Investigating Autophagy Impairment in Zebrafish Larvae: Studies on the Effects of a Natural Compound and Neutrophil Modulation in Intracerebral Hemorrhage


Student thesis: Doctoral Thesis

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Award date4 Sept 2023


Autophagy, a crucial cellular process, maintains health and equilibrium by decomposing and repurposing cellular parts. Particularly during nutrient shortages, autophagy allows cells to transform their own components into vital building blocks and energy. On a broader scale, autophagy has significant implications for organ health. For instance, in the heart, it aids in eliminating damaged proteins and organelles, shielding the organ from harm and preserving its functionality. Disruptions in autophagy have been associated with cardiac diseases. Furthermore, in the nervous system, autophagy plays an essential role in clearing aggregated proteins and damaged organelles from neurons. Abnormalities in this process are linked to neurodegenerative conditions such as Alzheimer's, Parkinson's, and Huntington's diseases.

My study is centered around investigating the effects of autophagy disruption in a zebrafish larvae model through two unique methodologies. Initially, I utilized the natural compound coumarin as an autophagy inhibitor in zebrafish larvae. My objective is to determine how autophagy impairment contributes to coumarin-induced malformations in cardiac and brain development. The secondary aspect of my research involves analyzing autophagy dysfunction within neutrophils in an intracerebral hemorrhage (ICH) zebrafish larvae model. Here, I aim to elucidate the role of autophagy-deficient neutrophils in the progression of ICH.

In Chapter 2 and 3 of my study, I explored the cardiotoxic and neurotoxic effects of coumarin using zebrafish larvae models. My research revealed that coumarin induces significant changes in the heart and brain morphology, function, and molecular composition of the larvae, with these alterations being closely tied to autophagy inhibition. Remarkably, I discovered that administering the autophagy enhancer, torin1, could partially counteract these coumarin-induced changes. This finding not only proposes a potential mechanism behind coumarin's harmful effects but also highlights the critical role of impaired autophagy in the cardiac and brain development of zebrafish larvae.

In Chapter 4, I explored the role of autophagy in the changing characteristics of neutrophils in the caudal hematopoietic tissue (CHT) following ICH in zebrafish larvae models. I showed that the level of autophagy activity in neutrophils, Tnf-α expression, granulation, and phagocytosis ability all decreased in these cells following ICH, whereas apoptosis increased. Furthermore, torin1 treatment resulted in an increase in Tnf-α expression, granulation and lifespan of neutrophil, indicating the role of autophagy in these ICH-related neutrophil characteristics changes. Furthermore, the autophagy enhancer torin1 reduced the number of neutrophils and the edema in the brain, suggesting that its autophagy induction effect might have beneficial effect in ICH.

In conclusion, this thesis underscores the potential health hazards associated with autophagy impairment and the role of autophagy within neutrophils in the context of ICH and its outcomes. These insights could pave the way for novel therapeutic strategies aimed at improving ICH recovery. Additionally, they provide a deeper understanding of safety considerations related to nutraceuticals and the impacts of autophagy disruption at the organ level.