Indole-3-Carbinol: Occurrence, Health-Beneficial Properties, and Cellular/Molecular Mechanisms

Indole-3-carbinol (I3C) is a bioactive phytochemical abundant in cruciferous vegetables. One of its main in vivo metabolites is 3,3'-diindolylmethane (DIM), formed by the condensation of two molecules of I3C. Both I3C and DIM alter multiple signaling pathways and related molecules controlling diverse cellular events, including oxidation, inflammation, proliferation, differentiation, apoptosis, angiogenesis, and immunity. There is a growing body of evidence from both in vitro and in vivo models that these compounds possess strong potential to prevent several forms of chronic disease such as inflammation, obesity, diabetes, cardiovascular disease, cancer, hypertension, neurodegenerative diseases, and osteoporosis. This article reviews current knowledge of the occurrence of I3C in nature and foods, along with the beneficial effects of I3C and DIM concerning prevention and treatment of human chronic diseases, focusing on preclinical studies and their mechanisms of action at cellular and molecular levels.

[Exploration of Indole Compounds as Candidate for Radiation Mitigators]

PURPOSE

In this study, to develop radiomitigators capable of the emergency medical care of patients involved in radiation accidents, we investigated the radiomitigative effects and their underlying mechanisms of indole compounds such as DIM, GRM, and INM.

METHODS

The human normal fibroblast cell line, MRC-5 cells were administered 0.1% DMSO or each indole compound at 10 µM within 50-60 minutes after X-irradiated with 0-4 Gy. Next, we evaluated the alteration in the number of alive cells, clonogenic potential, DNA double-strand breaks, DNA damage repair activities, and protein expression related to regulate the oxidative stress response.

RESULTS

Our results showed that DIM treatment suppressed radiation-induced decrease in the number of alive cells and clonogenic potential. Then, DIM treatment significantly decreased DNA double-strand breaks and highly increased Nrf2 via increased phospho-GSK-3β (Ser9) expression. These findings suggest that, in part, increased expression of p-GSK-3β (Ser9) by DIM treatment reduced DNA double-strand breaks via activation of Nrf2, resulting mitigated radiation-induced a decrease in the number of alive cells and clonogenic potential.

CONCLUSION

Therefore, DIM, not GRM and INM, is a potential candidate for radiomitigators that can be applied to the radiation emergency medicine.

3,3'-Diindolylmethane Promotes Gastric Cancer Progression via β-TrCP-Mediated NF-κB Activation in Gastric Cancer-Derived MSCs

Gastric cancer is a malignant tumor characterized by high morbidity and invasion. Surgery combined with chemo-radiotherapy is the most common treatment for gastric cancer, while multiple drug resistance always results in treatment failure. Once the anti-tumor drugs enter the tumor foci, tumor cells as well as those found in the microenvironment are affected. However, the effects of drugs on tumor microenvironment (TME) are easily overlooked. In this study, we investigated the effects of the anti-cancer drug 3,3’-diindolylmethane (DIM) on gastric cancer-derived mesenchymal stem cells (GC-MSCs) and their subsequent impact on cancer progression. Surprisingly, we found that the therapeutic concentration of DIM upregulated the expression level of tumor-related factors such as CCL-2, IL-6, and IL-8 in GC-MSCs. The conditioned medium of DIM-treated GC-MSCs promoted the proliferation, invasion, and migration of gastric cancer cells in vitro and tumor growth in vivo. Mechanistically, DIM enhanced the expression of β-TrCP, an E3 ubiquitin ligase leading to IκBα degradation and NF-κB activation in GC-MSCs. The β-TrCP knockdown partially eliminated positive results caused by DIM. Our results showed that the therapeutic dosage of DIM induced cell death in cancer cells, while enhancing MSC paracrine functions in the stroma to offset the original DIM effect on cancer cells. These findings provide a new mechanism of anti-cancer drug resistance and remind us to adjust the chemotherapeutic scheme by combining the anti-cancer drug with an appropriate signaling pathway inhibitor to block the side effects of drug on targeted TME cells.

Exogenous 3,3'-Diindolylmethane Improves Vanadium Stress Tolerance in Brassica napus Seedling Shoots by Modulating Antioxidant Enzyme Activities

3,3′-diindolylmethane (DIM) belongs to a family of indole glucosinolate compounds that have been shown to improve Brassica napus growth through the modulation of reactive oxygen species when applied exogenously. The B. napus cultivar AV Garnet was previously identified as a vanadium-sensitive cultivar. Therefore, in this study we investigated whether exogenous DIM could improve the vanadium tolerance of AV Garnet. We performed the following experiments: seed germination assessment, dry weight assessment, cell viability assay, chlorophyll content assay, malondialdehyde (MDA) assay, conjugated diene (CD) content assay, hydrogen peroxide (H₂O₂) content assay, superoxide (O₂⁻) content determination, methylglyoxal (MG) content determination, hydroxyl radical (·OH) concentration determination, ascorbate peroxidase (APX) activity assay, superoxide dismutase (SOD) activity assay, glyoxalase I (Gly I) activity assay, glutathione S-transferase (GST) activity assay and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis for vanadium content determination. Under vanadium stress, exogenous DIM increased the seed germination percentage, shoot dry weight, cell viability and chlorophyll content. Exogenous DIM also led to a decrease in MDA, CD, H₂O₂, O₂⁻, MG and ·OH, under vanadium stress in the shoots. Furthermore, DIM application led to an increase in the enzymatic activities of APX, SOD, Gly I and GST under vanadium stress. Interestingly, under vanadium stress, DIM treatment did not alter vanadium content in B. napus shoots. Our results indicate that exogenous application of DIM can improve B. napus seedling shoot growth and biomass under vanadium stress by priming the antioxidant enzymes via reactive oxygen species (ROS) signaling.

DIM mitigates the development of experimental autoimmune encephalomyelitis by maintaining the stability and suppressive function of regulatory T cells

Recent studies have revealed that indoles, dietary ligands of the aryl hydrocarbon receptor (AhR), have immunomodulatory characteristics of balancing the differentiation of regulatory T cells (Tregs) and Th17 cells in multiple autoimmune diseases. In this study, we aimed to investigate the potency of the indole, 3,3'-diindolylmethane (DIM), on the stability and suppressive function of Tregs in experimental autoimmune encephalomyelitis (EAE). Furthermore, we used the AhR antagonist CH223191 to verify that DIM exerts its effects on Tregs through the activation of AhR. We found that DIM treatment significantly alleviated the severity of EAE by maintaining the stability and suppressive function of Tregs instead of facilitating the differentiation of Tregs. Thus, these DIM-treated Tregs might indirectly inhibit the generation of Th17 cells and the production of proinflammatory cytokines. And we confirmed the critical role of AhR in the EAE model. Our study further investigated the mechanisms by which dietary indoles promote Treg activity in the EAE model. DIM may act as a novel therapeutic to restrain autoimmune inflammation in multiple sclerosis.

Amelioration of Hyperglycemia-Induced Nephropathy by 3,3'-Diindolylmethane in Diabetic Mice

Type 1 diabetes mellitus (insulin-dependent diabetes) is characterized by hyperglycemia caused by an insulin deficiency. Diabetic nephropathy is a major complication of hyperglycemia. 3,3′-diindolylmethane (DIM)-a natural compound produced from indole-3-carbinol, found in cruciferous vegetables-enhances glucose uptake by increasing the activation of the insulin signaling pathway in 3T3-L1 adipocytes. In this study, we investigated whether DIM could improve insulin-dependent diabetes and nephropathy in streptozotocin (STZ)-induced diabetic mice. In mice, STZ induced hyperglycemia, hunger, thirst, and abnormally increased kidney weight and serum creatinine, which is a renal functional parameter. DIM decreased STZ-increased high blood glucose levels and food and water intake in diabetic mice. DIM also improved diabetic nephropathy by inhibiting the expression of PKC-α, the marker of albuminuria, and TGF-β1, an indicator of renal hypertrophy, in diabetic mice. Our findings suggest that DIM may ameliorate hyperglycemia and diabetic nephropathy through the inhibition of PKC-α and TGF-β1 signaling.

Anti-Cancer Effects of 3, 3'-Diindolylmethane on Human Hepatocellular Carcinoma Cells Is Enhanced by Calcium Ionophore: The Role of Cytosolic Ca2+ and p38 MAPK

Purpose: 3,3'-Diindolylmethane (DIM), derived from indole-3-carbinol (I3C) in the Brassica species of cruciferous vegetables, has anticancer effects, but its exact underlying mechanism of action is unknown. We explored the roles of cytosolic free calcium ([Ca2+]i) and p38 MAPK in the anti-cancer effects of DIM in human hepatocellular carcinoma cells. Methods: Cell proliferation was measured with a Cell Counting Kit-8 (CCK-8) and the clonogenic formation assay. Cell apoptosis was examined by flow cytometric analysis and Hoechst dye staining. Cleaved-caspase3, cleaved-PARP, Bax, total, and phosphorylated p38 MAPK were assayed by western blotting. [Ca2+]i was measured with Fluo-3/AM by fluorescence microscopy. A23187, a calcium ionophore, was used to increase [Ca2+]i levels. Results: DIM inhibited cell proliferation in both SMMC-7721 and HepG2 cells in a concentration- and time-dependent manner. DIM also enhanced phosphorylation of p38 MAPK (p-p38), which was attenuated by SB203580. The proliferation inhibition and apoptosis induction by DIM were also blunted. In addition, DIM increased [Ca2+]i in HCC cells, and this effect was inhibited by the calcium chelator, BAPTA-AM, resulting in reduced p-p38 MAPK activation and apoptosis in DIM-treated cells, though the proliferation inhibition by DIM was unchanged. However, the DIM-induced cell proliferation inhibition and apoptosis were significantly enhanced by A23187, a selective calcium ionophore, which was attributed to exaggerated p-p38 MAPK. Conclusions: The calcium ionophore enhanced DIM-induced anti-cancer effects in hepatocellular carcinoma cells, secondary to [Ca2+]i-dependent activation of p38 MAPK. Treatment with a combination of DIM and calcium ionophore may offer a new approach to enhance the chemotherapeutic efficacy in liver cancer.

3,3'-Diindolylmethane Improves Intestinal Permeability Dysfunction in Cultured Human Intestinal Cells and the Model Animal Caenorhabditis elegans

3,3'-Diindolylmethane (DIM), a digestive metabolite originating from cruciferous vegetables, has dietary potential for the treatment of various human intestinal diseases. Although intestinal permeability dysfunction is closely related to the initiation and progression of human intestinal inflammatory diseases (IBDs), the effect of DIM on intestinal permeability is unclear. We evaluated the effect of DIM on the intestinal permeability of human intestinal cell monolayers and the animal model Caenorhabditis elegans, which were treated with IL-1β and Pseudomonas aeruginosa, respectively, to mimic IBD conditions. DIM substantially restored the intestinal permeability of differentiated Caco-2 cells by enhancing the expression of tight junction proteins (including occludin and ZO-1). Compared to the IL-1β single treatment (551.0 ± 49.0 Ω·cm²), DIM (10 μM) significantly increased the transepithelial electrical resistance (TEER) of Caco-2 cell monolayers (919.0 ± 66.4 Ω·cm², p < 0.001). DIM also ameliorated the impaired intestinal permeability and extended the lifespan of C. elegans fed P. aeruginosa. The mean lifespan of DIM-treated worms (10.8 ± 1.3 days) was higher than that of control-treated worms (9.7 ± 1.1 days, p < 0.01). Thus, DIM is a potential nutraceutical candidate for the treatment of leaky gut syndrome by improving intestinal permeability.

Synthesis and Evaluation of Diindole-Based MRI Contrast Agent for In Vivo Visualization of Necrosis

PURPOSE

Noninvasive imaging of cell necrosis can provide an early evaluation of tumor response to treatments. Here, we aimed to design and synthesize a novel diindole-based magnetic resonance imaging (MRI) contrast agent (Gd-bis-DOTA-diindolylmethane, Gd-DIM) for assessment of tumor response to therapy at an early stage.

PROCEDURES

The oil-water partition coefficient (Log P) and relaxivity of Gd-DIM were determined in vitro. Then, its necrosis avidity was examined in necrotic cells in vitro and in rat models with microwave ablation-induced muscle necrosis (MAMN) and ischemia reperfusion-induced liver necrosis (IRLN) by MRI. Visualization of tumor necrosis induced by combretastatin A-4 disodium phosphate (CA4P) was evaluated in rats bearing W256 orthotopic liver tumor by MRI. Finally, DNA binding assay was performed to explore the possible necrosis-avidity mechanism of Gd-DIM.

RESULTS

The Log P value and T1 relaxivity of Gd-DIM is - 2.15 ± 0.01 and 6.61 mM^-1 s^-1, respectively. Gd-DIM showed predominant necrosis avidity in vitro and in vivo. Clear visualization of the tumor necrosis induced by CA4P was achieved at 60 min after administration of Gd-DIM. DNA binding study indicated that the necrosis-avidity mechanism of Gd-DIM may be due to its binding to exposed DNA in necrotic cells.

CONCLUSION

Gd-DIM may serve as a promising necrosis-avid MRI contrast agent for early assessment of tumor response to therapy.

Interactions between β-Lactoglobulin and 3,3'-Diindolylmethane in Model System

The compound 3,3′-diindolylmethane (DIM) has a broad spectrum of anticancer activities. However, low stability and bioavailability limit its application. Elucidating interactions between DIM and β-lactoglobulin (β-LG) may be useful for fabricating whey protein-based protecting systems. Interaction with DIM increased the diameter and absolute zeta potential value of β-LG. UV-absorption spectra suggested that there was a complex of DIM and β-LG. β-LG showed enhanced fluorescence intensity by complexing with DIM with a binding constant of 6.7 × 10⁵ M⁻¹. Upon interaction with DIM, β-LG was decreased in secondary structure content of helix and turn while increased in β-sheet and unordered. FT-IR spectra and molecular docking results indicated the roles of hydrophobic interaction and hydrogen bond for the formation of DIM and β-LG nanocomplexes. Data suggested that β-LG may be a good vehicle for making a protein-based DIM protection and delivery system due to the tight binding of DIM to β-LG.

Physicochemical and Microstructural Properties of Polymerized Whey Protein Encapsulated 3,3'-Diindolylmethane Nanoparticles

The fat-soluble antioxidant 3,3′-diindolylmethane (DIM), is a natural phytochemical found in Brassica vegetables, such as cabbage, broccoli, and Brussels sprouts. The stability of this compound is a major challenge for its applications. Polymerized whey protein (PWP)-based DIM nanoparticles were prepared at different mass ratios of protein and DIM by mixing PWP and DIM followed by ultrasound treatment for 4 min. All the nanoparticles were studied for particle size, zeta potential, rheological and microstructural properties, and storage stability. The mean particle size of the PWP-based nanoparticles was significantly increased (p < 0.05) by the addition of DIM at different mass ratios, ranging from 241.33 ± 14.82 to 270.57 ± 15.28 nm. Zeta potential values of all nanoparticles were highly negative (greater than ±30 mV), suggesting a stable solution due its electrostatic repulsive forces. All samples exhibited shear thinning behavior (n < 1), fitted with Sisko model (R² > 0.997). Fourier Transform Infrared (FTIR)spectra revealed that the secondary structure was changed and the absorption intensity for hydrogen bonding got stronger by further incorporating DIM into PWP. Transmission electronic microscopy (TEM) images showed spherical and smooth surface shape of the PWP-based nanoparticles. DIM encapsulated by PWP showed enhanced stability at 4, 37 and 55 °C for 15 days evidenced by changes in mean particle size and color (a*-value and b*-value) compared with control (DIM only). In conclusion, the polymerized whey protein based 3,3′-diindolylmethane nanoparticles are stable and the encapsulation may protect the core material from oxidation.

Treatment with Phytoestrogens Reversed Triclosan and Bisphenol A-Induced Anti-Apoptosis in Breast Cancer Cells

Triclosan (TCS) and bisphenol A (BPA) are endocrine-disrupting chemicals that interfere with the hormone or endocrine system and may cause cancer. Kaempferol (Kaem) and 3,3'-diindolylmethane (DIM) are phytoestrogens that play chemopreventive roles in the inhibition of carcinogenesis and cancer progression. In this study, the influence of TCS, BPA, Kaem, and DIM on proliferation and apoptotic abilities of VM7Luc4E2 breast cancer cells were examined. MTT assay revealed that TCS (0.1-10 µM), BPA (0.1-10 µM) and E2 (0.01-0.0001 µM) induced significant cell proliferation of VM7Luc4E2 cells, which was restored to the control (0.1% DMSO) by co-treatment with Kaem (30 µM) or DIM (15 µM). Reactive oxygen species (ROS) production assays showed that TCS and BPA inhibited ROS production of VM7Luc4E2 cells similar to E2, but that co-treatment with Kaem or DIM on VM7Luc4E2 cells induced increased ROS production. Based on these results, the effects of TCS, BPA, Kaem, and DIM on protein expression of apoptosis and ROS production-related markers such as Bax and Bcl-xl, as well as endoplasmic reticulum (ER) stress-related markers such as eIF2α and CHOP were investigated by Western blot assay. The results revealed that TCS, and BPA induced anti-apoptosis by reducing ROS production and ER stress. However, Kaem and DIM effectively inhibited TCS and BPA-induced anti-apoptotic processes in VM7Luc4E2 cells. Overall, TCS and BPA were revealed to be distinct xenoestrogens that enhanced proliferation and anti-apoptosis, while Kaem and DIM were identified as natural chemopreventive compounds that effectively inhibited breast cancer cell proliferation and increased anti-apoptosis induced by TCS and BPA.

A combination of resveratrol and 3,3'-diindolylmethane, a potent radioprotector

PURPOSE

Exposure to ionizing radiation causes damage to the genomic integrity and stability of the cell. Though a large number of molecules have been studied for their radioprotective capability, no single agent is available today that meets all the requirements of a good radiprotector. In this study, we have investigated a combination of Resveratrol (RSV) and 3,3'-Diindolyl methane (DIM) for its efficacy for radioprotection. It is our hypothesis that this combination that possesses less toxicity than synthetic compounds, free radical scavenging potential, and the capacity to interfere with the several of the signaling cascades that trigger damage to cell by ionizing radiation may possess good radioprotective capability.

MATERIALS AND METHODS

Mice were pre-treated with a combination of RSV and DIM and the 30-day mortality assay, endogenous antioxidant levels in intestinal mucosa, metaphase chromosomal aberrations, and micronuclei formation were assessed after exposed to ionizing radiation.

RESULTS

The dose modifying factor (DRF) obtained for RSV, DIM, and the combination is 1.15, 1.17, and 1.3, respectively. Pre-treatment of mice with the combination results in significant (***p = .001) protection of the endogenous antioxidant levels, chromosomal aberrations, micronuclei formation, after exposure to ionizing radiation.

CONCLUSIONS

Our findings suggest that pre-treatment with the combination of RSV and DIM protects effectively from the ionizing radiation-induced damage at the molecular, cellular, and tissue levels by counteracting both the direct and indirect effects.

Elucidating the Role of CD84 and AHR in Modulation of LPS-Induced Cytokines Production by Cruciferous Vegetable-Derived Compounds Indole-3-Carbinol and 3,3'-Diindolylmethane

Modulation of the immune system by cancer protective food bioactives has preventive and therapeutic importance in prostate cancer, but the mechanisms remain largely unclear. The current study tests the hypothesis that the diet-derived cancer protective compounds, indole-3-carbinol (I3C) and 3,3′-diindolylmethane (DIM), affect the tumor microenvironment by regulation of inflammatory responses in monocytes and macrophages. We also ask whether I3C and DIM act through the aryl hydrocarbon (AHR)-dependent pathway or the signaling lymphocyte activation molecule (SLAM) family protein CD84-mediated pathway. The effect of I3C and DIM was examined using the human THP-1 monocytic cell in its un-differentiated (monocyte) and differentiated (macrophage) state. We observed that I3C and DIM inhibited lipopolysaccharide (LPS) induction of IL-1β mRNA and protein in the monocyte form but not the macrophage form of THP-1. Interestingly, CD84 mRNA but not protein was inhibited by I3C and DIM. AHR siRNA knockdown experiments confirmed that the inhibitory effects of I3C and DIM on IL-1β as well as CD84 mRNA are regulated through AHR-mediated pathways. Additionally, the AHR ligand appeared to differentially regulate other LPS-induced cytokines expression. Hence, cross-talk between AHR and inflammation-mediated pathways, but not CD84-mediated pathways, in monocytes but not macrophages may contribute to the modulation of tumor environments by I3C and DIM in prostate cancer.

Anti-cancer drug 3,3'-diindolylmethane activates Wnt4 signaling to enhance gastric cancer cell stemness and tumorigenesis

As a natural health supplement, 3,3′-diindolylmethane (DIM) is proposed as a preventive and chemotherapeutic agent for cancer by inhibiting cell proliferation and inducing cell apoptosis. However, we found that in contrary to high level of DIM (30 μM), low level of DIM (1 μM and 10 μM) obviously promoted gastric cancer cell growth and migration. In addition, we found that low level of DIM increased the expression of stemness factors and enhanced the pluripotency of gastric cancer cells. Low level of DIM promoted gastric cancer progression by inducing the PORCN-dependent secretion of Wnt4 and the activation of β-catenin signaling. Wnt4 knockdown reversed the effects of low level of DIM on gastric cancer cells. The results of in vivo studies showed that gastric cancer cells treated with low level of DIM (1 μM) grew faster and expressed higher level of Wnt4 than control cells. Taken together, our findings indicate that low level of DIM activates autocrine Wnt4 signaling to enhance the progression of gastric cancer, which may suggest an adverse aspect of DIM in cancer therapy. Our findings will provide a new aspect for the safety of DIM in its clinical application.

3,3'-Diindolylmethane Suppresses Adipogenesis Using AMPKα-Dependent Mechanism in 3T3-L1 Adipocytes and Caenorhabditis elegans

3,3'-diindolylmethane is a major in vivo metabolite of indole-3-carbinol, a bioactive compound found in cruciferous vegetables. Although 3,3'-diindolylmethane has been implicated to possess antitumorigenic and anti-inflammatory properties, the effect of 3,3'-diindolylmethane on adipogenesis has not been explored previously. Thus, the present study was conducted to determine if 3,3'-diindolylmethane affects adipogenesis using 3T3-L1 adipocytes and Caenorhabditis elegans. Treatment of 3,3'-diindolylmethane significantly reduced fat accumulation without affecting viability in 3T3-L1 adipocytes. 3,3'-diindolylmethane suppressed expression of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT-enhancer-binding protein α (C/EBPα), fatty acid binding protein 4 (FABP4), and perilipin. In addition, 3,3'-diindolylmethane activated AMP-activated protein kinase α (AMPKα), which subsequently inactivated acetyl CoA carboxylase (ACC), resulting in reduced fat accumulation. These observations were further confirmed in C. elegans as treatment with 3,3'-diindolylmethane significantly reduced body fat accumulation, which was partly associated with aak-1, but not aak-2, orthologs of AMPKα catalytic subunits α1 and α2, respectively. The current results demonstrate that 3,3'-diindolylmethane, a biologically active metabolite of indole-3-carbinol, may prevent adipogenesis through the AMPKα-dependent pathway.

3,3'-Diindolylmethane stimulates exosomal Wnt11 autocrine signaling in human umbilical cord mesenchymal stem cells to enhance wound healing

Human umbilical cord-derived mesenchymal stem cells (hucMSCs) are suggested as a promising therapeutic tool in regenerative medicine, however, their efficacy requires improvement. Small molecules and drugs come up to be a convenient strategy in regulating stem cells fate and function. Here, we evaluated 3,3′-diindolylmethane (DIM), a natural small-molecule compound involved in the repairing effects of hucMSCs on a deep second-degree burn injury rat model. HucMSCs primed with 50 μM of DIM exhibited desirable repairing effects compared with untreated hucMSCs. DIM enhanced the stemness of hucMSCs, which was related to the activation of Wnt/β-catenin signaling. β-catenin inhibition impaired the healing effects of DIM-primed hucMSCs (DIM-hucMSCs) in vivo. Moreover, we demonstrated that DIM upregulated Wnt11 expression in hucMSC-derived exosomes. Wnt11 knockdown inhibited β-catenin activation and stemness induction in DIM-hucMSCs and abrogated their therapeutic effects in vivo. Thus, our findings indicate that DIM promotes the stemness of hucMSCs through increased exosomal Wnt11 autocrine signaling, which provides a novel strategy for improving the therapeutic effects of hucMSCs on wound healing.

Effect of Oral Administration of 3,3'-Diindolylmethane on Dextran Sodium Sulfate-Induced Acute Colitis in Mice

In patients with inflammatory bowel disease (IBD), inflammation is induced and maintained by lymphangiogenesis and angiogenesis. 3,3'-Diindolylmethane (DIM) is a natural product formed in acidic conditions from indole-3-carbinol in cruciferous vegetables, and it is known for its chemotherapeutic activity. This study evaluated DIM's effects on angiogenesis, lymphangiogenesis, and inflammation in a mouse colitis model. Experimental colitis was induced in mice by administering 3% dextran sulfate sodium (DSS) via drinking water. DIM remarkably attenuated the clinical signs and histological characteristics in mice with DSS-induced colitis. DIM suppressed neutrophil infiltration and pro-inflammatory cytokines. Moreover, it significantly suppressed the expression of vascular endothelial growth factor (VEGF)-A and VEGF receptor (VEGFR)-2, indicating that the mechanism may be related to the repression of pro-angiogenesis activity. DIM also remarkably suppressed the expression of VEGF-C, VEGF-D, VEGFR-3, and angiopoietin-2; thus, the mechanism may also be related to the suppression of lymphangiogenesis. Therefore, DIM is a possible treatment option for inflammation of the intestine and associated angiogenesis and lymphangiogenesis.

3,3'-diindolylmethane mitigates total body irradiation-induced hematopoietic injury in mice

We have reported that hematopoietic system injury induced by total body irradiation (TBI) leads to generation of intracellular reactive oxygen species (ROS) and DNA damage, which are ameliorated by antioxidant agents. In the present study, we reported that administration of DIM, a potent antioxidant agent, not only protected mice against TBI-induced lethality, also ameliorated TBI-induced hematopoietic injury. The latter effect was probably attributable to DIM's inhibition of TBI-induced increases in ROS production in hematopoietic stem cells (HSCs) and the phosphorylation of histone H2AX (γ-H2AX). In particular, DIM led to significant improvements in bone marrow (BM) HSC frequency, hematopoietic progenitor cell (HPC) clonogenic function, and multilineage engraftment after transplantation. A downregulation of NADPH oxidase 4 (NOX4) and an upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression were observed following DIM treatment. Notably, the anti-apoptotic potential of DIM was correlated with increased expression of the anti-apoptotic protein Bcl-2 and decreased expression of the pro-apoptotic protein Bax. These findings suggest that DIM attenuates TBI-induced hematopoietic injury through the inhibition of both oxidative stress in HSCs and hematopoietic cell apoptosis. Furthermore, we demonstrated that DIM protected BM hematopoietic cells against ionizing radiation and led to increased clonogenicity in vitro. Therefore, DIM has the potential to be used as an effective radioprotectant to ameliorate TBI-induced hematopoietic injury.

Cellular and Molecular Mechanisms of 3,3'-Diindolylmethane in Gastrointestinal Cancer

Studies in humans have shown that 3,3′-diindolylmethane (DIM), which is found in cruciferous vegetables, such as cabbage and broccoli, is effective in the attenuation of gastrointestinal cancers. This review presents the latest findings on the use, targets, and modes of action of DIM for the treatment of human gastrointestinal cancers. DIM acts upon several cellular and molecular processes in gastrointestinal cancer cells, including apoptosis, autophagy, invasion, cell cycle regulation, metastasis, angiogenesis, and endoplasmic reticulum (ER) stress. In addition, DIM increases the efficacy of other drugs or therapeutic chemicals when used in combinatorial treatment for gastrointestinal cancer. The studies to date offer strong evidence to support the use of DIM as an anticancer and therapeutic agent for gastrointestinal cancer. Therefore, this review provides a comprehensive understanding of the preventive and therapeutic properties of DIM in addition to its different perspective on the safety of DIM in clinical applications for the treatment of gastrointestinal cancers.

Synergistic anticancer activity of capsaicin and 3,3'-diindolylmethane in human colorectal cancer

Cancer is a leading cause of morbidity and mortality worldwide. A promising area of cancer research is focused on chemoprevention by nutritional compounds. Epidemiological studies have shown a strong negative correlation between fruit, vegetable, and spice intake and rates of cancer. Although individual active compounds have demonstrated significant anticancer activity, an emerging area of research is focusing on the combination of multiple dietary compounds that act synergistically on cancer to exert greater effects. The current study evaluated the potential synergistic effects of capsaicin, an active compound from red chili peppers, in combination with 3,3'-diindolylmethane (DIM), from cruciferous vegetables. A synergistic induction of apoptosis and inhibition of cell proliferation was observed in human colorectal cancer cells treated with the combination of capsaicin and DIM. It was also observed that these two compounds activated transcriptional activity of NF-κB and p53 synergistically. Combination treatment stabilized nuclear p53 and up- or down-regulated expression of several target genes that are downstream of NF-κB and p53. The present study suggests capsaicin and DIM work synergistically to inhibit cell proliferation and induce apoptosis in colorectal cancer through modulating transcriptional activity of NF-κB, p53, and target genes associated with apoptosis.

3,3'-diindolylmethane potentiates tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis of gastric cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) specifically kills cancer cells without destroying the majority of healthy cells. However, numerous types of cancer cell, including gastric cancer cells, tend to be resistant to TRAIL. The bioactive product 3,3'-diindolylmethane (DIM), which is derived from cruciferous vegetables, is also currently recognized as a candidate anticancer agent. In the present study, a Cell Counting Kit 8 cell growth assay and an Annexin V-fluorescein isothiocyanate apoptosis assay were performed to investigate the potentiating effect of DIM on TRAIL-induced apoptosis in gastric cancer cells, and the possible mechanisms of this potentiation. The results obtained demonstrated that, compared with TRAIL or DIM treatment alone, co-treatment with TRAIL (25 or 50 ng/ml) and DIM (10 µmol/l) induced cytotoxic and apoptotic effects in BGC-823 and SGC-7901 gastric cancer cells. Furthermore, western blot analysis revealed that the protein expression levels of death receptor 5 (DR5), CCAAT/enhancer binding protein homologous protein (CHOP) and glucose-regulated protein 78 (GRP78) were upregulated in the co-treated gastric cancer cells. To the best of our knowledge, the present study is the first to provide evidence that DIM sensitizes TRAIL-induced inhibition of proliferation and apoptosis in gastric cancer cells, accompanied by the upregulated expression of DR5, CHOP and GRP78 proteins, which may be involved in endoplasmic reticulum stress mechanisms.

Androgen receptor splice variants contribute to prostate cancer aggressiveness through induction of EMT and expression of stem cell marker genes

BACKGROUND

The mechanism(s) by which androgen receptor (AR) splice variants contribute to castration-resistant prostate cancer (CRPC) is still lacking.

METHODS

Expressions of epithelial-to-mesenchymal transition (EMT) and stem cell markers were molecularly tested using prostate cancer (PCa) cells transfected with AR and AR3 (also known as AR-V7) plasmids or siRNA, and also cultured cells under androgen deprivation therapy (ADT) condition. Cell migration, clonogenicity, sphere-forming capacity was assessed using PCa cells under all experimental conditions and 3,3'-diindolylmethane (DIM; BR-DIM) treatment. Human PCa samples from BR-DIM untreated or treated patients were also used for assessing the expression of AR3 and stem cell markers.

RESULTS

Overexpression of AR led to the induction of EMT phenotype, while overexpression of AR3 not only induced EMT but also led to the expression of stem cell signature genes. More importantly, ADT enhanced the expression of AR and AR3 concomitant with up-regulated expression of EMT and stem cell marker genes. Dihydrotestosterone (DHT) treatment decreased the expression of AR and AR3, and reversed the expression of these EMT and stem cell marker genes. BR-DIM administered to PCa patients prior to radical prostatectomy inhibited the expression of cancer stem cell markers consistent with inhibition of self-renewal of PCa cells after BR-DIM treatment.

CONCLUSION

AR variants could contribute to PCa progression through induction of EMT and acquisition of stem cell characteristics, which could be attenuated by BR-DIM, suggesting that BR-DIM could become a promising agent for the prevention of CRPC and/or for the treatment of PCa.

3,3'-Diindolylmethane inhibits the invasion and metastasis of nasopharyngeal carcinoma cells in vitro and in vivo by regulation of epithelial mesenchymal transition

Nasopharyngeal carcinoma (NPC) is characterized by silent progression and atypical early symptoms. Early metastasis to the neck lymph nodes is common. However, conventional chemoradiotherapy is limited and unable to effectively control cervical lymph node metastasis of NPC. In addition, toxicities caused by chemoradiotherapy often induce damage to normal tissues and organs. Thus, the aim of this study was to investigate the ability of 3,3′-diindolylmethane (DIM) to inhibit the invasion and metastasis of NPC cells in vitro and in vivo. The migration and invasive abilities of the 5–8F human NPC cell line were detected using a Transwell assay. Lymph node metastasis in nude mice was observed following the implantation of xenograft tumors for 8 weeks. In addition, western blot analysis was used to detect the expression levels of epithelial mesenchymal transition (EMT)-associated key proteins in NPC cells treated with DIM in vitro and in vivo. The results demonstrated that DIM effectively inhibited the migration and invasion of NPC cells in vitro and the effect was concentration-dependent. In addition, DIM significantly delayed and reduced the occurrence of lymph node metastasis in the animal model. The expression levels of a number of key proteins associated with EMT were affected by DIM treatment. In the animal model, there were no signs of toxicity in the vital organs, including the heart, liver and kidney, of animals fed a diet containing DIM. Therefore, the results of the present study indicate that DIM affects the expression levels of a number of EMT-associated key proteins and induces the inhibition of invasion and metastasis of NPC cells in vitro and in vivo.

Natural indoles, indole-3-carbinol and 3,3'-diindolymethane, inhibit T cell activation by staphylococcal enterotoxin B through epigenetic regulation involving HDAC expression

Staphylococcal enterotoxin B (SEB) is a potent exotoxin produced by the Staphylococcus aureus. This toxin is classified as a superantigen because of its ability to directly bind with MHC-II class molecules followed by activation of a large proportion of T cells bearing specific Vβ-T cell receptors. Commonly associated with classic food poisoning, SEB has also been shown to induce toxic shock syndrome, and is also considered to be a potential biological warfare agent because it is easily aerosolized. In the present study, we assessed the ability of indole-3-carbinol (I3C) and one of its byproducts, 3,3'-diindolylmethane (DIM), found in cruciferous vegetables, to counteract the effects of SEB-induced activation of T cells in mice. Both I3C and DIM were found to decrease the activation, proliferation, and cytokine production by SEB-activated Vβ8(+) T cells in vitro and in vivo. Interestingly, inhibitors of histone deacetylase class I (HDAC-I), but not class II (HDAC-II), showed significant decrease in SEB-induced T cell activation and cytokine production, thereby suggesting that epigenetic modulation plays a critical role in the regulation of SEB-induced inflammation. In addition, I3C and DIM caused a decrease in HDAC-I but not HDAC-II in SEB-activated T cells, thereby suggesting that I3C and DIM may inhibit SEB-mediated T cell activation by acting as HDAC-I inhibitors. These studies not only suggest for the first time that plant-derived indoles are potent suppressors of SEB-induced T cell activation and cytokine storm but also that they may mediate these effects by acting as HDAC inhibitors.

Contamination of deconjugation enzymes derived from Helix pomatia with the plant bioactive compounds 3,3'-diindolylmethane, 5-methoxypsoralen, and 8-methoxypsoralen

Bioactive compounds from plant foods are intensely investigated for effects on disease prevention. β-Glucuronidase/arylsulfatase from Helix pomatia (snail) is commonly used when quantifying exposure to metabolized dietary components. However, we describe here the contamination of multiple formulations of this enzyme preparation with 3,3'-diindolylmethane (DIM), 8-methoxypsoralen (8-MOP), and 5-methoxypsoralen (5-MOP), bioactives from cruciferous and apiaceous vegetables under investigation as putative cancer chemopreventive agents. We identified an Escherichia coli preparation of β-glucuronidase as free from contamination with any of the compounds tested. These results demonstrate the importance of selecting appropriate enzyme preparations when quantifying naturally occurring, trace level compounds in biological fluids.

3,3'-diindolylmethane rapidly and selectively inhibits hepatocyte growth factor/c-Met signaling in breast cancer cells

3,3'-Diindolylmethane (DIM), an indole derivative from vegetables of the Brassica genus, has antiproliferative activity in breast cancer cells. Part of this activity is thought to be due to DIM inhibition of Akt signaling, but an upstream mechanism of DIM-induced Akt inhibition has not been described. The goals of this study were to investigate the kinetics of inhibition of Akt by physiologically relevant concentrations of DIM and to identify an upstream factor that mediates this effect. Here we report that DIM (5-25 μM) inhibited Akt activation from 30 min to 24h in tumorigenic MDA-MB-231 cells but did not inhibit Akt activation in non-tumorigenic preneoplastic MCF10AT cells. DIM inhibited hepatocyte growth factor (HGF)-induced Akt activation by up to 46%, cell migration by 66% and cell proliferation by up to 54%, but did not inhibit induction of Akt by epidermal growth factor or insulin-like growth factor-1. DIM decreased phosphorylation of the HGF receptor, c-Met, at tyrosines 1234 and 1235, indicating decreased activation of the receptor. This decrease was reversed by pretreatment with inhibitors of p38 or calcineurin. Our results demonstrate the important role of HGF and c-Met in DIM's anti-proliferative effect on breast cancer cells and suggest that DIM could have preventive or clinical value as an inhibitor of c-Met signaling.

Anticancer effects of 3,3'-diindolylmethane are associated with G1 arrest and mitochondria-dependent apoptosis in human nasopharyngeal carcinoma cells

The antitumor effects of 3,3′-diindolylmethane (DIM) are exhibited in a number of human cancer cells. However, there have been few studies performed concerning the effect of DIM on nasopharyngeal cancer (NPC) cells. In the present study, we examined the in vitro antitumor activity of DIM on the poorly differentiated NPC cell line CNE-2. The potential molecular mechanisms of the activity were also explored. CNE-2 cells were treated with varying concentrations of DIM for different times. Cell proliferation and apoptosis were detected and the molecular mechanisms involved in these effects were characterized. The results demonstrated that DIM at concentrations of 15–100 μM caused dose- and time-dependent inhibition of CNE-2 cell proliferation. Flow cytometry analysis revealed a high sub-G1 cell peak following treatment with DIM, and the rate of apoptosis increased. DIM may elevate the levels of cleaved Bid and Bax and enhance mitochondrial membrane depolarization, allowing the efflux of cytochrome c, Smac and Omi into the cytosol. The levels of caspases-3, -8 and -9 and cleaved poly (ADP-ribose) polymerase (PARP) were upregulated following DIM treatment in a dose-dependent manner. DIM also inhibits the phosphorylation of IκB-α, and showed dose-dependent inhibition of Bcl-2, XIAP and NF-κB in CNE-2 cells in vitro. These results indicate that DIM inhibits cell proliferation by inducing cell cycle arrest at G0/G1 phase and induces the apoptosis of CNE-2 cells by regulating multiple molecules in a mitochondria-dependent pathway. DIM may be a preventive and therapeutic agent against NPC.

3,3'-Diindolylmethane stimulates murine immune function in vitro and in vivo

3,3'-Diindolylmethane (DIM), a major condensation product of indole-3-carbinol, exhibits chemopreventive properties in animal models of cancer. Recent studies have shown that DIM stimulates interferon-gamma (IFN-gamma) production and potentiates the IFN-gamma signaling pathway in human breast cancer cells via a mechanism that includes increased expression of the IFN-gamma receptor. The goal of this study was to test the hypothesis that DIM modulates the murine immune function. Specifically, the effects of DIM were evaluated in a panel of murine immune function tests that included splenocyte proliferation, reactive oxygen species (ROS) generation, cytokine production and resistance to viral infection. DIM was found to induce proliferation of splenocytes as well as augment mitogen- and interleukin (IL)-2-induced splenocyte proliferation. DIM also stimulated the production of ROS by murine peritoneal macrophage cultures. Oral administration of DIM, but not intraperitoneal injection, induced elevation of serum cytokines in mice, including IL-6, granulocyte colony-stimulating factor (G-CSF), IL-12 and IFN-gamma. Finally, in a model of enteric virus infection, oral DIM administration to mice enhanced both clearance of reovirus from the GI tract and the subsequent mucosal IgA response. Thus, DIM is a potent stimulator of immune function. This property might contribute to the cancer inhibitory effects of this indole.