Cytolysis by tumor necrosis factor is preceded by a rapid and specific dissolution of microfilaments.

Abstract

Tumor necrosis factor (TNF) is cytotoxic to certain transformed cells, whereas normal cells are resistant to its effects. The resistance of normal cells can often be overcome by treatment with inhibitors of transcription or translation such as actinomycin D or cycloheximide (CHI), suggesting that normal cells produce a protein(s) that protects them from TNF-induced cytolysis. In this report, we examine the mechanism of cytolysis in a 3T3-like mouse cell line, C3HA, which was sensitized to TNF by treatment with CHI. We found that an early change in TNF/CHI-treated cells was a significant loss of stress fibers in perinuclear areas of the cytoplasm. The disruption of microfilaments, which was observed within 15 min of treatment, was not seen in untreated cells or in cells treated with either TNF or CHI alone. The dissolution of microfilaments spread peripherally over time and preceded other TNF/CHI-induced effects such as cytoplasmic "boiling," decrease in cell volume, and lysis of the plasma membrane. The breakdown of stress fibers occurred without a change in microtubules or intermediate filaments. Cytochalasin E, which disrupts microfilaments, induced cytolysis of TNF-treated cells even in the absence of CHI; however, demecolcine, which depolymerizes microtubules, did not sensitize cells to TNF. We propose that the TNF-induced cytolysis of certain cell types is preceded by a selective disruption of the microfilament lattice.

Tumour‐necrosis‐factor‐mediated cytotoxicity is correlated with phospholipase‐A2 activity, but not with arachidonic acid release per se

“…Later on, and more particularly subsequent to cell death, this specificity was lost. We have no experimental data to explain the inolccular basis of the latter phenomenon, but it has been shown that TNF, albeit at very high concentrations, increases the permeability of liposomes [54], and that TNF-induced loss of cell viability is accompanied by lysis of the plasma membrane [55]. Furthermore, it is known that PL activity is affected by structural perturbations of the cell membrane [56].…”

Distinctive role of integrin-mediated adhesion in TNF-induced PKB/Akt and NF-κB activation and endothelial cell survival

“…Cytochalasin D treatment abolished the protective effect of PKB/Akt, placing actin polymerization downstream of PI3K and PKB/Akt in cell survival. TNFinduced death by cycloheximide has been associated with the disruption of the actin cytoskeleton (Scanlon et al, 1989), and recent reports implicate changes in the dynamics of the actin cytoskeleton to mitochondrial changes in cell death (Gourlay and Ayscough, 2005). Mitochondria are key to the execution of apoptosis and PKB/Akt controls the expression or translocation of antiapoptotic proteins (e.g.…”

Looking beyond death: a morphogenetic role for the TNF signalling pathway

“…The effects of TNF signalling on the actin cytoskeleton were initially discovered in the context of cell death (Scanlon et al, 1989). Among the most apparent results of TNF-induced apoptosis are drastic changes in cell morphology -such as the rounding-up of the cell and blebbing of the plasma membrane -and the concomitant reorganization of the cytoskeleton.…”

“…In addition, some effects of TNF signalling that have been primarily defined in pro-apoptotic signalling may rather be part of the inflammatory repertoire. Several pro-inflammatory changes that are associated with TNFα treatment [such as increased pulmonary or vascular endothelial-cell permeability (Kohno et al, 1993;Koss et al, 2006;WojciakStothard et al, 1998), and neutrophil or fibroblast recruitment to sites of inflammation (Lokuta and Huttenlocher, 2005;Postlethwaite and Seyer, 1990)] and pro-apoptotic effects associated with TNFα treatment [such as osteoblast apoptosis, fibroblast cytolysis or epithelial-cell apoptosis (Domnina et al, 2002;Domnina et al, 2004;Scanlon et al, 1989;Triplett and Pavalko, 2006)] all involve effects on the cytoskeleton and the cellular machinery regulating the cytoskeleton. The pro-inflammatory effects of TNFα treatment on cultured cells and the associated effects on the cytoskeleton are summarized in Table 1.…”