Deficiency of circadian clock gene Bmal1 exacerbates noncanonical inflammasome-mediated pyroptosis and lethality via Rev-erbα-C/EBPß-SAA1 axis.

Circadian arrhythmia has been linked to increased susceptibility to multiple inflammatory diseases, such as sepsis. However, it remains unclear how disruption of the circadian clock modulates molecular aspects of innate immune responses, including inflammasome signaling. Here, we examined the potential role of the circadian clock in inflammasome-mediated responses through myeloid-specific deletion of BMAL1, a master circadian clock regulator. Intriguingly, Bmal1 deficiency significantly enhanced pyroptosis of macrophages and lethality of mice under noncanonical inflammasome-activating conditions but did not alter canonical inflammasome responses. Transcriptome analysis of enriched peritoneal myeloid cells revealed that Bmal1 deficiency led to a marked reduction in Rev-erbα expression at steady state and a significant increase in serum amyloid A1 (SAA1) expression upon poly(I:C) stimulation. Notably, we found that the circadian regulator Rev-erbα is critical for poly(I:C)- or interferon (IFN)-ß-induced SAA1 production, resulting in the circadian oscillation pattern of SAA1 expression in myeloid cells. Furthermore, exogenously applied SAA1 markedly increased noncanonical inflammasome-mediated pyroptosis of macrophages and lethality of mice. Intriguingly, our results revealed that type 1 IFN receptor signaling is needed for poly(I:C)- or IFN-ß-induced SAA1 production. Downstream of the type 1 IFN receptor, Rev-erbα inhibited the IFN-ß-induced association of C/EBPß with the promoter region of Saa1, leading to the reduced transcription of Saa1 in macrophages. Bmal1-deficient macrophages exhibited enhanced binding of C/EBPß to Saa1. Consistently, the blockade of Rev-erbα by SR8278 significantly increased poly(I:C)-stimulated SAA1 transcription and noncanonical inflammasome-mediated lethality in mice. Collectively, our data demonstrate a potent suppressive effect of the circadian clock BMAL1 on the noncanonical inflammasome response via the Rev-erbα-C/EBPß-SAA1 axis.

Neutrophils Facilitate Prolonged Inflammasome Response in the DAMP-Rich Inflammatory Milieu.

Aberrant inflammasome activation contributes to various chronic inflammatory diseases; however, pyroptosis of inflammasome-active cells promptly terminates local inflammasome response. Molecular mechanisms underlying prolonged inflammasome signaling thus require further elucidation. Here, we report that neutrophil-specific resistance to pyroptosis and NLRP3 desensitization can facilitate sustained inflammasome response and interleukin-1ß secretion. Unlike macrophages, inflammasome-activated neutrophils did not undergo pyroptosis, indicated by using in vitro cell-based assay and in vivo mouse model. Intriguingly, danger-associated molecular patterns (DAMP)-rich milieu in the inflammatory region significantly abrogated NLRP3-activating potential of macrophages, but not of neutrophils. This macrophage-specific NLRP3 desensitization was associated with DAMP-induced mitochondrial depolarization that was not observed in neutrophils due to a lack of SARM1 expression. Indeed, valinomycin-induced compulsory mitochondrial depolarization in neutrophils restored inflammasome-dependent cell death and ATP-induced NLRP3 desensitization in neutrophils. Alongside prolonged inflammasome-activating potential, neutrophils predominantly secreted interleukin-1ß rather than other proinflammatory cytokines upon NLRP3 stimulation. Furthermore, inflammasome-activated neutrophils did not trigger efferocytosis-mediated M2 macrophage polarization essential for the initiation of inflammation resolution. Taken together, our results indicate that neutrophils can prolong inflammasome response via mitochondria-dependent resistance to NLRP3 desensitization and function as major interleukin-1ß-secreting cells in DAMP-rich inflammatory region.

Intracellular NAD+ Depletion Confers a Priming Signal for NLRP3 Inflammasome Activation.

Nicotinamide adenine dinucleotide (NAD+) is an important cofactor in many redox and non-redox NAD+-consuming enzyme reactions. Intracellular NAD+ level steadily declines with age, but its role in the innate immune potential of myeloid cells remains elusive. In this study, we explored whether NAD+ depletion by FK866, a highly specific inhibitor of the NAD salvage pathway, can affect pattern recognition receptor-mediated responses in macrophages. NAD+-depleted mouse bone marrow-derived macrophages (BMDMs) exhibited similar levels of proinflammatory cytokine production in response to LPS or poly (I:C) stimulation compared with untreated cells. Instead, FK866 facilitated robust caspase-1 activation in BMDMs in the presence of NLRP3-activating signals such as ATP and nigericin, a potassium ionophore. However, this FK866-mediated caspase-1 activation was completely abolished in Nlrp3-deficient macrophages. FK866 plus nigericin stimulation caused an NLRP3-dependent assembly of inflammasome complex. In contrast, restoration of NAD+ level by supplementation with nicotinamide mononucleotide abrogated the FK866-mediated caspase-1 cleavage. FK866 did not induce or increase the expression levels of NLRP3 and interleukin (IL)-1ß but drove mitochondrial retrograde transport into the perinuclear region. FK866-nigericin-induced mitochondrial transport is critical for caspase-1 cleavage in macrophages. Consistent with the in vitro experiments, intradermal coinjection of FK866 and ATP resulted in robust IL-1ß expression and caspase-1 activation in the skin of wild-type, but not Nlrp3-deficient mice. Collectively, our data suggest that NAD+ depletion provides a non-transcriptional priming signal for NLRP3 activation via mitochondrial perinuclear clustering, and aging-associated NAD+ decline can trigger NLRP3 inflammasome activation in ATP-rich environments.

Chemotherapeutic Agent Paclitaxel Mediates Priming of NLRP3 Inflammasome Activation.

Paclitaxel is a chemotherapeutic drug commonly used to treat different types of cancer. In addition to its antitumor effect, paclitaxel is also known to promote Toll-like receptor (TLR) 4-dependent inflammatory responses, which may lower its chemotherapeutic efficacy. However, it remains unclear whether paclitaxel is able to affect inflammasome signaling in myeloid or cancer cells. Therefore, we examined the potential effect of paclitaxel on the activation of an inflammasome complex by examining caspase-1 activation and interleukin (IL)-1ß secretion in bone marrow-derived macrophages (BMDMs). The results showed that treatment with paclitaxel alone or following LPS priming failed to trigger the secretion of active caspase-1 and IL-1ß from BMDMs. However, paclitaxel could induce robust activation of caspase-1 in BMDMs in the presence of NLRP3 inflammasome-activating signal 2, such as ATP or nigericin. This paclitaxel/ATP-mediated inflammasome activation was completely abrogated in Nlrp3-deficient macrophages. Mechanistically, paclitaxel treatment induced robust activation of the TLR4 signaling cascade, including phosphorylation of IκB and JNK and upregulation of proinflammatory cytokine mRNA levels in a TLR4-dependent manner. In contrast, paclitaxel treatment alone did not induce mitochondrial damages such as the loss of the mitochondrial membrane potential and production of mitochondrial ROS. These findings suggest that paclitaxel can drive the priming of signal-mediated events for NLRP3 activation but not a second signal-triggered phenomenon such as mitochondrial damage. This suggestion was supported by the observations that paclitaxel treatment caused robust IL-1ß production in macrophages in the presence of cell-free medium derived from growth of injured cells and also in the spleen of mice. Collectively, our data strongly indicate that paclitaxel is able to facilitate the activation of NLRP3 inflammasome signaling in a certain physiological environment.

Zika Virus Impairs Host NLRP3-mediated Inflammasome Activation in an NS3-dependent Manner.

Zika virus (ZIKV) is a mosquito-borne flavivirus associated with severe neurological disorders including Guillain-Barré syndrome and microcephaly. The host innate immune responses against ZIKV infection are essential for protection; however, ZIKV has evolved strategies to evade and antagonize antiviral responses via its nonstructural (NS) proteins. Here, we demonstrated that ZIKV infection unexpectedly inhibits NLRP3-dependent inflammasome activation in bone marrow-derived macrophages and mixed glial cells from mouse brain. ZIKV infection led to increased transcript levels of proinflammatory cytokines such as IL-1ß and IL-6 via activating NF-κB signaling. However, ZIKV infection failed to trigger the secretion of active caspase-1 and IL-1ß from macrophages and glial cells even in the presence of LPS priming or ATP costimulation. Intriguingly, ZIKV infection significantly attenuated NLRP3-dependent, but not absent in melanoma 2-dependent caspase-1 activation and IL-1ß secretion from both cells. ZIKV infection further blocked apoptosis-associated speck-like protein containing a caspase recruitment domain oligomerization in LPS/ATP-stimulated macrophages. Interestingly, expression of ZIKV NS3 protein reduced NLRP3-mediated caspase-1 activation and IL-1ß secretion in macrophages, whereas NS1 and NS5 proteins showed no effects. Furthermore, NLRP3 was found to be degraded by the overexpression of ZIKV NS3 in 293T cells. Collectively, these results indicate that ZIKV evades host NLRP3 inflammasome-mediated innate immune responses in macrophages and glial cells; this may facilitate ZIKV's ability to enhance the replication and dissemination in these cells.

Posttranslational Regulation of the NLR Family Pyrin Domain-Containing 3 Inflammasome.

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a multi-protein complex that can be activated by a variety of pathogen-associated molecular patterns or damage-associated molecular patterns. Inappropriate NLRP3 inflammasome activation can induce autoinflammatory, autoimmune, or metabolic disorders. Therefore, NLRP3 is an attractive target against NLRP3 inflammasome activation, and specific targeting of NLRP3 might be an intriguing approach to the development of drugs for the treatment of NLRP3 inflammasome-related diseases. Although many studies with varied mechanistic approaches were reported in inhibition of NLRP3 inflammasome activation, mechanisms related to regulation of posttranslational modification (PTM) of NLRP3, as a focal point has not been thoroughly addressed. Recently, extensive investigations of PTMs of NLRP3 have led to partial understanding of the mechanisms involved in NLRP3 inflammasome activation. In this review, we focused on the role of PTMs regulating NLRP3 inflammasome activation.

Inhibitory Effect and Mechanism of Arctium lappa Extract on NLRP3 Inflammasome Activation.

Arctium lappa (A. lappa), Compositae, is considered a potential source of nutrition and is used as a traditional medicine in East Asian countries for centuries. Although several studies have shown its biological activities as an anti-inflammatory agent, there have been no reports on A. lappa with regard to regulatory role in inflammasome activation. The purpose of this study was to investigate the inhibitory effects of A. lappa extract (ALE) on NLRP3 inflammasome activation and explore the underlying mechanisms. We found that ALE inhibited IL-1ß secretion from NLRP3 inflammasome activated bone marrow derived macrophages but not that secreted by NLRC4 and AIM2 inflammasomes activation. Mechanistic studies revealed that ALE suppressed the ATPase activity of purified NLRP3 and reduced mitochondrial reactive oxygen species (mROS) generated during NLRP3 activation. Therefore, the inhibitory effect of ALE on NLRP3 inflammasome might be attributed to its ability to inhibit the NLRP3 ATPase function and attenuated the mROS during inflammasome activation. In addition, ALE significantly reduced the LPS-induced increase of plasma IL-1ß in mouse peritonitis model. These results provide evidence of novel anti-inflammatory mechanisms of A. lappa, which might be used for therapeutic applications in the treatment of NLRP3 inflammasome-associated inflammatory disorders.

Actinidia arguta extract attenuates inflammasome activation: Potential involvement in NLRP3 ubiquitination.

ETHNOPHARMACOLOGICAL RELEVANCE: Actinidia arguta (A. arguta) has been widely used in Asian countries as a traditional medicinal herb to treat inflammation-related diseases, such as gastritis, bronchitis, and arthritis. AIM OF THE STUDY: The inhibitory effect of A. arguta leaves' extract (AA) on inflammasome activation was investigated to verify its traditional use in treating inflammation-related diseases. MATERIALS AND METHODS: Bone marrow-derived macrophages (BMDMs) primed by lipopolysaccharide (LPS) were activated by selective inflammasome stimulators, and the effect of AA on inflammasome activation was investigated. A monosodium urate crystal (MSU)-induced peritonitis mouse model was used to study the in vivo efficacy of AA on inflammasome activation. RESULTS: In the in vitro study, AA regulated NLRP3 ubiquitination and apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization, leading to the inhibition of NLRP3 inflammasome-mediated interleukin (IL)-1ß secretion. The inhibitory effect of AA on inflammasome activation in vitro was further confirmed in vivo using an MSU-induced peritonitis mouse model. CONCLUSION: AA provided scientific evidence, substantiating the traditional claims for its use in the treatment of inflammation and inflammation-mediated metabolic disorders, including gout.

BOT-4-one attenuates NLRP3 inflammasome activation: NLRP3 alkylation leading to the regulation of its ATPase activity and ubiquitination.

The ATPase activity of NLRP3 has pivotal role in inflammasome activation and is recognized as a good target for the development of the NLRP3 inflammasome-specific inhibitor. However, signals in the vicinity of the ATPase activity of NLRP3 have not been fully elucidated. Here, we demonstrate NLRP3 inflammasome-specific action of a benzoxathiole derivative, BOT-4-one. BOT-4-one exhibited an inhibition of NLRP3 inflammasome activation, which was attributable to its alkylating capability to NLRP3. In particular, the NLRP3 alkylation by BOT-4-one led to an impaired ATPase activity of NLRP3, thereby obstructing the assembly of the NLRP3 inflammasome. Additionally, we found that NLRP3 alkylators, including BOT-4-one, enhance the ubiquitination level of NLRP3, which might also contribute to the inhibition of NLRP3 inflammasome activation. Finally, BOT-4-one appeared to be superior to other known NLRP3 alkylators in inhibiting the functionality of the NLRP3 inflammasome and its resulting anti-inflammatory activity was confirmed in vivo using a monosodium urate-induced peritonitis mouse model. Collectively, the results suggest that NLRP3 alkylators function by inhibiting ATPase activity and increasing the ubiquitination level of NLRP3, and BOT-4-one could be the type of NLRP3 inhibitor that may be potentially useful for the novel development of a therapeutic agent in controlling NLRP3 inflammasome-related diseases.

Protective effects of Cinnamomum cassia (Lamaceae) against gout and septic responses via attenuation of inflammasome activation in experimental models.

ETHNOPHARMACOLOGICAL RELEVANCE: Cinnamomum cassia (C. cassia, Lauraceae family), commonly used for treating dyspepsia, gastritis, blood circulation, and inflammatory diseases is considered as one of the 50 fundamental herbs in traditional Chinese medicine. AIM OF THE STUDY: The anti-inflammatory action of an ethanol extract of C. cassia (CA), and its underlying mechanisms were explored in both in vitro cellular and in vivo murine models. MATERIALS AND METHODS: Bone marrow-derived macrophages (BMDMs) were used to study the regulatory effect of CA on inflammasome activation. A lipopolysaccharide (LPS)-induced sepsis mouse model and a monosodium urate (MSU)-induced gout model were employed to study the effect of CA on in vivo efficacy. RESULTS: CA improved the survival rate in the LPS-induced septic shock mouse model and inhibited inflammasome activation including NLRP3, NLRC4, and AIM2, leading to suppression of interleukin-1ß secretion. Further, ASC oligomerization and its speck formation in cytosol were attenuated by CA treatment. Furthermore, CA improved both survival rate of LPS-induced septic shock and gout murine model. CONCLUSIONS: CA treatment significantly attenuated danger signals-induced inflammatory responses via regulation of inflammasome activation, substantiating the traditional claims of its use in the treatment of inflammation-related disorders.

Juniperus rigida Sieb. extract inhibits inflammatory responses via attenuation of TRIF-dependent signaling and inflammasome activation.

ETHNOPHARMACOLOGICAL RELEVANCE: Juniperus rigida Sieb. (J. rigida) is used for medicinal purposes in Asian countries to treat inflammation-related disorders, such as neuralgia, dropsy, and gout. AIM OF THE STUDY: The anti-inflammatory effects of J. rigida extract (JR) and its underlying mechanisms were explored both in in vitro cell lines and in vivo metabolic disease models. MATERIAL AND METHODS: Lipopolysaccharide (LPS)-stimulated RAW264.7 murine macrophages were used to study the changes in inflammatory responses in vitro. Bone marrow-derived macrophages (BMDMs) were used to study the regulatory effect of JR on inflammasome activation. The murine model for monosodium urate (MSU)-induced peritonitis and high-fat diet (HFD)-induced type 2 diabetes were employed to study the effect of JR on in vivo efficacy. RESULTS: JR suppressed the MSU-induced in vivo inflammatory response by attenuation of proinflammatory cytokines, including interleukin (IL)-1ß, IL-6, and tumor necrosis factor-alpha (TNF-α). In the in vitro study, JR suppressed IL-1ß secretion via regulation of apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization, leading to the inhibition of inflammasome activation. JR also inhibited the LPS-stimulated release of proinflammatory mediators, such as nitric oxide (NO), TNF-α, and IL-6 in RAW264.7 cells. The inhibitory effects of JR were mediated through the regulation of the TRIF-dependent signaling pathway from JAK1/STAT1 phosphorylation. Furthermore, JR showed inhibitory effects on HFD-induced type 2 diabetes in a mouse model through the regulation of blood glucose and serum IL-1ß. CONCLUSIONS: Our results indicate that JR attenuates both LPS-stimulated and danger-signal-induced inflammatory responses in macrophages via regulation of the key inflammatory mechanisms, providing scientific support for its traditional use in the treatment of various inflammation-related metabolic disorders.

Cichorium intybus Linn. Extract Prevents Type 2 Diabetes Through Inhibition of NLRP3 Inflammasome Activation.

This study provides the scientific basis for the inhibitory effect of the aerial parts of Cichorium intybus Linn. (C. intybus) on the activation of the NLRP3 inflammasome in vitro and on high-fat diet (HFD)-induced type-2 diabetes (T2D). Lipopolysaccharide (LPS)-primed bone marrow-derived macrophages were used to study the effects methanolic extract of C. intybus leaf (CI) on inflammasome activation. An insulin resistance model (mice fed a HFD) was used to study the in vivo effect of CI on T2D. CI attenuated interleukin-1ß (IL-1ß) secretion by inhibiting the activation of the NLRP3 inflammasome in mouse bone marrow macrophages. The CI treatment attenuated the intracellular movement of NLRP3 in Triton X-100 insoluble fraction, without affecting the expression of other NLRP3 inflammasome-related proteins. Attenuated IL-1ß secretion may improve glucose metabolism in the HFD-fed insulin resistance mouse model. CI also attenuated the infiltration of M1 macrophages and increased the M2 macrophage population in white adipose tissue. Collectively, our data showed that CI inhibits IL-1ß secretion through attenuation of NLRP3 inflammasome activation, leading to an antidiabetic effect by improving glucose metabolism and inhibiting metainflammation.

Inhibition of glutamine utilization sensitizes lung cancer cells to apigenin-induced apoptosis resulting from metabolic and oxidative stress.

Recent studies have shown anticancer activity of apigenin by suppressing glucose transporter 1 (GLUT1) expression in cultured cancer cells; however, it is not clear whether apigenin can suppress glucose metabolism in lung cancer cells or sensitize them to inhibition of glutamine utilization-mediated apoptosis through metabolic and oxidative stress. We show that apigenin significantly decreases GLUT1 expression in mice. Furthermore, we demonstrate that apigenin induces growth retardation and apoptosis through metabolic and oxidative stress caused by suppression of glucose utilization in lung cancer cells. The underlying mechanisms were defined that the anticancer effects of apigenin were reversed by ectopic GLUT1 overexpression and galactose supplementation, through activation of pentose phosphate pathway-mediated NADPH generation. Importantly, we showed that severe metabolic stress using a glutaminase inhibitor, compound 968, was involved in the mechanism of sensitization by apigenin. Taken together, the combination of apigenin with inhibitors of glutamine metabolism may provide a promising therapeutic strategy for cancer treatment.

Anti-inflammatory properties of Morus bombycis Koidzumi via inhibiting IFN-ß signaling and NLRP3 inflammasome activation.

ETHNOPHARMACOLOGICAL RELEVANCE: Morus bombycis Koidzumi (M. bombycis, Moraceae) has been used in Asian countries as a traditional medicine for the treatment of hypertension, diabetes, and inflammation-related disorders. AIM OF STUDY: Although its anti-inflammatory actions have been partly documented, scientific evidence involving its molecular mechanisms related to inflammasome activation signaling pathways remains unknown. MATERIALS AND METHODS: Lipopolysaccharide-stimulated RAW 264.7 cells and bone marrow-derived murine macrophages were used to study the in vitro effect of methanolic extract of M. bombycis (MB) on inflammatory responses. A monosodium urate crystal (MSU)-induced peritonitis murine model was used to study the in vivo effects. RESULTS: MB attenuated the production of nitric oxide and interleukin-6, through the regulation of the interferon-ß receptor signaling pathway. MB also inhibited IL-1ß secretion via attenuation of NLRP3 inflammasome activation. Furthermore, MB inhibited MSU-induced peritonitis in the in vivo murine model. CONCLUSIONS: This study provides the key molecular mechanisms involved in the anti-inflammatory effects of M. bombycis, substantiating the traditional claims of its use in the treatment of inflammation-related disorders.

Anti-Inflammatory Action of an Antimicrobial Model Peptide That Suppresses the TRIF-Dependent Signaling Pathway via Inhibition of Toll-Like Receptor 4 Endocytosis in Lipopolysaccharide-Stimulated Macrophages.

Antimicrobial peptides (AMPs), also called host defense peptides, particularly those with amphipathic helical structures, are emerging as target molecules for therapeutic development due to their immunomodulatory properties. Although the antimicrobial activity of AMPs is known to be exerted primarily by permeation of the bacterial membrane, the mechanism underlying its anti-inflammatory activity remains to be elucidated. We report potent anti-inflammatory activity of WALK11.3, an antimicrobial model peptide with an amphipathic helical conformation, in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. This peptide inhibited the expression of inflammatory mediators, including nitric oxide, COX-2, IL-1ß, IL-6, INF-ß, and TNF-α. Although WALK11.3 did not exert a major effect on all downstream signaling in the MyD88-dependent pathway, toll-like receptor 4 (TLR4)- mediated pro-inflammatory signals were markedly attenuated in the TRIF-dependent pathway due to inhibition of the phosphorylation of STAT1 by attenuation of IRF3 phosphorylation. WALK11.3 specifically inhibited the endocytosis of TLR4, which is essential for triggering TRIF-mediated signaling in macrophage cells. Hence, we suggest that specific interference with TLR4 endocytosis could be one of the major modes of the anti-inflammatory action of AMPs. Our designed WALK11 peptides, which possess both antimicrobial and anti-inflammatory activities, may be promising molecules for the development of therapies for infectious inflammation.

Anti-inflammatory effect of Impatiens textori Miq. extract via inhibition of NLRP3 inflammasome activation in in vitro and in vivo experimental models.

ETHNOPHARMACOLOGICAL RELEVANCE: Impatiens textori Miq. (I. textori, Balsaminaceae) is a traditional medicinal herb used for centuries to treat several inflammatory related skin infections and allergic disorders in Asian countries. AIM OF THE STUDY: In this study, we elucidated the effects of whole plant extracts of I. textori on inflammasome activation using in vitro and in vivo models. MATERIALS AND METHODS: LPS-stimulated murine bone marrow macrophages were used to study the regulatory effect of I. textori extract (IT) on inflammasome activation. ATP, nigericin and MSU were used as danger-associated molecules to activate the NLRP3 inflammasome. An LPS-induced acute lung injury (ALI) mouse model was used to study the in vivo effect of IT on inflammasome activation. RESULTS: IT treated at 25, 50, and 100µg/mL concentrations suppressed interleukin-1ß secretion through the attenuation of NLRP3 inflammasome activation (p<0.001 at 100µg/mL) leading to the decreased amount of ASC oligomerization and caspase-1 maturation. For the in vivo model, IT inhibited the NLRP3 expression and cell recruitment at the lung tissue in the ALI mouse model. CONCLUSION: IT exhibited potent anti-inflammatory effects via the attenuation of NLRP3 inflammasome activation supporting the traditional claims and may provide a valuable therapeutic strategy in treating various inflammation-related disorders.

Anti-inflammatory effect of emodin via attenuation of NLRP3 inflammasome activation.

Emodin, an active constituent of oriental herbs, is widely used to treat allergy, inflammation, and other symptoms. This study provides the scientific basis for the anti-inflammasome effects of emodin on both in vitro and in vivo experimental models. Bone marrow-derived macrophages were used to study the effects of emodin on inflammasome activation by using inflammasome inducers such as ATP, nigericin, and silica crystals. The lipopolysaccharide (LPS)-induced endotoxin shock model was employed to study the effect of emodin on in vivo efficacy. Emodin treatment attenuated interleukin (IL)-1ß secretion via the inhibition of NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation induced by ATP, nigericin, and silica crystals. Further, emodin ameliorated the severity of NLRP3 inflammasome-mediated symptoms in LPS-induced endotoxin mouse models. This study is the first to reveal mechanism-based evidence, especially with respect to regulation of inflammasome activation, substantiating traditional claims of emodin in the treatment of inflammation-related disorders.

Syneilesis palmata (Thunb.) Maxim. extract attenuates inflammatory responses via the regulation of TRIF-dependent signaling and inflammasome activation.

ETHNOPHARMACOLOGICAL RELEVANCE: Syneilesis palmata (Thunb.) Maxim. (S. palmata, Asteraceae) is a traditional Korean therapeutic herb widely used to treat pain, arthritis, and other symptoms. This study provides the scientific basis for the anti-inflammatory effects of S. palmata extract (SP) in both in vitro and in vivo experimental models. MATERIALS AND METHODS: Lipopolysaccharide (LPS)-stimulated murine macrophages were used to study the regulatory effect of SP on the inflammatory mediators in vitro. Bone marrow-derived macrophages were used to study the effects of SP on inflammasome activation. Escherichia coli-induced sepsis mouse model and LPS-induced endotoxin shock model were employed to study the effect of SP on in vivo efficacy. RESULTS: SP inhibited the LPS-stimulated release of proinflammatory mediators, such as nitric oxide and interleukin (IL)-6 in RAW 264.7 cells. SP treatment also attenuated IL-1ß secretion via the inhibition of NLRP3 inflammasome activation induced by monosodium urate, ATP, and nigericin. Further, SP ameliorated the severity of NLRP3 inflammasome-mediated symptoms in LPS-induced endotoxin and E. coli-induced sepsis mouse models. Mechanistic studies revealed that inhibitory effects of SP were mediated through the regulation of TRIF-dependent signaling and inflammasome activation. CONCLUSION: This study was the first to reveal mechanistic-based evidence substantiating the traditional claims of SP in the treatment of inflammation-related disorders, such as pain and arthritis.

Anti-inflammatory effect of Streptochlorin via TRIF-dependent signaling pathways in cellular and mouse models.

Streptochlorin, a small compound derived from marine actinomycete, has been shown to have anti-angiogenic, anti-tumor, and anti-allergic activities. However, the anti-inflammatory effects and underlying mechanisms have not yet been reported. In the present study, we investigated the effect of streptochlorin on lipopolysaccharide (LPS)-induced inflammatory responses in vitro and in vivo. Streptochlorin attenuated the production of proinflammatory mediators such as nitric oxide, cyclooxygenase-2, pro-interleukin (IL)-1ß, and IL-6 in LPS-stimulated RAW264.7 cells through inhibition of the Toll/interleukin-1 receptor (TIR)-domain-containing adapter-inducing interferon-ß (TRIF)-dependent signaling pathway. Furthermore, streptochlorin suppressed the infiltration of immune cells such as neutrophils into the lung and proinflammatory cytokine production such as IL-6 and TNF-α in broncho-alveolar lavage fluid (BALF) in the LPS-induced acute lung injury (ALI) mouse model. Streptochlorin has potent anti-inflammatory effects through regulating TRIF-dependent signaling pathways, suggesting that streptochlorin may provide a valuable therapeutic strategy in treating various inflammatory diseases.

A novel synthetic derivative of melatonin, 5-hydroxy-2'-isobutyl-streptochlorin (HIS), inhibits inflammatory responses via regulation of TRIF-dependent signaling and inflammasome activation.

Melatonin is substantially reported to possess anti-inflammatory properties. In the present study, we synthesized a novel melatonin derivative, 5-hydroxy-2'-isobutyl-streptochlorin (HIS), which displayed superior anti-inflammatory properties to its parent compound. Further, we explored its underlying mechanisms in cellular and experimental animal models. Lipopolysaccharide was used to induce in vitro inflammatory responses in RAW 264.7 macrophages. LPS-primed macrophages were pulsed with biologically unrelated toxic molecules to evaluate the role of HIS on inflammasome activation. In vivo verifications were carried out using acute lung injury (ALI) and Escherichia coli-induced septic shock mouse models. HIS inhibited the production of proinflammatory mediators and cytokines such as nitric oxide, cyclooxygenase 2, IL-1ß, IL-6 and TNF-α in LPS-stimulated RAW 264.7 macrophages. HIS suppressed the infiltration of immune cells into the lung and the production of pro-inflammatory cytokines such as IL-6 and TNF-α in broncho-alveolar lavage fluid in the ALI mouse model. Mechanistic studies revealed that the inhibitory effects of HIS were mediated through the regulation of the TIR domain-containing, adaptor-inducing, interferon-ß (TRIF)-dependent signaling pathway from toll-like receptors. Further, HIS attenuated IL-1ß secretion via the inhibition of NLRP3 inflammasome activation independent of mitochondrial ROS production. Furthermore, HIS suppressed IL-1ß, IL-6 and interferon-ß production in peritoneal lavage in the Escherichia coli-induced sepsis mouse model. In conclusion, HIS exerted potent anti-inflammatory effects via the regulation of TRIF-dependent signaling and inflammasome activation. Notably, the superior anti-inflammatory properties of this derivative compared with its parent compound could be a promising lead for treating various inflammatory-mediated diseases.