Cytotoxicity of peroxisome proliferator-activated receptor α and γ agonists in renal proximal tubular cell lines

Fibrates and thiazolidinediones are agonists of peroxisome proliferator-activated receptors (PPAR) α and γ, pharmacologically designed to control dyslipidemia and insulin resistance, respectively. Several works have reported the toxicity of some agonists in a number of tissues. In this work we have analyzed the toxicity of two PPARα (WY14643 and clofibrate) and two PPARγ (pioglitazone and ciglitazone) agonists, using three different renal proximal tubular cell lines: Opossum OK, pig LLC-PK1, and murine MCT. Cell death was determined by the activity of intracellular lactate dehydrogenase. WY14643 and ciglitazone increased cell death with LC50 values of 92–124 μM and 8.6–14.8 μM, respectively, depending on the cell line. Clofibrate and pioglitazone were, however, non-cytotoxic even at concentrations of 10 and 100 higher than the corresponding EC50, which suggests that cell death is independent of PPAR activation. Discrimination between apoptosis or necrosis was analyzed by light microscopy and stress fiber morphology, double staining with acridine orange and ethidium bromide, binding of annexin V, caspase-3 activity, and DNA laddering. With these methods, no signs of apoptosis were observed, which suggests a direct necrosis of the compounds on these renal proximal tubular cell lines.