Exercise may improve lung immunity after surgical stress: Evidence from a nephrectomy model via a bioinformatic analysis.

Exercise offers numerous benefits to cancer patients and plays an essential role in postsurgical cancer rehabilitation. However, there is a lack of research examining the effects of exercise after the surgical stress of nephrectomy. To address this gap, we created an animal model that simulated patients who had undergone nephrectomy with or without an exercise intervention. Next, we performed a bioinformatic analysis based on the data generated by the RNA sequencing of the lung tissue sample. An overrepresentation analysis was conducted using two genome databases (Gene Ontology and Kyoto Encyclopedia of Genes and Genomes [KEGG]). A KEGG analysis of the exercise-treated nephrectomy mice revealed enrichment in immune-related pathways, particularly in the NF-κB and B cell-related pathways. The expression of CD79A and IGHD, which are responsible for B cell differentiation and proliferation, was upregulated in the nephrectomy mice. Differential gene expression was categorized as significantly upregulated or downregulated according to nephrectomy and exercise groups. Notably, we identified several gene expression reversals in the nephrectomy groups with exercise that were not found in the nephrectomy without exercise or control groups. Our preliminary results potentially reveal a genetic landscape for the underlying mechanisms of the effects of exercise on our nephrectomy model.

Identification, diversity, and evolution analysis of Commd gene family in Haliotis discus hannai and immune response to biotic and abiotic stresses.

The Commd (Copper Metabolism gene MURR1 Domain) family genes play crucial roles in various biological processes, including copper and sodium transport regulation, NF-κB activity, and cell cycle progression. Their function in Haliotis discus hannai, however, remains unclear. This study focused on identifying and analyzing the Commd genes in H. discus hannai, including their gene structure, phylogenetic relationships, expression profiles, sequence diversity, and alternative splicing. The results revealed significant homology between H. discus hannai's Commd genes and those of other mollusks. Both transcriptome quantitative analysis and qRT-PCR demonstrated the responsiveness of these genes to heat stress and Vibrio parahaemolyticus infection. Notably, alternative splicing analysis revealed that COMMD2, COMMD4, COMMD5, and COMMD7 produce multiple alternative splice variants. Furthermore, sequence diversity analysis uncovered numerous missense mutations, specifically 9 in COMMD5 and 14 in COMMD10. These findings contribute to expanding knowledge on the function and evolution of the Commd gene family and underscore the potential role of COMMD in the innate immune response of H. discus hannai. This research, therefore, offers a novel perspective on the molecular mechanisms underpinning the involvement of Commd genes in innate immunity, paving the way for further explorations in this field.

Baseline and stress-induced steroid plasma levels and immune function vary annually and are associated with vocal activity in male toads (Rhinella icterica).

Theoretical models predict that elevated androgen and glucocorticoid levels in males during the reproductive season promote immunosuppression. However, some studies report decreased stress response during this season. This study investigated annual variation in plasma corticosterone and testosterone levels, plasma bacterial killing ability (BKA), and neutrophil to lymphocyte ratio (NLR) in free-living male toads (Rhinella icterica). Toads were sampled in the field (baseline) and 1 h-post restraint over five months, and we considered the occurrence of vocal activity. Baseline corticosterone, testosterone, and BKA showed higher values during the reproductive period, specifically in calling male toads. The NLR was similar throughout the year, but higher values were observed in calling toads. Moreover, baseline NLR and BKA were positively correlated with both testosterone and corticosterone, suggesting higher steroid levels during reproduction are associated with enhanced cellular and humoral immunity. Despite fluctuation of baseline values, post-restraint corticosterone levels remained uniform over the year, indicating that toads reached similar maximum values throughout the year. Testosterone levels decreased following restraint before one specific reproductive period but increased in response to restraint during and after this period. Meanwhile, BKA decreased due to restraint only after the reproductive period, indicating immune protection and resilience to immunosuppression by stressors associated with steroid hormones during reproduction. Our results show that baseline and stress-induced hormonal and immune regulation varies throughout the year and are associated with vocal activity in R. icterica males, indicating a possible compromise between steroids and immune function in anuran males.

Effects of immunosuppression-associated gga-miR-146a-5p on immune regulation in chicken macrophages by targeting the IRKA2 gene.

Stress-induced immunosuppression (SIIS) is one of the common problems in intensive poultry production, which brings enormous economic losses to the poultry industry. Accumulating evidence has shown that microRNAs (miRNAs) were important regulators of gene expression in the immune system. However, the miRNA-mediated molecular mechanisms underlying SIIS in chickens are still poorly understood. This study aimed to investigate the biological functions and regulatory mechanism of miRNAs in chicken SIIS. A stress-induced immunosuppression model was successfully established via daily injection of dexamethasone and analyzed miRNA expression in spleen. Seventy-four differentially expressed miRNAs (DEMs) was identified, and 229 target genes of the DEMs were predicted. Functional enrichment analysis the target genes revealed pathways related to immunity, such as MAPK signaling pathway and FoxO signaling pathway. The candidate miRNA, gga-miR-146a-5p, was found to be significantly downregulated in the Dex-induced chicken spleen, and we found that Dex stimulation significantly inhibited the expression of gga-miR-146a-5p in Chicken macrophages (HD11). Flow cytometry, 5-ethynyl-2'-deoxyuridine (EdU), cell counting kit-8 (CCK-8) and other assays indicated that gga-miR-146a-5p can promote the proliferation and inhibit apoptosis of HD11 cells. A dual-luciferase reporter assay suggested that the Interleukin 1 receptor associated kinase 2 (IRAK2) gene, which encoded a transcriptional factor, was a direct target of gga-miR-146a-5p, gga-miR-146a-5p suppressed the post-transcriptional activity of IRAK2. These findings not only improve our understanding of the specific functions of miRNAs in avian stress but also provide potential targets for genetic improvement of stress resistance in poultry.

Sleep deprivation reduced LPS-induced IgG2b production by up-regulating BMAL1 and CLOCK expression.

Sleep deprivation (SD) weakens the immune system and leads to increased susceptibility to infectious or inflammatory diseases. However, it is still unclear how SD affects humoral immunity. In the present study, sleep disturbance was conducted using an sleep deprivation instrument, and the bacterial endotoxin lipopolysaccharide (LPS) was used to activate the immune response. It was found that SD-pretreatment reduced LPS-induced IgG2b+ B cells and IgG2b isotype antibody production in lymphocytes of spleen. And, SD-pretreatment decreased the proportion of CD4+T cells, production of CD4+T cells derived TGF-ß1 and its contribution in helping IgG2b production. Additionally, BMAL1 and CLOCK were selectively up-regulated in lymphocytes after SD. Importantly, BMAL1 and CLOCK deficiency contributed to TGF-ß1 expression and production of IgG2b+ B cells. Thus, our results provide a novel insight to explain the involvement of BMAL1 and CLOCK under SD stress condition, and their roles in inhibiting TGF-ß1 expression and contributing to reduction of LPS induced IgG2b production.

PKR-mediated stress response enhances dengue and Zika virus replication.

IMPORTANCE: One of the fundamental features that make viruses intracellular parasites is the necessity to use cellular translational machinery. Hence, this is a crucial checkpoint for controlling infections. Here, we show that dengue and Zika viruses, responsible for nearly 400 million infections every year worldwide, explore such control for optimal replication. Using immunocompetent cells, we demonstrate that arrest of protein translations happens after sensing of dsRNA and that the information required to avoid this blocking is contained in viral 5'-UTR. Our work, therefore, suggests that the non-canonical translation described for these viruses is engaged when the intracellular stress response is activated.

Stress Signal ULBP4, an NKG2D Ligand, Is Upregulated in Multiple Sclerosis and Shapes CD8+ T-Cell Behaviors.

BACKGROUND AND OBJECTIVES: We posit the involvement of the natural killer group 2D (NKG2D) pathway in multiple sclerosis (MS) pathology via the presence of specific NKG2D ligands (NKG2DLs). We aim to evaluate the expression of NKG2DLs in the CNS and CSF of patients with MS and to identify cellular stressors inducing the expression of UL16-binding protein 4 (ULBP4), the only detectable NKG2DL. Finally, we evaluate the impact of ULBP4 on functions such as cytokine production and motility by CD8+ T lymphocytes, a subset largely expressing NKG2D, the cognate receptor. METHODS: Human postmortem brain samples and CSF from patients with MS and controls were used to evaluate NKG2DL expression. In vitro assays using primary cultures of human astrocytes and neurons were performed to identify stressors inducing ULBP4 expression. Human CD8+ T lymphocytes from MS donors and age/sex-matched healthy controls were isolated to evaluate the functional impact of soluble ULBP4. RESULTS: We detected mRNA coding for the 8 identified human NKG2DLs in brain samples from patients with MS and controls, but only ULBP4 protein expression was detectable by Western blot. ULBP4 levels were greater in patients with MS, particularly in active and chronic active lesions and normal-appearing white matter, compared with normal-appearing gray matter from MS donors and white and gray matter from controls. Soluble ULBP4 was also detected in CSF of patients with MS and controls, but a smaller shed/soluble form of 25 kDa was significantly elevated in CSF from female patients with MS compared with controls and male patients with MS. Our data indicate that soluble ULBP4 affects various functions of CD8+ T lymphocytes. First, it enhanced the production of the proinflammatory cytokines GM-CSF and interferon-γ (IFNγ). Second, it increased CD8+ T lymphocyte motility and favored a kinapse-like behavior when cultured in the presence of human astrocytes. CD8+ T lymphocytes from patients with MS were especially altered by the presence of soluble ULBP4 compared with healthy controls. DISCUSSION: Our study provides new evidence for the involvement of NKG2D and its ligand ULBP4 in MS pathology. Our results point to ULBP4 as a viable target to specifically block 1 component of the NKG2D pathway without altering immune surveillance involving other NKG2DL.

Transcriptomic analysis of gills in nitrite-tolerant and -sensitive families of Litopenaeus vannamei.

Nitrite stress is a major environmental factor that limits aquatic animal growth, reproduction and survival. Even so, some shrimps still can withstand somewhat high concentrations of nitrite environment. However, few studies have been conducted about the tolerance molecular mechanism of Litopenaeus vannamei in the high concentration nitrite. To identify the genes and pathways involved in the regulation of nitrite tolerance, we performed comparative transcriptomic analysis in the L. vannamei nitrite-tolerant (NT) and nitrite-sensitive (NS) families, and untreated shrimps were used as the control group. After 24 h of nitrite exposure (NaNO2, 112.5 mg/L), a total of 1521 and 868 differentially expressed genes (DEGs) were obtained from NT compared with NS and control group, respectively. Functional enrichment analysis revealed that most of these DEGs were involved in immune defense, energy metabolism processes and endoplasmic reticulum (ER) stress. During nitrite stress, energy metabolism in NT was significantly enhanced by activating the related genes expression of oxidative phosphorylation (OXPHOS) pathway and tricarboxylic acid (TCA) cycle. Meanwhile, some DEGs involved in innate immunity- related genes and pathways, and ER stress responses also were highly expressed in NT. Therefore, we speculate that accelerated energy metabolism, higher expression of immunity and ER related genes might be the important adaptive strategies for NT in relative to NS under nitrite stress. These results will provide new insights on the potential tolerant molecular mechanisms and the breeding of new varieties of nitrite tolerant L. vannamei.

Investigating the growth performance, meat quality, immune function and proteomic profiles of plasmal exosomes in Lactobacillus plantarum-treated broilers with immunological stress.

Exosomes are extracellular membranous nanovesicles that carry functional molecules to mediate cell-to-cell communication. To date, whether probiotics improve the immune function of broilers by plasmal exosome cargo is unclear. In this study, 300 broilers were allocated to three treatments: control diet (CON group), control diet + dexamethasone injection (DEX group), and control diet containing 1 × 108 cfu g-1 P8 + DEX injection (P8 + DEX group). The growth performance, meat quality and immune function of plasma and jejunal mucosa were detected. Exosomes were isolated from the plasma and characterized. Then, the exosome protein profile was determined by proteomic analysis. Correlation analyses between the exosomal proteins and growth performance, meat quality, immune function were performed. Lastly, the related protein levels were verified by multiple reaction monitoring (MRM). Results showed that P8 treatment increased the growth performance, meat quality and immune function of DEX-induced broilers with immunological stress. Moreover, the average diameters, cup-shaped morphology and expressed exosomal proteins confirmed that the isolated extracellular vesicles were exosomes. A total of 784 proteins were identified in the exosomes; among which, 126 differentially expressed proteins (DEPs) were found between the DEX and CON groups and 102 DEPs were found between the P8 + DEX and DEX groups. Gene ontology analysis indicated that DEPs between the DEX and CON groups are mainly involved in the metabolic process, cellular anatomical entity, cytoplasm, etc. DEPs between the P8 + DEX and DEX groups are mainly involved in the multicellular organismal process, response to stimulus, cytoplasm, etc. Pathway analysis revealed that most of the DEPs between the DEX and CON groups participated in the ECM-receptor interaction, focal adhesion, regulation of actin cytoskeleton, etc. Most of the DEPs between the P8 + DEX and DEX groups participated in the ErbB and PPAR signaling pathways. Moreover, many DEPs were correlated with the altered parameters of growth performance, meat quality and immunity in P8-treated broilers. MRM further revealed that the upregulated FABP6 and EPCAM in the DEX group were decreased by P8 + DEX treatment, and the downregulated C1QTNF3 in the DEX group was increased by P8 + DEX treatment. In conclusion, our findings demonstrated that P8 may promote the immune function, growth performance and meat quality of broilers with immunological stress by regulating the plasma exosomal proteins, especially the proteins of FABP6, EPCAM and C1QTNF3 and the pathway of PPAR (ILK/FABP6).

L. rhamnosus improves the immune response and tryptophan catabolism in laying hen pullets.

In mammals, early-life probiotic supplementation is a promising tool for preventing unfavourable, gut microbiome-related behavioural, immunological, and aromatic amino acid alterations later in life. In laying hens, feather-pecking behaviour is proposed to be a consequence of gut-brain axis dysregulation. Lactobacillus rhamnosus decreases stress-induced severe feather pecking in adult hens, but whether its effect in pullets is more robust is unknown. Consequently, we investigated whether early-life, oral supplementation with a single Lactobacillus rhamnosus strain can prevent stress-induced feather-pecking behaviour in chickens. To this end, we monitored both the short- and long-term effects of the probiotic supplement on behaviour and related physiological parameters. We hypothesized that L. rhamnosus would reduce pecking behaviour by modulating the biological pathways associated with this detrimental behaviour, namely aromatic amino acid turnover linked to neurotransmitter production and stress-related immune responses. We report that stress decreased the proportion of cytotoxic T cells in the tonsils (P = 0.047). Counteracting this T cell depression, birds receiving the L. rhamnosus supplementation significantly increased all T lymphocyte subset proportions (P < 0.05). Both phenotypic and genotypic feather peckers had lower plasma tryptophan concentrations compared to their non-pecking counterparts. The probiotic supplement caused a short-term increase in plasma tryptophan (P < 0.001) and the TRP:(PHE + TYR) ratio (P < 0.001). The administration of stressors did not significantly increase feather pecking in pullets, an observation consistent with the age-dependent onset of pecking behaviour. Despite minimal changes to behaviour, our data demonstrate the impact of L. rhamnosus supplementation on the immune system and the turnover of the serotonin precursor tryptophan. Our findings indicate that L. rhamnosus exerts a transient, beneficial effect on the immune response and tryptophan catabolism in pullets.

Pleiotropic Effects of Glucocorticoids on the Immune System in Circadian Rhythm and Stress.

Glucocorticoids (GCs) are a class of steroid hormones secreted from the adrenal cortex. Their production is controlled by circadian rhythm and stress, the latter of which includes physical restraint, hunger, and inflammation. Importantly, GCs have various effects on immunity, metabolism, and cognition, including pleiotropic effects on the immune system. In general, GCs have strong anti-inflammatory and immunosuppressive effects. Indeed, they suppress inflammatory cytokine expression and cell-mediated immunity, leading to increased risks of some infections. However, recent studies have shown that endogenous GCs induced by the diurnal cycle and dietary restriction enhance immune responses against some infections by promoting the survival, redistribution, and response of T and B cells via cytokine and chemokine receptors. Furthermore, although GCs are reported to reduce expression of Th2 cytokines, GCs enhance type 2 immunity and IL-17-associated immunity in some stress conditions. Taken together, GCs have both immunoenhancing and immunosuppressive effects on the immune system.

Interferons Are Pro-Inflammatory Cytokines in Sheared-Stressed Human Aortic Valve Endothelial Cells.

Calcific aortic valve disease (CAVD) is an athero-inflammatory process. Growing evidence supports the inflammation-driven calcification model, mediated by cytokines such as interferons (IFNs) and tumor necrosis factor (TNF)-α. Our goal was investigating IFNs' effects in human aortic valve endothelial cells (VEC) and the potential differences between aortic (aVEC) and ventricular (vVEC) side cells. The endothelial phenotype was analyzed by Western blot, qPCR, ELISA, monocyte adhesion, and migration assays. In mixed VEC populations, IFNs promoted the activation of signal transducers and activators of transcription-1 and nuclear factor-κB, and the subsequent up-regulation of pro-inflammatory molecules. Side-specific VEC were activated with IFN-γ and TNF-α in an orbital shaker flow system. TNF-α, but not IFN-γ, induced hypoxia-inducible factor (HIF)-1α stabilization or endothelial nitric oxide synthase downregulation. Additionally, IFN-γ inhibited TNF-α-induced migration of aVEC. Also, IFN-γ triggered cytokine secretion and adhesion molecule expression in aVEC and vVEC. Finally, aVEC were more prone to cytokine-mediated monocyte adhesion under multiaxial flow conditions as compared with uniaxial flow. In conclusion, IFNs promote inflammation and reduce TNF-α-mediated migration in human VEC. Moreover, monocyte adhesion was higher in inflamed aVEC sheared under multiaxial flow, which may be relevant to understanding the initial stages of CAVD.

Transport Stress Induces Skin Innate Immunity Response in Hybrid Yellow Catfish (Tachysurus fulvidraco♀ × P. vachellii♂) Through TLR/NLR Signaling Pathways and Regulation of Mucus Secretion.

The transport of live fish is a necessary step for commercial production. The skin of teleost fish is the first non-specific immune barrier against exogenous stimuli, and it plays an important protective role under transport stress. Thus, the aim of this study was to explore the skin responses to transport stress in hybrid yellow catfish (Tachysurus fulvidraco♀ × Pseudobagrus vachellii♂) through transcriptome and biochemical analyses. Water samples were collected during a simulated transport treatment. Biochemical indexes and/or gene expression in blood, skin, and mucus in fish in control groups and transport-stress groups (0 h, 2 h, 4 h, 8 h, 16 h) were assayed. The levels of total ammonia-nitrogen and nitrite-nitrogen in the water increased with increasing transport time. Comparison of skin transcriptomes between the control group and the group subjected to 16 h of transport revealed 1547 differentially expressed genes (868 up-regulated and 679 down-regulated). The results of the transcriptome analysis were validated by analyses of the expression levels of selected genes by qRT-PCR. The results indicated that the toll-like receptors and nod-like receptors signaling pathways mediate the skin's immune response to transport stress: tlr9, mfn2, and ikbke were significantly up-regulated and nfkbia and map3k7cl were significantly down-regulated under transport stress. With increasing transport time, lysozyme activity and the immunoglobulin M content in skin mucus first increased and then decreased. The number of mucous cells peaked at 8 h of transport stress, and then decreased. The mucus cells changed from types II and IV to types I, II, III, and IV. The amounts of red and white blood cells and the levels of hemoglobin and hematocrit first increased and then decreased during 16 h of transport stress. Together, the results showed that the skin responds to transport stress by activating the immune signaling pathway and regulating mucus secretion. These findings have important biological significance for selecting strains that tolerate transport, as well as economic significance for optimizing the transport conditions for scaleless fish.

Stress Induces Release of Extracellular Vesicles by Trypanosoma cruzi Trypomastigotes.

All extracellular forms of Trypanosoma cruzi, the causative agent of Chagas disease, release extracellular vesicles (EVs) containing major surface molecules of the parasite. EV release depends on several mechanisms (internal and external). However, most of the environmental conditions affecting this phenomenon are still unknown. In this work, we evaluated EV release under different stress conditions and their ability to be internalized by the parasites. In addition, we investigated whether the release conditions would affect their immunomodulatory properties in preactivated bone marrow-derived macrophages (BMDM). Sodium azide and methyl-cyclo-ß-dextrin (CDB) reduced EV release, indicating that this phenomenon relies on membrane organization. EV release was increased at low temperatures (4°C) and acidic conditions (pH 5.0). Under this pH, trypomastigotes differentiated into amastigotes. EVs are rapidly liberated and reabsorbed by the trypomastigotes in a concentration-dependent manner. Nitrosative stress caused by sodium nitrite in acid medium or S-nitrosoglutathione also stimulated the secretion of EVs. EVs released under all stress conditions also maintained their proinflammatory activity and increased the expression of iNOS, Arg 1, IL-12, and IL-23 genes in IFN-γ and LPS preactivated BMDM. In conclusion, our results suggest a budding mechanism of release, dependent on the membrane structure and parasite integrity. Stress conditions did not affect functional properties of EVs during interaction with host cells. EV release variations under stress conditions may be a physiological response against environmental changes.

Resident human dermal γδT-cells operate as stress-sentinels: Lessons from the hair follicle.

Murine γδT-cells have stress-surveillance functions and are implicated in autoimmunity. Yet, whether human γδT-cells are also stress sentinels and directly promote autoimmune responses in the skin is unknown. Using a novel (mini-)organ assay, we tested if human dermis resident γδT-cells can recognize stressed human scalp hair follicles (HFs) to promote an alopecia areata (AA)-like autoimmune response. Accordingly, we show that γδT-cells from healthy human scalp skin are activated (CD69+), up-regulate the expression of NKG2D and IFN-γ, and become cytotoxic when co-cultured with autologous stressed HFs ex vivo. These autologous γδT-cells induce HF immune privilege collapse, dystrophy, and premature catagen, i.e. three hallmarks of the human autoimmune HF disorder, AA. This is mediated by CXCL12, MICA, and in part by IFN-γ and CD1d. In conclusion, human dermal γδT-cells exert physiological stress-sentinel functions in human skin, where their excessive activity can promote autoimmunity towards stressed HFs that overexpress CD1d, CXCL12, and/or MICA.

The neuroimmune response during stress: A physiological perspective.

Stress is an essential adaptive response that enables the organism to cope with challenges and restore homeostasis. Different stressors require distinctive corrective responses in which immune cells play a critical role. Hence, effects of stress on immunity may vary accordingly. Indeed, epidemiologically, stress can induce either inflammation or immune suppression in an organism. However, in the absence of a conceptual framework, these effects appear chaotic, leading to confusion. Here, we examine how stressor diversity is imbedded in the neuroimmune axis. Stressors differ in the brain patterns they induce, diversifying the neuronal and endocrine mediators dispatched to the periphery and generating a wide range of potential immune effects. Uncovering this complexity and diversity of the immune response to different stressors will allow us to understand the involvement of stress in pathological conditions, identify ways to modulate it, and even harness the therapeutic potential embedded in an adaptive response to stress.

Functional and metabolic fitness of human CD4+ T lymphocytes during metabolic stress.

Human CD4+ T cells are essential mediators of immune responses. By altering the mitochondrial and metabolic states, we defined metabolic requirements of human CD4+ T cells for in vitro activation, expansion, and effector function. T-cell activation and proliferation were reduced by inhibiting oxidative phosphorylation, whereas early cytokine production was maintained by either OXPHOS or glycolytic activity. Glucose deprivation in the presence of mild mitochondrial stress markedly reduced all three T-cell functions, contrasting the exposure to resveratrol, an antioxidant and sirtuin-1 activator, which specifically inhibited cytokine production and T-cell proliferation, but not T-cell activation. Conditions that inhibited T-cell activation were associated with the down-regulation of 2',5'-oligoadenylate synthetase genes via interferon response pathways. Our findings indicate that T-cell function is grossly impaired by stressors combined with nutrient deprivation, suggesting that correcting nutrient availability, metabolic stress, and/or the function of T cells in these conditions will improve the efficacy of T-cell-based therapies.

Activation of mitochondrial unfolded protein response protects against multiple exogenous stressors.

The mitochondrial unfolded protein response (mitoUPR) is an evolutionarily conserved pathway that responds to mitochondria insults through transcriptional changes, mediated by the transcription factor ATFS-1/ATF-5, which acts to restore mitochondrial homeostasis. In this work, we characterized the role of ATFS-1 in responding to organismal stress. We found that activation of ATFS-1 is sufficient to cause up-regulation of genes involved in multiple stress response pathways including the DAF-16-mediated stress response pathway, the cytosolic unfolded protein response, the endoplasmic reticulum unfolded protein response, the SKN-1-mediated oxidative stress response pathway, the HIF-1-mediated hypoxia response pathway, the p38-mediated innate immune response pathway, and antioxidant genes. Constitutive activation of ATFS-1 increases resistance to multiple acute exogenous stressors, whereas disruption of atfs-1 decreases stress resistance. Although ATFS-1-dependent genes are up-regulated in multiple long-lived mutants, constitutive activation of ATFS-1 decreases lifespan in wild-type animals. Overall, our work demonstrates that ATFS-1 serves a vital role in organismal survival of acute stressors through its ability to activate multiple stress response pathways but that chronic ATFS-1 activation is detrimental for longevity.

Drosophila as a Model to Study Cellular Communication Between the Hematopoietic Niche and Blood Progenitors Under Homeostatic Conditions and in Response to an Immune Stress.

In adult mammals, blood cells are formed from hematopoietic stem progenitor cells, which are controlled by a complex cellular microenvironment called "niche". Drosophila melanogaster is a powerful model organism to decipher the mechanisms controlling hematopoiesis, due both to its limited number of blood cell lineages and to the conservation of genes and signaling pathways throughout bilaterian evolution. Insect blood cells or hemocytes are similar to the mammalian myeloid lineage that ensures innate immunity functions. Like in vertebrates, two waves of hematopoiesis occur in Drosophila. The first wave takes place during embryogenesis. The second wave occurs at larval stages, where two distinct hematopoietic sites are identified: subcuticular hematopoietic pockets and a specialized hematopoietic organ called the lymph gland. In both sites, hematopoiesis is regulated by distinct niches. In hematopoietic pockets, sensory neurons of the peripheral nervous system provide a microenvironment that promotes embryonic hemocyte expansion and differentiation. In the lymph gland blood cells are produced from hematopoietic progenitors. A small cluster of cells called Posterior Signaling Centre (PSC) and the vascular system, along which the lymph gland develops, act collectively as a niche, under homeostatic conditions, to control the balance between maintenance and differentiation of lymph gland progenitors. In response to an immune stress such as wasp parasitism, lymph gland hematopoiesis is drastically modified and shifts towards emergency hematopoiesis, leading to increased progenitor proliferation and their differentiation into lamellocyte, a specific blood cell type which will neutralize the parasite. The PSC is essential to control this emergency response. In this review, we summarize Drosophila cellular and molecular mechanisms involved in the communication between the niche and hematopoietic progenitors, both under homeostatic and stress conditions. Finally, we discuss similarities between mechanisms by which niches regulate hematopoietic stem/progenitor cells in Drosophila and mammals.