The Transcriptional Regulator Id2 Is Critical for Adipose-Resident Regulatory T Cell Differentiation, Survival, and Function.

Adipose regulatory T cells (aTregs) have emerged as critical cells for the control of local and systemic inflammation. In this study, we show a distinctive role for the transcriptional regulator Id2 in the differentiation, survival, and function of aTregs in mice. Id2 was highly expressed in aTregs compared with high Id3 expression in lymphoid regulatory T cells (Tregs). Treg-specific deletion of Id2 resulted in a substantial decrease in aTregs, whereas Tregs in the spleen and lymph nodes were unaffected. Additionally, loss of Id2 resulted in decreased expression of aTreg-associated markers, including ST2, CCR2, KLRG1, and GATA3. Gene expression analysis revealed that Id2 expression was essential for the survival of aTregs, and loss of Id2 increased cell death in aTregs due to increased Fas expression. Id2-mediated aTreg depletion resulted in increased systemic inflammation, increased inflammatory macrophages and CD8+ effector T cells, and loss of glucose tolerance under standard diet conditions. Thus, we reveal an unexpected and novel function for Id2 in mediating differentiation, survival, and function of aTregs that when lost result in increased metabolic perturbation.

The Lysophosphatidylcholine Transporter MFSD2A Is Essential for CD8+ Memory T Cell Maintenance and Secondary Response to Infection.

Access to nutrients is critical for an effective T cell immune response to infection. Although transporters for sugars and amino acids have previously been described in the context of the CD8+ T cell immune response, the active transport of exogenous fatty acids has remained enigmatic. In this study, we discovered that the sodium-dependent lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (MFSD2A) is upregulated on activated CD8+ T cells and is required for memory T cell maintenance. MFSD2A deficiency in mice resulted in decreased import of LPC esterified to long chain fatty acids into activated CD8+ T cells, and MFSD2A-deficient cells are at a competitive disadvantage resulting in reduced memory T cell formation and maintenance and reduced response to secondary infection. Mechanistically, import of LPCs was required to maintain T cell homeostatic turnover, which when lost resulted in a decreased memory T cell pool and thus a reduced secondary response to repeat infection.

Invariant natural killer T-cell development and function with loss of microRNA-155.

Invariant natural killer T (iNKT) cells are adaptive T cells with innate-like characteristics including rapid cytokine production and a proliferative response to stimulation. Development of these cells in the thymus is dependent on expression of the microRNA (miRNA) processing enzyme Dicer, indicating that iNKT cells probably have distinct miRNA requirements for gene regulation during development. The miRNA miR-155 has previously been shown to have numerous roles in T cells, including regulation of proliferation and differentiation, and positive modulation of interferon-γ expression. We examined the role of miR-155 in the development and function of iNKT cells. Using germline-deficient miR-155 mice, we showed that loss of miR-155 resulted in unchanged iNKT cell frequency and cell number. Although miR-155 was up-regulated in iNKT cells upon activation with α-galactosylceramide, loss of miR-155 did not affect cytokine production or proliferation by iNKT cells. Hence, cytokine production occurs in iNKT cells independently of miR-155 expression.

Stages versus subsets: Invariant Natural Killer T cell lineage differentiation.

Invariant Natural Killer T (iNKT) cells represent a population of innate T lymphocytes which act as 'first-responders' to infection. While they have long been considered a versatile cell, capable of secretion of multiple cytokines upon activation, recent evidence now indicates that distinct lineages of iNKT cells with unique transcriptional and cytokine profiles exist in different peripheral tissue and as such represent 'fine-tuning' of these cells, which act as mediators between the innate and adaptive immune systems. Here we discuss the molecules regulating the differentiation of iNKT cell lineages, the transcription factors associated with their development, and the role of E protein transcription factors and their negative regulators the Id proteins, as these cells develop from immature progenitor cells to terminally differentiated cells in peripheral tissue.

Acute psychosocial stress in mid-aged male rats causes hyperthermia, cognitive decline, and increased deep sleep power, but does not alter deep sleep duration.

Aging is associated with altered sleep architecture and worsened hippocampus-dependent cognition, highly prevalent clinical conditions that detract from quality of life for the elderly. Interestingly, exposure to psychosocial stress causes similar responses in young subjects, suggesting that age itself may act as a stressor. In prior work, we demonstrated that young animals show loss of deep sleep, deficits in cognition, and elevated body temperature after acute stress exposure, whereas aged animals are hyporesponsive on these measures. However, it is unclear if these age-altered stress responses occur in parallel over the course of aging. To address this, here we repeated the experiment in mid-aged animals. We hypothesized that mid-aged stress responses would be intermediate between those of young and aged subjects. Sixteen mid-aged (12 months) male F344 rats were implanted with EEG/EMG emitters to monitor sleep architecture and body temperature, and were trained on the Morris water maze for 3 days. On the fourth day, half of the subjects were restrained for 3 hours immediately before the water maze probe trial. Sleep architecture and body temperature were measured during the ensuing inactive period, and on the following day, endpoint measures were taken. Restrained mid-aged animals showed resistance to deep sleep loss, but demonstrated stress-induced water maze probe trial performance deficits as well as postrestraint hyperthermia. Taken in the context of prior work, these data suggest that age-related loss of sleep architecture stress sensitivity may precede both cognitive and body temperature-related stress insensitivity.

Aged rats are hypo-responsive to acute restraint: implications for psychosocial stress in aging.

Cognitive processes associated with prefrontal cortex and hippocampus decline with age and are vulnerable to disruption by stress. The stress/stress hormone/allostatic load hypotheses of brain aging posit that brain aging, at least in part, is the manifestation of life-long stress exposure. In addition, as humans age, there is a profound increase in the incidence of new onset stressors, many of which are psychosocial (e.g., loss of job, death of spouse, social isolation), and aged humans are well-understood to be more vulnerable to the negative consequences of such new-onset chronic psychosocial stress events. However, the mechanistic underpinnings of this age-related shift in chronic psychosocial stress response, or the initial acute phase of that chronic response, have been less well-studied. Here, we separated young (3 month) and aged (21 month) male F344 rats into control and acute restraint (an animal model of psychosocial stress) groups (n = 9-12/group). We then assessed hippocampus-associated behavioral, electrophysiological, and transcriptional outcomes, as well as blood glucocorticoid and sleep architecture changes. Aged rats showed characteristic water maze, deep sleep, transcriptome, and synaptic sensitivity changes compared to young. Young and aged rats showed similar levels of distress during the 3 h restraint, as well as highly significant increases in blood glucocorticoid levels 21 h after restraint. However, young, but not aged, animals responded to stress exposure with water maze deficits, loss of deep sleep and hyperthermia. These results demonstrate that aged subjects are hypo-responsive to new-onset acute psychosocial stress, which may have negative consequences for long-term stress adaptation and suggest that age itself may act as a stressor occluding the influence of new onset stressors.

Hippocampal CA1 transcriptional profile of sleep deprivation: relation to aging and stress.

BACKGROUND: Many aging changes seem similar to those elicited by sleep-deprivation and psychosocial stress. Further, sleep architecture changes with age suggest an age-related loss of sleep. Here, we hypothesized that sleep deprivation in young subjects would elicit both stress and aging-like transcriptional responses. METHODOLOGY/PRINCIPAL FINDINGS: F344 rats were divided into control and sleep deprivation groups. Body weight, adrenal weight, corticosterone level and hippocampal CA1 transcriptional profiles were measured. A second group of animals was exposed to novel environment stress (NES), and their hippocampal transcriptional profiles measured. A third cohort exposed to control or SD was used to validate transcriptional results with Western blots. Microarray results were statistically contrasted with prior transcriptional studies. Microarray results pointed to sleep pressure signaling and macromolecular synthesis disruptions in the hippocampal CA1 region. Animals exposed to NES recapitulated nearly one third of the SD transcriptional profile. However, the SD-aging relationship was more complex. Compared to aging, SD profiles influenced a significant subset of genes. mRNA associated with neurogenesis and energy pathways showed agreement between aging and SD, while immune, glial, and macromolecular synthesis pathways showed SD profiles that opposed those seen in aging. CONCLUSIONS/SIGNIFICANCE: We conclude that although NES and SD exert similar transcriptional changes, selective presynaptic release machinery and Homer1 expression changes are seen in SD. Among other changes, the marked decrease in Homer1 expression with age may represent an important divergence between young and aged brain response to SD. Based on this, it seems reasonable to conclude that therapeutic strategies designed to promote sleep in young subjects may have off-target effects in the aged. Finally, this work identifies presynaptic vesicular release and intercellular adhesion molecular signatures as novel therapeutic targets to counter effects of SD in young subjects.

Microarray analyses of laser-captured hippocampus reveal distinct gray and white matter signatures associated with incipient Alzheimer's disease.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that threatens to reach epidemic proportions as our population ages. Although much research has examined molecular pathways associated with AD, relatively few such studies have focused on the disease's critical early stages. In a prior microarray study we correlated gene expression in hippocampus with degree of Alzheimer's disease and found close associations between upregulation of apparent glial transcription factor/epigenetic/tumor suppressor genes and incipient AD. The results suggested a new model in which AD pathology spreads along myelinated axons (Blalock et al., 2004). However, the microarray analyses were performed on RNA extracted from frozen hand-dissected hippocampal CA1 tissue blocks containing both gray and white matter, limiting the confidence with which transcriptional changes in gray matter could be distinguished from those in white matter. Here, we used laser capture microdissection (LCM) to exclude major white matter tracts while selectively collecting CA1 hippocampal gray matter from formalin-fixed, paraffin-embedded (FFPE) hippocampal sections of the same subjects assessed in our prior study. Microarray analyses of this gray matter-enriched tissue revealed many transcriptional changes similar to those seen in our past study and in studies by others, particularly for downregulated neuron-related genes. Additionally, the present analyses identified several previously undetected pathway alterations, including downregulation of molecules that stabilize ryanodine receptor Ca2+ release and upregulation of vasculature development. Conversely, we found a striking paucity of the upregulated changes in the putative glial and growth-related genes that had been strongly overrepresented in the prior mixed-tissue study. We conclude that FFPE tissue can be a reliable resource for microarray studies of brain tissue, that upregulation of growth-related epigenetic/transcription factors during incipient AD is predominantly localized in and around white matter (supporting our prior findings and model), and that novel alterations in vascular and ryanodine receptor-related pathways in gray matter are closely associated with incipient AD.

Deep sleep and parietal cortex gene expression changes are related to cognitive deficits with age.

BACKGROUND: Age-related cognitive deficits negatively affect quality of life and can presage serious neurodegenerative disorders. Despite sleep disruption's well-recognized negative influence on cognition, and its prevalence with age, surprisingly few studies have tested sleep's relationship to cognitive aging. METHODOLOGY: We measured sleep stages in young adult and aged F344 rats during inactive (enhanced sleep) and active (enhanced wake) periods. Animals were behaviorally characterized on the Morris water maze and gene expression profiles of their parietal cortices were taken. PRINCIPAL FINDINGS: Water maze performance was impaired, and inactive period deep sleep was decreased with age. However, increased deep sleep during the active period was most strongly correlated to maze performance. Transcriptional profiles were strongly associated with behavior and age, and were validated against prior studies. Bioinformatic analysis revealed increased translation and decreased myelin/neuronal pathways. CONCLUSIONS: The F344 rat appears to serve as a reasonable model for some common sleep architecture and cognitive changes seen with age in humans, including the cognitively disrupting influence of active period deep sleep. Microarray analysis suggests that the processes engaged by this sleep are consistent with its function. Thus, active period deep sleep appears temporally misaligned but mechanistically intact, leading to the following: first, aged brain tissue appears capable of generating the slow waves necessary for deep sleep, albeit at a weaker intensity than in young. Second, this activity, presented during the active period, seems disruptive rather than beneficial to cognition. Third, this active period deep sleep may be a cognitively pathologic attempt to recover age-related loss of inactive period deep sleep. Finally, therapeutic strategies aimed at reducing active period deep sleep (e.g., by promoting active period wakefulness and/or inactive period deep sleep) may be highly relevant to cognitive function in the aging community.