Nox2 signaling and muscle fiber remodeling are attenuated by losartan administration during skeletal muscle unloading. Issue 1 (5th January 2021)

• Record Type: Journal Article
• Authors: Hord, Jeffrey M.; Garcia, Marcela M.; Farris, Katherine R.; Guzzoni, Vinicius; Lee, Yang; Lawler, Matthew S.; Lawler, John M.
• Is Part Of: Physiological reports. Volume 9:Issue 1(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-01-05
• Subjects: Angiotensin II type 1 receptor -- hindlimb unloading -- NADPH oxidase‐2 -- neuronal nitric oxide synthase -- skeletal muscle atrophy; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.14606
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Reduced mechanical loading results in atrophy of skeletal muscle fibers. Increased reactive oxygen species (ROS) are causal in sarcolemmal dislocation of nNOS and FoxO3a activation. The Nox2 isoform of NADPH oxidase and mitochondria release ROS during disuse in skeletal muscle. Activation of the angiotensin II type 1 receptor (AT1R) can elicit Nox2 complex formation. The AT1R blocker losartan was used to test the hypothesis that AT1R activation drives Nox2 assembly, nNOS dislocation, FoxO3a activation, and thus alterations in morphology in the unloaded rat soleus. Male Fischer 344 rats were divided into four groups: ambulatory control (CON), ambulatory + losartan (40 mg kg −1 day −1 ) (CONL), 7 days of tail‐traction hindlimb unloading (HU), and HU + losartan (HUL). Losartan attenuated unloading‐induced loss of muscle fiber cross‐sectional area (CSA) and fiber‐type shift. Losartan mitigated unloading‐induced elevation of ROS levels and upregulation of Nox2. Furthermore, AT1R blockade abrogated nNOS dislocation away from the sarcolemma and elevation of nuclear FoxO3a. We conclude that AT1R blockade attenuates disuse remodeling by inhibiting Nox2, thereby lessening nNOS dislocation and activation of FoxO3a. Abstract : Angiotensin receptor blockade (ARB) reduced unloading‐induced atrophy of skeletal muscle. Losartan mitigated assembly of the Nox2 complex, and thus oxidative stress ARB attenuated loss of sarcolemmal nNOSµ and nuclear levels of FoxO3a.