Biomedical subjects

David R Greaves

Publications and source records attributed to David R Greaves.

At least 19 recordsLinked to original sources

PubMed2007

Increased in-stent stenosis in ApoE knockout mice: insights from a novel mouse model of balloon angioplasty and stenting.

OBJECTIVE: We aimed to develop and validate a model of angioplasty and stenting in mice that would allow investigation of the response to stent injury using genetically modified mouse strains. METHODS AND RESULTS: Aortic segments from either C57BL/6 wild-type or atherosclerotic ApoE-KO mice underwent balloon angioplasty alone or balloon angioplasty and stenting with a 1.25x2.5 mm stainless steel stent. Vessels were carotid-interposition grafted into genetically identical littermate recipients and harvested at 1, 7, 14, or 28 days. In wild-type mice, stenting generated an inflammatory vascular injury response between days 1 to 7, leading to the development of neointimal hyperplasia by day 14, which further increased in area by day 28 leading to the development of in-stent stenosis. Uninjured vessels and vessels injured by balloon angioplasty alone developed minimal neointimal hyperplasia. In stented ApoE-KO mice, neointimal area at 28 days was 30% greater compared with wild-type mice. CONCLUSIONS: By reproducing important features of human stenting in atherosclerotic mice, we provide the potential to investigate molecular pathways and evaluate novel therapeutic targets for stent injury and restenosis.

Angioplasty, Balloon↗

PubMed2006

Interleukin-4 induction of the CC chemokine TARC (CCL17) in murine macrophages is mediated by multiple STAT6 sites in the TARC gene promoter.

BACKGROUND: Macrophages (Mtheta) play a central role in the innate immune response and in the pathology of chronic inflammatory diseases. Macrophages treated with Th2-type cytokines such as Interleukin-4 (IL-4) and Interleukin-13 (IL-13) exhibit an altered phenotype and such alternatively activated macrophages are important in the pathology of diseases characterised by allergic inflammation including asthma and atopic dermatitis. The CC chemokine Thymus and Activation-Regulated Chemokine (TARC/CCL17) and its murine homologue (mTARC/ABCD-2) bind to the chemokine receptor CCR4, and direct T-cell and macrophage recruitment into areas of allergic inflammation. Delineating the molecular mechanisms responsible for the IL-4 induction of TARC expression will be important for a better understanding of the role of Th2 cytokines in allergic disease. RESULTS: We demonstrate that mTARC mRNA and protein are potently induced by the Th2 cytokine, Interleukin-4 (IL-4), and inhibited by Interferon-gamma (IFN-gamma) in primary macrophages (Mtheta). IL-4 induction of mTARC occurs in the presence of PI3 kinase pathway and translation inhibitors, but not in the absence of STAT6 transcription factor, suggesting a direct-acting STAT6-mediated pathway of mTARC transcriptional activation. We have functionally characterised eleven putative STAT6 sites identified in the mTARC proximal promoter and determined that five of these contribute to the IL-4 induction of mTARC. By in vitro binding assays and transient transfection of isolated sites into the RAW 264.7 Mtheta cell-line, we demonstrate that these sites have widely different capacities for binding and activation by STAT6. Site-directed mutagenesis of these sites within the context of the mTARC proximal promoter revealed that the two most proximal sites, conserved between the human and mouse genes, are important mediators of the IL-4 response. CONCLUSION: The induction of mTARC by IL-4 results from cooperative interactions between STAT6 sites within the mTARC gene promoter. Significantly, we have shown that transfer of the nine most proximal mTARC STAT6 sites in their endogenous conformation confers potent (up to 130-fold) IL-4 inducibility on heterologous promoters. These promoter elements constitute important and sensitive IL-4-responsive transcriptional units that could be used to drive transgene expression in sites of Th2 inflammation in vivo.

Animals↗

PubMed2006

Membrane-bound CC chemokine inhibitor 35K provides localized inhibition of CC chemokine activity in vitro and in vivo.

CC chemokines mediate mononuclear cell recruitment and activation in chronic inflammation. We have shown previously that gene transfer using recombinant adenoviruses, encoding a soluble CC chemokine-binding protein of vaccinia virus 35K, can dramatically reduce atherosclerosis and vein graft remodeling in apolipoprotein E knockout mice. In this study, we report the development of a membrane-bound form of 35K (m35K), tagged with GFP, which allows for localized, broad-spectrum CC chemokine blockade. In vitro experiments indicate that m35K-expressing cells no longer undergo CC chemokine-induced chemotaxis, and m35K-expressing cells can locally deplete the CC chemokines RANTES (CCL5) and MIP-1alpha (CCL3) from supernatant medium. This sequestration of CC chemokines can prevent chemotaxis of bystander cells to CC, but not CX(3)C chemokines. Intraperitoneal injection of mice with an adenovirus-encoding m35K leads to a significant (44%) decrease in leukocyte recruitment into the peritoneal cavity in a sterile peritonitis model. Intravenous adenovirus-encoding m35K delivery leads to m35K expression in hepatocytes, which confers significant protection against liver damage (75% reduction in liver enzymes) in a Con A-induced hepatitis model. In summary, we have generated a membrane-bound CC chemokine-binding protein (m35K) that provides localized broad-spectrum CC chemokine inhibition in vitro and in vivo. m35K may be a useful tool to study the role of CC chemokines in leukocyte trafficking and block the recruitment of monocytes in chronic inflammation.

Animals↗

PubMed2006

Novel candidate genes in unstable areas of human atherosclerotic plaques.

OBJECTIVE: Comparison of gene expression in stable versus unstable atherosclerotic plaque may be confounded by interpatient variability. The aim of this study was to identify differences in gene expression between stable and unstable segments of plaque obtained from the same patient. METHODS AND RESULTS: Human carotid endarterectomy specimens were segmented and macroscopically classified using a morphological classification system. Two analytical methods, an intraplaque and an interplaque analysis, revealed 170 and 1916 differentially expressed genes, respectively using Affymetrix gene chip analysis. A total of 115 genes were identified from both analyses. The differential expression of 27 genes was also confirmed using quantitative-polymerase chain reaction on a larger panel of samples. Eighteen of these genes have not been associated previously with plaque instability, including the metalloproteinase, ADAMDEC1 (approximately 37-fold), retinoic acid receptor responder-1 (approximately 5-fold), and cysteine protease legumain (approximately 3-fold). Matrix metalloproteinase-9 (MMP-9), cathepsin B, and a novel gene, legumain, a potential activator of MMPs and cathepsins, were also confirmed at the protein level. CONCLUSIONS: The differential expression of 18 genes not previously associated with plaque rupture has been confirmed in stable and unstable regions of the same atherosclerotic plaque. These genes may represent novel targets for the treatment of unstable plaque or useful diagnostic markers of plaque instability.

Atherosclerosis↗

PubMed2006

Oxidative metabolism and PGC-1beta attenuate macrophage-mediated inflammation.

Complex interplay between T helper (Th) cells and macrophages contributes to the formation and progression of atherosclerotic plaques. While Th1 cytokines promote inflammatory activation of lesion macrophages, Th2 cytokines attenuate macrophage-mediated inflammation and enhance their repair functions. In spite of its biologic importance, the biochemical and molecular basis of how Th2 cytokines promote maturation of anti-inflammatory macrophages is not understood. We show here that in response to interleukin-4 (IL-4), signal transducer and activator of transcription 6 (STAT6) and PPARgamma-coactivator-1beta (PGC-1beta) induce macrophage programs for fatty acid oxidation and mitochondrial biogenesis. Transgenic expression of PGC-1beta primes macrophages for alternative activation and strongly inhibits proinflammatory cytokine production, whereas inhibition of oxidative metabolism or RNAi-mediated knockdown of PGC-1beta attenuates this immune response. These data elucidate a molecular pathway that directly links mitochondrial oxidative metabolism to the anti-inflammatory program of macrophage activation, suggesting a potential role for metabolic therapies in treating atherogenic inflammation.

Animals↗

PubMed2006

MafB is essential for renal development and F4/80 expression in macrophages.

MafB is a member of the large Maf family of transcription factors that share similar basic region/leucine zipper DNA binding motifs and N-terminal activation domains. Although it is well known that MafB is specifically expressed in glomerular epithelial cells (podocytes) and macrophages, characterization of the null mutant phenotype in these tissues has not been previously reported. To investigate suspected MafB functions in the kidney and in macrophages, we generated mafB/green fluorescent protein (GFP) knock-in null mutant mice. MafB homozygous mutants displayed renal dysgenesis with abnormal podocyte differentiation as well as tubular apoptosis. Interestingly, these kidney phenotypes were associated with diminished expression of several kidney disease-related genes. In hematopoietic cells, GFP fluorescence was observed in both Mac-1- and F4/80-expressing macrophages in the fetal liver. Interestingly, F4/80 expression in macrophages was suppressed in the homozygous mutant, although development of the Mac-1-positive macrophage population was unaffected. In primary cultures of fetal liver hematopoietic cells, MafB deficiency was found to dramatically suppress F4/80 expression in nonadherent macrophages, whereas the Mac-1-positive macrophage population developed normally. These results demonstrate that MafB is essential for podocyte differentiation, renal tubule survival, and F4/80 maturation in a distinct subpopulation of nonadherent mature macrophages.

Animals↗

PubMed2005

Gene transfer of a broad spectrum CC-chemokine inhibitor reduces vein graft atherosclerosis in apolipoprotein E-knockout mice.

BACKGROUND: Accelerated atherosclerosis is a major cause of vein graft failure after bypass surgery. Several CC-chemokines (CC-CKs) mediate monocyte/macrophage recruitment in native atherosclerotic plaques; we hypothesized that CC-CKs may be critical in the development of accelerated atherosclerosis in vein grafts. METHODS AND RESULTS: Using in vivo gene transfer, we administered a soluble CC-CK binding protein ("35K") to apolipoprotein E-knockout (ApoE-/-) mice that underwent interposition bypass grafting of the vena cava from isogenic donor mice to the common carotid artery. Two days before operation, a recombinant adenovirus encoding either 35K (Ad35K) or green fluorescent protein (AdGFP; control) was injected into recipient mice via the tail vein. 35K greatly reduced CC-CK activity in mouse plasma. After 14 days, vein graft atherosclerotic lesion area, smooth muscle alpha-actin-positive neointimal area, and total vessel wall thickness were strikingly reduced by Ad35K gene transfer compared with AdGFP controls. Furthermore, 35K gene transfer dramatically reduced macrophage content by approximately 90% and cell proliferation by 95%. After 28 days, lesion area and vessel wall thickness remained significantly less in Ad35K mice. CONCLUSIONS: A single intravenous injection of the CC-CK inhibitor 35K significantly reduced atherosclerosis in carotid-caval vein grafts in ApoE-/- mice. This study highlights the importance of the CC-CK class in accelerated atherosclerosis, and its role as a potential target for improving vein graft patency.

Adenoviridae↗

PubMed2005

deltaBAFF, a splice isoform of BAFF, opposes full-length BAFF activity in vivo in transgenic mouse models.

DeltaBAFF is a novel splicing isoform of the regulator B cell-activating factor (BAFF, BLyS), a TNF family protein with powerful immunoregulatory effects. Overexpression of BAFF leads to excessive B cell accumulation, activation, autoantibodies, and lupus-like disease, whereas an absence of BAFF causes peripheral B cell immunodeficiency. Based on the ability of DeltaBAFF to multimerize with full-length BAFF and to limit BAFF proteolytic shedding from the cell surface, we previously proposed a role for DeltaBAFF in restraining the effects of BAFF and in regulating B lymphocyte homeostasis. To test these ideas we generated mice transgenic for DeltaBAFF under the control of human CD68 regulatory elements, which target expression to myeloid and dendritic cells. We also generated in parallel BAFF transgenic mice using the same expression elements. Analysis of the transgenic mice revealed that DeltaBAFF and BAFF had opposing effects on B cell survival and marginal zone B cell numbers. DeltaBAFF transgenic mice had reduced B cell numbers and T cell-dependent Ab responses, but normal preimmune serum Ig levels. In contrast, BAFF transgenic mice had extraordinarily elevated Ig levels and increases in subsets of B cells. Unexpectedly, both BAFF and DeltaBAFF appeared to modulate the numbers of B-1 phenotype B cells.

Alternative Splicing↗

PubMed2005

Urokinase plasminogen activator receptor promotes macrophage infiltration into the vascular wall of ApoE deficient mice.

The urokinase plasminogen activator receptor (uPAR) regulates macrophage adhesion and migration by binding directly to matrix proteins and signaling through integrin complexes. In this study, we examined the role of uPAR on macrophage infiltration into the vascular wall. Stable murine macrophage (Raw264.7) cell lines expressing high levels of human uPAR, human urokinase plasminogen activator (uPA), or both were established using expression vectors driven by the human CD68 promoter. Stimulation with human uPA specifically induced phosphorylation of early response regulated kinase (ERK) in cells expressing human uPAR but not in sham transfected cells. The human uPAR expressing Raw264.7 cells showed increased adhesion to both human uPA and vitronectin (Vn). Raw264.7 cells expressing human uPAR or both human uPAR and uPA, but not uPA alone, were detected in the aortic wall of ApoE(-/-) mice, and no cells were detected in that of age-matched C57BL/6J mice after intravenous infusion of the cells. Blocking of Mac-1/ICAM-1 interaction by anti-alphaM antibody (M1/70) significantly reduced the infiltration of huPAR-expressing Raw264.1 cells into aorta of ApoE(-/-) mice. Treatment of C57BL/6J mice with angiotensin II resulted in infiltration of Raw264.7 cells expressing human uPAR. These data demonstrate that uPAR plays a key role in promoting macrophage infiltration into the arterial wall of ApoE(-/-) mice.

Animals↗

PubMed2005

Mechanisms of disease: macrophage-derived foam cells emerging as therapeutic targets in atherosclerosis.

The limited efficacy of current treatment strategies for targeting atherosclerosis and its complications requires new therapeutic options to be explored. From early fatty-streak lesions to advanced plaques, macrophage-derived foam cells are integral to the development and progression of atherosclerosis. Elucidation of molecular and cellular processes involving macrophages has led to numerous therapeutic targets being suggested. Potential sites of intervention range from monocyte recruitment, through cholesterol uptake and esterification, to cholesterol evacuation and macrophage egress from plaque. In addition, complex patterns of transcriptional regulation of genes involved in macrophage lipid homeostasis and in the regulation of inflammation have been partly unraveled. Recognition of ATP-binding cassette cholesterol transport mechanisms and cellular interactions with cholesterol-accepting apolipoproteins (or synthetic mimetics) opens up new potential therapies to induce atherosclerosis regression in humans. This review presents a systematic evaluation of actual and potential macrophage-directed pharmacologic interventions. It reflects the timely convergence of three important strands: advances in molecular and cell biology that have suggested therapeutic targets in macrophages; the development of multiple classes of drugs targeting these pathways; and the emergence of sensitive imaging techniques that have enabled identification of changes in plaque size and composition in response to treatment.

Arteriosclerosis↗

PubMed2004

Thematic review series: the immune system and atherogenesis. Recent insights into the biology of macrophage scavenger receptors.

Scavenger receptors were originally defined by their ability to bind and internalize modified lipoproteins. Macrophages express at least six structurally different cell surface receptors for modified forms of LDL that contribute to foam cell formation in atherosclerosis. In addition to their role in the pathology of atherosclerosis, macrophage scavenger receptors, especially SR-A, play critical roles in innate immunity, apoptotic cell clearance, and tissue homeostasis. In this review, we highlight recent advances in understanding the biology of macrophage scavenger receptors as pattern recognition receptors for both infectious nonself (pathogens) and modified self (apoptotic cells and modified LDL). We critically evaluate the potential of scavenger receptors and their ligands as targets for therapeutic intervention in human disease.

Animals↗

PubMed2004

Broad-spectrum CC-chemokine blockade by gene transfer inhibits macrophage recruitment and atherosclerotic plaque formation in apolipoprotein E-knockout mice.

BACKGROUND: The CC-chemokines (CKs) recruit monocytes/macrophages to sites of inflammation; several different CC-CKs play a role in the pathogenesis of atherosclerosis. The vaccinia virus expresses a 35-kDa soluble protein (35K) that binds to and inactivates nearly all of the CC-CKs, providing a potentially useful therapeutic strategy for broad-spectrum CC-CK inhibition in atherosclerosis. A recombinant adenovirus encoding soluble 35K (Ad35K) was generated to investigate the effect of 35K gene transfer on atherosclerosis in Western diet-fed apolipoprotein E-knockout (ApoE KO) mice. METHODS AND RESULTS: ApoE KO mice received tail-vein injections of phosphate-buffered saline, Ad35K, or control adenovirus AdGFP encoding green fluorescence protein. Two weeks after Ad35K gene transfer, atherosclerotic lesion area was significantly reduced in aortic roots by 55% compared with PBS or AdGFP control mice (P<0.05). Furthermore, 35K gene transfer strikingly reduced the macrophage content in aortic root lesions by 85% (P<0.01) and reduced lipid deposition in descending aortas by more than half (P<0.05). By an in vitro chemotaxis assay, plasma and aortic homogenates from 35K gene transfer mice promoted significantly less CC-CK-induced cell migration than did PBS or AdGFP controls. CONCLUSIONS: These findings show that a single intravenous injection of a recombinant adenovirus encoding the broad-spectrum CC-CK inhibitor 35K can reduce atherosclerosis by inhibiting CC-CK-induced macrophage recruitment in atherosclerotic ApoE KO mice. These experiments suggest that CC-CKs play an important role in atherogenesis and are a rational target for therapeutic intervention.

Adenoviridae↗

PubMed2004

Functional analysis of the murine Emr1 promoter identifies a novel purine-rich regulatory motif required for high-level gene expression in macrophages.

This study has investigated the transcriptional regulation of the Emr1 gene in murine macrophages and defined an enhancer element within the proximal promoter that is necessary for Emr1 expression in myeloid cells. This element consists of an extended purine-rich sequence (PuRS) of 83 consecutive purine residues containing 9 GGAA sequences, the core binding sequence for members of the Ets family of transcription factors. The Ets factor PU.1 associates with this PuRS element both in vitro and in vivo. Using a standard BLAST search we identified similar PuRS elements in other myeloid and nonmyeloid genes. All PuRS elements tested confer enhancer activity onto a heterologous promoter and chromatin immunoprecipitation experiments revealed that PU.1 associates in vivo with the PuRS elements from the genes expressed in myeloid cells. Our results provide evidence that extended purine-rich sequence elements may constitute a new transcription regulatory motif and that PU.1 association is a prerequisite for macrophage-specific expression.

Animals↗

PubMed2004

The role of chemokines in atherosclerosis: recent evidence from experimental models and population genetics.

PURPOSE OF REVIEW: Atherosclerosis is an inflammatory disease process. This review discusses the recent genetic evidence from animal models and human populations that highlight the importance of chemokines in atherosclerosis. RECENT FINDINGS: CC-chemokine/CC-chemokine receptors (CCR), including CCR2/ MCP-1 (monocyte chemoattractant protein-1) and CCR5/RANTES (regulated on activation, normal T-cell expressed and secreted), have been shown in animal knockout and transgenic studies to have significant effects on atherosclerotic lesion size and macrophage recruitment. More recently fractalkine (CX3C1) and its receptor (CX3CR1) have emerged as another important pathway in atherosclerosis. For example, fractalkine is present in human atherosclerotic lesions and is able to stimulate platelet activation and adhesion. CX3CR1 is expressed on human aortic smooth muscle cells and CX3CR1/apolipoprotein E double knockout mice have significantly reduced atherosclerotic lesion size and macrophage recruitment. Human population genetic studies have tried to assess the importance of chemokines in human atherosclerosis. Currently, there is conflicting evidence regarding an association between polymorphisms in CCR2/MCP-1 and CCR5/RANTES and coronary artery disease. There is evidence, however, for an association between the fractalkine receptor polymorphism (CX3CR1-I249) and coronary artery disease in both human population and function studies. SUMMARY: Recent transgenic and gene knockout studies in murine models of atherosclerosis have highlighted the importance of chemokines and their receptors in atherosclerosis. Genetic evidence for a role of chemokines and their receptors in human population studies remains under investigation. Identifying chemokine polymorphisms could help to determine pathways that are important in atherosclerosis disease pathology and that may suggest novel therapeutic targets.

Animals↗

PubMed2003

Smooth muscle cells in human atherosclerotic plaques express the fractalkine receptor CX3CR1 and undergo chemotaxis to the CX3C chemokine fractalkine (CX3CL1).

BACKGROUND: Chemokines are important mediators of inflammatory cell recruitment that play a significant role in atherosclerosis. Fractalkine (CX3CL1) is an unusual membrane-bound chemokine that mediates chemotaxis through the CX3CR1 receptor. Recently, functional polymorphisms in the human CX3CR1 gene have been described that are associated with coronary artery disease. METHODS AND RESULTS: We investigated the expression of the CX3C chemokine fractalkine and its receptor CX3CR1 in human coronary artery plaques by immunocytometry. We show that a subset of mononuclear cells expresses high levels of fractalkine in human coronary atherosclerotic plaques and that smooth muscle cells within the neointima express the fractalkine receptor CX3CR1. There is a positive correlation between the number of fractalkine-expressing cells and the number of CX3CR1-positive cells in human atherosclerotic plaques (r=0.70, n=15 plaques). Furthermore, we demonstrate that cultured vascular smooth muscle cells express the CX3CR1 receptor and undergo chemotaxis to fractalkine that can be inhibited by G protein inactivation by pertussis toxin. CONCLUSIONS: These results suggest that in human atherosclerosis, fractalkine, rather than mediating inflammatory cell recruitment, can act as a mediator of smooth muscle cell migration.

Adult↗

PubMed2003

Multiple Ets factors and interferon regulatory factor-4 modulate CD68 expression in a cell type-specific manner.

CD68 is a transmembrane glycoprotein expressed in all cells of the mononuclear phagocyte lineage including monocytes and tissue resident macrophages. Deletion analysis of the 5'-flanking sequences of the gene demonstrated that the proximal -150-bp sequence of the CD68 promoter exhibits high level promoter activity in macrophages. Mutations that abolish Ets factor binding at positions -106 and -89 reduce promoter activity in macrophages to 12 and 30%, respectively. Band shift experiments show that PU.1 associates with the -89 site whereas, Elf-1 preferentially binds the -106 Ets binding site and enhances CD68 activity in vitro. Furthermore, chromatin immunoprecipitation experiments confirm that Elf-1 and PU.1 associate with the CD68 proximal promoter in vivo in THP-1 cells. PU.1 does not bind to the CD68 promoter alone but instead forms heterocomplexes with members of the interferon regulatory factor family (IRF) including IRF-4 and IRF-8. IRF-4 and IRF-8 typically mediate transcriptional activation when associated with PU.1 on composite elements. However, our data show that PU.1/IRF-4 and IRF-8 heterocomplexes down-regulate CD68 promoter activity in macrophages and repression is dependent on the integrity of both the IRF and PU.1 half-sites of this composite element. Chromatin immunoprecipitation data reveal that neither IRF-4 nor IRF-8 associate with the CD68 proximal promoter in macrophages in vivo but IRF-4 is associated with the promoter in B lymphocytes. We propose that expression of CD68 in myeloid cells requires the Ets transcription factors Elf-1 and PU.1 and CD68 expression is down-regulated in lymphoid cells by combinatorial interactions between PU.1 and IRF-4.

Amino Acid Motifs↗

PubMed2003

Adeno-associated virus-mediated gene transfer of a secreted decoy human macrophage scavenger receptor reduces atherosclerotic lesion formation in LDL receptor knockout mice.

Macrophage scavenger receptors (MSR) promote atherosclerotic lesion formation, and modulation of MSR activity has been shown to influence atherosclerosis. Soluble receptors are effective in inhibiting receptor-mediated functions in various diseases. We have generated a secreted macrophage scavenger receptor (sMSR) that consists of the bovine growth hormone signal sequence and the human MSR A I extracellular domains. sMSR reduces degradation of atherogenic modified low-density lipoproteins and monocyte/macrophage adhesion on endothelial cells in vitro. To test long-term effects of sMSR, atherosclerosis-susceptible LDLR knockout mice were transduced via the tail vein with an adeno-associated virus (AAV) expressing sMSR or control enhanced green fluorescent protein (EGFP), and a Western-type diet was started. Gene transfer caused a temporary elevation in alkaline phosphatase and aspartate amino transferase values without a change in C-reactive protein. sMSR protein was detected in the plasma of the transduced mice by a specific ELISA 6 months after the gene transfer. AAV-mediated sMSR gene transfer reduced atherosclerotic lesion area in the aorta by 21% (P < 0.05) compared to EGFP-transduced control mice. Even though eradication of established disease was not possible, atherosclerotic lesion formation could be modified using AAV-mediated gene transfer of the decoy sMSR.

Animals↗

PubMed2003

Adenovirus-mediated gene transfer of a secreted decoy human macrophage scavenger receptor (SR-AI) in LDL receptor knock-out mice.

Macrophage scavenger receptors (MSR) play an important role in the pathogenesis of atherosclerosis. Therefore, modulation of MSR activity could have a beneficial effect on atherogenesis. One way to antagonize the function of a cell surface scavenger receptor is to use a soluble decoy receptor. We have constructed a soluble, chimaeric fusion protein that consists of the bovine growth hormone signal sequence and the human MSR AI extracellular domains. This secreted decoy MSR (sMSR) was cloned into an adenoviral vector and the recombinant adenoviruses were used for gene transfer experiments in vivo. We have previously shown that the secreted MSR inhibits degradation of acetylated LDL and oxidized LDL in mouse macrophages and reduces foam cell formation in vitro. We now report that in comparison to LacZ transfected control mice gene transfer with sMSR adenoviruses via tail vein injection (1 x 10(9) pfu) reduces atherosclerotic lesion area in hypercholesterolemic LDL receptor knock-out mice by 14 (P<0.05) and 19% (P=0.01), 4 and 6 weeks after the gene transfer. However, a statistically significant difference in the aortic root atherosclerosis was not detected. This is the first demonstration that the decoy sMSR can affect atherogenesis in mice after recombinant adenovirus-mediated gene transfer. Even though the achieved reduction in atherosclerosis was relatively modest the results suggest that sMSR may offer new strategies for the treatment of atherosclerosis and lipid accumulation in the vessel wall.

Adenoviridae↗