The State of the System of Signaling Pattern Recognition Receptors of Monocytes and Granulocytes in the Cosmonauts’ Peripheral Blood before and after Long-Term Flights on Board the International Space Station

Abstract

The system of signaling pattern recognition receptors was studied in eight cosmonauts at the ages from 35 to 56 years before and after long-term space flights (SFs) on board the International Space Station (ISS). The peripheral blood samples were analyzed for the content of monocytes and granulocytes that express the signaling pattern recognition Toll-like receptors (TLRs) with surface (TLR1, TLR2, TLR4, TLR5, and TLR6) and intracellular (TLR3, TLR8, and TLR9) localization. The serum concentration of basic ligands of TLR2 (HSP60) and TLR4 (HSP70 and HMGB1) were also measured. The results of the studies showed a growth of the HSP60, HSP70, and HMGB1 concentrations on the first day after long-term flight. The increase in the concentration of endogenous ligands was followed by a growth of the number of both monocytes and granulocytes that express the respective pattern recognition receptors, TLR2 and TLR4, in the overwhelming majority of the examined cosmonauts. Thesse relationships suggest that changes in the system of signaling pattern recognition receptors may be due to the prevailing influence of endogenous ligands in response to the effect of long-term spaceflight factors on the human body.