Endoplasmic reticulum stress-induced neuronal inflammatory response and apoptosis likely plays a key role in the development of diabetic encephalopathy

Oncotarget. 2016 Nov 29;7(48):78455-78472. doi: 10.18632/oncotarget.12925.

Abstract

We assumed that diabetic encephalopathy (DEP) may be induced by endoplasmic reticulum (ER)-mediated inflammation and apoptosis in central nervous system. To test this notion, here we investigated the neuronal ER stress and associated inflammation and apoptosis in a type 2 diabetes model induced with high-fat diet/streptozotocin in Sprague-Dawley rats. Elevated expressions of ER stress markers, including glucose-regulated protein 78 (GRP78), activating transcription factor-6 (ATF-6), X-box binding protein-1 (XBP-1), and C/EBP homologous protein, and phosphor-Jun N-terminal kinase (p-JNK) were evident in the hippocampus CA1 of diabetic rats. These changes were also accompanied with the activation of NF-κB and the increased levels of inflammatory cytokines, tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6). Mechanistic study with in vitro cultured hippocampus neurons exposed to high glucose (HG), which induced a diabetes-like effects, shown by increased ER stress, JNK and NF-κB activation, and inflammatory response. Inhibition of ER stress by 4-phenylbutyrate (4-PBA) or blockade of JNK activity by specific inhibitor or transfection of DN-JNK attenuated HG-induced inflammation and associated apoptosis. To validate the in vitro finding, in vivo application of 4-PBA resulted in a significant reduction of diabetes-induced neuronal ER stress, inflammation and cell death, leading to the prevention of DEP. These results suggest that diabetes-induced neuronal ER stress plays the critical role for diabetes-induced neuronal inflammation and cell death, leading to the development of DEP.

Keywords: ER stress; apoptosis; diabetes; inflammation; p-JNK.

MeSH terms

  • Activating Transcription Factor 6 / metabolism
  • Animals
  • Anti-Inflammatory Agents / pharmacology
  • Apoptosis* / drug effects
  • Behavior, Animal
  • Brain Diseases / etiology*
  • Brain Diseases / metabolism
  • Brain Diseases / pathology
  • Brain Diseases / prevention & control
  • Cells, Cultured
  • Cognition
  • Diabetes Mellitus, Experimental / complications*
  • Diabetes Mellitus, Experimental / drug therapy
  • Diabetes Mellitus, Experimental / metabolism
  • Diabetes Mellitus, Experimental / pathology
  • Diabetes Mellitus, Type 2 / complications*
  • Diabetes Mellitus, Type 2 / drug therapy
  • Diabetes Mellitus, Type 2 / metabolism
  • Diabetes Mellitus, Type 2 / pathology
  • Dose-Response Relationship, Drug
  • Endoplasmic Reticulum Stress* / drug effects
  • Heat-Shock Proteins / metabolism
  • Hippocampus / drug effects
  • Hippocampus / metabolism
  • Hippocampus / pathology*
  • Interleukin-6 / metabolism
  • JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • JNK Mitogen-Activated Protein Kinases / genetics
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • NF-kappa B / metabolism
  • Neurons / drug effects
  • Neurons / metabolism
  • Neurons / pathology*
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Rats, Sprague-Dawley
  • Signal Transduction
  • Time Factors
  • Transcription Factor CHOP / metabolism
  • Transfection
  • Tumor Necrosis Factor-alpha / metabolism
  • X-Box Binding Protein 1 / metabolism

Substances

  • Activating Transcription Factor 6
  • Anti-Inflammatory Agents
  • Atf6 protein, rat
  • Ddit3 protein, rat
  • GRP78 protein, rat
  • Heat-Shock Proteins
  • Interleukin-6
  • NF-kappa B
  • Protein Kinase Inhibitors
  • Tumor Necrosis Factor-alpha
  • X-Box Binding Protein 1
  • Xbp1 protein, rat
  • Transcription Factor CHOP
  • JNK Mitogen-Activated Protein Kinases