Limonin Attenuates LPS-Induced Hepatotoxicity by Inhibiting Pyroptosis via NLRP3/Gasdermin D Signaling Pathway

Valtrate alleviates inflammation by targeting USP9X to enhance NLRP3 degradation

BACKGROUND

The NLRP3 inflammasome is a key regulator of innate immunity and plays a critical role in the pathogenesis of various inflammatory diseases. Regulating NLRP3 has emerged as a promising strategy for the development of anti-inflammatory therapies. Valtrate (Val), a natural compound derived from Valeriana officinalis Jones, has demonstrated significant anti-inflammatory activity. However, its precise mechanism of action remains unclear.

PURPOSE

This study elucidates the molecular mechanisms of Val suppressing NLRP3 inflammasome activation.

METHODS

We screened 100 natural compounds for anti-pyroptotic in lipopolysaccharide (LPS)/nigericin-stimulated THP-1 cells and bone marrow-derived macrophages (BMDMs) using lactate dehydrogenase (LDH) release assays. Val's effect on NLRP3 were assessed via immunoblotting and ELISA. Target identification employed DARTS, proteomics, thermal shift assay (TSA), microscale thermophoresis (MST), and molecular dynamics (MD) simulations. In vivo efficacy was evaluated in acetaminophen (APAP)- and LPS-induced liver injury models.

RESULTS

Val potently inhibited pyroptosis (99.20 % LDH reduction) and selectively degraded NLRP3 via post-translation mechanisms (PTMs) without altering its mRNA. DARTS and CETSA confirmed that Val directly interacts with the C2 fragment of USP9X without inhibiting its enzymatic activity, while RMSD, RMSF, and Gibbs energy landscape analyses supported its stable binding to USP9X, which was further confirmed by MST. Mechanistically, Val downregulated USP9X protein expression and promoted K48- and K63-linked ubiquitination and proteasomal degradation of NLRP3. In vivo, Val exhibited therapeutic potential in murine models of acute liver injury induced by APAP and LPS. Val reduced serum ALT and AST levels, inflammatory cytokines, and liver injury (histopathological analysis (H&E) and TUNEL).

CONCLUSION

This study uncovers an unrecognized mechanism by which Val attenuates NLRP3 inflammasome activation by disrupting the USP9X-NLRP3 axis, thereby promoting NLRP3 ubiquitination and proteasomal degradation. Notably, Val down-regulates USP9X protein levels without impairing its catalytic activity, representing a distinct mechanism from existing USP9X inhibitors. These findings not only deepen our understanding of Val's anti-inflammatory action but also underscore its promise as a lead compound for the development of novel therapeutics targeting NLRP3-driven inflammatory diseases.

Potential protective role of Lycium ruthenicum Murray polysaccharides against lipopolysaccharide-induced liver injury via mitochondrial biogenesis

Acute liver injury (ALI), which manifests as abnormal liver function and hepatocyte damage, lacks effective treatment modalities and is associated with a high mortality rate. Recent studies have revealed that hepatoprotection is related to polysaccharide components. In this study, we examined the effect and mechanism of Lycium ruthenicum Murray polysaccharides (LRMP) on liver injury induced by lipopolysaccharide (LPS). Male ICR mice were pre-administered LRMP (100 and 400 mg/kg BW) once daily for 21 days. A single injection of LPS (10 mg/kg BW) was administered on day 21 to induce ALI. The difference between the groups indicated that LRMP supplementation had no adverse effect on body weight. LRMP administration considerably alleviated liver injury, as evidenced by the decreased levels of aspartate transaminase and alanine transaminase, increased levels of albumin, and preservation of liver structural integrity. Moreover, LRMP reduced oxidative stress and inflammatory responses in the liver, maintained mitochondrial structure, regulated mitochondrial apoptotic pathway, and upregulated Sirtuin 1/peroxisome proliferator-activated receptor γ coactivator-1α signalling pathway involved in mitochondrial biogenesis. This study suggests the potential therapeutic application of LRMP in liver-related diseases, which will provide a basis for innovative strategies.

Mechanism of effect and therapeutic potential of NLRP3 inflammasome in spinal cord injury

Spinal cord injury (SCI) is a serious and disabling central nervous system injury that can trigger various neuropathological conditions, resulting in neuronal damage and release of various pro-inflammatory mediators, leading to neurological dysfunction. Currently, surgical decompression, drugs and rehabilitation are primarily used to relieve symptoms and improve endogenous repair mechanisms; however, they cannot directly promote nerve regeneration and functional recovery. SCI can be divided into primary and secondary injuries. Secondary injury is key to determining the severity of injury, whereas inflammation and cell death are important pathological mechanisms in the process of secondary SCI. The activation of the inflammasome complex is thought to be a necessary step in neuro-inflammation and a key trigger for neuronal death. The NLRP3 inflammasome is a cytoplasmic multiprotein complex that is considered an important factor in the development of SCI. Once the NLRP3 inflammasome is activated after SCI, NLRP3 nucleates the assembly of an inflammasome, leading to caspase 1-mediated proteolytic activation of the interleukin-1β (IL-1β) family of cytokines, and induces an inflammatory, pyroptotic cell death. Inhibition of inflammasomes can effectively inhibit inflammation and cell death in the body and promote the recovery of nerve function after SCI. Therefore, inhibition of NLRP3 inflammasome activation may be a promising approach for the treatment of SCI. In this review, we describe the current understanding of NLRP3 inflammasome activation in SCI pathogenesis and its subsequent impact on SCI and summarize drugs and other potential inhibitors based on NLRP3 inflammasome regulation. The objective of this study was to emphasize the role of the NLRP3 inflammasome in SCI, and provide a new therapeutic strategy and theoretical basis for targeting the NLRP3 inflammasome as a therapy for SCI.

Pyroptosis: A Novel Therapeutic Target for Bioactive Compounds in Human Disease Treatment? A Narrative Review

Background/Objectives: Bioactive compounds possess the ability to maintain health and improve diseases by regulating inflammation and cell death processes. Pyroptosis is programmed cell death related to inflammation and exerts a critical role in the development and progression of different types of diseases. This narrative review aims to investigate and discuss the effects of dietary bioactive compounds on pyroptosis in different common human pathologies, such as inflammatory disease, bacterial infection, injury disease, cancer, diabetes and heart disease, etc. Method: Studies published in the major databases until December 2024 in English were considered, for a total of 50 papers. Results: The current evidence demonstrated that the bioactive compounds are able to regulate the pyroptosis process by modulating different inflammasome sensors (NLRP1, NLRP3, and AIM2), caspase family proteins (caspase-1, caspase-3, and caspase-11), and gasdermins (GSDMD and GSDME) in many pathological conditions related to inflammation, including cancer and cardiovascular diseases. Conclusions: Bioactive compounds have powerful potential to be the candidate drug for pyroptosis modulation in inflammatory diseases, even if more clinical studies are needed to confirm the effects and establish efficient doses for humans.

Limonin Exhibits Anti-Inflammatory Effects by Inhibiting mTORC1 and Mitochondrial Reactive Oxygen Species in Psoriatic-like Skin Inflammation

Psoriasis is a chronic inflammatory skin disorder characterized by abnormal immune responses and keratinocyte hyperproliferation. Limonin, a bioactive compound found in citrus fruits, has anti-inflammatory properties in various models; however, its effects on psoriasis are not fully understood. We investigated the therapeutic potential of limonin in a 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced psoriasis mouse model. Mice were treated with TPA to induce psoriasis-like skin lesions, followed by intraperitoneal administration of limonin (200 or 400 μg/mouse) for six days. The results showed that limonin improved psoriasis-related symptoms in a psoriasis-like mouse model by suppressing the mRNA expression of pro-inflammatory cytokines and inflammation-related antimicrobial peptides and regulating the expansion of myeloid cells and T cells. Specifically, limonin reduced glucose uptake and oxidative phosphorylation to shift the metabolic program in the inflamed skin cells of psoriasis-like mice. Limonin activates AMPK and proteins related to mTOR inhibition, thereby suppressing the mTOR signaling pathway. It also inhibits mitochondrial mass and mitochondrial ROS production, thereby preventing the development of dysfunctional mitochondria in inflamed skin cells. Overall, limonin modulates key immune responses and metabolic pathways related to inflammation and mitochondrial health in psoriasis. Therefore, it is a promising natural candidate for the treatment of psoriasis and various inflammatory skin diseases.

Targeting both ferroptosis and pyroptosis may represent potential therapies for acute liver failure

In this editorial, we comment on the article published in the recent issue of the World Journal of Gastroenterology. Acute liver failure (ALF) is a fatal disease that causes uncontrolled massive hepatocyte death and rapid loss of liver function. Ferroptosis and pyroptosis, cell death forms that can be initiated or blocked concurrently, can play significant roles in developing inflammation and various malignancies. However, their roles in ALF remain unclear. The article discovered the positive feedback between ferroptosis and pyroptosis in the progression of ALF, and revealed that the silent information regulator sirtuin 1 (SIRT1) inhibits both pathways through p53, dramatically reducing inflammation and protecting hepatocytes. This suggests the potential use of SIRT1 and its downstream molecules as therapeutics for ALF. Thus, we will discuss the role of ferroptosis and pyroptosis in ALF and the crosstalk between these cell death mechanisms. Additionally, we address potential treatments that could alleviate ALF by simultaneously inhibiting both cell death pathways, as well as examples of SIRT1 activators being used as disease treatment strategies, providing new insights into the therapy of ALF.

Effects of limonin on oxidative stress and early apoptosis in oocytes during in vitro maturation

To investigate the effects of limonin (Lim) on oxidative stress and early apoptosis in bovine oocytes during in vitro maturation (IVM), different concentrations of Lim (0, 10, 20, 50 μmol/L) were added to bovine IVM medium. Oocyte maturation rates and development 24 h after in vitro fertilization (IVF) were examined to determine the optimal Lim concentration. The optimal Lim concentration was added to the IVM medium, and 0 μmol/L Lim was used as the control. Immunofluorescence staining was used to detect the abnormal rate of spindle assembly, reactive oxygen species (ROS), glutathione (GSH), mitochondrial membrane potential (MMP) levels, mitochondrial distribution, and the fluorescence intensity of cathepsin B (CB)-active LC3 protein. RT‒qPCR was used to detect the mRNA expression levels of antioxidant-, apoptosis- and autophagy-related genes in oocytes. The total number of blastocysts and the proportion of apoptotic cells among blastocysts were detected. The results showed that the PBI ejection rate, cleavage rate and blastocyst rate of bovine oocytes in the 20 μmol/L Lim group were significantly higher than those in the control group (P < 0.05). Compared with those in the control group, ROS levels, abnormal mitochondrial distribution, the proportion of abnormal spindle assembly, CB activity and LC3 protein fluorescence intensity of oocytes in the 20 μmol/L Lim group were significantly decreased (P < 0.05), and GSH and MMP levels were significantly increased (P < 0.05). The expression of antioxidant genes (Prdx3, Prdx6, Sirt1) and antiapoptotic genes (Bcl-xl, Survivin) were significantly upregulated (P < 0.05), and the expression levels of proapoptotic genes (Caspase-4, BAX) and autophagy-related genes (LC3) were significantly downregulated (P < 0.05). The total number of cells among in vitro fertilized embryos was significantly increased (P < 0.05), and the apoptosis rate of blastocysts was significantly decreased (P < 0.05). Here, we show that Lim exerts positive effects on bovine oocyte IVM by regulating REDOX homeostasis, reducing spindle damage and enhancing mitochondrial function during IVM, thereby inhibiting oocyte apoptosis and autophagy.

Alcohol-Associated Liver Disease Outcomes: Critical Mechanisms of Liver Injury Progression

Alcohol-associated liver disease (ALD) is a substantial cause of morbidity and mortality worldwide and represents a spectrum of liver injury beginning with hepatic steatosis (fatty liver) progressing to inflammation and culminating in cirrhosis. Multiple factors contribute to ALD progression and disease severity. Here, we overview several crucial mechanisms related to ALD end-stage outcome development, such as epigenetic changes, cell death, hemolysis, hepatic stellate cells activation, and hepatic fatty acid binding protein 4. Additionally, in this review, we also present two clinically relevant models using human precision-cut liver slices and hepatic organoids to examine ALD pathogenesis and progression.

PKR inhibitor protects spinal cord injury through mitigating endoplasmic reticulum stress and pyroptosis

OBJECTIVES

The goal of the study was to reveal the regulatory role of protein kinase R (PKR) in spinal cord injury (SCI), a devasting disorder of the neurological system, and to elucidate its potential mechanism.

METHODS

The established animal and cellular models of SCI were treated by the PKR inhibitor C12. Histological injury and tissue apoptosis were assessed via H&E staining and TUNEL assays, respectively. Basso-Beattie-Bresnahan (BBB) scoring as well as forelimb grip strength tests were employed to evaluate functional recovery. The production of ROS and cytokines were appraised via their related commercial kits. Western blot and immunofluorescence assay were used to examine protein expression. CCK-8 method was used to assay cell activity. Co-immunoprecipitation assay was conducted to measure the affinity of PKR with STAT1.

RESULTS

PKR expression was enhanced following SCI, and the PKR inhibitor C16 mitigated histological injury, cell apoptosis and water content in spinal cord, and improved function recovery following SCI. Meanwhile, C16 attenuated ER stress, pyroptosis, NLRP3 inflammasome and inflammation in mice with SCI and in BV-2 cells challenged with LPS. Additionally, PKR interacted with STAT1 in BV-2 cells, and STAT1 knockdown inhibited ER stress, pyroptosis and inflammation in BV-2 cells challenged with LPS. The protective role of C16 in BV-2 cells exposed to LPS were partly abolished by STAT1 overexpression.

CONCLUSION

PKR inhibition might be a prospective effective approach to attenuating SCI and accelerating function recovery through modulating microglial pyroptosis and ER stress.

Natural Products for Acetaminophen-Induced Acute Liver Injury: A Review

The liver plays a vital role in metabolism, synthesis, and detoxification, but it is susceptible to damage from various factors such as viral infections, drug reactions, excessive alcohol consumption, and autoimmune diseases. This susceptibility is particularly problematic for patients requiring medication, as drug-induced liver injury often leads to underestimation, misdiagnosis, and difficulties in treatment. Acetaminophen (APAP) is a widely used and safe drug in therapeutic doses but can cause liver toxicity when taken in excessive amounts. This study aimed to investigate the hepatotoxicity of APAP and explore potential treatment strategies using a mouse model of APAP-induced liver injury. The study involved the evaluation of various natural products for their therapeutic potential. The findings revealed that natural products demonstrated promising hepatoprotective effects, potentially alleviating liver damage and improving liver function through various mechanisms such as oxidative stress and inflammation, which cause changes in signaling pathways. These results underscore the importance of exploring novel treatment options for drug-induced liver injury, suggesting that further research in this area could lead to the development of effective preventive and therapeutic interventions, ultimately benefiting patients with liver injury caused by medicine.

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

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

Limonin ameliorates cisplatin-induced acute liver injury by inhibiting 11β-hydroxysteroid dehydrogenase type 1

BACKGROUND

Acute liver injury (ALI) is a common side effect of cisplatin treatment in the clinic and can lead to liver failure if not treated promptly. Previous studies have revealed that Limonin, a critical bioactive substance in citrus fruits, can protect multiple organs from various medical conditions. However, whether Limonin could ameliorate cisplatin-induced ALI remains unclear.

METHODS

In vivo and in vitro models were induced by cisplatin in the present study. Non-targeted metabolomics was employed to analyze the metabolic changes in the liver after ALI. In addition, molecular docking was utilized to predict the potential targets of Limonin.

RESULTS

Limonin attenuated hepatic histopathological injury by reducing hepatocyte apoptosis, lipid peroxidation, and inflammation in cisplatin-challenged mice. Employing metabolomics, we revealed that Limonin mediated the balance of various disturbed metabolic pathways in the liver after cisplatin-induced ALI. Integrating public data mining, molecular docking studies, and in vitro experiments demonstrated that Limonin suppressed the expression and activity of its direct target, 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), in the liver, thus reducing the production of corticosterone (CORT), a key metabolite promoted hepatocyte apoptosis.

CONCLUSIONS

Limonin improves the liver metabolic microenvironment by inhibiting 11β-HSD1 to protect against cisplatin-induced ALI.

The role and mechanisms of macrophage polarization and hepatocyte pyroptosis in acute liver failure

Acute liver failure (ALF) is a severe liver disease caused by disruptions in the body's immune microenvironment. In the early stages of ALF, Kupffer cells (KCs) become depleted and recruit monocytes derived from the bone marrow or abdomen to replace the depleted macrophages entering the liver. These monocytes differentiate into mature macrophages, which are activated in the immune microenvironment of the liver and polarized to perform various functions. Macrophage polarization can occur in two directions: pro-inflammatory M1 macrophages and anti-inflammatory M2 macrophages. Controlling the ratio and direction of M1 and M2 in ALF can help reduce liver injury. However, the liver damage caused by pyroptosis should not be underestimated, as it is a caspase-dependent form of cell death. Inhibiting pyroptosis has been shown to effectively reduce liver damage induced by ALF. Furthermore, macrophage polarization and pyroptosis share common binding sites, signaling pathways, and outcomes. In the review, we describe the role of macrophage polarization and pyroptosis in the pathogenesis of ALF. Additionally, we preliminarily explore the relationship between macrophage polarization and pyroptosis, as well as their effects on ALF.

Limonin, a novel AMPK activator, protects against LPS-induced acute lung injury

AMP-activated protein kinase (AMPK) activation plays crucial roles in the treatment of many oxidative stress- and inflammation-induced diseases, including acute lung injury (ALI). Limonin is a naturally occurring tetracyclic triterpenoid extracted from the plants of Rutaceae and Meliaceae. Limonin also serves as an AMPK activator with anti-inflammatory and anti-oxidation effects. However, the potential beneficial effects of limonin on ALI and the possible mechanisms have never been disclosed till now. Here, the effects of limonin on lipopolysaccharide (LPS)-induced ALI in C57 BL/6 mice, plus bone marrow-derived macrophages (BMDM) stimulated with LPS to induce in vitro ALI model were investigated. Limonin significantly improved pulmonary function and alleviated lung pathological injury in LPS-induced mice. Meanwhile, limonin also markedly decreased inflammation and oxidative stress in lung tissues from LPS-treated mice. In vitro experiments also unveiled that limonin could decrease inflammation and oxidative stress in LPS-induced BMDM in a concentration-dependent manner. Mechanically, limonin could promote the activation of AMPKα and upregulate the expression of nuclear factor erythroid 2-related factor 2 (NRF2) in lung tissues and BMDM. Pharmacological inhibition of AMPKα by Compound C or AMPKα knockout could abolish the pulmonary protection from limonin during ALI. In conclusion, limonin mediates the activation of AMPKα/NRF2 pathway, providing an attractive therapeutic target for ALI in the future.

Apigenin Alleviated High-Fat-Diet-Induced Hepatic Pyroptosis by Mitophagy-ROS-CTSB-NLRP3 Pathway in Mice and AML12 Cells

Apigenin is considered the most-known natural flavonoid and is abundant in a wide variety of fruits and vegetables. A high fat diet (HFD) can induce liver injury and hepatocyte death in multiple ways. Pyroptosis is an innovative type of programmed cell death. Moreover, excessive pyroptosis of hepatocytes leads to liver injury. We used HFD to induce liver cell pyroptosis in C57BL/6J mice in this work. After gavage of apigenin, apigenin can significantly reduce the level of lactate dehydrogenase (LDH) in liver tissue ignited by HFD and reduce the levels of NLRP3 (NOD-like receptor family pyrin domain containing 3), the N-terminal domain of GSDMD (GSDMD-N), cleaved-caspase 1, cathepsin B (CTSB), interleukin-1β (IL-1β) and interleukin-18 (IL-18) protein expression and the colocalization of NLRP3 and CTSB and increase the level of lysosomal associated membrane protein-1 (LAMP-1) protein expression, thus alleviating cell pyroptosis. In a further in vitro mechanism study, we find that palmitic acid (PA) can induce pyroptosis in AML12 cells. After adding apigenin, apigenin can clear the damaged mitochondria through mitophagy and reduce the generation of intracellular reactive oxygen species (ROS), thus alleviating CTSB release caused by lysosomal membrane permeabilization (LMP), reducing the LDH release caused by PA and reducing the levels of NLRP3, GSDMD-N, cleaved-caspase 1, CTSB, IL-1β, and IL-18 protein expression. By adding the mitophagy inhibitor cyclosporin A (CsA), LC3-siRNA, the CTSB inhibitor CA-074 methyl ester (CA-074 Me), and the NLRP3 inhibitor MCC950, the aforementioned results were further confirmed. Therefore, our results show that HFD-fed and PA can damage mitochondria, promote the production of intracellular ROS, enhance the lysosomal membrane permeabilization (LMP), and cause the leakage of CTSB, thus activating the NLRP3 inflammatory body and inducing pyroptosis in C57BL/6J mice and AML12 cells, while apigenin alleviates this phenomenon through the mitophagy-ROS-CTSB-NLRP3 pathway.

Hesperetin ameliorates spinal cord injury by inhibiting NLRP3 inflammasome activation and pyroptosis through enhancing Nrf2 signaling

Neuroinflammation is a prominent feature of traumatic spinal cord injuries (SCIs). Hesperetin exhibits anti-inflammatory effects in neurological disorders; however, the potential neuroprotective effects of hesperetin in cases of SCI remain unclear. Sprague-Dawley rats with C5 hemi-contusion injuries were used as an SCI model. Hesperetin was administered to the experimental rats in order to investigate its neuroprotective effects after SCI, and BV2 cells were pretreated with hesperetin or silencing of nuclear factor erythroid 2-related factor 2 (siNrf2), and then stimulated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP). The therapeutic impact and molecular mechanism of hesperetin were elucidated in a series of in vivo and in vitro investigations conducted using a combination of experiments. The results of the present in vivo experiment indicated that hesperetin improved functional recovery and protected spinal cord tissue after SCI. Hesperetin attenuated oxidative stress and microglial activation, lowered malondialdehyde (MDA) levels, and elevated catalase (CAT), glutathione (GSH)-Px, and superoxide dismutase (SOD) levels. Moreover, hesperetin downregulated the expression of advanced oxygenation protein products (AOPPs), ionized calcium-binding adapter molecule 1 (Iba-1), NOD-like receptor protein 3 (NLRP3), and interleukin-1 beta (IL-1β), but increased the expression of Nrf2. In vitro studies have shown that hesperetin inhibits the generation of reactive oxygen species (ROS), as well as the neuroinflammation associated with the upregulation of Nrf2 and heme oxygenase-1 (HO-1) in BV2 cells. The results of the present study indicated that hesperetin inhibited BV2 cell pyroptosis and significantly blocked the expression of NLRP3 inflammasome proteins (NLRP3 Caspase-1 p10 apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain [ASC]) and pro-inflammatory mediators (IL-18, IL-1β). Furthermore, the silencing of Nrf2 by small interfering ribonucleic acid (siRNA) partially abolished its antioxidant effect in the aforementioned cell experiments. Collectively, these findings illustrate that through an increase in Nrf2 signaling hesperetin reduces oxidative stress and neuroinflammation by suppressing NLRP3 inflammasome activation and pyroptosis.

Effects of Herbs and Derived Natural Products on Lipopolysaccharide-Induced Toxicity: A Literature Review

Introduction

Oxidative stress (OS) during inflammation can increase inflammatory responses and damage tissue. Lipopolysaccharide (LPS) can induce oxidative stress and inflammation in several organs. Natural products have several biological activities including anti-inflammatory, antioxidant, and immunoregulatory properties. The aims of the study are to study the possible therapeutic effects of natural products on LPS inducing toxicity on the nervous system, lung, liver, and immune system.

Methods

The in vitro and in vivo research articles that were published in the last 5 years were included in the current study. The keywords included "lipopolysaccharide," "toxicity," "natural products," and "plant extract" were searched in different databases such as Scopus, PubMed, and Google Scholar until October 2021.

Results

The results of most studies indicated that some medicinal herbs and their potent natural products can help to prevent, treat, and manage LPS-induced toxicity. Medicinal herbs and plant-derived natural products showed promising effects on managing and treating oxidative stress, inflammation, and immunomodulation by several mechanisms.

Conclusion

However, these findings provide information about natural products for the prevention and treatment of LPS-induced toxicity, but the scientific validation of natural products requires more evidence on animal models to replace modern commercial medicine.

Trilobatin alleviates non-alcoholic fatty liver disease in high-fat diet plus streptozotocin-induced diabetic mice by suppressing NLRP3 inflammasome activation

Diabetes mellitus (DM) is a factor with great risk in the course of non-alcoholic fatty liver disease (NAFLD) due to its high glucotoxicity and lipotoxicity. Trilobatin, a glycosylated dihydrochalcone derived from the leaves of the Chinese sweet tea Lithocarpus polystachyus Rehd, is reported to possess various pharmacological activities. Nevertheless, it is still unclear regarding if trilobatin can alleviate liver injury in diabetic mice with NAFLD and its mechanism. Our aim was to investigative the protective effects of trilobatin against DM with NAFLD and its mechanism of action. A DM mice model was established by high-fat diet (HFD) feeding with streptozocin (STZ) injections, and treated with trilobatin for 10 weeks. The biochemical results showed that trilobatin restored glucose metabolic disorder and liver function in diabetic mice. The histopathological evaluation revealed that trilobatin improved liver injury by alleviating lipid accumulation and liver fibrosis. Mechanistically, trilobatin decreased expression of NLRP3, p65 NF-κB, cleaved-Caspase-1 and N-GSDMD, as well as the release of IL-18 and IL-1β, leading to a alleviation of inflammation and pyroptosis. Taken together, we determined for the first time found that trilobatin could prevent liver injury in diabetic mice with NAFLD by suppressing NLRP3 inflammasome activation to reduce inflammation and pyroptosis.

11S Glycinin Up-Regulated NLRP-3-Induced Pyroptosis by Triggering Reactive Oxygen Species in Porcine Intestinal Epithelial Cells

11S glycinin is a major soybean antigenic protein, which induces human and animal allergies. It has been reported to induce intestinal porcine epithelial (IPEC-J2) cell apoptosis, but the role of pyroptosis in 11S glycinin allergies remains unknown. In this study, IPEC-J2 cells were used as an in vitro physiological model to explore the mechanism of 11S glycinin-induced pyroptosis. The cells were incubated with 0, 1, 5, and 10 mg·ml⁻¹ 11S glycinin for 24 h. Our results revealed that 11S glycinin significantly inhibited cell proliferation, induced DNA damage, generated active oxygen, decreased mitochondrial membrane potential, and increased the NOD-like receptor protein 3 (NLRP-3) expression of IPEC-J2 cells in a dose-dependent manner. Further, IPEC-J2 cells were transfected with designed sh-NLRP-3 lentivirus to silence NLRP-3. The results showed that 11S glycinin up-regulated the silenced NLRP-3 gene and increased the expression levels of apoptosis-related spot-like protein (ASC), caspase-1, the cleaved gasdermin D, and interleukin-1β. The IPEC-J2 cells showed pyrolysis morphology. Moreover, we revealed that N-acetyl-L-cysteine can significantly inhibit the production of reactive oxygen species and reduce the expression levels of NLRP-3 and the cleaved gasdermin D. Taken together, 11S glycinin up-regulated NLRP-3-induced pyroptosis by triggering reactive oxygen species in IPEC-J2 cells.

Limonin relieves TGF-β-induced hepatocyte EMT and hepatic stellate cell activation in vitro and CCl4-induced liver fibrosis in mice via upregulating Smad7 and subsequent suppression of TGF-β/Smad cascade

Liver fibrosis is a pathological process as a result of intrahepatic deposition of excessive extracellular matrix. Epithelial-mesenchymal transition (EMT) of hepatocytes and activation of hepatic stellate cells (HSCs) both play important roles in the etiology of liver fibrosis. Here, we found that limonin repressed transforming growth factor-β1 (TGF-β)-induced EMT in AML-12 hepatocytes and activation of LX-2 HSCs. In both kinds of cells, limonin suppressed TGF-β-provoked Smad2/3 C-terminal phosphorylation and subsequent nuclear translocation. Transcription of Smad2/3-downstream genes was in turn reduced. However, limonin exerted few effects on Smad2/3 phosphorylation at linker region. Mechanistically, limonin increased Smad7 at mRNA level in both AML-12 and LX-2 cells. Knockdown of Smad7 abrogated inhibitory effects of limonin on TGF-β-induced EMT in AML-12 cells and activation of LX-2 cells. Further studies revealed that limonin alleviated mouse liver fibrosis induced by CCl₄. In livers of model mice, limonin upregulated Smad7 and declined C-terminal phosphorylation and nuclear translocation of Smad2/3. Transcription of Smad2/3-responsive genes was also attenuated. Our findings indicated that limonin inhibits TGF-β-induced EMT of hepatocytes and activation of HSCs in vitro and CCl₄-induced liver fibrosis in mice. Upregulated Smad7 which suppresses Smad2/3-dependent gene transcription is implicated in the hepatoprotective activity of limonin.

Computational studies on the interaction of SARS-CoV-2 Omicron SGp RBD with human receptor ACE2, limonin and glycyrrhizic acid

On November 24, 2021, the SARS-CoV-2 Omicron variant (B.1.1.529) was first identified in South Africa. The World Health Organization (WHO) declared the Omicron as a variant of concern (VoC) because of the unexpected and large numbers of mutations occurred in the genome, higher viral transmission and immune evasions. The present study was performed to explore the interactions of SARS-CoV-2 spike glycoprotein receptor-binding domain (SGp RBD) of the three variants (Omicron, Delta, and WT) with the receptor hACE2. The structural changes occurred in Omicron due to the mutations at key positions improved the ability to mediate SARS-CoV-2 viral infection compared to other VoCs. The phytochemicals limonin and glycyrrhizic acid were docked with the SGp RBD of the variants WT, Delta and Omicron. The computed dock score revealed that limonin and glycyrrhizic acid binds effectively at the SGp RBD of all three variants, and showed almost similar binding affinity at the binding interface of ACE2. Therefore, despite the multiple mutations occurred in Omicron and its viral transmission is comparatively high, the computed binding affinity of the phytochemicals limonin and glycyrrhizic acid supported that the traditional medicines can be useful in formulating adjuvant therapies to fight against the SARS-CoV-2 Omicron.

Advances in cell death - related signaling pathways in acute-on-chronic liver failure

Acute-on-chronic liver failure (ACLF) has been a hot spot in the field of liver disease research in recent years, with high morbidity, rapid course change and high mortality. Currently, there is the absence of specific treatment in clinical practice. Liver transplantation has the best therapeutic effect, but it is prone to have internal environment disorder and liver cell death after transplantation, which leads to the failure of transplantation.In recent years, with the development of molecular biology, scholars have explored the treatment of ACLF at the molecular level, and more and more molecular signaling pathways related to the treatment of ACLF have been discovered. Modulating the relevant signaling pathways to reduce the mortality of liver cells after transplantation may effectively improve the success rate of transplantation. In this review, we introduce some signaling pathways related to cell death and their research progress in acute-on-chronic liver failure.

Limonin, an AMPK Activator, Inhibits Hepatic Lipid Accumulation in High Fat Diet Fed Mice

NAFLD is the most prevalent liver disease in human history. The treatment is still limited yet. In the current study, we reported that limonin inhibited hepatic lipid accumulation and fatty acid synthesis in HFD fed mice. Using AMPK inhibitor and AMPK deficient C. elegans, we revealed the effect was dependent on the activation of AMPK. We found that limonin activated AMPK through inhibition of cellular energy metabolism and increasing ADP:ATP ratio. Furthermore, the treatment of limonin induced AMPK mediated suppression of the transcriptional activity of SREBP1/2. Our study suggests that limonin may a promising therapeutic agent for the treatment of NAFLD.

Limonin Alleviates Non-alcoholic Fatty Liver Disease by Reducing Lipid Accumulation, Suppressing Inflammation and Oxidative Stress

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and continues to rise in the worldwide. Limonin is a triterpenoid compound widely found in the fruits of citrus plants with a wide range of pharmacological effects, including anti-cancer, anti-inflammation, anti-viral, anti-oxidation and liver protection properties. However, the potential molecular mechanism of limonin on NAFLD in zebrafish remains unknown. In this study, zebrafish larvae were exposed to thioacetamide to establish an NAFLD model and the larvae were treated with limonin for 72 h simultaneously. The human liver cell line was stimulated with lipid mixture and meanwhile incubated with limonin for 24 h. The results showed that Limonin significantly reduced the accumulation of lipid droplets in the liver and down-regulated the levels of lipogenic transcription factors FASN and SREBP1 in NAFLD. Limonin suppressed macrophages infiltration and the down-regulated the relative expression levels of the pro-inflammatory factors IL-6, IL-1β and TNF-α secreted by macrophages. Besides, limonin could reversed the reduction of glutathione and the accumulation of reactive oxygen species through up-regulating NRF2/HO-1 signaling pathway in the liver. In conclusion, this study revealed that limonin has a protective effect on NAFLD due to its resistance to lipid deposition as well as antioxidant and anti-inflammatory actions.

Alliin alleviates LPS-induced pyroptosis via promoting mitophagy in THP-1 macrophages and mice

Pyroptosis is a new type of programmed cell death associated with inflammation. Excessive pyroptosis can cause body damage. Alliin is an organosulfur compound extracted from garlic, bearing anti-oxidation and anti-inflammatory properties. In this study, we revealed that alliin alleviated LPS-induced macrophage pyroptosis by detecting PI staining, IL-1β and IL-18 release in vitro and in vivo. In the study of mechanism, we found that alliin might reduce the activation of NLRP3 inflammosome by decreasing intracellular ROS generation. Subsequently, we detected the effect of alliin on mitophagy which degraded damaged mitochondria. The results showed that alliin promoted PINK 1/Parkin-mediated mitophagy. After adding the mitophagy inhibitor CsA, the alleviating effect of alliin on mitochondrial damage and mitochondrial ROS were reversed and the relieving effect of alliin on LPS-induced pyroptosis was inhibited. These results suggested that alliin might reduce intracellular ROS production by promoting mitophagy, thus alleviating LPS-induced macrophages pyroptosis. Our study provides a new perspective and theoretical basis for alliin to alleviate pyroptosis which could further induce body damage.

Limonin ameliorates acute pancreatitis by suppressing JAK2/STAT3 signaling pathway

Acute pancreatitis (AP) is one of the most common acute abdomen of digestive system and has the characteristics of dangerous condition and rapid development. Limonin has been confirmed to hold anti-inflammatory and antioxidant effects in various diseases. However, its potential beneficial effect on AP and the concrete mechanisms have never been revealed. Here, two mouse models were used to investigate the protective effects of limonin on AP, the caerulein-induced mild acute pancreatitis (MAP) model and L-arginine-induced severe AP (SAP) model. Firstly, it was found that limonin administration attenuated lipase and serum amylase levels and ameliorated the histopathological manifestations of pancreatic tissue in a dose-dependent manner. Additionally, the amelioration of AP by limonin was associated with reduced levels of inflammation initiators (IL-6, IL-1β, CCL2, and TNF-α). Mechanistically, we found that limonin suppressed the Janus Activating Kinase 2 (JAK2)/Signal Transducer and Activator of Transcription 3 (STAT3) signaling pathway, as evident by the decreased levels of JAK2 and p-STAT3. And activation of JAK2 using JAK2 activator rescued the protective effects of limonin on AP. Thus, our results demonstrate that limonin can ameliorate AP in two mice models via suppressing JAK2/STAT3 signaling pathway.

Design, Synthesis, and In Vitro and In Vivo Biological Evaluation of Limonin Derivatives for Anti-Inflammation Therapy

In this study, limonin derivatives were used to design new anti-inflammatory compounds with high pharmacological activity and low toxicity. A total of 23 new limonin derivatives were discovered, synthesized, and screened for their anti-inflammatory activity against lipopolysaccharide (LPS)-treated RAW 264.7 cells. Of them, compound f4 was found to be the most active, with a higher efficiency compared with limonin and celecoxib. Subsequently, we studied the mechanism underlying the activity of f4 and found that it inhibited proinflammatory cytokines by blocking the NF-κB/MAPK signaling pathway in LPS-treated RAW 264.7 cells as well as mice. In conclusion, f4 may be a promising anti-inflammatory lead compound.

Sodium Sulfite-Induced Mast Cell Pyroptosis and Degranulation

Sodium sulfite, a common food additive, has been proved to cause allergic reaction. Pyroptosis is an inflammatory form of programmed cell death with plasma membrane lysis. In this study, we found that sodium sulfite triggered pyroptosis, which depended on reactive oxygen species (ROS)/NOD-like receptor protein 3 (NLRP3) in RBL-2H3 mast cells. Sodium sulfite increased the generation of ROS and the expression of NLRP3, caspase-1, gasdermin D N-terminal (GSDMD-N), interleukin-1β (IL-1β), and interleukin-18 (IL-18). The ROS scavenger N-acetyl-L-carnosine (NAC) and the NLRP3 inhibitor MCC950 reversed these effects. Furthermore, using a lactate dehydrogenase kit, propidium iodide staining, scanning electron microscopy, colocalization of GSDMD-N with histamine, and neutral red staining, we found that sodium sulfite notably induced cell membrane rupture. Because β-Hexosaminidase and histamine play a key role in allergic reactions, we detected the release of β-Hexosaminidase and histamine. The data showed that the release of β-Hexosaminidase and histamine induced by sodium sulfite was increased with dose independence, which were inhibited after treatment with NAC or MCC950. Overall, evidence suggested that pyroptosis induced by sodium sulfite may rupture the cell membrane and result in degranulation of mast cells. Our study may provide new insights for the mechanism by which sodium sulfite induces mast cell death and sensitization.