IP3R2-mediated Ca2+ release promotes LPS-induced cardiomyocyte pyroptosis via the activation of NLRP3/Caspase-1/GSDMD pathway

Metal ions-induced programmed cell death: how does oxidative stress regulate cell death?

In recent years, the mechanisms of ferroptosis and cuproptosis, two novel modes of cell death, have been elucidated and have attracted much attention. Ferroptosis is dependent on the metabolic disruption of iron ions and lipid peroxidation, whereas cuproptosis is closely related to intracellular accumulation of copper ions, aggregation of lipoylated proteins and damage to FeS cluster proteins. In particular, oxidative stress plays an important role in both types of cell death. During ferroptosis, the central role of oxidative stress is reflected in the overproduction of reactive oxygen species (ROS) and lipid peroxidation of the cell membrane. Recent studies have revealed that ROS can propagate over long distances across cells in the form of trigger waves, triggering large-scale ferroptosis. In embryonic development, different regional redox states can limit the long-distance propagation of ferroptosis waves, which is critical for muscle remodeling and tissue formation during development. In cuproptosis, processes such as copper ions accumulation, tricarboxylic acid (TCA) cycle blockade, and reduced level of FeS cluster proteins are closely associated with oxidative stress. In addition, there is a close link between oxidative stress and death induced by other metal ions (Ca2+, Zn2+, etc.). In this paper, we review the role of oxidative stress in ferroptosis and cuproptosis and the related research progress to provide new ideas for understanding the mechanism of cell death and the occurrence and treatment of related diseases.

ROS-mediated ferroptosis and pyroptosis in cardiomyocytes: An update

The cardiomyocyte is an essential component of the heart, communicating and coordinating with non-cardiomyocytes (endothelial cells, fibroblasts, and immune cells), and are critical for the regulation of structural deformation, electrical conduction, and contractile properties of healthy and remodeled myocardium. Reactive oxygen species (ROS) in cardiomyocytes are mainly produced by the mitochondrial oxidative respiratory chain, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX), xanthine oxidoreductase (XOR), monoamine oxidase (MAO), and p66shc. Under physiological conditions, ROS are involved in the regulation of cardiac development and cardiomyocyte maturation, cardiac calcium handling, and excitation-contraction coupling. In contrast, dysregulation of ROS metabolism is involved in the development and progression of cardiovascular diseases (CVDs), including myocardial hypertrophy, hyperlipidemia, myocardial ischemia/reperfusion injury, arrhythmias and diabetic cardiomyopathy. Further oxidative stress induced by ROS dyshomeostasis was found to be the major reason for cardiomyocyte death in cardiac diseases, and in recent years, ferroptosis induced by oxidative stress have been considered to be fatal to cardiomyocytes. In addition, ROS is also a key trigger for the activation of pyroptosis, which induces and exacerbates the inflammatory response caused by various cardiac diseases and plays a critical role in CVDs. Therefore, in this review, the sources and destinations of ROS in cardiomyocytes will be systematically addressed, so as to reveal the molecular mechanisms by which ROS accumulation triggers cardiomyocyte ferroptosis and pyroptosis under pathological conditions, and provide a new concept for the research and treatment of heart-related diseases.

Updated insights into the molecular networks for NLRP3 inflammasome activation

Over the past decade, significant advances have been made in our understanding of how NACHT-, leucine-rich-repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes are activated. These findings provide detailed insights into the transcriptional and posttranslational regulatory processes, the structural-functional relationship of the activation processes, and the spatiotemporal dynamics of NLRP3 activation. Notably, the multifaceted mechanisms underlying the licensing of NLRP3 inflammasome activation constitute a focal point of intense research. Extensive research has revealed the interactions of NLRP3 and its inflammasome components with partner molecules in terms of positive and negative regulation. In this Review, we provide the current understanding of the complex molecular networks that play pivotal roles in regulating NLRP3 inflammasome priming, licensing and assembly. In addition, we highlight the intricate and interconnected mechanisms involved in the activation of the NLRP3 inflammasome and the associated regulatory pathways. Furthermore, we discuss recent advances in the development of therapeutic strategies targeting the NLRP3 inflammasome to identify potential therapeutics for NLRP3-associated inflammatory diseases. As research continues to uncover the intricacies of the molecular networks governing NLRP3 activation, novel approaches for therapeutic interventions against NLRP3-related pathologies are emerging.

NOD2 promotes sepsis-induced neuroinflammation by increasing brain endoplasmic reticulum stress mediated by LACC1

BACKGROUND

Although nucleotide-binding oligomerization domain-containing protein 2 (NOD2) has been associated with diverse inflammatory states and some neurological diseases, its role in regulating sepsis-induced neuroinflammation remains unexplored. This study aimed to determine the role of NOD2 in modulating sepsis-induced neuroinflammation and to elucidate its potential mechanisms.

METHODS

mRNA and protein expression levels of NOD2 were measured in the periventricular white matter (PWM) of C57BL/6 mice and the microglia. NOD2-/- mice were generated using the CRISPR/Cas9 technology, and the septic mouse model was established by using cecal ligation puncture (CLP). Microglia were transfected with siRNA specific to NOD2 or laccase domain-containing protein 1 (LACC1) or treated with the endoplasmic reticulum stress (ER stress) inhibitor 4-phenylbutyrate (4-PBA) in vitro under muramyl dipeptide (MDP)-induced neuroinflammation. Immunofluorescence staining, Western blotting, and quantitative reverse transcription polymerase chain reaction were performed to evaluate neuroinflammation and ER stress. The ER structure was observed using transmission electron microscopy.

RESULTS

NOD2 expression level was upregulated in the mouse model of sepsis-induced neuroinflammation. The absence of NOD2 led to a protective effect against neuroinflammation, which was correlated with ER stress both in vitro and in vivo. LACC1 was identified as a notable mediator of ER stress, contributing to the exacerbation of neuroinflammation. Mechanistically, elevated NOD2 expression level promoted neuroinflammation by enhancing ER stress through LACC1. Notably, these effects were partially mitigated by LACC1 downregulation.

CONCLUSIONS

These findings highlight the pivotal role of NOD2 in promoting sepsis-induced neuroinflammation via regulating ER stress mediated by LACC1, and provide a new potential strategy for treating human neuroinflammation.

Identification of TMEM71 as a hub NLRP3-related gene suppressing malignant behavior in nasopharyngeal carcinoma via the NLRP3/Caspase-1/GSDMD signaling pathway

OBJECTIVE

NLRP3 plays a key role in cellular pyroptosis and tumor progression. However, research on NLRP3-Related Genes (NRGs) in Nasopharyngeal Carcinoma (NPC) is limited.

METHODS

We analyzed the GSE53819 dataset to identify genes positively correlated with NLRP3 mRNA and downregulated in NPC tumors, termed NRGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used to characterize their biological functions. Validation was performed using the GSE64634 and GSE102349 datasets. The GSE102349 dataset was used to evaluate the impact of NRGs on the Progression-Free Survival (PFS) and their association with immune cell infiltration. A cohort of 421 NPC patients from a local hospital underwent multivariate Cox regression to assess the prognostic significance of hub NRGs. Cellular experiments further investigated the role of hub NRGs in NPC.

RESULTS

In the GSE53819 dataset, 26 NRGs were identified, correlated with NLRP3 expression, and downregulated in tumor tissues. GO and KEGG analyses linked these 26 NRGs to the inflammasome complex. TMEM71, identified in the GSE64634 and GSE102349 datasets, was downregulated in tumor tissues and positively correlated with NLRP3 expression. It was the only NRG with prognostic value, with higher expression correlating with improved PFS. Immune cell infiltration analysis showed significant differences between high and low TMEM71 expression groups (e.g., naïve B cells). Local analysis confirmed that positive TMEM71 expression in tumor serves as an independent prognostic marker for NPC (HR = 0.53, 95% CI 0.366‒0.780). in vitro, TMEM71 activation of the NLRP3/caspase-1/GSDMD pathway suppressed malignant behaviors in NPC cell.

CONCLUSION

TMEM71 may serve as a prognostic biomarker for NPC and influence immune cell infiltration. Its overexpression could exert anticancer effects via the NLRP3/caspase-1/GSDMD pathway, highlight its potential as a therapeutic target in NPC.

Adenosine triphosphate-induced cell death in heart failure: Is there a link?

Heart failure (HF) has emerged as one of the foremost global health threats due to its intricate pathophysiological mechanisms and multifactorial etiology. Adenosine triphosphate (ATP)-induced cell death represents a novel form of regulated cell deaths, marked by cellular energy depletion and metabolic dysregulation stemming from excessive ATP accumulation, identifying its uniqueness compared to other cell death processes modalities such as programmed cell death and necrosis. Growing evidence suggests that ATP-induced cell death (AICD) is predominantly governed by various biological pathways, including energy metabolism, redox homeostasis and intracellular calcium equilibrium. Recent research has shown that AICD is crucial in HF induced by pathological conditions like myocardial infarction, ischemia-reperfusion injury, and chemotherapy. Thus, it is essential to investigate the function of AICD in the pathogenesis of HF, as this may provide a foundation for the development of targeted therapies and novel treatment strategies. This review synthesizes current advancements in understanding the link between AICD and HF, while further elucidating its involvement in cardiac remodeling and HF progression.

Sepsis-induced cardiac dysfunction: mitochondria and energy metabolism

Sepsis is a life-threatening multi-organ dysfunction syndrome caused by dysregulated host response to infection, posing a significant global healthcare challenge. Sepsis-induced myocardial dysfunction (SIMD) is a common complication of sepsis, significantly increasing mortality due to its high energy demands and low compensatory reserves. The substantial mitochondrial damage rather than cell apoptosis in SIMD suggests disrupted cardiac energy metabolism as a crucial pathophysiological mechanism. Therefore, we systematically reviewed the mechanisms underlying energy metabolism dysfunction in SIMD, including alterations in myocardial cell energy metabolism substrates, excitation-contraction coupling processes, mitochondrial dysfunction, and mitochondrial autophagy and biogenesis, summarizing potential therapeutic targets within them.

NLRP3 Inflammasome Targeting Offers a Novel Therapeutic Paradigm for Sepsis-Induced Myocardial Injury

Cardiac or myocardial dysfunction induced by sepsis, known as sepsis-induced cardiomyopathy or sepsis-induced myocardial injury (SIMI), is a common complication of sepsis and is associated with poor outcomes. However, the pathogenesis and molecular mechanisms underlying SIMI remain poorly understood, requiring further investigations. Emerging evidence has shown that NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes contribute to SIMI. Compounds that inhibit NLRP3-associated pyroptosis may exert therapeutic effects against SIMI. In this review, we first outlined the principal elements of the NLRP3 signaling cascade and summarized the recent studies highlighting how NLRP3 activation contributes to the pathogenesis of SIMI. We outlined selective small-molecule modulators that function as NLRP3 inhibitors and delineated their mechanisms of action to attenuate SIMI. Finally, we discuss the major limitations of the current therapeutic paradigm and propose possible strategies to overcome them. This review highlights the pharmacological inhibition of SIMI as a promising therapeutic strategy.

The role of programmed cell death in organ dysfunction induced by opportunistic pathogens

Sepsis is a life-threatening condition resulting from pathogen infection and characterized by organ dysfunction. Programmed cell death (PCD) during sepsis has been associated with the development of multiple organ dysfunction syndrome (MODS), impacting various physiological systems including respiratory, cardiovascular, renal, neurological, hematological, hepatic, and intestinal systems. It is well-established that pathogen infections lead to immune dysregulation, which subsequently contributes to MODS in sepsis. However, recent evidence suggests that sepsis-related opportunistic pathogens can directly induce organ failure by promoting PCD in parenchymal cells of each affected organ. This study provides an overview of PCD in damaged organ and the induction of PCD in host parenchymal cells by opportunistic pathogens, proposing innovative strategies for preventing organ failure in sepsis.

Intranasal Delivery of Lithium Salt Suppresses Inflammatory Pyroptosis in the brain and Ameliorates Memory Loss and Depression-like Behavior in 5XFAD mice

Background

Alzheimer's disease (AD) is a devastating neurodegenerative disease (AD) and has no treatment that can cure or halt the disease progression. This study explored the therapeutic potential of lithium salt dissolved in Ryanodex formulation vehicle (RFV) and delivered to the brain by intranasal application. We first compared lithium concentrations in the brain and blood of wild-type mice following intranasal or oral administration of lithium chloride (LiCl) dissolved in either RFV or water. The beneficial and side effects of intranasal versus oral LiCl in RFV in these mice were assessed and potential mechanisms underlying the efficacy of anti-inflammation and anti-pyroptosis in the brains were also investigated in both wild-type (WT) and 5XFAD Alzheimer's Disease (AD) mice brains.

Methods

For the study of brain versus blood lithium concentrations, WT B6SJLF1/J mice at 2 months of age were treated with intranasal or oral LiCl (3 mmol/kg) dissolved in RFV or in water. Brain and blood lithium concentrations were measured at various times after drugs administration. Brain/blood lithium concentration ratios were then determined. For studying therapeutic efficacy versus side effects and their underlying mechanisms, 5XFAD and WT B6SJLF1/J mice were treated with intranasal LiCl (3 mmol/kg) daily, Monday to Friday each week, in RFV beginning at 2 or 9 months of age with a 12-week treatment duration. Animal behaviors were assessed for depression (tail suspension), cognition (fear conditioning and Y maze), olfaction (buried food test), and motor functions (rotarod) at the age of 5 and 12 months. Blood and brain tissue were harvested from these mice at 13 months. Blood biomarkers for the functions of thyroid (thyroid stimulating hormone, TSH) and kidney (creatinine) were measured using ELISA. Changes in protein expression levels of the endoplasmic reticulum Ca2+ release channels type 1 InsP3 receptors (InsP3R-1), malondialdehyde (MDA)-modified proteins and 4-hydroxy-2-nonenal (4-HNE), pyroptosis regulatory proteins (NLR family pyrin domain containing 3 (NLRP3), cleaved caspase-1, N-terminal of Gasdermin D (GSDMD)), cytotoxic (IL-1β, IL-18, IL-6, TNF-α) and cytoprotective (IL-10) cytokines and synapse proteins (PSD-95, synapsin-1) were determined using immunoblotting. Mouse body weights were monitored regularly.

Results

Compared to oral LiCl in RFV nanoparticles, intranasal treatment of WT mice with LiCl in RFV markedly decreased blood concentrations at the time frame of 30-120 minutes. The ratio of brain/blood lithium concentration after Intranasal lithium chloride in RFV significantly increased, in comparison to those after oral administration lithium chloride in RFV or intranasal administration of lithium chloride in water. Intranasal lithium chloride in RFV inhibited both memory loss and depressive behavior in adult and aged 5XFAD mice. Additionally intranasal treatment of aged 5XFAD mice with LiCl in RFV effectively suppressed the increases in InsP3R-1, intracellular oxidative stress markers (4-HNE-bound and MDA-modified proteins), pyroptosis activation proteins (NLRP3, cleaved caspase-1, N-terminal GSDMD) and cytotoxic cytokines (IL-1β, IL-6, TNF-α), but reversed the down-regulation of cytoprotective cytokine IL-10. Intranasal LiCl in RFV also alleviated the loss of the postsynaptic synapse protein PSD-95, but not synapsin-1, in aged 5XFAD mice. Blood level of the kidney function marker creatinine was significantly increased in 5XFAD than in WT mice in an age-dependent manner and this elevation was abolished by intranasal delivery of LiCl in RFV. Intranasal LiCl in RFV for 12 weeks in both WT or 5XFAD mice did not affect blood biomarkers for thyroid function, nor did it affect smell or muscle function or body weight.

Conclusion

Intranasal administration of LiCl in RFV significantly decreased lithium blood concentrations and increased brain/blood lithium concentration ratio, in comparison to its oral administration. Intranasal administration of LiCl in RFV robustly protected against both memory loss and depressive-like behavior, while had no side effects concerning thyroid and kidney toxicity in 5XFAD mice. These lithium-induced beneficial effects were strongly associated with lithium's suppression of InsP3R-1 Ca2+ channel receptor increase, pathological neuroinflammation and activation of the pyroptosis pathway, as well as the loss of some synaptic proteins. Intranasal delivery of lithium salt in RFV could become an effective and potent inhibitor of pathological inflammation/pyroptosis in the CNS and serve as a new treatment for both AD-associated dementia and depression with minimal unwanted side effects including peripheral organ toxicity.

Potential Roles of IP3 Receptors and Calcium in Programmed Cell Death and Implications in Cardiovascular Diseases

Inositol 1,4,5-trisphosphate receptors (IP3Rs) play a crucial role in maintaining intracellular/cytosolic calcium ion (Ca2+i) homeostasis. The release of Ca2+ from IP3Rs serves as a second messenger and a modulatory factor influencing various intracellular and interorganelle communications during both physiological and pathological processes. Accumulating evidence from in vitro, in vivo, and clinical studies supports the notion that the overactivation of IP3Rs is linked to the pathogenesis of various cardiac conditions. The overactivation of IP3Rs results in the dysregulation of Ca2+ concentration ([Ca2+]) within cytosolic, mitochondrial, and nucleoplasmic cellular compartments. In cardiovascular pathologies, two isoforms of IP3Rs, i.e., IP3R1 and IP3R2, have been identified. Notably, IP3R1 plays a pivotal role in cardiac ischemia and diabetes-induced arrhythmias, while IP3R2 is implicated in sepsis-induced cardiomyopathy and cardiac hypertrophy. Furthermore, IP3Rs have been reported to be involved in various programmed cell death (PCD) pathways, such as apoptosis, pyroptosis, and ferroptosis underscoring their multifaceted roles in cardiac pathophysiology. Based on these findings, it is evident that exploring potential therapeutic avenues becomes crucial. Both genetic ablation and pharmacological intervention using IP3R antagonists have emerged as promising strategies against IP3R-related pathologies suggesting their potential therapeutic potency. This review summarizes the roles of IP3Rs in cardiac physiology and pathology and establishes a foundational understanding with a particular focus on their involvement in the various PCD pathways within the context of cardiovascular diseases.

Vaccarin alleviates septic cardiomyopathy by potentiating NLRP3 palmitoylation and inactivation

BACKGROUND

Sepsis often leads to significant morbidity and mortality due to severe myocardial injury. As is known, the activation of NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome crucially contributes to septic cardiomyopathy (SCM) by facilitating the secretion of interleukin (IL)-1β and IL-18. The removal of palmitoyl groups from NLRP3 is a crucial step in the activation of the NLRP3 inflammasome. Thus, the potential inhibitors that regulate the palmitoylation and inactivation of NLRP3 may significantly diminish sepsis-induced cardiac dysfunction.

PURPOSE

The present study sought to explore the effects of the prospective flavonoid compounds targeting NLRP3 on SCM and to elucidate the associated underlying mechanisms.

STUDY DESIGN

The palmitoylation and activation of NLRP3 were detected in H9c2 cells and C57BL/6 J mice.

METHODS/RESULTS

Echocardiography, histological staining, western blotting, co-immunoprecipitation, qPCR, ELISA and network pharmacology were used to assess the impact of vaccarin (VAC) on SCM in mice subjected to lipopolysaccharide (LPS) injection. From the collection of 74 compounds, we identified that VAC had the strongest capability to suppress NLRP3 luciferase report gene activity in cardiomyocytes, and the anti-inflammatory characteristics of VAC were further ascertained by the network pharmacology. Exposure of LPS triggered apoptosis, inflammation, oxidative stress, mitochondrial disorder in cardiomyocytes. The detrimental alterations were significantly reversed upon VAC treatment in both septic mice and H9c2 cells exposed to LPS. In vivo experiments demonstrated that VAC treatment alleviated septic myocardial injury, indicated by enhanced cardiac function parameters, preserved cardiac structure, and reduced inflammation/oxidative response. Mechanistically, VAC induced NLRP3 palmitoylation to inactivate NLRP3 inflammasome by acting on zDHHC12. In support, the NLRP3 agonist ATP and the acylation inhibitor 2-bromopalmitate (2-BP) prevented the effects of VAC.

CONCLUSION

Our findings suggest that VAC holds promise in protecting against SCM by mitigating cardiac oxidative stress and inflammation via priming NLRP3 palmitoylation and inactivation. These results lay the solid basis for further assessment of the therapeutic potential of VAC against SCM.