Inflammatory Cytokine Response to Ambient Particles Varies due to Field Collection Procedures

Abstract

In vitro assays of biological activity induced by particulate matter (PM) are a tool for investigating mechanisms of PM health effects. They have potential application to exposure assessment in chronic disease epidemiology. However, there has been little reporting of the impact of real-world PM collection techniques on assay results. Therefore, we examined the effect of sampling duration and postsampling delays in freezing on PM-induced biological activity. Duplicate samples of respirable ambient Los Angeles PM were collected on polyurethane foam filters during 17 days and during three contemporaneous consecutive shorter periods. After collection, one duplicate was stored at ambient temperature for 24 hours before freezing; the other was frozen immediately. Cytokine response (IL-1b, IL-6, IL-8, and TNF-a) to PM aqueous extract was assessed in THP-1 cells, a model for evaluating monocyte/macrophage lineage cell responses. There was consistent 3-to 4-fold variation in PM-induced cytokine levels across the three collection intervals. Compared with levels induced by PM pooled across the three periods, continuously collected PM-induced levels were reduced by 25% (IL-6) to 39% (IL-8). The pattern of cytokine gene expression response was similar. Cytokine level variation by time to freezing was not statistically significant. PM-induced inflammatory response varied substantially over a weekly time scale. We conclude that long PM sampling interval induced less activity than the average of equivalent shorter consecutive sampling intervals. Time to freezing was less important. Implications for development of metrics of long-term spatial variation in biological exposure metrics for study of chronic disease merit further investigation.

Inflammatory Response of Monocytes to Ambient Particles Varies by Highway Proximity

“…For example, we have previously shown that biological activity varies with duration of collection of sample (15). Another recent study demonstrated that PM-induced biological activity varied depending on the collection method (39).…”

“…Size-resolved PM was collected with a Harvard Cascade Impactor (14) modified for the Southern California Children's Health Study to include an additional cut-point of 0.2 and 0.5 mm in addition to standard size cuts at 2.5 and 10 mm, as previously described, and operated at 5 liters per minute (15,16). The collection substrate was polyurethane foam (PUF), which allows larger PM mass accumulations before particle bounce or overloading occurs (14,17).…”

“…A Teflon backup filter was used to collect PM 0.2 . Filters were prepared to remove endotoxin from the PUF as previously described (15,16).…”

Petrodiesel and waste grease biodiesel (B20) emission particles at a rural recycling center: characterization and effects on lung epithelial cells and macrophages

“…The 4 pro-inflammatory cytokines (IL-6, IL-8, TNF-α and MIP-1α) measured in this study have been reported in PM- and diesel exhaust particles (DEP)-exposed cells or animals (Arimoto et al 2007; Sawyer et al 2010; Levesque et al 2011; McConnell et al 2013). The present work is the first to show that WG-derived B20 particles also induced these responses.…”

Inflammatory Response of Monocytes to Ambient Particles Varies by Highway Proximity

“…There are potential limitations to using PM-induced biological activity for exposure assessment in chronic disease epidemiology, which typically require temporally synchronized deployment at multiple locations during several 2-week or longer periods throughout the year (37,38). For example, we have previously shown that biological activity varies with duration of collection of sample (15). Another recent study demonstrated that PM-induced biological activity varied depending on the collection method (39).…”