| 1. |
- Elander, Louise, 1980-
(författare)
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Prostaglandin E2 in Brain-mediated Illness Responses
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We are unceasingly exposed to potentially harmful microorganisms. The battle against threatening infectious agents includes activation of both the innate and of the adaptive immune systems. Illness responses are elicited and include inflammation, fever, decreased appetite, lethargy and increased sensitivity to painful stimuli in order to defeat invaders. While many of these signs of disease are controlled by the central nervous system, it has remained an enigma how signals from the peripheral immune system reach the brain through its blood-brain barrier, which precludes macromolecules, including cytokines, from diffusing into the brain parenchyma.Previous findings indicate the existence of a pathway across the blood-brain barrier, which includes binding of the cytokine interleukin-1 (IL-1) to its receptor in the brain vessels, thereby inducing the production of the prostaglandin E2 (PGE2) synthesizing enzymes cyclooxygenase-2 (Cox-2) and microsomal prostaglandin E synthase-1 (mPGES-1), which ultimately synthesize PGE2. PGE2 subsequently binds to any of the four prostaglandin E2 (EP) -receptors. Previous results from our laboratory have suggested that this pathway plays a critical role in the febrile response to infectious stimuli. The present thesis aims at further investigating the molecular events underlying immune-to-brain signalling, with special emphasis on fever, hypothalamic-pituitary-adrenal (HPA) -axis activation and anorexia and their connection to signalling molecules of the cytokine and prostaglandin families, respectively.In paper I, the molecular processes linking the proinflammatory cytokine interleukin-6 (IL-6) and PGE2 in the febrile response were investigated. Both IL-6 and PGE2 have been shown to be critical players in the febrile response, although the molecular connections are not known, i.e. if IL-6 exerts its effects up- or downstream of PGE2. Mice deficient in IL-6 were unable to respond to bacterial lipopolysaccharide (LPS) with a febrile response, but displayed similar induction of Cox-2 and mPGES-1, and similar concentrations of PGE2 in the cerebrospinal fluid as wild-type mice. Paradoxically, the IL-6 deficient mice responded with a dose-dependent elevation of body temperature in response to intracerebroventricularly injected PGE2. Furthermore, IL-6 per se was not pyrogenic when injected peripherally in mice, and did not cause increased levels of PGE2 in cerebrospinal fluid. IL-6 deficient mice were not refractory to the action of PGE2 because of excess production of some hypothermia-producing factor, since administration of a Cox-2 inhibitor in LPS-challenged IL-6 deficient mice did not unmask any hypothermic response, and neutralization of tumor necrosis factor α (TNFα), associated with hypothermia, did not produce fever in LPS-challenged IL-6 deficient mice. These data indicate that IL-6 rather than exerting its effects up- or down-stream of PGE2 affects some process in parallel to PGE2, perhaps by influencing the diffusion and binding of PGE2 onto its target neurons.In papers II and III, we injected the proinflammatory cytokine IL-1β in free-fed wild-type mice, in mice with a deletion of the gene encoding mPGES-1, or in mice deficient in the EP1, EP2 and EP3. Food intake was continuously measured during their active period, revealing that mPGES-1 deficient mice were almost completely resistant to anorexia induced by IL-1β. However, all of the investigated EP receptor deficient mice exhibited a normal profound anorexic response to IL-1β challenge, suggesting that the EP4 is the critical receptor that mediates IL-1β-induced anorexia. We also investigated the role of mPGES-1 in anorexia induced by lipopolysaccharide (LPS) in mPGES-1 deficient mice. The profound anorexic response after LPS-challenge was similar in mPGES-1 deficient and wild-type mice. To further investigate the anorectic behaviour after LPS injection, we pre-starved the animals for 22 hours before injecting them with LPS. In this paradigm, the anorexia was less profound in mPGES-1 knock-out mice. Our results suggest that while the inflammatory anorexia elicited by peripheral IL-1β seems largely to be dependent on mPGES-1-mediated PGE2 synthesis, similar to the febrile response, the LPS-induced anorexia is independent of this mechanism in free-fed mice but not in pre-starved animals.In papers IV and V, the role of prostanoids for the immune-induced HPA-axis response was investigated in mice after genetic deletion or pharmacological inhibition of prostanoid-synthesizing enzymes, including Cox-1, Cox-2, and mPGES-1. The immediate LPS-induced release of ACTH (adrenocorticotropic hormone and corticosteroids was critically dependent on Cox-1 derived prostanoids and occurred independently of Cox-2 and mPGES-1 derived PGE2. In contrast, the delayed HPA-axis response was critically dependent on immune-induced PGE2, synthesized by Cox-2 and mPGES-1, and occurred independently of Cox-1 derived enzymes. In addition, in the mPGES-1 deficient mice, the synthesis of CRH hnRNA and mRNA was decreased in the paraventricular nucleus of the hypothalamus after LPS-challenge, indicating that the delayed hormone secretion was mediated by PGE2-induced gene-transcription of CRH in the hypothalamus. The expression of the c-fos gene and Fos protein, an index of synaptic activation, was maintained in the paraventricular nucleus and its brainstem afferents both after unselective and Cox-2 selective inhibition as well as in Cox-1, Cox-2, and mPGES-1 knock-out mice. This suggests that the immune-induced neuronal activation of autonomic relay nuclei occurs independently of prostanoid synthesis and that it is insufficient for eliciting stress hormone release.
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| 2. |
- Freund-Levi, Yvonne, 1956-, et al.
(författare)
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Effects of supplementation with omega-3 fatty acids on oxidative stress and inflammation in patients with Alzheimer's disease : the OmegAD study
- 2014
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Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 42:3, s. 823-831
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Oxidative stress and inflammation are two key mechanisms suggested to be involved in the pathogenesis of Alzheimer's disease (AD). Omega-3 fatty acids (ω-3 FAs) found in fish and fish oil have several biological properties that may be beneficial in AD. However, they may also auto-oxidize and induce in vivo lipid peroxidation.OBJECTIVE: The objective of this study was to evaluate systemic oxidative stress and inflammatory biomarkers following oral supplementation of dietary ω-3 FA.METHODS: Forty patients with moderate AD were randomized to receive 1.7 g DHA (22:6) and 0.6 g EPA (20:5) or placebo for 6 months. Urinary samples were collected before and after supplementation. The levels of the major F2-isoprostane, 8-iso-PGF2α, a consistent in vivo biomarker of oxidative stress, and 15-keto-dihydro-PGF2α, a major metabolite of PGF2α and biomarker of inflammatory response, were measured.RESULTS: F2-isoprostane in urine increased in the placebo group after 6 months, but there was no clear difference in treatment effect between supplemented and non-supplemented patients on the urinary levels of F2-isoprostanes and 15-keto-dihydro-PGF2α. At baseline, the levels of 15-keto-dihydro-PGF2α showed negative correlative relationships to ω-3 FAs, and a positive correlation to linoleic acid. 8-iso-PGF2α correlated negatively to the ω-6 FA arachidonic acid.CONCLUSION: The findings indicate that supplementation of ω-3 FAs to patients with AD for 6 months does not have a clear effect on free radical-mediated formation of F2-isoprostane or cyclooxygenase-mediated formation of prostaglandin F2α. The correlative relationships to FAs indicate a potential role of FAs in immunoregulation.
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| 3. |
- Hjorth, Erik, et al.
(författare)
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Omega-3 fatty acids enhance phagocytosis of Alzheimer's disease-related amyloid-β42 by human microglia and decrease inflammatory markers
- 2013
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Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 35:4, s. 697-713
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Tidskriftsartikel (refereegranskat)abstract
- The use of supplements with omega-3 (ω3) fatty acids (FAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) is widespread due to proposed beneficial effects on the nervous and cardiovascular systems. Many effects of ω3 FAs are believed to be caused by down-regulation and resolution of inflammation. Alzheimer's disease (AD) is associated with inflammation mediated by microglia and astrocytes, and ω3 FAs have been proposed as potential treatments for AD. The focus of the present study is on the effects of DHA and EPA on microglial phagocytosis of the AD pathogen amyloid-β (Aβ), on secreted and cellular markers of immune activity, and on production of brain-derived neurotrophic factor (BDNF). Human CHME3 microglial cells were exposed to DHA or EPA, with or without the presence of Aβ42. Phagocytosis of Aβ42 was analyzed by flow cytometry in conjunction with immunocytochemistry using antibodies to cellular proteins. Secreted proteins were analyzed by ELISA. Both DHA and EPA were found to stimulate microglial phagocytosis of Aβ42. Phagocytosis of Aβ42 was performed by microglia with a predominance of M2 markers. EPA increased the levels of BDNF in the culture medium. The levels of TNF-α were decreased by DHA. Both DHA and EPA decreased the pro-inflammatory M1 markers CD40 and CD86, and DHA had a stimulatory effect on the anti-inflammatory M2 marker CD206. DHA and EPA can be beneficial in AD by enhancing removal of Aβ42, increasing neurotrophin production, decreasing pro-inflammatory cytokine production, and by inducing a shift in phenotype away from pro-inflammatory M1 activation.
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| 4. |
- Holmgren, Simon, et al.
(författare)
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Neuropsychiatric symptoms in dementia : a role for neuroinflammation?
- 2014
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Ingår i: Brain Research Bulletin. - : Elsevier. - 0361-9230 .- 1873-2747. ; 108, s. 88-93
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Tidskriftsartikel (refereegranskat)abstract
- Dementia is characterized by a progressive cognitive decline and neuropsychiatric symptoms (NPSD) such as agitation, apathy and sleeping problems. There is some evidence of activation of inflammatory pathways in the brain in dementia, but little research has been performed regarding the role of neuroinflammation in NPSD, which might represent a potential novel target for treatment. The aim of this study was to examine the possible association between NPSD and cerebrospinal fluid (CSF) levels of the cytokines IL-6, TNF-α and IL-10, and the cytokine receptor sIL-1RII, in patients with dementia and NPSD. Ninety-four patients (mean age 79±8; 67% female) with a score on the neuropsychiatric inventory (NPI) ≥10 points, were included. Clinical assessment included administration of NPI, the mini-mental state examination (MMSE) and the Cohen-Mansfield agitation inventory (CMAI). The cytokine levels in CSF samples were analysed by enzyme-linked immunosorbent assay. Correlations were statistically examined using Spearman's rank correlation coefficient (r), and simple- and multiple-linear regression. The anti-inflammatory cytokine IL-10 showed reverse correlations with total NPI score (NPI-total=-0.001, t(90)= 8.50, p=0.004) and NPI sub-items agitation (agitation=-0.007, t(90)=7.02, p=0.009) and night-time behaviour (night time behaviour=-0.006, t(90)=6.34, p=0.01). There was a trend towards reverse correlation between IL-10 and depression (depression=-0.004, t(90)=2.96, p=0.09). Also, the soluble cytokine receptor sIL-1RII showed a trend towards correlation with apathy (apathy=0.82, t(82)=3.62, p=0.06). The levels of IL-6 showed no significant correlations with NPSD. Levels of TNF-α were non-detectable. In Alzheimer's disease (AD) subjects (n=33), IL-6 showed reverse correlation with anxiety (r=-0.35, p=0.049). In mixed AD subjects (n=26), IL-10 showed reverse correlations with the total NPI score (r=-0.46, p=0.02) and depression (r=-0.45, p=0.02). The findings indicate a relationship between neuroinflammation and neuropsychiatric symptoms in AD in which anti-inflammatory signalling by IL-10 is beneficial from a mental health perspective.
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| 5. |
- Lekander, Mats, et al.
(författare)
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Cytokines and memory across the mature life span of women
- 2011
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Ingår i: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 52:3, s. 229-235
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Tidskriftsartikel (refereegranskat)abstract
- Increasing evidence suggests a role of the immune system in modulation of cognition, but details on affected memory systems are largely lacking. We therefore aimed to study the relation between selected cytokines and subsets of memory, and the impact of age in these relations. From a random population-based sample (the Betula Prospective Cohort Study), 298 women (age 45-90) were studied in terms of episodic recall and recognition, semantic fluency and knowledge, and prospective memory. Circulating cytokines of relevance for cognition and aging were measured with ELISA. Levels of interleukin (IL)-6 and sIL-2R were significantly and negatively associated with most cognitive variables, while the opposite was true for IL-1 beta. Age shared substantial variance with both cytokines and memory, and turned most correlations non-significant when controlled for together with education, BMI and presence of disease. Interactions between age and cytokines were further analyzed in multiple regressions. For IL-6, significant negative interactions with age were found for semantic fluency (p < 0.05) and prospective memory (p < 0.01), and for sIL-2R in predicting semantic knowledge (p < 0.05), indicating an increased negative impact of these cytokines on memory with increasing age. In conclusion, the study indicates a relation between cytokines and memory that appears to be largely mediated by age, and supports the suggestion that cytokine dysregulation with higher age may interact with cognitive aging.
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| 6. |
- Sarlus, Heela, et al.
(författare)
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Allergy influences the inflammatory status of the brain and enhances tau-phosphorylation
- 2012
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Ingår i: Journal of Cellular and Molecular Medicine (Print). - : Wiley. - 1582-1838 .- 1582-4934. ; 16:10, s. 2401-2412
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Tidskriftsartikel (refereegranskat)abstract
- Despite the existing knowledge regarding the neuropathology of Alzheimer's disease (AD), the cause of sporadic forms of the disease is unknown. It has been suggested that systemic inflammation may have a role, but the exact mechanisms through which inflammatory processes influence the pathogenesis and progress of AD are not obvious. Allergy is a chronic inflammatory disease affecting more than 20% of the Western population, but the effects of allergic conditions on brain functions are largely unknown. The aim of this study was to investigate whether or not chronic peripheral inflammation associated with allergy affects the expression of AD-related proteins and inflammatory markers in the brain. On the basis of previously described models for allergy in mice we developed a model of chronic airway allergy in mouse, with ovalbumin as allergen. The validity of the chronic allergy model was confirmed by a consistent and reproducible eosinophilia in the bronchoalveolar lavage (BAL) fluid of allergic animals. Allergic mice were shown to have increased brain levels of both immunoglobulin (Ig) G and IgE with a widespread distribution. Allergy was also found to increase phosphorylation of tau protein in the brain. The present data support the notion that allergy-dependent chronic peripheral inflammation modifies the brain inflammatory status, and influences phosphorylation of an AD-related protein, indicating that allergy may be yet another factor to be considered for the development and/or progression of neurodegenerative diseases such as AD.
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| 7. |
- Vedin, Inger, et al.
(författare)
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Reduced prostaglandin F-2 alpha release from blood mononuclear leukocytes after oral supplementation of omega 3 fatty acids : the OmegAD study
- 2010
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Ingår i: Journal of Lipid Research. - : American Society for Biochemistry and Molecular Biology. - 0022-2275 .- 1539-7262. ; 51:5, s. 1179-1185
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Tidskriftsartikel (refereegranskat)abstract
- Omega-3 fatty acids, e. g., dokosahexaenoic acid (DHA) and eikosapentaenoic acid (EPA), ameliorate inflammatory reactions by various mechanisms, but the role of prostaglandins remains unclear. Our aim was to determine if dietary supplementation with a DHA-rich fish oil influenced the release of PGF(2 alpha) from peripheral blood mononuclear cells (PBMC). In the OmegAD study, 174 Alzheimer disease patients received either 1.7 g DHA plus 0.6 g EPA or a placebo daily for six months. PBMCs from the 21 ( 9 on fish oil and 12 on placebo) first-randomized patients were stimulated with either lipopolysaccharide (LPS) or phytohemagglutinin (PHA) before and after 6 months. Our results showed that plasma concentrations of DHA and EPA increased significantly at 6 months in the omega-3 group. PGF(2 alpha) release from LPS- ( but not from PHA-) stimulated PBMC was significantly diminished in this group; no change was noted in the placebo group. PGF(2 alpha) changes correlated inversely with changes in plasma DHA and EPA. Decreased IL-6 and IL-1(beta) levels correlated with decreased PGF(2 alpha) levels. The stimulus-specific PGF(2 alpha) release from PBMC after 6 months of oral supplementation with the DHA-rich fish oil might be one event related to reduced inflammatory reactions associated with omega-3 fatty acid intake.
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