Regulation Of Host Defense Research Articles

Do Oral Pathogens Inhabit the Eye and Play a Role in Ocular Diseases?

Fascinatingly, the immune-privileged healthy eye has a small unique population of microbiota. The human microbiome project led to continuing interest in the ocular microbiome. Typically, ocular microflorae are commensals of low diversity that colonize the external and internal sites of the eye, without instigating any disorders. Ocular commensals modulate immunity and optimally regulate host defense against pathogenic invasion, both on the ocular surface and neuroretina. Yet, any alteration in this symbiotic relationship culminates in the perturbation of ocular homeostasis and shifts the equilibrium toward local or systemic inflammation and, in turn, impaired visual function. A compositional variation in the ocular microbiota is associated with surface disorders such as keratitis, blepharitis, and conjunctivitis. Nevertheless, innovative studies now implicate non-ocular microbial dysbiosis in glaucoma, age-related macular degeneration (AMD), uveitis, and diabetic retinopathy. Accordingly, prompt identification of the extra-ocular etiology and a methodical understanding of the mechanisms of invasion and host-microbial interaction is of paramount importance for preventative and therapeutic interventions for vision-threatening conditions. This review article aims to explore the current literature evidence to better comprehend the role of oral pathogens in the etiopathogenesis of ocular diseases, specifically AMD.

Human Guanylate-Binding Protein 1 Positively Regulates Japanese Encephalitis Virus Replication in an Interferon Gamma Primed Environment.

RNA virus infection triggers interferon (IFN) receptor signaling, leading to the activation of hundreds of interferon-stimulated genes (ISGs). Guanylate-binding proteins (GBPs) belong to one such IFN inducible subfamily of guanosine triphosphatases (GTPases) that have been reported to exert broad anti-microbial activity and regulate host defenses against several intracellular pathogens. Here, we investigated the role of human GBP1 (hGBP1) in Japanese encephalitis virus (JEV) infection of HeLa cells in both an IFNγ unprimed and primed environment. We observed enhanced expression of GBP1 both at transcript and protein levels upon JEV infection, and GBP1 association with the virus replication membranes. Depletion of hGBP1 through siRNA had no effect on JEV replication or virus induced cell death in the IFNγ unprimed environment. IFNγ stimulation provided robust protection against JEV infection. Knockdown of GBP1 in the primed environment upregulated expression and phosphorylation of signal transducer and activator of transcription 1 (STAT1) and significantly reduced JEV replication. Depletion of GBP1 in an IFNγ primed environment also inhibited virus replication in human neuroblastoma SH-SH5Y cells. Our data suggests that in the presence of IFNγ, GBP1 displays a proviral role by inhibiting innate immune responses to JEV infection.

INTERLEUKIN-17 RECEPTOR SIGNALING TO PANETH CELLS HELPS MAINTAIN INTESTINAL INTEGRITY AFTER GAMMA RADIATION INDUCED INJURY

Abstract BACKGROUND IL-17A/F signaling through the IL-17RA/RC receptor complex plays a vital role in immunity and inflammation. The expression of IL-17RA/RC by diverse intestinal epithelial cell types including Paneth cells and the observation that therapies neutralizing IL-17A or IL-17RA in Crohn’s disease (CD) patients induce adverse events suggest essential homeostatic functions of this cytokine. Paneth cells and their antimicrobial products (a-defensins, lysozyme etc.) play a critical role in mediating small intestinal host defense under homeostatic conditions as well as after injury or infection, and their dysregulation constitutes a pathogenic factor for CD. The specific role of intestinal IL-17A signaling in Paneth cells to regulate host defense at steady state or after intestinal inflammation remains poorly understood. Thus, we hypothesize that intestinal IL-17A signaling, specifically in Paneth cells, plays an important role in regulating microbiota colonization as well as maintaining intestinal integrity after gamma radiation induced injury. METHODS To examine the importance of IL-17RA signaling to Paneth cells, we utilized total, entire gut epithelium (Il17rafl/fl;villin-cre) and Paneth cell-specific IL-17RA knockout mice (Il17rafl/fl;Defa6-cre+). We subjected these mice with gamma irradiation (1200 cGy) to study intestinal injury and regenerative responses. Mice were sacrificed 3/5 days post irradiation. Terminal ilium was collected from naïve or irradiated mice for immunofluorescence imaging, RT-PCR, RNA sequencing, and enteroid cultures. RESULTS Our preliminary data from irradiated Il17ra-/- and Il17rafl/fl;villin-cre mice suggest that IL-17A signaling is important in maintaining intestinal barrier integrity. Specifically, these mice revealed increased microbial dissemination to liver and spleen compared to their respective control mice. Reduced expression of Lyz1 3 days post radiation in the terminal ileum of Il17ra-/- mice suggest impaired Paneth cell function. Cessation of Paneth cell specific IL-17RA signaling, also resulted in systemic bacterial dissemination 5 days post radiation. We also observed increased level of fecal Lcn2 in irradiated Il17rafl/fl;Defa6-cre+ mice. To understand Paneth cell-specific IL-17RA functions, we performed 16S microbial and RNA sequencing from ileum luminal contents and terminal ilea of naïve Il17rafl/fl;Defa6-cre+/- mice, respectively. While microbial 16s sequencing revealed no change to the overall microbial community, specific changes were observed at a select family level. Specifically, the level of Streptococcaceae was increased. RNA sequencing data showed no difference in Paneth cell antimicrobial peptides but did show reduced Caspase 4 expression in Il17rafl/fl;Defa6-cre+ mice. Collectively, our data revealed an important role of IL-17RA signaling in Paneth cell function at steady state and after injury.

Biological functions and diagnostic implications of microRNAs in Mycobacterium tuberculosis infection

MicroRNAs (miRNAs), small non-coding RNAs, play important roles in regulating host defense against pathogenic infections. This review provides information on the role of miRNAs in the antimycobacterial immune response and summarizes their possible diagnostic utility. It was compiled using scientific literature retrieved from such databases as PubMed, Scopus, ScienceDirect, Google Scholar, and PubMed Central. Relevant articles published in the English language until December 2020 were taken into consideration. It has been revealed that specific host miRNAs induced by Mycobacterium tuberculosis can target diverse factors and pathways in immune signaling to ensure longer pathogen survival inside the phagocytes. The potential use of miRNAs in tuberculosis diagnosis or therapeutic strategies has been attracting increasing attention in recent years. However, despite considerable efforts devoted to miRNA profiling, further studies are needed to elucidate the full potential of miRNAs as novel tuberculosis biomarkers or therapeutic targets.

Molecular basis of transcriptional repression of anti-CRISPR by anti-CRISPR-associated 2.

CRISPR-Cas systems are well known host defense mechanisms that are conserved in bacteria and archaea. To counteract CRISPR-Cas systems, phages and viruses have evolved to possess multiple anti-CRISPR (Acr) proteins that can inhibit the host CRISPR-Cas system via different strategies. The expression of acr genes is controlled by anti-CRISPR-associated (Aca) proteins that bind toan upstream promoter and regulate the expression of acr genes during transcription. Although the role of Aca as a transcriptional repressor has been demonstrated, the mechanism of action of Aca has not been determined. Here, the molecular mechanism underlying the Aca2-mediated transcriptional control of acr genes was elucidated by determining the crystal structure of Aca2 from Oceanimonas smirnovii at a high resolution of 1.92 Å. Aca2 forms a dimer in solution, and dimerization of Aca2 is critical for specific promoter binding. The promoter-binding strategy of dimeric Aca2 was also revealed by performing mutagenesis studies. The atomic structure of the Aca family shown in this study provides insights into the fine regulation of host defense and immune-escape mechanisms and also demonstrates the conserved working mechanism of the Aca family.

Mycobacterium tuberculosis ESAT6 modulates host innate immunity by downregulating miR-222-3p target PTEN

Tuberculosis (TB) remains a major cause of mortality and morbidity worldwide, and it is instant to discover novel anti-TB drugs due to the rapidly growing drug-resistance TB. Mycobacterium tuberculosis (Mtb) secreted effector ESAT6 plays a critical role in modulation miRNAs to regulate host defense mechanisms during Mtb infection, it can be a possible target for new tuberculosis drugs. The non-tuberculous mycobacteria Mycobacterium smegmatis (M. smegmatis) and Mtb have high gene homology but no pathogenicity. We used ESAT6 to interfere with macrophages or mice infected by M. smegmatis and determined that it enhanced the survival rate of bacteria and regulated miR-222-3p target PTEN. Expression of miR-222-3p reduced and PTEN enhanced with the progression of macrophages infected by M. smegmatis with ESAT6 co-incubation. MiR-222-3p overexpression diminished M. smegmatis survival and upregulated proinflammatory cytokines. VO-Ohpic trihydrate (PTEN inhibitor) reduced M. smegmatis survival and upregulated proinflammatory cytokines in vivo and in vitro, and VO-Ohpic trihydrate reversed the tissue damage of mouse organs caused by ESAT6. These results uncover an ESAT6 dependent role for miR-222-3p and its target PTEN in regulating host immune responses to bacterial infection and may provide a potential site for the development of anti-tuberculosis drugs that specifically antagonize the virulence of ESAT6.

217 Tofacitinib suppresses IL-10/IL-10R signaling and modulates host defense responses in human macrophages

JAK inhibitors are increasingly used in dermatology. Despite broad inhibitory effects on cytokine signaling cascades, they only modestly increase the risk for infectious diseases. To address molecular mechanisms underlying this unexpected clinical observation, we investigated how tofacintib, a first-in-class JAK inhibitor, regulates host defense responses in TLR4-activated human macrophages. Specifically, we asked if tofacitinib inhibits anti-inflammatory IL-10 signaling, thereby counteracting downregulation of inflammatory, host-protective pathways. We found that tofacitinib blocked macrophage responses to IL-10 at the level of STAT3 phosphorylation. Furthermore, TLR4-induced, auto-/paracrine IL-10/IL-10R activation promoted expression of hepcidin, the master regulator of iron metabolism, resulting in intracellular iron sequestration. In contrast, auto-/paracrine IL-10/IL-10R activation repressed expression of cathelicidin antimicrobial peptide, as well as antigen-presenting molecules, thus together, inducing a pathogen-favoring environment. While tofacitinib further repressed cathelicidin, it prevented induction of intracellular hepcidin, and restored expression of antigen-presentation molecules in TLR4-activated macrophages. Our study supports the concept that induction of IL-10/IL-10R signaling drives a complex immune evasion strategy of intracellular microbes. Moreover, we conclude that tofacitinib has diverging effects on macrophage host response pathways, and we identify the TLR4-IL-10-STAT3-hepcidin axis as a potential therapeutic target to counteract immune evasion.

Tofacitinib Suppresses IL-10/IL-10R Signaling and Modulates Host Defense Responses in Human Macrophages

Jak inhibitors are increasingly used in dermatology. Despite broad inhibitory effects on cytokine signaling cascades, they only modestly increase the risk for infectious diseases. To address the molecular mechanisms underlying this unexpected clinical observation, we investigated how tofacintib (tofa), a first-in-class Jak inhibitor, regulates host defense responses in toll-like receptor 4-activated human macrophages. Specifically, we asked whether tofa inhibits anti-inflammatory IL-10 signaling, thereby counteracting the downregulation of inflammatory, host-protective pathways. We found that tofa blocked macrophage responses to IL-10 at the level of signal transducer and activator of transcription 3 phosphorylation. Furthermore, toll-like receptor 4-induced, autocrine/paracrine IL-10/IL-10R activation promoted the expression of hepcidin, the master regulator of iron metabolism, resulting in intracellular iron sequestration. In contrast, autocrine/paracrine IL-10/IL-10R activation repressed the expression of cathelicidin antimicrobial peptide as well as antigen-presenting molecules, thus together, inducing a pathogen-favoring environment. Although tofa further repressed cathelicidin, it prevented the induction of intracellular HAMP and restored the expression of antigen-presentation molecules in toll-like receptor 4-activated macrophages. Our study supports the concept that induction of IL-10/IL-10R signaling drives a complex immune evasion strategy of intracellular microbes. Moreover, we conclude that tofa has diverging effects on macrophage host response pathways, and we identify the toll-like receptor 4-IL-10-signal transducer and activator of transcription 3-HAMP axis as a potential therapeutic target to counteract immune evasion.

Favorable prognostic role of IL-26 in HCC patients associated with JAK-STAT3-dependent autophagy

Abstract Interleukin-26 (IL-26), a recently identified cytokine of the IL-20 subfamily, plays an important role in the regulation of host defense and inflammatory diseases. However, whether the role of IL-26 in the progression of hepatocellular carcinoma (HCC) occurs via autophagy remains unclear. Here, we investigated the IL-26 levels in the blood and tissues of subjects, its possible cellular source and its relationship with the prognosis of HCC patients. We also explored the mechanisms by which different pathophysiological levels of IL-26 affect the outcomes of patients; these studies were conducted only in vitro due to the lack of IL-26 gene expression in rodents. We found that IL-26 was highly expressed in HCC patients and was mainly derived from tumor-associated macrophages. Furthermore, we found that high expression of IL-26 was associated with good prognosis due to its inhibition of HCC cell migration and invasion abilities. This function of IL-26 was driven by JAK-STAT3-dependent autophagy. These findings suggest that the levels of IL-26 may be a useful prognostic marker for HCC patients and may offer insights into the clinical application of IL-26 in the future.

Stabilin-1 plays a protective role against Listeria monocytogenes infection through the regulation of cytokine and chemokine production and immune cell recruitment

ABSTRACT Scavenger receptors are part of a complex surveillance system expressed by host cells to efficiently orchestrate innate immune response against bacterial infections. Stabilin-1 (STAB-1) is a scavenger receptor involved in cell trafficking, inflammation, and cancer; however, its role in infection remains to be elucidated. Listeria monocytogenes (Lm) is a major intracellular human food-borne pathogen causing severe infections in susceptible hosts. Using a mouse model of infection, we demonstrate here that STAB-1 controls Lm-induced cytokine and chemokine production and immune cell accumulation in Lm-infected organs. We show that STAB-1 also regulates the recruitment of myeloid cells in response to Lm infection and contributes to clear circulating bacteria. In addition, whereas STAB-1 appears to promote bacterial uptake by macrophages, infection by pathogenic Listeria induces the down regulation of STAB-1 expression and its delocalization from the host cell membrane. We propose STAB-1 as a new SR involved in the control of Lm infection through the regulation of host defense mechanisms, a process that would be targeted by bacterial virulence factors to promote infection.

Clinically Healthy Human Gingival Tissues Show Significant Inter-individual Variability in GCF Chemokine Expression and Subgingival Plaque Microbial Composition.

Aim: Clinically healthy gingival tissue is maintained through controlled regulation of host defense mechanisms against plaque biofilm overgrowth. One key component is the transit of neutrophils from the vasculature into gingival tissue where the expression of different neutrophil chemokines are tightly regulated. This cross-sectional study examines the inter-individual variability in chemokine profiles within gingival crevicular fluid (GCF) in relation to the subgingival bacterial community in a state of gingival health.Methods: Gingival crevicular fluid and subgingival plaque samples were collected from mesiobuccal surfaces of all six Ramfjord teeth of 20 systemically healthy individuals (14.55 ± 1.67 years). A multiplex immunoassay was carried out to quantify the expression of 40 different chemokines in the healthy gingival tissue. Neutrophils were assessed indirectly by myeloperoxidase (MPO) in GCF using traditional ELISA. Characterization of healthy subgingival plaque was conducted with the Illumina Miseq targeting the 16S rRNA gene.Results: In health, there are distinct variations within individual gingival crevicular fluid chemokine expression profiles, as well as in the concentration of neutrophils, that divided the participants into high or low chemokine expressing groups. Specifically, key differences were identified within MIF (2683.54 ± 985.82 pg per 30-s sample), IL-8/CXCL8 (170.98 ± 176.96 pg per 30-s sample), Gro-α/CXCL1 (160.42 ± 94.21 pg per 30-s sample), ENA-78/CXCL5 (137.76 ± 76.02 pg per 30-s sample), IL-1β (51.39 ± 37.23 pg per 30-s sample), TNF-α (1.76 ± 1.79 pg per 30-s sample), and IFN-γ (0.92 ± 0.54 pg per 30-s sample). Of these identified chemokines, the highest correlation was associated between IL-8/CXCL8 and neutrophils (r = 0.54, p = 0.014). Furthermore, species characterization of healthy subgingival plaque revealed significant inter-individual variability that identified two unique groups unrelated to the previously identified chemokine groups.Conclusion: The lack of concordance between the microbial composition and chemokine profile during health may be a reflection of the unique microbial composition of each individual coupled with variations within their host response, emphasizing the vast complexity of the defense mechanisms in place to maintain gingival health.

The Role of microRNAs and Long Non-Coding RNAs in the Regulation of the Immune Response to Mycobacterium tuberculosis Infection.

Non-coding RNAs have emerged as critical regulators of the immune response to infection. MicroRNAs (miRNAs) are small non-coding RNAs which regulate host defense mechanisms against viruses, bacteria and fungi. They are involved in the delicate interplay between Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), and its host, which dictates the course of infection. Differential expression of miRNAs upon infection with M. tuberculosis, regulates host signaling pathways linked to inflammation, autophagy, apoptosis and polarization of macrophages. Experimental evidence suggests that virulent M. tuberculosis often utilize host miRNAs to promote pathogenicity by restricting host-mediated antibacterial signaling pathways. At the same time, host- induced miRNAs augment antibacterial processes such as autophagy, to limit bacterial proliferation. Targeting miRNAs is an emerging option for host-directed therapies. Recent studies have explored the role of long non-coding RNA (lncRNAs) in the regulation of the host response to mycobacterial infection. Among other functions, lncRNAs interact with chromatin remodelers to regulate gene expression and also function as miRNA sponges. In this review we attempt to summarize recent literature on how miRNAs and lncRNAs are differentially expressed during the course of M. tuberculosis infection, and how they influence the outcome of infection. We also discuss the potential use of non-coding RNAs as biomarkers of active and latent tuberculosis. Comprehensive understanding of the role of these non-coding RNAs is the first step towards developing RNA-based therapeutics and diagnostic tools for the treatment of TB.

Effect of Reactive Oxygen Species on the Endoplasmic Reticulum and Mitochondria during Intracellular Pathogen Infection of Mammalian Cells.

Oxidative stress, particularly reactive oxygen species (ROS), are important for innate immunity against pathogens. ROS directly attack pathogens, regulate and amplify immune signals, induce autophagy and activate inflammation. In addition, production of ROS by pathogens affects the endoplasmic reticulum (ER) and mitochondria, leading to cell death. However, it is unclear how ROS regulate host defense mechanisms. This review outlines the role of ROS during intracellular pathogen infection, mechanisms of ROS production and regulation of host defense mechanisms by ROS. Finally, the interaction between microbial pathogen-induced ROS and the ER and mitochondria is described.

The Ubiquitination System within Bacterial Host-Pathogen Interactions.

Ubiquitination of proteins, like phosphorylation and acetylation, is an important regulatory aspect influencing numerous and various cell processes, such as immune response signaling and autophagy. The study of ubiquitination has become essential to learning about host–pathogen interactions, and a better understanding of the detailed mechanisms through which pathogens affect ubiquitination processes in host cell will contribute to vaccine development and effective treatment of diseases. Pathogenic bacteria (e.g., Salmonella enterica, Legionella pneumophila and Shigella flexneri) encode many effector proteins, such as deubiquitinating enzymes (DUBs), targeting the host ubiquitin machinery and thus disrupting pertinent ubiquitin-dependent anti-bacterial response. We focus here upon the host ubiquitination system as an integral unit, its interconnection with the regulation of inflammation and autophagy, and primarily while examining pathogens manipulating the host ubiquitination system. Many bacterial effector proteins have already been described as being translocated into the host cell, where they directly regulate host defense processes. Due to their importance in pathogenic bacteria progression within the host, they are regarded as virulence factors essential for bacterial evasion. However, in some cases (e.g., Francisella tularensis) the host ubiquitination system is influenced by bacterial infection, although the responsible bacterial effectors are still unknown.

TLR7 Expression Aggravates Invasive Pulmonary Aspergillosis by Suppressing Anti-Aspergillus Immunity of Macrophages.

Toll-like receptors (TLRs) play a critical role in early immune recognition of Aspergillus, which can regulate host defense during invasive pulmonary Aspergillosis (IPA). However, the role of TLR7 in the pathogenesis of IPA remains unknown. In this study, an in vivo model of IPA was established to investigate the contribution of TLR7 to host anti-Aspergillus immunity upon invasive pulmonary Aspergillus fumigatus infection. The effects of TLR7 on phagocytosis and killing capacities of A. fumigatus by macrophages and neutrophils were investigated in vitro We found that TLR7 knockout mice exhibited lower lung inflammatory response and tissue injury, higher fungal clearance, and greater survival in an in vivo model of IPA compared with wild-type mice. TLR7 activation by R837 ligand led to wild-type mice being more susceptible to invasive pulmonary Aspergillus fumigatus infection. Macrophages, but not neutrophils, were required for the protection against IPA observed in TLR7 knockout mice. Mechanistically, TLR7 impaired phagocytosis and killing of A. fumigatus by macrophages but not neutrophils. Together, these data identify TLR7 as an important negative regulator of anti-Aspergillus innate immunity in IPA, and we propose that targeting TLR7 will be beneficial in the treatment of IPA.

PCTR1 Enhances Repair and Bacterial Clearance in Skin Wounds

Tissue injury elicits an inflammatory response that facilitates host defense. Resolution of inflammation promotes the transition to tissue repair and is governed, in part, by specialized pro-resolving mediators (SPM). The complete structures of a novel series of cysteinyl-SPM (cys-SPM) were recently elucidated, and proved to stimulate tissue regeneration in planaria and resolve acute inflammation in mice. Their functions in mammalian tissue repair are of interest. Here, nine structurally distinct cys-SPM were screened and PCTR1 uniquely enhanced human keratinocyte migration with efficacy similar to epidermal growth factor. In skin wounds of mice, PCTR1 accelerated closure. Wound infection increased PCTR1 that coincided with decreased bacterial burden. Addition of PCTR1 reduced wound bacteria levels and decreased inflammatory monocytes/macrophages, which was coupled with increased expression of genes involved in host defense and tissue repair. These results suggest that PCTR1 is a novel regulator of host defense and tissue repair, which could inform new approaches for therapeutic management of delayed tissue repair and infection.

The UPR sensor IRE1α promotes dendritic cell responses to control Toxoplasma gondii infection.

The unfolded protein response (UPR) has emerged as a central regulator of immune cell responses in several pathologic contexts including infections. However, how intracellular residing pathogens modulate the UPR in dendritic cells (DCs) and thereby affect T cell-mediated immunity remains uncharacterized. Here, we demonstrate that infection of DCs with Toxoplasma gondii (T.gondii) triggers a unique UPR signature hallmarked by the MyD88-dependent activation of the IRE1α pathway and the inhibition of the ATF6 pathway. Induction of XBP1s controls pro-inflammatory cytokine secretion in infected DCs, while IRE1α promotes MHCI antigen presentation of secreted parasite antigens. In mice, infection leads to a specific activation of the IRE1α pathway, which is restricted to the cDC1 subset. Mice deficient for IRE1α and XBP1 in DCs display a severe susceptibility to T.gondii and succumb during the acute phase of the infection. This early mortality is correlated with increased parasite burden and a defect in splenic T-cell responses. Thus, we identify the IRE1α/XBP1s branch of the UPR as a key regulator of host defense upon T.gondii infection.

Bronchial Epithelial Tet2 Maintains Epithelial Integrity during Acute Pseudomonas aeruginosa Pneumonia.

Respiratory epithelial cells are important for pulmonary innate immune responses during Pseudomonas aeruginosa infection. Tet methylcytosine dioxygenase 2 (Tet2) has been implicated in the regulation of host defense by myeloid and lymphoid cells, but whether Tet2 also contributes to epithelial responses during pneumonia is unknown. The aim of this study was to investigate the role of bronchial epithelial Tet2 in acute pneumonia caused by P. aeruginosa To this end, we crossed mice with Tet2 flanked by two Lox-P sites (Tet2fl/fl mice) with mice expressing Cre recombinase under the bronchial epithelial cell-specific Cc10 promoter (Cc10Cre mice) to generate bronchial epithelial cell-specific Tet2-deficient (Tet2fl/fl Cc10Cre ) mice. Six hours after infection with P. aeruginosa,Tet2fl/fl Cc10Cre and wild-type mice had similar bacterial loads in bronchoalveolar lavage fluid (BALF). At this time point, Tet2fl/fl Cc10Cre mice displayed reduced mRNA levels of the chemokines Cxcl1, Cxcl2, and Ccl20 in bronchial brushes. However, Cxcl1, Cxcl2, and Ccl20 protein levels and leukocyte recruitment in BALF were not different between groups. Tet2fl/fl Cc10Cre mice had increased protein levels in BALF after infection, indicating a disturbed epithelial barrier function, which was corroborated by reduced mRNA expression of tight junction protein 1 and occludin in bronchial brushes. Differences detected between Tet2fl/fl Cc10Cre and wild-type mice were no longer present at 24 h after infection. These results suggest that bronchial epithelial Tet2 contributes to maintaining epithelial integrity by enhancing intracellular connections between epithelial cells during the early phase of P. aeruginosa pneumonia.

Beyond arbitrium: identification of a second communication system in Bacillus phage phi3T that may regulate host defense mechanisms

The evolutionary stability of temperate bacteriophages at low abundance of susceptible bacterial hosts lies in the trade-off between the maximization of phage replication, performed by the host-destructive lytic cycle, and the protection of the phage-host collective, enacted by lysogeny. Upon Bacillus infection, Bacillus phages phi3T rely on the “arbitrium” quorum sensing (QS) system to communicate on their population density in order to orchestrate the lysis-to-lysogeny transition. At high phage densities, where there may be limited host cells to infect, lysogeny is induced to preserve chances of phage survival. Here, we report the presence of an additional, host-derived QS system in the phi3T genome, making it the first known virus with two communication systems. Specifically, this additional system, coined “Rapφ-Phrφ”, is predicted to downregulate host defense mechanisms during the viral infection, but only upon stress or high abundance of Bacillus cells and at low density of population of the phi3T phages. Post-lysogenization, Rapφ-Phrφ is also predicted to provide the lysogenized bacteria with an immediate fitness advantage: delaying the costly production of public goods while nonetheless benefiting from the public goods produced by other non-lysogenized Bacillus bacteria. The discovered “Rapφ-Phrφ” QS system hence provides novel mechanistic insights into how phage communication systems could contribute to the phage-host evolutionary stability.

WD40 Repeat Protein 26 Negatively Regulates Formyl Peptide Receptor-1 Mediated Wound Healing in Intestinal Epithelial Cells

N-formyl peptide receptors (FPRs) serve as phagocyte pattern-recognition receptors that play a crucial role in the regulation of host defense against infection. Epithelial cells also express FPRs, and their activation during inflammation or injury results in enhanced epithelial migration and proliferation and improved mucosal wound repair. However, signaling mechanisms that govern epithelial FPR1 activity are not well understood. This study identified a novel FPR1-interacting protein, WD40 repeat protein (WDR)-26, which negatively regulates FPR1-mediated wound healing in intestinal epithelial cells. We show that WDR26-mediated inhibition of wound repair is mediated through the inhibition of Rac family small GTPase 1 and cell division cycle 42 activation, as well as downstream intracellular reactive oxygen species production. Furthermore, on FPR1 activation with N-formyl-methionyl-leucyl phenylalanine, WDR26 dissociates from FPR1, resulting in the activation of downstream cell division cycle 42/Rac family small GTPase 1 signaling, increased epithelial cell migration, and mucosal wound repair. These findings elucidate a novel regulatory function of WDR26 in FPR1-mediated wound healing in intestinal epithelial cells.