Age-related changes in glutathione and glutathione-related enzymes in rat brain

Abstract

The most reliable and robust risk factor for some neurodegenerative diseases is aging. It has been proposed that processes of aging are associated with the generation of reactive oxygen species and a disturbance of glutathione homeostasis in the brain. Yet, aged animals have rarely been used to model the diseases that are considered to be age-related such as Parkinson's or Alzheimer's disease. This suggests that the results from these studies would be more valuable if aged animals were used. The present study was designed to provide insight into the glutathione redox state in young and aged rat siblings of both genders by studying the enzyme activities related to glutathione synthesis, cycling, and usage. The results suggested a significant age-related reduction of reduced glutathione (GSH) level in all brain regions examined, associated with an increase of GSH oxidation to glutathione disulfide (GSSG) and decrease of the GSH/GSSG ratio. These changes were accompanied by diminished gamma-glutamylcysteine synthetase activity in de novo glutathione synthesis and increased lipid peroxidation. In addition, these changes were associated with increased enzyme activities related to the GSH usage (glutathione peroxidase, gamma-glutamyl transpeptidase, and glutathione S-transferase). The results indicate that aged animals are likely more vulnerable to oxidative stress and insinuate the roles of aged animals in modeling age-related neurodegeneration diseases.

Fig. 1

The levels of reduced glutathione (GSH), glutathione disulfide (GSSG), and GSH/GSSG ratio in rat regional brain tissues. GSH and GSSG were measured in cortex, striatum, midbrain, and cerebellum of male and female rats at 4 and 17 months of age. (A) GSH, (B) GSSG, and (C) ratio of GSH over GSSG. Data are the means ± SEM from 5 animals in each group. *P < 0.05, **P < 0.01 compared with the corresponding young group.

Fig. 2

The levels of lipid peroxide (LPO) in rat brain tissues. LPO was measured in cortex, striatum, midbrain, and cerebellum of male and female rats at 4 and 17 months of age. Data are the means ± SEM from 5 animals in each group. **P < 0.01 compared with the corresponding young group.

Fig. 3

The subunits of γ-glutamylcysteine synthetase (GCS) protein in rat brain tissues. Heavy subunit of GCS (GCS-HS) and light subunit of GCS (GCS-LS) were immunoblotted for cortex, striatum, midbrain, and cerebellum of male and female rats at 4 and 17 months of age. A and B were representative Western blot images for GCS-HS (A) and GCS-LS (B). C (GCS-HS) and D (GCS-LS) represent percent of optical density of immunoblot bands relative to the band density in cerebellum in male rat at 4 months of age. Data are the means ± SEM from 5 animals in each group. *P < 0.05; **P < 0.01 compared with the corresponding young group.