Design and synthesis of celastrol derivatives as anticancer agents

Insights into the role of mitophagy in lung cancer: current evidence and perspectives

Lung cancer, recognized globally as a leading cause of malignancy-associated morbidity and mortality, is marked by its high prevalence and lethality, garnering extensive attention within the medical community. Mitophagy is a critical cellular process that plays a crucial role in regulating metabolism and ensuring quality control within cells. Its relevance to lung cancer has garnered significant attention among researchers and scientists. Mitophagy's involvement in lung cancer encompasses its initiation, progression, metastatic dissemination and treatment. The regulatory landscape of mitophagy is complex, involving numerous signaling proteins and pathways that may exhibit aberrant alterations or mutations within the tumor environment. In the field of treatment, the regulation of mitophagy is considered key to determining cancer chemotherapy, radiation therapy, other treatment options, and drug resistance. Contemporary investigations are directed towards harnessing mitophagy modulators, both inhibitors and activators, in therapeutic strategies, with an emphasis on achieving specificity to minimize collateral damage to healthy cellular populations. Furthermore, molecular constituents and pathways affiliated with mitophagy, serving as potential biomarkers, offer promising avenues for enhancing diagnostic accuracy, prognostic assessment, and prediction of therapeutic responses in lung cancer. Future endeavors will also involve investigating the impact of mitophagy on the composition and function of immune cells within the tumor microenvironment, aiming to enhance our understanding of how mitophagy modulates the immune response to lung cancer. This review aims to comprehensively overview recent advancements about the role of mitophagy in the tumor genesis, progenesis and metastasis, and the impact of mitophagy on the treatment of lung cancer. We also discussed the future research direction of mitophagy in the field of lung cancer.

Native Endophytes of Tripterygium wilfordii-Mediated Biotransformation Reduces Toxicity of Celastrol

Celastrol (1), obtained from the roots of Tripterygium wilfordii Hook F., is most likely to become an antitumor drug, but with severe cytotoxicity. Due to the lack of modifiable sites in the structure of celastrol, the structural diversity of the modified products obtained by synthesis in the previous studies is insufficient, which hinders the pace of its patent medicine. This study describes a method of microbial transformation to increase the modification site of celastrol and reduce its toxicity. The screening of endophytes from native plants was introduced in this context, which led to two novel stereoselective oxidation products such as S-16-hydroxyl celastrol (2) and A-ring aromatized S-16-hydroxyl celastrol (3), along with a rare 7,9-octadecadienoic acid ester of celastrol (4). Their structures were determined by extensive spectroscopic data analysis, especially 1D and 2D NMR. Compared with 1, compounds 3 and 4 exhibited similar antitumor activity in U251, A549, KG-1, and B16 cell lines. Compound 2 had slightly decreased antitumor activity when compared with compound 1. Furthermore, compound 2–4 showed lower cytotoxicity against BV-2 (about 21-fold lower, 2: 92.82 μM, 3: 34.25 μM, and 4: 74.75 μM vs. celastrol: 4.35 μM), and also identical trends against H9c2 and PC12 cell lines.

Celastrol Inhibits Canine Mammary Tumor Cells by Inducing Apoptosis via the Caspase Pathway

Canine mammary tumor is a serious disease threatening the health of dogs and can be used as a research model for human breast cancer. The study of canine mammary tumor has a role in improving the welfare of dogs. Most common canine mammary tumor chemotherapy drugs have limited effects and drug resistance. Celastrol is an extract of Tripterygium wilfordii, which has a wide range of biological activities, including significant anti-tumor effects. At present, celastrol has not been used in the clinical treatment for canine mammary tumor. This study investigated the anti-tumor properties of celastrol through in vitro assay of cell proliferation inhibition, cell colony, cell migration, and invasion; flow cytometry, qPCR, and Western Blot methods were used to explore the anti-tumor mechanism of celastrol. The results showed that celastrol can inhibit the proliferation of canine mammary tumor cells in vitro, and decrease the migration and invasion ability of canine mammary tumor cells. We also found that celastrol can upregulate Cleaved Caspase-3 and Cleaved Caspase-9 protein expression levels to promote cell apoptosis, and can regulate cell cycle-related proteins to induce cell cycle arrest. In summary, celastrol may inhibit canine mammary tumor cells through the Caspase pathway, providing a new direction for anti-canine mammary tumor drugs, and is expected to become a new anti-cancer drug for canine mammary tumors.

In Silico Design, Synthesis, and Biological Evaluation of Anticancer Arylsulfonamide Endowed with Anti-Telomerase Activity

Telomerase, a reverse transcriptase enzyme involved in DNA synthesis, has a tangible role in tumor progression. Several studies have evidenced telomerase as a promising target for developing cancer therapeutics. The main reason is due to the overexpression of telomerase in cancer cells (85–90%) compared with normal cells where it is almost unexpressed. In this paper, we used a structure-based approach to design potential inhibitors of the telomerase active site. The MYSHAPE (Molecular dYnamics SHared PharmacophorE) approach and docking were used to screen an in-house library of 126 arylsulfonamide derivatives. Promising compounds were synthesized using classical and green methods. Compound 2C revealed an interesting IC₅₀ (33 ± 4 µM) against the K-562 cell line compared with the known telomerase inhibitor BIBR1532 IC₅₀ (208 ± 11 µM) with an SI ~10 compared to the BALB/3-T3 cell line. A 100 ns MD simulation of 2C in the telomerase active site evidenced Phe494 as the key residue as well as in BIBR1532. Each moiety of compound 2C was involved in key interactions with some residues of the active site: Arg557, Ile550, and Gly553. Compound 2C, as an arylsulfonamide derivative, is an interesting hit compound that deserves further investigation in terms of optimization of its structure to obtain more active telomerase inhibitors

Novel cannabidiol-carbamate hybrids as selective BuChE inhibitors: Docking-based fragment reassembly for the development of potential therapeutic agents against Alzheimer's disease

Cannabidiol (CBD) and rivastigmine have been launched as drugs for treating dementia and cholinesterases (ChEs) are ideal drug targets. This study focused on developing novel ChE inhibitors as drug leads against dementia through molecular modeling and fragment reassembly approaches. A potent carbamate fragment binding to active site gorge of BuChE was found via a docking-based structural splicing approach, thus, 17 novel compounds were designed by structural reassembly. Compound C16 was identified as a highly selective potent BuChE inhibitor (IC₅₀ = 5.3 nM, SI > 4000), superior to CBD (IC₅₀ = 0.67 μM). C16 possessed BBB penetrating ability, benign safety, neuroprotection, antioxidant and pseudo-irreversible BuChE inhibition (K_d = 13 nM, k₂ = 0.26 min^-1), showing good drug-like properties. In vivo studies confirmed that C16 significantly ameliorated the scopolamine-induced cognition impairment, almost entirely recovered the Aβ_1-42 (icv)-impaired cognitive function to the normal level, showed better behavioral performance than donepezil and good anti-amyloidogenic effect. Hence, the potential BuChE inhibitor C16 can be developed as a promising disease-modifying treatment of AD.

Ferroptosis inducer erastin sensitizes NSCLC cells to celastrol through activation of the ROS-mitochondrial fission-mitophagy axis

Despite recent progress in non-small-cell lung cancer (NSCLC) treatment, treatment outcomes remain poor, mainly because of treatment resistance or toxicity. Erastin is a ferroptosis inducer that has shown promising cytotoxic effects in various types of cancers, including NSCLC. Celastrol is a triterpene extracted from the Tripterygium wilfordii that exhibits potential anticancer activity. However, the side effects of celastrol are severe and limit its clinical application. Combination therapy is a promising strategy to overcome the compensatory mechanisms and unwanted off-target effects. In the present study, we found that erastin synergized with celastrol to induce cell death at nontoxic concentrations. The combined treatment with celastrol and erastin significantly increased reactive oxygen species (ROS) generation, disrupted mitochondrial membrane potential, and promoted mitochondrial fission. Furthermore, cotreatment with erastin and celastrol initiated ATG5/ATG7-dependent autophagy, PINK1/Parkin-dependent mitophagy, and the expression of heat shock proteins (HSPs) in an HSF1-dependent manner. HSF1 knockdown further enhanced cell death in vitro and inhibited tumor growth in vivo. Our findings indicate that the combination of celastrol with erastin may represent a novel therapeutic regimen for patients with NSCLC and warrants further clinical evaluation.

Piperazine skeleton in the structural modification of natural products: a review

Piperazine moiety is a cyclic molecule containing two nitrogen atoms in positions 1 and 4, as well as four carbon atoms. Piperazine is one of the most sought heterocyclics for the development of new drug candidates with a wide range of applications. Over 100 molecules with a broad range of bioactivities, including antitumor, antibacterial, anti-inflammatory, antioxidant, and other activities, were reviewed. This article reviewed investigations regarding piperazine groups for the modification of natural product derivatives in the last decade, highlighting parameters that affect their biological activity.

Design, synthesis of novel celastrol derivatives and study on their antitumor growth through HIF-1α pathway

Four series of hypoxia-inducible factor-1 alpha (HIF-1α) functioning derivatives stemming from modifications to the C-29 carboxyl group of celastrol were designed and synthesized, and their anticancer activities were evaluated. To address the structure and activity relationship of each derivative, extensive structural changes were made. HRE luciferase reporter assay demonstrated that 12 modified compounds showed superior HIF-1α inhibitory activity. Among them, compound C6 exhibited the best features: firstly, the strongest HIF-1α inhibitory activity (IC₅₀ = 0.05 μM, 5-fold higher than that of celastrol); secondly, lower cytotoxicity (22-fold lower, C6-16.85 μM vs celastrol-0.76 μM). Thus, the safety factor of C6 was about 112 times higher than that of celastrol. Western blot assay indicated that C6 may inhibit the expression of HIF-1α protein in cells. Additionally, C6 hindered tumor cell cloning, migration and induced cell apoptosis. It is worth mentioning that in the mouse tumor xenograft model, C6 (10 mg/kg) displayed good antitumor activity in vivo, showing a better inhibition rate (74.03%) than the reference compound 5-fluorouracil (inhibition rate, 59.58%). However, the celastrol treatment group experienced collective death after four doses of the drug. Moreover, C6 minimally affected the mouse weight, indicating that its application in vivo has little toxic effect. H&E staining experiments show that it could also exacerbate the degree of tumor cell damage. The results of water solubility experiment show that the solubility of C6 is increased by 1.36 times than that of celastrol. In conclusion, C6 is a promising antitumor agent through HIF-1α pathway.

Celastrol: A Review of Useful Strategies Overcoming its Limitation in Anticancer Application

Celastrol, a natural bioactive ingredient derived from Tripterygium wilfordii Hook F, exhibits significant broad-spectrum anticancer activities for the treatment of a variety of cancers including liver cancer, breast cancer, prostate tumor, multiple myeloma, glioma, etc. However, the poor water stability, low bioavailability, narrow therapeutic window, and undesired side effects greatly limit its clinical application. To address this issue, some strategies were employed to improve the anticancer efficacy and reduce the side-effects of celastrol. The present review comprehensively focuses on the various challenges associated with the anticancer efficiency and drug delivery of celastrol, and the useful approaches including combination therapy, structural derivatives and nano/micro-systems development. The specific advantages for the use of celastrol mediated by these strategies are presented. Moreover, the challenges and future research directions are also discussed. Based on this review, it would provide a reference to develop a natural anticancer compound for cancer treatment.

Biosynthesis, total synthesis, structural modifications, bioactivity, and mechanism of action of the quinone-methide triterpenoid celastrol

Celastrol, a quinone-methide triterpenoid, was extracted from Tripterygium wilfordii Hook. F. in 1936 for the first time. Almost 70 years later, it is considered one of the molecules most likely to be developed into modern drugs, as it exhibits notable bioactivity, including anticancer and anti-inflammatory activity, and exerts antiobesity effects. In addition, the molecular mechanisms underlying its bioactivity are being widely studied, which offers new avenues for its development as a pharmaceutical reagent. Owing to its potential therapeutic effects and unique chemical structure, celastrol has attracted considerable interest in the fields of organic, biosynthesis, and medicinal chemistry. As several steps in the biosynthesis of celastrol have been revealed, the mechanisms of key enzymes catalyzing the formation and postmodifications of the celastrol scaffold have been gradually elucidated, which lays a good foundation for the future heterogeneous biosynthesis of celastrol. Chemical synthesis is also an effective approach to obtain celastrol. The total synthesis of celastrol was realized for the first time in 2015, which established a new strategy to obtain celastroid natural products. However, owing to the toxic effects and suboptimal pharmacological properties of celastrol, its clinical applications remain limited. To search for drug-like derivatives, several structurally modified compounds were synthesized and tested. This review focuses primarily on the latest research progress in the biosynthesis, total synthesis, structural modifications, bioactivity, and mechanism of action of celastrol. We anticipate that this paper will facilitate a more comprehensive understanding of this promising compound and provide constructive references for future research in this field.

Synthesis of celastrol derivatives as potential non-nucleoside hepatitis B virus inhibitors

A series of para-quinone methide (pQM) moiety and C-20- modified derivatives of celastrol were synthesized and evaluated for their inhibitory effect on the secretion of HBsAg and HBeAg as well as the inhibitory effect against HBV DNA replication. The results suggested that amidation of C-20 carboxylic group could generate derivatives with good anti-HBV profile, among them compound 14 showed the best inhibitory activity on the secretion of HBsAg (IC₅₀  = 11.9 µμ) and HBeAg (IC₅₀  = 13.1 µμ) with SI of 3.3 and 3.0, respectively. In addition, 14 also showed potent inhibitory effect against HBV DNA replication (48.5 ± 15.1%, 25 µM). This is, to our knowledge, the first report of celastrol derivatives as potential non-nucleoside HBV inhibitors.

In silico design of telomerase inhibitors

Telomerase is a reverse transcriptase enzyme involved in DNA synthesis at the end of linear chromosomes. Unlike in most other cells, telomerase is reactivated most cancerous cells and, therefore, has become a promising new anticancer target. Despite extensive research, direct telomerase inhibitors have yet not been introduced to the clinics because of the complexity of this enzyme. Structures of this protein from simple organisms and human homology models are currently available and have been used in structure-based drug design efforts to find potential inhibitors. Different is silico strategies have been applied and different chemical groups have been explored. Here, we provide an overview of recent discoveries.

Potential Anticancer Effect of Celastrol on Hepatocellular Carcinoma by Suppressing CXCR4-related Signal and Impeding Tumor Growth in Vivo

BACKGROUND

Potential agents that can effectively treat hepatocellular carcinoma (HCC) are being continuously explored.

METHODS

Celastrol extracted from roots of an ancient Chinese herb, Tripterygium wilfordii (Thunder god vine), has been identified as a potential anti-tumor agent. In this study, the molecular mechanisms underlying the action of celastrol on cell proliferation and chemokine CXCR4-related signal pathway associated with tumor growth were investigated.

RESULTS

The CXCR4 expression was diminished by celastrol treatment in a dose-dependent manner, and its downstream associated pathways, including PI3K and Akt were also downregulated. Celastrol also significantly attenuated proliferation and migration ability of HCC cells, and induced cell apoptosis in vitro. Additionally, significant inhibition of HCC growth was observed in the celastrol-treated group as compared with the control group in vivo as well.

CONCLUSION

Celastrol is capable of attenuating cell proliferation and inducing apoptosis, leading to inhibition of HCC growth through the suppression of CXCR4-related signal pathway.

DNA Related Enzymes as Molecular Targets for Antiviral and Antitumoral Chemotherapy. A Natural Overview of the Current Perspectives

BACKGROUND

The discovery of new chemotherapeutic agents still remains a continuous goal to achieve. DNA polymerases and topoisomerases act in nucleic acids metabolism modulating different processes like replication, mitosis, damage repair, DNA topology and transcription. It has been widely documented that Polymerases serve as molecular targets for antiviral and antitumoral chemotherapy. Furthermore, telomerase is a ribonucleoprotein with exacerbated activity in most of the tumor cell lines, becoming as an emergent target in Cancer treatment.

METHODS

We undertook an exhaustive search of bibliographic databases for peer-reviewed research literature related to the last decade. The characteristics of screened bibliography describe structure activity relationships and show the principal moieties involved. This work tries to summarize the investigation about natural and semi-synthetic products with natural origin with the faculty to inhibit key enzymes that play a crucial role in DNA metabolism.

RESULTS

Eighty-five data references were included in this review, showing natural products widely distributed throughout the plant kingdom and their bioactive properties such as tumor growing inhibitory effects, and anti-AIDS activity.

CONCLUSION

The findings of this review confirm the importance to find new drugs and biologically active natural products, and their potential medicinally useful benefits.

Design and synthesis of novel celastrol derivative and its antitumor activity in hepatoma cells and antiangiogenic activity in zebrafish

Two series of celastrol derivatives were designed and synthesized by modifying carboxylic acid at the 28th position with amino acid, and their intermediates with isobutyrate at the third position. All compounds were evaluated for their antiproliferation activity by four human cancer cell lines (SCG7901, HGC27, HepG2, and Bel7402) and one normal cell LO2. The most promising compound, compound 8, showed superior bioactivity and lower toxicity than others including celastrol. Further underlying tests illustrated that compound 8 induced apoptosis and cell arrest at G2/M and inhibited proliferation and mobility of human hepatoma cells by suppressing the signal transducer and activator of transcription-3 signaling pathway. Besides these, a highly accurate and reproducible high performance liquid chromatography protocol was established to determine celastrol and compound 8 absorption in zebrafish, and results demonstrated that their concentration increased rapidly within 4 hr in a time-dependent manner and the concentration of compound 8 was higher than that of celastrol. In addition, without detection at 12 hr, compound 8 was rapidly metabolized in vivo. These findings are very helpful for the structural modification of celastrol and other bioactive compounds to improve their bioactivity, toxicity, and absorption.

Design, Synthesis and Molecular Docking Analysis of Flavonoid Derivatives as Potential Telomerase Inhibitors

Based on the structural scaffolds of natural products, two series of flavonoid derivatives, for a total of twelve compounds, were designed and synthesized as potential human telomerase inhibitors. Using a modified TRAP-PCR assay, compound 5c exhibited the most potent inhibitory activity against human telomerase with an IC₅₀ value of less than 50 μM. In vitro, the results demonstrated that compound 5c had potent anticancer activity against five classes of tumor cell lines. The molecular docking and molecular dynamics analyses binding to the human telomerase holoenzyme were performed to elucidate the binding mode of active compound 5c. This finding helps the rational design of more potent telomerase inhibitors based on the structural scaffolds of natural products.

Synthesis and biological evaluation of celastrol derivatives as anti-ovarian cancer stem cell agents

Ovarian cancer is associated with a high percentage of recurrence of tumors and resistance to chemotherapy. Cancer stem cells (CSCs) are responsible for cancer progression, tumor recurrence, metastasis, and chemoresistance. Thus, developing CSC-targeting therapy is an urgent need in cancer research and clinical application. In an attempt to achieve potent and selective anti-CSC agents, a series of celastrol derivatives with cinnamamide chains were synthesized and evaluated for their anti-ovarian cancer activities. Most of the compounds exhibited stronger antiproliferative activity than celastrol, and celastrol derivative 7g with a 3,4,5-trimethoxycinnamamide side chain was found to be the most potent antiproliferative agent against ovarian cancer cells with an IC₅₀ value of 0.6 μM. Additionally, compound 7g significantly inhibited the colony formation ability and reduced the number of tumor spheres. Furthermore, compound 7g decreased the percentage of CD44⁺, CD133⁺ and ALDH⁺ cells. Thus, compound 7g is a promising anti-CSC agent and could serve as a candidate for the development of new anti-ovarian cancer drugs.

Raising the bar in anticancer therapy: recent advances in, and perspectives on, telomerase inhibitors

Telomerase is a ribonucleic reverse transcriptase enzyme that uses an integral RNA component as a template to add tandem telomeric DNA repeats, TTAGGG, at the 3' end of the chromosomes. 85-90% of human tumors and their derived cell lines predominantly express high levels of telomerase, therefore contributing to cancer cell development. However, in normal cells, telomerase activity is almost always absent except in germ cells and stem cells. This differential expression has been exploited to develop highly specific and potent cancer therapeutics. In this review, we outline recent advances in the development of telomerase inhibitors as anticancer agents.

Axl is a novel target of celastrol that inhibits cell proliferation and migration, and increases the cytotoxicity of gefitinib in EGFR mutant non‑small cell lung cancer cells

Gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‑TKI) is an excellent therapeutic agent to treat EGFR mutation‑positive non‑small cell lung cancer (NSCLC). However, the initial response decreases as chemoresistance develops. In the present study, gefitinib‑resistant EGFR mutant NSCLC PC‑9/GR cells were established to examine the characteristics and mechanisms associated with chemoresistance. Axl expression in PC‑9/GR cells was transcriptionally upregulated, since Axl protein and mRNA expression levels were identified to be increased according to western blot analysis and reverse transcription polymerase chain reaction results. The inhibitory effect of celastrol on Axl protein expression level, cell viability and clonogenicity were identified in parental and gefitinib‑resistant PC‑9 cells. In addition, treatment of PC‑9/GR cells with celastrol and gefitinib in combination was demonstrated to synergistically suppress Axl protein expression level, cell proliferation and migration. Taken together, upregulation of Axl expression seems to be associated with chemoresistance of PC‑9/GR cells. Furthermore, celastrol targets Axl to exert its anticancer effects in order to increase the susceptibility of PC‑9/GR cells to gefitinib and overcome chemoresistance.

Design, synthesis and biological evaluation of tricyclic pyrazolo[1,5-c][1,3]benzoxazin-5(5H)-one scaffolds as selective BuChE inhibitors

Based on the structural analysis of tricyclic scaffolds as butyrylcholinesterase (BuChE) inhibitors, a series of pyrazolo[1,5-c][1,3]benzoxazin-5(5H)-one derivatives were designed, synthesized and evaluated for their acetylcholinesterase (AChE) and BuChE inhibitory activity. Compounds with 5-carbonyl and 7- or/and 9-halogen substitutions showed potential BuChE inhibitory activity, among which compounds 6a, 6c and 6g showed the best BuChE inhibition (IC₅₀ = 1.06, 1.63 and 1.63 µM, respectively). The structure–activity relationship showed that the 5-carbonyl and halogen substituents significantly influenced BuChE activity. Compounds 6a and 6g were found nontoxic, lipophilic and exhibited remarkable neuroprotective activity and mixed-type inhibition against BuChE (K_i = 7.46 and 3.09 µM, respectively). Docking studies revealed that compound 6a can be accommodated into BuChE via five hydrogen bonds, one Pi–Sigma interaction and three Pi–Alkyl interactions.

Protective effects of celastrol against γ irradiation-induced oxidative stress in human umbilical vein endothelial cells

High-dose ionizing radiation can cause harmful effects on the cardiovascular system. Notably, endothelial cells are critical targets in radiation-induced damage. γ radiation exerts its biological effects through the radiolysis of water, which further generates ROS and induces lipid peroxidation and DNA damage. The present study aimed to evaluate the potential protective effects of celastrol against γ radiation-induced oxidative stress in human umbilical vein endothelial cells (HUVECs). HUVECs were exposed to γ radiation at different doses with or without celastrol treatment. Cell viability and cytotoxicity, migratory ability, ROS production, lipid peroxidation, oxidative DNA damage and antioxidative enzyme levels were evaluated in HUVECs at 24 h post-irradiation. It was observed that HUVECs exhibited decreased cell viability, increased cytotoxicity and a decreased migratory ability after exposure to 20-Gy γ radiation. Celastrol treatment concentration-dependently reversed these effects. γ irradiation was also demonstrated to increase the production of ROS, enhance lipid peroxidation and oxidative DNA damage and decrease the levels of SOD, catalase, GST and GPx in HUVECs. These detrimental effects were blocked by treatment with celastrol for 24 h. These data suggested that celastrol not only attenuated γ radiation-induced cytotoxicity, but also effectively blocked oxidative stress in HUVECs. As an antioxidant agent, celastrol may have potential protective effects in HUVECs against γ irradiation-induced injury.

Synthesis and characterisation of celastrol derivatives as potential anticancer agents

In the present study, three series of novel celastrol derivatives were designed and synthesised by modifying the carboxylic acid at the 20th position with amino acid, amine, and triazole derivatives. All the synthesised compounds were screened for their anticancer activities using MTT assay against AGS, MGC-803, SGC-7901, HCT-116, A549, HeLa, BEL-7402, and HepG-2 cell lines. Most of the synthesised compounds exhibited potent antiproliferative effects. The most promising compound 3-Hydroxy-9β,13α-dimethyl-2-oxo-24,25,26-trinoroleana-1(10),3,5,7-tetraen-29-oic amide, N-(R)-methyl-3-(1H-indol-2-yl)propanoate (11) showed considerable high anticancer activity against AGS cell lines, with an IC₅₀ value of 0.44 μM, and considerably higher activities against HCT-116, BEL-7402, and HepG-2 cell lines, with IC₅₀ values of 0.78, 0.63, and 0.76 μM, respectively. The results of apoptosis tests and molecular docking study of compound 11 binding to Caspase-3 revealed that its mechanism of action with antiproliferative was possibly involved in inducing apoptosis by inducing the activation of caspase-3.

Inhibition of IKKβ by celastrol and its analogues - an in silico and in vitro approach

CONTEXT

Alzheimer's disease (AD) is the most common form of dementia affecting the aged population and neuroinflammation is one of the most observed AD pathologies. NF-κB is the central regulator of inflammation and inhibitor κB kinase (IKK) is the converging point in NF-κB activation. Celastrol is a natural triterpene used as a treatment for inflammatory conditions.

OBJECTIVE

This study determines the neuroprotective and inhibitory effect of celastrol on amyloid beta_1-42 (Aβ_1-42) induced cytotoxicity and IKKβ activity, respectively.

MATERIALS AND METHODS

Retinoic acid differentiated IMR-32 cells were treated with celastrol (1 μM) before treatment with Aβ_1-42 (IC₃₀ 10 μM) for 24 h. The cytotoxicity and IKK phosphorylation were measured by MTT and western blotting analysis, respectively. We screened 36 celastrol analogues for the IKKβ inhibition by molecular docking and evaluated their drug like properties to delineate the neuroprotective effects.

RESULTS

Celastrol (1 μM) inhibited Aβ_1-42 (10 μM) induced IκBα phosphorylation and protected IMR-32 cells from cell death. Celastrol and 25 analogues showed strong binding affinity with IKKβ as evidenced by strong hydrogen-bonding interactions with critical active site residues. All the 25 analogues displayed strong anti-inflammatory properties but only 11 analogues showed drug-likeness. Collectively, molecule 15 has highest binding affinity, CNS activity and more drug likeness than parent compound celastrol.

DISCUSSION AND CONCLUSION

The decreased expression of pIκBα in celastrol pretreated cells affirms the functional representation of inhibited IKKβ activity in these cells. The neuroprotective potentials of celastrol and its analogues may be related to IKK inhibition.

Celastrol: A Spectrum of Treatment Opportunities in Chronic Diseases

The identification of new bioactive compounds derived from medicinal plants with significant therapeutic properties has attracted considerable interest in recent years. Such is the case of the Tripterygium wilfordii (TW), an herb used in Chinese medicine. Clinical trials performed so far using its root extracts have shown impressive therapeutic properties but also revealed substantial gastrointestinal side effects. The most promising bioactive compound obtained from TW is celastrol. During the last decade, an increasing number of studies were published highlighting the medicinal usefulness of celastrol in diverse clinical areas. Here we systematically review the mechanism of action and the therapeutic properties of celastrol in inflammatory diseases, namely, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel diseases, osteoarthritis and allergy, as well as in cancer, neurodegenerative disorders and other diseases, such as diabetes, obesity, atherosclerosis, and hearing loss. We will also focus in the toxicological profile and limitations of celastrol formulation, namely, solubility, bioavailability, and dosage issues that still limit its further clinical application and usefulness.

Synthesis of 3- and 29-substituted celastrol derivatives and structure-activity relationship studies of their cytotoxic activities

A series of 3-carbamate and 29-ester celastrol derivatives (compounds 1-26) were designed and synthesized. These analogues were evaluated for their cytotoxic activities against several cancer cell lines. Cytotoxicity data revealed that the properties of substituents and substitution position had important influence on cytotoxic activity. Modification of C-3 hydroxyl with size-limited groups did not reduce the activity obviously. The introduction of polarity group like piperazine could improve the solubility. Compound 23 was chosen to further evaluate anti-tumor efficacy in vivo. It showed higher inhibition rate and better safety than celastrol during in vivo experiment by intragastric administration. The preliminary antitumor studies of compound 23in vivo showed that it might be promising for the development of new antitumor agents.

AlCl₃·6H₂O-Catalyzed Friedel-Crafts Alkylation of Indoles by the para-Quinone Methide Moiety of Celastrol

A classical Friedel-Crafts alkylation of different indoles catalyzed by AlCl₃·6H₂O has been developed for a well-known important natural product, celastrol, resulting in a series of derivatives for further biological evaluation. The catalyst loading was reduced to 5 mol %, the reaction proceeds at ambient temperature and reaction time is only 3 h. The product yields range from 20% to 99%. A reaction mechanism is also proposed, based on our experiment results.

Targeting telomerase with radiolabeled inhibitors

The expression of telomerase in approximately 85% of cancers and its absence in the majority of normal cells makes it an attractive target for cancer therapy. However the lag period between initiation of telomerase inhibition and growth arrest makes direct inhibition alone an insufficient method of treatment. However, telomerase inhibition has been shown to enhance cancer cell radiosensitivity. To investigate the strategy of simultaneously inhibiting telomerase while delivering targeted radionuclide therapy to cancer cells, 123I-radiolabeled inhibitors of telomerase were synthesized and their effects on cancer cell survival studied. An 123I-labeled analogue of the telomerase inhibitor MST-312 inhibited telomerase with an IC50 of 1.58 μM (MST-312 IC50: 0.23 μM). Clonogenic assays showed a dose dependant effect of 123I-MST-312 on cell survival in a telomerase positive cell line, MDA-MB-435.

Hesperetin derivatives: Synthesis and anti-inflammatory activity

Sixteen novel hesperetin derivatives containing Mannich base moiety were designed and synthesized and their anti-inflammatory activities were evaluated by inhibiting tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in mouse RAW264.7 macrophages. Compounds 3a-3k showed better hydrophilic, while compounds 3l-3p with aromatic groups was hydrophobic. The anti-inflammatory activity of title compounds was correlated with logP values, among them, compounds 3c, 3e and 3i with minus logP values exhibited best anti-inflammatory activity through decreasing both IL-6 and TNF-α. Furthermore, the expression of LPS-induced notch1 and inos was reduced by compounds 3c, 3e, and 3i, and compound 3e attenuated LPS-induced inos protein levels in a dose-dependent manner.