miR-429-3p mediates memory decline by targeting MKP-1 to reduce surface GluA1- containing AMPA receptors in a mouse model of Alzheimer’s disease

Alzheimer ’s disease(AD) is a leading cause of dementia in the elderly.Mitogen-activated protein kinase phosphatase 1(MKP-1) plays a neuroprotective role in AD.However,the molecular mechanisms underlying the effects of MKP-1 on AD have not been extensively studied.MicroRNAs(miRNAs) regulate gene expression at the post-transcriptional level,thereby repressing mRNA translation.Here,we reported that the microRNA-429-3p(miR-429-3p) was significantly increased in the brain of APP23/PS45 AD model mice and N2AAPPAD model cells.We further found that miR-429-3p could downregulate MKP-1 expression by directly binding to its 3’-untranslated region(3’ UTR).Inhibition of miR-429-3p by its antagomir(A-miR-429) restored the expression of MKP-1 to a control level and consequently reduced the amyloidogenic processing of APP and Aβ accumulation.More importantly,intranasal administration of A-miR-429 successfully ameliorated the deficits of hippocampal CA1 long-term potentiation and spatial learning and memory in AD model mice by suppressing extracellular signal-regulated kinase(ERK1/2)-mediated GluAl hyperphosphorylation at Ser831 site,thereby increasing the surface expression of GluAl-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors(AMPARs).Together,these results demonstrate that inhibiting miR-429-3p to upregulate MKP-1 effectively improves cognitive and synaptic functions in AD model mice,suggesting that miR-429/MKP-1 pathway may be a novel therapeutic target for AD treatment.

Cellular apoptosis and Caspase-12 expression in a rat model of progressive spinal cord compression

BACKGROUND:Studies have demonstrated that the mechanisms underlying cellular apoptosis signal transduction focus on two pathways:intracellular mitochondria and extracellular death receptor.The current evidence supports that signal transduction of cellular apoptosis also includes endoplasmic reticulum stress signal transduction. OBJECTIVE:To observe Caspase-12 expression and cellular apoptosis following ischemia in rats with progressive spinal cord compression,and to verify the influence of endoplasmic reticulum stress on the apoptosis induced by spinal cord injury. DESIGN,TIME AND SETTING:A randomized,controlled,animal trial was performed at the Institute of Neuroscience in Chongqing Medical University between January and October in 2006. MATERIALS:Immunohistochemical kit,diaminobenzidine,and TUNEL kit were purchased from Beijing Zhongshan Biotechnology,China;rabbit anti-rat Caspase-12 monoclonal antibody was provided by Santa Cruz,USA. METHODS:Sixty Wistar rats,aged 3-4 months,were randomly assigned to a model group(n=50), which underwent spinal cord compression in the L_1 segment following L_1 laminectomy and articular process excision to establish a model of progressive spinal cord compression,and a sham-surgery group(n=10),which underwent only laminectomy.Starting with the first day after surgery,the rats were locally anesthetized,the skin was opened,and the screw was rotated by 1/4 of a cycle,twice weekly. MAIN OUTCOME MEASURES:At 3,7,14,21,and 28 days after surgery,rats from each group were anesthetized,and the spinal cords were resected.Pathological changes following spinal cord compression were determined using hematoxylin-eosin staining,Nissl dye,and transmission electron microscopy.The TUNEL method was used to observe neuronal apoptosis in the compressed spinal cord segments.Immunohistochemistry and Western blot were utilized to detect Caspase-12 expression in the compressed segments. RESULTS:Cellular swelling,neural degeneration,and altered endoplasmic reticulum structures were observed at 3 days following compression.Symptoms became gradually aggravated with increasing compression time.Compared with the sham-surgery group,the number of apoptotic neurons was remarkably increased in compressed segments of the model group(P<0.05),and Caspase-12 expression was also shown to increase(P<0.05). CONCLUSION:Neuronal apoptosis was a predominant pathological factor resulting in secondary spinal cord injury during progressive spinal cord compression,and Caspase-12 was shown to be possibly involved in neuronal apoptosis induced by progressive spinal cord compression.

Coexistence of dopamine-beta-hydroxylase and activated protein-2 alpha in rat cerebellar Purkinje cells

BACKGROUND:Tyrosine hydroxylase and phenylethanolamine-n-methyl transferase expression coexist in Purkinje cells of the rat cerebellum.Numerous reports have also been published addressing whether dopamine-beta-hydroxylase(DBH) expression exists in cerebellar Purkinje cells. OBJECTIVE:To investigate the coexistence of DBH and activator protein-2αexpression in rat cerebellar Purkinje cells. DESIGN,TIME AND SETTING:A cell morphological study was performed at the Institute of Neuroscience,Chongqing Medical University,China in May 2007. MATERIALS:Ten healthy Wistar rats,of either gender,aged 14 weeks,served as experimental animals.Rabbit anti-mouse DBH,goat anti-mouse activator protein-2αand rabbit anti-mouseβ-actin (Santa Cruz Biotechnology,Inc.,USA),horseradish peroxidase-labeled goat anti-rabbit IgG, FITC-labeled mouse anti-rabbit IgG,and Cy3-labeled mouse anti-goat IgG(Boster,Wuhan,China), were used in this study. METHODS:Immunohistochemical staining was used to measure the expression of DBH or activator protein-2α,with double-label immunofluorescence being employed to determine coexpression of both,in the cerebellum of 5 randomly selected rats.Western blot assay was utilized to determine the expression of DBH and activator protein-2αin the cerebellum of the remaining 5 rats. MAIN OUTCOME MEASURES:Expression,localization and coexistence of DBH and activator protein-2αin the cerebellum were measured separately. RESULTS:Immunohistochemical staining demonstrated that cerebellar Purkinje cells stained positive for DBH and activator protein-2α.Western blot assay also demonstrated DBH and activator protein-2αexpression in the cerebellum.Double-labeling immunofluorescence showed the coexistence of DBH and activator protein-2αin cerebellar Purkinje cells. CONCLUSION:Norepinephrine and activator protein-2αcoexist in rat cerebellar Purkinje cells.

MKP-1 reduces Aβ generation and alleviates cognitive impairments in Alzheimer’s disease models

Mitogen-activated protein kinase(MAPK)phosphatase 1(MKP-1)is an essential negative regulator of MAPKs by dephosphorylating MAPKs at both tyrosine and threonine residues.Dysregulation of the MAPK signaling pathway has been associated with Alzheimer’s disease(AD).However,the role of MKP-1 in AD pathogenesis remains elusive.Here,we report that MKP-1 levels were decreased in the brain tissues of patients with AD and an AD mouse model.The reduction in MKP-1 gene expression appeared to be a result of transcriptional inhibition via transcription factor specificity protein 1(Sp1)cis-acting binding elements in the MKP-1 gene promoter.Amyloid-β(Aβ)-induced Sp1 activation decreased MKP-1 expression.However,upregulation of MKP-1 inhibited the expression of both Aβprecursor protein(APP)andβ-site APP-cleaving enzyme 1 by inactivating the extracellular signal-regulated kinase 1/2(ERK)/MAPK signaling pathway.Furthermore,upregulation of MKP-1 reduced Aβproduction and plaque formation and improved hippocampal long-term potentiation(LTP)and cognitive deficits in APP/PS1 transgenic mice.Our results demonstrate that MKP-1 impairment facilitates the pathogenesis of AD,whereas upregulation of MKP-1 plays a neuroprotective role to reduce Alzheimer-related phenotypes.Thus,this study suggests that MKP-1 is a novel molecule for AD treatment.

Liquiritigenin promotes osteogenic differentiation and prevents bone loss via inducing auto-lysosomal degradation and inhibiting apoptosis

Osteoporosis(OP)is a debilitating skeletal abnormality involving bone remodeling and bone cell homeostasis characterized by decreased bone strength and high fracture risk.A novel therapeutic intervention for OP by manipulating cellular autophagy-apoptosis processes to promote skeletal homeostasis is presented.Protective effects of the naturally occurring plant extract Liquiritigenin(LG)were demonstrated in an ovariectomy(OvX)-OP mouse model and preosteoblast MC3T3-E1 cells.Micro-CT and histological staining assessments of skeletal phenotype were applied alongside detection of autophagy activity in osteocytes and MC3T3-E1 cells by transmission electron microscopy(TEM).The effects of LG on chloroquine(CQ)-and the apoptosis-inducing TS-treated osteogenic differentiations and status of lysosomes within MC3T3-E1 cells were analyzed by Neutral red,Alizarin red S and alkaline phosphatase(ALP)staining and Western blot assays.Treatment with LG prevented bone loss,increased osteogenic differentiation in vivo and in vitro,and inhibited osteoclast formation to some extent.TEM analyses revealed that LG can improve auto-lysosomal degradation within osteocytes from OVX mice and MC3T3-E1 cells.The abnormal status of lysosomes associated with CQ and TS treatments was notably alleviated by LG which also reduced levels of apoptosis-induced inhibition of osteogenic differentiation and averted abnormal osteogenic differentiation as a consequence of a blockage in autolysosome degradation.Overall,LG stimulates bone growth in Oovx mice through increased osteogenic differentiation and regulation of autophagyapoptosis mechanisms,presenting an auspicious natural therapy for Op.

Structure,function,and pathology of Neurexin-3

Neurexin-3 is primarily localized in the presynaptic membrane and forms complexes with various ligands located in the postsynaptic membrane.Neurexin-3 has important roles in synapse development and synapse functions.Neurexin-3 mediates excitatory presynaptic differentiation by interacting with leucine-rich-repeat transmembrane neuronal proteins.Meanwhile,neurexin-3 modulates the expression of presynapticα-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors andγ-aminobutyric acid A receptors by interacting with neuroligins at excitatory and inhibitory synapses.Numerous studies have documented the potential contribution of neurexin-3 to neurodegenerative and neuropsychiatric disorders,such as Alzheimer's disease,addiction behaviors,and other diseases,which raises hopes that understanding the mechanisms of neurexin-3 may hold the key to developing new strategies for related illnesses.This review comprehensively covers the literature to provide current knowledge of the structure,function,and clinical role of neurexin-3.

Estrogen deficiency exacerbates learning and memory deficits associated with glucose metabolism disorder in APP/PS1 double transgenic female mice

Alterations in glucose metabolism occur in the brain in the early stage of Alzheimer's disease(AD),and menopausal women have more severe metabolic dysfunction and are more prone to dementia than men.Although estrogen deficiency-induced changes in glucose metabolism have been previously studied in animal models,their molecular mechanisms in AD remain elusive.To investigate this issue,double transgenic(APP/PS1)female mice were subjected to bilateral ovariectomy at 3 months of age and were sacrificed 1 week,1 month and 3 months after surgery to simulate early,middle and late postmenopause,respectively.Our analysis demonstrated that estrogen deficiency exacerbates learning and memory deficits in this mouse model of postmenopause.Estrogen deficiency impairs the function of mitochondria in glucose metabolism.It is possible that the occurrence of AD is associated with the aberrant mitochondrial ERβ-mediated IGF-1/IGF-1R/GSK-3βsignaling pathway.In this study,we established a potential mechanism for the increased risk of AD in postmenopausal women and proposed a therapeutic target for AD due to postmenopause.