Celastrol-Induced Nur77 Interaction with TRAF2 Alleviates Inflammation by Promoting Mitochondrial Ubiquitination and Autophagy

Nur77 increases mitophagy and decreases aggregation of α-synuclein by modulating the p-c-Abl/p-PHB2 Y121 in α-synuclein PFF SH-SY5Y cells and mice

Parkinson's disease (PD) is characterized by the progressive death of dopamine (DA) neurons and the pathological accumulation of α-synuclein (α-syn) fibrils. In our previous study, simulated PHB2 phosphorylation was utilized to clarify the regulatory role of c-Abl in PHB2-mediated mitophagy in PD models. In this investigation, we employed an independently patented PHB2Y121 phosphorylated antibody in the PD model to further verify that the c-Abl inhibitor STI571 can impede PHB2Y121 phosphorylation, decrease the formation of α-Syn polymers, and improve autophagic levels. The specific involvement of Nur77 in PD pathology has remained elusive. We also investigate the contribution of Nur77, a nuclear transcription factor, to α-syn and mitophagy in PD. Our findings demonstrate that under α-syn, Nur77 translocates from the cytoplasm to the mitochondria, improving PHB-mediated mitophagy by regulating c-Abl phosphorylation. Moreover, Nur77 overexpression alleviates the expression level of pS129-α-syn and the loss of DA neurons in α-syn PFF mice, potentially associated with the p-c-Abl/p-PHB2 Y121 axis. This study provides initial in vivo and in vitro evidence that Nur77 protects PD DA neurons by modulating the p-c-Abl/p-PHB2 Y121 axis, and STI571 holds promise as a treatment for PD.

Spinosin inhibits activated hepatic stellate cell to attenuate liver fibrosis by targeting Nur77/ASK1/p38 MAPK signaling pathway

AIM

Liver fibrosis remains a great challenge in the world. Spinosin (SPI), a natural flavonoid-C-glycoside, possesses various pharmacological activities including anti-inflammatory and anti-myocardial fibrosis effects. In this study, we investigate whether SPI can be a potential lead for the treatment of liver fibrosis and explore whether the orphan nuclear receptor Nur77, a negative regulator of liver fibrosis development, plays a critical role in SPI's action.

METHODS

A dual luciferase reporter system of α-SMA was established to evaluate the effect of SPI on hepatic stellate cell (HSC) activation in LX2 and HSC-T6 cells. A mouse model of CCl4-induced liver fibrosis was used to test the efficacy of SPI against liver fibrosis. The expression levels of Nur77, inflammatory cytokines and collagen were determined by Western blotting and qPCR. Potential kinase pathways involved were also analyzed. The affinity of Nur77 with SPI was documented by fluorescence titration.

RESULTS

SPI can strongly suppress TGF-β1-mediated activation of both LX2 and HSC-T6 cells in a dose-dependent manner. SPI increases the expression of Nur77 and reduces TGF-β1-mediated phosphorylation levels of ASK1 and p38 MAPK, which can be reversed by knocking out of Nur77. SPI strongly inhibits collagen deposition (COLA1) and reduces inflammatory cytokines (IL-6 and IL-1β), which is followed by improved liver function in the CCl4-induced mouse model. SPI can directly bind to R515 and R563 in the Nur77-LBD pocket with a Kd of 2.14 μM.

CONCLUSION

Spinosin is the major pharmacological active component of Ziziphus jujuba Mill. var. spinosa which has been frequently prescribed in traditional Chinese medicine. We demonstrate here for the first time that spinosin is a new therapeutic lead for treatment of liver fibrosis by targeting Nur77 and blocking the ASK1/p38 MAPK signaling pathway.

PROTAC-mediated NR4A1 degradation as a novel strategy for cancer immunotherapy

An effective cancer therapy requires killing cancer cells and targeting the tumor microenvironment (TME). Searching for molecules critical for multiple cell types in the TME, we identified NR4A1 as one such molecule that can maintain the immune suppressive TME. Here, we establish NR4A1 as a valid target for cancer immunotherapy and describe a first-of-its-kind proteolysis-targeting chimera (PROTAC, named NR-V04) against NR4A1. NR-V04 degrades NR4A1 within hours in vitro and exhibits long-lasting NR4A1 degradation in tumors with an excellent safety profile. NR-V04 inhibits and frequently eradicates established tumors. At the mechanistic level, NR-V04 induces the tumor-infiltrating (TI) B cells and effector memory CD8+ T (Tem) cells and reduces monocytic myeloid-derived suppressor cells (m-MDSC), all of which are known to be clinically relevant immune cell populations in human melanomas. Overall, NR-V04-mediated NR4A1 degradation holds promise for enhancing anticancer immune responses and offers a new avenue for treating various types of cancers such as melanoma.

Phase separation of Nur77 mediates XS561-induced apoptosis by promoting the formation of Nur77/Bcl-2 condensates

The orphan nuclear receptor Nur77 is a critical regulator of the survival and death of tumor cells. The pro-death effect of Nur77 can be regulated by its interaction with Bcl-2, resulting in conversion of Bcl-2 from a survival to killer. As Bcl-2 is overexpressed in various cancers preventing them from apoptosis and promoting their resistance to chemotherapy, targeting the apoptotic pathway of Nur77/Bcl-2 may lead to new cancer therapeutics. Here, we report our identification of XS561 as a novel Nur77 ligand that induces apoptosis of tumor cells by activating the Nur77/Bcl-2 pathway. In vitro and animal studies revealed an apoptotic effect of XS561 in a range of tumor cell lines including MDA-MB-231 triple-negative breast cancer (TNBC) and MCF-7/LCC2 tamoxifen-resistant breast cancer (TAMR) in a Nur77-dependent manner. Mechanistic studies showed XS561 potently induced the translocation of Nur77 from the nucleus to mitochondria, resulting in mitochondria-related apoptosis. Interestingly, XS561-induced accumulation of Nur77 at mitochondria was associated with XS561 induction of Nur77 phase separation and the formation of Nur77/Bcl-2 condensates. Together, our studies identify XS561 as a new activator of the Nur77/Bcl-2 apoptotic pathway and reveal a role of phase separation in mediating the apoptotic effect of Nur77 at mitochondria.

Recent advances in drug delivery of celastrol for enhancing efficiency and reducing the toxicity

Celastrol is a quinone methyl triterpenoid monomeric ingredient extracted from the root of Tripterygium wilfordii. Celastrol shows potential pharmacological activities in various diseases, which include inflammatory, obesity, cancer, and bacterial diseases. However, the application prospect of celastrol is largely limited by its low bioavailability, poor water solubility, and undesired off-target cytotoxicity. To address these problems, a number of drug delivery methods and technologies have been reported to enhance the efficiency and reduce the toxicity of celastrol. We classified the current drug delivery technologies into two parts. The direct chemical modification includes nucleic acid aptamer-celastrol conjugate, nucleic acid aptamer-dendrimer-celastrol conjugate, and glucolipid-celastrol conjugate. The indirect modification includes dendrimers, polymers, albumins, and vesicular carriers. The current technologies can covalently bond or encapsulate celastrol, which improves its selectivity. Here, we present a review that focalizes the recent advances of drug delivery strategies in enhancing the efficiency and reducing the toxicity of celastrol.

Natural compounds as obesity pharmacotherapies

Obesity has become a serious global public health problem, affecting over 988 million people worldwide. Nevertheless, current pharmacotherapies have proven inadequate. Natural compounds have garnered significant attention due to their potential antiobesity effects. Over the past three decades, ca. 50 natural compounds have been evaluated for the preventive and/or therapeutic effects on obesity in animals and humans. However, variations in the antiobesity efficacies among these natural compounds have been substantial, owing to differences in experimental designs, including variations in animal models, dosages, treatment durations, and administration methods. The feasibility of employing these natural compounds as pharmacotherapies for obesity remained uncertain. In this review, we systematically summarized the antiobesity efficacy and mechanisms of action of each natural compound in animal models. This comprehensive review furnishes valuable insights for the development of antiobesity medications based on natural compounds.

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.

Discovery of 5-(Pyrimidin-2-ylamino)-1H-indole-2-carboxamide Derivatives as Nur77 Modulators with Selective and Potent Activity Against Triple-Negative Breast Cancer

The orphan nuclear receptor Nur77 has been validated as a potential drug target for treating breast cancer. Therefore, focusing on the SAR study of the lead 8b (KDSPR(Nur77) = 354 nM), we found the active compound ja which exhibited improved Nur77-binding capability (KDSPR(Nur77) = 91 nM) and excellent antiproliferative activities against breast cancer cell lines. Interestingly, ja acted as a potent and selective Nur77 antagonist, displaying good potency against triple-negative breast cancer (TNBC) cell lines but did not inhibit human normal breast cancer cell line MCF-10A (SI > 20). Exceptionally, ja Nur77-dependently caused mitochondria dysfunction and induced the caspase-dependent apoptosis by mediating the TP53 phosphorylation pathway. Moreover, ja significantly suppressed MDA-MB-231 xenograft tumor growth but had no apparent side effects in mice and zebrafish. Overall, ja demonstrated to be the first Nur77 modulator mediating the TP53 phosphorylation pathway that has the potential as a novel anticancer agent for TNBC.

Celastrol as an intestinal FXR inhibitor triggers tripolide-induced intestinal bleeding: Underlying mechanism of gastrointestinal injury induced by Tripterygium wilfordii

BACKGROUND

Tripterygium wilfordii has been widely used for the treatment of rheumatoid arthritis, which is frequently accompanied by severe gastrointestinal damage. The molecular mechanism underlying the gastrointestinal injury of Tripterygium wilfordii are yet to be elucidated.

METHODS

Transmission electron microscopy, and pathological and biochemical analyses were applied to assess intestinal bleeding. Metabolic changes in the serum and intestine were determined by metabolomics. In vivo (time-dependent effect and dose-response) and in vitro (double luciferase reporter gene system, DRATs, molecular docking, HepG2 cells and small intestinal organoids) studies were used to identify the inhibitory role of celastrol on intestinal farnesoid X receptor (FXR) signaling. Fxr-knockout mice and FXR inhibitors and agonists were used to evaluate the role of FXR in the intestinal bleeding induced by Tripterygium wilfordii.

RESULTS

Co-treatment with triptolide + celastrol (from Tripterygium wilfordii) induced intestinal bleeding in mice. Metabolomic analysis indicated that celastrol suppressed intestinal FXR signaling, and further molecular studies revealed that celastrol was a novel intestinal FXR antagonist. In Fxr-knockout mice or the wild-type mice pre-treated with pharmacological inhibitors of FXR, triptolide alone could activate the duodenal JNK pathway and induce intestinal bleeding, which recapitulated the pathogenic features obtained by co-treatment with triptolide and celastrol. Lastly, intestinal bleeding induced by co-treatment with triptolide and celastrol could be effectively attenuated by the FXR or gut-restricted FXR agonist through downregulation of the duodenal JNK pathway.

CONCLUSIONS

The synergistic effect between triptolide and celastrol contributed to the gastrointestinal injury induced by Tripterygium wilfordii via dysregulation of the FXR-JNK axis, suggesting that celastrol should be included in the quality standards system for evaluation of Tripterygium wilfordii preparations. Determining the mechanism of the FXR-JNK axis in intestinal bleeding could aid in the identification of additional therapeutic targets for the treatment of gastrointestinal hemorrhage diseases. This study also provides a new standard for the quality assessment of Tripterygium wilfordii used in the treatment of gastrointestinal disorders.

Pyroptosis in neurodegenerative diseases: from bench to bedside

The central nervous system regulates all aspects of physiology to some extent. Neurodegenerative diseases (NDDs) lead to the progressive loss and dysfunction of neurons, which are particularly evident in Alzheimer's disease, Parkinson's disease, and many other conditions. NDDs are multifactorial diseases with complex pathogeneses, and there has been a rapid increase in the prevalence of NDDs. However, none of these diseases can be cured, making the development of novel treatment strategies an urgent necessity. Numerous studies have indicated how pyroptosis induces inflammation and affects many aspects of NDD. Therefore, components related to pyroptosis are potential therapeutic candidates and are attracting increasing attention. Here, we review the role of pyroptosis in the pathogenesis of NDDs and potential treatment options. Additionally, several of the current drugs and relevant inhibitors are discussed. Through this article, we provide theoretical support for exploring new therapeutic targets and updating clinical treatment strategies for NDDs. Notably, pyroptosis, a recently widely studied mode of cell death, is still under-researched compared to other traditional forms of cell death. Moreover, the focus of research has been on the onset and progression of NDDs, and the lack of organ-specific target discovery and drug development is a common problem for many basic studies. This urgent problem requires scientists and companies worldwide to collaborate in order to develop more effective drugs against NDDs.

COG1410 regulates microglial states and protects retinal ganglion cells in retinal ischemia-reperfusion injury

Progressive loss of retinal ganglion cells (RGCs) caused by retinal ischemia-reperfusion (IR) injury can lead to irreversible vision impairment, with neuroinflammatory responses playing an important role in this process. COG1410, a mimetic peptide of apolipoprotein E, has demonstrated protective potential in the central nervous system, but its effects on retinal IR injury remain unexplored. In this study, we established a mouse model of retinal IR injury to investigate the effects of COG1410 on retinal microglia and RGCs. We observed CD16/32-marked and CD206-marked microglia and RGCs using immunofluorescence staining, detected the expression of inflammatory factors by PCR, and evaluated retinal apoptosis with TUNEL staining. We further investigated the potential mechanism by detecting the expression of key proteins via Western blot. The results reveal that COG1410 decreased the number of CD16/32-marked microglia and increased the number of CD206-marked microglia, alleviated the expression of IL-1β and TNF-α, and reduced the loss of RGCs by inhibiting the mitochondrial-related apoptotic pathway. COG1410 was found to increase the expression of ERK1/2 and Nr4a1 but decrease the expression of NF-κB. The expression of TREM2 showed an increasing trend after COG1410 administration, but it was not statistically significant. In conclusion, COG1410 regulates microglial states and protects RGCs in retinal IR injury, showing promising potential for the treatment of eye diseases.

Precise delivery of celastrol by PEGylated aptamer dendrimer nanoconjugates for enormous therapeutic effect via superior intratumor penetration over antibody counterparts

Antibody-coated nanoparticles have been reported to have the extremely low delivery efficiency in solid tumors in preclinical trials. Though aptamers were considered to be superior over antibodies in cancer theranostics, whether PEGylated aptamer nanoparticles are better than antibody nanoparticles in improving delivery specificity and penetration efficiency of chemotherapeutics is still unknown. Here, we conjugate celastrol, a natural product with anti-tumor effect, onto PEGylated EpCAM aptamer or antibody dendrimers to obtain two nanoconjugates, and for the first time, conduct a comprehensive study to compare their performance in delivery specificity, intratumoral penetration ability and therapeutic outcomes. Our results showed that compared to antibody counterparts, PEGylated aptamer nanoconjugates exhibited the enhanced accumulation and retention specificities at tumor sites and the stronger intratumoral penetration capabilities by reducing the macrophage reservoir effects in solid tumors. When delivered celastrol to a colorectal xenograft tumor mice model by PEGylated aptamer dendrimers, 20 % of enhanced therapeutic efficiency was achieved compared to that by antibody-modified ones. Moreover, celastrol at 2 mg/kg delivered by PEGylated aptamer dendrimers showed the prominent anticancer efficiency (nearly 92 %) but without obvious side effects. These data firstly provide the proof-of-concept implementation that PEGylated aptamer nanoconjugates will display the great potential in the effective and safe cancer treatment with regard to the superiority over antibody ones in penetration abilities.

A comprehensive review of Tripterygium wilfordii hook. f. in the treatment of rheumatic and autoimmune diseases: Bioactive compounds, mechanisms of action, and future directions

Rheumatic and autoimmune diseases are a group of immune system-related disorders wherein the immune system mistakenly attacks and damages the body's tissues and organs. This excessive immune response leads to inflammation, tissue damage, and functional impairment. Therapeutic approaches typically involve medications that regulate immune responses, reduce inflammation, alleviate symptoms, and target specific damaged organs. Tripterygium wilfordii Hook. f., a traditional Chinese medicinal plant, has been widely studied in recent years for its application in the treatment of autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis. Numerous studies have shown that preparations of Tripterygium wilfordii have anti-inflammatory, immunomodulatory, and immunosuppressive effects, which effectively improve the symptoms and quality of life of patients with autoimmune diseases, whereas the active metabolites of T. wilfordii have been demonstrated to inhibit immune cell activation, regulate the production of inflammatory factors, and modulate the immune system. However, although these effects contribute to reductions in inflammatory responses and the suppression of autoimmune reactions, as well as minimize tissue and organ damage, the underlying mechanisms of action require further investigation. Moreover, despite the efficacy of T. wilfordii in the treatment of autoimmune diseases, its toxicity and side effects, including its potential hepatotoxicity and nephrotoxicity, warrant a thorough assessment. Furthermore, to maximize the therapeutic benefits of this plant in the treatment of autoimmune diseases and enable more patients to utilize these benefits, efforts should be made to strengthen the regulation and standardized use of T. wilfordii.

Overview of Ursolic Acid Potential for the Treatment of Metabolic Disorders, Autoimmune Diseases, and Cancers via Nuclear Receptor Pathways

Nuclear receptors (NRs) form a family of druggable transcription factors that are regulated by ligand binding to orchestrate multifaceted physiological functions, including reproduction, immunity, metabolism, and growth. NRs represent attractive and valid targets for the management and treatment of a vast array of ailments. Pentacyclic triterpenes (PTs) are ubiquitously distributed natural products in medicinal and aromatic plants, of which ursolic acid (UA) is an extensively studied member, due to its diverse bio-pertinent activities against different cancers, inflammation, aging, obesity, diabetes, dyslipidemia, and liver injury. In fact, PTs share a common lipophilic structure that resembles NRs' endogenous ligands. Herein, we present a review of the literature on UA's effect on NRs, showcasing the resulting health benefits and potential therapeutic outcomes. De facto, UA exhibited numerous pharmacodynamic effects on PPAR, LXR, FXR, and PXR, resulting in remarkable anti-inflammatory, anti-hyperlipidemic, and hepatoprotective properties, by lowering lipid accumulation in hepatocytes and mitigating non-alcoholic steatohepatitis (NASH) and its subsequent liver fibrosis. Furthermore, UA reversed valproate and rifampicin-induced hepatic lipid accumulation. Additionally, UA showed great promise for the treatment of autoimmune inflammatory diseases such as multiple sclerosis and autoimmune arthritis by antagonizing RORγ. UA exhibited antiproliferative effects against skin, prostate, and breast cancers, partially via PPARα and RORγ pathways. Herein, for the first time, we explore and provide insights into UA bioactivity with respect to NR modulation.

NR4A1 Aggravates Myocardial Ischaemia-Reperfusion Injury by Inhibiting OPA1-Mediated Mitochondrial Fusion

Mitochondrial fusion is an important process that protects the myocardium. However, mitochondrial fusion is often inhibited in myocardial ischaemia-reperfusion injury (IR). The upstream mechanism of this effect is unclear. Nuclear receptor subfamily 4 group A member 1 (NR4A1) can aggravate myocardial IR and increase the level of oxidative stress, thereby affecting mitochondrial function and morphology. Inhibiting NR4A1 can improve oxidative stress levels and mitochondrial function and morphology, thereby reducing IR. Downregulating NR4A1 increases the expression level of the mitochondrial fusion-related protein optic atrophy 1 (OPA1), which is associated with these benefits. Inhibiting OPA1 expression with MYLS22 abrogates the effects of NR4A1 downregulation on IR. Furthermore, NR4A1 disrupts mitochondrial dynamics and activates the STING and NF-κB pathways. Insufficient mitochondrial fusion and increased apoptosis and inflammatory reactions worsen irreversible damage to cardiomyocytes. In conclusion, NR4A1 can exacerbate IR by inhibiting OPA1, causing mitochondrial damage.

Crotonylated BEX2 interacts with NDP52 and enhances mitophagy to modulate chemotherapeutic agent-induced apoptosis in non-small-cell lung cancer cells

Brain expressed X-linked gene 2 (BEX2) encoded protein was originally identified to promote transcription by interacting with several transcription factors in the DNA-binding complexes. Recently, BEX2 was found to be localized in cytosol and/or mitochondria and regulate apoptosis in cancer cells and tumor growth. However, the molecular mechanism underlying its roles in cancer cells remains unclear. Here, we report that crotonylated BEX2 plays an important role in inhibiting chemotherapeutic agent-induced apoptosis via enhancing mitophagy in human lung cancer cells. BEX2 promotes mitophagy by facilitating interaction between NDP52 and LC3B. Moreover, BEX2 crotonylation at K59 is critical in the BEX2-mediated mitophagy in lung cancer cells. The K59R mutation of BEX2 inhibits mitophagy by affecting the interaction of NDP52 and LC3B. BEX2 expression is elevated after anticancer drug treatment, and its overexpression inhibits chemotherapy-induced apoptosis. In addition, inhibition of BEX2-regulated mitophagy sensitizes tumor cells to apoptosis. Furthermore, BEX2 promotes tumor growth and inhibits apoptosis by regulating mitophagy in vivo. We also confirm that BEX2 is overexpressed in lung adenocarcinoma and is associated with poor prognosis in lymph node metastasis-free cancer. Therefore, combination treatment with pharmaceutical approaches targeting BEX2-induced mitophagy and anticancer drugs may represent a potential strategy for NSCLC therapy.

Harnessing Oleanolic Acid and Its Derivatives as Modulators of Metabolic Nuclear Receptors

Nuclear receptors (NRs) constitute a superfamily of ligand-activated transcription factors with a paramount role in ubiquitous physiological functions such as metabolism, growth, and reproduction. Owing to their physiological role and druggability, NRs are deemed attractive and valid targets for medicinal chemists. Pentacyclic triterpenes (PTs) represent one of the most important phytochemical classes present in higher plants, where oleanolic acid (OA) is the most studied PTs representative owing to its multitude of biological activities against cancer, inflammation, diabetes, and liver injury. PTs possess a lipophilic skeleton that imitates the NRs endogenous ligands. Herein, we report a literature overview on the modulation of metabolic NRs by OA and its semi-synthetic derivatives, highlighting their health benefits and potential therapeutic applications. Indeed, OA exhibited varying pharmacological effects on FXR, PPAR, LXR, RXR, PXR, and ROR in a tissue-specific manner. Owing to these NRs modulation, OA showed prominent hepatoprotective properties comparable to ursodeoxycholic acid (UDCA) in a bile duct ligation mice model and antiatherosclerosis effect as simvastatin in a model of New Zealand white (NZW) rabbits. It also demonstrated a great promise in alleviating non-alcoholic steatohepatitis (NASH) and liver fibrosis, attenuated alpha-naphthol isothiocyanate (ANIT)-induced cholestatic liver injury, and controlled blood glucose levels, making it a key player in the therapy of metabolic diseases. We also compiled OA semi-synthetic derivatives and explored their synthetic pathways and pharmacological effects on NRs, showcasing their structure-activity relationship (SAR). To the best of our knowledge, this is the first review article to highlight OA activity in terms of NRs modulation.

Orphan nuclear receptor nr4a1 regulates winter depression-like behavior in medaka

About 10% of the population suffers from depression in winter at high latitude. Although it has become a serious public health issue, its underlying mechanism remains unknown and new treatments and therapies are required. As an adaptive strategy, many animals also exhibit depression-like behavior in winter. Previously, it has been reported that celastrol, a traditional Chinese medicine, can rescue winter depression-like behavior in medaka, an excellent model of winter depression. Nuclear receptor subfamily 4 group A member 1 (nr4a1, also known as nur77) is a known target of celastrol, and the signaling pathway of nr4a1 was suggested to be inactive in medaka brain during winter, implying the association of nr4a1 and winter depression-like behavior. However, the direct evidence for its involvement in winter depression-like behavior remains unclear. The present study found that nr4a1 was suppressed in the medaka brain under winter conditions. Cytosporone B, nr4a1 chemical activator, reversed winter depression-like behavior under winter conditions. Additionally, nr4a1 mutant fish generated by CRISPR/Cas9 system showed decreased sociability under summer conditions. Therefore, our results demonstrate that the seasonal regulation of nr4a1 regulates winter depression-like behavior and offers potential therapeutic target.

Piperlongumine is a ligand for the orphan nuclear receptor 4A1 (NR4A1)

Piperlongumine and derivatives are being developed as anticancer agents which act primarily as inducers of reactive oxygen species (ROS) in cancer cell lines. Many of the anticancer activities of piperlongumine resemble those observed for bis-indole derived compounds that bind the orphan nuclear receptor 4A1 (NR4A1) and act as inverse receptor agonists to inhibit NR4A1-regulated pro-oncogenic pathways and genes. In this study we show that like other NR4A1 inverse agonists piperlongumine inhibited RKO, SW480 and HCT116 colon cancer cell growth migration and invasion and induced apoptosis. Piperlongumine also downregulated the pro-reductant isocitrate dehydrogenase 1 (IDH1) and thioredoxin domain-containing 5 (TXNDC5) gene products resulting in the induction of ROS as previously observed for other inverse NR4A1 agonists. ROS also induced sestrin2 and this resulted in activation of AMPK phosphorylation and inhibition of mTOR pathway signaling. It has previously been reported that these pathways/genes are also regulated by inverse NR4A1 agonists or by knockdown of NR4A1. We also observed that piperlongumine directly bound NR4A1, inhibited NR4A1-dependent transactivation and interactions of the NR4A1/Sp1 complex bound to the GC-rich promoter of the NR4A1-regulated G9a gene.

Biosynthesis and biotechnological production of the anti-obesity agent celastrol

Obesity is a major health risk still lacking effective pharmacological treatment. A potent anti-obesity agent, celastrol, has been identified in the roots of Tripterygium wilfordii. However, an efficient synthetic method is required to better explore its biological utility. Here we elucidate the 11 missing steps for the celastrol biosynthetic route to enable its de novo biosynthesis in yeast. First, we reveal the cytochrome P450 enzymes that catalyse the four oxidation steps that produce the key intermediate celastrogenic acid. Subsequently, we show that non-enzymatic decarboxylation-triggered activation of celastrogenic acid leads to a cascade of tandem catechol oxidation-driven double-bond extension events that generate the characteristic quinone methide moiety of celastrol. Using this acquired knowledge, we have developed a method for producing celastrol starting from table sugar. This work highlights the effectiveness of combining plant biochemistry with metabolic engineering and chemistry for the scalable synthesis of complex specialized metabolites.

Natural compounds targeting nuclear receptors for effective cancer therapy

Human nuclear receptors (NRs) are a family of forty-eight transcription factors that modulate gene expression both spatially and temporally. Numerous biochemical, physiological, and pathological processes including cell survival, proliferation, differentiation, metabolism, immune modulation, development, reproduction, and aging are extensively orchestrated by different NRs. The involvement of dysregulated NRs and NR-mediated signaling pathways in driving cancer cell hallmarks has been thoroughly investigated. Targeting NRs has been one of the major focuses of drug development strategies for cancer interventions. Interestingly, rapid progress in molecular biology and drug screening reveals that the naturally occurring compounds are promising modern oncology drugs which are free of potentially inevitable repercussions that are associated with synthetic compounds. Therefore, the purpose of this review is to draw our attention to the potential therapeutic effects of various classes of natural compounds that target NRs such as phytochemicals, dietary components, venom constituents, royal jelly-derived compounds, and microbial derivatives in the establishment of novel and safe medications for cancer treatment. This review also emphasizes molecular mechanisms and signaling pathways that are leveraged to promote the anti-cancer effects of these natural compounds. We have also critically reviewed and assessed the advantages and limitations of current preclinical and clinical studies on this subject for cancer prophylaxis. This might subsequently pave the way for new paradigms in the discovery of drugs that target specific cancer types.

Targeting SIRT1-regulated autophagic cell death as a novel therapeutic avenue for cancer prevention

Cellular localization and deacetylation activity of sirtuin 1 (SIRT1) has a significant role in cancer regulation. The multifactorial role of SIRT1 in autophagy regulates several cancer-associated cellular phenotypes, aiding cellular survival and cell death induction. SIRT1-mediated deacetylation of autophagy-related genes (ATGs) and associated signaling mediators control carcinogenesis. The hyperactivation of bulk autophagy, disrupted lysosomal and mitochondrial biogenesis, and excessive mitophagy are key mechanism for SIRT1-mediated autophagic cell death (ACD). In terms of the SIRT1-ACD nexus, identifying SIRT1-activating small molecules and understanding the possible mechanism triggering ACD could be a potential therapeutic avenue for cancer prevention. In this review, we provide an update on the structural and functional intricacy of SIRT1 and SIRT1-mediated autophagy activation as an alternative cell death modality for cancer prevention.

Unleashing the Power of NR4A1 Degradation as a Novel Strategy for Cancer Immunotherapy

An effective cancer therapy requires both killing cancer cells and targeting tumor-promoting pathways or cell populations within the tumor microenvironment (TME). We purposely search for molecules that are critical for multiple tumor-promoting cell types and identified nuclear receptor subfamily 4 group A member 1 (NR4A1) as one such molecule. NR4A1 has been shown to promote the aggressiveness of cancer cells and maintain the immune suppressive TME. Using genetic and pharmacological approaches, we establish NR4A1 as a valid therapeutic target for cancer therapy. Importantly, we have developed the first-of-its kind proteolysis-targeting chimera (PROTAC, named NR-V04) against NR4A1. NR-V04 effectively degrades NR4A1 within hours of treatment in vitro and sustains for at least 4 days in vivo, exhibiting long-lasting NR4A1-degradation in tumors and an excellent safety profile. NR-V04 leads to robust tumor inhibition and sometimes eradication of established melanoma tumors. At the mechanistic level, we have identified an unexpected novel mechanism via significant induction of tumor-infiltrating (TI) B cells as well as an inhibition of monocytic myeloid derived suppressor cells (m-MDSC), two clinically relevant immune cell populations in human melanomas. Overall, NR-V04-mediated NR4A1 degradation holds promise for enhancing anti-cancer immune responses and offers a new avenue for treating various types of cancer.

A celastrol-based nanodrug with reduced hepatotoxicity for primary and metastatic cancer treatment

BACKGROUND

Cancer is the world's leading cause of death and a key hindrance to extending life expectancy. Celastrol, a bioactive compound derived from Tripterygium wilfordii, has been shown to have excellent antitumor activity, but its poor solubility and severe organ toxicity side effects have hampered its clinical application.

METHODS

In this study, a self-assembled nanodrug (PLC-NP) was designed to deliver celastrol to tumor sites while efficiently reducing its side effects by conjugating celastrol with the bioactive material LMWH and P-selectin targeting peptide (PSN). Extensive in vitro and in vivo experiments were performed to investigate both therapeutic efficacy and adverse effects. Furthermore, the specific mechanism of the antitumor activity has also been explored.

FINDING

The PLC-NP nanodrugs were spherical in shape, with a mean particle size of 115.83 ± 6.93 nm. PLC-NP was sufficiently stable during blood circulation, with a selective target to P-selectin-highly expressed tumor cells, followed by releasing the containing celastrol under acidic environment and high levels of esterase in tumor cells. Both in vitro and in vivo results confirmed that celastrol's antitumor and anti-metastatic abilities were not attenuated and were actually strengthened after being formed into nanodrugs. More importantly, the organ toxicities of the modified celastrol nanodrug were dramatically reduced. Mechanistic study indicated that the inactivation of PI3K/Akt/mTOR signaling pathway and ROS-mediated mitochondrial dysfunction play critical roles in celastrol-mediated autophagy and apoptosis.

INTERPRETATION

Our findings could offer a potential strategy for the translation of toxic compounds into clinical therapeutic nanomedicine.

FUNDING

See a detailed list of funding bodies in the Acknowledgements section at the end of the manuscript.

Noncanonical contribution of microglial transcription factor NR4A1 to post-stroke recovery through TNF mRNA destabilization

Microglia-mediated neuroinflammation is involved in various neurological diseases, including ischemic stroke, but the endogenous mechanisms preventing unstrained inflammation is still unclear. The anti-inflammatory role of transcription factor nuclear receptor subfamily 4 group A member 1 (NR4A1) in macrophages and microglia has previously been identified. However, the endogenous mechanisms that how NR4A1 restricts unstrained inflammation remain elusive. Here, we observed that NR4A1 is up-regulated in the cytoplasm of activated microglia and localizes to processing bodies (P-bodies). In addition, we found that cytoplasmic NR4A1 functions as an RNA-binding protein (RBP) that directly binds and destabilizes Tnf mRNA in an N6-methyladenosine (m6A)-dependent manner. Remarkably, conditional microglial deletion of Nr4a1 elevates Tnf expression and worsens outcomes in a mouse model of ischemic stroke, in which case NR4A1 expression is significantly induced in the cytoplasm of microglia. Thus, our study illustrates a novel mechanism that NR4A1 posttranscriptionally regulates Tnf expression in microglia and determines stroke outcomes.

Acid-Responsive Macroporous Silica Nanoparticles for Bcl-2-Functional-Converting Peptide Release and Synergism with Celastrol for Enhanced Therapy against Resistant Cancer

Combination of chemotherapeutics with polypeptide/protein drugs has been demonstrated to be an effective approach for treatment against cancer multidrug resistance. However, due to the low biostability and weak cell penetrating ability of biomacromolecules, intracellular delivery and release of biomacromolecules in a spatiotemporally controllable manner in target sites in vivo face great challenges, and synergistic effects will not be achieved as expected just by simple drug combination. Here, we conceived an inspired strategy to combat the drug-resistant tumors by fabricating multiarm PEG-gated large pore-sized mesoporous silica nanoparticles for the Bcl-2-functional-converting peptide (denoted as N9@M-CA∼8P) payload and controlled release and realizing synergistic effects with celastrol integration at a low dosage as a curative sensitizer. Our results demonstrated that the N9 peptide could be pH-responsively released from the macropores of the M-CA∼8P nanosystem both in simulated physiological environments and in cancer cells and at tumor sites. Biosafe and enhanced therapeutic outcomes (90% tumor inhibition) were obtained by combination of the N9@M-CA∼8P nanosystem with celastrol coordinatively inducing mitochondrion-mediated cell apoptosis in resistant cancer cell lines and in the corresponding xenografted mice models. Overall, this study provides convincing evidence for effective and safe resistant cancer treatment through a stimulus-responsive biomacromolecule nanosystem combined with a low dosage of a natural compound.

Autophagy in the pharmacological activities of celastrol (Review)

Celastrol, a natural compound extracted from the traditional Chinese medicinal herb Tripterygium wilfordii Hook F, possesses broad-spectrum pharmacological properties. Autophagy is an evolutionarily conserved catabolic process through which cytoplasmic cargo is delivered to the lysosomes for degradation. Autophagy dysregulation contributes to multiple pathological processes. Therefore, targeting autophagic activity is a promising therapy for various diseases, as well as a drug-development strategy. According to previous studies, autophagy is specifically targeted and may be altered in response to celastrol treatment, highlighting that autophagy modulation is an important mechanism underlying the therapeutic efficacy of celastrol for the treatment of various diseases. The present study summarizes the currently available information regarding the role of autophagy in the effect of celastrol to exert anti-tumor, anti-inflammatory, immunomodulatory, neuroprotective, anti-atherosclerosis, anti-pulmonary fibrosis and anti-macular degeneration activities. The diverse signaling pathways involved are also analyzed to provide insight into the mechanisms of action of celastrol and thereby pave the way for establishing celastrol as an efficacious autophagy modulator in clinical practice.

Flavone and Hydroxyflavones Are Ligands That Bind the Orphan Nuclear Receptor 4A1 (NR4A1)

It was recently reported that the hydroxyflavones quercetin and kaempferol bind the orphan nuclear receptor 4A1 (NR4A1, Nur77) and act as antagonists in cancer cells and tumors, and they inhibit pro-oncogenic NR4A1-regulated genes and pathways. In this study, we investigated the interactions of flavone, six hydroxyflavones, seven dihydroxyflavones, three trihydroxyflavones, two tetrahydroxyflavones, and one pentahydroxyflavone with the ligand-binding domain (LBD) of NR4A1 using direct-binding fluorescence and an isothermal titration calorimetry (ITC) assays. Flavone and the hydroxyflavones bound NR4A1, and their KD values ranged from 0.36 µM for 3,5,7-trihydroxyflavone (galangin) to 45.8 µM for 3'-hydroxyflavone. KD values determined using ITC and KD values for most (15/20) of the hydroxyflavones were decreased compared to those obtained using the fluorescence assay. The results of binding, transactivation and receptor-ligand modeling assays showed that KD values, transactivation data and docking scores for these compounds are highly variable with respect to the number and position of the hydroxyl groups on the flavone backbone structure, suggesting that hydroxyflavones are selective NR4A1 modulators. Nevertheless, the data show that hydroxyflavone-based neutraceuticals are NR4A1 ligands and that some of these compounds can now be repurposed and used to target sub-populations of patients that overexpress NR4A1.

The TRAF2-p62 axis promotes proliferation and survival of liver cancer by activating mTORC1 pathway

TRAF2 (Tumor necrosis factor receptor-associated factor 2) is a dual function protein, acting as an adaptor protein and a ubiquitin E3 ligase, which plays an essential role in mediating the TNFα-NFκB signal pathway. Dysregulated expression of TRAF2 has been reported in a variety of human cancers. Whether and how TRAF2 regulates the growth of liver cancer cells remains elusive. The goal of this study is to investigate potential dysregulation of TRAF2 and its biological function in liver cancer, and to elucidate the underlying mechanism, leading to validation of TRAF2 as an attractive liver cancer target. Here, we reported TRAF2 is up-regulated in human liver cancer cell lines and tissues, and high TRAF2 expression is associated with a poor prognosis of HCC patients. Proteomics profiling along with Co-immunoprecipitation analysis revealed that p62 is a new substrate of TRAF2, which is subjected to TRAF2-induced polyubiquitination via the K63 linkage at the K420 residue. A strong negative correlation was found between the protein levels of p62 and TRAF2 in human HCC samples. TRAF2 depletion inhibited growth and survival of liver cancer cells both in vitro and in vivo by causing p62 accumulation, which is partially rescued by simultaneous p62 knockdown. Mechanistically, TRAF2-mediated p62 polyubiquitylation activates the mTORC1 by forming the p62-mTORC1-Rag complex, which facilitates the lysosome localization of mTORC1. TRAF2 depletion inhibited mTORC1 activity through the disruption of interaction between p62 and the mTORC1 complex. In conclusion, our study provides the proof-of-concept evidence that TRAF2 is a valid target for liver cancer.

Liquiritin exhibits anti-acute lung injury activities through suppressing the JNK/Nur77/c-Jun pathway

BACKGROUND

Licorice (Glycyrrhiza uralensis Fisch.), a well-known traditional medicine, is traditionally used for the treatment of respiratory disorders, such as cough, sore throat, asthma and bronchitis. We aim to investigate the effects of liquiritin (LQ), the main bioactive compound in licorice against acute lung injury (ALI) and explore the potential mechanism.

METHODS

Lipopolysaccharide (LPS) was used to induce inflammation in RAW264.7 cells and zebrafish. Intratracheal instillation of 3 mg/kg of LPS was used for induction an ALI mice model. The concentrations of IL-6 and TNF-α were tested using the enzyme linked immunosorbent assay. Western blot analysis was used to detect the expression of JNK/Nur77/c-Jun related proteins. Protein levels in bronchoalveolar lavage fluid (BALF) was measured by BCA protein assay. The effect of JNK on Nur77 transcriptional activity was determined by luciferase reporter assay, while electrophoretic mobility shift assay was used to examine the c-Jun DNA binding activity.

RESULTS

LQ has significant anti-inflammatory effects in zebrafish and RAW264.7 cells. LQ inhibited the expression levels of p-JNK (Thr183/Tyr185), p-Nur77 (Ser351) and p-c-Jun (Ser63), while elevated the Nur77 expression level. Inhibition of JNK by a specific inhibitor or small interfering RNA enhanced the regulatory effect of LQ on Nur77/c-Jun, while JNK agonist abrogated LQ-mediated effects. Moreover, Nur77-luciferase reporter activity was suppressed after JNK overexpression. The effects of LQ on the expression level of c-Jun and the binding activity of c-Jun with DNA were attenuated after Nur77 siRNA treatment. LQ significantly ameliorated LPS-induced ALI with the reduction of lung water content and BALF protein content, the downregulation of TNF-α and IL-6 levels in lung BALF and the suppression of JNK/Nur77/c-Jun signaling, which can be reversed by a specific JNK agonist.

CONCLUSION

Our results indicated that LQ exerts significant protective effects against LPS-induced inflammation both in vivo and in vitro via suppressing the activation of JNK, and consequently inhibiting the Nur77/c-Jun signaling pathway. Our study suggests that LQ may be a potential therapeutic candidate for ALI and inflammatory disorders.

Celastrol inhibits necroptosis by attenuating the RIPK1/RIPK3/MLKL pathway and confers protection against acute pancreatitis in mice

Necroptosis is a necrotic form of regulated cell death, which is primarily mediated by the receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like (MLKL) pathway in a caspase-independent manner. Necroptosis has been found to occur in virtually all tissues and diseases evaluated, including pancreatitis. Celastrol, a pentacyclic triterpene extracted from the roots of Tripterygium wilfordii (thunder god vine), possesses potent anti-inflammatory and anti-oxidative activities. Yet, it is unclear whether celastrol has any effects on necroptosis and necroptotic-related diseases. Here we showed that celastrol significantly suppressed necroptosis induced by lipopolysaccharide (LPS) plus pan-caspase inhibitor (IDN-6556) or by tumor-necrosis factor-α in combination with LCL-161 (Smac mimetic) and IDN-6556 (TSI). In these in vitro cellular models, celastrol inhibited the phosphorylation of RIPK1, RIPK3, and MLKL and the formation of necrosome during necroptotic induction, suggesting its possible action on upstream signaling of the necroptotic pathway. Consistent with the known role of mitochondrial dysfunction in necroptosis, we found that celastrol significantly rescued TSI-induced loss of mitochondrial membrane potential. TSI-induced intracellular and mitochondrial reactive oxygen species (mtROS), which are involved in the autophosphorylation of RIPK1 and recruitment of RIPK3, were significantly attenuated by celastrol. Moreover, in a mouse model of acute pancreatitis that is associated with necroptosis, celastrol administration significantly reduced the severity of caerulein-induced acute pancreatitis accompanied by decreased phosphorylation of MLKL in pancreatic tissues. Collectively, celastrol can attenuate the activation of RIPK1/RIPK3/MLKL signaling likely by attenuating mtROS production, thereby inhibiting necroptosis and conferring protection against caerulein-induced pancreatitis in mice.

Celastrol suppresses humoral immune responses and autoimmunity by targeting the COMMD3/8 complex

Celastrol, a bioactive molecule extracted from the Tripterygium wilfordii plant, has been shown to exhibit anti-inflammatory properties. However, its mechanism of action has not been fully elucidated. Here, we show that celastrol suppresses humoral immune responses and autoimmunity by disabling a protein complex consisting of copper metabolism MURR1 domain–containing (COMMD) 3 and COMMD8 (COMMD3/8 complex), a signaling adaptor for chemoattractant receptors. Having demonstrated the involvement of the COMMD3/8 complex in a mouse model of rheumatoid arthritis, we identified celastrol as a compound that covalently bound to and dissociated the COMMD3/8 complex. Celastrol inhibited B cell migration, reduced antibody responses, and blocked arthritis progression, recapitulating deficiency of the COMMD3/8 complex. These effects of celastrol were abolished in mice expressing a celastrol-resistant mutant of the COMMD3/8 complex. These findings establish that celastrol exerts immunosuppressive activity by targeting the COMMD3/8 complex. Our study suggests that the COMMD3/8 complex is a potentially druggable target in autoimmune diseases and points to celastrol as a lead pharmacologic candidate in this capacity.

Lipidome remodeling activities of DPA-EA in palmitic acid-stimulated HepG2 cells and the in vivo anti-obesity effect of the DPA-EA and DHA-EA mixture prepared from algae oil

Background: The nuclear receptor Nur77 has been demonstrated to play a vital role in the inflammatory response and cellular metabolisms, and its ligands exhibit efficacy in the treatment of inflammation-related diseases (e.g., improving mouse acute lung injury (ALI) and obesity. Recently, ω-3 polyunsaturated fatty acid-ethanolamine derivatives (ω-3 PUFA-EAs), including DPA-EA and DHA-EA, have been reported as new Nur77-targeting anti-inflammatory agents. However, the lipid-lowering effect of ω-3 PUFA-EAs is still unknown, and lipid profile changes induced by Nur77-targeting anti-inflammatory agents also remain unclear.

Objective: This study aimed to evaluate the lipid-lowering effect and the underlying mechanism of DPA-EA acting as Nur77-targeting anti-inflammatory agents. It also aimed to investigate the in vitro and in vivo lipid-lowering effects of the DPA-EA and DHA-EA mixture prepared from algae oil.

Methods: The in vitro lipid-lowing effect of DPA-EA and its mixture with DHA-EA was first evaluated in palmitic acid-stimulated HepG2 Cells. To confirm the lipid-lowering effect and explore the underlying mechanism, we performed untargeted lipidomic analysis using ultra-performance liquid chromatography/triple quadrupole-time-of-flight (TOF) mass spectrometry coupled with multivariate statistical analysis, with another Nur77-targeting anti-inflammatory compound Celastrol (Cel) as a reference. Finally, we examined the anti-obesity effect of the DPA-EA and DHA-EA mixture synthesized from algae oil in a high-fat diet (HFD)-fed mice model.

Results: DPA-EA significantly alleviated lipid accumulation with lower toxicity than Celastrol. Nur77-targeting compounds DPA-EA and Celastrol could simultaneously reduce 14 lipids (9 TGs, 2 PCs, 1 PA, 1 SM, and 1 LacCer) and increase 13 lipids (4 DGs, 6 LPEs, 2 PEs, and 1PC) in Pal-stimulated HepG2 cells. However, Cer lipids were more sensitive to DPA-EA, while the over-downregulation of SM lipids might be associated with the off-target toxicity of Celastrol. The mixture of DPA-EA and DHA-EA synthesized from algae oil could significantly decrease TG, TC, and LDL levels and increase HDL levels in HFD-fed mice, exerting an excellent anti-obesity effect.

Conclusion: Nur77-targeting anti-inflammatory compound DAP-EA could promote the hydrolysis of PEs and TGs to ameliorate lipid accumulation. The DPA-EA and DHA-EA mixture prepared from algae oil might be a potential therapeutic agent for obesity and other inflammation-related diseases.

N-Trimethylated chitosan coating white adipose tissue vascular-targeting oral nano-system for the enhanced anti-obesity effects of celastrol

Oral nanoparticles (NPs) are more suitable for obesity control compared to NPs administered intravenously, as their convenience increases patient compliance. Herein, we developed an oral nano-system to improve the anti-obesity efficacy of celastrol (Cel). The observed enhanced efficacy was mediated by zein core NPs decorated with adipose-homing peptides that were coated with N-trimethylated chitosan. The optimized Cel/AHP-NPs@TMC exhibited spherical morphology by TEM, as well as narrow size distribution (221.76 ± 6.73 nm) and adequate stability in a gastrointestinal environment. Based on the combined delivery advantages of AHP-NPs@TMC - i.e., improved cellular internalization within Caco-2 cells and enhanced white adipose tissue (WAT) vascular targeting - Cel/AHP-NPs@TMC significantly reduced the body weight, blood lipid levels, adipose inflammation, and WAT distribution in diet-induced obese mice without side-effects. In short, this study provides clear evidence that TMC-based oral NPs can effectively improve celastrol for obesity treatment.

Oxidative stress impairs the Nur77-Sirt1 axis resulting in a decline in organism homeostasis during aging

Sirt1 is an NAD⁺ -dependent deacetylase that protects against premature aging and cell senescence. Aging accompanied by oxidative stress leads to a decrease in Sirt1 levels and activity, but the regulatory mechanism that connects these events remains unclear. Here, we reported that Nur77, which shares similar biological pathways with Sirt1, was also decreased with age in multiple organs. Our in vivo and in vitro results revealed that Nur77 and Sirt1 decreased during aging and oxidative stress-induced cell senescence. Deletion of Nr4a1 shortened the lifespan and accelerated the aging process in multiple mouse tissues. Overexpression of Nr4a1 protected the Sirt1 protein from proteasomal degradation through negative transcriptional regulation of the E3 ligase MDM2. Our results showed that Nur77 deficiency markedly aggravated aging-related nephropathy and elucidated a key role for Nur77 in the stabilization of Sirt1 homeostasis during renal aging. We proposed a model wherein a reduction of Nur77 in response to oxidative stress promotes Sirt1 protein degradation through MDM2, which triggers cell senescence. This creates additional oxidative stress and provides positive feedback for premature aging by further decreasing Nur77 expression. Our findings reveal the mechanism by which oxidative stress reduces Sirt1 expression during aging and offers an attractive therapeutic strategy for targeting aging and homeostasis in organisms.

Self-delivery biomedicine for enhanced photodynamic therapy by feedback promotion of tumor autophagy

Reactive oxygen species (ROS) generated during photodynamic therapy (PDT) can induce autophagy to protect tumor cell from PDT-induced apoptosis. In this work, a self-delivery autophagy regulator (designated as CeCe) is developed for autophagy promotion sensitized PDT against tumor. Briefly, CeCe is prepared by the assembly of a photosensitizer of chlorin e6 (Ce6) and autophagy promoter of celastrol. By virtue of intermolecular interactions, Ce6 and celastrol are able to self-assemble into nanomedicine with great photodynamic performance and autophagy regulation capacity. Under light irradiation, CeCe would produce ROS in tumor cells to amplify the oxidative stress and promote cell autophagy. As a result, CeCe exhibits an enhanced photo toxicity by inducing autophagic cell death. In vivo experiments indicate that CeCe can predominantly accumulate in tumor tissue for a robust PDT. Moreover, CeCe has a superior therapeutic efficiency compared to monotherapy and combined treatment of Ce6 and celastrol, suggesting a synergistic antitumor effect of PDT and autophagy promotion. This self-delivery nanomedicine may advance the development of the co-delivery nanoplatform to improve the antitumor efficacy of PDT by promoting autophagy. STATEMENT OF SIGNIFICANCE: Autophagy is a "double-edged sword" in cellular homeostasis and metabolism, which can promote tumor progression but also induce an unknown impact on tumor inhibition. In this work, a self-delivery autophagy regulator (designated as CeCe) was developed for autophagy promotion sensitized photodynamic therapy (PDT). By virtue of intermolecular interactions, Ce6 and celastrol were found to self-assemble into stable CeCe without drug excipients, which exhibited great photodynamic performance and autophagy regulation capacity. In vitro and in vivo findings demonstrated a superior tumor suppression ability of CeCe over the monotherapy as well as the combined treatment of Ce6 and celastrol, suggesting a synergistic antitumor efficacy by PDT and autophagy promotion.

Network pharmacology and in vivo studies reveal the pharmacological effects and molecular mechanisms of Celastrol against acute hepatic injury induced by LPS

Sepsis is currently the main factor of death in the ICU, and the liver, as an important organ of immunity and stable metabolism, can be acutely damaged during sepsis, and the mortality rate of patients with sepsis complicated by acute liver injury is greatly increased. Celastrol (CEL) is derived from the root bark of Tripterygium wilfordii Hook.f.. As a traditional Chinese medicine, CEL has anti-inflammatory, anti-cancer, anti-oxidant, and other biological activities. Obtain CEL and AHI intersection targets via database and construct protein-protein interaction (PPI) network by STRING. GO functional enrichment and KEGG pathway analyses were performed by R studio. Targets were finally selected to perform molecular docking simulations with CEL. In vivo experiments based on the model of AHI were established by intraperitoneal injection of Lipopolysaccharide (LPS) 4 h, and pre-treated with CEL (0.5 mg/kg, 1 mg/kg, 1.5 mg/kg). The results are as follows: 273 genes with the intersection of CEL and AHI were obtained, and GO and KEGG enrichment analysis were used to design the mechanism of inflammation, apoptosis, and oxidative stress-related injury. By constructing the PPI network selected top 10 targets are: STAT3, RELA, MAPK1, MAPK3, TP53, AKT1, HSP90AA1, JUN, TNF, MAPK14, predicted CEL protection AHI design related pathways of MAPK and PI3K/AKT-related signal pathways. In vivo experiments, CEL inhibited the activation of MAPK and PI3K/AKT related pathways, reduced inflammatory response, apoptosis, and oxidative stress, and significantly improved LPS-induced AHI. In summary, this study predicted the mechanisms involved in the protective effect of CEL on AHI through network pharmacology. In vivo, CEL inhibited MAPK and PI3K/AKT-related signaling pathways, and reduced inflammatory response, apoptosis, and oxidative stress to protect LPS-induced AHI.

Venlafaxine, an anti-depressant drug, induces apoptosis in MV3 human melanoma cells through JNK1/2-Nur77 signaling pathway

Introduction: Venlafaxine is one of the most commonly used anti-depressant and antineoplastic drug. Previous studies have predicted venlafaxine as an anti-cancer compound, but the therapeutic effects of venlafaxine in melanoma have not yet been demonstrated. Nur77 is an orphan nuclear receptor that highly expressed in melanoma cells and can interact with Bcl-2 to convert Bcl-2 from an antiapoptotic to a pro-apoptotic protein. Method: We examined the effects of venlafaxine in MV3 cells in vitro and MV3 xenograft tumor in nude mice. Western-blot, PCR, TUNEL assay and immunofluorescence were used to reveal the growth of melanoma cells. Results: Here, our data revealed that venlafaxine could reduce the growth, and induce apoptosis of melanoma cells through a Nur77-dependent way. Our results also showed that treatment with venlafaxine (20 mg/kg, i.p.) potently inhibited the growth of melanoma cells in nude mice. Mechanistically, venlafaxine activated JNK1/2 signaling, induced Nur77 expressions and mitochondrial localization, thereby promoting apoptosis of melanoma cells. Knockdown of Nur77 and JNK1/2, or inhibition of JNK1/2 signaling with its inhibitor SP600125 attenuated the anti-cancer effects of venlafaxine. Conclusion: In summary, our results suggested venlafaxine as a potential therapy for melanoma.

Celastrol directly binds with VAMP7 and RAB7 to inhibit autophagy and induce apoptosis in preadipocytes

Obesity is one of the most prevalent chronic metabolic diseases, and induction of apoptosis in preadipocytes and adipocytes is a potential strategy to treat obesity. Celastrol represents one of the most robust anti-obesity phytochemicals so far, yet its direct binding target remains elusive. Here, we determined that celastrol could induce apoptosis in preadipocytes via mitochondrial mediated pathway. Further study clarified that celastrol inhibited the fusion of autophagosome and lysosome to prohibit autophagy, leading to cell apoptosis. By conducting virtual screening and genetic manipulation, we verified that overexpression of VAMP7 and RAB7 could block the effects of celastrol on inhibiting autophagy and inducing apoptosis. The Surface Plasmon Resonance study confirmed the direct binding of celastrol with VAMP7 and RAB7. The functional study illustrated the inhibition of RAB7 GTPase activity after celastrol treatment. Moreover, celastrol induced comparable apoptosis in murine epididymal adipose tissue, human preadipocytes and adipocytes, but not in human hepatocytes. An inhibitory effect on differentiation of human primary visceral preadipocytes was also observed. In conclusion, celastrol exhibited inhibitory effect of autophagy via direct binding with VAMP7 and RAB7, leading to an increase in preadipocytes apoptosis. These results advance our understanding in the potential application of celastrol in treating obesity.

Multi-transcriptomics reveals RLMF axis-mediated signaling molecules associated with bovine feed efficiency

The regulatory axis plays a vital role in interpreting the information exchange and interactions among mammal organs. In this study on feed efficiency, it was hypothesized that a rumen-liver-muscle-fat (RLMF) regulatory axis exists and scrutinized the flow of energy along the RLMF axis employing consensus network analysis from a spatial transcriptomic standpoint. Based on enrichment analysis and protein-protein interaction analysis of the consensus network and tissue-specific genes, it was discovered that carbohydrate metabolism, energy metabolism, immune and inflammatory responses were likely to be the biological processes that contribute most to feed efficiency variation on the RLMF regulatory axis. In addition, clusters of genes related to the electron respiratory chain, including ND (2,3,4,4L,5,6), NDUF (A13, A7, S6, B3, B6), COX (1,3), CYTB, UQCR11, ATP (6,8), clusters of genes related to fatty acid metabolism including APO (A1, A2, A4, B, C3), ALB, FG (A, G), as well as clusters of the ribosomal-related gene including RPL (8,18A,18,15,13, P1), the RPS (23,27A,3A,4X), and the PSM (A1-A7, B6, C1, C3, D2-D4, D8 D9, E1) could be the primary effector genes responsible for feed efficiency variation. The findings demonstrate that high feed efficiency cattle, through the synergistic action of the regulatory axis RLMF, may improve the efficiency of biological processes (carbohydrate metabolism, protein ubiquitination, and energy metabolism). Meanwhile, high feed efficiency cattle might enhance the ability to respond to immunity and inflammation, allowing nutrients to be efficiently distributed across these organs associated with digestion and absorption, energy-producing, and energy-storing organs. Elucidating the distribution of nutrients on the RLMF regulatory axis could facilitate an understanding of feed efficiency variation and achieve the study on its molecular regulation.

Celastrol-regulated gut microbiota and bile acid metabolism alleviate hepatocellular carcinoma proliferation by regulating the interaction between FXR and RXRα in vivo and in vitro

Celastrol, a triterpene derived from Thunder God Vine (Tripterygium wilfordii Hook f; Celastraceae), a traditional Chinese herb, has promising anticancer activity. The present study aimed to elucidate an indirect mechanism of celastrol-mediated alleviation of hepatocellular carcinoma (HCC) via gut microbiota-regulated bile acid metabolism and downstream signaling. Here, we constructed a rat model of orthotopic HCC and performed 16S rDNA sequencing and UPLC-MS analysis. The results showed that celastrol could regulate gut bacteria; suppress the abundance of Bacteroides fragilis; raise the levels of glycoursodeoxycholic acid (GUDCA), a bile acid; and alleviate HCC. We found that GUDCA suppressed cellular proliferation and induced the arrest of mTOR/S6K1 pathway-associated cell cycle G0/G1 phase in HepG2 cells. Further analyses using molecular simulations, Co-IP, and immunofluorescence assays revealed that GUDCA binds to farnesoid X receptor (FXR) and regulates the interaction of FXR with retinoid X receptor a (RXRα). Transfection experiments using the FXR mutant confirmed that FXR is essential for GUCDA-mediated suppression of HCC cellular proliferation. Finally, animal experiments showed that the treatment with the combination of celastrol/GUDCA alleviated the adverse effects of celastrol alone treatment on body weight loss and improved survival in rats with HCC. In conclusion, the findings of this study suggest that celastrol exerts an alleviating effect on HCC, in part via regulation of the B. fragilis-GUDCA-FXR/RXRα-mTOR axis.

The Ginsenoside Compound K Suppresses Stem-Cell-like Properties and Colorectal Cancer Metastasis by Targeting Hypoxia-Driven Nur77-Akt Feed-Forward Signaling

Hypoxia reprograms cancer stem cells. Nur77, an orphan nuclear receptor, highly expresses and facilitates colorectal cancer (CRC) stemness and metastasis under a hypoxic microenvironment. However, safe and effective small molecules that target Nur77 for CSC depletion remain unexplored. Here, we report our identification of the ginsenoside compound K (CK) as a new ligand of Nur77. CK strongly inhibits hypoxia-induced CRC sphere formation and CSC phenotypes in a Nur77-dependent manner. Hypoxia induces an intriguing Nur77-Akt feed-forward loop, resulting in reinforced PI3K/Akt signaling that is druggable by targeting Nur77. CK directly binds and modulates Nur77 phosphorylation to block the Nur77-Akt activation loop by disassociating Nur77 from the p63-bound Dicer promoter. The transcription of Dicer that is silenced under a hypoxia microenvironment is thus reactivated by CK. Consequently, the expression and processing capability of microRNA let-7i-5p are significantly increased, which targets PIK3CA mRNA for decay. The in vivo results showed that CK suppresses cancer stemness and metastasis without causing significant adverse effects. Given that the majority of FDA-approved and currently clinically tested PI3K/Akt inhibitors are reversible ATP-competitive kinase antagonists, targeting Nur77 for PI3K/Akt inactivation may provide an alternative strategy to overcoming concerns about drug selectivity and safety. The mechanistic target identification provides a basis for exploring CK as a promising nutraceutical against CRC.

Orchestration of selective autophagy by cargo receptors

Cellular homeostasis requires the swift and specific removal of damaged material. Selective autophagy represents a major pathway for the degradation of such cargo material. This is achieved by the sequestration of the cargo within double-membrane vesicles termed autophagosomes, which form de novo around the cargo and subsequently deliver their content to lysosomes for degradation. The importance of selective autophagy is exemplified by the various neurodegenerative diseases associated with defects in this pathway, including Parkinson's disease, amyotrophic lateral sclerosis, and frontotemporal dementia. It has become evident that cargo receptors are acting as Swiss army knives in selective autophagy by recognizing the cargo, orchestrating the recruitment of the machinery for autophagosome biogenesis, and closely aligning the membrane with the cargo. Furthermore, cargo receptors sequester ubiquitinated proteins into larger condensates upstream of autophagy induction. Here, we review recent insights into the mechanisms of action of cargo receptors in selective autophagy by focusing on the roles of sequestosome-like cargo receptors in the degradation of misfolded, ubiquitinated proteins and damaged mitochondria. We also highlight at which steps defects in their function result in the accumulation of harmful material and how this knowledge may guide the design of future therapies.

Mechanism of Mitochondrial Homeostasis Controlling Ovarian Physiology

Ovarian cells, including oocytes, granulosa/cumulus cells, theca cells, and stromal cells, contain abundant mitochondria, which play indispensable roles in the processes of ovarian follicle development. Ovarian function is closely controlled by mitochondrial proteostasis and mitostasis. While mitochondrial proteostasis and mitostasis are disturbed by several factors, leading to dysfunction of ovarian function and initiating the mitochondrial unfolded protein response (UPRmt) and mitophagy to maintain or recover ovarian function and mitochondrial function, clear interactions between the 2 pathways in the ovary have not been fully elucidated. Here, we comprehensively summarize the molecular networks or regulatory mechanisms behind further mitochondrial research in the ovary. This review provides novel insights into the interactions between the UPRmt and mitophagy in ovarian functions.

New opportunities and challenges of natural products research: When target identification meets single-cell multiomics

Natural products, and especially the active ingredients found in traditional Chinese medicine (TCM), have a thousand-year-long history of clinical use and a strong theoretical basis in TCM. As such, traditional remedies provide shortcuts for the development of original new drugs in China, and increasing numbers of natural products are showing great therapeutic potential in various diseases. This paper reviews the molecular mechanisms of action of natural products from different sources used in the treatment of inflammatory diseases and cancer, introduces the methods and newly emerging technologies used to identify and validate the targets of natural active ingredients, enumerates the expansive list of TCM used to treat inflammatory diseases and cancer, and summarizes the patterns of action of emerging technologies such as single-cell multiomics, network pharmacology, and artificial intelligence in the pharmacological studies of natural products to provide insights for the development of innovative natural product-based drugs. Our hope is that we can make use of advances in target identification and single-cell multiomics to obtain a deeper understanding of actions of mechanisms of natural products that will allow innovation and revitalization of TCM and its swift industrialization and internationalization.

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.

Multifunctions of CRIF1 in cancers and mitochondrial dysfunction

Sustaining proliferative signaling and enabling replicative immortality are two important hallmarks of cancer. The complex of cyclin-dependent kinase (CDK) and its cyclin plays a decisive role in the transformation of the cell cycle and is also critical in the initiation and progression of cancer. CRIF1, a multifunctional factor, plays a pivotal role in a series of cell biological progresses such as cell cycle, cell proliferation, and energy metabolism. CRIF1 is best known as a negative regulator of the cell cycle, on account of directly binding to Gadd45 family proteins or CDK2. In addition, CRIF1 acts as a regulator of several transcription factors such as Nur77 and STAT3 and partly determines the proliferation of cancer cells. Many studies showed that the expression of CRIF1 is significantly altered in cancers and potentially regarded as a tumor suppressor. This suggests that targeting CRIF1 would enhance the selectivity and sensitivity of cancer treatment. Moreover, CRIF1 might be an indispensable part of mitoribosome and is involved in the regulation of OXPHOS capacity. Further, CRIF1 is thought to be a novel target for the underlying mechanism of diseases with mitochondrial dysfunctions. In summary, this review would conclude the latest aspects of studies about CRIF1 in cancers and mitochondria-related diseases, shed new light on targeted therapy, and provide a more comprehensive holistic view.

[Nur77 promotes invasion and migration of gastric cancer cells through the NF-κB/IL-6 pathway]

OBJECTIVE

To analyze the association of Nur77 with overall survival of gastric cancer patients and investigate the role of Nur77 in invasion and migration of gastric cancer cells.

METHODS

Oncomine database was used to analyze the expression of Nur77 in gastric cancer and gastric mucosa tissues, and the distribution characteristics of Nur77 protein between gastric cancer and normal tissues were compared using Human Protein Atlas. GEPIA2 was used to analyze the relationship of Nur77 expression and the patients' survival. The expression of Nur77 in gastric cancer cell lines GES-1, AGS and MKN-45 were detected by Western blotting. The regulatory interactions between IL-6 and Nur77 were verified by transfecting the cells with specific Nur-77 siRNA and Nur-77-overexpressing plasmid. The changes in migration ability of the cells following Nur-77 knockdown were assessed with scratch assay. The effect of Nur-77 overexpression or IL-6 knockdown, or their combination, on migration and invasion of the gastric cancer cells were examined using Transwell assay. The effect of Nur77 expression level on NF-κB/IL-6 pathway activation was analyzed using Western blotting.

RESULTS

Oncomine database showed that gastric cancer tissues expressed a significantly higher level of Nur77 mRNA than normal tissues (P < 0.05). Nur77 expression was detected mostly in the nucleus, and a high Nur77 expression was associated with a poor survival outcome of the patients (P < 0.05). In gastric cancer cells, the high expression of Nur77 participated in the regulation of IL-6. Nur77 silencing significantly lowered the migration ability of the cells (P < 0.05), and IL-6 silencing significantly attenuated the enhanced migration caused by Nur77 overexpression (P < 0.05). Nur77 participates in the activation of NF-κB/IL-6 signaling pathway by regulating the expression of p-p65, p65, p-Stat3 and Stat3.

CONCLUSION

A high Nur77 expression is strongly correlated with a poor prognosis of gastric cancer patients. Nur77 promotes the invasion and migration of gastric cancer cells possibly by regulating the NF-κB/IL-6 signaling pathway.

Fragment-based discovery of orphan nuclear receptor Nur77/NGFI-B ligands

The transcription factor nerve growth factor-induced clone B (NGFI-B, Nur77, NR4A1) is an orphan nuclear receptor playing a role in cell survival and apoptosis regulation. Pharmacological Nur77 modulation holds promise for cancer and (neuro-)inflammatory disease treatment. The available Nur77 ligand scaffolds based on highly lipophilic natural products cytosporone B, celastrol and isoalantolactone are inadequate for the development of potent Nur77 modulators with favorable properties as chemical tools and future drugs. By fragment library screening and subsequent modeling for fragment extension, we have obtained a set of new Nur77 ligands offering alternative chemotypes for the development of Nur77 agonists and inverse agonists. Computer-aided fragment extension in a second stage screening yielded a Nur77 agonist with significant activation efficacy and preference over the related NR4A receptors.