Differential effects of hypergravity on immune dysfunctions induced by simulated microgravity

Microgravity (mu g) is among the major stressors in space causing immune cell dysregulations. These are frequently expressed as increased pro-inflammatory states of monocytes and reduced activation capacities in T cells. Hypergravity (as artificial gravity) has shown to have beneficial effects on the musculoskeletal and cardiovascular system both as a countermeasure option for mu g-related deconditioning and as gravitational therapy on Earth. Since the impact of hypergravity on immune cells is sparsely explored, we investigated if an application of mild mechanical loading of 2.8 g is able to avoid or treat mu g-mediated immune dysregulations. For this, T cell and monocyte activation states and cytokine pattern were first analyzed after whole blood antigen incubation in simulated mu g (s-mu g) by using the principle of fast clinorotation or in hypergravity. Subsequent hypergravity countermeasure approaches were run at three different sequences: one preconditioning setting, where 2.8 g was applied before s-mu g exposure and two therapeutic approaches in which 2.8 g was set either intermediately or at the end of s-mu g. In single g-grade exposure experiments, monocyte pro-inflammatory state was enhanced in s-mu g and reduced in hypergravity, whereas T cells displayed reduced activation when antigen incubation was performed in s-mu g. Hypergravity application in all three sequences did not alleviate the increased pro-inflammatory potential of monocytes. However, in T cells the preconditioning approach restored antigen-induced CD69 expression and IFN gamma secretion to 1 g control values and beyond. This in vitro study demonstrates a proof of concept that mild hypergravity is a gravitational preconditioning option to avoid adaptive immune cell dysfunctions induced by (s-)mu g and that it may act as a booster of immune cell functions.

Automated summary

Microgravity is a major stressor in space that affects immune cell function. Hypergravity has been shown to have beneficial effects on the musculoskeletal and cardiovascular system. This study investigated whether mild mechanical loading could prevent immune dysregulation caused by microgravity.