Captopril suppresses Post-transplantation angiogenic activity in rat allograft coronary vessels

Platelet activating factor in the eye: Physiological roles, diseases and future perspectives

Platelet Activating Factor (PAF) is a known phospholipid mediator of inflammation. Since its first description in 1972, it has emerged as a key regulator of vital cellular signaling functions, as proliferation, cell adhesion, and apoptosis. Evidence suggests that interactions between PAF and its receptor (PAFR) play a critical role in nervous system tissues, including the retina. The retina is a very important constituent of the visual system, along with the cornea, sclera, choroid, iris, and ciliary body, that acts synergistically to provide vision and to maintain optical homeostasis. There is evidence that PAF may regulate a wide range of physiological functions in the visual system tissues, such as eye development, inflammation, epithelial wound healing, and synapsis. Due to their multiple functions, PAF and PAFR also have important pathological and clinical implications in ocular disorders such as Choroidal Neovascularization (CNV), Age Macular Degeneration, (AMD), Diabetic Retinopathy (DR), transplant responses, and pharmacological interactions. Studies with PAFR antagonists have shown promising results such as inhibition of neovascularization and chloroquine-induced retinopathies, as well as reducing inflammation and retinal cell death. Due to the importance of PAFR signaling in the visual system and ophthalmology research, this review aims to provide a general overview of current and future perspectives about PAF in eye biology.

MHC class I signaling: new functional perspectives for an old molecule

Donor-specific antibodies are associated with refractory rejection episodes and poor allograft outcomes in solid organ transplantation. Our understanding of antibody-mediated allograft injury is expanding beyond complement deposition. In fact, unique mechanisms of alloantibodies are advancing our knowledge about transplant vasculopathy and antibody-mediated rejection. These include direct effects on the endothelium, resulting in the recruitment of leukocytes, chemokine and cytokine production, and stimulation of innate and adaptive alloresponses. These effects will be the focus of the following review.

Antiangiogenic activity and pharmacogenomics of medicinal plants from traditional korean medicine

Aim. In the present study, we investigated the antiangiogenic properties of 59 plants used in traditional Korean medicine. Selected phytochemicals were investigated in more detail for their modes of action. Methods. A modified chicken-chorioallantoic-membrane (CAM) assay using quail eggs was applied to test for antiangiogenic effects of plant extracts. A molecular docking in silico approached the binding of plant constituents to the vascular endothelial growth factor receptors 1 and 2 (VEGFR1, VEGFR2). Microarray-based mRNA expression profiling was employed to correlate the 50% inhibition concentrations (IC₅₀) of a panel of 60 NCI cell lines to these phytochemicals. Results. Extracts from Acer mono leaves, Reynoutria sachalniensis fruits, Cinnamomum japonicum stems, Eurya japonica leaves, Adenophora racemosa whole plant, Caryopteris incana leaves-stems, and Schisandra chinensis stems inhibited angiogenesis more than 50% in quail eggs. Selected phytochemicals from Korean plants were analyzed in more detail using microarray-based mRNA expression profiles and molecular docking to VEGFR1 and VEGFR2. These results indicate multifactorial modes of action of these natural products. Conclusion. The antiangiogenic activity of plants used in traditional Korean medicine implicates their possible application for diseases where inhibition of blood vessel formation is desired, for example, cancer, macular degeneration, diabetic retinopathy and others.

HLA class I-mediated stress fiber formation requires ERK1/2 activation in the absence of an increase in intracellular Ca2+ in human aortic endothelial cells

Following transplantation, HLA class I antibodies targeting donor endothelium stimulate cell proliferation and migration, which contribute to the development of transplant vasculopathy and chronic allograft rejection. Dynamic remodeling of the actin cytoskeleton regulates cell proliferation and migration in endothelial cells (ECs), but the mechanism(s) involved remain incompletely understood. We explored anti-HLA class I antibody-mediated alterations of the cytoskeleton in human aortic ECs (HAECs) and contrasted these findings to thrombin-induced cytoskeleton remodeling. Our results identify two different signaling pathways leading to myosin light chain (MLC) phosphorylation in HAECs. Stimulation of HAECs with thrombin at 1 U/ml induced a robust elevation of intracellular Ca(2+) concentration, increased MLC phosphorylation, and promoted stress fiber formation via MLC kinase (MLCK) and Rho kinase (ROK) in an ERK-independent manner. In contrast, HAECs stimulated with HLA class I antibodies did not promote any detectable change in intracellular Ca(2+) concentration but instead induced MLC phosphorylation and stress fiber assembly via MLCK and ROK in an ERK1/2-dependent manner. Stimulation of HAECs with low-dose thrombin (1 mU/ml) induced signaling cascades that were similar to stimulation with HLA class I antibodies. HLA class I antibodies also stimulated the translocation of mammalian target of rapamycin complex 2 (mTORC2) and ERK1/2 from the cytoplasm to the plasma membrane independently of stress fiber assembly. These findings identify novel roles for HLA class I signaling in ECs and provide new insights into the role of ERK1/2 and mTORC2 in cytoskeleton regulation, which may be important in promoting transplant vasculopathy, tumor angiogenesis, and atherosclerosis.

Cardiac allograft vasculopathy: The achilles’ heel of long-term survival after cardiac transplantation

Over the past 40 years, cardiac transplantation has evolved as the single best long-term option for eligible candidates with end-stage heart failure. Approximately 2000 transplants are performed annually in the United States, and with the institution of calcineurin-based immunotherapy, surveillance biopsies, and programmatic-based patient care, life expectancy at 1 and 12 years is 85% and 50%, respectively. Cardiac allograft vasculopathy (CAV) is the number one cause of death after the first year of transplantation. The incidence of CAV remains as high as 50% at 5 years, with life expectancy significantly abbreviated once it is recognized. Although current immunotherapy has reduced the likelihood of cellular rejection, it has not impacted CAV substantially. Better treatment of established risk factors and the advent of newer antiproliferative immunotherapy may hold promise in treating CAV. However, future therapies must address the multitude of mechanisms underlying CAV. This manuscript reviews the pathophysiology, clinical manifestations, screening, and diagnostic strategies for cardiac allograft vasculopathy while emphasizing current treatment paradigms designed to stave off or retard the progression of CAV.

Vascular Endothelial Growth Factor C–induced Collateral Formation in a Model of Myocardial Ischemia

BACKGROUND

Besides being a known lymphangiogenic activator, vascular endothelial growth factor (VEGF)-C may express angiogenic potential by proteolytic cleavage and activation of endothelial cells. We assessed myocardial collateral formation and functional changes after adenovirus-mediated VEGF-C gene transfer in an ischemic porcine model.

METHODS

Fifteen Landrace piglets underwent Ameroid-induced gradual occlusion of the left circumflex artery (LCx) and consequent progressive myocardial ischemia. Three weeks after Ameroid placement, the animals underwent gated 99mTc SPECT during rest and stress, in vivo angiography and 18FDG PET. Pigs were randomized to intramyocardial injections of adenoviruses encoding vascular endothelial growth factor (VEGF-C; n = 7) or control beta-galactosidase (LacZ; n = 5). Four weeks later, the examinations were repeated and histology was analyzed.

RESULTS

Angiography showed significant progression of LCx stenosis in both groups during the treatment period. Left ventricular wall thickening (LVWT) at the LCx area in gated 99mTc SPECT remained unchanged in the VEGF-C group, indicating that VEGF-C prevented progression of myocardial ischemia, whereas LVWT deteriorated in the LacZ group (p = 0.042). Semi-quantitative assessment of 18FDG PET suggests more reduction in ischemia in the adVEGF-C group than in controls (p = 0.052). Angiography showed significant clustering of collaterals in the adVEGF-C gene transfer area compared that in LacZ (p = 0.004). von Willebrand factor staining revealed a significantly (p = 0.03) greater number of microvessels in the adVEGF-C-treated myocardium.

CONCLUSIONS

This appears to be the first large-animal study in which, during progressive ischemia, functional and metabolic benefits of intramyocardial VEGF-C gene transfer were apparent. VEGF-C-induced collateral formation occurred at the site of gene transfer. The angiogenic potency of VEGF-C deserves further study as a therapeutic option.