Key result
Mechanical stretch activates Nox2-dependent ROS generation via the microtubule network (X-ROS signaling), which tunes Ca(2+) signaling physiologically but can promote arrhythmias or dystrophy in excess.
X-ROS signaling, mediated by the microtubule network and Nox2, is a critical mechanotransduction pathway regulating Ca2+ signaling in striated muscle, with implications for arrhythmias and muscular dystrophy.
Nox2-specific ROS targeting merits exploration in muscle disorders; leaves open prospective human validation before any clinical consideration.
SIGNIFICANCE: Mechanical activation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) occurs in striated muscle and affects Ca(2+) signaling and contractile function. ROS/RNS signaling is tightly controlled, spatially compartmentalized, and source specific. RECENT ADVANCES: Here, we review the evidence that within the contracting myocyte, the trans-membrane protein NADPH oxidase 2 (Nox2) is the primary source of ROS generated during contraction. We also review a newly characterized signaling cascade in cardiac and skeletal muscle in which the microtubule network acts as a mechanotransduction element that activates Nox2-dependent ROS generation during mechanical stretch, a pathway termed X-ROS signaling. CRITICAL ISSUES: In the heart, X-ROS acts locally and affects the sarcoplasmic reticulum (SR) Ca(2+) release channels (ryanodine receptors) and tunes Ca(2+) signaling during physiological behavior, but excessive X-ROS can promote Ca(2+)-dependent arrhythmias in pathology. In skeletal muscle, X-ROS sensitizes Ca(2+)-permeable sarcolemmal "transient receptor potential" channels, a pathway that is critical for sustaining SR load during repetitive contractions, but when in excess, it is maladaptive in diseases such as Duchenne Musclar dystrophy. FUTURE DIRECTIONS: New advances in ROS/RNS detection as well as molecular manipulation of signaling pathways will provide critical new mechanistic insights into the details of X-ROS signaling. These efforts will undoubtedly reveal new avenues for therapeutic intervention in the numerous diseases of striated muscle in which altered mechanoactivation of ROS/RNS production has been identified.
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Ward et al. (2013) conducted a review in Diseases of striated muscle (e.g., Duchenne Muscular dystrophy, arrhythmias). Mechanical stretch-induced activation of ROS/RNS signaling (X-ROS signaling) was evaluated. Mechanical stretch activates Nox2-dependent ROS generation via the microtubule network (X-ROS signaling), which tunes Ca(2+) signaling physiologically but can promote arrhythmias or dystrophy in excess.
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