Submitted to: Journal of Aquatic Animal Health
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/5/2012
Publication Date: 10/31/2012
Citation: Beck, B.H., Fuller, S.A. 2012. The impact of mitochondrial and thermal stress on the bioenergetics and reserve respiratory capacity of fish cell lines. Journal of Aquatic Animal Health. 24(4):244-250. Interpretive Summary: Both wild fish and farmed fish alike are frequently exposed to numerous environmental stressors such as high temperature, low oxygen, and poor water quality which can negatively affect fish metabolism, ultimately resulting in poor growth and increased disease susceptibility. To better understand how stress specifically affects cellular metabolism in fish, a laboratory study was conducted to examine the metabolic responses of cells derived from three important species of warmwater fish to compounds inhibiting respiration and to rapid temperature increases. This study was the first to use extracellular flux technology on fish cells, which led us to discover that each cell type responded uniquely to stressors. These responses were used to generate metabolic ‘signatures’ which will be employed as novel biomarkers to predict how fish may cope with stress encountered in production settings.
Technical Abstract: Various stressors negatively affect wild and cultured fish and can result in metabolic disturbances that first manifest at the level of the cell. In the present study, we sought to further our understanding of cellular metabolism in fish by examining the stress responses of cells derived from three fish species: channel catfish (CCO), white bass (WBE), and fathead minnow (EPC). We used an instrument that detects minute changes in oxygen levels and pH within the media directly surrounding cells utilizing extracellular flux (EF) technology. By measuring the oxygen consumption rate (OCR), an indicator of mitochondrial respiration, cells exhibited different aerobic phenotypes. Simultaneously, we measured the extracellular acidification rate (ECAR), an indicator of glycolysis, and found that amongst all cell lines the ECAR was generally low (approximately 1 mpH/min/microgram protein). Next, we performed a mitochondrial function protocol whereby compounds modulating different components of mitochondrial respiration were sequentially exposed to cells. This provided us with basal and maximal OCR, OCR dedicated to ATP production, OCR from ion movement across the mitochondrial inner membrane, the reserve respiratory capacity, and OCR independent of the electron transport chain. From these parameters we generated metabolic signatures for each cell type. After a heat shock, EPC and CCO cells significantly decreased OCR and all three cell lines modestly increased ECAR. After heat shock, the reserve capacity was relatively unaffected in EPC and CCO cells, but markedly decreased in WBE cells. These findings are the first description of EF technology employed on fish cell lines and provide key proof-of-concept data demonstrating the utility of fish cells as tools for modeling bioenergetics. We hope to extend these findings to develop assays predictive of how fish may cope with cellular insults encountered in production settings.