α-Linolenic Acid Reduces TNF-Induced Apoptosis in C2C12 Myoblasts by Regulating Expression of Apoptotic Proteins.

Key Findings:

Tumor necrosis factor-α (TNF) is known to be an inflammatory cytokine and one of the key regulators of skeletal muscle homeostasis. Previous findings demonstrated that flaxseed preserves dystrophic skeletal muscle regeneration in an animal model characterized by increased plasma levels of tumor necrosis factor-α. In this research, a possible cellular mechanism was studied to determine the protective effect of ALA against TNF-induced apoptosis (cell death) on C2C12 cells during differentiation. ALA interrupted mitochondria-dependent apoptotic pathway triggered by sustained cytokine stimulation. ALA significantly reduced apoptosis, decreasing the caspase-3 activity, increasing the anti-apoptotic protein Bcl-2 levels and thus shifting the Bcl-2/Bax ratio to higher levels. ALA leads C2C12 myoblasts to survival instead of undergoing apoptosis TNF-induced directly affecting key proteins involved in balancing survival/death in skeletal muscle. ALA is able to modulate apoptotic protein expression by largely rescuing Bcl-2 down expression and in a lesser extent also decreasing Bax levels and inhibiting its mitochondrial translocation in C2C12 myoblasts treated with TNF. TNF is a major pro-inflammatory cytokine that is expressed in damaged skeletal muscle. Thus, counteracting inflammatory signals by ALA, in the muscle microenvironment, represents a valuable strategy to ameliorate skeletal muscle pathologies such as dystrophies.

ABSTRACT:

Impaired regeneration and consequent muscle wasting is a major feature of muscle degenerative diseases. Nutritional interventions such as adjuvant strategy for preventing these conditions are recently gaining increasing attention. Ingestion of n3-polyunsaturated fatty acids has been suggested as having a positive impact on muscle diseases. We recently demonstrated that a diet enriched with plant derived n3-fatty acid, α-linolenic acid (ALA), exerts potent beneficial effects in preserving skeletal muscle regeneration in models of muscle dystrophy. To better elucidate the underlying mechanism we here investigate on the expression level of the anti- and pro-apoptotic proteins, as well as caspase-3 activity, in C2C12 myoblasts challenged with pathological levels of tumor necrosis factor-α (TNF). The results demonstrated that ALA protective effect on C2C12 myoblasts was associated with a decrease in caspase-3 activity and an increase of the Bcl-2/Bax ratio. Indeed, the effect of ALA was directed to rescuing Bcl-2 expression and to revert Bax translocation to mitochondria both affected in an opposite way by TNF, a major pro-inflammatory cytokine expressed in damaged skeletal muscle. Therefore, ALA counteracts inflammatory signals in the muscle microenvironment and may represent a valuable strategy for ameliorating skeletal muscle pathologies.