Inhibition of quorum sensing-controlled virulence factors in Pseudomonas aeruginosa by human serum paraoxonase

Abstract

The role of quorum sensing (QS) in the regulation of virulence factor production in Pseudomonas aeruginosa is well established. Increased antibiotic resistance in this bacterium has led to the search for new treatment options, and inhibition of the QS system has been explored for potential therapeutic benefits. If the use of QS inhibitory agents were to lead to a reduction in bacterial virulence, new approaches in the treatment of P. aeruginosa infections could be further developed. Accordingly, we examined whether human serum paraoxonase 1 (hPON1), which uses lactonase activity to hydrolyse N-acyl homoserine lactones, could cleave P. aeruginosa-derived signalling molecules. hPON1 was purified using ammonium sulfate precipitation and hydrophobic interaction chromatography (Sepharose 4B-L-tyrosine-1-naphthylamine). Different concentrations of hPON1 were found to reduce various virulence factors including pyocyanin, rhamnolipid, elastase, staphylolytic LasA protease and alkaline protease. Although treatment with 0.1-10 mg hPON1 ml 21 did not show a highly inhibitory effect on elastase and staphylolytic LasA protease production, it resulted in good inhibitory effects on alkaline protease production at concentrations as low as 0.1 mg ml 21. hPON1 also reduced the production of pyocyanin and rhamnolipid at a concentration of 1.25 mg ml 21(within a range of 0.312-5 mg ml 21). In addition, rhamnolipid, an effective biosurfactant reported to stimulate the biodegradation of hydrocarbons, was able to degrade oil only in the absence of hPON1. INTRODUCTIONQuorum sensing (QS) is a process of bacterial communication used to collectively control group behaviours (Ng & Bassler, 2009;Rutherford & Bassler, 2012). Pseudomonas aeruginosa perceives its local population density using a QS system: as the concentration of the signalling molecules passes a given threshold, the bacteria regulate production of certain virulence factors. To orchestrate the synchronous production of virulence factors, P. aeruginosa relies on two major LuxI/R QS systems: the Las and Rhl systems (Pesci et al., 1997;Schuster et al., 2003). The LuxI homologues LasI and RhlI are responsible for synthesis of the Las and Rhl signals, N-(3-oxododecanoyl)-L-homoserine lactone (PAI1) and N-butanoyl-L-homoserine lactone (PAI2), respectively. PAI1 activates the LuxR-type transcription factor LasR, and, in turn, LasR-PAI1 induces the production of LasB elastase, LasA protease, alkaline protease and LasRI (Gambello et al., , 1993Seed et al., 1995). PAI2 cooperates with the cognate regulator RhlR to enhance the production of rhamnolipid, pyocyanin and LasB elastase (Latifi et al., 1995;Pearson et al., 1995). Expression of many of the virulence factors in P. aeruginosa is controlled by the QS system (Venturi, 2006). Different strains of P. aeruginosa secrete several extracellular proteolytic enzymes that have been implicated as virulence factors. These enzymes include protease IV, alkaline protease, and LasA and LasB elastases (Caballero et al., 2001). These proteases pr...

Pitfalls associated with evaluating enzymatic quorum quenching activity: the case of MomL and its effect onPseudomonas aeruginosaandAcinetobacter baumanniibiofilms

“…The biofilm-forming ability of an abaI mutant was reduced by around 40% compared to the corresponding wildtype strain (Niu et al, 2008). Compared to the extensive literature on inhibiting QS pathways and virulence in P. aeruginosa (Aybey & Demirkan, 2016; Furiga et al, 2016; Hentzer et al, 2003; O’Loughlin et al, 2013; Yin et al, 2015), there are fewer reports on inhibiting QS and biofilm formation in A. baumannii (Bhargava et al, 2015; Chow et al, 2014; Saroj & Rather, 2013). …”

Methanolic Extract of Plectranthus tenuiflorus Attenuates Quorum Sensing Mediated Virulence and Biofilm Formation in Pseudomonas aeruginosa PAO1

“…The pyocyanin containing chloroform phase (blue organic phase) was reextracted with 0.2 M HCl. The absorbance of the upper aqueous layer was determined at 520 nm 12 . The ablity of P. tenuiflorus extract on Staphylolytic activity of P. aeruginosa PAO1 was examined as per the standard protocol 13 .…”

Rhamnolipids fromPseudomonas aeruginosaDisperse the Biofilms of Sulfate-Reducing Bacteria

“…To determine mechanisms behind these strong dispersal results, we hypothesized that the compounds in the P. aeruginosa supernatant may be related to QS since PA14 is the best known strain for QS, and QS controls extracellular compounds like protease 24 and rhamnolipids 24 . Hence, we tested the supernatant of mutants related to QS as well as those related to virulence factors (e.g., lasI 25 , lasB 26 , pelA 27 , phzM 28 , phzS 28 , pvdF 29 , pchE 30 , lecA 31 , toxA 32 , 70 sodM 33 , rhlI 34 , rhlR 34 ).…”