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

Triterpenes as Potential Drug Candidates for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease characterized by joint inflammation, swelling and pain. Although RA mainly affects the joints, the disease can also have systemic implications. The presence of autoantibodies, such as anti-cyclic citrullinated peptide antibodies and rheumatoid factors, is a hallmark of the disease. RA is a significant cause of disability worldwide associated with advancing age, genetic predisposition, infectious agents, obesity and smoking, among other risk factors. Currently, RA treatment depends on anti-inflammatory and disease-modifying anti-rheumatic drugs intended to reduce joint inflammation and chronic pain, preventing or slowing down joint damage and disease progression. However, these drugs are associated with severe side effects upon long-term use, including immunosuppression and development of opportunistic infections. Natural products, namely triterpenes with anti-inflammatory properties, have shown relevant anti-arthritic activity in several animal models of RA without undesirable side effects. Therefore, this review covers the recent studies (2017-2022) on triterpenes as safe and promising drug candidates for the treatment of RA. These bioactive compounds were able to produce a reduction in several RA activity indices and immunological markers. Celastrol, betulinic acid, nimbolide and some ginsenosides stand out as the most relevant drug candidates for RA treatment.

Celastrol as an emerging anticancer agent: Current status, challenges and therapeutic strategies

Celastrol is a pentacyclic triterpenoid extracted from the traditional Chinese medicine Tripterygium wilfordii Hook F., which has multiple pharmacological activities. In particular, modern pharmacological studies have demonstrated that celastrol exhibits significant broad-spectrum anticancer activities in the treatment of a variety of cancers, including lung cancer, liver cancer, colorectal cancer, hematological malignancies, gastric cancer, prostate cancer, renal carcinoma, breast cancer, bone tumor, brain tumor, cervical cancer, and ovarian cancer. Therefore, by searching the databases of PubMed, Web of Science, ScienceDirect and CNKI, this review comprehensively summarizes the molecular mechanisms of the anticancer effects of celastrol. According to the data, the anticancer effects of celastrol can be mediated by inhibiting tumor cell proliferation, migration and invasion, inducing cell apoptosis, suppressing autophagy, hindering angiogenesis and inhibiting tumor metastasis. More importantly, PI3K/Akt/mTOR, Bcl-2/Bax-caspase 9/3, EGFR, ROS/JNK, NF-κB, STAT3, JNK/Nrf2/HO-1, VEGF, AR/miR-101, HSF1-LKB1-AMPKα-YAP, Wnt/β-catenin and CIP2A/c-MYC signaling pathways are considered as important molecular targets for the anticancer effects of celastrol. Subsequently, studies of its toxicity and pharmacokinetic properties showed that celastrol has some adverse effects, low oral bioavailability and a narrow therapeutic window. In addition, the current challenges of celastrol and the corresponding therapeutic strategies are also discussed, thus providing a theoretical basis for the development and application of celastrol in the clinic.

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.

Inhibitory effects of traditional Chinese medicine colquhounia root tablet on the pharmacokinetics of tacrolimus in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tacrolimus (TAC) was widely used in various renal diseases while high recurrence rate and high expense restricted its applications. Traditional herbal medicine has become increasingly popular as an adjuvant therapy to minimize the adverse effects of TAC. Colquhounia root tablet (CRT), a prescribed drug prepared from the water extract of the peeled root of Tripterygium hypoglaucum (H. Lév.) Hutch., showed excellent anti-inflammatory, analgesic and immunosuppressive pharmacological properties. TAC used in combination with CRT was substantially more efficacious and safer than the monotherapy for the treatment of nephrotic syndrome. However, studies on their herb-drug interaction were scanty.

AIM OF THE STUDY

The study was proposed to examine the effect of CRT on the pharmacokinetics of TAC in rats and identify the key natural constituents in CRT that affected the metabolism of TAC.

MATERIALS AND METHODS

TAC was orally and intravenously administered to rats alone or in combination with CRT and the pharmacokinetic parameters of TAC were compared. After pretreatment with CRT for 15 d, the expressions of the drug-metabolizing enzymes (DMEs), drug transporters (DTs) and nuclear receptors (NRs) were determined by polymerase chain reaction and western blotting and compared with the control group. The hepatic microsomal incubation system was employed to confirm the inhibitory effects of CRT and its major components on rat cytochrome P450 (CYP) 3A2. The roles of the primary components in the regulation of human CYP3A4 and mouse P-gp activities were evaluated by using docking analysis.

RESULTS

The blood concentrations of TAC were significantly increased in a dose- and pretreatment time-dependent manner after combined administration of CRT. The maximal effect was found at 300 mg/kg (43.70 ± 8.77 ng/mL and 141.45 ± 21.58 h·ng/mL) in a single dose run and the pharmacokinetic parameters gradually returned to the normal levels at 24 h interval of long-term CRT pretreatment. In contrast, CRT had no effect on the pharmacokinetics of intravenous TAC. Further study indicated that the mRNA and protein expressions of DMEs and DTs, such as CYP3A1, CYP3A2, P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 in rat intestine and liver were down-regulated, whereas the expressions of NRs like constitutive androstane receptor and pregnane X receptor were up-regulated after multiple oral doses of CRT. Molecular docking showed the binding potency of five CRT major constituents with both human CYP3A4 and mouse P-gp. Celastrol, wilforgine and wilforine were the strongest inhibitors towards midazolam metabolism in rat liver microsomes, with the 50% inhibition concentrations being at 8.33 μM, 22.18 μM and 22.22 μM, respectively.

CONCLUSIONS

Our results revealed that co-dosing of CRT could lead to a significant increase in blood concentration of TAC and this effect could be ascribed to the resultant co-regulation of DMEs, DTs and NRs. Our study provided an experimental basis for the combination use of CRT and TAC in clinical practice.

Celastrol in cancer therapy: Recent developments, challenges and prospects

Cancer is one of the world's biggest healthcare burdens and despite the current advancements made in treatment plans, the outcomes for oncology patients have yet to reach their full potential. Hence, there is a pressing need to develop novel anti-cancer drugs. A popular drug class for research are natural compounds, due to their multi-targeting potential and enhanced safety profile. One such promising natural bioactive compound derived from a vine, Tripterygium wilfordii is celastrol. Pre-clinical studies revolving around the use of celastrol have revealed positive pharmacological activities in various types of cancers, thus suggesting the chemical's potential anti-cancerous effects. However, despite the numerous preclinical studies carried out over the past few decades, celastrol has not reached human trials for cancer. In this review, we summarize the mechanisms and therapeutic potentials of celastrol in treatment for different types of cancer. Subsequently, we also explore the possible reasons hindering its development for human use as cancer therapy, like its narrow therapeutic window and poor pharmacokinetic properties. Additionally, after critically analysing both in vitro and in vivo evidence, we discuss about the key pathways effected by celastrol and the suitable types of cancer that can be targeted by the natural drug, thus giving insight into future directions that can be taken, such as in-depth analysis and research of the druggability of celastrol derivatives, to aid the clinical translation of this promising anti-cancer lead compound.

Modulation of cellular circadian clocks by triterpenoids

Many living organisms on earth have clock systems in their body. It has increasingly become clear that a disturbance in the internal clocks has negative effects on our body. Terpenes are organic compounds found in various plants that are reported to have several pharmacological actions. In this study, we focused on commercially available 27 triterpenoids and evaluated their influence on the circadian rhythm of human U2OS cells and mouse NIH3T3 cells. The expression level of Per2, one of the core clock genes, was measured using luminescent reporters over the time period of a few days. We found that 8 triterpenoids reset the phase of the circadian clocks. Representative compounds were corosolic acid, cucurbitacin B, and celastrol; similar effects were also confirmed with some structural analogues of cucurbitacin B and celastrol. These compounds shifted the phase bilaterally depending on the stimulus timing and also acted as synchronizers in desynchronized cells. The effective concentrations of cucurbitacin B and celastrol were less than 0.5 μM. In addition, cucurbitacin B and celastrol were also found to be effective in tissue explants in mice. Furthermore, celastrol dose-dependently shortened the period length of NIH3T3 cells. Some of these compounds are found in edible and medicinal plants and may help regulate our circadian clocks in everyday life.

Oral Bioavailability Evaluation of Celastrol-Encapsulated Silk Fibroin Nanoparticles Using an Optimized LC-MS/MS Method

Celastrol (CL), a compound isolated from Tripterygium wilfordii, possesses various bioactivities such as antitumor, anti-inflammatory and anti-obesity effects. In previous studies, we developed CL-encapsulated silk fibroin nanoparticles (CL-SFNP) with satisfactory formulation properties and in vitro cancer cytotoxicity effect. For further in vivo oral bioavailability evaluation, in this study, a simple and reliable LC-MS/MS method was optimized and validated to determine CL concentration in rat plasma. The separation of CL was performed on a C18 column (150 by 2 mm, 5 µm) following sample preparation using liquid–liquid extraction with the optimized extraction solvent of tert-butyl methylether. The assay exhibited a good linearity in the concentration range of 0.5–500 ng/mL with the lower limit of quantification (LLOQ) of 0.5 ng/mL. The method was validated to meet the requirements for bioassay with accuracy of 91.1–110.0%, precision (RSD%) less than 9.1%, extraction recovery of 63.5–74.7% and matrix effect of 87.3–101.2%. The developed method was successfully applied to the oral bioavailability evaluation of CL-SFNP. The pharmacokinetic results indicated the AUC_0-∞ values of CL were both significantly (p < 0.05) higher than those for pure CL after intravenous (IV) or oral (PO) administration of equivalent CL in rats. The oral absolute bioavailability (F, %) of CL significantly (p < 0.05) increased from 3.14% for pure CL to 7.56% for CL-SFNP after dosage normalization. This study provides valuable information for future CL product development.