The involvement of Nox4 in fine particulate matter exposure-induced cardiac injury in mice

: Epidemiological studies have confirmed that ambient fine particulate matter (PM2.5) exposure is associated with cardiovascular disease (CVD). However, the underlying mechanisms in PM2.5 exposure-induced heart injury are largely unknown. It has been acknowledged that NADPH oxidase (Nox) 4 plays a critical role in CVD development. To investigate the acute effects of PM2.5 on the mouse heart and the role of Nox4 in PM2.5 exposure-induced cardiac injury, C57BL/6J mice were instilled with saline or 1.5, 3.0, 6.0 mg/kg BW PM2.5 suspension for two weeks (five days per week). The levels of malondialdehyde (MDA), super oxide dismutase (SOD), inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β in heart supernatants were determined using related kits. The expression of Nox4, p67phox, p47phox and p22phox in heart tissue was evaluated by immunofluorescence staining or Western blotting, respectively. Protein levels of p53, Bax, Bcl-2 and Caspase-3 in the heart were examined using immunohistochemical staining and Western blotting. TUNEL assay was used to measure myocardial apoptosis. PM2.5 exposure leads to obvious cardiac injury. PM2.5 exposure increases MDA level and iNOS activity, and decreases activity of SOD in heart supernatants of mice. High levels of TNF-α and IL-1β in heart supernatants of mice with PM2.5 instillation were determined. Nox4 and Nox-associated subunits such as p67phox, p47phox and p22phox expression levels were increased in heart tissue of mice after PM2.5 exposure. Additionally, PM2.5 exposure causes myocardial apoptosis in the mouse heart. This study suggested that Nox4 is involved in PM2.5 exposure-induced cardiac injury in mice.