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Triptolide Inhibited Cytotoxicity of Differentiated PC12 Cells Induced by Amyloid-Beta????? via the Autophagy Pathway.

ABSTRACT: Evidence shows that an abnormal deposition of amyloid beta-peptide25-35 (A?25-35) was the primary cause of the pathogenesis of Alzheimer's disease (AD). And the elimination of A?25-35 is considered an important target for the treatment of AD. Triptolide (TP), isolated from Tripterygium wilfordii Hook.f. (TWHF), has been shown to possess a broad spectrum of biological profiles, including neurotrophic and neuroprotective effects. In our study investigating the effect and potential mechanism of triptolide on cytotoxicity of differentiated rat pheochromocytoma cell line (the PC12 cell line is often used as a neuronal developmental model) induced by Amyloid-Beta25-35 (A?25-35), we used 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) assay, flow cytometry, Western blot, and acridine orange staining to detect whether triptolide could inhibit A?25-35-induced cell apoptosis. We focused on the potential role of the autophagy pathway in A?25-35-treated differentiated PC12 cells. Our experiments show that cell viability is significantly decreased, and the apoptosis increased in A?25-35-treated differentiated PC12 cells. Meanwhile, A?25-35 treatment increased the expression of microtubule-associated protein light chain 3 II (LC3 II), which indicates an activation of autophagy. However, triptolide could protect differentiated PC12 cells against A?25-35-induced cytotoxicity and attenuate A?25-35-induced differentiated PC12 cell apoptosis. Triptolide could also suppress the level of autophagy. In order to assess the effect of autophagy on the protective effects of triptolide in differentiated PC12 cells treated with A?25-35, we used 3-Methyladenine (3-MA, an autophagy inhibitor) and rapamycin (an autophagy activator). MTT assay showed that 3-MA elevated cell viability compared with the A?25-35-treated group and rapamycin inhibits the protection of triptolide. These results suggest that triptolide will repair the neurological damage in AD caused by deposition of A?25-35 via the autophagy pathway, all of which may provide an exciting view of the potential application of triptolide or TWHF as a future research for AD.

SUBMITTER: Xu P

PROVIDER: S-EPMC4640509 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Triptolide Inhibited Cytotoxicity of Differentiated PC12 Cells Induced by Amyloid-Beta₂₅₋₃₅ via the Autophagy Pathway.

Xu Pengjuan P Li Zhigui Z Wang Hui H Zhang Xiaochen X Yang Zhuo Z

PloS one 20151110 11

Evidence shows that an abnormal deposition of amyloid beta-peptide25-35 (Aβ25-35) was the primary cause of the pathogenesis of Alzheimer's disease (AD). And the elimination of Aβ25-35 is considered an important target for the treatment of AD. Triptolide (TP), isolated from Tripterygium wilfordii Hook.f. (TWHF), has been shown to possess a broad spectrum of biological profiles, including neurotrophic and neuroprotective effects. In our study investigating the effect and potential mechanism of tri ...[more]

PMID: 26554937

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Project description:Alzheimer disease (AD) is usually accompanied by two prominent pathological features, cerebral accumulation of amyloid-β (Aβ) plaques and presence of MAPT/tau neurofibrillary tangles. Dysregulated clearance of Aβ largely contributes to its accumulation and plaque formation in the brain. Macroautophagy/autophagy is a lysosomal degradative process, which plays an important role in the clearance of Aβ. Failure of autophagic clearance of Aβ is currently acknowledged as a contributing factor to increased accumulation of Aβ in AD brains. In this study, we have identified crocetin, a pharmacologically active constituent from the flower stigmas of Crocus sativus, as a potential inducer of autophagy in AD. In the cellular model, crocetin induced autophagy in N9 microglial and primary neuron cells through STK11/LKB1 (serine/threonine kinase 11)-mediated AMP-activated protein kinase (AMPK) pathway activation. Autophagy induction by crocetin significantly increased Aβ clearance in N9 cells. Moreover, crocetin crossed the blood-brain barrier and induced autophagy in the brains' hippocampi of wild-type male C57BL/6 mice. Further studies in transgenic male 5XFAD mice, as a model of AD, revealed that one-month treatment with crocetin significantly reduced Aβ levels and neuroinflammation in the mice brains and improved memory function by inducing autophagy that was mediated by AMPK pathway activation. Our findings support further development of crocetin as a pharmacological inducer of autophagy to prevent, slow down progression, and/or treat AD.Abbreviations: Aβ: amyloid-β; ABCB1/P-gp/P-glycoprotein: ATP-binding cassette, subfamily B (MDR/TAP), member 1; AD: Alzheimer disease; AMPK/PRKAA: AMP-activated protein kinase; APP: amyloid beta (A4) precursor protein; ATG: autophagy related; BBB: blood-brain barrier; BECN1: beclin 1, autophagy related; CAMKK2/CaMKKβ: calcium/calmodulin-dependent protein kinase kinase 2, beta; CSE: Crocus sativus extract; CTSB: cathepsin B; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; GFAP: glial fibrillary acidic protein; GSK3B/GSK3β: glycogen synthase kinase 3 beta; Kp: brain partition coefficient; LRP1: low density lipoprotein receptor-related protein 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAP2: microtubule-associated protein 2; MAPK/ERK: mitogen-activated protein kinase; MAPT/tau: microtubule-associated protein tau; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; MTOR: mechanistic target of rapamycin kinase; MWM: Morris water maze; NFKB/NF-κB: nuclear factor of kappa light polypeptide gene enhancer in B cells; NMDA: N-methyl-d-aspartic acid; RPTOR: regulatory associated protein of MTOR; RPS6KB1/p70S6K: ribosomal protein S6 kinase 1; SQSTM1: sequestosome 1; SRB: sulforhodamine B; STK11/LKB1: serine/threonine kinase 11; TFEB: transcription factor EB; TSC2: TSC complex subunit 2; ULK1: unc-51 like kinase 1.

Project description:Complement inhibitor C4b-binding protein (C4BP) is synthesized in liver and pancreas and composed of 7 identical alpha chains and one unique beta chain. We showed previously that C4BP binds islet amyloid polypeptide (IAPP) and affects fibril formation in vitro. Now we found that polymeric C4BP inhibited lysis of human erythrocytes incubated with monomeric IAPP while no erythrocyte lysis was observed after incubation with preformed IAPP fibrils. In contrast, monomeric alpha chain of C4BP had significantly reduced activity. Further, addition of monomeric IAPP to a rat insulinoma cell line (INS-1) resulted in decreased cell viability, which was restored in the presence of physiological concentrations of C4BP. Accordingly, addition of C4BP rescued the ability of INS-1 cells and isolated rat islets to respond to glucose stimulation with insulin secretion, which was impaired in the presence of IAPP alone. C4BP was internalized together with IAPP into INS-1 cells and therefore we aimed to study its effect on gene expression. Pathway analyses of mRNA expression microarray data indicated that cells exposed to C4BP and IAPP in comparison to IAPP alone increased expression of genes involved in cholesterol synthesis. Depletion of cholesterol through methyl-Î²-cyclodextrin or cholesterol oxidase abolished the protective effect of C4BP on IAPP cytotoxicity of INS-1 cells. Also, inhibition of phosphoinositide 3-kinase but not NF-ÎºB had a similar effect. Taken together, one of the mechanisms by which C4BP protects beta-cells from IAPP cytotoxicity is by enhancing cholesterol synthesis. The INS-1 cells were grown as 5 separate clones for 10 passages before plating in a 12-well plate (Nunc) at 100.000 cells per well and grown in complete RPMI 1640 medium to 70% confluency for approximately 48 h. The cells were then challenged by adding 77 Î¼M monomeric IAPP alone or together with C4BP (0.6 Î¼M). DMSO (1%) used as solvent for IAPP as well as C4BP (0.6 Î¼M) alone were used as controls. RNA was extracted after 10h incubation and analysis carried out using Rat Gene 2.0 array chip (Affymetrix).

Project description:BackgroundTo observe the effects of triptolide (TP) on the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of glioma cells, and to explore the possible mechanisms of phenotypic changes in EMT.MethodsThe U87 and U251 glioma cell lines were treated TP. The Cell Counting Kit-8 (CCK-8) method was used to detect the half-maximal inhibitory concentration (IC50) of TP in these two cell lines and the inhibition of cell proliferation at the IC50 concentration. The wound-healing experiment and Transwell invasion assay were used to detect the cells' migration and invasion abilities, respectively. Using western blot protocol, the expression levels of the EMT markers were analyzed, and the levels of the autophagy markers were also detected. The pEGFP-C2-LC3B plasmid was transfected into glioma cells, and the effect of TP on autophagy was detected by immunofluorescence. A subcutaneous tumor model in nude mice was established to observe the effect of TP on cell proliferation in vivo, and immunohistochemistry (IHC) was used to detect the expression levels of EMT markers in mouse tumor tissues.ResultsTP significantly inhibited the proliferation of U87 and U251 cells in a dose- and time-dependent manner. TP had a significant inhibitory effect on the migration and invasion of U87 and U251 cells. Western blot showed that TP reversed the process of EMT in glioma cells, which was evidenced by the upregulated expression of the epithelial marker E-cadherin, and the downregulated expression of the mesenchymal markers N-cadherin, Vimentin, ZEB1, Snail, and Slug. TP increased autophagy in glioma cells, increased the LC3B II/I ratio, and upregulated Beclin-1 and Atg-7 expression. Immunofluorescence showed that the number of autophagosomes increased significantly after TP was applied to cells. In the nude mouse subcutaneous tumor model, experiments revealed an inhibitory effect of TP on glioma cell proliferation in vivo. IHC confirmed that the expression of E-cadherin was upregulated in mouse tumor tissues, while the expression levels of N-Cadherin and Vimentin were downregulated.ConclusionsTP can inhibit glioma cell proliferation, migration, and invasion, and reverse EMT progression. The possible mechanism of EMT reversal in glioma cells is that TP induces autophagy.

Dataset Information

Triptolide Inhibited Cytotoxicity of Differentiated PC12 Cells Induced by Amyloid-Beta????? via the Autophagy Pathway.

Publications

Triptolide Inhibited Cytotoxicity of Differentiated PC12 Cells Induced by Amyloid-Beta₂₅₋₃₅ via the Autophagy Pathway.

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