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.

Role of T regulatory lymphocytes in the pathogenesis of high-fructose diet-induced metabolic syndrome

We recently showed that T regulatory lymphocytes (Treg), which are immune suppressors of inflammatory responses, play a role blunting the development of hypertension-induced injury. Treg are unchanged or decreased in children with metabolic syndrome, and therefore, their role in metabolic syndrome remains unclear. We hypothesized that Treg number or function would be depressed in a high-fructose diet-induced metabolic syndrome-like model in rats. Sprague-Dawley rats were fed normal chow or a high-fructose diet for 5 weeks. The high-fructose diet-induced a 3.8-fold increase in plasma triglycerides and a 14% reduction in high-density lipoprotein cholesterol (P<0.001). The high-fructose diet increased reactive oxygen species in aorta and periaortic adipose tissue 2.8-fold (P<0.05), and reduced nicotinamide adenine dinucleotide phosphate oxidase activity 1.9-fold in aorta, and 2.5-fold in the heart (P<0.05). It also increased plasma nitric oxide metabolite levels 6.4-fold (P<0.001). Western blots showed that the high-fructose diet increased ≥2.3-fold vascular and in platelet endothelial cell adhesion molecule 1 in aorta (P<0.01). It did not affect monocyte/macrophage aortic infiltration but caused a 2.4-fold increase in collagen deposition in the aortic media (P<0.01). No change in plasma interleukin-10 was detected. The percentage of spleen CD4+ CD25- and Treg (CD4+ CD25(high)) cells was unaltered by the high-fructose diet. However, cultured Treg from high-fructose diet-fed rats secreted 62% less interleukin-10 than control cells (P<0.05), suggesting a decreased Treg function, which could play a role in the development of cardiovascular complications of the metabolic syndrome.

Protective role of vascular smooth muscle cell PPARγ in angiotensin II-induced vascular disease

AIMS

Vascular peroxisome proliferator-activated receptor γ (PPARγ) activation improves vascular remodelling and endothelial function in hypertensive rodents. The goal of this study was to determine that vascular smooth muscle cell (VSMC) PPARγ exerts a vascular protective role beyond its metabolic effects.

METHODS AND RESULTS

We generated a model of adult inducible VSMC-specific Pparγ inactivation to test the hypothesis that PPARγ counteracts angiotensin (Ang) II-induced vascular remodelling and endothelial dysfunction. Inducible VSMC Pparγ knockout mice were generated by crossing Pparγ floxed mice with mice expressing a tamoxifen-inducible Cre recombinase Smooth muscle (Sm) myosin heavy chain promoter control. Eight-to-ten-week-old SmPparγ(-/-) and control mice were infused with a nonpressor dose of Ang II for 7 days. Blood pressure was unaffected. Mesenteric arteries showed eutrophic remodelling in Ang II-infused control mice and hypertrophic remodelling in Ang II-infused SmPparγ(-/-) mice. Endothelium-dependent relaxation to acetylcholine was reduced in SmPparγ(-/-) mice and further impaired by Ang II infusion, and was unaffected by an inhibitor of NO synthase, suggesting a defect of NO-mediated relaxation. SmPparγ deletion increased the sensitivity to Ang II-induced contraction. SmPparγ(-/-) mice exhibited enhanced Ang II-induced vascular NADPH oxidase activity and adhesion molecule ICAM-1 and chemokine monocyte chemotactic protein-1 expression. The antioxidant Superoxide dismutase 3 expression was decreased by SmPparγ deletion. Ang II infusion increased the expression of CD3 T-cell co-receptor chain δ and decreased Adiponectin in perivascular adipose tissue of SmPparγ(-/-) mice.

CONCLUSION

Inducible Pparγ inactivation in VSMCs exacerbated Ang II-induced vascular remodelling and endothelial dysfunction via enhanced vascular oxidative stress and inflammation, revealing the protective role of VSMC PPARγ in angiotensin II-induced vascular injury.

Abstract 519: Endothelin-1-Induced Oxidative Stress and Inflammatory Cell Infiltration Play a Role in High-Fat Diet Induced-Atherosclerosis in Apolipoprotein E Knockout Mice

Background: Endothelin (ET)-1 plays an important role in generation of reactive oxygen species (ROS) and inflammation in the vasculature. ET-1has been implicated in the pathogenesis of atherosclerosis since plasma and tissue ET-1 are increased in human and animal models of atherosclerosis. We observed that ET-1 overexpression exacerbates high-fat diet (HFD)-induced atherosclerosis in apolipoprotein E knockout ( apoE -/- ) mice. We hypothesized that ET-1-induced ROS and inflammation contribute to the development of atherosclerosis.

Design and methods: Eight-week-old male transgenic mice overexpressing preproET-1 in the endothelium (eET-1), apoE -/- , eET-1/ apoE -/- and wild type mice were fed a HFD for 8 weeks. Aortic atherosclerotic lesions were quantified using Oil Red O staining. ROS production using dihydroethidium staining and monocyte/macrophage and T cell infiltration using immunofluorescence with MOMA-2 and anti-CD4 antibodies, respectively, were determined in perivascular fat, media and plaque in ascending aortic sections.

Results: eET-1/ apoE -/- presented 3.8-fold more atherosclerotic lesions in whole aorta compared to apoE -/- ( P <0.01). ET-1 overexpression caused 2.6-, 1.9- and 1.9-fold increase in ROS production in perivascular fat, media and plaque of apoE -/- , respectively ( P <0.05). ET-1 overexpression increased monocyte/macrophage infiltration by 5- and 8-fold in perivascular fat and media, respectively ( P <0.05). CD4 + T cell infiltration was observed in perivascular fat and plaque of 3 and 5 of 6 eET-1/ apoE -/- compared to 0 and 1 of 6 apoE -/- , respectively ( P <0.05).

Conclusions: These results suggest that ET-1 play an important role in progression of atherosclerotic lesions by increasing the oxidative stress and monocyte/macrophage and T cell infiltration in the atherosclerotic aorta, including the perivascular fat.

Abstract 485: Transglutaminase 2 is a Regulator of Angiotensin II-induced ERK1/2 Activation in Vascular Smooth Muscle Cells

Background: In essential hypertension, angiotensin (Ang) II induces arterial remodeling that is dependent on the activation of ERK1/2 pathway in vascular smooth muscle cells (VSMC). Arterial remodeling is also dependent on transglutaminase 2 (TG2), a protein with an emerging role in vascular pathophysiology. Beside its effect on extracellular matrix, TG2 is a multifunctional protein with GTPase activity and as such, could potentially be a signaling molecule. We hypothesized that TG2 mediates Ang II-induced ERK1/2 activation in VSMC during arterial remodeling.

Methods and Results: To determine the role of TG2 in Ang II type 1 receptor (AT 1 R) signaling, His 6 tagged-TG2 was overexpressed in the human embryonic kidney (HEK) 293 cell line stably overexpressing HA tagged-AT 1 R. Protein and phosphorylation levels were determined by Western blot. When stimulated for 2-60 min, TG2 overexpression potentiated 100 nM Ang II-induced ERK1/2 phosphorylation compared to control cells overexpressing green fluorescent protein (GFP, P <0.05, n=4). Maximal potentiation was observed after 2 min of stimulation at which time TG2 transfected cells showed an increase of 64±31% compared to GFP transfected cells. The role of TG2 in Ang II-induced phosphorylation of ERK1/2 was studied by TG2 siRNA knockdown in mouse vascular smooth muscle cell line (MOVAS). TG2 siRNA decreased TG2 expression by 83±5% compared to cells treated with control siRNA (n=4). Transfection of TG2 siRNA did not significantly change cell viability when compared to ctrl siRNA (n=3). Ten min stimulation with 1 and 100 nM Ang II increased ERK1/2 phosphorylation by 38±18% and 60±29%, respectively, and this was prevented by TG2 knockdown ( P <0.01). Using western blots, HA-AT 1 R dimer/monomer ratio was increased by co-expression of His 6 -TG2 compared to HA-AT1R expressed alone.

Conclusion: These results suggest that TG2 mediates ERK1/2 activation by Ang II through a mechanism involving TG2-induced AT 1 R dimerization. Overall, our results demonstrate that TG2 is involved in the activation of ERK1/2 in response to Ang II and could participate in arterial remodeling induced by Ang II.

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 449: Develoment of Endothelin-1 Induced Aneurysms in High-Fat Diet-Fed Apolipoprotein E Knockout Mice Through a Mechanism Involving Oxidative Stress and Inflammatory Cell Infiltration

Background: Endothelin (ET)-1 has been implicated in the pathogenesis of atherosclerosis. Plasma and tissue ET-1 are increased in human and animal with atherosclerosis. ET-1 overexpression exacerbates high-fat diet (HFD)-induced atherosclerosis in apolipoprotein E knockout ( apoE -/- ) mouse. Abdominal aorta aneurysms (AAA) occur in association with atherosclerosis. We hypothesized that ET-1-induced ROS and inflammation would increase the occurrence of AAA in HFD fed apoE -/- mice.

Design and methods: Eight-week-old male transgenic mice overexpressing preproET-1 in the endothelium (eET-1), apoE -/- , eET-1/ apoE -/- and wild type mice were fed a HFD for 8 weeks. Suprarenal aortic perimeter was determined using Oil Red O stained-sections. ROS production using dihydroethidium staining and monocyte/macrophage and T cell infiltration using immunofluorescence with MOMA-2 and anti-CD4 antibodies, respectively, were determined in perivascular fat and media in suprarenal aorta sections.

Results: Aneurysms were observed at a suprarenal level in 6 of 15 eET-1/ apoE -/- compared to none of 15 apoE -/- ( P <0.05). The aortic perimeter was increased 2.5-fold in eET-1/ apoE -/- with AAA compared to apoE -/- ( P <0.01). ROS production was increased 2.8- and 3.8-fold in perivascular fat and media of eET-1/ apoE -/- compared to apoE -/- , respectively ( P <0.05). Monocyte/macrophage infiltration was increased 2.6-fold in perivascular fat of eET-1/ apoE -/- compared to apoE -/- ( P <0.01). CD4 + T cell infiltration was observed in perivascular fat and plaque of 6 eET-1/ apoE -/- compared to none of 6 apoE -/- , respectively ( P <0.05).

Conclusions: These results suggest that ET-1 plays an important role in development of AAA by increasing oxidative stress and monocyte/macrophage and T cell infiltration in the aorta.

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.

Cyclin D2 rescues size and function of GATA4 haplo-insufficient hearts

Transcription factor GATA4 is a key regulator of cardiomyocyte growth, and differentiation and 50% reduction in GATA4 levels results in hypoplastic hearts. Search for GATA4 targets/effectors revealed cyclin D(2) (CD2), a member of the D-type cyclins (D(1), D(2), and D(3)) that play a vital role in cell growth and differentiation as a direct transcriptional target and a mediator of GATA4 growth in postnatal cardiomyocytes. GATA4 associates with the CD2 promoter in cardiomyocytes and is sufficient to induce endogenous CD2 transcription and to dose-dependently activate the CD2 promoter in heterologous cells. Cardiomyocyte-specific overexpression of CD2 results in enhanced postnatal cardiac growth because of increased cardiomyocyte proliferation. When these transgenic mice are crossed with Gata4 heterozygote mice, they rescue the hypoplastic cardiac phenotype of Gata4(+/-) mice and enhance cardiomyocyte survival and heart function. The data uncover a role for CD2 in the postnatal heart as an effector of GATA4 in myocyte growth and survival. The finding that postnatal upregulation of a cell-cycle gene in GATA4 haplo-insufficient hearts may be protective opens new avenues for maintaining or restoring cardiac function in GATA4-dependent cardiac disease.

Agonist-Independent Constitutive Activity of Angiotensin II Receptor Promotes Cardiac Remodeling in Mice

The angiotensin II (Ang II) type 1 (AT 1 ) receptor mainly mediates the physiological and pathological actions of Ang II, but recent studies have suggested that AT 1 receptor inherently shows spontaneous constitutive activity even in the absence of Ang II in culture cells. To elucidate the role of Ang II–independent AT 1 receptor activation in the pathogenesis of cardiac remodeling, we generated transgenic mice overexpressing AT 1 receptor under the control of α-myosin heavy chain promoter in angiotensinogen-knockout background (AT 1 Tg-AgtKO mice). In AT 1 Tg-AgtKO hearts, redistributions of the Gα q11 subunit into cytosol and phosphorylation of extracellular signal-regulated kinases were significantly increased, compared with angiotensinogen-knockout mice hearts, suggesting that the AT 1 receptor is constitutively activated independent of Ang II. As a consequence, AT 1 Tg-AgtKO mice showed spontaneous systolic dysfunction and chamber dilatation, accompanied by severe interstitial fibrosis. Progression of cardiac remodeling in AT 1 Tg-AgtKO mice was prevented by treatment with candesartan, an inverse agonist for the AT 1 receptor, but not by its derivative candesartan-7H, deficient of inverse agonism attributed to a lack of the carboxyl group at the benzimidazole ring. Our results demonstrate that constitutive activity of the AT 1 receptor under basal conditions contributes to the cardiac remodeling even in the absence of Ang II, when the AT 1 receptor is upregulated in the heart.

Angiotensin type 2 receptor agonist compound 21 reduces vascular injury and myocardial fibrosis in stroke-prone spontaneously hypertensive rats

-Angiotensin type 2 receptor-mediated effects of angiotensin II appear to counteract many of the effects mediated via the angiotensin type 1 receptor. Compound 21 (C21), a selective angiotensin type 2 receptor agonist, has demonstrated beneficial effects on cardiac function after myocardial infarction in rodents. We hypothesized that C21 alone or in combination with an angiotensin type 1 receptor antagonist would blunt the development of hypertension and vascular damage in stroke-prone spontaneously hypertensive rats. Six-week-old stroke-prone spontaneously hypertensive rats received C21 (1 mg/kg per day), the angiotensin type 1 receptor antagonist losartan (10 mg/kg per day), C21 plus losartan, or vehicle PO for 6 weeks. Systolic blood pressure was lower in losartan and C21-losartan combination groups (P<0.001). Endothelium-dependent relaxation was enhanced (P<0.001) in the C21-losartan combination group at lower acetylcholine concentrations. C21 or C21-losartan combination reduced vascular stiffness, aortic medial and myocardial interstitial collagen content, and aortic fibronectin (P<0.05). C21 and losartan decreased the expression of 2 genes associated with cardiac hypertrophy, myosin heavy chain-β (myh7) by 30 to 50%, and α-skeletal muscle actin by 30% to 35% (P<0.05). C21-losartan combination caused an additional 40% reduction in myh7 compared with C21 (P<0.01). Aortic superoxide generation was reduced equally by the 3 treatments (P<0.001). Monocyte/macrophage infiltration in the aorta and kidney (P<0.001) and T-lymphocyte infiltration in the renal cortex (P<0.05) were lowered similarly by the 3 treatments. These data suggest that C21 alone or in combination with losartan may improve endothelial function and vascular composition and mechanics by reducing oxidative stress, collagen content, fibronectin, and inflammatory cell infiltration in stroke-prone spontaneously hypertensive rats.

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.

Overexpression of type 1 angiotensin II receptors impairs excitation-contraction coupling in the mouse heart

Transgenic mice that overexpress human type 1 angiotensin II receptor (AT1R) in the heart develop cardiac hypertrophy. Previously, we have shown that in 6-mo AT1R mice, which exhibit significant cardiac remodeling, fractional shortening is decreased. However, it is not clear whether altered contractility is attributable to AT1R overexpression or is secondary to cardiac hypertrophy/remodeling. Thus the present study characterized the effects of AT1R overexpression on ventricular L-type Ca2+ currents ( ICaL), cell shortening, and Ca2+ handling in 50-day and 6-mo-old male AT1R mice. Echocardiography showed there was no evidence of cardiac hypertrophy in 50-day AT1R mice but that fractional shortening was decreased. Cellular experiments showed that cell shortening, ICaL, and Cav1.2 mRNA expression were significantly reduced in 50-day and 6-mo-old AT1R mice compared with controls. In addition, Ca2+ transients and caffeine-induced Ca2+ transients were reduced whereas the time to 90% Ca2+ transient decay was prolonged in both age groups of AT1R mice. Western blot analysis revealed that sarcoplasmic reticulum Ca2+-ATPase and Na+/Ca2+ exchanger protein expression was significantly decreased in 50-day and 6-mo AT1R mice. Overall, the data show that cardiac contractility and the mechanisms that underlie excitation-contraction coupling are altered in AT1R mice. Furthermore, since the alterations in contractility occur before the development of cardiac hypertrophy, it is likely that these changes are attributable to the increased activity of the renin-angiotensin system brought about by AT1R overexpression. Thus it is possible that AT1R blockade may help maintain cardiac contractility in individuals with heart disease.

Cross-talk between aldosterone and angiotensin signaling in vascular smooth muscle cells

In hypertension or other forms of cardiovascular disease, the chronic activation of the renin-angiotensin-aldosterone system (RAAS) leads to dysfunction of the vasculature, including, increased vascular tone, inflammation, fibrosis and thrombosis. Cross-talk between the main mediators of the RAAS, aldosterone and angiotensin (Ang) II, participates in the development of this vascular dysfunction. Recent studies have highlighted the molecular mechanisms supporting this cross-talk in vascular smooth muscle cells (VSMCs). Some of the signaling pathways activated by the Ang II type 1 receptor (AT(1)R) are dependent on the mineralocorticoid receptor (MR) and vice versa. VSMC signaling pathways involved in migration and growth are under the control of cross-talk between aldosterone and Ang II. A synergistic mechanism leads to potentiation of signaling pathways activated by each agent. The genomic and non-genomic mechanisms activated by aldosterone cooperate with Ang II to regulate vascular tone and gene expression of pro-inflammatory and pro-fibrotic molecules. This cross-talk is dependent on the non-receptor tyrosine kinase c-Src, and on receptor tyrosine kinases, EGFR and PDGFR, and leads to activation of MAP kinases and growth, migration and inflammatory effects. These new findings will contribute to development of better treatments for conditions in which the RAAS is excessively activated.

A novel and simplified method of culture of human blood-derived early endothelial progenitor cells for the treatment of ischemic vascular disease

Endothelial progenitor cells (EPCs) consist of two different subpopulations named early (eEPCs) and late EPCs (lEPCs) that are derived from CD14(+) and CD14(-) circulating cells, respectively. These cells are regularly cultured over fibronectin-coated surfaces in endothelial basal medium (EBM)-2 supplemented with insulin-like growth factor (IGF-1), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and fibroblast growth factor (FGF). We have developed a new and simplified method for culturing human EPCs obtained from peripheral blood and tested their ability to preserve cardiac function following infarction. We first demonstrated that eEPCs derived from human peripheral blood mononuclear cells (PBMCs) and cultured in EBM-2 medium supplemented with autologous serum (10%) over fibronectin-coated surfaces (10 μg/ml) in the presence of IGF-1 (50 ng/ml) only, have a secretome similar to eEPCs cultured under regular conditions with IGF-1, VEGF, EGF, and FGF. Our data also indicate that IGF-1 modulates PBMC secretome in a dose-dependent manner. In another series of experiments, we showed that PBMCs cultured in suspension in bags (S-PBMCs) in basal medium supplemented with fibronectin and IGF-1 secrete significant amounts of stem cell factor (SCF, 31.3 ± 3.1 pg/ml)), hepatocyte growth factor (HGF, 438.6 ± 41.4 pg/ml), soluble tumor necrosis factor receptor 1 (sTNFR1, 127.1 ± 9.9 pg/ml), VEGF (139.3 ± 9.6 pg/ml), and IGF-1 (147.2 ± 46.1 pg/ml) but very low levels of TNF-α (13.4 ± 2.5 pg/ml). S-PBMCs injected intravenously into NOD SCID mice migrated to the injured myocardium, reduced cardiac fibrosis, enhanced angiogenesis, and preserved cardiac function after myocardial infarction (MI) in a manner similar to eEPCs cultured under standard conditions. In conclusion, we show in this study a refined and optimized method for culturing eEPCs. Our data indicate that S-PBMCs are composed of several cell populations including eEPCs and that they secrete high amounts of antiapoptotic, anti-inflammatory, and proangiogenic factors capable of preserving cardiac function following MI.

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.

Mitogen-activated protein kinase-activated protein kinase 2 in angiotensin II-induced inflammation and hypertension: regulation of oxidative stress

Vascular oxidative stress and inflammation play an important role in angiotensin II-induced hypertension, and mitogen-activated protein kinases participate in these processes. We questioned whether mitogen-activated protein kinase-activated protein kinase 2 (MK2), a downstream target of p38 mitogen-activated protein kinase, is involved in angiotensin II-induced vascular responses. In vivo experiments were performed in wild-type and Mk2 knockout mice infused intravenously with angiotensin II. Angiotensin II induced a 30 mm Hg increase in mean blood pressure in wild-type that was delayed in Mk2 knockout mice. Angiotensin II increased superoxide production and vascular cell adhesion molecule-1 in blood vessels of wild-type but not in Mk2 knockout mice. Mk2 knockdown by small interfering RNA in mouse mesenteric vascular smooth muscle cells caused a 42% reduction in MK2 protein and blunted the angiotensin II-induced 40% increase of MK2 expression. Mk2 knockdown blunted angiotensin II-induced doubling of intracellular adhesion molecule-1 expression, 2.4-fold increase of nuclear p65, and 1.4-fold increase in Ets-1. Mk2 knockdown abrogated the angiotensin II-induced 4.7-fold and 1.3-fold increase of monocyte chemoattractant protein-1 mRNA and protein. Angiotensin II enhanced reactive oxygen species levels (by 29%) and nicotinamide adenine dinucleotide phosphate oxidase activity (by 48%), both abolished by Mk2 knockdown. Reduction of MK2 blocked angiotensin II-induced p47phox translocation to the membrane, associated with a 53% enhanced catalase expression. Angiotensin II-induced increase of MK2 was prevented by the nicotinamide adenine dinucleotide phosphate oxidase inhibitor Nox2ds-tat. Mk2 small interfering RNA prevented the angiotensin II-induced 30% increase of proliferation. In conclusion, MK2 plays a critical role in angiotensin II signaling, leading to hypertension, oxidative stress via activation of p47phox and inhibition of antioxidants, and vascular inflammation and proliferation.

Mthfr deficiency induces endothelial progenitor cell senescence via uncoupling of eNOS and downregulation of SIRT1

Hyperhomocysteinemia (HHcy) has been shown to induce endothelial dysfunction in part as a result of enhanced oxidative stress. Function and survival of endothelial progenitor cells (EPCs, defined as sca1(+) c-kit(+) flk-1(+) bone marrow-derived cells), which significantly contribute to neovascularization and endothelial regeneration, depend on controlled production of reactive oxygen species (ROS). Mice heterozygous for the gene deletion of methylenetetrahydrofolate reductase (Mthfr(+/-)) have a 1.5- to 2-fold elevation in plasma homocysteine. This mild HHcy significantly reduced the number of circulating EPCs as well as their differentiation. Mthfr deficiency was also associated with increased ROS production and reduced nitric oxide (NO) generation in Mthfr(+/-) EPCs. Treatment of EPCs with sepiapterin, a precursor of tetrahydrobiopterin (BH(4)), a cofactor of endothelial nitric oxide synthase (eNOS), significantly reduced ROS and improved NO production. mRNA and protein expression of eNOS and the relative amount of eNOS dimer compared with monomer were decreased by Mthfr deficiency. Impaired differentiation of EPCs induced by Mthfr deficiency correlated with increased senescence, decreased telomere length, and reduced expression of SIRT1. Addition of sepiapterin maintained cell senescence and SIRT1 expression at levels comparable to the wild type. Taken together, these results demonstrate that Mthfr deficiency impairs EPC formation and increases EPC senescence by eNOS uncoupling and downregulation of SIRT1.

Vascular gene expression in mice overexpressing human endothelin-1 targeted to the endothelium

Endothelin (ET)-1 plays an important pathophysiological role in several vascular diseases including hypertension and atherosclerosis. Transgenic mice overexpressing human preproET-1 selectively in the endothelium (eET-1) exhibit vascular injury in the absence of blood pressure elevation. ET-1 overexpression may induce vascular injury by inducing changes in gene expression. To understand mechanisms whereby ET-1 induces vascular damage, vascular gene expression profiling was performed using DNA microarrays. RNA from mesenteric arteries of male and female young (6-7 wk) and mature (6-8 mo) eET-1 and wild-type (WT) mice was isolated, and changes in gene expression were determined by genome-wide expression profiling using Illumina microarray and FlexArray software. Data were analyzed using a relaxed and a stringent statistical approach. The gene lists were compared and analyzed as well with Ingenuity Pathway Analysis. The most common change was an increase in the expression of lipid metabolism genes. Four of these genes were validated by qPCR, cyp51, dgat2, and scd1 genes in young and elovl6 in both young and mature male mice, supporting a role of ET-1 in atherosclerosis. To test the hypothesis that ET-1 participates in mechanisms leading to atherosclerosis, we crossed eET-1 with atherosclerosis-prone apoE(-/-) mice to determine whether ET-1 overexpression exacerbates high-fat diet (HFD)-induced atherosclerosis using oil red O staining of descending thoracic aorta. HFD increased lipid plaques by 3-, 27-, and 86-fold in eET-1, apoE(-/-), and crossed mice, respectively, vs. WT. This suggests that increased endothelial ET-1 expression results in early changes in gene expression in the vascular wall that enhance lipid biosynthesis and accelerate progression of atherosclerosis.

Induction of cardiac angiogenesis requires killer cell lectin-like receptor 1 and α4β7 integrin expression by NK cells

Recent findings indicate that NK cells are involved in cardiac repair following myocardial infarction. The aim of this study is to investigate the role NK cells in infarct angiogenesis and cardiac remodeling. In normal C57BL/6 mice, myelomonocytic inflammatory cells invaded infarcted heart within 24 h followed by a lymphoid/NK cell infiltrate by day 6, accompanied by substantial expression of IL-2, TNF-α, and CCL2. In contrast, NOD SCID mice had virtually no lymphoid cells infiltrating the heart and did not upregulate IL-2 levels. In vitro and in vivo, IL-2-activated NK cells promoted TNF-α-stimulated endothelial cell proliferation, enhanced angiogenesis and reduced fibrosis within the infarcted myocardium. Adoptive transfer of IL-2-activated NK cells to NOD SCID mice improved post-myocardial infarction angiogenesis. RNA silencing technology and neutralizing Abs demonstrated that this process involved α4β7 integrin/VCAM-1 and killer cell lectin-like receptor 1/N-cadherin-specific binding. In this study, we show that IL-2-activated NK cells reduce myocardial collagen deposition along with an increase in neovascularization following acute cardiac ischemia through specific interaction with endothelial cells. These data define a potential role of activated NK cells in cardiac angiogenesis and open new perspectives for the treatment of ischemic diseases.

Monocyte Derivatives Promote Angiogenesis and Myocyte Survival in a Model of Myocardial Infarction

In this study, we have investigated the hypothesis that previously reported beneficial effect of peripheral blood mononuclear cells cultured under angiogenic conditions on cardiovascular function following ischemia is not limited to EPCs but also to monocytes contained therein. We first purified and analyzed the phenotype and secretome of human and murine blood monocytes cultured under angiogenic conditions (named MDs for monocyte derivatives) and tested their effect in a mouse model of myocardial infarction (MI). FACS analysis of MDs shows that these cells express mature endothelial cell markers and that their proliferative capacity is virtually absent, consistent with their end-differentiated monocytic ontogeny. MDs secreted significant levels of HGF, IGF-1, MCP-1, and sTNFR-1 relative to their monocyte precursors. MDs were unable to form vascular networks in vitro when cultured on matrix coated flasks. Treatment of murine HL-1 cardiomyocyte cell line with MD-conditioned medium reduced their death induced by TNF-α, staurosporine, and oxidative stress, and this effect was dependent upon MD-derived sTNFR-1, HGF, and IGF-1. We further demonstrate that MD secretome promoted endothelial cell proliferation and capacity to form vessels in vitro and this was dependent upon MD-derived MCP-1, HGF, and IGF-1. Echocardiography analysis showed that MD myocardial implantation improved left ventricle fractional shortening of mouse hearts following MI and was associated with reduced myocardial fibrosis and enhancement of angiogenesis. Transplanted MDs and their secretome participate in preserving functional myocardium after ischemic insult and attenuate pathological remodeling.

Immune regulation and vascular inflammation in genetic hypertension

Immune cells have been implicated in the pathogenesis of hypertension. We hypothesized that under the influence of chromosome (chr)2, T lymphocytes contribute to vascular inflammation in genetic salt-sensitive hypertension. Normotensive (Brown Norway), hypertensive (Dahl salt-sensitive), and consomic rats (SSBN2; in which chr2 has been transferred from Brown Norway to Dahl rats) were studied. Systolic blood pressure, measured by tail cuff, and aortic preproendothelin mRNA, measured by quantitative RT-PCR, were elevated in Dahl rats compared with Brown Norway rats and were reduced in SSBN2 rats compared with Dahl rats (P < 0.01). Compared with Brown Norway rats, Dahl rats exhibited increased inflammatory markers and mediators such as nuclear translocation of the aortic p65 subunit of NF-kappaB as well as VCAM-1, ICAM-1, chemokine (C-C motif) receptor 5, and CD4 mRNA, all of which were reduced in SSBN2 rats. Aortic CD8 mRNA was equally increased in Dahl and SSBN2 rats relative to Brown Norway rats. CD4(+) T cell infiltration in the aorta of SSBN2 rats was reduced compared with Dahl rats, whereas the aortic protein expression of Foxp3b and immunosuppressors transforming growth factor (TGF)-beta(1) and IL-10, the three markers associated with the regulatory T cell lineage, were enhanced in SSBN2 rats. Activation in vitro of T cells demonstrated that CD4(+)CD25(+) and CD8(+)CD25(+) cells (Tregs) produce IL-10 in SSBN2 rats. Thus, increased vascular inflammatory responses and hypertension in a genetic salt-sensitive hypertensive rodent model are reduced by transfer of chr2 from a normotensive strain, and this is associated with enhanced levels of immunosuppressive mediators.

Endothelial nitric oxide synthase uncoupling and perivascular adipose oxidative stress and inflammation contribute to vascular dysfunction in a rodent model of metabolic syndrome

The metabolic syndrome represents a constellation of cardiovascular risk factors that promote the development of cardiovascular disease. Oxidative stress is a mediator of endothelial dysfunction and vascular remodeling. We investigated vascular dysfunction in the metabolic syndrome and the oxidant mechanisms involved. New Zealand obese (NZO) mice with metabolic syndrome and New Zealand black control mice were studied. NZO mice showed insulin resistance and increased visceral fat and blood pressure compared with New Zealand black mice. Mesenteric resistance arteries from NZO mice exhibited increased media:lumen ratio and media cross-sectional area, demonstrating hypertrophic vascular remodeling. Endothelium-dependent relaxation to acetylcholine, assessed by pressurized myography, was impaired in NZO mice, not affected by N(G)-nitro-l-arginine methyl ester, inhibitor of endothelial NO synthase, and improved by the antioxidant Tempol, suggesting reduced NO bioavailability and increased oxidative stress. Dimer:monomer ratio of endothelial NO synthase was decreased in NZO mice compared with New Zealand black mice, suggesting endothelial NO synthase uncoupling. Furthermore, vascular superoxide and peroxynitrite production was increased, as well as adhesion molecule expression. Perivascular adipose tissue of NZO mice showed increased superoxide production and NADPH oxidase activity, as well as adipocyte hypertrophy, associated with inflammatory Mac-3-positive cell infiltration. Vasoconstriction to norepinephrine decreased in the presence of perivascular adipose tissue in New Zealand black mice but was unaffected by perivascular adipose tissue in NZO mice, suggesting loss of perivascular adipose tissue anticontractile properties. Our data suggest that this rodent model of metabolic syndrome is associated with perivascular adipose inflammation and oxidative stress, hypertrophic resistance artery remodeling, and endothelial dysfunction, the latter a result of decreased NO and enhanced superoxide generated by uncoupled endothelial NO synthase.

Aldosterone-induced activation of signaling pathways requires activity of angiotensin type 1a receptors

RATIONALE

Aldosterone has been shown to induce vascular damage, endothelial dysfunction, and myocardial fibrosis, which depend in part on activation of angiotensin II (Ang II)-mediated pathways. However, mechanisms underlying crosstalk between Ang II type 1 receptor (AT(1)R) and mineralocorticoid receptor (MR) are mostly unknown.

OBJECTIVES

We tested whether the lack of Ang II type 1a receptor (AT(1a)R) or Ang II type 1b receptor (AT(1b)R) would decrease cellular effects induced by aldosterone.

METHODS AND RESULTS

We examined the effect of Ang II or aldosterone after transfection of mesenteric vascular smooth muscle cells (VSMCs) from C57Bl/6 mice with small interference RNA for AT(1a)R, AT(1b)R, or MR for 48 hours. Ang II and aldosterone separately induced ERK1/2, c-Jun NH2-terminal protein kinase (JNK), and nuclear factor (NF)-kappaB phosphorylation after a 20-minute stimulation. Small interference RNA for AT(1a)R downregulated phosphorylation of ERK1/2, JNK, and NF-kappaB after aldosterone stimulation compared to controls. Downregulation of AT(1b)R or MR only abolished the activation of NF-kappaB. In VSMCs from C57Bl/6 mice, aldosterone and Ang II induced the activation of the c-fos promoter from 30 minutes to 1 hour. This effect was blocked when using VSMCs from AT(1a)R knockout mice.

CONCLUSION

We show for the first time that nongenomic and genomic effects of aldosterone are differentially dependent on activity of both AT(1a)R and AT(1b)R. Our data suggest that aldosterone augments AT(1)R-dependent activation of ERK1/2, JNK, and NF-kappaB in VSMCs. We provide mechanistic understanding and experimental in vitro support for the benefit of combination therapy with dual blockade of AT(1)R and MR to treat hypertension and progression of heart failure as reported in clinical studies and animal models.

Mechanisms of Angiotensin II-Dependent Progression to Heart Failure

Up-regulation of angiotensin II (AII) signalling plays an important role in the pathogenesis of cardiac hypertrophy and failure as evidenced by the efficacy of AII receptor blockers or inhibitors of AII biosynthesis in reversing ventricular hypertrophy and preventing human heart failure. The mechanisms underlying AII action in the heart remain undefined. Myocardial-specific expression of the AII type 1 receptor (AT1R) in mice is sufficient for inducing progressive myocyte hypertrophy and cardiac remodelling leading to adult heart failure with a disease progression course reminiscent of work overload-induced human heart failure. We examined the functional, structural and genetic changes associated with disease progression in this model. The results reveal that AT1R-dependent interaction between myocytes and non-myocytes is critical in cardiac remodelling. At the level of cardiomyocytes, decreased mitochondrial function is one of the earliest events of AII action leading to mitochondrial depletion and increased apoptosis. Up-regulation of cardiac Bcl-2 prevents mitochondrial deterioration, cardiomyocyte loss and pathologic remodelling. Importantly, Bcl-2 completely rescues premature death due to heart failure and maintains the 'compensated' state. The data suggest that targeting Bcl-2 or interfering with mitochondrial dysfunction may offer new therapeutic opportunities for preventing transition from compensated hypertrophy to heart failure.

Role of the renin-angiotensin system in vascular inflammation

Angiotensin (Ang) II, the main effector of the renin-angiotensin system (RAS), is one of the major mediators of vascular remodeling in hypertension. Besides being a potent vasoactive peptide, Ang II exerts proinflammatory effects on the vasculature by inducing integrins, adhesion molecules, cytokines and growth and profibrotic mediators through activation of redox-sensitive pathways and transcription factors. Clinical findings suggest that inflammation participates in the mechanisms involved in the pathophysiology of hypertension and its complications. Antagonists of the RAS have been shown to exert cardiovascular protection, in part through their vascular anti-inflammatory effects. However, further studies are needed to better understand whether inflammatory biomarkers might be clinically useful for cardiovascular risk stratification and whether targeting inflammation pharmacologically will improve cardiovascular outcomes beyond blood pressure reduction. The present review addresses recent findings regarding the pathophysiology of vascular inflammation in hypertension, focusing specifically on the role of Ang II.

Cardiac-specific overexpression of the human type 1 angiotensin II receptor causes delayed repolarization

AIMS

Mice with cardiac-specific overexpression of human angiotensin II type 1 receptor (AT1R) undergo cardiac remodelling and die prematurely of sudden death. Since excessive QT prolongation is a major risk factor for ventricular arrhythmias and sudden death, we hypothesize that chronic stimulation of AT1R might contribute to sudden death by promoting delayed repolarization and ventricular arrhythmias.

METHODS

In the present study, a detailed analysis of ventricular repolarization parameters was undertaken in AT1R mice.

RESULTS

Measurement of K+ currents in ventricular myocytes isolated from 6-8 months AT1R male mice revealed a significant reduction of the Ca2+-independent transient outward (I(to)), the ultra-rapid delayed rectifier (I Kur)), and the inward rectifier (I K1) K+ currents compared with littermate controls (CTL). The expression of the underlying K+ channels was also decreased in AT1R ventricles. Moreover, reactivation of I(to) was slower in AT1R mice. Consistent with these findings, AT1R mice presented a longer action potential duration (APD90, CTL: 19.0 +/- 1.8 ms; AT1R: 39.1 +/- 4.7 ms, P = 0.0001) and QTc interval (CTL: 53.6 +/- 1.5 ms, AT1R: 64.2 +/- 1.4 ms, P = 0.0005). In addition, spontaneous ventricular arrhythmias were reported in the AT1R mice. Importantly, the increased incidence of arrhythmia and the repolarization defects also occurred in much younger AT1R mice that do not present signs of hypertrophy, confirming that these arrhythmogenic changes are not secondary to cardiac remodelling.

CONCLUSION

These results strongly suggest that chronic stimulation of AT1R directly leads to an increased incidence of cardiac arrhythmia associated with delayed repolarization.

Cardiac BNP gene activation by angiotensin II in vivo

The transcription factors involved in the activation of cardiac gene expression by angiotensin II (Ang II) in vivo are not well understood. Here we studied the contribution of transcriptional elements to the activation of the cardiac B-type natriuretic peptide (BNP) gene promoter by Ang II in conscious rats and in angiotensin II type 1 receptor (AT1R) transgenic mice. Rat BNP luciferase reporter gene constructs were injected into the left ventricular wall. The mean luciferase activity was 1.8-fold higher (P<0.05) in the ventricles of animals subjected to 2-week Ang II infusion as compared with vehicle infusion. Our results indicate that GATA binding sites at -90 and -81 in the rat BNP promoter are essential for the in vivo response to Ang II. The GATA factor binding to these sites is GATA-4. BNP mRNA levels and GATA-4 binding activity are also increased in the hypertrophied hearts of aged AT1R transgenic mice.

Convergence of protein kinase C and JAK-STAT signaling on transcription factor GATA-4

Angiotensin II (AII), a potent vasoactive hormone, acts on numerous organs via G-protein-coupled receptors and elicits cell-specific responses. At the level of the heart, AII stimulation alters gene transcription and leads to cardiomyocyte hypertrophy. Numerous intracellular signaling pathways are activated in this process; however, which of these directly link receptor activation to transcriptional regulation remains undefined. We used the atrial natriuretic factor (ANF) gene (NPPA) as a marker to elucidate the signaling cascades involved in AII transcriptional responses. We show that ANF transcription is activated directly by the AII type 1 receptor and precedes the development of myocyte hypertrophy. This response maps to STAT and GATA binding sites, and the two elements transcriptionally cooperate to mediate signaling through the JAK-STAT and protein kinase C (PKC)-GATA-4 pathways. PKC phosphorylation enhances GATA-4 DNA binding activity, and STAT-1 functionally and physically interacts with GATA-4 to synergistically activate AII and other growth factor-inducible promoters. Moreover, GATA factors are able to recruit STAT proteins to target promoters via GATA binding sites, which are sufficient to support synergy. Thus, STAT proteins can act as growth factor-inducible coactivators of tissue-specific transcription factors. Interactions between STAT and GATA proteins may provide a general paradigm for understanding cell specificity of cytokine and growth factor signaling.

The zinc finger-only protein Zfp260 is a novel cardiac regulator and a nuclear effector of alpha1-adrenergic signaling

alpha1-Adrenergic receptors mediate several biological effects of catecholamines, including the regulation of myocyte growth and contractility and transcriptional regulation of the atrial natriuretic factor (ANF) gene whose promoter contains an alpha1-adrenergic response element. The nuclear pathways and effectors that link receptor activation to genetic changes remain poorly understood. Here, we describe the isolation by the yeast one-hybrid system of a cardiac cDNA encoding a novel nuclear zinc finger protein, Zfp260, belonging to the Krüppel family of transcriptional regulators. Zfp260 is highly expressed in the embryonic heart but is downregulated during postnatal development. Functional studies indicate that Zfp260 is a transcriptional activator of ANF and a cofactor for GATA-4, a key cardiac regulator. Knockdown of Zfp260 in cardiac cells decreases endogenous ANF gene expression and abrogates its response to alpha1-adrenergic stimulation. Interestingly, Zfp260 transcripts are induced by alpha1-adrenergic agonists and are elevated in genetic models of hypertension and cardiac hypertrophy. The data identify Zfp260 as a novel transcriptional regulator in normal and pathological heart development and a nuclear effector of alpha1-adrenergic signaling.

L'hygiène hospitalière et le conseil en antibiothérapie : un duo opérationnel face au problème de la diffusion des bactéries multirésistantes aux antibiotiques

OBJECTIVES

The authors had for aim to show that preventing the diffusion of multidrug-resistant organism (MRO) is possible thanks to the coordination of recommended preventive actions and the implementation of a sensible anti-infective prescription policy. They also wanted to highlight the role played by the nursing care staff in enforcing recommendations.

METHOD

We compared the results of two health care facilities having both implemented the same strategy aimed at preventing cross-transmission and prescribing anti-infective drugs.

RESULTS

Audits reported a very variable enforcement of recommendations. The results obtained from microbiological monitoring confirmed the essential impact of protocol enactment by every team, on the control of MRO diffusion. The antibiotherapy specialist has a key role in the suggested strategy, allowing a significant decrease in the number of anti-infective prescriptions and a more rational use.

CONCLUSION

The collaboration of a hygiene specialist with an antibiotherapy specialist has proved operational in the fight against MRO diffusion, as long as the competences of both specialists are acknowledged and their cross-disciplinary activities accepted. For the entire staff, enacting a corporate culture is a crucial asset.

Évaluation prospective de la prescription des glycopeptides dans un hôpital général

OBJECTIVE

The authors had for aim to analyze the indications, quality, and volumes of glycopeptide (GP) prescriptions in all in-patient units of a general hospital. CLINICAL MATERIAL AND METHODOLOGY: A 4 month prospective study assessed the compliance of curative and prophylactic treatment prescriptions administered according to guidelines. The assessment criteria were as follows: prescription indicated or not, prescription modalities (administration of loading dose, performing of serum tests, dosage appropriateness, appropriateness with antibiogram data when available).

RESULTS

Over the 46 assessed prescriptions, 84.7% were curative treatments (N = 39), whereas 15.2% (N = 7) were written out for surgical antibioprophylaxis. The prescription incidence and density were, respectively, 0.60 prescription/100 admissions and 20.8 DDJ/1000 hospitalization days, i.e. 24% of the total antibiotics budget. Prescriptions were always indicated for surgical antibioprophylaxis, but met standards in only 14% of cases. As for curative prescriptions, treatments were appropriate in 56.5% of cases, but only 18% met standards. GP use modalities proved incorrect at various levels: non existing load dose and lack of serum tests, subinhibiting daily doses, no dose lowering when possible, exaggerated duration of surgical antibioprophylaxis. Average GP serum levels were 16 mg/L and were higher than the target level in no more than 40% of properly prescribed treatments.

CONCLUSION

Prescription modalities and treatment monitoring must be improved, given the development of bacterial resistance.

Long-term effects of the PPAR gamma activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats

We investigated the long-term effects of the thiazolidinedione PPARgamma activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats (SHRSP), a model of malignant of hypertension. Six-week-old SHRSP were treated with pioglitazone (10 mg/kg per day p.o.) for 20 weeks. The rise in systolic blood pressure (SBP) in SHRSP was only transiently and slightly attenuated by pioglitazone (P < 0.05). On one hand, cardiac hypertrophy was little affected by the pioglitazone treatment, and there was only a reduction of subepicardial interstitial fibrosis. On the other hand, left ventricular NFkappaB and AP-1 binding activities, the expression of TNFalpha, and the adhesion of molecule PECAM were significantly decreased by pioglitazone treatment. Expression of the pro-apoptotic proteins p53 and bax was significantly increased by pioglitazone. Thus, pioglitazone-attenuated cardiac inflammation in SHRSP had little effect on BP or cardiac hypertrophy. PPARgamma activation may play a preventive cardiovascular role by offsetting the cardiac inflammatory response as demonstrated in this genetic model of malignant hypertension.

Essential role of GATA-4 in cell survival and drug-induced cardiotoxicity

In recent years, significant progress has been made in understanding cardiomyocyte differentiation. However, little is known about the regulation of myocyte survival despite the fact that myocyte apoptosis is a leading cause of heart failure. Here we report that transcription factor GATA-4 is a survival factor for differentiated, postnatal cardiomyocytes and an upstream activator of the antiapoptotic gene Bcl-X. An early event in the cardiotoxic effect of the antitumor drug doxorubicin is GATA-4 depletion, which in turn causes cardiomyocyte apoptosis. Mouse heterozygotes for a null Gata4 allele have enhanced susceptibility to doxorubicin cardiotoxicity. Genetic or pharmacologic enhancement of GATA-4 prevents cardiomyocyte apoptosis and drug-induced cardiotoxicity. The results indicate that GATA-4 is an antiapoptotic factor required for the adaptive stress response of the adult heart. Modulation of survival/apoptosis genes by tissue-specific transcription factors may be a general paradigm that can be exploited effectively for cell-specific regulation of apoptosis in disease states.

Peroxisome proliferator-activated receptor-alpha and receptor-gamma activators prevent cardiac fibrosis in mineralocorticoid-dependent hypertension

Peroxisome proliferator-activated receptor (PPAR) activation may prevent cardiac hypertrophy and inhibit production of endothelin-1 (ET-1), a hypertrophic agent. The aim of this in vivo study was to investigate the effects of PPAR activators on cardiac remodeling in DOCA-salt rats, a model overexpressing ET-1. Unilaterally nephrectomized 16-week-old Sprague-Dawley rats (Uni-Nx) were randomly divided into 4 groups: control rats, DOCA-salt, DOCA-salt+rosiglitazone (PPAR-gamma activator, 5 mg/kg per day), and DOCA-salt+fenofibrate (PPAR-alpha activator, 100 mg/kg per day). After 3 weeks of treatment, mean arterial blood pressure was significantly increased in DOCA-salt by 36 mm Hg. Mean arterial blood pressure was normalized by coadministration of rosiglitazone but not by fenofibrate. Both PPAR activators prevented cardiac fibrosis and abrogated the increase in prepro-ET-1 mRNA content in the left ventricle of DOCA-salt rats. Coadministration of rosiglitazone or fenofibrate failed to prevent thickening of left ventricle (LV) walls as measured by echocardiography and the increase in atrial natriuretic peptide mRNA levels. However, rosiglitazone and fenofibrate prevented the decrease in LV internal diameter and thus concentric remodeling of the LV found in DOCA-salt rats. Taken together, these data indicate a modulatory role of PPAR activators on cardiac remodeling in mineralocorticoid-induced hypertension, in part associated with decreased ET-1 production.

Use of a biological peptide pump to study chronic peptide hormone action in transgenic mice. Direct and indirect effects of angiotensin II on the heart

Angiotensin II is a peptide hormone regulator of blood pressure and fluid balance in mammals. Evidence obtained largely in vitro has also suggested that angiotensin II has growth-promoting effects and that it might thereby contribute to such pathological phenomena as cardiac hypertrophy, a major risk factor for cardiovascular mortality. It has been difficult to test for the direct growth-promoting effects of angiotensin II in vivo, however, because of the generalized effects of the peptide on hemodynamics. To overcome this limitation and to test for cardiac-specific functions of angiotensin II, we generated transgenic mice expressing an angiotensin II-producing fusion protein exclusively in cardiac myocytes. Our findings are the first to distinguish between local and systemic effects of angiotensin II on the heart and introduce a novel technique for studying tissue-specific peptide function.

GATA4 mediates activation of the B-type natriuretic peptide gene expression in response to hemodynamic stress

To identify the mechanisms that couple hemodynamic stress to alterations in cardiac gene expression, DNA constructs containing the rat B-type natriuretic peptide (BNP) promoter were injected into the myocardium of rats, which underwent bilateral nephrectomy or were sham-operated. Ventricular BNP mRNA levels were induced about 4-fold; and the BNP reporter construct containing the proximal 2200 bp, 5-fold, in response to 1-d nephrectomy. Deletion of sequences between bp -2200 and -114 did not affect basal or inducible activity of the BNP promoter. An activator protein-1-like site and two tandem GATA elements are located within this 114-bp sequence. Both deletion and mutation of the AP-1-like motif decreased basal activity but did not abolish the response to nephrectomy. In contrast, mutation or deletion of -90 bp GATA-sites abrogated the response to hemodynamic stress. The importance of these GATA elements to BNP promoter activation was further confirmed by the corresponding 38-bp oligonucleotide conferring hemodynamic stress responsiveness to a minimal BNP promoter. In gel mobility shift assays, nephrectomy increased left ventricular BNP GATA4 binding activity significantly. In conclusion, GATA elements are necessary and sufficient to confer transcriptional activation of BNP gene in response to hemodynamic stress.

Serum response factor-GATA ternary complex required for nuclear signaling by a G-protein-coupled receptor

Endothelins are a family of biologically active peptides that are critical for development and function of neural crest-derived and cardiovascular cells. These effects are mediated by two G-protein-coupled receptors and involve transcriptional regulation of growth-responsive and/or tissue-specific genes. We have used the cardiac ANF promoter, which represents the best-studied tissue-specific endothelin target, to elucidate the nuclear pathways responsible for the transcriptional effects of endothelins. We found that cardiac-specific response to endothelin 1 (ET-1) requires the combined action of the serum response factor (SRF) and the tissue-restricted GATA proteins which bind over their adjacent sites, within a 30-bp ET-1 response element. We show that SRF and GATA proteins form a novel ternary complex reminiscent of the well-characterized SRF-ternary complex factor interaction required for transcriptional induction of c-fos in response to growth factors. In transient cotransfections, GATA factors and SRF synergistically activate atrial natriuretic factor and other ET-1-inducible promoters that contain both GATA and SRF binding sites. Thus, GATA factors may represent a new class of tissue-specific SRF accessory factors that account for muscle- and other cell-specific SRF actions.

Overexpression of angiotensin II type I receptor in cardiomyocytes induces cardiac hypertrophy and remodeling

Angiotensin II (AII) is a major determinant of arterial pressure and volume homeostasis, mainly because of its vascular action via the AII type 1 receptor (AT1R). AII has also been implicated in the development of cardiac hypertrophy because angiotensin I-converting enzyme inhibitors and AT1R antagonists prevent or regress ventricular hypertrophy in animal models and in human. However, because these treatments impede the action of AII at cardiac as well as vascular levels, and reduce blood pressure, it has been difficult to determine whether AII action on the heart is direct or a consequence of pressure-overload. To determine whether AII can induce cardiac hypertrophy directly via myocardial AT1R in the absence of vascular changes, transgenic mice overexpressing the human AT1R under the control of the mouse alpha-myosin heavy chain promoter were generated. Cardiomyocyte-specific overexpression of AT1R induced, in basal conditions, morphologic changes of myocytes and nonmyocytes that mimic those observed during the development of cardiac hypertrophy in human and in other mammals. These mice displayed significant cardiac hypertrophy and remodeling with increased expression of ventricular atrial natriuretic factor and interstitial collagen deposition and died prematurely of heart failure. Neither the systolic blood pressure nor the heart rate were changed. The data demonstrate a direct myocardial role for AII in the development of cardiac hypertrophy and failure and provide a useful model to elucidate the mechanisms of action of AII in the pathogenesis of cardiac diseases.

How to convince your manager to invest in an HIS preimplementation methodology for appraisal of material, process and human costs and benefits

Investing in information technology has become a crucial process in hospital management today. Medical and administrative managers are faced with difficulties in measuring medical information technology costs and benefits due to the complexity of the domain. This paper proposes a preimplementation methodology for evaluating and appraising material, process and human costs and benefits. Based on the users needs and organizational process analysis, the methodology provides an evaluative set of financial and non financial indicators which can be integrated in a decision making and investment evaluation process. We describe the first results obtained after a few months of operation for the Computer-Based Patient Record (CPR) project. Its full acceptance, in spite of some difficulties, encourages us to diffuse the method for the entire project.

Cooperative interaction between GATA-4 and GATA-6 regulates myocardial gene expression

Two members of the GATA family of transcription factors, GATA-4 and GATA-6, are expressed in the developing and postnatal myocardium and are equally potent transactivators of several cardiac promoters. However, several in vitro and in vivo lines of evidence suggest distinct roles for the two factors in the heart. Since identification of the endogenous downstream targets of GATA factors would greatly help to elucidate their exact functions, we have developed an adenovirus-mediated antisense strategy to specifically inhibit GATA-4 and GATA-6 protein production in postnatal cardiomyocytes. Expression of several endogenous cardiac genes was significantly down-regulated in cells lacking GATA-4 or GATA-6, indicating that these factors are required for the maintenance of the cardiac genetic program. Interestingly, transcription of some genes like the alpha- and beta-myosin heavy-chain (alpha- and beta-MHC) genes was preferentially regulated by GATA-4 due, in part, to higher affinity of GATA-4 for their promoter GATA element. However, transcription of several other genes, including the atrial natriuretic factor and B-type natriuretic peptide (ANF and BNP) genes, was similarly down-regulated in cardiomyocytes lacking one or both GATA factors, suggesting that GATA-4 and GATA-6 could act through the same transcriptional pathway. Consistent with this, GATA-4 and GATA-6 were found to colocalize in postnatal cardiomyocytes and to interact functionally and physically to provide cooperative activation of the ANF and BNP promoters. The results identify for the first time bona fide in vivo targets for GATA-4 and GATA-6 in the myocardium. The data also show that GATA factors act in concert to regulate distinct subsets of genes, suggesting that combinatorial interactions among GATA factors may differentially control various cellular processes.

High dose rate intracoronary radiation for inhibition of neointimal formation in the stented and balloon-injured porcine models of restenosis: angiographic, morphometric, and histopathologic analyses

PURPOSE

We examined the effects of intracoronary irradiation delivered at a high dose rate on neointimal hyperplasia after injury induced by two methods: balloon overstretch injury, and stent implantation in a porcine model of coronary restenosis.

METHODS AND MATERIALS

In 34 Hanford miniature swine, a segment of each coronary artery was targeted for injury and treatment. The artery segments were treated with 192Ir at doses of 10 Gy over 4 min (eight animals), 15 Gy over 6 min (nine animals), 25 Gy over 10 min (nine animals) or control (simulation wire only; eight animals). The treated segments were subjected to stent implantation (left anterior descending and right coronary artery) or balloon overstretch (circumflex) injury. Twenty-eight days later, repeat coronary angiography and sacrifice were done. Quantitative coronary angiography, morphometry, and extensive histopathologic analyses were carried out in a blinded fashion.

RESULTS

The change in minimal lumen diameter from postinjury to presacrifice in the stent-injured left anterior descending was -0.79 +/- 0.34 (mean: +/- SD) mm in the control group, compared to -0.43 +/- 0.35 mm in the 15 Gy (p = 0.04) and -0.21 +/- 0.50 mm in the 25 Gy (p = 0.01) groups; and in the balloon-injured circumflex was -0.31 +/- 0.22 mm in the control group compared to -0.03 +/- 0.18 mm in the 10 Gy (p = 0.05) and 0.00 +/- 0.33 in the 15 Gy (p = 0.01) groups. Percent area stenosis in the left anterior descending was 36 +/- 9% in the control group compared to 18 +/- 12% in the 15 Gy (p = 0.003) and 11 +/- 11% in the 25 Gy (p < 0.001) groups; and in the circumflex was 16 +/- 10% in the control groups, compared to 5 +/- 5% in the 15 Gy (p = 0.02) and 2 +/- 2% in the 25 Gy (p = 0.009) groups. Histopathology showed a striking reduction in the amount of neointima in the irradiated arteries compared with control vessels. Other radiation effects were stromal fibrin exudate, thinning of the media, and adventitial fibrosis and leukocyte infiltration in the radiated arterial segments.

CONCLUSIONS

High dose rate intracoronary irradiation with 192Ir effectively inhibits intimal proliferation after stent-induced as well as balloon-overstretch injury. This shorter treatment time (4 to 10 min) may provide a clinically practical approach to the prevention of restenosis after angioplasty.