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. 2005 Aug 17:2:4.
doi: 10.1186/1743-8977-2-4.

Cytokine release from alveolar macrophages exposed to ambient particulate matter: heterogeneity in relation to size, city and season

Ragna B Hetland  1 , Flemming R Cassee, Marit Låg, Magne Refsnes, Erik Dybing, Per E Schwarze
Affiliations

Cytokine release from alveolar macrophages exposed to ambient particulate matter: heterogeneity in relation to size, city and season

Ragna B Hetland et al. Part Fibre Toxicol. .

Abstract

Background: Several studies have demonstrated an association between exposure to ambient particulate matter (PM) and respiratory and cardiovascular diseases. Inflammation seems to play an important role in the observed health effects. However, the predominant particle component(s) that drives the inflammation is still not fully clarified. In this study representative coarse (2.5-10 microm) and fine (0.1-2.5 microm) particulate samples from a western, an eastern, a northern and a southern European city (Amsterdam, Lodz, Oslo and Rome) were collected during three seasons (spring, summer and winter). All fractions were investigated with respect to cytokine-inducing potential in primary macrophages isolated from rat lung. The results were related to the physical and chemical parameters of the samples in order to disclose possible connections between inflammatory potential and specific characteristics of the particles.

Results: Compared on a gram-by gram basis, both site-specific and seasonal variations in the PM-induced cytokine responses were demonstrated. The samples collected in the eastern (Lodz) and southern (Rome) cities appeared to be the most potent. Seasonal variation was most obvious with the samples from Lodz, with the highest responses induced by the spring and summer samples. The site-specific or seasonal variation in cytokine release could not be attributed to variations in any of the chemical parameters. Coarse fractions from all cities were more potent to induce the inflammatory cytokines interleukin-6 and tumour necrosis factor-alpha than the corresponding fine fractions. Higher levels of specific elements such as iron and copper, some polycyclic aromatic hydrocarbons (PAHs) and endotoxin/lipopolysaccaride seemed to be prevalent in the coarse fractions. However, variations in the content of these components did not reflect the variation in cytokine release induced by the different coarse fractions. Addition of polymyxin B did not affect the particle-induced cytokine release, indicating that the variations in potency among the coarse fractions are not explained by endootoxin.

Conclusion: The inflammatory potential of ambient PM demonstrated heterogeneity in relation to city and season. The coarse particle fractions were consistently more potent than the respective fine fractions. Though a higher level of some elements, PAH and endotoxin was found in the coarse fractions, the presence of specific components was not sufficient to explain all variations in PM-induced cytokine release.

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Figures

Figure 1
Figure 1
Release of IL-6 after exposure of alveolar rat macrophages to increasing concentrations of coarse (lane A) and fine (lane B) fractions of ambient PM collected in Oslo, Rome, Lodz and Amsterdam during spring (upper), summer (middle) and winter (lower) seasons. Values are mean ± SEM (n = 3).
Figure 2
Figure 2
Seasonal variations in release of IL-6 (lane A) and TNF-α (lane B) from alveolar rat macrophages after exposure to the coarse fractions of ambient PM collected in Oslo, Rome, Lodz and Amsterdam (top to bottom). Values are shown as fold increase compared to control levels (IL-6ctr.: 455 – 477 pg/ml, SEM: 172 – 230; TNF-αctr.: 382 – 679 pg/ml, SEM: 13 – 23). Values are mean ± SEM (n = 3).
Figure 3
Figure 3
The concentrations of selected elements in the PM samples presented together with the respective PM-induced IL-6 from alveolar rat macrophages after exposure to 20 μg/ml of coarse (C) and fine (F) fraction collected in Oslo, Rome, Lodz and Amsterdam in spring (upper), summer (middle) and winter (lower) seasons. IL-6 release is shown on the left ordinate, values in diagram are mean ± SEM (n = 3). Concentration of elements is shown on the right ordinate (ng/mg PM). Indicated values in the diagram for Fe and Al should be multiplied by 103, values for Zn and Cu by 102 and values for V by 101.
Figure 4
Figure 4
The concentrations of subgroups of PAH in the collected samples presented together with the respective PM-induced IL-6 from alveolar rat macrophages after exposure to 20 μg/ml of coarse (C) and fine (F) fraction collected in Oslo, Rome, Lodz and Amsterdam in spring (upper), summer (middle) and winter (lower) seasons. IL-6 release is shown on the left ordinate, values in the diagram are mean ± SEM (n = 3). Concentration of PAH are shown on the right ordinate (ng/mg PM). Values of the subgroup of PAH representing emissions from combustion of diesel are the summarised concentrations of phenantrene, 1-methylphenantrene, fluoranthene and pyrene in each PM-sample. Values of the subgroup of PAH representing emissions from gasoline engines and wood burning are the summarised concentrations of naphthalene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[g,h,i]perylene in each sample. Values of other PAH represent the sum of acenaphthene and benzo[a]pyrene in each sample.
Figure 5
Figure 5
The concentrations of selected inorganic components in the collected samples presented together with the PM-induced IL-6 from alveolar rat macrophages after exposure to 20 μg/ml of coarse (C) and fine (F) fractions collected in Oslo, Rome, Lodz and Amsterdam in spring (upper), summer (middle) and winter (lower) seasons. IL-6 is shown on the left ordinate, values are mean ± SEM (n = 3). The concentration of inorganics is shown on the right ordinate (μg/mg PM).
Figure 6
Figure 6
The concentrations of endotoxins in the collected samples presented together with PM-induced IL-6 from alveolar rat macrophages after exposure to 20 μg/ml of coarse (C) and fine (F) fractions collected in Oslo, Rome, Lodz and Amsterdam in spring (upper), summer (middle) and winter (lower) seasons. IL-6 release is shown on the left ordinate, values in diagram are mean ± SEM (n = 3). Concentration of endotoxin is shown on the right ordinate (ng/mg PM). Endotoxin content in PM samples measured by the LAL-method and the EPT-method are shown. LAL-analysis of the Oslo spring samples is missing due to shortage of sample material.
Figure 7
Figure 7
Release of IL-6 from alveolar rat macrophages after exposure to 20 μg/ml of the coarse (C) PM samples collected during the summer season, EHC-93 or LPS with or without treatment of polymyxin B sulphate. Values are mean ± SEM (n = 3).
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