Size-dependent toxicity and interactions of calcium oxalate dihydrate crystals on Vero renal epithelial cells.

Abstract

Vero cells were exposed to COD crystals of varying sizes at a concentration of 200 μg mL-1 for 6 h. The effects of COD crystals on Vero cell viability, apoptosis rate, and cellular biochemical parameters [lactate dehydrogenase (LDH), superoxide dismutase (SOD), reactive oxygen species (ROS), hyaluronic acid (HA), osteopontin (OPN), and mitochondrial membrane potential (Δψm)] were determined using biochemical and morphological analyses. Vero cell viability and apoptotic rate were closely associated with the size of COD crystals; lower cell viability and higher apoptosis rate were observed in cells exposed to smaller COD crystal size. The expression of SOD, ROS, HA and OPN also changed in a size-dependent manner after exposure to the five different sizes of COD crystals. The area ratio of the (100) face with a high density of Ca2+ ions to the total surface area was also found to influence the severity of cell injury. Cell injury induced by COD crystals was mainly caused by excessive expression of intracellular ROS and reduction of free-radical scavenger SOD. Moreover, binding of large crystals on the cell membrane surface takes more time to cause cell injury than internalized small-sized crystals. The cell death rate was found to be positively correlated with the amount of internalized COD crystals. although the COD toxicity is often disregarded, the size-dependent cytotoxicity of COD crystals toward Vero cells is demonstrated in this study.