Dynamics of tissue neutrophil sequestration after cutaneous burns in rats

Abstract

Background: Neutrophil recruitment in organs after burns may cause local vascular damage, which can be reduced by agents blocking neutrophil adhesion to the vascular wall. Because these agents may increase susceptibility to infection, it is important to characterize the dynamics of neutrophil sequestration in order to optimize an eventual anti-adhesion therapy.

Materials and methods: Rats were scald burned over 20 or 40% of their total body surface area (TBSA) and saline resuscitated. Sham controls were used. Myeloperoxidase (MPO) activity was measured in lungs, liver, kidney, gut, and burned skin up to 1 week postburn. Extravascular accumulation of (125)I-labeled bovine serum albumin ((125)I-BSA) was measured at 12 h postburn.

Results: MPO activity in lungs, liver, and kidney was increased within 3 h postburn and returned to normal within 24-48 h. Peak MPO levels occurred at 6-12 h postburn and were similar for both burn sizes. No MPO increase was observed in gut. MPO levels in burned skin did not increase before 6 h, peaked at 24 h, decreased at 48 h, but remained elevated for up to 7 days. Neutrophil recruitment in lungs and liver was confirmed histochemically. No neutrophils were found in kidneys. Extravascular (125)I-BSA was increased in lungs, liver, kidneys, and gut, in the 40% TBSA group only.

Conclusions: Neutrophil sequestration in remote organs is a transient phenomenon while neutrophil homing into the wound site is sustained. Neutrophil accumulation dynamics are independent of burn size, although a minimum size is required to trigger vascular damage. Temporary early anti-adhesion therapy to reduce lung and liver neutrophil sequestration with little impact on neutrophil homing into the burn wound may be possible.