Caffeine Inhibits NLRP3 Inflammasome Activation by Downregulating TLR4/MAPK/NF-κB Signaling Pathway in an Experimental NASH Model

Transcriptomic analysis reveals the mechanisms underlying the differential effects of caffeine, theophylline, and theobromine in regulating hepatic fat accumulation

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease, characterized by excessive fat accumulation in the liver. Caffeine, theophylline, and theobromine are the primary naturally occurring methylxanthines found in various foods and beverages such as coffee, tea, and chocolate. They exhibit diverse pharmacological effects. Although caffeine can inhibit hepatic fat accumulation in mice, the effects and regulatory mechanisms of theophylline and theobromine remain unclear. In this study, we observed that theophylline significantly reduced body weight and triglyceride levels and attenuated hepatic fat accumulation in mice fed a high-fat diet. Conversely, theobromine did not exhibit these effects. Transcriptomic results showed that caffeine and theophylline significantly activated the TNF signaling pathway in C2C12 myoblasts, induced p38MAPK expression and increased Il1b and Il6 secretion, but did not elevate Tnfa and Mcp1 expression. Notably, theobromine neither activated the TNF pathway nor significantly induced p38MAPK expression and Il1b and Il6 secretion. In conclusion, the differences in the regulating NAFLD activity of caffeine, theophylline, and theobromine-three structurally similar compounds used as food ingredients, may be attributed to their distinct regulation of the TNF signaling pathway.

Resveratrol Alleviates Liver Fibrosis by Targeting Cross-Talk Between TLR2/MyD88/ERK and NF-κB/NLRP3 Inflammasome Pathways in Macrophages

Resveratrol alleviates liver fibrosis in mice by upregulating IL-10 to reprogram the macrophage phenotype; however, the mechanism remains to be elucidated. Building on our previous work, in this study, we aimed to determine the role of the TLR2/MyD88/ERK and NF-κB/NLRP3 inflammasome pathways in mediating the effects of resveratrol on liver fibrosis and macrophage polarization. We investigated the expression of cytokines in these inflammasome pathways in a mouse model of liver fibrosis and resveratrol-treated macrophages. The results showed that expression of TLR2, MyD88, ERK, and NF-κB1 in liver tissues was increased in the fourth week after treatment with resveratrol but decreased in the fifth week. Similar results were obtained for the NF-κB/NLRP3 inflammasome pathway. The results also showed that cytokines in both the TLR2/MyD88/ERK and NF-κB/NLRP3 inflammasome pathways in macrophages were elevated after 24 h and reduced after 36 h of treatment with resveratrol. Immunofluorescence and nucleocytoplasmic separation assays showed that resveratrol inhibited the translocation of NF-κB from the cytoplasm to the nucleus in macrophages, and increased NF-κB1 was associated with inhibition of the TLR2/MyD88/ERK pathway. Silencing NF-κB1 increased the expression of TLR2, MyD88, and ERK. In conclusion, the TLR2/MyD88/ERK and NF-κB/NLRP3 inflammasome pathways are involved in the effect of resveratrol on macrophage polarization and the subsequent modulation of liver fibrosis. NF-κB1 acts as the common cytokine that coordinates the crosstalk between the two pathways. Our findings highlight the potential of the members of these pathways as therapeutic targets toward the treatment of liver fibrosis.

Caffeine ameliorates metabolic-associated steatohepatitis by rescuing hepatic Dusp9

Caffeine (CAFF) is abundant in black coffee. As one of the most widely consumed beverages globally, coffee has been the focus of increasing clinical and basic research, particularly regarding its benefits in alleviating metabolic dysfunction-associated steatotic liver disease (MASLD). However, the therapeutic effects of CAFF on metabolic-associated steatohepatitis (MASH) and the underlying mechanisms remain unclear. In this study, we demonstrated that CAFF potently reduced hepatic steatosis, inflammation, and early-stage liver fibrosis in MASH mice induced by prolonged (36 weeks) high-fat high-carbohydrate (HFHC) diets and high-fat diets combined with carbon tetrachloride (CCl4) injections. By using multiple target-identifying strategies, including surface plasmon resonance (SPR), cellular thermal shift assay (CETSA), and drug affinity responsive target stability (DARTS) assay, we identified dual-specificity phosphatase 9 (Dusp9) as a key therapeutic target, which was diminished by HFHC but restored with CAFF treatment. Dusp9 knockdown in vivo and in vitro exacerbated glycolipid metabolism disorders and stunningly counteracted the systemic therapeutic effects of CAFF in the MASH models. In addition, CAFF inactivated the ASK1-p38/JNK, a downstream signaling pathway of Dusp9, which regulates inflammation and apoptosis. Our study highlights the multifaceted benefits of CAFF in treating MASH by rescuing hepatic Dusp9 expression, thereby reversing glycolipid metabolism disorders, liver inflammation, and fibrosis. These findings provide experimental evidence supporting the clinical and daily use of CAFF and black coffee in managing MASH patients.

Cadmium exposure induced spleen inflammation by activating the MAPK/NF-κB/ NLRP3 signaling pathway and the intervention effect of astilbin

Cadmium (Cd) is an environmental pollutant with strong immunotoxicity effects. Despite this, the mechanisms by which Cd causes spleen damage in chickens are not well understood. Astilbin (ASB) is a dihydroflavone glycoside with anti-inflammatory and anti-oxidation properties. In the present study, a chicken spleen injury model induced by cadmium exposure (90d) was established to explore the specific mechanisms of Cd-induced spleen injury. If and how ASB ameliorates the damage was also explored. A total of 60 chickens were randomly divided into four groups: Con, Cd, ASB, and Cd+ASB groups. The pathological changes in the spleen were observed by H&E staining. Cd-induced oxidative stress, inflammation, and the involvement of the MAPK/NF-κB/NLRP3 in ameliorating spleen damage were also analyzed by Western blotting, qRT-PCR, and immunohistochemistry. Our results showed that Cd exposure for 90 days damaged the spleen, which mainly manifested as eosinophil infiltration, an increase in MDA content, a decrease in the CAT, GSH, SOD, and T-AOC, and activation of MAPK/NF-κB/NLRP3 signaling pathway. The overall outcome of these events was the induction of oxidative stress and inflammation in the spleen of the chickens. Interestingly, ASB treatment ameliorated Cd-induced damages. In conclusion, the present study revealed the specific mechanism of Cd-induced spleen damage using a chicken model. But ASB ameliorates Cd-induced cadmium poisoning.

Caffeine's protective role in dry eye disease and meibomian gland dysfunction: insights from clinical and experimental models

PURPOSE

Inflammation and apoptosis contribute to the development of dry eye disease (DED) and meibomian gland dysfunction (MGD). This study aimed to investigate the effect of caffeine on the ocular surface and tear inflammatory cytokines through clinical, in vivo, and in vitro experiments.

METHODS

In the clinical study, comprehensive ophthalmic examinations of participants in the control and the caffeine groups were compared, including ocular surface and tears inflammatory cytokines. For in vitro study, rat meibomian gland epithelial cells (RMGECs) and human corneal epithelial cells (HCECs) were pretreated with or without caffeine and then stimulated with lipopolysaccharide (LPS). Inflammatory responses, apoptosis, and differentiation in cells were analyzed. In vivo study, apolipoprotein E knockout (ApoE-/-) mice were given caffeine-diet or no caffeine-diet, and their meibomian glands (MGs) and corneal tissue were compared.

RESULTS

Participants in the caffeine group exhibited significantly healthier ocular surface, lower tears inflammatory cytokines and a reduced prevalence of DED compared to the control group. In vitro study, caffeine pretreatment attenuated inflammatory responses, apoptosis and differentiation in LPS-induced RMGECs. Meanwhile, caffeine also markedly suppressed inflammatory responses and apoptosis in LPS-induced HCECs. In vivo study showed that ApoE-/- mice with caffeine-diet had more normal morphology of MGs and corneas compared to those without caffeine-diet, along with reduced inflammatory responses, cells apoptosis and ductal keratinization. Both in vitro and in vivo studies indicated that caffeine treatment was observed to inactivate of nuclear factor kappa B (NF-κB) phosphorylation.

CONCLUSIONS

Our study indicated that caffeine may be a protective potential of ocular surface, providing a new perspective on clinical treatment for DED and MGD.

Threshold effects between caffeine intake and urine flow rate: a population-based cross-sectional study

PURPOSE

The potential benefits of caffeine intake are currently receiving much attention and exploration. Urine flow rate (UFR) is an objective index to comprehensively reflect bladder function. The aim of this study was to investigate the association between caffeine intake and UFR using the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

14,142 participants were enrolled in this study. Weighted multivariate adjusted regression models were used to explore the relationship between caffeine intake and UFR. The dose-response relationships were explored using a restricted cubic spline (RCS) and a threshold effect analysis was conducted based on the inflection points identified by the two-segment linear regression model. In addition, subgroup analysis and sensitivity analysis were applied.

RESULTS

The findings suggested that the intake of caffeine was correlated with improved UFR [Model 3: 0.091 (0.057, 0.126), P value < 0.001]. In addition, the RCS supported a nonlinear relationship between them. The analysis of threshold effect further revealed a specific level of caffeine intake (34.51 mg/day) that exhibited a significant enhancement in UFR. Finally, through re-analyzing the data set obtained after multiple imputation (MI), we obtained similar results.

CONCLUSION

This study found a nonlinear beneficial relationship between caffeine intake and UFR, and revealed the recommended intake of caffeine. The values varied by gender, race, education, and smoking status.

Total glucosides of Picrorhizae Rhizome alleviate non-alcoholic steatohepatitis (NASH) by specifically targeting acyl-CoA oxidase 1

Nonalcoholic steatohepatitis (NASH), a chronic liver disease characterized by the accumulation of fat in the liver, is highly prevalent on a global scale. In this study, we investigated the effects of total glucosides of Picrorhizae Rhizome (TGPR), the primary active ingredients in traditional Chinese herbal medicine derived from Picrorhiza scrophulariiflora Pennell. TGPR is known for its efficiency in attenuating NASH, in mouse models induced by methionine-choline deficient (MCD) diet or high-fat diet (HFD). Our findings indicated that TGPR exhibited efficacy in reducing hepatic steatosis and lowering serum lipid levels, specifically triglyceride and total cholesterol in the NASH model. Meanwhile, TGPR exhibited a suppressive effect on the production of pro-inflammatory cytokines. Mechanistically, we identified acyl-CoA oxidase 1 (Acox1) as a crucial cellular target of TGPR, influencing lipid metabolism and ATP production to treat NASH. Additionally, we found that the major components of TGPR, including Picroside I, Picroside II, and Picroside IV, exhibit significant binding abilities to the target Acox1 at its catalytic C-terminal α-domain, stabilizing its protein expression. TGPR binding to Acox1 facilitated the degradation of fatty acids via the Acox1-mediated MAPK signaling pathways, and consequently plays a role in regulating energy metabolism and reducing liver inflammation. In summary, our study demonstrates that TGPR effectively counteracts NASH by specifically targeting Acox1, thereby providing a significant clinical solution for the treatment of NASH.

Peptidoglycan-Chi3l1 interaction shapes gut microbiota in intestinal mucus layer

The balanced gut microbiota in intestinal mucus layer plays an instrumental role in the health of the host. However, the mechanisms by which the host regulates microbial communities in the mucus layer remain largely unknown. Here, we discovered that the host regulates bacterial colonization in the gut mucus layer by producing a protein called Chitinase 3-like protein 1 (Chi3l1). Intestinal epithelial cells are stimulated by the gut microbiota to express Chi3l1. Once expressed, Chi3l1 is secreted into the mucus layer where it interacts with the gut microbiota, specifically through a component of bacterial cell walls called peptidoglycan. This interaction between Chi3l1 and bacteria is beneficial for the colonization of bacteria in the mucus, particularly for Gram-positive bacteria like Lactobacillus. Moreover, a deficiency of Chi3l1 leads to an imbalance in the gut microbiota, which exacerbates colitis induced by dextran sodium sulfate. By performing fecal microbiota transplantation from Villin-cre mice or replenishing Lactobacillus in IEC∆Chil1 mice, we were able to restore their colitis to the same level as that of Villin-cre mice. In summary, this study shows a 'scaffold model' for microbiota homeostasis by interaction between intestinal Chi3l1 and bacteria cell wall interaction, and it also highlights that an unbalanced gut microbiota in the intestinal mucus contributes to the development of colitis.

Salidroside may target PPARα to exert preventive and therapeutic activities on NASH

Background

Salidroside (SDS), a phenylpropanoid glycoside, is an antioxidant component isolated from the traditional Chinese medicine Rhodiola rosea and has multifunctional bioactivities, particularly possessing potent hepatoprotective function. Non-alcoholic steatohepatitis (NASH) is one of the most prevalent chronic liver diseases worldwide, but it still lacks efficient drugs. This study aimed to assess the preventive and therapeutic effects of SDS on NASH and its underlying mechanisms in a mouse model subjected to a methionine- and choline-deficient (MCD) diet.

Methods

C57BL/6J mice were fed an MCD diet to induce NASH. During or after the formation of the MCD-induced NASH model, SDS (24 mg/kg/day) was supplied as a form of diet for 4 weeks. The histopathological changes were evaluated by H&E staining. Oil Red O staining and Sirius Red staining were used to quantitatively determine the lipid accumulation and collagen fibers in the liver. Serum lipid and liver enzyme levels were measured. The morphology of autophagic vesicles and autophagosomes was observed by transmission electron microscopy (TEM), and qRT-PCR and Western blotting were used to detect autophagy-related factor levels. Immunohistochemistry and TUNEL staining were used to evaluate the apoptosis of liver tissues. Flow cytometry was used to detect the composition of immune cells. ELISA was used to evaluate the expression of serum inflammatory factors. Transcript-proteome sequencing, molecular docking, qRT-PCR, and Western blotting were performed to explore the mechanism and target of SDS in NASH.

Results

The oral administration of SDS demonstrated comprehensive efficacy in NASH. SDS showed both promising preventive and therapeutic effects on NASH in vivo. SDS could upregulate autophagy, downregulate apoptosis, rebalance immunity, and alleviate inflammation to exert anti-NASH properties. Finally, the results of transcript-proteome sequencing, molecular docking evaluation, and experimental validation showed that SDS might exert its multiple effects through targeting PPARα.

Conclusion

Our findings revealed that SDS could regulate liver autophagy and apoptosis, regulating both innate immunity and adaptive immunity and alleviating inflammation in NASH prevention and therapy via the PPAR pathway, suggesting that SDS could be a potential anti-NASH drug in the future.

Pathophysiological role and potential drug target of NLRP3 inflammasome in the metabolic disorders

NLRP3 plays a role in the development of autoinflammatory diseases. NLRP3, ASC, and Caspases 1 or 8 make up the NLRP3 inflammasome, which is an important part of innate immune system. The NLRP3 inflammasome-mediated inflammatory cytokines may also participate in metabolic disorders, such as diabetes, hyperlipidemia, atherosclerosis, non-alcoholic fatty liver disease, and gout. Hence, an overview of the NLRP3 regulation in these metabolic diseases and the potential drugs targeting NLRP3 is the focus of this review.

Recent advances in the treatment of gout with NLRP3 inflammasome inhibitors

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

The Other Side of the Perfect Cup: Coffee-Derived Non-Polyphenols and Their Roles in Mitigating Factors Affecting the Pathogenesis of Type 2 Diabetes

The global prevalence of type 2 diabetes (T2D) is 10.5% among adults in the age range of 20-79 years. The primary marker of T2D is persistent fasting hyperglycemia, resulting from insulin resistance and β-cell dysfunction. Multiple factors can promote the development of T2D, including obesity, inflammation, and oxidative stress. In contrast, dietary choices have been shown to prevent the onset of T2D. Oatmeal, lean proteins, fruits, and non-starchy vegetables have all been reported to decrease the likelihood of T2D onset. One of the most widely consumed beverages in the world, coffee, has also demonstrated an impressive ability to reduce T2D risk. Coffee contains a diverse array of bioactive molecules. The antidiabetic effects of coffee-derived polyphenols have been thoroughly described and recently reviewed; however, several non-polyphenolic molecules are less prominent but still elicit potent physiological actions. This review summarizes the effects of select coffee-derived non-polyphenols on various aspects of T2D pathogenesis.

Protective Effect of Caffeine and Chlorogenic Acids of Coffee in Liver Disease

Coffee is one of the most widely consumed beverages in the world due to its unique aroma and psychostimulant effects, mainly due to the presence of caffeine. In recent years, experimental evidence has shown that the moderate consumption of coffee (3/4 cups per day) is safe and beneficial to human health, revealing protective effects against numerous chronic metabolic diseases such as diabetes, cardiovascular, neurodegenerative, and hepatic diseases. This review focuses on two of coffee's main bioactive compounds, i.e., caffeine and chlorogenic acids, and their effects on the progression of chronic liver diseases, demonstrating that regular coffee consumption correlates with a lower risk of the development and progression of non-alcoholic steatohepatitis, viral hepatitis, liver cirrhosis, and hepatocellular carcinoma. In particular, this review analyzes caffeine and chlorogenic acid from a pharmacological point of view and explores the molecular mechanism through which these compounds are responsible for the protective role of coffee. Both bioactive compounds, therefore, have antifibrotic effects on hepatic stellate cells and hepatocytes, induce a decrease in connective tissue growth factor, stimulate increased apoptosis with anti-cancer effects, and promote a major inhibition of focal adhesion kinase, actin, and protocollagen synthesis. In conclusion, coffee shows many beneficial effects, and experimental data in favor of coffee consumption in patients with liver diseases are encouraging, but further prospective studies are needed to demonstrate its preventive and therapeutic role in chronic liver diseases.

Caffeine and neonatal acute kidney injury

Acute kidney injury is one of the most threatening diseases in neonates, with complex pathogenesis and limited treatment options. Caffeine is a commonly used central nervous system stimulant for treating apnea in preterm infants. There is compelling evidence that caffeine may have potential benefits for preventing neonatal acute kidney injury, but comprehensive reports are lacking in this area. Hence, this review aims to provide a summary of clinical data on the potential benefits of caffeine in improving neonatal acute kidney injury. Additionally, it delves into the molecular mechanisms underlying caffeine's effects on acute kidney injury, with a focus on various aspects such as oxidative stress, adenosine receptors, mitochondrial dysfunction, endoplasmic reticulum stress, inflammasome, autophagy, p53, and gut microbiota. The ultimate goal of this review is to provide information for healthcare professionals regarding the link between caffeine and neonatal acute kidney injury and to identify gaps in our current understanding.

Huanglian-Hongqu herb pair improves nonalcoholic fatty liver disease via NF-κB/NLRP3 pathway in mice: network pharmacology, molecular docking and experimental validation

The Huanglian-Hongqu herb pair (HH) is a carefully crafted traditional Chinese herbal compound designed to address disorders related to glucose and lipid metabolism. Its primary application lies in treating hyperlipidemia and fatty liver conditions. This study explored the potential mechanism of HH in treating non-alcoholic fatty liver disease (NAFLD) through network pharmacology, molecular docking, and in vivo animal experiments. Ultrahigh performanceliquid chromatography-quadrupole/orbitrapmass spectrometry (UPLC-Q-TOF-MS) was employed to identify the chemical composition of HH. Network pharmacology was used to analyze the related signaling pathways affected by HH. Subsequently, the prediction was verified by animal experiment. Finally, we identified 29 components within HH. Network pharmacology unveiled interactions between HH and 153 NAFLD-related targets, highlighting HH's potential to alleviate NAFLD through NF-κB signaling pathway. Molecular docking analyses illuminated the binding interactions between HH components and key regulatory proteins, including NF-κB, NLRP3, ASC, and Caspase-1. In vivo experiments demonstrated that HH alleviated NAFLD by reducing serum and liver lipid levels, improving liver function, and lowering inflammatory cytokine levels in the serum. Moreover, HH administration downregulated mRNA and protein levels of the NF-κB/NLRP3 pathway. In conclusion, our findings demonstrated that HH has potential therapeutic benefits in ameliorating NAFLD by targeting the NF-κB/NLRP3 pathway, facilitating the broader application of HH in the field of NAFLD.

Metabolic Insights into Caffeine's Anti-Adipogenic Effects: An Exploration through Intestinal Microbiota Modulation in Obesity

Obesity, a chronic condition marked by the excessive accumulation of adipose tissue, not only affects individual well-being but also significantly inflates healthcare costs. The physiological excess of fat manifests as triglyceride (TG) deposition within adipose tissue, with white adipose tissue (WAT) expansion via adipocyte hyperplasia being a key adipogenesis mechanism. As efforts intensify to address this global health crisis, understanding the complex interplay of contributing factors becomes critical for effective public health interventions and improved patient outcomes. In this context, gut microbiota-derived metabolites play an important role in orchestrating obesity modulation. Microbial lipopolysaccharides (LPS), secondary bile acids (BA), short-chain fatty acids (SCFAs), and trimethylamine (TMA) are the main intestinal metabolites in dyslipidemic states. Emerging evidence highlights the microbiota's substantial role in influencing host metabolism and subsequent health outcomes, presenting new avenues for therapeutic strategies, including polyphenol-based manipulations of these microbial populations. Among various agents, caffeine emerges as a potent modulator of metabolic pathways, exhibiting anti-inflammatory, antioxidant, and obesity-mitigating properties. Notably, caffeine's anti-adipogenic potential, attributed to the downregulation of key adipogenesis regulators, has been established. Recent findings further indicate that caffeine's influence on obesity may be mediated through alterations in the gut microbiota and its metabolic byproducts. Therefore, the present review summarizes the anti-adipogenic effect of caffeine in modulating obesity through the intestinal microbiota and its metabolites.

Natural Products in Liver Fibrosis Management: A Five-year Review

Liver fibrosis, characterized by the overproduction of extracellular matrix proteins within liver tissue, poses a rising global health concern. However, no approved antifibrotic drugs are currently available, highlighting the critical need for understanding the molecular mechanisms of liver fibrosis. This knowledge could not only aid in developing therapies but also enable early intervention, enhance disease prediction, and improve our understanding of the interaction between various underlying conditions and the liver. Notably, natural products used in traditional medicine systems worldwide and demonstrating diverse biochemical and pharmacological activities are increasingly recognized for their potential in treating liver fibrosis. This review aims to comprehensively understand liver fibrosis, emphasizing the molecular mechanisms and advancements in exploring natural products' antifibrotic potential over the past five years. It also acknowledges the challenges in their development and seeks to underscore their potency in enhancing patient prognosis and reducing the global burden of liver disease.

NLRP3 inflammasome in hepatic diseases: A pharmacological target

The NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome pathway is mainly responsible for the activation and release of a cascade of proinflammatory mediators that contribute to the development of hepatic diseases. During alcoholic liver disease development, the NLRP3 inflammasome pathway contributes to the maturation of caspase-1, interleukin (IL)-1β, and IL-18, which induce a robust inflammatory response, leading to fibrosis by inducing profibrogenic hepatic stellate cell (HSC) activation. Substantial evidence demonstrates that nonalcoholic fatty liver disease (NAFLD) progresses to nonalcoholic steatohepatitis (NASH) via NLRP3 inflammasome activation, ultimately leading to fibrosis and hepatocellular carcinoma (HCC). Activation of the NLRP3 inflammasome in NASH can be attributed to several factors, such as reactive oxygen species (ROS), gut dysbiosis, leaky gut, which allow triggers such as cardiolipin, cholesterol crystals, endoplasmic reticulum stress, and uric acid to reach the liver. Because inflammation triggers HSC activation, the NLRP3 inflammasome pathway performs a central function in fibrogenesis regardless of the etiology. Chronic hepatic activation of the NLRP3 inflammasome can ultimately lead to HCC; however, inflammation also plays a role in decreasing tumor growth. Some data indicate that NLRP3 inflammasome activation plays an important role in autoimmune hepatitis, but the evidence is scarce. Most researchers have reported that NLRP3 inflammasome activation is essential in liver injury induced by a variety of drugs and hepatotropic virus infection; however, few reports indicate that this pathway can play a beneficial role by inducing liver regeneration. Modulation of the NLRP3 inflammasome appears to be a suitable strategy to treat liver diseases.

Nicotinic acid attenuates experimental non-alcoholic steatohepatitis by inhibiting the NLRP3 inflammasome/pyroptosis pathway

Non-alcoholic steatohepatitis (NASH) is a global public health concern that may progress into fibrosis, cirrhosis, and liver cancer, with limited curative treatment options. While the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is closely linked to NASH progression, nicotinic acid (NA), a vitamin used for the treatment of dyslipidemia, is an emerging pharmaceutical treatment for hepatic steatosis and fibrosis. Here, we investigated pharmacological effects of NA on experimental NASH and whether NLRP3 inflammasome/pyroptosis inhibition is an associated mechanism of action. Rats were fed a high-fat sucrose diet supplemented with cholesterol and a low dose of CCl4. NA significantly reduced inflammation by decreasing the protein levels of tumor necrosis factor-alpha and nuclear factor kappa B. Moreover, NA inhibited the formation of NLRP3- apoptosis-associated speck-like protein containing caspase recruitment domain-Caspase-1, decreasing interleukin-1beta, interleukin-18, and gasdermin D protein. In addition, NA reduced tumor growth factor-beta, alpha-smooth muscle actin, and hepatic levels of collagen-1, consequently decreasing extracellular matrix synthesis. Our results indicate that NA can inhibit NASH progression and encourage further basic and clinical studies on the use of NA for the treatment of human NASH.

Blockade of C5aR1 alleviates liver inflammation and fibrosis in a mouse model of NASH by regulating TLR4 signaling and macrophage polarization

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is an advanced form of chronic fatty liver disease, which is a driver of hepatocellular carcinoma. However, the roles of the C5aR1 in the NASH remain poorly understood. Here, we aimed to investigate the functions and mechanisms of the C5aR1 on hepatic inflammation and fibrosis in murine NASH model.

METHODS

Mice were fed a normal chow diet with corn oil (ND + Oil), a Western diet with corn oil (WD + Oil) or a Western diet with carbon tetrachloride (WD + CCl4) for 12 weeks. The effects of the C5a-C5aR1 axis on the progression of NASH were analyzed and the underlying mechanisms were explored.

RESULTS

Complement factor C5a was elevated in NASH mice. C5 deficiency reduced hepatic lipid droplet accumulation in the NASH mice. The hepatic expression levels of TNFα, IL-1β and F4/80 were decreased in C5-deficient mice. C5 loss alleviated hepatic fibrosis and downregulated the expression levels of α-SMA and TGFβ1. C5aR1 deletion reduced inflammation and fibrosis in NASH mice. Transcriptional profiling of liver tissues and KEGG pathway analysis revealed that several pathways such as Toll-like receptor signaling, NFκB signaling, TNF signaling, and NOD-like receptor signaling pathway were enriched between C5aR1 deficiency and wild-type mice. Mechanistically, C5aR1 deletion decreased the expression of TLR4 and NLRP3, subsequently regulating macrophage polarization. Moreover, C5aR1 antagonist PMX-53 treatment mitigated the progression of NASH in mice.

CONCLUSIONS

Blockade of the C5a-C5aR1 axis reduces hepatic steatosis, inflammation, and fibrosis in NASH mice. Our data suggest that C5aR1 may be a potential target for drug development and therapeutic intervention of NASH.

NOD-like receptors in the pathogenesis of metabolic (dysfunction)-associated fatty liver disease: Therapeutic agents targeting NOD-like receptors

BACKGROUND AND AIMS

In metabolic (dysfunction)-associated fatty liver disease (MAFLD), activation of inflammatory processes marks the transition of simple steatosis to steatohepatitis, which can further evolve to advanced fibrosis or hepatocellular carcinoma. Under the stress of chronic overnutrition, the innate immune system orchestrates hepatic inflammation through pattern recognition receptors (PRRs). Cytosolic PRRs that include NOD-like receptors (NLRs) are crucial for inducing inflammatory processes in the liver.

METHODS

A literature search was performed with Medline (PubMed), Google Scholar and Scopus electronic databases till January 2023, using relevant keywords to extract studies describing the role of NLRs in the pathogenesis of MAFLD.

RESULTS

Several NLRs operate through the formation of inflammasomes, which are multimolecular complexes that generate pro-inflammatory cytokines and induce pyroptotic cell death. A multitude of pharmacological agents target NLRs and improve several aspects of MAFLD. In this review, we discuss the current concepts related to the role of NLRs in the pathogenesis of MAFLD and its complications. We also discuss the latest research on MAFLD therapeutics functioning through NLRs.

CONCLUSIONS

NLRs play a significant role in the pathogenesis of MAFLD and its consequences, especially through generation of inflammasomes, such as NLRP3 inflammasomes. Lifestyle changes (exercise, coffee consumption) and therapeutic agents (GLP-1 receptor agonists, sodium-glucose cotransporter-2 inhibitors, obeticholic acid) improve MAFLD and its complications partly through blockade of NLRP3 inflammasome activation. New studies are required to explore these inflammatory pathways fully for the treatment of MAFLD.

The antioxidant and anti-inflammatory activities of caffeine effectively attenuate nonalcoholic steatohepatitis and thioacetamide-induced hepatic injury in male rats

The antioxidant effect of caffeine, associated with its ability to upregulate the nuclear factor-E2-related factor-2 (Nrf2)-signaling pathway, was explored as a possible mechanism for the attenuation of liver damage. Nonalcoholic steatohepatitis (NASH) was induced in rats by the administration of a high-fat, high-sucrose, high-cholesterol diet (HFSCD) for 15 weeks. Liver damage was induced in rats by intraperitoneal administration of thioacetamide (TAA) for six weeks. Caffeine was administered orally at a daily dose of 50 mg/kg body weight during the period of NASH induction to evaluate its ability to prevent disease development. Meanwhile, rats received TAA for three weeks, after which 50 mg/kg caffeine was administered daily for three weeks with TAA to evaluate its capacity to interfere with the progression of hepatic injury. HFSCD administration induced hepatic steatosis, decreased Nrf2 levels, increased oxidative stress, induced the activation of nuclear factor-κB (NF-κB), and elevated proinflammatory cytokine levels, leading to hepatic damage. TAA administration produced similar effects, excluding steatosis. Caffeine increased Nrf2 levels; attenuated oxidative stress markers, including malondialdehyde and 4-hydroxynonenal; restored normal, reduced glutathione levels; and reduced NF-κB activation, inflammatory cytokine levels, and damage. Our findings suggest that caffeine may be useful in the treatment of human liver diseases.

Activation of the NLRP3 inflammasome by CCl4 exacerbates hepatopathogenic diet-induced experimental NASH

INTRODUCTION AND OBJECTIVES

Administration of carbon tetrachloride (CCl₄), along with an hepatopathogenic diet, is widely employed as a chemical inducer to replicate human nonalcoholic steatohepatitis (NASH) in rodents; however, the role of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome in this model remains unclear. We aimed to determine the relevance of NLRP3 inflammasome activation in the development of NASH induced by CCl₄ along with an hepatopathogenic diet in male Wistar rats.

MATERIALS AND METHODS

Animals were fed either a high fat, sucrose, and cholesterol diet (HFSCD) or a HFSCD plus intraperitoneal injections of low doses of CCl₄ (400 mg/kg) once a week for 15 weeks. Liver steatosis, inflammation, fibrosis, and NLRP3 inflammasome activation were evaluated using biochemical, histological, ultrastructural, and immunofluorescence analyses, western blotting, and immunohistochemistry.

RESULTS

Our experimental model reproduced several aspects of the human NASH pathophysiology. NLRP3 inflammasome activation was induced by the combined effect of HFSCD plus CCl₄ and significantly increased levels of both proinflammatory and profibrogenic cytokines and collagen deposition in the liver; thus, NASH severity was higher in the HFSCD+CCl₄ group than that in the HFSCD group, to which CCl₄ was not administered. Hepatic stellate cells, the most profibrogenic cells, were activated by HFSCD plus CCl₄, as indicated by elevated levels of α-smooth muscle actin. Thus, activation of the NLRP3 inflammasome, triggered by low doses of CCl₄, exacerbates the severity of NASH.

CONCLUSIONS

Our results indicate that NLRP3 inflammasome activation plays a key role and may be an important therapeutic target for NASH treatment.

Lycopene prevents non-alcoholic fatty liver disease through regulating hepatic NF-κB/NLRP3 inflammasome pathway and intestinal microbiota in mice fed with high-fat and high-fructose diet

Lycopene (LY) belongs to carotenoids and is abundant in red fruits and vegetables. Several previous studies suggested that LY is beneficial for ameliorating non-alcoholic fatty liver disease (NAFLD), while the potential mechanisms are unclear. The present study aimed to clarify the potential mechanisms of LY in preventing NAFLD via exploring the hepatic NF-κB/NLRP3 inflammasome pathway and intestinal microbiota composition in high-fat and high-fructose diet (HFFD)-fed mice. Fifty eight-week-old male C57BL/6J mice were randomly assigned into 5 groups: Normal control group (NC); HFFD group; HFFD with low dose of lycopene group (LLY, 20 mg/kg/d); HFFD with high dose of lycopene group (HLY, 60 mg/kg/d) and HFFD with resveratrol group (RSV, 50 mg/kg/d, positive control). After 8 weeks, feces were collected and the 12 h fasted mice were sacrificed to acquire tissues and blood for parameters measurement. The results showed that the mice in LLY, HLY and RSV groups had significantly lower body weight gain, weight of white adipose tissue, serum levels of high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), lipopolysaccharide (LPS), alanine aminotransferase (ALT), and hepatic concentrations of triglyceride (TG) and interleukin-6 (IL-6) than that in the HFFD group (p < 0.05). HLY and RSV groups also displayed lower serum levels of TG, total cholesterol (TC) and hepatic levels of tumor necrosis factor-α (TNF-α) than the HFFD group (p < 0.05). Liver protein expressions of NLRP3, Pro-Caspase-1, Caspase-1 and NF-κB were lower in the LLY, HLY and RSV groups than those in the HFFD group (p < 0.05). The feces of LY -treated mice had higher relative levels of SCFAs producing bacteria Allobaculum and lower destructive bacteria, including Firmicutes, Lachnospiraceae_NK4A136_group, Desulfovibrio, and Alistipes over the HFFD group (p < 0.05). RSV group also displayed lower fecal levels of Lachnospiraceae_NK4A136_group, Desulfovibrio, and Alistipes than the HFFD group (p < 0.05). In conclusion, LY might prevent NAFLD by suppressing hepatic NF-κB/NLRP3 inflammasome pathway and attenuating gut microbiota dysbiosis.