Development of Alginate Biosynthesis Inhibitors and Identification of their Targets

ABSTRACT Pseudomonas aeruginosa is a bacterial pathogen that is associated with a decline in lung function in cystic fibrosis (CF) patients. The airways of a majority CF patients are colonized by P. aeruginosa which often lead to a life-long colonization with the same initial strain Over the course of this chronic, lifelong infection, P. aeruginosa undergoes a slow rate of mutation that eventually leads to mutation of the mutS gene that is responsible for DNA repair of replication errors. As a consequence of this increased rate of mutagenesis, the mucA gene encoding for the AlgT/AlgU antisigma factor can be mutated. The result is the constitutive activation of the AlgT/AlgU sigma factor that leads to activation of the algD-A operon that encodes the alginate biosynthetic machinery. This “mucoid conversion” event is associated with a decline in airway function, morbidity and mortality. The lifelong infection of CF patients indicate both failure with current therapeutics and difficulty in the development of treatment options, particularly against mucoid P. aeruginosa. One approach to eliminate alginate production by mucoid P. aeruginosa is to restore MucA expression. This is problematic since any bacterium that is made wild-type will become susceptible to antibiotic treatment and eliminated from the population. Thus, an alternative approach is required to prevent the function of the alginate biosynthetic complex. We have exciting preliminary data showing that ebselen (Eb) and ebselen oxide (EbO) can effectively block alginate production by P. aeruginosa. Eb is a lead compound that has been previously demonstrated to be safe for human use through testing in several Phase III clinical trials. In this proposal, we have formed a collaborative team between Dr. Sylvie Garneau-Tsodikova at University of Kentucky who is an expert in the synthesis of Eb/EbO analogues and Dr. Vincent Lee at University of Maryland who has expertise in P. aeruginosa. Together, we seek to: (1) utilize medicinal chemistry approach to optimize Eb/EbO for alginate inhibition by structure-activity relationship studies and (2) identify the target of inhibition for Eb and EbO. These two synergistic aims will aid the development of potent alginate inhibitors through an iterative process that can be used for future clinical studies.