Hydrogen peroxide (H 2 O 2 ) induces actin and some heat‐shock proteins in Drosophila cells

Drosophila cells of a clone derived from line Kc were treated with various concentrations of hydrogen peroxide (H 2 O 2 ). The concentration of 10 mM was lethal, whereas concentrations of 1–100 μM did not affect cell viability, rate of multiplication or protein synthesis. The intermediate concentration of 1 mM H 2 O 2 was used to study the response of the cells to an oxidative stress. We observed a transitory decrease of the global protein synthesis, which was accompanied by changes in the polypeptide pattern. There was a 2.5‐fold increase of the synthesis of the heat‐shock proteins 70–68 and 23. The most prominent response was a 6.5‐fold increase of actin synthesis 3 h after a 1 mM H 2 O 2 treatment. When aminotriazole (an inhibitor of catalase) was added in association with H 2 O 2 , the increase of actin synthesis became 8.5‐fold. Experiments in which catalase was added at various times after H 2 O 2 showed that a 10‐min treatment with H 2 O 2 was sufficient to induce actin and heat‐shock protein synthesis 3 h later. H 2 O 2 was shown to induce the transcriptional activation of an actin gene and of the heat‐shock protein genes 70 and 23 within minutes. These results are coherent with the hypothesis that the byproducts of O 2 reduction (the superoxide ion and hydrogen peroxide) could be inducers of the heat‐shock response. Whether the increase of actin synthesis is a stress‐related response, and the mode of action of H 2 O 2 are discussed