Conclusions
Apoptosis and inflammation are enhanced in the diabetic cornea; NGF attenuates these responses-both in vivo and in vitro. Therefore, NGF therapy may represent a novel approach for the management of diabetic keratopathy.
Methods
To investigate the effects of NGF on glucose-induced apoptosis, we stained human corneal epithelial cells (HCECs) for annexin-V and propidium iodide (PI), and measured expression of cleaved caspase-3 and the Bcl-2-associated X protein (BAX). Moreover, to examine the effects of NGF on inflammation, we quantified the expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) using multiplex cytokine analysis, and analyzed nuclear factor-κB (NF-κB) activation and NF-κ-B inhibitor α (IκBα) degradation using Western blot analysis. To investigate the effects in vivo, we induced diabetes in male Sprague-Dawley rats using streptozotocin. The rats were divided into three groups: control, diabetic control, and diabetic NGF; topical NGF was applied three times daily for 3 weeks. We used the TUNEL assay to detect apoptosis in corneal tissue, and immunohistochemistry to identify cleaved caspase-3 and IL-1β.
Purpose
To examine the effects of nerve growth factor (NGF) on apoptosis and inflammation in the diabetic cornea.
Results
In HCECs, high glucose concentration (≥25 mM) led to reactive oxygen species (ROS) generation, apoptosis, and the release of inflammatory cytokines. Nerve growth factor markedly reduced ROS activation, annexin-PI-positive cells, and levels of cleaved caspase-3, BAX, IL-1β, and TNF-α. In the diabetic rat cornea, apoptosis and inflammation were enhanced, as were levels of cleaved caspase-3 and IL-1β. These responses were markedly reduced by NGF. Conclusions: Apoptosis and inflammation are enhanced in the diabetic cornea; NGF attenuates these responses-both in vivo and in vitro. Therefore, NGF therapy may represent a novel approach for the management of diabetic keratopathy.