NLRP3 Inflammasome Is Involved in Q-VD-OPH Induced Necroptosis Following Cerebral Ischemia-Reperfusion Injury

Necroptosis is a manner of caspase-independent cell death,which accounts for delayed ischemic cerebral injury, and can be used as a novel tool to expand the treatment time window in ischemic cerebral injury. Q-VD-OPH, a novel pan caspase inhibitor, has been identified as an inducer of necroptosis. In this study, we determined the optimal dose of Q-VD-OPH, which induces necroptosis in rats by the middle cerebral artery occlusion, followed by reperfusion. Furthermore, we report that the NLRP3 inflammasome is involved in necroptosis, with levels of NLRP3 inflammasome proteins as well as inflammatory cytokines, such as IL-1β, being elevated. We also demonstrated that NLRP3 was not only expressed in microglia and vascular endothelial cell, but also in neurons when necroptosis is induced with Q-VD-OPH. Inhibition of NLRP3 by glyburide strongly suppressed the expression of NLRP3 inflammasome proteins and IL-1β, and markedly reduced brain tissue damage. Our findings provide evidence that pretreatment with Q-VD-OPH suppresses apoptosis and induces necroptosis in the cerebral ischemia-reperfusion model. We also identified that the NLRP3 inflammasome plays an important role in neuronal necroptosis, and that NLRP3 inflammasome deficiency reduces brain tissue damage after cerebral ischemia-reperfusion injury in rats.     

Reduced expression of NLRP3 and MEFV in human ischemic heart tissue

The innate immune system and, in particular, activation of the multi-protein complex known as the inflammasome complex are involved in ischemic injury in myocardial cells. The nucleotide-binding leucine-rich repeat-containing pyrin receptor 3 (NLRP3) inflammasome has been linked to inflammation and NLRP3 is especially important for increased inflammation in atherosclerosis, which may lead to myocardial infarction. Here we investigated how inflammasome molecules are affected in human ischemic heart tissue. Surprisingly the important member of the inflammasome complex, NLRP3, displayed markedly decreased levels in human ischemic heart tissue compared with non ischemic control heart tissue. However, subsequent gene analysis revealed mutations in NLRP3 in human ischemic heart tissues but not in non-ischemic control tissue. Gene polymorphisms in the NLRP3 inflammasome have been shown to be associated with increased IL-1β and IL-18 production and severe inflammation.The autoinflammatory disorder familial Mediterranean fever (FMF) is associated with decreased expression of the Mediterranean fever gene (MEFV) and increased inflammation. We also observed reduced expression of MEFV in ischemic versus non-ischemic heart tissue. Further analyses showed a mutation in MEFV in human ischemic heart tissue but not in non-ischemic control tissue.Our data show that defects in the inflammasome and associated proteins may be involved in promoting ischemic heart disease.     

Mechanisms of NLRP3 priming in inflammaging and age related diseases

The NLRP3 inflammasome is a vital part of the innate immune response, whilst its aberrant activation drives the progression of a number of non-communicable diseases. Thus, NLRP3 inflammasome assembly must be tightly controlled at several checkpoints. The priming step of NLRP3 inflammasome activation is associated with increased NLRP3 gene expression, as well as post-translational modifications that control NLRP3 levels and licence the NLRP3 protein for inflammasome assembly. Increasing life expectancy in modern society is accompanied by a growing percentage of elderly individuals. The process of aging is associated with chronic inflammation that drives and/or worsens a range of age related non-communicable conditions. The NLRP3 inflammasome is known to contribute to pathological inflammation in many settings, but the mechanisms that prime NLRP3 for activation throughout aging and related co-morbidities have not been extensively reviewed. Here we dissect the biochemical changes that occur during aging and the pathogenesis of age related diseases and analyse the mechanisms by which they prime the NLRP3 inflammasome, thus exacerbating inflammation.     

NLRP3 inflammasome suppression improves longevity and prevents cardiac aging in male mice

While NLRP3‐inflammasome has been implicated in cardiovascular diseases, its role in physiological cardiac aging is largely unknown. During aging, many alterations occur in the organism, which are associated with progressive impairment of metabolic pathways related to insulin resistance, autophagy dysfunction, and inflammation. Here, we investigated the molecular mechanisms through which NLRP3 inhibition may attenuate cardiac aging. Ablation of NLRP3‐inflammasome protected mice from age‐related increased insulin sensitivity, reduced IGF‐1 and leptin/adiponectin ratio levels, and reduced cardiac damage with protection of the prolongation of the age‐dependent PR interval, which is associated with atrial fibrillation by cardiovascular aging and reduced telomere shortening. Furthermore, old NLRP3 KO mice showed an inhibition of the PI3K/AKT/mTOR pathway and autophagy improvement, compared with old wild mice and preserved Nampt‐mediated NAD⁺ levels with increased SIRT1 protein expression. These findings suggest that suppression of NLRP3 prevented many age‐associated changes in the heart, preserved cardiac function of aged mice and increased lifespan.     

Intravenous immunoglobulin suppresses NLRP1 and NLRP3 inflammasome-mediated neuronal death in ischemic stroke

Multi-protein complexes called inflammasomes have recently been identified and shown to contribute to cell death in tissue injury. Intravenous immunoglobulin (IVIg) is an FDA-approved therapeutic modality used for various inflammatory diseases. The objective of this study is to investigate dynamic responses of the NLRP1 and NLRP3 inflammasomes in stroke and to determine whether the NLRP1 and NLRP3 inflammasomes can be targeted with IVIg for therapeutic intervention. Primary cortical neurons were subjected to glucose deprivation (GD), oxygen–glucose deprivation (OGD) or simulated ischemia-reperfusion (I/R). Ischemic stroke was induced in C57BL/6J mice by middle cerebral artery occlusion, followed by reperfusion. Neurological assessment was performed, brain tissue damage was quantified, and NLRP1 and NLRP3 inflammasome protein levels were evaluated. NLRP1 and NLRP3 inflammasome components were also analyzed in postmortem brain tissue samples from stroke patients. Ischemia-like conditions increased the levels of NLRP1 and NLRP3 inflammasome proteins, and IL-1β and IL-18, in primary cortical neurons. Similarly, levels of NLRP1 and NLRP3 inflammasome proteins, IL-1β and IL-18 were elevated in ipsilateral brain tissues of cerebral I/R mice and stroke patients. Caspase-1 inhibitor treatment protected cultured cortical neurons and brain cells in vivo in experimental stroke models. IVIg treatment protected neurons in experimental stroke models by a mechanism involving suppression of NLRP1 and NLRP3 inflammasome activity. Our findings provide evidence that the NLRP1 and NLRP3 inflammasomes have a major role in neuronal cell death and behavioral deficits in stroke. We also identified NLRP1 and NLRP3 inflammasome inhibition as a novel mechanism by which IVIg can protect brain cells against ischemic damage, suggesting a potential clinical benefit of therapeutic interventions that target inflammasome assembly and activity.     

Salidroside Alleviates Chronic Constriction Injury-Induced Neuropathic Pain and Inhibits of TXNIP/NLRP3 Pathway

Neuropathic pain is one of the most common conditions requiring treatment worldwide. Salidroside (SAL), a phenylpropanoid glucoside extracted from Rhodiola, has been suggested to produce an analgesic effect in chronic pain. However, whether SAL could alleviate pain hypersensitivity after peripheral nerve injury and its mode of action remains unclear. Several studies suggest that activation of the spinal NOD-like receptor protein 3 (NLRP3) inflammasome and its related proteins contribute to neuropathic pain’s pathogenesis. This study investigates the time course of activation of spinal NLRP3 inflammasome axis in the development of neuropathic pain and also whether SAL could be an effective treatment for this type of pain by modulating NLRP3 inflammasome. In the chronic constriction injury (CCI) mice model, spinal NLRP3 inflammasome-related proteins and TXNIP, the mediator of NLRP3, were upregulated from the 14th to the 28th day after injury. The TXNIP and NLRP3 inflammasome-related proteins were mainly present in neurons and microglial cells in the spinal dorsal horn after CCI. Intraperitoneal injection of SAL at 200 mg/kg for 14 consecutive days starting from the 7th day of CCI injury could ameliorate mechanical and thermal hypersensitivity in the CCI model. Moreover, SAL inhibited the activation of the TXNIP/NLRP3 inflammasome axis and mitigated the neuronal loss of spinal dorsal horn induced by nerve injury. These results indicate that SAL could produce analgesic and neuroprotective effects in the CCI model of neuropathic pain.

     

Age-dependent loss of hepatic SIRT1 enhances NLRP3 inflammasome signaling and impairs capacity for liver fibrosis resolution

Our studies indicate that the longevity factor SIRT1 is implicated in metabolic disease; however, whether and how hepatocyte-specific SIRT1 signaling is involved in liver fibrosis remains undefined. We characterized a functional link of age-mediated defects in SIRT1 to the NLRP3 inflammasome during age-related liver fibrosis. In multiple experimental murine models of liver fibrosis, we compared the development of liver fibrosis in young and old mice, as well as in liver-specific SIRT1 knockout (SIRT1 LKO) mice and wild-type (WT) mice. Liver injury, fibrosis, and inflammation were assessed histologically and quantified by real-time PCR analysis. In a model of hepatotoxin-induced liver fibrosis, old mice displayed more severe and persistent liver fibrosis than young mice during liver injury and after injury cessation, as characterized by inhibition of SIRT1, induction of NLRP3, infiltration of macrophages and neutrophils, activation of hepatic stellate cells (HSCs), and excessive deposition and remodeling of the extracellular matrix. Mechanistically, deletion of SIRT1 in hepatocytes resulted in NLRP3 and IL-1β induction, pro-inflammatory response, and severe liver fibrosis in young mice, mimicking the ability of aging to impair the resolution of established fibrosis. In an aging mouse model, chronic-plus-binge alcohol feeding-induced liver fibrosis was attenuated by treatment with MCC950, a selective NLRP3 inhibitor. NLRP3 inhibition ameliorated alcoholic liver fibrosis in old mice by repressing inflammation and reducing hepatocyte-derived danger signaling—ASK1 and HMGB1. In conclusion, age-dependent SIRT1 defects lead to NLRP3 activation and inflammation, which in turn impairs the capacity to resolve fibrosis during aging.     

Quercetin and allopurinol ameliorate kidney injury in STZ-treated rats with regulation of renal NLRP3 inflammasome activation and lipid accumulation

Hyperuricemia, hyperlipidemia and inflammation are associated with diabetic nephropathy. The NLRP3 inflammasome-mediated inflammation is recently recognized in the development of kidney injury. Urate and lipid are considered as danger signals in the NLRP3 inflammasome activation. Although dietary flavonoid quercetin and allopurinol alleviate hyperuricemia, dyslipidmia and inflammation, their nephroprotective effects are currently unknown. In this study, we used streptozotocin (STZ)-induced diabetic nephropathy model with hyperuricemia and dyslipidemia in rats, and found over-expression of renal inflammasome components NLRP3, apoptosis-associated speck-like protein and Caspase-1, resulting in elevation of IL-1β and IL-18, with subsequently deteriorated renal injury. These findings demonstrated the possible association between renal NLRP3 inflammasome activation and lipid accumulation to superimpose causes of nephrotoxicity in STZ-treated rats. The treatment of quercetin and allopurinol regulated renal urate transport-related proteins to reduce hyperuricemia, and lipid metabolism-related genes to alleviate kidney lipid accumulation in STZ-treated rats. Furthermore, quercetin and allopurinol were found to suppress renal NLRP3 inflammasome activation, at least partly, via their anti-hyperuricemic and anti-dyslipidemic effects, resulting in the amelioration of STZ-induced the superimposed nephrotoxicity in rats. These results may provide a basis for the prevention of diabetes-associated nephrotoxicity with urate-lowering agents such as quercetin and allopurinol.     

Evidence that NF-κB and MAPK Signaling Promotes NLRP Inflammasome Activation in Neurons Following Ischemic Stroke

Multi-protein complexes, termed “inflammasomes,” are known to contribute to neuronal cell death and brain injury following ischemic stroke. Ischemic stroke increases the expression and activation of nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) Pyrin domain containing 1 and 3 (NLRP1 and NLRP3) inflammasome proteins and both interleukin (IL)-1β and IL-18 in neurons. In this study, we provide evidence that activation of either the NF-κB and MAPK signaling pathways was partly responsible for inducing the expression and activation of NLRP1 and NLRP3 inflammasome proteins and that these effects can be attenuated using pharmacological inhibitors of these two pathways in neurons and brain tissue under in vitro and in vivo ischemic conditions, respectively. Moreover, these findings provided supporting evidence that treatment with intravenous immunoglobulin (IVIg) preparation can reduce activation of the NF-κB and MAPK signaling pathways resulting in decreased expression and activation of NLRP1 and NLRP3 inflammasomes, as well as increasing expression of anti-apoptotic proteins, Bcl-2 and Bcl-xL, in primary cortical neurons and/or cerebral tissue under in vitro and in vivo ischemic conditions. In summary, these results provide compelling evidence that both the NF-κB and MAPK signaling pathways play a pivotal role in regulating the expression and activation of NLRP1 and NLRP3 inflammasomes in primary cortical neurons and brain tissue under ischemic conditions. In addition, treatment with IVIg preparation decreased the activation of the NF-κB and MAPK signaling pathways, and thus attenuated the expression and activation of NLRP1 and NLRP3 inflammasomes in primary cortical neurons under ischemic conditions. Hence, these findings suggest that therapeutic interventions that target inflammasome activation in neurons may provide new opportunities in the future treatment of ischemic stroke.     

Intermittent electrical stimulation redistributes pressure and promotes tissue oxygenation in loaded muscles of individuals with spinal cord injury

Deep tissue injury (DTI) is a severe form of pressure ulcer that originates at the bone-muscle interface. It results from mechanical damage and ischemic injury due to unrelieved pressure. Currently, there are no established clinical methods to detect the formation of DTI. Moreover, despite the many recommended methods for preventing pressure ulcers, none so far has significantly reduced the incidence of DTI. The goal of this study was to assess the effectiveness of a new electrical stimulation-based intervention, termed intermittent electrical stimulation (IES), in ameliorating the factors leading to DTI in individuals with compromised mobility and sensation. Specifically, we sought to determine whether IES-induced contractions in the gluteal muscles can 1) reduce pressure in tissue surrounding bony prominences susceptible to the development of DTI and 2) increase oxygenation in deep tissue. Experiments were conducted in individuals with spinal cord injury, and two paradigms of IES were utilized to induce contractions in the gluteus maximus muscles of the seated participants. Changes in surface pressure around the ischial tuberosities were assessed using a pressure-sensing mattress, and changes in deep tissue oxygenation were indirectly assessed using T?*-weighted magnetic resonance imaging (MRI) techniques. Both IES paradigms significantly reduced pressure around the bony prominences in the buttocks by an average of 10-26% (P < 0.05). Furthermore, both IES paradigms induced significant increases in T?* signal intensity (SI), indicating significant increases in tissue oxygenation, which were sustained for the duration of each 10-min trial (P < 0.05). Maximal increases in SI ranged from 2-3.3% (arbitrary units). Direct measurements of oxygenation in adult rats revealed that IES produces up to a 100% increase in tissue oxygenation. The results suggest that IES directly targets factors contributing to the development of DTI in people with reduced mobility and sensation and may therefore be an effective method for the prevention of deep pressure ulcers.     

Proteomic Analysis Reveals Age-related Changes in Tendon Matrix Composition,with Age- and Injury-specific Matrix Fragmentation

Energy storing tendons, such as the human Achilles and equine superficial digital flexor tendon (SDFT), are highly prone to injury, the incidence of which increases with aging. The cellular and molecular mechanisms that result in increased injury in aged tendons are not well established but are thought to result in altered matrix turnover. However, little attempt has been made to fully characterize the tendon proteome nor determine how the abundance of specific tendon proteins changes with aging and/or injury. The aim of this study was, therefore, to assess the protein profile of normal SDFTs from young and old horses using label-free relative quantification to identify differentially abundant proteins and peptide fragments between age groups. The protein profile of injured SDFTs from young and old horses was also assessed. The results demonstrate distinct proteomic profiles in young and old tendon, with alterations in the levels of proteins involved in matrix organization and regulation of cell tension. Furthermore, we identified several new peptide fragments (neopeptides) present in aged tendons, suggesting that there are age-specific cleavage patterns within the SDFT. Proteomic profile also differed between young and old injured tendon, with a greater number of neopeptides identified in young injured tendon. This study has increased the knowledge of molecular events associated with tendon aging and injury, suggesting that maintenance and repair of tendon tissue may be reduced in aged individuals and may help to explain why the risk of injury increases with aging.     

Autophagy and NLRP3 inflammasome crosstalk in neuroinflammation in aged bovine brains

NLRP3 inflammasome is a multiprotein complex that can sense several stimuli such as autophagy dysregulation and increased reactive oxygen species production stimulating inflammation by priming the maturation of proinflammatory cytokines interleukin-1β and interleukin-18 in their active form. In the aging brain, these cytokines can mediate the innate immunity response priming microglial activation. Here, we describe the results of immunohistochemical and molecular analysis carried out on bovine brains. Our results support the hypothesis that the age-related impairment in cellular housekeeping mechanisms and the increased oxidative stress can trigger the inflammatory danger sensor NLRP3. Moreover, according to the recent scientific literature, we demonstrate the presence of an age-related proinflammatory environment in aged brains consisting in an upregulation of interleukin-1β, an increased microglial activation and increased NLRP3 expression. Finally, we suggest that bovine may potentially be a pivotal animal model for brain aging studies.     

Interaction Between Nonviral Reprogrammed Fibroblast Stem Cells and Trophic Factors for Brain Repair

Diabetic encephalopathy is one of the most common complications of diabetes. Inflammatory events during diabetes may be an important mechanism of diabetic encephalopathy. Inflammasome is a multiprotein complex consisting of Nod-like receptor proteins (NLRPs), apoptosis-associated speck-like protein (ASC), and caspase 1 or 5, which functions to switch on the inflammatory process and the release of inflammatory factors. The present study hypothesized that the formation and activation of NLRP1 inflammasome turns on neuroinflammation and neuron injury during hyperglycemia. The results demonstrated that the levels of interleukin-1 beta (IL-1β) were increased in the cortex of streptozocin (STZ)-induced diabetic rats. The levels of mature IL-1β and IL-18 were also elevated in culture medium of neurons treated with high glucose (50 mM). The expression of three essential components of the NLRP1 inflammasome complex, namely, NLRP1, ASC, and caspase 1, was also upregulated in vivo and in vitro under high glucose. Silencing the ASC gene prevented the caspase-1 activation, and inhibiting caspase 1 activity blocked hyperglycemia-induced release of inflammatory factors and neuron injury. Moreover, we found that pannexin 1 mediated the actvitation of NLRP1 inflammasome under high glucose. These results suggest that hyperglycemia induces neuroinflammation through activation of NLRP1 inflammasome, which represents a novel mechanism of diabetes-associated neuron injury.     

Impaired NLRP3 inflammasome function in elderly mice during influenza infection is rescued by treatment with nigericin

The NLRP3 inflammasome is activated in the lung during influenza viral infection; however, the impact of aging on inflammasome function during influenza infection has not been examined. In this study, we show that elderly mice infected with a mouse-adapted strain of influenza produced lower levels of IL-1β during in vitro and in vivo infection. Dendritic cells from elderly mice exhibited decreased expression of ASC, NLRP3, and capase-1 but increased expression of pro-IL-1β, pro-IL-18, and pro-IL-33 compared with dendritic cells from young infected mice. Treatment with nigericin during influenza infection augmented IL-1β production, increased caspase-1 activity, and decreased morbidity and mortality in elderly mice. Our study demonstrates for the first time, to our knowledge, that during influenza viral infection, elderly mice have impaired NLRP3 inflammasome activity and that treatment with nigericin rescues NLRP3 activation in elderly hosts.     

Sulforaphene targets NLRP3 inflammasome to suppress M1 polarization of macrophages and inflammatory response in rheumatoid arthritis

This work aimed to explore the therapeutic effect and target of sulforaphene (LF) in mice with rheumatoid arthritis (RA). Lipopolysaccharide (LPS) and IFN-γ were added to induce the M1 polarization of SMG cells, and later cells were pretreated with 5 μM and 15 μM LF. M1 cell proportion was detected by flow cytometry (FCM), inflammatory factors were measured by enzyme-linked immunosorbent assay, and protein levels were analyzed by western blotting (WB) assay. Besides, small molecule-protein docking and pull-down assays were carried out to detect the binding of LF to NLRP3. After the knockdown of NLRP3 in SMG cells, the effect of LF was further detected. The RA mouse model was induced with collagen antibody and LPS, after LF intervention, H&E staining was performed to detect the pathological changes in mouse synovial membrane, whereas safranin O-fast green staining was performed to detect cartilage injury, NLRP3 inflammasome and inflammatory factor levels in tissues. LF suppressed M1 polarization of macrophages, reduced M1 cell proportion and inflammatory factor levels, and suppressed the activation of NLRP3 inflammasome. After NLRP3 knockdown, LF did not further suppress the M1 polarization of macrophages. Pull-down assay suggested that LF bound to NLRP3. As revealed by mouse experimental results, LF inhibited bone injury in mice, decreased M1 cell infiltration and inflammatory response in tissues, and inhibited NLRP3 inflammasome expression in tissues. LF targets NLRP3 to suppress the M1 polarization of macrophages and decrease tissue inflammation in RA.     

3,4-Methylenedioxy-β-nitrostyrene Inhibits NLRP3 Inflammasome Activation by Blocking Assembly of the Inflammasome

The NLRP3 inflammasome is a critical component of the innate immune system. NLRP3 activation is induced by diverse stimuli associated with bacterial infection or tissue damage, but its inappropriate activation is involved in the pathogenesis of inherited and acquired inflammatory diseases. However, the mechanism by which NLRP3 is activated remains poorly understood. In this study, we explored the role of kinases in NLRP3 inflammasome activation by screening a kinase inhibitor library and identified 3,4-methylenedioxy-β-nitrostyrene (MNS) as an inhibitor for NLRP3 inflammasome activation. Notably, MNS did not affect the activation of the NLRC4 or AIM2 (absent in melanoma 2) inflammasome. Mechanistically, MNS specifically prevented NLRP3-mediated ASC speck formation and oligomerization without blocking potassium efflux induced by NLRP3 agonists. Surprisingly, Syk kinase, the reported target of MNS, did not mediate the inhibitory activity of MNS on NLRP3 inflammasome activation. We also found that the nitrovinyl group of MNS is essential for the inhibitory activity of MNS. Immunoprecipitation, mass spectrometry, and mutation studies suggest that both the nucleotide binding oligomerization domain and the leucine-rich repeat domain of NLRP3 were the intracellular targets of MNS. Administration of MNS also inhibited NLRP3 ATPase activity in vitro, suggesting that MNS blocks the NLRP3 inflammasome by directly targeting NLRP3 or NLRP3-associated complexes. These studies identified a novel chemical probe for studying the molecular mechanism of NLRP3 inflammasome activation which may advance the development of novel strategies to treat diseases associated with abnormal activation of NLRP3 inflammasome.     

CD36 aggravates podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy in lupus nephritis

A major cause of proteinuria in lupus nephritis (LN) is podocyte injury, and determining potential therapeutic targets to prevent podocyte injury is important from a clinical perspective in the treatment of LN. CD36 is involved in podocyte injury in several glomerulopathies and was reported to be a vital candidate gene in LN. Here, we determined the role of CD36 in the podocyte injury of LN and the underlying mechanisms. We observed that CD36 and NLRP3 (NLR family pyrin domain containing 3) were upregulated in the podocytes of lupus nephritis patients and MRL/lpr mice with renal impairment. In vitro, CD36, NLRP3 inflammasome, and autophagy were elevated accompanied with increased podocyte injury stimulated by IgG extracted from lupus nephritis patients compared that from healthy donors. Knocking out CD36 with the CRISPR/cas9 system decreased the NLRP3 inflammasome levels, increased the autophagy levels and alleviated podocyte injury. By enhancing autophagy, NLRP3 inflammasome was decreased and podocyte injury was alleviated. These results demonstrated that, in lupus nephritis, CD36 promoted podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy by enhancing which could decrease NLRP3 inflammasome and alleviate podocyte injury.Subject terms: Mechanisms of disease, Inflammasome, Lupus nephritis, Autophagy     

Aging aggravated liver ischemia and reperfusion injury by promoting STING‐mediated NLRP3 activation in macrophages

Although aggravated liver injury has been reported in aged livers post‐ischemia and reperfusion (IR), the underlying mechanism of innate immune activation of aged macrophages is not well understood. Here, we investigated whether and how Stimulator of interferon genes (STING) signaling regulated macrophage proinflammatory activation and liver IR injury. Mice were subjected to hepatic IR in vivo. Macrophages isolated from IR‐stressed livers and bone marrow‐derived macrophages (BMDMs) from young and aged mice were used for in vitro studies. Enhanced nucleotide‐binding domain and leucine‐rich repeat containing protein 3 (NLRP3) activation was found in both livers and macrophages of aged mice post‐IR. NLRP3 knockdown in macrophages inhibited intrahepatic inflammation and liver injury in both young and aged mice. Interestingly, enhanced activation of the STING/ TANK‐binding kinase 1 (TBK1) signaling pathway was observed in aged macrophages post‐IR and mitochondria DNA (mtDNA) stimulation. STING suppression blocked over‐activation of NLRP3 signaling and excessive secretion of proinflammatory cytokines/chemokines in the mtDNA‐stimulated BMDMs from aged mice. More importantly, STING knockdown in macrophages abrogated the detrimental role of aging in aggravating liver IR injury and intrahepatic inflammation. Finally, peripheral blood from the recipients undergoing liver transplantation was collected and analyzed. The results showed that the elderly recipients had much higher levels of TNF‐α, IL‐6, IL‐1β, and IL‐18 post‐transplantation, indicating increased NLRP3 activation in lR‐stressed livers of elderly recipients. In summary, our study demonstrated that the STING‐NLRP3 axis was critical for the proinflammatory response of aged macrophages and would be a novel therapeutic target to reduce IR injury in elderly patients.     

The NLRP3 Inflammasome: An Important Driver of Neuroinflammation in Hemorrhagic Stroke

Hemorrhagic stroke is a devastating clinical event with no effective medical treatment. Neuroinflammation, which follows a hemorrhagic stroke, is an important element that involves both acute brain injury and subsequent brain rehabilitation. Therefore, delineating the key inflammatory mediators and deciphering their pathophysiological roles in hemorrhagic strokes is of great importance in the development of novel therapeutic targets for this disease. The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a multi-protein complex that is localized within the cytoplasm. This NOD-like receptor orchestrates innate immune responses to pathogenic organisms and cell stress through the activation of caspase-1 and the maturation of the proinflammatory cytokines such as interleukin-1β (IL-1β) and IL-18. Mounting evidence has demonstrated that when the NLRP3 inflammasome is activated, it exerts harmful effects on brain tissue after a hemorrhagic stroke. This review article summarizes the current knowledge regarding the role and the underlying mechanisms of the NLRP3 inflammasome in the pathophysiological processes of hemorrhagic strokes. A better understanding of the function and regulation of the NLRP3 inflammasome in hemorrhagic strokes will provide clues for devising novel therapeutic strategies to fight this disease.