The role of solar radiation and tidal emersion on oxidative stress and glutathione synthesis in mussels exposed to air

Abstract

Preparation for oxidative stress (POS) is a widespread adaptive response to harsh environmental conditions, whose hallmark is the upregulation of antioxidants. In contrast to controlled laboratory settings, animals are exposed to multiple abiotic stressors under natural field conditions. Still, the interplay between different environmental factors in modulating redox metabolism in natural settings remains largely unexplored. Here, we aim to shed light on this topic by assessing changes in redox metabolism in the mussel Brachidontes solisianus naturally exposed to a tidal cycle. We compared the redox biochemical response of mussels under six different natural conditions in the field along two consecutive days. These conditions differ in terms of chronology, immersion/emersion, and solar radiation, but not in terms of temperature. Animals were collected after being exposed to air early morning (7:30), immersed during late morning and afternoon (8:45–15:30), and then exposed to air again late afternoon towards evening (17:45–21:25), in two days. Whole body homogenates were used to measure the activity of antioxidant (catalase, glutathione transferase and glutathione reductase) and metabolic (glucose 6-phosphate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase and pyruvate kinase) enzymes, reduced (GSH) and disulfide (GSSG) glutathione levels, and oxidative stress markers (protein carbonyl and thiobarbituric acid reactive substances). Air and water temperature remained stable between 22.5 °C and 26 °C during both days. Global solar radiation (GSR) greatly differed between days, with a cumulative GSR of 15,381 kJ/m2 for day 1 and 5,489 kJ/m2 for day 2, whose peaks were 2,240 kJ/m2/h at 14:00 on day 1 and 952 kJ/m2/h at 12:00 on day 2. Compared with animals underwater, emersion during early morning did not elicit any alteration in redox biomarkers in both days. Air exposure for 4 h in the late afternoon towards evening caused oxidative damage to proteins and lipids and elicited GSH synthesis in animals that had been previously exposed to high GSR during the day. In the following day, when GSR was much lower, exposure to air under the same conditions (duration, time, and temperature) had no effect on any redox biomarker. These findings suggest that air exposure under low-intensity solar radiation is not sufficient to trigger POS in B. solisianus in its natural habitat. Thus, natural UV radiation is possibly a key environmental factor that combined to air exposure induces the POS-response to the stressful event of tidal variation in this coastal species.

Environmental factors influence cross-talk between a heat shock protein and an oxidative stress protein modification in the lizard Gallotia galloti

“…Further support to this pattern comes from and another lacertid species ( Psammodromus algirus) , which exhibited levels of oxidative stress decreasing at higher elevation [ 118 ] and higher elevations (with higher UV radiation) not inducing significantly more oxidative damage or an antioxidant response [ 119 ]. A high threshold level of solar radiation may be required for oxidative stress to occur, and that may also depend on other stressors [ 120 ].…”

Glutathione Depletion Disrupts Redox Homeostasis in an Anoxia-Tolerant Invertebrate

“…The upregulation of antioxidant systems under environmental stress was coined “Preparation for Oxidative Stress” (POS) [ 2 , 4 , 5 ], which has been described to occur in over 80 animal species from 8 phyla, under laboratory simulations of harsh environmental conditions [ 6 , 7 ]. More recently, the POS phenotype has also been observed to happen naturally in the field for a few animal taxa, including mollusks [ 8 , 9 , 10 , 11 ].…”