Type I interferon inhibits interleukin-1 production and inflammasome activation

The Contribution of Innate Immunity in Large-Vessel Vasculitis: Detangling New Pathomechanisms beyond the Onset of Vascular Inflammation

Large-vessel vasculitis (LVV) are autoimmune and autoinflammatory diseases focused on vascular inflammation. The central core of the intricate immunological and molecular network resides in the disruption of the "privileged immune state" of the arterial wall. The outbreak, initially primed by dendritic cells (DC), is then continuously powered in a feed-forward loop by the intimate cooperation between innate and adaptive immunity. If the role of adaptive immunity has been largely elucidated, knowledge of the critical function of innate immunity in LVV is still fragile. A growing body of evidence has strengthened the active role of innate immunity players and their key signaling pathways in orchestrating the complex pathomechanisms underlying LVV. Besides DC, macrophages are crucial culprits in LVV development and participate across all phases of vascular inflammation, culminating in vessel wall remodeling. In recent years, the variety of potential pathogenic actors has expanded to include neutrophils, mast cells, and soluble mediators, including the complement system. Interestingly, new insights have recently linked the inflammasome to vascular inflammation, paving the way for its potential pathogenic role in LVV. Overall, these observations encourage a new conceptual approach that includes a more in-depth study of innate immunity pathways in LVV to guide future targeted therapies.

Variants at the Interleukin 1 Gene Locus and Pericarditis

Importance

Recurrent pericarditis is a treatment challenge and often a debilitating condition. Drugs inhibiting interleukin 1 cytokines are a promising new treatment option, but their use is based on scarce biological evidence and clinical trials of modest sizes, and the contributions of innate and adaptive immune processes to the pathophysiology are incompletely understood.

Objective

To use human genomics, transcriptomics, and proteomics to shed light on the pathogenesis of pericarditis.

Design, Setting, and Participants

This was a meta-analysis of genome-wide association studies of pericarditis from 5 countries. Associations were examined between the pericarditis-associated variants and pericarditis subtypes (including recurrent pericarditis) and secondary phenotypes. To explore mechanisms, associations with messenger RNA expression (cis-eQTL), plasma protein levels (pQTL), and CpG methylation of DNA (ASM-QTL) were assessed. Data from Iceland (deCODE genetics, 1983-2020), Denmark (Copenhagen Hospital Biobank/Danish Blood Donor Study, 1977-2022), the UK (UK Biobank, 1953-2021), the US (Intermountain, 1996-2022), and Finland (FinnGen, 1970-2022) were included. Data were analyzed from September 2022 to August 2023.

Exposure

Genotype.

Main Outcomes and Measures

Pericarditis.

Results

In this genome-wide association study of 4894 individuals with pericarditis (mean [SD] age at diagnosis, 51.4 [17.9] years, 2734 [67.6%] male, excluding the FinnGen cohort), associations were identified with 2 independent common intergenic variants at the interleukin 1 locus on chromosome 2q14. The lead variant was rs12992780 (T) (effect allele frequency [EAF], 31%-40%; odds ratio [OR], 0.83; 95% CI, 0.79-0.87; P = 6.67 × 10-16), downstream of IL1B and the secondary variant rs7575402 (A or T) (EAF, 45%-55%; adjusted OR, 0.89; 95% CI, 0.85-0.93; adjusted P = 9.6 × 10-8). The lead variant rs12992780 had a smaller odds ratio for recurrent pericarditis (0.76) than the acute form (0.86) (P for heterogeneity = .03) and rs7575402 was associated with CpG methylation overlapping binding sites of 4 transcription factors known to regulate interleukin 1 production: PU.1 (encoded by SPI1), STAT1, STAT3, and CCAAT/enhancer-binding protein β (encoded by CEBPB).

Conclusions and Relevance

This study found an association between pericarditis and 2 independent sequence variants at the interleukin 1 gene locus. This finding has the potential to contribute to development of more targeted and personalized therapy of pericarditis with interleukin 1-blocking drugs.

Distinct clinico-molecular arterial and venous thrombosis scores for myeloproliferative neoplasms risk stratification

Current recommended risk scores to predict thrombotic events associated with myeloproliferative neoplasms (MPN) do not discriminate between arterial and venous thrombosis despite their different physiopathology. To define novel stratification systems, we delineated a comprehensive landscape of MPN associated thrombosis across a large long-term follow-up MPN cohort. Prior arterial thrombosis, age >60 years, cardiovascular risk factors and presence of TET2 or DNMT3A mutations were independently associated with arterial thrombosis in multivariable analysis. ARTS, an ARterial Thrombosis Score, based on these four factors, defined low- (0.37% patients-year) and high-risk (1.19% patients-year) patients. ARTS performance was superior to the two-tiered conventional risk stratification in our training cohort, across all MPN subtypes, as well as in two external validation cohorts. Prior venous thrombosis and presence of a JAK2V617F mutation with a variant allelic frequency ≥50% were independently associated with venous thrombosis. The discrimination potential of VETS, a VEnous Thrombosis Score based on these two factors, was poor, similar to the two-tiered conventional risk stratification. Our study pinpoints arterial and venous thrombosis clinico-molecular differences and proposes an arterial risk score for more accurate patients' stratification. Further improvement of venous risk scores, accounting for additional factors and considering venous thrombosis as a heterogeneous entity is warranted.

Raymond E, Sakleshpur S, Steed AL. Aromatic amino acid metabolites alter interferon signaling and influenza pathogenesis

The ability of gut microbial metabolites to influence the host is increasingly recognized. The microbiota extensively metabolizes the three aromatic amino acids, tryptophan, tyrosine, and phenylalanine. Previously we have found that a metabolite of tyrosine, 4-OH-phenylpropionic acid, can enhance type I interferon (IFN) signaling and protect from influenza pathogenesis in a murine model. Herein we screened 17 related aromatic amino acid metabolites for effects on IFN signaling in human lung epithelial cells and monocytes alone and in the presence of IFN-β, influenza, and LPS. While the tryptophan family metabolites reduced IFN signaling in both cell types, the tyrosine and phenylalanine metabolites had varied effects, which were cell-type dependent. Pooled treatment of all these metabolites reduced IFN signaling in both cell types and suggested a tryptophan metabolite effect dominance. Strikingly, when all the metabolites were pooled together, we found reduced influenza recovery in both cell types. RNA sequencing further validated reduced viral loads and decreased IFN signaling. Single gene silencing of significantly upregulated genes identified by RNA sequencing (EGR2, ATP6VD02, SPOCK1, and IL31RA) did not completely abrogate the metabolite induced decrease in IFN signaling. However, these upregulated targets suggested a mechanistic link to TGF-beta signaling. Treatment with a TGF-beta inhibitor and combined targeted gene silencing led to a significant reversal of metabolite induced IFN signaling suppression. Finally, we demonstrated that intranasal administration of these metabolites prior to influenza infection led to reduced animal morbidity, viral titers, and inflammation. Our work implies that microbial metabolites can alter IFN signaling mechanistically through TGF-beta and promote beneficial outcomes during influenza infection.

cGAS-STING, inflammasomes and pyroptosis: an overview of crosstalk mechanism of activation and regulation

BACKGROUND

Intracellular DNA-sensing pathway cGAS-STING, inflammasomes and pyroptosis act as critical natural immune signaling axes for microbial infection, chronic inflammation, cancer progression and organ degeneration, but the mechanism and regulation of the crosstalk network remain unclear. Cellular stress disrupts mitochondrial homeostasis, facilitates the opening of mitochondrial permeability transition pore and the leakage of mitochondrial DNA to cell membrane, triggers inflammatory responses by activating cGAS-STING signaling, and subsequently induces inflammasomes activation and the onset of pyroptosis. Meanwhile, the inflammasome-associated protein caspase-1, Gasdermin D, the CARD domain of ASC and the potassium channel are involved in regulating cGAS-STING pathway. Importantly, this crosstalk network has a cascade amplification effect that exacerbates the immuno-inflammatory response, worsening the pathological process of inflammatory and autoimmune diseases. Given the importance of this crosstalk network of cGAS-STING, inflammasomes and pyroptosis in the regulation of innate immunity, it is emerging as a new avenue to explore the mechanisms of multiple disease pathogenesis. Therefore, efforts to define strategies to selectively modulate cGAS-STING, inflammasomes and pyroptosis in different disease settings have been or are ongoing. In this review, we will describe how this mechanistic understanding is driving possible therapeutics targeting this crosstalk network, focusing on the interacting or regulatory proteins, pathways, and a regulatory mitochondrial hub between cGAS-STING, inflammasomes, and pyroptosis.

SHORT CONCLUSION

This review aims to provide insight into the critical roles and regulatory mechanisms of the crosstalk network of cGAS-STING, inflammasomes and pyroptosis, and to highlight some promising directions for future research and intervention.

Absence of Type I Interferon Autoantibodies or Significant Interferon Signature Alterations in Adults With Post-COVID-19 Syndrome

Genetic defects in the interferon (IFN) system or neutralizing autoantibodies against type I IFNs contribute to severe COVID-19. Such autoantibodies were proposed to affect post-COVID-19 syndrome (PCS), possibly causing persistent fatigue for >12 weeks after confirmed SARS-CoV-2 infection. In the current study, we investigated 128 patients with PCS, 21 survivors of severe COVID-19, and 38 individuals who were asymptomatic. We checked for autoantibodies against IFN-α, IFN-β, and IFN-ω. Few patients with PCS had autoantibodies against IFNs but with no neutralizing activity, indicating a limited role of type I IFNs in PCS pathogenesis. In a subset consisting of 28 patients with PCS, we evaluated IFN-stimulated gene activity and showed that it did not correlate with fatigue. In conclusion, impairment of the type I IFN system is unlikely responsible for adult PCS.

Impact of Disease-Modifying Therapies on Gut-Brain Axis in Multiple Sclerosis

Multiple sclerosis is a chronic, autoimmune-mediated, demyelinating disease whose pathogenesis remains to be defined. In past years, in consideration of a constantly growing number of patients diagnosed with multiple sclerosis, the impacts of different environmental factors in the pathogenesis of the disease have been largely studied. Alterations in gut microbiome composition and intestinal barrier permeability have been suggested to play an essential role in the regulation of autoimmunity. Thus, increased efforts are being conducted to demonstrate the complex interplay between gut homeostasis and disease pathogenesis. Numerous results confirm that disease-modifying therapies (DMTs) used for the treatment of MS, in addition to their immunomodulatory effect, could exert an impact on the intestinal microbiota, contributing to the modulation of the immune response itself. However, to date, the direct influence of these treatments on the microbiota is still unclear. This review intends to underline the impact of DMTs on the complex system of the microbiota-gut-brain axis in patients with multiple sclerosis.

Inhibition of the lysine demethylase LSD1 modulates the balance between inflammatory and antiviral responses against coronaviruses

Innate immune responses to coronavirus infections are highly cell specific. Tissue-resident macrophages, which are infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients but are inconsistently infected in vitro, exert critical but conflicting effects by secreting both antiviral type I interferons (IFNs) and tissue-damaging inflammatory cytokines. Steroids, the only class of host-targeting drugs approved for the treatment of coronavirus disease 2019 (COVID-19), indiscriminately suppress both responses, possibly impairing viral clearance. Here, we established in vitro cell culture systems that enabled us to separately investigate the cell-intrinsic and cell-extrinsic proinflammatory and antiviral activities of mouse macrophages infected with the prototypical murine coronavirus MHV-A59. We showed that the nuclear factor κB-dependent inflammatory response to viral infection was selectively inhibited by loss of the lysine demethylase LSD1, which was previously implicated in innate immune responses to cancer, with negligible effects on the antiviral IFN response. LSD1 ablation also enhanced an IFN-independent antiviral response, blocking viral egress through the lysosomal pathway. The macrophage-intrinsic antiviral and anti-inflammatory activity of Lsd1 inhibition was confirmed in vitro and in a humanized mouse model of SARS-CoV-2 infection. These results suggest that LSD1 controls innate immune responses against coronaviruses at multiple levels and provide a mechanistic rationale for potentially repurposing LSD1 inhibitors for COVID-19 treatment.

Type-I interferon pathway and DNA damage accumulation in peripheral blood of patients with psoriatic arthritis

Objectives

The abnormal DNA damage response is associated with upregulation of the type-1 interferon (IFN-I) pathway in certain rheumatic diseases. We investigated whether such aberrant mechanisms operate in psoriatic arthritis (PsA).

Methods

DNA damage levels were measured by alkaline comet assay in peripheral blood mononuclear cells from 52 PsA patients and age-sex-matched healthy individuals. RNA expression of IFIT1, MX1 and IFI44, which are selectively induced by IFN-I, was quantitated by real-time polymerase chain reaction and their composite normalized expression resulted in IFN-I score calculation. RNA expression of IL1β, IL6, TNF, IL17A and IL23A was also assessed in PsA and control subgroups.

Results

In PsA, DNA damage accumulation was increased by almost two-fold compared to healthy individuals (olive tail moment arbitrary units, mean ± SD; 9.42 ± 2.71 vs 4.88 ± 1.98, p<0.0001). DNA damage levels significantly correlated with serum C-Reactive-protein and IL6 RNA expression in PBMCs. Despite increased DNA damage, the IFN-I score was strikingly lower in PsA patients compared to controls (-0.49 ± 6.99 vs 4.24 ± 4.26; p<0.0001). No correlation was found between IFN-I pathway downregulation and DNA damage. However, the IFN-I score in a PsA subgroup was lower in those patients with higher IL1β expression, as well as in those with higher TNF/IL23A PBMCs expression.

Conclusion

DNA damage in PsA correlates with measures of inflammation but is not associated with the IFN-I pathway induction. The unexpected IFN-I downregulation, albeit reminiscent to findings in experimental models of spondyloarthritis, may be implicated in PsA pathogenesis and explained by operation of other cytokines.

Mutated Toll-like receptor 9 increases Alzheimer's disease risk by compromising innate immunity protection

The development of Alzheimer's disease (AD) involves central and peripheral immune deregulation. Gene identification and studies of AD genetic variants of peripheral immune components may aid understanding of peripheral-central immune crosstalk and facilitate new opportunities for therapeutic intervention. In this study, we have identified in a Flanders-Belgian family a novel variant p.E317D in the Toll-like receptor 9 gene (TLR9), co-segregating with EOAD in an autosomal dominant manner. In human, TLR9 is an essential innate and adaptive immune component predominantly expressed in peripheral immune cells. The p.E317D variant caused 50% reduction in TLR9 activation in the NF-κB luciferase assay suggesting that p.E317D is a loss-of-function mutation. Cytokine profiling of human PBMCs upon TLR9 activation revealed a predominantly anti-inflammatory response in contrast to the inflammatory responses from TLR7/8 activation. The cytokines released upon TLR9 activation suppressed inflammation and promoted phagocytosis of Aβ42 oligomers in human iPSC-derived microglia. Transcriptome analysis identified upregulation of AXL, RUBICON and associated signaling pathways, which may underline the effects of TLR9 signaling-induced cytokines in regulating the inflammatory status and phagocytic property of microglia. Our data suggest a protective role of TLR9 signaling in AD pathogenesis, and we propose that TLR9 loss-of-function may disrupt a peripheral-central immune crosstalk that promotes dampening of inflammation and clearance of toxic protein species, leading to the build-up of neuroinflammation and pathogenic protein aggregates in AD development.

Inflammasomes cross-talk with lymphocytes to connect the innate and adaptive immune response

BACKGROUND

Innate and adaptive immunity are two different parts of the immune system that have different characteristics and work together to provide immune protection. Inflammasomes are a major part of the innate immune system that are expressed widely in myeloid cells and are responsible for inflammatory responses. Recent studies have shown that inflammasomes are also expressed and activated in lymphocytes, especially in T and B cells, to regulate the adaptive immune response. Activation of inflammasomes is also under the control of lymphocytes. Therefore, we propose that inflammasomes act as a bridge and they provide crosstalk between the innate and adaptive immune systems to obtain a fine balance in immune responses.

AIM OF REVIEW

This review systematially summarizes the interaction between inflammasomes and lymphocytes and describes the crosstalk between the innate and adaptive immune systems induced by inflammasomes, with the aim of providing new directions and important areas for further research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

When considering the novel function of inflammasomes in various lymphocytes, attention should be given to the activity of specific inflammasomes in studies of lymphocyte function. Moreover, research on the function of various inflammasomes in lymphocytes will help advance knowledge on the mechanisms and treatment of various diseases, including autoimmune diseases and tumors. In addition, when studying inflammatory responses, inflammasomes in both lymphocytes and myeloid cells need to be considered.

Single-cell resolution of the adult zebrafish intestine under conventional conditions and in response to an acute Vibrio cholerae infection

Vibrio cholerae is an aquatic bacterium that causes severe and potentially deadly diarrheal disease. Despite the impact on global health, our understanding of host mucosal responses to Vibrio remains limited, highlighting a knowledge gap critical for the development of effective prevention and treatment strategies. Using a natural infection model, we combine physiological and single-cell transcriptomic studies to characterize conventionally reared adult zebrafish guts and guts challenged with Vibrio. We demonstrate that Vibrio causes a mild mucosal immune response characterized by T cell activation and enhanced antigen capture; Vibrio suppresses host interferon signaling; and ectopic activation of interferon alters the course of infection. We show that the adult zebrafish gut shares similarities with mammalian counterparts, including the presence of Best4+ cells, tuft cells, and a population of basal cycling cells. These findings provide important insights into host-pathogen interactions and emphasize the utility of zebrafish as a natural model of Vibrio infection.

Dichotomous roles of RIPK3 in regulating the IFN response and NLRP3 inflammasome in human monocytes

Regulation of the profile and magnitude of toll-like receptor (TLR) responses is important for effective host defense against infections while minimizing inflammatory toxicity. The chemokine CXCL4 regulates the TLR8 response to amplify inflammatory gene and inflammasome activation while attenuating the interferon (IFN) response in primary monocytes. In this study, we describe an unexpected role for the kinase RIPK3 in suppressing the CXCL4 + TLR8-induced IFN response and providing signal 2 to activate the NLRP3 inflammasome and interleukin (IL)-1 production in primary human monocytes. RIPK3 also amplifies induction of inflammatory genes such as TNF, IL6, and IL1B while suppressing IL12B. Mechanistically, RIPK3 inhibits STAT1 activation and activates PI3K-Akt-dependent and XBP1- and NRF2-mediated stress responses to regulate downstream genes in a dichotomous manner. These findings identify new functions for RIPK3 in modulating TLR responses and provide potential mechanisms by which RIPK3 plays roles in inflammatory diseases and suggest targeting RIPK3 and XBP1- and NRF2-mediated stress responses as therapeutic strategies to suppress inflammation while preserving the IFN response for host defense.

NLRP3 Inflammasome Involvement in Heart, Liver, and Lung Diseases-A Lesson from Cytokine Storm Syndrome

Inflammation and inflammasomes have been proposed as important regulators of the host-microorganism interaction, playing a key role in morbidity and mortality due to the coronavirus disease 2019 (COVID-19) in subjects with chronic conditions and compromised immune system. The inflammasome consists of a multiprotein complex that finely regulates the activation of caspase-1 and the production and secretion of potent pro-inflammatory cytokines such as IL-1β and IL-18. The pyrin containing NOD (nucleotide-binding oligomerization domain) like receptor (NLRP) is a family of intracellular receptors, sensing patterns associated to pathogens or danger signals and NLRP3 inflammasome is the most deeply analyzed for its involvement in the innate and adaptive immune system as well as its contribution to several autoinflammatory and autoimmune diseases. It is highly expressed in leukocytes and up-regulated in sentinel cells upon inflammatory stimuli. NLRP3 expression has also been reported in B and T lymphocytes, in epithelial cells of oral and genital mucosa, in specific parenchymal cells as cardiomyocytes, and keratinocytes, and chondrocytes. It is well known that a dysregulated activation of the inflammasome is involved in the pathogenesis of different disorders that share the common red line of inflammation in their pathogenetic fingerprint. Here, we review the potential roles of the NLRP3 inflammasome in cardiovascular events, liver damage, pulmonary diseases, and in that wide range of systemic inflammatory syndromes named as a cytokine storm.

NLRP3 inflammasome in cognitive impairment and pharmacological properties of its inhibitors

Cognitive impairment is a multifactorial and multi-step pathological process that places a heavy burden on patients and the society. Neuroinflammation is one of the main factors leading to cognitive impairment. The inflammasomes are multi-protein complexes that respond to various microorganisms and endogenous danger signals, helping to initiate innate protective responses in inflammatory diseases. NLRP3 inflammasomes produce proinflammatory cytokines (interleukin IL-1β and IL-18) by activating caspase-1. In this review, we comprehensively describe the structure and functions of the NLRP3 inflammasome. We also explore the intrinsic relationship between the NLRP3 inflammasome and cognitive impairment, which involves immune cell activation, cell apoptosis, oxidative stress, mitochondrial autophagy, and neuroinflammation. Finally, we describe NLRP3 inflammasome antagonists as targeted therapies to improve cognitive impairment.

Research progress on pyroptosis and its effect on the central nervous system

Pyroptosis is an inflammatory and lysis type of programmed cell death. In the canonical pyroptosis signaling pathway, the NLRP3 inflammasome activates inflammatory caspase-1, which then shears cut the executor protein GSDMD. The N domains of GSDMD move to heterogeneous membranes, form pores, and release inflammatory cytokines IL-1β and IL-18, causing cell membrane swelling and rupture. Pyroptosis is mainly regulated by the key proteins in the signaling pathway, including inflammasome, caspase-1, GSDMD, IL-1β, and IL-18, as well as their agonists and inhibitors. Appropriate pyroptosis can improve host defense mechanisms, while excessive pyroptosis would derive pathological effects on central nervous system, leding to neuroinflammatory response, blood-brain barrier damage, and cognitive disfunction.

Posttranslational ISGylation of NLRP3 by HERC enzymes facilitates inflammasome activation in models of inflammation

The NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a crucial component of the innate immune system that initiates inflammatory responses. Posttranslational modifications (PTMs) of NLRP3, including ubiquitination and phosphorylation, control inflammasome activation and determine the intensity of inflammation. However, the role of other PTMs in controlling NLRP3 inflammasome activation remains unclear. This study found that TLR priming induced NLRP3 ISGylation (a type of PTM in which ISG15 covalently binds to the target protein) to stabilize the NLRP3 protein. Viral infection, represented by SARS-COV-2 infection, and type I IFNs induced expression of ISG15 and the predominant E3 ISGylation ligases HECT domain- and RCC1-like domain-containing proteins (HERCs; HERC5 in humans and HERC6 in mice). HERCs promoted NLRP3 ISGylation and inhibited K48-linked ubiquitination and proteasomal degradation, resulting in the enhancement of NLRP3 inflammasome activation. Concordantly, Herc6 deficiency ameliorated NLRP3-dependent inflammation as well as hyperinflammation caused by viral infection. The results illustrate the mechanism by which type I IFNs responses control inflammasome activation and viral infection-induced aberrant NLRP3 activation. This work identifies ISGylation as a PTM of NLRP3, revealing a priming target that modulates NLRP3-dependent immunopathology.

Adverse outcomes in SARS-CoV-2-infected pregnant mice are gestational age-dependent and resolve with antiviral treatment

SARS-CoV-2 infection during pregnancy is associated with severe COVID-19 and adverse fetal outcomes, but the underlying mechanisms remain poorly understood. Moreover, clinical studies assessing therapeutics against SARS-CoV-2 in pregnancy are limited. To address these gaps, we developed a mouse model of SARS-CoV-2 infection during pregnancy. Outbred CD1 mice were infected at E6, E10, or E16 with a mouse-adapted SARS-CoV-2 (maSCV2) virus. Outcomes were gestational age-dependent, with greater morbidity, reduced antiviral immunity, greater viral titers, and impaired fetal growth and neurodevelopment occurring with infection at E16 (third trimester equivalent) than with infection at either E6 (first trimester equivalent) or E10 (second trimester equivalent). To assess the efficacy of ritonavir-boosted nirmatrelvir, which is recommended for individuals who are pregnant with COVID-19, we treated E16-infected dams with mouse-equivalent doses of nirmatrelvir and ritonavir. Treatment reduced pulmonary viral titers, decreased maternal morbidity, and prevented offspring growth restriction and neurodevelopmental impairments. Our results highlight that severe COVID-19 during pregnancy and fetal growth restriction is associated with heightened virus replication in maternal lungs. Ritonavir-boosted nirmatrelvir mitigated maternal morbidity along with fetal growth and neurodevelopment restriction after SARS-CoV-2 infection. These findings prompt the need for further consideration of pregnancy in preclinical and clinical studies of therapeutics against viral infections.

12/15-lipoxygenase inhibition attenuates neuroinflammation by suppressing inflammasomes

Introduction

Lipoxygenases (LOXs) have essential roles in stroke, atherosclerosis, diabetes, and hypertension. 12/15-LOX inhibition was shown to reduce infarct size and brain edema in the acute phase of experimental stroke. However, the significance of 12/15-LOX on neuroinflammation, which has an essential role in the pathophysiology of stroke, has not been clarified yet.

Methods

In this study, ischemia/recanalization (I/R) was performed by occluding the proximal middle cerebral artery (pMCAo) in mice. Either the 12/15-LOX inhibitor (ML351, 50 mg/kg) or its solvent (DMSO) was injected i.p. at recanalization after 1 h of occlusion. Mice were sacrificed at 6, 24, and 72-h after ischemia induction. Infarct volumes were calculated on Nissl-stained sections. Neurological deficit scoring was used for functional analysis. Lipid peroxidation was determined by the MDA assay, and the inflammatory cytokines IL-6, TNF-alpha, IL-1beta, IL-10, and TGF-beta were quantified by ELISA. The inflammasome proteins NLRP1 and NLRP3, 12/15-LOX, and caspase-1 were detected with immunofluorescence staining.

Results

Infarct volumes, neurological deficit scores, and lipid peroxidation were significantly attenuated in ML351-treated groups at 6, 24, and 72-h. ELISA results revealed that the pro-inflammatory cytokines IL-1beta, IL-6, and TNF-alpha were significantly decreased at 6-h and/or 24-h of I/R, while the anti-inflammatory cytokines IL-10 and TNF-alpha were increased at 24-h or 72-h of ML351 treatment. NLRP1 and NLRP3 immunosignaling were enhanced at three time points after I/R, which were significantly diminished by the ML351 application. Interestingly, NLRP3 immunoreactivity was more pronounced than NLRP1. Hence, we proceeded to study the co-localization of NLRP3 immunoreactivity with 12/15-LOX and caspase-1, which indicated that NLRP3 was co-localized with 12/15-LOX and caspase-1 signaling. Additionally, NLRP3 was found in neurons at all time points but in non-neuronal cells 72 h after I/R.

Discussion

These results suggest that 12/15-LOX inhibition suppresses ischemia-induced inflammation in the acute and subacute phases of stroke via suppressing inflammasome activation. Understanding the mechanisms underlying lipid peroxidation and its associated pathways, like inflammasome activation, may have broader implications for the treatment of stroke and other neurological diseases characterized by neuroinflammation.

Innate immune response restarts adaptive immune response in tumors

The imbalance of immune response plays a crucial role in the development of diseases, including glioblastoma. It is essential to comprehend how the innate immune system detects tumors and pathogens. Endosomal and cytoplasmic sensors can identify diverse cancer cell antigens, triggering the production of type I interferon and pro-inflammatory cytokines. This, in turn, stimulates interferon stimulating genes, enhancing the presentation of cancer antigens, and promoting T cell recognition and destruction of cancer cells. While RNA and DNA sensing of tumors and pathogens typically involve different receptors and adapters, their interaction can activate adaptive immune response mechanisms. This review highlights the similarity in RNA and DNA sensing mechanisms in the innate immunity of both tumors and pathogens. The aim is to enhance the anti-tumor innate immune response, identify regions of the tumor that are not responsive to treatment, and explore new targets to improve the response to conventional tumor therapy and immunotherapy.

A Transcriptional Analysis of Cattle Immune Cells Reveals a Central Role of Type 1 Interferon in the In Vitro Innate Immune Response against Mycobacterium bovis

Bovine tuberculosis is a chronic infectious disease primarily caused by Mycobacterium bovis, a bacterium that affects cattle and other mammals, including humans. Despite the availability of vast research about the immune response mechanisms of human tuberculosis caused by Mycobacterium tuberculosis, the knowledge of bovine tuberculosis's immunology, particularly regarding the innate immune response, still remains scarce. In this study, we compared the transcriptome of cell cultures containing lymphocytes and M. bovis infected-macrophages with two strains of variable virulence, the virulent Mb04-303 strain and the attenuated Mb534. To that end, we infected bovine macrophages at a multiplicity of infection of one, and co-cultured the infections with autologous lymphocytes. RNA obtained from the co-cultures was sequenced to identify differentially expressed gene pathways by using the database Reactome. The RNA-seq analysis showed that the Mb04-303 infection upregulated the type 1 interferon signalling pathway, while it downregulated the KEAP1-NFE2L2 pathway. According to the literature, this last pathway is involved in the activation of antioxidant genes and inflammasome. In addition, the macrophages infected with Mb04-303 recruited more Galectin 8 than those infected with Mb534. This result indicates that Mb04-303 induced higher phagosome membrane damage, with the possible concomitant release of bacterial compounds into the cytoplasm that activates the type I signalling pathway. Altogether, Mb04-303 repressed the antioxidant and anti-inflammatory responses, likely impairing interleukin-1β activation, and trigged the canonical type 1 interferon signalling. Although these responses led to the control of bacterial replication during early infection, the virulent strain eventually managed to establish a successful infection.

Diverse roles of lung macrophages in the immune response to influenza A virus

Influenza viruses are one of the major causes of human respiratory infections and the newly emerging and re-emerging strains of influenza virus are the cause of seasonal epidemics and occasional pandemics, resulting in a huge threat to global public health systems. As one of the early immune cells can rapidly recognize and respond to influenza viruses in the respiratory, lung macrophages play an important role in controlling the severity of influenza disease by limiting viral replication, modulating the local inflammatory response, and initiating subsequent adaptive immune responses. However, influenza virus reproduction in macrophages is both strain- and macrophage type-dependent, and ineffective replication of some viral strains in mouse macrophages has been observed. This review discusses the function of lung macrophages in influenza virus infection in order to better understand the pathogenesis of the influenza virus.

Cytokines and their role in cardiovascular diseases

The evaluation of diagnostic and prognostic biomarkers has always been a hot topic in various diseases. Considering that cardiovascular diseases (CVDs) have the highest mortality and morbidity rates in the world, various studies have been conducted so far to find CVD associated biomarkers, including cardiac troponin (cTn) and NT-proBNP. Cytokines are components of the immune system that are involved in the pathogenesis of CVD due to their contribution to the inflammation process. The level of cytokines varies in many cardiovascular diseases. For instance, the plasma level of IL-1α, IL-18, IL-33, IL-6 and IL-8 is positively correlated with atherosclerosis and that of some other interleukins such as IL-35 is negatively correlated with acute myocardial infarction or cardiac angina. Due to its pivotal role in the inflammation process, IL-1 super family is involved in many CVDs, including atherosclerosis. IL-20 among the interleukins of IL-10 family has a pro-atherogenic role, while others, such as IL-10 and IL-19, play an anti-atherogenic role. In the present review, we have collected the latest published evidence in this respect to discuss valuable cytokines from the diagnostic and prognostic stand point in CVDs.

Molecular Studies for the Early Detection of Philadelphia-Negative Myeloproliferative Neoplasms

JAK2 V617F is the predominant driver mutation in patients with Philadelphia-negative myeloproliferative neoplasms (MPN). JAK2 mutations are also frequent in clonal hematopoiesis of indeterminate potential (CHIP) in otherwise "healthy" individuals. However, the period between mutation acquisition and MPN diagnosis (known as latency) varies widely between individuals, with JAK2 mutations detectable several decades before diagnosis and even from birth in some individuals. Here, we will review the current evidence on the biological factors, such as additional mutations and chronic inflammation, which influence clonal expansion and may determine why some JAK2-mutated individuals will progress to an overt neoplasm during their lifetime while others will not. We will also introduce several germline variants that predispose individuals to CHIP (as well as MPN) identified from genome-wide association studies. Finally, we will explore possible mutation screening or interventions that could help to minimize MPN-associated cardiovascular complications or even delay malignant progression.

Targeted removal of macrophage-secreted interleukin-1 receptor antagonist protects against lethal Candida albicans sepsis

Invasive fungal infections are associated with high mortality rates, and the lack of efficient treatment options emphasizes an urgency to identify underlying disease mechanisms. We report that disseminated Candida albicans infection is facilitated by interleukin-1 receptor antagonist (IL-1Ra) secreted from macrophages in two temporally and spatially distinct waves. Splenic CD169+ macrophages release IL-1Ra into the bloodstream, impeding early neutrophil recruitment. IL-1Ra secreted by monocyte-derived tissue macrophages further impairs pathogen containment. Therapeutic IL-1Ra neutralization restored the functional competence of neutrophils, corrected maladapted hyper-inflammation, and eradicated the otherwise lethal infection. Conversely, augmentation of macrophage-secreted IL-1Ra by type I interferon severely aggravated disease mortality. Our study uncovers how a fundamental immunoregulatory mechanism mediates the high disease susceptibility to invasive candidiasis. Furthermore, interferon-stimulated IL-1Ra secretion may exacerbate fungal dissemination in human patients with secondary candidemia. Macrophage-secreted IL-1Ra should be considered as an additional biomarker and potential therapeutic target in severe systemic candidiasis.

The NLRP3 inflammasome and gut dysbiosis as a putative link between HIV-1 infection and ischemic stroke

HIV-associated comorbidities, such as ischemic stroke, are prevalent in people with HIV (PWH). Several studies both in animal models and humans have revealed an association between activation of the inflammasome in HIV-1 infection and stroke. The gut microbiota is an important component in controlling neuroinflammation in the CNS. It has also been proposed to be involved in the pathobiology of HIV-1 infection, and has been associated with an increase in activation of the inflammasome. In this review, we provide an overview of the microbiota-gut-inflammasome-brain axis, focusing on the NLRP3 inflammasome and dysregulation of the microbiome as risk factors that may contribute to the outcome of ischemic stroke and recovery in PWH. We also focus on the potential of targeting the NLRP3 inflammasome as a novel therapeutic approach for PWH who are at risk of developing cerebrovascular diseases.

Type-I interferons promote innate immune tolerance in macrophages exposed to Mycobacterium ulcerans vesicles

Buruli ulcer is a chronic infectious disease caused by Mycobacterium ulcerans. The pathogen persistence in host skin is associated with the development of ulcerative and necrotic lesions leading to permanent disabilities in most patients. However, few of diagnosed cases are thought to resolve through an unknown self-healing process. Using in vitro and in vivo mouse models and M. ulcerans purified vesicles and mycolactone, we showed that the development of an innate immune tolerance was only specific to macrophages from mice able to heal spontaneously. This tolerance mechanism depends on a type I interferon response and can be induced by interferon beta. A type I interferon signature was further detected during in vivo infection in mice as well as in skin samples from patients under antibiotics regiment. Our results indicate that type I interferon-related genes expressed in macrophages may promote tolerance and healing during infection with skin damaging pathogen.

Human metapneumovirus driven IFN-β production antagonizes macrophage transcriptional induction of IL1-β in response to bacterial pathogens

Human metapneumovirus (HMPV) is a pneumovirus that may cause severe respiratory disease in humans. HMPV infection has been found to increase susceptibility to bacterial superinfections leading to increased morbidity and mortality. The molecular mechanisms underlying HMPV-mediated increase in bacterial susceptibility are poorly understood and largely understudied. Type I interferons (IFNs), while critical for antiviral defenses, may often have detrimental effects by skewing the host immune response and cytokine output of immune cells. It is currently unknown if HMPV skews the inflammatory response in human macrophages triggered by bacterial stimuli. Here we report that HMPV pre-infection impacts production of specific cytokines. HMPV strongly suppresses IL-1β transcription in response to LPS or heat-killed Pseudomonas aeruginosa and Streptococcus pneumonia, while enhancing mRNA levels of IL-6, TNF-α and IFN-β. We demonstrate that in human macrophages the HMPV-mediated suppression of IL-1β transcription requires TANK-binding kinase 1 (TBK1) and signaling via the IFN-β-IFNAR axis. Interestingly, our results show that HMPV pre-infection did not impair the LPS-stimulated activation of NF-κB and HIF-1α, transcription factors that stimulate IL-1β mRNA synthesis in human cells. Furthermore, we determined that sequential HMPV-LPS treatment resulted in accumulation of the repressive epigenetic mark H3K27me3 at the IL1B promoter. Thus, for the first time we present data revealing the molecular mechanisms by which HMPV shapes the cytokine output of human macrophages exposed to bacterial pathogens/LPS, which appears to be dependent on epigenetic reprogramming at the IL1B promoter leading to reduced synthesis of IL-1β. These results may improve current understanding of the role of type I IFNs in respiratory disease mediated not only by HMPV, but also by other respiratory viruses that are associated with superinfections.

Dexmedetomidine suppresses hippocampal astrocyte pyroptosis in cerebral hypoxic-ischemic neonatal rats by upregulating microRNA-148a-3p to inactivate the STAT/JMJD3 axis

OBJECTIVE

Dexmedetomidine (DEX), a selective α2-adrenoceptor agonist, is an anesthetic and sedative agent and has been reported to confer neuroprotective effects after cerebral hypoxic ischemia (CHI). This study was undertaken to elucidate the mechanisms by which microRNA (miR)-148a-3p is involved in the neuroprotective effect of DEX on hypoxic-ischemic brain damage in neonatal rats.

METHODS

Neonatal rats were exposed to CHI conditions, a miR-148a-3p inhibitor, and DEX. Hippocampal astrocytes were isolated to construct an oxygen-glucose deprivation (OGD) model. qRT-PCR and western blot were utilized to inspect miR-148a-3p, STAT1, STAT3, JMJD3, cleaved-Caspase-1, ASC, NLRP3, GSDMD, and GSDMD-N expression in rats and astrocytes. TUNEL staining was employed to measure astrocyte apoptosis rate, immunofluorescence to inspect cleaved-Caspase-1 and ASC levels, and ELISA to determine IL-1β and IL-18 expression. The target genes of miR-148a-3p were predicted using online software and verified by a dual-luciferase reporter gene assay.

RESULTS

A prominent increase in astrocyte apoptosis rate and the expression of pyroptosis- and inflammation-related factors were found in rats with CHI and OGD-treated astrocytes. DEX suppressed astrocyte apoptosis rate and decreased expression of pyroptosis- and inflammation-related factors. Knockdown of miR-148a-3p facilitated astrocyte pyroptosis, indicating that DEX exerted its protective effect by upregulating miR-148a-3p. miR-148a-3p negatively mediated STAT to inactivate JMJD3. Overexpression of STAT1 and STAT3 facilitated pyroptosis in astrocytes, which was negated by the overexpression of miR-148a-3p.

CONCLUSION

DEX inhibited hippocampal astrocyte pyroptosis by upregulating miR-148a-3p to inactivate the STAT/JMJD3 axis, thereby alleviating cerebral damage in neonatal rats with CHI.

Scoparone suppresses mitophagy-mediated NLRP3 inflammasome activation in inflammatory diseases

Recent evidence shows that targeting NLRP3 inflammasome activation is an important means to treat inflammasome-driven diseases. Scoparone, a natural compound isolated from the Chinese herb Artemisia capillaris Thunb, has anti-inflammatory activity. In this study we investigated the effect of scoparone on NLRP3 inflammasome activation in inflammatory diseases. In LPS-primed, ATP or nigericin-stimulated mouse macrophage J774A.1 cells and bone marrow-derived macrophages (BMDMs), pretreatment with scoparone (50 μM) markedly restrained canonical and noncanonical NLRP3 inflammasome activation, evidenced by suppressed caspase-1 cleavage, GSDMD-mediated pyroptosis, mature IL-1β secretion and the formation of ASC specks. We then conducted a transcriptome analysis in scoparone-pretreated BMDMs, and found that the differentially expressed genes were significantly enriched in mitochondrial reactive oxygen species (ROS) metabolic process, mitochondrial translation and assembly process, as well as in inflammatory response. We demonstrated in J774A.1 cells and BMDMs that scoparone promoted mitophagy, a well-characterized mechanism to control mitochondrial quality and reduce ROS production and subsequent NLRP3 inflammasome activation. Mitophagy blockade by 3-methyladenine (3-MA, 5 mM) reversed the protective effects of scoparone on mitochondrial damage and inflammation in the murine macrophages. Moreover, administration of scoparone (50 mg/kg) exerted significant preventive effects via inhibition of NLRP3 activation in mouse models of bacterial enteritis and septic shock. Collectively, scoparone displays potent anti-inflammatory effects via blocking NLRP3 inflammasome activation through enhancing mitophagy, highlighting a potential action mechanism in treating inflammasome-related diseases for further clinical investigation.

Aberrant inflammasome activation as a driving force of human autoimmune skin disease

Autoimmune skin diseases are understood as conditions in which the adaptive immune system with autoantigen-specific T cells and autoantibody-producing B cells reacting against self-tissues plays a crucial pathogenic role. However, there is increasing evidence that inflammasomes, which are large multiprotein complexes that were first described 20 years ago, contribute to autoimmune disease progression. The inflammasome and its contribution to the bioactivation of interleukins IL-1β and IL-18 play an essential role in combating foreign pathogens or tissue damage, but may also act as a pathogenic driver of myriad chronic inflammatory diseases when dysfunctionally regulated. Inflammasomes containing the NOD-like receptor family members NLRP1 and NLRP3 as well as the AIM2-like receptor family member AIM2 have been increasingly investigated in inflammatory skin conditions. In addition to autoinflammatory diseases, which are often associated with skin involvement, the aberrant activation of the inflammasome has also been implied in autoimmune diseases that can either affect the skin besides other organs such as systemic lupus erythematosus and systemic sclerosis or are isolated to the skin in humans. The latter include, among others, the T-cell mediated disorders vitiligo, alopecia areata, lichen planus and cutaneous lupus erythematosus as well as the autoantibody-driven blistering skin disease bullous pemphigoid. Some diseases are characterized by both autoinflammatory and autoimmune responses such as the chronic inflammatory skin disease psoriasis. Further insights into inflammasome dysregulation and associated pathways as well as their role in forming adaptive immune responses in human autoimmune skin pathology could potentially offer a new field of therapeutic options in the future.

Roles of inflammasomes in viral myocarditis

Viral myocarditis (VMC), characterized by viral infection-induced inflammation, is a life-threatening disease associated with dilated cardiomyopathy or heart failure. Innate immunity plays a crucial role in the progression of inflammation, in which inflammasomes provide a platform for the secretion of cytokines and mediate pyroptosis. Inflammasomes are rising stars gaining increasing attention. The nucleotide oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, the caspase recruitment domain-containing protein 8 (CARD8) inflammasome, and the caspase-11 inflammasome are three inflammasomes that were reported to affect the process and prognosis of VMC. These inflammasomes can be activated by a wide range of cellular events. Accumulating evidence has suggested that inflammasomes are involved in different stages of VMC, including the trigger and progression of myocardial injury and remodeling after infection. In this review, we summarized the pathways involving inflammasomes in VMC and discussed the potential therapies targeting inflammasomes and related pathways.

Cause or consequence? The role of IL-1 family cytokines and receptors in neuroinflammatory and neurodegenerative diseases

Cytokines and receptors of the IL-1 family are key mediators in innate immune and inflammatory reactions in physiological defensive conditions, but are also significantly involved in immune-mediated inflammatory diseases. Here, we will address the role of cytokines of the IL-1 superfamily and their receptors in neuroinflammatory and neurodegenerative diseases, in particular Multiple Sclerosis and Alzheimer's disease. Notably, several members of the IL-1 family are present in the brain as tissue-specific splice variants. Attention will be devoted to understanding whether these molecules are involved in the disease onset or are effectors of the downstream degenerative events. We will focus on the balance between the inflammatory cytokines IL-1β and IL-18 and inhibitory cytokines and receptors, in view of future therapeutic approaches.

Genetic basis and molecular profiling in myeloproliferative neoplasms

BCR::ABL1-negative myeloproliferative neoplasms (MPNs) are clonal diseases originating from a single hematopoietic stem cell that cause excessive production of mature blood cells. The 3 subtypes, that is, polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are diagnosed according to the World Health Organization (WHO) and international consensus classification (ICC) criteria. Acquired gain-of-function mutations in 1 of 3 disease driver genes (JAK2, CALR, and MPL) are the causative events that can alone initiate and promote MPN disease without requiring additional cooperating mutations. JAK2-p.V617F is present in >95% of PV patients, and also in about half of the patients with ET or PMF. ET and PMF are also caused by mutations in CALR or MPL. In ∼10% of MPN patients, those referred to as being "triple negative," none of the known driver gene mutations can be detected. The common theme between the 3 driver gene mutations and triple-negative MPN is that the Janus kinase-signal transducer and activator of transcription (JAK/STAT) signaling pathway is constitutively activated. We review the recent advances in our understanding of the early events after the acquisition of a driver gene mutation. The limiting factor that determines the frequency at which MPN disease develops with a long latency is not the acquisition of driver gene mutations, but rather the expansion of the clone. Factors that control the conversion from clonal hematopoiesis to MPN disease include inherited predisposition, presence of additional mutations, and inflammation. The full extent of knowledge of the mutational landscape in individual MPN patients is now increasingly being used to predict outcome and chose the optimal therapy.

Inborn Error of STAT2-Dependent IFN-I Immunity in a Patient Presented with Hemophagocytic Lymphohistiocytosis and Multisystem Inflammatory Syndrome in Children

Human inborn errors of immunity (IEI) affecting the type I interferon (IFN-I) induction pathway have been associated with predisposition to severe viral infections. Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening systemic hyperinflammatory syndrome that has been increasingly associated with inborn errors of IFN-I-mediated innate immunity. Here is reported a novel case of complete deficiency of STAT2 in a 3-year-old child that presented with typical features of HLH after mumps, measles, and rubella vaccination at the age of 12 months. Due to the life-threatening risk of viral infection, she received SARS-CoV-2 mRNA vaccination. Unfortunately, she developed multisystem inflammatory syndrome in children (MIS-C) after SARS-CoV-2 infection, 4 months after the last dose. Functional studies showed an impaired IFN-I-induced response and a defective IFNα expression at later stages of STAT2 pathway induction. These results suggest a possible more complex mechanism for hyperinflammatory reactions in this type of patients involving a possible defect in the IFN-I production. Understanding the cellular and molecular links between IFN-I-induced signaling and hyperinflammatory syndromes can be critical for the diagnosis and tailored management of these patients with predisposition to severe viral infection.

Inflammation and Epstein-Barr Virus at the Crossroads of Multiple Sclerosis and Post-Acute Sequelae of COVID-19 Infection

Recent studies have strengthened the evidence for Epstein-Barr Virus (EBV) as an important contributing factor in the development of multiple sclerosis (MS). Chronic inflammation is a key feature of MS. EBV+ B cells can express cytokines and exosomes that promote inflammation, and EBV is known to be reactivated through the upregulation of cellular inflammasomes. Inflammation is a possible cause of the breakdown of the blood-brain barrier (BBB), which allows the infiltration of lymphocytes into the central nervous system. Once resident, EBV+ or EBV-specific B cells could both plausibly exacerbate MS plaques through continued inflammatory processes, EBV reactivation, T cell exhaustion, and/or molecular mimicry. Another virus, SARS-CoV-2, the cause of COVID-19, is known to elicit a strong inflammatory response in infected and immune cells. COVID-19 is also associated with EBV reactivation, particularly in severely ill patients. Following viral clearance, continued inflammation may be a contributor to post-acute sequelae of COVID-19 infection (PASC). Evidence of aberrant cytokine activation in patients with PASC supports this hypothesis. If unaddressed, long-term inflammation could put patients at risk for reactivation of EBV. Determining mechanisms by which viruses can cause inflammation and finding treatments for reducing that inflammation may help reduce the disease burden for patients suffering from PASC, MS, and EBV diseases.

The balance between gasdermin D and STING signaling shapes the severity of schistosome immunopathology

There is significant disease heterogeneity among mouse strains infected with the helminth Schistosoma mansoni. Here, we uncover a unique balance in two critical innate pathways governing the severity of disease. In the low-pathology setting, parasite egg-stimulated dendritic cells (DCs) induce robust interferon (IFN)β production, which is dependent on the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) cytosolic DNA sensing pathway and results in a Th2 response with suppression of proinflammatory cytokine production and Th17 cell activation. IFNβ induces signal transducer and activator of transcription (STAT)1, which suppresses CD209a, a C-type lectin receptor associated with severe disease. In contrast, in the high-pathology setting, enhanced DC expression of the pore-forming protein gasdermin D (Gsdmd) results in reduced expression of cGAS/STING, impaired IFNβ, and enhanced pyroptosis. Our findings demonstrate that cGAS/STING signaling represents a unique mechanism inducing protective type I IFN, which is counteracted by Gsdmd.

A single-cell atlas reveals shared and distinct immune responses and metabolic profiles in SARS-CoV-2 and HIV-1 infections

Introduction: Within the inflammatory immune response to viral infection, the distribution and cell type-specific profiles of immune cell populations and the immune-mediated viral clearance pathways vary according to the specific virus. Uncovering the immunological similarities and differences between viral infections is critical to understanding disease progression and developing effective vaccines and therapies. Insight into COVID-19 disease progression has been bolstered by the integration of single-cell (sc)RNA-seq data from COVID-19 patients with data from related viruses to compare immune responses. Expanding this concept, we propose that a high-resolution, systematic comparison between immune cells from SARS-CoV-2 infection and an inflammatory infectious disease with a different pathophysiology will provide a more comprehensive picture of the viral clearance pathways that underscore immunological and clinical differences between infections. Methods: Using a novel consensus single-cell annotation method, we integrate previously published scRNA-seq data from 111,566 single PBMCs from 7 COVID-19, 10 HIV-1+, and 3 healthy patients into a unified cellular atlas. We compare in detail the phenotypic features and regulatory pathways in the major immune cell clusters. Results: While immune cells in both COVID-19 and HIV-1+ cohorts show shared inflammation and disrupted mitochondrial function, COVID-19 patients exhibit stronger humoral immunity, broader IFN-I signaling, elevated Rho GTPase and mTOR pathway activity, and downregulated mitophagy. Discussion: Our results indicate that differential IFN-I signaling regulates the distinct immune responses in the two diseases, revealing insight into fundamental disease biology and potential therapeutic candidates.

The protein kinase R modifies gut physiology to limit colitis

Here we investigate the function of the innate immune molecule protein kinase R (PKR) in intestinal inflammation. To model a colitogenic role of PKR, we determine the physiological response to dextran sulfate sodium (DSS) of wild-type and two transgenic mice strains mutated to express either a kinase-dead PKR or to ablate expression of the kinase. These experiments recognize kinase-dependent and -independent protection from DSS-induced weight loss and inflammation, against a kinase-dependent increase in the susceptibility to DSS-induced injury. We propose these effects arise through PKR-dependent alteration of gut physiology, evidenced as altered goblet cell function and changes to the gut microbiota at homeostasis that suppresses inflammasome activity by controlling autophagy. These findings establish that PKR functions as both a protein kinase and a signaling molecule in instituting immune homeostasis in the gut.

Understanding immunity: an alternative framework beyond defense and strength

In this paper we address the issue of how to think about immunity. Many immunological writings suggest a straightforward option: the view that the immune system is primarily a system of defense, which naturally invites the talk of strong immunity and strong immune response. Despite their undisputable positive role in immunology, such metaphors can also pose a risk of establishing a narrow perspective, omitting from consideration phenomena that do not neatly fit those powerful metaphors. Building on this analysis, we argue two things. First, we argue that the immune system is involved not only in defense. Second, by disentangling various possible meanings of 'strength' and 'weakness' in immunology, we also argue that such a construal of immunity generally contributes to the distortion of the overall picture of what the immune system is, what it does, and why it sometimes fails. Instead, we propose to understand the nature of the immune system in terms of contextuality, regulation, and trade-offs. We suggest that our approach provides lessons for a general understanding of the organizing principles of the immune system in health and disease. For all this to work, we discuss a wide range of immunological phenomena.

NLRP3 inflammasome in neurodegenerative disease

Neurodegenerative diseases are characterized by a dysregulated neuro-glial microenvironment, culminating in functional deficits resulting from neuronal cell death. Inflammation is a hallmark of the neurodegenerative microenvironment and despite a critical role in tissue homeostasis, increasing evidence suggests that chronic inflammatory insult can contribute to progressive neuronal loss. Inflammation has been studied in the context of neurodegenerative disorders for decades but few anti-inflammatory treatments have advanced to clinical use. This is likely due to the related challenges of predicting and mitigating off-target effects impacting the normal immune response while detecting inflammatory signatures that are specific to the progression of neurological disorders. Inflammasomes are pro-inflammatory cytosolic pattern recognition receptors functioning in the innate immune system. Compelling pre-clinical data has prompted an intense interest in the role of the NLR family pyrin domain containing 3 (NLRP3) inflammasome in neurodegenerative disease. NLRP3 is typically inactive but can respond to sterile triggers commonly associated with neurodegenerative disorders including protein misfolding and aggregation, mitochondrial and oxidative stress, and exposure to disease-associated environmental toxicants. Clear evidence of enhanced NLRP3 inflammasome activity in common neurodegenerative diseases has coincided with rapid advancement of novel small molecule therapeutics making the NLRP3 inflammasome an attractive target for near-term interventional studies. In this review, we highlight evidence from model systems and patients indicating inflammasome activity in neurodegenerative disease associated with the NLRP3 inflammasome's ability to recognize pathologic forms of amyloid-β, tau, and α-synuclein. We discuss inflammasome-driven pyroptotic processes highlighting the potential utility of evaluating extracellular inflammasome-related proteins in the context of biomarker discovery. We complete the report by pointing out gaps in our understanding of intracellular modifiers of inflammasome activity and mechanisms regulating the resolution of inflammasome activation. The literature review and perspectives provide a conceptual platform for continued analysis of inflammation in neurodegenerative diseases through the study of inflammasomes and pyroptosis, mechanisms of inflammation and cell death now recognized to function in multiple highly prevalent neurological disorders.

The NLRP3 Inflammasome in Age-Related Cerebral Small Vessel Disease Manifestations: Untying the Innate Immune Response Connection

In this narrative review, we present the evidence on nucleotide-binding and oligomerization (NOD) domain-like receptor (NLR) family pyrin domain (PYD)-containing 3 (NLRP3) inflammasome activation for its putative roles in the elusive pathomechanism of aging-related cerebral small vessel disease (CSVD). Although NLRP3 inflammasome-interleukin (IL)-1β has been implicated in the pathophysiology of coronary artery disease, its roles in cerebral arteriothrombotic micro-circulation disease such as CSVD remains unexplored. Here, we elaborate on the current manifestations of CSVD and its' complex pathogenesis and relate the array of activators and aberrant activation involving NLRP3 inflammasome with this condition. These neuroinflammatory insights would expand on our current understanding of CSVD clinical (and subclinical) heterogenous manifestations whilst highlighting plausible NLRP3-linked therapeutic targets.

The lysosomal Ragulator complex activates NLRP3 inflammasome in vivo via HDAC6

The cellular activation of the NLRP3 inflammasome is spatiotemporally orchestrated by various organelles, but whether lysosomes contribute to this process remains unclear. Here, we show the vital role of the lysosomal membrane-tethered Ragulator complex in NLRP3 inflammasome activation. Deficiency of Lamtor1, an essential component of the Ragulator complex, abrogated NLRP3 inflammasome activation in murine macrophages and human monocytic cells. Myeloid-specific Lamtor1-deficient mice showed marked attenuation of NLRP3-associated inflammatory disease severity, including LPS-induced sepsis, alum-induced peritonitis, and monosodium urate (MSU)-induced arthritis. Mechanistically, Lamtor1 interacted with both NLRP3 and histone deacetylase 6 (HDAC6). HDAC6 enhances the interaction between Lamtor1 and NLRP3, resulting in NLRP3 inflammasome activation. DL-all-rac-α-tocopherol, a synthetic form of vitamin E, inhibited the Lamtor1-HDAC6 interaction, resulting in diminished NLRP3 inflammasome activation. Further, DL-all-rac-α-tocopherol alleviated acute gouty arthritis and MSU-induced peritonitis. These results provide novel insights into the role of lysosomes in the activation of NLRP3 inflammasomes by the Ragulator complex.

Inflammasome Activation Dampens Type I IFN Signaling to Strengthen Anti-Toxoplasma Immunity

Innate immunity acts as the first line of defense against pathogen invasion. During Toxoplasma gondii infection, multiple innate immune sensors are activated by invading microbes or pathogen-associated molecular patterns (PAMPs). However, how inflammasome is activated and its regulatory mechanisms during T. gondii infection remain elusive. Here, we showed that the infection of PRU, a lethal type II T. gondii strain, activates inflammasome at the early stage of infection. PRU tachyzoites, RNA and soluble tachyzoite antigen (STAg) mainly triggered the NLRP3 inflammasome, while PRU genomic DNA (gDNA) specially activated the AIM2 inflammasome. Furthermore, mice deficient in AIM2, NLRP3, or caspase-1/11 were more susceptible to T. gondii PRU infection, and the ablation of inflammasome signaling impaired antitoxoplasmosis immune responses by enhancing type I interferon (IFN-I) production. Blockage of IFN-I receptor fulfilled inflammasome-deficient mice competent immune responses as WT mice. Moreover, we have identified that the suppressor of cytokine signaling 1 (SOCS1) is a key negative regulator induced by inflammasome-activated IL-1β signaling and inhibits IFN-I production by targeting interferon regulatory factor 3 (IRF3). In general, our study defines a novel protective role of inflammasome activation during toxoplasmosis and identifies a critical regulatory mechanism of the cross talk between inflammasome and IFN-I signaling for understanding infectious diseases. IMPORTANCE As a key component of innate immunity, inflammasome is critical for host antitoxoplasmosis immunity, but the underlying mechanisms are still elusive. In this study, we found that inflammasome signaling was activated by PAMPs of T. gondii, which generated a protective immunity against T. gondii invasion by suppressing type I interferon (IFN-I) production. Mechanically, inflammasome-coupled IL-1β signaling triggered the expression of negative regulator SOCS1, which bound to IRF3 to inhibit IFN-I production. The role of IFN-I in anti-T. gondii immunity is little studied and controversial, and here we also found IFN-I is harmful to host antitoxoplasmosis immunity by using knockout mice and recombinant proteins. In general, our study identifies a protective role of inflammasomes to the host during T. gondii infection and a novel mechanism by which inflammasome suppresses IFN-I signaling in antitoxoplasmosis immunity, which will likely provide new insights into therapeutic targets for toxoplasmosis and highlight the cross talk between innate immune signaling in infectious diseases prevention.

Dysregulated inflammasome activity in intestinal inflammation - Insights from patients with very early onset IBD

Inflammatory bowel disease (IBD) is a multifactorial disorder triggered by imbalances of the microbiome and immune dysregulations in genetically susceptible individuals. Several mouse and human studies have demonstrated that multimeric inflammasomes are critical regulators of host defense and gut homeostasis by modulating immune responses to pathogen- or damage-associated molecular patterns. In the context of IBD, excessive production of pro-inflammatory Interleukin-1β has been detected in patient-derived intestinal tissues and correlated with the disease severity or failure to respond to anti-tumor necrosis factor therapy. Correspondingly, genome-wide association studies have suggested that single nucleotide polymorphisms in inflammasome components might be associated with risk of IBD development. The relevance of inflammasomes in controlling human intestinal homeostasis has been further exemplified by the discovery of very early onset IBD (VEO-IBD) patients with monogenic defects affecting different molecules in the complex regulatory network of inflammasome activity. This review provides an overview of known causative monogenic entities of VEO-IBD associated with altered inflammasome activity. A better understanding of the molecular mechanisms controlling inflammasomes in monogenic VEO-IBD may open novel therapeutic avenues for rare and common inflammatory diseases.

Recombinant Interferon-β in the Treatment of Polycythemia Vera and Related Neoplasms: Rationales and Perspectives

About 30 years ago, the first clinical trials of the safety and efficacy of recombinant interferon-α2 (rIFN-α2) were performed. Since then, several single-arm studies have shown rIFN-α2 to be a highly potent anticancer agent against several cancer types. Unfortunately, however, a high toxicity profile in early studies with rIFN-α2 -among other reasons likely due to the high dosages being used-disqualified rIFN-α2, which was accordingly replaced with competitive drugs that might at first glance look more attractive to clinicians. Later, pegylated IFN-α2a (Pegasys) and pegylated IFN-α2b (PegIntron) were introduced, which have since been reported to be better tolerated due to reduced toxicity. Today, treatment with rIFN-α2 is virtually outdated in non-hematological cancers, where other immunotherapies-e.g., immune-checkpoint inhibitors-are routinely used in several cancer types and are being intensively investigated in others, either as monotherapy or in combination with immunomodulatory agents, although only rarely in combination with rIFN-α2. Within the hematological malignancies, rIFN-α2 has been used off-label for decades in patients with Philadelphia-negative chronic myeloproliferative neoplasms (MPNs)-i.e., essential thrombocythemia, polycythemia vera, and myelofibrosis-and in recent years rIFN-α2 has been revived with the marketing of ropeginterferon-α2b (Besremi) for the treatment of polycythemia vera patients. Additionally, rIFN-α2 has been revived for the treatment of chronic myelogenous leukemia in combination with tyrosine kinase inhibitors. Another rIFN formulation-recombinant interferon-β (rIFN-β)-has been used for decades in the treatment of multiple sclerosis but has never been studied as a potential agent to be used in patients with MPNs, although several studies and reviews have repeatedly described rIFN-β as an effective anticancer agent as well. In this paper, we describe the rationales and perspectives for launching studies on the safety and efficacy of rIFN-β in patients with MPNs.

TLR4-Pathway-Associated Biomarkers in Subarachnoid Hemorrhage (SAH): Potential Targets for Future Anti-Inflammatory Therapies

Subarachnoid hemorrhage is associated with severe neurological deficits for survivors. Among survivors of the initial bleeding, secondary brain injury leads to additional brain damage. Apart from cerebral vasospasm, secondary brain injury mainly results from cerebral inflammation taking place in the brain parenchyma after bleeding. The brain’s innate immune system is activated, which leads to disturbances in brain homeostasis, cleavage of inflammatory cytokines and, subsequently, neuronal cell death. The toll-like receptor (TLR)4 signaling pathway has been found to play an essential role in the pathophysiology of acute brain injuries such as subarachnoid hemorrhage (SAH). TLR4 is expressed on the cell surface of microglia, which are key players in the cellular immune responses of the brain. The participants in the signaling pathway, such as TLR4-pathway-like ligands, the receptor itself, and inflammatory cytokines, can act as biomarkers, serving as clues regarding the inflammatory status after SAH. Moreover, protein complexes such as the NLRP3 inflammasome or receptors such as TREM1 frame the TLR4 pathway and are indicative of inflammation. In this review, we focus on the activity of the TLR4 pathway and its contributors, which can act as biomarkers of neuroinflammation or even offer potential new treatment targets for secondary neuronal cell death after SAH.

Interactions between the NLRP3-Dependent IL-1β and the Type I Interferon Pathways in Human Plasmacytoid Dendritic Cells

Generally, a reciprocal antagonistic interaction exists between the antiviral type I interferon (IFN) and the antibacterial nucleotide-binding oligomerization domain (NOD)-like receptor pyrin domain containing 3 (NLRP3)-dependent IL-1β pathways that can significantly shape immune responses. Plasmacytoid dendritic cells (pDCs), as professional type I IFN-producing cells, are the major coordinators of antiviral immunity; however, their NLRP3-dependent IL-1β secretory pathway is poorly studied. Our aim was to determine the functional activity of the IL-1β pathway and its possible interaction with the type I IFN pathway in pDCs. We found that potent nuclear factor-kappa B (NF-κB) inducers promote higher levels of pro-IL-1β during priming compared to those activation signals, which mainly trigger interferon regulatory factor (IRF)-mediated type I IFN production. The generation of cleaved IL-1β requires certain secondary signals in pDCs and IFN-α or type I IFN-inducing viruses inhibit IL-1β production of pDCs, presumably by promoting the expression of various NLRP3 pathway inhibitors. In line with that, we detected significantly lower IL-1β production in pDCs of psoriasis patients with elevated IFN-α levels. Collectively, our results show that the NLRP3-dependent IL-1β secretory pathway is inducible in pDCs; however, it may only prevail under inflammatory conditions, in which the type I IFN pathway is not dominant.

USP3 deubiquitinates and stabilizes the adapter protein ASC to regulate inflammasome activation

Inflammasomes are essential components of the innate immune system and its defense against infections, whereas the dysregulation of inflammasome activation has a detrimental effect on human health. The activation of inflammasomes is subjected to tight regulation to maintain immune homeostasis, yet the underlying mechanism remains elusive. Here, we identify USP3 as a direct deubiquitinating enzyme (DUB) for ASC, the central adapter mediating the assembly and activation of most inflammasomes. USP3 removes the K48-linked ubiquitination on ASC and strengthens its stability by blocking proteasomal degradation. Additionally, USP3 promotes inflammasome activation, and this function was confirmed in mouse models of aluminum (Alum)-induced peritonitis, F. novicida infection and flagellin-induced pneumonia in vivo. Our work unveils that USP3 functions as a key regulator of ASC ubiquitination and maintains the physiological role of ASC in mediating inflammasome activation, and we propose a new mechanism by which the ubiquitination of ASC regulates inflammasome activation.