IL11 (Interleukin-11) is a member of the IL-6 family of cytokines that plays important roles in hematopoiesis, immune regulation, and tissue protection. Originally discovered for its role in platelet production, IL-11 has since been recognized for its anti-inflammatory properties and potential neuroprotective effects. In the nervous system, IL-11 is expressed in various cell types and has been implicated in neuroinflammation, astrocyte function, and neurodegenerative diseases.
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|
| Symbol |
IL11 |
| NCBI Gene ID |
3609 |
| Chromosome |
19q13.4 |
| Protein Class |
IL-6 family cytokine |
| Molecular Weight |
~19 kDa |
| UniProt |
P20815 |
| OMIM |
147681 |
| Aliases |
AGIF, OPN, oprelvekin |
IL-11 is a secreted cytokine composed of 199 amino acids in its mature form. The protein adopts a characteristic four-helix bundle fold shared by the IL-6 family cytokines. The structure consists of:
- Four α-helices (A, B, C, D) arranged in an up-up-down-down topology
- Long connecting loops between helices
- N-terminal signal peptide (21 amino acids) for secretion
The receptor-binding sites are located on the exposed surfaces of helices A and C, allowing interaction with the IL-11 receptor complex.
IL-11 has diverse biological functions spanning multiple organ systems:
- Thrombopoiesis: Stimulates platelet production from megakaryocytes, the primary clinical use of recombinant IL-11 (oprelvekin)
- Erythropoiesis: Supports red blood cell production
- Megakaryocyte maturation: Promotes differentiation and platelet release
- Anti-inflammatory: Inhibits pro-inflammatory cytokine production (TNF-α, IL-1β, IL-6)
- T cell regulation: Modulates T cell responses and Th17 differentiation
- Dendritic cell function: Affects antigen presentation and immune activation
- Astrocyte function: Supports astrocyte survival, proliferation, and function
- Neuroprotection: Exhibits protective effects in neuronal injury models
- Blood-brain barrier: May modulate BBB integrity and function
- Neuroinflammation: Regulates glial activation and inflammatory responses
- Cardiac fibroblasts: Promotes cardiac fibroblast function and cardiac remodeling
- Cancer-associated fibroblasts: Supports tumor stroma in certain cancers
- Fibrosis: Plays roles in tissue fibrosis and wound healing
IL-11 signals through a heterodimeric receptor complex:
- IL11RA (Interleukin-11 Receptor Subunit Alpha, gene ID 3590): Ligand-binding subunit, primarily expressed in many cell types including neurons and astrocytes
- IL6ST (GP130, gene ID 3572): Signal-transducing subunit, shared across the IL-6 family (IL-6, LIF, OSM, CNTF, CT-1)
The receptor complex forms a high-affinity binding site for IL-11, triggering intracellular signaling cascades.
IL-11 activates multiple signaling cascades through GP130-mediated activation:
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JAK/STAT pathway: Primarily JAK1/JAK2 and STAT3, the dominant pathway
- STAT3 phosphorylation and dimerization
- Nuclear translocation and gene transcription
- Anti-apoptotic and anti-inflammatory gene expression
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MAPK/ERK pathway: Cell proliferation and differentiation
- RAS/RAF/MEK/ERK cascade activation
- Cell growth and survival signals
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PI3K/Akt pathway: Cell survival and metabolism
- Akt activation promotes cell survival
- Anti-apoptotic signaling
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PKC pathway: Additional cellular responses
- PKC isoform activation
- Cytoskeletal and functional responses
IL-11 is widely expressed in various tissues with cell-type specificity:
| Cell Type |
Expression Level |
Notes |
| Astrocytes |
Moderate-High |
Important in CNS, upregulated in inflammation |
| Neurons |
Low-Moderate |
Constitutive expression in various brain regions |
| Osteoblasts |
High |
Bone metabolism and remodeling |
| Fibroblasts |
High |
Stromal cells, wound healing |
| Megakaryocytes |
High |
Platelet production |
| Cardiac fibroblasts |
High |
Cardiac tissue remodeling |
| Cancer-associated fibroblasts |
High |
Tumor microenvironment |
IL-11 has been studied in Alzheimer's disease pathogenesis. Chen et al. (2014) demonstrated altered IL-11 expression in AD brain tissue, with potential neuroprotective roles through anti-inflammatory mechanisms. Further studies have shown:
- IL-11 levels are reduced in AD patient brains
- The cytokine exhibits protective effects against amyloid-beta toxicity
- May modulate neuroinflammation characteristic of AD pathology
Astrocytic IL-11 has been investigated in PD models:
- Astrocyte-derived IL-11 may provide neuroprotective effects in dopaminergic neurons
- Anti-inflammatory properties may reduce microglial activation
- Potential therapeutic target for slowing disease progression
Recent research has explored IL-11 in ALS:
- Altered expression in ALS models and patient tissue
- Cytokine therapy approaches using IL-11 have been investigated
- May modulate neuroinflammation in motor neuron disease
IL-11 has immunomodulatory roles in CNS autoimmunity:
- Dysregulated expression in MS lesions
- Potential therapeutic applications
- Effects on T cell polarization and demyelination
IL-11 demonstrates neuroprotective properties in injury models:
- Promotes neuronal survival after injury
- Modulates inflammatory responses
- Supports tissue repair mechanisms
- Thrombocytopenia: Recombinant human IL-11 (oprelvekin) FDA-approved for chemotherapy-induced thrombocytopenia
- Inflammatory bowel disease: Immunomodulatory roles
- Rheumatoid arthritis: Anti-inflammatory properties
- Fibrosis: Both pro-fibrotic and anti-fibrotic roles depending on context
- Cancer: Controversial roles - both tumor-promoting and tumor-suppressing
The involvement of IL-11 in Alzheimer's disease has been increasingly recognized through multiple lines of evidence. In AD brain tissue, IL-11 expression is altered compared to age-matched controls, with reduced levels observed in key brain regions affected by the disease. This reduction may have pathophysiological consequences:
Amyloid-Beta Interaction:
- IL-11 demonstrates protective effects against amyloid-beta toxicity in neuronal cultures
- The cytokine can modulate the inflammatory response triggered by amyloid-beta accumulation
- STAT3 activation by IL-11 may promote expression of anti-apoptotic proteins that protect neurons from amyloid-induced cell death
Neuroinflammatory Modulation:
- IL-11 inhibits production of pro-inflammatory cytokines including TNF-α, IL-1β, and IL-6
- This anti-inflammatory effect may counteract the chronic neuroinflammation characteristic of AD
- Astrocyte-derived IL-11 may provide a regulatory signal that limits microglial activation
Tau Pathology:
- Evidence suggests IL-11 may influence tau phosphorylation pathways
- The cytokine's effects on neuronal survival could impact tau-induced neurodegeneration
- Further research is needed to fully delineate these mechanisms
In Parkinson's disease, IL-11 has emerged as a potentially protective cytokine in the context of dopaminergic neuron survival:
Astrocyte-Mediated Neuroprotection:
- Astrocytes produce IL-11 in response to various cellular stresses
- This astrocyte-derived IL-11 may protect neighboring dopaminergic neurons
- The JAK/STAT pathway activated by IL-11 promotes expression of genes that support neuronal survival
Inflammatory Regulation:
- IL-11's anti-inflammatory properties may reduce microglial activation in the substantia nigra
- This could slow the progression of dopaminergic neuron loss
- The cytokine may also modulate the inflammatory environment associated with alpha-synuclein pathology
Therapeutic Potential:
- Recombinant IL-11 or IL-11 receptor agonists are being explored as disease-modifying approaches
- Gene therapy strategies to increase IL-11 expression in the brain are under investigation
- Combination approaches targeting multiple neuroprotective pathways may prove most effective
Recent studies have investigated IL-11 in ALS, where it may play complex roles:
Expression Changes:
- Altered IL-11 expression has been observed in ALS patient tissue and animal models
- Both increased and decreased IL-11 levels have been reported, depending on disease stage and model system
- The cell type-specific sources of IL-11 in ALS remain under investigation
Potential Mechanisms:
- IL-11 may modulate neuroinflammation in the motor neuron microenvironment
- The cytokine's effects on RNA metabolism may intersect with other ALS-related pathways
- STAT3-mediated signaling could promote motor neuron survival
Therapeutic Applications:
- IL-11 cytokine therapy approaches are being explored in preclinical models
- Delivery methods including viral vectors and protein administration are under investigation
- Combination with other neuroprotective factors represents a promising direction
In multiple sclerosis and related autoimmune demyelinating diseases, IL-11 has immunomodulatory properties that may be therapeutically relevant:
Immune System Effects:
- IL-11 inhibits production of pro-inflammatory cytokines from immune cells
- The cytokine promotes a shift toward anti-inflammatory immune responses
- Regulatory T cell function may be enhanced by IL-11
CNS Effects:
- In demyelinating lesions, IL-11 expression is dysregulated
- The cytokine may support remyelination processes
- Neuroprotective effects could limit axon loss during inflammatory attacks
Therapeutic Considerations:
- Recombinant IL-11 has been investigated in clinical trials for MS
- The complex immunomodulatory effects require careful dosing considerations
- Patient selection based on cytokine profiles may improve outcomes
IL-11 demonstrates neuroprotective properties in models of spinal cord injury:
Acute Phase Effects:
- IL-11 is upregulated following spinal cord injury
- The cytokine promotes survival of damaged neurons
- Anti-inflammatory effects limit secondary damage from inflammation
Recovery Promotion:
- IL-11 supports tissue repair mechanisms
- The cytokine may promote axonal regeneration
- Functional recovery has been observed in animal models with IL-11 treatment
Mechanisms:
- STAT3 activation is a key mediator of IL-11's protective effects
- The cytokine modulates the injury microenvironment
- Anti-apoptotic signaling contributes to neuronal survival
The JAK/STAT pathway is the primary signaling cascade activated by IL-11 receptor engagement:
Receptor Activation:
- IL-11 binding to IL11RA triggers association with IL6ST/GP130
- GP130 dimerization brings JAK1 and JAK2 kinases into proximity
- These JAKs transphosphorylate and become activated
STAT3 Activation:
- Activated JAKs phosphorylate STAT3 on specific tyrosine residues
- Phosphorylated STAT3 dimerizes and translocates to the nucleus
- STAT3 dimers bind to specific DNA sequences and regulate gene transcription
Biological Effects:
- Anti-apoptotic genes (Bcl-xL, Mcl-1, Survivin)
- Anti-inflammatory genes (SOCS3, IL-10)
- Acute phase proteins and tissue repair factors
IL-11 also activates the MAPK cascade:
Ras/Raf/MEK/ERK Pathway:
- GP130 engages adaptor proteins that activate Ras
- Ras activates Raf kinase, which phosphorylates MEK
- MEK phosphorylates ERK, which enters the nucleus
Cellular Outcomes:
- Cell proliferation and differentiation
- Cell survival signals
- Integration with other pathways
The PI3K/Akt pathway provides additional survival signals:
Signaling Cascade:
- Receptor engagement activates PI3K
- PI3K generates PIP3, which activates Akt
- Akt phosphorylates multiple downstream targets
Neuroprotective Effects:
- Phosphorylation of BAD, promoting cell survival
- Activation of mTOR for protein synthesis
- Regulation of glucose metabolism
Recombinant human IL-11 (oprelvekin) has known pharmacokinetic properties:
- Absorption: Subcutaneous administration results in slow absorption
- Distribution: Limited tissue distribution, primarily circulating
- Metabolism: Renal metabolism and clearance
- Half-life: Approximately 6-7 hours in healthy subjects
Clinical use of IL-11 is associated with several side effects:
- Fluid retention: Peripheral edema, weight gain
- Fatigue: Common with systemically administered IL-11
- Arthralgia: Joint pain and stiffness
- Myalgia: Muscle pain
- Thrombocytosis: Elevated platelet counts above therapeutic range
Current FDA-approved indication:
- Chemotherapy-induced thrombocytopenia
- Investigational for neuroprotective applications
IL-11's role in neurodegenerative diseases involves multiple mechanisms:
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Anti-inflammatory effects: IL-11 inhibits pro-inflammatory cytokine production, reducing neuroinflammation that drives neurodegeneration
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STAT3-mediated neuroprotection: IL-11 activates STAT3 signaling, which promotes anti-apoptotic gene expression and neuronal survival
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Astrocyte modulation: IL-11 affects astrocyte function, which is critical for neuronal support and neuroinflammation regulation
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Blood-brain barrier: May improve or modulate BBB function in neurodegenerative conditions
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Protein homeostasis: Emerging evidence suggests roles in cellular protein quality control mechanisms