Protective effects of curcumin on short and long-term particulate matter (PM10/2.5) induced lung damage severity via modulation of neutrophil extracellular traps (NETs) formation in mouse model.

Particulate matter (PM10/2.5) exposure and lung damage have recently been found to be associated with Neutrophil extracellular trap (NETs) formation and NETosis. NETs are the structures released from neutrophils in response to pathogens and during inflammatory response. This study was undertaken to investigate lung damage after short and long-term exposures to PM10/2.5 collected from Varanasi, one of the oldest Indian cities and its association with NETs formation in neutrophils. BALB/c mice were exposed to PM10/2.5(0.5 mg/kg, i.n.) for 2-4 weeks where wet/dry lung tissue weight ratio were significantly increased, indicating pulmonary edema, where higher severity was observed with PM2.5 exposure groups. Marked increase in protein content and LDH level in longer duration of PM2.5 exposure reflect duration dependent lung damage severity. Elevated neutrophil and macrophage populations in bronchoalveolar lavage fluid (BALF) following PM exposure was confirmed by CD11b+ and Gr-1+ cells. Histopathological analysis revealed increased inflammatory cell infiltrations and bronchial wall thickening, with granuloma formation which was evident in 4 weeks of PM2.5 exposure with higher granuloma score. PM exposures also triggered oxidative stress, evidenced by increased reactive oxygen species (ROS), nitric oxide (NO), and malondialdehyde (MDA) levels, along with decreased glutathione (GSH) and glutathione peroxidase (GPx) activities. Duration dependent gradual enhancement in NETosis was characterized by the co-localization of citrullinated histone H3 (Cit-H3) and myeloperoxidase (MPO) in both, lung tissues and BALF. Elevated expressions of Neutrophil Elastase (NE) also confirmed NETs formation in 2-4 weeks of PM exposure. Enhanced CXCL1 expression in long-term PM2.5 exposure confirmed neutrophil accumulation and NETs formation. Enhanced NF-kB and IL-33 expressions in 4 weeks of PM2.5 exposure established inflammation eseverity where upregulated inflammatory cytokine IL-6 and TNF-α expressions along with oxidative DNA damage appeared NETosis mediated. Intranasal curcumin pretreatment has alleviated PM10/2.5 induced NETs formation which may serve as a promising therapeutic approach in mitigating PM-induced lung damage.