Particle retention by respiratory epithelial cells is associated with persistent biological effect

The biological effect of particles on respiratory epithelial cells involves, in part, the generation of an oxidative stress and a consequent cascade of reactions culminating in inflammatory mediator release. Whether there is either an immediate, transitory activation or a persistent response of the cells to the particles has not been established. We tested the postulate that respiratory epithelial cells exposed to wood smoke particle (WSP) would demonstrate increased oxidative stress and mediator release following re-seeding and propagation of the cells for two generations post-initial exposure. BEAS-2B cells grown to confluence (G0) in 75 cm(2) flasks were treated for 18 h with the WSP at 0, 25, 50 and 100 µg/ml. The flasks were then used to seed another set of flasks as well as 12- and 96-well plates (G1). These flasks were similarly grown to confluence and the process repeated (G2). Cell viability was assayed using trypan blue dye exclusion and was >85%. Dichlorohydrofluorescein fluorescence after exposure of BEAS-2B cells to 50 and 100 µg/ml WSP increased in all three generations when expressed as a ratio to unexposed cells. Similarly, IL-6 and IL-8 release following the initial exposure of cells to 100 µg/ml WSP increased in all three generations when expressed as a ratio to unexposed cells. The persistence of oxidative stress and inflammatory mediator release for two generations of cells beyond the initial exposure supports a postulate of continued cell response to retained particle.