Effect of hyperglycemia on human monocyte activation

Area of Science:

• Immunology
• Endocrinology
• Cell Biology

Background:

• Chemokine signaling in monocytes under normal glucose conditions was previously defined.
• The impact of hyperglycemia on monocyte behavior without chemokines remains less understood.

Purpose of the Study:

• To investigate hyperglycemia-induced human monocyte signaling.
• To determine if elevated glucose concentrations alone can modulate monocyte adhesion, migration, and intracellular pathways.

Main Methods:

• Human monocytes (THP-1 cell line) were exposed to normal (5 mM) and high (10, 20 mM) glucose concentrations.
• Adhesion, migration, transmigration, and stress fiber assays were performed.
• Western blotting assessed phosphorylation of Akt, GSK3β, and PI-3 kinase subunits; PI-3 kinase inhibitor LY was used to assess pathway involvement.

Main Results:

• Monocyte adhesion increased significantly at 10 mM glucose compared to 5 mM.
• Monocyte migration, transmigration, and stress fiber formation showed incremental increases at 10 mM and 20 mM glucose.
• Hyperglycemia elevated phosphorylation of Akt, GSK3β, and PI-3 kinase (p101, p110γ).
• Inhibition of PI-3 kinase reversed hyperglycemia-induced monocyte migration.

Conclusions:

• Modest hyperglycemia alone potently stimulates human monocyte activity, including adhesion and migration.
• The PI-3 kinase/Akt pathway is critically involved in mediating hyperglycemia's effects on monocyte function.
• These findings highlight a direct mechanism by which hyperglycemia, common in diabetes, can enhance immune cell activity independently of chemokines.