Small leucine-rich proteoglycans in atherosclerotic lesions: novel targets of chronic statin treatment?

Small leucine-rich proteoglycans (SLRPs), such as decorin and biglycan, regulate the assembly and turnover of collagenous matrix. The aim of the study was to analyse the effect of chronic rosuvastatin treatment on decorin, biglycan and the collagen matrix in ApoE-deficient mice. Twenty-week-old male ApoE-deficient mice received normal chow or 20 mg rosuvastatin/kg × day for 32 weeks. Subsequently, matrix composition was analysed by histochemistry and immunostaining at the aortic root and in innominate arteries of ApoE deficient mice as well as in human carotid endarterectomy specimens. Immunoblotting of proteoglycans was performed from aortic extracts of ApoE-deficient mice. Immunohistochemistry and immunoblotting revealed strongly increased decorin and biglycan deposition in atherosclerotic plaques at the aortic root and in innominate arteries. In contrast, versican and perlecan expression was not changed by rosuvastatin. Furthermore, matrix metalloproteinase 2 and gelatinolytic activity were decreased in response to rosuvastatin and a condensed collagen-rich matrix was formed. In carotid endarterectomy specimens of statin-treated patients increased decorin and biglycan accumulation was detected as well. Drug treatment did not change low-density lipoprotein (LDL) plasma levels in ApoE-deficient mice and did not significantly affect lipid retention at the aortic root level as demonstrated by oil-red O staining and immunohistochemistry of LDL. Long-term treatment with rosuvastatin caused pronounced remodelling of atherosclerotic plaque matrix characterized specifically by enrichment with SLRPs and formation of a condensed collagen matrix. Therefore, decorin and biglycan might represent novel targets of statin treatment that contribute to a stable plaque phenotype.

Cyclooxygenase inhibitors repress vascular hyaluronan-synthesis in murine atherosclerosis and neointimal thickening.

Hyaluronan (HA) is a key molecule of the extracellular matrix that is thought to be critically involved in both atherosclerosis and restenosis. Recently, it has been demonstrated that the cyclooxygenase (COX) products, prostacyclin and prostaglandin E(2), induce HA synthesis in vitro by transcriptional up-regulation of HA-synthase 2 (HAS2) and HAS1. The relative roles in atherosclerotic and restenotic artery disease of tissue specifically expressed COX-1 and COX-2 are still under debate. Thus, the present study aimed to investigate the effect of COX isoform inhibition on HA-accumulation and regulation of HAS isoform expression in two models of pathologic artery remodelling in vivo. Firstly, ApoE-deficient mice were treated with a prototypic isoform non-selective inhibitor, indomethacin or with a prototypic COX-2 selective inhibitor, rofecoxib, for 8 weeks. Aortic HAS mRNA expression and HA-accumulation in atherosclerotic aortic root lesions were analyzed. Secondly, neointimal hyperplasia was induced by carotid artery ligation in ApoE-deficient mice on a high fat diet and the effects of the COX inhibitors were determined after 4 weeks of treatment. Intimal HA-accumulation was markedly reduced in both models by indomethacin and rofecoxib. This coincided with a strong inhibition of HAS1 mRNA expression in both models and with decreased HAS2 mRNA in the aorta of ApoE-deficient mice. HAS3 was not affected. The repression of HA-accumulation by both COX-2 selective and non-selective COX inhibition implicates COX-2 in the regulation of HA synthesis via stimulation of HAS1 and HAS2 expression in vivo. Modulation of vascular HA-accumulation might play a role in chronic effects of COX inhibitors on the progression of atherosclerosis.

Differential effects of medroxyprogesterone acetate on thrombosis and atherosclerosis in mice.

BACKGROUND AND PURPOSE: The risk for cardiovascular events including venous and arterial disease and stroke is elevated after treatment with estrogen and medroxyprogesterone acetate (MPA) in postmenopausal women. Here, we have investigated the effect of MPA on arterial thrombosis and atherosclerosis in a murine model of atherosclerosis. EXPERIMENTAL APPROACH: Apolipoprotein E (ApoE)-/- mice were bilaterally ovariectomized and treated with placebo, MPA (27.7 microg day(-1)) and MPA + 17-beta-oestradiol (E2; 1.1 microg day(-1)) for 90 days, on a Western-type diet. Thrombotic response was measured in a photothrombosis model, platelet activation by fluorescence activated cell sorting (FACS) analysis (CD62P) and thrombin generation by the endogenous thrombin potential (ETP). Furthermore, aortic plaque burden and aortic root plaque composition were determined. KEY RESULTS: MPA and MPA + E2-treated animals showed an aggravated thrombotic response shown by significantly reduced time to stable occlusion. The pro-thrombotic effect of MPA was paralleled by increased ETP whereas platelet activation was not affected. Furthermore, MPA + E2 reduced the number of cells positive for alpha-smooth muscle actin and increased hyaluronan in the plaque matrix. Interestingly, total plaque burden was reduced by MPA but unchanged by MPA + E2. CONCLUSION AND IMPLICATIONS: Long-term treatment with MPA and MPA + E2 increased arterial thrombosis despite inhibitory effects of MPA on atherosclerosis in ApoE-deficient mice. Increased thrombin formation, reduced smooth muscle content and remodelling of non-collagenous plaque matrix may be involved in the pro-thrombotic effects. Thus, MPA exhibits differential effects on arterial thrombosis and on atherosclerosis.

Overexpression of prostaglandin EP3 receptors activates calcineurin and promotes hypertrophy in the murine heart.

AIMS: Prostaglandin E(2) (PGE(2)) has been shown to mediate anti-ischaemic effects and cardiomyocyte hypertrophy and there is evidence for an involvement of the prostaglandin EP(3)-receptor subtype. This study focuses on the EP(3)-mediated hypertrophic action and investigates intracellular signalling pathways of the EP(3)-receptor subtype in the murine heart. METHODS AND RESULTS: Cardiac function was analyzed in vivo by magnetic resonance imaging (MRI) in transgenic (tg) mice with cardio-specific overexpression of the EP(3) receptor in comparison with wild-type (wt) mice. Left ventricular (LV) function was determined in isolated perfused hearts subjected to 60 min of zero-flow ischaemia and 45 min of reperfusion. Calcineurin activity and nuclear activity of nuclear factor of activated T-cells (NFAT) were determined by a modified malachite green assay and ELISA, respectively. Extracellular matrix compounds were analyzed by RT-PCR and histology. MRI indicated a significant increase in end-diastolic and end-systolic volume in tg hearts. LV ejection fraction was severely decreased in tg hearts while the relative LV mass was significantly increased. In Langendorff perfused hearts, EP(3)-receptor overexpression resulted in a marked blunting of the ischaemia-induced increase in LV end-diastolic pressure and creatine kinase release. Analysis of EP(3)-receptor-mediated signalling revealed significantly increased calcineurin activity and nuclear activity of NFAT in tg hearts. Moreover, elevated mRNA levels of collagen types I and III as well as the collagen-binding proteoglycans biglycan and decorin were detected in tg hearts. CONCLUSION: EP(3)-receptor-mediated signalling results in a significant anti-ischaemic action and activation of the pro-hypertrophic calcineurin signalling pathway, suggesting the involvement of the EP(3) subtype in both PGE(2)-mediated cardioprotection as well as cardiac hypertrophy.