Duchenne muscular dystrophy (DMD) is the most devastating type of muscular dystrophy, caused by a defect in the dystrophin gene resulting in progressive wasting and weakness of respiratory and locomotor muscles. By age twelve, DMD patients are no longer able to breathe or walk on their own. Muscle damage, weakness, and fiber loss (via necrosis, apoptosis) in diaphragm and limb muscles with DMD result from (a) material fatigue injury and (b) inflammation. While the link between inflammation with weakness, damage, and wasting in the diaphragm is unresolved, elevated """"""""oxidative stress"""""""" has been proposed as a mechanism. Indeed, oxidative stress is elevated and linked to muscle wasting with heart disease, lung disease, AIDS, cancer, and spaceflight. We propose that oxidative stress in the DMD diaphragm is a function of elevated NAD(P)H oxidase (NOX) with an impaired stress response of protective HSP70.
The Specific Aims of the current investigation are to (a) identify the mechanisms by which NOX oxidase leads to diaphragm weakness, apoptosis, necrosis, and wasting with DMD; and (b) determine if boosting levels of key stress proteins (e.g., HSP70) protect against oxidative stress and impaired contractile function in the dystrophic diaphragm. We hypothesize that inhibition of NOX (via apocynin) and genetic manipulation via knockout of gp91phox (regulatory subunit of NOX) will reduce oxidative stress, damage, apoptosis, necrosis, and impaired contractile function in the diaphragm. We further hypothesize that upregulation of heat shock protein70 (HSP70) by guanylguanylacetone and HSP70 overexpression will reduce oxidative stress, apoptosis, necrosis, and weakness in the diaphragm. We will use an mdx mouse model form DMD (with C57 wild types as controls) to accomplish our Specific Aims. Mice will be euthanized at 4 weeks of age, the time of peak inflammation and similar to a 3-year-old human patient. Cell protective proteins, prooxidant proteins, oxidative stress markers, indicators of apoptosis and necrosis, and damage in diaphragm samples will be assessed using Western immunoblot analysis, ELISA, and immunohistochemistry. In addition, contractile function of mdx and wild-type diaphragms will also be assessed. We anticipate that our results will have important clinical significance, as we expect to elucidate mechanisms by which oxidative stress contributes to damage, cell loss, and weakness in the dystrophic diaphragm. ? ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Small Research Grants (R03)
Project #
5R03AR054084-03
Application #
7429804
Study Section
Special Emphasis Panel (ZAR1-EHB-J (M1))
Program Officer
Nuckolls, Glen H
Project Start
2006-07-10
Project End
2011-05-31
Budget Start
2008-06-01
Budget End
2011-05-31
Support Year
3
Fiscal Year
2008
Total Cost
$66,360
Indirect Cost
Name
Texas A&M University
Department
Miscellaneous
Type
Schools of Education
DUNS #
078592789
City
College Station
State
TX
Country
United States
Zip Code
77845
Lawler, John M; Rodriguez, Dinah A; Hord, Jeffrey M (2016) Mitochondria in the middle: exercise preconditioning protection of striated muscle. J Physiol 594:5161-83
Hord, Jeffrey M; Botchlett, Rachel; Lawler, John M (2016) Age-related alterations in the sarcolemmal environment are attenuated by lifelong caloric restriction and voluntary exercise. Exp Gerontol 83:148-57
Kim, Jong-Hee; Lee, Yang; Kwak, Hyo-Bum et al. (2015) Lifelong wheel running exercise and mild caloric restriction attenuate nuclear EndoG in the aging plantaris muscle. Exp Gerontol 69:122-8
Kwak, Hyo-Bum; Lee, Yang; Kim, Jong-Hee et al. (2015) MnSOD overexpression reduces fibrosis and pro-apoptotic signaling in the aging mouse heart. J Gerontol A Biol Sci Med Sci 70:533-44
Lawler, John M; Kunst, Mary; Hord, Jeff M et al. (2014) EUK-134 ameliorates nNOS? translocation and skeletal muscle fiber atrophy during short-term mechanical unloading. Am J Physiol Regul Integr Comp Physiol 306:R470-82
Kim, Jong-Hee; Kwak, Hyo-Bum; Thompson, LaDora V et al. (2013) Contribution of oxidative stress to pathology in diaphragm and limb muscles with Duchenne muscular dystrophy. J Muscle Res Cell Motil 34:1-13
Kim, Jong-Hee; Lawler, John M (2012) Amplification of proinflammatory phenotype, damage, and weakness by oxidative stress in the diaphragm muscle of mdx mice. Free Radic Biol Med 52:1597-606
Lawler, John M; Kwak, Hyo-Bum; Kim, Jong-Hee et al. (2012) Biphasic stress response in the soleus during reloading after hind limb unloading. Med Sci Sports Exerc 44:600-9
Lawler, John M; Hindle, Allyson (2011) Living in a box or call of the wild? Revisiting lifetime inactivity and sarcopenia. Antioxid Redox Signal 15:2529-41
Lawler, John M (2011) Exacerbation of pathology by oxidative stress in respiratory and locomotor muscles with Duchenne muscular dystrophy. J Physiol 589:2161-70

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