Background:  There are no surrogate markers that can differentiate active from inactive HIV-associated dementia (HAD) in HAART-treated patients, and clinical studies have failed to clearly show differences in neuropsychological outcomes between drug and non-drug abusers. In this study, we investigated the relationship between the levels of the 3-nitrotyrosine modified proteins (3-NT) in cerebrospinal fluid (CSF) and the progression of HAD and identified 3-NT from CSF of HAD patients.

Methods:  CSF samples from 43 patients with HIV infection from the North Eastern AIDS Dementia (NEAD) cohort were analyzed for 3-NT by Western blot and semi-quantitative slot blot. The 3-NT from CSF were then identified by immunoprecipitation and mass spectrometry.

Results:  The level of 3-NT in CSF was higher (p <0.05) in HIV patients with history of injection drug use (n = 20) compared to patients with other risk factors (n = 16) regardless of severity of HAD. Patients with active HAD (n = 9) had increased 3-NT (p <0.05) in CSF compared to patients with inactive HAD (n = 16), although there was no significant difference in 3-NT levels between demented (n = 25) and non-demented patients (n = 18). By immunoprecipitation and liquid chromatography/mass spectrometry (LC/MS/MS), we identified 9 potential proteins with 3-NT modification. Most importantly, we found that although prostaglandin D2 synthase is abundant in both normal and disease CSF, it is only nitrated in CSF of HAD patients.

Conclusions:  Protein nitration due to increased production of nitric oxide as a result of oxidative stress in the brain may be an important biomarker for active HAD and injection drug abuse. Nitration of prostaglandin D2 synthase may play an important role in the pathogenesis of HAD.