Abstract
BACKGROUND: Cachexia, characterized by severe weight loss and muscle atrophy, frequently occurs in chronic conditions such as sepsis, cancer and chemotherapy, with limited effective treatments. Despite similar clinical manifestations, the underlying mechanisms across different disease contexts remain unclear. Identifying common pathways could lead to novel therapies. This study examines the role of Toll-like receptor 4 (TLR4), which is upregulated in various cachexia models, and assesses the therapeutic potential of the TLR4-inhibiting peptide OH-CATH30 in mitigating muscle atrophy. METHODS: In vivo models using 8-week-old mice treated with lipopolysaccharide (LPS), 4T1 tumour cells and cisplatin were used to investigate common pathways in cachexia. In vitro models were established by treating C2C12 myotubes with TNF-α, 4T1 culture supernatants and cisplatin. OH-CATH30's effects on muscle atrophy were assessed by measuring myotube diameter, grip strength, muscle weight and muscle fibre cross-sectional area (CSA) via H&E staining. RNA-seq, qPCR, ELISA and Western blotting were performed to explore pathways in cachexia-induced muscle atrophy and OH-CATH30's action mechanism. RESULTS: Transcriptomic analysis showed significant enrichment of inflammation and protein degradation pathways in skeletal muscle in LPS-induced sepsis, 4T1 tumour-induced cancer cachexia and cisplatin-induced cachexia models, with upregulated expression of TLR4 pathway genes such as Cd14, Tlr4 and Irak4 (p < 0.05). In myotube atrophy models induced by TNF-α, 4T1 and cisplatin, OH-CATH30 significantly increased MyHC protein levels (p < 0.05) and myotube diameter (p < 0.05). In mouse cachexia models induced by LPS, 4T1 and cisplatin, OH-CATH30 treatment significantly increased body weight (p < 0.05), muscle weight (p < 0.001), CSA (p < 0.05) and improved grip strength (p < 0.05). Transcriptomic analysis further revealed that OH-CATH30 treatment downregulated expression of inflammation and protein degradation-related genes across all cachexia models. In 4T1-treated mice, qPCR confirmed OH-CATH30 reduced mRNA levels of Il6 (p = 0.05), Mstn (p < 0.0001) and protein degradation genes such as Trim63, Fbxo32, Bnip3, Gabarapl1 and Ulk1 (p < 0.05). ELISA showed reduced serum IL-6 levels, and Western blot confirmed downregulation of atrogin1 (p < 0.05) and autophagy marker LC3II (p < 0.05) with OH-CATH30 treatment. Pharmacological inhibition of TLR4 using TAK-242 recapitulated the protective effects of OH-CATH30, with no additive benefit observed (p > 0.05). CONCLUSIONS: Our findings underscore the critical role of TLR4 signalling in cachexia-associated muscle wasting across different disease contexts and demonstrate the efficacy of OH-CATH30, a TLR4 inhibitor, in alleviating muscle atrophy in various cachexia models.