Zebrafish Model Reveals Crucial Role of Ctla-4 in Maintaining Intestinal Immune Homeostasis and Preventing Inflammatory Bowel Disease

Belangrijkste concepten

Ctla-4 deficiency leads to intestinal inflammation, epithelial barrier disruption, altered immune cell composition, and dysbiosis in the zebrafish intestine, closely resembling the pathological features of inflammatory bowel disease.

Samenvatting

The study identified the zebrafish homolog of Ctla-4 and generated a ctla-4-deficient zebrafish line to investigate the role of Ctla-4 in maintaining intestinal immune homeostasis. The key findings are:

Ctla-4-deficient zebrafish exhibit reduced body weight, impaired intestinal epithelial barrier integrity, and lymphocytic infiltration in the intestine, resembling the pathological features of inflammatory bowel disease (IBD).

Transcriptomic analysis revealed upregulation of inflammation-related genes and disturbance of immune system homeostasis in the intestines of ctla-4-deficient zebrafish. Single-cell RNA sequencing further showed increased Th2 cells, decreased innate lymphoid cells, and upregulated proinflammatory cytokines.

The intestinal microbiota of ctla-4-deficient zebrafish exhibited decreased diversity and altered composition, with expansion of potential pathobionts.

Mechanistically, Ctla-4 exerts its inhibitory function by competing with Cd28 for binding to Cd80/86, thereby suppressing T cell activation and proliferation.

Supplementation with recombinant soluble Ctla-4-Ig successfully alleviated the intestinal inflammation in ctla-4-deficient zebrafish, suggesting its potential as a therapeutic intervention for CTLA-4 deficiency-induced IBD.

Overall, this study establishes the ctla-4-deficient zebrafish as a novel model for investigating the pathogenesis and potential treatments of CTLA-4-associated inflammatory bowel disease.

Statistieken

Ctla-4-deficient zebrafish exhibited a significant reduction in body weight compared to wild-type zebrafish.
The intestine length was shorter in ctla-4-deficient zebrafish compared to wild-type.
The spleen size was larger in ctla-4-deficient zebrafish compared to wild-type.
The number of goblet cells in the anterior intestine was significantly decreased in ctla-4-deficient zebrafish compared to wild-type.
The myeloperoxidase (MPO) activity was markedly increased in the intestines and peripheral blood of ctla-4-deficient zebrafish compared to wild-type.

Citaten

"Ctla-4 deficiency leads to an IBD-like phenotype in zebrafish characterized by altered intestinal epithelial cells morphology, abnormal inflammatory response, defects in microbial stratification and composition."
"Supplementation with Ctla-4-Ig successfully alleviated intestinal inflammation in these ctla-4-deficient mutants."
"Ctla-4 exerts its inhibitory function by competing with Cd28 for binding to Cd80/86, thereby suppressing T cell activation and proliferation."

Belangrijkste Inzichten Gedestilleerd Uit

Unraveling the Role of Ctla-4 in Intestinal Immune Homeostasis: Insights from a novel Zebrafish Model of Inflammatory Bowel Disease

by Qin,L., Hu,C... om www.biorxiv.org 07-24-2024

https://www.biorxiv.org/content/10.1101/2024.07.24.604955v1

Diepere vragen

How do the specific immune cell subsets and their interactions contribute to the pathogenesis of CTLA-4 deficiency-induced IBD in this zebrafish model?

The pathogenesis of CTLA-4 deficiency-induced inflammatory bowel disease (IBD) in the zebrafish model is significantly influenced by the dynamics of specific immune cell subsets and their interactions. In the absence of CTLA-4, there is a marked increase in the abundance of Th2 cells, particularly a unique subset of Th2 cells that is rarely observed in wild-type zebrafish. These Th2 cells exhibit elevated expression of interleukin-13 (il13), a cytokine known to exacerbate intestinal inflammation by disrupting epithelial integrity and promoting goblet cell loss. The upregulation of il13, along with other pro-inflammatory cytokines such as tumor necrosis factor-alpha (tnfa) and interleukin-1 beta (il1b), creates a pro-inflammatory environment that contributes to the IBD-like phenotype observed in ctla-4-/- zebrafish.
Additionally, the single-cell RNA sequencing analysis reveals a decrease in innate lymphoid cells (ILC3-like cells), which are crucial for maintaining intestinal homeostasis and promoting epithelial cell survival through the production of protective cytokines like IL-22. The reduction of ILC3-like cells, coupled with the increased Th2 cell activity, leads to a dysregulated immune response characterized by heightened inflammation and impaired epithelial barrier function. The interactions between these immune cell subsets—where Th2 cells promote inflammation and ILC3-like cells are diminished—underscore the complex interplay that drives the pathogenesis of IBD in this model. This dysregulation highlights the critical role of CTLA-4 as a negative regulator of T cell activation, which, when absent, leads to an imbalance in immune responses and contributes to the development of IBD.

What are the potential therapeutic targets beyond CTLA-4 that could be explored based on the insights gained from this zebrafish model?

The insights gained from the ctla-4-/- zebrafish model of IBD suggest several potential therapeutic targets beyond CTLA-4. One promising avenue is the modulation of Th2 cell activity, particularly targeting the pathways associated with interleukin-13 (il13) signaling. Given that Th2 cells are significantly upregulated in the absence of CTLA-4 and are linked to the exacerbation of intestinal inflammation, therapies aimed at inhibiting il13 or its receptor could mitigate the inflammatory response and restore intestinal homeostasis.
Another potential target is the enhancement of ILC3 function or the restoration of their population in the intestines. Since ILC3-like cells play a protective role in maintaining epithelial integrity and promoting a balanced immune response, strategies that aim to increase their abundance or activity could be beneficial in counteracting the inflammatory effects observed in CTLA-4 deficiency.
Furthermore, the dysbiosis observed in ctla-4-/- zebrafish, characterized by reduced microbial diversity and an increase in potentially pathogenic bacteria, suggests that microbiota modulation could serve as a therapeutic strategy. Probiotics or prebiotics that promote the growth of beneficial microbial populations may help restore a healthy gut microbiome and alleviate inflammation.
Lastly, targeting the inflammatory cytokine pathways, particularly those involving TNF-alpha and IL-1 beta, could provide additional therapeutic avenues. Inhibitors of these cytokines have been effective in treating IBD in humans and could be explored in the context of this zebrafish model to assess their efficacy in mitigating the IBD-like phenotype.

Given the conserved role of CTLA-4 in regulating immune homeostasis, how might this zebrafish model provide insights into the involvement of CTLA-4 in other immune-mediated diseases?

The ctla-4-/- zebrafish model offers a unique platform for investigating the role of CTLA-4 in various immune-mediated diseases due to the conserved nature of this immune checkpoint across species. The findings from this model, particularly the dysregulation of immune responses and the resultant IBD-like phenotype, can be extrapolated to other conditions where CTLA-4 plays a critical role, such as autoimmune diseases and allergies.
For instance, the model can be utilized to study the mechanisms by which CTLA-4 deficiency leads to autoimmune responses, as seen in diseases like rheumatoid arthritis or lupus. The increased activation of T cells and the imbalance between pro-inflammatory and anti-inflammatory cytokines observed in the zebrafish model may mirror similar processes in these diseases, providing insights into potential therapeutic interventions.
Moreover, the zebrafish model allows for the exploration of the interactions between CTLA-4 and other immune pathways, such as those involving regulatory T cells (Tregs) and their role in maintaining immune tolerance. Understanding how CTLA-4 influences Treg function and stability in the context of various immune-mediated diseases could lead to novel strategies for enhancing Treg activity and promoting immune tolerance.
Additionally, the model can facilitate high-throughput screening of compounds that modulate CTLA-4 activity or its downstream signaling pathways, paving the way for the development of targeted therapies for a range of immune-mediated disorders. Overall, the ctla-4-/- zebrafish model serves as a valuable tool for elucidating the multifaceted roles of CTLA-4 in immune regulation and its implications in various diseases.