Regulation of the NLRP3 inflammasome with natural products against chemical-induced liver injury

Isolicoflavonol ameliorates acute liver injury via inhibiting NLRP3 inflammasome activation through boosting Nrf2 signaling in vitro and in vivo

BACKGROUND

NOD like receptor pyrin domain containing 3 (NLRP3) inflammasome is involved in innate immunity, and related to liver injury. However, no inflammasome inhibitors are clinically available until now. Our previous research suggests that isolicoflavonol (ILF), isolated from Macaranga indica, is a potent NLRP3 inflammasome inhibitor, but its mechanism is unclear.

METHODS

Fluorescent imaging and Western blot assay were used to ascertain the effects of ILF on pyroptosis and NLRP3 inflammasome activation in macrophages. Next, Nrf2 signal pathway, its downstream gene transcription and expression were further investigated. ML385, a Nrf2 inhibitor, was used to verify whether ILF targets Nrf2 signaling. A carbon tetrachloride induced liver injury model was introduced to evaluate the liver protection activity of ILF in mice.

RESULTS

This work revealed that ILF inhibited macrophage LDH release and IL-1β secretion in a dose-dependent manner. ILF had no significant cytotoxic effect on macrophage, it reduced pyroptosis and Gasdermin D N-terminal fragment formation. Moreover, ILF inhibited IL-1β maturation and Caspase-1 cleavage, but did not affect NLRP3, pro-Caspase-1, pro-IL-1β and ASC expression. ILF decreased ASC speck rate and reduced ASC oligomer formation. ILF decreased aggregated JC-1 formation restoring mitochondria membrane potential. In addition, ILF increased Nrf2 expression, extended Nrf2 lifespan and upregulated Nrf2 signaling pathway in macrophages whether the NLRP3 inflammasome was activated or not. Besides, ILF increased Nrf2 nuclear translocation, maintained a high proportion of Nrf2 in the nucleus, and upregulated ARE-related gene transcription and expression. Furthermore, Nrf2 signal inhibition attenuated compound ILF-mediated inhibition of pyroptosis, inflammasome activation and upregulation of Nrf2 signaling. ILF in a liver injury mouse model inhibited NLRP3 inflammasome activation and enhanced Nrf2 signaling.

CONCLUSION

Our study verified that ILF ameliorates liver injury via inhibiting NLRP3 inflammasome activation through boosting Nrf2 signaling, and highlighted that ILF is a potent anti-inflammatory drug for inflammasome-related liver diseases.

PKM2-mediated STAT3 phosphorylation promotes acute liver failure via regulating NLRP3-dependent pyroptosis

Acute liver failure (ALF) is a life-threatening clinical syndrome characterized by high-grade inflammation and multi-organ failure. Our previous study shows that targeting the M2 isoform of pyruvate kinase (PKM2) to inhibit macrophage inflammation may be a promising strategy for ALF treatment. however, the mechanism by which PKM2 regulates the inflammatory response is unclear. Here we demonstrate that PKM2 contributes to ALF by modulating NLRP3-mediated pyroptosis activation in liver macrophages. The specific knockout of PKM2 in myeloid cells reduces mortality and alleviates hepatic injury in D-galactosamine/LPS-induced ALF mice. Single-cell transcriptome analysis suggests that NLRP3 inflammasome activation of macrophages involves in ALF, knockout of PKM2 in macrophages reduces the expression of NLRP3, and activation of pyroptosis. Pharmacological inhibition of the PKM2 nuclear translocation, but not glycolytic activity, protects mice from ALF. Pharmacological and genetic inhibition of PKM2 attenuates NLRP3-mediated pyroptosis activation and consequently reduces the release of IL-1β and IL-18 by macrophages. Mechanistically, PKM2 translocates into the nucleus and combines with STAT3, enhancing its phosphorylation and recruitment to the NLRP3 promoter region, thereby increasing NLRP3 expression. This work defines PKM2 acts as an important nonmetabolic regulator of NLRP3 that modulates pyroptosis activation in macrophages and guides future therapeutic strategies development for ALF.

Podophyllotoxin mediates hepatic toxicity via the C5a/C5aR/ROS/NLRP3 and cGMP/PKG/mTOR axis in rats based on toxicological evidence chain (TEC) concept by phosphoproteomic analysis

BACKGROUND

Podophyllotoxin (PPT), a highly active compound extracted from the rhizome of Dysosma versipellis (DV), has been used as an effective anti-cancer drug clinically since the 1950s. It possesses various biological activities, including antiviral and antitumor effects. However, its clinical application is severely limited due to its hepatotoxicity, and the underlying mechanisms remain unclear. This study aims to elucidate the mechanisms of PPT-induced hepatotoxicity using tandem quality tag (TMT) based quantitative proteomics and phosphoproteomics, providing potential targets and directions for developing new therapeutic strategies to facilitate the safe and rational use of podophyllotoxin in clinical settings.

METHODS

We employed a comprehensive assessment of PPT-induced hepatotoxicity based on the Toxicology Evidence Chain (TEC) concept, originally proposed by our research group in 2018. This approach involves a tiered search for evidence of Harmful Ingredients Evidence (HIE), Injury Phenotype Evidence (IPE), Adverse Outcomes Evidence (AOE), and Toxic Events Evidence (TEE) during the development of PPT-induced hepatotoxicity, thereby constructing a guiding toxicology evidence chain. Sprague-Dawley (SD) rats were administered 20 mg/kg PPT for 4 consecutive days (HIE). Indicators such as hepatic function, oxidative stress, inflammatory factors, as well as the histopathology of liver tissue were evaluated to assess liver damage and synthetic function (AOE). Proteomics and phosphoproteomics were conducted to systematically assess PPT-induced hepatotoxicity at the level of modified proteins and verify the molecular mechanisms of key molecular pathways (TEE1). Furthermore, in vitro THLE-2 cell models were used in conjunction with CCK8, immunofluorescence, and ELISA assays to validate cytotoxicity and its underlying mechanisms (TEE2).

RESULTS

Our results showed that after 4 days of PPT administration at 20 mg/kg (HIE), serum levels of AST/ALT, TBA, TP, and ALB in SD rats were significantly increased (P < 0.05), indicating severe liver damage. SOD and T-AOC levels were significantly decreased (P < 0.05), suggesting an oxidative stress state. TNF-α levels were significantly elevated, while IL-10 and IL-3 levels were significantly reduced (P < 0.05), indicating strong activation of the inflammatory response in the liver. Histopathological examination revealed liver sinusoidal congestion in the liver tissue (AOE). Omics analysis revealed that hepatotoxicity primarily affected the complement-pyroptosis and cGMP-PKG-autophagy pathways. Western blot (WB) and RT-qPCR results showed significant upregulation of complement-pyroptosis pathway proteins (C5a, C5aR, NLRP3) and cGMP-PKG-autophagy pathway proteins (PKG, mTOR) in the PPT group (P < 0.05) (TEE1). In vitro cell experiments showed that PPT significantly reduced cell viability (P < 0.05) and increased the expression of proteins associated with pyroptosis and autophagy pathways, including ROS, NLRP3, PKG, and mTOR (P < 0.05) (TEE2).

CONCLUSION

PPT activates the complement system through the C5a/C5aR/ROS/NLRP3 pathway and induces the formation of inflammasomes, promoting pyroptosis. Simultaneously, PPT activates the cGMP-PKG pathway, inhibiting autophagy and further accelerating pyroptosis, ultimately leading to hepatotoxicity. In conclusion, this study comprehensively revealed the underlying mechanisms of PPT-induced hepatotoxicity using the TEC concept. This approach transforms fragmented toxicity indicators into systematic evidence of toxicity, presenting a hierarchical progression of toxicity evidence and avoiding data accumulation in natural drug toxicology. Our findings represent a significant breakthrough in the elucidation of the mechanisms of hepatotoxicity induced by podophyllotoxin.

Nicardipine-chitosan nanoparticles alleviate thioacetamide-induced acute liver injury by targeting NFκB/NLRP3/IL-1β signaling in rats: Unraveling new roles beyond calcium channel blocking

Liver inflammatory diseases are marked by serious complications. Notably, nicardipine (NCD) has demonstrated anti-inflammatory properties, but its benefits in liver inflammation have not been studied yet. However, the therapeutic efficacy of NCD is limited by its short half-life and low bioavailability. Therefore, we aimed to evaluate the potential of NCD-loaded chitosan nanoparticles (ChNPs) to improve its pharmacokinetic profile and hepatic accumulation. Four formulations of NCD-ChNPs were synthesized and characterized. The optimal formulation (NP2) exhibited a mean particle diameter of 172.6 ± 1.94 nm, a surface charge of +25.66 ± 0.93 mV, and an encapsulation efficiency of 88.86 ± 1.17 %. NP2 showed good physical stability as a lyophilized powder over three months. It displayed pH-sensitive release characteristics, releasing 77.15 ± 5.09 % of NCD at pH 6 (mimicking the inflammatory microenvironment) and 52.15 ± 3.65 % at pH 7.4, indicating targeted release in inflamed liver tissues. Pharmacokinetic and biodistribution studies revealed that NCD-ChNPs significantly prolonged NCD circulation time and enhanced its concentration in liver tissues compared to plain NCD. Additionally, the study investigated the protective effects of NCD-ChNPs in thioacetamide-induced liver injury in rats by modulating the NFκB/NLRP3/IL-1β signaling axis. NCD-ChNPs effectively inhibited NFκB activation, reduced NLRP3 inflammasome activation, and subsequent release of IL-1β, which correlated with improved hepatic function and reduced inflammation and oxidative stress. These findings highlight the potential of NCD-ChNPs as a promising nanomedicine strategy for the treatment of liver inflammatory diseases, warranting further investigation into their clinical applications, particularly in hypertensive patients with liver inflammatory conditions.

Protective effects of Panax ginseng as a medical food against chemical toxic agents: molecular and cellular mechanisms

Humans are exposed to different types of toxic agents, which may directly induce organ malfunction or indirectly alter gene expression, leading to carcinogenic and teratogenic effects, and eventually death. Ginseng (Panax ginseng) is the most valuable of all medicinal herbs. Nevertheless, specific data on the antidotal mechanisms of this golden herb are currently unavailable. Based on the findings of in vitro, in vivo, and clinical studies, this review focused on the probable protective mechanisms of ginseng and its major components, such as protopanaxadiols, protopanaxatriols, and pentacyclic ginsenosides against various chemical toxic agents. Relevant articles from 2000 to 2023 were gathered from PubMed/Medline, Scopus, and Google Scholar. This literature review shows that P. ginseng and its main components have protective and antidotal effects against the deteriorative effects of pesticides, pharmaceutical agents, including acetaminophen, doxorubicin, isoproterenol, cyclosporine A, tacrolimus, and gentamicin, ethanol, and some chemical agents. These improvements occur through multi-functional mechanisms. They exhibit antioxidant activity, induce anti-inflammatory action, and block intrinsic and extrinsic apoptotic pathways. However, relevant clinical trials are necessary to validate the mentioned effects and translate the knowledge from basic science to human benefit, fulfilling the fundamental goal of all toxicologists.

Brazilin is a natural product inhibitor of the NLRP3 inflammasome

Excessive or aberrant NLRP3 inflammasome activation has been implicated in the progression and initiation of many inflammatory conditions; however, currently no NLRP3 inflammasome inhibitors have been approved for therapeutic use in the clinic. Here we have identified that the natural product brazilin effectively inhibits both priming and activation of the NLRP3 inflammasome in cultured murine macrophages, a human iPSC microglial cell line and in a mouse model of acute peritoneal inflammation. Through computational modeling, we predict that brazilin can adopt a favorable binding pose within a site of the NLRP3 protein which is essential for its conformational activation. Our results not only encourage further evaluation of brazilin as a therapeutic agent for NLRP3-related inflammatory diseases, but also introduce this small-molecule as a promising scaffold structure for the development of derivative NLRP3 inhibitor compounds.

Chemistry and bioactivity of lindenane sesquiterpenoids and their oligomers

Covering: 1925 to July 2023Among the sesquiterpenoids with rich structural diversity and potential bioactivities, lindenane sesquiterpenoids (LSs) possess a characteristic cis, trans-3,5,6-carbocyclic skeleton and mainly exist as monomers and diverse oligomers in plants from the Lindera genus and Chloranthaceae family. Since the first identification of lindeneol from Lindera strychnifolia in 1925, 354 natural LSs and their oligomers with anti-inflammatory, antitumor, and anti-infective activities have been discovered. Structurally, two-thirds of LSs exist as oligomers with interesting skeletons through diverse polymeric patterns, especially Diels-Alder [4 + 2] cycloaddition. Fascinated by their diverse bioactivities and intriguing polycyclic architectures, synthetic chemists have engaged in the total synthesis of natural LSs in recent decades. In this review, the research achievements related to LSs from 1925 to July of 2023 are systematically and comprehensively summarized, focusing on the classification of their structures, chemical synthesis, and bioactivities, which will be helpful for further research on LSs and their oligomers.

Recent advances in pyroptosis, liver disease, and traditional Chinese medicine: A review

In recent years, the incidence of liver disease has increased, becoming a major cause of death. Various liver diseases are intricately linked to pyroptosis, which is one of the most common forms of programmed cell death. As a powerful weapon in the fight against liver diseases, traditional Chinese medicine (TCM) can affect pyroptosis via a number of routes, including the classical, nucleotide oligomerization domain-like receptors protein 3/caspase-1/gasdermin D (GSDMD) pathway, the nonclassical lipopolysaccharide/caspase-11/GSDMD pathway, the ROS/caspase-3/gasdermin E pathway, the caspase-9/caspase-3/GSDMD pathway, and the Apaf-1/caspase-11/caspase-3 pathway. In this review, we provide an overview of pyroptosis, the interplay between pyroptosis and liver diseases, and the mechanisms through which TCM regulates pyroptosis in liver diseases. The information used in the text was collected and compiled from the databases of PubMed, Web of Science, Scopus, CNKI, and Wanfang Data up to June 2023. The search was not limited with regard to the language and country of the articles. Research and review articles were included, and papers with duplicate results or unrelated content were excluded. We examined the current understanding of the relationship between pyroptosis and liver diseases as well as the advances in TCM interventions to provide a resource for the identification of potential targets for TCM in the treatment of liver diseases.

Trans-anethole pretreatment ameliorates hepatic ischemia-reperfusion injury via regulation of soluble epoxide hydrolase

Hepatic ischemia reperfusion injury (IRI) is a risk factor for early graft nonfunction and graft rejection after liver transplantation (LT). The process of liver IRI involves inflammatory response, oxidative stress, apoptosis and other pathophysiological processes. So far, there is still a lack of effective drugs to ameliorate liver IRI. Trans-anethole (TA) is an aromatic compound. Many medications as well as natural foods contain TA. TA has multiple effects such as anti-inflammation, anti-oxidative stress and anti-apoptosis. However, the mechanism of TA pretreatment in liver IRI is unclear. The mice hepatic IRI model was constructed after gavage pretreatment with TA (10 mg/kg, 20 mg/kg, 40 mg/kg) for 7 consecutive days. Our study confirmed that TA pretreatment significantly improve liver function and reduce serum AST, ALT in hepatic IRI. HE staining showed that TA pretreatment alleviated liver injury. Meanwhile, TA (20 mg/kg) pretreatment attenuated hepatocyte apoptosis in hepatic IRI. In addition, TA (20 mg/kg) pretreatment reduced the inflammatory factors TNF-α, IL-6 and infiltration of CD11b positive cells in liver tissues during hepatic IRI in mice. TA pretreatment also alleviated oxidative stress in mice hepatic IRI. Our study further indicated that TA pretreatment attenuated mice hepatic IRI through inhibiting NLRP3 inflammasome activation via regulation of soluble epoxide hydrolase (sEH). This study provides a novel and effective potential drug with few side effects for easing liver IRI.

Ginsenoside Rk2, a dehydroprotopanaxadiol saponin, alleviates alcoholic liver disease via regulating NLRP3 and NLRP6 inflammasome signaling pathways in mice

Heavy alcohol consumption results in alcoholic liver disease (ALD) with inadequate therapeutic options. Here, we first report the potential beneficial effects of ginsenoside Rk2 (Rk2), a rare dehydroprotopanaxadiol saponin isolated from streamed ginseng, against alcoholic liver injury in mice. Chronic-plus-single-binge ethanol feeding caused severe liver injury, as manifested by significantly elevated serum aminotransferase levels, hepatic histological changes, increased lipid accumulation, oxidative stress, and inflammation in the liver. These deleterious effects were alleviated by the treatment with Rk2 (5 and 30 mg/kg). Acting as an nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inhibitor, Rk2 ameliorates alcohol-induced liver inflammation by inhibiting NLRP3 inflammasome signaling in the liver. Meanwhile, the treatment with Rk2 alleviated the alcohol-induced intestinal barrier dysfunction via enhancing NLRP6 inflammasome in the intestine. Our findings indicate that Rk2 is a promising agent for the prevention and treatment of ALD and other NLPR3-driven diseases.

Tabersonine, a natural NLRP3 inhibitor, suppresses inflammasome activation in macrophages and attenuate NLRP3-driven diseases in mice

Aberrant activation of NLRP3 inflammasome causes the progression of various inflammation-related diseases, but the small-molecule inhibitors of NLRP3 are not currently available for clinical use. Tabersonine (Tab) is a natural product derived from a traditional Chinese herb Catharanthus roseus that is usually used as an anti-tumor agent. In this study we investigated the anti-inflammatory effects and molecular targets of Tab. We first screened 151 in-house natural compounds for their inhibitory activity against IL-1β production in BMDMs. We found that Tab potently inhibited NLRP3-mediated IL-1β production with an IC50 value of 0.71 μM. Furthermore, we demonstrated that Tab suppressed the assembly of NLRP3 inflammasome, especially the interaction between NLRP3 and ASC. Interestingly, we found that Tab directly bound to NLRP3 NACHT domain, thereby reducing the self-oligomerization of NLRP3. In addition, we showed that administration of Tab significantly ameliorated NLRP3-driven diseases, such as peritonitis, acute lung injury, and sepsis in mouse models. The preventive effects of Tab were not observed in the models of NLRP3 knockout mouse. In conclusion, we have identified Tab as a natural NLRP3 inhibitor and a lead compound for the design and discovery of novel NLRP3 inhibitors.

Tricyclic antidepressants induce liver inflammation by targeting NLRP3 inflammasome activation

BACKGROUND

Idiosyncratic drug-induced liver injury (IDILI) is common in hepatology practices and, in some cases, lethal. Increasing evidence show that tricyclic antidepressants (TCAs) can induce IDILI in clinical applications but the underlying mechanisms are still poorly understood.

METHODS

We assessed the specificity of several TCAs for NLRP3 inflammasome via MCC950 (a selective NLRP3 inhibitor) pretreatment and Nlrp3 knockout (Nlrp3^-/-) BMDMs. Meanwhile, the role of NLRP3 inflammasome in the TCA nortriptyline-induced hepatotoxicity was demonstrated in Nlrp3^-/- mice.

RESULTS

We reported here that nortriptyline, a common TCA, induced idiosyncratic hepatotoxicity in a NLRP3 inflammasome-dependent manner in mildly inflammatory states. In parallel in vitro studies, nortriptyline triggered the inflammasome activation, which was completely blocked by Nlrp3 deficiency or MCC950 pretreatment. Furthermore, nortriptyline treatment led to mitochondrial damage and subsequent mitochondrial reactive oxygen species (mtROS) production resulting in aberrant activation of the NLRP3 inflammasome; a selective mitochondrial ROS inhibitor pretreatment dramatically abrogated nortriptyline-triggered the NLRP3 inflammasome activation. Notably, exposure to other TCAs also induced aberrant activation of the NLRP3 inflammasome by triggering upstream signaling events.

CONCLUSION

Collectively, our findings revealed that the NLRP3 inflammasome may act as a crucial target for TCA agents and suggested that the core structures of TCAs may contribute to the aberrant activation of NLRP3 inflammasome induced by them, an important factor involved in the pathogenesis of TCA-induced liver injury. Video Abstract.

Nootkatone Supplementation Ameliorates Carbon Tetrachloride-Induced Acute Liver Injury via the Inhibition of Oxidative Stress, NF-κB Pathways, and the Activation of Nrf2/HO-1 Pathway

Acute liver injury is a type of liver diseases, and it has raised concerns worldwide due to the lack of effective therapies. The aim of this study is to investigate the protective effects of nootkatone (NOOT) on carbon tetrachloride (CCl₄)-caused acute liver injury in mice. Mice were randomly divided into control, CCl₄ model, NOOT, and NOOT (5, 10, and 20 mg/kg/day) plus CCl₄ groups, respectively. Mice in the CCl₄ plus NOOT groups were orally administrated with NOOT at 5, 10, and 20 mg/kg/days for seven days prior to 0.3% CCl₄ injection at 10 mL/kg body weight, respectively. Our results showed that NOOT supplementation significantly ameliorated CCl₄-induced increases of serum AST and ALT levels, hepatocyte necrosis, inflammatory response, oxidative stress, and caspases-9 and -3 activities in the livers of mice. Moreover, NOOT supplementation significantly upregulated the expression of Nrf2 and HO-1 mRNAs but downregulated the expression of NF-κB mRNAs and the levels of IL-1β, IL-6, and TNF-α proteins in the liver tissues, compared to those in the CCl₄ model group. In conclusion, for the first time, our results reveal that NOOT could offer protective effects against CCl₄-caused oxidative stress and inflammatory response via the opposite regulation of Nrf2/HO-1 pathway and NF-κB pathway.

Targeted modulation of gut microbiota by traditional Chinese medicine and natural products for liver disease therapy

The gut microbiota not only constitutes intestinal microenvironment homeostasis and human health but also exerts indispensable roles in the occurrence and progression of multiple liver diseases, including alcohol-related liver disease, nonalcoholic fatty liver disease, autoimmune liver disease and liver cancer. Given the therapeutic status of these diseases, their prevention and early therapy are crucial, and the detailed mechanism of gut microbiota in liver disease urgently needs to be explored. Meanwhile, multiple studies have shown that various traditional Chinese medicines, such as Si Miao Formula, Jiangzhi Granules, Liushen Capsules, Chaihu-Shugan Power, Cassiae Semen and Gynostemma, as well as some natural products, including Costunolide, Coprinus comatus polysaccharide, Antarctic krill oil, Oridonin and Berberine, can repair liver injury, improve fatty liver, regulate liver immunity, and even inhibit liver cancer through multiple targets, links, and pathways. Intriguingly, the aforementioned effects demonstrated by these traditional Chinese medicines and natural products have been shown to be closely related to the gut microbiota, directly driving the strategy of traditional Chinese medicines and natural products to regulate the gut microbiota as one of the breakthroughs in the treatment of liver diseases. Based on this, this review comprehensively summarizes and discusses the characteristics, functions and potential mechanisms of these medicines targeting gut microbiota during liver disease treatment. Research on the potential effects on gut microbiota and the regulatory mechanisms of traditional Chinese medicine and natural products provides novel insights and significant references for developing liver disease treatment strategies. In parallel, such explorations will enhance the comprehension of traditional Chinese medicine and natural products modulating gut microbiota during disease treatment, thus facilitating their clinical investigation and application.

A Selective Review and Virtual Screening Analysis of Natural Product Inhibitors of the NLRP3 Inflammasome

The NLRP3 inflammasome is currently an exciting target for drug discovery due to its role in various inflammatory diseases; however, to date, no NLRP3 inhibitors have reached the clinic. Several studies have used natural products as hit compounds to facilitate the design of novel selective NLRP3 inhibitors. Here, we review selected natural products reported in the literature as NLRP3 inhibitors, with a particular focus on those targeting gout. To complement this survey, we also report a virtual screen of the ZINC20 natural product database, predicting favored chemical features that can aid in the design of novel small molecule NLRP3 inhibitors.

Cyclo(-Phe-Phe) alleviates chick embryo liver injury via activating the Nrf2 pathway

Excessive reactive oxygen species (ROS) accumulation is involved in the pathogenesis of liver fibrosis and damage, specifically in the developing embryo that is extremely sensitive to oxidative stress. Herein, a liver injury model in chick embryo was established by using 2,2-azobis (2-amidinopropane) dihydrochloride (AAPH), which was used to investigate the effect of cyclo(-Phe-Phe) (CPP), a natural dipeptide found in foods and beverages. The results showed that CPP significantly alleviated AAPH-induced liver pathological damage, hepatic dysfunction and inhibited the excessive production of ROS in both chick embryo liver and HepG2 cells. Additionally, CPP increased the antioxidative activity of glutathione peroxidase (GPx) and superoxide dismutase (SOD), as well as elevated the level of glutathione (GSH), suggesting that CPP combating liver injury probably depends on its antioxidant capability. Mechanistically, CPP upregulated the mRNA and protein expression of heme oxyense-1 (HO-1) and NADPH quinone oxidoreductase 1 (NQO1) in vivo and in vitro, along with promoting the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) while inhibiting its degradation through binding with Kelch-like ECH-associated protein 1 (Keap1). In conclusion, this study proposes a potential peptide drug for the treatment of hepatic damage induced by oxidative stress and also unravels its mechanism of action.

Pro-Inflammatory Signalling PRRopels Cisplatin-Induced Toxicity

Cisplatin is a platinum-based chemotherapeutic that has long since been effective against a variety of solid-cancers, substantially improving the five-year survival rates for cancer patients. Its use has also historically been limited by its adverse drug reactions, or cisplatin-induced toxicities (CITs). Of these reactions, cisplatin-induced nephrotoxicity (CIN), cisplatin-induced peripheral neuropathy (CIPN), and cisplatin-induced ototoxicity (CIO) are the three most common of several CITs recognised thus far. While the anti-cancer activity of cisplatin is well understood, the mechanisms driving its toxicities have only begun to be defined. Most of the literature pertains to damage caused by oxidative stress that occurs downstream of cisplatin treatment, but recent evidence suggests that the instigator of CIT development is inflammation. Cisplatin has been shown to induce pro-inflammatory signalling in CIN, CIPN, and CIO, all of which are associated with persisting markers of inflammation, particularly from the innate immune system. This review covered the hallmarks of inflammation common and distinct between different CITs, the role of innate immune components in development of CITs, as well as current treatments targeting pro-inflammatory signalling pathways to conserve the use of cisplatin in chemotherapy and improve long-term health outcomes of cancer patients.

An Experimental Study Reveals the Protective Effect of Autophagy against Realgar-Induced Liver Injury via Suppressing ROS-Mediated NLRP3 Inflammasome Pathway

Realgar, a poisonous traditional Chinese medicine, has been shown to cause liver injury when used for long periods or overdoses. However, the underlying molecular mechanisms and therapeutic targets have not been fully elucidated. The aim of this study is to explore the role of autophagy in sub-chronic realgar exposure-induced liver injury. Here, the liver injury model was established by continuously administrating mice with 1.35 g/kg realgar for 8 weeks. 3-methyladenine (3-MA) and rapamycin (RAPA) were used to regulate autophagy. The results showed that realgar induced abnormal changes in liver function, pathological morphology, expression of inflammatory cytokines, and upregulated NLRP3 inflammasome pathway in mouse livers. RAPA treatment (an inducer of autophagy) significantly improved realgar-induced liver injury and NLRP3 inflammasome activation, while 3-MA (an inhibitor of autophagy) aggravated the realgar-induced liver injury and NLRP3 inflammasome activation. Furthermore, we found that realgar-induced NLRP3 inflammasome activation in mouse livers is mediated by ROS. RAPA eliminates excessive ROS, inhibits NF-κB nuclear translocation and down-regulates the TXNIP/NLRP3 axis, consequently suppressing ROS-mediated NLRP3 inflammasome activation, which may be the underlying mechanism of the protective effect of autophagy on realgar-induced liver injury. In conclusion, the results of this study suggest that autophagy alleviates realgar-induced liver injury by inhibiting ROS-mediated NLRP3 inflammasome activation. Autophagy may represent a therapeutic target in modulating realgar-induced liver injury.

Red yeast rice ameliorates non-alcoholic fatty liver disease through inhibiting lipid synthesis and NF-κB/NLRP3 inflammasome-mediated hepatic inflammation in mice

BACKGROUND

Red yeast rice (RYR), a nutraceutical with a profound cholesterol-lowering effect, was found to attenuate non-alcoholic fatty liver disease (NAFLD) in mice. Despite monacolin K in RYR being a specific inhibitor of hydroxymethylglutaryl-coenzyme A reductase (HMCGR), the mechanisms underlying the protective effects of RYR against NAFLD are not fully elucidated.

METHODS

Using a mouse model of high-fat diet (HFD) feeding and a cellular model of HepG2 cells challenged by lipopolysaccharide (LPS) and palmitic acid (PA), the possible molecular mechanisms were exploited in the aspects of NF-κB/NLRP3 inflammasome and mTORC1-SREBPs signaling pathways by examining the relevant gene/protein expressions. Subsequently, the correlation between these two signals was also verified using cellular experiments.

RESULTS

RYR ameliorated lipid accumulation and hepatic inflammation in vivo and in vitro. RYR improved lipid metabolism through modulating mTORC1-SREBPs and their target genes related to triglyceride and cholesterol synthesis. Furthermore, RYR suppressed hepatic inflammation by inhibiting the NF-κB/NLRP3 inflammasome signaling. Interestingly, the treatment with RYR or MCC950, a specific NLRP3 inhibitor, resulted in the reduced lipid accumulation in HepG2 cells challenged by LPS plus PA, suggesting that the inhibitory effects of RYR on NLRP3 inflammasome-mediated hepatic inflammation may partially, in turn, contribute to the lipid-lowering effect of RYR.

CONCLUSIONS

The modulation of NF-κB/NLRP3 inflammasome and lipid synthesis may contribute to the ameliorative effects of RYR against HFD-induced NAFLD.

Thioredoxin interacting protein, a key molecular switch between oxidative stress and sterile inflammation in cellular response

Tissue and systemic inflammation have been the main culprit behind the cellular response to multiple insults and maintaining homeostasis. Obesity is an independent disease state that has been reported as a common risk factor for multiple metabolic and microvascular diseases including nonalcoholic fatty liver disease (NAFLD), retinopathy, critical limb ischemia, and impaired angiogenesis. Sterile inflammation driven by high-fat diet, increased formation of reactive oxygen species, alteration of intracellular calcium level and associated release of inflammatory mediators, are the main common underlying forces in the pathophysiology of NAFLD, ischemic retinopathy, stroke, and aging brain. This work aims to examine the contribution of the pro-oxidative and pro-inflammatory thioredoxin interacting protein (TXNIP) to the expression and activation of NLRP3-inflammasome resulting in initiation or exacerbation of sterile inflammation in these disease states. Finally, the potential for TXNIP as a therapeutic target and whether TXNIP expression can be modulated using natural antioxidants or repurposing other drugs will be discussed.

MCC950 Ameliorates Acute Liver Injury Through Modulating Macrophage Polarization and Myeloid-Derived Suppressor Cells Function

Acute liver injury (ALI) raises high mortality rates due to a rapid pathological process. MCC950, a highly selective nod-like receptor family pyrin domain containing 3 (NLRP3) inhibitor, has already been reported to show strong hepatoprotective effects in many different liver diseases. In this study, we unveiled the role of MCC950 in carbon tetrachloride (CCl₄)-induced ALI and its underlying molecular mechanisms on days 1, 2, and 3. MCC950 could significantly inhibit liver injury, evidenced by decreased serum alamine aminotransferase (ALT) and aspartate aminotransferase (AST) levels on days 1 and 2, increased Albumin (ALB) level on day 3, and decreased histological score during the whole period. Moreover, lower M1 macrophage related to pro-inflammatory genes expression was observed in MCC950-treated ALI mice on day 1, while MCC950 pretreatment also polarized macrophage to M2 phenotype indicating anti-inflammatory response on days 2 and 3. Additionally, MDSC was significantly increased in blood, liver, and spleen in ALI mice at different time courses. Specifically, upregulated myeloid-derived suppressor cell (MDSC) proportions were found in blood and spleen on days 1 and 2, but showed decreased trend on day 3. However, liver MDSC numbers were increased on days 2 and 3, but no significance on day 1. In conclusion, MCC950 pretreatment alleviates CCl₄-induced ALI through enhanced M2 macrophage and MDSC function at different time points of ALI. Further understanding of MCC950 in ALI may be a new potential therapeutic strategy.

Sub-chronic exposure to realgar induces liver injury via upregulating the TXNIP/NLRP3 pathway and disturbing bile acid homeostasis in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Realgar is a traditional Chinese medicine used in China for a long history. Long-time or excessive use of realgar causes liver injury. However, its underlying mechanism is not fully clarified.

AIM OF THE STUDY

In this study, we investigated the toxic effect of sub-chronic exposure to realgar on mice liver, and further revealed its underlying mechanism focused on the TXNIP/NLRP3 pathway and bile acid homeostasis.

MATERIAL AND METHODS

Mice were divided into control and different doses of sub-chronic realgar exposed groups. Total arsenic levels in the blood and liver were determined by atomic fluorescence spectrometry. The effect of realgar on liver function was evaluated by biochemical analysis and histopathological examination. Assay kits were applied for the measurement of oxidative stress indexes, MPO and plasma inflammatory cytokines. The mRNA and proteins involved in the TXNIP/NLRP3 and NF-κB pathways were determined by RT-qPCR, western blot, Immunofluorescence and Immunohistochemistry. UHPLC/MS/MS was used for the quantitative analysis of bile acids (BAs) in mice plasma, liver and urine. The genes related to BAs metabolism were measured by RT-qPCR.

RESULTS

Sub-chronic exposure to realgar led to arsenic accumulation and caused oxidative damage and inflammatory infiltration in mouse liver, finally resulting in liver injury. Realgar treatment activated the NF-κB pathway and significantly upregulated the TXNIP/NLRP3 pathway in mouse liver. Realgar altered the metabolic balance of BAs, which is related to the abnormal expression of BAs transporters and enzymes.

CONCLUSION

Sub-chronic exposure to realgar caused liver injury in mouse, and the mechanism may involve the upregulation of the TXNIP/NLRP3 pathway and disordered BAs homeostasis.

AICAR, an AMP-Activated Protein Kinase Activator, Ameliorates Acute Pancreatitis-Associated Liver Injury Partially Through Nrf2-Mediated Antioxidant Effects and Inhibition of NLRP3 Inflammasome Activation

Acute pancreatitis (AP) is a highly fatal acute inflammation and is often accompanied by multiple organ dysfunction syndrome (MODS). The liver, one of the most vulnerable extrapancreatic organs in AP, is the major organ involved in the evolution of the disease and correlates strongly with the occurrence of MODS. However, the etiology of pancreatitis-associated liver injury (PALI) has not been clarified and currently lacks an effective treatment. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) is a cell permeable nucleoside with pleiotropic effects on anti-inflammatory and antioxidant stress that binds with adenosine monophosphate protein kinase (AMPK) and induces AMPK activation. However, the role of AICAR in PALI remains elusive. Here, we show that activation of AMPK by AICAR, a direct AMPK agonist, significantly ameliorates sodium taurocholate-induced PALI in rats, whereas treatment of PALI rats with the AMPK antagonist Compound C profoundly exacerbates the degree of liver injury, suggesting that hepatic AMPK activation exerts an essential protective role in PALI. Mechanistically, AICAR induces AMPK activation, which in turn activates nuclear factor erythroid 2-related factor 2(Nrf2) -regulated hepatic antioxidant capacity and inhibits NLRP3 inflammasome-mediated pyrolysis, protecting rats from sodium taurocholate-induced PALI. In addition, Nrf2 deficiency strikingly weakens the beneficial effects of AICAR on alleviation of liver injury, oxidative stress and NLRP3 inflammasome activation in L-arginine-induced PALI mice. Thus, AICAR protects against PALI in rodents by triggering AMPK, which is mediated at least in part by Nrf2-modulated antioxidant effects and NLRP3 inflammasome activation.

Inflammasomes and Fibrosis

Fibrosis is the final common pathway of inflammatory diseases in various organs. The inflammasomes play an important role in the progression of fibrosis as innate immune receptors. There are four main members of the inflammasomes, such as NOD-like receptor protein 1 (NLRP1), NOD-like receptor protein 3 (NLRP3), NOD-like receptor C4 (NLRC4), and absent in melanoma 2 (AIM2), among which NLRP3 inflammasome is the most studied. NLRP3 inflammasome is typically composed of NLRP3, ASC and pro-caspase-1. The activation of inflammasome involves both "classical" and "non-classical" pathways and the former pathway is better understood. The "classical" activation pathway of inflammasome is that the backbone protein is activated by endogenous/exogenous stimulation, leading to inflammasome assembly. After the formation of "classic" inflammasome, pro-caspase-1 could self-activate. Caspase-1 cleaves cytokine precursors into mature cytokines, which are secreted extracellularly. At present, the "non-classical" activation pathway of inflammasome has not formed a unified model for activation process. This article reviews the role of NLRP1, NLRP3, NLRC4, AIM2 inflammasome, Caspase-1, IL-1β, IL-18 and IL-33 in the fibrogenesis.

NLRP3 Inflammasome: A Promising Therapeutic Target for Drug-Induced Toxicity

Drug-induced toxicity, which impairs human organ function, is a serious problem during drug development that hinders the clinical use of many marketed drugs, and the underlying mechanisms are complicated. As a sensor of infections and external stimuli, nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome plays a key role in the pathological process of various diseases. In this review, we specifically focused on the role of NLRP3 inflammasome in drug-induced diverse organ toxicities, especially the hepatotoxicity, nephrotoxicity, and cardiotoxicity. NLRP3 inflammasome is involved in the initiation and deterioration of drug-induced toxicity through multiple signaling pathways. Therapeutic strategies via inhibiting NLRP3 inflammasome for drug-induced toxicity have made significant progress, especially in the protective effects of the phytochemicals. Growing evidence collected in this review indicates that NLRP3 is a promising therapeutic target for drug-induced toxicity.