Aspirin May Exert Its Antipyresis by Inhibiting the N-Methyl-D-aspartate Receptor-Dependent Hydroxyl Radical Pathways in the Hypothalamus

Quantification of Prostaglandin E2 Concentration in Interstitial Fluid from the Hypothalamic Region of Free-moving Mice

Prostaglandin E₂ (PGE₂) is a well-established chemical mediator for the generation of the fever at the hypothalamus of the brain. PGE₂ mediates fever generation via PGE receptor 3 (i.e., EP3) on neurons in the preoptic area. The role of PGE₂ has been analyzed by measuring PGE₂ concentration in cerebrospinal fluid (C_csf); however, local PGE₂ concentration at the hypothalamus may not necessarily be consistent with C_csf. In this protocol, we introduce our method to measure directly the alteration in PGE₂ concentration in interstitial fluid in the hypothalamus (C_isf) of awake (free-moving) mice using a microdialysis technique. Male mice (c57BL/6J) were anesthetized and fixed in the stereotaxic instrument, and a microdialysis probe was inserted into the hypothalamus through a guide cannula. On the fifth postoperative day, C_isf was monitored in free-moving mice that were intraperitoneally (i.p.) injected with lipopolysaccharide (LPS). PGE₂ and other eicosanoids recovered in Krebs-Ringer phosphate buffer and defused through a microdialysis probe were extracted into ethyl acetate/formic acid and then quantified with LC-MS/MS. Our method is useful to understand the role of key regulators of prostaglandin concentration such as those of transporters, which have been unappreciated in inflammation-based brain diseases.

Antipyretic and antioxidant activities of the aqueous extract of Cornu bubali (water buffalo horn)

Cornu Bubali (water buffalo horn, WBH) is an animal-derived product which is widely used in Traditional Chinese Medicine (TCM) for dispelling heat, relieving convulsions and cooling blood. The purpose of this study was to investigate the antipyretic activity of WBH aqueous extract and its potential mechanism. Two hyperthermia models, yeast-induced (infectious) and skimmed milk-induced (noninfectious) hyperthermia were employed to evaluate the antipyretic effect and the results showed that rectal temperature of hyperthermia animals was decreased significantly after oral administration of WBH extract. The production of tumor necrosis factor-alpha (TNF-alpha)-induced prostaglandin E(2) (PGE(2)) in rat cerebral microvascular endothelial cells (rCMECs) was inhibited by WBH extract in the concentrations of 10 microg/ml and 100 microg/ml. The WBH extract protected rCMECs survival from hydrogen peroxide (H(2)O(2))-induced toxicity and inhibited the H(2)O(2)-induced leakage of lactate dehydrogenase (LDH) enzyme release at a dose ranging from 5 microg/ml to 100 microg/ml. It could also increase the superoxide dismutase (SOD) and catalase (CAT) enzyme activities. The results suggest that Cornu Bubali exhibits antipyretic activity on both infectious and noninfectious hyperthermia. The antipyretic activity of WBH may be due to the effects on enhancing antioxidation enzyme activities, decreasing PGE(2) production, and protecting the rCMECs against H(2)O(2)-induced injury.

Curcumin inhibits the increase of glutamate, hydroxyl radicals and PGE2 in the hypothalamus and reduces fever during LPS-induced systemic inflammation in rabbits

Evidence has accumulated to suggest that systemic administration of lipopolysaccharide (LPS), in addition to elevating tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) as well as fever, induces overproduction of glutamate, hydroxyl radicals and prostaglandin E(2) (PGE(2)) in the rabbit's hypothalamus. Current study was attempted to assess whether Curcumin exerts its antipyresis by reducing circulating pro-inflammatory cytokines and hypothalamic glutamate, hydroxyl radicals and PGE(2) in rabbits. The microdialysis probes were stereotaxically and chronically implanted into the preoptic anterior hypothalamus of rabbit brain for determination of glutamate, hydroxyl radicals, and PGE(2) in situ. It was found that systemic administration of LPS (2 microg/kg) induced increased levels of both core temperature and hypothalamic levels of both glutamate and hydroxyl radicals accompanied by increased plasma levels of TNF-alpha, IL-1beta, and IL-6. The rise in both the core temperature and hypothalamic glutamate and hydroxyl radicals could also be induced by direct injection of TNF-alpha, IL-1beta, or IL-6 into the lateral ventricle of rabbit brain. Pretreatment with Curcumin (5-40 mg/kg, i.p.) 1 h before an i.v. dose of LPS significantly reduced the LPS-induced overproduction of circulating TNF-alpha, IL-1beta, and IL-6, and brain glutamate, PGE(2), and hydroxyl radicals. Both the febrile response and overproduction of both glutamate and hydroxyl radicals in the hypothalamus caused by central administration of TNF-alpha, IL-1beta, or IL-6 could be suppressed by Curcumin. These results indicate that systemic injection of Curcumin may exert its antipyresis by inhibiting the glutamate-hydroxyl radicals-PGE(2) pathways in the hypothalamus and circulating TNF-alpha, IL-1beta, and IL-6 accumulation during LPS fever.

Lipopolysaccharide- and Glutamate-Induced Hypothalamic Hydroxyl Radical Elevation and Fever Can Be Suppressed by N-Methyl-D-aspartate-Receptor Antagonists

The purpose of the current study was to explore the effects of N-methyl-D-aspartate (NMDA)-receptor antagonists (MK-801 and LY235959) administered intracerebroventricularly on the changes of both core temperature and hypothalamic levels of 2,3-dihydroxybenzoic acid (2,3-DHBA) induced by intracerebroventricular injection of glutamate (100 - 400 microg at 10 microl/rabbit) or intravenous administration of lipopolysaccharide (LPS) (2 microg/kg) in rabbits. The measurements of 2,3-DHBA were used as an index of the intrahypothalamic levels of hydroxyl radicals. The rise in both the core temperature and hypothalamic 2,3-DHBA could be induced by intracerebroventricular injection of glutamate or intravenous administration of LPS. The glutamate- or LPS-induced fever and increased hypothalamic levels of 2,3-DHBA were significantly antagonized by pretreatment with injection of MK-801 or LY235959 1 h before glutamate or LPS injection. The increased levels of prostaglandin E2 in the hypothalamus induced by glutamate or LPS could be suppressed by MK-801 or LY235959. The data demonstrate that prior antagonism of NMDA receptors in the brain, in addition to reducing prostaglandin E2 production in the hypothalamus, suppresses both the glutamate- and LPS-induced fever and increased hypothalamic hydroxyl radicals.