Oral Pyruvate Effects on Dorsal Root Ganglia in Simulated Weightlessness Rats

Background: Long-term microgravity in spaceflight has been demonstrated with induction of multi-organ damage and dysfunction, including the dorsal root ganglia (DRG) injury. Present studies investigated protective effects of oral pyruvate in drinking water on lumbar 5 (L5) DRG tissues in rats subjected with hindlimb unweighting (HU). Methods: Sprague-Dawley male rats were randomly divided into four groups (N = 10): the control (CON) group, the suspension (SUS) group, the normal saline (SAL) group and the sodium pyruvate (PYR) group, respectively. Rats in the SUS, SAL and PYR groups were treated with simulated microgravity by HU with tail suspension for an 8-week period. Rats in the SAL and PYR groups were fed with normal saline and pyruvate saline, respectively. Histopathological hematoxylin-eosin (H&E) staining and Nissl-stained neurons as well as myelin sheath immunofluorescence examinations in L5 DRG tissues were carried out. The protein expression of glial cell line-derived neurotrophic factor (GDNF), glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE) and S100 calcium-binding protein B (S100B) as well as the levels of adenosine triphosphate (ATP) and adenosine triphosphatase (ATPase) were also determined after HU procedures. Results: Data showed that nerve tissues’ structure and function were robustly altered in L5 DRG of the SUS and SAL groups, whereas morphological changes were not significantly different between the PYR group and the CON group; levels of GDNF, GFAP, NSE and S100B were significantly changed in the SUS and SAL groups, but mostly preserved or overexpressed in group PYR following the HU injury. However, levels of ATP and ATPase were significantly retained, but still worse in the PYR group than in the CON group. The significance of oral pyruvate protection against DRG injury following the HU and the dose and formula of oral pyruvate solutions were discussed for the use of astronauts in space missions. Conclusions: This study indicates that oral pyruvate can effectively protect L5 DRG against the damage of pathological alterations and dysfunction induced by the HU in rats. Further investigations are needed.