Cytochemical and ultrastructural study of anoikis and secondary necrosis in enterocytes detached in vivo

Abstract

Detachment-induced apoptosis of enterocytes (anoikis) has not been investigated in vivo. Here we describe anoikis of fish enterocytes following detachment in a septicemia by Photobacterium damselae subsp. piscicida, or following injection of its exotoxin. The in vivo study was complemented with an ex vivo time-lapse analysis using conditions duplicating the in vivo situation. Linings of enterocytes detached from intestine mucosa dissociate into isolated enterocytes which undergo caspase 3-mediated anoikis with cell rounding, loss of polarization, condensation of chromatin and fragmentation of the nuclear envelope, early swelling of mitochondria with rupture of the outer membrane, and brush border disappearance. One mechanism for brush border loss was shedding of apoptotic bodies incorporating the apical part of the enterocyte. Brush border disappearance was also associated with disassembly of the F-actin microvillar core and involved re-absorption into the cell, or expansion and vesiculation followed by shedding of microvillar fragments. The enterocyte anoikis terminates by secondary necrosis and lysis due to lack of elimination by phagocytosis of apoptosing enterocytes. The conditions prevailing in vivo in the gut lumen accelerate enterocyte secondary necrosis. Our results underscore the importance of analyzing anoikis under conditions similar to those occurring in vivo.

Light and electron microscopic studies on turbot Psetta maxima infected with Enteromyxum scophthalmi: histopathology of turbot enteromyxosis

“…The detached enterocytes showed features of apoptosis such as cell rounding and shrinkage, chromatin condensation and nuclear fragmentation. These detached epithelial cells underwent anoikis, a mode of apoptosis triggered by the loss of anchorage, as described by do Vale et al (2007) in Dicentrarchus labrax infected with Photobacterium damselae ssp. piscicida.…”

“…piscicida. Infectious agents are able to induce apoptosis in host cells (Abbasi et al 2003, Boettner & Petri 2005 and even that apoptosis and epithelial proliferation are increased in those epithelia under infective pressure (Von Herbay & Rudy 2000, do Vale et al 2007). In turbot enteromyxosis it remains unclear if the increase in apoptotic rates in the lining epithelium is induced by the etiologic agent or the anoikis is an attempt to prevent the local spread of the pathogen (Sherman & Petrak 2005).…”

Secondary necrosis in multicellular animals: an outcome of apoptosis with pathogenic implications

“…4 and Ref. [134]). Also typical of apoptotic secondary necrotic cells is the association of nuclear apoptotic alterations and cytoplasmic membrane rupture detected by transmission electron microscopy (Fig.…”

A Lymphocyte Serine Protease Granzyme A Causes Detachment of a Small-Intestinal Epithelial Cell Line (IEC-6)

“…3,4) Hence, it is important to ask whether the rGzmA-induced detachment of IEC-6 cells is accompanied by anoikis. STS (0.1-1 mM) is known to induce apoptosis in IEC-6 cells.…”

“…[1][2][3] At the villus tip, their short life cycle is terminated because the cells lose cell-cell and cell-basement membrane adhesion and are shed into the lumen in the process of apoptosis. 3,4) Although various proteolytic events might be involved in the reduction of cell adhesions, details of the underlying mechanisms are largely unknown. Granzyme A (GzmA) is a serine protease with trypsin-like specificity found in large granules of activated cytotoxic T lymphocytes and natural killer cells located in the peripheral blood and lymphoid tissues.…”