Bradykinin inhibits ceramide production and activates phospholipase D in rabbit cortical collecting duct cells

Abstract

Recent reports suggest that inflammatory cytokines, growth factors, and vasoconstrictor peptides induce sphingomyelinase (SMase) activity. This results in the hydrolysis of sphingomyelin (SM) into ceramide, which is implicated in various cellular functions. Although ceramide regulates phospholipase D (PLD) activity, there is controversy about this relationship. Thus we investigated whether the effect of bradykinin (BK), a proinflammatory factor and vasodilator, was mediated by ceramide signal transduction and by PLD. In rabbit cortical collecting duct (RCCD) cells, BK increased SM levels and decreased ceramide levels in a time-dependent manner. Thus SMase activity was inhibited by BK. Also, the production of ceramide was regulated in a concentration-dependent manner. The BK-B1 antagonist [Lys-des-Arg9,Leu8]BK did not affect ceramide signal transduction but the BK-B2 antagonist (Hoe-140) blocked the effect of BK on SMase, suggesting that the BK-B2 receptor mediates BK-induced inhibition of ceramide generation. Our results show that exogenous SMase significantly hydrolyzed endogenous SM to form ceramide and weakly activated PLD. In contrast, BK induced a significant activation of PLD. However, additive effects of BK and ceramide on PLD activity were not observed. We concluded that in RCCD cells, the BK-induced second messengers ceramide and phosphatidic acid were generated by distinct signal transduction mechanisms, namely the SMase and PLD pathways.

Disruption of Lipid Rafts Stimulates Phospholipase D Activity in Human Lymphocytes: Implication in the Regulation of Immune Function

“…Conflicting results concerning the effect of bSMase on PLD activity have been reported, depending on the cell model considered. Thus, 100 mU/ml bSMase has been shown to modestly increase (50%) the basal PLD activity of fibroblasts (31) and rabbit cortical collecting duct cells (32), whereas it had no effect on the bradykinin-stimulated PLD activity in the same cells. On the opposite, bSMase used in similar experimental conditions completely abolished EGF-or TPA-induced PLD activation in A-431 cells while inducing a large increase in ceramide level (33).…”

“…The amount of ceramide present in the gradient fractions was quantified by the DAG kinase assay (21) as 32 P incorporated upon phosphorylation of ceramide to ceramide 1-phosphate by diacylglycerol kinase from E. coli. Ceramide 1-phosphate was resolved by TLC using chloroform/methanol/ acetic acid (65:15:5, by volume) as solvent.…”

Bradykinin stimulates ceramide production by activating specific BK-B1receptor in rat small artery

“…Experimental results (18,19) suggest that ceramide has important roles in many cell types. Sphingomyelin (SM) is composed of long chain saturated or monounsaturated fatty acid, a sphingosine base backbone, and a phosphocholine head group (3,5,37).…”

“…Ceramide has been proposed as a novel second messenger that mediates a variety of biological processes (18,19). Specific stimuli induce SMase activity, which results in SM hydrolysis and ceramide production.…”

“…Ceramide may activate or inhibit a variety of signals, for example: protein kinases, phosphatases, or phospholipases, which affect multiple downstream targets, including activation of nuclear transcription factors, leading to a variety of distinct cellular effects (19). A large variety of stimuli induce SM hydrolysis and ceramide formation (18,19). There is evidence for extensive tissue specificity as indicated by the fact that for any given SMase activating stimulus, not all cells or tissues respond to that agent by hydrolyzing sphingomyelin; furthermore, different final effects can be obtained in different cell types in response to the same SMase activating agent (1,12,13).…”