HSP70 response in Mediterranean mussels exposed to the antibiotic oxytetracycline

Heat shock proteins (HSP) are highly conserved intracellular proteins expressed in all living organisms from prokaryotes to eukaryotes, and grouped according to their molecular weight (e.g. the HSP70 family). They are also distinguished into constitutive isoforms (heat shock cognate, HSC) expressed at physiological conditions serving as molecular chaperones, and inducible isoforms (heat shock protein, HSP) over-expressed under stressful conditions with a cytoprotective role. Although the term HSP specifically refers to heat shock, the accumulation of these proteins is not increased only by heat. A variety of stimuli increases their concentrations, probably acting through several mechanisms; however, proteotoxi- city remains at the moment the sole common factor at the cellular level. Pharmaceutical residues were shown to survive conventional water-treatment processes, thus contaminate aquatic ecosystems as a resul t of very wi despread human and veterinary usage. We investigated whether environmental concentrations of oxytetracycline (OTC) may represent a stress factors for mussels Mytilus galloprovincialis and elicit the HSP response. OTC is a broad-spectrum antibiotic active against a wide variety of bacteria, which works by interfering with the ability of bacteria to produce essential proteins. Its presence in the marine environment has been recently reported. Mussels exposed at 16 °C for 4 days to 5 concentrations of OTC (from 0.1 to 1000 μg/L) showed an increase in the inducible HSP70 protein expression, with a maximum effect of about 185% vs control values reached at 1 μg/L OTC and slightly decreasing thereafter. The constitutive isoform expression was not changed after OTC exposure. Further effects at 20 and 24 °C are currently under investigation. The present research is carried out in the framework of 7FP-EU MEECE.