Ion-Dependent ATPase Activity and Metabolic Gene Expression in TNF-α-Challenged Skeletal Muscle Cells: Mechanistic Characterisation of Carvacrol's Bioenergetic Effects.

Tumour necrosis factor-alpha (TNF-α) disrupts bioenergetic homeostasis in skeletal muscle cells through the suppression of ion-dependent ATPase activities, mitochondrial depolarisation, and impairment of antioxidant defences. Carvacrol, a phenolic monoterpenoid constituent of thyme and oregano essential oil, has been shown to exert cytoprotective effects in TNF-α-challenged L6 rat myoblasts. The mechanistic basis of these effects, specifically the relationship between membrane-associated ATPase function, mitochondrial polarisation status, and transcriptional regulation of metabolic stress-response genes, has not been formally characterised. L6 rat myoblasts were exposed to TNF-α (10 ng/mL, 1 h), then treated with carvacrol (6.25 µg/mL, 24 h) in a post-inflammatory rescue paradigm. Cell viability (MTT), membrane integrity (LDH), ion-dependent ATPase activities (Na+/K+, Ca2+, Mg2+), antioxidant enzyme activities (catalase, SOD), mitochondrial membrane potential (Muse™ MitoPotential flow cytometry), and SIRT1/AMPK mRNA expression were quantified. TNF-α significantly suppressed Na+/K+, Ca2+, and Mg2+-dependent ATPase activities (all p < 0.001), consistent with impaired membrane-associated bioenergetic function. Post-TNF-α carvacrol treatment partially restored all three ATPase activities (p < 0.05) and reduced the proportion of mitochondrially depolarised cells from 31.65 ± 4.25% to 19.0 ± 2.6% (p < 0.05). LDH release, catalase activity, and SOD activity were also significantly modulated. At the transcriptional level, carvacrol increased SIRT1 mRNA by 1.6-fold and AMPK mRNA by 2.0-fold relative to TNF-α-treated cells. An integrative bioenergetic model is proposed in which carvacrol's membrane-intercalating properties restore the phospholipid environment required for ATPase conformational cycling, attenuating the Ca2+ overload that drives mitochondrial permeability transition, and thereby partially preserving Δψm. Transcriptional upregulation of SIRT1 and AMPKα may represent an adaptive response to residual energetic stress. The mechanistic relationships among these endpoints and the causal contribution of SIRT1 and AMPK to observed bioenergetic changes require protein-level and pathway-specific experimental validation.