Platelet-activating factor increases the expression of metalloproteinase-9 in human bronchial epithelial cells

Ceramide induces MMP-9 expression through JAK2/STAT3 pathway in airway epithelium

BACKGROUND

Ceramide, a bioactive lipid, plays an essential role in the development of several pulmonary inflammatory diseases. Matrix metallopeptidase 9 (MMP-9) regulates the synthesis and degradation of extracellular matrix, and is associated with airway remodeling and tissue injury. This study was conducted to investigate the effects and underlying mechanisms of ceramide on MMP-9 expression in airway epithelium.

METHODS

BEAS-2B cells, normal human bronchial epithelium cell lines, were pretreated with AG490, a selective janus tyrosine kinase 2 (JAK2) inhibitor, or Stattic, a selective signal transducer and activator of transcription 3 (STAT3) inhibitor. The cells were then stimulated with C6-ceramide. The levels of MMP-9 were determined by ELISA and real-time quantitative PCR (RT-qPCR). JAK2, phosphorylated JAK2 (p-JAK2), STAT3, and phosphorylated STAT3 (p-STAT3) expression was examined by Western blotting. BALB/c mice were pretreated with AG490 or Stattic before intratracheally instillated with C6-ceramide. Pathological changes in lung tissues were examined by Hematoxylin and Eosin staining, Periodic-acid Schiff staining, and Masson's trichrome staining. MMP-9, JAK2, p-JAK2, STAT3, and p-STAT3 expression in the lung tissues was examined by Western blotting.

RESULTS

The expression of MMP-9, p-JAK2 and p-STAT3 in BEAS-2B cells was significantly increased after the treatment of C6-ceramide. Furthermore, the increased expression of MMP-9 induced by C6-ceramide was inhibited by AG490 and Stattic. Similar results were obtained in the lung tissues of C6-ceramide-exposed mice which were treated with AG490 or Stattic.

CONCLUSIONS

Ceramide could up-regulate MMP-9 expression through the activation of the JAK2/STAT3 pathway in airway epithelium. Targeted modulation of the ceramide signaling pathway may offer a potential therapeutic approach for inhibiting MMP-9 expression. This study points to a potentially novel approach to alleviating airway remodeling in inflammatory airway diseases.

Platelet activating factor as a mediator and therapeutic approach in bronchial asthma

Platelet activating factor (PAF) is a potent phospholipid mediator involved in anaphylaxis and chronic inflammatory disorders, including bronchial asthma. PAF is able to act both, directly as a chemotactic factor and indirectly through the release of other inflammatory agents. Apart from its known potent ability to activate platelets, PAF influences other immune and inflammatory cells function involved in asthma, which may be of importance in the pathogenesis of the disease. In addition, PAF administration can mimic some of abnormalities observed in asthma, including bronchoconstriction, bronchial hyper responsiveness, and gas exchange impairment, which may be mediated by leukotrienes acting as secondary mediators of some PAF effects. Therefore, there has been an extensive interest in the role of PAF in human asthma and major efforts have been continued to discover drugs acting thorough inhibition of PAF effects in the disease. Surprisingly, PAF receptor antagonists have not clearly proven their clinical benefits. It may appear that the combined blockage of PAF effects and other mediators involved in asthma is a way to improve clinical efficacy and also an interesting approach to control inflammation in the disease. This review will focus on two main issues: the role of PAF and PAF antagonists in asthma.

Critical role for matrix metalloproteinase-9 in platelet-activating factor-induced experimental tumor metastasis

In this study, the roles of matrix metalloproteinase (MMP)-2 and MMP-9 in platelet-activating factor (PAF)-induced experimental pulmonary metastasis of the murine melanoma cell, B16F10, were investigated. An injection of PAF resulted in increases in mRNA expression, protein levels and the activities of both MMP-2 and MMP-9 in the lungs. The overall expression of MMP-9 was stronger than that of MMP-2. The increased MMP-9 expression was inhibited by both NF-kappaB and AP-1 inhibitors, whereas the increased MMP-2 expression was inhibited by only AP-1 inhibitors. Immunohistochemical analysis revealed that MMP-9 was expressed in bronchial epithelial cells as well as in the walls of blood vessels, whereas MMP-2 expression was observed only in bronchial epithelial cells. PAF significantly enhanced the pulmonary metastasis of B16F10, which was inhibited by both NF-kappaB and c-jun inhibitors. MMP-9 inhibitor, but not that of MMP-2, completely inhibited PAF-induced B16F10 metastasis. These data indicate that MMP-9, the expression of which was regulated by NF-kappaB and AP-1, plays a critical role in PAF-induced enhancement of pulmonary melanoma metastasis.

The Genetic Basis of Abdominal Aortic Aneurysms: A Review

INTRODUCTION

The pathogenesis of abdominal aortic aneurysm (AAA) remains poorly understood, however significant evidence has emerged in recent years to suggest a chronic inflammatory process. Observational studies have highlighted a familial trend towards AAA development among relatives of affected individuals and it is thought that inflammatory genes may influence an individual's susceptibility. Conflicting reports exist over single gene versus multiple gene inheritance patterns in addition to a collection of studies examining individual inflammatory genes. This paper reviews the evidence for a genetic predisposition to aneurysm formation including familial and segregation studies in addition to experimental evidence investigating specific candidate genes.

METHOD

Medline and Pubmed database searches were conducted using the search terms abdominal aortic aneurysm and gene. Papers were reviewed and references manually searched for further relevant publications which were added to the data. Papers were categorised under the headings familial, segregation and candidate gene studies.

RESULTS

A review of 58 papers is presented under sub-headings as above. In the case of the candidate gene section, a brief report of the functional relevance of each gene is included.

CONCLUSION

A summary of the evidence presented is given and the direction of future work in this field is briefly considered.

Inflammatory responses involving tumor necrosis factor receptor-associated factor 6 contribute to in-stent lesion formation in a stent implantation model of rabbit carotid artery

OBJECTIVE

Inflammatory responses are considered to represent a unique property after stent implantation, and we previously demonstrated that inflammatory signaling involving tumor necrosis factor receptor-associated factor 6 (TRAF6) contributes to neointimal formation in a balloon injury model of rabbit carotid artery. The purpose of this study was to examine the role of TRAF6 in in-stent lesion formation after stent implantation in the rabbit carotid artery.

METHODS

Rabbit carotid arteries were injured with a 2F Fogarty catheter, and 28 days later, the same arteries were implanted with a 3-mm-diameter Palmaz-Schatz stent. A dominant negative (DN) form of TRAF6 (pME-FLAG-T6deltaRZ5) was then transferred using a plasmid-based electroporation method. Its effects were evaluated compared with the findings in arteries treated with control plasmid (pME-FLAG).

RESULTS

Immunostaining with anti-FLAG tag antibody showed that an expression plasmid vector containing the DN-TRAF6 sequence was successfully transferred to the arterial intima and media. Morphometric analyses revealed that the increase of intimal area in in-stent lesions was significantly inhibited by DN-TRAF6 14 days after stent implantation (DN-TRAF6 group, 3.01 +/- 0.25 x 10(5) microm2 vs control group, 4.25 +/- 0.23 x 10(5) microm2, P < .01), and the cell density was increased compared with that in the control group. In the DN-TRAF6 plasmid-treated vessels, cell replication was prevented in both the intima and media, and fewer leukocytes adhered to the luminal surface. Moreover, DN-TRAF6 suppressed macrophage infiltration, activation of proteases, and proteoglycan accumulation in the in-stent intima.

CONCLUSIONS

These findings suggest that TRAF6 plays an important role in cell replication, inflammatory cell infiltration, protease activity, and extracellular matrix accumulation that contributes to in-stent lesion development.

Platelet-activating factor induces matrix metalloproteinase-9 expression through Ca2+- or PI3K-dependent signaling pathway in a human vascular endothelial cell line

Platelet-activating factor (PAF) augments angiogenesis by promoting the synthesis of a variety of angiogenic factors, via the nuclear factor (NF)-kappaB activation. Recently, we reported that PAF upregulates MMP-9 expression in a NF-kappaB-dependent manner. In this study, we investigated the signaling pathway involved in PAF-induced MMP-9 expression in ECV304 cells. Our current data indicate that the Ca(2+)- or phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathway is necessary for PAF-induced MMP-9 expression. Furthermore, PAF-induced NF-kappaB activation was blocked by selective inhibitors of Ca(2+), PI3K, or extracellular signal-regulated kinase (ERK). Our results suggest that PAF-induced MMP-9 expression, in a NF-kappaB-dependent manner, is regulated by Ca(2+), PI3K and ERK signaling pathways.

Involvement of matrix metalloproteinase-9 in platelet-activating factor-induced angiogenesis

Platelet-activating factor (PAF) augments angiogenesis by promoting the synthesis of various angiogenic factors, via the activation of NF-kappaB. In this study, we investigated the role of the matrix metalloproteinase (MMP)-9, in PAF-induced angiogenesis. PAF increased mRNA expression, protein synthesis, and MMP-9 activity in ECV304 cells, in a NF-kappaB-dependent manner. PAF increased MMP-9 promoter activity in ECV304, which was inhibited by WEB2107, and NF-kappaB inhibitors. Transfected NF-kappaB subunits, p65 or/and p50, increased luciferase activity in the reporter plasmid MMP-9, resulting in an increase not only of MMP-9 luciferase activity, but also of mRNA expression in MMP-9. MMP-9 or NF-kappaB inhibitors significantly inhibited PAF-induced angiogenesis, in a dose-dependent manner, in an in vivo mouse Matrigel implantation model. In a parallel to the Matrigel implantation study, MMP-9 or NF-kappaB inhibitors inhibited PAF-induced sprouting of porcine pulmonary arterial endothelial cells. These data indicate that NF-kappaB-dependent MMP-9 plays a key role in PAF-induced angiogenesis.

Cell replication induces in-stent lesion growth in rabbit carotid artery with preexisting intimal hyperplasia

This study examined the responses of rabbit carotid artery with a preexisting intimal lesion, to stent implantation and balloon dilation. Rabbit carotid arteries were injured with a Fogarty catheter, and 28 days later the same arteries were subjected to implantation of a Palmaz-Schatz stent or balloon dilation angioplasty. Intimal size was significantly increased after stent implantation and balloon dilation, and no significant difference was detected between the two procedures. After stent implantation, replicating intimal cells were increased mainly in the inner intima, and the increase of cell replication was prolonged until day 28. In contrast, a significant increase of intimal cell replication was detected only at 2 days after balloon dilation. Intimal cell number after stent implantation was significantly higher than that after balloon dilation from day 7. Abundant leukocytes adhered to the luminal surface until 14 days after stent implantation, and significant infiltration of macrophages was observed in the mid-intima. Activation of proteases was prolonged, and obvious accumulation of proteoglycans was detected after stent implantation as compared with balloon dilation. These findings suggest that, an increase in cell replication is critical in the development of in-stent restenosis, and that inflammatory responses represent a unique property after stent implantation.

Association of a G994 -->T missense mutation in the plasma platelet-activating factor acetylhydrolase gene with risk of abdominal aortic aneurysm in Japanese

OBJECTIVE

To investigate a possible association with plasma platelet activating factor acetylhydrolase (PAF-AH) gene mutation with the risk of abdominal aortic aneurysm (AAA).

SUMMARY BACKGROUND DATA

Plasma platelet activating factor acetylhydrolase is known to catalyze platelet activating factor (PAF), thereby inactivating its inflammatory function. Deficiency of this enzyme is caused by a missense mutation (G994 -->T) in exon 9 of the plasma PAF-AH gene.

METHODS

We did a case-control study including 131 patients (median age 73.4 [range 50-84] years) and 106 controls matched for age and sex. Genomic DNA was analyzed for the mutant allele by a specific polymerase-chain reaction. Plasma PAF-AH activity was measured in both groups.

RESULTS

The frequency of the mutant allele (T allele) in the plasma PAF-AH gene in AAA patients was significantly higher than in control subjects. The association of the missense mutation with AAA was statistically significant and independent of other risk factors. Among AAA patients with normal genomic type, plasma PAF-AH activity was strongly correlated to the plasma concentration of low density lipoprotein cholesterol (LDL-C), while the correlation was not observed among AAA patients with heterozygotes genotype. Patients having AAA with both T allele and hyperlipidemia were more likely to have other atherosclerotic diseases such as ischemic heart disease, stroke and peripheral arterial occlusive diseases than patients with the normal genomic type and normal lipid level.

CONCLUSIONS

The genetic mutation of plasma PAF-AH gene appear to be an independent risk factor for AAA. Our findings need to be confirmed in a larger, prospective study including patients from different populations.

Induction of MMP-9 in normal human bronchial epithelial cells by TNF-alpha via NF-kappa B-mediated pathway

In this study, we determined whether the proinflammatory cytokines tumor necrosis factor (TNF)-alpha and interleukin-1 beta contribute to the regulation of matrix metalloproteinase (MMP)-9 in human bronchial epithelial cells and whether the induction of MMP-9 is regulated by the transcription factor nuclear factor (NF)-kappa B. We demonstrated that TNF-alpha induced MMP-9 at both the protein and mRNA levels in human bronchial epithelial cells and that interleukin-1 beta did not. In contrast, induction of the tissue inhibitor of metalloproteinase-1 by TNF-alpha was less than that of interleukin-1 beta. Increased expression of MMP-9 and NF-kappa B activation induced by TNF-alpha were inhibited by pyrrolidine dithiocarbamate and N-acetyl-L-cysteine but were not inhibited by curcumin. These results suggest that TNF-alpha induces the expression of MMP-9 in human bronchial epithelial cells and that this induction is mediated via the NF-kappa B-mediated pathway.