Anti‐apoptotic mechanism and reduced expression of phospholipase D in spontaneous and Fas‐stimulated apoptosis of human neutrophils

Abstract

Neutrophil apoptosis is a constitutive process that can be enhanced or delayed by signals triggered by various stimuli. In this work, we investigated the action mechanism of phospholipase D (PLD) and its expression in the inhibition of spontaneous and Fas-mediated apoptosis. Anti-Fas antibody-stimulated apoptosis of neutrophils was significantly blocked by the exogenous addition of bacterial PLD from Streptomyces chromofuscus (scPLD), and neutrophils cultured for 24 h in the presence of anti-Fas antibody showed lower agoniststimulated PLD activity compared to untreated cells. The amount of PLD1a protein reduced time-dependently in cultured neutrophils, but was recovered by treating with LPS or GM-CSF. The reduction in PLD1a protein level was blocked by caspase inhibitors. The exogenous addition of scPLD blocked the up-regulation of Fas-associated death domain expression, mitochondrial permeability, and the cleavages of procaspase-8, procaspase-3, and protein kinase C-d. We also found that the protein level of apoptosis-inducing factor was increased in cultured neutrophils but its expression was reduced by scPLD. However, sulfasalazineinduced apoptosis and change of protein expression were not blocked by scPLD. Taken together, the activity and protein levels of PLD play a role as an anti-apoptotic factor by acting at multiple levels of the apoptotic cascade in neutrophils.

Toll-like receptors types 2 and 6 and the apoptotic process in human neutrophils

“…Leung et al [19] observed no effect of IL-18, while Brach et al [3] and Klein et al [14] saw no effect of fMLP on neutrophil apoptosis. However, Colotta et al [4], Hu et al [11] and Lee et al [16,17] noted that fMLP inhibits neutrophil apoptosis despite high intracellular concentrations of Ca 2+ ions, which disturb cell potential and induce apoptosis. Inhibition of neutrophil apoptosis by rhIL-18 or fMLP action prolongs the effective action of these cells, which may affect the conditions occurring with excessive amounts of these agents.…”

Tulathromycin Exerts Proresolving Effects in Bovine Neutrophils by Inhibiting Phospholipases and Altering Leukotriene B4, Prostaglandin E2, and Lipoxin A4Production

“…In addition to its physiological functions (membrane trafficking), PLD is involved in microbial killing (54), neutrophil degranulation (55), and migration in leukocytes (56). In neutrophils, PLD also has an antiapoptotic role (33). Moreover, activated caspases were shown to reduce the expression and activity of PLD in human neutrophils (33).…”

“…In neutrophils, PLD also has an antiapoptotic role (33). Moreover, activated caspases were shown to reduce the expression and activity of PLD in human neutrophils (33). In view of our previous observations that tulathromycin was able to promote neutrophil apoptosis (28), we investigated the effect of tulathromycin on PLD activity.…”

Expression of dendritic cell markers on cultured neutrophils and its modulation by anti-apoptotic and pro-apoptotic compounds

“…These pro-apoptotic compounds increased the rate of apoptosis by up to 90% after 24 h culture (Lee et al, 2004). The CD80, CD83, and CD86 levels were higher in the neutrophils treated with brefeldin A or PDTC than in the neutrophils cultured with media alone (Figure 4).…”

“…The neutrophils rapidly underwent spontaneous apoptosis in the in vitro culture. More than 50-60% of the cells were annexin V-positive and had a typical apoptotic cell morphology after 24 h of culture (Lee et al, 2004). The cells were then double stained for the PE-conjugated DC markers and annexin V-FITC.…”