Department of Life Sciences, Dezhou University, Dezhou, China; School of Life Sciences, Lanzhou University, Lanzhou, China.
Department of Life Sciences, Dezhou University, Dezhou, China.
J Therm Biol. 2021 Dec;102:103132. doi: 10.1016/j.jtherbio.2021.103132. Epub 2021 Nov 19.
The Xizang plateau frog Nanorana parkeri can tolerate brief and partial freezing of their body. To determine the significant role of antioxidant defense and non-specific immune defense in freezing survival of this species, we assayed parameters of oxidative damage, antioxidant defense and non-specific immune enzymes during freezing exposure (-2 °C for 12 h) in five organs (heart, brain, liver, kidney, and skeletal muscle). The results showed that freezing led to a significant rise in the content of malondialdehyde (MDA) and carbonyl groups (CG) in brain, liver and kidney tissues. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) increased significantly in brain and liver tissues with an augmentation of total antioxidant capacity (T-AOC). Apparent increments in muscle SOD activity and liver GST activity were also observed during freezing exposure. Vitamin C content significantly decreased in liver and kidney but a significant increase occurred in brain. Activities of non-specific immune enzymes, acid phosphatase (ACP) and alkaline phosphatase (AKP), were also assessed. ACP activity was significantly reduced in all five tissues tested whereas AKP activity decreased significantly in four tissues but rose in brain. In summary, freezing is accompanied by oxidative stress in the high-altitude frog, N. parkeri, as documented by increases in the content of MDA and CG in tissues. Freezing exposure also induced tissue-specific changes in the antioxidant defenses showing that activation of antioxidant systems is a part of the survival strategy of this in a high-altitude frog during freezing. Such up-regulation of antioxidant enzymes suggests a particularly important role for them in the liver and brain, serving as an anticipatory mechanism to deal with the ROS challenge during freeze/thaw episodes. Our findings contribute to extending the current understanding of the mechanisms of freeze tolerance in high-altitude frogs.
青藏高原蛙 Nanorana parkeri 能够耐受短暂的局部身体冻结。为了确定抗氧化防御和非特异性免疫防御在该物种冻结生存中的重要作用，我们在五个器官（心脏、大脑、肝脏、肾脏和骨骼肌）中测定了氧化损伤、抗氧化防御和非特异性免疫酶的参数，这些器官在冻结暴露期间（-2°C 持续 12 小时）。结果表明，冻结导致大脑、肝脏和肾脏组织中丙二醛（MDA）和羰基（CG）含量显著升高。超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和谷胱甘肽过氧化物酶（GPX）的活性在大脑和肝脏组织中显著增加，总抗氧化能力（T-AOC）也增加。在冻结暴露期间，肌肉 SOD 活性和肝脏 GST 活性也明显增加。维生素 C 含量在肝脏和肾脏中显著降低，但大脑中含量显著增加。还评估了非特异性免疫酶、酸性磷酸酶（ACP）和碱性磷酸酶（AKP）的活性。ACP 活性在所有五种测试组织中均显著降低，而 AKP 活性在四种组织中显著降低，但在大脑中升高。总之，在高山蛙 N. parkeri 中，冻结伴随着氧化应激，这可以通过组织中 MDA 和 CG 含量的增加来证明。冻结暴露还导致抗氧化防御的组织特异性变化，表明抗氧化系统的激活是该高山蛙在冻结期间生存策略的一部分。抗氧化酶的这种上调表明它们在肝脏和大脑中具有特别重要的作用，作为应对冷冻/解冻过程中 ROS 挑战的预期机制。我们的研究结果有助于扩展对高山蛙耐冻结机制的现有认识。
