Effect of the activation and secretion function of macrophage Notch1 after the stimulation of severe burn rat serum

Objective To investigate the dynamic expression of Notch1 signaling and the secretion of interleukin-6 (IL-6) and tumor necrosis factor alpha(TNF-α) from macrophage RAW264.7 cells induced by severe burn rat serum. Methods Twenty-four male Sprague-Dawley rats were divided into sham burn group and burn at 24 h and 7 d groups randomly, each group had eight rats. The rats of burn groups were made the third degree burns about 30% total body surface area. The serum of burn rats were collected at 24 h and 7 d after burn. The sham burn group was employed 37℃ water-bath and the serum was treated as a control. The mixed culture medium contained 20% burned serum, RAW264.7 cells were cultivated with each group of burned serum for immediate moment, 4, 8, 12, 24, 48 h. In addition, 100 ng/mL lipopolysaccharide+ 20% sham burn serum were applied to culture medium, which were employed to cultivate RAW 264.7. The Notch1 signaling of macrophages were detected after cultivation and the secretion of IL-6 and TNF-α in culture supernatants of each group was measured by enzyme linked immunosorbent assay. Results (1) The expression of Notch1 protein had no obvious change at immediate moment, 4, 8, 12, 24, 48 h after stimulation of sham burn serum.(2) In burn at 24 h group, the expression of Notch 1 protein was significantly increased and as time progresses the signaling peaked. (3) In burn at 7 d group, the expression of Notch 1 protein had no obvious change, which was flat as the sham burn serum group.(4) In the mixed culture medium of lipopolysaccharide+ sham burn serum group, the level of Notch1 signaling was significantly increased after stimulation. (5) The contents of IL-6 and TNF-α in burn at 24 h group and in lipopolysaccharide+ sham burn serum group were significantly higher than those of the sham burn serum group and the burn at 7 d group. Conclusion The Notch1 signaling and the secretion of IL-6 and TNF-α of macrophage could be stimulated by burn serum and this kind of high level signaling could be imitated by lipopolysaccharide. Key words: Burns; Lipopolysaccharides; Interleukin-6; Tumor necrosis factor-alpha; Notch signaling