TH17 Endogenous IL-1β–STAT5 Axis Drives Steroid Resistance in Autoimmune Neuroinflammation

Academic Background

Steroid resistance is a major challenge in managing various inflammatory diseases, including autoimmune neuroinflammation. T helper 17 (TH17) cells are widely believed to be associated with steroid resistance. However, the specific mechanisms remain unclear. Experimental autoimmune encephalomyelitis (EAE) is a widely-used animal model for studying the immunopathology of autoimmune central nervous system (CNS) inflammation. These studies indicate that the inflammatory process leading to EAE onset consists of two phases: Firstly, T cells are initially activated and infiltrate the CNS, and then, T cells are re-activated within the CNS, triggering inflammation and the appearance of clinical symptoms.

Paper Source

This paper was written by William A. Miller-Little, Xing Chen, Vanessa Salazar, Caini Liu, Katarzyna Bulek, Julie Y. Zhou, Xiao Li, Olaf Stüve, Thaddeus Stappenbeck, George Dubyak, Junjie Zhao, and Xiaoxia Li from Case Western Reserve University School of Medicine, Cleveland Clinic Lerner Research Institute, VA North Texas Health Care System, and University of Texas Southwestern Medical Center. It was published in the May 3, 2024 issue of Science Immunology.

Research Process

This study employed a series of experimental steps to reveal the role of the IL-1β-STAT5 signaling pathway in TH17 cells and verify how these pathways drive steroid resistance.

Experimental Design and Methods

1. Establishment and Treatment of the EAE Model:
   • Conducted with C57BL/6 mice induced with EAE by injecting myelin oligodendrocyte glycoprotein peptide (MOG35-55) and complete Freund’s adjuvant (CFA).
   • When the mice’s pathological score reached 1, they were treated with dexamethasone (Dex), anti-IL-1R, or both combined for three days to observe the treatment effects.
2. Cell and Tissue Analysis:
   • Flow cytometry used to analyze infiltrating CD4+ T cells in the CNS and to fluorescently label IL-17A and IFNγ in these T cells for further classification.
   • Tissue sections and staining (such as H&E staining and Luxol Fast Blue staining) used to observe demyelination and inflammatory infiltration in the spinal cord.
3. In Vitro Polarization and Analysis of TH17 Cells:
   • TH17 cells polarized using minimal cytokine combinations (TGF-β1 and IL-6) and further stimulated with IL-1β and IL-23 to observe their resistance to dexamethasone.
   • RNA sequencing (RNA-seq) experiments analyzed the full gene expression profile of polarized TH17 cells under different conditions.

Main Results

1. IL-1R Blockade Enhances GC Treatment Sensitivity:
   • The study found that single treatments with dexamethasone or anti-IL-1R alone were less effective, whereas combined treatment significantly reduced pathological scores and demyelination in the spinal cord.
   • Flow cytometry analysis showed that combined treatment significantly reduced the number of CD4+ T cells and IL-17A-secreting TH17 cells infiltrating the CNS.
2. IL-1β Induces Steroid Resistance in TH17 Cells:
   • Experiments demonstrated that IL-1β significantly reduced dexamethasone’s inhibitory effect on inflammatory cytokines such as IL-17A and CSF2 in TH17 cells; in contrast, IL-23 did not exhibit this effect.
3. Role of STAT5 in IL-1β-Induced Steroid Resistance:
   • Gene knockout experiments showed that when STAT5 was deleted in TH17 cells, IL-1β could no longer induce a steroid resistance transcriptional program, making these cells resensitive to dexamethasone treatment.
4. Effectiveness of Combined Treatment in Relapsing-Remitting EAE Model:
   • In a relapsing-remitting model, combination anti-IL-1R and dexamethasone treatment significantly reduced disease severity, with many mice being entirely symptom-free by the end of the experiment.

Conclusion

This study reveals how the IL-1β-STAT5 axis mediates steroid resistance within TH17 cells and proposes a potential therapeutic strategy by blocking the IL-1R signaling pathway to reverse steroid resistance in TH17-mediated CNS autoimmune inflammation. The study also suggests that combining IL-1R blockade with dexamethasone may have significant therapeutic potential in clinical settings for diseases like multiple sclerosis.

Research Highlights

1. Uncovered the critical role of the IL-1β-STAT5 signaling axis in TH17 cells, providing new molecular mechanisms for understanding steroid resistance.
2. Proposed a treatment strategy to overcome steroid resistance by blocking the IL-1R signaling pathway, offering a new approach for treating relapsing neuroinflammation.
3. Identified CD69+ TH17 cells in human multiple sclerosis brain lesions, highlighting the clinical relevance of these findings to human disease.

Research Significance and Value

This study not only advances the scientific understanding of the mechanisms of TH17 cell-mediated steroid resistance, but also proposes a novel therapeutic approach combining dexamethasone and IL-1R blockade. This is of significant clinical value in addressing the problem of steroid resistance and provides new methodologies and theoretical foundations for treating relapsing multiple sclerosis and other conditions.