Myostatin Activates the Ubiquitin-Proteasome and Autophagy-Lysosome Systems Contributing to Muscle Wasting in Chronic Kidney Disease

Figure 7

TNF-α regulates myostatin expression via nuclear factor (NF)-κB. (a) The expression of TNF-α mRNA was measured by RT-PCR in rat muscle and is presented as corrected for GAPDH and normalized to Sham group. (b) The expression of TNF-R1 protein was measured by immunoblotting in rat muscle and is presented as corrected for GAPDH and normalized to Sham group. (c) The expression of p-IkBa protein was measured by immunoblotting in rat muscle and is presented as corrected for GAPDH and normalized to sham group. (d) C2C12 cells were infected with a NF-κB-promoter luciferase construct. Following their differentiation, the myotubes were treated with 100 ng/mL TNF-α. Activation of the NF-κB promoter at times listed was measured and the fold change over 0 h was quantified. (e) Myotubes were treated with 100 ng/mL TNF-α with or without the NF-κB inhibitor (QNZ). Representative immunoblots of myostatin and GAPDH and the ratio of myostatin and GAPDH normalized to control. (f) Upper: representative fluorescent images of MHC. Lower: measurements of average myotube diameter after 24 hr of 100 ng/mL TNF-α treatment with or without the QNZ. Scale bar = 50 μm. Values were described means, with SD represented by vertical bars. Significantly different (, ) from control group, (^†, independent experiments) from TNF-α group.

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