Indole-3-Carbinol (I3C)

Klebsiella pneumoniae (K. pneumoniae), a major hospital-acquired infection, poses a significant threat to life and global public health. Indole compounds have been found to affect bacterial growth through multiple metabolic pathways, but the mechanism is unclear. To investigate the combination of indole-3-carbinol (I3C) and polymyxin B (PMNB) as a new strategy to combat bloodstream infections caused by K. pneumoniae. The antibacterial synergy between I3C and PMNB was comprehensively assessed both in vitro and in vivo through a variety of methods including drug sensitivity tests, checkerboard assays, time-kill curves, growth curves, and a murine bloodstream infection model. Furthermore, the mechanisms underpinning the synergistic antibacterial effects of I3C as an adjuvant to PMNB were explored and substantiated via cell morphology studies, reactive oxygen species (ROS) analysis, efflux pump activity assays, and transcriptomic analyses. When combined with PMNB, I3C exhibited synergistic antibacterial effects in vitro, affecting cell morphology and ROS production. Moreover, this combination significantly enhanced outcomes in a murine model of K. pneumoniae infection, evidenced by increased survival rates, recovery of body weight, reduced bacterial loads, and diminished pathological damage. Additionally, I3C influenced the lipid metabolism pathways of K. pneumoniae and altered the structure of the cellular membrane. This investigation evaluates the synergistic antibacterial properties of I3C and PMNB as adjuvants and offers a detailed analysis of their capacity to augment the bactericidal efficacy of PMNB by modulating bacterial lipid metabolism. This work provides a solid research foundation for managing K. pneumoniae infections in clinical practice.

The purpose of this study was to evaluate the antimicrobial activity of indole-3-carbinol (I3C) with membrane-active agents, namely carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and ethylenediaminetetraacetic acid (EDTA) against multidrug-resistant (MDR) Gram-negative bacteria and bacterial persisters. The determination of minimal inhibitory concentration (MIC) showed that I3C was effective against Acinetobacter baumannii (3.13‒6.25 × 10-3 mol l-1), Klebsiella pneumoniae (8 × 10-3 mol l-1), Pseudomonas aeruginosa (6.25‒12.5 × 10-3 mol l-1), and Escherichia coli (6.25‒12.5 × 10-3 mol l-1). Our study demonstrated that EDTA synergistically enhanced the bactericidal activity of I3C against most MDR Gram-negative bacteria isolates and contributed to an 8- to 64-fold MIC reduction compared with that of I3C alone, yet CCCP only displayed synergy with I3C against P. aeruginosa and A. baumannii. The EDTA-I3C combination also significantly reduced the viable number of testing bacteria (P = 7.2E-05), effectively reduced bacterial persisters, and repressed bacterial growth compared with that the use of I3C alone. Our data demonstrate that use of EDTA as adjuvant molecules can effectively improve the antibacterial activity of I3C and may help to reduce the development of antimicrobial resistance. © The Author(s) 2023. Published by Oxford University Press on behalf of Applied Microbiology International.

Phytochemicals such as phenethyl isothiocyanate (PEITC), indole-3-carbinol (I3C), xanthohumol (XAN), and resveratrol (RES) have been shown to target signaling pathways that are involved in the proliferation and survival of different pancreatic cancer (PC) cell lines. While the activity of these compounds alone was extensively studied, their combinations were never assessed. Thus, the aim of this study was to evaluate and compare the effect of PEITC, I3C, XAN, and RES and their combinations on the expression and activation of NF-κB and Nrf2 in human PC cell line PANC-1. The combination of XAN and PEITC was more efficient than the single compounds in reducing the binding of NF-κB p65 subunits to DNA by 47-60% and expression of p65 gene by 28-48%. The combination of XAN and PEITC also enhanced the activation and expression of Nrf2 and subsequently the expression of GSTP, NQO1, and SOD genes which are controlled by this transcription factor. Modulation of the activity of NF-κB and Nrf2 by the combination of XAN and PEITC was found to lead to reduced proliferation of PANC-1 cells. These results suggest that the combination of XAN and PEITC might be considered as a novel strategy for the prophylaxis and/or treatment of PC.

1. Humans and animals are commonly exposed to indole-3-carbinol (I3C) and resveratrol (RES) via food or beverages. Moreover, these compounds have been demonstrated to potentially cause food-drug interactions. However, information about their combined effects is limited. Therefore, we investigated the effects of I3C and RES, both as single compounds and in combination, on cytochrome P450 1A and 3A activity and gene expression. 2. Using porcine microsomes, we demonstrated that RES caused non-competitive inhibition of CYP1A activity and un-competitive inhibition of CYP3A activity. Compared to the effect of single compounds, co-treatment with I3C and RES increased a degree of inhibition of CYP1A activity. 3. In porcine primary hepatocytes, treatment with I3C and RES resulted in induction of CYP1A1, CYP1A2 and CYP3A29 mRNA expression. 4. In conclusion, we demonstrated that both RES and I3C could cause food-drug interactions and that the combined effect could be more potent in doing so.

Sorafenib is the only chemotherapeutic agent currently approved for unresectable hepatocellular carcinoma (HCC). However, poor response rates have been widely reported. Indole-3-carbinol (I3C) is a potential chemopreventive phytochemical. The present study aimed to explore the potential chemomodulatory effects of I3C on sorafenib in HCC cells as well as the possible underlying mechanisms. I3C exhibited a greater cytotoxicity in HepG2 cells compared to Huh-7 cells (p < 0.0001). Moreover, the co-treatment of HepG2 cells with I3C and sorafenib was more effective (p = 0.002). Accordingly, subsequent mechanistic studies were carried on HepG2 cells. The results show that the ability of I3C to enhance sorafenib cytotoxicity in HCC cells could be partially attributed to increasing the apoptotic activity and decreasing the angiogenic potentials. The combination had a negative effect on epithelial-mesenchymal transition (EMT). Increased NOX-1 expression was also observed which may indicate the involvement of NOX-1 in I3C chemomodulatory effects. Additionally, the combination induced cell cycle arrest at the G0/G1 phase. In conclusion, these findings provide evidence that I3C enhances sorafenib anti-cancer activity in HCC cells.

Antiproliferative signaling of combinations of the nonsteroidal anti-inflammatory drug acetylsalicylic acid (aspirin) and indole-3-carbinol (I3C), a natural indolecarbinol compound derived from cruciferous vegetables, was investigated in human melanoma cells. Melanoma cell lines with distinct mutational profiles were sensitive to different extents to the antiproliferative response of aspirin, with oncogenic BRAF-expressing G361 cells and wild-type BRAF-expressing SK-MEL-30 cells being the most responsive. I3C triggered a strong proliferative arrest of G361 melanoma cells and caused only a modest decrease in the proliferation of SK-MEL-30 cells. In both cell lines, combinations of aspirin and I3C cooperatively arrested cell proliferation and induced a G1 cell cycle arrest, and nearly ablated protein and transcript levels of the melanocyte master regulator microphthalmia-associated transcription factor isoform M (MITF-M). In melanoma cells transfected with a -333/+120-bp MITF-M promoter-luciferase reporter plasmid, treatment with aspirin and I3C cooperatively disrupted MITF-M promoter activity, which accounted for the loss of MITF-M gene products. Mutational analysis revealed that the aspirin required the LEF1 binding site, whereas I3C required the BRN2 binding site to mediate their combined and individual effects on MITF-M promoter activity. Consistent with LEF1 being a downstream effector of Wnt signaling, aspirin, but not I3C, downregulated protein levels of the Wnt co-receptor LDL receptor-related protein-6 and β-catenin and upregulated the β-catenin destruction complex component Axin. Taken together, our results demonstrate that aspirin-regulated Wnt signaling and I3C-targeted signaling pathways converge at distinct DNA elements in the MITF-M promoter to cooperatively disrupt MITF-M expression and melanoma cell proliferation.

Doxorubicin (DOX) is a broad-spectrum antitumor antibiotic used in treatment of cancer. Its effect may be complicated by increased risk of cardiotoxicity. It was suggested that natural compounds with anticancer properties can be used in combination with DOX to decrease its dose and side effects. Indole-3-carbinol (I3C) is one of the phytochemicals that was shown to have anti-cancer effect. Our aim was to detect the possible chemosensitizing effects of I3C in DOX-induced cytotoxicity and the possible cardioprotective effects of I3C in DOX-induced cardiotoxicity. One hundred mice were divided into five equal groups: Control untreated group, solid Ehrlich carcinoma (SEC), SEC + DOX, SEC + I3C, SEC + DOX + I3C. Tumor volume, serum creatinine kinase and lactate dehydrogenase were measured. Also, tissue malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), sphingosine kinase-1 (SphK1) activity and interleukin-6 (IL-6) were determined. Parts of the tumor and cardiac tissues were subjected to histopathological examination. DOX or I3C alone or in combination induced significant increase in tumor CAT and SOD with significant decrease in tumor volume, tumor MDA, SphK1 activity and IL-6 and alleviated the histopathological changes with significant increase in the apoptotic index and significant decrease in tissue bcl2 compared to SEC group. Also, DOX induced cardiotoxicity which was ameliorated by I3C. In conclusion, DOX/I3C combination had a better effect than each of DOX or I3C alone against SEC in mice with marked improvement of the cardiotoxicity induced by DOX.

PURPOSE: Chronic lymphocytic leukemia (CLL) still is lacking a cure. Relapse and development of refractoriness to current treatments are common. New therapies are needed to improve patient prognosis and survival. EXPERIMENTAL DESIGN: Indole-3-carbinol (I3C) is a natural product with antitumor properties already clinically tested. The effect of I3C, F-ara-A, and combinations of both drugs on CLL cells from patients representing different Rai stages, IGHV mutation status, cytogenetic alterations, p53 functionality, and treatment resistances was tested, as well as the toxicity of these treatments in mice. RESULTS: I3C induces cytotoxicity in CLL cells but not in normal lymphocytes. I3C strongly synergized with F-ara-A in all CLL cells tested, including those with p53 deficiency and/or F-ara-A resistance. The mechanism of cell death involved p53-dependent and -independent apoptosis. The combination of I3C + F-ara-A was equally effective in CLL cells irrespective of IGHV mutation stage and patient refractoriness. Moreover, CLL survival and treatment resistance induced by co-culturing CLL cells on stroma cells were overcome by the combinatory I3C + F-ara-A treatment. No toxicity was associated with the combined I3C + fludarabine treatment in mice. CONCLUSIONS: I3C in combination with F-ara-A is highly cytotoxic in CLL cells from refractory patients and those with p53 deficiency. The striking dose reduction index for F-ara-A in combination with I3C would reduce fludarabine toxicity while having a similar or better anti-CLL effectiveness. Moreover, the low toxicity of I3C, already clinically tested, supports its use as adjuvant and combinatory therapy in CLL, particularly for patients with relapsed or refractory disease. ©2015 American Association for Cancer Research.

Natural products such as aromatase inhibitors have been the object of growing attention in recent years because of their potential to inhibit aromatase with fewer side effects and the possible translation of their current use as chemotherapeutic agents to future clinical applications in breast cancer chemoprevention. We have previously investigated CTet, a novel anticancer agent obtained from the broccoli-derived compound indole-3- carbinol (I3C), that shows great anticancer potential in both in vitro and in vivo studies. Here we evaluated the potential of CTet as a chemopreventive agent in aromatase expressing MCF-7/AROM-1 breast cancer cells. The testosterone (TE) aromatization in estradiol (E2) was indirectly evaluated in terms of inhibition of TE-induced cell proliferation, ERα phosphorylation/activation and Bcl-2 and IGF-1R ERE-regulated protein accumulation. Our results showed that CTet inhibited TE-driven ERα phosphorylation of both cytosolic and nuclear ERα pools, suggesting an inhibitory effect of TE aromatization in E2. CTet did not inhibit E2-driven nuclear ERα phosphorylation, but partially inhibited E2-driven cytosolic ERα phosphorylation. Moreover, CTet inhibited Bcl-2 and IGF-1R accumulation induced by TE but not that which was induced by E2. A cell-free enzymatic assay showed that CTet did not inhibit aromatase activity directly; however, since CTet treatment induced endoplasmic reticulum stress, the TE aromatization could be affected because the aromatase enzyme is located within the endoplasmic reticulum. Finally, CTet and letrozole synergistically inhibited TE-induced cell proliferation. These results showed the potential of the I3C derivative CTet as a chemopreventive agent that interferes with aromatase activity.

Epidemiological studies suggest that high intake of cruciferous vegetables is associated with a lower risk of cancer. Experiments have shown that indole-3-carbinol (I3C), a naturally occurring compound derived from cruciferous vegetables, exhibits potent anticarcinogenic properties in a wide range of cancers. In this study, we showed that higher doses of I3C (≥400 μM) induced apoptotic cancer cell death and lower doses of I3C (≤200 μM) repressed cancer cell growth concurrently with suppressed expression of cyclin E and its partner CDK2. Notably, we found that pretreatment with low doses of I3C enhanced Ad-mediated oncolysis and cytotoxicity of human carcinoma cells by synergistic upregulation of apoptosis. Thus, the vegetable compound I3C as a dietary supplement may benefit cancer prevention and improve Ad oncolytic therapies.