Effects of coarse chalk dust particles (2.5–10 μm) on respiratory burst and oxidative stress in alveolar macrophages

The main aim of the present study was to examine in vitro responses of rat alveolar macrophages (AMs) exposed to coarse chalk dust particles (particulate matter in the size range 2.5–10 μm, PMcoarse) by respiratory burst and oxidative stress. Chalk PMcoarse-induced respiratory burst in AMs was measured by using a luminol-dependent chemiluminescence (CL) method. Also, the cell viability; lactate dehydrogenase (LDH) release; levels of cellular superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), malondialdehyde (MDA), and acid phosphatase (ACP); plasma membrane ATPase; and extracellular nitric oxide (NO) level were determined 4 h following the treatment with the different dosages of chalk PMcoarse. The results showed that chalk PMcoarse initiated the respiratory burst of AMs as indicated by strong CL, which was inhibited by diphenyleneiodonium chloride and l-N-nitro-l-arginine methyl ester hydrochloride. It suggested that chalk PMcoarse induced the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in AMs. This hypothesis was confirmed by the fact that chalk PMcoarse resulted in a significant decrease of intracellular SOD, GSH, ACP, and ATPase levels and a notable increase of intracellular CAT, MDA content, and extracellular NO level, consequently leading to a decrease of the cell viability and a increase of LDH release. It was concluded that AMs exposed to chalk PMcoarse can suffer from cytotoxicity which may be mediated by generation of excessive ROS/RNS.