Molecular modulators of celastrol as the keystones for its diverse pharmacological activities

Autophagy: A potential target for natural products in the treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease primarily affecting the mucosa of the colon and rectum. UC is characterized by recurrent episodes, often necessitating lifelong medication use, imposing a significant burden on patients. Current conventional and advanced treatments for UC have the disadvantages of insufficient efficiency, susceptibility to drug resistance, and notable adverse effects. Therefore, developing effective and safe drugs has become an urgent need. Autophagy is an intracellular degradation process that plays an important role in intestinal homeostasis. Emerging evidence suggests that aberrant autophagy is involved in the development of UC, and modulating autophagy can effectively alleviate experimental colitis. A growing number of studies have established that autophagy can interplay with endoplasmic reticulum stress, gut microbiota, apoptosis, and the NLRP3 inflammasome, all of which contribute to the pathogenesis of UC. In addition, a variety of intestinal epithelial cells, including absorptive cells, goblet cells, and Paneth cells, as well as other cell types like neutrophils, antigen-presenting cells, and stem cells in the gut, mediate the development of UC through autophagy. To date, many studies have found that natural products hold the potential to exert therapeutic effects on UC by regulating autophagy. This review focuses on the possible effects and pharmacological mechanisms of natural products to alleviate UC with autophagy as a potential target in recent years, aiming to provide a basis for new drug development.

Glomerulus-Targeted ROS-Responsive Polymeric Nanoparticles for Effective Membranous Nephropathy Therapy

Membranous nephropathy (MN) is a common immune-mediated glomerular disease that requires the development of safe and highly effective therapies. Celastrol (CLT) has shown promise as a therapeutic molecule candidate, but its clinical use is currently limited due to off-target toxicity. Given that excess levels of reactive oxygen species (ROS) contributing to podocyte damage is a key driver of MN progression to end-stage renal disease, we rationally designed ROS-responsive cationic polymeric nanoparticles (PPS-CPNs) with a well-defined particle size and surface charge by employing poly(propylene sulfide)-polyethylene glycol (PPS-PEG) and poly(propylene sulfide)-polyethylenimine (PPS-PEI) to selectively deliver CLT to the damaged glomerulus for MN therapy. Experimental results show that PPS-CPNs successfully crossed the fenestrated endothelium, accumulated in the glomerular basement membrane (GBM), and were internalized by podocytes where rapid drug release was triggered by the overproduction of ROS, thereby outperforming nonresponsive CLT nanotherapy to alleviate subepithelial immune deposits, podocyte foot process effacement, and GBM expansion in a rat MN model. Moreover, the ROS-responsive CLT nanotherapy was associated with significantly lower toxicity to major organs than free CLT. These results suggest that encapsulating CLT into PPS-CPNs can improve efficacy and reduce toxicity as a promising treatment option for MN.

Celastrol alleviates subconjunctival fibrosis induced by silicone implants mimicking glaucoma surgery

Subconjunctival fibrosis is critical to the outcomes of several ophthalmic conditions or procedures, such as glaucoma filtering surgery. This study aimed to investigate the anti-fibrotic effect of celastrol on subconjunctival fibrosis and to further reveal the underlying mechanisms. Given the toxicity and poor water solubility of celastrol, we fabricated celastrol-loaded nanomicelles hydrogel hybrid to attenuate subconjunctival fibrosis around silicone implant. The results in vitro demonstrated that celastrol-nanodrug suppressed TGF-β1-induced fibroblast activation and extracellular matrix deposition in human pterygium fibroblasts by inhibiting the TGF-β1/Smad2/3-YAP/TAZ signaling. Further, the results in vivo showed that the celastrol-nanodrug reduced subconjunctival fibrosis in the rabbit model of silicone implantation. These findings suggested that celastrol could serve as a promising therapy for controlling subconjunctival fibrosis. This study aimed to investigate the anti-fibrotic effect of celastrol on subconjunctival fibrosis and to further reveal the underlying mechanisms. We used celastrol-loaded nanomicelles hydrogel hybrid as a sustained-release drug. A rabbit model of subconjunctival fibrosis following silicone implantation was used for in vivo study and TGF-β1-induced human pterygium fibroblast (HPF) activation as an in vitro model. The effects of celastrol on inhibiting TGF-β1-induced migration and proliferation of HPFs were evaluated by scratch wound assay and CCK-8, respectively. Immunofluorescence and western blotting were used to examine the effect of celastrol on the expression of α-SMA, collagen I, fibronectin, and the targets of the Hippo signaling pathway. We found that in vivo celastrol treatment reduced the expression of YAP and TAZ in subconjunctival tissue. Moreover, celastrol alleviated collagen deposition and subconjunctival fibrosis at 8weeks. No obvious tissue toxicity was observed in the rabbit models. Mechanistically, celastrol significantly inhibited TGF-β1-induced proliferation and migration of HPFs. Pretreatment of HPFs with celastrol also suppressed the TGF-β1-induced protein expression of α-SMA, collagen I, fibronectin, TGF-βRII, phosphorylated Smad2/3, YAP, TAZ, and TEAD1. In conclusion, celastrol effectively prevented subconjunctival fibrosis through inhibiting TGF- β1/Smad2/3-YAP/TAZ pathway. Celastrol could serve as a promising therapy for subconjunctival fibrosis.

Modulators of Candida albicans Membrane Drug Transporters: A Lucrative Portfolio for the Development of Effective Antifungals

The escalating prevalence of membrane drug transporters and drug efflux pumps in pathogenic yeast like Candida albicans necessitates a comprehensive understanding of their roles in MDR. The overexpression of drug transporter families, ABC and MFS, implicated in MDR through drug efflux and poses a significant challenge in the diagnosis and treatment of fungal infection. Various mechanisms have been proposed for MDR; however, the upregulation of ABC and MFS superfamily transporters is most noticeable in MDR. The direct inhibition of these transporters seems an efficient strategy to overcome this problem. The goal of the article is to present an overview of the prospect of utilizing these modulators of C. albicans drug transports as effective antifungal molecules against MDR addressing a critical gap in the field. The review tries to address to prevent drug extrusion by modulating the expression of drug transporters of C. albicans. The review discussed the progress in identifying potent, selective, and non-toxic modulators of these transporters to develop some effective antifungals and overcome MDR. We reviewed major studies in this area and found that recent work has shifted toward the exploration of natural compounds as potential modulators to restore drug sensitivity in MDR fungal cells. The focus of this review is to survey and interpret current research information on modulators of C. albicans drug transporters from natural sources emphasizing those compounds that are potent antifungal agents.

TRAIL and Celastrol Combinational Treatment Suppresses Proliferation, Migration, and Invasion of Human Glioblastoma Cells via Targeting Wnt/β-catenin Signaling Pathway

OBJECTIVE

To investigate the mechanistic basis for the anti-proliferation and anti-invasion effect of tumor necrosis factor-related apoptosis-induced ligand (TRAIL) and celastrol combination treatment (TCCT) in glioblastoma cells.

METHODS

Cell counting kit-8 was used to detect the effects of different concentrations of celastrol (0-16 µmol/L) and TRAIL (0-500 ng/mL) on the cell viability of glioblastoma cells. U87 cells were randomly divided into 4 groups, namely control, TRAIL (TRAIL 100 ng/mL), Cel (celastrol 0.5 µmol/L) and TCCT (TRAIL 100 ng/mL+ celastrol 0.5 µmol/L). Cell proliferation, migration, and invasion were detected by colony formation, wound healing, and Transwell assays, respectively. Quantitative reverse transcription polymerase chain reaction and Western blotting were performed to assess the levels of epithelial-mesenchymal transition (EMT) markers (zona occludens, N-cadherin, vimentin, zinc finger E-box-binding homeobox, Slug, and β-catenin). Wnt pathway was activated by lithium chloride (LiCl, 20 mol/L) and the mechanism for action of TCCT was explored.

RESULTS

Celastrol and TRAIL synergistically inhibited the proliferation, migration, invasion, and EMT of U87 cells (P<0.01). TCCT up-regulated the expression of GSK-3β and down-regulated the expression of β-catenin and its associated proteins (P<0.05 or P<0.01), including c-Myc, Cyclin-D1, and matrix metalloproteinase (MMP)-2. In addition, LiCl, an activator of the Wnt signaling pathway, restored the inhibitory effects of TCCT on the expression of β-catenin and its downstream genes, as well as the migration and invasion of glioblastoma cells (P<0.05 or P<0.01).

CONCLUSIONS

Celastrol and TRAIL can synergistically suppress glioblastoma cell migration, invasion, and EMT, potentially through inhibition of Wnt/β-catenin pathway. This underlies a novel mechanism of action for TCCT as an effective therapy for glioblastoma.

Recent advances in drug delivery of celastrol for enhancing efficiency and reducing the toxicity

Celastrol is a quinone methyl triterpenoid monomeric ingredient extracted from the root of Tripterygium wilfordii. Celastrol shows potential pharmacological activities in various diseases, which include inflammatory, obesity, cancer, and bacterial diseases. However, the application prospect of celastrol is largely limited by its low bioavailability, poor water solubility, and undesired off-target cytotoxicity. To address these problems, a number of drug delivery methods and technologies have been reported to enhance the efficiency and reduce the toxicity of celastrol. We classified the current drug delivery technologies into two parts. The direct chemical modification includes nucleic acid aptamer-celastrol conjugate, nucleic acid aptamer-dendrimer-celastrol conjugate, and glucolipid-celastrol conjugate. The indirect modification includes dendrimers, polymers, albumins, and vesicular carriers. The current technologies can covalently bond or encapsulate celastrol, which improves its selectivity. Here, we present a review that focalizes the recent advances of drug delivery strategies in enhancing the efficiency and reducing the toxicity of celastrol.

Bioactive phytocompounds for oral cancer prevention and treatment: A comprehensive and critical evaluation

The high incidence of oral cancer combined with excessive treatment cost underscores the need for novel oral cancer preventive and therapeutic options. The value of natural agents, including plant secondary metabolites (phytochemicals), in preventing carcinogenesis and representing expansive source of anticancer drugs have been established. While fragmentary research data are available on antioral cancer effects of phytochemicals, a comprehensive and critical evaluation of the potential of these agents for the prevention and intervention of human oral malignancies has not been conducted according to our knowledge. This study presents a complete and critical analysis of current preclinical and clinical results on the prevention and treatment of oral cancer using phytochemicals. Our in-depth analysis highlights anticancer effects of various phytochemicals, such as phenolics, terpenoids, alkaloids, and sulfur-containing compounds, against numerous oral cancer cells and/or in vivo oral cancer models by antiproliferative, proapoptotic, cell cycle-regulatory, antiinvasive, antiangiogenic, and antimetastatic effects. Bioactive phytochemicals exert their antineoplastic effects by modulating various signaling pathways, specifically involving the epidermal growth factor receptor, cytokine receptors, toll-like receptors, and tumor necrosis factor receptor and consequently alter the expression of downstream genes and proteins. Interestingly, phytochemicals demonstrate encouraging effects in clinical trials, such as reduction of oral lesion size, cell growth, pain score, and development of new lesions. While most phytochemicals displayed minimal toxicity, concerns with bioavailability may limit their clinical application. Future directions for research include more in-depth mechanistic in vivo studies, administration of phytochemicals using novel formulations, investigation of phytocompounds as adjuvants to conventional treatment, and randomized clinical trials.

Effect of the Functional VP1 Unique Region of Human Parvovirus B19 in Causing Skin Fibrosis of Systemic Sclerosis

Human parvovirus B19 (B19V) is a single-stranded non-enveloped DNA virus of the family Parvoviridae that has been associated with various autoimmune disorders. Systemic sclerosis (SSc) is an autoimmune connective tissue disorder with high mortality and has been linked to B19V infection. However, the precise mechanism underlying the B19V contribution to the development of SSc remains uncertain. This study investigated the impacts of the functional B19V-VP1 unique region (VP1u) in macrophages and bleomycin (BLE)-induced SSc mice. Cell experimental data showed that significantly decreased viability and migration of both B19V-VP1u-treated U937 and THP-1 macrophages are detected in the presence of celastrol. Significantly increased MMP9 activity and elevated NF-kB, MMP9, IL-6, TNF-α, and IL-1β expressions were detected in both B19V-VP1u-treated U937 and THP-1 macrophages. Conversely, celastrol revealed an inhibitory effect on these molecules. Notably, celastrol intervened in this pathogenic process by suppressing the sPLA2 activity of B19V-VP1u and subsequently reducing the inflammatory response. Notably, the administration of B19V-VP1u exacerbated BLE-induced skin fibrosis in mice, with augmented expressions of TGF-β, IL-6, IL-17A, IL-18, and TNF-α, ultimately leading to α-SMA and collagen I deposits in the dermal regions of BLE-induced SSc mice. Altogether, this study sheds light on parvovirus B19 VP1u linked to scleroderma and aggravated dermal fibrosis.

Celastrol attenuates streptozotocin-induced diabetic cardiomyopathy in mice by inhibiting the ACE / Ang II / AGTR1 signaling pathway

BACKGROUND

Heart failure is closely correlated with diabetic cardiomyopathy (DCM) and can lead to mortality. Celastrol has long been utilized for the treatment of immune and inflammatory disorders. However, whether celastrol would exert protective effects on DCM has not been determined. This work aimed to explore the protective actions of celastrol on DCM and unravel the underlying mechanisms involved.

METHODS

A DCM model was constructed in mice by intraperitoneal administration of streptozotocin. ELISA and echocardiography were performed to examine myocardial injury markers and cardiac function, respectively. Morphological changes and fibrosis were assessed using H&E staining and Masson's staining. Inflammatory cytokines and fibrotic markers were detected by ELISA and RT-PCR. Endothelial nitric oxide synthase, apoptosis, and reactive oxygen species were detected by microscopic staining. Network pharmacology approaches, molecular docking analysis, ELISA, and Western blot were used for mechanism studies.

RESULTS

Celastrol alleviated diabetes-induced cardiac injury and remodeling. Celastrol also suppressed diabetes-induced production of inflammatory cytokines and reactive oxygen species, as well as cardiomyocyte apoptosis. The cardioprotective effects of celastrol were associated with its inhibition on the angiotensin-converting enzyme / angiotensin II / angiotensin II receptor type 1 signaling pathway.

CONCLUSION

Celastrol exhibits significant potential as an effective cardioprotective drug for DCM treatment. The underlying mechanisms can be attributed to the blockage of celastrol on the angiotensin-converting enzyme signaling pathway.

Celastrol functions as an emerging manager of lipid metabolism: Mechanism and therapeutic potential

Lipid metabolism disorders are pivotal in the development of various lipid-related diseases, such as obesity, atherosclerosis, non-alcoholic fatty liver disease, type 2 diabetes, and cancer. Celastrol, a bioactive compound extracted from the Chinese herb Tripterygium wilfordii Hook F, has recently demonstrated potent lipid-regulating abilities and promising therapeutic effects for lipid-related diseases. There is substantial evidence indicating that celastrol can ameliorate lipid metabolism disorders by regulating lipid profiles and related metabolic processes, including lipid synthesis, catabolism, absorption, transport, and peroxidation. Even wild-type mice show augmented lipid metabolism after treatment with celastrol. This review aims to provide an overview of recent advancements in the lipid-regulating properties of celastrol, as well as to elucidate its underlying molecular mechanisms. Besides, potential strategies for targeted drug delivery and combination therapy are proposed to enhance the lipid-regulating effects of celastrol and avoid the limitations of its clinical application.

Targeting transcription factors for therapeutic benefit in rheumatoid arthritis

Rheumatoid arthritis (RA) is a destructive inflammatory autoimmune disease that causes pain and disability. Many of the currently available drugs for treating RA patients are aimed at halting the progression of the disease and alleviating inflammation. Further, some of these treatment options have drawbacks, including disease recurrence and adverse effects due to long-term use. These inefficiencies have created a need for a different approach to treating RA. Recently, the focus has shifted to direct targeting of transcription factors (TFs), as they play a vital role in the pathogenesis of RA, activating key cytokines, chemokines, adhesion molecules, and enzymes. In light of this, synthetic drugs and natural compounds are being explored to target key TFs or their signaling pathways in RA. This review discusses the role of four key TFs in inflammation, namely NF-κB, STATs, AP-1 and IRFs, and their potential for being targeted to treat RA.

Bioactive Phytoconstituents and Their Therapeutic Potentials in the Treatment of Haematological Cancers: A Review

Haematological (blood) cancers are the cancers of the blood and lymphoid forming tissues which represents approximately 10% of all cancers. It has been reported that approximately 60% of all blood cancers are incurable. Despite substantial improvement in access to detection/diagnosis, chemotherapy and bone marrow transplantation, there is still high recurrence and unpredictable but clearly defined relapses indicating that effective therapies are still lacking. Over the past two decades, medicinal plants and their biologically active compounds are being used as potential remedies and alternative therapies for the treatment of cancer. This is due to their anti-oxidant, anti-inflammatory, anti-mutagenic, anti-angiogenic, anti-cancer activities and negligible side effects. These bioactive compounds have the capacity to reduce proliferation of haematological cancers via various mechanisms such as promoting apoptosis, transcription regulation, inhibition of signalling pathways, downregulating receptors and blocking cell cycle. This review study highlights the mechanistic and beneficial effects of nine bioactive compounds (quercetin, ursolic acid, fisetin, resveratrol, epigallocatechin gallate, curcumin, gambogic acid, butein and celastrol) as potential remedies for chemoprevention of haematological cancers. The study provides useful insights on the effectiveness of the use of bioactive compounds from plants for chemoprevention of haematological cancers.

Disruption of Proteostasis by Natural Products and Synthetic Compounds That Induce Pervasive Unfolding of Proteins: Therapeutic Implications

Exposure of many cancer cells, including multiple myeloma cells, to cytotoxic concentrations of natural products celastrol and withaferin A or synthetic compounds of the IHSF series resulted in denaturation of a luciferase reporter protein. Proteomic analysis of detergent-insoluble extract fractions from HeLa-derived cells revealed that withaferin A, IHSF058 and IHSF115 caused denaturation of 915, 722 and 991 of 5132 detected cellular proteins, respectively, of which 440 were targeted by all three compounds. Western blots showed that important fractions of these proteins, in some cases approaching half of total protein amounts, unfolded. Relatively indiscriminate covalent modification of target proteins was observed; 1178 different proteins were modified by IHSF058. Further illustrating the depth of the induced proteostasis crisis, only 13% of these proteins detectably aggregated, and 79% of the proteins that aggregated were not targets of covalent modification. Numerous proteostasis network components were modified and/or found in aggregates. Proteostasis disruption caused by the study compounds may be more profound than that mediated by proteasome inhibitors. The compounds act by a different mechanism that may be less susceptible to resistance development. Multiple myeloma cells were particularly sensitive to the compounds. Development of an additional proteostasis-disrupting therapy of multiple myeloma is suggested.

Self-assembling nanoarchitectonics of size-controllable celastrol nanoparticles for efficient cancer chemotherapy with reduced systemic toxicity

Celastrol, extracted from Tripterygium wilfordii Hook F, is one of the most promising natural extract for cancer treatment. Nevertheless, insufficient tumor retention and severe systemic toxicity still hinder its application. Herein, we report for the first time that Celastrol can directly self-assemble into size-controllable nanoparticles through the anti-solvent method by using different good solvent or by the variation of Celastrol concentrations. In vitro anti-cancer experiment revealed that the as-prepared nanoparticles can kill MCF-7 cells more effectively. Moreover, the nanoparticles can efficiently accumulate in tumors of the tumor bearing mice after tail vein injection. Under the administration of lethal dosage of Celastrol, the tumors are greatly suppressed and the mice maintain the activity. These results demonstrate that anti-solvent method may be a promising strategy to fabricate Celastrol nano-drugs with controllable size and less systemic toxicity for further clinical cancer treatment.

Ferroptosis in lung cancer: a novel pathway regulating cell death and a promising target for drug therapy

Lung cancer is a common malignant tumor that occurs in the human body and poses a serious threat to human health and quality of life. The existing treatment methods mainly include surgical treatment, chemotherapy, and radiotherapy. However, due to the strong metastatic characteristics of lung cancer and the emergence of related drug resistance and radiation resistance, the overall survival rate of lung cancer patients is not ideal. There is an urgent need to develop new treatment strategies or new effective drugs to treat lung cancer. Ferroptosis, a novel type of programmed cell death, is different from the traditional cell death pathways such as apoptosis, necrosis, pyroptosis and so on. It is caused by the increase of iron-dependent reactive oxygen species due to intracellular iron overload, which leads to the accumulation of lipid peroxides, thus inducing cell membrane oxidative damage, affecting the normal life process of cells, and finally promoting the process of ferroptosis. The regulation of ferroptosis is closely related to the normal physiological process of cells, and it involves iron metabolism, lipid metabolism, and the balance between oxygen-free radical reaction and lipid peroxidation. A large number of studies have confirmed that ferroptosis is a result of the combined action of the cellular oxidation/antioxidant system and cell membrane damage/repair, which has great potential application in tumor therapy. Therefore, this review aims to explore potential therapeutic targets for ferroptosis in lung cancer by clarifying the regulatory pathway of ferroptosis. Based on the study of ferroptosis, the regulation mechanism of ferroptosis in lung cancer was understood and the existing chemical drugs and natural compounds targeting ferroptosis in lung cancer were summarized, with the aim of providing new ideas for the treatment of lung cancer. In addition, it also provides the basis for the discovery and clinical application of chemical drugs and natural compounds targeting ferroptosis to effectively treat lung cancer.

Site-specific nanomodulator capable of modulation apoptosis for enhanced colorectal cancer chemo-photothermal therapy

BACKGROUND

Colorectal cancer (CRC) is a common malignancy with the second highest mortality and the third highest morbidity worldwide. However, the overall survival of patients is unsatisfactory, thus requiring more effective clinical strategies. Celastrol (CLT), a natural bioactive compound, has been reported to induce reactive oxygen species (ROS)-mediated apoptosis to exhibit significant antitumor effects against CRC. However, the poor water solubility, low targeting ability, and bioavailability of CLT have limited its application, and CLT-induced protective autophagy weakens its therapeutic efficiency.

RESULTS

We designed a targeted chemo-phototherapy nanoplatform (HCR NPs) to improve the application of CLT. The codelivery of IR820 and CLT in HCR NPs solved the water-soluble problem of CLT and enhanced apoptosis via IR820-mediated hyperthermia. In addition, hydroxychloroquine (HCQ) conjugated to hyaluronic acid (HA) not only increased the active targeting of HCR NPs but also inhibited CLT-induced protective autophagy to exacerbate apoptosis, thus achieving an amplified antitumor effect. Importantly, the HCR NPs exhibited an excellent therapeutic effect on CRC both in vitro and in vivo.

CONCLUSION

The HCR NPs presented in this study may not merely provide a new reference for the clinical application of CLT but also result in an attractive strategy for CRC treatment.

Celastrol-regulated gut microbiota and bile acid metabolism alleviate hepatocellular carcinoma proliferation by regulating the interaction between FXR and RXRα in vivo and in vitro

Celastrol, a triterpene derived from Thunder God Vine (Tripterygium wilfordii Hook f; Celastraceae), a traditional Chinese herb, has promising anticancer activity. The present study aimed to elucidate an indirect mechanism of celastrol-mediated alleviation of hepatocellular carcinoma (HCC) via gut microbiota-regulated bile acid metabolism and downstream signaling. Here, we constructed a rat model of orthotopic HCC and performed 16S rDNA sequencing and UPLC-MS analysis. The results showed that celastrol could regulate gut bacteria; suppress the abundance of Bacteroides fragilis; raise the levels of glycoursodeoxycholic acid (GUDCA), a bile acid; and alleviate HCC. We found that GUDCA suppressed cellular proliferation and induced the arrest of mTOR/S6K1 pathway-associated cell cycle G0/G1 phase in HepG2 cells. Further analyses using molecular simulations, Co-IP, and immunofluorescence assays revealed that GUDCA binds to farnesoid X receptor (FXR) and regulates the interaction of FXR with retinoid X receptor a (RXRα). Transfection experiments using the FXR mutant confirmed that FXR is essential for GUCDA-mediated suppression of HCC cellular proliferation. Finally, animal experiments showed that the treatment with the combination of celastrol/GUDCA alleviated the adverse effects of celastrol alone treatment on body weight loss and improved survival in rats with HCC. In conclusion, the findings of this study suggest that celastrol exerts an alleviating effect on HCC, in part via regulation of the B. fragilis-GUDCA-FXR/RXRα-mTOR axis.

SHP2 inhibition improves celastrol-induced growth suppression of colorectal cancer

This study aimed to explore novel targets for celastrol sensitization in colorectal cancer (CRC) based on differentially regulated signals in response to high- or low-dose celastrol. Targeting signals were investigated using Western blotting or phosphorylated receptor tyrosine kinase (RTK) arrays. Corresponding inhibitors for the signals were individually combined with low-dose celastrol for the assessment of combined anti-CRC effects, based on proliferation, apoptosis, colony assays, and xenograft models. The potential mechanism for the combination of celastrol and SHP2 inhibition was further examined. Low-dose celastrol (&lt;1 µM) did not effectively suppress AKT and ERK signals in CRC cells compared to high-dose celastrol (&gt;1 µM). However, when combined with an AKT or ERK inhibitor, low-dose celastrol could cooperatively suppress CRC proliferation. Furthermore, failed AKT or ERK inhibition by low-dose celastrol may be due to reactivated RTK-SHP2 signaling with negative feedback. The combination of celastrol and the SHP2 inhibitor resulted in greatly reduced AKT and ERK signals, as well as greater inhibition of CRC growth than celastrol alone. Moreover, the mechanism underlying combination suppression was also involved in the activation of immune cell infiltration (mainly for CD8+ cells) in CRC tissues. Failure to inhibit RTK-SHP2-AKT/ERK signaling contributed to the lack of CRC growth suppression by low-dose celastrol. However, the combination of celastrol and the SHP2 inhibitor resulted in synergistic inhibition of CRC growth and provided a promising therapeutic target.

Celastrol: A Promising Agent Fighting against Cardiovascular Diseases

Cardiovascular diseases (CVD) are leading causes of morbidity and mortality worldwide; therefore, seeking effective therapeutics to reduce the global burden of CVD has become increasingly urgent. Celastrol, a bioactive compound isolated from the roots of the plant Tripterygium wilfordii (TW), has been attracting increasing research attention in recent years, as it exerts cardiovascular treatment benefits targeting both CVD and their associated risk factors. Substantial evidence has revealed a protective role of celastrol against a broad spectrum of CVD including obesity, diabetes, atherosclerosis, cerebrovascular injury, calcific aortic valve disease and heart failure through complicated and interlinked mechanisms such as direct protection against cardiomyocyte hypertrophy and death, and indirect action on oxidation and inflammation. This review will mainly summarize the beneficial effects of celastrol against CVD, largely based on in vitro and in vivo preclinical studies, and the potential underlying mechanisms. We will also briefly discuss celastrol’s pharmacokinetic limitations, which hamper its further clinical applications, and prospective future directions.

Quantitative chemical proteomics reveals anti-cancer targets of Celastrol in HCT116 human colon cancer cells

BACKGROUND

Celastrol (Cel) is a naturally-derived compound with anti-cancer properties and exerts beneficial effects against various diseases. Although an extensive body of research already exists for Cel, the vast majority are inductive studies with limited validation of specific pathways and functions. The cellular targets that bind to Cel remain poorly characterized, which limits attempts to uncover its mechanism of action.

PURPOSE

The present study aims to comprehensively identify the protein targets of Cel in HCT116 cells in an unbiased manner, and elucidate the mechanism of the anti-cancer activity of Cel based on target information.

METHODS

A comprehensive analysis of protein targets that bind to Cel was performed in HCT116 colon cancer cells using a quantitative chemical biology method. A Cel probe (Cel-P) was synthesized to allow in situ monitoring of treatment in living HCT116 cells, and specific targets were identified with a quantitative chemical biology method (isobaric tags for relative and absolute quantitation) using mass spectrometry.

RESULTS

In total, 100 protein targets were identified as specific targets of Cel. Pathways associated with the targets were investigated. Multiple pathways were demonstrated to be potential effectors of Cel. These pathways included the suppression of protein synthesis, deregulation of cellular reactive oxygen species, and suppression of fatty acid metabolism, and they were validated with in vitro experiments.

CONCLUSION

The extensive information on the protein targets of Cel and their functions uncovered by this study will enhance the current understanding of the mechanism of action of Cel and serve as a valuable knowledge base for future studies.

Celastrol inhibits pathologic neovascularization in oxygen-induced retinopathy by targeting the miR-17-5p/HIF-1α/VEGF pathway

Retinopathy of prematurity (ROP), which is characterized by retinal neovascularization (RNV), is a major cause of neonatal blindness. The primary treatment for ROP is anti-vascular endothelial growth factor (VEGF) therapy, which is costly and can rapidly lead to desensitization. Celastrol, a bioactive compound extracted from Tripterygium wilfordii Hook F. ("Thunder of God Vine"), has been shown to exert anticancer and anti-inflammatory effects. However, whether celastrol has antiangiogenic activity and can suppress inflammation to inhibit ROP progression is unclear. This was investigated in the present study in vitro as well as in vivo using a mouse model of oxygen-induced retinopathy (OIR). Our results showed that celastrol treatment reduced neovascular and avascular areas in the retina and inhibited microglia activation and inflammation in OIR mice. Celastrol also inhibited proliferation, migration, and tube formation in cultured human retinal microvascular endothelial cells, and reversed the activation of the microRNA (miR)-17-5p/hypoxia-inducible factor (HIF)-1α/VEGF pathway in the retina of OIR mice. These results indicate that celastrol alleviates pathologic RNV in the retina by protecting neuroglia and suppressing inflammation via inhibition of miR-17-5p/HIF-1α/VEGF signaling, and thus has therapeutic potential for the prevention and treatment of ROP.Abbreviations: BSA, bovine serum albumin; COX2, cyclooxygenase 2; ECM, endothelial cell medium; FBS, fetal bovine serum; HDAC, histone deacetylase; HIF-1, hypoxia-inducible factor 1; HRMEC, human retinal microvascular endothelial cell; Hsp70, heat shock protein; IB4, isolectin B4; ICAM-1, intercellular adhesion molecule 1; IL-1β/6, interleukin 1 beta/6; MAPK, mitogen-activated protein kinase; MCP-1, monocyte chemoattractant protein 1; miRNA, microRNA; MMP, matrix metalloproteinase; mTOR, mammalian target of rapamycin; NF-κB, nuclear factor-kappa B; OIR, oxygen-induced retinopathy; PBS, phosphate-buffered saline; PCNA, proliferating cell nuclear antigen; PI3K, phosphatidylinositol-3-kinase; qRT-PCR, quantitative real-time PCR; RNV, retinal neovascularization; ROP, retinopathy of prematurity; RTCA, real-time cell analyzer; RVO, retinal vaso-obliteration; TNF-α, tumor necrosis factor alpha; VCAM-1, vascular cell adhesion molecule 1; VEGF, vascular endothelial growth factor.

Modulation of Inflammation-Related Lipid Mediator Pathways by Celastrol During Human Macrophage Polarization

Background and Purpose

Celastrol (CS) is a major active ingredient of the Chinese/Asian herb Tripterygium wilfordii that is frequently used as phytomedicine to treat inflammation and autoimmune diseases. We showed before that short-term exposure to CS (1 µM) favorably impacts the biosynthesis of inflammation-related lipid mediators (LM) in human polarized macrophages by modulating the activities of different lipoxygenases (LOXs). However, whether CS regulates the expression of LOXs and other related LM-biosynthetic enzymes during macrophage polarization is unknown. Here, we investigated how CS affects LM-biosynthetic enzyme expression on the protein level and studied concomitant LM signature profiles during polarization of human monocyte-derived macrophages (MDM) towards M1- and M2-like phenotypes.

Methods and Results

We used LM metabololipidomics to study the long-term effects of CS on LM profile signatures after manipulation of human monocyte-derived macrophages (MDM) during polarization. Exposure of MDM to low concentrations of CS (ie, 0.2 µM) during polarization to an inflammatory M1 phenotype potently suppressed the formation of pro-inflammatory cyclooxygenase (COX)- and 5-LOX-derived LM, especially prostaglandin (PG)E₂. Notably, gene and enzyme expression of COX-2 and microsomal PGE₂ synthase (mPGES)-1 as well as M1 markers were strongly decreased by CS during M1-MDM polarization, along with impaired activation of nuclear factor-κB and p38 mitogen-activated protein kinase. During IL-4-induced M2 polarization, CS decreased the capacity of the resulting M2-MDM to generate pro-inflammatory COX and 5-LOX products as well but it also reduced the formation of 12/15-LOX products and specialized pro-resolving mediators, without affecting the levels of liberated fatty acid substrates.

Conclusion

Depending on the timing and concentration, CS not only favorably affects LOX activities in macrophages but also the expression of LM-biosynthetic enzymes during macrophage polarization connected to changes of inflammation-related LM which might be of relevance for potential application of CS to treat inflammatory disorders.

Neuroprotective Effects of Celastrol in Neurodegenerative Diseases-Unscramble Its Major Mechanisms of Action and Targets

There are rarely new therapeutic breakthroughs present for neurodegenerative diseases in the last decades. Thus, new effective drugs are urgently needed for millions of patients with neurodegenerative diseases. Celastrol, a pentacyclic triterpenoid compound, is one of the main active ingredients isolated from Tripterygium wilfordii Hook. f. that has multiple biological activities. Recently, amount evidence indicates that celastrol exerts neuroprotective effects and holds therapeutic potential to serve as a novel agent for neurodegenerative diseases. This review focuses on the therapeutic efficacy and major regulatory mechanisms of celastrol to rescue damaged neurons, restore normal cognitive and sensory motor functions in neurodegenerative diseases. Importantly, we highlight recent progress regarding identification of the drug targets of celastrol by using advanced quantitative chemical proteomics technology. Overall, this review provides novel insights into the pharmacological activities and therapeutic potential of celastrol for incurable neurodegenerative diseases.

Identifying the Effect of Celastrol Against Ovarian Cancer With Network Pharmacology and In Vitro Experiments

Aim: We aimed to reveal the function of celastrol in the treatment of ovarian cancer using network pharmacology and molecular docking.

Background: Ovarian cancer is a growth of cells that forms in the ovaries. Celastrol is a useful bioactive compound derived from the root of the thunder god vine.

Method: Celastrol and ovarian cancer targets were determined by analyzing datasets. Protein–protein interaction (PPI) networks were obtained with network pharmacology. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed. Molecular docking using SWISS-MODEL, CB-Dock and Discovery Studio was conducted. A methylthiazolyltetrazolium bromide (MTT) assay was performed to evaluate cell proliferation. Cell apoptosis and cell cycle were measured with a fluorescence assay. Reverse transcription PCR (RT-PCR) and Western blot were performed to measure the expression of core targets.

Result: Celastrol possessed 29 potential targets, while ovarian cancer possessed 471 potential targets. The core PPI network contained 163 nodes and 4,483 edges. The biological processes identified in the GO analysis indicated that the targets were related with the cellular response to DNA damage stimulus, DNA recombination, and cell proliferation, among other processes. The KEGG analysis indicated that the pathways were related with the cell cycle, viral carcinogenesis, and MAPK signaling pathway, among others. The three core targets shared between the core PPI network and celastrol targets were MYC, CDC37, and FN1. Celastrol directly combined with the targets according to the results from CB-Dock and Discovery Studio. Celastrol inhibited ovarian cancer cell proliferation and promoted ovarian cancer cell apoptosis in a dose-dependent manner. RT-PCR and Western blot analyses showed that celastrol inhibited core target expression. In addition, celastrol also influenced the related inflammatory signaling pathways in ovarian cancer cells.

Conclusion: Celastrol exerts effective antitumor activity toward ovarian cancer. Celastrol regulated cell proliferation, DNA repair and replication, apoptotic processes, and inflammatory responses in ovarian cancer cells.

Discovery of Novel Celastrol-Imidazole Derivatives with Anticancer Activity In Vitro and In Vivo

To discover celastrol (CEL) derivatives with enhanced Hsp90-Cdc37 inhibition, C-20-COOH was introduced with various substituted imidazoles, which might affect the Michael addition of CEL by nucleophilic attack. The most potent compound 9, which showed higher antiproliferation, covalent-binding ability, and Hsp90-Cdc37 inhibition than CEL, was selected from 28 new target compounds. Then, the binding sites and the docking mode of 9 to Hsp90 and Cdc37 were studied. Furthermore, the activity of 9 sharply decreased or even disappeared in the Hsp90- and/or Cdc37-overexpressing A549 cells, indicating that the activity was related to its combination with Hsp90 and Cdc37. Moreover, 9 could more effectively induce apoptosis and inhibit tumor growth than CEL in vivo. This study first found that imidazoles linked to C-20 of CEL might affect its Michael addition, which will provide support of CEL or even the other Michael acceptors for the development as antitumor agents.

Metabolomics reveals the role of PPARα in Tripterygium Wilfordii-induced liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium glycosides tablets (TGT) and Tripterygium wilfordii tablets (TWT) have been used to treat autoimmune diseases clinically, however, the side effects of TWT are higher than TGT, especially for hepatotoxicity.

THE AIM OF THE STUDY

This study aims to determine the mechanism of TWT-induced liver injury.

MATERIALS AND METHODS

We performed metabolomic analysis of samples from mice with liver injury induced by TGT and TWT. Ppara-null mice were used to determine the role of PPARα in TWT-induced liver injury.

RESULTS

The results indicated that TWT induced the accumulation of medium- and long-chain carnitines metabolism, which was associated with the disruption of PPARα-IL6-STAT3 axis. PPARα agonists fenofibrate could reverse the liver injury from TWT and TP/Cel, and its protective role could be attenuated in Ppara-null mice. The toxicity difference of TWT and TGT was due to the different ratio of triptolide (TP) and celastrol (Cel) in the tablet in which TP/Cel was lower in TWT than TGT. The hepatotoxicity induced by TP and Cel also inhibited PPARα and upregulated IL6-STAT3 axis, which could be alleviated following by PPARα activation.

CONCLUSIONS

These results indicated that PPARα plays an important role in the hepatotoxicity of Tripterygium wilfordii, and PPARα activation may offer a promising approach to prevent hepatotoxicity induced by the preparations of Tripterygium wilfordii.

Leptin, the brain and energy homeostasis: From an apparently simple to a highly complex neuronal system

Leptin, produced and secreted by white adipose tissue in tight relationship with adipose mass, informs the brain about the status of the energy stores serving as the main peripheral signal for energy balance regulation through interaction with a multitude of highly interconnected neuronal populations. Most obese patients display resistance to the anorectic effect of the hormone. The present review unravels the multiple levels of complexity that trigger hypothalamic response to leptin with the objective of highlighting those critical hubs that, mainly in the hypothalamic arcuate nucleus, may undergo obesity-induced alterations and create an obstacle to leptin action. Several mechanisms underlying leptin resistance have been proposed, possibly representing useful targets to empower leptin effects. Among these, a special focus is herein dedicated to detail how leptin gains access into the brain and how neuronal plasticity may interfere with leptin function.

Celastrol attenuates high-fructose diet-induced inflammation and insulin resistance via inhibition of 11β-hydroxysteroid dehydrogenase type 1 activity in rat adipose tissues

High fructose consumption has been linked to low-grade inflammation and insulin resistance that results in increased intracellular 11ß-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity. Celastrol, a pentacyclic triterpene, has been demonstrated to exhibit multifaceted targets to attenuate various metabolic diseases associated with inflammation. However, the underlying mechanisms by which celastrol exerts its attributive properties on high fructose diet (HFrD)-induced metabolic syndrome remain elusive. Herein, the present study was aimed to elucidate the mechanistic targets of celastrol co-administrations upon HFrD in rats and evaluate its potential to modulate 11β-HSD1 activity. Celastrol remarkably improved glucose tolerance, lipid profiles, and insulin sensitivity along with suppression of hepatic glucose production. In rat adipose tissues, celastrol attenuated nuclear factor-kappa B (NF-κB)-driven inflammation, reduced c-Jun N-terminal kinases (JNK) phosphorylation, and mitigated oxidative stress via upregulated genes expression involved in mitochondrial biogenesis. Furthermore, insulin signaling pathways were significantly improved through the restoration of Akt phosphorylation levels at Ser473 and Thr308 residues. Celastrol exhibited a potent, selective and specific inhibitor of intracellular 11β-HSD1 towards oxidoreductase activity (IC₅₀ value = 4.3 nM) in comparison to other HSD-related enzymes. Inhibition of 11β-HSD1 expression in rat adipose microsomes reduced the availability of its cofactor NADPH and substrate H6PDH in couple to upregulated mRNA and protein expressions of glucocorticoid receptor. In conclusion, our results underscore the most likely conceivable mechanisms exhibited by celastrol against HFrD-induced metabolic dysregulations mainly through attenuating inflammation and insulin resistance, at least via specific inhibitions on 11β-HSD1 activity in adipose tissues.

Celastrol inhibits the proliferation and migration of MCF-7 cells through the leptin-triggered PI3K/AKT pathway

Leptin is the pivotal modulator in the onset and progression of breast cancer and obesity. Celastrol, which is extracted from the roots of Tripterygium wilfordi plants, exerts various anticancer bioactivities and has recently emerged as a candidate to treat obesity by improving leptin sensitivity. However, the relationship between leptin and celastrol in the treatment of breast cancer is unknown. Here, the growth and migration of MCF-7 cells induced by leptin were tested to demonstrate the antineoplastic activity of celastrol. Transcriptomic analysis and western blotting were conducted to explore the biological roles of leptin in treating breast cancer with celastrol. The present findings showed that celastrol remarkably reversed leptin-triggered cell proliferation and migration in MCF-7 cells. Fifty-two mRNAs with fivefold higher counts and 149 mRNAs with fivefold lower counts were identified in the celastrol-treated MCF-7 cells. According to the GO and KEGG analyses, the effects of celastrol on MCF-7 cells forced lipid metabolism and the endocrine system. Moreover, leptin treatment induced phosphorylation of leptin receptor and PI3K/AKT in MCF-7 cells, whereas pretreatment with celastrol partly abrogated leptin activation. The binding of celastrol to the leptin receptor was also confirmed by molecular docking. The antitumor effect of celastrol is proposed to be mediated by its binding to the leptin receptor and controlled downregulation of the PI3K/AKT pathway.

Heme oxygenase-1 inhibits DENV-induced endothelial hyperpermeability and serves as a potential target against dengue hemorrhagic fever

Dengue virus (DENV) is a cause of vascular endothelial dysfunction and vascular leakage, which are characterized as hallmarks of dengue hemorrhagic fever or dengue shock syndrome, which become a severe global health emergency with substantial morbidity and mortality. Currently, there are still no promising therapeutics to alleviate the dengue-associated vascular hemorrhage in a clinical setting. In the present study, we first observed that heme oxygenase-1 (HO-1) expression level was highly suppressed in severe DENV-infected patients. In contrast, the overexpression of HO-1 could attenuate DENV-induced pathogenesis, including plasma leakage and thrombocytopenia, in an AG129 mouse model. Our data indicate that overexpression of HO-1 or its metabolite biliverdin can maintain endothelial integrity upon DENV infection in vitro and in vivo. We further characterized the positive regulatory effect of HO-1 on the endothelial adhesion factor vascular endothelial-cadherin to decrease DENV-induced endothelial hyperpermeability. Subsequently, we confirmed that two medicinal plant-derived compounds, andrographolide, and celastrol, widely used as a nutritional or medicinal supplement are useful to attenuate DENV-induced plasma leakage through induction of the HO-1 expression in DENV-infected AG129 mice. In conclusion, our findings reveal that induction of the HO-1 signal pathway is a promising option for the treatment of DENV-induced vascular pathologies.

Synthesis and biological evaluation of celastrol derivatives as potent antitumor agents with STAT3 inhibition

Using STAT3 inhibitors as a potential strategy in cancer therapy have attracted much attention. Recently, celastrol has been reported that it could directly bind to and suppress the activity of STAT3 in the cardiac dysfunction model. To explore more effective STAT3 inhibiting anti-tumour drug candidates, we synthesised a series of celastrol derivatives and biologically evaluated them with several human cancer cell lines. The western blotting analysis showed that compound 4 m, the most active derivative, could suppress the STAT3's phosphorylation as well as its downstream genes. SPR analysis, molecular docking and dynamics simulations' results indicated that the 4m could bind with STAT3 protein more tightly than celastrol. Then we found that the 4m could block cell-cycle and induce apoptosis on HCT-116 cells. Furthermore, the anti-tumour effect of 4m was verified on colorectal cancer organoid. This is the first research that discovered effective STAT3 inhibitors as potent anti-tumour agents from celastrol derivatives.

Celastrol and Melatonin Modify SIRT1, SIRT6 and SIRT7 Gene Expression and Improve the Response of Human Granulosa-Lutein Cells to Oxidative Stress

An excess of oxidative stress (OS) may affect several physiological processes fundamental to reproduction. SIRT1, SIRT6 and SIRT7 are involved in protection stress systems caused by OS, and they can be activated by antioxidants such as celastrol or melatonin. In this study, we evaluate SIRT1, SIRT6 and SIRT7 gene expression in cultured human granulosa-lutein (hGL) cells in response to OS inductors (glucose or peroxynitrite) and/or antioxidants. Our results show that celastrol and melatonin improve cell survival in the presence and absence of OS inductors. In addition, melatonin induced SIRT1, SIRT6 and SIRT7 gene expression while celastrol only induced SIRT7 gene expression. This response was not altered by the addition of OS inductors. Our previous data for cultured hGL cells showed a dual role of celastrol as a free radical scavenger and as a protective agent by regulating gene expression. This study shows a direct effect of celastrol on SIRT7 gene expression. Melatonin may protect from OS in a receptor-mediated manner rather than as a scavenger. In conclusion, our results show increased hGL cells survival with melatonin or celastrol treatment under OS conditions, probably through the regulation of nuclear sirtuins' gene expression.

Celastrol inhibits the proliferation and induces apoptosis of colorectal cancer cells via downregulating NF-κB/COX-2 signaling pathways

BACKGROUND

Colorectal cancer (CRC) is the third-ranked malignant tumor in the world that contributes to the death of a major population of the world. Celastrol, a bioactive natural product isolated from the medicinal plant Tripterygium wilfordii Hook F, has been proved to be an effective anti-tumor inhibitor for multiple tumors.

OBJECTIVE

To reveal the therapeutic effect and underlying mechanisms of celastrol on CRC cells.

METHODS

CCK-8 and clonogenic assay were used to analyze the cell proliferation in CRC cells. Flow cytometry analysis was conducted to assess the cell cycle and cell apoptosis. Wound-healing and cell invasion assay were used to evaluate the migrating and invasion capability of CRC cells. The potential antitumor mechanism of celastrol was investigated by qPCR, western blot, and confocal immunofluorescence analyses.

RESULTS

Celastrol effectively inhibited CRC cell proliferation by activating caspase-dependent cell apoptosis and facilitating G1 cell cycle arrest in a dose-dependent manner, as well as cell migration and invasion by downregulating the MMP2 and MMP9. Mechanistic protein expression revealed that celastrol suppressed the expression of COX-2 by inhibiting the phosphorylation of NF-κB p65 and subsequently leading to cytoplasmic retention of p65 protein, thereby inhibiting its nuclear translocation and transcription activities.

CONCLUSION

These findings indicate that celastrol is an effective inhibitor for CRC, regulating the NF-κB/COX-2 pathway, leading to the inhibition of cell proliferation characterized by cell cycle arrest and caspase-dependent apoptosis, providing a potential alternative therapeutic agent for CRC patients.

Recent progress in nanotechnology-based drug carriers for celastrol delivery

Celastrol (CLT) is an active ingredient that was initially discovered and extracted from the root of Tripterygium wilfordii. The potential pharmacological activities of CLT in cancer, obesity, and inflammatory, auto-immune, and neurodegenerative diseases have been demonstrated in recent years. However, CLT's clinical application is extremely restricted by its low solubility/permeability, poor bioavailability, and potential off-target toxicity. The advent of nanotechnology provides a solution to improve the oral bioavailability, therapeutic effects or tissue-targeting ability of CLT. This review focuses on the most recent advances, improvements, inventions, and updated literature of various nanocarrier systems for CLT.

Tripterine and all-trans retinoic acid (ATRA) - loaded lipid-polymer hybrid nanoparticles for synergistic anti-arthritic therapy against inflammatory arthritis

Arthritis of joints remains a hard-to-treat disease due to the low drug exposure to the articular cavity. Present study was intended to develop a Tripterine (TRI) and all-trans retinoic acid (ATRA)-loaded lipid-polymer hybrid nanoparticles (ATLP) for enhanced antiarthritic efficacy in arthritis conditions. We have showed that two drugs could be loaded with high loading capacity and control the release kinetics in a pH-responsive manner. The ATLP showed strong inhibitory effects on the expressions of TNF-α, IL-6 and IL-1β in lipopolysaccharide (LPS)-stimulated RAW264.7 cells at the in vitro conditions. Compared to individual drugs (TRI and ATRA), ATLP significantly reduced the paw thickness exhibiting potent inhibition of inflammation. Consistently, ATLP resulted in lowest clinical score compared to that of individual drug indicating the remarkable improvement in the recession of inflammation. We have clearly demonstrated that the nanoparticulate based co-delivery of drugs could abolish the adverse effects of free drug as indicated by the body weight changes. Importantly, ATLP resulted in significant reduction of mRNA of TNF-α, IL-6, IFN-ϒ and IL-17 compared to either free drugs or CIA mice. Overall, ATLP represent a promising therapeutic strategy for the treatment of arthritis conditions.

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.

Celastrol ameliorates vascular neointimal hyperplasia through Wnt5a-involved autophagy

Neointimal hyperplasia caused by the excessive proliferation of vascular smooth muscle cells (VSMCs) is the pathological basis of restenosis. However, there are few effective strategies to prevent restenosis. Celastrol, a pentacyclic triterpene, has been recently documented to be beneficial to certain cardiovascular diseases. Based on its significant effect on autophagy, we proposed that celastrol could attenuate restenosis through enhancing autophagy of VSMCs. In the present study, we found that celastrol effectively inhibited the intimal hyperplasia and hyperproliferation of VSMCs by inducing autophagy. It was revealed that autophagy promoted by celastrol could induce the lysosomal degradation of c-MYC, which might be a possible mechanism contributing to the reduction of VSMCs proliferation. The Wnt5a/PKC/mTOR signaling pathway was found to be an underlying mechanism for celastrol to induce autophagy and inhibit the VSMCs proliferation. These observations indicate that celastrol may be a novel drug with a great potential to prevent restenosis.

Multiple Myeloma Inhibitory Activity of Plant Natural Products

A literature search on plant natural products with antimyeloma activity until the end of 2020 resulted in 92 compounds with effects on at least one human myeloma cell line. Compounds were divided in different compound classes and both their structure-activity-relationships as well as eventual correlations with the pathways described for Multiple Myeloma were discussed. Each of the major compound classes in this review (alkaloids, phenolics, terpenes) revealed interesting candidates, such as dioncophyllines, a group of naphtylisoquinoline alkaloids, which showed pronounced and selective induction of apoptosis when substituted in position 7 of the isoquinoline moiety. Interestingly, out of the phenolic compound class, two of the most noteworthy constituents belong to the relatively small subclass of xanthones, rendering this group a good starting point for possible further drug development. The class of terpenoids also provides noteworthy constituents, such as the highly oxygenated diterpenoid oridonin, which exhibited antiproliferative effects equal to those of bortezomib on RPMI8226 cells. Moreover, triterpenoids containing a lactone ring and/or quinone-like substructures, e.g., bruceantin, whitaferin A, withanolide F, celastrol, and pristimerin, displayed remarkable activity, with the latter two compounds acting as inhibitors of both NF-κB and proteasome chymotrypsin-like 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.

Natural Bioactive Compounds as Potential Browning Agents in White Adipose Tissue

The epidemic of overweight and obesity underlies many common metabolic diseases. Approaches aimed to reduce energy intake and/or stimulate energy expenditure represent potential strategies to control weight gain. Adipose tissue is a major energy balancing organ. It can be classified as white adipose tissue (WAT) and brown adipose tissue (BAT). While WAT stores excess metabolic energy, BAT dissipates it as heat via adaptive thermogenesis. WAT also participates in thermogenesis by providing thermogenic fuels and by directly generating heat after browning. Browned WAT resembles BAT morphologically and metabolically and is classified as beige fat. Like BAT, beige fat can produce heat. Human adults have BAT-like or beige fat. Recruitment and activation of this fat type have the potential to increase energy expenditure, thereby countering against obesity and its metabolic complications. Given this, agents capable of inducing WAT browning have recently attracted broad attention from biomedical, nutritional and pharmaceutical societies. In this review, we summarize natural bioactive compounds that have been shown to promote beige adipocyte recruitment and activation in animals and cultured cells. We also discuss potential molecular mechanisms for each compound to induce adipose browning and metabolic benefits.

Anti-inflammatory celastrol promotes a switch from leukotriene biosynthesis to formation of specialized pro-resolving lipid mediators

The pentacyclic triterpenoid quinone methide celastrol (CS) from Tripterygium wilfordii Hook. F. effectively ameliorates inflammation with potential as therapeutics for inflammatory diseases. However, the molecular mechanisms underlying the anti-inflammatory and inflammation-resolving features of CS are incompletely understood. Here we demonstrate that CS potently inhibits the activity of human 5-lipoxygenase (5-LOX), the key enzyme in pro-inflammatory leukotriene (LT) formation, in cell-free assays with IC₅₀ = 0.19-0.49 µM. Employing metabololipidomics using ultra-performance liquid chromatography coupled to tandem mass spectrometry in activated human polymorphonuclear leukocytes or M1 macrophages we found that CS (1 µM) potently suppresses 5-LOX-derived products without impairing the formation of lipid mediators (LM) formed by 12-/15-LOXs as well as fatty acid substrate release. Intriguingly, CS induced the generation of 12-/15-LOX-derived LM including the specialized pro-resolving mediator (SPM) resolvin D5 in human M2 macrophages. Finally, intraperitoneal pre-treatment of mice with 10 mg/kg CS strongly impaired zymosan-induced LT formation and simultaneously elevated the levels of SPM and related 12-/15-LOX-derived LM in peritoneal exudates, spleen and plasma in vivo. Conclusively, CS promotes a switch from LT biosynthesis to formation of SPM which may underlie the anti-inflammatory and inflammation-resolving effects of CS, representing an interesting pharmacological strategy for intervention with inflammatory disorders.

Discovery of novel celastrol-triazole derivatives with Hsp90-Cdc37 disruption to induce tumor cell apoptosis

To enhance the disruption of Hsp90-Cdc37, we designed and synthesized a series (27) of CEL-triazole derivatives. Most of the target compounds showed enhanced anti-proliferative activity on four cancer cell lines (MDA-MB-231, MCF-7, HepG2 and A459). Among them, compound 6 showed the best anti-proliferation (IC₅₀ = 0.34 ± 0.01 μM) on MDA-MB-231. Pharmacological studies had found that compound 6 showed a higher ability to disrupt Hsp90-Cdc37 interaction in cells and inhibited the expression of the key Hsp90-Cdc37 clients in a concentration-dependent manner. Further studies indicated that an enhanced covalent binding between compound 6 and thiols (cysteine) might be one of the reasons for the increased activity. Furthermore, compound 6 arrested cells in the G₀/G₁ phase and induced tumor cell apoptosis significantly. Overall, for cancer treatment, compound 6 was worth further exploring.

Celastrol in metabolic diseases: Progress and application prospects

Metabolic diseases are becoming increasingly common in modern society. Therefore, it is essential to develop effective drugs or new treatments for metabolic diseases. As an active ingredient derived from plants, celastrol has shown great potential in the treatment of a wide variety of metabolic diseases and received considerable attention in recent years. In reported studies, the anti-obesity effect of celastrol resulted from regulating leptin sensitivity, energy metabolism, inflammation, lipid metabolism and even gut microbiota. Celastrol reversed insulin resistance via multiple routes to protect against type 2 diabetes. Celastrol also showed effects on atherosclerosis, cholestasis and osteoporosis. Celastrol in treating metabolic diseases seem to be versatile and the targets or pathways were diverse. Here, we systematically review the mechanism of action, and the therapeutic properties of celastrol in various metabolic diseases and complications. Based on this review, potential research strategies might contribute to the celastrol's clinical application in the future.

Design, Synthesis and In Vitro Investigation of Novel Basic Celastrol Carboxamides as Bio-Inspired Leishmanicidal Agents Endowed with Inhibitory Activity against Leishmania Hsp90

The natural triterpene celastrol (CE) is here used as lead compound for the design and synthesis of a panel of eleven CE carboxamides that were tested in vitro for their growth inhibitory activity against Leishmania infantum and L.tropica parasites. Among them, in vitro screening identified four basic CE carboxamides endowed with nanomolar leishmanicidal activity, against both the promastigotes and the intramacrophage Leishmania amastigotes forms. These compounds also showed low toxicity toward two human (HMEC-1 and THP-1) and one murine (BMDM) cell lines. Interestingly, the most selective CE analogue (compound 3) was also endowed with the ability to inhibit the ATPase activity of the Leishmania protein chaperone Hsp90 as demonstrated by the in vitro assay conducted on a purified, full-length recombinant protein. Preliminary investigations by comparing it with the naturally occurring Hsp90 active site inhibitor Geldanamycin (GA) in two different in vitro experiments were performed. These promising results set the basis for a future biochemical investigation of the mode of interaction of celastrol and CE-inspired compounds with Leishmania Hsp90.

Eating behaviour in contrasting adiposity phenotypes: Monogenic obesity and congenital generalized lipodystrophy

Most known types of nonsyndromic monogenic obesity are caused by rare mutations in genes of the leptin-melanocortin pathway controlling appetite and adiposity. In contrast, congenital generalized lipodystrophy represents the most extreme form of leanness in humans caused by recessive mutations in four genes involved in phospholipid/triglyceride synthesis and lipid droplet/caveolae structure. In this disease, the inability to store triglyceride in adipocytes results in hypoleptinemia and ectopic hepatic and muscle fat accumulation leading to fatty liver, hypertriglyceridemia and severe insulin resistance. As a result of hypoleptinemia, patients with lipodystrophy show alterations in eating behaviour characterized by constant increased energy intake. As it occurs in obesity caused by genetic leptin deficiency, exogenous leptin rapidly reduces hunger scores in patients with congenital generalized lipodystrophy, with additional beneficial effects on glucose homeostasis and metabolic profile normalization. The melanocortin-4 receptor agonist setmelanotide has been used in the treatment of monogenic obesities. There is only one report on the effect of setmelanotide in a patient with partial lipodystrophy resulting in mild reductions in hunger scores, with no improvements in metabolic status. The assessment of contrasting phenotypes of obesity/leanness represents an adequate strategy to understand the pathophysiology and altered eating behaviour associated with adipose tissue excessive accumulation/paucity.