Acute Kidney Injury Model Induced by Cisplatin in Adult Zebrafish.

Cisplatin is commonly used as chemotherapy. Although it has positive effects in cancer-treated individuals, cisplatin can easily accumulate in the kidney due to its low molecular weight. Such accumulation causes the death of tubular cells and can induce the development of Acute Kidney Injury (AKI), which is characterized by a quick decrease in kidney function, tissue damage, and immune cells infiltration. If administered in specific doses cisplatin can be a useful tool as an AKI inducer in animal models. The zebrafish has appeared as an interesting model to study renal function, kidney regeneration, and injury, as renal structures conserve functional similarities with mammals. Adult zebrafish injected with cisplatin shows decreased survival, kidney cell death, and increased inflammation markers after 24 h post-injection (hpi). In this model, immune cells infiltration and cell death can be assessed by flow cytometry and TUNEL assay. This protocol describes the procedures to induce AKI in adult zebrafish by intraperitoneal cisplatin injection and subsequently demonstrates how to collect the renal tissue for flow cytometry processing and cell death TUNEL assay. These techniques will be useful to understand the effects of cisplatin as a nephrotoxic agent and will contribute to the expansion of AKI models in adult zebrafish. This model can also be used to study kidney regeneration, in the search for compounds that treat or prevent kidney damage and to study inflammation in AKI. Moreover, the methods used in this protocol will improve the characterization of tissue damage and inflammation, which are therapeutic targets in kidney-associated comorbidities.

Metabolic Alterations in SARS-CoV-2 Infection and Its Implication in Kidney Dysfunction.

Clinical strategies focusing on pathogen elimination are expected in an infectious-disease outbreak, such as the severe coronavirus disease 2019 (COVID-19), to avoid organ dysfunction. However, understanding the host response to viral infection is crucial to develop an effective treatment to optimize the patient's conditions. The pathogenic viruses can promote metabolic changes during viral infection, favoring its survival, altering cell phenotype and function, and causing sustained inflammation and tissue injury. Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, provokes systemic and cell metabolic changes and possibly altering lipid and glucose metabolism. Besides severe acute respiratory syndrome (SARS), SARS-CoV-2 can cause acute kidney injury, which has been associated with the severity of the disease. Although it is not clear the mechanisms whereby SARS-CoV-2 induces kidney dysfunction, it is known that the virus presents kidney tropism, namely, podocytes and proximal tubular epithelial cells. Changes in renal cell metabolism and systemic metabolic disorders are important events in kidney injury progression. Here, we explored the metabolism and its interface with SARS-CoV-2 infection and raised the perspective on metabolism disturbances as a critical event to kidney dysfunction in COVID-19.

Distinct macrophage phenotypes and redox environment during the fin fold regenerative process in zebrafish.

In contrast to mammals, zebrafish (Danio rerio) has the ability to regenerate injured sites such as different tissues present in the fin. It is known that cells of the innate immune system play essential roles in regeneration; however, some aspects of the molecular mechanisms by which these cells orchestrate regeneration remain unknown. This study aimed to evaluate the infiltration dynamics of neutrophils and macrophages in the regenerative process of fin fold in regard to the influence of the redox environment and oxidative pathways. Fin fold amputation was performed on transgenic larvae for macrophage-expressed gene 1 (mpeg1), lysozyme (lyz), myeloperoxidase (mpo) and tumour necrosis factor alpha (TNFα) at 3 days post-fertilization, followed by confocal microscopy imaging and measurement of the activities of oxidant and antioxidant enzymes. We observed initially an increase in the number of neutrophils (lyz:DsRed+/mpx:GFP+) and then macrophages (mpeg1+) in the injury site followed by a decrease in neutrophils at 7 days post-amputation (dpa). Moreover, macrophages switch from a pro-inflammatory to an anti-inflammatory profile throughout the process, while the activity of superoxide dismutase (SOD) increased at 1 dpa and catalase (CAT) at 5 dpa. Higher levels of lipid peroxidation were also detected during regeneration. Despite oxidative stress, there is, therefore, an antioxidant response throughout the regeneration of the caudal fin. The present work can contribute to future studies on the development of cell therapies, achieving greater effectiveness in the treatment of diseases related to the formation of fibrotic tissue.

Mitochondrial connections with immune system in Zebrafish.

Mitochondria are organelles commonly associated with adenosine triphosphate (ATP) formation through the oxidative phosphorylation (OXPHOS) process. However, mitochondria are also responsible for functions such as calcium homeostasis, apoptosis, autophagy, and production of reactive oxygen species (ROS) that, in conjunction, can lead to different cell fate decisions. Mitochondrial morphology changes rely on nutrients' availability and the bioenergetics demands of the cells, in a process known as mitochondrial dynamics, which includes both fusion and fission. This organelle senses the microenvironment and can modify the cells to either a pro or anti-inflammatory profile. The zebrafish has been increasingly used to research mitochondrial dynamics and its connection with the immune system since the pathways and molecules involved in these processes are conserved on this fish. Several genetic tools and technologies are currently available to analyze the behavior of mitochondria in zebrafish. However, even though zebrafish presents several similar processes known in mammals, the effect of the mitochondria in the immune system has not been so broadly studied in this model. In this review, we summarize the current knowledge in zebrafish studies regarding mitochondrial function and immuno metabolism.