Proinflammatory Cytokine Production In Macrophages Research Articles

TolC facilitates the intracellular survival and immunomodulation of Salmonella Typhi in human host cells

ABSTRACT Salmonella enterica serovar Typhi (S. Typhi) causes typhoid fever, a systemic infection that affects millions of people worldwide. S. Typhi can invade and survive within host cells, such as intestinal epithelial cells and macrophages, by modulating their immune responses. However, the immunomodulatory capability of S. Typhi in relation to TolC-facilitated efflux pump function remains unclear. The role of TolC, an outer membrane protein that facilitates efflux pump function, in the invasion and immunomodulation of S. Typhi, was studied in human intestinal epithelial cells and macrophages. The tolC deletion mutant of S. Typhi was compared with the wild-type and its complemented strain in terms of their ability to invade epithelial cells, survive and induce cytotoxicity in macrophages, and elicit proinflammatory cytokine production in macrophages. The tolC mutant, which has a defective outer membrane, was impaired in invading epithelial cells compared to the wild-type strain, but the intracellular presence of the tolC mutant exhibited greater cytotoxicity and induced higher levels of proinflammatory cytokines (IL-1β and IL-8) in macrophages compared to the wild-type strain. These effects were reversed by complementing the tolC mutant with a functional tolC gene. Our results suggest that TolC plays a role in S. Typhi to efficiently invade epithelial cells and suppress host immune responses during infection. TolC may be a potential target for the development of novel therapeutics against typhoid fever.

Induction of MTHFD2 in Macrophages Inhibits Reactive Oxygen Species-mediated NF-κB Activation and Protects against Inflammatory Responses.

The one-carbon metabolism enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is critical for cancer cell proliferation and immune cell phenotypes, but whether it can contribute to macrophage inflammatory responses remains unclear. In this study, we show that MTHFD2 was upregulated by LPS in murine macrophages upon activation of the TLR4-MyD88-IKKα/β-NF-κB signaling pathway. MTHFD2 significantly attenuated LPS-induced macrophage proinflammatory cytokine production through its enzymatic activity. Notably, ablation of myeloid MTHFD2 rendered mice more sensitive to septic shock and CCl4-induced acute hepatitis. Mechanistically, MTHFD2 restrained IKKα/β-NF-κB activation and macrophage inflammatory phenotype by scavenging reactive oxygen species through the generation of NADPH. Our study reveals MTHFD2 as a "self-control" mechanism in macrophage-mediated inflammatory responses.

Extracellular vesicles from Pneumocystis carinii-infected rats impair fungal viability but are dispensable for macrophage functions.

Pneumocystis spp. are host obligate fungal pathogens that can cause severe pneumonia in mammals and rely heavily on their host for essential nutrients. The lack of a sustainable in vitro culture system poses challenges in understanding their metabolism, and the acquisition of essential nutrients from host lungs remains unexplored. Transmission electron micrographs show that extracellular vesicles (EVs) are found near Pneumocystis spp. within the lung. We hypothesized that EVs transport essential nutrients to the fungi during infection. To investigate this, EVs from P. carinii- and P. murina-infected rodents were biochemically and functionally characterized. These EVs contained host proteins involved in cellular, metabolic, and immune processes as well as proteins with homologs found in other fungal EV proteomes, indicating that Pneumocystis may release EVs. Notably, EV uptake by P. carinii indicated their potential involvement in nutrient acquisition and a possibility for using engineered EVs for efficient therapeutic delivery. However, EVs added to P. carinii in vitro did not show increased growth or viability, implying that additional nutrients or factors are necessary to support their metabolic requirements. Exposure of macrophages to EVs increased proinflammatory cytokine levels but did not affect macrophages' ability to kill or phagocytose P. carinii. These findings provide vital insights into P. carinii and host EV interactions, yet the mechanisms underlying P. carinii's survival in the lung remain uncertain. These studies are the first to isolate, characterize, and functionally assess EVs from Pneumocystis-infected rodents, promising to enhance our understanding of host-pathogen dynamics and therapeutic potential.IMPORTANCEPneumocystis spp. are fungal pathogens that can cause severe pneumonia in mammals, relying heavily on the host for essential nutrients. The absence of an in vitro culture system poses challenges in understanding their metabolism, and the acquisition of vital nutrients from host lungs remains unexplored. Extracellular vesicles (EVs) are found near Pneumocystis spp., and it is hypothesized that these vesicles transport nutrients to the pathogenic fungi. Pneumocystis proteins within the EVs showed homology to other fungal EV proteomes, suggesting that Pneumocystis spp. release EVs. While EVs did not significantly enhance P. carinii growth in vitro, P. carinii displayed active uptake of these vesicles. Moreover, EVs induced proinflammatory cytokine production in macrophages without compromising their ability to combat P. carinii. These findings provide valuable insights into EV dynamics during host-pathogen interactions in Pneumocystis pneumonia. However, the precise underlying mechanisms remain uncertain. This research also raises the potential for engineered EVs in therapeutic applications.

Zanubrutinib Ameliorates Cardiac Fibrosis and Inflammation Induced by Chronic Sympathetic Activation.

(1) Background: Heart failure (HF) is the final stage of multiple cardiac diseases, which have now become a severe public health problem worldwide. β-Adrenergic receptor (β-AR) overactivation is a major pathological factor associated with multiple cardiac diseases and mediates cardiac fibrosis and inflammation. Previous research has demonstrated that Bruton's tyrosine kinase (BTK) mediated cardiac fibrosis by TGF-β related signal pathways, indicating that BTK was a potential drug target for cardiac fibrosis. Zanubrutinib, a second-generation BTK inhibitor, has shown anti-fibrosis effects in previous research. However, it is unclear whether Zanubrutinib can alleviate cardiac fibrosis induced by β-AR overactivation; (2) Methods: In vivo: Male C57BL/6J mice were treated with or without the β-AR agonist isoproterenol (ISO) to establish a cardiac fibrosis animal model; (3) Results: In vivo: Results showed that the BTK inhibitor Zanubrutinib (ZB) had a great effect on cardiac fibrosis and inflammation induced by β-AR. In vitro: Results showed that ZB alleviated β-AR-induced cardiac fibroblast activation and macrophage pro-inflammatory cytokine production. Further mechanism studies demonstrated that ZB inhibited β-AR-induced cardiac fibrosis and inflammation by the BTK, STAT3, NF-κB, and PI3K/Akt signal pathways both in vivo and in vitro; (4) Conclusions: our research provides evidence that ZB ameliorates β-AR-induced cardiac fibrosis and inflammation.

Sialic acid exacerbates gut dysbiosis-associated mastitis through the microbiota-gut-mammary axis by fueling gut microbiota disruption

BackgroundMastitis is one of the most severe diseases in humans and animals, especially on dairy farms. Mounting evidence indicates that gastrointestinal dysbiosis caused by induction of subacute ruminal acidosis (SARA) by high-grain diet consumption and low in dietary fiber is associated with mastitis initiation and development, however, the underlying mechanism remains unknown.ResultsIn the present study, we found that cows with SARA-associated mastitis have altered metabolic profiles in the rumen, with increased sialic acids level in particular. Consumption of sialic acid (SA) in antibiotic-treated mice, but not healthy mice, induced marked mastitis. SA treatment of antibiotic-treated mice also induced mucosal and systemic inflammatory responses, as evidenced by increased colon and liver injuries and several inflammatory markers. In addition, gut dysbiosis caused by antibiotic impaired gut barrier integrity, which was aggravated by SA treatment. SA potentiated serum LPS level caused by antibiotic treatment, leading to increased activation of the TLR4-NF-κB/NLRP3 pathways in the mammary gland and colon. Moreover, SA facilitated gut dysbiosis caused by antibiotic, and especially enhanced Enterobacteriaceae and Akkermansiaceae, which correlated with mastitis parameters. Fecal microbiota transplantation from SA-antibiotic-treated mice mimicked mastitis in recipient mice. In vitro experiments showed that SA prompted Escherichia coli growth and virulence gene expression, leading to higher proinflammatory cytokine production in macrophages. Targeting the inhibition of Enterobacteriaceae by sodium tungstate or treating with the commensal Lactobacillus reuteri alleviated SA-facilitated mastitis. In addition, SARA cows had distinct ruminal microbial structure by the enrichment of SA-utilizing opportunistic pathogenic Moraxellaceae and the depletion of SA-utilizing commensal Prevotellaceae. Treating mice with the specific sialidase inhibitor zanamivir reduced SA production and Moraxellaceae abundance, and improved mastitis in mice caused by ruminal microbiota transplantation from cows with SARA-associated mastitis.ConclusionsThis study, for the first time, indicates that SA aggravates gut dysbiosis-induced mastitis by promoting gut microbiota disturbance and is regulated by commensal bacteria, indicating the important role of the microbiota-gut-mammary axis in mastitis pathogenesis and suggesting a potential strategy for mastitis intervention based on gut metabolism regulation.-WPXBcu1emhBxPP-wo4QqAVideo

Histone demethylase KDM5B licenses macrophage-mediated inflammatory responses by repressing Nfkbia transcription.

Macrophages play a critical role in the immune homeostasis and host defense against invading pathogens. However, uncontrolled activation of inflammatory macrophages leads to tissue injury and even fuels autoimmunity. Hence the molecular mechanisms underlying macrophage activation need to be further elucidated. The effects of epigenetic modifications on the function of immune cells draw increasing attention. Here, we demonstrated that lysine-specific demethylase 5B (KDM5B), a classical transcriptional repressor in stem cell development and cancer, was required for the full activation of NF-κB signaling cascade and pro-inflammatory cytokine production in macrophages. KDM5B deficiency or inhibitor treatment protected mice from immunologic injury in both collagen-induced arthritis (CIA) model and endotoxin shock model. Genome-wide analysis of KDM5B-binding peaks identified that KDM5B was selectively recruited to the promoter of Nfkbia, the gene encoding IκBα, in activated macrophages. KDM5B mediated the H3K4me3 modification erasing and decreased chromatin accessibility of Nfkbia gene locus, coordinating the elaborate suppression of IκBα expression and the enhanced NF-κB-mediated macrophage activation. Our finding identifies the indispensable role of KDM5B in macrophage-mediated inflammatory responses and provides a candidate therapeutic target for autoimmune and inflammatory disorders.

Depletion of creatine phosphagen energetics with a covalent creatine kinase inhibitor.

Creatine kinases (CKs) provide local ATP production in periods of elevated energetic demand, such as during rapid anabolism and growth. Thus, creatine energetics has emerged as a major metabolic liability in many rapidly proliferating cancers. Whether CKs can be targeted therapeutically is unknown because no potent or selective CK inhibitors have been developed. Here we leverage an active site cysteine present in all CK isoforms to develop a selective covalent inhibitor of creatine phosphagen energetics, CKi. Using deep chemoproteomics, we discover that CKi selectively engages the active site cysteine of CKs in cells. A co-crystal structure of CKi with creatine kinase B indicates active site inhibition that prevents bidirectional phosphotransfer. In cells, CKi and its analogs rapidly and selectively deplete creatine phosphate, and drive toxicity selectively in CK-dependent acute myeloid leukemia. Finally, we use CKi to uncover an essential role for CKs in the regulation of proinflammatory cytokine production in macrophages.

CX3CR1 deficiency exacerbates immune-mediated hepatitis by increasing NF-κB-mediated cytokine production in macrophage and T cell.

Immune-mediated hepatitis is marked by liver inflammation characterized by immune cell infiltration, chemokine/cytokine production, and hepatocyte injury. C-X3C motif receptor 1 (CX3CR1), as the receptor of chemokine C-X3C motif ligand 1 (CX3CL1)/fractalkine, is mainly expressed on immune cells including monocytes and T cells. Previous studies have shown that CX3CR1 protects against liver fibrosis, but the exact role of CX3CL1/CX3CR1 in acute immune-mediated hepatitis remains unknown. Here, we investigate the role of the CX3CL1/CX3CR1 axis in immune-mediated hepatitis using concanavalin A (ConA)-induced liver injury model in CX3CR1-deficient (Cx3cr1-/-) mice. We observed that Cx3cr1-/- mice had severe liver injury and increased pro-inflammatory cytokines (tumor necrosis factor-alpha [TNF-α], interferon-gamma [IFN-γ], interleukin-1 beta [IL-1β], and IL-6) in serum and liver compared to wild-type (Cx3cr1+/+) mice after ConA injection. The deficiency of CX3CR1 did not affect ConA-induced immune cell infiltration in liver but led to elevated production of TNF-α in macrophages as well as IFN-γ in T cells after ConA treatment. On the contrary, exogenous CX3CL1 attenuated ConA-induced cytokine production in wild type, but not CX3CR1-deficient macrophages and T cells. Furthermore, in vitro results showed that CX3CR1 deficiency promoted the pro-inflammatory cytokine expression by increasing the phosphorylation of nuclear factor kappa B (NF-κB) p65 (p-NF-κB p65). Finally, pre-treatment of p-NF-κB p65 inhibitor, resveratrol, attenuated ConA-induced liver injury and inflammatory responses, especially in Cx3cr1-/- mice. In conclusion, our data show that the deficiency of CX3CR1 promotes pro-inflammatory cytokine production in macrophages and T cells by enhancing the phosphorylation of NF-κB p65, which exacerbates liver injury in ConA-induced hepatitis.

Abstract PO026: Bile acid signaling remodels the iCCA immune microenvironment

Abstract Intrahepatic cholangiocarcinoma (iCCA) primarily arises from the transformation of cholangiocytes (epithelial cells of the bile ducts), is diagnosed at late stage and has a dismal prognosis (average 5-year survival after resection is 32%). An alarming increase in its incidence over the past decades and the scarce treatment options available urges for the development of novel therapeutic strategies to tackle this malignancy. Immunotherapy has had limited success in iCCA. Possible explanations are that iCCA immune microenvironment is poor in CD8+ T cells and rich in immunosuppressive innate immune cells. The immune landscape of iCCA is determined by the aetiology of the liver insult (e.g. viral, cholestatic) and these different iCCA immune landscapes have not yet been characterized. Therefore, in depth studies on the immunobiology of iCCA are essential to develop new immunotherapy strategies where innate immune cells play a prominent role. We hypothesized that bile acids (BA) are a potential, valid therapeutic target for iCCA, as they strongly influence liver immune microenvironment and proliferation. This idea is supported by the fact that BA have an immunomodulatory role through inhibition of NF-KB and reduction of macrophage production of pro-inflammatory cytokines, suppressing cholangiocyte transformation in iCCA. Since BA and derivatives have recently been approved for the treatment of human chronic cholestatic diseases and primary sclerosis cholangitis, but have not yet been tested to treat iCCA, the proposed project might directly offer evidence for a second use of these drugs in patients with iCCA. Using novel preclinical mouse models of iCCA and human iCCA samples, our objective is to develop new therapeutic strategies for iCCA treatment based on BA signalling, that would impair tumour growth and foster the immune response against the tumour. In order to investigate the effects that BA can exert in tumour initiation and development, we adopted a iCCA mouse model based on the hydrodynamic tail-vein delivery of genetic elements specifically in hepatocytes, which differentiate into cholangiocytes and ultimately leads to the development of iCCA, while conserving a competent immune system. We found that by feeding the animals with an endogenous BA-enriched diet (BA diet), we reduced the overall tumor burden and strikingly increased overall survival. The positive response to the BA diet was associated to an inhibition of tumor proliferation and a robust increase in the abundance and activation of inflammatory monocytes and T cells. Our preliminary results indicate that mimicking the effect of BA could represent a novel immunotherapeutic strategy for iCCA. We will present these data as well as ongoing studies including fluorescence-activated cell sorting and single-cell RNA seq sequencing, focused on understanding the cooperation between different immune cell types that foster response against the tumor. Citation Format: María García-Beccaria, Mirian Fernández-Vaquero, Maria Reich, Dominik Pfister, Diran Herebian, Benjamin Goeppert, Darjus Felix Tschaharganeh, Verena Keitel, Mathias Heikenwälder. Bile acid signaling remodels the iCCA immune microenvironment [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PO026.

Immunostimulatory Effect of Heat-Killed Probiotics on RAW264.7 Macrophages.

Probiotics modulate the gut microbiota, which in turn regulate immune responses to maintain balanced immune homeostasis in the host. However, it is unclear how probiotic bacteria regulate immune responses. In this study we investigated the immunomodulatory effects of heat-killed probiotics, including Lactiplantibacillus plantarum KC3 (LP3), Lactiplantibacillus plantarum CKDB008 (LP8), and Limosilactobacillus fermentum SRK414 (LF4), via phagocytosis, nitric oxide (NO), and pro-inflammatory cytokine production in macrophages. We thus found that heat-killed LP8 could promote the clearance of foreign pathogens by enhancing the phagocytosis of macrophages. Treatment with heat-killed LP8 induced the production of NO and pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1β. In addition, heat-killed LP8 suppressed the production of NO and cytokines in LPS-induced RAW264.7 cells, suggesting that heat-killed LP8 exerts immunomodulatory effects depending on the host condition. In sum, these results indicate that heat-killed LP8 possesses the potential for immune modulation while providing a molecular basis for the development of functional probiotics prepared from inactivated bacterial cells.

RNA-binding protein hnRNP UL1 binds κB sites to attenuate NF-κB-mediated inflammation

Heterogeneous nuclear ribonucleoproteins (hnRNPs), a family of RNA-binding proteins, play important roles in various biological processes. However, the roles of hnRNPs members in immunity and inflammation remain to be fully understood. By a functional screening for hnRNPs members in LPS-stimulated macrophage inflammatory response, we identified hnRNP UL1 as a negative regulator of NF-κB-mediated inflammation. hnRNP UL1 constrains NF-κB-triggered transcriptional expression of pro-inflammatory cytokines in response to innate stimuli. Perturbation of hnRNP UL1 enhanced pro-inflammatory cytokine production in macrophages. In vivo deficiency of hnRNP UL1 increased the pro-inflammatory cytokine production once challenged with LPS. Accordingly, the expression of hnRNP UL1 decreased in peripheral blood mononuclear cells of rheumatoid arthritis patients. Mechanistically, hnRNP UL1 competes with NF-κB to bind κB sites to constrain the magnitude and duration of inflammatory response. Meanwhile, the broadly and dynamically binding of hnRNP UL1 on the target genes’ promoter during inflammatory response is unraveled. Our study adds new insight into the functions of hnRNPs in NF-κB-mediated inflammation, proposing a potential therapeutic strategy for controlling inflammatory autoimmune diseases.

Anisomycin protects against sepsis by attenuating IκB kinase-dependent NF-κB activation and inflammatory gene expression

Anisomycin is known to inhibit eukaryotic protein synthesis and has been established as an antibiotic and anticancer drug. However, the molecular targets of anisomycin and its mechanism of action have not been explained in macrophages. Here, we demonstrated the anti-inflammatory effects of anisomycin both in vivo and in vitro. We found that anisomycin decreased the mortality rate of macrophages in cecal ligation and puncture (CLP)- and lipopolysaccharide (LPS)-induced acute sepsis. It also declined the gene expression of proinflammatory mediators such as inducible nitric oxide synthase, tumor necrosis factor-α, and interleukin-1β as well as the nitric oxide and proinflammatory cytokines production in macrophages subjected to LPS-induced acute sepsis. Furthermore, anisomycin attenuated nuclear factor (NF)-κB activation in LPS-induced macrophages, which correlated with the inhibition of phosphorylation of NF-κB-inducing kinase and IκB kinase, phosphorylation and IκBα proteolytic degradation, and NF-κB p65 subunit nuclear translocation. These results suggest that anisomycin prevented acute inflammation by inhibiting NF-κB-related inflammatory gene expression and could be a potential therapeutic candidate for sepsis.

Traditional Chinese Medicine, Qingfei Paidu Decoction and Xuanfei Baidu Decoction, Inhibited Cytokine Production via NF-κB Signaling Pathway in Macrophages: Implications for Coronavirus Disease 2019 (COVID-19) Therapy.

Background and Aims: Qingfei Paidu decoction (QPD) and Xuanfei Baidu decoction (XBD) are two typical traditional Chinese medicines with proven efficacy for the treatment of SARS-CoV-2, although the underlying mechanism is not well defined. Blunted immune response and enhanced production of pro-inflammatory cytokines (cytokine storm) are two main features observed in patients infected with SARS-CoV-2. Analysis based on network pharmacology has revealed that both QPD and XBD played an important role in the regulation of host immunity. We therefore investigated the role of QPD and XBD in the modulation of innate immunity in vitro, focusing on the type 1 interferon (IFN) signaling pathway in A549 cells and pro-inflammatory cytokine production in macrophages. Methods: A549 cells were treated with QPD or XBD and the production of endogenous IFNα and IFNβ as well as the expression levels of some interferon-stimulated genes (ISGs) were detected by reverse transcriptase-quantitative PCR (RT-qPCR). Macrophages derived from THP-1 cells were treated with QPD or XBD and their pro-inflammatory cytokine expression levels were measured by RT-qPCR, 6 h post LPS stimulation. In addition, the expression levels of some pro-inflammatory cytokines were further analyzed by ELISA. The effect of QPD and XBD on the NF-κB signaling pathway and the pinocytosis activity of THP-1-derived macrophages were evaluated by Western blot and neutral red uptake assay, respectively. Results: Although QPD and XBD showed very little effect on the type 1 IFN signaling pathway in A549 cells, either QPD or XBD markedly inhibited the production of pro-inflammatory markers including interleukin-6, tumor necrosis factor-α, monocyte chemotactic protein-1, and chemokine ligand 10 in THP-1-derived M1 macrophages. In addition, the phosphorylation of IκBα and NF-κB p65 during the process of macrophage polarization was significantly suppressed following QPD or XBD treatment. QPD and XBD also suppressed the pinocytosis activity of macrophages. Conclusion: QPD and XBD have been shown to have robust anti-inflammatory activities in vitro. Our study demonstrated that both QPD and XBD decreased pro-inflammatory cytokine expression, inhibited the activation of the NF-κB signaling pathway, and blunted pinocytosis activity in THP-1-derived macrophages.

The E3 Ubiquitin Ligase HERC5 Promotes Antimycobacterial Immunity in Macrophages Through Regulating ISGylation and Degradation of PTEN

HERC5 (homologous to mouse HERC6) is an E3 enzyme that mediates interferon-stimulated gene 15 (ISG15)-induced ISGylation of protein targets to inhibit protein function, thereby playing a vital role in various physiological functions. However, the direct role of HERC5 in macrophages after M. tuberculosis infection has not yet been studied. In the present study, we showed that HERC5 plays a vital role in promoting the inflammatory immune response. HERC5 deficiency in macrophages enhanced bacterial growth, both in vitro and in vivo. We demonstrated that HERC5 increased pro-inflammatory cytokine production in macrophages by positively regulating the PI3K-AKT signaling pathway. Finally, we found that HERC5 regulated PTEN ISGylation and degradation, thereby promoting activation of the PI3K-AKT signaling pathway. Our findings identified an essential role of HERC5 in the ISGylation of PTEN and contributed to our understanding of its protective effects against M. tuberculosis infection. Therefore, HERC5 is a potential target for therapeutic intervention against tuberculosis. Funding Information: This work was supported National Natural Science Foundation of China (81772150, 81901614, 82072242, 82070906), Guangdong Basic and Applied Basic Research Foundation (2019A1515011103). Declaration of Interests: The authors declare no competing financial interests. Ethics Approval Statement: All the mice were maintained under specific pathogen-free conditions with the approval of the Scientific Investigation Board of the Biosafety Management Committee of Southern Medical University

The interplay between ER stress, inflammation, and lipid metabolism

Background and Aims: The endoplasmic reticulum (ER) stress is an important event in the pathogenesis of human diseases, including atherosclerosis. ER stress may lead to foam cell formation and pro-inflammatory cytokines production in macrophages. In atherosclerosis, several cell types can be affected by ER stress, including endothelial cells, macrophages, and smooth muscle cells. Atherogenic low-density lipoproteins and/or inflammatory cytokines can induce ER stress, which can promote lipid accumulation and cytokine production in macrophages.

SARS-CoV-2/ACE2 Interaction Suppresses IRAK-M Expression and Promotes Pro-Inflammatory Cytokine Production in Macrophages.

The major cause of death in SARS-CoV-2 infected patients is due to de-regulation of the innate immune system and development of cytokine storm. SARS-CoV-2 infects multiple cell types in the lung, including macrophages, by engagement of its spike (S) protein on angiotensin converting enzyme 2 (ACE2) receptor. ACE2 receptor initiates signals in macrophages that modulate their activation, including production of cytokines and chemokines. IL-1R-associated kinase (IRAK)-M is a central regulator of inflammatory responses regulating the magnitude of TLR responsiveness. Aim of the work was to investigate whether SARS-CoV-2 S protein-initiated signals modulate pro-inflammatory cytokine production in macrophages. For this purpose, we treated PMA-differentiated THP-1 human macrophages with SARS-CoV-2 S protein and measured the induction of inflammatory mediators including IL6, TNFα, IL8, CXCL5, and MIP1a. The results showed that SARS-CoV-2 S protein induced IL6, MIP1a and TNFα mRNA expression, while it had no effect on IL8 and CXCL5 mRNA levels. We further examined whether SARS-CoV-2 S protein altered the responsiveness of macrophages to TLR signals. Treatment of LPS-activated macrophages with SARS-CoV-2 S protein augmented IL6 and MIP1a mRNA, an effect that was evident at the protein level only for IL6. Similarly, treatment of PAM3csk4 stimulated macrophages with SARS-CoV-2 S protein resulted in increased mRNA of IL6, while TNFα and MIP1a were unaffected. The results were confirmed in primary human peripheral monocytic cells (PBMCs) and isolated CD14+ monocytes. Macrophage responsiveness to TLR ligands is regulated by IRAK-M, an inactive IRAK kinase isoform. Indeed, we found that SARS-CoV-2 S protein suppressed IRAK-M mRNA and protein expression both in THP1 macrophages and primary human PBMCs and CD14+ monocytes. Engagement of SARS-CoV-2 S protein with ACE2 results in internalization of ACE2 and suppression of its activity. Activation of ACE2 has been previously shown to induce anti-inflammatory responses in macrophages. Treatment of macrophages with the ACE2 activator DIZE suppressed the pro-inflammatory action of SARS-CoV-2. Our results demonstrated that SARS-CoV-2/ACE2 interaction rendered macrophages hyper-responsive to TLR signals, suppressed IRAK-M and promoted pro-inflammatory cytokine expression. Thus, activation of ACE2 may be a potential anti-inflammatory therapeutic strategy to eliminate the development of cytokine storm observed in COVID-19 patients.

Phase 1, first-in-human trial of JTX-8064, an anti-LILRB2/ILT4 monoclonal antibody, as monotherapy and in combination with anti-PD-1 in adult patients with advanced solid tumors (INNATE).

TPS2672 Background: Leukocyte Immunoglobulin-like receptor B2 [LILRB2; immunoglobulin-like transcript 4 (ILT4)] is an immunoinhibitory protein expressed on the surface of myeloid cells and is a therapeutic target of interest in immuno-oncology. Published data showed that antagonism of LILRB2 resulted in the repolarization of human macrophages from an M2 (suppressive) to M1 (pro-inflammatory) phenotype, and enhancement of anti-tumor immunity in a mouse model (Chen 2018). JTX-8064 is a novel humanized IgG4 monoclonal antagonist antibody that selectively binds LILRB2 and prevents it from binding its ligands, classical and non-classical MHC I molecules. By blocking the ability of LILRB2 to bind HLA-A/B and/or HLA-G, a marker of immunotolerance on cancer cells, JTX-8064 has been shown to enhance pro-inflammatory cytokine production in macrophages (Cohen 2019). Additionally, blocking HLA-A/B-LILRB2 binding with JTX-8064 may augment antigen presentation and has been shown to lead to enhanced T cell activation and IFNg production (McGrath 2021). Using an ex vivo tumor explant model, we observed an IFNg-associated pharmacodynamic response in tumor tissue treated with JTX-8064 and a PD-1 inhibitor (PD-1i) that was not observed with PD-1i alone. Biomarkers were identified that predicted this JTX-8064 driven response (Hashambhoy-Ramsay 2020). It is hypothesized that JTX-8064 is a novel macrophage immune checkpoint inhibitor that may overcome mechanisms of resistance to PD-1i in tumors not responsive to JTX-8064 or PD-1i alone. Methods: The primary objectives of this open-label, phase 1, first-in-human, multicenter trial are to determine the safety and tolerability, and the recommended phase 2 dose (RP2D) of JTX-8064 as a monotherapy and in combination with a PD-1i, JTX-4014 (a Jounce investigational agent) or pembrolizumab, in patients with advanced solid tumors (NCT04669899). The INNATE study will consist of 4 stages: 1) JTX-8064 monotherapy dose escalation, 2) JTX-8064 dose escalation in combination with a PD-1i, 3) JTX-8064 monotherapy in indication-specific expansion cohorts and 4) JTX-8064 in combination with a PD-1i in indication-specific expansion cohorts. Stages 1 and 2 will employ an innovative interval i3 + 3 design with Bayesian decision framework to guide dose escalation. Safety, pharmacokinetic and receptor occupancy data will be considered during dose escalation. INNATE will assess pharmacodynamic and potential predictive biomarkers of response, and the expansion cohorts will explore multiple patient populations, including PD-(L)1i sensitive and PD-(L)1i-resistant (primary or acquired) patients to address current unmet medical needs. Enrolment in INNATE began in January 2021. Clinical trial information: NCT04669899.

ErbB4 regulates interferon signaling in classically activated macrophages

Background Classically activated macrophages drive intestinal inflammation, which is necessary to limit infection. However, over-aggressive responses from these cells, including elevated cytokine release, may contribute to inflammatory bowel disease. Previous studies have implicated the receptor tyrosine kinase ErbB4 and its ligands (neuregulins/NRGs) in regulating macrophage activity and survival. However, the influence of ErbB4 and its specific ligand NRG4 on cytokine expression and downstream signaling pathways in these cells remains untested. We hypothesized that ErbB4 regulates pathways associated with cytokine production in macrophages. Methods We generated bone-marrow derived macrophages from mice lacking ErbB4 in cells of myeloid lineage (LysMCre/ErbB4FF) or sex-matched littermate controls (ErbB4FF), and stimulated pro-inflammatory activation with interferon (IFN)-gamma plus lipopolysaccharide (classical activation). Cells were analyzed by RNA sequencing, and gene-set enrichment analysis (GSEA) was performed using publicly available Hallmark gene-sets. To test the role of NRG4, activated cells were treated with recombinant ligand at 100 ng/ml for 24 hours to determine effects on cytokine expression. RNA was collected and analyzed for cytokines by qPCR. Results Classically activated macrophages from LysMCre/ErbB4FF mice displayed an enhanced pro-inflammatory cytokine profile by GSEA (p<0.05) compared to ErbB4FF mice. We confirmed elevated levels of Tnf (32% higher, p<0.05) and Cxcl1 (69% higher, p<0.05) by qPCR. NRG4 treatment limited Tnf (p<0.05) and Cxcl1 (p<0.05) expression in classically activated macrophages from wild-type mice. GSEA showed a reduced type-I and type-II IFN gene expression signature in cells from LysMCre/ErbB4FF mice versus ErbB4FF mice. Conclusion Loss of ErbB4 in macrophages leads to dysregulated IFN signaling and enhanced pro-inflammatory cytokine production in macrophages. NRG/ErbB4 signaling in macrophages drives an anti-inflammatory feedback loop and may limit aberrant intestinal inflammation.

NRG4-ErbB4 signaling represses proinflammatory macrophage activity.

Proinflammatory macrophages are essential drivers of colitis and express the growth factor receptor ErbB4. This study tested the role of ErbB4 and its specific ligand, NRG4, in regulating macrophage function. We show that endogenous NRG4-ErbB4 signaling limits macrophage production of proinflammatory cytokines in vitro and limits colitis severity in vivo and thus is a potential target for therapeutic intervention.

The Unusual Immune System of the Naked Mole-Rat.

The immune system plays a critical role in host defense to pathogens, tissue homeostasis, cancer development, and several aging-associated chronic inflammatory diseases. The naked mole-rat (Heterocephalus glaber) is a subterranean rodent with both extraordinary longevity and cancer-resistant phenotypes. Unlike the immune system of standard laboratory rodents, that of the naked mole-rat features a higher myeloid-to-lymphoid ratio, lacks natural killer cells, has higher pro-inflammatory cytokine production in macrophages, and exhibits a novel LPS-responsive neutrophil subset that highly expresses several antimicrobials. Given these unusual features, the potential involvement of the naked mole-rat's immune system in their longevity and cancer-resistance remains enigmatic. In this chapter, we summarize the current knowledge of the immune system in the naked mole-rat, including the immune cell repertoire, the primary and secondary lymphoid organs, and the inflammatory responses to the pathogenic stimulation such as bacterial toxins. We compare these findings to published studies of the other subterranean rodents and discuss how the environmental factors in which they have evolved may have influenced their immune function.