Abstract 300: Targeted Deletion of Matrix Metalloproteinase 2 Prevents Angiotensin II-Induced Endothelial Dysfunction and Vascular Remodeling, Oxidative Stress and Inflammation

Background: Matrix metalloproteinase 2 (MMP2) is involved in vascular remodeling in atherosclerosis. Whether MMP2 plays a role in angiotensin (Ang) II-induced hypertension, vascular remodeling, oxidative stress and inflammation is unknown. We hypothesized that Mmp2 knockout will prevent Ang II-induced vascular injury.

Methods: Ten to 12-week-old male Mmp2 knockout ( Mmp2 -/- ) and wild type (WT) mice were infused with Ang II (1000 ng/kg/min, sc) for 14 days. Systolic blood pressure (SBP) was measured by telemetry. Mesenteric arteries (MA) were studied by pressurized myography. NADPH oxidase activity was evaluated by lucigenin chemiluminescence, and aortic reactive oxygen species (ROS) generation using dihydroethidium staining. Aortic expression of vascular cell adhesion protein 1 (VCAM-1) and monocyte chemotactic protein-1 (MCP-1), and monocyte/macrophage infiltration were assessed by immunofluorescence. Spleen T cells and monocytes were assessed by flow cytometry.

Results: Ang II increased SBP by 50 mmHg ( P <0.01), decreased vasodilatory responses to acetylcholine by 70 % ( P <0.01), induced MA hypertrophic remodeling, indicated by a 1.5-fold increase ( P <0.01) in media-to-lumen ratio and 1.3-fold increase ( P <0.05) in media cross-sectional area, and enhanced MA stiffness ( P <0.01), as shown by a leftward shift of the stress/strain relationship, in WT mice. Ang II increased NADPH oxidase activity 1.4-fold in aorta ( P <0.05), 2-fold in the heart ( P <0.01) and 2.6-fold in the renal cortex ( P <0.01) and aortic ROS generation 25-fold in WT mice ( P <0.01). Ang II increased aortic VCAM-1 and MCP-1 expression 3- and 6-fold, respectively, and monocyte/macrophage infiltration 8-fold in WT ( P <0.05). Ang II increased ≥1.8-fold spleen activated CD4 + CD69 + and CD8 + CD69 + T cells and pro-inflammatory Ly-6C hi monocytes ( P <0.001) in WT mice. Mmp knockout prevented or reduced all of the above except SBP elevation ( P <0.05).

Conclusion: MMP2 plays a role in Ang II-induced endothelial dysfunction, vascular remodeling, oxidative stress and inflammation but not in blood pressure elevation.

Abstract 46: FOXP3+ T Regulatory Lymphocytes Counteract Angiotensin II-Induced Vascular Injury

Introduction: T lymphocytes participate in the low-grade inflammatory response that causes vascular injury in angiotensin (Ang) II-induced hypertension. Ang II-induced hypertension and endothelial dysfunction are blunted in T and B lymphocyte-deficient ( Rag1 -/- ) mice, and restored with reconstitution of T cells. However, the role of T regulatory lymphocytes (Treg) in Ang II-induced vascular injury is unclear. We hypothesized that adoptive transfer of FOXP3-deficient (Scurfy) T lymphocytes vs. wild-type (WT) cells will exacerbate Ang II-induced vascular damage in Rag1 -/- mice.

Methods: Eleven-week old male Rag1 -/- mice were injected IV with PBS/2% FBS (control), 10 7 WT or Scurfy T lymphocytes, and 2 weeks later underwent sham surgery or were infused with Ang II (490 ng/kg/min, s.c.) using mini-osmotic pumps for 14 days (n=3-8). Systolic (SBP) and diastolic (DBP) blood pressure were measured by telemetry. Vascular function and structure were assessed in second order mesenteric arteries by pressurized myography. Reactive oxygen species (ROS) production and fibronectin and collagen I and III expression were determined in aorta.

Results: Ang II induced a 40 mmHg SBP rise in Rag1 -/- mice for all treatment groups, but DBP rise was ~10 mmHg greater for WT and Scurfy T cell-injected mice than for control mice ( P <0.01). Adoptive transfer of WT T cells restored Ang II induced-endothelial dysfunction in mesenteric arteries ( P <0.05), which was exaggerated in Scurfy T cell-injected mice ( P <0.01). Ang II induced a greater increase in ROS production in aortic perivascular fat of Scurfy T cell-injected mice compared to WT T cell-injected mice ( P <0.05). Ang II induced mesenteric artery stiffness ( P <0.01) and hypertrophic remodeling ( P <0.05) in control and Scurfy T cell-injected mice, but not in WT T cell-injected mice. Ang II increased fibronectin expression to a greater extent in the aorta of control and Scurfy T cell-injected mice compared to WT T cell-injected mice ( P <0.01). Collagen I and III content was greater in the aorta of control and Scurfy T cell-injected mice than in WT T cell-injected mice ( P <0.01), but expression was unaltered by Ang II treatment.

Conclusion: Foxp3+ T regulatory lymphocytes have a protective role against Ang II-induced vascular remodeling.

Abstract 257: Mapping of Chromosome 2 Regions Linked to Vascular Inflammation using Congenic Rats

Background: Chromosome 2 introgression from normotensive Brown Norway rats (BN) into hypertensive Dahl salt sensitive (SS) background (consomic SB2) reduced vascular inflammation and restored Treg function. We hypothesized that the BN chromosome 2 contains genes that reduce vascular inflammation, which could be mapped using congenic rats containing different portions of BN chromosome 2 on the SS background.

Methods: Twelve-to-13 week old male BN, SS, SB2, congenic (SB)A,

SBB and SBE rats fed normal salt diet were studied. Systolic blood pressure (SBP) was measured by telemetry. Aortic vascular cell adhesion molecule 1 (VCAM-1) and fibronectin expression, collagen content and reactive oxygen species (ROS) production were determined. Spleen Treg (CD4 + CD25 hi ) and CD4 + CD25 - T lymphocytes were characterized and cultured. Transforming growth factor (TGF)-β, tumor necrosis factor (TNF)-α, interleukin (IL)-10, IL-17 and IL-6 were measured in culture media.

Results: SS, SB2 and SBE exhibited 20 mmHg higher SBP compared

to BN, SBA, and SBB ( P <0.05). Aortic and perivascular ROS production and aortic VCAM-1 expression were ≥2.7- and ~1.5-fold greater, respectively, in SS and SBB ( P <0.05) compared to BN, SB2, SBA and SBE. Aortic media collagen content was 3-fold greater in SS and 1.7-fold in SB2 and SBB ( P <0.05) compared to BN, SBA and SBE. Aortic fibronectin expression was ~1.5-fold higher in SS and SBE ( P <0.05) compared to SB2 and SBA or BN. The percentage of spleen CD4 + CD25 - cells was higher in SS, SB2 and SBE (~16%) compared to BN, SBA and SBB (~12%, <0.05). Treg percentage was lower in SBA (2%) compared to SS and SB2 (3%, P <0.05). CD4 + CD25 - from SS or SBB secreted less TNF-α, IFN-γ and IL-6 (≤141, 1428 and 13 pg/10 5 cells, respectively, P <0.05), compared to SB2 and SBE (~320, 2350 and 50 pg/10 5 cells, respectively) or BN (458, 3552 and 57 pg/10 5 cells, respectively). Treg IL-10 and IL-17 production was higher in SB2 (9597 pg/10 5 cells), and SS and SB2 (>90 pg/10 5 cells), respectively ( P <0.05), compared to congenic rats (~2540 and 23 pg/10 5 cells, respectively) or BN (2497 and 9 pg/10 5 cells).

Conclusion: Some genes regulating vascular injury and inflammatory responses are contained within the fragment of BN-chromosome 2 present in congenic SBA and SBE rats.

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.

Reduced Macrophage-Dependent Inflammation Improves Endothelin-1–Induced Vascular Injury

Transgenic mice with endothelium-specific endothelin-1 (ET-1) overexpression exhibit endothelial dysfunction and vascular remodeling, oxidative stress, and inflammation. We previously observed that monocytes/macrophages play a role in angiotensin II, aldosterone, and deoxycorticosterone acetate/salt-induced vascular remodeling, oxidative stress, and inflammation using a model with reduced monocytes/macrophages, the osteopetrotic (Op) mouse, which has a mutation in the macrophage colony stimulating factor ( Csf1 ) gene. However, it is unknown whether monocytes/macrophages are implicated in adverse vascular effects of ET-1. We hypothesized that reduction in monocytes/macrophages would blunt ET-1–induced vascular injury. We performed a study on 4- to 6-month-old male mice with endothelium-specific ET-1 overexpression (eET-1), reduction in CSF1 ( Csf1 Op/+ ), or both (eET-1/ Csf1 Op/+ ), and their wild-type littermate control mice. There was no difference in systolic blood pressure between groups. Endothelial function and vascular structure were determined on a pressurized myograph. Endothelium-dependent relaxation in response to acetylcholine was similar in eET-1 and eET-1/ Csf1 Op/+ mice. Media:lumen ratio and media cross-sectional area were ≈1.5-fold greater in eET-1 than in wild-type mice ( P <0.05), which was not observed in mice deficient in CSF1. ET-1–induced oxidative stress measured by dihydroethidium staining ( P <0.05) and NADPH oxidase activity assessed with lucigenin chemiluminescence ( P <0.05) were blunted by CSF1 deficiency. ET-1 caused a 2.5-fold increase in monocyte/macrophage infiltration compared with wild-type mice ( P <0.001), which was blunted in the mice deficient in CSF1. Reduction of monocyte/macrophage-dependent inflammation in mice overexpressing ET-1 in endothelium results in reduced vascular remodeling and oxidative stress, providing evidence for a role of monocytes/macrophages and innate immunity in ET-1–induced vascular injury.

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 m²) 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.

Abstract 60: Reduced Macrophage-dependent Inflammation Improves Endothelial Function and Vascular Remodeling, Oxidative Stress and Inflammation in a Model Of Endothelin-1 Induced Vascular Injury

Background: Transgenic mice with endothelium specific preproendothelin-1 overexpression (eET-1) exhibit endothelial dysfunction and vascular remodeling, oxidative stress and inflammation independently of hemodynamic effects. However, it is unclear whether vascular inflammation is causally implicated in adverse vascular effects of endothelin-1 (ET-1). We hypothesized that ET-1-induced vascular injury is decreased in a model of reduced macrophage-dependent inflammation, macrophage colony stimulating factor ( mCsf ) mice heterozygote for the osteopetrosis (Op) mutation.

Methods and Results: Wild type (WT), eET-1, mCsf Op/+ and eET-1/ mCsf Op/+ mice were studied. There was no difference in tail-cuff systolic blood pressure between groups. Endothelial function and vascular structure were determined on a pressurized myograph. Endothelium-dependent relaxation in response to acetylcholine was similar in eET-1 and eET-1/ mCsf Op/+ . However, in the presence of L-NAME, the magnitude of NO-independent relaxation was greater in eET-1/ mCsf Op/+ compared to eET-1 (72.4±6.7% vs. 40.8±14.4%, P <0.001). Media-to-lumen ratio was greater in eET-1 than WT (0.13±0.01 vs. 0.08±0.01, P <0.01) and unchanged in eET-1/ mCsf Op/+ (0.10±0.01). Media cross-sectional area (μm 2 ) was greater in eET-1 than WT (13521±2106 vs. 8112±381, P <0.05) and unchanged in eET-1/ mCsf Op/+ (8966±1125). Dihydroethidium staining revealed that reactive oxygen species production in aorta was 4-fold higher in eET-1 than WT ( P <0.01) and unchanged in eET-1/mCsf Op/+ . Aortic monocyte/macrophage infiltration was increased 2.6-fold in eET-1 ( P <0.01) and tended to decrease by 45% in eET-1/mCsf Op/+ compared to WT.

Conclusion: Reduction of macrophage-dependent inflammation in mice overexpressing ET-1 in endothelium results in improved vascular relaxation and reduced vascular remodeling, oxidative stress and inflammation, providing evidence for a role of macrophages and innate immunity in ET-1-induced vascular damage.

Abstract 43: A Functional Angiotensin Type 1a Receptor Is Required for Aldosterone to Induce Small Artery Endothelial Dysfunction, Inflammation and Oxidative Stress

Background: Aldosterone induces hypertension, endothelial dysfunction, vascular inflammation and oxidative stress. Recent in vitro studies suggest that there may be cross-talk between angiotensin II and aldosterone pathways. We hypothesized that in vivo vascular effects of aldosterone require a functional angiotensin II type 1a receptor (Agtr1a).

Design and methods: Eight to 10-week old male agtr1a knockout ( agtr1a -/- ) and wild-type mice were implanted with a dummy pump or infused with aldosterone (600 μg/kg/d, s.c.) for 14 days while receiving 1% saline in the drinking water (n=8-10). Systolic blood pressure (SBP) was measured by telemetry. Endothelial function, and reactive oxygen species (ROS) production were assessed in mesenteric arteries using pressurized myography and dihydroethidium staining, respectively. Levels of collagen by Sirius red staining and fibronectin, VCAM-1, and MCP-1 by immunofluorescence were determined in aortic sections.

Results: Aldosterone-induced higher levels of SBP in agtr1a -/- compared to wild-type mice (about 15 mmHg, P <0.01). Maximal vasodilatory responses to acetylcholine in mesenteric small arteries were similar in agtr1a -/- and wild-type mice. Aldosterone reduced maximal vasodilatory responses to acetylcholine in wild-type mice by 48% ( P <0.05) whereas there was no effect in agtr1a -/- mice. Aldosterone increased ROS production 2-fold in mesenteric arteries of wild-type mice ( P <0.05) whereas it had no effect in agtr1a -/- mice. Aldosterone increased VCAM-1 (1.8-fold, P <0.05), MCP-1 (2.7-fold, P <0.05), fibronectin (3-fold, P <0.01) and collagen (3.9-fold, P <0.05) in aorta of wild-type but not in agtr1a -/- mice.

Conclusion: Aldosterone requires functional Agtr1a to induce small artery endothelial dysfunction and vascular oxidative stress, inflammation and fibrosis.

Abstract 264: Erythropoietin-induced Hypertension and Vascular Injury in Mice Overexpressing Human Endothelin-1 Was Attenuated by Exercise

Background: Erythropoietin (EPO) is used to correct anemia in chronic kidney disease (CKD). EPO has been shown to increase blood pressure (BP) in patients and animals with CKD. This BP rise can be blunted by endothelin (ET) A receptor blockers. Chronic exercise prevents or reduces development of cardiovascular disease. However, it is unknown whether exercise prevents EPO-induced hypertension. We hypothesized that EPO treatment would exacerbate endothelin (ET)-1-induced vascular damage and increase BP, and that exercise training might prevent these effects.

Methods: Eight to 10-week old male mice overexpressing human preproET-1 in the endothelium (eET-1) were treated with EPO (100 U/kg, s.c, 3 times/week) or not, and subjected to swimming exercise (1 h/d, 5 d/week) for 8 weeks or maintained in sedentary condition (n=7-8). Wild-type (WT) mice were also treated or not with EPO. Systolic BP (SBP) was measured by the tail-cuff method. Endothelial function was assessed in mesenteric arteries by pressurized myography. NADPH oxidase activity was assessed in aorta or renal cortex of by lucigenin chemiluminescence, reactive oxygen species (ROS) by dihydroethidium staining, and monocyte/macrophage and T regulatory cell (FoxP3) infiltration, and VCAM-1 by immunofluorescence staining.

Results: EPO increased SBP by 24 mmHg ( P <0.05) and impaired vasodilatory responses to acetylcholine in eET-1 (68% vs. 91%, P <0.01). NADPH oxidase activity was 2-fold higher in eET-1 than in WT ( P <0.05), and further increased 1.5-fold by EPO ( P <0.01). ROS production in aorta of WT was enhanced 2-fold ( P <0.01) by EPO, which increased ROS in eET-1 a further 9-fold ( P <0.01). EPO increased monocyte/macrophage infiltration in aorta of WT 2.5-fold ( P <0.01), and in eET-1 a further 2.7-fold ( P <0.05). VCAM-1 expression in aorta was 2.7-fold higher in eET-1 than in WT ( P <0.05). All of the above was prevented by exercise ( P <0.05). Exercise with or without EPO increased T regulatory FoxP3 + lymphocytes in renal cortex 3-fold compared to eET-1 and WT ( P <0.01).

Conclusions: Exercise prevents EPO-induced BP elevation and vascular damage through a mechanism involving decreased vascular oxidative stress and inflammation.

Abstract 167: Mapping of Chromosome 2 Regions Linked to Vascular Inflammation Using Congenic Rats

Background: Immune cells have been implicated in hypertension and vascular inflammation. We demonstrated that chromosome 2 modulates immune responses in genetic hypertension via T regulatory lymphocytes (Treg). Introgression of chromosome 2 from normotensive Brown Norway (BN) rats into hypertensive Dahl salt sensitive (SS) background (consomic SB2) reduced vascular inflammation and restored Treg function. We hypothesized that the BN chromosome 2 contains genes that reduce vascular inflammation, which could be mapped using congenic rats containing portions of BN chromosome 2 on the SS background.

Methods: Twelve-to-13 week old male BN, SS, SB2, congenic (SB)A, SBB and SBE rats fed normal salt diet were studied. Systolic blood pressure (SBP) was measured by telemetry. Spleen Treg (CD4 + CD25 hi ) and CD4 + CD25 - T lymphocytes were isolated and characterized by fluorescence-activated cell sorting (FACS) and cultured. Transforming growth factor (TGF)-β, tumor necrosis factor (TNF)-α, interleukin (IL)-10, IL-17 and IL-6 secreted by 10 5 cells in culture media was measured by microbead multiplex immunoassays. Aortic collagen content was determined by Sirius red staining.

Results: SS, SB2 and SBE exhibited 20 mmHg higher SBP compared to BN, SBA, and SBB ( P <0.05). The % of CD4 + CD25 - was higher in SS, SB2 and SBE (∼16 %) compared to BN, SBA and SBB (∼12%, P <0.05). The % of Treg was lower in SBA (2%) compared to SS and SB2 (3%, P <0.05). CD4 + CD25 - secretion of TNF-α, IFN-γ and IL-6 was always lower in SS and SBB (≤141, 1428 and 13 pg/10 5 cells, respectively, P <0.05), and consistently unchanged in SB2 and SBE (∼320, 22350 and 50 pg/10 5 cells, respectively) compared to BN (458, 3552 and 57 pg/10 5 cells, respectively). Treg IL-10 and IL-17 production was increased in SB2 (9597 pg/10 5 cells), and SS and SB2 (>90 pg/10 5 cells), respectively ( P <0.05) and unchanged in congenic rats (∼2540 and 23 pg/10 5 cells, respectively), compared to BN (2497 and 9 pg/10 5 cells). Aortic collagen was increased 3-fold in SS, 1.7-fold in SB2 and SBB ( P <0.05) and unchanged in SBA and SBE compared to BN.

Conclusion: These results suggest that some of the genes that regulate vascular inflammatory responses are contained within the fragment of chromosome 2 from Brown-Norway rats present in congenic SBE rats.

Abstract 16: Adoptive Transfer of T Lymphocytes Prevents Angiotensin II-induced Vascular Stiffness in rag-1 Knockout Mice

Background: Both innate and adoptive immune systems are involved in the pathogenesis of hypertension and vascular damage. T lymphocytes participate in the low-grade inflammatory response that contributes to vascular injury in cardiovascular disease, including hypertension. Angiotensin (Ang) II-induced hypertension and endothelial dysfunction are blunted in rag1 knockout (rag1-/-) mice, which are deficient in T and B lymphocytes, and restored with adoptive transfer of T but not B lymphocytes. We hypothesized that adoptive transfer of T lymphocytes from C57Bl/6 mice (WT) will exacerbate Ang II-induced vascular damage in rag1-/- mice.

METHODS: Eleven-week old male rag1-/- mice were injected i.v. with PBS or 10 x 106 pan T lymphocytes, and 2 weeks later implanted with a dummy pump (control) or infused with Ang II (490 ng/kg/min, s.c.) for 14 days (n=5-8). Systolic (SBP) and diastolic blood pressure (SBP) were measured by telemetry. Endothelial function and vessel structure were assessed in second order mesenteric arteries by pressurized myography. Successful adoptive transfer was confirmed at time of sacrifice by determining numbers of T cells in the spleen by flow cytometry.

Results: Ang II induced a similar 40 mmHg SBP rise in rag-1-/- mice injected with PBS or T cells, but DBP rise was greater for T cell-injected mice (24 mmHg) than for PBS injected mice (9 mmHg). Ang II impaired vasodilatory responses to acetylcholine in T cell-injected mice (54.0±5.9%) but not in PBS injected mice (82.1±2.9%). Ang II treatment induced hypertrophic remodeling in PBS injected mice, but not in T cell-injected mice (media-to-lumen ratio: 4.1±0.3 from 2.7±0.3 vs. 3.3±0.2 from 2.6±0.1, media cross-sectional area (μm2): 5757±565 from 4382±580 vs. 4811±281 from 4350±254). Ang II increased vascular stiffness, indicated by a leftward shift of the small artery stress/strain relationship, in PBS injected mice but to a lower extent in T cell-injected mice.

Conclusions: These findings suggest that T lymphocytes have a protective role in Ang II-induced vascular stiffness.

T regulatory lymphocytes prevent aldosterone-induced vascular injury

Aldosterone mediates actions of the renin-angiotensin-aldosterone system inducing hypertension, oxidative stress, and vascular inflammation. Recently, we showed that angiotensin II-induced hypertension and vascular damage are mediated at least in part by macrophages and T-helper effector lymphocytes. Adoptive transfer of suppressor T-regulatory lymphocytes (Tregs) prevented angiotensin II action. We hypothesized that Treg adoptive transfer would blunt aldosterone-induced hypertension and vascular damage. Thirteen to 15-week-old male C57BL/6 mice were injected intravenously at 1-week intervals with 3×10(5) CD4(+)CD25(+) cells (representing Treg) or control CD4(+)CD25(-) cells and then infused or not for 14 days with aldosterone (600 μg/kg per day, SC) while receiving 1% saline to drink. Aldosterone induced a small but sustained increase in blood pressure (P<0.001), decreased vasodilatory responses to acetylcholine by 66% (P<0.001), increased both media:lumen ratio (P<0.001) and media cross-sectional area of resistance arteries by 60% (P<0.05), and increased NADPH oxidase activity 2-fold in aorta (P<0.001), kidney and heart (P<0.05), and aortic superoxide production. As well, aldosterone enhanced aortic and renal cortex macrophage infiltration and aortic T-cell infiltration (all P<0.05), and tended to decrease Treg in the renal cortex. Treg adoptive transfer prevented all of the vascular and renal effects induced by aldosterone. Adoptive transfer of CD4(+)CD25(-) cells exacerbated aldosterone effects except endothelial dysfunction and increases in media:lumen ratio of resistance arteries. Thus, Tregs suppress aldosterone-mediated vascular injury, in part through effects on innate and adaptive immunity, suggesting that aldosterone-induced vascular damage could be prevented by an immunomodulatory approach.

T regulatory lymphocytes prevent aldosterone-induced vascular injury

Aldosterone mediates actions of the renin-angiotensin-aldosterone system inducing hypertension, oxidative stress, and vascular inflammation. Recently, we showed that angiotensin II-induced hypertension and vascular damage are mediated at least in part by macrophages and T-helper effector lymphocytes. Adoptive transfer of suppressor T-regulatory lymphocytes (Tregs) prevented angiotensin II action. We hypothesized that Treg adoptive transfer would blunt aldosterone-induced hypertension and vascular damage. Thirteen to 15-week-old male C57BL/6 mice were injected intravenously at 1-week intervals with 3×10(5) CD4(+)CD25(+) cells (representing Treg) or control CD4(+)CD25(-) cells and then infused or not for 14 days with aldosterone (600 μg/kg per day, SC) while receiving 1% saline to drink. Aldosterone induced a small but sustained increase in blood pressure (P<0.001), decreased vasodilatory responses to acetylcholine by 66% (P<0.001), increased both media:lumen ratio (P<0.001) and media cross-sectional area of resistance arteries by 60% (P<0.05), and increased NADPH oxidase activity 2-fold in aorta (P<0.001), kidney and heart (P<0.05), and aortic superoxide production. As well, aldosterone enhanced aortic and renal cortex macrophage infiltration and aortic T-cell infiltration (all P<0.05), and tended to decrease Treg in the renal cortex. Treg adoptive transfer prevented all of the vascular and renal effects induced by aldosterone. Adoptive transfer of CD4(+)CD25(-) cells exacerbated aldosterone effects except endothelial dysfunction and increases in media:lumen ratio of resistance arteries. Thus, Tregs suppress aldosterone-mediated vascular injury, in part through effects on innate and adaptive immunity, suggesting that aldosterone-induced vascular damage could be prevented by an immunomodulatory approach.

Human recombinant erythropoietin alters the flow-dependent vasodilatation of in vitro perfused rat mesenteric arteries with unbalanced endothelial endothelin-1 / nitric oxide ratio

Chronic use of human recombinant erythropoietin (r-HuEPO) is accompanied by serious vascular side effects related to the rise in blood viscosity and shear stress. We investigated the direct effects of r-HuEPO on endothelium and nitric oxide (NO)-dependent vasodilatation induced by shear stress of cannulated and pressurized rat mesenteric resistance arteries. Intravascular flow was increased in the presence or absence of the NO synthase inhibitor NG-nitro-l-arginine methyl ester (L-NAME; 10−4 mol/L). In the presence of r-HuEPO, the flow-dependent vasodilatation was attenuated, while L-NAME completely inhibited it. The association of r-HuEPO and L-NAME caused a vasoconstriction in response to the rise in intravascular flow. Bosentan (10−5 mol/L), an inhibitor of endothelin-1 (ET-1) receptors, corrected the attenuated vasodilatation observed with r-HuEPO and inhibited the vasoconstriction induced by flow in the presence of r-HuEPO and L-NAME. r-HuEPO and L-NAME exacerbated ET-1 vasoconstriction. At shear stress values of 2 and 14 dyn/cm2 (1 dyn = 10–5 N), cultured EA.hy926 endothelial cells incubated with r-HuEPO, L-NAME, or both released greater ET-1 than untreated cells. In conclusion, r-HuEPO diminishes flow-induced vasodilatation. This inhibitory effect seems to implicate ET-1 release. NO withdrawal exacerbates the vascular effects of ET-1 in the presence of r-HuEPO. These findings support the importance of a balanced endothelial ET-1:NO ratio to avoid the vasopressor effects of r-HuEPO.

T regulatory lymphocytes prevent angiotensin II-induced hypertension and vascular injury

Angiotensin (Ang) II induces hypertension by mechanisms mediated in part by adaptive immunity and T effector lymphocytes. T regulatory lymphocytes (Tregs) suppress T effector lymphocytes. We questioned whether Treg adoptive transfer would blunt Ang II-induced hypertension and vascular injury. Ten- to 12-week-old male C57BL/6 mice were injected IV with 3 ×10(5) Treg (CD4(+)CD25(+)) or T effector (CD4(+)CD25(-)) cells, 3 times at 2-week intervals, and then infused or not with Ang II (1 μg/kg per minute, SC) for 14 days. Ang II increased systolic blood pressure by 43 mm Hg (P<0.05), NADPH oxidase activity 1.5-fold in aorta and 1.8-fold in the heart (P<0.05), impaired acetylcholine vasodilatory responses by 70% compared with control (P<0.05), and increased vascular stiffness (P<0.001), mesenteric artery vascular cell adhesion molecule expression (2-fold; P<0.05), and aortic macrophage and T-cell infiltration (P<0.001). All of the above were prevented by Treg but not T effector adoptive transfer. Ang II caused a 43% decrease in Foxp3(+) cells in the renal cortex, whereas Treg adoptive transfer increased Foxp3(+) cells 2-fold compared with control. Thus, Tregs suppress Ang II-mediated vascular injury in part through anti-inflammatory actions. Immune mechanisms modulate Ang II-induced blood pressure elevation, vascular oxidative stress, inflammation, and endothelial dysfunction.