Figure 4: Tamoxifen enhances neutrophil killing.

(a) Bacterial growth curves for USA300 methicillin-resistant Staphylococcus aureus (MRSA), K1 strain E. coli or PA01 strain P. aeruginosa (n=6) in the presence or absence of 10μM TAM or 4-hydroxytamoxifen (4-OHT). (b) Bactericidal assays evaluating the effect of a 4-h TAM or 4-OHT pre-treatment on neutrophil killing (represented by a reduction of CFUs) of USA300 MRSA, E. coli and P. aeruginosa (n=9–12). (c) Live/dead cell analysis of fixed cells; dead bacteria (red: propidium iodide, indicated by arrows) can be observed in tamoxifen-stimulated NETs (left panel). Live bacteria (green: SYTO 8) can be observed outside of the NETs and surrounding unstimulated cells (right panel). Images shown are representative of three independent experiments (scale bar, 10 μm). (d) Addition of DNAse before addition of bacteria to tamoxifen-treated neutrophils significantly reduces killing (n=9). (e) Neutrophils were incubated with TAM and bacteria concurrently to determine killing of USA300 MRSA opsonized using pooled human serum (n=8–9). Where applicable, results were analysed by one-way analysis of variance and post hoc Newman Keuls test. *P<0.05, **P<0.01, ***P<0.001 versus control values.