Journal of Vascular Research

Endogenous neuropeptides released from nociceptors can induce vasodilation and enhanced protein extravasation (neurogenic inflammation). The role of nitric oxide (NO) in the induction of neurogenic inflammation is controversial. In this study, dermal microdialysis was used in awake humans (n = 39) to deliver substance P (SP; 10^–7 and 10^–6<i>M</i>) or calcitonin gene-related peptide (CGRP; 5 × 10^–7<i>M</i> and 2 × 10^–6<i>M</i>). Neuropeptide-induced local and axon reflex erythema was assessed by laser Doppler imaging. Total protein concentration in the dialysate was measured to quantify local protein extravasation. The responses were assessed in the absence and the presence of the nitric oxide synthase inhibitor, N-nitro-<i>L</i>-arginine-methyl ester (<i>L</i>-NAME) added to the perfusate at concentrations of 5, 10 or 20 m<i>M</i>. <i>L</i>-NAME (5 m<i>M</i>) applied via the dialysis catheters reduced local blood flow by approximately 30%. In addition, <i>L</i>-NAME inhibited SP-induced vasodilation by about 40% for 10^–7<i>M</i> SP and 30% for 10^–6<i>M</i> SP (n = 11, p < 0.01). In contrast, CGRP-induced vasodilation was only marginally inhibited by <i>L</i>-NAME. SP, but not CGRP, provoked a dose-dependent increase in protein extravasation. <i>L</i>-NAME (5 m<i>M</i>) inhibited this increase by up to 40% for both SP concentrations used (n = 11, p < 0.01). Higher concentrations of <i>L</i>-NAME did not further reduce SP- or CGRP-induced vasodilation or SP-induced protein extravasation. Exogenously applied SP induces vasodilation and protein extravasation, which is partly NO mediated, whereas CGRP-induced vasodilation appears to be NO independent.

Insulin-like growth factors (IGFs) are mediators of growth hormone-induced metabolic and anabolic actions, but also regulate cell growth, differentiation, and apoptosis and show beneficial effects in acute myocardial ischemia. Since endothelial progenitor cells (EPCs) improve myocardial function after acute myocardial infarction, we sought to investigate whether overexpression of IGF-2 in expanded EPCs (eEPCs) further contributes to improvement in left ventricular function after myocardial infarction. EPCs were isolated from human cord blood and transduced by a retroviral vector expression of IGF-2 (IGF-2 eEPCs) or vector only. Expression levels were confirmed by RT-PCR. Vector only-transduced eEPCs or IGF-2 eEPCs were transplanted after ligation of the left anterior descending coronary artery in athymic nude rats. Transplantation of eEPCs improved the left ventricular ejection fraction after 2 weeks. Overexpression of IGF-2 further improved the left ventricular ejection fraction and reduced the myocardial infarction size. Immunohistological analysis revealed an increase in proliferating cells and a decrease in monocytes and apoptotic myocytes within the infarction zone after transplantation of IGF-2-overexpressing eEPCs. Transplantation of IGF-2-overexpressing eEPCs in acute myocardial infarction may improve early myocardial function by enhancing proliferation and limiting the inflammatory response and apoptosis.

<b><i>Background/Aims:</i></b> MicroRNA miR-21, miR-221 and miR-145 have been implicated in the cardiovascular system. We aimed to compare the serum levels of the three microRNAs (miRNAs) in different severities of cerebrovascular diseases and evaluate the feasibility of using these miRNAs as biomarkers for stroke. <b><i>Methods:</i></b> We enrolled 167 subjects with ischemic stroke, 66 atherosclerosis subjects with any carotid plaque score and 157 healthy controls. These three types of subjects represent three levels of severity in cerebrovascular diseases. Analysis of covariance was used to evaluate the relationship between miRNAs and disease severity with adjustment for conventional risk factors. To test the prediction for stroke, we built regression models containing the serum miRNA levels and risk factors. Prediction capabilities were compared by the receiver operating characteristic curves. <b><i>Results:</i></b> Stroke patients and atherosclerosis subjects had significantly higher miR-21 and lower miR-221 serum levels than healthy controls, while the miR-145 expression was too low to provide useful information in this regard. The best model showed that miR-21 and miR-221 were independent predictors. There was a 6.2-fold increase for stroke risk when miR-21 levels increase by log₁₀2^-&#x0394;Ct = 1, while a 10.4-fold increase was observed as miR-221 decreases by log₁₀2^-&#x0394;Ct = 1. <b><i>Conclusions:</i></b> Serum miR-145 was not detected in over 50% of the patients and it may not be an ideal marker to predict stroke. MiR-21 and miR-221 are novel biomarkers for atherosclerosis and stroke.

Constrictive arterial remodeling accounts for a significant proportion of lumen loss in atherosclerotic progression and postangioplasty stenosis. Recent research suggests that constrictive remodeling is mediated by turnover of the extracellular matrix. We hypothesized that remodeling could be attenuated by treatment with the safe, effective matrix metalloproteinase (MMP) inhibitor doxycycline. Female rabbit abdominal aortas were denuded using a 4-Fr balloon embolectomy catheter, and reinjured 3 weeks later. Treatment with 30 mg/kg/day doxycycline was begun the day before the second injury. At 6 weeks after injury, lumen area measured 13.1 ± 1.2 mm² in controls compared to 17.5 ± 1.6 mm² in doxycycline-treated rabbits (p = 0.05). At 4 days after injury, MMP-2 activity was increased compared to uninjured controls, but doxycycline treatment reduced MMP-2 activity. Doxycycline treatment also inhibited fibrillar collagen deposition in the intima by 87% as detected by polarized light microscopy. Doxycycline was an effective inhibitor of constrictive arterial remodeling in the rabbit aorta. Treatment reduced MMP activity and attenuated the deposition of extracellular matrix particularly in the intima.

<i>Background/Aims:</i> Aminopeptidase P (APP) is specifically enriched in caveolae on the luminal surface of pulmonary vascular endothelium. APP antibodies bind lung endothelium in vivo and are rapidly and actively pumped across the endothelium into lung tissue. Here we characterize the immunotargeting properties and pharmacokinetics of the APP-specific recombinant antibody 833c. <i>Methods:</i> We used in situ binding, biodistribution analysis and in vivo imaging to assess the lung targeting of 833c. <i>Results:</i> More than 80% of 833c bound during the first pass through isolated perfused lungs. Dynamic SPECT acquisition showed that 833c rapidly and specifically targeted the lungs in vivo, reaching maximum levels within 2 min after intravenous injection. CT-SPECT imaging revealed specific targeting of 833c to the thoracic cavity and co-localization with a lung perfusion marker, Tc99m-labeled macroaggregated albumin. Biodistribution analysis confirmed lung-specific uptake of 833c which declined by first-order kinetics (t_½ = 110 h) with significant levels of 833c still present 30 days after injection. <i>Conclusion:</i> These data show that APP expressed in endothelial caveolae appears to be readily accessible to circulating antibody rather specifically in lung. Targeting lung-specific caveolar APP provides an extraordinarily rapid and specific means to target pulmonary vasculature and potentially deliver therapeutic agents into the lung tissue.

<i>Background:</i> Lactoferrin, LF, a multifunctional iron- and heparin-binding protein, present in exocrine body secretions and leukocytes, is remarkably resistant to proteolysis. Ingested bovine iron-unsaturated LF, apo-bLF, suppresses VEGF-A-mediated angiogenesis in a previously described rat mesentery angiogenesis assay, possibly explaining, at least in part, its established anticancer effect in rats and mice. <i>Methods:</i> Using the same experimental system, we have now studied the effect of (i) ingested human apo-LF, apo-hLF, on angiogenesis mediated by VEGF-A and bFGF, (ii) ingested human iron-saturated LF, holo-hLF, on VEGF-A-mediated angiogenesis and (iii) subcutaneous continuously infused apo-hLF on VEGF-A-mediated angiogenesis. <i>Results:</i> Ingested holo-hLF did not affect VEGF-A-mediated angiogenesis. Ingested apo-hLF (from one and the same batch) significantly enhanced VEGF-A-mediated angiogenesis but did not affect bFGF-mediated angiogenesis. Moreover, subcutaneously infused apo-hLF also significantly stimulated VEGF-A-mediated angiogenesis. <i>Conclusion:</i> Taken together, the data suggest that apo-hLF exerts a specific proangiogenic effect in VEGF-A-mediated angiogenesis. Clearly, human and bovine apo-LF exert opposite effects on VEGF-A-induced angiogenesis. Differences in molecular features between human and bovine LFs of possible significance for the outcome are discussed. In hypoxia, compensatory collateral circulation is mediated primarily by VEGF-A. We hypothesize that systemically administered apo-hLF may promote collateral blood vessel formation at hypoxic sites in normal tissue, thus counteracting ischemia and infarction.

Ryanodine receptors (RyR) play an important role in the regulation of intracellular Ca²⁺ concentration and in the control of vascular tone. However, the mechanism regulating the activity of RyR is poorly understood. The present study determined whether protein methylation participates in the control of RyR activity. Using a planar lipid bilayer clamping system, S-adenosyl-<i>L</i>-methionine (SAM), a methyl donor, significantly increased the activity of a 245-pS reconstituted Ca²⁺ release channel from coronary arterial smooth muscle (CASM) in a concentration-dependent manner. Addition of the protein methylation blockers, 3-deazaadenosine, S-adenosylhomocysteine or sinefungin into the <i>cis</i> solution markedly attenuated SAM-induced activation of RyR/Ca²⁺ release channels. By Western blot analysis, arginine N-methyltransferase (PRMT1) and FK506 binding protein (FKBP) were detected in the SR used for reconstitution of RyR. In the presence of anti-PRMT1 antibody (1:100), SAM-induced activation of RyR/Ca²⁺ channel was completely abolished. In addition, this SAM-induced increase in RyR/Ca²⁺ channel activity was blocked by 30 µ<i>M</i> ryanodine and by FK506 (100 µ<i>M</i>), a ligand for the RyR accessory protein. These results suggest that protein methylation activates RyR/Ca²⁺ release channels and may participate in the control of intracellular Ca²⁺ mobilization in CASM cells by transferring a methyl group to the arginine moiety of the RyR accessory protein, FKBP 12.

Selective inhibitors of cyclooxygenase-2 (COX-2, ‘coxibs’) are highly effective anti-inflammatory and analgesic drugs that exert their action by preventing the formation of prostanoids. Recently some coxibs, which were designed to exploit the advantageous effects of non-steroidal anti-inflammatory drugs while evading their side effects, have been reported to increase the risk of myo cardial infarction and atherothrombotic events. This has led to the withdrawal of rofecoxib from global markets, and warnings have been issued by drug authorities about similar events during the use of celecoxib or valdecoxib/parecoxib, bringing about questions of an inherent atherothrombotic risk of all coxibs and consequences that should be drawn by health care professionals. These questions need to be addressed in light of the known effects of selective inhibition of COX-2 on the cardiovascular system. Although COX-2, in contrast to the cyclooxygenase-1 (COX-1) isoform, is regarded as an inducible enzyme that only has a role in pathophysiological processes like pain and inflammation, experimental and clinical studies have shown that COX-2 is constitutively expressed in tissues like the kidney or vascular endothelium, where it executes important physiological functions. COX-2-dependent formation of prostanoids not only results in the mediation of pain or inflammatory signals but also in the maintenance of vascular integrity. Especially prostacyclin (PGI₂), which exerts vasodilatory and antiplatelet properties, is formed to a significant extent by COX-2, and its levels are reduced to less than half of normal when COX-2 is inhibited. This review outlines the rationale for the development of selective COX-2 inhibitors and the pathophysiological consequences of selective inhibition of COX-2 with special regard to vasoactive prostaglandins. It describes coxibs that are current ly available, evaluates the current knowledge on the risk of atherothrombotic events associated with their intake and critically discusses the consequences that should be drawn from these insights.

Tortuous arteries and veins are commonly observed in humans and animals. While mild tortuosity is asymptomatic, severe tortuosity can lead to ischemic attack in distal organs. Clinical observations have linked tortuous arteries and veins with aging, atherosclerosis, hypertension, genetic defects and diabetes mellitus. However, the mechanisms of their formation and development are poorly understood. This review summarizes the current clinical and biomechanical studies on the initiation, development and treatment of tortuous blood vessels. We submit a new hypothesis that mechanical instability and remodeling could be mechanisms for the initiation and development of these tortuous vessels.