Abstract
Purpose: Emerging evidence suggests that 27-Hydroxycholesterol (27-OHC) causes neurodegenerative diseases through the induction of cytotoxicity and cholesterol metabolism disorder. The objective of this study is to determine the impacts of 27-OHC on lysosomal membrane permeabilization (LMP) and pyroptosis in neurons in the development of neural degenerative diseases.Methods: In this study, SH-SY5Y cells and C6 cells were co-cultured in vitro to investigate the influence of 27-OHC on the function of lysosome, LMP and pyroptosis related factors in neuron. Lyso Tracker Red (LTR) was used to detect the changes of lysosome pH, volume and number. Acridine orange (AO) staining was also used to detect the LMP in neurons. Then the morphological changes of cells were observed by a scanning electron microscope (SEM). The content of lysosome function associated proteins [including Cathepsin B (CTSB), Cathepsin D (CTSD), lysosomal-associated membraneprotein-1 (LAMP-1), LAMP-2] and the pyroptosis associated proteins [including nod-like recepto P3 (NLRP3), gasdermin D (GSDMD), caspase-1 and interleukin (IL)-1β] were detected through Western blot.Results: Results showed higher levels of lysosome function associated proteins, such as CTSB (p < 0.05), CTSD (p < 0.05), LAMP-1 (p < 0.01), LAMP-2; p < 0.01) in 27-OHC treated group than that in the control group. AO staining and LTR staining showed that 27-OHC induced lysosome dysfunction with LMP. Content of pyroptosis related factor proteins, such as GSDMD (p < 0.01), NLRP3 (p < 0.001), caspase-1 (p < 0.01) and IL-1β (p < 0.01) were increased in 27-OHC treated neurons. Additionally, CTSB was leaked through LMP into the cytosol and induced pyroptosis. Results from the present study also suggested that the CTSB is involved in activation of pyroptosis.Conclusion: Our data indicate that 27-OHC contributes to the pathogenesis of cell death by inducing LMP and pyroptosis in neurons.
Highlights
Cholesterol plays a key role in brain physiology and function
Our data indicate that 27-OHC contributes to the pathogenesis of cell death by inducing lysosomal membrane permeabilization (LMP) and pyroptosis in neurons
We report that 27-OHC treatment can destroy the lysosomal membrane of SH-SY5Y cells and C6 cells accompany with the increased content of cathepsin B (CTSB) and cathepsin D (CTSD) and increased enzymatic activity of CTSB
Summary
Cholesterol plays a key role in brain physiology and function. Its alterations in homeostasis and levels have been linked to neurodegeneration such as Alzheimer’s disease (AD; Arenas et al, 2017). Evidences have suggested that increased occurrence of AD is associated with raised cholesterol level (Martins et al, 2009; Di Paolo and Kim, 2011). Only the oxysterol metabolites of 27-hydroxycholesterol (27-OHC) and 24S-hydroxycholesterol (24S-OHC) can be exchanged with the blood circulation (Czuba et al, 2017). Several studies have already described increased levels of 27-OHC in serum (Popp et al, 2012) and cerebrospinal fluid (CSF; Besga et al, 2012) of AD patients as a reflection of the severity of disease and the loss of metabolically active neurons and the degree of structural atrophy (Leoni et al, 2011; Popp et al, 2013), suggesting the critical role of 27-OHC in neuro-degeneration
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