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The bi-component leukotoxins; γ-hemolysin and Panton and Valentin Leukocidin (PVL) from Staphylococcus aureus induce two independent cellular events 1) the formation of trans-membrane pores not permeable to chloride (Cl-) ions and 2) the activation of at least, two modes of chloride fluxes (efflux/influx), including pre-existing Ca2+-activated Cl- channels (CaCC) in human polymorphonuclear neutrophils (PMNs). This was investigated by using spectrofluorometry techniques and the chloride-sensitive quencher fluorescent indicator, MQAE (N-(6-methoxyquinolyl) acetoacethyl ester). The ethidium bromide was used as an indicator for the trans-membrane pores formation by staphylococcal leukotoxins. In the absence of extracellular Ca2+, HlgA/HlgB, HlgC/HlgB and LukS-PV/LukF-PV leukotoxins from S. aureus induced a massive efflux of chloride (Cl-) ions. Interestingly, in the presence of extracellular Ca2+, the HlgA/HlgB γ-hemolysin provoked a biphasic response of Cl- movements (efflux/influx). Conversely to HlgA/HlgB and LukS-PV/LukF-PV, HlgC/HlgB leukotoxins did not induce any Cl- movement under this condition (e.g. in the presence of extracellular Ca2+). The potent Cl- channel inhibitor, DIDS, did inhibit significantly the Cl- fluxes caused by all pairs of staphylococcal leukotoxins tested in both conditions. In the present study, we found that the inhibitory effect of flufenamic acid, known as a Cl- channel inhibitor, was restricted only to the Ca2+-dependent Cl- influx triggered only by HlgA/HlgB and LukS-PV/LukF-PV leukotoxins. These findings might suggest that, Cl- fluxes in human neutrophils did involve at least, two different types of Cl- pathways, depending on the absence or presence of extracellular Ca2+. Both Cl- channels blockers, DIDS and flufenamic acid did not alter the pores formation by staphylococcal leukotoxins. Furthermore, under conditions when the membrane pores formation was blocked by divalent ions (Ca2+ and/or Zn2+), Cl- ions movements were still observed. Taken together, our results strongly provide an evidence that: i) trans-membrane pores formed by staphylococcal leukotoxins: HlgA/HlgB, HlgC/HlgB (γ-hemolysin) and LukS-PV/LukF-PV (PVL) do not drive Cl- ions fluxes ii) at least, two different types of Cl- ions pathways are activated, depending on the absence or presence of extracellular Ca2+, including Ca2+-activated Cl- channels (CaCC) and, iii) Ca2+-activated Cl- channels are mediated only by HlgA/HlgB and LukS-PV/LukF-PV leukotoxins.

international journal of microbiology and biotechnology

Bi-component Staphylococcal Leukotoxins Induce Chloride Ions Fluxes in Human Neutrophils: Opening of Ca&amp;lt;sup&amp;gt;2+&amp;lt;/sup&amp;gt;-activated Cl&amp;lt;sup&amp;gt;-&amp;lt;/sup&amp;gt; Channels