Celastrol inhibits migration, proliferation and transforming growth factor-β2-induced epithelial-mesenchymal transition in lens epithelial cells

Celastrol alleviates subconjunctival fibrosis induced by silicone implants mimicking glaucoma surgery

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

The Promising Therapeutic Potential of Celastrol for Fibrotic Diseases: A Systematic Literature Review on Its Mechanism

Celastrol is a pentacyclic tripterine sourced from Tripterygium wilfordii hook root. Celastrol can exert certain biological functions such as antitumor, anti-inflammatory, and antiproliferative properties. Celastrol was shown from the previous literature to be capable of attenuating many fibrotic diseases. As the effects of various fibrotic diseases such as atherosclerosis, cancer, and ischemia affect more people with devastating repercussions, this warrants celastrol to be exploited as a phytotherapeutic drug. The purpose of this study is to review previous research and identify the proposed therapeutic mechanisms of celastrol in fibrotic diseases focusing on both the in vitro and in vivo experimental models.  A systematic literature search on Web of Science (WoS), Scopus, and ScienceDirect that included articles published between 2012 and 2022 was carried out using the keywords "celastrol", "tripterine", "fibrotic disease", and "fibrosis". After screening the initial search yield of 405 articles, 25 articles were included in this review.  The study findings summarize the potential therapeutic mechanism of celastrol in the attenuation of fibrotic diseases in in vivo and in vitro experimental models. It shows that celastrol is useful as a treatment means. However, more studies are needed on the effects of celastrol on humans to carry out clinical trials to verify the long-term benefits of celastrol.

Celastrol-based nanomedicine hydrogels eliminate posterior capsule opacification

Aim: To formulate an injectable thermosensitive micelle-hydrogel hybrid system loaded with celastrol (celastrol-loaded micelle hydrogel: CMG) to prevent posterior capsule opacification (PCO). Materials & methods: Celastrol-loaded micelles were embedded in a thermosensitive hydrogel matrix to enable controlled on-demand celastrol delivery into the residual capsule. The efficacy and mechanisms of the system for eliminating PCO were evaluated in rabbits. Results: Celastrol-loaded micelles inhibited the migration and proliferation of lens epithelial cells induced by TGF-β1. Celastrol prevents epithelial-mesenchymal transition in lens epithelial cells induced by TGF-β1 through the TGF-β1/Smad2/3/TEAD1 signaling pathway. In vivo efficiency evaluations showed that CMG demonstrated an excellent inhibitory effect on PCO in rabbits and had no obvious tissue toxicity. Conclusion: Injectable CMG may represent a promising ophthalmic platform for preventing PCO. This versatile injectable micelle-hydrogel hybrid represents a clinically relevant platform to achieve localized therapy and controlled release of drugs in other disease therapies.

Role and Mechanism of Epithelial-Mesenchymal Transition Mediated by Inflammatory Stress-Induced TGF-β1 in Promoting Arteriovenous Fistula Stenosis

Objective

To explore the role and mechanism of epithelial-mesenchymal transition (EMT) mediated by inflammatory stress-induced TGF-β1 in promoting arteriovenous fistula stenosis.

Methods

The inflammatory cells HK-2 were cultured by adding TGF-β1. The optimal stimulation time was determined after TGF-β1 was added. HK-2 cells were divided into two groups, DMEM/F12 medium was added to one group (the control group), and the other group was treated with TGF-β1 (10 ng/ml) in serum-free DMEM/F12 medium to stimulate cell differentiation to mesenchymal.

Results

TGF-β1 was stably expressed after being transfected into EMT. The expression of TGF-β1 in the experimental group was higher than that in the control group (P < 0.05) 7 days after transfection. Western blot showed that TGF-β1 protein expression was higher in the experimental group 7 days after transfection, and no TGF-β1 protein expression was detected in the control group. The smooth muscle cells showed α-SMA expression in the control group, but no cells with expression of SMA and CD31/vWF were found at the same time; α-SMA expression was shown in smooth muscle cells and proliferative myofibroblasts, but no cells with expressions of SMA and CD31/vWF were found at the same time. The observation group showed that the expression of α-SMA was detected in smooth muscle cells and proliferative myofibroblasts, CD31/vWF was also expressed in endothelial cells, and α-SMA and vWF were also observed in endothelial cells, but no CD31 expression was found.

Conclusion

The inflammatory stress-induced TGF-β1 could act on epithelial-mesenchymal transition and promote the degree of arteriovenous fistula stenosis.

Circ-GGA3 promotes the biological functions of human lens epithelial cells depending on the regulation of miR-497-5p/SMAD4 axis

The cause of posterior capsular opacification (PCO) is the dysfunction of lens epithelial cells (LECs). Circular RNA (circRNA) was found to regulate cell biological functions, including LECs. However, the role of circ-GGA3 in PCO formation is unclear. Quantitative real-time PCR was used to measure the expression of circ-GGA3, miR-497-5p and SMAD4. Cell proliferation, invasion and migration were determined via MTT assay, EdU staining, transwell assay and wound healing assay. The protein expression of epithelial-mesenchymal transition (EMT) markers, fibrosis markers, TGF-β/SMAD pathway markers and SMAD4 were determined by western blot assay. The interaction between miR-497-5p and circ-GGA3 or SMAD4 was confirmed using dual-luciferase reporter assay. Circ-GGA3 was highly expressed in PCO patients, and its silencing inhibited the proliferation, invasion, migration, EMT process and fibrosis of TGF-β2-induced LECs. Circ-GGA3 could sponge miR-497-5p to regulate SMAD4. Further experiments revealed that miR-497-5p inhibitor recovered the negative regulation of circ-GGA3 knockdown on the biological functions of TGF-β2-induced LECs, and SMAD4 overexpression also abolished the suppressive effect of miR-497-5p. In addition, circ-GGA3/miR-497-5p/SMAD4 axis could activate the TGF-β/SMAD pathway. Our results indicated that circ-GGA3 could enhance the biological functions of LECs, suggesting that circ-GGA3 might be a potential target for PCO therapy.

Targeted inhibition of TAK1 abrogates TGFβ1 non-canonical signaling axis, NFκB/Smad7 inhibiting human endometriotic cells proliferation and inducing cell death involving autophagy

Transforming growth factor (TGFβ) is known to play a major role in establishment and maintenance of endometriosis as reported by our group earlier, the underlying mechanism remains to be explored. We deciphered the involvement of TAK1 in TGFβ1- induced cellular responses and delineated the signaling mechanism in human endometriotic cells. The endometriotic cells showed elevated expression of TGFβ1 signaling-effector molecules. TGFβ1 exposure to endometriotic cells induced the expression of the downstream target molecules indicating that TGFβ1 is implicated in the commencement ofTAK1/NFκB-p65/Smad7 cascade. The silencing of TAK1 in endometriotic cells attenuated the TGFβ1 -induced NFκB transcriptional activation and nuclear translocation of NFκB-p65 subunit. The pharmacological inhibition of NFκB by QNZ or knockdown of TAK1 reduced the expression of Smad7 and Cox2. The knockdown of TAK1 in endometriotic cells showed G1 phase cell-cycle arrest and showed low BrdU-incorporation in the presence of TGFβ1. The inhibition of TAK1 attenuated the TGFβ1 signaling activation indicating that TAK1 is a crucial mediator for TGFβ1 action in endometriotic cells. The exposure of endometriotic cells to TAK1 inhibitor, celastrol caused activation of caspase-3 and -9 that led to PARP cleavage and induced apoptosis. Simultaneously, autophagy occurred in celastrol-treated and TAK1-silenced cells as was evidenced by the formation of autophagosome and the increased expression of autophagic markers. Thus, TAK1 activation appears to protect the growth of endometriotic cells by suppressing the cell death process. Overall, our study provided the evidence that of TAK1 significant in the endometriotic cell regulation and mediates a functional cross-talk between TGFβ1 and NFκB-p65 that promotes the growth and inflammatory response in endometriotic cells.

Celastrol: A Review of Useful Strategies Overcoming its Limitation in Anticancer Application

Celastrol, a natural bioactive ingredient derived from Tripterygium wilfordii Hook F, exhibits significant broad-spectrum anticancer activities for the treatment of a variety of cancers including liver cancer, breast cancer, prostate tumor, multiple myeloma, glioma, etc. However, the poor water stability, low bioavailability, narrow therapeutic window, and undesired side effects greatly limit its clinical application. To address this issue, some strategies were employed to improve the anticancer efficacy and reduce the side-effects of celastrol. The present review comprehensively focuses on the various challenges associated with the anticancer efficiency and drug delivery of celastrol, and the useful approaches including combination therapy, structural derivatives and nano/micro-systems development. The specific advantages for the use of celastrol mediated by these strategies are presented. Moreover, the challenges and future research directions are also discussed. Based on this review, it would provide a reference to develop a natural anticancer compound for cancer treatment.

Celastrol Loaded Nanoparticles With ROS-Response and ROS-Inducer for the Treatment of Ovarian Cancer

Ovarian cancer is a gynecological cancer from which it is difficult to be completely cured. It is common to use regimens as an effective treatment for ovarian cancer, but these inevitably bring serious side effects. New treatment strategies and special drugs are needed to improve the prognosis of patients. Celastrol is a natural product, isolated from traditional medicine, that has been proven to be curative for inflammation and cancers. However, the non-targeting and low solubility of celastrol limit its clinical application. We prepared celastrol-loaded nanoparticles for the efficient treatment of ovarian cancer via oxidative stress amplification. In this work, a tumor-targeted, ROS-sensitive nanoparticle was designed, synthesized, and assembled into a drug delivery system that used celastrol. Folic acid (FA) groups on the surface of nanoparticles guide them to actively target the surface of the tumor cell membrane. Thioketal (TK) bonds in nanoparticles can be oxidized and broken into -SH within the ROS level of tumor tissues, which causes the breaking of the PEG hydrophilic shell layer of nanoparticles and promotes the release of celastrol. The released celastrol further stimulated the production of ROS and amplified the intracellular ROS level to promote the apoptosis of tumor cells, thus achieving a therapeutic effect on the celastrol treated ovarian cancer.

Identification of Putative Non-Substrate-Based XT-I Inhibitors by Natural Product Library Screening

Fibroproliferative diseases are characterized by excessive accumulation of extracellular matrix (ECM) components leading to organ dysfunction. This process is characterized by an increase in myofibroblast content and enzyme activity of xylosyltransferase-I (XT-I), the initial enzyme in proteoglycan (PG) biosynthesis. Therefore, the inhibition of XT-I could be a promising treatment for fibrosis. We used a natural product-inspired compound library to identify non-substrate-based inhibitors of human XT-I by UPLC-MS/MS. We combined this cell-free approach with virtual and molecular biological analyses to confirm and prioritize the inhibitory potential of the compounds identified. The characterization for compound potency in TGF-β1-driven XYLT1 transcription regulation in primary dermal human fibroblasts (key cells in ECM remodeling) was addressed by gene expression analysis. Consequently, we identified amphotericin B and celastrol as new non-substrate-based XT-I protein inhibitors. Their XT-I inhibitory effects were mediated by an uncompetitive or a competitive inhibition mode, respectively. Both compounds reduced the cellular XYLT1 expression level and XT-I activity. We showed that these cellular inhibitor-mediated changes involve the TGF-β and microRNA-21 signaling pathway. The results of our study provide a strong rationale for the further optimization and future usage of the XT-I inhibitors identified as promising therapeutic agents of fibroproliferative diseases.