PGE₂EP₃receptor downregulates COX-2 expression in the medullary thick ascending limb induced by hypertonic NaCl

Abstract

We tested the hypothesis that inhibition of EP3 receptors enhances cyclooxygenase (COX)-2 expression in the thick ascending limb (TAL) induced by hypertonic stimuli. COX-2 protein expression in the outer medulla increased approximately twofold in mice given free access to 1% NaCl in the drinking water for 3 days. The increase was associated with an approximate threefold elevation in COX-2 mRNA accumulation and an increase in PGE2 production by isolated medullary (m)TAL tubules from 77.3 ± 8.4 to 165.7 ± 10.8 pg/mg protein. Moreover, administration of NS-398 abolished the increase in PGE2 production induced by 1% NaCl. EP3 receptor mRNA levels also increased approximately twofold in the outer medulla of mice that ingested 1% NaCl. The selective EP3 receptor antagonist L-798106 increased COX-2 mRNA by twofold in mTAL tubules, and the elevation in COX-2 protein induced by 1% NaCl increased an additional 50% in mice given L-798106. COX-2 mRNA in primary mTAL cells increased twofold in response to media made hypertonic by the addition of NaCl (400 mosmol/kg H2O). L-798106 increased COX-2 mRNA twofold in isotonic media and fourfold in cells exposed to 400 mosmol/kg H2O. PGE2 production by mTAL cells increased from 79.3 ± 4.6 to 286.7 ± 6.3 pg/mg protein after challenge with 400 mosmol/kg H2O and was inhibited in cells transiently transfected with a lentivirus short hairpin RNA construct targeting exon 5 of COX-2 to silence COX-2. Collectively, the data suggest that local hypertonicity in the mTAL is associated with an increase in COX-2 expression concomitant with elevated EP3 receptor expression, which limits COX-2 activity in this segment of the nephron.

Prostaglandin E2 Induces Prorenin-Dependent Activation of (Pro)renin Receptor and Upregulation of Cyclooxygenase-2 in Collecting Duct Cells

“…PRR shRNA impairs COX-2 upregulation (Figure 4A and C) at 12 h (107 ± 8 vs. 100 ± 13%, P=NS, Figure 4D) and blunted ERK1/2 phosphorylation (Figure 4E). A transient decrease in COX-2 expression was also observed at 4 h, indicating that PGE 2 causes an initial reduction of COX-2 expression as described before 15 .…”

“…Importantly, downregulation of COX-2 by EP receptors has been described in thick ascending limb 15 . Our data suggest that PGE 2 may be the initial stimuli to promote prorenin-renin mediated stimulation of PRR and COX-2 augmentation in CD cells.…”

“…The EP4 receptors are predominantly expressed in the MD cells, whereas EP3 receptors are more abundant in the thick ascending limb 15 . The CD segment expresses EP1, EP3, and EP4 receptors 16 .…”

PGE2 EP1 receptor inhibits vasopressin-dependent water reabsorption and sodium transport in mouse collecting duct

“…Interestingly, EP3 downregulates medullary TAL COX2 in hypertonic states, providing a means to limit TAL sodium transport in response to high tonicity. 37 More work is needed to fully appreciate the respective roles of EP1 and EP3 in TAL sodium transport in both normotensive and hypertensive states.…”

Regulation of PGE2 signaling pathways and TNF-alpha signaling pathways on the function of bone marrow-derived dendritic cells and the effects of CP-25

“…The EP 1 is a well-known activator of Gaq, which enhances intracellular Ca 2+ levels [Bai et al, 2014]. The EP 3 inhibits adenylate cyclase (AC) via Gai, reducing cyclic adenosine monophosphate (cAMP) levels [Hao et al, 2014].…”