No involvement of alveolar macrophages in the initiation of carbon nanoparticle induced acute lung inflammation in mice

Abstract

BackgroundCarbonaceous nanoparticles (CNP) represent a major constituent of urban particulate air pollution, and inhalation of high CNP levels has been described to trigger a pro-inflammatory response of the lung. While several studies identified specific particle characteristics driving respiratory toxicity of low-solubility and low-toxicity particles such as CNP, the major lung cell type, which initiates and drives that response, remains still uncertain. Since alveolar macrophages (AM) are known to effectively phagocytose inhaled particles and play a crucial role for the initiation of pulmonary inflammation caused by invading microbes, we aimed to determine their role for sterile stimuli such as CNP by profiling the primary alveolar cell compartments of the lung. We exposed C57BL/6 mice to 20 μg CNP by intratracheal instillation and comprehensively investigated the expression of the underlying mediators during a time span of 3 to 72 h in three different lung cell populations: CD45- (negative) structural cells, CD45+ (positive) leukocytes, and by BAL recovered cells.ResultsBronchoalveolar lavage (BAL) analysis revealed an acute inflammatory response characterized by the most prominent culmination of neutrophil granulocytes from 12 to 24 h after instillation, which declined to basal levels by day 7. As early as 3 h after CNP exposure 50 % of the AM revealed particle laden. BAL concentrations and lung gene expression profiles of TNFα, and the neutrophil chemoattractants CXCL1,-2 and-5 preceded the neutrophil recruitment and showed highest levels after 12 h of CNP exposure, pointing to a significant activation of the inflammation-evoking lung cells at this point of time. AM, isolated from lungs 3 to 12 h after CNP instillation, however, did not show a pro-inflammatory signature. On the contrary, gene expression analysis of different lung cell populations isolated 12 h after CNP instillation revealed CD45-, mainly representing alveolar epithelial type II (ATII) cells as major producer of inflammatory CXCL cytokines. Particularly by CD45- cells expressed Cxcl5 proved to be the most abundant chemokine, being 12 h after CNP exposure 24 (±11) fold induced.ConclusionOur data suggests that AM are noninvolved in the initiation of the inflammatory response. ATII cells, which induced highest CXCL levels early on, might in contrast be the driver of acute neutrophilic inflammation upon pulmonary CNP exposure.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0144-6) contains supplementary material, which is available to authorized users.

Macrophage sensing of single-walled carbon nanotubes via Toll-like receptors

“…Chen et al . 62 concluded in a recent study that alveolar epithelial cells, and not macrophages, are the major producers of cytokines/chemokines in mice exposed to small, spherical carbon nanoparticles, and Katwa et al . 63 showed that mast cells are required for certain pulmonary and cardiovascular responses to MWCNTs.…”

Cellular Toxicity and Immunological Effects of Carbon-based Nanomaterials

“… [ 126 ] Carbon nanoparticles Intratracheal instillation 20 μg/mouse Pyrogene-free distilled water 3, 6, 12, 18, 24 h, and 3 or 7 days Female C57BL/6 J mice aged 8–10 weeks Prominent culmination of neutrophil granulocytes 12 to 24 h after instillation; BAL concentrations and increased levels of neutrophil chemoattractants (CXCL1, -2 and-5) from alveolar epithelial type II cells. [ 127 ] MWCNTs Intranasal instillation administered on days 0, 7, and 14 (75 μg/dose) A synthetic lung surfactant On the day 23 Male BALB/cByJ mice aged 9 weeks Aggravated airway inflammation and the generation of epithelium-derived innate cytokines caused by the coexposure of MWCNTs and HDM compared to HDM alone. [ 128 ] Rod-like MWCNTs and tangled MWCNTs Inhalation 6.2-8.2 mg/m 3 for rCNT and 17.5-18.5 mg/m 3 for tCNT (4 hours at a time once or on four consecutive days) — 4 h, 24 h Female C57BL/6 and BALB/c mice aged 7–8 weeks Allergic-like airway inflammation and the upregulation of innate immunity-relevant genes and cytokine/chemokine pathways caused by rod-like CNTs after 4-hour exposure.…”

“…As early as 3 h, 50% of AMs were loaded with black particle, and extracted AMs from the lungs presented no proinflammatory signature. In contrast, through gene expression analysis, alveolar epithelial type II cells were identified as the primary source of CXCL cytokines [ 127 ]. A mouse model of asthma was induced using house dust mites (HDM), and the mice were then exposed to MWCNTs by intranasal instillation.…”

Acute Phase Response as a Biological Mechanism‐of‐Action of (Nano)particle‐Induced Cardiovascular Disease

“…A body of studies shows particle-induced induction of acute phase response in terms of increased Saa3 transcription and SAA3 release. [13,14,39,40,42,45,46,52,[91][92][93][94][95][96] Furthermore, Saa3 mRNA levels were increased within a few hours and SAA3 protein was measured by ELISA as early as 6 h after LPS instillation accumulating up to 24 h before slowly declining to base levels over a course of days. [97] (unpublished data) However, all these studies were conducted in bronchoalveolar lavage or whole lung tissue, and the responsible cell types have not yet been identified.…”