Proteomic identification of nitrated brain proteins in amnestic mild cognitive impairment: a regional study

Abstract

Oxidative stress is an imbalance between the level of antioxidants and oxidants in a cell. Oxidative stress has been shown in brain of subjects with mild cognitive impairment (MCI) as well Alzheimer's disease (AD). MCI is considered as a transition phase between control and AD. The focus of the current study was to identify nitrated proteins in the hippocampus and inferior parietal lobule (IPL) brain regions of subjects with amnestic MCI using proteomics. The identified nitrated proteins in MCI brain were compared to those previously reported to be nitrated and oxidatively modified in AD brain, a comparison that might provide an invaluable insight into the progression of the disease.

1A

Sypro ruby stained gels from control (A) and MCI hippocampus (B). ‘(C)’ and ‘(D)’ represent Western blots for detection of the level of nitrated proteins from control and MCI hippocampus. In hippocampus, total protein nitration was significantly increased in MCI brain compared to that of control. Protein (250 g) was loaded per gel for detection of protein expression and oxidation. A box is drawn around the area that is enlarged in Figure 1B.

1B

Enlarged section of Figure 1A.

2A

Sypro ruby stained gels from control (A) and MCI IPL (B). ‘(C)’ and ‘(D)’ represent Western blots for detection of the level of nitrated proteins from control and MCI IPL. In IPL, total protein nitration was significantly increased in MCI brain compared to that of control. Protein (250 g) was loaded per gel for detection of protein expression and oxidation. A box is drawn around the area that is enlarged in Figure 2B. GRP78- Glucose regulated protein, MRP3-Multidrug resistance protein 3.

2B

Enlarged section of Figure 2A.

3

Validation of protein identified by MS using immunoprecipitation and Western blot analysis: ‘A’ represent gel of total hippocampus protein, a box is drawn around the HSPA8, which is one of the nitrated protein. ‘B’ represents gel obtained from the supernatant of immunoprecipitation sample that lacks the HSPA8 protein. Represent blot probed with 3- NT antibody. n = 3.