Effects of nickel poisoning on expression pattern of the 72/73 and 94 kDa stress proteins in rat organs and in the COS-7, HepG2, and A549 cell lines

Synergistic effects of toxic elements on heat shock proteins

Heat shock proteins show remarkable variations in their expression levels under a variety of toxic conditions. A research span expanded over five decades has revealed their molecular characterization, gene regulation, expression patterns, vast similarity in diverse groups, and broad range of functional capabilities. Their functions include protection and tolerance against cytotoxic conditions through their molecular chaperoning activity, maintaining cytoskeleton stability, and assisting in cell signaling. However, their role as biomarkers for monitoring the environmental risk assessment is controversial due to a number of conflicting, validating, and nonvalidating reports. The current knowledge regarding the interpretation of HSPs expression levels has been discussed in the present review. The candidature of heat shock proteins as biomarkers of toxicity is thus far unreliable due to synergistic effects of toxicants and other environmental factors. The adoption of heat shock proteins as "suit of biomarkers in a set of organisms" requires further investigation.

Titanium dioxide nanoparticles-mediated in vitro cytotoxicity does not induce Hsp70 and Grp78 expression in human bronchial epithelial A549 cells

Titanium dioxide nanoparticles (TiO(2)NPs) are increasingly being used in various industrial applications including the production of paper, plastics, cosmetics and paints. With the increasing number of nano-related products, the concern of governments and the general public about the health and environmental risks, especially with regard to occupational and other environmental exposure, are gradually increasing. However, there is insufficient knowledge about the actual affects upon human health and the environment, as well as a lack of suitable biomarkers for assessing TiO(2)NP-induced cytotoxicity. Since the respiratory tract is likely to be the main exposure route of industrial workers to TiO(2)NPs, we investigated the cytotoxicity of the anatase and rutile crystalline forms of TiO(2)NPs in A549 cells, a human alveolar type II-like epithelial cell line. In addition, we evaluated the transcript and protein expression levels of two heat shock protein (HSP) members, Grp78 and Hsp70, to ascertain their suitability as biomarkers of TiO(2)NP-induced toxicity in the respiratory system. Ultrastructural observations confirmed the presence of TiO(2)NPs inside cells. In vitro exposure of A549 cells to the anatase or rutile forms of TiO(2)NPs led to cell death and induced intracellular ROS generation in a dose-dependent manner, as determined by the MTS and dichlorofluorescein (DCF) assays, respectively. In contrast, the transcript and protein expression levels of Hsp70 and Grp78 did not change within the same TiO(2)NPs dose range (25-500 μg/ml). Thus, whilst TiO(2)NPs can cause cytotoxicity in A549 cells, and thus potentially in respiratory cells, Hsp70 and Grp78 are not suitable biomarkers for evaluating the acute toxicological effects of TiO(2)NPs in the respiratory system.

Toxicity profiles of four metals and 17 xenobiotics in the human hepatoma cell line HepG2 and the protozoa Tetrahymena pyriformis--a comparison

We performed an interspecies comparison for the human hepatoma cell line HepG2 and the eukaryotic single cell organism Tetrahymena pyriformis (T. pyriformis) for 17 xenobiotics with diverse structures and four metals. The cytotoxicity was assessed by four different cell viability assays (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide reduction (MTT), neutral red uptake (NRU), resazurin dye (AlamarBlue), 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM)) for the HepG2 and by cell count and MTT for T. pyriformis. For HepG2 cells, the results revealed interassay variations depending on the compound. The highest assay conformity was found for the metal Hg(2+) and the fungicide prochloraz. The AlamarBlue assay was the most sensitive assay according to low-effect concentrations. By contrast, the NRU assay was comprised of more frequent whole concentration response relationships and was more susceptible to EC(50). For T. pyriformis the EC(50) values of the two applied assays displayed a high conformity (R(2) = 0.97). Comparing the EC(50) values obtained by the MTT assay for the two cell models, a direct correlation was absent for the xenobiotics and only present for the metals (Cd(2+), Cu(2+), and Ni(2+)). Moreover, the protozoa T. pyriformis displayed a 20 times higher sensitivity than the cell line. The highest interspecies difference of three log degrees was obtained for the polycyclic aromatic hydrocarbon fluoranthene. In addition, a correlation of the EC(50) values and octanol-water partition coefficient (log K(OW)) of the xenobiotics was performed. No correlation was found for HepG2, and a weak one for T. pyriformis. Interestingly, the interspecies difference of logarithmized EC(50) correlated positive with the log K(OW) (R(2) = 0.65). In conclusion, to obtain reliable evidence for human cytotoxicity, more than one viability/cytotoxicity assay had to be applied for cell lines. Second, the human hepatoma cell line was less affected by the organic compounds than the eukaryotic single-cell organism and was also less dependent on the log K(OW) of the xenobiotic.