Dynamin and perforin are associated with neovascularisation in advanced carotid plaques

Intimal plaque neovascularization is associated with the development of symptomatic disease and thrombosis, with new 'leaky' fragile microvessels prone to haemorrhage. Perforin or pore forming protein is involved in vascular cell death by forming pores in target cells. Enzymes, in particular, granzyme B are secreted by immune infiltrates present in inflammatory plaque regions and have been shown to induce endothelial cell apoptosis. Similarly, dynamin-2 is a GTPase which mediates oxidised low density lipoprotein-induced apoptosis and is also required for granzyme B-mediated exocytosis and apoptosis. Our pilot studies identified increased expression of these proteins in complicated atherosclerotic plaques. Here we demonstrate by immunohistochemistry that both proteins are over-expressed in angiogenic regions of complicated carotid plaques. Dynamin-2 was extensively localised around microvessels and in immune infiltrating cells whilst perforin was localised in immune infiltrating cells, endothelial cells and smooth muscle cells. Over-expression of these proteins may contribute to plaque destabilisation by increasing cellular apoptosis in vulnerable atherosclerotic plaques.

Angiogenesis and inflammation in carotid atherosclerosis

Carotid atherosclerosis is a leading cause of cerebrovascular events. The control of cardiovascular risk factors, i.e. tobacco smoking, alcohol abuse, hypertension, dyslipidemia, diabetes and obesity proved to reduce number of fatal and non-fatal strokes but failed to prevent important number of them. Screening for biomarkers in individuals at high risk of symptomatic vascular disease helped to identify some of them. However, as disease is by its nature multifocal, global testing for biomarkers may have limited practical application. New imaging techniques, including direct visualization of artery metabolism, by 18-FDG-PET, has brought new tools to study local atherosclerosis progression and individual plaque metabolic activity. Advances in molecular biology helped to identify inflammatory genes and its strong link to angiogenesis. The later, is thought to play a key role in the transformation to unstable plaque. Studies of the complex role that plays angiogenesis in plaque development will help in future to design effective therapies addressed at the individual cell level. The purpose of the review is to bring new insights into complicated pathophysiology of carotid atherosclerosis.

Overexpression of hypoxia/inflammatory markers in atherosclerotic carotid plaques

Hypoxia, angiogenesis and inflammation leads to plaque progression and remodelling and may significantly contribute towards plaque rupture and subsequent cerebrovascular events. Our aim was to study, markers of hypoxia and inflammation previously identified by microarray analysis, in atherosclerotic carotid arteries with low to moderate stenosis. We hoped to describe different cellular populations expressing the studied markers. The location of selected inflammatory molecules obtained as vascular transplants from organ donors were analysed by immunohistochemistry with monoclonal and polyclonal antibodies. Paraffin-embedded sections were cut and probed with antibodies recognizing active B and T-lymphocytes (CD30), hypoxia-inducible factor-1alpha, endoglin (CD105), Interleukin-6 and C-reactive protein. We observed a notable overexpression of HIF-1alpha in inflammatory and hypoxic areas of carotid arteries in all types of lesions from type II-V taken from the patients with carotid stenosis less than 50%. This suggests that HIF-1alpha may have a putative role in atherosclerosis progression and angiogenesis. Dynamic changes in the non-occluding plaques may explain some of the clinical events in patients with low to moderate carotid stenosis.

Cheiradone: a vascular endothelial cell growth factor receptor antagonist

BACKGROUND

Angiogenesis, the growth of new blood vessels from the pre-existing vasculature is associated with physiological (for example wound healing) and pathological conditions (tumour development). Vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF) are the major angiogenic regulators. We have identified a natural product (cheiradone) isolated from a Euphorbia species which inhibited in vivo and in vitro VEGF- stimulated angiogenesis but had no effect on FGF-2 or EGF activity. Two primary cultures, bovine aortic and human dermal endothelial cells were used in in vitro (proliferation, wound healing, invasion in Matrigel and tube formation) and in vivo (the chick chorioallantoic membrane) models of angiogenesis in the presence of growth factors and cheiradone. In all cases, the concentration of cheiradone which caused 50% inhibition (IC50) was determined. The effect of cheiradone on the binding of growth factors to their receptors was also investigated.

RESULTS

Cheiradone inhibited all stages of VEGF-induced angiogenesis with IC50 values in the range 5.20-7.50 microM but did not inhibit FGF-2 or EGF-induced angiogenesis. It also inhibited VEGF binding to VEGF receptor-1 and 2 with IC50 values of 2.9 and 0.61 microM respectively.

CONCLUSION

Cheiradone inhibited VEGF-induced angiogenesis by binding to VEGF receptors -1 and -2 and may be a useful investigative tool to study the specific contribution of VEGF to angiogenesis and may have therapeutic potential.

Expression of signaling molecules associated with apoptosis in human ischemic stroke tissue

There is growing evidence that, because of the highly significant differences in gene activation/protein expression between animal models of stroke and stroke patients, the current treatment strategies based on animal stroke models have been unsuccessful. Therefore, it is imperative that the pathobiology of human stroke be studied. As a first step here, Western blotting and immunohistochemistry were employed to examine expression and tissue localization of key apoptotic proteins in infarct and peri-infarcted (penumbra) from grey and white matter in human postmortem tissue of 18 patients who died between 2 and 37 d after stroke caused by large vessel disease. The contralateral hemisphere was used as a control. JNK1, JNK2, and p53 were upregulated in the majority of samples, whereas Bcl-2, caspase-3, active caspase-3, phosphorylated p53 (p-p53), phosphorylated JNK1 (p-JNK1), and phosphorylated JNK2 (p-JNK2) were upregulated in approximately half of the samples. JNK1 expression was positively correlated with JNK2 expression in grey and white matter infarct and penumbra, whereas active caspase-3 levels were positively correlated with p-JNK2 levels in grey and white matter infarct. Using indirect immunoperoxidase staining of paraffin-embedded sections, active caspase-3 was found in infarcted neurons that co-localized with TUNEL-positive cells. p-JNK localization in the nuclei of TUNELpositive cells with the morphological appearance of neurons from infarct and penumbra was also demonstrated. The use of Kaplan Meier survival data demonstrated that the presence of Bcl-2 in penumbra of grey matter correlated significantly with shorter survival (p = 0.006). In conclusion, the present study has identified significantly altered expression of apoptotic proteins in human stroke tissue and shown that the presence of Bcl-2 in penumbra of grey matter has prognostic value. It is tempting to suggest that further studies of apoptotic proteins in human stroke may lead to identification of novel targets for drug discovery.

Leukaemia inhibitory factor is over-expressed by ischaemic brain tissue concomitant with reduced plasma expression following acute stroke

Leukaemia inhibitory factor (LIF) is a glycoprotein of the interleukin-6 family, which has potent pro-inflammatory properties and is involved in regulation of neuronal differentiation. We have previously identified its upregulation in gene microarrays following acute ischaemic stroke in man. LIF expression and localization was measured in human ischaemic stroke autopsy specimens, in a rat model of middle cerebral artery occlusion (MCAO) and in human foetal neural cell cultures following oxygen-glucose deprivation (OGD) by Western blotting and immunohistochemistry. Circulating LIF was determined in the plasma of patients in the hyper-acute stroke phase using a multiplex enzyme-linked-immunosorbent serologic assay system. Patients demonstrated an increase in LIF expression in peri-infarcted regions with localization in neurons and endothelial cells of microvessels surrounding the infarcted core. The rat MCAO model showed similar upregulation in neurons with a peak increase at 90 min. Circulating serum LIF expression was significantly decreased in the hyper-acute phase of stroke. Brain-derived neurons and glia cultured in vitro demonstrated an increase in gene/protein and protein expression respectively following exposure to OGD. Increased LIF expression in peri-infarcted regions and sequestration from the peripheral circulation in acute stroke patients are characteristic of the pathobiological response to ischaemia and tissue damage.

Blood-borne tissue factor activity predicts major cerebrovascular events in patients undergoing carotid endarterectomy: results from a 1-year follow-up study

BACKGROUND

Tissue factor (TF) expression is increased in inflammatory atherosclerotic plaques and has been related to plaque thrombogenicity. Blood-borne TF activity seems to contribute to a procoagulant state in patients with vascular risk factors. The aim of this study was to assess whether the expression of TF in carotid plaques from patients undergoing carotid endarterectomy (CEA) or/and blood-borne ('circulating') TF activity could predict future vascular complications.

METHODS

A total of 105 consecutive patients (85 male and 20 female aged 61-77 years)undergoing CEA for high-grade internal carotid artery were included in the study. Carotid artery specimens were classified into active (n = 52; rich in inflammatory cells) and nonactive plaques (n = 53; poor in inflammatory cells or fibrous). TF mRNA levels in carotid plaques were assessed by real-time PCR (TaqMan Low-Density Arrays) and TF protein levels by Western blot. Blood-borne TF activity and other biochemical parameters, including low-density lipoprotein cholesterol (LDLc) levels and high-sensitivity C-reactive protein, were measured prior to surgery. Patients were followed up for 1 year and vascular and nonvascular complications were scored.

RESULTS

TF expression was higher in active CEA plaques. Patients with active CEA plaques exhibited higher plasma LDLc levels (3.6 +/- 0.7 vs. 2.1 +/- 1 mM, p < 0.05) that positively correlated with plaque TF mRNA levels (p = 0.0125; r = 0.9). Blood-borne TF activity did not correlate with plasma LDLc levels and was unrelated to the anatomo-pathological characteristic of the CEA plaques (thrombosis, rupture, inflammation, lipid core, necrosis or calcification). Circulating TF activity predicted vascular complications at 1 year, including fatal (OR, 1.18; 95% CI, 0.6-2.2, p < 0.01) and nonfatal ischemic stroke (OR, 1.22; 95% CI, 0.5-2.0, p < 0.05) and symptomatic peripheral vascular disease (OR, 1.48; 95% CI, 0.4-2.6, p < 0.005).

CONCLUSIONS

Blood-borne TF activity prior to CEA but not local TF expression or plasma LDLc levels predict cerebrovascular and peripheral vascular disease events at 1 year in elderly patients subjected to CEA for high-grade carotid stenosis.

Increased tissue factor, MMP-8, and D-dimer expression in diabetic patients with unstable advanced carotid atherosclerosis

Advanced atherogenesis is characterized by the presence of markers of enhanced prothrombotic capacity, attenuated fibrinolysis, and by clinical conditions associated with defective coagulation. Diabetes may be associated with enhanced lesion instability and atherosclerotic plaque rupture. Plaques obtained from 206 patients undergoing carotid endarterectomy were divided into diabetic (type 2) and nondiabetic and analyzed by Western blotting and immunohistochemistry to detect tissue factor (TF), metalloproteinases (MMP)-2, -8, -9, and fibrin/fibrinogen related antigens, and in situ zymography to detect MMP activity. Plasma samples were quantified for TF procoagulant activity, C-reactive protein, fibrinogen and D-dimer. Diabetic and symptomatic patients with hypoechogenic plaques had increased plasma TF activity and D-dimer, compared with those with hyperechogenic plaques (p = 0.03, p = 0.007, respectively). Diabetic, symptomatic patients had higher plasma D-dimer levels than asymptomatic patients (p = 0.03). There was a significant correlation between intramural TF levels and D-dimer in diabetic patients with symptomatic disease (p = 0.001, r2 = 0.4). In diabetic patients, plasma fibrinogen levels were higher in patients with hypoechogenic plaques (p = 0.007). Diabetic patients with ulcerated plaques had higher plasma D-dimer and MMP-8 levels than those with fibrous plaques (p = 0.02, p = 0.01, respectively). This data suggests that currently available circulating markers may be clinically useful to select diabetic patients at higher risk of atherothrombosis. Increased procoagulant activity in diabetic patients may be linked to increased mural remodeling.

Expression of cyclin-dependent kinase 5 mRNA and protein in the human brain following acute ischemic stroke

Neuronal cell death after brain ischemia may be regulated by activation of cyclin-dependent kinase 5 (Cdk5). In this study, expression of Cdk5 and its activator p35/p25 was examined in human post-mortem stroke tissue and in human cerebral cortical fetal neurons and human brain microvascular endothelial cells exposed to oxygen-glucose deficiency and reperfusion. The majority of patients demonstrated increased expression of Cdk5 and p-Cdk5 in stroke-affected tissue, with about a third showing increased p35 and p25 cleaved fragment as determined by Western blotting. An increase in Cdk5-, p-Cdk5- and p35-positive neurons and microvessels occurred in stroke-affected regions of patients. Staining of neurons became irregular and clumped in the cytoplasm, and nuclear translocation occurred, with colocalization of p35 and Cdk5. Association of Cdk5 with nuclear damage was demonstrated by coexpression of nuclear Cdk5 in TUNEL-positive neurons and microvessels in peri-infarcted regions. In vitro studies showed up-regulation and/or nuclear translocation of Cdk5, p-Cdk5 and p35 in neurons and endothelial cells subjected to oxygen-glucose deficiency, and strong staining was associated with propidium iodide positive nuclei, an indicator of cellular damage. These results provide new evidence for a role of Cdk5 in the events associated with response to ischemic injury in humans.

Cellular prion protein is increased in the plasma and peri-infarcted brain tissue after acute stroke

The physiologic properties of the normal cellular prion protein (PrP(C)) have not been established fully, although recent evidence showed its upregulation in cerebral ischaemia. Using patients, animal models, and in vitro studies we aimed to identify in detail the expression and localization of PrP(C) in ischemic stroke. Patients in acute phase of ischaemic stroke had increased plasma levels of circulating PrP(C) as compared to healthy age- and gender-matched controls (3.1 +/- 1.4 vs. 1.9 +/- 0.7 ng/ml, P = 0.002). Immunohistochemistry showed increased expression of PrP(C) in the soma of peri-infarcted neurones as well as in the endothelial cells (EC) of micro-vessels and inflammatory cells in peri-infarcted brain tissue from patients who survived for 2-34 days after an initial stroke. The same pattern was repeated 1-48 hr after MCAO. RT-PCR showed increased gene expression of PrP(C) by human foetal neurons (HFN) after 12 hr of oxygen glucose deprivation (OGD), which remained increased after 24 hr reperfusion. Western blotting confirmed that protein expression was similarly upregulated, and fluorescent labeling showed a notable increase in peri-nuclear and axonal PrP(C) staining intensity. Increased plasma PrP(C) seems to reflect endogenous expression in acute stroke-affected brain tissue. Increased cellular expression in peri-infarcted regions may influence hypoxia-induced cell damage, although the effects on EC survival and angiogenesis remain to be elucidated.

Investigation of downstream target genes of PAX3c, PAX3e and PAX3g isoforms in melanocytes by microarray analysis

PAX3 encodes a transcription factor, which with Zic1 is necessary for induction of the neural crest during early embryonic development. There are 7 human PAX3 isoforms (a-h). PAX3e is the full length isoform comprising 10 exons. PAX3c comprises 8 exons plus 5 codons of intron 8, while PAX3g has a truncated transactivation domain. Previous studies by us indicated that these isoforms have different activities in melanocytes in vitro. In this study, a mouse gene oligo array ( approximately 7.5 k oligos), from the Human Genome Mapping Project (HGMP) Resource Centre, was used to screen for alterations in downstream gene expression in PAX3c, PAX3e and PAX3g melanocyte transfectants, compared with empty vector controls. The data analyses identified 109 genes up or downregulated, at least 2-fold, and involved in cell differentiation, proliferation, migration, adhesion, apoptosis and angiogenesis. Semi-quantitative RT-PCR and Western blotting confirmed the changes identified by microarrays for several putative targets of PAX3, including Met, MyoD and Muc18, and previously undescribed targets, including Dhh, Fgf17, Kitl and Rac1. Thus, our data reveal that PAX3 isoforms regulate distinct but overlapping sets of genes in melanocytes in vitro.

PAX3 and PAX3-FKHR promote rhabdomyosarcoma cell survival through downregulation of PTEN

PAX3 or PAX3-FKHR expression is implicated in cell transformation and tumourigenesis. Here, C2C12 myoblasts were transfected with a sense Pax3 vector and a pTet-On system to induce Pax3 expression, whereas to downregulate PAX3-FKHR, Rh18 was transfected with an antisense Pax3 with a pTet-On system. The inhibition of PAX3-FKHR in Rh18 induced upregulation of PTEN. Decreased resistance to apoptosis and increased transformation ability were observed in the Rh18 cells with PAX3-FKHR downregulation. Conversely, Pax3 induction in C2C12 cells downregulated the expression of PTEN and p27(Kip1). These results indicate that the involvement of PAX3 and PAX3-FKHR in rhabdomyosarcoma tumourigenesis may be through downregulation of PTEN tumour suppressor gene, affecting the PTEN/AKT survival pathway.

Can angiogenesis be exploited to improve stroke outcome? Mechanisms and therapeutic potential

Recent developments in our understanding of the pathophysiological events that follow acute ischaemic stroke suggest an important role for angiogenesis which, through new blood vessel formation, results in improved collateral circulation and may impact on the medium-to-long term recovery of patients. Future treatment regimens may focus on optimization of this process in the ischaemic boundary zones or 'penumbra' region adjacent to the infarct, where partially affected neurons exposed to intermediate perfusion levels have the capability of survival if perfusion is maintained or normalized. In this review, we present evidence that angiogenesis is a key feature of ischaemic stroke recovery and neuronal post-stroke re-organization, examine the signalling mechanisms through which it occurs, and describe the therapeutic potential of treatments aimed at stimulating revascularization and neuroprotection after stroke.

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.

Pathophysiology of Acute Ischaemic Stroke: An Analysis of Common Signalling Mechanisms and Identification of New Molecular Targets

Stroke continues to be a major cause of death and disability. The currently available therapies have proven to be highly unsatisfactory (except thrombolysis) and attempts are being made to identify and characterize signalling proteins which could be exploited to design novel therapeutic modalities. The pathophysiology of stroke is a complex process. Delaying interventions from the first hours to days or even weeks following blood vessel occlusion may lead to worsening or impairment of recovery in later stages. The objective of this review is to critically evaluate the major mechanisms underlying stroke pathophysiology, especially the role of cell signalling in excitotoxicity, inflammation, apoptosis, neuroprotection and angiogenesis, and highlight potential novel targets for drug discovery.

Hyaluronan-mediated angiogenesis in vascular disease: uncovering RHAMM and CD44 receptor signaling pathways

The correct formation of new blood vessels from existing vasculature (angiogenesis) is essential for embryogenesis and the effective repair of damaged or wounded tissues. However, excessive and detrimental vascularization also occurs in neoplasia, promoting tumour growth and metastasis, as well as in proliferative diabetic retinopathy and atherosclerosis. Greater understanding of the mechanisms controlling the angiogenic process will allow optimization of wound healing, and provide mechanisms to inhibit vascularization in tumours and other diseases. Evidence supports a cascade of events in which the perturbation of one of the steps is sufficient to significantly inhibit neovascularization. The extracellular macromolecules, notably glycosaminoglycans (GAGs), are important mediators of angiogenesis. Hyaluronan (HA), a large, non-sulphated GAG, was first discovered in the vitreous of the eye [.], and is ubiquitously expressed in the extracellular matrix (ECM) of tissues. Native high molecular weight HA (n-HA) is anti-angiogenic, whereas HA degradation products (o-HA; 3-10 disaccharides) stimulate endothelial cell (EC) proliferation, migration and tube formation following activation of specific HA receptors in particular, CD44 and Receptor for HA-Mediated Motility (RHAMM, CD168). The involvement of HA in the regulation of angiogenesis makes it an attractive therapeutic target. We review the role of o-HA in modulation of angiogenesis during tissue injury, and vascular disease, focusing on receptor-mediated signal transduction pathways that have been evaluated.

Functional Analysis of Alternative Isoforms of the Transcription Factor PAX3 in MelanocytesIn vitro

Transcription factor PAX3 has seven isoforms of which PAX3c has been studied extensively whereas the functions of the other isoforms are less well known. Here, we found that PAX3 isoforms in a stable transfection system have different biological functions in mouse melanocytes in vitro. PAX3a and PAX3b had negative effects on melanocyte proliferation but had no discernable effect on melanocyte growth in soft agar. PAX3a did not affect cell migration and apoptosis but PAX3b reduced migration and accelerated apoptosis. PAX3c and PAX3d promoted cell proliferation, migration, transformation, and survival. PAX3e reduced melanocyte growth; transformation and migration were unchanged and apoptosis was increased in vitro. PAX3g did not influence cell proliferation or apoptosis. Cells expressing PAX3g were able to grow in soft agar but migration was reduced. PAX3h increased cell proliferation, migration, survival, and transformation. These functional studies have advanced our understanding of the effects of PAX3 isoforms in melanocytes and their potential contribution in tumorigenesis.

D-dimer local expression is increased in symptomatic patients undergoing carotid endarterectomy

BACKGROUND

Although atherosclerosis is a silent widespread disease, the focal character of the lesions triggering the clinical manifestations is unquestionable. We hypothesized that symptomatic patients with advanced, unstable carotid plaques have increased local intraplaque and circulating levels of fibrin-fibrinogen related products.

METHODS

Plaque tissue and plasma samples were studied in 106 patients undergoing endarterectomy for symptomatic and asymptomatic carotid disease. Fibrin-fibrinogen related products were evaluated by ELISA, Western-blotting, and histology. All tested parameters were compared with patient carotid symptomatology, multiple vascular risk factors (VRF), bilateral carotid pathology, ultrasound examination, and previous therapies with statins and/or antiplatelet drugs.

RESULTS

In symptomatic patients, plasma D-dimer was elevated in patients with unstable carotid plaques (UNS) compared with stable (STA) ones (857+/-121 vs. 692+/-156 ng/ml, p=0. 026). Furthermore, plasma D-dimer was significantly increased in patients with a coexistence of carotid and coronary artery disease, compared to others (976+/-325 vs. 714+/-197 ng/ml; p<0.001). Intra-plaque D-dimer content was increased in ulcerated-complicated (UC) plaques compared with fibrous non-complicated (F) plaques in symptomatic patients (5.9+/-1 vs. 1.8+/-1, p<0.001), and in patients with hypercholesterolaemia, compared with those with normal cholesterol levels (6.1+/-1 vs. 2.9+/-0.7; p=0.027). However, there was no correlation between D-dimer content in the carotid plaque and plasma D-dimer levels.

CONCLUSIONS

Hypercholesterolemia and UC plaques appear to be associated with high fibrin intraplaque turnover as demonstrated by higher intraplaque D-dimer. Plasma markers of fibrin turnover were increased in UNS plaques, and in patients with coexisting carotid and coronary artery disease. Although, both plasma and plaque D-dimers were associated with unstable carotid disease, the usefulness of the measurement of plasma D-dimer in these patients should be confirmed by prospective studies.

Hyaluronan expression following middle cerebral artery occlusion in the rat

Hyaluronic acid, a major component of the brain extracellular matrix, is a regulator of angiogenesis, cell differentiation and migration. We used the rat middle cerebral artery occlusion model to show hyaluronan accumulation in stroke-affected areas. Using reverse transcription-polymerase chain reaction and Western blotting we showed up-regulation of hyaluronidase-1 and 2 between 1 h and 21 days after stroke. Hyaluronidase-1 was up-regulated earlier than hyaluronidase-2. The hyaladherins, receptor for hyaluronan-mediated motility and CD44 were also increased after stroke. Using immunohistochemistry, we showed association of hyaluronidases 1/2 and hyaladherins with neurons in the infarcted and peri-infarcted regions and hyaluronidase-1 with microvessels. Hyaluronan synthesis and degradation in the stroke hemisphere might have an impact on neuronal survival, angiogenesis and general tissue remodelling after stroke.

Changes in hyaluronan production and metabolism following ischaemic stroke in man

The extent of recovery from stroke is dependent on the survival of neurons, particularly in peri-infarcted regions. Angiogenesis is critical for the development of new microvessels and leads to re-formation of collateral circulation, reperfusion and better recovery. Hyaluronan (HA) is an important component of the brain extracellular matrix and a regulator of cellular differentiation, migration, proliferation and angiogenesis. We have found that the production of total HA and low molecular mass 3-10 disaccharides of HA (o-HA) was increased in post-mortem tissue and in the serum of patients 1, 3, 7 and 14 days (peaking at 7 days) after ischaemic stroke. Hyaluronidase activity was also increased in serum samples (peaking after 3 days), which might explain the subsequent increase in o-HA. Affinity-histochemical staining was performed using a HA-specific biotinylated binding protein, and it showed enhanced deposition of HA in blood vessels and intracellularly as well as in the nuclei of peri-infarcted neurons. Western blotting and immunohistochemistry demonstrated upregulation of HA synthases (HAS1 and 2) and hyaluronidases (HYAL1 and 2) in inflammatory cells from both stroke and peri-infarcted regions of the brain. HYAL1 was upregulated in microvesssels and intracellularly in neurons, whilst HAS2 became translocated into the nuclei of neurons in peri-infarcted areas. Receptor for HA-mediated motility was observed intracellularly and in the nuclei of neurons, in the tunica media of larger blood vessels and in the endothelial cells of microvessels in stroke-affected tissue, whilst expression of other receptors for HA, CD44 and tumour necrosis factor-stimulated gene 6 (TSG-6) were mainly increased in infiltrating mononuclear cells from inflammatory regions. The data presented here demonstrate that HA breakdown is a feature of the acute stage of stroke injury. Increased o-HA production soon after stroke may be detrimental through enhancement of the inflammatory response, whilst activation of HA and/or o-HA-induced cellular signalling pathways in neurons and microvessels may impact on the remodelling process by stimulating angiogenesis and revascularization, as well as the survival of susceptible neurons.

Comparison of protective effects of aspirin, d-penicillamine and vitamin E against high glucose-mediated toxicity in cultured endothelial cells

This study compared the protective effects of three different anti-glycation compounds, aspirin, D-penicillamine and vitamin E, against high glucose and advanced glycation endproduct (AGE) mediated toxicity in cultured bovine aortic endothelial cells using two approaches. Their proliferation was assessed in culture in different concentrations of glucose (5.5-100 mmol/l) with and without these inhibitors. A monolayer of cultured endothelial cells was wounded and recovery at the wound site was measured following exposure to different concentrations of glucose with and without inhibitors. The ability of these compounds to protect cultured endothelial cells following exposure to bovine serum albumin-derived advanced glycation endproducts (BSA-AGE) was also studied. Addition of glucose to cultured endothelial cells inhibited their proliferation in a dose dependent manner. All three compounds protected against the anti-proliferative effects of high glucose, with vitamin E being the most effective. The migration of cultured endothelial cells following wounding was inhibited by increasing concentrations of glucose but was maintained in the presence of all three anti-glycation compounds with vitamin E, again giving the greatest protection. Vitamin E was also the most effective at protecting against the anti-proliferative effects of BSA-AGE. D-penicillamine was not as effective as vitamin E whereas aspirin offered no significant protection against AGE-induced cellular toxicity. Our studies suggest that compounds, such as vitamin E, with combined antiglycation and antioxidant properties offer maximum therapeutic potential in protection against high glucose and AGE-mediated cellular toxicity.