Beyond Alzheimer's story: How an engineered molecule gained an endogenous essence.

A hallmark of Alzheimer's disease (AD) is extra-neuronal protein aggregates formed mainly by the amyloid-β peptide (Aβ), that are deposited inside the brain as amyloid plaques. The formation of amyloid plaques requires participation of zinc ions. The 11-Glu-Val-His-His-14 region of Aβ is critical for interaction between Aβ and zinc ions. The engineered peptide Ac-His-Ala-Glu-Glu-NH2 (HAEE) acts as competitive inhibitor of such interactions and suppresses formation of Aβ aggregates in animal models of AD. We sought to develop a reliable method for studying the behavior of the synthetic HAEE peptide in the human blood in preparation for clinical trials of this peptide as a potential anti-amyloid drug for AD. The analytical method to monitor HAEE concentration in blood plasma combines separation by high-performance liquid chromatography and registration on a mass detector of the parent quasi-molecular ion and fragment ions. We discover that HAEE peptide represents a normal endogenous component of human blood plasma. Moreover, the HAEE level has been significantly reduced in patients with a clinical diagnosis of AD (n = 200) as compared with the control participants with no clinical diagnosis of cognitive impairment (n = 150). Deficiency of endogenous HAEE may be considered as a potential blood-based biomarker in the diagnosis of AD, while exogenous synthetic HAEE may serve as a drug in AD-modifying therapy.