Temporal expression of the PGE₂ synthetic system in the kidney is associated with the time frame of renal developmental vulnerability to cyclooxygenase-2 inhibition

Abstract

Pharmacological blockade of cyclooxygenase-2 (COX-2) causes impairment of kidney development. The present study was aimed at determining temporal expression pattern and activity of the PGE(2) synthetic pathway during postnatal nephrogenesis in mice and its association to the time window sensitive to COX-2 inhibition. During the first 10 days after birth, we observed transient induction of mRNA and protein for microsomal PGE synthase (mPGES)-1 between postnatal days 4 (P4) and P8, but not for mPGES-2 or cytosolic PGE synthase (cPGES). PGE(2) synthetic activity using arachidonic acid and PGH(2) as substrates and also urinary excretion of PGE(2) were enhanced during this time frame. In parallel to the PGE(2) system, COX-2 but not COX-1 expression was also transiently induced. Studying glomerulogenesis in EP receptor knockout mice revealed a reduction in glomerular size in EP1(-/-), EP2(-/-), and EP4(-/-) mice, supporting the developmental role of PGE(2). The most vulnerable time window to COX-2 inhibition by SC-236 was found closely related to the temporal expression of COX-2 and mPGES-1. The strongest effects of COX-2 inhibition were achieved following 8 days of drug administration. Similar developmental damage was caused by application of rofecoxib, but not by the COX-1-selective inhibitor SC-560. COX-2 inhibition starting after P10 has had no effect on the size of glomeruli or on the relative number of superficial glomeruli; however, growth of the renal cortex was significantly diminished, indicating the requirement of COX-2 activity after P10. Effects of COX-2 inhibition on renal cell differentiation and on renal fibrosis needed a prolonged time of exposition of at least 10 days. In conclusion, temporal expression of the PGE(2) synthetic system coincides with the most vulnerable age interval for the induction of irreversible renal abnormalities. We assume that mPGES-1 is coregulated with COX-2 for PGE(2) synthesis to orchestrate postnatal kidney development and growth.

Eicosanoid post-mortem induction in kidney tissue is prevented by microwave irradiation

“…Most PG were continuously synthesized during incubation (Fig. 4 A), which is consistent with the high level of PG synthesis during kidney homogenate incubation [12, 21, 36]. Similar to PG increase in non-fixed tissue (Fig.…”

Prostaglandin E2 increases proximal tubule fluid reabsorption, and modulates cultured proximal tubule cell responses via EP1 and EP4 receptors

“…10 The contribution of PGE 2 to regulation of cell cycle in healthy and injured renal cells has been described 16,[33][34][35][36] but not in the PT. Our work showed that PGE 2 and SLP inhibit the cell cycle in MCT cells similar to TGFβ, reducing both protein and DNA synthesis.…”

E-type prostanoid receptor 4 (EP4) in disease and therapy

“…PGE 2 and EP receptors including EP4 play important roles in kidney development, as suggested by a reduced glomerular size in EP4-deficient mice (Frolich et al, 2012). In vitro, PGE 2 acting via EP4 receptors augmented the survival of glomerular epithelial cells deprived of serum (Aoudjit et al, 2006), and an EP4 receptor agonist stimulated proliferation and decreased apoptosis of renal epithelial cells (Yamamoto et al, 2010).…”