To model the effects of estrogen on adaptive immunity in the brain, we examined the effects of 17beta-estradiol on microglial parameters related to antigen presentation and T cell activation. Specifically, the effects of 17beta-estradiol on basal and LPS-induced surface staining of Class I and II MHC, as well as CD40, CD80, CD86, CD152, CD28, CD8, CD11b, Fas, FasL, and also ERalpha and ERbeta, were examined in N9 microglial cells. Additionally, the effects of 17beta-estradiol on basal and LPS-induced release of cytokines (TNF-alpha, IFN-gamma, IL-2, IL-4, and IL-10) were determined. Data indicate that estrogen increases IL-10 while decreasing TNFalpha and IFNgamma release from resting and LPS-stimulated N9 cells. Additionally, LPS-induced surface staining of MHC Class I, CD40, and CD86 was significantly attenuated by estrogen pretreatment. The basal percentage of cells positive for MHC Class I and II, CD40, and CD152, Fas, and FasL was significantly decreased by estrogen exposure. However, CD8, CD86, CD11b, and CD28 were unaffected by estrogen, and CD80 cell surface staining significantly increased following estrogen exposure. Taken together, these data indicate that estrogen can significantly decrease components of adaptive immunity in microglial cells, and highlight the multi-faceted regulatory effects of estrogen on microglial parameters related to antigen presentation and T cell interaction.
"In contrast to this however, Dimayuga et al. showed a significant attenuation of basal and surface staining of CD40 in microglial cells . As several cohort studies demonstrated, smoking is one of the main risk factor for atherosclerosis and thrombosis and is associated with proinflammatory and prothrombotic responses   . "
[Show abstract][Hide abstract] ABSTRACT: Objective:
Atherosclerosis, as an inflammatory disease, is characterized by pathologically altered levels of cytokines. We investigated whether smoking and/or oral contraceptives (OCs) affect the CD40/CD40L plasma levels and expression in young females without other risk factors for atherosclerosis.
Patients and methods:
A case-control single-center design was used. Expression levels of CD40/CD40L were analyzed in healthy non-pregnant, pre-menopausal, non-smoking women who did not take OCs (n=49), women who currently smoke and take OCs (n=40), and women who are only smokers (n=40) or currently take OCs (n=42).
In OC users, there was a significant increase in CD40 mRNA expression in circulating monocytes as compared with smokers and control group. However, there were no significant differences in CD40 mRNA expression in monocytes between smokers and non-smokers. Interestingly, CD40 mRNA expression in women taking OCs and currently smoking was significantly decreased compared to only OC users (p<0.001). With regard to plasma CD40 levels there were significant differences between OC-users and control group. However, contrary to our expectations, there were no significant differences in expression levels of CD40L between four groups. In vitro experiments demonstrated enhanced CD40 mRNA and surface expression in human monocyte-derived macrophages stimulated with estrogens. Furthermore, nicotine pretreatment led to a suppression of estrogens stimulated CD40 induction.
In young healthy females without additional risk factors for atherosclerosis, OCs, but not smoking, are associated with dramatic changes in CD40 gene and plasma levels. These findings may be providing an important link between OCs and enhancement of pro-inflammatory and atherothrombotic conditions in healthy women.
Thrombosis Research 12/2014; 135(2). DOI:10.1016/j.thromres.2014.11.035 · 2.45 Impact Factor
"3.4. Estradiol correlates with hippocampal microglial gene expression Given the reported modulating effects of estradiol on microglia activation (Dimayuga et al., 2005; Loram et al., 2012; Soucy et al., 2005), a multiple linear regression analysis was used to determine the extent to which circulating estradiol, stress, and LPS treatment predicted hippocampal CD11b gene expression among females. "
[Show abstract][Hide abstract] ABSTRACT: Both basic and clinical research indicates that females are more susceptible to stress-related affective disorders than males. One of the mechanisms by which stress induces depression is via inflammatory signaling in the brain. Stress during adolescence, in particular, can also disrupt the activation and continued development of both the hypothalamic-pituitary-adrenal (HPA) and -gonadal (HPG) axes, both of which modulate inflammatory pathways and brain regions involved in affective behavior. Therefore, we tested the hypothesis that adolescent stress differentially alters brain inflammatory mechanisms associated with affective-like behavior into adulthood based on sex. Male and female Wistar rats underwent mixed-modality stress during adolescence (PND 37-48) and were challenged with lipopolysaccharide (LPS; 250 μg/kg, i.p.) or saline 4.5 weeks later (in adulthood). Hippocampal inflammatory marker gene expression and circulating HPA and HPG axis hormone concentrations were then determined. Despite previous studies indicating that adolescent stress induces affective-like behaviors in female rats only, this study demonstrated that adolescent stress increased hippocampal inflammatory responses to LPS in males only, suggesting that differences in neuroinflammatory signaling do not drive the divergent affective-like behaviors. The sex differences in inflammatory markers were not associated with differences in corticosterone. In females that experienced adolescent stress, LPS increased circulating estradiol. Estradiol positively correlated with hippocampal microglial gene expression in control female rats, whereas adolescent stress negated this relationship. Thus, estradiol in females may potentially protect against stress-induced increases in neuroinflammation.
"Microglia cell lines cannot be regarded as reliable model system to study microglia action due to conflicting differences in their physiological properties   . This also applies to steroid effects and signaling where both types of classical nuclear estrogen receptors are expressed by N9 microglia , whereas only estrogen receptor-␤ is expressed in the BV-2 cell line  "
[Show abstract][Hide abstract] ABSTRACT: The neuroactive steroids 17ß-estradiol and progesterone control a broad spectrum of neural functions. Besides their roles in the regulation of classical neuroendocrine loops, they strongly influence motor and cognitive systems, behavior, and modulate brain performance at almost every level. Such a statement is underpinned by the widespread and lifelong expression pattern of all types of classical and non-classical estrogen and progesterone receptors in the CNS. The life-sustaining power of neurosteroids for tattered or seriously damaged neurons aroused interest in the scientific community in the past years to study their ability for therapeutic use under neuropathological challenges. Documented by excellent studies either performed in vitro or in adequate animal models mimicking acute toxic or chronic neurodegenerative brain disorders, both hormones revealed a high potency to protect neurons from damage and saved neural systems from collapse. Unfortunately, neurons, astroglia, microglia, and oligodendrocytes are comparably target cells for both steroid hormones. This hampers the precise assignment and understanding of neuroprotective cellular mechanisms activated by both steroids. In this article, we strive for a better comprehension of the mutual reaction between these steroid hormones and the two major glial cell types involved in the maintenance of brain homeostasis, astroglia and microglia, during acute traumatic brain injuries such as stroke and hypoxia. In particular, we attempt to summarize steroid-activated cellular signaling pathways and molecular responses in these cells and their contribution to dampening neuroinflammation and neural destruction.
The Journal of steroid biochemistry and molecular biology 11/2012; 137. DOI:10.1016/j.jsbmb.2012.11.006 · 3.63 Impact Factor
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