The effect of hypercholesterolemia induced immune response and inflammation on progression of atherosclerosis in ApoB(tm25gy) LDLr(tm1Her) mice, expressing only ApoB100 and deficient in the low density lipoprotein (LDL) receptor, thus closely resembling human cholesterol transport is not well defined. Atherosclerosis was induced by a high cholesterol diet and its progression was studied at 8, 14 and 20 weeks. Antibody response was determined by ELISA. Lymphocytes in spleen and aortic expression of inflammatory markers were studied by flow cytometry, and immunohistochemistry respectively. A rapid increase in plasma LDL levels in the first 8 weeks was followed by the exponential development of atherosclerosis between 8 and 14 weeks. Progression of the disease was accompanied by an accumulation of macrophages and increased expression of IL17 and IFN-γ in the aorta. Hypercholesterolemia resulted in increased immune response to modified lipids and aortic inflammation, with an expansion of Th17 cells in the spleen. Progression of atherosclerosis showed a positive correlation (r = 0.84, P < 0.001) with Th17 cells and a negative correlation with Treg cells (r = 0.83, P < 0.001). IgM antibodies to Ox-LDL and Th17 cells in spleen showed greatest association with disease development. Our results suggest that anti Ox-LDL IgM antibodies, Th17 cells could be developed as a potential marker to study disease progression and to study the effect of therapeutic regulation of inflammation.

No abstract

Atherosclerosis is the leading cause for cardiovascular mortality. We determined the effect of multi-antigenic construct expressing three peptides AHC (ApoB100, HSP60 and outer membrane protein of chlamydia pneumonia) in stabilizing advanced atherosclerosis in Apobtm2Sgy/Ldlrtm1Her/J mice. Atherosclerosis was induced by feeding high fat diet (HFD) to mice for 10 weeks, followed by five oral dosing with purified AHC or ovalbumin on alternate days and continued on HFD for another 10 weeks. Tolerance was associated with significantly higher numbers of regulatory T cells both in aortic sinus and spleen with higher mRNA expression of CTLA4 (3 fold), Foxp3 (1.4 folds) and TGF-β (1.62) in aorta. Tregs cells were found to induce alternate activation of macrophages to M2 phenotype, with a reduction in plaque inflammation. AHC treatment showed evidence of plaque stabilization as observed by reduction in plaque necrosis in aortic sinus (35.8%) and in brachiocephalic artery (26%), with reduced expression of Tissue factor and MMP9. Macrophage apoptosis was reduced and collagen content was enhanced by treatment. Our results suggest that tolerance to atherogenic peptides increases regulatory T cells which activate M2 macrophages, prevent T cell proliferation and reduce plaque destabilization and inflammatory markers thus providing evidences for plaque stabilization in mice with advanced atherosclerosis.