Helicobacter pylori-Induced invasion and angiogenesis of gastric cells is mediated by cyclooxygenase-2 induction through TLR2/TLR9 and promoter regulation

A novel mitogen-activated protein kinase phosphatase-1 and glucocorticoid receptor (GR) interacting protein-1-dependent combinatorial mechanism of gene transrepression by GR

Glucocorticoids have major antiinflammatory effects. Because COX-2 is the rate-limiting enzyme for proinflammatory prostaglandins, this study investigated the combinatorial inhibitory role of glucocorticoid receptor (GR) in COX-2 gene induction in macrophages and sought to identify the molecular mechanisms for that inhibition. Glucocorticoid-activated GR repressed COX-2 gene induction by lipopolysaccharide (LPS). Activated GR inhibited LPS-induced activator protein 1 activity, which in turn decreased activating transcription factor 2/c-Jun phosphorylation. The inhibition of MAPK-dependent activating transcription factor 2/c-Jun phosphorylation by GR in COX-2 repression was a result of MAPK phosphatase-1 (MKP-1) induction. Although GR did not inhibit LPS-induced p65 phosphorylation or nuclear factor-kappaB DNA binding activity, deletion of the nuclear factor-kappaB binding site in the COX-2 gene suppressed the ability of glucocorticoid to attenuate COX-2 induction. Chromatin immunoprecipitation and transfection assays revealed that a p65 DNA complex involving GR-bound GR-interacting protein 1 (GRIP1) also contributed to COX-2 repression. Additional knockdown and transfection assays identified other inflammatory genes coordinately regulated by MKP-1 and GRIP1. In summary, activated GR was found to antagonize the LPS-dependent induction of the COX-2 gene via a novel combinatorial mechanism involving MKP-1-mediated activator protein 1 inhibition and GR/GRIP1 recruitment to the p65 DNA complex; moreover, this work facilitated the identification of other GR-responding MKP-1/GRIP1-regulated genes.

Helicobacter pylori and mitogen-activated protein kinases mediate activator protein-1 (AP-1) subcomponent protein expression and DNA-binding activity in gastric epithelial cells

Emerging evidence has suggested a critical role for activator protein-1 (AP)-1 in regulating various cellular functions. The goal of this study was to investigate the effects of Helicobacter pylori and mitogen-activated protein kinases (MAPK) on AP-1 subcomponents expression and AP-1 DNA-binding activity in gastric epithelial cells. We found that H. pylori infection resulted in a time- and dose-dependent increase in the expression of the proteins c-Jun, JunB, JunD, Fra-1, and c-Fos, which make up the major AP-1 DNA-binding proteins in AGS and MKN45 cells, while the expression levels of Fra-2 and FosB remained unchanged. Helicobacter pylori infection and MAPK inhibition altered AP-1 subcomponent protein expression and AP-1 DNA-binding activity, but did not change the overall subcomponent composition. Different clinical isolates of H. pylori showed various abilities to induce AP-1 DNA binding. Mutation of cagA, cagPAI, or vacA, and the nonphosphorylateable CagA mutant (cagA(EPISA)) resulted in less H. pylori-induced AP-1 DNA-binding activity, while mutation of the H. pylori flagella had no effect. extracellular signal-related kinase (ERK), p38, and c-Jun N-terminal kinase (JNK) each selectively regulated AP-1 subcomponent expression and DNA-binding activity. These results provide more insight into how H. pylori and MAPK modulate AP-1 subcomponents in gastric epithelial cells to alter the expression of downstream target genes and affect cellular functions.

The beta1 integrin activates JNK independent of CagA, and JNK activation is required for Helicobacter pylori CagA+-induced motility of gastric cancer cells

The Helicobacter pylori CagA protein is translocated into gastric epithelial cells through a type IV secretion system (TFSS), and published studies suggest CagA is critical for H. pylori-associated carcinogenesis. CagA is thought to be necessary and sufficient to induce the motogenic response observed in response to CagA+ strains, as CagA interacts with proteins involved in adhesion and motility. We report that H. pylori strain 60190 stimulated AGS cell motility through a CagA- and TFSS-dependent mechanism, because strains 60190DeltacagA or 60190DeltacagE (TFSS-defective) did not increase motility. The JNK pathway is critical for H. pylori-dependent cell motility, as inhibition using SP600125 (JNK1/2/3 inhibitor) or a JNK2/3-specific inhibitor blocked motility. JNK mediates H. pylori-induced cell motility by activating paxillin, because JNK inhibition blocked paxillinTyr-118 phosphorylation, and paxillin expression knockdown completely abrogated bacteria-induced motility. Furthermore, JNK and paxillinTyr-118 were activated by 60190DeltacagA but not 60190DeltacagE, demonstrating CagA-independent signaling critical for cell motility. A beta1 integrin-blocking antibody significantly inhibited JNK and paxillinTyr-118 phosphorylation and cell scattering, demonstrating that CagA-independent signaling required for cell motility occurs through beta1. The requirement of both Src and focal adhesion kinase for signaling and motility further suggests the importance of integrin signaling in H. pylori-induced cell motility. Finally, we show that JNK activation occurs independent of known upstream kinases and signaling molecules, including Nod1, Cdc42, Rac1, MKK4, and MKK7, which demonstrates novel signaling leading to JNK activation. We report for the first time that H. pylori mediates CagA-independent signaling that promotes cell motility through the beta1 integrin pathway.

Peptidoglycan and lipopolysaccharide activate PLCgamma2, leading to enhanced cytokine production in macrophages and dendritic cells

In macrophages and monocytes, microbial components trigger the production of pro-inflammatory cytokine through Toll-like receptors (TLRs). Although major TLR signaling pathways are mediated by serine/threonine kinases, including TAK1, IKK and MAP kinases, tyrosine phosphorylation of intracellular proteins by TLR ligands has been suggested in a number of reports. Here, we demonstrated that peptidoglycan (PGN) of a Gram-positive bacterial cell wall component, a TLR2 ligand and lipopoysaccharide (LPS) of a Gram-positive bacterial component, a TLR4 ligand induced tyrosine phosphorylation of phospholipase Cgamma-2 (PLCgamma2), leading to intracellular free Ca2+ mobilization in bone marrow-derived macrophages (BMMphi) and bone marrow-derived dendritic cells (BMDC). PGN- and LPS-induced Ca2+ mobilization was not observed in BMDC from PLCgamma2 knockout mice. Thus, PLCgamma2 is essential for TLR2 and TLR4-mediated Ca2+ flux. In PLCgamma2-knockdown cells, PGN-induced IkappaB-alpha phosphorylation and p38 activation were reduced. Moreover, PLCgamma2 was necessary for the full production of TNF-alpha and IL-6. These data indicate that the PLCgamma2 pathway plays an important role in bacterial ligands-induced activation of macrophages and dendritic cells.

Increased toll-like receptor 9 expression in cervical neoplasia

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) and enable innate immune responses. Although TLR9 has been previously considered to be expressed only in immune cells, there is now increasing evidence that TLR9 expression is present in nonimmune cells as well. In this study, we undertook to determine whether TLR9 expression was associated with disease progression in cervical neoplasia. TLR9 expression was evaluated by immunohistochemistry in 55 formalin-fixed paraffin-embedded cervical tissues; nine normal cervical specimens, 10 low-grade cervical intraepithelial neoplasias (CINs), 12 high-grade CINs, and 24 invasive squamous cell carcinomas (ISCCs). In addition, TLR9 expression was evaluated, at the RNA level, in fresh frozen cervical carcinoma tissues by real-time quantitative RT-PCR. Immunohistochemical staining showed that TLR9 expression was undetectable (55.6%) or weak (44.4%) in normal cervical squamous epithelial tissues, however, variable staining was observed in the basal layer of all normal endocervical glands. TLR9 expression, which was mainly observed as cytoplasmic staining, gradually increased in accordance with the histopathological grade in the following order: low-grade CIN<high-grade CIN<ISCC (P<0.001), and in particular, was moderate to strong in 70% of ISCC cases. Furthermore, real-time quantitative RT-PCR revealed that TLR9 expression, in tumors, was significantly enhanced compared to normal cervical tissues (P=0.012). These results suggest that TLR9 may play a significant role in tumor progression of cervical neoplasia and may represent a useful marker for malignant transformation of cervical squamous cells.

Cyclooxygenase-2 (cox-2) and the inflammogenesis of cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that aberrant induction of COX-2 and up-regulation of the prostaglandin cascade play a significant role in carcinogenesis, and reciprocally, blockade of the process has strong potential for cancer prevention and therapy. Supporting evidence includes the following: [1] expression of constitutive COX-2-catalyzed prostaglandin biosynthesis is induced by most cancer-causing agents including tobacco smoke and its components (polycylic aromatic amines, heterocyclic amines, nitrosamines), essential polyunsaturated fatty acids (unconjugated linoleic acid), mitogens, growth factors, proinflammatory cytokines, microbial agents, tumor promoters, and other epigenetic factors, [2] COX-2 expression is a characteristic feature of all premalignant neoplasms, [3] COX-2 expression is a characteristic feature of all malignant neoplasms, and expression intensifies with stage at detection and cancer progression and metastasis, [4] all essential features of carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis, and immunosuppression) are linked to COX-2-driven prostaglandin (PGE-2) biosynthesis, [5] animal studies show that COX-2 up-regulation (in the absence of genetic mutations) is sufficient to stimulate the transformation of normal cells to invasive cancer and metastatic disease, [6] non-selective COX-2 inhibitors, such as aspirin and ibuprofen, reduce the risk of human cancer and precancerous lesions, and [7] selective COX-2 inhibitors, such as celecoxib, reduce the risk of human cancer and precancerous lesions at all anatomic sites thus far investigated. Results confirming that COX-2 blockade is effective for both cancer prevention and therapy have been tempered by observations that some COX2 inhibitors pose a risk to the cardiovascular system, and more studies are needed in order to determine if certain of these drugs can be taken at dosages that prevent cancer without increasing cardiovascular risk. It is emphasized that the "inflammogenesis model of cancer" is not mutually exclusive and may in fact be synergistic with the accumulation of somatic mutations in tumor suppressor genes and oncogenes or epigenetic factors in the development of cancer.

Characterization of the Effects of Cyclooxygenase-2 Inhibition in the Regulation of Apoptosis in Human Small and Non–Small Cell Lung Cancer Cell Lines

BACKGROUND

Cyclooxygenase-2 enzyme (COX-2) is overexpressed in human non-small cell lung cancer (NSCLC) but is not expressed in small cell lung cancer. Selective COX-2 inhibitors have been shown to induce apoptosis in NSCLC cells, an effect which is associated with the regulation of intracellular MAP kinase (MAPK) signal pathways. Our aims were to characterize the effects of COX-2 inhibition by rofecoxib on apoptosis in human NSCLC and small cell lung cancer cell lines.

METHODS

The human NSCLC cell line NCI-H2126 and small cell lung cancer cell line DMS-79 were used. Constitutive COX-2 protein levels were first determined by Western blot test. Levels of apoptosis were evaluated by using propidium iodide staining on FACScan analysis after incubation of NCI-H2126 and DMS-79 with p38 MAPK inhibitor SB202190 (25 ?microM), NF-kappaB inhibitor SN50 (75 microg/mL), and rofecoxib at 100 and 250 microM. All statistical analysis was performed by analysis of variance.

RESULTS

Western blot test confirmed the presence of COX-2 enzyme in NCI-H2126 and absence in DMS-79. Interestingly, rofecoxib treatment demonstrated a dose-dependent increase in apoptosis in both cell lines. Given this finding, the effect of rofecoxib on NF-kappaB and p38 MAPK pathways was also examined. Apoptosis in both cell lines was unaltered by SN50, either alone or in combination with rofecoxib. A similar phenomenon was observed in NCI-H2126 cells treated with SB202190, either alone or in combination with rofecoxib. In contrast, p38 MAPK inhibition greatly upregulated DMS-79 apoptosis in a manner that was unaltered by the addition of rofecoxib.

CONCLUSIONS

Rofecoxib led to a dose-dependent increase in apoptosis in both tumor cell lines. This effect occurred independently of COX-2, NF-kappaB, and p38 MAPK pathways in DMS-79 cells. As such, rofecoxib must act on alternative pathways to regulate apoptosis in human small cell lung cancer cells.

The Toll‐like receptor 7/8‐ligand resiquimod (R‐848) primes human neutrophils for leukotriene B4, prostaglandin E2and platelet‐activating factor biosynthesis

Toll-like receptors (TLR) recognize pathogen-associated molecular patterns and play important roles in the innate immune system. While single-stranded viral RNA is the natural ligand of TLR7/TLR8, the imidazoquinoline resiquimod (R-848) is recognized as a potent synthetic agonist of TLR7/TLR8. We investigated the effects of TLR7/8 activation on lipid mediator production in polymorphonuclear leukocytes exposed to R-848. Although R-848 had minimal effects by itself, it strongly enhanced leukotriene B4 formation on subsequent stimulation by fMLP, platelet-activating factor, and the ionophore A23187. R-848 acted via TLR8 but not TLR7 as shown by the lack of effect of the TLR7-specific ligand imiquimod. Priming with R-848 also resulted in enhanced arachidonic acid release and platelet-activating factor formation following fMLP stimulation, as well as enhanced prostaglandin E2 synthesis following the addition of arachidonic acid. Western blot analysis demonstrated that R-848 induced the phosphorylation of the cytosolic phospholipase A2alpha, promoted 5-lipoxygenase translocation and potently stimulated the expression of the type 2 cyclooxygenase. Bafilomycin A1, an inhibitor of endosomal acidification, efficiently inhibited all R-848-induced effects. These studies demonstrate that TLR8 signaling strongly promotes inflammatory lipid mediator biosynthesis and provide novel insights on innate immune response to viral infections.

Pathogenesis of Helicobacter pylori infection

Much interest has been shown in the relationship between Helicobacter pylori infection and gastric carcinogenesis. It is becoming clearer that H. pylori strains carrying a functional cag pathogenicity island (cagPAI), which encodes the type IV secretion system (TFSS) and its effector CagA, play an important role in the development of gastric carcinoma. Furthermore, genetic polymorphism present in the cagA gene appears to influence the degree of an individual cagPAI-positive H. pylori to elicit gastric mucosal lesions, and this process is significantly affected by host genetic polymorphisms such as proinflammatory cytokine gene polymorphisms. Pathomechanism of gastric carcinogenesis associated with H. pylori includes bacteria-host interaction leading to morphologic alterations such as atrophic gastritis and gastrointestinal metaplasia mediated by COX-2 overexpression, cancer cell invasion, and neo-angiogenesis via TLR2/TLR9 system and transcription factors (e.g., NF-kappaB) activation. In addition, H. pylori infection triggers adhesion molecule expression and activity and produces an enhancement in oxidative stress interacting with gastric production of appetite hormone ghrelin and nonsteroidal anti-inflammatory drugs.

Toll-like receptor 9 agonists promote cellular invasion by increasing matrix metalloproteinase activity

Toll-like receptor 9 (TLR9) recognizes microbial DNA. We show here that TLR9 protein is expressed in human breast cancer cells and clinical breast cancer samples. Stimulation of TLR9-expressing breast cancer cells with the TLR9 agonistic CpG oligonucleotides (1-10 mumol/L) dramatically increased their in vitro invasion in both Matrigel assays and three-dimensional collagen cultures. Similar effects on invasion were seen in TLR9-expressing astrocytoma and glioblastoma cells and in the immortalized human breast epithelial cell line MCF-10A. This effect was not, however, dependent on the CpG content of the TLR9 ligands because the non-CpG oligonucleotides induced invasion of TLR9-expressing cells. CpG or non-CpG oligonucleotide-induced invasion in MDA-MB-231 cells was blunted by chloroquine and they did not induce invasion of TLR9(-) breast cancer cells. Treatment of MDA-MB-231 cells with CpG or non-CpG oligonucleotides induced the formation of approximately 50-kDa gelatinolytic band in zymograms. This band and the increased invasion were abolished by a matrix metalloproteinase (MMP) inhibitor GM6001 but not by a serine proteinase inhibitor aprotinin. Furthermore, CpG oligonucleotide treatment decreased tissue inhibitor of metalloproteinase-3 expression and increased levels of active MMP-13 in TLR9-expressing but not TLR9(-) breast cancer cells without affecting MMP-8. Neutralizing anti-MMP-13 antibodies inhibited the CpG oligonucleotide-induced invasion. These findings suggest that infections may promote cancer progression through a novel TLR9-mediated mechanism. They also propose a new molecular target for cancer therapy, because TLR9 has not been associated with cancer invasiveness previously.

Balance between polyoma enhancing activator 3 and activator protein 1 regulates Helicobacter pylori-stimulated matrix metalloproteinase 1 expression

Helicobacter pylori infection and elevated expression of tissue matrix metalloproteinase 1 (MMP-1) are both associated with gastric cancer. We investigated the regulation of MMP-1 expression during H. pylori infection. Real-time reverse transcription-PCR was used to examine mucosal MMP-1 mRNA levels in 55 patients with gastric cancers and 61 control patients. Increased MMP-1 mRNA levels in the gastric mucosa and epithelial cells were observed in H. pylori infections in which both the cag pathogenicity island (PAI) and outer inflammatory protein A (OipA) were expressed. The combined induction of c-fos, c-jun, and polyoma enhancing activator-3 (pea-3) by H. pylori caused maximal increase in MMP-1 expression. Activation of the MMP-1 promoter by H. pylori involved occupation of the activator protein 1 (AP-1) sites at -72 and -181 and, surprisingly, vacancy of the -88 PEA-3 site. Electrophoretic mobility shift, supershift, and chromatin immunoprecipitation assays showed increased binding of c-Fos and c-Jun to the -72 and -181 AP-1 sites during H. pylori infection. Importantly, during wild-type H. pylori infection, we detected increased PEA-3 binding to the -72AP-1 site and decreased PEA-3 binding to the -88 PEA-3 site. However, during infection with the cag PAI and oipA mutants, PEA-3 binding to the -88 site was detected. MMP-1 and pea-3 activities are increased in gastric cancers. Maximal activation of MMP-1 transcription requires the cag PAI and OipA, which regulate AP-1 and PEA-3 binding. Thus, cag PAI and OipA provide a possible link between bacterial virulence factors and important host factors related to disease pathogenesis.

Mechanisms for Helicobacter pylori CagA-induced cyclin D1 expression that affect cell cycle

Particular Helicobacter pylori genotypes differentially induce epithelial cell proliferation, but the mechanisms are not characterized. We explored the effect of H. pylori CagA on expression of cyclin D1, an important cell cycle regulator. H. pylori-induced cell survival and cyclin D1 expression were attenuated in a cagA mutant. AP1 and cAMP response element (CRE), but not NF-kappaB, were involved in the induced cyclin D1 expression. Diminished mitogen-activated protein kinase (MAPK) activation, especially involving p38, with downstream effects on AP1 and CRE activation, was observed for the cagA mutant. In total, these data show that cagA+ H. pylori strains are enhanced in their ability to activate MAPKs and downstream transcription factors, increasing cyclin D1 expression, G1-S phase progression, and host cell survival, explaining both the preferential survival of affected host cells, and the enhanced oncogenesis by these bacteria.