Joanna M Mercado

Lankenau Institute for Medical Research, Wynnewood, Oklahoma, United States

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Publications (4)9.26 Total impact

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    ABSTRACT: Background: Delivery of a pharmacologically effective drug dosage to a target tissue is critical. Barrett's epithelia are a unique challenge for drug delivery of orally administered zinc due to rapid transit down the esophageal lumen, incomplete absorptive differentiation of these epithelia, and the use of proton-pump inhibitor drugs abrogating intestinal uptake of supplemental zinc. Methods: Barrett's esophagus patients were administered oral zinc gluconate (26 mg zinc twice daily) for 14 days prior to biopsy procurement. Barrett's biopsies were analyzed for total zinc content by atomic absorption spectroscopy and by western immunoblot for cellular proteins known to be regulated by zinc. Results: Cellular levels of both the Znt-1 transport protein and the alpha isoform of PKC were over 50% lower in the zinc treatment group. Conclusion: Oral zinc administration can result in effective delivery of zinc to Barrett's epithelia with resulting effects on intracellular signal transduction.
    Therapeutic delivery 03/2014; 5(3):257-64.
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    ABSTRACT: BACKGROUND AND AIMS: 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. RESULTS AND 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.
    Clinical nutrition (Edinburgh, Scotland) 05/2013; · 3.27 Impact Factor
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    ABSTRACT: Amid an increasing number of reports in the literature concerning epithelial barrier enhancement by various nutrient compounds, there has never been a study performing side-by-side comparisons of these agents in a single epithelial model. We compare five nutrient compounds (previously reported in various epithelial models to enhance barrier function) regarding their ability to increase transepithelial electrical resistance (Rt) and decrease transepithelial mannitol permeability (Jm) across LLC-PK1 renal epithelial cell layers. The effects of these nutrients on the abundance of various tight junctional proteins are also compared. In the overall group of nutrients tested - zinc, indole, quercetin, butyrate and nicotine - only nicotine failed to improve barrier function by either parameter. Nicotine also was without effect on tight junctional proteins. Quercetin simultaneously increased Rt and decreased Jm. Zinc, butyrate and indole only exhibited statistically significant enhancement of Rt. Each of these four effective nutrient compounds had unique patterns of effects on the panel of tight junctional proteins studied. No two compounds produced the same pattern of effects. This unique pattern of effects on tight junctional complex composition by each compound establishes the chance for additive or even synergistic improvement of barrier function by combinations of compounds. A synergistic effect of the combination of quercetin and zinc on Rt is shown.
    PLoS ONE 01/2013; 8(11):e78775. · 3.73 Impact Factor
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    ABSTRACT: BACKGROUND: Zinc deficiency is known to result in epithelial barrier leak in the GI tract. Precise effects of zinc on epithelial tight junctions (TJs) are only beginning to be described and understood. Along with nutritional regimens like methionine-restriction and compounds such as berberine, quercetin, indole, glutamine and rapamycin, zinc has the potential to function as a TJ modifier and selective enhancer of epithelial barrier function. AIMS: The purpose of this study was to determine the effects of zinc-supplementation on the TJs of a well-studied in vitro GI model, CACO-2 cells. METHODS: Barrier function was assessed electrophysiologically by measuring transepithelial electrical resistance (R(t)), and radiochemically, by measuring transepithelial (paracellular) diffusion of (14)C-D-mannitol and (14)C-polyethyleneglycol. TJ composition was studied by Western immunoblot analyses of occludin, tricellulin and claudins-1 to -5 and -7. RESULTS: Fifty- and 100-μM zinc concentrations (control medium is 2 μM) significantly increase R(t) but simultaneously increase paracellular leak to D-mannitol. Claudins 2 and 7 are downregulated in total cell lysates, while occludin, tricellulin and claudins-1, -3, -4 and -5 are unchanged. Claudins-2 and -7 as well as tricellulin exhibit decreased cytosolic content as a result of zinc supplementation. CONCLUSIONS: Zinc alters CACO-2 TJ composition and modifies TJ barrier function selectively. Zinc is one of a growing number of "nutraceutical" substances capable of enhancing epithelial barrier function, and may find use in countering TJ leakiness induced in various disease states.
    Digestive Diseases and Sciences 08/2012; · 2.26 Impact Factor