Integrated metabolomics and flow cytometry assessment reveals immune-metabolic modulation of Crassostrea (=Magallana) gigas hemolymph under hypoxic and elevated temperature conditions

초록

Marine bivalves generally exhibit high tolerance to hypoxia; however, their adaptive capacity can be compromised when hypoxic conditions are exacerbated by elevated seawater temperatures. This study investigated the metabolomic profiles and hemocyte phenotypes of Pacific oysters (Crassostrea gigas) following exposure to hypoxia and combined hypoxia with high seawater temperature stress. Oysters were subjected to three experimental conditions for 13 days: control (22 degrees C, 6 mg O2/L), hypoxia (22 degrees C, 1 mg O2/L), and hypoxia with high seawater temperature (28 degrees C, 1 mg O2/L). A gas chromatography-mass spectrometry (GC-MS) metabolomics approach was used to assess the metabolic modulation of hemolymph to hypoxia and thermal stress. Additionally, hemocyte phenotypic parameters, including total hemocyte count (THC), hemocyte mortality, phagocytosis, nitric oxide (NO) production, and oxidative capacity, were evaluated using flow cytometry. Metabolomics results showed depletion of amino acids involved in anaerobic respiration and the urea cycle, under hypoxia and elevated seawater temperatures. Additionally, reactive oxygen species (ROS)-related metabolites, including glutathione, glutamate, glycine and lysine were reduced under hypoxic and heat stress, while NO production increased under combined stress conditions. Lipid metabolites including 13,16-docosadienoic acid, margaric acid, myristic acid and oleic acid associated with a reduced ability to maintain cellular homeostasis and cell proliferation were elevated, accompanied by an increase in THC. Hemocyte mortality was significantly higher under hypoxia and high seawater temperature stress, while phagocytosis and its associated eicosapentaenoic acid and oleic acid were reduced. These findings suggest that the suppression of metabolic activity via anaerobic respiration, aimed at energy conservation, consequently, impairs immune function. This metabolic immune trade-off potentially exacerbates susceptibility to stressors, contributing to summer mortality in Pacific oysters.

키워드