Responses of peripheral blood mononuclear cells to malachite green in the Asian catfish combining in vitro and in vivo approaches

  • Marie-Aline Pierrard

Student thesis: Doc typesDoctor of Sciences


Malachite green (MG) is used as antiseptic to prevent and treat parasites, fungal and bacterial infections in fish. This disinfectant has been controversial and reported to have carcinogenic properties in mammals and to cause significant toxic effects in fish. Prohibited for use on fish intended for human consumption, this chemical and its residues are still commonly detected in fish products. Our concern is more about the rearing of one particular species, the Asian catfish, Pangasianodon hypophthalmus, one of the most economically important fish worldwide. The repeated violations concerning this species raise some questions on human health and risk assessment. Peripheral blood mononuclear cells (PBMC) were chosen to allow regular sampling in a limited invasive way. Through the combination of in vitro and in vivo approaches, some potential routes of research on the toxicity of MG in fish PBMC were highlighted. Proteomic analyses performed on both approaches suggested that MG could lead to possible disturbances of DNA transcription and replication as well as of DNA repair processes, potential disruption of normal cell division, disorganization of the cytoskeleton, modification of the expression of several molecular chaperones as well as of proteins linked to the ubiquitin proteasome system. Studies on MG toxicity should focus on the mitochondria that seemed to be an important target of the prohibited disinfectant. No protein involved in the oxidative stress response has been identified in any of the proteomic analyses performed. The glutathione peroxidase (GPx) and the glutathione S-transferase (GST) measured in the gills and in the liver did not show any significant changes while a significant decrease of hepatic catalase activity (47 %) was observed directly after MG exposure. Another aim of this study was to suggest a robust biomarker Protein Expression Signature (PES) to detect the illegal use of MG with the final objective to apply this biomarker signature to an in situ monitoring in fish farm conditions. This PES would consist of 11 suggested proteins differentially expressed following MG treatment up to one month after depuration. Before the use for regulatory purposes, a lot of work is still required and further studies on the suggested proteins are unavoidable to ensure the reliability of these biomarker candidates. Overall, the research project largely contributes to the investigation of MG toxic mechanism of action. Since it seems challenging to replace MG as fungicide, researches on MG toxicity should continue.
Date of Award15 Nov 2011
Original languageEnglish
Awarding Institution
  • University of Namur
SupervisorPatrick Kestemont (Supervisor), Frederic Silvestre (Co-Supervisor), Eric Depiereux (President), Martine Raes (Jury), Marie-Claire Gillet (Jury) & Helmut Segner (Jury)

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