Osteoprotegerin (OPG) is localized to the Weibel-Palade bodies of human vascular endothelial cells and is physically associated with von Willebrand factor

Recent studies demonstrate roles for osteoprotegerin (OPG) in both skeletal and extra-skeletal tissues. Although its role in preventing osteoclast (OC) formation and activity is well documented, emerging evidence suggests a role of OPG in endothelial cell survival and the prevention of arterial calcification. In this communication, we show that vascular endothelial cells in situ, and human umbilical vein endothelial cells (HUVEC) in vitro, express abundant OPG. In HUVEC, OPG co-localizes with P-selectin and von Willebrand factor (vWF), within the Weibel-Palade bodies (WPB). Treatment of HUVEC with the pro-inflammatory cytokines, tumor necrosis factor (TNF)-alpha and IL-1beta, resulted in mobilization from the WPBs and subsequent secretion of OPG protein into the culture supernatant. Furthermore, TNF-alpha treatment of HUVEC resulted in a sustained increase in OPG mRNA levels and protein secretion over the 24-h treatment period. Reciprocal immunoprecipitation experiments revealed that while not associated with P-Selectin, OPG is physically complexed with vWF both within the WPB and following secretion from endothelial cells. Interestingly, this association was also identified in human peripheral blood plasma. In addition to its interaction with vWF, we show that OPG also binds with high avidity to the vWF reductase, thrombospondin (TSP-1), raising the intriguing possibility that OPG may provide a link between TSP-1 and vWF. In summary, the intracellular localization of OPG in HUVEC, in association with vWF, together with its rapid and sustained secretory response to inflammatory stimuli, strongly support a modulatory role in vascular injury, inflammation and hemostasis.     

D2-receptor-linked signaling pathways regulate the expression of hepatic CYP2E1

This study investigated the role of catecholamine-related signaling pathways in the regulation of hepatic cytochrome P450 (CYP2E1). Central and peripheral catecholamine depletion with reserpine down-regulated CYP2E1. On the other hand, selective peripheral catecholamine depletion with guanethidine increased CYP2E1 apoprotein levels. Enrichment of peripheral catecholamines with adrenaline suppressed p-nitrophenol hydroxylase activity (PNP). PNP activity was also markedly suppressed by l-DOPA. Stimulation of D(2)-receptors with bromocriptine up-regulated CYP2E1, as assessed by enzyme activity and protein levels, whereas blockade of D(2)-dopaminergic receptors with sulpiride down-regulated this isozyme. These findings indicate that central and peripheral catecholamines have different effects on CYP2E1. Central catecholamines appear related to the up-regulation, whereas the role of peripheral catecholamines is clearly related to the type and location of adrenoceptors involved. D(2)-receptor-linked signaling pathways have an up-regulating effect on CYP2E1, while D(1)-receptor pathways may down-regulate this isozyme. It is worth noting that the widespread environmental pollutant benzo(alpha)pyrene (B(alpha)P) altered the modulating effect of catecholaminergic systems on CYP2E1 regulation. In particular, whereas stimulation or blockade of adrenoceptors had no effect on constitutive PNP activity, exposure to B(alpha)P modified the impact of central and peripheral catecholamines and alpha(2)-adrenoceptors on CYP2E1 expression. It appears that under the influence of B(alpha)P, alpha(2)-adrenergic receptor-linked signaling pathways increased CYP2E1 apoprotein levels. Given that a wide range of xenobiotics and clinically used drugs are activated by CYP2E1 to toxic metabolites, including the production of reactive oxygen species (ROS), it is possible that therapies challenging dopaminergic receptor- and/or alpha(2)-adrenoceptor-linked signaling pathways may alter the expression of CYP2E1, thus affecting the progress and development of several pathologies.     

Cytogeography of the Phleum pratense group (Poaceae) in the Carpathians and Pannonia

Cytogeographical variability within the Phleum pratense group in the Carpathians and adjacent part of Pannonian lowland, based on 132 populations analysed by flow cytometry, is described. Only diploid and hexaploid plants were detected among 635 samples from the studied area. Diploids were found to be less frequent (127 plants, 20%) than hexaploids (508, 80%). With the exception of the single pure diploid population, diploids always co-occured with hexaploids (30 localities, 22.7%). The majority of populations (101, 76.5%) consisted of hexaploid plants. Most mixed populations occur in the Western Carpathians (26). In the Eastern Carpathians, mixed populations are much rarer, with three populations in Ukraine and one in Romania. In the Southern Carpathians, only hexaploids occur. The conventional taxonomic concept of the two species, diploid P. bertolonii and hexaploid P. pratense , was followed in spite of their sympatric occurence. Distribution maps based on chromosome number data from previous studies and on ploidy level estimates are given for both species in the studied area. The pattern of different distribution of the two taxa within the Carpathians is discussed.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 475–485.     

An investigation into lanthanide–lanthanide magnetic interactions in a series of [Ln2(mdeaH2)2(piv)6] dimers

A series of six isostructural lanthanide dimers of general formula [Ln₂(mdeaH₂)₂(piv)₆], where mdeaH₂ is N-methyldiethanolamine, piv is pivalate, and Ln = La, Ce, Pr, Nd, Sm, and Gd, has been surveyed to gauge the nature of the magnetic interactions between the lanthanide centres. Single-crystal X-ray structure analyses indicate that the lanthanides are connected by syn,syn-carboxylate bridges. It was found from an analysis of their bulk magnetic susceptibilities as a function of temperature that this type of bridge mediates vanishingly small magnetic interactions. This finding is important in the context of developing synthetic strategies for the preparation of new molecular based magnetic materials.     

Benzo(alpha)pyrene-induced up-regulation of CYP1A2 gene expression: role of adrenoceptor-linked signaling pathways

CYP1A2, a principal catalyst for metabolism of various therapeutic drugs and carcinogens, among others, is in part regulated by the stress response. This study was designed to assess whether catecholamines and in particular adrenergic receptor-dependent pathways, modulate benzo(alpha)pyrene (B(alpha)P)-induced hepatic CYP1A2. To distinguish between the role of central and peripheral catecholamines in the regulation of CYP1A2 induction, the effect of central and peripheral catecholamine depletion using reserpine was compared to that of peripheral catecholamine depletion using guanethidine. The effects of peripheral adrenaline and L-DOPA administration were also assessed. The results suggest that alterations in central catecholamines modulate 7-methoxyresorufin O-demethylase activity (MROD), CYP1A2 mRNA and protein levels in the B(alpha)P-induced state. In particular, central catecholamine depletion, dexmedetomidine-induced inhibition of noradrenaline release and blockade of alpha(1)-adrenoceptors with prazosin, up-regulated CYP1A2 expression. Phenylephrine and dexmedetomidine-induced up-regulation may be mediated, in part, via peripheral alpha(1)- and alpha(2)-adrenoceptors, respectively. On the other hand, the L-DOPA-induced increase in central dopaminergic activity was not followed by any change in the up-regulation of CYP1A2 expression by B(alpha)P. Central noradrenergic systems appeared to counteract up-regulating factors, most likely via alpha(1)- and alpha(2)-adrenoceptors. In contrast, peripheral alpha- and beta-adrenoceptor-related signaling pathways are linked to up-regulating processes. The findings suggest that drugs that bind to adrenoceptors or affect central noradrenergic neurotransmission, as well as factors that challenge the adrenoceptor-linked signaling pathways may deregulate CYP1A2 induction. This, in turn, may result in drug-therapy and drug-toxicity complications.     

Design and synthesis of novel amino-substituted xanthenones and benzo[b]xanthenones: evaluation of their antiproliferative activity and their ability to overcome multidrug resistance toward MES-SA/D x 5 cells

A number of new xanthenone and benzo[b]xanthenone amino derivatives and their pyrazole-fused counterparts have been designed and synthesized possessing structural analogy to the potent anticancer agent 9-methoxypyrazoloacridine. The synthesis of the compounds proceeds through nucleophilic substitution of 1-chloro-4-nitroxanthenone or the corresponding benzo[b]xanthenone by the appropriately substituted amine or hydrazine, reduction of the nitro group, and conversion into the suitable dialkylaminoacetamides. This method cannot be applied for synthesis of the pyrazole-fused benzo[b]xanthenones, consequently a different, simple, and high-yielding synthetic procedure was developed for the preparation of the target molecules. In vitro cytotoxic potencies of the new derivatives toward the murine leukemia L1210 cell line, human colorectal adenocarcinoma (HT-29), and human uterine sarcoma (MES-SA and its 100-fold resistant to doxorubicin variant MES-SA/D x 5) cell lines are described and compared to those of reference drugs. The compounds exhibited significant cytotoxic activity against the tested cell lines and in addition they retain activity against the multidrug resistant MES-SA/D x 5 subline, showing resistant factors close to 1. A number of derivatives were found to possess DNA binding capacity, according to a standard ethidium bromide displacement assay. The majority of the studied compounds induce a G2/M arrest, although among them some G1 or S blockers have also been identified.     

The supramolecular architecture of the second coordination sphere complex between the ammonia adduct of tris(pentafluorophenyl)borane and pyrimidine: Two interpenetrating chiral (10,3)-a (srs) nets assembled through hydrogen bonding

Treatment of the ammonia adduct of tris(pentafluorophenyl)borane with 1.5 equivalents of pyrimidine affords a crystalline supramolecular complex. The solid state structure of the chloroform solvate has been determined by X-ray crystallography and is composed of two interpenetrating chiral (10,3)-a (srs) nets assembled through N-H?N hydrogen bonding interactions.     

Crosstalk between autophagy and DNA repair systems

Autophagy and DNA repair are two essential biological mechanisms that maintain cellular homeostasis. Impairment of these mechanisms was associated with several pathologies such as premature aging, neurodegenerative diseases, and cancer. Intrinsic or extrinsic stress stimuli (e.g., reactive oxygen species or ionizing radiation) cause DNA damage. As a biological stress response, autophagy is activated following insults that threaten DNA integrity. Hence, in collaboration with DNA damage repair and response mechanisms, autophagy contributes to the maintenance of genomic stability and integrity. Yet, connections and interactions between these two systems are not fully understood. In this review article, current status of the associations and crosstalk between autophagy and DNA repair systems is documented and discussed.     

Design and synthesis of some new pyranoxanthenone aminoderivatives with cytotoxic activity

The synthesis, DNA binding and in vitro cytotoxicity of a series of novel pyranoxanthones, analogues of the acridone alcaloid acronycine, are described. The new compounds proved to bind weakly to DNA. On the contrary, they exhibited interesting cytotoxic activity against murine leukemia L1210 cell line, as well as against some human solid tumor cell lines.