Linear ubiquitination of LKB1 activates AMPK pathway to inhibit NLRP3 inflammasome response and reduce chondrocyte pyroptosis in osteoarthritis

OTULIN orchestrates NCOA4-FTH1 complex to alleviate APAP-induced hepatocyte Ferroptosis

BACKGROUND

Acetaminophen (APAP) overdose is a leading cause of drug-induced liver injury (DILI) and can progress to acute liver failure (ALF). Hepatocyte death is widely recognized as the central event in APAP-induced liver injury; however, the underlying mechanisms are complex and not yet fully elucidated. Ferroptosis, a recently identified form of programmed cell death characterized by glutathione (GSH) depletion and disruption of cellular redox homeostasis, shares key features with APAP-induced hepatotoxicity. This study aimed to investigate the role of ferroptosis in APAP-induced liver injury and to explore potential therapeutic targets.

EXPERIMENTAL APPROACHES

C57BL/6 mice were administered APAP to evaluate ferroptosis and hepatic injury in vivo through histological and biochemical analyses. A range of molecular techniques, along with the establishment of stable cell lines, were employed to elucidate the underlying mechanisms in vitro.

RESULTS

We demonstrated that APAP disrupts iron homeostasis and promotes hepatocyte ferroptosis. OTULIN, a deubiquitinase involved in linear ubiquitination, was found to regulate the ubiquitination modification of NCOA4, leading to NCOA4 depletion and FTH1 accumulation. This process enhanced the resistance and adaptability of hepatocytes to APAP-induced damage.

CONCLUSION

Our findings reveal that OTULIN modulates the NCOA4-FTH1 complex to protect against APAP-induced hepatocyte ferroptosis. Targeted upregulation of OTULIN in hepatocytes may represent a promising therapeutic strategy for APAP-induced DILI.

LncRNA EMBP1 sponges miR-454-3p to upregulate IRF1 and activate NLRP3-mediated chondrocyte pyroptosis to drive osteoarthritis progression

BACKGROUND

Osteoarthritis (OA) is the most common degenerative joint disease worldwide. Studies have confirmed that pyroptosis is closely associated with the OA onset and progression, particularly via the classical pathway mediated by the NLRP3 inflammasome. However, the intrinsic regulatory mechanisms underlying pyroptosis in OA remain unclear.

METHODS

We conducted RNA sequencing (RNA-seq) analysis on clinical cartilage samples and identified hub genes connecting OA and pyroptosis. We validated NLRP3-mediated pyroptosis activation, evaluated the diagnostic potential of the hub gene, and explored its regulatory role using a papain-induced rabbit OA model and IL-1β-induced chondrocytes. Subsequently, we constructed a competitive endogenous RNA (ceRNA) network based on the hub gene and validated its competitive binding interactions and regulatory function in NLRP3-mediated pyroptosis. Additionally, hub gene interferon regulatory factor 1 (IRF1) serves as a recognized upstream regulator of the novel cell death paradigm PANoptosis, which integrates apoptosis, necrosis, and pyroptosis. We preliminarily explored the potential molecular mechanisms of PANoptosis in OA through clinical sample analysis and in vitro experiments.

RESULTS

RNA-seq revealed that IRF1, a hub gene linking OA and pyroptosis, is upregulated in OA cartilage and is associated with NLRP3, consistent with the in vivo and in vitro results. Dual-luciferase assays, clinical sample analysis, and in vitro experiments confirmed the competitive binding of the embigin pseudogene 1 (EMBP1)/miR-454-3p/IRF1 ceRNA network. Silencing EMBP1 increased miR-454-3p, inhibiting IRF1 and NLRP3-mediated pyroptosis in vitro; however, miR-454-3p inhibitor rescue experiments abolished the beneficial effects of si-EMBP1. Furthermore, we preliminarily characterized the occurrence of PANoptosis in OA and provided initial evidence suggesting a potential regulatory role for the EMBP1/miR-454-3p/IRF1 axis in this process.

CONCLUSIONS

In OA, EMBP1 acts as a sponge for miR-454-3p, inhibiting its negative regulatory effect on IRF1 and exacerbating NLRP3-mediated chondrocyte pyroptosis. Furthermore, EMBP1/miR-454-3p/IRF1-mediated pyroptosis may be integrated into the broader PANoptosis process, interacting with apoptosis and necrosis to influence OA progression.

Lycium barbarum Polysaccharides Alleviate Ethanol-Induced Liver Injury by Activating PPAR-α and Inhibiting NLRP-3/Caspase-1-Mediated Pyroptosis

This Research Aimed to Discuss the Protective Mechanism of Lycium barbarum Polysaccharides (LBPs) Against Ethanol (EtOH)-caused Hepatocellular Damage. Normal human hepatocytes (L-02 cells) were processed with 100 μg/mL EtOH to simulate liver injury, followed by treatment with LBPs at different concentrations (12, 24, 48 μg/mL) to determine the optimal dose. Cells were divided into the control, EtOH, EtOH+LBP-treated, and EtOH+LBP-treated with siRNA against PPAR-α groups. To evaluate treatment effects, the MTT assay was utilized for measuring cell viability, succeeded by the assessment of liver injury markers (ALT, AST, TG) and inflammatory cytokines (IL-1β, TNF-α, and IL-6). Besides, the GSDMD, NLRP-3, caspase-1, and PPAR-α protein levels were analyzed via western blotting. Relative to the Control group, EtOH exposure remarkably decreased cell viability, increased TG, AST, and ALT levels (p < 0.01), and induced cell damage and lipid accumulation. It also elevated inflammatory cytokine levels and triggered pyroptosis (p < 0.01). However, LBP treatment alleviated EtOH-induced damage, reduced lipid accumulation, inhibited pyroptosis-related protein expression, suppressed inflammatory responses, and upregulated PPAR-α protein expression (p < 0.01). LBPs can alleviate EtOH-induced L-02 cell injury, lipid accumulation, inflammatory response, and pyroptosis. The mechanism is possibly associated with inhibiting NLRP-3/caspase-1-mediated cell pyroptosis by activating PPAR-α expression, thus protecting hepatocytes from injury.

Injectable sustainable andrographolide-releasing hydrogel for long-lasting alleviation of osteoarthritis and regulation of chondrocyte autophagy via PRKCA/EGFR

Osteoarthritis is one of the most prevalent age-related joint diseases, with chondrocyte inflammation and autophagy dysregulation serving as pivotal pathogenesis factors. Andrographolide (AD), a phytochemical identified in Andrographis paniculata, exhibits anti-inflammatory properties and regulates autophagy to safeguard cells from damage. Nevertheless, the precise mechanism underlying the influence of AD on autophagy in osteoarthritis (OA) chondrocytes remains unelucidated. Concurrently, sustained efficacy of andrographolide typically necessitates prolonged administration, posing a challenge for its clinical application. We engineered an injectable 4-arm PEG-Mix-Hydrogel/PF system capable of encapsulating lipophilic drugs and achieving sustained release over a period of up to 24 days, substantially reducing the frequency of medication. Our findings indicate that andrographolide augments chondrocyte autophagy via the PRKCA/EGFR pathway and modulates chondrocyte inflammation as well as extracellular matrix degradation. Subsequent experimentation revealed that the injectable 4-arm PEG-Mix-Hydrogel/PF@AD (PHPF@AD) exhibited excellent biocompatibility with chondrocytes, possessed a rapid in-situ gelation time, and a single injection was sufficient to alleviate joint degeneration, abnormal gait, and weakened chondrocyte autophagy in OA mice, while ameliorating inflammation, matrix degradation, and apoptosis levels, and maintaining a certain degree of bone mass around the joints. In summary, this injectable hydrogel with spontaneous andrographolide release is anticipated to be a promising therapeutic modality for OA.

Pyroptosis for osteoarthritis treatment: insights into cellular and molecular interactions inflammatory

Osteoarthritis (OA) is a widely prevalent chronic degenerative disease often associated with significant pain and disability. It is characterized by the deterioration of cartilage and the extracellular matrix (ECM), synovial inflammation, and subchondral bone remodeling. Recent studies have highlighted pyroptosis-a form of programmed cell death triggered by the inflammasome-as a key factor in sustaining chronic inflammation. Central to this process are the inflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18), which play crucial roles mediating intra-articular pyroptosis through the NOD-like receptor protein 3 (NLRP3) inflammasome. This paper investigates the role of the pyroptosis pathway in perpetuating chronic inflammatory diseases and its linkage with OA. Furthermore, it explores the mechanisms of pyroptosis, mediated by nuclear factor κB (NF-κB), the purinergic receptor P2X ligand-gated ion channel 7 (P2X7R), adenosine monophosphate (AMP)-activated protein kinase (AMPK), and hypoxia-inducible factor-1α (HIF-1α). Additionally, it examines the interactions among various cellular components in the context of OA. These insights indicate that targeting the regulation of pyroptosis presents a promising therapeutic approach for the prevention and treatment of OA, offering valuable theoretical perspectives for its effective management.

Comprehensive multiomics analysis identifies PYCARD as a key pyroptosis-related gene in osteoarthritis synovial macrophages

Background

Osteoarthritis (OA) is a chronic joint disease that significantly impairs quality of life. Synovitis plays a pivotal role in OA progression, and pyroptosis, a form of programmed cell death associated with innate immune inflammation, may contribute to the pathogenesis of OA synovitis. Nevertheless, the precise role of pyroptosis in OA pathogenesis remains poorly understood.

Methods

We performed an analysis of bulk RNA sequencing data to examine the expression profiles of pyroptosis-related genes in the OA synovium. A LASSO-Cox regression model was employed to identify pivotal genes. Single-cell RNA sequencing data were used to validate the expression of these genes in specific synovial cell clusters. Differentially expressed genes (DEGs) in macrophages with high or low expression levels of core genes were subjected to enrichment analysis. A protein-protein interaction (PPI) network was constructed to identify hub genes, and potential therapeutic compounds were predicted. Consensus clustering analysis was performed to examine the correlations between hub genes and disease status. After identifying PYCARD as the core pyroptosis gene in OA macrophages, we assessed the expression levels of PYCARD in the OA synovium and validated the expression of PYCARD and its related core genes in M1 macrophages.

Results

A total of twenty pyroptosis-related DEGs were identified, and six core genes were selected through LASSO regression. PYCARD was identified as the key pyroptosis gene in macrophages. Furthermore, 57 therapeutic compounds targeting these genes were predicted. Validation confirmed the upregulation of PYCARD in the OA synovium and M1 macrophages.

Conclusion

PYCARD was identified as the core pyroptosis gene in OA macrophages, and 57 potential therapeutic compounds were identified. This study offers valuable insights into potential treatment targets for OA.

Sodium butyrate alleviates spinal cord injury via inhibition of NLRP3/Caspase-1/GSDMD-mediated pyroptosis

NOD-like receptor protein 3 (NLRP3)/cysteinyl aspartate-specific proteinase 1 (Caspase-1)/gasdermin D (GSDMD)-mediated pyroptosis is linked to spinal cord injury (SCI) pathogenesis. The levels of short-chain fatty acids (SCFAs), especially butyric acid, are significantly altered after SCI. Sodium butyrate (NaB) has anti-inflammatory effects on SCI; however, its effect on pyroptosis is unknown. The aim of this study was to determine the role of NaB in SCI functional recovery and its effect on NLRP3/Caspase-1/GSDMD-mediated pyroptosis. SCI model rats were established using aneurysm clips. After SCI, rats were administered NaB (300 mg/kg) via gavage. SCFAs in faeces were measured using gas chromatography-mass spectrometry. Motor function recovery was assessed using cylinder rearing and grooming tests. Histopathological analysis was performed using haematoxylin-eosin staining, transmission electron microscopy, and terminal deoxynucleotidyl transferase dUTP nick-end labelling. The expression of proteins associated with pyroptosis signalling pathways was analysed using enzyme-linked immunosorbent assay, western blotting, and immunohistochemistry. SCFAs levels, particularly butyric acid, significantly decreased after SCI. NaB treatment promoted forelimb motor function recovery and attenuated pathological SCI. NaB also decreased spinal pro-inflammatory factors (interleukin-18 and interleukin-1β) and downregulated pyroptosis-related proteins, including NLRP3, apoptosis-associated speck-like protein, Caspase-1, and GSDMD. NaB inhibits NLRP3/Caspase-1/GSDMD-mediated neuronal pyroptosis and inflammation, exerting protective and therapeutic effects in SCI, suggesting NaB as an effective SCI treatment.

Stromal Vascular Fraction Therapy to Reduce Inflammation and Improve Cartilage Regeneration in Osteoarthritis Nude Rats

Aims: To evaluate the efficacy of stromal vascular fraction (SVF) in treating osteoarthritis (OA). Background: OA is a common degenerative disease, the most important manifestation of which is cartilage destruction and inflammation. The SVF is a mixed group of multiple cells extracted from adipose tissue with a certain ability to promote tissue repair. However, the biological safety and efficacy of human derived SVF in treating OA have not been confirmed. Methods: Seventy-six nude rats were used in this experiment. The rat OA model was constructed with anterior cruciate ligament transection (ACLT). After 4 weeks, SVF cells were injected into the joint cavity once. After 12 weeks, the experimental animals were sacrificed and decalcified sections were subjected to hematoxylin and eosin (H&E), safranine O staining, and AP-PAS staining and immunohistochemistry for inflammation markers. Results: After surgery, the knee joint swells, pain intensifies, and the joint space narrows. The results of H&E, safranine O, and AP-PAS staining showed that the cartilage tissue was damaged in the ACLT-OA group and the treatment of SVF can reduce cartilage degradation. The numbers of ADAMTS-5-, MMP-13-, and IL-1β-positive cells significantly decreased and type II collagen-positive cells were more frequently detected in the ACLT-OA group compared with that in the control group, the treatment of SVF can reduce inflammation. Conclusion: SVF cells can be safely used to treat OA and can both effectively reduce the progression of joint inflammation and promote cartilage regeneration.

Triptolide attenuates LPS-induced chondrocyte inflammation by inhibiting inflammasome activation via the Wnt/β-catenin and NF-κB signaling pathways

Osteoarthritis (OA) is a common form of arthritis characterized by subchondral bone proliferation and articular cartilage degeneration. Recently, the Nod-like receptor pyrin domain 3 (NLRP3) inflammasome has gained attention due to its association with synovial inflammation in OA. Triptolide (TP), known for its immunosuppressive and anti-inflammatory effects, has been studied in various diseases. However, the specific impact of TP on OA and its underlying mechanism remains largely unexplored. In this study, chondrocytes were treated with a specific concentration of TP, and subsequent analysis through Western blotting and immunofluorescence staining revealed decreased expression levels of MMP-13, NLRP3, Caspase-1, ASC, β-catenin, p-p65, and IκB compared to the model group. ELISA results demonstrated significantly lower levels of IL-1β, IL-18, and TNF-α in the TP treatment group compared to the model group. In addition, triptolide ameliorates the degradation of the extracellular matrix (ECM) by enhancing the expression of collagen-II. In conclusion, our findings suggest that TP exhibits anti-inflammatory effects on chondrocytes in the presence of LPS-induced inflammation by inhibiting the activation of the NLRP3 inflammasome via the Wnt/β-catenin and NF-κB pathway. These results contribute to a better understanding of TP's potential therapeutic benefits in managing OA.

The LKB1-AMPK Signaling Axis Modulates Ferroptosis in Fibroblast-Like Synoviocytes Derived from Rheumatoid Arthritis

BACKGROUND/OBJECTIVES

Ferroptosis is a type of regulated cell death that involves iron-dependent accumulation of lipid peroxides. Because fibroblast-like synoviocytes (FLSs) in patients with rheumatoid arthritis (RA) have a hyperplastic and inflammatory phenotype, selective induction of FLS cell death is considered a potential treatment strategy for RA. Liver kinase B1 (LKB1)-activated AMP-activated protein kinase (AMPK) signaling regulates the inflammation and migration of RA FLSs, contributing to RA pathogenesis. Here, we aimed to determine the effect of LKB1 knockdown on the ferroptosis pathway in RA FLSs.

METHODS

Synovial tissues from patients with RA (n = 5) were transfected with siRNA targeting LKB1. Cell viability was evaluated via 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay and Annexin V/7-aminoactinomycin D (7-AAD) staining. Ferroptosis was assessed using boron-dipyrromethene (BODIPY) lipid probes, a ferrous ion detection kit, and a glutathione detection assay. Expression of hallmarks of various cell death pathways was analyzed using western blot.

RESULTS

RA FLS cell death significantly increased after transfection with LKB1 siRNA (p < 0.01). Lipid peroxidation was upregulated and the expression levels of glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11) were suppressed in LKB1-deficient cells. Additionally, LKB1 inhibition made RA FLSs highly sensitive to ferroptosis. When RA FLSs were incubated with an activator of AMPK, LKB1 knockdown-mediated inhibition was restored through upregulated expression of GPX4 and SLC7A11.

CONCLUSIONS

these findings suggest that LKB1-AMPK signaling is essential to protect RA FLSs against ferroptosis.

NLRP3 Inflammasome-Mediated Osteoarthritis: The Role of Epigenetics

The prevalence of osteoarthritis (OA) notably surges with age and weight gain. The most common clinical therapeutic drugs are painkillers, yet they cannot impede the deteriorating course of OA. Thus, understanding OA's pathogenesis and devising effective therapies is crucial. It is generally recognized that inflammation, pyroptosis, and OA progression are tightly linked. The activation of NLRP3 inflammasome can lead to the discharge of the pro-inflammatory cytokines Interleukin-1β and IL-18, intensifying subsequent inflammatory reactions and promoting OA development. Conversely, the imbalance caused by deacetylase-regulated NLRP3 inflammasome underlies the chronic mild inflammation related to degenerative diseases. Therefore, this article expounds on the mechanism of OA pathogenesis and the role of histone deacetylases (HDACs) in NLRP3 inflammasome-triggered OA, and illustrates the application of HDAC inhibitors in OA, striving to provide more insights into novel OA treatment approaches.

Immune aging and infectious diseases

ABSTRACT

The rise in global life expectancy has led to an increase in the older population, presenting significant challenges in managing infectious diseases. Aging affects the innate and adaptive immune systems, resulting in chronic low-grade inflammation (inflammaging) and immune function decline (immunosenescence). These changes would impair defense mechanisms, increase susceptibility to infections and reduce vaccine efficacy in older adults. Cellular senescence exacerbates these issues by releasing pro-inflammatory factors, further perpetuating chronic inflammation. Moreover, comorbidities, such as cardiovascular disease and diabetes, which are common in older adults, amplify immune dysfunction, while immunosuppressive medications further complicate responses to infections. This review explores the molecular and cellular mechanisms driving inflammaging and immunosenescence, focusing on genomic instability, telomere attrition, and mitochondrial dysfunction. Additionally, we discussed how aging-associated immune alterations influence responses to bacterial, viral, and parasitic infections and evaluated emerging antiaging strategies, aimed at mitigating these effects to improve health outcomes in the aging population.

Natural Modulators of Key Signaling Pathways in Skin Inflammageing

Low-grade chronic inflammation without obvious infection is defined as "inflammageing" and a key driver of skin ageing. Although the importance of modulating inflammageing for treating skin diseases and restoring cutaneous homeostasis is increasingly being recognized. However, the mechanisms underlying skin inflammageing, particularly those associated with natural treatments, have not been systematically elucidated. This review explores the signaling pathways associated with skin inflammageing, as well as the natural plants and compounds that directly or indirectly target these pathways. Nine signaling pathways and 60 plants/constituents related to skin anti-inflammageing are discussed, exploring plant mechanisms to mitigate skin inflammageing. Common natural plants with anti-inflammageing activity are detailed by active ingredients, mechanisms, therapeutic potential, and quantitative effects on skin inflammageing modulation. This review strengthens our understanding of these botanical ingredients as natural interventions against skin inflammageing and provides directions for future research.

Cynaroside regulates the AMPK/SIRT3/Nrf2 pathway to inhibit doxorubicin-induced cardiomyocyte pyroptosis

Doxorubicin (DOX) is a commonly administered chemotherapy drug for treating hematological malignancies and solid tumors; however, its clinical application is limited by significant cardiotoxicity. Cynaroside (Cyn) is a flavonoid glycoside distributed in honeysuckle, with confirmed potential biological functions in regulating inflammation, pyroptosis, and oxidative stress. Herein, the effects of Cyn were evaluated in a DOX-induced cardiotoxicity (DIC) mouse model, which was established by intraperitoneal injections of DOX (5 mg/kg) once a week for three weeks. The mice in the treatment group received dexrazoxane, MCC950, and Cyn every two days. Blood biochemistry, histopathology, immunohistochemistry, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and western blotting were conducted to investigate the cardioprotective effects and potential mechanisms of Cyn treatment. The results demonstrated the significant benefits of Cyn treatment in mitigating DIC; it could effectively alleviate oxidative stress to a certain extent, maintain the equilibrium of cell apoptosis, and enhance the cardiac function of mice. These effects were realized via regulating the transcription levels of pyroptosis-related genes, such as nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), caspase-1, and gasdermin D (GSDMD). Mechanistically, for DOX-induced myocardial injury, Cyn could significantly modulate the expression of pivotal genes, including adenosine monophosphate-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), sirtuin 3 (SIRT3), and nuclear factor erythroid 2-related factor 2 (Nrf2). We attribute it to the mediation of AMPK/SIRT3/Nrf2 pathway, which plays a central role in preventing DOX-induced cardiomyocyte injury. In conclusion, the present study confirms the therapeutic potential of Cyn in DIC by regulating the AMPK/SIRT3/Nrf2 pathway.

METTL14-mediated HOXA5 m6A modification alleviates osteoporosis via promoting WNK1 transcription to suppress NLRP3-dependent macrophage pyroptosis

Background

Osteoporosis is a commonly diagnosed metabolic bone disease. NLRP3 inflammasome activation and pyroptosis are observed during osteoporosis. However, the mechanism by which NLRP3-mediated pyroptosis contributes to osteoporosis remains largely undefined.

Methods

Ovariectomized (OVX) mice were employed as an in vivo model of osteoclastogenesis. H&E staining and micro-CT detected the histological changes and bone parameters in the femur tissues. RANKL-treated macrophages were used as the in vitro model of osteoclastogenesis, and LPS/ATP treatment was used as the macrophage pyroptosis model. The cytotoxicity, cytokine secretion and caspase-1 activity were assessed by LDH release assay, ELISA and flow cytometry, respectively. The osteoclast formation ability was detected by TRAP staining. qRT-PCR, IHC and Western blotting detected the expression and localization of METTL14, pyroptosis-related or osteoclast-specific molecules in femur tissues or macrophages. Mechanistically, MeRIP assessed the m6A modification of HOXA5. Luciferase and ChIP assays were employed to detect the direct association between HOXA5 and WNK1 promoter in macrophages.

Results

METTL14, HOXA5 and WNK1 were decreased in OVX mice, which was associated with pyroptosis. METTL14 or HOXA5 overexpression suppressed macrophage-osteoclast differentiation and pyroptosis, along with the upregulation of WNK1. METTL14-mediated m6A modification stabilized HOXA5 mRNA and increased its expression, and HOXA5 regulated WNK1 expression via direct binding to its promoter. Functional studies showed that WNK1 knockdown counteracted METTL14- or HOXA5-suppressed pyroptosis and macrophage-osteoclast differentiation. In OVX mice, overexpression of METTL14 or HOXA5 alleviated osteoporosis via suppressing WNK1-dependent NLRP3 signaling.

Conclusion

METTL14-mediated HOXA5 m6A modification increased its expression, thereby inducing WNK1 expression and suppressing NLRP3-dependent pyroptosis to alleviate osteoporosis. The combination of METTL14 or HOXA5 agonist with pyroptosis targeted therapy may be a promising therapeutic approach for osteoporosis.

The Translational Potential of this Article·

•METTL14 or HOXA5 overexpression suppressed macrophage-osteoclast differentiation and pyroptosis in macrophages.·•METTL14-mediated m6A modification stabilized HOXA5 mRNA and increased its expression.•HOXA5 regulated WNK1 expression via direct binding to its promoter.•Silencing of WNK1 reversed METTL14- or HOXA5-suppressed pyroptosis and macrophageosteoclast differentiation.·•METTL14 or HOXA5 overexpression alleviated osteoporosis via suppressing WNK1-dependent NLRP3 signaling in OVX mice.

Met1-linked ubiquitination in cell signaling regulation

Met1-linked ubiquitination (Met1-Ub), also known as linear ubiquitination, is a newly identified atypical type of polyubiquitination that is assembled via the N-terminal methionine (Met1) rather than an internal lysine (Lys) residue of ubiquitin. The linear ubiquitin chain assembly complex (LUBAC) composed of HOIP, HOIL-1L and SHARPIN is the sole E3 ubiquitin ligase that specifically generates Met1-linked ubiquitin chains. The physiological role of LUBAC-mediated Met1-Ub has been first described as activating NF-κB signaling through the Met1-Ub modification of NEMO. However, accumulating evidence shows that Met1-Ub is broadly involved in other cellular pathways including MAPK, Wnt/β-Catenin, PI3K/AKT and interferon signaling, and participates in various cellular processes including angiogenesis, protein quality control and autophagy, suggesting that Met1-Ub harbors a potent signaling capacity. Here, we review the formation and cellular functions of Met1-linked ubiquitin chains, with an emphasis on the recent advances in the cellular mechanisms by which Met1-Ub controls signaling transduction.

Fatty acids metabolism in ozone-induced pulmonary inflammatory injury: Evidence, mechanism and prevention

Ozone (O3) is a major air pollutant that directly threatens the respiratory system, lung fatty acid metabolism disorder is an important molecular event in pulmonary inflammatory diseases. Liver kinase B1 (LKB1) and nucleotide-binding domain leucine-rich repeat-containing protein 3 (NLRP3) inflammasome not only regulate inflammation, but also have close relationship with fatty acid metabolism. However, the role and mechanism of LKB1 and NLRP3 inflammasome in lung fatty acid metabolism, which may contribute to ozone-induced lung inflammation, remain unclear, and effective strategy for preventing O3-induced pulmonary inflammatory injury is lacking. To explore these, mice were exposed to 1.00 ppm O3 (3 h/d, 5 days), and pulmonary inflammation was determined by airway hyperresponsiveness, histopathological examination, total cells and cytokines in bronchoalveolar lavage fluid (BALF). Targeted fatty acids metabolomics was used to detect medium and long fatty acid in lung tissue. Then, using LKB1-overexpressing adenovirus and NLRP3 knockout (NLRP3-/-) mice to explore the mechanism of O3-induced lung fatty acid metabolism disorder. Results demonstrated that O3 exposure caused pulmonary inflammatory injury and lung medium and long chain fatty acids metabolism disorder, especially decreased dihomo-γ-linolenic acid (DGLA). Meanwhile, LKB1 expression was decreased, and NLRP3 inflammasome was activated in lung of mice after O3 exposure. Additionally, LKB1 overexpression alleviated O3-induced lung inflammation and inhibited the activation of NLRP3 inflammasome. And we found that pulmonary fatty acid metabolism disorder was ameliorated of NLRP3 -/- mice compared with those in wide type mice after O3 exposure. Furthermore, administrating DGLA intratracheally prior to O3 exposure significantly attenuated O3-induced pulmonary inflammatory injury. Taken together, these findings suggest that fatty acids metabolism disorder is involved in O3-induced pulmonary inflammation, which is regulated by LKB1-mediated NLRP3 pathway, DGLA supplement could be a useful preventive strategy to ameliorate ozone-associated lung inflammatory injury.

Central administration of AICAR attenuates hypertension via AMPK/Nrf2 pathway in the hypothalamic paraventricular nucleus of hypertensive rats

BACKGROUND

Oxidative stress and inflammatory cytokines in the hypothalamus paraventricular nucleus (PVN) have been implicated in sympathetic nerve activity and the development of hypertension, but the specific mechanisms underlying their production in the PVN remains to be elucidated. Previous studies have demonstrated that activation of nuclear transcription related factor-2 (Nrf2) in the PVN reduced the production of reactive oxygen species (ROS) and inflammatory mediators. Moreover, AMP-activated protein kinase (AMPK), has been observed to decrease ROS and inflammatory cytokine production when activated in the periphery. 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide (AICAR) is an AMPK agonist. However, little research has been conducted on the role of AMPK in the PVN during hypertension. Therefore, we hypothesized that AICAR in the PVN is involved in regulating AMPK/Nrf2 pathway, affecting ROS and inflammatory cytokine expression, influencing sympathetic nerve activity.

METHODS

Adult male Sprague-Dawley rats were utilized to induce two-kidney, one-clip (2K1C) hypertension via constriction of the right renal artery. Bilateral PVN was microinjected with either artificial cerebrospinal fluid or AICAR once a day for 4 weeks.

RESULTS

Compared to the SHAM group, the PVN of 2K1C hypertensive rats decreased p-AMPK and p-Nrf2 expression, increased Fra-Like, NAD(P)H oxidase (NOX)2, NOX4, tumor necrosis factor-α and interleukin (IL)-1β expression, elevated ROS levels, decreased superoxide dismutase 1 and IL-10 expression, and elevated plasma norepinephrine levels. Bilateral PVN microinjection of AICAR significantly ameliorated these changes.

CONCLUSION

These findings suggest that repeated injection of AICAR in the PVN suppresses ROS and inflammatory cytokine production through the AMPK/Nrf2 pathway, reducing sympathetic nerve activity and improving hypertension.

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.

Kaempferol Alleviates Hepatic Injury in Nonalcoholic Steatohepatitis (NASH) by Suppressing Neutrophil-Mediated NLRP3-ASC/TMS1-Caspase 3 Signaling

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a significant hepatic condition that has gained worldwide attention. Kaempferol (Kae), renowned for its diverse biological activities, including anti-inflammatory, antioxidant, anti-aging, and cardio-protective properties, has emerged as a potential therapeutic candidate for non-alcoholic steatohepatitis (NASH). Despite its promising therapeutic potential, the precise underlying mechanism of Kae's beneficial effects in NASH remains unclear. Therefore, this study aims to clarify the mechanism by conducting comprehensive in vivo and in vitro experiments.

RESULTS

In this study, a murine model of non-alcoholic steatohepatitis (NASH) was established by feeding C57BL/6 female mice a high-fat diet for 12 weeks. Kaempferol (Kae) was investigated for its ability to modulate systemic inflammatory responses and lipid metabolism in this model (20 mg/kg per day). Notably, Kae significantly reduced the expression of NLRP3-ASC/TMS1-Caspase 3, a crucial mediator of liver tissue inflammation. Additionally, in a HepG2 cell model induced with palmitic acid/oleic acid (PA/OA) to mimic NASH conditions, Kae demonstrated the capacity to decrease lipid droplet accumulation and downregulate the expression of NLRP3-ASC/TMS1-Caspase 3 (20 µM and the final concentration to 20 nM). These findings suggest that Kae may hold therapeutic potential in the treatment of NASH by targeting inflammatory and metabolic pathways.

CONCLUSIONS

These findings suggest that kaempferol holds potential as a promising therapeutic intervention for ameliorating non-alcoholic fatty liver disease (NAFLD).

Spinosin ameliorates osteoarthritis through enhancing the Nrf2/HO-1 signaling pathway

Osteoarthritis (OA) is a common degenerative joint disease in the elderly, while oxidative stress-induced chondrocyte degeneration plays a key role in the pathologic progression of OA. One possible reason is that the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), which acts as the intracellular defense factor against oxidative stress, is significantly inhibited in chondrocytes. Spinosin (SPI) is a potent Nrf2 agonist, but its effect on OA is still unknown. In this study, we found that SPI can alleviate tert-Butyl hydroperoxide (TBHP)-induced extracellular matrix degradation of chondrocytes. Additionally, SPI can effectively activate Nrf2, heme oxygenase-1 (HO-1), and NADPH quinone oxidoreductase 1 (NQO1) in chondrocytes under the TBHP environment. When Nrf2 was silenced by siRNA, the cartilage protective effect of SPI was also weakened. Finally, SPI showed good alleviative effects on OA in mice. Thus, SPI can ameliorate oxidative stress-induced chondrocyte dysfunction and exhibit a chondroprotective effect through activating the Nrf2/HO-1 pathway, which may provide a novel and promising option for the treatment of OA.

Targeting epigenetic and post-translational modifications regulating pyroptosis for the treatment of inflammatory diseases

Inflammatory diseases, including infectious diseases, diabetes-related diseases, arthritis-related diseases, neurological diseases, digestive diseases, and tumor, continue to threaten human health and impose a significant financial burden despite advancements in clinical treatment. Pyroptosis, a pro-inflammatory programmed cell death pathway, plays an important role in the regulation of inflammation. Moderate pyroptosis contributes to the activation of native immunity, whereas excessive pyroptosis is associated with the occurrence and progression of inflammation. Pyroptosis is complicated and tightly controlled by various factors. Accumulating evidence has confirmed that epigenetic modifications and post-translational modifications (PTMs) play vital roles in the regulation of pyroptosis. Epigenetic modifications, which include DNA methylation and histone modifications (such as methylation and acetylation), and post-translational modifications (such as ubiquitination, phosphorylation, and acetylation) precisely manipulate gene expression and protein functions at the transcriptional and post-translational levels, respectively. In this review, we summarize the major pathways of pyroptosis and focus on the regulatory roles and mechanisms of epigenetic and post-translational modifications of pyroptotic components. We also illustrate these within pyroptosis-associated inflammatory diseases. In addition, we discuss the effects of novel therapeutic strategies targeting epigenetic and post-translational modifications on pyroptosis, and provide prospective insight into the regulation of pyroptosis for the treatment of inflammatory diseases.

Transcription factor STAT4 counteracts radiotherapy resistance in breast carcinoma cells by activating the MALAT1/miR-21-5p/THRB regulatory network

Considering the limited research and the prevailing evidence of STAT4's tumor-suppressing role in breast carcinoma (BC) or in breast radiotherapy (RT) sensitivity requires more in-depth exploration. Our study delves into how STAT4, a transcription factor, affects BC cell resistance to radiotherapy by regulating the MALAT1/miR-21-5p/THRB axis. Bioinformatics analysis was performed to predict the regulatory mechanisms associated with STAT4 in BC. Subsequently, we identified the expression profiles of STAT4, MALAT1, miR-21-5p, and THRB in various tissues and cell lines, exploring their interactions and impact on RT resistance in BC cells. Moreover, animal models were established with X-ray irradiation for further validation. We discovered that STAT4, which is found to be minimally expressed in breast carcinoma (BC) tissues and cell lines, has been associated with a poorer prognosis. In vitro cellular assays indicated that STAT4 could mitigate radiotherapy resistance in BC cells by transcriptional activation of MALAT1. Additionally, MALAT1 up-regulated THRB expression by adsorbing miR-21-5p. As demonstrated in vitro and in vivo, overexpressing STAT4 inhibited miR-21-5p and enhanced THRB levels through transcriptional activation of MALAT1, which ultimately contributes to the reversal of radiotherapy resistance in BC cells and the suppression of tumor formation in nude mice. Collectively, STAT4 could inhibit miR-21-5p and up-regulate THRB expression through transcriptional activation of MALAT1, thereby mitigating BC cell resistance to radiotherapy and ultimately preventing BC development and progression.

Gentiopicroside ameliorates the lipopolysaccharide-induced inflammatory response and hypertrophy in chondrocytes

PURPOSE

This study aimed to evaluate the protective effects of gentiopicroside against lipopolysaccharide-induced chondrocyte inflammation.

METHODS

SW 1353 chondrosarcoma cells were stimulated with LPS (5 μg/ml) for 24 h and treated with different concentrations of gentiopicroside (GPS) for 24 h. The toxic effects of GPS on chondrocytes were determined using a CCK-8 assay and EdU staining. Western blotting, qPCR, and immunofluorescence analysis were used to examine the protective effect of GPS against the inflammatory response in chondrocytes induced by lipopolysaccharide (LPS). One-way ANOVA was used to compare the differences between the groups (significance level of 0.05).

RESULTS

The CCK-8 results showed that 10, 20 and 40 μM GPS had no significant toxic effects on chondrocytes; GPS effectively reduced the production of IL-1β and PGE2, reversed LPS-induced extracellular matrix degradation in cartilage by inhibiting the Stat3/Runx2 signaling pathway, and suppressed the hypertrophic transformation of SW 1353 chondrosarcoma cells.

CONCLUSION

Our study demonstrated that GPS significantly inhibited the LPS-induced inflammatory response and hypertrophic cellular degeneration in SW 1353 chondrosarcoma cells and is a valuable traditional Chinese medicine for the treatment of knee osteoarthritis.

Mechanisms of NLRP3 inflammasome in rheumatoid arthritis and osteoarthritis and the effects of traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

It has been widely reported that various anti-rheumatic traditional Chinese medicines (TCMs) ameliorate rheumatoid arthritis (RA) and osteoarthritis (OA) through regulating the abnormal production, assembly, and activation of the NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome. These TCMs include monomers isolated from Chinese herbs, extracts of Chinese herbs, and Chinese medical formulae with a lengthy application history.

AIM OF THE STUDY

This review aimed to summarize and analyze the published articles about the NLRP3 inflammasome and its role in the pathogenesis of RA and OA. We also reviewed existing knowledge on the therapeutic mechanism of TCMs in RA and OA via the regulation of the NLRP3 inflammasome.

MATERIALS AND METHODS

We searched for relevant articles with the keywords "NLRP3 inflammasome", "traditional Chinese medicine," "Chinese herbal drugs," "rheumatoid arthritis," and "osteoarthritis." The information retrieval was conducted in medical Chinese and English databases from the date of construction to April 19, 2023, including PubMed, MEDLINE, Web of Science, Scopus, Ovid, China National Knowledge Infrastructure (CNKI), Chinese Biomedicine Literature Database (CBM), Chinese Science and Technology Periodicals Database (VIP), and China Online Journals (COJ).

RESULTS

According to retrieval results, 35 TCMs have been demonstrated to relieve RA by targeting the NLRP3 inflammasome, including six traditional Chinese prescriptions, seven extracts of Chinese herbs, and 22 monomers extracted from traditional Chinese herbs and formulae. Additionally, 23 TCMs have shown anti-OA effects with abilities to modulate the NLRP3 inflammasome, including five traditional Chinese prescriptions, one extract of Chinese herbs, and 17 monomers from Chinese herbs.

CONCLUSIONS

We summarized mechanism research about the pivotal roles of the NLRP3 inflammasome in the pathogenesis of RA and OA. Moreover, a review of TCMs with targets of the NLRP3 inflammasome in RA and OA treatment was also conducted. Our work is conducive to a better application of TCMs in complementary and alternative therapies in RA and 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.

The roles of ubiquitination and deubiquitination of NLRP3 inflammasome in inflammation-related diseases: A review

The inflammatory response is a natural immune response that prevents microbial invasion and repairs damaged tissues. However, excessive inflammatory responses can lead to various inflammation-related diseases, posing a significant threat to human health. The NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome is a vital mediator in the activation of the inflammatory cascade. Targeting the hyperactivation of the NLRP3 inflammasome may offer potential strategies for the prevention or treatment of inflammation-related diseases. It has been established that the ubiquitination and deubiquitination modifications of the NLRP3 inflammasome can provide protective effects in inflammation-related diseases. These modifications modulate several pathological processes, including excessive inflammatory responses, pyroptosis, abnormal autophagy, proliferation disorders, and oxidative stress damage. Therefore, this review discusses the regulation of NLRP3 inflammasome activation by ubiquitination and deubiquitination modifications, explores the role of these modifications in inflammation-related diseases, and examines the potential underlying mechanisms.

Reactive oxygen species (ROS) scavenging biomaterials for anti-inflammatory diseases: from mechanism to therapy

Inflammation is a fundamental defensive response to harmful stimuli, but the overactivation of inflammatory responses is associated with most human diseases. Reactive oxygen species (ROS) are a class of chemicals that are generated after the incomplete reduction of molecular oxygen. At moderate levels, ROS function as critical signaling molecules in the modulation of various physiological functions, including inflammatory responses. However, at excessive levels, ROS exert toxic effects and directly oxidize biological macromolecules, such as proteins, nucleic acids and lipids, further exacerbating the development of inflammatory responses and causing various inflammatory diseases. Therefore, designing and manufacturing biomaterials that scavenge ROS has emerged an important approach for restoring ROS homeostasis, limiting inflammatory responses and protecting the host against damage. This review systematically outlines the dynamic balance of ROS production and clearance under physiological conditions. We focus on the mechanisms by which ROS regulate cell signaling proteins and how these cell signaling proteins further affect inflammation. Furthermore, we discuss the use of potential and currently available-biomaterials that scavenge ROS, including agents that were engineered to reduce ROS levels by blocking ROS generation, directly chemically reacting with ROS, or catalytically accelerating ROS clearance, in the treatment of inflammatory diseases. Finally, we evaluate the challenges and prospects for the controlled production and material design of ROS scavenging biomaterials.

Mechanisms underlying linear ubiquitination and implications in tumorigenesis and drug discovery

Linear ubiquitination is a distinct type of ubiquitination that involves attaching a head-to-tail polyubiquitin chain to a substrate protein. Early studies found that linear ubiquitin chains are essential for the TNFα- and IL-1-mediated NF-κB signaling pathways. However, recent studies have discovered at least sixteen linear ubiquitination substrates, which exhibit a broader activity than expected and mediate many other signaling pathways beyond NF-κB signaling. Dysregulation of linear ubiquitination in these pathways has been linked to many types of cancers, such as lymphoma, liver cancer, and breast cancer. Since the discovery of linear ubiquitin, extensive effort has been made to delineate the molecular mechanisms of how dysregulation of linear ubiquitination causes tumorigenesis and cancer development. In this review, we highlight newly discovered linear ubiquitination-mediated signaling pathways, recent advances in the role of linear ubiquitin in different types of cancers, and the development of linear ubiquitin inhibitors. Video Abstract.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.

Elucidating the role of ubiquitination and deubiquitination in osteoarthritis progression

Osteoarthritis is non-inflammatory degenerative joint arthritis, which exacerbates disability in elder persons. The molecular mechanisms of osteoarthritis are elusive. Ubiquitination, one type of post-translational modifications, has been demonstrated to accelerate or ameliorate the development and progression of osteoarthritis via targeting specific proteins for ubiquitination and determining protein stability and localization. Ubiquitination process can be reversed by a class of deubiquitinases via deubiquitination. In this review, we summarize the current knowledge regarding the multifaceted role of E3 ubiquitin ligases in the pathogenesis of osteoarthritis. We also describe the molecular insight of deubiquitinases into osteoarthritis processes. Moreover, we highlight the multiple compounds that target E3 ubiquitin ligases or deubiquitinases to influence osteoarthritis progression. We discuss the challenge and future perspectives via modulation of E3 ubiquitin ligases and deubiquitinases expression for enhancement of the therapeutic efficacy in osteoarthritis patients. We conclude that modulating ubiquitination and deubiquitination could alleviate the osteoarthritis pathogenesis to achieve the better treatment outcomes in osteoarthritis patients.