In Vitro and In Vivo Characterization of Reactive Intermediates of Corynoline

Corynoline ameliorates dextran sulfate sodium-induced colitis in mice by modulating Nrf2/NF-κB pathway

OBJECTIVE

Corynoline is an active substance extracted from Corydalis bungeana Turcz and exerts a therapeutic effect in multiple diseases by alleviating inflammatory response. The present study sought to elucidate the role of corynoline in ulcerative colitis (UC).

METHODS

The experimental colitis models were induced in BALB/c mice via receiving a drinking water supplemented with 3.5% (I) dextran sulfate sodium (DSS) ad libitum for 7 days.

RESULTS

Corynoline administration inhibited body weight loss, colon shortening, disease activity index and colonic pathomorphological changes in DSS-treated mice. Besides, corynoline down-regulated the levels of pro-inflammatory interleukin (IL)-1β, IL-6 and tumor necrosis factor Alpha (TNF-α), as well as decreased myeloperoxidase (MPO) activity in the colon of DSS-treated mice. In addition, severe oxidative stress in the colonic tissues of DSS-treated was mitigated by corynoline treatment. However, these beneficial effects were reversed by a specific nuclear factor E2-related factor 2 (Nrf2) inhibitor ML385 intervention. Further evidence confirmed that corynoline promoted Nrf2 nuclear migration and heme oxygenase-1 gene expression in the colonic tissues of UC mice. Besides, corynoline treatment restrained colonic nuclear factor-kappa B (NF-κB) activation as proved by the decrease in phosphorylation and nuclear translocation of NF-κB.

CONCLUSIONS

Corynoline ameliorates DSS-induced mouse colitis, which may provide a promising therapeutic strategy for UC treatment.

Evidence for Metabolic Activation of Omeprazole In Vitro and In Vivo

Omeprazole (OPZ) is a proton pump inhibitor commonly used for the treatment of gastric acid hypersecretion. Studies have revealed that use of OPZ can induce hepatotoxicity, but the mechanisms by which it induces liver injury are unclear. This study aimed to identify reactive metabolites of OPZ, determine the pathways of the metabolic activation, and define the correlation of the bioactivation with OPZ cytotoxicity. Quinone imine-derived glutathione (GSH), N-acetylcysteine (NAC), and cysteine (Cys) conjugates were detected in OPZ-fortified rat and human liver microsomal incubations captured with GSH, NAC, or Cys. The same GSH conjugates were detected in bile of rats and cultured liver primary cells after exposure to OPZ. Similarly, the same NAC conjugates were detected in urine of OPZ-treated rats. The resulting quinone imine was found to react with Cys residues of hepatic protein. CYP3A4 dominated the metabolic activation of OPZ. Exposure to OPZ resulted in decreased cell survival in cultured primary hepatocytes. Pretreatment with ketoconazole attenuated the susceptibility of hepatocytes to the cytotoxicity of OPZ.

Glutathione conjugation and protein modification resulting from metabolic activation of venlafaxine in vitro and in vivo

Venlafaxine (VLF), an antidepressant agent, is widely used to combat major depressive disorders, particularly for the treatment of selective serotonin reuptake inhibitor-resistant depression. VLF has been shown to cause liver injury. The present study aimed to investigate the metabolic activation of VLF and explore the mechanisms of hepatotoxicity induced by VLF.One glutathione (GSH) conjugate and one cysteine conjugate were both detected in mouse and human liver microsomal incubations containing VLF and GSH or cysteine. The two conjugates were also detected in cultured mouse primary hepatocytes and bile of rats after exposure to VLF. The in vitro and in vivo studies demonstrated that VLF was metabolized to a quinone methide intermediate reactive to GSH and cysteine residues of hepatic protein. The observed protein covalent binding revealed dose-dependency. The metabolic activation of VLF was P450-dependent, and CYP3A4 was found as the predominant enzyme involved in the bioactivation process.These findings facilitate better understanding of the metabolic activation-hepatotoxicity relationship of VLF and provide chemists with information about new potential structural alerts during drug design process.

Establishment of a High-Resolution Liquid Chromatography-Mass Spectrometry Spectral Library for Screening Toxic Natural Products

Many natural products have biological effects on humans and animals. Poisoning caused by natural products is common in clinical toxicology cases. Liquid chromatography-high-resolution-mass spectrometry (LC-HRMS) has recently emerged as a powerful analytical tool for large-scale target screening, and the application of LC-HRMS can be expanded to evaluate potential natural product poisoning in clinical cases. We report the construction of an LC-HRMS spectral library of 95 natural products commonly implicated in poisoning, and an LC-HRMS assay was validated for definitive detection of natural products in urine and serum samples. For each compound, the limit of detection (LOD) was determined in the analytical range of 1.0 - 1000 ng/mL for urine samples and 0.50 - 500 ng/mL for serum samples. The mean (SD) of matrix effects for urine samples and that for serum samples were both -21% (22%), and the mean (SD) of recovery for serum samples was 89% (26%). The LC-HRMS assay was successfully applied to identify natural products in clinical cases. The spectral library parameters of each compound are provided in the supplementary material to aid other laboratories in identification of unknown natural toxins and development of similar methods on different mass spectrometry platforms.

Natural product corynoline suppresses melanoma cell growth through inducing oxidative stress

Natural product corynoline is a unique isoquinoline alkaloid extracted from traditional Chinese medicine Corydalis bungeana Turcz, whereas its anticancer properties have not been investigated. In this study, we found that corynoline potently impairs the growth of melanoma cells, B16F10, and A375 in a concentration-dependent manner. Treatment of melanoma cells with corynoline results in G2 cell arrest accompanied by reduced cdc2 activation. Furthermore, corynoline triggers apoptosis of melanoma cells, which is associated with increased expression of Bax and cleaved caspase-3. Mechanistic study indicates that corynoline strongly induces reactive oxygen species (ROS) generation and subsequent DNA damage as evidenced by γ-H2AX accumulation. Notably, the effect of corynoline on melanoma cell cycle and apoptosis is abolished by a ROS scavenger N-acetyl cysteine (NAC), indicating a ROS-dependent mechanism. Finally, corynoline significantly inhibits in vivo B16F10 melanoma tumor growth accompanied by reduced expression of Ki-67 in tumor tissue. Taken together, our data suggest that corynoline suppresses melanoma cell growth in vitro and in vivo by inducing oxidative stress and represents a potential therapeutic agent for melanoma patients.

In vitro and in vivo studies of the metabolic activation of chelidonine

Chelidonium majus L. is a herbal medicine widely employed in Europe and Western Asia. Chelidonine (CHE) is a major constituent of the herb and has been reported to be an inhibitor of the cytochrome P450 enzymes (CYP). The major objective of the present study was to study the metabolic pathways of CHE in order to identify potential reactive metabolites responsible for the enzyme inhibition. Three oxidative metabolites (M1-M3) were detected in human liver microsomal incubations after exposure to CHE. M1 and M2 were two isomers of catechol derivatives, and M3 was a dicatechol compound. The M1-M3 metabolites were also observed in bile of rats given CHE. A total of five glutathione (GSH) conjugates (M4-M8) were detected in microsomes containing CHE, GSH, and NADPH. Moreover, M4 and M6 originated from M1, M5 and M7 resulted from M2, and M8 was a M3-derived GSH conjugate. Three biliary CHE-derived GSH conjugates (M4, M5 and M8) were found in CHE-treated rats. This indicates that CHE was bioactivated to ortho-quinone derivatives both in vitro and in vivo. Recombinant P450 enzyme incubations demonstrated that the CYPs3A4, 1A2, 2C19 and 2D6 were mainly involved in metabolic activation of CHE. This study generated data that may be useful in understanding possible mechanisms of CHE-induced P450 inhibition.

Metabolism-based herb-drug interaction of Corydalis Bungeanae Herba with berberine in vitro and in vivo in rats

Corynoline (CRL) and berberine (BER) are the major bioactive components found in traditional Chinese medicines Corydalis Bungeanae Herba (Corydalis bungeanae) and Coptidis Rhizoma, respectively. The two herbs serve as anti-inflammatory agents and are generally applied to many prescriptions. The aims of the study were to evaluate herb-drug interaction of C. bungeanae with BER and to investigate the mechanisms of the interaction action. Pre-treatment of BER caused reduction of plasma CRL in rats with increased formation of its three oxidative metabolites (M1-M3). Compared with the vehicle-treated group, the peak concentration and area under the concentration-time curve of CRL decreased by ~60% (given CRL) and ~50% (given extracts) in rats pre-treated with BER, respectively, along with 130 and 100% increases in apparent clearance. More M1-M3 were formed in liver microsomes of rats pretreated with BER (7 days) than in those pretreated with vehicle. Additionally, elevated activities of rCYPs2D2 and 1A2 (CYPs2D6 and 1A2) were observed in the BER-induced group. Up-regulated expression of hepatic rCYP2D2 (CYP2D6) was found in animals after 7 days of treatment of BER. The study illustrated that C. Bungeanae and BER produced metabolic herb-drug interaction and provided important information that combination of C. bungeanae with BER-containing herbal medicines may encounter the risk of decreased efficacy of CRL.

Characterization of glutathione conjugates derived from reactive metabolites of seven silymarin isomers

1. Silymarin refers to a class of flavonoid lignans occurring in the fruits and seeds of the Silybum manalttlm (L). Gaertn, and is widely used in dietary supplements. 2. The main active ingredients of silymarin are silychristins A and B, silydianin, silybins A and B, and isosilybins A and B. However, the metabolism of silymarin has never been investigated. The major objectives of the present study were to investigate the metabolic pathways of silymarin isomers and to identify reactive metabolites. 3. Fourteen glutathione (GSH) conjugates were detected in rat/human liver microsomes incubations containing NADPH, GSH and seven individual isomers. Seven GSH conjugates (M1-M7) resulted from demethylated silymarin. M8-M14 originated from hydroxylated silymarin. Moreover, we found that GSH was probably conjugated on either ring A or ring E of silymarin based on the mass spectrometric fragments. In addition, recombinant enzyme incubation experiments demonstrated that CYP3A4 was the predominant P450 responsible for the metabolism of silymarin. 4. Several P450 enzymes were reportedly inactivated by some of bioactive constituents of silymarin to some extent. Our findings facilitate the understanding of mechanisms of the reported inactivation of P450 enzymes induced by silymarin.

Metabolism and Bioactivation of Corynoline With Characterization of the Glutathione/Cysteine Conjugate and Evaluation of Its Hepatotoxicity in Mice

Corynoline (CRL), an isoquinoline alkaloid, is the major constituent derived from Corydalis bungeana Herba, which is a well-known Chinese herbal medicine widely used in many prescriptions. The purpose of this study was to comprehensively investigate the metabolism and bioactivation of CRL, and identify the CYP450 isoforms involved in reactive ortho-benzoquinone metabolites formation and evaluate its hepatotoxicity in mice. Here, high resolution and triple quadrupole mass spectrometry were used for studying the metabolism of CRL. Three metabolites (M1-M3) and four glutathione conjugates (M4-M7) of CRL ortho-benzoquinone reactive metabolite were found in vitro using rat and human liver microsomes supplemented with NADPH and glutathione. Four cysteine conjugates (M8-M11) were trapped in mice besides M1-M7. Using human recombinant CYP450 enzymes and chemical inhibitor method, we found that CYP3A4, CYP2C19, CYP2C9, and CYP2D6 were mainly involved in the bioactivation of CRL. Furthermore, CRL had no obvious hepatotoxicity and did not induce acute liver injuries in the experimental dosage (125-500 mg/kg) used in this study. However, phenomena of abnormal behaviors and low body temperature appeared in mice after drug administration, and three of them were dead. Tissue distribution study of CRL in mice showed that the main target organ of CRL was liver, then kidney, heart, and brain. CRL could traverse the blood-brain barrier, and have relative high concentration in brain. So, we surmise that toxicity effect of CRL on other organs may have occurred, and more attention should be paid on the traditional Chinese medicine contained CRL in clinic.