Adenanthin targets peroxiredoxin I and II to induce differentiation of leukemic cells

Identification and characterization of Bufalin as a novel EGFR degrader

Esophageal squamous cell carcinoma (ESCC) stands out as a common cancer type worldwide, characterized by its notably high rates of occurrence and mortality. The epidermal growth factor receptor (EGFR) is one of the main targets for cancer treatment as it is one of the genes whose expression is often altered by overexpression, amplification, and mutation in a variety of solid tumors. Substantial efforts have been made to develop EGFR-targeted therapeutic agents, including monoclonal antibodies and tyrosine kinase inhibitors (TKIs). However, these agents exhibited limited efficacy due to the emergence of acquired resistance. Therefore, novel treatment strategies targeting EGFR are urgently needed. Recent studies have identified a few natural compounds that can efficiently inhibit EGFR, indicating that natural products may be potential sources for the development of new EGFR inhibitors. Here, using the Drug Affinity Responsive Target Stability (DARTS) assay combined with liquid chromatography/tandem mass spectrometry analysis, co-crystal method, we discovered that Bufalin directly interacts with EGFR and causes EGFR endocytosis and degradation in the lysosome. Moreover, Bufalin exhibits superior anti-tumor activity compared with another EGFR TKIs. Our study identified Bufalin as the first natural small-molecule EGFR degrader, which suppresses EGFR signaling by inducing the degradation of EGFR via the endosome-lysosome pathway.

The latest advances with natural products in drug discovery and opportunities for the future: a 2025 update

INTRODUCTION

The landscape of drug discovery is rapidly evolving, with natural products (NPs) playing a pivotal role in the development of novel therapeutics. Despite their historical significance, challenges persist in fully harnessing their potential in the development of modern medicine.

AREAS COVERED

This perspective discusses the recent advances and opportunities in NP-based drug discovery. This includes exploration of the recently approved representative NP-derived drugs, innovative target identification strategies and advancements in hybrid NP molecules for addressing complex diseases. Moreover, the authors also discuss the role of NP-derived payloads in antibody-drug conjugates (ADCs) for targeted cancer therapy. This article is based on searches using the FDA and DrugBank database as well the Derwent Innovations Index from Web of Science between the period of 2017 to 2025.

EXPERT OPINION

NPs remain vital to drug discovery, demonstrating adaptability in tackling complex medical challenges. Future efforts should focus on integrating advanced methodologies, such as artificial intelligence (AI), high-throughput screening, chemical biology, bioinformatics, gene regulation, the highly accurate non-labeling chemical proteomics approach to explore novel NPs targets. Emphasizing these developments will be crucial for maximizing the therapeutic potential of NPs in combating unmet medical needs.

Targeting Senescence with Apigenin Improves Chemotherapeutic Efficacy and Ameliorates Age-Related Conditions in Mice

Cellular senescence is a cell fate triggered by stressful stimuli and displays a hypersecretory feature, the senescence-associated secretory phenotype (SASP). Senescent cell burden increases with aging and contributes to age-related organ dysfunction and multiple chronic disorders. In this study, a large scale screening of a natural product library for senotherapeutic candidates is performed. Apigenin, a dietary flavonoid previously reported with antioxidant and anti-inflammatory activities, exhibits capacity for targeting senescent cells as a senomorphic agent. This compound blocks the interactions between ATM/p38MAPK and HSPA8, preventing the transition of an acute stress-associated phenotype (ASAP) toward the SASP. Mechanistically, apigenin targets peroxiredoxin 6 (PRDX6), an intracellular redox-active molecule, suppressing the iPLA2 activity of PRDX6 and disrupting downstream reactions underlying SASP development. Apigenin reduces the severity of cancer cell malignancy promoted by senescent stromal cells in culture, while restraining chemoresistance when combined with chemotherapy in anticancer regimens. In preclinical trials, apigenin improves the physical function of animals with a premature aging-like state, alleviating physical frailty and cognitive impairment. Together, the study demonstrates the feasibility of exploiting a natural compound with senomorphic capacity to achieve geroprotective effects by modulating the SASP, thus providing a baseline for future exploration of natural agents for alleviating age-related conditions.

Recent advances in target identification technology of natural products

Natural products, characterized by their structural diversity, broad spectrum of biological activities, and safe yet effective therapeutic potential, have become pivotal resources in drug research and development. However, the target proteins of many natural products remain unidentified, a significant challenge that impedes their development into viable drug candidates. Therefore, the target identification is crucial for elucidating the pharmacological mechanisms of natural products and facilitating their therapeutic applications. In this review, we present a comprehensive overview of recent advancements in methodologies for target identification of natural products. Additionally, we predict future developments in new technologies for target discovery. Collectively, this review establishes a methodological framework for uncovering the cellular targets and pharmacological mechanisms of natural products, thereby advancing the development of innovative natural product-based drugs.

BE-43547A2 exerts hypoxia-selective inhibition on human pancreatic cancer cells through targeting eEF1A1 and disrupting its association with FoxO1

Hypoxia is a key feature of the tumor microenvironment that leads to the failure of many chemotherapies and induces more aggressive and resistant cancer phenotypes. Up to date, there are very few compounds and treatments that can target hypoxia. BE-43547A2 from Streptomyces sp. was one of the most hypoxia-selective compounds against PANC-1, MCF-7, and K562 cell lines. In this study, we investigated the molecular mechanism underlying the hypoxia selectivity of BE-43547A2 in human pancreatic cancer cells. We showed that BE-43547A2 displayed hypoxia-selective cytotoxicity in five pancreatic cancer cells (PANC-1, Capan-2, MIA PaCa-2, AsPC-1, and PaTu8988T) with IC50 values under hypoxia considerably lower than those under normoxia. We demonstrated that BE-43547A2 is directly bound to eEF1A1 protein in PaTu8988T cells under hypoxia. Furthermore, we revealed that hypoxia significantly elevated the expression levels of HIF1α, FoxO1, and eEF1A1 in the five pancreatic cancer cells; eEF1A1 interacted with FoxO1 in the cytoplasm, which was disrupted by BE-43547A2 followed by the nuclear translocation of FoxO1 and ultimate inhibition of JAK/STAT3 signaling pathway under hypoxia. This study reveals that BE-43547A2, targeting eEF1A1, disrupts its interaction with FoxO1 in human pancreatic cancer cells under hypoxia. This compound could serve as a potential hypoxia-selective therapy.

Towards site-specific manipulation in cysteine-mediated redox signaling

Cysteine sulfenic acid (SOH) modifications are pivotal in redox signaling, yet establishing their causal biological roles remains challenging due to methodological limitations. Traditional approaches often lack precision or disrupt non-redox cysteine functions. This perspective highlights two innovative chemical biology strategies to address these challenges: (1) integrating bioorthogonal cleavage chemistry with genetic code expansion for site-specific SOH incorporation in proteins of interest, enabling controlled activation of redox events, and (2) developing redox-targeted covalent inhibitors (TCIs) to selectively block SOH modifications. By bridging technological innovation with mechanistic inquiry, these strategies not only help elucidate SOH-mediated signaling networks for a better understanding of redox biology, but also hold therapeutic promise for precise redox medicine.

Discovery of Natural Resorcylic Acid Lactones as Novel Potent Copper Ionophores Covalently Targeting PRDX1 to Induce Cuproptosis for Triple-Negative Breast Cancer Therapy

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer. Cuproptosis, a novel identified cell death form, is triggered by the direct binding of copper to lipoylated components of the tricarboxylic acid cycle. Identifying new effective drug targets and copper ionophores inducing cuproptosis for TNBC therapy is an urgent clinical need. In this study, a total of 24 resorcylic acid lactones (RALs, 1-24), including 9 previously unreported ones, were isolated from the endophyte Ilyonectria sp. Various assays demonstrated that pochonin D (16, PoD) effectively inhibited the proliferation of TNBC cells in vivo and in vitro. Further investigations, including transcriptomics, proteomics, bioinformatics analysis, CMap, OTTER, clinical samples, and the use of PoD as molecular probe, revealed that PRDX1 is associated with cuproptosis and served as a potential target in TNBC. Mechanistically, PRDX1 was involved in the process of cuproptosis, and PoD bound to the Cys173 site of PRDX1, inhibited its enzymatic activity, and intervened with cuproptosis, thereby exerting anti-TNBC activity. Our study revealed that PRDX1 is not only a promising biomarker associated with cuproptosis but also a therapeutic target for TNBC, and PoD is a novel copper ionophore capable of inducing cuproptosis in TNBC cells by targeting PRDX1.

Inhibited peroxidase activity of peroxiredoxin 1 by palmitic acid exacerbates nonalcoholic steatohepatitis in male mice

Reactive oxygen species exacerbate nonalcoholic steatohepatitis (NASH) by oxidizing macromolecules; yet how they promote NASH remains poorly understood. Here, we show that peroxidase activity of global hepatic peroxiredoxin (PRDX) is significantly decreased in NASH, and palmitic acid (PA) binds to PRDX1 and inhibits its peroxidase activity. Using three genetic models, we demonstrate that hepatic PRDX1 protects against NASH in male mice. Mechanistically, PRDX1 suppresses STAT signaling and protects mitochondrial function by scavenging hydrogen peroxide, and mitigating the oxidation of protein tyrosine phosphatases and lipid peroxidation. We further identify rosmarinic acid (RA) as a potent agonist of PRDX1. As revealed by the complex crystal structure, RA binds to PRDX1 and stabilizes its peroxidatic cysteine. RA alleviates NASH through specifically activating PRDX1's peroxidase activity. Thus, beyond revealing the molecular mechanism underlying PA promoting oxidative stress and NASH, our study suggests that boosting PRDX1's peroxidase activity is a promising intervention for treating NASH.

Adenanthin exhibits anti-inflammatory effects by covalently targeting the p65 subunit in the NF-κB signaling pathway

Adenanthin is a structurally unique ent-kaurane diterpenoid isolated from Rabdosia adenantha, a traditional Chinese medicinal plant with potent anti-cancer and anti-inflammatory activities. However, its anti-inflammatory molecular mechanism remains largely elusive to date. Here, we developed an affinity-based label-free protein profiling (ALFPP) to identify potential covalent targets of electrophilic natural products with ketone or aldehyde groups. Using ALFPP, we identified 27 potential covalent targets of adenanthin, among which p65 (RelA) has been associated with its anti-inflammatory activities. Through a series of experiments, including LC-MS/MS, molecular docking, electrophoretic mobility shift assays (EMSA), and genome editing, we demonstrated that adenanthin could covalently modify the Cys38 residue of p65 to affect the binding of DNA to p65, thereby inhibiting the NF-κB signaling pathway. ALFPP will facilitate the target identification of electrophilic carbonylated natural products, especially those containing α, β-unsaturated keto groups. Furthermore, the elucidation of the molecular mechanism of adenanthin will contribute to new drug development of adenanthin to treat inflammations and cancers, enhancing the possibility for its clinical application.

Identification of USP2 as a novel target to induce degradation of KRAS in myeloma cells

Inducing the degradation of KRAS represents a novel strategy to combat cancers with KRAS mutation. In this study, we identify ubiquitin-specific protease 2 (USP2) as a novel deubiquitinating enzyme of KRAS in multiple myeloma (MM). Specifically, we demonstrate that gambogic acid (GA) forms a covalent bond with the cysteine 284 residue of USP2 through an allosteric pocket, inhibiting its deubiquitinating activity. Inactivation or knockdown of USP2 leads to the degradation of KRAS, resulting in the suppression of MM cell proliferation in vitro and in vivo. Conversely, overexpressing USP2 stabilizes KRAS and partially abrogates GA-induced apoptosis in MM cells. Furthermore, elevated USP2 levels may be associated with poorer prognoses in MM patients. These findings highlight the potential of the USP2/KRAS axis as a therapeutic target in MM, suggesting that strategically inducing KRAS degradation via USP2 inhibition could be a promising approach for treating cancers with KRAS mutations.

Labeled and Label-Free Target Identifications of Natural Products

Target identification, employing chemical proteomics, constitutes a continuous challenging endeavor in the drug development of natural products (NPs). Understanding their targets is crucial for deciphering their mechanisms and developing potential probes or drugs. Identifications fall into two main categories: labeled and label-free techniques. Labeled methods use the molecules tagged with markers such as biotin or fluorescent labels to easily detect interactions with target proteins. Thorough structure-activity relationships are essential before labeling to avoid changes in the biological activity or binding specificity. In contrast, label-free technologies identify target proteins without modifying natural products, relying on changes in the stability, thermal properties, or precipitation in the presence or absence of these products. Each approach has its advantages and disadvantages, offering a comprehensive understanding of the mechanisms and therapeutic potential of the NPs. Here, we summarize target identification techniques for natural molecules, highlight case studies of notable NPs, and explore future applications and directions.

Annonaceous acetogenins mimic AA005 targets mitochondrial trifunctional enzyme alpha subunit to treat obesity in male mice

Obesity and related diseases pose a major health risk, yet current anti-obesity drugs inadequately addressing clinical needs. Here we show AA005, an annonaceous acetogenin mimic, resists obesity induced by high-fat diets and leptin mutations at non-toxic doses, with the alpha subunit of the mitochondrial trifunctional protein (HADHA) as a target identified through proteomics and in vitro validation. Pharmacokinetic analysis shows AA005 enriches in adipose tissue, prompting the creation of adipose-specific Hadha-deficient mice. These mice significantly mitigate diet-induced obesity, echoing AA005's anti-obesity effects. AA005 treatment and Hadha deletion in adipose tissues increase body temperature and energy expenditure in high-fat diet-fed mice. The beneficial impact of AA005 on obesity mitigation is ineffective without uncoupling protein 1 (UCP1), essential for thermogenesis regulation. Our investigation shows the interaction between AA005 and HADHA in mitochondria, activating the UCP1-mediated thermogenic pathway. This substantiates AA005 as a promising compound for obesity treatment, targeting HADHA specifically.

Quantitative Chemical Proteomics Reveals Triptolide Selectively Inhibits HCT116 Human Colon Cancer Cell Viability and Migration Through Binding to Peroxiredoxin 1 and Annexin A1

Triptolide (TPL), a natural product extracted from Tripterygium wilfordii Hook F, exerts potential anti-cancer activity. Studies have shown that TPL is involved in multiple cellular processes and signal pathways; however, its pharmaceutical activity in human colorectal cancer (CRC) as well as the underlying molecular mechanism remain elusive. In this study, the effects of TPL on HCT116 human colon cancer cells and CCD841 human colon epithelial cells are first evaluated. Next, the protein targets of TPL in HCT116 cells are identified through an activity-based protein profiling approach. With subsequent in vitro experiments, the mode of action of TPL in HCT116 cells is elucidated. As a result, TPL is found to selectively inhibit HCT116 cell viability and migration. A total of 54 proteins are identified as the targets of TPL in HCT116 cells, among which, Annexin A1 (ANXA1) and Peroxiredoxin I/II (Prdx I/II) are picked out for further investigation due to their important role in CRC. The interaction between TPL and ANXA1 or Prdx I is confirmed, and it is discovered that TPL exerts inhibitory effect against HCT116 cells through binding to ANXA1 and Prdx I. The study reinforces the potential of TPL in the CRC therapy, and provides novel therapeutic targets for the treatment of CRC.

Erianin induces ferroptosis in GSCs via REST/LRSAM1 mediated SLC40A1 ubiquitination to overcome TMZ resistance

In recent studies, erianin, a natural product isolated from Dendrobium chrysotoxum Lindl, has exhibited notable anticancer properties. Ferroptosis, a novel form of programmed cell death, holds potential as a strategy to overcome Temozolomide (TMZ) resistance in glioma by inducing ferroptosis in TMZ-resistant glioma cells. Here, utilizing various phenotyping experiments, including cell counting kit-8 (CCK-8) assays, EdU assays, transwell assays, neurosphere formation assays and extreme limiting dilution (ELDA) assays, we demonstrated that erianin exerts its anticancer activity on both TMZ sensitive and TMZ-resistant glioma stem cells (GSCs). Furthermore, we made an exciting discovery that erianin enhances TMZ sensitivity in TMZ-resistant GSCs. Subsequently, we demonstrated that erianin induced ferroptosis in TMZ-resistant GSCs and enhances TMZ sensitivity through inducing ferroptosis, which was confirmed by intracellular measurements of ROS, GSH, and MDA, as well as through the use of BODIPY (581/591) C11 and transmission electron microscopy. Conversely, the ferroptosis inhibitor ferrostatin-1 (Fer-1) blocked the effects of erianin. The underlying mechanism of ferroptosis induced by erianin was further explored through co-immunoprecipitation (Co-IP) assays, ubiquitination assays, protein stability assessments, chromatin immunoprecipitation (ChIP) assays and luciferase reporter gene assays. We found that erianin specifically targets REST, inhibiting its transcriptional repression function without altering its expression levels. Consequently, this suppression of REST's role leads to an upregulation of LRSAM1 expression. In turn, LRSAM1 ubiquitinates and degrades SLC40A1, a protein that inhibits ferroptosis by exporting ferrous ions. By downregulating SLC40A1, erianin ultimately induces ferroptosis in TMZ-resistant GSCs. Taken together, our research demonstrates that the natural product erianin inhibits the malignant phenotype of GSCs and increases the sensitivity of TMZ in TMZ-resistant GSCs by inducing ferroptosis. These findings suggest erianin as a prospective compound for the treatment of TMZ-resistant glioma.

Recent advances in identifying protein targets of bioactive natural products

Background

Natural products exhibit structural complexity, diversity, and historical therapeutic significance, boasting attractive functions and biological activities that have significantly influenced drug discovery endeavors. The identification of target proteins of active natural compounds is crucial for advancing novel drug innovation. Currently, methods for identifying targets of natural products can be categorized into labeling and label-free approaches based on whether the natural bioactive constituents are modified into active probes. In addition, there is a new avenue for rapidly exploring the targets of natural products based on their innate functions.

Aim

This review aimed to summarize recent advancements in both labeling and label-free approaches to the identification of targets for natural products, as well as the novel target identification method based on the natural functions of natural products.

Methods

We systematically collected relevant articles published in recent years from PubMed, Web of Science, and ScienceDirect, focusing on methods employed for identifying protein targets of bioactive natural products. Furthermore, we systematically summarized the principles, procedures, and successful cases, as well as the advantages and limitations of each method.

Results

Labeling methods allow for the direct labeling of target proteins and the exclusion of indirectly targeted proteins. However, these methods are not suitable for studying post-modified compounds with abolished activity, chemically challenging synthesis, or trace amounts of natural active compounds. Label-free methods can be employed to identify targets of any natural active compounds, including trace amounts and multicomponent mixtures, but their reliability is not as high as labeling methods. The structural complementarity between natural products and their innate receptors significantly increase the opportunities for finding more promising structural analogues of the natural products, and natural products may interact with several structural analogues of receptors in humans.

Conclusion

Each approach presents benefits and drawbacks. In practice, a combination of methods is employed to identify targets of natural products. And natural products' innate functions-based approach is a rapid and selective strategy for target identification. This review provides valuable references for future research in this field, offering insights into techniques and methodologies.

Discovery of Urea Derivatives of Celastrol as Selective Peroxiredoxin 1 Inhibitors against Colorectal Cancer Cells

Peroxiredoxin (PRDX1) is a tumor-overexpressed antioxidant enzyme for eliminating excessive reactive oxygen species (ROS) to protect tumor cells from oxidative damage. Herein, a series of celastrol urea derivatives were developed based on its cocrystal structure with PRDX1, with the aim of pursuing a PRDX1-specific inhibitor. Among them, derivative 15 displayed potent anti-PRDX1 activity (IC50 = 0.35 μM) and antiproliferative potency against colon cancer cells. It covalently bound to Cys-173 of PRDX1 (KD = 0.37 μM), which was secured by the cocrystal structure of PRDX1 with an analogue of 15 while exhibiting weak inhibitory effects on PRDX2-PRDX6 (IC50 > 50 μM), indicating excellent PRDX1 selectivity. Treatment with 15 dose-dependently decreased the mitochondria membrane potential of SW620 cells, probably due to ROS induced by PRDX1 inhibition, leading to cell apoptosis. In colorectal cancer cell xenograft model, it displayed potent antitumor efficacy with superior safety to celastrol. Collectively, 15 represents a promising PRDX1 selective inhibitor for the development of anticolorectal cancer agents.

Mechanisms of cancer cell death induction by triptolide: A comprehensive overview

The need for naturally occurring constituents is driven by the rise in the cancer prevalence and the unpleasant side effects associated with chemotherapeutics. Triptolide, the primary active component of "Tripterygium Wilfordii", has exploited for biological mechanisms and therapeutic potential against various tumors. Based on the recent pre-clinical investigations, triptolide is linked to the induction of death of cancerous cells by triggering cellular apoptosis via inhibiting heat shock protein expression (HSP70), and cyclin dependent kinase (CDKs) by up regulating expression of P21. MKP1, histone methyl transferases and RNA polymerases have all recently identified as potential targets of triptolide in cells. Autophagy, AKT signaling pathway and various pathways involving targeted proteins such as A-disintegrin & metalloprotease-10 (ADAM10), Polycystin-2 (PC-2), dCTP pyro-phosphatase 1 (DCTP1), peroxiredoxin-I (Prx-I), TAK1 binding protein (TAB1), kinase subunit (DNA-PKcs) and the xeroderma-pigmentosum B (XPB or ERCC3) have been exploited. Besides that, triptolide is responsible for enhancing the effectiveness of various chemotherapeutics. In addition, several triptolide moieties, including minnelide and LLDT8, have progressed in investigations on humans for the treatment of cancer. Targeted strategies, such as triptolide conjugation with ligands or triptolide loaded nano-carriers, are efficient techniques to confront toxicities associated with triptolide. We expect and anticipate that advances in near future, regarding combination therapies of triptolide, might be beneficial against cancerous cells.

Dual role of PRDX1 in redox-regulation and tumorigenesis: Past and future

Tumour cells often display an active metabolic profile, leading to the intracellular accumulation of reactive oxygen species. As a member of the peroxidase family, peroxiredoxin 1 (PRDX1) functions generally in protecting against cell damage caused by H2O2. Additionally, PRDX1 plays a role as a molecular chaperone in various malignant tumours, exhibiting either tumour-promoting or tumour-suppressing effects. Currently, PRDX1-targeting drugs have demonstrated in vitro anticancer effects, indicating the potential of PRDX1 as a molecular target. Here we discussed the diverse functions of PRDX1 in tumour biology and provided a comprehensive analysis of the therapeutic potential of targeting PRDX1 signalling across various types of cancer.

Schwann cell derived-peroxiredoxin protects motor neurons against hydrogen peroxide-induced cell death in mouse motor neuron cell line NSC-34

Schwann cells and oligodendrocytes secrete proteins that promote neuron survival, but their role in amyotrophic lateral sclerosis (ALS) is unclear. To address this question, we evaluated the effect of molecules secreted by Schwann cells on reactive oxygen species (ROS)-induced motor neuronal cell death. We observed that in motor neuron cell line NSC-34 cultures, the conditioned medium (CM) from Schwann cell line YST-1 (YST-1 CM) cultures had a protective effect against hydrogen peroxide-induced cell death. However, this protective effect of YST-1 CM was abolished by removing peroxiredoxin 1-4 (PRDX1-4) from the CM. We found that the expression of PRDX1 mRNA was markedly downregulated in the lumbar spinal cord of the superoxide dismutase 1 (SOD1)G93A mouse model of ALS. We also found that transient transfection of YST-1 cells with G93A SOD1 resulted in reduced PRDX1 mRNA expression. Additionally, in the mutant transfected cells, YST-1 CM showed decreased neuroprotective effect against hydrogen peroxide-induced NSC-34 cell death compared to those transfected with WT SOD1. Our results suggest that Schwann cells protect motor neurons from oxidative stress by secreting PRDX1 and that the reduction of PRDX secreted from Schwann cells contributes to increased ROS and associated motor neuronal death in ALS.

The multifaceted nature of peroxiredoxins in chemical biology

Peroxiredoxins (Prx), thiol-dependent peroxidases, were first identified as H2O2 detoxifiers, and more recently as H2O2 sensors, intermediates in redox-signaling pathways, metabolism modulators, and chaperones. The multifaceted nature of Prx is not only dependent on their peroxidase activity but also strongly associated with specific protein-protein interactions that are being identified, and where the Prx oligomerization dynamics plays a role. Their oxidation by a peroxide substrate forms a sulfenic acid that opens a route to channel the redox signal to diverse protein targets. Recent research underscores the importance of different Prx isoforms in the cellular processes behind disease development with potential therapeutic applications.

Small-molecule probes from bench to bedside: advancing molecular analysis of drug-target interactions toward precision medicine

Over the past decade, remarkable advances have been witnessed in the development of small-molecule probes. These molecular tools have been widely applied for interrogating proteins, pathways and drug-target interactions in preclinical research. While novel structures and designs are commonly explored in probe development, the clinical translation of small-molecule probes remains limited, primarily due to safety and regulatory considerations. Recent synergistic developments - interfacing novel chemical probes with complementary analytical technologies - have introduced and expedited diverse biomedical opportunities to molecularly characterize targeted drug interactions directly in the human body or through accessible clinical specimens (e.g., blood and ascites fluid). These integrated developments thus offer unprecedented opportunities for drug development, disease diagnostics and treatment monitoring. In this review, we discuss recent advances in the structure and design of small-molecule probes with novel functionalities and the integrated development with imaging, proteomics and other emerging technologies. We further highlight recent applications of integrated small-molecule technologies for the molecular analysis of drug-target interactions, including translational applications and emerging opportunities for whole-body imaging, tissue-based measurement and blood-based analysis.

Conoidin A, a Covalent Inhibitor of Peroxiredoxin 2, Reduces Growth of Glioblastoma Cells by Triggering ROS Production

Compounds that cause oxidative stress have recently gained considerable interest as potential anticancer treatment modalities. Nevertheless, their efficiency may be diminished by the antioxidant systems often upregulated in cancer cells. Peroxiredoxins (PRDXs) are antioxidant enzymes that scavenge peroxides and contribute to redox homeostasis. They play a role in carcinogenesis and are upregulated in several cancer types. Here, we assessed the expression pattern of PRDX1 and PRDX2 in glioblastoma (GBM) and examined the efficacy of their inhibitors in GBM cell lines and patient-derived GBM cells. Both PRDX1 and PRDX2 were upregulated in GBM compared to non-tumor brain tissues and their considerable amounts were observed in GBM cells. Adenanthin, a compound inhibiting PRDX1 activity, slightly decreased GBM cell viability, while conoidin A (CONA), a covalent PRDX2 inhibitor, displayed high toxicity in GBM cells. CONA elevated the intracellular reactive oxygen species (ROS) level. Pre-treatment with an ROS scavenger protected cells from CONA-induced death, indicating that ROS accumulation plays a crucial role in this phenomenon. Menadione or celecoxib, both of which are ROS-inducing agents, potentiated the anticancer activity of CONA. Collectively, our results unveil PRDX1 and PRDX2 as potential targets for GBM therapy, and substantiate the further exploration of their inhibitors.

Peroxiredoxin 2: An Important Element of the Antioxidant Defense of the Erythrocyte

Peroxiredoxin 2 (Prdx2) is the third most abundant erythrocyte protein. It was known previously as calpromotin since its binding to the membrane stimulates the calcium-dependent potassium channel. Prdx2 is present mostly in cytosol in the form of non-covalent dimers but may associate into doughnut-like decamers and other oligomers. Prdx2 reacts rapidly with hydrogen peroxide (k > 10⁷ M^-1 s^-1). It is the main erythrocyte antioxidant that removes hydrogen peroxide formed endogenously by hemoglobin autoxidation. Prdx2 also reduces other peroxides including lipid, urate, amino acid, and protein hydroperoxides and peroxynitrite. Oxidized Prdx2 can be reduced at the expense of thioredoxin but also of other thiols, especially glutathione. Further reactions of Prdx2 with oxidants lead to hyperoxidation (formation of sulfinyl or sulfonyl derivatives of the peroxidative cysteine). The sulfinyl derivative can be reduced by sulfiredoxin. Circadian oscillations in the level of hyperoxidation of erythrocyte Prdx2 were reported. The protein can be subject to post-translational modifications; some of them, such as phosphorylation, nitration, and acetylation, increase its activity. Prdx2 can also act as a chaperone for hemoglobin and erythrocyte membrane proteins, especially during the maturation of erythrocyte precursors. The extent of Prdx2 oxidation is increased in various diseases and can be an index of oxidative stress.

Ainsliadimer A induces ROS-mediated apoptosis in colorectal cancer cells via directly targeting peroxiredoxin 1 and 2

The peroxiredoxin (PRDX) family is a class of antioxidant enzymes with peroxidase activity. Human PRDXs currently have six members (PRDX1-6), which are gradually becoming potential therapeutic targets for major diseases such as cancer. In this study, we reported ainsliadimer A (AIN), a sesquiterpene lactone dimer with antitumor activity. We found that AIN directly targets Cys173 of PRDX1 and Cys172 of PRDX2 and then inhibits their peroxidase activities. As a result, the level of intracellular ROS increases, causing oxidative stress damage in mitochondria, inhibiting mitochondrial respiration, and significantly inhibiting ATP production. AIN inhibits the proliferation and induces apoptosis of colorectal cancer cells. Additionally, it inhibits tumor growth in mice and the growth of tumor organoid models. Therefore, AIN can be one of the natural compounds targeting PRDX1 and PRDX2 in the treatment of colorectal cancer.

A chromosome-level genome assembly reveals that tandem-duplicated CYP706V oxidase genes control oridonin biosynthesis in the shoot apex of Isodon rubescens

The ent-kaurenoids (e.g., oridonin and enmein) from the Isodon genus (Lamiaceae) are one class of diterpenoids with rich structural diversity and intriguing pharmaceutical activity. In contrast to the well-established gibberellin pathway, oxidative modifications diversifying the ent-kaurene skeleton in Isodon have remained undetermined for half a century. Here we report a chromosome-level genome assembly of I. rubescens, a well-recognized oridonin producer long favored by Asian people as a traditional herb with antitumor effects. The shoot apex was confirmed to be the actual region actively producing ent-kaurene diterpenoids. Through comparative genomics and phylogenetic analyses, we discovered a cluster of tandem-duplicated CYP706V oxygenase-encoding genes located on an ancient genomic block widely distributed in eudicots, whereas almost exclusively emerged in Isodon plants. In the shoot apex, IrCYP706V2 and IrCYP706V7 oxidized the ent-kaurene core in the initial stage of oridonin biosynthesis. Loss of CYP706Vs in other Lamiaceae plants offered an explanation for the specific kaurenoid production in Isodon plants. Moreover, we found that the Isodon genomes encode multiple diterpenoid synthases that are potentially involved in generating diterpenoid diversity. These findings provided new insights into the evolution of the lineage-specific diterpenoid pathway and laid a foundation for improving production of bioactive ent-kaurene-type diterpenoids by molecular breeding and synthetic biology approaches.

Exploring functional and structural features of chemically related natural prenylated hydroquinone and benzoic acid from Piper crassinervium (Piperaceae) on bacterial peroxiredoxin inhibition

Multiple drug resistance (MDR) bacterial strains are responsible by 1.2 million of human deaths all over the world. The pathogens possess efficient enzymes which are able to mitigate the toxicity of reactive oxygen species (ROS) produced by some antibiotics and the host immune cells. Among them, the bacterial peroxiredoxin alkyl hydroperoxide reductase C (AhpC) is able to decompose efficiently several kinds of hydroperoxides. To decompose their substrates AhpC use a reactive cysteine residue (peroxidatic cysteine-CysP) that together with two other polar residues (Thr/Ser and Arg) comprise the catalytic triad of these enzymes and are involved in the substrate targeting/stabilization to allow a bimolecular nucleophilic substitution (SN2) reaction. Additionally to the high efficiency the AhpC is very abundant in the cells and present virulent properties in some bacterial species. Despite the importance of AhpC in bacteria, few studies aimed at using natural compounds as inhibitors of this class of enzymes. Some natural products were identified as human isoforms, presenting as common characteristics a bulk hydrophobic moiety and an α, β-unsaturated carbonylic system able to perform a thiol-Michael reaction. In this work, we evaluated two chemically related natural products: 1,4-dihydroxy-2-(3',7'-dimethyl-1'-oxo-2'E,6'-octadienyl) benzene (C1) and 4-hydroxy-2-(3',7'-dimethyl-1'-oxo-2'E,6'-octadienyl) benzoic acid (C2), both were isolated from branches Piper crassinervium (Piperaceae), over the peroxidase activity of AhpC from Pseudomonas aeruginosa (PaAhpC) and Staphylococcus epidermidis (SeAhpC). By biochemical assays we show that although both compounds can perform the Michael addition reaction, only compound C2 was able to inhibit the PaAhpC peroxidase activity but not SeAhpC, presenting IC50 = 20.3 μM. SDS-PAGE analysis revealed that the compound was not able to perform a thiol-Michael addition, suggesting another inhibition behavior. Using computer-assisted simulations, we also show that an acidic group present in the structure of compound C2 may be involved in the stabilization by polar interactions with the Thr and Arg residues from the catalytic triad and several apolar interactions with hydrophobic residues. Finally, C2 was not able to interfere in the peroxidase activity of the isoform Prx2 from humans or even the thiol proteins of the Trx reducing system from Escherichia coli (EcTrx and EcTrxR), indicating specificity for P. aeruginosa AhpC.

Peroxiredoxin 2 Is a Potential Objective Indicator for Severity and the Clinical Status of Subarachnoid Hemorrhage Patients

Purpose

We have demonstrated that peroxiredoxin 2 (Prx2) released from lytic erythrocytes and damaged neurons into the subarachnoid space could activate microglia and then result in neuronal apoptosis. In this study, we tested the possibility of using Prx2 as an objective indicator for severity of the subarachnoid hemorrhage (SAH) and the clinical status of the patient.

Materials and Methods

SAH patients were prospectively enrolled and followed up for 3 months. Cerebrospinal fluid (CSF) and blood samples were collected 0-3 and 5-7 days after SAH onset. The levels of Prx2 in the CSF and the blood were measured by an enzyme-linked immunosorbent assay (ELISA). We used Spearman's rank coefficient to assess the correlation between Prx2 and the clinical scores. Receiver operating characteristic (ROC) curves were used for Prx2 levels to predict the outcome of SAH by calculating the area under the curve (AUC). Unpaired Student's t-test was used to analyze the differences in continuous variables across cohorts.

Results

Prx2 levels in the CSF increased after onset while those in the blood decreased. Existing data showed that Prx2 levels within 3 days in the CSF after SAH were positively correlated with the Hunt-Hess score (R = 0.761, P < 0.001). Patients with CVS had higher levels of Prx2 in their CSF within 5-7 days after onset. Prx2 levels in the CSF within 5-7 days can be used as a predictor of prognosis. The ratio of Prx2 in the CSF and the blood within 3 days of onset was positively correlated with the Hunt-Hess score and negatively correlated with Glasgow Outcome Scale (GOS; R = -0.605, P < 0.05).

Conclusion

We found that the levels of Prx2 in the CSF and the ratio of Prx2 in the CSF and the blood within 3 days of onset can be used as a biomarker to detect the severity of the disease and the clinical status of the patient.

Celastrol suppresses colorectal cancer via covalent targeting peroxiredoxin 1

As a terpenoids natural product isolated from the plant Thunder God Vine, Celastrol is widely studied for its pharmacological activities, including anti-tumor activities. The clinical application of Celastrol is strictly limited due to its severe side effects, whereas previously revealed targets and mechanism of Celastrol seldom reduce its in vivo toxicity via structural optimization. Target identification has a far-reaching influence on the development of innovative drugs, and omics data has been widely used for unbiased target prediction. However, it is difficult to enrich target of specific phenotype from thousands of genes or proteins, especially for natural products with broad promising activities. Here, we developed a text-mining-based web-server tool to enrich targets from omics data of inquired compounds. Then peroxiredoxin 1 (PRDX1) was identified as the ROS-manipulating target protein of Celastrol in colorectal cancer. Our solved high-resolution crystal structure revealed the unique covalent binding mode of Celastrol with PRDX1. New derivative compound 19-048 with improved potency against PRDX1 and selectivity towards PRDX2~PRDX6 were synthesized based on crystal structure analysis. Both Celastrol and 19-048 effectively suppressed the proliferation of colorectal cancer cells. The anti-tumor efficacy of Celastrol and 19-048 was significantly diminished on xenograft nude mice bearing PRDX1 knock-down colorectal cancer cells. Several downstream genes of p53 signaling pathway were dramatically up-regulated with Celastrol or 19-048 treatment. Our findings reveal that the side effects of Celastrol could be reduced via structural modification, and PRDX1 inhibition is promising for the treatment of colorectal cancer.

Thioredoxin Signaling Pathways in Cancer

Significance: Thioredoxin (Trx) is a powerful antioxidant that reduces protein disulfides to maintain redox stability in cells and is involved in regulating multiple redox-dependent signaling pathways. Recent Advance: The current accumulation of findings suggests that Trx participates in signaling pathways that interact with various proteins to manipulate their dynamic regulation of structure and function. These network pathways are critical for cancer pathogenesis and therapy. Promising clinical advances have been presented by most anticancer agents targeting such signaling pathways. Critical Issues: We herein link the signaling pathways regulated by the Trx system to potential cancer therapeutic opportunities, focusing on the coordination and strengths of the Trx signaling pathways in apoptosis, ferroptosis, immunomodulation, and drug resistance. We also provide a mechanistic network for the exploitation of therapeutic small molecules targeting the Trx signaling pathways. Future Directions: As research data accumulate, future complex networks of Trx-related signaling pathways will gain in detail. In-depth exploration and establishment of these signaling pathways, including Trx upstream and downstream regulatory proteins, will be critical to advancing novel cancer therapeutics. Antioxid. Redox Signal. 38, 403-424.

New opportunities and challenges of natural products research: When target identification meets single-cell multiomics

Natural products, and especially the active ingredients found in traditional Chinese medicine (TCM), have a thousand-year-long history of clinical use and a strong theoretical basis in TCM. As such, traditional remedies provide shortcuts for the development of original new drugs in China, and increasing numbers of natural products are showing great therapeutic potential in various diseases. This paper reviews the molecular mechanisms of action of natural products from different sources used in the treatment of inflammatory diseases and cancer, introduces the methods and newly emerging technologies used to identify and validate the targets of natural active ingredients, enumerates the expansive list of TCM used to treat inflammatory diseases and cancer, and summarizes the patterns of action of emerging technologies such as single-cell multiomics, network pharmacology, and artificial intelligence in the pharmacological studies of natural products to provide insights for the development of innovative natural product-based drugs. Our hope is that we can make use of advances in target identification and single-cell multiomics to obtain a deeper understanding of actions of mechanisms of natural products that will allow innovation and revitalization of TCM and its swift industrialization and internationalization.

Peroxiredoxin, Senescence, and Cancer

Peroxiredoxins are multifunctional enzymes that play a key role in protecting cells from stresses and maintaining the homeostasis of many cellular processes. Peroxiredoxins were firstly identified as antioxidant enzymes that can be found in all living organisms. Later studies demonstrated that peroxiredoxins also act as redox signaling regulators, chaperones, and proinflammatory factors and play important roles in oxidative defense, redox signaling, protein folding, cycle cell progression, DNA integrity, inflammation, and carcinogenesis. The versatility of peroxiredoxins is mainly based on their unique active center cysteine with a wide range of redox states and the ability to switch between low- and high-molecular-weight species for regulating their peroxidase and chaperone activities. Understanding the molecular mechanisms of peroxiredoxin in these processes will allow the development of new approaches to enhance longevity and to treat various cancers. In this article, we briefly review the history of peroxiredoxins, summarize recent advances in our understanding of peroxiredoxins in aging- and cancer-related biological processes, and discuss the future perspectives of using peroxiredoxins in disease diagnostics and treatments.

Adenanthin Is an Efficient Inhibitor of Peroxiredoxins from Pathogens, Inhibits Bacterial Growth, and Potentiates Antibiotic Activities

The emergence and re-emergence of bacterial strains resistant to multiple drugs represent a global health threat, and the search for novel biological targets is a worldwide concern. AhpC are enzymes involved in bacterial redox homeostasis by metabolizing diverse kinds of hydroperoxides. In pathogenic bacteria, AhpC are related to several functions, as some isoforms are characterized as virulence factors. However, no inhibitor has been systematically evaluated to date. Here we show that the natural ent-kaurane Adenanthin (Adn) efficiently inhibits AhpC and molecular interactions were explored by computer assisted simulations. Additionally, Adn interferes with growth and potentializes the effect of antibiotics (kanamycin and PMBN), positioning Adn as a promising compound to treat infections caused by multiresistant bacterial strains.

Celastrol induces ferroptosis in activated HSCs to ameliorate hepatic fibrosis via targeting peroxiredoxins and HO-1

Ferroptosis is a form of regulated cell death, characterized by excessive membrane lipid peroxidation in an iron- and ROS-dependent manner. Celastrol, a natural bioactive triterpenoid extracted from Tripterygium wilfordii, shows effective anti-fibrotic and anti-inflammatory activities in multiple hepatic diseases. However, the exact molecular mechanisms of action and the direct protein targets of celastrol in the treatment of liver fibrosis remain largely elusive. Here, we discover that celastrol exerts anti-fibrotic effects via promoting the production of reactive oxygen species (ROS) and inducing ferroptosis in activated hepatic stellate cells (HSCs). By using activity-based protein profiling (ABPP) in combination with bio-orthogonal click chemistry reaction and cellular thermal shift assay (CETSA), we show that celastrol directly binds to peroxiredoxins (PRDXs), including PRDX1, PRDX2, PRDX4 and PRDX6, through the active cysteine sites, and inhibits their anti-oxidant activities. Celastrol also targets to heme oxygenase 1 (HO-1) and upregulates its expression in activated-HSCs. Knockdown of PRDX1, PRDX2, PRDX4, PRDX6 or HO-1 in HSCs, to varying extent, elevated cellular ROS levels and induced ferroptosis. Taken together, our findings reveal the direct protein targets and molecular mechanisms via which celastrol ameliorates hepatic fibrosis, thus supporting the further development of celastrol as a promising therapeutic agent for liver fibrosis.

Wangzaozin A, a potent novel microtubule stabilizer, targets both the taxane and laulimalide sites on β-tubulin through molecular dynamics simulations

Wangzaozin A, an ent-kaurene diterpenoid isolated from Isodon racemosa (Hemsl) Hara, promotes the polymerization of intracellular microtubules as well as purified tubulin, which is similar to other known microtubule stabilizers. Our pharmacological results showed that wangzaozin A induced G2/M cell cycle arrest and the significant inhibition of cancer cell proliferation. A molecular docking study indicated that wangzaozin A could bind to both the taxane and laulimalide (lau) sites on β-tubulin, which is a novel binding mode that differs from that of known microtubule stabilizers. Furthermore, molecular dynamics simulation and binding free energy calculations demonstrated that wangzaozin A could stably bind to taxane and lau sites simultaneously and form a double-bonded complex. The binding mode of wangzaozin A to the taxane site was more similar to that of epothilone A than paclitaxel. Our results demonstrate that wangzaozin A represents a novel class of microtubule stabilizers, and may serve as a potential microtubule-targeting lead compound for further structural optimization.

Two new 7,20-epoxy-ent-kaurane diterpenoids from the aerial parts of Isodon serra

Two new compounds (1 and 2), belonging to C-20 oxygenated ent-kauranes-type diterpenoids, were identified from the aerial parts of Isodon serra. Their structures were elucidated by extensive analysis of HRESI-MS and NMR spectroscopic data. Both these two compounds possess a common 7,20-epoxy-ent-kauranes skeleton with a hydroxyl group rarely occurring at C-13. Compounds 1 and 2 were evaluated for their cytotoxic activity against Hela-60 and HepG2 as well as the antibacterial activity against Staphylococcus aureus, Bacillus cereus and Escherichia coli.

Cytotoxic Activities of 9,10-seco-Cycloartane-Type Triterpenoids from the Chinese Liverwort Lepidozia reptans

Ten new triterpenoids, including nine 9,10-seco-cycloartanes (1-9) and one 9,19-cyclolanostane (10), as well as one sesquiterpenoid (11) and four known compounds (12-15), were extracted and purified from the whole plant of the Chinese liverwort Lepidozia reptans. Multiple techniques (NMR, HRESIMS, IR, and X-ray crystallographic analysis) were applied to determine the structures of the isolated compounds. Bioassay determinations showed that compound 7, which contains an α,β-unsaturated carbonyl moiety in its structure, inhibited the growth of a panel of cancer cell lines with IC₅₀ values ranging from 4.2 ± 0.2 to 5.7 ± 0.5 μM. Further investigation revealed that compound 7 induces PC-3 cell death via mitochondrial-related apoptosis.

Reactive Oxygen Species in Acute Lymphoblastic Leukaemia: Reducing Radicals to Refine Responses

Acute lymphoblastic leukaemia (ALL) is the most common cancer diagnosed in children and adolescents. Approximately 70% of patients survive >5-years following diagnosis, however, for those that fail upfront therapies, survival is poor. Reactive oxygen species (ROS) are elevated in a range of cancers and are emerging as significant contributors to the leukaemogenesis of ALL. ROS modulate the function of signalling proteins through oxidation of cysteine residues, as well as promote genomic instability by damaging DNA, to promote chemotherapy resistance. Current therapeutic approaches exploit the pro-oxidant intracellular environment of malignant B and T lymphoblasts to cause irreversible DNA damage and cell death, however these strategies impact normal haematopoiesis and lead to long lasting side-effects. Therapies suppressing ROS production, especially those targeting ROS producing enzymes such as the NADPH oxidases (NOXs), are emerging alternatives to treat cancers and may be exploited to improve the ALL treatment. Here, we discuss the roles that ROS play in normal haematopoiesis and in ALL. We explore the molecular mechanisms underpinning overproduction of ROS in ALL, and their roles in disease progression and drug resistance. Finally, we examine strategies to target ROS production, with a specific focus on the NOX enzymes, to improve the treatment of ALL.

Currently Available Strategies for Target Identification of Bioactive Natural Products

In recent years, biologically active natural products have gradually become important agents in the field of drug research and development because of their wide availability and variety. However, the target sites of many natural products are yet to be identified, which is a setback in the pharmaceutical industry and has seriously hindered the translation of research findings of these natural products as viable candidates for new drug exploitation. This review systematically describes the commonly used strategies for target identification via the application of probe and non-probe approaches. The merits and demerits of each method were summarized using recent examples, with the goal of comparing currently available methods and selecting the optimum techniques for identifying the targets of bioactive natural products.

Synthesis of 3'-O-Alkyl Homologues and a Biotin Probe of Isorhamnetin and Evaluation of Cytotoxic Efficacy on Cancer Cells

Isorhamnetin is a natural flavonoid which shows a variety of biological activities such as antioxidant, anti-inflammatory and antitumor. In order to identify the cellular binding protein of isorhamnetin as potential anti-cancer target, we first synthesized 3'-O-substituted quercetin as isorhamnetin homologues and evaluated the growth inhibitory activity of these derivatives on breast, colon and prostate cancer cell lines. The preliminary results showed that the 3'-O modification did not affect the cytotoxic activity of the scaffold. Analysis of the co-crystal structure and the docking pose of isorhamnetin with reported binding protein of isorhamnetin or quercetin indicated the 3'-O-substitution groups located outside of the binding pocket, which is in accordance with activity of 3'-O derivatives. Then a biotin conjugate of isorhamnetin with a tetraethylene glycol (PEG)₄ linker at the 3' position was synthesized and the resulting probe retained the anti-proliferative activity on cancer cell lines, while the cellular fluorescence analysis showed the distribution of probe inside the cells which indicated the probe had limited cell permeability. Finally, pull down assay both in situ inside cells and in the cell lysates indicated the isorhamnetin biotin probe was capable of protein labeling in cell lysates. These findings provide the isorhamnetin 3'-O-biotin probe as a tool to reveal the target proteins of isorhamnetin.

The diterpenoid adenanthin upregulates the expression of natural killer group 2D receptor ligands in hepatocellular carcinoma cells

OBJECTIVE

The natural killer (NK) group 2D (NKG2D) receptor plays a crucial role in NK cell-mediated anti-tumor immunity. NKG2D anti-proliferative effect is mediated by direct interactions of the receptor with its ligands that may be considered as a potential target for NK-based immunotherapeutic strategy in cancer cells.

METHODS

Here we report that a natural product adenanthin significantly promotes NKG2D ligands expression in hepatoma cells. The effect was determined using flow cytometry analysis. The activity of NK cell was evaluated by measuring its degranulation activity and cytotoxicity.

RESULTS

Our data indicates that the induction of NKG2D ligand binding to liver cancer cell surface receptors greatly improves the killing activity of NK cells against the cancer cells.

CONCLUSIONS

This is the first report of a new mechanism anti-cancer effects of adenanthin mediated by an indirect activation of NK cells. Our data suggests that adenanthin may be used to sensitize NK cells in tumor immunotherapy.

Synthesis of a biotinylated heptose 1,7-bisphosphate analogue, a probe to study immunity and inflammation

d-glycero-d-manno-Heptose-1β,7-bisphosphate (HBP) is a bacterial metabolite that can induce a TIFA-dependent innate immune response in mammals. It was recently discovered that after HBP enters into the cytoplasm of the host cell, it is transformed into ADP-heptose-7-phosphate, which then leads to ALPK1-TIFA-dependent inflammatory response. In order to provide a molecular tool allowing the discovery of the proteins involved in this novel inflammatory pathway, we designed and synthesized a biotinylated analogue of HBP. This chemical probe displays an anomeric β-phosphate and a phosphonate at the 7-position, and a d-configured 6-position to which is attached the biotin moiety. To do so, different synthetic strategies were explored and described in this report. Moreover, we demonstrated that the biotinylated version of HBP is still biologically active and can activate the NF-κB pathway in HEK293T cells.

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.

Elucidating direct kinase targets of compound Danshen dropping pills employing archived data and prediction models

Research on direct targets of traditional Chinese medicine (TCM) is the key to study the mechanism and material basis of it, but there is still no effective methods at present. We took Compound Danshen dropping pills (CDDP) as a study case to establish a strategy to identify significant direct targets of TCM. As a result, thirty potential active kinase targets of CDDP were identified. Nine of them had potential dose-dependent effects. In addition, the direct inhibitory effect of CDDP on three kinases, AURKB, MET and PIM1 were observed both on biochemical level and cellular level, which could not only shed light on the mechanisms of action involved in CDDP, but also suggesting the potency of drug repositioning of CDDP. Our results indicated that the research strategy including both in silico models and experimental validation that we built, were relatively efficient and reliable for direct targets identification for TCM prescription, which will help elucidating the mechanisms of TCM and promoting the modernization of TCM.

NOX4 links metabolic regulation in pancreatic cancer to endoplasmic reticulum redox vulnerability and dependence on PRDX4

There is an urgent need to identify vulnerabilities in pancreatic ductal adenocarcinoma (PDAC). PDAC cells acquire metabolic changes that augment NADPH production and cytosolic redox homeostasis. Here, we show that high NADPH levels drive activity of NADPH oxidase 4 (NOX4) expressed in the endoplasmic reticulum (ER) membrane. NOX4 produces H₂O₂ metabolized by peroxiredoxin 4 (PRDX4) in the ER lumen. Using functional genomics and subsequent in vitro and in vivo validations, we find that PDAC cell lines with high NADPH levels are dependent on PRDX4 for their growth and survival. PRDX4 addiction is associated with increased reactive oxygen species, a DNA-PKcs-governed DNA damage response and radiosensitivity, which can be rescued by depletion of NOX4 or NADPH. Hence, this study has identified NOX4 as a protein that paradoxically converts the reducing power of the cytosol to an ER-specific oxidative stress vulnerability in PDAC that may be therapeutically exploited by targeting PRDX4.

ent-Kaurane diterpenoids induce apoptosis and ferroptosis through targeting redox resetting to overcome cisplatin resistance

Reactive oxygen species (ROS) induction is an effective mechanism to kill cancer cells for many chemotherapeutics, while resettled redox homeostasis induced by the anticancer drugs will promote cancer chemoresistance. Natural ent-kaurane diterpenoids have been found to bind glutathione (GSH) and sulfhydryl group in antioxidant enzymes covalently, which leads to the destruction of intracellular redox homeostasis. Therefore, redox resetting destruction by ent-kaurane diterpenoids may emerge as a viable strategy for cancer therapy. In this study, we isolated 30 ent-kaurane diterpenoids including 20 new samples from Chinese liverworts Jungermannia tetragona Lindenb and studied their specific targets and possible application in cancer drug resistance through redox resetting destruction. 11β-hydroxy-ent-16-kaurene-15-one (23) possessed strong inhibitory activity against several cancer cell lines. Moreover, compound 23 induced both apoptosis and ferroptosis through increasing cellular ROS levels in HepG2 cells. ROS accumulation induced by compound 23 was caused by inhibition of antioxidant systems through targeting peroxiredoxin I/II (Prdx I/II) and depletion of GSH. Furthermore, compound 23 sensitized cisplatin (CDDP)-resistant A549/CDDP cancer cells in vitro and in vivo by inducing apoptosis and ferroptosis. Thus, the ent-kaurane derivative showed potential application for sensitizing CDDP resistance by redox resetting destruction through dual inhibition of Prdx I/II and GSH in cancer chemotherapy.

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Thirty ent-kaurane diterpenoids were isolated from the Chinese liverworts, Jungermannia tetragona.

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11β-hydroxy-ent-16-kaurene-15-one (23) was identified to induce apoptosis and ferroptosis for the first time.

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Compound 23 could disorder the intracellular redox system by directly targeting Prdx I/II and GSH.

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Compound 23 could sensitize A549/CDDP cancer cells in vitro and in vivo through redox resetting destruction.