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The Effect of PM2.5 on the Inflammatory Responses in Human Upper Airway Mucosa.

RATIONALE
Particulate matter with an aerodynamic diameter equal or less than 2.5 µm (PM2.5) represents a main constituent of polluted air with a potential detrimental impact on human health.


OBJECTIVES
To investigate the effect of PM2.5 on human nasal mucosa under healthy and pre-existing inflammatory condition.


METHODS
Healthy subjects and 6 patients with type-2 inflammations (CRSwNP/AR) were recruited for in vivo sampling of nasal secretions before and after days with high PM2.5 values. Nasal polyp (NP) samples from patients with CRSwNP and control uninflamed nasal tissue were stimulated with PM2.5 ex vivo. The concentrations of IL-1ß, IL-5, IL-6, IL-8, IL-17, and TNF-α were measured.


MEASUREMENTS AND MAIN RESULTS
In healthy subjects, the concentrations of IL-6, IL-8 and TNF-α in nasal secretions were significantly higher in samples taken during PM high days. In line with these observations, IL-8 also significantly increased in ex vivo stimulations with PM2.5 in healthy mucosa. In patients with airway disease, concentrations of IL-1ß, IL-6 and IL-8, but also IL-5 were significantly increased in nasal secretion samples during PM high days; a similar pattern was demonstrated in chronically inflamed sinonasal tissue ex vivo after exposure to PM2.5 over 24 and 48h.


CONCLUSIONS
The present study demonstrates that PM2.5 is able to initiate a neutrophilic immune response in healthy uninflamed nasal mucosa. In type-2 inflammatory disease, however, PM2.5 initiates not only a proinflammatory reaction, but also aggravates a type-2 response in vivo and ex vivo.