Apoptosis of neutrophils, expression of TREM-1 on neutrophils and IL-17 responses in experimental burn in injury are related to the type and time of burn exposure

Introduction

To define inflammatory responses in experimental burn injury in relation with the type and time of burn exposure.

Methods

Burn injury was induced in 110 C57/B6 male mice after time exposure of their back as follows: group 0, sham; group A, 60°C for 60 seconds; group B, 60°C for 45 seconds and 4°C for 45 seconds; group C, 75°C for 60 seconds; group D, 90°C for 5 seconds; and group E, 4°C for 45 seconds and 60°C for 45 seconds. Mice were sacrificed at 24 and 48 hours. Tissues were cultured and splenocytes were isolated and stimulated with heat-killed Staphylococcus aureus and Candida albicans for 5 days for release of IL-17. Neutrophil apoptosis and expression of TREM-1 were determined after staining for ANNEXIN-V, PI and anti-TREM-1-PE and flow cytometry analysis.

Results

Mean respective apoptosis of groups 0, A, B, C, D and E at 24 hours were 37.9%, 77.6%, 81.9%, 73.8%, 83.6% and 75.4%; and at 48 hours 78.5%, 79.4%, 77.7%, 78.2%, 81% and 84.9% (P < 0.05 group 0 vs. others). Mean respective MFI of TREM-1 of groups 0, A, B, C, D and E at 24 hours were 2.4, 4.4, 3.4, 3, 3.2 and 3; and at 48 hours 2.7, 2.8, 2.8, 2.6, 2.8 and 2.7 (P < 0.05 group 0 vs. others). Tissue cultures were sterile. Release of IL-17 was greater by splenocytes of group D (Figure 1).

Figure 1

Release of IL-17 by mice splenocytes in relation to the type of thermal injury.

Conclusion

Increased neutrophil apoptosis and TREM-1 expression and modulated IL-17 responses are found within burn injury.