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Selected AbstractsHeparin regulates colon cancer cell growth through p38 mitogen-activated protein kinase signallingCELL PROLIFERATION, Issue 1 2010G. Chatzinikolaou Objectives:, Heparin acts as an extracellular stimulus capable of activating major cell signalling pathways. Thus, we examined the putative mechanisms utilized by heparin to stimulate HT29, SW1116 and HCT116 colon cancer cell growth. Materials and methods:, Possible participation of the mitogen-activated protein kinase (MAPK) cascade on heparin-induced HT29, SW1116 and HCT116 colon cancer cell growth was evaluated using specific MAPK cascade inhibitors, Western blot analysis, real-time quantitative PCR and FACS apoptosis analysis. Results:, Treatment with a highly specific p38 kinase inhibitor, SB203580, significantly (50,70%) inhibited heparin-induced colon cancer cell growth, demonstrating that p38 MAPK signalling is involved in their heparin-induced proliferative response. This was shown to be correlated with increased (up to 3-fold) phosphorylation of 181/182 threonine/tyrosine residues on p38 MAP kinase. Furthermore, heparin inhibited cyclin-dependent kinase inhibitor p21WAF1/CIP1 and p53 tumour suppressor gene and protein expression up to 2-fold or 1.8-fold, respectively, and stimulated cyclin D1 expression up to 1.8-fold, in these cell lines through a p38-mediated mechanism. On the other hand, treatment with heparin did not appear to affect HT29, SW1116 and HCT116 cell levels of apoptosis. Conclusions:, This study demonstrates that an extracellular glycosaminoglycan, heparin, finely modulates expression of genes crucial to cell cycle regulation through specific activation of p38 MAP kinase to stimulate colon cancer cell growth. [source] Stabilizing effects of extracellular ATP on synaptic efficacy and plasticity in hippocampal pyramidal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2005Eduardo D. Martín Abstract The role of adenosine triphosphate (ATP) as a neurotransmitter and extracellular diffusible messenger has recently received considerable attention because of its possible participation in the regulation of synaptic plasticity. However, the possible contribution of extracellular ATP in maintaining and regulating synaptic efficacy during intracellular ATP depletion is understudied. We tested the effects of extracellular ATP on excitatory postsynaptic currents (EPSCs) evoked in CA1 pyramidal neurons by Schaffer collateral stimulation. In the absence of intracellular ATP, EPSC rundown was neutralized when a low concentration of ATP (1 µm) was added to the extracellular solution. Adenosine and ATP analogues did not prevent the EPSC rundown. The P2 antagonists piridoxal-5,-phosphate-azophenyl 2,,4,-disulphonate (PPADS) and reactive blue-2, and the P1 adenosine receptor antagonist 8-cyclopentyltheophylline (CPT) had no detectable effects in cells depleted of ATP. However, the protective action of extracellular ATP on synaptic efficacy was blocked by extracellular application of the protein kinase inhibitors K252b and staurosporine. In contrast, K252b and staurosporine per se did not interfere with synaptic transmission in ATP loaded cells. Without intracellular ATP, bath-applied caffeine induced a transient (< 35 min) EPSC potentiation that was transformed into a persistent long-term potentiation (> 80 min) when 1 µm ATP was added extracellularly. An increased probability of transmitter release paralleled the long-term potentiation induced by caffeine, suggesting that it originated presynaptically. Therefore, we conclude that extracellular ATP may operate to maintain and regulate synaptic efficacy and plasticity in conditions of abnormal intracellular ATP depletion by phosphorylation of a surface protein substrate via activation of ecto-protein kinases. [source] Prevalence of heparin-induced antibodies in patients with chronic renal failure undergoing hemodialysisJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 5 2005Iván Palomo Abstract Heparin-induced thrombocytopenia (HIT) type II is a serious complication of heparin therapy. It presents initially as thrombocytopenia, and is associated with thrombosis in 20,50% of the cases. HIT is related to the presence of heparin-induced antibodies (HIA), which show specificity for the PF4-heparin (PF4-H) complex. The Fc,RIIa receptor has been suggested to participate in the pathogenic mechanism of HIA. Since patients undergoing chronic hemodialysis (HD) are exposed repeatedly to heparin, we studied the prevalence of HIA and their eventual relationship with thrombocytopenia and/or thrombosis, and the possible participation of the Fc,RIIa polymorphism. We studied 207 patients with chronic renal failure (CRF) undergoing HD. As a control we included 130 blood donors and 28 patients with CRF without HD. The HIA patients were studied with the use of a PF4-H ELISA. Additionally, in some positive cases for the previous test, a 14C- serotonin release assay (14C-SRA) was performed. The polymorphism Fc,RIIa H/R131 was studied by polymerase chain reaction (PCR) with allele-specific primers. Thirty-seven patients (17.9%) undergoing HD presented with HIA. The majority of these antibodies were IgG, IgM, and IgA. The HIA investigated presented specificity against the PF4-H complex, but not against PF4 alone (P<0.001). Twelve out of 22 (54.5%) PF4-H antibodies were positive when tested with the 14C-SRA. The distribution of the Fc,RIIa polymorphism in patients and healthy controls was 42.6% and 41.6% for H/H131, 41% and 48.9% for the H/R131 isoform, and 16.4% and 9.5% for the R/R131 isoform, respectively. No statistically significant difference in the Fc,RIIa isoform distribution was found. Twenty-nine out of 156 patients (18.5%) presented thrombocytopenia, and 21/207 (12.4%) had thrombosis of the native vein arterio-venous fistula (AVF). We did not find any statistically significant between HIA and thrombocytopenia or thrombosis. An important proportion of patients with CRF undergoing HD developed HIA, but these cases were not associated with thrombocytopenia or thrombosis of AVF. The frequency of the Fc,RIIa polymorphism did not statistically differ between HIT type II and normal controls. J. Clin. Lab. Anal. 19:189,195, 2005. © 2005 Wiley-Liss, Inc. [source] Melatonin induces neuritogenesis at early stages in N1E-115 cells through actin rearrangements via activation of protein kinase C and Rho-associated kinaseJOURNAL OF PINEAL RESEARCH, Issue 3 2007Alfredo Bellon Abstract:, Melatonin increases neurite formation in N1E-115 cells through microtubule enlargement elicited by calmodulin antagonism and vimentin intermediate filament reorganization caused by protein kinase C (PKC) activation. Microfilament rearrangement is also a necessary process in growth cone formation during neurite outgrowth. In this work, we studied the effect of melatonin on microfilament rearrangements present at early stages of neurite formation and the possible participation of PKC and the Rho-associated kinase (ROCK), which is a downstream kinase in the PKC signaling pathway. The results showed that 1 nm melatonin increased both the number of cells with filopodia and with long neurites. Similar results were obtained with the PKC activator phorbol 12-myristate 13-acetate (PMA). Both melatonin and PMA increased the quantity of filamentous actin. In contrast, the PKC inhibitor bisindolylmaleimide abolished microfilament organization elicited by either melatonin or PMA, while the Rho inhibitor C3, or the ROCK inhibitor Y27632, abolished the bipolar neurite morphology of N1E-115 cells. Instead, these inhibitors prompted neurite ramification. ROCK activity measured in whole cell extracts and in N1E-115 cells was increased in the presence of melatonin and PMA. The results indicate that melatonin increases the number of cells with immature neurites and suggest that these neurites can be susceptible to differentiation by incoming extracellular signals. Data also indicate that PKC and ROCK are involved at initial stages of neurite formation in the mechanism by which melatonin recruits cells for later differentiation. [source] Identification of testis-specific ubiquitin-conjugating enzyme in the ascidian Ciona intestinalisMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 7 2010Naoto Yokota The ubiquitin,proteasome system is known to play a key role in fertilization in ascidians, sea urchins, and mammals. To obtain insights into the ubiquitin-conjugating enzymes (Ube2) involved in reproductive systems, we systematically explored Ube2 enzymes expressed in the testis of the ascidian Ciona intestinalis. Here, we report cDNA cloning and characterization of a novel type of Ube2r (Ci0100152677) that is capable of making a thiolester bond with ubiquitin. Northern analysis, whole-mount in situ hybridization and immunocytochemistry indicate that this enzyme is exclusively expressed in the testis, mainly in the germ cells during the late stage of spermatogenesis, and is localized in the sperm head and tail, suggesting possible participation in fertilization or spermatogenesis/spermiogenesis. Mol. Reprod. Dev. 77: 640,647, 2010. © 2010 Wiley-Liss, Inc. [source] | ||||||||||