Apoptosis, shape change and reactive oxygen species generation in human neutrophils exposed to olanzapine, an a typical antipsychotic drug

The effects of olanzapine (OLZ) on the viability and functioning of human polymorphonuclearcells (PMNs) are clearly opposite to those previously reported forclozapine (CLZ). In fact, after 4- or 24-h-treatment with 20-50 μM OLZ, a significant inhibition of the respiratory burst in PMNs activated with opsonized zimosanor phorbol myristate acetate (PMA) was observed, whereas the burst provoked byformyl-methionyl-leucyl-phenylalanine (fMLP) was only inhibited at 50 μM OLZ.Under the same conditions, spontaneous apoptosis was accelerated at 20-50 μMOLZ, while the exogenous addition of H2O2 resulted in the PMN apoptosis beingdose-dependently inhibited by OLZ in the entire range of concentrations. However,when H2O2 was intracellularly generated by treatment with PMA, the induced apoptosis was only decreased at 2 μM OLZ. Absorbance scans revealed that OLZis able to react with equimolar quantities of either H2O2 or HOCl. These results suggest that OLZ inhibits both ROS-induced PMN apoptosis and respiratory burst due to extracellular scavenging of released ROS.

Los efectos de olanzapine (olz) sobre la viabilidad y el funcionamiento de células humanas polimorfonucleares (pmn, por sus siglas en inglés) claramente son opuestosa los señalados para la clozapine (clz). En efecto, después de 4-24 h de tratamiento con 20-50 μM olz, se observó una inhibición significativa del estallido respiratorio en pmn activados con zimosan o con forbol acetato miristato, mientras que la inhibición provocada por el formil-metionil-leucil-fenilalanina fue sólo inhibida a 50μM de olz. En las mismas condiciones, la apoptosis espontánea se aceleró con 20-50μM olz, mientras que la adición exógena de H2O2 dio lugar a la apoptosis de pmn en dosis dependiente inhibida por olz en el rango entero de concentraciones. Sin embargo, cuando se generó H2O2 intracelular por tratamiento con pma, la apoptosis inducida se disminuyó solamente con 2 μM olz. Las exploraciones de los espectros de absorbancia revelaron que olz puede reaccionar con cantidades equimolares de H2O2 o de HOCL. Estos resultados sugieren que olz inhibe ambos tipos de apoptosis de pmn (la inducida por especies reactivas oxigenadas y por estallido respiratorio debido a atrapadores extracelulares de estas especies reactivas oxigenadas).

Clozapine prevents apoptosis and enhances receptor-dependent respiratory burst in human neutrophils.

The present study was undertaken to determine if the antipsychotic drug clozapine (CLZ) in the concentration range 2-50 microM can rescue polymorphonuclear cells (PMNs) from undergoing apoptosis. Our results indicate that 20 microM CLZ can rescue PMNs both from UVB-accelerated (28.0% vs. 45.9% for control without CLZ; P < 0.05) and from spontaneous (35.8% vs. 57.6%; P < 0.05) apoptosis whereas 50 microM CLZ could rescue PMNs from spontaneous (34.3% vs. 57.6%; P < 0.05) apoptosis only. Furthermore, since apoptosis has been reported to involve the impairment of PMN function, we evaluated the effects of CLZ on respiratory burst in UVB-irradiated and in unirradiated PMNs. When 20 or 50 microM CLZ-pretreated PMNs were aged in a culture during 4 h, the luminol-dependent chemiluminescence (CL) response was 3-fold (P < 0.01) and 2.5-fold (P < 0.05) increased, respectively, by subsequent exposure to serum opsonized zymosan (OZ). When 50 microM-pretreated PMNs were either UVB-irradiated or unirradiated, the CL response was 2.6-fold (P < 0.05) and 3.3-fold (P < 0.05) increased, respectively, after subsequent exposure to formyl-methionyl-leucyl-phenylalanine (fMLP). In contrast, the degree of enhancement was negligible upon subsequent exposure to ionomycin or phorbol myristate acetate (PMA). When incubation times were extended up to 22 h, the CL response induced by OZ in 20 microM CLZ-treated PMNs had a 4.9-fold increase (P < 0.001). This priming effect could be reverted when 20 microM CLZ-treated PMNs (aged 4 h in culture) were coincubated for 5 min with the protein tyrosine kinase inhibitor genistein as well as with the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin. These findings suggest that CLZ primes respiratory burst and prevents PMN apoptosis as a consequence of tyrosine phosphorylation- and PI3-K activation-dependent signal transduction pathways.

Antioxidant properties of dipyridamole as assessed by chemiluminescence.

The ability of dipyridamole (DIP) to scavenge oxygen metabolites generated by either activated human neutrophils (PMNs) or cell-free systems using luminol(s)- and lucigenin-enhanced chemiluminescence was investigated. In the presence of DIP (15-50 microM) a dose-dependent inhibition period was seen in phorbol myristate acetate (PMA)-stimulated PMNs as assayed by isoluminol-enhanced chemiluminescence (ILCL) with horseradish peroxidase (HRP). Although such a lag period was not observed in the absence of HRP, 50 microM DIP inhibited extracellular ILCL by more than 50%. Intracellular luminol-enhanced chemiluminescence (LCL) as assayed in either PMA- or in ionomycin-activated PMNs was not affected by dipyridamole (15-50 microM). In cell-free systems, DIP produced concentration-dependent inhibition in H2O2-(45% at 50 microM), OH- (40%, at 0.1 microM) and HOCl-(20% at 10 microM). Both absorbance and fluorescence scans revealed that DIP is able to react with equimolar quantities of either H202 or HOCl. These results suggest that DIP scavenges reactive oxygen species (ROS) presumably secreted by activated human PMNs in the following decreasing order: *OH > HOCl > H2O2 >> O2-.