Epinephrine upregulates calpain activity in cultured C2C12 muscle cells

Effect of cortisol on calpains in the C2C12 and 3T3-L1 cells

The present study was carried out to understand the effect of cortisol on calpain system in the C2C12 and 3T3-L1 adipocyte cells under co-culture system. Cells were co-cultured by using transwell inserts with a 0.4 μm porous membrane to separate C2C12 and 3T3-L1 preadipocyte cells. Each cell type was grown independently on the transwell plates. Following cell differentiation, inserts containing 3T3-L1 cells were transferred to C2C12 plates. Ten microgram per milliliter of cortisol was added to the medium. Following treatment for 3 days, the cells in the lower well were harvested for analysis. Calpains such as μ-calpain, m-calpain, and calpastatin were selected for the analysis. RT-PCR results indicated the significant increase in the mRNA expression of μ-calpain, m-calpain, and calpastatin. In addition, the confocal microscopical investigation indicated the cortisol treatment increases calpain expression in the C2C12 and 3T3-L1 cells. Taking all these together, cortisol treatment with co-culture system shows most reliable status of calpains expression in the cells, which is quite distinct from one-dimensional monocultured cells.

Skeletal muscle cytokines: regulation by pathogen-associated molecules and catabolic hormones

PURPOSE OF REVIEW

This review will update clinicians and basic scientists who study the molecular mechanisms of muscle wasting associated with infection, trauma, cancer cachexia, and AIDS. A special emphasis is placed on recent studies that examine the interaction of insulin-like growth factor 1 and proinflammatory cytokines as positive and negative regulators of muscle mass.

RECENT FINDINGS

Potential mediators of the wasting syndromes include catabolic hormones, such as glucocorticoids, as well as the inflammatory cytokines tumour necrosis factor, IL-1, and IL-6. Cytokines may function either systemically or locally within muscle per se. Lipopolysaccharide and other pathogen-associated molecules stimulate cytokine expression in muscle. The failure to clear pathogen-associated molecules or the introduction of muscle damage may initiate a protracted activation of enzymes and transcription factors that orchestrate a genetic programme that ultimately produces muscle wasting.

SUMMARY

This review highlights recent advances in our understanding of the expression of the afferent and efferent limbs of the innate immune system in skeletal muscle. A special emphasis is placed on the recognition of pathogen-associated molecules by skeletal muscle cells and how these molecules regulate the expression of inflammatory cytokines and other muscle genes to result in muscle wasting, and when sustained, the erosion of lean body mass.