Caspase-1 deficiency decreases atherosclerosis in apolipoprotein E-null mice

Background

Caspase-1 is a cysteine protease that contributes to mammalian immunity through proteolytic activation of the proinflammatory cytokines, interleukin (IL)-1β and IL-18.

Methods

To determine if caspase-1 deficiency can protect apolipoprotein E-null (Apoe^−/−) mice from atherosclerosis, gender-matched, paired-littermate Apoe^−/− mice with (Casp1^+/+Apoe^−/−) or without (Casp1^−/−Apoe^−/−) a functional caspase-1 (Casp1) gene were fed either a low fat diet for 26 weeks, or a saturated fat and cholesterol-enriched diet for 8 weeks. Plasma lipids and lipoproteins were determined and atherosclerosis was quantified in the aortic sinus and aortic arch.

Results

On either diet, caspase-1 deficiency did not affect total serum cholesterol concentrations and lipoprotein-cholesterol distributions. However, caspase-1 deficiency significantly decreased atherosclerosis in the ascending aorta by 35%-45% in both sexes of mice fed either diet. We further examined atherosclerotic lesions for 2 indices of immune cell activation: Major Histocompatibility Complex (MHC) class II and interferon (IFN)-γ expression. There was a 40%-50% reduction in the number of lesion-associated cells expressing MHC class II from both sexes of Casp1^−/−Apoe^−/− mice compared with Casp1^+/+Apoe^−/− mice and, a significant reduction in lesion-associated IFN-γ in female Casp1^−/−Apoe^−/− compared with their Casp1^+/+Apoe^−/− counterparts.

Conclusions

We conclude that caspase-1 promotes atherosclerosis by enhancing the inflammatory status of the lesion through a mechanism likely involving activation of lesion-associated immune cells and IFN-γ expression.     

Topical HDL administration reduces vein graft atherosclerosis in apo E deficient mice

ObjectiveUse of autologous vein grafts for surgical revascularisation is limited by vein graft failure. Topical high-density lipoprotein (HDL) administration on the adventitial side of vein grafts was evaluated as a new therapeutic modality to improve vein graft patency and function.MethodsCaval veins of C57BL/6 apo E^?/? mice were grafted to the right carotid arteries of recipient 3 month-old C57BL/6 TIE2-LacZ/apo E^?/? mice. HDL (200 μg/ml; 50 μl) in 20% pluronic F-127 gel was applied on the adventitial side of vein grafts.ResultsTopical HDL application reduced intimal area by 55% (p < 0.001) at day 28 compared to control mice. Blood flow quantified by micro magnetic resonance imaging at day 28 was 2.8-fold (p < 0.0001) higher in grafts of topical HDL treated mice than in control mice. Topical HDL potently reduced intimal inflammation and resulted in enhanced endothelial regeneration as evidenced by a 1.9-fold (p < 0.05) increase in the number of CD31 positive endothelial cells. HDL potently enhanced migration and adhesion of endothelial colony-forming cells (ECFCs) in vitro, and these effects were dependent on signaling via scavenger receptor-BI, extracellular signal-regulated kinases, and NO, and on increased β1 integrin expression. Correspondingly, the number of CD31 β-galactosidase double positive cells, reflecting incorporated circulating progenitor cells, was 3.9-fold (p < 0.01) higher in grafts of HDL treated mice than in control grafts.ConclusionsTopical HDL administration on the adventitial side of vein grafts attenuates vein graft atherosclerosis via increased incorporation of circulating progenitor cells in the endothelium, enhanced endothelial regeneration, and reduced intimal inflammation.     

Decorin overexpression reduces atherosclerosis development in apolipoprotein E-deficient mice

Atherosclerosis results from accumulation of macrophages and extracellular matrix in the arterial wall. Decorin, a small matrix proteoglycan, is able to regulate cell proliferation, migration and growth factors' activity. We investigated the effect of decorin overexpression on atherosclerosis progression in apolipoprotein E-deficient (ApoE(-/-)) mice. Female ApoE(-/-) mice, 10 weeks old (early treatment, n = 20) and 20 weeks old (delayed treatment, n = 20) were administered intravenously with either an adenovirus (2.5 x 10(9) plaque-forming units/mouse) containing human decorin gene (Ad-Dcn) or beta-galactosidase (LacZ), or PBS. Transgenic decorin was mainly expressed in the liver, and was secreted in the plasma up to 4 weeks. Six weeks after treatment, no significant difference in aortic root lesion size was observed between LacZ- and PBS-control groups. In contrast, Ad-Dcn-treated mice showed significantly reduced atherosclerotic lesions as compared to controls in both early and delayed treatment groups (2.9 +/- 1.1% versus 5.5 +/- 0.4%; p = 0.004 and 13.4 +/- 1.3% versus 19.9 +/- 1.41%; p = 0.009, respectively). In parallel, macrophage, gelatinase activity and collagen plaque content were also reduced. Interestingly, plasma triglycerides were reduced and decorin formed complexes with transforming growth factor-beta1 (TGF-beta1) that resulted in reduced circulating free-TGF-beta1. In conclusion, systemic overexpression of decorin reduces inflammation, triglycerides and fibrosis in atherosclerotic plaques of ApoE(-/-) mice resulting in slowing down of disease progression.     

Passive protection against fasciolosis in mice by immunization with a monoclonal antibody (ES-78 MoAb)

Recently, we reported a partial characterization of the epitope recognized by the ES-78 monoclonal antibody (MoAb). This monoclonal antibody was obtained from spleen lymphocytes of a mouse immunized with excretory-secretory antigens of Fasciola hepatica adult worms. In the present study, we report the results obtained in experiments of passive protection using this MoAb in BALB/c mice infected with 15 Fasciola hepatica metacercariae. The monoclonal antibody was able to reduce the parasite burden when administered 24 h before challenge but not when delivered 7 days after challenge. The antibody recognition of digestive tract structures in 3-week-old parasites was demonstrated by immune histochemical techniques. The antigens purified by affinity chromatography using this antibody had molecular weights of 14-20, 25-29 and 36-45 kDa and demonstrated proteinase activity similar to cathepsin L. These results suggest that the antigens carrying the epitope recognized by the ES-78 MoAb may be used as target in the protection against fasciolosis.     

Protection against gram-negative bacteremia and endotoxemia with human monoclonal IgM antibodies.

Hybridomas producing human monoclonal IgM antibodies (mAbs) against bacterial lipopolysaccharide (LPS) were generated by fusion of B lymphocytes from sensitized human spleen with heteromyeloma cells. The splenocytes were from patients undergoing splenectomy during staging for Hodgkin disease after vaccination with the J5 mutant of Escherichia coli, which is deficient in O antigenic side chains. This deficiency exposes the core oligosaccharide, common to LPS of all Gram-negative bacteria. The mAbs cross-reacted strongly with endotoxins from a wide range of unrelated species of Gram-negative bacteria. The mAbs also gave strong protection against LPS in the dermal Shwartzman reaction and against lethal Gram-negative bacteremia in mice. These findings indicate that monoclonal IgM against LPS endotoxin can neutralize its toxicity in vivo and might be valuable for treatment of patients with Gram-negative bacteremia. Analysis of one of the hybridoma clones, A6(H4C5), showed that the IgM mAb is directed against the covalently bound lipid A, which represents the most conservative and least variable structural element of LPS.     

Absence of CC chemokine receptor-2 reduces atherosclerosis in apolipoprotein E-deficient mice

The accumulation of circulating monocytes in the arterial wall is an early event in atherosclerotic plaque formation. Monocyte chemoattractant protein-1 (MCP-1) has been implicated as the primary source of monocyte chemoattractant functioning in these early stages of atherogenesis. To determine whether the receptor for MCP-1, CC chemokine receptor CCR2, plays a role in atherogenesis, CCR2-deficient animals were crossed with mice lacking apo E, a well characterized model of atherosclerosis. While lipid levels were unchanged, the double knockout mice exhibited a 3-fold reduction in mean aortic lesion area compared to apo E-deficient control mice. Furthermore, the lesions in the double mutants were less advanced, consisting primarily of foam cell deposits and fatty streaks located on or directly adjacent to the aortic valve attachment sites. These studies directly demonstrate that the MCP-1 receptor, CCR2, plays an important role in atherogenesis.