Macrophage CGI-58 deficiency activates ROS-inflammasome pathway to promote insulin resistance in mice

Association between PPAR polymorphisms and neurological functional disability of ischemic stroke

Peroxisome proliferator-activated receptor-γ (PPARγ) plays a protective role against brain injury after stroke in mice. However, the relationship between PPARγ gene polymorphisms and the functional outcome of acute ischemic stroke (AIS) remains unknown. 8822 patients from The Third China National Stroke Registry (CNSR-III) after whole-genome sequencing, two functional single nucleotide polymorphisms(SNPs) in PPARγ, rs1801282 C > G and rs3856806 C > T, were further analysed. The primary outcome was neurological functional disability at three months. Of the 8822 patients, 968 (11.0%) and 3497 (39.6%) were carriers of rs1801282 and rs3856806, respectively. Carriers of rs3856806 showed reduced risks for three-month neurological functional disability (OR, 0.84; 95% CI, 0.73-0.98; p = 0.02) and reduced risks for higher infarct volume (OR 0.90, 95% CI, 0.81-0.99, p = 0.04). They also had a reduced risk of neurological functional disability only in case of lower baseline IL-6 levels (OR 0.64, 95% CI 0.48-0.84, Pinteraction = 0.01). Carriers of rs1801282 had a reduced risk for three-month neurological functional disability (OR 0.77, 95% CI, 0.61-0.99, p = 0.04). Our study suggested that PPARγ polymorphisms are associated with a reduced risk for neurological functional disability and higher infarct volume in AIS. Therefore, PPARγ can be a potential therapeutic target in AIS.

Diverse Functions of Macrophages in Obesity and Metabolic Dysfunction-Associated Steatotic Liver Disease: Bridging Inflammation and Metabolism

Macrophages play crucial roles in immune response and tissue homeostasis, with their functions becoming increasingly complex in obesity-mediated metabolic disorders. This review explores the extensive range of macrophage activities within adipose and liver tissues, emphasizing their contribution to the pathogenesis and progression of obesity and its related metabolic dysfunction-associated steatotic liver disease (MASLD). In the context of obesity, macrophages respond adaptively to lipid overloads and inflammatory cues in adipose tissue, profoundly influencing insulin resistance and metabolic homeostasis. Concurrently, their role in the liver extends to moderating inflammation and orchestrating fibrotic responses, integral to the development of MASLD. Highlighting the spectrum of macrophage phenotypes across these metabolic landscapes, we summarize their diverse roles in linking inflammatory processes with metabolic functions. This review advocates for a deeper understanding of macrophage subsets in metabolic tissues, proposing targeted research to harness their therapeutic potential in mitigating MASLD and other metabolic disorders.

Stearic acid metabolism in human health and disease

Named after the Greek term for "hard fat", stearic acid has gradually entered people's field of vision. As an important component of various physiological cellular functions, stearic acid plays a regulatory role in diverse aspects of energy metabolism and signal transduction. Its applications range from serving as a bodily energy source to participating in endogenous biosynthesis. Similar to palmitate, stearic acid serves as a primary substrate for the stearoyl coenzyme A desaturase, which catalyzes the conversion of stearate to oleate and is involved in the synthesis of triglyceride and other complex lipids. Additionally, stearic acid functions as a vital signaling molecule in pathological processes such as cardiovascular diseases, diabetes development, liver injury and even nervous system disorders. Therefore, we conduct a comprehensive review of stearic acid, summarizing its role in various diseases and attempting to provide a systematic overview of its homeostasis, physiological functions, and pathological process. From a medical standpoint, we also explore potential applications and discuss stearic acid as a potential therapeutic target for the treatment of human diseases.

Identification of immune-related hub genes in spinal cord injury

OBJECTIVES

Immune regulation is a pivotal factor in the pathogenesis and repair of spinal cord injury (SCI). This study aims to explore potential immune center genes associated with spinal cord injury.

METHODS

The public data set GSE151371 was obtained from the GEO database. The R software package "limma" was used to identify differentially expressed genes (DEGs) in SCI. GO, KEGG and GSEA pathway analyses were performed using the DEGs. The key module genes related to spinal cord injury were selected through WGCNA analysis. Overlapping genes were extracted from WGCNA, DEGs, and immune-related genes. LASSO analysis was employed to identify central genes associated with SCI immunity. Pearson correlation analysis assessed the correlation between hub genes and immune cells in SCI. In addition, we further investigated the hub genes' expression, diagnostic potential, function, and targeted drugs.

RESULTS

We have identified three immunity-related hub genes (ABHD5, EDNRB, EDN3). Immune infiltration analysis showed that the hub gene was significantly associated with resting NK cells, M2 macrophages, and monocytes in the immune microenvironment of SCI. ROC analysis demonstrated that these hub genes have favorable diagnostic performance for SCI. Functional analysis revealed that ABHD5 is primarily associated with lipid metabolism pathways, while EDN3 and EDNRB are mainly involved in endothelin, downstream GPCR signaling, and ERK signaling transduction. In addition, we identified six potential targeted drugs based on our findings.

CONCLUSIONS

ABHD5, EDNRB, and EDN3 are involved in processes such as SCI progression or repair through immunomodulation and deserve further study.

Insulin combined with N-acetylcysteine attenuates type 1 diabetes-induced splenic inflammatory injury in canines by inhibiting the MAPKs-NF-κB signaling pathway and pyroptosis

PURPOSE

Type 1 diabetes (T1DM) is a chronic metabolic disorder that can cause damage to multiple organs including the spleen. Sole insulin therapy is not satisfactory. This study aims to investigate the effects and mechanisms of combined treatment with insulin and N-acetylcysteine (NAC) on spleen damage in T1DM canines, in order to identify drugs that may better assist patients in the management of diabetes and its complications.

METHODS

The canine model of T1DM was established by intravenous injection of alloxan (ALX) and streptozotocin (STZ). The therapeutic effects of insulin and NAC were evaluated by clinical manifestations, spleen protein and mRNA expression.

RESULTS

The results indicate that the combined treatment of insulin and NAC can alleviate hyperglycemia and hematologic abnormalities, improve splenic histopathological changes, prevent fibrous tissue proliferation, and glycogen deposition. In addition, we observed that this combination treatment significantly suppressed the protein expression of p-P65/P65 (17.6 %, P < 0.05), NLRP3 (46.8 %, P < 0.05), and p-P38/P38 (37.1 %, P < 0.05) induced by T1DM when compared to insulin treatment alone. Moreover, it also significantly decreased the mRNA expression of TLR4 (45.0 %, P < 0.01), TNF-α (30.3 %, P < 0.05), and NLRP3 (43.3 %, P < 0.05).

CONCLUSIONS

This combination has the potential to mitigate splenic inflammatory injury in T1DM canines by suppressing the activation of MAPKs-NF-κB pathway and pyroptosis. These findings provide a reference for the treatment strategies of diabetes and its complications.

TRPC absence induces pro-inflammatory macrophage polarization to promote obesity and exacerbate colorectal cancer

During the past half-century, although numerous interventions for obesity have arisen, the condition's prevalence has relentlessly escalated annually. Obesity represents a substantial public health challenge, especially due to its robust correlation with co-morbidities, such as colorectal cancer (CRC), which often thrives in an inflammatory tumor milieu. Of note, individuals with obesity commonly present with calcium and vitamin D insufficiencies. Transient receptor potential canonical (TRPC) channels, a subclass within the broader TRP family, function as critical calcium transporters in calcium-mediated signaling pathways. However, the exact role of TRPC channels in both obesity and CRC pathogenesis remains poorly understood. This study set out to elucidate the part played by TRPC channels in obesity and CRC development using a mouse model lacking all seven TRPC proteins (TRPC HeptaKO mice). Relative to wild-type counterparts, TRPC HeptaKO mice manifested severe obesity, evidenced by significantly heightened body weights, augmented weights of epididymal white adipose tissue (eWAT) and inguinal white adipose tissue (iWAT), increased hepatic lipid deposition, and raised serum levels of total cholesterol (T-CHO) and low-density lipoprotein cholesterol (LDL-C). Moreover, TRPC deficiency was accompanied by an decrease in thermogenic molecules like PGC1-α and UCP1, alongside a upsurge in inflammatory factors within adipose tissue. Mechanistically, it was revealed that pro-inflammatory factors originating from inflammatory macrophages in adipose tissue triggered lipid accumulation and exacerbated obesity-related phenotypes. Intriguingly, considering the well-established connection between obesity and disrupted gut microbiota balance, substantial changes in the gut microbiota composition were detected in TRPC HeptaKO mice, contributing to CRC development. This study provides valuable insights into the role and underlying mechanisms of TRPC deficiency in obesity and its related complication, CRC. Our findings offer a theoretical foundation for the prevention of adverse effects associated with TRPC inhibitors, potentially leading to new therapeutic strategies for obesity and CRC prevention.

The potential of short-chain fatty acid epigenetic regulation in chronic low-grade inflammation and obesity

Obesity and chronic low-grade inflammation, often occurring together, significantly contribute to severe metabolic and inflammatory conditions like type 2 diabetes (T2D), cardiovascular disease (CVD), and cancer. A key player is elevated levels of gut dysbiosis-associated lipopolysaccharide (LPS), which disrupts metabolic and immune signaling leading to metabolic endotoxemia, while short-chain fatty acids (SCFAs) beneficially regulate these processes during homeostasis. SCFAs not only safeguard the gut barrier but also exert metabolic and immunomodulatory effects via G protein-coupled receptor binding and epigenetic regulation. SCFAs are emerging as potential agents to counteract dysbiosis-induced epigenetic changes, specifically targeting metabolic and inflammatory genes through DNA methylation, histone acetylation, microRNAs (miRNAs), and long non-coding RNAs (lncRNAs). To assess whether SCFAs can effectively interrupt the detrimental cascade of obesity and inflammation, this review aims to provide a comprehensive overview of the current evidence for their clinical application. The review emphasizes factors influencing SCFA production, the intricate connections between metabolism, the immune system, and the gut microbiome, and the epigenetic mechanisms regulated by SCFAs that impact metabolism and the immune system.

Nutrient-sensing growth hormone secretagogue receptor in macrophage programming and meta-inflammation

OBJECTIVE

Obesity-associated chronic inflammation, aka meta-inflammation, is a key pathogenic driver for obesity-associated comorbidity. Growth hormone secretagogue receptor (GHSR) is known to mediate the effects of nutrient-sensing hormone ghrelin in food intake and fat deposition. We previously reported that global Ghsr ablation protects against diet-induced inflammation and insulin resistance, but the site(s) of action and mechanism are unknown. Macrophages are key drivers of meta-inflammation. To unravel the role of GHSR in macrophages, we generated myeloid-specific Ghsr knockout mice (LysM-Cre;Ghsrf/f).

METHODS

LysM-Cre;Ghsrf/f and control Ghsrf/f mice were subjected to 5 months of high-fat diet (HFD) feeding to induce obesity. In vivo, metabolic profiling of food intake, physical activity, and energy expenditure, as well as glucose and insulin tolerance tests (GTT and ITT) were performed. At termination, peritoneal macrophages (PMs), epididymal white adipose tissue (eWAT), and liver were analyzed by flow cytometry and histology. For ex vivo studies, bone marrow-derived macrophages (BMDMs) were generated from the mice and treated with palmitic acid (PA) or lipopolysaccharide (LPS). For in vitro studies, macrophage RAW264.7 cells with Ghsr overexpression or Insulin receptor substrate 2 (Irs2) knockdown were studied.

RESULTS

We found that Ghsr expression in PMs was increased under HFD feeding. In vivo, HFD-fed LysM-Cre;Ghsrf/f mice exhibited significantly attenuated systemic inflammation and insulin resistance without affecting food intake or body weight. Tissue analysis showed that HFD-fed LysM-Cre;Ghsrf/f mice have significantly decreased monocyte/macrophage infiltration, pro-inflammatory activation, and lipid accumulation, showing elevated lipid-associated macrophages (LAMs) in eWAT and liver. Ex vivo, Ghsr-deficient macrophages protected against PA- or LPS-induced pro-inflammatory polarization, showing reduced glycolysis, increased fatty acid oxidation, and decreased NF-κB nuclear translocation. At molecular level, GHSR metabolically programs macrophage polarization through PKA-CREB-IRS2-AKT2 signaling pathway.

CONCLUSIONS

These novel results demonstrate that macrophage GHSR plays a key role in the pathogenesis of meta-inflammation, and macrophage GHSR promotes macrophage infiltration and induces pro-inflammatory polarization. These exciting findings suggest that GHSR may serve as a novel immunotherapeutic target for the treatment of obesity and its associated comorbidity.

Effects of Calorie Restriction and Fasting on Macrophage: Potential Impact on Disease Outcomes?

Energy restriction, including calorie restriction and fasting, has garnered significant attention for its potential therapeutic effects on a range of chronic diseases (such as diabetes, obesity, and cancer) and aging. Since macrophages are critical players in many diseases, their response to energy restriction may impact disease outcomes. However, the diverse metabolic patterns and functions of macrophages can lead to variability in the effects of energy restriction on macrophages across different tissues and disease states. This review outlines the effects of energy restriction on macrophages in several diseases, offering valuable guidance for future studies and insights into the clinical applications of calorie restriction and fasting.

Early diagnosis for the onset of peri-implantitis based on artificial neural network

The aim of this study is to construct an artificial neural network (ANN) based on bioinformatic analysis to enable early diagnosis of peri-implantitis (PI). PI-related datasets were retrieved from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) and functional enrichment analyses were performed between PI and the control group. Furthermore, the infiltration of 22 immune cells in PI was analyzed using CIBERSORT. Hub genes were identified with random forest (RF) classification. The ANN model was then constructed for early diagnosis of PI. A total of 1,380 DEGs were identified. Enrichment analysis revealed the involvement of neutrophil-mediated immunity and the NF-kappa B signaling pathway in PI. Additionally, higher proportion of naive B cells, activated memory CD4 T cells, activated NK cells, M0 macrophages, M1 macrophages, and neutrophils were observed in the soft tissues surrounding PI. From the RF analysis, 13 hub genes (ST6GALNAC4, MTMR11, SKAP2, AKR1B1, PTGS2, CHP2, CPEB2, SYT17, GRIP1, IL10, RAB8B, ABHD5, and IGSF6) were selected. Subsequently, the ANN model for early diagnosis of PI was constructed with high performance. We identified 13 hub genes and developed an ANN model that accurately enables early diagnosis of PI.

[Role of metaflammation as a systemic manifestation of metabolic diseases]

Visceral obesity as a component of the metabolic syndrome is characterized by systemic and local inflammation, which can be quantified in organs (metaflammation). This process can be regarded as a chronic, sterile, and low-grade state of inflammation without infection, trauma, tumor or autoimmunity. It is caused by an inflammation of the visceral adipose tissue (adipose inflammation or adipoflammation) due to adipocyte hypertrophy and hyperplasia with increased infiltration by monocytes and macrophages. Important is the presence of proinflammatory, so-called polarized M1 macrophages that are induced by interferon gamma (IFN-γ) and lipopolysaccharides (LPS) with secretion of interleukin (IL)-6, tumor necrosis factor (TNF) and IL‑1. In contrast, the anti-inflammatory, so-called polarized M2 macrophages induced by IL‑4 and IL-13 with secretion of IL‑8 and IL-10 decrease. In addition, the secreted adipokine pattern changes from anti-inflammatory to proinflammatory. Adipocyte necrosis, local hypoxia, dysregulated autophagy, activation of inflammasomes, modulation of toll-like receptors, and epigenetic factors play a complex role. This mechanism results in local insulin resistance and subsequently a systemic insulin resistance of peripheral organs as well as a spillover of local mediators of inflammation into the systemic circulation (measured as obesity C‑reactive protein, CRP). The activation of inflammatory signal transduction cascades leads to inhibitory phosphorylation of the insulin signaling pathway and a weakening of the effect of insulin. In parallel, ectopic lipid accumulation occurs in the liver, musculature, pancreas, pericardium and lungs. Diacylglycerol (DAG) activates specific isoforms of protein kinase C (ε in the liver and τ in the musculature), which in turn lead to inhibition of the insulin signaling pathway. Insulin resistance in obesity and type 2 diabetes mellitus is an inflammatory disease. The aim of future translational approaches is an anti-inflammatory, molecularly individualized (precision medicine) treatment in adipose tissue (targeted therapy) and in organs of insulin resistance.

HMG-CoA Reductase Inhibitors Suppress Monosodium Urate-Induced NLRP3 Inflammasome Activation through Peroxisome Proliferator-Activated Receptor-γ Activation in THP-1 Cells

Peroxisome proliferator-activated receptor γ (PPAR-γ) is thought to negatively regulate NLRP3 inflammasome activation. The aim of this study was to identify the inhibitory effect of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) on monosodium urate (MSU) crystal-induced NLRP3 inflammasome activation through the regulation of PPAR-γ in THP-1 cells. The expression of PPAR-γ, NLRP3, caspase-1, and interleukin-1β (IL-1β) in human monocytic THP-1 cells transfected with PPAR-γ siRNA or not and stimulated with MSU crystals was assessed using quantitative a real time-polymerase chain reaction and Western blotting. The expression of those markers in THP-1 cells pretreated with statins (atorvastatin, simvastatin, and mevastatin) was also evaluated. Intracellular reactive oxygen species (ROS) were measured using H2DCF-DA and flow cytometry analyses. THP-1 cells treated with MSU crystals (0.3 mg/mL) inhibited PARR-γ and increased NLRP3, caspase-1, and IL-1β mRNA and protein expression, and all those changes were significantly reversed by treatment with atorvastatin, simvastatin, or mevastatin. PPAR-γ activity revealed that MSU crystals suppressed PPAR-γ activity, which was markedly augmented by atorvastatin, simvastatin, and mevastatin. Transfecting cells with PPAR-γ siRNA attenuated the inhibitory effect of statins on MSU crystal-mediated NLRP3 inflammasome activation. Statins also significantly reduced the intracellular ROS generation caused by stimulation with MSU crystals. The inhibitory effects of atorvastatin and simvastatin on intracellular ROS generation were reduced in THP-1 cells transfected with PPAR-γ siRNA. This study demonstrates that PPAR-γ is responsible for suppressing MSU-mediated NLRP3 inflammasome activation. The inhibitory effect of statins on MSU-induced NLRP3 inflammasome activation depends on PPAR-γ activity and production and the inhibition of ROS generation.

TRPC absence induces pro-inflammatory macrophages and gut microbe disorder, sensitizing mice to colitis

The transient receptor potential canonical (TRPC) channels, encoded in seven non-allelic genes, are important contributors to calcium fluxes, are strongly associated with various diseases. Here we explored the consequences of ablating all seven TRPCs in mice focusing on colitis. We discovered that absence of all seven TRPC proteins in mice (TRPC HeptaKO mice) promotes the development of dextran sulfate sodium (DSS)-induced colitis. RNA-sequence analysis highlighted an extremely pro-inflammatory profile in colons of DSS-treated TRPC HeptaKO mice, with an amount of increased pro-inflammatory cytokines and chemokines. Flow cytometry analysis showed that the infiltration of Ly6C^hi monocytes and neutrophils in colonic lamina propria was significantly increased in DSS-treated TRPC HeptaKO mice. Results also revealed that macrophages from TRPC HeptaKO mice exhibited M1 polarization and enhanced secretion of pro-inflammatory factors. In addition, the composition of gut microbiota was markedly disturbed in DSS-treated TRPC HeptaKO mice. However, upon antibiotic cocktail (Abx)-treatment, TRPC HeptaKO mice showed no significant differences with WT mice in disease severity. Collectively, these data suggest that ablation of all TRPCs promotes the development of DSS-induced colitis by inducing pro-inflammatory macrophages and gut microbiota disorder.

ABHD5-A Regulator of Lipid Metabolism Essential for Diverse Cellular Functions

The α/β-Hydrolase domain-containing protein 5 (ABHD5; also known as comparative gene identification-58, or CGI-58) is the causative gene of the Chanarin-Dorfman syndrome (CDS), a disorder mainly characterized by systemic triacylglycerol accumulation and a severe defect in skin barrier function. The clinical phenotype of CDS patients and the characterization of global and tissue-specific ABHD5-deficient mouse strains have demonstrated that ABHD5 is a crucial regulator of lipid and energy homeostasis in various tissues. Although ABHD5 lacks intrinsic hydrolase activity, it functions as a co-activating enzyme of the patatin-like phospholipase domain-containing (PNPLA) protein family that is involved in triacylglycerol and glycerophospholipid, as well as sphingolipid and retinyl ester metabolism. Moreover, ABHD5 interacts with perilipins (PLINs) and fatty acid-binding proteins (FABPs), which are important regulators of lipid homeostasis in adipose and non-adipose tissues. This review focuses on the multifaceted role of ABHD5 in modulating the function of key enzymes in lipid metabolism.

The Roles of Adipose Tissue Macrophages in Human Disease

Macrophages are a population of immune cells functioning in antigen presentation and inflammatory response. Research has demonstrated that macrophages belong to a cell lineage with strong plasticity and heterogeneity and can be polarized into different phenotypes under different microenvironments or stimuli. Many macrophages can be recruited by various cytokines secreted by adipose tissue. The recruited macrophages further secrete various inflammatory factors to act on adipocytes, and the interaction between the two leads to chronic inflammation. Previous studies have indicated that adipose tissue macrophages (ATMs) are closely related to metabolic diseases like obesity and diabetes. Here, we will not only conclude the current progress of factors affecting the polarization of adipose tissue macrophages but also elucidate the relationship between ATMs and human diseases. Furthermore, we will highlight its potential in preventing and treating metabolic diseases as immunotherapy targets.

Peroxisomes Regulate Cellular Free Fatty Acids to Modulate Mast Cell TLR2, TLR4, and IgE-Mediated Activation

Mast cells are specialized, tissue resident, immune effector cells able to respond to a wide range of stimuli. MCs are involved in the regulation of a variety of physiological functions, including vasodilation, angiogenesis and pathogen elimination. In addition, MCs recruit and regulate the functions of many immune cells such as dendritic cells, macrophages, T cells, B cells and eosinophils through their selective production of multiple cytokines and chemokines. MCs generate and release multi-potent molecules, such as histamine, proteases, prostanoids, leukotrienes, heparin, and many cytokines, chemokines, and growth factors through both degranulation dependent and independent pathways. Recent studies suggested that metabolic shifts dictate the activation and granule content secretion by MCs, however the metabolic signaling promoting these events is at its infancy. Lipid metabolism is recognized as a pivotal immunometabolic regulator during immune cell activation. Peroxisomes are organelles found across all eukaryotes, with a pivotal role in lipid metabolism and the detoxification of reactive oxygen species. Peroxisomes are one of the emerging axes in immunometabolism. Here we identified the peroxisome as an essential player in MCs activation. We determined that lack of functional peroxisomes in murine MCs causes a significant reduction of interleukin-6, Tumor necrosis factor and InterleukinL-13 following immunoglobulin IgE-mediated and Toll like receptor 2 and 4 activation compared to the Wild type (WT) BMMCs. We linked these defects in cytokine release to defects in free fatty acids homeostasis. In conclusion, our study identified the importance of peroxisomal fatty acids homeostasis in regulating mast cell-mediated immune functions.

Protective Effects of Tiaoganquzhi Decoction in Treating inflammatory Injury of Nonalcoholic Fatty liver Disease by Promoting CGI-58 and Inhibiting Expression of NLRP3 Inflammasome

Tiaoganquzhi Decoction (TGQZD) is a traditional Chinese herbal formulation demonstrated to be a clinically effective treatment for nonalcoholic fatty liver disease (NAFLD), although details concerning its clinical mechanism are poor. This study aimed to explore the mechanism of TGQZD on improvement of inflammatory damage and dyslipidemia caused by NAFLD through the CGI-58/ROS/NLRP3 inflammasome pathway. In our research, the in vivo protective effects of TGQZD on HFD-induced liver injury in rats and in vitro using lipopolysaccharide (LPS)+palmitate (PA)-stimulated HepG-2 cells model. Histological changes were evaluated by hematoxylin-eosin and Oil Red O staining. Inflammatory cytokines and protein expression were analyzed by ELISA, Real time PCR and western blotting. Liver function, blood lipids, free fatty acids (FFA), and reactive oxygen species (ROS) were determined by biochemical detection. Our results indicated that TGQZD exhibited anti-inflammatory activity, reduced the severity of NAFLD and ameliorated the pathological changes. Further, TGQZD improved liver function and lipid metabolism in NAFLD rats. TGQZD lowered serum aspartate aminotransferase, alanine aminotransferase, triglyceride, and total cholesterol levels. TGQZD suppressed the formulation of FFA and ROS. It also reduced the expression and release of the inflammatory cytokine interleukin-1β by promoting CGI-58 expression and inhibiting the expression of FFA, TNF-α, and the NLRP3 inflammasome induced by ROS. TGQZD exhibited anti-inflammatory effects via the CGI-58, ROS and NLRP3 inflammasome pathway in vivo and in vitro, respectively. Our findings demonstrated that TGQZD is a useful and effective therapeutic agent for treating NAFLD via promotion of CGI-58 to inhibit the expression of ROS-induced NLRP3 inflammasome.

5-aza-2'-deoxycytidine potentiates anti-tumor immunity in colorectal peritoneal metastasis by modulating ABC A9-mediated cholesterol accumulation in macrophages

Background: 5-aza-2'-deoxycytidine (5Aza), a DNA methyltransferase (DNMT) inhibitor, could activate tumor adaptive immunity to inhibit tumor progression. However, the molecular mechanisms by which 5Aza regulates tumor immune microenvironment are still not fully understood.

Methods: The role of 5Aza in immune microenvironment of peritoneal carcinomatosis (PC) of colorectal cancer (CRC) was investigated. The effects of 5Aza on macrophage activation were studied by flow cytometry, real-time PCR, Western blotting assays, and Drug Affinity Responsive Target Stability (DARTS). The effects of 5Aza on tumor immunity were validated in stromal macrophages and T cells from CRC patients.

Results: 5Aza could stimulate the activation of macrophages toward an M1-like phenotype and subsequent activation of T cells in premetastatic fat tissues, and ultimately suppress CRC-PC in immune-competent mouse models. Mechanistically, 5Aza stimulated primary mouse macrophages toward to a M1-like phenotype characterized by the increase of p65 phosphorylation and IL-6 expression. Furthermore, we screened and identified ATP-binding cassette transporter A9 (ABC A9) as a binding target of 5Aza. 5Aza induced cholesterol accumulation, p65 phosphorylation and IL-6 expression in an ABC A9-dependent manner. Pharmacological inhibition of NF-κB, or genetic depletion of IL-6 abolished the antitumor effect of 5Aza in mice. In addition, the antitumor effect of 5Aza was synergistically potentiated by conventional chemotherapeutic drugs 5-Fu or OXP. Finally, we validated the reprogramming role of 5Aza in antitumor immunity in stromal macrophages and T cells from CRC patients.

Conclusions: Taken together, our findings showed for the first time that 5Aza suppressed CRC-PC by regulating macrophage-dependent T cell activation in premetastatic microenvironment, meanwhile uncovered a DNA methylation-independent mechanism of 5Aza in regulating ABC A9-associated cholesterol metabolism and macrophage activation.

Peroxisome Proliferator-Activated Receptors (PPARs) and Oxidative Stress in Physiological Conditions and in Cancer

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor superfamily. Originally described as “orphan nuclear receptors”, they can bind both natural and synthetic ligands acting as agonists or antagonists. In humans three subtypes, PPARα, β/δ, γ, are encoded by different genes, show tissue-specific expression patterns, and contribute to the regulation of lipid and carbohydrate metabolisms, of different cell functions, including proliferation, death, differentiation, and of processes, as inflammation, angiogenesis, immune response. The PPAR ability in increasing the expression of various antioxidant genes and decreasing the synthesis of pro-inflammatory mediators, makes them be considered among the most important regulators of the cellular response to oxidative stress conditions. Based on the multiplicity of physiological effects, PPAR involvement in cancer development and progression has attracted great scientific interest with the aim to describe changes occurring in their expression in cancer cells, and to investigate the correlation with some characteristics of cancer phenotype, including increased proliferation, decreased susceptibility to apoptosis, malignancy degree and onset of resistance to anticancer drugs. This review focuses on mechanisms underlying the antioxidant and anti-inflammatory properties of PPARs in physiological conditions, and on the reported beneficial effects of PPAR activation in cancer.

Macrophage deletion of Noc4l triggers endosomal TLR4/TRIF signal and leads to insulin resistance

In obesity, macrophages drive a low-grade systemic inflammation (LSI) and insulin resistance (IR). The ribosome biosynthesis protein NOC4 (NOC4) mediates 40 S ribosomal subunits synthesis in yeast. Hereby, we reported an unexpected location and function of NOC4L, which was preferentially expressed in human and mouse macrophages. NOC4L was decreased in both obese human and mice. The macrophage-specific deletion of Noc4l in mice displayed IR and LSI. Conversely, Noc4l overexpression by lentivirus treatment and transgenic mouse model improved glucose metabolism in mice. Importantly, we found that Noc4l can interact with TLR4 to inhibit its endocytosis and block the TRIF pathway, thereafter ameliorated LSI and IR in mice.

NLRP3 inflammasome and IL-1β pathway in type 2 diabetes and atherosclerosis: Friend or foe?

Type 2 diabetes and atherosclerosis have gradually garnered great attention as inflammatory diseases. Previously, the fact that Interleukin-1β (IL-1β) accelerates the development of type 2 diabetes and atherosclerosis has been proved in animal experiments and clinical trials. However, the continued studies found that the effect of IL-1β on type 2 diabetes and atherosclerosis is much more complicated than the negative impact. Nucleotide-binding oligomerization domain and leucine-rich repeat pyrin 3 domain (NLRP3) inflammasome, whose activation and assembly significantly affect the release of IL-1β, is a crucial effector activated by a variety of metabolites. The diversity of NLRP3 activation mode is one of the fundamental reasons for the intricate effects on the progression of type 2 diabetes and atherosclerosis, providing many new insights for us to intervene in metabolic diseases. This review focuses on how NLRP3 inflammasome affects the progression of type 2 diabetes and atherosclerosis and what opportunities and challenges it can bring us.

Association between the levels of CGI-58 and lipoprotein lipase in the placenta of patients with preeclampsia

Preeclampsia is an idiopathic disease of pregnancy, which seriously endangers the life of both the mother and the infant. The pathogenesis of preeclampsia has not been fully elucidated, although it is generally considered to be associated with abnormal lipid metabolism during pregnancy. Comparative gene identification-58 (CGI-58) and lipoprotein lipase (LPL) are involved in the first step of triglyceride hydrolysis and serve an important role in lipid transport in the placenta. The present study aimed therefore to investigate the association between CGI-58 and LPL in the placentas of patients with or without preeclampsia and to evaluate blood lipid levels. The patient cohort was divided into two groups, pregnant women with preeclampsia and normal pregnant women (control). According to biochemical analyses, reverse transcription-quantitative PCR, immunohistochemistry analysis and western blotting, the expression of CGI-58 and LPL in the placenta was detected, the blood lipid levels were evaluated and other clinical data were collected. Compared with the control group, triglycerides (TGs), low density lipoprotein-cholesterol (LDL-C), apolipoprotein B (ApoB) and atherosclerotic index (AI) were significantly higher in the preeclampsia group, whereas high density lipoprotein-cholesterol (HDL-C) and apolipoprotein A (ApoA) were significantly lower (P<0.05). Furthermore, the expression levels of CGI-58 and LPL in the placental tissue of the preeclampsia group was significantly lower than that of the control group (P<0.05). Linear correlation analysis demonstrated that there was a positive association between CGI-58 and LPL (r=0.602; P<0.05), that CGI-58 was positively associated with HDL-C (r=0.63; P<0.01) but negatively associated with TG and ApoB (r=0.840; P<0.01; and r=0.514; P<0.05, respectively), that LPL was positively associated with HDL-C (r=0.524; P<0.01) but negatively associated with TG and AI (r=0.659; P<0.01; and r=0.496; P<0.01, respectively). These results suggested that the expression of CGI-58 and LPL in the placenta was associated with the pathogenesis of preeclampsia and maternal lipids and the risk of preeclampsia was increased with decreasing expression levels of CGI-58 and LPL. Hence, CGI-58 and LPL may be used as important indicators for the diagnosis of preeclampsia and for the prevention of preeclampsia in pregnant women.

Inhibition of thioredoxin-interacting protein and inflammasome assembly using verapamil mitigates diabetic retinopathy and pancreatic injury

It has been previously demonstrated by our group that genetic inhibition of thioredoxin-interacting-protein (TXNIP) preserved retinal neuronal function in chemically-induced retinopathy. Moreover, elevated intracellular levels of TXNIP and calcium ions play important roles in hyperglycemia-induced oxidative stress and inflammation. Current study aimed to appraise the potential therapeutic benefits of pharmacological inhibition of TXNIP using verapamil in diabetic retinopathy. Diabetic retinopathy was assessed in type-1 diabetes rat model induced by a single intravenous injection of streptozotocin (45 mg/kg), with or without daily treatment with verapamil (10 mg/kg, oral) for 4 months. Verapamil treatment commenced 48 h post-streptozotocin insult and continued for 16 weeks. Untreated diabetic rats exhibited higher expression of toll-like-receptor-4 (TLR4), TXNIP, nucleotide-binding domain-like receptor protein-3 (NLRP3), caspase-1, cytochrome-c, and ssDNA as assessed immunohistochemically in both retinal and pancreatic tissues 16 weeks post-diabetes induction. This was associated with a reduced thioredoxin reductase (Trx-R) activity, increased release of TNF-α and IL-1β into vitreous fluid along with retinal ganglion cell (RGC) loss, pancreatic islets shrinkage, and enhanced CD34 expression. The treatment with verapamil enhanced Trx-R activity, significantly inhibited TLR4 mediated NLRP3-inflammasome assembly with subsequent diminishing of inflammatory markers (TNF-α and IL-1β) release into the vitreous, suppression of pathological angiogenesis, and preservation of RGC count and pancreatic islets diameter. Current study showed that using the calcium channel blocker, verapamil, interferes with the pathogenesis of diabetic retinopathy and pancreatic islets damage at multiple levels mainly through the inhibition of TLR4, TXNIP and NLRP3-inflammasome, suggesting its promising role as an anti-diabetic and a neuroprotective agent.

Telmisartan Inhibits the NLRP3 Inflammasome by Activating the PI3K Pathway in Neural Stem Cells Injured by Oxygen-Glucose Deprivation

Angiotensin II receptor blockers (ARBs) have been shown to exert neuroprotective effects by suppressing inflammatory and apoptotic responses. In the present study, the effects of the ARB telmisartan on the NLRP3 inflammasome induced by oxygen-glucose deprivation (OGD) in neural stem cells (NSCs) were investigated, as well as their possible association with the activation of the PI3K pathway. Cultured NSCs were treated with different concentrations of telmisartan and subjected to various durations of OGD. Cell counting, lactate dehydrogenase, bromodeoxyuridine, and colony-forming unit assays were performed to measure cell viability and proliferation. In addition, the activity of intracellular signaling pathways associated with the PI3K pathway and NLRP3 inflammasome was evaluated. Telmisartan alone did not affect NSCs up to a concentration of 10 μM under normal conditions but showed toxicity at a concentration of 100 μM. Moreover, OGD reduced the viability of NSCs in a time-dependent manner. Nevertheless, treatment with telmisartan increased the viability and proliferation of OGD-injured NSCs. Furthermore, telmisartan promoted the expression of survival-related proteins and mRNA while inhibiting the expression of death-related proteins induced by OGD. In particular, telmisartan attenuated OGD-dependent expression of the NLRP3 inflammasome and its related signaling proteins. These beneficial effects of telmisartan were blocked by a PI3K inhibitor. Together, these results indicate that telmisartan attenuated the activation of the NLRP3 inflammasome by triggering the PI3K pathway, thereby contributing to neuroprotection.

Nuclear Receptors as Multiple Regulators of NLRP3 Inflammasome Function

Nuclear receptors are important bridges between lipid signaling molecules and transcription responses. Beside their role in several developmental and physiological processes, many of these receptors have been shown to regulate and determine the fate of immune cells, and the outcome of immune responses under physiological and pathological conditions. While NLRP3 inflammasome is assumed as key regulator for innate and adaptive immune responses, and has been associated with various pathological events, the precise impact of the nuclear receptors on the function of inflammasome is hardly investigated. A wide variety of factors and conditions have been identified as modulators of NLRP3 inflammasome activation, and at the same time, many of the nuclear receptors are known to regulate, and interact with these factors, including cellular metabolism and various signaling pathways. Nuclear receptors are in the focus of many researches, as these receptors are easy to manipulate by lipid soluble molecules. Importantly, nuclear receptors mediate regulatory mechanisms at multiple levels: not only at transcription level, but also in the cytosol via non-genomic effects. Their importance is also reflected by the numerous approved drugs that have been developed in the past decade to specifically target nuclear receptors subtypes. Researches aiming to delineate mechanisms that regulate NLRP3 inflammasome activation draw a wide range of attention due to their unquestionable importance in infectious and sterile inflammatory conditions. In this review, we provide an overview of current reports and knowledge about NLRP3 inflammasome regulation from the perspective of nuclear receptors, in order to bring new insight to the potentially therapeutic aspect in targeting NLRP3 inflammasome and NLRP3 inflammasome-associated diseases.

Xiaoyaosan Exerts Therapeutic Effects on the Colon of Chronic Restraint Stress Model Rats via the Regulation of Immunoinflammatory Activation Induced by the TLR4/NLRP3 Inflammasome Signaling Pathway

Depression is the neurological manifestation most commonly associated with gastrointestinal diseases. The release of inflammatory cytokines mediated by TLR4/NLRP3 inflammasome signaling-induced immunoinflammatory activation may represent a common pathogenic process underlying the development of gastrointestinal diseases and depression. Clinical studies have indicated that Xiaoyaosan (XYS) can relieve depressive behavior by improving gastrointestinal symptoms. We previously demonstrated that XYS can reduce colonic inflammation in a rat model of chronic unpredictable mild stress; however, the precise anti-inflammatory mechanisms involved remain unclear. Here, we investigated whether XYS can ameliorate depressive behavior through regulating the TLR4/NLRP3 inflammasome signaling pathway, thereby inhibiting immunoinflammatory activation and reducing colonic proinflammatory cytokine levels. Fifty-two healthy male Sprague–Dawley rats were randomly divided into four groups (control, model, XYS, and fluoxetine). The latter three groups were subjected to 21 days of chronic restraint stress to generate a model of stress-induced depression. XYS and fluoxetine were administered intragastrically. Behavioral changes in the rats were assessed after 21 days. Serum and colon samples were collected, and the relative levels of the inflammation indicators IL-6, IL-1β, and TNF-α were determined by ELISA. Pathological changes in colon tissue were assessed by hematoxylin and eosin staining. The levels of TLR4, MyD88, NF-κB-p65, TAK1, IRAK1, and TRAF6 were detected by immunohistochemistry, while the gene and protein expression levels of TLR4, MyD88, NF-κB-p65, TAK1, IRAK1, TRAF6, NLRP3, ASC, and caspase-1 were detected by quantitative polymerase chain reaction (qPCR) and Western blotting. The results indicated that XYS could improve the depressive-like behavior and the weight loss of rats with stress-induced depression. Furthermore, depressed rats treated with XYS exhibited decreased expression levels of TLR4, MyD88, NF-κB-p65, TAK1, IRAK1, TRAF6, NLRP3, ASC, and caspase-1 in colonic tissue; reduced colon and serum concentrations of the inflammatory factors IL-6, IL-1β, and TNF-α; and lowered levels of colonic inflammation.

Effects of Early-Life Stress, Postnatal Diet Modulation and Long-Term Western-Style Diet on Peripheral and Central Inflammatory Markers

Early-life stress (ES) exposure increases the risk of developing obesity. Breastfeeding can markedly decrease this risk, and it is thought that the physical properties of the lipid droplets in human milk contribute to this benefit. A concept infant milk formula (IMF) has been developed that mimics these physical properties of human milk (Nuturis®, N-IMF). Previously, we have shown that N-IMF reduces, while ES increases, western-style diet (WSD)-induced fat accumulation in mice. Peripheral and central inflammation are considered to be important for obesity development. We therefore set out to test the effects of ES, Nuturis® and WSD on adipose tissue inflammatory gene expression and microglia in the arcuate nucleus of the hypothalamus. ES was induced in mice by limiting the nesting and bedding material from postnatal day (P) 2 to P9. Mice were fed a standard IMF (S-IMF) or N-IMF from P16 to P42, followed by a standard diet (STD) or WSD until P230. ES modulated adipose tissue inflammatory gene expression early in life, while N-IMF had lasting effects into adulthood. Centrally, ES led to a higher microglia density and more amoeboid microglia at P9. In adulthood, WSD increased the number of amoeboid microglia, and while ES exposure increased microglia coverage, Nuturis® reduced the numbers of amoeboid microglia upon the WSD challenge. These results highlight the impact of the early environment on central and peripheral inflammatory profiles, which may be key in the vulnerability to develop metabolic derangements later in life.

Inhibitory effect of PPARγ on NLRP3 inflammasome activation

Rationale: Stimulation of the NLRP3 inflammasome by metabolic byproducts is known to result in inflammatory responses and metabolic diseases. However, how the host controls aberrant NLRP3 inflammasome activation remains unclear. PPARγ, a known regulator of energy metabolism, plays an anti-inflammatory role through the inhibition of NF-κB activation and additionally attenuates NLRP3-dependent IL-1β and IL-18 production. Therefore, we hypothesized that PPARγ serves as an endogenous modulator that attenuates NLRP3 inflammasome activation in macrophages.

Methods: Mouse peritoneal macrophages with exposure to a PPARγ agonist at different stages and the NLRP3 inflammasome-reconstituted system in HEK293T cells were used to investigate the additional anti-inflammatory effect of PPARγ on NLRP3 inflammasome regulation. Circulating mononuclear cells of obese patients with weight-loss surgery were used to identify the in vivo correlation between PPARγ and the NLRP3 inflammasome.

Results: Exposure to the PPARγ agonist, rosiglitazone, during the second signal of NLRP3 inflammasome activation attenuated caspase-1 and IL-1β maturation. Moreover, PPARγ interfered with NLRP3 inflammasome formation by decreasing NLRP3-ASC and NLRP3-NLRP3 interactions as well as NLRP3-dependent ASC oligomerization, which is mediated through interaction between the PPARγ DNA-binding domain and the nucleotide-binding and leucine-rich repeat domains of NLRP3. Furthermore, PPARγ was required to limit metabolic damage-associated molecular pattern-induced NLRP3 inflammasome activation in mouse macrophages. Finally, the mature caspase-1/PPARγ ratio was reduced in circulating mononuclear cells of obese patients after weight-loss surgery, which we define as an “NLRP3 accelerating index”.

Conclusions: These results revealed an additional anti-inflammatory role for PPARγ in suppressing NLRP3 inflammasome activation through interaction with NLRP3. Thus, our study highlights that PPARγ agonism may be a therapeutic option for targeting NLRP3-related metabolic diseases.

Dietary fats suppress the peritoneal seeding of colorectal cancer cells through the TLR4/Cxcl10 axis in adipose tissue macrophages

Peritoneal carcinomatosis (PC) of colorectal cancer (CRC) is a terminal phase of malignancy with no effective strategies for the prevention of this condition. Here we established PC models in mice by intraperitoneal engraftment of CRC cells and revealed an unexpected role for a high-fat diet (HFD) in preventing metastatic seeding in the visceral fat. Mechanistically, the HFD stimulated the activation of adipose tissue macrophages (ATMs) toward an M1-like phenotype and enhanced ATM tumor phagocytosis in a TLR4-dependent manner. Furthermore, the TLR4–Cxcl10 axis in ATMs promoted T cell recruitment, and M1-like macrophages stimulated T cell activation in tumor-seeded fats. The inhibitory effect of the HFD on tumor seeding was abolished with the ablation of macrophages, inactivation of T cells, or blockade of the TLR4–Cxcl10 axis in macrophages. Finally, we showed that a HFD and conventional chemotherapeutic agents (oxaliplatin or 5-fluorouracil) synergistically improved the survival of tumor-seeded mice. Collectively, our findings demonstrate that peritoneal seeding of CRC can be suppressed by short-term treatment with a HFD in the early phase, providing a novel concept for the management of these patients in the clinic.

Stearic Acid and TNF-α Co-Operatively Potentiate MIP-1α Production in Monocytic Cells via MyD88 Independent TLR4/TBK/IRF3 Signaling Pathway

Increased circulatory and adipose tissue expression of macrophage inflammatory protein (MIP)-1α (CC motif chemokine ligand-3/CCL3) and its association with inflammation in the state of obesity is well documented. Since obesity is associated with increases in both stearic acid and tumor necrosis factor α (TNF-α) in circulation, we investigated whether stearic acid and TNF-α together could regulate MIP-1α/CCL3 expression in human monocytic cells, and if so, which signaling pathways were involved in MIP-1α/CCL3 modulation. Monocytic cells were treated with stearic acid and TNF-α resulted in enhanced production of MIP-1α/CCL3 compared to stearic acid or TNF-α alone. To explore the underlying mechanisms, cooperative effect of stearic acid for MIP-α/CCL3 expression was reduced by TLR4 blocking, and unexpectedly we found that the synergistic production of MIP-α/CCL3 in MyD88 knockout (KO) cells was not suppressed. In contrast, this MIP-α/CCL3 expression was attenuated by inhibiting TBK1/IRF3 activity. Cells deficient in IRF3 did not show cooperative effect of stearate/TNF-α on MIP-1α/CCL3 production. Furthermore, activation of IRF3 by polyinosinic-polycytidylic acid (poly I:C) produced a cooperative effect with TNF-α for MIP-1α/CCL3 production that was comparable to stearic acid. Individuals with obesity show high IRF3 expression in monocytes as compared to lean individuals. Furthermore, elevated levels of MIP-1α/CCL3 positively correlate with TNF-α and CD163 in fat tissues from individuals with obesity. Taken together, this study provides a novel model for the pathologic role of stearic acid to produce MIP-1α/CCL3 in the presence of TNF-α associated with obesity settings.

High Glucose-Aggravated Hepatic Insulin Resistance: Role of the NLRP3 Inflammasome in Kupffer Cells

OBJECTIVE

This study aimed to investigate whether the NLRP3 inflammasome in Kupffer cells (KCs) can be activated in response to high glucose (HG) and to evaluate its influence on hepatic insulin sensitivity.

METHODS

Primary KCs and hepatocytes were isolated from mice, and lipid accumulation, glucose output, and insulin sensitivity of hepatocytes were investigated after culturing either alone or with KCs exposed to HG. The influence of HG-induced NLRP3 inflammasome activation in KCs on insulin sensitivity of hepatocytes was examined. Treatment with gadolinium trichloride caused KC depletion, and, subsequently, a streptozotocin-induced hyperglycemic mouse model was used to confirm the influence of KCs on hepatic insulin sensitivity.

RESULTS

Hepatocytes cocultured with KCs showed enhanced lipid accumulation, glucose output, and impaired insulin sensitivity when exposed to HG. Enhanced NLRP3 inflammasome activation was also evident in both hepatocytes and KCs. Moreover, KCs that were pretreated with caspase-1 inhibitor, NLRP3 inhibitor, and NLRP3 small interfering RNA corrected coculture-induced aberrances in insulin action and NLRP3 inflammasome activation in hepatocytes. KC coculture also increased interleukin-1β (IL-1β)-mediated nuclear factor-κB (NF-κB) activation in hepatocytes. In hyperglycemic mice, KC depletion inhibited NLRP3 inflammasome activation and improved hepatic insulin sensitivity.

CONCLUSIONS

NLRP3 inflammasome activation impaired insulin sensitivity through KC-derived IL-1β-mediated NF-κB activation in hepatocytes exposed to HG.

OSBPL2 Is Required for the Binding of COPB1 to ATGL and the Regulation of Lipid Droplet Lipolysis

The accumulation of giant lipid droplets (LDs) increases the risk of metabolic disorders including obesity and insulin resistance. The lipolysis process involves the activation and transfer of lipase, but the molecular mechanism is not completely understood. The translocation of ATGL, a critical lipolysis lipase, from the ER to the LD surface is mediated by an energy catabolism complex. Oxysterol-binding protein-like 2 (OSBPL2/ORP2) is one of the lipid transfer proteins that regulates intracellular cholesterol homeostasis. A recent study has proven that Osbpl2^−/− pigs exhibit hypercholesterolemia and obesity phenotypes with an increase in adipocytes. In this study, we identified that OSBPL2 links the endoplasmic reticulum (ER) with LDs, binds to COPB1, and mediates ATGL transport. We provide important insights into the function of OSBPL2, indicating that it is required for the regulation of lipid droplet lipolysis.

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LD lipolysis is impaired in OSBPL2/osbpl2b-mutant HepG2 cells and zebrafish

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OSBPL2 interacts with COPB1, a subunit of the COPI complex located on LDs

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Altered COPI complexes on LDs may perturb the trafficking of lipolysis lipase ATGL

Inflammasome activation and regulation: toward a better understanding of complex mechanisms

Inflammasomes are cytoplasmic multiprotein complexes comprising a sensor protein, inflammatory caspases, and in some but not all cases an adapter protein connecting the two. They can be activated by a repertoire of endogenous and exogenous stimuli, leading to enzymatic activation of canonical caspase-1, noncanonical caspase-11 (or the equivalent caspase-4 and caspase-5 in humans) or caspase-8, resulting in secretion of IL-1β and IL-18, as well as apoptotic and pyroptotic cell death. Appropriate inflammasome activation is vital for the host to cope with foreign pathogens or tissue damage, while aberrant inflammasome activation can cause uncontrolled tissue responses that may contribute to various diseases, including autoinflammatory disorders, cardiometabolic diseases, cancer and neurodegenerative diseases. Therefore, it is imperative to maintain a fine balance between inflammasome activation and inhibition, which requires a fine-tuned regulation of inflammasome assembly and effector function. Recently, a growing body of studies have been focusing on delineating the structural and molecular mechanisms underlying the regulation of inflammasome signaling. In the present review, we summarize the most recent advances and remaining challenges in understanding the ordered inflammasome assembly and activation upon sensing of diverse stimuli, as well as the tight regulations of these processes. Furthermore, we review recent progress and challenges in translating inflammasome research into therapeutic tools, aimed at modifying inflammasome-regulated human diseases.

Dietary natural products as epigenetic modifiers in aging-associated inflammation and disease

Covering: up to 2020Chronic, low-grade inflammation is linked to aging and has been termed "inflammaging". Inflammaging is considered a key contributor to the development of metabolic dysfunction and a broad spectrum of diseases or disorders including declines in brain and heart function. Genome-wide association studies (GWAS) coupled with epigenome-wide association studies (EWAS) have shown the importance of diet in the development of chronic and age-related diseases. Moreover, dietary interventions e.g. caloric restriction can attenuate inflammation to delay and/or prevent these diseases. Common themes in these studies entail the use of phytochemicals (plant-derived compounds) or the production of short chain fatty acids (SCFAs) as epigenetic modifiers of DNA and histone proteins. Epigenetic modifications are dynamically regulated and as such, serve as potential therapeutic targets for the treatment or prevention of age-related disease. In this review, we will focus on the role for natural products that include phytochemicals and short chain fatty acids (SCFAs) as regulators of these epigenetic adaptations. Specifically, we discuss regulators of methylation, acetylation and acylation, in the protection from chronic inflammation driven metabolic dysfunction and deterioration of neurocognitive and cardiac function.

An Acetylation Switch of the NLRP3 Inflammasome Regulates Aging-Associated Chronic Inflammation and Insulin Resistance

It is well documented that the rate of aging can be slowed, but it remains unclear to which extent aging-associated conditions can be reversed. How the interface of immunity and metabolism impinges upon the diabetes pandemic is largely unknown. Here, we show that NLRP3, a pattern recognition receptor, is modified by acetylation in macrophages and is deacetylated by SIRT2, an NAD⁺-dependent deacetylase and a metabolic sensor. We have developed a cell-based system that models aging-associated inflammation, a defined co-culture system that simulates the effects of inflammatory milieu on insulin resistance in metabolic tissues during aging, and aging mouse models; and demonstrate that SIRT2 and NLRP3 deacetylation prevent, and can be targeted to reverse, aging-associated inflammation and insulin resistance. These results establish the dysregulation of the acetylation switch of the NLRP3 inflammasome as an origin of aging-associated chronic inflammation and highlight the reversibility of aging-associated chronic inflammation and insulin resistance.

CGI-58: Versatile Regulator of Intracellular Lipid Droplet Homeostasis

Comparative gene identification-58 (CGI-58), also known as α/β-hydrolase domain-containing 5 (ABHD5), is a member of a large family of proteins containing an α/β-hydrolase-fold. CGI-58 is well-known as the co-activator of adipose triglyceride lipase (ATGL), which is a key enzyme initiating cytosolic lipid droplet lipolysis. Mutations in either the human CGI-58 or ATGL gene cause an autosomal recessive neutral lipid storage disease, characterized by the excessive accumulation of triglyceride (TAG)-rich lipid droplets in the cytoplasm of almost all cell types. CGI-58, however, has ATGL-independent functions. Distinct phenotypes associated with CGI-58 deficiency commonly include ichthyosis (scaly dry skin), nonalcoholic steatohepatitis, and hepatic fibrosis. Through regulated interactions with multiple protein families, CGI-58 controls many metabolic and signaling pathways, such as lipid and glucose metabolism, energy balance, insulin signaling, inflammatory responses, and thermogenesis. Recent studies have shown that CGI-58 regulates the pathogenesis of common metabolic diseases in a tissue-specific manner. Future studies are needed to molecularly define ATGL-independent functions of CGI-58, including the newly identified serine protease activity of CGI-58. Elucidation of these versatile functions of CGI-58 may uncover fundamental cellular processes governing lipid and energy homeostasis, which may help develop novel approaches that counter against obesity and its associated metabolic sequelae.

The strategies of targeting the NLRP3 inflammasome to treat inflammatory diseases

The NLRP3 inflammasome is a cytoplasmic multiprotein complex, the assembly of which can be initiated in response to various exogenous or endogenous danger signals. Excessive activation of the NLRP3 inflammasome has been implicated in the pathogenesis of a wide variety of human inflammatory diseases, suggesting that the NLRP3 inflammasome is a potential target for the treatment of these diseases. However, clinical drugs targeting the NLRP3 inflammasome are still not available. Recent data have elucidated the different signaling pathways or events that can control NLRP3 inflammasome activation and have provided some potential compounds with anti-NLRP3 inflammasome activity. Here, we summarize the molecular mechanisms and diseases involved in NLRP3 inflammasome activation and discuss the potential strategies targeting different aspects of the NLRP3 inflammasome and its implications for the treatment of inflammatory diseases.

Macrophage ABHD5 Suppresses NFκB-Dependent Matrix Metalloproteinase Expression and Cancer Metastasis

Metabolic reprogramming in tumor-associated macrophages (TAM) is associated with cancer development, however, the role of macrophage triglyceride metabolism in cancer metastasis is unclear. Here, we showed that TAMs exhibited heterogeneous expression of abhydrolase domain containing 5 (ABHD5), an activator of triglyceride hydrolysis, with migratory TAMs expressing lower levels of ABHD5 compared with the nonmigratory TAMs. ABHD5 expression in macrophages inhibited cancer cell migration in vitro in xenograft models and in genetic cancer models. The effects of macrophage ABHD5 on cancer cell migration were dissociated from its metabolic function as neither triglycerides nor ABHD5-regulated metabolites from macrophages affected cancer cell migration. Instead, ABHD5 deficiency in migrating macrophages promoted NFκB p65-dependent production of matrix metalloproteinases (MMP). ABHD5 expression negatively correlated with MMP expression in TAMs and was associated with better survival in patients with colorectal cancer. Taken together, our findings show that macrophage ABHD5 suppresses NFκB-dependent MMP production and cancer metastasis and may serve as a prognostic marker in colorectal cancer. SIGNIFICANCE: These findings highlight the mechanism by which reduced expression of the metabolic enzyme ABHD5 in macrophages promotes cancer metastasis.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/21/5513/F1.large.jpg.

MicroRNA Post-transcriptional Regulation of the NLRP3 Inflammasome in Immunopathologies

Inflammation has a crucial role in protection against various pathogens. The inflammasome is an intracellular multiprotein signaling complex that is linked to pathogen sensing and initiation of the inflammatory response in physiological and pathological conditions. The most characterized inflammasome is the NLRP3 inflammasome, which is a known sensor of cell stress and is tightly regulated in resting cells. However, altered regulation of the NLRP3 inflammasome is found in several pathological conditions, including autoimmune disease and cancer. NLRP3 expression was shown to be post-transcriptionally regulated and multiple miRNA have been implicated in post-transcriptional regulation of the inflammasome. Therefore, in recent years, miRNA based post-transcriptional control of NLRP3 has become a focus of much research, especially as a potential therapeutic approach. In this review, we provide a summary of the recent investigations on the role of miRNA in the post-transcriptional control of the NLRP3 inflammasome, a key regulator of pro-inflammatory IL-1β and IL-18 cytokine production. Current approaches to targeting the inflammasome product were shown to be an effective treatment for diseases linked to NLRP3 overexpression. Although utilizing NLRP3 targeting miRNAs was shown to be a successful therapeutic approach in several animal models, their therapeutic application in patients remains to be determined.

ABHD5 blunts the sensitivity of colorectal cancer to fluorouracil via promoting autophagic uracil yield

The efficacy of Fluorouracil (FU) in the treatment of colorectal cancer (CRC) is greatly limited by drug resistance. Autophagy has been implicated in chemoresistance, but the role of selective autophagic degradation in regulating chemoresistance remains unknown. In this study, we revealed a critical role of ABHD5 in charging CRC sensitivity to FU via regulating autophagic uracil yield. We demonstrated that ABHD5 localizes to lysosome and interacts with PDIA5 to prevent PDIA5 from interacting with RNASET2 and inactivating RNASET2. ABHD5 deficiency releases PDIA5 to directly interact with RNASET2 and leave RNASET2 in an inactivate state, which impairs RNASET2-mediated autophagic uracil yield and promotes CRC cells to uptake FU as an exogenous uracil, thus increasing their sensitivity to FU. Our findings for the first time reveal a novel role of ABHD5 in regulating lysosome function, highlighting the significance of ABHD5 as a compelling biomarker predicting the sensitivity of CRCs to FU-based chemotherapy.

Reactive oxygen species (ROS) in macrophage activation and function in diabetes

In a diabetic milieu high levels of reactive oxygen species (ROS) are induced. This contributes to the vascular complications of diabetes. Recent studies have shown that ROS formation is exacerbated in diabetic monocytes and macrophages due to a glycolytic metabolic shift. Macrophages are important players in the progression of diabetes and promote inflammation through the release of pro-inflammatory cytokines and proteases. Because ROS is an important mediator for the activation of pro-inflammatory signaling pathways, obesity and hyperglycemia-induced ROS production may favor induction of M1-like pro-inflammatory macrophages during diabetes onset and progression. ROS induces MAPK, STAT1, STAT6 and NFκB signaling, and interferes with macrophage differentiation via epigenetic (re)programming. Therefore, a comprehensive understanding of the impact of ROS on macrophage phenotype and function is needed in order to improve treatment of diabetes and its vascular complications. In the current comprehensive review, we dissect the role of ROS in macrophage polarization, and analyze how ROS production links metabolism and inflammation in diabetes and its complications. Finally, we discuss the contribution of ROS to the crosstalk between macrophages and endothelial cells in diabetic complications.

Myeloid-specific deletion of Zfp36 protects against insulin resistance and fatty liver in diet-induced obese mice

Obesity is associated with adipose tissue inflammation that contributes to insulin resistance. Zinc finger protein 36 (Zfp36) is an mRNA-binding protein that reduces inflammation by binding to cytokine transcripts and promoting their degradation. We hypothesized that myeloid-specific deficiency of Zfp36 would lead to increased adipose tissue inflammation and reduced insulin sensitivity in diet-induced obese mice. As expected, wild-type (Control) mice became obese and diabetic on a high-fat diet, and obese mice with myeloid-specific loss of Zfp36 [knockout (KO)] demonstrated increased adipose tissue and liver cytokine mRNA expression compared with Control mice. Unexpectedly, in glucose tolerance testing and hyperinsulinemic-euglycemic clamp studies, myeloid Zfp36 KO mice demonstrated improved insulin sensitivity compared with Control mice. Obese KO and Control mice had similar macrophage infiltration of the adipose depots and similar peripheral cytokine levels, but lean and obese KO mice demonstrated increased Kupffer cell (KC; the hepatic macrophage)-expressed Mac2 compared with lean Control mice. Insulin resistance in obese Control mice was associated with enhanced Zfp36 expression in KCs. Compared with Control mice, KO mice demonstrated increased hepatic mRNA expression of a multitude of classical (M1) inflammatory cytokines/chemokines, and this M1-inflammatory hepatic milieu was associated with enhanced nuclear localization of IKKβ and the p65 subunit of NF-κB. Our data confirm the important role of innate immune cells in regulating hepatic insulin sensitivity and lipid metabolism, challenge-prevailing models in which M1 inflammatory responses predict insulin resistance, and indicate that myeloid-expressed Zfp36 modulates the response to insulin in mice.

Epigallocatechin gallate improves insulin resistance in HepG2 cells through alleviating inflammation and lipotoxicity

AIMS

High levels of circulating free fatty acids (FFAs), inflammation and oxidative stress are important causes for insulin resistance (IR) and type 2 diabetes mellitus. The aim of this study was to investigate the mechanisms of EGCG in alleviating IR in HepG2 cells.

METHODS

HepG2 cells were treated with 25 mM glucose, 0.25 mM palmitic acid (PA), or 50 μM EGCG for 24 h.

RESULTS

EGCG increased glucose uptake and decreased glucose content. EGCG markedly decreased the levels of inflammatory and oxidative stress factors including nuclear factor κB (NF-κB), tumor necrosis factor-α, interleukin-6, reactive oxygen species, malondialdehyde and p53 protein, and markedly increased superoxide dismutases (SOD), glutathione peroxidase and SOD2 protein. EGCG significantly downregulated the levels of FFAs, triacylglycerol and cholesterol in HepG2 cells. The glucose transporter 2 (GLUT2) protein and its downstream proteins peroxisome proliferator-activated receptor γ coactivator (PGC)-1β were significantly increased, and sterol regulatory element-binding-1c (SREBP-1c) protein, and fatty acid synthase (FAS) were significantly decreased by EGCG in HepG2. Moreover, the foregoing effects were reversed by siRNA-mediated knockdown of GLUT2.

CONCLUSION

Our data demonstrated that EGCG improved IR, possibly through ameliorating glucose (25 mM) and PA (0.25 mM)-induced inflammation, oxidative stress, and FFAs via the GLUT2/PGC-1β/SREBP-1c/FAS pathway in HepG2 cells.

Monoacylglycerol lipase regulates cannabinoid receptor 2-dependent macrophage activation and cancer progression

Metabolic reprogramming greatly contributes to the regulation of macrophage activation. However, the mechanism of lipid accumulation and the corresponding function in tumor-associated macrophages (TAMs) remain unclear. With primary investigation in colon cancer and confirmation in other cancer models, here we determine that deficiency of monoacylglycerol lipase (MGLL) results in lipid overload in TAMs. Functionally, macrophage MGLL inhibits CB2 cannabinoid receptor-dependent tumor progression in inoculated and genetic cancer models. Mechanistically, MGLL deficiency promotes CB2/TLR4-dependent macrophage activation, which further suppresses the function of tumor-associated CD8+ T cells. Treatment with CB2 antagonists delays tumor progression in inoculated and genetic cancer models. Finally, we verify that expression of macrophage MGLL is decreased in cancer tissues and positively correlated with the survival of cancer patients. Taken together, our findings identify MGLL as a switch for CB2/TLR4-dependent macrophage activation and provide potential targets for cancer therapy.

Identification of a fluorescent small-molecule enhancer for therapeutic autophagy in colorectal cancer by targeting mitochondrial protein translocase TIM44

OBJECTIVE

As the modulation of autophagic processes can be therapeutically beneficial to cancer treatment, the identification of novel autophagic enhancers is highly anticipated. However, current autophagy-inducing anticancer agents exert undesired side effects owing to their non-specific biodistribution in off-target tissues. This study aims to develop a multifunctional agent to integrate cancer targeting, imaging and therapy and to investigate its mechanism.

DESIGN

A series of mitochondria-targeting near-infrared (NIR) fluorophores were synthesised, screened and identified for their autophagy-enhancing activity. The optical properties and biological effects were tested both in vitro and in vivo. The underlying mechanism was investigated using inhibitors, small interfering RNA (siRNA), RNA sequencing, mass spectrometry and human samples.

RESULTS

We have screened and identified a new NIR autophagy-enhancer, IR-58, which exhibits significant tumour-selective killing effects. IR-58 preferentially accumulates in the mitochondria of colorectal cancer (CRC) cells and xenografts, a process that is glycolysis-dependent and organic anion transporter polypeptide-dependent. IR-58 kills tumour cells and induces apoptosis via inducing excessive autophagy, which is mediated through the reactive oxygen species (ROS)-Akt-mammalian target of rapamycin (mTOR) pathway. RNA sequencing, mass spectrometry and siRNA interference studies demonstrate that translocase of inner mitochondrial membrane 44 (TIM44)-superoxide dismutase 2 (SOD2) pathway inhibition is responsible for the excessive ROS, autophagy and apoptosis induced by IR-58. TIM44 expression correlates positively with CRC development and poor prognosis in patients.

CONCLUSIONS

A novel NIR small-molecule autophagy-enhancer, IR-58, with mitochondria-targeted imaging and therapy capabilities was developed for CRC treatment. Additionally, TIM44 was identified for the first time as a potential oncogene, which plays an important role in autophagy through the TIM44-SOD2-ROS-mTOR pathway.

MicroRNA‑33 regulates the NLRP3 inflammasome signaling pathway in macrophages

The nucleotide binding domain and leucine-rich repeat pyrin 3 domain (NLRP3) inflammasome/interleukin (IL)-1β axis serves an essential role in regulating the development of rheumatoid arthritis (RA). The dysregulation of cellular metabolism, such as mitochondrial dysfunction, results in the activation of the NLRP3 inflammasome. microRNA (miR)‑33 has previously been identified to be a regulator of lipid metabolism and mitochondrial function. However, whether miR‑33 regulates the NLRP3 inflammasome/IL‑1β axis remains unknown. In the present study, it was observed that an miR‑33 mimic or anti‑miR‑33 markedly stimulated or inhibited, respectively, IL‑1β protein expression levels in mouse peritoneal macrophages. Mechanistically, miR‑33 upregulated the expression of NLRP3 mRNA and protein as well as caspase‑1 activity in primary macrophages. In addition, the results demonstrated that miR‑33 impaired mitochondrial oxygen consumption rates, resulting in the accumulation of cellular reactive oxygen species, which stimulated NLRP3 expression, caspase‑1 activity and IL‑1β secretion. The results of the present study demonstrated that miR‑33 levels and NLRP3 inflammasome activity were increased in peripheral blood monocytes from patients with RA patients compared with healthy donors. In conclusion, the present study identified miR‑33 to be a positive regulator of the NLRP3 inflammasome in macrophages. The miR‑33/NLRP3 inflammasome pathway may therefore be involved in RA development.