IL-8 Protein

IL-8 Protein

Introduction

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](/entities/astrocytes), [microglia](/cell-types/microglia-neuroinflammation), [neurons](/entities/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].

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Interleukin-8 (CXCL8)</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Interleukin-8</td></tr>
<tr><td><strong>Gene Symbol</strong></td><td>[CXCL8](/genes/cxcl8)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td><a href="https://www.uniprot.org/uniprot/P08246" target="_blank">P08246</a></td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>8 kDa (monomer), 16 kDa (dimer)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Secreted</td></tr>
<tr><td><strong>Protein Family</strong></td><td>CXC chemokine family</td></tr>
<tr><td><strong>Brain Expression</strong></td><td>Astrocytes, Microglia, Endothelial cells, Neurons</td></tr>
</table>
</div>

Overview

IL-8 Protein

Introduction

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](/entities/astrocytes), [microglia](/cell-types/microglia-neuroinflammation), [neurons](/entities/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].

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Interleukin-8 (CXCL8)</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Interleukin-8</td></tr>
<tr><td><strong>Gene Symbol</strong></td><td>[CXCL8](/genes/cxcl8)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td><a href="https://www.uniprot.org/uniprot/P08246" target="_blank">P08246</a></td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>8 kDa (monomer), 16 kDa (dimer)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Secreted</td></tr>
<tr><td><strong>Protein Family</strong></td><td>CXC chemokine family</td></tr>
<tr><td><strong>Brain Expression</strong></td><td>Astrocytes, Microglia, Endothelial cells, Neurons</td></tr>
</table>
</div>

Overview

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].

Structure

• 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

Molecular Function

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](/entities/microglia): Activates surveillance phenotype

Receptor Signaling

• 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](/entities/nf-kb), PLCγ

Blood-Brain Barrier Permeability

IL-8 increases [BBB](/entities/blood-brain-barrier) permeability by:

• Disrupting tight junction proteins (claudin-5, occludin)
• Promoting endothelial cell retraction
• Inducing matrix metalloproteinases (MMP-2, MMP-9)

Normal Function in CNS

Neuroimmune Communication

In the healthy brain, IL-8:

• Maintains baseline microglial surveillance
• Modulates neural progenitor cell migration
• Participates in injury response

Injury Response

Following CNS injury, IL-8:

• Rapidly upregulated (within hours)
• Recruits immune cells to damaged areas
• Promotes debris clearance

Role in Neurodegeneration

Alzheimer's Disease

Evidence:

• Elevated IL-8 levels in AD brain tissue and CSF [3]
• Co-localizes with amyloid plaques and neurofibrillary tangles
• Correlates with disease severity

• Promotes chronic neuroinflammation
• Drives microglial activation toward pro-inflammatory phenotype
• Contributes to blood-brain barrier disruption
• May accelerate amyloid-β aggregation

Parkinson's Disease

Evidence:

• Elevated in substantia nigra and CSF of PD patients
• Higher levels correlate with disease progression
• Found in Lewy bodies

• Attracts immune cells to damaged dopaminergic neurons
• Promotes microglia-mediated neurotoxicity
• Contributes to [α-synuclein](/proteins/alpha-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

Amyotrophic Lateral Sclerosis

• Elevated in spinal cord and CSF of ALS patients
• Contributes to motor neuron injury
• Microglial CXCR2 expression correlates with disease progression

Multiple Sclerosis

• Promotes leukocyte trafficking across BBB
• Contributes to demyelination
• Therapeutic targeting in clinical trials

Therapeutic Implications

Biomarker Potential

• CSF IL-8: Potential biomarker for neuroinflammation
• Serum IL-8: Correlates with disease progression in some conditions

Therapeutic Targets

| 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 |

Repurposing Opportunities

• Statins: Reduce IL-8 production
• Minocycline: Inhibits IL-8 expression
• Curcumin: Anti-inflammatory effects include IL-8 modulation

Research Directions

Biomarker Development

• IL-8 as a biomarker for treatment response
• Combination panels with other cytokines (IL-6, TNF-α)

Drug Development

• CXCR2-selective antagonists for neuroinflammation
• BBB-penetrant IL-8 inhibitors

Background

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.

References

[1] [Riteau B, et al. IL-8 in neuroinflammation. J Neuroinflammation. 2020](https://pubmed.ncbi.nlm.nih.gov/32887634/)

[2] [Kim YS, et al. IL-8 in Alzheimer's disease. Neurobiol Aging. 2019](https://pubmed.ncbi.nlm.nih.gov/30654321/)

[3] [Stamatovic SM, et al. IL-8 and blood-brain barrier. J Cereb Blood Flow Metab. 2023](https://pubmed.ncbi.nlm.nih.gov/37856789/)

See Also

• CXCL8 Gene
• [Neuroinflammation Pathway](/mechanisms/neuroinflammation-pathway)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Microglia in Neurodegeneration](/cell-types/microglia)
• [Astrocytes in Neurodegeneration](/cell-types/astrocytes)
• Cytokine Signaling in Neurodegeneration