Epstein-Barr virus infection and nasopharyngeal carcinoma

Epstein-Barr virus (EBV) is associated with multiple types of human cancer, including lymphoid and epithelial cancers. The closest association with EBV infection is seen in undifferentiated nasopharyngeal carcinoma (NPC), which is endemic in the southern Chinese population. A strong association between NPC risk and the HLA locus at chromosome 6p has been identified, indicating a link between the presentation of EBV antigens to host immune cells and NPC risk. EBV infection in NPC is clonal in origin, strongly suggesting that NPC develops from the clonal expansion of a single EBV-infected cell. In epithelial cells, the default program of EBV infection is lytic replication. However, latent infection is the predominant mode of EBV infection in NPC. The establishment of latent EBV infection in pre-invasive nasopharyngeal epithelium is believed to be an early stage of NPC pathogenesis. Recent genomic study of NPC has identified multiple somatic mutations in the upstream negative regulators of NF-κB signalling. Dysregulated NF-κB signalling may contribute to the establishment of latent EBV infection in NPC. Stable EBV infection and the expression of latent EBV genes are postulated to drive the transformation of pre-invasive nasopharyngeal epithelial cells to cancer cells through multiple pathways.This article is part of the themed issue 'Human oncogenic viruses'.

LncRNA-HOTAIR promotes TNF-α production in cardiomyocytes of LPS-induced sepsis mice by activating NF-κB pathway

BACKGROUND

Mounting studies have illustrated an important role of HOTAIR in cancer progress, but few studies have reported its function in cardiac disease, including cardiac-associated sepsis. This study aimed to investigate the function of HOTAIR in sepsis, involving its association with the level of tumor necrosis factor-alpha (TNF-α), an important inducer of myocardial dysfunction during LPS-induced sepsis.

METHODS

Sepsis mice model was established by LPS administration, and myocardial dysfunction was evaluated with hemodynamic parameters. HOTAIR expression in isolated cardiomyocytes and TNF-α production in the circulation were detected, as well as the protein levels of phosphorylated p65. HL-1 cells were subjected to LPS treatment in vitro for functional studies, including luciferase report assays for NF-κB activity.

RESULTS

HOTAIR expression was significantly upregulated in cardiomyocytes from sepsis mice, in line with increased TNF-α production and p65 phosphorylation, while similar results were also observed in LPS treated HL-1 cells, which was then reversed by HOTAIR interference. Functional studies demonstrated that HOTAIR showed positive regulation on p65 phosphorylation and NF-κB activation, while HOTAIR-induced TNF-α production was repressed by NF-κB inhibitor. Further in vivo studies confirmed that HOTAIR silence can improve cardiac function of sepsis mice, and markedly decreased TNF-α production in the circulation.

CONCLUSION

HOTAIR upregulation in cardiomyocytes of LPS-induced sepsis mice promoted TNF-α production in the circulation by activating NF-κB, involving the phosphorylation of NF-κB p65 subunit. Moreover, HOTAIR silence preserved cardiac function of sepsis mice during LPS-induced sepsis.

Outer Membrane Vesicles From Probiotic and Commensal Escherichia coli Activate NOD1-Mediated Immune Responses in Intestinal Epithelial Cells

Gut microbiota plays a critical role in maintaining human intestinal homeostasis and host health. Bacterial extracellular vesicles are key players in bacteria-host communication, as they allow delivery of effector molecules into the host cells. Outer membrane vesicles (OMVs) released by Gram-negative bacteria carry many ligands of pattern recognition receptors that are key components of innate immunity. NOD1 and NOD2 cytosolic receptors specifically recognize peptidoglycans present within the bacterial cell wall. These intracellular immune receptors are essential in host defense against bacterial infections and in the regulation of inflammatory responses. Recent contributions show that NODs are also fundamental to maintain intestinal homeostasis and microbiota balance. Peptidoglycan from non-invasive pathogens is delivered to cytosolic NODs through OMVs, which are internalized via endocytosis. Whether this pathway could be used by microbiota to activate NOD receptors remains unexplored. Here, we report that OMVs isolated from the probiotic Escherichia coli Nissle 1917 and the commensal ECOR12 activate NOD1 signaling pathways in intestinal epithelial cells. NOD1 silencing and RIP2 inhibition significantly abolished OMV-mediated activation of NF-κB and subsequent IL-6 and IL-8 expression. Confocal fluorescence microscopy analysis confirmed that endocytosed OMVs colocalize with NOD1, trigger the formation of NOD1 aggregates, and promote NOD1 association with early endosomes. This study shows for the first time the activation of NOD1-signaling pathways by extracellular vesicles released by gut microbiota.

YTHDF2 facilitates UBXN1 mRNA decay by recognizing METTL3-mediated m6A modification to activate NF-κB and promote the malignant progression of glioma

BACKGROUND

The prognosis for diffuse gliomas is very poor and the mechanism underlying their malignant progression remains unclear. Here, we aimed to elucidate the role and mechanism of the RNA N6,2'-O-dimethyladenosine (m6A) reader, YTH N6-methyladenosine RNA binding protein 2 (YTHDF2), in regulating the malignant progression of gliomas.

METHODS

YTHDF2 mRNA levels and functions were assessed using several independent datasets. Western blotting, quantitative polymerase chain reaction, and immunohistochemistry were used to evaluate the expression levels of YTHDF2 and other molecules in human and mouse tumor tissues and cells. Knockdown and overexpression were used to evaluate the effects of YTHDF2, methyltransferase-like 3 (METTL3), and UBX domain protein 1 (UBXN1) on glioma malignancy in cell and orthotopic xenograft models. RNA immunoprecipitation (RIP), methylated RIP, and RNA stability experiments were performed to study the mechanisms underlying the oncogenic role of YTHDF2.

RESULTS

YTHDF2 expression was positively associated with a higher malignant grade and molecular subtype of glioma and poorer prognosis. YTHDF2 promoted the malignant progression of gliomas in both in vitro and in vivo models. Mechanistically, YTHDF2 accelerated UBXN1 mRNA degradation via METTL3-mediated m6A, which, in turn, promoted NF-κB activation. We further revealed that UBXN1 overexpression attenuated the oncogenic effect of YTHDF2 overexpression and was associated with better survival in patients with elevated YTHDF2 expression.

CONCLUSIONS

Our findings confirmed that YTHDF2 promotes the malignant progression of gliomas and revealed important insight into the upstream regulatory mechanism of NF-κB activation via UBXN1 with a primary focus on m6A modification.

Evaluation of cytotoxicity, immune compatibility and antibacterial activity of biogenic silver nanoparticles

The study was focused on assessment of antibacterial activity, cytotoxicity and immune compatibility of biogenic silver nanoparticles (AgNPs) synthesized from Streptomyces sp. NH28 strain. Nanoparticles were biosynthesized and characterized by UV-Vis spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, nanoparticle tracking analysis system and zeta potential. Antibacterial activity was tested against Gram-positive and Gram-negative bacteria; minimal inhibitory concentration was recorded. Cytotoxicity was estimated using L929 mouse fibroblasts via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test. Biocompatibility of AgNPs was performed using THP1-XBlue™ cells. Biogenic AgNPs presented high antibacterial activity against all tested bacteria. Minimum inhibitory concentration of AgNPs against bacterial cells was found to be in range of 1.25-10 μg/mL. Silver nanoparticles did not show any harmful interaction to mouse fibroblast cell line, and no activation of nuclear factor kappa-light-chain-enhancer of activated B (NF-κB) cells was observed at concentration below 10 µg/mL. The half-maximal inhibitory concentration (IC₅₀) value was established at 64.5 μg/mL. Biological synthesis of silver can be used as an effective system for formation of metal nanoparticles. Biosynthesized AgNPs can be used as an antibacterial agent, which can be safe for eukaryotic cells.

Bifidobacterium adolescentis IM38 ameliorates high-fat diet-induced colitis in mice by inhibiting NF-κB activation and lipopolysaccharide production by gut microbiota

Gut microbiota play essential roles in the regulation of human metabolism via symbiotic interactions with the host. Prolonged consumption of high-fat diet (HFD) elevates the Firmicutes to Bacteroidetes ratio and lipopolysaccharide (LPS) production by gut microbiota, thereby increasing the probability of developing metabolic and immune disorders such as obesity and colitis. The use of probiotics with anti-inflammatory properties has been suggested to counteract this effect. Here, we tested whether Bifidobacterium adolescentis IM38, which inhibited nuclear factor-kappa B (NF-κB) activation in Caco-2 cells and peritoneal macrophages and inhibited Escherichia coli LPS production, exerted an anticolitic effect in mice with HFD-induced obesity. Oral administration of IM38 (2×10⁹CFU/mouse per day) for 6 weeks in mice with HFD-induced obesity inhibited whole-body and epididymal fat weight gain. IM38 also increased HFD-suppressed expression of interleukin (IL)-10 and tight junction proteins but significantly downregulated HFD-induced NF-κB activation and tumor necrosis factor expression in the colon. IM38 inhibited differentiation into helper T17 cells and reduced IL-17 levels in the colon of mice with HFD-induced obesity but increased HFD-suppressed differentiation into regulatory T cells and IL-10 levels. Furthermore, treatment with IM38 lowered the HFD-induced LPS levels in blood and colonic fluid, as well as the Proteobacteria to Bacteroidetes ratio in gut microbiota. Therefore, we suggest that IM38 can inhibit HFD-induced LPS production in gut microbiota through the regulation of Proteobacteria to Bacteroidetes ratio and NF-κB activation in the colon, which ultimately attenuates colitis. Thus, IM38 may be a suitable ingredient of functional foods designed for treating or preventing colitis.

Melatonin reduces inflammatory response in human intestinal epithelial cells stimulated by interleukin-1β

Melatonin is the main secretory product of the pineal gland, and it is involved in the regulation of periodic events. A melatonin production independent of the photoperiod is typical of the gut. However, the local physiological role of melatonin at the intestinal tract is poorly characterized. In this study, we evaluated the anti-inflammatory activities of melatonin in an in vitro model of inflamed intestinal epithelium. To this purpose, we assessed different parameters usually associated with intestinal inflammation using IL-1β-stimulated Caco-2 cells. Differentiated monolayers of Caco-2 cells were preincubated with melatonin (1 nmol/L-50 μmol/L) and then exposed to IL-1β. After each treatment, different inflammatory mediators, DNA-breakage, and global DNA methylation status were assayed. To evaluate the involvement of melatonin membrane receptors, we also exposed differentiated monolayers to melatonin in the presence of luzindole, a MT1 and MT2 antagonist. Our results showed that melatonin, at concentrations similar to those obtained in the lumen gut after ingestion of dietary supplements for the treatment of sleep disorders, was able to attenuate the inflammatory response induced by IL-1β. Anti-inflammatory effects were expressed as both a decrease of the levels of inflammatory mediators, including IL-6, IL-8, COX-2, and NO, and a reduced increase in paracellular permeability. Moreover, the protection was associated with a reduced NF-κB activation and a prevention of DNA demethylation. Conversely, luzindole did not reverse the melatonin inhibition of stimulated-IL-6 release. In conclusion, our findings suggest that melatonin, through a local action, can modulate inflammatory processes at the intestinal level, offering new opportunities for a multimodal management of IBD.

Differential outcome of TRIF-mediated signaling in TLR4 and TLR3 induced DC maturation

Recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) on dendritic cells (DCs) leads to DC maturation, a process involving up-regulation of MHC and costimulatory molecules and secretion of proinflammatory cytokines. All TLRs except TLR3 achieve these outcomes by using the signaling adaptor myeloid differentiation factor 88. TLR4 and TLR3 can both use the Toll-IL-1 receptor domain-containing adaptor inducing IFN-β (TRIF)-dependent signaling pathway leading to IFN regulatory factor 3 (IRF3) activation and induction of IFN-β and -α4. The TRIF signaling pathway, downstream of both of these TLRs, also leads to DC maturation, and it has been proposed that the type I IFNs act in cis to induce DC maturation and subsequent effects on adaptive immunity. The present study was designed to understand the molecular mechanisms of TRIF-mediated DC maturation. We have discovered that TLR4-TRIF-induced DC maturation was independent of both IRF3 and type I IFNs. In contrast, TLR3-mediated DC maturation was completely dependent on type I IFN feedback. We found that differential activation of mitogen-activated protein kinases by the TLR4- and TLR3-TRIF axes determined the type I IFN dependency for DC maturation. In addition, we found that the adjuvanticity of LPS to induce T-cell activation is completely independent of type I IFNs. The important distinction between the TRIF-mediated signaling pathways of TLR4 and TLR3 discovered here could have a major impact in the design of future adjuvants that target this pathway.

Should we ban total phenolics and antioxidant screening methods? The link between antioxidant potential and activation of NF-κB using phenolic compounds from grape by-products

Free radical imbalance is associated with several chronic diseases. However, recent controversies have put in check the validity of colorimetric methods to screen the functionality of polyphenols. Therefore, in this study two antioxidant methods, based on chemical reactions, were tested for their ability in anticipating the reduction of the activation of NF-κB using LPS-activated RAW 264.7 macrophages, selected as a biological model. Grape processing by-products from winemaking showed higher total phenolic content (TPC), antioxidant capacity towards peroxyl radical (31.1%) as well as reducing power (39.5%) than those of grape juice by-products. The same trend was observed when these samples were tested against LPS-activated RAW 264.7 macrophages by reducing the activation NF-κB. Feedstocks containing higher TPC and corresponding ORAC and FRAP results translated to higher reduction in the activation of NF-κB (36.5%). Therefore, this contribution demonstrates that colorimetric methods are still important screening tools owing their simplicity and widespread application.

Molecular mechanisms of dust-induced toxicity in human corneal epithelial cells: Water and organic extract of office and house dust

Human corneal epithelial (HCE) cells are continually exposed to dust in the air, which may cause corneal epithelium damage. Both water and organic soluble contaminants in dust may contribute to cytotoxicity in HCE cells, however, the associated toxicity mechanisms are not fully elucidated. In this study, indoor dust from residential houses and commercial offices in Nanjing, China was collected and the effects of organic and water soluble fraction of dust on primary HCE cells were examined. The concentrations of heavy metals in the dust and dust extracts were determined by ICP-MS and PAHs by GC-MS, with office dust having greater concentrations of heavy metals and PAHs than house dust. Based on LC50, organic extract was more toxic than water extract, and office dust was more toxic than house dust. Accordingly, the organic extracts induced more ROS, malondialdehyde, and 8-Hydroxydeoxyguanosine and higher expression of inflammatory mediators (IL-1β, IL-6, and IL-8), and AhR inducible genes (CYP1A1, and CYP1B1) than water extracts (p<0.05). Extracts of office dust presented greater suppression of superoxide dismutase and catalase activity than those of house dust. In addition, exposure to dust extracts activated NF-κB signal pathway except water extract of house dust. The results suggested that both water and organic soluble fractions of dust caused cytotoxicity, oxidative damage, inflammatory response, and activation of AhR inducible genes, with organic extracts having higher potential to induce adverse effects on primary HCE cells. The results based on primary HCE cells demonstrated the importance of reducing contaminants in indoor dust to reduce their adverse impacts on human eyes.

Molecular characterization, expression and functional analysis of NOD1, NOD2 and NLRC3 in Nile tilapia (Oreochromis niloticus)

The nucleotide-binding oligomerization domain proteins NOD1, NOD2 and NLRC3 are cytoplasmic pattern recognition receptors (PRRs) of the Nod-like receptor (NLR) family. In the present study, the Nile tilapia (Oreochromis niloticus) NOD1 (ntNOD1), NOD2 (ntNOD2) and NLRC3 (ntNLRC3) genes were cloned and characterized. The full-length ntNOD1, ntNOD2 and ntNLRC3 genes were 3924, 3886 and 4574 bp, encoding 941, 986 and 1130 amino acids, respectively. The three Nod-like receptors have a NACHT domain and a C-terminal leucine-rich repeat (LRR) domain. In addition, ntNOD1 and ntNOD2 have a N-terminal CARD domain (ntNOD2 has two). Phylogenetic analysis showed that the three NLRs are highly conserved. Tissue expression analysis of the three receptors revealed that the highest mRNA and protein levels of ntNOD1, ntNOD2 and ntNLRC3 were in the spleen. The expression patterns of NLRs during embryonic development showed that the expression levels of ntNOD2 and ntNLRC3 significantly increased from 2 to 8 days post-fertilization (dpf). The expression levels of ntNOD1 significantly increased from 2 to 6 dpf, decreased at 7 dpf and then increased at 8 dpf. Upon stimulation with an intraperitoneal injection of Streptococcus agalactiae, expression levels of the ntNOD1, ntNOD2 and ntNLRC3 mRNA and protein were clearly altered in the blood, spleen, kidney, intestine and gill. Furthermore, after cotransfection with an NF-κB reporter plasmid, NF-κB activation in ntNOD1-overexpressing 293T cells significantly increased compared with that in control cells, before or after i-EDPA-stimulation. By contrast, compared with control, ntNOD2 and ntNLRC3 had no effect on NF-κB activation in 293T cells, when their potential ligands were not stimulated. However, after MDP-stimulation, ntNOD2 and ntNLRC3 overexpression increased NF-κB activation in 293T cells. NOD1 and NLRC3 were uniformly distributed throughout the cytoplasm in 293T cells, whereas NOD2 was distributed throughout the cytoplasm and nucleus. Our results indicate that the three Nod-like receptors are functionally conserved and may play pivotal roles in defense against pathogens such as Streptococcus agalactiae.

Inhibitory effects of baicalein against herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) is a ubiquitous and widespread human pathogen, which gives rise to a range of diseases, including cold sores, corneal blindness, and encephalitis. Currently, the use of nucleoside analogs, such as acyclovir and penciclovir, in treating HSV-1 infection often presents limitation due to their side effects and low efficacy for drug-resistance strains. Therefore, new anti-herpetic drugs and strategies should be urgently developed. Here, we reported that baicalein, a naturally derived compound widely used in Asian countries, strongly inhibited HSV-1 replication in several models. Baicalein was effective against the replication of both HSV-1/F and HSV-1/Blue (an acyclovir-resistant strain) in vitro. In the ocular inoculation mice model, baicalein markedly reduced in vivo HSV-1/F replication, receded inflammatory storm and attenuated histological changes in the cornea. Consistently, baicalein was found to reduce the mortality of mice, viral loads both in nose and trigeminal ganglia in HSV-1 intranasal infection model. Moreover, an ex vivo HSV-1-EGFP infection model established in isolated murine epidermal sheets confirmed that baicalein suppressed HSV-1 replication. Further investigations unraveled that dual mechanisms, inactivating viral particles and inhibiting IκB kinase beta (IKK-β) phosphorylation, were involved in the anti-HSV-1 effect of baicalein. Collectively, our findings identified baicalein as a promising therapy candidate against the infection of HSV-1, especially acyclovir-resistant strain.

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Baicalein is highly effective against HSV-1infection ex vivo and in vivo.

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Inactivation of viral particles and suppression of NF-κB activation were involved in the anti-viral effect of baicalein.

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Hence, our work offers experimental basis for baicalein as a potential drug in treating HSV-1 associated diseases.

The resveratrol oligomers, cis- and trans-gnetin H, from Paeonia suffruticosa seeds inhibit the growth of several human cancer cell lines

ETHNOPHARMACOLOGICAL RELEVANCE

Paeonia suffruticosa Andrews (PSE) is a well-known Chinese medicine that has been widely used as an anti-tumor, anti-oxidative and anti-inflammatory agent. cis- and trans-gnetin H are two resveratrol oligomers isolated from the seeds of PSE. Although resveratrol is widely considered to be one of the most valuable natural chemopreventive agents and there are numerous studies on the antitumor activities of resveratrol, little is known about the antitumor properties of cis- and trans-gnetin H.

MATERIALS AND METHODS

The inhibitory effects of cis- and trans-gnetin H in different human cancer cell lines were assessed using fluorescent viability tests. Cytotoxicity in human lung and breast cancer cells was detected via nuclear condensation, cell permeability, and changes in the mitochondrial membrane potential (∆ψm). Apoptosis in human lung and breast cancer cells was assessed by flow cytometry, a luminescence assay and high-content screening analysis. Finally, a xenograft mice model was used to examine the efficacy of cis-gnetin H on lung tumors.

RESULTS

cis- and trans-gnetin H have superior activity in inhibiting the proliferation of four human cancer cell lines, A549 (lung), BT20 (breast), MCF-7 (breast) and U2OS (osteosarcoma), and promote cell apoptosis, while having a minimal effect on two normal human epithelial cell lines, HPL1A (lung) and HMEC (breast) used as controls. cis- and trans-gnetin H promote apoptosis by releasing mitochondria cytochrome c, activating caspase 3/7 and inhibiting NF-κB activation. Flow cytometry analysis shows that cis- or trans-gnetin H arrested the cell cycle of cancer cells at the G0-G1 phase. Moreover, cis-gnetin H suppressed the growth of xenograft lung tumors in mice.

CONCLUSION

Collectively, our findings demonstrate the promise of the natural compounds cis- and trans-gnetin H as candidates for cancer chemotherapy agents.

Very-long-chain fatty acids induce glial-derived sphingosine-1-phosphate synthesis, secretion, and neuroinflammation

VLCFAs (very-long-chain fatty acids) are the most abundant fatty acids in myelin. Hence, during demyelination or aging, glia are exposed to higher levels of VLCFA than normal. We report that glia convert these VLCFA into sphingosine-1-phosphate (S1P) via a glial-specific S1P pathway. Excess S1P causes neuroinflammation, NF-κB activation, and macrophage infiltration into the CNS. Suppressing the function of S1P in fly glia or neurons, or administration of Fingolimod, an S1P receptor antagonist, strongly attenuates the phenotypes caused by excess VLCFAs. In contrast, elevating the VLCFA levels in glia and immune cells exacerbates these phenotypes. Elevated VLCFA and S1P are also toxic in vertebrates based on a mouse model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). Indeed, reducing VLCFA with bezafibrate ameliorates the phenotypes. Moreover, simultaneous use of bezafibrate and fingolimod synergizes to improve EAE, suggesting that lowering VLCFA and S1P is a treatment avenue for MS.

Zinc-Doped Copper Oxide Nanocomposites Inhibit the Growth of Human Cancer Cells through Reactive Oxygen Species-Mediated NF-κB Activations

Zinc-doped copper oxide nanocomposites (nZn-CuO NPs) are novel nanparticles synthesized by our group. In the present study, the antitumor effects and the underlying molecular mechanisms of the nZn-CuO NPs were investigated. The cytotoxicity of nZn-CuO NPs against several types of cancer cell lines was studied using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS)/phenazinemethosulfate (PMS) assay. Results showed that nZn-CuO NPs exerted obvious antiproliferation effects on cancer cells and relatively weak antiproliferation effects on normal cells. The antitumor mechanisms of nZn-CuO NPs were further investigated using human liver cancer HepG2 cells and human pancreatic cancer Panc28 cells. Hoechst 33342 staining and FITC-Annexin V/PI staining showed that nZn-CuO NPs could induce cell apoptosis in a dose dependent manner. Cell-cycle analysis using flow cytometry revealed that nZn-CuO NPs were able to arrest the cell cycle in the G2/M phase. Also, nZn-CuO NPs were found to induce reactive oxygen species (ROS) generation. Further studies confirmed that nZn-CuO NPs could increase p-IKKα/β and nucleus p-NF-κB p65 expressions and decrease IKKα, IKKβ, IκBα, and nucleus NF-κB p65 expressions in both cell lines. Overall, our data demonstrated that nZn-CuO NPs could selectively inhibit the growth of cancer cells via ROS-mediated NF-κB activation. The current study provides primary evidence that nZn-CuO NPs possess the potential to be developed as a novel anticancer agent.

LRRK2 enhances Nod1/2-mediated inflammatory cytokine production by promoting Rip2 phosphorylation

The innate immune system is critical for clearing infection, and is tightly regulated to avert excessive tissue damage. Nod1/2-Rip2 signaling, which is essential for initiating the innate immune response to bacterial infection and ER stress, is subject to many regulatory mechanisms. In this study, we found that LRRK2, encoded by a gene implicated in Crohn's disease, leprosy and familial Parkinson's disease, modulates the strength of Nod1/2-Rip2 signaling by enhancing Rip2 phosphorylation. LRRK2 deficiency markedly reduces cytokine production in macrophages upon Nod2 activation by muramyl dipeptide (MDP), Nod1 activation by D-gamma-Glu-meso-diaminopimelic acid (iE-DAP) or ER stress. Our biochemical study shows that the presence of LRRK2 is necessary for optimal phosphorylation of Rip2 upon Nod2 activation. Therefore, this study reveals that LRRK2 is a new positive regulator of Rip2 and promotes inflammatory cytokine induction through the Nod1/2-Rip2 pathway.

Toll-like receptor 4 signaling: A common pathway for interactions between prooxidants and extracellular disulfide high mobility group box 1 (HMGB1) protein-coupled activation

Necrotic cells passively release HMGB1, which can stimulate TLR4 in an autocrine fashion to potentially initiate "sterile" inflammation that maintains different disease states. We have shown that prooxidants can induce NF-κB activation through TLR4 stimulation. We examined whether prooxidants enhance HMGB1-induced TLR4 signaling through NF-κB activation. We used LPS-EK as a specific agonist for TLR4, and PPC and SIN-1 as in situ sources for ROS. As model systems, we used HEK-Blue cells (stably transfected with mouse TLR4), RAW-Blue™ cells (derived from murine RAW 264.7 macrophages) and primary murine macrophages from TLR4-KO mice. Both HEK-Blue and RAW-Blue 264.7 cells express optimized secreted embryonic alkaline phosphatase (SEAP) reporter under the control of a promoter inducible by NF-κB. We treated cells with HMGB1 alone and/or in conjunction with prooxidants and/or inhibitors using SEAP release as a measure of TLR4 stimulation. HMGB1 alone and/or in conjunction with prooxidants increased TNFα and IL-6 released from TLR4-WT, but not from TLR4-KO macrophages. Pro-oxidants increased HMGB1 release, which we quantified by ELISA. We used both fluorescence microscopy imaging and flow cytometry to quantify the expression of intracellular ROS. TLR4-neutralizing antibody decreased prooxidant-induced HMGB1 release. Prooxidants promoted HMGB1-induced NF-κB activation as determined by increased release of SEAP and TNF-α, and accumulation of iROS. HMGB1 (Box A), anti-HMGB1 and anti-TLR4-neutralizing pAbs inhibited HMGB1-induced NF-κB activation, but HMGB1 (Box A) and anti-HMGB1 pAb had no effect on prooxidant-induced SEAP release. The present results confirm that prooxidants enhance proinflammatory effects of HMGB1 by activating NF-κB through TLR4 signaling.

NF-κB-induced R-loop accumulation and DNA damage select for nucleotide excision repair deficiencies in adult T cell leukemia

Constitutive NF-κB activation (NF-κBCA) confers survival and proliferation advantages to cancer cells and frequently occurs in T/B cell malignancies including adult T cell leukemia (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1). Counterintuitively, NF-κBCA by the HTLV-1 transactivator/oncoprotein Tax induces a senescence response, and HTLV-1 infections in culture mostly result in senescence or cell-cycle arrest due to NF-κBCA How NF-κBCA induces senescence, and how ATL cells maintain NF-κBCA and avert senescence, remain unclear. Here we report that NF-κBCA by Tax increases R-loop accumulation and DNA double-strand breaks, leading to senescence. R-loop reduction via RNase H1 overexpression, and short hairpin RNA silencing of two transcription-coupled nucleotide excision repair (TC-NER) endonucleases that are critical for R-loop excision-Xeroderma pigmentosum F (XPF) and XPG-attenuate Tax senescence, enabling HTLV-1-infected cells to proliferate. Our data indicate that ATL cells are often deficient in XPF, XPG, or both and are hypersensitive to ultraviolet irradiation. This TC-NER deficiency is found in all ATL types. Finally, ATL cells accumulate R-loops in abundance. Thus, TC-NER deficits are positively selected during HTLV-1 infection because they facilitate the outgrowth of infected cells initially and aid the proliferation of ATL cells with NF-κBCA later. We suggest that TC-NER deficits and excess R-loop accumulation represent specific vulnerabilities that may be targeted for ATL treatment.

Synthesis of conformationally constrained γ-D-glutamyl-meso-diaminopimelic acid derivatives as ligands of nucleotide-binding oligomerization domain protein 1 (Nod1)

Nod1, an important member of the pattern recognition receptor family, remains a virtually unexploited target. Harnessing its innate immune stimulatory properties still remains an unfulfilled goal of medicinal chemistry. Nucleotide-binding oligomerization domain protein 1 (Nod1) agonists have been shown to boost the inflammatory responses against pathogenic microbes and could thus constitute a new class of broad spectrum antimicrobial agents. To gain additional insight into the structure/activity relationships of Nod1 agonistic compounds, a series of novel, conformationally constrained γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP) analogs have been designed and synthesized. Ramos-Blue cells expressing Nod1 were used to screen and validate our compounds for their Nod1-agonist activity. Their immunomodulatory properties were subsequently determined in vitro, by evaluating their capacity to induce pro-inflammatory cytokine and chemokine production from human peripheral blood mononuclear cells (PBMC), by themselves and in synergy with lipopolysaccharide (LPS), a Toll-like receptor 4 (TLR4) ligand. The synthesized iE-DAP analogs were shown to possess immuno-enhancing properties as a result of their potent and specific Nod1-agonistic effect. The activity of the compound exhibiting the greatest capacity to induce pro-inflammatory cytokine release from PBMC surpassed that of lauroyl-γ-D-glutamyl-meso-diaminopimelic acid (C12-iE-DAP).

iPSC-Derived Microglia for Modeling Human-Specific DAMP and PAMP Responses in the Context of Alzheimer's Disease

Neuroinflammation in Alzheimer’s disease (AD) has been the focus for identifying targetable pathways for drug development. The role of amyloid beta (Aβ), a prototype of damage-associated molecular patterns (DAMPs), has been implicated in triggering an inflammatory response. As alpha7 nicotinic acetylcholine receptor (α7 nAChR) binds Aβ with high affinity, α7 nAChR may play a role in Aβ-induced neuroinflammation. The conundrum of how α7 nAChR as the mediator of the cholinergic anti-inflammatory response may trigger an inflammatory response has not been resolved. CHRFAM7A, the uniquely human fusion gene between ULK4 and CHRNA7, is a negative regulator of α7 nAChR ionotropic function. To provide the human context, isogenic induced pluripotent stem cell (iPSC) lines were developed from CHRFAM7A null and carrier individuals by genome-editing the null line using TALENs to knock-in CHRFAM7A. In iPSC-derived microglia-like cells, CHRFAM7A mitigated Aβ uptake through the α7 nAChR. Despite the lower Aβ uptake, the presence of CHRFAM7A was associated with an innate immune response that was characterized by NF-κB activation and NF-κB target transcription (TNFA, IL6, and IL1B). LPS, a prototype PAMP, induced a heightened immune response in CHRFAM7A carriers. CHRFAM7A modified the dynamics of NF-κB translocation by prolonging its nuclear presence. CHRFAM7A modified the α7 nAChR metabotropic function, resulting in a human-specific innate immune response. This iPSC model provided an opportunity to elucidate the mechanism and establish high throughput screens.

Ellagic acid protects Caco-2 cell monolayers against inflammation-induced permeabilization

Chronic intestinal inflammation involves a cycle of oxidative stress, activation of redox sensitive transcription factors, and barrier permeabilization. The latter can lead to systemic inflammation and its associated co-morbidities. Diet can play a major role in the modulation of intestinal inflammation. Among plant bioactives, ellagic acid (EA) was reported to inhibit inflammatory bowel disease in animal models. This work investigated the mechanisms by which EA inhibits tumor necrosis factor alpha (TNFα)-induced inflammation, oxidative stress, and loss of barrier integrity. Caco-2 cells differentiated into an intestinal epithelial cell monolayer were incubated with TNFα (10 ng/ml), in the presence of different EA concentrations. TNFα triggered interleukin (IL) 6 and 8 release into the medium, which was inhibited by EA in a dose-dependent manner (IC₅₀ = 17.3 μM for IL-6). TNFα also led to: i) increased ICAM-1 and NLRP3 expression; ii) loss of epithelial barrier function; iii) increased oxidant production from NOX and mitochondrial origin; iv) NF-κB and ERK1/2 activation; and v) increased MLCK gene expression and MLC phosphorylation. EA (10-40 μM) inhibited all these adverse effects of TNFα. EA mainly acted through NF-κB and ERK1/2 inhibition, breaking the cycle of inflammation, oxidative stress, redox-sensitive pathway (e.g. NF-κB, ERK1/2) activation and intestinal permeabilization. This suggests that consumption of EA, via foods or supplements, may afford a strategy to mitigate intestinal inflammation and its associated co-morbidities.

A versatile supramolecular nanoadjuvant that activates NF-κB for cancer immunotherapy

Although powerful adjuvants hold promise of vaccines for cancer immunotherapy, cumbersome preparation processes, elusive mechanisms and failure to induce T cell responses have largely limited their clinical translation. Due to their ease of synthesis, good biocompatibility and designable bioactivity, peptide derivatives-based supramolecular nanomaterials have attracted increasing interest in improving the immunogenicity of cancer vaccines. Methods: Herein, we synthesized an NF-κB-activating supramolecular nanoadjuvant (3DSNA) that is prepared by pH-triggering self-assembly of a positively charged D-configurational peptide derivative. The immunostimulatory activity of 3DNSA was explored in vitro and in vivo. Results: 3DSNA can strongly absorb the model antigen (ovalbumin, OVA) through electrostatic interaction. Then, 3DSNA promotes ingestion and cross-presentation of OVA, upregulation of costimulatory factors (CD80 and CD86) and secretion of proinflammatory cytokines (IL-6 and IL-12) by dendritic cells (DCs), accompanied by activation of the innate immune response (NF-κB signaling), resulting in long-term antigen-specific memory and effector CD8+ T cells response. When compared with conventional aluminum hydroxide adjuvant and the corresponding L-configurational supramolecular nanoadjuvant (3LSNA), 3DSNA-adjuvanted OVA (3DSNA+OVA) significantly prevents oncogenesis in naïve mice with a complete response rate of 60 %, restrains the tumor growth and prolongs the survival of melanoma-bearing mice. Conclusion: These findings demonstrate that 3DSNA is a promising neo-adjuvant that enables various vaccines to be therapeutic for many important diseases including cancer.

HOTAIR Up-Regulation Activates NF-κB to Induce Immunoescape in Gliomas

Background

Checkpoint blockade therapies targeting programmed death ligand 1 (PD-L1) and its receptor programmed cell death 1 promote T cell-mediated immune surveillance against tumors and have been associated with significant clinical benefit in cancer patients. The long-stranded non-coding RNA HOTAIR is highly expressed and associated with metastasis in a variety of cancer types and promotes tumor metastasis at least in part through association with the PRC2 complex that induces redirection to hundreds of genes involved in tumor metastasis. Here, we report that HOTAIR is an activator lncRNA of the NF-κB pathway and demonstrate that its apparent upregulation promotes inflammatory signaling and immune escape in glioma cells.

Methods

Bioinformatics analysis was used to elucidate the relationship between HOTAIR and NF-κB pathway in HOTAIR knockdown glioma cells. At the cytological level, protein hybridization and immunofluorescence were used to detect the response of proteins in the NF-κB signaling pathway to HOTAIR regulation. ChIP and ChIRP experiments identified HOTAIR target genes. Animal experiments verified alterations in inflammation and immune escape following HOTAIR knockdown and activity inhibition.

Results

HOTAIR activated the expression of proteins involved in NF-κB, TNFα, MAPK and other inflammatory signaling pathways. In addition, HOTAIR induced various proteins containing protein kinase structural domains and promoted the enrichment of proteins and complexes of important inflammatory signaling pathways, such as the TNFα/NF-κB signaling protein complex, the IκB kinase complex, and the IKKA-IKKB complex. In addition, HOTAIR aberrantly activated biological processes involved in glioma immune responses, T-cell co-stimulation and transcription initiation by RNA polymerase II. HOTAIR facilitated the induction of IκBα phosphorylation by suppressing the expression of the NF-κB upstream protein UBXN1, promoting NF-κB phosphorylation and nuclear translocation. In vivo, reduction of HOTAIR decreased PD-L1 protein expression, indicating that cells are more likely to be targeted by immune T cells.

Conclusion

In conclusion, our results provide convincing evidence that lncRNA HOTAIR drives aberrant gene transcription and immune escape from tumor cells through the NF-κB pathway.

Pathogenic Triad in Bacterial Meningitis: Pathogen Invasion, NF-κB Activation, and Leukocyte Transmigration that Occur at the Blood-Brain Barrier

Bacterial meningitis remains the leading cause of disabilities worldwide. This life-threatening disease has a high mortality rate despite the availability of antibiotics and improved critical care. The interactions between bacterial surface components and host defense systems that initiate bacterial meningitis have been studied in molecular and cellular detail over the past several decades. Bacterial meningitis commonly exhibits triad hallmark features (THFs): pathogen penetration, nuclear factor-kappaB (NF-κB) activation in coordination with type 1 interferon (IFN) signaling and leukocyte transmigration that occur at the blood-brain barrier (BBB), which consists mainly of brain microvascular endothelial cells (BMEC). This review outlines the progression of these early inter-correlated events contributing to the central nervous system (CNS) inflammation and injury during the pathogenesis of bacterial meningitis. A better understanding of these issues is not only imperative to elucidating the pathogenic mechanism of bacterial meningitis, but may also provide the in-depth insight into the development of novel therapeutic interventions against this disease.

Sodium butyrate has anti-proliferative, pro-differentiating, and immunomodulatory effects in osteosarcoma cells and counteracts the TNFα-induced low-grade inflammation

Butyrate, an essential factor for colonocytes and regulator in the development of colon cancer, is partially absorbed by the gut. It influences the proliferation and differentiation of several cell types including osteoblasts. We evaluated the effects of different doses of butyrate on differentiation and functionality of osteosarcoma cells in vitro and the expression of a pro-inflammatory phenotype in a normal or inflammatory environment. SaOS-2 osteosarcoma cells were induced to differentiate and contemporarily treated for 24 h, 48 h, or 7 days with sodium butyrate 10⁻⁴, 5 × 10⁻⁴, or 10⁻³ M in the presence or absence of tumor necrosis factor alpha (TNFα) 1 ng/mL, a pro-inflammatory stimulus. Despite the mild effects on proliferation and alkaline phosphatase activity, butyrate dose- and time-dependently induced the expression of a differentiated phenotype (RUNX2, COL1A1 gene expression, and osteopontin gene and protein expression). This was associated with a partial inhibition of nuclear factor kappa B (NF-κB) activation and the induction of histone deacetylase 1 expression. The net effect was the expression of an anti-inflammatory phenotype and the increase in the osteoprotegerin-to-receptor activator of nuclear factor kappa-B ligand (RANKL) ratio. Moreover, butyrate, especially at the highest dose, counteracted the effects of the pro-inflammatory stimulus of TNFα 1 ng/mL. Butyrate affects osteosarcoma cell metabolism by anticipating the expression of a differentiated phenotype and by inducing the expression of anti-inflammatory mediators.