Prostaglandin Receptor Subtypes, EP3C and EP4, Mediate the Prostaglandin E2-induced cAMP Production and Sensitization of Sensory Neurons

Abstract

Although a number of prostaglandin E 2 (PGE 2 ) receptor subtypes have been cloned, limited studies have been performed to elucidate subtypes that subserve specific actions of this eicosanoid, in part because of a paucity of selective receptor antagonists. Using reverse transcription-polymerase chain reaction (PCR) and antisense oligonucleotides, we examined which prostaglandin E 2 receptor (EP receptor) subtypes are expressed in sensory neurons and which mediate the PGE 2 -induced increase in cAMP production and augmentation of peptide release. Reverse transcription-PCR of cDNA isolated from rat sensory neurons grown in culture revealed PCR products for the EP1, EP2, EP3C, and EP4 receptor subtypes but not the EP3A or EP3B. Preexposing neuronal cultures for 48 h to antisense oligonucleotides of EP3C and EP4 mRNA diminished expression of the respective receptors by ϳ80%, abolished the PGE 2 -stimulated production of cAMP, and blocked the ability of PGE 2 to augment release of immunoreactive substance P and calcitonin gene-related peptide. Pretreating with individual antisense against the EP2, EP3C, or EP4 receptors or combinations of missense oligonucleotides had no effect on PGE 2 -induced activity. Treatment with antisense to EP3C and EP4 receptor subtypes did not alter the ability of forskolin to increase cAMP or enhance peptide release. These results demonstrate that sensory neurons are capable of expressing multiple EP receptor subtypes but that only the EP3C and EP4 receptors mediate PGE 2 -induced sensitization of sensory neurons. Prostaglandin E 2 receptors (EP receptors)1 have been classified into four general subtypes, EP1, EP2, EP3, and EP4, based on cloning and pharmacological manipulations (1, 2). These receptors are G-protein-coupled, and binding of agonists results in activation of various transduction cascades depending on the receptor subtype activated and the cells being studied. Activation of the EP1 receptor in kidney tubule cells increases the concentration of intracellular calcium, phosphoinositol turnover, and PKC activity (3, 4). EP2 and EP4 receptors are coupled through G s (1) to increase intracellular cAMP in a number of preparations (5-8). The EP3 receptor undergoes post-transcriptional RNA splicing to produce multiple EP3 isoforms, and activation of these splice variants can increase calcium mobilization or either stimulate or inhibit cAMP production (9 -11). Because subtypes of the EP receptor can be linked to different transduction cascades in different types of cells, it is critical to determine which receptors and receptorassociated signal transduction pathways are responsible for specific physiological actions of E-series prostaglandins.Although PGE 2 has a number of diverse physiological actions (12), its role in pain and inflammation is of primary importance. Indeed, both the analgesic and the anti-inflammatory actions of the nonsteroidal anti-inflammatory drugs are attributed to their ability to inhibit prostaglandin synthesis (13). In addition, PGE 2 is produced at sites of ...

Extracellular Matrix Fibronectin Increases Prostaglandin E2 Receptor Subtype EP4 in Lung Carcinoma Cells through Multiple Signaling Pathways

“…This is consistent with data from others who reported that EP4 antisense oligonucleotides diminished EP4 protein expression and abolished the PGE 2 -stimulated production of cAMP and blocked the ability of PGE 2 to augment release of immunoreactive substance P and calcitonin gene-related peptide in sensory neurons (33). The EP4 antagonist, ONO-AE3-208, and the EP4 siRNA have been shown to inhibit extracellular matrix-induced metalloproteinase-9 expression in macrophages (34).…”

Constitutive Spinal Cyclooxygenase-2 Participates in the Initiation of Tissue Injury-Induced Hyperalgesia

“…These data support the concept that the more intense the stimulus or its tendency to produce an ongoing postinjury barrage, the more likely COX-2 will be involved in initiating the prostanoid cascade (Baba et al, 2001;Southall and Vasko, 2001). In addition, these data suggest that the earlier the spinal COX-2 activation can be blocked (either preemptively or after injury), the more effectively a COX-2 inhibitor will be at blocking the hyperalgesia and allodynia that results from peripheral tissue injury such as the musculoskeletal injury used in the present study (Portenoy, 2000).…”

Anti-chemorepulsive Effects of Vascular Endothelial Growth Factor and Placental Growth Factor-2 in Dorsal Root Ganglion Neurons Are Mediated via Neuropilin-1 and Cyclooxygenase-derived Prostanoid Production

“…Given that NP-1 does not have a known signaling function, we next examined other signaling pathways that could be responsible for mediating VEGF-dependent inhibition of DRG growth cone collapse. Prostaglandins exert direct effects on sensory neurons via specific EP and IP receptors (37)(38)(39)(40) and also mediate biological functions of VEGF (12,16). The role of prostanoids in regulating neurotrophic or growth cone activity has not been examined previously, however (Fig.…”

“…IP receptors for prostacyclins and EP receptors for PGE 1 and PGE 2 are strongly expressed in DRG neurons (39,44), and prostacyclin analogues and PGE 1 and PGE 2 stimulate a variety of responses in sensory neurons, including adenylyl cyclase activity, cyclic AMP production (45), sensitization to bradykinin (46,47), and neuropeptide release (39,45,47). COX-derived prostanoids are thought to have important physiological roles in the mediation of pain and inflammation (48), and IP receptor-deficient mice display impaired nociception, anti-thrombosis, and inflammatory responses (38).…”