Figure 13.

The bioactive factor signals via nicotinic acetylcholine receptor (nAChR) subunits α7, α9, and α10 and Src kinase. Human monocytic U937 cells were primed with LPS (1 μg/ml) for 5 h and cultured for additional 30 min in the absence (M1) or presence (M2) of SLPI (10 μg/ml). Conditioned media were collected and separated by ultrafiltration (cut-off 3 kDa) into high (HMMF) and low molecular mass fractions (LMMF). Conditioned medium M1 was supplemented with SLPI shortly before ultrafiltration. LPS-primed U937 cells were stimulated with 2′(3′)-O-(4-benzoylbenzoyl)adenosine 5′-triphosphate triethylammonium salt (BzATP; 100 mM) for 30 min in the presence or absence of M1 or M2. (A) Application of nicotinic antagonists α-bungarotoxin (α-Bun), RgIA4, or ArIB or (B) treatment with the Src kinase inhibitor PP2 abolished the inhibition mediated by the LMMF of M2. The inactive PP2 analogue PP3 had no effect on the inhibitory function of the LMMF of M2. ^*p ≤ 0.05 significantly different compared to U937 cells treated with LPS, BzATP, and LMMF of M2. Experimental groups were compared by Kruskal-Wallis test followed by Mann-Whitney rank sum test.