3,3'-Diindolylmethane Exhibits Significant Metabolism after Oral Dosing in Humans

1,4-dihydroxy-2-naphthoic acid prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced motor function deficits

Parkinson's disease (PD), characterized by death of dopaminergic neurons in the substantia nigra, is the second most prevalent progressive neurodegenerative disease. However, the etiology of PD is largely elusive. This study employed the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) rodent model to examine the effectiveness of 1,4-dihydroxy-2-naphthoic acid (1,4-DHNA), an aryl hydrocarbon receptor (AhR) active gut bacteria-derived metabolite, in mitigating MPTP's motoric deficits, and the role of AhR in mediating these effects. Male C57BL/6 mice were fed daily with vehicle, 20 mg/kg 1,4-DHNA, or AhR-inactive isomer 3,7-DHNA, for 3 weeks before administration of 80 mg/kg MPTP or vehicle. Four weeks later, mice were assessed for motoric functions. Both 1,4-DHNA and 3,7-DHNA prevented MPTP-induced deficits in the motor pole test and in the adhesive strip removal test. Additionally, 1,4-DHNA improved balance beam performance and completely prevented MPTP-induced reduction in stride length. In contrast, 3,7-DHNA, an AhR-inactive compound, did not improve balance beam performance and had only a partial effect on stride length. This study suggests that natural metabolites of gut microbiota, such as 1,4-DHNA, could be beneficial to counteract the development of motor deficits observed in PD. Thus, this study further supports the hypothesis that pathological and mitigating processes in the gut could play an essential role in PD development. Moreover, this indicates that 1,4-DHNA's ability to combat various motor deficits is likely mediated via multiple underlying molecular mechanisms. Specifically, AhR is involved, at least partially, in control of gait and bradykinesia, but it likely does not mediate the effects on fine motor skills.

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) induces depression-like phenotype

The etiology of major depressive disorder (MDD) remains poorly understood. Our previous studies suggest a role for the aryl hydrocarbon receptor (AhR) in depression. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a toxic environmental contaminant, with a high AhR binding affinity, and an established benchmark for assessing AhR activity. Therefore, this study examined the effect of TCDD on depression-like behaviors. Female mice were fed standard chow or a high-fat diet (HFD) for 11 weeks, and their weight was recorded. Subsequently, they were tested for baseline sucrose preference and splash test grooming. Then, TCDD (0.1 µg/kg/day) or vehicle was administered orally for 28 days, and mice were examined for their sucrose preference and performances in the splash test, forced swim test (FST), and Morris water maze (MWM) task. TCDD significantly decreased sucrose preference, increased FST immobility time, and decreased groom time in chow-fed mice. HFD itself significantly reduced sucrose preference. However, TCDD significantly increased FST immobility time and decreased groom time in HFD-fed mice. A small decrease in bodyweight was observed only at the fourth week of daily TCDD administration in chow-fed mice, and no significant effects of TCDD on bodyweights were observed in HFD-fed mice. TCDD did not have a significant effect on spatial learning in the MWM. Thus, this study demonstrated that TCDD induces a depression-like state, and the effects were not due to gross lethal toxicity. This study further suggests that more studies should examine a possible role for AhR and AhR-active environmental pollutants in precipitating or worsening MDD.

Protective effect of diindolylmethane-enriched dietary cabbage against doxorubicin-induced cardiotoxicity in mice

Chemotherapy with doxorubicin (Dox) can lead to cardiotoxic effects, presenting a major complication in cancer therapy. Diindolylmethane (DIM), derived from cruciferous vegetables like cabbage, exhibits numerous health benefits. However, its clinical application is limited because of low bioavailability and suboptimal natural concentrations in dietary sources. To address this limitation, we developed a processing methodology, specifically fermentation and boiling, to enhance DIM levels in cabbage. High-performance liquid chromatography (HPLC) analysis revealed a threefold DIM increase in fermented cabbage and a substantial ninefold increase in fermented-boiled cabbage compared to raw cabbage. To evaluate the clinical implications, we formulated a DIM-enriched diet and administered it to mice undergoing Dox treatment. Our in vivo results revealed that Dox treatment led to cardiotoxicity, manifested by changes in body and heart weight, increased mortality, and severe myocardial tissue degeneration. Dietary administration of the DIM-enriched diet enhanced antioxidant defenses and inhibited apoptosis in the cardiac tissue by interfering with mitoptosis and increasing antioxidant enzyme expression. Interestingly, we found that the DIM-enriched diet inhibited the nuclear translocation of NF-kB in cardiac tissue, thereby downregulating the expression of inflammatory mediators such as TNF-α and IL-6. Further, the DIM-enriched diet significantly reduced serum cardiac injury markers elevated by Dox treatment. These results suggest that the DIM-enriched cabbage diet can serve as a complementary dietary intervention for cancer patients undergoing chemotherapy. Further, our research highlights the role of plant-based diets in reducing treatment side effects and improving the quality of life for cancer patients.

Polyphenol and glucosinolate-derived AhR modulators regulate GPR15 expression on human CD4+ T cells

Diets high in fruit and vegetables are perceived to be beneficial for intestinal homeostasis, in health as well as in the context of inflammatory bowel diseases (IBDs). Recent breakthroughs in the field of immunology have highlighted the importance of the ligand-activated transcription factor aryl hydrocarbon receptor (AhR) as a critical regulator of mucosal immunity, including the intestinal trafficking of CD4+ helper T cells, an immune cell subset implicated in a wide range of homeostatic and pathogenic processes. Specifically, the AhR has been shown to directly regulate the expression of the chemoattractant receptor G Protein-Coupled Receptor 15 (GPR15) on CD4+ T cells. GPR15 is an important gut homing marker whose expression on CD4+ T cells in the peripheral circulation is elevated in patients suffering from ulcerative colitis, raising the possibility that, in this setting, the beneficial effect of a diet rich in fruits and vegetables may be mediated through the modulation of GPR15 expression. To address this, we screened physiologically-relevant polyphenol and glucosinolate metabolites for their ability to affect both AhR activity and GPR15 expression. Our complementary approach and associated findings suggest that polyphenol and glucosinolate metabolites can regulate GPR15 expression on human CD4+ T cells in an AhR-dependent manner.

Phytochemicals for the prevention and treatment of pancreatic cancer: Current progress and future prospects

Pancreatic cancer is the third leading cause of cancer-related deaths in the United States, owing to its aggressive nature and suboptimal treatment options, emphasizing the need for novel therapeutic approaches. Emerging studies have exhibited promising results regarding the therapeutic utility of plant-derived compounds (phytochemicals) in pancreatic cancer. The purpose of this review is to evaluate the potential of phytochemicals in the treatment and prevention of pancreatic cancer. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses was applied to collect articles for this review. Scholarly databases, including PubMed, Scopus and ScienceDirect, were queried for relevant studies using the following keywords: phytochemicals, phenolics, terpenoids, alkaloids, sulfur-containing compounds, in vitro, in vivo, clinical studies, pancreatic cancer, tumour, treatment and prevention. Aggregate results pooled from qualified studies indicate phytochemicals can inhibit pancreatic cancer cell growth or decrease tumour size and volume in animal models. These effects have been attributed to various mechanisms, such as increasing proapoptotic factors, decreasing antiapoptotic factors, or inducing cell death and cell cycle arrest. Notable signalling pathways modulated by phytochemicals include the rat sarcoma/mitogen activated protein kinase, wingless-related integration site/β-catenin and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signal transduction pathways. Clinically, phytochemicals have been found to increase survival while being well-tolerated and safe, though research is scarce. While these promising results have produced great interest in this field, further in-depth studies are required to characterize the anticancer activities of phytochemicals before they can be utilized to prevent or treat pancreatic cancer in clinical practice.

Selective aryl hydrocarbon receptor modulators can act as antidepressants in obese female mice

BACKGROUND

Obese females are more likely to suffer from depression and are also more likely to be resistant to current medications. This study examined the potential antidepressant-like effects of 1,4-dihydroxy-2-napthoic acid (DHNA), a selective aryl hydrocarbon receptor modulator (SAhRM), in obese female mice.

METHODS

Obesity was established by feeding C57BL/6N female mice a high fat diet (HFD) for 9-10 weeks. Subsequently, mice were subjected to unpredictable chronic mild stress (UCMS) or remained unstressed. Daily administration of vehicle or 20 mg/kg DHNA began three weeks prior or on the third week of UCMS. Mice were examined for depression-like behaviors (sucrose preference, forced swim test (FST), splash and tape groom tests), anxiety (open-field test, light/dark test, novelty-induced hypophagia), and cognition (object location recognition, novel object recognition, Morris water maze).

RESULTS

UCMS did not alter, and DHNA slightly increased, weight gain in HFD-fed females. HFD decreased sucrose preference, increased FST immobility time, but did not alter splash and tape tests' grooming time. UCMS did not have additional effects on sucrose preference. UCMS further increased FST immobility time and decreased splash and tape tests' grooming time; these effects were prevented and reversed by DHNA treatment. HFD did not affect behaviors in the cognitive tests. UCMS impaired spatial learning; this effect was not prevented nor reversed by DHNA.

CONCLUSIONS

DHNA protected against UCMS-induced depression-like behaviors in HFD-fed female mice. DHNA neither improved nor worsened UCMS-induced impairment of spatial learning. Our findings indicate that DHNA has high potential to act as an antidepressant in obese females.

Intestinal epithelium aryl hydrocarbon receptor is involved in stress sensitivity and maintaining depressive symptoms

The aryl hydrocarbon receptor (AhR) is a key regulator in the microbiome-gut-brain axis, and AhR-active microbial metabolites modulate multiple neuronal responses. We recently demonstrated that 3,3'-diindolylmethane (DIM) and 1,4-dihydroxy-2-naphthoic acid (DHNA), two selective AhR modulators (SAhRMs), act as antidepressants in female mice. Thus, to examine the role of intestinal AhR in depression, anxiety, and spatial learning, this study employed transgenic mice in which the AhR was knockout only in the intestinal epithelium (AhRΔIEC). Additionally, this study examined whether the antidepressant effects of dietary DIM and DHNA is mediated by intestinal AhR. AhRΔIEC and WT female mice were fed daily with vehicle, 20 mg/kg DIM or DHNA for three weeks prior to four weeks of unpredictable chronic mild stress (UCMS). Mice were examined for weight gain, anhedonia-like behavior (sucrose preference test), anxiety levels (open field, light/dark, elevated plus maze, novelty-induced hypophagia, and marble burying tests), and spatial learning (Morris water maze). UCMS reduced weight gain in AhRΔIECs, but not WTs. Moreover, UCMS initially reduced sucrose preference in both AhRΔIECs and WTs, but over 4 weeks of UCMS, AhRΔIECs develop resilience to UCMS-induced anhedonia. Additionally, AhRΔIECs exhibit slightly reduced anxiety in certain tests and faster spatial learning. DIM and DHNA acted as antidepressants in both AhRΔIECs and WTs. Thus, this study suggests that intestinal AhR plays differential roles, mitigating stress effects on weight gain, and increasing stress effects on mood. However, the site of antidepressant action of SAhRMs, such as DIM and DHNA, is not dependent on the expression of intestinal AhR.

Benzo[a]pyrene toxicokinetics in humans following dietary supplementation with 3,3'-diindolylmethane (DIM) or Brussels sprouts

Utilizing the atto-zeptomole sensitivity of UPLC-accelerator mass spectrometry (UPLC-AMS), we previously demonstrated significant first-pass metabolism following escalating (25-250 ng) oral micro-dosing in humans of [14C]-benzo[a]pyrene ([14C]-BaP). The present study examines the potential for supplementation with Brussels sprouts (BS) or 3,3'-diindolylmethane (DIM) to alter plasma levels of [14C]-BaP and metabolites over a 48-h period following micro-dosing with 50 ng (5.4 nCi) [14C]-BaP. Volunteers were dosed with [14C]-BaP following fourteen days on a cruciferous vegetable restricted diet, or the same diet supplemented for seven days with 50 g of BS or 300 mg of BR-DIM® prior to dosing. BS or DIM reduced total [14C] recovered from plasma by 56-67% relative to non-intervention. Dietary supplementation with DIM markedly increased Tmax and reduced Cmax for [14C]-BaP indicative of slower absorption. Both dietary treatments significantly reduced Cmax values of four downstream BaP metabolites, consistent with delaying BaP absorption. Dietary treatments also appeared to reduce the T1/2 and the plasma AUC(0,∞) for Unknown Metabolite C, indicating some effect in accelerating clearance of this metabolite. Toxicokinetic constants for other metabolites followed the pattern for [14C]-BaP (metabolite profiles remained relatively consistent) and non-compartmental analysis did not indicate other significant alterations. Significant amounts of metabolites in plasma were at the bay region of [14C]-BaP irrespective of treatment. Although the number of subjects and large interindividual variation are limitations of this study, it represents the first human trial showing dietary intervention altering toxicokinetics of a defined dose of a known human carcinogen.

Sex-dependent differences in the stress mitigating and antidepressant effects of selective aryl hydrocarbon receptor modulators

BACKGROUND

Our recent study demonstrated that selective aryl hydrocarbon receptor modulators (SAhRMs), such as 1,4-dihydroxy-2-napthoic acid (DHNA) act as antidepressants in female mice. Given that some effects of certain SAhRMs are known to also be mediated via estrogen receptor signaling, this study examined whether the effects of SAhRMs on mood, emotional state, and cognition are sex-dependent.

METHODS

C57BL/6N mice were fed with vehicle or 20 mg/kg DHNA for three weeks prior to four weeks of unpredictable chronic mild stress (UCMS). Mice were examined for depression-like behaviors (sucrose preference, forced swim test (FST), splash test, tape groom test), emotional state (open-field test, light/dark test, marble burying, novelty-induced hypophagia, elevated-plus maze), and cognition (object location recognition, novel object recognition, Morris water maze).

RESULTS

In females, UCMS decreased sucrose preference and increased FST immobility time; both effects were prevented by DHNA. In males, UCMS increased FST immobility time, and increased the latency to groom in the splash test. These effects were not mitigated by DHNA. However, in males, UCMS induced an increase in novelty-induced locomotion, an increase in the time spent in the light compartment in the L/D test, and an increase in the time spent with an object in a novel location. These effects were prevented by DHNA.

CONCLUSIONS

Our findings indicate that DHNA has high potential to act as antidepressants in females. However, given classical interpretation, DHNA did not appear to act as an antidepressant in males. Nonetheless, our findings indicate that DHNA can mitigate stress effects and reactivity in males.

3,3'-Diindolylmethane and 1,4-dihydroxy-2-naphthoic acid prevent chronic mild stress induced depressive-like behaviors in female mice

BACKGROUND

Current pharmaceutical treatments for depression are sometimes ineffective and may have unwanted side effects that interfere with patient compliance. This study examined the potential antidepressant-like effects of dietary- and microbial-derived aryl hydrocarbon receptor (AhR) ligands, 3,3'-diindolylmethane (DIM) and 1,4-dihydroxy-2-naphthoic acid (1,4-DHNA).

METHODS

Female C57BL/6 mice were subjected to unpredictable chronic mild stress (UCMS) or were unstressed. For three weeks prior to UCMS mice were fed daily with vehicle or 20 mg/kg DIM, 1,4-DHNA or AhR-inactive isomer 3,7-DHNA; another group was subjected to two weeks UCMS before ligand administration began. Mice were examined for anhedonia-like behavior as measured by the sucrose preference test. Additionally, anxiety levels of the mice were examined before UCMS and ligand administration began and at the end in the open field, light/dark, elevated plus maze, novelty-induced hypophagia, and marble burying tests. At the end of the experiment they were also examined in the Morris water maze (MWM) task.

RESULTS

Both DIM and 1,4-DHNA, but not 3,7-DHNA, successfully prevented and reversed UCMS-induced anhedonia-like behavior. Furthermore, both DIM and DHNA had little to no effect on anxiety levels and did not induce spatial learning deficits.

LIMITATIONS

Additional studies are required to determine to what degree the antidepressant-like effects of DIM and 1,4-DHNA can be attributed to their activities as AhR ligands.

CONCLUSIONS

Our findings indicate that dietary and microbial-derived AhR ligands may have clinical applications as potential antidepressants. Future studies are necessary to elucidate the role of AhR in depression-like states and the underlying mechanisms of action.

Indoles Derived From Glucobrassicin: Cancer Chemoprevention by Indole-3-Carbinol and 3,3'-Diindolylmethane

Hydrolysis of glucobrassicin by plant or bacterial myrosinase produces multiple indoles predominantly indole-3-carbinol (I3C). I3C and its major in vivo product, 3,3'-diindolylmethane (DIM), are effective cancer chemopreventive agents in pre-clinical models and show promise in clinical trials. The pharmacokinetics/pharmacodynamics of DIM have been studied in both rodents and humans and urinary DIM is a proposed biomarker of dietary intake of cruciferous vegetables. Recent clinical studies at Oregon State University show surprisingly robust metabolism of DIM in vivo with mono- and di-hydroxylation followed by conjugation with sulfate or glucuronic acid. DIM has multiple mechanisms of action, the most well-characterized is modulation of aryl hydrocarbon receptor (AHR) signaling. In rainbow trout dose-dependent cancer chemoprevention by dietary I3C is achieved when given prior to or concurrent with aflatoxin B1, polycyclic aromatic hydrocarbons, nitrosamines or direct acting carcinogens such as N-methyl-N'-nitro-nitrosoguanidine. Feeding pregnant mice I3C inhibits transplacental carcinogenesis. In humans much of the focus has been on chemoprevention of breast and prostate cancer. Alteration of cytochrome P450-dependent estrogen metabolism is hypothesized to be an important driver of DIM-dependent breast cancer prevention. The few studies done to date comparing glucobrassicin-rich crucifers such as Brussels sprouts with I3C/DIM supplements have shown the greater impact of the latter is due to dose. Daily ingestion of kg quantities of Brussels sprouts is required to produce in vivo levels of DIM achievable by supplementation. In clinical trials these supplement doses have elicited few if any adverse effects. Sulforaphane from glucoraphanin can act synergistically with glucobrassicin-derived DIM and this may lead to opportunities for combinatorial approaches (supplement and food-based) in the clinic.