Article Text
Abstract
BACKGROUND Interleukin 1β (IL-1β) is a potent inhibitor of gastric acid secretion. Regulatory actions at several levels have previously been demonstrated, including direct inhibition of parietal cell acid secretion. Although IL-1β may activate several intracellular signalling pathways, the mechanisms responsible for inhibition of carbachol stimulated acid secretion have not been determined.
AIMS To investigate the roles of protein kinase C (PKC) and the sphingomyelinase signalling pathways in the regulation of acid secretion by IL-1β.
METHODS Rabbit parietal cells were obtained by collagenase-EDTA digestion and centrifugal elutriation. Acid secretion stimulated by carbachol andA23187 (to mimic elevations in intracellular calcium) was assessed by14C aminopyrine uptake in response to IL-1β, PKC, and sphingomyelinase manipulation.
RESULTS IL-1β inhibited carbachol and A23187 stimulated acid secretion in a dose dependent manner. The inhibitory actions were completely reversed by each of three different PKC inhibitors, staurosporine, H-7, and chelerythrine, as well as by PKC depletion with high dose phorbol ester pretreatment. IL-1β did not downregulate parietal cell muscarinic receptor. IL-1β significantly increased membrane PKC activity. Activation of the sphingomyelinase/ceramide pathway had no effect on basal or stimulated acid secretion. The inhibitory action of IL-1β was independent of protein kinase A and protein kinase G activity.
CONCLUSIONS IL-1β directly inhibits parietal cell carbachol stimulated acid secretion. This action occurs distal to muscarinic receptor activation and elevations in intracellular calcium and requires PKC.
- carbachol
- gastric acid
- interleukin 1β
- parietal cell
- protein kinase C
- sphingomyelinase
Abbreviations used in this paper
- BSA
- bovine serum albumin
- CHL
- chelerythrine
- db-cGMP
- guanosine 3′, 5′- cyclic monophosphate
- DMEM
- Dulbecco's modified Eagle's medium
- EBSS
- Earle's balanced salt solution
- EGTA
- ethylene glycol-bis(beta-aminoethyl ether)-N,N,N′,N′-tetra acetic acid
- EGF
- epidermal growth factor
- ECL
- enterochromaffin-like
- HBSS
- Hanks' balanced salt solution
- HEPES
- N-2-hydroxyethylpiperazine-N′-ethansulphonic acid
- IL-1β
- interleukin 1β
- MLCK
- myosin light chain kinase
- PKA
- protein kinase A
- PKC
- protein kinase C
- PKG
- protein kinase G
- PMA
- phorbol-12-myristate-13-acetate
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Abbreviations used in this paper
- BSA
- bovine serum albumin
- CHL
- chelerythrine
- db-cGMP
- guanosine 3′, 5′- cyclic monophosphate
- DMEM
- Dulbecco's modified Eagle's medium
- EBSS
- Earle's balanced salt solution
- EGTA
- ethylene glycol-bis(beta-aminoethyl ether)-N,N,N′,N′-tetra acetic acid
- EGF
- epidermal growth factor
- ECL
- enterochromaffin-like
- HBSS
- Hanks' balanced salt solution
- HEPES
- N-2-hydroxyethylpiperazine-N′-ethansulphonic acid
- IL-1β
- interleukin 1β
- MLCK
- myosin light chain kinase
- PKA
- protein kinase A
- PKC
- protein kinase C
- PKG
- protein kinase G
- PMA
- phorbol-12-myristate-13-acetate