γδ T Cells Mediate Angiotensin II-Induced Hypertension and Vascular Injury.

BACKGROUND: Innate antigen-presenting cells and adaptive immune T cells have been implicated in the development of hypertension. However, the T-lymphocyte subsets involved in the pathophysiology of hypertension remain unclear. A small subset of innate-like T cells expressing the γδ T cell receptor (TCR) rather than the αß TCR could play a role in the initiation of the immune response in hypertension. We aimed to determine whether angiotensin (Ang) II caused kinetic changes in γδ T cells; deficiency in γδ T cells blunted Ang II-induced hypertension, vascular injury, and T-cell activation; and γδ T cells are associated with human hypertension. METHODS: Male C57BL/6 wild-type and Tcrδ-/- mice, which are devoid of γδ T cells, or wild-type mice injected IP with control isotype IgG or γδ T cell-depleting antibodies, were infused or not with Ang II for 3, 7, or 14 days. T-cell profiling was determined by flow cytometry, systolic blood pressure (SBP) by telemetry, and mesentery artery endothelial function by pressurized myography. TCR γ constant region gene expression levels and clinical data of a whole blood gene expression microarray study, including normotensive and hypertensive subjects, were used to demonstrate an association between γδ T cells and SBP. RESULTS: Seven- and 14-day Ang II infusion increased γδ T-cell numbers and activation in the spleen of wild-type mice (P<0.05). Fourteen days of Ang II infusion increased SBP (P<0.01) and decreased mesenteric artery endothelial function (P<0.01) in wild-type mice, both of which were abrogated in Tcrδ-/- mice (P<0.01). Anti-TCRγδ antibody-induced γδ T-cell depletion blunted Ang II-induced SBP rise and endothelial dysfunction (P<0.05), compared with isotype antibody-treated Ang II-infused mice. Ang II-induced T-cell activation in the spleen and perivascular adipose tissue was blunted in Tcrδ-/- mice (P<0.01). In humans, the association between SBP and γδ T cells was demonstrated by a multiple linear regression model integrating whole blood TCR γ constant region gene expression levels and age and sex (R2=0.12, P<1×10-6). CONCLUSIONS: γδ T cells mediate Ang II-induced SBP elevation, vascular injury, and T-cell activation in mice. γδ T cells might contribute to the development of hypertension in humans.

Dual opposing roles of adaptive immunity in hypertension.

Hypertension involves remodelling and inflammation of the arterial wall. Interactions between vascular and inflammatory cells play a critical role in disease initiation and progression. T effector and regulatory lymphocytes, members of the adaptive immune system, play contrasting roles in hypertension. Signals from the central nervous system and the innate immune system antigen-presenting cells activate T effector lymphocytes and promote their differentiation towards pro-inflammatory T helper (Th) 1 and Th17 phenotypes. Th1 and Th17 effector cells, via production of pro-inflammatory mediators, participate in the low-grade inflammation that leads to blood pressure elevation and end-organ damage. T regulatory lymphocytes, on the other hand, counteract hypertensive effects by suppressing innate and adaptive immune responses. The present review summarizes and discusses the adaptive immune mechanisms that participate in the pathophysiology in hypertension.

Innate immunity in hypertension.

Despite intensive research, the exact cause of hypertension remains unknown. Low-grade inflammation has been proposed to play a key role in the pathogenesis of hypertension. Both innate and adaptive immune responses may participate in this process. Several studies have addressed the contribution of adaptive immunity to the pathophysiology of high blood pressure; however, the role of innate immunity is less clear. Innate immunity may be an important mediator of chronic inflammation in hypertension. Slight elevation of blood pressure due to increased sympathetic and/or decreased parasympathetic outflow, or low-grade infections may generate neoantigens and damage-activated molecular patterns (DAMPs) or pathogen-activated molecular patterns (PAMPs), which can trigger Toll-like receptors on innate effector cells. Innate responses, mediated by monocytes, macrophages, dendritic cells and natural killer cells, may contribute to inflammation either directly or by activating adaptive immune responses mediated by T lymphocytes. In this review, we discuss the recent evidence regarding the contribution of different innate effector cells, their response and their mechanisms of activation in hypertension.

Endothelin-1 overexpression exacerbates atherosclerosis and induces aortic aneurysms in apolipoprotein E knockout mice.

OBJECTIVE: Endothelin (ET)-1 plays a role in vascular reactive oxygen species production and inflammation. ET-1 has been implicated in human atherosclerosis and abdominal aortic aneurysm (AAA) development. ET-1 overexpression exacerbates high-fat diet-induced atherosclerosis in apolipoprotein E(-/-) (Apoe(-/-)) mice. ET-1-induced reactive oxygen species and inflammation may contribute to atherosclerosis progression and AAA development. APPROACH AND RESULTS: Eight-week-old male wild-type mice, transgenic mice overexpressing ET-1 selectively in endothelium (eET-1), Apoe(-/-) mice, and eET-1/Apoe(-/-) mice were fed high-fat diet for 8 weeks. eET-1/Apoe(-/-) had a 45% reduction in plasma high-density lipoprotein (P<0.05) and presented ≥ 2-fold more aortic atherosclerotic lesions compared with Apoe(-/-) (P<0.01). AAAs were detected only in eET-1/Apoe(-/-) (8/21; P<0.05). Reactive oxygen species production was increased ≥ 2-fold in perivascular fat, media, or atherosclerotic lesions in the ascending aorta and AAAs of eET-1/Apoe(-/-) compared with Apoe(-/-) (P<0.05). Monocyte/macrophage infiltration was enhanced ≥ 2.5-fold in perivascular fat of ascending aorta and AAAs in eET-1/Apoe(-/-) compared with Apoe(-/-) (P<0.05). CD4(+) T cells were detected almost exclusively in perivascular fat (3/6) and atherosclerotic lesions (5/6) in ascending aorta of eET-1/Apoe(-/-) (P<0.05). The percentage of spleen proinflammatory Ly-6C(hi) monocytes was enhanced 26% by ET-1 overexpression in Apoe(-/-) (P<0.05), and matrix metalloproteinase-2 was increased 2-fold in plaques of eET-1/Apoe(-/-) (P<0.05) compared with Apoe(-/-). CONCLUSIONS: ET-1 plays a role in progression of atherosclerosis and AAA formation by decreasing high-density lipoprotein, and increasing oxidative stress, inflammatory cell infiltration, and matrix metalloproteinase-2 in perivascular fat, vascular wall, and atherosclerotic lesions.

Preservation of endothelium-dependent relaxation in atherosclerotic mice with endothelium-restricted endothelin-1 overexpression.

In human atherosclerosis, which is associated with elevated plasma and coronary endothelin (ET)-1 levels, ETA receptor antagonists improve coronary endothelial function. Mice overexpressing ET-1 specifically in the endothelium (eET-1) crossed with atherosclerosis-prone apolipoprotein E knockout mice (Apoe(-/-)) exhibit exaggerated high-fat diet (HFD)-induced atherosclerosis. Since endothelial dysfunction often precedes atherosclerosis development, we hypothesized that mice overexpressing endothelial ET-1 on a genetic background deficient in apolipoprotein E (eET-1/Apoe(-/-)) would have severe endothelial dysfunction. To test this hypothesis, we investigated endothelium-dependent relaxation (EDR) to acetylcholine in eET-1/Apoe(-/-) mice. EDR in mesenteric resistance arteries from 8- and 16-week-old mice fed a normal diet or HFD was improved in eET-1/Apoe(-/-) compared with Apoe(-/-) mice. Nitric oxide synthase (NOS) inhibition abolished EDR in Apoe(-/-). EDR in eET-1/Apoe(-/-) mice was resistant to NOS inhibition irrespective of age or diet. Inhibition of cyclooxygenase, the cytochrome P450 pathway, and endothelium-dependent hyperpolarization (EDH) resulted in little or no inhibition of EDR in eET-1/Apoe(-/-) compared with wild-type (WT) mice. In eET-1/Apoe(-/-) mice, blocking of EDH or soluble guanylate cyclase (sGC), in addition to NOS inhibition, decreased EDR by 36 and 30%, respectively. The activation of 4-aminopyridine-sensitive voltage-dependent potassium channels (Kv) during EDR was increased in eET-1/Apoe(-/-) compared with WT mice. We conclude that increasing eET-1 in mice that develop atherosclerosis results in decreased mutual dependence of endothelial signaling pathways responsible for EDR, and that NOS-independent activation of sGC and increased activation of Kv are responsible for enhanced EDR in this model of atherosclerosis associated with elevated endothelial and circulating ET-1.

Left Ventricle Structure and Function in Young Adults Born Very Preterm and Association with Neonatal Characteristics.

Preterm birth increases risk of cardiovascular disease and early death. A body of evidence suggests left ventricle (LV) echocardiographic alterations in children and adults born preterm. We aimed to determine if neonatal characteristics were associated with alterations in LV structure and function in preterm adults. We evaluated a cohort of 86 young adults born preterm below 30 weeks of gestation, and 85 full-term controls. We determined LV dimensions and function using tissue Doppler imaging, conventional and speckle tracking echocardiography (STE). Adults born preterm had smaller LV dimensions, but these differences did not remain after adjustment for body surface area (BSA), which was smaller in the preterm group. Stroke volume and cardiac output were reduced even after adjustment for BSA. We found a smaller e' wave in the preterm group, but other markers of systolic and diastolic function did not differ. Use of antenatal steroids may be associated with a further reduced cardiac output in those born preterm. Adults born preterm show alterations in markers of LV dimensions and function. Identification of these markers may represent opportunities for early prevention of cardiovascular events in this at-risk population.

TLR (Toll-Like Receptor) 4 Antagonism Prevents Left Ventricular Hypertrophy and Dysfunction Caused by Neonatal Hyperoxia Exposure in Rats.

Preterm birth is associated with proinflammatory conditions and alterations in adult cardiac shape and function. Neonatal exposure to high oxygen, a rat model of prematurity-related conditions, leads to cardiac remodeling, fibrosis, and dysfunction. TLR (Toll-like receptor) 4 signaling is a critical link between oxidative stress, inflammation, and the pathogenesis of cardiovascular diseases. The current study sought to investigate the role of TLR4 signaling in neonatal oxygen-induced cardiomyopathy. Male Sprague-Dawley pups were kept in 80% oxygen or room air from day 3 to 10 of life and treated with TLR4 antagonist lipopolysaccharide from the photosynthetic bacterium Rhodobacter sphaeroides(LPS-RS) or saline. Echocardiography was performed at 4, 7, and 12 weeks. At 12 weeks, intraarterial blood pressure was measured before euthanization for histological and biochemical analyses. At day 10, cardiac TLR4, Il (interleukin) 18, and Il1ß expression were increased in oxygen-exposed compared with room air controls. At 4 weeks, compared with room air-saline, saline-, but not LPS-RS treated-, oxygen-exposed animals, exhibited increased left ventricle mass index, reduced ejection fraction, and cardiac output index. Findings were similar at 7 and 12 weeks. LPS-RS did not influence echocardiography in 12 weeks room air animals. Systolic blood pressure was higher in saline- but not LPS-RS treated-oxygen-exposed animals compared with room air-saline and -LPS-RS controls. LPS-RS prevented cardiac fibrosis and cardiomyocytes hypertrophy, the increased TLR4, Myd88, and Il18 gene expression, TRIF expression, and CD68+ macrophages infiltration associated with neonatal oxygen exposure, without impact in room air rats. This study indicates that neonatal exposure to high oxygen programs TLR4 activation, which contributes to cardiac remodeling and dysfunction.

Kidney Size, Renal Function, Ang (Angiotensin) Peptides, and Blood Pressure in Young Adults Born Preterm.

Preterm birth incurs a higher risk for adult cardiovascular diseases, including hypertension. Because preterm birth may impact nephrogenesis, study objectives were to assess renal size and function of adults born preterm versus full term and to examine their relationship with blood pressure (BP; 24-hour ambulatory BP monitoring) and circulating renin-Ang (angiotensin) system peptides. The study included 92 young adults born (1987-1997) preterm (≤29 weeks of gestation) and term (n=92) matched for age, sex, and race. Young adults born preterm had smaller kidneys (80±17 versus 90±18 cm3/m2; P<0.001), higher urine albumin-to-creatinine ratio (0.70; interquartile range, 0.47-1.14 versus 0.58, interquartile range 0.42 to 0.78 mg/mmol, P=0.007), higher 24-hour systolic (121±9 versus 116±8 mm Hg; P=0.001) and diastolic (69±5 versus 66±6 mm Hg; P=0.004) BP, but similar estimated glomerular filtration rate. BP was inversely correlated with kidney size in preterm participants. Plasma Ang I was higher in preterm versus term participants (36.3; interquartile range, 13.2-62.3 versus 19.4; interquartile range, 9.9-28.1 pg/mL; P<0.001). There was no group difference in renin, Ang II, Ang (1-7), and alamandine. In the preterm, but not in the term group, higher BP was significantly associated with higher renin and alamandine and lower birth weight and gestational age with smaller adult kidney size. Young adults born preterm have smaller kidneys, higher urine albumin-to-creatinine ratio, higher BP, and higher circulating Ang I levels compared with term controls. Preterm young adults with smaller kidneys have higher BP. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT03261609.

Matrix metalloproteinase-2 knockout prevents angiotensin II-induced vascular injury.

AIMS: Matrix metalloproteinases (MMPs) have been implicated in the development of hypertension in animal models and humans. Mmp2 deletion did not change Ang II-induced blood pressure (BP) rise. However, whether Mmp2 knockout affects angiotensin (Ang) II-induced vascular injury has not been tested. We sought to determine whether Mmp2 knockout will prevent Ang II-induced vascular injury. METHODS AND RESULTS: A fourteen-day Ang II infusion (1000 ng/kg/min, SC) increased systolic BP, decreased vasodilatory responses to acetylcholine, induced mesenteric artery (MA) hypertrophic remodelling, and enhanced MA stiffness in wild-type (WT) mice. Ang II enhanced aortic media and perivascular reactive oxygen species generation, aortic vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 expression, perivascular monocyte/macrophage and T cell infiltration, and the fraction of spleen activated CD4+CD69+ and CD8+CD69+ T cells, and Ly-6Chi monocytes. Study of intracellular signalling showed that Ang II increased phosphorylation of epidermal growth factor receptor and extracellular-signal-regulated kinase 1/2 in vascular smooth muscle cells isolated from WT mice. All these effects were reduced or prevented by Mmp2 knockout, except for systolic BP elevation. Ang II increased Mmp2 expression in immune cells infiltrating the aorta and perivascular fat. Bone marrow (BM) transplantation experiments revealed that in absence of MMP2 in immune cells, Ang II-induced BP elevation was decreased, and that when MMP2 was deficient in either immune or vascular cells, Ang II-induced endothelial dysfunction was blunted. CONCLUSIONS: Mmp2 knockout impaired Ang II-induced vascular injury but not BP elevation. BM transplantation revealed a role for immune cells in Ang II-induced BP elevation, and for both vascular and immune cell MMP2 in Ang II-induced endothelial dysfunction.

Deficiency of T-regulatory cells exaggerates angiotensin II-induced microvascular injury by enhancing immune responses.

AIMS: T-regulatory lymphocyte (Treg) adoptive transfer prevented angiotensin (Ang) II-induced hypertension and microvascular injury. Scurfy mice are deficient in Treg because of a mutation in the transcription factor forkhead box P3 (Foxp3) gene. Enhanced Ang II effects in the absence of Treg would unambiguously demonstrate their vascular protective role. We hypothesized that adoptive transfer of Scurfy vs. wild-type T cells will exacerbate Ang II-induced microvascular damage in T and B-cell-deficient recombination-activating gene 1 (Rag1) knockout mice. METHODS AND RESULTS: Rag1 knockout mice were injected with vehicle, 10(7) T cells from wild-type or Scurfy mice or 10 (6)wild-type Treg alone or in combination with Scurfy T cells, and then infused or not with Ang II (490 ng/kg per min, subcutaneous) for 14 days. Ang II increased SBP in all the groups, but DBP only in wild-type and Scurfy T-cell groups. Ang II-induced endothelial dysfunction and oxidative stress in perivascular adipose tissue (PVAT) of mesenteric arteries of the wild-type T-cell group, whereas these were exaggerated in the Scurfy T-cell group. Ang II enhanced microvascular remodeling and stiffness in vehicle and Scurfy T-cell groups. Ang II increased monocyte chemotactic protein-1 expression in the vascular wall and PVAT, monocyte/macrophage infiltration and proinflammatory polarization in PVAT and the renal cortex, and T-cell infiltration in the renal cortex only in the Scurfy T-cell group. Treg coinjection in the vehicle and Scurfy T-cell groups prevented or reduced the effects of Ang II. CONCLUSION: FOXP3+ Treg deficiency exaggerates Ang II-induced microvascular injury by modulating innate and adaptive immune responses.

Endothelin-1 Overexpression Exaggerates Diabetes-Induced Endothelial Dysfunction by Altering Oxidative Stress.

BACKGROUND: Increased endothelin (ET)-1 expression causes endothelial dysfunction and oxidative stress. Plasma ET-1 is increased in patients with diabetes mellitus. Since endothelial dysfunction often precedes vascular complications in diabetes, we hypothesized that overexpression of ET-1 in the endothelium would exaggerate diabetes-induced endothelial dysfunction. METHODS: Diabetes was induced by streptozotocin treatment (55mg/kg/day, i.p.) for 5 days in 6-week-old male wild type (WT) mice and in mice overexpressing human ET-1 restricted to the endothelium (eET-1). Mice were studied 14 weeks later. Small mesenteric artery (MA) endothelial function and vascular remodeling by pressurized myography, reactive oxygen species (ROS) production by dihydroethidium staining and mRNA expression by reverse transcription/quantitative PCR were determined. RESULTS: Endothelium-dependent vasodilatory responses to acetylcholine of MA were reduced 24% by diabetes in WT ( P < 0.05), and further decreased by 12% in eET-1 ( P < 0.05). Diabetes decreased MA media/lumen in WT and eET-1 ( P < 0.05), whereas ET-1 overexpression increased MA media/lumen similarly in diabetic and nondiabetic WT mice ( P < 0.05). Vascular ROS production was increased 2-fold by diabetes in WT ( P < 0.05) and further augmented 1.7-fold in eET-1 ( P < 0.05). Diabetes reduced endothelial nitric oxide synthase (eNOS, Nos3 ) expression in eET-1 by 31% ( P < 0.05) but not in WT. Induction of diabetes caused a 52% ( P < 0.05) increase in superoxide dismutase 1 ( Sod1 ) and a 32% ( P < 0.05) increase in Sod2 expression in WT but not in eET-1. CONCLUSIONS: Increased expression of ET-1 exaggerates diabetes-induced endothelial dysfunction. This may be caused by decrease in eNOS expression, increase in vascular oxidative stress, and decrease in antioxidant capacity.

Aldosterone-Induced Vascular Remodeling and Endothelial Dysfunction Require Functional Angiotensin Type 1a Receptors.

We investigated the role of angiotensin type 1a receptors (AGTR1a) in vascular injury induced by aldosterone activation of mineralocorticoid receptors in Agtr1a(-/-) and wild-type (WT) mice infused with aldosterone for 14 days while receiving 1% NaCl in drinking water. Aldosterone increased systolic blood pressure (BP) by ≈30 mm Hg in WT mice and ≈50 mm Hg in Agtr1a(-/-) mice. Aldosterone induced aortic and small artery remodeling, impaired endothelium-dependent relaxation in WT mice, and enhanced fibronectin and collagen deposition and vascular inflammation. None of these vascular effects were observed in Agtr1a(-/-) mice. Aldosterone effects were prevented by the AGTR1 antagonist losartan in WT mice. In contrast to aldosterone, norepinephrine caused similar BP increase and mesenteric artery remodeling in WT and Agtr1a(-/-) mice. Agtr1a(-/-) mice infused with aldosterone did not increase sodium excretion in response to a sodium chloride challenge, suggesting that sodium retention could contribute to the exaggerated BP rise induced by aldosterone. Agtr1a(-/-) mice had decreased mesenteric artery expression of the calcium-activated potassium channel Kcnmb1, which may enhance myogenic tone and together with sodium retention, exacerbate BP responses to aldosterone/salt in Agtr1a(-/-) mice. We conclude that although aldosterone activation of mineralocorticoid receptors raises BP more in Agtr1a(-/-) mice, AGTR1a is required for mineralocorticoid receptor stimulation to induce vascular remodeling and inflammation and endothelial dysfunction.

Effects of recombinant human erythropoietin on resistance artery endothelial function in stage 4 chronic kidney disease.

BACKGROUND: Recent studies have raised concern about the safety of erythropoiesis-stimulating agents because of evidence of increased risk of hypertension and cardiovascular morbidity and mortality in chronic kidney disease (CKD) patients. In the present study, we investigated the effects of recombinant human erythropoietin (EPO) on endothelial function of gluteal subcutaneous resistance arteries isolated from 17 stage 4 patients (estimated glomerular filtration rate 21.9±7.4 mL/min per 1.73 m(2)) aged 63±13 years. METHODS AND RESULTS: Arteries were mounted on a pressurized myograph. EPO impaired endothelium-dependent relaxation in a concentration-dependent manner. The maximal response to acetylcholine with EPO at 1, 10, and 20 IU/mL was reduced by 12%, 34%, and 43%, respectively, compared with the absence of EPO (P<0.001). EPO-induced endothelial dysfunction was significantly associated with carotid stiffness and history of cardiovascular events. EPO had no effect on norepinephrine-induced vasoconstriction or sodium nitroprusside-induced relaxation. ABT-627, an endothelin type A receptor antagonist, and tempol, a superoxide dismutase mimetic, partially reversed the altered endothelial function in the presence of EPO (P<0.01). Increased expression of endothelin-1 was found in the vessel wall after incubation with EPO. CONCLUSIONS: EPO alters endothelial function of resistance arteries in CKD patients via a mechanism involving in part oxidative stress and signaling through an endothelin type A receptor. EPO-induced endothelial dysfunction could contribute to deleterious effects of EPO described in large interventional trials.