RESUMO
AIM: To investigate the effect of high concentration of glucose (HCG) on double stranded RNA-activated protein kinase-like ER kinase (PERK)-eukaryotic initiation factor-2α (eIF2α)-transcription factor C/EBP homologous protein (CHOP)-cysteine aspartate specific proteinase (caspase-12) signaling pathway activation and apoptosis in rabbit corneal epithelial cells (RCECs). METHODS: RCECs were treated by different concentrations of glucose for 0-48h. The expressions of PERK, p-PERK, eIF2α, p-eIF2α, 78 kDa glucose-regulated protein 78 (GRP78), CHOP, B-cell lymphoma 2 (Bcl-2), B-cell lymphoma-2-associated X protein (Bax) and caspase-12 were determined by Western blot. Apoptosis was detected by TUNEL assay. Meanwhile, the function of PERK-eIF2α-CHOP-caspase-12 signaling pathway activation in high glucose-induced apoptosis was evaluated using PERK inhibitor, GSK2606414. RESULTS: HCG significantly promoted the expression of p-PERK, p-eIF2α, GRP78, CHOP, Bax and cleaved caspase-12 in RCECs (P<0.05), while remarkably decreased the expression of Bcl-2 and caspase-12 (P<0.05), and the alterations caused by glucose were in concentration- and time-dependent manners. Meanwhile, PERK and eIF2α expressions were not affected in all groups (P>0.05). TUNEL assay showed that the apoptosis rate of RCECs in the HCG group increased significantly in contrast with that in the normal concentration of glucose or osmotic pressure control group (P<0.05), and the apoptosis rate increased with the increase of glucose concentration within limits (P<0.05). GSK2606414 down-regulated the expression of p-PERK and p-eIF2α in the HCG group (P<0.05), while still did not affect the expression of PERK and eIF2α among groups (P>0.05). Correspondingly, GSK2606414 also significantly reduced the apoptosis rate induced by high glucose (P<0.05). CONCLUSION: HCG activates PERK-eIF2α-CHOP-caspase-12 signaling pathway and promotes apoptosis of RCECs.
RESUMO
MicroRNA-126 (miR-126) was found down-regulated in different types of cancer including esophageal squamous cell carcinoma (ESCC). However, the onco-genetic role of miR-126 in ESCC still remains unknown. In the present study, we found the relative expression of miR-126 in ESCC was significant decreased in ESCC tissues compared to adjacent normal tissues. Overexpression of miR-126 in EC109 cells resulted in significant decrease in cell proliferation, colon formation and migration. PI3K regulatory subunit p85 beta (PIK3R2), a member of PI3K/AKT signaling pathway was found upregulated in ESCC tissues and there is a negative relation between expression of PIK3R2 and miR-126. Restoration of miR-126 in EC109 cells induced a reduction in PIK3R2 protein levels, accompanied with a substantial reduction in phosphorylated AKT levels in EC109 cells, suggesting impairment in PI3K/AKT signaling pathway. The luciferase reporter assay confirmed that PIK3R2 was a direct target of miR-126. Furthermore, we also indicated overexpression of miR-126 suppresses G2/M transition in EC109 cells. Taken together, our study suggests that miR-126 functions as a potential tumor suppressor in ESCC progression via regulating PI3K/AKT signaling pathway partly by targeting PIK3R2, and targeting of miR-126 may provide a novel strategy for the diagnosis and treatment of ESCC.
