The Effects Of β-defensin-2, N-acyl Homoserine Lactonases On Chronic Pseudomonas Aeruginosa Lung Infection

Objective:Beta-defensin-2 (BD-2) plays an important role in host defense against pathogenic microbe challenge by its direct antimicrobial activity and immunomodulatory functions. The present study aimed to determine whether genetic up-regulation of rat BD-2 (rBD-2) could ameliorate chronic Pseudomonas aeruginosa lung infection in rats.Methods:Plasmid-encoding rBD-2 was delivered to lungs in vivo using linear polyethylenimine at 48 h before challenging with seaweed alginate beads containing P. aeruginosa. Macroscopic and histopathological changes of the lungs, bacterial loads, inflammatory infiltration, and the levels of cytokines/chemokines [interleukin (IL)-1β, tumor necrosis factor (TNF)-α, kertinocyte-derived chemokine (KC), macrophage inflammatory protein-2 (MIP-2)] were measured at 3 and 7 days post-infection (p.i.).Results:The overexpression of rBD-2 resulted in a significant increase in animal survival rate (at 3 days p.i.), a significant decrease in bacterial loads in the lungs (at 3 and 7 days p.i.), and significantly milder lung pathology. In addition, the overexpression of rBD-2 led to increased infiltration of polymorphonuclear neutrophils (PMN), and elevated protein expression of cytokines/chemokines (IL-1β, TNF-α, KC and MIP-2) at the early stage of infection (at 3 days p.i.), at the same time as being dramatically decreased at the later stage of infection (at 7 days p.i.).Conclusions:Genetic up-regulation of rBD-2 increased animal survival rate, and reduced bacterial loads in lungs after bacterial infection. The overexpression of rBD-2 also modulated the production of several cytokines/chemokines and increased PMN recruitment at the early stage of infection. Our findings indicate that the enhancement of BD-2 may be an efficacious intervention for chronic P. aeruginosa lung infection. Objective:Pseudomonas aeruginosa uses quorum sensing, an interbacterial comm-unication system, to regulate gene expression. The signaling molecule N-3-oxo-dodecanoyl homoserine lactone (3OC12-HSL) is thought to play a central role in quorum sensing. Since 3OC12-HSL can be degraded by paraoxonase-1 (PON1), and PON1 expression protected against Pseudomonas aeruginosa lethality in Drosophila, suggesting that PON1 can interfere with quorum sensing in vivo, we hypothesized that the therapeutic potential of rat PON1 gene transfer in rats with P.aeruginosa-induced lung infection.Methods:Rats intratracheally infected with P.aeruginosa (PAO1) encapsulated in alginate beads were treated with a plasmid encoding PON1 or empty plasmid, which are complexed with linear polyethylenimine (L-PEI) and examined for survival of animals, lung bacterial load, inflammation, cytokine levels up to 3 and 7 days post-infection (p.i.). And rats intratracheally infected flies with a quorum-sensing reporter strain of P. aeruginosa (PAO1-qsc102-lacZ) that expressesβ-galactosidase under control of qsc102, which responds primarily to 3OC12-HSLResults:The overexpression of PON1 was associated with significant reductions in bacterial load and significantly milder lung pathology at 7 days post-infection. In addition, the overexpression of PON 1 led to increased infiltration of polymorphonuclear neutrophils (PMN) at the early stage of infection (at 3 days p.i.), at the same time as being dramatically decreased at the later stage of infection (at 7 days p.i.). And genetic up-regulation of PON 1 had less pronounced significant X-gal staining in rats.Conclusions:Overexpression of PON 1 ameliorates chronic P. aeruginosa lung infection in rats, probably through interfering with quorum sensing in vivo and increasing neutrophil recruitment an the early stage of P. aeruginosa infection. Novel therapeutic interventions aimed at directly regulating quorum sensing or PON activity may show promise for treatment with chronic P. aeruginosa lung infection.