Specific reaction of alpha,beta-unsaturated carbonyl compounds such as 6-shogaol with sulfhydryl groups in tubulin leading to microtubule damage

An overview of 6-shogaol: new insights into its pharmacological properties and potential therapeutic activities

Ginger (Zingiber officinale Roscoe) has traditionally been used as a cooking spice and herbal medicine for treating nausea and vomiting. More recently, ginger was found to effectively reduce the risk of diseases such as gastroenteritis, migraine, gonarthritis, etc., due to its various bioactive compounds. 6-Shogaol, the pungent phenolic substance in ginger, is the most pharmacologically active among such compounds. The aim of the present study was to review the pharmacological characteristic of 6-shogaol, including the properties of anti-inflammatory, antioxidant and antitumour, and its corresponding molecular mechanism. With its multiple mechanisms, 6-shogaol is considered a beneficial natural compound, and therefore, this review will shed some light on the therapeutic role of 6-shogaol and provide a theoretical basis for the development and clinical application of 6-shogaol.

Review of the anticancer properties of 6-shogaol: Mechanisms of action in cancer cells and future research opportunities

Cancer is a major global health challenge that affects every nation and accounts for a large portion of the worldwide disease burden. Furthermore, cancer cases will rise significantly in the next few decades. The Food and Drug Administration has approved more than 600 drugs for treating diverse types of cancer. However, many conventional anticancer medications cause side effects, and drug resistance develops as the treatment proceeds with a concomitant impact on patients' quality of life. Thus, exploring natural products with antitumor properties and nontoxic action mechanisms is essential. Ginger (Zingiber officinale Roscoe) rhizome has a long history of use in traditional medicine, and it contains biologically active compounds, gingerols and shogaols. The main ginger shogaol is 6-shogaol, whose concentration dramatically increases during the processing of ginger, primarily due to the heat-induced conversion of 6-gingerol. Some studies have demonstrated that 6-shogaol possesses biological and pharmacological properties, such as antioxidant, anti-inflammatory, and anticancer activities. The mechanism of action of 6-shogaol as an anticancer drug includes induction of paraptosis, induction of apoptosis, increase in the production of reactive oxygen species, induction of autophagy, and the inhibition of AKT/mTOR signaling. Despite this knowledge, the mechanism of action of 6-shogaol is not fully understood, and the scientific data on its therapeutic dose, safety, and toxicity are not entirely described. This review article examines the potential of 6-shogaol as an anticancer drug, addressing the limitations of current medications; it covers 6-shogaol's attributes, mechanism of action in cancer cells, and opportunities for future research.

Anticancer perspective of 6-shogaol: anticancer properties, mechanism of action, synergism and delivery system

Cancer is a malignant disease that has plagued human beings all the time, but the treatment effect of commonly used anticancer drugs in clinical practice is not ideal by reason of their drug tolerance and Strong adverse reactions to patients. Therefore, it is imperative to find effective and low-toxic anticancer drugs. Many research works have shown that natural products in Chinese herbal medicine have great anticancer potential, such as 6-shogaol, a monomer composition obtained from Chinese herbal ginger, which has been confirmed by numerous in vitro or vivo studies to be an excellent anti-cancer active substance. In addition, most notably, 6-shogaol has different selectivity for normal and cancer cells during treatment, which makes it valuable for further research and clinical development. Therefore, this review focus on the anti-cancer attributes, the mechanism and the regulation of related signaling pathways of 6-shogaol. In addition, its synergy with commonly used anticancer drugs, potential drug delivery systems and prospects for future research are discussed. This is the first review to comprehensively summarize the anti-cancer mechanism of 6-shogaol, hoping to provide a theoretical basis and guiding significance for future anti-cancer research and clinical development of 6-shogaol.

Michael acceptor-dependent pro-oxidative intervention against angiogenesis by [6]-dehydroshogaol, a pungent constituent of ginger

Accumulating evidence suggests that ginger and its pungent constituents harbor a wealth of biological activities including cancer chemopreventive activity. However, relatively few researches focus on [6]-dehydroshogaol (6-DHS) compared with other ginger pungent constituents such as [6]-shogaol (6S). In this work, we selected three ginger compounds, 6-DHS, 6S and [6]-paradol (6P) differentiated by the presence and number of the Michael acceptor units, to probe structural basis and mechanism of 6-DHS in inhibiting angiogenesis, a key step for tumor growth and metastasis. It was found that their antiangiogenic activity is significantly dependent on the presence and number of Michael acceptor units. Benefiting from its two Michael acceptor units, 6-DHS is the most potent inhibitor of thioredoxin reductase and depletor of glutathione, thereby being the most active generator of reactive oxygen species, which is responsible for its strongest ability to inhibit angiogenesis. This work highlights 6-DHS being a Michael acceptor-dependent pro-oxidative angiogenesis inhibitor.

6-Shogaol from ginger shows anti-tumor effect in cervical carcinoma via PI3K/Akt/mTOR pathway

PURPOSE

6-Shogaol, an active phenolic compound from ginger (Zingiber officinale), can inhibit the growth of a variety of human cancer cells. Nevertheless, its underlying molecular mechanisms in cervical cancer remain unclear. In this study, we systematically examine the inhibitory effect of 6-shogaol on cervical cancer in vitro and in vivo.

METHODS

Cell proliferation was assessed by CCK8 assay and colony formation assay in HeLa and SiHa cells. We analyzed cell cycle and apoptosis through flow cytometry. GFP-LC3 puncta and transmission electron microscopy were used to observe autophagic bodies. Wound-healing assay and transwell assay were used for evaluating the migration of cells. Western blot was applied to detect protein expression levels.

RESULTS

6-Shogaol could suppress cell proliferation and migration, cause cell cycle arrest in the G2/M phase in HeLa and SiHa cells. Moreover, 6-shogaol triggered the apoptosis process through the mitochondrial pathway by downregulating the expression levels of p-PI3K, p-Akt and p-mTOR. Further research indicated that the induction of apoptosis by 6-shogaol was remarkably decreased after the treatment of ROS scavenger and PI3K agonist. Additionally, 6-shogaol increased the number of LC3-positive puncta and autophagic bodies per cell in both HeLa and SiHa cells. Pretreatment of cells with Bafilomycin A1, an autophagy inhibitor, accelerated 6-shogaol mediated cell apoptosis, suggesting that induction of autophagy by 6-shogaol is suppressive to apoptosis. Furthermore, in vivo data revealed that 6-shogaol significantly inhibited tumor growth and cell proliferation in tumor tissues.

CONCLUSION

These findings suggested that 6-shogaol could be developed as a functional food ingredient, which is potentially used as therapeutic agents for patients with cervical cancer.

Carnosine synthase deficiency is compatible with normal skeletal muscle and olfactory function but causes reduced olfactory sensitivity in aging mice

Carnosine (β-alanyl-l-histidine) and anserine (β-alanyl-3-methyl-l-histidine) are abundant peptides in the nervous system and skeletal muscle of many vertebrates. Many in vitro and in vivo studies demonstrated that exogenously added carnosine can improve muscle contraction, has antioxidant activity, and can quench various reactive aldehydes. Some of these functions likely contribute to the proposed anti-aging activity of carnosine. However, the physiological role of carnosine and related histidine-containing dipeptides (HCDs) is not clear. In this study, we generated a mouse line deficient in carnosine synthase (Carns1). HCDs were undetectable in the primary olfactory system and skeletal muscle of Carns1-deficient mice. Skeletal muscle contraction in these mice, however, was unaltered, and there was no evidence for reduced pH-buffering capacity in the skeletal muscle. Olfactory tests did not reveal any deterioration in 8-month-old mice lacking carnosine. In contrast, aging (18-24-month-old) Carns1-deficient mice exhibited olfactory sensitivity impairments that correlated with an age-dependent reduction in the number of olfactory receptor neurons. Whereas we found no evidence for elevated levels of lipoxidation and glycation end products in the primary olfactory system, protein carbonylation was increased in the olfactory bulb of aged Carns1-deficient mice. Taken together, these results suggest that carnosine in the olfactory system is not essential for information processing in the olfactory signaling pathway but does have a role in the long-term protection of olfactory receptor neurons, possibly through its antioxidant activity.

Nutritional implications of ginger: chemistry, biological activities and signaling pathways

Ginger (Zingiber officinale Roscoe) has been used as a food, spice, supplement and flavoring agent and in traditional medicines due to its beneficial characteristics such as pungency, aroma, nutrients and pharmacological activity. Ginger and ginger extracts were reported to have numerous effects, such as those on diabetes and metabolic syndrome, cholesterol levels and lipid metabolism, and inflammation, revealed by epidemiological studies. To understand the beneficial characteristics of ginger, especially its physiological and pharmacological activities at the molecular level, the biological effects of ginger constituents, such as monoterpenes (cineole, citral, limonene and α/β-pinenes), sesquiterpenes (β-elemene, farnesene and zerumbone), phenolics (gingerols, [6]-shogaol, [6]-paradol and zingerone) and diarylheptanoids (curcumin), and the associated signaling pathways are summarized. Ginger constituents are involved in biological activities, such as apoptosis, cell cycle/DNA damage, chromatin/epigenetic regulation, cytoskeletal regulation and adhesion, immunology and inflammation, and neuroscience, and exert their effects through specific signaling pathways associated with cell functions/mechanisms such as autophagy, cellular metabolism, mitogen-activated protein kinase and other signaling, and development/differentiation. Estrogens, such as phytoestrogens, are one of the most important bioactive materials in nature, and the molecular mechanisms of estrogen actions and the assays to detect them have been discussed. The molecular mechanisms of estrogen actions induced by ginger constituents and related applications, such as the chemoprevention of cancers, and the improvement of menopausal syndromes, osteoporosis, endometriosis, prostatic hyperplasia, polycystic ovary syndrome and Alzheimer's disease, were summarized by a comprehensive search of references to understand more about their health benefits and associated health risks.

6-Shogaol suppresses the growth of breast cancer cells by inducing apoptosis and suppressing autophagy via targeting notch signaling pathway

OBJECTIVES

Breast cancer is one of the most commonly diagnosed cancer among women globally. Shogaol, the active constituent of many spices belonging to the Zingiberaceae family, has received wide attention among other shogaols in terms of its anticancer activity against different neoplasms. To date, its efficacy at the detailed molecular level against breast cancer has not been established.

METHODS

In the current study, we investigated the cytotoxic potential and the underlying molecular details of 6-shogaol against breast adenocarcinomacells (MCF-7), and breast ductal carcinoma cells (T47D). Cytotoxicity assay, cell cycle analysis. Real-time PCR (qPCR), apoptosis and autophagy techniques were used for the determination and molecular investigation of its anticancer properties.

RESULTS

The current study shows that, Notch signaling downregulation (Hes1 and CyclinD1 genes), caused by 6-shogaol, lead to antiproliferative activity in breast cancer cells. The study further shows that treatment with 6-shogaol induced significant and time dependent cell cycle accumulation in G₂/M-phase. 6-Shogaol also induced significant apoptosis in breast cancer cells. Interestingly, 6-shogaol inhibited autophagy in breast cancer cell lines, which might force these cells to undergo apoptosis.

CONCLUSION

6-Shogaol is a promising candidate to be considered as a treatment of breast cancer.

Gingers and Their Purified Components as Cancer Chemopreventative Agents

Chemoprevention by ingested substituents is the process through which nutraceuticals and/or their bioactive components antagonize carcinogenesis. Carcinogenesis is the course of action whereby a normal cell is transformed into a neoplastic cell. This latter action involves several steps, starting with initiation and followed by promotion and progression. Driving these stages is continued oxidative stress and inflammation, which in turn, causes a myriad of aberrant gene expressions and mutations within the transforming cell population and abnormal gene expressions by the cells within the surrounding lesion. Chemoprevention of cancer with bioreactive foods or their extracted/purified components occurs primarily via normalizing these inappropriate gene activities. Various foods/agents have been shown to affect different gene expressions. In this review, we discuss how the chemoprevention activities of gingers antagonize cancer development.

Applying an Electrophilicity-Based Strategy to Develop a Novel Nrf2 Activator Inspired from Dietary [6]-Shogaol

Activation of nuclear factor erythroid-2-related factor 2 (Nrf2) is a crucial cellular defense mechanisms against oxidative stress and also an effective means to decrease the risk of oxidative stress-related diseases including cancer. Thus, identifying novel Nrf2 activators is highly anticipated. Inspired from [6]-shogaol (6S), an active component of ginger, herein we developed a novel potent Nrf2 activator, (1E,4E)-1-(4-hydroxy-3-methoxyphenyl)-7-methylocta-1,4,6-trien-3-one (SA) by an electrophilicity-based strategy. Compared with the parent 6S, SA bearing a short but entirely conjugated unsaturated ketone chain manifested the improved electrophilicity and cytoprotection (cell viability for the 10 μM 6S- and SA-treated group being 48.9 ± 5.3% and 76.1 ± 3.2%, respectively) against tert-butylhydroperoxide ( t-BHP)-induced cell death (cell viability for the t-BHP-stimulated group being 42.4 ± 0.4%) of HepG2. Mechanistic study uncovers that SA works as a potent Nrf2 activator by inducing Keap1 modification, inhibiting Nrf2 ubiquitylation and phosphorylating ERK in a Michael acceptor-dependent fashion. Taking 6S as an example, this works illustrates the feasibility and importance of applying an electrophilicity-based strategy to develop Nrf2 activators with dietary molecules as an inspiration due to their low toxicity and extraordinarily diverse chemical scaffolds.

Occurrence, biological activity and metabolism of 6-shogaol

As one of the main bioactive compounds of dried ginger, 6-shogaol has been widely used to alleviate many ailments. It is also a major pungent flavor component, and its precursor prior to dehydration is 6-gingerol, which is reported to be responsible for the pungent flavor and biological activity of fresh ginger. Structurally, gingerols including 6-gingerol have a β-hydroxyl ketone moiety and is liable to dehydrate to generate an α,β-unsaturated ketone under heat and/or acidic conditions. The conjugation of the α,β-unsaturated ketone skeleton in the chemical structure of 6-shogaol explicates its higher potency and efficacy than 6-gingerol in terms of antioxidant, anti-inflammatory, anticancer, antiemetic and other bioactivities. Research on the health benefits of 6-shogaol has been conducted and results have been reported recently; however, scientific data are scattered due to a lack of systematic collection. In addition, action mechanisms of the preventive and/or therapeutic actions of 6-shogaol remain obscurely non-collective. Herein, we review the preparations, biological activity and mechanisms, and metabolism of 6-shogaol as well as the properties of 6-shogaol metabolites.

6-Shogaol induces caspase-independent paraptosis in cancer cells via proteasomal inhibition

An α, β-unsaturated carbonyl compound of ginger, 6-Shogaol (6S), induced extensive cytoplasmic vacuolation and cell death in breast cancer cell (MDA-MB-231) and non-small lung cancer (A549) cells. In the presence of autophagic inhibitors the cells continued to exhibit cytoplasmic vacuolation and cell death clearly distinguishing it from the classic autophagic process. 6S induced death did not exhibit the characteristic apoptotic features like caspase cleavage, phosphatidyl serine exposure and DNA fragmentation. The immunofluorescence with the Endoplasmic Reticulum (ER) resident protein, calreticulin indicated that the vacuoles were of ER origin, typical of paraptosis. This was supported by the increase in level of microtubule associated protein light chain 3B (LC3 I and LC3 II) and polyubiquitin binding protein, p62. The level of ER stress markers like polyubiquitinated proteins, Bip and CHOP also consistently increased. We have found that 6S inhibits the 26S proteasome. The proteasomal inhibitory activity was elucidated by a) molecular docking of 6S onto the active site of β5 subunit and b) reduced fluorescence by the fluorogenic substrate of the chymotrypsin-like subunit. In conclusion these studies demonstrate for the first time that proteasomal inhibition by 6S induces cell death via paraptosis. So 6-shogaol may act as a template for anti-cancer lead discovery against the apoptosis resistant cancer cells.

[6]-Shogaol attenuates inflammation, cell proliferation via modulate NF-κB and AP-1 oncogenic signaling in 7,12-dimethylbenz[a]anthracene induced oral carcinogenesis

Nuclear factor-kappaB (NF-κB) and activator protein 1 (AP-1) is a major transcription factor which regulates many biological and pathological processes such as inflammation and cell proliferation, which are major implicates in cancer progression. [6]-Shogaol ([6]-SHO) is a major constituent of ginger, exhibits various biological properties such as anti-oxidants, anti-inflammation and anti-tumor. Recently, we proven that [6]-SHO prevents oral squamous cell carcinoma by activating proapoptotic factors in in vitro and in vivo experimental model. However, the preventive efficacy of [6]-SHO in 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch carcinogenesis (HBP) has not been fully elucidated, so far. Hence, we aimed to investigate the effect of [6]-SHO on inflammation and cell proliferation by inhibiting the translocation of NF-κB and AP-1 in DMBA induced HBP carcinogenesis. In this study, we observed upregulation of inflammatory markers (COX-2, iNOS, TNF-α, interleukin-1 and -6), cell proliferative markers (Cyclin D1, PCNA and Ki-67) and aberrant activation of NF-κB, AP-1, IKKβ, c-jun, c-fos and decreased IκB-α in DMBA induced hamsters. Conversely, oral administration of [6]-SHO strongly inhibited constitutive phosphorylation and degradation of IκB and inhibit phosphorylation of c-jun, c-fos, resulting in inhibition of nuclear translocation of NF-κBp65 and AP-1. Thus, inhibition of NF-κB and AP-1 activation by [6]-SHO attenuates inflammation and cell proliferative response in DMBA induced hamsters. Our finding suggested that [6]-SHO is a novel functional agent capable of preventing DMBA induced inflammation and cell proliferation associated tumorigenesis by modulating multiple signalling molecules.

Neuroprotective Effect and Molecular Mechanism of [6]-Gingerol against Scopolamine-Induced Amnesia in C57BL/6 Mice

We have investigated the neuroprotective and memory enhancing effect of [6]-gingerol (GIN), a pungent ingredient of ginger, using an animal model of amnesia. To determine the neuroprotective effect of GIN on cognitive dysfunction, scopolamine (SCO, 1 mg/kg, i.p.) was injected into C57BL/6 mice, and a series of behavioral tests were conducted. SCO-induced behavior changes and memory impairments, such as decreased alteration (%) in Y-maze test, increased mean escape latency in water maze test, diminished step-through latency in passive avoidance test, and shortened freezing time in fear condition test, were significantly prevented and restored by the oral administration of GIN (10 or 25 mg/kg/day). To further verify the neuroprotective mechanism of GIN, we have focused on the brain-derived neurotrophic factor (BDNF). The administration of GIN elevated the protein expression of BDNF, which was mediated via the activation of protein kinase B/Akt- and cAMP-response element binding protein (CREB) signaling pathway. These results suggest that GIN may have preventive and/or therapeutic potentials in the management of memory deficit and cognitive impairment in mice with amnesia.

6-shogaol induces autophagic cell death then triggered apoptosis in colorectal adenocarcinoma HT-29 cells

6-shogaol is a phytochemical of dietary ginger, we found that 6-shogaol could induced both autophagic and apoptotic death in human colon adenocarcinoma (HT-29) cells. Results of this study showed that 6-shogal induced cell cycle arrest, autophagy, and apoptosis in HT-29 cells in a time sequence. After 6h, 6-shogal induced apparent G2/M arrest, then the HT-29 cells formed numerous autophagosomes in each phase of the cell cycle. After 18h, increases in acidic vesicles and LAMP-1 (Lysosome-associated membrane proteins 1) showed that 6-shogaol had caused autophagic cell death. After 24h, cell shrinkage and Caspase-3/7 activities rising, suggesting that apoptotic cell death had increased. And after 48h, the result of TUNEL assay indicated the highest occurrence of apoptosis upon 6-shogaol treatment. It appeared that apoptosis is triggered by autophagy in 6-shogaol treated HT-29 cells, the damage of autophagic cell death initiated apoptosis program.

Nitrite enhances liver graft protection against cold ischemia reperfusion injury through a NOS independent pathway

Introduction: Nitrite has been found to protect liver graft from cold preservation injury. However, the cell signaling pathway involved in this protection remains unclear. Here, we attempt to clarify if the NOS pathway by using the NOS inhibitor, L-NAME (L-N^G-Nitroarginine methyl ester).

Animals and methods: Rat livers were conserved for 24 h at 4°C in (IGL-1) solution enriched or not with nitrite at 50 nM. In a third group, rats were pretreated with 50 mg/kg of L-NAME before their liver procurement and preservation in IGL-1 supplemented with nitrite (50 nM) and L-NAME (1 mM). After 24 h of cold storage, rat livers were ex-vivo perfused at 37°C during 2 h. Control livers were perfused without cold storage.

Results: Nitrite effectively protected the rat liver grafts from the onset of cold I/R injury. L-NAME treatment did not abolish the beneficial effects of nitrite. Liver damage, protein oxidation and lipid peroxidation remained at low levels in both nitrite-treated groups when compared to IGL-1 group. Antioxidant enzyme activities and functional parameters were unchanged after NOS inhibition.

Conclusion: Despite NOS inhibition by L-NAME, nitrite can still provide hepatic protection during cold I/R preservation. This suggests that nitrite acts through a NOS-independent pathway.

Efficient dehydration of 6-gingerol to 6-shogaol catalyzed by an acidic ionic liquid under ultrasound irradiation

6-Gingerol and 6-shogaol are the main bioactive compounds in ginger. Although 6-shogaol has more and better bioactivities than its precursor 6-gingerol, the low content of 6-shogaol in ginger restricts its bioactive effects in functional foods. The traditional preparation methods of 6-shogaol are defective because of the environmental hazards and low efficiency of the processes. In this study, an efficient, easy and eco-friendly dehydration conversion of 6-gingerol to 6-shogaol is presented using an acidic ionic liquid 1-butyl-3-methylimidazolium hydrosulfate ([Bmim]HSO4) under ultrasound irradiation. The key parameters, including reaction temperature, reaction time, mass ratio of catalyst to substrate and ultrasonic power in each reaction process, were investigated. The yield of 6-shogaol reached as high as 97.16% under optimized condition. The catalyst could be separated from the reaction mixture and reused five times with only a slight loss of activity.

[6]-Shogaol, a dietary phenolic compound, induces oxidative stress mediated mitochondrial dependant apoptosis through activation of proapoptotic factors in Hep-2 cells

Ginger (Zingiber officinale) is a well-known herb used in ethnomedicine. [6]-shogaol, a phenolic nature is a major constituent of ginger. In this study, we investigated the anticancer activity of [6]-shogaol in Laryngeal cancer (Hep-2) cells. We demonstrated the effects of [6]-shogaol on the cell growth and apoptosis in Hep-2 cells were analyzed by the generation of reactive oxygen species (ROS), the level of mitochondrial membrane potential (ΔYm), DNA damage and apoptotic morphological changes were analyzed by AO/EtBr, AO and Hoechst staining. Further, apoptotic protein expressions were analyzed by western blot analysis. Our results indicated that [6]-shogaol induces apoptosis as evidenced by loss of cell viability, enhanced ROS, lipid peroxidation results in altered mitochondrial membrane potential, increased DNA damage in Hep-2 cells. Further, the prooxidant role of [6]-shogaol inhibit Bcl-2 expression with the simultaneous up-regulation of Bax, Cytochrome c, Caspase-9 and -3 protein expressions were observed in Hep-2 cells. Thus, [6]-shogaol induces apoptosis in Hep-2 cells through inducing oxidative damage and modulate apoptotic marker expressions. Therefore, [6]-shogaol might be used as a therapeutic agent for the treatment of laryngeal cancer.

[6]-Shogaol, a Novel Chemopreventor in 7,12-Dimethylbenz[a]anthracene-induced Hamster Buccal Pouch Carcinogenesis

Oral cancer is a major cause of morbidity and mortality in developing countries. Despite advances in chemotherapy for the cancer management, the survival rate has not yet been improved. Dietary nutrient has been receiving a lot of attention and interest in the chemotherapeutic development. [6]-Shogaol is a major bioactive compound identified in ginger that possesses many pharmacological properties. The aim of the present study is to investigate the effect of [6]-shogaol on 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch (HBP) carcinogenesis. Oral squamous cell carcinoma induced in HBP by painting with 0.5% 7,12-dimethylbenz(a)anthracene (DMBA), thrice in a week for 16 weeks. We observed 100% tumour incidence, decreased levels of lipid peroxidation, antioxidant, and phase II detoxification enzymes (GST, GR and GSH) in DMBA-induced hamsters. Further, enhanced activity of phase I enzymes (cytochrome p450 and b5) and over-expression of mutant p53, Bcl-2 and decreased expression of wild type p53 and Bax were noticed in DMBA-induced hamsters. Our results indicated that [6]-shogaol (10, 20 and 40 mg/kg body weight) treated with DMBA-painted hamsters, considerably reversed tumour incidence, improved antioxidant status, phase II detoxification enzymes, and also inhibit lipid peroxidation and phase I enzymes. Moreover, [6]-shogaol inhibits mutant p53 and Bcl-2 expression and significantly restored normal p53, Bax levels. Thus, we concluded that [6]-shogaol prevents DMBA-induced HBP carcinogenesis through its antioxidant as well as modulating apoptotic signals.

6-Shogaol Inhibits Breast Cancer Cells and Stem Cell-Like Spheroids by Modulation of Notch Signaling Pathway and Induction of Autophagic Cell Death

Cancer stem cells (CSCs) pose a serious obstacle to cancer therapy as they can be responsible for poor prognosis and tumour relapse. In this study, we have investigated inhibitory activity of the ginger-derived compound 6-shogaol against breast cancer cells both in monolayer and in cancer-stem cell-like spheroid culture. The spheroids were generated from adherent breast cancer cells. 6-shogaol was effective in killing both breast cancer monolayer cells and spheroids at doses that were not toxic to noncancerous cells. The percentages of CD44⁺CD24^-/^low cells and the secondary sphere content were reduced drastically upon treatment with 6-shogaol confirming its action on CSCs. Treatment with 6-shogaol caused cytoplasmic vacuole formation and cleavage of microtubule associated protein Light Chain3 (LC3) in both monolayer and spheroid culture indicating that it induced autophagy. Kinetic analysis of the LC3 expression and a combination treatment with chloroquine revealed that the autophagic flux instigated cell death in 6-shogaol treated breast cancer cells in contrast to the autophagy inhibitor chloroquine. Furthermore, 6-shogaol-induced cell death got suppressed in the presence of chloroquine and a very low level of apoptosis was exhibited even after prolonged treatment of the compound, suggesting that autophagy is the major mode of cell death induced by 6-shogaol in breast cancer cells. 6-shogaol reduced the expression levels of Cleaved Notch1 and its target proteins Hes1 and Cyclin D1 in spheroids, and the reduction was further pronounced in the presence of a γ-secretase inhibitor. Secondary sphere formation in the presence of the inhibitor was also further reduced by 6-shogaol. Together, these results indicate that the inhibitory action of 6-shogaol on spheroid growth and sustainability is conferred through γ-secretase mediated down-regulation of Notch signaling. The efficacy of 6-shogaol in monolayer and cancer stem cell-like spheroids raise hope for its therapeutic benefit in breast cancer treatment.

Hexamethoxylated Monocarbonyl Analogues of Curcumin Cause G2/M Cell Cycle Arrest in NCI-H460 Cells via Michael Acceptor-Dependent Redox Intervention

Curcumin, derived from the dietary spice turmeric, holds promise for cancer prevention. This prompts much interest in investigating the action mechanisms of curcumin and its analogues. Two symmetrical hexamethoxy-diarylpentadienones (1 and 2) as cucumin analogues were reported to possess significantly enhanced cytotoxicity compared with the parent molecule. However, the detailed mechanisms remain unclear. In this study, compounds 1 and 2 were identified as the G2/M cell cycle arrest agents to mediate the cytotoxicity toward NCI-H460 cells via Michael acceptor-dependent redox intervention. Compared with curcumin, they could more easily induce a burst of reactive oxygen species (ROS) and collapse of the redox buffering system. One possible reason is that they could more effectively target intracellular TrxR to convert this antioxidant enzyme into a ROS promoter. Additionally, they caused up-regulation of p53 and p21 and down-regulation of redox-sensitive Cdc25C along with cyclin B1/Cdk1 in a Michael acceptor- and ROS-dependent fashion. Interestingly, in comparison with compound 2, compound 1 displayed a relatively weak ability to generate ROS but increased cell cycle arrest activity and cytotoxicity probably due to its Michael acceptor-dependent microtubule-destabilizing effect and greater GST-inhibitory activity, as well as its enhanced cellular uptake. This work provides useful information for understanding Michael acceptor-dependent and redox-mediated cytotoxic mechanisms of curcumin and its active analogues.

Ginger compound [6]-shogaol and its cysteine-conjugated metabolite (M2) activate Nrf2 in colon epithelial cells in vitro and in vivo

In this study, we identified Nrf2 as a molecular target of [6]-shogaol (6S), a bioactive compound isolated from ginger, in colon epithelial cells in vitro and in vivo. Following 6S treatment of HCT-116 cells, the intracellular GSH/GSSG ratio was initially diminished but was then elevated above the basal level. Intracellular reactive oxygen species (ROS) correlated inversely with the GSH/GSSG ratio. Further analysis using gene microarray showed that 6S upregulated the expression of Nrf2 target genes (AKR1B10, FTL, GGTLA4, and HMOX1) in HCT-116 cells. Western blotting confirmed upregulation, phosphorylation, and nuclear translocation of Nrf2 protein followed by Keap1 decrease and upregulation of Nrf2 target genes (AKR1B10, FTL, GGTLA4, HMOX1, and MT1) and glutathione synthesis genes (GCLC and GCLM). Pretreatment of cells with a specific inhibitor of p38 (SB202190), PI3K (LY294002), or MEK1 (PD098059) attenuated these effects of 6S. Using ultra-high-performance liquid chromatography-tandem mass spectrometry, we found that 6S modified multiple cysteine residues of Keap1 protein. In vivo 6S treatment induced Nrf2 nuclear translocation and significantly upregulated the expression of MT1, HMOX1, and GCLC in the colon of wild-type mice but not Nrf2(-/-) mice. Similar to 6S, a cysteine-conjugated metabolite of 6S (M2), which was previously found to be a carrier of 6S in vitro and in vivo, also activated Nrf2. Our data demonstrated that 6S and its cysteine-conjugated metabolite M2 activate Nrf2 in colon epithelial cells in vitro and in vivo through Keap1-dependent and -independent mechanisms.

Influence of side chain structure changes on antioxidant potency of the [6]-gingerol related compounds

[6]-Gingerol and [6]-shogaol are the major pungent components in ginger with a variety of biological activities including antioxidant activity. To explore their structure determinants for antioxidant activity, we synthesized eight compounds differentiated by their side chains which are characteristic of the C1-C2 double bond, the C4-C5 double bond or the 5-OH, and the six- or twelve-carbon unbranched alkyl chain. Our results show that their antioxidant activity depends significantly on the side chain structure, the reaction mediums and substrates. Noticeably, existence of the 5-OH decreases their formal hydrogen-transfer and electron-donating abilities, but increases their DNA damage- and lipid peroxidation-protecting abilities. Additionally, despite significantly reducing their DNA strand breakage-inhibiting activity, extension of the chain length from six to twelve carbons enhances their anti-haemolysis activity.

Antitumor activity of gemcitabine can be potentiated in pancreatic cancer through modulation of TLR4/NF-κB signaling by 6-shogaol

Advanced pancreatic cancer still has a poor prognosis, even with the approval of several drugs, such as gemcitabine. Therefore, developing effective and safe antitumor agents is urgently needed. 6-Shogaol, a phenol extracted from ginger, has been linked to suppression of proliferation and survival of cancer with different mechanisms. In the present study, we investigated whether 6-shogaol could suppress pancreatic cancer progress and potentiate pancreatic cancer to gemcitabine treatment in vitro and in vivo. We found that 6-shogaol prevented the activation of toll like receptor 4 (TLR4)/NF-κB signaling. The modulation of NF-κB signaling by 6-shogaol was ascertained by electrophoretic mobility shift assay and western blot analysis. The suppression of NF-κB signaling and key cell survival regulators including COX-2, cyclinD1, survivin, cIAP-1, XIAP, Bcl-2, and MMP-9 brought the anti-proliferation effects in pancreatic cancer cells and sensitized them to gemcitabine treatment. Furthermore, in a pancreatic cancer xenograft model, we found a decreased proliferation index (Ki-67) and increased apoptosis by TUNEL staining in 6-shogaol treated tumors. It was also shown that 6-shogaol combined with gemcitabine treatment was more effective than drug alone, consistent with the downregulation of NF-κB activity along with its target genes COX-2, cyclinD1, survivin, cIAP-1, and XIAP. Overall, our results suggest that 6-shogaol can inhibit the growth of human pancreatic tumors and sensitize them to gemcitabine by suppressing of TLR4/NF-κB-mediated inflammatory pathways linked to tumorigenesis.

6-Shogaol induces apoptosis in human leukemia cells through a process involving caspase-mediated cleavage of eIF2α

Background

6-Shogaol is a promising antitumor agent isolated from dietary ginger (Zingiber officinale). However, little is known about the efficacy of 6-shogaol on leukemia cells. Here we investigated the underlying mechanism of 6-shogaol induced apoptosis in human leukemia cells in vitro and in vivo.

Methods

Three leukemia cell lines and primary leukemia cells were used to investigate the apoptosis effect of 6-shogaol. A shotgun approach based on label-free proteome with LC-CHIP Q-TOF MS/MS was employed to identify the cellular targets of 6-shogaol and the differentially expressed proteins were analyzed by bioinformatics protocols.

Results

The present study indicated that 6-shogaol selectively induced apoptosis in transformed and primary leukemia cells but not in normal cells. Eukaryotic translation initiation factor 2 alpha (eIF2α), a key regulator in apoptosis signaling pathway, was significantly affected in both Jurkat and U937 proteome profiles. The docking results suggested that 6-shogaol might bind well to eIF2α at Ser51 of the N-terminal domain. Immunoblotting data indicated that 6-shogaol induced apoptosis through a process involving dephosphorylation of eIF2α and caspase activation–dependent cleavage of eIF2α. Furthermore, 6-shogaol markedly inhibited tumor growth and induced apoptosis in U937 xenograft mouse model.

Conclusion

The potent anti-leukemia activity of 6-shogaol found both in vitro and in vivo in our study make this compound a potential anti-tumor agent for hematologic malignancies.

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.

Induction of tumor cell death through targeting tubulin and evoking dysregulation of cell cycle regulatory proteins by multifunctional cinnamaldehydes

Multifunctional trans-cinnamaldehyde (CA) and its analogs display anti-cancer properties, with 2-benzoyloxycinnamaldehyde (BCA) and 5-fluoro-2-hydroxycinnamaldehyde (FHCA) being identified as the ortho-substituted analogs that possess potent anti-tumor activities. In this study, BCA, FHCA and a novel analog 5-fluoro-2-benzoyloxycinnamaldehyde (FBCA), were demonstrated to decrease growth and colony formation of human colon-derived HCT 116 and mammary-derived MCF-7 carcinoma cells under non-adhesive conditions. The 2-benzoyloxy and 5-fluoro substituents rendered FBCA more potent than BCA and equipotent to FHCA. The cellular events by which these cinnamaldehydes caused G(2)/M phase arrest and halted proliferation of HCT 116 cells were thereby investigated. Lack of significant accumulation of mitosis marker phospho-histone H3 in cinnamaldehyde-treated cells indicated that the analogs arrested cells in G(2) phase. G(2) arrest was brought about partly by cinnamaldehyde-mediated depletion of cell cycle proteins involved in regulating G(2) to M transition and spindle assembly, namely cdk1, cdc25C, mad2, cdc20 and survivin. Cyclin B1 levels were found to be increased, which in the absence of active cdk1, would fail to drive cells into M phase. Concentrations of cinnamaldehydes that brought about dysregulation of levels of cell cycle proteins also caused tubulin aggregation, as evident from immunodetection of dose-dependent tubulin accumulation in the insoluble cell lysate fractions. In a cell-free system, reduced biotin-conjugated iodoacetamide (BIAM) labeling of tubulin protein pretreated with cinnamaldehydes was indicative of drug interaction with the sulfhydryl groups in tubulin. In conclusion, cinnamaldehydes treatment at proapoptotic concentrations caused tubulin aggregation and dysegulation of cell cycle regulatory proteins cdk1 and cdc25C that contributed at least in part to arresting cells at G(2) phase, resulting in apoptotic cell death characterized by emergence of cleaved forms of caspase 3 and poly (ADP-ribose) polymerase (PARP). Results presented in this study have thus provided further insights into the intricate network of cellular events by which cinnamaldehydes induce tumor cell death.

Molecular mechanism inhibiting human hepatocarcinoma cell invasion by 6-shogaol and 6-gingerol

SCOPE

We previously demonstrated that 6-shogaol and 6-gingerol, two active compounds in ginger (Zingiber officinale), possess antiinvasive activity against highly metastatic hepatoma cells. The aims of this study were to evaluate the inhibitory effect and molecular mechanism underlying the transcription and translation of matrix metalloproteinases (MMPs) and urokinase-type plasminogen activator (uPA) in Hep3B cells as well as the antiangiogenic activity of 6-gingerol and 6-shogaol.

METHODS AND RESULTS

By gelatin zymography and luciferase reporter gene assays, we found that 6-gingerol and 6-shogaol regulate MMP-2/-9 transcription. Moreover, 6-gingerol directly decreased expression of uPA, but the 6-shogaol-mediated decrease in uPA was accompanied by up-regulation of plasminogen activator inhibitor (PAI)-1. 6-Gingerol and 6-shogaol concentrations of ≥ 10 μM and ≥ 2.5 μM, respectively, significantly inhibited the phosphorylation of mitogen-activated protein kinase (MAPK) and PI3K/Akt signaling, the activation of NF-κB, and the translocation of NF-κB and STAT3. Incubation of 6-gingerol or 6-shogaol with human umbilical vein endothelial cells or rat aortas significantly attenuated tube formation.

CONCLUSION

6-Shogaol and 6-gingerol effectively inhibit invasion and metastasis of hepatocellular carcinoma through diverse molecular mechanisms, including inhibition of the MAPK and PI3k/Akt pathways and NF-κB and STAT3 activities to suppress expression of MMP-2/-9 and uPA and block angiogenesis.

Shogaols at proapoptotic concentrations induce G(2)/M arrest and aberrant mitotic cell death associated with tubulin aggregation

Shogaols have been previously reported to induce cancer cell death via multiple mechanisms, among which one analog 6-shogaol has been reported to cause microtubule damage through specific reaction with sulfhydryl groups in tubulin. In this study, a series of shogaols with different side chain lengths (4-, 6-, 8- and 10-shogaol) was synthesized and evaluated for antiproliferative activity in HCT 116 colon carcinoma and SH-SY5Y neuroblastoma cells. 4- and 6-shogaol were identified as lead compounds possessing the strongest antiproliferative activity. In the soft agar assay, the lead shogaols displayed dose-dependent inhibition on cancer cell colony formation under anchorage-independent conditions. Using HCT 116 as the selected cancer cell line, the molecular events linking shogaols-induced G(2)/M cell cycle arrest to apoptosis characterized by caspase 3 and PARP cleavage were investigated. At sublethal concentrations, the halt at G(2)/M phase was alleviated along time and cells survived. Conversely, proapoptotic concentrations of 4- and 6-shogaol induced irreversible G(2)/M arrest that was at least in part associated with down-regulation of cell cycle checkpoint proteins cdk1, cyclin B and cdc25C, as well as spindle assembly checkpoint proteins mad2, cdc20 and survivin. A dose- and time-dependent accumulation of insoluble tubulin in the insoluble fractions of cell lysates provided evidence that G(2) checkpoint failure led to disruption of microtubule turnover. In summary, our results conclude that shogaols cause apoptosis by inducing aberrant mitosis at least through the attenuation of cell cycle and spindle assembly checkpoint proteins.

Ginger and its health claims: molecular aspects

Recent research has rejuvenated centuries-old traditional herbs to cure various ailments by using modern tools like diet-based therapy and other regimens. Ginger is one of the classic examples of an herb used for not only culinary preparations but also for unique therapeutic significance owing to its antioxidant, antimicrobial, and anti-inflammatory potential. The pungent fractions of ginger, namely gingerols, shogaols, paradols, and volatile constituents like sesquiterpenes and monoterpenes, are mainly attributed to the health-enhancing perspectives of ginger. This review elucidates the health claims of ginger and the molecular aspects and targets, with special reference to anticancer perspectives, immunonutrition, antioxidant potential, and cardiovascular cure. The molecular targets involved in chemoprevention like the inhibition of NF-κB activation via impairing nuclear translocation, suppresses cIAP1 expression, increases caspase-3/7 activation, arrests cell cycle in G2 + M phases, up-regulates Cytochrome-c, Apaf-1, activates PI3K/Akt/I kappaB kinases IKK, suppresses cell proliferation, and inducts apoptosis and chromatin condensation. Similarly, facts are presented regarding the anti-inflammatory response of ginger components and molecular targets including inhibition of prostaglandin and leukotriene biosynthesis and suppression of 5-lipoxygenase. Furthermore, inhibition of phosphorylation of three mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinases 1 and 2 (ERK1/2), and c-Jun N-terminal kinase (JNK) are also discussed. The role of ginger in reducing the extent of cardiovascular disorders, diabetes mellitus, and digestive problems has also been described in detail. Although, current review articles summarized the literature pertaining to ginger and its components. However, authors are still of the view that further research should be immediately carried out for meticulousness.

Synthesis and antitumor evaluation of methyl spongoate analogs

A series of novel methyl spongoate (1) analogs has been synthesized and evaluated for their in vitro cytotoxic properties. It was found that the nature of the C-20 side chain had significant effects on their bioactivities and some analogs showed higher cytotoxicity than 1 against A549, HCT-116, HepG2, SW-1990, MCF-7 and NCI-H460 tumor cell lines. The pharmacological results confirmed that the α,β-unsaturated carbonyl moiety, a Michael acceptor in ring A, plays a pivotal role in the cytotoxic effect of these derivatives. The compiled pharmacological data may be useful for the design of novel analogous anticancer drugs.