低氧复合运动通过NO-ATF1通路上调大鼠骨骼肌线粒体解偶联蛋白3表达**◆

背景：低氧复合运动可上调解偶联蛋白3的表达，提高骨骼肌线粒体对低氧的抵抗力，但其生物学效应及作用机制尚不清楚。 目的：观察单纯低氧及低氧复合运动对骨骼肌线粒体力能学及解偶联蛋白3表达的影响，并探讨NO-ATF1信号通路在其中的生物学效应。 方法：将60只SD大鼠随机分成常氧对照组、单纯低氧组、低氧复合运动训练组、低氧+ L-NAME组和低氧复合运动训 练+L-NAME组。低氧干预为常压低氧帐篷，模拟11.3%的氧体积分数；运动干预为低氧帐篷内跑台训练；L-NAME干预为饮用水中添加一氧化氮合酶抑制剂左旋硝基精氨酸甲酯。各种干预持续4周，硝酸还原酶法测定骨骼肌一氧化氮含量，荧光素酶发光法检测线粒体ATP合成活力，二氯荧光素法检测线粒体过氧化氢生成速率，实时荧光定量PCR法检测骨骼肌激活转录因子1和解偶联蛋白3 mRNA的表达，Western blot法检测骨骼肌磷酸化激活转录因子1和线粒体解偶联蛋白3蛋白的表达。 结果与结论：低氧复合运动显著上调骨骼肌解偶联蛋白3的表达及线粒体ATP的合成活力，抑制线粒体过氧化氢的产生，同时增加骨骼肌一氧化氮含量及激活转录因子1磷酸化水平，左旋硝基精氨酸甲酯抑制了低氧复合运动对线粒体的保护效应。说明低氧复合运动可通过NO-ATF1途径上调解偶联蛋白3的表达提高骨骼肌线粒体对低氧的抵抗力。 关键词：低氧复合运动；线粒体；一氧化氮；激活转录因子1；解偶联蛋白3；骨骼肌

Hypoxic exercise upregulates mitochondrial uncoupling protein 3 expression in rat skeletal muscle through NO-ATF1 signaling pathway

BACKGROUND: Hypoxic exercise can upregulate uncoupling proteins 3 expression, and promote the resistance of skeletal muscle mitochondria to hypoxia, but its biological effect and mechanism are still unclear. OBJECTIVE: To observe the effect of hypoxia alone and hypoxic exercise on mitochondrial energetics and uncoupling proteins 3 expression, and to discuss the biological effect of NO-ATF1 signaling pathway in this process. METHODS: Sixty SD rats were randomly divided into five groups: normoxia control group, hypoxia group, hypoxic exercise group, hypoxia + L-NAME group and hypoxic exercise + L-NAME group. Animals in the hypoxia group were subjected to hypoxia exposure in normobaric hypoxic tent with 11.3% O2. Those in the hypoxic exercise groups were exercised on a motor-driven rodent treadmill in the normobaric hypoxic tent with11.3% O2. And the drinking water for L-NAME animals contained L-NAME at dose of 1 g/L. All these interventions lasted for 4 weeks. The content of nitric oxide (NO) was measured with nitrate reductase method. Adenodine triphospate (ATP) synthesis capacity was determined using a bioluminescence technique. Mitochondrial H2O2 generation was determined using dichlorofluorescein (DCF). The expression of uncoupling proteins 3 (UCP3) and ATF1 in muscle were detected by real-time quantitative PCR. And the phosphorylation of ATF1 and mitochondrial UCP3 protein expression were measured by Western-blotting. RESULTS AND CONCLUSION: Exercise training in hypoxia markedly enhanced mitochondrial UCP3 expression and ATP synthesis capacity, and suppressed mitochondrial H2O2 generation, which accompanied with elevated NO content and ATF1 phosphorylation level. L-NAME restrained the protective effect of hypoxic exercise on mitochondria. These findings indicated that hypoxic exercise can increase uncoupling proteins 3 expression through the NO-ATF1 signaling pathway so as to increase the mitochondrial resistance to hypoxia.