Natural amines inhibit activation of human plasmacytoid dendritic cells through CXCR4 engagement

Single-cell RNA sequencing in autoimmune diseases: New insights and challenges

Autoimmune diseases involve a variety of cell types, yet the intricacies of their individual roles within molecular mechanisms and therapeutic strategies remain poorly understood. Single-cell RNA sequencing (scRNA-seq) offers detailed insights into transcriptional diversity at the single-cell level, significantly advancing research in autoimmune diseases. This article explores how scRNA-seq enhances the understanding of cellular heterogeneity and its potential applications in the etiology, diagnosis, treatment, and prognosis of autoimmune diseases. By revealing a comprehensive cellular landscape, scRNA-seq illuminates the functional regulation of different cell subtypes during disease progression. It aids in identifying diagnostic and prognostic markers, and analyzing cell communication networks to uncover potential therapeutic targets. Despite its valuable contributions, addressing the limitations of scRNA-seq is essential for making further advancements.

Curdione combined with borneol treats bacterial mixed HPV infection by regulating the crosstalk among immune cells

Background

Human papillomavirus (HPV) infection is a worldwide reproductive system disease. Baofukang suppository, a traditional herbal preparation that includes curdione and borneol, has been reported to treat bacterial vaginosis (BV) and HPV infection in China. However, the therapeutic mechanism is still unknown. This study aims to explore the molecular mechanisms of curdione and borneol in treating HPV infection.

Methods

We conducted a retrospective cohort analysis of medical records from a single-center study involving 205 HPV patients, focusing on the correlation between HPV clearance and co-infection with other pathogens, confirming the efficacy of Baofukang suppository. Bioinformatics and network pharmacology approaches were employed to identify therapeutic targets of Baofukang suppository for BV/HPV co-infections. qRT-PCR, Western blot, immunofluorescence staining, and flow cytometry were utilized to validate the therapeutic targets of curdione and borneol, along with the associated immune molecular changes. Finally, the molecular mechanisms and therapeutic efficacy of curdione and borneol were confirmed in vivo using an LPS/TC-1 cervical orthotopic injection model.

Results

Curdione and borneol selectively inhibit the secretion of interleukin-6 (IL-6) and interleukin-1β (IL-1β) by macrophages. The reduction in IL-6 and IL-1β levels effectively inhibits the expression of CD274 (Programmed death ligand 1, PD-L1) in infected epithelial cells by inhibiting STAT3 phosphorylation, thereby suppressing their immune evasion capabilities. Furthermore, curdione and borneol enhance the expression of tumor necrosis factor α (TNF-α) and caspase 1 (CASP1) in macrophages, as well as the expression of interleukin 12 (IL-12) and interleukin 23 (IL-23) in dendritic cells (DCs). The expression of these inflammatory factors effectively promotes the migration and differentiation of T cells to the site of infection, completing the clearance of infected epithelial cells.

Conclusion

The main components of Baofukang suppository, curdione and borneol, inhibit the progression of HPV infection and the occurrence of cervical cancer by modulating the communication between innate and adaptive immunity, promoting the recruitment and recognition of CD8+ T cells to eliminate HPV-infected epithelial cells.

The histamine analogue clobenpropit modulates IRF7 phosphorylation and interferon production by targeting CXCR4 in systemic lupus erythematosus models

Introduction

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by an overactive immune response, particularly involving excessive production of type I interferons. This overproduction is driven by the phosphorylation of IRF7, a crucial factor in interferon gene activation. Current treatments for SLE are often not very effective and can have serious side effects.

Methods

Our study introduces clobenpropit, a histamine analogue, as a potential new therapy targeting the CXCR4 receptor to reduce IRF7 phosphorylation and subsequent interferon production. We employed various laboratory techniques to investigate how clobenpropit interacts with CXCR4 and its effects on immune cells from healthy individuals and SLE patients.

Results

Clobenpropit binds effectively to CXCR4, significantly inhibiting IRF7 phosphorylation and reducing interferon production. Additionally, clobenpropit lowered levels of pro-inflammatory cytokines in a mouse model of lupus, demonstrating efficacy comparable to the standard treatment, prednisolone.

Discussion

These results suggest that clobenpropit could be a promising new treatment for SLE, offering a targeted approach with potential advantages over current therapies.

The story of clobenpropit and CXCR4: can be an effective drug in cancer and autoimmune diseases?

Clobenpropit is a histamine H3 receptor antagonist and has developed as a potential therapeutic drug due to its ability to inhibit CXCR4, a chemokine receptor involved in autoimmune diseases and cancer pathogenesis. The CXCL12/CXCR4 axis involves several biological phenomena, including cell proliferation, migration, angiogenesis, inflammation, and metastasis. Accordingly, inhibiting CXCR4 can have promising clinical outcomes in patients with malignancy or autoimmune disorders. Based on available knowledge, Clobenpropit can effectively regulate the release of monocyte-derived inflammatory cytokine in autoimmune diseases such as juvenile idiopathic arthritis (JIA), presenting a potential targeted target with possible advantages over current therapeutic approaches. This review summarizes the intricate interplay between Clobenpropit and CXCR4 and the molecular mechanisms underlying their interactions, comprehensively analyzing their impact on immune regulation. Furthermore, we discuss preclinical and clinical investigations highlighting the probable efficacy of Clobenpropit for managing autoimmune diseases and cancer. Through this study, we aim to clarify the immunomodulatory role of Clobenpropit and its advantages and disadvantages as a novel therapeutic opportunity.

CXCR4: from B-cell development to B cell-mediated diseases

Chemokine receptors are members of the G protein-coupled receptor superfamily. The C-X-C chemokine receptor type 4 (CXCR4), one of the most studied chemokine receptors, is widely expressed in hematopoietic and immune cell populations. It is involved in leukocyte trafficking in lymphoid organs and inflammatory sites through its interaction with its natural ligand CXCL12. CXCR4 assumes a pivotal role in B-cell development, ranging from early progenitors to the differentiation of antibody-secreting cells. This review emphasizes the significance of CXCR4 across the various stages of B-cell development, including central tolerance, and delves into the association between CXCR4 and B cell-mediated disorders, from immunodeficiencies such as WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome to autoimmune diseases such as systemic lupus erythematosus. The potential of CXCR4 as a therapeutic target is discussed, especially through the identification of novel molecules capable of modulating specific pockets of the CXCR4 molecule. These insights provide a basis for innovative therapeutic approaches in the field.

HIV and gp120-induced lipid droplets loss in hepatic stellate cells contribute to profibrotic profile

Liver fibrosis is the excessive accumulation of extracellular matrix proteins, primarily collagen, in response to liver injury caused by chronic liver diseases. HIV infection accelerates the progression of liver fibrosis in patients co-infected with HCV or HBV compared to those who are only mono-infected. The early event in the progression of liver fibrosis involves the activation of hepatic stellate cells (HSCs), which entails the loss of lipid droplets (LD) to fuel the production of extracellular matrix components crucial for liver tissue healing. Thus, we are examining the mechanism by which HIV stimulates the progression of liver fibrosis. HIV-R5 tropic infection was unable to induce the expression of TGF-β, collagen deposition, α-smooth muscle actin (α-SMA), and cellular proliferation. However, this infection induced the secretion of the profibrogenic cytokine IL-6 and the loss of LD. This process involved the participation of peroxisome proliferator-activated receptor (PPAR)-α and an increase in lysosomal acid lipase (LAL), along with the involvement of Microtubule-associated protein 1 A/1B-light chain 3 (LC3), strongly suggesting that LD loss could occur through acid lipolysis. These phenomena were mimicked by the gp120 protein from the R5 tropic strain of HIV. Preincubation of HSCs with the CCR5 receptor antagonist, TAK-779, blocked gp120 activity. Additionally, experiments performed with pseudotyped-HIV revealed that HIV replication could also contribute to LD loss. These results demonstrate that the cross-talk between HSCs and HIV involves a series of interactions that help explain some of the mechanisms involved in the exacerbation of liver damage observed in co-infected individuals.

Rational design and optimization of acylthioureas as novel potent influenza virus non-nucleoside polymerase inhibitors

Evidence suggests that rapidly evolving virus subvariants risk rendering current vaccines and anti-influenza drugs ineffective. Hence, exploring novel scaffolds or new targets of anti-influenza drugs is of great urgency. Herein, we report the discovery of a series of acylthiourea derivatives produced via a scaffold-hopping strategy as potent antiviral agents against influenza A and B subtypes. The most effective compound 10m displayed subnanomolar activity against H1N1 proliferation (EC50 = 0.8 nM) and exhibited inhibitory activity toward other influenza strains, including influenza B virus and H1N1 variant (H1N1, H274Y). Additionally, druggability evaluation revealed that 10m exhibited favorable pharmacokinetic properties and was metabolically stable in liver microsome preparations from three different species as well as in human plasma. In vitro and in vivo toxicity studies confirmed that 10m demonstrated a high safety profile. Furthermore, 10m exhibited satisfactory antiviral activity in a lethal influenza virus mouse model. Moreover, mechanistic studies indicated that these acylthiourea derivatives inhibited influenza virus proliferation by targeting influenza virus RNA-dependent RNA polymerase. Thus, 10m is a potential lead compound for the further exploration of treatment options for influenza.

Immunometabolism of dendritic cells in health and disease

Dendritic cells (DCs) are crucial mediators that bridge the innate and adaptive immune responses. Cellular rewiring of metabolism is an emerging regulator of the activation, migration, and functional specialization of DC subsets in specific microenvironments and immunological conditions. DCs undergo metabolic adaptation to exert immunogenic or tolerogenic effects in different contexts. Also, beyond their intracellular metabolic and signaling roles, metabolites and nutrients mediate the intercellular crosstalk between DCs and other cell types, and such crosstalk orchestrates DC function and immune responses. Here, we provide a comprehensive review of the metabolic regulation of DC biology in various contexts and summarize the current understanding of such regulation in directing immune homeostasis and inflammation, specifically with respect to infections, autoimmunity, tolerance, cancer, metabolic diseases, and crosstalk with gut microbes. Understanding context-specific metabolic alterations in DCs may identify mechanisms for physiological and pathological functions of DCs and yield potential opportunities for therapeutic targeting of DC metabolism in many diseases.

Targeting the chemokine receptor CXCR4 with histamine analog to reduce inflammation in juvenile arthritis

Introduction

Among immune cells, activated monocytes play a detrimental role in chronic and viral-induced inflammatory pathologies, particularly in Juvenile Idiopathic Arthritis (JIA), a childhood rheumatoid arthritis (RA) disease. The uncontrolled activation of monocytes and excessive production of inflammatory factors contribute to the damage of bone-cartilage joints. Despite the moderate beneficial effect of current therapies and clinical trials, there is still a need for alternative strategies targeting monocytes to treat RA.

Methods

To explore such an alternative strategy, we investigated the effects of targeting the CXCR4 receptor using the histamine analog clobenpropit (CB). Monocytes were isolated from the blood and synovial fluids of JIA patients to assess CB's impact on their production of key inflammatory cytokines. Additionally, we administered daily intraperitoneal CB treatment to arthritic mice to evaluate its effects on circulating inflammatory cytokine levels, immune cell infiltrates, joints erosion, and bone resorption, as indicators of disease progression.

Results

Our findings demonstrated that CXCR4 targeting with CB significantly inhibited the spontaneous and induced-production of key inflammatory cytokines by monocytes isolated from JIA patients. Furthermore, CB treatment in a mouse model of collagen-induce arthritis resulted in a significant decrease in circulating inflammatory cytokine levels, immune cell infiltrates, joints erosion, and bone resorption, leading to a reduction in disease progression.

Discussion

In conclusion, targeting CXCR4 with the small amino compound CB shows promise as a therapeutic option for chronic and viral-induced inflammatory diseases, including RA. CB effectively regulated inflammatory cytokine production of monocytes, presenting a potential targeted approach with potential advantages over current therapies. These results warrant further research and clinical trials to explore the full therapeutic potential of targeting CXCR4 with CB-like molecules in the management of various inflammatory diseases.

Spermine and spermidine bind CXCR4 and inhibit CXCR4- but not CCR5-tropic HIV-1 infection

Semen is an important vector for sexual HIV-1 transmission. Although CXCR4-tropic (X4) HIV-1 may be present in semen, almost exclusively CCR5-tropic (R5) HIV-1 causes systemic infection after sexual intercourse. To identify factors that may limit sexual X4-HIV-1 transmission, we generated a seminal fluid-derived compound library and screened it for antiviral agents. We identified four adjacent fractions that blocked X4-HIV-1 but not R5-HIV-1 and found that they all contained spermine and spermidine, abundant polyamines in semen. We showed that spermine, which is present in semen at concentrations up to 14 mM, binds CXCR4 and selectively inhibits cell-free and cell-associated X4-HIV-1 infection of cell lines and primary target cells at micromolar concentrations. Our findings suggest that seminal spermine restricts sexual X4-HIV-1 transmission.

Toll-like Receptor Response to Human Immunodeficiency Virus Type 1 or Co-Infection with Hepatitis B or C Virus: An Overview

Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors that play important roles in the early detection of pathogen-associated molecular patterns and shaping innate and adaptive immune responses, which may influence the consequences of infection. Similarly to other viral infections, human immunodeficiency virus type 1 (HIV-1) also modulates the host TLR response; therefore, a proper understanding of the response induced by human HIV-1 or co-infection with hepatitis B virus (HBV) or hepatitis C virus (HCV), due to the common mode of transmission of these viruses, is essential for understanding HIV-1 pathogenesis during mono- or co-infection with HBV or HCV, as well as for HIV-1 cure strategies. In this review, we discuss the host TLR response during HIV-1 infection and the innate immune evasion mechanisms adopted by HIV-1 for infection establishment. We also examine changes in the host TLR response during HIV-1 co-infection with HBV or HCV; however, this type of study is extremely scarce. Moreover, we discuss studies investigating TLR agonists as latency-reverting agents and immune stimulators towards new strategies for curing HIV. This understanding will help develop a new strategy for curing HIV-1 mono-infection or co-infection with HBV or HCV.

Discovery of Bis-Imidazoline Derivatives as New CXCR4 Ligands

The chemokine receptor CXCR4 and its ligand CXCL12 regulate leukocyte trafficking, homeostasis and functions and are potential therapeutic targets in many diseases such as HIV-1 infection and cancers. Here, we identified new CXCR4 ligands in the CERMN chemical library using a FRET-based high-throughput screening assay. These are bis-imidazoline compounds comprising two imidazole rings linked by an alkyl chain. The molecules displace CXCL12 binding with submicromolar potencies, similarly to AMD3100, the only marketed CXCR4 ligand. They also inhibit anti-CXCR4 mAb 12G5 binding, CXCL12-mediated chemotaxis and HIV-1 infection. Further studies with newly synthesized derivatives pointed out to a role of alkyl chain length on the bis-imidazoline properties, with molecules with an even number of carbons equal to 8, 10 or 12 being the most potent. Interestingly, these differ in the functions of CXCR4 that they influence. Site-directed mutagenesis and molecular docking predict that the alkyl chain folds in such a way that the two imidazole groups become lodged in the transmembrane binding cavity of CXCR4. Results also suggest that the alkyl chain length influences how the imidazole rings positions in the cavity. These results may provide a basis for the design of new CXCR4 antagonists targeting specific functions of the receptor.

CXCR4 as a novel target in immunology: moving away from typical antagonists

CXCR4 has been a target of interest in drug discovery for numerous years. However, so far, most if not all studies focused on finding antagonists of CXCR4 function. Recent studies demonstrate that targeting a minor allosteric pocket of CXCR4 induces an immunomodulating effect in immune cells expressing CXCR4, connected to the TLR pathway. Compounds binding in this minor pocket seem to be functionally selective with inverse agonistic properties in selected GPCR signaling pathways (Gi activation), but additional signaling pathways are likely to be involved in the immunomodulating effects. In depth research into these CXCR4-targeted immunomodulators could lead to novel treatment options for (auto)-immune diseases.

Effective Anti-SARS-CoV-2 Immune Response in Patients With Clonal Mast Cell Disorders

BACKGROUND

Mast cells are key players in innate immunity and the TH2 adaptive immune response. The latter counterbalances the TH1 response, which is critical for antiviral immunity. Clonal mast cell activation disorders (cMCADs, such as mastocytosis and clonal mast cell activation syndrome) are characterized by abnormal mast cell accumulation and/or activation. No data on the antiviral immune response in patients with MCADs have been published.

OBJECTIVE

To study a comprehensive range of outcomes in patients with cMCAD with PCR- or serologically confirmed coronavirus disease 2019 and to characterize the specific anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immune response in this setting.

METHODS

Clinical follow-up and outcome data were collected prospectively over a 12-month period by members of the French Centre de Référence des Mastocytoses rare disease network. Anti-SARS-CoV-2-specific T-cell activity was measured with an ELISA, and humoral responses were evaluated by assaying circulating levels of specific IgG, IgA, and neutralizing antibodies.

RESULTS

Overall, 32 patients with cMCAD were evaluated. None required noninvasive or mechanical ventilation. Two patients were admitted to hospital for oxygen and steroid therapy. The SARS-CoV-2-specific immune response was characterized in 21 of the 32 patients. Most had high counts of circulating SARS-CoV-2-specific, IFN-γ-producing T cells and high titers of neutralizing antispike IgGs. The patients frequently showed spontaneous T-cell IFN-γ production in the absence of stimulation; this production was correlated with basal circulating tryptase levels (a marker of the mast cell burden).

CONCLUSIONS

Patients with cMCADs might not be at risk of severe coronavirus disease 2019, perhaps due to their spontaneous production of IFN-γ.

IFN-α: A key therapeutic target for multiple autoimmune rheumatic diseases

Interferon (IFN)-α has emerged as a major therapeutic target for several autoimmune rheumatic diseases. In this review, we focus on clinical and preclinical advances in anti-IFN-α treatments in systemic lupus erythematosus (SLE), primary Sjögren syndrome (pSS), systemic sclerosis (SSc), and dermatomyositis (DM), for which a high medical need persists. Promising achievements were obtained following direct IFN-α neutralization, targeting its production through the cytosolic nucleic acid sensor pathways or by blocking its downstream effects through the type I IFN receptor. We further focus on molecular profiling and data integration approaches as crucial steps to select patients most likely to benefit from anti-IFN-α therapies within a precision medicine approach.

Cutaneous and systemic connections in lupus

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with multiple manifestations, with a majority of SLE patients having cutaneous involvement. Despite ongoing research, the relationship between SLE and cutaneous lupus erythematosus (CLE) pathogeneses remains unknown. This review will compare advances in understanding the cause and pathogenesis of SLE and CLE.

RECENT FINDINGS

Recently, mechanisms by which immune cell populations contribute to the pathogenesis of SLE and CLE have been queried. Studies have pointed to transitional B cells and B-cell activating factor (BAFF) signaling as potential drivers of SLE and CLE, with belimumab clinical data supporting these hypotheses. Ustekinumab trials and an exciting regulatory T cell (Treg) adoptive transfer in an SLE patient with cutaneous disease have suggested a role for T-cell-targeted therapies. The theory that neutrophil extracellular traps may be a source of autoantigens in SLE remains controversial, while neutrophils have been suggested as early drivers of cutaneous disease. Finally, plasmacytoid dendritic cells (pDCs) have been studied as a potential therapeutic target in SLE, and anti-blood DC antigen (anti-BDCA) antibody clinical trials have shown promise in treating cutaneous disease.

SUMMARY

Although recent findings have contributed to understanding SLE and CLE pathogenesis, the mechanistic link between these diseases remains an area requiring further research.

Type I Interferon Production of Plasmacytoid Dendritic Cells under Control

One of the most powerful and multifaceted cytokines produced by immune cells are type I interferons (IFNs), the basal secretion of which contributes to the maintenance of immune homeostasis, while their activation-induced production is essential to effective immune responses. Although, each cell is capable of producing type I IFNs, plasmacytoid dendritic cells (pDCs) possess a unique ability to rapidly produce large amounts of them. Importantly, type I IFNs have a prominent role in the pathomechanism of various pDC-associated diseases. Deficiency in type I IFN production increases the risk of more severe viral infections and the development of certain allergic reactions, and supports tumor resistance; nevertheless, its overproduction promotes autoimmune reactions. Therefore, the tight regulation of type I IFN responses of pDCs is essential to maintain an adequate level of immune response without causing adverse effects. Here, our goal was to summarize those endogenous factors that can influence the type I IFN responses of pDCs, and thus might serve as possible therapeutic targets in pDC-associated diseases. Furthermore, we briefly discuss the current therapeutic approaches targeting the pDC-type I IFN axis in viral infections, cancer, autoimmunity, and allergy, together with their limitations defined by the Janus-faced nature of pDC-derived type I IFNs.

CXCR4 and CXCR7 Signaling Pathways: A Focus on the Cross-Talk Between Cancer Cells and Tumor Microenvironment

The chemokine receptor 4 (CXCR4) and 7 (CXCR7) are G-protein-coupled receptors (GPCRs) activated through their shared ligand CXCL12 in multiple human cancers. They play a key role in the tumor/tumor microenvironment (TME) promoting tumor progression, targeting cell proliferation and migration, while orchestrating the recruitment of immune and stromal cells within the TME. CXCL12 excludes T cells from TME through a concentration gradient that inhibits immunoactive cells access and promotes tumor vascularization. Thus, dual CXCR4/CXCR7 inhibition will target different cancer components. CXCR4/CXCR7 antagonism should prevent the development of metastases by interfering with tumor cell growth, migration and chemotaxis and favoring the frequency of T cells in TME. Herein, we discuss the current understanding on the role of CXCL12/CXCR4/CXCR7 cross-talk in tumor progression and immune cells recruitment providing support for a combined CXCR4/CXCR7 targeting therapy. In addition, we consider emerging approaches that coordinately target both immune checkpoints and CXCL12/CXCR4/CXCR7 axis.

CXCL12 Signaling in the Tumor Microenvironment

Tumor microenvironment (TME) is the local environment of tumor, composed of tumor cells and blood vessels, extracellular matrix (ECM), immune cells, and metabolic and signaling molecules. Chemokines and their receptors play a fundamental role in the crosstalk between tumor cells and TME, regulating tumor-related angiogenesis, specific leukocyte infiltration, and activation of the immune response and directly influencing tumor cell growth, invasion, and cancer progression. The chemokine CXCL12 is a homeostatic chemokine that regulates physiological and pathological process such as inflammation, cell proliferation, and specific migration. CXCL12 activates CXCR4 and CXCR7 chemokine receptors, and the entire axis has been shown to be dysregulated in more than 20 different tumors. CXCL12 binding to CXCR4 triggers multiple signal transduction pathways that regulate intracellular calcium flux, chemotaxis, transcription, and cell survival. CXCR7 binds with high-affinity CXCL12 and with lower-affinity CXCL11, which binds also CXCR3. Although CXCR7 acts as a CXCL12 scavenger through ligand internalization and degradation, it transduces the signal mainly through β-arrestin with a pivotal role in endothelial and neural cells. Recent studies demonstrate that TME rich in CXCL12 leads to resistance to immune checkpoint inhibitors (ICI) therapy and that CXCL12 axis inhibitors sensitize resistant tumors to ICI effect. Thus targeting the CXCL12-mediated axis may control tumor and tumor microenvironment exerting an antitumor dual action. Herein CXCL12 physiology, role in cancer biology and in composite TME, prognostic role, and the relative inhibitors are addressed.

Discovery of HIV entry inhibitors via a hybrid CXCR4 and CCR5 receptor pharmacophore-based virtual screening approach

Chemokine receptors are key regulators of cell migration in terms of immunity and inflammation. Among these, CCR5 and CXCR4 play pivotal roles in cancer metastasis and HIV-1 transmission and infection. They act as essential co-receptors for HIV and furnish a route to the cell entry. In particular, inhibition of either CCR5 or CXCR4 leads very often the virus to shift to a more virulent dual-tropic strain. Therefore, dual receptor inhibition might improve the therapeutic strategies against HIV. In this study, we aimed to discover selective CCR5, CXCR4, and dual CCR5/CXCR4 antagonists using both receptor- and ligand-based computational methods. We employed this approach to fully incorporate the interaction attributes of the binding pocket together with molecular dynamics (MD) simulations and binding free energy calculations. The best hits were evaluated for their anti-HIV-1 activity against CXCR4- and CCR5-specific NL4.3 and BaL strains. Moreover, the Ca²⁺ mobilization assay was used to evaluate their antagonistic activity. From the 27 tested compounds, three were identified as inhibitors: compounds 27 (CCR5), 6 (CXCR4) and 3 (dual) with IC₅₀ values ranging from 10.64 to 64.56 μM. The binding mode analysis suggests that the active compounds form a salt bridge with the glutamates and π-stacking interactions with the aromatic side chains binding site residues of the respective co-receptor. The presented hierarchical virtual screening approach provides essential aspects in identifying potential antagonists in terms of selectivity against a specific co-receptor. The compounds having multiple heterocyclic nitrogen atoms proved to be relatively more specific towards CXCR4 inhibition as compared to CCR5. The identified compounds serve as a starting point for further development of HIV entry inhibitors through synthesis and quantitative structure-activity relationship studies.

Hizikia fusiforme extract enhances dendritic cell maturation in vitro and in vivo

Dendritic cells (DCs) are play critical roles in the priming and regulation of immune responses. DCs rapidly process and convey these antigens to prime antigen-specific T cells. Therefore, regulation of DCs functions is important for immunity and immunotherapies. Immune adjuvants for DCs activation are needed to improve the efficacy of vaccines against tumors and many infectious diseases. Therefore, we demonstrate that H. fusiformis extract can regulate DCs maturation and activation. H. fusiformis extract induced costimulatory molecules (CD 80 and CD86), antigen-presenting molecules (major histocompatibility complex (MHC) I and II), CCR7 expression, and interleukin (IL)-12 production in DCs. These effects are associated with upregulation of mitogen-activated protein kinase (MAPK) signaling pathway. In addition, H. fusiformis extract induces costimulatory molecules on splenic DCs and activated CD8+ T cells in vivo. Taken together, these findings suggest that H. fusiformis extract may be a potential efficient immune therapeutic compound in DCs-mediated immunotherapies.

ABBREVIATIONS

CTL: cytotoxic T lymphocytes; DCs: dendritic cells; ERK: extracellular signal-regulated kinases; IL: interleukini; JNK: c-Jun N-terminal kinase; MAPK: mitogen-activated protein kinase; MHC: major histocompatibility complex.

Interplay between SARS-CoV-2 and the type I interferon response

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the current COVID-19 pandemic. An unbalanced immune response, characterized by a weak production of type I interferons (IFN-Is) and an exacerbated release of proinflammatory cytokines, contributes to the severe forms of the disease. SARS-CoV-2 is genetically related to SARS-CoV and Middle East respiratory syndrome-related coronavirus (MERS-CoV), which caused outbreaks in 2003 and 2013, respectively. Although IFN treatment gave some encouraging results against SARS-CoV and MERS-CoV in animal models, its potential as a therapeutic against COVID-19 awaits validation. Here, we describe our current knowledge of the complex interplay between SARS-CoV-2 infection and the IFN system, highlighting some of the gaps that need to be filled for a better understanding of the underlying molecular mechanisms. In addition to the conserved IFN evasion strategies that are likely shared with SARS-CoV and MERS-CoV, novel counteraction mechanisms are being discovered in SARS-CoV-2-infected cells. Since the last coronavirus epidemic, we have made considerable progress in understanding the IFN-I response, including its spatiotemporal regulation and the prominent role of plasmacytoid dendritic cells (pDCs), which are the main IFN-I-producing cells. While awaiting the results of the many clinical trials that are evaluating the efficacy of IFN-I alone or in combination with antiviral molecules, we discuss the potential benefits of a well-timed IFN-I treatment and propose strategies to boost pDC-mediated IFN responses during the early stages of viral infection.

The quest for faithful in vitro models of human dendritic cells types

Dendritic cells (DCs) are mononuclear phagocytes that are specialized in the induction and functional polarization of effector lymphocytes, thus orchestrating immune defenses against infections and cancer. The population of DC encompasses distinct cell types that vary in their efficacy for complementary functions and are thus likely involved in defending the body against different threats. Plasmacytoid DCs specialize in the production of high levels of the antiviral cytokines type I interferons. Type 1 conventional DCs (cDC1s) excel in the activation of cytotoxic CD8⁺ T cells (CTLs) which are critical for defense against cancer and infections by intracellular pathogens. Type 2 conventional DCs (cDC2s) prime helper CD4⁺ T cells for the production of type 2 cytokines underpinning immune defenses against worms or of IL-17 promoting control of infections by extracellular bacteria or fungi. Hence, clinically manipulating the development and functions of DC types could have a major impact for improving treatments against many diseases. However, the rarity and fragility of human DC types is impeding advancement towards this goal. To overcome this roadblock, major efforts are ongoing to generate in vitro large numbers of distinct human DC types. We review here the current state of this research field, emphasizing recent breakthrough and proposing future priorities. We also pinpoint the necessity to develop a consensus nomenclature and rigorous methodologies to ensure proper identification and characterization of human DC types. Finally, we elaborate on how faithful in vitro models of human DC types can accelerate our understanding of the biology of these cells and the engineering of next generation vaccines or immunotherapies against viral infections or cancer.

Altered gene expression in CHO cells following polyamine starvation

AIM

To investigate the impact of polyamine deprivation on the transcriptome of CHO cells RESULTS: Polyamines play a central but poorly-understood role in cell proliferation. Most studies to date have utilised chemical inhibitors to probe polyamine function. Here we exploit the fact that CHO cells grown in serum-free medium have an absolute requirement for putrescine supplementation due to their deficiency in activity of the enzyme arginase. A gene expression microarray (Affymetrix) analysis of CHO-K1 cells starved of polyamines for 3 days showed that cessation of growth, associated with increased G1/S transition and inhibition of M/G1 transition was accompanied by increased mRNA levels of mitotic complex checkpoint genes (Mad2l1, Tkk, Bub1b) and in the transition of G1- to S-phase (such as Skp2 and Tfdp1). mRNAs associated with DNA homologous recombination and repair (including Fanconi's anaemia-related genes) and with RNA splicing were consistently increased. Alterations in mRNA levels for genes related to protein processing in the ER, to ER stress, and to p53-related and apoptosis pathways were also observed. mRNAs showing highest levels of fold-change included several which code for membrane-localised proteins and receptors (Thbs1, Tfrc1, Ackr3, Extl1).

CONCLUSIONS

Growth-arrest induced by polyamine deprivation was associated with significant alterations in levels of mRNAs associated with cell cycle progression, DNA repair, RNA splicing, ER trafficking and membrane signalling as well as p53 and apoptosis-related pathways.

Plasmacytoid dendritic cells promote acute kidney injury by producing interferon-α

Acute kidney injury (AKI) is a common clinical complication associated with high mortality in patients. Immune cells and cytokines have recently been described to play essential roles in AKI pathogenesis. Plasmacytoid dendritic cells (pDCs) are a unique DC subset that specializes in type I interferon (IFN) production. Here, we showed that pDCs rapidly infiltrated the kidney in response to AKI and contributed to kidney damage by producing IFN-α. Deletion of pDCs using DTR^BDCA2 transgenic (Tg) mice suppressed cisplatin-induced AKI, accompanied by marked reductions in proinflammatory cytokine production, immune cell infiltration and apoptosis in the kidney. In contrast, adoptive transfer of pDCs during AKI exacerbated kidney damage. We further identified IFN-α as the key factor that mediated the functions of pDCs during AKI, as IFN-α neutralization significantly attenuated kidney injury. Furthermore, IFN-α produced by pDCs directly induced the apoptosis of renal tubular epithelial cells (TECs) in vitro. In addition, our data demonstrated that apoptotic TECs induced the activation of pDCs, which was inhibited in the presence of an apoptosis inhibitor. Furthermore, similar deleterious effects of pDCs were observed in an ischemia reperfusion (IR)-induced AKI model. Clinically, increased expression of IFN-α in kidney biopsies was observed in kidney transplants with AKI. Taken together, the results of our study reveal that pDCs play a detrimental role in AKI via IFN-α.

Control of TLR7-mediated type I IFN signaling in pDCs through CXCR4 engagement-A new target for lupus treatment

Type I interferons are highly potent cytokines essential for self-protection against tumors and infections. Deregulations of type I interferon signaling are associated with multiple diseases that require novel therapeutic options. Here, we identified the small molecule, IT1t, a previously described CXCR4 ligand, as a highly potent inhibitor of Toll-like receptor 7 (TLR7)-mediated inflammation. IT1t inhibits chemical (R848) and natural (HIV) TLR7-mediated inflammation in purified human plasmacytoid dendritic cells from blood and human tonsils. In a TLR7-dependent lupus-like model, in vivo treatment of mice with IT1t drives drastic reduction of both systemic inflammation and anti-double-stranded DNA autoantibodies and prevents glomerulonephritis. Furthermore, IT1t controls inflammation, including interferon α secretion, in resting and stimulated cells from patients with systemic lupus erythematosus. Our findings highlight a groundbreaking immunoregulatory property of CXCR4 signaling that opens new therapeutic perspectives in inflammatory settings and autoimmune diseases.

Sensing of cell-associated HTLV by plasmacytoid dendritic cells is regulated by dense β-galactoside glycosylation

Human T Lymphotropic virus (HTLV) infection can persist in individuals resulting, at least in part, from viral escape of the innate immunity, including inhibition of type I interferon response in infected T-cells. Plasmacytoid dendritic cells (pDCs) are known to bypass viral escape by their robust type I interferon production. Here, we demonstrated that pDCs produce type I interferons upon physical cell contact with HTLV-infected cells, yet pDC activation inversely correlates with the ability of the HTLV-producing cells to transmit infection. We show that pDCs sense surface associated-HTLV present with glycan-rich structure referred to as biofilm-like structure, which thus represents a newly described viral structure triggering the antiviral response by pDCs. Consistently, heparan sulfate proteoglycans and especially the cell surface pattern of terminal β-galactoside glycosylation, modulate the transmission of the immunostimulatory RNA to pDCs. Altogether, our results uncover a function of virus-containing cell surface-associated glycosylated structures in the activation of innate immunity.

CCR5/CXCR4 Dual Antagonism for the Improvement of HIV Infection Therapy

HIV entry in the host cell requires the interaction with the CD4 membrane receptor, and depends on the activation of one or both co-receptors CCR5 and CXCR4. Former selective co-receptor antagonists, acting at early stages of infection, are able to impair the receptor functions, preventing the viral spread toward AIDS. Due to the capability of HIV to develop resistance by switching from CCR5 to CXCR4, dual co-receptor antagonists could represent the next generation of AIDS prophylaxis drugs. We herein present a survey on relevant results published in the last few years on compounds acting simultaneously on both co-receptors, potentially useful as preventing agents or in combination with classical anti-retroviral drugs based therapy.

Plasmacytoid Dendritic Cells: Development, Regulation, and Function

Plasmacytoid dendritic cells (pDCs) are a unique sentinel cell type that can detect pathogen-derived nucleic acids and respond with rapid and massive production of type I interferon. This review summarizes our current understanding of pDC biology, including transcriptional regulation, heterogeneity, role in antiviral immune responses, and involvement in immune pathology, particularly in autoimmune diseases, immunodeficiency, and cancer. We also highlight the remaining gaps in our knowledge and important questions for the field, such as the molecular basis of unique interferon-producing capacity of pDCs. A better understanding of cell type-specific positive and negative control of pDC function should pave the way for translational applications focused on this immune cell type.

A guide to chemokines and their receptors

The chemokines (or chemotactic cytokines) are a large family of small, secreted proteins that signal through cell surface G protein-coupled heptahelical chemokine receptors. They are best known for their ability to stimulate the migration of cells, most notably white blood cells (leukocytes). Consequently, chemokines play a central role in the development and homeostasis of the immune system, and are involved in all protective or destructive immune and inflammatory responses. Classically viewed as inducers of directed chemotactic migration, it is now clear that chemokines can stimulate a variety of other types of directed and undirected migratory behavior, such as haptotaxis, chemokinesis, and haptokinesis, in addition to inducing cell arrest or adhesion. However, chemokine receptors on leukocytes can do more than just direct migration, and these molecules can also be expressed on, and regulate the biology of, many nonleukocytic cell types. Chemokines are profoundly affected by post-translational modification, by interaction with the extracellular matrix (ECM), and by binding to heptahelical 'atypical' chemokine receptors that regulate chemokine localization and abundance. This guide gives a broad overview of the chemokine and chemokine receptor families; summarizes the complex physical interactions that occur in the chemokine network; and, using specific examples, discusses general principles of chemokine function, focusing particularly on their ability to direct leukocyte migration.