Simulated microgravity affects semicarbazide-sensitive amine oxidase expression in recombinant Escherichia coli by HPLC-ESI-QQQ analysis

Accumulation of formaldehyde causes motor deficits in an in vivo model of hindlimb unloading

During duration spaceflight, or after their return to earth, astronauts have often suffered from gait instability and cerebellar ataxia. Here, we use a mouse model of hindlimb unloading (HU) to explore a mechanism of how reduced hindlimb burden may contribute to motor deficits. The results showed that these mice which have experienced HU for 2 weeks exhibit a rapid accumulation of formaldehyde in the gastrocnemius muscle and fastigial nucleus of cerebellum. The activation of semicarbazide-sensitive amine oxidase and sarcosine dehydrogenase induced by HU-stress contributed to formaldehyde generation and loss of the abilities to maintain balance and coordinate motor activities. Further, knockout of formaldehyde dehydrogenase (FDH^-/-) in mice caused formaldehyde accumulation in the muscle and cerebellum that was associated with motor deficits. Remarkably, formaldehyde injection into the gastrocnemius muscle led to gait instability; especially, microinfusion of formaldehyde into the fastigial nucleus directly induced the same symptoms as HU-induced acute ataxia. Hence, excessive formaldehyde damages motor functions of the muscle and cerebellum.

Simulated microgravity alters the expression of plasma SSAO and its enzymatic activity in healthy rats and increases the mortality in high-fat diet/streptozotocin-induced diabetes

Semicarbazide-sensitive amine oxidase (SSAO) activity is known to be associated with certain pathologies including diabetes. In this study, SSAO expression and enzymatic activity in blood plasma of healthy rats were significantly upregulated under simulated microgravity (SMG) condition. Significant mortality was observed in SMG group of diabetic rats. Results indicate that microgravity might increase the risks of SSAO-associated alterations.

EcAMSat spaceflight measurements of the role of σs in antibiotic resistance of stationary phase Escherichia coli in microgravity

We report the results of the EcAMSat (Escherichia coli Antimicrobial Satellite) autonomous space flight experiment, investigating the role of σ^s in the development of antibiotic resistance in uropathogenic E. coli (UPEC) in microgravity (µ-g). The presence of σ^s, encoded by the rpoS gene, has been shown to increase antibiotic resistance in Earth gravity, but it was unknown if this effect occurs in µ-g. Two strains, wildtype (WT) UPEC and its isogenic ΔrpoS mutant, were grown to stationary phase aboard EcAMSat, an 11-kg small satellite, and in a parallel ground-based control experiment; cell growth rates for the two strains were found to be unaltered by µ-g. After starvation for over 24 h, stationary-phase cells were incubated with three doses of gentamicin (Gm), a common treatment for urinary tract infections (which have been reported in astronauts). Cellular metabolic activity was measured optically using the redox-based indicator alamarBlue (aB): both strains exhibited slower metabolism in µ-g, consistent with results from previous smallsat missions. The results also showed that µ-g did not enhance UPEC resistance to Gm; in fact, both strains were more susceptible to Gm in µ-g. It was also found, via a second ground-control experiment, that multi-week storage in the payload hardware stressed the cells, potentially obscuring small differential effects of the antibiotic between WT and mutant and/or between µ-g and ground. Overall, results showed that the ∆rpoS mutant was 34-37% less metabolically active than the WT for four different sets of conditions: ground without Gm, ground with Gm; µ-g without Gm, µ-g with Gm. We conclude therefore that the rpoS gene and its downstream products are important therapeutic targets for treating bacterial infections in space, much as they are on the ground.

Development of a HPLC-FL method to determine benzaldehyde after derivatization with N-acetylhydrazine acridone and its application for determination of semicarbazide-sensitive amine oxidase activity in human serum

A novel fluorescence labeling reagent N-acetylhydrazine acridone (AHAD) was designed and synthesized. A highly sensitive high performance liquid chromatography (HPLC) method coupled with fluorescence detection to determine benzaldehyde after derivatization with AHAD was developed. Optimum derivatization was obtained at 40 °C for 30 min with trichloroacetic acid as catalyst. Benzaldehyde derivative was separated on a reversed-phase SB-C18 column in conjunction with a gradient elution and detected by fluorescence detection at excitation and emission wavelengths of 371 nm and 421 nm. The established method exhibited excellent linearity over the injected amount of benzaldehyde of 0.003 to 5 nmol mL⁻¹. The method was successfully applied to the determination of serum semicarbazide-sensitive amine oxidase (SSAO) activity in humans. SSAO is a significant biomarker because serum SSAO activity is elevated in patients with Alzheimer's disease, vascular disorders, heart disease and diabetes mellitus. It was demonstrated that the SSAO activity of the hyperglycemic group (60 ± 4 nmol mL⁻¹ h⁻¹) was significantly higher than that of normal blood sugar group (44 ± 4 nmol mL⁻¹ h⁻¹) with P < 0.05.

A highly sensitive HPLC-FL method to determine semicarbazide-sensitive amine oxidase activity was developed utilizing AHAD as the novel fluorescence labeling reagent.

Simulated Microgravity Promotes Cell Apoptosis Through Suppressing Uev1A/TICAM/TRAF/NF-κB-Regulated Anti-Apoptosis and p53/PCNA- and ATM/ATR-Chk1/2-Controlled DNA-Damage Response Pathways

Microgravity has been known to induce cell death. However, its underlying mechanism is less studied. In this study, BL6-10 melanoma cells were cultured in flasks under simulated microgravity (SMG). We examined cell apoptosis, and assessed expression of genes associated with apoptosis and genes regulating apoptosis in cells under SMG. We demonstrate that SMG induces cell morphological changes and microtubule alterations by confocal microscopy, and enhances apoptosis by flow cytometry, which was associated with up- and down-regulation of pro-apoptotic and anti-apoptotic genes, respectively. Moreover, up- and down-regulation of pro-apoptotic (Caspases 3, 7, 8) and anti-apoptotic (Bcl2 and Bnip3) molecules was confirmed by Western blotting analysis. Western blot analysis also indicates that SMG causes inhibition of an apoptosis suppressor, pNF-κB-p65, which is complemented by the predominant localization of NF-κB-p65 in the cytoplasm. SMG also reduces expression of molecules regulating the NF-κB pathway including Uev1A, TICAM, TRAF2, and TRAF6. Interestingly, 10 DNA repair genes are down-regulated in cells exposed to SMG, among which down-regulation of Parp, Ercc8, Rad23, Rad51, and Ku70 was confirmed by Western blotting analysis. In addition, we demonstrate a significant inhibition of molecules involved in the DNA-damage response, such as p53, PCNA, ATM/ATR, and Chk1/2. Taken together, our work reveals that SMG promotes the apoptotic response through a combined modulation of the Uev1A/TICAM/TRAF/NF-κB-regulated apoptosis and the p53/PCNA- and ATM/ATR-Chk1/2-controlled DNA-damage response pathways. Thus, our investigation provides novel information, which may help us to determine the cause of negative alterations in human physiology occurring at spaceflight environment. J. Cell. Biochem. 117: 2138-2148, 2016. © 2016 Wiley Periodicals, Inc.

Transcriptome profiling of peanut (Arachis hypogaea) gynophores in gravitropic response

Peanut (Arachis hypogaea L.) produces flowers aerially, but the fruit develops underground. This process is mediated by the gynophore, which always grows vertically downwards. The genetic basis underlying gravitropic bending of gynophores is not well understood. To identify genes related to gynophore gravitropism, gene expression profiles of gynophores cultured in vitro with tip pointing upward (gravitropic stimulation sample) and downward (control) at both 6 and 12h were compared through a high-density peanut microarray. After gravitropic stimulation, there were 174 differentially expressed genes, including 91 upregulated and 83 downregulated genes at 6h, and 491 differentially expressed genes including 129 upregulated and 362 downregulated genes at 12h. The differentially expressed genes identified were assigned to 24 functional categories. Twenty pathways including carbon fixation, aminoacyl-tRNA biosynthesis, pentose phosphate pathway, starch and sucrose metabolism were identified. The quantitative real-time PCR analysis was performed for validation of microarray results. Our study paves the way to better understand the molecular mechanisms underlying the peanut gynophore gravitropism.

Comparative proteomic analysis of human SH-SY5Y neuroblastoma cells under simulated microgravity

Microgravity is one of the most important features in spaceflight. Previous evidence has shown that neurophysiological impairment signs occurred under microgravity. The present study was undertaken to explore the change in protein abundance in human SH-SY5Y neuroblastoma cells that were grown in a microgravity environment. The comparative proteomic method based on the (18)O labeling technique was applied to investigate the up-regulated proteins and down-regulated proteins in SH-SY5Y under simulated microgravity. Twenty-two differentially abundant proteins were quantified in human SH-SY5Y neuroblastoma cells. The cell microfilament network was disrupted under simulated microgravity, which was determined by the immunocytochemistry. The concentration of reactive oxygen species, malondialdehyde, and free Ca2+ ion significantly increased, and the level of ATP significantly decreased under simulated microgravity. However, there was no obvious cell apoptosis observed under simulated microgravity. These results provide new molecular evidence for the change in protein abundance in SH-SY5Y cells under simulated microgravity, which might unfold biological mechanisms and the development of effective countermeasures to deal with microgravity-related neurological problems. We believe that the state-of-the-art proteomic assay may be a means by which aerospace scientists will begin to understand the underlying mechanisms of space life activities at the protein level.