Celastrol inhibits pro-inflammatory cytokine secretion in Crohn's disease biopsies

Anti-Inflammatory and Antimicrobial Effects of Herbal Formulation Called Apo-Taat Using Extended-Spectrum ß-Lactamase-Producing Escherichia coli Isolates

Pathogens contaminate drinking water in tropical countries causing diarrheal diseases. The conventional treatment for diarrhea is antibiotics. However, overuse and misuse of antibiotics has enabled pathogens to adapt, causing global antibiotic resistance and proliferation of extended-spectrum ß-lactamase-producing Escherichia coli (ESBL-E. coli), which causes diarrhea and high levels of inflammatory cytokines. Apo-taat, consisting of equal proportions of Phyllanthus emblica and Caesalpinia sappan, has been used to treat diarrhea and bloody diarrhea. Its antibacterial activity against E. coli ATCC 25922 has been reported, but its inhibitory effect against ESBL-E. coli has yet to be documented. This study investigated the antibacterial effect of Apo-taat extract against ESBL-E. coli and its anti-inflammatory activity. Antibacterial activity was determined by the microtiter plate-based method. HPLC was used to determine the brazilin and gallic acid contents in Apo-taat extract. Effects of herbal extracts on nitric oxide, IL-6, and TNF-α were investigated in RAW 264.7 cells. Results were that Apo-taat extract showed MIC values against ESBL-E. coli in the range of 0.625 to 2.5 mg/mL. Its 50% inhibitory concentration against nitric oxide and IL-6 production was 83.96 ± 10.60 and 83.06 ± 2.07 μg/mL, respectively, and it had slight inhibition against TNF-α. These findings suggest that Apo-taat may have an antibacterial impact on ESBL-E. coli and anti-inflammatory activity. Furthermore, safety and clinical trials should be conducted in the future.

The role of celastrol in inflammation and diseases

Celastrol is one of the main active ingredients extracted from the plant Tripterygium wilfordii Hook F. A growing number of studies have shown that celastrol has various pharmacological effects, including anti-inflammation, anti-rheumatism, treatment of neurodegenerative diseases, and anti-tumor. This article systematically summarized the mechanism and role of celastrol in lipid metabolism and obesity, rheumatoid arthritis (RA), osteoarthritis (OA), gouty arthritis, inflammatory bowel disease, neurodegenerative diseases, and cancer and other diseases (such as diabetes, respiratory-related diseases, atherosclerosis, psoriasis, hearing loss, etc.). The celastrol played roles in inflammation response, cell apoptosis, autophagy, ferroptosis, and lipid metabolism mainly by acting on chondrocytes, macrophages, mitochondria, and endoplasmic reticulum (ER) through NF-κB, STAT, MAPK, TLR, PI3K-AKT-mTOR, and other signal pathways. This review could provide a reference for the clinical application and further development and utilization of celastrol.

Bilayered skin equivalent mimicking psoriasis as predictive tool for preclinical treatment studies

Psoriasis is a prevalent, inflammatory skin disease without cure. Further research is required to unravel dysregulated processes and develop new therapeutic interventions. The lack of suitable in vivo and in vitro preclinical models is an impediment in the psoriasis research. Recently, the development of 3D skin models has progressed including replicas with disease-like features. To investigate the use of in vitro models as preclinical test tools, the study focused on treatment responses of 3D skin replicas. Cytokine-priming of skin organoids induced psoriatic features like inflammation, antimicrobial peptides (AMP), hyperproliferation and impaired differentiation. Topical application of dexamethasone (DEX) or celastrol (CEL), a natural anti-inflammatory compound reduced the secretion of pro-inflammatory cytokines. DEX and CEL decreased the gene expression of inflammatory mediators. DEX barely affected the psoriatic AMP transcription but CEL downregulated psoriasis-driven AMP genes. Subcutaneous application of adalimumab (ADM) or bimekizumab (BMM) showed anti-psoriatic effects via protein induction of the differentiation marker keratin-10. Dual blockage of TNF-α and IL-17A repressed the inflammatory psoriasis phenotype. BMM inhibited the psoriatic expression of AMP genes and induced KRT10 and cell-cell contact genes. The present in vitro model provides a 3D environment with in vivo-like cutaneous responses and represents a promising tool for preclinical investigations.

Potential Application of Plant-Derived Compounds in Multiple Sclerosis Management

Multiple sclerosis (MS) is a chronic autoimmune disorder characterized by inflammation, demyelination, and neurodegeneration, resulting in significant disability and reduced quality of life. Current therapeutic strategies primarily target immune dysregulation, but limitations in efficacy and tolerability highlight the need for alternative treatments. Plant-derived compounds, including alkaloids, phenylpropanoids, and terpenoids, have demonstrated anti-inflammatory effects in both preclinical and clinical studies. By modulating immune responses and promoting neuroregeneration, these compounds offer potential as novel adjunctive therapies for MS. This review provides insights into the molecular and cellular basis of MS pathogenesis, emphasizing the role of inflammation in disease progression. It critically evaluates emerging evidence supporting the use of plant-derived compounds to attenuate inflammation and MS symptomology. In addition, we provide a comprehensive source of information detailing the known mechanisms of action and assessing the clinical potential of plant-derived compounds in the context of MS pathogenesis, with a focus on their anti-inflammatory and neuroprotective properties.

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.

Phytoimmunomodulators: A review of natural modulators for complex immune system

In the past few decades, the medicinal properties of plants and their effects on the human immune system are being studied extensively. Plants are an incredible source of traditional medicines that help cure various diseases, including altered immune mechanisms and are economical and benign compared to allopathic medicines. Reported data in written documents such as Traditional Chinese medicine, Indian Ayurvedic medicine support the supplementation of botanicals for immune defense reactions in the body and can lead to safe and effective immunity responses. Additionally, some botanicals are well-identified as magical herbal remedies because they act upon the pathogen directly and help boost the immunity of the host. Chemical compounds, also known as phytochemicals, obtained from these botanicals looked promising due to their effects on the human immune system by modulating the lymphocytes which subsequently reduce the chances of getting infected. This paper summarises most documented phytochemicals and how they act on the immune system, their properties and possible mechanisms, screening conventions, formulation guidelines, comparison with synthetic immunity-enhancers, marketed immunity-boosting products, and immune-booster role in the ongoing ghastly corona virus wave. However, it focuses mainly on plant metabolites as immunomodulators. In addition, it also sheds light on the current advancements and future possibilities in this field. From this thorough study, it can be stated that the plant-based secondary metabolites contribute significantly to immunity building and could prove to be valuable medicaments for the design and development of novel immunomodulators even for a pandemic like COVID-19.

Terpenes: Modulating anti-inflammatory signaling in inflammatory bowel disease

Inflammatory Bowel Disease (IBD) are autoimmune diseases characterized by chronic intestinal inflammation. Considered a western disease, IBD incidence in newly developed countries is skyrocketing. Accordingly, global prevalence is steadily increasing. There are two major IBD phenotypes, ulcerative colitis (UC) and Crohn's disease (CD). UC manifests as uninterrupted inflammation localized in the colon and rectum. Meanwhile, CD presents as interrupted inflammation that can occur throughout the digestive tract. As a result, therapeutics have focused on anti-inflammatory approaches for its treatment. Unfortunately, only 50% of patients benefit from current Food and Drug Administration approved treatments, and all are associated with serious adverse effects. Thus, there is a need for safer and novel therapeutics to increase the efficacy in this population. One aspect that is critical in understanding IBD is how food and phytochemicals therein may be associated with modifying the pathogenesis of IBD. A variety of retrospective and prospective studies, and clinical trials have shown benefits of plant-rich diets on the prevention and symptomatic improvement of IBD. The Mediterranean diet is rich in vegetables, fruits, legumes, and herbs; and characterized by the abundance of anti-inflammatory phytochemicals. An understudied phytochemical class enriched in this diet is terpenes; isoprene-based molecules are widely available in Mediterranean herbs and citrus fruits. Various terpenes have been evaluated in different IBD models. However, some present contradictory or inconclusive results. Therefore, in this review we evaluated preclinical studies of terpenes modulating basic inflammatory signaling related to IBD.

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 Mpro (main protease), PLpro (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.

Induction of the ER stress response in NRVMs is linked to cardiotoxicity caused by celastrol

Celastrol is a quinone methide triterpenoid extracted from the root bark of Tripterygium wilfordii Hook F, and it exhibits extensive biological activities such as anti-cancer effects. However, narrow therapeutic window together with undesired side effects limit its clinical application. In this study, we explore celastrol's cardiotoxicity using the methods of histology and cell biology. The results show that celastrol administration dose-dependently induces cardiac dysfunction in mice as manifested by left ventricular dilation, myocardial interstitial fibrosis, and cardiomyocyte hypertrophy. Exposure to celastrol greatly decreases neonatal rat ventricular myocyte (NRVM) viability and promotes its apoptosis. More importantly, we demonstrate that celastrol exerts its pro-apoptotic effects through endoplasmic reticulum (ER) stress and unfolded protein response. Furthermore, siRNA targeting C/EBP homologous protein, a pivotal component of ER stress-mediated apoptosis, effectively prevents the pro-apoptotic effect of celastrol. Taken together, our results demonstrate the potential cardiotoxicity of celastrol and a direct involvement of ER stress in the celastrol-induced apoptosis of NRVMs. Thus, we recommend careful evaluation of celastrol's cardiovascular effects when using it in the clinic.

Celastrol Alleviates Autoimmune Hepatitis Through the PI3K/AKT Signaling Pathway Based on Network Pharmacology and Experiments

Objective: This work aims to explore the potential targets and underlying therapeutic mechanisms of celastrol in autoimmune hepatitis (AIH) through network pharmacology and experiments on Laboratory Animals.

Methods: A drug-target interaction network was constructed to predict the possible targets of celastrol and their potential relationship with the drug; docking studies were also performed for validation. This study used both acute and chronic rodent models of autoimmune hepatitis. Gross appearance of liver and spleen were obtained from murine models, hematoxylin-eosin staining and Sirius red staining were performed to examine hepatic inflammation and fibrosis respectively. By combining molecular docking and enrichment analysis results, the most prominent signaling pathway was selected and further confirmed by Western blot in AIH models administered with celastrol.

Results: In total, 82 common targets of celastrol and AIH were obtained from databases, identified by network pharmacology, and adequately enriched. Among them, PIK3R1, SRC, MAPK1, AKT1, and HRAS were selected as the top 5 closely related targets to celastrol. They all performed effectively in molecular docking, with AKT1 and PIK3R1 exhibiting more-prominent binding energy. Subsequently, celastrol administration significantly ameliorated hepatitis and liver fibrosis by reducing AKT1 and PI3K phosphorylation in both acute liver injury and chronic models of autoimmune hepatitis.

Conclusion: In summary, celastrol significantly attenuates autoimmune hepatitis by suppressing the PI3K/AKT signaling pathway, confirmed by validated animal models. These findings may help identify the mechanism involved in the anti-inflammatory action of celastrol in autoimmune hepatitis and provide ideas for future comprehensive studies.

The Protective Role of Celastrol in Renal Ischemia-Reperfusion Injury by Activating Nrf2/HO-1, PI3K/AKT Signaling Pathways, Modulating NF-κb Signaling Pathways, and Inhibiting ERK Phosphorylation

Celastrol, a natural triterpenoid derived from Tripterygium wilfordii, possesses numerous biological effects. We investigated celastrol's antioxidant potential through nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) and its effect on phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling, nuclear factor-kappa B (NF-κB) pathways, and extracellular signal-regulated kinase (ERK) activation in kidney ischemia-reperfusion injury (IRI) rat model. Rats were given celastrol 2 mg/kg orally for 1 week before subjection to renal ischemia-reperfusion surgery. Kidney functions, renal MDA, and reduced glutathione were determined; also, renal levels of ERK1/2, HO-1, PI3K, IL-6, TNF-α, IκBα, NF-κB/p65, and cleaved caspase-3 were measured. In addition, gene expression of kidney injury molecule-1 (KIM-1), Nrf-2, and AKT were determined. Celastrol pretreatment attenuated oxidative stress and increased Nrf2 gene expression and HO-1 level. Also, it activated the PI3K/AKT signaling pathway and decreased the p-ERK:t- ERK ratio and NFκBp65 level, with a remarkable decrease in inflammatory cytokines and cleaved caspase-3 levels compared with those in renal IRI rats. Conclusively, celastrol showed a reno-protective potential against renal IRI by suppressing oxidative stress through enhancing the Nrf2/HO-1 pathway, augmenting cell survival PI3K/AKT signaling pathways, and reducing inflammation by inhibiting NF-κB activation.

Nanotechnology-Based Celastrol Formulations and Their Therapeutic Applications

Celastrol (also called tripterine) is a quinone methide triterpene isolated from the root extract of Tripterygium wilfordii (thunder god vine in traditional Chinese medicine). Over the past two decades, celastrol has gained wide attention as a potent anti-inflammatory, anti-autoimmune, anti-cancer, anti-oxidant, and neuroprotective agent. However, its clinical translation is very challenging due to its lower aqueous solubility, poor oral bioavailability, and high organ toxicity. To deal with these issues, various formulation strategies have been investigated to augment the overall celastrol efficacy in vivo by attempting to increase the bioavailability and/or reduce the toxicity. Among these, nanotechnology-based celastrol formulations are most widely explored by pharmaceutical scientists worldwide. Based on the survey of literature over the past 15 years, this mini-review is aimed at summarizing a multitude of celastrol nanoformulations that have been developed and tested for various therapeutic applications. In addition, the review highlights the unmet need in the clinical translation of celastrol nanoformulations and the path forward.

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.

The effect of nutmeg essential oil constituents on Novikoff hepatoma cell viability and communication through Cx43 gap junctions

Essential oils from plants are a potential source of molecules having anti-inflammatory, anticancer, cardiotropic, and other activities. However, most of these effects lack mechanistic explanations and structure-activity relationship testing. In the present study, we: 1) identified the nutmeg essential oil (NEO) composition; 2) using molecular docking, we determined the putative regulatory binding sites on the connexin 43 (Cx43) that is responsible for gap junction-dependent intercellular communication (GJIC) in the majority of tissues; 3) examined the effect of NEO and its three constituents - sabinene, α-pinene, and α-copaene - on GJ conductance and gating in Novikoff cells expressing endogenous Cx43; and 4) verified whether NEO effects on GJIC correlated with its action on Novikoff cell viability, proliferation, and colony formation capability. Our results revealed NEO and its constituents as potent and efficient Cx43 GJ inhibitors acting by slow gating mechanism. In addition, NEO reduced Novikoff hepatoma cell viability, proliferation, and colony formation capability; however, this was achieved at higher doses and was unrelated to its effects on GJIC.

Identification of Celastrol as a Novel Therapeutic Agent for Pulmonary Arterial Hypertension and Right Ventricular Failure Through Suppression of Bsg (Basigin)/CyPA (Cyclophilin A)

OBJECTIVE

Pulmonary arterial hypertension is characterized by abnormal proliferation of pulmonary artery smooth muscle cells and vascular remodeling, which leads to right ventricular (RV) failure. Bsg (Basigin) is a transmembrane glycoprotein that promotes myofibroblast differentiation, cell proliferation, and matrix metalloproteinase activation. CyPA (cyclophilin A) binds to its receptor Bsg and promotes pulmonary artery smooth muscle cell proliferation and inflammatory cell recruitment. We previously reported that Bsg promotes cardiac fibrosis and failure in the left ventricle in response to pressure-overload in mice. However, the roles of Bsg and CyPA in RV failure remain to be elucidated. Approach and Results: First, we found that protein levels of Bsg and CyPA were upregulated in the heart of hypoxia-induced pulmonary hypertension (PH) in mice and monocrotaline-induced PH in rats. Furthermore, cardiomyocyte-specific Bsg-overexpressing mice showed exacerbated RV hypertrophy, fibrosis, and dysfunction compared with their littermates under chronic hypoxia and pulmonary artery banding. Treatment with celastrol, which we identified as a suppressor of Bsg and CyPA by drug screening, decreased proliferation, reactive oxygen species, and inflammatory cytokines in pulmonary artery smooth muscle cells. Furthermore, celastrol treatment ameliorated RV systolic pressure, hypertrophy, fibrosis, and dysfunction in hypoxia-induced PH in mice and SU5416/hypoxia-induced PH in rats with reduced Bsg, CyPA, and inflammatory cytokines in the hearts and lungs.

CONCLUSIONS

These results indicate that elevated Bsg in pressure-overloaded RV exacerbates RV dysfunction and that celastrol ameliorates RV dysfunction in PH model animals by suppressing Bsg and its ligand CyPA. Thus, celastrol can be a novel drug for PH and RV failure that targets Bsg and CyPA. Graphic Abstract: A graphic abstract is available for this article.

Celastrol ameliorates Propionibacterium acnes/LPS-induced liver damage and MSU-induced gouty arthritis via inhibiting K63 deubiquitination of NLRP3

BACKGROUND

Celastrol, a pentacyclic triterpenoid quinonemethide isolated from several spp. of Celastraceae family, exhibits anti-inflammatory activities in a variety of diseases including arthritis.

PURPOSE

This study aims to investigate whether the inhibition of NLRP3 inflammasome is engaged in the anti-inflammatory activities of celastrol and delineate the underlying mechanism.

METHODS

The influence of celastrol on NLRP3 inflammasome activation was firstly studied in lipopolysaccharide (LPS)-primed mouse bone marrow-derived macrophages (BMDMs) and phorbol 12-myristate 13-acetate (PMA)-primed THP-1 cells treated with nigericin. Reconstituted inflammasome was also established by co-transfecting NLRP3, ASC, pro-caspase-1 and pro-IL-1β in HEK293T cells. The changes of inflammasome components including NLRP3, ASC, pro-caspase-1/caspase-1 and pro-IL-1β/IL-1β were examined by enzyme-linked immunosorbent assay (ELISA), western blotting and immunofluorescence. Furthermore, Propionibacterium acnes (P. acnes)/LPS-induced liver injury and monosodium urate (MSU)-induced gouty arthritis in mice were employed in vivo to validate the inhibitory effect of celastrol on NLRP3 inflammasome.

RESULTS

Celastrol significantly suppressed the cleavage of pro-caspase-1 and pro-IL-1β, while not affecting the protein expressions of NLRP3, ASC, pro-caspase-1 and pro-IL-1β in THP-1 cells, BMDMs and HEK293T cells. Celastrol suppressed NLRP3 inflammasome activation and alleviated P. acnes/LPS-induced liver damage and MSU-induced gouty arthritis. Mechanism study revealed that celastrol could interdict K63 deubiquitination of NLRP3, which may concern interaction of celastrol and BRCA1/BRCA2-containing complex subunit 3 (BRCC3), and thereby prohibited the formation of NLRP3, ASC and pro-caspase-1 complex to block the generation of mature IL-1β.

CONCLUSION

Celastrol suppresses NLRP3 inflammasome activation in P. acnes/LPS-induced liver damage and MSU-induced gouty arthritis via inhibiting K63 deubiquitination of NLRP3, which presents a novel insight into inhibition of celastrol on NLRP3 inflammasome and provides more evidences for its application in the therapy of inflammation-related diseases.

Current advances in the nano-delivery of celastrol for treating inflammation-associated diseases

Inflammation is ubiquitous in the body, and uncontrolled inflammation often contributes to various diseases. Celastrol, a compound isolated from a Chinese medicinal herb, holds great potential in treating multiple inflammation-associated diseases. However, its further clinical use is limited by its poor solubility, bioavailability, and high organ toxicity. With the advancement of nanotechnology, the nano-delivery of celastrol can effectively improve its oral bioavailability, maximize its efficacy and minimize its side effects. Here, we summarize the roles of celastrol in the treatment of various inflammation-associated diseases, with a special emphasis on its role in modulating immune cell signaling or non-immune cell signaling within the inflammatory microenvironment, and we highlight the latest advances in nano-delivery strategies for celastrol to treat diseases associated with inflammation.

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

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

Celastrol Dilates and Counteracts Ethanol-Induced Constriction of Cerebral Arteries

The increasing recognition of the role played by cerebral artery dysfunction in brain disorders has fueled the search for new cerebrovascular dilators. Celastrol, a natural triterpene undergoing clinical trials for treating obesity, exerts neuroprotection, which was linked to its antioxidant/anti-inflammatory activities. We previously showed that celastrol fit pharmacophore criteria for activating calcium- and voltage-gated potassium channels of large conductance (BK channels) made of subunits cloned from cerebrovascular smooth muscle (SM). These recombinant BK channels expressed in a heterologous system were activated by celastrol. Activation of native SM BK channels is well known to evoke cerebral artery dilation. Current data demonstrate that celastrol (1-100 µM) dilates de-endothelialized, ex vivo pressurized middle cerebral arteries (MCAs) from rats, with EC₅₀ = 45 µM and maximal effective concentration (E_max)= 100 µM and with MCA diameter reaching a 10% increase over vehicle-containing, time-matched values (P < 0.05). A similar vasodilatory efficacy is achieved when celastrol is probed on MCA segments with intact endothelium. Selective BK blocking with 1 μM paxilline blunts celastrol vasodilation. Similar blunting is achieved with 0.8 mM 4-aminopirydine, which blocks voltage-gated K⁺ channels other than BK. Using an in vivo rat cranial window, we further demonstrate that intracarotid injections of 45 μM celastrol into pial arteries branching from MCA mimics celastrol ex vivo action. MCA constriction by ethanol concentrations reached in blood during moderate-heavy alcohol drinking (50 mM), which involves SM BK inhibition, is both prevented and reverted by celastrol. We conclude that celastrol could be an effective cerebrovascular dilator and antagonist of alcohol-induced cerebrovascular constriction, with its efficacy being uncompromised by conditions that disrupt endothelial and/or BK function. SIGNIFICANCE STATEMENT: Our study demonstrates for the first time that celastrol significantly dilates rat cerebral arteries both ex vivo and in vivo and both prevents and reverses ethanol-induced cerebral artery constriction. Celastrol actions are endothelium-independent but mediated through voltage-gated (K_V) and calcium- and voltage-gated potassium channel of large conductance (BK) K⁺ channels. This makes celastrol an appealing new agent to evoke cerebrovascular dilation under conditions in which endothelial and/or BK channel function are impaired.

Heat shock protein 90 inhibition and multi-target approach to maximize cardioprotection in ischaemic injury

Despite several advances in medicine, ischaemic heart disease remains a major cause of morbidity and mortality. The unravelling of molecular mechanisms underlying disease pathophysiology has revealed targets for pharmacological interventions. However, transfer of these pharmcological possibilities to clinical use has been disappointing. Considering the complexity of ischaemic disease at the cellular and molecular levels, an equally multifaceted treatment approach may be envisioned. The pharmacological principle of 'one target, one key' may fall short in such contexts, and optimal treatment may involve one or many agents directed against complementary targets. Here, we introduce a 'multi-target approach to cardioprotection' and propose heat shock protein 90 (HSP90) as a target of interest. We report on a member of a distinct class of HSP90 inhibitor possessing pleiotropic activity, which we found to exhibit potent infarct-sparing effects.

Impact of Natural Dietary Agents on Multiple Myeloma Prevention and Treatment: Molecular Insights and Potential for Clinical Translation

Chemoprevention is based on the use of non-toxic, pharmacologically active agents to prevent tumor progression. In this regard, natural dietary agents have been described by the most recent literature as promising tools for controlling onset and progression of malignancies. Extensive research has been so far performed to shed light on the effects of natural products on tumor growth and survival, disclosing the most relevant signal transduction pathways targeted by such compounds. Overall, anti-inflammatory, anti-oxidant and cytotoxic effects of dietary agents on tumor cells are supported either by results from epidemiological or animal studies and even by clinical trials. Multiple myeloma is a hematologic malignancy characterized by abnormal proliferation of bone marrow plasma cells and subsequent hypercalcemia, renal dysfunction, anemia, or bone disease, which remains incurable despite novel emerging therapeutic strategies. Notably, increasing evidence supports the capability of dietary natural compounds to antagonize multiple myeloma growth in preclinical models of the disease, underscoring their potential as candidate anti-cancer agents. In this review, we aim at summarizing findings on the anti-tumor activity of dietary natural products, focusing on their molecular mechanisms, which include inhibition of oncogenic signal transduction pathways and/or epigenetic modulating effects, along with their potential clinical applications against multiple myeloma and its related bone disease.

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.

Integrated metabolomics and network toxicology to reveal molecular mechanism of celastrol induced cardiotoxicity

Celastrol (CS), an active triterpene derived from traditional Chinese medicine Tripterygium wilfordii Hook. f, has been used to treat chronic inflammation, arthritis and other diseases. However, it has been reported that CS can trigger cardiotoxicity and the molecular mechanism of heart injury induced by CS is not clear. Considering the wide application of Tripterygium wilfordii Hook. f in clinics, it is necessary to develop an accurate and reliable method to assess the safety of CS, and to elucidate as much as possible the mechanism of cardiotoxicity induced by CS. In this study, Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC-Q-TOF/MS)-based metabolomics revealed clues to the mechanism of CS-induced heart injury. Palmitic acid significantly increased in plasma from CS-treated rats, and this increase resulted in oxidative stress response in vivo. Excessive ROS further activate TNF signaling pathway and caspase family, which were obtained from the KEGG enrichment analysis of network toxicology strategy. Protein expression level of caspase-3, caspase-8, bax were significantly increased by western blot. Q-PCR also showed the similar results as western blot. It means that apoptosis plays a key role in the process of celastrol induced cardiotoxicity. Blocking this signal axis may be a potential way to protect myocardial tissue.

Celastrol enhances TRAIL-induced apoptosis in human glioblastoma via the death receptor pathway

PURPOSE

Glioblastoma is the most common, malignant and devastating type of primary brain tumor. Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) is characterized by its lethality to precancerous and cancerous cells. However, many kinds of tumor cells, including most glioma cells, tend to evade TRAIL-induced apoptosis. Celastrol is a pleiotropic compound from a traditional Chinese medicine that has proven to be useful as a sensitizer for TRAIL treatment. However, the underlying mechanism and role of celastrol in the sensitization of glioma cells remain to be elucidated.

METHODS

The viability of glioma cell lines was examined by the CCK-8 assay. The expression of DR5 was detected by reverse transcriptase quantitative real-time PCR. The protein expression of DR5, cleaved caspase-8, cleaved caspase-3 and PARP were measured by western blot. The apoptosis rates and the sub-G1 population were detected by flow cytometry. The cellular morphological changes were assessed by TUNEL apoptosis and Hoechst 33258 staining assays. The knockdown of DR5 expression was conducted by siRNA.

RESULTS

In this study, we observed that celastrol treatment inhibited cell viability in a dose-dependent manner, while glioma and normal human astroglial cell lines were resistant to TRAIL treatment. We also observed that the antiproliferative effects of TRAIL in combination with a noncytotoxic concentration of celastrol were significantly greater than those of celastrol or TRAIL alone. In addition, cell death induced by the combination treatment was apoptotic and occurred through the death receptor pathway via activation of caspase-8, caspase-3, and PARP. Furthermore, celastrol upregulated death receptor 5 (DR5) at the mRNA and protein levels, and siRNA-mediated DR5 knockdown reduced the killing effect of the combination drug treatment on glioma cells and reduced the activation of caspase-3, caspase-8 and PARP.

CONCLUSIONS

Taken together, the results of our study demonstrate that celastrol sensitizes glioma cells to TRAIL via the death receptor pathway and that DR5 plays an important role in the effects of this cotreatment. The results indicate that this cotreatment is a promising tumor-killing therapeutic strategy with high efficacy and low toxicity.

Autophagy flux inhibition mediated by celastrol sensitized lung cancer cells to TRAIL‑induced apoptosis via regulation of mitochondrial transmembrane potential and reactive oxygen species

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is well known as a transmembrane cytokine and has been proposed as one of the most effective anti-cancer therapeutic agents, owing to its efficiency to selectively induce cell death in a variety of tumor cells. Suppression of autophagy flux has been increasingly acknowledged as an effective and novel therapeutic intervention for cancer. The present study demonstrated that the anti-cancer and anti-inflammatory drug celastrol, through its anti-metastatic properties, may initiate TRAIL-mediated apoptotic cell death in lung cancer cells. This sensitization was negatively affected by N-acetyl-l-cysteine, which restored the mitochondrial membrane potential (ΔΨm) and inhibited reactive oxygen species (ROS) generation. Notably, treatment with celastrol caused an increase in microtubule-associated proteins 1A/1B light chain 3B-II and p62 levels, whereas co-treatment of celastrol and TRAIL increased active caspase 3 and 8 levels compared with the control, confirming inhibited autophagy flux. The combined use of TRAIL with celastrol may serve as a safe and adequate therapeutic technique for the treatment of TRAIL-resistant lung cancer, suggesting that celastrol-mediated autophagy flux inhibition sensitized TRAIL-initiated apoptosis via regulation of ROS and ΔΨm.

Effects of diclofenac on the pharmacokinetics of celastrol in rats and its transport

CONTEXT

Diclofenac and celastrol are always used together for the treatment of rheumatoid arthritis; the herb-drug interaction potential between diclofenac and celastrol is still unknown.

OBJECTIVE

This study investigates the effects of diclofenac on the pharmacokinetics of celastrol in rats.

MATERIALS AND METHODS

Twelve male Sprague-Dawley rats were divided into two groups and received celastrol (1 mg/kg) or both celastrol (1 mg/kg) and diclofenac (10 mg/kg) by oral gavage, and blood samples were collected via the oculi chorioideae vein and determined using the LC-MS method developed in this study. Additionally, the effects of diclofenac on the transport of celastrol were investigated using a Caco-2 cell transwell model.

RESULTS

Diclofenac could significantly (p < 0.05) decrease the C_max (from 66.93 ± 10.28 to 41.25 ± 8.06 ng/mL) and AUC_0-t (from 765.84 ± 163.61 to 451.33 ± 110.88 μg × h/L) of celastrol in rats. The efflux ratio of celastrol increased significantly (p < 0.05) from 3.12 to 4.55 with the treatment of diclofenac.

DISCUSSION AND CONCLUSION

These results indicated that diclofenac could decrease the system exposure of celastrol in rats when they are co-administered, and these effects might be exerted via decreasing its absorption in intestine.

Celastrol inhibits microglial pyroptosis and attenuates inflammatory reaction in acute spinal cord injury rats

Pyroptosis pathway is closely related to inflammation. However, Celastrol effect on pyroptosis pathway after spinal cord injury (SCI) are poorly understood. We studied the anti-inflammatory and neuroprotective effects of Celastrol on acute spinal cord injury in rats, and its anti-inflammatory effects on lipopolysaccharide (LPS)/ATP-induced microgliosis. Our results show that Celastrol can improve the recovery of hindlimb motor function after SCI in Sprague-Dawley (SD) rats, and reduce the cavity area of spinal cord injury along with the neuronal loss. Celastrol simultaneously reduced the activation of microglia (especially M1 microglia) in the spinal cord, inhibited the pyroptosis-related proteins (NLRP3 ASC Caspase-1 GSDMD), reduced the release of TNF-α IL-1β and IL-18 inflammatory factors, and increased the release of IL10 cytokines. In vitro studies showed that Celastrol reduced the toxicity resulting from the administration of LPS with ATP to BV-2 cells, inhibited the pyroptosis-related proteins (NLRP3 Caspase-1 GSDMD), and inhibited the release of corresponding inflammatory factors. Finally, Celastrol can inhibit the expression of NFκB/p-p65 in vitro and in vivo. Our results show that Celastrol can attenuate the inflammatory response of the spinal cord after SCI, which is associated with inhibition of microglial activation and pyroptosis pathway. Further study to explore the use of Celastrol to treat SCI is warranted.

Celastrol attenuates impairments associated with lipopolysaccharide-induced acute respiratory distress syndrome (ARDS) in rats

Celastrol, a constituent from a traditional Chinese medicinal herb belonging to the family Celastraceae, has been shown to impart anti-inflammatory properties, in part, by inhibiting NF-κB activity and related induction of pro-inflammatory cytokine formation/release. The present study investigated the effects of celastrol in an animal model of acute respiratory distress syndrome (ARDS) induced by intratracheal administration of lipopolysaccharides (LPSs). Celastrol pre-treatment groups received celastrol by intraperitoneal injection on seven consecutive days before LPS treatment. In rats evaluated 24 h after LPS administration, oxygenation indices and lung injury were measured, as were levels of inflammatory cells and cytokines in isolated bronchoalveolar lavage fluid (BALF). Lung tissue expression of proteins involved in NF-κB and ERK/MAPK pathways were measured by Western blot analyses. Celastrol pre-treatments appeared to attenuate LPS-induced lung injury and inflammatory responses in the rats, including decreases in inducible aggregation\infiltration of inflammatory cells and production/release of pro-inflammatory cytokines into the lung airways. Celastrol appeared to also inhibit NF-κB activation, but had no effect on ERK/MAPK pathways in the LPS-induced ARDS. The results here thus indicated that celastrol pre-treatment could impart protective effects against LPS-induced ARDS, and that these effects may be occurring through an inhibition of induction of NF-κB signaling pathways.

Celastrol as a pentacyclic triterpenoid with chemopreventive properties

Celastrol is a highly investigated anticancer moiety. It is a pentacyclic triterpenoid, isolated several decades ago with promising role in chemoprevention. Celastrol has been found to target multiple proinflammatory, angiogenic and metastatic proteins. Inhibition of these targets results in significant reduction of cancer growth, survival and metastasis. This review summarizes the varied molecular targets of celastrol along with insight into the various recently published clinical, preclinical and industrial patents (2011-2017).

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.

Self-assembled phospholipid-based phytosomal nanocarriers as promising platforms for improving oral bioavailability of the anticancer celastrol

Celastrol (CST) is a promising natural drug of herbal origin that gained a great interest in the recent years by virtue of its wide variety of pharmacological actions. Nowadays, CST is extensively studied as a natural anticancer surrogate with a potential activity against various types of cancers. However, CST suffers from many limitations that handicapped its clinical utility such as limited aqueous solubility and poor gastrointestinal absorption which resulted into its low oral bioavailability. This work spotlights, for the first time, development of self-assembled phytosomal nanocarriers (CST-PHY) for improving CST solubility and oral bioavailability. First CST-phospholipid complex was prepared by a simple solvent evaporation technique. Formation of CST-phospholipid complex was confirmed by differential scanning calorimetry (DSC), infrared spectroscopy (IR), powder X-ray diffraction (XRD) and partition coefficient determination. After dispersion into deionized water, CST-phospholipid complex was self-assembled to form CST-PHY. The optimized CST-PHY demonstrated a nanometric particle size of 178.4±7.07nm and a negative zeta potential of -38.7±3.61mV. Comparative in-vitro release study showed the ability of phytosomes to significantly enhance CST release compared with crude drug and physical mixture. Pharmacokinetic studies in rabbits revealed significant improvement in CST-PHY oral bioavailability compared with crude CST evidenced by 4-fold increase in AUC_0-8 and 5-fold increase in C_max of CST-PHY compared with crude CST. Conclusively, the results confirmed the potential of phytosomal nanocarriers to improve CST oral delivery paving the way for its use for oral cancer therapy.

Therapeutic potentials of natural compounds acting on cyclic nucleotide phosphodiesterase families

Intracellular cyclic AMP and/or cyclic GMP are characterized in the 1960th. These second messengers, hydrolysed specifically by cyclic nucleotide phosphodiesterase (PDE), play a major role in intracellular signalling. Natural products have been a rich source of drug discovery, Theophylline and Methylxanthine originated from tea leaves used for asthma treatment, whereas, Papaverine, a natural isoquinolein originated from Papaver somniferum traditionally used in impotency, altogether as caffeine where firstly described as PDE-inhibiting compounds. Since that time, the knowledge in PDE field has been drastically increased, allowing the design and development of new therapeutic drugs acting against different pathologies in the nanomolar range. During this period some natural compounds have been identified as PDE inhibitors and used in that context to investigate their therapeutic potential effects. The aim of this literature review is to point out the reported data and demonstrating the contribution of natural characterized molecules as PDE inhibitors in various pathologies that can open new fields of research for drug discovery, notably in epigenetic regulation.

A lipidomics investigation into the intervention of celastrol in experimental colitis

Celastrol is well known for its anti-inflammatory and anti-cancer effects. In this study, the efficacy of celastrol against dextran sulfate sodium (DSS)-induced inflammatory bowel disease (IBD) in mice was established and the mechanism was investigated using lipidomics. Celastrol treatment significantly alleviated DSS-induced colitis in mice, as revealed by the body weight, colon length, scores of rectal bleeding and diarrhea, serum TNF-α level, and histological analysis results. Lipidomics analysis based on UPLC/MS revealed characteristic changes in the metabolic profiles of the colitis mice, with altered levels of lipid markers associated with IBD, including LPC18 : 0, LPC18 : 1, LPC18 : 2, sphingomyelin (SM), and increased LPC18 : 0/LPC18 : 1 and LPC18 : 0/LPC18 : 2 ratios. For the celastrol-treated colitis mice, however, levels of the above lipid markers were restored, together with recovered saturated LPC/unsaturated LPC ratios. Accordingly, using GC-MS analysis, increased stearic acid (C18 : 0)/oleic acid (C18 : 1) and stearic acid (C18 : 0)/linoleic acid (C18 : 2) ratios were observed in colitis mice, which were later recovered after celastrol treatment. Quantitative real-time PCR analysis revealed that the liver expression of stearoyl-coenzyme A desaturase 1 (SCD1), the key enzyme controlling the desaturation of saturated fatty acid, was dramatically inhibited in IBD mice, and was obviously recovered after celastrol treatment. These results suggest that the increased saturated LPC/unsaturated LPC (and saturated fatty acid/unsaturated fatty acid) ratios associated with SCD1 down-regulation could be regarded as biomarkers of colitis, and celastrol alleviates DSS-induced colitis partially via up-regulation of SCD1, restoring the altered balance between stearic acid- and oleic acid-derived lipid species, which plays an important role in alleviating colitis. In all, this study provided the scientific basis for further development of celastrol in treating IBD.

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: 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.

N,N-Dimethyl Tertiary Amino Group Mediated Dual Pancreas- and Lung-Targeting Therapy against Acute Pancreatitis

Acute pancreatitis (AP) is a sudden inflammation of the pancreas with high mortality rate worldwide. As a severe complication to AP, acute lung injury has been the major cause of death among patients with AP. Poor penetration across the blood pancreas barrier (BPB) and insufficient drug accumulation at the target site often result in poor therapeutic outcome. Our previous work successfully demonstrated a dual-specific targeting strategy to pancreas and lung using a phenolic propanediamine moiety. Inspired by this, a simplified ligand structure, N,N-dimethyl tertiary amino group, was covalently conjugated to celastrol (CLT) to afford tertiary amino conjugates via either an ester (CP) or an amide linkage (CTA). With sufficient plasma stability, CTA was subjected to the following studies. Compared to CLT, CTA exhibited excellent cellular uptake efficiency in both rat pancreatic acinar cell line (AR42J) and human pulmonary alveolar epithelial cell line (A549). Organic cation transporters were proven to be responsible for this active transport process. Given systemically, CTA specifically distributed to pancreases and lungs in rats thus resulting in a 2.59-fold and 3.31-fold increase in tissue-specific accumulation as compared to CLT. After CTA treatment, tissue lesions were greatly alleviated and the levels of proinflammatory cytokines were downregulated in rats with sodium taurocholate induced AP. Furthermore, CTA demonstrated marginal adverse effect against major organs with reduced cardiac toxicity compared to CLT. Together, tertiary amine mediated dual pancreas- and lung-targeting therapy represents an efficient and safe strategy for AP management.

Optimizing stem cells for cardiac repair: Current status and new frontiers in regenerative cardiology

Cell therapy has the potential to improve healing of ischemic heart, repopulate injured myocardium and restore cardiac function. The tremendous hope and potential of stem cell therapy is well understood, yet recent trials involving cell therapy for cardiovascular diseases have yielded mixed results with inconsistent data thereby readdressing controversies and unresolved questions regarding stem cell efficacy for ischemic cardiac disease treatment. These controversies are believed to arise by the lack of uniformity of the clinical trial methodologies, uncertainty regarding the underlying reparative mechanisms of stem cells, questions concerning the most appropriate cell population to use, the proper delivery method and timing in relation to the moment of infarction, as well as the poor stem cell survival and engraftment especially in a diseased microenvironment which is collectively acknowledged as a major hindrance to any form of cell therapy. Indeed, the microenvironment of the failing heart exhibits pathological hypoxic, oxidative and inflammatory stressors impairing the survival of transplanted cells. Therefore, in order to observe any significant therapeutic benefit there is a need to increase resilience of stem cells to death in the transplant microenvironment while preserving or better yet improving their reparative functionality. Although stem cell differentiation into cardiomyocytes has been observed in some instance, the prevailing reparative benefits are afforded through paracrine mechanisms that promote angiogenesis, cell survival, transdifferentiate host cells and modulate immune responses. Therefore, to maximize their reparative functionality, ex vivo manipulation of stem cells through physical, genetic and pharmacological means have shown promise to enable cells to thrive in the post-ischemic transplant microenvironment. In the present work, we will overview the current status of stem cell therapy for ischemic heart disease, discuss the most recurring cell populations employed, the mechanisms by which stem cells deliver a therapeutic benefit and strategies that have been used to optimize and increase survival and functionality of stem cells including ex vivo preconditioning with drugs and a novel “pharmaco-optimizer” as well as genetic modifications.

In vitro immunomodulatory activity and in vivo anti-inflammatory and analgesic potential with gastroprotective effect of the Mediterranean red alga Laurencia obtusa

CONTEXT

Red algae have been recognized as a rich natural source of compounds possessing interesting biological and pharmacological activities.

OBJECTIVE

This work investigates anti-inflammatory, analgesic and gastroprotective activities of MeOH/CH₂Cl₂ crude extract and its fractions F1 (50% MeOH) and F2 (80% MeOH) from the whole alga plant Laurencia obtusa Hudson (Rhodomelaceae).

MATERIALS AND METHODS

Anti-inflammatory activity was evaluated in vitro using cytometric bead array (CBA) technology to follow up the secretion of tumour necrosis factor alpha (TNF-α) in lipopolysaccharide activated THP-1 monocytic cells at doses of 10-250 μg/mL and in vivo using carrageenan-induced paw oedema in Wistar rats at doses of 25, 50, 100 and 200 mg/kg. Crude extract and fractions were tested at the doses of 25, 50, 100 and 200 mg/kg for peripheral and central analgesic activity by acetic acid-induced writhing test and hot-plate method, respectively, in Swiss albino mice. Gastroprotective activity was evaluated using HCl/ethanol-induced gastric ulcer test in rats at doses of 25, 50, 100 and 200 mg/kg.

RESULTS

Crude extract, F1 and F2 showed an interesting inhibition of TNF-α secretion with IC₅₀ values of 25, 52 and 24 μg/mL, respectively, and a significant anti-inflammatory activity in vivo (p <  0.01), 3 h after carrageenan injection, the oedema inhibition was 55.37%, 52.18% and 62.86%, respectively, at the dose of 100 mg/kg. Furthermore, they showed a significant peripheral analgesic activity with 53.79%, 55.92% and 57.37% (p <  0.01) of writhing inhibition, respectively. However, no significant activity was found in the hot-plate test. An interesting gastroprotective effect was observed with crude extract and its fractions F1 and F2 with a gastric ulcer inhibition of 65.48%, 77.42% and 81.29%, respectively, at the dose of 50 mg/kg.

DISCUSSION AND CONCLUSION

These results suggest that L. obtusa might be used as a potential source of natural anti-inflammatory and analgesic agents with gastroprotective effect.

Necroptosis inhibitors as therapeutic targets in inflammation mediated disorders - a review of the current literature and patents

INTRODUCTION

Recent studies have shown substantial interplay between the apoptosis and necroptosis pathways. Necroptosis, a form of programmed cell death, has been found to stimulate the immune system contributing to the pathophysiology of several inflammation-mediated disorders. Determining the contribution of necroptotic signaling pathways to inflammation may lead to the development of selective and specific molecular target implicated necroptosis inhibitors. Areas covered: This review summarizes the recently published and patented necroptosis inhibitors as therapeutic targets in inflammation-mediated disorders. The role of several necroptosis inhibitors, focusing on specific signaling molecules, was discussed with particular attention to inflammation-mediated disorders. Data was obtained from Espacenet®, WIPO®, USPTO® patent websites, and other relevant sources (2006-2016). Expert opinion: Necroptosis inhibitors hold promise for treatment of inflammation-mediated clinical conditions in which necroptotic cell death plays a major role. Although necroptosis inhibitors reviewed in this survey showed inhibitory effects against several inflammation-mediated disorders, only a few have passed to the stage of clinical testing and need extensive research for therapeutic practice. Revisiting the existing drugs and developing novel necroptosis inhibiting agents as well as understanding their mechanism are essential. A detailed study of necroptosis function in animal models of inflammation may provide us an alternative strategy for the development of drug-like necroptosis inhibitors.

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.