Recombinant human klotho protects against hydrogen peroxide-mediated injury in human retinal pigment epithelial cells via the PI3K/Akt-Nrf2/HO-1 signaling pathway

Abstract

Globally, age-related macular degeneration (AMD) is a common irreversible ophthalmopathy. Oxidative stress of retinal pigment epithelial cells is involved in AMD occurrence and development. Klotho is an anti-aging protein with antioxidant properties. We investigated the protective properties of Klotho on hydrogen peroxide (H 2 O 2 )-induced injury of retinal pigment epithelial cells (ARPE-19 cells) and its associated pathomechanisms. We found that Klotho pretreatment for 24 h could up-regulate Bcl-2 levels, decrease the cleaved-caspase-3 and Bax levels, inhibit H 2 O 2 -induced ARPE-19 cell apoptosis, and promote cell proliferation. Klotho pretreatment inhibited the H 2 O 2 -mediated elevations of reactive oxygen species (ROS) in ARPE-19 cells. It enhanced antioxidant activities of the cells and restored the glutathione peroxidase (GPX), superoxide dismutase (SOD2), catalase (CAT), as well as malondialdehyde (MDA) levels to close to the normal level. N-acetylcysteine (NAC), a reactive oxygen scavenger, could reverse the harmful effects of H 2 O 2 on proliferation, apoptosis, and oxidative stress of ARPE-19 cells. Further, Klotho pretreatment enhanced Akt phosphorylation and expression as well as nuclear translocation of Nrf2 in H 2 O 2 -treated ARPE-19 cells. This indicates that Klotho protects cells from oxidative stress by activating phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt)-nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) signaling pathway. Klotho is, therefore, a potential preventive or treatment option for AMD.

Klotho increases antioxidant defenses in astrocytes and ubiquitin-proteasome activity in neurons

“…This suggests that the protective role of Klotho against oxidative stress may be attributed to the decrease in AKT-mTOR signaling, leading to an increase in FOXO3a activity and catalase levels. Our data reinforces the hypothesis that Klotho is an anti-aging protein with antioxidant properties 45 .…”

“…Previous literature has reported that Klotho pretreatment for 24 hours can protect retinal pigment epithelial cells from H 2 O 2 -induced cell death by decreasing cleaved-caspase 3 and Bax levels and increasing antioxidant activity such as superoxide dismutase (SOD2) and catalase (CAT) 45 . This suggests that the protective role of Klotho against oxidative stress may be attributed to the decrease in AKT-mTOR signaling, leading to an increase in FOXO3a activity and catalase levels.…”

Regulator of G-protein signaling 1 promotes choroidal neovascularization in age-related macular degeneration

“…The disease can be effectively slowed down by interfering with the functions of human retinal pigment cells. For example, sulforaphane ameliorates amyloid-β-induced injury in RPE cells ( 15 ), recombinant human klotho protects against hydrogen peroxide-mediated injury in human retinal pigment epithelial cells ( 16 ), and baicalin suppresses AMD in vitro and in vivo ( 17 ). In AMD, functional changes in the RPE play an important role; neovascularization is particularly important, and its occurrence is closely related to the proliferation and activity of vascular endothelial cells.…”

Klotho increases antioxidant defenses in astrocytes and ubiquitin–proteasome activity in neurons

“…Prior literature indicates that a 24-h pretreatment with Klotho can protect retinal pigment epithelial cells from H 2 O 2 -induced cell death. This protection is achieved by reducing cleaved-caspase 3 and Bax levels, and enhancing antioxidant activity, such as SOD2 and CAT 54 . These findings suggest that Klotho’s protective role against oxidative stress could be attributed to a decrease in AKT-mTOR signaling, which subsequently leads to an increase in FOXO3a activity and catalase levels.…”