Search

SH2B3 (SH2B adaptor protein 3) is an adaptor protein that negatively regulates cytokine signaling and cell proliferation. A common missense single nucleotide polymorphism inWe used CRISPR-Cas9 technology to create mice homozygous for the major (Arg/Arg) and minor (Trp/Trp) alleles of thisTrp/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 CD8Taken 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.

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 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 leads 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 (DOCA)-salt treatment. Conclusions These results suggest that B cells and serum immunoglobulins do not play a causal role in hypertension pathology. Translational perspective Our results suggest that in most cases of essential hypertension, B cells are not a causal factor in the pathophysiology of disease. Thus, elevated serum immunoglobulins seen in hypertensive animals and humans may reflect a biomarker of aberrant immune activation in hypertension and not a therapeutic target. However, autoantibodies may cause hypertension in special cases, and more work is needed to determine whether specific B cell subsets might play an important role that is masked by global B cell deficiency.

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.

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. SUMMARY: 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.

Extracellular fluid (ECF) potassium concentration ([K(+)]) is maintained by adaptations of kidney and skeletal muscle, responses heretofore studied separately. We aimed to determine how these organ systems work in concert to preserve ECF [K(+)] in male C57BL/6J mice fed a K(+)-deficient diet (0K) versus 1% K(+) diet (1K) for 10 days (n = 5–6/group). During 0K feeding, plasma [K(+)] fell from 4.5 to 2 mM; hindlimb muscle (gastrocnemius and soleus) lost 28 mM K(+) (from 115 ± 2 to 87 ± 2 mM) and gained 27 mM Na(+) (from 27 ± 0.4 to 54 ± 2 mM). Doubling of muscle tissue [Na(+)] was not associated with inflammation, cytokine production or hypertension as reported by others. Muscle transporter adaptations in 0K- versus 1K-fed mice, assessed by immunoblot, included decreased sodium pump α2-β2 subunits, decreased K(+)-Cl(−) cotransporter isoform 3, and increased phosphorylated (p) Na(+),K(+),2Cl(−) cotransporter isoform 1 (NKCC1p), Ste20/SPS-1-related proline-alanine rich kinase (SPAKp), and oxidative stress-responsive kinase 1 (OSR1p) consistent with intracellular fluid (ICF) K(+) loss and Na(+) gain. Renal transporters’ adaptations, effecting a 98% reduction in K(+) excretion, included two- to threefold increased phosphorylated Na(+)-Cl(−) cotransporter (NCCp), SPAKp, and OSR1p abundance, limiting Na(+) delivery to epithelial Na(+) channels where Na(+) reabsorption drives K(+) secretion; and renal K sensor Kir 4.1 abundance fell 25%. Mass balance estimations indicate that over 10 days of 0K feeding, mice lose ~48 μmol K(+) into the urine and muscle shifts ~47 μmol K(+) from ICF to ECF, illustrating the importance of the concerted responses during K(+) deficiency.

Visual Abstract, Highlights • IsoLGs are highly reactive lipid dicarbonyl metabolites that constitute a major component of oxidative stress-related injury, and they promote the formation of amyloid. • In a hypertensive murine model, IsoLG adducts and PAOs developed in the atria, along with inducible AF. • IsoLG and PAO accumulation and AF were prevented by the dicarbonyl scavenger 2-HOBA, but not by an inactive analog 4-hydroxybenzylamine. • Mechanically stretched atrial cells generated cytosolic IsoLG adducts and PAOs that were prevented by 2-HOBA. • Natriuretic peptides generated cytotoxic oligomers, a process accelerated by IsoLGs, contributing to atrial PAO formation. • These findings identify a novel pathway during oxidative stress to increase AF susceptibility, and they support the concept of preemptively scavenging reactive downstream mediators as a potential therapeutic approach to prevent AF., Summary Oxidative damage is implicated in atrial fibrillation (AF), but antioxidants are ineffective therapeutically. The authors tested the hypothesis that highly reactive lipid dicarbonyl metabolites, or isolevuglandins (IsoLGs), are principal drivers of AF during hypertension. In a hypertensive murine model and stretched atriomyocytes, the dicarbonyl scavenger 2-hydroxybenzylamine (2-HOBA) prevented IsoLG adducts and preamyloid oligomers (PAOs), and AF susceptibility, whereas the ineffective analog 4-hydroxybenzylamine (4-HOBA) had minimal effect. Natriuretic peptides generated cytotoxic oligomers, a process accelerated by IsoLGs, contributing to atrial PAO formation. These findings support the concept of pre-emptively scavenging reactive downstream oxidative stress mediators as a potential therapeutic approach to prevent AF.

To characterize the T cell subsets producing interleukin 17 (IL-17) isoforms A and F in hypertensive kidneys and vessels and determine whether inhibition of IL-17 signaling lowers blood pressure and end-organ damage in a mouse model of hypertension.T cell derived cytokines play a central role in the pathophysiology of hypertension and contribute to end-organ dysfunction. We previously showed that mice genetically deficient in IL-17A exhibited blunted hypertension and reduced renal and vascular dysfunction in response to angiotensin II (Ang II) infusion. Monoclonal antibodies to IL-17 isoforms or the IL-17 receptor are emerging as novel therapeutics for psoriasis and related autoimmune disorders.Mice were infused with Ang II for 4 weeks to induce hypertension. Using flow cytometry and intracellular staining, we determined that the primary T cell subsets producing IL-17A and IL-17F in the kidney and aorta are gamma delta (γδ) T cells and CD4+ T helper 17 (TMonoclonal antibodies to IL-17A or IL-17RA, but not IL-17F, may be a useful adjunct treatment for hypertension and the associated end-organ dysfunction.

T and B cells have been implicated in hypertension, but the mechanisms by which they produce a coordinated response is unknown. T follicular helper (Tfh) cells that produce interleukin 21 (IL21) promote germinal center (GC) B cell responses leading to immunoglobulin (Ig) production. Here we investigate the role of IL21 and Tfh cells in hypertension. In response to angiotensin (Ang) II-induced hypertension, T cell IL21 production is increased, and Il21-/- mice develop blunted hypertension, attenuated vascular end-organ damage, and decreased interleukin 17A (IL17A) and interferon gamma production. Tfh-like cells and GC B cells accumulate in the aorta and plasma IgG1 is increased in hypertensive WT but not Il21-/-mice. Furthermore, Tfh cell deficient mice develop blunted hypertension and vascular hypertrophy in response to Ang II infusion. Importantly, IL21 neutralization reduces blood pressure (BP) and reverses endothelial dysfunction and vascular inflammation. Moreover, recombinant IL21 impairs endothelium-dependent relaxation ex vivo and decreases nitric oxide production from cultured endothelial cells. Finally, we show in humans that peripheral blood T cell production of IL21 correlates with systolic BP and IL17A production. These data suggest that IL21 may be a novel therapeutic target for the treatment of hypertension and its micro- and macrovascular complications.

Genetic variants at SH2B3 are associated with blood pressure and circulating beta-2 microglobulin (β(2)M), a well-characterized kidney filtration biomarker. We hypothesize that circulating β(2)M is an independent risk predictor of hypertension and may causally contribute to its development. The study sample consisted of 7065 Framingham Heart Study participants with measurements of plasma β(2)M. Generalized estimating equations were used to test the association of β(2)M with prevalent and new-onset hypertension. There were 2145 (30%) cases of prevalent hypertension at baseline and 886 (21%) cases of incident hypertension during six years of follow-up. A 1-standard deviation increase in baseline plasma β(2)M was associated with a greater risk of prevalent (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.05–1.24) and new-onset (OR 1.18, 95% CI 1.07–1.32) hypertension. Individuals within the top β(2)M quartile had a greater risk than the bottom quartile for prevalent (OR 1.29, 95% CI .05–1.57) and new-onset (OR 1.59, 95% CI 1.20–2.11) hypertension. These associations remained essentially unchanged in analyses restricted to participants free of albuminuria and chronic kidney disease (CKD). Mendelian randomization demonstrated that lower SH2B3 expression is causal for increased circulating β(2)M levels, and in a hypertensive mouse model, knockout of Sh2b3 increased β(2)M gene expression. In a community-based study of healthy individuals, higher plasma β(2)M levels are associated with increased risk of prevalent and incident hypertension independent of CKD status. Overlapping genetic signals for hypertension and β(2)M, in conjunction with mouse knockout experiments, suggest that the SH2B3-β(2)M axis plays a causal role in hypertension.

Various hypertensive stimuli lead to exuberant adventitial collagen deposition in large arteries, exacerbating blood pressure elevation and end-organ damage. Collagen production is generally attributed to resident fibroblasts; however, other cells, including resident and bone marrow-derived stem cell antigen positive (Sca-1 + ) cells and endothelial and vascular smooth muscle cells, can produce collagen and contribute to vascular stiffening. Using flow cytometry and immunofluorescence, we found that adventitial Sca-1 + progenitor cells begin to produce collagen and acquire a fibroblast-like phenotype in hypertension. We also found that bone marrow-derived cells represent more than half of the matrix-producing cells in hypertension, and that one-third of these are Sca-1 + . Cell sorting and lineage-tracing studies showed that cells of endothelial origin contribute to no more than one fourth of adventitial collagen I + cells, whereas those of vascular smooth muscle lineage do not contribute. Our findings indicate that Sca-1 + progenitor cells and bone marrow-derived infiltrating fibrocytes are major sources of arterial fibrosis in hypertension. Endothelial to mesenchymal transition likely also contributes, albeit to a lesser extent and pre-existing resident fibroblasts represent a minority of aortic collagen-producing cells in hypertension. This study shows that vascular stiffening represents a complex process involving recruitment and transformation of multiple cells types that ultimately elaborate adventitial extracellular matrix.

Although systemic hypertension affects a large proportion of the population, its etiology remains poorly defined. Emerging evidence supports the concept that immune cells become activated and enter target organs, including the vasculature and the kidney, in this disease. Mediators released by these cells, including reactive oxygen species, metalloproteinases, cytokines, and antibodies promote dysfunction of the target organs and cause damage. In vessels, these factors enhance constriction, remodeling, and rarefaction. In the kidney, these mediators increase expression and activation of sodium transporters, and cause interstitial fibrosis and glomerular injury. Factors common to hypertension, including oxidative stress, increased interstitial sodium, cytokine production, and inflammasome activation promote immune activation in hypertension. Recent data suggest that isolevuglandin-modified self-proteins in antigen-presenting cells are immunogenic, promoting cytokine production by the cells in which they are formed and T cell activation. Efforts to prevent and reverse immune activation may prove beneficial in preventing the long-term sequelae of hypertension and its related cardiovascular diseases.

It is now well known that T lymphocytes play a critical role in the development of several cardiovascular diseases1,2,3,4,5. For example, studies from our group have shown that hypertension is associated with an excessive accumulation of T cells in the vessels and kidney during the development of experimental hypertension6. Once in these tissues, T cells produce several cytokines that affect both vascular and renal function leading to vasoconstriction and sodium and water retention1,2. To fully understand how T cells cause cardiovascular and renal diseases, it is important to be able to identify and quantify the specific T cell subsets present in these tissues. T cell subsets are defined by a combination of surface markers, the cytokines they secrete, and the transcription factors they express. The complexity of the T cell population makes flow cytometry and intracellular staining an invaluable technique to dissect the phenotypes of the lymphocytes present in tissues. Here, we provide a detailed protocol to identify the surface and intracellular markers (cytokines and transcription factors) in T cells isolated from murine kidney, aorta and aortic draining lymph nodes in a model of angiotensin II induced hypertension. The following steps are described in detail: isolation of the tissues, generation of the single cell suspensions, ex vivo stimulation, fixation, permeabilization and staining. In addition, several fundamental principles of flow cytometric analyses including choosing the proper controls and appropriate gating strategies are discussed.

Recent studies have emphasized a role of adaptive immunity, and particularly T cells, in the genesis of hypertension. We sought to determine the T-cell subtypes that contribute to hypertension and renal inflammation in angiotensin II–induced hypertension. Using T-cell receptor spectratyping to examine T-cell receptor usage, we demonstrated that CD8 + cells, but not CD4 + cells, in the kidney exhibited altered T-cell receptor transcript lengths in Vβ3, 8.1, and 17 families in response to angiotensin II–induced hypertension. Clonality was not observed in other organs. The hypertension caused by angiotensin II in CD4 −/− and MHCII −/− mice was similar to that observed in wild-type mice, whereas CD8 −/− mice and OT1xRAG-1 −/− mice, which have only 1 T-cell receptor, exhibited a blunted hypertensive response to angiotensin II. Adoptive transfer of pan T cells and CD8 + T cells but not CD4 + /CD25 − cells conferred hypertension to RAG-1 −/− mice. In contrast, transfer of CD4 + /CD25 + cells to wild-type mice receiving angiotensin II decreased blood pressure. Mice treated with angiotensin II exhibited increased numbers of kidney CD4 + and CD8 + T cells. In response to a sodium/volume challenge, wild-type and CD4 −/− mice infused with angiotensin II retained water and sodium, whereas CD8 −/− mice did not. CD8 −/− mice were also protected against angiotensin-induced endothelial dysfunction and vascular remodeling in the kidney. These data suggest that in the development of hypertension, an oligoclonal population of CD8 + cells accumulates in the kidney and likely contributes to hypertension by contributing to sodium and volume retention and vascular rarefaction.

Hypertension is growing in epidemic proportions worldwide and is now the leading preventable cause of premature death. For over a century, we have known that the kidney plays a critical role in blood pressure regulation. Specifically, abnormalities in renal sodium transport appear to be a final common pathway that gives rise to elevated blood pressure regardless of the nature of the initial hypertensive stimulus. However, it is only in the past decade that we have come to realize that inflammatory cytokines secreted by innate and adaptive immune cells, as well as renal epithelial cells, can modulate the expression and activity of sodium transporters all along the nephron, leading to alterations in pressure natriuresis, sodium and water balance, and ultimately hypertension. This mini-review highlights specific cytokines and the transporters that they regulate and discusses why inflammatory cytokines may have evolved to serve this function.

Angiotensin II–induced hypertension is associated with an increase in T-cell production of interleukin-17A (IL-17A). Recently, we reported that IL-17A −/− mice exhibit blunted hypertension, preserved natriuresis in response to a saline challenge, and decreased renal sodium hydrogen exchanger 3 expression after 2 weeks of angiotensin II infusion compared with wild-type mice. In the current study, we performed renal transporter profiling in mice deficient in IL-17A or the related isoform, IL-17F, after 4 weeks of Ang II infusion, the time when the blood pressure reduction in IL-17A −/− mice is most prominent. Deficiency of IL-17A abolished the activation of distal tubule transporters, specifically the sodium–chloride cotransporter and the epithelial sodium channel and protected mice from glomerular and tubular injury. In human proximal tubule (HK-2) cells, IL-17A increased sodium hydrogen exchanger 3 expression through a serum and glucocorticoid-regulated kinase 1–dependent pathway. In mouse distal convoluted tubule cells, IL-17A increased sodium–chloride cotransporter activity in a serum and glucocorticoid-regulated kinase 1/Nedd4-2–dependent pathway. In both cell types, acute treatment with IL-17A induced phosphorylation of serum and glucocorticoid-regulated kinase 1 at serine 78, and treatment with a serum and glucocorticoid-regulated kinase 1 inhibitor blocked the effects of IL-17A on sodium hydrogen exchanger 3 and sodium–chloride cotransporter. Interestingly, both HK-2 and mouse distal convoluted tubule 15 cells produce endogenous IL-17A. IL17F had little or no effect on blood pressure or renal sodium transporter abundance. These studies provide a mechanistic link by which IL-17A modulates renal sodium transport and suggest that IL-17A inhibition may improve renal function in hypertension and other autoimmune disorders.

Vascular oxidative injury accompanies many common conditions associated with hypertension. In the present study, we employed mouse models with excessive vascular production of ROS (tg(sm/p22phox) mice, which overexpress the NADPH oxidase subunit p22(phox) in smooth muscle, and mice with vascular-specific deletion of extracellular SOD) and have shown that these animals develop vascular collagen deposition, aortic stiffening, renal dysfunction, and hypertension with age. T cells from tg(sm/p22phox) mice produced high levels of IL-17A and IFN-γ. Crossing tg(sm/p22phox) mice with lymphocyte-deficient Rag1(-/-) mice eliminated vascular inflammation, aortic stiffening, renal dysfunction, and hypertension; however, adoptive transfer of T cells restored these processes. Isoketal-protein adducts, which are immunogenic, were increased in aortas, DCs, and macrophages of tg(sm/p22phox) mice. Autologous pulsing with tg(sm/p22phox) aortic homogenates promoted DCs of tg(sm/p22phox) mice to stimulate T cell proliferation and production of IFN-γ, IL-17A, and TNF-α. Treatment with the superoxide scavenger tempol or the isoketal scavenger 2-hydroxybenzylamine (2-HOBA) normalized blood pressure; prevented vascular inflammation, aortic stiffening, and hypertension; and prevented DC and T cell activation. Moreover, in human aortas, the aortic content of isoketal adducts correlated with fibrosis and inflammation severity. Together, these results define a pathway linking vascular oxidant stress to immune activation and aortic stiffening and provide insight into the systemic inflammation encountered in common vascular diseases.

Hypertension is a leading cause of cardiovascular and renal morbidity, and mortality. Genome-wide association studies identified a single-nucleotide polymorphism in the gene SH2B3 encoding the lymphocyte adaptor protein, LNK, but, until recently, little was known about how LNK contributes to hypertension. This review summarizes recent work highlighting a central role for LNK in inflammation and hypertension.Using a systems biology approach that integrates genomic data with whole blood transcriptomic data and network modeling, LNK/SH2B3 was identified as a key driver gene for hypertension in humans. LNK is an intracellular adaptor protein expressed predominantly in hematopoietic and endothelial cells that negatively regulates cell proliferation and cytokine signaling. Genetic animal models with deletion or mutation of LNK revealed an important role for LNK in renal and vascular inflammation, glomerular injury, oxidative stress, interferon-γ production, and hypertension. Bone marrow transplantation experiments revealed that LNK in hematopoietic cells is primarily responsible for blood pressure regulation.LNK/SH2B3 is a key driver gene for human hypertension, and alteration of LNK in animal models has a profound effect on inflammation and hypertension. Thus, LNK is a potential therapeutic target for this disease and its devastating consequences.

Emerging evidence supports an important role for T cells in the genesis of hypertension. Because this work has predominantly been performed in experimental animals, we sought to determine whether human T cells are activated in hypertension. We used a humanized mouse model in which the murine immune system is replaced by the human immune system. Angiotensin II increased systolic pressure to 162 versus 116 mm Hg for sham-treated animals. Flow cytometry of thoracic lymph nodes, thoracic aorta, and kidney revealed increased infiltration of human leukocytes (CD45 + ) and T lymphocytes (CD3 + and CD4 + ) in response to angiotensin II infusion. Interestingly, there was also an increase in the memory T cells (CD3 + /CD45RO + ) in the aortas and lymph nodes. Prevention of hypertension using hydralazine and hydrochlorothiazide prevented the accumulation of T cells in these tissues. Studies of isolated human T cells and monocytes indicated that angiotensin II had no direct effect on cytokine production by T cells or the ability of dendritic cells to drive T-cell proliferation. We also observed an increase in circulating interleukin-17A producing CD4 + T cells and both CD4 + and CD8 + T cells that produce interferon-γ in hypertensive compared with normotensive humans. Thus, human T cells become activated and invade critical end-organ tissues in response to hypertension in a humanized mouse model. This response likely reflects the hypertensive milieu encountered in vivo and is not a direct effect of the hormone angiotensin II.

Rationale: Accumulating evidence supports a role of adaptive immunity and particularly T cells in the pathogenesis of hypertension. Formation of memory T cells, which requires the costimulatory molecule CD70 on antigen-presenting cells, is a cardinal feature of adaptive immunity. Objective: To test the hypothesis that CD70 and immunologic memory contribute to the blood pressure elevation and renal dysfunction mediated by repeated hypertensive challenges. Methods and Results: We imposed repeated hypertensive challenges using either N ω -nitro-L-arginine methyl ester hydrochloride (L-NAME)/high salt or repeated angiotensin II stimulation in mice. During these challenges effector memory T cells (T EM ) accumulated in the kidney and bone marrow. In the L-NAME/high-salt model, memory T cells of the kidney were predominant sources of interferon-γ and interleukin-17A, known to contribute to hypertension. L-NAME/high salt increased macrophage and dendritic cell surface expression of CD70 by 3- to 5-fold. Mice lacking CD70 did not accumulate T EM cells and did not develop hypertension to either high salt or the second angiotensin II challenge and were protected against renal damage. Bone marrow–residing T EM cells proliferated and redistributed to the kidney in response to repeated salt feeding. Adoptively transferred T EM cells from hypertensive mice homed to the bone marrow and spleen and expanded on salt feeding of the recipient mice. Conclusions: Our findings illustrate a previously undefined role of CD70 and long-lived T EM cells in the development of blood pressure elevation and end-organ damage that occur on delayed exposure to mild hypertensive stimuli. Interventions to prevent repeated hypertensive surges could attenuate formation of hypertension-specific T EM cells.

Aprominent pathology textbook used in the United States includes an image illustrating the renal histopathology caused by malignant hypertension. The legend describes striking “onion skin” changes of a renal arteriole. Curiously, a sea of mononuclear inflammatory cells surrounding this arteriole is overlooked both in the legend and in the related text. Moreover, nothing regarding inflammation or immune reactions is discussed. This lack of attention to inflammatory cells is, however, not surprising. Although many experimental studies have implicated inflammation in hypertension, these have largely been performed in experimental animals; there is no proof that inflammation contributes to human hypertension. In fact, some anti-inflammatory or immune-suppressing drugs (eg, nonsteroidal anti-inflammatory drugs and cyclosporine) paradoxically cause hypertension in humans, likely via off-target effects. Often the term “inflammation” is used in the context of cardiovascular disease as a catchall referring to nonspecific phenomena, such as elevation of C-reactive protein or the presence of macrophages in a tissue. Most clinicians and investigators find this vague and difficult to understand. Even more puzzling is that many studies now implicate the adaptive immune response, and in particular, lymphocytes, in hypertension and vascular disease. Traditionally, bacterial, viral, or tumor antigens activate this arm of immune defense. As such, it has been hard to imagine how adaptive immunity could be involved in a disease such as hypertension. In this article, we will attempt to address some of these puzzling questions. We will briefly review components of the innate and adaptive immune response, discuss data from many groups, including our own, that suggest that common forms of hypertension are immune mediated, and provide a working hypothesis of how signals from the central nervous system trigger an immune response that causes hypertension. ### General Concepts Regarding Inflammation and Immunity #### Innate Immunity The first line of defense against pathogens is the innate immune response. Important components of this system include epithelial …

For >50 years, it has been recognized that immunity contributes to hypertension. Recent data have defined an important role of T cells and various T cell–derived cytokines in several models of experimental hypertension. These studies have shown that stimuli like angiotensin II, deoxycorticosterone acetate-salt, and excessive catecholamines lead to formation of effector like T cells that infiltrate the kidney and perivascular regions of both large arteries and arterioles. There is also accumulation of monocyte/macrophages in these regions. Cytokines released from these cells, including interleukin-17, interferon-γ, tumor necrosis factorα, and interleukin-6 promote both renal and vascular dysfunction and damage, leading to enhanced sodium retention and increased systemic vascular resistance. The renal effects of these cytokines remain to be fully defined, but include enhanced formation of angiotensinogen, increased sodium reabsorption, and increased renal fibrosis. Recent experiments have defined a link between oxidative stress and immune activation in hypertension. These have shown that hypertension is associated with formation of reactive oxygen species in dendritic cells that lead to formation of gamma ketoaldehydes, or isoketals. These rapidly adduct to protein lysines and are presented by dendritic cells as neoantigens that activate T cells and promote hypertension. Thus, cells of both the innate and adaptive immune system contribute to end-organ damage and dysfunction in hypertension. Therapeutic interventions to reduce activation of these cells may prove beneficial in reducing end-organ damage and preventing consequences of hypertension, including myocardial infarction, heart failure, renal failure, and stroke.

Ample genetic and physiological evidence establishes that renal salt handling is a critical regulator of blood pressure. Studies also establish a role for the immune system, T-cell infiltration, and immune cytokines in hypertension. This study aimed to connect immune cytokines, specifically interferon-γ (IFN-γ) and interleukin-17A (IL-17A), to sodium transporter regulation in the kidney during angiotensin-II (Ang-II) hypertension. C57BL/6J (wild-type) mice responded to Ang-II infusion (490 ng/kg per minute, 2 weeks) with a rise in blood pressure (170 mm Hg) and a significant decrease in the rate of excretion of a saline challenge. In comparison, mice that lacked the ability to produce either IFN-γ (IFN-γ −/− ) or IL-17A (IL-17A −/− ) exhibited a blunted rise in blood pressure (−/− but not in IFN-γ −/− mice; epithelial Na channel abundance increased similarly in all the 3 genotypes. In the proximal nephron, Ang-II infusion significantly decreased abundance of Na/H-exchanger isoform 3 and the motor myosin VI in IL-17A −/− and IFN-γ −/− , but not in wild-type; the Na-phosphate cotransporter decreased in all the 3 genotypes. Our results suggest that during Ang-II hypertension both IFN-γ and IL-17A production interfere with the pressure natriuretic decrease in proximal tubule sodium transport and that IFN-γ production is necessary to activate distal sodium reabsorption.

See related article, pp 126–133 In textbooks of physiology and in medical school classrooms around the world, hypertension is described as a disease characterized by vascular dysfunction, renal impairment, and altered sympathetic outflow. T lymphocytes are never mentioned, and the notion that hypertension may be an autoimmune disease is not even entertained. Yet, increasing evidence, dating back as early as the 1960s, supports a role of inflammation and immunity in the genesis of hypertension. Cells of both the innate and the adaptive immune systems infiltrate the vasculature and kidney in various animal models of hypertension, and efforts to suppress inflammation reduce end organ damage and, in some instances, lower blood pressure. Mice and rats lacking T cells are partially protected against both angiotensin II and salt-sensitive hypertension, and adoptive transfer of T cells restores blood pressure in these animals. It is currently thought that cytokines released by inflammatory cells, including interleukin 17 (IL17), tumor necrosis factor-α, and IL6 lead to vascular dysfunction and remodeling and promote renal sodium retention, leading to blood pressure elevation.1,2 Unfortunately, despite this growing body of evidence, almost all studies to date have been performed in experimental animals, and it is unclear whether adaptive immunity plays any role in human hypertension. Although there is considerable evidence in humans that inflammation is important in specialized cases, such as pulmonary hypertension3 or pre-eclampsia (hypertension of pregnancy),4 data that the immune system contributes to the pathophysiology of essential hypertension in nonpregnant adults are scarce. In 2005, Bautista et al5 found a positive correlation between blood pressure and serum levels of tumor necrosis factor-α and IL6 in 196 relatively healthy subjects. IL6 functions both upstream and downstream of another highly proinflammatory cytokine, IL17, which is secreted from specialized subsets of T cells. We found …

Oxidative damage and inflammation are both implicated in the genesis of hypertension; however, the mechanisms by which these stimuli promote hypertension are not fully understood. Here, we have described a pathway in which hypertensive stimuli promote dendritic cell (DC) activation of T cells, ultimately leading to hypertension. Using multiple murine models of hypertension, we determined that proteins oxidatively modified by highly reactive γ-ketoaldehydes (isoketals) are formed in hypertension and accumulate in DCs. Isoketal accumulation was associated with DC production of IL-6, IL-1β, and IL-23 and an increase in costimulatory proteins CD80 and CD86. These activated DCs promoted T cell, particularly CD8+ T cell, proliferation; production of IFN-γ and IL-17A; and hypertension. Moreover, isoketal scavengers prevented these hypertension-associated events. Plasma F2-isoprostanes, which are formed in concert with isoketals, were found to be elevated in humans with treated hypertension and were markedly elevated in patients with resistant hypertension. Isoketal-modified proteins were also markedly elevated in circulating monocytes and DCs from humans with hypertension. Our data reveal that hypertension activates DCs, in large part by promoting the formation of isoketals, and suggest that reducing isoketals has potential as a treatment strategy for this disease.

The lymphocyte adaptor protein LNK (also known as SH2B3) is primarily expressed in hematopoietic and endothelial cells, where it functions as a negative regulator of cytokine signaling and cell proliferation. Single-nucleotide polymorphisms in the gene encoding LNK are associated with autoimmune and cardiovascular disorders; however, it is not known how LNK contributes to hypertension. Here, we determined that loss of LNK exacerbates angiotensin II-induced (Ang II-induced) hypertension and the associated renal and vascular dysfunction. At baseline, kidneys from Lnk-/- mice exhibited greater levels of inflammation, oxidative stress, and glomerular injury compared with WT animals, and these parameters were further exacerbated by Ang II infusion. Aortas from Lnk-/- mice exhibited enhanced inflammation, reduced nitric oxide levels, and impaired endothelial-dependent relaxation. Bone marrow transplantation studies demonstrated that loss of LNK in hematopoietic cells is primarily responsible for the observed renal and vascular inflammation and predisposition to hypertension. Ang II infusion increased IFN-γ-producing CD8+ T cells in the spleen and kidneys of Lnk-/- mice compared with WT mice. Moreover, IFN-γ deficiency resulted in blunted hypertension in response to Ang II infusion. Together, these results suggest that LNK is a potential therapeutic target for hypertension and its associated renal and vascular sequela.

In the past several years, there has been increasing interest in the roles of inflammation and immunity in hypertension. Inflammatory cells, including macrophages and T cells, are commonly observed in the kidneys of hypertensive animals, and select immunosuppressive agents lower blood pressure and prevent end-organ damage in experimental hypertension.1,2 Depending on their phenotype, macrophages can release reactive oxygen species, matrix metalloproteinases, and cytokines that promote tissue damage, change gene expression, induce vascular remodeling, and lead to vasoconstriction and renal damage. Indeed, mice with reduced monocytes and macrophages develop less vascular remodeling, endothelial dysfunction, and vascular oxidative stress compared with wild-type mice in response to either angiotensin II or deoxycorticosterone acetate salt challenge.3 Recently, genetic deletion of macrophages has been shown to blunt virtually all consequences of angiotensin II infusion, including blood pressure elevation, induction of vascular adhesion molecules, vascular dysfunction, and superoxide production.4 Article, see p 1190 It is fairly easy to imagine that innate immune cells like macrophages are involved in hypertension, but, rather surprisingly, it seems that T cells of the adaptive immune system also contribute. Almost 50 years ago, Okuda and Grollman5 showed that injection of lymph node cells from hypertensive rats could raise blood pressure in normotensive recipient rats. Svendsen et al6 showed that the thymus played a role in the hypertension caused by partial renal infarction and in the sustained phase of DOCA-salt hypertension. When lymphocytes from Lyon rats with genetic hypertension are transferred into Lyon low-pressure rats, sustained hypertension develops in the recipients.7 Our group found that mice lacking lymphocytes are protected against several forms of hypertension, including angiotensin II, norepinephrine, and DOCA-salt and that adoptive transfer of T cells can restore hypertension in these models. We have proposed that neoantigens formed in target tissues such …

Recent studies have shown that both innate and adaptive immunity contribute to hypertension. Inflammatory cells, including macrophages and T cells accumulate in the vessel wall, particularly in the perivascular fat, and in the kidney of hypertensive animals. Mice lacking lymphocytes are resistant to the development of hypertension, and adoptive transfer of T cells restores hypertensive responses to angiotensin II and DOCA-salt challenge. Immune modulating agents have variable, but often-beneficial effects in ameliorating end-organ damage and blood pressure elevation in experimental hypertension. The mechanisms by which hypertension stimulates an immune response remain unclear, but might involve the formation of neoantigens that activate adaptive immunity. Identification of these neoantigens and understanding how they form might prove useful in the prevention and treatment of this widespread and devastating disease.

We have shown previously that T cells are required for the full development of angiotensin II–induced hypertension. However, the specific subsets of T cells that are important in this process are unknown. T helper 17 cells represent a novel subset that produces the proinflammatory cytokine interleukin 17 (IL-17). We found that angiotensin II infusion increased IL-17 production from T cells and IL-17 protein in the aortic media. To determine the effect of IL-17 on blood pressure and vascular function, we studied IL-17−/−mice. The initial hypertensive response to angiotensin II infusion was similar in IL-17−/−and C57BL/6J mice. However, hypertension was not sustained in IL-17−/−mice, reaching levels 30-mm Hg lower than in wild-type mice by 4 weeks of angiotensin II infusion. Vessels from IL-17−/−mice displayed preserved vascular function, decreased superoxide production, and reduced T-cell infiltration in response to angiotensin II. Gene array analysis of cultured human aortic smooth muscle cells revealed that IL-17, in conjunction with tumor necrosis factor-α, modulated expression of >30 genes, including a number of inflammatory cytokines/chemokines. Examination of IL-17 in diabetic humans showed that serum levels of this cytokine were significantly increased in those with hypertension compared with normotensive subjects. We conclude that IL-17 is critical for the maintenance of angiotensin II–induced hypertension and vascular dysfunction and might be a therapeutic target for this widespread disease.

© 2015 The Authors. Abstract Genome-wide association studies (GWAS) have identified numerous loci associated with blood pressure (BP). The molecular mechanisms underlying BP regulation, however, remain unclear. We investigated BP-associated molecular mechanisms by integrating BP GWAS with whole blood mRNA expression profiles in 3,679 individuals, using network approaches. BP transcriptomic signatures at the single-gene and the coexpression network module levels were identified. Four coexpression modules were identified as potentially causal based on genetic inference because expression-related SNPs for their corresponding genes demonstrated enrichment for BP GWAS signals. Genes from the four modules were further projected onto predefined molecular interaction networks, revealing key drivers. Gene subnetworks entailing molecular interactions between key drivers and BP-related genes were uncovered. As proof-of-concept, we validated SH2B3, one of the top key drivers, using Sh2b3-/- mice. We found that a significant number of genes predicted to be regulated by SH2B3 in gene networks are perturbed in Sh2b3-/- mice, which demonstrate an exaggerated pressor response to angiotensin II infusion. Our findings may help to identify novel targets for the prevention or treatment of hypertension. Synopsis A systems biology approach integrating genome-wide genetic variation and transcriptome profiling data from participants of the Framingham Heart Study identifies key regulatory genes and gene networks underlying blood pressure control. Association analysis of blood pressure (BP) and gene expression levels identified individual genes and coexpression network modules that are correlated with BP. Incorporation of data from BP genome-wide association studies (GWAS) revealed four BP coexpression network modules (coEMs) that are enriched with eSNPs that demonstrate low P-values in BP GWAS. Further integration of the BP coEMs with molecular networks uncovered key driver genes that serve as network hubs to interconnect genes within the BP coEMs. One of the top key drivers, SH2B3, was analyzed in a Sh2b3-/- mouse model, which validated its effect on BP regulation and its central role in the BP subnetwork. A systems biology approach integrating genome-wide genetic variation and transcriptome profiling data from participants of the Framingham Heart Study identifies key regulatory genes and gene networks underlying blood pressure control.