Abstract: Objective To observe the effects of endotoxin tolerance triggered by repeated stimulation of lipopolysaccharide (LPS) on TNF-α and IL-8 expressions in co-cultures of neutrophils and THP-1 cells. Methods Co-cultures of neutrophils and THP-1cells were pretreated with 1 μg/mL Porphyromonas gingivalis(P.gingivalis) LPS or 1 μg/mL Escherichia coli(E.coli) LPS for 24 h, washed and stimulated by the same LPS again for another 24 h. The levels of TNF-α and IL-8 in supernatants were detected by ELISA. Results The expression levels of TNF-α and IL-8 significantly increased in co-cultured cells stimulated by P.gingivalis LPS or E.coli LPS compared with those without any stimulation (P＜0.05). The expression levels of TNF-α in cells restimulated by P.gingivalis LPS or E.coli LPS were obviously down-regulated compared with those stimulated by the same LPS only once (P＜0.05), while the expression levels of IL-8 were significantly up-regulated in comparison with those secreted by co-cultures of neutrophils and THP-1 cells stimulated by the same LPS only once (P＜0.05). Conclusion Endotoxin tolerance may suppress the secretion of TNF-α and promote the production of IL-8 in co-cultures of neutrophils and THP-1 cells.

Key words: endotoxin tolerance, co-culture, neutrophils, THP-1 cells