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. 2018 Apr 25;9:877. doi: 10.3389/fimmu.2018.00877

Figure 4.

Figure 4

Alpha-1 antitrypsin (AAT) signaling involves activation of calcium-independent phospholipase A2β (iPLA2β). (A–D) Lipopolysaccharide (LPS)-primed U937 cells were stimulated with 2′(3′)-O-(4-Benzoylbenzoyl)adenosine-5′-triphosphate (BzATP) in the presence or absence of Prolastin® (AAT-P, 1 mg/ml). Interleukin (IL)-1β released to the supernatant was measured after 30 min. Different doses of thapsigargin (A), the unselective PLA2 inhibitor arachidonyl trifluoromethyl ketone [ATK, (B)] or the preferential iPLA2β inhibitor bromoenol lactone [BEL, (C)] were added together with BzATP and AAT-P. (D) Expression of iPLA2β by U937 cells was silenced by siRNA (si iPLA2β). In addition, cells were transfected with control siRNA (si con). U937 cells transfected with si con or with si iPLA2β were primed with LPS and the release of IL-1β was stimulated by BzATP. (E) Adherent peripheral blood mononuclear cells were isolated from wild type (WT) or iPLA2β gene-deficient mice (iPLA2β−/−) and stimulated with BzATP in the absence or presence of AAT-P. IL-1β released in response to BzATP was normalized to 100%. Data are presented as individual data points, bar represents median, whiskers encompass the 25th to 75th percentile, n-numbers of independent experiments are indicated in the figure. Experimental groups were compared by Kruskal–Wallis test followed by Mann–Whitney rank sum test.