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Thrombospondin-1 (TSP1) contributes to the development of vascular inflammation by regulating monocytic cell motility in mouse models of abdominal aortic aneurysm.

ABSTRACT: Histological examination of abdominal aortic aneurysm (AAA) tissues demonstrates extracellular matrix destruction and infiltration of inflammatory cells. Previous work with mouse models of AAA has shown that anti-inflammatory strategies can effectively attenuate aneurysm formation. Thrombospondin-1 is a matricellular protein involved in the maintenance of vascular structure and homeostasis through the regulation of biological functions, such as cell proliferation, apoptosis, and adhesion. Expression levels of thrombospondin-1 correlate with vascular disease conditions.To use thrombospondin-1-deficient (Thbs1(-/-)) mice to test the hypothesis that thrombospondin-1 contributes to pathogenesis of AAAs.Mouse experimental AAA was induced through perivascular treatment with calcium phosphate, intraluminal perfusion with porcine elastase, or systemic administration of angiotensin II. Induction of AAA increased thrombospondin-1 expression in aortas of C57BL/6 or apoE-/- mice. Compared with Thbs1(+/+) mice, Thbs1(-/-) mice developed significantly smaller aortic expansion when subjected to AAA inductions, which was associated with diminished infiltration of macrophages. Thbs1(-/-) monocytic cells had reduced adhesion and migratory capacity in vitro compared with wild-type counterparts. Adoptive transfer of Thbs1(+/+) monocytic cells or bone marrow reconstitution rescued aneurysm development in Thbs1(-/-) mice.Thrombospondin-1 expression plays a significant role in regulation of migration and adhesion of mononuclear cells, contributing to vascular inflammation during AAA development.

SUBMITTER: Liu Z

PROVIDER: S-EPMC4490953 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Thrombospondin-1 (TSP1) contributes to the development of vascular inflammation by regulating monocytic cell motility in mouse models of abdominal aortic aneurysm.

Liu Zhenjie Z Morgan Stephanie S Ren Jun J Wang Qiwei Q Annis Douglas S DS Mosher Deane F DF Zhang Jing J Sorenson Christine M CM Sheibani Nader N Liu Bo B

Circulation research 20150504 2

<h4>Rationale</h4>Histological examination of abdominal aortic aneurysm (AAA) tissues demonstrates extracellular matrix destruction and infiltration of inflammatory cells. Previous work with mouse models of AAA has shown that anti-inflammatory strategies can effectively attenuate aneurysm formation. Thrombospondin-1 is a matricellular protein involved in the maintenance of vascular structure and homeostasis through the regulation of biological functions, such as cell proliferation, apoptosis, an ...[more]

PMID: 25940549

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Project description:Abdominal aortic aneurysm (AAA) is characterized as dilation of the aortic wall. Dysregulation of vascular smooth muscle cells (VSMCs) can contribute to the development of this phenotype. Circular RNAs and microRNAs (miRNAs) can regulate the proliferation and apoptosis of VSMCs. This present study aimed to identify the mechanisms of action behind the regulation of cerebellar degeneration-related protein 1 antisense RNA (CDR1as)/miRNA (miR)-7 in VSMCs. The expression levels of miR-7 were upregulated, whereas the levels of CDR1as and cytoskeleton-associated protein 4 (CKAP4) were downregulated in aortic specimens obtained from 10 patients who underwent surgery for AAA compared with aortic specimens from 10 control patients who underwent coronary artery bypass surgery. The molecular mechanism of action of CDR1as/miR-7 was investigated in primary VSMCs. The results of Cell Counting kit-8 and cell growth curve assays revealed that overexpression of CDR1as and knockdown of miR-7, increased VSMC proliferation, whereas knockdown of CDR1as and overexpression of miR-7 suppressed VSMC proliferation. In addition, overexpression of CDR1as and knockdown of miR-7, suppressed apoptosis in VSMCs, indicated by the decreased levels of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) activity, whereas knockdown of CDR1as and overexpression of miR-7 exhibited the opposite effects. The results of luciferase reporter and biotin pull-down assays confirmed that CDR1as directly bound to miR-7 and suppressed its expression. Additionally, the CDR1as-induced proliferation and suppressed apoptosis was reversed by the overexpression of miR-7. Furthermore, luciferase reporter, reverse transcription-quantitative PCR and western blot assays revealed that miR-7 directly targeted CKAP4 and suppressed its expression. Additionally, the miR-7-suppressed proliferation and increased ROS and LDH activity were reversed by the overexpression of CKAP4. CDR1as also decreased caspase 3/7 activity, which was reversed by miR-7 mimics. miR-7 increased the activity of caspase 3/7, which was again reversed by the overexpression of CKAP4. Therefore, CDR1as, miR-7 and CKAP4 may act in the same pathway to regulate VSMC proliferation and apoptosis.

Project description:AimsAbdominal aortic aneurysm (AAA) is one of the number of diseases associated with a prominent inflammatory cell infiltration, matrix protein degradation, and smooth muscle cell apoptosis. CD95 is an inflammatory mediator and an apoptosis inducer. Previous studies have shown elevated expression of CD95 or CD95L in the aortic tissue of AAA patients. However, how the CD95L/CD95 contributes to aneurysm degeneration and whether blocking its signalling would be beneficial to disease progression remains largely unknown. In the present study, we sought to determine the role of CD95L and its downstream target, caspase 8, in AAA progression.Methods and resultsBy using the CaCl2 murine model of AAA, abdominal aortic aneurysms were induced in C57BL/6 mice. We found that both mRNA and protein levels of CD95L were increased in aneurysm tissue compared with NaCl-treated normal aortic tissue. To determine whether CD95L contributes directly to aneurysm formation, we used CD95L null (CD95L-/-) mice to examine their response to CaCl2 aneurysm induction. Six weeks after periaortic application of CaCl2, aortic diameters of CD95L-/- mice were significantly smaller compared to CaCl2-treated wild-type controls. Connective tissue staining of aortic sections from CaCl2-treated CD95L-/- mice showed minimal damage of medial elastic lamellae which was indistinguishable from the NaCl-treated sham control. Furthermore, CD95L deficiency attenuates macrophage and T cell infiltration into the aortic tissue. To study the role of CD95L in the myelogeous cells in AAA formation, we created chimaeric mice by infusing CD95L-/- bone marrow into sub-leathally irradiated wild-type mice (WT/CD95L-/-BM). As controls, wild-type bone marrow were infused into sub-leathally irradiated CD95L-/- mice (CD95L-/-/WTBM). WT/CD95L-/-BM mice were resistant to aneurysm formation compared to their controls. Inflammatory cell infiltration was blocked by the deletion of CD95L on myeloid cells. Western blot analysis showed the levels of caspase 8 in the aortas of CaCl2-treated wild-type mice were increased compared to NaCl-treated controls. CD95L deletion inhibited caspase 8 expression. Furthermore, a caspase 8-specific inhibitor was able to partially block aneurysm development in CaCl2-treated aneurysm models.ConclusionThese studies demonstrated that inflammatory cell infiltration during AAA formation is dependent on CD95L from myelogeous cells. Aneurysm inhibition by deletion of CD95L is mediated in part by down-regulation of caspase 8.

Project description:BackgroundAbdominal aortic aneurysm (AAA), a degenerative vascular pathology characterized by permanent dilation of the aorta, is considered a chronic inflammatory disease involving innate/adaptive immunity. However, the functional role of antibody-dependent immune response against antigens present in the damaged vessel remains unresolved. We hypothesized that engagement of immunoglobulin G (IgG) Fc receptors (FcγR) by immune complexes (IC) in the aortic wall contributes to AAA development. We therefore evaluated FcγR expression in AAA lesions and analysed whether inhibition of FcγR signaling molecules (γ-chain and Syk kinase) influences AAA formation in mice.MethodsFcγR gene/protein expression was assessed in human and mouse AAA tissues. Experimental AAA was induced by aortic elastase perfusion in wild-type (WT) mice and γ-chain knockout (γKO) mice (devoid of activating FcγR) in combination with macrophage adoptive transfer or Syk inhibitor treatment. To verify the mechanisms of FcγR in vitro, vascular smooth muscle cells (VSMC) and macrophages were stimulated with IgG IC.ResultsFcγR overexpression was detected in adventitia and media layers of human and mouse AAA. Elastase-perfused γKO mice exhibited a decrease in AAA incidence, aortic dilation, elastin degradation, and VSMC loss. This was associated with (1) reduced infiltrating leukocytes and immune deposits in AAA lesions, (2) inflammatory genes and metalloproteinases downregulation, (3) redox balance restoration, and (4) converse phenotype of anti-inflammatory macrophage M2 and contractile VSMC. Adoptive transfer of FcγR-expressing macrophages aggravated aneurysm in γKO mice. In vitro, FcγR deficiency attenuated inflammatory gene expression, oxidative stress, and phenotypic switch triggered by IC. Additionally, Syk inhibition prevented IC-mediated cell responses, reduced inflammation, and mitigated AAA formation.ConclusionOur findings provide insight into the role and mechanisms mediating IgG-FcγR-associated inflammation and aortic wall injury in AAA, which might represent therapeutic targets against AAA disease.

Dataset Information

Thrombospondin-1 (TSP1) contributes to the development of vascular inflammation by regulating monocytic cell motility in mouse models of abdominal aortic aneurysm.

Publications

Thrombospondin-1 (TSP1) contributes to the development of vascular inflammation by regulating monocytic cell motility in mouse models of abdominal aortic aneurysm.

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