Long term impact of systemic bacterial infection on the cerebral vasculature and microglia

Background: Systemic infection leads to generation of inflammatory mediators that result in metabolic and behavioural changes. Repeated or chronic systemic inflammation leads to a state of innate immune tolerance: a protective mechanism against over-activity of the immune system. In this study we investigated the immune adaptation of microglia and brain vascular endothelial cells in response to systemic inflammation or bacterial infection. Methods: Mice were given repeated doses of lipopolysaccharide (LPS) or a single injection of live Salmonella typhimurium. Inflammatory cytokines were measured in serum, spleen and brain, and microglial phenotype studied by immunohistochemistry.mice were infected with Salmonella typhimurium and subsequently challenged with a focal unilateral, intracerebral injection of LPS. Results: Repeated systemic LPS challenges resulted in increased brain IL-1?, TNF? and IL-12 levels, despite attenuated systemic cytokine production. Each LPS challenge induced significant changes in burrowing behaviour. In contrast, brain IL-1? and IL-12 levels in Salmonella typhimurium infected mice increased over three weeks, with high interferon-? levels in the circulation. Behavioural changes were only observed during the acute phase of the infection. Microglia and cerebral vasculature display an activated phenotype, and focal intracerebral injection of LPS 4 weeks after infection results in an exaggerated local inflammatory response when compared to non-infected mice. Conclusions: These studies reveal that the innate immune cells in the brain do not become tolerant to systemic infection, but are primed instead. This may lead to prolonged and damaging cytokine production that may have aprofound effect on the onset and/ or progression of pre-existing neurodegenerative disease.Humans and animals are regularly exposed to bacterial and viral pathogens that can have a considerable impact on our day-to-day living [1]. Upon infection, a set of immune, physiological, metabolic, and behavioural responses is initiated, representing a highly organized strategy of the organism to fight infection. Pro-inflammatory mediators generated in peripheral tissue communicate with the brain to modify behaviour [2], which aids our ability to fight and eliminate the pathogen. The communication pathways from the site of inflammation to the brain have been investigated in animal models and systemic challenge with lipopolysaccharide (LPS) or double stranded RNA (poly I:C) have been widely used to mimic aspects of bacterial and viral infection respectively [3, 4]. These studies have provided evidence that systemically generated inflammatory mediators signal to the brain via both neural and humoral routes, the latter signalling via the circumventricular organs or across the blood-brain barrier (BBB). Signalling into the brain via these routes evokes a response in the perivascular macrophages (PVMs) and microglia, which in turn synthesise diverse inflammatory mediators including cytokines, prostaglandins and nitric oxide [2, 5, 6]. Immune-to-brain communication also occurs in humans who show changes in mood and cognition following systemic inflammation or infection, which are associated with changes in activity in particular regions of the CNS [7-9]. While these changes are part of our normal homeostasis, it is increasingly evident that systemic inflammation has a detrimental effect in animals and also humans, that suffer from chronic neurodegeneration [10, 11]. We, and others, have shown that microglia become primed by on-going neuropathology in the brain, which increases their response towards subsequent inflammatory stimuli, including systemic inflammation [12, 13] Similar findings have been made in aged rodents [14, 15], where it has been shown that there is an exaggerated behavioural and innate immune response in the brainto systemic bacterial and viral infections, but the molecular mechanisms underlying the microglial priming under these conditions is far from understood.Humans and animals are rarely exposed to a single acute systemic inflammatory event: they rather encounter infectious pathogens that replicate in vivo or are exposed to low concentrations of LPS over a prolonged period of time. There is limited information on the impact of non-neurotrophic bacterial infections on the CNS and whether prolonged systemic inflammation will give rise to either a hyper-(priming) or hypo-(tolerance) innate immune response in the brain in response to a subsequent inflammatory stimulus.In this study we measured the levels of cytokines in the serum, spleen and brain as well as assessing sickness behaviour following a systemic bacterial infection using attenuated Salmonella typhimurium SL3261: we compared the effect to that of repeated LPS injections. We show that Salmonella typhimurium caused acute, transient behavioural changes and a robust peripheral immune response that peaks at day 7. Systemic inflammation resulted in a delayed increase in cytokine production in the brain and priming of microglia, which persisted up to four weeks post infection. These effects were not mimicked by repeated LPS challenges. It is well recognised that systemic bacterial and viral infections are significant contributors to morbidity in the elderly [16], and it has been suggested that primed microglia play a role in the increased clinical symptoms seen in patients with Alzheimer’s disease who have systemic inflammation or infections [11, 17]. We show here that systemic infection leads to prolonged cytokine synthesis in the brain and also priming of brain innate immune cells to a subsequent focal inflammatory challenge in the brain parenchyma

Choroidal metastases from thymic carcinoma during pregnancy: Case Report

BACKGROUND: Rare sites of metastases, atypical symptoms and paraneoplastic syndromes are often neglected or misinterpreted, especially when they represent early symptoms of an underlying malignant disease. Hence, an interdisciplinary approach to these patients is essential to avoid tumor progression and metastatic spread in order to provide curative treatment options to the patients. We here report the case of a young woman presenting with visual loss which led to diagnosis of a thymic carcinoma. CASE PRESENTATION: A 28-year old white woman presented with subacute loss of vision in the last trimester of her first pregnancy which was first interpreted as an exacerbation of a pre-existing dermatomyositis and treated with steroids. After failure of steroid therapy choroidal metastases from an undifferentiated thymic carcinoma were diagnosed. This also shed a new light on the dermatomyositis the patient had been suffering from for seven years possibly representing a paraneoplastic syndrome from the tumor. Despite aggressive chemotherapy, the patient died from progressive disease eight years after first onset of dermatomyositis and 14 months after initial diagnosis of the thymic carcinoma. CONCLUSIONS: Choroidal metastases from a thymic carcinoma have never been reported before but should be included into the differential diagnosis of choroidal masses

Water Framework Directive Intercalibration Technical Report: Alpine Lake Phytoplankton ecological assessment methods

One of the key actions identified by the Water Framework Directive (WFD; 2000/60/EC) is to develop ecological assessment tools and carry out a European intercalibration (IC) exercise. The aim of the Intercalibration is to ensure that the values assigned by each Member State to the good ecological class boundaries are consistent with the Directive’s generic description of these boundaries and comparable to the boundaries proposed by other MS. In total, 83 lake assessment methods were submitted for the 2nd phase of the WFD intercalibration (2008-2012) and 62 intercalibrated and included in the EC Decision on Intercalibration (EC 2013). The intercalibration was carried out in the 13 Lake Geographical Intercalibration Groups according to the ecoregion and biological quality element. In this report we describe how the intercalibration exercise has been carried out in the Alpine Lake Phytoplankton group.JRC.H.1-Water Resource

Copper Induces Protein Aggregation, a Toxic Process Compensated by Molecular Chaperones

International audienceCopper is well known for its antimicrobial and antiviral properties. Under aerobic conditions, copper toxicity relies in part on the production of reactive oxygen species (ROS), especially in the periplasmic compartment. However, copper is significantly more toxic under anaerobic conditions, in which ROS cannot be produced. This toxicity has been proposed to arise from the inactivation of proteins through mismetallations. Here, using the bacterium Escherichia coli, we discovered that copper treatment under anaerobic conditions leads to a significant increase in protein aggregation. In vitro experiments using E. coli lysates and tightly controlled redox conditions confirmed that treatment with Cu+ under anaerobic conditions leads to severe ROS-independent protein aggregation. Proteomic analysis of aggregated proteins revealed an enrichment of cysteine- and histidine-containing proteins in the Cu+-treated samples, suggesting that nonspecific interactions of Cu+ with these residues are likely responsible for the observed protein aggregation. In addition, E. coli strains lacking the cytosolic chaperone DnaK or trigger factor are highly sensitive to copper stress. These results reveal that bacteria rely on these chaperone systems to protect themselves against Cu-mediated protein aggregation and further support our finding that Cu toxicity is related to Cu-induced protein aggregation. Overall, our work provides new insights into the mechanism of Cu toxicity and the defense mechanisms that bacteria employ to survive. IMPORTANCE With the increase of antibiotic drug resistance, alternative antibacterial treatment strategies are needed. Copper is a well-known antimicrobial and antiviral agent; however, the underlying molecular mechanisms by which copper causes cell death are not yet fully understood. Herein, we report the finding that Cu+, the physiologically relevant copper species in bacteria, causes widespread protein aggregation. We demonstrate that the molecular chaperones DnaK and trigger factor protect bacteria against Cu-induced cell death, highlighting, for the first time, the central role of these chaperones under Cu+ stress. Our studies reveal Cu-induced protein aggregation to be a central mechanism of Cu toxicity, a finding that will serve to guide future mechanistic studies and drug development