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Certain determinants of ischemic resistance in the Brown Norway rat strain have been proposed, but no studies to date have focused on the role of the Wnt pathway in the ischemic resistance mechanism. We performed a comparative genomic study in Brown Norway vs. Sprague-Dawley rats. Selective manipulations of the Wnt pathway in vivo and in vitro allowed us to study whether the action of the Wnt pathway on apoptosis through the regulation of osteopontin was critical to the maintenance of inherent ischemic resistance mechanisms. The results revealed a major gene upregulation of the Wnt family in Brown Norway rats after renal ischemia-reperfusion. Manipulation of the Wnt signaling cascade by selective antibodies increased mitochondrial cytochrome c release and caspase 3 activity. The antiapoptotic role of Wnt was mediated by osteopontin, a direct Wnt target gene. Osteopontin was reduced by Wnt antibody administration in vivo, and osteopontin gene silencing in vitro significantly increased mitochondrial cytochrome c release. The overexpression of Wnt pathway genes detected in Brown Norway rats is critical in the maintenance of their inherent ischemic resistance. Activation of the Wnt signaling cascade reduces mitochondrial cytochrome c release and caspase 3 activity through the action of osteopontin. apoptosis; acute renal failure doi: 10.1152/ajprenal.00687.2009.

Song JH, Kim M, Park SW, Chen SW, Pitson SM, Lee HT. Isoflurane via TGF-[beta]1 release increases caveolae formation and organizes sphingosine kinase signaling in renal proximal tubules. Am J Physiol Renal Physiol 298: F1041-F1050, 2010. First published January 6, 2010; doi:10.1152/ajprenal.00115.2009.--We previously showed that the inhalational anesthetic isoflurane protects against renal proximal tubule necrosis via isoflurane-mediated stimulation and translocation of sphingosine kinase-1 (SKI) with subsequent synthesis of sphingosine-l-phosphate (S IP) in renal proximal tubule ceils (Kim M, Kim M, Kim N, D'Agati VD, Emala CW Sr, Lee HT. Am J Physiol Renal Physiol 293: F1827-FI835, 2007). We also demonstrated that the anti-necrotic and anti-inflammatory effect of isoflurane is due in part to phosphatidylserine (PS) externalization and subsequent release of transforming growth factor-[beta]1 (TGF-[beta]1) (Lee HT, Kim M, Kim J, Kim N, Emala CW. Am J Nephrol 27: 416-424, 2007). In this study, we tested the hypothesis that isoflurane, via TGF-[beta]1 release, increases caveolae formation in the buoyant fraction of the. cell membrane of human renal proximal tubule (HK-2) cells to organize SKI and SIP signaling. To detect SK1 protein in the caveolae/caveolin fractions, we overexpressed human SKI in HK-2 cells (SK1-HK-2). SK1-HK-2 cells exposed to isoflurane increased caveolae/caveolin formation in the buoyant membrane fractions which contained key signaling intermediates involved in isofluranemediated renal tubule protection, including SIP, SKI, ERK MAPK, and TGF-[beta]1 receptors. Furthermore, treating SK1-HK-2 cells with recombinant TGF-[beta]1 or PS liposome mixture increased caveolae formation, mimicking the effects of isoflurane. Conversely, TGF-[beta]1neutralizing antibody blocked the increase in caveolae formation induced by isoflurane in SK1-HK-2 cells. The increase in SK1 activity in the caveolae-enriched fractions from isoflurane-treated nonlentivirus-infected HK-2 cells, while smaller in magnitude, was qualitatively similar to that found in the SK1-HK-2 cell fine. Finally, isoflurane also increased caveolae formation in the kidneys of TGF-[beta]1 +/+ mice but not in TGF-[beta]1 +/- mice (mice with reduced levels of TGF-[beta]1). Our study demonstrates that isoflurane organizes several key cytoprotective signaling intermediates including TGF-[beta]1 receptors, SK1 and ERK, within the caveolae fraction of the plasma membrane. Our findings may help to unravel the cellular signaling pathways of volatile anesthetic-mediated renal protection and lead to new therapeutic applications of inhalational anesthetics during the perioperative period. acute kidney injury; acute renal failure; caveolin-1; volatile anesthetics doi: 10.1152/ajprenal.00115.2009.

Renal ischemia and reperfusion injury leads to acute renal failure when proinflammatory and apoptotic processes in the kidney are activated. The increase in hypoxia-inducible transcription factor-[alpha] (HIF-[alpha]), an important transcription factor for several genes, can attenuate ischemic renal injury. We recently identified a novel WD-repeat protein designated Morg 1 (MAPK organizer 1) that interacts with prolyl hydroxylase 3 (PHD3), an important enzyme involved in the regulation of HIF-1[alpha] and HIF-2[alpha] expression. While homozygous Morg1 -/- mice are embryonic lethal, heterozygous Morg1 +/- mice have a normal phenotype. We show here that Morg1 +/- were partially protected from renal ischemia-reperfusion injury compared with wild-type Morg1 +/+ animals. Morg1 +/- mice compared with wild-type animals revealed a stronger increase in HIF-1[alpha] and HIF-2[alpha] expression in the ischemic-reperfused kidney associated with enhanced serum erythropoietin levels. However, no significant expression of HIF-1[alpha] and HIF-2[alpha] was found in nonischemic kidneys without any difference between Morg1 +/- and Morg1 +/+ mice. Ischemic kidneys of Morg1 +/- mice expressed more erythropoietin mRNA than ischemic kidneys from wild-type animals. Renal ischemia in Morg1 +/- mice resulted in a decrease in renal inflammation and reduction of proinflammatory cytokines (MCP-1, IP-10, MIP-2) compared with wild-type mice. Furthermore, there was significantly less apoptosis and tubular damage in Morg1 +/- kidneys after ischemia-reperfusion, and this was also reflected in significantly improved renal function compared with wild-type. Thus Morg1 may be a novel therapeutic target to limit renal injury after ischemia-reperfusion. hypoxia; HIF-1[alpha]; HIF-2[alpha]; renal inflammation; chemokine expression; ischemic renal failure doi: 10.1152/ajprenal.00204.2009.

Methylglyoxal (MG), a highly reactive carbonyl compound generated by carbohydrate oxidation and glycolysis, is the major precursor of protein glycation and induces cytotoxicity leading to apoptosis. Although recent studies have emphasized that MG accumulates in not only chronic oxidative stress-related diseases but also acute hypoxic conditions, the pathogenic contribution of MG in acute diseases is unclear. MG is efficiently metabolized by the glyoxalase system, namely, glyoxalase I. We investigated the pathophysiological role of glyoxalase I as an MG detoxifier in rat renal ischemia-reperfusion (I/R) injury. I/R-induced tubulointerstitial injury was associated with a deterioration in renal glyoxalase I activity independent of its cofactor, GSH, as well as an increase in renal MG level. In in vitro studies, knockdown of glyoxalase I by small interference RNA transfection in rat tubular cells exacerbated cell death by hypoxia-reoxygenation compared with control cells. We also examined whether glyoxalase I overexpression prevented renal I/R damage in rats overexpressing human glyoxalase I with enzyme activity in the kidney 17-fold higher than in wild-type. The histological and functional manifestations of I/R in these rats were significantly ameliorated in association with a decrease in intracellular MG adduct accumulation, oxidative stress, and tubular cell apoptosis. In conclusion, glyoxalase I exerts renoprotective effects in renal I/R injury via a reduction in MG accumulation in tubular cells. acute renal failure; advanced glycation end products; methylglyoxal; oxidative stress; tubular cells

Salahudeen AK, Haider N, Jenkins J, Joshi M, Patel H, Huang H, Yang M, Zhe H. Antiapoptotic properties of erythropoiesis-stimulating proteins in models of cisplatin-induced acute kidney injury. Am J Physiol Renal Physiol 294: F1354-F1365, 2008. First published April 2, 2008; doi: 10.1152/ajprenal.00131.2008.--Erythropoietin (Epo) induces erythrocytosis by suppressing erythroid progenitor cell apoptosis through the Janus-activated kinase-signal transducers and activators of transcription (JAK-STAT) pathway. Since apoptosis contributes to cisplatin (CP)-induced nephrotoxicity and Epo receptors (EpoR) are expressed in the kidney, we examined the role of antiapoptosis in recombinant human erythropoietin (rHuEpo)-mediated renal protection. In human renal proximal tubular epithelial (RPTE) cells in culture, rHuEpo, but not inactive rHuEpo (I-rHuEpo), the receptor-binding sites of which are mutated, caused a significant reduction in CP-induced apoptosis at [greater than or equal to] 100 U/ml. rHuEpo, but not I-rHuEpo, increased STAT5 and Akt/PKB phosphorylation, demonstrating functional EpoR expression on RPTE cells. Furthermore, the JAK2 inhibitor tyrphostin AG-490 attenuated rHuEpo protection, suggesting a role of the JAK-STAT pathway in rHuEpo-mediated antiapoptosis. In rats, intravenous administration of 5,000 U/kg rHuEpo, but not an equivalent peptide mass of I-rHuEpo, before a single 5.5 mg/kg iv injection of CP, significantly increased hematocrit (Hct) and reduced the CP-induced increase in serum creatinine. Serum creatinine on day 4 was 3.4 [+ or -] 0.3, 1.9 [+ or -] 0.3, and 3.5 [+ or -] 0.4 mg/dl in the CP, CP + rHuEpo, and CP + I-rHuEpo groups, respectively. Similarly, darbepoietin-[alpha] (DA), a hyperglycosylated analog of rHuEpo with prolonged in vivo activity when injected at 25 [micro]g/kg iv before CP, significantly increased Hct and reduced serum creatinine. Renal clearance studies based on glomerular filtration rate and renal blood flow confirmed the significant renal protection by DA against CP. Tubular apoptosis and necrosis were significantly reduced in the kidneys of the CP + DA vs. the CP + saline group. Moreover, the equalization of Hct by venesection did not abrogate the DA-mediated renal protection. Administration of DA 48 h after CP injection also conferred significant renal protection. Thus our experiments confirm a role for erythropoiesis-stimulating proteins, including the new analog DA, in limiting CP-induced nephrotoxicity and suggest that antiapoptosis via the Epo-EpoR interaction is an important mechanism for renal protection. apoptosis; darbepoietin-[alpha]; cisplatin; toxic nephropathy; acute renal failure; recombinant human erythropoietin; erythropoietin receptor

Muscle wasting is a debilitating consequence of fasting, inactivity, cancer, and other systemic diseases that results primarily from accelerated protein degradation by the ubiquitin-proteasome pathway. To identify key factors in this process, we have used cDNA microarrays to compare normal and atrophying muscles and found a unique gene fragment that is induced more than ninefold in muscles of fasted mice. We cloned this gene, which is expressed specifically in striated muscles. Because this mRNA also markedly increases in muscles atrophying because of diabetes, cancer, and renal failure, we named it atrogin-1. It contains a functional F-box domain that binds to Skp1 and thereby to Roc1 and Cul1, the other components of SCF-type Ub-protein ligases (E3s), as well as a nuclear localization sequence and PDZ-binding domain. On fasting, atrogin-1 mRNA levels increase specifically in skeletal muscle and before atrophy occurs. Atrogin-1 is one of the few examples of an F-box protein or Ub-protein ligase (E3) expressed in a tissue-specific manner and appears to be a critical component in the enhanced proteolysis leading to muscle atrophy in diverse diseases.

Byline: A. Nobilis (1), I. Kocsis (2), P. Toth-Heyn (3), A. Treszl (2), A. Schuler (4), T. Tulassay (2), B. Vasarhelyi (2) Keywords: Keywords Acute renal failure; Very low birth weight infant; Angiotensin converting enzyme; Angiotensin II type 1 receptor; Genetic polymorphism Abstract: High neonatal activity of the renin-angiotensin system (RAS) is crucial for the maintenance of glomerular filtration of the newborn. The aim of the present study was to investigate whether genetic polymorphisms leading to lower angiotensin converting enzyme activity (ACE) or impaired functionality of angiotensin II (AII) type 1 receptor (AT1R) might predispose very low birth weight newborns (VLBWs) to the development of acute renal failure (ARF). The medical records of 110 VLBW infants were analyzed. ARF developed in 42 of them during the first postnatal week, while 68 neonates exhibited normal renal function. The ACE I/D polymorphism and the [A.sup.1166]C variants of AT1R were determined from dried blood samples. The frequency of the ACE I allele did not differ in ARF and non-ARF groups (0.307 and 0.284) the frequency of the AT1R C.sup.1166 variant was also the same in ARF and non-ARF groups (0.250 and 0.227). Although low activity of RAS has been implicated in the development of neonatal ARF and data indicated that the functionality of RAS is influenced by the I/D variants of the ACE gene and the [A.sup.1166]C variant of the AT1R gene, we could not demonstrate any effect of these polymorphisms on the development of ARF in VLBW infants. Author Affiliation: (1) Second Department of Obstetrics and Gynecology, Semmelweis University, Budapest, Hungary, HU (2) Joint Research Program of the First Department of Pediatrics and the Hungarian Academy of Sciences, Semmelweis University, Budapest, Hungary, HU (3) First Department of Pediatrics, Semmelweis University, Bokay u. 53, 1083 Budapest, Hungary. Vasbar@gyer1.sote.hu, HU (4) Budai Children's Hospital PKU Laboratory, Budapest, Hungary, HU Article note: Received: 7 March 2001 / Revised: 9 August 2001 / Accepted: 10 August 2001

The expression of the b-cell lymphoma/leukemia gene product two (bcl-2) and bax in the rat renal proximal tubules was analyzed following acute ischemic renal injury. Analysis of rat kidneys after postischemic injury indicated the presence of elevated levels of bcl-2 messenger RNA which returned to baseline levels during postischemic recovery. Furthermore, restoration of renal function after ischemic acute renal failure was mediated by bcl-2 and bax which modulated renal tubular regeneration.

The roles of Jun NH2-terminal kinases (JNKs) and N-acetyl-L-cysteine (NAC) on on immediate early (IE) gene response were analyzed during ischemic renal failure in anesthetized rats. Administration of NAc before and after renal ischemia inhibited IE gene response and mitigated the loss of renal function during reperfusion. Furthermore, ischemic renal failure activated the JNK pathway and induced the expression of c-jun and c-fos transcription factors which reduced glomerular filtration rate.