Introduction: Transcriptional activation of the TNF-alpha gene in LPS-stimulated macrophages is dependent upon nuclear factor kappa-B (NF-kappaB) activity. Salicylates may interfere with NF-kappaB activity through a MAPK (mitogen-activated protein kinase)-dependent process. These studies investigate the effects of sodium salicylate (NaSal) on TNF-alpha production and MAPK activation in macrophages.
Methods: Rat peritoneal macrophages were pretreated or not with sodium salicylate or ibuprofen for 1 h and then stimulated with 100 ng/ml LPS. Six hours following stimulation, cell viability was assessed by MTT assay. At specified time intervals after LPS stimulation, supernatant TNF-alpha was measured by ELISA. Western blots of cell lysates were performed for analysis of total and activated (phosphorylated) MAPKs.
Results: Salicylate and LPS, alone or combined, did not significantly alter macrophage viability. Salicylate, but not ibuprofen, significantly reduced TNF-alpha production in LPS-stimulated macrophages. LPS-stimulated activation of ERK and SAPK/JNK was inhibited by NaSal pretreatment. NaSal treatment of macrophages activated p38 MAPK independent of LPS stimulation. Pretreatment of samples with the specific p38 MAPK inhibitor, SB203580, did not significantly alter TNF-alpha production in either LPS or NaSal and LPS-treated samples.
Conclusions: Salicylates alter MAPK signaling and suppress TNF-alpha production in LPS-stimulated macrophages. Salicylate-induced control of inflammatory mediator production in macrophages may, in part, underlie the clinically significant anti-inflammatory effects of these compounds.
Copyright 1999 Academic Press.