Elevated interleukin-8 enhances prefrontal synaptic transmission in mice with persistent inflammatory pain

Area of Science:

• Neuroscience
• Immunology
• Pain Research

Background:

• Interleukin-8 (IL-8) is implicated in inflammation and pain development.
• IL-8 expression elevates in the brain following peripheral inflammation.
• The anterior cingulate cortex (ACC) processes pain, but IL-8's role in its synaptic changes during chronic pain is unclear.

Purpose of the Study:

• To investigate IL-8 expression in the ACC and spinal cord after peripheral inflammation.
• To determine the effect of IL-8 on synaptic transmission in the ACC.
• To assess the therapeutic potential of blocking IL-8 receptors in inflammatory pain.

Main Methods:

• Hind-paw administration of complete Freund's adjuvant (CFA) in mice to induce peripheral inflammation.
• ELISA for quantifying IL-8 protein levels in the ACC, somatosensory cortex, and spinal cord.
• In vitro whole-cell patch-clamp recordings to analyze ACC synaptic transmission.
• Local infusion of repertaxin (IL-8 receptor blocker) and assessment of paw withdrawal latency.

Main Results:

• CFA induced chronic inflammation, leading to increased IL-8 expression in the ACC and spinal cord.
• IL-8 significantly enhanced ACC synaptic transmission by increasing neurotransmitter release probability.
• Repertaxin administration prolonged paw withdrawal latency, indicating reduced pain sensitivity.

Conclusions:

• IL-8 up-regulation in the ACC contributes to enhanced prefrontal synaptic transmission in persistent inflammatory pain.
• Targeting IL-8 signaling pathways may offer a novel therapeutic strategy for managing chronic pain.