Correlation between intermediary metabolism, Hsp gene expression and oxidative stress related proteins in long-term thermal stressed Mytilus galloprovincialis.

Long-term exposure of Mytilus galloprovincialis to temperatures beyond 26oC triggers mussels' mortality. The present study aimed to integratively illustrate the correlation between intermediary metabolism, Hsp gene expression and oxidative stress related proteins in long-term thermally stressed Mytilus galloprovincialis and whether they are affected by thermal stress' magnitude and duration. We accordingly evaluated the gene expression profiles, in the posterior adductor muscle (PAM) and the mantle, concerning hsp70 and hsp90, and the antioxidant defense indicators Mn-SOD, Cu/Zn-SOD, catalase, glutathione S-transferase, and the metallothioneins mt-10 and mt-20. Moreover, we determined antioxidant enzymes' activities, oxidative stress through lipid peroxidation and activities of intermediary metabolism enzymes. The pattern of changes in relative mRNA expression levels indicate that mussels are able to sense thermal stress even when exposed to 22oC and before mussels' mortality is initiated. Data indicates a close correlation between the magnitude and duration of thermal stress with lipid peroxidation levels, changes in the activity of antioxidant enzymes and the enzymes of intermediary metabolism. The gene expression and increase in the activities of antioxidant enzymes support a scenario, according to which exposure to 24oC might trigger ROS production, which is closely correlated with anaerobic metabolism under hypometabolic conditions. Increase and maintenance of oxidative stress in conjunction with energy balance disturbance seems to trigger mussels' mortality after long term exposure at temperatures beyond 26oC. Eventually, in the context of preparation for oxidative stress, certain hypotheses and models are suggested, integrating the several steps of cellular stress response.