Resolution of inflammation by retrograde chemotaxis of neutrophils in transgenic zebrafish

Abstract

Neutrophil chemotaxis to sites of inflammation is a critical process during normal immune responses to tissue injury and infection and pathological immune responses leading to chronic inflammation. Although progress has been made in understanding the mechanisms that promote neutrophil recruitment to inflamed tissue, the mechanisms that regulate the resolution phase of the inflammatory response have remained relatively elusive. To define the mechanisms that regulate neutrophil-mediated inflammation in vivo, we have developed a novel transgenic zebrafish in which the neutrophils express GFP under control of the myeloperoxidase promoter (zMPO:GFP). Tissue injury induces a robust, inflammatory response, which is characterized by the rapid chemotaxis of neutrophils to the wound site. In vivo time-lapse imaging shows that neutrophils subsequently display directed retrograde chemotaxis back toward the vasculature. These findings implicate retrograde chemotaxis as a novel mechanism that regulates the resolution phase of the inflammatory response. The zMPO:GFP zebrafish provides unique insight into the mechanisms of neutrophil-mediated inflammation and thereby offers opportunities to identify new regulators of the inflammatory response in vivo.

Catch of the day: zebrafish as a human cancer model

“…These animals would greatly facilitate real-time imaging of the tumor-induced vascular remodeling events and the dynamic immune cell movements that occur in the tumor microenvironment. Many transgenic lines have already been developed including T cell, macrophage and neutrophil reporter animals (Langenau et al, 2004;Mathias et al, 2006;Hall et al, 2007).…”

Immunological tools: Engaging students in the use and analysis of flow cytometry and enzyme‐linked immunosorbent assay (ELISA)

“…The first laboratory exercise, which was performed during laboratory sessions 1 and 2, required students to identify the cell type expressing enhanced green fluorescent protein (EGFP) in a transgenic zebrafish line by comparing forward [25][26][27][28][29][30].…”

Fluorescent neutrophils throw the spotlight on inflammation

“…Renshaw et al used BAC recombination to construct a transgene placing EGFP under control of 130 kb of upstream regulatory sequence; very recently, another group has also reported the construction of a myeloperoxidase-promoter:EGFP-transgenic zebrafish, but using 8 kb of regulatory sequence. 1 et al) and their active departure from the inflammatory site. 1 These new transgenic zebrafish are a welcome addition to the now impressive range of zebrafish with fluorescently marked cell types relevant to inflammation (see table).…”

“…1 et al) and their active departure from the inflammatory site. 1 These new transgenic zebrafish are a welcome addition to the now impressive range of zebrafish with fluorescently marked cell types relevant to inflammation (see table). The involvement of fluorescent embryonic macrophages in acute inflammation has been studied in zebrafish with a fli1-driven EGFP, 2 and the same line has been used to study endothelial regeneration after wounding.…”

“…There is some evidence that myeloperoxidase may not be a totally specific marker for zebrafish neutrophils, but may mark some early macrophage-lineage cells as well. 1 At an ultrastructural level, zebrafish myeloperoxidase-containing neutrophil primary granules have a markedly different morphology from those of mammalian neutrophils 4 ; whether this is reflected in a functional difference remains to be determined. It has also not been formally demonstrated whether zebrafish neutrophils are phagocytic.…”