Impact of a Model Used to Simulate Chronic Socio-Environmental Stressors Encountered during Spaceflight on Murine Intestinal Microbiota

Antidepressant-like effects of hyperoside on chronic stress-induced depressive-like behaviors in mice: Gut microbiota and short-chain fatty acids

BACKGROUND

The antidepressant effect of hyperoside (HYP), which is the main component of Hypericum perforatum, is not established. This study aimed to determine the effects of HYP on depression.

METHODS

The antidepressant-like effect of HYP was studied in mice induced by chronic restraint stress (CRS). The effects of HYP on behavior, inflammation, neurotransmitters, gut microbiota, and short-chain fatty acids (SCFAs) were studied in CRS mice.

RESULTS

HYP improved depressive-like behavior in mice induced by CRS. Nissl staining analysis showed that HYP improved neuronal damage in CRS mice. Western blot (WB) analysis showed that HYP increased the expression levels of BDNF and PSD95 in the hippocampus of CRS mice. The results of ELISA showed that HYP down-regulated the expression levels of IL-6, IL-1β, TNF-α, and CORT in the hippocampus, blood, and intestinal tissues of mice and up-regulated the expression levels of 5-HT and BDNF. Hematoxylin and eosin (HE) staining results indicate that HYP can improve the intestinal histopathological injury of CRS mice. The results of 16S rRNA demonstrated that HYP attenuated the dysbiosis of the gut microbiota of depressed mice, along with altering the concentration of SCFAs.

LIMITATIONS

In the present study, direct evidence that HYP improves depressive behaviors via gut microbiota and SCFAs is lacking, and only female mice were evaluated, which limits the understanding of the effects of HYP on both sexes.

CONCLUSIONS

HYP can improve CRS-induced depressive-like behaviors in mice, which is associated with regulating the gut microbiota and SCFAs concentration.

Dihydroartemisinin Protects Mice from CUMS-induced Depression-like Behaviors by Regulating Gut Microbes

Depression is one of the most common forms of psychopathology, which is associated with gut microbiota dysfunction. Dihydroartemisinin (DHA) has been shown to regulate gut microbiota and ameliorate neuropathies, but whether it can be used to treat depression remains unclear. Our study found that DHA treatment raised the preference for sugar water in chronic unpredictable mild stress (CUMS)-induced mice and reduced the immobility time in open field, forced swimming and tail suspension experiments, and promoted doublecortin expression. Additionally, DHA up-regulated the diversity and richness of intestinal microbiota in depression-like mice, and restored the abnormal abundance of microbiota induced by CUMS, such as Turicibacter, Lachnospiraceae, Erysipelotrichaceae, Erysipelatoclostridium, Eubacterium, Psychrobacter, Atopostipes, Ileibacterium, Coriobacteriacea, Alistipes, Roseburia, Rikenella, Eggerthellaceae, Ruminococcus, Tyzzerella, and Clostridia. Furthermore, KEGG pathway analysis revealed that gut microbiota involved in the process of depression may be related to glucose metabolism, energy absorption and transport, and AMPK signaling pathway. These results indicated that DHA may play a protective role in CUMS-induced depression by mediating gut-microbiome.

Long-term space missions' effects on the human organism: what we do know and what requires further research

Space has always fascinated people. Many years have passed since the first spaceflight, and in addition to the enormous technological progress, the level of understanding of human physiology in space is also increasing. The presented paper aims to summarize the recent research findings on the influence of the space environment (microgravity, pressure differences, cosmic radiation, etc.) on the human body systems during short-term and long-term space missions. The review also presents the biggest challenges and problems that must be solved in order to extend safely the time of human stay in space. In the era of increasing engineering capabilities, plans to colonize other planets, and the growing interest in commercial space flights, the most topical issues of modern medicine seems to be understanding the effects of long-term stay in space, and finding solutions to minimize the harmful effects of the space environment on the human body.

The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective

The physiological consequences of stress often manifest in the gastrointestinal tract. Traumatic or chronic stress is associated with widespread maladaptive changes throughout the gut, although comparatively little is known about the effects of acute stress. Furthermore, these stress-induced changes in the gut may increase susceptibility to gastrointestinal disorders and infection, and impact critical features of the neural and behavioural consequences of the stress response by impairing gut-brain axis communication. Understanding the mechanisms behind changes in enteric nervous system circuitry, visceral sensitivity, gut barrier function, permeability, and the gut microbiota following stress is an important research objective with pathophysiological implications in both neurogastroenterology and psychiatry. Moreover, the gut microbiota has emerged as a key aspect of physiology sensitive to the effects of stress. In this review, we focus on different aspects of the gastrointestinal tract including gut barrier function as well as the immune, humoral and neuronal elements involved in gut-brain communication. Furthermore, we discuss the evidence for a role of stress in gastrointestinal disorders. Existing gaps in the current literature are highlighted, and possible avenues for future research with an integrated physiological perspective have been suggested. A more complete understanding of the spatial and temporal dynamics of the integrated host and microbial response to different kinds of stressors in the gastrointestinal tract will enable full exploitation of the diagnostic and therapeutic potential in the fast-evolving field of host-microbiome interactions.

Gallnut Tannic Acid Exerts Anti-stress Effects on Stress-Induced Inflammatory Response, Dysbiotic Gut Microbiota, and Alterations of Serum Metabolic Profile in Beagle Dogs

Stress exposure is a potential threat to humans who live or work in extreme environments, often leading to oxidative stress, inflammatory response, intestinal dysbiosis, and metabolic disorders. Gallnut tannic acid (TA), a naturally occurring polyphenolic compound, has become a compelling source due to its favorable anti-diarrheal, anti-oxidative, anti-inflammatory, and anti-microbial activities. Thus, this study aimed to evaluate the anti-stress effects of gallnut TA on the stress-induced inflammatory response, dysbiotic gut microbiota, and alterations of serum metabolic profile using beagle models. A total of 13 beagle dogs were randomly divided into the stress (ST) and ST + TA groups. Dietary supplementation with TA at 2.5 g/kg was individually fed to each dog in the ST + TA group for 14 consecutive days. On day 7, all dogs were transported for 3 h from a stressful environment (days 1–7) to a livable site (days 8–14). In our results, TA relieved environmental stress-induced diarrheal symptoms in dogs and were shown to protect from myocardial injury and help improve immunity by serum biochemistry and hematology analysis. Also, TA inhibited the secretion of serum hormones [cortisol (COR), glucocorticoid (GC), and adrenocorticotropic hormone (ACTH)] and the expression of heat shock protein (HSP) 70 to protect dogs from stress-induced injury, thereby relieving oxidative stress and inflammatory response. Fecal 16S rRNA gene sequencing revealed that TA stimulated the growth of beneficial bacteria (Allobaculum, Dubosiella, Coriobacteriaceae_UCG-002, and Faecalibaculum) and suppressed the growth of pathogenic bacteria (Escherichia-Shigella and Streptococcus), thereby increasing fecal butyrate levels. Serum metabolomics further showed that phytosphingosine, indoleacetic acid, arachidonic acid, and biotin, related to the metabolism of sphingolipid, tryptophan, arachidonic acid, and biotin, respectively, could serve as potential biomarkers of stress exposure. Furthermore, Spearman’s correlation analysis showed strong relationships between the four potential serum biomarkers and differential bacteria. Overall, gallnut TA may be a potential prebiotic for the prevention and treatment of stress-induced metabolic disorders by targeting intestinal microbiota.

Understanding the Complexities and Changes of the Astronaut Microbiome for Successful Long-Duration Space Missions

During space missions, astronauts are faced with a variety of challenges that are unique to spaceflight and that have been known to cause physiological changes in humans over a period of time. Several of these changes occur at the microbiome level, a complex ensemble of microbial communities residing in various anatomic sites of the human body, with a pivotal role in regulating the health and behavior of the host. The microbiome is essential for day-to-day physiological activities, and alterations in microbiome composition and function have been linked to various human diseases. For these reasons, understanding the impact of spaceflight and space conditions on the microbiome of astronauts is important to assess significant health risks that can emerge during long-term missions and to develop countermeasures. Here, we review various conditions that are caused by long-term space exploration and discuss the role of the microbiome in promoting or ameliorating these conditions, as well as space-related factors that impact microbiome composition. The topics explored pertain to microgravity, radiation, immunity, bone health, cognitive function, gender differences and pharmacomicrobiomics. Connections are made between the trifecta of spaceflight, the host and the microbiome, and the significance of these interactions for successful long-term space missions.

Space omics research in Europe: Contributions, geographical distribution and ESA member state funding schemes

The European research community, via European Space Agency (ESA) spaceflight opportunities, has significantly contributed toward our current understanding of spaceflight biology. Recent molecular biology experiments include "omic" analysis, which provides a holistic and systems level understanding of the mechanisms underlying phenotypic adaptation. Despite vast interest in, and the immense quantity of biological information gained from space omics research, the knowledge of ESA-related space omics works as a collective remains poorly defined due to the recent exponential application of omics approaches in space and the limited search capabilities of pre-existing records. Thus, a review of such contributions is necessary to clarify and promote the development of space omics among ESA and ESA state members. To address this gap, in this review, we i) identified and summarized omics works led by European researchers, ii) geographically described these omics works, and iii) highlighted potential caveats in complex funding scenarios among ESA member states.

Jasmine Tea Attenuates Chronic Unpredictable Mild Stress-Induced Depressive-like Behavior in Rats via the Gut-Brain Axis

The number of depressed people has increased worldwide. Dysfunction of the gut microbiota has been closely related to depression. The mechanism by which jasmine tea ameliorates depression via the brain-gut-microbiome (BGM) axis remains unclear. Here, the effects of jasmine tea on rats with depressive-like symptoms via the gut microbiome were investigated. We first established a chronic unpredictable mild stress (CUMS) rat model to induce depressive symptoms and measured the changes in depression-related indicators. Simultaneously, the changes in gut microbiota were investigated by 16S rRNA sequencing. Jasmine tea treatment improved depressive-like behaviors and neurotransmitters in CUMS rats. Jasmine tea increased the gut microbiota diversity and richness of depressed rats induced by CUMS. Spearman’s analysis showed correlations between the differential microbiota (Patescibacteria, Firmicutes, Bacteroidetes, Spirochaetes, Elusimicrobia, and Proteobacteria) and depressive-related indicators (BDNF, GLP-1, and 5-HT in the hippocampus and cerebral cortex). Combined with the correlation analysis of gut microbiota, the result indicated that jasmine tea could attenuate depression in rats via the brain- gut-microbiome axis.

Semen Sojae Praeparatum alters depression-like behaviors in chronic unpredictable mild stress rats via intestinal microbiota

A large number of Chinese medical books present that Semen Sojae Praeparatum, a fermented food, possesses antidepressant effect, but the mechanism of this antidepressant effect remains largely unknown. This study aimed to explore the effect of Semen Sojae Praeparatum on rats with chronic unpredictable mild stress (CUMS)-induced depression. The results showed that Semen Sojae Praeparatum improved depression-like behaviors (negative preference of sugar water and increased swimming immobility time and time spent in the dark zone) and effectively reduced cell morphological changes in the dentate gyrus of the hippocampus in CUMS rats. In addition, Semen Sojae Praeparatum significantly promoted the contents of norepinephrine (NE), 5-hydroxytryptamine (5-HT), brain-derived neurotrophic factor (BDNF), and gamma-aminobutyric acid (GABA) in the hippocampus and the content of BDNF in the serum (p < 0.05). 16S rRNA sequencing analysis results showed that Semen Sojae Praeparatum increased the abundance of genus Ruminococcaceae_UCG-008 and decreased those of genera Lactobacillus and Bacteroides. Genus Ruminococcaceae_UCG-008 was positively correlated with GABA and BDNF levels in the hippocampus; genus Lactobacillus had a positive correlation with 5-HT; and genus Bacteroides had negative correlations with 5-HT, BDNF, and NE. In addition, Semen Sojae Praeparatum considerably decreased the concentration of short-chain fatty acids (SCFAs). These results indicated that Semen Sojae Praeparatum fermented by Rhizopus chinensis 12 and Bacillus sp. DU-106 alleviated the neurotransmitter levels and structural changes in the neuronal morphology of the hippocampus associated with the modulation of gut microbiota and SCFAs. Therefore, this study confirmed that Semen Sojae Praeparatum could alter depression and provide a theoretical basis for the investigation of the relationship between the microbiota-gut-brain axis and antidepressant.

Surface Properties of Parabacteroides distasonis and Impacts of Stress-Induced Molecules on Its Surface Adhesion and Biofilm Formation Capacities

The gut microbiota is a complex and dynamic ecosystem whose balance and homeostasis are essential to the host's well-being and whose composition can be critically affected by various factors, including host stress. Parabacteroides distasonis causes well-known beneficial roles for its host, but is negatively impacted by stress. However, the mechanisms explaining its maintenance in the gut have not yet been explored, in particular its capacities to adhere onto (bio)surfaces, form biofilms and the way its physicochemical surface properties are affected by stressing conditions. In this paper, we reported adhesion and biofilm formation capacities of 14 unrelated strains of P. distasonis using a steam-based washing procedure, and the electrokinetic features of its surface. Results evidenced an important inter-strain variability for all experiments including the response to stress hormones. In fact, stress-induced molecules significantly impact P. distasonis adhesion and biofilm formation capacities in 35% and 23% of assays, respectively. This study not only provides basic data on the adhesion and biofilm formation capacities of P. distasonis to abiotic substrates but also paves the way for further research on how stress-molecules could be implicated in P. distasonis maintenance within the gut microbiota, which is a prerequisite for designing efficient solutions to optimize its survival within gut environment.

Gravitational Experimental Platform for Animal Models, a New Platform at ESA's Terrestrial Facilities to Study the Effects of Micro- and Hypergravity on Aquatic and Rodent Animal Models

Using rotors to expose animals to different levels of hypergravity is an efficient means of understanding how altered gravity affects physiological functions, interactions between physiological systems and animal development. Furthermore, rotors can be used to prepare space experiments, e.g., conducting hypergravity experiments to demonstrate the feasibility of a study before its implementation and to complement inflight experiments by comparing the effects of micro- and hypergravity. In this paper, we present a new platform called the Gravitational Experimental Platform for Animal Models (GEPAM), which has been part of European Space Agency (ESA)’s portfolio of ground-based facilities since 2020, to study the effects of altered gravity on aquatic animal models (amphibian embryos/tadpoles) and mice. This platform comprises rotors for hypergravity exposure (three aquatic rotors and one rodent rotor) and models to simulate microgravity (cages for mouse hindlimb unloading and a random positioning machine (RPM)). Four species of amphibians can be used at present. All murine strains can be used and are maintained in a specific pathogen-free area. This platform is surrounded by numerous facilities for sample preparation and analysis using state-of-the-art techniques. Finally, we illustrate how GEPAM can contribute to the understanding of molecular and cellular mechanisms and the identification of countermeasures.