[Influence of protamine on expression of tight junction proteins in Caco-2]

Action of polycation protein protamine on the expression of tight junction proteins (claudins-1, -2, -3 and occludin) which contribute to paracellular transport function was investigated on cellular models of tight (MDCK I cell line) and leaky (Caco-2 cell line) epithelium. The expression of claudins-1,-3 and occludin was observed in both cell lines by methods of immunocytochemistry. Influence of protamine (100 microg/ml; 30 min; apical) on fluorescence intensity of claudins-1, -3 was different in MDCK I and Caco-2 cells. Addition ofprotamine to the incubation medium of Caco-2 cells resulted in significant increase of claudin-3 expression by 45 % (p <0.01) in comparison with control, whereas claudin-1 and occludin expression did not alter. On the contrary, in MDCK I cells protamine induced the significant decrease ofclaudin-1 and -3 expression by 25 % (p <0.001) and 15 % (p < 0.01) respectively, whereas occludin expression did not alter. It was confirmed by the methods of confocal laser scanning microscopy that protamine alter the expression of claudins-1, -3 directly in the tight junctions. Our results suggest that charged chyme components may alter paracellular permeability of epithelium.