Nan Luo

Nanjing University, Nan-ching, Jiangsu Sheng, China

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Publications (4)10.26 Total impact

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    ABSTRACT: Tight junctions (TJs) are specialized membrane microdomains of plasma membrane and play an important role in barrier function. IFN-gamma and TNF-alpha have been implicated in intestinal barrier dysfunction. In the present study, we analyzed the effect of IFN-gamma and TNF-alpha on epithelial barrier function and determined the contribution of apoptosis to this process using T84 cells, a model intestinal epithelial cell line. We found that TNF-alpha and IFN-gamma synergistically affected the epithelial barrier and disrupted the structure of TJs. We demonstrated for the first time that treatment with TNF-alpha and IFN-gamma changed lipid composition and fatty acyl substitutions of phospholipids in membrane microdomains of TJs. Alterations of lipid environment affected TJs barrier function and partly removed flotillin-1 and displaced occludin from membrane microdomains of TJs to detergent-soluble fractions. The distribution of claudin isoforms was unaffected by TNF-alpha and IFN-gamma treatment. These findings indicated the interaction between inflammatory cytokines and alterations of lipid composition in membrane microdomains of TJs in the inflammatory processes. The apoptosis inhibitor did not prevent cytokine-induced decrease in TER and increase in permeability to FITC-dextran. Our results suggest that the cytokines directly influence TJ function and modulate both the membrane microdomain localization of TJ proteins and lipid composition of TJs. The effects of proinflammatory cytokines on TJ structure and function provide a mechanism in the pathophysiology of Crohn's disease (CD). Understanding the intracellular mechanisms involved could be important in devising future therapeutic strategies to induce retightening of the leaky TJ barrier.
    No preview · Article · Feb 2008 · Clinical Immunology
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    ABSTRACT: n-3 Polyunsaturated fatty acids are assumed to play an important role in the prevention and treatment of atherosclerosis. Endothelial nitric-oxide synthase (eNOS) is responsible for cardiovascular homeostasis involving in regulation of vascular function, and the subcellular localization is critical for its activation. Here we determined the effect of docosahexaenoic acid (DHA, 22:6 n-3) on distribution of eNOS and its activity. DHA treatment markedly altered lipid environment of caveolae microdomains, which was coincided with selective displacement of caveolin-1 and eNOS from caveolae. Akt was not detected in caveolae fractions and CaM was distributed in both of caveolin-1-enriched membranes and non-caveolar fractions, whose distribution was unaffected by DHA. These data demonstrated for the first time that DHA altered caveolae microenvironment not only by modifying membrane lipid composition, but also by changing distribution of major structural proteins. DHA-induced alterations in caveolae lipid/protein environment may be an important mechanism in the development of pathogenesis of atherosclerosis.
    No preview · Article · Nov 2007 · Archives of Biochemistry and Biophysics
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    ABSTRACT: Endothelial nitric oxide synthase (eNOS) plays a crucial role in the regulation of a variety of cardiovascular functions. Many studies have shown that dietary n-3 polyunsaturated fatty acids (PUFAs) have beneficial effects on coronary atherosclerosis. However, the mechanisms of n-3 PUFAs regulation in eNOS activation remain unknown. In the present study we investigated the effects of eicosapentaenoic acid (EPA, 20:5 n-3) on subcellular distribution of eNOS and lipid composition of caveolae. We demonstrated for the first time that EPA treatment profoundly altered lipid composition and fatty acyl substitutions of phospholipids in caveolae. We found that caveolin-1 was solely located in caveolae fractions in control cells, and EPA treatment displaced caveolin-1 from caveolae. eNOS was detected in the caveolin-enriched fractions and noncaveolae fractions in control cells. EPA treatment induced the translocation of eNOS from caveolae fractions to soluble fractions. P-eNOS was also distributed in both fractions. After EPA treatment, the level of p-eNOS in each fraction was increased but the distribution of which was unaffected. Moreover, the results of immunofluorescence confirmed that EPA could redistribute caveolin-1 and eNOS in plasma membrane. eNOS activity in HUVEC cells was increased after EPA treatment, which was in a dose dependent manner. And incubation with 50 μM EPA had the maximum effect on eNOS activity. Our results suggested that eNOS translocation was paralleled by a stimulated capacity for NO production in the cells. We found that total Akt and p-Akt were primarily presented in heavy membranes in control cells, and the relative level of p-Akt increased but the distribution did not change after EPA treatment. The distribution of CaM was slightly changed after EPA treatment.
    Full-text · Article · Feb 2007 · Biochimie
  • Li Tan · Fangnan Liu · Nan Luo · Jieshou Li
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    ABSTRACT: A high performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of γ‐aminobutyric acid (GABA) and glutamate (Glu) in human gastric mucosa. After gastric mucosa tissues were dried under liquid nitrogen, ground, and ultrafiltered, the amino acids in these tissues were derivatized with phenylisothiocyanate. The phenythiocyanates of amino acids (PTC‐amino acid) were then separated on Pico·Tag™ column, eluted with gradient mobile phases, and detected at a wavelength of 254 nm. The linear responses observed were 0.125–6.25 µM for GABA and 0.025–2.5 mM for Glu with the correlation coefficients of 0.9988 and 0.9998, respectively. The detection limits for GABA was 0.05 µM. The recoveries for GABA and Glu determinations were in the ranges of 90.4–104% and 88.1–105.5%, respectively. The intra‐ and inter‐day RSDs were less than 10%. The method was sensitive, specific, and accurate for clinical application of GABA and Glu in human gastric mucosa tissues. It was found that GABA and Glu concentrations in gastric cancer tissues were higher than those in normal gastric mucosa tissues.
    No preview · Article · Jun 2006 · Journal of Liquid Chromatography & Related Technologies