| Interleukin-10 (IL-10) | |
|---|---|
| Protein Name | Interleukin-10 |
| Gene Symbol | [IL10](/genes/il10) |
| UniProt ID | P08917 |
| Molecular Weight | ~18 kDa (monomer), ~36 kDa (homodimer) |
| Subcellular Localization | Secreted (extracellular) |
| Protein Family | IL-10 cytokine family (class 2 cytokines) |
| Brain Expression | [Microglia](/cell-types/microglia-neuroinflammation), astrocytes, neurons, Tregs |
| Receptor | IL-10R1 (CDW210a) + IL-10R2 (CRFB4) |
| Signaling Pathway | JAK-STAT3 (primary), PI3K-AKT, MAPK |
Interleukin-10 (IL-10) is a potent anti-inflammatory and immunomodulatory cytokine produced by a wide range of immune and non-immune cells, including microglia, astrocytes, neurons, regulatory T cells (Tregs), B cells, and macrophages[1]. As a cornerstone of the immune system's negative feedback mechanisms, IL-10 suppresses pro-inflammatory cytokine production, inhibits antigen presentation by myeloid cells, and promotes the development of regulatory immune populations. In the context of neurodegenerative diseases, IL-10 has emerged as a critical counterbalance to the chronic neuroinflammation that drives Alzheimer's disease (AD) and Parkinson's disease (PD) progression[2].
Unlike classical pro-inflammatory cytokines, IL-10 generally does not induce cell proliferation or direct cytotoxicity. Instead, it functions primarily to de-escalate immune responses once they have been initiated, preventing collateral damage to host tissues. However, the pleiotropic nature of IL-10 — its effects vary by cell type, concentration, and disease context — makes it a complex therapeutic target[3]. In neurodegeneration, the key questions are whether insufficient IL-10 signaling contributes to disease onset, and whether augmenting IL-10 could slow progression without causing harmful immunosuppression.
Human IL-10 is a non-covalent homodimer composed of two 160-amino acid monomers (approximately 18 kDa each), yielding a mature protein of approximately 36 kDa[4]. Each monomer adopts a characteristic four-helix bundle fold (经典的Class 2 cytokine fold) shared by other members of the IL-10 family (IL-19, IL-20, IL-22, IL-24, IL-26). The six helices (named A through F) are arranged in an anti-parallel bundle, with two disulphide bonds (Cys-12 to Cys-108, Cys-70 to Cys-112) providing structural stability. The dimer interface is formed primarily through interactions between the C-terminal helices D, E, and F of each monomer.
The homodimeric structure of IL-10 is essential for its biological activity. Each monomer contains one receptor-binding site, and the dimer simultaneously engages two IL-10R1 molecules (one per monomer), creating a 2:2 stoichiometric complex that is further stabilized by the accessory receptor IL-10R2. The structural basis for receptor recognition has been resolved by X-ray crystallography, revealing that IL-10 engages IL-10R1 primarily through its helices B, C, D, and F[4:1].
IL-10 signals through a heterodimeric receptor complex consisting of:
The high-affinity IL-10:IL-10R1 interaction (Kd ~ 10-100 pM) brings IL-10R2 into proximity, forming a stable ternary signaling complex that activates intracellular signaling cascades.
IL-10R1 is constitutively associated with the tyrosine kinases TYK2 (tyrosine kinase 2) and JAK1. Upon receptor engagement, these kinases phosphorylate tyrosine residues on the intracellular domain of IL-10R1, creating docking sites for STAT3 (Signal Transducer and Activator of Transcription 3)[4:2]. STAT3 binds via its SH2 domain, is then phosphorylated by JAK/TYK2, dimerizes, and translocates to the nucleus where it drives transcription of an extensive anti-inflammatory gene program:
STAT3 target genes include:
While JAK-STAT3 is the dominant pathway, IL-10 also activates:
The net result is a coordinated transcriptional program that simultaneously suppresses pro-inflammatory gene expression, promotes anti-inflammatory gene expression, and shifts cellular metabolism toward repair and homeostasis.
In the healthy central nervous system (CNS), IL-10 performs several important regulatory functions:
Immune homeostasis: IL-10 is the primary anti-inflammatory cytokine that prevents excessive immune responses to self-antigens, commensal microbiota, and environmental antigens that gain access to the CNS. Microglia and astrocytes produce low levels of IL-10 constitutively, maintaining a state of active immune tolerance[5].
Neuroprotection: IL-10 promotes the survival of neurons, oligodendrocytes, and neural progenitor cells under conditions of stress. This is achieved through STAT3-mediated upregulation of anti-apoptotic proteins (Bcl-2, Bcl-xL), inhibition of excitotoxic pathways, and promotion of neurotrophic factor production.
Myelin maintenance: In the healthy CNS, IL-10 supports oligodendrocyte function and myelin integrity. Deficiency of IL-10 or IL-10R1 leads to increased susceptibility to demyelination in animal models[6].
Synaptic plasticity: Emerging evidence suggests that IL-10 participates in the regulation of synaptic plasticity, potentially through effects on microglial surveillance of synaptic function. Under normal conditions, IL-10 may support the synaptic pruning and remodeling that underlies learning and memory.
Multiple cell types contribute to the IL-10 pool in the brain:
The role of IL-10 in AD is complex, with both protective and potentially detrimental effects documented[2:1]:
Microglia are the primary immune cells that encounter and attempt to clear amyloid deposits. In the presence of amyloid-beta plaques, microglia adopt a disease-associated microglia (DAM) or neurodegenerative microglia (MGnD) phenotype characterized by the production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), reactive oxygen/nitrogen species, and reduced phagocytic activity[8].
IL-10 counteracts this phenotype by:
In APP/PS1 transgenic mice (an AD model), IL-10 administration reduces amyloid plaque burden, improves spatial memory performance, and shifts microglial gene expression toward a regulatory phenotype[8:1].
The relationship between IL-10 and amyloid clearance is nuanced. While IL-10 promotes an anti-inflammatory milieu that may support microglial phagocytosis, excessive IL-10 signaling can impair amyloid clearance by suppressing the inflammatory signals needed for microglial activation and recruitment to plaques[2:2]. This creates a therapeutic window challenge: too little IL-10 allows neuroinflammation, too much may prevent beneficial inflammatory clearance of amyloid.
IL-10 protects neurons from amyloid-beta-induced toxicity through multiple mechanisms:
Less is known about the relationship between IL-10 and tau pathology specifically. However, by reducing neuroinflammation (which drives tau kinase activation and phosphorylation), IL-10 may indirectly reduce tau pathology progression. STAT3 activation in neurons may also have direct protective effects on tau metabolism.
Delivery of IL-10 to the CNS is challenging because:
Promising approaches include:
IL-10 has shown consistent neuroprotective effects in PD models, with translational relevance to human disease[9]:
IL-10 directly protects dopaminergic neurons in the substantia nigra pars compacta from toxic insults[9:1]:
Microglial activation in the substantia nigra is a major driver of dopaminergic neuron death in PD. IL-10 suppresses microglial production of:
Importantly, IL-10 inhibits NLRP3 inflammasome activation in microglia through STAT3-mediated pathways, preventing the caspase-1-dependent maturation and release of IL-1β and other inflammasome-associated cytokines[10]. This is particularly relevant for PD, as the NLRP3 inflammasome is strongly activated by α-synuclein aggregates.
The relationship between IL-10 and alpha-synuclein pathology in PD is being actively investigated. IL-10 may:
In mouse models of α-synucleinopathy, IL-10 overexpression reduces microglial activation, attenuates α-synuclein aggregation, and preserves dopaminergic function[11].
The neuroprotective potential of IL-10 in PD has been demonstrated across multiple animal models and delivery platforms[3:1]:
IL-10 is a critical negative regulator of CNS autoimmunity. In multiple sclerosis and EAE (the animal model of MS), IL-10 deficiency accelerates disease onset and severity, while IL-10 overexpression or administration is protective[6:1]:
In SOD1 transgenic mice (an ALS model), IL-10 is expressed at higher levels in microglia as disease progresses, likely as a compensatory anti-inflammatory response. Overexpression of IL-10 in astrocytes delays disease onset and extends survival, while IL-10 deficiency accelerates disease[1:1]. This suggests that the IL-10 response in ALS, while present, is insufficient to counteract the intense neuroinflammation driving motor neuron death.
Evidence for IL-10 in Huntington's disease is more limited, but studies in HD mouse models (R6/2, HdhQ150) suggest that boosting anti-inflammatory cytokines including IL-10 could modulate the microglial activation and neuroinflammation observed in HD.
IL-10 levels in CSF and brain tissue of FTD patients show variable changes depending on the underlying pathology (TDP-43 vs. tau). The relationship is less well-characterized than in AD and PD.
Microglia adopt different functional phenotypes in response to environmental cues. The classical M1 (pro-inflammatory) vs. M2 (regulatory) paradigm has been refined by single-cell RNA sequencing studies that reveal much greater heterogeneity:
Disease-Associated Microglia (DAM): These cells show altered homeostatic gene expression (downregulation of P2ry12, Tmem119) and upregulated inflammatory genes. IL-10 can shift the DAM toward a more regulatory phenotype, promoting tissue repair functions.
Neurodegenerative Microglia (MGnD): Characterized by high expression of Trem2-dependent genes and a strong pro-inflammatory, phagocytic state. IL-10 suppresses key MGnD genes while promoting expression of neuroprotective factors[12].
TREM2-dependent effects: TREM2 is a critical microglial receptor for amyloid clearance and microglial survival. IL-10 signaling can enhance TREM2 expression and function, creating a positive interaction between two key neuroprotective pathways.
Given its demonstrated neuroprotective potential, IL-10 is an attractive therapeutic target. However, the pleiotropic nature of this cytokine demands careful therapeutic design[3:2]:
| Approach | Agent/Strategy | Status | Notes |
|---|---|---|---|
| Recombinant IL-10 | rIL-10 (Tenovil) | Clinical trials (cancer, autoimmunity) | Limited BBB penetration; short half-life |
| AAV-IL-10 gene therapy | AAV-IL-10 | Preclinical | Sustained CNS expression; one-time treatment |
| IL-10-secreting Tregs | Adoptive cell therapy | Preclinical | Targeted delivery; additional immunomodulation |
| IL-10R agonists | Engineered variants | Preclinical | Enhanced potency, selectivity |
| IL-10 boosters | Small molecules, dietary interventions | Preclinical | Enhance endogenous IL-10 production |
| IL-10 fusion proteins | IL-10-Fc, BBB-penetrant variants | Preclinical | Improved half-life and CNS delivery |
| Combinatorial therapy | IL-10 + neurotrophic factors | Preclinical | Additive/synergistic effects |
CSF IL-10 levels are being evaluated as biomarkers of anti-inflammatory status in neurodegeneration:
Saraiva AM, et al. Interleukin-10: a cytokine with anti-inflammatory, immunomodulatory and regenerative properties. Cytokine & Growth Factor Reviews. 2020. ↩︎ ↩︎
Zhou XY, et al. IL-10 in neuroinflammation: the good, the bad, and the ugly. Neuroscience Bulletin. 2022. ↩︎ ↩︎ ↩︎
Thompson JA, et al. Therapeutic strategies targeting IL-10 in neurodegenerative diseases. Expert Opinion on Therapeutic Targets. 2023. ↩︎ ↩︎ ↩︎
Walter MR, et al. IL-10 signal transduction: new insights from structural biology. Trends in Immunology. 2021. ↩︎ ↩︎ ↩︎
Kelley GA, et al. IL-10 and microglial homeostasis in neurodegeneration. Trends in Neurosciences. 2022. ↩︎
Chen Q, et al. Role of IL-10 in demyelinating diseases and neuroautoimmunity. Journal of Immunology Research. 2021. ↩︎ ↩︎
Zhang K, et al. IL-10 polymorphisms and Alzheimer's disease risk: a meta-analysis. Neurobiology of Aging. 2020. ↩︎
Yang L, et al. IL-10 modulates amyloid-beta-induced microglial activation and neurotoxicity. Journal of Neuroinflammation. 2021. ↩︎ ↩︎
Johnston LC, et al. IL-10 protects dopaminergic neurons in Parkinson's disease models via inhibition of microglial activation. Brain. 2021. ↩︎ ↩︎
Li H, et al. IL-10 inhibits NLRP3 inflammasome activation in microglia through STAT3-mediated pathways. Cellular & Molecular Immunology. 2022. ↩︎
Lin Z, et al. Adeno-associated virus-delivered IL-10 for Parkinson's disease: long-term results in animal models. Molecular Therapy. 2023. ↩︎ ↩︎
Park ES, et al. IL-10 receptor expression on microglia and its role in amyloid clearance. Acta Neuropathologica Communications. 2024. ↩︎