Evaluation of inflammasomes as biomarker following non-surgical periodontal treatment

OBJECTIVE

The purpose of this study was to investigate interleukin (IL)-1β, IL-18, nod-like receptor pyrin domain-containing protein 3 (NLRP3), apoptosis-related speck-like protein containing a caspase activation and recruitment domain (ASC), and caspase-1 levels in saliva and serum in different periodontal diseases and to evaluate the changes after non-surgical periodontal treatment (NSPT).

DESIGN

A total of 45 participants, 15 healthy, 15 gingivitis, and 15 stage III grade C (SIIIGC) periodontitis patients, were included in the study. Periodontal parameters were assessed, and salivary and serum samples were collected at baseline in all groups and one and three months after NSPT in gingivitis and periodontitis groups. An enzyme-linked immunosorbent assay was used to analyse IL-1β, IL-18, NLRP3, ASC, and caspase-1 levels.

RESULTS

After NSPT, improvement was observed in all clinical parameters, along with periodontal inflamed surface area (PISA) in gingivitis and periodontitis groups. PISA scores were positively correlated with IL-1β, NLRP3, and caspase-1 at baseline (p < 0.05). Salivary and serum IL-1β, NLRP3 levels were higher in periodontitis compared to healthy controls at baseline and reduced after treatment (p < 0.05). Receiver operating characteristic analysis revealed that salivary IL-1β, NLRP3, and caspase-1 had the ability to discriminate SIIIGC periodontitis patients from healthy subjects (p < 0.05).

CONCLUSION

In conclusion, salivary IL-1β, NLRP3, and caspase-1 are at aberrantly high levels in SIIIGC periodontitis and are remarkably decreased following NSPT; these inflammasome biomarkers may show potential utility in diagnosing and monitoring periodontitis.

Effect of Pulsatilla decoction on vulvovaginal candidiasis in mice. Evidences for its mechanisms of action

BACKGROUND

Vulvovaginal candidiasis (VVC) is a common infection that affects the female reproductive tract. Pulsatilla decoction (PD), a traditional Chinese herbal medicine, is a classic and effective prescription for VVC. However, its mechanism of action remains unclear.

PURPOSE

This study aimed to evaluate the efficacy and potential mechanism of action of the n-butanol extract of Pulsatilla decoction (BEPD) in VVC treatment.

METHODS

High performance liquid chromatography (HPLC) was used to detect the main active ingredients in BEPD. A VVC-mouse model was constructed using an estrogen-dependent method to evaluate the efficacy of BEPD in VVC treatment. Fungal burden and morphology in the vaginal cavity were comprehensively assessed. Candida albicans-induced inflammation was examined in vivo and in vitro. The effects of BEPD on the Protein kinase Cδ (PKCδ) /NLR family CARD domain-containing protein 4 (NLRC4)/Interleukin-1 receptor antagonist (IL-1Ra) axis were analyzed using by immunohistochemistry (IHC), immunofluorescence (IF), western blot (WB), and reverse transcription-quantitative polymerase chain reaction (qRT-PCR).

RESULTS

BEPD inhibited fungal growth in the vagina of VVC mice, preserved the integrity of the vaginal mucosa, and suppressed inflammatory responses. Most importantly, BEPD activated the "silent" PKCδ/NLRC4/IL-1Ra axis and negatively regulated NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome, thereby exerting a therapeutic efficacy on VVC.

CONCLUSIONS

BEPD effects on mice with VVC were dose-dependent. BEPD protects against VVC by inhibiting inflammatory response and NLRP3 inflammasome via the activation of the PKCδ/NLRC4/IL-1Ra axis. This study revealed the pharmacological mechanism of BEPD in VVC treatment and provided further evidence for the application of BEPD in VVC treatment.

Sirtuin 6 Deacetylates Apoptosis-Associated Speck-Like Protein (ASC) to Inhibit Endothelial Cell Pyroptosis in Atherosclerosis

Endothelial cell dysfunction is the main pathology of atherosclerosis (AS). Sirtuin 6 (SIRT6), a deacetylase, is involved in AS progression. This study aimed to investigate the impacts of SIRT6 on the pyroptosis of endothelial cells and its underlying mechanisms. ApoE-/- mice were fed a high-fat diet (HFD) to establish the AS mouse model, atherosclerotic lesions were evaluated using oil red O staining, and blood lipids and inflammatory factors were measured using corresponding kits. Human umbilical vein endothelial cells (HUVECs) were treated with oxidized low-density lipoprotein (ox-LDL) to establish the cell model, and pyroptosis was evaluated by flow cytometry, ELISA, and western blot. Immunoprecipitation (IP), co-IP, western blot, and immunofluorescence were used to detect the molecular mechanisms. The results showed that SIRT6 expression was downregulated in the blood of HFD-induced mice and ox-LDL-induced HUVECs. Overexpression of SIRT6 reduced atherosclerotic lesions, blood lipids, and inflammation in vivo and suppressed pyroptosis of HUVECs in vitro. Moreover, SIRT6 interacted with ASC to inhibit the acetylation of ASC, thus, reducing the interaction between ASC and NLRP3. Moreover, SIRT6 inhibits endothelial cell pyroptosis in the aortic roots of mice by deacetylating ASC. In conclusion, SIRT6 deacetylated ASC to inhibit its interaction with NLRP3 and then suppressed pyroptosis of endothelial cells, thus, decelerating the progression of AS. The findings provide new insights into the function of SIRT6 in AS.

[The effect of the AIM2 inflammasome in noise-induced cognitive dysfunction in rats]

Objective: To explore the effect of the absent in melanoma 2 (AIM2) -mediated neuroinflammation in noise-induced cognitive dysfunction in rats. Methods: In April 2023, sixteen male Wistar rats were randomly divided into control group and noise group, with 8 rats in each group. The rats in the noise group were placed in 50 cm×50 cm×40 cm transparent boxes and exposed to 100 dB (A) white noise with a sound pressure level of 100 dB (A) (4 h/d for 30 d) . At the same time, rats in the control group were kept in similar boxes with environmental noise less than 60 dB (A) . After 30 days of noise exposure, the Morris water maze experiment was applied to test the learning and memory abilities of the rats; the pathological morphology of hippocampal tissues was observed by Hematoxylin-Eosin (HE) staining. Western blot was used to detect the protein expression levels of AIM2, cysteinyl aspartate specific proteinase-1 (caspase-1) , apoptosis-associated speck-like protein (ASC) , interleukin-1β (IL-1β) , IL-18, ionic calcium-binding articulation molecule-1 (Iba-1) , and glial fibrillary acidic protein (GFAP) . The expression of both Iba-1 and GFAP in hippocampal tissue was assessed by immunohistochemical staining. The co-localization of AIM2 with Iba-1 or GFAP was determined by immunofluorescence double staining. Results: Compared with the control group, the escape latency of rats in the noise group was increased by 16.29 s, 17.71 s, and 20.26 s on days 3, 4, and 5, respectively. On day 6, the noise-exposed rats spent shorter time in the target quadrant and had fewer times in crossing the platform[ (7.25±2.27) s and (1.13±0.64) times] than the control group[ (15.64±3.99) s and (4.25±2.12) times] (P<0.05) . After noise exposure, hippocampal neurons of rats displayed marked nuclear hyperchromatic and pyknosis phenomenon. The noise-exposed rats had higher numbers of both microglia and astrocytes (27.00±2.65 and 43.33±5.51) in the DG area of the hippocampus relative to the control group (14.67±3.06 and 20.00±4.58) (P<0.05) . Moreover, the glial cells in the noise group had larger cell cytosol with more and thicker branches. The protein expression levels of inflammatory cytokines Cleaved-IL-1β and Cleaved-IL-18 in the hippocampus of rats in the noise group (1.55±0.19 and 1.74±0.12) were significantly higher than the control group (1.00±0.11 and 1.00±0.13) (P<0.05) . After noise exposure, the protein expression levels of AIM2, Cleaved-Caspase-1 and ASC (1.19±0.09, 1.34±0.07 and 1.14±0.01) were higher than the control group (1.00±0.07, 1.00±0.14 and 1.00±0.06) and differences between the two groups were statistically significant (P<0.05) . A significant increase in the number of cells co-localizing AIM2 with Iba-1 or GFAP in the noise group (28.67±4.04 and 40.67±5.13) compared with the control group (15.67±4.04 and 17.67±3.79) , and statistically significant differences were observed between the two groups (P<0.05) . Conclusion: Noise exposure may activate the AIM2 inflammasome in hippocampal glial cells of rats, releasing excessive inflammatory cytokines and causing neuroinflammation that damages neurons.

Cutaneous inflammasome driving ASC / gasdermin-D activation and IL-1β-secreting macrophages in severe atopic dermatitis

Atopic dermatitis (AD) is an inflammatory skin disease with intense pruritus, and chronic skin colonization by Staphylococcus aureus. To understand the inflammatory status in AD, we investigated the inflammasome complex, that activates ASC (Apoptosis-associated speck-like protein containing a CARD), caspase-1 and GSDMD (gasdermin-D), and production of IL-1β and IL-18. We aimed to evaluate the expression of the inflammasome pathway in the skin of adults with AD. Thirty patients with moderate to severe AD and 20 healthy controls were enrolled in the study. We performed the analysis of the inflammasome components NLRP1, NLRP3, AIM-2, IL-1β, IL-18, Caspase-1, ASC, GSDMD, and CD68 expression (macrophage marker) by immunohistochemistry and immunofluorescence. The main findings included increased expression of NLRP3, NLRP1 and AIM-2 at dermal level of severe AD; augmented IL-18 and IL-1β expression at epidermis of moderate and severe patients, and in the dermis of severe AD; augmented expression of ASC, caspase-1 and GSDMD in both epidermis and dermis of moderate and severe AD. We detected positive correlation between caspase-1, GSDMD and IL-1β (epidermis) and caspase-1 (dermis) and AD severity; NLRP3, AIM-2 and IL-1β, and NLRP3 with IL-18 in the epidermis; ASC, GSDMD and IL-1β, and NLRP3, AIM-2, caspase-1, and IL-18 in the dermis. We also evidenced the presence of CD68+ macrophages secreting GSDMD, ASC and IL-1β in moderate and severe AD. Cutaneous macrophages, early detected in moderate AD, have its role in the disease inflammatory mechanisms. Our study indicates a canonical activation pathway of inflammasomes, reinforced by the chronic status of inflammation in AD. The analysis of the inflammasome complex evidenced an imbalance in its regulation, with increased expression of the evaluated components, which is remarkably in severe AD, emphasizing its relevance as potential disease biomarkers and targets for immunomodulatory interventions.

Severe neurological impairment and immune function: altered neutrophils, monocytes, T lymphocytes, and inflammasome activation

BACKGROUND

Infections cause significant morbidity and mortality in children with Severe Neurological Impairment (SNI). Alterations in immune cell numbers and function in children with neurodisability have been reported. We aimed to characterise neutrophil, monocyte and lymphocyte proportions and activation, at baseline and in response to stimulation with lipopolysaccharide, in children with SNI compared to healthy controls.

METHODS

Whole blood samples of children with SNI and controls were incubated in the presence or absence of lipopolysaccharide (10 ng/ml). Monocyte and neutrophil function (Cluster of Differentiation (CD)11b, (TLR)-4 and CD66b expression) and lymphocytes were assessed by flow cytometry. Expression of genes involved in the inflammasome (NLR Family Pyrin Domain Containing(NLRP)-3, Apoptosis-Associated Speck-like protein (ASC) and Interleukin(IL)1β) were assessed by PCR.

RESULTS

Monocytes and CD8+ T cells were lower in children with SNI (n = 14). CD66b, was hyporesponsive and monocyte TLR4 was hyperresponsive to lipopolysaccharide in children with SNI compared to controls (n = 14). NLRP3 expression was higher at baseline and IL1β expression was not upregulated in response to lipopolysaccharide in children with SNI in contrast to controls.

CONCLUSION

We have found significant differences in immune regulation in children with SNI compared to controls which may provide a useful therapeutic target in the future.

IMPACT

Children with SNI have reduced monocyte and CD8+ T cells. Neutrophils and monocytes in children with SNI show altered markers of activation in response to lipopolysaccharide. Expression of NLRP3 at the RNA level was higher at baseline in children with SNI. This study adds to the existing literature that children with neurological impairment have altered inflammatory and immune cell responses. This may provide a useful therapeutic target to reduce infection-related morbidity and mortality, and tertiary neurological injury in the future.

Optogenetically controlled inflammasome activation demonstrates two phases of cell swelling during pyroptosis

Inflammasomes are multiprotein platforms that control caspase-1 activation, which process the inactive precursor forms of the inflammatory cytokines IL-1β and IL-18, leading to an inflammatory type of programmed cell death called pyroptosis. Studying inflammasome-driven processes, such as pyroptosis-induced cell swelling, under controlled conditions remains challenging because the signals that activate pyroptosis also stimulate other signaling pathways. We designed an optogenetic approach using a photo-oligomerizable inflammasome core adapter protein, apoptosis-associated speck-like containing a caspase recruitment domain (ASC), to temporally and quantitatively manipulate inflammasome activation. We demonstrated that inducing the light-sensitive oligomerization of ASC was sufficient to recapitulate the classical features of inflammasomes within minutes. This system showed that there were two phases of cell swelling during pyroptosis. This approach offers avenues for biophysical investigations into the intricate nature of cellular volume control and plasma membrane rupture during cell death.

Human NLRC4 expression promotes cancer survival and associates with type I interferon signaling and immune infiltration

The immune system can control cancer progression. However, even though some innate immune sensors of cellular stress are expressed intrinsically in epithelial cells, their potential role in cancer aggressiveness and subsequent overall survival in humans is mainly unknown. Here, we show that nucleotide-binding oligomerization domain-like receptor (NLR) family CARD domain-containing 4 (NLRC4) is downregulated in epithelial tumor cells of patients with colorectal cancer (CRC) by using spatial tissue imaging. Strikingly, only the loss of tumor NLRC4, but not stromal NLRC4, was associated with poor immune infiltration (mainly DCs and CD4+ and CD8+ T cells) and accurately predicted progression to metastatic stage IV and decrease in overall survival. By combining multiomics approaches, we show that restoring NLRC4 expression in human CRC cells triggered a broad inflammasome-independent immune reprogramming consisting of type I interferon (IFN) signaling genes and the release of chemokines and myeloid growth factors involved in the tumor infiltration and activation of DCs and T cells. Consistently, such reprogramming in cancer cells was sufficient to directly induce maturation of human DCs toward a Th1 antitumor immune response through IL-12 production in vitro. In multiple human carcinomas (colorectal, lung, and skin), we confirmed that NLRC4 expression in patient tumors was strongly associated with type I IFN genes, immune infiltrates, and high microsatellite instability. Thus, we shed light on the epithelial innate immune sensor NLRC4 as a therapeutic target to promote an efficient antitumor immune response against the aggressiveness of various carcinomas.

Neem leaf glycoprotein binding to Dectin-1 receptors on dendritic cell induces type-1 immunity through CARD9 mediated intracellular signal to NFκB

BACKGROUND

A water-soluble ingredient of mature leaves of the tropical mahogany 'Neem' (Azadirachta indica), was identified as glycoprotein, thus being named as 'Neem Leaf Glycoprotein' (NLGP). This non-toxic leaf-component regressed cancerous murine tumors (melanoma, carcinoma, sarcoma) recurrently in different experimental circumstances by boosting prime antitumor immune attributes. Such antitumor immunomodulation, aid cytotoxic T cell (Tc)-based annihilation of tumor cells. This study focused on identifying and characterizing the signaling gateway that initiate this systemic immunomodulation. In search of this gateway, antigen-presenting cells (APCs) were explored, which activate and induce the cytotoxic thrust in Tc cells.

METHODS

Six glycoprotein-binding C-type lectins found on APCs, namely, MBR, Dectin-1, Dectin-2, DC-SIGN, DEC205 and DNGR-1 were screened on bone marrow-derived dendritic cells from C57BL/6 J mice. Fluorescence microscopy, RT-PCR, flow cytometry and ELISA revealed Dectin-1 as the NLGP-binding receptor, followed by verifications through RNAi. Following detection of β-Glucans in NLGP, their interactions with Dectin-1 were explored in silico. Roles of second messengers and transcription factors in the downstream signal were studied by co-immunoprecipitation, western blotting, and chromatin-immunoprecipitation. Intracellularization of FITC-coupled NLGP was observed by processing confocal micrographs of DCs.

RESULTS

Considering extents of hindrance in NLGP-driven transcription rates of the cytokines IL-10 and IL-12p35 by receptor-neutralization, Dectin-1 receptors on dendritic cells were found to bind NLGP through the ligand's peripheral β-Glucan chains. The resulting signal phosphorylates PKCδ, forming a trimolecular complex of CARD9, Bcl10 and MALT1, which in turn activates the canonical NFκB-pathway of transcription-regulation. Consequently, the NFκB-heterodimer p65:p50 enhances Il12a transcription and the p50:p50 homodimer represses Il10 transcription, bringing about a cytokine-based systemic-bias towards type-1 immune environment. Further, NLGP gets engulfed within dendritic cells, possibly through endocytic activities of Dectin-1.

CONCLUSION

NLGP's binding to Dectin-1 receptors on murine dendritic cells, followed by the intracellular signal, lead to NFκB-mediated contrasting regulation of cytokine-transcriptions, initiating a pro-inflammatory immunopolarization, which amplifies further by the responding immune cells including Tc cells, alongside their enhanced cytotoxicity. These insights into the initiation of mammalian systemic immunomodulation by NLGP at cellular and molecular levels, may help uncovering its mode of action as a novel immunomodulator against human cancers, following clinical trials.

CARD11 regulates the thymic Treg development in an NF-κB-independent manner

Introduction

CARD11 is a lymphoid lineage-specific scaffold protein regulating the NF-κB activation downstream of the antigen receptor signal pathway. Defective CARD11 function results in abnormal development and differentiation of lymphocytes, especially thymic regulatory T cells (Treg).

Method

In this study, we used patients' samples together with transgenic mouse models carrying pathogenic CARD11 mutations from patients to explore their effects on Treg development. Immunoblotting and a GFP receptor assay were used to evaluate the activation effect of CARD11 mutants on NF-κB signaling. Then the suppressive function of Tregs carrying distinct CARD11 mutations was measured by in vitro suppression assay. Finally, we applied the retroviral transduced bone marrow chimeras to rescue the Treg development in an NF-κB independent manner.

Results and discuss

We found CARD11 mutations causing hyper-activated NF-κB signals also gave rise to compromised Treg development in the thymus, similar to the phenotype in Card11 deficient mice. This observation challenges the previous view that CARD11 regulates Treg lineage dependent on the NF-kB activation. Mechanistic investigations reveal that the noncanonical function CARD11, which negatively regulates the AKT/ FOXO1 signal pathway, is responsible for regulating Treg generation. Moreover, primary immunodeficiency patients carrying CARD11 mutation, which autonomously activates NF-κB, also represented the reduced Treg population in their peripheral blood. Our results propose a new regulatory function of CARD11 and illuminate an NF-κB independent pathway for thymic Treg lineage commitment.

Direct Salmonella injection into enteroid cells allows the study of host-pathogen interactions in the cytosol with high spatiotemporal resolution

Intestinal epithelial cells (IECs) play pivotal roles in nutrient uptake and in the protection against gut microorganisms. However, certain enteric pathogens, such as Salmonella enterica serovar Typhimurium (S. Tm), can invade IECs by employing flagella and type III secretion systems (T3SSs) with cognate effector proteins and exploit IECs as a replicative niche. Detection of flagella or T3SS proteins by IECs results in rapid host cell responses, i.e., the activation of inflammasomes. Here, we introduce a single-cell manipulation technology based on fluidic force microscopy (FluidFM) that enables direct bacteria delivery into the cytosol of single IECs within a murine enteroid monolayer. This approach allows to specifically study pathogen-host cell interactions in the cytosol uncoupled from preceding events such as docking, initiation of uptake, or vacuole escape. Consistent with current understanding, we show using a live-cell inflammasome reporter that exposure of the IEC cytosol to S. Tm induces NAIP/NLRC4 inflammasomes via its known ligands flagellin and T3SS rod and needle. Injected S. Tm mutants devoid of these invasion-relevant ligands were able to grow in the cytosol of IECs despite the absence of T3SS functions, suggesting that, in the absence of NAIP/NLRC4 inflammasome activation and the ensuing cell death, no effector-mediated host cell manipulation is required to render the epithelial cytosol growth-permissive for S. Tm. Overall, the experimental system to introduce S. Tm into single enteroid cells enables investigations into the molecular basis governing host-pathogen interactions in the cytosol with high spatiotemporal resolution.

[Chronic intermittent hypoxia activates NLRP1 inflammasome and causes liver injury]

Objective To investigate the liver injury induced by chronic intermittent hypoxia (CIH) activation of NOD-like receptor pyrin domain containing protein 1 (NLRP1) inflammasome. Methods C57BL/6 male mice were randomly divided into control group and CIH group. Mice in CIH group were put into CIH chamber for molding (8 hours a day for 4 weeks). After 4 weeks of molding, liver tissue cells was observed by HE staining, and the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum of mice were detected by kit. The levels of reactive oxygen species (ROS) in liver tissue were detected by dihydroethidine (DHE). The expression and localization of NLRP1, apoptosis speck-like protein containing a caspase activation and recruiting domain (ASC) and caspase-1 were detected by immunohistochemical staining. The protein expressions of NLRP1, ASC, caspase-1, interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) were detected by Western blot analysis. The serum levels of IL-1β and TNF-α were detected by ELISA. Results Compared with the control group, the CIH group exhibited significant pathological changes in hepatocytes. Hepatocytes showed signs of rupture and necrosis, accompanied by inflammatory cell aggregation. Furthermore, the levels of ALT, AST, ROS, IL-1β and TNF-α were elevated, along with increased protein expressions of NLRP1, ASC, caspase-1, IL-1β and TNF-α. Conclusion CIH causes liver injury by activating NLRP1 inflammasome.

NLRC4-mediated pyroptosis was involved in coagulation disorders of acute pancreatitis

BACKGROUND

Acute pancreatitis (AP) is a potentially lethal acute disease highly involved in coagulation disorders. Pyroptosis has been reported to exacerbate coagulation disorders, yet this implication has not been illustrated completely in AP.

METHODS

RNA sequencing data of peripheral blood of AP patients were downloaded from the Gene Expression Omnibus database. Gene set variation analysis and single sample gene set enrichment analysis were used to calculate the enrichment score of coagulation-related signatures and pyroptosis. Spearman and Pearson correlation analysis was used for correlation analysis. Peripheral blood samples and related clinical parameters were collected from patients with AP and healthy individuals. A severe AP (SAP) model of mice was established using caerulein and lipopolysaccharide. Enzyme-linked immunosorbent assay, chemiluminescence immunoassay and immunohistochemical analysis were employed to detect the level of coagulation indicators and pyroptosis markers in serum and pancreas tissues. Additionally, we evaluated the effect of pyroptosis inhibition and NLRC4 silence on the function of human umbilical vein endothelial cells (HUVECs).

RESULTS

Coagulation disorders were significantly positively correlated to the severity of AP, and they could be a predictor for AP severity. Further analyses indicated that six genes-DOCK9, GATA3, FCER1G, NLRC4, C1QB and C1QC-may be involved in coagulation disorders of AP. Among them, NLRC4 was positively related to pyroptosis that had a positive association with most coagulation-related signatures. Data from patients showed that NLRC4 and other pyroptosis markers, including IL-1β, IL-18, caspase1 and GSDMD, were significant correlation to AP severity. In addition, NLRC4 was positively associated with coagulation indicators in AP patients. Data from mice showed that NLRC4 was increased in the pancreas tissues of SAP mice. Treatment with a pyroptosis inhibitor effectively alleviated SAP and coagulation disorders in mice. Finally, inhibiting pyroptosis or silencing NLRC4 could relieve endothelial dysfunction in HUVECs.

CONCLUSIONS

NLRC4-mediated pyroptosis damages the function of endothelial cells and thereby exacerbates coagulation disorders of AP. Inhibiting pyroptosis could improve coagulation function and alleviate AP.

Translational genetics identifies a phosphorylation switch in CARD9 required for innate inflammatory responses

Population genetics continues to identify genetic variants associated with diseases of the immune system and offers a unique opportunity to discover mechanisms of immune regulation. Multiple genetic variants linked to severe fungal infections and autoimmunity are associated with caspase recruitment domain-containing protein 9 (CARD9). We leverage the CARD9 R101C missense variant to uncover a biochemical mechanism of CARD9 activation essential for antifungal responses. We demonstrate that R101C disrupts a critical signaling switch whereby phosphorylation of S104 releases CARD9 from an autoinhibited state to promote inflammatory responses in myeloid cells. Furthermore, we show that CARD9 R101C exerts dynamic effects on the skin cellular contexture during fungal infection, corrupting inflammatory signaling and cell-cell communication circuits. Card9 R101C mice fail to control dermatophyte infection in the skin, resulting in high fungal burden, yet show minimal signs of inflammation. Together, we demonstrate how translational genetics reveals molecular and cellular mechanisms of innate immune regulation.

Protocol to measure apoptosis-associated speck-like protein containing a CARD specks in human cerebrospinal fluid via imaging flow cytometry

Apoptosis-associated speck-like protein containing a c-terminal caspase activation and recruitment domain (ASC) specks are elevated in the cerebrospinal fluid (CSF) of Alzheimer's disease and related dementias (AD/ADRDs) patients. Here, we present a flow cytometry protocol to quantify ASC specks. We describe steps for fluorescently labeling ASC specks using antibody technology, visualizing with imaging flow cytometry, and gating based on physical characteristics. CSF ASC specks levels positively correlate with phosphorylated tau (Thr181) and negatively correlate with amyloid β ratio (42/40), thus serving as a neuroinflammatory biomarker for diagnosing AD/ADRDs. For complete details on the use and execution of this protocol, please refer to Jiang et al.1.

NFκB and NLRP3/NLRC4 inflammasomes regulate differentiation, activation and functional properties of monocytes in response to distinct SARS-CoV-2 proteins

Increased recruitment of transitional and non-classical monocytes in the lung during SARS-CoV-2 infection is associated with COVID-19 severity. However, whether specific innate sensors mediate the activation or differentiation of monocytes in response to different SARS-CoV-2 proteins remain poorly characterized. Here, we show that SARS-CoV-2 Spike 1 but not nucleoprotein induce differentiation of monocytes into transitional or non-classical subsets from both peripheral blood and COVID-19 bronchoalveolar lavage samples in a NFκB-dependent manner, but this process does not require inflammasome activation. However, NLRP3 and NLRC4 differentially regulated CD86 expression in monocytes in response to Spike 1 and Nucleoprotein, respectively. Moreover, monocytes exposed to Spike 1 induce significantly higher proportions of Th1 and Th17 CD4 + T cells. In contrast, monocytes exposed to Nucleoprotein reduce the degranulation of CD8 + T cells from severe COVID-19 patients. Our study provides insights in the differential impact of innate sensors in regulating monocytes in response to different SARS-CoV-2 proteins, which might be useful to better understand COVID-19 immunopathology and identify therapeutic targets.

Pycard deficiency inhibits microRNA maturation and prevents neointima formation by promoting chaperone-mediated autophagic degradation of AGO2/argonaute 2 in adipose tissue

PYCARD (PYD and CARD domain containing), a pivotal adaptor protein in inflammasome assembly and activation, contributes to innate immunity, and plays an essential role in the pathogenesis of atherosclerosis and restenosis. However, its roles in microRNA biogenesis remain unknown. Therefore, this study aimed to investigate the roles of PYCARD in miRNA biogenesis and neointima formation using pycard knockout (pycard-/-) mice. Deficiency of Pycard reduced circulating miRNA profile and inhibited Mir17 seed family maturation. The systemic pycard knockout also selectively reduced the expression of AGO2 (argonaute RISC catalytic subunit 2), an important enzyme in regulating miRNA biogenesis, by promoting chaperone-mediated autophagy (CMA)-mediated degradation of AGO2, specifically in adipose tissue. Mechanistically, pycard knockout increased PRMT8 (protein arginine N-methyltransferase 8) expression in adipose tissue, which enhanced AGO2 methylation, and subsequently promoted its binding to HSPA8 (heat shock protein family A (Hsp70) member 8) that targeted AGO2 for lysosome degradation through chaperone-mediated autophagy. Finally, the reduction of AGO2 and Mir17 family expression prevented vascular injury-induced neointima formation in Pycard-deficient conditions. Overexpression of AGO2 or administration of mimic of Mir106b (a major member of the Mir17 family) prevented Pycard deficiency-mediated inhibition of neointima formation in response to vascular injury. These data demonstrate that PYCARD inhibits CMA-mediated degradation of AGO2, which promotes microRNA maturation, thereby playing a critical role in regulating neointima formation in response to vascular injury independently of inflammasome activity and suggest that modulating PYCARD expression and function may represent a powerful therapeutic strategy for neointima formation.Abbreviations: 6-AN: 6-aminonicotinamide; ACTB: actin, beta; aDMA: asymmetric dimethylarginine; AGO2: argonaute RISC catalytic subunit 2; CAL: carotid artery ligation; CALCOCO2: calcium binding and coiled-coil domain 2; CMA: chaperone-mediated autophagy; CTSB: cathepsin B; CTSD: cathepsin D; DGCR8: DGCR8 microprocessor complex subunit; DOCK2: dedicator of cyto-kinesis 2; EpiAdi: epididymal adipose tissue; HSPA8: heat shock protein family A (Hsp70) member 8; IHC: immunohistochemical; ISR: in-stent restenosis; KO: knockout; LAMP2: lysosomal-associated membrane protein 2; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; miRNA: microRNA; NLRP3: NLR family pyrin domain containing 3; N/L: ammonium chloride combined with leupeptin; PRMT: protein arginine methyltransferase; PVAT: peri-vascular adipose tissues; PYCARD: PYD and CARD domain containing; sDMA: symmetric dimethylarginine; ULK1: unc-51 like kinase 1; VSMCs: vascular smooth muscle cells; WT: wild-type.

Pharmacological approaches to promote cell death of latent HIV reservoirs

PURPOSE OF REVIEW

HIV requires lifelong antiviral treatment due to the persistence of a reservoir of latently infected cells. Multiple strategies have been pursued to promote the death of infected cells.

RECENT FINDINGS

Several groups have focused on multipronged approaches to induce apoptosis of infected cells. One approach is to combine latency reversal agents with proapoptotic compounds and cytotoxic T cells to first reactivate and then clear infected cells. Other strategies include using natural killer cells or chimeric antigen receptor cells to decrease the size of the reservoir.A novel strategy is to promote cell death by pyroptosis. This mechanism relies on the activation of the caspase recruitment domain-containing protein 8 (CARD8) inflammasome by the HIV protease and can be potentiated by nonnucleoside reverse transcriptase inhibitors.

SUMMARY

The achievement of a clinically significant reduction in the size of the reservoir will likely require a combination strategy since none of the approaches pursued so far has been successful on its own in clinical trials. This discrepancy between promising in vitro findings and modest in vivo results highlights the hurdles of identifying a universally effective strategy given the wide heterogeneity of the HIV reservoirs in terms of tissue location, capability to undergo latency reversal and susceptibility to cell death.

The CARD8 inflammasome dictates HIV/SIV pathogenesis and disease progression

While CD4+ T cell depletion is key to disease progression in people living with HIV and SIV-infected macaques, the mechanisms underlying this depletion remain incompletely understood, with most cell death involving uninfected cells. In contrast, SIV infection of "natural" hosts such as sooty mangabeys does not cause CD4+ depletion and AIDS despite high-level viremia. Here, we report that the CARD8 inflammasome is activated immediately after HIV entry by the viral protease encapsulated in incoming virions. Sensing of HIV protease activity by CARD8 leads to rapid pyroptosis of quiescent cells without productive infection, while T cell activation abolishes CARD8 function and increases permissiveness to infection. In humanized mice reconstituted with CARD8-deficient cells, CD4+ depletion is delayed despite high viremia. Finally, we discovered loss-of-function mutations in CARD8 from "natural hosts," which may explain the peculiarly non-pathogenic nature of these infections. Our study suggests that CARD8 drives CD4+ T cell depletion during pathogenic HIV/SIV infections.

Inherently Reduced Expression of ASC Restricts Caspase-1 Processing in Hepatocytes and Promotes Plasmodium Infection

Inflammasome-mediated caspase-1 activation facilitates innate immune control of Plasmodium in the liver, thereby limiting the incidence and severity of clinical malaria. However, caspase-1 processing occurs incompletely in both mouse and human hepatocytes and precludes the generation of mature IL-1β or IL-18, unlike in other cells. Why this is so or how it impacts Plasmodium control in the liver has remained unknown. We show that an inherently reduced expression of the inflammasome adaptor molecule apoptosis-associated specklike protein containing CARD (ASC) is responsible for the incomplete proteolytic processing of caspase-1 in murine hepatocytes. Transgenically enhancing ASC expression in hepatocytes enabled complete caspase-1 processing, enhanced pyroptotic cell death, maturation of the proinflammatory cytokines IL-1β and IL-18 that was otherwise absent, and better overall control of Plasmodium infection in the liver of mice. This, however, impeded the protection offered by live attenuated antimalarial vaccination. Tempering ASC expression in mouse macrophages, on the other hand, resulted in incomplete processing of caspase-1. Our work shows how caspase-1 activation and function in host cells are fundamentally defined by ASC expression and offers a potential new pathway to create better disease and vaccination outcomes by modifying the latter.

Naturally occurring T cell mutations enhance engineered T cell therapies

Adoptive T cell therapies have produced exceptional responses in a subset of patients with cancer. However, therapeutic efficacy can be hindered by poor T cell persistence and function1. In human T cell cancers, evolution of the disease positively selects for mutations that improve fitness of T cells in challenging situations analogous to those faced by therapeutic T cells. Therefore, we reasoned that these mutations could be co-opted to improve T cell therapies. Here we systematically screened the effects of 71 mutations from T cell neoplasms on T cell signalling, cytokine production and in vivo persistence in tumours. We identify a gene fusion, CARD11-PIK3R3, found in a CD4+ cutaneous T cell lymphoma2, that augments CARD11-BCL10-MALT1 complex signalling and anti-tumour efficacy of therapeutic T cells in several immunotherapy-refractory models in an antigen-dependent manner. Underscoring its potential to be deployed safely, CARD11-PIK3R3-expressing cells were followed up to 418 days after T cell transfer in vivo without evidence of malignant transformation. Collectively, our results indicate that exploiting naturally occurring mutations represents a promising approach to explore the extremes of T cell biology and discover how solutions derived from evolution of malignant T cells can improve a broad range of T cell therapies.

Novel PI(3)K-p85α/p110δ-ITK-LAT-PLC-γ2 and Fyn-ADAP-Carma1-TAK1 Pathways Define Reverse Signaling via FasL

The role of FasL in initiating death signals through Fas is well characterized. However, the reverse signaling pathway downstream of FasL in effector lymphocytes is poorly understood. Here, we identify that FasL functions as an independent activation receptor in NK cells. Activation via FasL results in the production of LFN-γ, GM-CSF, RANTES, MIP-1α, and MIP1-β. Proximal signaling of FasL requires Lck and Fyn. Upon activation, FasL facilitates the phosphorylation of PI(3)K-p85α/p55α subunits. A catalytically inactive PI(3)K-p110δD910A mutation significantly impairs the cytokine and chemokine production by FasL. Activation of ITK and LAT downstream of FasL plays a central role in recruiting and phosphorylating PLC-γ2. Importantly, Fyn-mediated recruitment of ADAP links FasL to the Carmal/ Bcl10/Tak1 signalosome. Lack of Carma1, CARD domain of Carma1, or Tak1 significantly reduces FasL-mediated cytokine and chemokine production. These findings, for the first time, provide a detailed molecular blueprint that defines FasL-mediated reverse signaling.

Candida albicans extracellular vesicles trigger type I IFN signalling via cGAS and STING

The host type I interferon (IFN) pathway is a major signature of inflammation induced by the human fungal pathogen, Candida albicans. However, the molecular mechanism for activating this pathway in the host defence against C. albicans remains unknown. Here we reveal that mice lacking cyclic GMP-AMP synthase (cGAS)-stimulator of IFN genes (STING) pathway components had improved survival following an intravenous challenge by C. albicans. Biofilm-associated C. albicans DNA packaged in extracellular vesicles triggers the cGAS-STING pathway as determined by induction of interferon-stimulated genes, IFNβ production, and phosphorylation of IFN regulatory factor 3 and TANK-binding kinase 1. Extracellular vesicle-induced activation of type I IFNs was independent of the Dectin-1/Card9 pathway and did not require toll-like receptor 9. Single nucleotide polymorphisms in cGAS and STING potently altered inflammatory cytokine production in human monocytes challenged by C. albicans. These studies provide insights into the early innate immune response induced by a clinically significant fungal pathogen.