Renal proximal tubular injury was reported as a result of Red Yeast Rice supplements intake, with puberulic acid identified as one of the causative agents. Although the compound has shown nephrotoxicity in animal models, the cytotoxicity of this compound on human kidney cells has not been investigated. In this study, we evaluated the cytotoxic effects of puberulic acid using three-dimensional cultured primary human renal proximal tubular epithelial cells (3D-RPTECs). Upon exposure to puberulic acid, the spheroid surface area and mitochondrial fluorescence intensity were reduced. Moreover, a time-dependent decrease in intracellular ATP levels was observed with the EC50 value at 7 d of 24.7 μM. Based on the carboxylic acid structure of puberulic acid, we investigated the effect of probenecid, a non-selective organic anion transporter (OAT) inhibitor, on puberulic acid cytotoxicity. The ATP reduction effect of puberulic acid was partially alleviated by probenecid. Furthermore, the uptake of OAT1 substrate furosemide by OAT1-expressing HEK293 cells was reduced by puberulic acid with an IC50 value of 5.4 μM. These findings suggest that puberulic acid has a highly cytotoxic effect on the proximal tubules.
Keywords: kidney injury; organic anion transporter; puberulic acid; red yeast rice supplement; three-dimensional cultured primary human renal proximal tubular epithelial cell (3D-RPTEC).