Mutated recombinant human glucagon-like peptide-1 protects SH-SY5Y cells from apoptosis induced by amyloid-β peptide (1-42)

Accumulation and deposition of amyloid β peptide (Aβ) in the brain causes neuronal apoptosis and eventually leads to Alzheimer's disease (AD). A therapeutic target for AD is to block the cascade reaction induced by Aβ. It has been demonstrated that glucagon-like peptide-1 (GLP-1), which is an endogenous insulinotropic peptide secreted from the gut, binds to its receptor in the brain and possesses neuroprotective effects. Using site-directed mutagenesis and gene recombination techniques, we generated a mutated recombinant human glucagon-like peptide-1 (mGLP-1) which has longer half-life as compared with native GLP-1. This present work aims to examine whether mGLP-1 attenuates Aβ_1-42-mediated cytotoxicity in SH-SY5Y cells and to explore the possible mechanisms. Our data indicate that ≥0.02 ng/ml of mGLP-1 facilitated cell proliferation and 0.1 ng/ml and 0.5 ng/ml of mGLP-1 rescued SH-SY5Y cells from Aβ_1-42-induced apoptosis. Moreover, Aβ_1-42 treatment dramatically stimulated the release of Ca²⁺ from internal calcium stores in SH-SY5Y cells, while mGLP-1 helped to maintain the intracellular Ca²⁺ homeostasis. Aβ_1-42 also significantly increased the expression level of TP53 and Bax genes which are involved in apoptotic pathways, and mGLP-1 decreased Aβ_1-42-induced up-regulation of TP53 and Bax. Since mGLP-1 treatment elevated cytosolic cAMP concentration in SH-SY5Y cells, we postulate that mGLP-1 may exert its influence via binding to GLP-1 receptors in SH-SY5Y cells and stimulating the production of cAMP. These results suggest that mGLP-1 exhibited neuronal protection properties, and could potentially be a novel therapeutic agent for intervention in Alzheimer's disease.