Modulation of Hydrogen Peroxide-Induced Oxidative Stress in Human Neuronal Cells by Thymoquinone-Rich Fraction and Thymoquinone via Transcriptomic Regulation of Antioxidant and Apoptotic Signaling Genes.

Nigella sativa Linn. (N. sativa) and its bioactive constituent Thymoquinone (TQ) have demonstrated numerous pharmacological attributes. In the present study, the neuroprotective properties of Thymoquinone-rich fraction (TQRF) and TQ against hydrogen peroxide- (H2O2-) induced neurotoxicity in differentiated human SH-SY5Y cells were investigated. TQRF was extracted using supercritical fluid extraction while TQ was acquired commercially, and their effects on H2O2 were evaluated using cell viability assay, reactive oxygen species (ROS) assay, morphological observation, and multiplex gene expression. Both TQRF and TQ protected the cells against H2O2 by preserving the mitochondrial metabolic enzymes, reducing intracellular ROS levels, preserving morphological architecture, and modulating the expression of genes related to antioxidants (SOD1, SOD2, and catalase) and signaling genes (p53, AKT1, ERK1/2, p38 MAPK, JNK, and NF-κß). In conclusion, the enhanced efficacy of TQRF over TQ was likely due to the synergism of multiple constituents in TQRF. The efficacy of TQRF was better than that of TQ alone when equal concentrations of TQ in TQRF were compared. In addition, TQRF also showed comparable effects to TQ when the same concentrations were tested. These findings provide further support for the use of TQRF as an alternative to combat oxidative stress insults in neurodegenerative diseases.

Mechanistic basis for protection of differentiated SH-SY5Y cells by oryzanol-rich fraction against hydrogen peroxide-induced neurotoxicity.

BACKGROUND: Apoptosis is often the end result of oxidative damage to neurons. Due to shared pathways between oxidative stress, apoptosis and antioxidant defence systems, an oxidative insult could end up causing cellular apoptosis or survival depending on the severity of the insult and cellular responses. Plant bioresources have received close attention in recent years for their potential role in regulating the pathways involved in apoptosis and oxidative stress in favour of cell survival. Rice bran is a bioactive-rich by-product of rice milling process. It possesses antioxidant properties, making it a promising source of antioxidants that could potentially prevent oxidative stress-induced neurodegenerative diseases. METHODS: Thus, the present study investigated the neuroprotective properties of oryzanol-rich fraction (ORF) against hydrogen peroxide (H2O2)-induced neurotoxicity in differentiated human neuroblastoma SH-SY5Y cells. ORF was extracted from rice bran using a green technology platform, supercritical fluid extraction system. Furthermore, its effects on cell viability, morphological changes, cell cycle, and apoptosis were evaluated. The underlying transcriptomic changes involved in regulation of oxidative stress, apoptosis and antioxidant defence systems were equally studied. RESULTS: ORF protected differentiated SH-SY5Y cells against H2O2-induced neurotoxicity through preserving the mitochondrial metabolic enzyme activities, thus reducing apoptosis. The mechanistic basis for the neuroprotective effects of ORF included upregulation of antioxidant genes (catalase, SOD 1 and SOD 2), downregulation of pro-apoptotic genes (JNK, TNF, ING3, BAK1, BAX, p21 and caspase-9), and upregulation of anti-apoptotic genes (ERK1/2, AKT1 and NF-Kß). CONCLUSION: These findings suggest ORF may be an effective antioxidant that could prevent oxidative stress-induced neurodegenerative disorders.