MiP2005: Session 1

Mitochondrial Physiology Network 10.9: 21 (2005) - download pdf

 

A feedback molecular regulation of uncoupling on ROS generation in muscle mitochondria during the prolonged exercise.

Yong Zhang1, GZ Zhang1, N Jiang1, GD Ma1, L Wen1, H Bo 1, DN Cao 1, F Zhao1, SS Liu 2

1Tianjin Research Inst. of Sports Medicine; Dept. of Health and Exercise Science, Tianjin Inst. of Physical Education, Tianjin 300381, China; 2National Key Lab. of Biomembrane and Membrane Biotechnology Ins. of Zoology, Chinese Academy of Sciences, Beijing 100080, China. - yzhang@tjipe.edu.cn

    The mitochondrial electron leak is an important source of endogenous ROS in exercise. The recent researches show that effect of ‘mild uncoupling’ of respiratory chain is involved in mitochondrial anti-oxidation event [1]. The purpose of present research is to investigate whether mitochondrial mild uncoupling is induced and/or activated during strenuous exercise and to explore its possible molecular regulation.

    SD rats were divided into 5 groups to rest or run for 45, 90, 120 and 150 min respectively on the treadmill according to the incremental protocol and sacrificed at rest or immediately after every exercise time course. The following parameters were determined: 1) Separated mitochondrial State 4 respiration rate in the presence of malate and glutamate by using Clark Oxygen Electrode; 2) ROS generation of separated mitochondria by fluorometric probe; 3) Expression of UCP-3 mRNA in muscle homogenate and its protein in mitochondria using RT-PCR and Western-Blotting respectively.

    (1) Mitochondrial ROS generation were significant higher at 45, 90, 120 min than at rest (P<0.05, P<0.001, and P<0.01, respectively) with the peak at the point of 120 min, then obviously declined at 150 min subsequently (P<0.001). (2) In a parallel change, state 4 rate increased significantly when exercising for 90 and 120 min (P<0.01 and P<0.001 respectively) and lowered in exercising to 150 min (P<0.001). (3) There were remarkably higher levels of UCP-3 mRNA at 90, 120 and 150 min (P<0.001, P<0.01 and P<0.01 respectively), and following UCP-3 protein contents increased at 120 and 150 min (both P<0.001).

    According to the observed changes, we hypothesize that ROS may contribute to activated and/or induced expression of UCPs. A functioning of the UCPs may cause mild uncoupling in response to matrix superoxide and other oxidants during exercise, leading to increased proton leak and feedback decreased superoxide production. This complicated and precise feedback loop would constitute a self-limiting cycle to protect against excessive superoxide production [2], leading to early protection against oxidation and regulation of cellular and mitochondrial redox.

1.  Echtay KS, Roussel D, St-Pierre J, et al. (2002) Superoxide activates mitochondrial uncoupling proteins. Nature 415: 96–99.

2.  Brand MD, Buckingham JA, Esteves TC, et al. (2004) Mitochondrial superoxide and aging: uncoupling-protein activity and superoxide production. Biochem. Soc. Symp. 71: 203-213.


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