ERM Complex, A Therapeutic Target for Vascular Leakage Induced by Diabetes
Olga Simó-Servat1,2, Hugo Ramos1,2, Patricia Bogdanov1,2
1Diabetes and Metabolism Research Unit, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain.
Background:
Ezrin, radixin, and moesin (the ERM complex) interact directly with membrane proteins regulating their attachment to actin filaments. ERM protein activation modifies cytoskeleton organization and alters the endothelial barrier function, thus favoring vascular leakage. However, little is known regarding the role of ERM proteins in diabetic retinopathy (DR).
Objective:
This study aimed to examine whether overexpression of the ERM complex exists in db/db mice and its main regulating factors.
Methods:
9 male db/db mice and 9 male db/+ aged 14 weeks were analyzed. ERM proteins were assessed by western blot and by immunohistochemistry. Vascular leakage was determined by the Evans blue method. To assess ERM regulation, HRECs were cultured in a medium containing 5.5 mM D-glucose (mimicking physiological conditions) and 25 mM D-glucose (mimicking hyperglycemia that occurs in diabetic patients). Moreover, treatment with TNF-α, IL-1β, or VEGF was added to a high glucose condition. The expression of ERM proteins was quantified by RT-PCR. Cell permeability was evaluated by measuring movements of FITC-dextran.
Results:
A significant increase of ERM in diabetic mice in comparison with non-diabetic mice was observed. A high glucose condition alone did not have any effect on ERM expression. However, TNF-α and IL-1β induced a significant increase in ERM proteins.
Conclusion:
The increase of ERM proteins induced by diabetes could be one of the mechanisms involved in vascular leakage and could be considered as a therapeutic target. Moreover, the upregulation of the ERM complex by diabetes is induced by inflammatory mediators rather than by high glucose itself.
Insights
Diabetic retinopathy involves increased ezrin, radixin, and moesin (ERM) proteins, which contribute to vascular leakage. Inflammatory mediators, not high glucose, appear to drive this ERM complex upregulation in diabetes.
Area of Science:
- Biochemistry
- Cell Biology
- Ophthalmology
Background:
- Ezrin, radixin, and moesin (ERM) proteins link membrane proteins to actin filaments.
- ERM activation alters cytoskeleton and endothelial barrier function, promoting vascular leakage.
- The role of ERM proteins in diabetic retinopathy (DR) is largely unknown.
Purpose of the Study:
- To investigate ERM complex overexpression in diabetic (db/db) mice.
- To identify key factors regulating ERM proteins in the context of diabetes.
Main Methods:
- Western blot and immunohistochemistry to assess ERM protein levels in db/db mice.
- In vitro studies using human retinal endothelial cells (HRECs) exposed to varying glucose concentrations and inflammatory cytokines (TNF-α, IL-1β, VEGF).
- RT-PCR and FITC-dextran assays to quantify ERM expression and cell permeability.
Main Results:
- Diabetic mice exhibited significantly increased ERM protein levels compared to controls.
- High glucose alone did not affect ERM expression in HRECs.
- TNF-α and IL-1β significantly increased ERM protein expression in HRECs.
Conclusions:
- Increased ERM proteins in diabetes may contribute to vascular leakage, presenting a potential therapeutic target.
- Diabetes-induced ERM upregulation is primarily mediated by inflammatory cytokines, not hyperglycemia itself.
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