Particulate matter exposure induces pulmonary T_H2 responses and oxidative stress-mediated NRF2 activation in mice

Introduction: Particulate matter (PM) is a harmful air pollutant associated with respiratory and cardiovascular diseases, but its effects on adaptive immunity are poorly understood. Objectives: This study investigates the role of NRF2 in T cells in mediating immune and pulmonary responses to long-term PM exposure, highlighting its impact on inhalation toxicity. Methods: To establish a mouse model of lung injury induced by PM exposure, C57BL/6 mice were intranasally administered 20 μg/kg PM₁₀ or PM_2.5 daily for 16 weeks. Lung injury parameters were analyzed in bronchoalveolar lavage fluid (BALF), plasma, and lung tissue. Changes in the proportion of immune cells in the lymph nodes and spleen were analyzed. Results: Mice exposed to PM for 16 weeks showed severe lung damage, such as inflammatory cell infiltration, thickened alveolar walls, and increased oxidative stress and apoptosis. PM exposure also increased collagen and fibronectin levels, indicating tissue remodeling. Immune cell analysis revealed reduced B cell expansion, increased IL-4-producing CD4⁺ T cells, and decreased IFN-γ- and TNF-α-producing CD4⁺ T cells, accompanied by higher T_H2 cytokines and plasma IgE and IgG1 levels. PM activated the NRF2 pathway, skewing immune responses toward T_H2 differentiation, which worsened lung inflammation. Conclusions: These findings highlight how PM exposure disrupts immune balance and exacerbates conditions like asthma and chronic obstructive pulmonary disease by promoting T_H2-driven inflammation through NRF2 activation.