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Mechanism Distinct (mechanism + distinct)
Selected AbstractsAscochlorin activates p53 in a manner distinct from DNA damaging agentsINTERNATIONAL JOURNAL OF CANCER, Issue 12 2009Ji-Hak Jeong Abstract Ascochlorin, a prenylphenol antitumor antibiotic, profoundly increases the expression of endogenous p53 by increasing protein stability in the human osteosarcoma cells and human colon cancer cells. Ascochlorin also increases DNA binding activity to the p53 consensus sequence in nuclear extract and enhances transcription of p53 downstream targets. Ascochlorin specifically induces p53 phosphorylation at ser 392 without affecting ser 15 or 20, whereas DNA damaging agents typically phosphorylate these serines. Moreover, ascochlorin does not induce phosphorylation of ATM and CHK1, an established substrate of ATR that is activated by genotoxins, nor does it increase DNA strand break, as confirmed by comet assay. The structure-activity relationship suggests that p53 activation by ascochlorin is related to inhibition of mitochondrial respiration, which is further supported by the observation that respiratory inhibitors activate p53 in a manner similar to ascochlorin. These results suggest that ascochlorin, through the inhibition of mitochondrial respiration, activates p53 through a mechanism distinct from genotoxins. © 2009 UICC [source] Rapid loss of motor nerve terminals following hypoxia,reperfusion injury occurs via mechanisms distinct from classic Wallerian degenerationJOURNAL OF ANATOMY, Issue 6 2008Becki Baxter Abstract Motor nerve terminals are known to be vulnerable to a wide range of pathological stimuli. To further characterize this vulnerability, we have developed a novel model system to examine the response of mouse motor nerve terminals in ex vivo nerve/muscle preparations to 2 h hypoxia followed by 2 h reperfusion. This insult induced a rapid loss of neurofilament and synaptic vesicle protein immunoreactivity at pre-synaptic motor nerve terminals but did not appear to affect post-synaptic endplates or muscle fibres. The severity of nerve terminal loss was dependent on the age of the mouse and muscle type: in 8,12-week-old mice the predominantly fast-twitch lumbrical muscles showed an 82.5% loss, whereas the predominantly slow-twitch muscles transversus abdominis and triangularis sterni showed a 57.8% and 27.2% loss, respectively. This was contrasted with a > 97% loss in the predominantly slow-twitch muscles from 5,6-week-old mice. We have also demonstrated that nerve terminal loss occurs by a mechanism distinct from Wallerian degeneration, as the slow Wallerian degeneration (Wlds) gene did not modify the extent of nerve terminal pathology. Together, these data show that our new model of hypoxia,reperfusion injury is robust and repeatable, that it induces rapid, quantitative changes in motor nerve terminals and that it can be used to further examine the mechanisms regulating nerve terminal vulnerability in response to hypoxia,reperfusion injury. [source] Dopamine modulates von Willebrand factor secretion in endothelial cells via D2,D4 receptorsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 7 2006S. ZAREI Summary.,Objective: von Willebrand factor (VWF) is acutely released from endothelial cells in response to numerous calcium-raising agents (e.g. thrombin, histamine) and cAMP-raising agents (e.g. epinephrine, adenosine, vasopressin). In contrast, very few inhibitors of endothelial VWF secretion have been described. The neurotransmitter dopamine is a modulator of exocytosis in several endocrine cells, and is possibly involved in the regulation of several endothelial cell functions. We therefore investigated the effect of dopamine on endothelial VWF secretion. Results: Dopamine, D2/D3- and D4-specific agonists inhibited histamine- but not thrombin-induced VWF secretion. Expression of dopamine D2, D3 and D4 receptors was demonstrated by reverse transcription polymerase chain reaction (RT-PCR) in both human aortic (HAEC) and umbilical vein (HUVEC) endothelial cells. D2,D4 agonists did not inhibit histamine-induced rise in [Ca2+]i: they inhibited histamine-induced secretion even in the absence of extracellular calcium. Thus, the dopamine effects are not mediated by [Ca2+]i -dependent signalling. D2/D3- and D4-specific agonists inhibited neither the rise in cAMP nor VWF secretion in response to epinephrine and adenosine, arguing against an effect on cAMP-mediated signalling. D1 and D5 receptors were not detected in HAEC or HUVEC by RT-PCR, and the D1/D5-specific agonist SKF 38 393 failed to modulate VWF secretion, arguing against a role for these receptors in endothelial exocytosis. Conclusions: Dopamine inhibits histamine-induced endothelial exocytosis by activating D2,D4 receptor, via a mechanism distinct from [Ca2+]i -or cAMP-mediated signaling. In contrast, D1 and D5 receptors are not functionally expressed in cultured endothelial cells. Dopamine agonists may be useful as inhibitors of endothelial activation in inflammation and cardiovascular disease. [source] Neuromyelitis optica/Devic's disease: Gene expression profiling of brain lesionsNEUROPATHOLOGY, Issue 6 2008Jun-ichi Satoh Neuromyelitis optica (NMO), also known as Devic's disease, is an inflammatory demyelinating disease that affects selectively the optic nerves and the spinal cord, possibly mediated by an immune mechanism distinct from that of multiple sclerosis (MS). Recent studies indicate that NMO also involves the brain. Here, we studied gene expression profile of brain lesions of a patient with NMO by using DNA microarray, along with gene expression profile of the brains of Parkinson disease and amyotrophic lateral sclerosis patients. We identified more than 200 genes up-regulated in NMO brain lesions. The top 20 genes were composed of the molecules closely associated with immune regulation, among which marked up-regulation of interferon gamma-inducible protein 30 (IFI30), CD163, and secreted phosphoprotein 1 (SPP1, osteopontin) was validated by real time RT-PCR, Northern blot and Western blot analysis. Pathologically, CD68+ macrophages and microglia expressed intense immunoreactivities for IFI30 and CD163 in NMO lesions, consisting of inflammatory demyelination, axonal loss, necrosis, cavity formation, and vascular fibrosis. KeyMolnet, a bioinformatics tool for analyzing molecular interaction on the curated knowledge database, suggested that the molecular network of up-regulated genes in NMO brain lesions involves transcriptional regulation by the nuclear factor-kappaB (NF-,B) and B-lymphocyte-induced maturation protein-1 (Blimp-1). These results suggest that profound activation of the macrophage-mediated proinflammatory immune mechanism plays a pivotal role in development of NMO brain lesions. [source] Divergent regulation of GIRK1 and GIRK2 subunits of the neuronal G protein gated K+ channel by G,iGDP and G,,THE JOURNAL OF PHYSIOLOGY, Issue 14 2009Moran Rubinstein G protein activated K+ channels (GIRK, Kir3) are switched on by direct binding of G,, following activation of Gi/o proteins via G protein-coupled receptors (GPCRs). Although G,i subunits do not activate GIRKs, they interact with the channels and regulate the gating pattern of the neuronal heterotetrameric GIRK1/2 channel (composed of GIRK1 and GIRK2 subunits) expressed in Xenopus oocytes. Coexpressed G,i3 decreases the basal activity (Ibasal) and increases the extent of activation by purified or coexpressed G,,. Here we show that this regulation is exerted by the ,inactive' GDP-bound G,i3GDP and involves the formation of G,i3,, heterotrimers, by a mechanism distinct from mere sequestration of G,,,away' from the channel. The regulation of basal and G,,-evoked current was produced by the ,constitutively inactive' mutant of G,i3, G,i3G203A, which strongly binds G,,, but not by the ,constitutively active' mutant, G,i3Q204L, or by G,,-scavenging proteins. Furthermore, regulation by G,i3G203A was unique to the GIRK1 subunit; it was not observed in homomeric GIRK2 channels. In vitro protein interaction experiments showed that purified G,, enhanced the binding of G,i3GDP to the cytosolic domain of GIRK1, but not GIRK2. Homomeric GIRK2 channels behaved as a ,classical' G,, effector, showing low Ibasal and strong G,,-dependent activation. Expression of G,i3G203A did not affect either Ibasal or G,,-induced activation. In contrast, homomeric GIRK1* (a pore mutant able to form functional homomeric channels) exhibited large Ibasal and was poorly activated by G,,. Expression of G,i3GDP reduced Ibasal and restored the ability of G,, to activate GIRK1*, like in GIRK1/2. Transferring the unique distal segment of the C terminus of GIRK1 to GIRK2 rendered the latter functionally similar to GIRK1*. These results demonstrate that GIRK1 containing channels are regulated by both G,i3GDP and G,,, while GIRK2 is a G,,-effector insensitive to G,i3GDP. [source] Lack of association of ,2-glycoprotein I polymorphisms Val247Leu and Trp316Ser with antiphospholipid antibodies in patients with thrombosis and pregnancy complicationsBRITISH JOURNAL OF HAEMATOLOGY, Issue 6 2003Raymond S. Camilleri Summary. Beta2 -glycoprotein I (,2GPI) is an important target antigen for antiphospholipid antibodies (aPL) and thus ,2GPI polymorphisms may influence aPL production and the development of antiphospholipid syndrome. We have studied the relationship between the Val247Leu and Trp316Ser ,2GPI polymorphisms and the aPL status of 230 patients referred for aPL screening. Sixty-one (26·5%) had persistent aPL [anticardiolipin antibodies (IgG and/or IgM), lupus anticoagulants and/or IgG anti-,2GPI antibodies]. A comparison of the genotypic and allelic frequencies of these two polymorphisms between the Caucasian patient population and an ethnic-matched normal control group (n = 308) showed no significant differences between aPL-positive patients, aPL-negative patients and the normal control group. This suggests that the Val or Leu allele at position 247 and the Trp or Ser allele at position 316 of ,2GPI do not play a role in the production of aPL. There was a significantly decreased prevalence of the Ser316 allele in aPL-negative women (n = 98) when compared with female normal control subjects (n = 249) {0·020 [95% confidence interval (CI) 0·00,0·04]vs 0·060 (95% CI 0·04,0·08), P = 0·0286}. Subgroup analysis showed no significant difference between female patients with thrombosis and female normal control subjects. Thus, the Ser316 allele may protect women from developing pregnancy complications by influencing an anticoagulant function of ,2GPI via a mechanism distinct from aPL production. [source] Rapid loss of motor nerve terminals following hypoxia,reperfusion injury occurs via mechanisms distinct from classic Wallerian degenerationJOURNAL OF ANATOMY, Issue 6 2008Becki Baxter Abstract Motor nerve terminals are known to be vulnerable to a wide range of pathological stimuli. To further characterize this vulnerability, we have developed a novel model system to examine the response of mouse motor nerve terminals in ex vivo nerve/muscle preparations to 2 h hypoxia followed by 2 h reperfusion. This insult induced a rapid loss of neurofilament and synaptic vesicle protein immunoreactivity at pre-synaptic motor nerve terminals but did not appear to affect post-synaptic endplates or muscle fibres. The severity of nerve terminal loss was dependent on the age of the mouse and muscle type: in 8,12-week-old mice the predominantly fast-twitch lumbrical muscles showed an 82.5% loss, whereas the predominantly slow-twitch muscles transversus abdominis and triangularis sterni showed a 57.8% and 27.2% loss, respectively. This was contrasted with a > 97% loss in the predominantly slow-twitch muscles from 5,6-week-old mice. We have also demonstrated that nerve terminal loss occurs by a mechanism distinct from Wallerian degeneration, as the slow Wallerian degeneration (Wlds) gene did not modify the extent of nerve terminal pathology. Together, these data show that our new model of hypoxia,reperfusion injury is robust and repeatable, that it induces rapid, quantitative changes in motor nerve terminals and that it can be used to further examine the mechanisms regulating nerve terminal vulnerability in response to hypoxia,reperfusion injury. [source] | |||||||||||||