IGF-1 Signaling via the PI3K/Akt Pathway Confers Neuroprotection in Human Retinal Pigment Epithelial Cells Exposed to Sodium Nitroprusside Insult

Abstract

The pathological increase in the levels of the second messenger nitric oxide (NO) in the vitreous cavity and retina leads to injury and cell death of the retinal pigment epithelium (RPE) cells and eventually may contribute to the occurrence and development of diabetic retinopathy. In this study, we developed a cellular model of retinopathy using D407 cells (a human RPE cell line) exposed to sodium nitroprusside (SNP) and investigated the protective effect of the insulin-like growth factor-1 (IGF-1) towards this insult. Cell death and apoptosis were examined by the methyl thiazolyl tetrazolium assay and Hoechst staining, respectively. Specific inhibitors were used and phosphorylation of relevant signaling proteins was determined by Western blotting. SNP, in a concentration-dependent fashion, increased the production of reactive oxygen species (ROS) and lipid peroxidation process causing cell death by apoptosis of D407 cells. IGF-1, in a time- and dose-dependent manner, conferred protection towards SNP-mediated insult. Both phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) and mitogen-activated protein kinase (MAPK) were activated by IGF-1 in relation to the protective effect. Blockade of the PI3K/Akt pathway abolished the protective effect of IGF-1 whereas inhibition of the MAPK pathway was ineffective. SNP decreased the phosphorylation of Akt in the cells while IGF-1 reversed this inhibitory effect. These results indicate that the protective effect of IGF-1 on D407 exposed to SNP insult is mediated by the PI3K/Akt pathway. This proposal may be exploited in the clinic to improve the viability of insulted retinal cells for maintaining physiological vision.

Klotho, an antiaging molecule, attenuates oxidant-induced alveolar epithelial cell mtDNA damage and apoptosis

“…For example, pathogenic activation of AKT is evident in fibroblasts and macrophages isolated in a murine model of bleomycin-induced lung fibrosis or in fibroblasts of IPF patients (31,33,57). In contrast, PI3K/AKT signaling is required to attenuate oxidant-induced cell injury in lung epithelial, retinal pigment epithelial, and neuronal cell injury, including asbestos-induced AEC apoptosis (2,34,41,54). AKT deficiency promotes oxidative DNA damage by decreasing DNA repair in renal cells (14).…”

Protective Effect of l-Theanine on Cadmium-Induced Apoptosis in PC12 Cells by Inhibiting the Mitochondria-Mediated Pathway

“…PI3K/Akt signaling pathways mediate cell death or survival, differentiation, and apoptosis responses [40,41]. PC12 and SH-SY5Y cells exposed to cadmium showed reduction in PTEN, resulting in increased PI3K/Akt signaling.…”

Insulin‐like growth factor‐1 activates PI3K/Akt signalling to protect human retinal pigment epithelial cells from amiodarone‐induced oxidative injury

“…Human retinal pigment epithelial cells (D407 cells) were maintained in 75 cm 2 tissue culture flasks in DMEM supplemented with 10% FBS, streptomycin 100 μg·mL −1 and penicillin 100 U·mL −1 and incubated at 37°C with 5% CO 2 humidified atmosphere. Stock cells were sub‐cultured twice a week to provide new stocks and cells for the experiments described (Wang et al, ).…”

“…This action of IGF‐1 occurs via the ubiquitous PI3K/ signalling pathway, although the complete pathway including upstream and downstream effectors is yet to be fully characterized (Zheng et al, ; Zheng and Quirion, , ; Sun et al, ; Wang et al, ). In the present study, we evaluated the toxic effect of amiodarone on D407 cells (a human RPE cell line) (Kennedy et al, ; Wang et al, ) and used a clinically relevant cellular model of oxidative injury to evaluate the role of IGF‐1 and its mechanism of action in the protection of D407 cells from the oxidative injury induced by amiodarone. We found that amiodarone inhibited the activation of Akt and induced apoptosis in D407 cells while IGF‐1 promoted the survival of D407 cells subjected to amiodarone‐induced oxidative stress.…”