Abstract
Transport proteins in the kidney have a detoxification function by excreting many xenobiotics, their metabolites, and metabolic waste products into the urine. Several compounds, like heavy metal salts, radiocontrast agents, and antibiotics are associated with renal injury. These compounds rapidly enhance the production of a protein, endothelin-1, leading to a diminished renal excretion of potentially toxic compounds. Inhibition of endothelin-1 production by gene silencing techniques, like antisense and short interfering RNA (siRNA), may prevent or reduce renal injury. In this thesis, in vitro and in vivo models were used to investigate several aspects of endothelin-1 expression and excretion, activity and regulation of renal drug transport (P-glycoprotein and multidrug resistance proteins), and inhibition of gene expression by antisense and siRNA. In epithelial cell lines of the kidney and intestine, we showed endothelin-1 expression, which was induced by exposure to inflammatory cytokines. Several trials to silence endothelin-1 expression using gene silencing techniques were not successful. Besides endothelin-1, these cell lines expressed drug transport proteins and showed transport activity. In isolated renal tubules of the killifish (Fundulus Heteroclitus), regulation of drug transport activity was investigated in more detail. In a third model, the rat in vivo, intravenously administered siRNA accumulated, like to antisense oligonucleotides, in the kidney. Here, it was capable of silencing gene function in the renal proximal tubule. In future research, these models could be useful to investigate the effects of endothelin-1 gene silencing on drug transport and renal injury in more detail.
