T Lymphocyte–Dependent and –Independent Regulation of Cxcl8 Expression in Zebrafish Intestines

Abstract

CXCL8 is a potent neutrophil recruiting chemokine. CXCL8 is produced by several innate immune cells, including neutrophils, macrophages, as well as epithelial cells. Although previously considered only to be produced as a result of TLR signaling in these cells, recent reports show that T cell–derived cytokines also induce CXCL8 in epithelial cells. Likewise, we observed that T cell inhibition diminished intestinal production of functional mouse homologs of CXCL8 in the early phase of enterocolitis. In this study, we specifically investigated whether adaptive cells contribute to innate cxcl8 expression in the intestines. To this end, we used the zebrafish as our model system. Unlike murine models that lack CXCL8, zebrafish have two CXCL8 chemokines that are both elevated after an acute inflammatory stimulus and recruit neutrophils. Furthermore, zebrafish develop innate and adaptive immunity sequentially, enabling analysis of intestinal cxcl8 expression in the absence (<3 wk of age) and presence (>3 wk of age) of adaptive immunity. In this study, we show that intestinal cxcl8-l1 but not cxcl8-l2 expression is regulated by T lymphocytes under homeostatic conditions. In contrast, during intestinal inflammation especially, cxcl8-l1 expression is upregulated independent of T lymphocyte presence. Furthermore, we show that human CXCL8 is able to induce intestinal zebrafish neutrophil recruitment and cxcl8-l1 expression, demonstrating that zebrafish can be used as a model to study CXCL8 function and regulation. In conclusion, these data provide evidence that Cxcl8-l1 and Cxcl8-l2 are differentially regulated via T lymphocyte–dependent and –independent mechanisms during homeostasis and inflammation.

Comparison of Two Chemically-Induced Colitis-Models in Adult Zebrafish, Using Optical Projection Tomography and Novel Transcriptional Markers

“…Considering the multifaceted and central role of IL-6 in a number of inflammatory conditions, including IBD [39], the results are not readily explained, but knowledge of IL-6 function and signaling is considered to be inadequate in fish at present [40]. Confirming earlier zebrafish-inflammatory studies [8] [9] [10] [41], the neutrophil-activating chemokineCxCL8 (IL-8) was significantly up-regulated in the TNBS groups after 72 hpi. In the oxazolone-exposed group, CxCL8 transcript levels were also elevated after 72 hpi, albeit at noticeably higher level than in the TNBS group.…”

Evaluation of intestinal histological damage in zebrafish exposed to environmentally relevant concentrations of manganese

“…Thus, the reduction in the frequency of these cells can lead to problems in intestinal immunity (CHEN et al, 2015). An inverse response can be observed in fish from chronic exposure to MnCl 2 , since there was an increase in the frequency of eosinophils at the concentrations tested, characterizing intestinal inflammation (BRUGMAN et al, 2014;WITTE et al, 2014).…”

The Mucosal Immune System of Teleost Fish

“…In mammals, naïve CD4 + T cells can acquire either a Th1 or a Th2 phenotype depending on the cytokine milieu in which they become activated, however we know very little about mucosal CD4 + T cells in fish. In zebrafish, intestinal T cells contribute to gut homeostasis by producing cxcl8-l1 but not cxcl8-l2 [ 49 ]. In other studies, teleost skin and gills showed a high constitutive expression of Th2 markers suggesting that these two mucosal surfaces have a skewed immune response targeted against parasites [ 50 ].…”