Revealing roles of S-layer protein (SlpA) in Clostridioides difficile pathogenicity by generating the first slpA gene deletion mutant

Clostridioides difficile infection (CDI) with high morbidity and high mortality is an urgent threat to public health, and C. difficile pathogenesis studies are eagerly required for CDI therapy. The major surface layer protein, SlpA, was supposed to play a key role in C. difficile pathogenesis; however, a lack of isogenic slpA mutants has greatly hampered analysis of SlpA functions. In this study, the whole slpA gene was successfully deleted for the first time via CRISPR-Cas9 system. Deletion of slpA in C. difficile resulted in smaller, smother-edged colonies, shorter bacterial cell size, and aggregation in suspension. For life cycle, the mutant demonstrated lower growth (changes of optical density at 600 nm, OD600) but higher cell density (colony-forming unit, CFU), decreased toxins production, and inhibited sporulation. Moreover, the mutant was more impaired in motility, more sensitive to vancomycin and Triton X-100-induced autolysis, releasing more lactate dehydrogenase. In addition, SlpA deficiency led to robust biofilm formation but weak adhesion to human host cells.IMPORTANCEClostridioides difficile infection (CDI) has been the most common hospital-acquired infection, with a high rate of antibiotic resistance and recurrence incidences, become a debilitating public health threat. It is urgently needed to study C. difficile pathogenesis for developing efficient strategies as CDI therapy. SlpA was indicated to play a key role in C. difficile pathogenesis. However, analysis of SlpA functions was hampered due to lack of isogenic slpA mutants. Surprisingly, the first slpA deletion C. difficile strain was generated in this study via CRISPR-Cas9, further negating the previous thought about slpA being essential. Results in this study will provide direct proof for roles of SlpA in C. difficile pathogenesis, which will facilitate future investigations for new targets as vaccines, new therapeutic agents, and intervention strategies in combating CDI.

Anti-Inflammatory and Therapeutic Effects of a Novel Small-Molecule Inhibitor of Inflammation in a Male C57BL/6J Mouse Model of Obesity-Induced NAFLD/MAFLD

Purpose

Non-alcoholic fatty liver disease (NAFLD), recently renamed metabolic (dysfunction) associated fatty liver disease (MAFLD), is the most common chronic liver disease in the United States. Presently, there is an intense and ongoing effort to identify and develop novel therapeutics for this disease. In this study, we explored the anti-inflammatory activity of a new compound, termed IOI-214, and its therapeutic potential to ameliorate NAFLD/MAFLD in male C57BL/6J mice fed a high fat (HF) diet.

Methods

Murine macrophages and hepatocytes in culture were treated with lipopolysaccharide (LPS) ± IOI-214 or DMSO (vehicle), and RT-qPCR analyses of inflammatory cytokine gene expression were used to assess IOI-214's anti-inflammatory properties in vitro. Male C57BL/6J mice were also placed on a HF diet and treated once daily with IOI-214 or DMSO for 16 weeks. Tissues were collected and analyzed to determine the effects of IOI-214 on HF diet-induced NAFL D/MAFLD. Measurements such as weight, blood glucose, serum cholesterol, liver/serum triglyceride, insulin, and glucose tolerance tests, ELISAs, metabolomics, Western blots, histology, gut microbiome, and serum LPS binding protein analyses were conducted.

Results

IOI-214 inhibited LPS-induced inflammation in macrophages and hepatocytes in culture and abrogated HF diet-induced mesenteric fat accumulation, hepatic inflammation and steatosis/hepatocellular ballooning, as well as fasting hyperglycemia without affecting insulin resistance or fasting insulin, cholesterol or TG levels despite overall obesity in vivo in male C57BL/6J mice. IOI-214 also decreased systemic inflammation in vivo and improved gut microbiota dysbiosis and leaky gut.

Conclusion

Combined, these data indicate that IOI-214 works at multiple levels in parallel to inhibit the inflammation that drives HF diet-induced NAFLD/MAFLD, suggesting that it may have therapeutic potential for NAFLD/MAFLD.

Modulation of LPS-induced inflammatory cytokine production by a novel glycogen synthase kinase-3 inhibitor

Sepsis is a serious condition that can lead to long-term organ damage and death. At the molecular level, the hallmark of sepsis is the elevated expression of a multitude of potent cytokines, i.e. a cytokine storm. For sepsis involving gram-negative bacteria, macrophages recognize lipopolysaccharide (LPS) shed from the bacteria, activating Toll-like-receptor 4 (TLR4), and triggering a cytokine storm. Glycogen synthase kinase-3 (GSK-3) is a highly active kinase that has been implicated in LPS-induced cytokine production. Thus, compounds that inhibit GSK-3 could be potential therapeutics for sepsis. Our group has recently described a novel and highly selective inhibitor of GSK-3 termed COB-187. In the present study, using THP-1 macrophages, we evaluated the ability of COB-187 to attenuate LPS-induced cytokine production. We found that COB-187 significantly reduced, at the protein and mRNA levels, cytokines induced by LPS (e.g. IL-6, TNF-α, IL-1β, CXCL10, and IFN-β). Further, the data suggest that the inhibition could be due, at least in part, to COB-187 reducing NF-κB (p65/p50) DNA binding activity as well as reducing IRF-3 phosphorylation at Serine 396. Thus, COB-187 appears to be a potent inhibitor of the cytokine storm induced by LPS.

Identification of a novel selective and potent inhibitor of glycogen synthase kinase-3

Glycogen synthase kinase-3 (GSK-3) is a multitasking protein kinase that regulates numerous critical cellular functions. Not surprisingly, elevated GSK-3 activity has been implicated in a host of diseases including pathological inflammation, diabetes, cancer, arthritis, asthma, bipolar disorder, and Alzheimer's. Therefore, reagents that inhibit GSK-3 activity provide a means to investigate the role of GSK-3 in cellular physiology and pathophysiology and could become valuable therapeutics. Finding a potent inhibitor of GSK-3 that can selectively target this kinase, among over 500 protein kinases in the human genome, is a significant challenge. Thus there remains a critical need for the identification of selective inhibitors of GSK-3. In this work, we introduce a novel small organic compound, namely COB-187, which exhibits potent and highly selective inhibition of GSK-3. Specifically, this study 1) utilized a molecular screen of 414 kinase assays, representing 404 unique kinases, to reveal that COB-187 is a highly potent and selective inhibitor of GSK-3; 2) utilized a cellular assay to reveal that COB-187 decreases the phosphorylation of canonical GSK-3 substrates indicating that COB-187 inhibits cellular GSK-3 activity; and 3) reveals that a close isomer of COB-187 is also a selective and potent inhibitor of GSK-3. Taken together, these results demonstrate that we have discovered a region of chemical design space that contains novel GSK-3 inhibitors. These inhibitors will help to elucidate the intricate function of GSK-3 and can serve as a starting point for the development of potential therapeutics for diseases that involve aberrant GSK-3 activity.

Toll-like receptor 3 is critical for coxsackievirus B4-induced type 1 diabetes in female NOD mice

Group B coxsackieviruses (CVBs) are involved in triggering some cases of type 1 diabetes mellitus (T1DM). However, the molecular mechanism(s) responsible for this remain elusive. Toll-like receptor 3 (TLR3), a receptor that recognizes viral double-stranded RNA, is hypothesized to play a role in virus-induced T1DM, although this hypothesis is yet to be substantiated. The objective of this study was to directly investigate the role of TLR3 in CVB-triggered T1DM in nonobese diabetic (NOD) mice, a mouse model of human T1DM that is widely used to study both spontaneous autoimmune and viral-induced T1DM. As such, we infected female wild-type (TLR3(+/+)) and TLR3 knockout (TLR3(-/-)) NOD mice with CVB4 and compared the incidence of diabetes in CVB4-infected mice with that of uninfected counterparts. We also evaluated the islets of uninfected and CVB4-infected wild-type and TLR3 knockout NOD mice by immunohistochemistry and insulitis scoring. TLR3 knockout mice were markedly protected from CVB4-induced diabetes compared with CVB4-infected wild-type mice. CVB4-induced T-lymphocyte-mediated insulitis was also significantly less severe in TLR3 knockout mice compared with wild-type mice. No differences in insulitis were observed between uninfected animals, either wild-type or TLR3 knockout mice. These data demonstrate for the first time that TLR3 is 1) critical for CVB4-induced T1DM, and 2) modulates CVB4-induced insulitis in genetically prone NOD mice.

LETAL, A Tumor-Associated NKG2D Immunoreceptor Ligand, Induces Activation and Expansion of Effector Immune Cells

NKG2D serves as one of the most potent activating receptors for effector lymphocytes. in peripheral tissues. Here we report the characterization of Letal, the first human trans-membrane NKG2D ligand lacking an immunoglobulin-like alpha-3 ectodomain. Letal is constitutively expressed by a variety of normal tissues, and is upregulated in tumor cells of different origins. Unlike other NKG2D ligands, Letal mRNA expression progressively decreased after treatment of tumor cells with retinoic acid. Simultaneous T-cell receptor activation and engagement of Letal stimulated proliferation of CD8(+) cells and dramatically increased IL-2 and IFNgamma secretion. In addition, Letal induced the killing of cancer cells by CD8(+) and NK cells. These results suggest that Letal delivers activating signals to NK cells and promotes tumor immune surveillance by inducing the expansion of anti-tumor cytotoxic lymphocytes.

Phenylmethimazole suppresses dsRNA-induced cytotoxicity and inflammatory cytokines in murine pancreatic beta cells and blocks viral acceleration of type 1 diabetes in NOD mice

Accumulating evidence supports a role for viruses in the pathogenesis of type 1 diabetes mellitus (T1DM). Activation of dsRNA-sensing pathways by viral dsRNA induces the production of inflammatory cytokines and chemokines that trigger beta cell apoptosis, insulitis, and autoimmune-mediated beta cell destruction. This study was designed to evaluate and describe potential protective effects of phenylmethimazole (C10), a small molecule which blocks dsRNA-mediated signaling, on preventing dsRNA activation of beta cell apoptosis and the inflammatory pathways important in the pathogenesis of T1DM. We first investigated the biological effects of C10, on dsRNA-treated pancreatic beta cells in culture. Cell viability assays, quantitative real-time PCR, and ELISAs were utilized to evaluate the effects of C10 on dsRNA-induced beta cell cytotoxicity and cytokine/chemokine production in murine pancreatic beta cells in culture. We found that C10 significantly impairs dsRNA-induced beta cell cytotoxicity and up-regulation of cytokines and chemokines involved in the pathogenesis of T1DM, which prompted us to evaluate C10 effects on viral acceleration of T1DM in NOD mice. C10 significantly inhibited viral acceleration of T1DM in NOD mice. These findings demonstrate that C10 (1) possesses novel beta cell protective activity which may have potential clinical relevance in T1DM and (2) may be a useful tool in achieving a better understanding of the role that dsRNA-mediated responses play in the pathogenesis of T1DM.

The interplay between surfaces and soluble factors define the immunologic and angiogenic properties of myeloid dendritic cells

BACKGROUND

Dendritic cells (DCs) are antigen presenting cells capable of inducing specific immune responses against microbial infections, transplant antigens, or tumors. Interestingly, microenvironment conditions such as those present in tumor settings might induce a DC phenotype that is poorly immunogenic and with the capability of promoting angiogenesis. We hypothesize that this plasticity may be caused not only by the action of specific cytokines or growth factors but also by the properties of the surfaces with which they interact, such as extracellular matrix (ECM) components.

RESULTS

Herewith we studied the effect of different surfaces and soluble factors on the biology of DCs. To accomplish this, we cultured murine myeloid(m) DCs on surfaces coated with fibronectin, collagen I, gelatin, and Matrigel using poly-D-lysine and polystyrene as non-biological surfaces. Further, we cultured these cells in the presence of regular DC medium (RPMI 10% FBS) or commercially available endothelial medium (EGM-2). We determined that mDCs could be kept in culture up to 3 weeks in these conditions, but only in the presence of GM-CSF. We were able to determine that long-term DC cultures produce an array of angiogenic factors, and that some of these cultures still retain the capability to induce T cell responses.

CONCLUSIONS

Altogether these data indicate that in order to design DC-based vaccines or treatments focused on changing the phenotype of DCs associated with diseases such as cancer or atherosclerosis, it becomes necessary to fully investigate the microenvironment in which these cells are present or will be delivered.

Oncolytic HSV exerts direct antiangiogenic activity in ovarian carcinoma

In the present study, we investigated the ability of replication-restricted herpes simplex virus (HSV) 1716 lacking ICP34.5 to infect endothelium and disrupt tumor vasculature. HSV-1716 efficiently infected and killed mouse endothelial cell lines H5V and MS1 cells, as well as human umbilical vein endothelial cells in vitro. Capillary tube formation by endothelial cells was inhibited by HSV-1716 in vitro and in vivo. Following intratumoral administration of oncolytic HSV-1716, HSV-glycoproteins could be detected in CD31-positive tumor vascular endothelium by immunostaining. Viral DNA was recovered from highly purified microdissected tumor vascular endothelium. Furthermore, endothelium of tumors treated with HSV-1716 exhibited expression of tissue factor, a marker of endothelial damage. Importantly, HSV antigen and DNA were also detected in endothelium distant from foci of active tumor infection. After intravascular inoculation of HSV-1716, viral glycoproteins were detected in association to tumor endothelium, but not vascular endothelium of different organs. Purified tumor endothelial cells showed high proliferative capability and were susceptible to HSV-1716 infection and killing ex vivo while endothelium from normal organs was not. We conclude that oncolytic HSV-1716 exerts direct antiangiogenic effects, which may contribute to the overall therapeutic efficacy of the virus.

Transcriptional coactivator Drosophila eyes absent homologue 2 is up-regulated in epithelial ovarian cancer and promotes tumor growth

Epithelial ovarian cancer is the most frequent cause of gynecologic malignancy-related mortality in women. To identify genes up-regulated in ovarian cancer, PCR-select cDNA subtraction was done and Drosophila Eyes Absent Homologue 2 (EYA2) was isolated as a promising candidate. The transcriptional coactivator eya controls essential cellular functions during organogenesis of Drosophila. EYA2 mRNA was found to be up-regulated in ovarian cancer by real-time reverse transcription-PCR, whereas its protein product was detected in 93.6% of ovarian cancer specimens by immunohistochemistry (n = 140). EYA2 was amplified in 14.8% of ovarian carcinomas, as detected by array-based comparative genomic hybridization (n = 88). Most importantly, EYA2 overexpression was significantly associated with short overall survival in advanced ovarian cancer (n = 99, P = 0.0361). EYA2 was found to function as transcriptional activator in ovarian cancer cells by Gal4 assay and to promote tumor growth in vivo in xenograft models. Therefore, this study suggests an important role of EYA2 in ovarian cancer and its potential application as a therapeutic target.

Transcriptional Coactivator Drosophila Eyes Absent Homologue 2 Is Up-Regulated in Epithelial Ovarian Cancer and Promotes Tumor Growth

Epithelial ovarian cancer is the most frequent cause of gynecologic malignancy-related mortality in women. To identify genes up-regulated in ovarian cancer, PCR-select cDNA subtraction was done and Drosophila Eyes Absent Homologue 2 (EYA2) was isolated as a promising candidate. The transcriptional coactivator eya controls essential cellular functions during organogenesis of Drosophila. EYA2 mRNA was found to be up-regulated in ovarian cancer by real-time reverse transcription–PCR, whereas its protein product was detected in 93.6% of ovarian cancer specimens by immunohistochemistry (n = 140). EYA2 was amplified in 14.8% of ovarian carcinomas, as detected by array-based comparative genomic hybridization (n = 88). Most importantly, EYA2 overexpression was significantly associated with short overall survival in advanced ovarian cancer (n = 99, P = 0.0361). EYA2 was found to function as transcriptional activator in ovarian cancer cells by Gal4 assay and to promote tumor growth in vivo in xenograft models. Therefore, this study suggests an important role of EYA2 in ovarian cancer and its potential application as a therapeutic target.

Nitric oxide modulation of the immune response against cholera toxin-adjuvated ovalbumin administered by the intranasal route

Here, we studied the effect of aminoguanidine (AG) treatment, a nitric oxide synthase (NOS)-2 inhibitor, during the immune response against intranasal administration of ovalbumin (OVA) mixed with cholera toxin (CT) in BALB/c mice. NOS-2 mRNA was detected by reverse transcription-PCR (RT-PCR) in samples of lungs and turbinates early post-inoculation of the antigen. Animals intranasally treated with AG, showed an increase in the levels of seric specific IgG and IgM. A higher IgG1/IgG2a ratio against OVA was also observed in sera of same animals. Moreover, high levels of specific IgA were detected in samples of pulmonar washings obtained from treated animals. On the contrary, treated animals showed a lower DTH response while splenocytes obtained from the same animals showed a reduced proliferative capability against OVA compared to controls. Finally, RT-PCR analysis showed increased expression of TGF-beta in turbinates, lungs and cells from pulmonar washings obtained from AG treated mice. Taken together, these data suggest a role of nitric oxide (NO) in modulating the primary immune response against intranasal antigens.

Vascular leukocytes contribute to tumor vascularization

There is no proof that hematopoietic cells contribute significantly to vasculogenesis in postnatal life. Here we report a novel leukocyte subset within ovarian carcinoma that coexpresses endothelial and dendritic cell markers. Fluorescence-activated cell sorter (FACS) analysis identified a high frequency of VE-cadherin+ CD45+ leukocytes (39% of host cells) in 10 of 10 solid tumors evaluated. This population represented less than 1% of nontumor cells in ascites and peripheral blood. At the protein level, more than 86% of these cells expressed the endothelial markers P1H12, CD34, and CD31 and leukocyte markers CD11c and major histocompatibility complex (MHC) class II. At the mRNA level, we detected TEM1, TEM7, and Thy-1, specific markers of angiogenic endothelium. Finally, this population has the capacity to generate functional blood vessels in vivo. Because of its mixed phenotype, we named this population vascular leukocytes (VLCs). Our data provide an important link between hematopoietic endothelial precursors and vascular development in postnatal life and a possible novel therapeutic target.

Early inhibition of nitric oxide production increases HSV-1 intranasal infection

Here, we studied the role of nitric oxide (NO) production during the first steps of the respiratory infection of BALB/c mice with herpes simplex virus type 1 (HSV-1), strain F. Nitric oxide synthase II (NOS-II) mRNA and protein were detected by reverse transcription (RT)-PCR and dot blot, respectively in samples of lungs and turbinates early post-infection (p.i.). Immunohistochemical analysis revealed pulmonar macrophages and PMN expressing NOS-II in the lungs of infected animals. Animals intranasally treated with aminoguanidine (AG), a NOS inhibitor, during the first steps of infection, showed a dose-dependent increase in pneumonitis compared to controls. Viral titres in turbinates, lungs, and brains were higher in AG treated mice. Finally, histopathology studies revealed a stronger inflammation in eyes, and lungs of these animals. Taken together, these results suggest a role of NO in controlling primary HSV intranasal infection.

Ovarian carcinoma expresses the NKG2D ligand Letal and promotes the survival and expansion of CD28- antitumor T cells

The role of the NKG2D immunoreceptor and its ligands in antitumor immune response is incompletely understood. Here, we report that effector immune cells infiltrating ovarian carcinoma are mostly CD8+ lymphocytes lacking CD28 but expressing the NKG2D costimulatory receptor. Human ovarian carcinoma expresses the novel NKG2D ligand lymphocyte effector cell toxicity-activating ligand (Letal). Letal was found to be an independent prognosticator of improved survival in advanced ovarian cancer. Higher levels of tumor-derived Letal were associated with stronger lymphocyte infiltration. Letal exerted marked costimulatory effects and induced type-1 polarization in CD8+CD28- tumor-infiltrating lymphocytes ex vivo. Letal engagement increased the expression of the glucose transporter Glut-1, enhanced glucose up-take, and protected CD8+ lymphocytes from cisplatin-induced killing. Letal also down-regulated the expression of Fas in CD8+ cells and rendered them resistant to Fas ligand-induced apoptosis. Our results indicate that Letal promotes tumor immune surveillance by promoting the survival and intratumoral expansion of antitumor cytotoxic lymphocytes. We propose that Letal could be used for the ex vivo expansion of apoptosis-resistant tumor-reactive cytotoxic lymphocytes for adoptive transfer.

Effect of undernourishment on Herpes Simplex Virus Type 1 ocular infection in the Wistar rat model

We have studied the susceptibility to Herpes Simplex Virus Type 1 (HSV-1) infection in malnourished rats. Groups of 10 rats were undernourished during suckling by offspring duplication. The animals were put on commercial diet and at 1, 2, 3, 5 and 8 weeks after weaning, infected in the eye by scarification with HSV-1, strain F. Significant differences in morbidity and mortality were observed between malnourished and control groups infected three weeks after weaning. Viral titres were higher in ocular washings and brains obtained from the malnourished group. This group showed a diminution in antigen dependent lymphocyte proliferation compared to control, and significantly lower delayed type hypersensitivity reaction against inactivated virus (malnourished = 0.16 +/- 0.02 mm, control = 0.26 +/- 0.03 mm, p < 0.05). Neutralizing antibodies in serum were lower in the malnourished group and lower levels of interferon were obtained in the malnourished group 24 h post-infection. We conclude that malnutrition during suckling induces a delay in the capability to overcome HSV infection.

Nitric oxide and macrophage antiviral extrinsic activity

In this study we evaluated the relationship between nitric oxide (NO) and macrophage antiviral extrinsic activity. Macrophages activated by intraperitoneal injection of herpes simplex virus-2 (HSV-2), showed both extrinsic antiviral activity and high nitrite production in contrast to non-activated, resident macrophages. The extrinsic antiviral activity was observed in cultures of Vero cells infected with HSV-1 and HSV-2. The NO inhibitor N-monomethyl-l-arginine acetate (l-NMA) impaired the antiviral activity of HSV-elicited macrophages. The effect was dose dependent and correlated with a reduction of nitrite in the culture media. The effect of l-NMA was reversed by the addition of l-arginine. These data indicate that NO could be responsible for the described activity. Furthermore, l-NMA treatment resulted in the aggravation of HSV-1-induced keratitis in the mouse model, supporting a defensive role of NO in the pathogenesis of HSV-1 corneal infection.

Meliacine, an antiviral compound from Melia azedarach L., inhibits interferon production

A glycopeptide isolated from the high plant Melia azedarach L. (meliacine) inhibits the in vitro replication of several RNA and DNA animal viruses. Interferon (IFN) production was depressed greatly in meliacine treated L929 cells and primary mouse embryo fibroblast cultures (MEF) induced with Newcastle disease virus (NDV) or poly(rI).poly(rC). This action was observed when meliacine was added before, simultaneously or early after induction with poly(rI).poly(rC) or NDV. In addition, accumulation of acid-resistant IFN was strongly diminished in adult mice treated intraperitoneally with meliacine. Though meliacine causes a strong inhibition of IFN both in vitro and in vivo, we do not know how selectively it affects the IFN system.