Substance P activates ADAM9 mRNA expression and induces α-secretase-mediated amyloid precursor protein cleavage.
ABSTRACT Altered levels of Substance P (SP), a neuropeptide endowed with neuroprotective and anti-apoptotic properties, were found in brain areas and spinal fluid of Alzheimer's disease (AD) patients. One of the hallmarks of AD is the abnormal extracellular deposition of neurotoxic beta amyloid (Aβ) peptides, derived from the proteolytic processing of amyloid precursor protein (APP). In the present study, we confirmed, the neurotrophic action of SP in cultured rat cerebellar granule cells (CGCs) and investigated its effects on APP metabolism. Incubation with low (5 mM) potassium induced apoptotic cell death of CGCs and amyloidogenic processing of APP, whereas treatment with SP (200 nM) reverted these effects via NK1 receptors. The non-amyloidogenic effect of SP consisted of reduction of Aβ(1-42), increase of sAPPα and enhanced α-secretase activity, without a significant change in steady-state levels of cellular APP. The intracellular mechanisms whereby SP alters APP metabolism were further investigated by measuring mRNA and/or steady-state protein levels of key enzymes involved with α-, β- and γ-secretase activity. Among them, Adam9, both at the mRNA and protein level, was the only enzyme to be significantly down-regulated following the induction of apoptosis (K5) and up-regulated after SP treatment. In addition to its neuroprotective properties, this study shows that SP is able to stimulate non-amyloidogenic APP processing, thereby reducing the possibility of generation of toxic Aβ peptides in brain.
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ABSTRACT: Reduced levels of Substance P (SP), an endogenous neuropeptide endowed with neuroprotective and anti-apoptotic properties, have been found in brain and spinal fluid of Alzheimer's disease (AD) patients. Potassium (K(+)) channel dysfunction is implicated in AD development and the amyloid-β (Aβ)-induced up-regulation of voltage-gated potassium channel subunits could be considered a significant step in Aβ brain toxicity. The aim of this study was to evaluate whether SP could reduce, in vivo, Aβ-induced overexpression of Kv subunits. Rats were intracerebroventricularly infused with amyloid-β 25-35 (Aβ25-35, 20 µg) peptide. SP (50 µg/Kg, i.p.) was daily administered, for 7 days starting from the day of the surgery. Here we demonstrate that the Aβ infused rats showed impairment in cognitive performances in the Morris water maze task 4 weeks after Aβ25-35 infusion and that this impairing effect was prevented by SP administration. Kv1.4, Kv2.1 and Kv4.2 subunit levels were quantified in hippocampus and in cerebral cortex by Western blot analysis and immunofluorescence. Interestingly, SP reduced Kv1.4 levels overexpressed by Aβ, both in hippocampus and cerebral cortex. Our findings provide in vivo evidence for a neuroprotective activity of systemic administration of SP in a rat model of AD and suggest a possible mechanism underlying this effect.PLoS ONE 11/2013; 8(11):e78036. DOI:10.1371/journal.pone.0078036 · 3.53 Impact Factor
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ABSTRACT: Recent experiments have explored the impact of Wnt/β-catenin signaling and Substance P (SP) on the regulation of osteogenesis. However, the molecular regulatory mechanisms of SP on the formation of osteoblasts is still unknown. In this study, we investigated the impact of SP on the differentiation of MC3T3-E1 cells. The osteogenic effect of SP was observed at different SP concentrations (ranging from 10-10 to 10-8 M). To unravel the underlying mechanism, the MC3T3-E1 cells were treated with SP after the pretreatment by neurokinin-1 (NK1) antagonists and Dickkopf-1 (DKK1) and gene expression levels of Wnt/β-catenin signaling pathway components, as well as osteoblast differentiation markers (collagen type I, alkaline phosphatase, osteocalcin, and Runx2), were measured using quantitative polymerase chain reaction (PCR). Furthermore, protein levels of Wnt/β-catenin signaling pathway were detected using Western blotting and the effects of SP, NK1 antagonist, and DKK1 on β-catenin activation were investigated by immunofluorescence staining. Our data indicated that SP (10-9 to 10-8 M) significantly up-regulated the expressions of osteoblastic genes. SP (10-8 M) also elevated the mRNA level of c-myc, cyclin D1, and lymphocyte enhancer factor-1 (Lef1), as well as c-myc and β-catenin protein levels, but decreased the expression of Tcf7 mRNA. Moreover, SP (10-8 M) promoted the transfer of β-catenin into nucleus. The effects of SP treatment were inhibited by the NK1 antagonist and DKK1. These findings suggest that SP may enhance differentiation of MC3T3-E1 cells via regulation of the Wnt/β-catenin signaling pathway.International Journal of Molecular Sciences 04/2014; 15(4):6224-40. DOI:10.3390/ijms15046224 · 2.34 Impact Factor
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ABSTRACT: Neurokinin B (NKB) is a member of the tachykinin family of neuropeptides that have neuroinflammatory, neuroimmunological, and neuroprotective functions. In a neuroprotective role, tachykinins can help protect cells against the neurotoxic processes observed in Alzheimer's disease. A change in copper homeostasis is a clear feature of Alzheimer's disease and the disregulation may be a contributory factor in toxicity. Copper has recently been shown to interact with neurokinin A and neuropeptide γ and can lead to generation of reactive oxygen species and peptide degradation, which suggests that copper may have a place in tachykinin function and potentially misfunction. To explore this we have utilized a range of spectroscopic techniques to show that NKB, but not substance P, can bind Cu(II) in an unusual [Cu(II)(NKB)2] neutral complex that utilizes two N-terminal amine and two imidazole nitrogen ligands (from each molecule of NKB) and the binding substantially alters the structure of the peptide. Using 1321N1 astrocytoma cells we show that copper can enter the cells and subsequently open plasma membrane calcium channels, but when bound to neurokinin B copper ion uptake is inhibited. This data suggests a novel role for neurokinin B in protecting cells against copper induced calcium changes and implicates the peptide in synaptic copper homeostasis.ACS Chemical Neuroscience 07/2013; DOI:10.1021/cn4000988 · 4.21 Impact Factor