Neutrophil microparticle production and inflammasome activation by hyperglycemia due to cytoskeletal instability

Area of Science:

• Cell Biology
• Immunology
• Metabolic Disorders

Background:

• Microparticles (MPs) are vesicles released by cells under oxidative stress.
• Elevated MP production is observed in diabetes patients, but mechanisms remain unclear.
• Hyperglycemia's effect on leukocyte-derived MPs and inflammasome activation needs elucidation.

Purpose of the Study:

• To investigate if elevated glucose stimulates leukocytes to produce MPs and activate the NLRP3 inflammasome.
• To identify cellular mechanisms linking hyperglycemia, oxidative stress, and MP production in neutrophils.

Main Methods:

• Incubation of human and murine neutrophils and monocytes in varying glucose concentrations (5.5–20 mm).
• Assessment of MP production, IL-1β content, reactive oxygen species (ROS) generation, and S-nitrosylation.
• Genetic depletion of key proteins including capon, ASC, pro-IL-1β, and evaluation of signaling pathways (PKC, IP3R).

Main Results:

• Hyperglycemia (up to 20 mm glucose) progressively increased MP production and IL-1β content in neutrophils, but not monocytes.
• Enhanced MP production was dependent on ROS generation from mitochondria, NADPH oxidase, and NOS-2, leading to actin S-nitrosylation.
• Depletion of capon, ASC, or pro-IL-1β abrogated hyperglycemia-induced ROS, MP, and IL-1β production.
• Inositol 1,3,5-triphosphate receptors, PKC, and actin turnover were essential for the response.

Conclusions:

• Hyperglycemia triggers an interdependent oxidative stress response in neutrophils.
• This response perturbs neutrophil cytoskeletal stability via S-nitrosylation, leading to MP production and IL-1β synthesis.
• The NLRP3 inflammasome and associated signaling pathways are critical mediators of this hyperglycemia-induced cellular response.