Transforming growth factor-beta 1 and splenocyte apoptotic cell death after burn injuries

Transforming growth factor (TGF)-beta 1 is a multifunctional cytokine that mediates apoptotic cell death in human lymphocytes in vitro. To better unde rstand the mechanism through which TGF-beta 1 exerts its apoptotic effect, we investigated the role of TGF-beta 1 in the relationship between burn inj ury and cell death of splenocytes in a mouse model of either 0%, 25%, or 40 % full-thickness burns. Mice were killed and spleens were harvested at 15 a nd 30 minutes and at 1, 2, 4, 8, 12, and 24 hours after the burn. The splee ns were divided and used for both histologic analyses with H-E stain and TU NEL stain and for total messenger RNA isolation and reverse transcriptase-p olymerase chain reaction amplification. Amplified polymerase chain reaction products were analyzed for signal strength by electrophoresis. TGF-beta 1 RNA expression was highest at 2 hours after the burn injuries in the 40% fu ll-thickness burns and at 4 hours after the burn injuries in the 25% full-t hickness burns. The relative increase in TGF-beta 1 RNA was 3 times greater with the Larger burn than with the smaller burn. In histologic analysis, s plenocyte apoptotic cell death was observed at 4 to 24 hours after the burn in the 40% full-thickness burns but at only 4 to 12 hours in the 25% full- thickness burns. TGF-beta 1 RNA peak expression was observed at different t imes after the burn in 25% and 40% full-thickness burns. Histologic analysi s showed apoptotic cell death in proportion with respective messanger RNA e xpressions. This suggests that TGF-beta 1 may be associated with apoptosis of splenocytes in vitro and that the effect of TGF-beta 1 after a burn inju ry may be important in the immune system.