Zebrafish IL-4-like cytokines and IL-10 suppress inflammation but only IL-10 is essential for gill homeostasis

Abstract

26Healthy fish stocks are central to global food security. Key to fish health is robust 27 immunity at mucosal surfaces, and especially at the gills. However, a balance must be 28 struck between tolerating commensal microorganisms and reacting appropriately 29 toward pathogens. In mammals, IL-4 and IL-13 in concert with IL-10 are essential 30 for balancing immune response to pathogens and suppressing inflammation. Whether 31 their fish counterparts perform similar roles is an open question. Here, we have 32 generated IL-4/13A and IL-4/13B mutant zebrafish and, together with existing IL-10 33 mutants, characterized the consequences of loss-of-function of these cytokines. We 34 demonstrate that these cytokines are required to suppress inflammation. Further, IL-35 4/13A and IL-4/13B are required for the maintenance of a Th2-like phenotype in the 36 gills. As in mammals, IL-10 appears to have a more striking anti-inflammatory 37 function than IL-4-like cytokines. Thus, both IL-10 and IL-4/13 paralogues in 38 zebrafish exhibit aspects of conserved function with their mammalian counterparts. 39 40 42cytokines that participate in several physiological processes but are mainly known for 43 stimulating type 2 immune responses (1), characterised by mucus overproduction, IgE 44 antibody production, eosinophilia and differentiation of alternatively activated (M2) 45 macrophages (2). These responses confer protection against parasites but, when 46 inappropriately activated, contribute to the development of asthma and allergic 47 inflammation (1). IL-4 and IL-13 are secreted by CD4 + Th2 cells, basophils, 48 eosinophils, mast cells and group 2 innate lymphoid cells (ILC2s) (3). They exert 49 their functions by binding to two types of receptor complexes: a type I receptor, 50 3 constituted by the IL-4Rα chain and the IL-2R common γ chain (γc) and a type II 51 receptor, which comprises IL-4Rα chain and IL-13Rα1 subunits. Both type I and type 52 II receptors signal through STAT6 transcription factor binding to promoter elements 53 within IL-4/IL-13 responsive genes (4). IL-4 and IL-13 suppress inflammatory 54 responses by antagonising production of TNFα, IL-1β and other pro-inflammatory 55 mediators (5) and act in opposition to IFN-γ, the canonical Th1 (type 1) cytokine (6). 56Indeed, co-ordinately with inducing type 2 immune response, IL-4 and IL-13 suppress 57 type 1 responses, characterised by immune cell mediated destruction of cells infected 58 with intracellular pathogens (7). 59Although IL-4 and IL-13 can negatively regulate inflammatory responses, IL-60 10 has the more central anti-inflammatory role in mammals, potently suppressing 61 IFN-γ responses. IL-10 can suppress a range of aberrant immune responses including 62 both type 1 and type 2 responses (8). IL-10 is produced by many cell types (9). It 63 regulates CD4 + Treg cell differentiation and function, and it is important in 64 maintaining homeostasis at mucosal surfaces (10). 65Evidence is emerging that fish immune responses can also be classified as 66 type 1 or t...

Cytokines IL-1β and IL-10 are required for Müller glia proliferation following light damage in the adult zebrafish retina

“…Similarly, TNF-α is required for Müller glia proliferation in the zebrafish retina, although it is produced in dying retinal neurons (Nelson et al, 2013). Outside the retina, IL-4 suppressed inflammation following zebrafish gill tissue damage (Bottiglione et al, 2020), while IL-10 and IL-4 signaling worked synergistically together to induce synaptogenesis in sensory hair cells and motor neurons in zebrafish (Denans et al, 2022). As numerous signaling events take place during damage and initiation of neuronal regeneration, the dynamic timing and interaction between these cytokines and both neuronal and non-neuronal cells found in the retina may play a critical role in determining the successful regeneration of neurons in the zebrafish retina following injury.…”

“…However, TNFα is not initially produced by the microglia, rather it is released from the dying retinal neurons (Nelson et al, 2013). In contrast, cytokines that are often associated with an anti-inflammatory effect, such as IL-4, IL-10, and IL-13, attenuate the inflammatory response over time to focus on tissue repair and homeostasis (Lively et al, 2018;Sun et al, 2019;Bottiglione et al, 2020;Miao et al, 2020;Shemer et al, 2020;Chen et al, 2022). A successful tissue recovery is achieved only when the appropriate balance of inflammatory cytokines is expressed (Cicchese et al, 2018;Soliman and Barreda, 2023).…”

Eye fluke effects on Danish freshwater fish: Field and experimental investigations

“…Thus, IL-4 mediates many specific pathways, including fine-tuning of the Th2 response through its ability to initiate, perpetuate or inhibit the response through the activation of multiple signalling pathways (Wills-Karp & Finkelman, 2008). IL-4 and IL-13 suppress inflammatory responses by antagonizing production of TNFα, IL-1β, IFNγ and other pro-inflammatory mediators (Bottiglione et al, 2020;Wang et al, 2016). This could explain the down-regulation of genes encoding TNFα, IFNγ and IL-1β.…”