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Triggering ferroptosis is a potential therapeutic pathway and strategy for the prospective treatment of lethal hepatocellular carcinoma (HCC). The asialo-glycoprotein receptor (ASGPR) is an over-expressed receptor on the membranes of hepatocellular carcinoma cells (HCCs) and binds specifically to galactose (Gal) ligand. Celastrol (CE) is a potent anticancer natural product, but its poor water solubility and severe toxicity restrict its clinical application. In this study, a carrier-free self-assembled nanoparticles, CE-Gal-NPs , were designed and prepared by nanoprecipitation method, which could recognize ASGPR receptor by active targeting (Gal ligand) and passive targeting (EPR effect), access to the cell through the clathrin pathway and finally internalize to lysosomes. CE-Gal-NPs triggered reactive oxygen species (ROS)-mediated ferroptosis pathway and exerted anti-HCC effects in vitro and in vivo by down-regulating GPX4 and up-regulating COX-2 expression, depleting glutathione (GSH) levels, and increasing lipid peroxidation levels in cells and tumor tissues. In the H22 xenograft mouse model, the CE-Gal-NPs group exhibited dramatically superior tumor inhibition than the CE group, while Gal conjugating diminished the systemic toxicity of CE. Consequently, this study presented a promising strategy for CE potentiation and toxicity reduction, as well as a potential guideline for the development of clinically targeted therapeutic agents for HCC. [Display omitted] • We designed and synthesized a carrier-free self-assembled nanoparticles (CE-Gal-NPs). • CE-Gal-NPs specifically recognized tumor cells through active and passive targeting. • CE-Gal-NPs demonstrated favorable anti-HCC activity by inducing ferroptosis. • CE-Gal-NPs showed lower toxicity in vivo compared to CE. • CE-Gal-NPs was expected to be a candidate drug for the treatment of HCC. [ABSTRACT FROM AUTHOR]

Nur77, an orphan member of the nuclear receptor superfamily, plays an important role in the regulation of inflammatory processes. Our previous work found that celastrol, a pentacyclic triterpene, bound to Nur77 to inhibit inflammation in a Nur77-dependent manner. Celastrol binding to Nur77 promotes Nur77 translocation from nucleus to cytoplasm, resulting in clearance of inflamed mitochondria and then alleviation of inflammation. Here, we report the design, synthesis, SAR study and biological evaluation of a series of celastrol analogs. A total of 24 celastrol derivatives were made. Compound 3a with a K d of 0.87 μM was found to be less toxic than celastrol and could be a hit molecule for further optimization. Image 1 • 24 celastrol derivatives were designed, synthesized and evaluated for their Nur77-mediated anti-inflammatory properties. • Compound 3a with comparable biological effects tp celastrol was significantly less toxic than celastrol. • 3a is a potential hit molecule for further optimization for anti-inflammatory application. [ABSTRACT FROM AUTHOR]

On the basis of the hybridization strategy of natural products, a total of 32 novel celastrol hybrids were designed, synthesized and evaluated for their antitumor activities. Most of these derivatives exihibited significant antiproliferative activities compared to celastrol, among which compound 29 displayed the strongest inhibitory capability [IC 50 = 0.15 ± 0.03 μM (A549),0.17 ± 0.03 μM (MCF-7), 0.26 ± 0.02 μM (HepG2)], which exhibited equal or superior anti-cancer activities in comparison to 2-cyano-3,12-dioxoolean-1,9 (11)-dien-28-oic acid methyl ester (CDDO-Me). The mechanism of pharmacological research indicated that 29 possessed the ability to disrupt Hsp90-Cdc37 complex which was stronger than celastrol. Meanwhile, compound 29 could induce abnormal regulation of clients (p -Akt and Cdk4) of Hsp90 and cell cycle arrest at G 0 /G 1 phase in a concentration-dependent manner. In addition, compound 29 could also induce cell apoptosis through the death receptor pathway on A549 cells. Taken together, our results demonstrated that 29 might be a promising novel candidate for further druggability research. Image 1 • A series of novel celastrol hybrids were designed, synthesized and evaluated. • 29 exhibited superior potency compared to the other compounds. • 29 disrupted Hsp90-Cdc37 complex and induced apoptosis through extrinsic signaling pathway in A549 cells. • 29 down-regulated the expression levels of Akt and Cdk4. [ABSTRACT FROM AUTHOR]

Abstract To develop multifunctional drugs, a series of celastrol/NO donor hybrids were designed, synthesized and evaluated. The detection of NO release amounts showed that the more NO of these hybrids released, the more tumor cells were inhibited. 11b , which released the highest level of NO in vitro , exhibited superior potency (IC 50 = 0.48 ± 0.06 μM) compared to the other compounds. Further pharmacological studies showed that 11b induced dysregulations of the Hsp90 clients (Akt and Cdk4), apoptosis, and cell cycle arrested at G 0 /G 1 phase against A549 cells. These results suggested that inhibition of Hsp90 and release of NO was synergistic in cancer cells. Overall, the NO-releasing capacity and the inhibition of Hsp90 pathway signaling might explain the potent anti-proliferative activities of these compounds. Graphical abstract A series of celastrol/NO donor hybrids were designed, synthesized and evaluated. 11b , which released the highest level of NO in vitro , exhibited the best antiproliferative effects. The results suggested that inhibition of Hsp90 and release of NO was synergistic in cancer cells. Image 1 Highlights • A series of celastrol/NO donor hybrids were designed, synthesized and evaluated. • 11b exhibited superior potency compared to the other compounds. • 11b induced degradation of the Hsp90 clients (Akt and Cdk4), apoptosis and the cell cycle arrested at the G 0 /G 1 phase in A549 cells. [ABSTRACT FROM AUTHOR]

Celastrol and its derivatives have been reported for their potent anticancer activity. Among other celastrol analogues, novel carbamate derivatives were designed and synthesised, and their biological activity on the viability of human cancer cell lines was evaluated. Additionally, a preliminary structure–activity relationship study was conducted. Derivative 18 showed the highest activity on cancer cell viability, combined with the best selectivity between malignant cells and non-malignant fibroblasts. Preliminary mechanistic studies of its anti-tumour action indicated that compound 18 has an antiproliferative effect on SKOV-3 human ovarian cancer cells (IC 50 = 0.54 μM). The results also suggested that its potent anticancer activity is mediated by apoptosis, and that this process was mainly the result of the activation of the extrinsic apoptotic pathway. Moreover, our results demonstrated the potential of derivative 18 as a new agent for combinatorial drug therapy for ovarian cancer. [ABSTRACT FROM AUTHOR]

Celastrol is one of the most active antitumour compounds among the natural triterpenoids. It has been reported to be highly active against a wide variety of tumours and to affect multiple cellular pathways. A series of new celastrol derivatives, including compounds bearing a urea group, have been synthesised and analysed for their biological activity against human cancer cell lines. Several compounds presented a stronger growth inhibition effect than celastrol on the cell lines studied. Among them, compound 24 was the most promising derivative, as it exhibited both a remarkable antiproliferative activity and an improved selectivity in tumour versus non-tumour cells. The anticancer molecular mechanism of compound 24 in the human ovary cancer cell line SKOV-3 was further studied and the results showed that compound 24 induced apoptosis through the activation of the extrinsic death receptor pathway. Interestingly, the results revealed that compound 24 might be able to decrease the levels of dysfunctional p53. The assays also suggested that compound 24 is an Hsp90 inhibitor, and that the Akt/mTOR pathway might be involved in the downstream regulation that leads to its antiproliferative activity. Moreover, a synergistic anticancer effect was evidenced when SKOV-3 cells were simultaneously treated with compound 24 and cisplatin. Taken together, these results suggest that compound 24 may be a promising lead for the development of new cancer therapies. [ABSTRACT FROM AUTHOR]

Three series of celastrol derivatives, namely, 6a – 6i , 11a – 11i and 15a – 15i, were designed based on the scaffold hopping strategy. The derivatives were synthesized and biologically evaluated against five human tumor cell lines (i.e. A549, MCF-7, Bel7402, HT-29 and PC3) using MTT assay in vitro. Results showed that compound 11i exhibited apparent antiproliferative activity against the MCF-7 cell line with an IC 50 value of 1.31 μ M and could remarkably inhibit the colony formation of the MCF-7 cells. Transmission electron microscopy assay, monodansylcadaverine incorporation assay and the expression of LC3 A/B, p62 and Beclin-1 in MCF-7 cells suggested that the potent antiproliferative activity of compound 11i was mainly due to its autophagy-inducing effect. Moreover, compound 11i could arrest the MCF-7 cells in the G2/M phase by regulating the cell-cycle-related proteins Cdk-1 and Cyclin B1. In the zebrafish xenograft model, compound 11i could obviously inhibit the proliferation of the MCF-7 cells. Thus, compound 11i could serve as a promising lead compound for breast cancer therapy. [Display omitted] • Three series of celastrol derivatives were designed based on the scaffold hopping strategy. • The derivatives were evaluated for their antiproliferative activities. • The structure-activity relationships were investigated. • Compound 11i exhibited remarkable growth inhibition in MCF-7 cells through inducing autophagy. • Compound 11i could inhibit the proliferation of MCF-7 cells in zebrafish xenograft model. [ABSTRACT FROM AUTHOR]

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 (IC 50 = 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. [Display omitted] • Four series of HIF-1α celastrol's functioning agents were synthesized. • C6 shows 5-fold higher HIF-1α inhibitory activity and 22-fold lower cytotoxicity than that of celastrol. • C6 displays good antitumor activity in vivo than the reference compound 5-fluorouracil (inhibition rate, 74.03% vs 59.58%). [ABSTRACT FROM AUTHOR]

Celastrol, a principal bioactive ingredient of Tripterygium wilfordii Hook F, has gained extensive exploration due to its unique structure features and multiple promising biological activities. This review will focus on the structural modifications, structure–activity relationships, pharmacology, and toxicology of celastrol in the past ten years. We hope this review would be helpful to get a better grasp of the progresses in the field and provide constructive suggestions for the further study of celastrol. Image 1 • Advances in celastrol-inspired medicinal chemistry. • Progresses in pharmacology & toxicology. • Future perspectives of celastrol. [ABSTRACT FROM AUTHOR]