7‑酮基胆固醇通过激活内质网应激通路诱导胰岛β细胞凋亡的研究.

Objective　To investigate the effect of 7‑ketocholesterol (7‑KC) on apoptosis and to elucidate its underlying mechanism in pancreatic β‑cells. Methods　INS‑1 cells were treated with 0, 0.25, 2.5 and 25 μmol/L 7‑KC for 24 h, and the concentration inducing apoptosis of INS‑1 cells was detected by western blotting. Furthermore, the cells were divided into four groups: blank group, 25 μmol/L 7‑KC treatment group, 7‑KC treatment and pretreated with 1 mmol/L endoplasmic reticulum (ER) stress inhibitor 4‑phenylbutyric acid (4‑PBA) group, and 1 mmol/L 4‑PBA group. The expression of ER stress marker proteins [inosital‑requiring enzyme‑1α (IRE‑1α), protein kinase R‑like endoplasmic reticulum kinase (PERK), activating transcription factor 4 (ATF4), phosphorylated α subunit of eukaryotic initiation factor 2 (p‑eIF‑2α), α subunit of eukaryotic initiation factor 2 (eIF‑2α), C/Ebp‑homologous protein (CHOP), phosphorylated inosital‑requiring enzyme‑1 (p‑IRE‑1α), phosphorylated protein kinase R‑like endoplasmic reticulum kinase (p‑PERK), activating transcription factor 6α (ATF‑6α)], apoptosis proteins [B‑cell lymphoma‑2 (Bcl‑2), Bcl2‑associated X (Bax), cleaved cysteinyl aspartate‑specific proteinase‑3 (cleaved‑Caspase 3)], ER morphology and interaction proteins of ER [glucose regulated protein 78 (GRP78)] were elucidated via western blotting, flow cytometry and immunofluorescence, transmission electron microscopy and co‑immunoprecipitation, in order to verify the role of ER stress in β‑cell function impairment by 7‑KC. Two‑tailed Student′s t tests were performed to compare means between two groups. ANOVA followed by Bonferroni′s multiple comparisons was used to compare means from three or more groups. Results　The cleaved‑Caspase3 was increased dose‑dependently and upregulated obviously at 25 μmol/L 7‑KC treatment group (P<0.01). Meanwhile, the dilation and vesiculation of ER, and ER stress‑sensing proteins p‑PERK, p‑IRE‑1α, ATF6, p‑eIF‑1, ATF4, and CHOP were dramatically upregulated at 25 μmol/L 7‑KC treatment group. Compared with 25 μmol/L 7‑KC treatment group, the further study showed that ER stress protein expressions were downregulated, and apoptosis proteins expressions were decreased at 25 μmol/L 7‑KC treatment and pretreated with 1 mmo/L 4‑PBA group (P<0.05). Co‑immunoprecipitation demonstrated that the binding of molecular chaperones GRP78 and PERK was inhibited at 25 μmol/L 7‑KC treatment group, and furthermore increased PERK autophosphorylation and then activated ER stress. Conclusion　7‑KC activates ER stress and promotes apoptosis by inhibiting the GRP78‑PERK interaction in pancreatic β cells. [ABSTRACT FROM AUTHOR]