Celastrus-derived celastrol suppresses autoimmune arthritis by modulating antigen-induced cellular and humoral effector responses

Mechanistic insights into anti-inflammatory and immunosuppressive effects of plant secondary metabolites and their therapeutic potential for rheumatoid arthritis

The anti-inflammatory and immunosuppressive activities of plant secondary metabolites are due to their diverse mechanisms of action against multifarious molecular targets such as modulation of the complex immune system associated with rheumatoid arthritis (RA). This review discussed and critically analyzed the potent anti-inflammatory and immunosuppressive effects of several phytochemicals and their underlying mechanisms in association with RA in experimental studies, including preliminary clinical studies of some of them. A wide range of phytochemicals including phenols, flavonoids, chalcones, xanthones, terpenoids, alkaloids, and glycosides have shown significant immunosuppressive and anti-inflammatory activities in experimental RA models and a few have undergone clinical trials for their efficacy and safety in reducing RA symptoms and improve patient outcomes. These phytochemicals have potential as safer alternatives to the existing drugs in the management of RA, which possess a wide range of serious side effects. Sufficient preclinical studies on safety and efficacy of these phytochemicals must be performed prior to proper clinical studies. Further studies are needed to address the barriers that have so far limited their human use before the therapeutic potential of these plant-based chemicals as anti-arthritic agents in the treatment of RA is fully realized.

Uptake of Cyclodextrin Nanoparticles by Macrophages is Dependent on Particle Size and Receptor-Mediated Interactions

Physiochemical properties of nanoparticles, such as their size and chemical composition, dictate their interaction with professional phagocytes of the innate immune system. Macrophages, in particular, are key regulators of the immune microenvironment that heavily influence particle biodistribution as a result of their uptake. This attribute enables macrophage-targeted delivery, including for phenotypic modulation. Saccharide-based materials, including polyglucose polymers and nanoparticles, are efficient vehicles for macrophage-targeted delivery. Here, we investigate the influence of particle size on cyclodextrin nanoparticle (CDNP) uptake by macrophages and further examine the receptor-mediated interactions that drive macrophage-targeted delivery. We designed and synthesized CDNPs ranging in size from 25 nm to >100 nm in diameter. Increasing particle size was correlated with greater uptake by macrophages in vitro. Both scavenger receptor A1 and mannose receptor were critical mediators of macrophage-targeted delivery, inhibition of which reduced the extent of uptake. Finally, we investigated the cellular bioavailability of drug-loaded CDNPs using a model anti-inflammatory drug, celastrol, which demonstrated that drug bioactivity is improved by CDNP loading relative to free drug alone. This study thus elucidates the interactions between the polyglucose nanoparticles and macrophages, thereby facilitating their application in macrophage-targeted drug delivery that has applications in the context of tissue injury and repair.

Seven lower toxicity celastrol derivatives by biotransformation of Pestalotiopsis sp. LGT-1

Biotransformation of toxic components by plant endophytes has become an effective method to reduce the toxicity of target compounds and discover lead compounds. In this context, an endophytic fungus, Pestalotiopsis sp. LGT-1, from Tripterygium wilfordii Hook F. (TwHF), was used to reduce the toxicity of celastrol which is also produced by TwHF and is considered an attractive molecule with a variety of biological activities. Seven celastrol derivatives (1-7) were isolated from the coculture fermentation broth of LGT-1 and celastrol. Their structures were elucidated by spectroscopic data analysis including 1D and 2D NMR, as well as HRESIMS. Their absolute configurations were determined by analysis of NOESY, ECD data and NMR calculations. In cell proliferation experiments, the toxicity of seven compounds was 10.11- to 1.24-fold lower in normal cells than the prototype compound celastrol. These derivatives serve as potential candidates for future pharmaceutical applications.

Ayurvedic management of neurological deficits post COVID-19 vaccination - A report of two cases

The world witnessed much research fund allocation on the COVID-19 outbreak's epidemiology, pathology, impact on lifestyles, social behaviours and treatment possibilities. The highly contagious nature of the disease compelled scientific communities and related organisations to hasten vaccine development and supplies. Well-timed international collaborations resulted in quicker development of varied forms of vaccines against COVID-19. Prospective observational studies and systematic reviews on vaccine trials reported their safety and efficacies. Nevertheless, post-marketing surveillance is quintessential to ascertain such safety and efficacy claims. There have been scattered reports lately of several adverse temporal events, such as haematological, immunological and neurological untoward occurrences following COVID-19 inoculation. There is a growing piece of evidence of the impact of COVID vaccination on patients with neurological-neuroimmunological disorders. Here two unrelated cases of neurological deficits post-COVID vaccination are reported. One was an incidence of Acute Disseminated Encephalomyelitis, while the other was an acute exacerbation of Multiple Sclerosis following vaccination. Ayurvedic treatments were effective in either of these conditions. Case series and case reports shall judiciously add information to vaccine safety data and acknowledge the necessity of clinician approval, based on detailed individualised assessments before mass vaccination.

Celastrol pretreatment attenuates concanavalin A-induced hepatitis in mice by suppressing interleukin-6/STAT3-interleukin-17 signaling

BACKGROUND AND AIM

Celastrol is extracted from Tripterygium wilfordii Hook F. It has been reported to have protective effects against various liver diseases and immune regulation of autoimmune diseases. However, little is known about whether celastrol protects against immune-mediated hepatitis. This study aimed to investigate the effect of celastrol on liver injury induced by concanavalin A (ConA) and the potential mechanisms.

METHODS

Intravenous administration of ConA was applied to induce acute liver injury in mice with or without pretreatment of celastrol. The effects of celastrol on ConA-induced liver injury were further demonstrated by biochemical and histopathological assessments, immunoblotting, and flow cytometry analysis.

RESULTS

Both biochemical and histopathological observations showed that pretreatment of celastrol significantly ameliorated liver injury induced by ConA. Moreover, the hepatocyte apoptosis and inflammatory responses induced by ConA were also improved in celastrol-pretreated mice. Further studies revealed that these improvements were characterized as the celastrol-mediated suppression of total interleukin (IL)-17 from liver mononuclear cells in ConA-treated mice. Flow cytometry analysis suggested that celastrol specifically decreased IL-17 production by CD4⁺ T cells but not by CD8⁺ T cells. Fundamentally, pretreatment with celastrol inhibited both the IL-6 produced by F4/80⁺ macrophages and the IL-6 receptor on Th17 cells in the liver, which further led to the downregulated activation of STAT3, thus accounting for blocked Th17 signaling.

CONCLUSIONS

Celastrol may exhibit immune regulatory effects by regulating IL-6/STAT3-IL-17 signaling in ConA-induced hepatitis, which suggested new potentials for celastrol to be applied in treating immune-mediated liver diseases.

Celastrol attenuates hepatitis C virus translation and inflammatory response in mice by suppressing heat shock protein 90β

Hepatitis C virus (HCV) infection is one of the major factors to trigger a sustained hepatic inflammatory response and hence hepatocellular carcinoma (HCC), but direct-acting-antiviral (DAAs) was not efficient to suppress HCC development. Heat shock protein 90 kDa (HSP90) is highly abundant in different types of cancers, and especially controls protein translation, endoplasmic reticulum stress, and viral replication. In this study we investigated the correlation between the expression levels of HSP90 isoforms and inflammatory response marker NLRP3 in different types of HCC patients as well as the effect of a natural product celastrol in suppression of HCV translation and associated inflammatory response in vivo. We identified that the expression level of HSP90β isoform was correlated with that of NLRP3 in the liver tissues of HCV positive HCC patients (R² = 0.3867, P < 0.0101), but not in hepatitis B virus-associated HCC or cirrhosis patients. We demonstrated that celastrol (3, 10, 30 μM) dose-dependently suppressed the ATPase activity of both HSP90α and HSP90β, while its anti-HCV activity was dependent on the Ala47 residue in the ATPase pocket of HSP90β. Celastrol (200 nM) halted HCV internal ribosomal entry site (IRES)-mediated translation at the initial step by disrupting the association between HSP90β and 4EBP1. The inhibitory activity of celastrol on HCV RNA-dependent RNA polymerase (RdRp)-triggered inflammatory response also depended on the Ala47 residue of HSP90β. Intravenous injection of adenovirus expressing HCV NS5B (pAde-NS5B) in mice induced severe hepatic inflammatory response characterized by significantly increased infiltration of immune cells and hepatic expression level of Nlrp3, which was dose-dependently ameliorated by pretreatment with celastrol (0.2, 0.5 mg/kg, i.p.). This study reveals a fundamental role of HSP90β in governing HCV IRES-mediated translation as well as hepatic inflammation, and celastrol as a novel inhibitor of HCV translation and associated inflammation by specifically targeting HSP90β, which could be developed as a lead for the treatment of HSP90β positive HCV-associated HCC.

Effects and mechanisms of Celastrol on the formation of neutrophil extracellular traps (NETs)

Background

To investigate the effect and mechanism of Celastrol on the formation of neutrophil extracellular traps (NETs), and to provide a theoretical basis for the clinical application of Tripterygium wilfordii.

Methods

First, we isolated neutrophils from the peripheral blood of healthy volunteers, and then observed the effect of Celastrol on Phorbol Myristate Acetate (PMA)-induced neutrophil release of NETs. The level of NETs was detected by using the membrane-impermeable nucleic acid dye, SytoxGreens. In addition, the levels of reactive oxygen species (ROS) were also examined to determine whether Celastrol affects ROS production during PMA-induced NETs.

Results

Celastrol produced significant cytotoxicity at a concentration of 5 µM (213.2±75.07), and the effect of stimulant PMA (25 nM) treatment was not statistically different (197.3±25.15) (P=0.9167). Celastrol (1.25, 0.625, and 0.3125 µM) did not exhibit cytotoxicity when treating neutrophils. Compared with the PMA (25 nM) + Celastrol (1.25, 0.625, and 0.3125 µM) group and the PMA (25 nM) monotherapy group, SytoxGreen showed a statistically significant reduction in fluorescence at 528 µM under 485 µM light excitation. Also, under the co-localization marker of Hochest and SytoxGreen double staining, we observed that the release of NETs in the PMA-treated group was higher than that in the control group. The PMA-induced neutrophil release of NETs was markedly reduced compared to the PMA-treated group. The NET release was substantially decreased under double staining with the Hochest and SytoxGreen co-localization markers. The fluorescence intensity of the Celastrol plus PMA group was significantly lower than that of the PMA treatment group alone, indicating a decrease in the level of intracellular ROS. Interestingly, the level of ROS in the treatment group who received Celastrol alone was lower than that in the control group, indicating that Tripterygium wilfordii could inhibit the spontaneous production of ROS by neutrophils in the absence of stimulation.

Conclusions

The molecular mechanism of Celastrol involves inhibition of PMA-stimulated neutrophil NETs formation in vitro, which is possibly related to the reduction of ROS levels. This indicates that Celastrol, the main component in Tripterygium wilfordii, can inhibit the formation of NETs, which provides a theoretical basis for the study of NETs-related diseases.

Celastrol: A lead compound that inhibits SARS-CoV-2 replication, the activity of viral and human cysteine proteases, and virus-induced IL-6 secretion

The global emergence of coronavirus disease 2019 (COVID‐19) has caused substantial human casualties. Clinical manifestations of this disease vary from asymptomatic to lethal, and the symptomatic form can be associated with cytokine storm and hyperinflammation. In face of the urgent demand for effective drugs to treat COVID‐19, we have searched for candidate compounds using in silico approach followed by experimental validation. Here we identified celastrol, a pentacyclic triterpene isolated from Tripterygium wilfordii Hook F, as one of the best compounds out of 39 drug candidates. Celastrol reverted the gene expression signature from severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)‐infected cells and irreversibly inhibited the recombinant forms of the viral and human cysteine proteases involved in virus invasion, such as M^pro (main protease), PL^pro (papain‐like protease), and recombinant human cathepsin L. Celastrol suppressed SARS‐CoV‐2 replication in human and monkey cell lines and decreased interleukin‐6 (IL‐6) secretion in the SARS‐CoV‐2‐infected human cell line. Celastrol acted in a concentration‐dependent manner, with undetectable signs of cytotoxicity, and inhibited in vitro replication of the parental and SARS‐CoV‐2 variant. Therefore, celastrol is a promising lead compound to develop new drug candidates to face COVID‐19 due to its ability to suppress SARS‐CoV‐2 replication and IL‐6 production in infected cells.

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.

Drug Candidates for Autoimmune Diseases

Most of the immunosuppressive drugs used in the clinic to prevent organ rejection or to treat autoimmune disorders were originally isolated from fungi or bacteria. Therefore, in addition to plants, these are valuable sources for identification of new potent drugs. Many side effects of established drugs limit their usage and make the identification of new immunosuppressants necessary. In this review, we present a comprehensive overview of natural products with potent anti-inflammatory activities that have been tested successfully in different models of chronic inflammatory autoimmune diseases. Some of these candidates already have passed first clinical trials. The anti-inflammatory potency of these natural products was often comparable to those of established drugs, and they could be used at least in addition to standard therapy to reduce their dose to minimize unwanted side effects. A frequent mode of action is the inhibition of classical inflammatory signaling pathways, such as NF-κB, in combination with downregulation of oxidative stress. A drawback for the therapeutic use of those natural products is their moderate bioavailability, which can be optimized by chemical modifications and, in addition, further safety studies are necessary. Altogether, very interesting candidate compounds exist which have the potential to serve as starting points for the development of new immunosuppressive drugs.

Celastrol Downmodulates Alpha-Synuclein-Specific T Cell Responses by Mediating Antigen Trafficking in Dendritic Cells

Parkinson’s Disease (PD) is a neurodegenerative disease that affects the elderly. It is associated with motor dysfunction due to the accumulation of misfolded or aggregated fibrillar alpha-synuclein (α-syn) in the mid-brain. Current treatments are mainly focused on relieving the symptoms but are accompanied by side effects and are limited in halting disease progression. Increasing evidence points to peripheral immune cells underlying disease development, especially T cells contributing to α-syn-related neuroinflammation in PD. The onset of these cells is likely mediated by dendritic cells (DCs), whose role in α-syn-specific responses remain less studied. Moreover, Traditional Chinese medicine (TCM)-derived compounds that are candidates to treat PD may alleviate DC-T cell-mediated immune responses. Therefore, our study focused on the role of DC in response to fibrillar α-syn and subsequent induction of antigen-specific T cell responses, and the effect of TCM Curcumin-analog C1 and Tripterygium wilfordii Hook F-derived Celastrol. We found that although fibrillar α-syn did not induce significant inflammatory or T cell-mediating cytokines, robust pro-inflammatory T cell responses were found by co-culturing fibrillar α-syn-pulsed DCs with α-syn-specific CD4⁺ T cells. Celastrol, but not C1, reduced the onset of pro-inflammatory T cell differentiation, through promoting interaction of endosomal, amphisomal, and autophagic vesicles with fibrillar α-syn, which likely lead to its degradation and less antigen peptides available for presentation and T cell recognition. In conclusion, regulating the intracellular trafficking/processing of α-syn by DCs can be a potential approach to control the progression of PD, in which Celastrol is a potential candidate to accomplish this.

PP2A and Its Inhibitors in Helper T-Cell Differentiation and Autoimmunity

Protein phosphatase 2A (PP2A) is a highly complex heterotrimeric Ser/Thr phosphatase that regulates many cellular processes. The role of PP2A as a tumor suppressor has been extensively studied and reviewed. However, emerging evidence suggests PP2A constrains inflammatory responses and is important in autoimmune and neuroinflammatory diseases. Here, we reviewed the existing literature on the role of PP2A in T-cell differentiation and autoimmunity. We have also discussed the modulation of PP2A activity by endogenous inhibitors and its small-molecule activators as potential therapeutic approaches against autoimmunity.

Celastrol Regulates the Secretion of Interleukin-17 in Patients with Sympathetic Ophthalmia Through Signal Transducer and Activator of Transcription 3

Purpose: The excessive secretion of interleukin (IL)-17 contributes to the pathological process of sympathetic ophthalmia (SO). Celastrol is a naturally active product and exhibits an immunosuppressive effect. However, whether the supplementation of celastrol relieves SO remains unclear. Methods: The peripheral blood mononuclear cells (PBMCs) were extracted from the venous blood samples of 20 SO patients and 20 healthy controls, followed by stimulating with various concentrations of celastrol. The levels of IL-23 and IL-17 were measured by enzyme-linked immunosorbent assay and real-time polymerase chain reaction assay. The activation of the signal transducer and activator of transcription 3 (STAT3) in PBMCs of SO patients was detected by Western blot. Results: The levels of IL-23 and IL-17 in PBMCs isolated from SO patients were significantly increased compared with those in PBMCs isolated from healthy controls. Celastrol treatment inhibited the production of both IL-23 and IL-17 in PBMCs of SO patients in a dose-dependent manner. In PBMCs isolated from SO patients and healthy controls, the administration of recombinant human IL-23 (rIL-23) enhanced the production of IL-17, which was then suppressed by co-stimulation with celastrol. Also, celastrol treatment reduced rIL-23-induced phosphorylation of STAT3 in PBMCs isolated from SO patients. Conclusions: Celastrol can reduce the production of IL-17 in PBMCs of SO patients. The mechanism may be related to the reduction of IL-23 secretion, which in turn inhibits the phosphorylation of STAT3.

Celastrol Prevents Oxidative Stress Effects on FSHR, PAPP, and CYP19A1 Gene Expression in Cultured Human Granulosa-Lutein Cells

Regulation of oxidative stress (OS) is important to prevent damage to female reproductive physiology. While normal OS levels may have a regulatory role, high OS levels may negatively affect vital processes such as folliculogenesis or embryogenesis. The aim of this work was to study OS induced by glucose, a reactive oxygen species generator, or peroxynitrite, a reactive nitrogen species generator, in cultured human granulosa-lutein (hGL) cells from oocyte donors, analyzing expression of genes involved in oocyte maturation (FSHR, PAPP, and CYP19A1) and OS damage response (ALDH3A2). We also evaluated the effect of celastrol as an antioxidant. Our results showed that although both glucose and peroxynitrite produce OS increments in hGL cells, only peroxynitrite treatment increases ALDH3A2 and PAPP gene expression levels and decreases FSHR gene expression levels. Celastrol pre-treatment prevents this effect of peroxynitrite. Interestingly, when celastrol alone was added, we observed a reduction of the expression of all genes studied, which was independent of both OS inductors. In conclusion, regulation of OS imbalance by antioxidant substances such as celastrol may prevent negative effects of OS in female fertility. In addition to the antioxidant activity, celastrol may well have an independent role on regulation of gene expression in hGL cells.

Tripterygium Ingredients for Pathogenicity Cells in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease mainly characterized by chronic polyarthritis. Many types of cells play pivotal roles in the pathogenicity of RA, such as T cells, B cells, macrophages, dendritic cells (DCs), osteoclasts (OCs), and fibroblast-like synoviocytes (FLS). Tripterygium wilfordii Hook f. (TwHf) and its ingredients are able to control disease activity by regulating the functions of cells mentioned above, and the clinical studies have highlighted the importance of TwHf ingredients in RA treatment. They have been demonstrated to improve the RA symptoms of animal models and patients. In this review, we discussed the effect of TwHf ingredients on pathogenicity cells, including disease/cell phenotypes and molecular mechanisms. Here, we constructed a cell-cell interaction network to visualize the effect of TwHf ingredients. We found that TwHf ingredients could inhibit the differentiation and proliferation of the pathogenicity cells. Besides, the components could decrease the levels of pathogenicity cytokines [i.e., interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α)]. Many signaling pathways are involved in the underlying mechanisms, such as PI3K, NF-κB, and MAPK signaling pathways.

Celastrol Efficacy by Oral Administration in the Adjuvant-Induced Arthritis Model

Background: We previously demonstrated that celastrol has significant anti-inflammatory and bone protective effects when administered via the intraperitoneal route. For further preclinical evaluation, an effective oral administration of celastrol is crucial. Here we aimed to study the therapeutic dose range for its oral administration.

Methods: Celastrol (1–25 μg/g/day, N = 5/group) was administrated orally to female adjuvant-induced arthritis (AIA) rats after 8 days of disease induction for a period of 14 days. A group of healthy (N = 8) and arthritic (N = 15) gender- and age-matched Wistar rats was used as controls. During the treatment period, the inflammatory score, ankle perimeter, and body weight were measured. At the end of the treatment, the animals were sacrificed, blood was collected for clinical pathology, necropsy was performed with collection of internal organs for histopathological analysis, and paw samples were used for disease scoring.

Results: Doses higher than 2.5 μg/g/day of celastrol reduced the inflammatory score and ankle swelling, preserved joint structure, halted bone destruction, and diminished the number of synovial CD68+ macrophages. Bone resorption and turnover were also reduced at 5 and 7.5 μg/g/day doses. However, the dose of 7.5 μg/g/day was associated with thymic and liver lesions, and higher doses showed severe toxicity.

Conclusion: Oral administration of celastrol above 2.5 μg/g/day ameliorates arthritis. This data supports and gives relevant information for the development of a preclinical test of celastrol in the setting of a chronic model of arthritis since rheumatoid arthritis is a long-term disease.

Terpenoids, Cannabimimetic Ligands, beyond the Cannabis Plant

Medicinal use of Cannabis sativa L. has an extensive history and it was essential in the discovery of phytocannabinoids, including the Cannabis major psychoactive compound—Δ9-tetrahydrocannabinol (Δ9-THC)—as well as the G-protein-coupled cannabinoid receptors (CBR), named cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R), both part of the now known endocannabinoid system (ECS). Cannabinoids is a vast term that defines several compounds that have been characterized in three categories: (i) endogenous, (ii) synthetic, and (iii) phytocannabinoids, and are able to modulate the CBR and ECS. Particularly, phytocannabinoids are natural terpenoids or phenolic compounds derived from Cannabis sativa. However, these terpenoids and phenolic compounds can also be derived from other plants (non-cannabinoids) and still induce cannabinoid-like properties. Cannabimimetic ligands, beyond the Cannabis plant, can act as CBR agonists or antagonists, or ECS enzyme inhibitors, besides being able of playing a role in immune-mediated inflammatory and infectious diseases, neuroinflammatory, neurological, and neurodegenerative diseases, as well as in cancer, and autoimmunity by itself. In this review, we summarize and critically highlight past, present, and future progress on the understanding of the role of cannabinoid-like molecules, mainly terpenes, as prospective therapeutics for different pathological conditions.

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.

Celastrol Alleviates Gamma Irradiation-Induced Damage by Modulating Diverse Inflammatory Mediators

The present study aimed to explore the possible radioprotective effects of celastrol and relevant molecular mechanisms in an in vitro cell and in vivo mouse models exposed to gamma radiation. Human keratinocytes (HaCaT) and foreskin fibroblast (BJ) cells were exposed to gamma radiation of 20 Gy, followed by treatment with celastrol for 24 h. Cell viability, reactive oxygen species (ROS), nitric oxide (NO) and glutathione (GSH) production, lipid peroxidation, DNA damage, inflammatory cytokine levels, and NF-κB pathway activation were examined. The survival rate, levels of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in blood, and p65 and phospho-p65 expression were also evaluated in mice after exposure to gamma radiation and celastrol treatment. The gamma irradiation of HaCaT cells induced decreased cell viability, but treatment with celastrol significantly blocked this cytotoxicity. Gamma irradiation also increased free radical production (e.g., ROS and NO), decreased the level of GSH, and enhanced oxidative DNA damage and lipid peroxidation in cells, which were effectively reversed by celastrol treatment. Moreover, inflammatory responses induced by gamma irradiation, as demonstrated by increased levels of IL-6, TNF-α, and IL-1β, were also blocked by celastrol. The increased activity of NF-κB DNA binding following gamma radiation was significantly attenuated after celastrol treatment. In the irradiated mice, treatment with celastrol significantly improved overall survival rate, reduced the excessive inflammatory responses, and decreased NF-κB activity. As a NF-κB pathway blocker and antioxidant, celastrol may represent a promising pharmacological agent with protective effects against gamma irradiation-induced injury.

Traditional uses, secondary metabolites, and pharmacology of Celastrus species - a review

ETHNOPHARMACOLOGICAL RELEVANCE

Plants of genus Celastrus (Celastraceae) have been widely used in traditional Chinese medicine (TCM) and Indian medicine to treat cognitive dysfunction, epilepsy, insomnia, rheumatism, gout, and dyspepsia for thousands of years.

AIM OF STUDY

We critically summarized the current evidence on the botanic characterization and distribution, ethnopharmacology, secondary metabolites, pharmacological activities, qualitative and quantitative analysis, and toxicology of Celastrus species to provide perspectives for developing more attractive pharmaceuticals of plant origin.

MATERIALS AND METHODS

The relevant information on Celastrus species was gathered from worldwide accepted scientific databases via electronic search (Web of Science, SciFinder, PubMed, Elsevier, SpringerLink, Wiley Online, China Knowledge Resource Integrated, and Google Scholar). Information was also obtained from the literature and books as well as PhD and MSc dissertations. Plant names were validated by "The Plant List" (www.theplantlist.org).

RESULTS

Comprehensive analysis of the above mentioned databases and other sources confirmed that ethnomedical uses of plants of Celastrus genus had been recorded in China, India, and other countries in Southern Asia. The phytochemical investigation revealed the presence of β-dihydroagarofuranoids, diterpenoids, triterpenoids, tetraterpenes, phenylpropanoids, alkaloids, flavonoids, lignans, and others. The crude extracts and isolated constituents have exhibited a wide range of in vitro and in vivo pharmacological effects, including antitumor, cytotoxic, insecticidal, antimicrobial, anti-rheumatoid arthritis (RA), anti-inflammatory, anti-ageing and antioxidative, and neuroprotective activities.

CONCLUSION

Plants of genus Celastrus have been confirmed to show a strong potential for therapeutic and health-maintaining effects, in light of their long traditional use and the phytochemical and pharmacological studies summarized here. Currently, pharmacological studies of this genus mainly focus on Celastrus paniculatus Willd. and Celastrus orbiculatus Thunb. Therefore, more pharmacological investigations should be implemented to support traditional uses of other medicinal plants of the genus Celastrus. Moreover, studies on the toxicity, bioavailability, and pharmacokinetics, in addition to clinical trials, are indispensable for assessing the safety and efficacy of the secondary metabolites or extracts obtained from plants belonging to this genus.

An effective and safe treatment strategy for rheumatoid arthritis based on human serum albumin and Kolliphor® HS 15

Aim: We aimed to construct human serum albumin-Kolliphor® HS 15 nanoparticles (HSA-HS15 NPs) to overcome the limitations in targeted therapy for rheumatoid arthritis (RA) and enhance the safety of drug-loaded HSA NPs. Methodology: Celastrol (CLT)-loaded HSA-HS15 NPs were prepared and the properties were adequately investigated; the treatment effect were evaluated in RA rats; in vitro and in vivo studies were performed to explain the mechanism. Results: CLT-HSA-HS15 NPs had remarkable treatment ability and enhanced safety in the treatment of RA compared with free CLT and CLT-HSA NPs. Conclusion: HSA-HS15 NPs could be a safe and efficient therapeutic strategy for the treatment of RA, because of the inflammatory targeting ability of albumin, the added HS15 and ELVIS effect (extravasation through leaky vasculature followed by inflammatory cell-mediated sequestration) of nanoparticles.

Natural Plants Compounds as Modulators of Epithelial-to-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is a self-regulated physiological process required for tissue repair that, in non-controled conditions may lead to fibrosis, angiogenesis, loss of normal organ function or cancer. Although several molecular pathways involved in EMT regulation have been described, this process does not have any specific treatment. This article introduces a systematic review of effective natural plant compounds and their extract that modulates the pathological EMT or its deleterious effects, through acting on different cellular signal transduction pathways both in vivo and in vitro. Thereby, cryptotanshinone, resveratrol, oxymatrine, ligustrazine, osthole, codonolactone, betanin, tannic acid, gentiopicroside, curcumin, genistein, paeoniflorin, gambogic acid and Cinnamomum cassia extracts inhibit EMT acting on transforming growth factor-β (TGF-β)/Smads signaling pathways. Gedunin, carnosol, celastrol, black rice anthocyanins, Duchesnea indica, cordycepin and Celastrus orbiculatus extract downregulate vimectin, fibronectin and N-cadherin. Sulforaphane, luteolin, celastrol, curcumin, arctigenin inhibit β-catenin signaling pathways. Salvianolic acid-A and plumbagin block oxidative stress, while honokiol, gallic acid, piperlongumine, brusatol and paeoniflorin inhibit EMT transcription factors such as SNAIL, TWIST and ZEB. Plectranthoic acid, resveratrol, genistein, baicalin, polyphyllin I, cairicoside E, luteolin, berberine, nimbolide, curcumin, withaferin-A, jatrophone, ginsenoside-Rb1, honokiol, parthenolide, phoyunnanin-E, epicatechin-3-gallate, gigantol, eupatolide, baicalin and baicalein and nitidine chloride inhibit EMT acting on other signaling pathways (SIRT1, p38 MAPK, NFAT1, SMAD, IL-6, STAT3, AQP5, notch 1, PI3K/Akt, Wnt/β-catenin, NF-κB, FAK/AKT, Hh). Despite the huge amount of preclinical data regarding EMT modulation by the natural compounds of plant, clinical translation is poor. Additionally, this review highlights some relevant examples of clinical trials using natural plant compounds to modulate EMT and its deleterious effects. Overall, this opens up new therapeutic alternatives in cancer, inflammatory and fibrosing diseases through the control of EMT process.

Ca2+ signalling plays a role in celastrol-mediated suppression of synovial fibroblasts of rheumatoid arthritis patients and experimental arthritis in rats

Background and Purpose

Celastrol exhibits anti‐arthritic effects in rheumatoid arthritis (RA), but the role of celastrol‐mediated Ca²⁺ mobilization in treatment of RA remains undefined. Here, we describe a regulatory role for celastrol‐induced Ca²⁺ signalling in synovial fibroblasts of RA patients and adjuvant‐induced arthritis (AIA) in rats.

Experimental Approach

We used computational docking, Ca²⁺ dynamics and functional assays to study the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase pump (SERCA). In rheumatoid arthritis synovial fibroblasts (RASFs)/rheumatoid arthritis fibroblast‐like synoviocytes (RAFLS), mechanisms of Ca²⁺‐mediated autophagy were analysed by histological, immunohistochemical and flow cytometric techniques. Anti‐arthritic effects of celastrol, autophagy induction, and growth rate of synovial fibroblasts in AIA rats were monitored by microCT and immunofluorescence staining. mRNA from joint tissues of AIA rats was isolated for transcriptional analysis of inflammatory genes, using siRNA methods to study calmodulin, calpains, and calcineurin.

Key Results

Celastrol inhibited SERCA to induce autophagy‐dependent cytotoxicity in RASFs/RAFLS via Ca²⁺/calmodulin‐dependent kinase kinase‐β–AMP‐activated protein kinase–mTOR pathway and repressed arthritis symptoms in AIA rats. BAPTA/AM hampered the in vitro and in vivo effectiveness of celastrol. Inflammatory‐ and autoimmunity‐associated genes down‐regulated by celastrol in joint tissues of AIA rat were restored by BAPTA/AM. Knockdown of calmodulin, calpains, and calcineurin in RAFLS confirmed the role of Ca²⁺ in celastrol‐regulated gene expression.

Conclusion and Implications

Celastrol triggered Ca²⁺ signalling to induce autophagic cell death in RASFs/RAFLS and ameliorated arthritis in AIA rats mediated by calcium‐dependent/‐binding proteins facilitating the exploitation of anti‐arthritic drugs based on manipulation of Ca²⁺ signalling.

Peptide-targeted liposomal delivery of dexamethasone for arthritis therapy

Aim: Rheumatoid arthritis is an autoimmune disease affecting the joints. Antiarthritic drugs are given systemically, thereby exposing various healthy organs to these drugs, resulting in adverse reactions. Accordingly, there is an urgent need for targeted drug delivery methods for inflamed joints. Materials & methods: We developed a liposomal drug delivery system using a novel peptide ligand (CKPFDRALC) named ART-2, which homes to the inflamed joints when injected intravenously to rats with adjuvant-induced arthritis. Results: The ART-2-coated liposomes encapsulating an antiarthritic drug, dexamethasone (DEX), were more effective in inhibiting arthritis progression than control-DEX liposomes or free DEX, despite a comparable safety profile. Conclusion: Peptide-targeted therapy has advantages over conventional drug delivery and can be adapted for rheumatoid arthritis therapy.

Intermicrobial interaction: Aspergillus fumigatus siderophores protect against competition by Pseudomonas aeruginosa

Pseudomonas aeruginosa and Aspergillus fumigatus are pathogens frequently co-inhabiting immunocompromised patient airways, particularly in people with cystic fibrosis. Both microbes depend on the availability of iron, and compete for iron in their microenvironment. We showed previously that the P. aeruginosa siderophore pyoverdine is the main instrument in battling A. fumigatus biofilms, by iron chelation and denial of iron to the fungus. Here we show that A. fumigatus siderophores defend against anti-fungal P. aeruginosa effects. P. aeruginosa supernatants produced in the presence of wildtype A. fumigatus planktonic supernatants (Afsup) showed less activity against A. fumigatus biofilms than P. aeruginosa supernatants without Afsup, despite higher production of pyoverdine by P. aeruginosa. Supernatants of A. fumigatus cultures lacking the sidA gene (AfΔsidA), unable to produce hydroxamate siderophores, were less capable of protecting A. fumigatus biofilms from P. aeruginosa supernatants and pyoverdine. AfΔsidA biofilm was more sensitive towards inhibitory effects of pyoverdine, the iron chelator deferiprone (DFP), or amphothericin B than wildtype A. fumigatus biofilm. Supplementation of sidA-deficient A. fumigatus biofilm with A. fumigatus siderophores restored resistance to pyoverdine. The A. fumigatus siderophore production inhibitor celastrol sensitized wildtype A. fumigatus biofilms towards the anti-fungal activity of DFP. In conclusion, A. fumigatus hydroxamate siderophores play a pivotal role in A. fumigatus competition for iron against P. aeruginosa.

Celastrol suppresses experimental autoimmune encephalomyelitis via MAPK/SGK1-regulated mediators of autoimmune pathology

OBJECTIVE AND DESIGN

Multiple sclerosis (MS) is a debilitating autoimmune disease involving immune dysregulation of the pathogenic T helper 17 (Th17) versus protective T regulatory (Treg) cell subsets, besides other cellular aberrations. Studies on the mechanisms underlying these changes have unraveled the involvement of mitogen-activated protein kinase (MAPK) pathway in the disease process. We describe here a gene expression- and bioinformatics-based study showing that celastrol, a natural triterpenoid, acting via MAPK pathway regulates the downstream genes encoding serum/glucocorticoid regulated kinase 1 (SGK1), which plays a vital role in Th17/Treg differentiation, and brain-derived neurotrophic factor (BDNF), which is a neurotrophic factor, thereby offering protection against experimental autoimmune encephalomyelitis (EAE) in mice.

METHODS

We first tested the gene expression profile of splenocytes of EAE mice in response to the disease-related antigen, myelin oligodendrocyte glycoprotein (MOG), and then examined the effect of celastrol on that profile.

RESULTS

Interestingly, celastrol reversed the expression of many MOG-induced genes involved in inflammation and immune pathology. The MAPK pathway involving p38MAPK and ERK was identified as one of the mediators of celastrol action. It involved suppression of SGK1 but upregulation of BDNF, which then contributed to protection against EAE.

CONCLUSION

Our results not only provide novel insights into disease pathogenesis, but also offer promising therapeutic targets for MS.

Shexiang-Wulong Pills Attenuate Rheumatoid Arthritis by Alleviating Inflammation in a Mouse Model of Collagen-Induced Arthritis

Shexiang-Wulong Pill (SWP) is derived from “Moschus Yuan,” first formulated during the Song Dynasty for the treatment of joint pain. The aim of this study was to evaluate the therapeutic effect of SWP in a mouse model of collagen-induced arthritis (CIA). Forty-five DBA/1 mice were randomly divided into control group, model group, and SWP-treated group. SWP was administered by oral gavage for 22 days after the booster immunization. The clinical arthritic scores and joint histopathology, including synovial hyperplasia and hypoxic regions, cartilage erosion, and bone destruction, were evaluated. Microcomputed tomography (micro-CT) was used to assess microstructural changes in the bone. Serum levels of TNF-a, IL-6, and IFN-γ were measured by enzyme-linked immunosorbent assay (ELISA). The results showed a statistically significant improvement in joint pathological changes in the SWP-treated group. Imaging assessment confirmed that SWP protected the bone tissue from CIA-induced erosion and increased the bone density. In addition, the serum levels of TNF-a, IL-6, and IFN-γ in SWP-treated mice were significantly lower than those in the model group (P<0.05). Taken together, Shexiang-Wulong Pill can effectively alleviate joint swelling in CIA mice, inhibit synovial tissue hyperplasia, reduce inflammatory cell infiltration, and delay bone destruction. These results indicate that Shexiang-Wulong Pills could be an efficient medication for the treatment of RA.

Celastrol protects human retinal pigment epithelial cells against hydrogen peroxide mediated oxidative stress, autophagy, and apoptosis through sirtuin 3 signal pathway

Age-related macular degeneration (AMD), one of the most common causes of visual impairment, often occurrs in the elderly in developed countries. Oxidative stress, autophagy, and apoptosis of retinal pigment epithelial (RPE) cells play roles in the pathogenesis of AMD. In the current study, the protective effect of celastrol against hydrogen peroxide (H₂ O₂ )-induced oxidative stress and apoptosis was investigated using a human RPE cell line (ARPE-19). H₂ O₂ inhibited ARPE-19 cells' survival and autophagy and induced their oxidative stress and apoptosis. Compared with the H₂ O₂ group, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay showed that celastrol increased ARPE-19 cells' survival in a dose- and time-dependent manner. Further, studies have suggested that celastrol has antioxidative stress and antiapoptosis effects in H₂ O₂ -treated ARPE-19 cells. Also, cell autophagy is activated by celastrol in H₂ O₂ -treated ARPE-19 cells. Reverse transcription polymerase chain reaction and Western blot showed that celastrol elevated the messenger RNA (mRNA) and protein expression of sirtuin 3 (SIRT3) in H₂ O₂ -induced ARPE-19 cells. Inhibition of the level of SIRT3 by SIRT3 small interfering RNA (siRNA) reversed the effects of celastrol on oxidative stress, autophagy, and apoptosis in H₂ O₂ -induced ARPE-19 cells. In conclusion, these observations suggest that celastrol activates the SIRT3 pathway in RPE cells and protects against H₂ O₂ -induced oxidative stress and apoptosis.

Systematic identification of Celastrol-binding proteins reveals that Shoc2 is inhibited by Celastrol

Colorectal cancer (CRC) is the third most commonly diagnosed cancer. Celastrol exhibits anti-tumor activities in a variety of cancers. However, the effect of Celastrol on human CRC and the underlying mechanisms still need to be elucidated. The present study aimed to use in vitro and in vivo methods to clarify the anti-tumor effect of Celastrol and use protein microarrays to explore its mechanisms. We demonstrated that Celastrol effectively inhibited SW480 CRC cell proliferation. Two weeks of Celastrol gavage significantly inhibited the growth of xenografts in nude mice. A total of 69 candidate proteins were identified in the protein microarray experiment, including the most highly enriched protein Shoc2, which is a scaffold protein that modulates cell motility and metastasis through the ERK pathway. Celastrol significantly inhibited ERK1/2 phosphorylation in cell lines and xenograft tumors. Down-regulation of Shoc2 expression using Shoc2 siRNA also inhibited ERK1/2 phosphorylation. Furthermore, down-regulation of Shoc2 expression also significantly inhibited proliferation, colony formation, and migration functions of tumor cells. In addition, the LD0 of Celastrol by gavage is equal or more than 80 mg/kg in C57 male mice. In summary, we unraveled the anti-CRC function of Celastrol and confirmed for the first time that it inhibited the ERK1/2 pathway through binding to Shoc2.

Natural Products for the Treatment of Autoimmune Arthritis: Their Mechanisms of Action, Targeted Delivery, and Interplay with the Host Microbiome

Rheumatoid arthritis (RA) is a chronic, debilitating illness characterized by painful swelling of the joints, inflammation of the synovial lining of the joints, and damage to cartilage and bone. Several anti-inflammatory and disease-modifying drugs are available for RA therapy. However, the prolonged use of these drugs is associated with severe side effects. Furthermore, these drugs are effective only in a proportion of RA patients. Hence, there is a need to search for new therapeutic agents that are effective yet safe. Interestingly, a variety of herbs and other natural products offer a vast resource for such anti-arthritic agents. We discuss here the basic features of RA pathogenesis; the commonly used animal models of RA; the mainstream drugs used for RA; the use of well-characterized natural products possessing anti-arthritic activity; the application of nanoparticles for efficient delivery of such products; and the interplay between dietary products and the host microbiome for maintenance of health and disease induction. We believe that with several advances in the past decade in the characterization and functional studies of natural products, the stage is set for widespread clinical testing and/or use of these products for the treatment of RA and other diseases.

The Micro-RNA Expression Profiles of Autoimmune Arthritis Reveal Novel Biomarkers of the Disease and Therapeutic Response

Rheumatoid arthritis (RA) is a chronic autoimmune disease of the joints affecting about 0.3–1% of the population in different countries. About 50–60 percent of RA patients respond to presently used drugs. Moreover, the current biomarkers for RA have inherent limitations. Consequently, there is a need for additional, new biomarkers for monitoring disease activity and responsiveness to therapy of RA patients. We examined the micro-RNA (miRNA) profile of immune (lymphoid) cells of arthritic Lewis rats and arthritic rats treated with celastrol, a natural triterpenoid. Experimental and bioinformatics analyses revealed 8 miRNAs (miR-22, miR-27a, miR-96, miR-142, miR-223, miR-296, miR-298, and miR-451) and their target genes in functional pathways important for RA pathogenesis. Interestingly, 6 of them (miR-22, miR-27a, miR-96, miR-142, miR-223, and miR-296) were further modulated by celastrol treatment. Interestingly, serum levels of miR-142, miR-155, and miR-223 were higher in arthritic versus control rats, whereas miR-212 showed increased expression in celastrol-treated rats compared with arthritic rats or control rats. This is the first study on comprehensive miRNA expression profiling in the adjuvant-induced arthritis (AA) model and it also has revealed new miRNA targets for celastrol in arthritis. We suggest that subsets of the above miRNAs may serve as novel biomarkers of disease activity and therapeutic response in arthritis.

Peptide-directed liposomal delivery improves the therapeutic index of an immunomodulatory cytokine in controlling autoimmune arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the synovial tissue of the joints. Inadequately controlled disease may cause severe joint damage and deformity. Currently, the anti-arthritic drugs are given systemically, and therefore, they are widely distributed to other organs that are not the intended therapeutic targets. Accordingly, using a particular dose/regimen of a drug to achieve an effective local concentration of the drug in arthritic joints may lead to expected adverse effects involving other organs. Thus, improved methods of drug delivery are needed for arthritis therapy. One attractive approach is the targeting of a systemically administered drug to the inflamed joints. We describe here a prototypic drug delivery system using a novel peptide ligand denoted as ART-1. We previously reported ART-1 (=ADK) as a peptide that preferentially homes to the inflamed joints of arthritic rats and binds to synovial endothelial cells. We tested the ART-1-coated liposomes encapsulating a fluorescent compound for binding to activated endothelial cells in vitro and homing to arthritic joints in vivo, compared to control liposomes lacking the ART-1 coating. Similar liposomes but encapsulating an immunomodulatory cytokine interleukin-27 (ART-1-IL-27 liposomes) were tested for their anti-arthritic activity compared with control liposomes. ART-1-displaying liposomes showed better binding to endothelial cells as well as in vivo homing to arthritic joints compared to control liposomes. Furthermore, ART-1-IL-27 liposomes, when intravenously injected to arthritic rats after the onset of arthritis, were more effective in suppressing disease progression than control-IL-27 liposomes lacking ART-1 or free IL-27 at an equivalent dose of IL-27. In addition, ART-1-directed liposomal IL-27 had a better safety profile than undirected liposomal IL-27 or free IL-27, thereby offering an improved therapeutic index for IL-27 therapy. These results provide a proof-of concept for the use of a novel joint-homing peptide for targeted delivery of drugs including biologics or small molecule compounds to arthritic joints with enhanced efficacy and reduced systemic exposure. This targeted therapy platform may be suitable for use in RA patients.

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.

Chemopreventive activity of celastrol in drug-resistant human colon carcinoma cell cultures

Celastrol (tripterine) a pentacyclic triterpenoid extracted from the roots of Tripterygium wilfordii Hook f., exhibits potent antioxidant and anti-inflammatory activity and also exerts important anti-cancer effects, as induction of apoptosis and lowering the level of drug resistance of several cancers. Increased level of cellular resistance to cytostatic drugs is typical for colorectal cancers, and largely determines the failure of chemotherapy for this tumor. The purpose of our research was to evaluate the chemopreventive effect of celastrol on cultures of colon cancer cells resistant to doxorubicin (LOVO/DX). With the use of flow cytometry we have shown that celastrol reduces the cell size of the SP (side population; subpopulation of cancer cells enriched with cancer stem cells), increases frequency of apoptosis and binds to Pgp protein in cell membranes inhibiting its transport function. The inhibition of the Pgp transport function has been shown to increase the accumulation of rhodamine-123 and standard cytostatic- doxorubicin in LOVO/DX cells. Our results prove that celastrol exhibits significant chemopreventive and chemosensitizing activities on drug resistant colon cancer cells. Celastrol appears to be a good candidate for adjuvant medicine that can improve the effectiveness of standard cytostatic therapy in humans.

The effect of celastrol on the ocular hypertension-induced degeneration of retinal ganglion cells

Celastrol, a quinine methide triterpene extracted from the perennial vine Tripterygium wilfordii, has been identified as a neuroprotective agent in various models of neurodegenerative disorders. We have reported earlier that systemic and intravitreal administration of celastrol stimulate the survival of retinal ganglion cells (RGCs) injured by optic nerve crush (ONC) and that mechanisms underlying celastrol׳s RGC protection may be associated with inhibition of TNF-alpha-mediated cell death. The present study evaluates the effect of celastrol on the survival of RGCs injured by ocular hypertension. Intraocular pressure (IOP) elevation resulted in approximately 23% of RGCs loss. Reduction in RGC numbers was observed in all four retinal quadrants: 30% in superior, 17% in inferior, 11% in nasal and 35% in temporal regions. Celastrol (1 mg/kg) or vehicle (DMSO) was administered three times per week by intraperitoneal injection, starting on the day of laser photocoagulation of the TM and continued for the entire duration of the experiment (5 weeks). Celastrol treatment stimulated RGC survival by an average of 24% in the entire retina compared to the vehicle-treated group. RGC numbers were increased in all four quadrants: approximately 40%, 17%, 15% and 30% more RGCs were counted in the superior, inferior, nasal and temporal regions, respectively. The average RGC numbers for the entire retinas of the celastrol/IOP group were only ∼5% and 10% lower than that in vehicle- or celastrol-injected animals with normal IOP, respectively. Our data indicate a significant celastrol-mediated neuroprotection against elevated IOP-induced injury.

Metabolomics profiles delineate uridine deficiency contributes to mitochondria-mediated apoptosis induced by celastrol in human acute promyelocytic leukemia cells

Celastrol, extracted from “Thunder of God Vine”, is a promising anti-cancer natural product. However, its effect on acute promyelocytic leukemia (APL) and underlying molecular mechanism are poorly understood. The purpose of this study was to explore its effect on APL and underlying mechanism based on metabolomics. Firstly, multiple assays indicated that celastrol could induce apoptosis of APL cells via p53-activated mitochondrial pathway. Secondly, unbiased metabolomics revealed that uridine was the most notable changed metabolite. Further study verified that uridine could reverse the apoptosis induced by celastrol. The decreased uridine was caused by suppressing the expression of gene encoding Dihydroorotate dehydrogenase, whose inhibitor could also induce apoptosis of APL cells. At last, mouse model confirmed that celastrol inhibited tumor growth through enhanced apoptosis. Celastrol could also decrease uridine and DHODH protein level in tumor tissues. Our in vivo study also indicated that celastrol had no systemic toxicity at pharmacological dose (2 mg/kg, i.p., 21 days). Altogether, our metabolomics study firstly reveals that uridine deficiency contributes to mitochondrial apoptosis induced by celastrol in APL cells. Celastrol shows great potential for the treatment of APL.

The Calcium-Induced Regulation in the Molecular and Transcriptional Circuitry of Human Inflammatory Response and Autoimmunity

Rheumatoid arthritis synovial fibroblasts (RASFs) are fundamental effector cells in RA driving the joint inflammation and deformities. Celastrol is a natural compound that exhibits a potent anti-arthritic effect promoting endoplasmic reticulum (ER) stress mediated by intracellular calcium (Ca²⁺) mobilization. Ca²⁺ is a second messenger regulating a variety of cellular processes. We hypothesized that the compound, celastrol, affecting cytosolic Ca²⁺ mobilization could serve as a novel strategy to combat RA. To address this issue, celastrol was used as a molecular tool to assay the inflammatory gene expression profile regulated by Ca²⁺. We confirmed that celastrol treatment mobilized cytosolic Ca²⁺ in patient-derived RASFs. It was found that 23 genes out of 370 were manipulated by Ca²⁺ mobilization using an inflammatory and autoimmunity PCR array following independent quantitative PCR validation. Most of the identified genes were downregulated and categorized into five groups corresponding to their cellular responses participating in RA pathogenesis. Accordingly, a signaling network map demonstrating the possible molecular circuitry connecting the functions of the products of these genes was generated based on literature review. In addition, a bioinformatics analysis revealed that celastrol-induced Ca²⁺ mobilization gene expression profile showed a novel mode of action compared with three FDA-approved rheumatic drugs (methotrexate, rituximab and tocilizumab). To the best of our knowledge, this is a pioneer work charting the Ca²⁺ signaling network on the regulation of RA-associated inflammatory gene expression.

Celastrol attenuates pain and cartilage damage via SDF-1/CXCR4 signalling pathway in osteoarthritis rats

OBJECTIVES

Celastrol has attracted wide interests for its anticancer and anti-inflammation properties, and studies have demonstrated that celastrol negatively modulates the stromal cell-derived factor-1 (SDF-1) and receptor C-X-C chemokine receptor type 4 (CXCR4) signalling. We aim in this study to investigate the effects of celastrol in osteoarthritis (OA) in vivo and explored the underlying molecular mechanisms.

METHODS

We established a monoiodoacetate (MIA)-induced rat OA model and evaluated the joint pain and cartilage damage with or without celastrol treatments. We further assessed the alterations of the SDF-1/CXCR4 pathway and cartilage-specific genes, at both mRNA and protein levels.

KEY FINDINGS

Celastrol significantly attenuated the joint pain and cartilage damage induced by MIA in OA rats and suppressed the upregulation of SDF-1/CXCR4 and associated genes caused by MIA injections. Furthermore, MIA induced a decrease in cartilage-specific genes which was also prevented by celastrol treatments.

CONCLUSIONS

Celastrol ameliorate OA in vivo as evidenced by the attenuated joint pain and less cartilage damage in OA rats given celastrol treatments, an effect mediated via suppression of the SDF-1/CXCR4 pathway.

Effect of celastrol on bone structure and mechanics in arthritic rats

OBJECTIVE

Rheumatoid arthritis (RA) is characterised by chronic inflammation leading to articular bone and cartilage damage. Despite recent progress in RA management, adverse effects, lack of efficacy and economic barriers to treatment access still limit therapeutic success. Therefore, safer and less expensive treatments that control inflammation and bone resorption are needed. We have previously shown that celastrol is a candidate for RA treatment. We have observed that it inhibits both interleukin (IL)-1β and tumor necrosis factor (TNF) in vitro, and that it has anti-inflammatory properties and ability to decrease synovial CD68+ macrophages in vivo. Herein our goal was to evaluate the effect of celastrol in local and systemic bone loss.

METHODS

Celastrol was administrated intraperitoneally at a dose of 1 µg/g/day to female Wistar adjuvant-induced arthritic rats. Rats were sacrificed after 22 days of disease progression, and blood, femurs, tibiae and paw samples were collected for bone remodelling markers quantification, 3-point bending test, micro-CT analysis, nanoindentation and Fourier transform infrared spectroscopy measurements, and immunohistochemical evaluation.

RESULTS

We have observed that celastrol preserved articular structures and decreased the number of osteoclasts and osteoblasts present in arthritic joints. Moreover, celastrol reduced tartrate-resistant acid phosphatase 5b, procollagen type 1 amino-terminal propeptide and C terminal crosslinked telopeptide of type II collagen serum levels. Importantly, celastrol prevented bone loss and bone microarchitecture degradation. Celastrol also preserved bone nanoproperties and mineral content. Additionally, animals treated with celastrol had less fragile bones, as depicted by an increase in maximum load and yield displacement.

CONCLUSIONS

These results suggest that celastrol reduces both bone resorption and cartilage degradation, and preserves bone structural properties.

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.

Celastrol and Its Role in Controlling Chronic Diseases

Celastrol, a triterpenoid derived from traditional Chinese medicinal plants, has anti-inflammatory, antioxidant, and anticancer activities. Celastrol has shown preventive/therapeutic effects in experimental models of several chronic diseases. These include, chronic inflammatory and autoimmune diseases (e.g., rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, inflammatory bowel disease, and psoriasis), neurodegenerative disorders (e.g., Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis), atherosclerosis, obesity, Type 2 diabetes, and cancer. Celastrol modulates intricate cellular pathways and networks associated with disease pathology, and it interrupts or redirects the aberrant cellular and molecular events so as to limit disease progression and facilitate recovery, where feasible. The major cell signaling pathways modulated by celastrol include the NF-kB pathway, MAPK pathway, JAK/STAT pathway, PI3K/Akt/mTOR pathway, and antioxidant defense mechanisms. Furthermore, celastrol modulates cell proliferation, apoptosis, proteasome activity, heat-shock protein response, innate and adaptive immune responses, angiogenesis, and bone remodeling. Current understanding of the mechanisms of action of celastrol and information about its disease-modulating activities in experimental models have set the stage for testing celastrol in clinical studies as a therapeutic agent for several chronic human diseases.

Celastrol reduces IL-1β induced matrix catabolism, oxidative stress and inflammation in human nucleus pulposus cells and attenuates rat intervertebral disc degeneration in vivo

Celastrol has been reported to exert therapeutic potential on pro-inflammatory diseases including asthma, Crohn's disease, arthritis and neurodegenerative disorders via inhibiting NF-κB pathway. While the effect of celastrol on intervertebral disc degeneration (IDD), which is also a pro-inflammatory disease, remains unknown. In this study, we evaluated the effect of celastrol on IDD in IL-1β treated human nucleus pulposus cells in vitro as well as in puncture induced rat IDD model in vivo. Our results showed that celastrol reduced the expression of catabolic genes (MMP-3, 9, 13, ADAMTS-4, 5), oxidative stress factors (COX-2, iNOS) and pro-inflammatory factors (IL-6, TNF-a) induced by IL-1β in nucleus pulposus cells, also phosphorylation of IκBα and p65 were attenuated by celastrol, indicating NF-κB pathway was inhibited by celastrol in nucleus pulposus cells. In vivo study showed that celastrol treated rats had stronger T2-weighted signal than vehicle-treated rats at 2 weeks and 6 weeks' time point, suggesting celastrol could attenuate intervertebral disc degeneration in vivo. Together, our study demonstrates that celastrol could reduce IL-1β induced matrix catabolism, oxidative stress and inflammation in human nucleus pulposus cells and attenuates rat intervertebral disc degeneration in vivo, which shows its potential to be a therapeutic drug for IDD.

Celastrol Attenuates Multiple Sclerosis and Optic Neuritis in an Experimental Autoimmune Encephalomyelitis Model

This study was aimed to evaluate the effects of celastrol, a natural compound with multiple bioactivities, on multiple sclerosis and optic neuritis (ON) in rat experimental autoimmune encephalomyelitis (EAE). EAE was induced in Sprague Dawley rats using myelin basic protein, and the animals received daily intraperitoneal injections of celastrol or vehicle for 13 days. The EAE rats showed abnormal neurobehavior and inflammatory infiltration and demyelination in the spinal cord. Significantly upregulated mRNA expression of pro-inflammatory cytokines interferon-γ and interleukin-17 and downregulated anti-inflammatory cytokines interleukin-4 were found in the spinal cord of EAE rats. In the study of ON, severely inflammatory responses like in the spinal cord were also seen in the optic nerve, as well as obvious microgliosis. Furthermore, activation of nuclear factor kappa-B and upregulated inducible nitric oxide synthase was observed in the optic nerve. In addition, apoptosis of retinal ganglion cells and dysregulation of apoptotic-associated proteins in the optic nerve were found in EAE rats. Treatment of celastrol potently restored these changes. In most of the indexes, the effects of high dose of celastrol were better than the low dose. Our data conclude that administration of celastrol attenuates multiple sclerosis and ON in EAE via anti-inflammatory and anti-apoptotic effects. These findings provide new pre-clinical evidence for the use of celastrol in treatment of multiple sclerosis.

STA-21, a STAT-3 inhibitor, attenuates the development and progression of inflammation in collagen antibody-induced arthritis

We set out to investigate the influence of STA-21, a dynamic STAT-3 inhibitor, on the expansion and progression of rheumatoid arthritis (RA), and to determine its potential mechanisms of action in a mouse model of collagen antibody-induced arthritis (CAIA). To this end, arthritis was induced via intravenous (IV) injection of Balb/c mice with a cocktail of antibodies directed against type II collagen (1.5μg/mouse, IV), followed by lipopolysaccharide (LPS) at a dose of (25μg/mouse, i.p.) on day 3. Mice were then left untreated or were simultaneously treated with STA-21 (0.5mg/kg, i.p., once daily for 2 weeks) followed by evaluation for clinical and histological features of arthritic inflammation and flow cytometric analysis of cytokines and transcription factors in peripheral blood. STA-21 enhanced the clinical course of arthritis in CAIA mice and decreased CD8⁺RORγt⁺ and CD8⁺IL-21⁺ cells while inducing the production of CD8⁺Foxp3⁺ cells. Furthermore, STA-21 prevented the production of TNF-α and IL-6 in peripheral blood and increased IL-27 production by CD14⁺ cells. Moreover, STA-21 not only regulates Th1/Th2 serum cytokine levels but also the mRNA and protein expression of key factors including NF-κB p65, RORγt, T-bet, IL-4, GATA-3, JAK1, Stat3, and IL-21. Thus, administration of the Stat3 inhibitor STA-21 inhibits cellular signaling pathways and downstream activation of key transcription factors previously shown to play key roles in the pathogenesis of RA. Therefore, these data suggest that STA-21 could be considered as a potential treatment for patients with RA.

Celastrol modulates inflammation through inhibition of the catalytic activity of mediators of arachidonic acid pathway: Secretory phospholipase A2 group IIA, 5-lipoxygenase and cyclooxygenase-2

Elevated production of arachidonic acid (AA)-derived pro-inflammatory eicosanoids due to the concerted action of secretory phospholipase A₂ group IIA (sPLA₂IIA), 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) is a common feature of many inflammatory disorders. Hence, modulation of the bioactivity of these 3 enzymes is an important strategy to control inflammation. However, the failure of drugs specific for an individual enzyme (sPLA₂IIA-, 5-LOX- or COX-2) and the success of 5-LOX/COX-2 dual inhibitors in effectively controlling inflammation in clinical trials prompted us to evaluate a common inhibitor for sPLA₂IIA, 5-LOX and COX-2 enzymes. Celastrol, a quinone methide triterpene, was selected in this regard through molecular docking studies. We provide the first evidence for celastrol's ability to inhibit the catalytic activity of sPLA₂IIA, 5-LOX and COX-2 enzymes. Celastrol significantly inhibited the catalytic activity of sPLA₂IIA (IC₅₀=6μM) in vitro, which is independent of substrate and calcium concentration. In addition, celastrol inhibited the catalytic activities of 5-LOX (IC₅₀=5μM) and COX-2 (IC₅₀=20μM) in vitro; sPLA₂IIA-induced edema and carrageenan-induced edema in mice; and lipopolysaccharide-stimulated production of PGE₂ in human neutrophils. Thus, celastrol modulates inflammatory responses by targeting multiple enzymes of AA pathway.

Control of autoimmune inflammation by celastrol, a natural triterpenoid

Celastrol is a bioactive compound derived from traditional Chinese medicinal herbs of the Celastraceae family. Celastrol is known to possess anti-inflammatory and anti-oxidant activities. Our studies have highlighted the immunomodulatory attributes of celastrol in adjuvant-induced arthritis (AA), an experimental model of human rheumatoid arthritis (RA). RA is an autoimmune disease characterized by chronic inflammation of the synovial lining of the joints, leading eventually to tissue damage and deformities. Identification of the molecular targets of celastrol such as the NF-κB pathway, MAPK pathway, JAK/STAT pathway and RANKL/OPG pathway has unraveled its strategic checkpoints in controlling arthritic inflammation and tissue damage in AA. The pathological events that are targeted and rectified by celastrol include increased production of pro-inflammatory cytokines; an imbalance between pathogenic T helper 17 and regulatory T cells; enhanced production of chemokines coupled with increased migration of immune cells into the joints; and increased release of mediators of osteoclastic bone damage. Accordingly, celastrol is a promising candidate for further testing in the clinic for RA therapy. Furthermore, the results of other preclinical studies suggest that celastrol might also be beneficial for the treatment of a few other autoimmune diseases besides arthritis.

Epicatechin isolated from Tripterygium wilfordii extract reduces tau-GFP-induced neurotoxicity in zebrafish embryo through the activation of Nrf2

Tau plays important roles in the assembly and stabilization of the microtubule structure to facilitate axonal transport in mammalian brain. The intracellular tau aggregates to form paired helical filaments leading to neurodegenerative disorders, collectively called tauopathies. In our previous report, we established a zebrafish model to express tau-GFP to induce neuronal death, which could be directly traced in vivo. Recently, we used this model to screen 400 herbal extracts and found 45 of them to be effective on reducing tau-GFP-induced neuronal death. One of the effective herbal extracts is the Tripterygium wilfordii stem extract. HPLC analysis and functional assay demonstrated that epicatechin (EC) is the major compound of Tripterygium wilfordii stem extract to decrease the neurotoxicity induced by tau-GFP. Using a luciferase reporter assay in the zebrafish, we confirmed that EC could activate Nrf2-dependent antioxidant responses to significantly increase the ARE-controlled expression of luciferase reporter gene. These data suggest that EC from the Tripterygium wilfordii stem extract could diminish tau-GFP-induced neuronal death through the activation of Nrf2.