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Elevated Level of Hypoxia Inducible Factor 1α Can Alter Renal Epithelial Function
Author(s) -
Nag Subhra S,
Resnick Andrew
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.968.27
Subject(s) - paracellular transport , tight junction , kidney , chemistry , hypoxia (environmental) , medicine , renal function , endocrinology , barrier function , lumen (anatomy) , secretion , microbiology and biotechnology , permeability (electromagnetism) , biology , biochemistry , membrane , oxygen , organic chemistry
In the United States, about 600,000 people have Polycystic Kidney Disease (PKD) characterized by fluid filled structures (cysts) formed inside the kidney. Cysts interfere with normal renal function and lead to kidney failure. In the cystic epithelia, hypoxia inducible factor 1α (HIF1α) and HIF2α were found to be elevated. It is hypothesized that kidney cystic epithelia transform from normal absorption to secretion leading to accumulation of fluid within the cyst lumen. The fluid accumulation and insufficient vascular supply result in localized chronic hypoxia i.e., elevated HIF1α levels which may further promote cyst growth. We hypothesize that increased level of HIF1α can promote switching of renal epithelial function from absorptive to a secretory phenotype, possibly due to loss of epithelial tight junction integrity and altered active ion transport. HIF1α level was pharmacologically elevated by cobalt chloride (CoCl 2 ) in monolayers of mouse cortical collecting duct cell line (mCCD 1296 (d)) grown on suspended permeable membranes in the presence or absence of fluid flow. In our analysis, transepithelial electrical resistance (TEER) and voltage values were recorded using an Endohm chamber. Higher TEER values reflect reduced paracellullar permeability indicating tight junction integrity which was verified by paracellular permeability assay using FITC‐conjugated dextran molecules. Short circuit current (Isc) was calculated using Ohm's law (I= V/R) to compare active ion transport. MTT assay was used in order to make sure CoCl 2 treated and untreated groups maintained same level of cellular viability. We found that elevated levels of HIF1α by CoCl 2 caused loss of tight junction integrity and increased paracellular permeability. Increased HIF1α also resulted in decreased sodium transport which was determined from ameloride‐sensitive Isc. Currently, we are investigating the effect of increased HIFα by CoCl 2 or deferoxamine on possible shift of active ion transport across the epithelial monolayer using specific sodium and chloride ion channel and transporter blockers. We are trying to understand the effect of increased level of HIF 1α on the localization and expression of tight junction proteins (e.g., zonula occludin 1 (ZO1) and claudins) and cotransporter proteins (e.g., Na + K + ATPase and NKCC1), leading to altered paracellular permeability and active ion transport. Thus, this study may provide a basis to understand how HIF1α or hypoxia may cause loss of normal epithelial function leading to cyst progression. This work could provide fresh insight into new treatment strategies for PKD. Support or Funding Information The project is supported by National Institute of Diabetes and Digestive and Kidney Diseases 1R15DK092716 to AR and Cleveland State University Dissertation Research Award to SN