Butyric Acid and Leucine Induce α-Defensin Secretion from Small Intestinal Paneth Cells.

The intestine not only plays a role in fundamental processes in digestion and nutrient absorption, but it also has a role in eliminating ingested pathogenic bacteria and viruses. Paneth cells, which reside at the base of small intestinal crypts, secrete α-defensins and contribute to enteric innate immunity through potent microbicidal activities. However, the relationship between food factors and the innate immune functions of Paneth cells remains unknown. Here, we examined whether short-chain fatty acids and amino acids induce α-defensin secretion from Paneth cells in the isolated crypts of small intestine. Butyric acid and leucine elicit α-defensin secretion by Paneth cells, which kills Salmonella typhimurium. We further measured Paneth cell secretion in response to butyric acid and leucine using enteroids, a three-dimensional ex vivo culture system of small intestinal epithelial cells. Paneth cells expressed short-chain fatty acid receptors, Gpr41, Gpr43, and Gpr109a mRNAs for butyric acid, and amino acid transporter Slc7a8 mRNA for leucine. Antagonists of Gpr41 and Slc7a8 inhibited granule secretion by Paneth cells, indicating that these receptor and transporter on Paneth cells induce granule secretion. Our findings suggest that Paneth cells may contribute to intestinal homeostasis by secreting α-defensins in response to certain nutrients or metabolites.

Function of SLC7A7 in T-Cell Acute Lymphoblastic Leukemia.

BACKGROUND/AIMS: Y+LAT1 protein, encoded by the SLC7A7 gene (a member of the SLC7 family), forms the cationic amino acid transport system y+L (system y+L). This system transports cationic amino acids such as arginine and lysine out of the cell. Arginine, in particular, is critical for T-cell activation and function in the immune response. METHODS: We analyzed the role of the SLC7A7 gene in the cellular activities of Jurkat cells, specifically the cell cycle and cell proliferation, apoptosis, migration, and invasion. Cell proliferation was assessed using the Cell Counting Kit-8. Apoptosis and the cell cycle were determined with a FACSCalibur flow cytometer. A Transwell chamber was used to measure cell invasion and migration. RESULTS: The proliferative ability of Jurkat cells was not significantly altered by transfection with SLC7A7 overexpression vectors. However, SLC7A7 overexpression significantly decreased the percentage of apoptotic Jurkat cells (P = 0.007) but significantly increased the proportion of G1 phase cells (P = 0.029) and cell migration (P < 0.001) and invasion (P < 0.001). Knockdown of SLC7A7 increased the cell apoptosis rate (P = 0.006) but decreased the G1 phase ratio (P = 0.002) and cell migration (P < 0.001) and invasion (P < 0.001). CONCLUSIONS: SLC7A7 plays a significant role in the pathogenesis of T-cell acute lymphoblastic leukemia.