Endoplasmic Reticulum Stress In Pathogenesis Research Articles

Elevation of liver endoplasmic reticulum stress in a modified choline-deficient l-amino acid-defined diet-fed non-alcoholic steatohepatitis mouse model

Endoplasmic reticulum (ER) stress caused by accumulation of misfolded proteins is observed in several kinds of diseases. Since ER stress is reported to be involved in the progression of non-alcoholic steatohepatitis (NASH), highly sensitive and simple measurement methods are required for research into developing novel therapy for NASH. To investigate the involvement of ER stress in NASH pathogenesis in a mouse model, an assay for liver ER stress was developed using ER stress activated indicator-luciferase (ERAI-Luc) mice.To establish the assay method for detection of ER stress in the liver, tunicamycin (TM) (0.3 mg/kg i. p.) was administered to ERAI-Luc mice, and the luciferase activity was measured in ex vivo and in vivo. To evaluate ER stress in the NASH model, ERAI-Luc mice were fed a modified choline-deficient l-amino acid-defined (mCDAA) diet for 14 weeks. After measurement of ER stress by luminescence imaging, levels of liver lipids and pro-fibrotic and pro-inflammatory gene expression were measured as NASH-related indexes.In non-invasive whole-body imaging, TM elevated luciferase activity in the liver, induced by activation of ER stress. The highest luminescence in the liver was confirmed by ex vivo imaging of isolated tissues. In parallel with progression of NASH, elevated luminescence induced by ER stress in liver was observed in mCDAA diet-fed ERAI-Luc mice. Luciferase activity was significantly and positively correlated to levels of triglyceride and free cholesterol in the liver, as well as to the mRNA expression of type 1 collagen α1 chain and tumor necrosis factor α.These data indicated that the use of ERAI-Luc mice was effective in the detection of ER stress in the liver. Moreover, the NASH model using ERAI-Luc mice can be a useful tool to clarify the role of ER stress in pathogenesis of NASH and to evaluate effects of drugs targeted against ER stress.

Potential Role of Endoplasmic Reticulum Stress in Pathogenesis of Diabetic Retinopathy.

Diabetes mellitus is a metabolic disease that leads to several complications which include retinopathy. Multiple biochemical abnormalities have been proposed to explain the development of retinopathy, including oxidative stress. Although the existence of oxidative stress has been established in the retina from long standing diabetic animals, pathogenesis and progression of retinopathy remain unclear. In order to gain insight into the pathogenesis of diabetic retinopathy, we analyzed the levels of different oxidative stress biomarkers in the retina at early stages during the progress of streptozotocin-induced diabetes. No significant changes in glutathione content, expression of NADPH-oxidase, levels of lipid peroxidation, nor production of free radicals were observed in the retina up to 45days of diabetes induction. Likewise, a transient decrease in aconitase activity, parallel to an increase in the superoxide dismutase activity was observed at 20days of hyperglycemia, suggesting a high capacity of retina to maintain its redox homeostasis, at least at early stages of diabetes. Nonetheless, we found an early and time-dependent increase in the levels of oxidized proteins, which was not affected by the administration of the antioxidant quercetin. Also, positive immunoreactivity to the reticulum stress protein CHOP was found in glial Müller cells of diabetic rat retinas. These findings suggest the occurrence of endoplasmic reticulum stress as a primary event in retina pathogenesis in diabetes.

The involvement of endoplasmic reticulum stress in pathogenesis after cerebral ischemia

Endoplasmic reticulum (ER)-stress, which is caused by an accumulation of unfolded proteins in the ER lumen, is associated with stroke and with neurodegenerative diseases such as Parkinson’s and Alzheimer diseases. However, there are a few reports regarding a role of ER stress on ischemiainduced neuronal damage. Therefore, we investigated the regional and time-dependent changes in ER stress-related markers after transient forebrain ischemia in gerbil and middle cerebral artery occlusion (MCAO) in mice. We assessed the expression patterns of immunoglobulin heavy chain binding protein (BiP) glucose-regulated protein (GRP) 78, activating transcription factor (ATF) -4, and C EBP homology protein (CHOP) after transient forebrain ischemia in gerbils. Double-fluorescent staining involving CHOP immunohistochemistry and TUNEL method was performed to clarify the involvement of CHOP in cell death. Immunohistochemical and Western blot analyses of the hippocampal CA1 subfield showed that BiP expression was increased at 12 h, peaked at 3 days, then decreased. A transient increase was detected in CA3 at 1 day after ischemia, but BiP expression was unchanged in dentate gyrus and cortex. Signals for ATF-4 and CHOP were increased at 1 day and 3 days in CA1, and at 12 h in CA3. Co-localization of CHOP immunoreactivity and DNA fragmentation was detected by the TUNEL method at 3 days after ischemia in CA1, but not at 12 h in CA3. ER stress-related markers in the striatum and the cortex were investigated after permanent MCAO in mice. Using ER stress-activated indicator ( ERAI ) transgenic mice, which show splicing of X-box protein 1 (XBP-1) mRNA as green fluorescence, we monitored the regional changes in fluorescence after MCAO. BiP mRNA was increased in the cortex at 6 h. In immunohistochemical and or Western blot analysis, the expressions of ER stress-related markers (BiP, ATF-4, and CHOP ) were increased in the infarct region, more strongly in the cortex than in the striatum. ERAI fluorescence was observed in the ischemic area starting from 6 h and 12 h, respectively, after MCAO, with the peaks at 1 day and the fluorescence co-localized with TTC-visible extension of brain infarction. These findings are consistent with ER stress playing a pivotal role in post-ischemic neuronal death in the gerbil hippocampal CA1 subfield and the mouse MCA territory.