Drosophila are protected from Pseudomonas aeruginosa lethality by transgenic expression of paraoxonase-1.

Pseudomonas aeruginosa uses quorum sensing, an interbacterial communication system, to regulate gene expression. The signaling molecule N-3-oxododecanoyl homoserine lactone (3OC12-HSL) is thought to play a central role in quorum sensing. Since 3OC12-HSL can be degraded by paraoxonase (PON) family members, we hypothesized that PONs regulate P. aeruginosa virulence in vivo. We chose Drosophila melanogaster as our model organism because it has been shown to be a tractable model for investigating host-pathogen interactions and lacks PONs. By using quorum-sensing-deficient P. aeruginosa, synthetic acyl-HSLs, and transgenic expression of human PON1, we investigated the role of 3OC12-HSL and PON1 on P. aeruginosa virulence. We found that P. aeruginosa virulence in flies was dependent upon 3OC12-HSL. PON1 transgenic flies expressed enzymatically active PON1 and thereby exhibited arylesterase activity and resistance to organophosphate toxicity. Moreover, PON1 flies were protected from P. aeruginosa lethality, and protection was dependent on the lactonase activity of PON1. Our findings show that PON1 can interfere with quorum sensing in vivo and provide insight into what we believe is a novel role for PON1 in the innate immune response to quorum-sensing-dependent pathogens. These results raise intriguing possibilities about human-pathogen interactions, including potential roles for PON1 as a modifier gene and for PON1 protein as a regulator of normal bacterial florae, a link between infection/inflammation and cardiovascular disease, and a potential therapeutic modality.

Inactivation of NADPH oxidase organizer 1 results in severe imbalance.

Otoconia are biominerals of the vestibular system that are indispensable for the perception of gravity. Despite their importance, the process of otoconia genesis is largely unknown. Reactive oxygen species (ROS) have been recognized for their toxic effects in antimicrobial host defense as well as in aging and carcinogenesis. Enzymes evolved for ROS production belong to the recently discovered NADPH oxidase (Nox) enzyme family . Here we show that the inactivation of a regulatory subunit, NADPH oxidase organizer 1 (Noxo1), resulted in the severe balance deficit seen in the spontaneous mutant "head slant" (hslt) mice whose phenotype was rescued by Noxo1 transgenes. Wild-type Noxo1 was expressed in the vestibular and cochlear epithelia and was required for ROS production by an oxidase complex. In contrast, the hslt mutation of Noxo1 was biochemically inactive and led to an arrest of otoconia genesis, characterized by a complete lack of calcium carbonate mineralization and an accumulation of otoconial protein, otoconin-90/95 (OC-90/95). These results suggest that ROS generated by a Noxo1-dependent vestibular oxidase are critical for otoconia formation and may be required for interactions among otoconial components. Noxo1 mutants implicate a constructive developmental role for ROS, in contrast to their previously described toxic effects.