Streptozotocin and L-Buthionine-Sulfoximine Decrease Neuron Membrane Lipid Packing and Alter Insulin Signaling.

Abstract

Membrane composition, permeability and fluidity are essential for proper cellular function. According to the membrane aging hypothesis, aging-related diseases, including neurodegenerative disorders, arise from the aging of cell membranes. Membrane proteins, such as the insulin receptor, rely on an optimal membrane environment for proper partitioning and functionality. Our goal was to investigate the effects of streptozotocin (STZ) and L-buthionine-sulfoximine (BSO), two commonly used agents to model aging and neurodegeneration, on membrane composition and permeability, as well as their impact on insulin signaling. Mouse neuroblastoma 2a cell line (neuro-2a) were treated with STZ (6 h) and BSO (24 h). Cell viability was assessed by the MTT assay. Cholesterol and sphingomyelin content were quantified by commercial kits, while membrane polarity was evaluated with the Laurdan probe. Gene expression of Srebf2 and Cyp46a1 was analyzed by qPCR. Proteins from the insulin signaling pathway were examined by immunoblotting. STZ treatment reduced neuronal cholesterol content, downregulated Srebf2 and Cyp46a1 gene expression, and decreased membrane packing. In contrast, BSO-treated cells exhibited increased sphingomyelin content, upregulated Srebf2 and Cyp46a1 gene expression, and decreased membrane packing. Both treatments induced an insulin-resistant state, which we attribute to alterations in the membrane environment.