Ji-Hyun Song

Treating lithium-induced nephrogenic diabetes insipidus with a COX-2 inhibitor improves polyuria via upregulation of AQP2 and NKCC2

Prostaglandin E(2) may antagonize vasopressin-stimulated salt absorption in the thick ascending limb and water absorption in the collecting duct. Blockade of prostaglandin E(2) synthesis by nonsteroidal anti-inflammatory drugs (NSAIDs) enhances urinary concentration, and these agents have antidiuretic effects in patients with nephrogenic diabetes insipidus (NDI) of different etiologies. Because renal prostaglandins are derived largely from cyclooxygenase-2 (COX-2), we hypothesized that treatment of NDI with a COX-2 inhibitor may relieve polyuria through increased expression of Na-K-2Cl cotransporter type 2 (NKCC2) in the thick ascending limb and aquaporin-2 (AQP2) in the collecting duct. To test this hypothesis, semiquantitative immunoblotting and immunohistochemistry were carried out from the kidneys of lithium-induced NDI rats with and without COX-2 inhibition. After male Sprague-Dawley rats were fed an LiCl-containing rat diet for 3 wk, the rats were randomly divided into control and experimental groups. The COX-2 inhibitor DFU (40 mg.kg(-1).day(-1)) was orally administered to the experimental rats for an additional week. Treatment with the COX-2 inhibitor significantly relieved polyuria and raised urine osmolality. Semiquantitative immunoblotting using whole-kidney homogenates revealed that COX-2 inhibition caused significant increases in the abundance of AQP2 and NKCC2. Immunohistochemistry for AQP2 and NKCC2 confirmed the effects of COX-2 inhibition in lithium-induced NDI rats. The upregulation of AQP2 and NKCC2 in response to the COX-2 inhibitor may underlie the therapeutic mechanisms by which NSAIDs enhance antidiuresis in patients with NDI.

Effect of Sirolimus on Calcineurin Inhibitor-Induced Nephrotoxicity Using Renal Expression of KLOTHO, an Antiaging Gene

Background. The aim of this study was to observe the effect of sirolimus (SRL) on calcineurin inhibitor (CNI)-induced nephrotoxicity in the aging process by using renal expression of KLOTHO, an antiaging gene. Methods. Mice were treated with vehicle (VH; 1 mL/kg/day of olive oil), cyclosporine A (CsA; 30 mg/kg/day), or tacrolimus (FK; 1 mg/kg/day) with or without SRL (0.3 mg/kg/day) for 2 weeks. KLOTHO expression was evaluated by using reverse-transcriptase polymerase chain reaction, immunoblotting, and immunohistochemistry. Oxidative stress was evaluated by using immunohistochemistry and urinary excretion of 8-hydroxy-2′-deoxyguanosine (8-OHdG). The calcium metabolism was evaluated by using renal ectopic calcification, serum intact parathyroid hormone level, and renal fibroblast factor 23 (FGF23) expression. Results. Treatment with CsA or FK alone significantly decreased KLOTHO expression and increased urinary 8-OHdG excretion compared with VH treatment but SRL treatment did not. Treatment SRL+CsA or SRL+FK further decreased KLOTHO expression and increased urinary 8-OHdG excretion compared with treatment of CsA or FK alone. There was a strong correlation between KLOTHO expression and urinary 8-OHdG excretion (r=−0.893; P<0.001). Treatment of CsA or FK alone increased renal ectopic calcification and serum intact parathyroid hormone level and decreased renal FGF23 expression compared with VH treatment (P<0.05) but SRL treatment did not. Treatment with SRL+CNI aggravated these parameters compared with CNI alone. Conclusions. SRL accelerates the CNI-induced oxidative process by down-regulating the renal antioxidant KLOTHO expression in the kidney.

Statin Upregulates the Expression of Klotho, an Anti-Aging Gene, in Experimental Cyclosporine Nephropathy

Background: We recently reported that long-term cyclosporine (CsA)-induced oxidative stress is associated with decreased expression of klotho, an anti-aging gene. This study evaluated whether the antioxidant effect of statin might upregulate klotho expression in CsA-induced renal injury. Methods: Two separate experiments were performed. First, the dose-dependent effect of statin on klotho expression was evaluated in normal mouse kidneys. Second, the effect of statin on klotho expression was evaluated in experimental chronic CsA nephropathy in mice. We performed immunohistochemistry and immunoblotting for klotho, Forkhead box O transcription factors [FoxOs; phosphorylated FoxO1 (p-FoxO1) and FoxO3a (p-FoxO3a)] and their target molecules, manganese superoxide dismutase (MnSOD), Bim and hemeoxygenase-1. Results: Statin treatment upregulated klotho expression in a dose-dependent manner in the normal mouse kidney and alleviated the decrease in klotho expression in kidneys exhibiting CsA nephropathy. CsA administration increased p-FoxO1 expression and decreased p-FoxO3a expression, whereas concurrent statin treatment reversed these changes, increased the expression of the antioxidant enzymes MnSOD and hemeoxygenase-1 and decreased the expression of the pro-apoptotic protein Bim. Conclusion: Statin-mediated upregulation of klotho expression and differential regulation of FoxO expression promote resistance to CsA-induced oxidative stress.

Drug interaction between cyclosporine and mTOR inhibitors in experimental model of chronic cyclosporine nephrotoxicity and pancreatic islet dysfunction.

Background. It is known that sirolimus (SRL) aggravates cyclosporine A (CsA)-induced nephrotoxicity and pancreatic injury, but the influence of everolimus (EVR) on CsA-induced organ injury is undetermined. Methods. Rats were treated with CsA (15 mg/kg) and EVR or SRL (0.3 mg/kg) subcutaneously for 4 weeks. The influences of EVR or SRL on CsA-induced nephrotoxicity and pancreatic islet dysfunction were compared, and drug interactions between CsA and EVR or SRL were evaluated at blood and tissue levels. Results. Treatment with EVR or SRL alone did not cause severe pancreatic dysfunction and renal injury, but when combined with CsA they aggravated CsA-induced pancreatic and renal injury. Drug interactions between CsA and EVR or SRL differed at the tissue level. Combined treatment with CsA and SRL significantly increased the CsA or SRL levels in kidney and pancreas compared with CsA or SRL alone. However, combined treatment with CsA and EVR did not increase CsA or EVR levels in kidney and pancreas. Conclusions. Both EVR and SRL aggravate CsA-induced organ injury, but the pharmacologic interaction between EVR and CsA at the tissue level is less than that between CsA and SRL. This finding provides better understanding of the difference between EVR and SRL when combined with CsA treatment.

Ischemia-induced changes of platelet endothelial cell adhesion molecule-1 in the hippocampal CA1 region in gerbils

We observed chronological changes of platelet endothelial cell adhesion molecule-1 (PECAM-1), final mediator of neutrophil transendothelial migration, immunoreactivity, and protein level in the gerbil hippocampus proper after 5 min of transient ischemia. One day after ischemic insult, PECAM-1 immunoreactivity and protein level increased slightly in the hippocampus proper. Thereafter, PECAM-1 immunoreactivity and protein level increased significantly in the hippocampus proper by 4 days after ischemic insult. Especially, PECAM-1 in the hippocampal CA1 region was higher than that in the CA2/3 region. Five days after ischemic insult, PECAM-1 immunoreactivity decreased compared to the 4 days post-ischemic group. However, the RNA levels of PECAM-1 in the hippocampus proper were significantly decreased in the 4 days post-ischemic groups compared to that in the sham-operated group. This result suggests that the increase of PECAM-1 and decrease of PECAM-1 RNA in the CA1 region 4 days after ischemia may be associated with transmigration of neurotrophil.

Upregulation of hyaluronan and its binding receptors in an experimental model of chronic cyclosporine nephropathy.

Aim:  Hyaluronan (HA) is an important extracellular matrix (ECM) proteoglycan. The localization of HA and its binding receptors, CD44 and LYVE‐1, was evaluated in an experimental model of chronic cyclosporine A (CsA)‐induced nephropathy.

Transient ischemia-induced changes of neurofilament 200 kDa immunoreactivity and protein content in the main olfactory bulb in gerbils

This study was carried out to investigate alterations of neurofilament 200 kDa (NF-200) and its polyphosphorylation form (RT97) immunoreactivity and protein content in the main olfactory bulb (MOB) after 5 min of transient forebrain ischemia in gerbils. In the sham-operated group, weak NF-200 immunoreactivity was detectable in a few somata of mitral cells, which projected weak NF-200-immunoreactive processes to the external plexiform layer (EPL). At 1-5 days after ischemia, strong NF-200 and RT97 immunoreactivity was shown by the mitral cell processes; however, somata of mitral cells did not show NF-200 immunoreactivity. At this time point, strong NF-200-immunoreactive mitral cell processes ran to the EPL and glomerular layer (GL). Thereafter, NF-200 and RT97 immunoreactivity was decreased up to 30 days after ischemia. In the 15 days post-ischemic group, the distribution pattern of NF-200 and RT97 immunoreactivity was slightly lower than that in the 1-5 days post-ischemic groups. In the 30 days post-ischemic group, moderate NF-200 and RT97 immunoreactivity was found in the mitral cells processes, but the immunoreactivity in the EPL and GL nearly disappeared. A Western blot study showed a pattern of NF-200 and RT97 expression at all post-ischemic time points similar to that of immunohistochemistry after ischemia. This result indicates that NF-200 and RT97 accumulates in injured mitral cell processes a few days after transient ischemia, which suggests that the axonal transport in the MOB may be disturbed during this period after transient ischemia.

Expression and changes of Ca2+-ATPase in neurons and astrocytes in the gerbil hippocampus after transient forebrain ischemia

Ca2+-ATPase is one of the most powerful modulators of intracellular calcium levels. In this study, we focused on chronological changes in the immunoreactivity and protein levels of Ca2+-ATPase in the hippocampus after 5 min of transient forebrain ischemia. Ca2+-ATPase immunoreactivity was significantly altered in the hippocampal CA1 region and in the dentate gyrus, but not in the CA2/3 region after ischemic insult. In the sham-operated group, Ca2+-ATPase immunoreactivity was detected in the hippocampus. Ca2+-ATPase immunoreactivity in the CA1 region and in the dentate gyrus, and its protein levels peaked 3 h after ischemic insult. At this time, CA1 pyramidal cells and dentate polymorphic cells showed strong Ca2+-ATPase immunoreactivity. Thereafter, Ca2+-ATPase immunoreactivity reduced in the CA1 region and in the dentate gyrus. One day after ischemic insult, Ca2+-ATPase immunoreactivity was observed in some CA1 non-pyramidal cells, and 4 days after ischemic insult, Ca2+-ATPase immunoreactivity was detected in astrocytes throughout the CA1 region, but Ca2+-ATPase immunoreactivity in the dentate gyrus had nearly disappeared. Our results suggest that Ca2+-ATPase changes may be associated with a response to ischemic damage in hippocampal CA1 pyramidal cells, and that increased Ca2+-ATPase immunoreactivity in the reactive astrocytes may be associated with the maintenance of intracellular calcium levels.

Contents Vol. 120, 2012

Clinical Nephrology Guidelines J. Cunningham, London G. Eknoyan, Houston, Tex. A. Khwaja, Sheffield Clinical Appraisal/Evidence Based Nephrology A.K. El-Sherif, Ismailia R.J. Glassock, Laguna Niguel, Calif. A. Meyrier, Paris Global CKD G. Remuzzi, Bergamo N. Perico, Bergamo R. Atkins, Melbourne, Vic. Clinical Trials D. de Zeeuw, Groningen F. Locatelli, Lecco D. Wheeler, London Continuing Nephrology Education R. Barsoum, Cairo M. Field, Sydney, N.S.W. C. Zoccali, Reggio Calabria Clinico-Pathological Conferences T.H. Jafar, Karachi Editor-in-Chief