Mechanism of altered TNF-α expression by macrophage and the modulatory effect of Panax notoginseng saponins in scald mice

Abstract

Aim To explore the mechanism of altered tumor necrosis factor-alpha (TNF-α) expression by peritoneal macrophages (PMΦ) and Panax notoginseng saponins (PNS) modulation in light of NF-κB signal transduction in severely scalded mice. Methods Eighteen percent total body surface area (TBSA) full-thickness scalded mice were used. PMΦ was collected at different time intervals (0, 2, 6, 12, 24 and 48 post-burn hour (PBH)) separately. The following parameters were measured: TNF-α mRNA and IL-10 mRNA expression (reverse transcription-polymerase chain reaction, RT-PCR), protein kinase C (PKC) activity (isotope incorporation analysis), NF-κB activity (electrophoretic mobility shift assay, EMSA), IκB-α expression (Western blot). Results After scald, increased expression of TNF-α mRNA of PMΦ peaked at 12 PBH. Meanwhile, expression of IL-10 mRNA dropped to the lowest level at 12 PBH. NF-κB activity was markedly activated and reached its peak at 2 PBH. Membrane PKC activity was up-regulated after scald and showed a positive correlation with the change of TNF-α mRNA. Expression of IκB-α first decreased at 2 PBH and then increased to high level at 24 PBH. When 12 PBH was chosen as the time point for in vitro intervention with the application of specific NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC), PKC inhibitor H-7 and PNS, both TNF-α mRNA expression and NF-κB activity decreased significantly. Conclusions These results indicate that abnormal expression of TNF-α mRNA of macrophages might be regulated by PKC-NF-κB signaling following severe burn. PNS might play an anti-inflammatory effect by inhibiting NF-κB activity and TNF-α mRNA expression.