Myelin-specific T helper 17 cells promote adult hippocampal neurogenesis through indirect mechanisms

Linkage of blood cell division cycle 42 with T helper cells, and their correlation with anxiety, depression, and cognitive impairment in stroke patients

Cell division cycle 42 (CDC42) regulates T helper (Th) cell differentiation and is related to psychological disorders. This study aimed to assess the correlation between blood CDC42 and Th cells, and their association with mental issues in stroke patients. Peripheral blood samples were obtained from 264 stroke patients and 50 controls. Then, serum CDC42 was measured by enzyme-linked immunosorbent assay, and Th1, Th2, and Th17 cells were detected by flow cytometry. Hospital Anxiety and Depression Scale (HADS) and Mini Mental State Examination (MMSE) were applied to patients. CDC42 was decreased (P<0.001), Th1 (P=0.013) and Th17 (P<0.001) cells were elevated, while Th2 cells (P=0.108) showed no difference in stroke patients compared to controls. In addition, CDC42 was negatively associated to Th1 (P=0.013) and Th17 (P<0.001) cells in stroke patients but were not associated with Th2 cells (P=0.223). Interestingly, CDC42 was negatively associated with HADS-anxiety (P<0.001) and HADS-depression scores (P=0.034) and positively associated with MMSE score (P<0.001) in stroke patients. Lower CDC42 was associated to lower occurrence of anxiety (P=0.002), depression (P=0.001), and cognitive impairment (P=0.036) in stroke patients. Furthermore, increased Th17 cells were positively correlated with HADS-anxiety and HADS-depression scores and inversely correlated with MMSE score, which were also associated with higher occurrence of anxiety, depression, and cognitive impairment in stroke patients (all P<0.05). Blood CDC42 and Th17 cells were correlated, and both of them were linked to the risk of anxiety, depression, and cognitive impairment. However, the findings need further large-scale validation, and the implicated mechanism needs more investigation.

From Youthful Vigor to Aging Decline: Unravelling the Intrinsic and Extrinsic Determinants of Hippocampal Neural Stem Cell Aging

Since Joseph Altman published his pioneering work demonstrating neurogenesis in the hippocampus of adult rats, the number of publications in this field increased exponentially. Today, we know that the adult hippocampus harbors a pool of adult neural stem cells (NSCs) that are the source of life-long neurogenesis and plasticity. The functions of these NSCs are regulated by extrinsic cues arising from neighboring cells and the systemic environment. However, this tight regulation is subject to imbalance with age, resulting in a decline in adult NSCs and neurogenesis, which contributes to the progressive deterioration of hippocampus-related cognitive functions. Despite extensive investigation, the mechanisms underlying this age-related decline in neurogenesis are only incompletely understood, but appear to include an increase in NSC quiescence, changes in differentiation patterns, and NSC exhaustion. In this review, we summarize recent work that has improved our knowledge of hippocampal NSC aging, focusing on NSC-intrinsic mechanisms as well as cellular and molecular changes in the niche and systemic environment that might be involved in the age-related decline in NSC functions. Additionally, we identify future directions that may advance our understanding of NSC aging and the concomitant loss of hippocampal neurogenesis and plasticity.

Longitudinal change of Th1, Th2, and Th17 cells and their relationship between cognitive impairment, stroke recurrence, and mortality among acute ischemic stroke patients

Background

T‐helper (Th) cells regulate immunity and inflammation, and modulate cognitive impairment in both cardio‐cerebrovascular and neurological diseases. This study aimed to explore the correlation of longitudinal change of Th1/2/17 cells with cognitive impairment and prognosis in acute ischemic stroke (AIS).

Methods

Th1/2/17 cells were detected by flow cytometry in peripheral blood samples from 150 AIS patients at admission (baseline), Day (D)1, D3, and D7 after admission, and from 30 controls. Mini‐Mental State Examination (MMSE) score among AIS patients at discharge was assessed. Stroke recurrence and mortality were evaluated.

Results

Th1 (p = 0.013) and Th17 cells (p < 0.001) but not Th2 cells (p = 0.105) were elevated in AIS patients versus controls. Th1 cells (p = 0.027) and Th17 cells (p < 0.001) but not Th2 cells (p = 0.227) were positively correlated with NIHSS score in AIS patients. Furthermore, Th1 and Th17 cells elevated from baseline to D3 and then decreased on D7 after AIS onset, while Th2 cells illustrated an opposite trend (all p < 0.001). Th17 cells on D1 (p = 0.011), D3 (p = 0.014), and D7 (p < 0.001) were correlated with lower MMSE score, and their levels on D3 (p = 0.033) and D7 (p = 0.004) were related to elevated cognitive impairment. Th1 and Th2 cells were not related to cognitive function (all p > 0.05). Additionally, Th17 cells at baseline, D1, D3, and D7 (all p < 0.05) were increased in recurrent patients versus non‐recurrent patients, and in survived patients versus dead patients, but Th1 or Th2 cells did not vary (all p > 0.05).

Conclusion

Th17 cells correlate with increased cognitive impairment, stroke recurrence, and mortality among AIS patients.

Blood T-helper 17 cells and interleukin-17A correlate with the elevated risk of postpartum depression and anxiety

Background

T‐helper (Th) cells regulate inflammation and immunity, which is implicated in psychological disorders. The current study aimed to explore the clinical role of blood Th1, Th2, and Th17 cells and their main secreted cytokines in postpartum depression (PPD) and postpartum anxiety (PPA).

Methods

A total of 226 postpartum women were included. At 6 weeks postpartum, Edinburgh Postnatal Depression Scale (EPDS) and State Trait Anxiety Inventory 6 item version (STAI6) scores were assessed; meanwhile, blood Th1, Th2, and Th17 cells were detected by flow cytometry, serum interferon‐gamma (IFN‐γ), interleukin‐4 (IL‐4), and IL‐17A were detected by enzyme‐linked immunosorbent assay.

Results

The incidence of PPD and PPA were 24.3% and 27.9%, respectively. Th17 cells and IL‐17A were positively correlated with EPDS score and STAI6 score (all p < 0.001). Besides, Th17 cells (p < 0.001) and IL‐17A (p = 0.002) were increased in PPD cases vs. non‐PPD cases, and they were also elevated in PPA cases vs. non‐PPA cases (both p < 0.05). However, Th1 cells, Th2 cells, IFN‐γ, and IL‐4 were not linked with EPDS score or STAI6 score (all p > 0.05); besides, they did not vary in PPD cases vs. non‐PPD cases or in PPA cases vs. non‐PPA cases (all p > 0.05). Multivariate logistic regression model analysis showed that Th17 cells were independently associated with an elevated risk of PPD (odds ratio [OR] = 1.600, p = 0.001) and PPA (OR = 1.371, p = 0.022).

Conclusion

Blood Th17 cells and IL‐17A are positively linked with the risk of PPD and PPA, indicating which may be involved in the development of PPD and PPA.

Th17 Cells in Depression: Are They Crucial for the Antidepressant Effect of Ketamine?

Background: Major depressive disorder is associated with inflammation and immune processes. Depressive symptoms correlate with inflammatory markers and alterations in the immune system including cytokine levels and immune cell function. Th17 cells are a T cell subset which exerts proinflammatory effects. Th17 cell accumulation and Th17/Treg imbalances have been reported to be critical in the pathophysiology of major depressive disorder and depressive-like behaviors in animal models. Th17 cells are thought to interfere with glutamate signaling, dopamine production, and other immune processes. Ketamine is a newly characterized antidepressant medication which has proved to be effective in rapidly reducing depressive symptoms. However, the mechanisms behind these antidepressant effects have not been fully elucidated.

Method: Literature about Th17 cells and their role in depression and the antidepressant effect of ketamine are reviewed, with the possible interaction networks discussed.

Result: The immune-modulating role of Th17 cells may participate in the antidepressant effect of ketamine.

Conclusion: As Th17 cells play multiple roles in depression, it is important to explore the mechanisms of action of ketamine on Th17 cells and Th17/Treg cell balance. This provides new perspectives for strengthening the antidepressant effect of ketamine while reducing its side effects and adverse reactions.

Natural killer cells protect white matter integrity in bipolar disorder

BACKGROUND

Bipolar Disorder (BD) associates with disrupted white matter (WM) microstructure and functional connectivity, and with a perturbation of the immune system. Higher cytokines, and reduced T cells, correlated with WM disruption and fMRI responses. A core component of the innate immune system, natural killer (NK) cells were detected in brain parenchyma, but never studied in BD.

METHODS

We studied Diffusion Tensor Imaging (DTI) measures of water diffusion, fMRI corticolimbic functional response and connectivity, and multi-parameter cytofluorometry analysis of NK (CD56⁺) subpopulations, in 30 inpatients with active Bipolar Disorder type I. NK cells were also obtained in 36 healthy controls.

RESULTS

Patients had significantly higher circulating counts of CD56⁺GMCSF⁺, CD56⁺INFγ⁺, and CD56⁺IL17⁺. NK cell levels positively associated to fractional anisotropy (FA) measures. CD56⁺TNFα⁺, CD56⁺INFγ⁺, and CD56⁺GMCSF⁺ directly correlated with FA, and inversely with radial (RD) and mean (MD) diffusivity. Duration of lithium treatment associated with higher CD56⁺TNFα⁺, CD56⁺IL2⁺, and CD56⁺IL4⁺, and positively associated with FA in tracts were NKs had significant effects. A mediation model suggested a partial mediation of CD56⁺TNFα⁺ cells, higher in patients on lithium, on the effects of lithium on FA. Frequencies of the same cytokine-producing NK cells also influenced fMRI cortico-limbic functional connectivity during processing of both, emotional and non-emotional stimuli.

DISCUSSION

Higher circulating cytokine-producing NK cells associated with lithium treatment, and with DTI measures of WM integrity, partially mediating the effect of lithium on WM. The same cells associated with fMRI responses and connectivity, thus suggesting an effect on structural and functional connectomics in BD.

Social Defeat Modulates T Helper Cell Percentages in Stress Susceptible and Resilient Mice

Altered adaptive immunity involving T lymphocytes has been found in depressed patients and in stress-induced depression-like behavior in animal models. Peripheral T cells play important roles in homeostasis and function of the central nervous system and thus modulate behavior. However, the T cell phenotype and function associated with susceptibility and resilience to depression remain largely unknown. Here, we characterized splenic T cells in susceptible and resilient mice after 10 days of social defeat stress (SDS). We found equally decreased T cell frequencies and comparably altered expression levels of genes associated with T helper (Th) cell function in resilient and susceptible mice. Interleukin (IL)-17 producing CD4⁺ and CD8⁺ T cell numbers in the spleen were significantly increased in susceptible mice. These animals further exhibited significantly reduced numbers of regulatory T cells (T_reg) and decreased gene expression levels of TGF-β. Mice with enhanced Th17 differentiation induced by conditional deletion of PPARγ in CD4⁺ cells (CD4-PPARγ^KO), an inhibitor of Th17 development, were equally susceptible to SDS when compared to CD4-PPARγ^WT controls. These data indicate that enhanced Th17 differentiation alone does not alter stress vulnerability. Thus, SDS promotes Th17 cell and suppresses T_reg cell differentiation predominantly in susceptible mice with yet unknown effects in immune responses after stress exposure.

Genetic and environmental influences on circulating NK and T cells and their relation to bipolar disorder

BACKGROUND

In previous studies we found mild deficiencies of circulating T cells in patients with bipolar disorder (BD) and children at risk for BD, correlating to a higher inflammatory state. The genetic and environmental influences on these T cell deficiencies in association with BD development are unknown.

OBJECTIVES

The aim is to quantify genetic and environmental factors that contribute to the association between the liability to develop BD and T cell deficiencies.

METHODS

Participants of a Dutch bipolar twin study (11 monozygotic BD twin pairs, 15 dizygotic BD twin pairs, 15 monozygotic and 12 dizygotic healthy twin pairs) were included. A detailed FACS analysis of frozen stored leukocytes was carried out to determine the percentages of T cells and various other leukocyte and lymphocyte subsets. A bivariate liability threshold twin model was used to determine genetic and environmental (common and unique) influences on the correlation between BD and the various subsets.

RESULTS

Lower percentages of T cells and higher percentages of NK cells were associated with the familial liability to develop BD. Neither genetic nor shared or unique environmental factors could explain the associations. Lithium usage explained part of the association for T cells, smoking in part that for NK cells.

CONCLUSIONS

Our results confirm that BD is the result of a complex interaction between various genetic and environmental risk factors, in which T and NK cells act as important intermediate immune players.

T Lymphocytes Contribute to the Control of Baseline Neural Precursor Cell Proliferation but Not the Exercise-Induced Up-Regulation of Adult Hippocampal Neurogenesis

Cross-talk between the peripheral immune system and the central nervous system is important for physiological brain health. T cells are required to maintain normal baseline levels of neural precursor proliferation in the hippocampus of adult mice. We show here that neither T cells, B cells, natural killer cells nor natural killer T cells are required for the increase in hippocampal precursor proliferation that occurs in response to physical exercise. In addition, we demonstrate that a subpopulation of T cells, regulatory T cells, is not involved in maintaining baseline levels of neural precursor proliferation. Even when applied at supraphysiological numbers, populations of both naive and stimulated lymphocytes had no effect on hippocampal precursor proliferation in vitro. In addition, physical activity had no effect on peripheral immune cells in terms of distribution in the bone marrow, lymph nodes or spleen, activation state or chemokine receptor (CXCR4 and CCR9) expression. Together these results suggest that lymphocytes are not involved in translating the peripheral effects of exercise to the neurogenic niche in the hippocampus and further support the idea that the exercise-induced regulation of adult neurogenesis is mechanistically distinct from its baseline control.

Redox Signaling, Neuroinflammation, and Neurodegeneration

Production of pro-inflammatory and anti-inflammatory cytokines is part of the defense system that mostly microglia and macrophages display to induce normal signaling to counteract the deleterious actions of invading pathogens in the brain. Also, redox activity in the central nervous system (CNS) constitutes an integral part of the metabolic processes needed by cells to exert their normal molecular and biochemical functions. Under normal conditions, the formation of reactive oxygen and nitrogen species, and the following oxidative activity encounter a healthy balance with immunological responses to preserve cell functions in the brain. However, under different pathological conditions, inflammatory responses recruit pro-oxidant signals and vice versa. The aim of this article is to review the basic concepts about the triggering of inflammatory and oxidative responses in the CNS. Recent Advances: Diverse concurrent toxic pathways are described to provide a solid mechanistic scope for considering intervention at the experimental and clinical levels that are aimed at diminishing the harmful actions of these two contributing factors to nerve cell damage. Critical Issues and Future Directions: The main conclusion supports the existence of a narrow cross-talk between pro-inflammatory and oxidative signals that can lead to neuronal damage and subsequent neurodegeneration. Further investigation about critical pathways crosslinking oxidative stress and inflammation will strength our knowlegde on this topic. Antioxid. Redox Signal. 28, 1626-1651.

A pilot study on immuno-psychiatry in the 22q11.2 deletion syndrome: A role for Th17 cells in psychosis?

BACKGROUND

A growing body of evidence supports a role for immune alterations in Schizophrenia Spectrum Disorders (SSD). A high prevalence (25-40%) of SSD has been found in patients with 22q11.2 deletion syndrome (22q11.2DS), which is known for T-cell deficits due to thymus hypoplasia. This study is the first to explore the association between the T-cell subsets and psychotic symptoms in adults with 22q11.2DS.

METHODS

34 individuals (aged 19-38 yrs.) with 22q11.2DS and 34 healthy age- and gender matched control individuals were included. FACS analysis of the blood samples was performed to define T-cell subsets. Ultra-high risk for psychosis or diagnosis of SSD was determined based on CAARMS interviews and DSM-5 criteria for SSD. Positive psychotic symptom severity was measured based on the PANSS positive symptoms subscale.

RESULTS

A partial T-cell immune deficiency in 22q11.2DS patients was confirmed by significantly reduced percentages of circulating T and T-helper cells. Significantly higher percentages of inflammatory Th1, Th17, and memory T-helper cells were found in adults with 22q11.2DS. Most importantly an increased Th17 percentage was found in adults with psychotic symptoms as compared to non-psychotic adults with 22q11.2DS, and Th17 percentage were related to the presence of positive psychotic symptoms.

CONCLUSIONS

Given the literature on the role of T cells and in particular of Th17 cells and IL-17 in hippocampus development, cognition and behavior, these results support the hypothesis for a role of Th17 cells in the development and/or regulation of psychotic symptoms in 22q11.2DS. This pilot study underlines the importance to further study the role of T-cell defects and of Th17 cells in the development of psychiatric symptoms. It also supports the possibility to use 22q11.2DS as a model to study T-cell involvement in the development of SSD.

Mast cells increase adult neural precursor proliferation and differentiation but this potential is not realized in vivo under physiological conditions

There is growing evidence that both peripheral and resident immune cells play an important part in regulating adult neural stem cell proliferation and neurogenesis, although the contribution of the various immune cell types is still unclear. Mast cells, a population of immune cells known for their role in the allergic response, have been implicated in the regulation of adult hippocampal neurogenesis. Mast cell-deficient c-kit^W-sh/W-sh mice have previously been shown to exhibit significantly decreased adult hippocampal neurogenesis and associated learning and memory deficits. However, given that numerous other cell types also express high levels of c-kit, the utility of these mice as a reliable model of mast cell-specific depletion is questionable. We show here, using a different model of mast cell deficiency (Mcpt5CreR26^DTA/DTA), that precursor proliferation and adult neurogenesis are not influenced by mast cells in vivo. Interestingly, when applied at supraphysiological doses, mast cells can activate latent hippocampal precursor cells and increase subventricular zone precursor proliferation in vitro, an effect that can be blocked with specific histamine-receptor antagonists. Thus, we conclude that while both mast cells and their major chemical mediator histamine have the potential to affect neural precursor proliferation and neurogenesis, this is unlikely to occur under physiological conditions.

Activation of Myeloid TLR4 Mediates T Lymphocyte Polarization after Traumatic Brain Injury

Traumatic brain injury (TBI) is a major public health issue, producing significant patient mortality and poor long-term outcomes. Increasing evidence suggests an important, yet poorly defined, role for the immune system in the development of secondary neurologic injury over the days and weeks following a TBI. In this study, we tested the hypothesis that peripheral macrophage infiltration initiates long-lasting adaptive immune responses after TBI. Using a murine controlled cortical impact model, we used adoptive transfer, transgenic, and bone marrow chimera approaches to show increased infiltration and proinflammatory (classically activated [M1]) polarization of macrophages for up to 3 wk post-TBI. Monocytes purified from the injured brain stimulated the proliferation of naive T lymphocytes, enhanced the polarization of T effector cells (T_H1/T_H17), and decreased the production of regulatory T cells in an MLR. Similarly, elevated T effector cell polarization within blood and brain tissue was attenuated by myeloid cell depletion after TBI. Functionally, C3H/HeJ (TLR4 mutant) mice reversed M1 macrophage and T_H1/T_H17 polarization after TBI compared with C3H/OuJ (wild-type) mice. Moreover, brain monocytes isolated from C3H/HeJ mice were less potent stimulators of T lymphocyte proliferation and T_H1/T_H17 polarization compared with C3H/OuJ monocytes. Taken together, our data implicate TLR4-dependent, M1 macrophage trafficking/polarization into the CNS as a key mechanistic link between acute TBI and long-term, adaptive immune responses.

Th17 cells correlate positively to the structural and functional integrity of the brain in bipolar depression and healthy controls

Abnormalities of T cell-mediated immune activation, in the absence of active somatic immune diseases, have consistently been reported in mood disorders. Apart from being important players in the regulation of cells of the immune system, T cells are essential for normal brain development. We here report studies on the relationship between circulating levels of T helper cells and structural and functional brain imaging in depressed bipolar patients. Since the CCL20-CCR6 axis is an important entry to the brain we differentiated the various T helper cell subpopulations on the basis of their chemokine receptor expression.

METHODS

FACS staining was performed for Th1, Th2, Th17, Th22 and T regulatory cells on frozen leukocytes of 25 consecutively admitted inpatients affected by a major depressive episode, without psychotic features, in the course of Bipolar Disorder I and 21 healthy controls. The frequency of the T helper populations was associated with DTI and fMRI data acquired on a Philips 3.0 Tesla scanner. Tract based spatial statistic was used to obtain measures of white matter integrity (fractional anisotropy, axial, radial and mean diffusivity) from a standard DTI sequence with 35 directions. Patients were also studied for fMRI through a moral valence decision task were subjects had to decide whether morally tuned stimuli were positive or negative.

RESULTS

The percentage of circulating Th17 (CCR6⁺CXCR3^negCCR4⁺CCR10^neg) cells correlated positively with higher fractional anisotropy in fiber tracts contributing to the functional integrity of the brain both in patients and healthy controls, while the frequency of circulating T regulatory (CD4⁺CD25⁺FOXP3⁺) cells correlated positively with higher radial and mean diffusivity in patients. The frequency of circulating T regulatory cells also correlated to lower neuronal responses to negative versus positive morally tuned stimuli in the right dorsolateral prefrontal cortex of patients. Th1 cells correlated negatively with white matter integrity in several tracts (healthy controls), while the cells showed a positive correlation to the levels of pro-inflammatory cytokines (patients).

CONCLUSION

This study shows a new putative role for Th17 cells. Th17 cells are not only playing a role in inducing autoimmunity and auto-inflammation, but might also play a counter intuitive anabolic role in the maintenance of the functional and structural integrity of the brain.

Hippocampal adult neurogenesis: Does the immune system matter?

Adult hippocampal neurogenesis involves proliferation, survival, differentiation and integration of newborn neurons into pre-existing neuronal networks. Although its functional significance in the central nervous system (CNS) has not comprehensively elucidated, adult neurogenesis has been attributed a role in cognition, learning and memory. There is a growing body of evidence that CNS resident as well as peripheral immune cells participate in regulating hippocampal adult neurogenesis. Microglial cells are closely associated with neural stem/progenitor cell (NSPC) in the neurogenic niche engaged in a bidirectional communication with neurons, which may be important for adult neurogenesis. Microglial and neuronal crosstalk is mediated in part by CX3CL1/CX3CR1 signaling and a disruption in this pathway has been associated with impaired neurogenesis. It has been also reported that microglial neuroprotective or neurotoxic effects in adult neurogenesis occur in a context-dependent manner. Apart from microglia other brain resident and peripheral immune cells including pericytes, perivascular macrophages, mast cells and T-cells also modulate this phenomenon. It is worth mentioning that under some physiological circumstances such as normal aging there is a significant decrease in hippocampal neurogenesis. A role for innate and adaptive immune system in adult neurogenesis has been also reported during aging. Here, we review the current evidence regarding neuro-immune interactions in the regulation of neurogenesis under distinct conditions, including aging.

Long-term effects of autoimmune CNS inflammation on adult hippocampal neurogenesis

Neurogenesis is a well-characterized phenomenon within the dentate gyrus (DG) of the adult hippocampus. Aging and chronic degenerative disorders have been shown to impair hippocampal neurogenesis, but the consequence of chronic inflammation remains controversial. In this study the chronic experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis was used to investigate the long-term effects of T cell-mediated central nervous system inflammation on hippocampal neurogenesis. 5-Bromodeoxyuridine (BrdU)-labeled subpopulations of hippocampal cells in EAE and control mice (coexpressing GFAP, doublecortin, NeuN, calretinin, and S100) were quantified at the recovery phase, 21 days after BrdU administration, to estimate alterations on the rate and differentiation pattern of the neurogenesis process. The core features of EAE mice DG are (i) elevated number of newborn (BrdU+) cells indicating vigorous proliferation, which in the long term subsided; (ii) enhanced migration of newborn cells into the granule cell layer; (iii) increased level of immature neuronal markers (including calretinin and doublecortin); (iv) trending decrease in the percentage of newborn mature neurons; and (v) augmented gliogenesis and differentiation of newborn neural precursor cells (NPCs) to mature astrocytes (BrdU+/S100+). Although the inflammatory environment in the brain of EAE mice enhances the proliferation of hippocampal NPCs, in the long term neurogenesis is progressively depleted, giving prominence to gliogenesis. The discrepancy between the high number of immature cells and the low number of mature newborn cells could be the result of a caused defect in the maturation pathway. © 2016 Wiley Periodicals, Inc.

Peripheral immuno-inflammatory abnormalities in ultra-high risk of developing psychosis

BACKGROUND

Immuno-inflammatory imbalances have been documented in schizophrenia, but very little is known about the immunological changes prior to the onset of disease.

OBJECTIVE

This work aimed to compare serum levels of pro- and anti-inflammatory cytokines in young subjects at ultra-high risk (UHR) of developing psychosis with age- and sex-matched healthy controls.

METHODS

A total of 12 UHR and 16 age- and sex-matched healthy controls (HC) subjects were enrolled in this study. Clinical profile was assessed using the Comprehensive Assessment of At-Risk Mental States (CAARMS), Semi-Structured Clinical Interview for DSM-IV Axis-I (SCID-I) or Kiddie-SADS-Present and Lifetime Version (K-SADS-PL), and Global Assessment of Functioning (GAF) scale. Serum interleukin (IL)-2, IL-4, IL-6, IL-10, tumor necrosis factor (TNF)-α, IFN-γ, and IL-17 were measured by flow cytometry using the Th1/Th2/Th17 cytometric bead array.

RESULTS

Compared with the healthy control group, patients in UHR showed increased IL-6 levels (Z=-2.370, p=0.018) and decreased IL-17 levels in serum (Z=-1.959, p=0.050). Levels of IL-17 positively correlated to the values in GAF symptoms (rho=0.632, p=0.028).

CONCLUSION

Our results suggest that immunological imbalances could be present in the early stages of psychosis, including in at-risk stages. Future studies should replicate and expand these results.

Lysophosphatidic Acid Receptor Is a Functional Marker of Adult Hippocampal Precursor Cells

Here, we show that the lysophosphatidic acid receptor 1 (LPA₁) is expressed by a defined population of type 1 stem cells and type 2a precursor cells in the adult mouse dentate gyrus. LPA₁, in contrast to Nestin, also marks the quiescent stem cell population. Combining LPA₁-GFP with EGFR and prominin-1 expression, we have enabled the prospective separation of both proliferative and non-proliferative precursor cell populations. Transcriptional profiling of the isolated proliferative precursor cells suggested immune mechanisms and cytokine signaling as molecular regulators of adult hippocampal precursor cell proliferation. In addition to LPA₁ being a marker of this important stem cell population, we also show that the corresponding ligand LPA is directly involved in the regulation of adult hippocampal precursor cell proliferation and neurogenesis, an effect that can be attributed to LPA signaling via the AKT and MAPK pathways.

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LPA₁-GFP⁺ allows the prospective isolation of hippocampal precursor cells

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Method for separation of proliferative from non-proliferative precursor cells

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Proliferative precursor cells have a unique immune-cell-like transcriptional profile

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LPA increases in vivo hippocampal neurogenesis via the LPA₁-AKT and MAPK pathways

Activated regulatory T cell regulates neural stem cell proliferation in the subventricular zone of normal and ischemic mouse brain through interleukin 10

Recent studies have demonstrated that the depletion of Regulatory T cells (Tregs) inhibits neural progenitor cell migration after brain ischemia. However, whether Tregs affect neural stem/progenitor cell proliferation is unclear. We explored the effect of Tregs on neurogenesis in the subventricular zone (SVZ) after ischemia. Tregs were isolated and activated in vitro. Adult male C57BL/6 mice underwent 60 min transient middle cerebral artery occlusion (tMCAO). Then Tregs (1 × 10⁵) were injected into the left lateral ventricle (LV) of normal and ischemic mouse brain. Neurogenesis was determined by immunostaining. The mechanism was examined by inhibiting interleukin 10 (IL-10) and transforming growth factor (TGF-β) signaling. We found that the number of BrdU⁺ cells in the SVZ was significantly increased in the activated Tregs-treated mice. Double immunostaining showed that these BrdU⁺ cells expressed Mash1. Blocking IL-10 reduced the number of Mash1⁺/BrdU⁺ cells, but increased the amount of GFAP⁺/BrdU⁺ cells. Here, we conclude that activated Tregs enhanced neural stem cell (NSC) proliferation in the SVZ of normal and ischemic mice; blockage of IL-10 abolished Tregs-mediated NSC proliferation in vivo and in vitro. Our results suggest that activated Tregs promoted NSC proliferation via IL-10, which provides a new therapeutic approach for ischemic stroke.