Recombinant Human Interleukin-1 receptor type 1 (IL1R1)

What is IL1R1 and what are its primary functions in physiological and pathological conditions?

Interleukin-1 Receptor Type 1 (IL1R1) is the cognate receptor for IL-1, a pro-inflammatory cytokine that exerts wide-ranging neurological and immunological effects throughout the central nervous system (CNS). IL1R1 mediates both homeostatic functions and pathological responses depending on context.

Under physiological conditions, basal IL-1 signaling through IL1R1 regulates:

• Neuroendocrine activity

• Normal sleep patterns

• Cognitive functioning

In pathological states, elevated IL-1 levels and enhanced IL1R1 activation are associated with:

• Neuroinflammation

• Altered HPA axis function

• Induction of sickness behaviors

• Enhanced microglial function

• Increased peripheral immune cell trafficking into the CNS

• Neural damage via astrocyte ROS production

• Various affective and mood disorders

• Decreased cognitive abilities

Methodological approach: To investigate IL1R1 function, researchers have developed conditional gene deletion/restoration models that allow selective manipulation of IL1R1 expression in specific cell types. This approach has revealed that IL1R1 signaling differs between cell types, with neurons utilizing an alternatively spliced accessory protein isoform (IL-1RAcPb) that prevents canonical MyD88-dependent signaling .

IL1R1 plays a central role in neuroinflammation through multiple mechanisms:

• Cell-type specific effects: Neuronal IL1R1 (nIL-1R1) expressing populations can become dysregulated during inflammation, leading to pathological responses. For example, IL1R1-expressing dentate gyrus neurons are necessary and sufficient for stress-induced social behavior abnormalities and working memory dysfunctions .

• Neurotransmitter modulation: IL1R1 in dorsal raphe nucleus neurons increases serotonin reuptake through enhanced SERT activity via P38-MAPK dependent mechanisms .

• Neural circuit dysfunction: Specific neural circuits expressing IL1R1 can become vulnerable targets during neuroinflammation, contributing to behavioral and cognitive impairments .

Methodological approach: Researchers can investigate IL1R1's role in neuroinflammation by combining conditional IL1R1 expression models with behavioral testing paradigms following inflammatory challenges. Functional outputs of IL1R1-expressing neuronal populations can be assessed through electrophysiology, calcium imaging, and behavioral assays .

What methodological approaches can be used to study cell-type specific IL1R1 signaling in the brain?

Advanced methodological approaches for investigating cell-type specific IL1R1 signaling include:

Implementation strategy:

• Generate cell-type specific IL1R1 expressing mice using appropriate Cre lines

• Confirm specificity of recombination for each Cre line

• Assess IL1R1 expression patterns using reporter systems and/or ISHH

• Test functional responses to inflammatory challenges or IL-1β administration

• Correlate molecular signaling with physiological or behavioral outcomes

This multilevel approach allows researchers to precisely map IL1R1 signaling pathways in specific cell populations and understand their contributions to both normal brain function and disease states.

What are the challenges and strategies in engineering optimized IL1R1 antagonists?

Engineering optimized IL1R1 antagonists presents several challenges requiring sophisticated approaches:

Methodological framework for IL1R1 antagonist optimization:

• Utilize protein BLAST and ZDOCK for ligand-receptor docking simulations

• Identify low-affinity sites common across IL-1RA/IL-1β/EBI-005

• Map deletion clusters with minimal impact on binding interface

• Create truncated versions and verify structural integrity

• Test binding affinity and antagonistic activity

This systematic approach has led to the development of a truncated IL-1RA with the potential for improved efficacy in treating peripheral inflammation .

How does IL1R1 signaling contribute to cardiovascular pathologies?

IL1R1 signaling plays a significant role in cardiovascular diseases, particularly atherosclerosis:

• Endothelial expression: IL-1 is predominantly expressed within the endothelium of human coronary atherosclerotic plaques, with enhanced IL1R1 signaling activation in progressive lesions .

• Flow-dependent regulation: Disturbed flow (d-flow) conditions induce IL1R1 activation both in vitro and in vivo .

• Cell phenotype changes: Single-cell RNA sequencing analysis of carotid arteries exposed to disturbed flow confirmed IL1R1 upregulation among endothelial-to-mesenchymal transition (EndMT) populations .

Methodological approach for studying IL1R1 in cardiovascular disease:

• Apply flow models (in vitro and in vivo) to simulate disturbed flow conditions

• Analyze IL1R1 expression patterns in vascular endothelium from different arterial regions

• Conduct transcriptomic profiling to identify associated pathways

• Perform interventional studies using IL1R1 antagonists in atherosclerosis models

These approaches reveal how IL1R1 signaling contributes to vascular inflammation and atherosclerotic plaque development, potentially identifying new targets for cardiovascular disease treatment.

What is the significance of IL1R1 genetic variations in disease susceptibility?

Genetic variations in IL1R1 and related genes can influence disease susceptibility, particularly for thrombotic conditions:

• Venous thrombosis risk: Homozygous carriership of haplotype 5 (H5) of IL1RN, tagged by SNP 13888T/G (rs2232354), increases the risk of venous thrombosis with an odds ratio of 3.9 (95% CI: 1.6-9.7, p=0.002) .

• Haplotype analysis: Comprehensive haplotype analysis can identify specific genetic variations that influence disease risk more effectively than single SNP analysis .

• Clinical implications: The prothrombotic effect of IL-1 signaling through IL1R1 may be modulated by genetic variations, affecting individual susceptibility to thrombotic events .

Methodological approach for genetic association studies:

• Conduct case-control studies with well-characterized patient populations

• Genotype multiple SNPs across IL1R1 and related genes

• Perform haplotype analysis to identify risk-associated genetic patterns

• Test functional consequences of identified variants

• Validate findings in independent cohorts

This approach has revealed specific genetic variations that influence thrombotic risk, potentially informing personalized risk assessment and targeted preventive strategies.

How can heterogeneity in IL1R1 antagonist treatment response be predicted and managed?

Clinical studies have demonstrated significant heterogeneity in response to IL1R1 antagonist therapy, necessitating precision medicine approaches:

• Biomarker identification: Plasma IL1R1 antagonist concentration can predict treatment response. In sepsis patients, those with baseline plasma IL1R1 antagonist above 2,071 pg/mL showed reduced mortality with recombinant human IL1R1 antagonist therapy (adjusted risk difference -0.12; 95% CI -0.23 to -0.01, p=0.044) .

• Response stratification: The table below summarizes treatment responses based on biomarker levels:

• Precision trial design: Evidence supports conducting precision clinical trials of recombinant human IL1R1 antagonist targeted specifically to patients with high plasma IL1R1 antagonist levels .

Methodological approach:

• Measure baseline biomarkers (plasma IL1R1 antagonist, IL-1β)

• Test for statistical interaction between treatment and biomarker levels

• Stratify patients based on identified biomarker thresholds

• Develop treatment algorithms incorporating biomarker data

This precision medicine approach could significantly improve outcomes by targeting IL1R1 antagonist therapy to patients most likely to benefit, while avoiding unnecessary treatment in non-responders.