Identification and characterization of in vitro and in vivo metabolites of steroidal alkaloid veratramine

Veratramine Inhibits the Cell Cycle Progression, Migration, and Invasion via ATM/ATR Pathway in Androgen-Independent Prostate Cancer

Prostate cancer (PC) is the second leading cause of cancer-related death among men. Treatment of PC becomes difficult after progression because PC that used to be androgen-dependent becomes androgen-independent prostate cancer (AIPC). Veratramine, an alkaloid extracted from the root of the Veratrum genus, has recently been reported to have anticancer effects that work against various cancers; however, its anticancer effects and the underlying mechanism of action in PC remain unknown. We investigated the anticancer effects of veratramine on AIPC using PC3 and DU145 cell lines, as well as a xenograft mouse model. The antitumor effects of veratramine were evaluated using the CCK-8, anchorage-independent colony formation, trans-well, wound healing assays, and flow cytometry in AIPC cell lines. Microarray and proteomics analyses were performed to investigate the differentially expressed genes and proteins induced by veratramine in AIPC cells. A xenograft mouse model was used to confirm the therapeutic response and in vivo efficacy of veratramine. Veratramine dose dependently reduced the proliferation of cancer cells both in vitro and in vivo. Moreover, veratramine treatment effectively suppressed the migration and invasion of PC cells. The immunoblot analysis revealed that veratramine significantly downregulated Cdk4/6 and cyclin D1 via the ATM/ATR and Akt pathways, both of which induce a DNA damage response that eventually leads to G1 phase arrest. In this study, we discovered that veratramine exerted antitumor effects on AIPC cells. We demonstrated that veratramine significantly inhibited the proliferation of cancer cells via G0/G1 phase arrest induced by the ATM/ATR and Akt pathways. These results suggest that veratramine is a promising natural therapeutic agent for AIPC.

METABOLOMICS REVEALS BIOMARKERS IN HUMAN URINE AND PLASMA TO PREDICT CYP2D6 ACTIVITY

Background and Purpose

Individualized assessment of cytochrome P450 2D6 (CYP2D6) activity is usually performed through phenotyping following administration of a probe drug to measure the enzyme's activity. To avoid any iatrogenic harm (allergic drug reaction, dosing error) related to the probe drug, the development of non‐burdensome tools for real‐time phenotyping of CYP2D6 could significantly contribute to precision medicine. This study focuses on the identification of markers of the CYP2D6 enzyme in human biofluids using an LC‐high‐resolution mass spectrometry‐based metabolomic approach.

Experimental Approach

Plasma and urine samples from healthy volunteers were analysed before and after intake of a daily dose of paroxetine 20 mg over 7 days. CYP2D6 genotyping and phenotyping, using single oral dose of dextromethorphan 5 mg, were also performed in all participants.

Key Results

We report four metabolites of solanidine and two unknown compounds as possible novel CYP2D6 markers. Mean relative intensities of these features were significantly reduced during the inhibition session compared with the control session (n = 37). Semi‐quantitative analysis showed that the largest decrease (−85%) was observed for the ion m/z 432.3108 normalized to solanidine (m/z 398.3417). Mean relative intensities of these ions were significantly higher in the CYP2D6 normal–ultrarapid metabolizer group (n = 37) compared with the poor metabolizer group (n = 6). Solanidine intensity was more than 15 times higher in CYP2D6‐deficient individuals compared with other volunteers.

Conclusion and Implications

The applied untargeted metabolomic strategy identified potential novel markers capable of semi‐quantitatively predicting CYP2D6 activity, a promising discovery for personalized medicine.

Hydroxylation of diverse flavonoids by CYP450 BM3 variants: biosynthesis of eriodictyol from naringenin in whole cells and its biological activities

BACKGROUND

Cytochrome P450 monooxygenase constitutes a significant group of oxidative enzymes that can introduce an oxygen atom in a high regio- and stereo-selectivity mode. We used the Bacillus megaterium cytochrome P450 BM3 (CYP450 BM3) and its variants namely mutant 13 (M13) and mutant 15 (M15) for the hydroxylation of diverse class of flavonoids.

RESULTS

Among 20 flavonoids, maximum seven flavonoids were hydroxylated by the variants while none of these molecules were accepted by CYP450 BM3 in in vitro reaction. Moreover, M13 exhibited higher conversion of substrates than M15 and CYP450 BM3 enzymes. We found that M13 carried out regiospecific 3'-hydroxylation reaction of naringenin with the highest conversion among all the tested flavonoids. The apparent K m and k cat values of M13 for naringenin were 446 µM and 1.955 s(-1), respectively. In whole-cell biotransformation experiment with 100 µM of naringenin in M9 minimal medium with 2 % glucose in shake flask culture, M13 showed 2.14- and 13.96-folds higher conversion yield in comparison with M15 (16.11 %) and wild type (2.47 %). The yield of eriodictyol was 46.95 µM [~40.7 mg (13.5 mg/L)] in a 3-L volume lab scale fermentor at 48 h in the same medium exhibiting approximately 49.81 % conversion of the substrate. In addition, eriodictyol exhibited higher antibacterial and anticancer potential than naringenin, flavanone and hesperetin.

CONCLUSIONS

We elucidated that eriodictyol being produced from naringenin using recombinant CYP450 BM3 and its variants from B. megaterium, which shows an approach for the production of important hydroxylated compounds of various polyphenols that may span pharmaceutical industries.

Pharmacokinetics and metabolism study of veratramine in mice after oral administration using LC-MS/MS

A simple and sensitive high-performance liquid chromatography coupled with hybrid triple quadrupole-linear ion trap mass spectrometry (Q-trap-MS) method was developed and validated for the determination of veratramine, the major bioactive and neurotoxic component in Veratrum nigrum L. Veratramine and the internal standard (IS) were separated with a Waters Symmetry C18 column and eluted with a gradient mobile phase system containing acetonitrile and 0.1% aqueous formic acid. The analysis was performed by using positive electrospray ionization mode with multiple reaction monitoring (MRM). Transition ions of m/z 410.2 → 295.2 for veratramine and m/z 426.1 → 113.8 for the IS were monitored. The method was validated with a good linearity in the range of 1-1000 ng/mL and lower limit of quantification of 1 ng/mL. The precision (CV) of intra- and inter-day ranged from 3.92 to 7.29%, while the accuracy (bias) intra- and inter-day were between -4.78 and 1.65%. The recovery, stability and matrix effect were within the acceptable ranges. Five metabolites of veratramine, including four hydroxylated and one sulfated metabolites, were tentatively identified using predictive MRM-information dependent acquisition-enhanced product ion mode (predictive MRM-IDA-EPI). The developed method was successfully applied to the pharmacokinetic and metabolic study of veratramine in mice after oral administration of veratramine. Copyright © 2016 John Wiley & Sons, Ltd.

Gender-Dependent Pharmacokinetics of Veratramine in Rats: In Vivo and In Vitro Evidence

Veratramine, a major alkaloid from Veratrum nigrum L., has distinct anti-tumor and anti-hypertension effects. Our previous study indicated that veratramine had severe toxicity toward male rats. In order to elucidate the underling mechanism, in vivo pharmacokinetic experiments and in vitro mechanistic studies have been conducted. Veratramine was administrated to male and female rats intravenously via the jugular vein at a dose of 50 μg/kg or orally via gavage at 20 mg/kg. As a result, significant pharmacokinetic differences were observed between male and female rats after oral administration with much lower concentrations of veratramine and 7-hydroxyl-veratramine and higher concentrations of veratramine-3-O-sulfate found in the plasma and urine of female rats. The absolute bioavailability of veratramine was 0.9% in female rats and 22.5% in male rats. Further experiments of veratramine on Caco-2 cell monolayer model and in vitro incubation with GI content or rat intestinal subcellular fractions demonstrated that its efficient passive diffusion mediated absorption with minimal intestinal metabolism, suggesting no gender-related difference during its absorption process. When veratramine was incubated with male or female rat liver microsomes/cytosols, significant male-predominant formation of 7-hydroxyl-veratramine and female-predominant formation of veratramine-3-O-sulfate were observed. In conclusion, the significant gender-dependent hepatic metabolism of veratramine could be the major contributor to its gender-dependent pharmacokinetics.