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Neutrophil Activation in Transitional Gravity.    AW. von Deutsch³, AS. Belton³, R Flowers⁴, J Wright⁸, C Williams⁹, NA. Silvestrov^3,6, DF. Paulsen⁴, BJ. Klement⁴ and DA. von Deutsch^3,6. Depts. of ³Pharmacology & Toxicology, ⁴Anatomy & Neurobiology and; ⁶Clinical Research Center, Morehouse School of Medicine, Atlanta, GA; ⁸Auburn University, ⁹UT Houston Health Sciences Center.

   The release of myeloperoxidase (MPO) from neutrophils represents one possible pathway for increasing the damage associated with space flight and recovery. Oxidative damage that occurs because of space flight might arise from many sources including radiation and the gravitational changes defined as transitional gravity (TG). The relationship existing between TG, oxidative stress and tissue damage is unclear. In particular, neutrophils generate reactive oxygen species in respond to stressful challenges such as those presented by TG. The purpose of this study was to determine whether TG would activate human neutrophils and thereby induce increased levels of oxidative stress. TG experiments were conducted aboard the NASA C-9 aircraft during parabolic flights. A flight-certified apparatus was used that consisted of a cell module (holding 5 cell cartridges) chamber and a multi-channeled peristaltic pump (N=5). Human neutrophils were isolated preflight from blood drawn from the faculty and student investigators (N=5). Neutrophils were counted, loaded into the cell cartridges and maintained at 37°C prior to flight. Half of the loaded cartridges were flown while the remainder served as the ground controls. Lipid peroxidation levels were significantly higher (248.1±50.6%) in the flight group than in the ground controls. However, MPO levels in flight neutrophils (6.7±5.8%) and that released into the media (19.6±11.3%) were both significantly less than levels observed in ground controls. Although the data only half supported our hypothesis-increased levels of cellular oxidative stress, it supported the literature with respect to decreased neutrophil function following space flight. This work was supported, in part, by NASA Grants NCC9-112 and NAG3-2611, NCRR 5P20RR11104, and MBRS Grant 506GM08248.