Prolonged Inhibition of the MEK1/2-ERK Signaling Axis Primes Interleukin-1 Beta Expression through Histone 3 Lysine 9 Demethylation in Murine Macrophages.

Macrophages undergo different cellular states upon activation that can be hyporesponsive (tolerated) or hyperresponsive (primed or trained) to subsequent stimuli. Epigenetic modifications are known to play key roles in determining these cellular states. However, little is known about the role of signaling pathways that lead to these epigenetic modifications.

HDAC8 Activates AKT through Upregulating PLCB1 and Suppressing DESC1 Expression in MEK1/2 Inhibition-Resistant Cells.

Inhibition of the RAF-MEK1/2-ERK signaling pathway is an ideal strategy for treating cancers with NRAS or BRAF mutations. However, the development of resistance due to incomplete inhibition of the pathway and activation of compensatory cell proliferation pathways is a major impediment of the targeted therapy. The anthrax lethal toxin (LT), which cleaves and inactivates MEKs, is a modifiable biomolecule that can be delivered selectively to tumor cells and potently kills various tumor cells.

The transcription factor PU.1 mediates enhancer-promoter looping that is required for IL-1β eRNA and mRNA transcription in mouse melanoma and macrophage cell lines.

The DNA-binding protein PU.1 is a myeloid lineage-determining and pioneering transcription factor due to its ability to bind "closed" genomic sites and maintain "open" chromatin state for myeloid lineage-specific genes. The precise mechanism of PU.

Histone deacetylase 8 protects human proximal tubular epithelial cells from hypoxia-mimetic cobalt- and hypoxia/reoxygenation-induced mitochondrial fission and cytotoxicity.

Cell death by hypoxia followed by reoxygenation (H/R) is responsible for tissue injury in multiple pathological conditions. Recent studies found that epigenetic reprogramming mediated by histone deacetylases (HDACs) is implicated in H/R-induced cell death. However, among 18 different isoforms comprising 4 classes (I-IV), the role of each HDAC in cell death is largely unknown.

Cathepsin B plays a key role in optimal production of the influenza A virus.

Background: Influenza A virus (IAV) is the etiologic agent of the febrile respiratory illness, commonly referred to as 'flu'. The lysosomal protease cathepsin B (CTSB) has shown to be involved in the lifecycle of various viruses. Here, we examined the role of CTSB in the IAV lifecycle.

HDAC8 Prevents Anthrax Lethal Toxin-induced Cell Cycle Arrest through Silencing PTEN in Human Monocytic THP-1 Cells.

Anthrax lethal toxin (LeTx) is a cytotoxic virulence factor that causes cell cycle arrest and cell death in various cell types. However, susceptibility to the cytotoxic effects varies depending on cell types. In proliferating monocytes, LeTx has only transient cytotoxic effects due to activation of the phosphoinositide 3-kinase (PI3K)-AKT-mediated adaptive responses.

Inhibition of Interleukin 1β (IL-1β) Expression by Anthrax Lethal Toxin (LeTx) Is Reversed by Histone Deacetylase 8 (HDAC8) Inhibition in Murine Macrophages.

Many pathogenic microbes often release toxins that subvert the host's immune responses to render the environment suitable for their survival and proliferation. LeTx is one of the toxins causing immune paralysis by cleaving and inactivating the mitogen-activated protein kinase (MAPK) kinases (MEKs). Here, we show that inhibition of the histone deacetylase 8 (HDAC8) by either the HDAC8-specific inhibitor PCI-34051 or small interference (si)RNAs rendered LeTx-exposed murine macrophages responsive to LPS in pro-IL-1β production.

Protective role of G-CSF in dextran sulfate sodium-induced acute colitis through generating gut-homing macrophages.

Granulocyte colony-stimulating factor (G-CSF) is a pleiotropic cytokine best known for its role in promoting the generation and function of neutrophils. G-CSF is also found to be involved in macrophage generation and immune regulation; however, its in vivo role in immune homeostasis is largely unknown. Here, we examined the role of G-CSF in dextran sulfate sodium (DSS)-induced acute colitis using G-CSF receptor-deficient (G-CSFR(-/-)) mice.

Preferential production of G-CSF by a protein-like Lactobacillus rhamnosus GR-1 secretory factor through activating TLR2-dependent signaling events without activation of JNKs.

Background: Different species and strains of probiotic bacteria confer distinct immunological responses on immune cells. Lactobacillus rhamnosus GR-1 (GR-1) is a probiotic bacterial strain found in both the intestinal and urogenital tracts, and has immunomodulatory effects on several cell types including macrophages. However, detailed immunological responses and the signaling mechanism involved in the response are largely unknown.

G-CSF preferentially supports the generation of gut-homing Gr-1high macrophages in M-CSF-treated bone marrow cells.

The G-CSF is best known for its activity in the generation and activation of neutrophils. In addition, studies on G-CSF(-/-) or G-CSFR(-/-) mice and BMC cultures suggested a role of G-CSF in macrophage generation. However, our understanding on the role of G-CSF in macrophage development is limited.

HDAC8-mediated epigenetic reprogramming plays a key role in resistance to anthrax lethal toxin-induced pyroptosis in macrophages.

Macrophages pre-exposed to a sublethal dose of anthrax lethal toxin (LeTx) are refractory to subsequent high cytolytic doses of LeTx, termed toxin-induced resistance (TIR). A small population of TIR cells (2-4%) retains TIR characteristics for up to 5-6 wk. Through studying these long-term TIR cells, we found that a high level of histone deacetylase (HDAC)8 expression was crucial for TIR.

p62/SQSTM1 enhances NOD2-mediated signaling and cytokine production through stabilizing NOD2 oligomerization.

NOD2 is a cytosolic pattern-recognition receptor that senses muramyl dipeptide of peptidoglycan that constitutes the bacterial cell wall, and plays an important role in maintaining immunological homeostasis in the intestine. To date, multiple molecules have shown to be involved in regulating NOD2 signaling cascades. p62 (sequestosome-1; SQSTM1) is a multifaceted scaffolding protein involved in trafficking molecules to autophagy, and regulating signal cascades activated by Toll-like receptors, inflammasomes and several cytokine receptors.

Cellular adaptation to anthrax lethal toxin-induced mitochondrial cholesterol enrichment, hyperpolarization, and reactive oxygen species generation through downregulating MLN64 in macrophages.

Cellular adaptation to different stresses related to survival and function has been demonstrated in several cell types. Anthrax lethal toxin (LeTx) induces rapid cell death, termed "pyroptosis," by activating NLRP1b/caspase-1 in murine macrophages. We and others (S.

Inhibition or deficiency of cathepsin B leads defects in HIV-1 Gag pseudoparticle release in macrophages and HEK293T cells.

Human immunodeficiency virus type 1 (HIV-1) egresses from infected cells through utilizing the host membrane budding mechanisms. Assembly of HIV-1 Gag particles occurs on membranes where the Gag multimers subsequently bud off and form enveloped viral particles. In certain cell types such as macrophages, HIV-1 Gag particles have shown to be released into intracellular virus containing compartments (VCC) such as late endosomes, multivesicular bodies (MVBs) or invaginated plasma membrane pockets.

AMPD3 is involved in anthrax LeTx-induced macrophage cell death.

The responses of macrophages to Bacillus anthracis infection are important for the survival of the host, since macrophages are required for the germination of B. anthracis spores in lymph nodes, and macrophage death exacerbates anthrax lethal toxin (LeTx)-induced organ collapse. To elucidate the mechanism of macrophage cell death induced by LeTx, we performed a genetic screen to search for genes associated with LeTx-induced macrophage cell death.

The anti-inflammatory role of granulocyte colony-stimulating factor in macrophage-dendritic cell crosstalk after Lactobacillus rhamnosus GR-1 exposure.

MΦs are important sensory cells of the innate immune system and regulate immune responses through releasing different combinations of cytokines. In this study, we examined whether cytokines released by MΦs in response to the probiotic bacterial strain GR-1 modulate the responses of DCs. The cytokine profile released by GR-1-treated MΦs was characterized by low levels of TNF-α, GM-CSF, IL-6, and IL-12 but very high levels of G-CSF.

Metaxin deficiency alters mitochondrial membrane permeability and leads to resistance to TNF-induced cell killing.

Metaxin, a mitochondrial outer membrane protein, is critical for TNF-induced cell death in L929 cells. Its deficiency, caused by retroviral insertion-mediated mutagenesis, renders L929 cells resistance to TNF killing. In this study, we further characterized metaxin deficiency-caused TNF resistance in parallel with Bcl-X(L) overexpression-mediated death resistance.

Phenotype based functional gene screening using retrovirus-mediated gene trapping in quasi-haploid RAW 264.7 cells.

In vitro random mutagenesis, followed by phenotype screening, provides a rapid and convenient tool for identifying novel genes involved in the phenotype of interest. However, the forward mutagenic approach in mammalian somatic cells is seriously limited by the diploidic nature of the genome. To overcome this impediment, we developed a method that allows functional screening for both haploid insufficient and sufficient genes involved in the phenotype of interest, utilizing a retrovirus gene trap mutagenesis in chemical mutagen-generated quasi-haploid cells.

Cathepsin B-mediated autophagy flux facilitates the anthrax toxin receptor 2-mediated delivery of anthrax lethal factor into the cytoplasm.

Anthrax lethal toxin (LeTx) is a virulence factor secreted by Bacillus anthracis and has direct cytotoxic effects on most cells once released into the cytoplasm. The cytoplasmic delivery of the proteolytically active component of LeTx, lethal factor (LF), is carried out by the transporter component, protective antigen, which interacts with either of two known surface receptors known as anthrax toxin receptor (ANTXR) 1 and 2. We found that the cytoplasmic delivery of LF by ANTXR2 was mediated by cathepsin B (CTSB) and required lysosomal fusion with LeTx-containing endosomes.

Reduced expression of basal and probiotic-inducible G-CSF in intestinal mononuclear cells is associated with inflammatory bowel disease.

Background: Granulocyte-colony stimulating factor (G-CSF) is a pleiotropic cytokine involved in the hematopoiesis of granulocytes, neuroprotection, and immunomodulation. Previously, we have shown that probiotic Lactobacillus rhamnosus GR-1 induces G-CSF production from bone marrow-derived macrophages. Whether this probiotic also induces G-CSF in intestinal mononuclear cells is unknown.

Cathepsin B is involved in the trafficking of TNF-alpha-containing vesicles to the plasma membrane in macrophages.

TNF-alpha is a potent proinflammatory cytokine, essential for initiating innate immune responses against invading microbes and a key mediator involved in the pathogenesis of acute and chronic inflammatory diseases. To identify molecules involved in the production of TNF-alpha, we used a functional gene identification method using retroviral integration-mediated mutagenesis, followed by LPS-stimulated TNF-alpha production analysis in macrophages. We found that cathepsin B, a lysosomal cysteine proteinase, was required for optimal posttranslational processing of TNF-alpha in response to the bacterial cell wall component LPS.

Critical role of the phosphatidylinositol 3-kinase/Akt/glycogen synthase kinase-3 signaling pathway in recovery from anthrax lethal toxin-induced cell cycle arrest and MEK cleavage in macrophages.

Anthrax lethal toxin (LeTx) is a virulence factor causing immune suppression and toxic shock of Bacillus anthracis infected host. It inhibits cytokine production and cell proliferation/differentiation in various immune cells. This study showed that a brief exposure of LeTx caused a continual MEK1 cleavage and prevented tumor necrosis factor-alpha (TNF) production in response to lipopolysaccharide (LPS) in non-proliferating cells such as human peripheral blood mononuclear cells or mouse primary peritoneal macrophages.

Mitochondrial proteins Bnip3 and Bnip3L are involved in anthrax lethal toxin-induced macrophage cell death.

Anthrax lethal toxin (LeTx) induces rapid cell death of RAW246.7 macrophages. We recently found that a small population of these macrophages is spontaneously and temporally refractory to LeTx-induced cytotoxicity.

Cell surface 4-1BBL mediates sequential signaling pathways 'downstream' of TLR and is required for sustained TNF production in macrophages.

The stimulation of Toll-like receptors (TLRs) on macrophages triggers production of the cytokine tumor necrosis factor (TNF). TNF production occurs within 1 h of TLR stimulation and is sustained for 1 d. Here we document a function for the TNF family member 4-1BB ligand (4-1BBL) in sustaining TLR-induced TNF production.