Mechanism of TNFα and IL-1 enhancing protein catabolism in skeletal muscles of mice in early stage after severe burn / 第三军医大学学报

ABSTRACT

Objective　To observe the effects and mechanism of TNFα and IL-1 on protein catabolism of skeletal muscles of mice in the early stage of severe burn. Methods　A BALB/c mice model was established with full thickness scalded of 18%～20% TBSA including the back and one hind limb. The catabolic rate of protein of soleus muscle was reflected with the net tyrosine releasing rate. The changes of the tyrosine releasing rates of the injured and uninjured limbs, the levels of TNFα and IL-1 of the plasma and soleus muscle, and the activities of lysosomal proteolytic enzymes were observed in 72 h after scald injury of the mice. Results　After injury, the levels of TNFα and IL-1 of plasma, injured and uninjured limbs were all increased, and reached the summit at the 48th h, but those of the injured limb were much higher than those of the uninjured one, then gradually the levels were decreased in 72 h. The protein catabolic rate of uninjured limb was higher than the normal at h 48, but it came to normal level at h 72. The rate of the injured limb was higher than that of normal and uninjured limbs significantly 72 h after the scalding. hrTNFα and hrIL-1 enhanced the protein catabolic rate and the activities of lysosomal protrolytic enzymes in the soleus muscle of normal mice in vivo and in vitro respectively. Conclusion　In the early stage of scald injury, TNFα and IL-1 could enhance the lysosomal protease activity, increase the protein catabolic rate in skeletal muscle and promote the negative nitrogen balance directly. These effects may not depend on the actions of emergent hormones.