Adaptive Gene Expression Induced by a Combination of IL-1β and LPS in Primary Cultures of Mouse Astrocytes

Primary cultures of both mouse astrocytes and neurons accumulate more 125I- than 36Cl- from the medium. The average cell/medium ratio of 125I- of astrocytes (1.01) is greater than that of neurons (0.74), whereas the ratio of 36Cl- of neurons (0.47) is greater than that of astrocytes (0.25). The equilibrium potentials of both 125I- and 36Cl- calculated from the cell/medium ratios in astrocytes and neurons are significantly lower than their corresponding resting transmembrane potentials which suggest that both iodide and chloride are actively transported into both cell types. With respect to different transport inhibitors, thiocyanate is more effective in inhibiting 125I- uptake whereas furosemide is more effective in inhibiting 36Cl- uptake. Radioiodide uptake by mouse astrocytes was directly proportional to the [Na+]o but was not significantly affected by changes of [Cl-]o or [HCO3-]o, except that it is low in bicarbonate-free medium. Radiochloride uptake by astrocytes was inversely related to [Cl-]o and [HCO3-]o and was not affected [Na+]o, except that it was low in sodium-free medium. Radioiodide uptake by neurons was directly related to [Na+]o between 60 and 140 mM and inversely related to [HCO3-]o between 10 and 40 mM, but it was not affected by [Cl-]o. Radiochloride uptake by neurons was directly related to [Cl-]o and to [Na+]o between 60 and 140 mM and was not affected by [HCO3-]o. However, in sodium-free medium both 125I- and 36Cl- uptakes into neurons were higher than those in [Na+]o between 5 and 60 mM. These results indicate that uptake of 125I- and 36Cl- into astrocytes and neurons are different in their ion dependence and that they are under separate regulation.

Cell death in primary cultures of mouse neurons and astrocytes during exposure to and ‘recovery’ from hypoxia, substrate deprivation and simulated ischemia

Dexamethasone prevents long-lasting learning impairment following a combination of lipopolysaccharide and hypoxia-ischemia in neonatal rats

Down-Regulation of the Monocarboxylate Transporter 1 Is Involved in Butyrate Deficiency During Intestinal Inflammation

Dual effect of glia maturation factor on astrocytes: Differentiation and release of interleukin-1 like factors

Inhibitory effect of Asparagus cochinchinensis on tumor necrosis factor-alpha secretion from astrocytes

Effects of noradrenaline and of adrenergic subtype specific agonists on the uptake and metabolism of [14C]glutamine and [14C]glutamate in primary cultures of mouse astrocytes have been investigated. The total uptake of radioactivity from extracellular [14C]glutamine into the cells was enhanced during exposure to 100 microM noradrenaline, isoproterenol, or clonidine. This is partly due to an increased radioactivity in the glutamine pool and partly due to an increased formation of labeled glutamate from glutamine, which had become very marked (66%) after 240 min of incubation. The CO2 formation from labeled glutamine during 4 hr of incubation was enhanced about twofold in the presence of noradrenaline. Ten millimolar amino oxyacetic acid (AOAA), a transamination inhibitor, had no effect on CO2 formation from glutamine, indicating that the formation of alpha-ketoglutarate from glutamate occurs as an oxidative deamination. The stimulation of 14CO2 production from labeled glutamine was at least as large when glucose was deleted from medium, suggesting that the increased 14CO2 formation represents a stimulation of glutamine metabolism as such and is not only a reflection of an increase in oxidative metabolism of glucose and a bidirectional exchange between alpha-ketoglutarate and glutamate. The opposite process, incorporation of radioactivity from labeled glutamate into glutamine, was not enhanced in the presence of noradrenaline. The findings suggest that noradrenaline stimulates the rates of glutamine uptake, glutamate synthesis, and CO2 production from glutamine and thus increases energy supply to astrocytes but has no effect on the opposite reaction, i.e., glutamine formation from glutamate, a reaction of importance for neuronal-astrocyte interations.

Effect of Polygala tenuifolia root extract on the tumor necrosis factor- α secretion from mouse astrocytes

Effects of lipopolysaccharide on glial phenotype and activity of glutamate transporters: Evidence for delayed up-regulation and redistribution of GLT-1

Cataplerotic TCA cycle flux determined as glutamate-sustained oxygen consumption in primary cultures of astrocytes

Effect of adrenergic agonists on glycogenolysis in primary cultures of astrocytes

Stimulation of β-adrenoceptors activates the canonical adenylate cyclase pathway (via G(s) protein) but can also evoke phosphorylation of extracellular-regulated kinases 1 and 2 (ERK(1/2) ) via G(s)/G(i) switching or β-arrestin-mediated recruitment of Src. In primary cultures of mouse astrocytes, activation of the former of these pathways required micromolar concentrations of the β(1)/β(2) -adrenergic agonist isoproterenol, that acted on β(1)-adrenoceptors, whereas the latter was activated already by nanomolar concentrations, acting on β(2) receptors. Protein kinase A activity was required for G(s)/G(i) switching, which was followed by Ca(2+) release from intracellular stores and G(iα)- and metalloproteinase-dependent transactivation of the epidermal growth factor receptor (EGFR; at its Y1173 phophorylation site), via its receptor-tyrosine kinase, β-arrestin 1/2 recruitment, and MAPK/ERK kinase-dependent ERK(1/2) phosphorylation. ERK(1/2) phosphorylation by Src activation depended on β-arrestin 2, but not β-arrestin 1, was accompanied by Src/EGFR co-precipitation and phosphorylation of the EGFR at the Src-phosphorylated Y845 site and the Y1045 autophosphorylation site; it was independent of transactivation but dependent on MAPK/ERK kinase activity, suggesting EGFR phosphorylation independently of the receptor-tyrosine kinase or activation of Ras or Raf directly from Src. Most astrocytic consequences of activating either pathway (or both) are unknown, but morphological differentiation and increase in glial fibrillary acidic protein in response to dibutyryl cAMP-mediated increase in cAMP depend on G(s)/G(i) switching and transactivation.

Glutamine (Gln) utilising cells suffer from Gln-starvation during critical illness when plasma Gln levels are decreased. This study investigates whether such cells activate adaptive mechanisms. Monocytic U937 cells were cultured at 0.6 and 0.2 mM Gln for up to four days. Within the first day a decrease of ATP (78% of control), intracellular free Gln (13%), Hsp70 (74%) and proliferation rate (79%) was observed. A prolonged culture at 0.6 mM Gln for additional three days led to a recovery of ATP (97%), Hsp70 (91%) and proliferation (92%). The intracellular free Gln increased only to 41%. At 0.2 mM Gln, however, all levels remained decreased. The activation of the metabolic sensor AMP activated kinase (AMPK) increased immediately in Gln-starving cells but regained normal values only in cells cultured at 0.6 mM. A proteomic analysis identified 23 proteins, which were affected by Gln starvation including metabolic enzymes, proteins involved in synthesis and degradation of RNA and proteins, and stress proteins. These data show that Gln-utilising cells activate adaptive mechanisms in response to Gln-starvation, which enable them to overcome a Gln shortage. At very low Gln concentrations, these adaptive mechanisms are not sufficient to countervail the lack of the amino acid.

Dopaminergic neurons are a primary target for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity. However, the conversion of MPTP to its neurotoxic 1-methyl-4-phenylpyridinium metabolite (MPP+) is likely to occur in astrocytes via the monoamine oxidase (MAO)-dependent formation of the 1-methyl-4-phenyl-2,3-dihydropyridinium intermediate (MPDP+). The main purpose of this study was to characterize the molecular mechanism(s) by which MPP+, once generated by astrocytes, may reach the extracellular space to become available for the active accumulation into dopaminergic neurons. Primary cultures of mouse astrocytes were used as an in vitro model system. After the addition of MPTP, levels of MPP+ were found to increase at constant rates both intracellularly and extracellularly at time points when no sign of cytotoxicity was evident. In contrast, MPDP+ levels remained quite stable during 4 days of incubation in the presence of MPTP. Finally, when astrocytes were allowed to accumulate MPP+ by pretreatment with either MPTP or MPP+ and then were incubated in fresh medium not containing MPTP or MPP+, intracellular levels of MPP+ rapidly declined and corresponding amounts of this compound were found in the incubation medium. Results of this study are compatible with the following conclusions: 1) the MPP+ accumulated in the extracellular compartment during incubations with MPTP is not released from astrocytes as a consequence of its own cytotoxic effects; 2) MPP+ can be formed extracellularly presumably via autoxidation of MPDP+ after this latter compound has been generated within astrocytes and has crossed astrocyte membranes; and 3) despite its charged chemical structure, MPP+ can cross the plasma membrane toward the extracellular space after being formed within astrocytes.

Toxic effects of cobalt in primary cultures of mouse astrocytes: Similarities with hypoxia and role of HIF-1α