17β-estradiol protects INS-1 insulinoma cells from mitophagy via G protein-coupled estrogen receptors and the PI3K/Akt signaling pathway

Abstract

17β-estradiol (17β-E2) is a steroid hormone that is known to exert effects on blood glucose homeostasis. The G protein‑coupled estrogen receptor (GPER) has been identified as a non-genomic estrogenic receptor, and is involved in numerous physiological processes, including cell survival, energy provision and metabolism. 17β-E2 may decrease apoptosis by binding to the GPER. The phosphoinositide 3-kinase (PI3K)/Akt signaling pathway is involved in physiological and pathological functions such as autophagy. The purpose of the present study was to investigate the role of the PI3K/Akt signaling pathway in the mediation of the effects of GPERs, and the effects of 17β-E2 on mitophagy in INS-1 cells, a rat insulin‑secreting β-cell line. In vitro, INS-1 cells were treated with different concentrations of 17β-E2 with and without pretreatment with a GPER antagonist (G15) or PI3K antagonist (LY294002) and compared with a negative control. An immunofluorescence assay demonstrated that GPERs are expressed in INS-1 cells. Western blot assays demonstrated that 17β-E2 increased GPER levels and the phosphorylation of Akt. Transmission electronic microscopy revealed that 17β-E2 reduced the formation of mitophagosomes and autophagosomes in INS-1 cells. An immunofluorescence staining assay indicated that the co-localization of translocase of mitochondrial outer membrane complex 20 (TOM20) with lysosomal-associated membrane protein 2 (LAMP2) was decreased in INS-1 cells treated with 17β-E2 alone. Western blotting demonstrated that 17β-E2 reduced the protein levels of activated microtubule-associated protein-1 light chain 3, and increased those of TOM20 and mitochondrial heat-shock protein 60. Notably, the protective effects of 17β-E2 were significantly diminished by G15 or LY294002. In conclusion, the present study suggests that 17β-E2 activates the PI3K/Akt pathway via the GPER in INS-1 cells. Furthermore, 17β-E2 may be involved in mitophagy by the regulating the GPER/PI3K/Akt pathway.

Effects of estrogen receptor GPR30 agonist G1 on neuronal apoptosis and microglia polarization in traumatic brain injury rats

“…It has been demonstrated that GPR30 activation can mediate PI3K/AKT pathway. 26 , 27 PI3K/Akt signaling pathway plays an important role in neuronal survival, proliferation and growth. Additionally, PI3K/Akt pathway can regulate microglial polarization and p-Akt contributes to microglia polarization to M2 type.…”

17β-Estradiol Regulates Glucose Metabolism and Insulin Secretion in Rat Islet β Cells Through GPER and Akt/mTOR/GLUT2 Pathway

“…After cell density reached 80% once every 2 days, cells were passaged. After incubation in an FBS-free medium for 24 h at normal and high glucose with or without E2 and inhibitors, INS-1 cells were divided into the following groups (i) NG: normal glucose (5 mmol/L) for 24 h, (ii) NE: normal glucose + 0.1 μM E2 for 24 h, (iii) NGI: normal glucose + 15 μM G15 (Tocris Bioscience Minneapolis, USA) for 24 h, (iv) NAI: normal glucose + 1 μM Akt inhibitor (PF-04691502, Selleck Company, USA) for 24 h, (v) NMI: normal glucose + 10 μM mTOR inhibitor (rapamycin, Selleck Company, USA) for 48 h, (vi) HG: high glucose (30 mmol/L) for 24 h (17), (vii) HE: high glucose + 0.1 μM E2 for 24 h, (viii) HGI: high glucose + 15 μM G15 for 24 h, (ix) HAI: high glucose + 1 μM Akt inhibitor for 24 h, (x) HMI: high glucose + 10 μM mTOR inhibitor for 48 h (18).…”

Integrated Analysis of DNA Methylation and Biochemical/Metabolic Parameter During the Long-Term Isolation Environment

“…It is worth noting that PI3K-Akt signaling pathway is one of the widely studied biological pathways. Phosphatidylinositol 3-kinases (PI3Ks) is a major downstream molecule of tyrosine kinases and G-protein coupled receptors, and it can activate Akt, glycogen synthase kinase-3 (GSK-3) through catalyzing the production of a second messenger 3,4,5-triphosphate phosphatidylinositol (PIP3), that transmit signals of various growth factors and cytokines into cells (Zhang L. et al, 2018). Thus, PI3K-Akt signaling pathway plays an important regulatory role in various biological processes such as cell proliferation, differentiation, apoptosis and glucose transport (Yu and Cui, 2016).…”