5-7-dihydroxy-6-methoxy-2-phenylchromen-4-one and Colonic-Neoplasms

Dietary fiber intake helps to maintain gut homeostasis. Fiber deficiency causes commensals to utilize mucins as an energy source to destroy mucus layer, thus promoting susceptibility to inflammatory bowel disease. Here, we reported that oroxylin A, a natural flavonoid, ameliorated low-grade colonic inflammation caused by fiber deficiency, alleviated colitis, and further prevented colitis-associated colon cancer in mice. The anti-inflammatory effect of oroxylin A was due to its alteration of gut microbiota. We found that the levels of Eubacterium coprostanoligenes was significantly increased by oroxylin A and the colonized Eubacterium coprostanoligenes significantly protected against colitis and carcinogenesis in colon of mice. Together, our results in this study suggest that oroxylin A may reduce the susceptibility to intestinal diseases by increasing the level of Eubacterium coprostanoligenes which could provide a therapeutic alternation for the treatment of intestinal diseases.

Topics: Animals; Colitis; Colon; Colonic Neoplasms; Dietary Fiber; Disease Susceptibility; Female; Flavonoids; Gastrointestinal Microbiome; Inflammation; Inflammatory Bowel Diseases; Intestinal Mucosa; Mice; Mice, Inbred C57BL

Oroxylin A is a flavonoid extracted from the root of Scutellaria baicalensis Georgi. We previously demonstrated that oroxylin A induced apoptosis in human colon cancer cells via the mitochondrial pathway. In the present study, we investigated the underlying mechanisms responsible for the mitochondrial apoptotic pathway triggered by oroxylin A. p53 regulates mitochondrial survival, mitochondrial DNA integrity, and protection from oxidative stress. We determined that oroxylin A induces p53 mitochondrial translocation and inhibits SOD2 activity. Additionally, our studies demonstrate that oroxylin A promotes the formation and mitochondrial translocation of the p53-Recql4 complex in HCT-116 cells. Finally, we showed that oroxylin A triggers cytosolic p53 activation, thereby promoting apoptosis. Mitochondrial translocation of p53 was also validated in vivo. Thus, oroxylin A induces mitochondrial translocation of p53 and leads to mitochondrial dysfunction in human colon cancer cells.

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Cell Line, Tumor; Colonic Neoplasms; Flavonoids; Heterografts; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Mitochondria; Protein Transport; Tumor Suppressor Protein p53

Oroxylin A is a flavonoid extracted from the root of Scutellaria baicalensis Georgi. Our previous research demonstrated that oroxylin A have various anti-tumor effects including apoptosis, cell cycle arrest, drug-resistant reversion, and others. This paper explores the mechanism how oroxylin A induce apoptosis by regulating uncoupling protein 2 (UCP2) in human colon cancer cells. We found that the inhibition of UCP2 by UCP2 siRNA significantly increased the sensitivity of cells to drugs, reactive oxygen species (ROS) generation and the opening of mitochondrial permeability transition pore (MPTP) of CaCo-2 cells. We also found that UCP2 inhibition could lead to ROS-mediated MPTP activation. Furthermore, we demonstrated that oroxylin A triggered MPTP-dependent pro-apoptotic protein release from mitochondria to matrix and then induced apoptotic cascade by inhibiting UCP2. Intriguingly, the inhibition of UCP2 by oroxylin A was able to block Bcl-2 translocation to the mitochondria, keeping MPTP at open-state. In conclusion, we have demonstrated that UCP2 plays a key role in mitochondrial apoptotic pathway; UCP2s inhibition by oroxylin A triggers the MPTP opening, and promotes the apoptosis in CaCo-2 cells.

Topics: Apoptosis; Caco-2 Cells; Colonic Neoplasms; Doxorubicin; Drug Screening Assays, Antitumor; Flavonoids; HCT116 Cells; Humans; Ion Channels; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Mitochondrial Proteins; Protein Transport; Proto-Oncogene Proteins c-bcl-2; Reactive Oxygen Species; Signal Transduction; Uncoupling Protein 2

Patients with inflammatory bowel disease, which includes ulcerative colitis and Crohn's disease, are at a significantly increased risk of developing colorectal cancer, and aberrant interleukin (IL)-6/STAT3 signaling pathway exists in both inflammatory bowel disease and inflammation-related gastrointestinal cancers. We have previously found that oroxylin A inhibited the NF-κB signaling in human colon tumor HCT-116 cells. However, whether oroxylin A could inhibit the colitis-associated carcinogenesis remains to be determined.. HCT-116 cells were treated with various concentrations of oroxylin A. Expression of relative proteins of IL-6/STAT3 signaling pathway was assayed by Western blot and immunofluorescence analysis. Mouse model for colitis-associated colorectal cancer was induced by a combined treatment with 10 mg/kg azoxymethane (AOM) followed by 3 cycles of 2.5% dextran sodium sulfate in C57BL/6 mice. IL-6 and IL-1β gene expression were analyzed by quantitative real-time PCR. Expression of relative proteins was examined by immunohistochemistry and Western blot.. Oroxylin A effectively inhibited IL-6/STAT3 pathway in human HCT-116 cells, and the effect of oroxylin A was reversible. Dietary administration of oroxylin A throughout the experimental period significantly reduced the tumor burden, inhibited cell proliferation, and induced apoptosis in colon carcinomas. The expression of inflammatory cytokines IL-6 and IL-1β decreased in tumors in oroxylin A-treated mice. The IL-6/STAT3 signaling pathway was attenuated in oroxylin A-treated mice.. Our results demonstrated that oroxylin A inhibits colitis-associated carcinogenesis through modulating IL-6/STAT3 pathway in AOM/dextran sodium sulfate mouse model and in HCT-116 cells.

Topics: Animals; Azoxymethane; Blotting, Western; Carcinogens; Cell Transformation, Neoplastic; Colitis; Colonic Neoplasms; Dextran Sulfate; Female; Flavonoids; Fluorescent Antibody Technique; Humans; Immunoenzyme Techniques; Interleukin-6; Male; Mice; Mice, Inbred C57BL; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; STAT3 Transcription Factor

5-Fluorouracil (5-FU) is a principal drug for the treatment of colorectal cancer. Due to its low response and high toxicity, synergistic effects of 5-FU in combination with other drugs have been widely researched. This study investigated whether oroxylin A improved the sensitivity of HT-29 human colon cancer cells to 5-FU. A correlation between COX-2 inhibition by oroxylin A and a synergistic effect of 5-FU on the growth of HT-29 cells was observed, and a COX-2 pathway for this effect was recognized; oroxylin A evidently elevated the level of reactive oxygen species in HT-29 cells, which subsequently inhibited COX-2 expression and enhanced the susceptibility of HT-29 cells to 5-FU. Likely also related to COX-2 inhibition, oroxylin A decreased PGE(2) levels in HT-29 cells. The synergistic effect of 5-FU induced by oroxylin A was also found in the suppression of Bcl-2 and in the activation of P53, Bax, PARP, and procaspase-3 proteins in HT-29 cells. Ultimately, a combination of 5-FU with oroxylin A significantly reduced the growth of HT-29 tumors in nude mice compared with treatment with 5-FU or oroxylin A alone. In conclusion, a combination of 5-FU and oroxylin A has a significant synergistic effect in the inhibition of HT-29 cell proliferation in vitro and controls HT-29 tumor growth in vivo. This synergistic effect may be mainly related to COX-2 inhibition by oroxylin A in HT-29 cells.

Topics: Animals; Antimetabolites, Antineoplastic; Apoptosis; Colonic Neoplasms; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Drug Synergism; Female; Flavonoids; Fluorouracil; HT29 Cells; Humans; Mice; Mice, Nude; Signal Transduction