Pyridoxine and pancreatic acinar cells: transport physiology and effect on gene expression profile

Pyridoxine (vitamin B₆), an essential micronutrient for normal cell physiology, plays an important role in the function of the exocrine pancreas. Pancreatic acinar cells (PACs) obtain vitamin B₆ from circulation, but little is known about the mechanism involved in the uptake process; limited information also exists on the effect of pyridoxine availability on the gene expression profile in these cells. We addressed both these issues in the current investigation using mouse-derived pancreatic acinar 266-6 cells (PAC 266-6) and human primary PACs (hPACs; obtained from organ donors), together with appropriate physiological and molecular (RNA-Seq) approaches. The results showed [³H]pyridoxine uptake to be 1) pH and temperature (but not Na⁺) dependent, 2) saturable as a function of concentration, 3) cis-inhibited by unlabeled pyridoxine and its close structural analogs, 4) trans-stimulated by unlabeled pyridoxine, 5) regulated by an intracellular Ca²⁺/calmodulin-mediated pathway, 6) adaptively-regulated by extracellular substrate (pyridoxine) availability, and 7) negatively impacted by exposure to cigarette smoke extract. Vitamin B₆ availability was found (by means of RNA-Seq) to significantly (FDR < 0.05) modulate the expression profile of many genes in PAC 266-6 cells (including those that are relevant to pancreatic health and development). These studies demonstrate, for the first time, the involvement of a regulatable and specific carrier-mediated mechanism for pyridoxine uptake by PACs; the results also show that pyridoxine availability exerts profound effects on the gene expression profile in mammalian PACs.