NLRP3 inflammasome activation from Kupffer cells is involved in liver fibrosis of Schistosoma japonicum-infected mice via NF-κB

Endogenous innate sensor NLRP3 is a key component in peritoneal macrophage dynamics required for cestode establishment

The NLRP3 receptor can assemble inflammasome platforms to trigger inflammatory responses; however, accumulating evidence suggests that it can also display anti-inflammatory properties. Here, we explored the role of nucleotide-binding oligomerization domain pyrin-containing protein 3 (NLRP3) in Taenia crassiceps experimental infection, which requires immune polarization into a Th2-type profile and peritoneal influx of suppressive macrophages for successful colonization. NLRP3 deficient mice (NLRP3-/-) were highly resistant against T. crassiceps, relative to wild-type (WT) mice. Resistance in NLRP3-/- mice was associated with a diminished IL-4 output, high levels of IL-15, growth factor for both innate and adaptive lymphocytes, and a dramatic decrease in peritoneum-infiltrating suppressive macrophages. Also, a transcriptional analysis on bone marrow-derived macrophages exposed to Taenia-secreted antigens and IL-4 revealed that NLRP3-/- macrophages express reduced transcripts of relm-α and PD-1 ligands, markers of alternative activation and suppressive ability, respectively. Finally, we found that the resistance displayed by NLRP3-/- mice is transferred through intestinal microbiota exchange, since WT mice co-housed with NLRP3-/- mice were significantly more resistant than WT animals preserving their native microbiota. Altogether, these data demonstrate that NLRP3 is a component of innate immunity required for T. crassiceps to establish, most likely contributing to macrophage recruitment, and controlling lymphocyte-stimulating cytokines such as IL-15.

mmu-miR-374b-5p modulated inflammatory factors via downregulation of C/EBP β/NF-κB signaling in Kupffer cells during Echinococcus multilocularis infection

BACKGROUND

Alveolar echinococcosis (AE) is an important infectious disease caused by the metacestode larvae of Echinococcus multilocularis, seriously threatening global public health security. Kupffer cells (KCs) play important roles in liver inflammatory response. However, their role in hepatic alveolar echinococcosis has not yet been fully elucidated.

METHODS

In this study, qRT-PCR was used to detect the expression level of miR-374b-5p in KCs. The target gene of miR-374b-5p was identified through luciferase reporter assays and loss of function and gains. Critical genes involved in NFκB signaling pathway were analyzed by qRT-PCR and western blot.

RESULTS

This study reported that miR-374b-5p was significantly upregulated in KCs during E. multilocularis infection and further showed that miR-374b-5p was able to bind to the 3'-UTR of the C/EBP β gene and suppressed its expression. The expression levels of NF-κBp65, p-NF-κBp65 and pro-inflammatory factors including iNOS, TNFα and IL6 were attenuated after overexpression of miR-374b-5p while enhanced after suppression of miR-374b-5p. However, the Arg1 expression level was promoted after overexpression of miR-374b-5p while suppressed after downregulation of miR-374b-5p. Additionally, increased protein levels of NF-κBp65 and p-NF-κBp65 were found in the C/EBP β-overexpressed KCs.

CONCLUSIONS

These results demonstrated that miR-374b-5p probably regulated the expression of inflammatory factors via C/EBP β/NF-κB signaling. This finding is helpful to explore the mechanism of inflammation regulation during E. multilocularis infection.

The Effect of Heat-Killed Lactobacillus plantarum on Oxidative Stress and Liver Damage in Rats with Bile Duct Ligation-Induced Hepatic Fibrosis

This study is aimed at evaluating the effects of heat-killed Lactobacillus plantarum (L. plantarum) on cholestatic liver injury induced by bile duct ligation (BDL) in rats. Rats in the first group were healthy (normal control) and in the second group underwent abdominal incision (sham control). Rats in the third and fourth groups underwent common bile duct ligation and were treated with either oral distilled water (BDL control group) or heat-killed L. plantarum (BDL + L. plantarum) for 28 days. Finally, rats were sacrificed, blood samples were analyzed through biochemical methods, liver and ileum tissue tissues were histologically assessed, and the expression of the αSMA, TNF-α, IL-6, and IL-10 genes in the liver and ZO-1 gene in ileum tissues were assessed through real-time PCR. The levels of bilirubin, liver function enzymes, NO, MDA, and carbonyl protein in the BDL + L. plantarum group were significantly lower than in the BDL control group (P ≤ 0.05). SOD and CAT activity in BDL + L. plantarum group was significantly greater than the BDL control group 1.4 and 3.0 times, respectively (P ≤ 0.001). Moreover, in the BDL + L. plantarum group, the expression of the α-SMA, TNF-α, and IL-6 genes was significantly lower (3.1, 2.9, and 2.5 times), and IL-10 and ZO-1 genes were significantly greater than the BDL control group by 2.1 and 3.6 times, respectively (P ≤ 0.05). The histological assessment also confirmed the greater effectiveness of heat-killed L. plantarum in improving the morphology and parenchymal structure of the liver. Taken together, our results suggest that heat-killed L. plantarum strains are potential therapeutic agents for hepatic fibrosis.

Auranofin attenuates Schistosoma mansoni egg-induced liver granuloma and fibrosis in mice

Schistosomiasis is a serious tropical disease. Despite extensive research into the etiology of liver fibrosis, effective therapeutic options remain limited. This study aims to assess the effectiveness of auranofin in treating hepatic granuloma and fibrogenesis produced by Schistosoma (S.) mansoni eggs. Auranofin is a gold complex that contains thioglucose tetraacetate and triethylphosphine. Eighty BALB/c male mice were divided into four groups (n=20/group): negative control (GI), positive control (GII), and early (GIII) and late (GIV) treatment groups with oral auranofin according to beginning of treatment 4th week and 6th week post-infection. Mice were infected subcutaneously in a dose of 60±10 cercariae/mouse. Worm counts, egg loads, and oogram patterns were determined. Biochemical, histological, and immunostaining of interleukin-1β (IL-1β), Sirtuin 3 (SIRT3), and smooth muscle actin (SMA) were assessed. GIII showed a significant decrease in the total S. mansoni worm burden and ova/gram in liver tissue (with reduction percent of 63.07% and 78.26%, respectively). Schistosomal oogram patterns, immature and mature ova, also showed a significant decrease. The reduction in granuloma number and size was 40.63% and 48.66%, respectively, in GIII, whereas in GIV, the reduction percent was 76.63% and 67.08%. In addition, the degree of fibrosis was significantly diminished in both treated groups. GIV showed significant reduction in IL-1β and SMA expression and increase in SIRT3 expression. These findings reveal how auranofin suppresses the development of liver fibrosis. Therefore, it is crucial to take another look at auranofin as a prospective medication for the treatment of S. mansoni egg-induced hepatic granuloma and consequent fibrosis.

Axitinib attenuates the progression of liver fibrosis by restoring mitochondrial function

Liver fibrosis can progress to cirrhosis and hepatocellular carcinoma, which may eventually lead to liver failure and even death. No direct anti-fibrosis drugs are available at present. Axitinib is a new generation of potent multitarget tyrosine kinase receptor inhibitors, but its role in liver fibrosis remains unclear. In this study, a CCl4-induced hepatic fibrosis mouse model and a TGF-β1-induced hepatic stellate cell model were used to explore the effect and mechanism of axitinib on hepatic fibrosis. Results confirmed that axitinib could alleviate the pathological damage of liver tissue induced by CCl4 and inhibit the production of glutamic-oxalacetic transaminase and glutamic-pyruvic transaminase. It also inhibited collagen and hydroxyproline deposition and the protein expression of Col-1 and α-SMA in CCl4-induced liver fibrosis. In addition, axitinib inhibited the expression of CTGF and α-SMA in TGF-β1-induced hepatic stellate cells. Further studies showed that axitinib inhibited mitochondrial damage and reduced oxidative stress and NLRP3 maturation. The use of rotenone and antimycin A confirmed that axitinib could restore the activity of mitochondrial complexes I and III, thereby inhibiting the maturation of NLRP3. In summary, axitinib inhibits the activation of HSCs by enhancing the activity of mitochondrial complexes I and III, thereby alleviating the progression of liver fibrosis. This study reveals the strong potential of axitinib in the treatment of liver fibrosis.

Pannexin1 channels in the liver: an open enemy

Pannexin1 proteins form communication channels at the cell plasma membrane surface, which allow the transfer of small molecules and ions between the intracellular compartment and extracellular environment. In this way, pannexin1 channels play an important role in various cellular processes and diseases. Indeed, a plethora of human pathologies is associated with the activation of pannexin1 channels. The present paper reviews and summarizes the structure, life cycle, regulation and (patho)physiological roles of pannexin1 channels, with a particular focus on the relevance of pannexin1 channels in liver diseases.

MicroRNA-29a-3p prevents Schistosoma japonicum-induced liver fibrosis by targeting Roundabout homolog 1 in hepatic stellate cells

BACKGROUND

Schistosomiasis is a serious but neglected parasitic disease in humans that may lead to liver fibrosis and death. Activated hepatic stellate cells (HSCs) are the principal effectors that promote the accumulation of extracellular matrix (ECM) proteins during hepatic fibrosis. Aberrant microRNA-29 expression is involved in the development of fibrotic diseases. However, less is known about the role of miR-29 in Schistosoma japonicum (S. japonicum)-induced hepatic fibrosis.

METHODS

The levels of microRNA-29a-3p (miR-29a-3p) and Roundabout homolog 1 (Robo1) were examined in liver tissues during S. japonicum infection. The possible involvement of the miR-29a-3p-Robo1 signaling pathway was determined. We used MIR29A conditional knock-in mice and mice injected with an miR-29a-3p agomir to investigate the role of miR-29a-3p in schistosomiasis-induced hepatic fibrosis. The functional contributions of miR-29a-3p-Robo1 signaling in liver fibrosis and HSC activation were investigated using primary mouse HSCs and the human HSC cell line LX-2.

RESULTS

MiR-29a-3p was downregulated in humans and mice with schistosome-induced fibrosis, and Robo1 was upregulated in liver tissues. The miR-29a-3p targeted Robo1 and negatively regulated its expression. Additionally, the expression level of miR-29a-3p in schistosomiasis patients was highly correlated with the portal vein and spleen thickness diameter, which represent the severity of fibrosis. Furthermore, we demonstrated that efficient and sustained elevation of miR-29a-3p reversed schistosome-induced hepatic fibrosis. Notably, we showed that miR-29a-3p targeted Robo1 in HSCs to prevent the activation of HSCs during infection.

CONCLUSIONS

Our results provide experimental and clinical evidence that the miR-29a-3p-Robo1 signaling pathway in HSCs plays an important role in the development of hepatic fibrosis. Therefore, our study highlights the potential of miR-29a-3p as a therapeutic intervention for schistosomiasis and other fibrotic diseases.

Autophagy in hepatic macrophages can be regulator and potential therapeutic target of liver diseases: A review

Hepatic macrophages are a complex population of cells that play an important role in the normal functioning of the liver and in liver diseases. Autophagy, as a maintainer of cellular homeostasis, is closely connected to many liver diseases. And its roles are not always beneficial, but manifesting as a double-edged sword. The polarization of macrophages and the activation of inflammasomes are mediated by intracellular and extracellular signals, respectively, and are important ways for macrophages to take part in a variety of liver diseases. More attention should be paid to autophagy of hepatic macrophages in liver diseases. In this review, we focus on the regulatory role of hepatic macrophages' autophagy in a variety of liver diseases; especially on the upstream regulator of polarization and inflammasomes activation of the hepatic macrophages. We believe that the autophagy of hepatic macrophages can become a potential therapeutic target for management of liver diseases.

Effect and mechanism of reactive oxygen species-mediated NOD-like receptor family pyrin domain-containing 3 inflammasome activation in hepatic alveolar echinococcosis

BACKGROUND

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a significant component of the innate immune system that plays a vital role in the development of various parasitic diseases. However, its role in hepatic alveolar echinococcosis (HAE) remains unclear.

AIM

To investigate the NLRP3 inflammasome and its mechanism of activation in HAE.

METHODS

We assessed the expression of NLRP3, caspase-1, interleukin (IL)-1β, and IL-18 in the marginal zone and corresponding normal liver of 60 patients with HAE. A rat model of HAE was employed to investigate the role of the NLRP3 inflammasome in the marginal zone of HAE. Transwell experiments were conducted to investigate the effect of Echinococcus multilocularis (E. multilocularis) in stimulating Kupffer cells and hepatocytes. Furthermore, immunohistochemistry, Western blotting, and enzyme-linked immunosorbent assay were used to evaluate NLRP3, caspase-1, IL-1β, and IL-18 expression; flow cytometry was used to detect apoptosis and reactive oxygen species (ROS).

RESULTS

NLRP3 inflammasome activation was significantly associated with ROS. Inhibition of ROS production decreased NLRP3-caspase-1-IL-1β pathway activation and mitigated hepatocyte damage and inflammation.

CONCLUSION

E. multilocularis induces hepatocyte damage and inflammation by activating the ROS-mediated NLRP3-caspase-1-IL-1β pathway in Kupffer cells, indicating that ROS may serve as a potential target for the treatment of HAE.

The balance between gasdermin D and STING signaling shapes the severity of schistosome immunopathology

There is significant disease heterogeneity among mouse strains infected with the helminth Schistosoma mansoni. Here, we uncover a unique balance in two critical innate pathways governing the severity of disease. In the low-pathology setting, parasite egg-stimulated dendritic cells (DCs) induce robust interferon (IFN)β production, which is dependent on the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) cytosolic DNA sensing pathway and results in a Th2 response with suppression of proinflammatory cytokine production and Th17 cell activation. IFNβ induces signal transducer and activator of transcription (STAT)1, which suppresses CD209a, a C-type lectin receptor associated with severe disease. In contrast, in the high-pathology setting, enhanced DC expression of the pore-forming protein gasdermin D (Gsdmd) results in reduced expression of cGAS/STING, impaired IFNβ, and enhanced pyroptosis. Our findings demonstrate that cGAS/STING signaling represents a unique mechanism inducing protective type I IFN, which is counteracted by Gsdmd.

Insights on drug and gene delivery systems in liver fibrosis

Complications of the liver are amongst the world's worst diseases. Liver fibrosis is the first stage of liver problems, while cirrhosis is the last stage, which can lead to death. The creation of effective anti-fibrotic drug delivery methods appears critical due to the liver's metabolic capacity for drugs and the presence of insurmountable physiological impediments in the way of targeting. Recent breakthroughs in anti-fibrotic agents have substantially assisted in fibrosis; nevertheless, the working mechanism of anti-fibrotic medications is not fully understood, and there is a need to design delivery systems that are well-understood and can aid in cirrhosis. Nanotechnology-based delivery systems are regarded to be effective but they have not been adequately researched for liver delivery. As a result, the capability of nanoparticles in hepatic delivery was explored. Another approach is targeted drug delivery, which can considerably improve efficacy if delivery systems are designed to target hepatic stellate cells (HSCs). We have addressed numerous delivery strategies that target HSCs, which can eventually aid in fibrosis. Recently genetics have proved to be useful, and methods for delivering genetic material to the target place have also been investigated where different techniques are depicted. To summarize, this review paper sheds light on the most recent breakthroughs in drug and gene-based nano and targeted delivery systems that have lately shown useful for the treatment of liver fibrosis and cirrhosis.

Quercetin potentiates the hepatoprotective effect of sildenafil and/or pentoxifylline against intrahepatic cholestasis: Role of Nrf2/ARE, TLR4/NF-κB, and NLRP3/IL-1β signaling pathways

AIM

Intrahepatic cholestasis is a common pathological condition of several types of liver disorders. In this study, we aimed to investigate the regulatory effects of quercetin (QU) on selected phosphodiesterase inhibitors against alpha-naphthyl isothiocyanate (ANIT)-induced acute intrahepatic cholestasis.

METHODS

Cholestasis was induced in Wistar albino rats by ANIT as a single dose (60 mg/kg; P·O.). QU (50 mg/kg, daily, P·O.), sildenafil (Sild; 10 mg/kg, twice daily, P·O.), and pentoxifylline (PTX; 50 mg/kg, daily, P.O.) were evaluated either alone or in combinations for 10 days for their antioxidant, anti-inflammatory, and anti-pyroptotic effects.

RESULTS

ANIT produced a prominent intrahepatic cholestasis as evidenced by a significant alteration in liver functions, histological structure, inflammatory response, and oxidative stress biomarkers. Furthermore, up-regulation of NF-κB-p65, TLR4, NLRP3, cleaved caspase-1, IKK-β, and IL-1β concurrently with down-regulation of Nrf-2, HO-1, and PPAR-γ expressions were observed after ANIT. QU, Sild, or PTX treatment significantly alleviated the disturbance induced by ANIT. These findings were further supported by the improvement in histopathological features. Additionally, co-administration of QU with Sild or PTX significantly improved liver defects due to ANIT as compared to the individual drugs.

SIGNIFICANCE

Combined QU with Sild or PTX exhibited promising hepatoprotective effects and anti-cholestatic properties through modulation of Nrf2/ARE, TLR4/NF- κB, and NLRP3/IL-1β signaling pathways.

Parasitological and histopathological studies to the effect of aqueous extract of Moringa oleifera Lam. leaves combined with praziquantel therapy in modulating the liver and spleen damage induced by Schistosoma mansoni to male mice

This study assessed the effectiveness of an aqueous extract of Moringa Oleifera Lam. leaves (MOL) alone or in combination with praziquantel (PZQ) drug targeting-infected mice with Schistosoma mansoni-induced liver and spleen damage. Mice were divided into eight groups control mice group treated orally with saline. PZQ group: non-infected mice treated orally with 300 mg/kg bwt PZQ three consecutive days. MOL group: non-infected mice treated orally with 150 mg/kg bwt MOL extract for 15 days. PZQ/ MOL group: non-infected mice treated orally with 300 mg/kg bwt PZQ for three consecutive days and 150 mg/kg bwt MOL extract for 15 days. IF group: infected mice with 100 cercariae/mouse of the Egyptian strain of S. mansoni. IF/PZQ group infected mice with S. mansoni cercariae and treated orally with 300 mg/kg bwt PZQ for three consecutive days. IF/MOL group: infected mice with S. mansoni cercariae treated orally with 150 mg/kg bwt MOL extract for 15 days. IF/PZQ +MOL group: infected mice with S. mansoni cercariae treated orally with 300 mg/kg bwt PZQ for three consecutive days and 150 mg/kg bwt MOL extract for 15 days. Blood, liver, spleen, worm, and eggs were collected at the end of the experimental period. Treatment of infected mice with MOL and PZQ together significantly reduced the number of ova/g tissue and eliminated the parasites. In addition, the liver and spleen of infected mice showed less histopathological alteration and immunohistochemical expression of nuclear factor kappa β (NF-Kβ). We can conclude that MOL extract combined with PZ has a curative effect on S. mansoni infection and helped to lessen its pathological effects.

microRNAs: Critical Players during Helminth Infections

microRNAs (miRNAs) are a group of small non-coding RNAs that regulate gene expression post-transcriptionally through their interaction with the 3' untranslated regions (3' UTR) of target mRNAs, affecting their stability and/or translation. Therefore, miRNAs regulate biological processes such as signal transduction, cell death, autophagy, metabolism, development, cellular proliferation, and differentiation. Dysregulated expression of microRNAs is associated with infectious diseases, where miRNAs modulate important aspects of the parasite-host interaction. Helminths are parasitic worms that cause various neglected tropical diseases affecting millions worldwide. These parasites have sophisticated mechanisms that give them a surprising immunomodulatory capacity favoring parasite persistence and establishment of infection. In this review, we analyze miRNAs in infections caused by helminths, emphasizing their role in immune regulation and its implication in diagnosis, prognosis, and the development of therapeutic strategies.

Emerging Role of NLRP3 Inflammasome and Pyroptosis in Liver Transplantation

The nucleotide-binding domain leucine-rich repeat-receptor, pyrin domain-containing-3 (NLRP3) inflammasome contributes to the inflammatory response by activating caspase-1, which in turn participates in the maturation of interleukin (IL)-1β and IL-18, which are mainly secreted via pyroptosis. Pyroptosis is a lytic type of cell death that is controlled by caspase-1 processing gasdermin D. The amino-terminal fragment of gasdermin D inserts into the plasma membrane, creating stable pores and enabling the release of several proinflammatory factors. The activation of NLRP3 inflammasome and pyroptosis has been involved in the progression of liver fibrosis and its end-stage cirrhosis, which is among the main etiologies for liver transplantation (LT). Moreover, the NLRP3 inflammasome is involved in ischemia-reperfusion injury and early inflammation and rejection after LT. In this review, we summarize the recent literature addressing the role of the NLRP3 inflammasome and pyroptosis in all stages involved in LT and argue the potential targeting of this pathway as a future therapeutic strategy to improve LT outcomes. Likewise, we also discuss the impact of graft quality influenced by donation after circulatory death and the expected role of machine perfusion technology to modify the injury response related to inflammasome activation.

Significance of elevated serum and hepatic NOD-like receptor pyrin domain containing 3 (NLRP3) in hepatitis C virus-related liver disease

NOD-like receptor pyrin domain containing 3 (NLRP3) is a microbial and danger signal sensor that acts as a regulator of inflammation via activation of Caspase-1 (CASP1) and has been identified as a major contributor to human liver diseases. The present study was conducted to investigate the association between NLRP3 and the progression of hepatitis C virus (HCV)-related liver disease. Serum NLRP3 levels were analyzed in 49 patients with chronic HCV infection and 18 healthy controls and liver tissues from 34 patients were examined to assess the protein expression of NLRP3 and its activation marker CASP1 using immunohistochemical staining. The results showed that the median serum NLRP3 levels was significantly higher in HCV-infected patients compared with healthy controls (1040 pg/ml vs 695 pg/ml respectively, P < 0.001) and were positively correlated with hepatic NLRP3 and CASP1 expression (r = 0.749, P < 0.001 and r = 0.557, P = 0.001 respectively). The NLRP3 levels in serum and the liver significantly increased with worsening liver pathology and showed positive correlations with serum aminotransferases levels, HCV viremia, and albumin-bilirubin score (P < 0.05). The receiver operating characteristic curve analysis revealed a high diagnostic performance of serum NLRP3 in determining the extent of liver necroinflammation, fibrosis, and steatosis (area under the curve = 0.951, 0.971, and 0.917 respectively, P < 0.001). In conclusion, NLRP3 plays an important role in liver disease progression during HCV infection via CASP1 activation and might be a promising therapeutic target. Serum NLRP3 could be an additional biomarker for liver inflammation and fibrosis.

Pathology and molecular mechanisms of Schistosoma japonicum-associated liver fibrosis

Schistosomiasis has been widely disseminated around the world, and poses a significant threat to human health. Schistosoma eggs and soluble egg antigen (SEA) mediated inflammatory responses promote the formation of egg granulomas and liver fibrosis. With continuous liver injuries and inflammatory stimulation, liver fibrosis can develop into liver cirrhosis and liver cancer. Therefore, anti-fibrotic therapy is crucial to increase the survival rate of patients. However, current research on antifibrotic treatments for schistosomiasis requires further exploration. In the complicated microenvironment of schistosome infections, it is important to understand the mechanism and pathology of schistosomiasis-associated liver fibrosis(SSLF). In this review, we discuss the role of SEA in inhibiting liver fibrosis, describe its mechanism, and comprehensively explore the role of host-derived and schistosome-derived microRNAs (miRNAs) in SSLF. Inflammasomes and cytokines are significant factors in promoting SSLF, and we discuss the mechanisms of some critical inflammatory signals and pro-fibrotic cytokines. Natural killer(NK) cells and Natural killer T(NKT) cells can inhibit SSLF but are rarely described, therefore, we highlight their significance. This summarizes and provides insights into the mechanisms of key molecules involved in SSLF development.

NLRP3 inflammasome in digestive diseases: From mechanism to therapy

Digestive system diseases remain a formidable challenge to human health. NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is the most characteristic multimeric protein complex and is involved in a wide range of digestive diseases as intracellular innate immune sensors. It has emerged as a research hotspot in recent years. In this context, we provide a comprehensive review of NLRP3 inflammasome priming and activation in the pathogenesis of digestive diseases, including clinical and preclinical studies. Moreover, the scientific evidence of small-molecule chemical drugs, biologics, and phytochemicals, which acts on different steps of the NLRP3 inflammasome, is reviewed. Above all, deep interrogation of the NLRP3 inflammasome is a better insight of the pathomechanism of digestive diseases. We believe that the NLRP3 inflammasome will hold promise as a novel valuable target and research direction for treating digestive disorders.

Pattern recognition receptor signaling and innate immune responses to schistosome infection

Schistosomiasis remains to be a significant public health problem in tropical and subtropical regions. Despite remarkable progress that has been made in the control of the disease over the past decades, its elimination remains a daunting challenge in many countries. This disease is an inflammatory response-driven, and the positive outcome after infection depends on the regulation of immune responses that efficiently clear worms and allow protective immunity to develop. The innate immune responses play a critical role in host defense against schistosome infection and pathogenesis. Initial pro-inflammatory responses are essential for clearing invading parasites by promoting appropriate cell-mediated and humoral immunity. However, elevated and prolonged inflammatory responses against the eggs trapped in the host tissues contribute to disease progression. A better understanding of the molecular mechanisms of innate immune responses is important for developing effective therapies and vaccines. Here, we update the recent advances in the definitive host innate immune response to schistosome infection, especially highlighting the critical roles of pattern recognition receptors and cytokines. The considerations for further research are also provided.

Cell-specific Deletion of NLRP3 Inflammasome Identifies Myeloid Cells as Key Drivers of Liver Inflammation and Fibrosis in Murine Steatohepatitis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide. The NLRP3 inflammasome, a platform for caspase-1 activation and release of interleukin 1β, is increasingly recognized in the induction of inflammation and liver fibrosis during NAFLD. However, the cell-specific contribution of NLRP3 inflammasome activation in NAFLD remains unknown.

METHODS

To investigate the role of NLRP3 inflammasome activation in hepatocytes, hepatic stellate cells (HSCs) and myeloid cells, a conditional Nlrp3 knock-out mouse was generated and bred to cell-specific Cre mice. Both acute and chronic liver injury models were used: lipopolysaccharide/adenosine-triphosphate to induce in vivo NLRP3 activation, choline-deficient, L-amino acid-defined high-fat diet, and Western-type diet to induce fibrotic nonalcoholic steatohepatitis (NASH). In vitro co-culture studies were performed to dissect the crosstalk between myeloid cells and HSCs.

RESULTS

Myeloid-specific deletion of Nlrp3 blunted the systemic and hepatic increase in interleukin 1β induced by lipopolysaccharide/adenosine-triphosphate injection. In the choline-deficient, L-amino acid-defined high-fat diet model of fibrotic NASH, myeloid-specific Nlrp3 knock-out but not hepatocyte- or HSC-specific knock-out mice showed significant reduction in inflammation independent of steatosis development. Moreover, myeloid-specific Nlrp3 knock-out mice showed ameliorated liver fibrosis and decreased HSC activation. These results were validated in the Western-type diet model. In vitro co-cultured studies with human cell lines demonstrated that HSC can be activated by inflammasome stimulation in monocytes, and this effect was significantly reduced if NLRP3 was downregulated in monocytes.

CONCLUSIONS

The study provides new insights in the cell-specific role of NLRP3 in liver inflammation and fibrosis. NLRP3 inflammasome activation in myeloid cells was identified as crucial for the progression of NAFLD to fibrotic NASH. These results may have implications for the development of cell-specific strategies for modulation of NLRP3 activation for treatment of fibrotic NASH.

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.

NLRP3 and pyroptosis blockers for treating inflammatory diseases

The nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome has emerged as a key mediator of pathological inflammation in many diseases and is an exciting drug target. Here, we review the molecular basis of NLRP3 inhibition by drug-like small molecules under development as novel therapeutics. We also summarize recent strategies to block pyroptosis as a novel approach to suppress chronic inflammation. Major recent developments in this area include the elucidation of mechanisms of action (MoAs) by which small molecules block NLRP3 inflammasome assembly and gasdermin D (GSDMD)-induced pyroptosis. We also discuss the status of clinical trials using agents that block specific components of the NLRP3 pathway, including their potential clinical applications for the treatment of many diseases.

The Mechanism and Regulation of the NLRP3 Inflammasome during Fibrosis

Fibrosis is often the end result of chronic inflammation. It is characterized by the excessive deposition of extracellular matrix. This leads to structural alterations in the tissue, causing permanent damage and organ dysfunction. Depending on the organ it effects, fibrosis can be a serious threat to human life. The molecular mechanism of fibrosis is still not fully understood, but the NLRP3 (NOD-, LRR- and pyrin–domain–containing protein 3) inflammasome appears to play a significant role in the pathogenesis of fibrotic disease. The NLRP3 inflammasome has been the most extensively studied inflammatory pathway to date. It is a crucial component of the innate immune system, and its activation mediates the secretion of interleukin (IL)-1β and IL-18. NLRP3 activation has been strongly linked with fibrosis and drives the differentiation of fibroblasts into myofibroblasts by the chronic upregulation of IL-1β and IL-18 and subsequent autocrine signaling that maintains an activated inflammasome. Both IL-1β and IL-18 are profibrotic, however IL-1β can have antifibrotic capabilities. NLRP3 responds to a plethora of different signals that have a common but unidentified unifying trigger. Even after 20 years of extensive investigation, regulation of the NLRP3 inflammasome is still not completely understood. However, what is known about NLRP3 is that its regulation and activation is complex and not only driven by various activators but controlled by numerous post-translational modifications. More recently, there has been an intensive attempt to discover NLRP3 inhibitors to treat chronic diseases. This review addresses the role of the NLRP3 inflammasome in fibrotic disorders across many different tissues. It discusses the relationships of various NLRP3 activators to fibrosis and covers different therapeutics that have been developed, or are currently in development, that directly target NLRP3 or its downstream products as treatments for fibrotic disorders.

Emerging Role of Nuclear Receptors for the Treatment of NAFLD and NASH

Non-alcoholic fatty liver (NAFLD) over the past years has become a metabolic pandemic linked to a collection of metabolic diseases. The nuclear receptors ERRs, REV-ERBs, RORs, FXR, PPARs, and LXR are master regulators of metabolism and liver physiology. The characterization of these nuclear receptors and their biology has promoted the development of synthetic ligands. The possibility of targeting these receptors to treat NAFLD is promising, as several compounds including Cilofexor, thiazolidinediones, and Saroglitazar are currently undergoing clinical trials. This review focuses on the latest development of the pharmacology of these metabolic nuclear receptors and how they may be utilized to treat NAFLD and subsequent comorbidities.

The Crucial Role of NLRP3 Inflammasome in Viral Infection-Associated Fibrosing Interstitial Lung Diseases

Idiopathic pulmonary fibrosis (IPF), one of the most common fibrosing interstitial lung diseases (ILD), is a chronic-age-related respiratory disease that rises from repeated micro-injury of the alveolar epithelium. Environmental influences, intrinsic factors, genetic and epigenetic risk factors that lead to chronic inflammation might be implicated in the development of IPF. The exact triggers that initiate the fibrotic response in IPF remain enigmatic, but there is now increasing evidence supporting the role of chronic exposure of viral infection. During viral infection, activation of the NLRP3 inflammasome by integrating multiple cellular and molecular signaling implicates robust inflammation, fibroblast proliferation, activation of myofibroblast, matrix deposition, and aberrant epithelial-mesenchymal function. Overall, the crosstalk of the NLRP3 inflammasome and viruses can activate immune responses and inflammasome-associated molecules in the development, progression, and exacerbation of IPF.

The NLRP3 inflammasome mediates liver failure by activating procaspase-1 and pro-IL-1 β and regulating downstream CD40-CD40L signaling

Objectives

In this prospective case–control study, we explored the regulatory roles of the NLRP3 inflammasome in hepatitis B virus-associated acute-on-chronic liver failure (HBV-ACLF).

Methods

Thirty patients with HBV-ACLF, 30 patients with chronic hepatitis B, and 30 healthy individuals were enrolled. Real-time reverse transcription polymerase chain reaction was used to assess mRNA levels in peripheral blood mononuclear cells and serum protein levels were assessed by enzyme-linked immunosorbent assay.

Results

Serum levels of alanine aminotransferase, asparagine aminotransferase, total bilirubin, and direct bilirubin in patients with HBV-ACLF were increased. Transcript levels of NLRP3 and ASC and protein levels of interleukin (IL)-1β, IL-18, and sCD40L were elevated in patients with HBV-ACLF. Expression of the NLRP3 inflammasome signaling pathway components procaspase-1 and pro-IL-1β was elevated in patients with HBV-ACLF.

Conclusions

This prospective case-control study demonstrated that significant activation of the NLRP3 inflammasome occurs in patients with HBV-ACLF. The activated NLRP3 inflammasome mediated liver failure by stimulating procaspase-1 and pro-IL-1 β and regulating downstream CD40-CD40L signaling.

Atorvastatin inhibited TNF-α induced matrix degradation in rat nucleus pulposus cells by suppressing NLRP3 inflammasome activity and inducing autophagy through NF-κB signaling

Intervertebral disc degeneration (IDD) is one of the main causes of lower back pain (LBP). It results from an imbalance between the degradation and synthesis of extracellular matrix (ECM) components in nucleus pulposus (NP) cells. Atorvastatin, an HMG-CoA reductase inhibitor, plays a vital role in many diseases, such as cardiovascular disease and osteoarthritis. However, the effect of atorvastatin on IDD is unclear. Herein, we demonstrated that atorvastatin affects matrix degradation induced by TNF-α and demonstrated the mechanism by which TNF-α modulates matrix metabolism in rat NP cells. Real-time PCR, western blotting and immunofluorescence staining were performed to detect the mRNA and protein expression of related genes. mRFP-GFP-LC3 adenovirus plasmid transfection and transmission electron microscopy (TEM) were used to detect cell autophagy. NLRP3 inhibitor and lentiviral vectors containing shRNA-NLRP3 were used to show the effect of NLRP3 on autophagic flux and the NF-κB signaling pathway. The results revealed that atorvastatin might suppress matrix degradation induced by TNF-α by suppressing NLRP3 inflammasome activity and inducing autophagic flux. Moreover, atorvastatin suppressed NF-κB signaling induced by TNF-α. NF-κB signaling inhibition suppressed NLRP3 inflammasome activity, and NLRP3 inhibition suppressed NF-κB signaling activation induced by TNF-α. NLRP3 inhibition or NLRP3 knockdown induced autophagic flux in the presence of TNF-α. Overall, the present study demonstrated that atorvastatin might suppress matrix degradation induced by TNF-α and further revealed the crosstalk among NLRP3 inflammasome activity, autophagy and NF-κB signaling.

Inflammation suppression in doxorubicin-induced cardiotoxicity: natural compounds as therapeutic options

Doxorubicin (DOX) is a potent chemotherapeutic agent; however, the accompanying cardiotoxicity is a significant complication of the usefulness of treatment with DOX. Multiple mechanisms have been suggested for this often fatal side effect, one of which is inflammation. Several pathways with different targets have been reported to result in DOX-induced heart inflammation. Some natural occurring compounds (NCs) have been reported to interact with the DOX-induced cardiotoxicity through targeting one or more of several pathways, including the Nrf2/NF-kB, TLR-4/NF-kB, MAPK/NF-kB, and NLRP3 inflammasome pathways. This article reviews several of these pathways and the potential protective effect of some NCs against the cardiac inflammation induced by DOX.

Alpinetin exerts anti-inflammatory, anti-oxidative and anti-angiogenic effects through activating the Nrf2 pathway and inhibiting NLRP3 pathway in carbon tetrachloride-induced liver fibrosis

Alpinetin is the major active ingredient of Alpiniakatsumadai Hayata. As a kind of novel plant-derived flavonoid, alpinetin has shown potent hepatoprotective effect against many liver diseases such as non-alcoholic fatty liver and lipopolysaccharide/d-Galactosamine-induced liver injury. However, its roles in liver fibrosis remain to be determined. The aim of the current study was to investigate the effect of alpinetin in mice with carbon tetrachloride (CCl4)-induced liver fibrosis, and to elucidate the underlying mechanisms of action. Alpinetin ameliorated the CCl4-induced liver injury and fibrosis in mice, as shown by decreased collagen deposition and the decreased expression of liver fibrosis marker proteins. Alpinetin suppressed the inflammation and oxidative stress in fibrotic livers of mice, as evidenced by decreased levels of proinflammatory factors, the decreased reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and the increased activities of antioxidant enzymes. In addition, alpinetin attenuated the angiogenesis in fibrotic livers of the test animals. Mechanistically, alpinetin inhibited the CCl4-induced expression of NLRP3, ASC, cleaved caspase-1, mature (cleaved-) IL-1β, and IL-18 in livers of mice. Furthermore, alpinetin resulted in an increased in the nuclear expression and a decrease in the cytoplasmic expression of Nrf2, as well as increased protein expression of downstream target enzymes, GCLC, HO-1, NQO1, and GCLM, thus exerting the antioxidant effect. Overall, these findings suggested that the anti-fibrotic effect of alpinetin can be attributed to the inhibition of NLRP3-mediated anti-inflammatory activities and Nrf2-mediated anti-oxidative activities, in addition to the decrement of hepatic angiogenesis.

Auranofin prevents liver fibrosis by system Xc-mediated inhibition of NLRP3 inflammasome

Demand for a cure of liver fibrosis is rising with its increasing morbidity and mortality. Therefore, it is an urgent issue to investigate its therapeutic candidates. Liver fibrosis progresses following 'multi-hit' processes involving hepatic stellate cells, macrophages, and hepatocytes. The NOD-like receptor protein 3 (NLRP3) inflammasome is emerging as a therapeutic target in liver fibrosis. Previous studies showed that the anti-rheumatic agent auranofin inhibits the NLRP3 inflammasome; thus, this study evaluates the antifibrotic effect of auranofin in vivo and explores the underlying molecular mechanism. The antifibrotic effect of auranofin is assessed in thioacetamide- and carbon tetrachloride-induced liver fibrosis models. Moreover, hepatic stellate cell (HSC), bone marrow-derived macrophage (BMDM), kupffer cell, and hepatocyte are used to examine the underlying mechanism of auranofin. Auranofin potently inhibits activation of the NLRP3 inflammasome in BMDM and kupffer cell. It also reduces the migration of HSC. The underlying molecular mechanism was inhibition of cystine-glutamate antiporter, system Xc. Auranofin inhibits system Xc activity and instantly induced oxidative burst, which mediated inhibition of the NLRP3 inflammasome in macrophages and HSCs. Therefore, to the best of our knowledge, we propose the use of auranofin as an anti-liver fibrotic agent.

Auranofin prevents liver fibrosis by system Xc-mediated inhibition of NLRP3 inflammasome

Demand for a cure of liver fibrosis is rising with its increasing morbidity and mortality. Therefore, it is an urgent issue to investigate its therapeutic candidates. Liver fibrosis progresses following 'multi-hit' processes involving hepatic stellate cells, macrophages, and hepatocytes. The NOD-like receptor protein 3 (NLRP3) inflammasome is emerging as a therapeutic target in liver fibrosis. Previous studies showed that the anti-rheumatic agent auranofin inhibits the NLRP3 inflammasome; thus, this study evaluates the antifibrotic effect of auranofin in vivo and explores the underlying molecular mechanism. The antifibrotic effect of auranofin is assessed in thioacetamide- and carbon tetrachloride-induced liver fibrosis models. Moreover, hepatic stellate cell (HSC), bone marrow-derived macrophage (BMDM), kupffer cell, and hepatocyte are used to examine the underlying mechanism of auranofin. Auranofin potently inhibits activation of the NLRP3 inflammasome in BMDM and kupffer cell. It also reduces the migration of HSC. The underlying molecular mechanism was inhibition of cystine-glutamate antiporter, system Xc. Auranofin inhibits system Xc activity and instantly induced oxidative burst, which mediated inhibition of the NLRP3 inflammasome in macrophages and HSCs. Therefore, to the best of our knowledge, we propose the use of auranofin as an anti-liver fibrotic agent.

Pharmacological Inhibition of the Nod-Like Receptor Family Pyrin Domain Containing 3 Inflammasome with MCC950

Activation of the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome drives release of the proinflammatory cytokines interleukin (IL)-1β and IL-18 and induces pyroptosis (lytic cell death). These events drive chronic inflammation, and as such, NLRP3 has been implicated in a large number of human diseases. These range from autoimmune conditions, the simplest of which is NLRP3 gain-of-function mutations leading to an orphan disease, cryopyrin-associated period syndrome, to large disease burden indications, such as atherosclerosis, heart failure, stroke, neurodegeneration, asthma, ulcerative colitis, and arthritis. The potential clinical utility of NLRP3 inhibitors is substantiated by an expanding list of indications in which NLRP3 activation has been shown to play a detrimental role. Studies of pharmacological inhibition of NLRP3 in nonclinical models of disease using MCC950 in combination with human genetics, epigenetics, and analyses of the efficacy of biologic inhibitors of IL-1β, such as anakinra and canakinumab, can help to prioritize clinical trials of NLRP3-directed therapeutics. Although MCC950 shows excellent (nanomolar) potency and high target selectivity, its pharmacokinetic and toxicokinetic properties limited its therapeutic development in the clinic. Several improved, next-generation inhibitors are now in clinical trials. Hence the body of research in a plethora of conditions reviewed herein may inform analysis of the potential translational value of NLRP3 inhibition in diseases with significant unmet medical need. SIGNIFICANCE STATEMENT: The nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is one of the most widely studied and best validated biological targets in innate immunity. Activation of NLRP3 can be inhibited with MCC950, resulting in efficacy in more than 100 nonclinical models of inflammatory diseases. As several next-generation NLRP3 inhibitors are entering proof-of-concept clinical trials in 2020, a review of the pharmacology of MCC950 is timely and significant.

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.

Punicalin Ameliorates Cell Pyroptosis Induced by LPS/ATP Through Suppression of ROS/NLRP3 Pathway

Purpose

Inflammation is the driving force of many inflammatory and autoimmune diseases, Pyroptosis is a process of cell death in response to excessive inflammation. Punicalin has been reported to have anti-inflammatory effects. However, the anti-pyroptosis is unknown. Hence, this study was aimed to research the inhibition of MG on LPS/ATP-induced pyroptosis in vitro.

Methods

Lipopolysaccharide (LPS)/ATP were used to simulate mouse J774A.1 cells to mimic the inflammatory response and the role of punicalin was examined. The secretion of proinflammatory cytokines was analyzed using enzyme-linked immunosorbent assay (ELISA). The expression of nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), caspase-1, and GSDMD-N in LPS/ATP-stimulated cells were examined by Western blot. N-acetylcysteine (NAC) was used to validate the role of Punicalin.

Results

Punicalin significantly blocked the production of endogenous ROS, reduced LPS/ATP-induced activation of NLRP3, caspase 1, ASC and GSDMD-N, IL-1b and IL-18 protein levels. Furthermore, N-acetylcysteine (NAC), an ROS scavenger, inhibited the LPS/ATP-stimulated activation of NLRP3 inflammasome mediated inflammation and pyroptosis.

Conclusion

Punicalin ameliorates LPS/ATP-induced pyroptosis in J774A.1 macrophages, the mechanism may involve downregulation of the ROS/NLRP3 inflammasome signaling pathway.

SS-31 ameliorates hepatic injury in rats subjected to severe burns plus delayed resuscitation via inhibiting the mtDNA/STING pathway in Kupffer cells

Hepatic injury is common in patients who suffer from severe burns plus delayed resuscitation (B + DR). Stimulator of interferon genes (STING) is primarily expressed in Kupffer cells (KCs). We demonstrated that B + DR caused hepatic injury and oxidative stress. Reactive oxygen species (ROS) damage mitochondrial membranes in hepatocytes, leading to the release of mitochondrial DNA (mtDNA) into the hepatocyte cytosol and the circulation. The damaged hepatocytes then activate the mtDNA/STING pathway in KCs and trigger KCs polarization towards pro-inflammatory phenotype. SS-31 is a strong antioxidant that specifically concentrates in the inner mitochondrial membrane. SS-31 prevented hepatic injury by neutralizing ROS, inhibiting the release of mtDNA, protecting hepatocyte mitochondria, suppressing the activation of the mtDNA/STING pathway and inhibiting KCs polarization into pro-inflammatory phenotype.

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.

Microcystin-LR Induces NLRP3 Inflammasome Activation via FOXO1 Phosphorylation, Resulting in Interleukin-1β Secretion and Pyroptosis in Hepatocytes

Microcystin-LR (MC-LR), the most common and toxic microcystin (MC) present in freshwater, poses a substantial threat to human health, especially hepatotoxicity. Recent evidence reveals that the NLRP3 inflammasome plays an important role in liver injury by activating caspase-1 to promote interleukin-1β (IL-1β) secretion. In this study, we investigated the possible role of NLRP3 inflammasome activation in MC-LR-induced mouse liver inflammatory injury. We found that MC-LR administered to mice by oral gavage mainly accumulated in liver and induced the activation of the NLRP3 inflammasome and production of mature IL-1β. Additionally, we observed an increase in the levels of NLRP3 inflammasome-related proteins and the proportion of pyroptosis in MC-LR-treated AML-12 cells. We also found that inhibition of NLRP3 in mice attenuated MC-LR-induced IL-1β production, indicating an essential role for NLRP3 in MC-LR-induced liver inflammatory injury. In addition, we found that inhibition of FOXO1 by AKT-mediated hyperphosphorylation, due to protein phosphatase 2A (PP2A) inhibition, is required for MC-LR-induced expression of NLRP3. Taken together, our in vivo and in vitro findings suggest a model in which the NLRP3 inflammasome activation, a result of AKT-mediated hyperphosphorylation of FOXO1 through inhibition of PP2A, plays a key role in MC-LR-induced liver inflammatory injury via IL-1β secretion and pyroptotic cell death.

Scutellarin ameliorates pulmonary fibrosis through inhibiting NF-κB/NLRP3-mediated epithelial-mesenchymal transition and inflammation

Idiopathic pulmonary fibrosis (IPF) is featured with inflammation and extensive lung remodeling caused by overloaded deposition of extracellular matrix. Scutellarin is the major effective ingredient of breviscapine and its anti-inflammation efficacy has been reported before. Nevertheless, the impact of scutellarin on IPF and the downstream molecular mechanism remain unclear. In this study, scutellarin suppressed BLM-induced inflammation via NF-κB/NLRP3 pathway both in vivo and in vitro. BLM significantly elevated p-p65/p65 ratio, IκBα degradation, and levels of NLRP3, caspase-1, caspase-11, ASC, GSDMD^Nterm, IL-1β, and IL-18, while scutellarin reversed the above alterations except for that of caspase-11. Scutellarin inhibited BLM-induced epithelial-mesenchymal transition (EMT) process in vivo and in vitro. The expression levels of EMT-related markers, including fibronectin, vimentin, N-cadherin, matrix metalloproteinase 2 (MMP-2) and MMP-9, were increased in BLM group, and suppressed by scutellarin. The expression level of E-cadherin showed the opposite changes. However, overexpression of NLRP3 eliminated the anti-inflammation and anti-EMT functions of scutellarin in vitro. In conclusion, scutellarin suppressed inflammation and EMT in BLM-induced pulmonary fibrosis through NF-κB/NLRP3 signaling.

Therapeutic Effect of Diminazene Aceturate on Parasitic Blood Fluke Schistosoma mansoni Infection

Praziquantel is currently the only drug available to treat schistosomiasis, a disease of enormous public health significance caused by a blood fluke of the genus Schistosoma Diminazene, a drug approved by the FDA, has been successfully used to treat diseases caused by blood protozoan parasites. In this study, we evaluated the antiparasitic properties of diminazene against Schistosoma mansoni ex vivo and in mice harboring either chronic or early S. mansoni infections. In vitro, we monitored phenotypic and tegumental changes as well as the effects of the drug on pairing and egg production. In mice infected with either adult (chronic infection) or immature (early infection) worms, diminazene was administered intraperitoneally (10 to 100 mg/kg of body weight) or by oral gavage (100 to 400 mg/kg), and we studied the influence of the drug on worm burden and egg production. Liver and spleen pathologies and serum aminotransferase levels were also analyzed. In vitro, 50% effective concentrations (EC₅₀) and EC₉₀ revealed that diminazene is able to kill both immature and adult parasites, and its effect was time and concentration dependent. In addition, confocal laser scanning microscopy showed morphological alterations in the teguments of schistosomes. In an animal model, the influence of the drug on worm burden, egg production, hepatomegaly, and splenomegaly depended on the dosing regimen applied and the route of administration. Diminazene also caused a significant reduction in aminotransferase levels. Comparatively, diminazene treatment was more effective in chronic infection than in early infection. In tandem, our study revealed that diminazene possesses anthelmintic properties and inhibits liver injury caused by Schistosoma eggs.

Interplays between inflammasomes and viruses, bacteria (pathogenic and probiotic), yeasts and parasites

In recent years, scientists studying the molecular mechanisms of inflammation have discovered an amazing phenomenon - the inflammasome - a component of the innate immune system that can regulate the functional activity of effector cells during inflammation. At present, it is known that inflammasomes are multimolecular complexes (cytosolic multiprotein oligomers of the innate immune system) that contain many copies of receptors recognizing the molecular structures of cell-damaging factors and pathogenic agents. Inflammasomes are mainly formed in myeloid cells, and their main function is participation in the cleavage of the pro-IL-1β and pro-IL-18 cytokines into their biologically active forms (IL-1β, IL-18). Each type of microorganism influences particular inflammasome activation, and long-term exposure of the organism to viruses, bacteria, yeasts or parasites, among others, can induce uncontrolled inflammation and autoinflammatory diseases. Therefore, this review aims to present the most current scientific data on the molecular interplay between inflammasomes and particular microorganisms. Knowledge about the mechanisms responsible for the interaction between the host and certain types of microorganisms could contribute to the individuation of innovative strategies for the treatment of uncontrolled inflammation targeting a specific type of inflammasome activated by a specific type of pathogen.

Schistosoma antigens as activators of inflammasome pathway: from an unexpected stimulus to an intriguing role

Parasites of the genus Schistosoma are organisms capable of living for decades within the definitive host. They interfere with the immune response by interacting with host's receptors. In this review, we discuss from the first reports to the most recent discoveries regarding the ability of Schistosoma antigens in triggering intracellular receptors and inducing inflammasome activation.

Activation of the NLRP3 Inflammasome by Particles from the Echinococcus granulosus Laminated Layer

The interaction of dendritic cells and macrophages with a variety of rigid noncellular particles triggers activation of the NLRP3 inflammasome and consequent secretion of interleukin 1β (IL-1β). Noncellular particles can also be generated in the context of helminth infection, since these large pathogens often shed their outermost structures during growth and/or molting. One such structure is the massive, mucin-based, soft, flexible laminated layer (LL), which protects the larval stages of cestodes of the genus Echinococcus.

The interaction of dendritic cells and macrophages with a variety of rigid noncellular particles triggers activation of the NLRP3 inflammasome and consequent secretion of interleukin 1β (IL-1β). Noncellular particles can also be generated in the context of helminth infection, since these large pathogens often shed their outermost structures during growth and/or molting. One such structure is the massive, mucin-based, soft, flexible laminated layer (LL), which protects the larval stages of cestodes of the genus Echinococcus. We show that particles from the Echinococcus granulosus LL (pLL) trigger NLRP3- and caspase-1-dependent IL-1β in lipopolysaccharide (LPS)-primed mouse bone marrow-derived dendritic cells (BMDC). This response can be elicited by pLL too large for phagocytosis and nonetheless requires actin dynamics, Syk, and phosphatidylinositol 3-kinase (PI3K). These three requirements had already been observed in our previous study on the alteration by pLL of CD86, CD40, IL-10, and IL-12 responses to LPS in BMDC; however, we now show that these alterations are independent of NLRP3 and caspase-1. In other words, an initial interaction with particles requiring actin dynamics, Syk, and PI3K, but not phagocytosis, elicits both NLRP3-dependent and NLRP3-independent responses. Intraperitoneal injection of pLL induced IL-1β, suggesting that contact with LL materials induces IL-1β in the E. granulosus infection setting. Our results extend our understanding of NLRP3 inflammasome activation by noncellular particulate materials both to helminth-derived materials and to flexible/soft materials.

Mechanism of TGF-β1 inhibiting Kupffer cell immune responses in cholestatic cirrhosis

Effect of exogenous transforming growth factor-β1 (TGF-β1) on cholestatic mice by inhibiting Kupffer cell immune responses in liver was investigated. To induce cholestasis, BALB/c mice received a sham operation (Mock group), or underwent a bile duct ligation (BDL group) and then were subcutaneously injected with TGF-β1 at multiple sites (TGF group). Liver functions were evaluated according to the levels of alanine aminotransferase (ALT), aspartate aminotransferase AST and γ-glutamyltranspeptidase (γ-GT) in serum samples. Expression of nuclear factor-κB (NF-κB), interleukin-6 (IL-6), IL-1β and tumor necrosis factor-α (TNF-α) was detected. Expression of inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) in Kupffer cells (KCs) of the liver was detected. The isolated KCs were divided into control group, LPS group, TGF group and Galunisertib group and western blot analysis was used to detect the expression of NF-κB, IL-6, IL-1β, TNF-α, iNOS and Arg-1. The percentage of CD40, CD86, CD204 and CD206 as macrophage cell surface antigens were measured by flow cytometry. The indexes of liver function and liver fibrosis of the mice in the TGF group were significantly lower than those in the BDL group (P<0.05). The levels of IL-1β, IL-6 and TNF-α in the liver were lower than those in the BDL group, while the level of IL-10 was significantly increased (P<0.05). M2-type transformation occurred in liver Kupffer cells of mice in the TGF group. In cell experiments, TGF treatment downregulated the expression of IL-1β, IL-6, TNF-α and NF-κB, increased the expression of IL-10, and induced M2-type transformation in macrophages (P<0.05). In conclusion, TGF-ß1 diminished the progression of cholestasis in mice by inhibiting the inflammatory response of KCs and regulating KC polarization.

Role of NLRP3 inflammasome in liver disease

Inflammasomes have become an important natural sensor of host immunity, and can protect various organs against pathogenic infections, metabolic syndromes, cellular stress and cancer metastasis. Inflammasomes are intracellular multi-protein complexes found in both parenchymal and non-parenchymal cells, stimulating the initiation of caspase-1 and interleukin (IL)-1β and IL-18 in response to cell danger signals. Inflammasomes induce cell death mechanisms. The potential role of NOD-like receptor protein 3 (NLRP3) inflammasome in alcoholic and non-alcoholic steatohepatitis, hepatitis, nanoparticle-induced liver injury and other liver diseases has recently attracted widespread attention from clinicians and researchers. In this review we summarize the role played by the NLRP3 inflammasome in molecular and pathophysiological mechanisms in the pathogenesis and progression of liver disease. This article aims to establish that targeting the NLRP3 inflammasome and other inflammasome components may make a significant therapeutic approach to the treatment of liver disease.

Inhibition of Lipopolysaccharide-Induced Inflammation of Chicken Liver Tissue by Selenomethionine via TLR4-NF-κB-NLRP3 Signaling Pathway

Selenium (Se) is important in many physiological processes, such as antioxidant processes and inflammation. The aim of our experiments was to investigate the molecular mechanism that selenomethionine could reduce the lipopolysaccharide (LPS)-induced inflammation by inhibiting the TLR4-NF-κB-NLRP3 signaling pathway. Eighty broilers were randomly and evenly divided into two groups, giving normal Se content diets (Con group, 0.2 mg Se/kg diet) and Se-rich basal diets (Se group, 0.5 mg selenomethionine/kg diet) for 90 days. Se-rich basal diets were based on 0.2 mg/kg sodium selenite contained. Five hours before euthanized, 20 broilers were randomly selected from each group and given lipopolysaccharide (200 μg/kg BW) by intraperitoneal injection, Con+LPS group and Se+LPS group, respectively. The Con group and Se group were given equal saline by intraperitoneal injection. We observed the microscopic pathological changes of liver tissue detected oxidative stress by kit and detected the expression of inflammatory factors, heat shock protein (HSP), and nod-like receptor protein 3 (NLRP3)-related genes by qRT-PCR and Western blot. With the microscope, we found the Con+LPS group had obvious inflammatory lesions such as sinusoidal congestion, but the damage was significantly alleviated in the Se+LPS group. In the Con+LPS group, the activity of GSH-Px and the content of GSH were significantly decreased compared with those in the Con group; however, they are increased in the Se group and in the Se + LPS group. Inflammatory factors (MyD88, NF-κB, TNF-α, IL-1β, IL-6, IL-12, IL-18, iNOS, and COX-2), heat shock proteins (HSP27, HSP60, HSP70, and HSP90), and the expression of NLRP3 and caspase-1 increased in the Con+LPS group compared with those in the Con group, while they were lower in the Se+LPS group than in the Con+LPS group. We concluded that selenomethionine inhibits the LPS-induced inflammation of liver tissue via suppressing the TLR4-NF-κB-NLRP3 signaling pathway.

MitoQ protects against liver injury induced by severe burn plus delayed resuscitation by suppressing the mtDNA-NLRP3 axis

INTRODUCTION

Liver injury induced by burn plus delayed resuscitation (B + DR) is life threatening in clinical settings. Mitochondrial damage and oxidative stress may account for the liver injury. MitoQ is a mitochondria-targeted antioxidant. We aimed to evaluate whether MitoQ protects against B + DR-induced liver injury.

METHODS

Rats were randomly divided into three groups: (1) the sham group; (2) the B + DR group, which was characterized by third-degree burn of 30% of the total body surface area plus delayed resuscitation, and (3) the treatment group, in which rats from the B + DR model received the target treatment. MitoQ was injected intraperitoneally (i.p) at 15 min before resuscitation and shortly after resuscitation. In the vitro experiments, Kupffer cells (KCs) were subjected to hypoxia/reoxygenation (H/R) injury to simulate the B + DR model. Mitochondrial characteristics, oxidative stress, liver function, KCs apoptosis and activation of the NLRP3 inflammasome in KCs were measured.

RESULTS

B + DR caused liver injury and oxidative stress. Excessive ROS lead to liver injury by damaging mitochondrial integrity and activating the mitochondrial DNA (mtDNA)-NLRP3 axis in KCs. The oxidized mtDNA, which was released into the cytosol during KCs apoptosis, directly bound and activated the NLRP3 inflammasome. MitoQ protected against liver injury by scavenging intracellular and mitochondrial ROS, preserving mitochondrial integrity and function, reducing KCs apoptosis, inhibiting the release of mtDNA, and suppressing the mtDNA-NLRP3 axis in KCs.

CONCLUSION

MitoQ protected against B + DR-induced liver injury by suppressing the mtDNA-NLRP3 axis.

Helminths Turning on the NLRP3 Inflammasome: Pros and Cons

Helminth infections can activate multimeric protein complexes called inflammasomes. In this forum we summarize the main effects of the NLRP3 inflammasome activation, including control of excessive Th2 response and immunopathology induction. These mechanisms would ensure the survival of both the host and the parasite.

Methane-Rich Saline Counteracts Cholestasis-Induced Liver Damage via Regulating the TLR4/NF-κB/NLRP3 Inflammasome Pathway

Cholestatic liver injury, due to obstruction of the biliary tract or genetic defects, is often accompanied by progressive inflammation and liver fibrosis. Methane-rich saline (MRS) has anti-inflammatory properties. However, whether MRS can provide protective effect in cholestatic liver injury is still unclear. In this study, Sprague-Dawley rats received bile duct ligation (BDL) to generate a cholestatic model followed by MRS treatment (10 mL/kg, ip treatment) every 12 h after the operation to explore the potential protective mechanism of MRS in cholestatic liver injury. We found that MRS effectively improved liver function, alleviated liver pathological damage, and localized infiltration of inflammatory cells. MRS treatment decreased the expression of hepatic fibrosis-associated proteins to alleviate liver fibrosis. Furthermore, MRS treatment suppressed the TLR4/NF-κB pathway and further reduced the levels of proinflammatory factors. Downregulation of NF-κB subsequently reduced the NLRP3 expression to inhibit pyroptosis. Our data indicated that methane treatment prevented cholestatic liver injury via anti-inflammatory properties that involved the TLR4/NF-κB/NLRP3 signaling pathway.

Taurine Alleviates Schistosoma-Induced Liver Injury by Inhibiting the TXNIP/NLRP3 Inflammasome Signal Pathway and Pyroptosis

Schistosomiasis is a parasitic helminth disease that can cause severe inflammatory pathology, leading to organ damage, in humans. During a schistosomal infection, the eggs are trapped in the host liver, and products derived from eggs induce a polarized Th2 cell response, resulting in granuloma formation and eventually fibrosis. Previous studies indicated that the nucleotide-binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is involved in schistosomiasis-associated liver fibrosis and that taurine could ameliorate hepatic granulomas and fibrosis caused by Schistosoma japonicum infection. Nevertheless, the precise role and molecular mechanism of the NLRP3 inflammasome and the protective effects of taurine in S. japonicum infection have not been extensively studied. In this study, we investigated the role of the NLRP3 inflammasome and the hepatoprotective mechanism of taurine in schistosoma-induced liver injury in mice. NLRP3 deficiency ameliorated S. japonicum-infection-induced hepatosplenomegaly, liver dysfunction, and hepatic granulomas and fibrosis; it also reduced NLRP3-dependent liver pyroptosis. Furthermore, taurine suppressed hepatic thioredoxin-interacting protein (TXNIP)/NLRP3 inflammasome activation in mice with S. japonicum infections, thereby inhibiting the activation of downstream inflammatory mediators such as interleukin-1β and subsequent pyroptosis. Our results suggest that the TXNIP/NLRP3 inflammasome pathway and mediating pyroptosis are involved in S. japonicum-induced liver injury and may be a potential therapeutic target for schistosomiasis treatment. In addition, taurine may be useful to alleviate or to prevent the occurrence of schistosomiasis-associated liver fibrosis.