BACKGROUND AND PURPOSEDeletion of the cyclooxygenase-2 (COX-2) gene causes impairment of kidney development, but the effect of selective inhibitors of COX-2 (coxibs) or the non-selective inhibitors of COX (the classical non-steroidal anti-inflammatory drugs; NSAIDs) on kidney development was less well described. EXPERIMENTAL APPROACHWe assessed the effects of equipotent analgesic doses of celecoxib, rofecoxib, valdecoxib, etoricoxib and lumiracoxib and of the NSAIDs, diclofenac and naproxen, on postpartum kidney development in mice, from postnatal day 1 (P1) to P21. KEY RESULTSAll the COX inhibitors, at the doses used, blocked COX-2 activity by more than 80% as assayed by PGE2 synthesis in lipopolysaccharide-stimulated mouse blood samples. Rofecoxib, etoricoxib and lumiracoxib exerted the most marked impairment of postpartum kidney development, demonstrated by attenuation of kidney growth, reduction in size of glomeruli, increase in immature superficial glomeruli, thinning of subcapsular cortical mass and reduction in size of juxtamedullary glomeruli. These defects were less severe than those in kidneys from COX-2 -/-mice. Administration of diclofenac and naproxen revealed renal defects similar to those after coxib treatment, but both NSAIDs induced greater arrest of immature superficial glomeruli in the outer cortex and increased the number of undifferentiated proliferating cell nuclear antigen-positive cells. Treatment with celecoxib or valdecoxib caused only minimal changes in renal morphology. CONCLUSIONS AND IMPLICATIONSClassical NSAIDs cause similar or even stronger nephrodysgenesis than the coxibs. Also, the ranking of coxibs regarding adverse effects on renal development, using equi-analgesic doses, is rofecoxib = etoricoxib = lumiracoxib > valdecoxib > celecoxib.

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.

Antagonist at specific prostaglandin receptors might provide analgesia with a more favourable toxicity profile compared with cyclooxygenase inhibitors. We analyzed nociceptive responses in prostaglandin D, E, F, prostacyclin and thromboxane receptor knockout mice and mice deficient of cyclooxygenase 1 or 2 to evaluate the contribution of individual prostaglandin receptors for heat, mechanical and formalin-evoked pain. None of the knockouts was uniformly protected from all of these pain stimuli but COX-1 and EP4 receptor knockouts presented with reduced heat pain and EP3 receptor and COX-2 knockout mice had reduced licking responses in the 2nd phase of the formalin assay. This was accompanied with reduced c-Fos immunoreactivity in the spinal cord dorsal horn in EP3 knockouts. Oppositely, heat pain sensitivity was increased in FP, EP1 and EP1+3 double mutant mice possibly due to a loss of FP or EP1 receptor mediated central control of thermal pain sensitivity. Deficiency of either EP2 or DP1 was associated with increased formalin-evoked flinching responses and c-Fos IR in dorsal horn neurons suggesting facilitated spinal cord pain reflex circuity. Thromboxane and prostacyclin receptor knockout mice showed normal pain behavior in all tests. The results suggest a differential, pain-stimulus and site-specific contribution of specific PG-receptors for the processing of the nociceptive stimuli, a differential modulation of nociceptive responses by COX-1 and COX-2 derived prostaglandins and compensatory and/or developmental adaptations in mice lacking specific PG receptors.