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1 Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
2 Graduate Program in Molecular and Systems Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
3 Department of Surgery, University of Rochester Medical Center, Rochester, NY, USA
4 Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA; Center for Clinical and Molecular Nutrition, Emory University School of Medicine, Atlanta, GA, USA
5 Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA; Center for Clinical and Molecular Nutrition, Emory University School of Medicine, Atlanta, GA, USA
* To whom correspondence should be addressed. E-mail: tzieg01{at}emory.edu.
Glutamine (Gln) and KGF each stimulate intestinal epithelial cell growth, but regulatory mechanisms are not well understood. We determined whether Gln and KGF alter intra- and extracellular thiol/disulfide redox pools in Caco-2 cells cultured in oxidizing or reducing cell medium and whether such redox variations are a determinent of proliferative responses to these agents. Cells were cultured over a physiologic range of oxidizing to reducing extracellular thiol/disulfide redox (Eh) conditions, obtained by varying cysteine (Cys) and cystine(CySS) concentrations in cell medium. Cell proliferation was determined by 5-bromo-2-deoxyuridine (BrdU)incorporation. Gln (10 mmol/L) or KGF (10 µg/L) did not alter BrdU incorporation at reducing Eh (-131 to -150 mV), but significantly increased incorporation at more oxidizing Eh (Gln at 0 to -109 mV; KGF at -46 to -80 mV). Cellular glutathione/glutathione disulfide (GSH/GSSG) Eh was unaffected by Gln, KGF or variations in extracellular Cys/CySS Eh. Control cells largely maintained extracellular Eh at initial values after 24 h (-36 to -136 mV). However, extracellular Eh shifted toward a narrow physiologic range with Gln and KGF treatment (Gln -56 to -88 mV and KGF -76 to -92 mV, respectively; P< 0.05 versus control). The results indicate that thiol/disulfide redox state in the extracellular milieu is an important determinant of Caco-2 cell proliferation induced by Gln and KGF, that this control is independent of intracellular GSH redox status and that both Gln and KGF enhance the capability of Caco-2 cells to modulate extremes of extracellular redox.
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