RESUMEN
Follicular atresia is a hormonally controlled degenerative process involving apoptosis of the somatic and germ cells. Since different signaling pathways can induce cell death, the aim of the present study was to investigate cell death signaling and crosstalk between autophagic, apoptotic, and lysosomal proteins during follicular atresia in Nile tilapia. For this, females were kept in controlled conditions for 21 days, and ovary samples were collected weekly. The atretic follicles (AF) were analyzed in three regression phases: Early, advanced, and late. Under electron microscopy, the follicular cells exhibited numerous protein synthesis organelles in the early AF. Immunoreactivity for Bcl2, Beclin1, Lc3, and Cathepsin D increased significantly in advanced AF (p < .001), when follicular cells were in intense yolk phagocytosis. In this phase, autophagosomes and autolysosomes were frequently observed. In the late AF, follicular cells had a markedly electron-lucid cytoplasm and immunoreactivity for Bax and TUNEL assay indicated an elevated apoptosis rate. Colocalisation of Lamp1/Cathepsin D and Lc3/Caspase-3 suggests dynamic crosstalk between the autophagy, apoptosis, and lysosome pathways. Taken together, the data indicate that autophagy plays a role in the homeostasis and clearance of the follicular cells preceding Cathepsin D mediated apoptosis during follicular atresia in Nile tilapia.
Asunto(s)
Apoptosis , Catepsina D/metabolismo , Proteínas de Peces/metabolismo , Atresia Folicular/metabolismo , Folículo Ovárico/enzimología , Tilapia/metabolismo , Animales , FemeninoRESUMEN
In this study we assessed the interaction of different strains of Bacillus cereus with murine peritoneal macrophages and cultured phagocytic cells (Raw 264.7 cells). Association, internalization, intracellular survival, routing of bacteria to different compartments and expression of MHCII were assessed in cells infected with different strains of B. cereus in vegetative form. Association values (adhering + internalized bacteria) and phagocytosis were higher for strain B10502 than those for strains 2 and M2. However, after 90 min interaction, intracellular survival was higher for strain 2 than for strains M2 and B10502. Acquisition of lysosomal markers by B. cereus containing vacuoles (BcCV), assessed by LAMP1 and Lysotracker labelling occurred shortly after internalization. The highest ratio of LAMP1(+)-BcCV was found for strain M2. This strain was able to survive longer than strain B10502 which routes to LAMP1 containing vacuoles to a lesser extent. In addition, strain M2 stimulated expression of MHCII by infected cells. Confocal analyses 60 or 90 min post-infection showed different percentages of co-localization of bacteria with Lysotracker. Results suggest strain-dependent interaction and intracellular killing of B. cereus by phagocytic cells. These findings could be relevant for the pathogenic potential of Bacillus cereus strains.