ROLE OF HEME IN ALZHEIMER'S DISEASE STUDIED BY HPLC-LC/MS

The (Ab) aggregation in the brain, known as amyloid plaques, is a hallmark of Alzheimer’s disease (AD). The molecular mechanism linking amyloid-beta peptide (Ab) to the neuro-degeneration of AD is not clear, moreover patients with mild cognitive impairment (MCI) are considered with a high risk factor for Alzheimer's diseases [1]. Atamna et al. proposed an important role for heme in AD [2]. Heme could prevent the aggregation of Ab in vivo, by forming Ab-heme complex with peroxidase activity. In order to investigate if the heme plasmatic concentration could represent a diagnostic parameter of AD, we designed a chromatographic method using HPLC in order study three groups of patients and one control: AD patients with different cognitive impairment; patients with MCI; patient with other neurological diseases (OND) and healthy controls. We collected peripheral blood mononuclear cells and Heme was extracted from cell lysate; results were referred to total protein content. The HPLC method was validated to determine heme concentration and mass spectrometric analysis has been performed in order to differentiate heme-a from heme-b. Our preliminary results indicate that heme-b is significantly decreased in AD and MCI patients compared to patients with other different neurological pathologies and healthy voluntaries. This reduction of the peripheral heme concentration may be due to the formation of Ab-heme complex in the brain, because the b-amyloid peptide aggregation is present not only in AD but also in MCI patients. [1] Grundman M, Petersen RC, Ferris SH, et al.. Arch. Neurol 2004 61 (1): 59–66. [2] Atamna H. and Frey W.H. PNAS July27 2004, vol.101, n°30:11153-11158.