Manipulating the air-filled zebrafish swim bladder as a neutrophilic inflammation model for acute lung injury

Abstract

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), are life-threatening diseases that are associated with high mortality rates due to treatment limitations. Neutrophils play key roles in the pathogenesis of ALI/ARDS by promoting the inflammation and injury of the alveolar microenvironment. To date, in vivo functional approaches have been limited by the inaccessibility to the alveolar sacs, which are located at the anatomical terminal of the respiratory duct in mammals. We are the first to characterize the swim bladder of the zebrafish larva, which is similar to the mammalian lung, as a real-time in vivo model for examining pulmonary neutrophil infiltration during ALI. We observed that the delivery of exogenous materials, including lipopolysaccharide (LPS), Poly IC and silica nanoparticles, by microinjection triggered significant time- and dose-dependent neutrophil recruitment into the swim bladder. Neutrophils infiltrated the LPS-injected swim bladder through the blood capillaries around the pneumatic duct or a site near the pronephric duct. An increase in the post-LPS inflammatory cytokine mRNA levels coincided with the in vivo neutrophil aggregation in the swim bladder. Microscopic examinations of the LPS-injected swim bladders further revealed in situ injuries, including epithelial distortion, endoplasmic reticulum swelling and mitochondrial injuries. Inhibitor screening assays with this model showed a reduction in neutrophil migration into the LPS-injected swim bladder in response to Shp2 inhibition. Moreover, the pharmacological suppression and targeted disruption of Shp2 in myeloid cells alleviated pulmonary inflammation in the LPS-induced ALI mouse model. Additionally, we used this model to assess pneumonia-induced neutrophil recruitment by microinjecting bronchoalveolar lavage fluid from patients into swim bladders; this injection enhanced neutrophil aggregation relative to the control. In conclusion, our findings highlight the swim bladder as a promising and powerful model for mechanistic and drug screening studies of alveolar injuries.

Candida albicans and Pseudomonas aeruginosa Interact To Enhance Virulence of Mucosal Infection in Transparent Zebrafish

“…Inflammation and IL-6 production are associated with edema, alveolar collapse, and acute injury in the lung, suggesting that loss of the air bubble in the swimbladder (deflation) serves as a noninvasive parallel indicator of inflammation and edema (33,39,47,48). To longitudinally test association of this inflammatory phenotype with mortality, we compared the proportion of fish with swimbladder deflation in single infection and coinfections.…”

Control of Mucosal Candidiasis in the Zebrafish Swim Bladder Depends on Neutrophils That Block Filament Invasion and Drive Extracellular-Trap Production

“…We recently developed the first microinjection mucosal infection model in the zebrafish larva, and it has been used to study sterile inflammation and infection with both viral and fungal pathogens (27)(28)(29). In this study, we leveraged this infection model to achieve a high spatiotemporal resolution of neutrophil-C. albicans dynamics at the mucosal level.…”

Role of Quzhou Fructus Aurantii Extract in Preventing and Treating Acute Lung Injury and Inflammation

“…Transgene-marked fluorescent zebrafish neutrophils play an effective role in the study of acute inflammation 32 , 33 . Commonly used inducers are LPS, Poly IC, silica nanoparticles, zinc and copper 34 – 36 . Copper is a metal capable of inducing inflammatory injury and cellular migration to the hair cells of lateral line of zebrafish and can easily imitate antioxidant and pro-inflammatory characteristics.…”