[Lysosomes and apoptosis].
In 1955, Christian de Duve and his coworkers from the School of Medicine in Louvain, Belgium, named a group of cytoplasmic formations surrounded by lipoprotein membrane and containing acid hydrolase enzymes as lysosomes. Biochemical and cytochemical studies showed lysosomes to be found in animal and vegetable eukaryotic cells. Later on, lysosomes were found to be involved in the dynamics of lysosomal system, which consists of a number of various cytoplasmic formations such as primary and secondary lysosomes, endosomes, autophagosomes and postlysosomes. These formations are inter-connected by the mechanism of membrane integration, and in some instances by the cell membrane. Lysosomal system is involved in numerous physiological processes such as degradation of endogenous and exogenous macromolecules (proteins, lipids, polysaccharides and nucleic acids), cytoplasmic formations (mitochondria, peroxisomes, Golgi complex) that have performed their functions, tissue regression (post-lactation mammary gland), hormone secretion regulation (proinsulin to insulin), etc. On the other hand, lysosomal system is also involved in a number of pathologic processes like inflammation, allergic reactions, ischemia, hypoxia, as well as in lysosomal diseases (thesaurismoses), e.g., type II glycogenosis, fucosidosis, mucolipidosis III, etc. In 1974, Christian de Duve introduced the term lysosomotropism, denoting entry of the pharmacologically active, toxic and carcinogenic substances in the lysosomal system irrespective of their chemical nature and mechanism of input. Lysosomotropic substances may act in two ways: (1) causing impairments in the intralysosomal area, with toxic manifestations; and (2) modifying their membrane properties by increasing or decreasing membrane permeability, or by inducing labilizing or stabilizing effects. Damage to the lysosomal system occurs in the late stage of necrosis, while destabilization of lysosomal formations has been recorded in primary processes during apoptosis.
Vikić-Topić
Drazen
D
NMR Center, Ruder Bosković Institute, Zagreb, Hrvatska.
Carević
Olga
O
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D006801:Humans; D008247:Lysosomes / Q000502:physiology* / Q000648:ultrastructure