Fibroblast growth factor-2 suppression of tumor necrosis factor alpha-mediated apoptosis requires Ras and the activation of mitogen-activated protein kinase

A time-resolved live cell imaging assay to identify small molecule inhibitors of FGF2 signaling

Fibroblast growth factor 2 (FGF2) is a cell survival factor with crucial functions in tumor-induced angiogenesis. Here, we describe a novel time-resolved FGF2 signaling assay based upon live cell imaging of neuroblastoma cells. To validate this system, we tested 8960 small molecules for inhibition of FGF2 signaling with kinetic resolution. Hit compounds were validated in dose-response experiments for FGF2 signaling, FGF receptor antagonism, downstream ERK phosphorylation and FGF2-dependent chemoresistance in a cellular leukemia model system. The new screening system for FGF2 signaling inhibitors has unique features, deselecting compounds with pleiotropic effects on cell proliferation and, along with the experimental pipeline reported, great potential for the discovery of new classes of FGF2 signaling inhibitors that block FGF2 dependent tumor cell survival.

Novel Functions of Death-Associated Protein Kinases through Mitogen-Activated Protein Kinase-Related Signals

Death associated protein kinase (DAPK) is a calcium/calmodulin-regulated serine/threonine kinase; its main function is to regulate cell death. DAPK family proteins consist of DAPK1, DAPK2, DAPK3, DAPK-related apoptosis-inducing protein kinases (DRAK)-1 and DRAK-2. In this review, we discuss the roles and regulatory mechanisms of DAPK family members and their relevance to diseases. Furthermore, a special focus is given to several reports describing cross-talks between DAPKs and mitogen-activated protein kinases (MAPK) family members in various pathologies. We also discuss small molecule inhibitors of DAPKs and their potential as therapeutic targets against human diseases.

Histamine synergistically promotes bFGF-induced angiogenesis by enhancing VEGF production via H1 receptor

Histamine, a major mediator present in mast cells that is released into the extracellular milieu upon degranulation, is well known to possess a wide range of biological activities in several classic physiological and pathological processes. However, whether and how it participates in angiogenesis remains obscure. In the present study, we observed its direct and synergistic action with basic fibroblast growth factor (bFGF), an important inducer of angiogenesis, on in vitro angiogenesis models of endothelial cells. Data showed that histamine (0.1, 1, 10 µM) itself was absent of direct effects on the processes of angiogenesis, including the proliferation, migration, and tube formation of endothelial cells. Nevertheless, it could concentration-dependently enhance bFGF-induced angiogenesis as well as production of vascular endothelial growth factor (VEGF) from endothelial cells. The synergistic effect of histamine on VEGF production could be reversed by pretreatments with diphenhydramine (H1-receptor antagonist), SB203580 (selective p38 mitogen-activated protein kinase (MAPK) inhibitor) and L-NAME (nitric oxide synthase (NOS) inhibitor), but not with cimetidine (H2-receptor antagonist) and indomethacin (cyclooxygenase (COX) inhibitor). Moreover, histamine could augment bFGF-incuced phosphorylation and degradation of IκBα, a key factor accounting for the activation and translocation of nuclear factor κB (NF-κB) in endothelial cells. These findings indicated that histamine was able to synergistically augment bFGF-induced angiogenesis, and this action was linked to VEGF production through H1-receptor and the activation of endothelial nitric oxide synthase (eNOS), p38 MAPK, and IκBα in endothelial cells.

Role of quercetin in preventing thioacetamide-induced liver injury in rats

In hepatic toxicity induced in rats by two injections of thioacetamide (TAA, 350 mg/kg with an interval of 8 hr), the action of quercetin was investigated. After 96 hr, TAA administration resulted in hepatic necrosis, significant increases in serum transaminase activity, and increases in hepatic lipoperoxidation. Thioacetamide-induced hepatotoxicity also showed changes in antioxidant enzymes in the liver of rats, with alterations in p-ERK 1/2 (phosphorylated extracellular-signal related kinase 1/2) as well as an imbalance between proapototic protein Bax and anti-apoptotic protein Bcl-2 expression. With administration of the flavonoid quercetin (50 mg/Kg i.p.) for four consecutive days following TAA, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity were close to normal values in rats. Histological findings suggested that quercetin had a preventive effect on TAA-induced hepatic necrosis. Quercetin treatment caused significant decreases in lipid peroxide levels in the TAA-treated rats, with some changes in antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Quercetin also inhibited the change of the p-ERK1/2 by TAA and significantly prevented the increase in Bax/Bcl-2 ratio, thus preventing apoptosis. Findings indicate that quercetin may have a preventive effect on TAA-induced hepatotoxicity by modulating the oxidative stress parameters and apoptosis pathway.

A gain-of-function germline mutation in Drosophila ras1 affects apoptosis and cell fate during development

The RAS/MAPK signal transduction pathway is an intracellular signaling cascade that transmits environmental signals from activated receptor tyrosine kinases (RTKs) on the cell surface and other endomembranes to transcription factors in the nucleus, thereby linking extracellular stimuli to changes in gene expression. Largely as a consequence of its role in oncogenesis, RAS signaling has been the subject of intense research efforts for many years. More recently, it has been shown that milder perturbations in Ras signaling during embryogenesis also contribute to the etiology of a group of human diseases. Here we report the identification and characterization of the first gain-of-function germline mutation in Drosophila ras1 (ras85D), the Drosophila homolog of human K-ras, N-ras and H-ras. A single amino acid substitution (R68Q) in the highly conserved switch II region of Ras causes a defective protein with reduced intrinsic GTPase activity, but with normal sensitivity to GAP stimulation. The ras1^R68Q mutant is homozygous viable but causes various developmental defects associated with elevated Ras signaling, including cell fate changes and ectopic survival of cells in the nervous system. These biochemical and functional properties are reminiscent of germline Ras mutants found in patients afflicted with Noonan, Costello or cardio-facio-cutaneous syndromes. Finally, we used ras1^R68Q to identify novel genes that interact with Ras and suppress cell death.

Rab11 regulates JNK and Raf/MAPK-ERK signalling pathways during Drosophila wing development

Developmental signalling pathways are regulated by intracellular vesicle trafficking in multicellular organisms. In our earlier communication, we have shown that mutation in Rab11 (a subfamily of the Ypt/Rab gene family) results in the activation of JNK signalling pathways in Drosophila eye. Here, we report that Rab11 regulates JNK and Raf/MAPK-ERK signalling pathways during Drosophila wing development. Using immunofluorescence and immunohistochemical analyses, we show that overexpression of Rab11 in mutant wing imaginal disc cells triggers the induction of apoptosis and activation of JNK and ERK. Further, using a genetic approach it has been shown that Rab11 interacts with the components of these pathways during Drosophila wing development. In addition to this, in Rab11 mutant wing imaginal discs JNK activity was monitored using puc(E)⁶⁹, a P-lacZ enhancer-trap line inserted in puckered (puc). A strong induction of puc in Rab11 mutant wing imaginal disc cells provided a strong support that Rab11 regulates the JNK signalling pathway during Drosophila wing development.

Compound K inhibits basic fibroblast growth factor-induced angiogenesis via regulation of p38 mitogen activated protein kinase and AKT in human umbilical vein endothelial cells

Compound K (CK; 20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol), an active ginseng saponin metabolite, exerts anticancer activity via apoptosis induction in various cancers. In the present study, we investigated the anti-angiogenic activity of CK and its molecular mechanisms in human umbilical vein endothelial cells (HUVECs). Angiogenesis was induced in HUVECS by basic fibroblast growth factor (bFGF), a potent angiogenic growth factor. CK significantly inhibited the proliferation and also attenuated the expression of a proliferating protein cyclin D1 in bFGF treated HUVECs. Also, CK significantly inhibited the migration and tube formation of bFGF treated HUVECs at non-cytotoxic concentrations, reduced secreted level of vascular endothelial growth factor (VEGF) and increased the secreted level of pigment epithelium-derived factor (PEDF) in HUVECs. In addition, CK effectively disrupted bFGF-induced neo-vascularization in the Matrigel plugs excised from mice in vivo. Notably, we have found that CK downregulated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and AKT in bFGF treated HUVECs. Taken together, our findings for the first time indicate that CK exerts anti-angiogenic activity via inhibition of p38 MAPK and AKT in HUVECs with the potential of a cancer chemopreventive agent.

The receptor tyrosine kinase FGFR4 negatively regulates NF-kappaB signaling

BACKGROUND

NFκB signaling is of paramount importance in the regulation of apoptosis, proliferation, and inflammatory responses during human development and homeostasis, as well as in many human cancers. Receptor Tyrosine Kinases (RTKs), including the Fibroblast Growth Factor Receptors (FGFRs) are also important in development and disease. However, a direct relationship between growth factor signaling pathways and NFκB activation has not been previously described, although FGFs have been known to antagonize TNFα-induced apoptosis.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we demonstrate an interaction between FGFR4 and IKKβ (Inhibitor of NFκB Kinase β subunit), an essential component in the NFκB pathway. This novel interaction was identified utilizing a yeast two-hybrid screen [1] and confirmed by coimmunoprecipitation and mass spectrometry analysis. We demonstrate tyrosine phosphorylation of IKKβ in the presence of activated FGFR4, but not kinase-dead FGFR4. Following stimulation by TNFα (Tumor Necrosis Factor α) to activate NFκB pathways, FGFR4 activation results in significant inhibition of NFκB signaling as measured by decreased nuclear NFκB localization, by reduced NFκB transcriptional activation in electophoretic mobility shift assays, and by inhibition of IKKβ kinase activity towards the substrate GST-IκBα in in vitro assays. FGF19 stimulation of endogenous FGFR4 in TNFα-treated DU145 prostate cancer cells also leads to a decrease in IKKβ activity, concomitant reduction in NFκB nuclear localization, and reduced apoptosis. Microarray analysis demonstrates that FGF19 + TNFα treatment of DU145 cells, in comparison with TNFα alone, favors proliferative genes while downregulating genes involved in apoptotic responses and NFκB signaling.

CONCLUSIONS/SIGNIFICANCE

These results identify a compelling link between FGFR4 signaling and the NFκB pathway, and reveal that FGFR4 activation leads to a negative effect on NFκB signaling including an inhibitory effect on proapoptotic signaling. We anticipate that this interaction between an RTK and a component of NFκB signaling will not be limited to FGFR4 alone.

RETRACTED: Identification of phosphorylated p38 as a novel DAPK-interacting partner during TNFalpha-induced apoptosis in colorectal tumor cells

Death-associated protein kinase (DAPK) is a serine/threonine kinase that contributes to pro-apoptotic signaling on cytokine exposure. The role of DAPK in macrophage-associated tumor cell death is currently unknown. Recently, we suggested a new function for DAPK in the induction of apoptosis during the interaction between colorectal tumor cells and tumor-associated macrophages. Using a cell-culture model with conditioned supernatants of differentiated/activated macrophages (U937) and human HCT116 colorectal tumor cells, we replicated DAPK-associated tumor cell death; this model likely reflects the in vivo tumor setting. In this study, we show that tumor necrosis factor-alpha exposure under conditions of macrophage activation induced DAPK-dependent apoptosis in the colorectal tumor cell line HCT116. Simultaneously, early phosphorylation of p38 mitogen-activated protein kinase (phospho-p38) was observed. We identified the phospho-p38 mitogen-activated protein kinase as a novel interacting protein of DAPK in tumor necrosis factor-alpha-induced apoptosis. The general relevance of this interaction was verified in two colorectal cell lines without functional p53 (ie, HCT116 p53(-/-) and HT29 mutant) and in human colon cancer and ulcerative colitis tissues. Supernatants of freshly isolated human macrophages were also able to induce DAPK and phospho-p38. Our findings highlight the mechanisms that underlie DAPK regulation in tumor cell death evoked by immune cells.

The effect of mGluR2 activation on signal transduction pathways and neuronal cell survival

In earlier studies, we found profound alterations in specific signal transduction pathways such as mitogen-activated protein kinase signal pathway that mirrored neuronal cell death in Alzheimer disease (AD). To further delineate the mechanism(s) involved in such aberrant signaling, we subsequently showed that mGluR2 is increased in pyramidal neurons in the hippocampus of AD and often co-localizes with neurofibrillary pathology. Based on these data, we suggested that selective neuronal degeneration in AD may arise through the differential expression and activation of specific receptor populations, such as, mGluR2. In this study, to examine the mechanistic relevance of the above-mentioned in vivo findings, we used cell culture models to show that the activation of mGluR2 leads to the activation of extracellular signal-related kinase (ERK) pathways. Importantly, attesting to the in vivo significance of our findings, this pro-survival signaling pathway is also found to be ectopically activated in AD. We also found that the activation of mGluR2 increases the phosphorylation of tau and that the specific activation of mGluR2 reduces oxidative stress mediated cytotoxicity in neuronal cells. Taken together our findings strongly suggest that mGluR2 may participate in mediating the survival of neurons in the face of selective neuronal dysfunction and degeneration in AD. Additionally, our findings lend support to the notion that tau phosphorylation is a neuroprotective antioxidant response to cellular insults.

Roles of extracellular signal-regulated kinase 1/2 on the suppression of myostatin gene expression induced by basic fibroblast growth factor

Basic fibroblast growth factor (bFGF, FGF-2) has an inhibitory effect on the expression of the myostatin gene in murine C2C12 myoblasts, as shown in our recent investigation. To further verify the regulatory effects of bFGF on the myostatin gene and to better understand its mechanism in skeletal muscle, and to promote clinical applications of bFGF to treat skeletal muscle diseases correlated to muscular dystrophy or AIDS and so on, recombinant human bFGF (rh-bFGF) was added into media and stimulated murine C2C12 myoblasts to investigate the dose-dependent effect of bFGF on suppression of myostatin gene expression and the role of extracellular signal-regulated kinase 1/2 (ERK1/2) in the regulatory mechanism. Simultaneously, complete coding sequence of ovine?8 kDa-bFGF gene was inserted into eukaryotic vector pCMV-neo (originated from pEGFP-N1 vector, from which the EGFP gene has been removed), the recombinant plasmid pCMV-neo-bFGF was harvested and injected into the mouse skeletal muscle of posterior limb. Expression levels of bFGF, myostatin, and ERK1/2 genes in murine C2C12 myoblasts and the skeletal muscle were analyzed by real-time reverse transcription-polymerase chain reaction and Western blotting analysis, respectively. The results showed that bFGF impaired the expression of myostatin gene in a dose-dependent manner in C2C12 cells, with increasing concentration of rh-bFGF, myostatin mRNA declined gradually. In addition, results in skeletal muscle indicated that bFGF also suppressed the expression of the myostatin gene in vivo. Furthermore, we found ERK1/2 participated in the regulatory mechanism of bFGF on the expression of the myostatin gene.

Hantaviruses and TNF-alpha act synergistically to induce ERK1/2 inactivation in Vero E6 cells

Background

We have previously reported that the apathogenic Tula hantavirus induces apoptosis in Vero E6 epithelial cells. To assess the molecular mechanisms behind the induced apoptosis we studied the effects of hantavirus infection on cellular signaling pathways which promote cell survival. We previously also observed that the Tula virus-induced cell death process is augmented by external TNF-α. Since TNF-α is involved in the pathogenesis of hantavirus-caused hemorrhagic fever with renal syndrome (HFRS) we investigated its effects on HFRS-causing hantavirus-infected cells.

Results

We studied both apathogenic (Tula and Topografov) and pathogenic (Puumala and Seoul) hantaviruses for their ability to regulate cellular signaling pathways and observed a direct virus-mediated down-regulation of external signal-regulated kinases 1 and 2 (ERK1/2) survival pathway activity, which was dramatically enhanced by TNF-α. The fold of ERK1/2 inhibition correlated with viral replication efficiencies, which varied drastically between the hantaviruses studied.

Conclusion

We demonstrate that in the presence of a cytokine TNF-α, which is increased in HFRS patients, hantaviruses are capable of inactivating proteins that promote cell survival (ERK1/2). These results imply that hantavirus-infected epithelial cell barrier functions might be compromised in diseased individuals and could at least partially explain the mechanisms of renal dysfunction and the resulting proteinuria seen in HFRS patients.

Elevated fibroblast growth factor-2 increases tumor necrosis factor-alpha induced endothelial cell death in high glucose

Glucose and tumor necrosis factor-alpha (TNFalpha) concentrations are elevated in diabetes. Both of these factors correlate with diabetic vasculopathy and endothelial cell apoptosis, yet their combined effects have not been measured. We have previously shown that the angiogenic growth factor fibroblast growth factor-2 (FGF-2), which is generally protective against endothelial cell death, is similarly elevated in high glucose conditions. We therefore investigated the effect of TNFalpha on endothelial cell death under normal and elevated glucose conditions, with a particular focus on FGF-2. Porcine aortic endothelial cells were cultured in 5 and 30 mM glucose and stimulated with TNFalpha, together with FGF-2 or a neutralizing FGF-2 antibody. Cell death was measured via cell counts or an annexin apoptotic assay, and cell cycle phase was determined by propidium iodide labeling. TNFalpha-induced endothelial cell death increased for cells in high glucose, and cell death was enhanced with increasing FGF-2 exposure and negated by a neutralizing FGF-2 antibody. Endothelial cells were most susceptible to TNFalpha-induced cell death when stimulated with FGF-2 18 h prior to TNFalpha, corresponding to cell entry into S phase of the proliferative cycle. The FGF-2 associated increase in TNFalpha-induced cell death was negated by blocking cell entry into S phase. Endothelial cell release of FGF-2 in high glucose leads to cell cycle progression, which makes cells more susceptible to TNFalpha-induced cell death. These data suggest that growth factor outcomes in high glucose depend on secondary mediators such as cytokines and stimulation cell cycle timing.

Evidence that cisplatin-induced auditory damage is attenuated by downregulation of pro-inflammatory cytokines via Nrf2/HO-1

Recently, we demonstrated that pro-inflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6 played a critical role in cisplatin-induced cochlear injury and that flunarizine, known as a T-type Ca(2+) channel antagonist, induced a cytoprotective effect against cisplatin cytotoxicity in HEI-OC1 cells by the activation of NF-E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) cascade through PI3K-Akt signaling but calcium-independent pathway. We report here that flunarizine markedly attenuates cisplatin-induced pro-inflammatory cytokine secretion and their messenger RNA transcription as well as cisplatin cytotoxicity through the activation of Nrf2/HO-1 and downregulation of NF-kappaB. In HEI-OC1 cells, overexpression of Nrf2/HO-1 by gene transfer or pharmacological approaches attenuated cisplatin-induced cytotoxicity and pro-inflammatory cytokine production. On the contrary, inhibition of Nrf2/HO-1 signaling by pharmacological inhibitors or specific small interfering RNAs significantly abolished the beneficial effects of flunarizine. Flunarizine also attenuated cisplatin-mediated MAPK activation and pharmacological inhibition of MAPKs, especially MEK1/ERK, blocked cisplatin-induced NF-kappaB activation in HEI-OC1 cells. Furthermore, WT-Nrf2 overexpression effectively blocked MAPK activation after cisplatin exposure. Finally, orally administrated Sibelium, the trade name of flunarizine, suppressed the increase of pro-inflammatory cytokines by cisplatin in both serum and cochleas of mice, whereas it increased HO-1 expression in cochleas. These results indicate that flunarizine induces a protective effect against cisplatin ototoxicity through the downregulation of NF-kappaB by Nrf2/HO-1 activation and the resulting inhibition of pro-inflammatory cytokine production in vitro and in vivo.

Role of epidermal growth factor receptor in maintaining airway goblet cell hyperplasia in rats sensitized to allergen

BACKGROUND

Stimulation of epidermal growth factor receptor (EGFR) induces airway goblet cell hyperplasia, but the role of this molecule in the maintenance of this pathologic change remains uncertain.

OBJECTIVE

To determine the mechanisms by which goblet cell hyperplasia is maintained in airway epithelium, we investigated EGFR-induced signalling pathways that lead to both mucin production and antiapoptosis in vitro. We also tested whether the inhibition of EGFR tyrosine kinase speeds reversal of established goblet cell hyperplasia to normal epithelial phenotype in vivo.

METHODS

MUC5AC production was measured by immunoassay, and antiapoptotic responses were determined by Bcl-2 expression and terminal deoxynucleotidyl transferase-mediated dUTP-biotin Nick End Labelling staining using NCI-H292 cells. The effect of an inhibitor of EGFR tyrosine kinase (AG1478) on goblet cell hyperplasia was also determined in rats sensitized with ovalbumin (OVA).

RESULTS

MUC5AC was constitutively expressed and few apoptotic cells were observed in NCI-H292 cells under non-stimulated condition. TGF-alpha increased MUC5AC and Bcl-2 expression, an effect that was prevented by inhibitors of EGFR tyrosine kinase (AG1478), MEK (PD98059), and NF-kappaB (CAPE). After the addition of TGF-alpha, AG1478 and an inhibitor of phosphatidylinositol 3 kinase/Akt (LY294002), but not PD98059, induced a marked apoptotic response, which was prevented by the caspase inhibitor Z-VAD fmk. Goblet cell hyperplasia and EGFR expression in airway epithelium were noted in the OVA-sensitized rats. Intratracheal instillation of AG1478 induced apoptosis of goblet cells, reverting the airway epithelium to normal epithelial phenotype.

CONCLUSION

These findings indicate that EGFR plays an important role in the maintenance of goblet cell hyperplasia. We speculate that inhibitors of the EGFR cascade might be an effective therapy of airway remodelling.

Effect of dimethyl sulphoxide on oxidative stress, activation of mitogen activated protein kinase and necrosis caused by thioacetamide in the rat liver

Thioacetamide (400 mg/kg body weight, i.p.) was administered to rats. After 12 h the activity of plasma glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) was significantly higher than that of the control group, and after 24 h plasma GOT and GPT activities strongly increased. These results indicated that the necrotic process was initiated at about 12 h and developed thereafter. By co-administration of dimethyl sulphoxide (DMSO, 18 and 1 h before, and 8 h after administration of thioacetamide: each time, 2.5 ml/kg body weight, p.o.), plasma GOT and GPT were significantly decreased and were even comparable to the control group, showing that DMSO totally prevented the necrotic action of thioacetamide. After 12 and 24 h of thioacetamide administration, the hepatic level of vitamin C, the most sensitive chemical indicator of oxidative stress, decreased significantly, indicating that oxidative stress was significantly enhanced 12 h after thioacetamide intoxication and thereafter. DMSO totally restored the liver vitamin C level, demonstrating that DMSO effectively ameliorated the oxidative stress caused by thioacetamide, resulting in the prevention of necrosis of the liver. Phosphorylated c-Jun NH(2)-terminal kinase (JNK) significantly increased transiently 12 h after treatment with thioacetamide. These results indicated that oxidative stress and the activation of JNK took place almost simultaneously. Phosphorylated extracellular signal-related kinase (ERK) 2 was significantly increased 6-12 h after thioacetamide injection. Phosphorylated p38 MAPK (mitogen activated protein kinase) was significantly decreased 24 h after administration of thioacetamide. DMSO treatment inhibited the change of these MAPKs by thioacetamide, corresponding with the prevention of the liver necrosis as well as the attenuation of oxidative stress.

Activation of mitogen activated protein kinase (MAPK) during carbon tetrachloride intoxication in the rat liver

Carbon tetrachloride (CCl(4): 4 ml/kg body weight as a 1:1 mixture of CCl(4) and mineral oil) was orally administered to rats. After 12 h the activity of plasma AST (aspartate aminotransferase) and ALT (alanine aminotransferase) was significantly higher than that of the control group and plasma AST and ALT activities increased thereafter. These results indicated that the necrotic process was active at about 12 h and developed thereafter. After 2-24 h of CCl(4) administration, the hepatic level of vitamin C, the most sensitive indicator of oxidative stress, decreased significantly, indicating that oxidative stress was significantly enhanced as early as 2 h after CCl(4) intoxication and thereafter. Phosphorylated JNK (c-Jun NH(2)-terminal kinase) and phospho-ERK1/2 (extracellular signal-regulated kinase1/2) were significantly increased transiently 1-3 h after treatment with CCl(4), while phosphorylated p38 decreased significantly 1-24 h after CCl(4) treatment. These results indicated that the change in MAPKs (mitogen activated protein kinases) slightly preceded that in vitamin C, the most sensitive chemical indicator of oxidative stress.

Fibroblast growth factor-2 suppresses oridonin-induced L929 apoptosis through extracellular signal-regulated kinase-dependent and phosphatidylinositol 3-kinase-independent pathway

Oridonin, isolated from Rabdosia rubescences, has been reported to exert cytotoxic effects on L929 cells. In this study, we investigated the mechanisms of FGF-2 protection of L929 cells from oridonin-induced apoptosis. Phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) signal did not mediate this effect because the PI3K inhibitor wortmannin failed to reverse this protection and PKB activation was not observed in this process. In contrast, the extracellular signal-regulated kinase (ERK) was responsible for this rescue because its inhibition abolished the protective effect of fibroblast growth factor (FGF)-2. ERK had dual regulatory functions: mediating cell apoptosis or preventing cells from initiating the apoptotic response by phosphorylation or promoting expression of Bcl-2 in dependence of different stimuli. In L929 cells treated with oridonin alone, the activated ERK decreased the ratio of Bcl-2/Bax by mediating the phosphorylation of Bcl-2, resulting in apoptosis; the Ras inhibitor manumycin A and Raf inhibitor GW5074 failed to inhibit this apoptosis, indicating that there is a signal other than Ras/Raf pathway activated ERK. However, in the presence of FGF-2, Bcl-2 phosphorylation was blocked, and the Ras/Raf/ERK signal pathway was activated and protected against the oridonin-induced apoptosis by the alternative function of promoting of Bcl-2 expression.

Inhibitory Effect of Dimethyl Sulfoxide (DMSO) on Necrosis and Oxidative Stress Caused by D-Galactosamine in the Rat Liver

D-Galactosamine (D-Galn: 300 mg/kg) was intraperitoneally administered to rats. After 6 h the activity of plasma GOT and GPT was significantly higher than that of the control group and plasma GOT and GPT activities increased thereafter. These results indicated that the necrotic process was initiated at about 6 h and developed thereafter. With coadministration of DMSO (1 h before administration of D-Galn: 2.5 mL/kg, oral), plasma GOT and GPT were significantly lower, showing that DMSO inhibited the necrotic action of D-Galn. After 6-24 h of D-Galn administration, the hepatic level of vitamin C, the most sensitive indicator of oxidative stress, decreased significantly, indicating that oxidative stress was significantly enhanced 6 h after D-Galn intoxication and thereafter. DMSO significantly restored the liver vitamin C level 24 h after D-Galn injection, demonstrating that DMSO effectively ameliorated the oxidative stress caused by D-Galn, resulting in the prevention of necrosis of the liver. Phosphorylated JNK and phospho-ERK were significantly increased transiently 6-12 h after treatment with D-Galn. These results indicated that oxidative stress and the activation of JNK took place almost simultaneously. Phosphorylated p38 MAPK was not changed and DMSO treatment did not affect the change of these MAPKs by D-Galn.

Samul extract protects against the H2O2-induced apoptosis of H9c2 cardiomyoblasts via activation of extracellular regulated kinases (Erk) 1/2

Samul extract, containing Radix Rehmanniae, Radix Angelicae Gigantis, Radix Paeoniae, and Rhizoma Cnidii, has been traditionally used for treatment of ischemic heart and brain damages in Oriental medicine. However, little is known about the mechanism by which Samul rescues cells from cytotoxic damage. This study was designed to investigate the protective mechanisms of Samul on H(2)O(2)-induced death of H9c2 cells. Treatment with H(2)O(2) markedly decreased the viability of H9c2 cells in a dose- and time-dependent manner, which was significantly prevented by pre-treatment with Samul. The nature of death of H9c2 cells by H(2)O(2) was demonstrated by apoptotic features, including ladder-pattern fragmentation of genomic DNA and chromatin condensation, which were markedly abolished by pretreatment of Samul in H(2)O(2)-treated cells. We further demonstrated that MEK inhibitor, PD98059, dose-dependently attenuated the protective effects of Samul against H(2)O(2), whereas inhibitors of Jnk and p38 did not. Consistently, Samul induced the early phosphorylation of Erk, p44, in H(2)O(2)-treated cells. In addition, treatment with Samul also resulted in an increase of expression of anti-apotogenic Bcl2 protein, which was decreased by H(2)O(2). However, it inhibited the expression of apotogenic Bax protein in H(2)O(2)-treated cells. Taken together, these results suggest that the protective effects of Samul against oxidative damage may be achieved via activation of MAP kinase, Erk as well as Bcl2 family proteins.

Expression of basic fibroblast growth factor results in the decrease of myostatin mRNA in murine C2C12 myoblasts

During the development and regeneration of skeletal muscle, many growth factors, such as basic fibroblast growth factor (bFGF, FGF-2) and myostatin, have been shown to play regulating roles. bFGF contributes to promote proliferation and to inhibit differentiation of skeletal muscle, whereas myostatin plays a series of contrasting roles. In order to elucidate whether the expression of bFGF has any relationship with the expression of myostatin in skeletal muscle cells, we constructed a eukaryotic expression vector for the expression of exogenous bFGF in murine C2C12 myoblasts. Quantitative RT-PCR assays indicated that with the increase of the expression of exogenous bFGF gene, the expression of endogenous myostatin gene was suppressed at mRNA level and protein level.

Essential role of tuberous sclerosis genes TSC1 and TSC2 in NF-kappaB activation and cell survival

The TSC1-TSC2 complex has recently been implicated in cell survival responses. We observed that NF-kappaB signaling is attenuated in TSC1- and TSC2-deficient MEFs concomitant with reduced survival following DNA damage or TNFalpha stimulation. Reconstitution of TSC2 expression in TSC2(-/-) MEFs rescued survival in an NF-kappaB activity-dependent manner. Furthermore, in TSC2(-/-) MEFs, the rapamycin-mediated inhibition of deregulated mTOR activity restored NF-kappaB activation and survival. This rapamycin-mediated effect was reversed by inhibition of NF-kappaB transcriptional activation or by inhibition of ERK1/2 MAP kinase or PI-3K pathways, which lie on signaling cascades that lead to NF-kappaB activation. These results provide evidence for a crosstalk between the TSC/Rheb/mTOR pathway and the NF-kappaB induction pathways and indicate that NF-kappaB functions as an important survival factor that regulates TSC2-dependent cell survival.

Epidermal growth factor protects prostate cancer cells from apoptosis by inducing BAD phosphorylation via redundant signaling pathways

Protection from apoptosis by receptor tyrosine kinases, resistant to the inhibition of phosphatidylinositol 3 '-kinase/Akt and Ras/MEK pathways, has been reported in several cell types, including fibroblasts and epithelial prostate cancer cells; however, mechanisms of this effect were not clear. Here we report that in prostate cancer cells, epidermal growth factor activates two antiapoptotic signaling pathways that impinge on the proapoptotic protein BAD. One signaling cascade operates via the Ras/MEK module and induces BAD phosphorylation on Ser112. Another pathway predominantly relies on Rac/PAK1 signaling that leads to BAD phosphorylation on Ser136. Each of these two pathways is sufficient to protect cells from apoptosis, and therefore both have to be inhibited simultaneously to block epidermal growth factor-dependent survival. Redundancy of antiapoptotic signaling pathways should be considered when therapies targeting antiapoptotic mechanisms are designed.

Coordinated fibroblast growth factor and heparan sulfate regulation of osteogenesis

Growth and lineage-specific differentiation constitute crucial phases in the development of stem cells. Control over these processes is exerted by particular elements of the extracellular matrix, which ultimately trigger a cascade of signals that regulate uncommitted cells, by modulating their survival and cell cycle progression, to shape developmental processes. Uncontrolled, constitutive activation of fibroblast growth factor receptors (FGFR) results in bone abnormalities, underlining the stringent control over fibroblast growth factor (FGF) activity that must be maintained for normal osteogenesis to proceed. Mounting evidence suggests that FGF signalling, together with a large number of other growth and adhesive factors, is controlled by the extracellular glycosaminoglycan sugar, heparan sulfate (HS). In this review, we focus on FGF activity during osteogenesis, their receptors, and the use of HS as a therapeutic adjuvant for bone repair.

Activation of mitogen activated protein kinase (MAPK) during D-galactosamine intoxication in the rat liver

A significant increase in plasma glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase was observed 6 h after intraperitoneal administration of D-galactosamine (D-Galn). Three hours after administration of D-Galn, the vitamin C concentration in the liver decreased significantly compared to that in a control group and thereafter the hepatic vitamin C concentration remained at a significantly lower level. Phosphorylated JNK (c-Jun NH2-terminal kinase) and phosphorylated ERK (extracellular signal-regulated kinase) started increasing 3 h after D-Galn treatment and remained at a high level for 6-12 h after the treatment, while phosphorylated p38 MAPK increased significantly 6 h after D-Galn administration. These results indicated that oxidative stress and the activation of JNK and ERK took place almost simultaneously, followed by the activation of p38 MAPK.

The Involvement of MAPK Signaling Pathways in Determining the Cellular Response to p53 Activation

The effect of ERK, p38, and JNK signaling on p53-dependent apoptosis and cell cycle arrest was investigated using a Friend murine erythroleukemia virus (FVP)-transformed cell line that expresses a temperature-sensitive p53 allele, DP16.1/p53ts. In response to p53 activation at 32 degrees C, DP16.1/p53ts cells undergo p53-dependent G(1) cell cycle arrest and apoptosis. As a result of viral transformation, these cells express the spleen focus forming env-related glycoprotein gp55, which can bind to the erythropoietin receptor (EPO-R) and mimics many aspects of EPO-induced EPO-R signaling. We demonstrate that ERK, p38 and JNK mitogen-activated protein kinases (MAPKs) are constitutively active in DP16.1/p53ts cells. Constitutive MEK activity contributes to p53-dependent apoptosis and phosphorylation of p53 on serine residue 15. The pro-apoptotic effect of this MAPK kinase signal likely reflects an aberrant Ras proliferative signal arising from FVP-induced viral transformation. Inhibition of MEK alters the p53-dependent cellular response of DP16.1/p53ts from apoptosis to G(1) cell cycle arrest, with a concomitant increase in p21(WAF1), suggesting that the Ras/MEK pathway may influence the cellular response to p53 activation. p38 and JNK activity in DP16.1/p53ts cells is anti-apoptotic and capable of limiting p53-dependent apoptosis at 32 degrees C. Moreover, JNK facilitates p53 protein turnover, which could account for the enhanced apoptotic effects of inhibiting this MAPK pathway in DP16.1/p53ts cells. Overall, these data show that intrinsic MAPK signaling pathways, active in transformed cells, can both positively and negatively influence p53-dependent apoptosis, and illustrate their potential to affect cancer therapies aimed at reconstituting or activating p53 function.

The activation of ERK1/2 via a tyrosine kinase pathway attenuates trail-induced apoptosis in HeLa cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) serves as an extracellular signal that triggers apoptosis in tumor cells. To characterize the molecular events involved in TRAIL-induced apoptotic signaling, we investigated the role of extracellular signal-regulated kinase 1/2 (ERK1/2) in HeLa cell death. Here we show that TRAIL-activated ERK1/2 through a tyrosine kinase-dependent pathway, subsequently elevated anti-apoptotic Bcl-2 protein levels. ERK1/2 inhibition with PD98059 promoted apoptotic cell death through the downregulation of ERK1/2 activity and Bcl-2 protein levels. Moreover, tyrosine kinase inhibition with Genistein in TRAIL-induced apoptosis effectively attenuated ERK1/2 activity and enhanced apoptotic cell death. Taken together, our results indicate that ERK1/2 activation via tyrosine kinase pathway plays a protective role as the cellular defense mechanism through the upregulation of Bcl-2 protein levels in TRAIL-induced apoptosis.

Long-term loading inhibits ERK1/2 phosphorylation and increases FGFR3 expression in MC3T3-E1 osteoblast cells

Bone tissue homeostasis relies upon the ability of cells to detect and interpret extracellular signals that direct changes in tissue architecture. This study utilized a four-point bending model to create both fluid shear and strain forces (loading) during the time-dependent progression of MC3T3-E1 preosteoblasts along the osteogenic lineage. Loading was shown to increase cell number, alkaline phosphatase (ALP) activity, collagen synthesis, and the mRNA expression levels of Runx2, osteocalcin (OC), osteopontin, and cyclo-oxygenase-2. However, mineralization in these cultures was inhibited, despite an increase in calcium accumulation, suggesting that loading may inhibit mineralization in order to increase matrix deposition. Loading also increased fibroblast growth factor receptor-3 (FGFR3) expression coincident with an inhibition of FGFR1, FGFR4, FGF1, and extracellular signal-related kinase (ERK)1/2 phosphorylation. To examine whether these loading-induced changes in cell phenotype and FGFR expression could be attributed to the inhibition of ERK1/2 phosphorylation, cells were grown for 25 days in the presence of the MEK1/2 inhibitor, U0126. Significant increases in the expression of FGFR3, ALP, and OC were observed, as well as the inhibition of FGFR1, FGFR4, and FGF1. However, U0126 also increased matrix mineralization, demonstrating that inhibition of ERK1/2 phosphorylation cannot fully account for the changes observed in response to loading. In conclusion, this study demonstrates that preosteoblasts are mechanoresponsive, and that long-term loading, whilst increasing proliferation and differentiation of preosteoblasts, inhibits matrix mineralization. In addition, the increase in FGFR3 expression suggests that it may have a role in osteoblast differentiation.

Basic fibroblast growth factor alleviates brain injury following global ischemia reperfusion in rabbits

The aim of this study was to explore the protective effect of basic fibroblast growth factor (bFGF) on brain injury following global ischemia reperfusion and its mechanisms. Brain injury following global ischemia was induced by four vessels occlusion and systemic hypotension. Twenty-four rabbits were randomized into three groups: group A, only dissection of vessels; group B, intravenous infusion of normal saline after reperfusion for 6 h; group C, 30 microg/kg bFGF injected intravenously at the onset of reperfusion, then infused with 10 microg/(kg.h) for 6 h. Serum neuron specific enolase (NSE), S-100B, tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), interleukin-8 (IL-8) were measured before ischemia, 30 min after ischemia, 0.5, 1, 3, 6 h after reperfusion. Brain water content was determined and cerebral histopathological damages were compared. NSE and S-100B were increased 1 h after reperfusion and reached their peaks 6 h after reperfusion, but were much higher in group B than those in group C 3, 6 h after reperfusion. In groups B and C, TNF-alpha was increased after ischemia and IL-1 and IL-8 were increased significantly 0.5 h after reperfusion, then reached their peaks 6 h, 3 h, 6 h after reperfusion respectively. TNF-alpha and IL-8 at the time points of 1 h and 3 h and IL-1 at 3 h and 6 h in group C were correspondingly lower than those in group B. These indices in group A were nearly unchanged. There were less severe cerebral histopathological damages in group C compared with group B, but no difference in brain water content. It could be concluded that bFGF alleviates brain injury following global ischemia and reperfusion by down-regulating expression of inflammatory factors and inhibiting their activities.

The role of erk1 and erk2 in multiple stages of T cell development

Activation of extracellular-signal-regulated protein kinase (Erk) is central to growth-factor-receptor-mediated signaling including that originating from the T cell antigen receptor. It integrates cytoplasmic signals to effect changes in transcription associated with differentiation, proliferation, and survival. In this report, we present an analysis of mice with targeted deletions in Erk1 and Erk2 to assess the relationship between Erk activity and cell-cycle progression, thymocyte development, and lineage commitment. These studies show that Erk is selectively retained during beta selection-driven proliferation, and yet Erk1/2 are not required to complete differentiation to CD4+CD8+ preselection stage of development. Erk activity is essential for the process of positive selection, and it differentially affects CD4 and CD8 T cell maturation; yet, diminished expression itself is not sufficient to alter lineage commitment.

Ha-Ras sensitizes transformed mouse skin cells to Anisomycin-induced apoptosis

Efforts have been made to develop a chemoprevention that selectively triggers apoptosis in malignant cancer cells. Here, we demonstrated that a mutated Ha-Ras activity is required in Anisomycin-induced apoptosis in transformed keratinocytes. Anisomycin stimulates JNK activity and apoptosis in oncogenic Ha-Ras positive cells, but not in normal keratinocytes. This effect was demonstrated in stably transfected cells with dominant negative Ha-Ras, that protected transformed cells, and oncogenic Ha-Ras that sensitized non-transformed cells to Anisomycin-induced apoptosis. Lastly, the treatment of cells with inhibitors of the JNK displayed resistance to Anisomycin induced apoptosis. These data suggests that the oncogenic Ha-Ras is important for Anisomycin-induced JNK activation and apoptosis in transformed keratinocytes.

KR-31378 protects cardiac H9c2 cells from chemical hypoxia-induced cell death via inhibition of JNK/p38 MAPK activation

Using a metabolic inhibition buffer as an ischemic model, we show here that KR-31378, a cardioselective ATP-sensitive potassium channel opener, protects H9c2 cells from chemical hypoxia (CH)-induced cell death. Our previous study showed that CH downregulated caspase activities, but led to differential activation of mitogen-activated protein kinases (MAPKs) in H9c2 cells. The repression of CH-induced c-jun N-terminal kinase (JNK)/p38 MAPK activation resulted in partial protection against CH- induced cell death, implying JNK/p38 MAPK's causative role in CH-induced cell death. This study furthers that research and examines if KR-31378's protective effect came from modulating MAPK activity and/or caspase activity in H9c2 cells. Although KR-31378 did not restore downregulated caspase-3 activity, it did block the activation of JNK and p38 MAPK in a dose-dependent manner. Extracellular signal-regulated kinase activity was not recovered by KR-31378 treatment. CH-induced reactive oxygen species (ROS) generation was suppressed by KR-31378. Thus our results indicate that the cardioprotective effect of KR-31378 in CH is due, at least in part, to the differential inhibition of MAPKs.

Transient transfection of epidermal growth factor receptor gene into MCF7 breast ductal carcinoma cell line

Epidermal growth factor receptor (EGFR) is activated by autocrine growth factors in many types of tumours, including breast tumours. This receptor has been linked to a poor prognosis in breast cancer and may promote proliferation, migration, invasion, and cell survival as well as inhibition of apoptosis. Human breast ductal carcinoma MCF7 cells were transfected using FuGENE 6 with 1 microg of pcDNA3-EGFR containing the full-length human EGFR promoter or 1 microg of the vectors alone (pcDNA3). The transfected cells were transferred into a 25-cm2 flask containing growth medium and G418. Confluent cultures were lysed, total protein levels measured and electrophoresed. The electrophoresed samples were transferred to nitrocellulose and incubated overnight at 4 degrees C with either anti-EGFR or anti-phospho-ERK and immunoreactive bands were visualized using HRP-linked secondary antibody. We created a model system of EGFR overexpression in MCF7 clones with stably transfected pcDNA3/EGFR plasmid. These cells have been shown to promote substantial phosphorylation of both ERK1 and ERK2. The high level of EGFR and ERK1/2 phosphorylation was not seen in the pcDNA3 vector control cells or in non-transfected cells. In this article we describe successful transient transfection experiments on MCF7 cells using the FuGENE 6 Transfection Reagent. The overexpression of EGFR could be a mediated stress response and a survival signal that involves ERK1 and ERK2 phosphorylation.

p38 MAPK mediates TNF-induced apoptosis in endothelial cells via phosphorylation and downregulation of Bcl-x(L)

The role of p38 mitogen-activated protein kinase (MAPK) in apoptosis is a matter of debate. Here, we investigated the involvement of p38 MAPK in endothelial apoptosis induced by tumor necrosis factor alpha (TNF). We found that activation of p38 MAPK preceded activation of caspase-3, and the early phase of p38 MAPK stimulation did not depend on caspase activity, as shown by pretreatment with the caspase inhibitors z-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD-fmk) and Boc-Asp(OMe)-fluoromethylketone (BAF). The p38 MAPK inhibitor SB203580 significantly attenuated TNF-induced apoptosis in endothelial cells, suggesting that p38 MAPK is essential for apoptotic signaling. Furthermore, we observed a time-dependent increase in active p38 MAPK in the mitochondrial subfraction of cells exposed to TNF. Notably, the level of Bcl-x(L) protein was reduced in cells undergoing TNF-induced apoptosis, and this reduction was prevented by treatment with SB203580. Immunoprecipitation experiments revealed p38 MAPK-dependent serine-threonine phosphorylation of Bcl-x(L) in TNF-treated cells. Exposure to lactacystin prevented both the downregulation of Bcl-x(L) and activation of caspase-3. Taken together, our results suggest that TNF-induced p38 MAPK-mediated phosphorylation of Bcl-x(L) in endothelial cells leads to degradation of Bcl-x(L) in proteasomes and subsequent induction of apoptosis.

Adenovirus-mediated expression of a soluble fibroblast growth factor receptor inhibits in vitro growth of prostate DU145 cells

BACKGROUND

Fibroblast growth factor (FGF) family plays a key role in prostate cancer. The soluble FGF receptor (sFGFR) has been studied with regards to inhibiting cancer growth and was shown to have a dominant negative effect on cellular signaling and function. Using replication deficient adenovirus-mediated gene transfer, we tested if sFGFR expression may have a suppressive effect on in vitro growth of prostate cancer cells.

METHODS

Western analysis was used to verify expression of sFGFR1 and to examine the effect of sFGFR1 on MAP kinase phosphorylation. The effect on proliferation and invasiveness of DU145 cells was examined using the WST-1 and Matrigel Invasion assay, respectively.

RESULTS

Activation of MAP kinase (pERK1 and 2) by exogenous FGF1, 2, and 7 was suppressed to baseline levels by sFGFR, which was not seen with EGF. Proliferation and invasion of DU145 cells were significantly suppressed by sFGFR.

CONCLUSIONS

A replication deficient adenoviral vector system reproducibly expresses sFGFR in prostate cells. Suppression of in vitro growth in DU145 cells by sFGFR provides the basis of a novel therapeutic approach.

Mixed lineage kinase 3 (MLK3)-activated p38 MAP kinase mediates transforming growth factor-beta-induced apoptosis in hepatoma cells

Although transforming growth factor beta1 (TGF-beta1) acts via the Smad signaling pathway to initiate de novo gene transcription, the TGF-beta1-induced MAPK kinase activation that is involved in the regulation of apoptosis is less well understood. Even though the p38 MAP kinase and c-Jun NH(2)-terminal kinases (JNKs) are involved in TGF-beta1-induced cell death in hepatoma cells, the upstream mediators of these kinases remain to be defined. We show here that the members of the mixed lineage kinase (MLK) family (including MLK1, MLK2, MLK3, and dual leucine zipper-bearing kinase (DLK)) are expressed in FaO rat hepatoma cells and are likely to act between p38 and TGF-beta receptor kinase in death signaling. TGF-beta1 treatment leads to an increase in MLK3 activity. Overexpression of MLK3 enhances TGF-beta1-induced apoptotic death in FaO cells and Hep3B human hepatoma cells, whereas expression of the dominant-negative forms of MLK3 suppresses cell death induced by TGF-beta1. The dominant-negative forms of MLK1 and -2 also suppress TGF-beta1-induced cell death. In MLK3-overexpressing cells, ERK, JNKs, and p38 MAP kinases were further activated in response to TGF-beta1 compared with the control cells. In contrast, overexpression of the dominant-negative MLK3 resulted in suppression of TGF-beta1-induced MAP kinase activation and TGF-beta1-induced caspase-3 activation. We also show that only the inhibition of the p38 pathway suppressed TGF-beta1-induced apoptosis. These observations support a role for MLKs in the TGF-beta1-induced cell death mechanism.

cAMP protects neutrophils against TNF-alpha-induced apoptosis by activation of cAMP-dependent protein kinase, independently of exchange protein directly activated by cAMP (Epac)

It is unclear by which receptor cyclic adenosine monophosphate (cAMP) acts to promote neutrophil survival. We found that 8-(4-chlorophenylthio)-2'-O-methyl-cAMP, a specific activator of the recently discovered cAMP receptor, cAMP-regulated guanosine 5'-triphosphate exchange protein directly activated by cAMP, failed to protect human neutrophils from cell death. In contrast, specific activators of cAMP-dependent protein kinase type I (cA-PKI) could protect against death receptor [tumor necrosis factor receptor 1 (TNFR-1), Fas]-mediated apoptosis as well as cycloheximide-accelerated "spontaneous" apoptosis. A novel "caged" cA-PK-activating analog, 8-bromo (8-Br)-acetoxymethyl-cAMP, was more than 20-fold more potent than 8-Br-cAMP to protect neutrophils challenged with TNF-alpha against apoptosis. This analog acted more rapidly than forskolin (which increases the endogenous cAMP production) and allowed us to demonstrate that cA-PK must be activated during the first 10 min after TNF-alpha challenge to protect against apoptosis. The protective effect was mediated solely through cA-PK activation, as it was abolished by the cA-PKI-directed inhibitor Rp-8-Br-cAMPS and the general cA-PK inhibitor H-89. Neutrophils not stimulated by cAMP-elevating agents showed increased apoptosis when exposed to the cA-PK inhibitors Rp-8-Br-cAMPS and H-89, suggesting that even moderate activation of cA-PK is sufficient to enhance neutrophil longevity and thereby contribute to neutrophil accumulation in chronic inflammation.

Suppression of tumor growth and angiogenesis in vivo by a truncated form of 24-kd fibroblast growth factor (FGF)-2

Efforts to treat tumors have routinely depended on disruption of cell proliferation by a variety of methods, many involving stimulation of apoptosis. We have previously shown that a truncated form of 24-kd basic fibroblast growth factor consisting of the amino terminal 86 amino acids inhibits migration of tumor and endothelial cells in vitro. In the present study, this peptide was tested for its ability to suppress angiogenesis and tumor growth using the murine dorsal skin-fold chamber model in vivo. Treatment of MCF-7 breast carcinoma tumor spheroids with this peptide resulted in cessation of the angiogenic response and a significant reduction in tumor size. Blood vessels that did form were poorly developed. In addition to inhibiting angiogenesis, the peptide also inhibited migration of Lewis lung carcinoma cells away from the tumor core before onset of angiogenesis indicating that the peptide-mediated inhibition of migration affects both angiogenesis and tumor growth independently. Despite inhibition of tumor cell migration, the peptide had no effect on neutrophil or eosinophil chemotaxis. This study demonstrates that the truncated form of 24-kd basic fibroblast growth factor is effective in suppressing tumor development in vivo through inhibition of angiogenesis as well as inhibition of tumor cell migration without compromising other homeostatic events.

Basic fibroblast growth factor (bFGF) regulation of the plasma membrane calcium ATPase (PMCA) as part of an anti-apoptotic mechanism of action

Basic fibroblast growth factor (bFGF) preserves the viability of at least 13 different cells, including epithelial, endothelial, smooth muscle and neuronal cells. In spite of this profound and rather universal effect on cell viability, detailed studies regarding the mechanism of bFGF's action have not been conducted. Rather, most studies have simply shown that bFGF inhibits cells from undergoing programmed cell death (i.e. apoptosis). The most mechanistic studies to date have been conducted on either neurons or ovarian (granulosa) cells. These studies have shown that bFGF prevents apoptosis through both genomic and acute actions. Basic FGF's acute actions involved the maintenance of normal levels of intracellular free calcium levels ([Ca(2+)](i)). In granulosa cells, bFGF maintained [Ca(2+)](i) through a protein kinase C(delta) (PKCdelta)-dependent mechanism. Further, bFGF-activated PKCdelta maintained [Ca(2+)](i) by stimulating calcium efflux. The ability of bFGF to stimulate calcium efflux involved the plasma membrane calcium ATPase (PMCA). Interestingly, bFGF-activated PKCdelta appeared to regulate PMCA activity in part by promoting its membrane localization.

Cytoplasmic c-Abl provides a molecular 'Rheostat' controlling carcinoma cell survival and invasion

Tumor cell metastasis involves the coordinated activation of migration and survival mechanisms necessary for cell invasion of foreign tissues. Here, we report that cytoplasmic c-Abl tyrosine kinase determines whether a cell invades the ECM or commits suicide. c-Abl phosphorylates the cytoskeleton-associated adaptor protein, Crk, at tyrosine 221, causing disassociation of Crk from the Crk-associated substrate (CAS) and disassembly of Crk/CAS complexes. c-Abl-induced disruption of Crk/CAS complexes inhibits cell migration and promotes apoptosis in normal cells, and is deregulated in highly invasive carcinoma cells. c-Abl-mediated disassembly of Crk/CAS complexes and induction of death occur via disruption of the cytoskeleton, which is distinct from nuclear c-Abl-induced apoptosis in response to DNA-damaging agents. Inhibition of c-Abl kinase activity or Crk binding to Abl's polyproline region prevents Crk phosphorylation and apoptosis, leading to increased cell survival and invasion of the extracellular matrix. Together, these data illustrate that c-Abl prevents aberrant motility and survival through Crk 221 phosphorylation and modulation of Crk/CAS complexes, and that deregulation of this pathway contributes to cell metastasis.

P2Y6 nucleotide receptor activates PKC to protect 1321N1 astrocytoma cells against tumor necrosis factor-induced apoptosis

1. We recently reported that the activation by UDP of rat P2Y6 nucleotide receptors expressed in 1321N1 astrocytoma cells protected them from TNFalpha-induced apoptosis by suppressing activation of caspase 3 and 8. This study aims to characterize the involvement of intracellular signaling pathways, including kinases involved in the antiapoptotic effect of UDP. 2. Cell death was induced in 1321N1 astrocytoma cells permanently expressing the rat P2Y6 receptor by exposure to TNFalpha in the presence of cycloheximide. The apoptotic fraction was analyzed using flow cytometry. 3. The activation of P2Y6 receptors by UDP both protected the astrocytes from TNF-alpha induced apoptosis and activated protein kinase C (PKC) isotypes. The phorbol ester PMA also activated PKC and protected the cells from TNFalpha-induced cell death. The alpha- and epsilon-isotypes of PKC were both activated in a persistent fashion upon 5-min exposure to either UDP (10 microM) or the phorbol ester PMA (100 nM). The PKCzeta isotype was markedly activated upon UDP treatment. 4. The addition of PKC inhibitors, GF109203X or Gö6976, partially antagonized the protective effect of UDP and reduced the UDP-induced phosphorylation of extracellular signal-regulated protein kinases (Erk). The inhibitors of Erk, PD98,059 or U0126, antagonized UDP-induced protection. 5. The antiapoptotic protein, Akt, was not affected by P2Y6 receptor activation. Incubation of the astrocytes with calcium modifiers BAPTA-AM or dantrolene, did not affect the UDP-induced protection from apoptosis. 6. The addition of phospholipase C (PLC) inhibitors, D609 or U73122, partially antagonized both UDP-induced protection and PKC activation.

Differential effects of low-dose docosahexaenoic acid and eicosapentaenoic acid on the regulation of mitogenic signaling pathways in mesangial cells

Although dietary fish oil supplementation has been used to prevent the progression of kidney disease in patients with IgA nephropathy, relatively few studies provide a mechanistic rationale for its use. Using an antithymocyte (ATS) model of mesangial proliferative glomerulonephritis, we recently demonstrated that fish oil inhibits mesangial cell (MC) activation and proliferation, reduces proteinuria, and decreases histologic evidence of glomerular damage. We therefore sought to define potential mechanisms underlying the antiproliferative effect of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the predominant omega-3 polyunsaturated fatty acids found in fish oil, in cultured MC. DHA and EPA were administered to MC as bovine serum albumin fatty-acid complexes. Low-dose (10-50 micromol/L) DHA, but not EPA, inhibited basal and epidermal growth factor (EGF)-stimulated [(3)H]-thymidine incorporation in MCs. At higher doses (100 micromol/L), EPA and DHA were equally effective in suppressing basal and EGF-stimulated MC mitogenesis. Low-dose DHA, but not EPA, decreased ERK activation by 30% (P <.01), as assessed with Western-blot analysis using phosphospecific antibodies. JNK activity was increased by low-dose DHA but not by EPA. p38 activity was not significantly altered by DHA or EPA. Cyclin E activity, as assessed with a histone H1 kinase assay, was inhibited by low-dose DHA but not by EPA. DHA increased expression of the cell cycle inhibitor p21 but not p27; EPA had no effect on p21 or p27. We propose that the differential effect of low-dose DHA vs EPA in suppressing MC mitogenesis is related to down-regulation of ERK and cyclin E activity and to induction of p21.

Inhibition of PKCalpha induces a PKCdelta-dependent apoptotic program in salivary epithelial cells

We have used expression of a kinase dead mutant of PKCalpha (PKCalphaKD) to explore the role of this isoform in salivary epithelial cell apoptosis. Expression of PKCalphaKD by adenovirus-mediated transduction results in a dose-dependent induction of apoptosis in salivary epithelial cells as measured by the accumulation of sub-G1 DNA, activation of caspase-3, and cleavage of PKCdelta and PKCzeta, known caspase substrates. Induction of apoptosis is accompanied by nine-fold activation of c-Jun-N-terminal kinase, and an approximately two to three-fold increase in activated mitogen-activated protein kinase (MAPK) as well as total MAPK protein. Previous studies from our laboratory have shown that PKCdelta activity is essential for the apoptotic response of salivary epithelial cells to a variety of cell toxins. To explore the contribution of PKCdelta to PKCalphaKD-induced apoptosis, salivary epithelial cells were cotransduced with PKCalphaKD and PKCdeltaKD expression vectors. Inhibition of endogenous PKCdelta blocked the ability of PKCalphaKD to induce apoptosis as indicated by cell morphology, DNA fragmentation, and caspase-3 activation, indicating that PKCdelta activity is required for the apoptotic program induced under conditions where PKCalpha is inhibited. These findings indicate that PKCalpha functions as a survival factor in salivary epithelial cells, while PKCdelta functions to regulate entry into the apoptotic pathway.

Discovery of CEP-1347/KT-7515, an inhibitor of the JNK/SAPK pathway for the treatment of neurodegenerative diseases

Apoptosis has been proposed as a mechanism of cell death in Alzheimer's, Huntington's and Parkinson's diseases and the occurrence of apoptosis in these disorders suggests a common mechanism. Events such as oxidative stress, calcium toxicity, mitochondria defects, excitatory toxicity, and deficiency of survival factors are all postulated to play varying roles in the pathogenesis of the diseases. However, the transcription factor c-jun may play a role in the pathology and cell death processes that occur in Alzheimer's disease. Parkinson's disease (PD) is also a progressive disorder involving the specific degeneration and death of dopamine neurons in the nigrostriatal pathway. In Parkinson's disease, dopaminergic neurons in the substantia nigra are hypothesized to undergo cell death by apoptotic processes. The commonality of biochemical events and pathways leading to cell death in these diseases continues to be an area under intense investigation. The current therapy for PD and AD remains targeting replacement of lost transmitter, but the ultimate objective in neurodegenerative therapy is the functional restoration and/or cessation of progression of neuronal loss. This chapter will describe a novel approach for the treatment of neurodegenerative diseases through the development of kinase inhibitors that block the active cell death process at an early transcriptional independent step in the stress activated kinase cascade. In particular, preclinical data will be presented on the c-Jun Amino Kinase pathway inhibitor, CEP-1347/KT-7515, with respect to it's properties that make it a desirable clinical candidate for treatment of various neurodegenerative diseases.

Deregulation of the Egfr/Ras signaling pathway induces age-related brain degeneration in the Drosophila mutant vap

Ras signaling has been shown to play an important role in promoting cell survival in many different tissues. Here we show that upregulation of Ras activity in adult Drosophila neurons induces neuronal cell death, as evident from the phenotype of vacuolar peduncle (vap) mutants defective in the Drosophila RasGAP gene, which encodes a Ras GTPase-activating protein. These mutants show age-related brain degeneration that is dependent on activation of the EGF receptor signaling pathway in adult neurons, leading to autophagic cell death (cell death type 2). These results provide the first evidence for a requirement of Egf receptor activity in differentiated adult Drosophila neurons and show that a delicate balance of Ras activity is essential for the survival of adult neurons.