Effect of eperisone on BLM-induced pulmonary fibrosis
Pulmonary
fibrosis was induced by intratracheal administration of BLM to male ICR
mice. Specifically, 10 days after BLM administration, mice were divided
into three groups based on the rate of change in body weight (excluding
the vehicle group), and the effect of oral eperisone administration on
lung fibrosis was examined. At 20 days after BLM administration, lung
tissue sections were prepared and stained for collagen using Masson’s
trichrome stain. Collagen deposition in the lungs was observed in a BLM
administration-dependent manner. In contrast, oral eperisone
administration suppressed the BLM-dependent collagen deposition in a
dose-dependent manner (Figure 3A and 3B). Next, we performed
quantitative analysis of hydroxyproline, a collagen-specific amino acid,
in lung tissue. As shown in Figure 3C, BLM treatment significantly
increased the amount of hydroxyproline in lung tissue, while eperisone
treatment suppressed this increase. When considering the clinical
application of eperisone for the treatment of lung fibrosis, it is
important to improve respiratory function as well as histological and
biochemical indices. Moreover, our previous analysis showed that lung
elastance is increased and FVC is decreased in BLM-induced pulmonary
fibrosis (Sugizaki et al., 2019; K. I. Tanaka et al., 2017). Thus, we
measured the respiratory function of mice using a computer-controlled
ventilator and negative pressure reservoir. As shown in Figure 3D, BLM
treatment increased the total elastance (elastance of the entire lung
including the bronchi, bronchioles, and alveoli) and tissue elastance
(elastance of the alveoli) and decreased the FVC. In contrast, eperisone
significantly improved the deterioration of respiratory function induced
by BLM administration. These results indicate that eperisone has an
ameliorating effect on BLM-dependent pulmonary fibrosis.
Fibroblasts are known to differentiate into myofibroblasts upon
activation and play an important role in the development and
exacerbation of lung fibrosis (Hinz et al., 2007; Scotton & Chambers,
2007). Thus, we performed an immunohistochemical analysis of α-SMA, a
myofibroblast marker. As shown in Figure 4A, BLM treatment increased the
number of α-SMA-positive cells in the lung, i.e., myofibroblasts
increased in a BLM-dependent manner. In contrast, administration of 50
mg/kg eperisone decreased the BLM-dependent increase in α-SMA-positive
cells in the lung to the same level as observed in the vehicle group.
These results suggest that eperisone inhibits fibroblast activation not
only in vitro but also in vivo and that it suppresses
BLM-dependent pulmonary fibrosis through its inhibitory effect on
fibroblast activation.