Changes and immune function mechanism of tumor necrosis factor-alpha in murine peritoneal macrophage after severe scald

Yong WANG; Daizhi PENG; Xin ZHOU; Wenhua HUANG; Jing LIU

ABSTRACT

BACKGROUND:

Severe scald injury leads to a variety of disorders in the immune system. Activated macrophages are known to secrete many kinds of biologically active transmitter, but the relation between the functional disorder of the macrophages and signal transduction after burn injury has not been fully understood.

OBJECTIVE:

To observe the changes in nuclear factor(NF) -κκB activity and expressions of IκκB-α and tumor necrosis factor(TNF) -α in peritoneal macrophage of mice at different time points after severe scald injury and after the application of specific NF-κκB inhibitor pyrrolidine dithiocarbamate (PDTC), thereby to explore the mechanism of macrophage dysfunction in light of signal transduction.

DESIGN:

A randomized controlled experimental research.

SETTING:

State Key Laboratory of Trauma, Burn and Combined Injury.MATERIALS The experiment was carried out in the State Key Laboratory of Institute of Burn Research, Third Military Medical University during the period from January to June, 1999, using 30 healthy clean-grade Kunming mice of inbred strain.

INTERVENTIONS:

Common scald injury models(with third degree burn of 15% total body surface area) were established in the mice, which were randomized into 6 groups according to different time points after the injury for observation, namely 0 hour(normal control group) and postburn 2, 6, 12,24 and 48 hours. Peritoneal macrophages were collected at these time points for examining TNF-α content using radio-immunoassay and NF-κκB activity by means of electrophoretic mobility shift assay(EMSA). The expressions of IκκB-α and TNF-α mRNA were determined by immunoblotting method and reverse transcription-PCR, respectively.MAIN OUTCOME

MEASURES:

Examinations of ① the content of TNF-α, ② NF-κκB activity,③ expression of IκB-α, and ④ expression of TNF-α mRNA.

RESULTS:

Macrophage secretion of TNF-α was enhanced postburn, reaching the peak level at 12 hours[(1085.65 ± 122.99) ng/L], which was significantly higher than that in the normal control group( t = 14.92, P ＜ 0.01) .Postburn NF-κκB activity significantly increased after the injury, peaking at 2 hours[ (56. 8 ± 7.3)RDU], which occurred much earlier than the peak of TNF-α secretion( t=13. 31, P ＜ 0.01 ). Compared with that in the normal control group, IκB-α expression decreased significantly 2 hours postburn ( t =4. 23, P ＜ 0. 01) to 0. 632 ±0. 086, followed by gradual increase to the peak level to 1. 161 ± 0. 097 24 hours after the burn injury( t = 7.06, P＜ 0. 01) and then by slight decrease to 1. 149 ±0. 167 till 48 hours(t = 4. 82, P ＜ 0.01) . Twelve hours after injury was the time point for intervention with PDTC application, when NF-κκB activity and TNF-α mRNA expression both decreased significantly( P ＜ 0.01 ).

CONCLUSION:

NF-κB activity and TNF-αmRNA expression decrease significantly after severe scald. At high levels, IκB-α and NF-κκB maintain an interaction for their restriction. After burn injury, NF-κκB signal transduction pathway is involved in the modulation of TNF-α expression in mouse peritoneal macrophage.