Phenethyl isothiocyanate suppresses receptor activator of NF-kappaB ligand (RANKL)-induced osteoclastogenesis by blocking activation of ERK1/2 and p38 MAPK in RAW264.7 macrophages

Isothiocyanates in medicine: A comprehensive review on phenylethyl-, allyl-, and benzyl-isothiocyanates

In recent years, isothiocyanates (ITCs), bioactive compounds primarily derived from Brassicaceae vegetables and herbs, have gained significant attention within the biomedical field due to their versatile biological effects. This comprehensive review provides an in-depth exploration of the therapeutic potential and individual biological mechanisms of the three specific ITCs phenylethyl isothiocyanate (PEITC), allyl isothiocyanate (AITC), and benzyl isothiocyanate (BITC), as well as their collective impact within the formulation of ANGOCIN® Anti-Infekt N (Angocin). Angocin comprises horseradish root (Armoracia rusticanae radix, 80 mg) and nasturtium (Tropaeoli majoris herba, 200 mg) and is authorized for treating inflammatory diseases affecting the respiratory and urinary tract. The antimicrobial efficacy of this substance has been confirmed both in vitro and in various clinical trials, with its primary effectiveness attributed to ITCs. PEITC, AITC, and BITC exhibit a wide array of health benefits, including potent anti-inflammatory, antioxidant, and antimicrobial properties, along with noteworthy anticancer potentials. Moreover, we highlight their ability to modulate critical biochemical pathways, such as the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and signal transducer and activator of transcription (STAT) pathways, shedding light on their involvement in cellular apoptosis and their intricate role to guide immune responses.

Benzyl isothiocyanate and its metabolites inhibit cell proliferation through protein modification in mouse preosteoclast RAW264.7 cells

Benzyl isothiocyanate (BITC), derived from cruciferous vegetables, is an organosulfur compound exerting antiproliferative effects in several human cancer cells. In this study, we assessed BITC as a potential osteoclastogenesis inhibitor and investigated its underlying mechanism. BITC at 5 μM significantly decreased the viability of the osteoclast-like differentiating RAW264.7 cells, coinciding with the downregulation of the primary biomarkers for osteoclast differentiation, such as the tartrate-resistant acid phosphatase activity and nuclear factor of activated T-cells gene expression. Not only BITC but also its metabolites, inhibited cell proliferation in the normal RAW264.7 cells, suggesting that BITC shows an anti-osteoclastogenesis effect in vivo after its ingestion and metabolism, possibly through an antiproliferative action. Both BITC and its metabolites also enhanced the DNA fragmentation and the caspase-3 activity, whereas their higher concentrations tended to suppress these effects. BITC was intracellularly accumulated when the cells were treated with its metabolites via their degradation into the free form. A quantitative experiment using the proteolysis/high performance liquid chromatography technique showed that the amount of BITC-lysine thiourea in the cells was also increased in a time-dependent manner, suggesting that lysine modification of the cellular proteins actually took place in the cells treated by BITC. Among the cellular proteins, the cleaved caspase-3 was identified as a potential target for lysine modification by BITC. Taken together, BITC dissociated from its metabolites as well as its free form might modulate osteoclastogenesis, possibly through inhibition of cell proliferation by protein modification.

Phenethyl Isothiocyanate Suppresses the Proinflammatory Cytokines in Human Glioblastoma Cells through the PI3K/Akt/NF-κB Signaling Pathway In Vitro

Phenethyl isothiocyanate (PEITC), extracted from cruciferous vegetables, showed anticancer activity in many human cancer cells. Our previous studies disclosed the anticancer activity of PEITC in human glioblastoma multiforme (GBM) 8401 cells, including suppressing the cell proliferation, inducing apoptotic cell death, and suppressing cell migration and invasion. Furthermore, PEITC also inhibited the growth of xenograft tumors of human glioblastoma cells. We are the first to investigate PEITC effects on the receptor tyrosine kinase (RTK) signaling pathway and the effects of proinflammatory cytokines on glioblastoma. The cell viability was analyzed by flow cytometric assay. The protein levels and mRNA expressions of cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), were determined by enzyme-linked immunosorbent assay (ELISA) reader and real-time polymerase chain reaction (PCR) analysis, respectively. Furthermore, nuclear factor-kappa B- (NF-κB-) associated proteins were evaluated by western blotting. NF-κB expression and nuclear translocation were confirmed by confocal laser microscopy. NF-κB binding to the DNA was examined by electrophoretic mobility shift assay (EMSA). Our results indicated that PEITC decreased the cell viability and inhibited the protein levels and expressions of IL-1β, IL-6, and TNF-α genes at the transcriptional level in GBM 8401 cells. PEITC inhibited the binding of NF-κB on promoter site of DNA in GBM 8401 cells. PEITC also altered the protein expressions of protein kinase B (Akt), extracellular signal-regulated kinase (ERK), and NF-κB signaling pathways. The inflammatory responses in human glioblastoma cells may be suppressed by PEITC through the phosphoinositide 3-kinase (PI3K)/Akt/NF-κB signaling pathway. Thus, PEITC may have the potential to be an anti-inflammatory agent for human glioblastoma in the future.

Nasturtium officinale Extract Suppresses Osteoclastogenesis in RAW 264 Cells by Inhibiting IκB-Kinase β

Osteoclasts are large, multinucleated, bone-absorbing cells and play a crucial role in osteolytic bone diseases such as osteopetrosis and rheumatoid arthritis. Therefore, controlling osteoclast differentiation and activation has been considered a promising strategy to prevent and treat osteolytic diseases. In this study, we demonstrate, using the mouse monocyte-derived macrophage-like cell line RAW 264, that extract from Nasturtium officinale or watercress, an herb of European origin, suppresses receptor activator of nuclear factor-κB ligand-induced osteoclast differentiation in vitro . N. officinale extract decreased the emergence of tartrate-resistant acid phosphatase-positive differentiated multinuclear cells and inhibited their bone-absorbing activity. The extract decreased expression of genes associated with osteoclast differentiation and function. Induction of nuclear factor of activated T cells c1 (NFATc1), the master transcriptional regulator of osteoclastogenesis, was blunted by N. officinale extract. Activation of nuclear factor-κB and mitogen-activated protein kinases pathways, both of which are necessary for NFATc1 induction and osteoclast differentiation, was also suppressed by the extract. Among upstream kinases, activity of IκB-kinase β (IKKβ), but not that of TGFβ-activated kinase 1, was inhibited by N. officinale extract in vitro. Pharmacological inhibition of IKKβ by a specific inhibitor PS1145 in RAW 264 cells mostly recaptured the inhibitory action of N. officinale extract. These findings provide a novel pharmacological action of N. officinale and its potential usefulness for the prevention of osteoporosis.

Inhibition of Osteoclast Differentiation by Carotenoid Derivatives through Inhibition of the NF-ƙB Pathway

The bone protective effects of carotenoids have been demonstrated in several studies, and the inhibition of RANKL-induced osteoclast differentiation by lycopene has also been demonstrated. We previously reported that carotenoid oxidation products are the active mediators in the activation of the transcription factor Nrf2 and the inhibition of the NF-ƙB transcription system by carotenoids. Here, we demonstrate that lycopene oxidation products are more potent than intact lycopene in inhibiting osteoclast differentiation. We analyzed the structure-activity relationship of a series of dialdehyde carotenoid derivatives (diapocarotene-dials) in inhibiting osteoclastogenesis. We found that the degree of inhibition depends on the electron density of the carbon atom that determines the reactivity of the conjugated double bond in reactions such as Michael addition to thiol groups in proteins. Moreover, the carotenoid derivatives attenuated the NF-ƙB signal through inhibition of IƙB phosphorylation and NF-ƙB translocation to the nucleus. In addition, we show a synergistic inhibition of osteoclast differentiation by combinations of an active carotenoid derivative with the polyphenols curcumin and carnosic acid with combination index (CI) values < 1. Our findings suggest that carotenoid derivatives inhibit osteoclast differentiation, partially by inhibiting the NF-ƙB pathway. In addition, carotenoid derivatives can synergistically inhibit osteoclast differentiation with curcumin and carnosic acid.

Cellular study of the LPS-induced osteoclastic multinucleated cell formation from RAW264.7 cells

Despite the response to the receptor activator of nuclear factor κ-Β ligand (RANKL), a study has reported that lipopolysaccharide (LPS) could induce RAW264.7 linage osteoclastic differentiation. However, on the contrary, another study recently showed that the LPS-induced multinuclear cells from RAW264.7 did not express osteoclastic functions. Interestingly, in our previous study, we found that RAW264.7 cells pretreated with 10 ng LPS plus macrophage-colony stimulating factor did not show any effects for enhancing RANKL-induced osteoclastic cell differentiation. Therefore, in our current study, we aim to investigate the oteoclastogesis induction ability and efficacy of LPS in the RAW264.7 cell line and relevant molecular signaling. The osteoclastogenic activity of LPS-treated RAW264.7 linage was studied by bone resorption pits and fibrous actin study. Besides that, through polymerase chain reaction and western blot, we showed that the transcriptional factor c-Fos and Nfatc1 might be associated with LPS-induced osteoclastogenesis. Overall, the results of our current study showed positive proof for osteoclast generation from LPS-independent treatment, as well as established an optimal and efficient method for this process.

Osteoclast Differentiation is Downregulated by Select Polyphenolic Fractions from Dried Plum via Suppression of MAPKs and Nfatc1 in Mouse C57BL/6 Primary Bone Marrow Cells

Background: Clinical and preclinical studies have shown that dietary supplementation with dried plum improves bone health. These osteoprotective effects are a result, in part, of the antiresorptive properties of the fruit, which appear to be mediated by its polyphenolic compounds. Objective: This study was designed to determine if certain fractions of the polyphenolic compounds in dried plums are responsible for the antiresorptive effects and whether they alter mitogen-activated protein kinase (MAPK) and calcium signaling, which are essential to osteoclast differentiation and activity, under normal and inflammatory conditions. Methods: Six polyphenolic fractions were derived from the total polyphenolic extract of dried plum based on solubility. Initial screening, with the use of the Raw 264.7 monocyte and macrophage cell line, showed that 3 fractions had the most marked capacity to downregulate osteoclast differentiation. This response was confirmed in 2 of the fractions by using primary bone marrow-derived cultures and in all subsequent experiments to determine how osteoclast differentiation and function were altered with a focus on these 2 fractions in primary cultures. Data were analyzed by using ANOVA followed by post hoc analyses. Results: Both of the polyphenol fractions decreased osteoclast differentiation and activity coincident with downregulating nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 (Nfatc1), which is required for osteoclast differentiation. Calcium signaling, essential for the auto-amplification of Nfatc1, was suppressed by the polyphenolic fractions under normal conditions as indicated by suppressed mRNA expression of costimulatory receptors osteoclast-associated receptor (Oscar), signaling regulatory protein β1 (Sirpb1), and triggering receptor expressed on myeloid cells 2 (Trem2). In contrast, in the presence of tumor necrosis factor α (TNF-α), only Sirpb1 was downregulated. In addition to calcium signaling, phosphorylation of extracellular signal-regulated kinase (Erk) and p38 MAPK, involved in the expression and activation of Nfatc1, was also suppressed by the polyphenolic fractions. Conclusion: These results show that certain types of polyphenolic compounds from dried plum downregulate calcium and MAPK signaling, resulting in suppression of Nfatc1 expression, which ultimately decreases osteoclast formation and activity.

Sulforaphane inhibits osteoclast differentiation by suppressing the cell-cell fusion molecules DC-STAMP and OC-STAMP

Sulforaphane (SFN), a kind of isothiocyanate, is derived from broccoli sprouts. It has anti-tumor, anti-inflammatory, and anti-oxidation activity. The molecular function of SFN in the inhibition of osteoclast differentiation is not well-documented. In this study, we assessed the effect of SFN on osteoclast differentiation in vitro. SFN inhibited osteoclast differentiation in both bone marrow cells and RAW264.7 cells. Key molecules involved in the inhibitory effects of SFN on osteoclast differentiation were determined using a microarray analysis, which showed that SFN inhibits osteoclast-associated genes, such as osteoclast-associated receptor (OSCAR), nuclear factor of activated T cells cytoplasmic-1, tartrate-resistant acid phosphatase, and cathepsin K. Moreover, the mRNA expression levels of the cell-cell fusion molecules dendritic cell specific transmembrane protein (DC-STAMP) and osteoclast stimulatory transmembrane protein (OC-STAMP) were strongly suppressed in cells treated with SFN. Furthermore, SFN increased the phosphorylation of signal transducer and activator of transcription 1 (STAT1), a regulator of macrophage and osteoclast cell fusion. Thus, our data suggested that SFN significantly inhibits the cell-cell fusion molecules DC-STAMP and OC-STAMP by inducing the phosphorylation of STAT1 (Tyr701), which might be regulated by interactions with OSCAR.

Nrf2 knockout attenuates the anti-inflammatory effects of phenethyl isothiocyanate and curcumin

The role of phytochemicals in preventive and therapeutic medicine is a major area of scientific research. Several studies have illustrated the mechanistic roles of phytochemicals in Nrf2 transcriptional activation. The present study aims to examine the importance of the transcription factor Nrf2 by treating peritoneal macrophages from Nrf2^+/+ and Nrf2^–/– mice ex vivo with phenethyl isothiocyanate (PEITC) and curcumin (CUR). The peritoneal macrophages were pretreated with the drugs and challenged with lipopolysaccharides (LPSs) alone and in combination with PEITC or CUR to assess their anti-inflammatory and antioxidative effects based on gene and protein expression in the treated cells. LPS treatment resulted in an increase in the expression of inflammatory markers such as cycloxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in both Nrf2^+/+ and Nrf2^–/– macrophages, detected by quantitative polymerase chain reaction (qPCR). Nrf2^+/+ macrophages treated with PEITC and CUR exhibited a significant decrease in the expression of these anti-inflammatory genes along with an increase in the expression of hemeoxygenase-1 (HO-1), which is an antioxidative stress gene downstream of the Nrf2 transcription factor battery. Although there was no significant decrease in the expression of the anti-inflammatory genes or an increase in HO-1 expression in Nrf2^–/– macrophages treated with either PEITC or CUR, there was a significant decrease in the protein expression of COX-2 and an increase in the expression of HO-1 in Nrf2^+/+ macrophages treated with PEITC compared to that with CUR treatment. No significant changes were observed in the macrophages from knockout animals. Additionally, there was a significant decrease in LPS-induced IL-6 and TNF-α production following PEITC treatment compared with that following CUR in Nrf2^+/+ macrophages, whereas no change was observed in the macrophages from knockout animals. The results from qPCR, western blot, and ELISA analyses in macrophages from Nrf2^+/+ and Nrf2 ^–/– mice indicate that Nrf2 plays an important role in the anti-inflammatory and antioxidative effects of PEITC and CUR, as observed by their decreased activities in Nrf2^–/– macrophages.

Molecular mechanisms for anti-aging by natural dietary compounds

Aging is defined as a normal decline in survival with advancing age; however, the recent researches have showed that physiological functions of the body change during the aging process. Majority of the changes are often subject to a higher risk of developing diseases, such as cardiovascular disease, type II diabetes, Alzheimer's disease, Parkinson's disease, as well as the dysregulated immune and inflammatory disorders. Aging process is controlled by a complicated and precise signaling network that involved in energy homeostasis, cellular metabolism and stress resistance. Over the past few decades, research in natural dietary compounds by various organism and animal models provides a new strategy for anti-aging. Natural dietary compounds act through a variety mechanisms to extend lifespan and prevent age-related diseases. This review summarizes the current understanding on signaling pathways of aging and knowledge and underlying mechanism of natural dietary compounds that provide potential application on anti-aging and improve heath in human.

Nuclear factor-erythroid 2-related factor 2 as a chemopreventive target in colorectal cancer

INTRODUCTION

Numerous epidemiological studies have linked consumption of cruciferous vegetables to a reduced risk of colorectal cancer (CRC) in individuals. It is currently well accepted that chronic inflammation is a contributing factor in 15 - 20% malignancies including CRC. Many chemopreventive compounds are effective in preclinical systems and many ongoing clinical trials are showing promising findings. Many of these compounds could activate the antioxidant responsive element (ARE), a critical regulatory element for Phase II protective/detoxification and antioxidative stress enzymes mediated by nuclear factor-erythroid 2-related factor 2 (Nrf2). Recently, Nrf2 has emerged as a novel target for the prevention of CRC.

AREAS COVERED

A full literature search was performed using PubMed with the key words 'ARE, Nrf2, colon, colorectal cancer, chemoprevention, cancer prevention', and all relevant publications are included.

EXPERT OPINION

The use of Nrf2 knockout mice has provided key insights into the toxicological and chemopreventive importance of this pathway. Mounting evidence has revealed that Nrf2 is a critical regulator of inflammation as well, a major driving force for CRC progression and formation. Targeting the Nrf2/ARE pathway may present a novel therapeutic approach for the treatment of not only colorectal inflammatory diseases but the frequent subsequent development of CRC as well.

Regulation of NF-E2-related factor 2 signaling for cancer chemoprevention: antioxidant coupled with antiinflammatory

Cancer chemoprevention is a process of using either natural or synthetic compounds to reduce the risk of developing cancer. Observations that NF-E2-related factor 2 (Nrf2)-deficient mice lack response to some chemopreventive agents point to the important role of Nrf2 in chemoprevention. Nrf2 is a member of basic-leucine zipper transcription factor family and has been shown to regulate gene expression by binding to a response element, antioxidant responsive element. It is generally believed that activation of Nrf2 signaling is an adaptive response to the environmental and endogenous stresses. Under homeostatic conditions, Nrf2 is suppressed by association with Kelch-like ECH-associated protein 1 (Keap1), but is stimulated upon exposure to oxidative or electrophilic stress. Once activated, Nrf2 translocates into nuclei and upregulates a group of genes that act in concert to combat oxidative stress. Nrf2 is also shown to have protective function against inflammation, a pathological process that could contribute to carcinogenesis. In this review, we will discuss the current progress in the study of Nrf2 signaling, in particular, the mechanisms of Nrf2 activation by chemopreventive agents. We will also discuss some of the potential caveats of Nrf2 in cancer treatment and future opportunity and challenges on regulation of Nrf2-mediated antioxidant and antiinflammatory signaling in the context of cancer prevention.

Modulation of inflammatory genes by natural dietary bioactive compounds

Several epidemiologic studies have shown that chronic inflammation predisposes individuals to various types of cancer. Many cancers arise from sites of infection, chronic irritation, and inflammation. Conversely, an oncogenic change induces an inflammatory microenvironment that promotes the development of tumors. Natural bioactive compounds in dietary plant products including fruits, vegetables, grains, legumes, tea, and wine are claimed to help prevent cancer, degenerative diseases, and chronic and acute inflammation. Modern methods in cell and molecular biology allow us to understand the interactions of different natural bioactive compounds with basic mechanisms of inflammatory response. The molecular pathways of this cancer-related inflammation are now unraveled. Natural bioactive compounds exert anti-inflammatory activity by modulating pro-inflammatory gene expressions have shown promising chemopreventive activity. This review summarizes current knowledge on natural bioactive compounds that act through the signaling pathways and modulate inflammatory gene expressions, thus providing evidence for these substances in cancer chemopreventive action.

Regulatory potential for concerted modulation of Nrf2- and Nfkb1-mediated gene expression in inflammation and carcinogenesis

Many studies have implicated nuclear factor E2-related factor 2 (Nrf2) and nuclear factor-kappaB1 (Nfkb1) in inflammation and cancer. However, the regulatory potential for crosstalk between these two important transcription factors in inflammation and carcinogenesis has not been explored. To delineate conserved transcription factor-binding site signatures, we performed bioinformatic analyses on the promoter regions of human and murine Nrf2 and Nfkb1. We performed multiple sequence alignment of Nrf2 and Nfkb1 genes in five mammalian species - human, chimpanzee, dog, mouse and rat - to explore conserved biological features. We constructed a canonical regulatory network for concerted modulation of Nrf2 and Nfkb1 involving several members of the mitogen-activated protein kinase (MAPK) family and present a putative model for concerted modulation of Nrf2 and Nfkb1 in inflammation/carcinogenesis. Our results reflect potential for putative crosstalk between Nrf2 and Nfkb1 modulated through the MAPK cascade that may influence inflammation-associated etiopathogenesis of cancer. Taken together, the elucidation of potential relationships between Nrf2 and Nfkb1 may help to better understand transcriptional regulation, as well as transcription factor networks, associated with the etiopathogenesis of inflammation and cancer.

Citrus nobiletin suppresses bone loss in ovariectomized ddY mice and collagen-induced arthritis in DBA/1J mice: possible involvement of receptor activator of NF-kappaB ligand (RANKL)-induced osteoclastogenesis regulation

Bone resorption is known to accelerate during the onset of several disorders, including osteoporosis (OP) and rheumatoid arthritis (RA). Some epidemiological surveys have suggested that a high intake of vegetables and fruits has an inverse relation to such disease incidence, though the number of active constituents elucidated thus far is limited. In the present study, we examined the efficacy of various food phytochemicals using two animal models. First, female ddY mice were ovariectomized (OVX) or sham-operated (sham), after which five different compounds (phenethyl isothiocyanate, zerumbone, auraptene, 1'-acetoxychavicol acetate, and nobiletin) were administered separately to OVX mice with a mini-osmotic pump at doses of 0.25 or 0.5 mg/day for 4 weeks, with 17beta-estradiol (E_{2}, 0.03 microg/day) used as a positive control. Nobiletin, in contrast to the other tested phytochemicals, significantly (P<0.05) suppressed the reduction of whole bone mineral density by 61%, which was comparable to or higher than the efficacy of E_{2}. Next, nobiletin given as an i.p. administration at 20 mg/kg of body weight, but not 2 mg/kg, to male DBA/1J mice every 2 days for 12 days led to a marked decrease in type II collagen-induced arthritis by 45% (P < 0.05). Furthermore, the flavonoid (4-50 microM) attenuated receptor activator of nuclear factor kappaB ligand (RANKL)-induced osteoclastogenesis of RAW264.7 cells, as detected by tartarate-resistant acid phosphatase activity and microscopic observations. Of note, nobiletin also suppressed RANKL-activated extracellular signal-regulated kinase1/2, c-Jun N-terminal kinase1/2, and p38 mitogen-activated protein kinase activities, and thereby regulated the promoter activation of nuclear factor kappaB (NFkappaB) and activator protein-1, key transcription factors for differentiation. Together, our results suggest that nobiletin is a promising phytochemical for the prevention or treatment of osteoclastogenesis-related disorders, including OP and RA, with reasonable action mechanisms.