Extracellular-Signal-Regulated Kinase Inhibition Switches APP Processing from β- to α-Secretase under Oxidative Stress: Modulation of ADAM10 by SIRT1/NF-κB Signaling.

The sequential cleavage of full-length amyloid precursor protein (APP) by secretases has been at the center of efforts for understanding the onset of Alzheimer's disease (AD). A decrease in α-secretase activity was observed during the progression of AD; however, the precise molecular mechanism involved in the downregulation of α-secretase under oxidative stress is not fully understood. In the present study, we have demonstrated that pharmacological inhibition of mitogen-activated protein kinase/extracellular-signal-regulated kinase (MAPK/ERK) by mitogen-activated protein kinase kinase-1 (MEK-1) inhibitor (PD98059) restored the expression of a disintegrin and metalloproteinase 10 (ADAM10) with a concomitant decrease in β-site APP cleavage enzyme 1 (BACE1) under oxidative stress. Silent mating-type information regulation 2 homologue 1 (SIRT1) activation by resveratrol also mitigated alterations in secretase levels through MAPK/ERK signaling. Intracerebroventricular (ICV) administration of streptozotocin in rats showed amyloidogenic processing of APP and altered the SIRT1/ERK axis in the hippocampus. We also observed that the ADAM10 expression is controlled at the transcriptional level by oxidative stress. Using the luciferase reporter activity of ADAM10 promoter deletion constructs, we have identified the region 290 bp upstream of the transcription start site (TSS) possessing regulatory elements responsible for ADAM10 downregulation with hydrogen peroxide (H2O2) treatment. Further, bioinformatics analysis revealed the presence of putative nuclear factor kappa B (NF-κB) binding sites in the ADAM10 promoter region. Treatment of cortical neurons with the NF-κB inhibitor (Bay 11-7082) mitigated the transcriptional upregulation of ADAM10 by PD98059. Overall, our findings suggest that SIRT1/ERK/NF-κB axis contributes to the downregulation of ADAM10, resulting in the shift from nonamyloidogenic to amyloidogenic processing of APP under oxidative stress.