Activity of the Di-Substituted Urea-Derived Compound I-17 in Leishmania In Vitro Infections

Protein synthesis has been a very rich target for developing drugs to control prokaryotic and eukaryotic pathogens. Despite the development of new drug formulations, treating human cutaneous and visceral Leishmaniasis still needs significant improvements due to the considerable side effects and low adherence associated with the current treatment regimen. In this work, we show that the di-substituted urea-derived compounds I-17 and 3m are effective in inhibiting the promastigote growth of different Leishmania species and reducing the macrophage intracellular load of amastigotes of the Leishmania (L.) amazonensis and L. major species, in addition to exhibiting low macrophage cytotoxicity. We also show a potential immunomodulatory effect of I-17 and 3m in infected macrophages, which exhibited increased expression of inducible Nitric Oxide Synthase (NOS2) and production of Nitric Oxide (NO). Our data indicate that I-17, 3m, and their analogs may be helpful in developing new drugs for treating leishmaniasis.

geno5mC: A Database to Explore the Association between Genetic Variation (SNPs) and CpG Methylation in the Human Genome

Genetic variation, gene expression and DNA methylation influence each other in a complex way. To study the impact of sequence variation and DNA methylation on gene expression, we generated geno⁵mC, a database that contains statistically significant SNP-CpG associations that are biologically classified either through co-localization with known regulatory regions (promoters and enhancers), or through known correlations with the expression levels of nearby genes. The SNP rs727563 can be used to illustrate the usefulness of this approach. This SNP has been associated with inflammatory bowel disease through GWAS, but it is not located near any gene related to this phenotype. However, geno⁵mC reveals that rs727563 is associated with the methylation state of several CpGs located in promoter regions of genes reported to be involved in inflammatory processes. This case exemplifies how geno⁵mC can be used to infer relevant and previously unknown interactions between described disease-associated SNPs and their functional targets.

Abstract P6-11-15: Comparison of QoL according to treatment received. First cohort study in Mexico

Background: In México, there are more than 57 million women with breast cancer, and more than 7 million of these patients live in Mexico State; 12.4% of breast cancer diagnosis are being made in here. The diagnosis and treatment of patients with breast cancer changes their quality of life (QOL) on a physical, psychological, social and sexual basis.

Objectives: The main purpose of this study is to examine the changes in the QOL of breast cancer patients treated at the State of Mexico Cancer Center (ISSEMyM), applying the EORT QLQ-C30 and QLQ-BR23. The secondary aim of the study is to describe the Health-Related Quality of Life (HRQoL), including partner relationships, sexual function, and body image concerns of breast cancer survivors. (BCS).

Design: A longitudinal, prospective, descriptive and analytical cohort study was made; with bivariate analysis and correlations search. We used Kolmogorov-Smirnov test for normal continuous variables. To evaluate changes in follow-up we use ANOVA test of repeated measures and post-hoc analysis. Significance was set at p <0.05

Method: QOL questionnaires were applied every 4 months followed for a year, the first one being done before the patient was informed of confirmed breast cancer diagnosis. A sample of 112 women with primary breast cancer were enrolled. The sample type is probability, non-confessional, consecutive cases.

Results: Primary cancer treatment has a negative impact on QOL comparing to data collected at the basal assessment (before confirmatory diagnosis of cancer). Average age 54 years (25-85). FIGO stage in situ in 5%, Ia, IIa and IIb 18%, IIIa 8%, IIIb 6%, IIIc 12% and IV 15%. LuminalA 40%, LuminalB 24%, Her2 15%, Triple negative 21%. The mean overall health score was 64.7±26.7 at baseline and 65.8±19.3, 65.3±19.6, 72.1±15.1 at 4.8 and 12 months, respectively. Physical, emotional, cognitive, sexual and social functioning, as well as symptoms and sexual pleasure present statistical significance (p.0000) regardless of age, stage or treatment received.

Conclusions: This is the first longitudinal, prospective, descriptive and analytical cohort made in Mexico that assesses changes in QOL of breast cancer patients. There is a significant decrease in post-surgery physical function in our patients. However, there is no significant difference between the results observed in patients undergoing conservative surgery versus those who received radical surgery, nor for patients receiving surgery plus radiation therapy versus surgery plus systemic therapy. Also in the body image category component in our study, an important decrease in the QOL of the patients undergoing surgery is demonstrated, this is more evident in early stages of disease. In patients who recieved chemotherapy, symptoms were a negative influence in QOL and just near a half came to a basal status a year after treatment started. Finally, patients with surgery as first treatment have a faster return to their basal QOL.

This work opens an invaluable opportunity to improve our medical behavior towards breast cancer patients, treated at the ISSEMyM State of Mexico Cancer Center. It obliges us to create a multidisciplinary team that permanently assesses patients, identifying the aspects of their daily work, which alter their QOL.

Citation Format: Medina JM, Gonzalez AB, Rivera F, Serrano R, Machado MM, García M. Comparison of QoL according to treatment received. First cohort study in Mexico [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-11-15.

The integrated endoplasmic reticulum stress response in Leishmania amazonensis macrophage infection: the role of X-box binding protein 1 transcription factor

Endoplasmic reticulum (ER) stress triggers the integrated ER-stress response (IERSR) that ensures cellular survival of ER stress and represents a primordial form of innate immunity. We investigated the role of IERSR duringLeishmania amazonensisinfection. Treatment of RAW 264.7 infected macrophages with the ER stress-inducing agent thapsigargin (TG; 1 μM) increasedL. amazonensisinfectivity in an IFN1-α receptor (IFNAR)-dependent manner. In Western blot assays, we showed thatL. amazonensisactivates the inositol-requiring enzyme (IRE1)/ X-box binding protein (XBP)-1-splicing arms of the IERSR in host cells. In chromatin immunoprecipitation (ChIP) assays, we showed an increased occupancy of enhancer and promoter sequences for theIfnbgene by XBP1 in infected RAW 264.7 cells. Knocking down XBP1 expression by transducing RAW 264.7 cells with the short hairpin XBP1 lentiviral vector significantly reduced the parasite proliferation associated with impaired translocation of phosphorylated IFN regulatory transcription factor (IRF)-3 to the nucleus and a decrease in IFN1-β expression. Knocking down XBP1 expression also increased NO concentration, as determined by Griess reaction and reduced the expression of antioxidant genes, such as heme oxygenase (HO)-1, that protect parasites from oxidative stress. We conclude thatL. amazonensisactivation of XBP1 plays a critical role in infection by protecting the parasites from oxidative stress and increasing IFN1-β expression.-Dias-Teixeira, K. L., Calegari-Silva, T. C., Dos Santos, G. R. R. M., Vitorino dos Santos, J., Lima, C., Medina, J. M., Aktas, B. H., Lopes, U. G. The integrated endoplasmic reticulum stress response inLeishmania amazonensismacrophage infection: the role of X-box binding protein 1 transcription factor.

The shape of dementia: new measures of morphological complexity in event-related potentials (ERP) and its application to the detection of Alzheimer's disease

In this paper, we address the problem of quantifying the commonly observed disorganization of the stereotyped wave form of the ERP associated with the P300 component in patients with Alzheimer's disease. To that extent, we propose two new measures of complexity which relate the spectral content of the signal with its temporal waveform: the spectral matching coefficient and the spectral matching entropy. We show by means of experiments that those measures effectively measure complexity and are related to the shape in an intuitive way. Those indexes are compared with commonly used measures of complexity when comparing AD patients against age-matched healthy controls. The results indicate that AD ERP signals are, indeed, more complex in the shape than that of controls, and this result is evidenced mainly by means of our new measures which have a better performance compared to similar ones. Finally, we try to explain this increase in complexity in light of the communication through coherence hypothesis framework, relating commonly found changes in the EEG with our own results.

The role of connexin43-Src interaction in astrocytomas: A molecular puzzle

Connexin43 (Cx43) as a building block of gap junction channels and hemichannels exerts important functions in astrocytes. When these cells acquire a malignant phenotype Cx43 protein but not mRNA levels are downregulated, being negligible in high-grade astrocytoma or glioblastoma multiforme, the most common and deadliest of malignant primary brain tumors in adults. Some microRNAs associated to glioma target Cx43 and could explain the lack of correlation between mRNA and protein levels of Cx43 found in some high-grade astrocytomas. More importantly, these microRNAs could be a promising therapeutic target. A great number of studies have confirmed the relationship between cancer and connexins that was proposed by Loewenstein more than 40years ago, but these studies have also revealed that this is a very complex relationship. Indeed, restoring Cx43 to glioma cells reduces their rate of proliferation and their tumorigenicity but this tumor suppressor effect could be counterbalanced by its effects on invasiveness, adhesion and migration. The mechanisms underlying these effects suggest the participation of a great variety of proteins that bind to different regions of Cx43. The present review focuses on an intrinsically disordered region of the C-terminal domain of Cx43 in which converges the interaction of several proteins, including the proto-oncogene Src. We summarize data that indicate that Cx43-Src interaction inhibits the oncogenic activity of Src and promotes a conformational change in the structure of Cx43 that allosterically modifies the binding to other important signaling proteins. As a consequence, crucial cell functions, such as proliferation or migration, could be strongly affected. We propose that the knowledge of the structural basis of the antitumorigenic effect of Cx43 on astrocytomas could help to design new therapies against this incurable disease.

Mechanisms of growth inhibition of Phytomonas serpens by the alkaloids tomatine and tomatidine

Phytomonas serpens are flagellates in the family Trypanosomatidae that parasitise the tomato plant (Solanum lycopersicum L.), which results in fruits with low commercial value. The tomato glycoalkaloid tomatine and its aglycone tomatidine inhibit the growth of P. serpens in axenic cultures. Tomatine, like many other saponins, induces permeabilisation of the cell membrane and a loss of cell content, including the cytosolic enzyme pyruvate kinase. In contrast, tomatidine does not cause permeabilisation of membranes, but instead provokes morphological changes, including vacuolisation. Phytomonas treated with tomatidine show an increased accumulation of labelled neutral lipids (BODYPY-palmitic), a notable decrease in the amount of C₂₄-alkylated sterols and an increase in zymosterol content. These results are consistent with the inhibition of 24-sterol methyltransferase (SMT), which is an important enzyme that is responsible for the methylation of sterols at the 24 position. We propose that the main target of tomatidine is the sterols biosynthetic pathway, specifically, inhibition of the 24-SMT. Altogether, the results obtained in the present paper suggest a more general effect of alkaloids in trypanosomatids, which opens potential therapeutic possibilities for the treatment of the diseases caused by these pathogens.

A cell-penetrating peptide based on the interaction between c-Src and connexin43 reverses glioma stem cell phenotype

Connexin43 (Cx43), the main gap junction channel-forming protein in astrocytes, is downregulated in malignant gliomas. These tumors are composed of a heterogeneous population of cells that include many with stem-cell-like properties, called glioma stem cells (GSCs), which are highly tumorigenic and lack Cx43 expression. Interestingly, restoring Cx43 reverses GSC phenotype and consequently reduces their tumorigenicity. In this study, we investigated the mechanism by which Cx43 exerts its antitumorigenic effects on GSCs. We have focused on the tyrosine kinase c-Src, which interacts with the intracellular carboxy tail of Cx43. We found that Cx43 regulates c-Src activity and proliferation in human GSCs expanded in adherent culture. Thus, restoring Cx43 in GSCs inhibited c-Src activity, which in turn promoted the downregulation of the inhibitor of differentiation Id1. Id1 sustains stem cell phenotype as it controls the expression of Sox2, responsible for stem cell self-renewal, and promotes cadherin switching, which has been associated to epithelial–mesenchymal transition. Our results show that both the ectopic expression of Cx43 and the inhibition of c-Src reduced Id1, Sox2 expression and promoted the switch from N- to E-cadherin, suggesting that Cx43, by inhibiting c-Src, downregulates Id1 with the subsequent changes in stem cell phenotype. On the basis of this mechanism, we found that a cell-penetrating peptide, containing the region of Cx43 that interacts with c-Src, mimics the effect of Cx43 on GSC phenotype, confirming the relevance of the interaction between Cx43 and c-Src in the regulation of the malignant phenotype and pinpointing this interaction as a promising therapeutic target.

Ventriculoperitoneal shunt as a primary neurosurgical procedure in newborn posthemorrhagic hydrocephalus: report of a series of 47 shunted patients

PURPOSE

Intraventricular hemorrhage is the most common cause of infantile acquired hydrocephalus. Our objective is to determine if the implantation of ventriculoperitoneal shunt in posthemorrhagic hydrocephalus as a primary and definitive neurosurgical treatment, with no previous temporary procedures, would decrease complication rates with good functional outcomes.

METHODS

Two hundred seventy-one patients with germinal matrix hemorrhage were diagnosed at the Carlos Haya Hospital between 2003 and 2010. Forty-seven patients underwent ventriculoperitoneal shunt after developing symptomatic hydrocephalus. The minimum weight required for shunt implantation was 1,500 g. We recorded complications related to the surgical procedure and analyzed functional state with a self-developed four-grade scale.

RESULTS

One hundred thirty-nine (51.3 %) patients with intraventricular hemorrhage developed ventricular dilatation, but only 47 patients (17.34 %) needed shunting. In seven cases, temporary neurosurgical procedures were performed, but in all of them, this was followed by ventriculoperitoneal shunt implantation. The infection rate was 4.25 %, and shunt obstruction rate was 4.25 %. More than 80 % of patients were classified as good or excellent functional state. Mean follow-up period was 38.75 months (SD, 27.09; range, 1-102 months).

CONCLUSIONS

Ventriculoperitoneal shunting as a primary neurosurgical treatment in posthemorrhagic hydrocephalus would decrease surgical morbidity with good functional outcome.

The effect of gamma radiation on the lipid profile of irradiated red blood cells

An investigation into the effects of irradiation and of the storage time on aging and quality are a relevant issue to ensure the safety and the efficiency of irradiation in the prevention of transfusion-associated graft-versus-host disease (TA-GVHD). In this work, the biochemical properties and alterations presented by erythrocyte membranes, up to 28-days post-irradiation, with a dose of 25 Gy, were studied as a function of storage and post-irradiation time. There was a considerable variation in the total of phospholipid content, when comparing the control and irradiated samples, mostly from the third day onwards; and at the same time, the effect occurred as a function on the storage time of blood bags. The levels of total cholesterol decreased 3-9 days after irradiation. TBARS levels were increased after irradiation and 7 days of storage, but no increment of catalase activity was observed after the irradiation. Furthermore, the protein profile was maintained throughout the irradiation and storage time, until the 21st day, with the presence of a protein fragmentation band of around 28 kDa on the 28th day. In conclusion, although gamma irradiation is the main agent for the prevention of TA-GVHD, a better understanding of the physical and biochemical properties of erythrocytes are necessary to better assess their viability, and to be able to issue more secure recommendations on the shelf life of blood bags, and the safe use of the irradiated red cells therein.

Connexin43 inhibits the oncogenic activity of c-Src in C6 glioma cells

One of the characteristics of gliomas is a decrease in the expression of connexin43, a protein that forms gap junctions. Restoring connexin43 expression in glioma cells reduces their exacerbated rate of cell growth, although it is not yet known how connexin43 modifies the expression of genes involved in cell proliferation. Here, we show that restoring connexin43 to C6 glioma cells impedes their progression from G0/G1 to the S phase of the cell cycle by reducing retinoblastoma phosphorylation and cyclin E expression through the upregulation of p21 and p27. Interestingly, connexin43 diminishes the oncogenic activity of c-Src exhibited by glioma cells. By studying a Tyr247 and Tyr265 mutant connexin43, we show that these residues are required for connexin43 to inhibit c-Src activity and cell proliferation. In conclusion, by acting as a substrate of c-Src, connexin43 reduces its oncogenic activity and decreases the rate of glioma cell proliferation, potentially an early step in the antiproliferative effects of connexin43. Although c-Src is known to phosphorylate connexin43, this study provides the first evidence that connexin43 can also inhibit c-Src activity.

The effect of pupil size on binocular summation at suprathreshold conditions

PURPOSE

To determine the influence of retinal illuminance on monocular or binocular visual reaction time (VRT).

METHODS

On two normal subjects, uniform circular stimuli were presented with respect to a reference stimulus at the fovea under suprathreshold conditions, and the detection of positive and negative luminance variations was recorded. Binocular and monocular reaction times were measured (by the index finger pressing on a mouse key) for viewing with both natural and artificial pupils.

RESULTS

Binocular reaction times were shorter than monocular reaction times; nevertheless, this binocular-summation effect was less marked in trials with the artificial pupil. Analyses of binocular-summation ratios for contrast changes for both pupil types indicated maximum and minimum binocular-saturation values depending on contrast variations in both positive and negative luminance changes.

CONCLUSIONS

Binocular summation can be influenced by pupil size under suprathreshold conditions. Results are discussed in terms of retinal illuminance and cortical pupil response mechanisms.

Binocular summation of chromatic changes as measured by visual reaction time

We determined visual reaction times to monocular and binocular changes in the luminance of isochromatic stimuli and to monocular and binocular changes in the color of isoluminant stimuli. Two isoluminant color changes were tested: chromatic variations along the red-green axis of Boynton's (1986) two-stage color vision model and chromatic variations along the yellow-blue axis of the same model. The results indicate a greater degree of binocular summation for luminance change than for color change. This result was largely independent of the motor component of reaction time.

Proliferation of C6 glioma cells is blunted by the increase in gap junction communication caused by tolbutamide

We have previously reported that tolbutamide prevents the inhibition of gap junction communication in astrocytes. Here, we show that tolbutamide increases gap junction communication and connexin 43 expression in poorly coupled C6 glioma cells. The increase in communication is concurrent with the inhibition of the rate of proliferation due to a block of the progression of C6 glioma cells through the S phase of the cell cycle. The effects of tolbutamide were quantitatively similar to that found after the elevation of intracellular cAMP. Furthermore, the effects of tolbutamide and cAMP were additive. The possible beneficial effect of tolbutamide on gene therapy for gliomas is discussed.

Oligodendrocytes use lactate as a source of energy and as a precursor of lipids

Lactate is an important metabolic substrate for the brain during the postnatal period and also plays a crucial role in the traffic of metabolites between astrocytes and neurons. However, to date there are no clues with regard to lactate utilization by oligodendrocytes, the myelin-forming cells in the brain. In the present work, lactate utilization by oligodendrocytes in culture was investigated and compared with its utilization by cultured neurons, type 1 and type 2 astrocytes. Our results clearly indicate that oligodendrocytes readily use lactate both as a metabolic fuel and as a precursor to build carbon skeletons. Oligodendrocytes oxidize lactate at a higher rate than that observed for neurons and astrocytes, and their rate of lipid synthesis from lactate was at least 6-fold higher than that found in astrocytes or neurons. The rate of glucose utilization through different pathways was also investigated. The flux of glucose through the pentose phosphate pathway and the rate of lipid synthesis were at least 2-fold higher in oligodendrocytes than in astrocytes or neurons. These findings indicate that oligodendrocyte metabolism is designed specifically for the synthesis of lipids, presumably those of myelin.

[Intercellular communication in the astrocyte culture as a measure of therapeutic efficacy in multiple sclerosis treated by interferon]

INTRODUCTION

Measurement of therapeutic efficacy in multiple sclerosis depends on the clinical and magnetic resonance findings on follow up. There are no biological markers. Measurement of interleukins and other markers of inflammation has not proved useful in the follow up of these patients. The response of astrocytes to mediators of inflammation gives rise to modification in their capacity for intercellular communication.

OBJECTIVE

To find whether culture of astrocytes in serum from patients with multiple sclerosis at different clinical stages and on different treatments gives rise to modification in intercellular communication.

PATIENTS AND METHODS

Astrocytes were cultured in serum from three patients with an untreated acute clinical episode of multiple sclerosis, and the results compared with those obtained after serum culture when the patients had been treated with interferon for a year. RESULTS. In astrocyte culture using serum from patients with an acute episode of multiple sclerosis, but not on treatment with interferon, there was a statistically significant reduction in intercellular communication as compared to astrocytes cultured with serum from these same patients treated with interferon for one year (*p< 0.05; **p< 0.01).

CONCLUSION

Measurement of the modifications in intercellular communication on astrocyte culture may be used as a marker for inflammatory activity in the serum of patients with multiple sclerosis, and therefore as an index of therapeutic efficacy.

Neuronal differentiation is triggered by oleic acid synthesized and released by astrocytes

Unlike in the adult brain, the newborn brain specifically takes up serum albumin during the postnatal period, coinciding with the stage of maximal brain development. Here we report that albumin stimulates oleic acid synthesis by astrocytes from the main metabolic substrates available during brain development. Oleic acid released by astrocytes is used by neurons for the synthesis of phospholipids and is specifically incorporated into growth cones. Oleic acid promotes axonal growth, neuronal clustering, and expression of the axonal growth-associated protein-43, GAP-43; all these observations indicating neuronal differentiation. The effect of oleic acid on GAP-43 synthesis is brought about by the activation of protein kinase C, since it was prevented by inhibitors of this kinase, such as H-7, polymyxin or sphingosine. The expression of GAP-43 was significantly increased in neurons co-cultured with astrocytes by the presence of albumin indicating that neuronal differentiation takes place in the presence of oleic acid synthesized and released by astrocytes in situ. In conclusion, during brain development the presence of albumin could play an important role by triggering the synthesis and release of oleic acid by astrocytes, which induces neuronal differentiation.

The enhancement of glucose uptake caused by the collapse of gap junction communication is due to an increase in astrocyte proliferation

We have previously shown that several gap junction uncouplers increase the uptake of glucose in astrocytes. The aim of the present work was to study whether the increase in glucose uptake was a consequence of the inhibition of gap junction communication and the purpose of this effect. Our results show that alpha-glycyrrhetinic acid and endothelin-1 increase the uptake of glucose in highly, but not in poorly, coupled astrocytes. This effect depended on connexin 43 levels and was abolished when the inhibition of gap junction communication was prevented by tolbutamide or ouabain. The inhibition of gap junctions increased the rate of glucose incorporation into DNA and RNA, which was inhibited by treatment with dehydroepiandrosterone, an inhibitor of glucose-6-phosphate dehydrogenase, the regulatory enzyme of the pentose phosphate pathway. The inhibition of gap junctions significantly increased astrocyte proliferation, which was counteracted by tolbutamide. These effects were not observed in poorly coupled astrocytes expressing low levels of connexin 43. The increase in astrocyte proliferation caused by gap junction inhibition was prevented when either glucose uptake or the pentose phosphate pathway were inhibited. We conclude that the inhibition of gap junction communication induces astrocyte proliferation, resulting in an enhancement of glucose uptake and its utilization through the pentose phosphate pathway to provide ribose-5-phosphate for the synthesis of nucleic acids.

ATP-sensitive potassium channel regulates astrocytic gap junction permeability by a Ca2+-independent mechanism

Using the scrape-loading technique in cultured astrocytes, we show that sulfonylureas such as tolbutamide and glybenzcyclamide, which inhibit the ATP-sensitive K+ channel, prevent the inhibition of gap junction permeability caused by several structurally unrelated uncouplers such as oleic acid, arachidonic acid, endothelin-1, octanol, and alpha-glycyrrhetinic acid. When the intracellular level of Ca2+ was diminished, all the uncouplers tested were still able to inhibit gap junction communication, indicating that their inhibitory effect was not mediated by Ca2+. In addition, tolbutamide and glybenzcyclamide prevented the inhibitory effect of these uncouplers in Ca(2+)-depleted astrocytes, suggesting that the inhibition of the ATP-sensitive K+ channel increases gap junction permeability through a Ca(2+)-independent mechanism. The activation of the ATP-sensitive K+ channel caused by potassium channel openers such as diazoxide and pinacidil led to the inhibition of gap junction communication and overcame the effect of sulfonylureas. These results suggest that the ATP-sensitive K+ channel regulates gap junctional permeability.

Peroxynitrite anion stimulates arginine release from cultured rat astrocytes

The biosynthesis of the physiological messenger nitric oxide (*NO) in neuronal cells is thought to depend on a glial-derived supply of the *NO synthase substrate arginine. To expand our knowledge of the mechanism responsible for this glial-neuronal interaction, we studied the possible roles of peroxynitrite anion (ONOO-), superoxide anion (O2*-), *NO, and H2O2 in L-[3H]arginine release in cultured rat astrocytes. After 5 min of incubation at 37 degrees C, initial concentrations of 0.05-2 mM ONOO- stimulated the release of arginine from astrocytes in a concentration-dependent way; this effect was maximum from 1 mM ONOO- and proved to be approximately 400% as compared with control cells. ONOO(-)-mediated arginine release was prevented by arginine transport inhibitors, such as L-lysine and N(G)-monomethyl-L-arginine, suggesting an involvement of the arginine transporter in the effect of ONOO-. In situ xanthine/xanthine oxidase-generated O2*- (20 nmol/min) stimulated arginine release to a similar extent to that found with 0.1 mM ONOO-, but this effect was not prevented by arginine transport inhibitors. *NO donors, such as sodium nitroprusside, S-nitroso-N-acetylpenicillamine, or 1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium+ ++-1,2-diolate, and H2O2 did not significantly modify arginine release. As limited arginine availability for neuronal *NO synthase activity may be neurotoxic due to ONOO- formation, our results suggest that ONOO(-)-mediated arginine release from astrocytes may contribute to replenishing neuronal arginine, hence avoiding further generation of ONOO- within these cells.

Nitric oxide mediates brain mitochondrial maturation immediately after birth

The possible role of nitric oxide (*NO) in brain mitochondrial maturation was studied. Within the first 5 min after birth, a sharp increase in ATP concentrations was observed, coinciding with an increase in mitochondrial complex II-III (succinate-cytochrome c reductase) activity, while complex I (NADH-CoQ1 reductase) and complex IV (cytochrome c oxidase) activities remained unchanged. Under the same circumstances, cGMP concentrations were increased by 5 min after birth, correlating significantly with ATP concentrations. Since ATP concentrations also correlated significantly with mitochondrial complex II-III activity, these three parameters may be associated. Inhibition of *NO synthase activity brought about by the administration of N(omega)-nitro-L-arginine monomethyl ester to mothers prevented the postnatal increase in cGMP and ATP levels and complex II-III activity. These results suggest that early postnatal mitochondrial maturation in the brain is a *NO-mediated process.

Induction of glucose-6-phosphate dehydrogenase by lipopolysaccharide contributes to preventing nitric oxide-mediated glutathione depletion in cultured rat astrocytes

Treatment of cultured rat astrocytes with lipopolysaccharide (LPS; 1 microg/ml) increased mRNA expression of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting step in the pentose phosphate pathway (PPP), in a time-dependent fashion (0-24 h). This effect was accompanied by an increase in G6PD activity (1.74-fold) and in the rate of glucose oxidation through the PPP (6.32-fold). Inhibition of inducible nitric oxide synthase (iNOS) activity by 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT; 50 microM) did not alter the LPS-mediated enhancement of G6PD mRNA expression or PPP activity. Blockade of nuclear factor-kappaB (NF-kappaB) activation by N-benzyloxycarbonyl-Ile-Glu-(O-tert-butyl)-Ala-leucinal (1 microM) prevented the expression of both iNOS mRNA and G6PD mRNA, suggesting that iNOS and G6PD are co-induced by LPS through a common transcriptional pathway involving NF-kappaB activation. Incubation of cells with LPS for 24 h increased intracellular NADPH concentrations (1.63-fold) as compared with untreated cells, but GSH concentrations were not modified by LPS treatment up to 60 h of incubation. However, inhibition of G6PD activity by dehydroepiandrosterone (DHEA; 100 microM), which prevented LPS-mediated enhancements in PPP activity and NADPH concentrations, caused a 50% decrease in the GSH/GSSG ratio after 24-36 h and in GSH concentrations after 60 h of incubation. Furthermore, the changes in glutathione concentrations caused by DHEA were abolished by AMT, suggesting that nitric oxide and/or its reactive derivatives would be involved in this process. From these results, we conclude that LPS-mediated G6PD expression prevents GSH depletion due to nitric oxide and suggest that this phenomenon may be a contributing factor in the defense mechanisms that protect astrocytes against nitric oxide-mediated cell injury.

Nitric oxide mediates glutamate-induced mitochondrial depolarization in rat cortical neurons

Mitochondria have been considered to be a target for glutamate neurotoxicity. The aim of the present work was to investigate the mechanisms leading to glutamate-mediated mitochondrial deenergization, as measured by mitochondrial membrane potential and cell respiration in cultured neurons. Glutamate exposure to cells induced pronounced mitochondrial depolarization associated with an impairment in neuronal respiration, leading to neuronal ATP depletion. These effects were prevented by both the nitric oxide (. NO) synthase inhibitor Nomega-nitro-l-arginine methyl ester and by the N-methyl-d-aspartate glutamate-subtype receptor inhibitor d-(-)-2-amino-5-phosphopentanoate. Our results suggest that glutamate causes ATP depletion by collapsing mitochondrial membrane potential through a.NO-mediated mechanism.

The effect of albumin on astrocyte energy metabolism is not brought about through the control of cytosolic Ca2+ concentrations but by free-fatty acid sequestration

Albumin is an important serum protein that under normal circumstances is not present in the brain. However, during development, under hypoxia, or after breakdown of the blood-brain barrier, albumin is found in the brain, where it is able to regulate energy metabolism. In this work the mechanism through which albumin regulates astrocyte metabolism was investigated. Our results show that albumin strongly increases (more than 100%) the flux of glucose and lactate through the pyruvate dehydrogenase-catalyzed reaction in astrocytes from primary culture. However, albumin only slightly stimulated other metabolic pathways, such as the tricarboxylic acid cycle or the pentose phosphate shunt, indicating that it exerts its effect specifically on the reaction catalyzed by pyruvate dehydrogenase. Although albumin increased cytosolic Ca2+ concentrations in astrocytes, our results show that the increase in pyruvate dehydrogenase activity promoted by albumin is not due to the enhancement of Ca2+ concentrations. Indeed, highly purified albumins failed to increase the Ca2+ concentration but did enhance lactate oxidation. In agreement with this, the effect of albumin on lactate oxidation was not abolished after Ca2+ depletion. Instead, the presence of fatty acids inhibited lactate oxidation and counteracted the effect of albumin, suggesting that albumin activates pyruvate dehydrogenase by binding free fatty acids and/or their CoA-derivatives.

The K-ATP channel regulates the effect of Ca2+ on gap junction permeability in cultured astrocytes

Using the scrape-loading technique we show that tolbutamide and glybenzcyclamide, two inhibitors of the K+ channel sensitive to ATP (K-ATP channel), partially prevent the inhibition of gap junction permeability promoted by Ca2+ in cultured astrocytes. This effect was dose-dependent, reaching a maximum at 400 microM and 1 microM of tolbutamide and glybenzcyclamide, respectively. The presence of the Ca2+ ionophore A-23187 strongly reduced the concentration of Ca2+ required to block gap junction permeability but did not abolish the effect of tolbutamide and glybenzcyclamide. These results suggest that the effect of these two compounds are not brought about by control of the intracellular concentration of Ca2+ but probably by the promotion of plasma membrane depolarization.

Glutamate neurotoxicity is associated with nitric oxide-mediated mitochondrial dysfunction and glutathione depletion

The role of mitochondrial energy metabolism in glutamate mediated neurotoxicity was studied in rat neurones in primary culture. A brief (15 min) exposure of the neurones to glutamate caused a dose-dependent (0.01-1 mM) increase in cyclic GMP levels together with delayed (24 h) neurotoxicity and ATP depletion. These effects were prevented by either the nitric oxide (.NO) synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (NAME; 1 mM) or by the N-methyl-D-aspartate (NMDA) glutamate-subtype receptor antagonist D-(-)-2-amino-5-phosphonopentanoate (APV; 0.1 mM). Glutamate exposure (0.1 mM and 1 mM) followed by 24 h of incubation caused the inhibition of succinate-cytochrome c reductase (20-25%) and cytochrome c oxidase (31%) activities in the surviving neurones, without affecting NADH-coenzyme-Q1 reductase activity. The rate of oxygen consumption was impaired in neurones exposed to 1 mM glutamate, either with glucose (by 26%) or succinate (by 39%) as substrates. These effects on the mitochondrial respiratory chain and neuronal respiration, together with the observed glutathione depletion (20%) by glutamate exposure were completely prevented by NAME or APV. Our results suggest that mitochondrial dysfunction and impairment of antioxidant status may account for glutamate-mediated neurotoxicity via a mechanism involving .NO biosynthesis.

Nitric oxide mediates brain mitochondrial damage during perinatal anoxia

The possible role of nitric oxide (.NO) in brain energy metabolism during perinatal asphyxia in the rat was studied. Exposure of early neonates to 5 min of anoxia significantly inhibited brain mitochondrial complex II-III activity by 25%, without affecting complex I, complex IV or citrate synthase activities. This insult was accompanied by ATP depletion (54%) and increased concentration of nitrites plus nitrates (1.4-fold), suggesting enhanced .NO synthesis. Administration of Nomega-nitro-L-arginine monomethyl ester (L-NAME) to the mothers inhibited neonatal brain .NO synthase activity, as reflected by the decreased (23%) cyclic GMP concentration. These L-NAME-treated neonates showed complete resistance to anoxic-mediated brain mitochondrial complex II-III damage. Our results suggest that brain mitochondrial dysfunction leading to energy deficiency during perinatal asphyxia is a .NO-mediated process.

A rapid method for the isolation of metabolically active mitochondria from rat neurons and astrocytes in primary culture

A rapid method (about 1.5 h) for the isolation of intact functional mitochondria from neurons and astrocytes in primary culture is described. Mitochondria isolated by this method are metabolically active and tightly coupled as shown by respiratory control ratio values, which were about 4 with glutamate-malate as substrate. The activities of marker enzymes revealed the occurrence of a low degree of cytosolic (5%) or synaptosomal (5.5%) contamination in the mitochondrial fractions. In addition, the activity of citrate synthase was increased by 4 fold in both neuronal and astrocytic mitochondria with respect to values found in cell homogenates. These results confirm that the method affords mitochondrial preparations from cultured brain cells at suitable levels of purity and enrichment for the study of their mitochondrial function. Since mitochondrial damage has been associated with the pathogenesis of certain neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases (P. Chagnon, C. Betard, Y. Robitaille, A. Cholette, D. Gauvreau, Distribution of brain cytochrome oxidase activity in various neurodegenerative disease, Neuroreport 6 (1995) 711-715 [6]; S.J. Kish, C. Bergeron, A. Rajput, S. Dozic, F. Mastrogiacomo, L. Chang, J.M. Wilson, L.M. DiStefano, J.N. Nobrega, Brain cytochrome oxidase in Alzheimer's disease, J. Neurochem. 59 (1992) 776-779 [10]; A.H.V. Schapira, J.M. Cooper, D. Dexter, J.B. Clark, P. Jenner, C.D. Marsden, Mitochondrial complex I deficiency in Parkinson's disease, J. Neurochem. 54 (1990) 823-827 [15]), the method described here shed light on the possible susceptibility of neuronal or astrocytic mitochondria to deleterious effects of these diseases.

cAMP and Ca2+ involvement in the mitochondrial response of cultured fetal rat hepatocytes to adrenaline

The effect of adrenaline on the control of respiratory activity of mitochondria from fetal hepatocytes in primary culture was studied. In the absence of adrenaline, the respiratory control ratio (RCR) of mitochondria increased during the first 3 days of culture due to a decrease in the rate of state 4 respiration. The presence of adrenaline in the incubation medium further increased the mitochondrial RCR through a decrease in the rate of respiration in state 4 and to an increase in the respiration rate in state 3. The effect of adrenaline was mimicked by dibutyryl-cAMP, forskolin, and isobutyl methyl xanthine. All these compounds increased cAMP concentrations, suggesting that cAMP may be involved in the effect of adrenaline. The increase in intracellular free Ca2+ concentrations caused by phenylephrine, vasopressin, or thapsigargin was also accompanied by an increase in the RCR, suggesting that both phenomena are associated. Dibutyryl-cAMP also increased free Ca2+ concentrations, suggesting that the effects of cAMP may be mediated by free Ca2+ concentrations. Adrenaline, dibutyryl-cAMP, phenylephrine, vasopressin, and thapsigargin promoted adenine nucleotide accumulation in mitochondria; this may be an intermediate step in the activation of mitochondrial respiratory function. These results suggest that the stimulatory effect of adrenaline on mitochondrial maturation in cultured fetal rat hepatocytes may be exerted through a mechanism in which both cAMP and Ca2+ act as second messengers. It is concluded that the effect of adrenaline on mitochondrial maturation is exerted by both alpha- and beta-adrenergic mechanisms and is mediated by the increase in adenine nucleotide contents of mitochondria.

Metabolic trafficking through astrocytic gap junctions

Astrocytes are interposed between the pericapillary space and neuronal membranes. Consequently, they may represent an important intermediary element between the source of energetic substrates and the main site of energy-consuming elements, respectively, the blood circulation and the neurons. A typical feature of astrocytes is the connections they establish between each other by specialized membrane structures, defined as gap junctions. These intercellular junctions allow direct cell-to-cell exchanges of ions and small molecules, including several compounds involved in major metabolic pathways occurring in astrocytes. The permeability of astrocytes gap junction channels is controlled by several endogenous compounds released by astrocytes themselves or by other brain cell types, including neurons and endothelial cells. In primary cultures of astrocytes, the intercellular diffusion, the utilization and the uptake of glucose and derivates are modified when gap junctional permeability is inhibited by uncoupling agents. Altogether these observations indicate that intercellular pathways constituted by groups of coupled astrocytes could participate to the metabolism and the distribution of energetic substrates throughout the brain.

Oleic acid inhibits gap junction permeability and increases glucose uptake in cultured rat astrocytes

The role of oleic acid in the modulation of gap junction permeability was studied in cultured rat astrocytes by the scrape-loading/Lucifer yellow transfer technique. Incubation with oleic acid caused a dose-dependent inhibition of gap junction permeability by 79.5% at 50 microM, and no further inhibition was observed by increasing the oleic acid concentration to 100 microM. The oleic acid-mediated inhibition of gap junction permeability was reversible and was prevented by bovine serum albumin. The potency of oleic acid-related compounds in inhibiting gap junction permeability was arachidonic acid > oleic acid > oleyl alcohol > palmitoleic acid > stearic acid > octanol > caprylic acid > palmitic acid > methyloleyl ester. Oleic acid and arachidonic acid, but not methyloleyl ester, increased glucose uptake by astrocytes. Neither oleic acid nor arachidonic acid increased glucose uptake in the poorly coupled glioma C6 cells. These results support that the inhibition of gap junction permeability is associated with the increase in glucose uptake. We suggest that oleic acid may be a physiological mediator of the transduction pathway leading to the inhibition of intercellular communication.

Isolation and characterization of tightly coupled mitochondria from neurons and astrocytes in primary culture

This work provides a rapid method for isolation of intact functional mitochondria from neurons and astrocytes in primary culture. By using this method, it was found that the respiratory control ratio was 1.5-fold greater in neuronal than in astrocytic mitochondria using both NAD-linked (glutamate/malate) and FAD-linked (succinate) substrates. The difference observed in RCR values was due to the lower rate of respiration in state 4 found in neurons as compared to that found in astrocytes, because both cell types showed the same rate of respiration in state 3. The P/O ratio was also higher in neurons than in astrocytes. Our results suggest that the coupling between the mitochondrial respiratory chain and oxidative phosphorylation is stronger in neurons than in astrocytes. These results may be of relevance for the understanding of the differential susceptibility of brain cells to impairments of energy metabolism observed in certain neurodegenerative diseases.

[Blood lead in the inhabitants of 4 Peruvian localities]

During 1994 and 1995, a cross-sectional study was carried out to investigate the concentrations of lead in the blood of inhabitants of four Peruvian cities (Lima, Huancayo, La Oroya, and Yaupi) with different population densities and degrees of industrial development. In a random sample of 180 men and 180 women without occupational exposure to lead, blood lead levels were measured by the atomic absorption method with a Perkin Elmer 603 spectrophotometer without a graphite oven. The results revealed blood lead concentrations of 269 +/- 63 micrograms per liter (micrograms/L) in Lima, 224 +/- 47 micrograms/L in Huancayo; 348 +/- 40 micrograms/L in La Oroya, and 140 +/- 27 micrograms/L in Yaupi. It was concluded that blood lead levels in the inhabitants of these cities were related to the degree of industrialization and the population density of each locality.

Thyroid hormones regulate the onset of osmotic activity of rat liver mitochondria after birth

The effect of thyroid hormone deprivation on the osmotic activity of liver mitochondria from early newborn rats was studied. Experimentally induced hypothyroidism prevented the increase in the osmotic activity of mitochondria observed immediately after birth. Osmotic activity was restored by T4 and T3 treatment to hypothyroid newborns but not when this treatment was supplemented with cycloheximide. Under the same circumstances, streptomycin had no effect. Hypothyroidism abolished the change in the slope of the osmotic curve (plot of inverse absorbance of mitochondrial suspensions incubated in sucrose solutions vs. inverse sucrose concentration) observed in mitochondria from euthyroid newborns at 110-120 mOsm sucrose, suggesting that hypothyroidism prevents the formation of tight physical connections between mitochondrial outer and inner membranes. Thyroid hormone deprivation increased the passive permeability of the mitochondrial inner membrane to protons, resulting in a decreased respiratory control ratio. Hypothyroidism prevented the sharp decrease in the affinity of mitochondria for ATP observed in euthyroid newborns immediately after birth. These results corroborate our previous suggestion (Endocrinology, 1995, 136:4448) that, during the early neonatal period, thyroid hormones control the synthesis of some nucleus-coded protein(s) involved in the assembly of F0,F1-ATPase.

Effect of valproate on the metabolism of the central nervous system

The effects of valproate on brain energy and lipid metabolism is reviewed. Increasing evidence suggests that valproate uses the monocarboxylic acid carrier in order to cross the blood brain barrier (BBB) and the neural cell plasma membranes. The uptake of valproate into the brain through this mechanism would compete with the uptake of energy precursors, such as the monocarboxylic acids 3-hydroxybutyrate, lactate or pyruvate and with some amino acids, but not with glucose. This could impair brain fuel utilization, specially during the neonatal period or childhood, when lactate or 3-hydroxybutyrate furnishes alternative substrates to glucose for the brain. It is concluded that valproate interference with energy metabolism may have implications for the therapeutic action of the drug, stressing the possibility that valproate-mediated alterations in brain lipid synthesis may contribute to the pharmacological action of the drug.

Lactate spares glucose as a metabolic fuel in neurons and astrocytes from primary culture

The effect of lactate on glucose metabolism in neurons and astrocytes from primary culture has been studied. The rates of glucose metabolism through the pentose-phosphate shunt, the pyruvate dehydrogenase-catalyzed reaction, the tricarboxylic acid cycle, the total lipogenesis and the synthesis of glycerol-borne lipids in astrocytes were 2-3 fold higher than in neurons. However, the rate of glucose incorporation into sterols and esterified fatty acids was similar in both types of cells. Total glucose utilization was inhibited by lactate to the same extend in both neurons and astrocytes. Lactate strongly inhibited glucose oxidation through the pyruvate dehydrogenase-catalyzed reaction and the tricarboxylic acid cycle, in both neurons (60 and 44%, respectively) and astrocytes (64 and 62%, respectively). Glucose incorporation into sterols and fatty acids was also inhibited by lactate in both neurons and astrocytes (57 and 76%, respectively) while the oxidation of glucose in the pentose-phosphate shunt and the synthesis of glycerol-borne lipids was not significantly affected. These results suggest that in the presence of lactate both neurons and astrocytes can utilize lactate as the major metabolic substrate, sparing glucose for the synthesis of NADPH(H+), ribose-5-phosphate and/or glycerol-borne lipids. An interaction between glucose and lactate metabolism at the level of the pyruvate dehydrogenase-catalyzed reaction is suggested.

Inhibition of astrocyte gap junctional communication by ATP depletion is reversed by calcium sequestration

We have studied the possible role of cellular energy status in the regulation of gap junction permeability in rat astrocytes in primary culture. Incubation with the mitochondrial respiratory chain inhibitor antimycin (5 ng/ml) for 16 h caused a significant decrease in ATP concentrations. This effect was accompanied by a dose-dependent inhibition of gap junction permeability as assessed by the scrape-loading/Lucifer yellow transfer technique. No cell death was observed following this treatment. Restoration of cellular ATP levels by a further 24 h incubation in antimycin-free medium reversed the inhibition of Lucifer yellow transfer caused by antimycin. The inhibition of Lucifer yellow transfer brought about by antimycin treatment was also reversed by a short incubation of the cells with the calcium chelator EGTA plus the calcium ionophore A23187. These results suggest that ATP depiction causes a reversible inhibition of gap junction permeability through a calcium-mediated mechanism.

Fuel utilization by early newborn brain is preserved under congenital hypothyroidism in the rat

Mental retardation associated with hypothyroidism may be caused by impairment of brain ketone body-metabolizing enzymes during the suckling period. However, much evidence suggests that, immediately after delivery, lactate, instead of ketone bodies or glucose, may be the best substrate for the brain. In this work, we have studied the effect of experimentally induced congenital hypothyroidism on the rate of lactate, glucose, and 3-hydroxybutyrate utilization in early neonatal brain slices. Methimazole (MMI) administration to the mothers caused a 5.4- and 1.7-fold decrease in neonatal plasma concentrations of L-thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3), respectively. Propylthiouracil (PTU) administration to the mothers caused a 7.3- and > 2-fold decrease in plasma T4 and T3 concentrations, respectively. MMI-induced hypothyroidism did not significantly modify the rate of lactate, glucose, or 3-hydroxybutyrate oxidation to CO2 and their incorporation into lipids by the neonatal brain. However, PTU-induced hypothyroidism decreased the rate of lactate and glucose oxidation to CO2 and their incorporation into lipids by 17% (p < 0.05). 3-Hydroxybutyrate utilization was not modified by this treatment. Separation by HPLC of the lipids revealed that PTU-mediated inhibition of lipid synthesis from lactate and glucose may be accounted for by specific inhibition of the rate of sterol synthesis (15%, p < 0.05), whereas the rate of phospholipid synthesis was unaffected. These results suggest that the early newborn may develop mechanisms aimed at avoiding the possible brain damage caused by the inhibition of lipid synthesis brought about by mild neonatal hypothyroidism.

Induction of nitric oxide synthase inhibits gap junction permeability in cultured rat astrocytes

Nitric oxide (.NO) synthase (NOS) was induced in cultured rat astrocytes by incubation with lipopolysaccharide (LPS) for 18 h and gap junction permeability was assessed by the scrape-loading/Lucifer yellow transfer technique. Induction of NOS was confirmed by determining either the NG-methyl-L-arginine (NMMA)-inhibitable production of nitrites and nitrates or the conversion of L-[3H]arginine to L-[3H]citrulline. Incubation with LPS dose-dependently inhibited gap junction permeability to 63.3% at 0.05 microgram/ml LPS and no further inhibition was observed on increasing the LPS concentration up to 0.5 microgram/ml. LPS-mediated gap junction inhibition was irreversible but was prevented by incubation with the NOS inhibitor NMMA and with the superoxide anion (O2.-) scavenger superoxide dismutase. Incubation of the cells with both the .NO donor S-nitroso-N-acetylpenicillamine and the O2.(-)-generating system xanthine/xanthine oxidase inhibited gap junction permeability. These results suggest that the in situ reaction between .NO and O2.-, to form the peroxynitrite anion (ONOO-), may be responsible for the inhibition of gap junction permeability. Scavenging the ONOO- derivative hydroxyl radical (.OH) with either dimethyl sulfoxide or mannitol prevented the LPS-mediated inhibition of gap junction permeability. Finally, exposure of astrocytes to authentic ONOO- caused a dose-dependent inhibition of gap junction permeability (65.7% of inhibition at 0.5 mM ONOO-). The pathophysiological relevance of ONOO(-)-mediated inhibition of gap junctional communication in astrocytes after NOS induction by LPS is discussed, stressing the possible role played by this mechanism in some neurodegenerative diseases.

Endothelin-1 regulates glucose utilization in cultured astrocytes by controlling intercellular communication through gap junctions

The role played by endothelin-1 and intercellular communication mediated by gap junctions in the regulation of glucose disposal by astrocytes has been studied in primary culture. Endothelin-1 increased glucose uptake by astrocytes as did one of its putative messenger arachidonic acid and the non-physiological gap junction uncoupler alpha-glycyrrhetinic acid (AGA). None of these agents increased glucose uptake by C6 glioma cells, a cell line in which gap junction proteins are poorly expressed. In confluent astrocytes, the inhibition of gap junction permeability caused by AGA doubled the activity of the pentose phosphate shunt with minimal changes in the activity of the pyruvate dehydrogenase-catalyzed reaction and that of the tricarboxylic acid cycle. By contrast, these effects were not observed in dissociated astrocytes in which intercellular communication is lacking. The scraped loading dye transfer technique was modified to follow the passage of glucose and its metabolites through astrocyte gap junctions. The diffusion of glucose, the phosphorylated derivative glucose-6-phosphate, the phosphorylisable but not metabolisable derivative ortho-methyl-glucose, and the anaerobic glycolytic product L-lactate was much higher in astrocytes than in C6 glioma cells and was inhibited by the inhibition of gap junction permeability caused by endothelin-1, arachidonic acid, octanol, or AGA. It is concluded that gap junction permeability may regulate brain metabolism by controlling the uptake, utilization, and intercellular distribution of glucose and its metabolites in astrocytes.

Astrocyte differentiation in primary culture followed by flow cytometry

Astrocyte proliferation and differentiation in primary culture were followed by flow cytometry. The time-courses of the percentages of astrocytes in the different cell-cycle phases suggest that astrocytes proliferate during the first 10 days in culture thereafter reaching confluence. Two types of astrocytes are identified immunocytochemically: one growing in the bed monolayer, identified as type-1 astrocytes, and another growing on the top of the monolayer, identified as type-2 astrocytes. In addition, three populations identified as being formed of type-1, type-2 and putative progenitor cells, respectively, were followed by flow cytometry. Progenitor cells were the major type 2 h after plating (89%) but their percentage decreases sharply (to 16%) during the first 5 days in culture, with no ensuing changes. In contrast, the percentage of type-1 cells (11%) rapidly increased after plating reaching a maximum 5 days later (73%). Later, it decreased (to 47%) and was maintained thereafter. The percentage of type-2 cells was undetectable immediately after plating but increased from the 3rd to the 10th day with no further changes. Our results suggest that progenitor cells differentiate into type-1 astrocytes triggered by the culture medium but the differentiation of progenitor cells into type-2 astrocytes is brought about by some type-1-secreted factor. In this work we report a rapid and simple method for following the growth and differentiation of rat brain astrocytes in primary culture.

Metabolic fuel utilization and pyruvate oxidation during the postnatal period

The transplacental supply of nutrients is interrupted at birth, which diverts maternal metabolism to lactation. After birth, energy homeostasis is rapidly regained through milk nutrients which supply the newborn with the fatty acids and ketone bodies required for neonatal development. However, immediately after birth and before the onset of suckling there is a time lapse in which the newborn undergoes a unique kind of starvation. During this period glucose is scarce and ketone bodies are not available owing to the delay in ketogenesis. Under these circumstances, the newborn is supplied with another metabolic fuel, lactate, which is utilized as a source of energy and carbon skeletons. Neonatal rat lung, heart, liver and brain utilize lactate for energy production and lipogenesis. Lactate is also utilized by the brain of human babies with type I glycogenosis. Both rat neurons and astrocytes in primary culture actively use lactate as an oxidizable substrate and as a precursor of phospholipids and sterols. Lactate oxidation is enhanced by dichloroacetate, an inhibitor of the pyruvate dehydrogenase kinase in neurons but not in astrocytes, suggesting that the pyruvate dehydrogenase is regulated differently in each type of cell. Despite the low activity of this enzyme in newborn brain, pyruvate decarboxylation is the main fate of glucose in both neurons and astrocytes. The occurrence of a yeast-like pyruvate decarboxylase activity in neonatal brain may explain these results.

Changes in adult rat liver mitochondrial populations at different energy states analyzed by flow cytometry

The present work studies the changes in green fluorescence intensity after Rh-123 staining of the low (LFP) and the high fluorescence populations (HFP) in isolated mitochondria from rat liver. The results show that the HFP represents a mitochondrial compartment less sensitive to changes in energy states. In addition, it is concluded that the use of Rh-123 to monitor changes in mitochondrial membrane potential should be undertaken with caution because, under certain circumstances, there is no correlation between the Rh-123 intensity of fluorescence due to its uptake by mitochondria and previously reported changes in the mitochondrial membrane potential.

Hypothyroidism prevents postnatal changes in rat liver mitochondrial populations defined by rhodamine-123 staining

The effect of hypothyroidism on the percentages of low fluorescence population (LFP) and high fluorescence population (HFP) rhodamine-123-stained mitochondria, respiratory parameters, and ATPase activity were studied in liver mitochondria from early newborn rats. Hypothyroidism prevented the decrease in the percentage of HFP and the subsequent increase in LFP that occurs immediately after birth. This effect coincides with the impairment of mitochondrial respiratory function, as shown by the low respiratory control ratio and the low activity of F0,F1-ATPase found in hypothyroid newborns. All of these changes were reversed by the administration of thyroid hormones. ATP in vitro promotes the conversion of HFP into LFP and increases the respiratory control ratio in hypothyroid newborns, although this effect was not observed after thyroid hormone treatment. The effect of thyroid hormones on both the postnatal changes in mitochondrial populations and in F0,F1-ATPase activity was prevented by cycloheximide, but not by streptomycin. Thus, the observed effects of thyroid hormones on neonatal mitochondria must be accomplished by the induction of the synthesis of some nuclei-coded protein, possibly involved in F0,F1-ATPase assembly.

Effect of ethanol consumption on adult rat liver mitochondrial populations analyzed by flow cytometry

In the present study, the effects of administering ethanol to adult male rats on the distribution of the low fluorescence population (LFP) and high fluorescence population (HFP), and the rhodamine-123 fluorescence intensity of these groups of mitochondria are analyzed by flow cytometry. Our results show that ethanol administration to adult male rats induces a redistribution of the HFP and LFP mitochondrial populations leading to an increase of the less functional HFP mitochondria. In addition, ethanol induced an increase in the mean intensity of green fluorescence of the HFP that is probably related to an increased number of rhodamine-123 binding sites per mitochondria resulting from mitochondria enlargement.

Postnatal changes in rhodamine-123 stained mitochondrial populations are sensitive to protein synthesis inhibitors but mimicked in vitro by ATP

The incubation of term fetus mitochondria with ATP mimicked in vitro the increase in the respiratory control index and in the percentage of the rhodamine-123-low fluorescence population that occurred in vivo immediately after birth, suggesting that both phenomena are closely associated. The administration of streptomycin inhibited the increase in the percentage of the low fluorescence population that occurred immediately after birth, while the administration of cycloheximide even reversed these changes. These results suggest that the in vivo interconversion between mitochondrial forms depends on both cytosolic and mitochondrial protein synthesis.

Inhibition of neonatal brain fuel utilization by valproate and E-delta 2-valproate is not a consequence of the stimulation of the gamma-aminobutyric acid shunt

Stimulation of the gamma-aminobutyric acid (GABA) shunt by valproate and its major metabolite, E-delta 2-valproate, has been proposed to decrease brain energy metabolism. In order to elucidate this hypothesis, the effect of these drugs on substrate utilization in neonatal rat brain slices was studied. The overall rate of lactate utilization was dose-dependently inhibited by both drugs. Valproate and E-delta 2-valproate inhibited both sterol and fatty acid syntheses from 3-hydroxybutyrate. The rate of glucose utilization was not affected by valproate nor E-delta 2-valproate. The inhibition of the GABA aminotransferase by aminooxyacetate decreased lipogenesis from lactate, 3-hydroxybutyrate and glucose. The inhibitor of the mitochondrial pyruvate carrier, alpha-cyano-4-hydroxycinnamate, strongly decreased the rate of lactate, 3-hydroxybutyrate and glucose utilization, suggesting that the inhibition of pyruvate mitochondrial carrier is not the mode of action of these drugs. It is suggested that inhibition of plasma membrane monocarboxylate carrier by valproate and E-delta 2-valproate, but not the activation of the GABA shunt, is responsible for the inhibition of the brain fuel utilization.