Effects of Five Substances with Different Modes of Action on Cathepsin H, C and L Activities in Zebrafish Embryos

Abstract

Cathepsins have been proposed as biomarkers of chemical exposure in the zebrafish embryo model but it is unclear whether they can also be used to detect sublethal stress. The present study evaluates three cathepsin types as candidate biomarkers in zebrafish embryos. In addition to other functions, cathepsins are also involved in yolk lysosomal processes for the internal nutrition of embryos of oviparous animals until external feeding starts. The baseline enzyme activity of cathepsin types H, C and L during the embryonic development of zebrafish in the first 96 h post fertilisation was studied. Secondly, the effect of leupeptin, a known cathepsin inhibitor, and four embryotoxic xenobiotic compounds with different modes of action (phenanthrene—baseline toxicity; rotenone—an inhibitor of electron transport chain in mitochondria; DNOC (Dinitro-ortho-cresol)—an inhibitor of ATP synthesis; and tebuconazole—a sterol biosynthesis inhibitor) on in vivo cathepsin H, C and L total activities have been tested. The positive control leupeptin showed effects on cathepsin L at a 20-fold lower concentration compared to the respective LC50 (0.4 mM) of the zebrafish embryo assay (FET). The observed effects on the enzyme activity of the four other xenobiotics were not or just slightly more sensitive (factor of 1.5 to 3), but the differences did not reach statistical significance. Results of this study indicate that the analysed cathepsins are not susceptible to toxins other than the known peptide-like inhibitors. However, specific cathepsin inhibitors might be identified using the zebrafish embryo.

Cathepsin L regulates oocyte meiosis and preimplantation embryo development

“…Consistent with our results, monitoring the activity of CTSL protease in zebrafish embryos from the start of fertilization until hatching revealed a time‐dependent increase in CTSL activity during the entire process of embryogenesis. 53 Moreover, CTSL is required for Caenorhabditis elegans embryo development and its disruption results in the accumulation of yolk platelets in the cytoplasm of early embryos, leading to a high percentage of arrested non‐viable embryos and decelerated progression of viable embryos. 54 , 55 Several potential mechanisms can explain the pivotal role of CTSL in early embryo development.…”

CLN3 deficiency leads to neurological and metabolic perturbations during early development

“…Cathepsin D activity in zebrafish extracts was assayed using a protocol adapted from references 56 and 69 . Total protein was extracted from a pool of 60 WT and mutant (MUT1) larvae at 5 dpf.…”

CLN3 deficiency leads to neurological and metabolic perturbations during early development

“…Cathepsin D activity in zebrafish extracts was assayed using a protocol adapted from (Kuster et al 2019) and (Matsui et al 2013). Total protein was extracted from a pool of 60 WT and mutant (MUT1) larvae at 5 dpf.…”