NLRP3 inflammasome in hepatic diseases: A pharmacological target

Naringenin attenuates early hepatocarcinogenesis induced by a MASH model

INTRODUCTION AND OBJECTIVES

Nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome plays a critical role in the progression of metabolic dysfunction-associated steatohepatitis (MASH). Here, we investigated the effects of naringenin (NAR) on early hepatocellular carcinoma (HCC) experimentally induced in a rat MASH model and whether the NLRP3 inflammasome/pyroptosis pathway was involved.

MATERIALS AND METHODS

The animals were fed a hepatopathogenic diet for 16 weeks and carbon tetrachloride (400 mg/kg, i.p.) and diethylnitrosamine (40 mg/kg, i.p.) were injected once a week. NAR was administered at 100 mg/kg p.o. The effects of NAR on the MASHHCC protocol were evaluated using biochemical, histological, in silico, and molecular biological approaches.

RESULTS

NAR significantly mitigated liver damage, as evidenced by the reduction in liver damage markers. It also reduced steatosis and inflammation, as determined by decreased lipid accumulation and sterol regulatory element-binding protein 1C, interleukins 1-beta and 18, and nuclear factor kappa B levels, and also increased peroxisome proliferator-activated receptor gamma levels. NAR inhibits the formation of NLRP3, including the recruitment of caspase-1 and gasdermin D proteins, and reduces the levels of transforming growth factor-beta, alpha-smooth muscle actin, and hepatic collagen 1, thereby diminishing extracellular matrix synthesis. Furthermore, gamma-glutamyl transpeptidase activity, glutathione S-transferase pi 1, and the proliferation marker KI67 were considerably reduced.

CONCLUSIONS

Our findings show that NAR has the potential to inhibit early HCC induced in the context of MASH, thereby suggesting that NAR could be used for MASH treatment in humans.

Dapansutrile Regulates Mitochondrial Oxidative Stress and Reduces Hepatic Lipid Accumulation in Diabetic Mice

(1) Background: Hepatic lipid accumulation is the initial factor in metabolic-associated fatty liver disease (MAFLD) in type 2 diabetics, leading to accelerated liver damage. The NOD-like receptor protein 3 (NLRP3) inflammasome plays a critical role in this process. Dapansutrile (DAPA) is a novel NLRP3 inflammasome inhibitor; however, its effect on ectopic lipid accumulation in the liver remains unclear. This study aimed to investigate the therapeutic effect of DAPA on hepatic lipid accumulation in a diabetic mouse model and its potential mechanisms. (2) Methods: The effects of DAPA on hepatic ectopic lipid deposition and liver function under metabolic stress were evaluated in vivo using db/db and high-fat diet (HFD) + streptozotocin (STZ) mouse models. Additionally, the role and mechanism of DAPA in cellular lipid deposition, mitochondrial oxidative stress, and inflammation were assessed in HepG2 cells treated with free fatty acids (FFA) and DAPA. (3) Results: Our findings indicated that DAPA treatment improved glucose and lipid metabolism in diabetic mice, particularly addressing liver heterotopic lipid deposition and insulin resistance. DAPA treatment also ameliorated lipid accumulation and mitochondrial-related functions and inflammation in HepG2 cells through the NLRP3-Caspase-1 signaling axis. (4) Conclusions: Targeting NLRP3 with DAPA may represent a novel therapeutic approach for diabetes-related fatty liver diseases.

Molecular mechanisms in liver repair and regeneration: from physiology to therapeutics

Liver repair and regeneration are crucial physiological responses to hepatic injury and are orchestrated through intricate cellular and molecular networks. This review systematically delineates advancements in the field, emphasizing the essential roles played by diverse liver cell types. Their coordinated actions, supported by complex crosstalk within the liver microenvironment, are pivotal to enhancing regenerative outcomes. Recent molecular investigations have elucidated key signaling pathways involved in liver injury and regeneration. Viewed through the lens of metabolic reprogramming, these pathways highlight how shifts in glucose, lipid, and amino acid metabolism support the cellular functions essential for liver repair and regeneration. An analysis of regenerative variability across pathological states reveals how disease conditions influence these dynamics, guiding the development of novel therapeutic strategies and advanced techniques to enhance liver repair and regeneration. Bridging laboratory findings with practical applications, recent clinical trials highlight the potential of optimizing liver regeneration strategies. These trials offer valuable insights into the effectiveness of novel therapies and underscore significant progress in translational research. In conclusion, this review intricately links molecular insights to therapeutic frontiers, systematically charting the trajectory from fundamental physiological mechanisms to innovative clinical applications in liver repair and regeneration.

Nintedanib attenuates NLRP3 inflammasome-driven liver fibrosis by targeting Src signaling

Liver injury induces an inflammatory response that activates hepatic stellate cells, which is the initial factor of liver fibrosis. Nintedanib, a multi-targeted tyrosine kinase inhibitor targeting the Src signalling pathway, has been approved for the treatment of idiopathic pulmonary fibrosis. However, it is still not known whether nintedanib ameliorates liver fibrosis by inhibiting inflammasome activation. Here, a carbon tetrachloride (CCl4)-induced liver fibrosis model was used to assess the anti-fibrotic efficacy of nintedanib in vivo. Lipopolysaccharide and ATP were used to activate nucleotide oligomerisation domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasomes in LX-2 cells, and the efficacy of nintedanib on NLRP3 inflammasome activation was evaluated. Moreover, we used Src-overexpressing and Src-downregulating lentiviruses to transfect LX-2 cells to explore the targets of nintedanib. Nintedanib attenuated inflammation and extracellular matrix accumulation in CCl4-induced fibrotic livers and reduced the expression of NLRP3, fibrotic makers, and the phosphorylation of Src, epidermal growth factor receptor (EGFR), AKT, ERK1/2 in LX-2 cells. Furthermore, nintedanib thwarted NLRP3 inflammasome activation by suppressing the phosphorylation of Src and its downstream signalling pathway and reducing reactive oxygen species production. Our study indicates that nintedanib effectively suppresses NLRP3 inflammasome activation and has the potential for the treatment of liver fibrosis.

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.

The role of inflammasomes in hepatocellular carcinoma: Mechanisms and therapeutic insights

Hepatocellular carcinoma is among the most frequent forms of primary liver cancer and develops within a context of chronic inflammation, frequently associated with a multitude of risk factors, including viral infections, metabolic dysfunction-associated fatty liver disease, metabolic dysfunction-associated steatohepatitis and liver fibrosis. The tumor microenvironment is crucial for the progression of HCC, as immune cells, tumor-associated fibroblasts and hepatic stellate cells interact to promote chronic inflammation and tumor spread. Inflammasomes, the multiprotein complexes that launch the innate immune response, emerge as important mediators in the pathogenesis of HCC. Among others, the inflammasome Nucleotide-binding oligomerization domain, Leucine rich Repeat (NLR) and Pyrin (NLRP) 3 (NLRP3), and absent in melanoma 2 (AIM2), exhibit a dual role in HCC background. It has been reported that they can exert oncosuppressive functions by triggering the inflammatory death of cancer cells. Vice versa, chronic activation contributes to the development of a pro-tumorigenic environment, thus supporting tumor growth. In addition, other inflammasomes such as Nucleotide-binding oligomerization domain, Leucine rich Repeat (NLR) and Pyrin (NLRP) 6 and 12 (NLRP6 and NLRP12, respectively) regulate HCC onset and progression, although more experimental evidence is required. This review focuses on the molecular mechanisms underpinning the inflammasome's contribution to the onset, progression and spread of HCC. Moreover, we will explore the potential therapeutic approaches currently under investigation, which aim to improve the efficacy and reduce the side effects of the treatments currently available. Targeting inflammasomes may be a promising therapeutic strategy for the treatment of HCC, offering new opportunities to improve patient prognosis.

Cholesterol crystals in the pathogenesis of atherosclerosis

The presence of cholesterol crystals (CCs) in tissues was first described more than 100 years ago. CCs have a pathogenic role in various cardiovascular diseases, including myocardial infarction, aortic aneurysm and, most prominently, atherosclerosis. Although the underlying mechanisms and signalling pathways involved in CC formation are incompletely understood, numerous studies have highlighted the existence of CCs at various stages of atheroma progression. In this Review, we summarize the mechanisms underlying CC formation and the role of CCs in cardiovascular disease. In particular, we explore the established links between lipid metabolism across various cell types and the formation of CCs, with a focus on CC occurrence in the vasculature. We also discuss CC-induced inflammation as one of the pathogenic features of CCs in the atheroma. Finally, we summarize the therapeutic strategies aimed at reducing CC-mediated atherosclerotic burden, including approaches to inhibit CC formation in the vasculature or to mitigate the inflammatory response triggered by CCs. Addressing CC formation might emerge as a crucial component in our broader efforts to combat cardiovascular disease.

Inflammation unleashed: The role of pyroptosis in chronic liver diseases

Pyroptosis, a newly identified form of programmed cell death intertwined with inflammatory responses, is facilitated by the Gasdermin family's pore-forming activity, leading to cell lysis and the release of pro-inflammatory cytokines. This process is a double-edged sword in innate immunity, offering protection against pathogens while risking excessive inflammation and tissue damage when dysregulated. Specifically, pyroptosis operates through two distinct signaling pathways, namely the Caspase-1 pathway and the Caspase-4/5/11 pathway. In the context of chronic liver diseases like fibrosis and cirrhosis, inflammation emerges as a central contributing factor to their pathogenesis. The identification of inflammation is characterized by the activation of innate immune cells and the secretion of pro-inflammatory cytokines such as IL-1α, IL-1β, and TNF-α. This review explores the interrelationship between pyroptosis and the inflammasome, a protein complex located in liver cells that recognizes danger signals and initiates Caspase-1 activation, resulting in the secretion of IL-1β and IL-18. The article delves into the influence of the inflammasome and pyroptosis on various liver disorders, with a specific focus on their molecular and pathophysiological mechanisms. Additionally, the potential therapeutic implications of targeting pyroptosis for liver diseases are highlighted for future consideration.

Gut microbiota-NLRP3 inflammasome crosstalk in metabolic dysfunction-associated steatotic liver disease

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease associated with metabolic dysfunction, ranging from hepatic steatosis with or without mild inflammation to nonalcoholic steatohepatitis, which can rapidly progress to liver fibrosis and even liver cancer. In 2023, after several rounds of Delphi surveys, a new consensus recommended renaming NAFLD as metabolic dysfunction-associated steatotic liver disease (MASLD). Ninety-nine percent of NAFLD patients meet the new MASLD criteria related to metabolic cardiovascular risk factors under the "multiple parallel hits" of lipotoxicity, insulin resistance (IR), a proinflammatory diet, and an intestinal microbiota disorder, and previous research on NAFLD remains valid. The NLRP3 inflammasome, a well-known member of the pattern recognition receptor (PRR) family, can be activated by danger signals transmitted by pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), as well as cytokines involved in immune and inflammatory responses. The activation of the NLRP3 inflammasome pathway by MASLD triggers the production of the inflammatory cytokines IL-1β and IL-18. In MASLD, while changes in the composition and metabolites of the intestinal microbiota occur, the disrupted intestinal microbiota can also generate the inflammatory cytokines IL-1β and IL-18 by damaging the intestinal barrier, negatively regulating the liver on the gut-liver axis, and further aggravating MASLD. Therefore, modulating the gut-microbiota-liver axis through the NLRP3 inflammasome may emerge as a novel therapeutic approach for MASLD patients. In this article, we review the evidence regarding the functions of the NLRP3 inflammasome and the intestinal microbiota in MASLD, as well as their interactions in this disease.

Recent advances in the treatment of gout with NLRP3 inflammasome inhibitors

Gout is an autoinflammatory disorder characterized by the accumulation of monosodium urate crystals in joints and other tissues, representing the predominant type of inflammatory arthritis with a notable prevalence and propensity for severe outcomes. The NLRP3 inflammasome, a member of the pyrin domain-containing NOD-like receptor family, exerts a substantial impact on both innate and adaptive immune responses and serves as a pivotal factor in the pathogenesis of gout. In recent years, there has been significant academic and industrial interest in the development of NLRP3-targeted small molecule inhibitors as a promising therapeutic approach for gout. To assess the advancements in NLRP3 inflammasome inhibitors for gout treatment, this review offers a comprehensive analysis and evaluation of current clinical candidates and other inhibitors targeting NLRP3 inflammasome from a chemical structure standpoint, with the goal of identifying more efficacious options for clinical management of gout.

Tanshinone IIA Inhibits the Endoplasmic Reticulum Stress-Induced Unfolded Protein Response by Activating the PPARα/FGF21 Axis to Ameliorate Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a critical stage in the progression of nonalcoholic fatty liver disease (NAFLD). Tanshinone IIA (TIIA) is a tanshinone extracted from Salvia miltiorrhiza; due to its powerful anti-inflammatory and antioxidant biological activities, it is commonly used for treating cardiovascular and hepatic diseases. A NASH model was established by feeding mice a methionine and choline-deficient (MCD) diet. Liver surface microblood flow scanning, biochemical examination, histopathological examination, cytokine analysis through ELISA, lipidomic analysis, transcriptomic analysis, and Western blot analysis were used to evaluate the therapeutic effect and mechanism of TIIA on NASH. The results showed that TIIA effectively reduced lipid accumulation, fibrosis, and inflammation and alleviated endoplasmic reticulum (ER) stress. Lipidomic analysis revealed that TIIA normalized liver phospholipid metabolism in NASH mice. A KEGG analysis of the transcriptome revealed that TIIA exerted its effect by regulating the PPAR signalling pathway, protein processing in the ER, and the NOD-like receptor signalling pathway. These results suggest that TIIA alleviates NASH by activating the PPARα/FGF21 axis to negatively regulate the ER stress-induced unfolded protein response (UPR).

New Biomarkers in Liver Fibrosis: A Pass through the Quicksand?

Chronic liver diseases (CLD) stem from various causes and lead to a gradual progression that ultimately may result in fibrosis and eventually cirrhosis. This process is typically prolonged and asymptomatic, characterized by the complex interplay among various cell types, signaling pathways, extracellular matrix components, and immune responses. With the prevalence of CLD increasing, diagnoses are often delayed, which leads to poor prognoses and in some cases, the need for liver transplants. Consequently, there is an urgent need for the development of novel, non-invasive methods for the diagnosis and monitoring of CLD. In this context, serum biomarkers-safer, repeatable, and more acceptable alternatives to tissue biopsies-are attracting significant research interest, although their clinical implementation is not yet widespread. This review summarizes the latest advancements in serum biomarkers for detecting hepatic fibrogenesis and advocates for concerted efforts to consolidate current knowledge, thereby providing patients with early, effective, and accessible diagnoses that facilitate personalized therapeutic strategies.

The role and mechanism of pyroptosis and potential therapeutic targets in non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a clinical pathological syndrome characterized by the excessive accumulation of fat within liver cells, which can progress to end-stage liver disease in severe cases, posing a threat to life. Pyroptosis is a distinct, pro-inflammatory form of cell death, differing from traditional apoptosis. In recent years, there has been growing research interest in the association between pyroptosis and NAFLD, encompassing the mechanisms and functions of pyroptosis in the progression of NAFLD, as well as potential therapeutic targets. Controlled pyroptosis can activate immune cells, eliciting host immune responses to shield the body from harm. However, undue activation of pyroptosis may worsen inflammatory responses, induce cellular or tissue damage, disrupt immune responses, and potentially impact liver function. This review elucidates the involvement of pyroptosis and key molecular players, including NOD-like receptor thermal protein domain associated protein 3(NLRP3) inflammasome, gasdermin D (GSDMD), and the caspase family, in the pathogenesis and progression of NAFLD. It emphasizes the promising prospects of targeting pyroptosis as a therapeutic approach for NAFLD and offers valuable insights into future directions in the field of NAFLD treatment.

Mairin from Huangqi Decoction Mitigates Liver Cirrhosis through Suppression of Pro-inflammatory Signaling Pathways: A Network Pharmacology and Experimental Study

Background::

Liver cirrhosis is a consequence of various chronic liver conditions and may lead to liver failure and cancer. Huangqi Decoction (HQD) is a Traditional Chinese Medicine (TCM) effective for treating liver conditions, including cirrhosis. Therefore, both the active ingredients and the pharmacological actions of HQD deserve further exploration. The active components and pharmacological actions of HQD in preventing and treating liver cirrhosis were investigated using network pharmacology. The actions of the principal active ingredient, Mairin, were investigated empirically.

Methods::

Using network pharmacology, the critical components of HQD were identified from multiple databases, and UPLC screening and targets were investigated using Swiss Target Prediction. Targets associated with liver cirrhosis were identified using the GeneCards database. GO and KEGG enrichment analysis of targets that overlapped between HQD and cirrhosis were analyzed in DAVID, and a “component-target-pathway” network for HQD was created in Cytoscape 3.7.2. The biological functions of the key active component, Mairin, were investigated using in silico docking, cell experiments, and evaluation in a carbon-tetrachloride (CCl4)-induced mouse model of liver cirrhosis. CCK-8 and F-actin assays were used to measure cell viability and hepatic stellate cell (HSC) activation, respectively; fibrosis was measured by histological and immunohistochemical evaluations, and the levels of the cirrhosis-related protein α-SMA and predicted essential target proteins in the PI3KAKT, NFκB-IκBα, and NLRP3-IL18 pathways were determined by western blotting.

Results::

Fourteen active HQD components, 72 targets, and 10 pathways common to HQD and cirrhosis were identified. Network analysis indicated the association of Mairin with most targets and with inflammation through the PI3K/Akt, NF-κB, and NLRP3 pathways. Dose-dependent reductions in the activation and proliferation of LX-2 cells after Mairin treatment were observed. Mairin reversed the histopathological changes in the livers of cirrhosis model mice. Mairin also significantly reduced the α-SMA, NF-κB, IκBα, NLRP3, and IL-18 protein levels while increasing those of p- PI3K and p-Akt, suggesting that Mairin mitigates liver cirrhosis through modulation of the PI3KAKT, NFκB-IκBα, and NLRP3-IL18 pathways.

Conclusions::

Using a comprehensive investigative process involving network pharmacology, bioinformatics, and experimental verification, it was found that Mairin, an active component of HQD, may be useful for developing specific treatments for preventing and treating liver cirrhosis.

Biological Functions and Potential Therapeutic Significance of O-GlcNAcylation in Hepatic Cellular Stress and Liver Diseases

O-linked-β-D-N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation), which is dynamically regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), is a post-translational modification involved in multiple cellular processes. O-GlcNAcylation of proteins can regulate their biological functions via crosstalk with other post-translational modifications, such as phosphorylation, ubiquitination, acetylation, and methylation. Liver diseases are a major cause of death worldwide; yet, key pathological features of the disease, such as inflammation, fibrosis, steatosis, and tumorigenesis, are not fully understood. The dysregulation of O-GlcNAcylation has been shown to be involved in some severe hepatic cellular stress, viral hepatitis, liver fibrosis, nonalcoholic fatty acid liver disease (NAFLD), malignant progression, and drug resistance of hepatocellular carcinoma (HCC) through multiple molecular signaling pathways. Here, we summarize the emerging link between O-GlcNAcylation and hepatic pathological processes and provide information about the development of therapeutic strategies for liver diseases.

An overview of the cholesterol metabolism and its proinflammatory role in the development of MASLD

Cholesterol is an essential lipid molecule in mammalian cells. It is not only involved in the formation of cell membranes but also serves as a raw material for the synthesis of bile acids, vitamin D, and steroid hormones. Additionally, it acts as a covalent modifier of proteins and plays a crucial role in numerous life processes. Generally, the metabolic processes of cholesterol absorption, synthesis, conversion, and efflux are strictly regulated. Excessive accumulation of cholesterol in the body is a risk factor for metabolic diseases such as cardiovascular disease, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). In this review, we first provide an overview of the discovery of cholesterol and the fundamental process of cholesterol metabolism. We then summarize the relationship between dietary cholesterol intake and the risk of developing MASLD, and also the animal models of MASLD specifically established with a cholesterol-containing diet. In the end, the role of cholesterol-induced inflammation in the initiation and development of MASLD is discussed.