Intestinal epithelial Caco-2 cells responses to lupin seed protein fractions

State of the art and aim: In the recent years biological active proteins have been found in lupin seeds, such as bowman-birk inhibitor and gamma-conglutin, which showed anticarcinogenic and hypoglycemic activity respectively (Duranti et al, 2008). Beside, a certain number of bioactive proteins and peptides have been described in soybean and other legumes. However, little is known about the responses at immunological level after the interactions of seed proteins with intestinal mucosae. The relationship between the consumption of certain foods and the reduction or the establishment of immunological diseases has been demonstrated. For example, from bovine milk can originate a number of casein hydrolysates with positive immunomodulatory properties (Sandré et al, 2001). Therefore, the aim of this study was to investigate the immune response of intestinal epithelial Caco-2 cells to different lupin seed protein fractions and assess possible other cellular effects. Results and discussion: Three protein fractions, namely alpha, beta and gamma -conglutin, were purified from lupin seeds through a well-established procedure (Magni et al, 2007). Stable transfected Caco-2 cell monolayers were incubated with the protein fractions (0,5 mg/mL) and interleukin 1b (2 ng/mL) for 4 hours. This cell line, containing the plasmid pNiFty2-Luc, expresses the nuclear factor (NF)-kB-binding sites on membrane, whose activation by pro-inflammatory molecules can be monitored measuring light emission. The results showed that gamma-conglutin, by interacting with NFkB receptor, activated significantly the inflammatory response of the transfected Caco-2 cells. A lower response was measured with alpha and beta -conglutins. The effects of gamma-conglutin on cell protein expression were also investigated in hepatic cells, a possible target of gamma-conglutin. HepG2 cells were incubated for 4 hours with or without the integer and the pepsin/pancreatin hydrolyzed gammaconglutin. The 2D electrophoretic maps of cell protein extracts did not show differences in the protein patterns. These preliminary results show that only gamma-conglutin negatively modulated the immune response of transfected Caco-2 cells after 4 hours of incubation but this protein did not induced major changes in the protein pattern of HepG2 cells as monitored in the 2D maps. Further researches will be necessary to investigate the cellular and immune responses of cell models to gamma-conglutin.