ABSTRACT
Endoplasmic reticulum (ER) stress triggers or amplifies inflammatory signals and cytokine production in immune cells. Upon the resolution of ER stress, the inducible phosphatase 1 cofactor GADD34 promotes the dephosphorylation of the initiation factor eIF2α, thereby enabling protein translation to resume. Several aminoguanidine compounds, such as guanabenz, perturb the eIF2α phosphorylation-dephosphorylation cycle and protect different cell or tissue types from protein misfolding and degeneration. We investigated how pharmacological interference with the eIF2α pathway could be beneficial to treat autoinflammatory diseases dependent on proinflammatory cytokines and type I interferons (IFNs), the production of which is regulated by GADD34 in dendritic cells (DCs). In mouse and human DCs and B cells, guanabenz prevented the activation of Toll-like receptor 9 (TLR9) by CpG oligodeoxynucleotides or DNA-immunoglobulin complexes in endosomes. In vivo, guanabenz protected mice from CpG oligonucleotide-dependent cytokine shock and decreased autoimmune symptom severity in a chemically induced model of systemic lupus erythematosus. However, we found that guanabenz exerted its inhibitory effect independently of GADD34 activity on eIF2α and instead decreased the abundance of CH25H, a cholesterol hydroxylase linked to antiviral immunity. Our results therefore suggest that guanabenz and similar compounds could be used to treat type I IFN-dependent pathologies and that CH25H could be a therapeutic target to control these diseases.
Subject(s)
Eukaryotic Initiation Factor-2/metabolism , Guanabenz/pharmacology , Protein Phosphatase 1/metabolism , Toll-Like Receptor 9/antagonists & inhibitors , Animals , Antihypertensive Agents/pharmacology , Cells, Cultured , Dendritic Cells/cytology , Dendritic Cells/drug effects , Dendritic Cells/metabolism , Endoplasmic Reticulum Stress , Gene Expression Regulation , Humans , Liver Diseases/drug therapy , Liver Diseases/etiology , Lupus Erythematosus, Systemic/chemically induced , Lupus Erythematosus, Systemic/drug therapy , Lupus Erythematosus, Systemic/immunology , Male , Mice , Mice, Inbred C57BL , Phosphorylation/drug effects , Protein Phosphatase 1/geneticsABSTRACT
Multi-organ failure in response to uncontrolled microbial infection is characterized by low blood pressure accompanied by a systemic over-inflammation state, caused by massive pro-inflammatory cytokines release and liver damage. Recently, the integrated stress response (ISR), characterized by eukaryotic translation initiation factor 2α (eIF2α) phosphorylation, was involved with controlling apoptosis in stressed hepatocytes and associated with poor survival to endotoxin challenge. Lipopolysaccharide (LPS) alone is able to induce the ISR in hepatocytes and can trigger massive liver damage along with tumor necrosis factor-alpha (TNF-α) expression. Consequently, drugs interfering with eIF2α phosphorylation may represent potential candidates for the treatment of such pathologies. We, therefore, used Guanabenz (GBZ), a small compound with enhancing eIF2α phosphorylation activity to evaluate its effect on bacterial LPS sensing and endotoxemia. GBZ is confirmed here to have an anti-inflammatory activity by increasing in vitro interleukin-10 (IL-10) production by LPS-stimulated dendritic cells. We further show that in the d-galactosamine (d-galN)/LPS-dependent lethality model, intraperitoneal injection of GBZ promoted mice survival, prevented liver damage, increased IL-10 levels, and inhibited TNF-α production. GBZ and its derivatives could therefore represent an interesting pharmacological solution to control systemic inflammation and associated acute liver failure.
ABSTRACT
Expression of long-lasting synaptic plasticity and long-term memory requires protein synthesis, which can be repressed by phosphorylation of eukaryotic initiation factor 2 α-subunit (eIF2α). Elevated phosphorylation of eIF2α has been observed in the brains of Alzheimer's disease patients and Alzheimer's disease model mice. Therefore, we tested whether suppressing eIF2α kinases could alleviate synaptic plasticity and memory deficits in Alzheimer's disease model mice. Genetic deletion of eIF2α kinase PERK prevented enhanced phosphorylation of eIF2α and deficits in protein synthesis, synaptic plasticity and spatial memory in mice that express familial Alzheimer's disease-related mutations in APP and PSEN1. Similarly, deletion of another eIF2α kinase, GCN2, prevented impairments of synaptic plasticity and defects in spatial memory exhibited by the Alzheimer's disease model mice. Our findings implicate aberrant eIF2α phosphorylation as a previously unidentified molecular mechanism underlying Alzheimer's disease-related synaptic pathophysioloy and memory dysfunction and suggest that PERK and GCN2 are potential therapeutic targets for treatment of individuals with Alzheimer's disease.
Subject(s)
Alzheimer Disease/complications , Alzheimer Disease/pathology , Memory Disorders/etiology , Neuronal Plasticity/genetics , eIF-2 Kinase/metabolism , Aged , Aged, 80 and over , Alzheimer Disease/genetics , Alzheimer Disease/therapy , Amyloid beta-Protein Precursor/genetics , Animals , Anisomycin/pharmacology , Anisomycin/therapeutic use , Disease Models, Animal , Female , Hippocampus/pathology , Humans , In Vitro Techniques , Male , Maze Learning/drug effects , Maze Learning/physiology , Memory Disorders/metabolism , Memory Disorders/therapy , Mice , Mice, Inbred C57BL , Mice, Transgenic , Mutation/genetics , Neuronal Plasticity/physiology , Presenilin-1/genetics , Protein Synthesis Inhibitors/pharmacology , Protein Synthesis Inhibitors/therapeutic use , Recognition, Psychology/drug effects , Recognition, Psychology/physiology , eIF-2 Kinase/geneticsABSTRACT
OBJECTIVE: Multiple sclerosis is a neurodegenerative disease characterized by episodes of immune attack of oligodendrocytes leading to demyelination and progressive functional deficit. One therapeutic strategy to address disease progression could consist in stimulating the spontaneous regenerative process observed in some patients. Myelin regeneration requires endogenous oligodendrocyte progenitor migration and activation of the myelination program at the lesion site. In this study, we have tested the ability of olesoxime, a neuroprotective and neuroregenerative agent, to promote remyelination in the rodent central nervous system in vivo. METHODS: The effect of olesoxime on oligodendrocyte progenitor cell (OPC) differentiation and myelin synthesis was tested directly in organotypic slice cultures and OPC-neuron cocultures. Using naive animals and different mouse models of demyelination, we morphologically and functionally assessed the effect of the compound on myelination in vivo. RESULTS: Olesoxime accelerated oligodendrocyte maturation and enhanced myelination in vitro and in vivo in naive animals during development and also in the adult brain without affecting oligodendrocyte survival or proliferation. In mouse models of demyelination and remyelination, olesoxime favored the repair process, promoting myelin formation with consequent functional improvement. INTERPRETATION: Our observations support the strategy of promoting oligodendrocyte maturation and myelin synthesis to enhance myelin repair and functional recovery. We also provide proof of concept that olesoxime could be useful for the treatment of demyelinating diseases.
Subject(s)
Cholestenones/therapeutic use , Demyelinating Diseases/drug therapy , Multiple Sclerosis/drug therapy , Myelin Sheath/drug effects , Oligodendroglia/drug effects , Animals , Cuprizone/toxicity , Demyelinating Diseases/chemically induced , Disease Models, Animal , Magnetic Resonance Imaging , Mice , Mice, Inbred C57BL , Monoamine Oxidase Inhibitors/toxicity , Multiple Sclerosis/physiopathology , Myelin Sheath/physiology , Oligodendroglia/physiology , Rats , Rats, Sprague-DawleyABSTRACT
Antimicrobial peptides are good leads to develop new antibiotics, but knowledge of their mode of action is a prerequisite. Destruction of the microbial membranes through a detergent-like mechanism is one of these modes of action. This is usually studied by using a fluorescent nucleic acid stain such as SYTOX Green, which is impermeable to living cells. Using a simple protocol based on the use of a standard real-time thermocycler, we confirmed that the actions of the antimicrobial peptides LL-37 and magainin 2 on bacterial cells are different.