title: Apoptotic events induced by high glucose in human hepatoma HepG2 cells involve endoplasmic reticulum stress and MAPK's activation.
abstract: To investigate whether endoplasmic reticulum (ER) stress participates in the induction of apoptosis in HepG2 cells exposed to high glucose and explore its probable mechanism. A series of experiments were performed following HepG2 cells treated with different concentrations of glucose for 48 h. The apoptosis was detected by means of Hoechst staining and flow cytometry. Caspase-3 activity assay was performed by measuring the pNA (p-nitroaniline) to indirectly reveal the catalytic activity of caspase-3. The expression levels of apoptosis-, ER stress-associated proteins and MAPKs were analyzed by western blot. To further characterize the molecular mechanisms, the effects of antioxidant alpha-lipoic acid (ALA) and specific inhibitors for JNK and p38 (SP600125 and SB203580, respectively) were examined by Hoechst staining, immunofluorescence, and western blot. After HepG2 cells were incubated with high glucose for 48 h, both Hoechst staining and flow cytometry analyses unveiled the apoptosis of HepG2 cells. Caspase-3 activity assay revealed that the activity of caspase-3 was enhanced. Western blot showed an enhancement of pro-caspase-9 degradation, a reduction of Bcl-2/Bax ratio, a decrease in GRP78 expression, and increases in CHOP and p47/phox levels. In addition, western blot analysis presented that phosphorylation of p38 and JNK was triggered and that the expression of ASK1 was elevated. In the case of the contributions of oxidative stress and the MAPK signaling pathways, all ALA, SP600125 and SB203580 were able to largely rescue high glucose-induced apoptosis. High glucose induced the apoptosis in HepG2 cells through the activation of ASK1-p38/JNK pathway mediated by ER stress and oxidative stress.
authors.affiliation: Laboratory of Molecular Biology and Department of Biochemistry, Anhui Medical University, Hefei, 230032, Anhui, People's Republic of China.
authors.forename: Qiaoling
authors.initials: Q
authors.lastname: Jiang
authors.forename: Yujun
authors.initials: Y
authors.lastname: Yuan
authors.forename: Jiali
authors.initials: J
authors.lastname: Zhou
authors.forename: Yan
authors.initials: Y
authors.lastname: Wu
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhou
authors.forename: Shuyu
authors.initials: S
authors.lastname: Gui
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D017209:Apoptosis; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress; D004789:Enzyme Activation; D005947:Glucose / Q000494:pharmacology / Q000502:physiology*; D056945:Hep G2 Cells; D006801:Humans; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018384:Oxidative Stress
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D020928:Mitogen-Activated Protein Kinases; D005947:Glucose