Caffeine causes glycerophosphorylcholine accumulation through ryanodine-inhibitable increase of cellular calcium and activation of phospholipase A2 in cultured MDCK cells.
- Author:
Do Kyung KIM
1
;
Kyu Yong JUNG
Author Information
1. Department of Pharmacology, Wonkwang University School of Medicine, Iksan, Korea.
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
caffeine;
[Ca2+]i;
glycerophosphorylcholine,;
phospholipase A2;
MDCK
- MeSH:
Animal;
Caffeine/pharmacology*;
Calcium/metabolism*;
Carbon Radioisotopes;
Cell Line;
Choline/metabolism;
Dogs;
Glycerylphosphorylcholine/metabolism*;
Kidney/cytology;
Phospholipases A/metabolism*;
Phospholipases A/drug effects;
Phospholipases A/antagonists & inhibitors;
Phosphoric Diester Hydrolases/metabolism;
Phosphoric Diester Hydrolases/drug effects;
Ryanodine/pharmacology*;
Ryanodine/metabolism
- From:Experimental & Molecular Medicine
1998;30(3):151-158
- CountryRepublic of Korea
- Language:English
-
Abstract:
Glycerophosphrylocholine (GPC) is a renal medullary compatible organic osmolyte that is derived from choline via phosphatidylcholine, which is catalyzed in part by phospholipase A2 (PLA2) and its degradation by GPC: choline phosphodiesterase (GPC: choline PDE). We found that caffeine elevated intracellular free calcium ([Ca2+]i) and GPC level in cultured MDCK cells, canine kidney epithelial cells, and propose a possible biochemical mechanism. When MDCK cells were incubated for 3 h with 1 to 10 mM caffeine, cellular GPC was elevated in a dose-dependent manner, and this occurred independently of the extracellular osmolality. Caffeine stimulated the rate of [14C]choline incorporation into [14C]GPC and PLA2 activity. Whereas, GPC: choline PDE activity was accompanied by less of increase. These enzyme changes demonstrate the increased net synthesis of MDCK GPC. In order to identify what triggers the PLA2 activation, [Ca2+]i was measured by using a fluorescence dye, Fura-2. Caffeine (10 mM) resulted in a typical transient increase in MDCK [Ca2+]i concentration, and this increase was greatly inhibited by pretreatment of MDCK cells with 10 mM ryanodine for 5 min. Ryanodine (10 mM) also inhibited the caffeine-induced stimulation of PLA2 activity. These findings provide the first evidence that caffeine in MDCK cells causes a ryanodine-inhibitable increase of [Ca2+]i and PLA2 activity, resulting in cellular GPC accumulation.
