Athanassios Giannis

NADPH Oxidase 4 Is Expressed in Pulmonary Artery Adventitia and Contributes to Hypertensive Vascular Remodeling

Objective— Pulmonary hypertension (PH) is a progressive disease arising from remodeling and narrowing of pulmonary arteries (PAs) resulting in high pulmonary blood pressure and ultimately right ventricular failure. Elevated production of reactive oxygen species by NADPH oxidase 4 (Nox4) is associated with increased pressure in PH. However, the cellular location of Nox4 and its contribution to aberrant vascular remodeling in PH remains poorly understood. Therefore, we sought to identify the vascular cells expressing Nox4 in PAs and determine the functional relevance of Nox4 in PH. Approach and Results— Elevated expression of Nox4 was detected in hypertensive PAs from 3 rat PH models and human PH using qualititative real-time reverse transcription polymerase chain reaction, Western blot, and immunofluorescence. In the vascular wall, Nox4 was detected in both endothelium and adventitia, and perivascular staining was prominently increased in hypertensive lung sections, colocalizing with cells expressing fibroblast and monocyte markers and matching the adventitial location of reactive oxygen species production. Small-molecule inhibitors of Nox4 reduced adventitial reactive oxygen species generation and vascular remodeling as well as ameliorating right ventricular hypertrophy and noninvasive indices of PA stiffness in monocrotaline-treated rats as determined by morphometric analysis and high-resolution digital ultrasound. Nox4 inhibitors improved PH in both prevention and reversal protocols and reduced the expression of fibroblast markers in isolated PAs. In fibroblasts, Nox4 overexpression stimulated migration and proliferation and was necessary for matrix gene expression. Conclusion— These findings indicate that Nox4 is prominently expressed in the adventitia and contributes to altered fibroblast behavior, hypertensive vascular remodeling, and development of PH.

Increasing Muscle Mass Improves Vascular Function in Obese (db/db) Mice

Background A sedentary lifestyle is an independent risk factor for cardiovascular disease and exercise has been shown to ameliorate this risk. Inactivity is associated with a loss of muscle mass, which is also reversed with isometric exercise training. The relationship between muscle mass and vascular function is poorly defined. The aims of the current study were to determine whether increasing muscle mass by genetic deletion of myostatin, a negative regulator of muscle growth, can influence vascular function in mesenteric arteries from obese db/db mice. Methods and Results Myostatin expression was elevated in skeletal muscle of obese mice and associated with reduced muscle mass (30% to 50%). Myostatin deletion increased muscle mass in lean (40% to 60%) and obese (80% to 115%) mice through increased muscle fiber size (P<0.05). Myostatin deletion decreased adipose tissue in lean mice, but not obese mice. Markers of insulin resistance and glucose tolerance were improved in obese myostatin knockout mice. Obese mice demonstrated an impaired endothelial vasodilation, compared to lean mice. This impairment was improved by superoxide dismutase mimic Tempol. Deletion of myostatin improved endothelial vasodilation in mesenteric arteries in obese, but not in lean, mice. This improvement was blunted by nitric oxide (NO) synthase inhibitor l‐NG‐nitroarginine methyl ester (l‐NAME). Prostacyclin (PGI2)‐ and endothelium‐derived hyperpolarizing factor (EDHF)‐mediated vasodilation were preserved in obese mice and unaffected by myostatin deletion. Reactive oxygen species) was elevated in the mesenteric endothelium of obese mice and down‐regulated by deletion of myostatin in obese mice. Impaired vasodilation in obese mice was improved by NADPH oxidase inhibitor (GKT136901). Treatment with sepiapterin, which increases levels of tetrahydrobiopterin, improved vasodilation in obese mice, an improvement blocked by l‐NAME. Conclusions Increasing muscle mass by genetic deletion of myostatin improves NO‐, but not PGI2‐ or EDHF‐mediated vasodilation in obese mice; this vasodilation improvement is mediated by down‐regulation of superoxide.

Sensitive and site-specific identification of carboxymethylated and carboxyethylated peptides in tryptic digests of proteins and human plasma.

Glycation refers to a nonenzymatic post-translational modification formed by the reaction of amino groups and reducing sugars. Consecutive oxidation and degradation can produce advanced glycation end products (AGEs), such as N(ε)-(carboxyethyl)lysine (CEL) and N(ε)-(carboxymethyl)lysine (CML). Although CEL and CML are considered to be markers of arteriosclerosis, diabetes mellitus, and aging, the modified proteins and the exact modification sites are mostly unknown due to their low frequency and a lack of enrichment strategies. Here, we report characteristic fragmentation patterns of CML- and CEL-containing peptides and two modification-specific reporter ions for each modification (CML, m/z 142.1 and 187.1; CEL, m/z 156.1 and 201.1). The protocol allowed sensitive and selective precursor ion scans to detect the modified peptides in complex sample mixtures. The corresponding m/z values identified eight CEL/CML-modification sites in glycated human serum albumin (HSA) by targeted nano-RPC-MS/MS. The same strategy revealed 21 CML sites in 17 different proteins, including modified lysine residues 88 and 396 of human serum albumin, in a pooled plasma sample that was obtained from patients with type 2 diabetes mellitus.

Tripolin A, a novel small-molecule inhibitor of aurora A kinase, reveals new regulation of HURP's distribution on microtubules.

Mitotic regulators exhibiting gain of function in tumor cells are considered useful cancer therapeutic targets for the development of small-molecule inhibitors. The human Aurora kinases are a family of such targets. In this study, from a panel of 105 potential small-molecule inhibitors, two compounds Tripolin A and Tripolin B, inhibited Aurora A kinase activity in vitro. In human cells however, only Tripolin A acted as an Aurora A inhibitor. We combined in vitro, in vivo single cell and in silico studies to demonstrate the biological action of Tripolin A, a non-ATP competitive inhibitor. Tripolin A reduced the localization of pAurora A on spindle microtubules (MTs), affected centrosome integrity, spindle formation and length, as well as MT dynamics in interphase, consistent with Aurora A inhibition by RNAi or other specific inhibitors, such as MLN8054 or MLN8237. Interestingly, Tripolin A affected the gradient distribution towards the chromosomes, but not the MT binding of HURP (Hepatoma Up-Regulated Protein), a MT-associated protein (MAP) and substrate of the Aurora A kinase. Therefore Tripolin A reveals a new way of regulating mitotic MT stabilizers through Aurora A phosphorylation. Tripolin A is predicted to bind Aurora A similarly but not identical to MLN8054, therefore it could be used to dissect pathways orchestrated by Aurora kinases as well as a scaffold for further inhibitor development.

A Fast Entry to Furanoditerpenoid-Based Hedgehog Signaling Inhibitors: Identifying Essential Structural Features

New, small molecule Hedgehog (Hh) pathway inhibitors, such as the furanoditerpenoid taepeenin D, are of high medicinal importance. To establish key structure-activity relationships (SARs) for this lead, a synthetic sequence has been developed for the expedient preparation of several derivatives and their evaluation as Hh inhibitors exploiting its structural similarity to abietic acid. While C(14) substitution is not essential for biological activity, the presence of a hydrogen bond acceptor at C(6) and an intact benzofuran moiety are.

Guanylyl Cyclase Activation Reverses Resistive Breathing–Induced Lung Injury and Inflammation

Inspiratory resistive breathing (RB), encountered in obstructive lung diseases, induces lung injury. The soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway is down-regulated in chronic and acute animal models of RB, such as asthma, chronic obstructive pulmonary disease, and in endotoxin-induced acute lung injury. Our objectives were to: (1) characterize the effects of increased concurrent inspiratory and expiratory resistance in mice via tracheal banding; and (2) investigate the contribution of the sGC/cGMP pathway in RB-induced lung injury. Anesthetized C57BL/6 mice underwent RB achieved by restricting tracheal surface area to 50% (tracheal banding). RB for 24 hours resulted in increased bronchoalveolar lavage fluid cellularity and protein content, marked leukocyte infiltration in the lungs, and perturbed respiratory mechanics (increased tissue resistance and elasticity, shifted static pressure-volume curve right and downwards, decreased static compliance), consistent with the presence of acute lung injury. RB down-regulated sGC expression in the lung. All manifestations of lung injury caused by RB were exacerbated by the administration of the sGC inhibitor, 1H-[1,2,4]oxodiazolo[4,3-]quinoxalin-l-one, or when RB was performed using sGCα1 knockout mice. Conversely, restoration of sGC signaling by prior administration of the sGC activator BAY 58-2667 (Bayer, Leverkusen, Germany) prevented RB-induced lung injury. Strikingly, direct pharmacological activation of sGC with BAY 58-2667 24 hours after RB reversed, within 6 hours, the established lung injury. These findings raise the possibility that pharmacological targeting of the sGC-cGMP axis could be used to ameliorate lung dysfunction in obstructive lung diseases.

Cyclopamine analogs bearing exocyclic methylenes are highly potent and acid-stable inhibitors of hedgehog signaling.

Summary The chemical synthesis and biological evaluation of new cyclopamine analogs bearing exocyclic methylenes in different positions is described. Bis-exo-cyclopamine 6 was identified as a potent inhibitor of the Gli1-dependent luciferase expression in Shh-LIGHTII cells. An extension of this study to F-ring-modified structures shows the necessity of a rigidly positioned nitrogen atom for bioactivity as well as the presence of the C21 methyl group for acid stability and bioactivity.

Insights into soluble guanylyl cyclase activation derived from improved heme-mimetics

Recently, the structure of BAY 58-2667 bound to the Nostoc sp. H-NOX domain was published. On the basis of this structural information, we designed BAY 58-2667 derivatives and tested their effects on soluble guanylyl cyclase (sGC) activity. Derivative 20 activated sGC 4.8-fold more than BAY 58-2667. Co-crystallization of 20 with the Ns H-NOX domain revealed that the increased conformational distortion at the C-terminal region of αF helix containing 110-114 residues contributes to the higher activation triggered by 20.

Anthraquinone Content in Noni (Morinda citrifolia L.)

Noni has been used in traditional medicine and as food for thousands of years. While the fruits serve as food and internal medicine, leaves were traditionally used only topically. In recent years, concern regarding the possible content of anthraquinones in noni has led to scrutiny by the European Food Safety Authority. Little research existed on the content of anthraquinones in different noni preparations, with no information about the potential effect of harvest and preparation methods. Our research focused on lucidin, alizarin, and rubiadin, the most important anthraquinones from a health perspective. We found that the production process (fermentation/juice production versus drying/lyophilization) has no effect on the anthraquinone content. The source product, however, does have implications: noni fruit puree from which seeds had been removed as well as consumer products produced from such puree had no detectable amounts of any anthraquinones. Products that did contain seed or leaf material in all cases did contain partly significant amounts of anthraquinones. To alleviate safety concerns, we suggest that noni products, whether fermented or unfermented juice or powder, should be derived only from fully ripe noni fruits, and that any seed material needs to be removed during the production process.

C–H-Functionalization logic guides the synthesis of a carbacyclopamine analog

Summary The chemical synthesis of carbacyclopamine analog 2, a cyclopamine analog with an all-carbon E-ring, is reported. The use of C–H-functionalization logic and further metal-catalyzed transformations allows for a concise entry to this new class of acid-stable cyclopamine analogs.