Evaluation for Hsp70 as a biomarker of effect of pollutants on the earthworm Lumbricus terrestris

Induction of heat shock proteins (Hsps) is often associated with a cellular response to a harmful stress or to adverse life conditions. The main aims of the present study were (1) to assess if stress-induced Hsp70 could be us ed to monitor exposure of the earthworm species Lumbricus terrestris to var ious soil pollutants, (2) to assess the specificity of pollutants in their tissue targeting and in Hsp70 induction, and (3) to evaluate if dose-respon se relationships could be established and if the stress-response observed w as specific. The midgut/intestinal tissues of L. terrestris are shown to ex press an inducible member of the Hsp70 family after heat shock treatment in vitro and exposures to different soil toxicants in vivo (re: artificial so il). Short-term (24-72 hours) and long-term (14-16 days) exposures to the c hemical standards chloroacetamide and pentachlorophenol and to heavy metals (Pb++, Gd++, Cu++, and Hg++) also affected the earthworms, and Hsp70 was i nduced in their midgut/intestinal tissues. After a 3-day exposure to heavy metals, the level of Hsp70 induction in the midgut/intestinal tissues appea rs to correlate well with the reported in vivo and in vitro toxicity data. Comparatively, in proximal and midbody wall muscle tissues of animals expos ed to the heavy metals, a decrease in expression of Hsp70 was sometimes det ected. Thus Hsp analysis by Western blot in L. terrestris tissues and parti cularly in the midgut/intestine proved to be a suitable and sensitive assay for adverse effects in earthworms and showed a good level of reproducibili ty despite some individual variations. The use of pristine/nonexposed anima ls transposed into contaminated environments as in the present study should therefore be of high ecological relevance. Induction of Hsp70 in earthworm s should represent not only a good wide-spectrum biomarker of exposure but also a biomarker of effect since known toxicants altered gene expression in tissues of these animals, as contrasted with a simple accumulation of Hsp, Hence, the detection of Hsp70 in earthworms can constitute an early-warnin g marker for the presence of potentially deleterious agents in soils, with L. terrestris in particular and earthworms in general acting as potential s entinel animal species.