Inhibition of NF-kappa B activation through targeting I kappa B kinase by celastrol, a quinone methide triterpenoid

Precise modulation and use of reactive oxygen species for immunotherapy

Reactive oxygen species (ROS) play an important role in regulating the immune system by affecting pathogens, cancer cells, and immune cells. Recent advances in biomaterials have leveraged this mechanism to precisely modulate ROS levels in target tissues for improving the effectiveness of immunotherapies in infectious diseases, cancer, and autoimmune diseases. Moreover, ROS-responsive biomaterials can trigger the release of immunotherapeutics and provide tunable release kinetics, which can further boost their efficacy. This review will discuss the latest biomaterial-based approaches for both precise modulation of ROS levels and using ROS as a stimulus to control the release kinetics of immunotherapeutics. Finally, we will discuss the existing challenges and potential solutions for clinical translation of ROS-modulating and ROS-responsive approaches for immunotherapy, and provide an outlook for future research.

Celastrol enhances the viability of random-pattern skin flaps by regulating autophagy through the AMPK-mTOR-TFEB axis

In reconstructive and plastic surgery, random-pattern skin flaps (RPSF) are often used to correct defects. However, their clinical usefulness is limited due to their susceptibility to necrosis, especially on the distal side of the RPSF. This study validates the protective effect of celastrol (CEL) on flap viability and explores in terms of underlying mechanisms of action. The viability of different groups of RPSF was evaluated by survival zone analysis, laser doppler blood flow, and histological analysis. The effects of CEL on flap angiogenesis, apoptosis, oxidative stress, and autophagy were evaluated by Western blot, immunohistochemistry, and immunofluorescence assays. Finally, its mechanistic aspects were explored by autophagy inhibitor and Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) inhibitor. On the seventh day after surgery, the survival area size, blood supply, and microvessel count of RPSF were augmented following the administration of CEL. Additionally, CEL stimulated angiogenesis, suppressed apoptosis, and lowered oxidative stress levels immediately after elevated autophagy in ischemic regions; These effects can be reversed using the autophagy inhibitor chloroquine (CQ). Specifically, CQ has been observed to counteract the protective impact of CEL on the RPSF. Moreover, it has also been discovered that CEL triggers the AMPK-mTOR-TFEB axis activation in the area affected by ischemia. In CEL-treated skin flaps, AMPK inhibitors were demonstrated to suppress the AMPK-mTOR-TFEB axis and reduce autophagy levels. This investigation suggests that CEL benefits the survival of RPSF by augmenting angiogenesis and impeding oxidative stress and apoptosis. The results are credited to increased autophagy, made possible by the AMPK-mTOR-TFEB axis activation.

Withaferin A and Celastrol Overwhelm Proteostasis

Withaferin A (WA) and celastrol (CEL) are major bioactive components of plants that have been widely employed in traditional medicine. The pleiotropic activities of plant preparations and the isolated compounds in vitro and in vivo have been documented in hundreds of studies. Both WA and CEL were shown to have anticancer activity. Although WA and CEL belong to different chemical classes, our synthesis of the available information suggests that the compounds share basic mechanisms of action. Both WA and CEL bind covalently to numerous proteins, causing the partial unfolding of some of these proteins and of many bystander proteins. The resulting proteotoxic stress, when excessive, leads to cell death. Both WA and CEL trigger the activation of the unfolded protein response (UPR) which, if the proteotoxic stress persists, results in apoptosis mediated by the PERK/eIF-2/ATF4/CHOP pathway or another UPR-dependent pathway. Other mechanisms of cell death may play contributory or even dominant roles depending on cell type. As shown in a proteomic study with WA, the compounds appear to function largely as electrophilic reactants, indiscriminately modifying reachable nucleophilic amino acid side chains of proteins. However, a remarkable degree of target specificity is imparted by the cellular context.

Design, synthesis, and evaluation of antitumor activity of novel C-6 sulfhydryl-substituted and 20-substituted derivatives of celastrol

Celastrol has been identified as a potential candidate for anticancer drug development. In this study, 28 novel celastrol derivatives with C-6 sulfhydryl substitution and 20-substitution were designed and synthesized, and their antiproliferative activity against human cancer cells and non-malignant human cells was evaluated, with cisplatin and celastrol being used as controls. The results showed that most of the derivatives had enhanced in vitro anticancer activity compared to the parent compound celastrol. Specifically, derivative 2f demonstrated the most potent inhibitory potential and selectivity against HOS with an IC50 value of 0.82 μM. Our study provides new insights into the structure-activity relationship of celastrol and suggests that compound 2f may be a promising drug candidate for the treatment of osteosarcoma.

Herbal medicine for the treatment of obesity-associated asthma: a comprehensive review

Obesity is fast growing as a global pandemic and is associated with numerous comorbidities like cardiovascular disease, hypertension, diabetes, gastroesophageal reflux disease, sleep disorders, nephropathy, neuropathy, as well as asthma. Studies stated that obese asthmatic subjects suffer from an increased risk of asthma, and encounter severe symptoms due to a number of pathophysiology. It is very vital to understand the copious relationship between obesity and asthma, however, a clear and pinpoint pathogenesis underlying the association between obesity and asthma is scarce. There is a plethora of obesity-asthma etiologies reported viz., increased circulating pro-inflammatory adipokines like leptin, resistin, and decreased anti-inflammatory adipokines like adiponectin, depletion of ROS controller Nrf2/HO-1 axis, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) associated macrophage polarization, hypertrophy of WAT, activation of Notch signaling pathway, and dysregulated melanocortin pathway reported, however, there is a very limited number of reports that interrelates these pathophysiologies. Due to the underlying complex pathophysiologies exaggerated by obese conditions, obese asthmatics respond poorly to anti-asthmatic drugs. The poor response towards anti-asthmatic drugs may be due to the anti-asthmatics approach only that ignores the anti-obesity target. So, aiming only at the conventional anti-asthmatic targets in obese-asthmatics may prove to be futile until and unless treatment is directed towards ameliorating obesity pathogenesis for a holistic approach towards amelioration of obesity-associated asthma. Herbal medicines for obesity as well as obesity-associated comorbidities are fast becoming safer and more effective alternatives to conventional drugs due to their multitargeted approach with fewer adverse effects. Although, herbal medicines are widely used for obesity-associated comorbidities, however, a limited number of herbal medicines have been scientifically validated and reported against obesity-associated asthma. Notable among them are quercetin, curcumin, geraniol, resveratrol, β-Caryophyllene, celastrol, tomatidine to name a few. In view of this, there is a dire need for a comprehensive review that may summarize the role of bioactive phytoconstituents from different sources like plants, marine as well as essential oils in terms of their therapeutic mechanisms. So, this review aims to critically discuss the therapeutic role of herbal medicine in the form of bioactive phytoconstituents against obesity-associated asthma available in the scientific literature to date.

In vitro and in silico perspectives to explain anticancer activity of a novel syringic acid analog ((4-(1H-1, 3-benzodiazol-2-yl)-2, 6-dimethoxy phenol)) through apoptosis activation and NFkB inhibition in K562 leukemia cells

Syringic acid (SA) is an active carcinogenesis inhibitor; however, the low bioavailability and unstable functional groups hinder its activity. Here, a chemically synthesized novel SA analog (SA10) is evaluated for its anticancer activity using in-vitro and in-silico studies. K562 cell line study revealed that SA10 had shown a higher rate of inhibition (IC50 = 50.40 μg/mL) than its parental compound, SA (IC50 = 96.92 μg/mL), at 50 μM concentration. The inhibition ratio was also been evaluated by checking the expression level of NFkB and Bcl-2 and showing that SA10 has two-fold increase in the inhibitory mechanism than SA. This result demonstrates that SA10 acts as an NFkB inhibitor and an apoptosis inducer. Further, molecular docking and simulation have been performed to get insights into the possible inhibitory mechanism of SA and SA10 on NFkB at the atomistic level. The molecular docking results exemplify that both SA and SA10 bind to the active site of NFkB, thereby interfering with the association between DNA and NFkB. SA10 exhibits a more robust binding affinity than SA and is firmly docked well into the interior of the NFkB, as confirmed by MM-PBSA calculations. In a nutshell, the Benzimidazole scaffold containing SA10 has shown more NFkB inhibitory activity in K562 cells than SA, which could be helpful as an ideal therapeutic NFkB inhibitor for treating cancers.

HSF1 and Its Role in Huntington's Disease Pathology

PURPOSE OF REVIEW

Heat shock factor 1 (HSF1) is the master transcriptional regulator of the heat shock response (HSR) in mammalian cells and is a critical element in maintaining protein homeostasis. HSF1 functions at the center of many physiological processes like embryogenesis, metabolism, immune response, aging, cancer, and neurodegeneration. However, the mechanisms that allow HSF1 to control these different biological and pathophysiological processes are not fully understood. This review focuses on Huntington's disease (HD), a neurodegenerative disease characterized by severe protein aggregation of the huntingtin (HTT) protein. The aggregation of HTT, in turn, leads to a halt in the function of HSF1. Understanding the pathways that regulate HSF1 in different contexts like HD may hold the key to understanding the pathomechanisms underlying other proteinopathies. We provide the most current information on HSF1 structure, function, and regulation, emphasizing HD, and discussing its potential as a biological target for therapy.

DATA SOURCES

We performed PubMed search to find established and recent reports in HSF1, heat shock proteins (Hsp), HD, Hsp inhibitors, HSF1 activators, and HSF1 in aging, inflammation, cancer, brain development, mitochondria, synaptic plasticity, polyglutamine (polyQ) diseases, and HD.

STUDY SELECTIONS

Research and review articles that described the mechanisms of action of HSF1 were selected based on terms used in PubMed search.

RESULTS

HSF1 plays a crucial role in the progression of HD and other protein-misfolding related neurodegenerative diseases. Different animal models of HD, as well as postmortem brains of patients with HD, reveal a connection between the levels of HSF1 and HSF1 dysfunction to mutant HTT (mHTT)-induced toxicity and protein aggregation, dysregulation of the ubiquitin-proteasome system (UPS), oxidative stress, mitochondrial dysfunction, and disruption of the structural and functional integrity of synaptic connections, which eventually leads to neuronal loss. These features are shared with other neurodegenerative diseases (NDs). Currently, several inhibitors against negative regulators of HSF1, as well as HSF1 activators, are developed and hold promise to prevent neurodegeneration in HD and other NDs.

CONCLUSION

Understanding the role of HSF1 during protein aggregation and neurodegeneration in HD may help to develop therapeutic strategies that could be effective across different NDs.

Celastrol Targets Cullin-Associated and Neddylation-Dissociated 1 to Prevent Fibroblast-Myofibroblast Transformation against Pulmonary Fibrosis

Celastrol (CEL), a pentacyclic triterpene compound, has been proven to have a definite antipulmonary fibrosis effect. However, its direct targets for antipulmonary fibrosis remain unknown. In this study, we designed and synthesized a series of celastrol-based probes to identify the direct targets in human pulmonary fibroblasts using an activity-based protein profiling strategy. Among many fished targets, we identified a key protein, cullin-associated and neddylation-dissociated 1 (CAND1), which was involved in fibroblast-myofibroblast transformation (FMT). More importantly, we found that the inhibitory effect of celastrol on FMT is dependent on CAND1, through improving the interactions between CAND1 and Cullin1 to promote the activity of Skp1/Cullin1/F-box ubiquitin ligases. In silico studies and cysteine mutation experiments further demonstrated that Cys264 of CAND1 is the site for conjugation of celastrol. This reveals a new mechanism of celastrol against pulmonary fibrosis and may provide a novel therapeutic option for antipulmonary fibrosis.

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.

NF-κB: A Druggable Target in Acute Myeloid Leukemia

Simple Summary

AML is a highly heterogeneous hematological disease and is the second most common form of leukemia. Around 40% of AML patients display elevated nuclear NF-κB activity, providing a compelling rationale for targeting the NF-κB pathway in AML. Here we summarize the main drivers of the NF-κB pathway in AML pathogenesis as well as the conventional and novel therapeutic strategies targeting NF-κB to improve the survival of AML patients.

Abstract

Acute Myeloid Leukemia (AML) is an aggressive hematological malignancy that relies on highly heterogeneous cytogenetic alterations. Although in the last few years new agents have been developed for AML treatment, the overall survival prospects for AML patients are still gloomy and new therapeutic options are still urgently needed. Constitutive NF-κB activation has been reported in around 40% of AML patients, where it sustains AML cell survival and chemoresistance. Given the central role of NF-κB in AML, targeting the NF-κB pathway represents an attractive strategy to treat AML. This review focuses on current knowledge of NF-κB’s roles in AML pathogenesis and summarizes the main therapeutic approaches used to treat NF-κB-driven AML.

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

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

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

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

Induction of Paraptosis by Cyclometalated Iridium Complex-Peptide Hybrids and CGP37157 via a Mitochondrial Ca2+ Overload Triggered by Membrane Fusion between Mitochondria and the Endoplasmic Reticulum

We previously reported that a cyclometalated iridium (Ir) complex-peptide hybrid (IPH) 4 functionalized with a cationic KKKGG peptide unit on the 2-phenylpyridine ligand induces paraptosis, a relatively newly found programmed cell death, in cancer cells (Jurkat cells) via the direct transport of calcium (Ca²⁺) from the endoplasmic reticulum (ER) to mitochondria. Here, we describe that CGP37157, an inhibitor of a mitochondrial sodium (Na⁺)/Ca²⁺ exchanger, induces paraptosis in Jurkat cells via intracellular pathways similar to those induced by 4. The findings allow us to suggest that the induction of paraptosis by 4 and CGP37157 is associated with membrane fusion between mitochondria and the ER, subsequent Ca²⁺ influx from the ER to mitochondria, and a decrease in the mitochondrial membrane potential (ΔΨ_m). On the contrary, celastrol, a naturally occurring triterpenoid that had been reported as a paraptosis inducer in cancer cells, negligibly induces mitochondria-ER membrane fusion. Consequently, we conclude that the paraptosis induced by 4 and CGP37157 (termed paraptosis II herein) proceeds via a signaling pathway different from that of the previously known paraptosis induced by celastrol, a process that negligibly involves membrane fusion between mitochondria and the ER (termed paraptosis I herein).

Integrated Mass Spectrometry Reveals Celastrol As a Novel Catechol-O-methyltransferase Inhibitor

Natural product celastrol is known to have various biological activities, yet its molecular targets that correspond to many activities remain unclear. Here, we used multiple mass-spectrometry-based approaches to identify catechol-O-methyltransferase (COMT) as a major binding target of celastrol and characterized their interaction comprehensively. Celastrol was found to inhibit the enzymatic activity of COMT and increased the dopamine level in neuroendocrine chromaffin cells significantly. Our study not only revealed a novel binding target of celastrol but also provided a new scaffold and cysteine hot spot for developing new generation COMT inhibitors in combating neurological disorders.

Isolation of Bioactive Pentacyclic Triterpenoid Acids from Olive Tree Leaves with Flash Chromatography

The present study reports on the use of the flash chromatography for the isolation and purification of oleanolic and maslinic acids from olive leaf extracts. Although the separation and identification of these acids is considered challenging due to the similarity in their structure, oleanolic and maslinic acids were detected, identified, and separated. Solubility prediction was used to help to match compatibility of extraction solvent with targeted triterpenoid acids. Aqueous washing was used, to first selectively remove unwanted interferents from the extraction solvent. The extracts obtained with different solvents and solvent mixtures were fractionated using flash chromatography and then analyzed. HPTLC chromatography was used to assess collected fractions as either semi-pure or pure, and to identify the fractions containing oleanolic and maslinic acids. The yields of oleanolic and maslinic acids reported here are significantly higher than yields obtained in previously reported isolations. The presence and purity of oleanolic and maslinic acid in collected fractions was confirmed by ATR-FTIR and NMR spectrometry.

Synthesis and biological evaluation of celastrol derivatives as potential anti-glioma agents by activating RIP1/RIP3/MLKL pathway to induce necroptosis

Celastrol, a quinone methide triterpenoid, possesses potential anti-glioma activity. However, its relatively low activity limit its application as an effective agent for glioma treatment. In search for effective anti-glioma agents, this work designed and synthesized two series of celastrol C-3 OH and C-20 COOH derivatives 4a-4o and 6a-6o containing 1, 2, 3-triazole moiety. Their anti-glioma activities against four human glioma cell lines (A172, LN229, U87, and U251) were then evaluated using MTT assay in vitro. Results showed that compound 6i (IC₅₀ = 0.94 μM) exhibited substantial antiproliferative activity against U251 cell line, that was 4.7-fold more potent than that of celastrol (IC₅₀ = 4.43 μM). In addition, compound 6i remarkably inhibited the colony formation and migration of U251 cells. Further transmission electron microscopy and mitochondrial depolarization assays in U251 cells indicated that the potent anti-glioma activity of 6i was attributed to necroptosis. Mechanism investigation revealed that compound 6i induced necroptosis mainly by activating the RIP1/RIP3/MLKL pathway. Additionally, compound 6i exerted acceptable BBB permeability in mice and inhibited U251 cell proliferation in an in vivo zebrafish xenograft model, obviously. In summary, compound 6i might be a promising lead compound for potent celastrol derivatives as anti-glioma agents.

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

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

Tripterygium hypoglaucum (Lévl.) Hutch and Its Main Bioactive Components: Recent Advances in Pharmacological Activity, Pharmacokinetics and Potential Toxicity

Tripterygium hypoglaucum (Lévl.) Hutch (THH) is believed to play an important role in health care and disease treatment according to traditional Chinese medicine. Moreover, it is also the representative of medicine with both significant efficacy and potential toxicity. This characteristic causes THH hard for embracing and fearing. In order to verify its prospect for clinic, a wide variety of studies were carried out in the most recent years. However, there has not been any review about THH yet. Therefore, this review summarized its characteristic of components, pharmacological effect, pharmacokinetics and toxicity to comprehensively shed light on the potential clinical application. More than 120 secondary metabolites including terpenoids, alkaloids, glycosides, sugars, organic acids, oleanolic acid, polysaccharides and other components were found in THH based on phytochemical research. All these components might be the pharmacological bases for immunosuppression, anti-inflammatory and anti-tumour effect. In addition, recent studies found that THH and its bioactive compounds also demonstrated remarkable effect on obesity, insulin resistance, fertility and infection of virus. The main mechanism seemed to be closely related to regulation the balance of immune, inflammation, apoptosis and so on in various disease. Furthermore, the study of pharmacokinetics revealed quick elimination of the main component triptolide. The feature of celastrol was also investigated by several models. Finally, the side effect of THH was thought to be the key for its limitation in clinical application. A series of reports indicated that multiple organs or systems including liver, kidney and genital system were involved in the toxicity. Its potential serious problem in liver was paid specific attention in recent years. In summary, considering the significant effect and potential toxicity of THH as well as its components, the combined medication to inhibit the toxicity, maintain effect might be a promising method for clinical conversion. Modern advanced technology such as structure optimization might be another way to reach the efficacy and safety. Thus, THH is still a crucial plant which remains for further investigation.

GRAS-microparticle microarrays identify dendritic cell tolerogenic marker-inducing formulations

Microarrays, miniaturized platforms used for high-content studies, provide potential advantages over traditional in vitro investigation in terms of time, cost, and parallel analyses. Recently, microarrays have been leveraged to investigate immune cell biology by providing a platform with which to systematically investigate the effects of various agents on a wide variety of cellular processes, including those giving rise to immune regulation for application toward curtailing autoimmunity. A specific embodiment incorporates dendritic cells cultured on microarrays containing biodegradable microparticles. Such an approach allows immune cell and microparticle co-localization and release of compounds on small, isolated populations of cells, enabling a quick, convenient method to quantify a variety of cellular responses in parallel. In this study, the microparticle microarray platform was utilized to investigate a small library of sixteen generally regarded as safe (GRAS) compounds (ascorbic acid, aspirin, capsaicin, celastrol, curcumin, epigallocatechin-3-gallate, ergosterol, hemin, hydrocortisone, indomethacin, menadione, naproxen, resveratrol, retinoic acid, α-tocopherol, vitamin D3) for their ability to induce suppressive phenotypes in murine dendritic cells. Two complementary tolerogenic index ranking systems were proposed to summarize dendritic cell responses and suggested several lead compounds (celastrol, ergosterol, vitamin D3) and two secondary compounds (hemin, capsaicin), which warrant further investigation for applications toward suppression and tolerance.

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.

Gambogic acid and gambogenic acid induce a thiol-dependent heat shock response and disrupt the interaction between HSP90 and HSF1 or HSF2

Cancer cells rely on heat shock proteins (HSPs) for growth and survival. Especially HSP90 has multiple client proteins and plays a critical role in malignant transformation, and therefore different types of HSP90 inhibitors are being developed. The bioactive natural compound gambogic acid (GB) is a prenylated xanthone with antitumor activity, and it has been proposed to function as an HSP90 inhibitor. However, there are contradicting reports whether GB induces a heat shock response (HSR), which is cytoprotective for cancer cells and therefore a potentially problematic feature for an anticancer drug. In this study, we show that GB and a structurally related compound, called gambogenic acid (GBA), induce a robust HSR, in a thiol-dependent manner. Using heat shock factor 1 (HSF1) or HSF2 knockout cells, we show that the GB or GBA-induced HSR is HSF1-dependent. Intriguingly, using closed form ATP-bound HSP90 mutants that can be co-precipitated with HSF1, a known facilitator of cancer, we show that also endogenous HSF2 co-precipitates with HSP90. GB and GBA treatment disrupt the interaction between HSP90 and HSF1 and HSP90 and HSF2. Our study implies that these compounds should be used cautiously if developed for cancer therapies, since GB and its derivative GBA are strong inducers of the HSR, in multiple cell types, by involving the dissociation of a HSP90-HSF1/HSF2 complex.

Targeting the CDK6 Dependence of Ph+ Acute Lymphoblastic Leukemia

Ph+ ALL is a poor-prognosis leukemia subtype driven by the BCR-ABL1 oncogene, either the p190- or the p210-BCR/ABL isoform in a 70:30 ratio. Tyrosine Kinase inhibitors (TKIs) are the drugs of choice in the therapy of Ph+ ALL. In combination with standard chemotherapy, TKIs have markedly improved the outcome of Ph+ ALL, in particular if this treatment is followed by bone marrow transplantation. However, resistance to TKIs develops with high frequency, causing leukemia relapse that results in <5-year overall survival. Thus, new therapies are needed to address relapsed/TKI-resistant Ph+ ALL. We have shown that expression of cell cycle regulatory kinase CDK6, but not of the highly related CDK4 kinase, is required for the proliferation and survival of Ph+ ALL cells. Comparison of leukemia suppression induced by treatment with the clinically-approved dual CDK4/6 inhibitor palbociclib versus CDK6 silencing revealed that the latter treatment was markedly more effective, probably reflecting inhibition of CDK6 kinase-independent effects. Thus, we developed CDK4/6-targeted proteolysis-targeting chimeras (PROTACs) that preferentially degrade CDK6 over CDK4. One compound termed PROTAC YX-2-107, which degrades CDK6 by recruiting the Cereblon ubiquitin ligase, markedly suppressed leukemia burden in mice injected with de novo or TKI-resistant Ph+ ALL. The effect of PROTAC YX-2-107 was comparable or superior to that of palbociclib. The development of CDK6-selective PROTACs represents an effective strategy to exploit the “CDK6 dependence” of Ph+ ALL cells while sparing a high proportion of normal hematopoietic progenitors that depend on both CDK6 and CDK6 for their survival. In combination with other agents, CDK6-selective PROTACs may be valuable components of chemotherapy-free protocols for the therapy of Ph+ ALL and other CDK6-dependent hematological malignancies.

In vitro 3D phenotypic drug screen identifies celastrol as an effective in vivo inhibitor of polycystic kidney disease

Polycystic kidney disease (PKD) is a prevalent genetic disorder, characterized by the formation of kidney cysts that progressively lead to kidney failure. The currently available drug tolvaptan is not well tolerated by all patients and there remains a strong need for alternative treatments. The signaling rewiring in PKD that drives cyst formation is highly complex and not fully understood. As a consequence, the effects of drugs are sometimes difficult to predict. We previously established a high throughput microscopy phenotypic screening method for quantitative assessment of renal cyst growth. Here, we applied this 3D cyst growth phenotypic assay and screened 2320 small drug-like molecules, including approved drugs. We identified 81 active molecules that inhibit cyst growth. Multi-parametric phenotypic profiling of the effects on 3D cultured cysts discriminated molecules that showed preferred pharmacological effects above genuine toxicological properties. Celastrol, a triterpenoid from Tripterygium Wilfordii, was identified as a potent inhibitor of cyst growth in vitro. In an in vivo iKspCre-Pkd1^lox,lox mouse model for PKD, celastrol inhibited the growth of renal cysts and maintained kidney function.

The Therapeutic Potential of Celastrol in Central Nervous System Disorders: Highlights from In Vitro and In Vivo Approaches

Celastrol, the most abundant compound derived from the root of Tripterygium wilfordii, largely used in traditional Chinese medicine, has shown preclinical and clinical efficacy for a broad range of disorders, acting via numerous mechanisms, including the induction of the expression of several neuroprotective factors, the inhibition of cellular apoptosis, and the decrease of reactive oxygen species (ROS). Given the crucial implication of these pathways in the pathogenesis of Central Nervous System disorders, both in vitro and in vivo studies have focused their attention on the possible use of this compound in these diseases. However, although most of the available studies have reported significant neuroprotective effects of celastrol in cellular and animal models of these pathological conditions, some of these data could not be replicated. This review aims to discuss current in vitro and in vivo lines of evidence on the therapeutic potential of celastrol in neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases, amyotrophic lateral sclerosis, Huntington’s disease, multiple sclerosis, and cadmium-induced neurodegeneration, as well as in psychiatric disorders, such as psychosis and depression. In vitro and in vivo studies focused on celastrol effects in cerebral ischemia, ischemic stroke, traumatic brain injury, and epilepsy are also described.

Celastrol Attenuates Learning and Memory Deficits in an Alzheimer's Disease Rat Model

Alzheimer's disease (AD) is a chronic progressive neurodegenerative disorder that is associated with learning, memory, and cognitive deficits. Neuroinflammation and synapse loss are involved in the pathology of AD. Diverse measures have been applied to treat AD, but currently, there is no effective treatment. Celastrol (CEL) is a pentacyclic triterpene isolated from Tripterygium wilfordii Hook F that has been shown to enhance cell viability and inhibit amyloid-β production induced by lipopolysaccharides in vitro. In the present study, the protective effect of CEL on Aβ 25-35-induced rat model of AD was assessed. Our results showed that CEL administration at a dose of 2 mg/kg/day improved spatial memory in the Morris water maze. Further biochemical analysis showed that CEL treatment of intrahippocampal Aβ 25-35-microinjected rats attenuated hippocampal NF-κB activity; inhibited proinflammatory markers, namely, IL-1β, IL-6, and TNF-α; and upregulated anti-inflammatory factors, such as IL-4 and IL-10. Furthermore, CEL upregulated hippocampal neurexin-1β, neuroligin-1, CA1, and PSD95 expression levels, which may improve synaptic function. Simultaneously, CEL also increased glucose metabolism in Aβ 25-35-microinjected rats. In conclusion, CEL could exert protective effects against learning and memory decline induced by intrahippocampal Aβ 25-35 through anti-inflammation, promote synaptic development, and maintain hippocampal energy metabolism.

Natural Terpenoids as Neuroinflammatory Inhibitors in LPS-stimulated BV-2 Microglia

Neuroinflammation is a typical feature of many neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Microglia, the resident immune cells of the brain, readily become activated in response to an infection or an injury. Uncontrolled and overactivated microglia can release pro-inflammatory and cytotoxic factors and are the major culprits in neuroinflammation. Hence, research on novel neuroinflammatory inhibitors is of paramount importance for the treatment of neurodegenerative diseases. Bacterial lipopolysaccharide, widely used in the studies of brain inflammation, initiates several major cellular activities that critically contribute to the pathogenesis of neuroinflammation. This review will highlight the progress on terpenoids, an important and structurally diverse group of natural compounds, as neuroinflammatory inhibitors in lipopolysaccharidestimulated BV-2 microglial cells over the last 20 years.

Celastrol inhibits rheumatoid arthritis through the ROS-NF-κB-NLRP3 inflammasome axis

Emerging evidence indicates that NOD-like receptor protein 3 (NLRP3) inflammasome-induced inflammation plays a critical role in the pathogenesis of rheumatoid arthritis (RA). Celastrol (Cel) is a quinone-methylated triterpenoid extracted from Tripterygium wilfordii that is used to treat RA. However, researchers have not determined whether Cel exerts anti-RA effects by regulating the activation of the NLRP3 inflammasome. In the present study, complete Freund's adjuvant (CFA)- induced rats and human mononuclear macrophages (THP-1 cells) were used to explore the anti-RA effects of Cel and its underlying mechanism. Joint swelling, the arthritis index score, inflammatory cell infiltration, and synovial hyperplasia in CFA-induced rats were correspondingly reduced after Cel treatment. The secretion of interleukin (IL)-1β and IL-18 in the serum of CFA-induced rats and supernatants of THP-1 cells exposed to Cel was significantly decreased. These inhibitory effects occurred because Cel blocked the nuclear factor-kappa B (NF-κB) signaling pathway and inhibited the activation of the NLRP3 inflammasome. Furthermore, Cel inhibited reactive oxygen species (ROS) production induced by lipopolysaccharide (LPS) and adenosine triphosphate (ATP). We speculated that Cel relieves RA symptoms and inhibits inflammation by inhibiting the ROS-NF-κB-NLRP3 axis.

Identification of celastrol as a novel HIV-1 latency reversal agent by an image-based screen

Although current antiretroviral therapies (ART) are successful in controlling HIV-1 infection, a stable viral reservoir reactivates when ART is discontinued. Consequently, there is a major research effort to develop approaches to disrupt the latent viral reservoir and enhance the immune system’s ability to clear HIV-1. A number of small molecules, termed latency reversal agents (LRAs), have been identified which can reactivate latent HIV-1 in cell lines and patients’ cells ex vivo. However, clinical trials have suggested that combinations of LRAs will be required to efficiently reactivate HIV-1 in vivo, especially LRAs that act synergistically by functioning through distinct pathways. To identify novel LRAs, we used an image-based assay to screen a natural compound library for the ability to induce a low level of aggregation of resting primary CD4⁺ T cells from healthy donors. We identified celastrol as a novel LRA. Celastrol functions synergistically with other classes of LRA to reactivate latent HIV-1 in a Jurkat cell line, suggesting a novel mechanism in its LRA activity. Additionally, celastrol does not appear to activate resting CD4⁺ T cells at levels at which it can reactivate latent HIV-1. Celastrol appears to represent a novel class of LRAs and it therefore can serve as a lead compound for LRA development.

Celastrol in metabolic diseases: Progress and application prospects

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

Interactions with Commensal and Pathogenic Bacteria Induce HIV-1 Latency in Macrophages through Altered Transcription Factor Recruitment to the LTR

Macrophages are infected by HIV-1 in vivo and contribute to both viral spread and pathogenesis. Recent human and animal studies suggest that HIV-1-infected macrophages serve as a reservoir that contributes to HIV-1 persistence during anti-retroviral therapy. The ability of macrophages to serve as persistent viral reservoirs is likely influenced by the local tissue microenvironment, including interactions with pathogenic and commensal microbes. Here we show that the sexually transmitted pathogen Neisseria gonorrhoeae (GC) and the gut-associated microbe Escherichia coli (E. coli), which encode ligands for both Toll-like receptor 2 (TLR2) and TLR4, repressed HIV-1 replication in macrophages and thereby induced a state reminiscent of viral latency. This repression was mediated by signaling through TLR4 and the adaptor protein TRIF and was associated with increased production of type I interferons. Inhibiting TLR4 signaling, blocking type 1 interferon, or knocking-down TRIF reversed LPS- and GC-mediated repression of HIV-1. Finally, the repression of HIV-1 in macrophages was associated with the recruitment of interferon regulatory factor 8 (IRF8) to the interferon stimulated response element (ISRE) downstream of the 5' HIV-1 long terminal repeat (LTR). Our data indicate that IRF8 is responsible for repression of HIV-1 replication in macrophages in response to TRIF-dependent signaling during GC and E. coli co-infection. These findings highlight the potential role of macrophages as HIV-1 reservoirs as well as the role of the tissue microenvironment and co-infections as modulators of HIV-1 persistence.IMPORTANCE The major barrier toward the eradication of HIV-1 infection is the presence of a small reservoir of latently infected cells, which include CD4+ T cells and macrophages that escape immune-mediated clearance and the effects of anti-retroviral therapy. There remain crucial gaps in our understanding of the molecular mechanisms that lead to transcriptionally silent or latent HIV-1 infection of macrophages. The significance of our research is in identifying microenvironmental factors, such as commensal and pathogenic microbes, that can contribute to the establishment and maintenance of latent HIV-1 infection in macrophages. It is hoped that identifying key processes contributing to HIV-1 persistence in macrophages may ultimately lead to novel therapeutics to eliminate latent HIV-1 reservoirs in vivo.

Celastrol inhibits intestinal lipid absorption by reprofiling the gut microbiota to attenuate high-fat diet-induced obesity

Celastrol, a compound extracted from traditional Chinese medicine, has been reported as a potent anti-obesity agent with controversial mechanisms. Here both C57BL/6J and leptin-deficient (ob/ob) mice fed a high-fat diet (HFD) displayed body weight loss after celastrol therapy, opposing the previous viewpoint that celastrol improves obesity by sensitizing leptin signaling. More importantly, celastrol downregulated lipid transporters in the intestine, increased lipid excretion in feces, and reduced body weight gain in HFD mice. Meanwhile, analysis of gut microbiota revealed that celastrol altered the gut microbiota composition in HFD-fed mice, and modulating gut microbiota by antibiotics or fecal microbiota transplantation blocked the celastrol effect on intestinal lipid transport and body weight gain, suggesting a critical role of the gut microbiota composition in mediating the anti-obesity role of celastrol under HFD. Together, the findings revealed that celastrol reduces intestinal lipid absorption to antagonize obesity by resetting the gut microbiota profile under HFD feeding.

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Celastrol reduced intestinal lipid transporters and lipids absorption

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Celastrol reset gut microbiota profile to modulate intestinal lipid transport

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Celastrol attenuated obesity in leptin-deficient (ob/ob) mice fed high fat diet

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.

Assessment of NR4A Ligands That Directly Bind and Modulate the Orphan Nuclear Receptor Nurr1

Nurr1/NR4A2 is an orphan nuclear receptor transcription factor implicated as a drug target for neurological disorders including Alzheimer's and Parkinson's diseases. Previous studies identified small-molecule NR4A nuclear receptor modulators, but it remains unclear if these ligands affect transcription via direct binding to Nurr1. We assessed 12 ligands reported to affect NR4A activity for Nurr1-dependent and Nurr1-independent transcriptional effects and the ability to bind the Nurr1 ligand-binding domain (LBD). Protein NMR structural footprinting data show that amodiaquine, chloroquine, and cytosporone B bind the Nurr1 LBD; ligands that do not bind include C-DIM12, celastrol, camptothecin, IP7e, isoalantolactone, ethyl 2-[2,3,4-trimethoxy-6-(1-octanoyl)phenyl]acetate (TMPA), and three high-throughput screening hit derivatives. Importantly, ligands that modulate Nurr1 transcription also show Nurr1-independent effects on transcription in a cell type-specific manner, indicating that care should be taken when interpreting the functional response of these ligands in transcriptional assays. These findings should help focus medicinal chemistry efforts that desire to optimize Nurr1-binding ligands.

Interrelated Mechanism by Which the Methide Quinone Celastrol, Obtained from the Roots of Tripterygium wilfordii, Inhibits Main Protease 3CLpro of COVID-19 and Acts as Superoxide Radical Scavenger

We describe the potential anti coronavirus disease 2019 (COVID-19) action of the methide quinone inhibitor, celastrol. The related methide quinone dexamethasone is, so far, among COVID-19 medications perhaps the most effective drug for patients with severe symptoms. We observe a parallel redox biology behavior between the antioxidant action of celastrol when scavenging the superoxide radical, and the adduct formation of celastrol with the main COVID-19 protease. The related molecular mechanism is envisioned using molecular mechanics and dynamics calculations. It proposes a covalent bond between the S(Cys145) amino acid thiolate and the celastrol A ring, assisted by proton transfers by His164 and His41 amino acids, and a π interaction from Met49 to the celastrol B ring. Specifically, celastrol possesses two moieties that are able to independently scavenge the superoxide radical: the carboxylic framework located at ring E, and the methide-quinone ring A. The latter captures the superoxide electron, releasing molecular oxygen, and is the feature of interest that correlates with the mechanism of COVID-19 inhibition. This unusual scavenging of the superoxide radical is described using density functional theory (DFT) methods, and is supported experimentally by cyclic voltammetry and X-ray diffraction.

Drug discovery and formulation development for acute pancreatitis

Acute pancreatitis is a sudden inflammation and only last for a short time, but might lead to a life-threatening emergency. Traditional drug therapy is an essential supportive method for acute pancreatitis treatment, yet, failed to achieve satisfactory therapeutic outcomes. To date, it is still challenging to develop therapeutic medicine to redress the intricate microenvironment promptly in the inflamed pancreas, and more importantly, avoid multi-organ failure. The understanding of the acute pancreatitis, including the causes, mechanism, and severity judgment, could help the scientists bring up more effective intervention and treatment strategies. New formulation approaches have been investigated to precisely deliver therapeutics to inflammatory lesions in the pancreas, and some even could directly attenuate the pancreatic damages. In this review, we will briefly introduce the involved pathogenesis and underlying mechanisms of acute pancreatitis, as well as the traditional Chinese medicine and the new drug option. Most of all, we will summarize the drug delivery strategies to reduce inflammation and potentially prevent the further development of pancreatitis, with an emphasis on the bifunctional nanoparticles that act as both drug delivery carriers and therapeutics.

Inflammation-Targeted Celastrol Nanodrug Attenuates Collagen-Induced Arthritis through NF-κB and Notch1 Pathways

Rheumatoid arthritis (RA) is a systemic inflammatory disorder which can cause bone and cartilage damage leading to disability, yet the treatment remains unsatisfactory nowadays. Celastrol (Cel) has shown antirheumatic activity against RA. However, the frequent parenteral delivery and poor water solubility of Cel restrict its further therapeutic applications. Here, aiming at effectively overcoming the poor water solubility and short half-life of Cel to boost its beneficial effects for treating RA, we developed a polymeric micelle for Cel delivery based on a reactive oxygen species (ROS) sensitive polymer. Our results demonstrated that Cel may inhibit the repolarization of macrophages toward the pro-inflammatory M1 pheno-type via regulating the NF-κB and Notch1 pathways, which resulted in significantly decreased secretion of multiple pro-inflammatory cytokines to suppress the RA progression. Consequently, the Cel-loaded micelle effectively alleviated the major RA-associated symptoms including articular scores, ankle thickness, synovial inflammation, bone erosion, and cartilage degradation.

Lactoferrin-dual drug nanoconjugate: Synergistic anti-tumor efficacy of docetaxel and the NF-κB inhibitor celastrol

Despite the progress in cancer nanotherapeutics, some obstacles still impede the success of nanocarriers and hinder their clinical translation. Low drug loading, premature drug release, off-target toxicity and multi-drug resistance are among the most difficult challenges. Lactoferrin (LF) has demonstrated a great tumor targeting capacity via its high binding affinity to low density lipoprotein (LDL) and transferrin (Tf) receptors overexpressed by various cancer cells. Herein, docetaxel (DTX) and celastrol (CST) could be successfully conjugated to LF backbone for synergistic breast cancer therapy. Most importantly, the conjugate self-assembled forming nanoparticles of 157.8 nm with elevated loading for both drugs (6.94 and 5.98% for DTX and CST, respectively) without risk of nanocarrier instability. Moreover, the nanoconjugate demonstrated enhanced in vivo anti-tumor efficacy in breast cancer-bearing mice, as reflected by a reduction in tumor volume, prolonged survival rate and significant suppression of NF-κB p65, TNF-α, COX-2 and Ki-67 expression levels compared to the group given free combined DTX/CST therapy and to positive control. This study demonstrated the proof-of-principle for dual drug coupling to LF as a versatile nanoplatform that could augment their synergistic anticancer efficacy.

Combination of magnetic targeting with synergistic inhibition of NF-κB and glutathione via micellar drug nanomedicine enhances its anti-tumor efficacy

Breast cancer is not only one of the most prevalent types of cancer, but also it is a prime cause of death in women aged between 20 and 59. Although chemotherapy is the most common therapy approach, multiple side effects can result from lack of specificity and the use of overdose as safe doses may not completely cure cancer. Therefore, we aimed in this study is to combine the merits of NF-κB inhibiting potential of celastrol (CST) with glutathione inhibitory effect of sulfasalazine (SFZ) which prevents CST inactivation and thus enhances its anti-tumor activity. Inspired by the CD44-mediated tumor targeting effect of the hydrophilic polysaccharide chondroitin sulphate (ChS), we chemically synthesized amphiphilic zein-ChS micelles. While the water insoluble SFZ was chemically coupled to zein, CST was physically entrapped within the hydrophobic zein/SFZ micellar core. Moreover, physical encapsulation of oleic acid-capped SPIONs in the hydrophobic core of micelles enabled both magnetic tumor targeting as well as MRI theranostic capacity. Combining magnetic targeting to with the active targeting effect of ChS resulted in enhanced cellular internalization of the micelles in MCF-7 cancer cells and hence higher cytotoxic effect against MCF-7 and MDA-MB-231 breast cancer cells. In the in vivo experiments, magnetically-targeted micelles (154.4 nm) succeeded in achieving the lowest percentage increase in the tumor volume in tumor bearing mice, the highest percentage of tumor necrosis associated with significant reduction in the levels of TNF-α, Ki-67, NF-κB, VEGF, COX-2 markers compared to non-magnetically targeted micelles-, free drug-treated and positive control groups. Collectively, the developed magnetically targeted micelles pave the way for design of cancer nano-theranostic drug combinations.

Drainage of inflammatory macromolecules from the brain to periphery targets the liver for macrophage infiltration

Many brain pathologies are associated with liver damage, but a direct link has long remained elusive. Here, we establish a new paradigm for interrogating brain-periphery interactions by leveraging zebrafish for its unparalleled access to the intact whole animal for in vivo analysis in real time after triggering focal brain inflammation. Using traceable lipopolysaccharides (LPS), we reveal that drainage of these inflammatory macromolecules from the brain led to a strikingly robust peripheral infiltration of macrophages into the liver independent of Kupffer cells. We further demonstrate that this macrophage recruitment requires signaling from the cytokine IL-34 and Toll-like receptor adaptor MyD88, and occurs in coordination with neutrophils. These results highlight the possibility for circulation of brain-derived substances to serve as a rapid mode of communication from brain to the liver. Understanding how the brain engages the periphery at times of danger may offer new perspectives for detecting and treating brain pathologies.

Celastrol regulates bone marrow mesenchymal stem cell fate and bone-fat balance in osteoporosis and skeletal aging by inducing PGC-1α signaling

Celastrol has recently been identified as a prospective new treatment for obesity and several metabolic complications. However, the effect of Celastrol in osteoporosis (OP) remains unknown. In this study, we demonstrated that Celastrol promotes osteoblast differentiation and prevents adipocyte differentiation in bone marrow mesenchymal stem cells (BM-MSCs) in vitro. Mechanistically, Celastrol was able to control the differentiation of BM-MSCs by stimulating PGC-1α signaling. Moreover, administration of Celastrol could alleviate bone loss and bone marrow adipose tissue (MAT) accumulation in ovariectomized (OVX) mice and aged mice. Together, these results recommended that Celastrol could regulate BM-MSCs fate and bone-fat balance in OP and skeletal aging by stimulating PGC-1α, which might act as a possible therapeutic target for OP and for the prevention of skeletal aging.

Synthesis of celastrol derivatives as potential non-nucleoside hepatitis B virus inhibitors

A series of para-quinone methide (pQM) moiety and C-20- modified derivatives of celastrol were synthesized and evaluated for their inhibitory effect on the secretion of HBsAg and HBeAg as well as the inhibitory effect against HBV DNA replication. The results suggested that amidation of C-20 carboxylic group could generate derivatives with good anti-HBV profile, among them compound 14 showed the best inhibitory activity on the secretion of HBsAg (IC₅₀  = 11.9 µμ) and HBeAg (IC₅₀  = 13.1 µμ) with SI of 3.3 and 3.0, respectively. In addition, 14 also showed potent inhibitory effect against HBV DNA replication (48.5 ± 15.1%, 25 µM). This is, to our knowledge, the first report of celastrol derivatives as potential non-nucleoside HBV inhibitors.

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.

Structure-Activity-Relationship and Mechanistic Insights for Anti-HIV Natural Products

Acquired Immunodeficiency Syndrome (AIDS), which chiefly originatesfroma retrovirus named Human Immunodeficiency Virus (HIV), has impacted about 70 million people worldwide. Even though several advances have been made in the field of antiretroviral combination therapy, HIV is still responsible for a considerable number of deaths in Africa. The current antiretroviral therapies have achieved success in providing instant HIV suppression but with countless undesirable adverse effects. Presently, the biodiversity of the plant kingdom is being explored by several researchers for the discovery of potent anti-HIV drugs with different mechanisms of action. The primary challenge is to afford a treatment that is free from any sort of risk of drug resistance and serious side effects. Hence, there is a strong demand to evaluate drugs derived from plants as well as their derivatives. Several plants, such as Andrographis paniculata, Dioscorea bulbifera, Aegle marmelos, Wistaria floribunda, Lindera chunii, Xanthoceras sorbifolia and others have displayed significant anti-HIV activity. Here, weattempt to summarize the main results, which focus on the structures of most potent plant-based natural products having anti-HIV activity along with their mechanisms of action and IC50 values, structure-activity-relationships and important key findings.

Therapeutic targets of thunder god vine (Tripterygium wilfordii hook) in rheumatoid arthritis (Review)

Celastrol and triptolide, chemical compounds isolated from Tripterygium wilfordii hook (also known as thunder god vine), are effective against rheumatoid arthritis (RA). Celastrol targets numerous signaling pathways involving NF‑κB, endoplasmic reticulum Ca2+‑ATPase, myeloid differentiation factor 2, toll‑like receptor 4, pro‑inflammatory chemokines, DNA damage, cell cycle arrest and apoptosis. Triptolide, inhibits NF‑κB, the receptor activator of NF‑κB (RANK)/RANK ligand/osteoprotegerin signaling pathway, cyclooxygenase‑2, matrix metalloproteases and cytokines. The present review examined the chemistry and bioavailability of celastrol and triptolide, and their molecular targets in treating RA. Clinical studies have demonstrated that T. wilfordii has several promising bioactivities, but its multi‑target toxicity has restricted its application. Thus, dosage control and structural modification of T. wilfordii are required to reduce the toxicity. In this review, future directions for research into these promising natural products are discussed.