Metabolism of [6]-shogaol in mice and in cancer cells

Induction of lung cancer cell apoptosis through a p53 pathway by [6]-shogaol and its cysteine-conjugated metabolite M2

Dietary chemoprevention of cancer offers the possibility to suppress or inhibit cancer growth before it develops into more advanced and lethal stages. To this end, identification of novel compounds and their mechanisms of action is constantly needed. In this study, we describe that a major component of dry ginger (Zingiber officinalis), [6]-shogaol (6S), can be quickly metabolized in A549 human lung cancer cell line. One of the resulting metabolites, the cysteine-conjugated 6S (M2), exhibits toxicity to cancer cells similar to the parent compound 6S, but is relatively less toxic toward normal cells than 6S. We further demonstrate that both compounds can cause cancer cell death by activating the mitochondrial apoptotic pathway. Our results show that the cancer cell toxicity is initiated by early modulation of glutathione (GSH) intracellular content. The subsequently generated oxidative stress activates a p53 pathway that ultimately leads to the release of mitochondria-associated apoptotic molecules such as cytochrome C, and cleaved caspases 3 and 9. In a xenograft nude mouse model, a dose of 30 mg/kg of 6S or M2 was able to significantly decrease tumor burden, without any associated toxicity to the animals. This effect was correlated with an induction of apoptosis and reduction of cell proliferation in the tumor tissues. Taken together, our results show that 6S metabolism is an integral part of its anticancer activities in vitro and in vivo. This allows us to characterize M2 as a novel compound with superior in vivo chemopreventive properties that targets similar anticancer mechanisms as 6S.

6-Shogaol inhibits breast and colon cancer cell proliferation through activation of peroxisomal proliferator activated receptor γ (PPARγ)

6-Shogaol has been shown to possess many antitumor properties including inhibition of cancer cell growth, inhibition of cancer metastasis, induction of apoptosis in cancer cells and induction of cancer cell differentiation. Despite its prominent antitumor effects, the direct molecular target of 6-shogaol has remained elusive. To identify the direct targets of 6-shogaol, a comprehensive antitumor profile of 6-shogaol (NSC752389) was tested in the NCI-60 cell line in an in vitro screen. The results show that 6-shogaol is COMPARE negative suggesting that it functions via a mechanism of action distinct from existing classes of therapeutic agents. Further analysis using microarray gene profiling and Connectivity Map analysis showed that MCF-7 cells treated with 6-shogaol display gene expression signatures characteristic of peroxisome proliferator activated receptor γ (PPARγ) agonists, suggesting that 6-shogaol may activate the PPARγ signaling pathway for its antitumor effects. Indeed, treatment of MCF-7 and HT29 cells with 6-shogaol induced PPARγ transcriptional activity, suppressed NFκB activity, and induced apoptosis in breast and colon cancer cells in a PPARγ-dependent manner. Furthermore, 6-shogaol is capable of binding to PPARγ with a binding affinity comparable to 15-delta prostaglandin J2, a natural ligand for PPARγ. Together, our findings suggest that the antitumor effects of 6-shogaol are mediated through activation of PPARγ and imply that activation of PPARγ might be beneficial for breast and colon cancer treatment.

Cysteine-conjugated metabolite of ginger component [6]-shogaol serves as a carrier of [6]-shogaol in cancer cells and in mice

Shogaols, a series of major constituents in dried ginger (Zingiber officinale), show high anticancer potencies. Previously, we reported that a major metabolite resulting from the mercapturic acid pathway, 5-cysteinyl-[6]-shogaol (M2), showed comparable growth inhibitory effects toward cancer cells to [6]-shogaol (6S). Here, we probe the mechanism by which M2 exerts its bioactivity. We utilized a series of chemical stability tests in conjunction with bioassays to show that thiol-conjugates display chemopreventative potency by acting as carriers of active ginger component 6S. M2 chemical degradation to 6S was observed in an environment most resembling physiological conditions, with a pH of 7.4 at 37 °C. The metabolic profiles of M2 in cancer cells HCT-116 and H-1299 resembled those of 6S, indicating that its biotransformation route was initiated by deconjugation. Further, the presence of excess glutathione significantly delayed 6S and M2 metabolism and counteracted cell death induced by 6S and M2, suggesting that increasing available free thiols exogenously both promoted the formation of 5-glutathionyl-[6]-shogaol (M13) and inhibited the production of free 6S from M2 deconjugation, resulting in delayed 6S cell entry and bioactivity. Given the chemopreventative properties of M2 and our observations in vitro, we investigated its metabolism in mice. M2 and 6S showed similar metabolic profiles in mouse urine and fecal samples. Six new thiol-conjugated metabolites (M16-M21), together with previously reported ones, were identified by LC/MS. In particular, the increase of 5-N-acetylcystenyl-[6]-shogaol (M5) and its 3'-demethylated product (M16) abundance in mouse feces after treatment with M2 indicates that in addition to acting as a carrier of 6S, M2 is also directly acetylated to M5, which is further demethylated to M16 in vivo. In conclusion, the cysteine-conjugated metabolite of [6]-shogaol M2 exerts its bioactivity by acting as a carrier of 6S in both cancer cells and in mice.

[10]-Gingerdiols as the major metabolites of [10]-gingerol in zebrafish embryos and in humans and their hematopoietic effects in zebrafish embryos

Gingerols are a series of major constituents in fresh ginger with the most abundant being [6]-, [8]-, and [10]-gingerols (6G, 8G, and 10G). We previously found that ginger extract and its purified components, especially 10G, potentially stimulate both the primitive and definitive waves of hematopoiesis (blood cell formation) in zebrafish embryos. However, it is still unclear if the metabolites of 10G retain the efficacy of the parent compound toward pathological anemia treatment. In the present study, we first investigated the metabolism of 10G in zebrafish embryos and then explored the biotransformation of 10G in humans. Our results show that 10G was extensively metabolized in both zebrafish embryos and humans, in which two major metabolites, (3S,5S)-[10]-gingerdiol and (3R,5S)-[10]-gingerdiol, were identified by analysis of the MS(n) spectra and comparison to authentic standards that we synthesized. After 24 h of treatment of zebrafish embryos, 10G was mostly converted to its metabolites. Our results clearly indicate that the reductive pathway is a major metabolic route for 10G in both zebrafish embryos and humans. Furthermore, we investigated the hematopoietic effect of 10G and its two metabolites, which show similar hematopoietic effects as 10G in zebrafish embryos.

Metabolism of ginger component [6]-shogaol in liver microsomes from mouse, rat, dog, monkey, and human

SCOPE

There are limited data on the metabolism of [6]-shogaol (6S), a major bioactive component of ginger. This study demonstrates metabolism of 6S in liver microsomes from mouse, rat, dog, monkey, and human.

METHODS AND RESULTS

The in vitro metabolism of 6S was compared among five species using liver microsomes from mouse, rat, dog, monkey, and human. Following incubations with 6S, three major reductive metabolites 1-(4'-hydroxy-3'-methoxyphenyl)-4-decen-3-ol (M6), 1-(4'-hydroxy-3'-methoxyphenyl)-decan-3-ol (M9), and 1-(4'-hydroxy-3'-methoxyphenyl)-decan-3-one (M11), as well as two new oxidative metabolites (1E,4E)-1-(4'-hydroxy-3'-methoxyphenyl)-deca-1,4-dien-3-one (M14) and (E)-1-(4'-hydroxy-3'-methoxyphenyl)-dec-1-en-3-one (M15) were found in all species. The kinetic parameters of M6 in liver microsomes from each respective species were quantified using Michaelis-Menten theory. A broad CYP-450 inhibitor, 1-aminobenzotriazole, precluded the formation of oxidative metabolites, M14 and M15, and 18β-glycyrrhetinic acid, an aldo-keto reductase inhibitor, eradicated the formation of the reductive metabolites M6, M9, and M11 in all species. Metabolites M14 and M15 were tested for cancer cell growth inhibition and induction of apoptosis and both showed substantial activity, with M14 displaying greater potency than 6S.

CONCLUSION

We conclude that 6S is metabolized extensively in mammalian species mouse, rat, dog, monkey, and human, and that there are significant interspecies differences to consider when planning preclinical trials toward 6S chemoprevention.

Characterization of thiol-conjugated metabolites of ginger components shogaols in mouse and human urine and modulation of the glutathione levels in cancer cells by [6]-shogaol

SCOPE

Shogaols, a series of major constituents in dried ginger with the most abundant being [6]-, [8]-, and [10]-shogaols, show much higher anticancer potencies than gingerols. Previously, we reported the mercapturic acid pathway as a major metabolic route for [6]-shogaol in mice. However, it is still unclear how the side chain length affects the metabolism of shogaols and how shogaols are metabolized in humans.

METHODS AND RESULTS

We first investigate the metabolism of [10]-shogaol in mouse urine, and then investigate the biotransformation of shogaols in human urine. Our results show that eight major thiol-conjugated metabolites of [10]-shogaol were detected in mouse urine, while six major thiol-conjugated metabolites of [6]-shogaol, two thiol-conjugated metabolites of [8]-shogaol, and two thiol-conjugated metabolites of [10]-shogaol were detected in urine collected from human after drinking ginger tea, using LC/ESI-MS/MS. Our results clearly indicate the mercapturic acid pathway is a major metabolic route for [10]-shogaol in mice and for shogaols in human. Furthermore, we also investigated the regulation of glutathione (GSH) by [6]-shogaol in human colon cancer cells HCT-116. Our results show [6]-shogaol, after initially depleting glutathione levels, can subsequently restore and increase GSH levels over time.

CONCLUSION

Shogaols are metabolized extensively in mouse and human to form thiol-conjugated metabolites and GSH might play an important role in the cancer-preventive activity of ginger.

Invadopodia-associated proteins blockade as a novel mechanism for 6-shogaol and pterostilbene to reduce breast cancer cell motility and invasion

SCOPE

Invadopodia are actin-rich membrane protrusions of tumor cells that are thought to initiate the local migration and invasion during cancer metastasis. The blockade of invadopodia-associated proteins has been reported as a promising approach for prevention of tumor metastasis. The aim of this study was to investigate the modulatory effects of 6-shogaol and pterostilbene on invadopodia in aggressive breast cancer cells.

METHODS AND RESULTS

By wound-healing, transwell, and gelatin zymography assays, we found that 6-shogaol and pterostilbene effectively attenuated the motility and invasion of MDA-MB-231 cells, and suppressed the activities of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). Further investigation into the underlying molecular mechanisms revealed that the levels of key modulators of invadopodium maturation, including c-Src kinase, cortactin, and membrane type 1-matrix metalloproteinase (MT1-MMP) decreased when cells were treated with 6-shogaol or pterostilbene.

CONCLUSION

These data suggest that the repression of these factors might affect the maturation of invadopodia, inhibiting the metastasis of MDA-MB-231 cells. In conclusion, the present study demonstrates for the first time that 6-shogaol and pterostilbene can inhibit invadopodium formation and MMP activity in highly invasive breast cancer cells. We suggest that these compounds may be clinically useful in chemopreventive treatments for metastatic breast cancer.

Metabolites of ginger component [6]-shogaol remain bioactive in cancer cells and have low toxicity in normal cells: chemical synthesis and biological evaluation

Our previous study found that [6]-shogaol, a major bioactive component in ginger, is extensively metabolized in cancer cells and in mice. It is unclear whether these metabolites retain bioactivity. The aim of the current study is to synthesize the major metabolites of [6]-shogaol and evaluate their inhibition of growth and induction of apoptosis in human cancer cells. Twelve metabolites of [6]-shogaol (M1, M2, and M4-M13) were successfully synthesized using simple and easily accessible chemical methods. Growth inhibition assays showed that most metabolites of [6]-shogaol had measurable activities against human cancer cells HCT-116 and H-1299. In particular, metabolite M2 greatly retained the biological activities of [6]-shogaol, with an IC(50) of 24.43 µM in HCT-116 human colon cancer cells and an IC(50) of 25.82 µM in H-1299 human lung cancer cells. Also exhibiting a relatively high potency was thiol-conjugate M13, with IC(50) values of 45.47 and 47.77 µM toward HCT-116 and H-1299 cells, respectively. The toxicity evaluation of the synthetic metabolites (M1, M2, and M4-M13) against human normal fibroblast colon cells CCD-18Co and human normal lung cells IMR-90 demonstrated a detoxifying metabolic biotransformation of [6]-shogaol. The most active metabolite M2 had almost no toxicity to CCD-18Co and IMR-90 normal cells with IC(50)s of 99.18 and 98.30 µM, respectively. TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) assay indicated that apoptosis was triggered by metabolites M2, M13, and its two diastereomers M13-1 and M13-2. There was no significant difference between the apoptotic effect of [6]-shogaol and the effect of M2 and M13 after 6 hour treatment.

Identification of phase II metabolites of thiol-conjugated [6]-shogaol in mouse urine using high-performance liquid chromatography tandem mass spectrometry

Ginger is frequently consumed as a spice and has numerous medicinal properties. Extensive research has characterized the anti-inflammatory, antioxidant, and antitumor activities of ginger. Previously, we reported the mercapturic acid pathway as a major metabolic route of [6]-shogaol in mice and the thiol conjugates of [6]-shogaol existed in the glucuronidated and sulfated forms in mouse urine. However, their structures are still unknown. In the present study, we further investigated the phase II metabolism of thiol-conjugated [6]-shogaol in mouse urine, in which we identified sixteen phase II metabolites of thiol-conjugated [6]-shogaol: 5-cysteinyl-[6]-shogaol glucuronide (9), 5-N-acetylcysteinyl-[6]-shogaol glucuronide (10), 5-cysteinylglycinyl-[6]-shogaol glucuronide (11), 5-methylthio-[6]-shogaol glucuronide (12), 5-cysteinyl-M6 glucuronide (13 and 14), 5-cysteinyl-M6 sulfate (15 and 16), 5-N-acetylcysteinyl-M6 glucuronide (17 and 18), 5-cysteinylglycinyl-M6 glucuronide (19 and 20), 5-cysteinylglycinyl-M6 sulfate (21 and 22), and 5-methylthio-M6 glucuronide (23 and 24) using liquid chromatography/electrospray ionization tandem mass spectrometry. The structures of these metabolites were confirmed by analyzing their MS(n) (n=1-4) spectra as well as comparing with the tandem mass spectra of authentic standards. To the best of our knowledge, this is the first report involving identification of phase II urinary metabolites of [6]-shogaol in mice.