The systemic response to topical Aldara treatment is mediated through direct TLR7 stimulation as Imiquimod enters the circulation

Topical application of Aldara cream, containing the Toll-like receptor 7/8 agonist Imiquimod, is a widely used mouse model for investigating the pathogenesis of psoriasis. We have previously used this model to study the effects of peripheral inflammation on the brain, and reported a brain-specific response characterised by increased transcription, infiltration of immune cells and anhedonic-like behavior. Here, we perform a more robust characterisation of the systemic response to Aldara application and find a potent but transient response in the periphery, followed by a prolonged response in the brain. Mass spectrometry analysis of plasma and brain samples identified significant levels of Imiquimod in both compartments at molar concentrations likely to evoke a biological response. Indeed, the association of Imiquimod with the brain correlated with increased Iba1 and GFAP staining, indicative of microglia and astrocyte reactivity. These results highlight the potency of this model and raise the question of how useful it is for interpreting the systemic response in psoriasis-like skin inflammation. In addition, the potential impact on the brain should be considered with regards to human use and may explain why fatigue, headaches and nervousness have been reported as side effects following prolonged Aldara use

Peripheral inflammation is associated with remote global gene expression changes in the brain

Background: Although the central nervous system (CNS) was once considered an immunologically privileged site, in recent years it has become increasingly evident that cross talk between the immune system and the CNS does occur. As a result, patients with chronic inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease or psoriasis, are often further burdened with neuropsychiatric symptoms, such as depression, anxiety and fatigue. Despite the recent advances in our understanding of neuroimmune communication pathways, the precise effect of peripheral immune activation on neural circuitry remains unclear. Utilizing transcriptomics in a well-characterized murine model of systemic inflammation, we have started to investigate the molecular mechanisms by which inflammation originating in the periphery can induce transcriptional modulation in the brain.<p></p> Methods: Several different systemic and tissue-specific models of peripheral toll-like-receptor-(TLR)-driven (lipopolysaccharide (LPS), lipoteichoic acid and Imiquimod) and sterile (tumour necrosis factor (TNF) and 12-O-tetradecanoylphorbol-13-acetate (TPA)) inflammation were induced in C57BL/6 mice. Whole brain transcriptional profiles were assessed and compared 48 hours after intraperitoneal injection of lipopolysaccharide or vehicle, using Affymetrix GeneChip microarrays. Target gene induction, identified by microarray analysis, was validated independently using qPCR. Expression of the same panel of target genes was then investigated in a number of sterile and other TLR-dependent models of peripheral inflammation.<p></p> Results: Microarray analysis of whole brains collected 48 hr after LPS challenge revealed increased transcription of a range of interferon-stimulated genes (ISGs) in the brain. In addition to acute LPS challenge, ISGs were induced in the brain following both chronic LPS-induced systemic inflammation and Imiquimod-induced skin inflammation. Unique to the brain, this transcriptional response is indicative of peripherally triggered, interferon-mediated CNS inflammation. Similar models of sterile inflammation and lipoteichoic-acid-induced systemic inflammation did not share the capacity to trigger ISG induction in the brain.<p></p> Conclusions: These data highlight ISG induction in the brain as being a consequence of a TLR-induced type I interferon response. As considerable evidence links type I interferons to psychiatric disorders, we hypothesize that interferon production in the brain could represent an important mechanism, linking peripheral TLR-induced inflammation with behavioural changes.<p></p&gt

The brain response to peripheral inflammation

Communication between the immune system and the central nervous system (CNS) is becoming increasingly topical as evidence suggests the two systems are intricately linked. Although the brain is considered an ‘immune-specialised’ tissue, it is not free from the influences of the periphery. Recent data indicate that peripheral immune stimulation can significantly affect the CNS, and patients with chronic inflammatory diseases, including rheumatoid arthritis (RA) and psoriasis, are often further burdened by the onset of neuropsychiatric conditions such as major depressive disorder (MDD), schizophrenia and anxiety. However, despite increases in our understanding, the precise mechanisms underpinning this relationship remain unclear. Therefore, the aim of this thesis is to investigate the communication pathways that exist between the immune system and the nervous system and to enhance our understanding of this bidirectional relationship. Using a well-characterised animal model of psoriasis-like skin inflammation, I have investigated the effects of cutaneous, peripheral inflammation on the brain. Psoriasis-like skin inflammation was induced in female C57BL/6 mice via the repeated application of Aldara cream to the shaved dorsal skin. Twenty-four hours after the fifth application, the transcriptional response in the brain was assessed and compared with mice treated with an aqueous control cream, using Affymetrix GeneChip arrays. The induction of target genes, identified using microarray analysis, was confirmed in an independent model using QPCR and was compared to the gene induction following a number of other inflammatory models, including a sterile model of cutaneous inflammation. Transcriptional profiling techniques allowed me to identify a number of differentially expressed genes in the brains of Aldara- and Imiquimod (IMQ)- treated mice when compared with the brains of control mice. This response included a range of interferon-stimulated genes (ISGs) and chemokines that were not induced in the peripheral blood leukocytes (PBL), and occurred independently of an overt cytokine response in the PBL. The brain ISG and chemokine response was not detected following a sterile model of cutaneous inflammation or following the intraperitoneal administration of Imiquimod.  The central induction of a number of chemokines prompted the evaluation of immune cell infiltration into the brain parenchyma. In addition, the functional consequences of topical Aldara treatment, and the involvement of inflammatory chemokines, were determined by assessing dentate neurogenesis and burrowing behaviour in wild-type and ACKR2-deficient mice. The transcriptional response following cutaneous IMQ-induced inflammation is indicative of a peripherally triggered inflammatory response in the brain. In addition, the data described in this thesis demonstrate a functional consequence of peripheral immune stimulation and suggest that cutaneous inflammation could modulate the recruitment of leukocytes to the brain. These data highlight a potential mechanism of TLR-dependent communication between the periphery and the brain that could be mediated through the activation of the afferent vagus nerve

Sustained exposure to systemic endotoxin triggers chemokine induction in the brain followed by a rapid influx of leukocytes

Background: Recent years have seen an explosion of research pertaining to biological psychiatry, yet despite subsequent advances in our understanding of neuroimmune communication pathways, how the brain senses and responds to peripheral inflammation remains poorly understood. A better understanding of these pathways may be important for generating novel therapeutics to treat many patients with chronic inflammatory diseases who also suffer from neuropsychiatric comorbidities. Here we have systematically assessed the leukocyte infiltrate to the brain following systemic endotoxin exposure to better understand this novel route of neuroimmune communication. Methods: Mice were injected intraperitoneally with LPS daily for 2, 5 or 7 consecutive days. We systematically interrogated the subsequent induction of chemokine transcription in the brain using TaqMan low-density arrays. A combination of flow cytometry and immunohistochemistry was then used to characterise the accompanying leukocyte infiltrate Result: Repeated LPS challenges resulted in prolonged activation of brain-resident microglia, coupled with an increased local transcription of numerous chemokines. After 2 days of administering LPS, there was a marked increase in the expression of the neutrophil chemoattractants CXCL1 and CXCL2; the monocyte chemoattractants CCL2, CCL5, CCL7 and CCL8; and the lymphocyte chemoattractants CXCL9, CXCL10 and CXCL16. In a number of cases, this response was sustained for several days. Chemokine induction was associated with a transient recruitment of neutrophils and monocytes to the brain, coupled with a sustained accumulation of macrophages, CD8+ T cells, NK cells and NKT cells. Strikingly, neutrophils, monocytes and T cells appeared to extravasate from the vasculature and/or CSF to infiltrate the brain parenchyma. Conclusions: Prolonged exposure to a peripheral inflammatory stimulus triggers the recruitment of myeloid cells and lymphocytes to the brain. By altering the inflammatory or metabolic milieu of the brain, this novel method of immune-to-brain communication may have profound implications for patients with chronic inflammatory diseases, potentially leading to neuropsychiatric comorbidities

Distinct trans-placental effects of maternal immune activation by TLR3 and TLR7 agonists: implications for schizophrenia risk

Exposure to infection in utero predisposes towards psychiatric diseases such as autism, depression and schizophrenia in later life. The mechanisms involved are typically studied by administering mimetics of double-stranded (ds) virus or bacterial infection to pregnant rats or mice. The effect of single-stranded (ss) virus mimetics has been largely ignored, despite evidence linking prenatal ss virus exposure with psychiatric disease. Understanding the effects of gestational ss virus exposure has become even more important with recent events. In this study, in pregnant mice, we compare directly the effects, on the maternal blood, placenta and the embryonic brain, of maternal administration of ds-virus mimetic poly I:C (to activate Toll-like receptor 3, TLR3) and ss-virus mimetic resiquimod (to activate TLR7/8). We find that, 4 h after the administration, both poly I:C and resiquimod elevated the levels of IL-6, TNFα, and chemokines including CCL2 and CCL5, in maternal plasma. Both agents also increased placental mRNA levels of IL-6 and IL-10, but only resiquimod increased placental TNFα mRNA. In foetal brain, poly I:C produced no detectable immune-response-related increases, whereas pronounced increases in cytokine (e.g. Il-6, Tnfα) and chemokine (e.g. Ccl2, Ccl5) expression were observed with maternal resiquimod administration. The data show substantial differences between the effect of maternal exposure to a TLR7/8 activator as compared to a TLR3 activator. There are significant implications for future modelling of diseases where maternal ss virus exposure contributes to environmental disease risk in offspring

Mild inflammation in healthy males induces fatigue mediated by changes in effective connectivity within the insula

Background: Systemic inflammation is associated with sickness behaviors such as low mood and fatigue. Activity patterns within the insula are suggested to coordinate these behaviors but have not been modeled. We hypothesized that mild systemic inflammation would result in changes in effective connectivity between the viscerosensory and the visceromotor regions of the insula. Methods: We used a double-blind, crossover design to randomize 20 male subjects to receive either a Salmonella typhi vaccine or a placebo saline injection at two separate sessions. All participants underwent a resting-state functional magnetic resonance scan 3 hours after injection. We determined behavioral and inflammatory changes, using the Profile of Mood States questionnaire and interleukin-6 levels. We extracted effective connectivity matrices between bilateral mid/posterior (viscerosensory) and anterior (visceromotor) insular cortices using spectral dynamic causal modeling. We applied parametric empirical Bayes and mediation analysis to determine a vaccination effect on effective connectivity and whether this mediated behavioral changes. Results: The vaccine condition was associated with greater interleukin-6 levels and greater fatigue 3 hours after the injection. Activity within the right mid/posterior insula increased the activity within the bilateral anterior insular regions. This connectivity was augmented by vaccination over a 99% posterior confidence threshold. The right mid/posterior insula-to-left anterior insula connectivity was significantly associated with fatigue and mediated the association between inflammation and increased fatigue scores. Conclusions: These results demonstrate that increased effective connectivity between specific nodes of the insula can model and mediate the association between inflammation and fatigue in males

Preoperative behavioural intervention to reduce drinking before elective orthopaedic surgery: the PRE-OP BIRDS feasibility RCT.

Background Heavy alcohol consumption is associated with an increased risk of postoperative complications and extended hospital stay. Alcohol consumption therefore represents a modifiable risk factor for surgical outcomes. Brief behavioural interventions have been shown to be effective in reducing alcohol consumption among increased risk and risky drinkers in other health-care settings and may offer a method of addressing preoperative alcohol consumption. Objectives To investigate the feasibility of introducing a screening process to assess adult preoperative drinking levels and to deliver a brief behavioural intervention adapted for the target population group. To conduct a two-arm (brief behavioural intervention plus standard preoperative care vs. standard preoperative care alone), multicentre, pilot randomised controlled trial to assess the feasibility of proceeding to a definitive trial. To conduct focus groups and a national web-based survey to establish current treatment as usual for alcohol screening and intervention in preoperative assessment. Design A single-centre, qualitative, feasibility study was followed by a multicentre, two-arm (brief behavioural intervention vs. treatment as usual), individually randomised controlled pilot trial with an embedded qualitative process evaluation. Focus groups and a quantitative survey were employed to characterise treatment as usual in preoperative assessment. Setting The feasibility study took place at a secondary care hospital in the north-east of England. The pilot trial was conducted at three large secondary care centres in the north-east of England. Participants Nine health-care professionals and 15 patients (mean age 70.5 years, 86.7% male) participated in the feasibility study. Eleven health-care professionals and 68 patients (mean age 66.2 years, 80.9% male) participated in the pilot randomised trial. An additional 19 health-care professionals were recruited to one of three focus groups, while 62 completed an electronic survey to characterise treatment as usual. Interventions The brief behavioural intervention comprised two sessions. The first session, delivered face to face in the preoperative assessment clinic, involved 5 minutes of structured brief advice followed by 15–20 minutes of behaviour change counselling, including goal-setting, problem-solving and identifying sources of social support. The second session, an optional booster, took place approximately 1 week before surgery and offered the opportunity to assess progress and boost self-efficacy. Main outcome measures Feasibility was assessed using rates of eligibility, recruitment and retention. The progression criteria for a definitive trial were recruitment of ≥ 40% of eligible patients and retention of ≥ 70% at 6-month follow-up. Acceptability was assessed using themes identified in qualitative data. Results The initial recruitment of eligible patients was low but improved with the optimisation of recruitment processes. The recruitment of eligible participants to the pilot trial (34%) fell short of the progression criteria but was mitigated by very high retention (96%) at the 6-month follow-up. Multimethod analyses identified the methods as acceptable to the patients and professionals involved and offers recommendations of ways to further improve recruitment. Conclusions The evidence supports the feasibility of a definitive trial to assess the effectiveness of brief behavioural intervention in reducing preoperative alcohol consumption and for secondary outcomes of surgical complications if recommendations for further improvements are adopted. Trial registration Current Controlled Trials ISRCTN36257982. Funding This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 12. See the National Institute for Health Research Journals Library website for further project information

No evidence for differential gene expression in major depressive disorder PBMCs, but robust evidence of elevated biological ageing.

The increasingly compelling data supporting the involvement of immunobiological mechanisms in Major Depressive Disorder (MDD) might provide some explanation forthe variance in this heterogeneous condition. Peripheral blood measures of cytokines and chemokines constitute the bulk of evidence, with consistent meta-analytic data implicating raised proinflammatory cytokines such as IL6, IL1β and TNF. Among the potential mechanisms linking immunobiological changes to affective neurobiology is the accelerated biological ageing seen in MDD, particularly via the senescence associated secretory phenotype (SASP). However, the cellular source of immunobiological markers remains unclear. Pre-clinical evidence suggests a role for peripheral blood mononuclear cells (PBMC), thus here we aimed to explore the transcriptomic profile using RNA sequencing in PBMCs in a clinical sample of people with various levels of depression and treatment response comparing it with that in healthy controls (HCs). There were three groups with major depressive disorder (MDD): treatment-resistant (n = 94), treatment-responsive (n = 47) and untreated (n = 46). Healthy controls numbered 44. Using PBMCs gene expression analysis was conducted using RNAseq to a depth of 54.5 million reads. Differential gene expression analysis was performed using DESeq2. The data showed no robust signal differentiating MDD and HCs. There was, however, significant evidence of elevated biological ageing in MDD vs HC. Biological ageing was evident in these data as a transcriptional signature of 888 age-associated genes (adjusted p  0.6) that also correlated strongly with chronological age (spearman correlation coefficient of 0.72). Future work should expand clinical sample sizes and reduce clinical heterogeneity. Exploration of RNA-seq signatures in other leukocyte populations and single cell RNA sequencing may help uncover more subtle differences. However, currently the subtlety of any PBMC signature mitigates against its convincing use as a diagnostic or predictive biomarker

TLR7-mediated skin inflammation remotely triggers chemokine expression and leukocyte accumulation in the brain

Background: The relationship between the brain and the immune system has become increasingly topical as, although it is immune-specialised, the CNS is not free from the influences of the immune system. Recent data indicate that peripheral immune stimulation can significantly affect the CNS. But the mechanisms underpinning this relationship remain unclear. The standard approach to understanding this relationship has relied on systemic immune activation using bacterial components, finding that immune mediators, such as cytokines, can have a significant effect on brain function and behaviour. More rarely have studies used disease models that are representative of human disorders. Methods: Here we use a well-characterised animal model of psoriasis-like skin inflammation—imiquimod—to investigate the effects of tissue-specific peripheral inflammation on the brain. We used full genome array, flow cytometry analysis of immune cell infiltration, doublecortin staining for neural precursor cells and a behavioural read-out exploiting natural burrowing behaviour. Results: We found that a number of genes are upregulated in the brain following treatment, amongst which is a subset of inflammatory chemokines (CCL3, CCL5, CCL9, CXCL10, CXCL13, CXCL16 and CCR5). Strikingly, this model induced the infiltration of a number of immune cell subsets into the brain parenchyma, including T cells, NK cells and myeloid cells, along with a reduction in neurogenesis and a suppression of burrowing activity. Conclusions: These findings demonstrate that cutaneous, peripheral immune stimulation is associated with significant leukocyte infiltration into the brain and suggest that chemokines may be amongst the key mediators driving this response