551-P: Docosahexaenoic Acid Attenuates Oxidative Stress–Induced Autophagy and Cell Death in Immortalized Adult Rat Schwann (IFRS1) Cells
Authors: TATSUMI YASUAKI , KATO AYAKO , BANNO TAKAHIRO , NIIMI NAOKO , SANGO KAZUNORI , HIMENO TATSUHITO , KONDO MASAKI , TSUNEKAWA SHIN , KATO YOSHIRO , KAMIYA HIDEKI , NAKAMURA JIRO , KATO KOICHI 
Published: June 2020

We previously reported that the docosahexaenoic acid (DHA) induced the antioxidant enzyme, heme oxygenase-1 (HO-1) through the nuclear factor erythroid 2-related factor 2 (Nrf2) and protected immortalized adult mouse Schwann (IMS32) cells from oxidative stress. Whereas autophagy is the process by which intracellular components are degraded by the lysosomes, but it also involved in stabilization of Nrf2 and transcriptional activation of Nrf2 target genes. Therefore, autophagy is thought to be closely related to oxidative stress, which is one major cause of diabetic neuropathy. However, the relationship between autophagy and oxidative stress-induced cell death in diabetic neuropathy has not been elucidated. Treatment with tert-butyl hydroperoxide (tBHP) for 3 hours decreased cell viability measured by MTT assay in immortalized adult rat Schwann (IFRS1) cells, while pretreatment with 10 μM DHA for 12 hours significantly protected tBHP-induced cytotoxicity. Autophagy was assessed by immunoblotting of LC3B and p62. 50 μM tBHP increased the LC3B-II/LC3B-I ratio and decreased the p62 expression in IFRS1 cells, indicating that autophagy was induced by tBHP. DHA pretreatment alleviated tBHP-induced autophagy. Autophagosome and autolysosome were induced by 50 μM tBHP in IFRS1 cells, as demonstrated by DAPRed and DALGreen staining. DHA pretreatment significantly reduced the production of tBHP-induced autophagosome and autolysosome. These results suggest that oxidative stress induces autophagy and promotes cell death in Schwann cells and that treatment with DHA may protect against diabetic neuropathy by attenuating oxidative stress-induced autophagy and cell death in Schwann cells.

Disclosure
Y. Tatsumi: None. A. Kato: None. K. Sango: None. T. Himeno: None. M. Kondo: None. S. Tsunekawa: None. Y. Kato: None. H. Kamiya: Speaker’s Bureau; Self; Astellas Pharma Inc., AstraZeneca K.K., Boehringer Ingelheim K.K., Daiichi Sankyo, Eli Lilly Japan K.K., Fukuda Denshi, Kissei Pharmaceutical Co., Ltd., Kowa Company, Ltd., Kyowa Hakko Kirin Co., Ltd., Mitsubishi Tanabe Pharma Corporation, MSD K.K., Novartis Pharma K.K., Novo Nordisk Pharma Ltd., Ono Pharmaceutical Co., Ltd., Sanofi K.K., Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited. J. Nakamura: Research Support; Self; Astellas Pharma Inc., Boehlinger Ingelheim Japan Co., Ltd., Daiichi Sankyo, Eli Lilly Japan K.K., Japan Tobacco Inc., Kaken Pharmaceutical Co., Ltd., Kowa Company, Ltd., Kyowa Hakko Kirin Co., Ltd., Mitsubishi Tanabe Pharma Corporation, MSD K.K., Novartis Pharma K.K., Novo Nordisk Pharma Ltd., Ono Pharmaceutical Co., Ltd., Otsuka Pharmaceutical Co., Ltd., Pfizer Japan Inc., Sanofi K.K., Sanwa Kagaku Kenkyusho, Shionogi & Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited. Speaker’s Bureau; Self; Abbott Japan Co., Ltd., ARKRAY, Astellas Pharma Inc., AstraZeneca K.K., Boehlinger Ingelheim Japan Co., Ltd.,, Daiichi Sankyo, Eli Lilly Japan K.K., Fukuda Denshi, Kissei Pharmaceutical Co., Ltd., Kowa Company, Ltd., Mitsubishi Tanabe Pharma Corporation, MSD K.K., Mylan, Novartis Pharma K.K., Novo Nordisk Pharma Ltd, Ono Pharmaceutical Co., Ltd., Sanofi, Sanwa Kagaku Kenkyusho, Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited, Terumo Medical Corporation. K. Kato: None.

Funding
Japan Society for the Promotion of Science (18K06763)