Dietary Fatty Acid Regulation of the NLRP3 Inflammasome via the TLR4/NF-κB Signaling Pathway Affects Chondrocyte Pyroptosis

Soufeng sanjie formula alleviates osteoarthritis by inhibiting macrophage M1 polarization and modulating intestinal metabolites

ETHNOPHARMACOLOGICAL RELEVANCE

Osteoarthritis (OA) is defined as "bone bi" disease based on clinical symptoms in Chinese medicine. Soufeng sanjie formula (SF) is a traditional formula for treating "bone bi" disease, which consists of Scolopendra (dried body of Scolopendra subspinipes mutilans L. Koch) (0.5 g), Scorpions (dried body of Buthus martensii Karsch) (0.5 g), Astragali radix (dried root of Astragalus membranaceus (Fisch.) Bge) (20 g) and Black soybean seed coats (seed coats of Glycine max (L.) Merr) (30 g), and it can be used to treat rheumatoid arthritis. Nonetheless, the potential of SF to postpone the advancement of OA and its underlying mechanisms remain unexplored.

AIM OF THE STUDY

This study investigated whether SF could alleviate OA and the underlying mechanisms.

MATERIALS AND METHODS

Anterior cruciate ligament transection (ACLT) was performed to establish an OA mice model. Mechanical pain and cold pain were assessed to evaluate changes in pain sensitivity in OA mice. Micro-CT was used to observe the microstructure and quantify the bone morphological parameters of knee joints. Safranin O-fast green staining was used to evaluate cartilage damage, and Osteoarthritis Research Society International (OARSI) scores were calculated. Immunohistochemistry was used to assess the expression of inflammatory factors in the synovium of OA mice following SF administration. Immunofluorescence analyzed the fraction of CD80 and iNOS positive regions in the synovium of knee joints. The effect of SF on macrophage M1 polarization was investigated using flow cytometry, western blot and quantitative PCR (qPCR) in vitro. Untargeted metabolomics was used to identify the differential metabolites associated with OA.

RESULTS

SF-treatment markedly reduced the cartilage damage, lowered the OARSI score and downregulated the pain sensitivity in the OA mice. Secondly, SF decreased the expression of IL-6, IL-1β, and TNF-α in the OA synovium. SF also reduced the percentage of CD80 and iNOS in the synovium of the knee joint after ACLT surgery by immunofluorescence. Thirdly, SF inhibited the protein expression of iNOS and COX-2, decreased the percentage of CD80, and reduced the mRNA levels of IL-6, IL-1β, and TNF-α in BMDM cells. Furthermore, SF inhibited the macrophage M1 polarization-related AKT/NF-κB signaling pathway. Finally, untargeted metabolomics showed that SF effectively reduced the levels of intestinal metabolite 18-hydroxyoleic acid in OA mice.

CONCLUSION

Our results suggested that SF reduced pain symptoms and joint inflammation in mice with OA. Furthermore, SF inhibited synovial macrophage M1 polarization and modified the levels of the pro-inflammatory intestinal metabolite 18-hydroxyoleic acid in OA mice. Therefore, SF may be act as a potential Chinese medicine for the treatment of OA.

Regulating lipid metabolism in osteoarthritis: a complex area with important future therapeutic potential

BACKGROUND

Osteoarthritis (OA), which is characterized by pain, inflammation and pathological changes, is associated with abnormal lipid metabolism. Extensive studies have been conducted on the potential functions of lipids including cholesterol, fatty acids (FAs) and adipokines.

MATERIALS AND METHODS

By searching and screening the literature included in the PubMed and Web of Science databases from 1 January 2019 to 1 January 2024, providing an overview of research conducted on lipid metabolism and OA in the last 5 years.

RESULTS

In addition to adiponectin, several studies on the effects of lipid metabolism on OA have been consistent and complementary. Total cholesterol, triglycerides, low-density lipoprotein cholesterol, adipsin, leptin, resistin, saturated FAs, monounsaturated FAs, FA-binding protein 4 and the ratios of the FAs hexadecenoylcarnitine (C16:1) to dodecanoylcarnitine and C16:1 to tetradecanoylcarnitine induced mostly deleterious effects, whereas high-density lipoprotein cholesterol and apolipoprotein A/B/D had a positive impact on the health of joints. The situation for polyunsaturated FAs may be more complicated, as omega-3 increases the genetic susceptibility to OA, whereas omega-6 does the opposite.

Alterations in lipid or adipokine levels and the resulting pathological changes in cartilage and other tissues (such as bone and synovium) ultimately affect joint pain, inflammation and cartilage degradation. Lipid or adipokine regulation has potential as a future direction for the treatment of OA, this potential avenue of OA treatment requires high-quality randomized controlled trials of combined lipid regulation therapy, and more in-depth in vivo and in vitro studies to confirm the underlying mechanism.

DDX3X Activates Chondrocyte Pyroptosis to Promote Osteoarthritis Progression

The RNA-binding protein DDX3X is associated with several biological processes including inflammation and immunity. However, the role of DDX3X in the pathology of inflammation-related osteoarthritis (OA) remains unclear. This study was to explore the action of DDX3X in the progression of OA as well as the underlying mechanisms by using RNA immunoprecipitation (RIP), Immunohistochemical (IHC) and DDX3X knockout mice, etc. We found that DDX3X expression was upregulated in cartilage tissue of OA patient. The in vitro study also showed upregulation of DDX3X in the inflammatory chondrocytes stimulated by LPS. DDX3X overexpression reduced cell viability by inducing pyroptosis in chondrocytes. Knockdown of DDX3X rescued LPS-induced chondrocytes pyroptosis through regulating NLRP3 signaling. In addition, DDX3X deletion attenuates osteoarthritis in vivo. In conclusion, DDX3X promotes OA progression by regulating chondrocytes pyroptosis via the activation of NLRP3 signaling.

Gut Microbiota Disorders and Metabolic Syndrome: Tales of a Crosstalk Process

The microbiota in humans consists of trillions of microorganisms that are involved in the regulation of the gastrointestinal tract and immune and metabolic homeostasis. The gut microbiota (GM) has a prominent impact on the pathogenesis of metabolic syndrome (MetS). This process is reciprocal, constituting a crosstalk process between the GM and MetS. In this review, GM directly or indirectly inducing MetS via the host-microbial metabolic axis has been systematically reviewed. Additionally, the specifically altered GM in MetS are detailed in this review. Moreover, short-chain fatty acids (SCFAs), as unique gut microbial metabolites, have a remarkable effect on MetS, and the role of SCFAs in MetS-related diseases is highlighted to supplement the gaps in this area. Finally, the existing therapeutics are outlined, and the superiority and shortcomings of different therapeutic approaches are discussed, in hopes that this review can contribute to the development of potential treatment strategies.

Osteoarthritis rat serum-derived extracellular vesicles aggravate osteoarthritis development by inducing NLRP3-mediated pyroptotic cell death and cellular inflammation

Osteoarthritis (OA), degenerative joint disease, is the most prevalent form of arthritis worldwide. Besides its substantial burden on society, the high OA morbidity greatly diminishes patients' quality of life. According to recent research, patients-derived serum extracellular vesicles (EVs) are critically involved in sustaining the corresponding disease progression. However, limited research has fully explored the specific functions and molecular mechanisms of OA serum-derived EVs in disease progression. Consequently, we aimed to investigate the underlying mechanism of OA rats-derived serum EVs in regulating OA progression. Before constructing the exosome-cell co-culture system, EVs were extracted from OA and control rat serum and co-cultured with bone marrow mesenchymal stem cells (BM-MSCs). Western blotting (WB), RT-qPCR, and enzyme-linked immunosorbent assay (ELISA) results revealed that OA rat serum-derived EVs upregulated cell pyroptosis-related markers, including nod-Like receptor protein-3 (NLRP3), apoptosis-associated speck-like protein (ASC), gasdermin D (GSDMD), and cleaved caspase-1. The OA rat-EVs also induced the release of LDH and inflammatory cytokines, including interleukin (IL)-1β, IL-18, IL-6, and TNF-α. Additional experiments revealed that OA rat-EVs delivered miR-133a-3p to BM-MSCs and upregulated miR-133a-3p to degrade sirtuin 1 (SIRT1), and activating the downstream NF-κB signaling pathway. Furthermore, the rescuing experiments confirmed that silencing SIRT1 abrogated the miR-133a-3p-induced protective effects in OA-EVs-treated BM-MSCs. In conclusion, OA rats-derived miR-133a-3p-containing EVs modulated the downstream SIRT1/NF-κB pathway-mediated pyroptotic cell death and inflammation in OA. In other words, this study confirmed the role and underlying mechanisms by which OA-associated serum EVs regulate pyroptosis and inflammation response in OA development.

Effects and Mechanisms of Polyunsaturated Fatty Acids on Age-Related Musculoskeletal Diseases: Sarcopenia, Osteoporosis, and Osteoarthritis-A Narrative Review

Background: The process of the globally aging population has been accelerating, leading to an increasing social burden. As people age, the musculoskeletal system will gradually go through a series of degenerative and loss of function and eventually develop age-related musculoskeletal diseases, like sarcopenia, osteoporosis, and osteoarthritis. On the other hand, several studies have shown that polyunsaturated fatty acids (PUFAs) possess various important physiological functions on the health of muscles, bones, and joints. Objective: This narrative review paper provides a summary of the literature about the effects and mechanisms of PUFAs on age-related musculoskeletal diseases for the prevention and management of these diseases. Methods: Web of Science, PubMed, Science Direct, and Scopus databases have been searched to select the relevant literature on epidemiological, cellular, and animal experiments and clinical evidence in recent decades with keywords "polyunsaturated fatty acids", "PUFAs", "omega-3", "omega-6", "musculoskeletal diseases", "sarcopenia", "osteoporosis", "osteoarthritis", and so on. Results: PUFAs could prevent and treat age-related musculoskeletal diseases (sarcopenia, osteoporosis, and osteoarthritis) by reducing oxidative stress and inflammation and controlling the growth, differentiation, apoptosis, and autophagy of cells. This review paper provides comprehensive evidence of PUFAs on age-related musculoskeletal diseases, which will be helpful for exploitation into functional foods and drugs for their prevention and treatment. Conclusions: PUFAs could play an important role in the prevention and treatment of sarcopenia, osteoporosis, and osteoarthritis.

Pyroptosis in Skeleton Diseases: A Potential Therapeutic Target Based on Inflammatory Cell Death

Skeletal disorders, including fractures, osteoporosis, osteoarthritis, rheumatoid arthritis, and spinal degenerative conditions, along with associated spinal cord injuries, significantly impair daily life and impose a substantial burden. Many of these conditions are notably linked to inflammation, with some classified as inflammatory diseases. Pyroptosis, a newly recognized form of inflammatory cell death, is primarily triggered by inflammasomes and executed by caspases, leading to inflammation and cell death through gasdermin proteins. Emerging research underscores the pivotal role of pyroptosis in skeletal disorders. This review explores the pyroptosis signaling pathways and their involvement in skeletal diseases, the modulation of pyroptosis by other signals in these conditions, and the current evidence supporting the therapeutic potential of targeting pyroptosis in treating skeletal disorders, aiming to offer novel insights for their management.

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

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

Inhibiting the IRAK4/NF-κB/NLRP3 signaling pathway can reduce pyroptosis in hippocampal neurons and seizure episodes in epilepsy

BACKGROUND

Interleukin-1 receptor-associated kinase 4 (IRAK4) plays an important role in immune modulation in various central nervous system disorders. However, IRAK4 has not been reported in epilepsy models in animal and clinical studies, nor has its involvement in regulating pyroptosis in epilepsy.

METHOD

First, we performed transcriptome sequencing, quantitative real-time polymerase chain reaction, and western blot analysis on the hippocampal tissues of refractory epilepsy patients to measure the mRNA and protein levels of IRAK4 and pyroptosis-related proteins. Second, we successfully established a pentylenetetrazol (PTZ)-induced seizure mouse model. We conducted behavioral tests, electroencephalography, virus injection, and molecular biology experiments to investigate the role of IRAK4 in seizure activity regulation.

RESULTS

IRAK4 is upregulated in the hippocampus of epilepsy patients and PTZ-induced seizure model mice. IRAK4 expression is observed in the hilar neurons of PTZ-induced mice. Knocking down IRAK4 in PTZ-induced mice downregulated pyroptosis-related protein expression and alleviated seizure activity. Overexpressing IRAK4 in naive mice upregulated pyroptosis-related protein expression and increased PTZ-induced abnormal neuronal discharges. IRAK4 and NF-κB were found to bind to each other in patient hippocampal tissue samples. Pyrrolidine dithiocarbamate reversed the pyroptosis-related protein expression increase caused by PTZ. PF-06650833 alleviated seizure activity and inhibited pyroptosis in PTZ-induced seizure mice.

CONCLUSION

IRAK4 plays a key role in the pathological process of epilepsy, and its potential mechanism may be related to pyroptosis mediated by the NF-κB/NLRP3 signaling pathway. PF-06650833 has potential as a therapeutic agent for alleviating epilepsy.

Tributyltin chloride induces chondrocyte damage through the activation of NLRP3‑mediated inflammation and pyroptosis

Tributyltin chloride (TBTC) is known to have effects and mechanisms in various diseases; however, whether TBTC is detrimental to joints and causes osteoarthritis (OA), as well as its underlying mechanism, has not yet been fully elucidated. The present study explored the effects of TBTC on rat chondrocytes, as well as on mouse OA. The toxicity of TBTC toward rat chondrocytes was detected using a lactate dehydrogenase (LDH) leakage assay and cell viability was evaluated using the Cell Counting Kit‑8 assay. The results showed that TBTC decreased the viability of rat chondrocytes and increased the LDH leakage rate in a concentration‑dependent manner. Moreover, compared with in the control group, TBTC increased the expression levels of interleukin (IL)‑1β, IL‑18, matrix metalloproteinase (MMP)‑1, MMP‑13, NLR family pyrin domain containing 3 (NLRP3), caspase‑1, PYD and CARD domain containing, and gasdermin D in chondrocytes. Furthermore, knockdown of NLRP3 reversed the TBTC‑induced increases in LDH leakage and NLRP3 inflammasome‑associated protein levels. In vivo, TBTC exacerbated cartilage tissue damage in mice from the OA group, as evidenced by the attenuation of safranin O staining. In conclusion, TBTC may aggravate OA in mice by promoting chondrocyte damage and inducing pyroptosis through the activation of NLRP3 and caspase‑1 signaling. The present study demonstrated that TBTC can cause significant damage to the articular cartilage; therefore, TBTC contamination should be strictly monitored.

Pyroptosis-related crosstalk in osteoarthritis: Macrophages, fibroblast-like synoviocytes and chondrocytes

The pathogenesis of osteoarthritis (OA) involves a multifaceted interplay of inflammatory processes. The initiation of pyroptosis involves the secretion of pro-inflammatory cytokines and has been identified as a critical factor in regulating the development of OA. Upon initiation of pyroptosis, a multitude of inflammatory mediators are released and can be disseminated throughout the synovial fluid within the joint cavity, thereby facilitating intercellular communication across the entire joint. The main cellular components of joints include chondrocytes (CC), fibroblast-like synoviocytes (FLS) and macrophages (MC). Investigating their interplay can enhance our understanding of OA pathogenesis. Therefore, we comprehensively examine the mechanisms underlying pyroptosis and specifically investigate the intercellular interactions associated with pyroptosis among these three cell types, thereby elucidating their collective contribution to the progression of OA. We propose the concept of ' CC-FLS-MC pyroptosis-related crosstalk', describe the various pathways of pyroptotic interactions among these three cell types, and focus on recent advances in intervening pyroptosis in these three cell types for treating OA. We hope this will provide a possible direction for diversification of treatment for OA. The Translational potential of this article. The present study introduces the concept of 'MC-FLS-CC pyroptosis-related crosstalk' and provides an overview of the mechanisms underlying pyroptosis, as well as the pathways through which it affects MC, FLS, and CC. In addition, the role of regulation of these three types of cellular pyroptosis in OA has also been concerned. This review offers novel insights into the interplay between these cell types, with the aim of providing a promising avenue for diversified management of OA.

The consumption of lard oil during pregnancy and postpartum periods has negative effects on cognitive function by altering the fatty acid profile and activating neuroinflammation via calcium signaling pathway in the maternal mice brain

It has been suggested that dietary intake of lipids and fatty acids may influence cognitive function, however, the effect of lard intake during pregnancy and postpartum periods on cognitive function of mother remains to be elucidated. We investigated the effect and mechanism of consuming soybean oil (SO), the mixed oil of lard and soybean oil at the ratio of 1:1 (LS) and lard oil (LO) during the pregnancy and postpartum periods on cognitive function of the maternal mice. All pregnant C57BL/6JNifdc mice were fed with soybean oil diet during day 0-10 (the day when vaginal plugs appeared in female mice was recorded as day 0), and then randomly assigned to SO, LS and LO groups (n = 10) from day 11 to day 44. The time in center zone and the number of times to enter in center zone were significantly higher in the SO group than in the LO group detected by the open-field test. The levels of neuroglial cells, NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome complex and pyroptosis related proteins in brain of the LO group were significantly higher than those in the SO group. RNA-sequencing results showed that the calcium signaling pathway related genes in brain, including Adcy8, Ntsr1, Trhr, Oxtr, Htr5b and Camk2d levels significantly higher in the LO group than in the SO group. Lipidomic analysis indicated that PG 18:2_18:2, PG 20:5_22:6, and CL 12:0_16:0_22:3_22:5 of glycerophospholipid metabolism in brain significantly connected with Htr5b of calcium signaling pathway. In conclusion, the intake of lard during the pregnancy and postpartum periods is detrimental to the cognitive function of maternal mice, which probably due to changes in the composition of fatty acid in the brain, thereby activating neuroinflammation via calcium signaling pathway in brain.

The metabolic characteristics and changes of chondrocytes in vivo and in vitro in osteoarthritis

Osteoarthritis (OA) is an intricate pathological condition that primarily affects the entire synovial joint, especially the hip, hand, and knee joints. This results in inflammation in the synovium and osteochondral injuries, ultimately causing functional limitations and joint dysfunction. The key mechanism responsible for maintaining articular cartilage function is chondrocyte metabolism, which involves energy generation through glycolysis, oxidative phosphorylation, and other metabolic pathways. Some studies have shown that chondrocytes in OA exhibit increased glycolytic activity, leading to elevated lactate production and decreased cartilage matrix synthesis. In OA cartilage, chondrocytes display alterations in mitochondrial activity, such as decreased ATP generation and increased oxidative stress, which can contribute to cartilage deterioration. Chondrocyte metabolism also involves anabolic processes for extracellular matrix substrate production and energy generation. During OA, chondrocytes undergo considerable metabolic changes in different aspects, leading to articular cartilage homeostasis deterioration. Numerous studies have been carried out to provide tangible therapies for OA by using various models in vivo and in vitro targeting chondrocyte metabolism, although there are still certain limitations. With growing evidence indicating the essential role of chondrocyte metabolism in disease etiology, this literature review explores the metabolic characteristics and changes of chondrocytes in the presence of OA, both in vivo and in vitro. To provide insight into the complex metabolic reprogramming crucial in chondrocytes during OA progression, we investigate the dynamic interaction between metabolic pathways, such as glycolysis, lipid metabolism, and mitochondrial function. In addition, this review highlights prospective future research directions for novel approaches to diagnosis and treatment. Adopting a multifaceted strategy, our review aims to offer a comprehensive understanding of the metabolic intricacies within chondrocytes in OA, with the ultimate goal of identifying therapeutic targets capable of modulating chondrocyte metabolism for the treatment of OA.

Oleic and linoleic acids promote chondrocyte apoptosis by inhibiting autophagy via downregulation of SIRT1/FOXO1 signaling

Osteoarthritis (OA) is a complex joint disease that currently has no cure. OA involves metabolic disorders in chondrocytes and an imbalance between autophagy and apoptosis. As a common risk factor for OA, obesity induces changes in the fatty acid composition of synovial fluid, thereby disturbing chondrocyte homeostasis. However, whether unsaturated fatty acids affect the development of OA by regulating chondrocyte autophagy remains unclear. This study aimed to determine the effects of oleic and linoleic acids on chondrocyte autophagy and related mechanisms. Based on the mass spectrometry results, the levels of multiple unsaturated fatty acids, including oleic and linoleic acids, in the synovial fluid of patients with OA and obesity were significantly higher than those in patients with OA only. Moreover, we found that FOXO1 and SIRT1 were downregulated after oleic and linoleic acids treatment of chondrocytes, which inhibited chondrocyte autophagy. Importantly, the upregulation of SIRT1 and FOXO1 expression not only increased the level of autophagy but also improved the expression of chondrocyte extracellular matrix proteins. Furthermore, upregulated SIRT1 and FOXO1 expression alleviated the destruction of the articular cartilage in an OA rat model. Our results suggest that SIRT1/FOXO1 signaling can alleviate oleic acid- and linoleic acid-induced cartilage degradation both in vitro and in vivo and that the SIRT1/FOXO1 pathway may serve as an effective treatment target for inhibiting OA progression.

FOXQ1 inhibits the progression of osteoarthritis by regulating pyroptosis

BACKGROUND

Osteoarthritis (OA) is the most common age-related joint disease, and the NLRP3-induced pyroptosis has been demonstrated in its progression. The upstream molecules or specific mechanisms controlling NLRP3 and pyroptosis in OA remain unclear.

METHODS

Transcriptome sequencing was performed in the OA mice model, and the expression levels of differentially expressed genes were assessed by qRT-PCR. The cell model was constructed by IL-1β-induced ATDC5 cells. The cell proliferation was examined using CCK-8 assay, and apoptosis was tested using flow cytometry. Western blot was used in protein inspection, and ELISA was used in inflammatory response evaluation.

RESULTS

Compared with the control group, there were 229 up-regulated and 32 down-regulated genes in model group. We detected that FOXQ1 was down-regulated in the OA mice model, improved proliferation, and restrained apoptosis of chondrocytes. Over-expression of FOXQ1 could inhibit pyroptosis-related proteins and inflammatory cytokines, containing NLRP3, Caspase-1, GSDMD, IL-6, IL-18, and TNF-α, and in contrast, FOXQ1 silencing exerted the opposite trend.

CONCLUSIONS

FOXQ1 may inhibit OA progression via down-regulating NLRP3-induced pyroptosis in the present study.

n-3 polyunsaturated fatty acids alleviate the progression of obesity-related osteoarthritis and protect cartilage through inhibiting the HMGB1-RAGE/TLR4 signaling pathway

Osteoarthritis (OA) is a common joint degenerative disease. There is currently no cure for OA. Dietary fatty acids have potential value in the prevention and treatment of OA. n-3 polyunsaturated fatty acids (PUFAs) have anti-inflammatory effects, but their anti-OA mechanism remains unclear. High-mobility group box 1 (HMGB1) promotes inflammation and participates the pathogenesis of OA. The purpose of this study was to investigate the protective effect of n-3 PUFAs on cartilage and whether n-3 PUFAs could exert an anti-OA effect through inhibiting HMGB1-RAGE/TLR4 signaling pathway. We established an obesity-related post-traumatic OA mice model and an in vitro study was conducted to explore the regulatory mechanism of n-3 PUFAs on HMGB1 and its signal pathway against OA. We found that diet rich in n-3 PUFAs alleviated OA-like lesions of articular cartilage with the decrease of HMGB1-RAGE/TLR4 signaling protein in mice. In SW1353 cells, DHA significantly reduced the expression of HMGB1-RAGE/TLR4 signaling protein which was up-regulated by IL-1β stimulation. HMGB1 overexpression reversed the inhibitory effect of DHA on HMGB1-RAGE/TLR4 signaling pathway. The activation of SIRT1 may participate the inhibitory effect of DHA on HMGB1-RAGE/TLR4 signaling pathway. In conclusion, n-3 PUFAs could attenuate the progression of obesity-related OA and exert protective effect on cartilage by inhibiting HMGB1-RAGE/TLR4 signaling pathway, which may be associated with the activation of SIRT1. Dietary n-3 PUFAs supplements can be considered as a potential therapeutic substance for OA.

Pyroptosis in Osteoarthritis: Molecular Mechanisms and Therapeutic Implications

Osteoarthritis (OA) is a chronic disease that causes pain and functional impairment by affecting joint tissue. Its global impact is noteworthy, causing significant economic losses and property damage. Despite extensive research, the underlying pathogenesis of OA remain an area of ongoing investigation. It has recently been discovered that the OA progression is significantly influenced by pyroptosis. Pyroptosis is a complex process that involves three pathways culminating in the assembly of Gasdermin-D (GSDMD)-N-terminal (GSDMD-NT) into pores through aggregation on the plasma membrane. The aggregation of GSDMD-NT proteins stimulates the release of inflammatory mediators, such as Interleukin-1β (IL-1β), Interleukin-18 (IL-18), and Matrix Metallopeptidase 13 (MMP13), ultimately leading to cellular lysis. The pyroptosis process in specific cells, including synovial macrophages, fibroblast-like synoviocytes (FLS), chondrocytes, and subchondral osteoblasts, contributs factor to the development of OA. Currently, the specific cells that undergo pyroptosis first are not yet fully understood, and it remains unknown whether pyroptosis in one cell can trigger the same process in other cells. Therefore, targeting pyroptosis could potentially offer a novel treatment approach for OA patients. We present a comprehensive analysis of the molecular mechanisms and key features of pyroptosis. We also outline the current research progress on various aspects, including synovial tissue, articular cartilage, extracellular matrix (ECM), and subchondral bone, with a focus on pyroptosis. The aim is to provide theoretical references for the effective management of OA.

Resatorvid alleviates experimental inflammatory TMJOA by restraining chondrocyte pyroptosis and synovial inflammation

OBJECTIVES

Innate immunity plays a significant role in the pathogenesis of temporomandibular joint osteoarthritis (TMJOA), which is characterized by synovial inflammation and condylar cartilage degradation. We are urged to investigate the impact of Resatorvid, a preventative drug that inhibits Toll-like receptor 4 (TLR4), on experimental inflammatory TMJOA pathology.

METHODS

An intra-articular injection of complete Freund's adjuvant (CFA) was used to induce an experimental inflammatory mouse TMJOA model, and TLR4 expression was identified by immunofluorescent labeling. Intraperitoneal injections of Resatorvid were administered to CFA-induced TMJOA mice, and the pathology of TMJOA animals with and without Resatorvid treatment was examined by H&E, Safranin-O/Fast Green, and TRAP staining, as well as micro-CT, immunohistochemistry, and immunofluorescence. The impact of Resatorvid on chondrocyte pyroptosis and macrophage inflammation was further investigated using ATDC5 chondrocytes and RAW264.7 macrophages pretreated with relevant antagonists.

RESULTS

CFA-induced TMJOA mice revealed remarkable synovial inflammation, together with a time course of cartilage degradation and bone destruction, with TLR4 elevated in the synovium and condylar cartilage. Prophylactic treatment with Resatorvid mitigated synovial inflammation, cartilage degeneration, and bone destruction in CFA-induced TMJOA mice and downregulated MyD88/NF-κB expression. Ex vivo studies demonstrated that Resatorvid treatment alleviated NOD-like receptor protein 3 (NLRP3)-mediated chondrocyte pyroptosis and degeneration and relieved macrophage inflammation by preventing reactive oxygen species (ROS) production through NLRP3 signaling.

CONCLUSION

Prophylactic treatment with Resatorvid alleviates TMJOA pathology by inhibiting chondrocyte pyroptosis and degeneration, as well as ROS-induced macrophage inflammation, through TLR4/MyD88/NF-κB/NLRP3.

Advances in understanding effects of miRNAs on apoptosis, autophagy, and pyroptosis in knee osteoarthritis

MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs. MicroRNAs-mediated signaling pathways play a critical regulatory role in inducing apoptosis, autophagy, and pyroptosis in developing knee osteoarthritis (KOA). Given this, we searched databases, such as PubMed, using keywords including "miRNA," "knee osteoarthritis," "apoptosis," "autophagy," "pyroptosis", and their combinations. Through an extensive literature review, we conclude that miRNAs can be modulated through various signaling pathways, such as Wnt/β-catenin, TGF-β, PI3K/AKT/mTOR, and NLRP3/Caspase-1, to regulate apoptosis, autophagy, and pyroptosis in KOA. Furthermore, we note that P2X7R and HMGB1 may be crucial regulatory molecules involved in the interconnected regulation of apoptosis, autophagy, and pyroptosis in KOA. Additionally, we describe that miR-140-5p and miR-107 can modulate the advancement of KOA chondrocytes by targeting distinct molecules involved in apoptosis, autophagy, and pyroptosis, respectively. Therefore, we conclude that miRNAs may be potential biomarkers and therapeutic targets for the early prediction, diagnosis, and effective therapeutic approaches of KOA.

Mechanistic and therapeutic insights into the function of NLRP3 inflammasome in sterile arthritis

The NLRP3 inflammasome, which belongs to the pyrin domain containing 3 family of NOD-like receptors, has a significant impact on both the innate and adaptive immune responses. Regulating host immune function and protecting against microbial invasion and cell damage, the NLRP3 inflammasome plays a crucial role. By triggering caspase-1, it facilitates the development of the inflammatory cytokines IL-1β and IL-18, and triggers cell pyroptosis, resulting in cell lysis and demise. Common sterile arthritis includes osteoarthritis (OA), rheumatoid arthritis (RA) and gouty arthritis (GA), all of which manifest as bone destruction and synovial inflammation in a complex inflammatory state, placing a significant medical burden on the families of patients and government agencies. In the past few years, there has been a growing interest in investigating the impact of cell pyroptosis on arthritis development, particularly the widespread occurrence of pyroptosis mediated by the NLRP3 inflammasome. The NLRP3 inflammasome's biological properties are briefly described in this review, along with the presentation of the fundamental processes of pyroptosis resulting from its activation. Furthermore, we provide a summary of the advancements made in studying the NLRP3 inflammasome in various forms of arthritis and enumerate the intervention approaches that target the NLRP3-mediated pyroptosis, either directly or indirectly. These discoveries lay the groundwork for future investigations on medications for arthritis, offering fresh approaches for the clinical identification and treatment of this condition.

Tanshinone IIA inhibits cardiomyocyte pyroptosis through TLR4/NF-κB p65 pathway after acute myocardial infarction

Background: Tanshinone IIA, derived from Radix Salviae Miltiorrhizae (Salvia miltiorrhiza Bunge), constitutes a significant component of this traditional Chinese medicine. Numerous studies have reported positive outcomes regarding its influence on cardiac function. However, a comprehensive comprehension of the intricate mechanisms responsible for its cardioprotective effects is still lacking. Methods: A rat model of heart failure (HF) induced by acute myocardial infarction (AMI) was established via ligation of the left anterior descending coronary artery. Rats received oral administration of tanshinone IIA (1.5 mg/kg) and captopril (10 mg/kg) for 8 weeks. Cardiac function was assessed through various evaluations. Histological changes in myocardial tissue were observed using staining techniques, including Hematoxylin and Eosin (HE), Masson, and transmission electron microscopy. Tunel staining was used to detect cell apoptosis. Serum levels of NT-pro-BNP, IL-1β, and IL-18 were quantified using enzyme-linked immunosorbent assay (ELISA). Expression levels of TLR4, NF-κB p65, and pyroptosis-related proteins were determined via western blotting (WB). H9C2 cardiomyocytes underwent hypoxia-reoxygenation (H/R) to simulate ischemia-reperfusion (I/R) injury, and cell viability and apoptosis were assessed post treatment with different tanshinone IIA concentrations (0.05 μg/ml, 0.1 μg/ml). ELISA measured IL-1β, IL-18, and LDH expression in the cell supernatant, while WB analysis evaluated TLR4, NF-κB p65, and pyroptosis-related protein levels. NF-κB p65 protein nuclear translocation was observed using laser confocal microscopy. Results: Tanshinone IIA treatment exhibited enhanced cardiac function, mitigated histological cardiac tissue damage, lowered serum levels of NT-pro-BNP, IL-1β, and IL-18, and suppressed myocardial cell apoptosis. Moreover, tanshinone IIA downregulated the expression of TLR4, NF-κB p65, IL-1β, pro-IL-1β, NLRP3, Caspase-1, and GSDMD-N pyroptosis-related proteins in myocardial tissue. Additionally, it bolstered H/R H9C2 cardiomyocyte viability, curbed cardiomyocyte apoptosis, and reduced the levels of TLR4, NF-κB p65, IL-1β, pro-IL-1β, NLRP3, Caspase-1, and GSDMD-N pyroptosis-related proteins in H/R H9C2 cells. Furthermore, it hindered NF-κB p65 protein nuclear translocation. Conclusion: These findings indicate that tanshinone IIA enhances cardiac function and alleviates myocardial injury in HF rats following AMI. Moreover, tanshinone IIA demonstrates potential suppression of cardiomyocyte pyroptosis. These effects likely arise from the inhibition of the TLR4/NF-κB p65 signaling pathway, presenting a promising therapeutic target.

Tanshinone IIA alleviates chondrocyte apoptosis and extracellular matrix degeneration by inhibiting ferroptosis

Articular cartilage degeneration caused by chondrocyte damage is the primary pathological mechanism of osteoarthritis (OA). Oxidative stress is correlated with chondrocyte injury by potentiating ferroptosis, a newly identified form of cell death. Given the effects of Tanshinone IIA (Tan IIA) on alleviating oxidative stress, we further explored whether Tan IIA inhibited chondrocyte death and cartilage degeneration by decreasing ferroptosis. ATDC5 chondrocytes were treated with lipopolysaccharides (LPS) and Tan IIA, and cell viability was assessed using cell counting kit-8 (CCK-8) assays. Matrix metalloproteinase-13 (MMP13), a disintegrin and metalloproteinase with thrombospondin motif-5 (ADAMTS5), and type II collagen (Col II) levels were measured using quantitative real-time polymerase chain reaction (qRT‒PCR), western blotting, and immunofluorescence (IF) analysis. We demonstrated that Tan IIA treatment prominently increased ATDC5 cell viability and decreased cell apoptosis in the presence of LPS-induced stress. MMP13 and ADAMTS5 expression was increased, and Col II expression was decreased in ATDC5 cells after LPS stimulation, whereas these changes were reversed by Tan IIA. Mechanistically, Tan IIA inhibited LPS-induced ferroptosis in ATDC5 cells, as indicated by decreased levels of iron, reactive oxygen species, and malondialdehyde and increased GSH levels. Importantly, a ferroptosis agonist partially abrogated the effect of Tan IIA on alleviating chondrocyte damage and death. Taken together, these results suggest that Tan IIA ameliorates chondrocyte apoptosis and cartilage degeneration by inhibiting ferroptosis and may be a potential therapeutic agent for OA.

The role of pyroptosis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the main histologic type of liver cancer. It accounts for the majority of all diagnoses and deaths due to liver cancer. The induction of tumor cell death is an effective strategy to control tumor development. Pyroptosis is an inflammatory programmed cell death caused by microbial infection, accompanied by activation of inflammasomes and release of pro-inflammatory cytokines, interleukin-1β (IL-1β), and interleukin-18 (IL-18). The cleavage of gasdermins (GSDMs) promotes the occurrence of pyroptosis leading to cell swelling, lysis, and death. Accumulating evidence has indicated that pyroptosis influences the progression of HCC by regulating immune-mediated tumor cell death. Currently, some researchers hold the view that inhibition of pyroptosis-related components may prevent the incidence of HCC, but more researchers have the view that activation of pyroptosis exerts a tumor-inhibitory effect. Growing evidence indicates that pyroptosis can prevent or promote tumor development depending on the type of tumor. In this review, pyroptosis pathways and pyroptosis-related components were discussed. Next, the role of pyroptosis and its components in HCC was described. Finally, the therapeutic significance of pyroptosis in HCC was discussed.

Targeting the Inflammatory Hallmarks of Obesity-Associated Osteoarthritis: Towards Nutraceutical-Oriented Preventive and Complementary Therapeutic Strategies Based on n-3 Polyunsaturated Fatty Acids

Obesity (Ob), which has dramatically increased in the last decade, is one of the main risk factors that contribute to the incidence and progression of osteoarthritis (OA). Targeting the characteristics of obesity-associated osteoarthritis (ObOA) may offer new chances for precision medicine strategies in this patient cohort. First, this review outlines how the medical perspective of ObOA has shifted from a focus on biomechanics to the significant contribution of inflammation, mainly mediated by changes in the adipose tissue metabolism through the release of adipokines and the modification of fatty acid (FA) compositions in joint tissues. Preclinical and clinical studies on n-3 polyunsaturated FAs (PUFAs) are critically reviewed to outline the strengths and weaknesses of n-3 PUFAs' role in alleviating inflammatory, catabolic and painful processes. Emphasis is placed on potential preventive and therapeutic nutritional strategies based on n-3 PUFAs, with a focus on ObOA patients who could specifically benefit from reformulating the dietary composition of FAs towards a protective phenotype. Finally, tissue engineering approaches that involve the delivery of n-3 PUFAs directly into the joint are explored to address the perspectives and current limitations, such as safety and stability issues, for implementing preventive and therapeutic strategies based on dietary compounds in ObOA patients.

Fucoxanthin alleviated atherosclerosis by regulating PI3K/AKT and TLR4/NFκB mediated pyroptosis in endothelial cells

Fucoxanthin, a type of natural xanthophyll carotenoid, is mainly present in seaweeds and various microalgae. This compound has been proved to possess multiple functions including antioxidation, anti-inflammation and anti-tumor. Atherosclerosis is widely deemed as a chronic inflammation disease, and as the basis of vascular obstructive disease. However, there is rare research about fucoxanthin's effects on atherosclerosis. In this study, we demonstrated that the plaque area of mice treated with fucoxanthin was significantly reduced compared to the group that did not receive fucoxanthin. In addition, Bioinformatics analysis showed that PI3K/AKT signaling might be involved in the protective effect of fucoxanthin, and this hypothesis was then verified in vitro endothelial cell experiments. Besides, our further results showed that endothelial cell mortality measured by TUNEL and flow cytometry was significantly increased in the oxidized low-density lipoprotein (ox-LDL) treatment group while significantly decreased in the fucoxanthin treatment group. In addition, the pyroptosis protein expression level in the fucoxanthin group was significantly lower than that in the ox-LDL group, which indicated that fucoxanthin improved the pyroptosis level of endothelial cells. Furthermore, it was revealed that TLR4/NFκB signaling were also participated in the protection of fucoxanthin on endothelial pyroptosis. Moreover, the protection of fucoxanthin on endothelial cell pyroptosis was abrogated when PI3K/AKT was inhibited or TLR4 was overexpressed, which further suggested the anti-pyroptosis effect of fucoxanthin was mediated through regulations of PI3K/AKT and TLR4/NFκB signaling.

A Lipid Perspective on Regulated Pyroptosis

Pyroptosis is a novel pro-inflammatory cell programmed death dependent on Gasdermin (GSMD) family-mediated membrane pore formation and subsequent cell lysis, accompanied by the release of inflammatory factors and expanding inflammation in multiple tissues. All of these processes have impacts on a variety of metabolic disorders. Dysregulation of lipid metabolism is one of the most prominent metabolic alterations in many diseases, including the liver, cardiovascular system, and autoimmune diseases. Lipid metabolism produces many bioactive lipid molecules, which are important triggers and endogenous regulators of pyroptosis. Bioactive lipid molecules promote pyroptosis through intrinsic pathways involving reactive oxygen species (ROS) production, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, lysosomal disruption, and the expression of related molecules. Pyroptosis can also be regulated during the processes of lipid metabolism, including lipid uptake and transport, de novo synthesis, lipid storage, and lipid peroxidation. Taken together, understanding the correlation between lipid molecules such as cholesterol and fatty acids and pyroptosis during metabolic processes can help to gain insight into the pathogenesis of many diseases and develop effective strategies from the perspective of pyroptosis.

Cartilage-Sparing Properties of Equine Omega Complete in an Organ Culture Model of Cartilage Inflammation

The purpose of this study was to determine anti-inflammatory and/or chondroprotective effects of Equine Omega Complete (EOC) on cartilage explants stimulated with lipopolysaccharide (LPS). Explants were aseptically prepared from the intercarpal joints of 17 market-weight pigs and placed in culture at 37°C for a total of 120 hours. For the final 96 hours, explants were conditioned with a simulated digestion extract of EOC (0, 36 or 180 μL/mL), and for the final 48 hours explants were stimulated with LPS (0 or 15µg/mL). Media was removed and replaced every 24 hours. Samples from the final 48 hours were analyzed for biomarkers of cartilage inflammation (prostaglandin E₂ [PGE₂] and nitric oxide [NO]) and cartilage structure (glycosaminoglycan [GAG]). At the end of the culture period cartilage explants were stained for an estimate of cell viability. Stimulation of unconditioned explants with LPS significantly increased media concentrations of PGE₂, GAG and NO compared with that from unstimulated explants. LPS stimulation did not significantly affect cell viability. Both concentrations of EOC prevented significant LPS-stimulated cartilage release of GAG without impairing chondrocyte viability. No other effects of treatment were observed. These data provide evidence for a non-cytotoxic, chondroprotective effect of EOC in cartilage. This in vitro experiment supports the use of EOC in protecting against the detrimental effects of inflammation on cartilage structure.

DBP and BaP co-exposure induces kidney injury via promoting pyroptosis of renal tubular epithelial cells in rats

Dibutyl phthalate (DBP) and benzo(a)pyrene (BaP) are widespread environmental and foodborne contaminants that have detrimental effects on human health. Although people are often simultaneously exposed to DBP and BaP via the intake of polluted food and water, the combined effects on the kidney and potential mechanisms remain unclear. Hence, we treated rats with DBP and BaP for 90 days to investigate their effects on kidney histopathology and function. We also investigated the levels of paramount proteins and genes involved in pyroptosis and TLR4/NF-κB p65 signaling in the kidney. Our research showed that combined exposure to DBP and BaP triggered more severe histopathological and renal function abnormalities than in those exposed to DBP or BaP alone. Simultaneously, combined exposure to DBP and BaP enhanced the excretion of IL-1β and IL-18, along with the release of LDH in rat renal tubular epithelial cells (RTECs). Moreover, combined exposure to DBP and BaP increased the expression of pyroptosis marker molecules, including NLRP3, ASC, cleaved-Caspase-1, and GSDMD. Meanwhile, the combination of DBP and BaP activated TLR4/NF-κB signaling in the kidney. Taken together, the combined exposure to DBP and BaP causes more severe kidney injury than that caused by DBP or BaP exposure separately. In addition, pyroptosis of RTECs regulated by TLR4/NF-κB signaling may add to the kidney damage triggered by combined exposure to DBP and BaP.

Imperatorin Improves Obesity-Induced Cardiac Sympathetic Nerve Injury Mediated by P2X4 Receptor in Stellate Sympathetic Ganglion

Obesity can activate the inflammatory signal pathway, induce in the body a state of chronic inflammation, and increase the excitability of the sympathetic nervous system, which may induce sympathetic neuropathic injury. The stellate sympathetic ganglia (SG) can express the P2X4 receptor, and the abnormal expression of the P2X4 receptor is related to inflammation. Imperatorin (IMP) is a kind of furan coumarin plant which has anti-inflammatory effects. This project aimed to investigate whether IMP can affect the expression of P2X4 receptors in the SG of obese rats to display a protective effect from high-fat-triggered cardiac sympathetic neuropathic injury. Molecular docking through homology modelling revealed that IMP had good affinity for the P2X4 receptor. Our results showed that compared with the normal group, the administration of IMP or P2X4 shRNA decreased sympathetic excitement; reduced the serum levels of triglyceride, total cholesterol, and lactate dehydrogenase; downregulated the expression of P2X4 receptors in SG; and inhibited the expression of inflammatory factors in the SG and serum of obese rats significantly. In addition, the expression of factors associated with the cell pyroptosis GSDMD, caspase-1, NLRP-3, and IL-18 in obese rats were significantly higher than those of the normal rats, and such effects were decreased after treatment with IMP or P2X4 shRNA. Furthermore, IMP significantly reduced the ATP-activated currents in HEK293 cells transfected with P2X4 receptor. Thus, the P2X4 receptor may be a key target for the treatment of obesity-induced cardiac sympathetic excitement. IMP can improve obesity-induced cardiac sympathetic excitement, and its mechanism of action may be related to the inhibition of P2X4 receptor expression and activity in the SG, suppression of cellular pyroptosis in the SG, and reduction of inflammatory factor levels.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

A Bibliometric and Knowledge Map Analysis of Osteoarthritis Signaling Pathways from 2012 to 2022

Background

Osteoarthritis(OA) is one of the most common joint diseases, and signaling pathways play an essential role in the occurrence and development of OA, so it is significant to study OA with signaling pathways as an entry point.

Purpose

This study aims to visualize and map the knowledge of OA-related signaling pathway research between 2012 and 2022, summarise and analyze the current research status and potential development trends in the domain, and provide a reference for future OA-related research.

Methods

Retrieve relevant literature from the Web of Science database and use VOSviwer and CiteSpace software to visualize authors, institutions, country distribution, references, and keywords. The results are interpreted and analyzed in conjunction with the results obtained.

Results

According to the search strategy, a total of 4894 articles were published between January 2012 and January 2022; during these ten years, the number of reports increased annually, and the research became further intensive; through this analysis, it was found that China is the most prolific country in this field; The institution with the most articles was Xi'an Jiaotong University from China, and the most prolific author was Tang Chih Hsin; Among the cited references, the reports of Glyn-Jones S and Hunter DJ were ranked first and second respectively. In the keyword analysis, cartilage and expression were the popular keywords; Animal model, akt, and platelet-rich plasma had the highest centrality; Burst analysis revealed pi3k, senescence, Ampk, and exosomes had received more attention in recent years of research.

Conclusion

This study analyzes and summarizes the current research status and development trend of relevant signaling pathways in OA from the perspective of bibliometric and visual analysis, which can help researchers to keep track of hot topics and conduct more in-depth exploration of research hotspots and frontier knowledge areas.