Hyperbaric oxygen induces VEGF expression through ERK, JNK and c-Jun/AP-1 activation in human umbilical vein endothelial cells

Summary Hyperbaric oxygen (HBO) is increasingly used in a number of areas of medical practice, such as selected problem infections and wounds. The beneficial effects of HBO in treating ischemia-related wounds may be mediated by stimulating angiogenesis. We sought to investigate VEGF, the main angiogenic regulator, regulated by HBO in human umbilical vein endothelial cells (HUVECs). In this study, we found that VEGF was up regulated both at mRNA and protein levels in HUVECs treated with HBO dose- and time-dependently. Since there are several AP-1 sites in the VEGF promoter, and the c-Jun/AP-1 is activated through stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and extracellular signal regulated kinase (ERK), we further examined the c-Jun, JNK and ERK that might be involved in the VEGF induced by HBO. The VEGF mRNA induced by HBO was blocked by both PD98059 and SP600125, the ERK and JNK inhibitors respectively. HBO induced phospho-ERK and phospho-JNK expressions within 15 min. We further demonstrated that c-Jun phosphorylation was induced within 60 min of HBO treatment. HBO also induced the nuclear AP-1 binding ability within 30–60 min, but the AP-1 induction was blocked by treatment with either the ERK or JNK inhibitor. To verify that the VEGF expression induced by HBO is through the AP-1 trans-activation and VEGF promoter, both the VEGF promoter and AP-1 driving luciferase activity were found increased by the cells treated with HBO. The c-Jun mRNA, which is also driven by AP-1, was also induced by HBO, and the induction of c-Jun was blocked by ERK and JNK inhibitors. We suggest that VEGF induced by HBO is through c-Jun/AP-1 activation, and through simultaneous activation of ERK and JNK pathways.     

Cry1Ac toxin induces macrophage activation via ERK1/2, JNK and p38 mitogen-activated protein kinases

The Cry1Ac toxin from Bacillus thuringiensis is used commercially as a bio-insecticide and is expressed in transgenic plants that are used for human and animal consumption. Although it was originally considered innocuous for mammals, the Cry1Ac toxin is not inert and has the ability to induce mucosal and systemic immunogenicity. Herein, we examined whether the Cry1Ac toxin promotes macrophage activation and explored the signalling pathways that may mediate this effect. Treatment of primary and RAW264.7 macrophages with the Cry1Ac toxin resulted in upregulation of the costimulatory molecules CD80, CD86 and ICOS-L and enhanced production of nitric oxide, the chemokine MCP-1 and the proinflammatory cytokines TNF-α and IL-6. Remarkably, the Cry1Ac toxin induced phosphorylation of the mitogen-activated protein kinases (MAPKs) ERK1/2, JNK and p38 and promoted nuclear translocation of nuclear factor-kappa B (NF-κB) p50 and p65. p38 and ERK1/2 MAPKs were involved in this effect, as indicated by the Cry1Ac-induced upregulation of CD80 and IL-6 and TNF-α abrogation by the p38 MAPK inhibitor SB203580. Furthermore, treatment the MEK1/2 kinase inhibitor PD98059 blocked increases in MCP-1 secretion and augmented Cry1Ac-induced ICOS-L upregulation. These data demonstrate the capacity of the Cry1Ac toxin to induce macrophage activation via the MAPK and NF-κB pathways.     

Histone-like DNA binding protein of Streptococcus intermedius induces the expression of pro-inflammatory cytokines in human monocytes via activation of ERK1/2 and JNK pathways

Streptococcus intermedius is a commensal associated with serious, deep-seated purulent infections in major organs, such as the brain and liver. Histone-like DNA binding protein (HLP) is an accessory architectural protein in a variety of bacterial cellular processes. In this study, we investigated the mechanisms of pro-inflammatory cytokine inductions in THP-1 cells by stimulation with recombinant HLP of S. intermedius (r Si -HLP). r Si -HLP stimulation-induced production of pro-inflammatory cytokines (IL-8, IL-1β and TNF-α) occurred in a time- and dose-dependent manner. In contrast with the heat-stable activity of DNA binding, the induction activity of r Si -HLP was heat-unstable. In subsequent studies, r Si -HLP acted cooperatively with lipoteichoic acid, the synthetic Toll-like receptor 2 agonist, Pam3CSK4, and the cytosolic nucleotide binding oligomerization domain 2 receptor agonist, muramyldipeptide. Furthermore, Western blot and blocking assays with specific inhibitors showed that r Si -HLP stimulation induced the activation of cell signal transduction pathways, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK). In addition to its physiological role in bacterial growth through DNA binding, these results indicate that Si -HLP can trigger a cascade of events that induce pro-inflammatory responses via ERK1/2 and JNK signal pathways, and suggest that bacterial HLP may contribute to the activation of host innate immunity during bacterial infection.     

Cannabinoids inhibit ethanol-induced activation of liver toxicity in rats through JNK/ERK/MAPK signaling pathways

Cannabinoids (CBs) are psychoactive compounds, with reported anticancer, anti-inflammatory, and anti-neoplastic properties. The study was aimed at assessing the hepatoprotective effects of CB against ethanol (EtOH)-induced liver toxicity in rats. The animals were divided into seven groups: control (Group I) and Group II were treated with 50% ethanol (EtOH 5 mg/kg). Groups III, IV, and VI were treated with (EtOH + CB 10 mg/kg), (EtOH + CB 20 mg/kg), and (EtOH + CB 30 mg/kg), respectively. Groups V and VII consisted of animals treated with 20 and 30 mg/kg, of CB, respectively. Biochemical analysis revealed that Group IV (EtOH + CB 20 mg/kg) had reduced levels of ALT—alanine transferase, AST—aspartate aminotransferase, ALP—alanine peroxidase, MDA—malondialdehyde and increased levels of GSH-reduced glutathione. Histopathological analysis of liver and kidney tissues showed that EtOH + CB (20 and 30 mg/kg) treated animal groups exhibited normal tissue architecture similar to that of the control group. ELISA revealed that the inflammatory markers were reduced in the animal groups that were treated with EtOH + CB 20 mg/kg, in comparison to the animals treated only with EtOH. The mRNA expression levels of COX-2, CD-14, and MIP-2 showed a remarkable decrease in EtOH + CB treated animal groups to control groups. Western blot analysis revealed that CB downregulated p38/JNK/ERK thereby exhibiting its hepatoprotective property by inhibiting mitogen-activated protein kinase pathways. Thus, our findings suggest that CB is a potential candidate for the treatment of alcohol-induced hepatotoxicity.     

UVA induces Ser381 phosphorylation of p90RSK/MAPKAP-K1 via ERK and JNK pathways

UVA exposure plays an important role in the etiology of skin cancer. The family of p90-kDa ribosomal S6 kinases (p90(RSK)/MAPKAP-K1) are activated via phosphorylation. In this study, results show that UVA-induced phosphorylation of p90(RSK) at Ser(381) through ERKs and JNKs, but not p38 kinase pathways. We provide evidence that UVA-induced p90(RSK) phosphorylation and kinase activity were time- and dose-dependent. Both PD98059 and a dominant negative mutant of ERK2 blocked ERKs and p90(RSK) Ser(381) phosphorylation, as well as p90(RSK) activity. A dominant negative mutant of p38 kinase blocked UVA-induced phosphorylation of p38 kinase, but had no effect on UVA-induced Ser(381) phosphorylation of p90(RSK) or kinase activity. UVA-induced p90(RSK) phosphorylation and kinase activity were markedly attenuated in JnK1(-/-) and JnK2(-/-) cells. A dominant negative mutant of JNK1 inhibited UVA-induced JNKs and p90(RSK) phosphorylation and kinase activity, but had no effect on ERKs phosphorylation. PD169316, a novel inhibitor of JNKs and p38 kinase, inhibited phosphorylation of p90(RSK), JNKs, and p38 kinase, but not ERKs. However, SB202190, a selective inhibitor of p38 kinase, had no effect on p90(RSK) or JNKs phosphorylation. Significantly, ERKs and JNKs, but not p38 kinase, immunoprecipitated with p90(RSK) when stimulated by UVA and p90(RSK) was a substrate for ERK2 and JNK2, but not p38 kinase. These data indicate clearly that p90(RSK) Ser(381) may be phosphorylated by activation of JNKs or ERKs, but not p38 kinase.     

Arsenic trioxide induces apoptosis through JNK and ERK in human mesothelioma cells

Malignant mesothelioma is an aggressive tumor of serosal surfaces, which is refractory to current treatment options. Arsenic trioxide (As₂O₃) is used clinically to treat acute promyelocytic leukemia, and also to inhibit proliferation of several solid tumors including hepatoma, esophageal, and gastric cancer in vitro. Here we found that As₂O₃ inhibited cell viability of a mesothelioma cell line, NCI‐H2052. As₂O₃ induced apoptosis of NCI‐H2052 cells, which was accompanied by activation of c‐Jun NH₂‐terminal kinase (JNK)1/2, extracellular signal‐regulated kinase (ERK)1/2, and caspase‐3. zVAD‐fmk, a broad‐spectrum caspase inhibitor, inhibited As₂O₃‐induced apoptosis and activation of caspase‐3, but not that of JNK1/2 and ERK1/2. Small interfering RNAs (siRNAs) targeting JNK1/2 suppressed As₂O₃‐induced caspase‐3 activation and apoptosis, indicating that JNK1/2 regulate As₂O₃‐induced apoptosis though caspase cascade. Furthermore, JNK1 siRNA abrogated As₂O₃‐induced JNK2 phosphorylation and JNK2 siRNA abrogated As₂O₃‐induced JNK1 phosphorylation, suggesting that JNK1 and JNK2 interact with each other. Moreover, JNK1 siRNA, but not JNK2 siRNA, abrogated As₂O₃‐induced ERK1/2 phosphorylation. JNK2 siRNA together with PD98059, a specific MAPK/ERK kinase inhibitor, suppressed As₂O₃‐induced apoptosis more significantly than JNK2 siRNA alone. These results indicated that As₂O₃ induces apoptosis of NCI‐H2052 cells mainly through JNK1/2 activation, and that ERK1/2 is involved in As₂O₃‐induced apoptosis when JNK1/2 are inactivated. J. Cell. Physiol. 226: 762–768, 2011. © 2010 Wiley‐Liss, Inc.     

ICB3E induces iNOS expression by ROS-dependent JNK and ERK activation for apoptosis of leukemic cells

The role of c-Jun N terminal Kinase (JNK) has been well documented in various cellular stresses where it leads to cell death. Similarly, extracellular signal-regulated kinase (ERK) which was identified as a signalling molecule for survival pathway has been shown recently to be involved in apoptosis also. Recently we reported that ICB3E, a synthetic analogue of Piper betle leaf-derived apoptosis-inducing agent hydroxychavicol (HCH), possesses anti-chronic myeloid leukemia (CML) acitivity in vitro and in vivo without insight on mechanism of action. Here we report that ICB3E is three to four times more potent than HCH in inducing apoptosis of leukemic cells without having appreciable effects on normal human peripheral blood mononuclear cells, mouse fibroblast cell line NIH3T3 and monkey kidney epithelial cell line Vero. ICB3E causes early accumulation of mitochondria-derived reactive oxygen species (ROS) in K562 cells. Unlike HCH, ICB3E treatment caused ROS dependent activation of both JNK, ERK and induced the expression of iNOS leading to generation of nitric oxide (NO). This causes cleavage of caspase 9, 3 and PARP leading to apoptosis. Lack of cleavage of caspase 8 and inability of blocking chimera antibody to DR5 or neutralizing antibody to Fas to reverse ICB3E-mediated apoptosis suggest the involvement of only intrinsic pathway. Our data reveal a novel ROS-dependent JNK/ERK-mediated iNOS activation pathway which leads to NO mediated cell death by ICB3E.     

HIV-1 Tat activates dual Nox pathways leading to independent activation of ERK and JNK MAP kinases

Human immunodeficiency virus, type 1 Tat is known to exert pleiotropic effects on the vascular endothelium through mitogen-activated protein (MAP) kinases, although the signaling pathways leading to MAP kinase activation are incompletely understood. We focused on proximal pathways potentially governing downstream MAP kinase activity by Tat. Within 2 min, Tat activated both Ras and Rho GTPases in endothelial cells, leading to ERK phosphorylation by 10 min. Notably, Rac1 was necessary for downstream activation of RhoA and both Rac1 and RhoA acted upstream of the Ras/ERK cassette. Antioxidants and the oxidase inhibitor diphenylene iodonium blocked ERK phosphorylation, but specific interference with the canonical Nox2 oxidase had no effect on ERK. Instead, knock down of the novel oxidase Nox4 completely suppressed Tat-dependent Ras and ERK activation downstream of Rac1 and RhoA. Conversely, interference with Rac1, PAK1, and Nox2 blocked JNK phosphorylation, whereas RhoA(N19) and Nox4 knock down did not. Further, knock down of Nox2, but not Nox4, blocked Tat-induced cytoskeletal rearrangement, whereas knock down of Nox4, but not Nox2, blocked Tat-dependent proliferation. Rac1, therefore, bifurcates Tat signaling, leading to concurrent but separate Nox4-dependent Ras/ERK activation, and Nox2-dependent JNK activation. Tat signaling, therefore, provides an example of Nox-specific differential control of MAP kinase pathways.     

Mitogen stimulation of T-cells increases c-Fos and c-Jun protein levels, AP-1 binding and AP-1 transcriptional activity.

We have analysed the effect of mitogenic lectins on c-Fos and c-Jun protein levels as well as on activator protein-1 (AP-1) binding and enhancer activity in Jurkat T-cells. Both c-Fos and c-Jun protein levels were increased after Con A and PHA stimulation. Since T-cell stimulation increases both intracellular Ca2+ and cAMP levels and activates protein kinase C (PKC), the possible involvement of these intracellular messengers in c-Fos and c-Jun induction was tested. PMA, which directly activates PKC, mimicked the effect of the lectins on c-Fos and c-Jun, but elevation of either intracellular Ca2+ or cAMP levels had little or no effect. The mitogen-induced increase of c-Fos and c-Jun immunoreactivity was inhibited by H-7, a kinase inhibitor with relatively high specificity for PKC, and less efficiently by H-8, a structurally related kinase inhibitor less active on PKC, but more active on cyclic nucleotide-dependent kinases. Con A stimulation was found to increase both binding of AP-1 to the AP-1 consensus sequence, TRE, and AP-1 enhancer activity, in Jurkat cells. PMA was also found to increase the AP-1 enhancer activity, whereas elevation of Ca2+ or cAMP had only minor effects. We conclude that stimulation with mitogenic lectins is sufficient to increase both c-Fos and c-Jun protein levels, AP-1 binding and AP-1 enhancer activity in Jurkat cells and that they act via mechanisms that could involve the activation of PKC.     

Zinc deficiency induces oxidative stress and AP-1 activation in 3T3 cells

It has been postulated that one mechanism underlying zinc deficiency-induced tissue alterations is excessive cellular oxidative damage. In the present study we investigated if zinc deficiency can induce oxidative stress in 3T3 cells and trigger select intracellular responses that have been associated to oxidative stress. Cells were exposed to control media or to chelated media containing 0.5, 5, or 50 microM zinc for 24 or 48 h. The oxidative status of the cells was evaluated as an increase in the fluorescence of the probe 5(or 6)-carboxy-2'7'-dichlorodihydrofluorescein diacetate (DCDCDHF). After 24 and 48 h of exposure, the fluorescence intensity was significantly higher (4- to 15-fold) in the 0.5 and 5 microM Zn groups compared to the 50 microM Zn and control groups. The activity of the antioxidant enzymes CuZn (CuZnSOD) and Mn (MnSOD) superoxide dismutases was significantly higher in the 0.5 and 5 microM Zn cells compared to the 50 microM Zn and control groups at both the 24 and 48 h time points. These higher activities were associated with higher levels of MnSOD mRNA. After 24 h in culture, the level of activated AP-1 was markedly higher in the 0.5 and 5 microM Zn cells than in the control (72 and 58%, respectively) and 50 microM Zn cells (73 and 60%, respectively). NF-kappaB binding activity was lower in the 0.5 and 5 microM Zn cells than in controls. Thus, oxidative stress is induced by zinc deficiency in 3T3 cells. This oxidative stress results in an upregulation of oxidant defense mechanisms.