Genetic variant in 3' untranslated region of the mouse pycard gene regulates inflammasome activity

Quantitative trait locus mapping for interleukin-1β release after inflammasome priming and activation was performed on bone-marrow-derived macrophages (BMDM) from an AKRxDBA/2 mouse strain intercross. The strongest associated locus mapped very close to the Pycard gene on chromosome 7, which codes for the inflammasome adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC). The DBA/2 and AKR Pycard genes only differ at a single-nucleotide polymorphism (SNP) in their 3' untranslated region (UTR). DBA/2 vs. AKR BMDM had increased levels of Pycard mRNA expression and ASC protein, and increased inflammasome speck formation, which was associated with increased Pycard mRNA stability without an increased transcription rate. CRISPR/Cas9 gene editing was performed on DBA/2 embryonic stem cells to change the Pycard 3'UTR SNP from the DBA/2 to the AKR allele. This single base change significantly reduced Pycard expression and inflammasome activity after cells were differentiated into macrophages due to reduced Pycard mRNA stability.

Differential Expression of Inflammasome-Related Genes in Induced Pluripotent Stem-Cell-Derived Retinal Pigment Epithelial Cells with or without History of Age-Related Macular Degeneration

Inflammation is a key underlying factor of age-related macular degeneration (AMD) and inflammasome activation has been linked to disease development. Induced pluripotent stem-cell-derived retinal pigment epithelial cells (iPSC-RPE) are an attractive novel model system that can help to further elucidate disease pathways of this complex disease. Here, we analyzed the effect of dysfunctional protein clearance on inflammation and inflammasome activation in iPSC-RPE cells generated from a patient suffering from age-related macular degeneration (AMD) and an age-matched control. We primed iPSC-RPE cells with IL-1α and then inhibited both proteasomal degradation and autophagic clearance using MG-132 and bafilomycin A1, respectively, causing inflammasome activation. Subsequently, we determined cell viability, analyzed the expression levels of inflammasome-related genes using a PCR array, and measured the levels of pro-inflammatory cytokines IL-1β, IL-6, IL-8, and MCP-1 secreted into the medium. Cell treatments modified the expression of 48 inflammasome-related genes and increased the secretion of mature IL-1β, while reducing the levels of IL-6 and MCP-1. Interestingly, iPSC-RPE from an AMD donor secreted more IL-1β and expressed more Hsp90 prior to the inhibition of protein clearance, while MCP-1 and IL-6 were reduced at both protein and mRNA levels. Overall, our results suggest that cellular clearance mechanisms might already be dysfunctional, and the inflammasome activated, in cells with a disease origin.

Inflammasome genes polymorphisms may influence the development of hepatitis C in the Amazonas, Brazil

Hepatitis C is considered a major public health problem caused by the hepatitis C virus (HCV). Viral infections are known to induce production of IL1β through the signaling pathway of inflammasomes. Emerging evidences suggest that Inflammasome genes may influence the immune response against HCV as the host genetic background may contribute to the balance between acute and chronic inflammation. We investigated in 151 patients with chronic hepatitis C and 206 healthy blood donors’ individuals (HD). Polymorphisms in the IL1B and IL18 genes were genotyped by PCR-RFLP, while NLRP3, CARD8, CTSB and AIM2 by RT- PCR. Serum assay of IL-1β cytokine was performed by ELISA. 84 patients presented mild fibrosis (<F2) and 67 advanced fibrosis (≥ F2). Among the HD individuals the NLRP3-rs10754558 C/C genotype correlated with higher IL-1β levels compared to the G/G genotype. Similar pattern was observed in patients with hepatitis C, mean circulating IL-1β levels were 21,96 ± 4.5 and 10,62 ± 3.3pg/mL among the C/C and G/G genotypes, respectively. This pattern holds even after stratification of the patients into mild fibrosis and advanced fibrosis, demonstrating that the NLRP3-rs10754558 or another polymorphism in linkage disequilibrium with it possibly has an influence on the processing of pro-IL-1β. Notably, higher levels of IL-1β (Mann–Whitney test, p<0.0001) were observed among patients (mean ± SEM: 19,24 ±3.pg/mL) when compared with controls (mean ± SEM: 11,80 ±1.0pg/mL). Gene-gene interaction showed that individuals heterogyzotes for both CARD8-rs2009373 and IL1B-rs16944 are less prone to hepatitis C development (p_adj = 0.039). Similarly, herozygote carriers for CTSB-rs1692816 and AIM2-rs1103577 (p_adj = 0.008) or for IL18-rs187238 and NLRP3-rs10754558 (p_adj = 0.005), have less chances to the development of hepatitis C. However, between subgroups of <F2 and ≥F2, individuals homozygous for the T allele of CARD8-rs2009373 and heterozygous for IL18-rs187238 (p_adj = 0.028), have mild form of fibrosis.

Microglial NLRP3 inflammasome activation-mediated inflammation promotes prolactinoma development

Prolactinomas have harmful effects on human health, and the pathogenesis is still unknown. Furthermore, 25% of prolactinoma patients do not respond to the therapy of dopamine receptor agonist in the clinic. Thus, it is important to reveal the pathogenesis and develop new therapeutic methods for prolactinomas. Herein, two animal models of prolactinomas, namely oestrogen-treated rats and transgenic D2 dopamine receptor-deficient mice, were used. PET/CT imaging detection showed that translocator protein-mediated microglia activation and inflammation significantly increased in the pituitary glands of prolactinomas rats. Messenger RNA microarrays were used to analyze and compare the differential gene and signal pathways of the pituitary glands between control and prolactinomas rats. Statistical results pertaining to gene enrichment showed that the innate immune response genes were upregulated in the pituitary glands of prolactinoma rats. This suggested that the innate immune response was activated. We analyzed the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome that is one of the most important members of the innate immune system in mammals and found that the expressions of NLRP3, Caspase-1, apoptosis-associated speck-like, interleukin 1B (IL1B) and IL18 proteins of pituitary glands in prolactinomas rats were increased considerably compared with those in control rats. This suggested the activation of the NLRP3 inflammasome during the emergence and evolution of prolactinomas. Immunohistochemistry results also confirmed that the NLRP3 expression was elevated in human prolactinoma tissues, and the microglia marker-ionised calcium binding adaptor molecule-1 was co-located with the NLRP3 protein in prolactinomas by immunofluorescence assay. Finally, compared with the WT mice, NLRP3-/- mice had smaller pituitary glands (weight/body weight) and diminished prolactin (PRL) expressions and secretions. These findings were associated with a reduction in the caspase-1 activation and maturation of IL1B. Furthermore, MCC950 decreased the PRL expression and secretion following the inhibition of NLRP3 inflammasome activation in GH3 cells stimulated with lipopolysaccharide and nigericin. And MCC950 inhibited the pituitary tumor overgrowth and PRL expression and secretion in prolactinoma rats. These data confirm that the microglial NLRP3 inflammasome activation upregulates the inflammatory cytokines IL1/IL18 in the pituitary glands and induces prolactinomas. Our findings showed that microglial NLRP3 inflammasome activation-mediated IL1B-related inflammation promoted the development of prolactinomas and identified the inflammasome as a new therapeutic target for prolactinomas.

N-acetylcysteine alleviates ocular surface damage in STZ-induced diabetic mice by inhibiting the ROS/NLRP3/Caspase-1/IL-1β signaling pathway

Diabetes mellitus (DM) induces damage to the ocular surface, which leads to vision decline. In the current study, we investigated whether N-acetylcysteine (NAC) plays a protective role in diabetes-induced ocular surface damage. The diabetic mice model was treated with 0.3% NAC topically. Corneal epithelial integrity, tear volume and corneal sensitivity were examined by sodium fluorescein staining, phenol red cotton thread and esthesiometer respectively. The level of reactive oxygen species (ROS) was measured with 2',7-dichlorofluorescein diacetate. The expression of NLRP3, IL-1β and caspase-1 were evaluated by RT-PCR, western blot and immunostaining. The level of SOD1 was assessed by RT-PCR. We found that the expression of NLRP3, IL-1β and caspase-1 were elevated in diabetic cornea and conjunctiva. Treatment with NAC improved corneal epithelial integrity, increased tear production and corneal sensitivity in diabetic mice. Moreover, NAC markedly attenuated ROS accumulation and decreased NLRP3, IL-1β and caspase-1 levels in diabetic cornea and conjunctiva. These results suggest that NAC improves ocular surface damage in STZ-induced diabetic mice, which may be related to the inhibition of the ROS/NLRP3/Caspase-1/IL-1β signaling pathway.

The PKM2 activator TEPP-46 attenuates MCD feeding-induced nonalcoholic steatohepatitis by inhibiting the activation of Kupffer cells

OBJECTIVE

The present study aimed to investigate the effect and molecular mechanism of the PKM2 small molecule agonist TEPP-46 on the development of methionine choline-deficient (MCD) diet-induced nonalcoholic steatohepatitis (NASH) in mice.

MATERIALS AND METHODS

In this study, C57BL/6 mice were fed an MCD diet for 15 days to establish a NASH model. The protein expression levels of pyruvate kinase M2 (PKM2), PKM1, hypoxia-inducible factor-1α (HIF-1α) and NLRP3 in liver Kupffer cells (KCs) were measured by Western blotting. Immunofluorescence analysis was used to analyze the nuclear translocation of PKM2 in KCs, and the levels of IL-1β and TNF-α in mouse serum and the cell polarization indexes were determined. The MCD diet-fed mice were injected with 30 mg/kg of TEPP-46 intraperitoneally every 5 days. After 15 days, the liver tissue and peripheral blood were collected for analysis.

RESULTS

We found the NASH model was successfully established after the mice were fed an MCD diet for 15 days. MCD feeding promoted the expression of the PKM2 monomer/dimer and inhibited the expression of the PKM2 tetramer in KCs. Immunofluorescence analysis further confirmed that MCD feeding inhibited the nuclear translocation of PKM2. Besides, MCD feeding promoted the expression of HIF-1α and NLRP3 in KCs, promoted M1 KCs polarization and inhibited M2 KCs polarization. Intraperitoneal injection 30 mg/kg of TEPP-46 significantly inhibited the development of MCD diet-induced NASH, alleviated the pathological changes in the liver, improved liver function, promoted the expression of the PKM2 tetramer in KCs, and inhibited the expression of HIF-1α and NLRP3.

CONCLUSIONS

This study demonstrated that TEPP-46, a small molecule agonist of PKM2, may inhibit the nuclear translocation of PKM2 and the activation of KCs by promoting the expression of PKM2 tetramers in KCs, thus inhibiting the development of MCD diet-induced NASH in mice.

NLRP3 is involved in long bone edification and the maturation of osteogenic cells

Overexpression of the nucleotide-binding leucine-rich repeat protein 3 (NLRP3) inflammasome in chronic auto-immune diseases leads to skeletal anomalies, with severe osteopenia due to the activation of osteoclasts. Reproducing this phenotype in Nlrp3 knock-in mice has provided insights into the role of NLRP3 in bone metabolism. We studied the role of NLRP3 in physiological bone development using a complete Nlrp3 knock-out mouse model. We found impaired skeletal development in Nlrp3-/- mice, resulting in a shorter stature than that of Nlrp3+/+  mice. These growth defects were associated with altered femur bone growth, characterized by a deficient growth plate and an osteopenic profile of the trabeculae. No differences in osteoclast recruitment or activity were observed. Instead, Nlrp3-/- femurs showed a less mineralized matrix in the trabeculae than those of Nlrp3+/+  mice, as well as less bone sialoprotein (BSP) expressing hypertrophic chondrocytes. In vitro, primary osteoblasts lacking NLRP3 expression showed defective mineralization, together with the downregulation of BSP expression. Finally, follow-up by micro-CT highlighted the role of NLPR3 in bone growth, occurring early in living mice, as the osteopenic phenotype diminishes over time. Overall, our data suggest that NLRP3 is involved in bone edification via the regulation of hypertrophic chondrocyte maturation and osteoblast activity. Furthermore, the defect appeared to be transitory, as the skeleton recovered with aging.

Simvastatin mitigates depressive-like behavior in ovariectomized rats: Possible role of NLRP3 inflammasome and estrogen receptors' modulation

It is well known that females are more vulnerable than males to stress-related psychiatric disorders, particularly during perimenopausal and postmenopausal periods. Hormone replacement therapy (HRT) has been widely used for the management of postmenopausal depression. However, HRT could be associated with severe adverse effects, including increased risk for coronary heart disease, breast cancer and endometrial cancer. Thus, there is a pressing demand for novel therapeutic options for postmenopausal depression without sacrificing uterine health. Simvastatin (SIM) was proven to have neuroprotective activities besides its hypocholesterolemic effect, the former can be attributed to its, antioxidant, anti-apoptotic and anti-inflammatory activities. Moreover, many reports highlighted that SIM has estrogenic activity and was able to induce the expression of estrogen receptors in rats. The present study showed that SIM (20 mg/kg, p.o.) markedly attenuated depressive-like behavior in ovariectomized (OVX) rats. Moreover, SIM prohibited hippocampal microglial activation, abrogated P2X7 receptor, TLR2 and TLR4 expression, inhibited NLRP3 inflammasome activation, with subsequent reduction in the levels of pro-inflammatory mediators; IL-1β and IL-18. Furthermore, a marked elevation in hippocampal expression of ERα and ERβ was noted in SIM-treated animals, without any significant effect on uterine relative weight or ERα expression. Taken together, SIM could provide a safer alternative for HRT for the management of postmenopausal depression, without any hyperplastic effect on the uterus.

COVID-19 Severity Potentially Modulated by Cardiovascular-Disease-Associated Immune Dysregulation

Patients with underlying cardiovascular conditions are particularly vulnerable to severe COVID-19. In this project, we aimed to characterize similarities in dysregulated immune pathways between COVID-19 patients and patients with cardiomyopathy, venous thromboembolism (VTE), or coronary artery disease (CAD). We hypothesized that these similarly dysregulated pathways may be critical to how cardiovascular diseases (CVDs) exacerbate COVID-19. To evaluate immune dysregulation in different diseases, we used four separate datasets, including RNA-sequencing data from human left ventricular cardiac muscle samples of patients with dilated or ischemic cardiomyopathy and healthy controls; RNA-sequencing data of whole blood samples from patients with single or recurrent event VTE and healthy controls; RNA-sequencing data of human peripheral blood mononuclear cells (PBMCs) from patients with and without obstructive CAD; and RNA-sequencing data of platelets from COVID-19 subjects and healthy controls. We found similar immune dysregulation profiles between patients with CVDs and COVID-19 patients. Interestingly, cardiomyopathy patients display the most similar immune landscape to COVID-19 patients. Additionally, COVID-19 patients experience greater upregulation of cytokine- and inflammasome-related genes than patients with CVDs. In all, patients with CVDs have a significant overlap of cytokine- and inflammasome-related gene expression profiles with that of COVID-19 patients, possibly explaining their greater vulnerability to severe COVID-19.

Perfluoroalkyl substance pollutants activate the innate immune system through the AIM2 inflammasome

Perfluoroalkyl substances (PFAS) are widely used in various manufacturing processes. Accumulation of these chemicals has adverse effects on human health, including inflammation in multiple organs, yet how PFAS are sensed by host cells, and how tissue inflammation eventually incurs, is still unclear. Here, we show that the double-stranded DNA receptor AIM2 is able to recognize perfluorooctane sulfonate (PFOS), a common form of PFAS, to trigger IL-1β secretion and pyroptosis. Mechanistically, PFOS activates the AIM2 inflammasome in a process involving mitochondrial DNA release through the Ca2+-PKC-NF-κB/JNK-BAX/BAK axis. Accordingly, Aim2-/- mice have reduced PFOS-induced inflammation, as well as tissue damage in the lungs, livers, and kidneys in both their basic condition and in an asthmatic exacerbation model. Our results thus suggest a function of AIM2 in PFOS-mediated tissue inflammation, and identify AIM2 as a major pattern recognition receptor in response to the environmental organic pollutants.

Metal-induced delayed type hypersensitivity responses potentiate particle induced osteolysis in a sex and age dependent manner

It is widely recognized that innate macrophage immune reactions to implant debris are central to the inflammatory responses that drive biologic implant failure over the long term. Less common, adaptive lymphocyte immune reactions to implant debris, such as delayed type hypersensitivity (DTH), can also affect implant performance. It is unknown which key patient factors, if any, mediate these adaptive immune responses that potentiate particle/macrophage mediated osteolysis. The objective of this investigation was to determine to what degree known adaptive immune responses to metal implant debris can affect particle-induced osteolysis (PIO); and if this pathomechanism is dependent on: 1) innate immune danger signaling, i.e., NLRP3 inflammasome activity, 2) sex, and/or 3) age. We used an established murine calvaria model of PIO using male and female wild-type C57BL/6 vs. Caspase-1 deficient mice as well as young (12–16 weeks old) vs. aged (18–24 months old) female and male C57BL/6 mice. After induction of metal-DTH, and Cobalt-alloy particle (ASTM F-75, 0.4um median diameter) calvaria challenge, bone resorption was assessed using quantitative micro-computed tomography (micro-CT) analysis and immune responses were assessed by measuring paw inflammation, lymphocyte transformation test (LTT) reactivity and adaptive immune cytokines IFN-gamma and IL-17 (ELISA). Younger aged C57BL/6 female mice exhibited the highest rate and severity of metal sensitivity lymphocyte responses that also translated into higher PIO compared to any other experimental group. The absence of inflammasome/caspase-1 activity significantly suppressed DTH metal-reactivity and osteolysis in both male and female Caspase-1 deficient mice. These murine model results indicate that young female mice are more predisposed to metal-DTH augmented inflammatory responses to wear debris, which is highly influenced by active NLRP3 inflammasome/caspase-1 danger signaling. If these results are clinically meaningful for orthopedic patients, then younger female individuals should be appropriately assessed and followed for DTH derived peri-implant complications.

YAP promotes the activation of NLRP3 inflammasome via blocking K27-linked polyubiquitination of NLRP3

The transcription coactivator YAP plays a vital role in Hippo pathway for organ-size control and tissue homeostasis. Recent studies have demonstrated YAP is closely related to immune disorders and inflammatory diseases, but the underlying mechanisms remain less defined. Here, we find that YAP promotes the activation of NLRP3 inflammasome, an intracellular multi-protein complex that orchestrates host immune responses to infections or sterile injuries. YAP deficiency in myeloid cells significantly attenuates LPS-induced systemic inflammation and monosodium urate (MSU) crystals-induced peritonitis. Mechanistically, YAP physically interacts with NLRP3 and maintains the stability of NLRP3 through blocking the association between NLRP3 and the E3 ligase β-TrCP1, the latter increases the proteasomal degradation of NLRP3 via K27-linked ubiquitination at lys380. Together, these findings establish a role of YAP in the activation of NLRP3 inflammasome, and provide potential therapeutic target to treat the NLRP3 inflammasome-related diseases.

Genetic polymorphisms of inflammasome genes associated with pediatric acute lymphoblastic leukemia and clinical prognosis in the Brazilian Amazon

The immune system plays an important role in the control of cancer development. To investigate the possible association of inflammasome genes to childhood leukemia we performed a case-control study with 158 patients with acute lymphoblastic leukemia and 192 healthy individuals. The IL1B and IL18 genetic polymorphisms were genotyped by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) and NLRP1, NLRP3 and P2RX7 were genotyped using Real Time quantitative PCR (qPCR). The IL1B C/T rs19644 genotype was associated with the risk of developing ALL (C/C vs. C/T + T/T OR: 2.48 [95% CI: 1.26-4.88, p = 0.006]; C/C vs C/T OR: 2.74 [95% CI: 1.37-5.51, p = 0.003]) and the NLRP1 A/T rs12150220 (OR: 0.37 [95% CI: 0.16-0.87, p = 0.023]) was associated with protection against infectious comorbidities. It was not found association between NLRP3 and P2RX7 polymorphisms and acute lymphoblastic leukemia in our study. Our results suggest that the inflammasome single-variant polymorphisms (SNVs) may play a role in the development and prognostic of childhood leukemia. However, this finds requires further study within a larger population in order to prove it.

The AIM2 and NLRP3 inflammasomes trigger IL-1-mediated antitumor effects during radiation

The inflammasome promotes inflammation-associated diseases, including cancer, and contributes to the radiation-induced tissue damage. However, the role of inflammasome in radiation-induced antitumor effects is unclear. We observed that tumors transplanted in Casp1-/- mice were resistant to radiation treatment compared with tumors in wild-type (WT) mice. To map out which molecule in the inflammasome pathway contributed to this resistant, we investigated the antitumor effect of radiation in several inflammasome-deficient mice. Tumors grown in either Aim2-/- or Nlrp3-/- mice remained sensitive to radiation, like WT mice, whereas Aim2-/-Nlrp3-/- mice showed radioresistance. Mechanistically, extracellular vesicles (EVs) and EV-free supernatant derived from irradiated tumors activated both Aim2 and Nlrp3 inflammasomes in macrophages, leading to the production of interleukin-1β (IL-1β). IL-1β treatment helped overcome the radioresistance of tumors growing in Casp1-/- and Aim2-/-Nlrp3-/- mice. IL-1 signaling in dendritic cells (DCs) promoted radiation-induced antitumor immunity by enhancing the cross-priming activity of DCs. Overall, we demonstrated that radiation-induced activation of the AIM2 and NLRP3 inflammasomes coordinate to induce some of the antitumor effects of radiation by triggering IL-1 signaling in DCs, leading to their activation and cross-priming.

Genetically determined NLRP3 inflammasome activation associates with systemic inflammation and cardiovascular mortality

AIMS

Inflammation plays an important role in cardiovascular disease (CVD) development. The NOD-like receptor protein-3 (NLRP3) inflammasome contributes to the development of atherosclerosis in animal models. Components of the NLRP3 inflammasome pathway such as interleukin-1β can therapeutically be targeted. Associations of genetically determined inflammasome-mediated systemic inflammation with CVD and mortality in humans are unknown.

METHODS AND RESULTS

We explored the association of genetic NLRP3 variants with prevalent CVD and cardiovascular mortality in 538 167 subjects on the individual participant level in an explorative gene-centric approach without performing multiple testing. Functional relevance of single-nucleotide polymorphisms on NLRP3 inflammasome activation has been evaluated in monocyte-enriched peripheral blood mononuclear cells (PBMCs). Genetic analyses identified the highly prevalent (minor allele frequency 39.9%) intronic NLRP3 variant rs10754555 to affect NLRP3 gene expression. rs10754555 carriers showed significantly higher C-reactive protein and serum amyloid A plasma levels. Carriers of the G allele showed higher NLRP3 inflammasome activation in isolated human PBMCs. In carriers of the rs10754555 variant, the prevalence of coronary artery disease was significantly higher as compared to non-carriers with a significant interaction between rs10754555 and age. Importantly, rs10754555 carriers had significantly higher risk for cardiovascular mortality during follow-up. Inflammasome inducers (e.g. urate, triglycerides, apolipoprotein C3) modulated the association between rs10754555 and mortality.

CONCLUSION

The NLRP3 intronic variant rs10754555 is associated with increased systemic inflammation, inflammasome activation, prevalent coronary artery disease, and mortality. This study provides evidence for a substantial role of genetically driven systemic inflammation in CVD and highlights the NLRP3 inflammasome as a therapeutic target.

Heme Oxygenase-1 in Macrophages Impairs the Perfusion Recovery After Hindlimb Ischemia by Suppressing Autolysosome-Dependent Degradation of NLRP3

[Figure: see text].

AIM2 controls microglial inflammation to prevent experimental autoimmune encephalomyelitis

The role of the PYHIN family member absent in melanoma 2 (AIM2), another important inflammasome sensor, in EAE remains unclear. In this study, we found that AIM2 negatively regulates the pathogenesis of EAE independent of inflammasome activation. AIM2 deficiency enhanced microglia activation and infiltration of peripheral immune cells into the CNS, thereby promoting neuroinflammation and demyelination during EAE. Mechanistically, AIM2 negatively regulates the DNA-PK-AKT3 in microglia to control neuroinflammation synergistically induced by cGAS and DNA-PK. Administration of a DNA-PK inhibitor reduced the severity of the EAE. Collectively, these findings identify a new role for AIM2 in controlling the onset of EAE. Furthermore, delineation of the underlying inflammasome-independent mechanism highlights cGAS and DNA-PK signaling as potential targets for the treatment of heterogeneous MS.

Vincristine-induced peripheral neuropathy is driven by canonical NLRP3 activation and IL-1β release

Vincristine is an important component of many regimens used for pediatric and adult malignancies, but it causes a dose-limiting sensorimotor neuropathy for which there is no effective treatment. This study aimed to delineate the neuro-inflammatory mechanisms contributing to the development of mechanical allodynia and gait disturbances in a murine model of vincristine-induced neuropathy, as well as to identify novel treatment approaches. Here, we show that vincristine-induced peripheral neuropathy is driven by activation of the NLRP3 inflammasome and subsequent release of interleukin-1β from macrophages, with mechanical allodynia and gait disturbances significantly reduced in knockout mice lacking NLRP3 signaling pathway components, or after treatment with the NLRP3 inhibitor MCC950. Moreover, treatment with the IL-1 receptor antagonist anakinra prevented the development of vincristine-induced neuropathy without adversely affecting chemotherapy efficacy or tumor progression in patient-derived medulloblastoma xenograph models. These results detail the neuro-inflammatory mechanisms leading to vincristine-induced peripheral neuropathy and suggest that repurposing anakinra may be an effective co-treatment strategy to prevent vincristine-induced peripheral neuropathy.

Loss of Camk2n1 aggravates cardiac remodeling and malignant ventricular arrhythmia after myocardial infarction in mice via NLRP3 inflammasome activation

AIMS

Inflammation response and subsequent ventricular remodeling are critically involved in the development of ventricular arrhythmia post myocardial infarction (MI). However, as the vital endogenous inhibitor of calcium/calmodulin-dependent protein kinase II (CaMKII), the effects of CaMKII inhibitor 1 (Camk2n1) on the process of arrhythmia substrate generation following MI remains unclear. In this study, we investigated the role of Camk2n1 in ventricular arrhythmia post-MI and the underlying mechanisms.

METHODS AND RESULTS

Camk2n1 was mainly expressed in cardiomyocytes and inhibited the phosphorylation of CaMKIIδ in the infarcted border zone. Compared to wild type (WT) littermates mice, Camk2n1 knockout mice (Camk2n1^-/-) manifested exacerbated cardiac dysfunction, larger fibrosis area, higher incidence of premature ventricular contractions (PVCs) and higher vulnerability to ventricular tachycardia (VT) or ventricular fibrillation (VF) after MI. The results of RNA sequencing (RNA-seq) identified that excessive activation of NLRP3 inflammasome was responsible for aggravated inflammation response which led to adverse cardiac remodeling in Camk2n1^-/- mice subjected to MI. More importantly, both in vivo and in vitro experiments verified that aggravated NLRP3 inflammasome activation occurred via CaMKIIδ-p38/JNK pathway in Camk2n1^-/- mice.

CONCLUSIONS

Collectively, our results highlight the importance of Camk2n1 in alleviating ventricular remodeling and malignant ventricular arrhythmia post-MI by reducing cardiomyocytes inflammation activation via CaMKIIδ-p38/JNK-NLRP3 inflammasome pathway, targeting Camk2n1 might serve as a novel therapeutic strategy after MI.

PINK1 Inhibits Multimeric Aggregation and Signaling of MAVS and MAVS-Dependent Lung Pathology

Mitochondria have emerged as important signaling organelles where intracellular perturbations are integrated and, consequently, intracellular signaling pathways are modulated to execute appropriate cellular functions. MAVS (mitochondrial antiviral signaling protein) represents such an example that functions as a platform molecule to mediate mitochondrial innate immune signaling. Recently, multimeric aggregation of MAVS has been identified as a key molecular process for its signaling. The underlying mechanisms to regulate this, however, are still incompletely understood. We hypothesized that PINK1 (PTEN-induced kinase 1) plays an important role in the regulation of multimeric MAVS aggregation and its consequent pathobiology. To test whether PINK1 interacts with MAVS, bimolecular fluorescence complementation analysis and IP were performed. RLH (RIG-I-like helicase) and NLRP3 inflammasome signaling were evaluated by in vitro assay. In vivo functional significance of PINK1 in the regulation of MAVS signaling was evaluated from both murine modeling of influenza viral infection and bleomycin-induced experimental pulmonary fibrosis, wherein MAVS plays important roles. Multimeric MAVS aggregation was induced by mitochondria dysfunction, and, during this event, the stabilized PINK1 interacted physically with MAVS and antagonized multimeric MAVS aggregation. Accordingly, the MAVS-mediated antiviral innate immune and NLRP3 inflammasome signaling were enhanced in PINK1 deficiency. In addition, in vivo studies revealed that MAVS-mediated pulmonary antiviral innate immune responses and fibrotic responses after bleomycin injury were enhanced in PINK1 deficiency. In conclusion, these results establish a new role of PINK1 in the regulation of MAVS signaling and the consequent pulmonary pathobiology.

Stk24 protects against obesity-associated metabolic disorders by disrupting the NLRP3 inflammasome

Adipose tissue macrophages (ATMs) regulate the occurrence of obesity and its related diseases. Here, we found that serine/threonine protein kinase 24 (Stk24) expression is downregulated significantly in ATMs in obese subjects or obese subjects with type 2 diabetes and mice fed a high-fat diet (HFD). We further identified that glucolipotoxicity downregulated Stk24 expression in ATMs. Stk24-deficient mice develop severe HFD-induced metabolic disorders and insulin insensitivity. Mechanistically, Stk24 intervenes in NLRP3 inflammasome assembly in ATMs by associating directly with NLRP3, decreasing interleukin-1β (IL-1β) secretion. Accordingly, Stk24 deficiency in the hematopoietic system promotes NLRP3 inflammasome activation, which contributes to exacerbation of metabolic disorders. Intriguingly, Stk24 expression correlates negatively with body mass index (BMI) and the levels of glucose, cholesterol, triglycerides, and low-density lipoprotein in human subjects. These findings provide insights into the function and clinical implications of Stk24 in obesity-mediated metabolic disorders.

[Cathepsin-B involved in effect of electroacupuncture by inhibiting the activation of NLRP3 inflammasome in rats with acute gouty arthritis]

OBJECTIVE

To observe the effect of electroacupuncture (EA) on Cathepsin-B in the synovium of the knee joint of acute gouty arthritis(AGA) rats, so as to explore the mechanism of EA in the treatment of AGA.

METHODS

A total of 60 male Wistar rats were randomly divided into normal control,model, medication and EA groups, with 15 rats in each group. Rat model of AGA was established by injection of 0.2 mL sodium urate crystal suspension into the left knee joint cavity. The rats in the medication group were treated with colchicine by gavage(0.3 mg·kg^-1·d^-1), and the rats in the EA group were treated with EA at the left "Sanyinjiao" (SP6) and "Zusanli"(ST36) for 10 min each time, once a day for a week. The Coderre gait grading standard was used to score the gait of rats. The pathological morphology of synovial tissue of the left knee joint was observed by H.E. staining. The expression levels of Cathepsin-B protein and Nod-like receptor pyrin domain 3(NLRP3), apoptosis-associated speck-like protein containing CARD (ASC),Caspase-1, interleukin-1β(IL-1β) and IL-18 mRNAs were detected by Western blot and real-time fluorescence quantitative PCR, respectively.

RESULTS

Compared with the normal control group, the degree of synovitis infiltration in the model group was more serious. And the gait score，the protein expression level of Cathepsin-B and the mRNA expression levels of NLRP3,ASC,Caspase-1, IL-1β,IL-18 were significantly increased (P<0.01).After the interventions, the degree of inflammatory infiltration was mild, The gait score, the protein expression level of Cathepsin-B and the mRNA expression levels of NLRP3 and ASC,Caspase-1，IL-1β,IL-18 were significantly decreased in both medication and EA groups in contrast to the model group (P<0.01, P<0.05). Compared with medication group, the mRNA expression levels of Caspase-1 and IL-18 in the EA group were increased (P<0.05).

CONCLUSION

EA may inhibit the activation of NLRP3 inflammasome by reducing the activity of Cathepsin-B in the synovium of the knee joint, so as to treat AGA.

Immunomodulatory Effect of Curcumin in the Upregulation of Inflammasome Pathway Genes Induced by Sulfur Mustard Analog: An In-vitro Study

Sulfur Mustard (SM) induces cell injury via exerting oxidative stress, protease-anti protease imbalance, and inflammation. Inflammasome as one part of innate immunity has a critical role in the recognition of cell injuries and the initiation of the inflammation process by releasing IL-1β. Hence, the present study investigated the effects of the sub-lethal doses of 2-chloroethyl ethyl sulfide (CEES) as SM analog on the gene expression level of inflammasome-related genes as well as the potential protective effects of curcumin on this process. The effects of sub-lethal doses (500, 1000, and 2500 mM) of CEES on pulmonary epithelial cell line (A549) were determined at various time points (12, 24, and 48 h). Following the treatment of cells with CEES, the kinetic alterations of the expression levels of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB1), NLR family pyrin domain containing 1 (NLRP1), Caspase-1 (Casp1), and Interleukin-1β (IL-1β)  genes were analyzed; using real-time PCR. In addition, the concurrent protective effects of different doses of curcumin (20, 40, 80, and 160 mM) on modulating the effects of CEES were studied. Although it was found that the lowest sub-lethal dose of CEES (500 mM) was able to up-regulate the inflammasome-related genes, the maximum alterations occurred 48 h after the treatment with the higher sub-lethal dose (2500 mM) of CEES. The maximum alteration occurred in Casp1 (38 fold), IL-1β (19 fold), and NLRP1 (~4 fold) genes (p<0.0001). However, the NF-ĸB gene expression level did not alter following CEES exposure. Even though low doses of curcumin (20, 40, and 80 mM) were able to down-regulate the studied genes, it was found that the treatment of cells with 160 mM of curcumin for 48 h was able to normalize the expression level of all genes. The present study concludes that curcumin as an anti-inflammatory agent may have beneficial immunomodulatory effects following CEES exposure.

Gasdermin E permits interleukin-1 beta release in distinct sublytic and pyroptotic phases

Cellular inflammasome activation causes caspase-1 cleavage of the pore-forming protein gasdermin D (GSDMD) with subsequent pyroptotic cell death and cytokine release. Here, we clarify the ambiguous role of the related family member gasdermin E (GSDME) in this process. Inflammasome stimulation in GSDMD-deficient cells led to apoptotic caspase cleavage of GSDME. Endogenous GSDME activation permitted sublytic, continuous interleukin-1β (IL-1β) release and membrane leakage, even in GSDMD-sufficient cells, whereas ectopic expression led to pyroptosis with GSDME oligomerization and complete liberation of IL-1β akin to GSDMD pyroptosis. We find that NLRP3 and NLRP1 inflammasomes ultimately rely concurrently on both gasdermins for IL-1β processing and release separately from their ability to induce cell lysis. Our study thus identifies GSDME as a conduit for IL-1β release independent of its ability to cause cell death.

NLRP3 inflammasome-mediated cytokine production and pyroptosis cell death in breast cancer

Breast cancer is the most diagnosed malignancy in women. Increasing evidence has highlighted the importance of chronic inflammation at the local and/or systemic level in breast cancer pathobiology, influencing its progression, metastatic potential and therapeutic outcome by altering the tumor immune microenvironment. These processes are mediated by a variety of cytokines, chemokines and growth factors that exert their biological functions either locally or distantly. Inflammasomes are protein signaling complexes that form in response to damage- and pathogen-associated molecular patterns (DAMPS and PAMPS), triggering the release of pro-inflammatory cytokines. The dysregulation of inflammasome activation can lead to the development of inflammatory diseases, neurodegeneration, and cancer. A crucial signaling pathway leading to acute and chronic inflammation occurs through the activation of NLRP3 inflammasome followed by caspase 1-dependent release of IL-1β and IL-18 pro-inflammatory cytokines, as well as, by gasdermin D-mediated pyroptotic cell death. In this review we focus on the role of NLRP3 inflammasome and its components in breast cancer signaling, highlighting that a more detailed understanding of the clinical relevance of these pathways could significantly contribute to the development of novel therapeutic strategies for breast cancer.