Endothelial and cardiac effects of 5-fluorouracil. An experimental and clinical study

Sammanfattning: The cytostatic drug 5-fluorouracil (5-FU) has been shown to affect both morphology and function of vascular endothelium. These effects could be part of the pathophysiology for 5-FU induced cardiotoxicity. The present thesis explores the mechanisms of this endothelial toxicity. In an animal model, treatment with thromboprophylactic doses of the low-molecular weight heparin (LMWH) dalteparin could not protect the endothelium from damage caused by 5-FU, although the secondary thrombosis was prevented. A subsequent study with three different LMWH (dalteparin, enoxaparin and tinzaparin) showed a moderate endothelial injury after treatment with LMWH alone for up to 60 days. Probucol, a lipid-lowering drug with strong antioxidant properties, was given as prophylaxis for two weeks before 5-FU treatment. With this drug, the endothelium was protected from the negative effects of 5-FU and had a normal morphology. Patients receiving 5-days infusion of 5-FU, combined with cisplatin, were studied for endothelial and cardiac effects. There was a significant increase in markers for endothelial injury (von Willebrand factor and soluble thrombomodulin) and in malondialdehyde, a marker for increased lipoperoxidation and possibly free radical production. Myocardial and echocardiographic parameters were not changed. Human umbilical vein endothelial cells (HUVEC) were incubated with 5-FU. A dose-dependant increase in secretion of endothelin-1 (a potent vasoconstrictor) was shown. No influence of apoptosis was seen. The results indicate increased oxidative stress caused by 5-FU, followed by endothelial damage and secretion of a vasoactive peptide. This could be part of the pathophysiological mechanisms of 5-FU induced cardiotoxicity.