Activation of the transcription factor NF-kB by respirable organic particles (ROP) facilitates oxidative damage in lung through increased expression of pro-inflammatory genes. In previous studies, we found that NF-kB in alveolar macrophages was activated maximally at 2 hours following in vitro treatments with ROP. Because of the recent interest in identifying oxygen radical pathways of NF-kB activation, we have investigated inhibitory effects by specific antioxidant agents. NR8383 rat alveolar macrophage cells were treated with ROP, with and without antioxidants, and analyzed for NF-kB activation employing the electrophoretic mobility shift assay (EMSA). Densitometry analysis of EMSA gels revealed the following reductions in NF-KB activation (reported as % of positive control). 200 units/ml superoxide dismutase reduced activation by 51 %, whereas catalase had no inhibitory effect, strongly suggesting a primary role for the superoxide anion radical but not hydrogen peroxide, in the activation of NF-kB in alveolar macrophages. Furthermore, only a 270/0 reduction in NF-kB activation was observed following cell treatments with 1 nM melatonin, an efficient scavenger of hydrogen peroxide. A series of vitamin E species, alphatocopherol succinate, vitamin E acetate, and Trolox a vitamin E derivative, at 100 microM reduced NF-kB activation 63%, 33%, and 38%, respectively, clearly indicating that vitamin E analogs differ in their potencies of NF-kB inhibition. One microM pyrroHdinedithiocarbamate and 20 mM N-acetyl cysteine, which have effects on diverse oxygen free radical pathways, reduced NF-kB activation 54% and 66%, respectively, providing further support for a general role of reactive oxygen species in NF-kB activation. Ongoing studies are exploring the rote of lipopolysaccharide receptors and calcium regulatory pathways on NF-kB activation in lung cells following exposure to particulate matter.
The Toxicologist. Society of Toxicology 38th Annual Meeting, March 14-18, 1999, New Orleans, Louisiana