Effect Of L-cycloserine Research Articles

Inhibition of de novo ceramide biosynthesis affects aging phenotype in an in vitro model of neuronal senescence.

Although aging is considered to be an unavoidable event, recent experimental evidence suggests that the process can be counteracted. Intracellular calcium (Ca2+i) dyshomeostasis, mitochondrial dysfunction, oxidative stress, and lipid dysregulation are critical factors that contribute to senescence-related processes. Ceramides, a pleiotropic class of sphingolipids, are important mediators of cellular senescence, but their role in neuronal aging is still largely unexplored. In this study, we investigated the effects of L-cycloserine (L-CS), an inhibitor of thede novoceramide biosynthesis, on the aging phenotype of cortical neurons cultured for 22 days, a setting employed as anin vitromodel of senescence. Our findings indicate that, compared to control cultures, ‘aged’ neurons display dysregulation of [Ca2+]ilevels, mitochondrial dysfunction, increased generation of reactive oxygen species (ROS), altered synaptic activity as well as the activation of neuronal death-related molecules. Treatment with L-CS positively affected the senescent phenotype, a result associated with recovery of neuronal [Ca2+]isignaling and reduction of mitochondrial dysfunction and ROS generation. The results suggest that thede novoceramide biosynthesis represents a critical intermediate in the molecular and functional cascade leading to neuronal senescence and identify ceramide biosynthesis inhibitors as promising pharmacological tools to decrease age-related neuronal dysfunctions.

Effect of L-Cycloserine on Cellular Responses Mediated by Macrophages and T Cells

In this study, we examined the immunoregulatory roles of L-cycloserine (L-CS), a sphingolipid metabolism regulator with inhibitory activity of serine palmitoyltransferase (SPT), on immune responses mediated by monocytes/macrophages and T cells. Mitogenic responses of splenic lymphocytes induced by LPS, PHA, and Con A were very strongly suppressed by L-CS with IC(50) values ranging from 0.5 to 1 muM. In contrast, this compound less strongly blocked IL-2-induced CD8+ CTLL-2 cell proliferation with an IC(50) value of 540 muM. Interestingly, L-CS enhanced the number of IL-4-producing helper T cells, indicating the favored induction of Th2 condition. Although tumor necrosis factor (TNF)-alpha and nitric oxide (NO) production was not altered under 10% FCS condition, U937 cell-cell adhesion as well as the surface level of adhesion molecules (CD29 and CD98) were significantly suppressed by L-CS. In particular, reduced serum level (5%) under L-CS treatment strongly enhanced the production of TNF-alpha and the inhibitory potency of NO production and cell adhesion. Finally, sphingolipids (D-sphingosine and DL-dihydrosphingosine) did not remarkably abrogate L-CS-mediated T cell proliferation. Therefore our data suggest that de novo sphingolipid metabolism may represent an important aspect of immunomodulatory activities mediated by T cells and macrophages/monocytes, depending on serum level.

The effects of l-cycloserine on membrane fluidity and lipids of mouse brain

l-Cycloserine can inhibit the synthesis of some sphingolipids, which may play a role in determining membrane fluidity. To evaluate the effects of l-cycloserine on neural cell membranes, adult mice were treated with 100 mg/kg of this drug twice daily for 1, 2, 4, 6, 13 and 17 days. Body weights in the treated mice decreased significantly. Cholesterol and total phospholipid per mass total lipid significantly increased with time. Fluorescence depolarization after the incorporation of diphenylhexatriene into membranes was measured in order to assess membrane fluidity. it increased significantly starting at treatment day 4, with a maximum increase in polarization value of 8%. These results show that l-cycloserine significantly changes the fluidity of brain membrane, but this does not correlate with changes in major lipid classes of the brain.

The effects of l-cycloserine on gangliosides in the developing mouse brain

Marked changes in ganglioside composition occur during brain development and in cultured neurons concomitant with differentiation, and maximum ganglioside synthesis occurs during neuronal maturation and synaptogenesis. These findings indicate that gangliosides probably play an important role in brain development. In this study the effects of parenterally administered l-cycloserine (an inhibitor of sphingosine synthesis) on gangliosides during the period of rapid neonatal brain growth in mice were studied. Two groups of mice (saline control and l-cycloserine-20 mg/kg/day) were treated for 8 or 16 days, starting at postnatal day 6, and sacrificed at 14, 22, 32, 62 or 110 days of age. Undernourished controls were also sacrificed at the same times. Body and cerebral weights in the l-cycloserine group were less than those of saline control animals at early ages, but the l-cycloserine animals did not show sparing of cerebral weight in relation to body weight as did the undernourished controls. Compared to saline control animals the l-cycloserine group had significantly less total lipid extract and nonlipid residue over all age groups. Animals treated with l-cycloserine had less total ganglioside NeuNAc per hemisphere, but normal concentrations on a fresh weight basis. Both groups had identical ganglioside patterns. These results indicate that although l-cycloserine does affect some aspects of brain development, it is not useful as a selective inhibitor of ganglioside synthesis in neonatal ICR Swiss Webster mice treated with a dose equivalent to the LD-17. Its value in modifying ganglioside synthesis should be viewed with caution.

Effect of l-cycloserine on cortical neurons in the rat

L-Cycloserine but not D-cycloserine, depressed the firing of neurons in the sensorimotor cortex of the rat with a relatively slow time course when administered by microionophoresis or i.p. injection. The effect of GABA applied by microionophoresis or released synaptically were not modified by i.p. injections and microionophoretic administration of L-cycloserine. It is concluded that L-cycloserine depresses cell firing not by potentiation of the action of GABA but by elevating GABA-levels.

Effects of ischaemia on metabolite concentrations in rat liver.

1. Changes in the concentrations of ammonia, glutamine, glutamate, 2-oxoglutarate, 3-hydroxybutyrate, acetoacetate, alanine, aspartate, malate, lactate, pyruvate, NAD(+), NADH and adenine nucleotides were measured in freeze-clamped rat liver during ischaemia. 2. Although the concentrations of most of the metabolites changed rapidly during ischaemia the ratios [glutamate]/[2-oxoglutarate][NH(4) (+)] and [3-hydroxybutyrate]/[acetoacetate] changed equally and the value of the expression [3-hydroxybutyrate][2-oxoglutarate][NH(4) (+)]/[acetoacetate][glutamate] remained approximately constant, indicating that the 3-hydroxybutyrate dehydrogenase and glutamate dehydrogenase systems were at near-equilibrium with the mitochondrial NAD(+) couple. 3. The value of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] was about 0.7 in vivo and remained fairly constant during the ischaemic period of 5min, although the concentrations of alanine and oxoglutarate changed substantially. No explanation can be offered why the value of the ratio differed from that of the equilibrium constant of the alanine aminotransferase reaction, which is 1.48. 4. Injection of l-cycloserine 60min before the rats were killed increased the concentration of alanine in the liver fourfold and decreased the concentration of the other metabolites measured, except that of pyruvate. During ischaemia the concentration of alanine did not change but that of aspartate almost doubled. 5. After treatment with l-cycloserine the value in vivo of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] rose from 0.7 to 2.4. During ischaemia the value returned to 0.8. 6. The effects of l-cycloserine are consistent with the assumption that it specifically inhibits alanine aminotransferase. 7. Most of the alanine formed during ischaemia is probably derived from pyruvate and from ammonia released by the deamination of adenine nucleotides and glutamine. The alanine is presumably formed by the combined action of glutamate dehydrogenase and alanine aminotransferase. 8. The rate of anaerobic glycolysis, calculated from the increase in the lactate concentration, was 1.3mumol/min per g fresh wt. 9. Although the concentrations of the adenine nucleotides changed rapidly during ischaemia, the ratio [ATP][AMP]/[ADP](2) remained constant at 0.54, indicating that adenylate kinase established near-equilibrium under these conditions.