ER Stress Activates the NLRP3 Inflammasome: A Novel Mechanism of Atherosclerosis

The endoplasmic reticulum (ER) is an important organelle that regulates several fundamental cellular processes, and ER dysfunction has implications for many intracellular events. The nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is an intracellularly produced macromolecular complex that can trigger pyroptosis and inflammation, and its activation is induced by a variety of signals. ER stress has been found to affect NLRP3 inflammasome activation through multiple effects including the unfolded protein response (UPR), calcium or lipid metabolism, and reactive oxygen species (ROS) generation. Intriguingly, the role of ER stress in inflammasome activation has not attracted a great deal of attention. In addition, increasing evidence highlights that both ER stress and NLRP3 inflammasome activation contribute to atherosclerosis (AS). AS is a common cardiovascular disease with complex pathogenesis, and the precise mechanisms behind its pathogenesis remain to be determined. Both ER stress and the NLRP3 inflammasome have emerged as critical individual contributors of AS, and owing to the multiple associations between these two events, we speculate that they contribute to the mechanisms of pathogenesis in AS. In this review, we aim to summarize the molecular mechanisms of ER stress, NLRP3 inflammasome activation, and the cross talk between these two pathways in AS in the hopes of providing new pharmacological targets for AS treatment.

Download Full-text

Targeting NLRP3 Inflammasome Activation in Severe Asthma

Journal of Clinical Medicine ◽

10.3390/jcm8101615 ◽

2019 ◽

Vol 8 (10) ◽

pp. 1615 ◽

Cited By ~ 5

Author(s):

Efthymia Theofani ◽

Maria Semitekolou ◽

Ioannis Morianos ◽

Konstantinos Samitas ◽

Georgina Xanthou

Keyword(s):

Severe Asthma ◽

Nlrp3 Inflammasome ◽

Molecular Mechanisms ◽

Inflammatory Responses ◽

Pulmonary Inflammation ◽

Airflow Obstruction ◽

Inflammasome Activation ◽

Pyrin Domain ◽

Nlrp3 Inflammasome Activation ◽

Reversible Airflow Obstruction

Severe asthma (SA) is a chronic lung disease characterized by recurring symptoms of reversible airflow obstruction, airway hyper-responsiveness (AHR), and inflammation that is resistant to currently employed treatments. The nucleotide-binding oligomerization domain-like Receptor Family Pyrin Domain Containing 3 (NLRP3) inflammasome is an intracellular sensor that detects microbial motifs and endogenous danger signals and represents a key component of innate immune responses in the airways. Assembly of the NLRP3 inflammasome leads to caspase 1-dependent release of the pro-inflammatory cytokines IL-1β and IL-18 as well as pyroptosis. Accumulating evidence proposes that NLRP3 activation is critically involved in asthma pathogenesis. In fact, although NLRP3 facilitates the clearance of pathogens in the airways, persistent NLRP3 activation by inhaled irritants and/or innocuous environmental allergens can lead to overt pulmonary inflammation and exacerbation of asthma manifestations. Notably, administration of NLRP3 inhibitors in asthma models restrains AHR and pulmonary inflammation. Here, we provide an overview of the pathophysiology of SA, present molecular mechanisms underlying aberrant inflammatory responses in the airways, summarize recent studies pertinent to the biology and functions of NLRP3, and discuss the role of NLRP3 in the pathogenesis of asthma. Finally, we contemplate the potential of targeting NLRP3 as a novel therapeutic approach for the management of SA.

Download Full-text

An update on the regulatory mechanisms of NLRP3 inflammasome activation

Cellular and Molecular Immunology ◽

10.1038/s41423-021-00670-3 ◽

2021 ◽

Author(s):

Seungwha Paik ◽

Jin Kyung Kim ◽

Prashanta Silwal ◽

Chihiro Sasakawa ◽

Eun-Kyeong Jo

Keyword(s):

Protein Interactions ◽

Posttranslational Modifications ◽

Nlrp3 Inflammasome ◽

Molecular Mechanisms ◽

Inflammasome Activation ◽

Protein Protein Interactions ◽

Regulatory Pathways ◽

Pyrin Domain ◽

Spatiotemporal Regulation ◽

Nlrp3 Inflammasome Activation

AbstractThe NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a multiprotein complex involved in the release of mature interleukin-1β and triggering of pyroptosis, which is of paramount importance in a variety of physiological and pathological conditions. Over the past decade, considerable advances have been made in elucidating the molecular mechanisms underlying the priming/licensing (Signal 1) and assembly (Signal 2) involved in NLRP3 inflammasome activation. Recently, a number of studies have indicated that the priming/licensing step is regulated by complicated mechanisms at both the transcriptional and posttranslational levels. In this review, we discuss the current understanding of the mechanistic details of NLRP3 inflammasome activation with a particular emphasis on protein-protein interactions, posttranslational modifications, and spatiotemporal regulation of the NLRP3 inflammasome machinery. We also present a detailed summary of multiple positive and/or negative regulatory pathways providing upstream signals that culminate in NLRP3 inflammasome complex assembly. A better understanding of the molecular mechanisms underlying NLRP3 inflammasome activation will provide opportunities for the development of methods for the prevention and treatment of NLRP3 inflammasome-related diseases.

Download Full-text

Endoplasmic reticulum stress may activate NLRP3 inflammasomes via TXNIP in preeclampsia

10.1101/351650 ◽

2018 ◽

Author(s):

Yong Yang ◽

Jianxin Li ◽

Ting-Li Han ◽

Xiaobo Zhou ◽

Hongbo Qi ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Nlrp3 Inflammasome ◽

Critical Role ◽

Inflammasome Activation ◽

Interacting Protein ◽

Thioredoxin Interacting Protein ◽

Pyrin Domain ◽

Nlrp3 Inflammasome Activation ◽

Nlrp3 Inflammasomes

AbstractPreeclampsia (PE) development is often associated with placental immune and inflammatory dysregulation, as well as endoplasmic reticulum (ER) stress. However, the mechanisms linking ER stress and inflammatory dysregulation to PE have not been clarified. It has been reported that thioredoxin-interacting protein (TXNIP), which can bind with and activate the NLR family pyrin domain containing 3 (NLRP3) inflammasome, plays a critical role in immune regulation. Recent experimental evidence suggests that activated NLRP3 inflammasomes can activate interleukin-1β (IL-1β) production in the placenta of patients with PE. The objective of the current study was to explore if TXNIP plays a critical signaling role linking ER stress with NLRP3 inflammasome activation in PE. We hypothesised that ER stress would induce TXNIP production, which would bind with NLRP3 inflammasomes to activate IL-1β production. HTR8/SVneo cells were subjected to six hours hypoxia followed by six hours reoxygenation (H/R). These cells showed a higher protein level of NLRP3 and IL-1β, as well as a higher enzymatic activity of caspase-1, indicating enhanced inflammatory dysregulation and ER stress. Cells transfected with TXNIP siRNA showed reduced NLRP3 inflammasome activation. Cells treated with 4-phenylbutyric acid, an inhibitor of ER stress, showed a similar result. In addition, the outgrowth of explant with TXNIP lentivirus in H/R or Tunicamycin (inducers of ER stress) was also measured to verify our hypothesis. These findings demonstrated that TXNIP could influence inflammatory dysregulation by mediating ER stress and NLRP3 inflammasome activation in PE. This novel mechanism may further explain the inflammation observed at the maternal-fetal interface, which leads to placental dysfunction in a patient with PE.

Download Full-text

Coenzyme Q0 Inhibits NLRP3 Inflammasome Activation through Mitophagy Induction in LPS/ATP-Stimulated Macrophages

Oxidative Medicine and Cellular Longevity ◽

10.1155/2022/4266214 ◽

2022 ◽

Vol 2022 ◽

pp. 1-15

Author(s):

You-Cheng Hseu ◽

Yu-Fang Tseng ◽

Sudhir Pandey ◽

Sirjana Shrestha ◽

Kai-Yuan Lin ◽

...

Keyword(s):

Nlrp3 Inflammasome ◽

Coenzyme Q ◽

Antioxidant Properties ◽

Variable Number ◽

Ros Generation ◽

Inflammasome Activation ◽

Raw264.7 Macrophages ◽

Mitochondrial Ros ◽

Nlrp3 Inflammasome Activation ◽

Anti Inflammatory

Coenzyme Q (CoQ) analogs with a variable number of isoprenoid units have exhibited as anti-inflammatory as well as antioxidant molecules. Using novel quinone derivative CoQ0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone, zero side chain isoprenoid), we studied its molecular activities against LPS/ATP-induced inflammation and redox imbalance in murine RAW264.7 macrophages. CoQ0’s non- or subcytotoxic concentration suppressed the NLRP3 inflammasome and procaspase-1 activation, followed by downregulation of IL1β expression in LPS/ATP-stimulated RAW264.7 macrophages. Similarly, treatment of CoQ0 led to LC3-I/II accumulation and p62/SQSTM1 activation. An increase in the Beclin-1/Bcl-2 ratio and a decrease in the expression of phosphorylated PI3K/AKT, p70 S6 kinase, and mTOR showed that autophagy was activated. Besides, CoQ0 increased Parkin protein to recruit damaged mitochondria and induced mitophagy in LPS/ATP-stimulated RAW264.7 macrophages. CoQ0 inhibited LPS/ATP-stimulated ROS generation in RAW264.7 macrophages. Notably, when LPS/ATP-stimulated RAW264.7 macrophages were treated with CoQ0, Mito-TEMPO (a mitochondrial ROS inhibitor), or N-acetylcysteine (NAC, a ROS inhibitor), there was a significant reduction of LPS/ATP-stimulated NLRP3 inflammasome activation and IL1β expression. Interestingly, treatment with CoQ0 or Mito-TEMPO, but not NAC, significantly increased LPS/ATP-induced LC3-II accumulation indicating that mitophagy plays a key role in the regulation of CoQ0-inhibited NLRP3 inflammasome activation. Nrf2 knockdown significantly decreased IL1β expression in LPS/ATP-stimulated RAW264.7 macrophages suggesting that CoQ0 inhibited ROS-mediated NLRP3 inflammasome activation and IL1β expression was suppressed due to the Nrf2 activation. Hence, this study showed that CoQ0 might be a promising candidate for the therapeutics of inflammatory disorders due to its effective anti-inflammatory as well as antioxidant properties.

Download Full-text

Growth differentiation factor 11 ameliorates experimental colitis by inhibiting NLRP3 inflammasome activation

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00159.2018 ◽

2018 ◽

Vol 315 (6) ◽

pp. G909-G920 ◽

Cited By ~ 4

Author(s):

Lanju Wang ◽

Yaohui Wang ◽

Zhenfeng Wang ◽

Yu Qi ◽

Beibei Zong ◽

...

Keyword(s):

Ulcerative Colitis ◽

Nlrp3 Inflammasome ◽

Intestinal Inflammation ◽

Experimental Colitis ◽

Inflammasome Activation ◽

Acute Colitis ◽

Pyrin Domain ◽

Differentiation Factor ◽

Nlrp3 Inflammasome Activation ◽

Receptor Family

Growth differentiation factor 11 (GDF11) has an anti-inflammatory effect in the mouse model of atherosclerosis and Alzheimer's disease, but how GDF11 regulates intestinal inflammation during ulcerative colitis (UC) is poorly defined. The Nod-like receptor family pyrin domain-1 containing 3 (NLRP3) inflammasome is closely associated with intestinal inflammation because of its ability to increase IL-1β secretion. Our aim is to determine whether GDF11 has an effect on attenuating experimental colitis in mice. In this study, using a dextran sodium sulfate (DSS)-induced acute colitis mouse model, we reported that GDF11 treatment attenuated loss of body weight, the severity of the disease activity index, shortening of the colon, and histological changes in the colon. GDF11 remarkably suppressed IL-1β secretion and NLRP3 inflammasome activation in colon samples and RAW 264.7 cells, such as the levels of NLRP3 and activated caspase-1. Furthermore, we found that GDF11 inhibited NLRP3 inflammasome activation by downregulating the Toll-like receptor 4/NF-κB p65 pathway and reactive oxygen species production via the typical Smad2/3 pathway. Thus, our research shows that GDF11 alleviates DSS-induced colitis by inhibiting NLRP3 inflammasome activation, providing some basis for its potential use in the treatment of UC. NEW & NOTEWORTHY Here, we identify a new role for growth differentiation factor 11 (GDF11), which ameliorates dextran sodium sulfate-induced acute colitis. Meanwhile, we discover a new phenomenon of GDF11 inhibiting IL-1β secretion and Nod-like receptor family pyrin domain-1 containing 3 (NLRP3) inflammasome activation. These findings reveal that GDF11 is a new potential candidate for the treatment of ulcerative colitis patients with a hyperactive NLRP3 inflammasome.

Download Full-text

Abstract 11852: Role of Lox-1 in Mitochondrial Dna Damage and NLRP3 Inflammasome Activation

Circulation ◽

10.1161/circ.130.suppl_2.11852 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Zufeng Ding ◽

Sadip Pant ◽

Abhishek Deshmukh ◽

Jawahar L Mehta

Keyword(s):

Dna Damage ◽

Mitochondrial Dna ◽

Nlrp3 Inflammasome ◽

Ros Generation ◽

Inflammasome Activation ◽

Mtdna Damage ◽

Mitochondrial Dna Damage ◽

Mitochondrial Ros ◽

Nlrp3 Inflammasome Activation

Objective: This study tested the hypothesis that mitochondrial DNA damage could trigger NLRP3 inflammasome activation during inflammation, and LOX-1 may play a critical role in this process. Methods and Results: We performed studies in cultured human THP1 macrophages exposed to ox-LDL or LPS,which are often used as inflammation stimuli in vitro . We examined and confirmed the increase in LOX-1 expression when cells were treated with ox-LDL or LPS. Parallel groups of cells were treated with LOX-1 Ab to bind LOX-1. In accordance with our previous studies in endothelial cells and smooth muscle cells, LOX-1 Ab markedly reduced ox-LDL- as well as LPS-stimulated LOX-1 expression. To assess mitochondrial ROS generation, MitoSOX™ Red mitochondrial superoxide indicator was used. Both fluorescence staining and flow cytometry analysis showed that LPS induced (more than ox-LDL) mitochondrial ROS generation. Pretreatment with LOX-1 Ab significantly attenuated mitochondrial ROS generation in response to ox-LDL or LPS. Then we observed mtDNA damage in THP1 cells exposed to ox-LDL or LPS. Importantly, pretreatment with LOX-1 Ab protected mtDNA from damage in response to both stimuli. This was also confirmed by q-PCR (mtDNA/nDNA ratio) analysis. Further, ox-LDL or LPS induced the expression of phos-NF-kB p65, caspase-1 p10 and p20, and cleaved proteins IL-1β and IL-18. Of note, NLRP3 inflammasome was activated in response to ox-LDL or LPS in a similar manner. Pretreatment of cells with LOX-1 Ab treatment blocked or significantly attenuated these inflammatory responses. Conclusions: These observations based on in vitro observations indicate that LOX-1 via ROS generation plays a key role in mtDNA damage which then leads to NLRP3 inflammasome activation during inflammation.

Download Full-text

Progesterone Attenuates Stress-Induced NLRP3 Inflammasome Activation and Enhances Autophagy Following Ischemic Brain Injury

International Journal of Molecular Sciences ◽

10.3390/ijms21113740 ◽

2020 ◽

Vol 21 (11) ◽

pp. 3740 ◽

Cited By ~ 3

Author(s):

Claudia Espinosa-Garcia ◽

Fahim Atif ◽

Seema Yousuf ◽

Iqbal Sayeed ◽

Gretchen N. Neigh ◽

...

Keyword(s):

Brain Injury ◽

Nlrp3 Inflammasome ◽

Molecular Mechanisms ◽

Global Ischemia ◽

Inflammasome Activation ◽

Ischemic Brain Injury ◽

Primary Microglia ◽

Ischemic Brain ◽

Nlrp3 Inflammasome Activation ◽

The Impact

NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome inhibition and autophagy induction attenuate inflammation and improve outcome in rodent models of cerebral ischemia. However, the impact of chronic stress on NLRP3 inflammasome and autophagic response to ischemia remains unknown. Progesterone (PROG), a neuroprotective steroid, shows promise in reducing excessive inflammation associated with poor outcome in ischemic brain injury patients with comorbid conditions, including elevated stress. Stress primes microglia, mainly by the release of alarmins such as high-mobility group box-1 (HMGB1). HMGB1 activates the NLRP3 inflammasome, resulting in pro-inflammatory interleukin (IL)-1β production. In experiment 1, adult male Sprague-Dawley rats were exposed to social defeat stress for 8 days and then subjected to global ischemia by the 4-vessel occlusion model, a clinically relevant brain injury associated with cardiac arrest. PROG was administered 2 and 6 h after occlusion and then daily for 7 days. Animals were killed at 7 or 14 days post-ischemia. Here, we show that stress and global ischemia exert a synergistic effect in HMGB1 release, resulting in exacerbation of NLRP3 inflammasome activation and autophagy impairment in the hippocampus of ischemic animals. In experiment 2, an in vitro inflammasome assay, primary microglia isolated from neonatal brain tissue, were primed with lipopolysaccharide (LPS) and stimulated with adenosine triphosphate (ATP), displaying impaired autophagy and increased IL-1β production. In experiment 3, hippocampal microglia isolated from stressed and unstressed animals, were stimulated ex vivo with LPS, exhibiting similar changes than primary microglia. Treatment with PROG reduced HMGB1 release and NLRP3 inflammasome activation, and enhanced autophagy in stressed and unstressed ischemic animals. Pre-treatment with an autophagy inhibitor blocked Progesterone’s (PROG’s) beneficial effects in microglia. Our data suggest that modulation of microglial priming is one of the molecular mechanisms by which PROG ameliorates ischemic brain injury under stressful conditions.

Download Full-text

NLRP3 Inflammasome Is Involved in Calcium-Sensing Receptor-Induced Aortic Remodeling in SHRs

Mediators of Inflammation ◽

10.1155/2019/6847087 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13 ◽

Cited By ~ 2

Author(s):

Xin Zhang ◽

Siting Hong ◽

Shuhan Qi ◽

Wenxiu Liu ◽

Xiaohui Zhang ◽

...

Keyword(s):

Nlrp3 Inflammasome ◽

Activation Mechanism ◽

Inflammasome Activation ◽

Calcium Sensing Receptor ◽

Pyrin Domain ◽

Calcium Sensing ◽

Nlrp3 Inflammasome Activation ◽

Nucleotide Oligomerization ◽

Aortic Remodeling ◽

Receptor Family

Increasing evidence suggests that the NLRP3 (nucleotide oligomerization domain-like receptor family, pyrin domain containing 3) inflammasome participates in cardiovascular diseases. However, its role and activation mechanism during hypertension remains unclear. In this study, we tested the role and mechanism of calcium-sensing receptor (CaSR) in NLRP3 inflammasome activation during hypertension. We observed that the expressions of CaSR and NLRP3 were increased in spontaneous hypertensive rats (SHRs) along with aortic fibrosis. In vascular smooth muscle cells (VSMCs), the activation of NLRP3 inflammasome associated with CaSR and collagen synthesis was induced by angiotensin II (Ang II). Furthermore, inhibition of CaSR and NLRP3 inflammasome attenuated proinflammatory cytokine release, suggesting that CaSR-mediated activation of the NLRP3 inflammasome may be a therapeutic target in aortic dysfunction and vascular inflammatory lesions.

Download Full-text

The Roles of Endoplasmic Reticulum in NLRP3 Inflammasome Activation

Cells ◽

10.3390/cells9051219 ◽

2020 ◽

Vol 9 (5) ◽

pp. 1219 ◽

Cited By ~ 3

Author(s):

Yang Zhou ◽

Zhizi Tong ◽

Songhong Jiang ◽

Wenyan Zheng ◽

Jianjun Zhao ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Nlrp3 Inflammasome ◽

Critical Role ◽

Immune Defense ◽

Inflammasome Activation ◽

Nucleotide Binding Domain ◽

Cholesterol Trafficking ◽

Pyrin Domain ◽

Nlrp3 Inflammasome Activation ◽

Molecular Patterns

The NLRP3 (nucleotide-binding domain, leucine-rich-repeat-containing family, pyrin domain-containing 3) inflammasome senses pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs), and activates caspase-1, which provokes release of proinflammatory cytokines such as interleukin-1β (IL-1β) and IL-18 as well as pyroptosis to engage in innate immune defense. The endoplasmic reticulum (ER) is a large and dynamic endomembrane compartment, critical to cellular function of organelle networks. Recent studies have unveiled the pivotal roles of the ER in NLRP3 inflammasome activation. ER–mitochondria contact sites provide a location for NLRP3 activation, its association with ligands released from or residing in mitochondria, and rapid Ca2+ mobilization from ER stores to mitochondria. ER-stress signaling plays a critical role in NLRP3 inflammasome activation. Lipid perturbation and cholesterol trafficking to the ER activate the NLRP3 inflammasome. These findings emphasize the importance of the ER in initiation and regulation of the NLRP3 inflammasome.

Download Full-text

Distinct Molecular Mechanisms Underlying Potassium Efflux for NLRP3 Inflammasome Activation

Frontiers in Immunology ◽

10.3389/fimmu.2020.609441 ◽

2020 ◽

Vol 11 ◽

Author(s):

Ziwei Xu ◽

Zi-mo Chen ◽

Xiaoyan Wu ◽

Linjie Zhang ◽

Ying Cao ◽

...

Keyword(s):

Nlrp3 Inflammasome ◽

Molecular Mechanisms ◽

Current Knowledge ◽

Inflammasome Activation ◽

Potassium Efflux ◽

Pannexin 1 ◽

Nlrp3 Inflammasome Activation ◽

K2p Channels ◽

Pore Forming Proteins ◽

Molecular Patterns

The NLRP3 inflammasome is a core component of innate immunity, and dysregulation of NLRP3 inflammasome involves developing autoimmune, metabolic, and neurodegenerative diseases. Potassium efflux has been reported to be essential for NLRP3 inflammasome activation by structurally diverse pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs). Thus, the molecular mechanisms underlying potassium efflux to activate NLRP3 inflammasome are under extensive investigation. Here, we review current knowledge about the distinction channels or pore-forming proteins underlying potassium efflux for NLRP3 inflammasome activation with canonical/non-canonical signaling or following caspase-8 induced pyroptosis. Ion channels and pore-forming proteins, including P2X7 receptor, Gasdermin D, pannexin-1, and K2P channels involved present viable therapeutic targets for NLRP3 inflammasome related diseases.

Download Full-text