Effect of irradiation and bone marrow transplantation on angiotensin II-induced aortic inflammation in ApoE knockout mice

BACKGROUND AND AIMS

Angiotensin II (Ang II) infusion promotes the development of aortic aneurysms and accelerates atherosclerosis in ApoE^-/- mice. In order to elucidate the role of hematopoietic cells in these pathologies, irradiation and bone marrow transplantation (BMT) are commonly utilized. The aim of this study was to investigate the effects of irradiation and BMT on abdominal and thoracic aortic aneurysm formation and acute leukocyte recruitment in the aortic root and descending aorta, in an experimental mouse model of aortic aneurysm formation.

METHODS

ApoE^-/- mice were either lethally irradiated and reconstituted with ApoE^-/- bone marrow or non-irradiated. Following engraftment, mice were treated with Ang II to induce aortic inflammation and accelerate atherosclerosis.

RESULTS

Ang II infusion (0.8 mg/kg/day) in BMT mice resulted in reduced aortic aneurysms and atherosclerosis with decreased leukocyte infiltration in the aorta compared to non-BMT mice, when receiving the same dose of Ang II. Furthermore, the reduced aortic infiltration in BMT mice was accompanied by increased levels of monocytes in the spleen and bone marrow. A dose of 3 mg/kg/day Ang II was required to achieve a similar incidence of aneurysm formation as achieved with 0.8 mg/kg/day in non-BMT mice.

CONCLUSIONS

This study provides evidence that BMT can alter inflammatory cell recruitment in experimental mouse models of aortic aneurysm formation and atherosclerosis and suggests that irradiation and BMT have a considerably more complex effect on vascular inflammation, which should be evaluated.

Analysis of In Vivo Serpin Functions in Models of Inflammatory Vascular Disease

Serpins have a wide range of functions in regulation of serine proteases in the thrombotic cascade and in immune responses, representing up to 2-10% of circulating proteins in the blood. Selected serpins also have cross-class inhibitory actions for cysteine proteases in inflammasome and apoptosis pathways. The arterial and venous systems transport blood throughout the mammalian body representing a central site for interactions between coagulation proteases and circulating blood cells (immune cells) and target tissues, a very extensive and complex interaction. While analysis of serpin functions in vitro in kinetics or gel shift assays or in tissue culture provides very necessary information on molecular mechanisms, the penultimate assessment of biological or physiological functions and efficacy for serpins as therapeutics requires study in vivo in whole animal models (some also consider cell culture to be an in vivo approach).Mouse models of arterial transplant with immune rejection as well as models of inflammatory vasculitis induced by infection have been used to study the interplay between the coagulation and immune response pathways. We describe here three in vivo vasculitis models that are used to study the roles of serpins in disease and as therapeutics. The models described include (1) mouse aortic allograft transplantation, (2) human temporal artery (TA) xenograft into immunodeficient mouse aorta, and (3) mouse herpes virus (MHV68)-induced inflammatory vasculitis in interferon-gamma receptor (IFNγR) knockout mice.

Atypical chemokine receptor 1 deficiency reduces atherogenesis in ApoE-knockout mice

AIMS

Atypical chemokine receptor 1 (Ackr1; previously known as the Duffy antigen receptor for chemokines or Darc) is thought to regulate acute inflammatory responses in part by scavenging inflammatory CC and CXC chemokines; however, evidence for a role in chronic inflammation has been lacking. Here we investigated the role of Ackr1 in chronic inflammation, in particular in the setting of atherogenesis, using the apolipoprotein E-deficient (ApoE(-/-)) mouse model.

METHODS AND RESULTS

Ackr1(-/-)ApoE(-/-) and Ackr1(+/+)ApoE(-/-) littermates were obtained by crossing ApoE(-/-) mice and Ackr1(-/-) mice on a C57BL/6J background. Ackr1 (+/+)ApoE(-/-)mice fed a Western diet up-regulated Ackr1 expression in the aorta and had markedly increased atherosclerotic lesion size compared with Ackr1(-/-)ApoE(-/-) mice. This difference was observed in both the whole aorta and the aortic root in both early and late stages of the model. Ackr1 deficiency did not affect serum cholesterol levels or macrophage, collagen or smooth muscle cell content in atherosclerotic plaques, but significantly reduced the expression of Ccl2 and Cxcl1 in the whole aorta of ApoE(-/-) mice. In addition, Ackr1 deficiency resulted in a modest decrease in T cell subset frequency and inflammatory mononuclear phagocyte content in aorta and blood in the model.

CONCLUSIONS

Ackr1 deficiency appears to be protective in the ApoE knockout model of atherogenesis, but it is associated with only modest changes in cytokine and chemokine expression as well as T-cell subset frequency and inflammatory macrophage content.

Temporal changes in mouse aortic wall gene expression during the development of elastase-induced abdominal aortic aneurysms

OBJECTIVE

To characterize temporal changes in mouse aortic wall gene expression associated with the development of experimental abdominal aortic aneurysms.

METHODS

C57BL/6 mice underwent transient perfusion of the abdominal aorta with either elastase (n = 61) or heat-inactivated elastase as a control (n = 68). Triplicate samples of radiolabeled aortic wall complementary DNA were prepared at intervals of 0, 3, 7, 10, and 14 days, followed by hybridization to nylon microarrays (1181 genes). Autoradiographic intensity data were normalized by conversion to z scores, and differences in gene expression were defined by two-tailed z tests at a significance threshold of P < .01.

RESULTS

Elastase perfusion caused a progressive increase in aortic diameter up to 14 days accompanied by transmural inflammation and destructive remodeling of the elastic media. No aneurysms occurred in the control group. Compared with healthy aorta, 336 genes exhibited significant alterations during at least 1 interval after elastase perfusion (135 at more than 1 interval and 14 at all intervals), with pronounced increases for interleukin 6, cyclin E2, interleukin 1beta, osteopontin, CD14/lipopolysaccharide receptor, P-selectin glycoprotein ligand 1, and gelatinase B/matrix metalloproteinase 9 (all >20-fold on day 3). Sixty-two genes exhibited synchronous alterations in the elastase and control groups, thus suggesting a nonspecific response. By direct comparisons between the elastase and control groups, there were 384 genes with significant differences in expression for at least 1 interval after aortic perfusion, including 234 with differential upregulation (eg, p44MAPK/ERK1, osteopontin, heat shock protein 84, hypoxia-inducible factor 1alpha, apolipoprotein E, monocyte chemotactic protein 3, MIG (monokine induced by gamma interferon), and interleukin 2 receptor gamma) and 163 with differential downregulation (eg, prothrombin, granzyme B, ataxia telangiectasia mutated, and interleukin-converting enzyme).

CONCLUSIONS

Development of elastase-induced abdominal aortic aneurysms in mice is accompanied by altered aortic wall expression of genes associated with acute and chronic inflammation, matrix degradation, and vascular tissue remodeling. Knowledge of these alterations will facilitate further studies on the functional molecular mechanisms that underlie aneurysmal degeneration.

Association of the HLA-DRB1 gene with susceptibility to aortoarteritis in a Chinese Han population

Aortoarteritis is a chronic inflammatory disease mainly affecting the aorta and its major branches. Recent immunogenetic studies indicate that certain human leucocyte antigen (HLA) alleles are significantly associated with aortoarteritis in several populations. The purpose of the present study was to investigate the relationship between the HLA-DRB1 alleles and aortoarteritis in a Chinese Han population. HLA-DRB1 genotypes were identified by PCR-SSP and PCR-RFLP in 84 Chinese patients with aortoarteritis and 102 healthy Chinese controls. It was found that the HLA-DRB1*04 allele (38.1% in patients vs. 15.7% in controls, p<0.001, relative risk (RR)=2.43) and the HLA-DRB1*07 allele (47.6% vs. 10.8%, p<0.001, RR = 4.42) were significantly associated with aortoarteritis. Furthermore, there was no significant difference in the frequency of the DRB1*0405 subtype between the patient and control groups. Thus the susceptibility to aortoarteritis in this Chinese Han population was closely related with the HLA-DRB1*04 and DRB1*07 alleles. Thus individuals with the HLA-DRB1*04 and DRB1*07 alleles may be at higher risk for developing aortoarteritis.

HLA-B27 associated spondyloarthropathy and severe ascending aortitis

We describe a young woman who developed early and severe aortic regurgitation and subsequent aortitis with aneurysm formation requiring surgery.

HLA-B5 and B21 antigens in aortoarteritis

The distribution of class I HLA antigens (HLA-A, B) were determined in 50 patients of Aortoarteritis in an Indian population. This included 29 females and 21 males. The difference in antigen frequency was observed between patients and controls with reference to HLA-A19, B5 and B21 antigens. A decreased frequency of HLA-A19 was observed in the patients as compared to controls (14% vs 33.25%, X2 = 6.81, P less than 0.025). Of the B locus antigens, an increased frequency of HLA B5 was observed in the patients as compared to controls (48% vs 29.5%, X2 = 6.2, P less than 0.025). HLA-B21 was also increased in the patients as compared to the controls (18% vs 6.5%, X2 = 6.67, P less than 0.025). These data suggest the involvement of genetic factor (s) in the aetiopathogenesis of this disease. Further, the observations indicate that HLA-B5 and B21 may be associated with Aortoarteritis.

Hereditary angioedema and aortitis

A 28-year-old male with hereditary angioedema died of an extensive stroke. Autopsy revealed cicatricial aortitis with narrowing of the coronary ostia, myocardial infarctions, and a left ventricular mural thrombus. There was neither acute inflammation of the aorta nor systemic vasculitis. A possible association of the aortitis with the hereditary angioedema is discussed.