A rapid microplate-based fluorometric assay for phagocytosis

Mutant Isocitrate Dehydrogenase 1 Disrupts PKM2-β-Catenin-BRG1 Transcriptional Network-Driven CD47 Expression

A gain-of-function mutation in isocitrate dehydrogenase 1 (IDH1) affects immune surveillance in gliomas. As elevated CD47 levels are associated with immune evasion in cancers, its status in gliomas harboring mutant IDH1 (IDH1-MT cells) was investigated. Decreased CD47 expression in IDH1-R132H-overexpressing cells was accompanied by diminished nuclear β-catenin, pyruvate kinase isoform M2 (PKM2), and TCF4 levels compared to those in cells harboring wild-type IDH1 (IDH1-WT cells). The inhibition of β-catenin in IDH1-WT cells abrogated CD47 expression, β-catenin-TCF4 interaction, and the transactivational activity of β-catenin/TCF4. The reverse effect was observed in IDH1-MT cells upon the pharmacological elevation of nuclear β-catenin levels. Genetic and pharmacological manipulation of nuclear PKM2 levels in IDH1-WT and IDH1-MT cells suggested that PKM2 is a positive regulator of the β-catenin-TCF4 interaction. The Cancer Genome Atlas (TCGA) data sets indicated diminished CD47, PKM2, and β-catenin levels in IDH1-MT gliomas compared to IDH1-WT gliomas. Also, elevated BRG1 levels with mutations in the ATP-dependent chromatin-remodeling site were observed in IDH1-MT glioma. The ectopic expression of ATPase-deficient BRG1 diminished CD47 expression as well as TCF4 occupancy on its promoter. Sequential chromatin immunoprecipitation (ChIP-re-ChIP) revealed the recruitment of the PKM2-β-catenin-BRG1-TCF4 complex to the TCF4 site on the CD47 promoter. This occupancy translated into CD47 transcription, as a diminished recruitment of this complex was observed in glioma cells bearing IDH1-R132H. In addition to its involvement in CD47 transcriptional regulation, PKM2-β-catenin-BRG1 cross talk affected the phagocytosis of IDH1-MT cells by microglia.

The amelioration of phagocytic ability in microglial cells by curcumin through the inhibition of EMF-induced pro-inflammatory responses

Background

Insufficient clearance by microglial cells, prevalent in several neurological conditions and diseases, is intricately intertwined with MFG-E8 expression and inflammatory responses. Electromagnetic field (EMF) exposure can elicit the pro-inflammatory activation and may also trigger an alteration of the clearance function in microglial cells. Curcumin has important roles in the anti-inflammatory and phagocytic process. Here, we evaluated the ability of curcumin to ameliorate the phagocytic ability of EMF-exposed microglial cells (N9 cells) and documented relative pathways.

Methods

N9 cells were pretreated with or without recombinant murine MFG-E8 (rmMFG-E8), curcumin and an antibody of toll-like receptor 4 (anti-TLR4), and subsequently treated with EMF or a sham exposure. Their phagocytic ability was evaluated using phosphatidylserine-containing fluorescent bioparticles. The pro-inflammatory activation of microglia was assessed via CD11b immunoreactivity and the production of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and nitric oxide (NO) via the enzyme-linked immunosorbent assay or the Griess test. We evaluated the ability of curcumin to ameliorate the phagocytic ability of EMF-exposed N9 cells, including checking the expression of MFG-E8, α_vβ₃ integrin, TLR4, nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) using Western blotting.

Results

EMF exposure dramatically enhanced the expression of CD11b and depressed the phagocytic ability of N9 cells. rmMFG-E8 could clearly ameliorate the phagocytic ability of N9 cells after EMF exposure. We also found that EMF exposure significantly increased the secretion of pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) and the production of NO; however, these increases were efficiently chilled by the addition of curcumin to the culture medium. This reduction led to the amelioration of the phagocytic ability of EMF-exposed N9 cells. Western blot analysis revealed that curcumin and naloxone restored the expression of MFG-E8 but had no effect on TLR4 and cytosolic STAT3. Moreover, curcumin significantly reduced the expression of NF-κB p65 in nuclei and phospho-STAT3 (p-STAT3) in cytosols and nuclei.

Conclusions

This study indicates that curcumin ameliorates the depressed MFG-E8 expression and the attenuated phagocytic ability of EMF-exposed N9 cells, which is attributable to the inhibition of the pro-inflammatory response through the NF-κB and STAT3 pathways.

CEP-11004, an inhibitor of the SAPK/JNK pathway, reduces TNF-alpha release from lipopolysaccharide-treated cells and mice

CEP-11004, a mixed lineage kinase (MLK) inhibitor, was examined for its effects on tumor necrosis factor-alpha (TNF-alpha) production in human THP-1 monocytes, mouse BV-2 microglia, and C57Bl/6 mice. CEP-11004 inhibited TNF-alpha secretion up to 90% in THP-1 cells incubated with 3 mug/ml lipopolysaccharide, with an IC50 of 137+/-14 nM. CEP-11004 also inhibited TNF-alpha production in lipopolysaccharide-stimulated microglial cells, but did not inhibit the initial increase in TNF-alpha mRNA expression as measured by real-time polymerase chain reaction (PCR). The mitogen-activated protein kinases (MAPKs) phospho-c-jun N-terminal kinase (JNK), phospho-p38, and phospho-MAPK kinase 4 (MKK4) levels were increased in THP-1 cells following lipopolysaccharide treatment, and were reduced by CEP-11004 treatment. For in vivo studies, CEP-11004 was injected 2 h prior to lipopolysaccharide (20 mg/kg) administration. CEP-11004 significantly inhibited TNF-alpha production at doses of 1-10 mg/kg as measured by enzyme-linked immunosorbent assay (ELISA). These results suggest that MLK blockade may be useful in inhibiting pro-inflammatory cytokine production in a wide range of diseases.

Screening for Cell Migration Inhibitors via Automated Microscopy Reveals a Rho-Kinase Inhibitor

Small-molecule kinase inhibitors are predominantly discovered in pure protein assays. We have discovered an inhibitor of Rho-kinase (ROCK) through an image-based, high-throughput screen of cell monolayer wound healing. Using automated microscopy, we screened a library of approximately 16,000 compounds finding many that affected cell migration or cell morphology as well as compounds that blocked mitotic progression. We tested approximately 200 compounds in a series of subassays and chose one, 3-(4-pyridyl)indole (Rockout), for more detailed characterization. Rockout inhibits blebbing and causes dissolution of actin stress fibers, phenocopying Rho-kinase inhibitors. Testing Rho-kinase activity in vitro, Rockout inhibits with an IC50 of 25 microM ( approximately 5-fold less potent than Y-27632) but has a similar specificity profile. We also profile the wound healing assay with a library of compounds with known bioactivities, revealing multiple pathways involved in the biology.

Mitogen-activated protein kinase-activated protein kinase 2-deficient mice show increased susceptibility to Listeria monocytogenes infection

Mitogen-activated protein kinase-activated protein kinase 2 (MK2) is one of several kinases activated through direct phosphorylation by p38 mitogen-activated protein kinase. MK2 regulates LPS-induced TNF mRNA translation, and targeted mutation of the MK2 gene renders mice more resistant to D-galactosamine plus LPS-induced liver damage. In the present study, we investigated the role of MK2 in immune defense against Listeria monocytogenes infection. MK2-deficient mice displayed diminished resistance to L. monocytogenes due to impaired control of bacterial growth. The increase in bacterial load in MK2(-/-) mice was associated with normal levels of IL-1 beta, IL-6, and IFN-gamma, whereas TNF production was strongly attenuated. In line, MK2-deficient bone marrow-derived macrophages showed impaired release of TNF, but not of IL-1 beta, in response to various bacterial stimuli in addition to decreased phagocytosis of fluorescence-labeled bacteria. Furthermore, spleen cells from MK2(-/-) mice displayed diminished IFN-gamma synthesis after stimulation with L. monocytogenes. In contrast, MK2 deficiency had no effect on macrophage generation of NO or on oxidative burst activity in response to L. moocytogenes. These results indicate an essential role of MK2 in host defense against intracellular bacteria probably via regulation of TNF and IFN-gamma production required for activation of antibacterial effector mechanisms.

Opsonophagocytosis of fluorescent polystyrene beads coupled to Neisseria meningitidis serogroup A, C, Y, or W135 polysaccharide correlates with serum bactericidal activity

We developed a polysaccharide-specific flow cytometric opsonophagocytic assay (OPA) for the simultaneous measurement of functional antibody to Neisseria meningitidis serogroups A, C, Y, and W135. OPA titers significantly correlated with serum bactericidal assay titers for all serogroups tested (mean r = 0.96; P < 0.001). OPA could be used in meningococcal vaccine evaluation.

Recording of intracellular Ca2+, Cl-, pH and membrane potential in cultured astrocytes using a fluorescence plate reader

A multi-well fluorescence plate reader was used to determine changes in intracellular ionic concentrations and changes in transmembrane voltage in primary cortical or hippocampal astrocytes. Recordings were compared to those obtained using a traditional microscope-based imaging setup that utilizes a monochromatic light source for excitation and an intensified CCD camera for detection. Measurement of pHi with the ratiometric dye BCECF provided resolution similar to that of a microscopic approach. We also demonstrate using Fluo-3 that the measurement of glutamate-induced [Ca2+]i fluctuations are comparable to recordings on the microscope-based system when 25 cells were averaged. This is expected because the plate reader averages responses from many cells. Voltage changes induced by changes in K+(o) from 3 to 5 mM were readily resolvable with the plate reader using the potentiometric dye bis-oxynol, and overall sensitivity was similar to that of microscopically-determined voltage changes. We also found that the plate reader was capable of resolving GABA-induced Cl-(i) fluctuations using the Cl(-)-sensitive indicator MEQ. From these experiments we conclude that multi-well fluorescence plate readers can be used to effectively record changes in intracellular ion concentrations and transmembrane voltage of populations of cells affording time and amplitude resolution approaching that of conventional fluorescence imaging methods. In addition, plate reader-based fluorescence studies demonstrate the added capability to rapidly screen large numbers of samples.

Influence of soluble suture factors on in vitro macrophage function

Suture materials may interact with immune competent cells and thereby affect localized immunity. Macrophages are central to the inflammatory response and coordinate wound healing. They are also involved in the clearance of foreign material, bacteria and malignant cells. We studied the influence of soluble factors associated with silk, steel, nylon, polyglactin, polydioxanone and chromic catgut sutures on macrophage adherence, phagocytosis and the production of lysozyme and tumour necrosis factor. Soluble factors from suture materials influenced macrophage behaviour in vitro causing cellular activation, functional impairment and alterations in secreted levels of the cytokine tumour necrosis factor and the bactericidal agent lysozyme. Of the six materials studied, polyglactin had the most extreme effect, causing significant inhibition of cell adherence and lysozyme production. Silk also exerted a considerable effect on macrophages, significantly inhibiting adherence. In contrast, steel and polydioxanone media caused minimal inhibition of macrophage function although, as with all materials, they did activate the cells. This study has demonstrated that sutures release immunotoxic factors which considerably influence macrophage behaviour in vitro. These effects may have important clinical implications.