Differences in the Role of HDACs 4 and 5 in the Modulation of Processes Regulating MAFbx and MuRF1 Expression during Muscle Unloading

Abstract

Unloading leads to skeletal muscle atrophy via the upregulation of MuRF-1 and MAFbx E3-ligases expression. Reportedly, histone deacetylases (HDACs) 4 and 5 may regulate the expression of MuRF1 and MAFbx. To examine the HDAC-dependent mechanisms involved in the control of E3-ubiquitin ligases expression at the early stages of muscle unloading we used HDACs 4 and 5 inhibitor LMK-235 and HDAC 4 inhibitor Tasqinimod (Tq). Male Wistar rats were divided into four groups (eight rats per group): nontreated control (C), three days of unloading/hindlimb suspension (HS) and three days HS with HDACs inhibitor LMK-235 (HSLMK) or Tq (HSTq). Treatment with LMK-235 diminished unloading-induced of MAFbx, myogenin (MYOG), ubiquitin and calpain-1 mRNA expression (p < 0.05). Tq administration had no effect on the expression of E3-ligases. The mRNA expression of MuRF1 and MAFbx was significantly increased in both HS and HSTq groups (1.5 and 4.0 folds, respectively; p < 0.05) when compared with the C group. It is concluded that during three days of muscle unloading: (1) the HDACs 4 and 5 participate in the regulation of MAFbx expression as well as the expression of MYOG, ubiquitin and calpain-1; (2) the inhibition of HDAC 4 has no effect on MAFbx expression. Therefore, HDAC 5 is perhaps more important for the regulation of MAFbx expression than HDAC 4.

Keywords: HDACs 4 and 5; MAFbx; MYOG; MuRF1; muscle unloading.

Figure 1

Evaluation of acetylated histone H3 content (A), histone deacetylases (HDAC) 4 mRNA expression (B) and HDAC 5 nuclear content (C) in soleus muscles of nontreated control rats (C), rats after 3 days of unloading (HS), 3 days HS with LMK-265 inhibitor (HSLMK) or HS with Tq inhibitor (HSTq). Values are normalized to the levels of total histone H3 (A) or Lamin B1 (C) in each sample. Levels of HDAC 4 mRNA were normalized to the levels of GAPDH in each sample (B). n = 8. * indicates a significant difference from the control, p < 0.05.

Figure 2

Evaluation of the ubiquitin (A), calpain-1 (B) and eEF2k (C) mRNA expression in soleus muscles of nontreated control rats (C), rats after 3 days of unloading (HS), 3 days HS with LMK-265 inhibitor (HSLMK) or HS with Tq inhibitor (HSTq). Values are normalized to the levels of GAPDH mRNA expression in each sample. n = 8. * indicates a significant difference from the control, p < 0.05; # indicates a significant difference from the HS, p < 0.05.

Figure 3

Evaluation of the MAFbx (A) and MuRF1 (B) mRNA expression in soleus muscles of nontreated control rats (C), rats after 3 days of unloading (HS), 3 days HS with LMK-265 inhibitor (HSLMK) or HS with Tq inhibitor (HSTq). Values are normalized to the levels of GAPDH mRNA expression in each sample. n = 8. * indicates a significant difference from the control, p < 0.05; # indicates a significant difference from the HS, p < 0.05.

Figure 4

Evaluation of phosphorylated FoxO3 content (A), P300 nuclear content (B) and MYOG mRNA expression (C) in soleus muscles of nontreated control rats (C), rats after 3 days of unloading (HS), 3 days HS with LMK-265 inhibitor (HSLMK) or HS with Tq inhibitor (HSTq). Values are normalized to the levels of total FoxO3 protein (A) or Lamin B1 (B) in each sample. Levels of MYOG mRNA were normalized to the levels of GAPDH in each sample (C). n = 8. * indicates a significant difference from the control, p < 0.05; # indicates a significant difference from the HS, p < 0.05.