In Vitro Study of the Nephrotoxicity of Tripterygium Tablet Extract and Triptolide in Monolayer HK-2 Cells Cultured in a Transwell Chamber

We established a monolayer polarized cell model using human kidney 2 (HK-2) cells cultured in a transwell chamber to examine the changes in the morphology and physiological functions of human-derived renal proximal tubular epithelial cells caused by tripterygium tablet extract (TTE) and triptolide. HK-2 cells were cultured on PCF membranes to form a complete monolayer of cells. A MTT assay was used to select 10, 40, 160, 640 μg·ml^-1 TTE or 4, 16, 64, 256 ng·ml^-1 triptolide to treat HK-2 monolayer cells. After 24 hours, a FITC permeability assay was performed; GGT, LDH and NAG secretion on the apical (AP) and basolateral (BL) sides of the cells by HK-2 cells were examined. The morphology and the monolayer structure of HK-2 cells was observed via optical microscope and scanning electron microscope, respectively. The effect on the cytoskeleton of HK-2 cells was observed under a fluorescence microscope. The IC₅₀ of TTE was 277.122 μg·ml^-1, and the IC₅₀ of triptolide was 148.035 ng·ml^-1. Compared with the DMSO group, the FITC leakage rate with TTE 160, 640 μg·ml^-1 treated group and 4 - 256 ng·ml^-1 triptolide dose group exhibited statistically significant increase. TTE significantly increased secretion of GGT and LDH at 160, 640 μg·ml^-1, meanwhile, dramatically increased the AP/BL ratio of LDH at 160 μg·ml^-1; triptolide significantly increased secretion and AP/BL ratio of GGT and LDH at 256 ng·ml^-1. The morphological observations via optical and electron