CONICET | Buscador de Institutos y Recursos Humanos

SLPI is a serpin of 11,7 kDa that belongs to the family of four disulfide core proteins characterized by whey acid protein motif. The gene encoding SLPI is modulated at transcriptional and translational levels by pro-inflammatory cytokines. However, there is no data if the SLPI expression can be modulated by leukocytes recruited at the inflammation site. Therefore, the aim of this work was to examine the modulation of the SLPI expression by leukocytes on type II-like alveolar cell line (A549). SLPI was measured by sandwich ELISA in culture cells supenantant of A549, PMNL (resting and LPS-activated), PBMC (resting and IL-2-treated), lymphocyte (resting and IL-2-activated) or cocultures of leukocytes with A549 cells. CS were harvested at 18 h of incubation. SLPI (ng/ml) was present in the CS of A549 (0,06±0,02), PMNL (0,18±0,06), LPS activated-PMNL (0,54±0,06), PBMC (0,1±0,05), but not in IL-2-treated PBMC, lymphocytes or IL-2-treated lymphocytes. The co-culture of A549 with PMNL or PBMC, but not with LPS-activated PMNL, IL-2-treated PBMC, lymphocyte or IL-2-treated lymphocyte increased SLPI production (A549+PMNL: 0,84±0,21; A549+PBMC: 5,02±0,33,p<0.001 and p<0.001). In order to determined whether the increased in SLPI concentration in the co-culture of A549 with PMNL or PBMC were mediated by soluble factor released by leukocyte, A549 cells were cultured with CS derived from PMNL or PBMC. When A549 cells were treated with PMNL or PBMC-derived CS, the SLPI secretion was increased by three fold (p<0.001 and p<0.001). Interestingly, the CS-derived from activated-PMNL or IL-2-treated PBMC was not able to increase the SLPI secretion. However, if activated PBMC were pre-treated with SLPI, the SLPI secretion is restored. Overall these results demonstrate that epithelial cells secretion of SLPI may be upregulated by factors released by neutrophils and PBMC, but not lymphocytes or activated leukocytes.