Abstract: The effects of α-lactalbumin (α-LA) treated by pasteurization (63 ℃/30 min, 72 ℃/15 s, 85 ℃/15 s, or 95℃/10 min) on the proliferation, cell cycle and apoptosis of normal human intestinal epithelial cells (HIEC) were studied and compared. The secondary structure of α-LA with different pasteurization treatments was determined by circular dichroism spectroscopy. Then, the pasteurized α-LA was digested in vitro under simulated infant intestinal conditions and the effect of the resulting α-LA hydrolysates on the proliferation, cell cycle and apoptosis of HIEC cells at 48 h of culture was detected by cell counting kit-8 (CCK-8) assay and flow cytometry. The results showed that both raw and pasteurized α-LAs could significantly promote the proliferation of HIEC cells in a concentration-dependent manner in a certain range, and the most significant (P < 0.05) effect was achieved under the conditions of pasteurization at 72 ℃ for 15 s and 0.10 mg/mL concentration. Flow cytometry showed that both digested pasteurized α-LA and digested α-LA at a concentration of 0.10 mg/mL significantly reduced the percentage of HIEC cells in the G0/G1 phase (P < 0.05), increased the percentage of HIEC cells in the G2/M and S phase (P < 0.05), and decreased cell apoptosis (P < 0.05). These results indicated that pasteurized α-LA could significantly promote the proliferation of HIEC cells, and its mechanism may be related to the increase of the proportion of dividing cells and the consequent inhibition of apoptosis. The supplementation of α-LA pasteurized at 72 ℃ for 15 s at a recommended concentration of 0.10 mg/mL to infant formulas may improve immune function in infants, which needs to be further explored.

Key words: α-lactalbumin, normal human intestinal epithelial cells, secondary structure, intestinal immunity