Numerous
in vitro studies have shown that most
pyrrolizidine alkaloids (PAs) are hepatotoxic after being metabolically activated by
cytochrome P450 (CYP) 3A4. However, the key
role of
CYP3A4 has not been confirmed in vivo. Therefore, the
CYP3A4 chemical inhibitor
ritonavir was employed in this
work and the effect of
ritonavir on Gynura japonica-induced
liver injury in
rats was investigated. All experiments were approved by the
Animal Research Committee of Shanghai
University of
Traditional Chinese Medicine.
Animal welfare and the
animal experimental
protocols were strictly consistent with related
ethics regulations of Shanghai
University of
Traditional Chinese Medicine. Acute
liver injury was induced by a single gavage of Gynura japonica extracts (GJE, 8 g·kg-1);
rats in the
protection group were gavaged with
ritonavir (RIT, 30 mg·kg-1) 1 h before GJE
treatment. The results show that RIT could significantly attenuate GJE-induced
liver injury in
rats.
Rats in the
protection group showed decreased
serum activities for
alanine aminotransferase and
aspartate aminotransferase, as well as lower total
bile acids. In addition, the infiltration of inflammatory
cells, sinusoidal
hemorrhage, and hepatic
necrosis in GJE-treated
rats were markedly attenuated in the
protection group. The content of
pyrrole-
protein adducts (PPAs), a recommended
biomarker for PA-induced hepatotoxicity in clinics, was determined
at 10 min to 24 h after GJE
treatment. The content of 13
bile acids was also quantified. RIT
treatment reduced the content of PPAs in
serum dramatically and restored the impaired
bile acid homeostasis caused by GJE. These studies indicate that RIT attenuated Gynura japonica-induced
liver injury in
rats, which was closely related to the inhibition of the
metabolic activation of PAs and the
regulation of
bile acid metabolism. These results provide a better
understanding of the relationship between
CYP3A4 and PA-induced
toxicity. This
work will also be helpful in developing effective
treatments for PA-induced
liver injury and making a reasonable evaluation of the
safety of
drugs containing PAs in clinic.