Downregulation of signal transduction and STAT3 expression exacerbates oxidative stress mediated by NLRP3 inflammasome

High-Density Lipoproteins at the Interface between the NLRP3 Inflammasome and Myocardial Infarction

Despite significant therapeutic advancements, morbidity and mortality following myocardial infarction (MI) remain unacceptably high. This clinical challenge is primarily attributed to two significant factors: delayed reperfusion and the myocardial injury resulting from coronary reperfusion. Following reperfusion, there is a rapid intracellular pH shift, disruption of ionic balance, heightened oxidative stress, increased activity of proteolytic enzymes, initiation of inflammatory responses, and activation of several cell death pathways, encompassing apoptosis, necroptosis, and pyroptosis. The inflammatory cell death or pyroptosis encompasses the activation of the intracellular multiprotein complex known as the NLRP3 inflammasome. High-density lipoproteins (HDL) are endogenous particles whose components can either promote or mitigate the activation of the NLRP3 inflammasome. In this comprehensive review, we explore the role of inflammasome activation in the context of MI and provide a detailed analysis of how HDL can modulate this process.

Leukocyte differential gene expression prognostic value for high versus low seizure frequency in temporal lobe epilepsy

BACKGROUND

This study was performed to test the hypothesis that systemic leukocyte gene expression has prognostic value differentiating low from high seizure frequency refractory temporal lobe epilepsy (TLE).

METHODS

A consecutive series of patients with refractory temporal lobe epilepsy was studied. Based on a median baseline seizure frequency of 2.0 seizures per month, low versus high seizure frequency was defined as ≤ 2 seizures/month and > 2 seizures/month, respectively. Systemic leukocyte gene expression was analyzed for prognostic value for TLE seizure frequency. All differentially expressed genes were analyzed, with Ingenuity® Pathway Analysis (IPA®) and Reactome, to identify leukocyte gene expression and biological pathways with prognostic value for seizure frequency.

RESULTS

There were ten males and six females with a mean age of 39.4 years (range: 16 to 62 years, standard error of mean: 3.6 years). There were five patients in the high and eleven patients in the low seizure frequency cohorts, respectively. Based on a threshold of twofold change (p < 0.001, FC > 2.0, FDR < 0.05) and expression within at least two pathways from both Reactome and Ingenuity® Pathway Analysis (IPA®), 13 differentially expressed leukocyte genes were identified which were all over-expressed in the low when compared to the high seizure frequency groups, including NCF2, HMOX1, RHOB, FCGR2A, PRKCD, RAC2, TLR1, CHP1, TNFRSF1A, IFNGR1, LYN, MYD88, and CASP1. Similar analysis identified four differentially expressed genes which were all over-expressed in the high when compared to the low seizure frequency groups, including AK1, F2R, GNB5, and TYMS.

CONCLUSIONS

Low and high seizure frequency TLE are predicted by the respective upregulation and downregulation of specific leukocyte genes involved in canonical pathways of neuroinflammation, oxidative stress and lipid peroxidation, GABA (γ-aminobutyric acid) inhibition, and AMPA and NMDA receptor signaling. Furthermore, high seizure frequency-TLE is distinguished prognostically from low seizure frequency-TLE by differentially increased specific leukocyte gene expression involved in GABA inhibition and NMDA receptor signaling. High and low seizure frequency patients appear to represent two mechanistically different forms of temporal lobe epilepsy based on leukocyte gene expression.

Role of NLRP3 Inflammasome and Its Inhibitors as Emerging Therapeutic Drug Candidate for Alzheimer's Disease: a Review of Mechanism of Activation, Regulation, and Inhibition

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative disorders. The etiology and pathology of AD are complicated, variable, and yet to be completely discovered. However, the involvement of inflammasomes, particularly the NLRP3 inflammasome, has been emphasized recently. NLRP3 is a critical pattern recognition receptor involved in the expression of immune responses and has been found to play a significant role in the development of various immunological and neurological disorders such as multiple sclerosis, ulcerative colitis, gout, diabetes, and AD. It is a multimeric protein which releases various cytokines and causes caspase-1 activation through the process known as pyroptosis. Increased levels of cytokines (IL-1β and IL-18), caspase-1 activation, and neuropathogenic stimulus lead to the formation of proinflammatory microglial M1. Progressive researches have also shown that besides loss of neurons, the pathophysiology of AD primarily includes amyloid beta (Aβ) accumulation, generation of oxidative stress, and microglial damage leading to activation of NLRP3 inflammasome that eventually leads to neuroinflammation and dementia. It has been suggested in the literature that suppressing the activity of the NLRP3 inflammasome has substantial potential to prevent, manage, and treat Alzheimer's disease. The present review discusses the functional composition, various models, signaling molecules, pathways, and evidence of NLRP3 activation in AD. The manuscript also discusses the synthetic drugs, their clinical status, and projected natural products as a potential therapeutic approach to manage and treat NLRP3 mediated AD.

Different action mechanisms of low- and high-level quercetin in the brains of adult zebrafish (Danio rerio)

Quercetin is reported to be beneficial to or pose hazards to the health of animals, the inconsistence remains to be recognized and debated. This work was conducted to understand the neuroprotective or neurotoxic properties of quercetin, and investigate the different action mechanisms between low- and high-level quercetin. Therefore, we evaluated brain oxidative stress and monoamine neurotransmitters in adult zebrafish (Danio rerio) after exposure to 1 and 1000 μg/L quercetin. In addition, the brain transcriptional profiles were analyzed to identify genes and pathways that were differentially regulated in the brains. The results of oxidative stress and neurotransmitters suggest that low-level quercetin might be beneficial to nervous system, while high-level quercetin might exert detrimental effects. Furthermore, transcriptional profiles also suggested different toxic mechanisms occurred between low- and high-level quercetin. At 1 μg/L quercetin, enrichment analysis of differently expressed genes (DEGs) revealed that the fanconi anemia pathway might be an important mechanism in neuroprotective effects. At 1000 μg/L quercetin, the up-regulated DEGs were enriched in many Gene Ontology (GO) terms related to neuronal synapses, indicating potential neuroprotective effects; however, enrichment of up-regulated DEGs in GO terms of response to stimulus and the MAPK signaling pathway was also found, which indicated increases of stress. Notably, at 1000 μg/L quercetin, the down-regulated DEGs were enriched in several GO terms related to the proteostasis and the proteasome pathway, indicating impairment of proteasome functions which was involved in neurodegenerative diseases. Moreover, several hub genes involved in the pathology of neurodegenerative diseases were identified by Protein-protein interaction analysis at 1000 μg/L quercetin. Thus, high-level quercetin might pose potential risk inducing neurodegenerative diseases, which should receive more attention in the future. Additionally, our findings may provide awareness to society and researchers about toxicity possibilities of phytochemicals on wildlife and human.

Troxerutin regulates HIF-1α by activating JAK2/STAT3 signaling to inhibit oxidative stress, inflammation, and apoptosis of cardiomyocytes induced by H2 O2

Heart failure (HF) is greatly threatening human health and affecting morbidity and mortality worldwide. Troxerutin can alleviate myocardial injury induced by ischemia and hypoxia. The present study aimed to investigate the protective effect of troxerutin on H₂ O₂ -induced cardiomyocytes and the underlying molecular mechanism. Primary mouse cardiomyocytes morphology induced by H₂ O₂ in a different duration time was observed by a microscope. After indicated treatment, the viability and apoptosis of cardiomyocytes were detected by CCK-8 assay and flow cytometry analysis. The expression of inflammatory factors and oxidative stress biomarkers was detected by Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and assay kits. Hypoxia inducible factor-1a (HIF-1α) expression was determined by western blot analysis, RT-qPCR analysis and immunofluorescence staining. The apoptosis-related protein expression and the phosphorylation level of janus-activated kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) were detected by the western blot analysis. As a result, after the H₂ O₂ treatment in a different duration time, the primary mouse cardiomyocytes gradually stopped beating and the morphology of cardiomyocytes treated with H₂ O₂ was changed significantly from fusiform shape to round shape. The viability of cardiomyocytes was decreased after H₂ O₂ induction. The HIF-1α expression was increased after the H₂ O₂ treatment within 30 min while decreased over 30 min. In addition, troxerutin improved viability and suppressed apoptosis, inflammation and oxidative stress of H₂ O₂ -induced cardiomyocytes, which was reversed by KC7F2 (a HIF-1α inhibitor) or CHZ868 (a JAK inhibitor). To sum up, troxerutin could regulate HIF-1α by activating JAK2/STAT3 signaling to inhibit oxidative stress, inflammation, and apoptosis of cardiomyocytes induced by H₂ O₂ .

Activation of NLRP3 Inflammasome and Onset of Alzheimer's Disease

The nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor protein 3 (NLRP3) is an important pattern recognition receptor in human innate immunity. Activation of the NLRP3 inflammasome play a key role in the pathogenesis of Alzheimer’s disease (AD). Theories explaining activation of the NLRP3 inflammasome include the reactive oxygen species theory, the lysosomal damage theory and the mitochondrial DNA theory. The NLRP3 activation promotes occurrence of AD by producing IL-1β, IL-18 and other cytokines, and then by affecting the deposition of Aβ and tau proteins. Over-activated NLRP3 inflammasome often impair cell function and induces immune-related diseases. Some mechanisms have been found to negatively regulate activation of the NLRP3 inflammasome, which may be through receptor binding blocking mechanism, autophagy related mechanism, abnormal cytokine secretion mechanism, or interference related gene expression regulation mechanism. In this review, we summarize the possible mechanisms by which the activation of NLRP3 inflammasomes affects the pathogenesis of AD, and the recent advances in the prevention and treatment of AD by controlling the activation of NLRP3 inflammasomes. By researching the activation or inactivation of NLRP3 inflammasome, it is possible to reveal the pathogenesis of AD from a new perspective and provide a new idea for the prevention and treatment of AD.

miR-204 silencing reduces mitochondrial autophagy and ROS production in a murine AD model via the TRPML1-activated STAT3 pathway

Mitochondrial dysfunction is an early feature of Alzheimer's disease (AD), whereby accumulation of damaged mitochondria in conjunction with impaired mitophagy contributes to neurodegeneration. Various non-transcribed microRNAs (miRNAs) are involved in this process. In the present study, we aimed to decipher the participation of miR-204 in a murine AD model. Primary hippocampal neurons were isolated from mice and treated with β-amyloid 1-42 (Aβ1-42) to establish a cell model of AD. Dichloro-dihydro-fluorescein diacetate and dihydrorhodamine 123 staining assays were performed to measure total reactive oxygen species (ROS) and mitochondrial ROS production in neurons, and MitoSOX staining was done to analyze mitochondrial ROS production in hippocampus. Furthermore, mitochondrial autophagy was observed in hippocampus from amyloid precursor protein/pesenilin-1 AD modeled mice, and their cognitive function was assessed by Morris water maze. Mitochondrial damage, ROS production, and mitochondrial autophagy were observed in AD cell model induced by Aβ1-42. In AD, signal transducer and activator of transcription 3 (STAT3) and transient receptor potential mucolipin-1 (TRPML1) expression was downregulated, although miR-204 expression was upregulated. TRPML1 overexpression, downregulation of miR-204, or STAT3 pathway activation reduced the Aβ1-42-induced mitochondrial damage, along with ROS production and mitochondrial autophagy in vivo and in vitro. Silencing of miR-204 could upregulate TRPML1 expression, thus suppressing ROS production and mitochondrial autophagy in AD through STAT3 pathway.

Down-regulation of STAT3 enhanced chemokine expression and neutrophil recruitment in biliary atresia

Biliary atresia (BA) is an immune-related disorder and signal transducer and activator of transcription 3 (STAT3) is a key signalling molecule in inflammation. The present study was designed to clarify the function of STAT3 in BA. STAT3 expression was examined in patients and a mouse BA model in which STAT3 levels were further altered with a specific inhibitor or activator. Neutrophil accumulation and the levels of the neutrophil chemoattractants (C-X-C motif) ligand 1 (CXCL1) and IL-8 were determined. The effects of STAT3 inhibition on IL-8 expression were examined in human biliary epithelial cell (BEC) cultures. Functional changes in liver STAT3+ neutrophils in the mouse model were analysed with 10× single cell RNA-seq methods. Results showed STAT3 and p-STAT3 expression was reduced in BA liver tissue compared with control samples. Administration of a STAT3 inhibitor increased jaundice and mortality and reduced body weight in BA mice. In contrast, the STAT3 activator ameliorated BA symptoms. Extensive neutrophil accumulation together with CXCL1 up-regulation, both of which were suppressed by an anti-CXCL1 antibody, were observed in the STAT3 inhibitor-treated group. Recombinant IL-8 administration increased disease severity in BA mice, and the STAT3 activator had the reverse effect. Inhibiting STAT3 increased apoptosis of human BECs together with up-regulated IL-8 expression. RNA-seq analysis revealed reduced the numbers of STAT3 expressing neutrophil in BA which was accompanied by marked enhanced interferon-related antiviral activities. In conclusion, STAT3 reduction, enhanced IL-8 and CXCL1 expression and promoted the accumulation of interferon-responsive neutrophils resulting in BEC damage in BA.

Rosuvastatin corrects oxidative stress and inflammation induced by LPS to attenuate cardiac injury by inhibiting the NLRP3/TLR4 pathway

Rosuvastatin has been found to possess antioxidant and anti-inflammatory properties. The aim of the current study was to evaluate whether rosuvastatin was effective in attenuating cardiac injury in lipopolysaccharide (LPS) - challenged mice and H9C2 cells and identify the underlying mechanisms, focusing on the nod-like receptor protein 3 (NLRP3)/toll-like receptor 4 (TLR4) pathway. Cardiac injury, cardiac function, apoptosis, oxidative stress, inflammatory response, and the NLRP3/TLR4 pathway were evaluated in both in vivo and in vitro studies. LPS-induced cardiomyocyte injury was markedly attenuated by rosuvastatin treatment, evidenced by increased cell proliferation of H9C2 cells, rescued cardiac function, and improved morphological changes in mice and reduced lactate dehydrogenase (LDH), creatine kinase MB fraction (CK-MB), and troponin I (cTnI) in serum. Apoptosis was clearly ameliorated in myocardial tissue and H9C2 cells co-treated with rosuvastatin. In addition, after LPS challenge, excessive oxidative stress was present, indicated by increases in malondialdehyde (MDA) content, NADPH activity, and reactive oxygen species (ROS) production and decreased superoxide dismutase (SOD) activity. Rosuvastatin improved all the indicators of oxidative stress, with an effect similar to that of N-acetylcysteine (NAC) (an ROS scavenger). Notably, LPS-exposed H9C2 cells and mice showed significant NLRP3 and TLR4/nuclear factor-κB (NF-κB) pathway activation and inflammatory responses. Administration of rosuvastatin reduced the increases in NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), pro-caspase-1, TLR4, and p65 expression and decreased the tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), IL-18, and IL-6 contents, with an effect similar to that of MCC950 (an NLRP3 inhibitor). In conclusion, inhibition of the inflammatory response and oxidative stress contributes to cardioprotective effect of rosuvastatin against cardiac injury induced by LPS, and the effect of rosuvastatin was achieved through inactivation of the NF-κB/NLRP3 pathway.

Tofacitinib restores the balance of γδTreg/γδT17 cells in rheumatoid arthritis by inhibiting the NLRP3 inflammasome

Objective: Tofacitinib (TOF) is a Janus kinase (JAK) inhibitor used in the treatment of rheumatoid arthritis (RA), but the mechanism of its action remains unclear. In this study, we investigated the influence of TOF on gamma delta regulatory T-cell (γδTreg)/γδT17 cell balance in RA and the role of the nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) inflammasome in this process.

Methods: We detected levels of inflammatory factors in the serum of RA patients before and after administration of TOF using an enzyme-linked immunosorbent assay (ELISA). A collagen-induced arthritis (CIA) model was constructed to investigate the effect of TOF on arthritis symptoms, γδTreg/γδT17 cell balance and the NLRP3 inflammasome. We used bone marrow-derived macrophages (BMDMs) to study the effect of TOF on NLRP3 inflammasome activation. Nlrp3^-/- mice were introduced to assess the influence of NLRP3 on γδT17 cell activation in RA.

Results: TOF treatment decreased levels of γδT17 cell-related cytokine interleukin-17 (IL-17) in RA patients. In addition, TOF intervention in the CIA model reduced joint inflammation and damage, rebalanced the γδTreg/γδT17 cell ratio and inhibited excessive NLRP3 inflammasome activation in draining lymph nodes and arthritic joints. BMDM intervention experiments demonstrated that TOF decreased the level of secreted IL-1β via downregulation of NLRP3. Furthermore, experiments using Nlrp3^-/- mice verified that the NLRP3 inflammasome mediated the effect of TOF on γδT17 cell activation.

Conclusions: Recovery of γδTreg/γδT17 cell balance was a novel mechanism by which TOF alleviated RA. Meanwhile, NLRP3 played a pivotal role in the process of TOF-mediated γδT17 cell activation.

A tumor-intrinsic PD-L1/NLRP3 inflammasome signaling pathway drives resistance to anti-PD-1 immunotherapy

An in-depth understanding of immune escape mechanisms in cancer is likely to lead to innovative advances in immunotherapeutic strategies. However, much remains unknown regarding these mechanisms and how they impact immunotherapy resistance. Using several preclinical tumor models as well as clinical specimens, we identified a mechanism whereby CD8+ T cell activation in response to programmed cell death 1 (PD-1) blockade induced a programmed death ligand 1/NOD-, LRR-, and pyrin domain-containing protein 3 (PD-L1/NLRP3) inflammasome signaling cascade that ultimately led to the recruitment of granulocytic myeloid-derived suppressor cells (PMN-MDSCs) into tumor tissues, thereby dampening the resulting antitumor immune response. The genetic and pharmacologic inhibition of NLRP3 suppressed PMN-MDSC tumor infiltration and significantly augmented the efficacy of anti-PD-1 antibody immunotherapy. This pathway therefore represents a tumor-intrinsic mechanism of adaptive resistance to anti-PD-1 checkpoint inhibitor immunotherapy and is a promising target for future translational research.

Identification of Temporal Characteristic Networks of Peripheral Blood Changes in Alzheimer's Disease Based on Weighted Gene Co-expression Network Analysis

Alzheimer’s disease (AD) is a progressive neurodegenerative disease. The study of blood-based biomarkers has lasted for a long time in AD, because it supports the concept that peripheral changes are involved in AD pathology. But it is still unclear how peripheral blood is involved in the temporal characteristic molecular mechanisms of AD from aging to mild cognitive impairment (MCI) and which cells are responsible for the molecular mechanisms. The main purpose of our study is to gain a systematic and comprehensive understanding of temporal characteristic networks of peripheral blood in AD using whole blood samples with 329 case-control samples, including 104 normal elderly control subjects (CTL), 80 MCI who are susceptible to AD, and 145 AD, by the weighted gene co-expression network analysis (WGCNA). The module-trait relationships were constructed and module preservation was validated with independent datasets GSE63061, GSE97760, GSE18309, GSE29378, GSE28146, and GSE29652. Our results indicate that the down-regulated protein modification and ubiquitin degradation systems, and the up-regulated insulin resistance both play a major role in MCI, while the up-regulated inflammatory cascade dominates in AD, which is mainly mediated by monocytes, macrophages. Although there is mixed activation of M1 and M2 macrophages in all stages of AD, the immune neutral state or M2 polarization may predominate in MCI, and M1 polarization may predominate in AD. Moreover, we found that TRPV2, NDUFV1, ATF4, HSPA8, STAT3 and LUC7L3 may mediate the pathological changes in MCI, while SIRPA, LAMP-2, NDUFB5, HSPA8, STAT3 and FPR2 may mediate the conversion from MCI-AD or the pathological changes in AD, which provide a basis for the treatment based on the peripheral blood system. In addition, we also found that the combined diagnosis based on a panel of genes from the red, blue, and brown modules have a moderate diagnostic effect on distinguishing MCI and AD from CTL, suggesting that those panels of genes may be used for detection of MCI and prediction of this conversion from MCI to AD. Our research emphasizes that pathological changes, based on temporal characteristics of peripheral blood, provide a theoretical basis for targeted peripheral treatment based on appropriate times and identified several diagnostic markers.