Tumor necrosis factor induces contraction of mesangial cells and alters their cytoskeletons

Tumor necrosis factor induces contraction of mesangial cells and alters their cytoskeletons. Cultures of human mesangial cells (MC) were established from the renal cortex of surgical specimen. The characteristic spindle-shaped or stellate appearance of MC was altered after treatment with tumor necrosis factor (TNF). After two hours, the MC retracted and lost reciprocal contacts. Furthermore, this treatment altered the cytoskeletal organization of MC, since a peripheral band of actin and stress fibers disappeared while the streaks of vinculin at focal contacts decreased. These changes were reversible when the MC were cultured in fresh medium. After five minutes of treatment with platelet activating factor (PAF), changes similar to those induced by TNF were observed. Inhibitors of PAF synthesis, such as plasma α1-proteinase inhibitor and an anti-inflammatory peptide, blocked changes induced by TNF. PAF receptor antagonists inhibited changes induced by PAF and also by TNF. These results and the finding that MC are stimulated to produce PAF by TNF suggest that PAF is a secondary mediator of the changes in cell shape and cytoskeletal organization induced by this cytokine.