Research articleCurcumin attenuates paraquat-induced cell death in human neuroblastoma cells through modulating oxidative stress and autophagy
Introduction
AlzheimeÅs disease (AD) pathology is characterized by the accumulation of extracellular plaques, including aggregated amyloid-Ī² (AĪ²) peptide, and intracellular tangles in the brain. Genetic evidence implicates deregulated AĪ² homeostasis as an early event of AD pathology [29]. For this reason, most AD therapies have targeted at AĪ² production. Autophagy is involved in the intracellular turnover of proteins and cell organelles and has a key role in regulating cell fates in response to stress [22], [25]. Alteration of endocytic pathway can impede turnover of autophagic vacuoles and lead to diseases [33]. The modulation of autophagy was highlighted as a sophisticated mechanism in AD, since the induction and activation of autophagy can promote AĪ² degradation and consequently reduce AD pathology [37]. Disrupted autophagy would lead to the accumulation of intracellular proteins, and the aberration of the lysosomal pathway might lead to neurodegeneration. Reportedly, the impaired clearance of autophagic vacuoles was observed in AD animal models and also AD patients [4], [24].
Nowadays, therapies of AD patients are mostly palliative cares and rarely improve the disease symptoms. For this reason, the AD aetiology is attracted scientist attentions to investigate the causative molecular mechanisms of the disease, and develop novel therapeutic options. Curcumin is a naturally-occurring polyphenolic compound, extracted from turmeric, the powered rhizome of the plant Curcuma longa. Curcumin comprises 3 to 5% of turmeric and functions as pharmacologically active component [40]. Several in vitro, animal and human studies demonstrated potent antioxidant and anti-inflammatory properties of curcuminoids [3], [6], [32], [38]. The ability of curcumin to reduce AĪ² production, inflammation, and oxidative stress highlights its potential use for AD treatment.
In the present study, the exposure of SH-SY5Y cells to paraquat resulted in the increase of APP production/accumulation, exerted oxidative stress, and eventually led to cell death. Curcumin exhibited the protective roles on paraquat-induced neurotoxicity and its mechanisms of action involved in the activation of autophagy in human neuroblastoma SH-SY5Y cells.
Section snippets
Chemical and reagents
Curcumin (Sigma, USA) was dissolved in 100% DMSO (Dimethyl sulfoxide) to prepare a stock solution (10Ā mM), aliquoted, and stored at ā20Ā Ā°C. Paraquat was reconstituted with DMSO, aliquoted, and stored at ā20Ā Ā°C. Chloroquine, N-acetylcysteine (NAC), and 2ā²,7ā²- dichlorofluorescin diacetate (DCFDA) were supplied by Sigma (Sigma, USA). The following antibodies were used: mouse anti-Alzheimerās Precursor Protein A4, a.a. 66ā81 of APP (N-terminal), clone 22C11, rabbit anti-LC3-I/II antibody, goat
Effects of Curcumin on the mRNA Expression Levels of APP, PSI and PSII in paraquat-induced SH-SY5Y cells
To determine whether paraquat and curcumin have an effect on genes involving in AD pathology (APP, PS1 and PSII), the expression of these genes were examined. The exposure to 0.5Ā mM paraquat for 24Ā h caused a significant increase of APP and PSI mRNA (Fig. 1AāC). The pretreatment of 5Ā Ī¼M curcumin for 24Ā h significantly reduced APP expression (Fig. 1B), while the direct treatment of curcumin alone to SH-SY5Y cells significantly downregulated PsiI (Fig. 1D). Thus, curcumin could reduce
Discussion
Paraquat has been widely used to induce neuronal cells death, where it can affect on cell morphology and proliferation [11], [23], [28]. In this study, paraquat caused the degeneration of SH-SY5Y cells in a dose-dependent manner (Fig. 3B). Several studies demonstrated that paraquat is a neurotoxicant and associated with neurodegenerative diseases, such as Alzheimerās disease [5], [35]. Amyloid precursor protein (APP), Presenilin-1 (PSI), and Presenilin-2 (PSII) genes are primarily responsible
Conclusion
In conclusion, this study highlighted the neuroprotective functions of curcumin. Curcumin can protect against paraquat-induced neuronal cell death through suppressing ROS levels and enhancing autophagy activation. This suggested that curcumin serve as a promising therapeutic compound of neurodegenerative diseases, such as AlzheimeÅs disease. There is still a great need to improve efficacy and bioavailability of curcumin for future clinical uses.
Acknowledgments
This work was supported by the Cerebos Research Award, the National Research Council of Thailand, and Suranaree University of Technology Research and Development Fund.
References (49)
- et al.
Curcumin alleviates oxidative stress and mitochondrial dysfunction in astrocytes
Neuroscience
(2016) - et al.
Phenolic anti-inflammatory antioxidant reversal of Abeta-induced cognitive deficits and neuropathology
Neurobiol. Aging
(2001) - et al.
Autophagy, a guardian against neurodegeneration
Semin. Cell Dev. Biol.
(2010) - et al.
Genetic evidence for the involvement of lipid metabolism in Alzheimer's disease
Biochim. Biophys. Acta
(2010) - et al.
Curcumin-induced autophagy contributes to the decreased survival of oral cancer cells
Arch. Oral Biol.
(2012) - et al.
Docosahexaenoic acid prevents paraquat-induced reactive oxygen species production in dopaminergic neurons via enhancement of glutathione homeostasis
Biochem. Biophys. Res. Commun.
(2015) - et al.
Curcumin attenuates glutamate neurotoxicity in the hippocampus by suppression of ER stress-associated TXNIP/NLRP3 inflammasome activation in a manner dependent on AMPK
Toxicol. Appl. Pharmacol.
(2015) - et al.
Expression of APP pathway mRNAs and proteins in Alzheimer's disease
Brain Res.
(2007) - et al.
Curcumin induces permanent growth arrest of human colon cancer cells: link between senescence and autophagy
Mech. Ageing Dev.
(2012) - et al.
Curcumin inhibits Rift Valley fever virus replication in human cells
J. Biol. Chem.
(2012)