Using zebrafish as a model to study acute and chronic mucosal inflammation

Mucosal barriers of the intestine and the lung offer the first line of protection in the host defence mechanisms against ingested and inhaled antigens. During the 20th century, the incidence of chronic mucosal inflammatory diseases of unknown aetiology such as inflammatory bowel disease, chronic obstructive pulmonary disease and pulmonary fibrosis has risen markedly in the Western World. This PhD project used zebrafish, Danio rerio, as a model organism to study acute and chronic mucosal inflammatory responses in the intestine and the gills induced respectively by dietary components and respiratory irritants/injury associated with human disease. A single exposure to a diet rich in cholesterol (HCD) results in the accumulation of myeloid cells in the intestine in both zebrafish and mice. HCD-induced immune cell accumulation is dependent on NFkB activation and the microbiota and acute exposure to HCD leads to caspase-1 activation in intestinal epithelial cells. Extended HCD results in localised, inflammation-dependent, functional dysregulation. This model reveals a novel route by which dietary cholesterol can initiate intestinal inflammation. Acute exposure to cigarette smoke and silica particles leads to an acute inflammatory response in zebrafish gills similar to that seen in mammalian lungs. Despite gill tissue remodelling following long-term exposure to these irritants, no collagen deposition, i.e. fibrosis, could be detected. When combined with severe tissue damage induced by cryoinjury, exposure to silica delayed wound-healing responses and again no fibrotic changes were observed. Preliminary gene expression analysis by RNA-seq showed altered gene expression of similar genes to those involved during wound-healing processes in mammals. These results provide a basis for further investigations such as extensive comparisons of gene expression with fibrosis in mammals. Overall, these findings demonstrate that the zebrafish is a valuable and pathophysiologically relevant model in which to study mucosal inflammatory diseases.Open Acces

Dietary cholesterol directly induces acute inflammasome-dependent intestinal inflammation

Prolonged ingestion of a cholesterol- or saturated fatty acid-enriched diet induces chronic, often systemic, auto-inflammatory responses resulting in significant health problems worldwide. In vivo information regarding the local and direct inflammatory effect of these dietary components in the intestine and, in particular, on the intestinal epithelium is lacking. Here we report that both mice and zebrafish exposed to high-fat (HFDs) or high-cholesterol (HCDs) diets develop acute innate inflammatory responses within hours, reflected in the localized interleukin-1β-dependent accumulation of myeloid cells in the intestine. Acute HCD-induced intestinal inflammation is dependent on cholesterol uptake via Niemann-Pick C1-like 1 and inflammasome activation involving apoptosis-associated Speck-like protein containing a caspase recruitment domain, which leads to Caspase-1 activity in intestinal epithelial cells. Extended exposure to HCD results in localized, inflammation-dependent, functional dysregulation as well as systemic pathologies. Our model suggests that dietary cholesterol initiates intestinal inflammation in epithelial cells

Induction of innate cytokine responses by respiratory mucosal challenge with R848 in zebrafish, mice, and humans.

We compared live zebrafish, mouse and human nasal challenge responses to the TLR7/8 agonist resiquimod (R848). We found remarkably similar induction of mediators in the three species, offering novel mucosal models of innate anti-viral immunity

Transforming healthcare through regenerative medicine

Regenerative medicine therapies, underpinned by the core principles of rejuvenation, regeneration and replacement, are shifting the paradigm in healthcare from symptomatic treatment in the 20th century to curative treatment in the 21st century. By addressing the reasons behind the rapid expansion of regenerative medicine research and presenting an overview of current clinical trials, we explore the potential of regenerative medicine to reshape modern healthcare

In utero exposure to cigarette smoke and effects across generations:A conference of animals on asthma

Background: The prevalence of asthma and chronic obstructive pulmonary disease (COPD) has risen markedly over the last decades and is reaching epidemic proportions. However, underlying molecular mechanisms are not fully understood, hampering the urgently needed development of approaches to prevent these diseases. It is well established from epidemiological studies that prenatal exposure to cigarette smoke is one of the main risk factors for aberrant lung function development or reduced fetal growth, but also for the development of asthma and possibly COPD later in life. Of note, recent evidence suggests that the disease risk can be transferred across generations, that is, from grandparents to their grandchildren. While initial studies in mouse models on in utero smoke exposure have provided important mechanistic insights, there are still knowledge gaps that need to be filled. Objective: Thus, in this review, we summarize current knowledge on this topic derived from mouse models, while also introducing two other relevant animal models: the fruit fly Drosophila melanogaster and the zebrafish Danio rerio. Methods: This review is based on an intensive review of PubMed-listed transgenerational animal studies from 1902 to 2018 and focuses in detail on selected literature due to space limitations. Results: This review gives a comprehensive overview of mechanistic insights obtained in studies with the three species, while highlighting the remaining knowledge gaps. We will further discuss potential (dis)advantages of all three animal models. Conclusion/Clinical Relevance: Many studies have already addressed transgenerational inheritance of disease risk in mouse, zebrafish or fly models. We here propose a novel strategy for how these three model organisms can be synergistically combined to achieve a more detailed understanding of in utero cigarette smoke-induced transgenerational inheritance of disease risk

Septins restrict inflammation and protect zebrafish larvae from Shigella infection

Shigella flexneri, a Gram-negative enteroinvasive pathogen, causes inflammatory destruction of the human intestinal epithelium. Infection by S. flexneri has been well-studied in vitro and is a paradigm for bacterial interactions with the host immune system. Recent work has revealed that components of the cytoskeleton have important functions in innate immunity and inflammation control. Septins, highly conserved cytoskeletal proteins, have emerged as key players in innate immunity to bacterial infection, yet septin function in vivo is poorly understood. Here, we use S. flexneri infection of zebrafish (Danio rerio) larvae to study in vivo the role of septins in inflammation and infection control. We found that depletion of Sept15 or Sept7b, zebrafish orthologs of human SEPT7, significantly increased host susceptibility to bacterial infection. Live-cell imaging of Sept15-depleted larvae revealed increasing bacterial burdens and a failure of neutrophils to control infection. Strikingly, Sept15-depleted larvae present significantly increased activity of Caspase-1 and more cell death upon S. flexneri infection. Dampening of the inflammatory response with anakinra, an antagonist of interleukin-1 receptor (IL-1R), counteracts Sept15 deficiency in vivo by protecting zebrafish from hyper-inflammation and S. flexneri infection. These findings highlight a new role for septins in host defence against bacterial infection, and suggest that septin dysfunction may be an underlying factor in cases of hyper-inflammation

Human Kidney‐Derived Cells Ameliorate Acute Kidney Injury Without Engrafting into Renal Tissue

Previous studies have suggested that CD133+ cells isolated from human kidney biopsies have the potential to ameliorate injury following intravenous (IV) administration in rodent models of kidney disease by integrating into damaged renal tissue and generating specialized renal cells. However, whether renal engraftment of CD133+ cells is a prerequisite for ameliorating injury has not yet been unequivocally resolved. Here, we have established a cisplatin‐induced nephropathy model in immunodeficient rats to assess the efficacy of CD133+ human kidney cells in restoring renal health, and to determine the fate of these cells after systemic administration. Specifically, following IV administration, we evaluated the impact of the CD133+ cells on renal function by undertaking longitudinal measurements of the glomerular filtration rate using a novel transcutaneous device. Using histological assays, we assessed whether the human kidney cells could promote renal regeneration, and if this was related to their ability to integrate into the damaged kidneys. Our results show that both CD133+ and CD133− cells improve renal function and promote renal regeneration to a similar degree. However, this was not associated with engraftment of the cells into the kidneys. Instead, after IV administration, both cell types were exclusively located in the lungs, and had disappeared by 24 hours. Our data therefore indicate that renal repair is not mediated by CD133+ cells homing to the kidneys and generating specialized renal cells. Instead, renal repair is likely to be mediated by paracrine or endocrine factors. Stem Cells Translational Medicine 2017;6:1373–138

Trafficking of cholesterol to the ER is required for NLRP3 inflammasome activation

Cellular lipids determine membrane integrity and fluidity and are being increasingly recognized to influence immune responses. Cellular cholesterol requirements are fulfilled through biosynthesis and uptake programs. In an intricate pathway involving the lysosomal cholesterol transporter NPC1, the sterol gets unequally distributed across intracellular compartments. By using pharmacological and genetic approaches targeting NPC1, we reveal that blockade of cholesterol trafficking through the late endosome–lysosome pathway blunts NLRP3 inflammasome activation. Altered cholesterol localization at the plasma membrane (PM) in Npc1−/− cells abrogated AKT–mTOR signaling by TLR4. However, the inability to activate the NLRP3 inflammasome was traced to perturbed cholesterol trafficking to the ER but not the PM. Accordingly, acute cholesterol depletion in the ER membranes by statins abrogated casp-1 activation and IL-1β secretion and ablated NLRP3 inflammasome assembly. By contrast, assembly and activation of the AIM2 inflammasome progressed unrestricted. Together, this study reveals ER sterol levels as a metabolic rheostat for the activation of the NLRP3 inflammasome