Differential roles of integrins alpha(2)beta(1), and alpha(IIb)beta(3) in collagen and CRP-induced platelet activation

Collagen and collagen-related peptide (CRP) activate platelets by interacting with glycoprotein (GP)VI. In addition, collagen binds to integrin alpha(2)beta(1) and possibly to other receptors. In this study, we have compared the role of integrins alpha(2)beta(1) and alpha(IIb)beta(3) in platelet activation induced by collagen and CRP. Inhibitors of ADP and thromboxane A(2) (TxA(2)) substantially attenuated collagen-induced platelet aggregation and dense granule release, whereas CRP-induced responses were only partially inhibited. Under these conditions, a proportion of platelets adhered to the collagen fibres resulting in dense granule release and alpha(IIb)beta(3) activation. This adhesion was substantially mediated by alpha(2)beta(1). The alpha(IIb)beta(3) antagonist lotrafiban potentiated CRP-induced dense granule release, suggesting that alpha(IIb)beta(3) outside-in signalling may attenuate GPVI signals. By contrast, lotrafiban inhibited collagen-induced dense granule release. These results emphasise the differential roles of alpha(2)beta(1) and alpha(IIb)beta(3) in platelet activation induced by collagen and CRP. Further, they show that although ADP and TxA(2) greatly facilitate collagen-induced platelet activation, collagen can induce full activation of those platelets to which it binds in the absence of these mediators, via a mechanism that is dependent on adhesion to alpha(2)beta(1).

Activation of GPVI by collagen is regulated by alpha(2)beta(1) and secondary mediators

We have compared the roles of adenosine diphosphate (ADP), thromboxanes and the integrin alpha(2)beta(1) in the activation of washed platelets by collagen in the presence of the alpha(IIb)beta3 antagonist lotrafiban. The stimulation of protein tyrosine phosphorylation by a collagen suspension is markedly delayed in the presence of the above inhibitors but shows substantial recovery with time. In comparison, activation of phospholipase C (PLC), Ca2+ elevation and dense granule secretion are more severely suppressed by the above inhibitors. blockade has a slightly greater inhibitory effect on all of the above responses than a combination of ADP receptor antagonists and cyclooxygenase inhibitor. Platelets exposed to a collagen monolayer show robust elevation of Ca2+ that is delayed in the presence of the above inhibitors and which is accompanied by of-granule secretion. These results demonstrate that secondary mediators and alpha(2)beta(1) modulate collagen-induced intracellular signaling but have negligible effect on GPVI signaling induced by the specific agonist convulxin. This work supports the postulate that the major role of of alpha(2)beta(1) is to increase the avidity of collagen for the platelet surface and by doing so enhance activation of GPVI. Therefore we propose an important role of secondary mediators in collagen-induced signaling is the indirect regulation of GPVI signaling via activation of alpha(2)beta(1).

Distinct roles of GPVI and integrin alpha(2)beta(1) in platelet shape change and aggregation induced by different collagens

1 Various platelet membrane glycoproteins have been proposed as receptors for collagen, in some cases as receptors For specific collagen types. In this study we have compared the ability of a range of collagen types to activate platelets.

Endocrine disrupting effects of zearalenone, alpha- and beta-zearalenol at the level of nuclear receptor binding and steroidogenesis.

The mycotoxin zearalenone (ZEN) is a secondary metabolite of fungi which is produced by certain species of the genus Fusarium and can occur in cereals and other plant products. Reporter gene assays incorporating natural steroid receptors and the H295R steroidogenesis assay have been implemented to assess the endocrine disrupting activity of ZEN and its metabolites -zearalenol (-ZOL) and -zearalenol (-ZOL). -ZOL exhibited the strongest estrogenic potency (EC50 0.022 ± 0.001 nM), slightly less potent than 17- estradiol (EC50 0.015 ± 0.002 nM). ZEN was ~70 times less potent than -ZOL and twice as potent as -ZOL. Binding of progesterone to the progestagen receptor was shown to be synergistically increased in the presence of ZEN, -ZOL or -ZOL. ZEN, -ZOL or -ZOL increased production of progesterone, estradiol, testosterone and cortisol hormones in the H295R steroidogenesis assay, with peak productions at 10 M. At 100 M, cell viability decreased and levels of hormones were significantly reduced except for progesterone. -ZOL increased estradiol concentrations more than -ZOL or ZEN, with a maximum effect at 10 M, with -ZOL (562 ± 59 pg/ml) > -ZOL (494 ± 60 pg/ml) > ZEN (375 ± 43 pg/ml). The results indicate that ZEN and its metabolites can act as potential endocrine disruptors at the level of nuclear receptor signalling and by altering hormone production.

Connective tissue growth factor antagonizes transforming growth factor-beta 1/Smad signalling in renal mesangial cells

The critical involvement of TGF-beta 1 (transforming growth factor-beta 1) in DN (diabetic nephropathy) is well established. However, the role of CTGF (connective tissue growth factor) in regulating the complex interplay of TGF-beta 1 signalling networks is poorly understood. The purpose of the present study was to investigate co-operative signalling between CTGF and TGF-beta 1 and its physiological significance. CTGF was determined to bind directly to the T beta RIII (TGF-beta type III receptor) and antagonize TGF-beta 1-induced Smad phosphorylation and transcriptional responses via its N-terminal half. Furthermore, TGF-beta 1 binding to its receptor was inhibited by CTGF. A consequent shift towards non-canonical TGF-beta 1 signalling and expression of a unique profile of differentially regulated genes was observed in CTGF/TGF-beta 1-treated mesangial cells. Decreased levels of Smad2/3 phosphorylation were evident in STZ (streptozotocin)-induced diabetic mice, concomitant with increased levels of CTGF Knockdown of T beta RIII restored TGF-beta 1-mediated Smad signalling and cell contractility, suggesting that T beta RIII is key for CTGF-mediated regulation of TGF-beta 1. Comparison of gene expression profiles from CTGF/TGF-beta 1-treated mesangial cells and human renal biopsy material with histological diagnosis of DN revealed significant correlation among gene clusters. In summary, mesangial cell responses to TGF-beta 1 are regulated by cross-talk with CTGF, emphasizing the potential utility of targeting CTGF in DN.

Catalytic properties of beta zeolite exchanged with Pd and Fe for toluene total oxidation

Dealuminated beta zeolites exchanged with Pd and Fe were prepared to investigate the influence of iron and dealumination on the activity and selectivity of Pd/BEA zeolite for toluene total oxidation. The specific areas determined by BET method and EPR studies allowed to know that the palladium would be more easily agglomerated on the BEA than on the DBEA. Moreover, a quantification of the palladium saturation on the BEA zeolite was deduced by EPR. Effects of dynamic and static oxidation and weak and strong reduction treatments were studied by EPR. Several isolated and interacted Pd+ species and hole centers were detected. The Pd was much reduced after the catalytic test in dealuminated and Fe doped samples. This result could be directly correlated to the catalytic deactivation. The deactivation could be also explain by the type of coke deposed on the catalyst and by the hydroscopic behavior of the samples. Addition of Fe or dealumination could prevent the deactivation and then lead to better catalysts for VOCs oxidation.

Novel anti-inflammatory compound SEN1176 alleviates behavioural deficits induced following bilateral intrahippocampal injection of aggregated amyloid-beta(1-42).

Behavioral effects of a novel anti-inflammatory SEN1176 were investigated. This pyrrolo[3,2-e][1,2,4]triazolo[1,5-a]pyrimidine suppresses amyloid-ß (Aß)1-42-induced macrophage production of nitric oxide, TNF-a, IL-1ß, and IL-6 in a dose-dependent fashion, an activity profile consistent with SEN1176 being a neuroinflammation inhibitor. Using male Sprague-Dawley rats, SEN1176 was examined relative to detrimental behavioral effects induced following bilateral intrahippocampal (IH) injections of aggregated Aß1-42. The rats were trained to respond under an alternating-lever cyclic-ratio (ALCR) schedule of food reinforcement, enabling measurement of parameters of operant performance that reflect aspects of learning and memory. Under the ALCR schedule, orally administered SEN1176 at 5, 20, or 30 mg/kg was effective in reducing the behavioral deficit caused by bilateral IH aggregated Aß1-42 injections in a dose-related manner over a 90-day treatment period. SEN1176 at 20 and 30 mg/kg significantly reduced lever switching errors and, at doses of 5, 10, and 30 mg/kg, significantly reduced incorrect lever perseverations, indicating a reduction of the behavioral deficit induced as a result of inflammation following IH Aß1-42 injections. When treatment with SEN1176 was instigated 30 days after IH Aß1-42 injections, it resulted in progressive protection, and withdrawal of SEN1176 treatment 60 days after IH Aß1-42 injections revealed partial retention of the protective effect. SEN1176 also significantly reduced numbers of activated astrocytes adjacent to the aggregated Aß1-42 injection sites. These results indicate the potential of SEN1176 for alleviating chronic neuroinflammatory processes related to brain Aß deposition that affect learning and memory in Alzheimer's disease.

Gingival fibroblast response to cyclosporin A and transforming growth factor beta(1)

This study investigates a potential role for TGF beta(1), in the pathogenesis of cyclosporin A-induced gingival overgrowth (CsA-OG). TGF beta(1) was localized immunohistochemically in the connective tissue of both normal gingiva and CsA-OG. Intense staining for TGF beta(1) was detected at the tips of the dermal papillae of the overgrown gingiva. In addition, fibroblasts derived from healthy gingiva and fibroblasts derived from CsA-OG were cultured both as monolayers or embedded in a 3D-collagen gel. Fibroblast activity was monitored in terms of protein and collagen production in the presence of (i) 1 ng/ml TGF beta(1), (ii) 500 ng/ml CsA, or (iii) 500 ng/ml CsA and 1 ng/ml TGF beta(1). In monolayer culture TGF beta(1) significantly increased protein and collagen production in all cell strains (p

Genetic variation in the interleukin-1 beta-converting enzyme associates with cognitive function. The PROSPER study

Inflammation is thought to play an important role in the development of cognitive decline and dementia in old age. The interleukin-1 signalling pathway may play a prominent role in this process. The gene encoding for interleukin-1 beta-converting enzyme (ICE) is likely to influence IL-1 beta levels. Inhibition of ICE decreases the age-related increase in IL-1 beta levels and may therefore improve memory function. We assessed whether genetic variation in the ICE gene associates with cognitive function in an elderly population. All 5804 participants of the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) were genotyped for the 10643GC, 9323GA, 8996AG and 5352GA polymorphisms in the ICE gene. Cross-sectional associations between the polymorphisms and cognitive function were assessed with linear regression. Longitudinal associations between polymorphisms, haplotypes and cognitive function were assessed with linear mixed models. All associations were adjusted for sex, age, education, country, treatment with pravastatin and version of test where appropriate. Subjects carrying the variants 10643C and 5352A allele had significantly lower IL-1 beta production levels (P

High-performance liquid chromatographic determination of 17 beta-estradiol and 17 beta-estradiol-3-acetate solubilities and diffusion coefficients in silicone elastomeric intravaginal rings

A rapid, sensitive reversed-phase high-performance liquid chromatographic method has been developed for the determination of in vitro release of 17 beta-estradiol and its ester prodrug, 17 beta-estradiol-3-acetate, from silicone intravaginal rings. Partial hydrolysis of the acetate under the aqueous conditions provided by the 1% benzalkonium chloride release medium necessitates its conversion to 17 beta-estradiol prior to HPLC analysis. Both steroid peaks have been fully resolved from the benzalkonium chloride peaks by the reported chromatographic method,which employs a C-18 bonded reversed-phase column, an acetonitrile-water (50:50, v/v) mobile phase and a UV detection wavelength of 281 nm. The peak area versus 17 beta-estradiol concentration was found to be linear over the range of 0.0137-1347 mu g ml(-1) The HPLC method has also been used to determine the silicone solubilities and diffusion coefficients of the two related steroids. The almost 100-fold increase in 17 beta-estradiol-3-acetate release from the silicone core-type intravaginal rings compared to 17 beta-estradiol is shown to be due to a 60-fold increase in silicone solubility and a one and a half-fold increase in diffusitivity. The results demonstrate that an effective estrogen replacement therapy dose of 17 beta-estradiol may be administered from a silicone intravaginal reservoir device containing the labile 17 beta-estradiol-3-acetate prodrug. (C) 2000 Elsevier Science B.V. All rights reserved.