{{ infobox .infobox-gene
| gene = IL32
| name = Interleukin 32
| chromosome = 16p13.3
| ncbi_gene_id = 9235
| ensembl = ENSG00000127124
| uniprot = P24001
| gene_family = IL-32 cytokine family
| diseases = Rheumatoid Arthritis, Inflammatory Disorders, Alzheimer's Disease, Parkinson's Disease, Multiple Sclerosis
}}
IL32 (Interleukin 32) is a pro-inflammatory cytokine originally identified based on its elevated expression in activated natural killer (NK) cells and T cells [1/https://pubmed.ncbi.nlm.nih.gov/15816860/). Unlike typical interleukins, IL32 is a highly basic, heparin-binding protein that lacks the conventional cytokine structure. Instead, it adopts a unique three-dimensional fold that allows it to interact with multiple receptors and cell types. IL32 is now recognized as a potent mediator of inflammation in various diseases, including rheumatoid arthritis, inflammatory bowel disease, and potentially neurodegenerative diseases [2/https://pubmed.ncbi.nlm.nih.gov/12885573/).
The cytokine is expressed in various cell types including T cells, NK cells, monocytes, epithelial cells, and endothelial cells. More importantly, recent studies have detected IL32 expression in the central nervous system (CNS), where it may contribute to neuroinflammation and disease pathogenesis [8/https://pubmed.ncbi.nlm.nih.gov/22572556/). Given the central role of neuroinflammation in neurodegenerative diseases, IL32 represents a potentially important link between peripheral immune responses and CNS pathology.
The IL32 gene is located on chromosome 16p13.3 and encodes multiple protein isoforms through alternative splicing. The human IL32 gene produces at least eight isoforms (IL32α, β, γ, δ, ε, ζ, η, and θ), each with distinct biological activities and expression patterns.
The IL32 protein exhibits several unique features 1:
IL32 is expressed in various peripheral tissues and cell types:
In the CNS, IL32 expression has been documented in 8:
IL32 activates multiple signaling cascades 3:
IL32 exhibits multiple functions 5:
IL32 is highly expressed in rheumatoid arthritis (RA) and contributes to disease pathogenesis 2 26:
In Alzheimer's disease), IL32 may contribute through [9/https://pubmed.ncbi.nlm.nih.gov/16876765/):
Neuroinflammation: Elevated IL-32 in AD brains may amplify inflammatory responses
Microglial Activation: IL-32 can activate microglia, promoting chronic inflammation [11/https://pubmed.ncbi.nlm.nih.gov/26284489/) [12/https://pubmed.ncbi.nlm.nih.gov/22801412/)
TREM2 Interaction: IL-32 signaling may intersect with TREM2 pathways important in AD microglia 10
In Parkinson's disease), IL32 may contribute to:
IL32 is implicated in multiple sclerosis [9/https://pubmed.ncbi.nlm.nih.gov/24286046/):
Chronic neuroinflammation is a hallmark of neurodegenerative diseases [12/https://pubmed.ncbi.nlm.nih.gov/22801412/), and IL32 contributes through multiple mechanisms:
Microglial Activation: IL-32 activates microglial cells, promoting pro-inflammatory cytokine production 11
Astrocyte Reactivity: IL-32 influences astrocyte function and the neurotoxic A1 phenotype 14
Blood-Brain Barrier: IL-32 may affect BBB permeability, allowing immune cell infiltration 15
Cytokine Cascade: IL-32 induces other pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), amplifying inflammation
Aging-related changes in cytokine expression contribute to neurodegeneration 13:
IL32 participates in several molecular interactions:
| Partner | Interaction Type | Relevance |
|---|---|---|
| TNFR1/2 | Receptor binding | NF-κB activation |
| IL-6R | Cytokine cross-talk | Inflammation amplification |
| PKR | Apoptosis induction | Cell death signaling |
| TLR3 | Viral recognition | Anti-viral response |
| Caspase-1 | Inflammasome | IL-1β processing |
IL32 represents a potential therapeutic target [25/https://pubmed.ncbi.nlm.nih.gov/27429039/):
IL32 may serve as:
IL32 is a unique pro-inflammatory cytokine with important roles in immune regulation and inflammation. Its expression in the CNS and contribution to neuroinflammation make it relevant to neurodegenerative disease pathogenesis. The cytokine's ability to amplify inflammatory responses through multiple pathways suggests it may be an important therapeutic target for conditions like Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Further research into IL32's specific roles in neurodegeneration may reveal novel therapeutic opportunities.
IL-32 signals through multiple receptor interactions, though its precise receptor(s) remain under investigation [3/https://pubmed.ncbi.nlm.nih.gov/16502434/). Current evidence suggests IL-32 can engage:
Primary receptor candidates:
The diversity of receptor interactions explains IL-32's pleiotropic effects across different cell types and disease contexts.
Upon receptor engagement, IL-32 activates multiple intracellular pathways 3/https://pubmed.ncbi.nlm.nih.gov/16502434/):
NF-κB Pathway:
MAPK Pathways:
PKR-Dependent Apoptosis [4/https://pubmed.ncbi.nlm.nih.gov/17623080/):
IL-32 can activate caspase-1 through inflammasome formation:
IL-32 shows complex interactions with amyloid-beta (Aβ) pathology in Alzheimer's disease [9/https://pubmed.ncbi.nlm.nih.gov/16876765/):
Aβ-Induced IL-32:
IL-32 Effects on Amyloid Processing:
IL-32 may influence tau phosphorylation and spread:
IL-32 contributes to synaptic pathology in AD [12/https://pubmed.ncbi.nlm.nih.gov/22801412/):
The TREM2 variant in AD critically affects microglial responses to IL-32 [10/https://pubmed.ncbi.nlm.nih.gov/29453415/):
In Parkinson's disease, IL-32 contributes to the selective vulnerability of dopaminergic neurons 12:
IL-32 may interact with α-synuclein pathology:
Given LRRK2's importance in PD:
IL-32 plays complex roles in MS pathogenesis 9:
In demyelination:
In remyelination:
IL-32 affects BBB integrity 15:
Experimental autoimmune encephalomyelitis (EAE) provides insights:
Current models include:
Current model limitations:
Several approaches are being explored 25:
| Approach | Mechanism | Development Status |
|---|---|---|
| Anti-IL-32 antibodies | Neutralize IL-32 activity | Preclinical |
| IL-32 isoforms selective targeting | Target specific variants | Early research |
| Downstream pathway inhibitors | Block NF-κB, MAPK | Clinical for other diseases |
| Cell-penetrant inhibitors | Intracellular targeting | Preclinical |
| Gene therapy | Modulate expression | Early research |
Key obstacles to therapeutic development:
Future strategies may include:
IL-32 may serve as:
Prognostic applications include:
Therapeutic monitoring potential:
| Property | IL-32 | IL-1β | IL-6 | TNF-α |
|---|---|---|---|---|
| Receptor | Multiple | IL-1R1 | IL-6R | TNFR1/2 |
| Signaling | NF-κB, MAPK, PKR | NF-κB, MAPK | JAK-STAT | NF-κB |
| CNS expression | Neurons, glia | Glia | Neurons, glia | Glia |
| Therapeutic targeting | Emerging | Proven | Proven | Proven |
IL-32 interacts with other cytokines:
Current methodologies include:
Experimental approaches:
Human research approaches:
Critical gaps in knowledge:
New research directions:
Translation priorities:
The IL32 gene shows polymorphism across populations:
Genetic studies have examined IL32 variants:
IL32 expression is epigenetically regulated:
In neurons, IL-32 has distinct effects [8/https://pubmed.ncbi.nlm.nih.gov/22572556/):
Intracellular signaling:
Activity-dependent effects:
Microglia respond to IL-32 through multiple mechanisms [11/https://pubmed.ncbi.nlm.nih.gov/26284489/):
Activation states:
TREM2 relationship:
IL-32 affects astrocyte function [14/https://pubmed.ncbi.nlm.nih.gov/25309408/):
Reactive phenotypes:
Neurovascular unit:
IL-32 serves as a link between peripheral and CNS immunity:
Systemic inflammation:
Immune cell trafficking:
IL-32 interacts with the broader cytokine network:
Pro-inflammatory amplification:
Anti-inflammatory modulation:
IL-32 levels may help stratify patients:
Serial IL-32 measurement could track:
Understanding IL-32 biology informs:
Dietary factors influence IL-32:
Exercise modulates IL-32 30:
Psychological stress affects IL-32:
Single-cell approaches reveal:
Integration approaches provide:
Bioinformatics applications include:
IL-32 represents a critical nexus between peripheral immunity and neuroinflammation. Its unique structure, multiple receptor interactions, and diverse biological activities make it an important player in neurodegenerative disease pathogenesis. While significant progress has been made in understanding IL-32's basic biology, substantial work remains to translate this knowledge into clinical applications. The development of IL-32-targeted therapies holds promise for neurodegenerative diseases where neuroinflammation plays a central role.