Gut microbial metabolite deoxycholic acid facilitates Th17 differentiation through modulating cholesterol biosynthesis and participates in high-fat diet-associated colonic inflammation.

BACKGROUND: High-fat diet (HFD) is closely associated with the increased prevalence of inflammatory bowel disease (IBD). Excessive gut microbial metabolite deoxycholic acid (DCA) caused by HFD plays significant roles in eliciting intestinal inflammation, however, the mechanism underlining the induction of inflammatory response by DCA has not been fully elucidated. The purpose of this study was to investigate the role of DCA in the triggering of inflammation via affecting CD4+ T cell differentiation. RESULTS: Murine CD4+T cells were cultured under Th1, Th2 or Th17-polarizing conditions treated with or without different dosage of DCA, and flowcytometry was conducted to detect the effect of DCA on CD4+ T cell differentiation. Alteration of gene expression in CD4+ T cells upon DCA treatment was determined by RNA-sequencing and qRT-PCR. Bioinformatic analysis, cholesterol metabolic profiling, ChIP assay and immuno-fluorescent staining were further applied to explore the DCA-regulated pathway that involved in CD4+T cell differentiation. The results showed that DCA could dose-dependently promote the differentiation of CD4+ T cell into Th17 linage with pathogenic signature. Mechanistically, DCA stimulated the expression of cholesterol biosynthetic enzymes CYP51 and led to the increased generation of endogenous RORγt agonists, including zymosterol and desmosterol, therefore facilitating Th17 differentiation. Up-regulation of CYP51 by DCA was largely mediated via targeting transcription factor SREBP2 and at least partially through bile acid receptor TGR5. In addition, DCA-supplemented diet significantly increased intestinal Th17 cell infiltration and exacerbated TNBS-induced colitis. Administration of cholestyramine to eliminate fecal bile acid obviously alleviated colonic inflammation accompanied by decreased Th17 cells in HFD-fed mice. CONCLUSIONS: Our data establish a link between DCA-induced cholesterol biosynthesis in immune cells and gut inflammation. Modulation of bile acid level or targeting cholesterol metabolic pathway may be potential therapeutic measurements for HFD-related colitis.

Milk Fat Globule Epidermal Growth Factor 8a Regulates Neurogenesis in Telencephalon and Affects Larval Behavior in Zebrafish.

Mfge8, a secreted glycoprotein, is a key molecule that mediates the phagocytosis of apoptotic cells. Previous research reported that Mfge8 is critical for the proliferation and differentiation of radial glial cells (RGCs) in the dentate gyrus of adult mice. The treatment of Mfge8 is also beneficial for the repair of central nervous system (CNS) injury after cerebral ischemia. This study aimed to investigate whether the expression of mfge8a in zebrafish embryos was associated with the development of CNS and larval behavior. We found that zebrafish mfge8a was initially expressed at 48 hpf, and its expression was gradually increased in the ventricular zone. Knocking down mfge8a with antisense morpholino oligonucleotides impaired both spontaneous and photoinduced swimming locomotion in the behavioral tests. The neurogenesis analysis in telencephalon showed that mfge8a morphants excessively promoted neural differentiation over self-renewal after RGCs division, and consequently depleted proliferative RGC population during early neurogenesis. Furthermore, downregulation of mfge8a was shown to alter the expression patterns of genes associated with Notch signaling pathway. Our results demonstrated that mfge8a is involved in the maintenance of the progenitor identity of RGCs in embryonic zebrafish brain through regulating Notch signaling pathway, thereby contributing to consistent neurogenesis and locomotor development.

Trans-10-Hydroxy-2-Decenoic Acid Alleviates Dextran Sulfate Sodium-Induced Colitis in Mice via Regulating the Inflammasome-Mediated Pyroptotic Pathway and Enhancing Colonic Barrier Function.

SCOPE: The objective of this study is to explore the effects of 10-hydroxy-2-decenoic acid (10-HDA), the major fatty acid in royal jelly, on dextran sodium sulfate (DSS)-induced mice ulcerative colitis (UC) and its potential mechanism of action. METHODS AND RESULTS: Forty male C57BL/6 mice are randomly divided into five experimental groups: control, DSS, DSS + 25 (or 100)mg kg-1  d-1 10-HDA, and DSS + 200 mg kg-1  d-1 mesalazine (ME). UC is induced in mice using 2.5% DSS in drinking water for 7 days. During the induction, these UC mice are orally administrated 10-HDA or ME per day. Meanwhile, lipopolysaccharide (LPS)/adenosine-triphosphate (ATP)-stimulated THP1 cells are used as a model to test the effects of 10-HDA. 10-HDA reduces DSS-induced pathological damage, reactive oxygen species (ROS) accumulation, neutrophil infiltration, and cytokine production in colonic tissue. Compared with the DSS group, the expressions of thioredoxin interacting protein (TXNIP), NOD-like receptor family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC), cysteinyl aspartate specific proteinase-1 (Caspase-1), gasdermin-D (GSDMD), N-terminal domain of gasdermin-D (N-GSDMD), interleukin-1ß (IL-1ß), and interleukin-18 (IL-18) in the colon are decreased after administration of 10-HDA. 10-HDA also elevates the barrier integrity and the expressions of zonula occludens-1 (ZO-1) and Occludin in colonic epithelium exposed to DSS. In THP1 cells, the inflammasome-mediated pyroptosis induced by LPS/ATP is inhibited by 10-HDA pretreatment. CONCLUSION: 10-HDA alleviates DSS-induced colitis by regulating the NLRP3 inflammasome-mediated pyroptotic pathway and enhancing colonic barrier function.

Neonatal Supplementation of Oleamide During Suckling Promotes Learning Ability and Memory in Adolescent Mice.

BACKGROUND: Fatty acid amides (FAMs) are present in breast milk. Oleamide (ODA), a member of the FAM family, has been reported to affect learning and memory-related abilities in animal experiments. OBJECTIVES: This study aimed to characterize the temporal changes of FAMs in human milk and sought to examine the effect of ODA supplementation during suckling on postweaning cognitive performance in mice. METHODS: FAMs were measured in human milk (postpartum 1-24 wk) by ultra-performance liquid chromatography-triple quadruple mass spectrometry (UPLC-TQ-MS) analysis. We supplemented neonatal C57BL/6J mice of both sexes with vehicle (control), 5 mg/(kg · day) ODA (L-ODA), or 25 mg/(kg · day) ODA (H-ODA) throughout suckling by oral gavage. After weaning, the Morris water maze test and novel object recognition test were performed. Neurogenesis, spinal morphogenesis in the dentate gyrus (DG) region, and hippocampal expression of synaptic markers were analyzed. Data were analyzed by ANOVA and repeated-measures ANOVA. RESULTS: ODA (0.566-1.31 mg/L) was the most abundant FAM in breast milk, followed by palmitamide (0.135-0.269 mg/L) and linoleamide (0.046-0.242 mg/L). Compared with the control group, the H-ODA group demonstrated shorter escape latency, shorter travel distance, 113% more platform crossing, and 48% greater discrimination index in behavioral tests (P < 0.05). Additionally, the H-ODA group showed a higher density of 5-ethynyl-2'-deoxyuridine (EdU)+ and EdU+& doublecortin (DCX)+ cells (62% and 53%, respectively), and 52% greater spine density in the DG region than the control group (P < 0.05). The synaptic markers, postsynaptic density protein 95 (PSD95) and synaptophysin (SYP), were upregulated in the H-ODA group compared with the control group (P < 0.05). The L-ODA group also showed shorter escape latency in behavioral tests and 27% greater spine density in the DG region than the control group (P < 0.05). CONCLUSIONS: ODA is the most common FAM in human milk. ODA supplementation during suckling promotes learning and memory-related abilities in adolescent mice by augmenting hippocampal neuronal proliferation and boosting synaptic plasticity.

Milk Fat Globule Membrane Supplementation During Suckling Ameliorates Maternal High Fat Diet-Induced Hepatic Steatosis in Adult Male Offspring of Mice.

BACKGROUND: Exposure to a maternal high-fat diet (HFD) predisposes offspring to nonalcoholic fatty liver disease. OBJECTIVES: The aim of this study was to explore whether milk fat globule membrane (MFGM) supplementation during suckling exerts a long-term protective effect on hepatic lipid metabolism in adult offspring exposed to maternal HFD. METHODS: We fed 5-week-old female C57BL/6J mice either a HFD (60% kcal fat) or control diet (CD; 16.7% kcal fat) for 3 weeks before mating, as well as throughout gestation and lactation. After delivery, male offspring from HFD dams were supplemented with 1 g/(kg body weight·day) MFGM (HFD + MFGM group) or the same volume of vehicle (HFD group) during suckling. Male offspring from CD dams were also supplemented with vehicle during suckling (CD group). All offspring were weaned onto CD for 8 weeks. Histopathology, metabolic parameters, lipogenic level, oxidative stress, and mitochondria function in the liver were analyzed. A 1-way ANOVA and a Kruskal-Wallis test were used for multi-group comparisons. RESULTS: As compared to the CD group, the HFD group had more lipid droplets in livers, and exhibited ∼100% higher serum triglycerides, ∼38% higher hepatic triglycerides, ∼75% higher serum aspartate aminotransferase, and ∼130% higher fasting blood glucose (P < 0.05). The changes of these metabolic parameters were normalized in the HFD + MFGM group. Phosphorylated mammalian targets of rapamycin and AKT were downregulated, but phosphorylated adenosine monophosphate-activated protein kinase was upregulated in the HFD + MFGM group as compared to the HFD group (P < 0.05). As compared to the CD group, the HFD group showed an ∼80% higher malondialdehyde level, and ∼20% lower superoxide dismutase activity (P < 0.05), which were normalized in the HFD + MFGM group. Additionally, mitochondria function was also impaired in the HFD group and normalized in the HFD + MFGM group. CONCLUSIONS: MFGM supplementation during suckling ameliorates maternal HFD-induced hepatic steatosis in mice via suppressing de novo lipogenesis, reinforcing antioxidant defenses and improving mitochondrial function.

Bile salt-dependent lipase promotes the barrier integrity of Caco-2 cells by activating Wnt/ß-catenin signaling via LRP6 receptor.

Bile salt-dependent lipase (BSDL) within intestinal lumen can be endocytosed by enterocytes and support the intestinal barrier function. However, the epithelial-supporting effect of this protein has not been verified in a human cell line and neither the direct signaling pathway nor the function of endocytosis in this process has been clearly identified. We sought to investigate the signaling pathway and the membrane receptor through which BSDL might exert these effects using intestinal epithelial cells. Caco-2 cells were treated with recombinant BSDL, and the barrier function, cell proliferation, and activation of the Wnt signaling pathway were assessed. The effect of Wnt signaling activation induced by BSDL and BSDL endocytosis was investigated in LRP6-silenced and non-silenced cells. Moreover, caveolae- and clathrin-dependent endocytosis inhibitors were also applied respectively to analyze their effects on Wnt signaling activation induced by BSDL. BSDL treatment increased the barrier function but not proliferation of Caco-2 cells. It also induced ß-catenin nuclear translocation and activated Wnt target gene transcription. Moreover, in the Wnt pathway, BSDL increased the levels of non-phosphorylated-ß-catenin (Ser33/37/Thr41) and phosphorylated-ß-catenin (Ser552). Notably, the silencing of LRP6 expression impaired BSDL endocytosis and decreased BSDL-induced ß-catenin nuclear translocation. The inhibition of BSDL endocytosis induced by caveolae-mediated endocytosis inhibitor was stronger than that by clathrin-mediated endocytosis inhibitor, and the Wnt signaling activation associated with its endocytosis was also most likely caveolae-dependent. Our findings suggested that LRP6, a canonical Wnt pathway co-receptor, can mediate BSDL endocytosis and then activate Wnt signaling in Caco-2 cells.

Lin 28A/Occludin axis: An aberrantly activated pathway in intestinal epithelial cells leading to impaired barrier function under total parenteral nutrition.

Disassembly of tight junctions is a major cause of intestinal barrier dysfunction under total parenteral nutrition (TPN), but the precise mechanisms have not been fully understood. Normally, RNA binding protein Lin 28A is highly restricted to embryonic stem cells and dramatically decreases as differentiation progresses; however, in our preliminary study it was found aberrantly increased in the intestinal epithelial cells of TPN rats, and thus its mechanism of action needs to be addressed. Herein, we report a pivotal role of Lin 28A in the regulation of tight junctions, which induces a sustained translational repression of Occludin, leading to disruption of intestinal barrier function under TPN. Using a rat model of TPN, we found time-dependent upregulation of Lin 28A, negatively correlated with Occludin. Using mouse intestinal organoids and human gut-derived Caco-2 cells as in vitro models, we found that expression of Occludin could be significantly suppressed by ectopic overexpression of Lin 28A. The underlying mechanisms may be partially attributed to translational repression, as the abundance of Occludin transcripts in polysomes was dramatically reduced by Lin 28A (polysomal profiling). Furthermore, Lin 28A was found to directly bind to Occludin mRNA 3' untranslated coding region (UTR), thereby repressing the translation of Occludin transcripts through decapping enzyme 1A (DCP1a). Taken together, our findings revealed that Lin 28A/Occludin axis may be a novel mechanism accounting for the development of barrier dysfunction under TPN.

Carboxyl ester lipase is highly conserved in utilizing maternal supplied lipids during early development of zebrafish and human.

Carboxyl ester lipase (Cel), is a lipolytic enzyme secreted by the pancreas, which hydrolyzes various species of lipids in the gut. Cel is also secreted by mammary gland during lactation and exists in breast milk. It facilitates dietary fat digestion and absorption, thus contributing to normal infant development. This study aimed to examine whether the Cel in zebrafish embryos has a similar role of maternal lipid utilization as in human infants, and how Cel contributes to the utilization of yolk lipids in zebrafish. The cel1 and cel2 genes were expressed ubiquitously in the blastodisc and yolk syncytial layer before 24 hpf, and in the exocrine pancreas after 72 hpf. The cel1 and cel2 morphants exhibited developmental retardation and yolk sac retention. The total cholesterol, cholesterol ester, free cholesterol, and triglyceride were reduced in the morphants' body while accumulated in the yolk (except triglyceride). The FFA content of whole embryos was much lower in morphants than in standard controls. Moreover, the delayed development in cel (cel1/cel2) double morphants was partially rescued by FFA and cholesterol supplementation. Delayed and weakened cholesterol ester transport to the brain and eyes was observed in cel morphants. Correspondingly, shrunken midbrain tectum, microphthalmia, pigmentation-delayed eyes as well as down-regulated Shh target genes were observed in the CNS of double morphants. Interestingly, cholesterol injections reversed these CNS alterations. Our findings suggested that cel genes participate in the lipid releasing from yolk sac to developing body, thereby contributing to the normal growth rate and CNS development in zebrafish.

Milk Fat Globule Membrane Ameliorates Necrotizing Enterocolitis in Neonatal Rats and Suppresses Lipopolysaccharide-Induced Inflammatory Response in IEC-6 Enterocytes.

BACKGROUND: Evidence has provided support for the beneficial effects of milk fat globule membrane (MFGM) on inflammation in the intestinal tract. The objective of this study was to investigate the effects of MFGM on a rat model of necrotizing enterocolitis (NEC) and its potential mechanism of action. METHODS: Sixty-two newborn Sprague Dawley rats were randomly divided into 4 experimental groups: Breast-fed normal, formula fed (FF), FF + 6 g/L MFGM, and FF + 12 g/L MFGM. The FF rats and the FF rats supplemented with MFGM were exposed to asphyxia/cold stress to induce NEC. Body weight, histological score, survival time, oxidative stress injury, enterocyte proliferation/apoptosis, and inflammatory response were assessed. Meanwhile, lipopolysaccharide (LPS)-stimulated IEC-6 enterocytes were used as a model to test the anti-inflammatory effects of MFGM. RESULTS: Supplementation with 12 g/L MFGM alleviated body weight loss, reduced the incidence of NEC, increased the survival rate, and attenuated the severity of bowel damage in the NEC rat model. Furthermore, 12 g/L MFGM administration inhibited the protein expression of toll-like receptor 4 (TLR4) in the animal model. In IEC-6 enterocytes, the upregulation of TLR4, myeloid differentiation primary response gene 88 (MyD88), phosphorylated nuclear factor-κB (NF-κB) p65 subunit, and the nuclear translocation of NF-κBp65 induced by LPS was partially inhibited by MFGM pretreatment. CONCLUSION: Our findings suggested that MFGM has beneficial effects on neonatal rats with NEC by suppressing inflammation via the TLR4/MyD88/NF-κB pathway.

Curcumin alleviates DSS-induced colitis via inhibiting NLRP3 inflammsome activation and IL-1ß production.

BACKGROUND: NLRP3 inflammasome mediates IL-1ß maturation, therefore plays a vital role in the development of IBD. Curcumin is known for possessing strong anti-inflammatory property. OBJECTIVE: The present study was to investigate the protective effects of curcumin on dextran sulfate sodium (DSS)-induced colitis through inhibiting NLRP3 inflammasome activation and IL-1ß production. METHODS: LPS-primed macrophages were treated with curcumin prior to DSS triggering NLRP3 inflammasome activation, IL-1ß secretion and ASC oligomerization were observed. The mechanisms of curcumin in the inhibition of DSS-induced inflammasome activation were explored. Curcumin or caspase-1/NLRP3 inhibitor was administrated respectively in DSS-induced colitis mouse model. The changes of body weight, disease activity index, colon length were measured. Additionally, mature IL-1ß and other inflammatory cytokines, MPO activity and histopathological damage were analyzed for the evaluation of colitis severity. RESULTS: NLRP3 inflammasome activation was dramatically inhibited by curcumin in DSS-stimulated macrophages, as evidenced by decreased IL-1ß secretion, less caspase-1 activation and ASC specks. Mechanistically, curcumin prevented DSS-induced K+ efflux, intracellular ROS formation and cathepsin B release, three major cellular events mediating NLRP3 inflammasome activation. In DSS-induced colitis, curcumin administration significantly ameliorated colitis symptoms by reducing weight loss, DAI and colon length shortening. Meanwhile, curcumin significantly decreased the expression of multiple inflammatory cytokines (including mature IL-1ß, IL-6, MCP-1), MPO activity, caspase-1 activity as well as histopathological damage. Furthermore, blockage of NLRP3 inflammasome activation in vivo with specific NLRP3 inhibitor abrogated the further inhibitory effect of curcumin on DSS-induced colitis. CONCLUSION: Curcumin could strongly suppress DSS-induced NLRP3 inflammsome activation and alleviate DSS-induced colitis in mice, thus it may be a promising candidate drug in clinical application for IBD therapy.

Deoxycholic Acid-Mediated Sphingosine-1-Phosphate Receptor 2 Signaling Exacerbates DSS-Induced Colitis through Promoting Cathepsin B Release.

We recently have proved that excessive fecal DCA caused by high-fat diet may serve as an endogenous danger-associated molecular pattern to activate NLRP3 inflammasome and thus contributes to the development of inflammatory bowel disease (IBD). Moreover, the effect of DCA on inflammasome activation is mainly mediated through bile acid receptor sphingosine-1-phosphate receptor 2 (S1PR2); however, the intermediate process remains unclear. Here, we sought to explore the detailed molecular mechanism involved and examine the effect of S1PR2 blockage in a colitis mouse model. In this study, we found that DCA could dose dependently upregulate S1PR2 expression. Meanwhile, DCA-induced NLRP3 inflammasome activation is at least partially achieved through stimulating extracellular regulated protein kinases (ERK) signaling pathway downstream of S1PR2 followed by promoting of lysosomal cathepsin B release. DCA enema significantly aggravated DSS-induced colitis in mice and S1PR2 inhibitor as well as inflammasome inhibition by cathepsin B antagonist substantially reducing the mature IL-1ß production and alleviated colonic inflammation superimposed by DCA. Therefore, our findings suggest that S1PR2/ERK1/2/cathepsin B signaling plays a critical role in triggering inflammasome activation by DCA and S1PR2 may represent a new potential therapeutic target for the management of intestinal inflammation in individuals on a high-fat diet.

Bile salt dependent lipase promotes intestinal adaptation in rats with massive small bowel resection.

Intestinal adaptation is important for the short bowel syndrome (SBS) patients. Growing evidence has suggested that bile salt dependent lipase (BSDL) not only has the lipolytic activity, but also the immune-modulating and pro-proliferative activities. The purpose of the present study was to investigate the effects of BSDL on intestinal adaptive growth and gut barrier function in a rat model of SBS. Twenty-four male Sprague-Dawley rats were randomly divided into three experimental groups: sham group (rats underwent bowel transection and re-anastomosis), SBS group (rats underwent 80% bowel resection), SBS-BSDL group (SBS rats orally administered BSDL). The animals were weighed daily. The intestinal morpho-histochemical changes and intestinal barrier function were determined 14 days after the operations. Meanwhile, the expressions of Wnt signaling molecules in enterocytes were also analyzed by immunohistochemistry and Western blot. The postoperative weight gain was faster in the SBS rats treated with BSDL than in the SBS/untreated group. The SBS rats treated with BSDL had significantly greater villus height, crypt depth, and enterocyte proliferation in their residual intestines, as compared with the SBS/untreated group. The recovery of intestinal barrier function was promoted and the expressions of tight-junction proteins were increased in the SBS rats treated with BSDL. Additionally, the data indicated that the proadaptive activities of BSDL might be mediated by Wnt signaling activation in the enterocytes. These observations suggested that enteral BSDL administration promoted intestinal adaptive growth and barrier repairing by activating Wnt signaling pathway in SBS rats.

Deoxycholic Acid Triggers NLRP3 Inflammasome Activation and Aggravates DSS-Induced Colitis in Mice.

A westernized high-fat diet (HFD) is associated with the development of inflammatory bowel disease (IBD). High-level fecal deoxycholic acid (DCA) caused by HFD contributes to the colonic inflammatory injury of IBD; however, the mechanism concerning the initiation of inflammatory response by DCA remains unclear. In this study, we sought to investigate the role and mechanism of DCA in the induction of inflammation via promoting NLRP3 inflammasome activation. Here, we, for the first time, showed that DCA dose-dependently induced NLRP3 inflammasome activation and highly pro-inflammatory cytokine-IL-1ß production in macrophages. Mechanistically, DCA-triggered NLRP3 inflammasome activation by promoting cathepsin B release at least partially through sphingosine-1-phosphate receptor 2. Colorectal instillation of DCA significantly increased mature IL-1ß level in colonic tissue and exacerbated DSS-induced colitis, while in vivo blockage of NLRP3 inflammasome or macrophage depletion dramatically reduced the mature IL-1ß production and ameliorated the aggravated inflammatory injury imposed by DCA. Thus, our findings show that high-level fecal DCA may serve as an endogenous danger signal to activate NLRP3 inflammasome and contribute to HFD-related colonic inflammation. NLRP3 inflammasome may represent a new potential therapeutical target for treatment of IBD.

Chenodeoxycholic acid activates NLRP3 inflammasome and contributes to cholestatic liver fibrosis.

Accumulation of hydrophobic bile acids in the liver contributes to cholestatic liver injury. Inflammation induced by excessive bile acids is believed to play a crucial role, however, the mechanisms of bile acids triggered inflammatory response remain unclear. Recent studies have highlighted the effect of NLRP3 inflammasome in mediating liver inflammation and fibrosis. In this study, we for the first time showed that chenodeoxycholic acid (CDCA), the major hydrophobic primary bile acid involved in cholestatic liver injury, could dose-dependently induce NLRP3 inflammasome activation and secretion of pro-inflammatory cytokine-IL-1ß in macrophages by promoting ROS production and K+ efflux. Mechanistically, CDCA triggered ROS formation in part through TGR5/EGFR downstream signaling, including protein kinase B, extracellular regulated protein kinases and c-Jun N-terminal kinase pathways. Meanwhile, CDCA also induced ATP release from macrophages which subsequently causes K+ efflux via P2X7 receptor. Furthermore, in vivo inhibition of NLRP3 inflammasome with caspase-1 inhibitor dramatically decreased mature IL-1ß level of liver tissue and ameliorated liver fibrosis in bile duct ligation (BDL) mouse model. In conclusion, excessive CDCA may represent an endogenous danger signal to activate NLRP3 inflammasome and initiate liver inflammation during cholestasis. Our finding offers a mechanistic basis to ameliorate cholestatic liver fibrosis by targeting inflammasome activation.

Curcumin suppresses NLRP3 inflammasome activation and protects against LPS-induced septic shock.

SCOPE: The NLRP3 inflammasome responds to various pathogen-derived factors and danger-associated molecules, mediating IL-1ß maturation, therefore is involved in multiple inflammatory diseases. Curcumin has been shown to possess strong anti-inflammatory activity, but the underlying mechanism is not fully understood. Here, we sought to investigate the role and mechanism of curcumin on the inhibition of mature IL-1ß production via the regulation of NLRP3 inflammasome. METHODS AND RESULTS: Curcumin dramatically inhibited the production of mature IL-1ß in LPS-primed macrophages triggered by multiple NLRP3 inflammasome activators, and also reduced the level of cleaved caspase-1 as measured by western blot and ELISA. Curcumin prevented K(+) efflux, the common trigger for NLRP3 inflammasome activation, and attenuated lysosomes disruption and intracellular ROS formation as well. The inhibition of NLRP3 inflammasome by curcumin was in part mediated via the suppression of extracellular regulated protein kinases phosphorylation. Furthermore, administration of curcumin significantly reduced peritoneal IL-1ß and HMGB-1 concentration induced by LPS and improved the survival of mice suffering from lethal endotoxic shock. CONCLUSION: Curcumin potently inhibits the activation of NLRP3 inflammasome which may contribute to its anti-inflammatory activity. Our finding offers a mechanistic basis for the therapeutic potential of curcumin in septic shock and other NLRP3 inflammasome-driven diseases.

Dopamine inhibits the function of Gr-1+CD115+ myeloid-derived suppressor cells through D1-like receptors and enhances anti-tumor immunity.

MDSCs accumulate in tumor-bearing animals and cancer patients and are a major factor responsible for cancer-induced immunosuppression that limits effective cancer immunotherapy. Strategies aimed at effectively inhibiting the function of MDSCs are expected to enhance host anti-tumor immunity and improve cancer immunotherapy significantly. The neurotransmitter DA has been found to have anti-cancer activity, but the underlying mechanism is poorly understood. In this study, we sought to investigate the therapeutic mechanism and efficacy of DA on the inhibition of cancer development via the regulation of MDSC functions. The regulation of the suppressive function of Gr-1(+)CD115(+) MDSCs by DA was determined by use of murine syngeneic LLC and B16 graft models treated with DA in vivo, as well as Gr-1(+)CD115(+) MDSCs isolated from these model treated with DA ex vivo. Here, we show that Gr-1(+)CD115(+) monocytic MDSCs express D1-like DA receptors. DA dramatically attenuated the inhibitory function of tumor-induced monocytic MDSCs on T cell proliferation and IFN-γ production via D1-like DA receptors and retarded tumor growth. DA and other D1 receptor agonists inhibited IFN-γ-induced NO production by MDSCs from tumor-bearing mice and cancer patients. Decreased NO production was, in part, mediated via the suppression of p-ERK and p-JNK. In conclusion, the neurotransmitter DA potently inhibits the suppressive function of MDSC and enhances anti-tumor immunity. Our finding provides a mechanistic basis for the use of DA or D1-like receptor agonists to overcome tumor-induced immunosuppression in cancer immunotherapy.