Spermidine Alleviates High Glucose-induced Endoplasmic Reticulum Stress In HT22 Cells By Upregulation Of GDF11

[Background and Objective]High glucose(HG)-induced endoplasmic reticulum(ER)stress is an essential factor for diabetic encephalopathy(DE).Spermidine(Spd),as a natural polyamine,has a potential anti-ER stress effect.Therefore,whether Spd protects neurons from HG-induced ER stress?Growth differentiation factor 11(GDF11)plays protective role in nervous system.If Spd protects neurons from HG-induced ER stress,does GDF11 mediate this effect?Hence,the present work was to clarify the protection of Spd against HG-induced ER stress in mouse hippocampal neurons HT22 cells,and to detect the mediatory role of GDF11 in the protection of Spd against HG-casused neuronal ER stress.[Methods]1.Cell Counting Kit-8(CCK-8)was used to detect the viability of HT22 cells;2.Western blotting was used to measure the expressions of GDF11 and ER stress-related proteins Glucose-regulated protein 78(GRP78)and Cleaved cysteinyl aspartate specific protein(Cleaved caspase-12);3.GDF11 sh RNA was transfected into HT22 cells for silencing the expressions of GDF11 in HT22 cells;4.Reverse Transcription-Polymerase Chain Reaction(RT-PCR)was used to quantify the expressions of GDF11 m RNA in HT22 cells.[Results]1.HG elicits ER stress in HT22 cells1.1.The viability of HT22 cells was obviously inhibited by the increasing concentration of HG(13.5,27,and 40.5 mg/ml,24 h),demonstrating the neurotoxicity of HG in HT22 cells;1.2.After treatment with HG(13.5,27,and 40.5 mg/ml,24 h),the expressions of GRP78 and Cleaved caspase-12 in HT22 cells were markedly increased,indicating that HG induces ER stress in HT22 cells;2.Spd attenuates HG-induced ER stress in HT22 cells2.1.The inhibition of cell viability in HG(27 mg/ml,24 h)conditions was significantly reversed by pretreatment with Spd(0.25,0.5,or 1 ?M,30 min),indicating that Spd produces protective effect against HG-exposed neurotoxicity.2.2.Pretreatment with Spd(0.25,0.5,or 1 ?M,30 min)inhibited the upregulations of GRP78 and Cleaved caspase-12 induced by HG(27 mg/ml,24 h)in HT22 cells.These data illustrated that Spd presents HG-induced ER stress in HT22 cells.3.GDF11 mediates the protection of Spd against HG-induced ER stress in HT22 cells3.1.Treatment with HG(13.5,27,and 40.5 mg/ml,24 h)decreased the expressions of GDF11 in HT22 cells,implying that the downregulation of GDF11 is related to HG-elicited ER stress.3.2.After pretreatment with Spd(0.25,0.5,and 1?M)for 30 min,the decrease in GDF11 expressions elicited by HG(27 mg/ml,24 h)was significantly reversed.Spd(1 ?M)alone markedly upregulated the expressions of GDF11 in HT22 cells.These data indicated that the upregulation of GDF11 is related to Spd-alleviated ER stress in HG-exposed HT22 cells.3.3.GDF11 sh RNA abolished Spd-alleviated neurotoxicity and ER stress in HT22 cells exposed by HG,demonstrating that the inhibition of GDF11 reverses the protective effect of Spd on HG-induced ER stress.[Conclusion]Spd attenuates HG-induced ER stress in HT22 cells by upregulation of GDF11.