Primary alveolar macrophages exposed to diesel particulate matter increase RAGE expression and activate RAGE signaling

Abstract

Receptors for advanced glycation end-products (RAGE) are members of the immunoglobulin superfamily of cell-surface receptors implicated in mechanisms of pulmonary inflammation. In the current study, we test the hypothesis that RAGE mediates inflammation in primary alveolar macrophages (AMs) exposed to diesel particulate matter (DPM). Quantitative RT-PCR and immunoblotting revealed that RAGE was up-regulated in Raw264.7 cells, an immortalized murine macrophage cell line and primary AMs exposed to DPM for 2 h. Because DPM increased RAGE expression, we exposed Raw264.7 cells and primary AMs isolated from RAGE null and wild-type (WT) mice to DPM prior to the assessment of inflammatory signaling intermediates. DPM led to the activation of Rat sarcoma GTPase (Ras), p38 MAPK and NF-κB in WT AMs and, when compared to WT AMs, these intermediates were diminished in DPM-exposed AMs isolated from RAGE null mice. Furthermore, cytokines implicated in inflammation, including IL-4, IL-12, IL-13 and TNFα, were all significantly decreased in DPM-exposed RAGE null AMs compared to similarly exposed WT AMs. These results demonstrate that diesel-induced inflammatory responses by primary AMs are mediated, at least in part, via RAGE signaling mechanisms. Further work may show that RAGE signaling in both alveolar epithelial cells and resident macrophages is a potential target in the treatment of inflammatory lung diseases exacerbated by environmental pollution.

Human peripheral blood mononuclear cells (PBMCs) from smokers release higher levels of IL-1-like cytokines after exposure to combustion-generated ultrafine particles

“…The release of IL-1-like cytokines promotes the activation of NF-κB 28 , which is at the basis of inflammatory pathways. In support of this, several authors demonstrated that soot particles can lead to NF-κB activation in both macrophage/monocyte cell lines and a human epithelial cell line (A549) 29 30 .…”

The role of RAGE in host pathology and crosstalk between RAGE and TLR4 in innate immune signal transduction pathways

“…One of the most consistent associations of RAGE in the literature is with inflammation and activation innate signal transduction pathways. The activation of NF‐κB and the MAPK signaling pathway and the resulting production of cytokines like TNF‐α are observed routinely, and has been reported for AGE‐treated RAW 264.7 cells, 66–68 peritoneal macrophages, 69 BMDM, 70 and THP‐1 cells 68,71 or alveolar macrophages exposed to diesel particulate matter 18 or cigarette smoke extract 22 that contain RAGE ligands. Different AGE structures have different intrinsic abilities to induce cytokines in human peripheral blood mononuclear cells (PBMCs) 8,30 .…”

“…The lung is a key anatomical site for RAGE protein expression and within the lung of mice, isolated alveolar macrophages express less RAGE than whole lung tissue in terms of mRNA and protein 23 . Expression of RAGE in alveolar macrophages can be increased by external stimuli such as diesel particulate matter 18 or cigarette smoke extract 22 that may be encountered in lung. Hypoxia has also been shown to induce RAGE expression in human macrophage‐like THP‐1 cells 24 .…”

Potential contribution of alveolar epithelial type I cells to pulmonary fibrosis

“…RAGE is a strong activator of the proinflammatory transcription factor NF-κB (nuclear factor-κB) and thereby represents an important signaling molecule in the innate immune system. In the lung, RAGE is selectively present in AECI, in some endothelial cells of larger blood vessels, and in alveolar macrophages [ 124 – 126 ]. Immunoelectron microscopic studies revealed the presence of RAGE at the basolateral aspect of AECI of mouse, rat, and human lung [ 124 , 127 ] opposite to the common basement membrane of the air–blood barrier.…”