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Julie R Ingelfinger

Publications and source records attributed to Julie R Ingelfinger.

52 records · Page 3Linked to original sources
PubMed2003

Growth factor-mediated phosphorylation of proapoptotic BAD reduces tubule cell death in vitro and in vivo.

BACKGROUND: Exogenous growth factors administered during unilateral ureteral obstruction (UUO) in neonatal rats significantly reduce apoptosis and tubular atrophy. Because the mechanism underlying these salutary effects is largely unknown, we investigated signaling pathways potentially activated by growth factors to determine their roles in therapeutic action. METHODS: Mechanical strain was applied to confluent cultures of immortalized rat proximal tubule cells to simulate obstruction-induced stretch injury in vivo. Growth factors, inhibitory antibodies or pharmacological inhibitors were added to cultures that were subsequently processed for TUNEL analysis or immunoblots to identify signaling pathways that could be modulating cell survival. For in vivo studies, kidneys harvested from rats +/- UUO +/- epidermal growth factor (EGF) were fixed or frozen for immunohistochemistry or immunoblot analysis. RESULTS: Treatment with EGF or insulin-like growth factor-1 (IGF-1) during stretch decreased apoptosis by 50% (P < 0.001). Neutralizing antibodies (Abs) directed against either growth factor or its receptor blocked the reduction in apoptosis. Stretch decreased BAD phosphorylation by approximately 50% (P < 0.001) relative to unstretched cells and each growth factor restored phosphorylation to basal levels. Kinase-specific inhibitors that blocked growth factor-mediated BAD phosphorylation promoted apoptosis in vitro. BAD phosphorylation decreased by approximately 50% (P < 0.001) in the tubules of obstructed hydronephrotic rat kidneys and administration of EGF restored BAD phosphorylation to basal levels. CONCLUSIONS: Signaling pathways converging at BAD phosphorylation are key to growth factor-mediated attenuation of stretch-induced apoptosis in vitro and in vivo.

Animals↗
PubMed2003

Heme: a novel inducer of MCP-1 through HO-dependent and HO-independent mechanisms.

This study examined the effect of hemin on the expression of heme oxygenase-1 (HO-1) and monocyte chemoattractant protein-1 (MCP-1) in immortalized rat proximal tubular epithelial cells (IRPTCs). Hemin elicited a dose- and time-dependent induction of HO-1 and MCP-1 mRNA. HO activity contributed to MCP-1 mRNA expression at early time points (4-6 h) because inhibition of HO activity by zinc protoporphyrin (ZnPP) prevented hemin-induced expression of MCP-1 mRNA. Catalytically active intracellular iron was markedly increased in hemin-treated IRPTCs and contributed to the induction of HO-1 and MCP-1 mRNA because an iron chelator blocked hemin-induced upregulation of both genes, whereas a cell-permeant form of iron directly induced these genes. N-acetylcysteine completely blocked hemin-induced expression of HO-1 and MCP-1 mRNA, thereby providing added evidence for redox regulation of expression of these genes. The redox-sensitive transcription factor NF-kappaB was recruited in hemin-induced upregulation of MCP-1 because two different compounds that abrogate the activation of NF-kappaB (TPCK and BAY 11-7082) completely blocked hemin-induced upregulation of MCP-1 mRNA. In contrast to this HO-mediated induction of MCP-1 through redox-sensitive, iron-dependent, and NF-kappaB-involved pathways observed after 4-6 h, hemin also elicited a delayed induction of MCP-1 at 18 h through HO-independent pathways. We conclude that hemin is a potent inducer of MCP-1 in IRPTCs: HO-dependent, heme-degrading pathways lead to an early, robust, and self-remitting induction of MCP-1, whereas HO-independent mechanisms lead to a delayed expression of MCP-1.

Animals↗
PubMed2002

Heme activates the heme oxygenase-1 gene in renal epithelial cells by stabilizing Nrf2.

The mechanism of heme oxygenase-1 gene (ho-1) activation by heme in immortalized rat proximal tubular epithelial cells was examined. Analysis of the ho-1 promoter identified the heme-responsive sequences as the stress-response element (StRE), multiple copies of which are present in two enhancer regions, E1 and E2. Electrophoretic mobility shift assays identified Nrf2, MafG, ATF3, and Jun and Fos family members as StRE-binding proteins; binding of Nrf2, MafG, and ATF3 was increased in response to heme. Dominant-negative mutants of Nrf2 and Maf, but not of c-Fos and c-Jun, inhibited basal and heme-induced expression of an E1-controlled luciferase gene. Heme did not affect the transcription activity of Nrf2, dimerization between Nrf2 and MafG, or the level of MafG, but did stimulate expression of Nrf2. Heme did not influence the level of Nrf2 mRNA but increased the half-life of Nrf2 protein from approximately 10 min to nearly 110 min. These results indicate that heme promotes stabilization of Nrf2, leading to accumulation of Nrf2. MafG dimers that bind to StREs to activate the ho-1 gene.

Animals↗
PubMed2002

Global analysis of gene expression in renal ischemia-reperfusion in the mouse.

Ischemia-induced acute renal failure (ARF) is a relatively common disorder with major morbidity and mortality. To study global gene expression during ARF, 6-week-old C57BL/6 male mice underwent 30 min of bilateral renal ischemia followed by reperfusion [I/R] or sham operation. Oligonucleotide microarrays [Affymetrix] with approximately 10,000 genes, 6,643 of which were present in mouse kidney, were used to analyze mRNA expression for up to 4 days following I/R. Fifty-two genes at day 1 and 40 at day 4 were up-regulated more than 4-fold [400%]. Seventy genes at day 1 and 30 genes at day 4 were down-regulated to under 0.25-fold from baseline [25%]. Real-time quantitative RT-PCR confirmed changes in expression for 8 genes of interest. Most of the induced transcripts are involved in cell structure, extracellular matrix, intracellular calcium binding, and cell division/differentiation. Our data identified several novel genes that may be important in renal repair after ischemia.

ADP-Ribosylation Factor 6↗
PubMed2002

Perinatal programming, renal development, and adult renal function.

Substantial data indicate that maternal diet during gestation, as well as perinatal events, affect organogenesis and, furthermore, may affect organ function at maturity, thus determining whether an individual is prone or resistant to a variety of health problems such as hypertension, cardiovascular disease, or renal dysfunction. This concept is called perinatal programming, or the fetal origins of adult disease (FOAD), a concept that arose after the publication of epidemiologic observations by Barker and colleagues that birth weight among apparently normal individuals studied in midlife was inversely associated with the presence of cardiovascular disease and hypertension. We now review evidence from studies in experimental animal models that have used nutritional and pharmacologic manipulation to extend epidemiologic observations.

Aging↗
PubMed2002

Abnormal iron deposition in renal cells in the rat with chronic angiotensin II administration.

Acute experimental iron loading causes iron to accumulate in the renal tissue. The accumulation of iron may play a role in enhancing oxidant-induced tubular injury by producing increased amounts of reactive oxygen species. From findings in cells from heme oxygenase-1 (HO-1)-deficient mice, HO-1 is postulated to prevent abnormal intracellular iron accumulation. Recently, it has been reported that HO-1 is induced in the renal tubular epithelial cells, in which iron is deposited after iron loading, and that this HO-1 induction may be involved in ameliorating iron-induced renal toxicity. We previously showed that chronic administration of angiotensin II to rats induces HO-1 expression in the tubular epithelial cells. These observations led us to investigate whether there is a link between iron deposition and HO-1 induction in renal tubular cells in rats undergoing angiotensin II infusion. In the present study, rats were given angiotensin II for continuously 7 days. Prussian blue staining revealed the distinct deposits of iron in the proximal tubular epithelial cells after angiotensin II administration. Electron microscopy demonstrated that iron particles were present in the lysosomes of these cells. Histologic and immunohistochemical analyses showed that stainable iron and immunoreactive ferritin and HO-1 were colocalized in the tubular epithelial cells. Treatment of angiotensin II-infused rats with an iron chelator, deferoxamine, blocked the abnormal iron deposition in kidneys and also the induced expression of HO-1 and ferritin expression. Furthermore, deferoxamine treatment suppressed the angiotensin II-induced increase in the urinary excretion of protein and N-acetyl-beta-D-glucosaminidase, a marker of tubular injury; however, deferoxamine did not affect the angiotensin II-induced decrease in glomerular filtration rate. These results suggest that angiotensin II causes renal injury, in part, by inducing the deposition of iron in the kidney.

Acetylglucosaminidase↗
PubMed2002

Monitoring changes in gene expression in renal ischemia-reperfusion in the rat.

BACKGROUND: Although acute renal failure (ARF) is a relatively common disorder with major morbidity and mortality, its molecular basis remains incompletely defined. The present study examined global gene expression in the well-characterized ischemia-reperfusion model of ARF using DNA microarray technology. METHODS: Male Wistar rats underwent bilateral renal ischemia (30 min) or sham operation, followed by reperfusion for 1, 2, 3 or 4 days. Plasma creatinine increased approximately fivefold over baseline, peaking on day 1. Renal total RNA was used to probe cDNA microarrays. RESULTS: Alterations in expression of 18 genes were identified by microarray analysis. Nine genes were up-regulated (ADAM2, HO-1, UCP-2, and thymosin beta4 in the early phase and clusterin, vanin1, fibronectin, heat-responsive protein 12 and FK506 binding protein in the established phase), whereas another nine were down-regulated (glutamine synthetase, cytochrome p450 IId6, and cyp 2d9 in the early phase and cyp 4a14, Xist gene, PPARgamma, alpha-albumin, uromodulin, and ADH B2 in the established phase). The identities of these 18 genes were sequence-verified. Changes in gene expression of ADAM2, cyp2d6, fibronectin, HO-1 and PPARgamma were confirmed by quantitative real-time polymerase chain reaction (PCR). ADAM2, cyp2d6, and PPARgamma have not previously been known to be involved in ARF. CONCLUSION: Using DNA microarray technology, we identified changes in expression of 18 genes during renal ischemia-reperfusion injury in the rat. We confirmed changes in five genes (fibronectin, ADAM2, cyp 2d6, HO-1 and PPARgamma) by quantitative real-time PCR. Several genes, not previously been identified as playing a role in ischemic ARF, may have importance in this disease.

ADAM Proteins↗
PubMed2002

Pediatric hypertension: recent literature.

This article reviews selected recent literature specifically concerning pediatric hypertension, much of which has focused on measurement and monitoring of blood pressure, as well as on evaluating antihypertensive medications. Normative data for blood pressure in children have been widely available for some time, based upon seated in-office measurements. In recent years, ambulatory blood pressure monitoring (ABPM), facilitated by user-friendly instrumentation, has become more commonplace, though norms are not based on large populations. However, ABPM has important uses in assessing blood pressure as well as in monitoring antihypertensive. This review discusses issues involved in determining blood pressure, as well as the utility of ABPM in several situations. Recent developments concerning pediatric antihypertensive therapy are considered, as well as new information relevant to the diagnosis, course and treatment of hypertension in children and adolescents.

Adolescent↗
PubMed2002

Regulation and localization of HSP70 and HSP25 in the kidney of rats undergoing long-term administration of angiotensin II.

Various renal insults result in induction of heat shock protein (HSP) expression within the kidney. Some of the HSPs induced in that manner are postulated to have renoprotective effects via either chaperoning actions or antioxidative properties. We have previously reported that long-term angiotensin (Ang) II administration induces the expression of renal HSP32, also known as heme oxygenase-1 (HO-1). Here, we investigated the regulation of expression and localization of other HSPs, including HSP70, HSP25, and alphaB-crystallin, in the kidney of rats undergoing long-term administration of Ang II (0.7 mg. kg(-1). d(-1)). Immunoblot analysis demonstrated that Ang II increased renal expression of HSP70 and HSP25, as well as HO-1, but that expression of alphaB-crystallin was unaffected by this treatment. The Ang II-induced increase in renal HSP70 and HSP25 was dependent on the angiotensin type 1 receptor activation but not on hypertension per se. Immunohistochemistry revealed that HSP70 and HSP25 were expressed in the medullar regions and in the renal arterial wall in the kidney of control rats. After Ang II infusion, signals for HSP70, HSP25, and HO-1 proteins increased in intensity in the endothelium and medial smooth muscle of the renal artery. In addition, all of these HSPs were induced in proximal renal tubular epithelial cells from the same segments, suggesting that similar mechanisms are responsible for upregulating these HSPs. Our data show that Ang II infusion induces renal HSP70 and HSP25, as well as HO-1, and that Ang II can induce expression of these HSPs in renal cells in a pressor-independent manner.

Angiotensin II↗
PubMed2002

Insulin inhibits dexamethasone effect on angiotensinogen gene expression and induction of hypertrophy in rat kidney proximal tubular cells in high glucose.

The present studies investigated whether insulin inhibits the stimulatory effect of dexamethasone (DEX) on angiotensinogen (ANG) gene expression and induction of hypertrophy in rat immortalized renal proximal tubular cells (IRPTCs) in a high-glucose milieu. Rat IRPTCs were cultured in monolayer. ANG and ANG mRNA expression in IRPTCs were quantified by a specific RIA for rat ANG and by RT-PCR assay, respectively. A fusion gene containing the full length of the 5'-flanking region of the rat ANG gene linked to a chloramphenicol acetyl transferase reporter gene was introduced into IRPTCs. The level of fusion gene expression was determined by cellular chloramphenicol acetyl transferase enzymatic activity. Cellular hypertrophy was assessed by flow cytometry, cellular p27(Kip1) protein expression, and protein assay. Our results showed that high glucose (i.e. 25 mM) and DEX (10(-7) M) additively stimulated ANG gene expression and induced IRPTC hypertrophy. Insulin inhibited the effect of high glucose and DEX on these parameters. The inhibitory effect of insulin was reversed by PD 98059 (a MAPK inhibitor) but not by wortmannin (a phosphatidylinositol-3-kinase inhibitor). These results demonstrate that insulin is effective in blocking the stimulatory action of high glucose and DEX on ANG gene expression and induction of IRPTC hypertrophy, suggesting its important role in preventing local intrarenal renin-angiotensin system activation and renal proximal tubular cell hypertrophy induced by hyperglycemia and glucocorticoids in vivo.

Angiotensinogen↗
PubMed2002

High glucose stimulates angiotensinogen gene expression via reactive oxygen species generation in rat kidney proximal tubular cells.

The present studies investigated whether the effect of high glucose levels on angiotensinogen (ANG) gene expression in kidney proximal tubular cells is mediated via reactive oxygen species (ROS) generation and p38 MAPK activation. Rat immortalized renal proximal tubular cells (IRPTCs) were cultured in monolayer. Cellular ROS generation and p38 MAPK phosphorylation were assessed by lucigenin assay and Western blot analysis, respectively. The levels of immunoreactive rat ANG secreted into the media and cellular ANG mRNA were determined by a specific RIA and RT-PCR, respectively. High glucose (25 mM) evoked ROS generation and p38 MAPK phosphorylation as well as stimulated immunoreactive rat ANG secretion and ANG mRNA expression in IRPTCs. These effects of high glucose were blocked by antioxidants (taurine and tiron), inhibitors of mitochondrial electron transport chain complex I (rotenone) and II (thenoyltrifluoroacetone), an inhibitor of glycolysis-derived pyruvate transport into mitochondria (alpha-cyano-4-hydroxycinnamic acid), an uncoupler of oxidative phosphorylation (carbonyl cyanide m-chlorophenylhydrazone), a manganese superoxide dismutase mimetic, catalase, and a specific inhibitor of p38 MAPK (SB 203580), but were not affected by an inhibitor of the malate-aspartate shuttle (aminooxyacetate acid). Hydrogen peroxide (>/=10(-5) M) also stimulated p38 MAPK phosphorylation, ANG secretion, and ANG mRNA gene expression, but its stimulatory effect was blocked by catalase and SB 203580. These studies demonstrate that the stimulatory action of high glucose on ANG gene expression in IRPTCs is mediated at least in part via ROS generation and subsequent p38 MAPK activation.

Angiotensinogen↗
PubMed2002

Essential role(s) of the intrarenal renin-angiotensin system in transforming growth factor-beta1 gene expression and induction of hypertrophy of rat kidney proximal tubular cells in high glucose.

These studies investigated the question of whether the intrarenal renin-angiotensin system (RAS) is essential for transforming growth factor-beta1 (TGF-beta1) gene expression and induction of hypertrophy of renal proximal tubular cells in high glucose in vitro. Antisense and sense angiotensinogen (ANG) cDNAs were stably transfected into rat immortalized renal proximal tubular cells (IRPTC). ANG secretion from rat IRPTC was quantified by a specific RIA for rat ANG. Cellular ANG, TGF-beta1, and collagen alpha1 (type IV) mRNA levels were determined by Northern blot analysis or by reverse transcriptase-PCR assay. Hypertrophy of IRPTC was analyzed by Western blotting of cellular p27(Kip1) protein, flow cytometry, and cellular protein assay. The results showed that stable transfer of antisense ANG cDNA into IRPTC suppressed the basal TGF-beta1 and collagen alpha1 (type IV) mRNA expression and blocked the stimulatory effect of high glucose (i.e., 25 mM) on TGF-beta1 and collagen alpha1 (type IV) mRNA expression and induction of IRPTC hypertrophy. In contrast, stable transfer of sense ANG cDNA into IRPTC had no significant effect on these parameters. These data demonstrate that local intrarenal RAS activation is essential for TGF-beta1 gene expression and induction of hypertrophy of renal proximal tubular cells in high glucose.

Angiotensinogen↗