Interleukin-8 (IL-8), also known as CXCL8, is a pro-inflammatory CXC chemokine that functions as a major neutrophil chemoattractant. In the central nervous system, IL-8 is produced by astrocytes, microglia, neurons, and endothelial cells, where it plays roles in neuroinflammation and has been implicated in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease [1].
| Interleukin-8 (CXCL8) |
|---|
| Protein Name | Interleukin-8 |
| Gene Symbol | CXCL8 |
| UniProt ID | P08246 |
| Molecular Weight | 8 kDa (monomer), 16 kDa (dimer) |
| Subcellular Localization | Secreted |
| Protein Family | CXC chemokine family |
| Brain Expression | Astrocytes, Microglia, Endothelial cells, Neurons |
Interleukin-8 (IL-8/CXCL8) is a pro-inflammatory CXC chemokine that functions as a potent chemoattractant and activator of neutrophils, T cells, monocytes, and microglia. It signals through CXCR1 and CXCR2 receptors and has been extensively implicated in neuroinflammatory conditions characteristic of neurodegenerative diseases [2].
- Monomer: 72-residue polypeptide
- Dimerization: Forms functional dimers at physiological concentrations
- Receptor binding sites: N-terminal region critical for receptor engagement
- Heparin-binding domain: Mediates interaction with extracellular matrix
- Three disulfide bonds: Stabilize tertiary structure
¶ Chemotaxis and Cell Activation
IL-8 is a potent chemoattractant for:
- Neutrophils: Primary target, induces respiratory burst
- T lymphocytes: Recruitment to sites of inflammation
- Monocytes/macrophages: Promotes phagocytosis
- Microglia: Activates surveillance phenotype
- CXCR1 (IL-8RA): High affinity for IL-8, activates Gi/o proteins
- CXCR2 (IL-8RB): Lower affinity, binds other CXC chemokines
- Signaling pathways: PI3K/Akt, MAPK/ERK, NF-κB, PLCγ
IL-8 increases BBB permeability by:
- Disrupting tight junction proteins (claudin-5, occludin)
- Promoting endothelial cell retraction
- Inducing matrix metalloproteinases (MMP-2, MMP-9)
In the healthy brain, IL-8:
- Maintains baseline microglial surveillance
- Modulates neural progenitor cell migration
- Participates in injury response
Following CNS injury, IL-8:
- Rapidly upregulated (within hours)
- Recruits immune cells to damaged areas
- Promotes debris clearance
Evidence:
- Elevated IL-8 levels in AD brain tissue and CSF [3]
- Co-localizes with amyloid plaques and neurofibrillary tangles
- Correlates with disease severity
Mechanisms:
- Promotes chronic neuroinflammation
- Drives microglial activation toward pro-inflammatory phenotype
- Contributes to blood-brain barrier disruption
- May accelerate amyloid-β aggregation
Evidence:
- Elevated in substantia nigra and CSF of PD patients
- Higher levels correlate with disease progression
- Found in Lewy bodies
Mechanisms:
- Attracts immune cells to damaged dopaminergic neurons
- Promotes microglia-mediated neurotoxicity
- Contributes to α-synuclein aggregation
- Exacerbates mitochondrial dysfunction
¶ Stroke and Ischemia
- Strongly upregulated after cerebral ischemia (100-1000x)
- Contributes to secondary neuronal injury via neutrophil infiltration
- Blockade of IL-8 signaling is neuroprotective in experimental models
- Elevated in spinal cord and CSF of ALS patients
- Contributes to motor neuron injury
- Microglial CXCR2 expression correlates with disease progression
- Promotes leukocyte trafficking across BBB
- Contributes to demyelination
- Therapeutic targeting in clinical trials
- CSF IL-8: Potential biomarker for neuroinflammation
- Serum IL-8: Correlates with disease progression in some conditions
| Approach |
Status |
Notes |
| CXCR2 antagonists |
Clinical trials |
Reparixin, danirixin in MS |
| IL-8 neutralizing antibodies |
Preclinical |
High affinity binding |
| Small molecule inhibitors |
Research stage |
MAPK pathway blockers |
- Statins: Reduce IL-8 production
- Minocycline: Inhibits IL-8 expression
- Curcumin: Anti-inflammatory effects include IL-8 modulation
- IL-8 as a biomarker for treatment response
- Combination panels with other cytokines (IL-6, TNF-α)
- CXCR2-selective antagonists for neuroinflammation
- BBB-penetrant IL-8 inhibitors
The study of Il 8 Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
[1] Riteau B, et al. IL-8 in neuroinflammation. J Neuroinflammation. 2020
[2] Kim YS, et al. IL-8 in Alzheimer's disease. Neurobiol Aging. 2019
[3] Stamatovic SM, et al. IL-8 and blood-brain barrier. J Cereb Blood Flow Metab. 2023