Regulation of Intestinal CeIl Growth by Bavine Milk Proteins : Prevention and Healing from Gastroenteritis

一种主要的牛乳清蛋白α-乳清蛋白(α-LA)的商业制剂对培养的肠道细胞株IEC-6的细胞增殖有明显的抑制作用，尽管这种抑制作用具有批次依赖性。这种抑制是不可逆的，仅一次接触含有活性批次的α-LA的培养液30分钟就足以引起细胞死亡，可能是通过凋亡。另一种主要的牛乳清蛋白β-乳球蛋白(β-LG)的商业制剂被发现对IEC6细胞的生长有促进或抑制作用，这取决于其分子形式。因此，即使在添加10%胎牛血清的培养液中，β-LG的天然二聚体也能显著促进细胞增殖，而这种蛋白的寡聚体则完全抑制细胞的生长。然而，这种抑制是由于Ind…所致。在37℃，30%三氟乙醇(TFE)的醋酸盐溶液中，pH 5.5，在缓慢旋转的试管中孵育5天，使α-LA天然单体具有细胞毒性。在SDS-PAGE上出现稳定的30 kDa或更高的MR条带是α-LA的共同特征，具有诱导细胞死亡的活性。类似地，TFE在Tris-HCl中处理2天，使β-LG的天然二聚体受到抑制。同样，β-LG在SDS-PAGE上出现稳定的37 kDa或更高的MR条带是具有抑制活性的共同特征。最后，研究了α-LA对小鼠胃肠炎的治疗作用。因此，将人轮状病毒MO口服接种5日龄BALB/c乳鼠，并在接种后24小时即可观察到小鼠腹泻。接种后24、48、72小时口服正常牛乳制备的天然单体α-LA可缩短腹泻持续时间。综上所述，两种主要的牛乳乳清蛋白对体外培养的肠道细胞生长的调节作用，无论是促进作用还是抑制作用，都可能通过迅速消除处于不利状态的细胞或通过刺激正常成熟肠道细胞的供应来快速修复组织而起到维持胃肠健康的作用。较少

Potent inhibition of cell proliferation was found for the commercial preparations of a major bovine whey protein α-lactalbumin (α-LA) on cultured intestinal cell line IEC-6 albeit lot-dependent. The inhibition was irreversible and only a single exposure to the culture medium containing α-LA of an active lot for a period as short as 30 min was enough to provoke cells death, possibly through apoptosis. The oligomer fraction from size exclusion chromatography was significantly robust, while the monomer fraction remained inert, in inducing cell death.The commercial preparations of another major bovine whey protein β-lactoglobulin (β-LG) were found to be either promotive or inhibitory on the growth of IEC-6 cells depending on its molecular forms. Thus, native dimer of β-LG promote the cell proliferation significantly even in the medium supplemented with 10% fetal calf serum, whereas the oligomeric form of this protein totally inhibited the cell growth. However, the inhibition was due to ind … More ucing growth arrest, not through inducing cell death.Incubation at 37℃ for 5 days with 30% trifluoroethanol (TFE) in acetate, pH 5.5, in a slowly rotating test tube (TFE treatment) rendered the native monomer of α-LA cytotoxic. The occurrence of SDS-stable 30-kDa or higher Mr bands on SDS-PAGE was a common feature for α-LA with the activity inducing cell death. Similarly, TFE treatment in Tris-HCl, pH 8.0 for 2 days rendered the native dimer of β-LG inhibitory. Again, the occurrence of SDS-stable 37kDa or higher Mr bands on SDS-PAGE was a common feature for β-LG with the inhibitory activity.Finally, the therapeutic effect of α-LA was studied on murine model of gastroenteritis. Thus, human rotavirus MO was orally inoculated in 5-day-old BALB/c suckling mice, and diarrhea was observed in mice as soon as 24 hr after inoculation. When given orally 24, 48, 72 hr after inoculation, native monomer α-LA prepared from normal bovine milk either before or after the TFE treatment could reduce the duration of diarrhea.In conclusion, the regulative effect on the intestinal cell growth in vitro of the two major bovine milk whey proteins, either with promotive or with inhibitory action, could have an efficacy on maintaining gastrointestinal health either through rapid elimination of cells in adverse state or quick repair of the tissue by the stimulation of supplying normal mature intestinal cells. Less