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1.
Abstract: Brain inflammation includes microglial activation and enhanced production of diffusible chemical mediators, including prostaglandin E2. Prostaglandin E2 is generally considered a proinflammatory molecule, but it also promotes neuronal survival and down-regulates some aspects of microglial activation. It remains unknown, however, if and how prostaglandin E2 prevents microglial activation. In primary culture, microglial activation is predicted by a characteristic pattern of whole-cell potassium currents and interleukin-1β production. We investigated if prostaglandin E2 could alter these currents and, if so, whether these currents are necessary for microglial activation. Microglia were isolated from mixed cell cultures prepared from neonatal rat brains and exposed to 0–10 µ M prostaglandin E2 and lipopolysaccharide for 24 h. Currents were elicited by using standard patch-clamp technique, and interleukin-1β production was measured by ELISA. Peak outward current densities in microglia treated with lipopolysaccharide plus prostaglandin E2 (10 n M ) were reduced significantly from those of cells treated with lipopolysaccharide alone. Prostaglandin E2 and 4-aminopyridine (a blocker of outward potassium currents) also significantly reduced interleukin-1β production. Thus, although prostaglandin E2 is classified generally as a proinflammatory chemical, it has complex roles in brain inflammation that include preventing microglial activation, perhaps by reducing the outward potassium current.  相似文献   

2.
Abstract— Tritium labeled prostaglandin (PG) endoperoxides PGG2 and PGH2 were rapidly transformed (2 min, 37°C) in good yield (> 50%) by homogenates of whole rat brain into a mixture of products including prostaglandin E2 and F2x: under similar conditions (10min. 37°C) tritium labeled arachidonic acid remained essentially unoxidised. The ratio of PGE-like products: PGF2x formed was approx 0.5 as determined by radio thin layer chromatography. This ratio changed to unity when homogenates of cerebral cortex or cerebral hemispheres were employed. On the other hand cerebellar homogenates formed PGF2x in much greater amounts. The structures of the products were confirmed by mass spectrometry and were further supported by experiments using octadeuterio-endoperoxides. In the latter experiments the resulting PGE2 and PGF2x contained the expected seven and eight deuterium atoms respectively. Evidence for the formation of heptadeuterio PGD2. heptadeuterio-6-keto-PGF1, and hexadeuterio 12-hydroxyheptadecatrienoic acid was also obtained by mass spectrometry. These experiments demonstrate for the first time in brain tissue the biosynthesis of labeled prostaglandins from exogenous tritiated and deuterated precursors.  相似文献   

3.
Abstract: Adenylate cyclase in microvessels isolated from rat cerebral cortex was stimulated by guanine nucleotides, catecholamines, prostaglandin E1, prostaglandin E2, and 2-chloroadenosine. Catecholamine stimulation was mediated by interaction with β-adrenergic receptors. The order of relative potency was: isoproterenol > epinephrine > norepinephrine. Activation of microvessel adenylate cyclase by prostaglandins E1 and E2 as well as by 2-chloroadenosine was dose related. Twenty-two peptides were tested for possible effects on the microvessel adenylate cyclase. Only vasoactive intestinal polypeptide (VIP) was stimulatory. No inhibitory action was observed. Activation by VIP required guanosine triphosphate and was dose dependent from 10 n M to μ M (ED50= 0.1 μ M ). At 30°C, stimulation of adenylate cyclase by the peptide increased linearly with time for up to 15 min. The effect of VIP was not inhibited by phentolamine or propranolol, suggesting that its action was not elicited by interaction with α- or β-adrenergic receptors. Activation achieved by VIP and isoproterenol, prostaglandin E1, or 2-chloroadenosine was the sum of the individual stimulations, suggesting that receptors for VIP were distinct from those for isoproterenol, prostaglandin E1, and 2-chloroadenosine.  相似文献   

4.
Abstract: The presence of prostaglandins D2, E2, and F was demonstrated and their contents measured in various regions of postmortem human brain, pineal body, and pituitary by using specific radioimmunoassays and gas chromatography-mass spectrometry. The three prostaglandins were widely distributed in similar concentrations ranging from several hundred pg/g wet weight to about 40 ng/g wet weight. Prostaglandins D2 and E2 showed consistent and similar regional distributions in all six brains tested; amounts were high in pineal body, pituitary, olfactory bulb, and hypothalamus. On the other hand, prostaglandin F was distributed more evenly. Prosta- glandin D synthetase and prostaglandin E synthetase activities were found in cerebrum homogenate from a single subject and were recovered from the 100,000 × g supernatant. The presence of 1 m M glutathione, reduced form, markedly stimulated the activity of prostaglandin E synthetase, but did not affect prostaglandin D synthetase activity. Activity of 15-hydroxyprostaglandin dehydrogenase was found in the cerebrum homogenate and was partially purified. This enzyme required NADP as a cofactor and copurified with prostaglandin E 9-ketoreductase.  相似文献   

5.
The present study tests the hypothesis that agents known to elevate the level of intracellular cyclic adenine nucleotide may direct different epithelial cells onto a pathway of epidermoid (squamous) development and differentiation. We report here that the mixture of dibutyryl cyclic AMP (dbcAMP), prostaglandins E1, E2 and B1, (PG E1, E2, B1), and papaverine (pap) enhances the rate of normal squamous cell development in organ-cultured skin of chick embryos. The three components may act synergistically to elevate the level of intracellular cyclic adenine nucleotide. We recently reported that the same group of agents induces abnormal development (squamous metaplasia) and aberrant differentiation (keratin production) in the normally cuboidal epithelium of cultured whole mammary glands of mice [1]. Thus, dbcAMP, PG E1, E2, B1, and pap are effective in enhancing normal squamous cell development and also in inducing squamous metaplasia de novo in the epithelial components of two different organs of embryonic and adult animals of two classes of vertebrates. The combined findings are suggestive that cyclic adenine nucleotide together with the prostaglandins may act generally on diverse types of epithelia to bring about squamous cell development and a differentiation marked by keratin production.  相似文献   

6.
Administration of 17β-oestradiol (E2) to rainbow trout, in the form of hydrogenated coconut oil implants produced a stable, long-term elevation in plasma E2 levels. The elevation was doserelated (over the range 1–10mg kg-1 body weight) both 4 and 8 weeks after implantation. Dose-related increases were also observed with respect to liver weight-body weight ratios and plasma protein levels. Plasma T3 and total calcium levels were depressed and elevated, respectively, by E2 treatment but the responses were not linearly related to the dose of E2 administered; there was no significant effect of E2 on plasma T4 levels.
E2 induced a shift in the binding of T3 to plasma proteins, with T3 binding to smaller molecular weight proteins; neither T4 nor T3 bound to vitellogenin which was present at high levels in the plasma of E2-treated fish.  相似文献   

7.
Evidence for Two Distinct Forms of Fatty Acid Cyclooxygenase in Brain   总被引:2,自引:1,他引:1  
Abstract: The enzymatic metabolism of [14C]arachidonic acid (AA) was studied with microsomes prepared from rabbit medulla. Prostaglandin E2 (PGE2) levels, measured either by radiochemistry or radioimmunoassay, rose rapidly and abruptly plateaued within 5 min, while prostaglandin F2a (PGF2a) levels continued to rise for 30 min. The rapid termination of PGE2 biosynthesis was not the result of limited cofactor, substrate, or product feedback inhibition, nor was it due to PGE2-9-ketoreductase activity. Inhibition of the PGH2→ PGE2 isomerase by arachidonic acid or its metabolites could not explain the abrupt halt in PGE2 biosynthesis. Proof for two separate cyclooxygenases comes from our observation that a preincubation of the brain microsomes with unlabeled AA eliminated PGE2 biosynthesis while PGF2o production continued. Further evidence to suggest two cyclooxygenases in brain is derived from the observation that indomethacin inhibited PGE2 production at concentrations that did not affect PGF2a biosynthesis. These results suggest that one fatty acid cyclooxygenase is closely associated with PGH2→ PGE2 isomerase and readily undergoes autodestruction and the second cyclooxygenase is associated with a PGH2→ PGF2a reductase and is somewhat resistant to arachidonate-induced destruction and to nonsteroidal antiinflammatory agents.  相似文献   

8.
Abstract The 2-oxoglutarate dehydrogenase complex of the tricarboxylic acid cycle (TCA) consists of multiple copies of 3 different subenzymes; E1, E2 and E3. The E3 subenzyme is also a component of the pyruvate dehydrogenase complex. Bacillus subtilis 2-oxoglutarate dehydrogenase mutants were studied. The mutants defective in E1, E2 and E3 subenzyme activity, respectively, could be separated into 3 groups by biochemical complementation analyses. The groups correspond to the citK, citM and citL genes. A B. subtilis subenzyme defect, probably E1, could be complemented with the corresponding Escherichia coli wild-type subenzyme and vice versa. Mutations in citK and citM are closely linked. The gene order kauA——citK-citM was determined from 3-factor transformation crosses. It is concluded that the gene organization and the subenzyme structure of the 2-oxoglutarate dehydrogenase complex are similar in B. subtilis and E. coli .  相似文献   

9.
10.
11.
The effects of 17β-estradiol (E2) on dopamine (DA) transport could explain gender and life-stage differences in the incidence of some neurological disorders. We tested the effects of E2 at physiological concentrations on DA efflux in nerve growth factor-differentiated rat pheochromocytoma cells that express estrogen receptors (ER) α, ERβ, and G-protein coupled receptor 30 (GPR30), and DA transporter (DAT). DAT efflux was determined as the transporter-specific loss of 3H-DA from pre-loaded cells; a 9–15 min 10−9 M E2 treatment caused maximal DA efflux. Such rapid estrogenic action suggests a non-genomic response, and an E2-dendrimer conjugate (limited to non-nuclear actions) caused DA efflux within 5 min. Efflux dose–responses for E2 were non-monotonic, also characteristic of non-genomic estrogenic actions. ERα siRNA knockdown abolished E2-mediated DA efflux, while ERβ knockdown did not, and GPR30 knockdown increased E2-mediated DA efflux (suggesting GPR30 is inhibitory). Use of ER-selective agonists/antagonists demonstrated that ERα is the predominant mediator of E2-mediated DA efflux, with inhibitory contributions from GPR30 and ERβ. E2 also caused trafficking of ERα to the plasma membrane, trafficking of ERβ away from the plasma membrane, and unchanged membrane GPR30 levels. Therefore, ERα is largely responsible for non-genomic estrogenic effects on DAT activity.  相似文献   

12.
Recently, it has been demonstrated that the opportunistic fungal pathogen Cryptococcus neoformans can synthesize authentic immunomodulatory prostaglandins. The mechanism by which this takes place is unclear as there is no cyclooxygenase homologue in the cryptococcal genome. In this study, we show that cryptococcal production of both PGE2 and PGF can be chemically inhibited by caffeic acid, resveratrol and nordihydroguaiaretic acid. These polyphenolic molecules are frequently used as inhibitors of lipoxygenase enzymes; however, blast searches of the cryptococcal genome were unable to identify any homologues of mammalian, plant or fungal lipoxygenases. Next we investigated cryptococcal laccase, an enzyme known to bind polyphenols, and found that either antibody depletion or genetic deletion of the primary cryptococcal laccase ( lac1 Δ) resulted in a loss of cryptococcal prostaglandin production. To determine how laccase is involved, we tested recombinant laccase activity on the prostaglandin precursors, arachidonic acid (AA), PGG2 and PGH2. Using mass spectroscopy we determined that recombinant Lac1 does not modify AA or PGH2, but does have a marked activity toward PGG2 converting it to PGE2 and 15-keto-PGE2. These data demonstrate a critical role for laccase in cryptococcal prostaglandin production, and provides insight into a new and unique fungal prostaglandin pathway.  相似文献   

13.
Abstract: Despite a high degree of sequence homology, the dopamine D2 and D3 receptors have substantially different second messenger coupling properties. We have used chimeric D2/D3 receptors to investigate the contribution of the intracellular loops to the signaling properties of these receptors. In HEK 293 cells, D2 receptors inhibit prostaglandin E1-stimulated cyclic AMP levels by >90%, whereas D3 receptors inhibit cyclic AMP accumulation by only 20%. In chimeras that have the second or third intracellular loop, or both loops simultaneously, switched between the D2 and D3 receptors, the maximal inhibition of adenylyl cyclase is 60–90%. In addition, the potency of quinpirole to inhibit adenylyl cyclase activity at some of the chimeras is altered compared with the wild-type receptors. It appears that the intracellular loops of the D3 receptor are capable of interacting with G proteins, as when these loops are expressed in the D2 receptor, the chimeras inhibit adenylyl cyclase similarly to the wild-type D2 receptor. Our data suggest that the overall conformation of the D3 receptor may be such that it interacts with G proteins only weakly, but when the intracellular loops are expressed in another context or the D3 receptor structure is altered by the introduction of D2 receptor sequence, this constraint may be lifted.  相似文献   

14.
Abstract A partially purified Escherichia coli heat-stable (ST) enterotoxin had been shown to increase the 45Ca2+ uptake by rat intestinal brush-border membrane vesicles (BBMV). The effect of ST enterotoxin on calcium uptake by BBMV was significant compared with the control and was also dose-dependent. The stimulation of calcium uptake by ST enterotoxin was inhibited by chemical agents which block the calcium entry into the cell. These data indicate that the ST acts as calcium ionophore in this particular system.  相似文献   

15.
Ovarian follicles from striped trumpeter Latris lineata were incubated in L15 medium alone, or medium supplemented with gonadotropin (GtH) preparations (human chorionic GtH, carp maturational GtH or partially purified salmon GtH), testosterone (T) or 17-hydroxyprogesterone (17P). Levels of oestrone (E1), 17 β -oestradiol (E2), T, and 17,20 β -dihydroxy-4-pregnen-3-one (17,20 β P) in the medium after incubation were measured by radioimmunoassay. Basal production of E2 was high from previtellogenic follicles, whereas little T was produced. Both T and E2 production increased in response to treatment with GtH or steroid precursors. Vitellogenic follicles showed basal production of both T and E2, and T but not E2 levels generally increased in response to hormone treatment. Preparations containing follicles nearing final maturation showed low basal production of E2 but high production of T. Treatment with steroids resulted in little change in E2 but often very large increases in T production, whereas GtH stimulated lesser increases. 17,20 β P production was detectable from incubations of maturing follicles from two out of five fish, and in those two incubations, increased in response to treatment with 17P. E1 was not detectable in any incubations. The results indicate that there is a shift in steroidogenesis from E2 to T production during oocyte development, and provide further evidence that steroid biosynthesis in non-salmonids is principally regulated by substrate availability.  相似文献   

16.
Phenotype modulation in primary cultures of arterial smooth-muscle cells   总被引:1,自引:0,他引:1  
Abstract. The effects of prostaglandin E1 (PGE1) on the phenotypic state of enzymatically isolated arterial smooth-muscle cells in primary culture were studied by transmission electron microscopy, thymidine autoradiography, and cell counting. Early in culture (day 0–2), PGE1, stimulated conversion of the cells from contractile (less euchromatic nucleus and cytoplasm dominated by myofilament bundles) to synthetic state (more euchromatic nucleus and cytoplasm dominated by cisternae of rough endoplasmic reticulum and a large Golgi complex). The rate of entrance of the cells into DNA synthesis and mitosis was also increased at this time. Later on (day 3–6), when the majority of the cells had entered synthetic state, PGE1 inhibited DNA synthesis and cellular proliferation. These observations indicate that the effect of prostaglandins on arterial smooth muscle is dual in nature and dependent on the state of differentiation of the cells.  相似文献   

17.
Abstract: In homogenates of rat cerebral neocortex prostaglandin D2 (PGD2) was found to be quantitatively the main PG biosynthesized by a cytosolic PGD synthetase from en-dogenously released arachidonic acid. Amounts of 628 ng/g wet weight were found after 30-min incubation periods compared with basal levels of 2.3 ng/g wet weight. In human cerebral cortex, whether obtained at biopsy or postmortem, only small amounts of PGD2 (4.5–11.7 ng/g wet weight/30 min) were formed. Furthermore, PGD2, added to homogenates of human biopsy temporal cortex, was converted efficiently into 9α,11β-PGF2 by a NADPH-dependent 11-ke-toreductase as has been reported in other human tissues (liver and lung). PGF was determined directly as the fl-butylbo-ronate derivative. It became clear that 9α,11β-PGF2 was formed in considerably greater amounts than PGF and that other metabolites are also formed. These results can account for the low amounts of PGD2 found in incubations of human brain tissue. The rat brain does not contain 11-ketoreductase activity. The present results indicate that the 9α, 11β-PGF2 must be considered along with other eicosanoids in pathophysiological situations in brain.  相似文献   

18.
Abstract: Differences in prostaglandin H synthetase (PHS) activity in the substantia nigra of age- and post-mortem interval-matched parkinsonian, Alzheimer's, and normal control brain tissue were assessed. Prostaglandin E2 (PGE2, an index of PHS activity) was higher in substantia nigra of parkinsonian brain tissue than Alzheimer's or control tissue. Incubation of substantia nigra slices with arachidonic acid (AA) increased PGE2 synthesis. Dopamine stimulated PHS synthesis of PGE2. [3H]Dopamine was activated by PHS to electrophilic intermediate(s) that covalently bound to DNA, microtubulin protein, bovine serum albumin, and sulfhydryl reagents. When AA was replaced by hydrogen peroxide, PHS/H2O2-supported binding proceeded at rates similar to those observed with PHS/AA. Indomethacin and aspirin inhibited AA-mediated cooxidation of dopamine but not H2O2-mediated metabolism. PHS-mediated metabolism of dopamine was not affected by monoamine oxidase inhibitors. Substrate requirements and effects of specific inhibitors suggest cooxidation of dopamine is mediated by the hydroperoxidase activity of PHS. 32P-postlabeling was used to detect dopamine-DNA adducts. PHS/AA activation of dopamine in the presence of DNA resulted in the formation of five dopamine-DNA adducts, i.e., 23, 43, 114, 70, and 270 amol/µg DNA. DNA adduct formation was PHS, AA, and dopamine dependent. PHS catalyzed cooxidation of dopamine in dopaminergic neuronal degeneration is discussed.  相似文献   

19.
Plasma total lipids were significantly higher in 17β-oestradiol(E2)-treated immature rainbow trout Oncorhynchus mykiss at week 4 after implantation, due to increases in polar and neutral lipids. The lipid classes responding were phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, sterols and sterol esters, in a proportion that approximately reflected the increase in plasma vitellogenin (VtG) levels as measured by a non-competitive enzyme-linked immunosorbent assay (ELISA). Plasma non-esterified fatty acids and triacylglycerol were not affected by E2 treatment. Plasma growth hormone GH levels were increased, and plasma somatostatin-14 (SRIF) levels decreased in E2-treated fish, responses which could be secondary to elevated plasma lipid (VtG) content, although a direct E2 action on somatotroph function is possible. Plasma T4 concentrations were not affected by E2 treatment, but plasma T3 concentrations were significantly lower than in controls 1 week after implantation when plasma E2 concentrations were the highest; this is in support of the hypothesis that E2 has a suppressive action on T3 production.  相似文献   

20.
Abstract: Phospholipase A2 (PLA2) enzymes are critical regulators of prostaglandin and leukotriene synthesis, and they may also play an important role in the generation of intracellular free radicals. The group IV cytosolic form of phospholipase A2 (cPLA2) is regulated by changes in intracellular calcium concentration, and the enzyme preferentially acts to release arachidonic acid esterified at the sn -2 position of phospholipids. We examined the susceptibility of mice carrying a targeted mutation of the cPLA2 gene to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity. Mutant mice have no functional cPLA2 activity. Mice that were homozygous for the mutation (cPLA2−/−) were significantly resistant to MPTP-induced dopamine depletion as compared with littermate control (cPLA2+/+) and heterozygous mice (cPLA2+/−). These findings provide evidence that cPLA2 plays a role in MPTP neurotoxicity and suggest that cPLA2 may play a role in the development of Parkinson's disease in humans.  相似文献   

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