays an important role in the progression of ischemic stroke. IL-17A mediates the endothelial inflammatory response, promotes water and sodium retention, and changes the electrophysiological structure of the atrium, accelerating the progression of ischemic stroke risk factors such as atherosclerotic plaques, hypertension, and atrial fibrillation. In the acute phase of ischemic stroke, IL-17A mediates neuronal injury through neutrophil chemotaxis to the site of injury, the induction of neuronal apoptosis, and activation of the calpain-TRPC-6 (transient receptor potential channel-6) pathway. During ischemic stroke recovery, IL-17A, which is mainly derived from reactive astrocytes, promotes and maintains the survival of neural precursor cells (NPCs) in the subventricular zone (SVZ), neuronal differentiation, and synapse formation and participates in the repair of neurological function. Therapies targeting IL-17A-associated inflammatory signaling pathways can reduce the risk of ischemic stroke and neuronal damage and are a new therapeutic strategy for ischemic stroke and its risk factors. In this paper, we will briefly discuss the pathophysiological role of IL-17A in ischemic stroke risk factors, acute and chronic inflammatory responses, and the potential therapeutic value of targeting IL-17A.

Genetics of varicose veins reveals polygenic architecture and genetic overlap with arterial and venous disease

Varicose veins represent a common cause of cardiovascular morbidity, with limited available medical therapies. Although varicose veins are heritable and epidemiologic studies have identified several candidate varicose vein risk factors, the molecular and genetic basis remains uncertain. Here we analyzed the contribution of common genetic variants to varicose veins using data from the Veterans Affairs Million Veteran Program and four other large biobanks. Among 49,765 individuals with varicose veins and 1,334,301 disease-free controls, we identified 139 risk loci. We identified genetic overlap between varicose veins, other vascular diseases and dozens of anthropometric factors. Using Mendelian randomization, we prioritized therapeutic targets via integration of proteomic and transcriptomic data. Finally, topological enrichment analyses confirmed the biologic roles of endothelial shear flow disruption, inflammation, vascular remodeling and angiogenesis. These findings may facilitate future efforts to develop nonsurgical therapies for varicose veins.

Responses Triggered by the Immune System in Hypertensive Conditions and Repercussions on Target Organ Damage: A Review

BACKGROUND

Hypertension is a chronic, multifactorial clinical condition characterized by sustained high blood pressure levels. It is often associated with functional-structural alterations of target organs, which include heart, brain, kidneys, and vasculature.

OBJECTIVE

This study highlights the recent correlation between the immune system and hypertension and its repercussions on target-organ damage.

METHODS

The descriptors used for the search of the study were "hypertension", "immunity", and "target organs". The methodology of the study followed the main recommendations of the PRISMA statement.

RESULTS

The damage to the vasculature arises mainly from the migration of T cells and monocytes that become pro-inflammatory in the adventitia, releasing TNF-α, IFN-γ, and IL-17, which induce endothelial damage and hinder vascular relaxation. In the renal context, the inflammatory process associated with hypertension culminates in renal invasion by leukocytes, which contribute to the injury of this organ by mechanisms of intense sympathetic stimulation, activation of the reninangiotensin system, sodium retention, and aggravation of oxidative stress. In the cardiac context, hypertension increases the expression of pro-inflammatory elements, such as B, T, and NK cells, in addition to the secretion of IFN-γ, IL-17, IL-23, and TNF-α from angiotensin II, reactive oxygen species, and aldosterone. This pro-inflammatory action is also involved in brain damage through SphK1. In view of the above, the participation of the immune system in hypertension-induced injuries seems to be unequivocal.

CONCLUSION

Therefore, understanding the multifactorial mechanisms related to hypertension will certainly allow for more efficient interventions in this condition, preventing target organ damage.

A Single Nucleotide Polymorphism in SH2B3/LNK Promotes Hypertension Development and Renal Damage

BACKGROUND

SH2B3 (SH2B adaptor protein 3) is an adaptor protein that negatively regulates cytokine signaling and cell proliferation. A common missense single nucleotide polymorphism in SH2B3 (rs3184504) results in substitution of tryptophan (Trp) for arginine (Arg) at amino acid 262 and is a top association signal for hypertension in human genome-wide association studies. Whether this variant is causal for hypertension, and if so, the mechanism by which it impacts pathogenesis is unknown.

METHODS

We used CRISPR-Cas9 technology to create mice homozygous for the major (Arg/Arg) and minor (Trp/Trp) alleles of this SH2B3 polymorphism. Mice underwent angiotensin II (Ang II) infusion to evaluate differences in blood pressure (BP) elevation and end-organ damage including albuminuria and renal fibrosis. Cytokine production and Stat4 phosphorylation was also assessed in Arg/Arg and Trp/Trp T cells.

RESULTS

Trp/Trp mice exhibit 10 mmHg higher systolic BP during chronic Ang II infusion compared to Arg/Arg controls. Renal injury and perivascular fibrosis are exacerbated in Trp/Trp mice compared to Arg/Arg controls following Ang II infusion. Renal and ex vivo stimulated splenic CD8+ T cells from Ang II-infused Trp/Trp mice produce significantly more interferon gamma (IFNg) compared to Arg/Arg controls. Interleukin-12 (IL-12)-induced IFNg production is greater in Trp/Trp compared to Arg/Arg CD8+ T cells. In addition, IL-12 enhances Stat4 phosphorylation to a greater degree in Trp/Trp compared to Arg/Arg CD8+ T cells, suggesting that Trp-encoding SH2B3 exhibits less negative regulation of IL-12 signaling to promote IFNg production. Finally, we demonstrated that a multi-SNP model genetically predicting increased SH2B3 expression in lymphocytes is inversely associated with hypertension and hypertensive chronic kidney disease in humans..

CONCLUSIONS

Taken together, these results suggest that the Trp encoding allele of rs3184504 is causal for BP elevation and renal dysfunction, in part through loss of SH2B3-mediated repression of T cell IL-12 signaling leading to enhanced IFNg production.

Update on Immune Mechanisms in Hypertension

The contribution of immune cells in the initiation and maintenance of hypertension is undeniable. Several studies have established the association between hypertension, inflammation, and immune cells from the innate and adaptive immune systems. Here, we provide an update to our 2017 American Journal of Hypertension review on the overview of the cellular immune responses involved in hypertension. Further, we discuss the activation of immune cells and their contribution to the pathogenesis of hypertension in different in vivo models. We also highlight existing gaps in the field of hypertension that need attention. The main goal of this review is to provide a knowledge base for translational research to develop therapeutic strategies that can improve cardiovascular health in humans.

Pathophysiology and genetics of salt-sensitive hypertension

Most hypertensive cases are primary and heavily associated with modifiable risk factors like salt intake. Evidence suggests that even small reductions in salt consumption reduce blood pressure in all age groups. In that regard, the ACC/AHA described a distinct set of individuals who exhibit salt-sensitivity, regardless of their hypertensive status. Data has shown that salt-sensitivity is an independent risk factor for cardiovascular events and mortality. However, despite extensive research, the pathogenesis of salt-sensitive hypertension is still unclear and tremendously challenged by its multifactorial etiology, complicated genetic influences, and the unavailability of a diagnostic tool. So far, the important roles of the renin-angiotensin-aldosterone system, sympathetic nervous system, and immune system in the pathogenesis of salt-sensitive hypertension have been studied. In the first part of this review, we focus on how the systems mentioned above are aberrantly regulated in salt-sensitive hypertension. We follow this with an emphasis on genetic variants in those systems that are associated with and/or increase predisposition to salt-sensitivity in humans.

Hypertension and human immunodeficiency virus: A paradigm for epithelial sodium channels?

Hypertension is a risk factor for end organ damage and death and is more common in persons with HIV compared to the general population. Several mechanisms have been studied in the pathogenesis of hypertension. Current evidence suggests that the epithelial sodium channel (ENaC) plays a key role in regulating blood pressure through the transport of sodium and water across membranes in the kidney tubules, resulting in retention of sodium and water and an altered fluid balance. However, there is scarcity of information that elucidates the role of ENaC in HIV as it relates to increasing the risk for development or pathogenesis of hypertension. This review summarized the evidence to date implicating a potential role for altered ENaC activity in contributing to hypertension in patients with HIV.

Isolevuglandins disrupt PU.1-mediated C1q expression and promote autoimmunity and hypertension in systemic lupus erythematosus

We describe a mechanism responsible for systemic lupus erythematosus (SLE). In humans with SLE and in 2 SLE murine models, there was marked enrichment of isolevuglandin-adducted proteins (isoLG adducts) in monocytes and dendritic cells. We found that antibodies formed against isoLG adducts in both SLE-prone mice and humans with SLE. In addition, isoLG ligation of the transcription factor PU.1 at a critical DNA binding site markedly reduced transcription of all C1q subunits. Treatment of SLE-prone mice with the specific isoLG scavenger 2-hydroxybenzylamine (2-HOBA) ameliorated parameters of autoimmunity, including plasma cell expansion, circulating IgG levels, and anti-dsDNA antibody titers. 2-HOBA also lowered blood pressure, attenuated renal injury, and reduced inflammatory gene expression uniquely in C1q-expressing dendritic cells. Thus, isoLG adducts play an essential role in the genesis and maintenance of systemic autoimmunity and hypertension in SLE.

The Prevalence of Post-COVID-19 Hypertension in Children

Coronavirus disease 2019 (COVID-19) is the greatest pandemic in a century. In this study, children with mild COVID-19 infections were evaluated at least 8 weeks after the polymerase chain reaction (PCR) test positivity, and the frequency of hypertension (HT) in these children was investigated. These results were compared to those of the control group, which consisted of 32 healthy children in the same age range as the trial group but who did not have COVID-19. This prospective multicenter study was conducted including children aged 10 to 18 years. There were 16 patients (16%) who had elevated systolic blood pressure, while 11 patients (11%) had stage-1 HT and 1 patient (1%) had stage-2 HT. It was revealed that children with COVID-19 had significantly higher systolic and diastolic blood pressures than normal healthy children. The findings of this study contribute toward increasing the understanding of the sequelae of mild COVID-19 in pediatric patients.

The modulatory effect of high salt on immune cells and related diseases

BACKGROUND

The adverse effect of excessive salt intake has been recognized in decades. Researchers have mainly focused on the association between salt intake and hypertension. However, studies in recent years have proposed the existence of extra-renal sodium storage and provided insight into the immunomodulatory function of sodium.

OBJECTIVES

In this review, we discuss the modulatory effects of high salt on various innate and adaptive immune cells and immune-regulated diseases.

METHODS

We identified papers through electronic searches of PubMed database from inception to March 2022.

RESULTS

An increasing body of evidence has demonstrated that high salt can modulate the differentiation, activation and function of multiple immune cells. Furthermore, a high-salt diet can increase tissue sodium concentrations and influence the immune responses in microenvironments, thereby affecting the development of immune-regulated diseases, including hypertension, multiple sclerosis, cancer and infections. These findings provide a novel mechanism for the pathology of certain diseases and indicate that salt might serve as a target or potential therapeutic agent in different disease contexts.

CONCLUSION

High salt has a profound impact on the differentiation, activation and function of multiple immune cells. Additionally, an HSD can modulate the development of various immune-regulated diseases.

SGK1 in Cancer: Biomarker and Drug Target

Serum- and glucocorticoid-regulated kinases (SGKs) are members of the AGC family of serine/threonine kinases, consisting of three isoforms: SGK1, SGK2, and SGK3. SGK1 was initially cloned as a gene transcriptionally stimulated by serum and glucocorticoids in rat mammary tumor cells. It is upregulated in some cancers and downregulated in others. SGK1 increases tumor cell survival, adhesiveness, invasiveness, motility, and epithelial to mesenchymal transition. It stimulates tumor growth by mechanisms such as activation of K+ channels and Ca2+ channels, Na+/H+ exchanger, amino acid and glucose transporters, downregulation of Foxo3a and p53, and upregulation of β-catenin and NFκB. This chapter focuses on major aspects of SGK1 involvement in cancer, its use as biomarker as well as potential therapeutic target.

Perivascular Fibrosis Is Mediated by a KLF10-IL-9 Signaling Axis in CD4+ T Cells

BACKGROUND

Perivascular fibrosis, characterized by increased amount of connective tissue around vessels, is a hallmark for vascular disease. Ang II (angiotensin II) contributes to vascular disease and end-organ damage via promoting T-cell activation. Despite recent data suggesting the role of T cells in the progression of perivascular fibrosis, the underlying mechanisms are poorly understood.

METHODS

TF (transcription factor) profiling was performed in peripheral blood mononuclear cells of hypertensive patients. CD4-targeted KLF10 (Kruppel like factor 10)-deficient (Klf10^fl/flCD4^Cre+; [TKO]) and CD4-Cre (Klf10^+/+CD4^Cre+; (Cre)) control mice were subjected to Ang II infusion. End point characterization included cardiac echocardiography, aortic imaging, multiorgan histology, flow cytometry, cytokine analysis, aorta and fibroblast transcriptomic analysis, and aortic single-cell RNA-sequencing.

RESULTS

TF profiling identified increased KLF10 expression in hypertensive human subjects and in CD4+ T cells in Ang II-treated mice. TKO mice showed enhanced perivascular fibrosis, but not interstitial fibrosis, in aorta, heart, and kidney in response to Ang II, accompanied by alterations in global longitudinal strain, arterial stiffness, and kidney function compared with Cre control mice. However, blood pressure was unchanged between the 2 groups. Mechanistically, KLF10 bound to the IL (interleukin)-9 promoter and interacted with HDAC1 (histone deacetylase 1) inhibit IL-9 transcription. Increased IL-9 in TKO mice induced fibroblast intracellular calcium mobilization, fibroblast activation, and differentiation and increased production of collagen and extracellular matrix, thereby promoting the progression of perivascular fibrosis and impairing target organ function. Remarkably, injection of anti-IL9 antibodies reversed perivascular fibrosis in Ang II-infused TKO mice and C57BL/6 mice. Single-cell RNA-sequencing revealed fibroblast heterogeneity with activated signatures associated with robust ECM (extracellular matrix) and perivascular fibrosis in Ang II-treated TKO mice.

CONCLUSIONS

CD4+ T cell deficiency of Klf10 exacerbated perivascular fibrosis and multi-organ dysfunction in response to Ang II via upregulation of IL-9. Klf10 or IL-9 in T cells might represent novel therapeutic targets for treatment of vascular or fibrotic diseases.

Lipid droplets and autophagosomes together with chaperones fine-tune expression of SGK1

Serum-glucocorticoid-induced kinase-1 (SGK1) regulates ion homeostasis and promotes survival under stress conditions. The expression of SGK1 is under transcriptional and post-translational regulations that are frequently altered in cancer and immune disorders. We report that an N-terminal amphipathic alpha-helix determines SGK1 expression levels through two distinct mechanisms. It tethers SGK1 to intracellular organelles generating a large pool of membrane-bound SGK1, which is differentially stabilized in lipid droplets (LD) in fed conditions or degraded in the endoplasmic reticulum by ER-phagy in starvation. Association of the α-helix to organelles does not depend on dedicated receptors or special phospholipids rather, it is intrinsic to its physicochemical properties and depends on the presence of bulky hydrophobic residues for attachment to LDs. The second mechanism is recruitment of protein-chaperones that recognize the α-helix as an unfolded protein promoting survival of the cytosolic SGK1 fraction. Together, the findings unveil an unexpected link between levels of energy storage and abundance of SGK1 and how changes in calorie intake could be used to modulate SGK1 expression, whereas the inhibition of molecular chaperones could serve as an additional enhancer in the treatment of malignancies and autoimmune disorders with high levels of SGK1 expression.

Microenvironmental influences on T cell immunity in cancer and inflammation

T cell metabolism is dynamic and highly regulated. While the intrinsic metabolic programs of T cell subsets are integral to their distinct differentiation and functional patterns, the ability of cells to acquire nutrients and cope with hostile microenvironments can limit these pathways. T cells must function in a wide variety of tissue settings, and how T cells interpret these signals to maintain an appropriate metabolic program for their demands or if metabolic mechanisms of immune suppression restrain immunity is an area of growing importance. Both in inflamed and cancer tissues, a wide range of changes in physical conditions and nutrient availability are now acknowledged to shape immunity. These include fever and increased temperatures, depletion of critical micro and macro-nutrients, and accumulation of inhibitory waste products. Here we review several of these factors and how the tissue microenvironment both shapes and constrains immunity.

The Sweet and Salty Dietary Face of Hypertension and Cardiovascular Disease in Lebanon

According to the World Health Organization (WHO), an estimated 1.28 billion adults aged 30–79 years worldwide have hypertension; and every year, hypertension takes 7.6 million lives. High intakes of salt and sugar (mainly fructose from added sugars) have been linked to the etiology of hypertension, and this may be particularly true for countries undergoing the nutrition transition, such as Lebanon. Salt-induced hypertension and fructose-induced hypertension are manifested in different mechanisms, including Inflammation, aldosterone-mineralocorticoid receptor pathway, aldosterone independent mineralocorticoid receptor pathway, renin-angiotensin system (RAS), sympathetic nervous system (SNS) activity, and genetic mechanisms. This review describes the evolution of hypertension and cardiovascular diseases (CVDs) in Lebanon and aims to elucidate potential mechanisms where salt and fructose work together to induce hypertension. These mechanisms increase salt absorption, decrease salt excretion, induce endogenous fructose production, activate fructose-insulin-salt interaction, and trigger oxidative stress, thus leading to hypertension. The review also provides an up-to-date appraisal of current intake levels of salt and fructose in Lebanon and their main food contributors. It identifies ongoing salt and sugar intake reduction strategies in Lebanon while acknowledging the country’s limited scope of regulation and legislation. Finally, the review concludes with proposed public health strategies and suggestions for future research, which can reduce the intake levels of salt and fructose levels and contribute to curbing the CVD epidemic in the country.

CNS pharmacology of NKCC1 inhibitors

The Na-K-2Cl cotransporter NKCC1 and the neuron-specific K-Cl cotransporter KCC2 are considered attractive CNS drug targets because altered neuronal chloride regulation and consequent effects on GABAergic signaling have been implicated in numerous CNS disorders. While KCC2 modulators are not yet clinically available, the loop diuretic bumetanide has been used off-label in attempts to treat brain disorders and as a tool for NKCC1 inhibition in preclinical models. Bumetanide is known to have anticonvulsant and neuroprotective effects under some pathophysiological conditions. However, as shown in several species from neonates to adults (mice, rats, dogs, and by extrapolation in humans), at the low clinical doses of bumetanide approved for diuresis, this drug has negligible access into the CNS, reaching levels that are much lower than what is needed to inhibit NKCC1 in cells within the brain parenchyma. Several drug discovery strategies have been initiated over the last ∼15 years to develop brain-permeant compounds that, ideally, should be selective for NKCC1 to eliminate the diuresis mediated by inhibition of renal NKCC2. The strategies employed to improve the pharmacokinetic and pharmacodynamic properties of NKCC1 blockers include evaluation of other clinically approved loop diuretics; development of lipophilic prodrugs of bumetanide; development of side-chain derivatives of bumetanide; and unbiased high-throughput screening approaches of drug discovery based on large chemical compound libraries. The main outcomes are that (1), non-acidic loop diuretics such as azosemide and torasemide may have advantages as NKCC1 inhibitors vs. bumetanide; (2), bumetanide prodrugs lead to significantly higher brain levels than the parent drug and have lower diuretic activity; (3), the novel bumetanide side-chain derivatives do not exhibit any functionally relevant improvement of CNS accessibility or NKCC1 selectivity vs. bumetanide; (4) novel compounds discovered by high-throughput screening may resolve some of the inherent problems of bumetanide, but as yet this has not been achieved. Thus, further research is needed to optimize the design of brain-permeant NKCC1 inhibitors. In parallel, a major challenge is to identify the mechanisms whereby various NKCC1-expressing cellular targets of these drugs within (e.g., neurons, oligodendrocytes or astrocytes) and outside the brain parenchyma (e.g., the blood-brain barrier, the choroid plexus, and the endocrine system), as well as molecular off-target effects, might contribute to their reported therapeutic and adverse effects.

Ovariectomy and high salt increase blood pressure and alter sodium transport proteins in peripheral blood mononuclear cells of adult Wistar rats

NEW FINDINGS

What is the central question of this study? In a model of salt-sensitive hypertension in ovariectomized (oVx) adult Wistar rats, what is the expression of proteins related to sodium transport in peripheral blood mononuclear cells (PBMCs), and how does the response of proteins to high sodium intake compare with changes in blood pressure in intact female rats? What is the main finding and its importance? Sodium transport proteins in PBMCs react to high sodium and blood pressure markedly differently in oVx versus intact female rats. Protein expression shows sodium and pressure sensitivity. Renal immune cells increase in oVx under high salt.

ABSTRACT

Hypertension is a worldwide public health problem. High sodium consumption is associated with hypertension, and hypertensive mechanisms involve immunity cells. Peripheral blood mononuclear cells (PBMCs) are endowed with proteins related to sodium transport. We studied their abundance in PBMCs from intact (IF) or ovariectomized (oVx) adult Wistar rats under normal (NS) or high (HS) salt intake. Ovariectomy was performed at 60 days of life. At 145 days, one group of IF and oVx rats received NS or HS intake for 5 days. Another group of IF HS and oVx HS rats received hydralazine (HDZ) to reduce blood pressure (BP). Sodium balance and BP were recorded. Expression of Na⁺ ,K⁺ -ATPase (NKA), Na⁺ -K⁺ -2Cl^- cotransporter 1 (NKCC1), serum/glucocorticoid-regulated kinase 1 (SGK1), dopamine D1 like receptor (D1DR), CD4⁺ and CD8⁺ were determined in PBMCs and CD45⁺ leukocytes in renal tissue. IF HS rats showed increased natriuresis and normal BP. NKA and CD4⁺ expression diminished in IF HS. Instead, oVx HS rats had sodium retention and high BP and increased the expression of NKA, NKCC1, D1DR, CD4⁺ and CD8⁺ in PBMCs. Renal CD45⁺ leukocytes increased in oVx HS rats. HDZ decreased BP in all rats. Upon HDZ treatment, NKA did not change, NKCC1 decreased in oVx HS rats, while SGK1 increased in both IF HS and oVx HS rats. Hormonal background determines BP response and the expression of proteins related to sodium transport in PBMCs and renal immune cells at HS intake. The analysis of NKA, NKCC1 and SGK1 expression in PBMCs differentiated salt-sensitivity from BP variations.

Insulin resistance, cardiovascular stiffening and cardiovascular disease

The cardiometabolic syndrome (CMS) and obesity are typically characterized by a state of metabolic insulin resistance. As global and US rates of obesity increase there is an acceleration of the incidence and prevalence of insulin resistance along with associated cardiovascular disease (CVD). Under physiological conditions insulin regulates glucose homeostasis by enhancing glucose disposal in insulin sensitive tissues while also regulating delivery of nutrients through its vasodilation actions on small feed arteries. Specifically, insulin-mediated production of nitric oxide (NO) from the vascular endothelium leads to increased blood flow enhancing disposal of glucose. Typically, insulin resistance is considered as a decrease in sensitivity or responsiveness to the metabolic actions of insulin including insulin-mediated glucose disposal. However, a decreased sensitivity to the normal vascular actions of insulin, especially diminished nitric oxide production, plays an additional important role in the development of CVD in states of insulin resistance. One mechanism by which insulin resistance and attendant hyperinsulinemia promote CVD is via increases in vascular stiffness. Although obesity and insulin resistance are known to be associated with substantial increases in the prevalence of vascular fibrosis and stiffness the mechanisms and mediators that underlie vascular stiffening in insulin resistant states are complex and have only recently begun to be addressed. Current evidence supports the role of increased plasma levels of aldosterone and insulin and attendant reductions in bioavailable NO in the pathogenesis of impaired vascular relaxation and vascular stiffness in the CMS and obesity. Aldosterone and insulin both increase the activity of serum and glucocorticoid kinase 1 (SGK-1) which in turn is a major regulator of vascular and renal sodium (Na⁺⁾ channel activity.The importance of SGK-1 in the pathogenesis of the CMS is highlighted by observations that gain of function mutations in SGK-1 in humans promotes hypertension, insulin resistance and obesity. In endothelial cells, an increase in Na⁺ flux contributes to remodeling of the cytoskeleton, reduced NO bioavailability and vascular stiffening. Thus, endothelial SGK-1 may represent a point of convergence for insulin and aldosterone signaling in arterial stiffness associated with obesity and the CMS. This review examines our contemporary understanding of the link between insulin resistance and increased vascular stiffness with emphasis placed on a role for enhanced SGK-1 signaling as a key node in this pathological process.

Vascular control of kidney epithelial transporters

A major pathway in hypertension pathogenesis involves direct activation of ANG II type 1 (AT1) receptors in the kidney, stimulating Na+ reabsorption. AT1 receptors in tubular epithelia control expression and stimulation of Na+ transporters and channels. Recently, we found reduced blood pressure and enhanced natriuresis in mice with cell-specific deletion of AT1 receptors in smooth muscle (SMKO mice). Although impaired vasoconstriction and preserved renal blood flow might contribute to exaggerated urinary Na+ excretion in SMKO mice, we considered whether alterations in Na+ transporter expression might also play a role; therefore, we carried out proteomic analysis of key Na+ transporters and associated proteins. Here, we show that levels of Na+-K+-2Cl- cotransporter isoform 2 (NKCC2) and Na+/H+ exchanger isoform 3 (NHE3) are reduced at baseline in SMKO mice, accompanied by attenuated natriuretic and diuretic responses to furosemide. During ANG II hypertension, we found widespread remodeling of transporter expression in wild-type mice with significant increases in the levels of total NaCl cotransporter, phosphorylated NaCl cotransporter (Ser71), and phosphorylated NKCC2, along with the cleaved, activated forms of the α- and γ-epithelial Na+ channel. However, the increases in α- and γ-epithelial Na+ channel with ANG II were substantially attenuated in SMKO mice. This was accompanied by a reduced natriuretic response to amiloride. Thus, enhanced urinary Na+ excretion observed after cell-specific deletion of AT1 receptors from smooth muscle cells is associated with altered Na+ transporter abundance across epithelia in multiple nephron segments. These findings suggest a system of vascular-epithelial in the kidney, modulating the expression of Na+ transporters and contributing to the regulation of pressure natriuresis.NEW & NOTEWORTHY The use of drugs to block the renin-angiotensin system to reduce blood pressure is common. However, the precise mechanism for how these medications control blood pressure is incompletely understood. Here, we show that mice lacking angiotensin receptors specifically in smooth muscle cells lead to alternation in tubular transporter amount and function. Thus, demonstrating the importance of vascular-tubular cross talk in the control of blood pressure.

Empagliflozin Inhibits IL-1β-Mediated Inflammatory Response in Human Proximal Tubular Cells

SGLT2 inhibitor-related nephroprotection is—at least partially—mediated by anti-inflammatory drug effects, as previously demonstrated in diabetic animal and human studies, as well as hyperglycemic cell culture models. We recently presented first evidence for anti-inflammatory potential of empagliflozin (Empa) under normoglycemic conditions in human proximal tubular cells (HPTC) by demonstrating Empa-mediated inhibition of IL-1β-induced MCP-1/CCL2 and ET-1 expression on the mRNA and protein level. We now add corroborating evidence on a genome-wide level by demonstrating that Empa attenuates the expression of several inflammatory response genes in IL-1β-induced (10 ng/mL) normoglycemic HPTCs. Using microarray-hybridization analysis, 19 inflammatory response genes out of >30.000 human genes presented a consistent expression pattern, that is, inhibition of IL-1β (10 ng/mL)-stimulated gene expression by Empa (500 nM), in both HK-2 and RPTEC/TERT1 cells. Pathway enrichment analysis demonstrated statistically significant clustering of annotated pathways (enrichment score 3.64). Our transcriptomic approach reveals novel genes such as CXCL8/IL8, LOX, NOV, PTX3, and SGK1 that might be causally involved in glycemia-independent nephroprotection by SGLT2i.

Renal Inflammation Induces Salt Sensitivity in Male db/db Mice through Dysregulation of ENaC

BACKGROUND

Hypertension is considered a major risk factor for the progression of diabetic kidney disease. Type 2 diabetes is associated with increased renal sodium reabsorption and salt-sensitive hypertension. Clinical studies show that men have higher risk than premenopausal women for the development of diabetic kidney disease. However, the renal mechanisms that predispose to salt sensitivity during diabetes and whether sexual dimorphism is associated with these mechanisms remains unknown.

METHODS

Female and male db/db mice exposed to a high-salt diet were used to analyze the progression of diabetic kidney disease and the development of hypertension.

RESULTS

Male, 34-week-old, db/db mice display hypertension when exposed to a 4-week high-salt treatment, whereas equivalently treated female db/db mice remain normotensive. Salt-sensitive hypertension in male mice was associated with no suppression of the epithelial sodium channel (ENaC) in response to a high-salt diet, despite downregulation of several components of the intrarenal renin-angiotensin system. Male db/db mice show higher levels of proinflammatory cytokines and more immune-cell infiltration in the kidney than do female db/db mice. Blocking inflammation, with either mycophenolate mofetil or by reducing IL-6 levels with a neutralizing anti-IL-6 antibody, prevented the development of salt sensitivity in male db/db mice.

CONCLUSIONS

The inflammatory response observed in male, but not in female, db/db mice induces salt-sensitive hypertension by impairing ENaC downregulation in response to high salt. These data provide a mechanistic explanation for the sexual dimorphism associated with the development of diabetic kidney disease and salt sensitivity.

Hypertension: Do Inflammation and Immunity Hold the Key to Solving this Epidemic?

Elevated cardiovascular risk including stroke, heart failure, and heart attack is present even after normalization of blood pressure in patients with hypertension. Underlying immune cell activation is a likely culprit. Although immune cells are important for protection against invading pathogens, their chronic overactivation may lead to tissue damage and high blood pressure. Triggers that may initiate immune activation include viral infections, autoimmunity, and lifestyle factors such as excess dietary salt. These conditions activate the immune system either directly or through their impact on the gut microbiome, which ultimately produces chronic inflammation and hypertension. T cells are central to the immune responses contributing to hypertension. They are activated in part by binding specific antigens that are presented in major histocompatibility complex molecules on professional antigen-presenting cells, and they generate repertoires of rearranged T-cell receptors. Activated T cells infiltrate tissues and produce cytokines including interleukin 17A, which promote renal and vascular dysfunction and end-organ damage leading to hypertension. In this comprehensive review, we highlight environmental, genetic, and microbial associated mechanisms contributing to both innate and adaptive immune cell activation leading to hypertension. Targeting the underlying chronic immune cell activation in hypertension has the potential to mitigate the excess cardiovascular risk associated with this common and deadly disease.

Pathophysiology of Hypertension: The Mosaic Theory and Beyond

Dr Irvine Page proposed the Mosaic Theory of Hypertension in the 1940s advocating that hypertension is the result of many factors that interact to raise blood pressure and cause end-organ damage. Over the years, Dr Page modified his paradigm, and new concepts regarding oxidative stress, inflammation, genetics, sodium homeostasis, and the microbiome have arisen that allow further refinements of the Mosaic Theory. A constant feature of this approach to understanding hypertension is that the various nodes are interdependent and that these almost certainly vary between experimental models and between individuals with hypertension. This review discusses these new concepts and provides an introduction to other reviews in this compendium of Circulation Research.

Obesity, Adipose Tissue and Vascular Dysfunction

Cardiovascular diseases are the leading cause of death worldwide. Overweight and obesity are strongly associated with comorbidities such as hypertension and insulin resistance, which collectively contribute to the development of cardiovascular diseases and resultant morbidity and mortality. Forty-two percent of adults in the United States are obese, and a total of 1.9 billion adults worldwide are overweight or obese. These alarming numbers, which continue to climb, represent a major health and economic burden. Adipose tissue is a highly dynamic organ that can be classified based on the cellular composition of different depots and their distinct anatomical localization. Massive expansion and remodeling of adipose tissue during obesity differentially affects specific adipose tissue depots and significantly contributes to vascular dysfunction and cardiovascular diseases. Visceral adipose tissue accumulation results in increased immune cell infiltration and secretion of vasoconstrictor mediators, whereas expansion of subcutaneous adipose tissue is less harmful. Therefore, fat distribution more than overall body weight is a key determinant of the risk for cardiovascular diseases. Thermogenic brown and beige adipose tissue, in contrast to white adipose tissue, is associated with beneficial effects on the vasculature. The relationship between the type of adipose tissue and its influence on vascular function becomes particularly evident in the context of the heterogenous phenotype of perivascular adipose tissue that is strongly location dependent. In this review, we address the abnormal remodeling of specific adipose tissue depots during obesity and how this critically contributes to the development of hypertension, endothelial dysfunction, and vascular stiffness. We also discuss the local and systemic roles of adipose tissue derived secreted factors and increased systemic inflammation during obesity and highlight their detrimental impact on cardiovascular health.

Class switching and high-affinity immunoglobulin G production by B cells is dispensable for the development of hypertension in mice

AIMS

Elevated serum immunoglobulins have been associated with experimental and human hypertension for decades but whether immunoglobulins and B cells play a causal role in hypertension pathology is unclear. In this study, we sought to determine the role of B cells and high-affinity class-switched immunoglobulins on hypertension and hypertensive end-organ damage to determine if they might represent viable therapeutic targets for this disease.

METHODS AND RESULTS

We purified serum immunoglobulin G (IgG) from mice exposed to vehicle or angiotensin (Ang) II to induce hypertension and adoptively transferred these to wild type (WT) recipient mice receiving a subpressor dose of Ang II. We found that transfer of IgG from hypertensive animals does not affect blood pressure, endothelial function, renal inflammation, albuminuria, or T cell-derived cytokine production compared with transfer of IgG from vehicle infused animals. As an alternative approach to investigate the role of high-affinity, class-switched immunoglobulins, we studied mice with genetic deletion of activation-induced deaminase (Aicda-/-). These mice have elevated levels of IgM but virtual absence of class-switched immunoglobulins such as IgG subclasses and IgA. Neither male nor female Aicda-/- mice were protected from Ang II-induced hypertension and renal/vascular damage. To determine if IgM or non-immunoglobulin-dependent innate functions of B cells play a role in hypertension, we studied mice with severe global B-cell deficiency due to deletion of the membrane exon of the IgM heavy chain (µMT-/-). µMT-/- mice were also not protected from hypertension or end-organ damage induced by Ang II infusion or deoxycorticosterone acetate-salt treatment.

CONCLUSIONS

These results suggest that B cells and serum immunoglobulins do not play a causal role in hypertension pathology.

Interleukin 17A: Key Player in the Pathogenesis of Hypertension and a Potential Therapeutic Target

PURPOSE OF REVIEW

To summarize key advances in our understanding of the role of interleukin 17A (IL-17A) in the pathogenesis of hypertension and highlight important areas for future research and clinical translation.

RECENT FINDINGS

While T helper 17 (Th17) cells are major producers of IL-17A, there are several additional innate and adaptive immune cell sources including gamma-delta T cells, innate lymphoid cells, and natural killer cells. IL-17A promotes an increase in blood pressure through multiple mechanisms including inhibiting endothelial nitric oxide production, increasing reactive oxygen species formation, promoting vascular fibrosis, and enhancing renal sodium retention and glomerular injury. IL-17A production from Th17 cells is increased by high salt conditions in vitro and in vivo. There is also emerging data linking salt, the gut microbiome, and intestinal T cell IL-17A production. Novel therapeutics targeting IL-17A signaling are approved for the treatment of autoimmune diseases and show promise in both animal models of hypertension and human studies. Hypertensive stimuli enhance IL-17A production. IL-17A is a key mediator of renal and vascular dysfunction in hypertensive mouse models and correlates with hypertension in humans. Large randomized clinical trials are needed to determine whether targeting IL-17A might be an effective adjunct treatment for hypertension and its associated end-organ dysfunction.

Amplification of Salt-Sensitive Hypertension and Kidney Damage by Immune Mechanisms

Humans with salt-sensitive (SS) hypertension demonstrate increased morbidity, increased mortality, and renal end-organ damage when compared with normotensive subjects or those with salt-resistant hypertension. Increasing evidence indicates that immune mechanisms play an important role in the full development of SS hypertension and associated renal damage. Recent experimental advances and studies in animal models have permitted a greater understanding of the mechanisms of activation and action of immunity in this disease process. Evidence favors a role of both innate and adaptive immune mechanisms that are triggered by initial, immune-independent alterations in blood pressure, sympathetic activity, or tissue damage. Activation of immunity, which can be enhanced by a high-salt intake or by alterations in other components of the diet, leads to the release of cytokines, free radicals, or other factors that amplify renal damage and hypertension and mediate malignant disease.

Aldosterone, Inflammation, Immune System, and Hypertension

Aldosterone is a mineralocorticoid hormone that controls body fluid and electrolyte balance. Excess aldosterone is associated with cardiovascular and metabolic diseases. Inflammation plays a critical role on vascular damage promoted by aldosterone and aggravates vascular abnormalities, including endothelial dysfunction, vascular remodeling, fibrosis and oxidative stress, and other manifestations of end-organ damage that are associated with hypertension, other forms of cardiovascular disease, and diabetes mellitus and the metabolic syndrome. Over the past few years, many studies have consistently shown that aldosterone activates cells of the innate and adaptive immune systems. Macrophages and T cells accumulate in the kidneys, heart, and vasculature in response to aldosterone, and infiltration of immune cells contributes to end-organ damage in cardiovascular and metabolic diseases. Aldosterone activates various subsets of innate immune cells such as dendritic cells and monocytes/macrophages, as well as adaptive immune cells such as T lymphocytes, and, by activation of mineralocorticoid receptors stimulates proinflammatory transcription factors and the production of adhesion molecules and inflammatory cytokines and chemokines. This review will briefly highlight some of the studies on the involvement of aldosterone in activation of innate and adaptive immune cells and its impact on the cardiovascular system. Since aldosterone plays a key role in many cardiovascular and metabolic diseases, these data will open up promising perspectives for the identification of novel biomarkers and therapeutic targets for prevention and treatment of diseases associated with increased levels of aldosterone, such as arterial hypertension, obesity, the metabolic syndrome, and heart failure.

Increased SGK1 activity potentiates mineralocorticoid/NaCl-induced kidney injury

Serum and glucocorticoid-regulated kinase 1 (SGK1) stimulates aldosterone-dependent renal Na⁺ reabsorption and modulates blood pressure. In addition, genetic ablation or pharmacological inhibition of SGK1 limits the development of kidney inflammation and fibrosis in response to excess mineralocorticoid signaling. In this work, we tested the hypothesis that a systemic increase in SGK1 activity would potentiate mineralocorticoid/salt-induced hypertension and kidney injury. To that end, we used a transgenic mouse model with increased SGK1 activity. Mineralocorticoid/salt-induced hypertension and kidney damage was induced by unilateral nephrectomy and treatment with deoxycorticosterone acetate and NaCl in the drinking water for 6 wk. Our results show that although SGK1 activation did not induce significantly higher blood pressure, it produced a mild increase in glomerular filtration rate, increased albuminuria, and exacerbated glomerular hypertrophy and fibrosis. Transcriptomic analysis showed that extracellular matrix- and immune response-related terms were enriched in the downregulated and upregulated genes, respectively, in transgenic mice. In conclusion, we propose that systemically increased SGK1 activity is a risk factor for the development of mineralocorticoid-dependent kidney injury in the context of low renal mass and independently of blood pressure.NEW & NOTEWORTHY Increased activity of the protein kinase serum and glucocorticoid-regulated kinase 1 may be a risk factor for accelerated renal damage. Serum and glucocorticoid-regulated kinase 1 expression could be a marker for the rapid progression toward chronic kidney disease and a potential therapeutic target to slow down the process.

Emerging Role of the Inflammasome and Pyroptosis in Hypertension

Inflammasomes are components of the innate immune response that have recently emerged as crucial controllers of tissue homeostasis. In particular, the nucleotide-binding domain, leucine-rich-containing (NLR) family pyrin domain containing 3 (NLRP3) inflammasome is a complex platform involved in the activation of caspase-1 and the maturation of interleukin (IL)-1β and IL-18, which are mainly released via pyroptosis. Pyroptosis is a caspase-1-dependent type of cell death that is mediated by the cleavage of gasdermin D and the subsequent formation of structurally stable pores in the cell membrane. Through these pores formed by gasdermin proteins cytosolic contents are released into the extracellular space and act as damage-associated molecular patterns, which are pro-inflammatory signals. Inflammation is a main contributor to the development of hypertension and it also is known to stimulate fibrosis and end-organ damage. Patients with essential hypertension and animal models of hypertension exhibit elevated levels of circulating IL-1β. Downregulation of the expression of key components of the NLRP3 inflammasome delays the development of hypertension and pharmacological inhibition of this inflammasome leads to reduced blood pressure in animal models and humans. Although the relationship between pyroptosis and hypertension is not well established yet, pyroptosis has been associated with renal and cardiovascular diseases, instances where high blood pressure is a critical risk factor. In this review, we summarize the recent literature addressing the role of pyroptosis and the inflammasome in the development of hypertension and discuss the potential use of approaches targeting this pathway as future anti-hypertensive strategies.