The loss of susceptibility to apoptosis in exudated tissue neutrophils is associated with their nuclear factor-κB activation

Tissue neutrophils, human salivary neutrophils donated from healthy subjects and synovial fluid neutrophils collected from patients with rheumatoid arthritis were compared with circulating blood neutrophils. Concomitant treatment of circulating blood neutrophils with tumor necrosis factor-alpha (TNF-alpha) and cycloheximide induced neutrophil apoptosis, whereas the same treatment failed to induce significant apoptosis in salivary and synovial fluid neutrophils. Caspase-3 activation by TNF-alpha was observed in these tissue neutrophils, although its activity was significantly weaker than that in circulating blood neutrophils. In circulating blood neutrophils, TNF-alpha induced activation of nuclear factor-kappaB (NF-kappaB), whereas, in tissue neutrophils, NF-kappaB had been already activated without any stimulation, and no further activation was induced by the treatment with TNF-alpha. Furthermore, while pretreatment of neutrophils with an NF-kappaB inhibitor produced typical apoptotic changes in circulating blood neutrophils, this inhibitor did not produce any morphological apoptotic changes induced by TNF-alpha in tissue neutrophils. These results indicate that neutrophils undergo marked functional changes such as altered sensitivity to apoptosis-inducing stimuli in association with their exudation from blood into tissue, and that NF-kappaB activation is involved in the acquisition of resistance to TNF-alpha -induced apoptosis. (C) 2001 Elsevier Science B.V. All rights reserved.