Chronically elevated glucose-induced apoptosis is mediated by inactivation of Akt in cultured Müller cells

Area of Science:

• Cell Biology
• Diabetic Retinopathy
• Molecular Medicine

Background:

• Hyperglycemia is a hallmark of diabetes, contributing to cellular damage and apoptosis in various tissues.
• The precise mechanisms by which high glucose induces cell death, particularly in retinal Müller cells, remain incompletely understood.

Purpose of the Study:

• To investigate the role of the Akt signaling pathway in hyperglycemia-induced apoptosis of rat retinal Müller cells.
• To elucidate the molecular mechanisms linking chronic hyperglycemia to cell death in the diabetic retina.

Main Methods:

• Culturing rat retinal Müller cells with high glucose (25 mM) and assessing apoptosis and Akt activity.
• Analyzing Akt phosphorylation status, BAD dephosphorylation, cytochrome c release, and caspase activation in Müller cells from diabetic rats.
• Modulating Akt activity using overexpression of constitutively active Akt and dominant-negative Akt to evaluate its role in apoptosis.

Main Results:

• High glucose significantly inactivated Akt and induced apoptosis in cultured Müller cells.
• Hyperglycemia led to Akt dephosphorylation at serine-473, dephosphorylation of BAD, increased cytochrome c release, and activation of caspase-3 and caspase-9.
• Upregulating Akt activity protected against high glucose-induced apoptosis, while downregulating Akt exacerbated it.

Conclusions:

• Downregulation of the Akt survival pathway is a key mechanism mediating apoptosis induced by chronic hyperglycemia in Müller cells.
• While acute high glucose may support cell survival, chronic hyperglycemia promotes apoptosis through Akt pathway inactivation.
• Targeting the Akt pathway may offer a therapeutic strategy for preventing diabetic retinal cell death.