Evaluation of Small Molecule Inhibitors of Pseudomonas Virulence factor LasB as Non-Traditional Immunotherapeutics.

Pseudomonas aeruginosa can cause severe opportunistic pulmonary infections associated with mechanical ventilation and the genetic disease cystic fibrosis. Due to its multidrug resistance, it is a priority pathogen for therapeutic development. Inflammation during such infections, which causes destruction of lung architecture and function, is activated in part through the maturation of IL-1β by the virulence factor LasB. Previous results in mouse models suggest that matrix metalloprotease inhibitor drugs also inhibit LasB, preventing cell death and inflammation caused by caused by P. aeruginosa. We hypothesized that other inhibitors of matrix metalloproteases, including tetracycline-family antibiotics, could be used to target LasB. We evaluated small molecule inhibitors against LasB activation during infections of macrophages, neutrophils, and monocytes and the synergy of these inhibitors with conventional antibiotics and anti-inflammatories. We first optimized the drug concentration by testing the ability of the various drugs to inhibit LasB at various dilutions. Using an effective concentration, we then infected the various cell types with P. aeruginosa and analyzed the impact of the inhibitors on cell death and maturation of IL-1β in infected cells. The results indicate that several tetracycline-family compounds inhibit LasB during P. aeruginosa infections and decrease cell death. This was true for compounds that had no antimicrobial activity yet still inhibited LasB. In addition, the results suggest that the drugs target different cell types. Together, we find that tetracyclines may have therapeutic benefits, even against resistant bacteria, due to their ability to decrease inflammation. This may serve as an effective adjunctive therapy during infection to limit tissue damage and give the immune system and antibiotics more time to respond.