An updated review of the genus Rhododendron since 2010: Traditional uses, phytochemistry, and pharmacology.

Rhododendron, the largest genus of Ericaceae, consists of approximately 1000 species that are widely distributed in Europe, Asia, and North America but mainly exist in Asia. Rhododendron plants have not only good ornamental and economic value but also significant medicinal potential. In China, many Rhododendron plants are used as traditional Chinese medicine or ethnic medicine for the treatment of respiratory diseases, pain, bleeding and inflammation. Rhododendron is known for its abundant metabolites, especially diterpenoids. In the past 13 years, a total of 610 chemical constituents were reported from Rhododendron plants, including 222 diterpenoids, 122 triterpenoids, 103 meroterpenoids, 71 flavonoids and 92 other constituents (lignans, phenylpropanoids, phenolic acids, monoterpenoids, sesquiterpenoids, coumarins, steroids, fatty acids). Moreover, the bioactivities of various extracts and isolates, both in vitro and in vivo, were also investigated. Our review summarized the research progress of Rhododendron regarding traditional uses, phytochemistry and pharmacology in the past 13 years (2010 to December 2022), which will provide new insight for prompting further research on Rhododendron application and drug development.

Hepatoprotective Effect of Oplopanax elatus Nakai Adventitious Roots Extract by Regulating CYP450 and PPAR Signaling Pathway.

O. elatus Nakai is a traditional medicine that has been confirmed to exert effective antioxidant and anti-inflammatory functions, and is used for the treatment of different disorders. However, its potential beneficial effects on drug induced hepatotoxicity and relevant molecular mechanisms remain unclear. This study investigated the protective effect and further elucidated the mechanisms of action of O. elatus on liver protection. O. elatus chlorogenic acids-enriched fraction (OEB), which included chlorogenic acid and isochlorogenic acid A, were identified by HPLC-MS/MS. OEB was administrated orally daily for seven consecutive days, followed by a single intraperitoneal injection of an overdose of APAP after the final OEB administration. The effects of OEB on immune cells in mice liver were analyzed using flow cytometry. APAP metabolite content in serum was detected using HPLC-MS/MS in order to investigate whether OEB affects CYP450 activities. The intestinal content samples were processed for 16 s microbiota sequencing. Results demonstrated that OEB decreased alanine aminotransferase, aspartate aminotransferase contents, affected the metabolism of APAP, and decreased the concentrates of APAP, APAP-CYS and APAP-NAC by inhibiting CYP2E1 and CYP3A11 activity. Furthermore, OEB pretreatment regulated lipid metabolism by affecting the peroxisome proliferator-activated receptors (PPAR) signaling pathway in mice and also increased the abundance of Akkermansia and Parabacteroides. This study indicated that OEB is a potential drug candidate for treating hepatotoxicity because of its ability to affect drug metabolism and regulate lipid metabolism.

Schisandrol B promotes liver enlargement via activation of PXR and YAP pathways in mice.

BACKGROUND: Schisandrol B (SolB) is one of the bioactive components from a traditional Chinese medicine Schisandra chinensis or Schisandra sphenanthera. It has been demonstrated that SolB exerts hepatoprotective effects against drug-induced liver injury and promotes liver regeneration. It was found that SolB can induce hepatomegaly but the involved mechanisms remain unknown. PURPOSE: This study aimed to explore the mechanisms involved in SolB-induced hepatomegaly. METHODS: Male C57BL/6 mice were injected intraperitoneally with SolB (100 mg/kg) for 5 days. Serum and liver samples were collected for biochemical and histological analyses. The mechanisms of SolB were investigated by qRT-PCR and western blot analyses, luciferase reporter gene assays and immunofluorescence. RESULTS: SolB significantly increased hepatocyte size and proliferation, and then promoted liver enlargement without liver injury and inflammation. SolB transactivated human PXR, activated PXR in mice and upregulated hepatic expression of its downstream proteins, such as CYP3A11, CYP2B10 and UGT1A1. SolB also significantly enhanced nuclear translocation of PXR and YAP in human cell lines. YAP signal pathway was activated by SolB in mice. CONCLUSION: These findings demonstrated that SolB can significantly induce liver enlargement, which is associated with the activation of PXR and YAP pathways.

Co-administration of Wuzhi tablet (Schisandra sphenanthera extract) alters tacrolimus pharmacokinetics in a dose- and time-dependent manner in rats.

ETHNOPHARMACOLOGY RELEVANCE: Tacrolimus is a well-known potent but expensive immunosuppressant. We previously clarified the herb-drug interaction between tacrolimus and Wuzhi tablet (WZ), a prescribed drug of ethanol extract of Schisandra sphenanthera, and showed the ideal effect of WZ on maintaining therapeutic level of tacrolimus and reducing the total drug expense. However, WZ possesses a biphasic effect on regulating CYP3A (the major metabolizing enzyme of tacrolimus), which could induce the mRNA and protein expression after long-term treatment while transiently inhibit the activity of CYP3A. In clinic, clinicians are confused about the relationship between the blood concentration of tacrolimus and the dose and the duration of pretreatment of WZ. Therefore, the effects of the pretreatment time and the dose of WZ on the pharmacokinetics of tacrolimus is urgently needed to be clarified to better combine the use of WZ and tacrolimus in clinic. AIM OF THE STUDY AND METHOD: This study aimed to investigate the effects of the pretreatment time and the dose of WZ on the pharmacokinetics of tacrolimus in rats. RESULTS AND CONCLUSIONS: After pretreated rats with WZ for 0, 0.5, 2, 6, 12 or 24 h, the area under the curve (AUC) of tacrolimus was 2.27 ± 0.59, 1.87 ± 1.14, 2.86 ± 0.64, 1.62 ± 0.70, 1.54 ± 1.06 and 1.12 ± 0.69-fold of that of the tacrolimus alone group, respectively. The ratio of AUC of tacrolimus to that of the co-administration group with 0, 62.5, 125, 250, 500 or 750 mg/kg of WZ was 1.00: 1.07: 1.44: 2.60: 2.32: 2.42, respectively. These findings suggested that WZ increased tacrolimus AUC in a pretreatment time- and dose-dependent manner. In line with the in vivo findings, WZ extract inhibited CYP3A activity in a pre-treatment time- and concentration-dependent manner in human liver microsomes. In conclusion, the pharmacokinetics of tacrolimus was significantly affected by the pretreatment time and the dose of WZ. Oral pretreatment with WZ for 0-2 h or co-dosing of 250 mg/kg of WZ most significantly increased the blood concentration of tacrolimus. These findings would be helpful for guiding the reasonable use of WZ and tacrolimus in clinic.

Targeted bile acids and gut microbiome profiles reveal the hepato-protective effect of WZ tablet (Schisandra sphenanthera extract) against LCA-induced cholestasis.

Cholestasis is caused by the obstacle of bile formation or secretion and can develop into severe liver diseases. We previously reported the ethanol extract of Schisandra sphenanthera (Wuzhi tablet, WZ) can significantly protect against lithocholic acid (LCA)-induced intrahepatic cholestasis in mice, partially due to the activation of PXR pathway and promotion of liver regeneration. However, the effect of WZ on the bile acids profile and gut microbiome in cholestastic mice remain unknown. In this study, the effect of WZ against LCA-induced liver injury was evaluated and its effect on the bile acids metabolome and gut microbiome profiles in cholestastic mice was further investigated. Targeted metabolomics analysis was performed to examine the change of bile acids in the serum, liver, intestine and feces. The change of intestinal flora were detected by the genomics method. Targeted metabolomics analysis revealed that WZ enhanced the excretion of bile acids from serum and liver to intestine and feces. Genomics analysis of gut microbiome showed that WZ can reverse LCA-induced gut microbiome disorder to the normal level. In conclusion, WZ protects against LCA-induced cholestastic liver injury by reversing abnormal bile acids profiles and alteration of gut microbiome.

Schisandrol B protects against acetaminophen-induced acute hepatotoxicity in mice via activation of the NRF2/ARE signaling pathway.

AIM: The nuclear factor erythroid 2-related factor 2 (NRF2) acts through the antioxidant response element (ARE) to regulate the expression of many detoxifying and antioxidant genes responsible for cytoprotective processes. We previously reported that Schisandrol B (SolB) isolated from Schisandra sphenanthera produced a protective effect against acetaminophen (APAP)-induced liver injury. In this study we investigated whether the NRF2/ARE signaling pathway was involved in this hepato-protective effect. METHODS: Male C57BL/6 mice were treated with SolB (200 mg · kg(-1) · d(-1), ig) for 3 d before injection of APAP (400 mg/kg, ip). Serum and liver tissue samples were collected 6 h later. The mRNA and protein expression were measured using qRT-PCR and Western blot assay, respectively. The activation of NRF2 was examined in HepG2 cells using luciferase reporter gene assay. RESULTS: SolB pretreatment significantly alleviated the hepatic injury (large patchy necrosis and hyperemia of the hepatic sinus), the increase of serum AST, ALT levels and hepatic MDA contents, and the decrease of liver and mitochondrial glutathione levels in APAP-treated mice. Furthermore, SolB pretreatment significantly increased nuclear accumulation of NRF2 and increased hepatic expression of NRF2 downstream proteins, including GCLC, GSR, NQO1, GSTs, MRP2, MRP3 and MRP4 in APAP-treated mice. Moreover, treatment with SolB (2.5-20 µmol/L) dose-dependently increased the activity of NRF2 reporter gene in HepG2 cells. CONCLUSION: SolB exhibits a remarkable protective effect against APAP-induced hepatotoxicity, partially via activation of the NRF2/ARE pathway and regulation of NRF2 target genes, which induce detoxification and increase antioxidant capacity.

[Determination of hepatic and small intestinal distribution of lignans of Wuzhi tablet in rats by liquid chromatography tandem mass spectrometry method].

This study was aimed to determine the hepatic and small intestinal distribution of active lignans in rats after treated with Wuzhi tablet (WZ, Schisandra sphenanthera extract) by LC-MS/MS method. Male Sprague-Dawley rats were sacrificed at 0.25, 1.5, 4, 6, 10, 24 h after an oral administration of WZ, and then hepatic and small intestinal samples were collected for analysis. The results showed that concentrations of lignans in liver and small intestine of rats were decreased with WZ pretreated time. The concentrations of all lignans in rat liver and small intestine at 0.25 h were the highest after a single oral administration. All lignans was undetectable in all tissues 24 h after oral dosing, suggesting lignans of WZ were eliminated rapidly in rats. The concentrations of schisandrin A, schisandrol B and schisantherin A in small intestine were much higher than those in the liver, suggesting the effect of WZ on the intestinal metabolism enzyme might be more potent than that on the liver. In short, the current results suggest that lignans of WZ were not accumulated in rat liver and small intestine. The concentrations of lignans of WZ in small intestine were much higher than those in liver.

[Effect of long-term treatment of Wuzhi tablet on the expression and activity of cytochrome P450 3A in rats].

The study aims to evaluate the effect of long-term pretreatment of the rat with Wuzhi tablet（WZ） on hepatic and intestinal CYP3A mRNA and protein expression and activity. Male Sprague-Dawley rats were orally administered of midazolam (2 mg·kg-1) with or without 14 days of pretreatment of WZ (0.25 g·kg-1) to determine CYP3A activity. Meanwhile, RNA and protein of rats liver and intestine samples were prepared 24 h after the last dose of 14 days of WZ treatment to determine CYP3A mRNA and protein expression. Long-term treatment of WZ increased the mRNA expression of hepatic Cyp3a1, Cyp3a9 and intestinal Cyp3a9 by 54.6%, 188.3%（P < 0.05） and 48.2%（P < 0.05）, respectively; and increased the protein expression of hepatic CYP3A by 43.2%. However, after long-term treatment of WZ, the AUC of orally administered of midazolam in the WZ group was increased 29.9%（WZ pretreatment group） and 154.2%（WZ coadministered group） compared to that of control group. In conclusion, long-term treatment of WZ increased the m RNA and protein expression of CYP3A, while could inhibit the activity of CYP3A.

Erratum to "PXR-Mediated Upregulation of CYP3A Expression by Herb Compound Praeruptorin C from Peucedanum praeruptorum Dunn".

[This corrects the article DOI: 10.1155/2013/156574.].

Inhibiton of cytochrome P450 isoenzymes and P-gp activity by multiple extracts of Huang-Lian-Jie-Du decoction.

ETHNOPHARMACOLOGICAL RELEVANCE: Huang-Lian-Jie-Du-Decotion (HLJDD), an important traditional Chinese medicine formula, has been used for various diseases in clinical practice, and thus has high potential to induce cytochrome P450 (CYP) isoenzymes/P-glycoprotein (P-gp) mediated herb-drug interactions (HDIs) with other co-administered drugs. The purpose of this study was to investigate the in vitro effects of multiple extracts including aqueous extracts, total flavonoids, iridoids, alkaloids from HLJDD on the activities of CYPs in rats (CYP1A2, CYP2C6, CYP2D2, CYP2E1 and CYP3A1) and P-gp, and then to predict potential interactions with co-administered drugs. MATERIALS AND METHODS: The effects of the four extracts from HLJDD on the CYPs activity were evaluated in rat liver microsomes incubation system, and then determined by LC-MS/MS-based CYPs probe substrate assay. Caco-2 cell monolayer was used to investigate the effect of the four extracts on the efflux of Rhodamine 123 to evaluate their influences on P-gp activity. RESULTS: The results show that total flavonoids and alkaloids exibited strong inhibition on rat CYP isoenzymes activities. Total flavonoids exhibited different inhibitory effects on CYPs activities with an order of CYP3A1>CYP2C6>CYP2E1>CYP1A2>CYP2D2, and the values of IC50 were 4.24, 8.16, 17.56, 19.03, 29.51 µg/mL, respectively. Total alkaloids possessed similar inhibition on CYPs and could strongly inhibit the activity of CYP2D2 (IC50=2.38 µg/mL), CYP3A1 (IC50=2.61 µg/mL), CYP2E1 (IC50=22.35 µg/mL), CYP1A2 (IC50=23.2 µg/mL) and CYP2C6 (IC50=43.09 µg/mL). Moderate degree of inhibition on CYPs activities was observed in aqueous and total iridoids extracts. Results from transport assay revealed that total flavonoids and alkaloids exhibited significant inhibitory effect on P-gp activity as evidenced by strong inhibition on the efflux of Rhodamine-123 with IC50 of 104.6 and 82.6 µg/mL. But aqueous extract showed weak and iridoids had negligible effect on P-gp activity. CONCLUSIONS: This study clearly demonstrated that total flavonoids and alkaloids from HLJDD can significantly inhibit the activities of CYPs and P-gp, which should be taken into consideration to predict any potential HDIs when HLJDD and its bioactive components are co-administered with other therapeutic drugs metabolized by CYPs or transported by P-gp.

Effect of Tacrolimus on the pharmacokinetics of bioactive lignans of Wuzhi tablet (Schisandra sphenanthera extract) and the potential roles of CYP3A and P-gp.

We recently reported that Wuzhi tablet (WZ), a preparation of the ethanol extract of Wuweizi (Schisandra sphenanthera), had significant effects on blood concentrations of Tacrolimus (FK506) in renal transplant recipients and rats. The active lignans in WZ are schisandrin A, schisandrin B, schisandrin C, schisandrol A, schisandrol B, schisantherin A, and schisantherin B. Until now, whether the pharmacokinetics of these lignans in WZ would be affected by FK506 remained unknown. Therefore, this study aimed to investigate whether and how FK506 affected pharmacokinetics of lignans in WZ in rats and the potential roles of CYP3A and P-gp. After a single oral co-administration of FK506 and WZ, the blood concentration of lignans in WZ was decreased by FK506; furthermore, the AUC of schisantherin A, schisandrin A, schisandrol A and schisandrol B was only 64.5%, 47.2%, 55.1% and 57.4% of that of WZ alone group, respectively. Transport study in Caco-2 cells showed that these lignans were not substrates of P-gp, suggesting decreased blood concentration of lignans by FK506 was not via P-gp pathway. Metabolism study in the human recombinant CYP 3A showed that these lignans had higher affinity to CYP3A than that of FK506, and thus had a stronger CYP3A-mediated metabolism. It was concluded that the blood concentrations of these lignans were decreased and their CYP3A-mediated metabolisms were increased in the presence of FK506 since these lignans had higher affinity to CYP3A.

In vivo to in vitro effects of six bioactive lignans of Wuzhi tablet (Schisandra sphenanthera extract) on the CYP3A/P-glycoprotein-mediated absorption and metabolism of tacrolimus.

We recently reported that Wuzhi tablet (WZ; Schisandra sphenanthera extract) can inhibit P-glycoprotein (P-gp)-mediated efflux and CYP3A-mediated metabolism of tacrolimus (FK506) and thus increase the blood concentrations of FK506. Major active lignans of WZ include schisandrin A, schisandrin B, schisandrin C, schisandrol A, schisandrol B, and schisantherin A. Whether and how these six lignans affect the pharmacokinetics of FK506 remains unclear. Therefore, this study aimed to investigate the effects of these lignans on the first-pass absorption and metabolism of FK506 and the involved mechanisms in vitro and in vivo. The results showed that whole-blood concentrations of FK506 were increased to different degrees following coadministration of the six lignans, respectively. Schisandrol B showed the strongest effect on the increase of the area under the concentration-time curve, the oral bioavailability, the gut processes affecting availability, and the hepatic availability of FK506. The reduction of intestinal first-pass effect contributed most to the increase in oral bioavailability of FK506 when coadministered with schisandrol B. In vitro transport experiment showed that schisandrin A, schisandrin B, and schisandrol B inhibited P-gp-mediated efflux of FK506. In vitro metabolism study showed that the inhibitory effect of these six lignans on FK506 metabolism was dose-dependent. In conclusion, the exposure of FK506 in rats was increased when coadministered with these lignans, and schisandrol B showed the strongest effect. Lignans of WZ inhibited P-gp-mediated efflux and CYP3A-mediated metabolism of FK506, and the reduction of intestinal first-pass affected by the lignans was the major cause of the increased FK506 oral bioavailability.

Regulation of human pregnane X receptor and its target gene cytochrome P450 3A by praeruptorin A isolated from the herbal medicine Peucedanum praeruptorum.

Qianhu, the dried roots of Peucedanum praeruptorum, is a well-known traditional Chinese medicinal herb which was officially listed in the Chinese Pharmacopoeia. Praeruptorin A is the major active constituent of Qianhu. Our previous studies show that praeruptorin effectively transactivated the protein expression and catalytic activity of cytochrome P450 3A4 via the constitutive androstane receptor-mediated pathway. However, the effect of praeruptorin on the transactivation of cytochrome P450 3A4 through pregnane X receptor pathway is still unclear. To further elucidate the role of the pregnane X receptor pathway in the up-regulation of cytochrome P450 3A4 by praeruptorin, in this study, the effect of praeruptorin on the cytochrome P450 3A4 gene expression was investigated in mouse primary hepatocytes after knockdown of the pregnane X receptor by transient transfection of its siRNA; and the gene expression, protein expression, and catalytic activity of cytochrome P450 3A4 in the LS174T cells with pregnane X receptor overexpression were determined by real-time PCR, Western blot analysis, and LC-MS/MS-based cytochrome P450 3A4 substrate assay, respectively. We found that the level of cytochrome P450 3a11 gene expression in mouse primary hepatocytes was significantly increased by praeruptorin, but such an induction was suppressed after knockdown of pregnane X receptor by its siRNA. Praeruptorin significantly induced cytochrome P450 3A4 mRNA, protein expression, and functional activity through pregnane X receptor-mediated pathway in pregnane X receptor-overexpression LS174T cells; conversely, induction was not found in LS174T cells untransfected with pregnane X receptor plasmids. These findings suggest that praeruptorin can significantly up-regulate cytochrome P450 3A4 gene via the pregnane X receptor-mediated pathway, and this should be taken into consideration in potential herb-drug interactions.

[Induction of UGT1A1 expression by praeruptorin A and praeruptorin C through hCAR pathway].

This study is purposed to investigate the effects of praeruptorin A (PA) and praeruptorin C (PC) on UGT1A1 in HepG2 cells through hCAR pathway. PA and PC were incubated with HepG2 cells for 24 h and 48 h, mRNA and protein expressions of UGT1A1 were determined by real-time PCR and Western blotting assays. Additionally, effects of PA and PC on UGT1A1 mRNA and protein expressions were also measured after transient transfection of a specific CAR siRNA for 72 h in HepG2 cells. UGT1A1 mRNA and protein expression levels were significantly increased by PA and PC after incubation for 48 h. Moreover, the mRNA and protein up-regulations of UGT1A1 were attenuated by transient transfection of a specific CAR siRNA, suggesting the induction was mediated by CAR. The results suggest that PA and PC can significantly up-regulate UGT1A1 expression partially via the CAR-mediated pathway.

Up-regulatation of CYP3A expression through pregnent X receptor by praeruptorin D isolated from Peucedanum praeruptorum Dunn.

ETHNOPHARMACOLOGICAL RELEVANCE: Qianhu, the dried roots of Peucedanum praeruptorum DUNN (Umbelliferae), is a well-known traditional Chinese medicinal herb which was officially listed in the Chinese Pharmacopoeia. Praeruptorin D (PD) is one of the major active constituents of Peucedanum praeruptorum Dunn (Qianhu). The Pregnane X receptor (PXR) is an orphan nuclear receptor and plays a pivotal role in the activation of human cytochrome P450 3A4 (CYP3A4) gene. AIM OF THE STUDY: The purpose of this study was to investigate the effect of PD on the PXR-mediated transactivation of CYP3A4, and thus to predict potential herb-drug interactions between PD, Qianhu, and the other co-administered drugs that metabolized by CYP3A4. MATERIALS AND METHODS: The effect of PD on the Cyp3a11, mPXR mRNA expression in mice primary hepatocytes was measured using real-time PCR. The gene expression, protein expression, and catalytic activity of CYP3A4 in the LS174T cells after transfected with PXR expression plasmids were determined by real-time PCR, Western blot analysis, and LC-MS/MS based CYP3A4 substrate assay. RESULTS: The results revealed that the level of Cyp3a11 gene expression in mice primary hepatocytes was significantly increased by PD, but PD cannot induce the mPXR gene expression. On the other hand, CYP3A4 mRNA, protein expression and functional activity in PXR-over-expression LS174T cells were significantly increased by PD through PXR-mediated pathway; conversely, no significant change was found in the untransfected cells. CONCLUSIONS: These findings suggest that PD can significantly up-regulate CYP3A4 expression and activity via the PXR-mediated pathway and this should be taken into consideration to predict any potential herb-drug interactions when PD and Peucedanum praeruptorum Dunn are co-administered with other drugs.

PXR-Mediated Upregulation of CYP3A Expression by Herb Compound Praeruptorin C from Peucedanum praeruptorum Dunn.

We recently reported that Praeruptorin C effectively transactivated the mRNA, protein expression, and catalytic activity of CYP3A4 via the CAR-mediated pathway, but whether and how PC could affect the expression and catalytic activity of CYP3A4 via PXR pathway remains unknown. Therefore, in this study, the effect of PC on the CYP3A gene expression was investigated in mice primary hepatocytes after knockdown of PXR by transient transfection of PXR siRNA, and the gene expression, protein expression, and catalytic activity of CYP3A4 in the LS174T cells with PXR overexpression were determined by real-time PCR, western blot analysis, and LC-MS/MS-based CYP3A4 substrate assay, respectively. We found that the level of CYP3a11 gene expression in mouse primary hepatocytes was significantly increased by praeruptorin C, but such an induction was suppressed after knockdown of pregnane X receptor by its siRNA. In PXR-overexpressed LS174T cells, PC significantly enhanced CYP3A4 mRNA, protein expression, and functional activity through PXR-mediated pathway; conversely, no such increase was found in the untransfected cells. These findings suggest that PC can significantly upregulate CYP3A level via the PXR-mediated pathway, and this should be taken into consideration to predict any potential herb-drug interactions between PC, Qianhu, and the other coadministered drugs.

Effect of Wuzhi tablet (Schisandra sphenanthera extract) on the pharmacokinetics of cyclosporin A in rats.

In our previous reports, Wuzhi tablet (an herbal preparation of ethanol extract of Wuweizi (Schisandra sphenanthera)) can significantly increase the blood concentration of tacrolimus and paclitaxel in rats by inhibiting the CYP3A-mediated metabolism and the P-gp-mediated efflux. Cyclosporin A (CsA), a well-known immunosuppressant agent, is also a substrate of CYP3A and P-gp. Therefore, this study aimed to investigate whether and how WZ affects pharmacokinetics of CsA in rats. The AUC0-48 h and Cmax of CsA were increased by 40.1% and 13.1%, respectively, with a single oral co-administration of WZ and high dose of CsA (37.8 mg/kg). Interestingly, after a single oral co-administration of WZ and low dose of CsA (1.89 mg/kg), the AUC0-36 h and Cmax of CsA were dramatically increased by 293.1% (from 1103.2 ± 293.0 to 4336.5 ± 1728.3 ng.h/mL; p < 0.05) and 84.1% (from 208.5 ± 67.9 to 383.1 ± 92.5 ng/mL; p < 0.05), respectively. The CL/F was decreased from 1.7 L/h/kg to 0.5 L/h/kg. Thus, the effect of WZ on high dose of CsA was not significant, but pharmacokinetic parameters of CsA at low dose were significantly influenced by co-administration of WZ. The herb-drug interaction should be taken into consideration at this situation.

Effect of long-term co-administration of Wuzhi tablet (Schisandra sphenanthera extract) and prednisone on the pharmacokinetics of tacrolimus.

Tacrolimus (TAC) is an immunosuppressant that has been widely used alone or in combination with prednisone (PRED) to prevent acute rejection after organ transplantation. Wuzhi tablet (WZ, Schisandra sphenanthera extract) is often prescribed with TAC to prevent drug-induced hepatitis. We recently reported that WZ could significantly increase TAC blood exposure by inhibiting P-gp-mediated efflux and CYP3A-mediated metabolism of TAC. PRED is also a substrate of P-gp and is a weak inducer of CYP3A, and drug-drug interactions within this combination therapy might occur. Therefore, the purpose of this study was to investigate the effect of long-term treatment of WZ and PRED on the pharmacokinetics of TAC in rats. After 14 days of co-administration of WZ and PRED, the AUC(0-24h) of oral TAC was increased (from 59.6±37.3 to 95.3±39.4 ng h/ml, p=0.18) and the clearance was decreased (from 38.4±28.4 to 17.7±6.4 l/h/kg, p=0.15). When only co-administered with WZ, AUC(0-24h) of TAC was demonstrated a significantly increase (from 59.6±37.3 to 135.9±34.8 ng h/ml, p<0.05). The concomitant administration of PRED resulted in a reduction in the systemic exposure of TAC and an increase in its clearance, though neither was statistically significant. Thus, our study suggested that the presence of WZ and PRED still could increase the systemic exposure of TAC in rats. The drug-drug interactions among this combination therapy should still be taken into consideration in clinical practice.

CAR-mediated up-regulation of CYP3A4 expression in LS174T cells by Chinese herbal compounds.

The constitutive androstane receptor (CAR) is an orphan nuclear receptor which has been shown to participate in the activation of human CYP3A4, which metabolizes more than 50% of clinically used drugs. We investigated the effects of an array of compounds isolated from herbal medicines such as Rheum palmatum (Da Huang), Peucedanum praeruptorum Dunn (Qian Hu), Cortex Mori Radicis (Sang Bai Pi), Radix Asteris (Zi Wan), Salvia miltiorrhiza (Dan Shen), Polygonum cuspidatum Sieb. et Zucc (Hu Zhang), and Ginkgo biloba (Yin Xing) on the CAR-mediated transactivation of CYP3A4. The effect of herbal compounds on CYP3A4 expression was measured using a CYP3A4 luciferase reporter gene assay in transiently transfected human intestinal LS174T cells. The gene expression, protein expression, and catalytic activity of CYP3A4 in LS174T cells transfected with CAR were determined by using real-time PCR, Western blot analysis, and LC-MS/MS-based substrate assay. The study found that in CAR-transfected cells, praeruptorin A, C, and D significantly induced CYP3A4 luciferase activity, mRNA expression, and functional activity through the CAR-mediated pathway; conversely, induction was not found in untransfected cells. Our findings suggest that these herbal compounds can significantly up-regulate the CYP3A4 gene via the CAR-mediated pathway, which has important implications in herb-drug interactions.

Regulation of human pregnane X receptor and its target gene cytochrome P450 3A4 by Chinese herbal compounds and a molecular docking study.

The pregnane X receptor (PXR) plays a critical role in the regulation of human cytochrome P450 3A4 (CYP3A4) gene. In this study, we investigated the effect of an array of compounds isolated from Chinese herbal medicines on the activity of PXR using a luciferase reporter gene assay in transiently transfected HepG2 and Huh7 cells and on the expression of PXR and CYP3A4 in LS174T cells. Furthermore, molecular docking was performed to investigate the binding modes of herbal compounds with PXR. Praeruptorin A and C, salvianolic acid B, sodium danshensu, protocatechuic aldehyde, cryptotanshinone, emodin, morin, and tanshinone IIA significantly transactivated the CYP3A4 reporter gene construct in either HepG2 or Huh7 cells. The PXR mRNA expression in LS174T cells was significantly induced by physcion, protocatechuic aldehyde, salvianolic acid B, and sodium danshensu. However, epifriedelanol, morin, praeruptorin D, mulberroside A, tanshinone I, and tanshinone IIA significantly down-regulated the expression of PXR mRNA in LS174T cells. All the herbal compounds tested can be readily docked into the ligand-binding cavity of PXR mainly through hydrogen bond and aromatic interactions with Ser247, Gln285, His407, and Arg401. These findings suggest that herbal medicines can significantly regulate PXR and CYP3A4 and this has important implication in herb-drug interactions.