Volatile organic compounds cytotoxicity and expression of HSP72, HSP90 and GRP78 stress proteins in cultured human cells

Abstract

The aim of this study was to determine whether overexpression of stress proteins (SPs) could be a sensitive biomarker for cell injury due to exposure to low doses of volatile organic compounds (VOCs) such as benzene, ethylbenzene, toluene, xylene, and chlorinated derivatives (ClB). Sublethal and cytotoxic threshold concentrations of the VOCs were determined by studying the growth rate of normal (fibroblasts) or tumor-derived human cell lines (A549, HepG2) exposed for 4 days to VOCs. Changes in SP expression as a function of concentrations were investigated by Western blotting.VOC toxicity was found to be correlated with their degree of chlorination and their hydrophobicity. Cytotoxic threshold concentrations (no-observed effect concentration, NOEC) were found to be similar for the three cell lines. It was observed that using a mixture of VOCs, each of them at concentration below the NOEC, resulted in an actual toxicity to the cells. This finding reveals a synergistic effect and should be taken into account when assessing threshold risk and exposure limit values in the worker's environment when several pollutants may be present. HSP72 and HSP90 expression levels were not affected whereas GRP78 expression was increased by all the VOCs. Taking into account the specific molecular function of GRP78, it suggests that VOC exposure results in misfolded or underglycosylated protein accumulation in the endoplasmic reticulum. GRP78 overexpression was closely related to the magnitude of growth inhibition due to increasing concentrations of each VOC. The overexpression was found to be significant for concentrations 5 to 30 times higher than NOEC, indicating that, under our experimental conditions, GRP78 expression cannot be considered as a sensitive biomarker of exposure to environmental VOCs.

Combined Toxic Effects of Polar and Nonpolar Chemicals on Human Hepatocytes (HepG2) Cells by Quantitative Property - Activity Relationship Modeling

“…The individual substances composing mixed compounds undergo selective interaction, due to differences in physico-chemical properties and structures. As a result, differences in substance metabolism and toxicity are observed (18). Many studies are being conducted on the absorption and metabolic interactions of mixed compounds in the body; (19,20) however, studies determining toxicity and its mechanism are lacking (21,22).…”

“…When the toxicity level is compared with the time weight average (TWA) standard of the Ministry of Employment and Labor, TOL toxicity is higher (TOL is 50 ppm and XYL is 100 ppm) and LD 50 value is lower (2,600 mg/kg rat) than XYL (3,500 mg/kg rat), indicating that TOL is more toxic. However, Croute et al (18) reported that TOL cytotoxicity is higher than that of benzene, owing to the side chain attached to the benzene ring and the effect of the lipophilic properties. The EC 50 value of XYL is lower than that of TOL in this study, likely due to the structural properties of the chemicals.…”

The cytotoxicity of volatile JP-8 jet fuel components in keratinocytes

“…In vitro dosimetry with VOCs is influenced by the headspace and culture medium volume, chemical solubility, and partitioning of the chemical into the culture medium and cells. Moreover, aromatic hydrocarbons can interact with the polystyrene of tissue culture flasks and plates (Croute et al, 2002). Since most VOCs possess low solubility in aqueous solution, maintaining these chemicals in solution is important to achieve a uniform exposure.…”

“…In unsealed in vitro systems, evaporation of the VOC may occur from the culture medium, resulting in decreasing chemical concentration in the exposure medium. Croute et al (2002) suggested that adding VOCs directly to culture medium in unsealed containers results in transient chemical concentrations that decrease within 30 min due to evaporation into the surrounding atmosphere. Such decreases can lead to a non-uniform or unknown chemical dose throughout the exposure period, which may ultimately affect the interpretation of dose-response relationships.…”

Adhesives based on formaldehyde – environmental problems

“…These compounds may originate from paints, lacquers, floor coverings, wallpapers and other materials. Croute and coworkers (Croute et al, 2002) noted that painting, staining and lacquering can produce VOC air concentrations of up to 1000 mg/m 3 . This concentration is a million times higher than typical concentrations in outdoor air (Table 2).…”