Increased nuclear P-STAT3 levels were decreased by taxifolin (10 ~ 50 M; F3, 12= 12. 66, P < 0. 0005), cilostazol (10, 30, 50 M; F3, 8= 136. 2, P < 0. 0001), and by 20 M AG490 (p <0. 05), suggesting P-STAT3 expression was mediated via P-JAK2 activation (Fig 2B and 2C). cells, taxifolin, cilostazol, and resveratrol all failed to suppress A1-42-stimulated P-STAT3 and BACE1 expression. Consequently, taxifolin and cilostazol were found to significantly decrease lipopolysaccharide (110 g/ml)-induced iNOS and COX-2 expressions, and nitrite production in cultured BV-2 microglia cells and to increase N2a cell viability. In conclusion, taxifolin and cilostazol strongly inhibited amyloidogenesis in a synergistic manner by suppressing P-JAK2/P-STAT3-coupled NF-B-linked BACE1 expression via the up-regulation of SIRT1. == Introduction == Alzheimers disease (AD) is characterized by increased amyloid (A)-containing extracellular plaque and intracellular neurofibrillary tangles, which are associated with synaptic failure and cognitive deficits [1]. Enhanced amyloidogenic processing of amyloid precursor protein (APP) by - and -secretase increases intracellular level of soluble oligomeric A, which results in pronounced synaptic failure and eventually in memory decline [2, 3]. Theoretically, A accumulation can be CH5138303 reduced in AD patients by suppressing A production or enhancing A degradation and clearance. A membrane-associated C-terminal fragment of APP, C99, is liberated by the action of -secretase, and this is subsequently cleaved by -secretase to produce A peptide [4]. BACE1 (-secretase, a membrane-bound aspartyl protease -site APP cleaving enzyme 1) is a rate-limiting enzyme for -amyloid production [5]. The expression of BACE1 protein and its activity have been demonstrated to be elevated in the brains of AD patients [6, 7]. Buggia-Prevot et al. [8] proposed A142acts as Rabbit Polyclonal to MMP-7 a regulator of BACE1, and suggested exacerbated A production modulates BACE1 promoter transactivation CH5138303 and its CH5138303 activity via an NF-B-dependent pathway. Furthermore, A has been shown to activate nuclear transcription factor NF-B [9, 10], which is activated during the early stages of AD, where RelA/p65 plays a critical role in neurons and astrocytes surrounding amyloid plaques in the brain, and elevates oxidative stress [11]. In addition , constitutive Janus kinase 2 (JAK2)/signal transducer and activator of transcription 1 (STAT1) signaling has been demonstrated to contribute to endogenous BACE1 expression and subsequent A generation in neurons, and inhibition of the JAK2/STAT1 signaling pathway by AG490 (a JAK2 inhibitor) reduced the expression of endogenous BACE1 and A production[12]. Grivennikov and Karin [13] postulated STAT3-mediated nuclear NF-B activation plays an important role in the pathogenesis of cancer and neurodegenerative disease, despite the fact NF-B is not the only transcription factor that cooperates with STAT3. Taxifolin (dihydroquercetin, (2R, 3R)-2-(3, 4-dihydroxyphenyl)-3, 5, 7-trihydroxy-2, 3-dihydrochromen-4-one) is a potent flavonoid found in onions, French maritime pine bark, and milk thistle [14], and has been shown to ameliorate cerebral ischemia-reperfusion injury in rats due to its anti-oxidative effect and to modulate NF-B activation [15]. In addition , cilostazol (OPC-13013, 6-[4-(1-cyclohexyl-1H-tetrazol-5-yl) butoxy]-3, 4-dihydro-2-(1H)-quinolinone) increases intracellular cAMP levels by inhibiting type 3 phosphodiesterase, and recently, was reported to improve memory impairment induced by an intracerebroventricular injection of A2535in C57BL/6J mice [16]. Previous studies have shown [17, 18], cilostazol inhibits proinflammatory factor (including remnant lipoprotein particle, TNF and LPS)-stimulated increases in IB degradation and NF-B p65 activity, and thus, suppresses the productions of inflammatory cytokines. Interestingly, Paris et al. [19] showed NF-B inhibitors decreased both A140and A142production and suggested NF-B inhibitors might be of therapeutic importance for the treatment of AD. It is generally said that the currently available hitting-one-target drugs are insufficient for the treatment of AD, and thus, research designed to identify drug therapies that target multiple action sites is attracting more attention. Considering these points of view, combinatorial drug therapy that target multiple pathogenic factors are worthy of investigation for prevention and treatment of AD. For this reason, we investigated the efficacies of taxifolin alone and in combination with cilostazol with respect to the regulation of BACE1, A accumulation, and the inhibition of neuroinflammation with a view towards possible intervention in Alzheimers disease. In CH5138303 the present study, we examined the inhibitory effect of taxifolin and taxifolin plus cilostazol on the JAK2/STAT3/NF-B signaling axis in A production in N2a cells stably expressing human APP Swedish mutation (N2a Swe cells) with focus on the suppressive effects of taxifolin and of CH5138303 taxifolin plus cilostazol on the A-induced mRNA and protein expressions.
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