Jijun J Xu

Cleveland Clinic, Cleveland, Ohio, United States

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Publications (8)39.01 Total impact

  • Dataset: 1104.full
    No preview · Dataset · Jan 2015
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    [Show abstract] [Hide abstract] ABSTRACT: Amyloid-induced microglial activation and neuroinflammation impair central synapses and memory function, although the mechanism remains unclear. Neuroligin 1 (NLGN1), a postsynaptic protein found in central excitatory synapses, governs excitatory synaptic efficacy and plasticity in the brain. Here we found, in rodents, that amyloid fibril-induced neuroinflammation enhanced the interaction between histone deacetylase 2 and methyl-CpG-binding protein 2, leading to suppressed histone H3 acetylation and enhanced cytosine methylation in the Nlgn1 promoter region and decreased NLGN1 expression, underlying amyloid-induced memory deficiency. Manipulation of microglia-associated neuroinflammation modulated the epigenetic modification of the Nlgn1 promoter, hippocampal glutamatergic transmission and memory function. These findings link neuroinflammation, synaptic efficacy and memory, thus providing insight into the pathogenesis of amyloid-associated diseases.
    Full-text · Article · Jan 2014 · Nature Neuroscience
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    [Show abstract] [Hide abstract] ABSTRACT: Patients receiving paclitaxel often develop peripheral neuropathies. We found that a novel selective cannabinoid CB2 receptor agonist (MDA7) prevents paclitaxel-induced mechanical allodynia in rats and mice. Here we investigated gene expression profiling in the lumbar spinal cord after 14-day treatment of MDA7 in paclitaxel animals and analyzed possible signaling pathways underlying the preventive effect of MDA7 on paclitaxel-induced neuropathy. Peripheral mechanical allodynia was induced in rats or mice receiving intraperitoneal (i.p.) injection of paclitaxel at a dose of 1 mg/kg daily for four consecutive days. MDA7 was administered at a dose of 15 mg/kg 15 min before paclitaxel and then continued daily for another 10 days. Whole-genome gene expression profiling in the lumbar spinal cord of MDA7 and paclitaxel-treated rats was investigated using microarray analysis. The Ingenuity Pathway Analysis was performed to determine the potential relevant canonical pathways responsible for the effect of MDA7 on paclitaxel-induced peripheral neuropathy. We observed that the inflammatory molecular networks including tumor necrosis factor (TNF), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), transforming growth factor beta (TGFβ), and mitogen-activated protein kinases (MAPK) signaling are most relevant to the preventive effect of MDA7 on paclitaxel-induced peripheral neuropathy. In addition, genes encoding molecules that are important in central sensitization such as glutamate transporters and N-methyl-D-aspartate receptor 2B (NMDAR2B), and neuro-immune related genes such as neuronal nitric oxide synthase (nNOS1), chemokine CX3CL1 (a mediator for microglial activation), toll-like receptor 2 (TLR2), and leptin were differentially modulated by MDA7. The preventive effect of MDA7 on paclitaxel-induced peripheral allodynia in rats may be associated with genes involved in signal pathways in central sensitization, microglial activation, and neuroinflammation in the spinal cord.
    Full-text · Article · Dec 2013 · Neuroscience
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    [Show abstract] [Hide abstract] ABSTRACT: The abnormal accumulation of amyloid fibrils in the brain is pathognomonic of Alzheimer's disease. Amyloid fibrils induce significant neuroinflammation characterized by the activation of microglia and impairment of synaptic plasticity in the brain that eventually leads to cognitive decline. Chemokine fractalkine receptor (CX3CR1) is primarily located in the microglia in the brain and its role in the amyloid fibril-induced neuroinflammation and memory deficiency remains debated. We found that bilateral microinjection of amyloid beta (Aβ)1-40 fibrils into the hippocampal CA1 area of rats resulted in significant upregulation of CX3CR1 messenger RNA (mRNA) and protein expression (via increasing histone H3 acetylation in the Cx3cr1 promoter region), synaptic dysfunction, and cognitive impairment, compared with the control group. Suppressing CX3CR1 signaling with CX3CR1 small interfering RNA in rats injected with Aβ1-40 fibrils blunted Aβ1-40-induced CX3CR1 upregulation, microglial activation, interleukin-1β expression, restored basal glutamatergic strength and electric stimuli-induced long-term potentiation, and cognitive capacities. These findings suggest that activation of CX3CR1 plays an important role in the neuroinflammatory response and Aβ-induced neuroinflammation and neurotoxicity.
    Full-text · Article · Jul 2013 · Neurobiology of aging
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    [Show abstract] [Hide abstract] ABSTRACT: Enabling formulations based on hydroxypropyl-β-cyclodextrins (HPβCD), micellar preparation, and liposomes have been designed to deliver the racemic mixture of a lipophilic cannabinoid type 2 agonist, MDA7. The antiallodynic effects of MDA7 formulated in these three different systems were compared after intravenous (i.v.) administration in rats. Stoichiometry of the inclusion complex formed by MDA7 in HPβCD was determined by continuous variation plot, electrospray ionization-mass spectrometry (ESI-MS) analysis, phase solubility, and nuclear magnetic resonance studies and indicate formation of exclusively 1:1 adduct. Morphology and particle sizes determined by dynamic light scattering and transmission electron microscopy show the presence of a homogeneous population of closed round-shaped oligolamellar MDA7 containing liposomes, with an average size of 118 nm [polydispersity index (PDI) 0.03]. Monodisperse micelles exhibited an average size of 14 nm (PDI 0.09). HPβCD-based formulation administrated in vivo was composed of two discrete particles populations with a narrow size distribution of 3 nm (PDI 0.04) and 510 nm (PDI 0.02). HPβCD-based formulation dramatically improved antiallodynic effect of MDA7 in comparison with the liposomes preparation. Through inclusion complexation and possibly formation of aggregates, HPβCD can enhance the aqueous solubility of lipophilic drugs, thereby improving their bioavailability for i.v. administration. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
    Full-text · Article · Feb 2013 · Journal of Pharmaceutical Sciences
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    [Show abstract] [Hide abstract] ABSTRACT: Cannabinoid type 2 (CB(2)) agonists are neuroprotective and appear to play modulatory roles in neurodegenerative processes in Alzheimer's disease. We have studied the effect of 1-((3-benzyl-3-methyl-2,3-dihydro-1-benzofuran-6-yl) carbonyl) piperidine (MDA7)-a novel selective CB(2) agonist that lacks psychoactivity-on ameliorating the neuroinflammatory process, synaptic dysfunction, and cognitive impairment induced by bilateral microinjection of amyloid-β (Aβ)(1-40) fibrils into the hippocampal CA1 area of rats. In rats injected with Aβ(1-40) fibrils, compared with the administration of intraperitoneal saline for 14 days, treatment with 15 mg/kg of intraperitoneal MDA7 daily for 14 days (1) ameliorated the expression of CD11b (microglia marker) and glial fibrillary acidic protein (astrocyte marker), (2) decreased the secretion of interleukin-1β, (3) decreased the upsurge of CB(2) receptors, (4) promoted Aβ clearance, and (5) restored synaptic plasticity, cognition, and memory. Our findings suggest that MDA7 is an innovative therapeutic approach for the treatment of Alzheimer's disease.
    Full-text · Article · Jul 2012 · Neurobiology of aging
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    [Show abstract] [Hide abstract] ABSTRACT: Peripheral neuropathy is a major dose-limiting toxicity of chemotherapy, especially after multiple courses of paclitaxel. The development of paclitaxel-induced neuropathy is associated with the activation of microglia followed by the activation and proliferation of astrocytes, and the expression and release of proinflammatory cytokines in the spinal dorsal horn. Cannabinoid type 2 (CB(2)) receptors are expressed in the microglia in neurodegenerative disease models. To explore the potential of CB(2) agonists for preventing paclitaxel-induced neuropathy, we designed and synthesized a novel CB(2)-selective agonist, namely, MDA7. The effect of MDA7 in preventing paclitaxel-induced allodynia was assessed in rats and in CB(2)(+/+) and CB(2)(-/-) mice. We hypothesized that the CB(2) receptor functions in a negative-feedback loop and that early MDA7 administration can blunt the neuroinflammatory response to paclitaxel and prevent mechanical allodynia through interference with specific signaling pathways. We found that MDA7 prevents paclitaxel-induced mechanical allodynia in rats and mice in a dose- and time-dependent manner without compromising paclitaxel's antineoplastic effect. MDA7's neuroprotective effect was absent in CB(2)(-/-) mice and was blocked by CB(2) antagonists, suggesting that MDA7's action directly involves CB(2) receptor activation. MDA7 treatment was found to interfere with early events in the paclitaxel-induced neuroinflammatory response as evidenced by relatively reduced toll-like receptor and CB(2) expression in the lumbar spinal cord, reduced levels of extracellular signal-regulated kinase 1/2 activity, reduced numbers of activated microglia and astrocytes, and reduced secretion of proinflammatory mediators in vivo and in in vitro models. Our findings suggest an innovative therapeutic approach to prevent chemotherapy-induced neuropathy and may permit more aggressive use of active chemotherapeutic regimens with reduced long-term sequelae.
    Full-text · Article · Mar 2012 · Anesthesia and analgesia
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    [Show abstract] [Hide abstract] ABSTRACT: Cannabinoid receptor 2 (CB2) agonists have recently gained attention as potential therapeutic targets in the management of neuropathic pain. In this study, we characterized the pharmacological profile of the novel compound N'-[(3Z)-1-(1-hexyl)-2-oxo-1,2-dihydro-3H-indol-3-ylidene]benzohydrazide (MDA19), a CB2 agonist. We used radioligand binding assays and multiple in vitro functional assays at human and rat CB(1) and CB(2) receptors. The effects of MDA19 in reversing neuropathic pain were assessed in various neuropathic pain models in rats and in CB2(+/+) and CB2(-/-) mice. MDA19 displayed 4-fold-higher affinity at the human CB(2) than at the human CB1 receptor (K(i) = 43.3 +/- 10.3 vs 162.4 +/- 7.6 nM) and nearly 70-fold-higher affinity at the rat CB2 than at the rat CB1 receptor (K(i) = 16.3 +/- 2.1 vs 1130 +/- 574 nM). In guanosine triphosphate (GTP)gamma[(35)S] functional assays, MDA19 behaved as an agonist at the human CB1 and CB2 receptors and at the rat CB1 receptor but as an inverse agonist at the rat CB2 receptor. In 3',5'-cyclic adenosine monophosphate (cAMP) assays, MDA19 behaved as an agonist at the rat CB1 receptor and exhibited no functional activity at the rat CB(2) receptor. In extracellular signal-regulated kinases 1 and 2 activation assays, MDA19 behaved as an agonist at the rat CB2 receptor. MDA19 attenuated tactile allodynia produced by spinal nerve ligation or paclitaxel in a dose-related manner in rats and CB2(+/+) mice but not in CB2(-/-) mice, indicating that CB2 receptors mediated the effects of MDA19. MDA19 did not affect rat locomotor activity. We found that MDA19 exhibited a distinctive in vitro functional profile at rat CB2 receptors and behaved as a CB1/CB2 agonist in vivo, characteristics of a protean agonist. MDA19 has potential for alleviating neuropathic pain without producing adverse effects in the central nervous system.
    Full-text · Article · Jul 2010 · Anesthesia and analgesia