Hsp27 inhibits IKKβ-induced NF-κB activity and skeletal muscle atrophy

Heat shock protein 25/27 (Hsp25/27) is a cytoprotective protein that is ubiquitously expressed in most cells, and is up-regulated in response to cellular stress. Previous work, in nonmuscle cells, has shown that Hsp27 inhibits TNF-α-induced NF-κB activation. During skeletal muscle disuse, Hsp25/27 levels are decreased and NF-κB activity increased, and this increase in NF-κB activity is required for disuse muscle atrophy. Therefore, the purpose of the current study was to determine whether electrotransfer of Hsp27 into the soleus muscle of rats, prior to skeletal muscle disuse, is sufficient to inhibit skeletal muscle disuse atrophy and NF-κB activation. The 35% disuse muscle-fiber atrophy observed in nontransfected fibers was attenuated by 50% in fibers transfected with Hsp27. Hsp27 also inhibited the disuse-induced increase in MuRF1 and atrogin-1 transcription by 82 and 40%, respectively. Furthermore, disuse- and IKKβ-induced NF-κB transactivation were abolished by Hsp27. In contrast, Hsp27 had no effect on Foxo transactivation. In conclusion, Hsp27 is a negative regulator of NF-κB in skeletal muscle, in vivo, and is sufficient to inhibit MuRF1 and atrogin-1 and attenuate skeletal muscle disuse atrophy.--Dodd, S. L., Hain, B., Senf, S. M., Judge, A. R. Hsp27 inhibits IKKβ-induced NF-κB activity and skeletal muscle atrophy.