Celastrol ameliorates experimental colitis in IL-10 deficient mice via the up-regulation of autophagy

Autophagy: A potential target for natural products in the treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease primarily affecting the mucosa of the colon and rectum. UC is characterized by recurrent episodes, often necessitating lifelong medication use, imposing a significant burden on patients. Current conventional and advanced treatments for UC have the disadvantages of insufficient efficiency, susceptibility to drug resistance, and notable adverse effects. Therefore, developing effective and safe drugs has become an urgent need. Autophagy is an intracellular degradation process that plays an important role in intestinal homeostasis. Emerging evidence suggests that aberrant autophagy is involved in the development of UC, and modulating autophagy can effectively alleviate experimental colitis. A growing number of studies have established that autophagy can interplay with endoplasmic reticulum stress, gut microbiota, apoptosis, and the NLRP3 inflammasome, all of which contribute to the pathogenesis of UC. In addition, a variety of intestinal epithelial cells, including absorptive cells, goblet cells, and Paneth cells, as well as other cell types like neutrophils, antigen-presenting cells, and stem cells in the gut, mediate the development of UC through autophagy. To date, many studies have found that natural products hold the potential to exert therapeutic effects on UC by regulating autophagy. This review focuses on the possible effects and pharmacological mechanisms of natural products to alleviate UC with autophagy as a potential target in recent years, aiming to provide a basis for new drug development.

Recent developments and new directions in the use of natural products for the treatment of inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) represents a significant global health challenge, and there is an urgent need to explore novel therapeutic interventions. Natural products have demonstrated highly promising effectiveness in the treatment of IBD.

PURPOSE

This study systematically reviews the latest research advancements in leveraging natural products for IBD treatment.

METHODS

This manuscript strictly adheres to the PRISMA guidelines. Relevant literature on the effects of natural products on IBD was retrieved from the PubMed, Web of Science and Cochrane Library databases using the search terms "natural product," "inflammatory bowel disease," "colitis," "metagenomics", "target identification", "drug delivery systems", "polyphenols," "alkaloids," "terpenoids," and so on. The retrieved data were then systematically summarized and reviewed.

RESULTS

This review assessed the different effects of various natural products, such as polyphenols, alkaloids, terpenoids, quinones, and others, in the treatment of IBD. While these natural products offer promising avenues for IBD management, they also face challenges in terms of clinical translation and drug discovery. The advent of metagenomics, single-cell sequencing, target identification techniques, drug delivery systems, and other cutting-edge technologies heralds a new era in overcoming these challenges.

CONCLUSION

This paper provides an overview of current research progress in utilizing natural products for the treatment of IBD, exploring how contemporary technological innovations can aid in discovering and harnessing bioactive natural products for the treatment of IBD.

Targeting programmed cell death in inflammatory bowel disease through natural products: New insights from molecular mechanisms to targeted therapies

Inflammatory bowel disease (IBD) is an autoimmune disorder primarily characterized by intestinal inflammation and recurrent ulceration, leading to a compromised intestinal barrier and inflammatory infiltration. This disorder's pathogenesis is mainly attributed to extensive damage or death of intestinal epithelial cells, along with abnormal activation or impaired death regulation of immune cells and the release of various inflammatory factors, which contribute to the inflammatory environment in the intestines. Thus, maintaining intestinal homeostasis hinges on balancing the survival and functionality of various cell types. Programmed cell death (PCD) pathways, including apoptosis, pyroptosis, autophagy, ferroptosis, necroptosis, and neutrophil extracellular traps, are integral in the pathogenesis of IBD by mediating the death of intestinal epithelial and immune cells. Natural products derived from plants, fruits, and vegetables have shown potential in regulating PCD, offering preventive and therapeutic avenues for IBD. This article reviews the role of natural products in IBD treatment by focusing on targeting PCD pathways, opening new avenues for clinical IBD management.

Environmental pollutants and phosphoinositide signaling in autoimmunity

Environmental pollution stands as one of the most critical challenges affecting human health, with an estimated mortality rate linked to pollution-induced non-communicable diseases projected to range from 20% to 25%. These pollutants not only disrupt immune responses but can also trigger immunotoxicity. Phosphoinositide signaling, a pivotal regulator of immune responses, plays a central role in the development of autoimmune diseases and exhibits high sensitivity to environmental stressors. Among these stressors, environmental pollutants have become increasingly prevalent in our society, contributing to the initiation and exacerbation of autoimmune conditions. In this review, we summarize the intricate interplay between phosphoinositide signaling and autoimmune diseases within the context of environmental pollutants and contaminants. We provide an up-to-date overview of stress-induced phosphoinositide signaling, discuss 14 selected examples categorized into three groups of environmental pollutants and their connections to immune diseases, and shed light on the associated phosphoinositide signaling pathways. Through these discussions, this review advances our understanding of how phosphoinositide signaling influences the coordinated immune response to environmental stressors at a biological level. Furthermore, it offers valuable insights into potential research directions and therapeutic targets aimed at mitigating the impact of environmental pollutants on the pathogenesis of autoimmune diseases. SYNOPSIS: Phosphoinositide signaling at the intersection of environmental pollutants and autoimmunity provides novel insights for managing autoimmune diseases aggravated by pollutants.

Terpenes: Modulating anti-inflammatory signaling in inflammatory bowel disease

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

Polysaccharide from Strongylocentrotus nudus eggs regulates intestinal epithelial autophagy through CD36/PI3K-Akt pathway to ameliorate inflammatory bowel disease

Sea urchin is a popular food all over the world, of which eggs are main edible part. Previous studies suggested that polysaccharides from eggs of Strongylocentrotus nudus (SEP) exhibited immunomodulatory activities during anti-tumor therapy, nevertheless, effects of SEP on inflammatory bowel disease and its underlying mechanisms have never been reported. In the present study, we showed that the SEP inhibited dextran sodium sulfate-induced ulcerative colitis characterized by decreased disease activity index, restored colon length and body weight, improved histopathological changes, down-regulation of inflammatory cytokines levels and Th17/Treg ratios in C57BL/6 J mice. Moreover, immunofluorescence analysis suggested that SEP repaired gut barrier in UC mice, while 16S rDNA sequencing exhibited improved intestinal flora. Mechanistically, we found SEP significantly modulated autophagy-related factors in intestinal epithelial cells (IECs), while might contributed to pathogenesis of UC. Furthermore, we demonstrated PI3K/Akt pathway was involved in regulatory effect of SEP on lipopolysaccharide-induced autophagy of HT-29 cells. Besides, among possible polysaccharide binding receptors, change of the CD36 expression was most significant, which was associated with PI3K/Akt signals. Collectively, our study showed for the first time that the SEP might be used a prebiotic agent to improve IBD through regulating CD36-PI3K/Akt mediated autophagy of IECs.

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.

JI017 Induces Cell Autophagy and Apoptosis via Elevated Levels of Reactive Oxygen Species in Human Lung Cancer Cells

Lung cancer is one of the most common malignant tumors and a leading cause of cancer-related death in the worldwide. Various anticancer drugs, such as cisplatin and pemetrexed, have been developed for lung cancer treatment but due their drug resistance and side effects, novel treatments need to be developed. In this study, the efficacy of the natural drug JI017, which is known to have few side effects, was tested in lung cancer cells. JI017 inhibited A549, H460, and H1299 cell proliferation. JI017 induced apoptosis, regulated apoptotic molecules, and inhibited colony formation. Additionally, JI017 increased intracellular ROS generation. JI017 downregulated PI3K, AKT, and mTOR expression. JI017 increased the cytosolic accumulation of LC3. We found that JI017 promoted apoptosis through ROS-induced autophagy. Additionally, the xenograft tumor size was smaller in JI017-treated mice. We found that JI017 treatment increased MDA concentrations, decreased Ki-67 protein levels, and increased cleaved caspase-3 and LC3 levels in vivo. JI017 decreased cell proliferation and increased apoptosis by inducing autophagy signaling in H460 and H1299 lung cancer cells. Targeting JI017 and autophagy signaling could be useful in lung cancer treatment.

Selenized Polymer-Lipid Hybrid Nanoparticles for Oral Delivery of Tripterine with Ameliorative Oral Anti-Enteritis Activity and Bioavailability

The oral delivery of insoluble and enterotoxic drugs has been largely plagued by gastrointestinal irritation, side effects, and limited bioavailability. Tripterine (Tri) ranks as the hotspot of anti-inflammatory research other than inferior water-solubility and biocompatibility. This study was intended to develop selenized polymer-lipid hybrid nanoparticles loading Tri (Se@Tri-PLNs) for enteritis intervention by improving its cellular uptake and bioavailability. Se@Tri-PLNs were fabricated by a solvent diffusion-in situ reduction technique and characterized by particle size, ζ potential, morphology, and entrapment efficiency (EE). The cytotoxicity, cellular uptake, oral pharmacokinetics, and in vivo anti-inflammatory effect were evaluated. The resultant Se@Tri-PLNs were 123 nm around in particle size, with a PDI of 0.183, ζ potential of −29.70 mV, and EE of 98.95%. Se@Tri-PLNs exhibited retardant drug release and better stability in the digestive fluids compared with the unmodified counterpart (Tri-PLNs). Moreover, Se@Tri-PLNs manifested higher cellular uptake in Caco-2 cells as evidenced by flow cytometry and confocal microscopy. The oral bioavailability of Tri-PLNs and Se@Tri-PLNs was up to 280% and 397% relative to Tri suspensions, respectively. Furthermore, Se@Tri-PLNs demonstrated more potent in vivo anti-enteritis activity, which resulted in a marked resolution of ulcerative colitis. Polymer-lipid hybrid nanoparticles (PLNs) enabled drug supersaturation in the gut and the sustained release of Tri to facilitate absorption, while selenium surface engineering reinforced the formulation performance and in vivo anti-inflammatory efficacy. The present work provides a proof-of-concept for the combined therapy of inflammatory bowel disease (IBD) using phytomedicine and Se in an integrated nanosystem. Selenized PLNs loading anti-inflammatory phytomedicine may be valuable for the treatment of intractable inflammatory diseases.

Celastrol inhibits store operated calcium entry and suppresses psoriasis

Introduction: Psoriasis is an inflammatory autoimmune skin disease that is hard to cure and prone to relapse. Currently available global immunosuppressive agents for psoriasis may cause severe side effects, thus it is crucial to identify new therapeutic reagents and druggable signaling pathways for psoriasis. Methods: To check the effects of SOCE inhibitors on psoriasis, we used animal models, biochemical approaches, together with various imaging techniques, including calcium, confocal and FRET imaging. Results and discussion: Store operated calcium (Ca²⁺) entry (SOCE), mediated by STIM1 and Orai1, is crucial for the function of keratinocytes and immune cells, the two major players in psoriasis. Here we showed that a natural compound celastrol is a novel SOCE inhibitor, and it ameliorated the skin lesion and reduced PASI scores in imiquimod-induced psoriasis-like mice. Celastrol dose- and time-dependently inhibited SOCE in HEK cells and HaCaT cells, a keratinocyte cell line. Mechanistically, celastrol inhibited SOCE via its actions both on STIM1 and Orai1. It inhibited Ca²⁺ entry through constitutively-active Orai1 mutants independent of STIM1. Rather than blocking the conformational switch and oligomerization of STIM1 during SOCE activation, celastrol diminished the transition from oligomerized STIM1 into aggregates, thus locking STIM1 in a partially active state. As a result, it abolished the functional coupling between STIM1 and Orai1, diminishing SOCE signals. Overall, our findings identified a new SOCE inhibitor celastrol that suppresses psoriasis, suggesting that SOCE pathway may serve as a new druggable target for treating psoriasis.

Targeting the Interplay of Autophagy and ROS for Cancer Therapy: An Updated Overview on Phytochemicals

Autophagy is an evolutionarily conserved self-degradation system that recycles cellular components and damaged organelles, which is critical for the maintenance of cellular homeostasis. Intracellular reactive oxygen species (ROS) are short-lived molecules containing unpaired electrons that are formed by the partial reduction of molecular oxygen. It is widely known that autophagy and ROS can regulate each other to influence the progression of cancer. Recently, due to the wide potent anti-cancer effects with minimal side effects, phytochemicals, especially those that can modulate ROS and autophagy, have attracted great interest of researchers. In this review, we afford an overview of the complex regulatory relationship between autophagy and ROS in cancer, with an emphasis on phytochemicals that regulate ROS and autophagy for cancer therapy. We also discuss the effects of ROS/autophagy inhibitors on the anti-cancer effects of phytochemicals, and the challenges associated with harnessing the regulation potential on ROS and autophagy of phytochemicals for cancer therapy.

How autophagy, a potential therapeutic target, regulates intestinal inflammation

Inflammatory bowel disease (IBD) is a group of disorders that cause chronic inflammation in the intestines, with the primary types including ulcerative colitis and Crohn's disease. The link between autophagy, a catabolic mechanism in which cells clear protein aggregates and damaged organelles, and intestinal health has been widely studied. Experimental animal studies and human clinical studies have revealed that autophagy is pivotal for intestinal homeostasis maintenance, gut ecology regulation and other aspects. However, few articles have summarized and discussed the pathways by which autophagy improves or exacerbates IBD. Here, we review how autophagy alleviates IBD through the specific genes (e.g., ATG16L1, IRGM, NOD2 and LRRK2), crosstalk of multiple phenotypes with autophagy (e.g., Interaction of autophagy with endoplasmic reticulum stress, intestinal antimicrobial defense and apoptosis) and autophagy-associated signaling pathways. Moreover, we briefly discuss the role of autophagy in colorectal cancer and current status of autophagy-based drug research for IBD. It should be emphasized that autophagy has cell-specific and environment-specific effects on the gut. One of the problems of IBD research is to understand how autophagy plays a role in intestinal tract under specific environmental factors. A better understanding of the mechanism of autophagy in the occurrence and progression of IBD will provide references for the development of therapeutic drugs and disease management for IBD in the future.

Celastrol inhibits rheumatoid arthritis by inducing autophagy via inhibition of the PI3K/AKT/mTOR signaling pathway

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder of the synovial joints. Celastrol (Cel) is a quinone-methylated triterpenoid extracted from Tripterygium wilfordii Hook F (TwHF) that has been proven to be effective in treating RA. However, the underlying molecular mechanism of celastrol in the treatment of RA remains unknown. This study explored the protective effect of celastrol against RA and the specific mechanisms of celastrol in vitro and in vivo.

METHODS

A chicken type II collagen (CII)-induced arthritis (CIA) mouse model was used to explore the anti-arthritic effects of celastrol, and paw swelling degree, the poly-arthritis index score and serum cytokine levels were determined. Pathological morphology was observed using hematoxylin and eosin (H&E) staining. The influences of celastrol on the proliferation of tumor necrosis factor-α (TNF-α)-induced fibroblast-like synoviocytes (FLSs) were tested by Cell Counting Kit-8 (CCK-8) assays and5-ethynyl-2'-deoxyuridine (EdU) staining assays. The level of autophagy was detected by transmission electron microscopy (TEM). Furthermore, the PI3K/AKT/mTOR pathway and the status of autophagy in the CIA model and FLSs were also detected by western blot and immunofluorescence staining.

RESULTS

The results showed that celastrol decreased arthritis severity and inhibited TNF-α-induced FLSs proliferation. Additionally, celastrol decreased the secretion of pro-inflammatory cytokines. Moreover, celastrol increased autophagosome levels and LC3B protein expression in TNF-α-treated FLSs. Furthermore, celastrol increased the protein expression of LC3-II and Beclin-1 and decreased the phosphorylation degree of mTOR and AKT.

CONCLUSION

In conclusion, our findings confirmed that celastrol ameliorates RA via the up-regulation of autophagy by inhibiting the PI3K/AKT/mTOR axis.

Interactions of Autophagy and the Immune System in Health and Diseases

Autophagy is a highly conserved process that utilizes lysosomes to selectively degrade a variety of intracellular cargo, thus providing quality control over cellular components and maintaining cellular regulatory functions. Autophagy is triggered by multiple stimuli ranging from nutrient starvation to microbial infection. Autophagy extensively shapes and modulates the inflammatory response, the concerted action of immune cells, and secreted mediators aimed to eradicate a microbial infection or to heal sterile tissue damage. Here, we first review how autophagy affects innate immune signaling, cell-autonomous immune defense, and adaptive immunity. Then, we discuss the role of non-canonical autophagy in microbial infections and inflammation. Finally, we review how crosstalk between autophagy and inflammation influences infectious, metabolic, and autoimmune disorders.

MiR-21 regulates epithelial-mesenchymal transition in intestinal fibrosis of Crohn's disease by targeting PTEN/mTOR

BACKGROUND

Previous studies suggested miR-21 regulated epithelial-mesenchymal transition (EMT) and fibrosis in organs. The aim of this study was to explore the role and mechanism of miR-21 in EMT process of CD(Crohn's disease)-associated intestinal fibrosis.

METHODS

Tissue biopsies from fibrotic and nonfibrotic intestine of CD patients, and non-CD patients were obtained; chronic intestinal fibrosis model established by TNBS was treated with antagonist of miR-21; human intestinal epithelial cell, NCM460, were transfected with miR-21 mimics or inhibitor. The expressions of PTEN and mTOR, EMT-related markers and severity of colitis and fibrosis were examined.

RESULTS

Compared to the controls, miR-21 was significantly upregulated in the intestinal tissues from CD patients with fibro stenosis, followed by decreased PTEN expression, increased EMT markers, and mTOR expression, and imbalanced ratio of MMP9(matrix metalloproteinase 9)/TIMP1(tissue inhibitor of metalloproteinase 1). MiR-21 downregulated the expression of PTEN and upregulated mTOR signal in NCM460 cell. Also, knocking miR-21 down reduced EMT in vitro. Inhibiting miR-21 with antagonists reversed TNBS-induced intestinal fibrosis in vivo, through suppressing EMT and balancing MMPs/TIMPs.

CONCLUSION

We identified the involvement of miR-21 in EMT during intestinal fibrosis via targeting PTEN and mTOR, and miR-21 inhibition relieved intestinal fibrosis by regulating extracellular matrix (ECM) remodeling . Our results indicated miR-21 as a potential new target for the treatment of fibrosis complication in CD.

Targeting autophagy in ethnomedicine against human diseases

ETHNOPHARMACOLOGICAL RELEVANCE

In the past five years, ethnopharmacy-based drugs have been increasingly used in clinical practice. It has been reported that hundreds of ethnopharmacy-based drugs can modulate autophagy to regulate physiological and pathological processes, and ethnomedicines also have certain therapeutic effects on illnesses, revealing the important roles of these medicines in regulating autophagy and treating diseases.

AIM OF THE STUDY

This study reviews the regulatory effects of natural products on autophagy in recent years, and discusses their pharmacological effects and clinical applications in the process of diseases. It provides a preliminary literature basis and reference for the research of plant drugs in the regulation of autophagy.

MATERIALS AND METHODS

A comprehensive systematic review in the fields of relationship between autophagy and ethnomedicine in treating diseases from PubMed electronic database was performed. Information was obtained from documentary sources.

RESULTS

We recorded some illnesses associated with autophagy, then classified them into different categories reasonably. Based on the uses of these substances in different researches of diseases, a total of 80 active ingredients or compound preparations of natural drugs were searched. The autophagy mechanisms of these substances in the treatments of divers diseases have been summarized for the first time, we also looked forward to the clinical application of some of them.

CONCLUSIONS

Autophagy plays a key function in lots of illnesses, the regulation of autophagy has become one of the important means to prevent and treat these diseases. About 80 compounds and preparations involved in this review have been proved to have therapeutic effects on related diseases through the mechanism of autophagy. Experiments in vivo and in vitro showed that these compounds and preparations could treat these diseases by regulating autophagy. The typical natural products curcumin and tripterine have powerful roles in regulating autophagy and show good and diversified curative effects.

Celastrol attenuates the inflammatory response by inhibiting IL‑1β expression in triple‑negative breast cancer cells

IL-1 promotes cancer cell proliferation and invasiveness in various malignancies, such as breast and colorectal cancer. In the present study, the functional roles of IL-1β (IL1B) and the inhibitory effect of celastrol on IL1B expression were investigated in triple-negative breast cancer (TNBC) cells. The data revealed that celastrol markedly decreased IL1B expression and suppressed TNBC cell proliferation in a dose-dependent manner. The levels of IL1B and IL8 mRNA were significantly increased in TNBC cells compared with non-TNBC cells. In addition, IL1B augmented the expression levels of IL8 as well as matrix metalloproteinases (MMPs), including MMP-1 and MMP-9, in TNBC cells. Furthermore, IL1B expression was decreased by a specific MEK1/2 inhibitor, MEK162. Celastrol also promoted IL1B downregulation through the suppression of the MEK/ERK-dependent pathway. Furthermore, the results also revealed a decrease in IL1B-induced IL8, MMP-1, and MMP-9 expression in response to celastrol treatment. The induction of cellular invasion by IL1B was also markedly decreased by celastrol. Collectively, the present study results suggested celastrol as an effective drug for the treatment of TNBC, involving a reduction in IL1B expression, activity or signaling pathways.

Anti-inflammatory celastrol promotes a switch from leukotriene biosynthesis to formation of specialized pro-resolving lipid mediators

The pentacyclic triterpenoid quinone methide celastrol (CS) from Tripterygium wilfordii Hook. F. effectively ameliorates inflammation with potential as therapeutics for inflammatory diseases. However, the molecular mechanisms underlying the anti-inflammatory and inflammation-resolving features of CS are incompletely understood. Here we demonstrate that CS potently inhibits the activity of human 5-lipoxygenase (5-LOX), the key enzyme in pro-inflammatory leukotriene (LT) formation, in cell-free assays with IC₅₀ = 0.19-0.49 µM. Employing metabololipidomics using ultra-performance liquid chromatography coupled to tandem mass spectrometry in activated human polymorphonuclear leukocytes or M1 macrophages we found that CS (1 µM) potently suppresses 5-LOX-derived products without impairing the formation of lipid mediators (LM) formed by 12-/15-LOXs as well as fatty acid substrate release. Intriguingly, CS induced the generation of 12-/15-LOX-derived LM including the specialized pro-resolving mediator (SPM) resolvin D5 in human M2 macrophages. Finally, intraperitoneal pre-treatment of mice with 10 mg/kg CS strongly impaired zymosan-induced LT formation and simultaneously elevated the levels of SPM and related 12-/15-LOX-derived LM in peritoneal exudates, spleen and plasma in vivo. Conclusively, CS promotes a switch from LT biosynthesis to formation of SPM which may underlie the anti-inflammatory and inflammation-resolving effects of CS, representing an interesting pharmacological strategy for intervention with inflammatory disorders.

RNF8 induces autophagy and reduces inflammation by promoting AKT degradation via ubiquitination in ulcerative colitis mice

RING finger protein 8 (RNF8) is an E3 ligase that is pivotal for DNA repair. However, the role of RNF8 in ulcerative colitis (UC) remains unclear. The aim of this study is to investigate the effect and the mechanism of RNF8 on UC model induced by trinitrobenzene sulfonic acid (TNBS) in mice. Lentiviruses overexpressing RNF8 were injected into mice after the induction of UC. The histopathological changes in colon tissues were assessed by haematoxylin and eosin staining. The mRNA level of RNF8 was detected by real-time quantitative polymerase chain reaction. The protein levels of RNF8, autophagy-related proteins (LC3 and P62) and AKT/mammalian target of rapamycin (mTOR) signalling-related proteins were measured by Western blot. The pro-inflammatory cytokines (tumour necrosis factor-α and interleukin-1β) were examined by immunohistochemical analysis. Immunoprecipitation was performed to analyse the interaction between RNF8 and AKT1. The TNBS-induced UC mice exhibited colonic damage and inflammation, accompanied by decreased RNF8 expression, impaired autophagy and increased phosphorylation levels of AKT and mTOR in the colon. However, these alterations were reversed by RNF8 overexpression. Furthermore, RNF8 bound to AKT1 and mediated its ubiquitination. Collectively, RNF8 overexpression protects against TNBS-induced UC, which might be due to its enhancement of autophagy by suppressing the AKT/mTOR signalling via AKT1 ubiquitination.

Withaferin A alleviates fulminant hepatitis by targeting macrophage and NLRP3

Fulminant hepatitis (FH) is an incurable clinical syndrome where novel therapeutics are warranted. Withaferin A (WA), isolated from herb Withania Somnifera, is a hepatoprotective agent. Whether and how WA improves D-galactosamine (GalN)/lipopolysaccharide (LPS)-induced FH is unknown. This study was to evaluate the hepatoprotective role and mechanism of WA in GalN/LPS-induced FH. To determine the preventive and therapeutic effects of WA, wild-type mice were dosed with WA 0.5 h before or 2 h after GalN treatment, followed by LPS 30 min later, and then killed 6 h after LPS treatment. To explore the mechanism of the protective effect, the macrophage scavenger clodronate, autophagy inhibitor 3-methyladenine, or gene knockout mouse lines NLR family pyrin domain containing 3 (Nlrp3)-null, nuclear factor-erythroid 2-related factor 2 (Nrf2)-null, liver-specific AMP-activated protein kinase (Ampk)a1 knockout (Ampka1ΔHep) and liver-specific inhibitor of KB kinase β (Ikkb) knockout (IkkbΔHep) mice were subjected to GalN/LPS-induced FH. In wild-type mice, WA potently prevented GalN/LPS-induced FH and inhibited hepatic NLRP3 inflammasome activation, and upregulated NRF2 and autophagy signaling. Studies with Nrf2-null, Ampka1ΔHep, and IkkbΔHep mice demonstrated that the hepatoprotective effect was independent of NRF2, hepatic AMPKα1, and IκκB. Similarly, 3-methyladenine cotreatment failed to abolish the hepatoprotective effect of WA. The hepatoprotective effect of WA against GalN/LPS-induced FH was abolished after macrophage depletion, and partially reduced in Nlrp3-null mice. Consistently, WA alleviated LPS-induced inflammation partially dependent on the presence of NLRP3 in primary macrophage in vitro. Notably, WA potently and therapeutically attenuated GalN/LPS-induced hepatotoxicity. In conclusion, WA improves GalN/LPS-induced hepatotoxicity by targeting macrophage partially dependent on NLRP3 antagonism, while largely independent of NRF2 signaling, autophagy induction, and hepatic AMPKα1 and IκκB. These results support the concept of treating FH by pharmacologically targeting macrophage and suggest that WA has the potential to be repurposed for clinically treating FH as an immunoregulator.

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

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

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

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

Sanguisorba officinalis L. derived from herbal medicine prevents intestinal inflammation by inducing autophagy in macrophages

Disturbed activation of autophagy is implicated in the pathogenesis of inflammatory bowel disease. Accordingly, several autophagy-related genes have been identified as Crohn's disease susceptibility genes. We screened the autophagy activators from a library including 3,922 natural extracts using a high-throughput assay system. The extracts identified as autophagy activators were administered to mice with 2% dextran sodium sulfate (DSS). Among the autophagy inducers, Sanguisorba officinalis L. (SO) suppressed DSS-induced colitis. To identify the mechanism by which SO ameliorates colitis, epithelial cell and innate myeloid cells-specific Atg7-deficient mice (Villin-cre; Atg7^f/f and LysM-cre; Atg7^f/f mice, respectively) were analyzed. SO-mediated inhibition of colitis was observed in Villin-cre; Atg7^f/f mice. However, SO and a mixture of its components including catechin acid, ellagic acid, gallic acid, and ziyuglycoside II (Mix₄) did not suppressed colitis in LysM-cre; Atg7^f/f mice. In large intestinal macrophages (Mφ) of Atg7^f/f mice, SO and Mix₄ upregulated the expression of marker genes of anti-inflammatory Mφ including Arg1, Cd206, and Relma. However, these alterations were not induced in LysM-cre; Atg7^f/f mice. These findings indicate that SO and its active components ameliorate DSS-induced colitis by providing intestinal Mφ with anti-inflammatory profiles via promotion of Atg7-dependent autophagy.

Autophagy-mediated regulation of neutrophils and clinical applications

Autophagy, an adaptive catabolic process, plays a cytoprotective role in enabling cellular homeostasis in the innate and adaptive immune systems. Neutrophils, the most abundant immune cells in circulation, are professional killers that orchestrate a series of events during acute inflammation. The recent literature indicates that autophagy has important roles in regulating neutrophil functions, including differentiation, degranulation, metabolism and neutrophil extracellular trap formation, that dictate neutrophil fate. It is also becoming increasingly clear that autophagy regulation is critical for neutrophils to exert their immunological activity. However, evidence regarding the systematic communication between neutrophils and autophagy is insufficient. Here, we provide an updated overview of the function of autophagy as a regulator of neutrophils and discuss its clinical relevance to provide novel insight into potentially relevant treatment strategies.

Natural Products: Experimental Efficient Agents for Inflammatory Bowel Disease Therapy

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Inflammatory bowel disease (IBD) is a chronic, elusive disorder resulting in relapsing inflammation of intestine with incompletely elucidated etiology, whose two representative forms are ulcerative colitis (UC) and Crohn’s disease (CD). Accumulating researches have revealed that the individual genetic susceptibility, environmental risk elements, intestinal microbial flora, as well as innate and adaptive immune system are implicated in the pathogenesis and development of IBD. Despite remarkable progression of IBD therapy has been achieved by chemical drugs and biological therapies such as aminosalicylates, corticosteroids, antibiotics, anti-tumor necrosis factor (TNF)-α, anti-integrin agents, etc., healing outcome still cannot be obtained, along with inevitable side effects. Consequently, a variety of researches have focused on exploring new therapies, and found that natural products (NPs) isolated from herbs or plants may serve as promising therapeutic agents for IBD through antiinflammatory, anti-oxidant, anti-fibrotic and anti-apoptotic effects, which implicates the modulation on nucleotide- binding domain (NOD) like receptor protein (NLRP) 3 inflammasome, gut microbiota, intestinal microvascular endothelial cells, intestinal epithelia, immune system, etc. In the present review, we will summarize the research development of IBD pathogenesis and current mainstream therapy, as well as the therapeutic potential and intrinsic mechanisms of NPs in IBD.

New insights into the interplay between autophagy, gut microbiota and inflammatory responses in IBD

One of the most significant challenges of inflammatory bowel disease (IBD) research is to understand how alterations in the symbiotic relationship between the genetic composition of the host and the intestinal microbiota, under impact of specific environmental factors, lead to chronic intestinal inflammation. Genome-wide association studies, followed by functional studies, have identified a role for numerous autophagy genes in IBD, especially in Crohn disease. Studies using in vitro and in vivo models, in addition to human clinical studies have revealed that autophagy is pivotal for intestinal homeostasis maintenance, gut ecology regulation, appropriate intestinal immune responses and anti-microbial protection. This review describes the latest researches on the mechanisms by which dysfunctional autophagy leads to disrupted intestinal epithelial function, gut dysbiosis, defect in anti-microbial peptide secretion by Paneth cells, endoplasmic reticulum stress response and aberrant immune responses to pathogenic bacteria. A better understanding of the role of autophagy in IBD pathogenesis may provide better sub-classification of IBD phenotypes and novel approaches for disease management.Abbreviations: AIEC: adherent-invasive Escherichia coli; AMPK: AMP-activated protein kinase; ATF6: activating transcription factor 6; ATG: autophagy related; Atg16l1[ΔIEC] mice: mice with Atg16l1 depletion specifically in intestinal epithelial cells; Atg16l1[HM] mice: mice hypomorphic for Atg16l1 expression; BCL2: B cell leukemia/lymphoma 2; BECN1: beclin 1, autophagy related; CALCOCO2: calcium binding and coiled-coil domain 2; CASP: caspase; CD: Crohn disease; CGAS: cyclic GMP-AMP synthase; CHUK/IKKA: conserved helix-loop-helix ubiquitous kinase; CLDN2: claudin 2; DAPK1: death associated protein kinase 1; DCs: dendritic cells; DSS: dextran sulfate sodium; EIF2A: eukaryotic translation initiation factor 2A; EIF2AK: eukaryotic translation initiation factor 2 alpha kinase; ER: endoplasmic reticulum; ERBIN: Erbb2 interacting protein; ERN1/IRE1A: ER to nucleus signaling 1; FNBP1L: formin binding protein 1-like; FOXP3: forkhead box P3; GPR65: G-protein coupled receptor 65; GSK3B: glycogen synthase kinase 3 beta; IBD: inflammatory bowel disease; IECs: intestinal epithelial cells; IFN: interferon; IL: interleukin; IL10R: interleukin 10 receptor; IRGM: immunity related GTPase M; ISC: intestinal stem cell; LAMP1: lysosomal-associated membrane protein 1; LAP: LC3-associated phagocytosis; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; LPS: lipopolysaccharide; LRRK2: leucine-rich repeat kinase 2; MAPK: mitogen-activated protein kinase; MHC: major histocompatibility complex; MIF: macrophage migration inhibitory factor; MIR/miRNA: microRNA; MTMR3: myotubularin related protein 3; MTOR: mechanistic target of rapamycin kinase; MYD88: myeloid differentiation primary response gene 88; NLRP3: NLR family, pyrin domain containing 3; NOD2: nucleotide-binding oligomerization domain containing 2; NPC: Niemann-Pick disease type C; NPC1: NPC intracellular cholesterol transporter 1; OMVs: outer membrane vesicles; OPTN: optineurin; PI3K: phosphoinositide 3-kinase; PRR: pattern-recognition receptor; PTPN2: protein tyrosine phosphatase, non-receptor type 2; PTPN22: protein tyrosine phosphatase, non-receptor type 22 (lymphoid); PYCARD/ASC: PYD and CARD domain containing; RAB2A: RAB2A, member RAS oncogene family; RELA: v-rel reticuloendotheliosis viral oncogene homolog A (avian); RIPK2: receptor (TNFRSF)-interacting serine-threonine kinase 2; ROS: reactive oxygen species; SNPs: single nucleotide polymorphisms; SQSTM1: sequestosome 1; TAX1BP1: Tax1 binding protein 1; Th: T helper 1; TIRAP/TRIF: toll-interleukin 1 receptor (TIR) domain-containing adaptor protein; TLR: toll-like receptor; TMEM173/STING: transmembrane protein 173; TMEM59: transmembrane protein 59; TNF/TNFA: tumor necrosis factor; Treg: regulatory T; TREM1: triggering receptor expressed on myeloid cells 1; UC: ulcerative colitis; ULK1: unc-51 like autophagy activating kinase 1; WT: wild-type; XBP1: X-box binding protein 1; XIAP: X-linked inhibitor of apoptosis.

Plant protein diet suppressed immune function by inhibiting spiral valve intestinal mucosal barrier integrity, anti-oxidation, apoptosis, autophagy and proliferation responses in amur sturgeon (Acipenser schrenckii)

An 8-week growth trial was conducted to investigate the effects of replacing dietary fishmeal with a plant protein blend on the growth performance, mucosal barrier integrity and the related regulation mechanism in Amur Sturgeon (Acipenser schrenckii) with initial weight of 87.48 g. Three isonitrogenous and isoenergetic diets were prepared. A basal diet containing 540 g/kg fishmeal (P0), whereas the other two diets were formulated by replacing 50% and 100% of FM with plant protein blend (soybean protein concentrate and cottonseed protein concentrate), and named as P50 and P100, respectively. Although essential amino acids, fatty acids, and available phosphorus had been balanced according to the nutrient requirement of sturgeon, compared with the fish of P0 and P50, the full plant protein diet (P100) significantly reduced growth performance and survival, and accompanied with serious spiral valve intestinal (SVI) damage. The increased tissue necrosis and failed responses in anti-oxidation, programming apoptosis, autophagy and cell proliferation system were regulated by inhibiting ERK1 phosphorylation, which indicated that SVI hypoimmunity and functional degradation were the main reasons for the high mortality and low utilization ability of plant protein in Amur sturgeon.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Hierarchical assembly of hyaluronan coated albumin nanoparticles for pancreatic cancer chemoimmunotherapy

Pancreatic cancer is a highly malignant carcinoma with limited effective treatment options, resulting in a poor patient survival rate of less than 5%. In this study, cationic albumin nanoparticles were assembled with negatively charged hyaluronic acid (HA) to achieve a hierarchical nanostructure and efficient delivery of small molecule drugs to the tumor site in the pancreas. A combination of chemotherapy with indoleamine-2,3-dioxygenase (IDO) inhibition was explored to enhance the chemotherapeutic efficacy in vivo. Hydrophobic celastrol (CLT) and hydrophilic 1-methyltryptophan (MT) were concurrently loaded in HA coated cationic albumin nanoparticles (HNPs) with an average size of ∼300 nm. The size of HNPs was reduced in the presence of hyaluronidase to facilitate penetration into deep tumor tissues. Also, the biodistribution study in the C57BL/6 mice xenograft model showed enhanced tumor accumulation and prolonged circulation of HNPs. Compared with CLT solution, the combination of CLT with MT showed significantly enhanced tumor inhibition in both xenograft and orthotopic pancreatic cancer mice models via downregulating the immunosuppressive tumor microenvironment. Taken together, the combination of CLT with MT administered via HNPs represents a highly promising strategy for targeted pancreatic cancer therapy.

Bryostatin-1 ameliorated experimental colitis in Il-10-/- Mice by protecting the intestinal barrier and limiting immune dysfunction

Bryostatin‐1 (Bry‐1) has been proven to be effective and safe in clinical trials of a variety of immune‐related diseases. However, little is known about its effect on Crohn's disease (CD). We aimed to investigate the impact of Bry‐1 on CD‐like colitis and determine the mechanism underlying this effect. In the present study, 15‐week‐old male Il‐10^−/− mice with spontaneous colitis were divided into positive control and Bry‐1‐treated (Bry‐1, 30 μg/kg every other day, injected intraperitoneally for 4 weeks) groups. Age‐matched, male wild‐type (WT) mice were used as a negative control. The effects of Bry‐1 on colitis, intestinal barrier function and T cell responses as well as the potential regulatory mechanisms were evaluated. We found that the systemic delivery of Bry‐1 significantly ameliorated colitis in Il‐10^−/− mice, as demonstrated by decreases in the disease activity index (DAI), inflammatory score and proinflammatory mediator levels. The protective effects of Bry‐1 on CD‐like colitis included the maintenance of intestinal barrier integrity and the helper T cell (Th)/regulatory T cell (Treg) balance. These effects of Bry‐1 may act in part through nuclear factor erythroid 2‐related factor 2 (Nrf2) signalling activation and STAT3/4 signalling inhibition. The protective effect of Bry‐1 on CD‐like colitis suggests Bry‐1 has therapeutic potential in human CD, particularly given the established clinical safety of Bry‐1.

Celastrol ameliorates Aspergillus fumigatus keratitis via inhibiting LOX-1

PURPOSE

To investigate the effect of Celastrol (CLT) on Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

Primary peritoneal macrophages of C57BL/6 mice were pretreated with CLT before A. fumigatus hyphae stimulation. C57BL/6 mice were infected with A. fumigatus. Mice corneas were treated with CLT from 1 day post infection. Clinical score, PCR, ELISA and Western blot were used to test expression of anti-inflammatory mediators, proinflammatory mediators and Lectin-like oxidized low-density lipoprotein receptor 1(LOX-1). The protein levels of p38MAPK after pretreated with CLT in macrophages of C57BL/6 mice challenged with A. fumigatus were tested by Western blot.

RESULTS

C57BL/6 mice treated with CLT from 1 day post infection showed decreased disease, IL-1β, TNF-α, IL-10, TGF-β, MIP-2 and LOX-1 levels. CLT treatment markedly inhibiting mRNA and proteins levels of anti-inflammatory mediators, proinflammatory mediators and LOX-1 in macrophages of C57BL/6 mice compared with control group. CLT pretreatment before A. fumigatus stimulation obviously inhibiting protein levels of p38MAPK versus DMSO pretreated group in macrophages of C57BL/6 mice challenged with A. fumigatus.

CONCLUSION

These data provide evidences that CLT ameliorates A. fumigatus keratitis of C57BL/6 mice via inhibiting LOX-1. CLT pretreatment before A. fumigatus stimulation decreased levels of inflammation in macrophages of C57BL/6 mice, which may be regulated by p-p38MAPK.

Autophagy: roles in intestinal mucosal homeostasis and inflammation

The intestinal mucosa is a site of multiple stressors and forms the barrier between the internal and external environment. In the intestine, a complex interplay between the microbiota, epithelial barrier and the local immune system maintains homeostasis and promotes a healthy gut. One of the major cellular catabolic processes that regulate this homeostasis is autophagy. Autophagy is required to maintain anti-microbial defense, epithelial barrier integrity and mucosal immune response. Dysregulation of the autophagy process causes disruption of several aspects of the intestinal epithelium and the immune system that can lead to an inappropriate immune response and subsequent inflammation. Genome-wide association studies have found an association between several risk loci in autophagy genes and inflammatory bowel disease. The aim of the current review is to provide an update on the role of autophagy in intestinal mucosal physiology and in the control of inappropriate inflammation.

Autophagy in Human Health and Disease: Novel Therapeutic Opportunities

SIGNIFICANCE

In eukaryotes, autophagy represents a highly evolutionary conserved process, through which macromolecules and cytoplasmic material are degraded into lysosomes and recycled for biosynthetic or energetic purposes. Dysfunction of the autophagic process has been associated with the onset and development of many human chronic pathologies, such as cardiovascular, metabolic, and neurodegenerative diseases as well as cancer. Recent Advances: Currently, comprehensive research is being carried out to discover new therapeutic agents that are able to modulate the autophagic process in vivo. Recent evidence has shown that a large number of natural bioactive compounds are involved in the regulation of autophagy by modulating several transcriptional factors and signaling pathways.

CRITICAL ISSUES

Critical issues that deserve particular attention are the inadequate understanding of the complex role of autophagy in disease pathogenesis, the limited availability of therapeutic drugs, and the lack of clinical trials. In this context, the effects that natural bioactive compounds exert on autophagic modulation should be clearly highlighted, since they depend on the type and stage of the pathological conditions of diseases.

FUTURE DIRECTIONS

Research efforts should now focus on understanding the survival-supporting and death-promoting roles of autophagy, how natural compounds interact exactly with the autophagic targets so as to induce or inhibit autophagy and on the evaluation of their pharmacological effects in a more in-depth and mechanistic way. In addition, clinical studies on autophagy-inducing natural products are strongly encouraged, also to highlight some fundamental aspects, such as the dose, the duration, and the possible synergistic action of these compounds with conventional therapy.

The relationship between autophagy and the immune system and its applications for tumor immunotherapy

Autophagy is a genetically well-controlled cellular process that is tightly controlled by a set of core genes, including the family of autophagy-related genes (ATG). Autophagy is a “double-edged sword” in tumors. It can promote or suppress tumor development, which depends on the cell and tissue types and the stages of tumor. At present, tumor immunotherapy is a promising treatment strategy against tumors. Recent studies have shown that autophagy significantly controls immune responses by modulating the functions of immune cells and the production of cytokines. Conversely, some cytokines and immune cells have a great effect on the function of autophagy. Therapies aiming at autophagy to enhance the immune responses and anti-tumor effects of immunotherapy have become the prospective strategy, with enhanced antigen presentation and higher sensitivity to CTLs. However, the induction of autophagy may also benefit tumor cells escape from immune surveillance and result in intrinsic resistance against anti-tumor immunotherapy. Increasing studies have proven the optimal use of either ATG inducers or inhibitors can restrain tumor growth and progression by enhancing anti-tumor immune responses and overcoming the anti-tumor immune resistance in combination with several immunotherapeutic strategies, indicating that induction or inhibition of autophagy might show us a prospective therapeutic strategy when combined with immunotherapy. In this article, the possible mechanisms of autophagy regulating immune system, and the potential applications of autophagy in tumor immunotherapy will be discussed.

The Autophagy in Osteoimmonology: Self-Eating, Maintenance, and Beyond

It has been long realized that the immune and skeletal systems are closely linked. This crosstalk, also known as osteoimmunology, is a primary process required for bone health. For example, the immune system acts as a key regulator in osteoclasts-osteoblasts coupling to maintain the balanced bone remodeling. Osteoimmunology is achieved through many cellular and molecular processes, among which autophagy has recently been found to play an indispensable role. Autophagy is a highly conserved process in eukaryotic cells, by which the cytoplasm components such as dysfunctional organelles are degraded through lysosomes and then returned to the cytosol for reuse. Autophagy is present in all cells at basal levels to maintain homeostasis and to promote cell survival in response to cellular stress conditions such as nutrition deprivation and hypoxia. Autophagy is a required process in immune cell activation/polarization and osteoclast differentiation, which protecting cells from oxidative stress. The essential of autophagy in osteogenesis is its involvement in osteoblast differentiation and mineralization, especially the role of autophagosome in extracellular calcium transportation. The modulatory feature of autophagy in both immune and skeleton systems suggests its crucial roles in osteoimmunology. Furthermore, autophagy also participates in the maintenance of bone marrow hematopoietic stem cell niche. The focus of this review is to highlight the role of autophagy in the immune-skeleton interactions and the effects on bone physiology, as well as the future application in translational research.

Targeting Autophagy with Small-Molecule Modulators in Immune-Related Diseases

Autophagy, a highly conserved and multistep lysosomal degradation process, plays a pivotal role in maintaining cellular and physiological homeostasis. Of note, autophagy controls intracellular homeostasis and cell responses to stresses by regulating the self-renewal, maturation, and survival of immune cells. And dysregulation of autophagy in immune cells may contribute to the inflammatory disorders and defect in immune responses against invasive pathogens. Accumulating evidence have indicated that dysregulated autophagy participates in the pathology of immune-related diseases. Therefore, targeting autophagy might represent a promising therapeutic strategy for treatment of immune-related diseases. In this chapter, we focus on discussing the link between autophagy and pathogenesis of immune-related diseases, as well as the dysregulation of autophagy-related signaling pathways, in different diseases. Moreover, we highlight the therapeutic potential of currently used small-molecule modulators of autophagy for treatment of immune-related diseases and illustrate the mechanisms of these small-molecule modulators.

The role of autophagy in colitis-associated colorectal cancer

Autophagy is an evolutionarily conserved catabolic process that eliminates harmful components through lysosomal degradation. In addition to its role in maintaining cellular homeostasis, autophagy is critical to pathological processes, such as inflammation and cancer. Colitis-associated colorectal cancer (CAC) is a specific type of colorectal cancer that develops from long-standing colitis in inflammatory bowel disease (IBD) patients. Accumulating evidence indicates that autophagy of microenvironmental cells plays different but vital roles during tumorigenesis and CAC development. Herein, after summarizing the recent advances in understanding the role of autophagy in regulating the tumor microenvironment during different CAC stages, we draw the following conclusions: autophagy in intestinal epithelial cells inhibits colitis and CAC initiation but promotes CAC progression; autophagy in macrophages inhibits colitis, but its function on CAC is currently unclear; autophagy in neutrophils and cancer-associated fibroblasts (CAFs) promotes both colitis and CAC; autophagy in dendritic cells (DCs) and T cells represses both colitis and CAC; autophagy in natural killer cells (NKs) inhibits colitis, but promotes CAC; and autophagy in endothelial cells plays a controversial role in colitis and CAC. Understanding the role of autophagy in specific compartments of the tumor microenvironment during different stages of CAC may provide insight into malignant transformation, tumor progression, and combination therapy strategies for CAC.

Boosting mTOR-dependent autophagy via upstream TLR4-MyD88-MAPK signalling and downstream NF-κB pathway quenches intestinal inflammation and oxidative stress injury

BACKGROUND AND AIMS

Defective autophagy has been proposed as an important event in a growing number of autoimmune and inflammatory diseases such as rheumatoid arthritis and lupus. However, the precise role of mechanistic target of rapamycin (mTOR)-dependent autophagy and its underlying regulatory mechanisms in the intestinal epithelium in response to inflammation and oxidative stress remain poorly understood.

METHODS

The levels of p-mTOR, LC3B, p62 and autophagy in mice and LPS-treated cells were examined by immunoblotting, immunohistochemistry, confocal microscopy and transmission electron microscopy (TEM). We evaluated the expression of IL-1β, IL-8, TNF-α, MDA, SOD and T-AOC by quantitative real time-polymerase chain reaction (qRT-PCR) and commercially available kits after silencing of mTOR and ATG5. In vivo modulation of mTOR and autophagy was achieved by using AZD8055, rapamycin and 3-methyladenine. Finally, to verify the involvement of TLR4 signalling and the NF-κB pathway in cells and active ulcerative colitis (UC) patients, immunofluorescence, qRT-PCR, immunoblotting and TEM were performed to determine TLR4 signalling relevance to autophagy and inflammation.

RESULTS

The mTOR-dependent autophagic flux impairment in a murine model of colitis, human intestinal epithelial cells and active UC patients is probably regulated by TLR4-MyD88-MAPK signalling and the NF-κB pathway. Silencing mTOR remarkably attenuated, whereas inhibiting ATG5 aggravated, LPS-induced inflammation and oxidative injury. Pharmacological administration of mTOR inhibitors and autophagy stimulators markedly ameliorated experimental colitis and oxidative stress in vivo.

CONCLUSIONS

Our findings not only shed light on the regulatory mechanism of mTOR-dependent autophagy, but also provided potential therapeutic targets for intestinal inflammatory diseases such as refractory inflammatory bowel disease.

GPR120, a potential therapeutic target for experimental colitis in IL-10 deficient mice

It has been proved that interleukin-10-knockout (IL-10 KO) mice display the most similar characteristics to that of human Crohn's disease (CD). Docosahexaenoic acid (DHA) has well established beneficial effects on human and animal models health with potent anti-inflammatory effects with poorly understood mechanisms. This study was aimed at figuring out whether DHA could ameliorate the Crohn's colitis by activating GPR120 and whether GPR120 could be a potential therapeutic target for CD.16 week-old mice included in our present study were divided into three groups, WT group, IL-10 KO group and DHA group(IL-10 KO mice with DHA treatment, i.g., 35.5mg/kg/d), containing 8 mice in each group. The severity of colitis, pro-inflammatory cytokines concentrations, the expression/distribution of protein GPR120 and TAK1/IKK-α/IkB-α/p65 pathway in the proximal colons were evaluated at the end of the experiment. Administration of DHA showed promising results in the experimental chronic colitis (demonstrated by reduced infiltration of inflammatory cells, lowered inflammation scores, decreased pro-inflammatory cytokines) and body weight loss improvement. Moreover, in the DHA-treated mice, enhanced expression and improved distribution integrity of protein GPR120 were observed, which was probably associated with the regulation of TAK1/IKK-α/IkB-α/p65 pathway. Our results indicated that triggering GPR120 via the inhibition of TAK1/IKK-α/IkB-α/p65 pathway might be an important target for Crohn's colitis.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.

Autophagy: a new pathway for traditional Chinese medicine

Autophagy is a major intracellular degradation pathway that sequesters multiple cytoplasmic components, including accumulated proteins, damaged organelles, or invading micro-organisms and delivers them to lysosomes for degradation. Autophagy dysregulation is implicated in the pathogenesis of multiple diseases, such as aging, cancers, diabetes. The latest insights into molecular mechanisms of autophagy lead to the discovery of potential drug targets. Traditional drugs with new clinical applications are not only commonly found in western medicines, but also highlighted in traditional Chinese medicines (TCMs). Recent research findings shed light on the potential novel applications and formulation of TCMs via regulation of autophagy, indicating autophagy modulation may be an important mechanism underlying the therapeutic effect of TCMs in treating diseases. Here, we summarize the roles of autophagy in the pharmacological actions of TCMs and discuss to discover ideal autophagy modulators from TCMs with considerably higher selectivity for various human disease treatment.

Celastrol alleviates angiotensin II‑mediated vascular smooth muscle cell senescence via induction of autophagy

Reactive oxygen species (ROS) production has been implicated in the promotion of cellular senescence. Celastrol, a quinone methide triterpenoid isolated from the Celastraceae family, exerts antioxidant effects and enhances autophagy in various cell types. Since autophagy serves an important role in regulating ROS, it was hypothesized that the antioxidant effect of celastrol is via enhanced autophagy, thus inhibiting cell senescence. Therefore, the present study used a Senescence β‑Galactosidase Staining kit, western blot analysis and cell cycle analysis to investigate whether celastrol alleviates angiotensin (Ang) II‑induced cellular senescence by upregulating autophagy in vascular smooth muscle cells (VSMCs). The results demonstrated that celastrol reduced Ang II‑induced senescence of VSMCs. Ang II‑induced generation of ROS and the subsequent VSMC senescence were counteracted by pretreatment with celastrol, determined by a ROS assay kit. Celastrol significantly upregulated VSMC autophagy, which reduced intracellular ROS and the subsequent cellular senescence induced by Ang II. Furthermore, celastrol markedly suppressed activity of the mechanistic target of rapamycin signaling pathway in VSMCs. In conclusion, the present study demonstrated that celastrol counteracts VSMC senescence probably by reducing ROS production via activation of autophagy, which may hold promise for the prevention and treatment of aging‑associated cardiovascular disorders such as atherosclerosis.

Selective degradation of PU.1 during autophagy represses the differentiation and antitumour activity of TH9 cells

Autophagy, a catabolic mechanism that involves degradation of cellular components, is essential for cell homeostasis. Although autophagy favours the lineage stability of regulatory T cells, the contribution of autophagy to the differentiation of effector CD4 T cells remains unclear. Here we show that autophagy selectively represses T helper 9 (T_H9) cell differentiation. CD4 T cells lacking Atg3 or Atg5 have increased interleukin-9 (IL-9) expression upon differentiation into T_H9 cells relative to Atg3- or Atg5-expressing control cells. In addition, the T_H9 cell transcription factor, PU.1, undergoes K63 ubiquitination and degradation through p62-dependent selective autophagy. Finally, the blockade of autophagy enhances T_H9 cell anticancer functions in vivo, and mice with T cell-specific deletion of Atg5 have reduced tumour outgrowth in an IL-9-dependent manner. Overall, our findings reveal an unexpected function of autophagy in the modulation of T_H9 cell differentiation and antitumour activity, and prompt potential autophagy-dependent modulations of T_H9 activity for cancer immunotherapy.

Autophagy is a cellular process for recycling cell constituents, and is essential for T cell activation, but its function in T cell polarization is still unclear. Here the authors show that autophagy induces the degradation of transcription factor PU.1 to negatively modulate T_H9 homeostasis and antitumour immunity.

Celastrol ameliorates inflammation through inhibition of NLRP3 inflammasome activation

Celastrol exhibits potential anti-inflammatory activity in a variety of inflammatory diseases, but the mechanism remains poorly understood. Activation of NLRP3 inflammasome is involved in multiple inflammatory diseases. Here, we show that celastrol abolishes the NLRP3 inflammasome activation, inhibits subsequent caspase-1 activation and IL-1β secretion both in vitro and in vivo. Notably, interruption of ASC oligomerization and autophagy activation are involved in NLRP3 inflammasome inactivation by celastrol. Importantly, in vivo results indicate that celastrol attenuates NLRP3 inflammasome-dependent inflammation diseases via autophagy-related pathway. Our results thus reveal celastrol as an inhibitor of NLRP3 inflammasome, implying the potential for clinical use of celastrol in treatment of NLRP3 inflammasome-driven inflammatory diseases.

A lipidomics investigation into the intervention of celastrol in experimental colitis

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