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Sepsis is a complex disorder related to dysregulation of the host response to infection and is a major health problem worldwide owing to its high mortality rates. However, the exact mechanisms causing sepsis remains unclear because of the complexity of the underlying pathways. Dysregulation of non-canonical NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome activation induces septic shock by promoting pyroptosis and pro-inflammatory cytokine production (e.g., interleukin-1β) via caspase-11 and Gasdermin-D. Herein, we describe a rapid, simple method for evaluation of the degree of sepsis by investigating non-canonical inflammasome activation in both in vitro and in vivo models. The method is expected to be useful for testing and screening drugs for the treatment of sepsis., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

In response to diverse pathogenic and danger signals, the cytosolic activation of the NLRP3 (NOD-, LRR-, and pyrin domain-containing (3)) inflammasome complex is a critical event in the maturation and release of some inflammatory cytokines in the state of an inflammatory response. After activation of the NLRP3 inflammasome, a series of cellular events occurs, including caspase 1-mediated proteolytic cleavage and maturation of the IL-1β and IL-18, followed by pyroptotic cell death. Therefore, the NLRP3 inflammasome has become a prime target for the resolution of many inflammatory disorders. Since NLRP3 inflammasome activation can be triggered by a wide range of stimuli and the activation process occurs in a complex, it is difficult to target the NLRP3 inflammasome. During the activation process, various post-translational modifications (PTM) of the NLRP3 protein are required to form a complex with other components. The regulation of ubiquitination and deubiquitination of NLRP3 has emerged as a potential therapeutic target for NLRP3 inflammasome-associated inflammatory disorders. In this review, we discuss the ubiquitination and deubiquitination system for NLRP3 inflammasome activation and the inhibitors that can be used as potential therapeutic agents to modulate the activation of the NLRP3 inflammasome.

Ethnopharmacological Relevance: Panax ginseng C.A. Meyer (Araliaceae), has been used in traditional medicine for preventive and therapeutic purposes in Asian countries. One of the active ginsenoside metabolites, 20(S)-Protopanaxatriol (PPT), has been associated with diverse pharmacological effects, including anti-inflammatory properties., Aim of the Study: Although the capacity of PPT as an anti-inflammatory agent has been studied, this study aimed to explore the intrinsic mechanism of PPT in regulating inflammasome activation-mediated inflammatory responses in experimental models., Materials and Methods: Lipopolysaccharide (LPS)-primed peritoneal macrophages in vitro was used to study the role of PPT on inflammasome activation. LPS-induced septic shock and monosodium urate (MSU)-induced murine peritonitis models were employed for in vivo evaluations., Results: PPT attenuated NLRP3 inflammasome activation and also reduced ASC oligomerization, leading to attenuation of interleukin (IL)-1β secretion. Further, PPT inhibited IL-1β secretion in both LPS-induced septic shock and MSU-induced mouse peritonitis models., Conclusions: This study revealed that ginsenoside metabolite PPT, inhibits inflammation-mediated inflammasome activation and supported the traditional use of ginseng in treating various inflammatory disorders., Competing Interests: Declaration of competing interest The authors declared no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Programmed cell death pathways and inflammasome activation pathways can be genetically and functionally separated. Inflammasomes are specialized protein complexes that process pro-inflammatory cytokines, interleukin-1β (IL-1β), and IL-18 to bioactive forms for protection from a wide range of pathogens, as well as environmental and host-derived danger molecules. Programmed cell death has been extensively studied, and its role in the development, homeostasis, and control of infection and danger is widely appreciated. Apoptosis and the recently recognized necroptosis are the best-characterized forms of programmed death, and the interplay between them through death receptor signaling is also being studied. Moreover, growing evidence suggests that many of the signaling molecules known to regulate programmed cell death can also modulate inflammasome activation in a cell-intrinsic manner. Therefore, in this review, we will discuss the current knowledge concerning the role of the signaling molecules originally associated with programmed cell death in the activation of inflammasome and IL-1β processing.

Ethnopharmacological Relevance: Chrysanthemum indicum (C. indicum), a perennial plant, has long been used to treat inflammation-related disorders, such as pneumonia, hypertension, gastritis, and gastroenteritis., Aim of the Study: The inhibitory effect of C. indicum extract (C.I) on inflammasome activation was investigated to validate its potential in treating inflammation related disorders., Materials and Methods: LPS-primed bone marrow-derived macrophages (BMDMs) were used to confirm the inhibitory effect of C.I on selective inflammasome activation in vitro. A monosodium urate (MSU)-induced murine peritonitis model was employed to study the effect of C.I in vivo., Results: C.I inhibited activation of NLRP3 and AIM2 inflammasomes, leading to suppression of interleukin-1β secretion in vitro. Further, C.I regulates the phosphorylation of apoptosis-associated speck-like protein containing a CARD (ASC), which could be the main contribution to attenuate these inflammasomes activation. C.I also suppressed secretion of pro-inflammatory cytokines and neutrophils recruitment in MSU-induced murine peritonitis model., Conclusions: This study provides scientific evidence substantiating the traditional use of C. indicum in the treatment of inflammatory diseases, including gout, which is induced by physiologically analogous cause to MSU-induced peritonitis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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.

Artemisia princeps var. orientalis (Asteraceae, A. princeps ) is a well-known traditional medicinal herb used for treating various inflammatory disorders in Korea, Japan, China, and other Asian countries. In the present study, we investigated the effects of A. princeps extract (APO) on interleukin- (IL-) 1 β regulation and inflammasome activation in bone marrow-derived macrophages (BMDMs) and monosodium urate- (MSU-) induced peritonitis mouse model in vivo . The APO treatment to BMDMs primed with lipopolysaccharide (LPS) attenuated the NLRP3 and AIM2 inflammasome activation induced by danger signals, such as ATP, nigericin, silica crystals, and poly (dA:dT), respectively. Mechanistic study revealed that APO suppressed the ASC oligomerization and speck formation, which are required for inflammasome activation. APO treatment also reduced the ASC phosphorylation induced by the combination of LPS and a tyrosine phosphatase inhibitor. In vivo evaluation revealed that intraperitoneal administration of APO reduced IL-1 β levels, significantly ( p < 0.05) and dose dependently, in the MSU-induced peritonitis mouse model. In conclusion, our study is the first to report that the extract of A. princeps inhibits inflammasome activation through the modulation of ASC phosphorylation. Therefore, APO might be developed as therapeutic potential in the treatment of inflammasome-mediated inflammatory disorders, such as gouty arthritis.

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)-1β 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., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Eucalyptus globulus Labill. (E. globulus, Myrtaceae) is used in Europe as a traditional folk remedy for inflammation-related disorders such as arthritis, diabetes, asthma, and gout. We investigated this study to evaluate the protective effects of E. globulus extract (EG) on inflammatory responses, and provide scientific and mechanistic evidence in in vitro and in vivo experimental models. LPS-stimulated murine bone marrow-derived macrophages (BMDMs) were used to study the regulatory effect of EG on inflammasome activation in vitro. Monosodium urate (MSU)-induced peritonitis was used to study the effect of EG in an in vivo murine model. EG suppressed IL-[Formula: see text] secretion via the regulation of apoptosis-associated speck-like proteins containing a CARD (ASC) oligomerization and caspase-1 maturation, leading to the inhibition of inflammasome activation. In the in vivo study, EG suppressed the MSU-induced peritonitis by attenuating interleukin (IL)-1[Formula: see text], providing scientific support for its traditional use in the treatment of inflammation-related disorders.

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.

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-1β 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., (Copyright © 2017. Published by Elsevier B.V.)

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)-1β, IL-6, and tumor necrosis factor-alpha (TNF-α). In the in vitro study, JR suppressed IL-1β 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-1β., 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., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

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-1β (IL-1β) 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-1β 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-1β secretion through attenuation of NLRP3 inflammasome activation, leading to an antidiabetic effect by improving glucose metabolism and inhibiting metainflammation.

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-1β 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., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

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-1β, 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-β (TRIF)-dependent signaling pathway from toll-like receptors. Further, HIS attenuated IL-1β secretion via the inhibition of NLRP3 inflammasome activation independent of mitochondrial ROS production. Furthermore, HIS suppressed IL-1β, IL-6 and interferon-β 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., (Copyright © 2015 Elsevier Inc. All rights reserved.)

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)-1β 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.