Changes in Hyaluronan Metabolism and RHAMM Receptor Expression Accompany Formation of Complicated Carotid Lesions and May be Pro-Angiogenic Mediators of Intimal Neovessel Growth.

Previous studies have shown that changes in expression of the glycosaminoglycan, hyaluronan (HA) were associated with erosion in areas of post-mortem coronary artery liable to rupture. Angiogenesis is an important feature of ulcerating haemorrhagic plaques prone to rupture. HA is a glycosaminoglycan known to possess potent angiogenic properties on metabolism to oligosaccharides of HA (o-HA) in the presence of hyaluronidase (HYAL) enzymes. In this study, we have examined HA receptor and HYAL enzyme expression in a series of carotid artery specimens used as vascular transplants and exhibiting various stages of atherosclerotic lesions as determined by anatomo-pathology. Our results demonstrated dramatically increased expression of HYAL-1 in regions of inflammation associated with complicated plaques. Receptor for HA-mediated motility (RHAMM), which is known to be important in transducing angiogenic signals in vascular endothelium, was strongly expressed on intimal blood vessels from complicated lesions but almost absent from other regions including adventitial vessels. Metabolism of HA, together with up-regulation of RHAMM in complicated plaque lesions might be partly responsible for over-production of leaky neovessels and predisposition to plaque rupture.

Endogenous expression of C-reactive protein is increased in active (ulcerated noncomplicated) human carotid artery plaques.

BACKGROUND AND PURPOSE: There is growing evidence suggesting that C-reactive protein (CRP) is an effecter molecule able to induce and promote atherothrombosis. The presence of CRP in atherosclerotic plaques may reflect local production or infiltration from circulating CRP increased in general inflammatory responses. Our aim was to analyze the presence of CRP in human advanced carotid artery plaques with differential anatomo-pathological characteristics and to assess local expression of CRP and other proinflammatory genes in these lesions. METHODS: Human carotid artery specimens from 38 patients undergoing scheduled endarterectomy were classified into 3 groups: ulcerated (noncomplicated) (UNC, n=19), fibrous (F, n=12) and ulcerated (complicated/hemorrhagic) plaques (UC, n=7). The presence of CRP was evaluated by immunohistochemistry, and plasma samples were screened for circulating high-sensitivity C-reactive protein. TaqMan Low-density Arrays were used for study of genes related to inflammation (CRP, interleukin-6, macrophage colony-stimulating factor-1, monocyte chemotactic protein-1, cyclooxygenase-2). RESULTS: CRP mRNA levels were predominantly detected in UNC-high risk plaques but not in UC (P=0.001). UNC also exhibit the highest expression levels of other genes involved in the inflammatory responses: cyclooxygenase-2 (P<0.005 versus F and versus UC), IL-6 (P<0.005 versus F and versus UC) and monocyte chemoattractant protein-1 (P<0.01 versus F and versus UC). Plaque CRP mRNA levels correlated with immunohistochemical findings but were independent of plasma high-sensitivity CRP. In UNC plaques endothelial cells and inflammatory cells were strongly positive for CRP around areas of newly formed microvessels. CONCLUSIONS: In human high-risk carotid artery plaques (UNC) CRP expression reflects an active proinflammatory stage. Local synthesis of CRP could be involved in plaque neovascularization and increased risk of hemorrhagic transformation.

Intraplaque MMP-8 levels are increased in asymptomatic patients with carotid plaque progression on ultrasound.

Carotid atherosclerotic plaque remodelling and increased risk of symptomatic plaque rupture seem to be partially mediated by matrix metalloproteinases (MMPs). In this study, we have investigated whether different MMPs are related to carotid atherosclerosis or to recent ischaemic brain disease. Eighty-four consecutive patients undergoing carotid endarterectomy for symptomatic and asymptomatic disease were studied. Plaques were analysed by ultrasound and later by morphology. Plasma MMP-2, MMP-8 and MMP-9 levels were quantified by ELISA. MMP expression and activity in carotid plaques was analysed by Western blotting and in situ zymography. Results were analysed with respect to plaque stability, morphology, symptomatic disease, presence of vascular risk factors and plasma markers of acute inflammation as high sensitivity C-reactive protein (hsCRP), fibrinogen, D-dimer and white blood cell counts. Patients with hypoechogenic plaques on ultrasound had more plasma MMP-8 (p = 0.04) and increased MMP activity as assessed by in situ zymography. Asymptomatic patients with plaque progression had more active intraplaque MMP-8 than asymptomatic patients without plaque progression. Presence of recent intraplaque haemorrhage or past history of CAD was related to increased activity of MMPs as assessed by in situ zymography (p < 0.01, CI 95% 0.8-1.0). Plasma MMP-8 and MMP-9, but not MMP-2 levels, decrease with time after ischaemic stroke. Patients with hypertension had more intraplaque active MMP-9 than normotensive (p = 0.03, CI 95% 0.7-1.0). Hypoechogenic carotid plaques had increased MMP activity and asymptomatic patients with plaque progression show increase intraplaque MMP-8 levels.