[80]

Concomitant Cytokine Secretion and Amino Acid Metabolism Alterations in Human Leucocytes Subjected to Microgravity Analog and  Cortisol Treatment In Vitro.       P.N.Uchakin¹, S.M.Smith², O.N.Uchakina¹, and B.W.Tobin¹. ¹Mercer University School of Medicine, Macon, GA; ²NASA Johnson Space Center, Houston, TX.

   Space flight is complex environment and consists of many physical and physiological stress-factors which are able to diminish immune responsiveness. The objective of this work was to investigate the underlying metabolic mechanisms of stress-induced immune suppression using High Aspect Ratio Vessel (HARV) tissue culture as a microgravity (10^‑2g) analog. Peripheral blood mononuclear cells from 6 healthy donors were activated with LPS+PHA mixture and cultured in the HARV or in a 2-dimensional static (STAT) environment for 48h in a 5% CO₂, 95% humidity atmosphere, at 37^OC. Additionally, cell cultures were treated with sub- (10^-8M) and supra-physiological  (10^-6M) “stress” doses of hydrocortisone (HCS). Secretion of interleukin(IL)-2, interferon (IFN)-γ, IL-4, IL-10, and concentrations of 41 amino-metabolites were assessed in the supernatants. Two-way RM ANOVA with post hoc Tukey test was used to determine statistical significance (p<0.05). The level of all cytokines was significantly (P<0.05) lower in HARV environment. This effect was HCS-depended only for IFN-γ and IL-4 (power of performed tests with α=0.05: 0.953 and 0.8 correspondingly). Concurrently, significantly higher concentrations of ala, arg, asn, asp, gln, gly, tyr, his, ile, leu, lys, phe, try, and orn were registered in HARV. In contrast, concentration of arg was lower in HARV compare to STAT conditions. The concentration of hys in HARV was dependent on HCS treatment (power 0.8; α=0.05). Physical and endocrine stress-factors of microgravity are able to significantly alter metabolism of amino acids and immune competence in vitro. Understanding the cause and implications of these alterations will help to develop nutritional or other countermeasures for stress-induced immune suppression. Funded in part by NIH R15 GM62795-03 and NASA NSBRI through Cooperative Agreement NCC 9‑58 with NASA.