title: Zinc enhancement of LLC-PK(1) renal epithelial barrier function.
abstract: OBJECTIVE
  Earlier work by our group and others has documented improvement of epithelial barrier function in human gastrointestinal models. Here we tested zinc's ability to improve a renal epithelial model. Our aim was to compare the functional and structural effects of zinc on the tight junctional (TJ) complexes of these two very distinct epithelial cell types. Zinc's ability to achieve barrier enhancement in very different epithelial cell types by action upon distinct molecular targets in each epithelial model may suggest a fundamental general role for supplemental zinc in epithelial barrier improvement throughout the body.
  
  
  METHODS
  Cell layers were exposed to 50 or 100 μM zinc on both cell surfaces for 48 h followed by measurement of transepithelial electrical resistance (Rt) and transepithelial (14)C-mannitol flux (Jm). TJ proteins in cell layers were analyzed by Western immunoblot.
  
  
  CONCLUSIONS
  Zinc supplementation improved the basal TJ barrier function of LLC-PK1 renal cell layers, exemplified by increased Rt and decreased Jm. These zinc-induced changes were also accompanied by decreased NaCl dilution potentials. Of the tight junctional proteins that were tested (occludin, claudins 1, 2, 3, 4, and 5, and tricellulin), we did not observe a zinc-induced change in abundance of any of them, in detergent-soluble fractions of lysates of confluent differentiated cell layers. However, examination of cytosolic fractions showed concentration-dependent increases in the levels of claudins -2 and -4 in this compartment as a result of supplemental zinc. The effects of supplemental zinc on the tight junctional complexes and barrier properties of this renal epithelial model are contrasted with zinc effects on the CACO-2 gastrointestinal model.
authors.affiliation: Lankenau Institute for Medical Research, Wynnewood, PA 19096, USA.
authors.forename: Xuexuan
authors.initials: X
authors.lastname: Wang
authors.affiliation: Lankenau Institute for Medical Research, Wynnewood, PA 19096, USA.
authors.forename: Mary Carmen
authors.initials: MC
authors.lastname: Valenzano
authors.affiliation: Lankenau Institute for Medical Research, Wynnewood, PA 19096, USA.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Mercado
authors.affiliation: Department of Chemistry, Saint Joseph's University, 5600 City Avenue, Philadelphia, PA 19131, USA.
authors.forename: E Peter
authors.initials: EP
authors.lastname: Zurbach
authors.affiliation: School of Biomedical Engineering Science and Health Systems, Drexel University, Philadelphia, PA 19104, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Flounders
authors.affiliation: Lankenau Institute for Medical Research, Wynnewood, PA 19096, USA; Division of Gastroenterology, Lankenau Medical Center, Wynnewood, PA 19096, USA. Electronic address: MullinJ@mlhs.org.
authors.forename: James M
authors.initials: JM
authors.lastname: Mullin
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018938:Caco-2 Cells; D057167:Claudins / Q000235:genetics / Q000378:metabolism; D019587:Dietary Supplements; D004847:Epithelial Cells / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018374:LLC-PK1 Cells; D062794:MARVEL Domain Containing 2 Protein / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D013552:Swine; D019108:Tight Junctions / Q000187:drug effects / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
chemical_list: D057167:Claudins; D062794:MARVEL Domain Containing 2 Protein; D014409:Tumor Necrosis Factor-alpha; D015032:Zinc
keywords: CACO-2; Claudin; LLC-PK(1); Nutrition; Tight junction; Zinc