Cyclic AMP mimics, but does not mediate, interleukin-1- and tumour-necrosis-factor-stimulated phospholipase A2 secretion from rat renal mesangial cells.
We have previously shown that recombinant interleukin 1 (IL-1) and recombinant tumour necrosis factor (TNF) synergistically stimulate phospholipase A2 release from mesangial cells. We now report that treatment of mesangial cells with the beta-agonist salbutamol, prostaglandin E2 (PGE2), cholera toxin or forskolin, which all activate adenylate cyclase, increased release of phospholipase A2 activity. Likewise, addition of a membrane-permeant cyclic AMP (cAMP) analogue or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine enhanced release of phospholipase A2 activity from mesangial cells. There was a lag period of about 8 h before a significantly enhanced secretion could be detected. Furthermore, actinomycin D or cycloheximide completely suppressed cAMP-stimulated secretion of phospholipase A2. Angiotensin II, the phorbol ester phorbol 12-myristate 13-acetate, the Ca2+ ionophore A23187 and a membrane-permeant cGMP analogue did not stimulate phospholipase A2 release from the cells. Treatment with indomethacin completely inhibited IL-1 beta- and TNF-stimulated PGE2 synthesis, without having any effect on phospholipase A2 secretion, thus excluding cytokine-induced PGE2 synthesis as the mediator of phospholipase A2 release. Neither IL-1 beta nor TNF induced any increase in intracellular cAMP in mesangial cells. Furthermore, incubation of the cells with 2',5'-dideoxyadenosine, an inhibitor of adenylate cyclase, did not block cytokine-stimulated phospholipase A2 secretion. In addition, IL-1 beta and TNF synergistically interacted with forskolin to stimulate phospholipase A2 release from the cells. The protein kinase inhibitors H-8, staurosporine, K252a and amiloride inhibited IL-1 beta- and TNF-stimulated phospholipase A2 secretion. However, high concentrations that inhibit other protein kinases were needed. These observations suggest that IL-1 beta and TNF cause secretion of phospholipase A2 by a mechanism independent of cAMP. The signalling pathways used by IL-1 beta and TNF may involve a protein kinase that is probably different from protein kinase A or protein kinase C.
Pfeilschifter
J
J
Research Department, Pharmaceuticals Division, Ciba-Geigy Ltd., Basel, Switzerland.
Leighton
J
J
Pignat
W
W
Märki
F
F
Vosbeck
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D004357:Drug Synergism; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D006868:Hydrolysis; D007375:Interleukin-1 / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000378:metabolism; D010741:Phospholipases A / Q000032:analysis / Q000378:metabolism*; D054467:Phospholipases A2; D011448:Prostaglandin Antagonists / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007375:Interleukin-1; D010716:Phosphatidylinositols; D011448:Prostaglandin Antagonists; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D000242:Cyclic AMP; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D006152:Cyclic GMP; D002118:Calcium