Flow cytometric analysis of p21 protein expression on irradiated human lymphocytes.

Abstract

Cell cycle blockage in G1 is a mechanism p21 protein-regulated and coupled to DNA damage response to permit genetic content analysis, damage repair and cell death. Analysis of proteins that participates of this response has progressed with new analytic tools, and data contributes to comprehension of radioinduced molecular events as well as to new approaches on practices that employ ionizing radiation. On this perspective, the aim of this research was to evaluate, by flow cytometry, p21 expression on irradiated human lymphocytes, maintained under different experimental conditions. Peripheral blood samples from 10 healthy subjects were irradiated with doses of 0 (non-irradiated), 1, 2 and 4 Gy. Lymphocytes were processed to analysis on ex vivo (no cultured) condition and after 24; 48 and 72 hours culture, with and without phytohemagglutinin stimulation. p21 protein expression levels were measured by flow cytometry, as percentage values. Results indicate that flow cytometric assay allows detection of changes on p21 expression, since it was detected significant increase on phytohemagglutinnin-stimulated samples, for all times, against basal expression (ex vivo). However, it was not observed significant alterations on p21 protein radioinduced levels, for all doses, times and culture conditions analyzed. These results not indicate so p21 protein as bioindicator of ionizing radiation exposure. Nevertheless, data confirmation may to require analysis of a more numerous population.