Glyceraldehyde caused Alzheimer's disease-like alterations in diagnostic marker levels in SH-SY5Y human neuroblastoma cells

Abstract

Clinical evidence has implicated diabetes mellitus as one of the risk factors for the development and progression of Alzheimer's disease (AD). However, the neurotoxic pathway activated due to abnormalities in glucose metabolism has not yet been identified in AD. In order to investigate the relationship between impaired cerebral glucose metabolism and the pathophysiology of AD, SH-SY5Y human neuroblastoma cells were exposed to glyceraldehyde (GA), an inhibitor of glycolysis. GA induced the production of GA-derived advanced glycation end-products (GA-AGEs) and cell apoptosis, glycolytic inhibition, decreases in the medium concentrations of diagnostic markers of AD, such as amyloid β 1-42 (Aβ42), and increases in tau phosphorylation. These results suggest that the production of GA-AGEs and/or inhibition of glycolysis induce AD-like alterations, and this model may be useful for examining the pathophysiology of AD.

Figure 1. Cytotoxicity of GA in SH-SY5Y cells.

(a–d) Microscopic images of SH-SY5Y cells after a 24 h treatment with GA at 0 (a), 0.3 (b), 0.7 (c), and 1 mM (d). Scale bar = 50 μm. (e) GA dose-dependently induced cell death in SH-SY5Y cells. *P < 0.05, **P < 0.01 vs. 0 mM GA (n = 6). (f–i) GA-induced apoptosis was observed by staining with green fluorescent YO-PRO®-1 (g, 0 mM GA; i, 1 mM GA). (f) and (h) show the same visual field of phase contrast images to (g) and (i). Scale bar = 20 μm.

Figure 2. Characterization of GA-induced cytotoxicity in SH-SY5Y cells.

(a) GAPDH mRNA levels increased in a dose-dependent manner. *P < 0.05, **P < 0.01 vs. 0 mM GA (n = 3). (b) Production of GA-AGEs by the GA treatment for 24 h. GA-AGEs were measured by slot blotting analyses with an immunopurified anti-GA-AGE antibody. Graphical representation of GA-AGE bands in the slot blot. *P < 0.05, **P < 0.01 vs. 0 mM GA (n = 3). (c) Evaluation of lactic acid concentrations after the treatment with GA. SH-SY5Y cells were pre-incubated with ACAC at concentrations of 0, 1, and 10 mM for 15 min, then incubated with 1 mM GA for 24 h. **P < 0.01 vs. 0 mM GA + 0 mM ACAC (n = 3). (d) ACAC prevented GA-induced cytotoxicity. ACAC significantly recovered cell death induced by 1 mM GA in a dose-dependent manner. **P < 0.01 vs. 0 mM GA + 0 mM ACAC (n = 6). ⁺P < 0.05, ⁺⁺P < 0.01 vs. 1 mM GA + 0 mM ACAC.

Figure 3. Changes in AD biomarkers after the GA treatment.

(a-c) Changes in AD biomarkers of Aβ42 (a), total tau (T-tau, b), and p-tauT181 (P-tau, c) after a 24 h treatment with GA. *P < 0.05, **P < 0.01 vs. 0 mM GA (n = 3). (d) Intracellular changes in T-tau and P-tau after a 24 h treatment with GA. GA-dose dependently increased P-tau/T-tau after the GA treatment. *P < 0.05, **P < 0.01 vs. 0 mM GA (n = 3). (e,f) Level changes in other AD biomarkers after the GA treatment. mRNA expression levels were analyzed by real-time PCR after the GA treatment for 24 h. GA significantly increased the levels of VEGF (e) and TGF-β (f) from a GA concentration of 0.7 mM. *P < 0.05, **P < 0.01 vs. 0 mM GA (n = 3).