Heme Oxygenase-1 Protects Retinal Endothelial Cells against High Glucose- and Oxidative/Nitrosative Stress-Induced Toxicity

Abstract

Diabetic retinopathy is a leading cause of visual loss and blindness, characterized by microvascular dysfunction. Hyperglycemia is considered the major pathogenic factor for the development of diabetic retinopathy and is associated with increased oxidative/nitrosative stress in the retina. Since heme oxygenase-1 (HO-1) is an enzyme with antioxidant and protective properties, we investigated the potential protective role of HO-1 in retinal endothelial cells exposed to high glucose and oxidative/nitrosative stress conditions. Retinal endothelial cells were exposed to elevated glucose, nitric oxide (NO) and hydrogen peroxide (H2O2). Cell viability and apoptosis were assessed by MTT assay, Hoechst staining, TUNEL assay and Annexin V labeling. The production of reactive oxygen species (ROS) was detected by the oxidation of 2′,7′-dichlorodihydrofluorescein diacetate. The content of HO-1 was assessed by immunobloting and immunofluorescence. HO activity was determined by bilirubin production. Long-term exposure (7 days) of retinal endothelial cells to elevated glucose decreased cell viability and had no effect on HO-1 content. However, a short-time exposure (24 h) to elevated glucose did not alter cell viability, but increased both the levels of intracellular ROS and HO-1 content. Moreover, the inhibition of HO with SnPPIX unmasked the toxic effect of high glucose and revealed the protection conferred by HO-1. Oxidative/nitrosative stress conditions increased cell death and HO-1 protein levels. These effects of elevated glucose and HO inhibition on cell death were confirmed in primary endothelial cells (HUVECs). When cells were exposed to oxidative/nitrosative stress conditions there was also an increase in retinal endothelial cell death and HO-1 content. The inhibition of HO enhanced ROS production and the toxic effect induced by exposure to H2O2 and NOC-18 (NO donor). Overexpression of HO-1 prevented the toxic effect induced by H2O2 and NOC-18. In conclusion, HO-1 exerts a protective effect in retinal endothelial cells exposed to hyperglycemic and oxidative/nitrosative stress conditions.

myo-Inositol Oxygenase Overexpression Accentuates Generation of Reactive Oxygen Species and Exacerbates Cellular Injury following High Glucose Ambience

“…However, following 30 h of culture, their expression began to decline remarkably, suggesting exhaustion of the defensive systems, as has been known in diabetic states in other culture systems (52). The prototype of adaptive increase followed by decline in the expression of heme oxygenase-1 following high glucose ambience has also been highlighted in recent studies on retinal endothelial cells (53). Of note, the ROS generated in MIOX-overexpressing cells are derived from both mitochondria and the NADPH oxidase system, as assessed by flow cytometric analysis (Fig.…”

Effect of lycopene on the blood-spinal cord barrier after spinal cord injury in mice

“…HO-1 expression is an adaptive and protective response to oxidative stress. HO-1 can be induced by a variety of stimuli and various agents that cause oxidative stress, and it protects cells from the oxidative damage caused by reactive oxygen species (31). Lycopene has been found to protect against oxidation of lipids, proteins, and DNA in vivo.…”

Heme oxygenase-1 protects H2O2-insulted glomerular mesangial cells from excessive autophagy

“…Due to its beneficial effects, including oxidative stress relief and the inhibition of cell apoptosis, HO-1 has previously been proposed as a potential therapeutic target for ischemia/reperfusion or hypertension-induced glomerular injuries (2,3), and diabetic retinopathy (4). HO-1 has also been considered a potential biomarker of acute kidney injury (5).…”