Activation of the hsp70 promoter by environmental inorganic and organic chemicals: relationships with cytotoxicity and lipophilicity

Abstract

Stress proteins (heat shock proteins, HSPs) have been proposed as general markers of cellular aggression and their use for environmental monitoring is often suggested. The aim of this work was to study the potency of various environmentally relevant organic and inorganic chemicals to induce the expression of the HSP70 marker. For this purpose, we used an established HeLa cell line containing the chloramphenicol acetyl transferase (CAT) gene under the control of the hsp70 promoter. The screening of three metallic and 15 organic chemicals revealed differences in their capacities to induce the hsp70 promoter. The three metals tested (cadmium, zinc and mercury) were able to induce a stress response. Some organochlorine compounds (chlorophenol derivatives, tetrachlorohydroquinone, 3, 4-dichloroaniline, ethyl parathion and 1-chloro-2,4-dinitrobenzene) induced a response, whereas other common halogenated pesticides or aromatic hydrocarbons (e.g. benzo(a)pyrene, 2, 4-dichlorophenoxyacetic acid, endosulfan, diuron, 4-nonylphenol) did not. The potency to induce hsp70 was significantly correlated to the octanol-water partition coefficient (log K(ow)) of the inducing chemicals, except for 1-chloro-2,4-dinitrobenzene and ethyl parathion. Cytotoxicity assays run in parallel to the induction measurements revealed that the three metals were effective at non cytotoxic doses whereas all organic compounds, except tetrachlorohydroquinone and 1-chloro-2,4-dinitrobenzene, induced the promoter at cytotoxic doses. These results suggest that hsp70 is induced by different mechanisms of toxicity. We propose that this model can be used in mechanistic studies for the detection of toxic effects of certain pollutants.

Developmental toxicology of cadmium in living embryos of a stable transgenic zebrafish line.

“…A variety of cytotoxic agents including Cd have been shown to up-regulate hsp70, and hsp70 expression has been examined as a potential marker in toxicologic screening for a number of vertebrate species. The most commonly used assays include Northern and Western blots, as well as hsp70 gene promoters linked to reporter genes in transfected cells (4)(5)(6)(7). Although such assays can serve as a rapid and accurate means to assess toxin impact in cultured cells, they are of limited value in assessing toxicity or elucidating mechanisms in intact individuals during development.…”

Heat shock response: hsp70 in environmental monitoring

“…Extensive studies in this field revealed that virtually every other nonthermal stress could induce Hsps [31][32][33]. Owing to their responsiveness to diverse forms of stress, the stress proteins have undergone widespread application in biomonitoring and environmental toxicology [5,[34][35][36][37][38][39][40][41]. As members of the Hsp70 are often the prominent proteins to be expressed following environmental insults, these stress proteins are, therefore, very useful indicators of cellular aggression, and have been used to monitor the impact of environmental factors on various animal species [42][43][44][45] as well as in in vitro models [28,37,41,46,47].…”

“…Owing to their responsiveness to diverse forms of stress, the stress proteins have undergone widespread application in biomonitoring and environmental toxicology [5,[34][35][36][37][38][39][40][41]. As members of the Hsp70 are often the prominent proteins to be expressed following environmental insults, these stress proteins are, therefore, very useful indicators of cellular aggression, and have been used to monitor the impact of environmental factors on various animal species [42][43][44][45] as well as in in vitro models [28,37,41,46,47]. Hsp70 is the target molecule or molecule under investigation because it simultaneously takes part in defense, repair, or detoxification machinery of the cell and becomes a direct and specific indicator of cellular stress [30,[48][49][50][51].…”

“…They showed that the extent of DNA damage under such conditions paralleled the levels of Hsp70 expression. The potency of various environmentally relevant organic and inorganic chemicals to induce the expression of Hsp70 was investigated by Ait-Aissa et al [37] in HeLa cell line (containing chloramphenicol acetyl transferase gene under the control of Hsp70 promoter). They suggested that hsp70 was induced by different mechanisms of toxicity and suggested the use of Hsp70 in mechanistic studies for the detection of toxic effects of certain pollutants.…”

Development of stable HSPA1A promoter-driven luciferase reporter HepG2 cells for assessing the toxicity of organic pollutants present in air

“…Because of its stress responsiveness, HSPA1A expression is a potential marker in toxicological screening (Gupta et al 2010). In fact, human cells carrying an HSPA1A promoter-driven reporter gene have been used to assess the toxicity of heavy metals, organochlorine compounds, and eluates of industrial wastes (Aït-Aïssa et al 2003;Aït-Aïssa et al 2000). However, HeLa cells may not be metabolically competent enough to metabolize PAHs to more toxic metabolites, such as benzo[a]pyrene diolepoxide.…”