Activation of MAP kinase signaling pathway in the mussel Mytilus galloprovincialis as biomarker of environmental pollution

Stimulation of MAP kinase signal transduction pathway by various stressful stimuli was investigated in the marine bivalve Mytilus galloprovincialis. Analyses were performed in animals exposed in laboratory to selected pollutants and in mussels collected in winter and summer along the eastern Adriatic coast (Croatia). Effects of oxidative stress, induced by tributyltin, hydrogen peroxide and water soluble fraction of diesel fuel on the activation/phosphorylation of the three Mitogen-Activated Protein Kinases (MAPKs) p38, JNK and ERK using a newly developed ELISA procedure were evaluated. MAP kinase activation was analyzed 1 h after exposure of mussels to chemical agents, and after recovery periods of 6 and 24 h. Our results clearly indicated that pollutants generated different patterns of induction of the MAPK phosphorylation. Indeed, only pp38 and pJNK were activated with 11, 33 and 100 μg/L TBT, reaching a maximum activation after 6 h in seawater following treatment of mussels with 11 μg/L TBT. Treatment with 0.074 and 0.222 mM H2O2 enhanced activation of both p38 and ERK. These two kinases were activated after 1 h exposure, followed by a diminution after 6 h of recovery in seawater and a reactivation after 24 h. The levels of phoshorylated P38 and JNK were increased after mussel exposure with 7.5, 15 and 30% of water soluble fraction of diesel oil. P38 was activated concentration dependently at 1 h exposure. Additionally, field study pointed out seasonal differences in MAP kinases activation as mussels collected during summer had a higher enzyme activation state than in winter, as well as sampling site differences which could be correlated to the industrial/tourism activity and environmental stresses (salinity). All the results converge towards MAP kinase signaling pathway being induced by various pollutants in M. galloprovincialis. This signaling cascade should be considered as a possible biomarker of environmental stress and pollution.