Complement C5a receptors C5L2 and C5aR in renal fibrosis.

Complement factor C5a has two known receptors, C5aR, which mediates proinflammatory effects, and C5L2, a potential C5a decoy receptor. We previously identified C5a/C5aR signaling as a potent profibrotic pathway in the kidney. Here we tested for the first time the role of C5L2 in renal fibrosis. In unilateral ureteral obstruction (UUO)-induced kidney fibrosis, the expression of C5aR and C5L2 increased similarly and gradually as fibrosis progressed and was particularly prominent in injured dilated tubules. Genetic deficiency of either C5aR or C5L2 significantly reduced UUO-induced tubular injury. Expression of key proinflammatory mediators, however, significantly increased in C5L2- compared with C5aR-deficient mice, but this had no effect on the number of renal infiltrating macrophages or T cells. Moreover, in C5L2-/- mice, the cytokine and matrix metalloproteinase-inhibitor tissue inhibitor of matrix metalloproteinase-1 was specifically enhanced. Consequently, in C5L2-/- mice the degree of renal fibrosis was similar to wild type (WT), albeit with reduced mRNA expression of some fibrosis-related genes. In contrast, C5aR-/- mice had significantly reduced renal fibrosis compared with WT and C5L2-/- mice in UUO. In vitro experiments with primary tubular cells demonstrated that deficiency for either C5aR or C5L2 led to a significantly reduced expression of tubular injury and fibrosis markers. Vice versa, stimulation of WT tubular cells with C5a significantly induced the expression of these markers, whereas the absence of either receptor abolished this induction. In conclusion, in experimental renal fibrosis C5L2 and C5aR both contribute to tubular injury, and, while C5aR acts profibrotic, C5L2 does not play a role in extracellular matrix accumulation, arguing against C5L2 functioning simply as a decoy receptor.

High expression of C5L2 correlates with high proinflammatory cytokine expression in advanced human atherosclerotic plaques.

The complement anaphylatoxin C5a functions through its two receptors, C5aR (CD88) and C5a receptor-like 2 (C5L2). Their role in atherosclerosis is incompletely understood. We, therefore, analyzed C5aR and probed the yet unknown expression and function of C5L2 in human atherogenesis. Human atherosclerotic plaques obtained by endarterectomy were staged and analyzed for C5L2 and C5aR by IHC and quantitative real-time PCR. C5L2-expressing cells in plaques were mostly macrophages, less neutrophils and endothelial cells, as determined by double immunostaining. Although early influx of C5aR(+) cells was detected, C5L2 levels increased with lesion complexity and colocalized with C5aR and oxidized low-density lipoprotein. Gene expression of C5L2 and C5aR showed similar trends, such as the receptor-expressing cells. The expression of C5L2 in advanced lesions correlated with increased levels of IL-1ß and tumor necrosis factor-α in plaques. Furthermore, in vitro experiments in macrophages from wild-type and C5l2- and C5ar-deficient mice corroborated the contributing role of C5l2 in oxidized low-density lipoprotein-pretreated C5a-induced cytokine expression, as measured by enzyme-linked immunosorbent assay. Finally, C5l2- and C5ar-deficient peripheral blood mononuclear cells showed less arrest on tumor necrosis factor-α-stimulated mouse endothelial cells in vitro when compared with wild-type controls. Taken together, prominent C5L2 expression in advanced atherosclerotic stages directly correlates with high levels of proinflammatory cytokines. This might indicate a proinflammatory role of C5L2 in atherosclerosis that needs to be pursued in the future by applying in vivo mouse models.

Deficiency of endothelial CXCR4 reduces reendothelialization and enhances neointimal hyperplasia after vascular injury in atherosclerosis-prone mice.

OBJECTIVE: The Cxcl12/Cxcr4 chemokine ligand/receptor axis mediates the mobilization of smooth muscle cell progenitors, driving injury-induced neointimal hyperplasia. This study aimed to investigate the role of endothelial Cxcr4 in neointima formation. APPROACH AND RESULTS: ß-Galactosidase staining using bone marrow x kinase (Bmx)-CreER(T2) reporter mice and double immunofluorescence revealed an efficient and endothelial-specific deletion of Cxcr4 in Bmx-CreER(T2+) compared with Bmx-CreER(T2-) Cxcr4-floxed apolipoprotein E-deficient (Apoe(-/-)) mice (referred to as Cxcr4(EC-KO)ApoE(-/-) and Cxcr4(EC-WT) ApoE(-/-), respectively). Endothelial Cxcr4 deficiency significantly increased wire injury-induced neointima formation in carotid arteries from Cxcr4(EC-KO)ApoE(-/-) mice. The lesions displayed a higher number of macrophages, whereas the smooth muscle cell and collagen content were reduced. This was associated with a significant reduction in reendothelialization and endothelial cell proliferation in injured Cxcr4(EC-KO)ApoE(-/-) carotids compared with Cxcr4(EC-WT)ApoE(-/-) controls. Furthermore, stimulation of human aortic endothelial cells with chemokine (C-X-C motif) ligand 12 (CXCL12) significantly enhanced their wound-healing capacity in an in vitro scratch assay, an effect that could be reversed with the CXCR4 antagonist AMD3100. Also, flow cytometric analysis showed a reduced mobilization of Sca1(+)Flk1(+)Cd31(+) and of Lin(-)Sca1(+) progenitors in Cxcr4(EC-KO) ApoE(-/-) mice after vascular injury, although Cxcr4 surface expression was unaltered. No differences could be detected in plasma concentrations of Cxcl12, vascular endothelial growth factor, sphingosine 1-phosphate, or Flt3 (fms-related tyrosine kinase 3) ligand, all cytokines with an established role in progenitor cell mobilization. Nonetheless, double immunofluorescence revealed a significant reduction in local endothelial Cxcl12 staining in injured carotids from Cxcr4(EC-KO)ApoE(-/-) mice. CONCLUSIONS: Endothelial Cxcr4 is crucial for efficient reendothelialization after vascular injury through endothelial wound healing and proliferation, and through the mobilization of Sca1(+)Flk1(+)Cd31(+) cells, often referred to as circulating endothelial progenitor cells.

Hematopoietic interferon regulatory factor 8-deficiency accelerates atherosclerosis in mice.

OBJECTIVE: Inflammatory leukocyte accumulation drives atherosclerosis. Although monocytes/macrophages and polymorphonuclear neutrophilic leukocytes (PMN) contribute to lesion formation, sequelae of myeloproliferative disease remain to be elucidated. METHODS AND RESULTS: We used mice deficient in interferon regulatory factor 8 (IRF8(-/-)) in hematopoietic cells that develop a chronic myelogenous leukemia-like phenotype. Apolipoprotein E-deficient mice reconstituted with IRF8(-/-) or IRF8(-/-) apolipoprotein E-deficient bone marrow displayed an exacerbated atherosclerotic lesion formation compared with controls. The chronic myelogenous leukemia-like phenotype in mice with IRF8(-/-) bone marrow, reflected by an expansion of PMN in the circulation, was associated with an increased lesional accumulation and apoptosis of PMN, and enlarged necrotic cores. IRF8(-/-) compared with IRF8(+/+) PMN displayed unaffected reactive oxygen species formation and discharge of PMN granule components. In contrast, accumulating in equal numbers at sites of inflammation, IRF8(-/-) macrophages were defective in efferocytosis, lipid uptake, and interleukin-10 cytokine production. Importantly, depletion of PMN in low-density lipoprotein receptor or apolipoprotein E-deficient mice with IRF8(-/-) or IRF8(-/-) apolipoprotein E-deficient bone marrow abrogated increased lesion formation. CONCLUSIONS: These findings indicate that a chronic myelogenous leukemia-like phenotype contributes to accelerated atherosclerosis in mice. Among proatherosclerotic effects of other cell types, this, in part, is linked to an expansion of functionally intact PMN.

C5a receptor targeting in neointima formation after arterial injury in atherosclerosis-prone mice.

BACKGROUND: Receptor binding of complement C5a leads to proinflammatory activation of many cell types, but the role of receptor-mediated action during arterial remodeling after injury has not been studied. In the present study, we examined the contribution of the C5a receptor (C5aR) to neointima formation in apolipoprotein E-deficient mice employing a C5aR antagonist (C5aRA) and a C5aR-blocking monoclonal antibody. METHODS AND RESULTS: Mice fed an atherogenic diet were subjected to wire-induced endothelial denudation of the carotid artery and treated with C5aRA and anti-C5aR-blocking monoclonal antibody or vehicle control. Compared with controls, neointima formation was significantly reduced in mice receiving C5aRA or anti-C5aR-blocking monoclonal antibody for 1 week but not for 3 weeks, attributable to an increased content of vascular smooth muscle cells, whereas a marked decrease in monocyte and neutrophil content was associated with reduced vascular cell adhesion molecule-1. As assessed by immunohistochemistry, reverse transcription polymerase chain reaction, and flow cytometry, C5aR was expressed in lesional and cultured vascular smooth muscle cells, upregulated by injury or tumor necrosis factor-alpha, and reduced by C5aRA. Plasma levels and neointimal plasminogen activator inhibitor-1 peaked 1 week after injury and were downregulated in C5aRA-treated mice. In vitro, C5a induced plasminogen activator inhibitor-1 expression in endothelial cells and vascular smooth muscle cells in a C5aRA-dependent manner, possibly accounting for higher vascular smooth muscle cell immigration. CONCLUSIONS: One-week treatment with C5aRA or anti-C5aR-blocking monoclonal antibody limited neointimal hyperplasia and inflammatory cell content and was associated with reduced vascular cell adhesion molecule-1 expression. However, treatment for 3 weeks failed to reduce but rather stabilized plaques, likely by reducing vascular plasminogen activator inhibitor-1 and increasing vascular smooth muscle cell migration.

CX3CR1 is required for monocyte homeostasis and atherogenesis by promoting cell survival.

CX(3)CR1 is a chemokine receptor with a single ligand, the membrane-tethered chemokine CX(3)CL1 (fractalkine). All blood monocytes express CX(3)CR1, but its levels differ between the main 2 subsets, with human CD16(+) and murine Gr1(low) monocytes being CX(3)CR1(hi). Here, we report that absence of either CX(3)CR1 or CX(3)CL1 results in a significant reduction of Gr1(low) blood monocyte levels under both steady-state and inflammatory conditions. Introduction of a Bcl2 transgene restored the wild-type phenotype, suggesting that the CX(3)C axis provides an essential survival signal. Supporting this notion, we show that CX(3)CL1 specifically rescues cultured human monocytes from induced cell death. Human CX(3)CR1 gene polymorphisms are risk factors for atherosclerosis and mice deficient for the CX(3)C receptor or ligand are relatively protected from atherosclerosis development. However, the mechanistic role of CX(3)CR1 in atherogenesis remains unclear. Here, we show that enforced survival of monocytes and plaque-resident phagocytes, including foam cells, restored atherogenesis in CX(3)CR1-deficent mice. The fact that CX(3)CL1-CX(3)CR1 interactions confer an essential survival signal, whose absence leads to increased death of monocytes and/or foam cells, might provide a mechanistic explanation for the role of the CX(3)C chemokine family in atherogenesis.

Protective role of CXC receptor 4/CXC ligand 12 unveils the importance of neutrophils in atherosclerosis.

The CXC ligand (CXCL)12/CXC receptor (CXCR)4 chemokine-receptor axis controls hematopoiesis, organ development, and angiogenesis, but its role in the inflammatory pathogenesis of atherosclerosis is unknown. Here we show that interference with Cxcl12/Cxcr4 by a small-molecule antagonist, genetic Cxcr4 deficiency, or lentiviral transduction with Cxcr4 degrakine in bone marrow chimeras aggravated diet-induced atherosclerosis in apolipoprotein E-deficient (Apoe-/-) or LDL receptor-deficient (Ldlr-/-) mice. Chronic blockade of Cxcr4 caused leukocytosis and an expansion of neutrophils and increased neutrophil content in plaques, associated with apoptosis and a proinflammatory phenotype. Whereas circulating neutrophils were recruited to atherosclerotic lesions, depletion of neutrophils reduced plaque formation and prevented its exacerbation after blocking Cxcr4. Disrupting Cxcl12/Cxcr4 thus promotes lesion formation through deranged neutrophil homeostasis, indicating that Cxcl12/Cxcr4 controls the important contribution of neutrophils to atherogenesis in mice.

Importance of junctional adhesion molecule-C for neointimal hyperplasia and monocyte recruitment in atherosclerosis-prone mice-brief report.

OBJECTIVE: Although junctional adhesion molecule (JAM)-C has been implicated in the control of inflammatory leukocyte recruitment, its role in neointima formation after arterial injury has not been elucidated. METHODS AND RESULTS: In apolipoprotein E-deficient (Apoe(-/-)) mice fed an atherogenic diet, antibody blockade of JAM-C significantly reduced neointimal hyperplasia after wire injury of carotid arteries without altering medial area and decreased neointimal macrophage but not smooth muscle cell (SMC) content. An increased expression of JAM-C was detected in colocalization with luminal SMCs 1 day after injury and neointimal SMCs after 3 weeks. Blocking JAM-C inhibited monocytic cell arrest and leukocyte adhesion to carotid arteries perfused ex vivo and in vivo. Furthermore, monocyte adhesion to activated coronary artery SMCs under flow conditions in vitro was diminished by blocking JAM-C. CONCLUSIONS: Our data provide the first evidence for a crucial role of JAM-C in accelerated lesion formation and leukocyte recruitment in atherosclerosis-prone mice.

Differential Role for Activating FcγRIII in Neointima Formation After Arterial Injury and Diet-Induced Chronic Atherosclerosis in Apolipoprotein E-Deficient Mice.

Atherogenesis and arterial remodeling following mechanical injury are driven by inflammation and mononuclear cell infiltration. The binding of immune complexes (ICs) to immunoglobulin (Ig)-Fc gamma receptors (FcγRs) on most innate and adaptive immune cells induces a variety of inflammatory responses that promote atherogenesis. Here, we studied the role of FcγRIII in neointima formation after arterial injury in atherosclerosis-prone mice and compared the outcome and mechanism to that of FcγRIII in diet-induced "chronic" atherosclerosis. FcγrIII-/-/Apoe-/- and control Apoe-/- mice were subjected to wire-induced endothelial denudation of the carotid artery while on high-fat diet (HFD). FcγrIII deficiency mitigated neointimal plaque formation and lesional macrophage accumulation, and enhanced neointimal vascular smooth muscle cell (VSMC) numbers. This went along with a reduced expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1/CCL2), and vascular cell adhesion molecule-1 (VCAM-1) in the neointimal lesions. Interestingly, in a chronic model of diet-induced atherosclerosis, we unraveled a dichotomic role of FcγRIII in an early versus advanced stage of the disease. While FcγrIII deficiency conferred atheroprotection in the early stage, it promoted atherosclerosis in advanced stages. To this end, FcγrIII deficiency attenuated pro-inflammatory responses in early atherosclerosis but promoted these events in advanced stages. Analysis of the mechanism(s) underlying the athero-promoting effect of FcγrIII deficiency in late-stage atherosclerosis revealed increased serum levels of anti-oxidized-LDL immunoglobulins IgG2c and IgG2b. This was paralleled by enhanced lesional accumulation of IgGs without affecting levels of complement-activated products C5a or C5ar1, FcγRII, and FcγRIV. Moreover, FcγrIII-deficient macrophages expressed more FcγrII, Tnf-α, and Il-1ß mRNA when exposed to IgG1 or oxLDL-IgG1 ICs in vitro, and peripheral CD4+ and CD8+ T-cell levels were altered. Collectively, our data suggest that deficiency of activating FcγRIII limits neointima formation after arterial injury in atherosclerosis-prone mice as well as early stage chronic atherosclerosis, but augments late-stage atherosclerosis suggesting a dual role of FcγRIII in atherogenic inflammation.

C1-esterase inhibitor protects against neointima formation after arterial injury in atherosclerosis-prone mice.

BACKGROUND: Although activation of the complement system has been implicated in the progression of human atherosclerosis, its function during arterial remodeling after injury has not been investigated. Here, we examined the contribution of the complement cascade to neointima formation in apolipoprotein E-deficient mice using a C1-esterase inhibitor (C1-inhibitor). METHODS AND RESULTS: Apolipoprotein E-deficient mice fed an atherogenic diet were subjected to wire-induced endothelial denudation of the carotid artery and treated with C1-inhibitor (Berinert; 15 IU i.v.) or vehicle perioperatively and subsequently every 2 days. The effectiveness of C1-inhibitor treatment was confirmed by measurement of plasma C1-inhibitor activity. A significant reduction in serum triglyceride levels was observed in C1-inhibitor-treated mice, whereas cholesterol levels did not differ. After 3 weeks, neointimal area was significantly reduced in C1-inhibitor-treated mice versus controls, whereas medial area was unaltered. This was associated with a significant decrease in neointimal and medial macrophage and CD3+ T-cell content. Expression of C3 mRNA was significantly reduced in plaques of C1-inhibitor-treated mice 10 days after injury, as assessed by reverse-transcription polymerase chain reaction. The peak in serum C3 levels after injury was markedly downregulated by C1-inhibitor, as evidenced by ELISA. Immunohistochemistry revealed strong expression of C3 and C3c, which colocalized to plaque macrophages and was reduced in C1-inhibitor-treated mice. C1-inhibitor impaired monocyte arrest on activated endothelium and platelets under flow conditions in vitro and leukocyte recruitment to carotid arteries 1 day after injury in vivo. CONCLUSIONS: C1-inhibitor limits neointimal plaque formation and inflammation. This may involve blockade of complement activation, inhibition of leukocyte recruitment, and reduced triglyceride levels, thus providing a multimodal approach to treat arterial disease.

Novel role for inhibitor of differentiation 2 in the genesis of angiotensin II-induced hypertension.

BACKGROUND: Angiotensin (Ang) II-induced target-organ damage involves innate and acquired immunity. Mice deficient for the helix-loop-helix transcription factor inhibitor of differentiation (Id2(-/-)) lack Langerhans and splenic CD8a+ dendritic cells, have reduced natural killer cells, and have altered CD8 T-cell memory. We tested the hypothesis that an alteration in the number and quality of circulating blood cells caused by Id2 deletion would ameliorate Ang II-induced target-organ damage. METHODS AND RESULTS: We used gene-deleted and transgenic mice. We conducted kidney and bone marrow transplants. In contrast to Ang II-infused Id2(+/-), Id2(-/-) mice infused with Ang II remained normotensive and failed to develop albuminuria or renal damage. Bone marrow transplant of Id2(+/-) bone marrow to Id2(-/-) mice did not restore the blunted blood pressure response to Ang II. Transplantation of Id2(-/-) kidneys to Id2(+/-) mice also could not prevent Ang II-induced hypertension and renal damage. We verified the Ang II resistance in Id2(-/-) mice in a model of local tissue Ang II production by crossing hypertensive mice transgenic for rat angiotensinogen with Id2(-/-) or Id2(+/-) mice. Angiotensinogen-transgenic Id2(+/-) mice developed hypertension, albuminuria, and renal injury, whereas angiotensinogen-transgenic Id2(-/-) mice did not. We also found that vascular smooth muscle cells from Id2(-/-) mice showed an antisenescence phenotype. CONCLUSIONS: Our bone marrow and kidney transplant experiments suggest that alterations in circulating immune cells or Id2 in the kidney are not responsible for Ang II resistance. The present studies identify a previously undefined role for Id2 in the pathogenesis of Ang II-induced hypertension.

Importance of CXC chemokine receptor 2 in the homing of human peripheral blood endothelial progenitor cells to sites of arterial injury.

Circulating endothelial progenitor cells (EPCs) may contribute to endothelial regeneration; however, the exact mechanisms of their arterial homing remain elusive. We examined the role of the angiogenic chemokine receptor CXCR2 in the homing of human EPCs. Isolated EPCs expressed CXCR2 together with kinase insert domain-containing receptor, CD31, vascular endothelial cadherin, and CXCR4. Adhesion assays under flow conditions showed that EPCs preferentially adhered to beta(2)-integrin ligands, that firm arrest on fibronectin or fibrinogen was enhanced by the CXCR2 ligands CXCL1 or CXCL7, and that blockade of CXCR2 significantly reduced EPC adhesion on platelet-coated endothelial matrix. This was corroborated by the involvement of CXCR2 in EPC recruitment to denuded areas of murine carotid arteries ex vivo and in vivo. Notably, blocking CXCR2 inhibited the incorporation of human EPCs expressing CXCR2 at sites of arterial injury in athymic nude mice. Immunoreactivity for the beta-thromboglobulin isoform CXCL7 was observed in murine platelets and denuded smooth muscle cells (SMCs) early after wire injury, and transcripts for CXCL7 and CXCL1 were detected in isolated human arterial SMCs. Human KDR(+)CXCR2(+) cells showed better in situ adhesion to injured murine carotid arteries than KDR(+)CXCR2(-) cells, were predominantly CD14(+), and improved CXCR2-dependent endothelial recovery after injury in nude mice. In conclusion, our data clearly demonstrate the importance of CXCR2 for the homing of circulating EPCs to sites of arterial injury and for endothelial recovery in vivo.

Chemokines in atherosclerosis: an update.

The fundamental importance of chemokines for atherogenesis, progression, and destabilization of atherosclerotic plaques is now widely appreciated, but the degree of complexity, specificity, and cooperativity harnessed by these signal molecules to govern atherogenic cell recruitment and homeostasis is still being refined. Since the role of chemokines in atherosclerotic vascular disease has been reviewed in this journal, significant progress has been accomplished in defining the regulation of chemokine expression and function in atherosclerosis. In this update, we will highlight these recent developments, in particular the identification of components regulating the transcriptional machinery of the proatherogenic chemokine CCL5, distinct roles of its receptors CCR1 and CCR5 in plaque formation and immunobalance, and differential site- and stage-specific effects of T cell-activating chemokines and their receptors, eg, CXCL10 and CXCR3. The contribution of the transmembrane chemokines CX(3)CL1 and CXCL16 with their respective receptors CX(3)CR1 and CXCR6 in the recruitment of T cell and monocyte subsets and shear-mediated plaque modulation will be discussed. Finally, the role of CXCR2 and CXCR4, their respective ligands CXCL1 and CXCL12, and the noncanonical dual agonist MIF in atheroprogression will be dissected. The considerable leap in insight over recent years leads us to anticipate further advances in comprehending the role of chemokines in atherosclerosis, allowing targeted interventions for its prevention and therapy.

Y-box binding protein-1 controls CC chemokine ligand-5 (CCL5) expression in smooth muscle cells and contributes to neointima formation in atherosclerosis-prone mice.

BACKGROUND: The CC chemokine CCL5/Regulated on Activation, Normal T Cell Expressed and Secreted (RANTES) is upregulated in mononuclear cells or deposited by activated platelets during inflammation and has been implicated in atherosclerosis and neointimal hyperplasia. We investigated the influence of the transcriptional regulator Y-box binding protein (YB)-1 on CCL5 expression and wire-induced neointimal hyperplasia. METHODS AND RESULTS: Analysis of the CCL5 promoter revealed potential binding sites for YB-1, and interaction of YB-1 with a sequence at position -204/-173 was confirmed by DNA binding assays. Both YB-1 expression and CC chemokine ligand-5 (CCL5) mRNA expression were increased in neointimal versus medial smooth muscle cells, as analyzed by real-time polymerase chain reaction. Overexpression of YB-1 in smooth muscle cells (but not macrophages) enhanced CCL5 transcriptional activity in reporter assays, mRNA and protein expression, and CCL5-mediated monocyte arrest. Carotid arteries of hyperlipidemic apolipoprotein E-deficient mice were subjected to intraluminal transfection with a lentivirus encoding YB-1 short hairpin RNA or empty vector directly after wire injury. Double immunofluorescence revealed YB-1 expression in neointimal smooth muscle cells but not macrophages and colocalization with neointimal CCL5, which was downregulated by YB-1 short hairpin RNA. Neointima formation was decreased significantly after YB-1 knockdown compared with controls and was associated with a diminished content of lesional macrophages. A reduction of lesion formation by YB-1 knockdown was not observed in apolipoprotein E-deficient mice deficient in the CCL5 receptor CCR5 or after treatment with the CCL5 antagonist Met-RANTES, which indicates that YB-1 effects were dependent on CCL5. CONCLUSIONS: The transcriptional regulator YB-1 mediates CCL5 expression in smooth muscle cells and thereby contributes to neointimal hyperplasia, thus representing a novel target with which to limit vascular remodeling.

Ccr5 but not Ccr1 deficiency reduces development of diet-induced atherosclerosis in mice.

OBJECTIVE: Chemokines and their receptors are crucially involved in the development of atherosclerotic lesions by directing monocyte and T cell recruitment. The CC-chemokine receptors 1 (CCR1) and 5 (CCR5) expressed on these cells bind chemokines implicated in atherosclerosis, namely CCL5/RANTES. Although general blockade of CCL5 receptors reduces atherosclerosis, specific roles of CCR1 and CCR5 have not been unequivocally determined. METHODS AND RESULTS: We provide two independent lines of investigation to dissect the effects of Ccr1 and Ccr5 deletion in apolipoprotein E-deficient (ApoE-/-) mice in a collaboration between Aachen/Germany and Geneva/Switzerland. Different strains of ApoE-/- Ccr5-/- mice, ApoE-/- Ccr1-/- mice or respective littermates, were fed a high-fat diet for 10 to 12 weeks. Plaque areas were quantified in the aortic roots and thoracoabdominal aortas. Concordantly, both laboratories found that lesion formation was reduced in ApoE-/- Ccr5-/- mice. Plaque quality and immune cells were assessed by immunohistochemistry or mRNA analysis. Whereas lesional macrophage content, aortic CD4, and Th1-related Tim3 expression were reduced, smooth muscle cell (SMC) content and expression of interleukin-10 in plaques, lesional SMCs, and splenocytes were elevated. Protection against lesion formation by Ccr5 deficiency was sustained over 22 weeks of high-fat diet or over 26 weeks of chow diet. Conversely, plaque area, T cell, and interferon-gamma content were increased in ApoE-/- Ccr1-/- mice. CONCLUSIONS: Genetic deletion of Ccr5 but not Ccr1 in ApoE-/- mice protects from diet-induced atherosclerosis, associated with a more stable plaque phenotype, reduced mononuclear cell infiltration, Th1-type immune responses, and increased interleukin-10 expression. This corroborates CCR5 as a promising therapeutic target.

Nf-kappab and AP-1 activation is associated with late lumen loss after porcine coronary angioplasty and antiproliferative beta-irradiation.

OBJECTIVE: Despite the success of antiproliferative therapies, restenosis remains a common problem after percutaneous transluminal coronary angioplasty (PTCA). Longer-term clinical results of brachytherapy (intracoronary radiation), the lack of long-term clinical results after implantation of drug eluting stents, and the occurrence of late thrombosis after both procedures leave room for skepticism. Neointimal proliferation is not substantially inhibited at late time points after brachytherapy, and late lumen loss with a "catch-up" proliferation can occur. We hypothesized that the transcription factors nuclear factor-{kappa}B (NF-kappaB) and activator protein-1 (AP-1) are involved in these processes. We addressed the role of these mediators in a porcine model of coronary restenosis. METHODS: Thirty-nine pigs underwent PTCA in two major coronary arteries. One of the two balloon-injured arteries was randomly assigned to receive immediate 20 Gy beta-irradiation (Brachy group) using a noncentered source train ((90)Sr/Y Beta-Cath, Novoste). Animals were sacrificed after 1 day, 14 days, or 28 days. Proliferating cells were labeled prior to euthanasia. RESULTS: At late time points, lumen area was significantly smaller and the inflammatory response was more pronounced in the Brachy group than in the PTCA group. These findings coincided with sustained activation of MMP-9 and transcription factors like NF-kappaB and AP-1. Initially, cell proliferation was reduced in the Brachy group; however, at late time points, differences between the two treatment groups were no longer significant. CONCLUSIONS: Brachytherapy initially inhibits cell proliferation; however, cellular and molecular inflammatory processes (e.g. activation of NF-kappaB) are enhanced within the arterial wall. This proinflammatory side effect may be responsible for the observed delayed proliferation and the resulting lumen loss.

Complement activation in angiotensin II-induced organ damage.

We tested whether or not complement activation participates in angiotensin (Ang) II-induced vasculopathy. We used double transgenic rats harboring human renin and angiotensinogen genes (dTGR) with or without losartan or the human renin inhibitor aliskiren. Sprague-Dawley (SD) rats were controls. DTGR had increased blood pressure at week 5 that increased further by week 7. Albuminuria was absent at week 5 but increased markedly in weeks 6 and 7. C-reactive protein (CRP) elevation, macrophages, T cells, tumor necrosis factor (TNF)-alpha, C1q, C3, C3c, and C5b-9 expression preceded albuminuria. C1q, C3, C3c, and C5b-9 were observed in the dTGR vessel media. C5b-9 colocalized with interleukin (IL)-6. Losartan and aliskiren reduced albuminuria and complement expression. We also studied vascular smooth muscle cells (VSMC) from dTGR compared VSMC from SD. C3 and IL-6 mRNA were analyzed after Ang II, TNF-alpha, and CRP stimulation. VSMC from dTGR showed increased proliferation and C3 expression compared with SD. Ang II did not induce C3 mRNA in either VSMC type. However, TNF-alpha and CRP induced C3 mRNA slightly in SD VSMC but markedly in dTGR VSMC, whereas IL-6 induction was similar in both. Thus, complement activation and cell infiltration occurred before the onset of albuminuria in Ang II-mediated renal damage. TNF-alpha and CRP played a major role in C3 activation. VSMC from dTGR are more sensitive for C3 activation. Our data show that, in this Ang II-induced model, complement activation is a major participant and suggest that TNF-alpha and CRP may play a role in its induction.

Low-dose renin inhibitor and low-dose AT(1)-receptor blocker therapy ameliorate target-organ damage in rats harbouring human renin and angiotensinogen genes.

We studied the effects of extremely low-dose human renin inhibition (aliskiren) with low angiotensin II receptor blockade (losartan) in a novel double-transgenic rat model harbouring both human renin and angiotensinogen genes. We found that low-dose aliskiren and low-dose losartan effectively reduced mortality and target-organ damage with minimal, non-significant, effects on blood pressure (BP). Our data suggest that renin-angiotensin system (RAS) inhibition ameliorates target-organ damage in an Ang II-driven model of hypertension. Direct renin inhibition is equally efficacious in this regard. Our study does not fully answer the question of BP-lowering versus RAS inhibition. This question is important and was at least partially addressed with our low-dose model.

Aldosterone synthase inhibitor ameliorates angiotensin II-induced organ damage.

BACKGROUND: Aldosterone and angiotensin (Ang) II both may cause organ damage. Circulating aldosterone is produced in the adrenals; however, local cardiac synthesis has been reported. Aldosterone concentrations depend on the activity of aldosterone synthase (CYP11B2). We tested the hypothesis that reducing aldosterone by inhibiting CYP11B2 or by adrenalectomy (ADX) may ameliorate organ damage. Furthermore, we investigated how much local cardiac aldosterone originates from the adrenal gland. METHODS AND RESULTS: We investigated the effect of the CYP11B2 inhibitor FAD286, losartan, and the consequences of ADX in transgenic rats overexpressing both the human renin and angiotensinogen genes (dTGR). dTGR-ADX received dexamethasone and 1% salt. Dexamethasone-treated dTGR-salt served as a control group in the ADX protocol. Untreated dTGR developed hypertension and cardiac and renal damage and had a 40% mortality rate (5/13) at 7 weeks. FAD286 reduced mortality to 10% (1/10) and ameliorated cardiac hypertrophy, albuminuria, cell infiltration, and matrix deposition in the heart and kidney. FAD286 had no effect on blood pressure at weeks 5 and 6 but slightly reduced blood pressure at week 7 (177+/-6 mm Hg in dTGR+FAD286 and 200+/-5 mm Hg in dTGR). Losartan normalized blood pressure during the entire study. Circulating and cardiac aldosterone levels were reduced in FAD286 or losartan-treated dTGR. ADX combined with dexamethasone and salt treatment decreased circulating and cardiac aldosterone to barely detectable levels. At week 7, ADX-dTGR-dexamethasone-salt had a 22% mortality rate compared with 73% in dTGR-dexamethasone-salt. Both groups were similarly hypertensive (190+/-9 and 187+/-4 mm Hg). In contrast, cardiac hypertrophy index, albuminuria, cell infiltration, and matrix deposition were significantly reduced after ADX (P<0.05). CONCLUSIONS: Aldosterone plays a key role in the pathogenesis of Ang II-induced organ damage. Both FAD286 and ADX reduced circulating and cardiac aldosterone levels. The present results show that aldosterone produced in the adrenals is the main source of cardiac aldosterone.

Cardiac gene expression profile in rats with terminal heart failure and cachexia.

About one-half of double transgenic rats (dTGR) overexpressing the human renin and angiotensinogen genes die by age 7 wk of terminal heart failure (THF); the other (preterminal) one-half develop cardiac damage but survive. Our study's aim was to elucidate cardiac gene expression differences in dTGR-THF compared with dTGR showing compensated cardiac hypertrophy but not yet THF. dTGR treated with losartan (LOS) and nontransgenic rats (SD) served as controls. THF-dTGR body weight was significantly lower than for all other groups. At death, THF-dTGR had blood pressures of 228 +/- 7 mmHg (cardiac hypertrophy index 6.2 +/- 0.1 mg/g). Tissue Doppler showed reduced peak early (Ea) to late (Aa) diastolic expansion in THF-dTGR, indicating diastolic function. Preterminal dTGR had blood pressures of 197 +/- 5 mmHg (cardiac hypertrophy index 5.1 +/- 0.1 mg/g); Ea < Aa compared with LOS-dTGR (141 +/- 6 mmHg; 3.7+/-0.1 mg/g; Ea > Aa) and SD (112 +/- 4 mmHg; 3.6 +/- 0.1 mg/g; Ea > Aa). Left ventricular RNA was isolated for the Affymetrix system and TaqMan RT-PCR. THF-dTGR and dTGR showed upregulation of hypertrophy markers and alpha/beta-myosin heavy chain switch to the fetal isoform. THF-dTGR (vs. dTGR) showed upregulation of 239 and downregulation of 150 genes. Various genes of mitochodrial respiratory chain and lipid catabolism were reduced. In addition, genes encoding transcription factors (CEBP-beta, c-fos, Fra-1), coagulation, remodeling/repair components (HSP70, HSP27, heme oxygenase), immune system (complement components, IL-6), and metabolic pathway were differentially expressed. In contrast, LOS-dTGR and SD had similar expression profiles. These data demonstrate that THF-dTGR show an altered expression profile compared with preterminal dTGR.