Low-dose fine particulate matter induces inflammatory responses in primary macrophages and increases systemic nitric oxide production in mice

Airborne fine particulate matter (FPM) is a major environmental health threat associated with inflammatory responses. Although previous studies have reported FPM-induced inflammation in macrophage cell lines, the effects of FPM on primary bone marrow-derived macrophages (BMMs) and systemic nitric oxide metabolite (NOx) levels have not been fully characterized. This study evaluated whether low-dose FPM exposure induces inflammatory responses in vitro and in vivo. BMMs isolated from ICR mice were treated with FPM (0.0-12.5 ㎍/mL), and proinflammatory cytokine production was measured by enzyme-linked immunosorbent assay. For in vivo assessment, mice were administered FPM (7.5 mg/kg) by intraperitoneal injection under short-term exposure conditions, and serum NOx levels were quantified using the Griess assay. Exposure to FPM at 6.25 and 12.5 ㎍/mL significantly increased tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 production by BMMs compared with the control group (p < 0.05). In vivo, serum NOx levels were also significantly elevated in FPM-exposed mice compared with the control group (p = 0.026), consistent with results observed in the lipopolysaccharide-treated positive control group (p = 0.004). These findings suggest that low-dose transient FPM exposure activates innate immune cells and induces systemic inflammatory responses, supporting the potential role of FPM in the pathogenesis of inflammatory diseases.