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Published on: June 13, 2013
Adrenergic and serotonin receptors affect retinal superoxide generation in diabetic mice: relationship to capillary
Yunpeng Du1, Megan Cramer1, Chieh Allen Lee1
1*Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA; Department of Ophthalmology and Visual Sciences, The University of Michigan, Ann Arbor, Michigan, USA; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA; and Veterans Administration Medical Center Research Service 151, Cleveland, Ohio, USA.
Abstract:
Reactive oxygen species play an important role in the pathogenesis of diabetic retinopathy. We studied the role of adrenergic and serotonin receptors in the generation of superoxide by retina and 661W retinal cells in high glucose and of the α1-adrenergic receptor (AR) on vascular lesions of the retinopathy in experimentally diabetic C57Bl/6J mice (and controls) after 2 and 8 months. Compared with 5 mM glucose, incubating cells or retinal explants in 30 mM glucose induced superoxide generation. This response was reduced or ablated by pharmacologic inhibition of the α1-AR (a Gq-coupled receptor) or Gs-coupled serotonin (5-HT2, 5-HT4, 5-HT6, and 5-HT7) receptors or by activation of the Gi-coupled α2-AR. In elevated glucose, the α1-AR produced superoxide via phospholipase C, inositol triphosphate-induced Ca(2+) release, and NADPH oxidase, and pharmacologic inhibition of these reactions prevented the superoxide increase. Generation of retinal superoxide, expression of proinflammatory proteins, and degeneration of retinal capillaries in diabetes all were significantly inhibited with daily doxazosin or apocynin (inhibitors of α1-AR and NADPH oxidase, respectively), but increased vascular permeability was not significantly affected. Adrenergic receptors, and perhaps other GPCRs, represent novel targets for inhibiting the development of important features of diabetic retinopathy.
Insights
High glucose increases superoxide in the retina, contributing to diabetic retinopathy. Targeting alpha1-adrenergic receptors (AR) and related pathways may prevent retinal damage and inflammation.
Area of Science:
- Ophthalmology
- Endocrinology
- Molecular Biology
Background:
- Reactive oxygen species (ROS) are implicated in diabetic retinopathy pathogenesis.
- Adrenergic and serotonin receptors are investigated for their role in ROS generation.
Purpose of the Study:
- To investigate the role of adrenergic and serotonin receptors in superoxide generation in high glucose conditions.
- To evaluate the effect of alpha1-adrenergic receptor (AR) inhibition on diabetic retinopathy vascular lesions.
Main Methods:
- Incubation of retinal cells and explants in high glucose (30 mM) to induce superoxide generation.
- Pharmacologic inhibition of alpha1-AR, Gs-coupled serotonin receptors, and Gi-coupled alpha2-AR.
- Assessment of superoxide generation, inflammatory protein expression, and retinal capillary degeneration in diabetic mice treated with doxazosin or apocynin.
Main Results:
- High glucose significantly increased superoxide generation in retinal cells and explants.
- Inhibition of alpha1-AR and specific serotonin receptors reduced high glucose-induced superoxide.
- Alpha1-AR mediated superoxide production via phospholipase C, Ca(2+) release, and NADPH oxidase.
- Doxazosin and apocynin significantly inhibited retinal superoxide, inflammation, and capillary degeneration in diabetic mice.
Conclusions:
- Adrenergic receptors, particularly alpha1-AR, play a key role in high glucose-induced superoxide generation and diabetic retinopathy development.
- Targeting alpha1-AR and NADPH oxidase shows potential for preventing key features of diabetic retinopathy.
- GPCRs represent novel therapeutic targets for managing diabetic retinopathy.
