Tl(I) and Tl(III) Induce Alterations in MDCK Cell Lipid Metabolism

MARÍA DEL CARMEN FERNÁNDEZ; VERSTRAETEN, SANDRA; MOREL GOMEZ, EMANUEL

CHICAGO

Congreso; EXPERIMENTAL BIOLOGY; 2017

ASBMB

Thallium (Tl) is a toxic heavy metal that contaminates the environment and causes several human health-related problems. Tl can be found as monovalent (Tl(I)) or trivalent (Tl(III)) cations, the latter being a strong oxidant. Tl intoxication alters tissular functioning by altering the progression of cell cycle and/or by promoting programmed cell death. Tl intoxication affects several organs and tissues, being the kidney a main target of its toxicity. The mechanisms involved in such pathological conditions are still poorly understood.It has been reported that other heavy metals can disturb cell lipid homeostasis. Thus, in the present work we investigated the effects of Tl on renal lipid metabolism, which could be partially responsible for the toxic effects of this metal. For this purpose, we used as a model the Madin Darby Canine Kidney (MDCK) renal epithelial cells, either in their proliferative or differentiated states.For the experiments using proliferative MDCK cells, confluent cell cultures were incubated for either 24 or 48 h in the absence or presence of Tl(I) or Tl(III) (10 or 100 μM). For the experiments using differentiated cells, confluent cultures were differentiated in hypertonic medium (NaCl, 125 mOsm) for 72 h and further were incubated for 48 h in the absence or presence of Tl(I) or Tl(III) (10 or 100 μM). After treatment, cells were collected, counted, and lipids were extracted by the Bligh-Dyer method. Chloroformic extracts were resolved by thin layer chromatography (TLC) in different solvent systems to evaluate the profile of phospholipids (PLs), cholesterol (Cho), and triacylglycerides (TAG).Proliferative MDCK cells. Obtained results indicate that Tl(III) not only causes TAG accumulation, but also increases the content of lipid membrane components (PL and Cho) and alters membrane properties. Supporting that, Tl(III) induced alterations in the overall morphology of the cells and of the inner membranous structures, such as mitochondria and the endoplasmatic reticulum. In addition, we observed that the alteration of lipid profile in this experimental model was mostly caused by the enhancement of lipid biosynthesis.Differentiated MDCK cells. In this experimental model, both Tl(I) and Tl(III) increased significantly the content of PL, Cho and TAG. Accordingly, microscopy images showed morphological alterations in cells and increased the size and number of lipid droplets (LD). Also, Tl(I) and Tl(III) increased the endogenous biosynthesis of lipids.Taken together, obtained results using the proliferative and differentiated states of MDCK cells indicate that Tl-mediated damage would involve severe alterations in lipid metabolism.Considering that Tl causes several human health-related problems, the findings presented in this work will contribute to a clearer understanding of the mechanisms underlying such pathological conditions.