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TLR-2 IS INVOLVED IN AIRWAY EPITHELIAL CELL RESPONE TO AIR POLLUTION PARTICLES
Citation:
Becker, S E., L. A. Dailey, J M. Soukup, R Silbajoris, AND R B. Devlin. TLR-2 IS INVOLVED IN AIRWAY EPITHELIAL CELL RESPONE TO AIR POLLUTION PARTICLES. TOXICOLOGY AND APPLIED PHARMACOLOGY. Elsevier Online, New York, NY, 203:45-52, (2004).
Description:
Primary cultures of normal human airway epithelial cells (NHBE) respond to ambient air pollution particulate matter (PM) by increased production of the cytokine IL-8, and the induction of a number of oxidant stress response genes. Components of ambient air PM responsible for stimulating epithelial cells have not been conclusively identified, although metal contaminants, benzpyrene and biological matter have been implicated. Stimulation of IL-8 release from NHBE with coarse (PM2.5-10) , fine (PM2.5), and UF particle fractions has shown that the coarse particle fraction has the greatest effect on the epithelial cells as well as alveolar macrophages (AM). Since this fraction concentrates fugitive dusts and particle-associated microbial matter, it was hypothesized that NHBE may recognize PM through microbial pattern recognition receptors TLR2 and TLR4, as has been previously shown with AM. NHBE were shown to release IL-8 when exposed to a Gram positive environmental isolate of Staphylococcus lentus, and lower levels when exposed to Gram negative Pseudomonas spp. Comparison of TLR2 and TLR4 mRNA expression in NHBE and AM showed that NHBE express similar levels of TLR2 mRNA as the AM, but expressed very low levels of TLR4. When NHBE were stimulated with PM2.5-10, PM2.5 and UF PM, in the presence or absence of inhibitors of TLR2 and TLR4 activation, a blocking antibody to TLR2 inhibited production of IL-8 while TLR-4 antagonist E5531 or the LPS inhibitor Polymixin B had no effect. Furthermore, effects on expression of TLR2 and TLR4 mRNA, as well as the stress protein HSP70 was assessed in NHBE exposed to PM. TLR4 expression was increased in these cells while TLR2TLR2 mRNA levels were unchanged. Hsp70 was increased by PM2.5-10> PM2.5 > UF PM suggesting the possibility of indirect activation of TLR pathway by this endogenous TLR2/4 agonist.