STAT3 and pulmonary fibrosis: The Western blot results showed that Atrogin-1, a muscle-specific proteolysis marker, was generally increased in the muscle tissue of mice with BLM-induced lung fibrosis, which is associated with an increase in the activity of STAT3, a downstream mediator of IL-6 signaling, and AMP-activated protein kinase (AMPK), an important regulator of energy metabolism (Figure 6(a)).