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Biomedical subjects

A M Heagerty

Publications and source records attributed to A M Heagerty.

At least 19 recordsLinked to original sources
PubMed2007

Contribution of VCAF-positive cells to neovascularization and calcification in atherosclerotic plaque development.

Calcification of the vessel wall is a regulated process with many similarities to osteogenesis. Progenitor cells may play a role in this process. Previously, we identified a novel gene, Vascular Calcification Associated Factor (VCAF), which was shown to be important in pericyte osteogenic differentiation. The aim of this study was to determine the localization and expression pattern of VCAF in human cells and tissues. Immunohistochemical analysis of seven atherosclerotic arteries confirmed VCAF protein expression within calcified lesions. In addition, individual VCAF-positive cells were detected within the intima and adventitia in areas where sporadic 3G5-positive pericytes were localized. Furthermore, VCAF-positive cells were identified in newly formed microvessels in association with CD34-positive/CD146-positive/c-kit-positive cells as well as in intact CD31-positive endothelium in internal mammary arteries. Western blot analysis confirmed the presence of VCAF (18 kD) in protein lysates extracted from human smooth muscle cells, endothelial cells, macrophages, and osteoblasts. In fracture callus samples from three patients, VCAF was detected in osteoblasts and microvessels. This study demonstrates the presence of VCAF in neovessels and raises the possibility that VCAF could be a new marker for vascular progenitor cells involved in a number of differentiation pathways. These data may have implications for the prevention or treatment of vascular disease.

Atherosclerosis↗
PubMed2006

Upregulated TRPC1 channel in vascular injury in vivo and its role in human neointimal hyperplasia.

Occlusive vascular disease is a widespread abnormality leading to lethal or debilitating outcomes such as myocardial infarction and stroke. It is part of atherosclerosis and is evoked by clinical procedures including angioplasty and grafting of saphenous vein in bypass surgery. A causative factor is the switch in smooth muscle cells to an invasive and proliferative mode, leading to neointimal hyperplasia. Here we reveal the importance to this process of TRPC1, a homolog of Drosophila transient receptor potential. Using 2 different in vivo models of vascular injury in rodents we show hyperplasic smooth muscle cells have upregulated TRPC1 associated with enhanced calcium entry and cell cycle activity. Neointimal smooth muscle cells after balloon angioplasty of pig coronary artery also express TRPC1. Furthermore, human vein samples obtained during coronary artery bypass graft surgery commonly exhibit an intimal structure containing smooth muscle cells that expressed more TRPC1 than the medial layer cells. Veins were organ cultured to allow growth of neointimal smooth muscle cells over a 2-week period. To explore the functional relevance of TRPC1, we used a specific E3-targeted antibody to TRPC1 and chemical blocker 2-aminoethoxydiphenyl borate. Both agents significantly reduced neointimal growth in human vein, as well as calcium entry and proliferation of smooth muscle cells in culture. The data suggest upregulated TRPC1 is a general feature of smooth muscle cells in occlusive vascular disease and that TRPC1 inhibitors have potential as protective agents against human vascular failure.

Animals↗
PubMed2005

Adenosine and hypoxic dilation of rat coronary small arteries: roles of the ATP-sensitive potassium channel, endothelium, and nitric oxide.

The aims of the study were to examine the roles of the ATP-sensitive potassium (K(ATP)) channel, the endothelium, and nitric oxide (NO) in the responses of rat coronary small arteries to adenosine and hypoxia. Segments of rat coronary vessel were investigated in vitro using pressure myography; all vessels studied developed stable spontaneous myogenic tone during equilibration. Glibenclamide (a K(ATP) channel inhibitor) reversed pinacidil but not 2-deoxyglucose-induced dilation. Both adenosine and hypoxia dilated the vessels, and glibenclamide did not reverse these responses. Endothelial removal or N(G)-nitro-L-arginine methyl ester (L-NAME) inhibited the dilation to adenosine by approximately 50%; subsequent addition of glibenclamide was without effect. Hypoxic dilation was completely inhibited by endothelium removal or L-NAME. We conclude that adenosine- and hypoxia-induced dilation of rat coronary arteries does not appear to involve the K(ATP) channel. Adenosine-induced dilation is partially and hypoxic dilation is completely dependent on endothelium-derived NO.

ATP-Binding Cassette Transporters↗
PubMed2005

Nifedipine gastrointestinal therapeutic system--hypertension management to improve cardiovascular outcomes.

Hypertension is a major cardiovascular risk factor, and its increasing prevalence is of great clinical concern. Despite the availability of numerous effective therapies, hypertension remains under-diagnosed and under-treated. Hypertension often coexists with other risk factors, and current guidelines recommend a multifactorial approach to management, with the aim of not only controlling blood pressure but also reducing overall cardiovascular risk. Nifedipine gastrointestinal therapeutic system (GITS) is a long-acting formulation of a calcium channel blocker. Once-daily dosing with nifedipine GITS has been shown to achieve smooth and continuous blood pressure control, identical to conventional first-line diuretic therapy. Small-scale clinical trials have also shown that nifedipine GITS positively affects markers of atherosclerotic disease, which may signify an additional clinical benefit, but this is yet to be demonstrated. The recently completed ACTION (A Coronary Disease Trial Investigating Outcome with Nifedipine GITS) trial provides further evidence that nifedipine GITS can be used safely in high-risk patients to treat angina, lower blood pressure and significantly improve clinical outcomes.

Adult↗
PubMed2004

Functional evidence of a role for two-pore domain potassium channels in rat mesenteric and pulmonary arteries.

1. Experiments were performed to elucidate the mechanism by which alterations of extracellular pH (pH(o)) change membrane potential (E(M)) in rat mesenteric and pulmonary arteries. 2. Changing pH(o) from 7.4 to 6.4 or 8.4 produced a depolarisation or hyperpolarisation, respectively, in mesenteric and pulmonary arteries. Anandamide (10 microm) or bupivacaine (100 microm) reversed the hyperpolarisation associated with alkaline pH(o), shifting the E(M) of both vessels to levels comparable to that at pH 6.4. In pulmonary arteries, clofilium (100 microm) caused a significant reversal of hyperpolarisation seen at pH 8.4 but was without effect at pH 7.4. 3. K(+) channel blockade by 4-aminopyridine (4-AP) (5 mm), tetraethylammonium (TEA) (10 mm), Ba(2+) (30 microm) and glibenclamide (10 microm) depolarised the pulmonary artery. However, shifts in E(M) with changes in pH(o) remained and were sensitive to anandamide (10 microm), bupivacaine (100 microm) or Zn(2+) (200 microm). 4. Anandamide (0.3-60 microm) or bupivacaine (0.3-300 microm) caused a concentration-dependent increase in basal tone in pulmonary arteries. 5. RT-PCR demonstrated the expression of TASK-1, TASK-2, THIK-1, TRAAK, TREK-1, TWIK-1 and TWIK-2 in mesenteric arteries and TASK-1, TASK-2, THIK-1, TREK-2 and TWIK-2 in pulmonary arteries. TASK-1, TASK-2, TREK-1 and TWIK-2 protein was demonstrated in both arteries by immunostaining. 6. These experiments provide evidence for the presence of two-pore domain K(+) channels in rat mesenteric and pulmonary arteries. Collectively, they strongly suggest that modulation of TASK-1 channels is most likely to have mediated the pH-induced changes in membrane potential observed in these vessels, and that blockade of these channels by anandamide or bupivacaine generates a small increase in pulmonary artery tone.

Animals↗
PubMed2003

A novel combination of promoter and enhancers increases transgene expression in vascular smooth muscle cells in vitro and coronary arteries in vivo after adenovirus-mediated gene transfer.

Recombinant adenoviruses are employed widely for vascular gene transfer. Vascular smooth muscle cells (SMCs) are a relatively poor target for transgene expression after adenovirus-mediated gene delivery, however, even when expression is regulated by powerful, constitutive viral promoters. The major immediate-early murine cytomegalovirus enhancer/promoter (MIEmCMV) elicits substantially greater transgene expression than the human cytomegalovirus promoter (MIEhCMV) in all cell types in which they have been compared. The Woodchuck hepatitis virus post-transcriptional regulatory element (WPRE) increases transgene expression in numerous cell lines, and fragments of the smooth muscle myosin heavy chain (SMMHC) promoter increase expression within SMC from heterologous promoters. We therefore, compared the expression of beta-galactosidase after adenovirus-mediated gene transfer of lacZ under the transcriptional regulation of a variety of combinations of the promoters and enhancers described, in vitro and in porcine coronary arteries. We demonstrate that inclusion of WPRE and a fragment of the rabbit SMMHC promoter along with MIEmCMV increases beta-galactosidase expression 90-fold in SMC in vitro and approximately 40-fold in coronary arteries, compared with vectors in which expression is regulated by MIEhCMV alone. Expression cassette modification represents a simple method of improving adenovirus-mediated vascular gene transfer efficiency and has important implications for the development of efficient cardiovascular gene therapy strategies.

Animals↗
PubMed2002

The involvement of matrix glycoproteins in vascular calcification and fibrosis: an immunohistochemical study.

Calcification and fibrointimal proliferation are associated with advanced complicated atherosclerosis in large arteries but may also occur in smaller vessels, resulting in ischaemic tissue necrosis. This study investigates whether the mechanisms of calcification and intimal fibrosis are similar in vessels of different sizes. The localization of osteopontin (OPN), matrix Gla protein (MGP), thrombospondin-1 (TSP-1), and cartilage oligomeric matrix protein (COMP) was investigated in three types of human vascular lesions: atherosclerosis, chronic vascular rejection (CVR) in renal allografts, and calcific uraemic arteriolopathy (calciphylaxis). These lesions were chosen as they affect different sized blood vessels and they exhibit a fibroproliferative intimal reaction, with or without calcification, resulting in luminal obliteration and ischaemic complications. OPN, MGP, TSP-1, and COMP were not detected in normal blood vessels. However, OPN and MGP were expressed at sites of calcification within atherosclerotic lesions and in microvessels in calciphylaxis, suggesting that calcification in different sized vessels may occur by a common mechanism. These proteins were not detected in areas of fibrointimal proliferation. In contrast, TSP-1 was localized primarily within the fibrous tissue of atherosclerotic lesions and was also expressed in the expanded fibrous intima of arteries showing CVR. COMP was localized primarily within the fibrous tissue under the lipid core of the majority of advanced atherosclerotic lesions. TSP-1 and COMP were also detected in areas of microcalcification in atherosclerotic lesions and TSP-1 was detected adjacent to areas of calcification in calciphylaxis. However, neither TSP-1 nor COMP was localized to calcific foci within these lesions. The localization of OPN, MGP, TSP-1, and COMP to pathological, but not normal arterial intima supports a pathogenetic role for these proteins in the development of vascular fibrosis and calcification. Modulation of their production and activity may offer a novel approach to the therapy of a number of vascular diseases.

Adult↗
PubMed2001

Adenovirus-mediated gene transfer of a secreted transforming growth factor-beta type II receptor inhibits luminal loss and constrictive remodeling after coronary angioplasty and enhances adventitial collagen deposition.

BACKGROUND: Extracellular matrix (ECM) remodeling is central to the development of restenosis after coronary angioplasty (PTCA). As a regulator of ECM deposition by vascular cells, substantial evidence implicates transforming growth factor-beta1 (TGF-beta1) in the pathogenesis of restenosis. We investigated the effects of intracoronary expression of a transgenic antagonist of TGF-beta1 on luminal loss after PTCA. METHODS AND RESULTS: Porcine coronary arteries were randomized to receive a recombinant adenovirus expressing a secreted form of TGF-beta type II receptor (Ad5-RIIs), an adenovirus expressing beta-galactosidase (Ad5-lacZ), or vehicle only by intramural injection at the site of PTCA. Computerized morphometry 28 days after angioplasty revealed a greater minimum luminal area in Ad5-RIIs-injected arteries (1.71+/-0.12 mm(2)) than in the Ad5-lacZ (1.33+/-0.13 mm(2)) or vehicle-only (1.08+/-0.17 mm(2); P=0.010 by ANOVA) groups. This was accompanied by greater areas within the internal (P=0.013) and external (P=0.031) elastic laminae in Ad5-RIIs-treated vessels. Adventitial collagen content at the site of injury was increased in the Ad5-RIIs group, in contrast to decreases in the Ad5-lacZ and vehicle-only groups (P=0.004). CONCLUSIONS: Adenovirus-mediated antagonism of TGF-beta1 at the site of PTCA reduces luminal loss after PTCA by inhibiting constrictive remodeling. Antagonism of TGF-beta1 stimulates the formation of a dense collagenous adventitia, which prevents constrictive remodeling by acting as an external scaffold. These findings demonstrate the potential of gene therapy-mediated antagonism of TGF-beta1 as prophylactic therapy for restenosis.

Adenoviridae↗
PubMed2001

Upregulation of collagen VIII following porcine coronary artery angioplasty is related to smooth muscle cell migration not angiogenesis.

Type VIII collagen is upregulated after vessel injury, and this collagen has been implicated in both smooth muscle cell migration and angiogenesis. This study examines the temporal and spatial pattern of expression of type VIII collagen in porcine coronary vessels at specific time points after balloon angioplasty. In situ hybridization studies demonstrated that collagen VIII messenger ribonucleic acid (mRNA) was markedly elevated in the neoadventitia at 3 days post-angioplasty. By 14 days, elevated collagen VIII message was seen mainly in the neointima and this expression decreased to background levels by 90 days. The distribution of collagen VIII protein, detected using immunohistochemistry, was similar but the up-regulation lagged behind the mRNA increase by a few days. Pre-treatment of sections with pepsin highlighted variations in the organization and appearance of extracellular collagen VIII containing structures in both injured and normal vessels. New vessel formation was evident in the neoadventitia after 3 days, but there was no colocalization of type VIII collagen immunostaining with that of von Willebrand factor (a marker of endothelial cells) in the neoadventitia. These data show that up-regulation of collagen VIII in the neoadventitia is an important early marker of the coronary arterial response to injury, and is not associated with new vessel formation.

Angioplasty, Balloon, Coronary↗
PubMed1999

Impaired flow-dependent dilatation in distal mesenteric arteries from the spontaneously hypertensive rat.

1. The aim of the study was to examine the hypothesis that flow-dependent dilatation is impaired in distal mesenteric arteries from adult spontaneously hypertensive rats (SHR) compared with normotensive Wistar-Kyoto rat (WKY) controls and to assess the role of nitric oxide (NO). 2. Arterial segments were cannulated, pressurized to 80 mmHg and allowed to develop spontaneous myogenic tone. Flow was increased incrementally in vessels from both strains and responses were also assessed before and after incubation with the NO synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME). Responses to flow in control vessels were also assessed before and after intraluminal perfusion with antibody-complement to disrupt the endothelium. 3. At a flow rate of 5 microliter min-1, arteries from the WKY dilated significantly (22 +/- 5%, P < 0.01, n = 29) compared with the diameter at zero flow, whereas arteries from the SHR did not (4 +/- 4%, n.s., n = 16). Incubation with L-NAME had no inhibitory effect on the responses to flow in either rat strain. In control arteries, antibody-complement treatment abolished the dilatation in response to both flow and acetylcholine (ACh, 1 microM). 4. We conclude that flow-dependent dilatation is impaired in distal mesenteric arteries from adult SHR compared with WKY controls. Furthermore, flow-dependent dilatation is endothelium dependent, but L-NAME insensitive, thus excluding the NO pathway in this abnormality. Impaired flow-dependent dilatation may contribute to the increased peripheral resistance in hypertension.

Animals↗
PubMed1998

Lipid second messengers derived from glycerolipids and sphingolipids, and their role in smooth muscle function.

The processes that link activation of an external receptor to the internal mechanisms that elicit a physiological response have been the subject of extensive investigation. It has been established that rather than just being an inert barrier to protect the cell from environmental damage, there are populations of phospholipids located within the plasma membrane that act as a reservoir for signalling molecules and when a receptor binds its appropriate activating ligand a chain of events is initiated which leads to the breakdown of these lipids and the release of second messengers. Such processes are rapid enough for physiological responses to be effected. The purpose of this review is to examine the profile of lipid second messengers derived from glycerophospholipids and sphingolipids. In the former class are included phosphoinositide and phosphatidylcholine and the latter includes sphingomyelin. Hydrolysis of such parent compounds is mediated by phospholipases and the profile of metabolites appears to be agonist specific and modulated by a number of mechanisms including heterotrimeric G-protein subunits, small G-proteins, alterations in intracellular calcium concentration, protein kinase C and tyrosine kinases. The recent interest in sphingolipids, particularly in vascular smooth muscle cells, has been provoked by the observation that ceramide and sphingoid base formation is observed in response to vasoconstrictor hormones.

Animals↗