Altering microtubule polymerization in Sertoli cells strongly affects their lipid metabolism

Abstract

The aim of this work was to study the biological consequences of altering microtubule polymerization in Sertoli cells, with a special focus on their lipid metabolism. For this purpose, the effect of longterm exposures to nocodazole (NCZ) (0.01 µM) was studied on TM4 cells in culture. In addition to the expected effect of NCZ on the depolymerization of tubulin microtubules, a remarkable reorganization was observed in the intermediate flament network (vimentin), which showed a more peripheral distribution than in untreated cells. As compared to cells cultured in control conditions, those exposed to NCZ displayed an increased mitochondrial membrane depolarization (p<0.001). Their plasma membrane integrity was concomitantly altered, as shown by a considerable increase in the leakage of lactate dehydrogenase (p<0.01) released into the culture medium. In addition, the cell proliferation was signifcantly reduced (p<0.003) in NCZ-exposed cells. That the drug induced a major alteration on lipid biosynthesis was clearly apparent from a signifcant increase in triacylglycerol (TAG) levels (p<0.0002) and a massive accumulation of lipid droplets in the cytoplasm of cells. This observation was sustained by following the incorporation and distribution of labeled arachidonic acid ([3H]AA). After 1 hour of incubation, the most highly [3H]-labeled lipid class were TAG in control cells, but choline glycerophospholipids in drug-treated cells. Interestingly 72 hours later, the percentages of label in TAG and cholesterol esters were about twice higher in NCZ-treated than in control cells. We conclude that the cytoskeletal alterations that Sertoli cells undergo after being exposed to NCZ, through their impact on mitochondrial functions and cytoplasmic architecture, are closely involved in the deranged lipid metabolism induced by the drug.