Macrophages with reduced expressions of classical M1 and M2 surface markers in human bronchoalveolar lavage fluid exhibit pro-inflammatory gene signatures

Abstract

The classical M1/M2 polarity of macrophages may not be applicable to inflammatory lung diseases including chronic obstructive pulmonary disease (COPD) due to the complex microenvironment in lungs and the plasticity of macrophages. We examined macrophage sub-phenotypes in bronchoalveolar lavage (BAL) fluid in 25 participants with CD40 (a M1 marker) and CD163 (a M2 marker). Of these, we performed RNA-sequencing on each subtype in 10 patients using the Illumina NextSeq 500. Approximately 25% of the macrophages did not harbor classical M1 or M2 surface markers (double negative, DN), and these cells were significantly enriched in COPD patients compared with non-COPD patients (46.7% vs. 14.5%, p < 0.001). 1886 genes were differentially expressed in the DN subtype compared with all other subtypes at a 10% false discovery rate. The 602 up-regulated genes included 15 mitochondrial genes and were enriched in 86 gene ontology (GO) biological processes including inflammatory responses. Modules associated with cellular functions including oxidative phosphorylation were significantly down-regulated in the DN subtype. Macrophages in the human BAL fluid, which were negative for both M1/M2 surface markers, harbored a gene signature that was pro-inflammatory and suggested dysfunction in cellular homeostasis. These macrophages may contribute to the pathogenesis and manifestations of inflammatory lung diseases such as COPD.

Hsa-Mir-320c, Hsa-Mir-200c-3p, and Hsa-Mir-449c-5p as Potential Specific miRNA Biomarkers of COPD: A Pilot Study

“…EGFR, a member of the “ErbB signaling pathway”, has also been found to mediate macrophage activation in the pathological context [ 50 , 51 ]. Macrophages are key immune effector cells in the pathogenesis of COPD, and BAL-macrophages from COPD patients have been reported to present a non-polarized phenotype that confers them a poor immune response [ 52 , 53 ]. As the “ErbB signaling pathway” was also detected in our in silico analysis, the three miRNAs candidates might be implicated in the alteration of the EGFR role in macrophage function in COPD.…”

Pathological Mechanism and Targeted Drugs of COPD

“…M2 macrophages, on the other hand, are activated by a variety of cell factors (interleukin-4 (IL-4), interleukin-10 (IL-10) and interleukin-13 (IL-13) et al), and help the remodeling of airway by remodeling and repairing damaged tissues. 37 The inflammatory factor IL-6, produced by neutrophils and macrophages, can induce the production of elastase and oxygen radicals, which will increase the permeability of pulmonary vascular and aggravate the destruction of lung tissue. 38 , 39 TNF-α, on the other hand, can modulate endothelial adhesion molecules, which will make polymorphonuclear leukocytes accumulate, and then release large amounts of elastase and ROS’s destroyed alveolar epithelium.…”

Reduced phagocytic activity of human alveolar macrophages infected with Mycobacterium avium complex

“…Plasticity and phenotypic changes of macrophages in response to the microenvironment are well-known [21], and previous studies on alveolar macrophage phenotypes using human BALF revealed an increased proportion of non-polarized macrophages (46.7-77.9% of total alveolar macrophages) in patients with COPD [16,17] compared to those in healthy individuals (estimated to be ~25% of total alveolar macrophages) [17]. In addition, the highest and lowest phagocytic activities have been reported in double-polarized and non-polarized macrophages, respectively [16], which corroborates our results.…”

“…Among these cell types, alveolar macrophages provide the first line of defense against extrinsic organisms that reach the alveolar airspace, where distinct macrophage subpopulations exhibit distinct functional properties [14]. Macrophages have been characterized either as "classically" activated or M1 macrophages or "alternatively" activated or M2 macrophages [14,15]; however, macrophages negative for both M1 and M2 markers (non-polarized macrophages) are also reportedly associated with chronic inflammation [16,17]. A higher rate of non-polarized macrophages may account for impaired phagocytic activity and is associated with disease severity and progression in patients with chronic obstructive pulmonary disease (COPD) [16].…”