Dexamethasone attenuates inflammatory-mediated suppression of β2-adrenoceptor expression in rat primary mixed glia

β₂-adrenoceptors are G-protein coupled receptors expressed on both astrocytes and microglia that play a key role in mediating the anti-inflammatory actions of noradrenaline in the CNS. Here the effect of an inflammatory stimulus (LPS + IFN-γ) was examined on glial β₂-adrenoceptor expression and function. Exposure of glia to LPS + IFN-γ decreased β₂-adrenoceptor mRNA and agonist-stimulated production of the intracellular second messenger cAMP. Pre-treatment with the synthetic glucocorticoid and potent anti-inflammatory agent dexamethasone prevented the LPS + IFN-γ-induced suppression of β₂-adrenoceptor mRNA expression. These results raise the possibility that inflammation-mediated β₂-adrenoceptor downregulation in glia may dampen the innate anti-inflammatory properties of noradrenaline in the CNS.

Nanoparticle-induced neuronal toxicity across placental barriers is mediated by autophagy and dependent on astrocytes

The potential for maternal nanoparticle (NP) exposures to cause developmental toxicity in the fetus without the direct passage of NPs has previously been shown, but the mechanism remained elusive. We now demonstrate that exposure of cobalt and chromium NPs to BeWo cell barriers, an in vitro model of the human placenta, triggers impairment of the autophagic flux and release of interleukin-6. This contributes to the altered differentiation of human neural progenitor cells and DNA damage in the derived neurons and astrocytes. Crucially, neuronal DNA damage is mediated by astrocytes. Inhibiting the autophagic degradation in the BeWo barrier by overexpression of the dominant-negative human ATG4B^C74A significantly reduces the levels of DNA damage in astrocytes. In vivo, indirect NP toxicity in mice results in neurodevelopmental abnormalities with reactive astrogliosis and increased DNA damage in the fetal hippocampus. Our results demonstrate the potential importance of autophagy to elicit NP toxicity and the risk of indirect developmental neurotoxicity after maternal NP exposure.

C-reactive protein predicts fatigue independently of depression in breast cancer patients prior to chemotherapy

Heightened inflammatory activity has been proposed as a mechanism for the development of cancer-related fatigue (CRF), a common and distressing condition that can negatively affect quality of life. Inflammation is also implicated in the pathogenesis of depression, and depression is a strong predictor of CRF. Thus, the role of the pro-inflammatory cytokine network in CRF may be mediated by depression or both conditions may share similar underlying physiological processes. The current study investigated associations between fatigue, depression and inflammatory cytokine (IFN-γ, IL-6, TNF-α) and CRP concentrations, as well as kynurenine pathway (KP) activation, in 61 breast cancer patients prior to chemotherapy. Changes in inflammatory markers and KP activation over time were also explored, and associations with changes in fatigue and depression were examined. Higher levels of CRP were significantly correlated with fatigue and depression before chemotherapy; nevertheless, CRP predicted fatigue independently of depression. Although greater kynurenine concentrations were associated with increased immune activation, there was no evidence that the KP played a role in fatigue or depression. Furthermore, no relationships emerged between either fatigue or depression and IFN-γ, IL-6, or TNF-α before chemotherapy. Nevertheless, kynurenine levels pre- and post-treatment significantly predicted changes in depression, suggesting that heightened KP activation may contribute to depressive symptoms in patients treated for cancer. In addition, IL-6 significantly covaried with fatigue. These preliminary findings provide some support for the idea that low-grade inflammation contributes to the development of CRF, independently of depression; however, there was no evidence that this is mediated by KP activity.

Ischemic brain injury: a consortium analysis of key factors involved in mesenchymal stem cell-mediated inflammatory reduction

Increasing global birth rate, coupled with the aging population surviving into their eighth decade has lead to increased incidence diseases, hitherto designated as rare. Brain related ischemia, at birth, or later in life, during, for example stroke, is increasing in global prevalence. Reactive microglia can contribute to neuronal damage as well as compromising transplantion. One potential treatment strategy is cellular therapy, using mesenchymal stem cells (hMSCs), which possess immunomodulatory and cell repair properties. For effective clinical therapy, mechanisms of action must be understood better. Here multicentre international laboratories assessed this question together investigating application of hMSCs neural involvement, with interest in the role of reactive microglia. Modulation by hMSCs in our in vivo and in vitro study shows they decrease markers of microglial activation (lower ED1 and Iba) and astrogliosis (lower GFAP) following transplantation in an ouabain-induced brain ischemia rat model and in organotypic hippocampal cultures. The anti-inflammatory effect in vitro was demonstrated to be CD200 ligand dependent with ligand expression shown to be increased by IL-4 stimulation. hMSC transplant reduced rat microglial STAT3 gene expression and reduced activation of Y705 phosphorylated STAT3, but STAT3 in the hMSCs themselves was elevated upon grafting. Surprisingly, activity was dependent on heterodimerisation with STAT1 activated by IL-4 and Oncostatin M. Our study paves the way to preclinical stages of a clinical trial with hMSC, and suggests a non-canonical JAK-STAT signaling of unphosphorylated STAT3 in immunomodulatory effects of hMSCs.

Methylenedioxymethamphetamine ('Ecstasy')-induced immunosuppression: a cause for concern?

Methylenedioxymethamphetamine (MDMA; 'Ecstasy') is a ring-substituted amphetamine and a popular drug of abuse. In addition to ability to induce euphoria, MDMA abuse is associated with a range of acute and long-term hazardous effects. This paper is focused on once such adverse effect: its ability to negatively impact on functioning of the immune system. Research demonstrates that MDMA has immunosuppressive properties, with both innate and adaptive arms of the immune system being affected. The ability of MDMA to suppress innate immunity is indicated by impaired neutrophil phagocytosis and reduced production of dendritic cell/macrophage-derived pro-inflammatory cytokines including tumour necrosis factor-alpha, interleukin (IL)-1beta, IL-12 and IL-15. MDMA also suppresses innate IFN-gamma production, and considering the role of IFN-gamma in priming antigen-presenting cells, it is not surprising that MDMA reduces MHC class II expression on dendritic cells and macrophages, and inhibits co-stimulatory molecule expression. Paradoxically, studies demonstrate that MDMA elicits pro-inflammatory actions in the CNS by activating microglia, the resident innate immune cells in the brain. In terms of adaptive immunity, MDMA reduces circulating lymphocyte numbers, particularly CD4(+) T-cells; suppresses T-cell proliferation; and skews cytokine production in a Th(2) direction. For the most part, the immunosuppressive effects of MDMA cannot be attributed to a direct action of the drug on immune cells, but rather due to the release of endogenous immunomodulatory substances. In this regard, peripheral beta-adrenoceptors and cholinergic receptors have been shown to mediate some immunosuppressive effects of MDMA. Finally, we discuss emerging evidence indicating that MDMA-induced immunosuppression can translate into significant health risks for abusers.

Psychological stress suppresses innate IFN-gamma production via glucocorticoid receptor activation: reversal by the anxiolytic chlordiazepoxide

Studies in humans and in animals indicate that psychological stress can modulate immune responses. Here we demonstrate that exposure to psychological stress (restraint stress) suppresses innate interferon (IFN)-gamma production in mice following an in vivo lipopolysaccharide (LPS) challenge. IFN-gamma signaling was also impaired by stress, as indicated by reduced STAT1 phosphorylation and reduced expression of the IFN-gamma-inducible genes, inducible nitric oxide synthase (iNOS) and IFN-gamma-inducible protein 10 (IP-10/CXCL10). Furthermore, restraint stress suppressed production of the IFN-gamma inducing cytokine interleukin (IL)-12 and increased production of the anti-inflammatory cytokine IL-10, which can inhibit both IL-12 and IFN-gamma production. However, using IL-10 knockout mice, we demonstrate that IL-10 does not mediate the suppressive effect of restraint stress on innate IFN-gamma production. Restraint stress increased corticosterone concentrations in serum and spleen, and consistent with a role for glucocorticoids in the immunosuppressive actions of stress, pre-treatment with the glucocorticoid receptor antagonist mifepristone completely blocked the stress-related suppression of innate IFN-gamma production. Addition of exogenous IL-12 to LPS-stimulated spleen cells reversed the suppressive effect of both restraint stress and corticosterone on IFN-gamma production. These data suggest that reduced IL-12 production is a key event in stress-induced suppression of innate IFN-gamma production. Finally, we demonstrate that pre-treatment with the anxiolytic drug chlordiazepoxide prevents the suppressive effect of stress on innate IFN-gamma production, and also attenuates the stress-induced increase in circulating corticosterone concentrations.

MDMA (“Ecstasy”) suppresses the innate IFN-γ response in vivo: A critical role for the anti-inflammatory cytokine IL-10

Here we demonstrate that the widely abused drug methylenedioxymethamphetamine (MDMA; "Ecstasy") suppresses innate interferon (IFN)-gamma production in mice following an in vivo lipopolysaccharide (LPS) challenge. IFN-gamma signalling was also impaired by MDMA, as indicated by reduced phosphorylation of signal transducer and activator of transcription-1 (STAT1) and reduced expression of interferon-gamma inducible protein 10 (IP-10/CXCL10); a chemokine induced by IFN-gamma. MDMA also suppressed production of interleukin (IL)-12 and IL-15; two cytokines that induce IFN-gamma production. Our results demonstrate that in vitro exposure to MDMA does not mimic the suppression of innate IFN-gamma observed in vivo, indicating that observed suppression is most likely due to the release of endogenous immunomodulatory substances following drug administration. In this regard, we previously demonstrated that MDMA increases production of the anti-inflammatory cytokine IL-10 in vivo, an event that is mediated by beta-adrenoceptor activation on immune cells. Considering that increased IL-10 production precedes suppression of IFN-gamma induced by MDMA, and also considering that IL-10 can inhibit IL-12 and IFN-gamma production, we examined the possibility that IL-10 was an essential mediator of the suppressive effect of MDMA on the IFN-gamma response. By pre-treating mice with an anti-IL-10 receptor antibody we demonstrate that IL-10 is a critical mediator of MDMA-induced suppression of IFN- gamma production and signalling. Consistent with a role for beta-adrenoceptor activation in the immunosuppressive actions of MDMA, pre-treatment with the beta-adrenoceptor antagonist nadolol blocked the MDMA-induced increase in IL-10, and also inhibited the suppressive action of MDMA on the innate IFN-gamma response. The potential clinical significance of these findings for MDMA users is discussed.