Inflammasome: A Double-Edged Sword in Liver Diseases

Ginsenoside Rg1 attenuates lipopolysaccharide-induced chronic liver damage by activating Nrf2 signaling and inhibiting inflammasomes in hepatic cells

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng (Panax ginseng C. A. Meyer) is a precious traditional Chinese medicine with multiple pharmacological effects. Ginsenoside Rg1 is a main active ingredient extracted from ginseng, which is known for its age-delaying and antioxidant effects. Increasing evidence indicates that Rg1 exhibits anti-inflammatory properties in numerous diseases and may ameliorate oxidative damage and inflammation in many chronic liver diseases.

AIM OF THE STUDY

Chronic inflammatory injury in liver cells is an important pathological basis of many liver diseases. However, its mechanism remains unclear and therapeutic strategies to prevent its development need to be further explored. Thus, our study is to delve the protective effect and mechanism of Rg1 against chronic hepatic inflammatory injuries induced by lipopolysaccharide (LPS).

MATERIALS AND METHODS

The chronic liver damage model in mice was build up by injecting intraperitoneally with LPS (200 μg/kg) for 21 days. Serum liver function indicators and levels of IL-1β, IL-6 and TNF-α were examined by using corresponding Kits. Hematoxylin and Eosin (H&E), Periodic acid-Schiff (PAS), and Masson stains were utilized to visualize hepatic histopathological damage, glycogen deposition, and liver fibrosis. The nuclear import of p-Nrf2 and the generation of Col4 in the liver were detected by IF, while IHC was employed to detect the expressions of NLRP3 and AIM2 in the hepatic. The Western blot and q-PCR were used to survey the expressions of proteins and mRNAs of fibrosis and apoptosis, and the expressions of Keap1, p-Nrf2 and NLRP3, NLRP1, AIM2 inflammasome-related proteins in mouse liver. The cell viability of human hepatocellular carcinoma cells (HepG2) was detected by Cell Counting Kit-8 to select the action concentration of LPS, and intracellular ROS generation was detected using a kit. The expressions of Nuclear Nrf2, HO-1, NQO1 and NLRP3, NLRP1, and AIM2 inflammasome-related proteins in HepG2 cells were detected by Western blot. Finally, the feasibility of the molecular interlinking between Rg1 and Nrf2 was demonstrated by molecular docking.

RESULTS

Rg1 treatment for 21 days decreased the levels of ALT, AST, and inflammatory factors of serum IL-1β, IL-6 and TNF-α in mice induced by LPS. Pathological results indicated that Rg1 treatment obviously alleviated hepatocellular injury and apoptosis, inflammatory cell infiltration and liver fibrosis in LPS stimulated mice. Rg1 promoted Keap1 degradation and enhanced the expressions of p-Nrf2, HO-1 and decreased the levels of NLRP1, NLRP3, AIM2, cleaved caspase-1, IL-1β and IL-6 in livers caused by LPS. Furthermore, Rg1 effectively suppressed the rise of ROS in HepG2 cells induced by LPS, whereas inhibition of Nrf2 reversed the role of Rg1 in reducing the production of ROS and NLRP3, NLRP1, and AIM2 expressions in LPS-stimulated HepG2 cells. Finally, the molecular docking illustrated that Rg1 exhibits a strong affinity towards Nrf2.

CONCLUSION

The findings indicate that Rg1 significantly ameliorates chronic liver damage and fibrosis induced by LPS. The mechanism may be mediated through promoting the dissociation of Nrf2 from Keap1 and then activating Nrf2 signaling and further inhibiting NLRP3, NLRP1, and AIM2 inflammasomes in liver cells.

Inherently Reduced Expression of ASC Restricts Caspase-1 Processing in Hepatocytes and Promotes Plasmodium Infection

Inflammasome-mediated caspase-1 activation facilitates innate immune control of Plasmodium in the liver, thereby limiting the incidence and severity of clinical malaria. However, caspase-1 processing occurs incompletely in both mouse and human hepatocytes and precludes the generation of mature IL-1β or IL-18, unlike in other cells. Why this is so or how it impacts Plasmodium control in the liver has remained unknown. We show that an inherently reduced expression of the inflammasome adaptor molecule apoptosis-associated specklike protein containing CARD (ASC) is responsible for the incomplete proteolytic processing of caspase-1 in murine hepatocytes. Transgenically enhancing ASC expression in hepatocytes enabled complete caspase-1 processing, enhanced pyroptotic cell death, maturation of the proinflammatory cytokines IL-1β and IL-18 that was otherwise absent, and better overall control of Plasmodium infection in the liver of mice. This, however, impeded the protection offered by live attenuated antimalarial vaccination. Tempering ASC expression in mouse macrophages, on the other hand, resulted in incomplete processing of caspase-1. Our work shows how caspase-1 activation and function in host cells are fundamentally defined by ASC expression and offers a potential new pathway to create better disease and vaccination outcomes by modifying the latter.

Molecular Foundations of Inflammatory Diseases: Insights into Inflammation and Inflammasomes

Inflammatory diseases are a global health problem affecting millions of people with a wide range of conditions. These diseases, including inflammatory bowel disease (IBD), rheumatoid arthritis (RA), osteoarthritis (OA), gout, and diabetes, impose a significant burden on patients and healthcare systems. A complicated interaction between genetic variables, environmental stimuli, and dysregulated immune responses shows the complex biological foundation of various diseases. This review focuses on the molecular mechanisms underlying inflammatory diseases, including the function of inflammasomes and inflammation. We investigate the impact of environmental and genetic factors on the progression of inflammatory diseases, explore the connection between inflammation and inflammasome activation, and examine the incidence of various inflammatory diseases in relation to inflammasomes.

NLRP3 Inflammasome Involvement in Heart, Liver, and Lung Diseases-A Lesson from Cytokine Storm Syndrome

Inflammation and inflammasomes have been proposed as important regulators of the host-microorganism interaction, playing a key role in morbidity and mortality due to the coronavirus disease 2019 (COVID-19) in subjects with chronic conditions and compromised immune system. The inflammasome consists of a multiprotein complex that finely regulates the activation of caspase-1 and the production and secretion of potent pro-inflammatory cytokines such as IL-1β and IL-18. The pyrin containing NOD (nucleotide-binding oligomerization domain) like receptor (NLRP) is a family of intracellular receptors, sensing patterns associated to pathogens or danger signals and NLRP3 inflammasome is the most deeply analyzed for its involvement in the innate and adaptive immune system as well as its contribution to several autoinflammatory and autoimmune diseases. It is highly expressed in leukocytes and up-regulated in sentinel cells upon inflammatory stimuli. NLRP3 expression has also been reported in B and T lymphocytes, in epithelial cells of oral and genital mucosa, in specific parenchymal cells as cardiomyocytes, and keratinocytes, and chondrocytes. It is well known that a dysregulated activation of the inflammasome is involved in the pathogenesis of different disorders that share the common red line of inflammation in their pathogenetic fingerprint. Here, we review the potential roles of the NLRP3 inflammasome in cardiovascular events, liver damage, pulmonary diseases, and in that wide range of systemic inflammatory syndromes named as a cytokine storm.

Drug induced liver injury - a 2023 update

Drug-Induced Liver Injury (DILI) constitutes hepatic damage attributed to drug exposure. DILI may be categorized as hepatocellular, cholestatic or mixed and might also involve immune responses. When DILI occurs in dose-dependent manner, it is referred to as intrinsic, while if the injury occurs spontaneously, it is termed as idiosyncratic. This review predominately focused on idiosyncratic liver injury. The established molecular mechanisms for DILI include (1) mitochondria dysfunction, (2) increased reactive oxygen species levels, (3) presence of elevated apoptosis and necrosis, (4) and bile duct injuries associated with immune mediated pathways. However, it should be emphasized that the underlying mechanisms responsible for DILI are still unknown. Prevention strategies are critical as incidences occur frequently, and treatment options are limited once the injury has developed. The aim of this review was to utilize retrospective cohort studies from across the globe to gain insight into epidemiological patterns. This review considers (1) what is currently known regarding the mechanisms underlying DILI, (2) discusses potential risk factors and (3) implications of the coronavirus pandemic on DILI presentation and research. Future perspectives are also considered and discussed and include potential new biomarkers, causality assessment and reporting methods.

Role of inflammasomes and cytokines in immune dysfunction of liver cirrhosis

Liver cirrhosis develops as a result of persistent inflammation and liver injury. The prolonged inflammation triggers the buildup of fibrous tissue and regenerative nodules within the liver, leading to the distortion of the hepatic vascular structure and impaired liver function. Cirrhosis disrupts the ability of liver function to maintain homeostasis and hepatic immunosurveillance which causes immunological dysfunction in the body. In pathological conditions, the production of cytokines in the liver is carefully regulated by various cells in response to tissue stimulation. Cytokines and inflammasomes are the key regulators and systematically contribute to the development of cirrhosis which involves an inflammatory response. However, the crosstalk role of different cytokines in the cirrhosis progression is poorly understood. Tumour necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6), and interferon-gamma (IFN-γ), among others, are proinflammatory cytokines that contribute to liver cell necrosis, which in turn causes the development of fibrosis. While IL-10 exhibits a potent anti-inflammatory effect on the liver by inhibiting immune cell activation and neutralizing pro-inflammatory cytokine activity. Inflammasomes have also been implicated in the profibrotic processes of liver cirrhosis, as well as the production of chemokines such as CCL2/MCP-1. It is evident that inflammasomes have a role in the proinflammatory response seen in chronic liver illnesses. In conclusion, cirrhosis significantly impacts the immune system, leading to immunological dysfunction and alterations in both innate and acquired immunity. Proinflammatory cytokines like TNF-α, IL-1β, IL-6, and IFNγ are upregulated in cirrhosis, contributing to liver cell necrosis and fibrosis development. Managing cytokine-mediated inflammation and fibrosis is a key therapeutic approach to alleviate portal hypertension and its associated liver complications. This review attempted to focus largely on the role of immune dysfunction mediated by different cytokines and inflammasomes involved in the progression, regulation and development of liver cirrhosis.

Ambiguous Pathogenic Roles of Macrophages in Alcohol-Associated Liver Diseases

Alcohol-associated liver disease (ALD) represents a major public health issue worldwide and is a leading etiology of liver cirrhosis. Alcohol-related liver injuries include a range of manifestations including alcoholic hepatitis (AH), simple steatosis, steatohepatitis, hepatic fibrosis, cirrhosis and liver cancer. Liver disease occurs from several pathological disturbances such as the metabolism of ethanol, which generates reactive oxygen species (ROS) in hepatocytes, alterations in the gut microbiota, and the immune response to these changes. A common hallmark of these liver affections is the establishment of an inflammatory environment, and some (broad) anti-inflammatory approaches are used to treat AH (eg, corticosteroids). Macrophages, which represent the main innate immune cells in the liver, respond to a wide variety of (pathogenic) stimuli and adopt a large spectrum of phenotypes. This translates to a diversity of functions including pathogen and debris clearance, recruitment of other immune cells, activation of fibroblasts, or tissue repair. Thus, macrophage populations play a crucial role in the course of ALD, but the underlying mechanisms driving macrophage polarization and their functionality in ALD are complex. In this review, we explore the various populations of hepatic macrophages in alcohol-associated liver disease and the underlying mechanisms driving their polarization. Additionally, we summarize the crosstalk between hepatic macrophages and other hepatic cell types in ALD, in order to support the exploration of targeted therapeutics by modulating macrophage polarization.

Activation of NLRP3 Inflammasome in Liver of Long Evans Lactating Rats and Its Perinatal Effects in the Offspring after Bisphenol F Exposure

The liver is the organ responsible for the metabolism and detoxification of BPF, the BPA analogue that is replacing it in plastic-based products. It is not known whether BPF can trigger inflammatory responses via the NLRP3 inflammasome, which plays a major role in the development of liver disease. The aim of this study was to evaluate nitrosative stress species (RNS) and NLRP3 inflammasome activation in the liver of lactating dams after BPF exposure. Moreover, it was studied whether this effect could also be observed in the liver of female and male offspring at postnatal day 6 (PND6). 36 Long Evans rats were randomly distributed according to oral treatment into three groups: Control, BPF-low dose (LBPF; 0.0365 mg/kg b.w./day) group and BPF-high dose (HBPF; 3.65 mg/kg b.w./day) group. The levels of nitrosative stress-inducing proteins (eNOS, iNOS, HO-1d), NLRP3 inflammasome components (NLRP3, PyCARD, CASP1) and proinflammatory cytokines (IL-1β, IL-18, IFN-γ and TNF-α) were measured by gene and protein expression in the liver of lactating dams and in female and male PND6 offspring. Lactating dams treated with LBPF showed a significant increase in iNOS and HO-1d, activation of NLRP3 components (NLRP3, PyCARD, CASP1) and promoted the release of proinflammatory cytokines such as IL-1β, IL-18, IFN-γ and TNF-α. Similar effects were found in female and male PND6 offspring after perinatal exposure. LBPF oral administration and perinatal exposure caused an increase of nitrosative stress markers and proinflammatory cytokines. Also, NLRP3 inflammasome activation was significantly increased in in the liver of lactating dams and PND6 offspring.

Targeting inflammasome pathway by polyphenols as a strategy for pancreatitis, gastrointestinal and liver diseases management: an updated review

Obesity, pancreatitis, cardiovascular, gastrointestinal (GI), and liver diseases have all been linked to the Western lifestyle, characterized by increased unhealthy food consumption and decreased physical activity. Besides obesity and pancreatitis, many GI and liver diseases are associated with inflammation. Inflammasomes are multi-protein complexes that mediate acute and restorative inflammatory pathways. However, many aberrations in inflammasome activity originate from shifts in dietary habits. Evidence reveals that dietary polyphenols effectively modulate inflammasome-associated dysfunctions. With a focus on pancreatitis, GI, and liver disorders, this review set out to provide the most relevant evidence for the therapeutic impact of polyphenols via the regulation of the inflammasome pathway. Overall, flavonoid and non-flavonoid polyphenols maintain intestinal eubiosis, downregulate NLRP3 inflammasome canonical pathway, and restore redox status via upregulating Nrf2/HO-1 signaling. These effects at the level of the intestine, the liver, and the pancreas are associated with decreased systemic levels of key pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6.

NLRP3: a new therapeutic target in alcoholic liver disease

The liver is in charge of a wide range of critical physiological processes and it plays an important role in activating the innate immune system which elicits the inflammatory events. Chronic ethanol exposure disrupts hepatic inflammatory mechanism and leads to the release of proinflammatory mediators such as chemokines, cytokines and activation of inflammasomes. The mechanism of liver fibrosis/cirrhosis involve activation of NLRP3 inflammasome, leading to the destruction of hepatocytes and subsequent metabolic dysregulation in humans. In addition, increasing evidence suggests that alcohol intake significantly modifies liver epigenetics, promoting the development of alcoholic liver disease (ALD). Epigenetic changes including histone modification, microRNA-induced genetic modulation, and DNA methylation are crucial in alcohol-evoked cell signaling that affects gene expression in the hepatic system. Though we are at the beginning stage without having the entire print of epigenetic signature, it is time to focus more on NLRP3 inflammasome and epigenetic modifications. Here we review the novel aspect of ALD pathology linking to inflammation and highlighting the role of epigenetic modification associated with NLRP3 inflammasome and how it could be a therapeutic target in ALD.

Integration of nutrigenomics, melatonin, serotonin and inflammatory cytokines in the pathophysiology of pregnancy-specific urinary incontinence in women with gestational diabetes mellitus

Gestational diabetes mellitus is an important public health problem and has been associated with the development of pregnancy-specific urinary incontinence. The interaction is related to hyperglycemia, and inflammatory and hormonal patterns, which favor functional alterations in different organs and systems. Several genes associated with human diseases have been identified and partially characterized. Most of these genes are known to cause monogenic diseases. However, about 3 % of diseases do not fit the monogenic theory due to the complex interactions between multiple genes and environmental factors, as in chronic metabolic diseases such as diabetes. The nutritional, immunological, and hormonal patterns associated with changes in maternal metabolism may influence and contribute to greater susceptibility to urinary tract disorders. However, early systematic reviews have not yielded consistent findings for these associations. This literature review summarizes important new findings from integrating nutrigenomics, hormones, and cytokines in women with Gestational diabetes mellitus and pregnancy-specific urinary incontinence. Changes in maternal metabolism due to hyperglycemia can generate an inflammatory environment with increased inflammatory cytokines. This environment modulated by inflammation can alter tryptophan uptake through food and thus influence the production of serotonin and melatonin. As these hormones seem to have protective effects against smooth muscle dysfunction and to restore the impaired contractility of the detrusor muscle, it is assumed that these changes may favor the onset of urinary incontinence specific to pregnancy.

MicroRNA-29a-3p Prevents Drug-Induced Acute Liver Failure through Inflammation-Related Pyroptosis Inhibition

OBJECTIVE

Little is known about the role of microRNA-29a-3p (miR-29a-3p) in inflammation-related pyroptosis, especially in drug-induced acute liver failure (DIALF). This study aimed to identify the relationship between miR-29a-3p and inflammation-related pyroptosis in DIALF and confirm its underlying mechanisms.

METHODS

Thioacetamide (TAA)- and acetaminophen (APAP)-induced ALF mouse models were established, and human samples were collected. The expression levels of miR-29a-3p and inflammation and pyroptosis markers were measured by quantitative real-time polymerase chain reaction (qRT-PCR), Western blotting, or immunochemical staining in miR-29a-3p knock-in transgenic mouse (MIR29A(KI/KI)) DIALF models. In addition, RNA sequencing was conducted to explore the mechanisms.

RESULTS

MiR-29a-3p levels were decreased in TAA- and APAP-induced DIALF models. MiR-29a-3p prevented DIALF caused by TAA and APAP. RNA sequencing and further experiments showed that the protective effect of miR-29a-3p on DIALF was mainly achieved through inhibition of inflammation-related pyroptosis, and the inhibition was dependent on activation of the PI3K/AKT pathway. In addition, miR-29a-3p levels were reduced, and pyroptosis was activated in both peripheral blood mononuclear cells and liver tissues of DIALF patients.

CONCLUSION

The study supports the idea that miR-29a-3p inhibits pyroptosis by activating the PI3K/AKT pathway to prevent DIALF. MiR-29a-3p may be a promising therapeutic target for DIALF.

Acoustic radiation force impulse predicts long-term outcomes in a large-scale cohort: High liver cancer, low comorbidity in hepatitis B virus

BACKGROUND

Acoustic radiation force impulse (ARFI) is used to measure liver fibrosis and predict outcomes. The performance of elastography in assessment of fibrosis is poorer in hepatitis B virus (HBV) than in other etiologies of chronic liver disease.

AIM

To evaluate the performance of ARFI in long-term outcome prediction among different etiologies of chronic liver disease.

METHODS

Consecutive patients who received an ARFI study between 2011 and 2018 were enrolled. After excluding dual infection, alcoholism, autoimmune hepatitis, and others with incomplete data, this retrospective cohort were divided into hepatitis B (HBV, n = 1064), hepatitis C (HCV, n = 507), and non-HBV, non-HCV (NBNC, n = 391) groups. The indexed cases were linked to cancer registration (1987-2020) and national mortality databases. The differences in morbidity and mortality among the groups were analyzed.

RESULTS

At the enrollment, the HBV group showed more males (77.5%), a higher prevalence of pre-diagnosed hepatocellular carcinoma (HCC), and a lower prevalence of comorbidities than the other groups (P < 0.001). The HCV group was older and had a lower platelet count and higher ARFI score than the other groups (P < 0.001). The NBNC group showed a higher body mass index and platelet count, a higher prevalence of pre-diagnosed non-HCC cancers (P < 0.001), especially breast cancer, and a lower prevalence of cirrhosis. Male gender, ARFI score, and HBV were independent predictors of HCC. The 5-year risk of HCC was 5.9% and 9.8% for those ARFI-graded with severe fibrosis and cirrhosis. ARFI alone had an area under the receiver operating characteristic curve (AUROC) of 0.742 for prediction of HCC in 5 years. AUROC increased to 0.828 after adding etiology, gender, age, and platelet score. No difference was found in mortality rate among the groups.

CONCLUSION

The HBV group showed a higher prevalence of HCC but lower comorbidity that made mortality similar among the groups. Those patients with ARFI-graded severe fibrosis or cirrhosis should receive regular surveillance.

The Multifaceted Role and Regulation of Nlrp3 Inflammasome in Colitis-Associated Colo-Rectal Cancer: A Systematic Review

Colitis-associated colo-rectal cancer remains the leading cause of mortality in inflammatory bowel diseases, with inflammation remaining one of the bridging points between the two pathologies. The NLRP3 inflammasome complex plays an important role in innate immunity; however, its misregulation can be responsible for the apparition of various pathologies such as ulcerative colitis. Our review focuses on the potential pathways of upregulation or downregulation of the NLRP3 complex, in addition to evaluating its role in the current clinical setting. Eighteen studies highlighted the potential pathways of NLRP3 complex regulation as well as its role in the metastatic process in colo-rectal cancer, with promising results. Further research is, however, needed in order to validate the results in a clinical setting.

EuHD1 protects against inflammatory injury driven by NLRP3 inflammasome

Non-steroidal anti-inflammatory drugs (NSAIDs) possessing anti-inflammatory, analgesic and antipyretic activities, are widely used in the treatment of osteoarthritis, rheumatism and rheumatoid arthritis. However, its long-term or large use will cause serious gastrointestinal injury or cardiovascular adverse reactions, which limits its clinical application. We have synthesized a new class of NSAIDs, EuHD1, which can release hydrogen sulfide and have better gastrointestinal safety. However, the anti-inflammatory molecular mechanism of the drug is still unclear. In this paper, we explored the mechanism of EuHD1 on NLRP3 inflammasome and its effects on acute lung injury and acute liver injury in mice. In vitro results demonstrated that EuHD1 inhibited macrophage pyroptosis and LDH release induced by LPS combined with ATP. In addition, EuHD1 blocked NLRP3 inflammasome activation and suppressed following Caspase-1 activation and secretion of mature IL-1β. EuHD1 restrained intracellular ROS production and the formation of ASC oligomers, which inhibited the assembly and activation of NLRP3 inflammasome. In vivo results further showed that EuHD1 alleviated LPS-induced acute lung injury in mice, and inhibited the production of mature IL-1β and Caspase-1 (p20). Besides, EuHD1 improved D-GalN/LPS-induced acute liver injury, and inhibited SOD/MDA levels and oxidative stress injury, and blocked the activation of NLRP3 inflammasome. In summary, we found that EuHD1 inhibits the assembly and activation of NLRP3 inflammasome through restraining the production of ROS and the formation of ASC oligomers, and has therapeutic effects on acute lung injury and liver injury in mice, indicating that EuHD1 has the potential to treat NLRP3 inflammasome-related diseases.

Hepatic TNFRSF12A promotes bile acid-induced hepatocyte pyroptosis through NFκB/Caspase-1/GSDMD signaling in cholestasis

Tumor necrosis factor receptor superfamily member-12A (TNFRSF12A) plays a critical role in inflammation and cell death. It is expressed in multiple tissues yet extremely low in normal liver. To date, little is known about its role in cholestasis. Therefore, we sought to delineate the role of TNFRSF12A in cholestasis and its underlying mechanisms. Human liver tissues were collected from patients with obstructive cholestasis (OC) or primary biliary cholangitis (PBC). Tnfrsf12a knockout (KO) mice were generated. Cholestasis was induced by bile-duct ligation (BDL) or 0.1% 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-feeding. Human hepatoma PLC/PRF/5-ASBT and THP1 cell lines or primary mouse hepatocytes were used for mechanistic studies. Hepatic TNFRSF12A expression was markedly increased in OC or PBC patients. Genetic ablation of Tnfrsf12a in BDL- and 0.1%DDC-induced cholestatic mice significantly attenuated cholestatic liver injury with remarkable reduction of hepatocyte pyroptosis but without changing scores of necroptosis and apoptosis. Morphological features of hepatocyte pyroptosis and increased levels of pyroptosis-related proteins, NLRP3, cleaved-Caspase-1, and cleaved-GSDMD in OC patients and BDL-mice confirmed this observation. Further mechanistic studies revealed that bile acids (BAs) induced TNFRSF12A expression by enhancing the transcription factor c-JUN binding to the TNFRSF12A promoter and subsequently initiated hepatocyte pyroptosis by the NFκB/Caspase-1/GSDMD signaling. Interestingly, TWEAK, a typical ligand of TNFRSF12A, secreted by infiltrated macrophages in cholestatic livers, enhanced TNFRSF12A-induced hepatocyte pyroptosis. Taken together, we report, for the first time, that hepatic TNFRSF12A is dramatically increased in human cholestasis. Deletion of TNFRSF12A inhibits BAs-induced hepatocyte pyroptosis through the NFκB/Caspase-1/GSDMD signaling and thereby ameliorates cholestatic liver injury. As such, targeting TNFRSF12A could be a promising approach to treating cholestasis.

NLRP3 inflammasome activation By 17β-estradiol is a potential therapeutic target in hepatocellular carcinoma treatment

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and it mostly arises as a consequence of persistent chronic inflammation. Recently, NLRP3 inflammasome has caught the attention of many research groups due to its involvement in different types of cancer. However, its direct role in HCC remains elusive. Our study aimed to evaluate the role of NLRP3 inflammasome and pyroptosis in HCC and to clarify the potential mechanism by which 17β-estradiol (E2) can be used as a protective factor against HCC. NLRP3, caspase-1 (CASP1) as well as gasdermin-D (GSDMD) mRNA expression levels were assessed in human HCC tissues and adjacent non-cancerous liver tissues. Also, HepG2 HCC cells were cultured and treated with E2, followed by detection of the mRNA levels of these three genes. Our results revealed that NLRP3, CASP1, and GSDMD mRNA expressions were significantly lower in HCC tissues than in controls, and this under-expression was closely correlated with advanced HCC stages and grades. In contrast, HepG2 HCC cells displayed significantly higher expression levels of NLRP3 inflammasome components and GSDMD in the two E2-treated groups compared to the untreated group. Also, NLRP3, CASP1, and GSDMD mRNA expression levels were positively correlated with each other. This study confirmed that lack of NLRP3 inflammasome is involved in HCC progression and 17β-estradiol-induced activation of NLRP3 inflammasome may be effective in HCC treatment as it inhibited tumor cell growth and proliferation by triggering CASP1-dependent pyroptosis in HCC cells.

Thioredoxin reductase 1 regulates hepatic inflammation and macrophage activation during acute cholestatic liver injury

BACKGROUND AND AIMS

Cholestatic liver diseases, including primary sclerosing cholangitis, are characterized by periportal inflammation with progression to hepatic fibrosis and ultimately cirrhosis. We recently reported that the thioredoxin antioxidant response is dysregulated during primary sclerosing cholangitis. The objective of this study was to examine the impact of genetic and pharmacological targeting of thioredoxin reductase 1 (TrxR1) on hepatic inflammation and liver injury during acute cholestatic injury.

APPROACH AND RESULTS

Primary mouse hepatocytes and intrahepatic macrophages were isolated from 3-day bile duct ligated (BDL) mice and controls. Using wildtype and mice with a liver-specific deletion of TrxR1 (TrxR1LKO), we analyzed the effect of inhibition or ablation of TrxR1 signaling on liver injury and inflammation. Immunohistochemical analysis of livers from BDL mice and human cholestatic patients revealed increased TrxR1 staining in periportal macrophages and hepatocytes surrounding fibrosis. qPCR analysis of primary hepatocytes and intrahepatic macrophages revealed increased TrxR1 mRNA expression following BDL. Compared with sham controls, BDL mice exhibited increased inflammation, necrosis, and increased mRNA expression of pro-inflammatory cytokines, fibrogenesis, the NLRP3 inflammatory complex, and increased activation of NFkB, all of which were ameliorated in TrxR1LKO mice. Importantly, following BDL, TrxR1LKO induced periportal hepatocyte expression of Nrf2-dependent antioxidant proteins and increased mRNA expression of basolateral bile acid transporters with reduced expression of bile acid synthesis genes. In the acute BDL model, the TrxR1 inhibitor auranofin (10 mg/kg/1 d preincubation, 3 d BDL) ameliorated BDL-dependent increases in Nlrp3, GsdmD, Il1β, and TNFα mRNA expression despite increasing serum alanine aminotransferase, aspartate aminotransferase, bile acids, and bilirubin.

CONCLUSIONS

These data implicate TrxR1-signaling as an important regulator of inflammation and bile acid homeostasis in cholestatic liver injury.

Association of Common Polymorphisms in the Interleukin-1 Beta Gene with Hepatocellular Carcinoma in Caucasian Patients with Chronic Hepatitis B

Interleukin-1 beta (IL-1β) promotes liver disease progression and hepatocarcinogenesis in chronic hepatitis B (CHB). Single nucleotide polymorphisms (SNPs) within the promotor region of the IL-1β gene can affect the progression towards liver cirrhosis and hepatocellular carcinoma (HCC). Aims: We aimed to investigate the association of three common IL-1β SNPs with hepatitis B virus (HBV)-related HCC in Caucasian patients. Method: A Caucasian cohort of 99 patients with HBe antigen (Ag)-positive CHB, 255 patients with HBeAg-negative CHB and 278 inactive carriers (IC) were enrolled. 105 patients were diagnosed with liver cirrhosis, and 64 with HCC and cirrhosis. Genotyping of the IL-1β rs1143623, rs1143627 and rs16944 was performed. Results: The rs1143627 TT and rs16944 CC genotypes were more frequent in patients with HCC compared to patients without liver tumours (48% vs. 33%, p = 0.018 and 47% vs. 31%, p = 0.001, respectively). In multivariate analysis, the rs16944 CC genotype was independently associated with HCC (OR = 6.44 [95% CI 1.50-27.59] p = 0.012). The haplotype, including rs1143623 TT and rs16944 CC, was a risk factor for HCC development (OR = 1.55 [95% CI 1.04-2.32] p = 0.031). Conclusions: We identified an association of common IL-1β SNPs with HBV-related HCC in a Caucasian population. The effect was independent of the phases of chronic HBV infection, which are currently regarded as important HCC risk factors.

NLRP3 activation in neutrophils induces lethal autoinflammation, liver inflammation, and fibrosis

Sterile inflammation is a central element in liver diseases. The immune response following injurious stimuli involves hepatic infiltration of neutrophils and monocytes. Neutrophils are major effectors of liver inflammation, rapidly recruited to sites of inflammation, and can augment the recruitment of other leukocytes. The NLRP3 inflammasome has been increasingly implicated in severe liver inflammation, fibrosis, and cell death. In this study, the role of NLRP3 activation in neutrophils during liver inflammation and fibrosis was investigated. Mouse models with neutrophil-specific expression of mutant NLRP3 were developed. Mutant mice develop severe liver inflammation and lethal autoinflammation phenocopying mice with a systemic expression of mutant NLRP3. NLRP3 activation in neutrophils leads to a pro-inflammatory cytokine and chemokine profile in the liver, infiltration by neutrophils and macrophages, and an increase in cell death. Furthermore, mutant mice develop liver fibrosis associated with increased expression of pro-fibrogenic genes. Taken together, the present work demonstrates how neutrophils, driven by the NLRP3 inflammasome, coordinate other inflammatory myeloid cells in the liver, and propagate the inflammatory response in the context of inflammation-driven fibrosis.

LncRNA FENDRR with m6A RNA methylation regulates hypoxia-induced pulmonary artery endothelial cell pyroptosis by mediating DRP1 DNA methylation

Background

Pyroptosis is a form of programmed cell death involved in the pathophysiological progression of hypoxic pulmonary hypertension (HPH). Emerging evidence suggests that N6-methyladenosine (m6A)-modified transcripts of long noncoding RNAs (lncRNAs) are important regulators that participate in many diseases. However, whether m6A modified transcripts of lncRNAs can regulate pyroptosis in HPH progression remains unexplored.

Methods

The expression levels of FENDRR in hypoxic pulmonary artery endothelial cells (HPAECs) were detected by using quantitative real-time polymerase chain reaction (qRT-PCR) and fluorescence in situ hybridization (FISH). Western blot, Lactate dehydrogenase (LDH) release assay, Annexin V-FITC/PI double staining, Hoechst 33342/PI fluorescence staining and Caspase-1 activity assay were used to detect the role of FENDRR in HPAEC pyroptosis. The relationship between FENDRR and dynamin-related protein 1 (DRP1) was explored using bioinformatics analysis, Chromatin Isolation by RNA Purification (CHIRP), Electrophoretic mobility shift assay (EMSA) and Methylation-Specific PCR (MSP) assays. RNA immunoprecipitation (RIP) and m6A dot blot were used to detect the m6A modification levels of FENDRR. A hypoxia-induced mouse model of pulmonary hypertension (PH) was used to test preventive effect of conserved fragment TFO2 of FENDRR.

Results

We found that FENDRR was significantly downregulated in the nucleus of hypoxic HPAECs. FENDRR overexpression inhibited hypoxia-induced HPAEC pyroptosis. Additionally, DRP1 is a downstream target gene of FENDRR, and FENDRR formed an RNA–DNA triplex with the promoter of DRP1, which led to an increase in DRP1 promoter methylation that decreased the transcriptional level of DRP1. Notably, we illustrated that the m6A reader YTHDC1 plays an important role in m6A-modified FENDRR degradation. Additionally, conserved fragment TFO2 of FENDEE overexpression prevented HPH in vivo.

Conclusion

In summary, our results demonstrated that m6A-induced decay of FENDRR promotes HPAEC pyroptosis by regulating DRP1 promoter methylation and thereby provides a novel potential target for HPH therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00551-z.

Constructing novel molecular subtypes and an 11-gene signature based on pyroptosis signaling for lung adenocarcinoma

Pyroptosis plays important roles in various cancers. In this study, we focused on lung adenocarcinoma (LUAD) and aimed to develop new molecular subtypes based on pyroptosis signaling. Pyroptosis-related genes were used as a basis to classify molecular subtypes through unsupervised consensus clustering. Gene set enrichment analysis was performed to characterize tumor microenvironment (TME) and functional pathways. Univariate Cox regression and least absolute shrinkage and selection operator (LASSO) analysis were conducted to identify prognostic genes for establishing a prognostic model. Three molecular subtypes were established with distinct overall survival, TME and enriched pathways. C3 subtype had the longest survival and the highest immune infiltration. 11 prognostic genes were screened to build a prognostic signature for predicting LUAD prognosis. This study emphasized the important role of pyroptosis in LUAD development. Pyroptosis was considered to play critical roles in regulating TME. Moreover, the 11-gene signature could serve as an indicator for predicting LUAD prognosis, and was potential targets for developing targeted drugs.

Four-Pyroptosis Gene-Based Nomogram as a Novel Strategy for Predicting the Effect of Immunotherapy in Hepatocellular Carcinoma

Background

Immunotherapy has been considered as a promising cancer treatment for hepatocellular carcinoma (HCC). However, due to the particular immune environment of the liver, identifying patients who could benefit from immunotherapy is critical in clinical practice.

Methods

The pyroptosis gene expression database of 54 candidates from The Cancer Genome Atlas (TCGA) were collected to discover the critical prognostic-related pyroptosis genes. A novel pyroptosis gene model was established to calculate the risk score. Kaplan–Meier analysis and receiver operating characteristic curve (ROC) were used to verify its predictive ability. The International Cancer Genome Consortium (ICGC) data was collected as external validation data to verify the model's accuracy. We employed multiple bioinformatics tools and algorithms to evaluate the tumor immune microenvironment (TIME) and the response to immunotherapy.

Results

Our study found that most pyroptosis genes were expressed differently in normal and tumor tissues and that their expression was associated with the prognosis. Then, a precise four-pyroptosis gene model was generated. The one-year area under the curves (AUCs) among the training, internal, and external validation patients were 0.901, 0.727, and 0.671, respectively. An analysis of survival data revealed that individuals had a worse prognosis than patients with low risk. The analysis of TIME revealed that the low-risk group had more antitumor cells, fewer immunosuppressive cells, stronger immune function, less immune checkpoint gene expression, and better immunotherapy response than the high-risk group. Immunophenoscore (IPS) analysis also demonstrated that the low-risk score was related to superior immune checkpoint inhibitors therapy.

Conclusion

A nomogram based on the four-pyroptosis gene signature was a novel tool to predict the effectiveness of immunotherapy for HCC. Therefore, individualized treatment targeting the pyroptosis genes may influence TIME and play an essential role in improving the prognosis in HCC patients.

Role of Inflammasomes in Keloids and Hypertrophic Scars-Lessons Learned from Chronic Diabetic Wounds and Skin Fibrosis

Keloids and hypertrophic scars are pathological cutaneous scars. They arise from excessive wound healing, which induces chronic dermal inflammation and results in overwhelming fibroblast production of extracellular matrix. Their etiology is unclear. Inflammasomes are multiprotein complexes that are important in proinflammatory innate-immune system responses. We asked whether inflammasomes participate in pathological scarring by examining the literature on scarring, diabetic wounds (also characterized by chronic inflammation), and systemic sclerosis (also marked by fibrosis). Pathological scars are predominantly populated by anti-inflammatory M2 macrophages and recent literature hints that this could be driven by non-canonical inflammasome signaling. Diabetic-wound healing associates with inflammasome activation in immune (macrophages) and non-immune (keratinocytes) cells. Fibrotic conditions associate with inflammasome activation and inflammasome-induced transition of epithelial cells/endothelial cells/macrophages into myofibroblasts that deposit excessive extracellular matrix. Studies suggest that mechanical stimuli activate inflammasomes via the cytoskeleton and that mechanotransduction-inflammasome crosstalk is involved in fibrosis. Further research should examine (i) the roles that various inflammasome types in macrophages, (myo)fibroblasts, and other cell types play in keloid development and (ii) how mechanical stimuli interact with inflammasomes and thereby drive scar growth. Such research is likely to significantly advance our understanding of pathological scarring and aid the development of new therapeutic strategies.

Inflammasomes and Pyroptosis of Liver Cells in Liver Fibrosis

Inflammasomes are multiprotein complexes that can sense danger signals and activate caspase-1 to mediate pro-inflammatory cytokines release and pyroptotic cell death. There are two main canonical and non-canonical signaling pathways that trigger inflammasome activation. Inflammasomes are expressed and assembled in parenchymal and nonparenchymal cells in response to liver injury in the liver. Additionally, the hepatocytes, biliary epithelial cells (cholangiocytes), hepatic stellate cells (HSCs), hepatic macrophages, and liver sinusoidal endothelial cells (LSECs) contribute to liver fibrosis via different mechanisms. However, the underlying mechanism of the inflammasome and pyroptosis in these liver cells in liver fibrosis remains elusive. This review summarizes the activation and function of inflammasome complexes and then discusses the association between inflammasomes, pyroptosis, and liver fibrosis. Unlike other similar reviewers, we will focus on the effect of inflammasome activation and pyroptosis in the various liver cells during the development of liver fibrosis. We will also highlight the latest progress of pharmacological intervention in inflammasome-mediated liver fibrosis.

Oxidative Stress and Redox Signaling in the Pathophysiology of Liver Diseases

The increased production of derivatives of molecular oxygen and nitrogen in the form of reactive oxygen species (ROS) and reactive nitrogen species (RNS) lead to molecular damage called oxidative stress. Under normal physiological conditions, the ROS generation is tightly regulated in different cells and cellular compartments. Any disturbance in the balance between the cellular generation of ROS and antioxidant balance leads to oxidative stress. In this article, we discuss the sources of ROS (endogenous and exogenous) and antioxidant mechanisms. We also focus on the pathophysiological significance of oxidative stress in various cell types of the liver. Oxidative stress is implicated in the development and progression of various liver diseases. We narrate the master regulators of ROS-mediated signaling and their contribution to liver diseases. Nonalcoholic fatty liver diseases (NAFLD) are influenced by a "multiple parallel-hit model" in which oxidative stress plays a central role. We highlight the recent findings on the role of oxidative stress in the spectrum of NAFLD, including fibrosis and liver cancer. Finally, we provide a brief overview of oxidative stress biomarkers and their therapeutic applications in various liver-related disorders. Overall, the article sheds light on the significance of oxidative stress in the pathophysiology of the liver. © 2022 American Physiological Society. Compr Physiol 12:3167-3192, 2022.

Neutrophils and schistosomiasis: a missing piece in pathology

Schistosomiasis is a chronic human parasitic disease that causes serious health problems worldwide. The disease-associated liver pathology is one of the hallmarks of infections by S. mansoni and S. japonicum, and is accountable for the debilitating condition found in infected patients. In the past few years, investigative studies have highlighted the key role played by neutrophils and the influence of inflammasome signaling pathway in different pathological conditions. However, it is noteworthy that the study of inflammasome activation in neutrophils has been overlooked by reports concerning macrophages and monocytes. This interplay between neutrophils and inflammasomes is much more poorly investigated during schistosomiasis. Herein we reviewed the role of neutrophils during schistosomiasis and addressed the potential connection between these cells and inflammasome activation in this context.

Development and Validation of a Pyroptosis-Related Signature for Predicting Prognosis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) has emerged as a primary health problem and threat to global mortality, especially in China. Since pyroptosis as a new field for HCC prognosis is not well studied, it is important to open a specific prognostic model. In this study, consensus clustering method for 42 pyroptosis-related genes to classify 374 HCC patients in the TCGA database. After cox regression analysis of the differentially expressed genes between the two clusters, LASSO-Cox analysis was then performed to construct a pyroptosis-related prognostic model with 11 genes including MMP1, KPNA2, LPCAT1, NEIL3, CDCA8, SLC2A1, PSRC1, CBX2, HAVCR1, G6PD, MEX3A. The ICGC dataset was served as the validation cohort. Patients in the high-risk group had significantly lower overall survival (OS) rates than those in the low-risk group (p &lt; 0.05). COX regression analysis showed that our model could be used as an independent prognostic factor to predict prognosis of patients and was significantly correlated with clinicopathological characteristics. Nomogram showing the stability of the model predicting the 1, 3, 5 year survival probability of patients. In addition, based on the risk model, ssGSEA analysis revealed significant differences in the level of immune cell infiltration and activation of immune-related functional pathways between high and low-risk groups, and patients with the high-risk score may benefit more from treatment with immune checkpoint inhibitors. Furthermore, patients in the high-risk group were more tend to develop chemoresistance. Overall, we identified a novel pyroptosis-related risk signature for prognosis prediction in HCC patients and revealed the overall immune response intensity of the tumor microenvironment. All these findings make the pyroptosis signature shed light upon a latent therapeutic strategy aimed at the treatment and prevention of cancers.

Role of the Inflammasome in Liver Disease

The involvement of inflammasomes in the proinflammatory response observed in chronic liver diseases, such as alcohol-associated liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD), is widely recognized. Although there are different types of inflammasomes, most studies to date have given attention to NLRP3 (nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3) in the pathogenesis of ALD, NAFLD/nonalcoholic steatohepatitis, and fibrosis. Canonical inflammasomes are intracellular multiprotein complexes that are assembled after the sensing of danger signals and activate caspase-1, which matures interleukin (IL)-1β, IL-18, and IL-37 and also induces a form of cell death called pyroptosis. Noncanonical inflammasomes activate caspase-11 to induce pyroptosis. We discuss the different types of inflammasomes involved in liver diseases with a focus on (a) signals and mechanisms of inflammasome activation, (b) the role of different types of inflammasomes and their products in the pathogenesis of liver diseases, and (c) potential therapeutic strategies targeting components of the inflammasomes or cytokines produced upon inflammasome activation.

Cell Death in Hepatocellular Carcinoma: Pathogenesis and Therapeutic Opportunities

Simple Summary

The progression of liver tumors is highly influenced by the interactions between cancer cells and the surrounding environment, and, consequently, can determine whether the primary tumor regresses, metastasizes, or establishes micrometastases. In the context of liver cancer, cell death is a double-edged sword. On one hand, cell death promotes inflammation, fibrosis, and angiogenesis, which are tightly orchestrated by a variety of resident and infiltrating host cells. On the other hand, targeting cell death in advanced hepatocellular carcinoma could represent an attractive therapeutic approach for limiting tumor growth. Further studies are needed to investigate therapeutic strategies combining current chemotherapies with novel drugs targeting either cell death or the tumor microenvironment.

Abstract

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer and the third leading cause of cancer death worldwide. Closely associated with liver inflammation and fibrosis, hepatocyte cell death is a common trigger for acute and chronic liver disease arising from different etiologies, including viral hepatitis, alcohol abuse, and fatty liver. In this review, we discuss the contribution of different types of cell death, including apoptosis, necroptosis, pyroptosis, or autophagy, to the progression of liver disease and the development of HCC. Interestingly, inflammasomes have recently emerged as pivotal innate sensors with a highly pathogenic role in various liver diseases. In this regard, an increased inflammatory response would act as a key element promoting a pro-oncogenic microenvironment that may result not only in tumor growth, but also in the formation of a premetastatic niche. Importantly, nonparenchymal hepatic cells, such as liver sinusoidal endothelial cells, hepatic stellate cells, and hepatic macrophages, play an important role in establishing the tumor microenvironment, stimulating tumorigenesis by paracrine communication through cytokines and/or angiocrine factors. Finally, we update the potential therapeutic options to inhibit tumorigenesis, and we propose different mechanisms to consider in the tumor microenvironment field for HCC resolution.

Hepatoprotective effect and metabonomics studies of radix gentianae in rats with acute liver injury

CONTEXT

As a well-known traditional Chinese medicine for protecting the liver, the mechanism of Radix Gentianae (RG) remains unclear.

OBJECTIVE

The hepatoprotective effect and metabonomics of RG were studied to explore the molecular and metabolic mechanisms of RG protecting the liver.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into control and model group (n = 10, orally given distilled water), intervention group (4 subgroups, n = 10, prophylactically and orally given 0.63, 2.5 and 5.6 g/kg RG and 0.2 g/kg bifendatatum for 7 d). On day 7 of the intervention, all rats except the control were injected intraperitoneally with 2.5% carbon tetrachloride vegetable oil solution (1.5 mL/kg) to induce liver injury. After 24 h of carbon tetrachloride injection, rat serum and liver tissue were collected for determining AST, ALT, TNF-α, MCP-1, IL-6, SOD, MDA, GSH, and GSH-PX. Rat serum was used for analysing endogenous metabolism by UPLC-Q-TOF-MS.

RESULTS

Different doses of RG can significantly decrease the levels of AST, ALT, TNF-α, MCP-1, IL-6 and MDA, and increase the levels of SOD, GSH, and GSH-PX in rats with liver injury (p < 0.05; TNF-α, and IL-6, p < 0.05 only at 5.6 g/kg dose). Eight biomarkers of liver injury were obtained in serum metabonomics, involving five significant metabolic pathways. RG can improve steroid biosynthesis, linoleic acid metabolism, porphyrin and chlorophyll metabolism, and fatty acid biosynthesis.

CONCLUSION

RG demonstrated a good ability to protect the liver and improving endogenous metabolism in rats with liver injury. This can help us understand the mechanism of RG and more clinical verifications were inspired.

Alcoholic liver disease: Current insights into cellular mechanisms

Alcoholic liver disease (ALD) due to chronic alcohol consumption is a significant global disease burden and a leading cause of mortality. Alcohol abuse induces a myriad of aberrant changes in hepatocytes at both the cellular and molecular level. Although the disease spectrum of ALD is widely recognized, the precise triggers for disease progression are still to be fully elucidated. Oxidative stress, mitochondrial dysfunction, gut dysbiosis and altered immune system response plays an important role in disease pathogenesis, triggering the activation of inflammatory pathways and apoptosis. Despite many recent clinical studies treatment options for ALD are limited, especially at the alcoholic hepatitis stage. We have therefore reviewed some of the key pathways involved in the pathogenesis of ALD and highlighted current trials for treating patients.

Deubiquitination and Activation of the NLRP3 Inflammasome by UCHL5 in HCV-Infected Cells

Chronic hepatitis C virus (HCV) infection induces liver inflammation that can lead to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Inflammation is the outcome of the action of proinflammatory cytokines and chemokines, including interleukin-1 beta (IL-1β) and tumor necrosis factor alpha. Mature IL-1β production and secretion are facilitated by active inflammasome complexes, including the NACHT-LRR pyrin domain-containing protein 3 (NLRP3) inflammasome. Our study shows that the NLRP3 inflammasome is activated in HCV-infected hepatocytes and that the activation is regulated by posttranslational modifications. NLRP3 is modified by lysine-63 ubiquitin chains in hepatocytes and is deubiquitinated during HCV infection. Inhibition of deubiquitinases (DUBs) with chemical inhibitors or blocking UCHL5 DUB expression with small interfering RNA (siRNA) abrogated NLRP3 inflammasome assembly and activation. Inhibition of inflammasome deubiquitination was correlated with a reduction in IL-1β maturation, decrease in HCV protein expression, and reduction in release of HCV from the cells. Together, this study suggests that HCV-induced activation of the NLRP3 inflammasome through posttranslational modification is crucial for the HCV life cycle and pathogenesis. IMPORTANCE HCV infection induces inflammation leading to fibrosis, cirrhosis, and cancer. The current study identifies the mechanisms leading to the activation of the NLRP3 inflammasome in hepatocytes, which is an important site of viral replication. Deubiquitination of NLRP3 by UCHL5 is required for inflammasome activation. Inhibition of deubiquitination blocks NLRP3 inflammasome activation and IL-1β maturation and also decreases HCV replication, suggesting the importance of the NLRP3 inflammasome in inflammation as well as other signaling pathways.

Transcriptional enhancement of GBP-5 by BATF aggravates sepsis-associated liver injury via NLRP3 inflammasome activation

Strong inflammatory response triggered by the activation of the innate immune system is one typical characteristic of sepsis-associated liver injury (SALI). Guanylate-binding protein 5 (GBP-5) is a component of cell-autonomous immunity and known to be associated with inflammation. Currently, whether GBP-5 participates in SALI and its roles in this disease are yet to be investigated. Using a lipopolysaccharide (LPS)-induced SALI mouse model, we found GBP-5 was highly expressed in LPS-treated mice, and its expression was tightly related to the serum concentrations of live injury markers and inflammatory cytokines, liver damage scores by H&E staining, and amounts of apoptotic hepatocytes by TUNEL staining. Moreover, GBP-5 overexpression was found to aggravate LPS-induced SALI by promoting the activation of NLR family pyrin domain containing 3 (NLRP3) inflammasome, then facilitated the production of pro-inflammatory cytokines, eventually induced hepatocyte cell death. Direct transcriptional activation of GBP-5 by basic leucine zipper ATF-like transcription factor (BATF) was identified and further validated. This study unveils a transcriptional upregulation of GBP-5 by interacting with BATF, which promotes the progression of LPS-induced SALI through NLRP3 inflammasome activation, and provides novel therapeutic insights for halting the progression of liver injury in various liver diseases.

Hepatoprotective Effect of Apigenin Against Liver Injury via the Non-canonical NF-κB Pathway In Vivo and In Vitro

Apigenin, a flavonoid found in many plants, has various biological properties. We aimed to investigate the anti-inflammatory and anti-oxidative activity of apigenin against carbon tetrachloride (CCl₄)-induced acute liver injury in mice and hydrogen peroxide (H₂O₂)-induced oxidative stress in HepG2 cells and possible mechanism. In vivo, apigenin significantly reduced alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity in serum of mice challenged by CCl₄ and markedly alleviated the lipid peroxidation as indicated by the increased level of superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidases (GSH-Px) and catalase (CAT), and the decreased malondialdehyde (MDA) in liver tissue. Apigenin also ameliorated inflammation by downregulating tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and upregulating IL-10. Consistently, the elevated ALT and AST level; the impaired balance between SOD, GSH activity, and excessive ROS; and the increased gene expression of TNF-α and IL-6 resulting from H₂O₂-induced oxidative stress were restored by apigenin. Moreover, the results from Western blot, real-time qPCR, and immunofluorescence assay indicated that apigenin enhanced the activity of TNF receptor-associated factor (TRAF) 2/3 and cellular inhibitor of apoptosis protein (c-IAP) 1, ameliorated NF-κB-inducing kinase (NIK), and mediated the nuclear translocation of NF-κB2, therefore had an inhibitory effect on the non-canonical NF-κB pathway which was activated in both models. siNIK canceled the protective effect of apigenin on H₂O₂-induced HepG2 cells. Altogether, our results demonstrated that apigenin mitigated liver injury by ameliorating inflammation and oxidative stress through suppression of the non-canonical NF-κB pathway, indicating the potential of apigenin for treatment of the liver injury.

Pyroptosis, a new bridge to tumor immunity

Pyroptosis refers to the process of gasdermin (GSDM)‐mediated programmed cell death (PCD). Our understanding of pyroptosis has expanded beyond cells and is known to involve extracellular responses. Recently, there has been an increasing interest in pyroptosis due to its emerging role in activating the immune system. In the meantime, pyroptosis‐mediated therapies, which use the immune response to kill cancer cells, have also achieved notable success in a clinical setting. In this review, we discuss that the immune response induced by pyroptosis activation is a double‐edged sword that affects all stages of tumorigenesis. On the one hand, the activation of inflammasome‐mediated pyroptosis and the release of pyroptosis‐produced cytokines alter the immune microenvironment and promote the development of tumors by evading immune surveillance. On the other hand, pyroptosis‐produced cytokines can also collect immune cells and ignite the immune system to improve the efficiency of tumor immunotherapies. Pyroptosis is also related to some immune checkpoints, especially programmed death‐1 (PD‐1) or programmed death‐ ligand 1 (PD‐L1). In this review, we mainly focus on our current understanding of the interplay between the immune system and tumors that process through pyroptosis, and debate their use as potential therapeutic targets.

Liver Injury and the Macrophage Issue: Molecular and Mechanistic Facts and Their Clinical Relevance

The liver is an essential immunological organ due to its gatekeeper position to bypassing antigens from the intestinal blood flow and microbial products from the intestinal commensals. The tissue-resident liver macrophages, termed Kupffer cells, represent key phagocytes that closely interact with local parenchymal, interstitial and other immunological cells in the liver to maintain homeostasis and tolerance against harmless antigens. Upon liver injury, the pool of hepatic macrophages expands dramatically by infiltrating bone marrow-/monocyte-derived macrophages. The interplay of the injured microenvironment and altered macrophage pool skews the subsequent course of liver injuries. It may range from complete recovery to chronic inflammation, fibrosis, cirrhosis and eventually hepatocellular cancer. This review summarizes current knowledge on the classification and role of hepatic macrophages in the healthy and injured liver.

The Role of Melatonin on NLRP3 Inflammasome Activation in Diseases

NLRP3 inflammasome is a part of the innate immune system and responsible for the rapid identification and eradication of pathogenic microbes, metabolic stress products, reactive oxygen species, and other exogenous agents. NLRP3 inflammasome is overactivated in several neurodegenerative, cardiac, pulmonary, and metabolic diseases. Therefore, suppression of inflammasome activation is of utmost clinical importance. Melatonin is a ubiquitous hormone mainly produced in the pineal gland with circadian rhythm regulatory, antioxidant, and immunomodulatory functions. Melatonin is a natural product and safer than most chemicals to use for medicinal purposes. Many in vitro and in vivo studies have proved that melatonin alleviates NLRP3 inflammasome activity via various intracellular signaling pathways. In this review, the effect of melatonin on the NLRP3 inflammasome in the context of diseases will be discussed.

The relationship between liver pathological inflammation degree and pyroptosis in chronic hepatitis B patients

The aim of this study is to explore the relationship between liver pathological inflammation degree and pyroptosis in patients with chronic hepatitis B (CHB). One hundred and twenty CHB patients' liver tissue samples, including A0-A3 inflammatory grades, were selected. Six tissue sections were selected for each indicator in each inflammation grade. The results of immunohistochemical analysis on the pyroptosis-related molecules (NLRP3, GSDMD, caspase1, interleukin [IL]-1β, and IL-18) were determined. The correlation between the pyroptosis-related molecules and liver inflammatory activities was analyzed. The expression of NLRP3, GSDMD, caspase1, IL-18, and IL-1β was respectively significantly positively correlated with the grade of inflammatory activity (r_s  = 0.690, p < 0.01; r_s  = 0.681, p < 0.01; r_s  = 0.540, p < 0.01; r_s  = 0.725, p < 0.01; r_s  = 0.663, p < 0.01) and linear relationship (χ²  = 56.763, p < 0.01; χ²  = 55.350, p < 0.01; χ²  = 34.776, p < 0.01; χ²  = 62.523, p < 0.01; χ²  = 52.521, p < 0.01) in liver tissue. The high expression of NLRP3, GSDMD, caspase1, IL-1β, and IL-18 may be involved in the process of liver tissue inflammation and damage, which is positively correlated with liver tissue inflammation in patients with CHB.

The Impact of the NLRP3 Pathway in the Pathogenesis of Non-Alcoholic Fatty Liver Disease and Alcohol-Related Liver Disease

The presence of hepatic steatosis and inflammation is increasingly associated with both metabolic and alcohol-related liver conditions. Both are on the increase globally and, apart from liver transplantation, there are no licensed therapies that target the full complement of disease features. The presence of some shared pathogenic mechanisms and histological features in NAFLD and ALD suggests that it may be possible to develop markers for prognostication or staging, or indeed new therapeutic tools to treat both conditions. One such example of an approach exists in the form of the NACHT-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome pathway. Activation of the NLRP3 inflammasome results in hepatocyte pyroptosis, persistence, and amplification of liver inflammation and activation of profibrogenic signaling cascades. Thus, targeting elements of the pathway in NAFLD and ALD may provide a tractable route to pharmacological therapy. In this review, we summarize the contribution of this inflammasome to disease and review the current options for therapy.

Pathophysiology and Treatment Options for Hepatic Fibrosis: Can It Be Completely Cured?

Hepatic fibrosis is a dynamic process that occurs as a wound healing response against liver injury. During fibrosis, crosstalk between parenchymal and non-parenchymal cells, activation of different immune cells and signaling pathways, as well as a release of several inflammatory mediators take place, resulting in inflammation. Excessive inflammation drives hepatic stellate cell (HSC) activation, which then encounters various morphological and functional changes before transforming into proliferative and extracellular matrix (ECM)-producing myofibroblasts. Finally, enormous ECM accumulation interferes with hepatic function and leads to liver failure. To overcome this condition, several therapeutic approaches have been developed to inhibit inflammatory responses, HSC proliferation and activation. Preclinical studies also suggest several targets for the development of anti-fibrotic therapies; however, very few advanced to clinical trials. The pathophysiology of hepatic fibrosis is extremely complex and requires comprehensive understanding to identify effective therapeutic targets; therefore, in this review, we focus on the various cellular and molecular mechanisms associated with the pathophysiology of hepatic fibrosis and discuss potential strategies to control or reverse the fibrosis.

Inflammasome as an Effective Platform for Fibrosis Therapy

Fibrosis is the final stage of the development of chronic inflammation. It is characterized by excessive deposition of the extracellular matrix, leading to tissue structure damage and organ dysfunction, which is a serious threat to human health and life. However, the molecular mechanism of fibrosis is still unclear. Inflammasome is a molecular complex of proteins that has been becoming a key innate sensor for host immunity and is involved in pyroptosis, pathogen infection, metabolic syndrome, cellular stress, and tumor metastasis. Inflammasome signaling and downstream cytokine responses mediated by the inflammasome have been found to play an important role in fibrosis. The inflammasome regulates the secretion of IL-1β and IL-18, which are both critical for the process of fibrosis. Recently, researches on the function of inflammasome have attracted extensive attention, and data derived from these researches have increased our understanding of the effects and regulation of inflammasome during fibrosis. In this review, we emphasize the growing evidence for both indirect and direct effects of inflammasomes in triggering fibrosis as well as potential novel targets for antifibrotic therapies.

NLRP3 inflammasome priming and activation in cholestatic liver injury via the sphingosine 1-phosphate/S1P receptor 2/Gα(12/13)/MAPK signaling pathway

NLRP3 inflammasome-driven inflammation represents a key trigger for hepatic fibrogenesis during cholestatic liver injury. However, whether sphingosine 1-phosphate (S1P) plays a role in NLRP3 inflammasome priming and activation remains unknown. Here, we found that the expression of NLRP3 in macrophages and NLRP3 inflammasome activation were significantly elevated in the liver injured by bile duct ligation (BDL). In vitro, S1P promoted the NLRP3 inflammasome priming and activation via S1P receptor 2 (S1PR2) in bone marrow-derived monocyte/macrophages (BMMs). Focusing on BMMs, the gene silencing of Gα12 or Gα13 by specific siRNA suppressed NLRP3 inflammasome priming and pro-inflammatory cytokine (IL-1β and IL-18) secretion, whereas Gα(i/o) and Gαq were not involved in this process. The MAPK signaling pathways (P38, ERK, and JNK) mediated NLRP3 inflammasome priming and IL-1β and IL-18 secretion, whereas blockage of PI3K, ROCK, and Rho family had no such effect. Moreover, JTE-013 (S1PR2 inhibitor) treatment markedly reduced NLRP3 inflammasome priming and activation in BDL-injured liver. Collectively, S1P promotes NLRP3 inflammasome priming and pro-inflammatory cytokines (IL-1β and IL-18) secretion via the S1PR2/Gα(12/13)/MAPK pathway, which may represent an effective therapeutic strategy for liver disease. KEY MESSAGE: • Hepatic NLRP3 expression was significantly elevated in BMMs of BDL-injured mouse liver. • S1P promoted NLRP3 inflammasome priming and activation in BMMs, depending on the S1PR2/Gα(12/13)/MAPK pathway. • Blockade of S1PR2 by JTE-013 reduced NLRP3 inflammasome priming and activation inflammasome in vivo.

Long-Term Aspartame Administration Leads to Fibrosis, Inflammasome Activation, and Gluconeogenesis Impairment in the Liver of Mice

BACKGROUND

Aspartame is an artificial sweetener used in foods and beverages worldwide. However, it is linked to oxidative stress, inflammation, and liver damage through mechanisms that are not fully elucidated yet. This work aimed to investigate the effects of long-term administration of aspartame on the oxidative and inflammatory mechanisms associated with liver fibrosis progression in mice.

METHODS

Mice were divided into two groups with six animals each: control and aspartame. Aspartame (80 mg/kg, via oral) or vehicle was administrated for 12 weeks.

RESULTS

Aspartame caused liver damage and elevated serum transaminase levels. Aspartame also generated liver fibrosis, as evidenced by histology analysis, and pro-fibrotic markers' upregulation, including transforming growth factor β 1, collagen type I alpha 1, and alpha-smooth muscle actin. Furthermore, aspartame reduced nuclear factor erythroid 2-related factor 2 (Nrf2) activation and enzymatic antioxidant activity and increased lipid peroxidation, which triggered NOD-like receptor containing protein 3 (NLRP3) inflammasome activation and p53 induction. Furthermore, aspartame reduced peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) levels, possibly through p53 activation. This PGC-1α deficiency could be responsible for the changes in lipid profile in serum, total lipid accumulation, and gluconeogenesis impairment in liver, evidenced by the gluconeogenic enzymes' downregulation, thus causing hypoglycemia.

CONCLUSIONS

This work provides new insights to understand the mechanisms related to the adverse effects of aspartame on liver tissue.

Inhibition of heat shock protein 90 alleviates cholestatic liver injury by decreasing IL-1β and IL-18 expression

Severe cholestatic liver injury diseases, such as obstructive jaundice and the subsequent acute obstructive cholangitis, are induced by biliary tract occlusion. Heat shock protein 90 (HSP90) inhibitors have been demonstrated to be protective for various organs. The potential of HSP90 inhibitors in the treatment of cholestatic liver injury, however, remains unclear. In the present study, rat models of bile duct ligation (BDL) were established, the HSP90 inhibitor 17-dimethylamino-ethylamino-17-demethoxygeldanamycin (17-DMAG) was administered, and its ability to ameliorate the cholestasis-induced liver injuries was evaluated. In the BDL rat models and clinical samples, increased HSP90 expression was observed to be associated with cholestatic liver injury. Furthermore, 17-DMAG alleviated cholestasis-induced liver injury in the rat models, as revealed by the assessment of pathological changes and liver function. In addition, 17-DMAG protected hepatocytes against cholestatic injury in vitro. Further assays indicated that 17-DMAG administration prevented cholestasis-induced liver injury in the rats by decreasing the expression of interleukin (IL)-1β and IL-18. Moreover, 17-DMAG also decreased the cholestasis-induced upregulation of IL-1β and IL-18 in liver sinusoidal endothelial cells in vitro. In conclusion, the HSP90 inhibitor 17-DMAG is able to prevent liver injury in rats with biliary obstruction, and this phenomenon is associated with the reduction of IL-1β and IL-18 expression.

Secretoglobin 3A2 eliminates human cancer cells through pyroptosis

Non-canonical inflammasome activation that recognizes intracellular lipopolysaccharide (LPS) causes pyroptosis, the inflammatory death of innate immune cells. The role of pyroptosis in innate immune cells is to rapidly eliminate pathogen-infected cells and limit the replication niche in the host body. Whether this rapid cell elimination process of pyroptosis plays a role in elimination of cancer cells is largely unknown. Our earlier study demonstrated that a multi-functional secreted protein, secretoglobin (SCGB) 3A2, chaperones LPS to cytosol, and activates caspase-11 and the non-canonical inflammasome pathway, leading to pyroptosis. Here we show that SCGB3A2 exhibits marked anti-cancer activity against 5 out of 11 of human non-small cell lung cancer cell lines in mouse xenographs, while no effect was observed in 6 of 6 small cell lung cancer cell lines examined. All SCGB3A2-LPS-sensitive cells express syndecan 1 (SDC1), a SCGB3A2 cell surface receptor, and caspase-4 (CASP4), a critical component of the non-canonical inflammasome pathway. Two epithelial-derived colon cancer cell lines expressing SDC1 and CASP4 were also susceptible to SCGB3A2-LPS treatment. TCGA analysis revealed that lung adenocarcinoma patients with higher SCGB3A2 mRNA levels exhibited better survival. These data suggest that SCGB3A2 uses the machinery of pyroptosis for the elimination of human cancer cells via the non-canonical inflammasome pathway, and that SCGB3A2 may serve as a novel therapeutic to treat cancer, perhaps in combination with immuno and/or targeted therapies.

Liver Fibrosis in Non-alcoholic Fatty Liver Disease: From Liver Biopsy to Non-invasive Biomarkers in Diagnosis and Treatment

An increasing percentage of people have or are at risk to develop non-alcoholic fatty liver disease (NAFLD) worldwide. NAFLD comprises different stadia going from isolated steatosis to non-alcoholic steatohepatitis (NASH). NASH is a chronic state of liver inflammation that leads to the transformation of hepatic stellate cells to myofibroblasts. These cells produce extra-cellular matrix that results in liver fibrosis. In a normal situation, fibrogenesis is a wound healing process that preserves tissue integrity. However, sustained and progressive fibrosis can become pathogenic. This process takes many years and is often asymptomatic. Therefore, patients usually present themselves with end-stage liver disease e.g., liver cirrhosis, decompensated liver disease or even hepatocellular carcinoma. Fibrosis has also been identified as the most important predictor of prognosis in patients with NAFLD. Currently, only a minority of patients with liver fibrosis are identified to be at risk and hence referred for treatment. This is not only because the disease is largely asymptomatic, but also due to the fact that currently liver biopsy is still the golden standard for accurate detection of liver fibrosis. However, performing a liver biopsy harbors some risks and requires resources and expertise, hence is not applicable in every clinical setting and is unsuitable for screening. Consequently, different non-invasive diagnostic tools, mainly based on analysis of blood or other specimens or based on imaging have been developed or are in development. In this review, we will first give an overview of the pathogenic mechanisms of the evolution from isolated steatosis to fibrosis. This serves as the basis for the subsequent discussion of the current and future diagnostic biomarkers and anti-fibrotic drugs.

Sophocarpine attenuates septic liver injury through suppression of the NLRP3 inflammasome via autophagy-mediated degradation

Septic liver injury remains a challenge in sepsis treatment. Nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 3 (NLRP3) inflammasome activation has been suggested to be a major cause of hepatocyte cell death in liver diseases. However, insufficient research has been performed to explore the underlying mechanisms associated with this. In the present study, sophocarpine, a pharmaceutical monomer originally isolated from Sophora flavescens, was suggested to attenuate septic liver injury in a mouse cecal ligation and puncture (CLP) model. By utilizing western blotting, ELISA, H&E staining and immunohistochemistry, the results demonstrated that sophocarpine treatment reversed CLP-induced elevations in serum aspartate transaminase, alanine transaminase, interleukin (IL)-6 and IL-1β levels. Additionally, sophocarpine appeared to have suppressed the activation of the NLRP3 inflammasome, as indicated by observed reductions in liver IL-1β, NLRP3, caspase 1-p20 and gasdermin D-p30 protein levels. Further investigation suggested that sophocarpine-induced autophagy was essential for this suppression of NLRP3 inflammasome activation, the inhibition of which reversed the protective effects of sophocarpine on CLP-induced liver injury. Collectively, results from the present study suggested a protective role for sophocarpine against septic liver injury, where sophocarpine may suppress NLRP3 inflammasome activation by autophagy-mediated degradation.

The Emerging Relevance of AIM2 in Liver Disease

Absent in melanoma 2 (AIM2) is a cytosolic receptor that recognizes double-stranded DNA (dsDNA) and triggers the activation of the inflammasome cascade. Activation of the inflammasome results in the maturation of inflammatory cytokines, such as interleukin (IL)-1 β and IL-18, and a form of cell death known as pyroptosis. Owing to the conserved nature of its ligand, AIM2 is important during immune recognition of multiple pathogens. Additionally, AIM2 is also capable of recognizing host DNA during cellular damage or stress, thereby contributing to sterile inflammatory diseases. Inflammation, either in response to pathogens or due to sterile cellular damage, is at the center of the most prevalent and life-threatening liver diseases. Therefore, during the last 15 years, the study of inflammasome activation in the liver has emerged as a new research area in hepatology. Here, we discuss the known functions of AIM2 in the pathogenesis of different hepatic diseases, including non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), hepatitis B, liver fibrosis, and hepatocellular carcinoma (HCC).