Editorial [Hot Topic:Mechanisms of Cell Death: Life Evolution (Executive Editor: M. de Eguileor)]

Extensive studies have been devoted to mechanisms leading to the activation of cell death. Three major types of cell death are distinguished based on different criteria: apoptosis, oncosis and autophagic cell death. All these processes are well conserved in life evolution as highlighted in the reviews here gathered. Samara and Tavernarakis review the current understanding of cell death pathways in Caenorhabditis elegans, focusing on autophagy, the main cellular process for bulk protein and organelle recycling, in nematode cell death. These studies reveal that autophagic mechanisms have a prominent role in both apoptosis and necrosis. Tettamanti et al. summarize recent findings on the role of autophagy in two different invertebrate taxa, Platyhelminthes and Insects, focusing attention on two complex events occurring in those systems, namely planarian regeneration and insect metamorphosis. Both represent good models in which to investigate the process of autophagy and its relationship with other programmed cell death mechanisms. Malagoli highlights the findings on stress-induced cell death in a new in vitro invertebrate model, i.e. the IPLB-LdFB insect cell line derived from the larval fat body of the lepidopteron Lymantria dispar. Apoptotic, oncotic and autophagic cell death have been described in these cells as a consequence of oxidative stress or ATP deprivation, and similarities between IPLB-LdFB and mammalian apoptotic pathways have been demonstrated. Terahara and Takahashi focus on immunological roles and molecular mechanisms of apoptosis related to functions of hemocytes in molluscan species living in an environment that changes incessantly according to microorganisms, industrial pollutants, temperature, and salinity. Such environmental factors might directly or indirectly induce apoptosis in molluscan cells. Ballarin et al. reported in the the ascidian Botryllus schlosseri natural apoptosis can be studied in different phases of colony life. From these results B. schlosseri is proposed as a new invertebrate species alternative to Drosophila and Caenorhabditis for the study of apoptosis. Dos Santos et al. in their article review structural and functional data on the most important apoptosis-related molecules, namely deathreceptor, Bcl-2 and caspase families, and mechanisms. The data point to the existence in fish of apoptotic pathways equivalent to those of mammals. Silva et al. advance the knowledge about fish on the role of apoptosis in viral infections and of apoptosis and necrosis in bacterial infections. The use of fish for research on apoptosis-related issues relevant for human physiology and pathology and for the design of apoptosismodulating drugs will continue to increase. Penaloza et al. discuss the types and distributions of cell death in developing mammalian embryos as well as the gene products that may regulate the process. Several types of cell death, as identified by their morphological and biochemical features, can be seen in embryos, tissues associated with pregnancy, and in adult organisms. Cell deaths help sculpt the embryo from the grossest to the finest details of its development. Developmental abnormalities can be traced to aberrant patterns of cell death. References [1] Samara C, Tavernarakis N. Autophagy and cell death in Caenorhabditis elegans. Curr Pham Des 2008; 14(2): 97-115. [2] Tettamanti G, Salo E, Gonzales-Estevez C, Felix DA, Grimaldi A, de Eguileor M. Autophagy in invertebrates: insights into development, regeneration and body remodeling. Curr Pham Des 2008; 14(2): 116-125. [3] Malagoli D. Cell death in the IPLB-LdFB insect cell line: Facts and implications. Curr Pham Des 2008; 14(2): 126-130. [4] Terahara K, Takahashi KG. Mechanisms and immunological roles of apoptosis in molluscs. Curr Pham Des 2008; 14(2): 131-137. [5] Ballarin L, Burighel P, Cima F. A tale of death and life: Natural apoptosis in the colonial ascidian Botryllus schlosseri (Urochordata, Ascidiacea). Curr Pham Des 2008; 14(2): 138-147. [6] dos Santos NMS, do Vale A, Reis MIR, Silva MT. Fish and apoptosis: Molecules and pathways. Curr Pham Des 2008; 14(2): 148- 169. [7] Silva MT, do Vale A, dos Santos NMS. Fish and apoptosis: Studies in disease and pharmaceutical design. Curr Pham Des 2008; 14(2): 170-183. [8] Penaloza C, Orlanski S, Ye Y, Entezari-Zaher T, Javdan M, Zakeri Z. Cell death in mammalian development. Curr Pham Des 2008; 14(2): 184-196.