Modifications of immunological and neuro-endocrine parameters induced by antiorthostatic bed-rest in human healthy volunteers

Aim. Space flight has profound effects on immunological and neuroendocrine parameters. Microgravity plays a major role in the induction of these changes. The aim of the present study was the evaluation on ground of the effects induced by antigravitary posture on immune and neuroendocrine functions. Methods. Eight healthy male volunteers (mean age 24±1 years) were maintained in antigravitary posture (-10°) for 72 hours. Four of them were also maintained in supine posture for 72 hours as controls. The following immunological and neuroendocrine parameters have been analysed: peripheral white blood cells count, CD11b integrin expression and H₂O ₂ production by neutrophils, lymphocyte and monocyte phenotype, intracytoplasmic cytokine (IFN-γ, TNF-α and IL-4) pattern, lymphocyte proliferation to mitogens and antigens, cortisol, ACTH, catecholamines, GH, LH, prolactin and testosteron plasma levels. Results. In subjects maintained in antigravitary posture, norepinephrine, dopamine, cortisol, ACTH, GH and prolactin plasma levels increased whereas H ₂O₂ production by neutrophils, lymphocyte proliferation, NK cells number and intracytoplasmic IFN-γ expression decreased. No significant modifications were observed in subjects maintained in supine posture. Conclusion. The results of this study indicate that several neuroendocrine and immunological parameters are modulated by a prolonged antigravitary posture on ground and may negatively affect astronauts defenses against pathogens during space flights.