Amino Acid Metabolism and Immune Responsiveness in vitro in a Microgravity Analog

摘要

Nutrition is one of the major contributors to the health of space crews. Environmental changes associated with space flight (microgravity, radiation) may affect nutrient bioavailability as well as nutrient requirements. The objective of this study was to investigate amino acid metabolism and the mitogen-induced immune response in a model of the microgravity environment. Expression of activation marker (CD25) by T-cell helper (CD3+CD4+) and suppressor/cytotoxic (CD3+CD8+) subsets, cytokine secretion, and concentration of amino acids were assessed in cultures of peripheral blood mononuclear cells activated by a combination of lipopolysaccharide and phytohemagglutinin and subjected to clinorotation in a High Aspect Rotating Vessel (HARV). Significant decreases in mitogen-induced CD25 expression and cytokine secretion were observed in cultures subjected to the microgravity analog (HARV) compared to control cultures. Observed changes in immune system variables were associated with significantly greater concentrations of glutamine, isoleucine, leucine, lysine, ornithine, phenylalanine, tryptophan, and tyrosine concentrations in HARV cell cultures. The concentration of valine was significantly less in HARV cultures than in control cultures. Thus, physical stress factors associated with the modeled microgravity environment significantly affected metabolic processes and immune responsiveness in mitogen-activated cell culture.