Entamoeba histolytica induces human neutrophils to form NETs.

Entamoeba histolytica invades the intestine and other organs during the pathogenesis of amoebiasis. In the early stages, the host organism responds with an inflammatory infiltrate composed mostly of neutrophils. It has been reported that these immune cells, activated by E. histolytica, exert a protective role by releasing proteolytic enzymes and generating reactive oxygen/nitrogen species (ROS/RNS) and antimicrobial peptides. It is now known that neutrophils also produce neutrophil extracellular traps (NETs), which are able to damage and kill pathogens. Studies have shown that intracellular protozoan pathogens, including Toxoplasma gondi, Plasmodium falciparum and Leishmania spp, induce neutrophils to release NETs and are damaged by them. However, the action of this mechanism has not been explored in relation to E. histolytica trophozoites. Through scanning electron, epifluorescence microscopy and viability assays, we show for first time that during in vitro interaction with E. histolytica trophozoites, human neutrophils released NETs that covered amoebas and reduced amoebic viability. These NETs presented histones, myeloperoxidase and decondensed chromatin. The results suggest that NETs participate in the elimination of the parasite.

Modulation of amoebic hepatic abscess by the parasympathetic system.

The neuro-immune network, in which the vagus nerve is involved, provides feedback between its afferent branches for signalling central nervous system from sites of injury through cytokines and its efferent branches, which release acetylcholine, an anti-inflammatory neurotransmitter. For gain insight into the parasympathetic mechanisms participating in the inflammatory response in the liver, we studied the effects of a vagotomy on the innate immune response in hamsters with amoebic liver abscess. At 7 days post-infection, compared to the control, liver parasympathectomy resulted in a larger abscess size, a greater production of collagen fibres, fewer trophozoites, increased serum levels of IL-10 and IFN-γ and increased numbers of IL-10 and IFN-γ-positive cells in situ, with no change in the number of macrophages and NK cells. Data indicate that the vagotomy disrupted the inflammatory response, causing an increase in the response against infection, then could favour the innervation of the liver by the sympathetic nervous system and would then take the control of the immune response by stimulating the conversion of macrophages to epithelioid cells; and through increased IL-10 production would induce the hepatic stellar cells to become myofibroblast collagen producer cells, thus forming a barrier of collagen and blocking trophozoite migration.

Autofluorescence as a tool to study mucus secretion in Eisenia foetida.

Autofluorescence in living cells is due to the presence of endogenous substances that emit fluorescence upon excitation by incidental light. A type of fluorescence, bioluminescence, has been suggested to be linked to mucus secretion in earthworms; however, the origin and the physiological function of this fluorescence are not clear. The aims of this work were to describe autofluorescence in the earthworm Eisenia foetida by SEM, CLSM, and fluorescence microscopy and to examine the possible mechanism of mucus secretion by video microscopy. Earthworms were stimulated either chemically or electrically to induce the secretion of yellow mucus, which was subsequently studied by video microscopy. Mucus was released from the body wall and near the mouth. This phenomenon was associated with autofluorescence and involved at least four distinct stages: release of vesicles, formation of granules, muscular contraction, and organization of strands. The fluorescent molecules were stored in vesicles bound to the membranes. These vesicles were intact when shed from the body. The vesicles were stable but also changed to a granular material or formed strands. Video analyses demonstrated that secretion was dependent on the type of stimulus.

Ultrastructural analysis and identification of membrane proteins in the free-living amoeba Difflugia corona

Syntaxin-1 and 25-kDa Synaptosome-associated Protein (SNAP-25) are present in the plasma membrane of several different secretory cell types and are involved in the exocytosis process. In this work, the free-living amoeba Difflugia corona was studied in relation to ultrastructure, structural membrane proteins, and proteins such as Syntaxin-1 and SNAP-25. Our results obtained by scanning electron microscopy in the amoeba without its theca, showed many membrane projections and several pore-like structures. Using immunocytochemistry, we found structural proteins Syntaxin-1 and SNAP-25.

Ultrastructural analysis and identification of membrane proteins in the free-living amoeba Difflugia corona

Syntaxin-1 and 25-kDa Synaptosome-associated Protein (SNAP-25) are present in the plasma membrane of several different secretory cell types and are involved in the exocytosis process. In this work, the free-living amoeba Difflugia corona was studied in relation to ultrastructure, structural membrane proteins, and proteins such as Syntaxin-1 and SNAP-25. Our results obtained by scanning electron microscopy in the amoeba without its theca, showed many membrane projections and several pore-like structures. Using immunocytochemistry, we found structural proteins Syntaxin-1 and SNAP-25.(AU)