Premature immunosenescence: role of stress-related factors

The ageing of the immune system, immunosenescence, is associated with important remodelling changes in all lymphoid organs and its cells. However, the pace of ageing differs between people with the same chronological age, indicating that it may be thus influenced by extrinsic factors, including the chronic stress. In fact, young adults under chronic psychosocial stress may present immunosenescence features similarly to those found in older adults. Immunosenescence contributes to the onset and clinical course of age-related diseases such as neurodegenerative disorders, cancer, rheumatoid arthritis, cardiovascular and metabolic diseases. This article reviews that premature immunosenescence is observed in adults under chronic psychological stress as well as in healthy adolescents with history of childhood maltreatment. Superimposing stress during ageing is associated with further decline in adaptive immunity, increased inflammaging, accelerated cellular senescence and increased susceptibility to infections. This is of great interest for the COVID-19 pandemic, making the chronically stressed older adults of particular risk for worsen disease outcomes and poor vaccine responses.

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.

A 16-week aerobic exercise and mindfulness-based intervention on chronic psychosocial stress: a pilot and feasibility study

Objectives Researchers have begun delivering mindfulness and aerobic exercise training concurrently on the premise that a combination intervention will yield salutary outcomes over and above each intervention alone. An estimate of the effect of combination training on chronic psychosocial stress in a nonclinical population has not been established. The objective of this study was to establish protocol feasibility in preparation of a definitive RCT targeting healthy individuals, and to explore the preliminary effect of combination training on reducing chronic psychosocial stress in this population. Methods Twenty-four participants were allocated to a single-arm pre-post study and subjected to 16 weeks of concurrent mindfulness psychoeducation and aerobic exercise training. Feasibility criteria were collected and evaluated. Within-group changes in chronic psychosocial stress, mindfulness, emotion regulation, and cardiorespiratory fitness were also assessed. Primary analyses were based on 17 participants. Results Retention rate, response rate, recruitment rate, and sample size analyses indicate a definitive trial is feasible for detecting most effects with precision. There was also a decline in our primary dependent measure of chronic psychosocial stress (dpretest = −0.56, 95% CI [ −1.14,−0.06]). With regard to secondary measures, there was an increase in the use of cognitive reappraisal, and a reduction in use of maladaptive emotion regulation strategies. We are insufficiently confident to comment on changes in mindfulness and aerobic capacity $\left (\dot {V}O_{2max}\right)$ V ̇ O 2 max . However, there were subgroup improvements in aerobic economy at submaximal exercise intensities. Conclusions We recommend a definitive trial is feasible and should proceed. Trial registration ANZCTR (ID: ACTRN12619001726145). Retrospectively registered December 9, 2019.

Molecular origin of somatostatin-positive neuron vulnerability

Reduced somatostatin (SST) and SST-positive (SST+) neurons are hallmarks of neurological disorders and associated with mood disturbances, but their origin are unknown. Chronic psychosocial stress induces behavioral emotionality deficits and deregulates unfolded protein response (UPR) of the endoplasmic reticulum (ER) preferentially in SST+ neurons. Here we confirm that chronic stress increases ER stress levels in SST+ neurons of mouse prefrontal cortex, and show that genetically suppressing ER stress in SST+ neurons, but not in pyramidal neurons, normalized psychosocial stress-induced behavioral emotionality. Forced expression of SST precursor protein (preproSST), mimicking psychosocial stress-induced early proteomic changes, induces ER stress, whereas mature SST or processing-incompetent preproSST does not. Biochemical analyses further show that psychosocial stress induces SST protein aggregation under elevated ER stress conditions. These results demonstrate that SST processing is a SST+ neuron-intrinsic vulnerability factor under conditions of sustained or over-activated UPR in the ER, hence negatively impacting SST+ neuron functions.