Generation of reactive oxygen species (ROS) under physiological conditions is required for normal force production in skeletal muscle. However, high levels of ROS are observed during intense physical exercise and promote contractile dysfunction, resulting in muscle weakness and fatigue. There is growing evidence that sub-cellular site-specific ROS production governs the beneficial vs. damaging effects of ROS. NADPH oxidase (Nox2) is an enzyme complex that generates ROS. Ongoing work by PI has found that increased ROS generation from Nox2 during intense contractile activity contributes to fatigue. We have strong evidence that Src tyrosine kinase acts as a redox switch to activate Nox2. The central hypothesis of this proposal is that Nox2 and Src act through a feed-forward pathway leading to excessive ROS production and contractile dysfunction. We will use genetically modified mice lacking Nox2, genetically encoded site-specific redox sensors and a novel tool to measure force and Ca2+ transients simultaneously in living skeletal muscle fibers to address the following specific aims: 1. Define the mechanisms by which contractile activity increases Nox2 dependent ROS production in skeletal muscle, 2. Determine whether Src serves as a redox switch to modulate activity dependent ROS production, and 3. Assess the role of Nox2 and Src on cytosolic [Ca2+ ]i transients and force generation. The proposed research will identify the sub-cellular sites of ROS production and elucidate the signaling pathways that control ROS regulation of microdomain Ca2+ signaling in skeletal muscle. Furthermore, it will lay the foundation for the development of targeted antioxidant therapy to combat the deleterious effects of overproduction of ROS seen in muscle fatigue and disease.

Public Health Relevance

Skeletal muscle contraction is regulated by calcium inside the cell. Reactive oxygen species are also produced inside the cell. Excessive production of reactive oxygen species promotes muscle weakness and fatigue in patients with heart failure, cancer, HIV, emphysema and muscular dystrophy. Scientists working on this proposal have found that an NADPH oxidase plays an important biological role in promoting muscle weakness. The planned work will examine how local activation of NADPH oxidase leads to changes in cellular calcium and muscle weakness. The results from this study will have important implications for physical performance and disease therapy.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR061370-03
Application #
8707972
Study Section
Special Emphasis Panel (ZRG1-MOSS-T (02))
Program Officer
Boyce, Amanda T
Project Start
2012-08-01
Project End
2017-07-31
Budget Start
2014-08-01
Budget End
2015-07-31
Support Year
3
Fiscal Year
2014
Total Cost
$345,082
Indirect Cost
$124,582
Name
Baylor College of Medicine
Department
Physiology
Type
Schools of Medicine
DUNS #
051113330
City
Houston
State
TX
Country
United States
Zip Code
77030
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Pal, Rituraj; Bajaj, Lakshya; Sharma, Jaiprakash et al. (2016) NADPH oxidase promotes Parkinsonian phenotypes by impairing autophagic flux in an mTORC1-independent fashion in a cellular model of Parkinson's disease. Sci Rep 6:22866
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Pal, Rituraj; Monroe, Tanner O; Palmieri, Michela et al. (2014) Rotenone induces neurotoxicity through Rac1-dependent activation of NADPH oxidase in SHSY-5Y cells. FEBS Lett 588:472-81
Loehr, James A; Abo-Zahrah, Reem; Pal, Rituraj et al. (2014) Sphingomyelinase promotes oxidant production and skeletal muscle contractile dysfunction through activation of NADPH oxidase. Front Physiol 5:530
Pal, Rituraj; Palmieri, Michela; Loehr, James A et al. (2014) Src-dependent impairment of autophagy by oxidative stress in a mouse model of Duchenne muscular dystrophy. Nat Commun 5:4425

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