Sanguinarine as a new chemical entity of thioredoxin reductase inhibitor to elicit oxidative stress and promote tumor cell apoptosis

Targeting thioredoxin reductase by eupalinilide B promotes apoptosis of colorectal cancer cells in vitro and in vivo

Aberrant activation of thioredoxin reductase (TrxR) is correlated with tumor occurrence and progression, suggesting that TrxR inhibitors can be used as antitumor agents. In this study, we evaluated the anticancer efficacy of eupalinilides B on colorectal cancer cells. Eupalinilides B primarily targeted the conserved selenocysteine 498 residues in TrxR. Besides, it inhibited the enzyme activity in an irreversible manner. After eupalinilides B was used to pharmacologically inhibit TrxR, reactive oxygen species accumulated, and the intracellular redox balance was broken, finally causing oxidative stress-induced tumor cell apoptosis. Significantly, eupalinilides B treatment inhibited in vivo tumor growth. Targeting TrxR by eupalinilides B reveals the new mechanism underlying eupalinilides B and provides insight in developing eupalinilides B as the candidate antitumor chemotherapeutic agent for the treatment of cancer.

Bioactivity and mechanism of action of sanguinarine and its derivatives in the past 10 years

Sanguinarine is a quaternary ammonium benzophenanthine alkaloid found in traditional herbs such as Chelidonium, Corydalis, Sanguinarum, and Borovula. It has been proven to possess broad-spectrum biological activities, such as antitumor, anti-inflammatory, antiosteoporosis, neuroprotective, and antipathogenic microorganism activities. In this paper, recent progress on the biological activity and mechanism of action of sanguinarine and its derivatives over the past ten years is reviewed. The results showed that the biological activities of hematarginine and its derivatives are related mainly to the JAK/STAT, PI3K/Akt/mTOR, NF-κB, TGF-β, MAPK and Wnt/β-catenin signaling pathways. The limitations of using sanguinarine in clinical application are also discussed, and the research prospects of this subject are outlined. In general, sanguinarine, a natural medicine, has many pharmacological effects, but its toxicity and safety in clinical application still need to be further studied. This review provides useful information for the development of sanguinarine-based bioactive agents.

Benzophenanthridine Alkaloid Chelerythrine Elicits Necroptosis of Gastric Cancer Cells via Selective Conjugation at the Redox Hyperreactive C-Terminal Sec498 Residue of Cytosolic Selenoprotein Thioredoxin Reductase

Targeting thioredoxin reductase (TXNRD) with low-weight molecules is emerging as a high-efficacy anti-cancer strategy in chemotherapy. Sanguinarine has been reported to inhibit the activity of TXNRD1, indicating that benzophenanthridine alkaloid is a fascinating chemical entity in the field of TXNRD1 inhibitors. In this study, the inhibition of three benzophenanthridine alkaloids, including chelerythrine, sanguinarine, and nitidine, on recombinant TXNRD1 was investigated, and their anti-cancer mechanisms were revealed using three gastric cancer cell lines. Chelerythrine and sanguinarine are more potent inhibitors of TXNRD1 than nitidine, and the inhibitory effects take place in a dose- and time-dependent manner. Site-directed mutagenesis of TXNRD1 and in vitro inhibition analysis proved that chelerythrine or sanguinarine is primarily bound to the Sec498 residue of the enzyme, but the neighboring Cys497 and remaining N-terminal redox-active cysteines could also be modified after the conjugation of Sec498. With high similarity to sanguinarine, chelerythrine exhibited cytotoxic effects on multiple gastric cancer cell lines and suppressed the proliferation of tumor spheroids derived from NCI-N87 cells. Chelerythrine elevated cellular levels of reactive oxygen species (ROS) and induced endoplasmic reticulum (ER) stress. Moreover, the ROS induced by chelerythrine could be completely suppressed by the addition of N-acetyl-L-cysteine (NAC), and the same is true for sanguinarine. Notably, Nec-1, an RIPK1 inhibitor, rescued the chelerythrine-induced rapid cell death, indicating that chelerythrine triggers necroptosis in gastric cancer cells. Taken together, this study demonstrates that chelerythrine is a novel inhibitor of TXNRD1 by targeting Sec498 and possessing high anti-tumor properties on multiple gastric cancer cell lines by eliciting necroptosis.

Alterperylenol as a Novel Thioredoxin Reductase Inhibitor Induces Liver Cancer Cell Apoptosis and Ferroptosis

Natural products are a rich resource for discovering innovational drugs. Herein, we isolated and characterized two compounds dihydroalterperylenol (DAP) and alterperylenol (AP) from Alternaria sp. MG1, an endophytic fungus isolated from Vitis quinquangularis, and investigated the underlying antitumor mechanism of AP. Mechanistically, AP inhibits the growth of HepG2 cells by targeting the selenoprotein thioredoxin reductase (TrxR) and ultimately induces cell apoptosis and ferroptosis. Compared to DAP, the α,β-unsaturated carbonyl structure of AP is an indispensable moiety for its antitumor activity and TrxR inhibition. Specifically, inhibition of TrxR causes the extensive reactive oxygen species and consequently results in DNA damage, G2/M cell cycle arrest, and mitochondrial fission. Furthermore, ferroptosis is driven via excess toxic lipid peroxidation and elevation of intracellular iron levels via regulating iron-related proteins. In vivo validation also shows that AP owns anticancer activity in xenograft mice. Collectively, our results disclose a novel natural TrxR inhibitor AP exerting the antitumor effect via inducing cell apoptosis and ferroptosis and evidence that AP is a promising candidate agent for liver carcinoma therapy. The link of TrxR inhibition to ferroptosis further highlights the physiological importance of TrxR in regulating ferroptosis.

The Impact of Oxidative Stress and AKT Pathway on Cancer Cell Functions and Its Application to Natural Products

Oxidative stress and AKT serine-threonine kinase (AKT) are responsible for regulating several cell functions of cancer cells. Several natural products modulate both oxidative stress and AKT for anticancer effects. However, the impact of natural product-modulating oxidative stress and AKT on cell functions lacks systemic understanding. Notably, the contribution of regulating cell functions by AKT downstream effectors is not yet well integrated. This review explores the role of oxidative stress and AKT pathway (AKT/AKT effectors) on ten cell functions, including apoptosis, autophagy, endoplasmic reticulum stress, mitochondrial morphogenesis, ferroptosis, necroptosis, DNA damage response, senescence, migration, and cell-cycle progression. The impact of oxidative stress and AKT are connected to these cell functions through cell function mediators. Moreover, the AKT effectors related to cell functions are integrated. Based on this rationale, natural products with the modulating abilities for oxidative stress and AKT pathway exhibit the potential to regulate these cell functions, but some were rarely reported, particularly for AKT effectors. This review sheds light on understanding the roles of oxidative stress and AKT pathway in regulating cell functions, providing future directions for natural products in cancer treatment.

Mecheliolide elicits ROS-mediated ERS driven immunogenic cell death in hepatocellular carcinoma

The nonnegligible reason for the poor prognosis of hepatocellular carcinoma (HCC) is resistance to conventional chemotherapy. Immunogenic cell death (ICD) is a rare immunostimulatory form of cell death that can reengage the tumor-specific immune system. ICD can improve the clinical outcomes of chemotherapeutics by promoting a long-term cancer immunity. The discovery of potential ICD inducers is emerging as a promising direction. In the present study, micheliolide (MCL), a natural guaianolide sesquiterpene lactone, was screened out by the virtual screening strategies, identified as an inhibitor of thioredoxin reductase (TrxR) and was evaluated to have high potential to induce ICD. Here, we showed that MCL induced ICD-associated DAMPs (damage-associated molecular patterns, such as CRT exposure, ATP secretion and HMGB1 release). MCL significantly triggered the regression of established tumors in an immunocompetent mouse vaccine model, and induced ICD (DCs maturation, the stimulation of CD4⁺, and CD8⁺ T-cells responses) in vivo. Mechanistically, we found that the magnitude of ICD-associated effects induced upon exposure of HCC cells to MCL was dependent on the generation of reactive oxygen species (ROS)-mediated endoplasmic reticulum stress (ERS). In addition, the suppression of ROS normalized MCL-induced ERS, in contrast, the downregulation of TrxR synergized with the ERS driven by MCL. We also systematically detected the H₂O₂ generation using Hyper7 sensors in HCC cells exposed to MCL. Notably, MCL inhibited the development of HCC organoids. Collectively, our results reveal a potential association between the TrxR inhibitors and ICD, presenting valuable insights into the MCL-activated ICD in HCC cells.

Piperlongumine Inhibits Thioredoxin Reductase 1 by Targeting Selenocysteine Residues and Sensitizes Cancer Cells to Erastin

Piperlongumine, a natural alkaloid substance extracted from the fruit of the long pepper (Piper longum Linn.), is known to inhibit the cytosolic thioredoxin reductase (TXNRD1 or TrxR1) and selectively kill cancer cells. However, the details and mechanism of the inhibition by piperlongumine against TXNRD1 remain unclear. In this study, based on the classical DTNB reducing assay, irreversible inhibition of recombinant TXNRD1 by piperlongumine was found and showed an apparent kinact value of 0.206 × 10−3 µM−1 min−1. Meanwhile, compared with the wild-type TXNRD1 (-GCUG), the UGA-truncated form (-GC) of TXNRD1 was resistant to piperlongumine, suggesting the preferential target of piperlongumine is the selenol (-SeH) at the C-terminal redox motif of the enzyme. Interestingly, the high concentration of piperlongumine-inhibited TXNRD1 showed that its Sec-dependent activity is decayed but its intrinsic NADPH oxidase activity is retained. Furthermore, piperlongumine did not induce ferroptosis in HCT116 cells at 10 µM, whereas significantly promoted erastin-induced lipid oxidation, which could be alleviated by supplying glutathione (GSH) or N-acetyl L-cysteine (NAC). However, restricting GSH synthesis by inhibiting glutaminase (GLS) using the small molecule inhibitor CB-839 only slightly enhanced erastin-induced cell death. Taken together, this study elucidates the molecular mechanism of the antitumor capacity of piperlongumine by targeting TXNRD1 and reveals the potential possibility of inhibiting TXNRD1 to strengthen cancer cells’ ferroptosis.

Rheumatoid arthritis drug sinomenine induces apoptosis of cervical tumor cells by targeting thioredoxin reductase in vitro and in vivo

Overexpression of thioredoxin reductase (TrxR) has been linked to tumorigenesis and phenotypic maintenance of malignant tumors. Thus, targeting TrxR with natural molecules is a promising strategy for developing anticancer drugs. Sinomenine is a naturally occurring alkaloid isolated from Sinomenium acutum. The drug, Zhengqing Fengtongning made from sinomenine, has been universally applied in rheumatoid arthritis treatment in China as well as other Asian countries for decades. Recently, increasing evidence indicates that sinomenine appears to be a promising therapeutic agent against various cancer cells. However, the exact mechanism underlying the anticancer activity of sinomenine remains unclear. In this study, we identified sinomenine as a kind of new inhibitor for TrxR. Pharmacological inhibition of TrxR by sinomenine results in the decrease of thiols content, increases the levels of reactive oxygen species, and finally facilitates oxidative stress-mediated cancer cell apoptosis. It is vital that knockdown in TrxR1 by shRNA can increase cell sensitivity to sinomenine. Treatment with sinomenine in vivo leads to a decrease in TrxR activity and tumor growth, and an increase in apoptosis. Our findings provide a novel action mechanism related to sinomenine and presents an insight on how to develop sinomenine as a chemotherapeutic agent for cancer therapy.

Novel strategies for targeting the thioredoxin system for cancer therapy

INTRODUCTION

: The thioredoxin system is increasingly recognized as an important executor for maintaining cell redox homeostasis and regulating multiple cell signaling pathways. Targeting this system for cancer treatment has therefore attracted much attention.

AREAS COVERED

: The authors focus on providing coverage and emphasizing the strategy of targeting the thioredoxin system to develop anticancer therapeutics in the past five years, especially from the perspective of discovering novel protein functions or new downstream regulatory pathways, and designing new therapeutic reagents. The authors also provide the readers with their expert perspectives for future development.

EXPERT OPINION

: The limited pharmacophore of inhibitors and the slow progress of clinical research partially restrict the development of anticancer drugs targeting the thioredoxin system, necessitating thus novel strategies to accelerate the system for treating cancer. Nevertheless, the synergistic targeting of thioredoxin system for cancer therapy is a promising strategy, particularly with regards to chemotherapy resistance and/or sensitization immunotherapy.

Preventive effect of sanguinarine on intestinal injury in mice exposed to whole abdominal irradiation

Intestinal injury is one of the major side effects that are induced by medical radiation exposure, and has limited effective therapies. In this study, we investigated the beneficial effects of sanguinarine (SAN) on intestinal injury induced by ionizing radiation (IR) both in vitro and in vivo. Mice were exposed to whole abdominal irradiation (WAI) to mimic clinical scenarios. SAN was injected intraperitoneally to mitigate IR-induced injury. Histological examination was performed to assess the tissue injuries of the spleen and small intestine. A small intestinal epithelial cell line-6 (IEC-6) was analyzed for its viability and apoptosis in vitro under different treatments. Inflammation-related pathways and serum inflammatory cytokines were detected via Western blot analysis and ELISA, respectively. High-throughput sequencing was used to characterize the gut microbiota profile. High-performance liquid chromatography was performed to assess short-chain fatty acid contents in the colon. In vitro, SAN pretreatment protected cell viability and reduced apoptosis in IEC-6 cells. In vivo, SAN pretreatment protected immune organs, alleviated intestinal injury, and promoted intestinal recovery. SAN also reduced the levels of inflammatory cytokines, suppressed high mobility group box 1 (HMGB1)/ Toll-like receptor 4 (TLR4) pathway activation, and modulated gut microbiota composition. Our findings demonstrate that the beneficial properties of SAN alleviated intestinal radiation injury. Thus, SAN represents a therapeutic option for protecting against IR-induced intestinal injury in preclinical settings.

Natural diterpenoid eriocalyxin B covalently modifies glutathione and selectively inhibits thioredoxin reductase inducing potent oxidative stress-mediated apoptosis in colorectal carcinoma RKO cells

Increasing evidence suggests the significant contribution of high levels of thioredoxin reductase (TrxR) in various stages of tumorigenesis and resistance to tumor chemotherapy. Thus, inhibition of TrxR with small molecules is an attractive strategy for cancer therapy. Eriocalyxin B (EriB), a naturally occurring diterpenoid extracted from Isodon eriocalyx, has reflected potential anticancer activities through numerous pathways. Here, we describe that EriB covalently modifies GSH and selectively inhibits TrxR activity by targeting the Sec residue of the enzyme. Pharmacological inhibition of TrxR by EriB results in elevated ROS levels, reduced total GSH and thiols content, which ultimately induced potent RKO cell apoptosis mediated by oxidative stress. Importantly, EriB indicates potent synthetic lethality with GSH inhibitors, BSO, in RKO cells. In summary, our results highlight that targeting TrxR by EriB explores a novel mechanism for the biological action of EriB. This opened up a new therapeutic indication for using EriB to combat cancers.

Stimuli-Responsive and Reversible Nanoassemblies of G-Triplexes

G-triplex (G3) structures formed with three consecutive G-tracts have recently been identified as a new emerging guanine-rich DNA fold. There could likely be a wide range of biological functions for G3s as occurring for G-quadruplex (G4) structures formed with four consecutive G-tracts. However, in comparison to the many reports on G4 nanoassemblies that organize monomers together in a controllable manner, G3-favored nanoassemblies have yet to be explored. In this work, we found that a natural alkaloid of sanguinarine can serve as a dynamic ligand glue to reversibly switch the dimeric nanoassemblies of the thrombin binding aptamer G3 (TBA-G3). The glue planarity was considered to be a crucial factor for realizing this switching. More importantly, external stimuli including pH, sulfite, O₂ and H₂ O₂ can be employed as common regulators to easily modulate the glue's adhesivity for constructing and destructing the G3 nanoassemblies as a result of the ligand converting between isoforms. However, this assembly behavior does not occur with the counterpart TBA-G4. Our work demonstrates that higher-order G3 nanoassemblies can be reversibly operated by manipulating ligand adhesivity. This provides an alternative understanding of the unique behavior of guanine-rich sequences and focuses attention on the G3 fold since the nanoassembly event investigated herein might occur in living cells.

Structural Modification of Aminophenylarsenoxides Generates Candidates for Leukemia Treatment via Thioredoxin Reductase Inhibition

Upregulation of the selenoprotein thioredoxin reductase (TrxR) is of pathological significance in maintaining tumor phenotypes. Thus, TrxR inhibitors are promising cancer therapeutic agents. We prepared different amino-substituted phenylarsine oxides and evaluated their cytotoxicity and inhibition of TrxR. Compared with our reported p-substituted molecule (8), the o-substituted molecule (10) shows improved efficacy (nearly a fourfold increase) to kill leukemia HL-60 cells. Although the compounds 8 and 10 display similar potency to inhibit the purified TrxR, the o-substitution 10 exhibits higher potency than the p-substitution 8 to inhibit the cellular TrxR activity. Molecular docking results demonstrate the favorable weak interactions of the o-amino group with the TrxR C-terminal active site. Efficient inhibition of TrxR consequently induces the oxidative stress-mediated apoptosis of cancer cells. Silence of the TrxR expression sensitizes the cells to the arsenic compound treatment, further supporting the critical involvement of TrxR in the cellular actions of compound 10.

Phytochemistry and pharmacology of alkaloids from Glaucium spp

Glaucium Mill. comprising 28 species with 78 synonyms, 3 subspecies, and 3 varieties worldwide belongs to the Papaveraceae family. The plants are well known for their different types of alkaloids. In the present study, we attempted to review the chemistry and pharmacology of the alkaloids from the genus Glaucium. For this purpose, the relevant data were collected from different scientific databases including, "Google Scholar", "ISI Web of Knowledge", "PubMed", "Scopus", and available books and e-books. Our results showed that aporphine alkaloids are dominated in the species; however, other types of alkaloids including protopines, benzophenanthridines, benzylisoquinolines, protoberberines, and morphinanes have also been reported from the genus. The pharmacological studies have shown that the alkaloids from Glaucium species have several biological activities of which anti-cancer and anti-cholinesterase effects have been highly reported. Besides, the data indicated that most of the species have been investigated neither phytochemically nor pharmacologically. Glaucium flavum, known as yellow horn poppy, is the most studied species. According to the reports, the plants from this genus have anti-cancer and anti-cholinesterase potentials and can be used as a source for aporphine alkaloids.

Targeting thioredoxin reductase by deoxyelephantopin from Elephantopus scaber triggers cancer cell apoptosis

Elevated expression of thioredoxin reductase (TrxR) is associated with the tumorigenesis and resistance to cancer chemoradiotherapy, highlighting the potential of TrxR inhibitors as anticancer drugs. Deoxyelephantopin (DET) is the major active ingredient of Elephantopus scaber and reveals potent anticancer activity. However, the potential mechanism of action and the cellular target of DET are still unknown. Here, we found that DET primarily targets the Sec residue of TrxR and irreversibly prohibits enzyme activity. Suppression of TrxR by DET leads to accumulation of reactive oxygen species and dysregulation in intracellular redox balance, eventually inducing cancer cell apoptosis mediated by oxidative stress. Noticeably, down-regulation of TrxR1 by shRNA increases cell sensitivity to DET. Collectively, targeting of TrxR1 by DET uncovers a novel mechanism of action in DET and deepens the understanding of developing DET as a potential chemotherapeutic agent for treating cancers.

Reactive oxygen species (ROS) in cancer pathogenesis and therapy: An update on the role of ROS in anticancer action of benzophenanthridine alkaloids

Reactive oxygen species play crucial role in biological homeostasis and pathogenesis of human diseases including cancer. In this line, now it has become evident that ROS level/concentration is a major factor in the growth, progression and stemness of cancer cells. Moreover, cancer cells maintain a delicate balance between ROS and antioxidants to promote pathogenesis and clinical challenges via targeting a battery of signaling pathways converging to cancer hallmarks. Recent findings also entail the therapeutic importance of ROS for the better clinical outcomes in cancer patients as they induce apoptosis and autophagy. Moreover, poor clinical outcomes associated with cancer therapies are the major challenge and use of natural products have been vital in attenuation of these challenges due to their multitargeting potential with less adverse effects. In fact, most available drugs are derived from natural resources, either directly or indirectly and available evidence show the clinical importance of natural products in the management of various diseases, including cancer. ROS play a critical role in the anticancer actions of natural products, particularly phytochemicals. Benzophenanthridine alkaloids of the benzyl isoquinoline family of alkaloids, such as sanguinarine, possess several pharmacological properties and are thus being studied for the treatment of different human diseases, including cancer. In this article, we review recent findings, on how benzophenanthridine alkaloid-induced ROS play a critical role in the attenuation of pathological changes and stemness features associated with human cancers. In addition, we highlight the role of ROS in benzophenanthridine alkaloid-mediated activation of the signaling pathway associated with cancer cell apoptosis and autophagy.

Discovery of hydroxytyrosol as thioredoxin reductase 1 inhibitor to induce apoptosis and G1/S cell cycle arrest in human colorectal cancer cells via ROS generation

Colorectal cancer (CRC) is one of the most common cancer types and a leading cause of cancer-associated mortality in China. Increased thioredoxin reductase 1 (TrxR1) levels have been previously identified as possible target for CRC. The present study revealed that the natural product hydroxytyrosol (HT), which exhibits a polyphenol scaffold, is a potent inhibitor of TrxR1. Inhibition of TrxR1 was indicated to result in accumulation of reactive oxygen species, inhibit proliferation and induce apoptosis and G1/S cell cycle arrest of CRC cells. Using a C-terminal mutant TrxR1 enzyme activity assay, TrxR1 RNA interference assay and HT binding model assay, the present study demonstrated the core character of the selenocysteine residue in the interaction between HT and TrxR1. HT can serve as polyphenol scaffold to develop novel TrxR1 inhibitors for CRC treatment in the future.

Jolkinolide B targets thioredoxin and glutathione systems to induce ROS-mediated paraptosis and apoptosis in bladder cancer cells

Bladder cancer is a clinically heterogeneous disease with a poor prognosis. In the current study, anti-proliferation assay of a Euphorbiaceae diterpenoid library led to the identification of an anti-bladder cancer agent Jolkinolide B (JB). JB showed significant cytotoxicity against a panel of bladder cancer cell lines and suppressed the growth of cisplatin (CDDP)-resistant bladder cancer xenografts in single or combination treatments. Mechanistic study revealed that, besides inducing mitogen-activated protein kinase (MAPK)-related apoptosis, JB could trigger the paraptosis via activation of reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress and extracellular signal-regulated kinase (ERK) pathway. The excessive production of ROS could be induced by JB via inhibition of thioredoxin reductase 1 (TrxR1) and depletion of glutathione (GSH). Collectively, JB that targets thioredoxin and GSH systems to induce two distinct cell death modes may serve as a promising candidate in future anti-bladder cancer drug development.

Natural Molecules Targeting Thioredoxin System and Their Therapeutic Potential

Significance: Thioredoxin (Trx) and thioredoxin reductase are two core members of the Trx system. The system bridges the gap between the universal reducing equivalent NADPH and various biological molecules and plays an essential role in maintaining cellular redox homeostasis and regulating multiple cellular redox signaling pathways. Recent Advance: In recent years, the Trx system has been well documented as an important regulator of many diseases, especially tumorigenesis. Thus, the development of potential therapeutic molecules targeting the system is of great significance for disease treatment. Critical Issues: We herein first discuss the physiological functions of the Trx system and the role that the Trx system plays in various diseases. Then, we focus on the introduction of natural small molecules with potential therapeutic applications, especially the anticancer activity, and review their mechanisms of pharmacological actions via interfering with the Trx system. Finally, we further discuss several natural molecules that harbor therapeutic potential and have entered different clinical trials. Future Directions: Further studies on the functions of the Trx system in multiple diseases will not only improve our understanding of the pathogenesis of many human disorders but also help develop novel therapeutic strategies against these diseases. Antioxid. Redox Signal. 34, 1083-1107.

Thioredoxin reductase inhibitors: updated patent review (2017-present)

Introduction: Thioredoxin reductase (TrxR) is a selenocysteine-containing enzyme which is responsible - as a part of the thioredoxin system - for maintaining redox homeostasis in cells. It is upregulated in cancerous state as a defense against oxidative stress. TrxR has been mostly considered an anticancer drug target although it has applications in other therapeutic areas such as neurodegeneration, inflammation, microbial infections, and neonatal hyperoxic lung injury.Areas covered: The present review covers the patent literature that appeared in the period 2017-2020, i.e. since the publication of the previous expert opinion patent review on TrxR inhibitors. The recent additions to the following traditional classes of inhibitors are discussed: metal complexes, Michael acceptors as well as arsenic and selenium compounds. At the same time, a novel group of nitro (hetero)aromatic compounds have emerged which likely acts via covalent inhibition mechanism. Several miscellaneous chemotypes are grouped under Miscellaneous subsection.Expert opinion: While specificity over glutathione reductase is achieved easily, TrxR is still moving toward the later stages of development at a very slow rate. Michael acceptors, particularly based on TRXR substrate-mimicking scaffolds, are gaining impetus and so are dual and hybrid compounds. The development prospects of the emerging nitro (hetero)aromatic chemotypes remain uncertain.

Determination of Cytotoxic Activity of Sanguinaria canadensis Extracts against Human Melanoma Cells and Comparison of Their Cytotoxicity with Cytotoxicity of Some Anticancer Drugs

Melanoma is an enormous global health burden, and should be effectively addressed with better therapeutic strategies. Therefore, new therapeutic agents are needed for the management of this disease. The aim of this study was the investigation of cytotoxic activity of some isoquinoline alkaloid standards and extracts obtained from Sanguinaria canadensis—collected before, during, and after flowering—against three different human melanoma cells (A375, G361, SK-MEL-3). The cytotoxicity of these extracts was not previously tested on these melanoma cell lines. Determination of alkaloid contents was performed by HPLC-DAD using Polar RP column and mobile phase containing acetonitrile, water, and 1-butyl-3-methylimidazolium tetrafluoroborate. The cytotoxicity of alkaloid standards was investigated by determination of cell viability and calculation of IC₅₀ values. Significant differences were observed in the alkaloids content and cytotoxic activity of the extracts, depending on the season of collection of the plant material. In the Sanguinaria canadensis extracts high contents of sanguinarine (from 4.8543 to 9.5899 mg/g of dry plant material) and chelerythrine (from 42.7224 to 6.8722 mg/g of dry plant material) were found. For both of these alkaloids, very high cytotoxic activity against the tested cell lines were observed. The IC₅₀ values were in the range of 0.11–0.54 µg/mL for sanguinarine and 0.14 to 0.46 µg/mL for chelerythrine. IC₅₀ values obtained for Sanguinaria canadensis extracts against all tested cell lines were also very low (from 0.88 to 10.96 µg/mL). Cytotoxic activity of alkaloid standards and Sanguinaria canadensis extracts were compared with the cytotoxicity of anticancer drugs—etoposide, cisplatin, and hydroxyurea. In all cases except the one obtained for cisplatin against A375, which was similar to that obtained for Sanguinaria canadensis after flowering against the same cell line, IC₅₀ values obtained for anticancer drugs were higher than the IC₅₀ values obtained for sanguinarine, chelerythrine, and Sanguinaria canadensis extracts. Our results showed that Sanguinaria canadensis extracts and isoquinoline alkaloids, especially sanguinarine and chelerythrine, could be recommended for further in vivo experiments in order to confirm the possibility of their application in the treatment of human melanomas.

Design, synthesis, and biological evaluation of a novel indoleamine 2,3-dioxigenase 1 (IDO1) and thioredoxin reductase (TrxR) dual inhibitor

Targeting the Trp-Kyn pathway is an attractive approach for cancer immunotherapy. Thioredoxin reductase (TrxR) enzymes are reactive oxygen species (ROS) modulators that are involved in the tumor cell growth and survival processes. The 4-phenylimidazole scaffold is well-established as useful for indoleamine 2,3-dioxygenase 1 (IDO1) inhibition, while piperlongumine (PL) and its derivatives have been reported to be inhibitors of TrxR. To take advantage of both immunotherapy and TrxR inhibition, we designed a first-generation dual IDO1 and TrxR inhibitor (ZC0101) using the structural combination of 4-phenylimidazole and PL scaffolds. ZC0101 exhibited better dual inhibition against IDO1 and TrxR in vitro and in cell enzyme assays than the uncombined forms of 4-phenylimidazole and PL. It also showed antiproliferative activity in various cancer cell lines, and a selective killing effect between normal and cancer cells. Furthermore, ZC0101 effectively induced apoptosis and ROS accumulation in cancer cells. Knockdown of TrxR1 and IDO1 expression induced cellular enzyme inhibition and ROS accumulation effects during ZC0101 treatment, but only reduced TrxR1 expression was able to improve ZC0101's antiproliferation effect. This proof-of-concept study provides a novel strategy for cancer treatment. ZC0101 represents a promising lead compound for the development of novel antitumor agents that can also be used as a valuable probe to clarify the relationships and mechanisms of cancer immunotherapy and ROS modulators.

Isodeoxyelephantopin Inactivates Thioredoxin Reductase 1 and Activates ROS-Mediated JNK Signaling Pathway to Exacerbate Cisplatin Effectiveness in Human Colon Cancer Cells

Colon cancer is one of the leading causes of cancer-related death in the world. The development of new drugs and therapeutic strategies for patients with colon cancer are urgently needed. Isodeoxyelephantopin (ESI), a sesquiterpene lactone isolated from the medicinal plant Elephantopus scaber L., has been reported to exert antitumor effects on several cancer cells. However, the molecular mechanisms underlying the action of ESI is still elusive. In the present study, we found that ESI potently suppressed cell proliferation in human colon cancer cells. Furthermore, our results showed that ESI treatment markedly increased cellular reactive oxygen species (ROS) levels by inhibiting thioredoxin reductase 1 (TrxR1) activity, which leads to activation of the JNK signaling pathway and eventually cell death in HCT116 and RKO cells. Importantly, we found that ESI markedly enhanced cisplatin-induced cytotoxicity in HCT116 and RKO cells. Combination of ESI and cisplatin significantly increased the production of ROS, resulting in activation of the JNK signaling pathway in HCT116 and RKO cells. In vivo, we found that ESI combined with cisplatin significantly suppressed tumor growth in HCT116 xenograft models. Together, our study provide a preclinical proof-of-concept for ESI as a potential strategy for colon cancer treatment.

Sanguinarine modulate gut microbiome and intestinal morphology to enhance growth performance in broilers

Sanguinarine is a bioactive compound as a quaternary benzophenanthridine alkaloid from plant of the Macleaya cordata, Papaveraceae family. The present study was conducted to investigate the effects of dietary sanguinarine supplementation on growth performance, serum biochemistry parameters, intestinal mucosal morphology and gut microbiome in yellow feathered broilers. Two hundred and seventy 1-d-old female broilers were randomly assigned to 3 treatments ① Basal diet (NG); ② Basal diet containing bacitracin methylene disalicylate (50mg/Kg diet) (ANT); ③ Basal diet containing sanguinarine (0.7 mg/ kg of feed) (SAG). The statistical results showed that dietary sanguinarine supplementation enhanced growth performance and decreased glucose, uric acid as well as urea nitrogen levels of broilers at 28d of age (P<0.05). The 16S rRNA gene sequence analysis revealed that sanguinarine significantly decreased the species from the phyla Bacteroidetes, and increased the species from phyla Firmicutes. Moreover, dietary sanguinarine supplementation improved mucosal morphology to achieve higher ratio of intestinal villus height to crypt depth (P < 0.05), and decreased the concentrations of TNF-α and IL-4 in jejunum mucosal. This study demonstrated that sanguinarine supplementation in the diet of yellow feathered broilers improved intestinal morphology and microbiota community structure to promote growth performance on 1-28d.

PSAT1 Regulated Oxidation-Reduction Balance Affects the Growth and Prognosis of Epithelial Ovarian Cancer

Introduction

A growing number of studies have found that the serine-glycine biosynthesis pathway is highly activated for biosynthesis in cancer progression and metastasis. Phosphoserine aminotransferase 1 (PSAT1) catalyzes the second step of the serine-glycine biosynthesis pathway; the effects and mechanism of PSAT1 in epithelial ovarian cancer (EOC) remains unclear.

Materials and Methods

The expression of PSAT1 in clinical EOC samples and normal ovarian tissues was conducted by RT-PCR, Western blot, and immunohistochemical staining. Survival analysis of PSAT1 in ovarian cancer was performed by using the public database. Following the downregulation of PSAT1, the cell growth, cell apoptosis, and cell cycle in ovarian cancer cells were respectively examined by the soft agar colony formation assay and flow cytometry analysis. Then the glutathione (GSH) levels, the GSH/GSSG ratio, the NADPH/NADP ratio, and the cellular reactive oxygen species (ROS) levels were tested to analyze the oxidation-reduction balance in PSAT1-depleted ovarian cancer cells.

Results

PSAT1 is markedly over-expressed in clinical EOC samples (n = 90) compared to that in normal ovarian tissues (n = 10), and the expression of PSAT1 is correlated with histological subtype, FIGO stage, histological grade, lymph node metastasis, distant metastasis and the presence of ascites. Public database analysis shows that higher PSAT1 indicates poor survival in EOC patients. Downregulation of PSAT1 in EOC cells inhibits growth, induces apoptosis and cell cycle arrest in vitro. EOC cells with high PSAT1 levels have increased a higher GSH (reduced glutathione)/GSSG (oxidized glutathione) ratio and lower reactive oxygen species (ROS) content. The cancer-killing effects of PSAT1 knockdown are reversed by exogenous glutathione. PSAT1 participates in cancer growth by regulating oxidation-reduction balance.

Conclusion

Therefore, these results highlight the potential of PSAT1 inhibitors or metabolic substrate deprivation as therapeutic strategies for treating patients with EOC, especially those with advanced stages of cancer.