Postnatal regulation of 15-hydroxyprostaglandin dehydrogenase in the rat kidney

Abstract

Cyclooxygenase 2 (COX-2) has an established role in postnatal kidney development. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is recently identified as an endogenous inhibitor of COX-2, limiting the production of COX-2-derived prostanoids in several pathological conditions. The present study was undertaken to examine the regulation of renal 15-PGDH expression during postnatal kidney development in rats compared with COX-2. qRT-PCR and immunoblotting demonstrated that 15-PGDH mRNA and protein in the kidney were present in neonates, peaked in the second postnatal week, and then declined sharply to very low level in adulthood. Immunostaining demonstrated that at the second postnatal week, renal 15-PGDH protein was predominantly found in the proximal tubules stained positive for Na/H exchanger 3 and brush borders (periodic acid-Schiff), whereas COX-2 protein was restricted to macular densa and adjacent thick ascending limbs. Interestingly, in the fourth postnatal week, 15-PGDH protein was redistributed to thick ascending limbs stained positive for the Na-K-2Cl cotransporter. After 6 wk of age, 15-PGDH protein was found in the granules in subsets of the proximal tubules. Overall, these results support a possibility that 15-PGDH may regulate postnatal kidney development through interaction with COX-2.

Keywords: 15-PDGH; COX-2; postnatal kidney development; prostaglandin; proximal tubule.

Fig. 1.

15-Hydroxyprostaglandin dehydrogenase (15-PGDH) mRNA expression in the kidneys of Sprague-Dawley (SD) rats at different ages. Renal 15-PGDH mRNA expression was detected SD rats at various ages by quantitative (q) RT-PCR. Values are means ± SE.; n = 5 in each group.

Fig. 2.

15-PGDH protein expression in the kidneys of SD rats during different ages. A: renal 15-PGDH protein expression was detected in SD rats at various ages by Western blotting. B: 15-PGDH densitometry. Values are means ± SE.; n = 5 in each group.

Fig. 3.

Localization of 15-PGDH protein in the kidneys of 2-wk-old SD rats. A: immunostaining of kidney slides with anti-15-PGDH antibody in 2-wk-old SD rats (×50). B: 15-PGDH-blocking peptide was used to confirm the specificity of the antibody against 15-PGDH. Rabbit IgG staining was used as a negative control. C: immunostaining of kidney slides with anti-15-PGDH antibody in 2-wk-old SD rats (×400). Shown are representatives of 2–3 experiments.

Fig. 4.

Localization of 15-PGDH protein in renal proximal tubules of 2-wk-old SD rats. A: immunohistochemistry of 15-PGDH and periodic acid-Schiff (PAS) staining on consecutive kidney sections in 2-wk-old SD rats (×400). B: immunostaining with anti-15-PGDH and anti-Na/H exchanger 3 (NHE3) antibodies on consecutive kidney sections in 2-wk-old SD rats (×1,000). Shown are representatives of 2–3 experiments.

Fig. 5.

Localization of 15-PGDH protein in the kidneys of 4-wk-old SD rats. A: immunostaining of kidney slides with anti-15-PGDH antibody in 4-wk old SD rats (×400). B: immunostaining with anti-15-PGDH and anti-Na-K-2Cl cotransporter (NKCC2) antibodies on consecutive kidney sections in 2-wk-old SD rats (×1,000). C: immunostaining with anti-15-PGDH and anti-aquaporin-2 (AQP2) antibodies on consecutive kidney sections in 2-wk-old SD rats (×1,000). Shown are representatives of 2–3 experiments.

Fig. 6.

Localization of 15-PGDH protein in renal superficial cortex of 6- and 12-wk old SD rats. A: immunostaining of kidney slides with anti-15-PGDH antibody in 6- and 12-wk-old SD rats (×1,000). B: immunostaining with anti-15-PGDH and anti-NHE3 antibodies on consecutive kidney sections in 6-wk-old SD rats (×1,000). Shown are representatives of 2–3 experiments.

Fig. 7.

Localization of 15-PGDH protein and cyclooxygenase 2 (COX-2) protein in the kidneys of 2-, 4-, and 6-wk-old SD rats. Immunostaining was done with anti-15-PGDH and anti-COX-2 antibodies on consecutive kidney sections in 2-, 4-, and 6-wk-old SD rats (×1,000). Shown are representatives of 2–3 experiments.

Fig. 8.

Urinary excretion of 15-PGDH protein in rats at different ages. A: urinary 15-PGDH protein level was detected at 12-wk-old SD rats by immunoprecipitation. B: urinary 15-PGDH protein level was detected at 4- and 12-wk-old Wistar-Kyoto (WKY) rats by immunoprecipitation. C: immunostaining of kidney slides with anti-15-PGDH antibody in 4- and 12-wk-old WKY rats (×400). Shown are representatives of 2–3 experiments.