Hindlimb unloading, a physiological model of microgravity, modifies the murine bone marrow IgM repertoire in a similar manner as aging but less strongly.

BACKGROUND: The spaceflight environment is an extreme environment that affects the immune system of approximately 50% of astronauts. With planned long-duration missions, such as the deployment of the Lunar Gateway and possible interplanetary missions, it is mandatory to determine how all components of the immune system are affected, which will allow the establishment of countermeasures to preserve astronaut health. However, despite being an important component of the immune system, antibody-mediated humoral immunity has rarely been investigated in the context of the effects of the space environment. It has previously been demonstrated that 30 days aboard the BION-M1 satellite and 21 days of hindlimb unloading (HU), a model classically used to mimic the effects of microgravity, decrease murine B lymphopoiesis. Furthermore, modifications in B lymphopoiesis reported in young mice subjected to 21 days of HU were shown to be similar to those observed in aged mice (18-22 months). Since the primary antibody repertoire composed of IgM is created by V(D) J recombination during B lymphopoiesis, the objective of this study was to assess the degree of similarity between changes in the bone marrow IgM repertoire and in the V(D)J recombination process in 2.5-month-old mice subjected to 21 days of HU and aged (18 months) mice. RESULTS: We found that in 21 days, HU induced changes in the IgM repertoire that were approximately 3-fold less than those in aged mice, which is a rapid effect. Bone remodeling and epigenetics likely mediate these changes. Indeed, we previously demonstrated a significant decrease in tibial morphometric parameters from day 6 of HU and a progressive reduction in these parameters until day 21 of HU, and it has been shown that age and microgravity induce epigenetic changes. CONCLUSION: These data reveal novel immune changes that are akin to advanced aging and underline the importance of studying the effects of spaceflight on antibody-mediated humoral immunity.

Simulated Microgravity Disrupts Nuclear Factor κB Signaling and Impairs Murine Dendritic Cell Phenotype and Function.

During spaceflights, astronauts face different forms of stress (e.g., socio-environmental and gravity stresses) that impact physiological functions and particularly the immune system. In this context, little is known about the effect of such stress on dendritic cells (DCs). First, we showed that hypergravity, but not chronic ultra-mild stress, a socio-environmental stress, induced a less mature phenotype characterized by a decreased expression of MHCII and co-stimulatory molecules. Next, using the random positioning machine (RPM), we studied the direct effects of simulated microgravity on either splenic DCs or Flt-3L-differentiated bone marrow dendritic cells (BMDCs). Simulated microgravity was found to reduce the BM-conventional DC (cDC) and splenic cDC activation/maturation phenotype. Consistent with this, BMDCs displayed a decreased production of pro-inflammatory cytokines when exposed to microgravity compared to the normogravity condition. The induction of a more immature phenotype in microgravity than in control DCs correlated with an alteration of the NFκB signaling pathway. Since the DC phenotype is closely linked to their function, we studied the effects of microgravity on DCs and found that microgravity impaired their ability to induce naïve CD4 T cell survival, proliferation, and polarization. Thus, a deregulation of DC function is likely to induce immune deregulation, which could explain the reduced efficiency of astronauts' immune response.

Characterization of Biological Properties of Individual Phenolamides and Phenolamide-Enriched Leaf Tomato Extracts.

Resistance to conventional treatments renders urgent the discovery of new therapeutic molecules. Plant specialized metabolites such as phenolamides, a subclass of phenolic compounds, whose accumulation in tomato plants is mediated by the biotic and abiotic environment, constitute a source of natural molecules endowed with potential antioxidant, antimicrobial as well as anti-inflammatory properties. The aim of our study was to investigate whether three major phenolamides found in Tuta absoluta-infested tomato leaves exhibit antimicrobial, cytotoxic and/or anti-inflammatory properties. One of them, N1,N5,N14-tris(dihydrocaffeoyl)spermine, was specifically synthesized for this study. The three phenolamides showed low to moderate antibacterial activities but were able to counteract the LPS pro-inflammatory effect on THP-1 cells differentiated into macrophages. Extracts made from healthy but not T. absoluta-infested tomato leaf extracts were also able to reduce inflammation using the same cellular approach. Taken together, these results show that phenolamides from tomato leaves could be interesting alternatives to conventional drugs.

Screening of Anti-Inflammatory Activity and Metabolomics Analysis of Endophytic Fungal Extracts; Identification and Characterization of Perylenequinones and Terpenoids from the Interesting Active Alternaria Endophyte.

Patients suffering from inflammatory chronic diseases are classically treated with anti-inflammatory drugs but unfortunately are highly susceptible to becoming resistant to their treatment. Finding new drugs is therefore crucial and urgent and research on endophytic fungi is a promising way forward. Endophytic fungi are microorganisms that colonize healthy plants and live within their intercellular tissues. They are able to produce a large variety of secondary metabolites while allowing their host to stay healthy. A number of these molecules are endowed with antioxidant or antimicrobial as well as cytotoxic properties, making them very interesting/promising in the field of human therapy. The aim of our study was to investigate whether extracts from five endophytic fungi isolated from plants are endowed with anti-inflammatory activity. Extracts of the endophytic fungi Alternaria alternata from Calotropis procera leaves and Aspergillus terreus from Trigonella foenum-graecum seeds were able to counteract the lipopolysaccharide (LPS) pro-inflammatory effect on THP-1 cells differentiated into macrophages. Moreover, they were able to induce an anti-inflammatory state, rendering them less sensitive to the LPS pro-inflammatory stimulus. Taken together, these results show that these both endophytic fungi could be interesting alternatives to conventional anti-inflammatory drugs. To gain more detailed knowledge of their chemical richness, phytochemical analysis of the ethyl acetate extracts of the five endophytic fungi studied was performed using HPTLC, GC-MS and LC-MS with the Global Natural Products Social (GNPS) platform and the MolNetEnhancer tool. A large family of metabolites (carboxylic acids and derivatives, steroid derivatives, alkaloids, hydroxyanthraquinones, valerolactones and perylenequinones) were detected. The purification of endophytic fungus extract of Alternaria alternate, which diminished TNF-α production of 66% at 20 µg/mL, incubated one hour before LPS addition, led to the characterization of eight pure compounds. These molecules are altertoxins I, II, III, tricycloalternarenes 3a, 1b, 2b, anthranilic acid, and o-acetamidobenzoic acid. In the future, all these pure compounds will be evaluated for their anti-inflammatory activity, while altertoxin II has been shown in the literature as the most active mycotoxin in terms of anti-inflammatory activity.

The ß 1 -Adrenergic Receptor Contributes to Sepsis-Induced Immunosuppression Through Modulation of Regulatory T-Cell Inhibitory Function.

OBJECTIVES: Although cardiovascular benefits of ß 1 -adrenergic receptor blockade have been described in sepsis, little is known about its impact on the adaptive immune response, specifically CD4 T cells. Herein, we study the effects of ß 1 -adrenergic receptor modulation on CD4 T-cell function in a murine model of sepsis. DESIGN: Experimental study. SETTING: University laboratory. SUBJECTS: C57BL/6 mice. INTERVENTIONS: High-grade sepsis was induced by cecal ligation and puncture in wild-type mice (ß 1+/+ ) with or without esmolol (a selective ß 1 -adrenergic receptor blocker) or in ß 1 -adrenergic receptor knockout mice (ß 1-/- ). At 18 hours after surgery, echocardiography was performed with blood and spleen collected to analyze lymphocyte function. MEASUREMENTS AND MAIN RESULTS: At 18 hours, ß 1+/+ cecal ligation and puncture mice exhibited characteristics of high-grade sepsis and three surrogate markers of immunosuppression, namely decreased splenic CD4 T cells, reduced CD4 T-cell proliferation, and increased regulatory T lymphocyte cell proportions. Pharmacologic and genetic ß 1 -adrenergic receptor blockade reversed the impact of sepsis on CD4 T and regulatory T lymphocyte proportions and maintained CD4 T-cell proliferative capacity. ß 1 -adrenergic receptor blocked cecal ligation and puncture mice also exhibited a global decrease in both pro- and anti-inflammatory mediators and improved in vivo cardiovascular efficiency with maintained cardiac power index despite the expected decrease in heart rate. CONCLUSIONS: ß 1 -adrenergic receptor activation enhances regulatory T lymphocyte inhibitory function and thus contributes to sepsis-induced immunosuppression. This can be attenuated by ß 1 -adrenergic receptor blockade, suggesting a potential immunoregulatory role for this therapy in the management of sepsis.

Chronic Hypergravity Induces a Modification of Histone H3 Lysine 27 Trimethylation at TCRß Locus in Murine Thymocytes.

Gravity changes are major stressors encountered during spaceflight that affect the immune system. We previously evidenced that hypergravity exposure during gestation affects the TCRß repertoire of newborn pups. To identify the mechanisms underlying this observation, we studied post-translational histone modifications. We first showed that among the four studied post-translational histone H3 modifications, only lysine 27 trimethylation (H3K27me3) is downregulated in the thymus of mice exposed to 2× g for 21 days. We then asked whether the TCRß locus chromatin structure is altered by hypergravity exposure. ChIP studies performed on four Vß segments of the murine double-negative SCIET27 thymic cell line, which corresponds to the last maturation stage before V(D)J recombination, revealed increases in H3K27me3 after 2× g exposure. Finally, we evaluated the implication for the EZH2 methyltransferase in the regulation of the H3K27me3 level at these Vß segments by treating SCIET27 cells with the GSK126-specific inhibitor. These experiments showed that the downregulation of H3K27me3 contributes to the regulation of the Vß germline transcript expression that precedes V(D)J recombination. These data show that modifications of H3K27me3 at the TCRß locus likely contribute to an explanation of why the TCR repertoire is affected by gravity changes and imply, for the first time, EZH2 in the regulation of the TCRß locus chromatin structure.

Antioxidant Supplementation Does Not Affect Bone Turnover Markers During 60 Days of 6° Head-Down Tilt Bed Rest: Results from an Exploratory Randomized Controlled Trial.

BACKGROUND: Immobilization and related oxidative stress are associated with bone loss. Antioxidants like polyphenols, omega-3 fatty acids, vitamins, and micronutrients may mitigate these negative effects on bone metabolism through scavenging of free radicals. OBJECTIVES: We hypothesized that antioxidant supplementation during 60 days of 6° head-down tilt bed rest (HDBR) would reduce bone resorption and increase bone formation compared to nonsupplemented controls. METHODS: This exploratory randomized, controlled, single-blind intervention study conducted in a parallel design included 20 healthy male volunteers (age, 34 ± 8 years; weight, 74 ± 6 kg). The study consisted of a 14-day adaptation phase [baseline data collection (BDC)], followed by 60 days of HDBR and a 14-day recovery period (R). In the antioxidant group, volunteers received an antioxidant cocktail (741 mg/d polyphenols, 2.1 g/d omega-3 fatty acids, 168 mg/d vitamin E, and 80 µg/d selenium) with their daily meals. In the control group, volunteers received no supplement. Based on their body weight, all volunteers received an individually tailored and strictly controlled diet, consistent with DRIs. We analyzed biomarkers of calcium homeostasis, bone formation, and bone resorption during BDC, HDBR, and R, as well as for 30 days after the end of HDBR. Data were analyzed by linear mixed models. RESULTS: The antioxidant supplement did not affect serum calcium, parathyroid hormone, urinary C-telopeptide of type I collagen (CTX), urinary N-telopeptide of type I collagen, serum ß-C-telopeptide of type I collagen (ß-CTX), bone alkaline phosphatase, aminoterminal propeptide of type I collagen, osteocalcin, or urinary calcium excretion. In both groups, typical bed rest-related changes were observed. CONCLUSIONS: Supplementation of an antioxidant cocktail to a diet matching the DRIs did not affect bone resorption or formation during 60 days of HDBR in healthy young men. This trial was registered at clinicaltrials.gov as NCT03594799.

Plasticity of the human IgM repertoire in response to long-term spaceflight.

Immune dysregulation is among the main adverse outcomes of spaceflight. Despite the crucial role of the antibody repertoire in host protection, the effects of spaceflight on the human antibody repertoire are unknown. Consequently, using high-throughput sequencing, we examined the IgM repertoire of five cosmonauts 25 days before launch, after 64 ± 11 and 129 ± 20 days spent on the International Space Station (ISS), and at 1, 7, and 30 days after landing. This is the first study of this kind in humans. Our data revealed that the IgM repertoire of the cosmonauts was different from that of control subjects (n = 4) prior to launch and that two out the five analyzed cosmonauts presented significant changes in their IgM repertoire during the mission. These modifications persisted up to 30 days after landing, likely affected the specificities of IgM binding sites, correlated with changes in the V(D)J recombination process responsible for creating antibody genes, and coincided with a higher stress response. These data confirm that the immune system of approximately half of the astronauts who spent 6 months on the ISS is sensitive to spaceflight conditions, and reveal individual responses indicating that personalized approaches should be implemented during future deep-space exploration missions that will be of unprecedented durations.

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.

Identification and Capture of Phenolic Compounds from a Rapeseed Meal Protein Isolate Production Process By-Product by Macroporous Resin and Valorization Their Antioxidant Properties.

In this study, phenolic compounds from an aqueous protein by-product from rapeseed meal (RSM) were identified by HPLC-DAD and HPLC-ESI-MS, including sinapine, sinapic acid, sinapoyl glucose, and 1,2-di-sinapoyl gentibiose. The main phenolic compound in this by-product was sinapine. We also performed acid hydrolysis to convert sinapine, and sinapic acid derivatives present in the permeate, to sinapic acid. The adsorption of phenolic compounds was investigated using five macroporous resins, including XAD4, XAD7, XAD16, XAD1180, and HP20. Among them, XAD16 showed the highest total phenolic contents adsorption capacities. The adsorption behavior of phenolic compounds was described by pseudo-second-order and Langmuir models. Moreover, thermodynamics tests demonstrated that the adsorption process of phenolic compounds was exothermic and spontaneous. The highest desorption ratio was obtained with 30% (v/v) and 70% (v/v) ethanol for sinapine and sinapic acid, respectively, with a desorption ratio of 63.19 ± 0.03% and 94.68 ± 0.013%. DPPH and ABTS tests revealed that the antioxidant activity of the hydrolyzed fraction was higher than the non-hydrolyzed fraction and higher than the one of vitamin C. Antioxidant tests demonstrated that these phenolic compounds could be used as natural antioxidants, which can be applied in the food industry.

Socioenvironmental stressors encountered during spaceflight partially affect the murine TCR-ß repertoire and increase its self-reactivity.

Spaceflights are known to affect the immune system. In a previous study, we demonstrated that hypergravity exposure during murine development modified 85% of the T-cell receptor (TCR)-ß repertoire. In this study, we investigated whether socioenvironmental stressors encountered during space missions affect T lymphopoiesis and the TCR-ß repertoire. To address this question, pregnant mice were subjected throughout gestation to chronic unpredictable mild stressors (CUMS), a model used to mimic socioenvironmental stresses encountered during space missions. Then, newborn T lymphopoiesis and the TCR-ß repertoire were studied by flow cytometry and high-throughput sequencing, respectively. No change in thymocyte maturation or TCR expression were noted. TCR-ß repertoire analysis revealed that 75% of neonate TCR-ß sequences resulted from the expression of 3 variable (V)ß segments and that this core repertoire was not affected by CUMS. However, the minor repertoire, representing 25% of the global repertoire, was sensitive to CUMS exposure. We also showed that the variable (diversity) joining [V(D)J] recombination process was unlikely to be affected. Finally, we noted that the CUMS neonatal minor repertoire was more self-reactive than the one of control pups. These findings show that socioenvironmental stressors such as those encountered during space missions affect a fraction (25%) of the TCR-ß repertoire and that these stressors could increase self-reactivity.-Fonte, C., Kaminski, S., Vanet, A., Lanfumey, L., Cohen-Salmon, C., Ghislin, S., Frippiat, J.-P. Socioenvironmental stressors encountered during spaceflight partially affect the murine TCR-ß repertoire and increase its self-reactivity.

Analysis of femurs from mice embarked on board BION-M1 biosatellite reveals a decrease in immune cell development, including B cells, after 1 wk of recovery on Earth.

Bone loss and immune dysregulation are among the main adverse outcomes of spaceflight challenging astronauts' health and safety. However, consequences on B-cell development and responses are still under-investigated. To fill this gap, we used advanced proteomics analysis of femur bone and marrow to compare mice flown for 1 mo on board the BION-M1 biosatellite, followed or not by 1 wk of recovery on Earth, to control mice kept on Earth. Our data revealed an adverse effect on B lymphopoiesis 1 wk after landing. This phenomenon was associated with a 41% reduction of B cells in the spleen. These reductions may contribute to explain increased susceptibility to infection even if our data suggest that flown animals can mount a humoral immune response. Future studies should investigate the quality/efficiency of produced antibodies and whether longer missions worsen these immune alterations.-Tascher, G., Gerbaix, M., Maes, P., Chazarin, B., Ghislin, S., Antropova, E., Vassilieva, G., Ouzren-Zarhloul, N., Gauquelin-Koch, G., Vico, L., Frippiat, J.-P., Bertile, F. Analysis of femurs from mice embarked on board BION-M1 biosatellite reveals a decrease in immune cell development, including B cells, after 1 wk of recovery on Earth.

Comparison of sTREM-1 and associated periodontal and bacterial factors before/after periodontal therapy, and impact of psychosocial factors.

AIM: The immune receptor triggering receptor expressed on myeloid cell-1 (TREM-1) is responsible for an amplification of the immuno-inflammatory response in inflammatory diseases. Its role in the aetiopathogenesis of periodontitis is underexplored. The aim of this case-control and before-after study was to determine the evolution of soluble form of TREM-1 (sTREM-1) concentrations after scaling and root planing (SRP), and its prognostic value and evaluate associated microbial, periodontal and psychosocial factors. METHODS: Gingival crevicular fluid was collected in two pathological sites (periodontal pocket depth (PPD) ≥ 5 mm) and one healthy site (PPD ≤ 3 mm) from thirty periodontitis patients (before/after SRP), and in one healthy site from thirty controls (patients without periodontal disease). Each patient filled-in stress/anxiety self-assessment questionnaires and provided a saliva sample. Diseased patients were followed for a total of 13-15 weeks in initial periodontal treatment. sTREM-1 and salivary cortisol levels were determined by ELISA and periodontopathogens by PCR. RESULTS: Before SRP, higher crevicular sTREM-1 levels were positively associated with some increased clinical parameters (Plaque Index, tooth mobility, bleeding on probing, p < .05) and inversely with Aggregatibacter actinomycetemcomitans abundance (p = .03). No correlation with psychological factors nor cortisol was found with salivary sTREM-1 concentrations. After SRP, crevicular sTREM-1 levels decreased (p < .001) and were not linked to a PPD decrease but remained higher in pathological than in healthy sites (p < .001). Higher concentrations were also found out in unimproved sites (no change or increase in PPD) compared to improved ones (p = .02). Higher sTREM-1 levels were associated with Porphyromonas gingivalis, Treponema denticola and Campylobacter rectus in pathological sites after SRP (p < .05). CONCLUSION: Crevicular sTREM-1 level decreased after SRP but did not appear to be a site outcome predictive factor of periodontal healing and remained an inflammatory parameter.

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

During deep-space travels, crewmembers face various physical and psychosocial stressors that could alter gut microbiota composition. Since it is well known that intestinal dysbiosis is involved in the onset or exacerbation of several disorders, the aim of this study was to evaluate changes in intestinal microbiota in a murine model used to mimic chronic psychosocial stressors encountered during a long-term space mission. We demonstrate that 3 weeks of exposure to this model (called CUMS for Chronic Unpredictable Mild Stress) induce significant change in intracaecal ß-diversity characterized by an important increase of the Firmicutes/Bacteroidetes ratio. These alterations are associated with a decrease of Porphyromonadaceae, particularly of the genus Barnesiella, a major member of gut microbiota in mice and humans where it is described as having protective properties. These results raise the question of the impact of stress-induced decrease of beneficial taxa, support recent data deduced from in-flight experimentations and other ground-based models, and emphasize the critical need for further studies exploring the impact of spaceflight on intestinal microbiota in order to propose strategies to countermeasure spaceflight-associated dysbiosis and its consequences on health.

Modulation of Iberian Ribbed Newt Complement Component C3 by Stressors Similar to those Encountered during a Stay Onboard the International Space Station.

The complement system plays an important role in inflammation, innate and acquired immunity, as well as homeostasis. Despite these functions, the effects of spaceflight conditions on the complement system have not yet been intensively studied. Consequently, we investigated the effects of five types of chronic stressors, similar to those encountered during a stay onboard the International Space Station, on C3 expression in larvae of the urodele amphibian Pleurodeles waltl. We focused on C3 because it is a critical component of this system. These studies were completed by the analysis of adult mice exposed to two models of inflight stressors. Our data show that simulating space radiation, or combining a modification of the circadian rhythm with simulated microgravity, affects the amount of C3 proteins. These results suggest that C3 expression could be modified under real spaceflight conditions, potentially increasing the risk of inflammation and associated tissue damage.

Essential Oils and Their Natural Active Compounds Presenting Antifungal Properties.

The current rise in invasive fungal infections due to the increase in immunosuppressive therapies is a real concern. Moreover, the emergence of resistant strains induces therapeutic failures. In light of these issues, new classes of antifungals are anticipated. Therefore, the plant kingdom represents an immense potential of natural resources to exploit for these purposes. The aim of this review is to provide information about the antifungal effect of some important essential oils, and to describe the advances made in determining the mechanism of action more precisely. Finally, the issues of toxicity and resistance of fungi to essential oils will be discussed.

Hind limb unloading, a model of spaceflight conditions, leads to decreased B lymphopoiesis similar to aging.

Within the bone marrow, the endosteal niche plays a crucial role in B-cell differentiation. Because spaceflight is associated with osteoporosis, we investigated whether changes in bone microstructure induced by a ground-based model of spaceflight, hind limb unloading (HU), could affect B lymphopoiesis. To this end, we analyzed both bone parameters and the frequency of early hematopoietic precursors and cells of the B lineage after 3, 6, 13, and 21 d of HU. We found that limb disuse leads to a decrease in both bone microstructure and the frequency of B-cell progenitors in the bone marrow. Although multipotent hematopoietic progenitors were not affected by HU, a decrease in B lymphopoiesis was observed as of the common lymphoid progenitor (CLP) stage with a major block at the progenitor B (pro-B) to precursor B (pre-B) cell transition (5- to 10-fold decrease). The modifications in B lymphopoiesis were similar to those observed in aged mice and, as with aging, decreased B-cell generation in HU mice was associated with reduced expression of B-cell transcription factors, early B-cell factor (EBF) and Pax5, and an alteration in STAT5-mediated IL-7 signaling. These findings demonstrate that mechanical unloading of hind limbs results in a decrease in early B-cell differentiation resembling age-related modifications in B lymphopoiesis.

Aldosterone up-regulates MMP-9 and MMP-9/NGAL expression in human neutrophils through p38, ERK1/2 and PI3K pathways.

Aldosterone and mineralocorticoid receptors are important regulators of inflammation. During this process, chemokines and extracellular matrix degradation by matrix metalloproteases, such as MMP-9, help leukocytes reaching swiftly and infiltrating the injured tissue, two processes essential for tissue repair. Leukocytes, such as neutrophils, are a rich source of MMP-9 and possess mineralocorticoid receptors (MR). The aim of our study was to investigate whether aldosterone was able to regulate proMMP-9, active MMP-9 and MMP-9/NGAL production in human neutrophils. Here we show that aldosterone increased MMP-9 mRNA in a dose- and time-dependent manner. This hormone up-regulated also dose-dependently proMMP-9 and active MMP-9 protein release as well as the MMP-9/NGAL protein complex. PI3K, p38 and ERK1/2 inhibition diminished these aldosterone-induced neutrophil productions. Furthermore, spironolactone, a MR antagonist, counteracted aldosterone-induced increases of proMMP-9, active MMP-9 and MMP-9/NGAL complex. These findings indicate that aldosterone could participate in tissue repair by modulating neutrophil activity and favoring extracellular matrix degradation.

Gravity changes during animal development affect IgM heavy-chain transcription and probably lymphopoiesis.

Our previous research demonstrated that spaceflight conditions affect antibody production in response to an antigenic stimulation in adult amphibians. Here, we investigated whether antibody synthesis is affected when animal development occurs onboard a space station. To answer this question, embryos of the Iberian ribbed newt, Pleurodeles waltl, were sent to the International Space Station (ISS) before the initiation of immunoglobulin heavy-chain expression. Thus, antibody synthesis began in space. On landing, we determined the effects of spaceflight on P. waltl development and IgM heavy-chain transcription. Results were compared with those obtained using embryos that developed on Earth. We find that IgM heavy-chain transcription is doubled at landing and that spaceflight does not affect P. waltl development and does not induce inflammation. We also recreated the environmental modifications encountered by the embryos during their development onboard the ISS. This strategy allowed us to demonstrate that gravity change is the factor responsible for antibody heavy-chain transcription modifications that are associated with NF-κB mRNA level variations. Taken together, and given that the larvae were not immunized, these data suggest a modification of lymphopoiesis when gravity changes occur during ontogeny.

How are cell and tissue structure and function influenced by gravity and what are the gravity perception mechanisms?

Progress in mechanobiology allowed us to better understand the important role of mechanical forces in the regulation of biological processes. Space research in the field of life sciences clearly showed that gravity plays a crucial role in biological processes. The space environment offers the unique opportunity to carry out experiments without gravity, helping us not only to understand the effects of gravitational alterations on biological systems but also the mechanisms underlying mechanoperception and cell/tissue response to mechanical and gravitational stresses. Despite the progress made so far, for future space exploration programs it is necessary to increase our knowledge on the mechanotransduction processes as well as on the molecular mechanisms underlying microgravity-induced cell and tissue alterations. This white paper reports the suggestions and recommendations of the SciSpacE Science Community for the elaboration of the section of the European Space Agency roadmap "Biology in Space and Analogue Environments" focusing on "How are cells and tissues influenced by gravity and what are the gravity perception mechanisms?" The knowledge gaps that prevent the Science Community from fully answering this question and the activities proposed to fill them are discussed.