Evaluation of DNA damages in peripheral blood leukocytes of Alzheimer's disease patients by Comet test

Abstract

DNA damage is a powerful trigger of apoptosis in neurons and is present in patients with Alzheimer's disease (AB). Also, DNA damage is registered in cells that are not neurons, such as peripheral blood leukocytes and fibroblasts. In this paper we examined and compared the impact of AB and chronological aging on DNA damage in peripheral blood leukocytes. We used electrophoresis of individual cells on gel (comet test) as a modern and reliable method for registration of nuclear DNA damage whose fragments form a comet tail, which is not present in undamaged cells. We analyzed leukocytes of these groups: AB patients with sporadic form of the disease, healthy elderly of an appropriate age and healthy younger adults as controls. The results show that the frequency of AB patients with leukocyte DNA damage significantly is higher than in similar control age-matched controls. Also, a significant increase in the frequency of DNA damage has been observed during chronological aging. Based on the obtained data we can conclude that genetic instability, otherwise present in the elderly is more expressed in patients with sporadic AB, which indicates that it is not just an epiphenomenon of aging, but is characteristic of the disease.

Oštećenja DNK su snažan okidač apoptoze neurona i prisutna su kod obolelih od Alchajmerove bolesti (AB). Ona se registruju i u ćelijama koje nisu neuroni, kao što su leukociti periferne krvi i fibroblasti. U ovom radu smo ispitivali i poredili uticaj AB i hronološkog starenja na oštećenje DNK leukocita periferne krvi. Koristili smo elektroforezu pojedinačnih ćelija na gelu (Komet test), kao savremenu i pouzdanu metodu za registrovanje oštećenja jedarne DNK čiji fragmenti formiraju rep komete, koji nije prisutan u neoštećenim ćelijama. Analizarani su leukociti: AB pacijenata sa sporadičnim oblikom bolesti, zdravih starih osoba odgovarajuće starosti i zdravih odraslih mlađih kontrolnih osoba. Dobijeni rezultati pokazuju da je kod AB ispitanika frekvencija leukocita sa oštećenjima DNK statistički značajno veća nego kod kontrola slične starosti; značajan porast učestalosti oštećenja DNK zapaža se i tokom hronološkog starenja. Na osnovu dobijenih podataka možemo da zaključimo da je genetička nestabilnost, inače prisutna i kod starih osoba, jače izražena kod pacijenata sa sporadičnom AB, što ukazuje na to da ona nije samo epifenomen starenja, već je karakteristika same bolesti.