Panton-Valentine leukocidin (PVL) and other S. aureus β-stranded pore-forming toxins are important virulence factors involved in various but often necrotizing pathologies. This study characterized leukotoxin inhibition by selected para-sulfonato-calix[n]arenes (SCn): SC4, SC6 and SC8. These chemicals have no toxic effects on human erythrocytes or neutrophils, and some are able to inhibit both activity and cell lysis by leukotoxins in a dose-dependent manner. Depending on leukotoxins and SCn, flow cytometry revealed IC50 values between 6-22 µM for Ca2+-activation and between 2-50 µM for cell lysis. SCn were observed to affect membrane binding of class S proteins responsible for cell specificity. Electrospray Mass Spectrometry and Surface Plasmon Resonance established supramolecular interactions (1:1 stoichiometry) between SCn and class S proteins in solution, but not class F proteins. The membrane binding affinity of S proteins ranged from KD = 0.07-6.2 nM. The binding ability was completely abolished by SCn at concentrations according to the number of benzenes (30-300 µM; SC8 < SC6 << SC4). The inhibitory properties of SCn were also observed in vivo in a rabbit model of PVL-induced endophthalmitis. These calixarenes may represent new therapeutic avenues aimed at minimizing inflammatory reactions and necrosis due to certain virulence factors.
para-sulfonato-calix[n]arenes inhibit staphylococcal bicomponent leukotoxins by supramolecular interactions.
Potrich, Cristina;Viero, Gabriella;Antonini, Valeria;Dalla Serra, Mauro;
2013-01-01
Abstract
Panton-Valentine leukocidin (PVL) and other S. aureus β-stranded pore-forming toxins are important virulence factors involved in various but often necrotizing pathologies. This study characterized leukotoxin inhibition by selected para-sulfonato-calix[n]arenes (SCn): SC4, SC6 and SC8. These chemicals have no toxic effects on human erythrocytes or neutrophils, and some are able to inhibit both activity and cell lysis by leukotoxins in a dose-dependent manner. Depending on leukotoxins and SCn, flow cytometry revealed IC50 values between 6-22 µM for Ca2+-activation and between 2-50 µM for cell lysis. SCn were observed to affect membrane binding of class S proteins responsible for cell specificity. Electrospray Mass Spectrometry and Surface Plasmon Resonance established supramolecular interactions (1:1 stoichiometry) between SCn and class S proteins in solution, but not class F proteins. The membrane binding affinity of S proteins ranged from KD = 0.07-6.2 nM. The binding ability was completely abolished by SCn at concentrations according to the number of benzenes (30-300 µM; SC8 < SC6 << SC4). The inhibitory properties of SCn were also observed in vivo in a rabbit model of PVL-induced endophthalmitis. These calixarenes may represent new therapeutic avenues aimed at minimizing inflammatory reactions and necrosis due to certain virulence factors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
