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OBJECTVE To study the improvement effects of obacunone on renal interstitial fibrosis （RIF） in unilateral ureteral obstruction （UUO） model mice， and to investigate its mechanism based on ferroptosis mediated by nuclear factor erythroid 2- related factor 2（Nrf2）/glutathione peroxidase 4 （GPx4） signaling pathway. METHODS Thirty mice were randomly divided into sham operation group， model group， irbesartan group （positive control， 20 mg/kg）， obacunone low-dose and high-dose groups （10， 40 mg/kg）， with 6 mice in each group. Except for sham operation group， UUO model was established by ligation of unilateral ureter in other groups. After operation， administration groups were given intraperitoneal injection of relevant medicine， and sham operation group and model group were given intraperitoneal injection of constant volume of normal saline， once a day， for 7 consecutive days. The levels of creatinine （Cr） and blood urea nitrogen （BUN）， the content of malondialdehyde （MDA） and the activities of total superoxide dismutase （T-SOD） in serum and the concentration of Fe2+ in renal tissue were all detected. HE staining and Masson staining were performed to observe the morphology and the fibrosis of renal tissues. Immunohisto- chemical staining was used to determine expressions of the fibronectin （Fn）， α-smooth muscle actin （α-SMA）， GPx4 964083717@qq.com and Nrf2 in renal tissue. Western blot and real-time quantitative polymerase chain reaction （RT-qPCR） were used E-mail：834300205@qq.com to detect the protein and mRNA levels of Fn， α-SMA， Nrf2， GPx4 and SLC7A11 in the renal tissues. RESULTS Compared with sham operation group， serum levels of Cr and BUN， the concentration of Fe2+ in renal tissue， the protein and mRNA levels of Fn and α-SMA in model group were increased significantly （P＜0.05）， while the activity of T-SOD in serum， protein and mRNA expressions of Nrf2， GPx4， SLC7A11 in kidney tissue were significantly decreased （P＜0.05）； in the kidney tissue， the renal tubules were dilated， the collagen deposition was obvious， the fibrous bands were thicker and darker， and the renal interstitial inflammatory cells infiltrated significantly. After intervened with obacunone， the levels of above indexes （except for mRNA expression of SLC7A11 in obacunone low-dose group） in serum and renal tissue were reversed significantly （P＜0.05）， and pathological damage and collagen deposition of kidney tissue were alleviated. CONCLUSIONS Obacunone can improve renal interstitial fibrosis of UUO model mice， the mechanism of which may be associated with activating the Nrf2/GPx4 pathway and then inhibiting ferroptosis to relieve RIF in UUO model mice.
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Objective Nomilin and obacunone are two important limonoids that are well known for their anticancer effect. Previous studies showed that limonoids had inhibitory effect on cytochrome P450 3A4 (CYP3A4). However these effects are inconclusive with regards to prediction of potential drug interactions. Methods Nomilin or obacunone was pre-incubated with HLMs for 30 min. Following 10-fold dilution from the pre-incubation concentration, a second incubation was performed in the presence of NADPH and cytochrome P450 substrates for 15 min. The reaction was quenched and the supernatants were analyzed by chromatography/mass spectrometry. Results In this study, nomilin and obacunone showed potent inhibitory effect on CYP3A4 with the IC50 values of 3.50 and 6.08 µmol/L, respectively. The inhibition of CYP3A4 was in a time-, concentration- and NADPH-dependent manner with Ki values of 2.92 and 1.25 µmol/L and Kinact values of 0.033 and 0.078 min−1 for nomilin and obacunone respectively. These results elucidated that they were time-dependent inhibitors for CYP3A4. Conclusion Concomitant use of limonoids and other drugs may call for extra caution for purposes of clinical safety.