Impact of the flame retardant 2,2’4,4’-tetrabromodiphenyl ether (PBDE-47) in THP-1 macrophage-like cell function via small extracellular vesicles

Abstract

2,2’4,4’-tetrabromodiphenyl ether (PBDE-47) is one of the most widespread environmental brominated flame-retardant congeners which has also been detected in animal and human tissues. Several studies have reported the effects of PBDEs on different health issues, including neurobehavioral and developmental disorders, reproductive health, and alterations of thyroid function. Much less is known about its immunotoxicity. The aim of our study was to investigate the effects that treatment of THP-1 macrophage-like cells with PBDE-47 could have on the content of small extracellular vesicles’ (sEVs) microRNA (miRNA) cargo and their downstream effects on bystander macrophages. To achieve this, we purified sEVs from PBDE-47 treated M(LPS) THP-1 macrophage-like cells (sEVsPBDE+LPS) by means of ultra-centrifugation and characterized their miRNA cargo by microarray analysis detecting the modulation of 18 miRNAs. Furthermore, resting THP-1 derived M(0) macrophage-like cells were cultured with sEVsPBDE+LPS, showing that the treatment reshaped the miRNA profiles of 12 intracellular miRNAs. This dataset was studied in silico, identifying the biological pathways affected by these target genes. This analysis identified 12 pathways all involved in the maturation and polarization of macrophages. Therefore, to evaluate whether sEVsPBDE+LPS can have some immunomodulatory activity, naïve M(0) THP-1 macrophage-like cells cultured with purified sEVsPBDE+LPS were studied for IL-6, TNF-α and TGF-β mRNAs expression and immune stained with the HLA-DR, CD80, CCR7, CD38 and CD209 antigens and analyzed by flow cytometry. This analysis showed that the PBDE-47 treatment does not induce the expression of specific M1 and M2 cytokine markers of differentiation and may have impaired the ability to make immunological synapses and present antigens, down-regulating the expression of HLA-DR and CD209 antigens. Overall, our study supports the model that perturbation of miRNA cargo by PBDE-47 treatment contributes to the rewiring of cellular regulatory pathways capable of inducing perturbation of differentiation markers on naïve resting M(0) THP-1 macrophage-like cells.

Guardians Under Siege: Exploring Pollution's effects on Human Immunity

“…Studies performed on the Boston Birth Cohort provided evidence that in utero exposure to PBDEs may epigenetically reprogramme the offspring's immunological response through promoter methylation of a proinflammatory gene [203]. These data agree with the in vitro results using macrophage-like cell lines, where cytokine production and miRNA expression were modulated by BDE-47 treatment [97][98][99].…”

“…Furthermore, they demonstrated that BDE-47 treatment can regulate the sEVs' cargo with purposeful consequences toward downstream events and target bystander macrophages. Exacerbating the macrophage LPS-induced pro-inflammatory response [99] as well as altering A549 epithelial lung cells which modulate mRNA expression of tight junctions, adhesion molecules, cytokines and EMT (epithelial-mesenchymal transition) markers [100]. Finally, it has been shown that BDE-47 can also induce cardiovascular toxicity, activating PPARγ in THP-1 monocytes, inducing the foam cell formation typical of a proatherogenic process [101].…”

Extracellular Vesicles and Immunity: At the Crossroads of Cell Communication

“…Recently, research on the impact of polybrominated diphenyl ethers (PBDEs), a widespread environmental pollutant, on EVs has been extensively investigated. For instance, BDE-47 has been found to modulate small EV (sEV) biogenesis and their miRNA cargo, exacerbating the lipopolysaccharide (LPS)-induced pro-inflammatory response in THP-1 macrophages [133,134]. Purified sEVs from BDE-47-treated THP-1 macrophages may affect the expression of surface markers in a naïve resting M(0) macrophage cell line, impairing the ability to make immunological synapses and present antigens downregulating the expression of HLA-DR and CD209 antigens [133].…”

Toxic Effects and Mechanisms of Polybrominated Diphenyl Ethers

“…Persistent exposure to PBDE-47 can impair innate immunity in mammary tissue [280]. PBDE-47 can disrupt the secretion of proinflammatory cytokines (IL-6 and TNF-α) and interfere with basophil activation [281][282][283][284]. Peripheral blood mononuclear cells (PBMC) from subjects who had autism spectrum disorders (ASD) showed a higher response to lipopolysaccharide (LPS) when pretreated with PBDE-47 compared with the control group [285].…”