Aerts Johan, Metz Juriaan Rogier, Ampe Bart, Decostere Annemie, Flik Gert, De Saeger Sarah
Bio-analysis Research Group, Animal Sciences Unit, Institute for Agriculture and Fisheries Research, Melle, Belgium; Laboratory of Food Analysis, Department of Bio-analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
Department of Animal Physiology, Institute for Water and Wetland Research, Faculty of Science, Radboud University Nijmegen, Nijmegen, The Netherlands.
PLoS One. 2015 Apr 29;10(4):e0123411. doi: 10.1371/journal.pone.0123411. eCollection 2015.
Fish faced with stressful stimuli launch an endocrine stress response through activation of the hypothalamic-pituitary-interrenal (HPI-) axis to release cortisol into the blood. Scientifically validated biomarkers to capture systemic cortisol exposure over longer periods of time are of utmost importance to assess chronic stress in governmental, wildlife, aquaculture and scientific settings. Here we demonstrate that cortisol in scales of common carp (Cyprinus carpio L.) is the long-sought biomarker for chronic stress. Undisturbed (CTR) and daily stressed (STRESS) carp were compared. Dexamethasone (DEX) or cortisol (CORT) fed fish served as negative and positive controls, respectively. Scale cortisol was quantified with a validated ultra-performance liquid chromatography tandem mass spectrometry method. An increase in scale cortisol content was found in STRESS and CORT but not in CTR and DEX fish. Scale cortisol content reflects its accumulation in a stressor and time dependent manner and validates the scale cortisol content as biomarker for chronic stress. Plasma analyses confirmed that (i) CTR, DEX and CORT treatments were effective, (ii) plasma cortisol of STRESS fish showed no signs of chronic HPI-axis activation, and (iii) plasma cortisol is a poor predictor for chronic stress. The expression of HPI key genes crf, pomc, and star were up-regulated in STRESS fish in the absence of a plasma cortisol response, as was the target gene of cortisol encoding subunit α1 of the Na+/K+-ATPase in gills. When lost, scales of fish regenerate fast. Regenerated scales corroborate our findings, offering (i) unsurpassed time resolution for cortisol incorporation and as such for stressful events, and (ii) the possibility to investigate stress in a well defined and controlled environment and time frame creating novel opportunities for bone physiological research. We conclude that the cortisol content in ontogenetic and regenerated scales is an innovative biomarker for chronic stress offering ample applications in science and industry.
面对应激刺激的鱼类会通过激活下丘脑 - 垂体 - 肾间（HPI -）轴来启动内分泌应激反应，从而将皮质醇释放到血液中。对于评估政府、野生动物、水产养殖和科研环境中的慢性应激而言，经过科学验证的能够在较长时间内捕捉全身皮质醇暴露情况的生物标志物至关重要。在此，我们证明，鲤鱼（Cyprinus carpio L.）鳞片中的皮质醇就是长期以来寻找的慢性应激生物标志物。我们比较了未受干扰的（CTR）和每日应激的（STRESS）鲤鱼。分别用喂食地塞米松（DEX）或皮质醇（CORT）的鱼作为阴性和阳性对照。采用经过验证的超高效液相色谱串联质谱法对鳞片皮质醇进行定量。在STRESS组和CORT组鱼中发现鳞片皮质醇含量增加，而在CTR组和DEX组鱼中未发现。鳞片皮质醇含量以应激源和时间依赖的方式反映其积累情况，并验证了鳞片皮质醇含量作为慢性应激生物标志物的有效性。血浆分析证实：（i）CTR、DEX和CORT处理是有效的；（ii）STRESS组鱼的血浆皮质醇未显示出慢性HPI轴激活的迹象；（iii）血浆皮质醇对慢性应激的预测能力较差。在没有血浆皮质醇反应的情况下，STRESS组鱼中HPI关键基因crf、pomc和star的表达上调，鳃中皮质醇编码Na⁺/K⁺ - ATP酶α1亚基的靶基因表达也上调。鱼的鳞片脱落后会快速再生。再生鳞片证实了我们的发现，提供了（i）皮质醇掺入以及应激事件无与伦比的时间分辨率，以及（ii）在明确界定和可控环境及时间框架内研究应激的可能性，为骨骼生理学研究创造了新机会。我们得出结论，个体发育和再生鳞片中的皮质醇含量是一种用于慢性应激的创新生物标志物，在科学和工业领域有广泛应用。
