Early inflammatory response in rat brain after peripheral thermal injury

Previous studies have shown that the cerebral complications associated with skin burn victims are correlated with brain damage. The aim of this study was to determine whether systemic thermal injury induces inflammatory responses in the brain. Sprague Dawley rats (n=28) were studied in thermal injury and control groups. Animals from the thermal injury (n=14) and control (n=14) group were anesthetized and submerged to the neck vertically in 85°C water for 6s producing a third degree burn affecting 60–70% of the animal body surface area. The controls were submerged in 37°C water for 6s. Early expression of tumor necrosis factor-α (TNF-α), interleukin 1-β (IL-1β), and intracellular cell adhesion molecules (ICAM-1) protein levels in serum were determined at 3 (n=7) and 7h (n=7) by enzyme-linked immunoabsorbent assay (ELISA). mRNA of TNF-α, IL-1β, and ICAM-1 in the brain was measured at the same time points with a real-time reverse transcriptase-polymerase chain reaction (RT-PCR). An equal animal number was used for controls. Systemic inflammatory responses were demonstrated by dramatic up-regulations (5–50 fold) of TNF-α, IL-1β, and ICAM-1 protein level in serum at 7h after the thermal injury. However, as early as 3h after peripheral thermal injury, a significant increase (3–15 fold) in mRNA expression of TNF-α, IL-1β and ICAM-1 was observed in brain homogenates, with increased levels remaining at 7h after injury. This study demonstrated an early inflammatory response in the brain after severe peripheral thermal injury. The cerebral inflammatory reaction was associated with expression of systemic cytokines and an adhesion molecule.