Brusatol induces ferroptosis to inhibit hepatocellular carcinoma progression by targeting ATF3.

Ferroptosis is a novel form of programmed cell death that is triggered by iron-dependent lipid peroxidation. Brusatol (BRU), a natural nuclear factor erythroid 2-related factor 2 inhibitor, exhibits potent anticancer effects in various types of cancer. However, the exact mechanism of BRU in the treatment of hepatocellular carcinoma (HCC) remains unknown. The anticancer effects of BRU in HCC were detected using cell counting kit-8 and colony formation assays and a xenograft model. RNA sequencing (RNA-seq) and bioinformatics analyses of HCC cells were utilized to elucidate the mechanism underlying the effects of BRU in HCC. The levels of reactive oxygen species (ROS), glutathione (GSH), malondialdehyde (MDA), and Fe2+ were measured using assay kits. The expression of activating transcription factor 3 (ATF3) was tested using RT-qPCR, western blotting, and immunofluorescence staining. The role of ATF3 in BRU-induced ferroptosis was examined using siATF3. BRU significantly inhibited HCC cell proliferation, both in vitro and in vivo. BRU activated the ferroptosis signaling pathway and increased ATF3 expression. Furthermore, ATF3 knockdown impeded BRU-induced ferroptosis. BRU suppressed HCC growth through ATF3-mediated ferroptosis, supporting BRU as a promising therapeutic agent for HCC.

The Nrf2/HO-1 pathway participates in the antiapoptotic and anti-inflammatory effects of platelet-rich plasma in the treatment of osteoarthritis.

INTRODUCTION: We aimed to explore the molecular mechanisms through which platelet-rich plasma (PRP) attenuates osteoarthritis (OA)-induced pain, apoptosis, and inflammation. METHODS: An in vivo model of OA was established by injuring rats using the anterior cruciate ligament transection method, whereas an in vitro model was generated by exposing chondrocytes to interleukin (IL)-1ß. Both models were then treated with PRP. RESULTS: In both the in vivo and in vitro models, OA led to the suppression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway, whereas treatment with PRP reactivated this molecular axis. Inhibition of the Nrf2/HO-1 pathway using the Nrf2 inhibitor brusatol or through Nrf2 gene silencing counteracted the effects of PRP in reducing the tenderness and thermal pain thresholds of OA rats. Additionally, PRP reduced the mRNA expression of IL-1ß, IL-6, tumor necrosis factor-alpha (TNF-α), and matrix metallopeptidase 13 (MMP-13) and the protein expression of B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X-protein (Bax), and caspase-3. Furthermore, inflammation and apoptosis were induced by brusatol treatment or Nrf2 silencing. Additionally, in the in vitro model, PRP treatment increased the proliferation of chondrocytes and attenuated their inflammatory response and apoptosis, effects that were abrogated by Nrf2 depletion. CONCLUSIONS: The Nrf2/HO-1 pathway participates in the PRP-mediated attenuation of OA development by suppressing inflammation and apoptosis.

Modulators of the Nrf2 Signaling Pathway Enhance the Cytotoxic Effect of Standard Chemotherapeutic Drugs on Organoids of Metastatic Colorectal Cancer.

The activity of known modulators of the Nrf2 signaling pathway (bardoxolone and brusatol) was studied on cultures of tumor organoids of metastatic colorectal cancer previously obtained from three patients. The effect of modulators was studied both as monotherapy and in combination with standard chemotherapy drugs used to treat colorectal cancer. The Nrf2 inhibitor brusatol and the Nrf2 activator bardoxolone have antitumor activity. Moreover, bardoxolone and brusatol also significantly enhance the effect of the chemotherapy drugs 5-fluorouracil, oxaliplatin, and irinotecan metabolite SN-38. Thus, bardoxolone and brusatol can be considered promising candidates for further preclinical and clinical studies in the treatment of colorectal cancer.

Bruceantinol targeting STAT3 exerts promising antitumor effects in in vitro and in vivo osteosarcoma models.

Bruceantinol (BOL) is a quassinoid compound found in the fruits of Brucea javanica. Previous research has highlighted the manifold physiological and pharmacological activities of BOL. Notably, BOL has demonstrated antitumor cytotoxic and antibacterial effects, lending support to its potential as a promising therapeutic agent for various diseases. Despite being recognized as a potent antitumor inhibitor in multiple cancer types, its efficacy against osteosarcoma (OS) has not been elucidated. In this work, we investigated the antitumor properties of BOL against OS. Our findings showed that BOL significantly decreased the proliferation and migration of OS cells, induced apoptosis, and caused cell death without affecting the cell cycle. We further confirmed that BOL potently suppressed tumor growth in vivo. Mechanismly, we discovered that BOL directly bound to STAT3, and prevent the activation of STAT3 signaling at low nanomolar concentrations. Overall, our study demonstrated that BOL potently inhibited the growth and metastasis of OS, and efficiently suppressed STAT3 signaling pathway. These results suggest that BOL could be a promising therapeutic candidate for OS.

Brusatol: A potential sensitizing agent for cancer therapy from Brucea javanica.

Cancer is currently the most important problem endangering human health. As antitumor drugs have always been the most common methods for treating cancers, searching for new antitumor agents is of great significance. Brusatol, a quassinoid from the seeds of Brucea javanica, exhibits a potent tumor-suppressing effect with improved disease outcome. Studies have shown that brusatol not only shows potential tumor inhibition through multiple pharmacological effects, such as promoting apoptosis and inhibiting metastasis but also exhibits significant synergistic antitumor effects in combination with chemotherapeutic agents and overcoming chemical resistance in a wide range of cancer types. In this paper, the antitumor effects and mechanisms of brusatol were reviewed to provide evidence that brusatol has the exact antitumor efficacy of chemotherapeutic agents and show the potential of brusatol to be developed as a promising antitumor drug.

Brucein D augments the chemosensitivity of gemcitabine in pancreatic cancer via inhibiting the Nrf2 pathway.

BACKGROUND: Gemcitabine (GEM) is the first-line chemotherapeutic drug used to treat pancreatic ductal adenocarcinoma carcinoma (PDAC), but chemoresistance is often encountered clinically. Nrf2, an oxidative stress responsive transcription factor, is an important contributor to chemoresistance and poor prognosis of PDAC. Brucein D (BD), a naturally occurring quassinoid, has been reported to exert anti-tumor effect in several cancers including PDAC. In this study, we aimed to investigate the efficacy of BD and the role of Nrf2 axes on the chemosensitivity of GEM and elucidate the underlying molecular mechanisms. METHODS: Analyses of clinical samples of PDAC and GEPIA database were first conducted to identify the expression of Nrf2 in PDAC. We then established cell lines with stable deletion of Nrf2 through transfecting lentivirus into PDAC cells. Quantitative real-time PCR (qRT-PCR) and Western blotting were performed to determine the expression of Nrf2 in these cell lines. The effects of BD and Nrf2 axes on PDAC cell proliferation, colony-formation, tumor growth and chemosensitivity were determined both in vitro and in vivo. Orthotopic xenograft and genetically engineered KPC mouse models of PDAC were used to evaluate the anti-pancreatic cancer effects of BD and GEM. RESULTS: Nrf2 was highly expressed in PDAC in the clinical samples and GEPIA analysis. Gain- and lost-function study demonstrated that Nrf2 affected the chemosensitivity of GEM on PDAC cells both in vitro and in vivo. We further found that BD effectively inhibited PDAC cell proliferation and enhanced the chemosensitivity of GEM. Mechanistic studies revealed that BD sensitized GEM in PDAC cells through the ubiquitin-proteasome-dependent degradation of Nrf2, and downregulating the Nrf2 pathway. Silencing of Nrf2 plus BD treatment resulted in more potent inhibitory effects of GEM. In contrast, Nrf2 activation attenuated the chemosensitivity of GEM, indicating that the action of BD was Nrf2 dependent. Finally, the efficacy of BD alone and in combination with GEM on PDAC was validated on both orthotopic xenograft and genetically engineered KPC mouse models. CONCLUSIONS: BD was able to enhance the chemosensitivity of GEM in PDAC through inhibition of the Nrf2 pathway. Our experimental findings indicate that BD, a potent Nrf2 inhibitor, holds promise for further development into a novel adjuvant therapy for PDAC.

Brusatol has therapeutic efficacy in non-small cell lung cancer by targeting Skp1 to inhibit cancer growth and metastasis.

Skp1-Cul1-F-box protein (SCF) ubiquitin E3 ligases play important roles in cancer development and serve as a promising therapeutic target in cancer therapy. Brusatol (Bru), a known Nrf2 inhibitor, holds promise for treating a wide range of tumors; however, the direct targets of Bru and its anticancer mode of action remain unclear. In our study, 793 Bru-binding candidate proteins were identified by using a biotin-brusatol conjugate (Bio-Bru) followed by streptavidin-affinity pull down-based mass spectrometry. We found that Bru can directly bind to Skp1 and disrupt the interactions of Skp1 with the F-box protein Skp2, leading to the inhibition of the Skp2-SCF E3 ligase. Bru inhibited both proliferation and migration via promoting the accumulation of the substrates p27 and E-cadherin; Skp1 overexpression attenuated while Skp1 knockdown enhanced these effects of Bru in non-small cell lung cancer (NSCLC) cells. Moreover, Bru binding to Skp1 also inhibited the ß-TRCP-SCF E3 ligase. In both subcutaneous and orthotopic NSCLC xenografts, Bru significantly inhibited the growth and metastasis of NSCLC through targeting SCF complex and upregulating p27 and E-cadherin protein levels. These data demonstrate that Bru is a Skp1-targeting agent that may have therapeutic potentials in lung cancer.

Brusatol Inhibits Tumor Growth and Increases the Efficacy of Cabergoline against Pituitary Adenomas.

Cabergoline (CAB) is the first choice for treatment of prolactinoma and the most common subtype of pituitary adenoma. However, drug resistance and lack of effectiveness in other pituitary tumor types remain clinical challenges to this treatment. Brusatol (BT) is known to inhibit cell growth and promote apoptosis in a variety of cancer cells. In our present studies, we investigate the effects of BT on pituitary tumor cell proliferation in vitro and in vivo. BT treatment resulted in an increase in Annexin V-expressing cells and promoted the expression of apoptosis-related proteins in rat and human pituitary tumor cells. Investigation of the mechanism underlying this effect revealed that BT increased the production of reactive oxygen species (ROS) and inhibited the phosphorylation of 4EBP1 and S6K1. Furthermore, treatment with a combination of BT and CAB resulted in greater antitumor effects than either treatment alone in nude mice and pituitary tumor cells. Collectively, our results suggest that the BT-induced ROS accumulation and inhibition of mTORC1 signaling pathway leads to inhibition of tumor growth. Combined use of CAB and BT may increase the clinical effectiveness of treatment for human pituitary adenomas.

Inhibition of Nrf2-mediated glucose metabolism by brusatol synergistically sensitizes acute myeloid leukemia to Ara-C.

Chemotherapy resistance remains to be the primary barrier to acute myeloid leukemia (AML) treatment failure. Nuclear factor-erythroid 2-related factor 2 (Nrf2) has been well established as a truly pleiotropic transcription factor. Inhibition of Nrf2 function increases the sensitivity of various chemotherapeutics and overcomes chemoresistance effectively. Brusatol (Bru) has been reported to decrease Nrf2 protein expression specifically by ubiquitin degradation of Nrf2. However, it remains elusive whether combination of Brusatol and Cytarabine (Ara-C) elicits a synergistic antitumor effect in AML. Our results demonstrated that combination of Ara-C and Brusatol synergistically exerted remarkable pro-apoptosis effect in HL-60 and THP-1 cells. Mechanistically, synergistic anti-tumor effect of Ara-C/Brusatol in AML cells is mediated by attenuating Nrf2 expression. To our surprise, Nrf2 inhibition by Brusatol causes downregulation of the expression of glycolysis-related proteins and decreased glucose consumption and lactate production, whereas the level of ROS production was unaffected. The activation of Nrf2 by Sulforaphane (SFP) could reverse the chemotherapeutic effect and changes of glycolysis of concomitant of Ara-C with Brusatol in AML cell lines. Additionally, Ara-C/Brusatol co-treatment decreased Glucose-6-phosphate dehydrogenase (G6PD) protein expression and increased the sensitivity of Ara-C. Moreover, the mouse xenograft in vivo experiment confirmed that combining Ara-C with Brusatol exerted stronger antileukemia than Ara-C alone. The efficacy, together with the mechanistic observations, reveals the potential of simultaneously giving these two drugs and provides a rational basis for targeting glucose catabolism in future clinical therapeutic approach.

Bruceine A induces cell growth inhibition and apoptosis through PFKFB4/GSK3ß signaling in pancreatic cancer.

Pancreatic cancer is one of the most aggressive cancers with a poor prognosis and 5-year low survival rate. In the present study, we report that bruceine A, a quassinoid found in Brucea javanica (L.) Merr. has a strong antitumor activity against human pancreatic cancer cells both in vitro and in vivo. Human proteome microarray reveals that 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 4 (PFKFB4) is the candidate target of bruceine A and both fluorescence measurement and microscale thermophoresis suggest bruceine A binds to PFKFB4. Bruceine A suppresses glycolysis by inhibiting PFKFB4, leading to cell cycle arrest and apoptosis in MIA PaCa-2 cells. Furthermore, glycogen synthase kinase-3 ß (GSK3ß) is identified as a downstream target of PFKFB4 and an PFKFB4-interacting protein. Moreover, bruceine A induces cell growth inhibition and apoptosis through GSK3ß, which is dysregulated in pancreatic cancer and closely related to the prognosis. In all, these findings suggest that bruceine A inhibits human pancreatic cancer cell growth via PFKFB4/GSK3ß-mediated glycolysis, and it may serve as a potent agent for curing human pancreatic cancer.

HIPK2 is a potential predictive marker of a favorable response for adjuvant chemotherapy in stage II colorectal cancer.

Colorectal cancer (CRC) is the third most frequently diagnosed type of cancer worldwide. Stage II CRC accounts for ~25% all CRC cases and their management after surgical resection remains a clinical dilemma due to the lack of reliable criteria for identifying patients who may benefit from adjuvant chemotherapy. Homeodomain­interacting protein kinase 2 (HIPK2), a multifunctional kinase involved in numerous signaling pathways, serves several key roles in cell response to different types of stresses, including chemotherapy­induced genotoxic damage. In the present study, immunohistochemistry was performed for HIPK2 on a tissue microarray of primary human tumor samples from 84 patients with stage II CRC, treated (30 patients) or not treated (54 patients) with adjuvant chemotherapy, and sequenced for the TP53 gene, a key HIPK2 target in genotoxic damage response. It was observed that, regardless of the TP53 gene status, a high percentage of HIPK2+ cells was associated with therapeutic vulnerability in stage II CRC, suggesting a contribution of HIPK2 to drug­response in vivo. For the in vitro characterization, HIPK2 was depleted in human CRC cells by CRISPR/Cas9 or RNA interference. HIPK2­proficient and HIPK2­defective cells were evaluated for their response to 5­fluorouracil (5­FU) and oxaliplatin (OXA). The results revealed that HIPK2 depletion induced resistance to 5­FU and OXA, and that this resistance was not overcome by brusatol, an inhibitor of the antioxidant response regulator nuclear factor erythroid 2­related factor 2 (NRF2), which is frequently overexpressed in CRC. By contrast, cell sensitivity to 5­FU and OXA was further induced by brusatol supplementation in HIPK2­proficient cells, further supporting the contribution of HIPK2 in chemotherapy response. Overall, the present results suggested that HIPK2 may be a potential predictive marker for adjuvant­treated stage II CRC and for prospective therapy with NRF2 modulators.

A strategy to prevent atherosclerosis via TNF receptor regulation.

Atherosclerosis is a chronic inflammatory disease of the arterial wall. It has been known that development of atherosclerosis is closely related to activation of tumor necrosis factor α (TNF-α). The objective of this study was to elucidate the effects of TNF-α blockade with brusatol on endothelial activation under pro-atherosclerotic conditions. To this end, we examined the effects of brusatol on TNF-α-induced intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression in human aortic endothelial cells (HAECs) using western blot and THP-1 adhesion assays. Brusatol induced a decrease in TNF-α-induced ICAM-1 and VCAM-1 expression through inhibiting TNFR1 expression, leading to suppression of endothelial inflammation independently of the NRF2 (nuclear factor erythroid 2-related factor 2) pathway. The mechanism underlying brusatol-induced TNF receptor 1 (TNFR1) inhibition was investigated with the aid of protein synthesis, co-immunoprecipitation, and cytokine arrays. Notably, brusatol inhibited TNFR1 protein synthesis and suppressed both the canonical nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) signaling pathway and TNF-α-induced cytokine secretion. We further tested the functional effect of brusatol on atherosclerosis development in vivo using two different atherosclerosis mouse models, specifically, acute partial carotid ligation and conventional chronic high-fat diet-fed mouse models. Administration of brusatol led to significant suppression of atherosclerosis development in both mouse models. Our finding that brusatol prevents atherosclerosis via inhibition of TNFR1 protein synthesis supports the potential of downregulation of cell surface TNFR1 as an effective therapeutic approach to inhibit development of atherosclerosis.

Nrf2 Inhibitor, Brusatol in Combination with Trastuzumab Exerts Synergistic Antitumor Activity in HER2-Positive Cancers by Inhibiting Nrf2/HO-1 and HER2-AKT/ERK1/2 Pathways.

The HER2-targeting antibody trastuzumab has shown effectiveness in treating HER2-positive breast and gastric cancers; however, its responses are limited. Currently, Nrf2 has been deemed as a key transcription factor in promoting cancer progression and resistance by crosstalk with other proliferative signaling pathways. Brusatol as a novel Nrf2 inhibitor has been deemed as an efficacious and safe drug candidate in cancer therapy. In this study, we firstly reported that brusatol exerted the growth-inhibitory effects on HER2-positive cancer cells by regressing Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways in these cells. More importantly, we found that brusatol synergistically enhanced the antitumor activity of trastuzumab against HER2-positive SK-OV-3 and BT-474 cells, which may be attributed to the inhibition of Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways. Furthermore, the synergistic effects were also observed in BT-474 and SK-OV-3 tumor xenografts. In addition, our results showed that trastuzumab markedly enhanced brusatol-induced ROS accumulation and apoptosis level, which could further explain the synergistic effects. To conclude, the study provided a new insight on exploring Nrf2 inhibition in combination with HER2-targeted trastuzumab as a potential clinical treatment regimen in treating HER2-positive cancers.

Anticancer properties and mechanism of action of the quassinoid ailanthone.

Ailanthone (AIT) is a quassinoid natural product isolated from the worldwide-distributed plant Ailanthus altissima. The drug displays multiple pharmacological properties, in particular significant antitumor effects against a variety of cancer cell lines in vitro. Potent in vivo activities have been evidenced in mice bearing hepatocellular carcinoma, nonsmall cell lung cancer and castration-resistant prostate cancer. This review focusses on the mechanism of action of AIT, notably to highlight the capacity of the drug to activate DNA damage responses, to inhibit the Hsp90 co-chaperone p23 and to modulate the expression of several microRNA. The interconnexion between these effects is discussed. The unique capacity of AIT to downregulate oncogenic miR-21 and to upregulate the tumor suppressor miRNAs miR-126, miR-148a, miR-195, and miR-449a is presented. AIT exploits several microRNAs to exert its anticancer effects in distinct tumor types. AIT is one of the rare antitumor natural products that binds to and strongly inhibits cochaperone p23, opening interesting perspectives to treat cancers. However, the toxicity profile of the molecule may limit its development as an anticancer drug, unless it can be properly formulated to prevent AIT-induced gastro-intestinal damages in particular. The antitumor properties of AIT and analogs are underlined, with the aim to encourage further pharmacological studies with this underexplored natural product and related quassinoids. HIGHLIGHTS: Ailanthone (AIT) is an anticancer quassinoid isolated from Ailanthus altissima It inhibits proliferation and induces cell death of many cancer cell types The drug activates DNA damage response and targets p23 cochaperone Up or downregulation of several microRNA by AIT contributes to the anticancer activity Analogs or specific formulations must be developed to prevent the toxicity of AIT.

Bruceine D inhibits tumor growth and stem cell-like traits of osteosarcoma through inhibition of STAT3 signaling pathway.

Patients with osteosarcoma exhibiting resistance to chemotherapy or presenting with metastasis usually have a poor prognosis. Osteosarcoma stem cells (OSCs) are a potential cause of tumor metastasis, relapse, and chemotherapy resistance. Therefore, it is necessary to develop novel therapeutic drugs, which not only kill osteosarcoma cells but also target OSCs. This study aims to explore the anti-osteosarcoma effects of Bruceine D (BD), a natural compound derived from Brucea javanica, and investigate its underlying mechanisms. Results demonstrated that BD could significantly inhibit cell proliferation and migration, induce cell cycle arrest, and promote apoptosis in osteosarcoma cells. Besides, BD could also suppress the sphere-forming and self-renewal ability of OSCs. Mechanistically, the inhibitory role of BD on osteosarcoma cell growth and migration including OSC stemness was partially executed through the inhibition of STAT3 signaling pathway. More importantly, BD showed significant anti-osteosarcoma activity without obvious side effects in vivo. Collectively, the results of this study demonstrated that BD exerts a strong inhibitory effect on tumor growth and stem cell like traits of osteosarcoma which may be partially due to STAT3 inhibition, suggesting that BD maybe a promising therapeutic candidate against osteosarcoma.

Self-nanoemulsifying drug delivery system of bruceine D: a new approach for anti-ulcerative colitis.

BACKGROUND: Bruceine D (BD) is a major bioactive component isolated from the traditional Chinese medicinal plant Brucea javanica which has been widely utilized to treat dysentery (also known as ulcerative colitis [UC]). METHODS: To improve the water solubility and absolute bioavailability of BD, we developed a self-nanoemulsifying drug delivery system (SNEDDS) composing of MCT (oil), Solutol HS-15 (surfactant), propylene glycol (co-surfactant) and BD. The physicochemical properties and pharmacokinetics of BD-SNEDDS were characterized, and its anti-UC activity and potential mechanism were evaluated in TNBS-induced UC rat model. RESULTS: The prepared nanoemulsion has multiple beneficial aspects including small mean droplet size, low polydispersity index (PDI), high zeta potential (ZP) and excellent stability. Transmission electron microscopy showed that nanoemulsion droplets contained uniform shape and size of globules. Pharmacokinetic studies demonstrated that BD-SNEDDS exhibited enhanced pharmacokinetic parameters as compared with BD-suspension. Moreover, BD-SNEDDS significantly restored the colon length and body weight, reduced disease activity index (DAI) and colon pathology, decreased histological scores, diminished oxidative stress, and suppressed TLR4, MyD88, TRAF6, NF-κB p65 protein expressions in TNBS-induced UC rat model. CONCLUSION: These results demonstrated that BD-SNEDDS exhibited highly improved oral bioavailability and advanced anti-UC efficacy. In conclusion, our current results provided a foundation for further research of BD-SNEDDS as a potential complementary therapeutic agent for UC treatment.

Brusatol ameliorates 2, 4, 6-trinitrobenzenesulfonic acid-induced experimental colitis in rats: Involvement of NF-κB pathway and NLRP3 inflammasome.

Brusatol is a main bioactive component derived from the Chinese medicinal plant Brucea javanica, which is traditionally used for the treatment of dysentery (also known as ulcerative colitis, UC). Previously, we have designed a novel brusatol self-microemulsifying drug delivery system (BR-SMEDDS) to increase its solubility and bioavailability, and enhance its bioactivities. In the present study, we established 2, 4, 6-trinitrobenzenesulfonic acid (TNBS)-induced colitis rat model in vivo and lipopolysaccharide (LPS)-induced RAW 264.7 macrophages in vitro, to investigate the potential anti-inflammatory effect and underlying mechanism of BR-SMEDDS. Disease activity index (DAI) including body weight, stool consistency and gross bleeding was measured. Macroscopic and histological evaluations of colons were conducted. Relevant molecular events were determined by ELISA, qRT-PCR, immunohistochemistry or Western blotting. The results showed that BR notably inhibited the productions of TNF-α, pro-IL-1ß, PGE2 and NO, and suppressed the NF-κB signaling pathway in LPS-stimulated macrophages. In parallel with the vitro experimental results, BR significantly attenuated diarrhea, colonic shortening, macroscopic damage and histological injury. BR treatment also increased the levels of TGF-ß and IL-4, decreased the contents of IL-1ß and IL-18, and elevated the levels of CAT, GSH and SOD in the colons. Furthermore, BR also markedly activated the Nrf2 expression and suppressed the NLRP3 inflammasome activation. Taken together, the anti-UC effect of BR might be intimately associated with the suppression of NF-κB and NLRP3-mediated inflammatory responses, and regulation of Nrf2-mediated oxidative stress. BR might have the potential to be further developed into a promising therapeutic agent for colitis treatment.

Comprehensive anti-tumor effect of Brusatol through inhibition of cell viability and promotion of apoptosis caused by autophagy via the PI3K/Akt/mTOR pathway in hepatocellular carcinoma.

Brusatol, a natural quassinoid isolated from a traditional Chinese herbal medicine known as Bruceae Fructus, has recently been reported to possess powerful cytotoxic effects against various cancer cell lines, highlighting its potential as an anti-cancer drug. However, the precise molecular mechanisms by which Brusatol exerts its anti-cancer effects remain poorly understood in hepatocellular carcinoma (HCC). In this study, we demonstrated that Brusatol inhibited cell viability, proliferation and induced apoptosis in liver cancer lines. Furthermore, Brusatol could activate autophagy in diverse liver cell lines, and the autophagy inhibitor chloroquine (CQ) reversed Brusatol-induced apoptosis in Bel7404 cells. In addition, we found that Brusatol inhibited PI3K/Akt/mTOR. Brusatol may also inhibit invasion, migration and the epithelial-mesenchymal transition (EMT). In a human liver xenograft tumor model in nude mice, immunohistochemistry showed that Brusatol significantly inhibited tumor invasion and proliferation. Taken together, these results revealed that Brusatol effectively inhibited proliferation and induced apoptosis in HCC through autophagy induction, probably via the PI3K/Akt/mTOR pathway, and inhibited tumor invasion and migration in vivo and in vitro. All above indicated that Brusatol is an encouraging anti-tumor drug candidate or a supplement to the current chemotherapeutic systematic plan.

Dual effects of the Nrf2 inhibitor for inhibition of hepatitis C virus and hepatic cancer cells.

BACKGROUND: We previously showed that knockdown of nuclear factor E2-related factor 2 (Nrf2) resulted in suppression of hepatitis C virus (HCV) infection. In this study, whether brusatol, an Nrf2 inhibitor, has dual anti-HCV and anticancer effects was explored. METHODS: The anti-HCV effect of brusatol was investigated by analyzing HCV RNA and proteins in a hepatic cell line persistently-infected with HCV, HPI cells, and by analyzing HCV replication in a replicon-replicating hepatic cell line, OR6 cells. Then, dual anti-HCV and anticancer effects of brusatol and enhancement of the effects by the combination of brusatol with anticancer drugs including sorafenib, which has been reported to have the dual effects, were then investigated. RESULTS: Brusatol suppressed the persistent HCV infection at both the RNA and protein levels in association with a reduction in Nrf2 protein in the HPI cells. Analysis of the OR6 cells treated with brusatol indicated that brusatol inhibited HCV persistence by inhibiting HCV replication. Combination of brusatol with an anticancer drug not only enhanced the anticancer effect but also, in the case of the combination with sorafenib, strongly suppressed HCV infection. CONCLUSIONS: Brusatol has dual anti-HCV and anticancer effects and can enhance the comparable effects of sorafenib. There is therefore the potential for combination therapy of brusatol and sorafenib for HCV-related hepatocellular carcinoma.

UVA Irradiation Enhances Brusatol-Mediated Inhibition of Melanoma Growth by Downregulation of the Nrf2-Mediated Antioxidant Response.

Brusatol (BR) is a potent inhibitor of Nrf2, a transcription factor that is highly expressed in cancer tissues and confers chemoresistance. UVA-generated reactive oxygen species (ROS) can damage both normal and cancer cells and may be of potential use in phototherapy. In order to provide an alternative method to treat the aggressive melanoma, we sought to investigate whether low-dose UVA with BR is more effective in eliminating melanoma cells than the respective single treatments. We found that BR combined with UVA led to inhibition of A375 melanoma cell proliferation by cell cycle arrest in the G1 phase and triggers cell apoptosis. Furthermore, inhibition of Nrf2 expression attenuated colony formation and tumor development from A375 cells in heterotopic mouse models. In addition, cotreatment of UVA and BR partially suppressed Nrf2 and its downstream target genes such as HO-1 along with the PI3K/AKT pathway. We propose that cotreatment increased ROS-induced cell cycle arrest and cellular apoptosis and inhibits melanoma growth by regulating the AKT-Nrf2 pathway in A375 cells which offers a possible therapeutic intervention strategy for the treatment of human melanoma.