Iron-ascorbate alters the efficiency of Caco-2 cells to assemble and secrete lipoproteins

Although oxidative stress has been implicated in development of gut patholo gies, its role in intestinal fat transport has not been investigated. We as sessed the effect of Fe2+-ascorbate-mediated lipid peroxidation on lipid sy nthesis, apolipoprotein biogenesis, and lipoprotein assembly and secretion. Incubation of postconfluent Caco-2 cells with iron(II)- ascorbate (0.2 mM/ 2 mM) in the apical compartment significantly promoted malondialdehyde form ation without affecting sucrase activity, transepithelial resistance, DNA a nd protein content, and cell viability. However, addition of the oxygen rad ical-generating system reduced 1)[C-14] oleic acid incorporation into cellu lar triglycerides (15%, P< 0.0002) and phospholipids (16%, P< 0.0005); 2) d e novo synthesis of cellular apolipoprotein A-I (apo A-I) (18%, P< 0.05), a po A-IV (38%, P< 0.05), and apo B-48 (45%, P< 0.003) after [S-35] methionin e addition; and 3) production of chylomicrons (50%), VLDL (40%), LDL (37%), and HDL (30%) (all P< 0.0001). In contrast, increased total cellular chole sterol formation (96%, P< 0.0001), assayed by [C-14] acetate incorporation, was noted, attributable to marked elevation (70%, P<0.04) in activity of D L-3-hydroxy-3-methylglutaryl-CoA reductase, the rate-limiting enzyme in cho lesterol synthesis. The ratio of Acyl-CoA to cholesterol acyltransferase, t he esterifying cholesterol enzyme, remained unchanged. Fe2+-ascorbate-media ted lipid peroxidation modifies intracellular fat absorption and may decrea se enterocyte efficiency in assembling and transporting lipids during gut i nflammation.