Synergistic Neuroprotection Through Epigenetic Modulation by Combined Curcumin-Enriched Turmeric Extract and L-Ascorbic Acid in Oxidative Stress-Induced SH-SY5Y Cell Damage

Abstract

Epigenetic modulation plays a crucial role in neuroprotection by regulating cellular responses to stress, inflammation, and oxidative damage, particularly in neurodegenerative diseases. Recognizing the therapeutic potential of epigenetic regulators, this study investigated the synergistic neuroprotective effects of curcumin-enriched turmeric extract combined with L-ascorbic acid, focusing on its modulation of epigenetic pathways in oxidative stress-induced neuronal damage. SH-SY5Y neuronal cells were treated with the combination at 20 and 40 µg/mL, and subsequently exposed to 200 µM hydrogen peroxide (H₂O₂) to induce oxidative stress. Cell viability was assessed using the MTT assay, while neuroprotective mechanisms were evaluated by analyzing the markers of epigenetic modulation, oxidative stress, inflammation, and apoptosis. The combination significantly enhanced cell viability, upregulated sirtuin-1 (SIRT1), and reduced DNA methyltransferase 1 (DNMT1) expression, indicating effective epigenetic modulation. Enhanced antioxidant defenses were observed, as evidenced by increased activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), along with decreased malondialdehyde (MDA) and reactive oxygen species (ROS) levels, alleviating oxidative stress. Additionally, it suppressed nuclear factor kappa B (NF-κB) activity and its downstream mediator interleukin-6 (IL-6), thereby mitigating inflammation. The treatment also increased anti-apoptotic Bcl-2 expression while reducing pro-apoptotic markers, including caspase-3 and caspase-9, suggesting inhibition of the intrinsic apoptotic pathway. These findings highlight the novel neuroprotective effects of this combination, demonstrating its ability to modulate epigenetic pathways while reducing oxidative stress, suppressing inflammation, and preventing undesired apoptosis. Its multifaceted neuroprotective properties make it a promising functional ingredient in functional foods for neurodegenerative disease intervention. However, further investigations, including animal studies and clinical trials, are essential to evaluate its safety and therapeutic potential.

Keywords: L-ascorbic acid; curcumin; epigenetics; neurodegenerative diseases; turmeric.

Figure 1

Cytotoxicity of curcumin-enriched turmeric extract combined with L-ascorbic acid on the viability of SH-SY5Y cells. Data are presented as the mean ± SEM. *, **, *** p < 0.05, 0.01, and 0.001, respectively; compared with the naïve control (0 µg/mL).

Figure 2

Neuroprotective effects of curcumin-enriched turmeric extract combined with L-ascorbic acid on H₂O₂-induced oxidative damage in SH-SY5Y cells. (A) Representative images of SH-SY5Y cell density at 10× magnification. (B) Percentage of cell viability. Data are presented as the mean ± SEM. *** p < 0.001; compared with the naïve control group, ^### p < 0.001; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.

Figure 3

Effect of curcumin-enriched turmeric extract combined with L-ascorbic acid on epigenetic modulation in oxidative stress-induced SH-SY5Y cell damage. (A) Immunoblot showing the expression of SIRT1 and DNMT1. (B) Relative density of SIRT1, normalized to beta-actin. (C) Relative density of DNMT1, normalized to beta-actin. Data are presented as the mean ± SEM. **, *** p < 0.01 and 0.001, respectively; compared with the naïve control group, ^##, ^### p < 0.01 and 0.001, respectively; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.

Figure 4

Effect of curcumin-enriched turmeric extract combined with L-ascorbic acid on ROS generation in oxidative stress-induced SH-SY5Y cell damage. Data are presented as the mean ± SEM. *** p < 0.001; compared with the naïve control group; ^### p < 0.001; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.

Figure 5

Effect of curcumin-enriched turmeric extract combined with L-ascorbic acid on MDA level in oxidative stress-induced SH-SY5Y cell damage. Data are presented as the mean ± SEM. ** p < 0.01; compared with the naïve control group; ^# p < 0.05; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.

Figure 6

Effect of curcumin-enriched turmeric extract combined with L-ascorbic acid on antioxidant enzyme activities in oxidative stress-induced SH-SY5Y cell damage. Data are presented as the mean ± SEM. *** p < 0.001; compared with the naïve control group; ^#, ^### p < 0.05 and 0.001, respectively; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.

Figure 7

Effect of curcumin-enriched turmeric extract combined with L-ascorbic acid on inflammatory markers in oxidative stress-induced SH-SY5Y cell damage. (A) Immunoblot showing the expression of NF-κB and IL-6. (B) Relative density of NF-κB, normalized to beta-actin. (C) Relative density of IL-6, normalized to beta-actin. Data are presented as the mean ± SEM. **, *** p < 0.01 and 0.001, respectively; compared with the naïve control group, ^#, ^## p < 0.05 and 0.01, respectively; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.

Figure 8

Effects of curcumin-enriched turmeric extract combined with L-ascorbic acid on apoptotic markers in H₂O₂-induced oxidative damage in SH-SY5Y cells. (A) Immunoblot showing the expression of Bcl-2, caspase-3, and caspase-9. (B) Relative density of Bcl-2, normalized to beta-actin. (C) Relative density of caspase-3, normalized to beta-actin. (D) Relative density of caspase-9, normalized to beta-actin. Data are presented as the mean ± SEM. *, **, *** p < 0.05, 0.01, and 0.001, respectively; compared with the naïve control group, ^#, ^##, ^### p < 0.05, 0.01, and 0.001, respectively; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.

Figure 8

Effects of curcumin-enriched turmeric extract combined with L-ascorbic acid on apoptotic markers in H₂O₂-induced oxidative damage in SH-SY5Y cells. (A) Immunoblot showing the expression of Bcl-2, caspase-3, and caspase-9. (B) Relative density of Bcl-2, normalized to beta-actin. (C) Relative density of caspase-3, normalized to beta-actin. (D) Relative density of caspase-9, normalized to beta-actin. Data are presented as the mean ± SEM. *, **, *** p < 0.05, 0.01, and 0.001, respectively; compared with the naïve control group, ^#, ^##, ^### p < 0.05, 0.01, and 0.001, respectively; compared with the H₂O₂ and vehicle-treated group. H₂O₂: 200 µM hydrogen peroxide; CC: curcumin-enriched turmeric extract combined with L-ascorbic acid.