Interleukin-1α released from HSV-1-infected keratinocytes acts as a functional alarmin in the skin

Floxed Il1rl2 Locus with mCherry Reporter Element Reveals Distinct Expression Patterns of the IL-36 Receptor in Barrier Tissues

IL-36 cytokines are emerging as beneficial in immunity against pathogens and cancers but can also be detrimental when dysregulated in autoimmune and autoinflammatory conditions. Interest in targeting IL-36 activity for therapeutic purposes is rapidly growing, yet many unknowns about the functions of these cytokines remain. Thus, the availability of robust research tools is essential for both fundamental basic science and pre-clinical studies to fully access outcomes of any manipulation of the system. For this purpose, a floxed Il1rl2, the gene encoding the IL-36 receptor, mouse strain was developed to facilitate the generation of conditional knockout mice. The targeted locus was engineered to contain an inverted mCherry reporter sequence that upon Cre-mediated recombination will be flipped and expressed under the control of the endogenous Il1rl2 promoter. This feature can be used to confirm knockout in individual cells but also as a reporter to determine which cells express the IL-36 receptor IL-1RL2. The locus was confirmed to function as intended and further used to demonstrate the expression of IL-1RL2 in barrier tissues. Il1rl2 expression was detected in leukocytes in all barrier tissues. Interestingly, strong expression was observed in epithelial cells at locations in direct contact with the environment such as the skin, oral mucosa, the esophagus, and the upper airways, but almost absent from epithelial cells at more inward facing sites, including lung alveoli, the small intestine, and the colon. These findings suggest specialized functions of IL-1RL2 in outward facing epithelial tissues and cells. The generated mouse model should prove valuable in defining such functions and may also facilitate basic and translational research.

System analysis based on the pyroptosis-related genes identifes GSDMD as a novel therapy target for skin cutaneous melanoma

BACKGROUND

Skin cutaneous melanoma (SKCM) is the most aggressive skin cancer, accounting for more than 75% mortality rate of skin-related cancers. As a newly identified programmed cell death, pyroptosis has been found to be closely associated with tumor progression. Nevertheless, the prognostic significance of pyroptosis in SKCM remains elusive.

METHODS

A total of 469 SKCM samples and 812 normal samples were obtained from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. Firstly, differentially expressed pyroptosis-related genes (PRGs) between normal samples and SKCM samples were identified. Secondly, we established a prognostic model based on univariate Cox and LASSO Cox regression analyses, which was validated in the test cohort from GSE65904. Thirdly, a nomogram was used to predict the survival probability of SKCM patients. The R package "pRRophetic" was utilized to identify the drug sensitivity between the low- and high-risk groups. Tumor immune infiltration was evaluated using "immuneeconv" R package. Finally, the function of GSDMD and SB525334 was explored in A375 and A2058 cells.

RESULTS

Based on univariate Cox and LASSO regression analyses, we established a prognostic model with identified eight PRGs (AIM2, CASP3, GSDMA, GSDMC, GSDMD, IL18, NLRP3, and NOD2), which was validated in the test cohort. SKCM patients were divided into low- and high-risk groups based on the median of risk score. Kaplan-Meier survival analysis showed that high-risk patients had shorter overall survival than low-risk patients. Additionally, time-dependent ROC curves validated the accuracy of the risk model in predicting the prognosis of SKCM. More importantly, 4 small molecular compounds (SB525334, SR8278, Gemcitabine, AT13387) were identified, which might be potential drugs for patients in different risk groups. Finally, overexpression of GSDMD and SB525334 treatment inhibit the proliferation, migration, and invasion of SKCM cells.

CONCLUSION

In this study, we constructed a prognostic model based on PRGs and identified GSDMD as a potential therapeutic target, which provide new insights into SKCM treatment.

Pellino Proteins in Viral Immunity and Pathogenesis

Pellino proteins are a family of evolutionarily conserved ubiquitin ligases involved in intracellular signaling in a wide range of cell types. They are essential for microbe detection and the initiation of innate and adaptive immune responses. Some viruses specifically target the Pellino proteins as part of their immune evasion strategies. Through studies of mouse models of viral infections in the central nervous system, heart, lungs, and skin, the Pellino proteins have been linked to both beneficial and detrimental immune responses. Only in recent years have some of the involved mechanisms been identified. The objective of this review is to highlight the many diverse aspects of viral immunity and pathogenesis that the Pellino proteins have been associated with, in order to promote further research into their functions. After a brief introduction to the cellular signaling mechanisms involving Pellino proteins, their physiological roles in the initiation of immune responses, pathogenesis through excess inflammation, immune regulation, and cell death are presented. Known viral immune evasion strategies are also described. Throughout, areas that require more in-depth investigation are identified. Future research into the functions of the Pellino protein family may reveal fundamental insights into how our immune system works. Such knowledge may be leveraged in the fight against viral infections and their sequala.

The Intersection of Innate Immune Pathways with the Latent Herpes Simplex Virus Genome

Innate immune responses can impact different stages of viral life cycles. Herpes simplex virus latent infection of neurons and subsequent reactivation provide a unique context for immune responses to intersect with different stages of infection. Here, we discuss recent findings linking neuronal innate immune pathways with the modulation of latent infection, acting at the time of reactivation and during initial neuronal infection to have a long-term impact on the ability of the virus to reactivate.

Pellino1 Restricts Herpes Simplex Virus Infections in the Epidermis and Dissemination to Sebaceous Glands

Nearly all adults are infected with one or more herpes viruses. The most common are herpes simplex virus (HSV)-1 and HSV-2, which upon reactivation can cause painful skin and mucosal erosions. Patients who are immune compromised often experience frequent, atypical, or chronic lesions and thus a greatly diminished QOL. Pellino1 is a ubiquitin ligase involved in IL-1 and toll-like receptor signaling; however, the role of Pellino1 in skin immunity against HSV is unknown. In this study, using the mouse-flank HSV-1 skin infection model, we show that Pellino1 has several critical functions during active viral replication. Peli1‒/‒ mice succumb more than wild-type mice to systemic disease and develop larger zosteriform skin lesions along affected dermatomes. In Pellino1-deficient mice, the virus spread extensively through the epidermis and follicular infundibulum into sebaceous glands where sebocytes were found positive for the virus. The latter did not appear to involve a shift in how the virus migrated through the nervous system. Immunohistochemistry revealed delayed recruitment of myeloid and T cells to the infected epidermis in Peli1‒/‒ mice. This was associated with decreased expression of the cytokine mRNAs Il1a, Il36b and 2610528A11Rik; the latter also known as Gpr15l. In conclusion, Pellino1 plays important roles in restricting viral dissemination, and the involved pathways may represent novel therapeutic targets in patients with frequent or chronic HSV infections.

Cytokines and chemokines: The vital role they play in herpes simplex virus mucosal immunology

Herpes simplex viruses (HSV) types 1 and 2 are ubiquitous infections in humans. They cause orofacial and genital herpes with occasional severe complications. HSV2 also predisposes individuals to infection with HIV. There is currently no vaccine or immunotherapy for these diseases. Understanding the immunopathogenesis of HSV infections is essential to progress towards these goals. Both HSV viruses result in initial infections in two major sites - in the skin or mucosa, either after initial infection or recurrence, and in the dorsal root or trigeminal ganglia where the viruses establish latency. HSV1 can also cause recurrent infection in the eye. At all of these sites immune cells respond to control infection. T cells and resident dendritic cells (DCs) in the skin/mucosa and around reactivating neurones in the ganglia, as well as keratinocytes in the skin and mucosa, are major sources of cytokines and chemokines. Cytokines such as the Type I and II interferons synergise in their local antiviral effects. Chemokines such as CCL2, 3 and 4 are found in lesion vesicle fluid, but their exact role in determining the interactions between epidermal and dermal DCs and with resident memory and infiltrating CD4 and CD8 T cells in the skin/mucosa is unclear. Even less is known about these mechanisms in the ganglia. Here we review the data on known sources and actions of these cytokines and chemokines at cellular and tissue level and indicate their potential for preventative and therapeutic interventions.

Role of Caspases and Gasdermin A during HSV-1 Infection in Mice

Herpes simplex virus type 1 (HSV-1) infection can manifest locally as mucocutaneous lesions or keratitis and can also spread to the central nervous system to cause encephalitis. HSV-1 establishes a lifelong latent infection and neither cure nor vaccine is currently available. The innate immune response is the first line of defense against infection. Caspases and gasdermins are important components of innate immunity. Caspases are a family of cysteine proteases, most of which mediate regulated cell death. Gasdermins are a family of pore-forming proteins that trigger lytic cell death. To determine whether caspases or gasdermins contribute to innate immune defenses against HSV-1, we screened mice deficient in specific cell death genes. Our results indicate a modest role for caspase-6 in defense against HSV-1. Further, Asc–/–Casp1/11–/– mice also had a modest increased susceptibility to HSV-1 infection. Caspase-7, -8, and -14 did not have a notable role in controlling HSV-1 infection. We generated Gsdma1-Gsdma2-Gsdma3 triple knockout mice, which also had normal susceptibility to HSV-1. We confirmed that the previously published importance of RIPK3 during systemic HSV-1 infection also holds true during skin infection. Overall, our data highlight that as a successful pathogen, HSV-1 has multiple ways to evade host innate immune responses.

Pyroptosis participates in PM2.5-induced air-blood barrier dysfunction

Epidemiological studies have shown that particulate matters with diameter less than 2.5 μm (PM_2.5) play an important role in inducing and promoting respiratory diseases, but its underlying mechanism remains to be explored. The air-blood barrier, also known as the alveolar-capillary barrier, is the key element of the lung, working as the site of oxygen and carbon dioxide exchange between pulmonary vasculatures. In this study, a mouse PM_2.5 exposure model was established, which leads to an induced lung injury and air-blood barrier disruption. Oxidative stress and pyroptosis were observed in this process. After reducing the oxidative stress by N-acetyl-L-cysteine (NAC) treatment, the air-blood barrier function was improved and the effect of PM_2.5 was alleviated. The level of pyroptosis and related pathway were also effectively relieved. These results indicate that acute PM_2.5 exposure can cause lung injury and the alveolar-capillary barrier disruption by inducing reactive oxygen species (ROS) with the participation of pyroptosis pathway.

Crosstalk Between Epithelial Cells, Neurons and Immune Mediators in HSV-1 Skin Infection

Herpes simplex virus type 1 (HSV-1) infection is highly prevalent in humans, with approximately two-thirds of the world population living with this virus. However, only a fraction of those carrying HSV-1, which elicits lifelong infections, are symptomatic. HSV-1 mainly causes lesions in the skin and mucosae but reaches the termini of sensory neurons innervating these tissues and travels in a retrograde manner to the neuron cell body where it establishes persistent infection and remains in a latent state until reactivated by different stimuli. When productive reactivations occur, the virus travels back along axons to the primary infection site, where new rounds of replication are initiated in the skin, in recurrent or secondary infections. During this process, new neuron infections occur. Noteworthy, the mechanisms underlying viral reactivations and the exit of latency are somewhat poorly understood and may be regulated by a crosstalk between the infected neurons and components of the immune system. Here, we review and discuss the immune responses that occur at the skin during primary and recurrent infections by HSV-1, as well as at the interphase of latently-infected neurons. Moreover, we discuss the implications of neuronal signals over the priming and migration of immune cells in the context of HSV-1 infection.

HMGB1-mediated chromatin remodeling attenuates Il24 gene expression for the protection from allergic contact dermatitis

Dysregulation of inflammatory cytokines in keratinocytes promote the pathogenesis of the skin inflammation, such as allergic contact dermatitis (ACD). High-mobility group box 1 protein (HMGB1) has been implicated in the promotion of skin inflammation upon its extracellular release as a damage-associated molecular pattern molecule. However, whether and how HMGB1 in keratinocytes contributes to ACD and other skin disorders remain elusive. In this study, we generated conditional knockout mice in which the Hmgb1 gene is specifically deleted in keratinocytes, and examined its role in ACD models. Interestingly, the mutant mice showed exacerbated skin inflammation, accompanied by increased ear thickening in 2,4-dinitrofluorobenezene-induced ACDs. The mRNA expression of interleukin-24 (IL-24), a cytokine known to critically contribute to ACD pathogenesis, was elevated in skin lesions of the mutant mice. As with constitutively expressed, IL-4-induced Il24 mRNA, expression was also augmented in the Hmgb1-deficient keratinocytes, which would account for the exacerbation of ACD in the mutant mice. Mechanistically, we observed an increased binding of trimethyl histone H3 (lys4) (H3K4me3), a hallmark of transcriptionally active genes, to the promoter region of the Il24 gene in the hmgb1-deficient cells. Thus, the nuclear HMGB1 is a critical "gate keeper" in that the dermal homeostasis is contingent to its function in chromatin remodeling. Our study revealed a facet of nuclear HMGB1, namely its antiinflammatory function in keratinocytes for the skin homeostasis.

Skin Viral Infections: Host Antiviral Innate Immunity and Viral Immune Evasion

The skin is an active immune organ that functions as the first and largest site of defense to the outside environment. Serving as the primary interface between host and pathogen, the skin’s early immune responses to viral invaders often determine the course and severity of infection. We review the current literature pertaining to the mechanisms of cutaneous viral invasion for classical skin-tropic, oncogenic, and vector-borne skin viruses. We discuss the skin’s evolved mechanisms for innate immune viral defense against these invading pathogens, as well as unique strategies utilized by the viruses to escape immune detection. We additionally explore the roles that demographic and environmental factors, such as age, biological sex, and the cutaneous microbiome, play in altering the host immune response to viral threats.

Equine Herpesvirus Type 1 Modulates Cytokine and Chemokine Profiles of Mononuclear Cells for Efficient Dissemination to Target Organs

Equine herpesvirus type 1 (EHV-1) causes encephalomyelopathy and abortion, for which cell-associated viremia and subsequent virus transfer to and replication in endothelial cells (EC) are responsible and prerequisites. Viral and cellular molecules responsible for efficient cell-to-cell spread of EHV-1 between peripheral blood mononuclear cells (PBMC) and EC remain unclear. We have generated EHV-1 mutants lacking ORF1, ORF2, and ORF17 genes, either individually or in combination. Mutant viruses were analyzed for their replication properties in cultured equine dermal cells, PBMC infection efficiency, virus-induced changes in the PBMC proteome, and cytokine and chemokine expression profiles. ORF1, ORF2, and ORF17 are not essential for virus replication, but ORF17 deletion resulted in a significant reduction in plaque size. Deletion of ORF2 and ORF17 gene significantly reduced cell-to-cell virus transfer from virus-infected PBMC to EC. EHV-1 infection of PBMC resulted in upregulation of several pathways such as Ras signaling, oxidative phosphorylation, platelet activation and leukocyte transendothelial migration. In contrast, chemokine signaling, RNA degradation and apoptotic pathways were downregulated. Deletion of ORF1, ORF2 and ORF17 modulated chemokine signaling and MAPK pathways in infected PBMC, which may explain the impairment of virus spread between PBMC and EC. The proteomic results were further confirmed by chemokine assays, which showed that virus infection dramatically reduced the cytokine/chemokine release in infected PBMC. This study uncovers cellular proteins and pathways influenced by EHV-1 after PBMC infection and provide an important resource for EHV-1 pathogenesis. EHV-1-immunomodulatory genes could be potential targets for the development of live attenuated vaccines or therapeutics against virus infection.

Comparative analysis of the tear protein profile in herpes simplex virus type 1 epithelial keratitis

BACKGROUND

Herpes simplex virus type 1 (HSV-1) keratitis is a major cause of corneal blindness in the world, and an in-depth understanding of its pathogenesis may help improve existing diagnosis and treatment. The purpose of this study is to compare and analysis the total tear protein profile of HSV-1 epithelial keratitis patients, and to quantify the potential candidate biomarkers of HSV-1 epithelial keratitis.

METHODS

We investigated the proteome in tear fluid from three HSV-1 epithelial keratitis patients and three healthy control subjects using nano-scale liquid chromatography-tandem mass spectrometry (nLC-MS/MS) analysis. Functional annotation of differentially expressed proteins was done with the Gene Ontology (GO) analysis. ELISA was done to quantify the potential candidate biomarkers in 26 clinical cases.

RESULTS

Tear fluid from three HSV-1 epithelial keratitis patients and three healthy control subjects contained a total of 1275 proteins and 326 proteins were unique to tear fluid of HSV-1 epithelial keratitis patients. Bioinformatics analysis revealed that tear proteins from HSV-1 epithelial keratitis patients may be involved in metabolic processes, antigen presentation, inflammatory response, and in the TNF-mediated and T cell receptor pathways. Furthermore, IL1A, IL12B, DEFB4A, and CAMP, which are associated with the inflammatory response and inhibition of viral infection, were significantly more abundant in the HSV-1 epithelial keratitis patients than in the healthy control subjects.

CONCLUSIONS

This study reports the proteomic profile of tears in HSV-1 epithelial keratitis for the first time and identifies a number of unique differentially expressed proteins.

Cetylpyridinium chloride blocks herpes simplex virus replication in gingival fibroblasts

Infections with herpes simplex viruses are lifelong and highly prevalent worldwide. Individuals with clinical symptoms elicited by HSVs may suffer from occasional or recurrent herpetic lesions in the orofacial and genital areas. Despite the existence of nucleoside analogues that interfere with HSV replication, such as acyclovir, these drugs are somewhat ineffective in treating skin lesions as topical formulations only reduce in one or few days the duration of the herpetic ulcers. Cetylpyridinium chloride (CPC) is a quaternary ammonium compound present in numerous hygiene products, such as mouthwashes, deodorants, aphtae-treating formulations and oral tablets as an anti-septic to limit bacterial growth. Some reports indicate that CPC can also modulate host signaling pathways, namely NF-κB signaling. Because HSV infection is modulated by NF-κB, we sought to assess whether CPC has antiviral effects against HSVs. Using wild-type HSV-1 and HSV-2, as well as viruses that are acyclovir-resistant or encode GFP reporter genes, we assessed the antiviral capacity of CPC in epithelial cells and human gingival fibroblasts expanded from the oral cavity and its mechanism of action. We found that a short, 10-min exposure to CPC added after HSV entry into the cells, significantly limited viral replication in both cell types by impairing viral gene expression. Interestingly, our results suggest that CPC blocks HSV replication by interfering with the translocation of NF-κB into the nucleus of HSV-infected cells. Taken together, these findings suggest that formulations containing CPC may help limit HSV replication in infected tissues and consequently reduce viral shedding.

Programmed Cell Death in the Evolutionary Race against Bacterial Virulence Factors

Innate immune sensors can recognize when host cells are irrevocably compromised by pathogens, and in response can trigger programmed cell death (pyroptosis, apoptosis, and necroptosis). Innate sensors can directly bind microbial ligands; for example, NAIP/NLRC4 detects flagellin/rod/needle, whereas caspase-11 detects lipopolysaccharide. Other sensors are guards that monitor normal function of cellular proteins; for instance, pyrin monitors Rho GTPases, whereas caspase-8 and receptor-interacting protein kinase (RIPK)3 guards RIPK1 transcriptional signaling. Some proteins that need to be guarded can be duplicated as decoy domains, as seen in the integrated decoy domains within NLRP1 that watch for microbial attack. Here, we discuss the evolutionary battle between pathogens and host innate immune sensors/guards, illustrated by the Red Queen hypothesis. We discuss in depth four pathogens, and how they either fail in this evolutionary race (Chromobacterium violaceum, Burkholderia thailandensis), or how the evolutionary race generates increasingly complex virulence factors and host innate immune signaling pathways (Yersinia species, and enteropathogenic Escherichia coli [EPEC]).

IL-36 promotes anti-viral immunity by boosting sensitivity to IFN-α/β in IRF1 dependent and independent manners

The functions of the IL-36 cytokines remain poorly understood. We report a previously unrecognized mechanism whereby IL-36 promotes innate antiviral immunity in mouse and human models of herpes simplex virus-1 (HSV-1) infections. HSV-1 actively suppresses production of type I interferon (IFN); our data reveal that IL-36 overcomes this immune evasion strategy by increasing cellular sensitivity to IFN. IL-36β deficient mice display impaired IFN responses and poorly restrict viral replication in skin keratinocytes. In mouse and human keratinocytes IL-36 elicits an antiviral state driven by STAT1 and STAT2 via enhanced expression of IFNAR1 and IFNAR2 subunits of the type I IFN receptor. The degree of IFN regulatory factor 1 (IRF1) involvement is species dependent, with IRF1 playing a more prominent role in human cells. Similar mechanisms are activated by IL-1. Overall, IL-36 acts as an antiviral cytokine by potentiating type I IFN signaling and thereby upholds immune responses to viruses that limit the production of IFNs.

Common Differences: The Ability of Inflammasomes to Distinguish Between Self and Pathogen Nucleic Acids During Infection

The innate immune system detects the presence of pathogens based on detection of non-self. In other words, most pathogens possess intrinsic differences that can distinguish them from host cells. For example, bacteria and fungi have cell walls comprised of peptidoglycan and carbohydrates (like mannans), respectively. Germline encoded pattern recognition receptors (PRRs) of the Toll-like receptor (TLR) and C-type lectin receptor (CLR) family have the ability to detect such unique pathogen associated features. However, some TLRs and members of the RIG-I-like receptor (RLR), NOD-like receptor (NLR), or AIM2-like receptor (ALR) family can sense pathogen invasion based on pathogen nucleic acids. Nucleic acids are not unique to pathogens, thus raising the question of how such PRRs evolved to detect pathogens but not self. In this chapter, we will examine the PRRs that sense pathogen nucleic acids and subsequently activate the inflammasome signaling pathway. We will examine the selective mechanisms by which these receptors distinguish pathogens from "self" and discuss the importance of such pathways in disease development in animal models and human patients.

IL-36γ induces a transient HSV-2 resistant environment that protects against genital disease and pathogenesis

Herpes simplex virus 2 (HSV-2) causes a persistent, lifelong infection that increases risk for sexually transmitted infection acquisition. Both the lack of a vaccine and the need for chronic suppressive therapies to control infection presents the need to further understand immune mechanisms in response to acute HSV-2 infection. The IL-36 cytokines are recently identified members of the IL-1 family and function as inflammatory mediators at epithelial sites. Here, we first used a well-characterized three-dimensional (3-D) human vaginal epithelial cell (VEC) model to understand the role of IL-36γ in the context of HSV-2 infection. In 3-D VEC, IL-36γ is induced by HSV-2 infection, and pretreatment with exogenous IL-36γ significantly reduced HSV-2 replication. To assess the impact of IL-36γ treatment on HSV-2 disease pathogenesis, we employed a lethal genital infection model. We showed that IL-36γ treatment in mice prior to lethal intravaginal challenge significantly limited vaginal viral replication, delayed disease onset, decreased disease severity, and significantly increased survival. We demonstrated that IL-36γ treatment transiently induced pro-inflammatory cytokines, chemokines, and antimicrobial peptides in murine lower female reproductive tract (FRT) tissue and vaginal lavages. Induction of the chemokines CCL20 and KC in IL-36γ treated mice also corresponded with increased polymorphonuclear (PMN) leukocyte infiltration observed in vaginal smears. Altogether, these studies demonstrate that IL-36γ drives the transient production of immune mediators and promotes PMN recruitment in the vaginal microenvironment that increases resistance to HSV-2 infection and disease. Our data indicate that IL-36γ may participate as a key player in host defense mechanisms against invading pathogens in the FRT.

Liver kinase B1/AMP-activated protein kinase-mediated regulation by gentiopicroside ameliorates P2X7 receptor-dependent alcoholic hepatosteatosis

BACKGROUND AND PURPOSE

Regulating P2X7 receptor-mediated activation of NLRP3 inflammasomes could be a therapeutic strategy to treat alcoholic hepatosteatosis. We investigated whether this process was modulated by gentiopicroside, the main active secoiridoid glycoside from Gentiana manshurica Kitagawa.

EXPERIMENTAL APPROACH

In vivo models of acute and chronic alcoholic hepatosteatosis were established by intragastrically administered ethanol or using chronic plus binge ethanol feeding of Lieber-DeCarli liquid diet to male C57BL/6 mice. In vitro, HepG2 cells were treated with ethanol. RAW 264.7 macrophages and murine bone marrow-derived macrophages (BMDMs) were stimulated with LPS and ATP.

KEY RESULTS

In both the acute and chronic alcohol-induced mouse hepatosteatosis models, gentiopicroside decreased serum aminotransferases and triglyceride accumulation. Up-regulated SREBP1, down-regulated PPARα and phosphorylated acetyl-CoA carboxylase caused by acute and chronic alcohol feeding were modulated by gentiopicroside, through the elevation of LKB1 and AMPK. Suppression of P2X7 receptor-NLRP3 activation by gentiopicroside inhibited IL-1β production. In ethanol-exposed HepG2 cells, gentiopicroside reduced lipogenesis and promoted lipid oxidation via activation of P2X7 receptor-NLRP3 inflammasomes. Genetic or pharmacological blockade of P2X7 receptors enhanced AMPK activity and reduced SREBP1 expression in ethanol-treated HepG2 cells. Gentiopicroside down-regulated P2X7 receptor-mediated inflammatory responses in LPS/ATP-stimulated RAW 264.7 macrophages and BMDMs. IL-1β from macrophages accelerated lipid accumulation in hepatocytes. Depleting macrophages by clodronate liposomes ameliorated alcoholic hepatosteatosis, and it was further alleviated by gentiopicroside.

CONCLUSIONS AND IMPLICATIONS

Activation of LKB1/AMPK signalling by gentiopicroside was mediated by the P2X7 receptor-NLRP3 inflammasome, suggesting the therapeutic value of blocking P2X7 receptors in the treatment of alcoholic hepatosteatosis.

Function and regulation of IL-1α in inflammatory diseases and cancer

The interleukin (IL)-1 family of cytokines is currently comprised of 11 members that have pleiotropic functions in inflammation and cancer. IL-1α and IL-1β were the first members of the IL-1 family to be described, and both signal via the same receptor, IL-1R. Over the last decade, much progress has been made in our understanding of biogenesis of IL-1β and its functions in human diseases. Studies from our laboratory and others have highlighted the critical role of nod-like receptors (NLRs) and multi-protein complexes known as inflammasomes in the regulation of IL-1β maturation. Recent studies have increased our appreciation of the role played by IL-1α in inflammatory diseases and cancer. However, the mechanisms that regulate the production of IL-1α and its bioavailability are relatively understudied. In this review, we summarize the distinctive roles played by IL-1α in inflammatory diseases and cancer. We also discuss our current knowledge about the mechanisms that control IL-1α biogenesis and activity, and the major unanswered questions in its biology.

Interleukin 1α Is Critical for Resistance against Highly Virulent Aspergillus fumigatus Isolates

Heterogeneity among Aspergillus fumigatus isolates results in unique virulence potential and inflammatory responses. How these isolates drive specific immune responses and how this affects fungally induced lung damage and disease outcome are unresolved. We demonstrate that the highly virulent CEA10 strain is able to rapidly germinate within the immunocompetent lung environment, inducing greater lung damage, vascular leakage, and interleukin 1α (IL-1α) release than the low-virulence Af293 strain, which germinates with a lower frequency in this environment. Importantly, the clearance of CEA10 was consequently dependent on IL-1α, in contrast to Af293. The release of IL-1α occurred by a caspase 1/11- and P2XR7-independent mechanism but was dependent on calpain activity. Our finding that early fungal conidium germination drives greater lung damage and IL-1α-dependent inflammation is supported by three independent experimental lines. First, pregermination of Af293 prior to in vivo challenge drives greater lung damage and an IL-1α-dependent neutrophil response. Second, the more virulent EVOL20 strain, derived from Af293, is able to germinate in the airways, leading to enhanced lung damage and IL-1α-dependent inflammation and fungal clearance. Third, primary environmental A. fumigatus isolates that rapidly germinate under airway conditions follow the same trend toward IL-1α dependency. Our data support the hypothesis that A. fumigatus phenotypic variation significantly contributes to disease outcomes.

Dynamic Proteomics of Herpes Simplex Virus Infection

The cellular response to viral infection is usually studied at the level of cell populations. Currently, it remains an open question whether and to what extent cell-to-cell variability impacts the course of infection. Here we address this by dynamic proteomics-imaging and tracking 400 yellow fluorescent protein (YFP)-tagged host proteins in individual cells infected by herpes simplex virus 1. By quantifying time-lapse fluorescence imaging, we analyze how cell-to-cell variability impacts gene expression from the viral genome. We identify two proteins, RFX7 and geminin, whose levels at the time of infection correlate with successful initiation of gene expression. These proteins are cell cycle markers, and we find that the position in the cell cycle at the time of infection (along with the cell motility and local cell density) can reasonably predict in which individual cells gene expression from the viral genome will commence. We find that the onset of cell division dramatically impacts the progress of infection, with 70% of dividing cells showing no additional gene expression after mitosis. Last, we identify four host proteins that are specifically modulated in infected cells, of which only one has been previously recognized. SUMO2 and RPAP3 levels are rapidly reduced, while SLTM and YTHDC1 are redistributed to form nuclear foci. These modulations are dependent on the expression of ICP0, as shown by infection with two mutant viruses that lack ICP0. Taken together, our results provide experimental validation for the long-held notion that the success of infection is dependent on the state of the host cell at the time of infection.IMPORTANCE High-throughput assays have revolutionized many fields in biology, both by allowing a more global understanding of biological processes and by deciphering rare events in subpopulations. Here we use such an assay, dynamic proteomics, to study viral infection at the single-cell level. We follow tens of thousands of individual cells infected by herpes simplex virus using fluorescence live imaging. Our results link the state of a cell at the time of virus infection with its probability to successfully initiate gene expression from the viral genome. Further, we identified three cellular proteins that were previously unknown to respond to viral infection. We conclude that dynamic proteomics provides a powerful tool to study single-cell differences during viral infection.

Interplay between Keratinocytes and Myeloid Cells Drives Dengue Virus Spread in Human Skin

The skin is the site of dengue virus (DENV) transmission following the bite of an infected mosquito, but the contribution of individual cell types within skin to infection is unknown. We studied the dynamics of DENV infection in human skin explants using quantitative in situ imaging. DENV replicated primarily in the epidermis and induced a transient IFN-α response. DENV infected a wide range of cells, including Langerhans cells, macrophages, dermal dendritic cells, mast cells, fibroblasts, and lymphatic endothelium, but keratinocytes were the earliest targets of infection and made up 60% of infected cells over time. Virus inoculation led to recruitment and infection of Langerhans cells, macrophages, and dermal dendritic cells, and these cells emigrated from skin in increased numbers as a result of infection. DENV induced expression of proinflammatory cytokines and chemokines by infected keratinocytes. Blocking keratinocyte-derived IL-1β alone reduced infection of Langerhans cells, macrophages, and dermal dendritic cells by 75-90% and reduced the overall number of infected cells in dermis by 65%. These data show that the innate response of infected keratinocytes attracts virus-permissive myeloid cells that inadvertently spread DENV infection. Our findings highlight a role for keratinocytes and their interplay with myeloid cells in dengue.

Cytokine expression and barrier disruption in human corneal epithelial cells induced by alarmin released from necrotic cells

PURPOSE

Dying cells release endogenous molecules known as alarmins that signal danger to surrounding tissue. We investigated the effects of necrotic cell-derived alarmins on cytokine expression and barrier function in human corneal epithelial cells.

METHODS

The release of interleukin (IL)-6 and IL-8 from immortalized human corneal epithelial (HCE) cells in culture was measured with enzyme-linked immunosorbent assays. The abundance of IL-6 and 8 mRNAs was quantitated by reverse transcription and real-time polymerase chain reaction analysis. Barrier function of HCE cells was evaluated by measurement of transepithelial electrical resistance (TER). The subcellular localization of the p65 subunit of the transcription factor NF-κB was determined by immunofluorescence analysis, and phosphorylation of the endogenous NF-κB inhibitor IκBα was examined by immunoblot analysis.

RESULTS

A necrotic cell supernatant prepared from HCE cells induced the up-regulation of IL-6 and 8 expression at both mRNA and protein levels as well as reduced TER in intact HCE cells. Among alarmins tested, only IL-1α (not IL-33 or HMGB1) mimicked these effects of the necrotic cell supernatant. Furthermore, IL-1 receptor antagonist (IL-1RA) and neutralizing antibodies to IL-1α (but not those to IL-1β) each attenuated the effects of the necrotic cell supernatant. Exposure of HCE cells to the necrotic cell supernatant also induced the phosphorylation and degradation of IκBα as well as translocation of the p65 subunit of NF-κB to the nucleus.

CONCLUSION

IL-1α released from necrotic corneal epithelial cells may trigger inflammatory responses at the ocular surface, including cytokine production and barrier disruption.

Interleukin-36β provides protection against HSV-1 infection, but does not modulate initiation of adaptive immune responses

Interleukin-36 (IL-36) represents three cytokines, IL-36α, IL-36β and IL-36γ, which bind to the same receptor, IL-1RL2; however, their physiological function(s) remain poorly understood. Here, the role of IL-36 in immunity against HSV-1 was examined using the flank skin infection mouse model. Expression analyses revealed increased levels of IL-36α and IL-36β mRNA in infected skin, while constitutive IL-36γ levels remained largely unchanged. In human keratinocytes, IL-36α mRNA was induced by HSV-1, while IL-1β and TNFα increased all three IL-36 mRNAs. The dominant alternative splice variant of human IL-36β mRNA was isoform 2, which is the ortholog of the known mouse IL-36β mRNA. Mice deficient in IL-36β, but not IL-36α or IL-36γ, succumbed more frequently to HSV-1 infection than wild type mice. Furthermore, IL-36β^−/− mice developed larger zosteriform skin lesions along infected neurons. Levels of HSV-1 specific antibodies, CD8⁺ cells and IFNγ-producing CD4⁺ cells were statistically equal in wild type and IL-36β^−/− mice, suggesting similar initiation of adaptive immunity in the two strains. This correlated with the time at which HSV-1 genome and mRNA levels in primary skin lesions started to decline in both wild type and IL-36β^−/− mice. Our data indicate that IL-36β has previously unrecognized functions protective against HSV-1 infection.

Alarmin(g) the innate immune system to invasive fungal infections

Fungi encounter numerous stresses in a mammalian host, including the immune system, which they must adapt to in order to grow and cause disease. The host immune system tunes its response to the threat level posed by the invading pathogen. We discuss recent findings on how interleukin (IL)-1 signaling is central to tuning the immune response to the virulence potential of invasive fungi, as well as other pathogens. Moreover, we discuss fungal factors that may drive tissue invasion and destruction that regulate IL-1 cytokine release. Moving forward understanding the mechanisms of fungal adaption to the host, together with understanding how the host innate immune system recognizes invading fungal pathogens will increase our therapeutic options for treatment of invasive fungal infections.

EFFECT OF SELENIUM SUPPLEMENTATION ON PROTEOMIC SERUM BIOMARKERS IN ELDERLY MEN

OBJECTIVES

To determine the effect of selenium supplementation on the human proteomic profile.

DESIGN

Serum samples were collected in this pilot study from a randomized placebo controlled Phase 2 clinical trial (Watchful Waiting (WW)).

SETTING

Subjects were followed every three months for up to five years at the University of Arizona Prostate Cancer Prevention Program.

PARTICIPANTS

One hundred and forty men (age < 85 years) had biopsy-proven prostate cancer, a Gleason sum score less than eight, no metastatic cancer, and no prior treatment for prostate cancer.

INTERVENTION

As part of the WW trial, men were randomized to placebo, selenium 200 μg/day or selenium 800 μg/day. For the purpose of the current study, 40 subjects enrolled in the WW study (20 from the placebo group and 20 from Se 800 μg/day group) were selected.

MEASUREMENTS

Baseline serum samples were collected at each follow-up visit and stored at -80 degrees Celsius. A multiplexed proteomic panel investigated changes in 120 proteins markers simultaneously.

RESULTS

Thirteen proteins (Apolipoprotein J, IL-10, IL-1 alpha, MMP-3, IL-12p70, IL-2 receptor alpha, cathepsin B, eotaxin, EGFR, FGF-basic, myeloperoxidase, RANTES, TGF-beta) were determined to be either statistically (p-value < 0.05) or marginally significantly (0.05 < p-value <0.1) changed in the selenium supplemented group as compared to placebo.

CONCLUSION

Although independent validation of these results is needed, this study is the first of its kind to utilize high throughput fluorescence based protein multiplex panel in analyzing changes in the proteomic profile due to selenium supplementation. Results from this study provide insight into the ability of selenium to modulate numerous protein markers and thus impact various biological processes in humans.

The Inflammasome and the Epidermal Growth Factor Receptor (EGFR) Are Involved in the Staphylococcus aureus-Mediated Induction of IL-1alpha and IL-1beta in Human Keratinocytes

Staphylococcus (S.) aureus is an important pathogen causing various infections including those of the skin. Keratinocytes are able to sense invading S. aureus and to initiate a fast defense reaction by the rapid release of innate defense mediators such as antimicrobial peptides and cytokines. There is increasing evidence that the cytokines IL-1alpha and IL-1beta, which both signal through the IL-1 receptor, play an important role in cutaneous defense against S. aureus. The aim of this study was to gain more insight into the underlying mechanisms leading to the S. aureus-induced IL-1alpha and IL-1beta expression in keratinocytes. Infection of human primary keratinocytes with S. aureus led to the induction of gene expression and protein secretion of IL-1alpha and IL-1beta. Full S. aureus-induced IL-1 protein release required the inflammasome components caspase-1 and ASC (apoptosis-associated speck-like protein containing a CARD) whereas gene induction of IL-1alpha and IL-beta by S. aureus was not dependent on caspase-1 and ASC. Since patients receiving anti-cancer therapy by inhibition of the epidermal growth factor receptor (EGFR) often suffer from skin infections caused by S. aureus we additionally evaluated whether the EGFR pathway may be involved in the IL-1alpha and IL-1beta induction by S. aureus. Inactivation of the EGFR with a blocking antibody decreased the S. aureus-mediated IL-1alpha and IL-1beta induction in primary keratinocytes. Moreover, the use of siRNA experiments revealed that ADAM17 (A Disintegrin and A Metalloprotease 17), a metalloproteinase known to mediate the shedding and release of EGFR ligands, was required for full induction of IL-1alpha and IL-1beta in keratinocytes infected with S. aureus. A failure of keratinocytes to adequately upregulate IL-1alpha and IL-1beta may promote S. aureus skin infections.

IFN-γ Primes Keratinocytes for HSV-1-Induced Inflammasome Activation

Inflammasomes are immune complexes that induce an inflammatory response upon sensing of different stress signals. This effect is mainly mediated by activation and secretion of the proinflammatory cytokines proIL-1β and -18. Here we report that infection of human primary keratinocytes with the double-stranded DNA viruses modified vaccinia virus Ankara (MVA) or herpes simplex virus type 1 (HSV-1)-induced secretion of mature IL-1β and -18. This secretion was dependent on several inflammasome complexes; however, the absent in melanoma 2 (AIM2) inflammasome, which is activated by binding of double-stranded DNA, played the most important role. Whereas prestimulation of keratinocytes with IFN-γ moderately increased MVA-induced IL-1β and IL-18 secretion, it was essential for substantial secretion of these cytokines in response to herpes simplex virus type 1 infection. IFN-γ partially restored HSV-1 suppressed proIL-1β expression and was also required for inflammasome activation. Most importantly, IFN-γ strongly suppressed virus replication in keratinocytes in vitro and ex vivo, which was independent of inflammasome activation. Our results suggest that, similar to Herpesviridae infection in mice, HSV-1 replication in human skin is controlled by a positive feedback loop of keratinocyte-derived IL-1/IL-18 and IFN-γ expressed by immune cells.

Unprocessed Interleukin-36α Regulates Psoriasis-Like Skin Inflammation in Cooperation With Interleukin-1

Generalized pustular psoriasis is a severe skin disease characterized by epidermal hyperplasia, neutrophil-rich abscesses within the epidermis, and a mixed inflammatory infiltrate in the dermis. The disease may be caused by missense mutations in the IL-36 receptor antagonist, IL-36Ra. Curiously, the related IL-1Ra has therapeutic effects in some of these latter patients. Here, using an experimental mouse model of psoriasiform skin inflammation, we demonstrate in vivo connections between IL-36 and IL-1 expression. After disease initiation, IL-36α-deficient mice exhibited dramatically diminished skin pathology, including absence of epidermal neutrophils, reduced keratinocyte acanthosis, and less dermal edema. In contrast, IL-36β and IL-36γ knockout mice developed disease indistinguishable from that of wild-type mice. The endogenous IL-36α was not processed through proteolysis. Although IL-36α expression was strongly induced in an IL-1 signaling-dependent manner during disease, expression of IL-1α was also dependent upon IL-36α. Hence, after being upregulated by IL-1α, IL-36α acts through a feedback mechanism to boost IL-1α levels. Analyses of double knockout mice further revealed that IL-36α and IL-1α cooperate to promote psoriasis-like disease. In conclusion, IL-1α and IL-36α form a self-amplifying inflammatory loop in vivo that in patients with insufficient counter regulatory mechanisms may become hyper-engaged and/or chronic.