Contractile activity-induced oxidative stress: cellular origin and adaptive responses

Area of Science:

• Exercise physiology
• Cellular biology
• Biochemistry

Background:

• Oxidizing free radical species are generated during exercise.
• Their effects on exercising tissues are of considerable interest.
• The role of skeletal muscle as a source of these species is under investigation.

Purpose of the Study:

• To investigate if contracting skeletal muscle is a major source of oxidizing free radical species.
• To determine if untrained skeletal muscle adapts to oxidative stress from contractile activity.
• To examine if this adaptation occurs without overt cellular damage.

Main Methods:

• Induced aerobic contractile activity in mouse skeletal muscle in vivo for 15 minutes.
• Utilized contracting cultured skeletal muscle myotubes to confirm the source of oxidant release.
• Measured superoxide anion release, muscle protein thiol content, and activities of superoxide dismutase, catalase, and heat shock proteins.

Main Results:

• A rapid release of superoxide anions from mouse skeletal muscle during contractile activity was observed.
• Oxidant production was confirmed to originate from myocytes.
• A transient reduction in muscle protein thiol content was followed by increased activities of superoxide dismutase and catalase, and heat shock protein content.
• These adaptive changes occurred without overt muscle cell damage.

Conclusions:

• Contracting skeletal muscle is a significant source of exercise-induced superoxide anions.
• Skeletal muscle exhibits adaptive responses to oxidative stress, including upregulation of cytoprotective proteins.
• These adaptations can occur rapidly and without causing cellular damage, highlighting the resilience of muscle tissue.