Calcineurin regulates innate antifungal immunity in neutrophils

Calcineurin-NFAT signaling controls neutrophils' ability of chemoattraction upon fungal infection

Calcineurin-nuclear factor of activated T cells (CN-NFAT) inhibitors are widely clinically used drugs for immunosuppression, but besides their required T cell response inhibition, they also undesirably affect innate immune cells. Disruption of innate immune cell function can explain the observed susceptibility of CN-NFAT inhibitor-treated patients to opportunistic fungal infections. Neutrophils play an essential role in innate immunity as a defense against pathogens; however, the effect of CN-NFAT inhibitors on neutrophil function was poorly described. Thus, we tested the response of human neutrophils to opportunistic fungal pathogens, namely Candida albicans and Aspergillus fumigatus, in the presence of CN-NFAT inhibitors. Here, we report that the NFAT pathway members were expressed in neutrophils and mediated part of the neutrophil response to pathogens. Upon pathogen exposure, neutrophils underwent profound transcriptomic changes with subsequent production of effector molecules. Importantly, genes and proteins involved in the regulation of the immune response and chemotaxis, including the chemokines CCL2, CCL3, and CCL4 were significantly upregulated. The presence of CN-NFAT inhibitors attenuated the expression of these chemokines and impaired the ability of neutrophils to chemoattract other immune cells. Our results amend knowledge about the impact of CN-NFAT inhibition in human neutrophils.

The emerging role of neutrophil extracellular traps in ulcerative colitis

Ulcerative colitis (UC) is characterized by chronic non-recessive inflammation of the intestinal mucosa involving both innate and adaptive immune responses. Currently, new targeted therapies are urgently needed for UC, and neutrophil extracellular traps (NETs) are new therapeutic options. NETs are DNA-based networks released from neutrophils into the extracellular space after stimulation, in which a variety of granule proteins, proteolytic enzymes, antibacterial peptides, histones, and other network structures are embedded. With the deepening of the studies on NETs, their regulatory role in the development of autoimmune and autoinflammatory diseases has received extensive attention in recent years. Increasing evidence indicates that excess NETs exacerbate the inflammatory response in UC, disrupting the structure and function of the intestinal mucosal barrier and increasing the risk of thrombosis. Although NETs are usually assigned a deleterious role in promoting the pathological process of UC, they also appear to have a protective role in some models. Despite such progress, comprehensive reviews describing the therapeutic promise of NETs in UC remain limited. In this review, we discuss the latest evidence for the formation and degradation of NETs, focusing on their double-edged role in UC. Finally, the potential implications of NETs as therapeutic targets for UC will be discussed. This review aims to provide novel insights into the pathogenesis and therapeutic options for UC.

Effect of Mycolic Acids on Host Immunity and Lipid Metabolism

Mycolic acids constitute pivotal constituents within the cell wall structure of Mycobacterium tuberculosis. Due to their structural diversity, the composition of mycolic acids exhibits substantial variations among different strains, endowing them with the distinctive label of being the 'signature' feature of mycobacterial species. Within Mycobacterium tuberculosis, the primary classes of mycolic acids include α-, keto-, and methoxy-mycolic acids. While these mycolic acids are predominantly esterified to the cell wall components (such as arabinogalactan, alginate, or glucose) of Mycobacterium tuberculosis, a fraction of free mycolic acids are secreted during in vitro growth of the bacterium. Remarkably, different types of mycolic acids possess varying capabilities to induce foamy macro-phages and trigger immune responses. Additionally, mycolic acids play a regulatory role in the lipid metabolism of host cells, thereby exerting influence over the progression of tuberculosis. Consequently, the multifaceted properties of mycolic acids shape the immune evasion strategy employed by Mycobacterium tuberculosis. A comprehensive understanding of mycolic acids is of paramount significance in the pursuit of developing tuberculosis therapeutics and unraveling the intricacies of its pathogenic mechanisms.

Farnesol remodels the peritoneal cavity immune environment influencing Candida albicans pathogenesis during intra-abdominal infection

Candida albicans is a lifelong member of the mycobiome causing mucosal candidiasis and life-threatening, systemic, and intra-abdominal disease in immunocompromised and transplant patients. Despite the clinical importance of intra-abdominal candidiasis with mortality rates between 40% and 70%, the contribution of fungal virulence factors and host immune responses to disease has not been extensively studied. Secretion of the quorum-sensing molecule, farnesol, acts as a virulence factor for C. albicans during systemic infection, while inducing local, protective innate immune responses in oral models of infection. Previously, we reported that farnesol recruits macrophages to the peritoneal cavity in mice, suggesting a role for farnesol in innate immune responses. Here, we expand on our initial findings, showing that farnesol profoundly alters the peritoneal cavity microenvironment promoting innate inflammation. Intra-peritoneal injection of farnesol stimulates rapid local death of resident peritoneal cells followed by recruitment of neutrophils and inflammatory macrophages into the peritoneal cavity and peritoneal mesothelium associated with an early increase in chemokines followed by proinflammatory cytokines. These rapid inflammatory responses to farnesol significantly increase morbidity and mortality of mice with intra-abdominal candidiasis associated with increased formation of peritoneal adhesions, despite similar rates of fungal clearance from the peritoneal cavity and retro-peritoneal organs. C. albicans ddp3Δ/ddp3Δ knockout and reconstituted strains recapitulate these findings. This indicates that farnesol may be detrimental to the host during intra-abdominal infections. Importantly, our results highlight a need to understand how C. albicans virulence factors modulate the host immune response within the peritoneum, an exceedingly common site of Candida infection.

Investigation of the effects of urotensin II receptors in LPS-induced inflammatory response in HUVEC cell line through calcineurin/NFATc/IL-2 pathway

PURPOSE

The effect of urotensin II (U-II), a powerful endogenous vasoconstrictor substance, on the immune system and its mediators is very important. It was herein aimed to demonstrate the possible relationship between the calcineurin/nuclear factor of activated T-cells cytoplasmic 1/interleukin-2 (CaN/NFATc/IL-2) pathway and urotensin receptors (UTRs) in inflammatory response due to lipopolysaccharide (LPS).

METHODS

An LPS-induced inflammation model was used on the human umbilical vein endothelial cells (HUVEC) cell line and drugs were applied accordingly, forming the following groups: Control Group, LPS Group, Agonist Group (10-8 ​M U-II), Antagonist Group (10-6 ​M palosuran), Tacrolimus (TAC) Group (10 ​ng/mL FK-506), Agonist ​+ ​TAC Group, and Antagonist ​+ ​TAC Group. Gene expression analyses were performed using real-time polymerase chain reaction (RT-PCR).

RESULTS

In the analysis of the cell viability at 48 and 72 ​h, there was a decrease in the Agonist Group, while in the Agonist ​+ ​TAC Group, the cell viability increased. In the Antagonist Group, cell viability was maintained when compared to the LPS Group, while in the TAC Group, this effect was reduced. The mRNA expression levels of UTR, CaN, NFATc, IL-2 receptor (IL-2R), IL-6 and nuclear factor kappa B (NF-κB) were higher in the LPS Group than in the Control Group, and even the UTR, CaN, NFATc, IL-2R were higher with agonist administration. This effect of the agonist was shown to be completely mitigated in the presence of the CaN inhibitor.

CONCLUSION

U-II and its receptors can perform key functions regarding the endothelial cell damage via the CaN/NFATc/IL-2 pathway.

Inflammatory ER stress responses dictate the immunopathogenic progression of systemic candidiasis

Recognition of pathogen-associated molecular patterns can trigger the inositol-requiring enzyme 1 α (IRE1α) arm of the endoplasmic reticulum (ER) stress response in innate immune cells. This process maintains ER homeostasis and also coordinates diverse immunomodulatory programs during bacterial and viral infections. However, the role of innate IRE1α signaling in response to fungal pathogens remains elusive. Here, we report that systemic infection with the human opportunistic fungal pathogen Candida albicans induced proinflammatory IRE1α hyperactivation in myeloid cells that led to fatal kidney immunopathology. Mechanistically, simultaneous activation of the TLR/IL-1R adaptor protein MyD88 and the C-type lectin receptor dectin-1 by C. albicans induced NADPH oxidase-driven generation of ROS, which caused ER stress and IRE1α-dependent overexpression of key inflammatory mediators such as IL-1β, IL-6, chemokine (C-C motif) ligand 5 (CCL5), prostaglandin E2 (PGE2), and TNF-α. Selective ablation of IRE1α in leukocytes, or treatment with an IRE1α pharmacological inhibitor, mitigated kidney inflammation and prolonged the survival of mice with systemic C. albicans infection. Therefore, controlling IRE1α hyperactivation may be useful for impeding the immunopathogenic progression of disseminated candidiasis.

Effects of bacteriophage on Salmonella Enteritidis infection in broilers

Bacteriophages (BP) are viruses that can infect bacteria. The present study evaluated the effect of BP on Salmonella infected broilers. A number of 150 day-old broilers were used in a completely randomized design with five treatments that included: (1) basal diet from day 0 to 28; (2) basal diet + 0.3 g/kg of colistin from day 0 to 28; (3) basal diet from day 1 to 13, and basal diet + 0.4 g/kg of colistin from day 14 to 28; (4) basal diet + 1 g/kg of BP from day 0 to 28; (5) basal diet + 1.5 g/kg of BP from day 0 to 28. On day 13, 15 chickens from each treatment were challenged by Salmonella Enteritidis (SE), while fifteen from each treatment were not; instead, they were kept in the same cage with the challenged chickens (exposed chickens). At 7 and 14 days post-challenge, the number of SE and coliform bacteria in the cecum and liver of colistin and BP-fed birds was lower than the control treatment. In exposed and challenged chickens, the height and surface area of villus were greater in the BP and colistin-supplemented groups. Serum concentrations of aspartate aminotransferase and alanine transaminase were greater, while serum albumin and triglycerides concentrations were lower in the control treatment. The liver of the challenged chickens had more pathological lesions than exposed birds. BP significantly decreased PPARγ gene expression in exposed chickens. In the challenged and exposed chickens, TLR4 gene expression was lower in BP and colistin-treated birds as compared to the control. In conclusion, adding BP to the diet from the day of age prevents the spread of Salmonella.

Evolutionary mechanisms underlying the diversification of nuclear factor of activated T cells across vertebrates

The mechanisms of immunity linked to biological evolution are crucial for understanding animal morphogenesis, organogenesis, and biodiversity. The nuclear factor of activated T cells (NFAT) family consists of five members (NFATc1-c4, 5) with different functions in the immune system. However, the evolutionary dynamics of NFATs in vertebrates has not been explored. Herein, we investigated the origin and mechanisms underlying the diversification of NFATs by comparing the gene, transcript and protein sequences, and chromosome information. We defined an ancestral origin of NFATs during the bilaterian development, dated approximately 650 million years ago, where NFAT5 and NFATc1-c4 were derived independently. The conserved parallel evolution of NFATs in multiple species was probably attributed to their innate nature. Conversely, frequent gene duplications and chromosomal rearrangements in the recently evolved taxa have suggested their roles in the adaptive immune evolution. A significant correlation was observed between the chromosome rearrangements with gene duplications and the structural fixation changes in vertebrate NFATs, suggesting their role in NFAT diversification. Remarkably, a conserved gene structure around NFAT genes with vertebrate evolutionary-related breaking points indicated the inheritance of NFATs with their neighboring genes as a unit. The close relationship between NFAT diversification and vertebrate immune evolution was suggested.

Cyclosporine A Regulates Influenza A Virus-induced Macrophages Polarization and Inflammatory Responses by Targeting Cyclophilin A

Cyclosporine A (CsA) is an immunosuppressive drug that suppresses T cell responses and is broadly used in transplantation. Its immunosuppressive action is closely linked to its binding of cyclophilin A (CypA), which widely distributed in different cell types. CsA also regulates the functions of innate immune cells, but the mechanism remains elusive. Here, we investigate the role of CsA in regulating macrophages polarization in influenza A virus-infected mice and mouse bone marrow-derived macrophages. CsA downregulates pro-inflammatory cytokines expression and upregulates anti-inflammatory cytokines expression. Mechanically, CsA decreases the polarization of macrophages into pro-inflammatory M1 phenotype and increases the polarization of macrophages into anti-inflammatory M2 phenotype. Further studies show that CsA regulates macrophages polarization-associated IFN-γ/STAT1 and IL-4/STAT6 signaling pathways. Meanwhile, all these roles of CsA are eliminated when CypA is absent, suggesting that CsA regulates macrophages polarization and inflammatory responses depend on its binding to CypA. Collectively, these results reveal a crucial mechanism of CsA in attenuating IAV-induced inflammatory responses by a switch in macrophages polarization.

Microbiota-dependent activation of the myeloid calcineurin-NFAT pathway inhibits B7H3- and B7H4-dependent anti-tumor immunity in colorectal cancer

Bacterial sensing by intestinal tumor cells contributes to tumor growth through cell-intrinsic activation of the calcineurin-NFAT axis, but the role of this pathway in other intestinal cells remains unclear. Here, we found that myeloid-specific deletion of calcineurin in mice activated protective CD8⁺ T cell responses and inhibited colorectal cancer (CRC) growth. Microbial sensing by myeloid cells promoted calcineurin- and NFAT-dependent interleukin 6 (IL-6) release, expression of the co-inhibitory molecules B7H3 and B7H4 by tumor cells, and inhibition of CD8⁺ T cell-dependent anti-tumor immunity. Accordingly, targeting members of this pathway activated protective CD8⁺ T cell responses and inhibited primary and metastatic CRC growth. B7H3 and B7H4 were expressed by the majority of human primary CRCs and metastases, which was associated with low numbers of tumor-infiltrating CD8⁺ T cells and poor survival. Therefore, a microbiota-, calcineurin-, and B7H3/B7H4-dependent pathway controls anti-tumor immunity, revealing additional targets for immune checkpoint inhibition in microsatellite-stable CRC.

Rapid pathogen-specific recruitment of immune effector cells in the skin by secreted toxins

Swift recruitment of phagocytic leucocytes is critical in preventing infection when bacteria breach through the protective layers of the skin. According to canonical models, this occurs via an indirect process that is initiated by contact of bacteria with resident skin cells and which is independent of the pathogenic potential of the invader. Here we describe a more rapid mechanism of leucocyte recruitment to the site of intrusion of the important skin pathogen Staphylococcus aureus that is based on direct recognition of specific bacterial toxins, the phenol-soluble modulins (PSMs), by circulating leucocytes. We used a combination of intravital imaging, ear infection and skin abscess models, and in vitro gene expression studies to demonstrate that this early recruitment was dependent on the transcription factor EGR1 and contributed to the prevention of infection. Our findings refine the classical notion of the non-specific and resident cell-dependent character of the innate immune response to bacterial infection by demonstrating a pathogen-specific high-alert mechanism involving direct recruitment of immune effector cells by secreted bacterial products.

Immunosuppression Affects Neutrophil Functions: Does Calcineurin-NFAT Signaling Matter?

Neutrophils are innate immune cells with important roles in antimicrobial defense. However, impaired or dysregulated neutrophil function can result in host tissue damage, loss of homeostasis, hyperinflammation or pathological immunosuppression. A central link between neutrophil activation and immune outcomes is emerging to be the calcineurin-nuclear factor of activated T cells (NFAT) signaling pathway, which is activated by neutrophil detection of a microbial threat via pattern recognition receptors and results in inflammatory cytokine production. This potent pro-inflammatory pathway is also the target of several immunosuppressive drugs used for the treatment of autoimmune disorders, during solid organ and hematopoietic cell transplantations, and as a part of anti-cancer therapy: but what effects these drugs have on neutrophil function, and their broader consequences for immune homeostasis and microbial defense are not yet known. Here, we bring together the emerging literature describing pathology- and drug- induced neutrophil impairment, with particular focus on their effects on calcineurin-NFAT signaling in the innate immune compartment.

Cyclosporine A plus low-dose steroid treatment in COVID-19 improves clinical outcomes in patients with moderate to severe disease: A pilot study

BACKGROUND

COVID-19 pandemic causes high global morbidity and mortality and better medical treatments to reduce mortality are needed.

OBJECTIVE

To determine the added benefit of cyclosporine A (CsA), to low-dose steroid treatment, in patients with COVID-19.

METHODS

Open-label, non randomized pilot study of patients with confirmed infection of SARS-CoV-2 hospitalized from April to May 2020 at a single centre in Puebla, Mexico. Patients were assigned to receive either steroids or CsA plus steroids. Pneumonia severity was assessed by clinical, laboratory, and lung tomography. The death rate was evaluated at 28 days.

RESULTS

A total of 209 adult patients were studied, 105 received CsA plus steroids (age 55.3 ± 13.3; 69% men), and 104 steroids alone (age 54.06 ± 13.8; 61% men). All patients received clarithromycin, enoxaparin and methylprednisolone or prednisone up to 10 days. Patient's death was associated with hypertension (RR = 3.5) and diabetes (RR = 2.3). Mortality was 22 and 35% for CsA and control groups (P = 0.02), respectively, for all patients, and 24 and 48.5% for patients with moderate to severe disease (P = 0.001). Higher cumulative clinical improvement was seen for the CsA group (Nelson Aalen curve, P = 0.001, log-rank test) in moderate to severe patients. The Cox proportional hazard analysis showed the highest HR improvement value of 2.15 (1.39-3.34, 95%CI, P = 0.0005) for CsA treatment in moderate to severe patients, and HR = 1.95 (1.35-2.83, 95%CI, P = 0.0003) for all patients.

CONCLUSION

CsA used as an adjuvant to steroid treatment for COVID-19 patients showed to improve outcomes and reduce mortality, mainly in those with moderate to severe disease. Further investigation through controlled clinical trials is warranted.

Calcineurin Immune Signaling in Response to Zinc Challenge in the Naked Carp Gymnocypris eckloni

Zinc pollution impairs neural processes and protein function and also effects calcium-related transcriptional regulation and enzyme activity. In this study, we investigated pathways that potentially respond to calcium signaling under Zn²⁺ stress. Specifically we measured relative expressions of GeCNAα, GeCNB, GeMT, GeTNF-α, GeIL-1β, and GeHsp90 in gills, livers, and kidneys of the indicator species Gymnocypris eckloni and found wide variation in their expression between tissues during the course of Zn²⁺ exposure. Notably, GeCNAα, GeCNB, GeTNF-α, GeIL-1β, and GeMT were rapidly and strongly up-regulated in gills; GeIL-1β and GeHsp90 transcription was quickly induced in kidneys; and GeCNB, GeTNF-α, GeIL-1β, and GeHsp90 were most rapidly up-regulated in livers. GeCNAα and GeMT showed a contrasting late transcriptional up-regulation. These results suggest independent branches for chelation and immune responses during self-protection against Zn²⁺ toxicity, and the immune response appears to be faster than metal chelation.

Uncovering the multifaceted roles played by neutrophils in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a life-saving procedure used for the treatment of selected hematological malignancies, inborn errors of metabolism, and bone marrow failures. The role of neutrophils in alloHSCT has been traditionally evaluated only in the context of their ability to act as a first line of defense against infection. However, recent evidence has highlighted neutrophils as key effectors of innate and adaptive immune responses through a wide array of newly discovered functions. Accordingly, neutrophils are emerging as highly versatile cells that are able to acquire different, often opposite, functional capacities depending on the microenvironment and their differentiation status. Herein, we review the current knowledge on the multiple functions that neutrophils exhibit through the different stages of alloHSCT, from the hematopoietic stem cell (HSC) mobilization in the donor to the immunological reconstitution that occurs in the recipient following HSC infusion. We also discuss the influence exerted on neutrophils by the immunosuppressive drugs delivered in the course of alloHSCT as part of graft-versus-host disease (GVHD) prophylaxis. Finally, the potential involvement of neutrophils in alloHSCT-related complications, such as transplant-associated thrombotic microangiopathy (TA-TMA), acute and chronic GVHD, and cytomegalovirus (CMV) reactivation, is also discussed. Based on the data reviewed herein, the role played by neutrophils in alloHSCT is far greater than a simple antimicrobial role. However, much remains to be investigated in terms of the potential functions that neutrophils might exert during a highly complex procedure such as alloHSCT.

Inositol 1,4,5-trisphosphate 3-kinase B promotes Ca2+ mobilization and the inflammatory activity of dendritic cells

Innate immune responses to Gram-negative bacteria depend on the recognition of lipopolysaccharide (LPS) by a receptor complex that includes CD14 and TLR4. In dendritic cells (DCs), CD14 enhances the activation not only of TLR4 but also that of the NFAT family of transcription factors, which suppresses cell survival and promotes the production of inflammatory mediators. NFAT activation requires Ca²⁺ mobilization. In DCs, Ca²⁺ mobilization in response to LPS depends on phospholipase C γ2 (PLCγ2), which produces inositol 1,4,5-trisphosphate (IP₃). Here, we showed that the IP₃ receptor 3 (IP₃R3) and ITPKB, a kinase that converts IP₃ to inositol 1,3,4,5-tetrakisphosphate (IP₄), were both necessary for Ca²⁺ mobilization and NFAT activation in mouse and human DCs. A pool of IP₃R3 was located on the plasma membrane of DCs, where it colocalized with CD14 and ITPKB. Upon LPS binding to CD14, ITPKB was required for Ca²⁺ mobilization through plasma membrane-localized IP₃R3 and for NFAT nuclear translocation. Pharmacological inhibition of ITPKB in mice reduced both LPS-induced tissue swelling and the severity of inflammatory arthritis to a similar extent as that induced by the inhibition of NFAT using nanoparticles that delivered an NFAT-inhibiting peptide specifically to phagocytic cells. Our results suggest that ITPKB may represent a promising target for anti-inflammatory therapies that aim to inhibit specific DC functions.

Study on the Inhibitory Activity and Possible Mechanism of Myriocin on Clinically Relevant Drug-Resistant Candida albicans and Its Biofilms

In order to prevent and control the infection of Candida albicans, the antifungal activity, possible mechanism of myriocin against C. albicans and its biofilm were studied. The antifungal activity of myriocin was investigated by microdilution method. The effect of myriocin on fungal cell wall or membrane was evaluated by adding sorbitol, ergosterol or phytosphingosine (PHS). The damage to the cell membrane was investigated with propidium iodide (PI) staining and visualized by scanning electron microscope (SEM). The effects on biofilms and extracellular polysaccharides (EPS) were observed by crystal violet staining method and phenol-sulfuric acid method respectively. The adhesion of C. albicans cells to hydrocarbons was tested to evaluate cell surface hydrophobic (CSH). The combined effects of myriocin and antifungal drugs commonly used in clinical practice were investigated by using the checkerboard microdilution method. Minimal inhibitory concentrations (MICs) were found to be 0.125-4 µg/mL. Myriocin was found to affect both cell wall and cell membrane. After exposure to myriocin, biofilm and EPS were found to be inhibited and removed, and the CSH was decreased. The combined fungistasis of myriocin and voriconazole (VCZ) or amphotericin B (AMB) were additive. Myriocin had significant antifungal activity against C. albicans, and the antifungal mechanisms might be cell wall and membrane damage. Myriocin effectively inhibited and eliminated biofilms, and its mechanism may be related to the inhibition of EPS and CSH.

Genetic and Environmental Factors in Parkinson's Disease Converge on Immune Function and Inflammation

Idiopathic Parkinson's disease (iPD) is a movement disorder characterized by the degeneration of dopaminergic neurons and aggregation of the protein α-synuclein. Patients with iPD vary in age of symptom onset, rate of progression, severity of motor and non-motor symptoms, and extent of central and peripheral inflammation. Genetic and environmental factors are believed to act synergistically in iPD pathogenesis. We propose that environmental factors (pesticides and infections) increase the risk for iPD via the immune system and that the role of PD risk genes in immune cells is worthy of investigation. This review highlights the major PD-relevant genes expressed in immune cells and key environmental factors that activate immune cells and, alone or in combination with other factors, may contribute to iPD pathogenesis. By reviewing these interactions, we seek to enable the future development of immunomodulatory approaches to prevent or delay onset of iPD. © 2020 International Parkinson and Movement Disorder Society.

NFATc2-dependent epigenetic upregulation of CXCL14 is involved in the development of neuropathic pain induced by paclitaxel

Background

The major dose-limiting toxicity of paclitaxel, one of the most commonly used drugs to treat solid tumor, is painful neuropathy. However, the molecular mechanisms underlying paclitaxel-induced painful neuropathy are largely unclarified.

Methods

Paw withdrawal threshold was measured in the rats following intraperitoneal injection of paclitaxel. The qPCR, western blotting, protein or chromatin immunoprecipitation, ChIP-seq identification of NFATc2 binding sites, and microarray analysis were performed to explore the molecular mechanism.

Results

We found that paclitaxel treatment increased the nuclear expression of NFATc2 in the spinal dorsal horn, and knockdown of NFATc2 with NFATc2 siRNA significantly attenuated the mechanical allodynia induced by paclitaxel. Further binding site analysis utilizing ChIP-seq assay combining with gene expression profile revealed a shift of NFATc2 binding site closer to TTS of target genes in dorsal horn after paclitaxel treatment.

We further found that NFATc2 occupancy may directly upregulate the chemokine CXCL14 expression in dorsal horn, which was mediated by enhanced interaction between NFATc2 and p300 and consequently increased acetylation of histone H4 in CXCL14 promoter region. Also, knockdown of CXCL14 in dorsal horn significantly attenuated mechanical allodynia induced by paclitaxel.

Conclusion

These results suggested that enhanced interaction between p300 and NFATc2 mediated the epigenetic upregulation of CXCL14 in the spinal dorsal horn, which contributed to the chemotherapeutic paclitaxel-induced chronic pain.

Supplementary information

The online version contains supplementary material available at 10.1186/s12974-020-01992-1.

Interferon-γ signaling synergizes with LRRK2 in neurons and microglia derived from human induced pluripotent stem cells

Parkinson's disease-associated kinase LRRK2 has been linked to IFN type II (IFN-γ) response in infections and to dopaminergic neuronal loss. However, whether and how LRRK2 synergizes with IFN-γ remains unclear. In this study, we employed dopaminergic neurons and microglia differentiated from patient-derived induced pluripotent stem cells carrying LRRK2 G2019S, the most common Parkinson's disease-associated mutation. We show that IFN-γ enhances the LRRK2 G2019S-dependent negative regulation of AKT phosphorylation and NFAT activation, thereby increasing neuronal vulnerability to immune challenge. Mechanistically, LRRK2 G2019S suppresses NFAT translocation via calcium signaling and possibly through microtubule reorganization. In microglia, LRRK2 modulates cytokine production and the glycolytic switch in response to IFN-γ in an NFAT-independent manner. Activated LRRK2 G2019S microglia cause neurite shortening, indicating that LRRK2-driven immunological changes can be neurotoxic. We propose that synergistic LRRK2/IFN-γ activation serves as a potential link between inflammation and neurodegeneration in Parkinson's disease.

Immunosuppressive Agents and Infectious Risk in Transplantation: Managing the "Net State of Immunosuppression"

Successful solid organ transplantation reflects meticulous attention to the details of immunosuppression, balancing risks for graft rejection against risks for infection. The 'net state of immune suppression' is a conceptual framework of all factors contributing to infectious risk. Assays which measure immune function in the immunosuppressed transplant recipient relative to infectious risk and allograft function are lacking. The best measures of integrated immune function may be quantitative viral loads to assess the individual's ability to control latent viral infections. Few studies address adjustment of immunosuppression during active infections. Thus, confronted with infection in solid organ recipients, the management of immunosuppression is based largely on clinical experience. This review examines known measures of immune function and the immunologic effects of common immunosuppressive drugs and available studies reporting modification of drug regimens for specific infections. These data provide a conceptual framework for the management of immunosuppression during infection in organ recipients.

Characterization of calcineurin A and B genes in the abalone, Haliotis diversicolor, and their immune response role during bacterial infection

Calcineurin (CN) is known to be involved in many biological processes, particularly, the immune response mechanism in many invertebrates. In this study, we characterized both HcCNA and HcCNB genes in Haliotis diversicolor, documented their expression in many tissues, and discerned their function as immune responsive genes against Vibrio parahaemolyticus infection. Similar to other mollusk CNs, the HcCNA gene lacked a proline-rich domain and comprised only one isoform of its catalytic unit, in contrast to CNs found in mammals. HcCNB was highly conserved in both sequence and domain architecture. Quantitative PCR and in situ hybridization revealed that the genes were broadly expressed and were not restricted to tissues traditionally associated with immune function. Upon infection of H. diversicolor with V. parahaemolyticus (a bacteria that causes serious disease in crustaceans and mollusks), both HcCNA and HcCNB genes were highly up-regulated at the early phase of bacterial infection. HcCNB was expressed significantly higher than HcCNA in response to bacterial challenge, suggesting its independent or more rapid response to bacterial infection. Together, the two CN genes are unique in their gene structure (particular HcCNA) and distribution in mollusk species and likely function as immune responsive genes along with many other genes that are enhanced in the early phase of V. parahaemolyticus infection in abalone.

Correlation Between Neutrophil Count and Prognosis in STEMI Patients with Chronic Renal Dysfunction: A Retrospective Cohort Study

Neutrophil is a key element in inflammation and stress disease, which are associated with poor clinical outcomes in various cardiac diseases. However, the clinical availability of neutrophil in patients with ST-elevation myocardial infarction (STEMI) and chronic renal dysfunction has not been known. Accordingly, we designed this retrospective cohort study to evaluate the differences of major adverse cardiovascular events incidence between renal dysfunctional STEMI patients with normal and high neutrophil levels. The primary end point was all-cause mortality. We analyzed 377 consecutive STEMI patients with chronic renal dysfunction. The results showed that during 12-48 months follow-up, death from any-cause occurred in 1.4% patients (4 of 290) in normal-level neutrophil group, as compared with 3.4% in high-level neutrophil group (3 of 87) (hazard ratio, 2.174 95% confidence interval, 1.024-10.248; P = 0.025). Kaplan-Meier survival analysis showed that there were significant differences between the two groups with respect to the risk of death (P=0.018), and heart failure (P=0.037).

Effects of Antirejection Drugs on Innate Immune Cells After Kidney Transplantation

Over the last decades, our understanding of adaptive immune responses to solid organ transplantation increased considerably and allowed development of immunosuppressive drugs targeting key alloreactive T cells mechanism. As a result, rates of acute rejection dropped and short-term graft survival improved significantly. However, long-term outcomes are still disappointing. Recently, increasing evidence supports that innate immune responses plays roles in allograft rejection and represents a valuable target to further improve long-term allograft survival. Innate immune cells are activated by molecules with stereotypical motifs produced during injury (i.e., damage-associated molecular patterns, DAMPS) or infection (i.e., pathogen-associated molecular patterns, PAMPs). Activated innate immune cells can exert direct pro- and anti-inflammatory effects, while also priming adaptive immune responses. These cells are activated after transplantation by multiple stimuli, including ischemia-reperfusion injury, rejection, and infections. Data from animal models of graft rejection, show that inhibition of innate immunity promotes development of tolerance. Therefore, understanding mechanisms of innate immunity is important to improve graft outcomes. This review discusses effects of currently used immunosuppressive agents on innate immune responses in kidney transplantation.

CR3 Engaged by PGL-I Triggers Syk-Calcineurin-NFATc to Rewire the Innate Immune Response in Leprosy

Mycobacterium leprae, the causative agent of leprosy, is unique amongst human pathogens in its capacity to produce the virulence factor phenolic glycolipid (PGL)-I. In addition to mediating bacterial tropism for neurons, PGL-I interacts with Complement Receptor (CR)3 on macrophages (MPs) to promote infection. We demonstrate here that PGL-I binding to CR3 also enhances bacterial invasion of both polymorphonuclear neutrophils (PMNs) and dendritic cells (DCs). Moreover, in all cell types CR3 engagement by PGL-I activates the Syk tyrosine kinase, inducing calcineurin-dependent nuclear translocation of the transcription factor NFATc. This selectively augments the production of IL-2 by DCs, IL-10 by PMNs and IL-1β by MPs. In intranasally-infected mice PGL-I binding to CR3 heightens mycobacterial phagocytosis by lung PMNs and MPs, and stimulates NFATc-controlled production of Syk-dependent cytokines. Our study thus identifies the CR3-Syk-NFATc axis as a novel signaling pathway activated by PGL-I in innate immune cells, rewiring host cytokine responses to M. leprae.

Metalloimmunology: The metal ion-controlled immunity

Metals are essential components in all forms of life required for the function of nearly half of all enzymes and are critically involved in virtually all fundamental biological processes. Especially, the transition metals iron (Fe), zinc (Zn), manganese (Mn), nickel (Ni), copper (Cu) and cobalt (Co) are crucial micronutrients known to play vital roles in metabolism as well due to their unique redox properties. Metals carry out three major functions within metalloproteins: to provide structural support, to serve as enzymatic cofactors, and to mediate electron transportation. Metal ions are also involved in the immune system from metal allergies to nutritional immunity. Within the past decade, much attention has been drawn to the roles of metal ions in the immune system, since increasing evidence has mounted to suggest that metals are critically implicated in regulating both the innate immune sensing of and the host defense against invading pathogens. The importance of ions in immunity is also evidenced by the identification of various immunodeficiencies in patients with mutations in ion channels and transporters. In addition, cancer immunotherapy has recently been conclusively demonstrated to be effective and important for future tumor treatment, although only a small percentage of cancer patients respond to immunotherapy because of inadequate immune activation. Importantly, metal ion-activated immunotherapy is becoming an effective and potential way in tumor therapy for better clinical application. Nevertheless, we are still in a primary stage of discovering the diverse immunological functions of ions and mechanistically understanding the roles of these ions in immune regulation. This review summarizes recent advances in the understanding of metal-controlled immunity. Particular emphasis is put on the mechanisms of innate immune stimulation and T cell activation by the essential metal ions like calcium (Ca²⁺), zinc (Zn²⁺), manganese (Mn²⁺), iron (Fe²⁺/Fe³⁺), and potassium (K⁺), followed by a few unessential metals, in order to draw a general diagram of metalloimmunology.

Invasive fungal infections in the immunocompromised host: Mechanistic insights in an era of changing immunotherapeutics

The use of cytotoxic chemotherapy in the treatment of malignant and inflammatory disorders is beset by considerable adverse effects related to nonspecific cytotoxicity. Accordingly, a mechanistic approach to therapeutics has evolved in recent times with small molecular inhibitors of intracellular signaling pathways involved in disease pathogenesis being developed for clinical use, some with unparalleled efficacy and tolerability. Nevertheless, there are emerging concerns regarding an association with certain small molecular inhibitors and opportunistic infections, including invasive fungal diseases. This is perhaps unsurprising, given that the molecular targets of such agents play fundamental and multifaceted roles in orchestrating innate and adaptive immune responses. Nevertheless, some small molecular inhibitors appear to possess intrinsic antifungal activity and may therefore represent novel therapeutic options in future. This is particularly important given that antifungal resistance is a significant, emerging concern. This paper is a comprehensive review of the state-of-the-art in the molecular immunology to fungal pathogens as applied to existing and emerging small molecular inhibitors.

Calcineurin inhibitors reduce NFAT-dependent expression of antifungal pentraxin-3 by human monocytes

Calcineurin (CN) inhibitors are effective clinical immunosuppressants but leave patients vulnerable to potentially fatal fungal infections. This study tested the hypothesis that CN inhibition interferes with antifungal immune defenses mediated by monocytes. We showed that NFAT is expressed by human monocytes, and is activated by exposure to fungal ligands. We confirmed that NFAT translocation potently activated target gene transcription using a human monocytic reporter cell line. Inhibition of CN‐NFAT by cyclosporine A significantly reduced monocyte production of TNF‐α, IL‐10, and MCP‐1 proteins in response to pattern recognition receptor ligands as well as to Aspergillus fumigatus conidia. Moreover, we revealed that human monocytes express the antifungal protein pentraxin‐3 under control of NFAT. In conclusion, clinical CN inhibitors have the potential to interfere with the novel NFAT‐dependent pentraxin‐3 pathway as well as antifungal cytokine production in human monocytes, thereby impeding monocyte‐mediated defenses against fungal infection in immune‐suppressed patients.

Modulation of innate immunity by cyclosporine A

Cyclosporine A has long been known to suppress T cell responses by inhibiting the production of IL-2, which drives T cell proliferation, enabling its use as a therapeutic for transplantation or autoimmunity. However, cyclosporine A also impacts on innate immune cells including dendritic cells, macrophages and neutrophils. In dendritic cells, which are essential for T cell priming, cyclosporine A can modulate both expression of surface molecules that engage with T cells and cytokine secretion, leading to altered induction of T cell responses. In macrophages and neutrophils, which play key antimicrobial roles, cyclosporine A reduces the production of cytokines that can play protective roles against pathogens. Some of these molecules, if produced in the context of chronic disease, can also contribute to pathology. There have been a number of elegant recent studies addressing the mechanisms by which cyclosporine A can modulate innate immunity. In particular, cyclosporine A inhibits the release of mitochondrial factors that stimulate the production of type 1 interferons by innate immune cells. This review addresses the emerging literature on modulation of innate immune responses by cyclosporine A, its resultant impact on adaptive immune responses and how this offers potential for new therapeutic applications.

Calcineurin inhibitor Tacrolimus impairs host immune response against urinary tract infection

Calcineurin inhibitor Tacrolimus, is a potent immunosuppressive drug widely used in order to prevent acute graft rejection. Urinary tract infection (UTI) is the most frequent infectious complication in renal transplant patients and long-term use of Tacrolimus might be involved in higher susceptibility to bacterial infections. It remains largely unknown how Tacrolimus affects the host innate immune response against lower and upper UTI. To address this issue, we used experimental UTI model by intravesical inoculation of uropathogenic E.coli in female wild-type mice pre-treated with Tacrolimus or solvent (CTR). We found that Tacrolimus pre-treated mice displayed higher bacterial loads (cystitis, pyelonephritis and bacteremia) than CTR mice. Granulocytes from Tacrolimus pre-treated mice phagocytized less E. coli, released less MPO and expressed decreased levels of CXCR2 receptor upon infection. Moreover, Tacrolimus reduced TLR5 expression in bladder macrophages during UTI. This immunosuppressive state can be explained by the upregulation of TLR-signaling negative regulators (A20, ATF3, IRAK-M and SOCS1) and parallel downregulation of TLR5 as observed in Tacrolimus treated granulocytes and macrophages. We conclude that Tacrolimus impairs host innate immune responses against UTI.

Revisiting the Concept of Targeting NFAT to Control T Cell Immunity and Autoimmune Diseases

The nuclear factor of activated T cells (NFAT) family of transcription factors, which includes NFAT1, NFAT2, and NFAT4, are well-known to play important roles in T cell activation. Most of NFAT proteins are controlled by calcium influx upon T cell receptor and costimulatory signaling results increase of IL-2 and IL-2 receptor. NFAT3 however is not shown to be expressed in T cells and NFAT5 has not much highlighted in T cell functions yet. Recent studies demonstrate that the NFAT family proteins involve in function of lineage-specific transcription factors during differentiation of T helper 1 (Th1), Th2, Th17, regulatory T (Treg), and follicular helper T cells (Tfh). They have been studied to make physical interaction with the other transcription factors like GATA3 or Foxp3 and they also regulate Th cell signature gene expressions by direct binding on promotor region of target genes. From last decades, NFAT functions in T cells have been targeted to develop immune modulatory drugs for controlling T cell immunity in autoimmune diseases like cyclosporine A, FK506, etc. Due to their undesirable side defects, only limited application is available in human diseases. This review focuses on the recent advances in development of NFAT targeting drug as well as our understanding of each NFAT family protein in T cell biology. We also discuss updated detail molecular mechanism of NFAT functions in T cells, which would lead us to suggest an idea for developing specific NFAT inhibitors as a therapeutic drug for autoimmune diseases.

The enigmatic role of the neutrophil in asthma: Friend, foe or indifferent?

Whilst severe asthma has classically been categorized as a predominantly Th2-driven pathology, there has in recent years been a paradigm shift with the realization that it is a heterogeneous disease that may manifest with quite disparate underlying inflammatory and remodelling profiles. A subset of asthmatics, particularly those with a severe, corticosteroid refractory disease, present with a prominent neutrophilic component. Given the potential of neutrophils to impart extensive tissue damage and promote inflammation, it has been anticipated that these cells are closely implicated in the underlying pathophysiology of severe asthma. However, uncertainty persists as to why the neutrophil is present in the asthmatic lung and what precisely it is doing there, with evidence supporting its role as a protagonist of pathology being primarily circumstantial. Furthermore, our view of the neutrophil as a primitive, indiscriminate killer has evolved with the realization that neutrophils can exhibit a marked anti-inflammatory, pro-resolving and wound healing capacity. We suggest that the neutrophil likely exhibits pleiotropic and potentially conflicting roles in defining asthma pathophysiology-some almost certainly detrimental and some potentially beneficial-with context, timing and location all critical confounders. Accordingly, indiscriminate blockade of neutrophils with a broad sword approach is unlikely to be the answer, but rather we should first seek to understand their complex and multifaceted roles in the disease state and then target them with the same subtleties and specificity that they themselves exhibit.

Conservation of Intracellular Pathogenic Strategy among Distantly Related Cryptococcal Species

The genus Cryptococcus includes several species pathogenic for humans. Until recently, the two major pathogenic species were recognized to be Cryptococcus neoformans and Cryptococcus gattii We compared the interaction of murine macrophages with three C. gattii species complex strains (WM179, R265, and WM161, representing molecular types VGI, VGIIa, and VGIII, respectively) and one C. neoformans species complex strain (H99, molecular type VNI) to ascertain similarities and differences in the yeast intracellular pathogenic strategy. The parameters analyzed included nonlytic exocytosis frequency, phagolysosomal pH, intracellular capsular growth, phagolysosomal membrane permeabilization, and macrophage transcriptional response, assessed using time-lapse microscopy, fluorescence microscopy, flow cytometry, and gene expression microarray analysis. The most striking result was that the intracellular pathogenic strategies of C. neoformans and C. gattii species complex strains were qualitatively similar, despite the species having separated an estimated 100 million years ago. Macrophages exhibited a leaky phagolysosomal membrane phenotype and nonlytic exocytosis when infected with either C. gattii or C. neoformans Conservation of the intracellular strategy among species that separated long ago suggests that it is ancient and possibly maintained by similar selection pressures through eons.

Dendritic Cells in the Cross Hair for the Generation of Tailored Vaccines

Vaccines represent the discovery of utmost importance for global health, due to both prophylactic action to prevent infections and therapeutic intervention in neoplastic diseases. Despite this, current vaccination strategies need to be refined to successfully generate robust protective antigen-specific memory immune responses. To address this issue, one possibility is to exploit the high efficiency of dendritic cells (DCs) as antigen-presenting cells for T cell priming. DCs functional plasticity allows shaping the outcome of immune responses to achieve the required type of immunity. Therefore, the choice of adjuvants to guide and sustain DCs maturation, the design of multifaceted vehicles, and the choice of surface molecules to specifically target DCs represent the key issues currently explored in both preclinical and clinical settings. Here, we review advances in DCs-based vaccination approaches, which exploit direct in vivo DCs targeting and activation options. We also discuss the recent findings for efficient antitumor DCs-based vaccinations and combination strategies to reduce the immune tolerance promoted by the tumor microenvironment.

The role of neutrophils in host defense against invasive fungal infections

Purpose of Review

Invasive fungal infections caused by the commensal yeast Candida and the ubiquitous, inhaled mold Aspergillus have emerged as major causes of morbidity and mortality in critically ill and immunosuppressed patient populations. Here, we review how neutrophils contribute to effective immunity against these infections.

Recent Findings

Studies in mouse models of invasive candidiasis and aspergillosis, and observations in hematological patients with chemotherapy-induced neutropenia and in patients with primary immunodeficiency disorders that manifest with these infections have highlighted the critical role of neutrophils and have identified key immune factors that promote neutrophil-mediated effective host defense against invasive fungal disease.

Summary

Neutrophils are crucial in host protection against invasive candidiasis and aspergillosis. Recent advances in our understanding of the molecular cues that mediate protective neutrophil recruitment and effector function against these infections hold promise for developing immune-based strategies to improve the outcomes of affected patients.

It takes a village: Phagocytes play a central role in fungal immunity

Phagocytosis is an essential step in the innate immune response to invasive fungal infections. This process is carried out by a proverbial "village" of professional phagocytic cells, which have evolved efficient machinery to recognize and ingest pathogens, namely macrophages, neutrophils and dendritic cells. These innate immune cells drive early cytokine production, fungicidal activity, antigen presentation and activation of the adaptive immune system. Despite the development of antifungal agents with potent activity, the biological activity of professional phagocytic innate immune cells has proven indispensable in protecting a host from invasive fungal infections. Additionally, an emerging body of evidence suggests non-professional phagocytes, such as airway epithelial cells, carry out phagocytosis and may play a critical role in the elimination of fungal pathogens. Here, we review recent advances of phagocytosis by both professional and non-professional phagocytes in response to fungal pathogens, with a focus on invasive aspergillosis as a model disease.

Invasive candidiasis

Invasive candidiasis is an important health-care-associated fungal infection that can be caused by several Candida spp.; the most common species is Candida albicans, but the prevalence of these organisms varies considerably depending on geographical location. The spectrum of disease of invasive candidiasis ranges from minimally symptomatic candidaemia to fulminant sepsis with an associated mortality exceeding 70%. Candida spp. are common commensal organisms in the skin and gut microbiota, and disruptions in the cutaneous and gastrointestinal barriers (for example, owing to gastrointestinal perforation) promote invasive disease. A deeper understanding of specific Candida spp. virulence factors, host immune response and host susceptibility at the genetic level has led to key insights into the development of early intervention strategies and vaccine candidates. The early diagnosis of invasive candidiasis is challenging but key to the effective management, and the development of rapid molecular diagnostics could improve the ability to intervene rapidly and potentially reduce mortality. First-line drugs, including echinocandins and azoles, are effective, but the emergence of antifungal resistance, especially among Candida glabrata, is a matter of concern and underscores the need to administer antifungal medications in a judicious manner, avoiding overuse when possible. A newly described pathogen, Candida auris, is an emerging multidrug-resistant organism that poses a global threat.

Calcineurin-NFAT signalling in myeloid leucocytes: new prospects and pitfalls in immunosuppressive therapy

Myeloid leucocytes mediate host protection against infection and critically regulate inflammatory responses in body tissues. Pattern recognition receptor signalling is crucial for myeloid cell responses to pathogens, but growing evidence suggests an equally potent role for Calcineurin–NFAT signalling in control of myeloid cell function. All major subsets of myeloid leucocytes employ Calcineurin–NFAT signalling during immune responses to pathogens and/or tissue damage, but the influence this pathway exerts on pathogen clearance and host susceptibility to infection is not fully understood. Recent data from experimental models indicate that Calcineurin‐NFAT signalling is essential for infection control, and calcineurin inhibitors used in transplantation medicine (including cyclosporine A and tacrolimus) are now being tested for efficacy in a diverse range of inflammatory conditions and autoimmune pathologies. Efforts to repurpose calcineurin inhibitor drugs for new therapeutic applications may yield rapid improvements in clinical outcomes, but the potential impact of these compounds on myeloid cell function in treated patients is largely unknown. Here we discuss Calcineurin–NFAT control of myeloid leucocyte function in the context of recent therapeutic developments and ongoing clinical studies.

Murine neutrophils treated with alphaB-crystallin reduce IL-12p40 production by dendritic cells

Neutrophils are essential in the fight against invading pathogens. They utilize antimicrobial effector mechanisms, such as phagocytosis, release of proteases and other antimicrobial products, robust oxidative bursts and neutrophil extracellular traps to combat infections. Neutrophils also modulate immune responses through the production of eicosanoids, cytokines and chemokines, as well as via direct communication with other immune cells. This system of high-intensity offense against pathogens is exquisitely balanced through regulation to limit damage to host tissue. Unfortunately, the control of neutrophils is not failproof. In cases of sterile injury, autoimmunity and even during an infection, neutrophils can cause tissue destruction and become detrimental to the host. For that reason, there is a need to find means to regulate the aberrant activation of these cells. We found that alphaB-crystallin (αBC), a heat-shock protein known to have anti-inflammatory abilities, affects certain properties of mouse neutrophils that subsequently influence the pro-inflammatory state of antigen-presenting cells (APCs). More specifically, αBC mediated small but significant increases in the levels of IL-10 and matrix metalloproteinase 8, and altered hydrogen peroxide secretion by stimulated neutrophils. Further, the heat-shock protein influenced the communication between neutrophils and dendritic cells by decreasing the production of pro-inflammatory cytokines, specifically IL-12p40, by the APCs. αBC could thus contribute to dampening neutrophil inflammatory responses by impacting the effect of neutrophils on other immune cells.

Taurine chloramine potentiates phagocytic activity of peritoneal macrophages through up-regulation of dectin-1 mediated by heme oxygenase-1-derived carbon monoxide

Resolution of inflammation that occurs after microbial infection or tissue damage is an important physiologic process in maintaining or restoring host homeostasis. Taurine chloramine (TauCl) is formed by a reaction between taurine and hypochlorite in leukocytes, and it is especially abundant in activated neutrophils that encounter an oxidative burst. As neutrophils undergo apoptosis, TauCl is released to the extracellular matrix at the inflamed sites, thereby affecting coexisting macrophages in the inflammatory microenvironment. In this study, we investigated the role of TauCl in phagocytosis by macrophages during resolution of fungal infection-induced inflammation. We found that exogenous TauCl substantially increased the phagocytic efficiency of macrophages through up-regulation of dectin-1, a receptor for fungal β-1,3-glucans, which is present on the membrane of macrophages. Our previous studies demonstrated the induction of heme oxygenase-1 (HO-1) expression in murine peritoneal macrophages treated with TauCl. In the present study, knocking out HO-1 or pharmacologic inhibition of HO-1 with zinc protoporphyrin IX attenuated the TauCl-induced expression of dectin-1 and subsequent phagocytosis. Furthermore, carbon monoxide (CO), a by-product of the HO-1-catalyzed reaction, induced expression of dectin-1 and potentiated phagocytic capability of the macrophages, which appeared to be mediated through up-regulation of peroxisome proliferator-activated receptor γ. Taken together, induction of HO-1 expression and subsequent CO production by TauCl are essential for phagocytosis of fungi by macrophages. Our results suggest that TauCl has important roles in host defense against fungal infection and has therapeutic potential in the management of inflammatory diseases.-Kim, S. H., Zhong, X., Kim, W., Kim, K., Suh, Y.-G., Kim, C., Joe, Y., Chung, H. T., Cha, Y.-N., Surh, Y.-J. Taurine chloramine potentiates phagocytic activity of peritoneal macrophages through up-regulation of dectin-1 mediated by heme oxygenase-1-derived carbon monoxide.

Host Control of Fungal Infections: Lessons from Basic Studies and Human Cohorts

In the last few decades, the AIDS pandemic and the significant advances in the medical management of individuals with neoplastic and inflammatory conditions have resulted in a dramatic increase in the population of immunosuppressed patients with opportunistic, life-threatening fungal infections. The parallel development of clinically relevant mouse models of fungal disease and the discovery and characterization of several inborn errors of immune-related genes that underlie inherited human susceptibility to opportunistic mycoses have significantly expanded our understanding of the innate and adaptive immune mechanisms that protect against ubiquitous fungal exposures. This review synthesizes immunological knowledge derived from basic mouse studies and from human cohorts and provides an overview of mammalian antifungal host defenses that show promise for informing therapeutic and vaccination strategies for vulnerable patients.

Skin infections are eliminated by cooperation of the fibrinolytic and innate immune systems

Nuclear factor of activated T cells (NFAT) is activated in innate immune cells downstream of pattern recognition receptors, but little is known about NFAT's functions in innate immunity compared with adaptive immunity. We show that early activation of NFAT balances the two major phases of the innate response to Candida albicans skin infections: the protective containment (abscess) and the elimination (expulsion) phases. During the early containment phase, transforming growth factor-β (TGF-β) induces the deposit of collagen around newly recruited polymorphonuclear cells to prevent microbial spreading. During the elimination phase, interferon-γ (IFN-γ) blocks differentiation of fibroblasts into myofibroblasts by antagonizing TGF-β signaling. IFN-γ also induces the formation of plasmin that, in turn, promotes abscess capsule digestion and skin ulceration for microbial discharge. NFAT controls innate IFN-γ production and microbial expulsion. This cross-talk between the innate immune and the fibrinolytic systems also occurs during infection with Staphylococcus aureus and is a protective response to minimize tissue damage and optimize pathogen elimination.

Lectin Receptors Expressed on Myeloid Cells

Lectins recognize a diverse array of carbohydrate structures and perform numerous essential biological functions. Here we focus on only two families of lectins, the Siglecs and C-type lectins. Triggering of intracellular signaling cascades following ligand recognition by these receptors can have profound effects on the induction and modulation of immunity. In this chapter, we provide a brief overview of each family and then focus on selected examples that highlight how these lectins can influence myeloid cell functioning in health and disease. Receptors that are discussed include Sn (Siglec-1), CD33 (Siglec-3), and Siglec-5, -7, -8, -9, -10, -11, -14, -15, -E, -F, and -G as well as Dectin-1, MICL, Dectin-2, Mincle/MCL, and the macrophage mannose receptor.

STIM1 and STIM2 cooperatively regulate mouse neutrophil store-operated calcium entry and cytokine production

Neutrophils are key effector cells of the innate immune system. Calcium-dependent signaling pathways initiated by store-operated calcium entry (SOCE) are known to regulate neutrophil activation; however, the precise mechanism of this process remains unclear. STIM1 and STIM2 are calcium-sensing molecules that link calcium depletion of the endoplasmic reticulum with opening of plasma membrane calcium channels. Although a role for STIM1 in neutrophil SOCE and activation has been established, the function of STIM2 is unknown. Here we use mice with conditional ablation of Stim1 and/or Stim2 to investigate the role of STIM2 in neutrophil activation. We demonstrate that loss of STIM2 results in decreased SOCE, particularly at lower doses of agonists. Reactive oxygen species (ROS) production, degranulation, and phagocytosis are normal in the absence of STIM2, suggesting STIM1 is the dominant calcium sensor required for classical short-term neutrophil responses. However, neutrophil cytokine production required STIM2, but not STIM1, at least in part as a result of redox regulation of cytokine gene expression. In vivo loss of STIM2 results in lower cytokine levels and protection from mortality in a mouse model of systemic inflammatory response syndrome. These data, combined with previous studies focusing on STIM1, define distinct but cooperative functions for STIM1 and STIM2 in modulating neutrophil bactericidal and cytokine responses.

Treatment of Cyclosporin A retains host defense against invasive pulmonary aspergillosis in a non-immunosuppressive murine model by preserving the myeloid cell population

Cyclosporin A (CsA) is widely used as an immunosuppressive agent for organ transplant recipients. CsA inhibits calcineurin, which is highly conserved in mammals and fungi, and thus affects both types of organism. In mammals, the immunosuppressive effect of CsA is via hampering T cell activation. In fungi, the growth inhibitory effect of CsA is via interference with hyphal growth. The aim of this study was to determine whether CsA renders mice susceptible to invasive pulmonary aspergillosis (IPA) and whether it can protect immunosuppressed mice from infection. We therefore examined both the antifungal and the immunosuppressive activity of CsA in immunosuppressed and in immunocompetent mice infected with Aspergillus fumigatus to model IPA. We found that daily injections of CsA could not produce an antifungal effect sufficient to rescue immunosuppressed mice from lethal IPA. However, a 100% survival rate was obtained in non-immunosuppressed mice receiving daily CsA, indicating that CsA did not render the mice vulnerable to IPA. The lymphocyte subset was significantly suppressed by CsA, while the myeloid subset was not. Therefore, we speculate that CsA does not impair the host defense against IPA since the myeloid cells are preserved.

Immunity against fungi

Pathogenic fungi cause a wide range of syndromes in immune-competent and immune-compromised individuals, with life-threatening disease primarily seen in humans with HIV/AIDS and in patients receiving immunosuppressive therapies for cancer, autoimmunity, and end-organ failure. The discovery that specific primary immune deficiencies manifest with fungal infections and the development of animal models of mucosal and invasive mycoses have facilitated insight into fungus-specific recognition, signaling, effector pathways, and adaptive immune responses. Progress in deciphering the molecular and cellular basis of immunity against fungi is guiding preclinical studies into vaccine and immune reconstitution strategies for vulnerable patient groups. Furthermore, recent work has begun to address the role of endogenous fungal communities in human health and disease. In this review, we summarize a contemporary understanding of protective immunity against fungi.

A calcineurin antifungal strategy with analogs of FK506

A novel antifungal strategy targeting the inhibition of calcineurin is described. To develop a calcineurin based inhibitor of pathogenic fungi, analogs of FK506 were synthesized that were able to permeate mammalian but not fungal cells. Antagonists in combination with FK506 were not immunosuppressive and retained antifungal activity in A. fumigatus. To reduce the dosage burden of the antagonist, murine oral PK was improved an order of magnitude relative to previous FK506 antagonists.