Proteomic response to elevated PCO2 level in eastern oysters, Crassostrea virginica: evidence for oxidative stress

Abstract

SUMMARYEstuaries are characterized by extreme fluctuations in CO 2 levels due to bouts of CO 2 production by the resident biota that exceed its capacity of CO 2 consumption and/or the rates of gas exchange with the atmosphere and open ocean waters. Elevated partial pressures of CO 2 (P CO2; i.e. environmental hypercapnia) decrease the pH of estuarine waters and, ultimately, extracellular and intracellular pH levels of estuarine organisms such as mollusks that have limited capacity for pH regulation. We analyzed proteomic changes associated with exposure to elevated P CO2 in the mantle tissue of eastern oysters (Crassostrea virginica) after 2weeks of exposure to control (~39Pa P CO2 ) and hypercapnic (~357Pa P CO2 ) conditions using two-dimensional gel electrophoresis and tandem mass spectrometry. Exposure to high P CO2 resulted in a significant proteome shift in the mantle tissue, with 12% of proteins (54 out of 456) differentially expressed under the high P CO2 compared with control conditions. Of the 54 differentially expressed proteins, we were able to identify 17. Among the identified proteins, two main functional categories were upregulated in response to hypercapnia: those associated with the cytoskeleton (e.g. several actin isoforms) and those associated with oxidative stress (e.g. superoxide dismutase and several peroxiredoxins as well as the thioredoxin-related nucleoredoxin). This indicates that exposure to high P CO2 (~357Pa) induces oxidative stress and suggests that the cytoskeleton is a major target of oxidative stress. We discuss how elevated CO 2 levels may cause oxidative stress by increasing the production of reactive oxygen species (ROS) either indirectly by lowering organismal pH, which may enhance the Fenton reaction, and/or directly by CO 2 interacting with other ROS to form more free radicals. Although estuarine species are already exposed to higher and more variable levels of CO 2 than other marine species, climate change may further increase the extremes and thereby cause greater levels of oxidative stress.

Effects of ocean acidification on immune responses of the Pacific oyster Crassostrea gigas

“…The role of these antioxidant systems can be of great importance in response to environmental stress in aquatic animals [41]. Previous studies have demonstrated that OA exposure could generally cause oxidative stress in bivalve, sea urchin and coral [37,38,42,43]. In this study, the activities of antioxidant enzymes and GSH and MDA levels in gills did not change significantly on Day 7 and Day 14, suggesting this oyster could maintain its redox homeostasis in gills under elevated pCO 2 exposure levels.…”

“…However, the effects of OA on the physiological response of mollusks are variable among species and even within the same species [32]. In C. virginica, SOD expression was up-regulated in the mantle tissue of oysters under elevated pCO 2 condition (pH7.5) [42]. In the clam Chamelea gallina and the mussel Mytilus galloprovincialis, OA stress also generally caused increases in antioxidant enzyme activities after exposure for 7 days [43].…”

Is warmer better? Decreased oxidative damage in notothenioid fish after long-term acclimation to multiple stressors

“…Although temperature increases have long been known to impact oxidative stress in organisms (Lesser, 2006), ocean acidification has recently emerged as a potentially more pressing issue in the world's oceans, and to date, we still have a poor understanding of the cellular-level impact that ecologically relevant increases in seawater Ṗ CO 2 will have on cellular homeostasis. Increases in Ṗ CO2 are specifically hypothesized to exacerbate oxidative stress by directly affecting mitochondrial function (Murphy, 2009;Tomanek et al, 2011), and recent studies have indeed shown that hypercapnia can negatively affect mitochondrial capacities in Antarctic fish (Strobel et al, 2012;Strobel et al, 2013b). We found that oxidative damage was most apparent within the first 7 days of acclimation to the treatment conditions, which coincides with a spike in the resting metabolic rate (RMR) of all three species under these same acclimation conditions (Enzor et al, 2013).…”

“…Decreased oxidative damage in notothenioid fish after long-term acclimation to multiple stressors Laura A. Enzor and Sean P. Place* extent than temperate regions (Walther et al, 2002;Orr et al, 2005;Turner et al, 2005;McNeil and Matear, 2008;Fabry et al, 2008;Fabry et al, 2009;Halpern et al, 2008;McNeil et al, 2010;Mathis et al, 2011a;Mathis et al, 2011b), only a handful of studies have examined the effects of ecologically relevant increases in seawater Ṗ CO 2 on high latitude marine teleosts (Hurst et al, 2012;Strobel et al, 2012;Enzor et al, 2013;Strobel et al, 2013a;Strobel et al, 2013b). Similar to impacts seen with elevated temperature, ocean acidification may also perturb oxidative stress in marine teleosts (Murphy, 2009;Tomanek et al, 2011) and may even exacerbate the detrimental effects of reactive oxygen species at the cellular level (Ezraty et al, 2011).…”

Physiological, Immunological, Genotoxic and Histopathological Biomarker Responses of Molluscs to Heavy Metal and Water-Quality Parameter Exposures: A Critical Review

“…Britz et al [18] and Hooper et al [19] reported that high temperature of over 20°C has been shown to cause immunosuppression, reduced growth, heat shock to protein in abalone during summer season and could lead to serious disease outbreak. Tomanek et al [20] demonstrated that pH of 7.5 can cause oxidative stress in Crassostrea virginica. This is supported by Matozzo et al [21] who showed that decreased pH and high temperature can strongly affect the immune-parameters of clam, Chamelea gallina and mussel, Mytilus galloprovincialis.…”