Proteomic changes in human lung epithelial cells (A549) in response to carbon black and titanium dioxide exposures.

This study combined cytotoxicity assays with proteomic analysis to characterize the unique biological responses of the A549 human lung epithelial cell line to two physicochemically distinct respirable particles titanium dioxide (TiO2) and carbon black (CB). Cellular LDH, ATP, BrdU incorporation and resazurin reduction indicated that CB was more potent than TiO2. Proteomic analysis was done using 2D-GE and MALDI-TOF-TOF-MS. Proteomic changes reflected common and particle-specific responses. Particle-specific proteomic responses were associated with cell death (necrosis and apoptosis), viability and proliferation pathways. Our results suggested that these pathways were consistent with the cytotoxicity data. For instance, increased expressions of anti-proliferative proteins LMNA and PA2G4 were in agreement with the decreased BrdU incorporation in A549 cells after exposure to CB. Similarly, increased expression of HSPA5 that is associated with ATPase activity was consistent with decreased cellular ATP levels in these cells. These findings reveal that proteomic changes can explain the cellular cytotoxicity characteristics of the particles. In essence, our results demonstrate that the in vitro toxicoproteomic approach is a promising tool to gain insight into molecular mechanisms underlying particle exposure-specific cytotoxicity. BIOLOGICAL SIGNIFICANCE: In this study we have shown that toxicoproteomics is a sensitive and informative method to resolve the toxicity characteristics of particles with different physicochemical properties. This approach can be useful in the investigation of molecular mechanisms underpinning cellular cytotoxic responses elicited by particle exposures. Thus, the toxicoproteomic approach can be valuable in assessing the risk associated with particle exposures in vitro. Crown