Bonnie Blazer-Yost
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Dr. Bonnie Blazer-Yost’s primary interest is in epithelial cell biology as it relates to ion transport. Recently she has been investigating treatments for polycystic kidney disease. These studies resulted from a serendipitous finding regarding the potential use of Pioglitazone, a commonly used diabetes drug, in polycystic kidney disease patients. This research has progressed from tissue culture, through preclinical animal models and is currently funded as an initial clinical trial in polycystic kidney disease patients.
Dr. Blazer-Yost and her team are also researching potential treatments for hydrocephalus or “water on the brain.” Hydrocephalus may develop as a consequence of trauma, infection, tumors, intracranial hemorrhage or as a result of a congenital birth defect. Elderly patients may suffer from a poorly understood and underdiagnosed form called “normal pressure hydrocephalus,” characterized by urinary incontinence, gait instability, and dementia. Post-traumatic hydrocephalus occurs as the result of traumatic brain injury. Regardless of the form, brain surgery is currently the only effective long-term treatment. Dr. Blazer-Yost and her collaborators recently obtained a three-year Department of Defense grant to conduct translational studies in animal models with a goal of developing a drug treatment for hydrocephalus.
Dr. Blazer-Yost’s work to treat polycystic kidney disease and hydrocephalus is another example of how IUPUI faculty are TRANSLATING RESEARCH INTO PRACTICE.
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Recent Submissions
Item Functional Effects of Nanoparticle Exposure on Calu-3 Airway Epithelial Cells(2012) Banga, Amiraj; Witzmann, Frank A.; Petrache, Horia I.; Blazer-Yost, BonnieHigh concentrations of manufactured carbon nanoparticles (CNP) are known to cause oxidative stress, inflammatory responses and granuloma formation in respiratory epithelia. To examine the effects of lower, more physiologically relevant concentrations, the human airway epithelial cell line, Calu-3, was used to evaluate potential alterations in transepithelial permeability and cellular function of airway epithelia after exposure to environmentally realistic concentrations of carbon nanoparticles. Three common carbon nanoparticles, fullerenes, single- and multi-wall carbon nanotubes (SWCNT, MWCNT) were used in these experiments. Electrophysiological measurements were performed to assay transepithelial electrical resistance (TEER) and epinephrine-stimulated chloride (Cl(-)) ion secretion of epithelial cell monolayers that had been exposed to nanoparticles for three different times (1 h, 24 h and 48 h) and over a 7 log unit range of concentrations. Fullerenes did not have any effect on the TEER or stimulated ion transport. However, the carbon nanotubes (CNT) significantly decreased TEER and inhibited epinephrine-stimulated Cl(-) secretion. The changes were time dependent and at more chronic exposures caused functional effects which were evident at concentrations substantially lower than have been previously examined. The functional changes manifested in response to physiologically relevant exposures would inhibit mucociliary clearance mechanisms and compromise the barrier function of airway epithelia.Item Lysophosphatidic acid is a modulator of cyst growth in autosomal dominant polycystic kidney disease., Lysophosphatidic Acid is a Modulator of Cyst Growth in Autosomal Dominant Polycystic Kidney Disease(2011) Blazer-Yost, Bonnie; Blacklock, B. J.; Flaig, S.; Bacallao, R. L.; Gattone, V. H.Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the slow growth of multiple fluid-filled cysts predominately in the kidney tubules and liver bile ducts. Elucidation of mechanisms that control cyst growth will provide the basis for rational therapeutic intervention. We used electrophysiological methods to identify lysophosphatidic acid (LPA) as a component of cyst fluid and serum that stimulates secretory Cl- transport in the epithelial cell type that lines renal cysts. LPA effects are manifested through receptors located on the basolateral membrane of the epithelial cells resulting in stimulation of channel activity in the apical membrane. Concentrations of LPA measured in human ADPKD cyst fluid and in normal serum are sufficient to maximally stimulate ion transport. Thus, cyst fluid seepage and/or leakage of vascular LPA into the interstitial space are capable of stimulating epithelial cell secretion resulting in cyst enlargement. These observations are particularly relevant to the rapid decline in renal function in late-stage disease and to the "third hit" hypothesis that renal injury exacerbates cyst growth.Item Pioglitazone Attenuates Cystic Burden in the PCK Rodent Model of Polycystic Kidney Disease(2010) Blazer-Yost, Bonnie; Haydon, Julie; Eggleston-Gulyas, Tracy; Chen, Jey-Hsin; Wang, Xiaofang; Gattone, Vincent; Torres, Vicente E.Polycystic kidney disease (PKD) is a genetic disorder characterized by growth of fluid-filled cysts predominately in kidney tubules and liver bile ducts. Currently, the clinical management of PKD is limited to cyst aspiration, surgical resection or organ transplantation. Based on an observation that PPARγ agonists such as pioglitazone and rosiglitazone decrease mRNA levels of a Cl(-) transport protein, CFTR (cystic fibrosis transmembrane conductance regulator), and the Cl(-) secretory response to vasopressin in cultured renal cells, it is hypothesized that PPARγ agonists will inhibit cyst growth. The current studies show that a 7- or 14-week pioglitazone feeding regimen inhibits renal and hepatic bile duct cyst growth in the PCK rat, a rodent model orthologous to human PKD. These studies provide proof of concept for the mechanism of action of the PPARγ agonists and suggest that this class of drugs may be effective in controlling both renal and hepatic cyst growth and fibrosis in PKD.Item A human polymorphism affects NEDD4L subcellular targeting by leading to two isoforms that contain or lack a C2 domain(2009) Garrone, Nicholas F.; Blazer-Yost, Bonnie; Weiss, Robert B.; Lalouel, Jean-Marc; Rohrwasser, AndreasBACKGROUND: Ubiquitination serves multiple cellular functions, including proteasomal degradation and the control of stability, function, and intracellular localization of a wide variety of proteins. NEDD4L is a member of the HECT class of E3 ubiquitin ligases. A defining feature of NEDD4L protein isoforms is the presence or absence of an amino-terminal C2 domain, a class of subcellular, calcium-dependent targeting domains. We previously identified a common variant in human NEDD4L that generates isoforms that contain or lack a C2 domain. RESULTS: To address the potential functional significance of the NEDD4L common variant on NEDD4L subcellular localization, NEDD4L isoforms that either contained or lacked a C2 domain were tagged with enhanced green fluorescent protein, transfected into Xenopus laevis kidney epithelial cells, and imaged by performing confocal microscopy on live cells. We report that the presence or absence of this C2 domain exerts differential effects on the subcellular distribution of NEDD4L, the ability of C2 containing and lacking NEDD4L isoforms to mobilize in response to a calcium stimulus, and the intracellular transport of subunits of the NEDD4L substrate, ENaC. Furthermore, the ability of the C2-containing isoform to influence beta-ENaC mobilization from intracellular pools involves the NEDD4L active site for ubiquitination. We propose a model to account for the potential impact of this common genetic variant on protein function at the cellular level. CONCLUSION: NEDD4L isoforms that contain or lack a C2 domain target different intracellular locations. Additionally, whereas the C2-containing NEDD4L isoform is capable of shuttling between the plasma membrane and intracellular compartments in response to calcium stimulus the C2-lacking isoform can not. The C2-containing isoform differentially affects the mobilization of ENaC subunits from intracellular pools and this trafficking step requires NEDD4L ubiquitin ligase activity. This observation suggests a new mechanism for the requirement for the PY motif in cAMP-mediated exocytosis of ENaC. We have elucidated how a common genetic variant can underlie significant functional diversity in NEDD4L at the cellular level. We propose a model that describes how that functional variation may influence blood pressure. Moreover, our observations regarding differential function of the NEDD4L isoforms may impact other aspects of physiology that involve this ubiquitin ligase.Item PPAR Agonists: Blood Pressure and Edema(2010) Blazer-Yost, BonniePeroxisome proliferator activated receptor gamma (PPARgamma) agonists are widely used in the treatment of type 2 diabetes. Side effects of drug treatment include both fluid retention and a lowering of blood pressure. Data from animal and human studies suggest that these effects arise, at least in part, from drug-induced changes in the kidney. In order to capitalize on the positive aspect (lowering of blood pressure) and exclude the negative one (fluid retention), it is necessary to understand the mechanisms of action underlying each of the effects. When interpreted with known physiological principles, current hypotheses regarding potential mechanisms produce enigmas that are difficult to resolve. This paper is a summary of the current understanding of PPARgamma agonist effects on both blood pressure and fluid retention from a renal perspective and concludes with the newest studies that suggest alternative pathways within the kidney that could contribute to the observed drug-induced effects.Item 60kDa Lysophospholipase, a New Sgk1 Molecular Partner Involved in the Regulation of ENaC(2010) Menniti, Miranda; Iuliano, Rodolfo; Föller, Michael; Sopjani, Mentor; Alesutan, Ioana; Mariggiò, Stefania; Nofziger, Charity; Perri, Angela M.; Amato, Rosario; Blazer-Yost, Bonnie; Corda, Daniela; Lang, Florian; Perrotti, NicolaThe serum- and glucocorticoid-regulated kinase (Sgk1) is essential for hormonal regulation of ENaC-mediated sodium transport and is involved in the transduction of growth-factor-dependent cell survival and proliferation. The identification of molecular partners for Sgk1 is crucial for the understanding of its mechanisms of action. We performed a yeast two-hybrid screening based on a human kidney cDNA library to identify molecular partners of Sgk1. As a result the screening revealed a specific interaction between Sgk1 and a 60 kDa Lysophospholipase (LysoLP). LysoLP is a poorly characterized enzyme that, based on sequence analysis, might possess lysophospholipase and asparaginase activities. We demonstrate that LysoLP has indeed a lysophospholipase activity and affects metabolic functions related to cell proliferation and regulation of membrane channels. Moreover we demonstrate in the Xenopus oocyte expression system that LysoLP downregulates basal and Sgk1-dependent ENaC activity. In conclusion LysoLP may represent a new player in the regulation of ENaC and Sgk1-dependent signaling.Item PPARγ Agonists, Modulation of Ion Transporters, and Fluid Retention(2009) Nofziger, Charity; Blazer-Yost, BonnieItem Lack of the serum and glucocorticoid-inducible kinase SGK1 attenuates the volume retention after treatment with the PPARγ agonist pioglitazone(2008-05) Artunc, Ferruh; Sandulache, Diana; Nasir, Omaima; Boini, Krishna M.; Friedrich, Björn; Beier, Norbert; Dicks, Edith; Pötzsch, Sven; Klingel, Karin; Amann, Kerstin; Blazer-Yost, Bonnie; Scholz, Wolfgang; Risler, Teut; Kuhl, Dietmar; Lang, FlorianPPARgamma-agonists enhance insulin sensitivity and improve glucose utilization in diabetic patients. Adverse effects of PPARgamma-agonists include volume retention and edema formation. Recent observations pointed to the ability of PPARgamma agonists to enhance transcription of the serum and glucocorticoid-inducible kinase SGK1, a kinase that is genomically upregulated by mineralocorticoids and stimulates various renal channels and transporters including the renal epithelial Na+ channel ENaC. SGK1 has been proposed to mediate the volume retention after treatment with PPARgamma agonists. To test this hypothesis, food containing the PPARgamma agonist pioglitazone (0.02%, i.e., approximately 25 mg/kg bw/day) was administered to gene-targeted mice lacking SGK1 (sgk1-/-, n=12) and their wild-type littermates (sgk1+/+), n=12). According to in situ hybridization, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunofluorescence, treatment with pioglitazone significantly increased renal SGK1 mRNA and protein expression in sgk1+/+ mice. The treatment increased body weight significantly in both, sgk1+/+ mice (+2.2+/-0.3 g) and sgk-/- mice (+1.3+/-0.2 g), and decreased hematocrit significantly in sgk1+/+ mice (-6.5+/-1.0%) and sgk1-/- mice (-3.1+/-0.6%). Both effects were significantly (p<0.05) more pronounced in sgk1+/+ mice. According to Evans Blue distribution, pioglitazone increased plasma volume only in sgk1+/+ mice (from 50.9+/-3.9 to 63.7+/-2.5 microl/g bw) but not in sgk-/- mice (from 46.8+/-3.8 to 48.3+/-5.2 microl/g bw). Pioglitazone decreased aldosterone plasma levels and blood pressure and increased leptin plasma levels in both genotypes. We conclude that SGK1 contributes to but does not fully account for the volume retention during treatment with the PPARgamma agonist pioglitazone.Item Hormonal regulation of the epithelial Na+ channel: From amphibians to mammals(2006-05) Shane, Michael Anne; Nofziger, Charity; Blazer-Yost, BonnieHigh-resistance epithelia derived from amphibian sources such as frog skin, toad urinary bladder, and the A6 Xenopus laevis kidney cell line have been widely used to elucidate the underlying mechanisms involved in the regulation of vectorial ion transport. More recently, the isolation of high-resistance mammalian cell lines has provided model systems in which to study differences and similarities between the regulation of ion transporter function in amphibian and mammalian renal epithelia. In the present study, we have compared the natriferic (Na+ retaining) responses to aldosterone, insulin, and vasotocin/vasopressin in the A6 and mpkCCDcl4 (mouse principal cells of the kidney cortical collecting duct) cell lines. The functional responses of the epithelial Na+ channel (ENaC) to hormonal stimulation were remarkably similar in both the amphibian and mammalian lines. In addition, insulin- and aldosterone-stimulated, reabsorptive Na+ transport in both cell lines requires the presence of functional PI3-kinase.Item Structural and Functional Analyses of Liver Cysts from the BALB/c-cpk Mouse Model of Polycystic Kidney Disease(2009) Muchatuta, Monalisa N.; Gattone, Vincent H.; Witzmann, Frank A.; Blazer-Yost, BonnieLiver cysts arising from hepatic bile ducts are a common extra-renal pathology associated with both autosomal dominant and recessive polycystic kidney disease in humans. To elucidate the functional and structural changes inherent in cyst formation and growth, hepatic bile duct epithelia were isolated from the BALB/ c-cpk mouse model of polycystic kidney disease. Light and transmission electron microscopy revealed substantial fibrosis in the basal lamina surrounding hepatic bile duct cysts isolated from heterozygous (BALB/c-cpk/+) and homozygous (BALB/c-cpk/cpk) animals. Scanning electron microscopy and length analysis of normal, precystic and cystic bile ducts provided the unique observation that primary cilia in cholangiocytes isolated from bile ducts and cysts of animals expressing the mutated cpk gene had lengths outside the minimal and maximal ranges of those in cells lining bile ducts of wild-type animals. Based on the hypothesis that PKD is one of several diseases characterized as ciliopathies, this abnormal variability in the length of the primary cilia may have functional implications. Electrophysiological analyses of freshly isolated cysts indicate that the amiloride-sensitive epithelial Na(+) channel (ENaC) is inactive/absent and cAMP-mediated anion secretion is the electrogenic transport process contributing to cyst fluid accumulation. Anion secretion can be stimulated by the luminal stimulation of adenylyl cyclase.