Phorbol myristate acetate induces neutrophil NADPH-oxidase activity by two separate signal transduction pathways: dependent or independent of phosphatidylinositol 3-kinase

Abstract

The neutrophil NADPH-oxidase can be activated by protein kinase C (PKC) agonists such as phorbol myristate acetate (PMA), resulting in superoxide anion release. This superoxide release is independent of phosphatidylinositol 3-kinase (PI 3-kinase) because the inhibitor wortmannin does not affect the response. In this study, PMA is shown to also induce a wortmannin-sensitive NADPHoxidase activation, however, not resulting in release of superoxide but in intracellular production of the radical. This indicates that two pools of NADPH-oxidase, one localized in the plasma membrane and the other in the granule membranes, are separately regulated and the signal transduction pathways leading to activation of these pools differ regarding involvement of PI 3-kinase. Activation of both pools was dependent on ERK/MAPK kinase (MEK) activity and protein phosphatase 1 and/or 2A. As the two oxidase responses were differently affected by the inhibitor Gö -6850, different PKC isozymes are suggested to take part in the two signal transduction pathways. J. Leukoc. Biol. 67: 396-404; 2000.

Cytotoxicity of paraquat in microglial cells: Involvement of PKCδ- and ERK1/2-dependent NADPH oxidase

“…In our study, exposure of microglial cells to paraquat resulted in a rapid phosphorylation of ERK1/2 and inhibition of MEK by U0126 attenuated paraquat induced ROS production and cell death. Although antibodies for the p47 phox subunit did not work in our hands for Western analysis (data not shown), other studies have demonstrated ability for MEK inhibitors to block phosphorylation of this subunit (Dewas et al, 2000;Karlsson et al, 2000). In agreement with results from a study by Dewas et al (2000), our results show that inhibition of both PKC and ERK1/2 by GF109203x and U0126, respectively, could completely abrogate paraquat-induced ROS production and cytotoxic effects (data not shown).…”

“…7B and C). Our results are in agreement with other studies showing ERK1/2 dependency in the activation of NADPH oxidase and cell death (Dewas et al, 2000;Karlsson et al, 2000).…”

“…Mitogen activated protein kinases (MAPKs) also have been implicated in the activation of NADPH oxidase subunits, particularly the p47phox subunit (Dewas et al, 2000;Karlsson et al, 2000). In order to test whether paraquat increases phosphorylation of ERK 1/2, we examined both p-ERK1/2 and total ERK1/2 in cells after paraquat treatment.…”

A Genomic and Proteomic Analysis of Activation of the Human Neutrophil by Lipopolysaccharide and Its Mediation by p38 Mitogen-activated Protein Kinase

“…The modulation of genes involved in cytokine signaling, including the adapter molecules TRAF1 (LPS and TNF receptor signaling) and TNFAIP1 (TNF receptor signaling) and several kinases and phosphatases, may indicate a change in cytokine responsiveness after LPS treatment. Relevant in this regard from the proteomics data are: 1) the up-regulation of protein phosphatase 1, which has been shown to regulate PMN NADPH oxidase activation and translocation (43,44) and to regulate LPS-induced NF-B activation (45); 2) the down-regulation of Rho-GAP1, which has been shown to regulate NADPH oxidase activity in the PMN (46); and 3) the upregulation of PO 4 -stathmin (Table IV), a phosphoprotein postulated to function as a relayer and integrator of multiple signal transduction pathways (34). Several noncytokine, nonchemokine genes involved in the immune response were also up-regulated, including the complement pathway members C3, C3AR1, and PFC; the protease inhibitors ELANH2 (elastase inhibitor), SLPI, PI-3, and PI-9; and the acute phase protein orosomucoid.…”

Severity of E. coli mastitis is mainly determined by cow factors

“…Moreover, the ratio of stimulated milk to blood PMN CL was lower immediately after calving [158]. The low responsiveness of milk PMN towards PMA during early lactation could have resulted from a weaker stimulation of protein kinase C and NADPH-oxidase [117]. In addition, differences were observed in the kinetics of the PMN CL curve.…”