Abstract
Pseudomonas aeruginosa is a Gram-negative bacterium, which causes opportunistic infections in immuno-compromised individuals. Due to its multiple resistances toward antibiotics, the development of new drugs is required. Interfering with Quorum Sensing (QS), a cell-to-cell communication system, has shown to be highly efficient in reducing P. aeruginosa pathogenicity. One of its QS systems employs Pseudomonas Quinolone Signal (PQS) and 4-hydroxy-2-heptylquinoline (HHQ) as signal molecules. Both activate the transcriptional regulator MvfR (Multiple Virulence Factor Regulator), also called PqsR, driving the production of QS molecules as well as toxins and biofilm formation. The aim of this work was to elucidate the effects of QS inhibitors (QSIs), such as MvfR antagonists and PqsBC inhibitors, on the biosynthesis of the MvfR-regulated small molecules 2′-aminoacetophenone (2-AA), dihydroxyquinoline (DHQ), HHQ, PQS, and 4-hydroxy-2-heptylquinoline-N-oxide (HQNO). The employed synthetic MvfR antagonist fully inhibited pqs small molecule formation showing expected sigmoidal dose-response curves for 2-AA, HQNO, HHQ and PQS. Surprisingly, DHQ levels were enhanced at lower antagonist concentrations followed by a full suppression at higher QSI amounts. This particular bi-phasic profile hinted at the accumulation of a biosynthetic intermediate resulting in the observed overproduction of the shunt product DHQ. Additionally, investigations on PqsBC inhibitors showed a reduction of MvfR natural ligands, while increased 2-AA, DHQ and HQNO levels compared to the untreated cells were detected. Moreover, PqsBC inhibitors did not show any significant effect in PA14 pqsC mutant demonstrating their target selectivity. As 2-AA is important for antibacterial tolerance, the QSIs were evaluated in their capability to attenuate persistence. Indeed, persister cells were reduced along with 2-AA inhibition resulting from MvfR antagonism, but not from PqsBC inhibition. In conclusion, antagonizing MvfR using a dosage capable of fully suppressing this QS system will lead to a favorable therapeutic outcome as DHQ overproduction is avoided and bacterial persistence is reduced.
Highlights
Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium able to cause severe chronic infections in immuno-compromised patients, for example in people affected by cystic fibrosis (Gómez and Prince, 2007) or thermally injured individuals (Tredget et al, 2004)
The QS inhibitors (QSIs) evaluated in this study were the most potent developed MvfR antagonist 1 (Starkey et al, 2014), and the two PqsBC
The profiling of P. aeruginosa MvfR antagonist and PqsBC inhibitors emphasized the importance in selecting the target for the development of new anti-infectives, and confirmed that MvfR is an excellent target for a global AQ and 2-anthranilic acid (AA) inhibition
Summary
Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium able to cause severe chronic infections in immuno-compromised patients, for example in people affected by cystic fibrosis (Gómez and Prince, 2007) or thermally injured individuals (Tredget et al, 2004) The eradication of this pathogen with antibiotic treatments is becoming more and more difficult because of its intrinsic and acquired resistance (Hancock and Speert, 2000; Aloush et al, 2006) and tolerance (Mulcahy et al, 2010) toward these drugs. The pqs QS system is selectively expressed by P. aeruginosa and utilizes the signal molecule Pseudomonas Quinolone Signal (PQS) and its precursor 4-hydroxy-2-heptylquinoline (HHQ) for activating the transcriptional regulator MvfR (Multiple Virulence Factor Regulator), called PqsR This protein induces the production of different toxins, such as lectins, pyocyanin, and hydrogen cyanide. It regulates the expression of enzymes needed for the biosynthesis of its natural ligands encoded by the pqsABCDE operon (Xiao et al, 2006) and has been shown to be essential for persister cells development (Que et al, 2013)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
