Pseudomonas aeruginosa fimL regulates multiple virulence functions by intersecting with Vfr-modulated pathways.

Virulence of Pseudomonas aeruginosa involves the co-ordinate expression of a range of factors including type IV pili (tfp), the type III secretion system (TTSS) and quorum sensing. Tfp are required for twitching motility, efficient biofilm formation, and for adhesion and type III secretion (TTS)-mediated damage to mammalian cells. We describe a novel gene (fimL) that is required for tfp biogenesis and function, for TTS and for normal biofilm development in P. aeruginosa. The predicted product of fimL is homologous to the N-terminal domain of ChpA, except that its putative histidine and threonine phosphotransfer sites have been replaced with glutamine. fimL mutants resemble vfr mutants in many aspects including increased autolysis, reduced levels of surface-assembled tfp and diminished production of type III secreted effectors. Expression of vfr in trans can complement fimL mutants. vfr transcription and production is reduced in fimL mutants whereas cAMP levels are unaffected. Deletion and insertion mutants of fimL frequently revert to wild-type phenotypes suggesting that an extragenic suppressor mutation is able to overcome the loss of fimL. vfr transcription and production, as well as cAMP levels, are elevated in these revertants, while Pseudomonas quinolone signal (PQS) production is reduced. These results suggest that the site(s) of spontaneous mutation is in a gene(s) which lies upstream of vfr transcription, cAMP, production, and PQS synthesis. Our studies indicate that Vfr and FimL are components of intersecting pathways that control twitching motility, TTSS and autolysis in P. aeruginosa.

PPAR gamma represses VEGF expression in human endometrial cells: implications for uterine angiogenesis.

UNLABELLED: Endometrial vasculature supports physiological uterine growth, embryonic implantation and endometrial pathology. Vascular endothelial growth factor (VEGF) is regulated by diverse developmental and hormonal signals, including eicosanoid ligands of PPARgamma. The action of natural and synthetic PPARgamma ligands on VEGF expression in primary and transformed human endometrial cell cultures was established by quantifying endogenous gene expression and transfected VEGF gene reporters. VEGF promoter-luciferase constructs were truncated and mutated to map functional sequences. Endometrial tissues and cells express PPARgamma protein. Treatment of transformed and primary endometrial cells with rosiglitazone, a synthetic PPARgamma agonist, or prostaglandin 15-deoxy-Delta12-14 J(2), a naturally occurring eicosanoid ligand, decreased VEGF protein secretion. In transiently transfected Ishikawa cells, rosiglitazone repressed VEGF gene promoter-luciferase activation with an IC(50) approximately approximately 50 nM. Truncated and mutated VEGF promoter constructs revealed that the PPARgamma-regulated domain is a direct repeat (DR)-1 motif -443 bp upstream of the transcriptional start site. CONCLUSIONS: PPARgamma ligands repress VEGF gene expression via a PPARgamma-responsive element (PPRE) in the VEGF gene promoter. Agonists of this nuclear receptor might be exploited pharmacologically to inhibit pathological vascularization in complications of pregnancy, endometriosis and endometrial adenocarcinoma.

Circulating activators of peroxisome proliferator-activated receptors are reduced in preeclamptic pregnancy.

We previously described activators of peroxisome proliferator-activated receptor gamma (PPAR gamma) in the serum of pregnant women. We have also characterized this activating component by using a hexane-extracted serum fraction to examine PPAR activator levels in normal and preeclamptic (PE) pregnancies. In this study we report that the pregnancy PPAR activator is present in similar concentrations in serum and plasma. We also found that the activating fractions from pregnancy sera stimulate not only PPAR gamma, but also PPAR alpha, and are capable of inhibiting the production of inflammatory cytokines, consistent with known PPAR ligands. In experiments comparing extracts from normal and PE patients, we found that extracts from women with severe PE showed a reduced level of PPAR activation compared with extracts from normal pregnant women. This reduction was more pronounced for PPAR gamma than PPAR alpha activation. Finally, this reduction in circulating PPAR activator was observed weeks and sometimes months before the clinical diagnosis of PE. Based on these results, we conclude that PPAR activation is reduced in preeclamptic pregnancy before the onset of maternal symptoms. We speculate that endogenous regulators of PPAR play a role in maternal metabolism and immune function in normal and pathological pregnancies.

Peroxisome proliferator-activated receptor-gamma ligand inhibition of RANTES production by human endometriotic stromal cells is mediated through an upstream promoter element.

OBJECTIVE: To investigate the effect of peroxisome proliferator activated receptor-gamma (PPAR-gamma) ligands on transcription and secretion of regulated upon activation normal T-cell expressed and secreted (RANTES) in endometriotic stromal cells. DESIGN: Controlled laboratory study. SETTING: Academic research laboratory. Women in the follicular phase of the menstrual cycle undergoing laparoscopic resection for endometriosis. [1]. Transient transfection of endometriotic stromal cells with RANTES promoter vectors with and without a mutagenized PPAR-gamma response element (PPRE), then treatment with PPAR-gamma ligands; [2]. co-incubation of cells with PPAR-gamma ligands. MAIN OUTCOME MEASURE(S): RANTES promoter activity and RANTES secretion. In endometriotic stromal cells, addition of PPAR-gamma ligands (rosiglitazone and 15 deoxy-Delta(12,14) prostaglandin J(2)) inhibited RANTES promoter activity by 51% and 50%, respectively. In cells transfected with the same promoter after site-directed mutagenesis of the 5' PPRE, addition of PPAR-gamma ligands failed to inhibit promoter activity. When endometriotic stromal cells were treated with PPAR-gamma ligands, a decrease in RANTES secretion by 51% and 20%, respectively, was observed. CONCLUION(S): The PPAR-gamma ligands inhibit RANTES transcription and protein production in endometriotic stromal cells. Transcriptional repression appears to be mediated through a specific PPRE at -344 to -322 bp upstream from the RNA polymerase start site.