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      Radiodetoxified Lipopolysaccharide Fails to Activate the Hypophyseal- Pituitary-Adrenal Axis in the Rat

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      Neuroimmunomodulation
      S. Karger AG

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          Abstract

          Lipopolysaccharide (LPS) is known to raise the concentration of the circulating stress hormones such as ACTH, corticosterone and β-endorphin. This effect of endotoxin is mediated by different immune system-released hormone-like factors (e.g. interleukins, tumor necrosis factor etc.). Gamma-ray irradiation of LPS alters its biological properties and results in a radiodetoxified LPS preparation with numerous beneficial effects and decreased toxicity. In this study we compared the neuroendocrine effects of a commercial LPS and our native and radiodetoxified LPS preparations in rats. Plasma ACTH, corticosterone and β-endorphin levels were measured by specific radioimmunoassays 120 min after intraperitoneal LPS administration. Control animals were injected with saline. Results show a dramatic increase in all hormones after administration of commercial and our native LPS preparation. Hormone levels in saline-injected controls and radiodetoxified LPS-treated rats did not rise significantly. These results suggest that radio-detoxification disintegrated that part of the LPS molecule complex which is responsible for toxicity including an enhanced production of cytokines, which trigger the hypothalamo-pituitary-adrenal axis.

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          Regulation of the HPA axis by cytokines.

          Cytokines are a group of polypeptide mediators, classically associated with the regulation of immunity and inflammation. However, these peptides regulate not only local immune/inflammatory responses, but also elicit many CNS-mediated responses which accompany such immune/inflammatory reactions. This article reviews the evidence that interleukin (IL)-1, IL-6, and tumor necrosis factor alpha (TNFalpha) produce hypothalamo-pituitary-adrenal (HPA) axis activation in response to various threats to homeostasis. To aid such an examination, and to gain insights into the potential mechanisms by which these cytokines influence the HPA axis, experimental findings are discussed within a framework of criteria. If a particular cytokine plays a significant role in the regulation of the HPA axis in response to a particular pathophysiology, then necessarily: (1) receptors for that cytokine should be present within tissues associated with the HPA axis; (2) administration of that cytokine should elicit HPA activation; (3) the HPA axis should be exposed to that cytokine; and (4) inhibition of the action of that cytokine should prevent HPA activation. The evidence discussed indicates that some, if not all, of these criteria are met for each of IL-1, IL-6, and TNFalpha. However, the extensive interactions between different cytokines, the broad spectrum of pathophysiologies associated with increased cytokine production (including inflammatory and non-inflammatory stresses), and the number of tissues/cells capable of either synthesizing or responding to cytokines, suggest that multiple mechanisms mediate the influence of cytokines on the HPA axis.
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            • Record: found
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            Effects of mediobasal hypothalamic lesion on immunoreactive ACTH/β-endorphin levels in cerebrospinal fluid, in discrete brain regions, in plasma, and in pituitary of the rat

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              Author and article information

              Journal
              Neuroimmunomodulation
              Neuroimmunomodulation
              S. Karger AG
              1021-7401
              1423-0216
              December 1 2000
              2000
              December 15 2000
              : 8
              : 3
              : 128-131
              Article
              10.1159/000054272
              c4b8032d-1ed4-4c73-bc44-45b80227a852
              © 2000

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