Induction of DNA Strand Breaks and Expression of HSP70 and GRP78 Homolog by Cadmium in the Marine Sponge Suberites domuncula

Abstract

The marine sponge Suberites domuncula was used as a bioindicator to study the effects of cadmium on the occurrence of DNA strand breakage and on the induction of the expression of the stress biomarkers, heat shock protein 70 (HSP70) and glucose-regulated protein 78 (GRP78) homolog. The cDNA encoding GRP78 homolog from S. domuncula was isolated and characterized. The GRP78 cDNA has a length of 2.1 kb and displays characteristic features of the HSP70 family; it encodes an aa sequence of Mr 72,000. Exposure of S. domuncula to 1 mg/L of cadmium chloride for 24 h caused a strong (16. 6-fold) increase in cadmium content to 7.7 microg/g wet weight of sponge tissue; after an incubation period of 6 days, the accumulation was 20.4-fold. The increase in cadmium content was paralleled by a transient decrease in zinc content at days 1 and 3. Exposure of S. domuncula to cadmium chloride also resulted in a marked increase in the number of DNA single strand breaks, as assessed by a recently developed fast and sensitive microplate assay. The maximum increase in DNA damage was observed after an incubation of 12 h in the presence of 1 mg/L of cadmium chloride; after longer incubation, the number of damaged sites decreased, most likely due to DNA repair. Quantitative analysis of the expression of HSP70 (Mr 73 kDa) revealed that onset of maximal levels of HSP70 depends on the concentration of cadmium chloride in the ambient seawater. Maximal induction (8.9-fold increase compared to control) of HSP70 following exposure to 1 mg/L of cadmium chloride was found after 12 h, while longer incubation periods (3-6 days) were needed to reach maximum levels of HSP70 in the presence of lower concentrations of cadmium chloride (0.1 mg/L and 0.01 mg/L). Northern blot analysis revealed that the level of the 2.0 kb sponge GRP78 homolog mRNA transiently increased under cadmium stress; the maximum increase in the presence of 0.1 mg/L of cadmium chloride was observed at day 3. Our results suggest that sponges are useful indicator organisms to assess the genotoxic risks of cadmium pollution in marine environments.

Strict thermal threshold identified by quantitative PCR in the sponge Rhopaloeides odorabile

“…A similar phenomenon has also been reported in Aurelia spp. (Schroth et al 2005) and in sponges exposed to cadmium (Schröder et al 1999). The 31°C treatment is much less acute but appears to cause some 103 Mar Ecol Prog Ser 431: 97-105, 2011 sub-lethal molecular responses that are able to return to normal once the thermal stress has been removed.…”

Cadmium induces the expression of specific stress proteins in sea urchin embryos

“…The increased expression of hsps (hsp70, hsp60, and hsp27) in response to cadmium was demonstrated in tissues and cells of many organisms, e.g., sponges [5], Drosophila [7], nematodes [8,9], and human cells [10].…”

Cadmium induces an apoptotic response in sea urchin embryos

“…The metal is highly dangerous not only because it easily penetrates the cells but also because it is eliminated very slowly (Jarup et al 1998). In the majority of cases, it damages chromosomes and inhibits the mechanisms implicated in DNA repair (Schroder et al 1999). It is known that heavy metals interfere on gametogenesis, inhibit embryogenesis, and interrupt development at different stages (Au et al 2001;Fernandez and Beiras 2001).…”

“…It is known that heavy metals interfere on gametogenesis, inhibit embryogenesis, and interrupt development at different stages (Au et al 2001;Fernandez and Beiras 2001). Cadmium exposure can also induce apoptosis in testicular tissue of rat, mouse liver, human T-cells (Xu et al 1996;Habeebu et al 1998;Tsangaris and Tzortzatou-Stathopoulou 1998), and marine sponges (Schroder et al 1999); on the other hand, it has been demonstrated that caspase inhibitors attenuated Cd-induced apoptosis (Galan et al 2000). In response to different stresses, the cells activate the synthesis of heat shock proteins (Hsps), caused by the accumulation of denatured proteins.…”