The nitric oxide prodrug, V-PYRRO/NO, protects against cadmium toxicity and apoptosis at the cellular level

The liver is an important target tissue of cadmium. The compound O-2-vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2 diolate (V-PYRRO/NO) is a fiver-selective nitric oxide (NO) prodrug that is metabolized by hepatic P450 enzymes to release NO in hepatocytes. In vivo. V-PYRRO/NO call protect against the toxicity of various hepatotoxicants, including cadmium. Since NO is an effective vasodilator, whether this protective effect against cadmium toxicity is M the level of the hepatic vascular system or actually within the liver cells has not been defined. Thus, we studied the effects of V-PYRRO/NO pretreatment oil cadmium-induced toxicity and apoptosis in cultured rat liver epithelial (TRL 1215) cells. Cells were pretreated with V-PYRRO/NO at 500 or 1000 mu M for up to 24 h then exposed to cadmium (as CdCl2) for additional 24 h and cytotoxicity was measured. Cadmium was significantly less cytotoxic in V-PYRRO/NO (1000 mu M) pretreated cells (LC50 = 6.1 +/- 0.6 mu M) compared to control cells (LC50 = 3.5 +/- 0.4 mu M). TRL 1215 cells acted upon the prodrug to release NO. producing nitrite levels in the extracellular media after 24 It of exposure to 500 or 1000 mu M V-PYRRO/NO measured at 87.0 +/- 4.2 and 324 +/- 14.8 PM, respectively, compared to basal levels of 7.70 +/- 0.46 mu M. V-PYRRO/NO alone produced small increases in metallothionein (MT) a metal-binding, protein associated with cadmium tolerance. However, V-PYRRO/NO pretreatment greatly enhanced cadmium induction of MT. V-PYRRO/NO pretreatment also markedly reduced apoptotic cell death induced by cadmium (5 mu M) apparently by blocking cadmium-induced activation Or the c-Jun N-terminal kinase (JNK) pathway. Thus, the prodrug, V-PYRRO/NO, protects against the adverse effects of cadmium directly within rat liver cells apparently through generation of NO and, at least in part, by facilitation of cadmium-induced MT synthesis. Published by Elsevier Inc.