Oxindole-curcumin hybrid compound enhances the transcription of γ-glutamylcysteine ligase

Glutathione (GSH), which is particularly important for antioxidant defenses, is synthesized in two sequential enzymatic reactions catalyzed by gamma-glutamylcysteine ligase (GCL) and GSH synthase. GCL comprises catalytic (GCLC) and regulatory subunits and catalyzes the rate-limiting step in de novo GSH synthesis. Accumulating evidence suggests that substances that stimulate GSH synthesis are therapeutic modalities for neurodegenerative disorders and schizophrenia, in which a deficit in brain GSH content has been observed. In the present study, we attempted to develop small organic compounds that increase GCLC transcription. Using HT22 cells stably expressing a luciferase reporter that contains rat GCLC promoter region (-1764 to +2), we assessed the effects of the novel neuroprotective compound oxindole and related compounds on GCLC promoter activity. Among approximately 220 synthesized compounds, five compounds increased GCLC promoter activity by >200% at a concentration of 50 mu M, and 16 compounds increased promoter activity by approximately 150%. The most effective compound oxindole-curcumin hybrid GIF-2165X-G1 increased GCLC mRNA levels in HT22 mouse hippocampal cells, PC12 rat pheochromocytoma cells, and C6 rat glioma cells. Although GIF-2165X-G1 potently induced antioxidant response element (ARE)-driven transcription, the compound increased GCLC transcriptional activity through Sp1 pathway in a Keap1-Nrf2-ARE-independent manner. These results suggest that GIF-2165XG1 itself and further modification of the compound are useful interventions for promoting neuronal survival by augmenting resistance to oxidative stress.

Automated summary

The study focuses on developing small organic compounds that increase GCLC transcription to promote neuronal survival by augmenting resistance to oxidative stress. Among the synthesized compounds, GIF-2165X-G1 showed the most effective increase in GCLC mRNA levels through the Sp1 pathway. This compound and its modifications are considered useful interventions for enhancing neuronal survival against oxidative stress.