Negative charges in the flexible N-terminal domain of Rho GDP-dissociation inhibitors (RhoGDIs) regulate the targeting of the RhoGDI-Rac1 complex to membranes

In its resting state, Rho GDP-dissociation inhibitor (RhoGDI) α forms a soluble cytoplasmic heterodimer with the GDP-bound form of Rac. Upon stimulation, the dissociation of RhoGDIα from the RhoGDIα-Rac complex is a mandatory step for Rac activation; however, this mechanism is poorly understood. In this study, we examined how the cytoplasm/membrane cycles of the RhoGDI-Rac complex are regulated, as well as where RhoGDI dissociates from the RhoGDI-Rac complex, during FcγR-mediated phagocytosis. The negatively charged and flexible N terminus (25 residues) of RhoGDIα, particularly its second negative amino acid cluster possessing five negatively charged amino acids, was a pivotal regulator in the cytoplasm/membrane cycles of the RhoGDI-Rac complex. We also found that RhoGDIα translocated to the phagosomes as a RhoGDIα-Rac1 complex, and this translocation was mediated by an interaction between the polybasic motif in the C terminus of Rac1 and anionic phospholipids produced on phagosomes, such as phosphatidic acid, that is, by a phagosome-targeting mechanism of Rac1. Thus, we demonstrated that the targeting/accumulation of the RhoGDIα-Rac1 complex to phagosomes is regulated by a balance between three factors: 1) the negatively charged and flexible N-terminal of RhoGDIα, 2) the binding affinity of RhoGDIα for Rac1, and 3) anionic phospholipids produced on phagosomes. Moreover, we demonstrated that the mechanism of targeting/accumulation of the RhoGDIα-Rac1 complex is also applicable for the RhoGDIβ-Rac1 complex.

The efficacy of combined herbal extracts gel in reducing scar development at a split-thickness skin graft donor site

BACKGROUND

The aim of this study was to evaluate the efficacy of combined herbal extracts in a gel preparation (Cybele(®) Scagel) in reducing scar development at a split-thickness skin graft donor site.

METHODS

A prospective, randomized, double-blind control study was performed to evaluate the efficacy of Scagel in 15 patients who underwent a split-thickness skin graft operation. Both Scagel and placebo were applied equally to the donor site within 1 month after complete epithelialization. Scar assessments using the Vancouver Scar Scale (VSS) and patient self-evaluation were taken at 2, 4, 8, and 12 weeks.

RESULTS

Of the 15 patients, 10 were enrolled and evaluated in this study. There was no significant difference in each parameter of the VSS. The total VSS was significantly lower in the Scagel group compared to the placebo group after 4 weeks (p = 0.003, 0.003, and <0.001 at 4, 8, and 12 weeks, respectively). The patient satisfaction score in the Cybele(®) Scagel group was significantly higher (p = 0.002) at the 12-week evaluation.

CONCLUSION

Application of combined herbal extracts in gel preparation might reduce scar development at split-thickness skin graft donor sites. There was a positive trend in the reduction of postinflammatory hyperpigmentation.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Systems biology of host-mycobiota interactions: dissecting Dectin-1 and Dectin-2 signalling in immune cells with DC-ATLAS

Modelling the networks sustaining the fruitful coexistence between fungi and their mammalian hosts is becoming increasingly important to control emerging fungal pathogens. The C-type lectins Dectin-1 and Dectin-2 are involved in host defense mechanisms against fungal infection driving inflammatory and adaptive immune responses and complement in containing fungal burdens. Recognizing carbohydrate structures in pathogens, their engagement induces maturation of dendritic cells (DCs) into potent immuno-stimulatory cells endowed with the capacity to efficiently prime T cells. Owing to these properties, Dectin-1 and Dectin-2 agonists are currently under investigation as promising adjuvants in vaccination procedures for the treatment of fungal infection. Thus, a detailed understanding of events' cascade specifically triggered in DCs upon engagement is of great interest in translational research. Here, we summarize the current knowledge on Dectin-1 and Dectin-2 signalling in DCs highlighting similarities and differences. Detailed maps are annotated, using the Biological Connection Markup Language (BCML) data model, and stored in DC-ATLAS, a versatile resource for the interpretation of high-throughput data generated perturbing the signalling network of DCs.

Dectin-2 is predominately macrophage restricted and exhibits conspicuous expression during Aspergillus fumigatus invasion in human lung

We investigated the features of Dectin-2 expression both at transcriptional and translational levels during Aspergillus fumigatus infection in human lung. Simultaneously, the expression of CD206 was assayed as an activated marker of alveolar macrophages. The characteristic of Dectin-2 expression were then confirmed in Monocyte-derived macrophages (MDM) after A. fumigatus stimulation by Flow Cytometry. We found that the expression of Dectin-2 was low in normal lung, while it revealed a markedly up-regulation during A. fumigatus invasion. Dectin-2 expression was predominantly restricted to CD206 positive cells. There was salient positive correlation between Dectin-2 expression and CD206. We conclude that Dectin-2 expression is largely restricted to alveolar macrophages in human lung. The conspicuous expression of Dectin-2 during A. fumigatus invasion suggests its notable contribution to antifungal defenses in pulmonary aspergillosis.

C-type lectin receptors orchestrate antifungal immunity

Fungal infections are an emerging threat for human health. A coordinated host immune response is fundamental for successful elimination of an invading fungal microbe. A panel of C-type lectin receptors expressed on antigen-presenting dendritic cells enable innate recognition of fungal cell wall carbohydrates and tailors adaptive responses via the instruction of CD4+ T helper cell fates. Well-balanced T helper cell type 1 and IL-17-producing T helper cell responses are crucial in antifungal immunity and facilitate phagocytic clearance of fungal encounters. Strikingly, different classes of fungi trigger distinct sets of C-type lectin receptors to evoke a pathogen-specific T helper response. In this review, we outline the key roles of several C-type lectin receptors during the generation of protective antifungal immunity, with particular emphasis on the distinct signaling pathways and transcriptional programs triggered by these receptors, which collaborate to orchestrate polarization of the T helper response.

Caspase recruitment domain-containing protein 9 signaling in innate immunity and inflammation

Caspase recruitment domain-containing protein (Card)9 is a nonredundant adapter protein that functions in the innate immune system in the assembly of multifunctional signaling complexes. Together with B cell lymphoma (Bcl)10 and the paracaspase, mucosa-associated lymphoid tissue lymphoma translocation protein (Malt)1, Card9 links spleen-tyrosine kinase (Syk)-coupled C-type lectin receptors to inflammatory responses. Card9 signaling also responds to intracellular danger sensors, such as retinoic acid-inducible gene 1 (RIG-I)-like receptors (RLRs) and nucleotide-oligomerization domain (Nod)2. Card9 complexes are engaged upon fungal, bacterial, or viral recognition, and they are essential for host protection. Moreover, Card9 polymorphisms are commonly associated with human inflammatory diseases. Here, we discuss the molecular regulation and the physiological functions of Card9 in host defense and immune homeostasis, and provide a framework for the therapeutic targeting of Card9 signaling in immune-mediated diseases.

Robot-assisted radical cystectomy: description of an evolved approach to radical cystectomy

BACKGROUND

Although open radical cystectomy (ORC) remains the gold standard of care for muscle-invasive bladder cancer, robot-assisted radical cystectomy (RARC) continues to gain wider acceptance. In this article, we focus on the steps of RARC, describing our approach, which has been developed over the past 10 yr. Totally intracorporeal RARC aims to offer the benefits of a complete minimally invasive approach while replicating the oncologic outcomes of open surgery.

OBJECTIVE

We report our outcomes of a totally intracorporeal RARC procedure, describing step by step our technique and highlighting the variations on this standard template of nerve-sparing and female organ-preserving approaches in men and women.

DESIGN, SETTING, AND PARTICIPANTS

Between December 2003 and October 2012, a total of 113 patients (94 male and 19 female) underwent totally intracorporeal RARC.

SURGICAL PROCEDURE

We performed RARC, extended pelvic lymph node dissection, and a totally intracorporeal urinary diversion (UD) in all patients. In the accompanying video, we focus on the standard template for RARC, also describing nerve-sparing and female organ-preserving approaches.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Complications and oncologic outcomes are reported, including overall survival (OS) and cancer-specific survival (CSS) using Kaplan-Meier analysis.

RESULTS AND LIMITATIONS

RARC with intracorporeal UD was performed in 113 patients. Mean age was 64 yr (range: 37-84). Forty-three patients underwent intracorporeal ileal conduit, and 70 had intracorporeal neobladder. On surgical pathology, 48% of patients had ≤ pT1 disease, 27% had pT2 disease, 13% had pT3 disease, and 12% had pT4 disease. The mean number of lymph nodes removed was 21 (range: 0-57). Twenty percent of patients had lymph node-positive disease. Positive surgical margins occurred in six cases (5.3%). Median follow-up was 25 mo (range: 3-107). We recorded a total of 70 early complications (0-30 d) in 54 patients (47.8%), with 37 patients (32.7%) having Clavien grade ≥ 3. Thirty-six late complications (>30 d) were recorded in 30 patients (26.5%), with 20 patients (17.7%) having Clavien grade ≥ 3. One patient (0.9%) died within 90 days of operation from pulmonary embolism. Using Kaplan-Meier analysis, CSS was 81% at 3 yr and 67% at 5 yr.

CONCLUSIONS

Our structured approach to RARC has enabled us to develop this complex service while maintaining patient outcomes and complication rates comparable with ORC series. Our results demonstrate acceptable oncologic outcomes and encouraging long-term CSS rates.

The role of ERK and JNK signaling in connective tissue growth factor induced extracellular matrix protein production and scar formation

CCN2 plays an important role in the pathogenesis of hypertrophic scars (HTSs). Although CCN2 is involved in many fibroproliferative events, the CCN2 induction signaling pathway in HTSs is yet to be elucidated. Here, we first investigated the effect of the mitogen-activated protein kinases (MAPKs) on CCN2-induced α-smooth muscle actin (α-SMA) and collagen I expression in human HTS fibroblasts (HTSFs). Then, we established HTSs in a rabbit ear model and determined the effect of MAPKs on the pathogenesis of HTSs. MAPK pathways were activated by CCN2 in HTSFs. Extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) inhibitors significantly inhibited CCN2-induced expression of α-SMA and collagen I in HTSFs. In the rabbit ear model of the HTS, JNK and ERK inhibitors significantly improved the architecture of the rabbit ear scar and reduced scar formation on the rabbit ear. Our results indicate that ERK and JNK mediate collagen I expression and scarring of the rabbit ear, and may be considered for specific drug therapy targets for HTSs.

The NF-κB signaling protein Bcl10 regulates actin dynamics by controlling AP1 and OCRL-bearing vesicles

The protein Bcl10 contributes to adaptive and innate immunity through the assembly of a signaling complex that plays a key role in antigen receptor and FcR-induced NF-κB activation. Here we demonstrate that Bcl10 has an NF-κB-independent role in actin and membrane remodeling downstream of FcR in human macrophages. Depletion of Bcl10 impaired Rac1 and PI3K activation and led to an abortive phagocytic cup rich in PI(4,5)P(2), Cdc42, and F-actin, which could be rescued with low doses of F-actin depolymerizing drugs. Unexpectedly, we found Bcl10 in a complex with the clathrin adaptors AP1 and EpsinR. In particular, Bcl10 was required to locally deliver the vesicular OCRL phosphatase that regulates PI(4,5)P(2) and F-actin turnover, both crucial for the completion of phagosome closure. Thus, we identify Bcl10 as an early coordinator of NF-κB-mediated immune response with endosomal trafficking and signaling to F-actin remodeling.

Invasive fungal infection and impaired neutrophil killing in human CARD9 deficiency

Caspase recruitment domain-containing protein 9 (CARD9) is an adaptor molecule in the cytosol of myeloid cells, required for induction of T-helper cells producing interleukin-17 (Th17 cells) and important in antifungal immunity. In a patient suffering from Candida dubliniensis meningoencephalitis, mutations in the CARD9 gene were found to result in the loss of protein expression. Apart from the reduced numbers of CD4(+) Th17 lymphocytes, we identified a lack of monocyte-derived cytokines in response to Candida strains. Importantly, CARD9-deficient neutrophils showed a selective Candida albicans killing defect with abnormal ultrastructural phagolysosomes and outgrowth of hyphae. The neutrophil killing defect was independent of the generation of reactive oxygen species by the reduced NAD phosphate oxidase system. Taken together, this demonstrates that human CARD9 deficiency results in selective defect in the host defense against invasive fungal infection, caused by an impaired phagocyte killing.

Protection against TGF-β1-induced fibrosis effects of IL-10 on dermal fibroblasts and its potential therapeutics for the reduction of skin scarring

Scarring, tightly associated with fibrosis, is a significant symptomatic clinical problem. Interleukin 10 (IL-10) has been identified as a candidate scar-improving therapy based on preclinical studies. However, the molecular mechanism of IL-10 in scar improvement is still uncertain. In this study, human dermal fibroblasts stimulated with TGF-β1 were treated with IL-10 to analyze the mRNA and some of proteins' expression levels of type I collagen (Col1), type III collagen (Col3), alpha-smooth muscle actin (α-SMA), matrix metalloproteinase-1 (MMP1), MMP2, MMP8 and tissue inhibitor of metalloproteinase 1 (TIMP1), TIMP2 by real-time PCR and Western blot, to observe α-SMA-positive fibroblasts by immunocytochemistry. The contracture and improvement of fibroblast-populated collagen lattice (FPCL) and a murine model of wound healing were used to evaluate the scar-improving effects by histological staining. The results showed that IL-10 can significantly down-regulate the mRNA and protein expression levels of Col1, Col3, α-SMA, and up-regulate the mRNA expression levels of MMP1 and MMP8, and decrease α-SMA-positive fibroblasts. FPCL analysis showed that the IL-10 (20 ng/ml) can significantly inhibit the contracture, improve the architecture of FPCL. Wounds injected with IL-10 demonstrated that the appearance of scar was improved, the wound margin of scarring was narrow, and the deposition of collagens (Col1 and Col3) in regenerated tissue was relieved. These results provide direct evidences that IL-10 has the inhibitory effects on the excessive deposition of extracellular matrix components and fibroblast-to-myofibroblast transition, and show that IL-10 has the potential therapy in prevention and reduction of skin scarring.

Tracing conidial fate and measuring host cell antifungal activity using a reporter of microbial viability in the lung

Fluorescence can be harnessed to monitor microbial fate and to investigate functional outcomes of individual microbial cell-host cell encounters at portals of entry in native tissue environments. We illustrate this concept by introducing fluorescent Aspergillus reporter (FLARE) conidia that simultaneously report phagocytic uptake and fungal viability during cellular interactions with the murine respiratory innate immune system. Our studies using FLARE conidia reveal stepwise and cell-type-specific requirements for CARD9 and Syk, transducers of C-type lectin receptor and integrin signals, in neutrophil recruitment, conidial uptake, and conidial killing in the lung. By achieving single-event resolution in defined leukocyte populations, the FLARE method enables host cell profiling on the basis of pathogen uptake and killing and may be extended to other pathogens in diverse model host organisms to query molecular, cellular, and pharmacologic mechanisms that shape host-microbe interactions.

Tumor necrosis factor receptor-associated factor 6 (TRAF6) and TGFβ-activated kinase 1 (TAK1) play essential roles in the C-type lectin receptor signaling in response to Candida albicans infection

Tumor necrosis factor receptor-associated factor 6 (TRAF6) and TGFβ-activated kinase 1 (TAK1) are considered as key intermediates in Toll-like receptor (TLR) signaling. However, the role of TRAF6 and TAK1 in C-type lectin receptors (CLRs) in response to fungal infection has not been studied. In this study, we have utilized macrophages derived from TRAF6 knock-out mice and myeloid-specific TAK1-deficient mice and determined the role of TRAF6 and TAK1 in CLR-induced signal transduction events. We demonstrate that TRAF6 and TAK1 are required for NF-κB and JNK activation, and expression of proinflammatory cytokines in response to Candida albicans infection. Our results highlight TRAF6 and TAK1 as key components in the signaling cascade downstream of C-type lectin receptors and as critical mediators of the anti-fungal immune response. Therefore, our studies provide a mechanistic understanding of the host immune response to C. albicans, which has a significant impact for the development of anti-fungal therapeutics and in understanding risk-factors and determining susceptibility to C. albicans infection.

Asiaticoside enhances normal human skin cell migration, attachment and growth in vitro wound healing model

Wound healing proceeds through a complex collaborative process involving many types of cells. Keratinocytes and fibroblasts of epidermal and dermal layers of the skin play prominent roles in this process. Asiaticoside, an active component of Centella asiatica, is known for beneficial effects on keloid and hypertrophic scar. However, the effects of this compound on normal human skin cells are not well known. Using in vitro systems, we observed the effects of asiaticoside on normal human skin cell behaviors related to healing. In a wound closure seeding model, asiaticoside increased migration rates of skin cells. By observing the numbers of cells attached and the area occupied by the cells, we concluded that asiaticoside also enhanced the initial skin cell adhesion. In cell proliferation assays, asiaticoside induced an increase in the number of normal human dermal fibroblasts. In conclusion, asiaticoside promotes skin cell behaviors involved in wound healing; and as a bioactive component of an artificial skin, may have therapeutic value.

Th17 cells in immunity to Candida albicans

Our understanding of immunity to fungal pathogens has advanced considerably in recent years. Particularly significant have been the parallel discoveries in the C-type lectin receptor family and the Th effector arms of immunity, especially Th17 cells and their signature cytokine, IL-17. Many of these studies have focused on the most common human fungal pathogen, Candida albicans, which is typically a commensal microbe in healthy individuals but causes various disease manifestations in immunocompromised hosts, ranging from mild mucosal infections to lethal disseminated disease. Here, we discuss emerging fundamental discoveries with C. albicans that have informed our overall molecular understanding of fungal immunity. In particular, we focus on the importance of pattern recognition receptor-mediated fungal recognition and subsequent IL-17 responses in host defense against mucosal candidiasis. In light of these recent advances, we also discuss the implications for anticytokine biologic therapy and vaccine development.

Utilizing biologic assimilation of bovine fetal collagen in staged skin grafting

Seven patients underwent 2-stage skin grafting with bovine fetal collagen (BFC) as an initial wound cover. Split-thickness skin grafts were successfully placed on the wounds after completion of interval management. BFC proved to be a resilient acellular dermal matrix that could proceed to assimilation and skin grafting under a variety of wound conditions. BFC may prove to be a valuable material, as the role of acellular dermal matrices in skin grafting becomes better defined.

FK506 inhibits the enhancing effects of transforming growth factor (TGF)-β1 on collagen expression and TGF-β/Smad signalling in keloid fibroblasts: implication for new therapeutic approach

BACKGROUND

  Keloid is a unique proliferative disorder of fibroblasts resulting from derailment of the typical wound healing process. Due to lack of animal models for therapeutic testing, treatment of keloids remains a clinical challenge. Transforming growth factor (TGF)-β1-related signalling plays a key role in keloid formation. As tacrolimus (FK506) has been reported to inhibit the effects of TGF-β1 on cultured fibroblasts, we hypothesized that FK506 may be useful in treating keloids.

OBJECTIVES

To explore the effects of FK506 on TGF-β1-stimulated keloid fibroblasts (KFs) in terms of proliferation, migration and collagen production and to investigate the regulatory pathways involved.

METHODS

Fibroblasts derived from keloids were treated with TGF-β1 with or without FK506. Relevant assays including 5-bromo-2'-deoxyuridine incorporation assay, in vitro scratch assay, reverse transcription-polymerase chain reaction (PCR), quantitative PCR and Western blotting were performed.

RESULTS

The proliferation and migration of KFs were significantly higher than those of normal fibroblasts. FK506 markedly inhibited KF proliferation, migration and collagen production enhanced by TGF-β1. The increase in TGF-β receptor I and II expression in TGF-β1-treated KFs was suppressed by FK506 treatment. TGF-β1 increased the phosphorylation of Smad2/3 and Smad4 in KFs, and this enhancing effect was abrogated by FK506. In addition, FK506 significantly increased the expression of Smad7 which was suppressed by TGF-β1 treatment.

CONCLUSIONS

Our results demonstrate that FK506 effectively blocks the TGF-β/Smad signalling pathway in KFs by downregulation of TGF-β receptors and suggest that FK506 may be included in the armamentarium for treating keloids.

Regulation of NF-κB by the CARD proteins

Scaffold proteins play pivotal roles in the regulation of signal transduction pathways by connecting upstream receptors to downstream effector molecules. During the last decade, many scaffold proteins that contain caspase-recruitment domains (CARD) have been identified. Investigating the roles of CARD proteins has revealed that many of them play crucial roles in signaling cascades leading to activation of nuclear factor-κB (NF-κB). In this review, we discuss the contributions of CARD proteins to NF-κB activation in various signaling cascades. In particular, we share some of our personal experiences during the initial investigation of the functions of the CARMA family of CARD proteins and then summarize the roles of these proteins in signaling pathways induced by antigen receptors, G protein-coupled receptors, receptor tyrosine kinase, and C-type lectin receptors in the context of recent progress in these field.

The autophagy regulator Rubicon is a feedback inhibitor of CARD9-mediated host innate immunity

Assembly of a scaffold consisting of CARD9, BCL10, and MALT1 (CBM complex) is critical for effective signaling by multiple pattern recognition receptors (PRRs) including Dectin and RIG-I. The RUN domain Beclin-1-interacting cysteine-rich-containing Rubicon protein associates constitutively with the Beclin-UVRAG-Vps34 complex under normal conditions to regulate autophagy. Rubicon also interacts with the phagocytic NADPH-oxidase complex upon TLR stimulation to induce potent antimicrobial responses. Here, we show Rubicon is a physiological feedback inhibitor of CBM-mediated PRR signaling, preventing unbalanced proinflammatory responses. Upon Dectin-1- or RIG-I-mediated activation, Rubicon dynamically exchanges binding partners from 14-3-3β to CARD9 in a stimulation-specific and phosphorylation-dependent manner, disassembling the CBM signaling complex and ultimately terminating PRR-induced cytokine production. Remarkably, Rubicon's actions in the autophagy complex, phagocytosis complex, and CBM complex are functionally and genetically separable. Rubicon thus differentially targets signaling complexes, depending on environmental stimuli, and may function to coordinate various immune responses against microbial infection.

Implications of protein post-translational modifications in IBD

In recent years our understanding of the pathogenesis of inflammatory bowel disease (IBD) has greatly increased. Hallmarks of IBD include loss of intestinal barrier function, increased cytokine production, and failed resolution of tissue damage. Lasting treatments are still lacking and, therefore, a better understanding of the underlying molecular mechanisms is necessary to design novel therapeutic approaches. Apart from transcriptional and posttranscriptional regulation of relevant genes, mammals have evolved a complex and efficient series of mechanisms to rapidly modify newly made proteins for the purposes of signaling and adaptation. These posttranslational protein modifications include, among others, phosphorylation, hydroxylation, neddylation, and cytokine cleavage by the inflammasome. This review focuses on our current understanding of posttranslational protein modifications with a particular focus on their relevance to IBD pathogenesis.

Host-fungal interactions: key players of antifungal immunity

The increase in incidence of fungal infections is causing a considerable health burden worldwide. Despite recent advances in mucosal and systemic fungal diseases, a large gap exists in our knowledge of alterations to host homeostasis following fungal exposure and molecular mechanisms underlying fungal immune recognition, evasion and regulation. The EuroSciCon meeting on host-fungal interactions was expertly organized by Julian Naglik (King's College London, UK) and Neil Gow (University of Aberdeen, UK) and is aimed to be a premier forum in the UK for presentation of cutting-edge advances in relation to fungal pathogenicity and innate and adaptive immune responses. This article highlights principle topics that need to be better understood to provide improved means of diagnosis and optimization of therapies that would be instrumental in controlling fungal infections.

Role and relevance of mast cells in fungal infections

In addition to their detrimental role in allergic diseases, mast cells (MCs) are well known to be important cells of the innate immune system. In the last decade, they have been shown to contribute significantly to optimal host defense against numerous pathogens including parasites, bacteria, and viruses. The contribution of MCs to the immune responses in fungal infections, however, is largely unknown. In this review, we first discuss key features of mast cell responses to pathogens in general and then summarize the current knowledge on the function of MCs in the defense against fungal pathogens. We especially focus on the potential and proven mechanisms by which MCs can detect fungal infections and on possible MC effector mechanisms in protecting from fungal infections.

Asiatic acid inhibits liver fibrosis by blocking TGF-beta/Smad signaling in vivo and in vitro

Liver fibrosis is a major cause of liver failure, but treatment remains ineffective. In the present study, we investigated the mechanisms and anti-hepatofibrotic activities of asiatic acid (AA) in a rat model of liver fibrosis induced by carbon tetrachloride (CCl₄) and in vitro in TGF-beta1-stimulated rat hepatic stellate cell line (HSC-T6). Treatment with AA significantly attenuated CCl₄-induced liver fibrosis and functional impairment in a dosage-dependent manner, including blockade of the activation of HSC as determined by inhibiting de novo alpha smooth muscle actin (a-SMA) and collagen matrix expression, and an increase in ALT and AST (all p<0.01). The hepatoprotective effects of AA on fibrosis were associated with upregulation of hepatic Smad7, an inhibitor of TGF-beta signaling, thereby blocking upregulation of TGF-beta1 and CTGF and the activation of TGF-beta/Smad signaling. The anti-fibrosis activity and mechanisms of AA were further detected in vitro in HSC-T6. Addition of AA significantly induced Smad7 expression by HSC-T6 cells, thereby inhibiting TGF-beta1-induced Smad2/3 activation, myofibroblast transformation, and collagen matrix expression in a dosage-dependent manner. In contrast, knockdown of Smad7 in HSC-T6 cells prevented AA-induced inhibition of HSC-T6 cell activation and fibrosis in response to TGF-beta1, revealing an essential role for Smad7 in AA-induced anti-fibrotic activities during liver fibrosis in vivo and in vitro. In conclusion, AA may be a novel therapeutic agent for liver fibrosis. Induction of Smad7-dependent inhibition of TGF-beta/Smad-mediated fibrogenesis may be a central mechanism by which AA protects liver from injury.

C-type lectin receptor-induced NF-κB activation in innate immune and inflammatory responses

The C-type lectin receptors (CLRs) belong to a large family of proteins that contain a carbohydrate recognition domain (CRD) and calcium binding sites on their extracellular domains. Recent studies indicate that many CLRs, such as Dectin-1, Dectin-2 and Mincle, function as pattern recognition receptors (PRRs) recognizing carbohydrate ligands from infected microorganisms. Upon ligand binding, these CLRs induce multiple signal transduction cascades through their own immunoreceptor tyrosine-based activation motifs (ITAMs) or interacting with ITAM-containing adaptor proteins such as FcRγ. Emerging evidence indicate that CLR-induced signaling cascades lead to the activation of nuclear factor kappaB (NF-κB) family of transcriptional factors through a Syk- and CARD9-dependent pathway(s). The activation of NF-κB plays a critical role in the induction of innate immune and inflammatory responses following microbial infection and tissue damages. In this review, we will summarize the recent progress on the signal transduction pathways induced by CLRs, and how these CLRs activate NF-κB and contribute to innate immune and inflammatory responses.

Signaling by myeloid C-type lectin receptors in immunity and homeostasis

Myeloid cells are key drivers of physiological responses to pathogen invasion or tissue damage. Members of the C-type lectin receptor (CLR) family stand out among the specialized receptors utilized by myeloid cells to orchestrate these responses. CLR ligands include carbohydrate, protein, and lipid components of both pathogens and self, which variably trigger endocytic, phagocytic, proinflammatory, or anti-inflammatory reactions. These varied outcomes rely on a versatile system for CLR signaling that includes tyrosine-based motifs that recruit kinases, phosphatases, or endocytic adaptors as well as nontyrosine-based signals that modulate the activation of other pathways or couple to the uptake machinery. Here, we review the signaling properties of myeloid CLRs and how they impact the role of myeloid cells in innate and adaptive immunity.

Adaptive immunity to fungi

Only a handful of the more than 100,000 fungal species on our planet cause disease in humans, yet the number of life-threatening fungal infections in patients has recently skyrocketed as a result of advances in medical care that often suppress immunity intensely. This emerging crisis has created pressing needs to clarify immune defense mechanisms against fungi, with the ultimate goal of therapeutic applications. Herein, we describe recent insights in understanding the mammalian immune defenses deployed against pathogenic fungi. The review focuses on adaptive immune responses to the major medically important fungi and emphasizes how dendritic cells and subsets in various anatomic compartments respond to fungi, recognize their molecular patterns, and signal responses that nurture and shape the differentiation of T cell subsets and B cells. Also emphasized is how the latter deploy effector and regulatory mechanisms that eliminate these nasty invaders while also constraining collateral damage to vital tissue.

Mitoxosome: a mitochondrial platform for cross-talk between cellular stress and antiviral signaling

Evidence is accumulating that the mitochondria form an integral platform from which innate signaling takes place. Recent studies revealed that the mitochondria are shaping the innate response to intracellular pathogens, and mitochondrial function is modulating and being modulated by innate immune signaling. Further, cell biologic analyses have uncovered the dynamic relocalization of key components involved in cytosolic viral recognition and signaling to the mitochondria, as well as the mobilization of mitochondria to the sites of viral replication. In this review, we provide an integrated view of how cellular stress and signals following cytosolic viral recognition are intimately linked and coordinated at the mitochondria. We incorporate recent findings into our current understanding of the role of mitochondrial function in antiviral immunity and suggest the existence of a 'mitoxosome', a mitochondrial oxidative signalosome where multiple pathways of viral recognition and cellular stress converge on the surface of the mitochondria to facilitate a coordinated antiviral response.

Fungal surface and innate immune recognition of filamentous fungi

The innate immune system performs specific detection of molecules from infectious agents through pattern recognition receptors. This recognition triggers inflammatory responses and activation of microbicidal mechanisms by leukocytes. Infections caused by filamentous fungi have increased in incidence and represent an important cause of mortality and morbidity especially in individuals with immunosuppression. This review will discuss the innate immune recognition of filamentous fungi molecules and its importance to infection control and disease.

Candida albicans morphogenesis and host defence: discriminating invasion from colonization

Candida albicans is a common fungal pathogen of humans that colonizes the skin and mucosal surfaces of most healthy individuals. Until recently, little was known about the mechanisms by which mucosal antifungal defences tolerate colonizing C. albicans but react strongly when hyphae of the same microorganism attempt to invade tissue. In this Review, we describe the properties of yeast cells and hyphae that are relevant to their interaction with the host, and the immunological mechanisms that differentially recognize colonizing versus invading C. albicans.

Phospholipase Cγ2 (PLCγ2) is key component in Dectin-2 signaling pathway, mediating anti-fungal innate immune responses

C-type lectin receptors (CLRs) such as Dectin-2 function as pattern recognition receptors to sense fungal infection. However, the signaling pathways induced by these receptors remain largely unknown. Previous studies suggest that the CLR-induced signaling pathway may utilize similar signaling components as the B cell receptor-induced signaling pathway. Phospholipase Cγ2 (PLCγ2) is a key component in B cell receptor signaling, but its role in other signaling pathways has not been fully characterized. Here, we show that PLCγ2 functions downstream of Dectin-2 in response to the stimulation by the hyphal form of Candida albicans, an opportunistic pathogenic fungus. Using PLCγ2- and PLCγ1-deficient macrophages, we found that the lack of PLCγ2, but not PLCγ1, impairs cytokine production in response to infection with C. albicans. PLCγ2 deficiency results in the defective activation of NF-κB and MAPK and a significantly reduced production of reactive oxygen species following fungal challenge. In addition, PLCγ2-deficient mice are defective in clearing C. albicans infection in vivo. Together, these findings demonstrate that PLCγ2 plays a critical role in CLR-induced signaling pathways, governing antifungal innate immune responses.

Adjunctive immunotherapy with recombinant cytokines for the treatment of disseminated candidiasis

Despite the discovery in the last decade of azoles and echinocandins as novel and potent antimycotic drugs, systemic Candida infections are still accompanied by an unacceptably high burden of morbidity and mortality. A rational novel therapeutic approach would be the use of adjuvant immunotherapy, with the aim of improving host defence against Candida. Increases in our understanding of the mechanisms that underlie the pathogenesis of Candida infections, such as the role played by pattern recognition receptors and the induction of proinflammatory cytokines during the early phases of infection, have led to the hypothesis of a potential therapeutic role of recombinant cytokines in systemic candidiasis. In the present review, we give an update of both experimental data and proof-of-principle studies in humans that argue for the use of adjunctive immunotherapy with recombinant cytokines in invasive Candida infections. Sufficiently powered studies on the role of cytokine-based treatment regimens for invasive candidiasis are needed to fully demonstrate the feasibility of this immunotherapeutic approach to improve the prognosis of severe invasive Candida infections.

Insights into human antifungal immunity from primary immunodeficiencies

Some mendelian (monogenic) disorders directly conferring increased susceptibility are associated with diverse infectious organisms, whereas others are restricted in scope to specific genera or even to one species. So far, most investigations of primary immunodeficiency disorders have focused on those conferring susceptibility to viral, bacterial, or mycobacterial infections, providing powerful insight into human determinants of host resistance to these microbes. Monogenic disorders that increase susceptibility to fungal infections are increasingly being recognised. Although infections associated with these disorders are probably less common than are iatrogenic associated mycoses, they provide valuable insight into human immunity to fungal infections. Investigation of these immunological pathways will ultimately lead to improvements in management of such infections in secondarily immunocompromised patients.

Myeloid C-type lectin receptors in pathogen recognition and host defense

C-type lectin receptors (CLRs) comprise a heterogeneous group of transmembrane proteins. Many of them are expressed in myeloid cells and signal in response to pathogen-derived or self ligands to initiate or regulate cell activation. Here, we review the properties of myeloid CLRs, highlighting how their signaling function is coordinated with that of other innate receptor families to control immunity to infection.

Genetics and pathogenesis of inflammatory bowel disease

Recent advances have provided substantial insight into the maintenance of mucosal immunity and the pathogenesis of inflammatory bowel disease. Cellular programs responsible for intestinal homeostasis use diverse intracellular and intercellular networks to promote immune tolerance, inflammation or epithelial restitution. Complex interfaces integrate local host and microbial signals to activate appropriate effector programs selectively and even drive plasticity between these programs. In addition, genetic studies and mouse models have emphasized the role of genetic predispositions and how they affect interactions with microbial and environmental factors, leading to pro-colitogenic perturbations of the host-commensal relationship.

Genetics and pathogenesis of inflammatory bowel disease

Recent advances have provided substantial insight into the maintenance of mucosal immunity and the pathogenesis of inflammatory bowel disease. Cellular programs responsible for intestinal homeostasis use diverse intracellular and intercellular networks to promote immune tolerance, inflammation or epithelial restitution. Complex interfaces integrate local host and microbial signals to activate appropriate effector programs selectively and even drive plasticity between these programs. In addition, genetic studies and mouse models have emphasized the role of genetic predispositions and how they affect interactions with microbial and environmental factors, leading to pro-colitogenic perturbations of the host-commensal relationship.