Various stressors rapidly activate the p38-MAPK signaling pathway in Mytilus galloprovincialis (Lam.)

The stimulation of p38-MAPK signal transduction pathway by various stressful stimuli was investigated in the marine bivalve M. galloprovincialis. Oxidative stress (5 μM H₂O₂) induced a biphasic pattern of p38-MAPK phosphorylation with maximal values attained at 15 min (8.1-fold) and 1 h (8.0-fold) of treatment respectively. Furthermore, 1 μM SB203580 abolished the p38-MAPK phosphorylation induced by oxidative stress. Aerial exposure also induced a biphasic pattern of p38-MAPK phosphorylation, with maximal values attained at 1 h (6.8-fold) and 8 h (4.9-fold) respectively. Re-oxygenation following a 15 min of aerial exposure resulted in the progressive dephosphorylation of the kinase. Treatment with 0.5 M sorbitol (in normal seawater) induced the rapid kinase phosphorylation (9.2-fold) and this effect was reversible. Seawater salinities varying between 100-60% had no effect, whereas a salinity of 50% induced a significant p38-MAPK phosphorylation. Furthermore, hypertonicity (120% seawater) resulted in a moderate kinase phosphorylation. All the above results demonstrate for the first time in a marine invertebrate imposed to environmental and other forms of stress as an intact, living organism, that the p38-MAPK pathway is specifically activated by various stressful stimuli which this animal can often face and sustain in vivo.