Low-dose indomethacin after ischemic acute kidney injury prevents downregulation of Oat1/3 and improves renal outcome

Abstract

We have previously shown that expression of renal organic anion transporters Oat1 and Oat3 is diminished by prostaglandin E2 (PGE2) and that both transporters are downregulated after renal ischemia. Because PGE2 is increased after renal ischemia and is generated by cyclooxygenases (COX), we investigated the effect of the COX inhibitor indomethacin on expression of Oat1/3 after ischemic acute kidney injury (iAKI). iAKI was induced in rats by bilateral clamping of renal arteries for 45 min. Indomethacin (1 mg/kg) was given intraperitoneally as soon as reperfusion started. Sham-treated animals served as controls. Oat1/3 were determined by qPCR and Western blot. PGE2 in blood and urine was measured by enzyme-linked immunosorbent assay. Invasion of monocytes/macrophages was determined. Glomerular filtration rate and renal plasma flow were determined. All parameters were detected 24 h after ischemia. PAH net secretion, as well as clearance and secretion of PGE2 were calculated. In clamped animals, indomethacin restored expression of Oat1/3, as well as PAH net secretion, PGE2 clearance, or PGE2 secretion. Additionally, indomethacin substantially improved kidney function as measured by glomerular filtration and PAH clearance. Indomethacin did not affect ischemia-induced invasion of monocytes/macrophages. In conclusion, our study indicates that low-dose indomethacin applied after ischemia prevents ischemia-induced downregulation of Oat1/3 during reperfusion and has a substantial protective effect on kidney function after iAKI. The beneficial effect of low-dose indomethacin on renal outcome is likely due to an effect different from inhibition of inflammation. In accordance to the decreased PAH net secretion, renal excretion of an endogenous organic anion (PGE2) is also impaired after ischemia and reperfusion.

Nitric oxide-induced regulation of renal organic cation transport after renal ischemia-reperfusion injury

“…Inulin clearance was 0.58 Ϯ 0.077 ml/min (n ϭ 11) in untreated controls and 0.57 Ϯ 0.040 ml/min (n ϭ 9) in sham-operated animals, indicating that surgical intervention had no effect on glomerular filtration rate. These values agree well with previously published data (26), indicating that this model is reproducible and reliable. As expected, iAKI caused by I/R injury decreased inulin clearance to 0.19 Ϯ 0.023 ml/min (n ϭ 11).…”

“…I/R injury was induced in rats by bilateral clamping of the renal arteries for 45 min followed by a reperfusion period of 24 h as described previously (26). Female Sprague-Dawley (SD) rats (200 -250 g body wt) were obtained from Charles River Wiga (Kissleg, Germany).…”

“…Renal function was determined by measurement of inulin clearance reflecting glomerular filtration rate in vivo after the respective experimental procedures by detection of the FITC-inulin (Sigma-Aldrich, St. Louis, MO) concentration in plasma and urine samples that were taken 24 h after the I/R injury, as described previously in detail (26). Inulin clearance was calculated as follows: inulin clearance ϭ (inulin U ϫ VU)/(inulinP ϫ t), where inulinU is inulin concentration in urine; VU is urine volume; inulinP is inulin concentration in plasma; and t is time of measurement.…”

Protective effect of indomethacin in renal ischemia-reperfusion injury in mice

“…(Feitoza et al, 2002;. The research on rats showed low-dose (1 mg/kg) IMT had a substantial protective effect on kidney function after AKI (Schneider et al, 2009). In recent studies, we set 1, 3, 5, and 7 mg/kg IMT treatment in the mice IRI model, and found that 5 mg/kg IMT was the proper dose in this study.…”

“…An increasing number of studies reported that pretreatment with IMT alone tended to reduce the renal damage after IRI (Schneider et al, 2009). Feitoza et al (2008 showed that pretreatment of mice with 5 mg/kg IMT could protect the renal function and reduce long-term renal fibrosis.…”