Inhibition of inflammation-induced injury and cell migration by coelonin and militarine in PM2.5-exposed human lung alveolar epithelial A549 cells

Accumulating studies suggest that fine particulate matter (PM2.5) pollutants in the air are easily enter into alveoli and even the bloodstream, resulting in an inflammatory response that not only triggers respiratory disorders but also causes permanent damage to various organs. Recent findings suggest that coelonin and militarine enriched in orchids can inhibit inflammation-induced injury against respiratory diseases. Here, we evaluated the antiinflammatory properties of coelonin and militarine and examined their underlying molecular mechanisms in A549 cells exposed to PM2.5. PM2.5 induced significant intracellular reactive oxidative stress accumulation at a concentration of 250 mu g/ml, as determined using the dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescence assay. Cell viability was assessed via the MTS assay to determine the concentrations of compounds appropriate for use in subsequent experiments. Data from the enzyme-linked immunosorbent assay (ELISA) showed that both coelonin (10 and 20 mu g/ml) and militarine (5 and 10 mu g/ml) mitigated PM2.5-induced inflammation by reducing the generation of inflammatory factors, including interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha). Quantitative real-time PCR (qRT-PCR) analysis revealed a remarkable decrease in IL-6, TNF-alpha, cyclooxygenase-2 (COX-2) and interleukin-1 beta (IL-1 beta) mRNA levels in the coelonin and militarinepretreated groups. In Western blot analysis, expression of inhibitor of NF-kappa B (I kappa Ba) protein in the coelonin and militarine pretreatment groups was significantly increased compared with the PM2.5 (only) treatment group (P < 0.05), concomitant with a significant decrease in phospho-I kappa B kinase beta/I kappa B kinase beta (p-IKK beta/IKK beta), phospho-nuclear factor of kappa B p65/nuclear factor of kappa B p65 (p-NF-kappa Bp65/NF-kappa Bp65) and COX-2 proteins (P < 0.05). Both coelonin and militarine inhibited migration and inflammation by suppressing PM2.5-induced IKK phosphorylation, and followed by I.Ba protein degradation and NF-kappa B activation. Our collective data strongly supported the utility of coelonin and militarine as novel sources for development of treatments for PM2.5-induced lung diseases.

Automated summary

Studies suggest that compounds like coelonin and militarine found in orchids can inhibit the damage caused by PM2.5 pollutants by reducing inflammation factors. These compounds work by suppressing PM2.5-induced IKK phosphorylation, leading to inhibition of inflammation and migration.