The immunomodulatory Pseudomonas aeruginosa signalling molecule N‐(3‐oxododecanoyl)‐l‐homoserine lactone enters mammalian cells in an unregulated fashion

Abstract

The Pseudomonas aeruginosa quorum-sensing signal molecule N-3-oxododecanoyl)-L-homoserine lactone (OdDHL) has been reported to affect the function of a wide range of mammalian cell types, including cells of the immune system. In T cells, it has been reported to inhibit the production of most cytokines, and it has been reported to inhibit the function of antigen-presenting cells. The intracellular target of OdDHL in these cells remains to be identified, although the lipophilic nature of the molecule suggested that the target could be membrane associated. We explored the association of radiolabelled OdDHL with the membrane and cytoplasm of Jurkat T-cell lines and of primary murine T cells and dendritic cells. We found that not only did 3 H-OdDHL enter the cytoplasm of Jurkat cells without disproportionate association with the cell membrane, it also reached maximum levels in the cytoplasm very quickly, and that the intracellular concentration was proportional to the extracellular concentration. Similar results were obtained when 3 H-OdDHL was incubated with primary murine T cells or cultured dendritic cells. In addition, we show that the cellular distribution of OdDHL does not significantly alter after stimulation of Jurkat cells or primary murine CD4 T cells with immobilized anti-CD3, with little activity being associated with nuclear fractions. Together, these data strongly suggest that OdDHL enters mammalian cells by passive mechanisms, and that it does not preferentially associate with the membrane or nucleus upon T-cell receptor ligation.

Peroxisome Proliferator-Activated Receptors Mediate Host Cell Proinflammatory Responses toPseudomonas aeruginosaAutoinducer

“…Thus, we proposed that a second receptor was associated with the inflammatory response to AHLs. The candidacy of members of the NHR superfamily was supported by our previous data showing that autoinducers can enter and retain functionality in mammalian cells (56) and the recent direct demonstration that radiolabeled 3OC 12 -HSL can be detected in T cells (40). In addition, clear functional similarities exist between LuxR-AHL and NHR-ligand interactions, including the induction of conformational changes in the receptor protein upon ligand binding (3,19).…”

Aquaporins in Infection and Inflammation

“…The P. aeruginosa AHL 3O-C12-HSL can diffuse into cells [153,154] and modulate immune responses [152,155,156]. To further investigate the impact of P. aeruginosa QS on host cells and assess in greater detail the bacteria-host cell communication, we investigated the effects of P. aeruginosa 3O-C12-HSL on cell morphology, area, volume and AQP9 characteristics of human primary macrophages.…”

“…They trigger a diverse set of signaling pathways including MAPK, activation of Rho GTPases that are important in cell migration and the transcription factor NFκB that plays a central role in the expression of pro-inflammatory mediators [4,151,152]. 3O-C12-HSL may interact directly with phospholipids in membranes [153] and when entering the host cell [154], and use the peroxisome proliferator-activated receptor (PPAR) to interfere with NFκB signaling [155,156]. The IQ-motif-containing GTPase-activating protein IQGAP1 was identified as an allegeable target for 3O-C12-HSL [145].…”

Novel Paraoxonase 2-Dependent Mechanism Mediating the Biological Effects of the Pseudomonas aeruginosa Quorum-Sensing Molecule N -(3-Oxo-Dodecanoyl)- l -Homoserine Lactone

“…In sinonasal epithelial cells the taste receptor 2 member 38 (T2R38) mediated a rapid Ca 2ϩ and NO release by 3OC12; however, T2R38 likely only mediates responses in upper respiratory cell types (14). Due to its lipophilicity, 3OC12 rapidly enters mammalian cells (12). In Caco-2 intestinal epithelial cells, 3OC12 was found to alter cell migration, likely via interacting with the IQ-motif-containing GTPase activating protein (IQGAP1) and modulating its signaling (15).…”

“…Conversely, 3OC12 inhibited lipopolysaccharide (LPS) induction of proinflammatory mediators in macrophages, fibroblasts, and epithelial cells and in vivo by repressing nuclear factor -light chain enhancer of activated B-cell (NF-B) signaling (11). In antigen-stimulated T-lymphocytes, 3OC12 inhibits cell proliferation and production of gamma interferon and interleukin-4 (IL-4), critical regulators of immunity (8,12). These diverse responses suggest that 3OC12 acts through multiple, and cell-type-dependent, mechanisms.…”