Dynamic exercise evokes a rapid redeployment of cytotoxic T cell subsets with high surface expression of β2 adrenergic receptors, presumably to enhance immunosurveillance during acute stress. As this response is affected by age and infection history, this study examined latent CMV infection as a potential confounder to age-related differences in blood CD8+ T-cell responses to exercise. Healthy young (n=16) and older (n=16) humans counterbalanced by CMV IgG serostatus (positive or negative) exercised for 30-min at ∼80% peak cycling power. Those with CMV redeployed ∼2-times more CD8+ T-cells and ∼6-times more KLRG1+/CD28- and CD45RA+/CCR7- CD8+ subsets than non-infected exercisers. Seronegative older exercisers had an impaired redeployment of total CD8+ T-cells, CD45RA+/CCR7+ and KLRG1-/CD28+ CD8+ subsets compared to young. Redeployed CD8+ T-cell numbers were similar between infected young and old. CMVpp65 specific CD8+ cells in HLA/A2(∗) subjects increased ∼2.7-fold after exercise, a response that was driven by the KLRG1+/CD28-/CD8+ subset. Stimulating PBMCs before and after exercise with CMVpp65 and CMV IE-1 antigens and overlapping peptide pools revealed a 2.1 and 4.4-fold increases in CMVpp65 and CMV IE-1 IFN-γ secreting cells respectively. The breadth of the T cell response was maintained after exercise with the magnitude of the response being amplified across the entire epitope repertoire. To conclude, latent CMV infection overrides age-related impairments in CD8+ T-cell redeployment with exercise. We also show for the first time that many T-cells redeployed with exercise are specific to CMVpp65 and CMV IE-1 antigens, have broad epitope specificity, and are mostly of a high-differentiated effector memory phenotype.

BACKGROUND:

Multiple sclerosis (MS) incidence is higher in geographic regions with less sunlight exposure. Both vitamin D and melatonin are essential mediators of the effect of sunlight in health, and as such are candidates to play a key role in MS. We hypothesized that vitamin D and melatonin may have related influences in patients with MS.

METHODS:

In a randomized, double blind study of 40 IFN-β treated MS patients, 21 patients were assigned to 800IU of vitamin D3 per day (low dose), while 19 patients received 4,370IU vitamin D3 per day (high dose) for one year. Serum 25-hydroxy-vitamin-D (25-OH-D) and night time urine melatonin metabolite, 6-sulphatoxy-melatonin (6-SMT), were measured at baseline, 3months and 1year from enrolment.

RESULTS:

After 3months supplementation, 25-OH-D levels increased and night-time melatonin secretion decreased significantly in the high dose group, but not in the low dose group. After 1year, a decrease in 25-OH-D levels, accompanied by an increase of urine nighttime 6-SMT were observed in the high dose group. Percent change in serum 25-OH-D was significantly and negatively correlated with percent change in urine 6-SMT after 3months and between 3months to 1year. 25-OH-D levels by the end of the study were significantly and negatively correlated to BMI.

CONCLUSIONS:

Melatonin secretion is negatively correlated with alterations in serum 25-OH-D in IFN-β treated patients with MS. The finding suggests that melatonin should be considered as a potential mediator of vitamin D neuro-immunomodulatory effects in patients with MS.

There is emerging evidence for a link between sedentary behavior and mental health, although the mechanisms remain unknown. We tested if an underlying inflammatory process explains the association between sedentary behavior and depressive symptoms. We conducted a two year follow-up of 4964 (aged 64.5±8.9years) men and women from the English Longitudinal Study of Ageing, a cohort of community dwelling older adults. Self-reported TV viewing time was assessed at baseline as a marker of leisure time sedentary behavior. The eight-item Centre of Epidemiological Studies Depression (CES-D) scale was administered to measure depressive symptoms at follow-up. At baseline, TV time was associated with C-reactive protein (CRP), adjusted geometric mean CRP values were 2.94mg/L (<2h/d TV); 3.04mg/L (2-4h/d TV); 3.29mg/L (4-6h/d TV); 3.23mg/L (>6h/d TV). We observed both a direct association of TV time on CES-D score at follow-up (B=0.08, 95% CI, 0.05, 0.10) and indirect effects (B=0.07, 95% CI, 0.05, 0.08). The indirect effects were largely explained through lack of physical activity, smoking, and alcohol, but not by CRP or body mass index.

Alzheimer's disease (AD) is characterized, in part, by atrophy of the adult brain and increased presence of extracellular amyloid-beta (Aβ) plaques. Previous studies in our lab have shown that peripheral inflammation can lead to increased central Aβ and deficits in learning and memory. In order to determine whether Aβ accumulation in the brain is responsible for the learning deficits, we attempted to decrease peripheral production of Aβ in order to reduce central Aβ accumulation. It has previously been shown that Aβ is produced in large quantities in the liver, and is transferred across the blood-brain barrier (BBB). Recent research has shown that peripheral treatment with imatinib methanesulfonate salt (IM), known to interfere with the interaction between gamma (γ)-secretase and the γ-secretase activating protein (GSAP), decreases the cleavage of peripheral amyloid precursor protein into Aβ. Because IM poorly penetrates the BBB, we hypothesized that co-administration of IM with LPS would decrease peripheral production of Aβ in the presence of LPS-induced inflammation, leading to a decrease in Aβ accumulation in the hippocampus. We show that peripheral IM treatment eliminates hippocampal Aβ elevation that follows LPS-induced peripheral inflammation. Importantly, IM also eliminates the cognitive impairment seen following seven consecutive days of LPS administration, implicating Aβ peptides as a likely cause of these cognitive deficits.

The chemokine CCL21 is released from injured neurons and acts as a ligand of the chemokine receptor, CXCR3, which likely contributes to pro-inflammatory adaptations and secondary neuronal damage. CCL21-CXCR3 signalling may therefore impact on the development of neuropathic pain. By using the respective knockout mice we show that deficiency of CCL19/21 in plt/plt mice attenuates nerve injury evoked pain but not the hyperalgesia evoked by autoimmune encephalomyelitis (EAE). Oppositely, CXCR3-deficiency had no protective effect after traumatic nerve injury but reduced EAE-evoked hyperalgesia and was associated with reduced clinical EAE scores, a reduction of the pro-inflammatory cell infiltration and reduced upregulation of interferon gamma and interleukin-17 in the spinal cord. In contrast, microglia activation in the spinal cord after traumatic sciatic nerve injury was neither attenuated in CXCR3(-/-) nor plt/plt mice, nor in double knockouts. However, the severity of EAE, but not the hyperalgesia, was also reduced in plt/plt mice, which was associated with reduced infiltration of the spinal cord with CCR7+ T-cells, an increase of CD25+ T-cells and reduced upregulation of CXCL9 and 10, CCL11 and 12. The data show that CCL21 and CXCR3 have dichotomous functions in traumatic and EAE-evoked neuropathic pain suggesting diverse mechanisms likely requiring diverse treatments although both types of neuropathic pain are mediated in part through the immune activation.

Epidemiological studies have associated infection during pregnancy with increased risk of neurodevelopmental disorders in children, which is modeled in rodents by stimulating the immune system of pregnant dams with microorganisms or their mimics, such as poly(I:C) or LPS. In two prenatal mouse models, we show that in utero exposure of the fetus to cytokines/inflammatory mediators elicited by maternal immune stimulation with poly(I:C) yields offspring that exhibit a proinflammatory phenotype due to alterations in developmental programming of their immune system. Changes in the innate and adaptive immune elements of these pro-inflammatory offspring result in more robust responses following exposure to immune stimuli than those observed in control offspring from PBS-injected pregnant dams. In the first model, offspring from poly(I:C)-injected immunologically naïve dams showed heightened cellular and cytokine responses 4h after injection of zymosan, a TLR2 agonist. In the second model, using dams with immunological memory, poly(I:C) injection during pregnancy produced offspring that showed preferential differentiation toward Th17 cell development, and earlier onset of clinical symptoms of EAE following immunization with MOG35-55. Such "fetal programming" in offspring from poly(I:C)-injected dams not only persists into neonatal and adult life, but also can have profound consequences on health and disease.

Evolutionary imperatives bred a vigorous and highly orchestrated behavioral and immune response to the microbial world that served to promote species survival and propagation. The resultant legacy is an inflammatory bias which goes largely unchecked in the modern world and is provoked not only by pathogens but also now by people. In this commentary, the authors' contributions to the special issue on Inflammation and Mental Health are described, beginning with the origins of the inflammatory bias, its roots in genetic predispositions to behavioral adaptations and ultimately maladaptations, and its consequences on the developing brain. In addition, the mechanisms by which the immune system engages behavior are described including a central role for the inflammasome which may serve to link psychological stress with inflammatory and behavioral responses. Neurotransmitter systems that mediate effects of the immune system on behavior are also described along with interactions of the inflammatory bias with depression and their convergent impact on the response to stress and medical illness. Finally, translational implications are discussed including data from a clinical trial using a cytokine antagonist in depressed patients, which suggests an interaction of the inflammatory bias with other evolutionary legacies including those related to food consumption and their modern consequences of obesity and the metabolic syndrome. Taken together, the articles offer a sampling of the rich literature that has evolved regarding the role of the immune system in behavioral disorders. The grounding of this relationship in our evolutionary past may serve to inform future research both theoretically and therapeutically.

Dysfunctional serotoninergic regulation and hypothalamic-pituitary-adrenal (HPA) axis overreactivity have been consistently reported in research studies with eating disorders (ED). In addition, the links between stress response, serotonin function, HPA axis and inflammatory mechanisms in ED have also been suggested in a number of studies. In our study, inflammatory parameters in white blood cells were investigated in 26 female patients with ED and 25 healthy control subjects matched for sex, age and ethnicity. Patients were free of medication for at least two weeks at the time of the study. Results showed a significant increase in plasma levels of the proinflammatory cytokine IL1β and the protein expression of cyclooxygenase 2 (COX2) in peripheral mononuclear blood cells (PMBCs) in ED patients compared with controls. As well as a significant increase of the oxidative-nitrosative marker TBARS (Thiobarbituric Acid Reactive Substances) in plasma. These findings were associated with increased expression of the alpha7 subunit of the nicotinic receptor (α7nAChR) in PMBC in ED patients independent of plasma cotinine levels. These results suggest that a pro-inflammatory and oxidant phenotype might be present in ED patients. Further research on cellular inflammatory and anti-inflammatory pathways might be oriented to investigate differences between ED subtypes and to search for new potential targets for pharmacological treatment.

The tumor necrosis factor (TNF) antagonist infliximab was recently found to reduce depressive symptoms in patients with increased baseline inflammation as reflected by a plasma C-reactive protein concentration >5mg/L. To further explore predictors and targets of response to infliximab, differential gene expression was examined in peripheral blood mononuclear cells from infliximab responders (n=13) versus non-responders (n=14) compared to placebo at baseline and 6h, 24h, and 2weeks after the first infliximab infusion. Treatment response was defined as 50% reduction in depressive symptoms at any point during the 12-week trial. One-hundred-forty-eight gene transcripts were significantly associated (1.2-fold, adjusted p⩽0.01) with response to infliximab and were distinct from placebo responders. Transcripts predictive of infliximab response were associated with gluconeogenesis and cholesterol transport, and were enriched in a network regulated by hepatocyte nuclear factor (HNF)4-alpha, a transcription factor involved in gluconeogenesis and cholesterol and lipid homeostasis. Of the 148 transcripts differentially expressed at baseline, 48% were significantly regulated over time in infliximab responders, including genes related to gluconeogenesis and the HNF4-alpha network, indicating that these predictive genes were responsive to infliximab. Responders also demonstrated inhibition of genes related to apoptosis through TNF signaling at 6h and 24h after infusion. Transcripts down-regulated in responders 2weeks after infliximab were related to innate immune signaling and nuclear factor-kappa B. Thus, baseline transcriptional signatures reflective of alterations in glucose and lipid metabolism predicted antidepressant response to infliximab, and infliximab response involved regulation of metabolic genes and inhibition of genes related to innate immune activation.

Toll-like receptors (TLRs) mediate the induction of the innate immune system in response to pathogens, injury and disease. However, they also play non-immune roles and are expressed in the central nervous system (CNS) during prenatal and postnatal stages including adulthood. Little is known about their roles in the CNS in the absence of pathology. Several members of the TLR family have been implicated in the development of neural and cognitive function although the contribution of TLR9 to these processes has not been well defined. The current studies were undertaken to determine whether developmental TLR9 deficiency affects motor, sensory or cognitive functions. We report that TLR9 deficient (TLR9(-/-)) mice show a hyper-responsive sensory and motor phenotype compared to wild type (TLR9(+/+)) controls. This is indicated by hypersensitivity to thermal stimuli in the hot plate paw withdrawal test, enhanced motor-responsivity under anxious conditions in the open field test and greater sensorimotor reactivity in the acoustic startle response. Prepulse inhibition (PPI) of the acoustic startle response was also enhanced, which indicates abnormal sensorimotor gating. In addition, subtle, but significant, gait abnormalities were noted in the TLR9(-/-) mice on the horizontal balance beam test with higher foot slip numbers than TLR9(+/+) controls. In contrast, spatial learning and memory, assessed by the Morris water maze, was similar in the TLR9(-/-) and TLR9(+/+) mice. These findings support the notion that TLR9 is important for the appropriate development of sensory and motor behaviors.