Cellular oxidative stress and peroxisomal enzyme activities in pediatric liver transplant patients.

OBJECTIVES In this study, we examined the activities of key peroxisomal enzymes in peripheral blood lymphocytes (PBLs) of pediatric liver transplant patients. SUBJECTS AND METHODS Venous blood was drawn from 14 patients aged 5-16 years on FK-506 treatment and 18 healthy subjects for isolation of lymphocytes. β-Oxidation of very long chain fatty acids (VLCFAs) and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), NADPH oxidase (NOX), catalase and peroxisomal enzyme acyl CoA oxidase (ACO) were measured in cellular homogenates. Levels of malondialdehyde (MDA) were measured as an index of lipid peroxidation. Protein content and mRNA levels of catalase, peroxisomal membrane protein-70 (PMP-70) and ACO were measured using Western blotting and PCR techniques. RESULTS PBLs isolated from liver transplant patients showed significantly (p < 0.01) increased levels (226.9 ± 24.5 μmol/mg protein) of MDA as compared to the levels in controls (162.8 ± 19.6 μmol/mg protein), whereas enzyme activities of SOD and NOX remained unaltered in patients' cells. Enzyme activities of catalase and GPx were markedly (p < 0.01) decreased in cells isolated from liver transplant patients. ACO activity and β-oxidation of VLCFAs in PBLs from liver transplant patients were however found to be significantly increased by 38 and 52% respectively when compared with controls. Gene expression of PMP-70 and ACO was also significantly increased (p < 0.01) in PBLs of patients. CONCLUSION Our results clearly showed that peroxisomal metabolic activities are markedly altered in lymphocytes of liver transplant patients and might contribute to the development of cellular oxidative stress.