Effects of microgravity on living organisms revealed from space flight experiments using the nematode C. elegans.

Abstract

In spaceflight and simulated microgravity experiments (3D clinostat), we found that the gene expression of dopamine metabolic enzyme decreases reproducibly compared to 1 G control in C. elegans. Exogenous dopamine application increases the gene expression strongly suggesting that it is negatively regulated in response to endogenous dopamine levels. Therefore, we think the working hypothesis that "dopamine is reduced in the microgravity environment", and in December 2018 we performed another C. elegans spaceflight experiment with collaboration of UK research team as Molecular Muscle Experiment. As a result, the spaceflown C. elegans showed a marked decrease in endogenous dopamine levels, similar to the case of ground 3D clinostat culture. Similarly, in Rossian biosatellite BION-M1 experiment, in addition to loss of bone and muscle mass, the rate-limiting enzyme of the dopamine synthesis and its degradation enzyme were also reduced in striatum of spaceflown mice. These results strongly suggest that the microgravity may affect metabolism of the neurotransmitter dopamine across species. In this presentation, we also mention the action mechanism of microgravity on dopamine reduction.