Euglena gracilis-derived β-glucan ameliorates particulate matter (PM_2.5)-induced airway inflammation by modulating nuclear factor kappa B, mitogen-activated protein kinase, and nuclear factor erythroid 2-related factor 2 signaling pathways in A549 cells and BALB/c mice

This study aimed to investigate the effects of β-glucan derived from Euglena gracilis (EGB), an edible microalga, on particulate matter (PM_2.5)-induced airway inflammation in A549 cells and BALB/c mice. EGB effectively suppressed the mRNA and protein levels of inflammatory cytokines (IL-6, IL-1β, TNF-α, IL-8) and mediators (iNOS, COX-2), while inhibiting the NF-κB and MAPK signaling pathways triggered by PM_2.5 exposure and reducing nuclear NF-κB levels. Additionally, EGB decreased PM_2.5-induced ROS production and increased the protein levels of NRF2 and HO-1, along with genes encoding antioxidant enzymes (catalase, GPx, SOD1), associated with elevated nuclear NRF2 levels. EGB reduced immune cell infiltration and inflammatory cytokine levels in BALF and serum, both of which increased by PM_2.5 exposure. EGB also significantly increased alveolar numbers while decreasing the gene expression of MMP1/9/13. Furthermore, EGB suppressed PM_2.5-induced bronchial thickening and collagen-1 deposition by downregulating TGF-β1 expression, and alleviated goblet cell hyperplasia and mucin production in lung tissues. These results suggest that EGB effectively reduces PM_2.5-induced airway inflammation by suppressing NF-κB and MAPK signaling pathways, lowering pro-inflammatory cytokines, and activating the NRF2-HO-1 signaling pathway to enhance antioxidant enzyme expression. This study highlights the potential of EGB as an edible functional agent for controlling PM-related airway inflammation.