P1941The nuclear receptor corepressor 1 blocks CD36-mediated foam cell formation in atherogenesis

Background

Nuclear receptors and their cofactors regulate the expression of various target genes in different tissue and organs to orchestrate downstream (patho)physiological processes. Although the function of several nuclear receptors in atherosclerosis has been studied, very little is known about the role of nuclear receptor cofactors in atherosclerosis. Given its important role to suppress inflammatory processes, we speculated that macrophage nuclear receptor corepressor 1 (NCOR1) plays a protective function in atherosclerosis development.

Purpose

To evaluate the contribution of macrophage NCOR1 in atherosclerosis we used myeloid cell-specific Ncor1 knockout mice on an atherosclerosis-prone background.

Methods and results

8-week-old male and female mice were exposed to a high high-cholesterol diet for 12 weeks. Our findings demonstrate that the lack of macrophage Ncor1 leads to a severe atherosclerotic phenotype in both sexes. These mice show a higher content of plaques along the thoraco-abdominal aortae as well as at the aortic sinus, which were characterized by larger necrotic cores and thinner fibrous caps, a typical signature of unstable plaques. Moreover, we found that the pro-atherogenic effects of the Ncor1 deletion are mediated via derepression of peroxisome proliferator-activated receptor gamma (PPARγ) target genes in mouse and human macrophages, especially the enhanced expression of the CD36 scavenger receptor and the subsequent rise in oxLDL uptake. Interestingly, while the expression of NCOR1 is reduced, the PPARγ signature is increased in human atherosclerotic plaques, and this signature is further pronounced in ruptured compared to stable carotid plaques.

Conclusion

Our findings suggest that macrophage NCOR1 blocks the pro-atherogenic functions of PPARγ in atherosclerosis and prevents the disease development.

Acknowledgement/Funding

The Swiss National Science Foundation, the Novartis Foundation, Olga-Mayenfisch Foundation, the OPO foundation

P715Deletion of fibroblast activation protein decreases experimental atherosclerotic plaque formation and vulnerability

Background

Fibroblast activation protein (FAP) is a serine protease that is upregulated in sites of tissue remodeling, including arthritis, tumors and atherosclerosis. We have reported that FAP degrades type I collagen in human thin-cap fibroatheromata; its expression is enhanced in advanced human plaques and induced by inflammation. However, the role of endogenous FAP in atherosclerosis remains unknown.

Purpose

To investigate the effects of constitutive Fap loss-of-function on atherosclerotic plaque formation and vulnerability.

Methods and results

Male 8-week-old Apoe−/− Fap+/+ and Apoe−/− Fap−/− mice were fed a high-cholesterol diet (1.25% chol) for 12 weeks. En face analyses of thoracoabdominal aortae using Oil Red O (ORO) revealed decreased plaques in Apoe−/− Fap−/− mice (5.7±0.5%; n=21) compared to Apoe−/− Fap+/+ mice (10.7±0.7%; n=24; p<0.0001). In parallel, ORO analyses of serial aortic root cross sections showed diminished plaques in Fap-deficient mice (18.4±3.4% vs 27.6±2.1%). As a surrogate of plaque vulnerability, fibrous cap thickness was increased in Apoe−/− Fap−/− mice (65±6 mm vs 35±3 mm; p<0.01), whereas necrotic core size, plaque macrophages (CD68) and T cells (CD3) accumulation, as well as VCAM1 expression did not differ. These changes were independent of plasma triglycerides, total and LDL-cholesterol levels. Plasma of Fap-deficient mice showed decreased FAP activity compared to Fap wildtype controls. Notably, second harmonics generation in cross sections of aortic root plaques showed that the deposition and density of fibrillar collagens was enhanced in Fap-deficient (25.5±4.4%) compared to control plaques (13.8±2.5%; p<0.05). Consistently, Fap deletion led to an accumulation of uncleaved pre-COL3A1, a proteolytic target of FAP.

Conclusions

Constitutive Fap deletion decreases experimental atherosclerosis and features of plaque vulnerability. Thus, inhibition of FAP expression or activity may be a promising therapeutic target in atherosclerosis.

Acknowledgement/Funding

Swiss National Science Foundation, Swiss Heart Foundation

Unrelated bone marrow transplantation in thalassemia. The experience of the Italian Bone Marrow Transplant Group (GITMO)

BACKGROUND AND OBJECTIVES

Allogeneic bone marrow transplantation (BMT) is a widely accepted therapeutic approach in homozygous beta-thalassemia. However, the majority of patients do not have a genotypically identical donor within the family. This prompted us to conduct a pilot study to investigate the feasibility of matched unrelated bone marrow transplantation in thalassemia. The major drawback was the high risk of immunologic and transplant-related complications, mainly graft-versus-host disease (GvHD) and graft failure.

DESIGN AND METHODS

Our aim was to reduce this risk through careful selection of donor/recipient pairs. HLA haplotypes that show a high linkage disequilibrium among their class I, class II and class III alleles are considered extended or ancestral haplotypes.

RESULTS

These haplotypes are conserved and can be shared by apparently unrelated individuals. Our study shows that matching for these haplotypes significantly improves the outcome of unrelated bone marrow transplantation in thalassemia. In fact, results were comparable to those obtained in transplants using HLA-identifical family donors.

INTERPRETATION AND CONCLUSIONS

Better results were obtained in patients with lesser iron overload and when the donor shared an identity for the DPB1 alleles.