Significantly, LasR is also responsible for the development and maturation of biofilms, which are communities of surface-adherent microbial species implicated in chronic and resistant infections such as burn wounds, pneumonia in cystic fibrosis patients, and periodontitis[4]. == Figure 1. albicans,and represent niches with an active host response. Therefore, we will specifically provide five facts about how theP. aeruginosaQS molecule 3-oxo-dodecanoyl-L-homoserine lactone (3OC12HSL) plays a pivotal role in this triangle of interspecies interactions and how microbial behavior elicited by 3OC12HSL has consequences on host response. Tamsulosin hydrochloride == Quorum Sensing: A Sophisticated Communication System == QS is a system that enables microbes to Tamsulosin hydrochloride monitor population cell density through the production, secretion, and sensing of small diffusible molecules[1]. When such molecules reach a threshold concentration, microbial cells in the vicinity detect the signal and coordinately respond by modifying their gene expression; often these genes are associated with virulence and pathogenesis. Several different types of QS molecules have been described for a wide variety of microbial species. In the Gram-negative pathogenic bacteriumP. aeruginosa, the QS system is perhaps the most complex because several distinct QS sub-systems are hierarchically intertwined at different stages[2](Figure 1). The best-studied of these systems is the LasI/R, which consists of the LasI protein that catalyzes the synthesis of the diffusible molecule 3OC12HSL[3]. Intracellular accumulation of 3OC12HSL is sensed by the receptor LasR and induces expression of several virulence factors, such as exotoxins and proteases, and production of secondary metabolites. Significantly, LasR is also responsible Tamsulosin hydrochloride for the development and maturation of biofilms, which are communities of surface-adherent microbial species implicated in chronic and resistant infections such as burn wounds, pneumonia in cystic fibrosis patients, and periodontitis[4]. == Figure 1. Schematic overview of the complex QS systems present inP. aeruginosa. == The commanders represent the major regulatory systems, while the messengers are the signaling molecules. The soldiers represent the various virulence factors that have a function in the interaction ofP. aeruginosawith the host. == Host Immune Recognition of 3OC12HSL == 3OC12HSL is secreted in considerable amounts byP. aeruginosaduring growth and is therefore readily detected by the host. Several host cell types, including macrophages and epithelial cells, have been shown to respond to synthetic 3OC12HSL, resulting in both a pro- and anti-inflammatory immune-modulatory response[5]. For example, detection of 3OC12HSL by corneal epithelial cells of the eye results in production of the macrophage attractant cytokine IL-6, creating a strong pro-inflammatory response (Figure 2)[6]. Although intercepting and deciphering microbial communication by epithelial and Tamsulosin hydrochloride immune cells could be beneficial for the host, it is important to note that activation of the host immune system could also be beneficial for the pathogen, as over-stimulation of the inflammatory process results in extensive tissue damage. Moreover, 3OC12HSL selectively diminishes the regulation of NF-B signaling and attenuates TLR4-dependent innate immune responses, which potentially promote infection persistence, particularly in cystic fibrosis patients[7]. The production of 3OC12HSL byP. aeruginosaalso suppresses the activation of immune cells and induces apoptosis in macrophages, thereby compromising Tamsulosin hydrochloride host immune defenses. == Figure 2. Effects of 3OC12HSL onP. aeruginosa,S. aureus, andC. albicansthat are relevant to immune recognition. == Lines ending in arrows indicate induction and lines ending in circles indicate inhibition of the indicated process.C. albicans, in the hyphal morphology, induces phagotycosis during inflammation (1). Virulent hyphae can be inhibited and transformed to yeast cells by farnesol, the QS molecule secreted byC. Rabbit polyclonal to AMIGO1 albicans(2).Candidayeast cells prevent macrophages induction (3) and renderC. albicansinvisible for the immune system.C. albicanscoexisting withP. aeruginosaexerts a double-sided reaction; farnesol inhibitsPseudomonasQS production (4), whereas 3OC12HSL secreted byP. aeruginosapreventsC. albicansfilamentation without changing the growth rate (5). 3OC12HSL sensed by the host induces a pro-inflammatory response by activation of macrophages (6), but it can also give an anti-inflammatory reaction by selectively diminishing the regulation of NF-B signaling and attenuating TLR4-dependent innate immune responses (7).P. aeruginosa3OC12HSL influencesS. aureusby inhibiting growth and hemolysin and exotoxin production (8).