Role of mitochondrial disruption and oxidative stress in plasticizer phthalate-induced cytotoxicity to human bone osteoblasts

Phthalates are frequently utilized in a wide range of products such as plasticizers with reported negative effects on bones. The current study evaluated the effect of butyl cyclohexyl phthalate on the human osteoblasts via different assays. MTT and lactate dehydrogenase assays were used to examine the in-vitro cytotoxic effect of butyl cyclohexyl phthalate on human bone osteoblasts in concentrations 0.1, 1, 10, and 100 & mu;M for 12 to 72 h postexposures. Incubation of osteoblasts with butyl cyclohexyl phthalate significantly reduced cell viability based on its concentrations and durations of exposure. In parallel, osteoblast secretion of procollagen type 1, osteocalcin, as well as alkaline phosphatase was significantly decreased by butyl cyclohexyl phthalate in concentrations (1 or 2 & mu;M). Butyl cyclohexyl phthalate decreased ATP synthesis and mitochondrial complexes I and III activities, with increased lactate production, all of which were detrimental to cellular bioenergetics. The cellular redox defense systems were significantly depleted by increased lipid peroxidation, elevated reactive oxygen species, decreased catalase and superoxide dismutase enzymes activities, and decreased intracellular reduced glutathione (GSH). Redox stress was also induced. Interestingly, preincubating osteoblasts with reduced GSH before exposing them to butyl cyclohexyl phthalate significantly lowered the cytotoxicity of the butyl cyclohexyl phthalate, suggesting that antioxidants may play a helpful protective effect.