Effects of 2-Azafluorenones on Phosphatidyl-Inositol Specific Phospholipase C Activation in C6 Glioma Cells

10.4077/CJP.2012.BAA017

Hai-Long Wang；Jiann-Wu Wei

2-azafluorenone ； PI-PLC ； histamine receptor ； PI turnover ； ATP ； bradykinin

The Chinese Journal of Physiology

55卷2期（2012 / 04 / 01）

101 - 107

英文

Little information is known about the effects of 2-azafluorenones on the cellular signal transduction pathway. In this study, C6 glioma cells were used to test the effect of 2-azafluorenone and its related compounds on histamine-induced phophatidyl inositol (PI) turnover, because of some similarities in chemical structure between these compounds and histaminergic receptor antagonists, such as chlorpheniramine. To investigate the mode of action, studies of the effects of these compounds on PI turnover induced by AlF4(superscript -), Adenosine 5 triphosphate (ATP), bradykinin and A23187 were carried out. Histamine increased [3H]inositol 4-phosphate (IP1) formation via the activation of phophatidyl inositol specific phospholipase C (PI-PLC) to break down the labeled precursor substrate. This effect could be blocked by chlorpheniramine, 2-azafluorenone, and 4-methyl-2-azafluorenone in a dose and timedependent manner; this inhibitory effect was also found in chemically related compounds of 2- azafluorenones such as 6-chloro-2-azafluorenone and 6-methoxy-2-azafluorenone. The AlF4(superscript -)- induced [3H]IP1 accumulation was via an activation of G-protein coupled with PI-PLC to break down the labeled PI substrate. These effects could be inhibited by 2-azafluorenone and 4-methyl-2-azafluorenone. A23187 induced IP1 accumulation via an activation on PI-PLC to break down the labeled PI in a Gprotein- independent manner. The effect could also be inhibited by 2-azafluorenone and 4-methyl-2- azafluorenone. ATP- and bradykinin-induced IP1 formation occur via an activation of their individual receptor sites, which are different from the receptor sites of histamine. These effects could also be inhibited by 2-azafluorenone and 4-methyl-2-azaflureonone. Depletion of calcium ion by using a calcium free buffer, with or without the addition of TMB-8 (an intracellular calcium antagonist) decreased histamine-induced [3H] IP1 formation. Even in these conditions histamine-induced response was also inhibited by 2-azafluorenone and 4-methyl-2-azafluorenone. In summary, the inhibitory effect of 2- azafluorenone and its related compound 4-methyl-2-azafluorenone on PI-PLC is likely the cause of reduction in histamine-induced [3H] IP1 formation. Based on these results, the receptor site, its coupled G-proteins, and calcium ion are not the targets for their action.

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