MyD88: a critical adaptor protein in innate immunity signal transduction

Extracellular stimulation of VSIG4/complement receptor Ig suppresses intracellular bacterial infection by inducing autophagy

VSIG4/CRIg (V-set and immunoglobulin domain containing 4) is a transmembrane receptor of the immunoglobulin superfamily that is expressed specifically on macrophages and mature dendritic cells. VSIG4 signaling accelerates phagocytosis of C3-opsonized bacteria, thereby efficiently clearing pathogens within macrophages. We found that VSIG4 signaling triggered by C3-opsonized Listeria (opLM) or by agonistic anti-VSIG4 monoclonal antibody (mAb) induced macrophages to form autophagosomes. VSIG4-induced autophagosomes were selectively colocalized with the intracellular LM while starvation-induced autophagosomes were not. Consistent with these results, the frequency of autophagosomes induced by infection with opLM was lower in VSIG4-deficient bone marrow-derived macrophages (BMDMs) than in WT BMDMs. Furthermore, when VSIG4 molecules were overexpressed in HeLa cells, which are non-macrophage cells, VSIG4 triggering led to efficient uptake of LM, autophagosome formation, and killing of the infected LM. These findings suggest that VSIG4 signaling not only promotes rapid phagocytosis and killing of C3-opsonized intracellular bacteria, as previously reported, but also induces autophagosome formation, eliminating the LM that have escaped from phagosomes. We conclude that VSIG4 signaling provides an anti-immune evasion mechanism that prevents the outgrowth of intracellular bacteria in macrophages.

Role of interleukin-1 receptor 1/MyD88 signalling in the development and progression of pulmonary hypertension

Pulmonary artery smooth muscle cell (PA-SMC) proliferation and inflammation are key components of pulmonary arterial hypertension (PAH). Interleukin (IL)-1β binds to IL-1 receptor (R)1, thereby recruiting the molecular adaptor myeloid differentiation primary response protein 88 (MyD88) (involved in IL-1R1 and Toll-like receptor signal transduction) and inducing IL-1, IL-6 and tumour necrosis factor-α synthesis through nuclear factor-κB activation.

We investigated the IL-1R1/MyD88 pathway in the pathogenesis of pulmonary hypertension.

Marked IL-1R1 and MyD88 expression with predominant PA-SMC immunostaining was found in lungs from patients with idiopathic PAH, mice with hypoxia-induced pulmonary hypertension and SM22-5-HTT+mice. Elevations in lung IL-1β, IL-1R1, MyD88 and IL-6 preceded pulmonary hypertension in hypoxic mice. IL-1R1−/−, MyD88−/−and control mice given the IL-1R1 antagonist anakinra were protected similarly against hypoxic pulmonary hypertension and perivascular macrophage recruitment. Anakinra reversed pulmonary hypertension partially in SM22-5-HTT+mice and markedly in monocrotaline-treated rats. IL-1β-mediated stimulation of mouse PA-SMC growth was abolished by anakinra and absent in IL-1R1−/−and MyD88−/−mice. Gene deletion confined to the myeloid lineage (M.lys-Cre MyD88fl/flmice) decreased pulmonary hypertension severityversuscontrols, suggesting IL-1β-mediated effects on PA-SMCs and macrophages. The growth-promoting effect of media conditioned by M1 or M2 macrophages from M.lys-Cre MyD88fl/flmice was attenuated.

Pulmonary vessel remodelling and inflammation during pulmonary hypertension require IL-1R1/MyD88 signalling. Targeting the IL-1β/IL-1R1 pathway may hold promise for treating human PAH.

Hypothalamic TLR2 triggers sickness behavior via a microglia-neuronal axis

Various pathophysiologic mechanisms leading to sickness behaviors have been proposed. For example, an inflammatory process in the hypothalamus has been implicated, but the signaling modalities that involve inflammatory mechanisms and neuronal circuit functions are ill-defined. Here, we show that toll-like receptor 2 (TLR2) activation by intracerebroventricular injection of its ligand, Pam3CSK4, triggered hypothalamic inflammation and activation of arcuate nucleus microglia, resulting in altered input organization and increased activity of proopiomelanocortin (POMC) neurons. These animals developed sickness behavior symptoms, including anorexia, hypoactivity, and hyperthermia. Antagonists of nuclear factor kappa B (NF-κB), cyclooxygenase pathway and melanocortin receptors 3/4 reversed the anorexia and body weight loss induced by TLR2 activation. These results unmask an important role of TLR2 in the development of sickness behaviors via stimulation of hypothalamic microglia to promote POMC neuronal activation in association with hypothalamic inflammation.

The categorization and mutual modulation of expanded MyD88s in Crassostrea gigas

MyD88 serves as a critical cytosolic adaptor mediating activation of NF-κB in innate immunity. It has been found that there is a considerable expansion of MyD88 in Crassostrea gigas. In the present study, four typical MyD88 genes in Crassostrea gigas (CgMyD88-A to CgMyD88-D) were successfully cloned and their potential functions were investigated together with another two known ones (CgMyD88-T1 and CgMyD88-T2). Multiple alignments revealed that CgMyD88-B and CgMyD88-C remained the conserved DD and TIR domains, while there was a significant variation of E51Q in the DD of CgMyD88-A, and some variations in both DD and TIR domains of CgMyD88-D, respectively. Both truncated CgMyD88-T1 and CgMyD88-T2 lacked Box II in their only TIR domains. Expression pattern analysis showed that CgMyD88-B and CgMyD88-C genes possessed higher expression in normal tissues, compared with the other four. When oysters were under bacteria challenge, CgMyD88-B, CgMyD88-C, CgMyD88-T1 and CgMyD88-T2 were firstly induced, while CgMyD88-A and CgMyD88-D were suppressed. Dual luciferase reporter assays showed that CgMyD88-B and CgMyD88-C could promote the activation of NF-κB signaling pathway, while the other four CgMyD88 genes failed or even suppressed the activities of CgMyD88-B and CgMyD88-C on the activation of NF-κB signaling. It was deduced that after oysters were challenged by bacteria, CgMyD88-B and CgMyD88-C could rapidly and efficiently activate NF-κB signaling pathway to elicit anti-pathogen responses before suppressor CgMyD88 genes (CgMyD88-T1 and CgMyD88-T2) exceeding their expression level. These results suggested that there was mutual modulation of expanded CgMyD88 genes on activating NF-κB signaling pathway in oyster C. gigas.

Ibrutinib in Waldenström macroglobulinemia: latest evidence and clinical experience

Ibrutinib is an oral Bruton's tyrosine kinase (BTK) inhibitor, which has recently gained approval by the United States (US) Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of patients with symptomatic Waldenström macroglobulinemia (WM). Herein, we review the role of BTK in the pathophysiology of WM, and present the results of the preclinical and clinical studies that led to the initial investigation and later approval of ibrutinib in WM. We also discuss aspects associated with ibrutinib therapy in WM patients, especially focusing on genomic profiling and the impact on response to ibrutinib, and the management of adverse events.

SHP-2 Phosphatase Prevents Colonic Inflammation by Controlling Secretory Cell Differentiation and Maintaining Host-Microbiota Homeostasis

Polymorphisms in the PTPN11 gene encoding for the tyrosine phosphatase SHP‐2 were described in patients with ulcerative colitis. We have recently demonstrated that mice with an intestinal epithelial cell‐specific deletion of SHP‐2 (SHP‐2^IEC‐KO) develop severe colitis 1 month after birth. However, the mechanisms by which SHP‐2 deletion induces colonic inflammation remain to be elucidated. We generated SHP‐2^IEC‐KO mice lacking Myd88 exclusively in the intestinal epithelium. The colonic phenotype was histologically analyzed and cell differentiation was determined by electron microscopy and lysozyme or Alcian blue staining. Microbiota composition was analyzed by 16S sequencing. Results show that innate defense genes including those specific to Paneth cells were strongly up‐regulated in SHP‐2‐deficient colons. Expansion of intermediate cells (common progenitors of the Goblet and Paneth cell lineages) was found in the colon of SHP‐2^IEC‐KO mice whereas Goblet cell number was clearly diminished. These alterations in Goblet/intermediate cell ratio were noticed 2 weeks after birth, before the onset of inflammation and were associated with significant alterations in microbiota composition. Indeed, an increase in Enterobacteriaceae and a decrease in Firmicutes were observed in the colon of these mice, indicating that dysbiosis also occurred prior to inflammation. Importantly, loss of epithelial Myd88 expression inhibited colitis development in SHP‐2^IEC‐KO mice, rescued Goblet/intermediate cell ratio, and prevented NFκB hyperactivation and inflammation. These data indicate that SHP‐2 is functionally important for the maintenance of appropriate barrier function and host‐microbiota homeostasis in the large intestine. J. Cell. Physiol. 231: 2529–2540, 2016. © 2016 The Authors. Journal of Cellular Physiology published by Wiley Periodicals, Inc.

Knockdown of Myeloid Differentiation Factor 88 Attenuates Lipopolysaccharide-Induced Inflammatory Response in Pancreatic Ductal Cells

OBJECTIVES

The aim of the study was to explore the potential role of myeloid differentiation factor 88 (MyD88), which acts as an adaptor in the TLR4 signalling pathway, in immune responses of the pancreatic duct during acute pancreatitis.

METHODS

Primary cultures of pancreatic duct epithelial cells from Wistar rats and cultures of the pancreatic ductal ARIP cell line were treated with lipopolysaccharide (LPS), and expression of toll-like receptor 4 mRNA was determined using real-time PCR, expression of MyD88 protein using Western blot, and levels of inflammatory cytokines using enzyme-linked immunosorbent assay. These experiments were repeated using ARIP cells in which MyD88 expression was stably knocked down.

RESULTS

Toll-like receptor 4 and MyD88 expression were similar between pancreatic duct epithelial cells and ARIP cells after LPS stimulation. Myeloid differentiation factor 88 knockdown led to significantly lower levels of inflammatory cytokines after LPS induction in ARIP cells.

CONCLUSIONS

Myeloid differentiation factor 88 knockdown attenuates LPS-induced inflammatory responses in pancreatic ductal cells, suggesting that the MyD88 pathway plays a critical role in their immune defense activity.

Nod2-mediated recognition of the microbiota is critical for mucosal adjuvant activity of cholera toxin

Cholera toxin (CT) is a potent adjuvant for inducing mucosal immune responses. However, the mechanism by which CT induces adjuvant activity remains unclear. Here we show that the microbiota is critical for inducing antigen-specific IgG production after intranasal immunization. After mucosal vaccination with CT, both antibiotic-treated and germ-free (GF) mice had reduced amounts of antigen-specific IgG, smaller recall-stimulated cytokine responses, impaired follicular helper T (TFH) cell responses and reduced numbers of plasma cells. Recognition of symbiotic bacteria via the nucleotide-binding oligomerization domain containing 2 (Nod2) sensor in cells that express the integrin CD11c (encoded by Itgax) was required for the adjuvanticity of CT. Reconstitution of GF mice with a Nod2 agonist or monocolonization with Staphylococcus sciuri, which has high Nod2-stimulatory activity, was sufficient to promote robust CT adjuvant activity, whereas bacteria with low Nod2-stimulatory activity did not. Mechanistically, CT enhanced Nod2-mediated cytokine production in dendritic cells via intracellular cyclic AMP. These results show a role for the microbiota and the intracellular receptor Nod2 in promoting the mucosal adjuvant activity of CT.

Toll/Interleukin-1 Receptor Domain Derived from TcpC (TIR-TcpC) Ameliorates Experimental Autoimmune Arthritis by Down-modulating Th17 Cell Response

Evasion through immunomodulation is one of the several strategies adopted by pathogens to prolong their survival within the host. One such pathogen, Escherichia coli CFT073, utilizes an immunomodulatory protein, TcpC, to combat the host's innate immune defense. TcpC abrogates the function of MyD88 in macrophages, thus perturbing all the signaling processes that involve this adaptor protein. Although central to various signaling pathways initiated by IL-1, IL-18, and toll-like receptors, the precise contribution of MyD88 to the development of autoimmunity, particularly rheumatoid arthritis, still needs extensive exploration. Herein, by using the toll/interleukin-1 receptor (TIR) domain homologous C-terminal motif of TcpC, i.e. TIR-TcpC, we found MyD88 to be critical for the induction and progression of rheumatoid arthritis through its pivotal role in the development of Th17 cells, the subset of CD4(+) T-cells widely implicated in various autoimmune disorders. The TIR-TcpC mediated inhibition of signaling through MyD88, and subsequent amelioration of experimental autoimmune arthritis was observed to be an outcome of perturbations in the NFκB-RORγt (RAR-related orphan receptor γt) axis.

Inflammatory diseases modelling in zebrafish

The ingest of diets with high content of fats and carbohydrates, low or no physical exercise and a stressful routine are part of the everyday lifestyle of most people in the western world. These conditions are triggers for different diseases with complex interactions between the host genetics, the metabolism, the immune system and the microbiota, including inflammatory bowel diseases (IBD), obesity and diabetes. The incidence of these disorders is growing worldwide; therefore, new strategies for its study are needed. Nowadays, the majority of researches are in use of murine models for understand the genetics, physiopathology and interaction between cells and signaling pathways to find therapeutic solutions to these diseases. The zebrafish, a little tropical water fish, shares 70% of our genes and conserves anatomic and physiological characteristics, as well as metabolical pathways, with mammals, and is rising as a new complementary model for the study of metabolic and inflammatory diseases. Its high fecundity, fast development, transparency, versatility and low cost of maintenance makes the zebrafish an interesting option for new researches. In this review, we offer a discussion of the existing genetic and induced zebrafish models of two important Western diseases that have a strong inflammatory component, the IBD and the obesity.

Mycobacterium tuberculosis effectors interfering host apoptosis signaling

Tuberculosis remains a serious human public health concern. The coevolution between its pathogen Mycobacterium tuberculosis and human host complicated the way to prevent and cure TB. Apoptosis plays subtle role in this interaction. The pathogen endeavors to manipulate the apoptosis via diverse effectors targeting key signaling nodes. In this paper, we summarized the effectors pathogen used to subvert the apoptosis, such as LpqH, ESAT-6/CFP-10, LAMs. The interplay between different forms of cell deaths, such as apoptosis, autophagy, necrosis, is also discussed with a focus on the modes of action of effectors, and implications for better TB control.

Chlamydial plasmid-encoded virulence factor Pgp3 neutralizes the antichlamydial activity of human cathelicidin LL-37

Chlamydia trachomatis infection in the lower genital tract can ascend to and cause pathologies in the upper genital tract, potentially leading to severe complications, such as tubal infertility. However, chlamydial organisms depleted of plasmid or deficient in the plasmid-encoded Pgp3 are attenuated in ascending infection and no longer are able to induce the upper genital tract pathologies, indicating a significant role of Pgp3 in chlamydial pathogenesis. We now report that C. trachomatis Pgp3 can neutralize the antichlamydial activity of human cathelicidin LL-37, a host antimicrobial peptide secreted by both genital tract epithelial cells and infiltrating neutrophils. Pgp3 bound to and formed stable complexes with LL-37. We further showed that the middle region of Pgp3 (Pgp3m) was responsible for both the binding to and neutralization of LL-37, suggesting that Pgp3m can be targeted for attenuating chlamydial pathogenicity or developed for blocking LL-37-involved non-genital-tract pathologies, such as rosacea and psoriasis. Thus, the current study has provided significant information for both understanding the mechanisms of chlamydial pathogenesis and developing novel therapeutic agents.

Molecular deregulation of signaling in lymphoid tumors

Genomic studies have led to a significant impact both on the pace and the nature of understanding the molecular and biological bases of a variety of lymphoid tumors. An increasingly emerging aspect from genomic studies is that malignant lymphoid cells manipulate signaling pathways that are central to the homeostasis of their normal counterpart, including B- and T-cell receptor signaling, NF-κB signaling, Toll-like receptor signaling, cytokine signaling, MAP kinase signaling, and NOTCH signaling. This review aims at covering the signaling pathways that are affected by mutations in lymphoid tumors, and how genetic alteration of these pathways may contribute to disease pathogenesis and management.

The Tyrosine Kinase Adaptor Protein FRS2 Is Oncogenic and Amplified in High-Grade Serous Ovarian Cancer

High-grade serous ovarian cancers (HGSOC) are characterized by widespread recurrent regions of copy-number gain and loss. Here, we interrogated 50 genes that are recurrently amplified in HGSOC and essential for cancer proliferation and survival in ovarian cancer cell lines. FRS2 is one of the 50 genes located on chromosomal region 12q15 that is focally amplified in 12.5% of HGSOC. We found that FRS2-amplified cancer cell lines are dependent on FRS2 expression, and that FRS2 overexpression in immortalized human cell lines conferred the ability to grow in an anchorage-independent manner and as tumors in immunodeficient mice. FRS2, an adaptor protein in the FGFR pathway, induces downstream activation of the Ras-MAPK pathway. These observations identify FRS2 as an oncogene in a subset of HGSOC that harbor FRS2 amplifications.

IMPLICATIONS

These studies identify FRS2 as an amplified oncogene in a subset of HGSOC. FRS2 expression is essential to ovarian cancer cells that harbor 12q15 amplification.

In Vivo Role of TLR2 and MyD88 Signaling in Eliciting Innate Immune Responses in Staphylococcal Endophthalmitis

PURPOSE

The purpose of this study was to investigate the protective mechanisms evoked by TLR2 and MyD88 signaling in bacterial endophthalmitis in vivo.

METHODS

Endophthalmitis was induced in wild-type (WT), TLR2(-/-), MyD88(-/-), and Cnlp(-/-) mice by intravitreal injections of a laboratory strain (RN6390) and two endophthalmitis isolates of Staphylococcus aureus. Disease progression was monitored by assessing corneal and vitreous haze, bacterial burden, and retinal tissue damage. Levels of inflammatory cytokines/chemokines were determined using quantitative RT-PCR (qRT-PCR) and ELISA. Flow cytometry was used to assess neutrophil infiltration. Cathelicidin-related antimicrobial peptide (CRAMP) expression was determined by immunostaining and dot blot.

RESULTS

Eyes infected with either laboratory or clinical isolates exhibited higher levels of inflammatory mediators at the early stages of infection (≤24 hours) in WT mice than in TLR2(-/-) or MyD88(-/-) mice. However, their levels surpassed that of WT mice at the later stages of infection (>48 hours), coinciding with increased bacterial burden and retinal damage. Both TLR2(-/-) and MyD88(-/-) retinas produced reduced levels of CRAMP, and its deficiency (Cnlp(-/-)) rendered the mice susceptible to increased bacterial burden and retinal tissue damage as early as 1 day post infection. Analyses of inflammatory mediators and neutrophil levels in WT versus Cnlp(-/-) mice showed a trend similar to that observed in TLR2 and MyD88 KO mice. Furthermore, we observed that even a 10-fold lower infective dose of S. aureus was sufficient to cause endophthalmitis in TLR2(-/-) and MyD88(-/-) mice.

CONCLUSIONS

TLR2 and MyD88 signaling plays an important role in protecting the retina from staphylococcal endophthalmitis by production of the antimicrobial peptide CRAMP.

Role of MYD88 in lymphoplasmacytic lymphoma diagnosis and pathogenesis

Lymphoplasmacytic lymphoma (LPL) is a distinct B-cell lymphoproliferative disorder primarily characterized by bone marrow infiltration of lymphoplasmacytic cells. When LPL produces a serum monoclonal immunoglobulin of the IgM class, it is termed Waldenström macroglobulinemia (WM). The differential diagnosis between LPL and other types of morphologically similar B-cell tumors that may also have plasmacytic differentiation and/or secretion of IgM paraproteins is not always clear-cut based solely on the pathologic and phenotypic features of the tumor. Although the current treatments for LPL/WM are initially effective in inducing responses in most patients, they are not curative and show decreasing efficacy with repeated administrations, ultimately resulting in the selection of a chemoresistant clone. Next-generation sequencing studies have identified somatic mutations of MYD88, a key component of the Toll-like receptor signaling machinery, in ∼90% of LPL/WM. Deregulated MYD88 signaling promoted by mutations sustains tumor cell survival in LPL/WM, demonstrating that they are gain-of-function driver events in this lymphoma. This review discusses the molecular and biological mechanisms underlying MYD88 mutations in LPL/WM, the role of MYD88 mutations as molecular biomarker for the refinement of diagnosis and the improvement classification of LPL/WM, and novel targeted therapeutic strategies for LPL/WM based on the pharmacological manipulation of MYD88 signaling to which this lymphoma is addicted.

Implication of TLR- but not of NOD2-signaling pathways in dendritic cell activation by group B Streptococcus serotypes III and V

Group B Streptococcus (GBS) is an important agent of life-threatening invasive infection. It has been previously shown that encapsulated type III GBS is easily internalized by dendritic cells (DCs), and that this internalization had an impact on cytokine production. The receptors underlying these processes are poorly characterized. Knowledge on the mechanisms used by type V GBS to activate DCs is minimal. In this work, we investigated the role of Toll-like receptor (TLR)/MyD88 signaling pathway, the particular involvement of TLR2, and that of the intracellular sensing receptor NOD2 in the activation of DCs by types III and V GBS. The role of capsular polysaccharide (CPS, one of the most important GBS virulence factors) in bacterial-DC interactions was evaluated using non-encapsulated mutants. Despite differences in the role of CPS between types III and V GBS in bacterial internalization and intracellular survival, no major differences were observed in their capacity to modulate release of cytokines by DC. For both serotypes, CPS had a minor role in this response. Production of cytokines by DCs was shown to strongly rely on MyD88-dependent signaling pathways, suggesting that DCs recognize GBS and become activated mostly through TLR signaling. Yet, GBS-infected TLR2^-/- DCs only showed a partial reduction in the production of IL-6 and CXCL1 compared to control DCs. Surprisingly, CXCL10 release by type III or type V GBS-infected DCs was MyD88-independent. No differences in DC activation were observed between NOD2^-/- and control DCs. These results demonstrate the involvement of various receptors and the complexity of the cytokine production pathways activated by GBS upon DC infection.

Ostreid herpesvirus type 1 replication and host response in adult Pacific oysters, Crassostrea gigas

Since 2008, massive mortality outbreaks associated with OsHV-1 detection have been reported in Crassostrea gigas spat and juveniles in several countries. Nevertheless, adult oysters do not demonstrate mortality in the field related to OsHV-1 detection and were thus assumed to be more resistant to viral infection. Determining how virus and adult oyster interact is a major goal in understanding why mortality events are not reported among adult Pacific oysters. Dual transcriptomics of virus-host interactions were explored by real-time PCR in adult oysters after a virus injection. Thirty-nine viral genes and five host genes including MyD88, IFI44, IkB2, IAP and Gly were measured at 0.5, 10, 26, 72 and 144 hours post infection (hpi). No viral RNA among the 39 genes was detected at 144 hpi suggesting the adult oysters are able to inhibit viral replication. Moreover, the IAP gene (oyster gene) shows significant up-regulation in infected adults compared to control adults. This result suggests that over-expression of IAP could be a reaction to OsHV-1 infection, which may induce the apoptotic process. Apoptosis could be a main mechanism involved in disease resistance in adults. Antiviral activity of haemolymph against herpes simplex virus (HSV-1) was not significantly different between infected adults versus control.

Gene structure, cDNA characterization and RNAi-based functional analysis of a myeloid differentiation factor 88 homolog in Tenebrio molitor larvae exposed to Staphylococcus aureus infection

Myeloid differentiation factor 88 (MyD88), an intracellular adaptor protein involved in Toll/Toll-like receptor (TLR) signal processing, triggers activation of nuclear factor-kappaB (NF-κB) transcription factors. In the present study, we analyzed the gene structure and biological function of MyD88 in a coleopteran insect, Tenebrio molitor (TmMyD88). The TmMyD88 gene was 1380 bp in length and consisted of five exons and four introns. The 5'-flanking sequence revealed several putative transcription factor binding sites, such as STAT-4, AP-1, cJun, cfos, NF-1 and many heat shock factor binding elements. The cDNA contained a typical death domain, a conservative Toll-like interleukin-1 receptor (TIR) domain, and a C-terminal extension (CTE). The TmMyD88 TIR domain showed three significantly conserved motifs for interacting with the TIR domain of TLRs. TmMyD88 was grouped within the invertebrate cluster of the phylogenetic tree and shared 75% sequence identity with the TIR domain of Tribolium castaneum MyD88. Homology modeling of the TmMyD88 TIR domain revealed five parallel β-strands surrounded by five α-helices that adopted loop conformations to function as an adaptor. TmMyD88 expression was upregulated 7.3- and 4.79-fold after 12 and 6h, respectively, of challenge with Staphylococcus aureus and fungal β-1,3 glucan. Silencing of the TmMyD88 transcript by RNA interference led to reduced resistance of the host to infection by S. aureus. These results indicate that TmMyD88 is required for survival against Staphylococcus infection.

Clostridium difficile infection in diabetes

Diabetes-related hospitalization and hospital utilization is a serious challenge to the health care system, a situation which may be further aggravated by nosocomial Clostridium difficile (C. difficile) infection (CDI). Studies have demonstrated that diabetes increases the risk of recurrent CDI with OR (95% CI) 2.99 (1.88, 4.76). C. difficile is a gram-positive, spore-forming anaerobic bacterium which is widely distributed in the environment. Up to 7% of healthy adults and up to 45% of infants may have asymptomatic intestinal carriage of C. difficile. A large number of strains of C. difficile have been identified. A number of PCR or sequence-based molecular typing methods are available for typing C. difficile isolates. C. difficile virulence evolved independently in the highly epidemic lineages, associated with the expression of toxin genes and other virulence factors. This article briefly reviews recent progresses in the bateriology of C. difficile and highlights the limited knowledge of potential mechanisms for the increased risk of CDI in diabetes which warrants further research.

Chlamydia muridarum infection associated host MicroRNAs in the murine genital tract and contribution to generation of host immune response

PROBLEM

Chlamydia trachomatis (CT) is the leading sexually transmitted bacterial infection in humans and is associated with reproductive tract damage. However, little is known about the involvement and regulation of microRNAs (miRs) in genital CT.

METHODS

We analyzed miRs in the genital tract (GT) following C. muridarum (murine strain of CT) challenge of wild type (WT) and CD4(+) T-cell deficient (CD4(-/-)) C57BL/6 mice at days 6 and 12 post-challenge.

RESULTS

At day 6, miRs significantly downregulated in the lower GT were miR-125b-5p, -16, -214, -23b, -135a, -182, -183, -30c, and -30e while -146 and -451 were significantly upregulated, profiles not exhibited at day 12 post-bacterial challenge. Significant differences in miR-125b-5p (+5.06-fold change), -135a (+4.9), -183 (+7.9), and -182 (+3.2) were observed in C. muridarum-infected CD4(-/-) compared to WT mice. In silico prediction and mass spectrometry revealed regulation of miR-135a and -182 and associated proteins, that is, heat-shock protein B1 and alpha-2HS-glycoprotein.

CONCLUSION

This study provides evidence on regulation of miRs following genital chlamydial infection suggesting a role in pathogenesis and host immunity.

ARF6 inhibition stabilizes the vasculature and enhances survival during endotoxic shock

The vascular endothelium responds to infection by destabilizing endothelial cell-cell junctions to allow fluid and cells to pass into peripheral tissues, facilitating clearance of infection and tissue repair. During sepsis, endotoxin and other proinflammatory molecules induce excessive vascular leak, which can cause organ dysfunction, shock, and death. Current therapies for sepsis are limited to antibiotics and supportive care, which are often insufficient to reduce morbidity and prevent mortality. Previous attempts at blocking inflammatory cytokine responses in humans proved ineffective at reducing the pathologies associated with sepsis, highlighting the need for a new therapeutic strategy. The small GTPase ARF6 is activated by a MyD88-ARNO interaction to induce vascular leak through disruption of endothelial adherens junctions. In this study, we show that the MyD88-ARNO-ARF6-signaling axis is responsible for LPS-induced endothelial permeability and is a destabilizing convergence point used by multiple inflammatory cues. We also show that blocking ARF6 with a peptide construct of its N terminus is sufficient to reduce vascular leak and enhance survival during endotoxic shock, without inhibiting the host cytokine response. Our data highlight the therapeutic potential of blocking ARF6 and reducing vascular leak for the treatment of inflammatory conditions, such as endotoxemia.

A novel TLR-9 agonist C792 inhibits plasmacytoid dendritic cell-induced myeloma cell growth and enhance cytotoxicity of bortezomib

Our prior study in multiple myeloma (MM) patients showed increased numbers of plasmacytoid dendritic cells (pDCs) in the bone marrow (BM), which both contribute to immune dysfunction as well as promote tumor cell growth, survival and drug resistance. Here we show that a novel Toll-like receptor (TLR-9) agonist C792 restores the ability of MM patient-pDCs to stimulate T-cell proliferation. Coculture of pDCs with MM cells induces MM cell growth; and importantly, C792 inhibits pDC-induced MM cell growth and triggers apoptosis. In contrast, treatment of either MM cells or pDCs alone with C792 does not affect the viability of either cell type. In agreement with our in vitro data, C792 inhibits pDC-induced MM cell growth in vivo in a murine xenograft model of human MM. Mechanistic studies show that C792 triggers maturation of pDCs, enhances interferon-α and interferon-λ secretion and activates TLR-9/MyD88 signaling axis. Finally, C792 enhances the anti-MM activity of bortezomib, lenalidomide, SAHA or melphalan. Collectively, our preclinical studies provide the basis for clinical trials of C792, either alone or in combination, to both improve immune function and overcome drug resistance in MM.

The early monocytic response to cytomegalovirus infection is MyD88 dependent but occurs independently of common inflammatory cytokine signals

Cytomegalovirus latently infects myeloid cells; however, the acute effects of the virus on this cell subset are poorly characterised. We demonstrate that systemic cytomegalovirus infection induced rapid activation of monocytes in the bone marrow, characterised by upregulation of CD69, CD11c, Ly6C and M-CSF receptor. Activated bone marrow monocytes were more sensitive to M-CSF and less sensitive to granulocyte-monocyte colony stimulating factor in vitro, resulting in the generation of more macrophages and fewer dendritic cells, respectively. Monocyte activation was also observed in the periphery and resulted in significant accumulation of monocytes in the spleen. MyD88 expression was required within the haematopoietic compartment to initiate monocyte activation and recruitment. However, monocytes lacking MyD88 were activated and recruited in the presence of MyD88-sufficient cells in mixed bone marrow chimeras, indicating that once initiated, the process was MyD88 independent. Interestingly, we found that monocyte activation occurred in the absence of the common inflammatory cytokines, namely type I interferons (IFNs), IL-6, TNF-α and IL-1 as well as the NLRP3 inflammasome adaptor protein, ASC. We also excluded a role for the chemokine-like protein MCK-2 (m131/129) expressed by murine CMV. Taken together, these results challenge the notion that a single inflammatory cytokine mediates activation and recruitment of monocytes in response to infection.

LPS-stimulated inflammatory environment inhibits BMP-2-induced osteoblastic differentiation through crosstalk between TLR4/MyD88/NF-κB and BMP/Smad signaling

Bone morphogenetic protein-2 (BMP-2) is a novel differentiation factor that is capable of inducing osteoblast differentiation and bone formation, making it an attractive option in treatment of bone defects, fractures, and spine fusions. Inflammation, which was a common situation during bone healing, is recognized to inhibit osteogenic differentiation and bone formation. However, the effect of inflammation on BMP-2-induced osteoblastic differentiation remains ambiguous. In this study, we showed that an inflammatory environment triggered by lipopolysaccharide (LPS) in vitro would suppress BMP-2-induced osteogenic differentiation of bone marrow mesenchymal stem cells, which represented by decreased alkaline phosphatase (ALPase) activity and down-regulated osteogenic genes. In addition, LPS activated nuclear factor-κB (NF-κB) via a TLR4/MyD88-dependent manner and inhibited BMP-2-induced phosphorylation and nuclear translocation of Smad1/5/8. The blocking of NF-κB signaling by pretreatment with specific inhibitors such as BAY-11-7082, TPCK and PDTC, or by transfection with plasmids encoding p65 siRNA or IκBα siRNA could significantly reverse the inhibitory effect of LPS on BMP-2-induced BMP/Smad signaling and osteogenic differentiation. By contrast, even without stimulation of LPS, overexpression of p65 gene showed obvious inhibitory effects on BMP-2-induced BMP/Smad signaling and ALPase activity. These data indicate that the LPS-mediated inflammatory environment inhibits BMP-2-induced osteogenic differentiation, and that the crosstalk between TLR4/MyD88/NF-κB and BMP/Smad signaling negatively modulates the osteoinductive capacity of BMP-2.

Activation machinery of the small GTPase Arf6

The small GTPase ADP-ribosylation factor 6 (Arf6) plays pivotal roles in a wide variety of cellular events, including exocytosis, endocytosis, actin cytoskeleton reorganization and phosphoinositide metabolism, in various types of cells. To control such a wide variety of actions of Arf6, activation of Arf6 could be precisely controlled by its activators, guanine nucleotide exchange factors (GEFs), in spatial and temporal manners. In this manuscript, we summarize and discuss the characteristics of previously identified GEFs specific to Arf6 and activation machineries of Arf6.

Oviduct infection and hydrosalpinx in DBA1/j mice is induced by intracervical but not intravaginal inoculation with Chlamydia muridarum

Intravaginal infection with C. muridarum in mice often results in hydrosalpinx similar to that found in women urogenitally infected with C. trachomatis, making the C. muridarum lower genital tract infection murine model suitable for studying C. trachomatis pathogenesis. To our surprise, DBA1/j mice were highly resistant to hydrosalpinx following an intravaginal infection with C. muridarum although these mice were as susceptible to lower genital tract infection as other mouse strains. A significantly lower level of C. muridarum organisms was recovered from the oviduct of DBA1/j mice, correlating the resistance to hydrosalpinx with reduced ascension of C. muridarum to the oviduct. The DBA1/j resistance to hydrosalpinx was effectively overcome by intracervical inoculation with C. muridarum. The intracervically inoculated DBA1/j mice developed severe hydrosalpinx with the highest levels of live C. muridarum organisms recovered from uterine tissue on day 3 and oviduct tissue on day 7 post inoculation while in intravaginally inoculated DBA1/j mice, the peak of live organism recovery from uterine tissue was delayed to day 7 with no rise in the amount of live organisms recovered from the oviduct. These observations have not only validated the correlation between hydrosalpinx and live organism invasion in the oviduct but also demonstrated that the intracervical inoculation, by promoting rapid chlamydial replication in the uterine epithelial cells and ascension to the oviduct of DBA1/j mice, may be used for further understanding chlamydial pathogenic mechanisms. The above findings also suggest that strategies aimed at reducing tubal infection may be most effective in blocking tubal pathology.

Genetic aberrations of signaling pathways in lymphomagenesis: revelations from next generation sequencing studies

Next generation sequencing (NGS) technology has led to a burst of disease-relevant molecular information in a variety of lymphoid tumors, including chronic lymphocytic leukemia, diffuse large B-cell lymphoma, follicular lymphoma, mantle cell lymphoma, Burkitt lymphoma, Waldenström macroglobulinemia, hairy cell leukemia, and splenic marginal zone lymphoma. Beside disclosing comprehensive catalogs of somatic mutations and new insights into the genes that contribute to cellular transformation, NGS has also provided molecular clues useful for addressing a number of unmet clinical needs in the field of B-cell tumor management, including biomarkers for disease diagnosis and classification improvement (i.e. mutations of BRAF, MYD88 and NOTCH2), and new targets to be translated into therapeutic interventions (i.e. BCR, TLR, NOTCH, NF-κB and MAPK signaling pathways). This review summarizes the molecular lesions of signaling pathways that have been discovered in B-cell lymphoproliferative disorders by NGS studies.