| 1. |
- Engström, Linda, et al.
(författare)
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Acetaminophen reduces lipopolysaccharide-induced fever by inhibiting cyclooxygenase-2
- 2013
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Ingår i: Neuropharmacology. - : Elsevier. - 0028-3908 .- 1873-7064. ; 71, s. 124-129
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Tidskriftsartikel (refereegranskat)abstract
- Acetaminophen is one of the world's most commonly used drugs to treat fever and pain, yet its mechanism of action has remained unclear. Here we tested the hypothesis that acetaminophen blocks fever through inhibition of cyclooxygenase-2 (Cox-2), by monitoring lipopolysaccharide induced fever in mice with genetic manipulations of enzymes in the prostaglandin cascade. We exploited the fact that lowered levels of a specific enzyme make the system more sensitive to any further inhibition of the same enzyme. Mice were immune challenged by an intraperitoneal injection of bacterial wall lipopolysaccharide and their body temperature recorded by telemetry. We found that mice heterozygous for Cox-2, but not for microsomal prostaglandin E synthase-1 (mPGES-1), displayed attenuated fever, indicating a rate limiting role of Cox-2. We then titrated a dose of acetaminophen that did not inhibit the lipopolysaccharide-induced fever in wild-type mice. However, when the same dose of acetaminophen was given to Cox-2 heterozygous mice, the febrile response to lipopolysaccharide was strongly attenuated, resulting in an almost normalized temperature curve, whereas no difference was seen between wild-type and heterozygous mPGES-1 mice. Furthermore, the fever to intracerebrally injected prostaglandin E2 was unaffected by acetaminophen treatment. These findings reveal that acetaminophen, similar to aspirin and other non-steroidal anti-inflammatory drugs, is antipyretic by inhibiting cyclooxygenase-2, and not by inhibiting mPGES-1 or signaling cascades downstream of prostaglandin E2.
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| 2. |
- Engström, Linda, et al.
(författare)
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Lipopolysaccharide-Induced Fever Depends on Prostaglandin E2 Production Specifically in Brain Endothelial Cells
- 2012
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Ingår i: Endocrinology. - : Endocrine Society. - 0013-7227 .- 1945-7170. ; 153:10, s. 4849-4861
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Tidskriftsartikel (refereegranskat)abstract
- Immune-induced prostaglandin E2 (PGE2) synthesis is critical for fever and other centrally elicited disease symptoms. The production of PGE2 depends on cyclooxygenase-2 and microsomal prostaglandin E synthase-1 (mPGES-1), but the identity of the cells involved has been a matter of controversy. We generated mice expressing mPGES-1 either in cells of hematopoietic or nonhematopoietic origin. Mice lacking mPGES-1 in hematopoietic cells displayed an intact febrile response to lipopolysaccharide, associated with elevated levels of PGE2 in the cerebrospinal fluid. In contrast, mice that expressed mPGES-1 only in hematopoietic cells, although displaying elevated PGE2 levels in plasma but not in the cerebrospinal fluid, showed no febrile response to lipopolysaccharide, thus pointing to the critical role of brain-derived PGE2 for fever. Immunohistochemical stainings showed that induced cyclooxygenase-2 expression in the brain exclusively occurred in endothelial cells, and quantitative PCR analysis on brain cells isolated by flow cytometry demonstrated that mPGES-1 is induced in endothelial cells and not in vascular wall macrophages. Similar analysis on liver cells showed induced expression in macrophages and not in endothelial cells, pointing at the distinct role for brain endothelial cells in PGE2 synthesis. These results identify the brain endothelial cells as the PGE2-producing cells critical for immune-induced fever.
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| 3. |
- Eskilsson, Anna, et al.
(författare)
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Immune-Induced Fever Is Mediated by IL-6 Receptors on Brain Endothelial Cells Coupled to STAT3-Dependent Induction of Brain Endothelial Prostaglandin Synthesis
- 2014
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Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 34:48, s. 15957-15961
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Tidskriftsartikel (refereegranskat)abstract
- The cytokine IL-6, which is released upon peripheral immune challenge, is critical for the febrile response, but the mechanism by which IL-6 is pyrogenic has remained obscure. Herewegenerated mice with deletion of themembranebound IL-6 receptor alpha (IL-6R alpha) onneural cells, on peripheral nerves, on fine sensory afferent fibers, and on brain endothelial cells, respectively, and examined its role for the febrile response to peripherally injected lipopolysaccharide. We show that IL-6R alpha on neural cells, peripheral nerves, and fine sensory afferents are dispensable for the lipopolysaccharide-induced fever, whereas IL-6R alpha in the brain endothelium plays an important role. Hence deletion of IL-6R alpha on brain endothelial cells strongly attenuated the febrile response, and also led to reduced induction of the prostaglandin synthesizing enzyme Cox-2 in the hypothalamus, the temperature-regulating center in the brain, as well as reduced expression of SOCS3, suggesting involvement of the STAT signaling pathway. Furthermore, deletion of STAT3 in the brain endothelium also resulted in attenuated fever. These data show that IL-6, when endogenously released during systemic inflammation, is pyrogenic by binding to IL-6R alpha on brain endothelial cells to induce prostaglandin synthesis in these cells, probably in concerted action with other peripherally released cytokines.
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| 4. |
- Ruud, Johan, et al.
(författare)
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Inflammation- and tumor-induced anorexia and weight loss require MyD88 in hematopoietic/myeloid cells but not in brain endothelial or neural cells.
- 2013
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Ingår i: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - : Wiley. - 1530-6860 .- 0892-6638. ; 27:5, s. 1973-80
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Tidskriftsartikel (refereegranskat)abstract
- Loss of appetite is a hallmark of inflammatory diseases. The underlying mechanisms remain undefined, but it is known that myeloid differentiation primary response gene 88 (MyD88), an adaptor protein critical for Toll-like and IL-1 receptor family signaling, is involved. Here we addressed the question of determining in which cells the MyD88 signaling that results in anorexia development occurs by using chimeric mice and animals with cell-specific deletions. We found that MyD88-knockout mice, which are resistant to bacterial lipopolysaccharide (LPS)-induced anorexia, displayed anorexia when transplanted with wild-type bone marrow cells. Furthermore, mice with a targeted deletion of MyD88 in hematopoietic or myeloid cells were largely protected against LPS-induced anorexia and displayed attenuated weight loss, whereas mice with MyD88 deletion in hepatocytes or in neural cells or the cerebrovascular endothelium developed anorexia and weight loss of similar magnitude as wild-type mice. Furthermore, in a model for cancer-induced anorexia-cachexia, deletion of MyD88 in hematopoietic cells attenuated the anorexia and protected against body weight loss. These findings demonstrate that MyD88-dependent signaling within the brain is not required for eliciting inflammation-induced anorexia. Instead, we identify MyD88 signaling in hematopoietic/myeloid cells as a critical component for acute inflammatory-driven anorexia, as well as for chronic anorexia and weight loss associated with malignant disease.
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| 5. |
- Wilhelms, Daniel Björk, et al.
(författare)
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Deletion of Prostaglandin E-2 Synthesizing Enzymes in Brain Endothelial Cells Attenuates Inflammatory Fever
- 2014
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Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 34:35, s. 11684-11690
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Tidskriftsartikel (refereegranskat)abstract
- Fever is a hallmark of inflammatory and infectious diseases. The febrile response is triggered by prostaglandin E-2 synthesis mediated by induced expression of the enzymes cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase 1 (mPGES-1). The cellular source for pyrogenic PGE(2) remains a subject of debate; several hypotheses have been forwarded, including immune cells in the periphery and in the brain, as well as the brain endothelium. Here we generated mice with selective deletion of COX-2 and mPGES1 in brain endothelial cells. These mice displayed strongly attenuated febrile responses to peripheral immune challenge. In contrast, inflammation-induced hypoactivity was unaffected, demonstrating the physiological selectivity of the response to the targeted gene deletions. These findings demonstrate that PGE(2) synthesis in brain endothelial cells is critical for inflammation-induced fever.
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