Neutrophil extracellular traps mediate bone erosion in rheumatoid arthritis by enhancing RANKL-induced osteoclastogenesis.

BACKGROUND AND PURPOSE: Rheumatoid arthritis (RA) is a chronic autoimmune disease that can cause bone erosion due to increased osteoclastogenesis. Neutrophils involvement in osteoclastogenesis remains uncertain. Given that neutrophil extracellular traps (NETs) can act as inflammatory mediators in rheumatoid arthritis, we investigated the role of NETs in stimulating bone loss by potentiating osteoclastogenesis during arthritis. EXPERIMENTAL APPROACH: The level of NETs in synovial fluid from arthritis patients was assessed. Bone loss was evaluated by histology and micro-CT in antigen-induced arthritis (AIA)-induced WT mice treated with DNase or in Padi4-deficient mice (Padi4flox/flox LysMCRE ). The size and function of osteoclasts and the levels of RANKL and osteoprotegerin (OPG) released by osteoblasts that were incubated with NETs were measured. The expression of osteoclastogenic marker genes and protein levels were evaluated by qPCR and western blotting. To assess the participation of TLR4 and TLR9 in osteoclastogenesis, cells from Tlr4-/- and Tlr9-/- mice were cultured with NETs. KEY RESULTS: Rheumatoid arthritis patients had higher levels of NETs in synovial fluid than osteoarthritis patients, which correlated with increased levels of RANKL/OPG. Moreover, patients with bone erosion had higher levels of NETs. Inhibiting NETs with DNase or Padi4 deletion alleviated bone loss in arthritic mice. Consistently, NETs enhanced RANKL-induced osteoclastogenesis that was dependent on TLR4 and TLR9 and increased osteoclast resorptive functions in vitro. In addition, NETs stimulated the release of RANKL and inhibited osteoprotegerin in osteoblasts, favouring osteoclastogenesis. CONCLUSIONS AND IMPLICATIONS: Inhibiting NETs could be an alternative strategy to reduce bone erosion in arthritis patients.

Paediatric sepsis survivors are resistant to sepsis-induced long-term immune dysfunction.

BACKGROUND AND PURPOSE: Sepsis-surviving adult individuals commonly develop immunosuppression and increased susceptibility to secondary infections, an outcome mediated by the axis IL-33/ILC2s/M2 macrophages/Tregs. Nonetheless, the long-term immune consequences of paediatric sepsis are indeterminate. We sought to investigate the role of age in the genesis of immunosuppression following sepsis. EXPERIMENTAL APPROACH: Here, we compared the frequency of Tregs, the activation of the IL-33/ILC2s axis in M2 macrophages and the DNA methylation of epithelial lung cells from post-septic infant and adult mice. Likewise, sepsis-surviving mice were inoculated intranasally with Pseudomonas aeruginosa or by subcutaneous inoculation of the B16 melanoma cell line. Finally, blood samples from sepsis-surviving patients were collected and the concentration of IL-33 and Tregs frequency were assessed. KEY RESULTS: In contrast to 6-week-old mice, 2-week-old mice were resistant to secondary infection and did not show impairment in tumour controls upon melanoma challenge. Mechanistically, increased IL-33 levels, Tregs expansion, and activation of ILC2s and M2-macrophages were observed in 6-week-old but not 2-week-old post-septic mice. Moreover, impaired IL-33 production in 2-week-old post-septic mice was associated with increased DNA methylation in lung epithelial cells. Notably, IL-33 treatment boosted the expansion of Tregs and induced immunosuppression in 2-week-old mice. Clinically, adults but not paediatric post-septic patients exhibited higher counts of Tregs and seral IL-33 levels. CONCLUSION AND IMPLICATIONS: These findings demonstrate a crucial and age-dependent role for IL-33 in post-sepsis immunosuppression. Thus, a better understanding of this process may lead to differential treatments for adult and paediatric sepsis.

Isolation and primary culture of human abdominal aorta smooth muscle cells from brain-dead donors: an experimental model for vascular diseases.

Primary cell cultures are essential tools for elucidating the physiopathological mechanisms of the cardiovascular system. Therefore, a primary culture growth protocol of cardiovascular smooth muscle cells (VSMCs) obtained from human abdominal aortas was standardized. Ten abdominal aorta samples were obtained from patients diagnosed with brain death who were organ and tissue donors with family consent. After surgical ablation to capture the aorta, the aortic tissue was removed, immersed in a Custodiol® solution, and kept between 2 and 8 °C. In the laboratory, in a sterile environment, the tissue was fragmented and incubated in culture plates containing an enriched culture medium (DMEM/G/10% fetal bovine serum, L-glutamine, antibiotics and antifungals) and kept in an oven at 37 °C and 5% CO2. The aorta was removed after 24 h of incubation, and the culture medium was changed every six days for twenty days. Cell growth was confirmed through morphological analysis using an inverted optical microscope (Nikon®) and immunofluorescence for smooth muscle alpha-actin and nuclei. The development of the VSMCs was observed, and from the twelfth day, differentiation, long cytoplasmic projections, and adjacent cell connections occurred. On the twentieth day, the morphology of the VSMCs was confirmed by actin fiber immunofluorescence, which is a typical characteristic of VSMCs. The standardization allowed VSMC growth and the replicability of the in vitro test, providing a protocol that mimics natural physiological environments for a better understanding of the cardiovascular system. Its use is intended for investigation, tissue bioengineering, and pharmacological treatments.

Neutrophil virucidal activity against SARS-CoV-2 is mediated by NETs.

BACKGROUND: The inflammation in the lungs and other vital organs in COVID-19 are characterized by the presence of neutrophils and high concentration of neutrophil extracellular traps (NETs), which also seems to mediate host tissue damage. However, it is not known whether NETs could have virucidal activity against SARS-CoV-2. METHODS: We investigated whether NETs could prevent SARS-CoV-2 replication in neutrophils and epithelial cells, and what the consequence of NETs degradation in K18-humanized ACE2 transgenic mice infected with SARS-CoV-2. RESULTS: Here, by immunofluorescence microscopy we observed that viral particles co-localize with NETs in neutrophils isolated from COVID-19 patients or from healthy individuals and infected in vitro. The inhibition of NETs production increased virus replication in neutrophils. In parallel, we observed that NETs inhibited virus abilities to infect and replicate in epithelial cells after 24 h of infection. Degradation of NETs with DNase I prevented their virucidal effect in vitro. Using K18-humanized ACE2 transgenic mice we observed a higher viral load in animals treated with DNase I. On the other hand, the virucidal effect of NETs was not dependent on neutrophil elastase or myeloperoxidase activity. CONCLUSION: Our results provide evidence of the role of NETosis as a mechanism of SARS-CoV-2 viral capture and inhibition.

The metabolic function of pyruvate kinase M2 regulates reactive oxygen species production and microbial killing by neutrophils.

Neutrophils rely predominantly on glycolytic metabolism for their biological functions, including reactive oxygen species (ROS) production. Although pyruvate kinase M2 (PKM2) is a glycolytic enzyme known to be involved in metabolic reprogramming and gene transcription in many immune cell types, its role in neutrophils remains poorly understood. Here, we report that PKM2 regulates ROS production and microbial killing by neutrophils. Zymosan-activated neutrophils showed increased cytoplasmic expression of PKM2. Pharmacological inhibition or genetic deficiency of PKM2 in neutrophils reduced ROS production and Staphylococcus aureus killing in vitro. In addition, this also resulted in phosphoenolpyruvate (PEP) accumulation and decreased dihydroxyacetone phosphate (DHAP) production, which is required for de novo synthesis of diacylglycerol (DAG) from glycolysis. In vivo, PKM2 deficiency in myeloid cells impaired the control of infection with Staphylococcus aureus. Our results fill the gap in the current knowledge of the importance of lower glycolysis for ROS production in neutrophils, highlighting the role of PKM2 in regulating the DHAP and DAG synthesis to promote ROS production in neutrophils.

Tissue-specific metabolic profile drives iNKT cell function during obesity and liver injury.

Invariant natural killer T (iNKT) cells are a distinct population of lymphocytes characterized by their reactivity to glycolipids presented by CD1d. iNKT cells are found throughout the body, and little is known about their tissue-specific metabolic regulation. Here, we show that splenic and hepatic iNKT cells are metabolically comparable and rely on glycolytic metabolism to support their activation. Deletion of the pyruvate kinase M2 (Pkm2) gene in splenic and hepatic iNKT cells impairs their response to specific stimulation and their ability to mitigate acute liver injury. In contrast, adipose tissue (AT) iNKT cells exhibit a distinctive immunometabolic profile, with AMP-activated protein kinase (AMPK) being necessary for their function. AMPK deficiency impairs AT-iNKT physiology, blocking their capacity to maintain AT homeostasis and their ability to regulate AT inflammation during obesity. Our work deepens our understanding on the tissue-specific immunometabolic regulation of iNKT cells, which directly impacts the course of liver injury and obesity-induced inflammation.

FK506 impairs neutrophil migration that results in increased polymicrobial sepsis susceptibility.

OBJECTIVE: This study aimed to investigate the effects of FK506 on experimental sepsis immunopathology. It investigated the effect of FK506 on leukocyte recruitment to the site of infection, systemic cytokine production, and organ injury in mice with sepsis. METHODS: Using a murine cecal ligation and puncture (CLP) peritonitis model, the experiments were performed with wild-type (WT) mice and mice deficient in the gene Nfat1 (Nfat1-/-) in the C57BL/6 background. Animals were treated with 2.0 mg/kg of FK506, subcutaneously, 1 h before the sepsis model, twice a day (12 h/12 h). The number of bacteria colony forming units (CFU) was manually counted. The number of neutrophils in the lungs was estimated by the myeloperoxidase (MPO) assay. The expression of CXCR2 in neutrophils was determined using flow cytometry analysis. The expression of inflammatory cytokines in macrophage was determined using ELISA. The direct effect of FK506 on CXCR2 internalization was evaluated using HEK-293T cells after CXCL2 stimulation by the BRET method. RESULTS: FK506 treatment potentiated the failure of neutrophil migration into the peritoneal cavity, resulting in bacteremia and an exacerbated systemic inflammatory response, which led to higher organ damage and mortality rates. Failed neutrophil migration was associated with elevated CXCL2 chemokine plasma levels and lower expression of the CXCR2 receptor on circulating neutrophils compared with non-treated CLP-induced septic mice. FK506 did not directly affect CXCL2-induced CXCR2 internalization by transfected HEK-293 cells or mice neutrophils, despite increasing CXCL2 release by LPS-treated macrophages. Finally, the CLP-induced response of Nfat1-/- mice was similar to those observed in the Nfat1+/+ genotype, suggesting that the FK506 effect is not dependent on the NFAT1 pathway. CONCLUSION: Our data indicate that the increased susceptibility to infection of FK506-treated mice is associated with failed neutrophil migration due to the reduced membrane availability of CXCR2 receptors in response to exacerbated levels of circulating CXCL2.

Expression of B lymphocyte-induced maturation protein 1 (Blimp-1) in keratinocyte and cytokine signalling drives human Th17 response in psoriasis.

Transcriptional factor B lymphocyte-induced maturation protein 1 (Blimp-1) is pivotally implicated in T helper 17 (Th17) cell differentiation. This study investigated expression of the Blimp-1 protein, positive regulatory domain 1 (PRDM1), and cytokine genes in psoriasis (PsO). Affected (AS-PsO) and non-affected skin (nAS-PsO) samples were used to assess gene and protein expressions by reverse transcription-quantitative PCR (RT-qPCR), and immunostaining and confocal microscopy, respectively; the normalised public transcriptomic data permitted differential gene expression analyses. On RT-qPCR, PRDM1 and IL17A transcripts showed higher expression in AS-PsO than in nAS-PsO (n = 34) (p < 0.001; p < 0.0001, respectively). Confocal microscopy showed Blimp-1 protein expression in epidermal layer keratinocytes in AS-PsO, but not in nAS-PsO. Bioinformatic analysis of the transcriptomic dataset GSE13355 corroborated the increased PRDM1, signal transducer and activator of transcription 3 (STAT3), IL12B, TNF, IL17A, IL6, IL1B, IL22, and IL10 gene expression in AS-PsO, when compared to normal skin and nAS-PsO (p < 0.001). PRDM1 expression correlated positively (p < 0.0001) with that of IL17A (r = 0.7), IL1B (r = 0.67), IL12B (r = 0.6), IL6 (r = 0.59), IL22 (r = 0.53), IL23A (r = 0.47), IL21 (r = 0.47), IL27 (r = 0.34), IL23R (r = 0.32), S100 calcium binding protein A9 (r = 0.63), and lipocalin 2 (r = 0.50), and negatively with that of TGFB1 (r = - 0.28) and RORC (r = - 0.60). Blimp-1 may be critical in the pathogenesis of PsO dysregulation involving the Th17 inflammatory pathway. This knowledge may accelerate the development of new treatments.

Impact of Microbiota Depletion by Antibiotics on SARS-CoV-2 Infection of K18-hACE2 Mice.

Clinical and experimental data indicate that severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection is associated with significant changes in the composition and function of intestinal microbiota. However, the relevance of these effects for SARS-CoV-2 pathophysiology is unknown. In this study, we analyzed the impact of microbiota depletion after antibiotic treatment on the clinical and immunological responses of K18-hACE2 mice to SARS-CoV-2 infection. Mice were treated with a combination of antibiotics (kanamycin, gentamicin, metronidazole, vancomycin, and colistin, Abx) for 3 days, and 24 h later, they were infected with SARS-CoV-2 B lineage. Here, we show that more than 80% of mice succumbed to infection by day 11 post-infection. Treatment with Abx had no impact on mortality. However, Abx-treated mice presented better clinical symptoms, with similar weight loss between infected-treated and non-treated groups. We observed no differences in lung and colon histopathological scores or lung, colon, heart, brain and kidney viral load between groups on day 5 of infection. Despite some minor differences in the expression of antiviral and inflammatory markers in the lungs and colon, no robust change was observed in Abx-treated mice. Together, these findings indicate that microbiota depletion has no impact on SARS-CoV-2 infection in mice.

Gasdermin-D activation by SARS-CoV-2 triggers NET and mediate COVID-19 immunopathology.

BACKGROUND: The release of neutrophil extracellular traps (NETs) is associated with inflammation, coagulopathy, and organ damage found in severe cases of COVID-19. However, the molecular mechanisms underlying the release of NETs in COVID-19 remain unclear. OBJECTIVES: We aim to investigate the role of the Gasdermin-D (GSDMD) pathway on NETs release and the development of organ damage during COVID-19. METHODS: We performed a single-cell transcriptome analysis in public data of bronchoalveolar lavage. Then, we enrolled 63 hospitalized patients with moderate and severe COVID-19. We analyze in blood and lung tissue samples the expression of GSDMD, presence of NETs, and signaling pathways upstreaming. Furthermore, we analyzed the treatment with disulfiram in a mouse model of SARS-CoV-2 infection. RESULTS: We found that the SARS-CoV-2 virus directly activates the pore-forming protein GSDMD that triggers NET production and organ damage in COVID-19. Single-cell transcriptome analysis revealed that the expression of GSDMD and inflammasome-related genes were increased in COVID-19 patients. High expression of active GSDMD associated with NETs structures was found in the lung tissue of COVID-19 patients. Furthermore, we showed that activation of GSDMD in neutrophils requires active caspase1/4 and live SARS-CoV-2, which infects neutrophils. In a mouse model of SARS-CoV-2 infection, the treatment with disulfiram inhibited NETs release and reduced organ damage. CONCLUSION: These results demonstrated that GSDMD-dependent NETosis plays a critical role in COVID-19 immunopathology and suggests GSDMD as a novel potential target for improving the COVID-19 therapeutic strategy.

STING is an intrinsic checkpoint inhibitor that restrains the TH17 cell pathogenic program.

External and intrinsic factors regulate the transcriptional profile of T helper 17 (TH17) cells, thereby affecting their pathogenic potential and revealing their context-dependent plasticity. The stimulator of interferon genes (STING), a component of the intracellular DNA-sensing pathway, triggers immune responses but remains largely unexplored in T cells. Here, we describe an intrinsic role of STING in limiting the TH17 cell pathogenic program. We demonstrate that non-pathogenic TH17 cells express higher levels of STING than those activated under pathogenic conditions. Activation of STING induces interleukin-10 (IL-10) production in TH17 cells, decreasing IL-17A and IL-23R expression in a type I interferon (IFN)-independent manner. Mechanistically, STING-induced IL-10 production partially requires aryl hydrocarbon receptor (AhR) signaling, while the decrease of IL-17A expression occurs due to a reduction of Rorγt transcriptional activity. Our findings reveal a regulatory function of STING in the TH17 cell activation program, proposing it as a valuable target to limit TH17-cell-mediated inflammation.

Blockade of protease-activated receptor 2 attenuates allergenmediated acute lung inflammation and leukocyte recruitment in mice.

Protease-activated receptor (PAR)2 has been implicated in mediating allergic airway inflammation.We investigate the role of PAR2 in lung inflammation and neutrophil and eosinophil recruitment into the lungs in amousemodel of shortterm acute allergic inflammation. Allergic lung inflammation was induced in sensitized BALB/c mice through intranasal instillations of ovalbumin (OVA), and mice were pretreated with the PAR2 antagonist ENMD1068 or with the PAR2-activating peptide (PAR2-AP) 1 hour before each OVA challenge. Bronchoalveolar lavage fluid (BALF) was collected, and the lungs, trachea and lymph nodes were removed after the last challenge to analyze the airway inflammation. PAR2 blockade reduced OVA-induced eosinophil and neutrophil counts, CXCL1, CCL5, amphiregulin, and interleukin (IL)-6 and 13 levels.Moreover, PAR2 blockade reduced OVA-induced PAR2 expression in cells present in BALF 2 hour after OVA challenge, and PAR2-AP acted synergistically with OVA promoting eosinophil recruitment intoBALF and increased IL-4 and IL-13 levels in lymph nodes. Conversely, PAR2 blockade increased IL- 10 levels when compared with OVA-treated mice. Our results provide evidence for a mechanism by which PAR2 meditates acute lung inflammation triggered by multiple exposures to allergen through a modulatory role on cytokine production and vascular permeability implicated in the lung diseases such as asthma.

Citrullinated human fibrinogen triggers arthritis through an inflammatory response mediated by IL-23/IL-17 immune axis.

Rheumatoid arthritis (RA) is an autoimmune disease that causes joint destruction. Although its etiology remains unknown, citrullinated proteins have been considered as an auto-antigen able to trigger an inflammatory response in RA. Herein, we modified the classical antigen-induced arthritis (AIA) model by using citrullinated human plasma fibrinogen (hFIB) as an immunogen to investigate the mechanism of inflammation-driven joint damage by citrullinated hFIB in C57BL/6 mice. We found that hFIB-immunized mice showed high serum levels of anti-citrullinated peptides antibodies (ACPAs). Moreover, hFIB immunized mice showed increased mechanical hyperalgesia, massive leukocyte infiltration, high levels of inflammatory mediators, and progressive joint damage after the intra-articular challenge with citrullinated hFIB. Interestingly, hFIB-induced arthritis was dependent on IL-23/IL-17 immune axis-mediated inflammatory responses since leukocyte infiltration and mechanical hyperalgesia were abrogated in Il17ra-/- and Il23a-/- mice. Thus, we have characterized a novel model of experimental arthritis suitable to investigate the contribution of ACPAs and Th17 cell-mediated immune response in the pathogenesis of RA.

Kallikrein 5 Inhibition by the Lympho-Epithelial Kazal-Type Related Inhibitor Hinders Matriptase-Dependent Carcinogenesis.

Head and neck squamous cell carcinoma remains challenging to treat with no improvement in survival rates over the past 50 years. Thus, there is an urgent need to discover more reliable therapeutic targets and biomarkers for HNSCC. Matriptase, a type-II transmembrane serine protease, induces malignant transformation in epithelial stem cells through proteolytic activation of pro-HGF and PAR-2, triggering PI3K-AKT-mTOR and NFKB signaling. The serine protease inhibitor lympho-epithelial Kazal-type-related inhibitor (LEKTI) inhibits the matriptase-driven proteolytic pathway, directly blocking kallikreins in epithelial differentiation. Hence, we hypothesized LEKTI could inhibit matriptase-dependent squamous cell carcinogenesis, thus implicating kallikreins in this process. Double-transgenic mice with simultaneous expression of matriptase and LEKTI under the keratin-5 promoter showed a prominent rescue of K5-Matriptase+/0 premalignant phenotype. Notably, in DMBA-induced SCC, heterotopic co-expression of LEKTI and matriptase delayed matriptase-driven tumor incidence and progression. Co-expression of LEKTI reverted altered Kallikrein-5 expression observed in the skin of K5-Matriptase+/0 mice, indicating that matriptase-dependent proteolytic pathway inhibition by LEKTI occurs through kallikreins. Moreover, we showed that Kallikrein-5 is necessary for PAR-2-mediated IL-8 release, YAP1-TAZ/TEAD activation, and matriptase-mediated oral squamous cell carcinoma migration. Collectively, our data identify a third signaling pathway for matriptase-dependent carcinogenesis in vivo. These findings are critical for the identification of more reliable biomarkers and effective therapeutic targets in Head and Neck cancer.

Inhibition of Tryptophan Catabolism Is Associated With Neuroprotection During Zika Virus Infection.

Zika virus (ZIKV) is an arbovirus belonging to Flaviviridae family that emerged as a global health threat due to its association with microcephaly and other severe neurological complications, including Guillain-Barré Syndrome (GBS) and Congenital Zika Syndrome (CZS). ZIKV disease has been linked to neuroinflammation and neuronal cell death. Neurodegenerative processes may be exacerbated by metabolites produced by the kynurenine pathway, an important pathway for the degradation of tryptophan, which induces neuronal dysfunction due to enhanced excitotoxicity. Here, we exploited the hypothesis that ZIKV-induced neurodegeneration can be rescued by blocking a target enzyme of the kynurenine pathway, the Indoleamine 2,3-dioxygenase (IDO-1). RT-PCR analysis showed increased levels of IDO-1 RNA expression in undifferentiated primary neurons isolated from wild type (WT) mice infected by ZIKV ex vivo, as well as in the brain of ZIKV-infected A129 mice. Pharmacological inhibition of IDO-1 enzyme with 1-methyl-D-tryptophan (1-MT), in both in vitro and in vivo systems, led to significant reduction of ZIKV-induced neuronal death without interfering with the ability of ZIKV to replicate in those cells. Furthermore, in vivo analyses using both genetically modified mice (IDO-/- mice) and A129 mice treated with 1-MT resulted in reduced microgliosis, astrogliosis and Caspase-3 positive cells in the brain of ZIKV-infected A129 mice. Interestingly, increased levels of CCL5 and CXCL-1 chemokines were found in the brain of 1-MT treated-mice. Together, our data indicate that IDO-1 blockade provides a neuroprotective effect against ZIKV-induced neurodegeneration, and this is amenable to inhibition by pharmacological treatment.

P2x7 Receptor Signaling Blockade Reduces Lung Inflammation and Necrosis During Severe Experimental Tuberculosis.

The risk of developing severe forms of tuberculosis has increased by the acquired immunodeficiency syndrome (AIDS) epidemic, lack of effective drugs to eliminate latent infection and the emergence of drug-resistant mycobacterial strains. Excessive inflammatory response and tissue damage associated with severe tuberculosis contribute to poor outcome of the disease. Our previous studies using mice deficient in the ATP-gated ionotropic P2X7 receptor suggested this molecule as a promising target for host-directed therapy in severe pulmonary tuberculosis. In this study, we assessed the effects of P2X7 pharmacological blockade on disease severity. First, we observed an increase in P2RX7 gene expression in the peripheral blood of tuberculosis patients compared to healthy donors. Lung leukocytes of mice infected with hypervirulent mycobacteria also showed increased expression of the P2X7 receptor. P2X7 blockade in mice with advanced tuberculosis recapitulated in many aspects the disease in P2X7-deficient mice. P2X7-directed therapy reduced body weight loss and the development of inflammatory and necrotic lung lesions, as well as delayed mycobacterial growth. Lower TNF-α production by lung cells and a substantial reduction in the lung GR-1+ myeloid cell population were observed after P2X7 inhibition. The effector CD4+ T cell population also decreased, but IFN-γ production by lung cells increased. The presence of a large population with characteristics of myeloid dendritic cells, as well as the increase in IL-6 production by lung cells, also indicate a qualitative improvement in the pulmonary immune response due to P2X7 inhibition. These findings support the use of drugs that target the P2X7 receptor as a therapeutic strategy to improve the outcome of pulmonary tuberculosis.

STING regulates metabolic reprogramming in macrophages via HIF-1α during Brucella infection.

Macrophages metabolic reprogramming in response to microbial insults is a major determinant of pathogen growth or containment. Here, we reveal a distinct mechanism by which stimulator of interferon genes (STING), a cytosolic sensor that regulates innate immune responses, contributes to an inflammatory M1-like macrophage profile upon Brucella abortus infection. This metabolic reprogramming is induced by STING-dependent stabilization of hypoxia-inducible factor-1 alpha (HIF-1α), a global regulator of cellular metabolism and innate immune cell functions. HIF-1α stabilization reduces oxidative phosphorylation and increases glycolysis during infection with B. abortus and, likewise, enhances nitric oxide production, inflammasome activation and IL-1ß release in infected macrophages. Furthermore, the induction of this inflammatory profile participates in the control of bacterial replication since absence of HIF-1α renders mice more susceptible to B. abortus infection. Mechanistically, activation of STING by B. abortus infection drives the production of mitochondrial reactive oxygen species (mROS) that ultimately influences HIF-1α stabilization. Moreover, STING increases the intracellular succinate concentration in infected macrophages, and succinate pretreatment induces HIF-1α stabilization and IL-1ß release independently of its cognate receptor GPR91. Collectively, these data demonstrate a pivotal mechanism in the immunometabolic regulation of macrophages during B. abortus infection that is orchestrated by STING via HIF-1α pathway and highlight the metabolic reprogramming of macrophages as a potential treatment strategy for bacterial infections.

MMP-9 Mediates Cross-Talk between Neutrophils and Endothelial Cells in Psoriasis.

In their report, Chen et al. provide new insights into psoriasis pathogenesis, showing that neutrophil infiltration of skin lesions increases vascular endothelial cell (VEC) activation, leading to cutaneous vasodilation and enhanced vascular permeability. In patients with psoriasis, neutrophil-derived matrix metalloproteinase 9 (MMP-9) plays a pivotal role in VEC barrier dysfunction, via extracellular signal-regulated kinase-1/2 and p38 pathways. Pharmacologic inhibition of MMP-9 in two different models confers reduced cutaneous vasodilation, vascular permeability, and inflammation, suggesting MMP-9 as a target in psoriasis pathogenesis.

Inflammatory effect of Bothropstoxin-I from Bothrops jararacussu venom mediated by NLRP3 inflammasome involves ATP and P2X7 receptor.

Muscle tissue damage is one of the local effects described in bothropic envenomations. Bothropstoxin-I (BthTX-I), from Bothrops jararacussu venom, is a K49-phospholipase A2 (PLA2) that induces a massive muscle tissue injury, and, consequently, local inflammatory reaction. The NLRP3 inflammasome is a sensor that triggers inflammation by activating caspase 1 and releasing interleukin (IL)-1ß and/or inducing pyroptotic cell death in response to tissue damage. We, therefore, aimed to address activation of NLRP3 inflammasome by BthTX-I-associated injury and the mechanism involved in this process. Intramuscular injection of BthTX-I results in infiltration of neutrophils and macrophages in gastrocnemius muscle, which is reduced in NLRP3- and Caspase-1-deficient mice. The in vitro IL-1ß production induced by BthTX-I in peritoneal macrophages (PMs) requires caspase 1/11, ASC and NLRP3 and is dependent on adenosine 5'-triphosphate (ATP)-induced K+ efflux and P2X7 receptor (P2X7R). BthTX-I induces a dramatic release of ATP from C2C12 myotubes, therefore representing the major mechanism for P2X7R-dependent inflammasome activation in macrophages. A similar result was obtained when human monocyte-derived macrophages (HMDMs) were treated with BthTX-I. These findings demonstrated the inflammatory effect of BthTX-I on muscle tissue, pointing out a role for the ATP released by damaged cells for the NLRP3 activation on macrophages, contributing to the understanding of the microenvironment of the tissue damage of the Bothrops envenomation.

Cigarette smoke induces miR-132 in Th17 cells that enhance osteoclastogenesis in inflammatory arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by joint destruction and severe morbidity. Cigarette smoking (CS) can exacerbate the incidence and severity of RA. Although Th17 cells and the Aryl hydrocarbon receptor (AhR) have been implicated, the mechanism by which CS induces RA development remains unclear. Here, using transcriptomic analysis, we show that microRNA-132 is specifically induced in Th17 cells in the presence of either AhR agonist or CS-enriched medium. miRNA-132 thus induced is packaged into extracellular vesicles produced by Th17 and acts as a proinflammatory mediator increasing osteoclastogenesis through the down-regulation of COX2. In vivo, articular knockdown of miR-132 in murine arthritis models reduces the number of osteoclasts in the joints. Clinically, RA patients express higher levels of miR-132 than do healthy individuals. This increase is further elevated by cigarette smoking. Together, these results reveal a hitherto unrecognized mechanism by which CS could exacerbate RA and further advance understanding of the impact of environmental factors on the pathogenesis of chronic inflammatory diseases.