Acrolein increases the concentration of intracellular Zn²⁺ by producing mitochondrial reactive oxygen species in A549 cells

Smoking or occupational exposure leads to low concentrations of acrolein on the surface of the airways. Acrolein is involved in the pathophysiological processes of various respiratory diseases. Reports showed that acrolein induced an increase in mitochondrial reactive oxygen species (mROS). Furthermore, exogenous H₂O₂ was found to increase intracellular Zn²⁺ concentration ([Zn²⁺]ᵢ). However, the specific impact of acrolein on changes in intracellular Zn²⁺ levels has not been fully investigated. Therefore, this study aimed to investigate the effects of acrolein on mROS and [Zn²⁺]ᵢ in A549 cells. We used Mito Tracker Red CM-H₂Xros (MitoROS) and Fluozin-3 fluorescent probes to observe changes in mROS and intracellular Zn²⁺. The results revealed that acrolein increased [Zn²⁺]ᵢ in a time- and dose-dependent manner. Additionally, the production of mROS was observed in response to acrolein treatment. Subsequent experiments showed that the intracellular Zn²⁺ chelator TPEN could inhibit the acrolein-induced elevation of [Zn²⁺]ᵢ but did not affect the acrolein-induced mROS production. Conversely, the acrolein-induced elevation of mROS and [Zn²⁺]ᵢ were significantly decreased by the inhibitors of ROS formation (NaHSO₃, NAC). Furthermore, external oxygen free radicals increased both [Zn²⁺]ᵢ levels and mROS production. These results demonstrated that acrolein-induced elevation of [Zn²⁺]ᵢ in A549 cells was mediated by mROS generation, rather than through a pathway where [Zn²⁺]ᵢ elevation leads to mROS production.