[Show abstract][Hide abstract] ABSTRACT: Cilia are highly specialized antennae-like cellular organelles. Inositol polyphosphate 5-phosphatase E (INPP5E) converts PI(4,5)P2 into PI4P and is required for proper ciliary function. Although Inpp5e mutations are associated with ciliopathies in humans and mice, the precise molecular role INPP5E plays in cilia remains unclear. Here, we report that Drosophila INPP5E (dINPP5E) regulates ciliary protein trafficking by controlling the phosphoinositide composition of ciliary membranes. Mutations in dInpp5e lead to hearing deficits due to the mislocalization of dTULP and mechanotransduction channels, Inactive and NOMPC, in chordotonal cilia. Both loss of dINPP5E and ectopic expression of the phosphatidylinositol-4-phosphate 5-kinase Skittles increase PI(4,5)P2 levels in the ciliary base. The fact that Skittles expression phenocopies the dInpp5e mutants confirms a central role for PI(4,5)P2 in the regulation of dTULP, Inactive, and NOMPC localization. These data suggest that the spatial localization and levels of PI(4,5)P2 in ciliary membranes are important regulators of ciliary trafficking and function.
[Show abstract][Hide abstract] ABSTRACT: Abstract Staurosporine, a non-specific protein kinase inhibitor, has been shown to induce neurite outgrowth in PC12 cells, but the mechanism by which staurosporine induces neurite outgrowth is still obscure. In the present study, we investigated whether the activation of Rac1 was responsible for the neurite outgrowth triggered by staurosporine. Staurosporine caused rapid neurite outgrowth independently of ERK signaling pathways. In contrast, neurite outgrowth in response to staurosporine was accompanied by activation of Rac1, and the Rac1 inhibitor NSC23766 attenuated the staurosporine-induced neurite outgrowth in a concentration-dependent manner. In addition, suppression of Rac1 activity by expression of the dominant negative mutant Rac1N17 also blocked the staurosporine-induced morphological differentiation of PC12 cells. Staurosporine caused an activation of NADPH oxidase and increased the production of reactive oxygen species (ROS), which was prevented by NSC23766 and diphenyleneiodonium (DPI), an NADPH oxidase inhibitor. Staurosporine-induced neurite outgrowth was attenuated by pretreatment with DPI and exogenous addition of sublethal concentration of H(2)O(2) accelerated neurite outgrowth triggered by staurosporine. These results indicate that activation of Rac1, which leads to ROS generation, is required for neurite outgrowth induced by staurosporine in PC12 cells.
No preview · Article · Nov 2012 · Free Radical Research
[Show abstract][Hide abstract] ABSTRACT: Accumulation of reactive oxygen species (ROS) caused by the inhibition of glutathione reductase (GR) has been proposed as one of the mechanisms responsible for carmustine (1,3-bis(2-chloroethyl)-1-nitrosourea, BCNU)-induced cytotoxicity. Since mitogen-activated protein kinases (MAPKs) are known to mediate ROS-dependent cell death in multiple cell types, we examined whether redox-sensitive MAPK activation mediated the carmustine-induced cell death of neuronally differentiated PC12 cells. Carmustine induced a concentration- and time-dependent cell death, which was associated with increased caspase-3 activation, a reduction in GR activity accompanied by a concomitant decrease in reduced glutathione levels, and accumulation of ROS. Carmustine-induced caspase-3 activation and cell death were prevented by pretreatment with anti-oxidants or a reducing agent, indicating that carmustine-induced caspase-3 activation and cell death occur via redox-dependent processes. Carmustine induced phosphorylation of the MAPKs, such as extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. The activation of these kinases was inhibited by pretreatment with N-acetyl-L-cysteine (NAC). Although all the MAPKs were activated by carmustine, only the inhibitors of JNK and ERK prevented carmustine-induced cell death and caspase-3 activation. Our data suggest that carmustine-induced neurotoxicity is, at least in part, due to the activation of ROS-dependent JNK and ERK signaling.
No preview · Article · May 2011 · Toxicology in Vitro
[Show abstract][Hide abstract] ABSTRACT: 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) is known as a specific inhibitor of soluble guanylyl cyclase (sGC). Previously, however, ODQ was reported to induce cell death via sGC-dependent and sGC-independent means in a variety of cell types. The aim of this study was to investigate the mechanism by which ODQ induces cell death in HeLa cells. Treatment of HeLa cells with ODQ induced a concentration-dependent decrease in cell viability over the range from 10 to 100 μM. DNA fragmentation and fluorescence-activated cell sorting analysis using annexin V and propidium iodide staining revealed that ODQ triggered apoptosis at concentrations of 50 and 100 μM within 24 to 48 h. The addition of 8-Br-cGMP in the presence of ODQ failed to rescue HeLa cells from death, suggesting that the inhibition of sGC was not responsible for the pro-apoptotic action of ODQ. ODQ arrested the cell cycle at the G2/M phase and caused disassembly of the microtubule network. This process was reversed by dithiothreitol. In addition, ODQ was shown to inhibit the polymerization of purified tubulin, and this was also prevented by dithiothreitol. These results indicate that ODQ inhibits microtubule assembly by direct oxidation of tubulin, induces cell cycle arrest at the G2/M phase, and triggers apoptosis in HeLa cells.
No preview · Article · May 2011 · Biochemical and Biophysical Research Communications
[Show abstract][Hide abstract] ABSTRACT: RANKL is essential for the terminal differentiation of monocytes/macrophages into osteoclasts. RANKL induces long-lasting oscillations in the intracellular concentration of Ca(2+) ([Ca(2+)](i)) only after 24 h of stimulation. These Ca(2+) oscillations play a switch-on role in NFATc1 expression and osteoclast differentiation. Which Ca(2+) transporting pathway is induced by RANKL to evoke the Ca(2+) oscillations and its specific role in RANKL-mediated osteoclast differentiation is not known. This study examined the effect of a partial loss of sarco/endoplasmic reticulum Ca(2+) ATPase type 2 (SERCA2) on osteoclast differentiation in SERCA2 heterozygote mice (SERCA2(+/-)). The BMD in the tibias of SERCA2(+/-) mice increased >1.5-fold compared with wildtype mice (WT). RANKL-induced [Ca(2+)](i) oscillations were generated 48 h after RANKL treatment in the WT mice but not in the SERCA2(+/-) bone marrow-derived macrophages (BMMs). Forty-eight hours after RANKL treatment, there was a lower level of NFATc1 protein expression and markedly reduced translocation of NFATc1 into the nucleus during osteoclastogenesis of the SERCA2(+/-) BMMs. In addition, RANKL treatment of SERCA2(+/-) BMMs incompletely induced formation of multinucleated cells, leading to reduced bone resorption activity. These results suggest that RANKL-mediated induction of SERCA2 plays a critical role in the RANKL-induced [Ca(2+)](i) oscillations that are essential for osteoclastogenesis.
Preview · Article · Jun 2009 · Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research
[Show abstract][Hide abstract] ABSTRACT: Differentiation of neuronal cells has been shown to accelerate stress-induced cell death, but the underlying mechanisms are not completely understood. Here, we find that early and sustained increase in cytosolic ([Ca2(+)]c) and mitochondrial Ca2(+) levels ([Ca2(+)]m) is essential for the increased sensitivity to staurosporine- induced cell death following neuronal differentiation in PC12 cells. Consistently, pretreatment of differentiated PC12 cells with the intracellular Ca2(+)-chelator EGTA-AM diminished staurosporine-induced PARP cleavage and cell death. Furthermore, Ca2(+) overload and enhanced vulnerability to staurosporine in differentiated cells were prevented by Bcl-XL overexpression. Our data reveal a new regulatory role for differentiation-dependent alteration of Ca2(+) signaling in cell death in response to staurosporine.
Preview · Article · Apr 2009 · Experimental and Molecular Medicine
[Show abstract][Hide abstract] ABSTRACT: The effect of the potent soluble guanylyl cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) on neurite outgrowth and retraction was investigated in PC12 cells and SH-SY5Y human neuroblastoma cells. ODQ inhibited neurite outgrowth and triggered neurite retraction in the cells stimulated with nerve growth factor (NGF), staurosporine, or Y-27632. The nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (PTIO) had little effect on neurite outgrowth induced by Y-27632 or staurosporine. In the presence of ODQ, treatment of the cells with the cell-permeable cGMP analogue 8-bromo-cGMP failed to retrigger Y-27632- and staurosporine-induced neurite outgrowth. Furthermore, the depletion of sGC by RNA interference failed to prevent Y-27632- and staurosporine-induced neurite outgrowth. These results indicate that the NO/sGC/cGMP signaling cascade is not critically involved in ODQ-induced neurite remodeling. The MEK inhibitor PD98059 did not inhibit neurite outgrowth, and Y-27632 and staurosporine did not induce ERK phosphorylation, suggesting that the inhibitory effect of ODQ on neurite outgrowth is independent of the ERK signaling pathway. In contrast, pretreatment with dithionite or a hemin-glutathione mixture reversed the inhibitory effect of ODQ on Y-27632- and staurosporine-induced neurite outgrowth, indicating that ODQ might act on an intracellular redox-sensitive molecule. We conclude that ODQ inhibits Y-27632- and staurosporine-induced neurite outgrowth and triggers neurite retraction in an sGC-independent manner in neuronal cells and suggest that oxidation of unidentified redox-sensitive protein could be responsible for these effects.
No preview · Article · Jan 2009 · Journal of Neuroscience Research
[Show abstract][Hide abstract] ABSTRACT: Mammalian chitinase released by airway epithelia is thought to be an important mediator of disease manifestation in an experimental model of asthma. However, the intracellular signaling mechanisms engaged by exogenous chitinase in human airway epithelial cells are unknown. Here, we investigated the direct effects of exogenous chitinase from Streptomyces griseus on Ca(2+) signaling in human airway epithelial cells. Spectrofluorometry was used to measure intracellular Ca(2+) concentration ([Ca(2+)](i)) in fura-2-AM-loaded cells. S. griseus chitinase induced dose-dependent [Ca(2+)](i) increases in normal human bronchial epithelial cells and promoted [Ca(2+)](i) oscillations in H292 cells. Chitinase-induced [Ca(2+)](i) oscillations were independent of extracellular Ca(2+), suggesting that the observed [Ca(2+)](i) increases were due to Ca(2+) release from intracellular stores. Accordingly, after depleting endoplasmic reticulum (ER) Ca(2+) with the ER Ca(2+) ATPase inhibitor, thapsigargin, chitinase-mediated [Ca(2+)](i) increases were abolished. Treatment with the phospholipase C (PLC) inhibitor U73122 or the 1, 4, 5-trisinositolphosphate (IP(3)) receptor inhibitor 2-APB attenuated chitinase-induced [Ca(2+)](i) increases. Desensitization of protease-activated receptor-2 (PAR-2) by repetitive agonist stimulation or siRNA-mediated PAR-2 knock-down revealed that chitinase-mediated [Ca(2+)](i) increases were exclusively mediated by PAR-2 activation. Finally, chitinase was found to cleave a model peptide representing the cleavage site of PAR-2 and enhanced IL-8 production. These results indicate that exogenous chitinase is a potent proteolytic activator of PAR-2 that can directly induce PLC/IP(3)-dependent Ca(2+) signaling in human airway epithelial cells.
Full-text · Article · Jun 2008 · American Journal of Respiratory Cell and Molecular Biology
[Show abstract][Hide abstract] ABSTRACT: Reactive oxygen species, such as the superoxide anion, H2O2, and the hydroxyl radical, have been considered as cytotoxic by-products of cellular metabolism. However, recent studies have provided evidence that H2O2 serves as a signaling molecule modulating various physiological functions. Here we investigated the effect of H2O2 on the regulation of intracellular Ca2+ signaling in rat cortical astrocytes. H2O2 triggered the generation of oscillations of intracellular Ca2+ concentration ([Ca2+]i) in a concentration-dependent manner over the range 10-100 microM. The H2O2-induced [Ca2+]i oscillations persisted in the absence of extracellular Ca2+ and were prevented by depletion of intracellular Ca2+ stores with thapsigargin. The H2O2-induced [Ca2+]i oscillations were not inhibited by pretreatment with ryanodine but were prevented by 2-aminoethoxydiphenyl borate and caffeine, known antagonists of inositol 1,4,5-trisphosphate receptors. H2O2 activated phospholipase C (PLC) gamma1 in a dose-dependent manner, and U73122, an inhibitor of PLC, completely abolished the H2O2-induced [Ca2+]i oscillations. In addition, RNA interference against PLCgamma1 and the expression of the inositol 1,4,5-trisphosphate-sequestering "sponge" prevented the generation of [Ca2+]i oscillations. H2O2-induced [Ca2+]i oscillations and PLC1 phosphorylation were inhibited by pretreatment with dithiothreitol, a sulfhydryl-reducing agent. Finally, epidermal growth factor induced H2O2 production, PLCgamma1 activation, and [Ca2+]i increases, which were attenuated by N-acetylcysteine and diphenyleneiodonium and by the overexpression of peroxiredoxin type II. Therefore, we conclude that low concentrations of exogenously applied H2O2 generate [Ca2+]i oscillations by activating PLCgamma1 through sulfhydryl oxidation-dependent mechanisms. Furthermore, we show that this mechanism underlies the modulatory effect of endogenously produced H2O2 on epidermal growth factor-induced Ca2+ signaling in rat cortical astrocytes.
No preview · Article · Jun 2006 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Synaptotagmin is a Ca2+ sensing protein, which triggers a fusion of synaptic vesicles in neuronal transmission. Little is known regarding the expression of Ca2+-dependent synaptotagmin isoforms and their contribution to the release of secretory vesicles in mouse and rat parotid acinar cells. We investigated a type of Ca2+-dependent synaptotagmin and Ca2+ signaling in both rat and mouse parotid acinar cells using RT-PCR, microfluorometry, and amylase assay. Mouse parotid acinar cells exhibited much more sensitive amylase release in response to muscarinic stimulation than did rat parotid acinar cells. However, transient [Ca2+]i increases and Ca2+ influx in response to muscarinic stimulation in both cells were identical, suggesting that the expression or activity of the Ca2+ sensing proteins is different. Seven Ca2+-dependent synaptotagmins, from 1 to 7, were expressed in the mouse parotid acinar cells. However, in the rat parotid acinar cells, only synaptotagmins 1, 3, 4 and 7 were expressed. These results indicate that the expression of Ca2+-dependent synaptotagmins may contribute to the release of secretory vesicles in parotid acinar cells.
Preview · Article · Mar 2006 · Yonsei Medical Journal
[Show abstract][Hide abstract] ABSTRACT: We previously reported that rebamipide (2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinon-4-yl]-propionic acid) generated oscillations of intracellular Ca2+ concentration ([Ca2+]i) probably through the activation of cholecystokinin type 1 (CCK1) receptors in rat pancreatic acinar cells. Therefore, in the present study, we aimed to establish the pharmacological characteristics of rebamipide in rat pancreatic acinar cells. CCK-8S and rebamipide inhibited [125I]BH-CCK-8S binding to rat pancreatic acinar cell membranes with IC50 values of 3.13 nM and 37.7 microM, respectively. CCK-8S usually evoked [Ca2+]i oscillations at concentrations lower than 50 pM, and it induced biphasic [Ca2+]i increases at higher concentrations. In contrast to CCK-8S, rebamipide only induced [Ca2+]i oscillations at all the concentrations we used in this study. In addition, rebamipide was shown to inhibit high concentrations of CCK-8S-induced biphasic increases in [Ca2+]i, suggesting that rebamipide might be a partial agonist at cholecystokinin CCK1 receptors. Although rebamipide induced [Ca2+]i oscillations by activating the cholecystokinin CCK1 receptors, rebamipide did not cause amylase release and only inhibited CCK-stimulated amylase release reversibly and dose-dependently. However, rebamipide did not inhibit carbachol-, vasoactive intestinal polypeptide (VIP)-, and forskolin-induced amylase releases. These data indicate that rebamipide functions as a partial agonist for Ca2+ -mobilizing action, and it is also an antagonist for the amylase-releasing action of CCK.
No preview · Article · Dec 2004 · European Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: The German cockroach has been reported to act as an allergen that might be associated with a protease reaction in asthma. However, the molecular identities of the antigens in German cockroach extract (GCE) with protease activity and the protease-activated receptors (PARs) that are activated by GCE in human airway epithelial cells have not been characterized.
We investigated the direct effect of GCE on Ca(2+) signaling in human airway epithelial cells and the type of PARs activated by GCE.
The Ca(2+)-sensitive dye Fura2 was used to determine intracellular Ca(2+) concentration ([Ca(2+)](i)) by means of spectrofluorometry.
GCE induced a baseline type of [Ca(2+)](i) oscillations in a dose-dependent manner. The oscillations persisted for long periods of time in the absence of Ca(2+) entry across the plasma membrane, suggesting that the observed [Ca(2+)](i) increases were due to Ca(2+) release from intracellular stores. Accordingly, after depleting endoplasmic reticulum Ca(2+) with thapsigargin, an endoplasmic reticulum Ca(2+) ATPase inhibitor, the GCE-mediated [Ca(2+)](i) signals were abolished. Whereas desensitization of PAR-1, PAR-3, and PAR-4 had no effect on GCE-mediated Ca(2+) mobilization, no GCE-mediated [Ca(2+)](i) increase was observed after desensitization of PAR-2.
These results indicate that GCE has a direct effect on human airway epithelial cells, in particular generating [Ca(2+)](i) oscillations through Ca(2+) release from thapsigargin-sensitive Ca(2+) stores through activation of PAR-2.
No preview · Article · Mar 2004 · Journal of Allergy and Clinical Immunology
[Show abstract][Hide abstract] ABSTRACT: Dietary zinc is an important trace element in the body and is related to both cell proliferation and growth arrest. A recent study found that extracellular zinc-sensing receptors trigger intracellular signal transduction in HT-29 human colorectal cancer cells. However, the signaling mechanism causing this growth regulation by extracellular zinc is not clearly understood. At 10- and 100-microM levels of ZnCl2 treatment, HT-29 cell growth and proliferation increased and decreased, respectively, in a minimally serum-starved medium (MSSM). A lack of significant increase in intracellular zinc levels after zinc treatment suggested that this differential growth regulation of HT-29 cells by extracellular zinc is acquired by receptor-mediated signal transduction. Moreover, this zinc-induced growth regulation was differentially affected by PD-98059, suggesting the involvement of the ERK pathway. Transient ERK activation and subsequent cyclin D1 induction were observed on adding 10 microM ZnCl2 in MSSM in the presence of cell proliferation. On the other hand, prolonged ERK activity was observed with a subsequent increase of cyclin D1 and p21(Cip/WAF1) on adding 100 microM ZnCl2 in MSSM, and this was associated with nonproliferation. Moreover, this ERK activation and cyclin D1 and p21(Cip/WAF1) induction were abolished by PD-98059 pretreatment. The differential regulations of cell growth, ERK activities, and cyclin D1 and p21(Cip/WAF1) inductions were also observed in serum-enriched medium containing higher zinc concentrations. Therefore, differential cell cycle regulator induction occurs by a common ERK pathway in the differential growth regulation of HT-29 cells by extracellular zinc.
Preview · Article · Jan 2004 · AJP Gastrointestinal and Liver Physiology
[Show abstract][Hide abstract] ABSTRACT: AlF4-is known to generate oscillations in intracellular Ca2+ concentration ([Ca2+]i) by activating G proteins in many cell types. However, in rat pancreatic acinar cells, AlF4--evoked [Ca2+]i oscillations were reported to be dependent on extracellular Ca2+, which contrasts with the [Ca2+]i oscillations induced by cholecystokinin (CCK). Therefore, we investigated the mechanisms by which AlF4- generates extracellular Ca2+-dependent [Ca2+]i oscillations in rat pancreatic acinar cells. AlF4(-)-induced [Ca2+]i oscillations were stopped rapidly by the removal of extracellular Ca2+ and were abolished on the addition of 20 mM caffeine and 2 microM thapsigargin, indicating that Ca2+ influx plays a crucial role in maintenance of the oscillations and that an inositol 1,4,5-trisphosphate-sensitive Ca2+ store is also required. The amount of Ca2+ in the intracellular Ca2+ store was decreased as the AlF4--induced [Ca2+]i oscillations continued. Measurement of 45Ca2+ influx into isolated microsomes revealed that AlF4-directly inhibited sarco/endoplasmic reticulum Ca2+-ATPase (SERCA). The activity of plasma membrane Ca2+-ATPase during AlF4- stimulation was not significantly different from that during CCK stimulation. After partial inhibition of SERCA with 1 nM thapsigargin, 20 pM CCK-evoked [Ca2+]i oscillations were dependent on extracellular Ca2+. This study shows that AlF4- induces [Ca2+]i oscillations, probably by inositol 1,4,5-trisphosphate production via G protein activation but that these oscillations are strongly dependent on extracellular Ca2+ as a result of the partial inhibition of SERCA.
Preview · Article · Dec 2003 · AJP Cell Physiology
[Show abstract][Hide abstract] ABSTRACT: Protein kinases, such as protein kinase C, have been shown to be associated with secretory granules and to regulate the event of exocytosis in various tissues including parotid salivary acinar cells. However, in submandibular acinar cells that play an important role in the secretion of proteins into the oral cavity, kinase activity on the granule membrane has not been explored. Therefore, in the present study, we isolated the secretory granules from rat submandibular acinar cells and investigated the localisation of protein kinases on the granule membrane. Initially, we isolated and purified secretory granules from rat submandibular acinar cells. Addition of [gamma-32P] ATP to granule-membrane lysate phosphorylated the granule-membrane-associated 26, 32, 55 and 58kDa proteins, suggesting the presence of endogenous kinase activity on the membrane. Moreover, the phosphorylation of 26 and 32kDa proteins was inhibited by staurosporine and K252a, both non-specific protein kinase C inhibitors. However, the phosphorylation of 26 and 32kDa proteins was not inhibited by other protein kinase C inhibitors, such as calphostin C, GF109203X and chelerythrine, indicating that protein kinase C was not responsible for the phosphorylation. In addition, H-89, ML-9, KN-62 and genistein did not appear to inhibit this phosphorylation, indicating that protein kinase A, myosin light chain kinase (MLCK), Ca2+/calmodulin-dependent protein kinase II (CAMKII) and tyrosine kinase were not involved in the phosphorylation of 26 and 32kDa proteins. Moreover, Ca2+ had no effect on the kinase activity. Therefore, our results suggest that an unidentified, staurosporine-inhibitable protein kinase activity is associated with the secretory granule membrane of rat submandibular acinar cells.
No preview · Article · Sep 2003 · Archives of Oral Biology
[Show abstract][Hide abstract] ABSTRACT: Pyrrolidine dithiocarbamate (PDTC) is known to induce cell death by the stimulation of intracellular zinc transport and subsequent modulation of nuclear factor-kappaB (NF-kappaB) activity. Zinc is a signaling messenger that is released by neuronal activity at many central excitatory synapses. Excessive synaptic release of zinc followed by entry into vulnerable neurons contributes to severe neuronal cell death. In the present study, we explored how PDTC modulates intracellular signal transduction pathways, leading to neuronal cell death. The exposure of immortalized embryonic hippocampal cells (H19-7) to PDTC within the range of 1-100 microM caused cell death in a dose-dependent manner. During the cell death, NF-kappaB activity increased in response to PDTC, and this activity corresponded well with the increase of intracellular free zinc levels, implying that the activation of NF-kappaB transmits the cell death signals of PDTC. Furthermore, PDTC caused the activation of IkappaB kinase (IKK), casein kinase 2 (CK2), phosphatidylinositol 3-kinase (PI-3K), and Akt, as well as mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), but not p38 kinase. The blockade of PI-3K, JNK, and CK2 pathways resulted in a remarkable suppression of PDTC-induced cell death and also the activation of IKK, which subsequently led to a decrease of IkappaB phosphorylation. Although the overexpression of dominant-negative SEK in a transient manner did not inhibit the activation of Akt by PDTC, the transfection of kinase-inactive Akt mutants did cause a remarkable blockade of JNK activation, implying that Akt is present upstream of JNK in the PDTC-signaling pathways. Moreover, whereas selective CK2 inhibitors suppressed PDTC-induced JNK activation, the inhibition of JNK did not affect CK2 activity, suggesting that CK2 is directly related to the regulation of cell viability by PDTC and that the CK2-JNK pathway could be a downstream target of PDTC. Taken together, our results suggest that PDTC-mediated accumulation of intracellular zinc ions may affect cell viability by modulating several intracellular signaling pathways in neuronal hippocampal progenitor cells.
No preview · Article · Mar 2003 · Journal of Neuroscience Research
[Show abstract][Hide abstract] ABSTRACT: Reactive oxygen species are considered important regulators in the pathogenesis and in the development of pancreatitis. The transcription factor nuclear factor kappaB (NF-kappaB) is activated by reactive oxygen species and regulates the gene expressions of inflammatory cytokines. The present study investigates (1) the susceptibility of isolated rat pancreatic acinar cells to oxidant attacks produced by adenosine diphosphate/ferrous iron, hypoxanthine/xanthine oxidase, and neutrophils primed with 4beta-phorbol 12beta-myristate 13alpha-acetate (PMA) and (2) the potential of small-molecule antioxidants (N-acetylcysteine, beta-carotene, rebamipide, allopurinol) and superoxide dismutase (SOD) to prevent such injury and oxidant-mediated NF-kappaB activation and inflammatory cytokine production in the cells. As a result, oxidative stress resulted in a time-dependent increase in lipid peroxide production in pancreatic acinar cells which was inhibited by small-molecule antioxidants and SOD. PMA-primed neutrophils induced NF-kappaB activation and increased the production of cytokines (IL-6, TNF-alpha) in the cells. This was in parallel with lipid peroxide production. Small-molecule antioxidants and SOD inhibited NF-kappaB activation and cytokine production in acinar cells caused by PMA-primed neutrophils. In conclusion, oxidative stress activates NF-kappaB, resulting in upregulation of inflammatory cytokines in pancreatic acinar cells. Small-molecule antioxidants might be clinically useful anti-inflammatory agents by inhibiting oxidant-induced cytokine production.