Live imaging of chronic inflammation caused by mutation of zebrafish Hai1

Abstract

The hallmark of chronic inflammation is the infiltration and persistence of leukocytes within inflamed tissue. Here, we describe the first zebrafish chronic inflammation mutant identified in an insertional mutagenesis screen for mutants that exhibit abnormal tissue distribution of neutrophils. We identified a mutant line with an insertion in the Hepatocyte growth factor activator inhibitor 1 gene (hai1; also known as Spint1) that showed accumulation of neutrophils in the fin. The mutant embryos exhibited inflammation in areas of epidermal hyperproliferation that was rescued by knock-down of the type II transmembrane serine protease Matriptase 1 (also known as St14), suggesting a novel role for Hai1-Matriptase 1 pathway in regulating inflammation. Using time-lapse microscopy of mutant embryos that express GFP from a neutrophil-specific promoter, we found that individual neutrophils in inflamed tissue displayed random motility characterized by periods of pausing alternating with periods of motility. During periods of persistent movement the cells were highly polarized, while the pausing modes were characterized by a loss of cell polarity. In contrast to responses to acute injury, neutrophils did not exhibit clear retrograde chemotaxis or resolution of inflammation in the mutant. These findings illustrate the utility of zebrafish as a new model system to study chronic inflammation and to visualize immune responses with high resolution in vivo.

Cxcl8 (IL-8) Mediates Neutrophil Recruitment and Behavior in the Zebrafish Inflammatory Response

“…In view of this, we first addressed the expression of both zebrafish cxcl8 at different time points in 3 dpf Tg(mpx:gfp)i114 larvae under acute inflammatory conditions using quantitative PCR (qPCR). In this study, we made use of the tail fin transection model, a validated model to investigate acute inflammation (16)(17)(18)(19)(20)(21)(22)(23). We found that the mRNA levels of cxcl8-l1 and cxcl8-l2 were significantly increased in injured tail fin tissue and peaked at 1 hpw (Fig.…”

“…Additionally, the optical transparency of zebrafish and the development of fluorescent cell-specific transgenic lines have enabled the in vivo study of leukocyte biology (14,15). Zebrafish neutrophils have now been extensively studied in inflammation (16)(17)(18)(19)(20)(21)(22)(23), infection (24)(25)(26)(27), and tumor progression (28)(29)(30).…”

Defect of Hepatocyte Growth Factor Activator Inhibitor Type 1/Serine Protease Inhibitor, Kunitz Type 1 (Hai-1/Spint1) Leads to Ichthyosis-Like Condition and Abnormal Hair Development in Mice

“…32 The deletion of Hai-1/Spint1 in zebrafish resulted in disrupted epidermal integrity, susceptibility to apoptosis in keratinocytes, and inflammation. 32,33 Importantly, the epidermal phenotype of Hai-1/Spint1-deleted zebrafish was rescued by knockdown of matriptase. 32 The significant hyperkeratinization of the epidermis observed in B6Hai-1 Ϫ/ϪHigh mice is reminiscent of ichthyosis.…”

“…41 In Hai-1/Spint1-deleted zebrafish, epidermal hyperproliferation occurs in later periods. 32,33 Taken altogether, disturbance of the balance of Hai-1/Spint1 and its cognate proteinase, such as matriptase, leads to deranged intracellular signaling and a proliferative skin disease. In this regard, Hai-1/Spint1 may be a tumor suppressor.…”

Requirement of the activity of hepatocyte growth factor activator inhibitor type 1 for the extracellular appearance of a transmembrane serine protease matriptase in monkey kidney COS-1 cells

“…It has been shown that matriptase is not co-expressed with HAI-1 in certain cell types and cultured cells (e.g., in ovary granulosa cells and in human monocyte THP-1 cells) (Szabo et al 2008;Kilpatrick et al 2006). In addition, genetic studies using zebrafish indicated that matriptase does not require HAI-1 for biological activity (i.e., for extracellular occurrence) (Carney et al 2007;Mathias et al 2007). When HAI-1 is not co-expressed, HAI-2 (also known as bikunin) and the other serine protease inhibitors could prevent intracellular self-degradation of matriptase (Szabo et al 2008).…”