Long-term treatment with the mPXR agonist PCN promotes hepatomegaly and lipid accumulation without hepatocyte proliferation in mice.

Pregnane X receptor (PXR) is highly expressed in the liver and plays a pivotal role in xenobiotic and endobiotic metabolism. We previously reported that PXR activation by its specific mouse agonist pregnenolone 16α-carbonitrile (PCN) significantly induces liver enlargement and lipid accumulation. However, the effect of long-term PCN treatment on PXR and mouse liver is still unknown. This study aimed to explore the influence of long-term administration of PCN on mouse liver and hepatic lipid homeostasis. Male C57BL/6 mice were injected intraperitoneally with PCN (100 mg/kg once a week) for 42 weeks. Serum and liver samples were collected for biochemical and histological analysis. PXR activation was investigated by Western blot. Ultra-high-performance liquid chromatography coupled with electrospray ionization high-resolution mass spectrometry (UHPLC-ESI-HRMS)-based lipidomics analysis was performed to explore the change in different lipid categories. The results showed that long-term treatment with PCN significantly promoted hepatomegaly without hepatocyte proliferation and enlargement. Long-term treatment with PCN did not upregulate PXR target proteins in mice, and there was no significant upregulation of CYP3A11, CYP2B10, UGT1A1, MRP2, or MRP4. Lipidomics analysis showed obvious hepatic lipid accumulation in the PCN-treated mice, and the most significant change was found in triglycerides (TGs). Additionally, long-term treatment with PCN had no risk for carcinogenesis. These findings demonstrated that long-term PCN treatment induces hepatomegaly and lipid accumulation without hepatocyte proliferation or enlargement.

Peroxisome proliferator-activated receptor α agonist induces mouse hepatomegaly through the spatial hepatocyte enlargement and proliferation.

Peroxisome proliferator-activated receptor alpha (PPARα) activation-induced hepatomegaly is accompanied by hepatocyte hypertrophy around the central vein (CV) area and hepatocyte proliferation around the portal vein (PV) area. However, the molecular mechanisms underlying this spatial change of hepatocytes remains unclear. In this study, we examined the characteristics and possible reasons for the zonation distinction of hypertrophy and proliferation during PPARα activation-induced mouse liver enlargement. Mice were injected with corn oil or a typical mouse PPARα agonist WY-14643 (100 mg·kg-1·d-1, i.p.) for 1, 2, 3, 5 or 10 days. At each time point, the mice were sacrificed after the final dose, and liver tissues and serum were harvested for analysis. We showed that PPARα activation induced zonal changes in hepatocyte hypertrophy and proliferation in the mice. In order to determine the zonal expression of proteins related to hepatocyte hypertrophy and proliferation in PPARα-induced liver enlargement, we performed digitonin liver perfusion to separately destroy the hepatocytes around the CV or PV areas, and found that PPARα activation-induced increase magnitude of its downstream targets such as cytochrome P450 (CYP) 4 A and acyl-coenzyme A oxidase 1 (ACOX1) levels around the CV area were higher compared with those around the PV area. Upregulation of proliferation-related proteins such as cell nuclear antigen (PCNA) and cyclin A1 (CCNA1) after WY-14643-induced PPARα activation mainly occurred around the PV area. This study reveals that the zonal expression of PPARα targets and proliferation-related proteins is responsible for the spatial change of hepatocyte hypertrophy and proliferation after PPARα activation. These findings provide a new insight into the understanding of PPARα activation-induced liver enlargement and regeneration.

PXR mediates mifepristone-induced hepatomegaly in mice.

Mifepristone (Mif), an effective synthetic steroidal antiprogesterone drug, is widely used for medical abortion and pregnancy prevention. Due to its anti-glucocorticoid effect, high-dose Mif is also used to treat Cushing's syndrome. Mif was reported to active pregnane X receptor (PXR) in vitro and PXR can induce hepatomegaly via activation and interaction with yes-associated protein (YAP) pathway. High-dose Mif was reported to induce hepatomegaly in rats and mice, but the underlying mechanism remains unclear. Here, the role of PXR was studied in Mif-induced hepatomegaly in C57BL/6 mice and Pxr-knockout mice. The results demonstrated that high-dose Mif (100 mg · kg-1 · d-1, i.p.) treatment for 5 days significantly induced hepatomegaly with enlarged hepatocytes and promoted proliferation, but low dose of Mif (5 mg · kg-1 · d-1, i.p.) cannot induce hepatomegaly. The dual-luciferase reporter gene assays showed that Mif can activate human PXR in a concentration-dependent manner. In addition, Mif could promote nuclear translocation of PXR and YAP, and significantly induced the expression of PXR, YAP, and their target proteins such as CYP3A11, CYP2B10, UGT1A1, ANKRD, and CTGF. However, Mif (100 mg · kg-1 · d-1, i.p.) failed to induce hepatomegaly in Pxr-knockout mice, as well as hepatocyte enlargement and proliferation, further indicating that Mif-induced hepatomegaly is PXR-dependent. In summary, this study demonstrated that PXR-mediated Mif-induced hepatomegaly in mice probably via activation of YAP pathway. This study provides new insights in Mif-induced hepatomegaly, and provides novel evidence on the crucial function of PXR in liver enlargement and regeneration.

Hepatic Vps33b deficiency aggravates cholic acid-induced cholestatic liver injury in male mice.

Vacuolar protein sorting 33B (VPS33B) is important for intracellular vesicular trafficking process and protein interactions, which is closely associated with the arthrogryposis, renal dysfunction, and cholestasis syndrome. Our previous study has shown a crucial role of Vps33b in regulating metabolisms of bile acids and lipids in hepatic Vps33b deficiency mice with normal chow, but it remains unknown whether VPS33B could contribute to cholestatic liver injury. In this study we investigated the effects of hepatic Vps33b deficiency on bile acid metabolism and liver function in intrahepatic cholestatic mice. Cholestasis was induced in Vps33b hepatic knockout and wild-type male mice by feeding 1% CA chow diet for 5 consecutive days. We showed that compared with the wild-type mice, hepatic Vps33b deficiency greatly exacerbated CA-induced cholestatic liver injury as shown in markedly increased serum ALT, AST, and ALP activities, serum levels of total bilirubin, and total bile acid, as well as severe hepatocytes necrosis and inflammatory infiltration. Target metabolomics analysis revealed that hepatic Vps33b deficiency caused abnormal profiles of bile acids in cholestasis mice, evidenced by the upregulation of conjugated bile acids in serum, liver, and bile. We further demonstrated that the metabolomics alternation was accompanied by gene expression changes in bile acid metabolizing enzymes and transporters including Cyp3a11, Ugt1a1, Ntcp, Oatp1b1, Bsep, and Mrp2. Overall, these results suggest a crucial role of hepatic Vps33b deficiency in exacerbating cholestasis and liver injury, which is associated with the altered metabolism of bile acids.

Natural product-based screening led to the discovery of a novel PXR agonist with anti-cholestasis activity.

Cholestasis is a major cause of a series of bile flow malfunction-related liver diseases. Pregnane X receptor (PXR) is a key regulator in endo- and xeno-biotics metabolism, which has been considered as a promising therapeutic target for cholestasis. In this study we conducted human PXR (hPXR) agonistic screening using dual-luciferase reporter gene assays, which led to discovering a series of potent hPXR agonists from a small Euphorbiaceae diterpenoid library, containing 35 structurally diverse diterpenoids with eight different skeleton types. The most active compound 6, a lathyrane diterpenoid (5/11/3 ring system), dose-dependently activated hPXR with a high selectivity, and significantly upregulated the expression of hPXR downstream genes CYP3A4 and UGT1A1. In LCA-induced cholestasis mouse model, administration of compound 6 (50 mg· kg-1. d-1, ip) for 7 days significantly suppressed liver necrosis and decreased serum levels of AST, ALT, Tbili, ALP, and TBA, ameliorating LCA-induced cholestatic liver injury. We further revealed that compound 6 exerted its anti-cholestatic efficacy via activation of PXR pathway, accelerating the detoxification of toxic BAs and promoting liver regeneration. These results suggest that lathyrane diterpenoids may serve as a promising scaffold for future development of anti-cholestasis drugs.

[Regulation of P-glycoprotein gene expression by PKC/NF-κB-PXR signaling pathway].

P-glycoprotein (P-gp), an ATP binding cassette protein, plays a major role in efflux transport of drugs and xenobiotics due to its abundant expression on several barriers. This study aimed to investigate the potential role of PKC/NF-κB-PXR signaling pathway in modulation of P-gp gene expression in human colon adenocarcinoma LS174T. The effect of PMA on MDR1 luciferase activity was investigated by PXR-MDR1 dual luciferase reporter gene assay. Real-time qPCR assay and Western blot analysis were used to study the gene expression of P-gp and NF-κB, respectively. Compared to the vehicle-treated group, PMA statistically decreased P-gp luciferase activity, mRNA expression and protein expression. Moreover, PMA treatment yielded a significant and dose-dependent increase in RelA/p65 translocation to nucleus. Meanwhile, a remarkable increase of the pho-IκBα status was observed in LS174T cells after treatment with PMA (1-100 nmol·L(-1)). In addition, knockdown of PKCα, NF-κB or PXR can significantly attenuate PMA-induced P-gp suppression. These results suggested that PKC/NF-κB-PXR signaling pathway might play crucial roles in modulation of P-gp gene expression.

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.

[Optimization of midazolam dosage and pharmacokinetics of CYP3A probe substrate in rats].

The study was conducted to evaluate the pharmacokinetics of midazolam (MDZ) under different oral dosages in rats, and determine the optimum oral dosage of MDZ, a CYP3 A probe substrate in vivo. Male Sprague-Dawley rats were given a single oral dosages of MDZ at 1,2,5,10,15 or 20 mg·kg(-1). Plasma concentrations of MDZ and its major metabolite 1-hydroxyl midazolam (1-OH MDZ) were determined at different time points using a validated LC-MS/MS method. Pharmacokinetic parameters were calculated using non-compartmental model. The C(max), AUC(0-t) and AUC0(∞) of MDZ and 1-OH MDZ were linearly increased over the dose range of 1-5 mg·kg(-1) (r > 0.99), but not at the dose of 15 or 20 mg·kg(-1). The AUC/Dose at 1-10 mg·kg(-1) were not significant different, but that of 15 or 20 mg·kg(-1) were significantly higher. No significant sedative reaction was observed in all the rats at dosages of 1-5 mg·kg(-1), however loss of righting reflex was observed in rats receiving dosages of 10-20 mg·kg(-1). In conclusion, the optimized oral dose of MDZ was 1-5 mg·kg(-1) when MDZ is used as the CYP3 A probe substrate in rats.

[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.

[Construction and function identification of luciferase reporter gene vectors containing SNPs in NFKBIA gene 3'UTR].

This study aims to investigate the function of two SNPs (rs8904C > T and rs696G >A) in 3' untranslated region (3'UTR) of NFKBIA gene by constructing luciferase reporter gene. A patient's genomic DNA with rs8904 CC and rs696 GA genotype was used as the PCR template. Full-length 3'UTR of NFKBIA gene was amplified by different primers. After sequencing validation, these fragments were inserted to the luciferase reporter vector, pGL3-promoter to construct recombinant plasmids containing four kinds of haplotypes, pGL3-rs8904C/rs696G, pGL3-rs8904C/rs696A, pGL3-rs8904T/rs696G and pGL3-rs8904T/rs696A. Then these plasmids were transfected into LS174T cells and the luciferase activity was detected. Compared with pGL3-vector transfected cells (negative control), the luciferase activity of the four kinds of recombinant plasmids was significantly decreased (P < 0.001). For rs696G > A, the luciferase activity of the recombinant plasmids containing A allele (pGL3-rs8904C/rs696A and pGL3-rs8904T/rs696A) was about 45.1% (P < 0.05) and 56.1% (P < 0.001) lower than those containing G allele (pGL3-rs8904C/rs696G and pGL3-rs8904T/rs696G), respectively. For rs8904C > T, there were no significant differences in the luciferase activity between the recombinant plasmids containing T allele and those with C allele. Together, the luciferase reporter gene vectors containing SNPs in NFKBIA gene 3'UTR were constructed successfully and rs696G > A could decrease the luciferase activity while rs8904C >T didn't have much effect on the luciferase activity.

Effects of nicotinamide N-methyltransferase on PANC-1 cells proliferation, metastatic potential and survival under metabolic stress.

BACKGROUND: Aberrant expression of Nicotinamide N-methyltransferase (NNMT) has been reported in pancreatic cancer. However, the role of NNMT in pancreatic cancer development remains elusive. Therefore, the present study was to investigate the impact of NNMT on pancreatic cancer cell proliferation, metastatic potential and survival under metabolic stress. METHODS: Pancreatic cancer cell line PANC-1 was transfected with NNMT expression plasmid or small interfering RNA of NNMT to overexpress or knockdown intracellular NNMT expression, respectively. Rate of cell proliferation was monitored. Transwell migration and matrigel invasion assays were conducted to assess cell migration and invasion capacity. Resistance to glucose deprivation, sensitivity to glycolytic inhibition, mitochondrial inhibtion and resistance to rapamycin were examined to evaluate cell survival under metabolic stress. RESULTS: NNMT silencing markedly reduced cell proliferation, whereas NNMT overexpression promoted cell growth moderately. Knocking down NNMT also significantly suppressed the migration and invasion capacities of PANC-1 cells. Conversely, NNMT upregulation enhanced cell migration and invasion capacities. In addition, NNMT knockdown cells were much less resistant to glucose deprivation and rapamycin as well as glycolytic inhibitor 2-deoxyglucose whereas NNMT-expressing cells showed opposite effects although the effects were not so striking. CONCLUSIONS: These data sugguest that NNMT plays an important role in PANC-1 cell proliferation, metastatic potential and survival under metabolic stress.

N-methylnicotinamide and nicotinamide N-methyltransferase are associated with microRNA-1291-altered pancreatic carcinoma cell metabolome and suppressed tumorigenesis.

The cell metabolome comprises abundant information that may be predictive of cell functions in response to epigenetic or genetic changes at different stages of cell proliferation and metastasis. An unbiased ultra-performance liquid chromatography-mass spectrometry-based metabolomics study revealed a significantly altered metabolome for human pancreatic carcinoma PANC-1 cells with gain-of-function non-coding microRNA-1291 (miR-1291), which led to a lower migration and invasion capacity as well as suppressed tumorigenesis in a xenograft tumor mouse model. A number of metabolites, including N-methylnicotinamide, involved in nicotinamide metabolism, and l-carnitine, isobutyryl-carnitine and isovaleryl-carnitine, involved in fatty acid metabolism, were elevated in miR-1291-expressing PANC-1. Notably, N-methylnicotinamide was elevated to the greatest extent, and this was associated with a sharp increase in nicotinamide N-methyltransferase (NNMT) mRNA level in miR-1291-expressing PANC-1 cells. In addition, expression of NNMT mRNA was inversely correlated with pancreatic tumor size in the xenograft mouse model. These results indicate that miR-1291-altered PANC-1 cell function is associated with the increase in N-methylnicotinamide level and NNMT expression, and in turn NNMT may be indicative of the extent of pancreatic carcinogenesis.

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.

Roles of P-glycoprotein and multidrug resistance protein in transporting para-aminosalicylic acid and its N-acetylated metabolite in mice brain.

AIM: Para-aminosalicylic acid (PAS) is effective in the treatment of manganism-induced neurotoxicity (manganism). In this study we investigated the roles of P-glycoprotein (MDR1a) and multidrug resistance protein (MRP) in transporting PAS and its N-acetylated metabolite AcPAS through blood-brain barrier. METHODS: MDR1a-null or wild-type mice were intravenously injected with PAS (200 mg/kg). Thirty minutes after the injection, blood samples and brains were collected, and the concentrations of PAS and AcPAS in brain capillaries and parenchyma were measured using HPLC. Both MDCK-MDR1 and MDCK-MRP1 cells that overexpressed P-gp and MRP1, respectively, were used in two-chamber Transwell transport studies in vitro. RESULTS: After injection of PAS, the brain concentration of PAS was substantially higher in MDR1a-null mice than in wild-type mice, but the brain concentration of AcPAS had no significant difference between MDR1a-null mice and wild-type mice. Concomitant injection of PAS with the MRP-specific inhibitor MK-571 (50 mg/kg) further increased the brain concentration of PAS in MDR1a-null mice, and increased the brain concentration of AcPAS in both MDR1a-null mice and wild-type mice. Two-chamber Transwell studies with MDCK-MDR1 cells demonstrated that PAS was not only a substrate but also a competitive inhibitor of P-gp, while AcPAS was not a substrate of P-gp. Two-chamber Transwell studies with the MDCK-MRP1 cells showed that MRP1 had the ability to transport both PAS and AcPAS across the BBB. CONCLUSION: P-gp plays a major role in the efflux of PAS from brain parenchyma into blood in mice, while MRP1 is involved in both PAS and AcPAS transport in the brain.

Phorbol 12-myristate 13-acetate inhibits P-glycoprotein-mediated efflux of digoxin in MDCKII-MDR1 and Caco-2 cell monolayer models.

AIM: To investigate the effects of phorbol 12-myristate 13-acetate (PMA), a PKC activator, on P-glycoprotein-mediated efflux of digoxin in two cell transport models. METHODS: Caco-2 cells, wild MDCKII cells (MDCKII-WT) and MDCKII cells transfected stably with human MDR1-gene encoding P-gp (MDCKII-MDR1) were examined. Cell viability was evaluated with MTT assay. Bidirectional transport of digoxin was evaluated in these cells. Intracellular ATP level was measured using ATP assay. P-gp ATPase activity was analyzed using a Pgp-Glo(TM) assay. RESULTS: PMA (10 µmol/L) did not reduce the viability of the 3 types of cells. In Caco-2 and MDCKII-MDR1 cell monolayers, PMA (1, 10 and 100 nmol/L) dose-dependently inhibited the basolateral to apical transport of digoxin, but did not change the apical to basolateral transport. In addition, PMA did not affect both the basolateral to apical and apical to basolateral transport of digoxin in MDCKII-WT cell monolayer. In agreement with the above results, PMA dose-dependently reduced intracellular ATP level and stimulated P-gp ATPase activity in both Caco-2 and MDCKII-MDR1 cells. Verapamil (a positive control, 100 µmol/L) caused similar inhibition on digoxin efflux as PMA did, whereas 4α-PMA (a negative control, 100 nmol/L) had no effect. CONCLUSION: PMA significantly inhibited P-gp-mediated efflux of digoxin in both Caco-2 and MDCKII-MDR1 cell monolayers via PKC activation.

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.

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.

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.

Genetic polymorphisms of UGT1A8, UGT1A9, UGT2B7 and ABCC2 in Chinese renal transplant recipients and a comparison with other ethnic populations.

Mycophenolate mofetil (MMF), a widely used immunosuppressant, is characterized by highly variable pharmacokinetics. UGT1A8, UGT1A9, UGT2B7 and ABCC2 have been proved to be critical genes associated with inter-individual variation of MMF pharmacokinetics. In this study, we investigated the genetic polymorphisms of UGT1A8*2, UGT1A8*3, UGT1A9 C-2152T, UGT1A9 T-275A, UGT1A9 T98C, UGT2B7*2, ABCC2 C-24T and ABCC2 C3972T in 200 Chinese renal transplant recipients and compared them with those in other ethnic groups reported in the literature, to start the exploration of a better use of MMF in Chinese. A much higher frequency of UGT1A8*2 variant allele was found in Chinese than in Caucasians and Africans, while the UGT2B7*2 variant allele was significantly rarer in Chinese than in Caucasians and Africans. For ABCC2, -24T allele was more common and 3972T allele was less common in Chinese than in Caucasians and Africans. However, none of the SNPs in UGT1A9 were present in our study population. The findings of this study suggest that Chinese renal transplant recipients may exhibit a response profile to MMF that is different from those of other ethnic groups.