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Protein Kinase C Activation Reduces Microglial Cyclic AMP Response to Prostaglandin E 2 by Interfering with EP2 Receptors
Author(s) -
Patrizio Mario,
Colucci Mariantonella,
Levi Giulio
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.0740400.x
Subject(s) - adenylyl cyclase , forskolin , protein kinase c , prostaglandin e2 receptor , agonist , receptor , endocrinology , medicine , calphostin c , prostaglandin e , phorbol , pertussis toxin , protein kinase a , chemistry , g protein , signal transduction , biology , biochemistry , kinase
We studied the modulation by protein kinase C (PKC) of the cyclic AMP (cAMP) accumulation induced by prostaglandin (PG) E 2 in rat neonatal microglial cultures. Short pretreatment of microglia with phorbol 12‐myristate 13‐acetate (PMA) or 4β‐phorbol 12,13‐didecanoate, which activate PKC, but not with the inactive 4α‐phorbol 12,13‐didecanoate, substantially reduced cAMP accumulation induced by 1 μ M PGE 2 . The action of PMA was dose and time dependent, and the maximal inhibition (∼85%) was obtained after 10‐min preincubation with 100 n M PMA. The inhibitory effect of PMA was mimicked by diacylglycerol and was prevented by the PKC inhibitor calphostin C. As PMA did not affect isoproterenol‐ or forskolin‐stimulated cAMP accumulation, we investigated whether activation of PKC decreased cAMP production by acting directly at PGE 2 EP receptors. Neither sulprostone (10 ‐9 ‐10 ‐5 M ), a potent agonist at EP3 receptors (coupled to adenylyl cyclase inhibition), nor 17‐phenyl‐PGE 2 (10 ‐6 ‐10 ‐5 M ), an agonist of EP1 receptors, modified cAMP accumulation induced by forskolin. On the contrary, 11‐deoxy‐16, 16‐dimethyl PGE 2 , which does not discriminate between EP2 and EP4 receptors, both coupled to the activation of adenylyl cyclase, and butaprost, a selective EP2 agonist, induced a dose‐dependent elevation of cAMP that was largely reduced by PMA pretreatment, as in the case of PGE 2 . These results indicated EP2 receptors as a possible target of PKC and suggest that PKC‐activating agents present in the pathological brain may prevent the cAMP‐mediated microglia‐deactivating function of PGE 2 .