Adventitial Side Research Articles

Abstract 9313: Contrast-Enhanced Ultrasound Imaging of Carotid Plaque Neovascularization is Useful for Identification of High-Risk Patients for Atherosclerotic Cardiovascular Diseases

Increased neovascularization in atherosclerotic plaques represents a feature of unstable plaques. Contrast-enhanced ultrasound (CEU) could be a potential technique for imaging plaque neovascularization in the carotid artery. This study examined whether CEU of the carotid artery may provide information of risk of cardiovascular diseases. Methods and Results: A total of 117 patients with CAD and a carotid plaque (IMT > 1.1 mm) underwent CEU study of the carotid artery. The carotid CEU was performed using perfluorobutane microbubbles as an ultrasound contrast agent and harmonic imaging software. The intra-plaque neovascularization was identified based on the rapid movement of the echogenic reflectors of microbubbles within the plaque. The plaque neovascularization was graded: Grade (G) 0, no visible microbubbles within the plaque; G1, moderate microbubbles confined to plaque adventitial side and/or shoulder; G2, extensive microbubbles throughout the plaque. In a total of 252 plaques from the study patients, the G1 plaque neovascularization was noted in 51 plaques (20%) and G2 in 27 plaques (11%). Patients with higher grade of the plaque neovascularization had higher prevalence of smoking, older age, higher levels of LDL-C and HbA1c, higher systolic blood pressure, greater PWV and carotid IMT (p < 0.05 in all). In logistic regression analysis, the G1/G2 plaque neovascularization was associated with acute coronary syndromes, multi-vessel coronary disease, chronic total coronary occlusions, ASO and previous stroke (OR 1.5, 2.0, 1.8, 2.2 and 1.6, 95% CI 1.2-2.5, 1.5-2.8, 1.1-3.1, 1.4-3.4 and 1.2-2.9, respectively, p < 0.01 in all), that was independent of carotid IMT. The change in plaque neovascularization during 6 months was examined in a subgroup of 30 patients. Plaque neovascularization regressed in 16 ( 80%) of 20 plaques graded as G1/G2 of 16 patients taking statin, while the regression did not occur in any plaques in 14 patients taking no statin. The carotid IMT did not change in either patients with or without statin treatment. Conclusions: The contrast-enhanced ultrasound study of the carotid artery may provide valuable information for risk status of systemic atherosclerosis and for efficacy of anti-atherosclerotic treatment beyond carotid IMT.

Variations in local elastic modulus along the length of the aorta as observed by use of a scanning haptic microscope (SHM)

Variations in microscopic elastic structures along the entire length of canine aorta were evaluated by use of a scanning haptic microscope (SHM). The total aorta from the aortic arch to the abdominal aorta was divided into 6 approximately equal segments. After embedding the aorta in agar, it was cut into horizontal circumferential segments to obtain disk-like agar portions containing ring-like samples of aorta with flat surfaces (thickness, approximately 1 mm). The elastic modulus and topography of the samples under no-load conditions were simultaneously measured along the entire thickness of the wall by SHM by using a probe with a diameter of 5 μm and a spatial resolution of 2 μm at a rate of 0.3 s/point. The elastic modulus of the wall was the highest on the side of the luminal surface and decreased gradually toward the adventitial side. This tendency was similar to that of the change in the elastin fiber content. During the evaluation of the mid-portion of each tunica media segment, the highest elastic modulus (40.8 ± 3.5 kPa) was identified at the thoracic section of the aorta that had the highest density of elastic fibers. Under no-load conditions, portions of the aorta with high elastin density have a high elastic modulus.

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 (200μg/ml; 50μl) 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.

New perspectives on vascular wall signaling: role of perivascular adipocytes and fibroblasts.

This communication represents personal perspectives of recent development in the newly evolved areas in vascular signaling mechanisms at the anatomical level of vascular walls from outside in, that is, from perivascular adventitial side to effectuate the control of vascular reactivity. Since half a century ago, the focus of interest in vascular biology has been confined primarily to the study of the excitation-contraction coupling of vascular smooth muscle (VSM) as well as neuroeffector mechanisms. During the past 3 decades, considerable advancement in the understanding of vascular signaling has been made via the discovery of endothelium-derived relaxation factors (EDRF), endothelium-derived hyperpolarizing factors (EDHF) and endothelium-derived contracting factors (EDCF). The discovery of nitric oxide (NO) as a major cellular messenger has also helped open up another huge area of research in oxidative stress and vascular diseases. In the past decade, concepts on vascular wall signaling have been extended from vascular endothelial cells and then translated to the other seemingly inert cellular components, such as perivascular adipocytes and adventitial fibroblasts. Growing body of evidences show that these cellularities contribute to both functional as well as structural integrity in vasculature with significant pathophysiological implications.

Theoretical study on the effects of pressure-induced remodeling on geometry and mechanical non-homogeneity of conduit arteries

A structure-based mathematical model for the remodeling of arteries in response to sustained hypertension is proposed. The model is based on the concepts of volumetric growth and constitutive modeling of the arterial tissue within the framework of the constrained mixture theory. The major novel result of this study is that remodeling is associated with a local change in the mass fractions of the wall constituents that ultimately leads to mechanical non-homogeneity of the arterial wall. In the new homeostatic state that develops after a sustained increase in arterial pressure, the mass fraction of elastin decreases from the intimal side to the adventitial side of arteries, while the collagen fraction manifests an opposite trend. The results obtained are supported by some experimental observations reported in the literature.

Adipose tissue-derived stem cells inhibit neointimal formation in a paracrine fashion in rat femoral artery

Subcutaneous adipose tissue contains a lot of stem cells [adipose-derived stem cells (ASCs)] that can differentiate into a variety of cell lineages. In this study, we isolated ASCs from Wistar rats and examined whether ASCs would efficiently differentiate into vascular endothelial cells (ECs) in vitro. We also administered ASCs in a wire injury model of rat femoral artery and examined their effects. ASCs expressed CD29 and CD90, but not CD34, suggesting that ASCs resemble bone marrow-derived mesenchymal stem cells. When induced to differentiate into ECs with endothelial growth medium (EGM), ASCs expressed Flt-1, but not Flk-1 or mature EC markers such as CD31 and vascular endothelial cadherin. ASCs produced angiopoietin-1 when they were cultured in EGM. ASCs stimulated the migration of EC, as assessed by chemotaxis assay. When ASCs that were cultured in EGM were injected in the femoral artery, the ASCs potently and significantly inhibited neointimal formation without being integrated in the endothelial layer. EGM-treated ASCs significantly suppressed neointimal formation even when they were administered from the adventitial side. ASC administration significantly promoted endothelial repair. These results suggested that although ASCs appear to have little capacity to differentiate into mature ECs, ASCs have the potential to secrete paracrine factors that stimulate endothelial repair. Our results also suggested that ASCs inhibited neointimal formation via their paracrine effect of stimulation of EC migration in situ rather than the direct integration into the endothelial layer.

Orthotopic replacement of the aortic valve with decellularized allograft in a sheep model

Tissue engineered (TE) allografts have been successfully applied in pulmonary circulation. The behavior of TE valves based on decellularized scaffolds in systemic circulation remains unexplored. We investigated the function, histological changes, potential of in-vivo re-endothelialization of decellularized aortic valve allografts in orthotopic position in sheep. Ovine aortic valve conduits ( n = 12) were decellularized with detergents and implanted as an aortic root in lambs (35–45 kg). For controls, fresh native ovine aortic valve conduits ( n = 6) were implanted. The valves were explanted at 3 and 9 months. In the experimental group, the valves exhibited trivial regurgitation and normal morphology with no signs of graft dilatation, degeneration or rejection. In some animals ( n = 2), we documented minimal calcification in the area of arterial anastomosis and in one, microthrombi formation on the leaflet surface. The luminal sides of the grafts were partially covered with an endothelial cell monolayer, neovasculogenesis was observed at the adventitial side. The valves in the control group appeared thickened, shrunken with marked calcification/degeneration signs, and advanced valve insufficiency. Detergent decellularized aortic valve allografts satisfy the higher requirements of the systemic circulation in sheep. As valve conduits become repopulated by endothelial and interstitial cells, they may re-gain the potential for growth.

Lateral Circumflex Femoral Artery: Not Always Atherosclerosis-Resistant

Sir: We read with great interest the article by Halvorson, Taylor, and Orgill (Plast. Reconst. Surg. 121: 121, 2008) about the radiographic patency of the descending branch of the lateral circumflex femoral artery. The group noted radiographic mean stenosis rates of 10 percent in the descending branch of the lateral circumflex femoral artery and 12.5 percent in the profunda femoris artery, suggesting that the vascular territory supplied by the profunda femoris is largely “atherosclerosis-resistant.” We are submitting a cautionary statement that in the end-stage renal disease patient these findings may not hold true. We recently reconstructed a 13 × 9-cm full-thickness defect of the anterior scalp created after excision of a malignant fibrous histiocytoma. The patient, a 75-year-old man with hypertension and coronary artery disease, underwent a renal transplant 12 years ago. Preoperatively, there was no overt evidence of significant lower extremity vascular disease, as he was noted to have palpable pulses distally. Two lateral thigh perforating vessels were identified on Doppler ultrasonography. We performed an anterolateral thigh flap reconstruction based on a single intramuscular perforator from the lateral circumflex femoral artery to the superficial temporal vessels. Although the flap perforator itself was relatively soft, the entirety of the lateral circumflex femoral artery was extensively and completely calcified. The extensive calcification resulted in a challenging anastomosis, possible only by using a slightly larger needle/suture (8-0) taking bites from the inside aspect of the flap vessels, as coming through the calcified vessel wall from the adventitial side proved impossible. The recipient vessels were soft and had good inflow without evidence of calcification. Postoperatively, the patient did well and the flap survived in its entirety. Pathologic calcification of the vascular system in dialysis patients and transplant recipients has been recognized since the 1960s. In 1973, Tatler and Baillod2 examined plain radiographs and described calcium deposition in a “ring” or “tubular” pattern in 27 percent of patients starting dialysis, with this proportion doubling over a 3- to 4-year period. Using more sophisticated imaging, such as electron beam technology, a 60 to 90 percent prevalence in dialysis patients is noted, with the most consistently associated factors being advanced age and number of years on dialysis.3 The cause of arterial calcification is unclear but may be related to dialysis calcium concentration and the pathologic process of renal osteodystrophy. In dialysis patients, angiographic studies note that arterial calcifications are not necessarily associated with stenotic coronary artery lesions. Although some intimal calcification is present in dialysis patients, the pipe and tubular patterns described by Tatler and Baillod and others are more consistent with calcium deposition in the tunica media. These observations have led to an alternative arterial abnormality occurring in chronic kidney disease, a process called chronic kidney disease–associated arteriopathy.4 Although not causing arterial occlusion, as would be visualized on angiography, medial calcification in these patients leads to extensive arterial thickening and stiffening, making microanastomosis of these vessels extremely difficult. Although Halvorson et al. provide radiographic support for the relative atherosclerosis-sparing of the profunda femoris system, the findings were not correlated with the clinical appearance of the vessels because their patients never went on to surgery. For the surgeon planning any microsurgical reconstruction in patients with a history of end-stage renal disease, we have learned that the lateral circumflex femoral artery system may not be spared from disease. Mehul R. Kamdar, M.D. Christine Rohde, M.D. Jason A. Spector, M.D. Division of Plastic Surgery New York Presbyterian Hospital Columbia University College of Physicians and Surgeons New York, N.Y.

Tissue Factor Pathway Inhibitor-2 gene methylation is associated with low expression in carotid atherosclerotic plaques

The tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine-protease inhibitor which is expressed in atherosclerotic plaques. Epigenetic regulation of the TFPI-2 gene, through methylation of CpG islands, has been advocated in cancer. We hypothesized that TFPI-2 gene methylation could regulate TFPI-2 expression in atherosclerosis. We used Methylation Specific PCR (MSP) and pyrosequencing in order to identify 18 CpG of the TFPI-2 promoter, in 59 carotid atherosclerotic plaques and 26 control mammary arteries. MSP showed methylation of the TFPI-2 gene (MSP+) in 16 plaques (27%), while no methylation (MSP-) was found in control arteries. Pyrosequencing confirmed that MSP+ plaques presented higher methylation levels than MSP- ones and arteries (p=0.03 and 0.01). Moreover, the TFPI-2 mRNA levels were lower in methylated plaques than in unmethylated ones and than in arteries (p=0.04 and <0.0001). The methylated plaques contained less lipids and macrophage infiltration than unmethylated ones. Their TFPI-2 immunoreactivity was mainly detected in the macrophages located in the media on the adventitial side, rather than in the lipid-rich core. Methylation of the TFPI-2 gene takes place in atherosclerotic plaques and is associated with decreased TFPI-2 expression. The place of this process in atherosclerosis progression remains to be investigated.

B12 Trafficking in Mammals: A Case for Coenzyme Escort Service

Many coenzymes are vitamins that are assimilated in mammals into their active form from precursors obtained from the diet. They are often both rare and reactive rendering the likelihood low that the cell uses a collision-based strategy for their delivery to dependent enzymes. In humans, there are only two known B12 or cobalamin-dependent enzymes: methionine synthase and methylmalonyl-CoA mutase. However, the pathway for intracellular assimilation and utilization of this cofactor is complex as revealed by careful clinical analyses of fibroblasts from patients with disorders of cobalamin metabolism. In the recent past, six of the eight human genes involved in the B12 pathway have been identified and these have yielded important insights into their roles. The recent literature on the encoded proteins is reviewed, and a model for intracellular B12 trafficking is proposed in which B12 is escorted to its target proteins in the cytoplasmic and mitochondrial compartments in complex with chaperones, thereby averting problems of dilution and adventitious side reactions.

Adjacent bronchus attenuates pulmonary arterial contractility

Bronchus-derived relaxing factor (BrDRF) decreases contractility of newborn rat pulmonary arteries (PA) and is dependent on nitric oxide (NO) synthesis. In vivo, this factor appears to gain access via the adventitial side of the PA. However, the adventitia has been reported to be a barrier to NO. We studied the effect of an adjacent bronchus on PA contractility to norepinephrine in nine juvenile lambs in the presence and absence of inhibitors of the NO pathway (LNA, ODQ, and Rp-8-Br-PET-cGMPS), cytochrome P-450 inhibitor (17-ODYA), perivascular nerve activity blocker (TTX), and superoxide scavenger (tiron), and following disruption of bronchial epithelium. We also evaluated whether BrDRF was effective on both the endothelial and/or adventitial side of PA. Fifth-generation PA rings with and without an attached bronchus were contracted in standard baths with norepinephrine. PA were dissected, cut open, and placed in a sided chamber in which adventitial and endothelial sides of the PA were exposed to unattached bronchus separately. Norepinephrine (10(-8) to 10(-5) M) contractions were expressed as a fraction of maximal KCl (118 mM) contractions. Norepinephrine contractions were significantly reduced by the presence of an attached bronchus, an effect reversed by pretreatment with LNA, ODQ, and Rp-8-Br-PET-cGMPS, and removal of bronchial epithelium. Unattached bronchus in the bath perfusing the adventitial side was effective in inhibiting the contractile response in PA. NO gas relaxed PA when administered on the endothelial side only. We speculate that BrDRF is a diffusible factor that crosses the adventitia and stimulates production of NO within the PA.

The identification of 5′-fluoro-5-deoxyinosine as a shunt product in cell free extracts of Streptomyces cattleya

5′-Fluoro-5′-deoxyinosine (5′-FDI) is identified as an adventitious side product that accumulates in cell free incubations of SAM and fluoride ion in Streptomyces cattleya. 5′-FDI was identified by a combination of isotopic labelling studies and co-synthesis studies as well as enzymatic degradation. Although it is an efficiently generated end product of the cell free incubations, 5′-FDI is not a biosynthetic intermediate and it does not accumulate as a fluorometabolite with fluoroacetate and 4-fluorothreonine in whole cell incubations of S. cattleya. Clearly the purine deaminase which converts 5′-fluoro-5′-deoxyadenosine (5′-FDA) to 5′-FDI in the cell free extract does not come into contact with 5′-FDA in whole cells, suggesting some level of compartmentalisation in cells of S. cattleya. The biotransformation of 5′-FDI from fluoride ion extends the range of organofluorine products, beyond biosynthetic intermediates, that can be generated by this system, for applications such as enzymatic labelling with fluorine-18 for positron emission tomography applications.

Methodology to study intimal failure mechanics in human internal carotid arteries

While the incidence of blunt carotid artery injuries is low, the mortality rate is extremely high (40%). Clinical evidence indicates that the intimal region of the artery often sustains failure, while maintaining the integrity of the outer layers. This condition may lead to delayed ischemic symptoms, commonly reported in clinical literature. To date, the mechanical properties of the intima relative to the outer vessel layers have not been quantified in the human carotid artery. The purpose of the present study was to develop a methodology to determine the longitudinal mechanical properties of the human internal carotid artery in tension, with an emphasis on intimal failure. This was accomplished by opening the vessel at the mid-diameter level, creating an ‘I’-shaped testing specimen, subjecting the specimen to failure loading, documenting the stretch characteristics of the intimal and adventitial sides in the temporal domain, and correlating the synchronized videography with mechanical loading. Intimal failure data were quantified using stress and strain parameters in conjunction with digital videography of the intimal and adventitial sides. The present methodology can be used to determine the mechanical properties of the intima relative to ultimate carotid artery failure. These data will assist in the understanding of blunt carotid artery injuries, its diagnosis and treatment.

Abundant progenitor cells in the adventitia contribute to atherosclerosis of vein grafts in ApoE-deficient mice.

Recent evidence indicates that vascular progenitor cells may be the source of smooth muscle cells (SMCs) that accumulate in atherosclerotic lesions, but the origin of these progenitor cells is unknown. To explore the possibility of vascular progenitor cells existing in adults, a variety of tissues from ApoE-deficient mice were extensively examined. Immunohistochemical staining revealed that the adventitia in aortic roots harbored large numbers of cells having stem cell markers, e.g., Sca-1(+) (21%), c-kit(+) (9%), CD34(+) (15%), and Flk1(+) cells (4%), but not SSEA-1(+) embryonic stem cells. Explanted cultures of adventitial tissues using stem cell medium displayed a heterogeneous outgrowth, for example, islands of round-shaped cells surrounded by fibroblast-like cell monolayers. Isolated Sca-1(+) cells were able to differentiate into SMCs in response to PDGF-BB stimulation in vitro. When Sca-1(+) cells carrying the LacZ gene were transferred to the adventitial side of vein grafts in ApoE-deficient mice, beta-gal(+) cells were found in atherosclerotic lesions of the intima, and these cells enhanced the development of the lesions. Thus, a large population of vascular progenitor cells existing in the adventitia can differentiate into SMCs that contribute to atherosclerosis. Our findings indicate that ex vivo expansion of these progenitor cells may have implications for cellular, genetic, and tissue engineering approaches to vascular disease.

Abdominal aortic aneurysm related to Takayasu arteritis during pregnancy

Y. Umeda (*) · Y. Mori · H. Takagi · H. Iwata · Y. Fukumoto · H. Hirose First Department of Surgery, Gifu University School of Medicine, 40 Tsukasa-machi, Gifu 500-8705, Japan Tel. 81-58-267-2619; Fax 81-58-267-2955 e-mail: umeda@cc.gifu-u.ac.jp A cystic lesion in a 34-year-old woman was found incidentally at the dorsal side of the uterus during her pregnancy on ultrasound examination and magnetic resonance (MR) imaging (Fig. 1). Computed tomography (CT) was not performed at that time because of her pregnancy. An ovarian cyst was suspected and followed up by the obstetrician. After a natural delivery, a pulsatile mass was found in the left upper abdomen and she was then referred to our hospital. An infrarenal fusiform abdominal aortic aneurysm with a maximum diameter of 6cm was revealed on a CT scan (Fig. 2). She had no history of hypertension or abdominal trauma. The abdominal aortic aneurysm was repaired with a tube graft via a midline laparotomy. She recovered uneventfully after the operation and was discharged from the hospital. Histological examination revealed fibrous thickening of the intima, diffuse lymphohistiocytic infiltration and marked destruction of elastic fibers especially on the adventitial side of the media, and proliferation of the vasa vasorum with perivascular infiltration of lymphocytes in the adventitia. These changes corresponded with the pathologic finding of Takayasu arteritis. Takayasu arteritis is an idiopathic inflammatory arteriopathic disease that leads to stenotic or occlusive changes in the aorta and its main branches. However, aneurysmal formation has also been reported in 2%–30% of Takayasu arteritis patients. Therefore, even in young people, aortic aneurysm related to Takayasu arteritis should not be excluded from the diagnosis of abnormality in an aortic lesion.

Microvascular anastomosis using cyanoacrylate adhesives.

This paper describes a new technique for microvascular anastomosis, which involves the overlapping of the adventitias of the two ends of a severed blood vessel, and then painting a cyanoacrylate adhesive on the outer surface of the vessel around the anastomosed part. Sixteen anastomoses were performed in both radial arteries and cephalic veins in eight dogs. All vessels were patent without thrombus. The described method of anastomosis was faster and easier to perform than the conventional suture anastomosis. Histologic studies revealed that the adhesive did not flow into the lumen, and that normal healing of the endothelium and of the internal elastic lamina occurred across the anastomotic site, even though the adhesive remained on the adventitial side of the vessel at 4 weeks. This technique deserves to be considered as an alternative to conventional suture anastomosis.

Dose effects of stents in intravascular brachytherapy for in-stent restenosis: a Monte Carlo calculation

Purpose: Intravascular brachytherapy (IVBT) has been recognized as a preferred treatment for coronary in-stent restenosis (ISR) in routine practice. Stents made of high-Z materials will inevitably perturb the dose distribution of IVBT. In this work, we have conducted a systematic study on these dose perturbations for three commercially available IVBT sources. Methods and Materials: The EGSnrc Monte Carlo codes were used to calculate the dose distributions for the 90Sr, 32P, and 192Ir IVBT sources with and without a metallic stent in place. The ring stent type made of different material and with different strut size, metallic surface area (MSA), and radius was studied. Results: Calculations show that dose enhancement of 5% to 20% occurs inside stent in the region close to the stent struts (luminal side) for all three sources. In the region outside stent (adventitial side), dose reduction of 5% to 20% is observed for a beta source, whereas the dose effect is negligible for the gamma source. For a given stent design, the tantalum stent yields a larger dose effect than other stents made of steel, Ti, Ni, or nitinol. It is found that the dose effect significantly depends on strut thickness, and it is strongly correlated to MSA. The MSA may be used to characterize the dose effect of a stent. Sample empiric equations to relate the dose perturbations to MSA for a given source, a stent material, and a strut thickness were derived. Conclusions: The dose perturbations due to the presence of metallic stents were found to be significant in IVBT for ISR. The dose effects of a stent can be estimated from its MSA based on derived empiric equations. The data presented are practically useful to consider the dose effects of stents in dose evaluation/treatment planning for using IVBT to treat ISR.

Perivascular superoxide anion contributes to impairment of endothelium-dependent relaxation: role of gp91(phox).

Like endothelial and smooth muscle cells, vascular adventitial fibroblasts contain a substantial NAD(P)H oxidase superoxide anion (O2-)-generating system activated by angiotensin II (Ang II). Based on the ability of nitric oxide (NO*) to diffuse rapidly through tissue and the fast reaction rate of NO* and O2-, we postulated that the interaction between NO. and adventitial NAD(P)H oxidase-derived O2- contributes to impairment of endothelium-dependent relaxation (EDR). C57Bl/6 mouse abdominal aortas were simultaneously perfused intraluminally and suffused adventitially with physiological buffer at 37 degrees C. After constricting the vessels with phenylephrine, an acetylcholine dose-response curve was obtained while monitoring changes in diameter by videomicroscopy. Endogenous O2- was increased by treating the adventitial side of the aortas with Ang II (10 pmol/L), leading to impairment of EDR. EDR impairment was reversed by adventitial suffusion of superoxide dismutase (SOD) of aortas from wild-type mice. Ang II-treated aortas from gp91(phox-/-) mice, which lack significant adventitial O2-, exhibited greater EDR and were not affected by SOD. Adventitially suffused SOD failed to penetrate the media, indicating that the effects of SOD were localized to the adventitia. Adventitial application of the O2--generating system xanthine/xanthine oxidase or the potent NO scavenger oxyhemoglobin impaired EDR. O2- derived from adventitial gp91(phox)-based NAD(P)H oxidase contributes to impairment of the action of endothelium-derived NO.

Potential roles of interstitial fluid adenosine in the regulation of renal hemodynamics

Adenosine exerts membrane receptor-mediated effects on renal hemodynamics and function. Endogenously produced adenosine is proposed to be formed primarily by renal tubular epithelial cells and approaches the vascular smooth cells of the renal vasculature from the extracellular space, i.e. the interstitium. Hence, it is important to determine the dynamics of adenosine levels in renal interstitial fluid. Indeed, many studies have indicated that the effects of adenosine on renal hemodynamics depend on its concentration in the interstitium. Furthermore, in vitro studies reveal that adenosine in the renal interstitial fluid binds to membrane receptors from the adventitial side and initiates renal microvascular responses. Recently, we developed a renal microdialysis method to monitor the concentration of adenosine in renal interstitial fluid. This method is well suited for in vivo studies investigating alterations in renal interstitial adenosine levels. In this review, we summarize the literature pertaining to alterations in renal interstitial fluid concentrations of adenosine in some pathophysiological conditions. Potential roles of interstitial adenosine for regulating renal hemodynamics were also discussed.

Determining the temperature distribution of swine aorta with simulated atheromatous plaque under pulsed laser irradiation: an experimental attempt to detect the vulnerability of atherosclerosis

We developed a method to determine the temperature distribution of swine aortas with simulated atheromatous plaques in order to measure the temperature of atherosclerotic lesions. The inflammation associated with temperature elevation is considered to be one of the aggravating mechanisms of atherosclerosis resulting in fissuring or rupture of atheromatous plaques. The temperature distribution of plaques covered by fibrous caps cannot be measured by conventional thermistors. Indocyanine green (ICG) solution was injected into the subintima of swine aorta to simulate the light absorption coefficient of human atheromatous plaques. The temperature distribution was calculated from measured temperature changes of the aortic intima under pulsed laser irradiation. The aorta was heated from the adventitial side with a halogen lamp to simulate the temperature elevation derived from inflammation. The temperature distribution of the aorta was obtained by solving the heat transfer equation using the surface layer thickness (corresponding to the fibrous cap thickness). The surface layer thickness can be calculated using the following working formula: D( µm)=1363-398 – T +35 – T 2, where s s – T s denotes intimal surface temperature change under pulsed laser irradiation. The calculated temperature of the ICG layer (corresponding to the atheromatous core) correlated well with the measured temperature (r=0.97, p<0.0001).