Role of cytochrome P450 and glutathione S-transferase α in the metabolism and cytotoxicity of trichloroethylene in rat kidney

Abstract

The toxicity and metabolism of trichloroethylene (TRI) were studied in renal proximal tubular (PT) and distal tubular (DT) cells from male Fischer 344 rats. TRI was slightly toxic to both PT and DT cells, and inhibition of cytochrome P450 (P450; substrate, reduced-flavoprotein:oxygen oxidoreductase [RH-hydroxylating or -epoxidizing]; EC 1.14.14.1) increased TRI toxicity only in DT cells. In untreated cells, glutathione (GSH) conjugation of TRI to form S-(1,2-dichlorovinyl)glutathione (DCVG) was detected only in PT cells. Inhibition of P450 transiently increased DCVG formation in PT cells and resulted in detection of DCVG formation in DT cells. Formation of DCVG in PT cells was described by a two-component model (apparent V max values of 0.65 and 0.47 nmol/min per mg protein and K m values of 2.91 and 0.46 mM). Cytosol isolated from rat renal cortical, PT, and DT cells expressed high levels of GSH S-transferase (GST; RX:glutathione R-transferase; EC 2.5.1.18) α (GSTα) but not GSTπ. Low levels of GSTμ were detected in cortical and DT cells. Purified rat GSTα2–2 exhibited markedly higher affinity for TRI than did GSTα1–1 or GSTα1–2, but each isoform exhibited similar V max values. Triethyltinbromide (TETB) (9 μM) inhibited DCVG formation by purified GSTα1–1 and GSTα2–2, but not GSTα1–2. Bromosulfophthalein (BSP) (4 μM) only inhibited DCVG formation by GSTα2–2. TETB and BSP inhibited approximately 90% of DCVG formation in PT cytosol but had no effect in DT cytosol. This suggests that GSTα1–1 is the primary isoform in rat renal PT cells responsible for GSH conjugation of TRI. These data, for the first time, describe the metabolism of TRI by individual GST isoforms and suggest that DCVG feedback inhibits TRI metabolism by GSTs.