| 1. |
- Björk Wilhelms, Daniel, et al.
(författare)
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Cyclooxygenase isoform exchange blocks inflammatory symptoms
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Cyclooxygenase‐2 (COX‐2) is the main source of inducible prostaglandin E2 production and mediates inflammatory symptoms including fever, loss of appetite and hyperalgesia. In contrast, COX‐1 is dispensable for most inflammatory symptoms. Global deletion of COX‐2 leads to a blockade of inflammation‐induced fever and appetite loss but also to high rates of fetal mortality. The latter is unfortunate since mice without COX‐2 are powerful tools in the study of inflammation and cardiovascular medicine. The differential functionality of the COX isoforms could be due to differences in regulatory regions of the genes, leading to different expression patterns, or to differences in the coding sequence, leading to distinct functional properties of the proteins. To study this in the context of inflammatory symptoms, we used mice in which the coding sequence of COX‐2 was replaced by the corresponding sequence of COX‐1. In these mice, COX‐1 mRNA was induced by inflammation but COX‐1 protein expression did not fully mimic inflammation‐induced COX‐2 expression. Just like mice globally lacking COX‐2, these mice showed a complete lack of fever and inflammation‐induced anorexia. However, as previously reported, they displayed close to normal survival rates. This shows that the COX activity generated from the hybrid gene was strong enough to allow survival but not strong enough to mediate inflammatory symptoms, making the line an interesting alternative to COX‐2 knockouts for the study of inflammation. Our results also show that the functional differences between COX‐1 and COX‐2 in the context of inflammatory symptoms is not only dependent on the features of the promoter regions. Instead they indicate that there are fundamental differences between the isoforms at translational or posttranslational levels, which make hybrid genes less functional.
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| 2. |
- Elander, Louise, 1980-, et al.
(författare)
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Prostaglandin E2 receptors in IL-1β induced anorexia
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Anorexia in response to immune challenge by Interleukin-1β (IL-1β) has been shown to be dependent on Prostaglandin E2 (PGE2) produced by the inducible enzyme microsomal prostaglandin E synthase-1 (mPGES-1). However, it is not known which of the four known PGE2 receptors EP1-4, encoded by the genes Ptger 1-4, that mediates the PGE2-induced anorexia. Here we examined food intake in mice deficient in EP1, EP2 and EP3, respectively, during normal conditions and following treatment with IL-1β. Neither of the gene deletions affected baseline food intake, and all the three genotypes displayed anorexia following IL-1β injection, similar to wild type mice. Previous work has demonstrated that the EP3 receptor is critical for the generation of fever, and that EP1 and EP3 receptors mediate inflammationinduced activation of the hypothalamic-pituitary-adrenal (HPA) axis. The present data, showing intact anorexigenic responses in EP1 and EP3 deficient mice, as well as in mice with deletion of the EP2 receptor, hence suggest that PGE2-elicited acute phase responses are mediated by distinct set or sets of PGE2-receptors.
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| 3. |
- Ruud, Johan, et al.
(författare)
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A putative role for Cox-1 in the initiation of cancer anorexia independent of mPGES-1, PGE2 and neuronal EP4 receptors
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- It is well-established that prostaglandins (PGs) affect tumorigenesis, and evidence indicates that PGs also are important for the reduced food intake and body weight loss, the so called anorexia-cachexia syndrome, in malignant cancer. However, the identity of the PG and the cyclooxygenase (Cox) species responsible for cancer anorexia-cachexia is unknown. Here, we addressed this issue by transplanting mice with a tumor that elicits anorexia. Meal pattern analysis revealed that the reduced food intake in the tumor-bearing animals was due to decreased meal frequency. Treatment with a nonselective Cox inhibitor attenuated the anorexia, and also tumor growth. However, when given at manifest anorexia, the nonselective Cox inhibitors restored appetite and prevented body weight loss without affecting tumor size. Despite the pronounced effect of nonselective Cox-inhibitors, a selective Cox-2 inhibitor had no effect on the anorexia, whereas Cox-1 inhibition delayed its onset. Tumor growth was associated with robust increase of PGE2 levels in plasma - a response blocked by nonselective Cox-inhibition - but not in the cerebrospinal fluid, and there was no rise in body temperature. Neutralization of PGE2 with specific antibodies did not ameliorate the anorexia, and genetic deletion of microsomal PGE synthase-1 (mPGES-1), the inducible terminal isomerase for PGE2 synthesis, affected neither anorexia nor tumor growth. Furthermore, tumor-bearing mice lacking EP4 receptors selectively in the nervous system developed anorexia. These observations suggest that Cox-enzymes, most likely Cox-1, are involved in cancer-elicited anorexia and weight loss, but that these phenomena occur independently of host mPGES-1, PGE2 and neuronal EP4 signaling.
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| 4. |
- Ruud, Johan, et al.
(författare)
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MyD88 in hematopoietic cells, but not in cerebrovascular endothelial cells or neural cells, is critical for inflammation- and cancer-induced loss of appetite
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Loss of appetite concomitant with reduced food intake is a hallmark of both acute and chronic inflammatory diseases. Yet, despite extensive investigations, the underlying mechanisms remain undefined. Here we addressed this issue using mice lacking MyD88, critical for Tolllike and IL-1 receptor family signaling, generally or in specific cell types. Ubiquitous null deletions conferred complete resistance to bacterial lipopolysaccharide (LPS) induced anorexia, but this resistance was lost when knock-out mice subjected to whole-body irradiation to delete hematopoietic cells were transplanted with wild-type bone-marrow. In line with this observation, mice lacking MyD88 in hematopoietic cells were largely protected against LPS-induced anorexia, whereas mice with abrogated MyD88 signaling in neural cells, being leaner and smaller, developed anorexia of similar magnitude as wild-type littermates. The effect of hematopoietic MyD88-deletion on feeding seemed however partially dissociated from the effect on body weight, since LPS triggered weight loss, although attenuated, in these mutants. Furthermore, MyD88 deficiency in the cerebrovascular endothelium affected neither LPS-induced anorexia nor weight loss. In a model for the cancer anorexia-cachexia syndrome, inactivation of MyD88 in hematopoietic cells strongly impaired the anorexia development and protected against body weight loss. These findings identify hematopoietic cells as a critical nexus for acute inflammatory driven anorexia as well as for chronic anorexia associated with malignant disease.
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