The 5-aminolaevulinic acid-based photodynamic effects on nuclei and nucleoli of HL-60 leukemic granulocytic precursors

To provide more information on the 5-aminolaevulinic acid (ALA)-based photo dynamic effect (PDE) on nuclei and nucleoli of individual leukemic cells, t hese structures were studied in cultured HL-60 cells which originated from leukemic highly immature and less differentiated precursors of granulocytes . The nuclear morphology was visualized by panoptic May-Grunwald/Giemsa sta ining and cytochemical method for DNA, nucleoli were visualized by cytochem ical methods for the demonstration of RNA and silver stainable proteins inc luding those of interphase silver stained nucleolus organizer regions (AgNO Rs). In most cells ALA-based photodynamic treatment (PDT) produced marked a lterations such as formation of apoptotic bodies, and large condensation of nuclear chromatin structure but without nuclear segmentation. Such changes are in harmony with the apoptotic process induced in these cells but witho ut previous terminal differentiation. In nucleoli ALA-based PDT produced th e reduction and disappearance of nucleolar silver stainable particles (SSPs ) representing AgNORs which apparently reflected the alteration of the nucl eolar biosynthetic activity and cell proliferation. The latter is also refl ected by the disappearance of mitotic divisions. On the other hand, a small subpopulation of cells was less sensitive or resistant to the ALA-based PD E since they did not show mentioned nuclear and nucleolar alterations. (C) 2000 Elsevier Science B.V. All rights reserved.