ABSTRACT
Background: Neuroinflammation plays a crucial part in the initial onset and progression of Alzheimer's disease (AD). NLRP3 inflammasome was demonstrated to get involved in amyloid-ß (Aß)-induced neuroinflammation. However, the mechanism of Aß-triggered activation of NLRP3 inflammasome remains poorly understood. Objective: Based on our previous data, the study aimed to identify the downstream signals that bridge the activation of TLR4 and NLRP3 inflammasome associated with Aß. Methods: BV-2 cells were transfected with TLR4siRNA or pretreated with a CLI-095 or NSC23766, followed by Aß1-42 treatment. APP/PS1 mice were injected intraperitoneally with CLI-095 or NSC23766. NLRP3 inflammasome and microglia activation was detected with immunostaining and western blot. G-LISA and Rac1 pull-down activation test were performed to investigate the activation of Rac1. Real-time PCR and ELISA were used to detect the inflammatory cytokines. Aß plaques were assessed by western blotting and immunofluorescence staining. Morris water maze test was conducted to determine the spatial memory in mice. Results: Rac1 and NLRP3 inflammasome were activated by Aß in both in vitro and in vivo experiments. Inhibition of TLR4 reduced the activity of Rac1 and NLRP3 inflammasome induced by Aß1-42. Furthermore, inhibition of Rac1 blocked NLRP3 inflammasome activation mediated by TLR4. Blocking the pathway by CLI095 or NSC23766 suppressed Aß1-42-triggered activation of microglia, reduced the expression of pro-inflammatory mediators and ameliorated the cognition deficits in APP/PS1 mice. Conclusions: Our study demonstrated that TLR4/Rac1/NLRP3 pathway mediated Aß-induced neuroinflammation, which unveiled a novel pathway and key contributors underlying the pathogenic mechanism of Aß.
Subject(s)
Alzheimer Disease , Amyloid beta-Peptides , Mice, Transgenic , NLR Family, Pyrin Domain-Containing 3 Protein , Neuroinflammatory Diseases , Toll-Like Receptor 4 , rac1 GTP-Binding Protein , Animals , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , Amyloid beta-Peptides/metabolism , Toll-Like Receptor 4/metabolism , Alzheimer Disease/metabolism , Mice , rac1 GTP-Binding Protein/metabolism , Neuroinflammatory Diseases/metabolism , Signal Transduction/drug effects , Signal Transduction/physiology , Microglia/metabolism , Microglia/drug effects , Inflammasomes/metabolism , Male , Peptide Fragments/toxicity , Mice, Inbred C57BL , Disease Models, Animal , NeuropeptidesABSTRACT
BACKGROUND: Toll-like receptor 3 (TLR3) plays an important role in the immune/inflammatory response in the nervous system and is a main pathological feature of Alzheimer's disease (AD). This study investigates the role of early activation of TLR3 in the pathophysiological process of AD. METHODS: In the experiment, the agonist of TLR3, Poly(I:C), was intraperitoneally injected into the APP/PS1 mouse model of AD and wild-type control mice starting from the age of 4 to 9 months. At the age of 14 months, behavioral tests were conducted. Western blot and immunohistochemistry staining were used to evaluate the level of amyloid ß-protein (Aß), the activation of inflammatory cells, and neuron loss. In addition, the levels of inflammatory cytokines were measured using a quantitative polymerase chain reaction. RESULTS: The results demonstrated that the early activation of TLR3 attenuated neuronal loss and neurobehavioral dysfunction. Moreover, the early activation of TLR3 reduced Aß deposition, inhibited the activation of microglia and astrocytes, and decreased the transcription of pro-inflammatory factors in the hippocampus. CONCLUSIONS: The results indicated that the activation of TLR3 by Poly (I:C) in the early stage of development of AD in a mouse model attenuated neuron loss and improved neurobehavioral functions. The underlying mechanisms could be attributed to its role in Aß clearance, the inhibition of glial cells, and the regulation of neuroinflammation in the hippocampus.
Subject(s)
Alzheimer Disease , Toll-Like Receptor 3 , Animals , Mice , Alzheimer Disease/genetics , Alzheimer Disease/pathology , Amyloid beta-Peptides , Amyloid beta-Protein Precursor/genetics , Disease Models, Animal , Mice, Transgenic , Presenilin-1/genetics , Toll-Like Receptor 3/genetics , Toll-Like Receptor 3/metabolismABSTRACT
OBJECTIVE: Progesterone receptor membrane component 2 (PGRMC2) belongs to the membrane-associated progesterone receptor family, which regulates multiple pathophysiological processes. However, the role of PGRMC2 in ischemic stroke remains unexplored. The present study sought to determine the regulatory role of PGRMC2 in ischemic stroke. METHODS: Male C57BL/6J mice were subjected to middle cerebral artery occlusion (MCAO). The protein expression level and localization of PGRMC2 were examined by western blotting and immunofluorescence staining. The gain-of-function ligand of PGRMC2 (CPAG-1, 45 mg/kg) was intraperitoneally injected into sham/MCAO mice, and brain infarction, blood-brain barrier (BBB) leakage, and sensorimotor functions were evaluated by magnetic resonance imaging, brain water content, Evans blue extravasation, immunofluorescence staining, and neurobehavioral tests. The astrocyte and microglial activation, neuronal functions, and gene expression profiles were revealed by RNA sequencing, qPCR, western blotting, and immunofluorescence staining after surgery and CPAG-1 treatment. RESULTS: Progesterone receptor membrane component 2 was elevated in different brain cells after ischemic stroke. Intraperitoneal delivery of CPAG-1 reduced infarct size, brain edema, BBB leakage, astrocyte and microglial activation, and neuronal death, and improved sensorimotor deficits after ischemic stroke. CONCLUSION: CPAG-1 acts as a novel neuroprotective compound that could reduce neuropathologic damage and improve functional recovery after ischemic stroke.
Subject(s)
Brain Injuries , Brain Ischemia , Ischemic Stroke , Stroke , Animals , Male , Mice , Blood-Brain Barrier/metabolism , Brain Injuries/pathology , Brain Ischemia/metabolism , Gain of Function Mutation , Infarction, Middle Cerebral Artery/pathology , Ischemic Stroke/pathology , Mice, Inbred C57BL , Receptors, Progesterone/metabolism , Stroke/pathologyABSTRACT
Alzheimer's disease (AD) has become the most common age-related dementia in the world and is currently incurable. Although many efforts have been made, the underlying mechanisms of AD remain unclear. Extracellular amyloid-beta deposition, intracellular tau hyperphosphorylation, neuronal death, glial cell activation, white matter damage, blood-brain barrier disruption, and other mechanisms all take part in this complicated disease, making it difficult to find an effective therapy. In the study of therapeutic methods, how to restore functional neurons and integrate myelin becomes the main point. In recent years, with the improvement and maturity of induced pluripotent stem cell technology and direct cell reprogramming technology, it has become possible to induce non-neuronal cells, such as fibroblasts or glial cells, directly into neuronal cells in vitro and in vivo. Remarkably, the induced neurons are functional and capable of entering the local neural net. These encouraging results provide a potential new approach for AD therapy. In this review, we summarized the characteristics of AD, the reprogramming technique, and the current research on the application of cellular reprogramming in AD. The existing problems regarding cellular reprogramming and its therapeutic potential for AD were also reviewed.
