Eccentric exercise induces nitric oxide synthase expression through nuclear factor-kappaB modulation in rat skeletal...

Area of Science:

• Exercise Physiology
• Molecular Biology
• Skeletal Muscle Biology

Background:

• Eccentric exercise, characterized by muscle lengthening under tension, can induce significant molecular adaptations in skeletal muscle.
• Nitric oxide synthase (NOS) plays crucial roles in vascular function, muscle metabolism, and cellular signaling.
• The transcription factor nuclear factor-kappaB (NF-kappaB) is a key regulator of inflammatory and stress responses in cells.

Purpose of the Study:

• To investigate the impact of acute eccentric exercise on the expression of neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS) in rat skeletal muscle.
• To determine the role of the NF-kappaB signaling pathway in mediating exercise-induced changes in NOS isoform expression.
• To examine the influence of pyrrolidine dithiocarbamate (PDTC) and prior eccentric training on these molecular responses.

Main Methods:

• Rats were subjected to acute eccentric exercise, PDTC treatment, or an 8-week eccentric training program.
• Analysis of protein tyrosine nitration, NF-kappaB binding activity, and phospho-I kappaB alpha content.
• Quantitative real-time PCR and Western blotting were used to measure NOS mRNA and protein levels.
• Chromatin immunoprecipitation (ChIP) assays were performed to assess NF-kappaB binding to NOS gene promoters.

Main Results:

• Acute eccentric exercise significantly increased protein tyrosine nitration, NF-kappaB activation, and phospho-I kappaB alpha levels.
• Expression of nNOS, iNOS, and eNOS (mRNA and protein) was significantly upregulated following eccentric exercise.
• NF-kappaB binding to NOS promoters was detected in exercised rats but not in rested controls.
• PDTC treatment and prior eccentric training partially abolished the exercise-induced increases in NF-kappaB activity and NOS expression.

Conclusions:

• Eccentric exercise activates the NF-kappaB signaling cascade in skeletal muscle.
• NF-kappaB directly influences the expression of nNOS, iNOS, and eNOS isoforms following eccentric exercise.
• Both pharmacological inhibition and chronic training can modulate the NF-kappaB-mediated regulation of NOS expression in response to eccentric exercise.