Pulmonary Surfactant Phosphatidylglycerol Inhibits Mycoplasma pneumoniae-stimulated Eicosanoid Production from Human and Mouse Macrophages
ABSTRACT Mycoplasma pneumoniae is a human pathogen causing respiratory infections that are also associated with serious exacerbations of chronic lung diseases.
Membranes and lipoproteins from M. pneumoniae induced a 4-fold increase in arachidonic acid (AA) release from RAW264.7 and a 2-fold increase in AA release from primary
human alveolar macrophages. The bacterial lipoprotein mimic and TLR2/1 agonist Pam3Cys and the TLR2/6 agonist MALP-2 produced
effects similar to those elicited by M. pneumoniae in macrophages by inducing the phosphorylation of p38MAPK and p44/42ERK1/2 MAP kinases and cyclooxygenase-2 (COX-2) expression. M. pneumoniae induced the generation of prostaglandins PGD2 and PGE2 from RAW264.7 cells and thromboxane B2 (TXB2) from human alveolar macrophages. Anti-TLR2 antibody completely abolished M. pneumoniae-induced AA release and TNFα secretion from RAW264.7 cells and human alveolar macrophages. Disruption of the phosphorylation
of p44/42ERK1/2 or inactivation of cytosolic phospholipase A2α (cPLA2α) completely inhibited M. pneumoniae-induced AA release from macrophages. The minor pulmonary surfactant phospholipid, palmitoyl-oleoyl-phosphatidylglycerol (POPG),
antagonized the proinflammatory actions of M. pneumoniae, Pam3Cys, and MALP-2 by reducing the production of AA metabolites from macrophages. The effect of POPG was specific, insofar
as saturated PG, and saturated and unsaturated phosphatidylcholines did not have significant effect on M. pneumoniae-induced AA release. Collectively, these data demonstrate that M. pneumoniae stimulates the production of eicosanoids from macrophages through TLR2, and POPG suppresses this pathogen-induced response.
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- "During the inflammatory response to infection, bacterial products, such as endotoxins and cytokines, rapidly induce upregulation of COX-2 (Smith et al., 2003; Oshima et al., 2011). Several reports have shown that the induction of COX-2 expression participates in the modulation of inflammatory responses following bacterial infection (Goldmann et al., 2010; Toller et al., 2010; Kandasamy et al., 2011). It has been demonstrated that the COX-2 protein expression and urinary PGE 2 production were upregulated in patients with UTIs (Wheeler et al., 2002). "
ABSTRACT: The type 1 fimbriae of uropathogenic Escherichia coli (UPEC) have been described as important for the establishment of bladder infections and urinary tract infections (UTI). Urinary prostaglandin (PG) levels and cyclooxygenase (COX)-2 expression in urine particulates may increase with infectious and inflammatory processes, including UTIs. We investigated the mechanisms underlying the modulation of COX-2 expression through the invasion of type 1 fimbriated UPEC strain J96 (J96-1) in human bladder 5637 cells. Bladder 5637 cells infected with J96-1 induced increases in the expression of COX-2 and secretion of PGE(2) . By using specific inhibitors and short hairpin RNA (shRNA), we have demonstrated that the activation of extracellular signal-related kinase (ERK), c-Jun-NH(2) -terminal kinase (JNK) and p38 MAPK pathways is critical for J96-1-induced COX-2 expression. Luciferase reporters and chromatin immunoprecipitation assays suggest that J96-1 invasion increases NF-κB- and AP-1-DNA-binding activities in 5637 cells. Inhibition of NF-κB and AP-1 activations blocked the J96-1-induced COX-2 promoter activity and expression. The effect of J96-1 on 5637 cell signalling and COX-2 expression is mediated by Toll-like receptor (TLR)-4. In summary, our findings provide the molecular pathways underlying type 1 fimbriated J96-dependent COX-2 expression in 5637 cells, providing insight into the function of UPEC invasion in bladder epithelial cells.Cellular Microbiology 07/2011; 13(11):1703-13. DOI:10.1111/j.1462-5822.2011.01650.x · 4.82 Impact Factor
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ABSTRACT: Influenza A virus (IAV) is a worldwide public health problem causing 500,000 deaths each year. Palmitoyl-oleoyl-phosphatidylglycerol (POPG) is a minor component of pulmonary surfactant, which has recently been reported to exert potent regulatory functions upon the innate immune system. In this article, we demonstrate that POPG acts as a strong antiviral agent against IAV. POPG markedly attenuated IL-8 production and cell death induced by IAV in cultured human bronchial epithelial cells. The lipid also suppressed viral attachment to the plasma membrane and subsequent replication in Madin-Darby canine kidney cells. Two virus strains, H1N1-PR8-IAV and H3N2-IAV, bind to POPG with high affinity, but exhibit only low-affinity interactions with the structurally related lipid, palmitoyl-oleoyl-phosphatidylcholine. Intranasal inoculation of H1N1-PR8-IAV in mice, in the presence of POPG, markedly suppressed the development of inflammatory cell infiltrates, the induction of IFN-γ recovered in bronchoalveolar lavage, and viral titers recovered from the lungs after 5 days of infection. These findings identify supplementary POPG as a potentially important new approach for treatment of IAV infections.American Journal of Respiratory Cell and Molecular Biology 11/2011; 46(4):479-87. DOI:10.1165/rcmb.2011-0194OC · 4.11 Impact Factor
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ABSTRACT: During an inflammatory response, resident and newly recruited tissue macrophages adhere to extracellular matrix and cell-bound integrin ligands. This interaction induces the expression of pro-inflammatory mediators that include matrix metalloproteinases (MMPs). Arhgef1 is an intracellular signaling molecule expressed by myeloid cells that normally attenuates murine macrophage MMP production in vivo and in vitro after cell culture on the extracellular matrix protein, fibronectin. In this study, we have extended the characterization of this fibronectin-induced Arhgef1-regulated signaling pathway in both human and murine myeloid cells. Our results show that MMP9 production by fibronectin-stimulated monocytes and macrophages depends on autocrine thromboxane receptor signaling and that under normal conditions, this signaling pathway is attenuated by Arhgef1. Finally, we show that the expression of ARHGEF1 by human peripheral blood monocytes varies between individuals and inversely correlates with fibronectin-mediated MMP9 production.Journal of Biological Chemistry 11/2011; 286(52):44521-31. DOI:10.1074/jbc.M111.282772 · 4.57 Impact Factor