The effects of cytokines involved in cancer cachexia on skeletal muscle cells

Abstract

Cancer cachexia (CC) is a paraneoplastic wasting syndrome involving skeletal muscle depletion due to elevated interleukin (IL)-6 and tumour necrosis factor (TNF)-α. Muscle dysfunction in CC correlates with endoplasmic reticulum (ER) stress, disruptions in calcium-signalling and repressed skeletal muscle protein translation. The effects of elevated cytokines on ER stress-related disruptions in skeletal muscle are undefined. We examined alterations in gene and/or protein expression of: (i) ER stress markers; (ii) ER calcium chaperones; and (iii) translation repressor 4EBP1 in skeletal muscle cells due to elevated IL-6 and TNF-α. Murine C2C12 myotubes were treated with IL-6 or TNF-α (both at 10ng/mL) or IL-6/TNF-α. Gene and protein expression profiling of candidate molecules was assessed with qPCR, RT-PCR and Western blotting. Myotubes treated with cytokines showed: (i) increased mRNA of ER stress markers Xbp1 and Hspa5 but decreased mRNA and protein levels of IRE1α, (ii) decreased gene expression of ER calcium chaperone Casq1 whilst Canx transcription was unaltered, (iii) translation repressor 4EBP1 gene and protein expression and phosphorylation state were unchanged. Elevated IL-6/TNF-α can directly alter the expression of molecules responsive to ER stress in skeletal muscle cells and may be relevant to understanding the pathophysiological changes in skeletal muscle due to CC.