Glutamine deficiency shifts the asthmatic state toward neutrophilic airway inflammation.

BACKGROUND: The administration of L-glutamine (Gln) suppresses allergic airway inflammation via the rapid upregulation of MAPK phosphatase (MKP)-1, which functions as a negative regulator of inflammation by deactivating p38 and JNK mitogen-activated protein kinases (MAPKs). However, the role of endogenous Gln remains to be elucidated. Therefore, we investigated the mechanism by which endogenous Gln regulates MKP-1 induction and allergic airway inflammation in an ovalbumin-based murine asthma model. METHODS: We depleted endogenous Gln levels using L-γ-glutamyl-p-nitroanilide (GPNA), an inhibitor of the Gln transporter ASCT2 and glutamine synthetase small interfering siRNA. Lentivirus expressing MKP-1 was injected to achieve overexpression of MKP-1. Asthmatic phenotypes were assessed using our previously developed ovalbumin-based murine model, which is suitable for examining sequential asthmatic events, including neutrophil infiltration. Gln levels were analyzed using a Gln assay kit. RESULTS: GPNA or glutamine synthetase siRNA successfully depleted endogenous Gln levels. Importantly, homeostatic MKP-1 induction did not occur at all, which resulted in prolonged p38 MAPK and cytosolic phospholipase A2 (cPLA2 ) phosphorylation in Gln-deficient mice. Gln deficiency augmented all examined asthmatic reactions, but it exhibited a strong bias toward increasing the neutrophil count, which was not observed in MKP-1-overexpressing lungs. This neutrophilia was inhibited by a cPLA2 inhibitor and a leukotriene B4 inhibitor but not by dexamethasone. CONCLUSION: Gln deficiency leads to the impairment of MKP-1 induction and activation of p38 MAPK and cPLA2 , resulting in the augmentation of neutrophilic, more so than eosinophilic, airway inflammation.

GPCR Kinase (GRK)-2 Is a Key Negative Regulator of Itch: l-Glutamine Attenuates Itch via a Rapid Induction of GRK2 in an ERK-Dependent Way.

Many itch mediators activate GPCR and trigger itch via activation of GPCR-mediated signaling pathways. GPCRs are desensitized by GPCR kinases (GRKs). The aim of this study is to explore the role of GRKs in itch response and the link between GRKs and glutamine, an amino acid previously shown to be an itch reliever. Itch responses were evoked by histamine, chloroquine, and dinitrochlorobenzene-induced contact dermatitis (CD). Phosphorylation and protein expression were detected by immunofluorescent staining and Western blotting. GRK2 knockdown using small interfering RNA enhanced itch responses evoked by histamine, chloroquine, and dinitrochlorobenzene-induced CD, whereas GRK2 overexpression using GRK2-expressing adenovirus reduced the itch responses. Glutamine reduced all itch evoked by histamine, chloroquine, and dinitrochlorobenzene-induced CD. Glutamine-mediated inhibition of itch was abolished by GRK2 knockdown. Glutamine application resulted in a rapid and strong expression of GRK2 in not only dinitrochlorobenzene-induced CD (within 10 minutes) but also cultured rat dorsal root ganglion cells, F11 (within 1 minute). ERK inhibitor abrogates glutamine-mediated GRK2 expression and inhibition of itch in dinitrochlorobenzene-induced CD. Our data indicate that GRK2 is a key negative regulator of itch and that glutamine attenuates itch via a rapid induction of GRK2 in an ERK-dependent way.

l-Glutamine Attenuates DSS-Induced Colitis via Induction of MAPK Phosphatase-1.

Inflammatory bowel disease (IBD), encompassing ulcerative colitis and Crohn's disease, is a multifactorial inflammatory disease of the small intestine and colon. Many investigators have reported that l-glutamine (Gln) therapy improves outcomes of experimental colitis models, although the mechanism is not fully understood. Regarding the anti-inflammatory properties of Gln, we have shown that Gln can effectively deactivate cytosolic phospholipase A2 (cPLA2) by rapid induction of MAPK phosphatase (MKP)-1. In this study, we explore the possibility that Gln ameliorates dextran sulfate sodium (DSS)-induced colitis via MKP-1 induction, resulting in inhibition of cPLA2, which has been reported to play a key role in the pathogenesis of IBD. Oral Gln intake attenuated DSS-induced colitis. Gln inhibited cPLA2 phosphorylation, as well as colonic levels of TNF-α and leukotriene (LT)B4. Gln administration resulted in early and enhanced MKP-1 induction. Importantly, MKP-1 small interfering RNA (siRNA), but not control siRNA, significantly abrogated the Gln-mediated (1) induction of MKP-1; (2) attenuation of colitis (colon length, histological abnormality, and inflammation; and (3) inhibition of cPLA2 phosphorylation and colonic levels of TNF-α and LTB4. These data indicated that Gln ameliorated DSS-induced colitis via MKP-1 induction.

FcγR/ROS/CK2α Is the Key Inducer of NF-κB Activation in a Murine Model of Asthma.

BACKGROUND: The transcription factor nuclear factor (NF)-κB plays a pivotal role in the development of allergic airway inflammation. However, the mechanism of NF-κB activation in asthma remains to be elucidated. METHODS: CK2α activation was assessed by CK2α phosphorylation and protein expression. Airway levels of histamine and cytokines were determined by ELISA. We used 2 (active and passive) forms of allergic pulmonary inflammation models. In the active form, the animals were immunized with ovalbumin (OVA) intraperitoneally, followed by an airway challenge with OVA. In the passive form, the animals were passively sensitized by intratracheal instillation with either anti-OVA IgE or anti-OVA IgG, followed by an airway challenge with OVA. The role of NADPH oxidase (NOX) in CK2α activation was assessed using NOX2-/- and NOX4-/- mice because NOX2 and NOX4 contribute to many inflammatory diseases. RESULTS: The second airway challenge increased CK2α phosphorylation and protein expression in airway epithelial cells as well as nuclear translocation of the p50 and p65 subunits of NF-κB, all of which were inhibited by the CK2α inhibitor 4,5,6,7-tetrabromobenzotriazole and the antioxidant N-acetyl-L-cysteine. CK2α phosphorylation and protein expression were significantly impaired in NOX2-/-, but not in NOX4-/-, mice. Induction of passive sensitization using anti-OVA IgE activated neither CK2α nor NF-κB. In contrast, induction of passive sensitization using anti-OVA IgG activated both CK2α and NF-κB. CONCLUSIONS: These data suggest that Fcγ receptor/reactive oxygen species/CK2α is a key inducer of NF-κB activation in airway epithelial cells in a murine model of asthma.

The extracellular matrix protein Edil3 stimulates osteoblast differentiation through the integrin α5ß1/ERK/Runx2 pathway.

Epidermal growth factor-like repeats and discoidin I-like domain 3 (Edil3) is an extracellular matrix protein containing an Arg-Gly-Asp (RGD) motif that binds integrin. Recently, Edil3 has been implicated in various biological processes, including angiogenesis and cellular differentiation. It can inhibit inflammatory bone destruction. The objective of this study was to explore the role of Edil3 in osteoblast differentiation and its underlying molecular mechanisms. In wild-type mice, high expression levels of Edil3 mRNA were observed in isolated calvaria and tibia/femur bones. Immunohistochemical analysis showed that Edil3 protein was localized along periosteum and calcified regions surrounding bone tissues. When murine calvaria-derived MC3T3-E1 cells were cultured in osteogenic medium containing 50 µg/ml ascorbic acid and 5 mM ß-glycerophosphate, Edil3 mRNA and protein expression levels were increased. Treatment with Edil3 protein in growth media increased expression levels of alkaline phosphatase and osteocalcin gene and phosphorylation level of extracellular signal-regulated kinase (ERK). Edil3 treatment with osteogenic medium induced mineralization. Treatment with a neutralizing antibody against α5ß1 and MEK inhibitor U0126 inhibited Edil3-enhanced osteogenic marker gene expression and mineral deposition. Edil3 increased protein expression levels of transcription factor runt-related transcription factor2 (Runx2). Edil3-induced Runx2 protein expression was suppressed by pretreatment with U0126. Taken together, these results suggest that Edil3 may stimulate osteoblast differentiation and matrix mineralization by increasing expression of Runx2 through α5ß1 integrin /ERK pathway.

Glutamine Prevents Late-Phase Anaphylaxis via MAPK Phosphatase 1-Dependent Cytosolic Phospholipase A2 Deactivation.

BACKGROUND: Cytosolic phospholipase A2 (cPLA2) plays a key role in the development of late-phase anaphylaxis. L-Glutamine (Gln), a nonessential amino acid, has anti-inflammatory activity via inhibiting cPLA2. METHODS: We used a penicillin-induced murine model of anaphylaxis, and late-phase anaphylaxis was quantified by measuring the increase in the hematocrit (Ht) value. Various inhibitors, small interfering RNA, and knockout mice were used in inhibition experiments. Phosphorylation and protein expression of cPLA2, ERK, and MAPK phosphatase 1 (MKP-1) were detected by Western blotting. RESULTS: Leukotriene (LT) B4 was found to be another potent inducer of late-phase anaphylaxis besides the known mediator platelet-activating-factor (PAF). Gln efficiently prevented late-phase anaphylaxis when it was administered up to 3 h after challenge injection via inhibiting cPLA2. Inhibition studies indicated that p38 MAPK was the major upstream regulator of cPLA2. Gln dephosphorylated p38 and cPLA2 via up-regulating the negative regulator of p38 MAPK, i.e., MKP-1 protein. MKP-1 blockade abrogated all the effects of Gln. CONCLUSION: Of the cPLA2 metabolites, PAF and LTB4 play a key role in the development of late-phase anaphylaxis, and Gln prevents the reaction via MKP-1-dependent deactivation of cPLA2.

Glutamine up-regulates MAPK phosphatase-1 induction via activation of Ca2+→ ERK cascade pathway.

The non-essential amino acid L-glutamine (Gln) displays potent anti-inflammatory activity by deactivating p38 mitogen activating protein kinase and cytosolic phospholipase A2 via induction of MAPK phosphatase-1 (MKP-1) in an extracellular signal-regulated kinase (ERK)-dependent way. In this study, the mechanism of Gln-mediated ERK-dependency in MKP-1 induction was investigated. Gln increased ERK phosphorylation and activity, and phosphorylations of Ras, c-Raf, and MEK, located in the upstream pathway of ERK, in response to lipopolysaccharidein vitro and in vivo. Gln-induced dose-dependent transient increases in intracellular calcium ([Ca2+]i) in MHS macrophage cells. Ionomycin increased [Ca2+]i and activation of Ras → ERK pathway, and MKP-1 induction, in the presence, but not in the absence, of LPS. The Gln-induced pathways involving Ca2+→ MKP-1 induction were abrogated by a calcium blocker. Besides Gln, other amino acids including L-phenylalanine and l-cysteine (Cys) also induced Ca2+ response, activation of Ras → ERK, and MKP-1 induction, albeit to a lesser degree. Gln and Cys were comparable in suppression against 2, 4-dinitrofluorobenzene-induced contact dermatitis. Gln-mediated, but not Cys-mediated, suppression was abolished by MKP-1 small interfering RNA. These data indicate that Gln induces MKP-1 by activating Ca2+→ ERK pathway, which plays a key role in suppression of inflammatory reactions.

Platelet-activating factor enhances tumour metastasis via the reactive oxygen species-dependent protein kinase casein kinase 2-mediated nuclear factor-κB activation.

Platelet-activating factor (PAF) promotes tumour metastasis via activation of the transcription factor nuclear factor-κB (NF-κB). We here investigated the role of the protein kinase CK2 (formerly Casein Kinase 2 or II) in PAF-induced NF-κB activation and tumour metastasis, given that PAF has been reported to increase CK2 activity, and that CK2 plays a key role in NF-κB activation. PAF increased CK2 activity, phosphorylation and protein expression in vivo as well as in vitro. CK2 inhibitors inhibited the PAF-mediated NF-κB activation and expression of NF-κB-dependent pro-inflammatory cytokines and anti-apoptotic factors. Pre-treatment with the antioxidant N-Acetyl-L-Cysteine (NAC) resulted in a significant inhibition in PAF-induced enhancement of CK2 activity, phosphorylation and protein expression in vivo as well as in vitro. H2 O2 and known reactive oxygen species inducers, lipopolysaccharide (LPS) and tumour necrosis factor-α (TNF-α) enhanced CK2 activity, phosphorylation and protein expression, which was again inhibited by antioxidant. PAF, LPS and TNF-α induced increased CK2 activity, phosphorylationand protein expression, which were inhibited by p38 inhibitor. PAF, LPS or TNF-α increased pulmonary metastasis of B16F10, which was inhibited by antioxidants, CK2 inhibitor and p38 inhibitor. Our data suggest that (i) reactive oxygen species activate CK2 via p38, which, in turn, induces NF-κB activation, and (ii) PAF, LPS and TNF-α increase pulmonary tumour metastasis via the induction of the reactive oxygen species (ROS)/p38/CK2/NF-κB pathway.

Cholera toxin breakdowns oral tolerance via activation of canonical NF-κB.

The mechanisms of mucosal immunogenicity and adjuvanticity of bacterial exotoxins remains unknown. In this study, we investigated the role of the transcription factor nuclear factor-κB (NF-κB) in cholera toxin (CT)-induced alteration of oral tolerance. Feeding CT abrogated ovalbumin (OVA)-induced oral tolerance, as evaluated by OVA-specific serum antibody responses, and CD4(+) T cell proliferation. CT feeding activated canonical NF-κB (one heterodimer type, p50-p65) and mRNA expression of NF-κB-dependent proinflammatory cytokines in mesenteric lymph node (MLN) and Peyer's patch (PP) cells. CT no longer showed abrogation of oral tolerance in mice pretreated with p50 small interfering RNAs (siRNAs). ADP-ribosylation inhibitors inhibited CT-induced NF-κB activation. These data suggest that CT induces canonical NF-κB activation in intestinal lymphoid cells, which plays a key role in mucosal immunogenicity and adjuvanticity.

Glutamine suppresses DNFB-induced contact dermatitis by deactivating p38 mitogen-activated protein kinase via induction of MAPK phosphatase-1.

L-glutamine (Gln) is a nonessential amino acid that is the most abundant amino acid in plasma. Gln has been reported to have an anti-inflammatory activity that involves deactivation of mitogen-activated protein kinases (MAPKs) in a MAPK phosphatase (MKP)-1-dependent manner. This study investigated the role of Gln in the inhibition of DNFB-induced allergic contact dermatitis (CD) in the ears of mice, and specifically the involvement of Gln in p38 MAPK inhibition. Topical application of Gln or the p38 inhibitor, SB202190, suppressed DNFB-induced CD. Gln application inhibited DNFB-induced p38 phosphorylation. Western blot analysis revealed that Gln application resulted in early phosphorylation and protein induction of MKP-1. MKP-1 small interfering RNA (siRNA), but not control siRNA, abrogated Gln-mediated early phosphorylation, protein induction of MKP-1, deactivation of p38, and Gln-mediated suppression of CD. The extracellular signal-regulated kinase (ERK) inhibitor, U0126, blocked Gln-induced MKP-1 phosphorylation and protein induction, as well as Gln suppression of CD. These results suggest that Gln suppresses DNFB-induced CD via deactivation of p38 MAPK through the early induction of MKP-1, the negative regulator of p38, in an ERK-dependent manner.

PTEN/MAPK pathways play a key role in platelet-activating factor-induced experimental pulmonary tumor metastasis.

In this study, we investigated the role of PTEN (phosphatase and tensin homolog deleted on chromosome 10) in a platelet-activating factor (PAF)-induced experimental pulmonary tumor metastasis model. An adenovirus carrying PTEN cDNA (Ad-PTEN) reversed PAF-induced increase in phosphorylation of AKT as well as pulmonary metastasis of B16F10. PAF-induced pulmonary metastasis was inhibited by MAPK inhibitors, but not by PI3K inhibitor. Ad-PTEN abrogated PAF-induced phosphorylation of MAPKs. These data indicate PTEN/MAPK pathways play a key role in PAF-induced tumor metastasis.

Glutamine suppresses airway neutrophilia by blocking cytosolic phospholipase A(2) via an induction of MAPK phosphatase-1.

Neutrophils are inflammatory cells that may contribute in a crucial way to the pathophysiology of steroid-resistant severe asthma. We previously reported that the nonessential amino acid l-glutamine (Gln) suppressed the recruitment of neutrophils into the airway in a murine model of asthma. In this study, we investigated the mechanisms by which Gln exerts beneficial effects in airway neutrophilia. We used the model we previously developed, which is suitable for examining sequential early asthmatic events, including neutrophil infiltration. Gln suppressed airway neutrophilia in a CXC chemokine-independent way. Airway neutrophilia was associated with cytosolic phospholipase A(2) (cPLA(2)) and 5-lipoxygenase (5-LO) activities. p38 MAPK, the upstream pathway of cPLA(2) and 5-LO, played a key role in inducing airway neutrophilia. Gln inhibited not only the phosphorylation of cPLA(2) and p38 MAPK but also leukotriene B(4) levels in the airways. Gln induced the early induction of MAPK phosphatase-1 (MKP-1) protein, a negative regulator of p38. MKP-1 small interfering RNA abrogated all the effects of Gln. Our results suggest that pathways involving p38/cPLA(2)/5-LO have a major role in airway neutrophilia. Gln suppresses airway neutrophilia via inhibiting p38 MAPK and its downstream pathways in an MKP-1-dependent way, which may provide a novel therapeutic strategy for pulmonary neutrophilic inflammatory diseases.

Glutamine suppresses dinitrophenol fluorobenzene-induced allergic contact dermatitis and itching: inhibition of contact dermatitis by glutamine.

BACKGROUND: Cytoplasmic phospholipase A(2) (cPLA(2)) is importantly implicated in a variety of inflammatory diseases by liberating arachidonic acid from phospholipids. The increased cPLA(2) activities as well as increased levels of cPLA(2) metabolites are associated with pathogenesis of many inflammatory skin disorders including atopic dermatitis. The non-essential amino acid l-glutamine (Gln) has been reported to have an anti-inflammatory activity. Regarding the molecular mechanism of Gln, we have recently shown that Gln effectively inhibits cPLA(2) phosphorylation and activity. OBJECTIVE: To examine whether Gln could suppress allergic contact dermatitis (CD) induced on mouse ears by dinitrophenol fluorobenzene (DNFB). METHODS: Mice were sensitized five times on their ears with a 0.15% solution of DNFB in a 3 day interval. To examine Gln effects, Gln solution (4% in saline) was applied three times a day onto both sides of DNFB-applied ears from the last day of DNFB application. The inflammatory reactions of ears were evaluated by measuring ear thickness and hematoxylin and eosin (H&E) staining. Mouse scratching behavior was objectively evaluated using a MicroAct apparatus. cPLA(2) phosphorylation and activity were analyzed using Western blotting and a cPLA(2) assay kit, respectively. RESULTS: Topical application of Gln significantly attenuated inflammatory symptoms (ear thickness, histological inflammatory skin reactions) as well as itching. Gln inhibited cPLA(2) phosphorylation and enzymatic activity. Arachidonyl trifluoromethyl ketone (AACOCF(3)) inhibited cPLA(2) activity in DNFB-challenged ears and attenuated DNFB-induced ear inflammation and itching. CONCLUSION: The results indicate that Gln suppresses DNFB-induced dermatitis and itching, at least in part, by inhibiting cPLA(2) activity.

Glutamine inhibits platelet-activating factor-mediated pulmonary tumour metastasis.

Inflammation has been increasingly recognised as an important component of tumourigenesis. Platelet-activating factor (PAF), a potent inflammatory mediator, has the ability to enhance tumour growth and metastasis. In this study, we have investigated (i) the role of mitogen-activated protein kinases (MAPKs) and (ii) the therapeutic efficacy of the non-essential amino acid, l-glutamine (Gln), which evidences MAPKs inhibition activity in PAF-mediated B16F10 melanoma metastasis to the lungs. Mice were given intraperitoneal injection of PAF. ERK, JNK, and p38 MAPKs were activated rapidly by PAF in the lungs, and the PAF-induced metastasis of B16F10 was inhibited in a dose-dependent manner by pretreatment with either U0126 (ERK inhibitor), SP600125 (JNK inhibitor), or SB202190 (p38 inhibitor). Intraperitoneal administration of Gln after, but not before, PAF injection deactivated ERK, JNK, and p38 by dephosphorylating them. Gln inhibited PAF-induced metastasis when Gln was administered either intraperitoneally or orally. PAF induced pronounced angiogenic activity in an in vivo mouse Matrigel implantation model. MAPK inhibitors as well as Gln significantly inhibited PAF-induced angiogenesis. These data indicate that Gln exerts a beneficial effect against inflammation-associated enhanced tumour metastasis via the deactivation of MAPKs.

IgG immune complex induces the recruitment of inflammatory cells into the airway and TNF-mediated late airway hyperresponsiveness via NF-κB activation in mice.

BACKGROUND: Many of the inflammatory proteins that are expressed in asthmatic airways are regulated, at least partially, by nuclear factor (NF)-κB. Blockade of NF-κB activity has resulted in attenuation of the cardinal features of asthma. Thus, delineating the mechanisms involved in NF-κB activation in asthma might provide an interesting approach to improving the management of asthma. However, despite its importance, the mechanism for NF-κB activation in asthma has not yet been determined. OBJECTIVE: To examine the role of IgE and IgG antibodies (Abs) in the activation of NF-κB in mouse lungs. METHODS: To examine the effect of IgE, mice underwent intratracheal (i.t.) instillation of an IgE immune complex (IgE-IC) (anti-2,4-dinitrophenyl hapten (DNP) IgE + DNP-BSA or DNP-OVA) and anaphylactogenic anti-IgE (LO-ME-2). For IgG, mice underwent i.t. instillation with a complex of anti-chicken gamma globulin (CGG) IgG1 mAb + CGG. NF-κB activation was determined by gel shift assay. Small interfering RNA was used for blockade of p50 expression. The effect of tumor necrosis factor (TNF) blockade was determined using anti-TNF Ab. A previously established murine model of asthma was used to assess airway hyperresponsiveness (AHR). RESULTS: A single i.t. instillation of either IgE-IC or LO-ME-2 failed to induce activation of NF-κB in the lungs. In contrast, single i.t. instillation of IgG-IC was capable of inducing NF-κB activation, as well as NF-κB-dependent proinflammatory molecules, such as TNF and CXC chemokines. Pretreatment of p50 small interfering RNA decreased bronchoalveolar lavage fluid levels of TNF and macrophage inflammatory protein-2 induced by IgG-IC instillation. Single i.t. instillation of IgG-IC caused the recruitment of neutrophils and macrophages into the airway and TNF-mediated late AHR, but failed to induce Th2 cell-mediated asthmatic phenotypes. CONCLUSION: IgG, but not IgE, is the major Ab that induces not only NF-κB activation and NF-κB-dependent proinflammatory molecules in the lungs but also subsequent recruitment of inflammatory cells into the airway and TNF-mediated late AHR.

Protein kinase CK2/PTEN pathway plays a key role in platelet-activating factor-mediated murine anaphylactic shock.

Platelet-activating factor (PAF) is a major mediator in the induction of fatal hypovolemic shock in murine anaphylaxis. This PAF-mediated effect has been reported to be associated with PI3K/Akt-dependent eNOS-derived NO. The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is phosphatidylinositol phosphate phosphatase, which negatively controls PI3K by dephosphorylating the signaling lipid, phosphatidylinositol 3,4,5-triphosphate. In this study, we examined the possible involvement of PTEN in PAF-mediated anaphylactic shock. Induction of anaphylaxis or PAF injection resulted in a rapid decrease in PTEN activity, followed by increases in PI3K activity and phosphorylation of Akt and eNOS. Systemic administration of adenoviruses carrying PTEN cDNA (adenoviral PTEN), but not the control AdLacZ, not only attenuated anaphylactic symptoms, but also reversed anaphylaxis- or PAF-induced changes in PTEN and PI3K activities, as well as phosphorylation of Akt and eNOS. We found that the decreased PTEN activity was associated with PTEN phosphorylation, the latter effect being prevented by the protein kinase CK2 inhibitor, DMAT. DMAT also inhibited anaphylactic symptoms as well as the anaphylaxis- or PAF-mediated PTEN/PI3K/Akt/eNOS signaling cascade. CK2 activity was increased by PAF. The present data provide, as the key mechanism underlying anaphylactic shock, PAF triggers the upstream pathway CK2/PTEN, which ultimately leads to the activation of PI3K/Akt/eNOS. Therefore, CK2/PTEN may be a potent target in the control of anaphylaxis and other many PAF-mediated pathologic conditions.

Mechanisms of platelet-activating factor-induced enhancement of VEGF expression.

It has been previously reported that platelet-activating factor (PAF) induces the expression of vascular endothelial growth factor (VEGF) via the downregulation of p53 activity. In this study, we attempted to characterize the mechanism by which p53 activity negatively regulates PAF-induced VEGF expression. PAF increased luciferase activity as well as VEGF mRNA expression in human non-small cell lung cancer cell line H1299 transfected with VEGF luciferase reporter plasmid (VEGF-Luc). Cotransfection of the cells with wt p53, but not mutant p53, effected a blockage of PAF-induced VEGF mRNA expression. The ChIP assay revealed that p53 did not bind to the VEGF promoter. Transfection of Egr-1 or Sp-1 expression vector increased VEGF luciferase activity in VEGF-Luc-transfected cells, and this was inhibited by transfection with wt p53. The results of the Immunoprecipitation and immunoblot analysis showed that p53 binds to Egr-1 and Sp-1. Additionally, our electrophoretic mobility shift assay demonstrated that PAF induced the mobilization of Egr-1 and Sp-1 to the nucleus, and this activity was inhibited by transfection with wt p53. These data indicate that PAF inhibits protein complexes between p53 and Egr-1/Sp-1 via the downregulation of p53 levels, thus increasing the free form levels of Egr-1 and Sp-1, ultimately resulting in the transcriptional activation of VEGF.

Cytoplasmic phospholipase A2 metabolites play a critical role in pulmonary tumor metastasis in mice.

BACKGROUND: Cytoplasmic PLA(2) (cPLA2) has been shown to be the major enzyme responsible for arachidonic acid (AA) release. Because of this key role of cPLA(2) in AA production, cPLA(2) involvement in tumorigenesis has been suggested. However, contradictory data are found in the literature. Additionally, little is known regarding the role of cPLA(2) in pulmonary tumor metastasis. MATERIALS AND METHODS: Tumor metastases were detected by lung colonization and angiogenesis was assayed as growth of blood vessels from subcutaneous tissue into an implanted matrigel of basement membrane. The matrix metalloproteinases (MMP)-2, and MMP-9 were detected by PCR with sequence-specific primers. RESULTS: In this study, the effects of inhibitors of cPLA2, 5-lipoxygenase (5-LO), and cyclooxygenase (COX)-2 on pulmonary metastasis formation by B16F10 melanoma cells were investigated. All of these inhibitors reduced B16F10 pulmonary metastasis formation in a dose-dependent manner. Importantly, cPLA2, and 5-LO, and COX-2 inhibitors reduced platelet-activating factor-induced angiogenesis in an in vivo mouse model employing Matrigel injected subcutaneously, and also reduced expression of MMP-2 and MMP-9 in the lungs. CONCLUSION: This study demonstrates that cPLA(2) metabolites play critical roles in tumor metastasis via the promotion, at least in part, of angiogenesis and MMP expression.

Glutamine protects mice from lethal endotoxic shock via a rapid induction of MAPK phosphatase-1.

The nonessential amino acid L-glutamine (Gln) is the most abundant amino acid in plasma. Clinical trials have demonstrated that Gln therapy is safe and improves clinical outcomes in critically ill patients. We have previously shown that Gln protect animals from endotoxic shock through the inhibition of cytosolic phospholipase A(2) activity. In this study, we investigated how Gln regulates MAPK activation, as the molecular mechanism underlying Gln-induced cytosolic phospholipase A(2) inactivation. Gln rapidly (within 10 min) inactivated p38 and JNK, but not ERK, by dephosphorylating them only when these MAPKs were phosphorylated in response to LPS in vivo as well as in vitro. Western blot analysis revealed that Gln administration resulted in rapid ( approximately 5 min) phosphorylation and protein induction of MAP kinase phosphatase-1 (MKP-1). MKP-1 siRNA abrogated the Gln-mediated 1) inactivation of p38 and JNK, 2) induction of MKP-1, and 3) protection against endotoxic shock. The ERK inhibitor U0126 blocked Gln-induced MKP-1 phosphorylation and protein induction, as well as Gln's protective activity against endotoxic shock. These data suggest that Gln exerts a beneficial effect on endotoxic shock by inactivating p38 and JNK via a rapid induction of MKP-1 protein in an ERK-dependent way.

CpG-ODN-based immunotherapy is effective in controlling the growth of metastasized tumor cells.

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs (CpG-ODN) act as potent immune stimulators by activating innate immunity through toll-like receptor 9. These immunomodulatory effects of CpG-ODN have been reported to be associated with anti-tumor immunity. In this study, we used a murine B16F10 melanoma model and a CT26 colon cancer model to assess whether CpG-ODN-based immunotherapy was effective in inhibiting tumor cells that have already metastasized to distant organs. Systemic administration of CpG-ODN after melanoma cell injection resulted in a significant inhibition of pulmonary colonization. When CpG-ODN was administered after tumor cell injection, it also inhibited pulmonary metastasis of the tumor cells, albeit to a lesser degree in the latter case. Systemic administration of CpG-ODN after subcutaneous inoculation of CT26 colon cancer cells diminished pulmonary metastasis from the primary tumor sites. Additionally, CpG-ODN also inhibited the growth of pulmonary colonization of the colon tumor cells when CpG-ODN was administered after the primary tumors had been surgically removed. These data indicate that CpG-ODN was effective in inhibiting pulmonary metastasis of the B16F10 melanoma and CT26 colon cancer cells, as well as the growth of metastasized tumor cells. Our results suggest that CpG-ODN-based immunotherapy may be beneficial in controlling micrometastasis after surgery in clinical settings.