Acute stress modulates the outcome of traumatic brain injury-associated gene expression and behavioral responses.

Psychological stress and traumatic brain injury (TBI) result in long-lasting emotional and behavioral impairments in patients. So far, the interaction of psychological stress with TBI not only in the brain but also in peripheral organs is poorly understood. Herein, the impact of acute stress (AS) occurring immediately before TBI is investigated. For this, a mouse model of restraint stress and TBI was employed, and their influence on behavior and gene expression in brain regions, the hypothalamic-pituitary-adrenal (HPA) axis, and peripheral organs was analyzed. Results demonstrate that, compared to single AS or TBI exposure, mice treated with AS prior to TBI showed sex-specific alterations in body weight, memory function, and locomotion. The induction of immediate early genes (IEGs, e.g., c-Fos) by TBI was modulated by previous AS in several brain regions. Furthermore, IEG upregulation along the HPA axis (e.g., pituitary, adrenal glands) and other peripheral organs (e.g., heart) was modulated by AS-TBI interaction. Proteomics of plasma samples revealed proteins potentially mediating this interaction. Finally, the deletion of Atf3 diminished the TBI-induced induction of IEGs in peripheral organs but left them largely unaltered in the brain. In summary, AS immediately before brain injury affects the brain and, to a strong degree, also responses in peripheral organs.

Mycobacterium vaccae protects against glucocorticoid resistance resulting from combined physical and psychosocial trauma in mice.

Stress-related somatic and psychiatric disorders are often associated with a decline in regulatory T cell (Treg) counts and chronic low-grade inflammation. Recent preclinical evidence suggests that the latter is at least partly mediated by stress-induced upregulation of toll-like receptor (TLR)2 in newly generated neutrophils and polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), as well as glucocorticoid (GC) resistance in predominantly PMN-MDSCs following stress-induced upregulation of TLR4 expression. Here we show in mice exposed to the chronic subordinate colony housing (CSC) paradigm that repeated intragastric (i.g.) administrations of a heat-killed preparation of Mycobacterium vaccae NCTC 11659, a saprophytic microorganism with immunoregulatory properties, protected against the stress-induced reduction in systemic Tregs, increase in basal and LPS-induced in vitro splenocyte viability, as well as splenic in vitro GC resistance. Our findings further support the hypothesis that i.g. M. vaccae protects against CSC-associated splenic GC resistance via directly affecting the myeloid compartment, thereby preventing the CSC-induced upregulation of TLR4 in newly generated PMN-MDSCs. In contrast, the protective effects of i.g. M. vaccae on the CSC-induced upregulation of TLR2 in neutrophils and the subsequent increase in basal and LPS-induced in vitro splenocyte viability seems to be indirectly mediated via the Treg compartment. These data highlight the potential for use of oral administration of M. vaccae NCTC 11659 to prevent stress-induced exaggeration of inflammation, a risk factor for development of stress-related psychiatric disorders.

The PMN-MDSC - A key player in glucocorticoid resistance following combined physical and psychosocial trauma.

Stress-associated somatic and psychiatric disorders are often linked to non-resolving low-grade inflammation, which is promoted at least in part by glucocorticoid (GC) resistance of distinct immune cell subpopulations. While the monocyte/macrophage compartment was in the focus of many clinical and preclinical studies, the role of myeloid-derived suppressor cells (MDSCs) in stress-associated pathologies and GC resistance is less understood. As GC resistance is a clear risk factor for posttraumatic complications in patients on intensive care, the exact interplay of physical and psychosocial traumatization in the development of GC resistance needs to be further clarified. In the current study we employ the chronic subordinate colony housing (CSC) paradigm, a well-characterized mouse model of chronic psychosocial stress, to study the role of myeloid cells, in particular of MDSCs, in innate immune activation and GC resistance following combined psychosocial and physical (e.g., bite wounds) trauma. Our findings support the hypothesis that stress-induced neutrophils, polymorphonuclear (PMN)-MDSCs and monocytes/monocyte-like (MO)-MDSCs get primed and activated locally in the bone marrow as determined by toll-like receptor (TLR)2 upregulation and increased basal and lipopolysaccharide (LPS)-induced in vitro cell viability. These primed and activated myeloid cells emigrate into the peripheral circulation and subsequently, if CSC is accompanied by significant bite wounding, accumulate in the spleen. Here, PMN-MDSCs and monocytes/MO-MDSCs upregulate TLR4 expression, which exclusively in PMN-MDSCs promotes NF-κB hyperactivation upon LPS-stimulation, thereby exceeding the anti-inflammatory capacities of GCs and resulting in GC resistance.

Rapidly Growing Mycobacterium Species: The Long and Winding Road from Tuberculosis Vaccines to Potent Stress-Resilience Agents.

Inflammatory diseases and stressor-related psychiatric disorders, for which inflammation is a risk factor, are increasing in modern Western societies. Recent studies suggest that immunoregulatory approaches are a promising tool in reducing the risk of suffering from such disorders. Specifically, the environmental saprophyte Mycobacterium vaccae National Collection of Type Cultures (NCTC) 11659 has recently gained attention for the prevention and treatment of stress-related psychiatric disorders. However, effective use requires a sophisticated understanding of the effects of M. vaccae NCTC 11659 and related rapidly growing mycobacteria (RGMs) on microbiome-gut-immune-brain interactions. This historical narrative review is intended as a first step in exploring these mechanisms and provides an overview of preclinical and clinical studies on M. vaccae NCTC 11659 and related RGMs. The overall objective of this review article is to increase the comprehension of, and interest in, the mechanisms through which M. vaccae NCTC 11659 and related RGMs promote stress resilience, with the intention of fostering novel clinical strategies for the prevention and treatment of stressor-related disorders.

Changes in Functional Glucocorticoid Sensitivity of Isolated Splenocytes Induced by Chronic Psychosocial Stress - A Time Course Study.

Chronic psychosocial stress is a risk factor for the development of numerous disorders, of which most are associated with chronic low-grade inflammation. Given the immunosuppressive effects of glucocorticoids (GC), one underlying mechanism might be the development of stress-induced GC resistance in certain immune cell subpopulations. In line with this hypothesis, male mice exposed to the chronic subordinate colony housing (CSC, 19 days) model develop GC resistance of in vitro lipopolysaccharide (LPS)-stimulated splenocytes, splenomegaly and an increased percentage of splenic CD11b+ cells. Here male C57BL/6N mice were euthanized at different days during CSC, and following 30 days of single housing after stressor termination to assess when CSC-induced splenic GC resistance starts to develop and whether this is a transient effect. Moreover, splenic CD11b, GC receptor (GR) and/or macrophage migration inhibiting factor (MIF) protein levels were quantified at respective days. While mild forms of CSC-induced GC resistance, increased splenic CD11b expression and/or splenomegaly were detectable on days 8 and 9 of CSC, more severe forms took until days 15 and 16 to develop, but normalized almost completely within 30 days following stressor termination (day 51). In contrast, splenic GR expression was decreased in CSC versus single-housed control (SHC) mice at all days assessed. While MIF expression was increased on days 15 and 16 of CSC, it was decreased in CSC versus SHC mice on day 20 despite persisting splenomegaly, increased CD11b expression and functional GC resistance. In summary, our data indicate that GC resistance and CD11b+ cell-mediated splenomegaly develop gradually and in parallel over time during CSC exposure and are transient in nature. Moreover, while we can exclude that CSC-induced reduction in splenic GR expression is sufficient to induce functional GC resistance, the role of MIF in CD11b+ cell-mediated splenomegaly and GC resistance requires further investigation.

Inducing a stressed phenotype in healthy recipient mice by adoptively transferring CD4+ lymphocytes from mice undergoing chronic psychosocial stress.

Although chronic stress is an acknowledged risk factor for the development of somatic and affective disorders, the cellular and molecular mechanisms underlying stress-induced pathologies are not fully understood. Interestingly, rodent studies involving immune cell transfer suggest that CD4+ T cells might be at least in part involved in reactivation of a chemically-induced colitis by stress. However, until now evidence is lacking that these immune cell types are indeed involved in the development of a "stressed phenotype". The aim of the present study was, therefore, to assess the effects of adoptively transferring total mesenteric lymph node cells (mesLNCs) and CD4+ mesLNCs isolated from chronically-stressed mice into healthy recipient mice on various physiological, immunological and behavioral parameters. To induce chronic psychosocial stress in donor mice we employed the chronic subordinate colony housing (CSC) paradigm. Our data indicate that transfer of total or CD4+ mesLNCs from CSC mice, compared with respective cells from single-housed control (SHC) mice, promoted splenomegaly and interferon (IFN)-γ secretion from in vitro anti-CD3-stimulated mesLNCs in naïve recipient mice. This effect was independent of recipient mice additionally being administered with dextran sulfate sodium (DSS) or not. Transfer of CD4+ mesLNCs additionally increased adrenal weight and secretion of IL-6 from in vitro anti-CD3 stimulated mesLNCs in recipients administered with DSS. Importantly, transfer of neither cell type from CSC vs. SHC donor mice affected anxiety-related behavior of recipient mice in the light-dark box. Taken together, our data demonstrate that typical physiological and immunological, but not behavioral, effects of chronic stress can be induced in naïve recipient mice by adoptively transferring mesLNCs, in particular CD4+ mesLNCs, from chronically stressed donor mice.

Subcutaneous Mycobacterium vaccae promotes resilience in a mouse model of chronic psychosocial stress when administered prior to or during psychosocial stress.

Chronic psychosocial stress is a risk factor for many mental disorders, including affective disorders, anxiety disorders, and trauma- and stressor-related disorders (i.e., posttraumatic stress disorder, PTSD). As these disorders are associated with an overreactive immune system and chronic low-grade inflammation, immunoregulatory approaches counterbalancing basal and/or stress-induced immune activation should be protective in this context. In support of this hypothesis, we recently demonstrated that repeated subcutaneous (s.c.) preimmunization with a heat-killed preparation of the immunoregulatory bacterium Mycobacterium vaccae (M. vaccae; National Collection of Type Culture (NCTC) 11659) promoted proactive stress coping and protected against stress-induced anxiety and intestinal pathology in a mouse model of chronic psychosocial stress. To induce development of a chronic anxiety-like state, the chronic subordinate colony housing (CSC) paradigm was used. Here we employed the CSC paradigm (start day 1) to confirm the stress-protective effects of repeated s.c. M. vaccae administrations prior to CSC exposure (days -21, -14, and -7) and to extend these findings to the stress-protective role of M. vaccae when administered repeatedly during CSC exposure (days 2, 8 and 15). As readouts we assessed the stress coping behavior on days 1, 8, and 15 and general and/or social anxiety-related behavior on days 19 (elevated plus-maze), 20 (open-field/novel object test), and day 21 (social preference/avoidance test) of CSC exposure. In line with our previous study, M. vaccae administered prior to CSC strongly promoted active stress coping and moderately reduced CSC-induced general and social anxiety. Although M. vaccae administered during CSC did not affect stress coping, this treatment protocol profoundly protected against CSC-induced general, and to a lesser extent social, anxiety. Taken together, these data broaden the framework for developing bioimmunoregulatory approaches, based on the administration of immunoregulatory microorganisms, for the prevention and/or treatment of affective disorders, anxiety disorders, and trauma- and stressor-related psychiatric disorders like PTSD.

Intranasal Mycobacterium vaccae administration prevents stress-induced aggravation of dextran sulfate sodium (DSS) colitis.

An increasing body of evidence indicates that immunodysregulation and subsequent chronic low-grade inflammation can promote the development of stress-related somatic and psychiatric pathologies, including inflammatory bowel disease (IBD) and posttraumatic stress disorder (PTSD). Thus, immunoregulatory approaches counterbalancing basal and/or stress-induced immune activation should have stress-protective potential. In support of this hypothesis, we recently demonstrated that repeated s.c. preimmunization with a heat-killed preparation of the immunoregulatory bacterium Mycobacterium vaccae (M. vaccae; National Collection of Type Culture (NCTC) 11659), protects mice against stress-induced general anxiety, spontaneous colitis, and aggravation of dextran sulfate sodium (DSS)-induced colitis in the chronic subordinate colony housing (CSC) paradigm, a validated model for PTSD in male mice. In the current study, we repeatedly administered M. vaccae via the non-invasive intranasal (i.n.; 0.1 mg/mouse/administration) route, prior to or during CSC exposure or single housed control (SHC) conditions, and assessed the effects on general and social anxiety, and on parameters related to the severity of DSS-induced colitis. While administration of M. vaccae prior to the onset of CSC exposure only had minor stress-protective effects, administration of M. vaccae during CSC completely prevented CSC-induced aggravation of DSS colitis. As CSC in the current experimental setting did not reliably increase general anxiety-related behavior, potential stress-protective effects of M.vaccae are difficult to interpret. Taken together, these data broaden the framework for developing bioimmunoregulatory approaches, based on the administration of microorganisms with anti-inflammatory and immunoregulatory properties, for the prevention of stress-related disorders.