Inhibition of Histone Deacetylase 1 Prevents the Decrease in Titin (Connectin) Content and Development of Atrophy in Rat m. soleus after 3-Day Hindlimb Unloading.

We studied the effect of histone deacetylase 1 (HDAC1) inhibition on titin content and expression of TTN gene in rat m. soleus after 3-day gravitational unloading. Male Wistar rats weighing 210±10 g were randomly divided into 3 groups: control, 3-day hindlimb suspension, and 3-day hindlimb suspension and injection of HDAC1 inhibitor CI-994 (1 mg/kg/day). In hindlimb-suspended rats, the muscle weight/animal body weight ratio was reduced by 13.8% (p<0.05) in comparison with the control, which attested to the development of atrophic changes in the soleus muscle. This was associated with a decrease in the content of NT-isoform of intact titin-1 by 28.6% (p˂0.05) and an increase in TTN gene expression by 1.81 times (p˂0.05) in the soleus muscle. Inhibition of HDAC1 by CI-994 during 3-day hindlimb suspension prevented the decrease in titin content and development of atrophy in rat soleus muscle. No significant differences in the TTN gene expression from the control were found. These results can be used when finding the ways of preventing or reducing the negative changes in the muscle caused by gravitational unloading.