Microcystic cyanobacteria extract induces cytoskeletal disruption and intracellular glutathione alteration in hepatocytes

Abstract

Microcystins are a group of highly liver-specific toxins, although their exact mechanisms of action remain unclear. We examined the effects of microcystic cyanobacteria extract (MCE) collected from a contaminated water source on the organization of cellular microtubules (MTs) and microfilaments (MFs) in hepatocytes. We also investigated the effects on lactate dehydrogenase (LDH) leakage and intracellular glutathione (GSH). Primary cultured rat hepatocytes exposed to MCE (equivalent to 125 μg/mL lyophilized algae cells) showed a characteristic disruption of MTs and MFs in a time-dependent manner. Under these conditions, MCE caused aggregation of MTs and MFs and a severe loss of MTs in some cells. Moreover, MCE-induced cytoskeletal alterations preceded the LDH leakage. On the other hand, the treatment of cells with MCE led to a dose-dependent increase of intracellular GSH. However, time-course study showed a biphasic change of intracellular GSH levels with a significant increase in the initial stage followed by a decrease after prolonged treatment. Furthemore, pretreatment with N-acetycystein (NAC), a GSH precursor, significantly enhanced the intracellular GSH level and decreased the MCE-induced cytoxicity as well as cytoskeleton changes. In contrast, buthionine-(S,R)-sulfoximine, a specific GSH synthesis inhibitor, increased the cell susceptiblity to MCE -induced cytoxicity by depleting the intracellular GSH level. These findings suggests that intracellular GSH plays an important role in MCE-induced cytoxicity and cytoskeleton changes in primary cultured rat hepacytocytes. Increasing intracellular GSH levels protect cells from MCE-induced cytoxicity and cytoskeleton changes.