The signal transduction mechanism involved in kazinol B‐stimulated superoxide anion generation in rat neutrophils

Abstract

1 In this study, the underlying mechanism of stimulation of respiratory burst by kazinol B, a natural isoprenylated¯avan, in rat neutrophils in vitro was investigated. 2 Kazinol B concentration-dependently stimulated the superoxide anion (O 2 ⋅7 ) generation, with a lag but transient activation pro®le, in neutrophils but not in a cell-free system. The maximum response (13.2+1.4 nmol O 2 ⋅7 10 min 71 per 10 6 cells) was observed at 10 mM kazinol B.3 Pretreatment of neutrophils with phorbol 12-myristate 13-acetate (PMA) or formylmethionyl-leucylphenylalanine (fMLP) signi®cantly enhanced the O 2 ⋅7 generation following the subsequent stimulation of cells with kazinol B. 4 Cells pretreated with EGTA or a protein kinase inhibitor staurosporine e ectively attenuated the kazinol B-induced O 2 ⋅7 generation. However, a p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 and a phosphoinositide 3-kinase (PI3K) inhibitor wortmannin had no e ect on the kazinol Binduced response. 5 Kazinol B signi®cantly stimulated [Ca 2+ ] i elevation in neutrophils, with a lag and slow rate of rise activation pro®le, and this response was attenuated by a phospholipase C (PLC) inhibitor U73122. Kazinol B also stimulated the inositol bis-and trisphosphate (IP 2 and IP 3 ) formation with a 1 min lag time. 6 The membrane-associated PKC-a and PKC-y but not PKC-i were increased following the stimulation of neutrophils with kazinol B. It was more rapid and sensitive in the activation of PKC-y than PKC-a by kazinol B. Kazinol B partially inhibited the [ 3 H]phorbol 12,13-dibutyrate ([ 3 H]PDB) binding to the neutrophil cytosolic PKC. 7 Neither the cellular mass of phosphatidic acid (PA) and phosphatidylethanol (PEt), in the presence of ethanol, nor the protein tyrosine phosphorylation were stimulated by kazinol B. In addition, the kazinol B-induced O 2 ⋅7 generation remained relatively unchanged in cells pretreated with ethanol or a tyrosine kinase inhibitor genistein. 8 Collectively, these results indicate that the stimulation of the respiratory burst by kazinol B is probably mediated by the synergism of PKC activation and [Ca 2+ ] i elevation in rat neutrophils.

Possible role of exogenous cAMP to improve vascular endothelial dysfunction in hypertensive rats

“…The mixture was centrifuged at 20 000 g for 20 min, the resultant pellet were resuspended in 1.5 mL of pyridine and kept at 80 °C for 1.5 h to extract formazon. The mixture was centrifuged at 10 000 g for 10 min and the absorbance of the formazon was determined spectophotometrically (DU 640B Spectrophotometer, Beckman Coulter Inc.) at 540 nm [34]. The amount of reduced NBT was calculated using the following formula: …”

Signal transduction pathways involved in low intensity He–Ne laser‐induced respiratory burst in bovine neutrophils: A potential mechanism of low intensity laser biostimulation

“…The signal transduction mechanism involved in superoxide anion generation, in response to chemical substances, has been extensively studied [19], and some of Fig. 2.…”

The Genus Broussonetia: A Review of its Phytochemistry and Pharmacology

“…Several bioactive substances including coumarins, polyphenols, alkaloids, glycosides, flavonoids, lignans and diterpenes were isolated from bioassay‐guided fractionation of the extracts of these plants (Takasugi et al , ; Gunatilaka et al , ; Ikuta et al , ; Kato et al , ; Dehmlow et al , ; Fang et al , ; Shibano et al , ; Son et al , ; Zhang et al , ; Mei et al , ). Some members of these compounds have been reported to possess antiosteoporotic, antidiabetic, antioxidant, antitumoural, antimicrobial, antiplatelet, antiinflammatory and antityrosinase properties (Takasugi et al , ; Lin et al , ; Ko et al , ; Shibano et al , ; Wang et al , ; Lee et al , ; Zhang et al , ; Zheng et al , ; Zhou et al , ); for example, broussochalcone A inhibited both formylmethionyl‐leucyl‐phenylalanine (fMLP)‐ and phorbol 12‐myristate 13‐acetate (PMA) induced respiratory burst in neutrophils (Wang et al , ), broussonin C exhibited inhibitory activities against both the monophenolase and diphenolase actions of tyrosinase (Baek et al , ), and broussonin A showed estrogenic and transcriptional activity (Lee et al , ).…”