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

ABSTRACT

In this study, we examined the activities of key peroxisomal enzymes in peripheral blood lymphocytes [PBLs] of pediatric liver transplant patients. Venous blood was drawn from 14 patients aged 5-16 years on FK-506 treatment and 18 healthy subjects for isolation of lymphocytes. Beta -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. PBLs isolated from liver transplant patients showed significantly [p < 0.01] increased levels [226.9 +/- 24.5 micro mol/mg protein] of MDA as compared to the levels in controls [162.8 +/- 19.6 micro mol/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 beta -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. 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