Effect of extract from Boswellia serrata gum resin on decrease of GAD65 autoantibodies in a patient with Latent Autoimmune Diabetes in Adults

BACKGROUND

Extracts from Boswellia serrata gum resin have anti-inflammatory effect and are used for treatment of a variety of chronic inflammatory diseases. It was previously demonstrated that the treatment with Boswellia serrata gum resin of LADA (Latent Autoimmune Diabetes in Adults) patients decreased blood levels of IA2 antibodies, one of the markers associated with LADA autoimmune diabetes.

PRIMARY STUDY OBJECTIVE

The purpose of this study was to test whether Boswellia serrata gum resin also influences GAD65 autoantibodies as the other marker associated with LADA.

METHODS/DESIGN

We report a case study of male patient diagnosed with LADA with positive GAD65 autoantibodies who was treated with extract from Boswellia serrata gum resin, during 9 months. Blood levels of GAD65 autoantibodies, fasting blood glucose levels and HbA1c were measured before the treatment and periodically during the treatment.

RESULTS

Over the observed period, the blood levels of GAD65 autoantibodies linearly decreased about 25%.

CONCLUSION

The study confirms that extract of Boswellia serrata gum resin seems to prevent insulitis in patients with LADA, as indicated by its action on both markers of autoimmune diabetes, i.e., GAD65 and IA2 autoantibodies. The possibility that the treatment with boswellic acids of LADA patients with positive autoantibodies could be beneficial on the course of the disease, calls for further investigation and a clinical study.

Substrate inactivation of bacterial L-aspartate α-decarboxylase from Corynebacterium jeikeium K411 and improvement of molecular stability by saturation mutagenesis

Bacterial L-aspartate α-decarboxylase (PanD) is a potential biocatalyst for the green production of β-alanine, an important block chemical for manufacturing nitrogen-containing chemicals in bio-refinery field. It was reported that the poor catalytic stability caused by substrate inactivation limited the large-scale application. Here, we investigated the characters of inactivation by L-aspartate of PanD from Corynebacterium jeikeium (PD_Cjei), and found that L-aspartate induced a time-, and concentration-dependent inactivation of PD_Cjei with the values of K_I and k_inact being 288.4 mM and 0.235/min, respectively. To improve the catalytic stability of PD_Cjei, conserved amino acid residues essential to catalytic stability were analyzed by comparing the discrepancy in the observed inactivation rate of various sources. By an efficient colorimetric high-throughput screening method, four mutants with 3.18-24.69% higher activity were obtained from mutant libraries. Among them, the best mutation (R3K) also performed 66.38% higher catalytic stability than the wild type, showing great potential for industrial bio-production of β-alanine.

Abamectin treatment affects glutamate decarboxylase expression and induces higher GABA levels in the citrus red mite, Panonychus citri

The citrus red mite, Panonychus citri, is one of the most economically and globally destructive mite pests of citrus. Acaricide resistance has been a growing problem in controlling this pest. As the main inhibitory neurotransmitter in organisms, γ-aminobutyric acid (GABA) is synthesized from the amino acid glutamate by the action of glutamate decarboxylases (GADs). In the present study, one novel GAD gene, PcGAD, was identified and characterized from P. citri. The opening reading frame of PcGAD contained 1548 nucleotides that encode 515 amino acids. The subsequent spatiotemporal expression pattern by RT-qPCR revealed that the expression levels of PcGAD were significantly higher in larvae than in adults. Challenging with various concentrations of abamectin resulted in the upregulation of PcGAD transcript levels. Furthermore, biochemical characterization indicated that changes in GAD activity coincided with its mRNA levels. High-performance liquid chromatography confirmed that the GABA contents of P. citri increased upon abamectin treatment. The application of abamectin induces PcGAD expression and activates GAD activity, thereby resulting in an increase in GABA content in P. citri, which contributes to the adaptability of the mite to abamectin challenge.

Rapid Normalization of High Glutamic Acid Decarboxylase Autoantibody Titers and Preserved Endogenous Insulin Secretion in a Patient with Diabetes Mellitus: A Case Report and Literature Review

A 59-year-old Japanese woman developed diabetes mellitus without ketoacidosis in the presence of glutamic acid decarboxylase autoantibody (GADA) (24.7 U/mL). After the amelioration of her hyperglycemia, the patient had a relatively preserved serum C-peptide level. Her endogenous insulin secretion capacity remained almost unchanged during 5 years of insulin therapy. The patient's GADA titers normalized within 15 months. The islet-related autoantibodies, including GADA, are believed to be produced following the autoimmune destruction of pancreatic beta cells and are predictive markers of type 1 diabetes mellitus. Therefore, the transient appearance of GADA in our patient may have reflected pancreatic autoimmune processes that terminated without progression to insulin deficiency.

Time course of changes in pyridoxal 5'-phosphate (vitamin B6 active form) and its neuroprotection in experimental ischemic damage

In the present study, we investigated ischemia-induced changes of pyridoxal 5'-phosphate synthesizing enzyme and degrading enzyme and neuroprotective effects and roles of pyridoxal 5'-phosphate against ischemic damage in the gerbil hippocampal CA1 region. Pyridoxal 5'-phosphate oxidase and pyridoxal phosphate phosphatase immunoreactivities were changed in neurons up to 2 days after ischemia, while 4 days after ischemia their immunoreactivities were expressed in astrocytes. Pyridoxal 5'-phosphate oxidase immunoreactivity and its protein level were highest 12 h after ischemia, while those in pyridoxal phosphate phosphatase were highest 2 days after ischemia. Total activities of these enzymes were changed after ischemia, but specific activities of the enzymes were not altered. Treatment with pyridoxal 5'-phosphate into brains (4 microg/5 microl, i.c.v.) at 30 min before transient ischemia protected about 80% of CA1 pyramidal cells 4 days after ischemia and induced elevation of glutamic acid decarboxylase 67 immunoreactivity in the CA1 region. However, pyridoxal 5'-phosphate treatment into ischemic brains decreased GABA transaminase immunoreactivity in the CA1 region after ischemia. These results indicate that pyridoxal 5'-phosphate may be associated with the inhibitory discharge of GABA in the hippocampal CA1 neurons, and the increased level of GABA may protect hippocampal CA1 pyramidal cells from ischemic damage.

Neuroprotection by estradiol: A role of aromatase against spine synapse loss after blockade of GABAA receptors

Estrogen has been suggested to be pro-epileptic by reducing GABA synthesis, resulting in increased spine density and a decreased threshold for seizures in the hippocampus, which, once they occur, are characterized by a dramatic spine loss in the affected brain areas. As considerable amounts of estradiol are synthesized in the hippocampus, in this study we focused on aromatase, the rate-limiting enzyme in estrogen synthesis in order to examine the role of locally synthesized estrogens in epilepsy. To this end, we first examined the effects of letrozole, a potent aromatase inhibitor, on GABA metabolism in single interneurons of hippocampal dispersion cultures. Letrozole downregulated estradiol release into the medium, as well as glutamate decarboxylase (GAD) expression and GABA synthesis, and decreased the number of GAD positive cells in the cultures. Next, we counted spine synapses and measured estradiol release of hippocampal slice cultures, in which GABA(A) receptors had been blocked by bicuculline, in order to mimic epileptic activity. Treatment of slice cultures with bicuculline resulted in a dramatic decrease in the number of spine synapses and in a significant suppression of estrogen synthesis. The decrease in synapse number in response to bicuculline was restored by combined application of estradiol and bicuculline. Surprisingly, estradiol alone had no effect on either spine synapse number or on GAD expression and GABA synthesis. "Rescue" of synapse number in "epileptic slices" by estradiol and maintenance of GABA metabolism by hippocampus-derived estradiol points to a neuroprotective role of aromatase in epilepsy. Re-filling of estradiol stores after their depletion due to overexcitation may therefore add to therapeutical strategies in epilepsy.

Estradiol alters only GAD67 mRNA levels in ischemic rat brain with no consequent effects on GABA

The present study tested the hypothesis that estradiol reduces tissue infarction after middle cerebral artery occlusion (MCAO) in estradiol-deficient females by augmenting glutamic acid decarboxylase (GAD) expression and thus activity, leading to increases in gamma-amino-butyric acid (GABA) tissue levels. Glutamic acid decarboxylase is the principal enzyme for GABA synthesis and has two isoforms, GAD65 and GAD67, which differ in size and cellular distribution. Rats were ovariectomized 7 to 8 days before receiving no hormone, placebo, or 25 microg estradiol via subcutaneous implant 7 to 10 days before harvesting tissue in either ischemic cohorts after 2 h of MCAO (end-ischemia) or in nonischemic cohorts. Selected cortical and striatal regions were microdissected from harvested brains. GAD65/67 mRNA levels were determined by microlysate ribonuclease protection assay. End-ischemic GABA concentrations were determined by HPLC. Steroid treatment selectively decreased ischemic cortical GAD67 mRNA levels. In most brain regions evaluated, regional GABA concentrations increased with ischemia regardless of treatment. Estradiol blocked MCAO-induced increases in GABA concentration only in dorsomedial cortex. These data suggest that estradiol repletion in ischemic rat brain selectively decreases GAD67 mRNA levels but does not alter steady-state GABA concentrations. It may be that estradiol under ischemic conditions is attenuating GABA metabolism rather than enhancing synthesis or is augmenting other aspects of GABAergic transmission such as GABA transporters and receptors.

Expression of GAD65 and GAD67 immunoreactivity in MPTP-treated monkeys with or without l-DOPA administration

This study investigated the consequences of levodopa treatment on the expression of the 65- and 67-kDa isoforms of glutamate decarboxylase (GAD65 and GAD67) immunoreactivity in the basal ganglia and cortex of monkeys rendered Parkinsonian by systemic MPTP administration. All MPTP-treated monkeys showed Parkinsonian impairment and selective loss of tyrosine hydroxylase (TH) with sparing of GAD immunoreactive (-ir) fibers and terminals in basal ganglia. The distribution of GAD65- and GAD67-ir in the cortex, caudate, and putamen was not significantly different in MPTP vs. naïve monkeys nor as a function of L-DOPA treatment. In comparison, the expression of GAD67- but not GAD65-ir was augmented in the globus pallidus in MPTP-treated monkeys. Quantification revealed significant increases in number of GAD67-ir neurons in the external and internal segments of the globus pallidus while no significant difference in the number of GAD65-ir neurons was observed. L-DOPA treatment did not significantly change the number of GAD65- or GAD67-ir pallidal neurons following MPTP. These results support and extend the findings that transcriptional elevation of GAD67 occurs in the globus pallidus and demonstrate that GAD65 and GAD67 are differentially altered following lesion. The finding of elevated GAD67 expression in the pallidum is consistent with alterations in inhibitory neurocircuitry playing a key role in the pathophysiology of motor disturbances in Parkinson's disease.

Remodeling of hippocampal GABAergic system in adult offspring after maternal hypoxia and magnesium sulfate load: Immunohistochemical study

A strong relationship between hypoxia and fetal brain damage has been described. Specific susceptibility of the GABAergic neurons to these conditions may be crucial to the damage induced. We have previously shown, in a mouse model, that maternal pretreatment with magnesium sulfate (Mg) partially prevented the behavioral consequences of maternal hypoxia in the adult offspring. Here, we tested the effect of maternal hypoxia and maternal Mg load on the GABAergic system of 8-month-old offspring. The immunoreactivity (IR) of several proteins expressed in GABAergic neurons and inhibitory synapses was analyzed in the following regions of the adult offspring brain: hippocampus, cortical M1, caudate putamen, and lateral globus pallidus. Maternal hypoxia reduced the density of parvalbumin (PV)-IR neurons in the hippocampus. The density of PV-IR and calbindin (CB)-IR neurons was also reduced in the deep and superficial layers of the M1. Maternal pretreatment with Mg had a prophylactic action in the superficial, but not the deep, layers of M1. Also, in offspring from the maternal hypoxia group, the vesicular GABA transporter (VGAT)-IR was enhanced in the hippocampal CA1 and hilus regions. No effect of maternal hypoxia on VGAT-IR was observed in the M1. However, maternal pretreatment with Mg enhanced VGAT-IR and glutamate decarboxylase-IR in the deep layers of the M1. In the globus pallidus, maternal hypoxia enhanced CB-IR, which was prevented by maternal pretreatment with Mg. In conclusion, maternal hypoxia induced a loss of PV-IR and CB-IR neurons; maternal pretreatment with Mg partially protected these neuron populations. An increase in proteins of inhibitory synapses, observed under hypoxic conditions in several brain regions, may be a result of some compensatory mechanism.

Neurochemical correlates of differential neuroprotection by long-term dietary creatine supplementation

Dietary supplementation with creatine has proven to be beneficial in models of acute and chronic neurodegeneration. We report here data on the neurochemical correlates of differential protection of long-term creatine supplementation in two models of excitotoxicity in rats, as well as in the mouse model for ALS (G93A mice). In rats, the fall in cholinergic and GABAergic markers due to the excitotoxic death of intrinsic neurons caused by intrastriatal infusion of the neurotoxin, ibotenic acid, was significantly prevented by long-term dietary supplementation with creatine. On the contrary, creatine was unable to recover a cholinergic marker in the cortex of rats subjected to the excitotoxic death of the cholinergic basal forebrain neurons. In G93A mice, long-term creatine supplementation marginally but significantly increased mean lifespan, as previously observed by others, and reverted the cholinergic deficit present in some forebrain areas at an intermediate stage of the disease. In both rats and mice, creatine supplementation increased the activity of the GABAergic enzyme, glutamate decarboxylase, in the striatum but not in other brain regions. The present data point at alterations of neurochemical parameters marking specific neuronal populations, as a useful way to evaluate neuroprotective effects of long-term creatine supplementation in animal models of neurodegeneration.

Fos-like immunoreactivity in the brain associated with freezing or escape induced by inhibition of either glutamic acid decarboxylase or GABAA receptors in the dorsal periaqueductal gray

GABAergic neurons exert tonic control over the neural substrates of aversion in the dorsal periaqueductal gray (dPAG). It has been shown that electrical stimulation of this region at freezing or escape thresholds activates different neural circuits in the brain. Since electrical stimulation activates cell bodies and fibers of passage, it is necessary to use chemical stimulation that activates only post-synaptic receptors. To investigate this issue further, reduction of GABA transmission was performed with local injections of either the GABA-A receptor antagonist bicuculline or the glutamic acid decarboxylase (GAD) inhibitor semicarbazide into the dorsolateral periaqueductal gray (dlPAG). Local infusions of semicarbazide (5.0 microg/0.2 microl) or bicuculline (40 ng/0.2 microl) into this region caused freezing and escape, respectively. The results obtained showed that freezing behavior induced by semicarbazide was associated with an increase in Fos expression in the laterodorsal nucleus of the thalamus (LD) and ventrolateral periaqueductal gray (vlPAG), while bicuculline-induced escape was related to widespread increase in Fos labeling, notably in the columns of the periaqueductal gray, hypothalamus nuclei, the central amygdaloid nucleus (Ce), the LD, the cuneiform nucleus (CnF) and the locus coeruleus (LC). Thus, the present data support the notion that freezing and escape behaviors induced by GABA blockade in the dlPAG are neurally segregated: freezing activates only structures that are mainly involved in sensory processing, and bicuculline-induced escape activates structures involved in both sensory processing and motor output of defensive behavior. Therefore, the freezing elicited by activation of dlPAG appears to be related to the acquisition of aversive information, whereas most brain structures involved in the defense reaction are recruited during escape.

A serotonin 5-HT1A receptor agonist prevents behavioral sensitization to L-DOPA in a rodent model of Parkinson's disease

Marked fluctuation of dopamine concentration in the striatum following long-term L-DOPA administration contributes to the development of L-DOPA-induced motor complications including L-DOPA-induced dyskinesias and wearing-off in patients with Parkinson's disease. We have shown that pretreatment with 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a 5-HT1A (5-hydroxytryptamine) receptor agonist, alleviates fluctuation of dopamine levels in the dopamine-denervated striatum of 6-hydroxydopamine-lesioned (hemiparkinsonian) rats after L-DOPA treatment. To determine whether co-administration of 8-OH-DPAT with L-DOPA prevents L-DOPA-induced motor complications, we examined rotation behavior and levels of messenger RNAs coding for dynorphin and glutamic acid decarboxylase in the striatum of 6-hydroxydopamine-lesioned rats treated with L-DOPA alone or L-DOPA + 8-OH-DPAT, twice daily, for 2 weeks. Co-administration of 8-OH-DPAT inhibited an increase of rotation behavior to L-DOPA and L-DOPA-induced increases in levels of messenger RNAs coding for dynorphin and glutamic acid decarboxylase in the dopamine-denervated striatum, both of which are established indices of L-DOPA-induced motor complications. These results suggest that pharmaceutical products that stimulate 5-HT1A receptors could prove useful in prevention of the development of L-DOPA-induced motor complications in patients with Parkinson's disease.

Estrogen and ovariectomy regulate mRNA and protein of glutamic acid decarboxylases and cation-chloride cotransporters in the adult rat hippocampus

17beta-Estradiol spatiotemporally regulates the gamma-aminobutyric acid (GABAergic) tone in the adult hippocampus. However, the complex estrogenic effect on the GABAergic system is still unclear. In adult central nervous system (CNS) neurons, GABA can induce both inhibitory and excitatory actions, which are predominantly controlled by the cation-chloride cotransporters NKCC1 and KCC2. We therefore studied the estrogenic regulation of two glutamate decarboxylase (GAD) isoforms, GAD65 and GAD67, as well as NKCC1 and KCC2 in the adult female rat hippocampus by immunohistochemistry and in situ hybridization. First, we focused on the duration after ovariectomy (OVX) and its effects on GAD65 protein levels. The basal number of GAD65-immunoreactive cells decreased after long-term (10 days) OVX compared to short-term (3 days) OVX. We found that, only after long-term OVX but not after short-term OVX, estradiol increased the number of GAD65-immunoreactive cells in the CA1 pyramidal cell layer. Furthermore, estradiol did not alter the GAD65-immunoreactive cell population in any other CA1 subregion. Second, we therefore focused on long-term OVX and the estrogenic regulation of GAD and cation-chloride cotransporter mRNA levels. In the pyramidal cell layer, estradiol affected GAD65, GAD67 and NKCC1 mRNA levels, but not KCC2 mRNA levels. Both GAD65 and NKCC1 mRNA levels increased within 24 h after estradiol treatment, followed by a subsequent increase in GAD67 mRNA levels. These findings suggest that basal levels of estrogen might contribute to a balance between the excitatory and inhibitory synaptic transmission onto CA1 pyramidal cells by regulating perisomatic GAD and NKCC1 expression in the adult hippocampus.

Intralaminar thalamic nuclei lesions: widespread impact on dopamine denervation-mediated cellular defects in the rat basal ganglia

Intralaminar thalamic nuclei represent a major site of non-dopaminergic degeneration in Parkinson disease, but the impact of this degeneration on the pathophysiological functioning of basal ganglia remains unknown. To address this issue, we compared the effects of 6-hydroxydopamine-induced lesions of nigral dopamine neurons alone or combined with ibotenate-induced lesions of intralaminar thalamic neurons on markers of neuronal metabolic activity in the rat basal ganglia using in situ hybridization histochemistry. Thalamic lesions prevented most of the dopamine denervation-induced changes (i.e. the increases in mRNA levels of enkephalin and GAD67 in the striatum, of GAD67 in the globus pallidus and entopeduncular nucleus, and of cytochrome oxidase subunit-I in the subthalamic nucleus), but did not affect the downregulation of striatal substance P and upregulation of GAD67 in the substantia nigra pars reticulata. We also provide immunohistochemical evidence that thalamic lesions markedly decreased striatal expression of the vesicular glutamate transporter vGluT2, confirming the association of this transporter with the thalamic projections to the basal ganglia. Altogether, these data reveal a major antagonistic influence of thalamic and dopaminergic afferents onto the basal ganglia and suggest that degeneration of thalamic neurons in Parkinson disease may represent an important factor counteracting expression of the defects associated with the dopamine denervation.

Growth hormone treatment attenuates age-related changes in hippocampal short-term plasticity and spatial learning

Downregulation of the growth hormone/insulin-like growth factor-1 (IGF-1)axis is one of the most robust biomarkers of mammalian aging. Reports have suggested that age-related changes in secretion of growth hormone and IGF-1 contribute to the development of some peripheral characteristics of the aged phenotype including decreased bone density and lean body mass. Recent work has focused on the identification of a role for age-related reductions in growth hormone and IGF-1 in the development of cognitive impairments associated with aging. In the current study, we report that aged (30 month-old) Brown Norway x Fisher rats demonstrate impairments in spatial learning compared with adult (10 month-old) animals, and that 4-month treatment with growth hormone (300 microg twice daily) attenuates age-related learning impairments. After 6 months of treatment, we employed an extracellular paired-pulse protocol to investigate age-related changes in hippocampal short-term plasticity, and found that aged rats exhibit significantly increased paired-pulse ratios (PPRs) at an interpulse interval of 50 ms compared with adult rats. Long-term growth hormone administration restored PPRs in aged animals to values comparable to those observed in adult controls. Since the age-related changes observed in PPR may result from decreases in hippocampal inhibitory tone mediated by GABA(A) receptors, we assessed GABA(A) receptor subunit expression by immunoblot analysis. Data revealed significant age-related decreases in GABA(A) receptor alpha-1 subunit expression which were attenuated by growth hormone treatment. However, hippocampal levels of the gamma2 subunit, glutamic acid decarboxylase (GAD)(65), and GAD(67) protein concentrations were not significantly affected by age or growth hormone treatment. In conclusion, we suggest that age-related decreases in growth hormone and IGF-1 contribute to cognitive decline, in part, via alterations in hippocampal short-term plasticity. Changes in plasticity may reflect a shift in the balance of hippocampal inhibitory and excitatory function.

Blockade of A2A receptors plus l-DOPA after nigrostriatal lesion results in GAD67 mRNA changes different from l-DOPA alone in the rat globus pallidus and substantia nigra reticulata

Studies in animal models of Parkinson's disease (PD) suggest the potential utility of adenosine A(2A) antagonists in the treatment of this disease. In the present study, unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats received chronic intermittent treatment with the adenosine A(2A) antagonist SCH58261 (5 mg/kg) plus l-DOPA (3 mg/kg) or l-DOPA (6 mg/kg) alone, at doses producing the same intensity of contralateral turning on first administration. Three days after discontinuation of treatments, GABA synthesizing enzyme glutamic acid decarboxylase (GAD67) mRNA was evaluated at cellular level in the globus pallidus (GP) and substantia nigra pars reticulata (SNr) by in situ hybridization. 6-OHDA lesion significantly increased GAD67 mRNA levels in both the GP and SNr ipsilateral to the lesion. Chronic l-DOPA (6 mg/kg), in contrast to SCH58261 plus l-DOPA (3 mg/kg), produced a sensitized contralateral turning indicative of dyskinetic potential and further increased GAD67 mRNA in the GP. In the SNr, a significant decrease in GAD67 mRNA was observed after either treatments. However, while l-DOPA (6 mg/kg) decreased SNr GAD67 mRNA below the intact side, SCH58261 plus l-DOPA (3 mg/kg) brought GAD67 mRNA to the same level of the intact SNr. l-DOPA (3 mg/kg) or SCH58261 (5 mg/kg) alone failed to modify GAD67 mRNA. Results suggest that an increase in GAD67 mRNA in GP and a decrease in SNr might underlie dyskinetic movements induced by chronic l-DOPA. In contrast, the lack of GAD67 mRNA changes in the GP and a less marked inhibition of SNr might correlate with the absence of dyskinetic potential observed after SCH58261 plus l-DOPA.

Dendritic spine plasticity in hippocampus

Most excitatory input in the hippocampus and cerebral cortex impinges on dendritic spines. Alterations in dendritic spine density or shape are suspected to be morphological manifestations of changes in physiology or behavior. The links between spine plasticity and physiological responses have probably been best studied in the hippocampus in the context of changes in the circulating levels of steroid hormones or long-term potentiation. Here we review and present data which indicate that both the age of the preparation and the timing of the analysis can dramatically effect the results obtained. Collectively the data suggest that different cellular and morphological strategies may be utilized at different ages and under different circumstances to effect similar physiological responses or behaviors.

New potential nonsteroidal anti-inflammatory drugs with antileukotrienic effects: influence on model proteins with catalytic activity

Unspecific and side effects caused by interaction with proteins belong to common problems of many structures synthesized as potential medicaments. Possible in vitro interactions with proteins of a group of phenylsulfonyl benzoic acid derivatives (VUFB 19363, 19369, 19370, 19371, and 19760) as new potential anti-inflammatory compounds with anti-leukotrienic activities were studied in the present work. Three purified enzymes were used as model proteins with catalytic activities: Pig heart aspartate aminotransferase (AST, EC 2.6.1.1), alanine aminotransferase (ALT, EC 2.6.1.2), and glutamate decarboxylase (GAD, EC 4.1.1.15) from E. coli. Catalytic activities during incubation of individual compounds (6 x 10(-5) M solution to 5 x 10(-2) M suspension) at 37 degrees C with enzymes served as criteria of stability and function of the proteins. No immediate influence of any compound studied on enzyme activities was found. Aminotransferase activities were not affected even during incubation up to 20 d. In the case of GAD, the compounds VUFB 19369, 19370, 19371, and 19760 had stabilizing influence on GAD activity during incubation at enzyme concentrations of 11.25 and 5.62 mg prot/l. The lack of an immediate effect of compounds and the stability of enzymes during incubation them are favorable and support the prospective of the compounds as potential drugs.

Decrease in GABA synthesis rate in rat cortex following GABA-transaminase inhibition correlates with the decrease in GAD(67) protein

gamma-Aminobutyric acid (GABA) synthesis in the brain is mediated by two major isoforms of glutamic acid decarboxylase, GAD(65) and GAD(67). The contribution of these isoforms to GABA synthesis flux (V(GAD)) is not known quantitatively. In the present study we compared V(GAD) in cortex of control and vigabatrin-treated rats under alpha-chloralose/70% nitrous oxide anesthesia, with total GAD activity and GAD isoform composition (GAD(65) and GAD(67)) measured by enzymatic assay and quantitative immunoblotting. V(GAD) was determined by re-analysis of 13C NMR data obtained ex vivo and in vivo during infusions of [1-13C]glucose using an extension of a model of glutamate-glutamine cycling that included a discrete GABAergic neuronal compartment with relevant interconnecting fluxes. V(GAD) was significantly lower in vigabatrin-treated rats (0.030-0.05 micromol/min per g, P<0.003) compared to the non-treated control group (0.10-0.15 micromol/min per g). The 67-70% decrease in V(GAD) was associated with a 13% decrease in total GAD activity (P=0.01) and a selective 44+/-15% decrease in GAD(67) protein (from 0.63+/-0.10 to 0.35+/-0.08 microg protein/mg tissue, P<0.05); GAD(65) protein was unchanged. The reduction in GAD(67) protein could account for a maximum of approximately 65% of the decrease in V(GAD) in vigabatrin-treated animals suggesting that inhibition of GAD(65) must have also occurred in these experiments, although product inhibition of GAD(67) by increased GABA could play a role. GAD(67) could account for 56-85% of cortical GABA synthesis flux under basal conditions and the entire flux after vigabatrin treatment.

Acute ethanol induction of c-Fos immunoreactivity in pre-pro-enkephalin expressing neurons of the central nucleus of the amygdala

Previous studies have shown that acute ethanol administration induces expression of c-Fos immunoreactivity in the central nucleus of the amygdala (CNA) [S.L. Chang, N.A. Patel, A.A. Romero, Activation and desensitization of Fos immunoreactivity in the rat brain following ethanol administration, Brain Res., 679 (1995) 89-98; M. Morales, J.R. Criado, P.P. Sanna, S.J. Henriksen, F.E. Bloom, Acute ethanol induces c-fos immunoreactivity in GABAergic neurons of the central nucleus of the amygdala, Brain Res., 798 (1998) 333-336; A.E. Ryabinin, J.R. Criado, S.J. Henriksen, F.E. Bloom, M.C. Wilson, Differential sensitivity of c-Fos expression in hippocampus and other brain regions to moderate and low doses of alcohol, Mol. Psychiatry, 2 (1997) 32-43]. We recently showed that over 70% of these c-Fos immunoreactive neurons are GABAergic [M. Morales, J.R. Criado, P.P. Sanna, S.J. Henriksen, F.E. Bloom, Acute ethanol induces c-fos immunoreactivity in GABAergic neurons of the central nucleus of the amygdala, Brain Res, 798 (1998) 333-336]. In the present study, we report that ethanol-induced c-Fos immunoreactivity was mainly confined to neurons that express pro-enkephalin (ENK). In contrast, a small number of c-Fos immunoreactive neurons express corticotrophin releasing factor (CRF). Our results thus provide anatomical evidence indicating that within the amygdala, GABAergic neurons that contain ENK are responsive to acute ethanol exposure.

Effects of bilobalide on gamma-aminobutyric acid levels and glutamic acid decarboxylase in mouse brain

We have previously demonstrated that bilobalide, a constituent of the Ginkgo biloba extract, possesses anticonvulsant activity, and suggested that the mechanism of its anticonvulsant action involves modulation of y-aminobutyric acid (GABA)-related neuronal transmission. This study examined the effects of bilobalide on the level of GABA and glutamate, the activity and the amount of glutamic acid decarboxylase (EC 4.1.1.15), and the function of GABA(A) receptors in the hippocampus, cerebral cortex and striatum of the mouse. GABA levels, glutamic acid decarboxylase activity, and the protein amount of 67 kDa glutamic acid decarboxylase in the hippocampus of mice treated with bilobalide (30 mg/kg, p.o., once a day for 4 days) were significantly higher than those in controls. However, there were no significant differences in glutamate levels or, the number and the dissociation constants of GABA(A) receptors in the hippocampus between control and bilobalide-treated mice. These results suggest that the anticonvulsant effect of bilobalide is due to elevation of GABA levels, possibly through potentiation of glutamic acid decarboxylase activity and enhancement of the protein amount of 67 kDa glutamic acid decarboxylase by bilobalide.

Delay of type I diabetes in high risk, first degree relatives by parenteral antigen administration: the Schwabing Insulin Prophylaxis Pilot Trial

The Schwabing Insulin Prophylaxis Trial is a randomised, controlled pilot study designed to examine whether insulin therapy can delay or prevent the clinical onset of Type I diabetes in high risk first degree relatives of people with the disease. First degree relatives of patients with Type I diabetes, who were aged 4 years or more, had an islet cell antibody (ICA) value more than 20 Juvenile Diabetes Foundation Units (JDF-U), a reduced first phase insulin response (FPI) to an i.v. glucose tolerance test less than the 5th centile, and a normal oral glucose tolerance test were eligible for the trial. Between January 1989 and October 1995, 1736 relatives of patients with Type I diabetes were screened for ICA. We identified 64 cases (3.7%) with ICA values more than 20 JDF-U. Of ICA positive relatives, 17 (27%) had a low FPI and were eligible for enrolment. Of these 14 agreed to participate, of whom 7 were randomised to the treatment group and 7 to the control group. In the treatment group, human insulin was administered i.v. by continuous infusion for 7 days, followed by daily s. c. injections for 6 months. Intravenous insulin infusions were repeated every 12 months. In the treatment group 3 of the 7 individuals (follow-up from time of eligibility: 2.3 to 7.1 years) and in the control group 6 of the 7 untreated individuals (1.7 to 7.1 years) developed clinical diabetes. Life table analysis showed that clinical onset of Type I diabetes was delayed in insulin-treated subjects compared with control subjects (means+/-SEM diabetes-free survival: 5.0+/-0.9 years vs 2.3+/-0.7 years, p < 0.03). Insulin levels after i.v. glucose increased in the first year of intervention therapy. Titres of ICA, and antibodies to glutamic acid decarboxylase, and tyrosine phosphatase-like protein IA2 remained unchanged. These data suggest that insulin prophylaxis can delay the onset of overt diabetes in high risk relatives. This is encouraging in view of 1) the continuing American Diabetes Prevention Trial, which is currently testing the effect of parenteral insulin in a large nation-wide study and 2) the initiation of pilot trials to determine whether new antigen-specific intervention is more effective in delaying the clinical onset of Type I diabetes.

Regulation of GAD expression in rat pancreatic islets and brain by gamma-vinyl-GABA and glucose

Glutamic acid decarboxylase (GAD) is an important autoantigen in insulin-dependent diabetes mellitus (IDDM), but little is known about its regulation and function in islet cells. We investigated the effects of the GABA-transaminase inhibitor gamma-vinyl-GABA (GVG) on GAD expression in rat islets and brain in vitro and in vivo. In islets incubated in high glucose culture medium there was an increase in GAD activity, GAD65 and GAD67 protein levels compared to low-glucose conditions; however, even in high glucose, GVG still significantly suppressed GAD activity and GAD67 expression. Our observations suggest that glucose and GVG act on GAD in islets through different mechanisms. Quantitative immunohistochemistry of pancreatic sections from rats treated with GVG in vivo using novel monoclonal antibodies specific for GAD65 and GAD67, showed a decrease in GAD67 expression (p < 0.005) relative to untreated rats. The effects of GVG on rat pancreatic islets were very similar to those observed in brain of rats treated with GVG in vivo. In homogenates of cerebral tissue from GVG treated rats containing both membrane-bound and soluble protein GAD67 levels were significantly decreased while GAD65 levels were not significantly changed compared to untreated rats. In contrast, in homogenates of cerebral tissues containing only soluble cytosolic protein, GVG-treatment was also significantly found to decrease GAD65 levels. Taken together, these results suggest that GVG potentially could be of use to decrease GAD expression in islet cells and consequently to deviate/inhibit the autoimmune response against the beta cells seen in IDDM.

Cloning and characterization of a tobacco cDNA encoding calcium/calmodulin-dependent glutamate decarboxylase

In plants, gamma-aminobutyric acid (GABA), a major transmitter in the central nervous system in animals, is synthesized by glutamate decarboxylase (GAD), the activity of which is tightly modulated by Ca2+/calmodulin. To study the molecular mechanism of GAD regulation and examine the physiological role of GABA in plants, we isolated and characterized a 1771 bp tobacco cDNA clone, pNtGAD2. The 496 amino acid sequence deduced from pNtGAD2 showed 97, 92, and 81% identity to NtGAD1, petunia, and tomato GAD, respectively. The 26 amino acid sequence within the putative calmodulin binding domain at the carboxy terminus showed a typical alpha-helical structure with hydrophobic and charged amino acid clusters. The pNtGAD2-encoded 56 kDa protein interacted strongly with a monoclonal antibody against the petunia GAD and its GAD activity was stimulated markedly by the addition of exogenous calcium and calmodulin. The molecular sequence of pNtGAD2 and biochemical characteristics of the pNtGAD2-encoded protein confirmed that pNtGAD2 is a clone encoding a functional calmodulin-binding and Ca2+/calmodulin-dependent tobacco glutamate decarboxylase. This result indicates that tobacco plants also have Ca2+/calmodulin-dependent GADs.

The activation of cannabinoid receptors in striatonigral GABAergic neurons inhibited GABA uptake

Cannabinoid receptors (CNRs) in basal ganglia are located on striatal efferent neurons which are gamma-aminobutiric acid (GABA)-containing neurons. Recently, we have demonstrated that CN-induced motor inhibition is reversed by GABA-B, but not GABA-A, receptor antagonists, presumably indicating that the activation of CNRs in striatal outflow nuclei, mainly in the substantia nigra, should be followed by an increase of GABA concentrations into the synaptic cleft of GABA-B receptor synapses. The present study was designed to examine whether this was originated by increasing GABA synthesis and/or release or by decreasing GABA uptake. We analyzed: (i) GABA synthesis, by measuring the activity of glutamic acid decarboxylase (GAD) and GABA contents in brain regions that contain striatonigral GABAergic neurons, after in vivo administration of CNs and/or the CNR antagonist SR141716; (ii) [3H]GABA release in vitro in the presence or the absence of a synthetic CN agonist, HU-210, by using perifusion of small fragments of substantia nigra; and (iii) [3H]GABA uptake in vitro in the presence or the absence of WIN-55,212-2, by using synaptosomes obtained from either globus pallidus or substantia nigra. Results were as follows. Delta9-tetrahydrocannabinol (delta9-THC) and HU-210, did not alter neither GAD activity nor GABA contents in both the striatum and the ventral midbrain at any of the two times tested, thus suggesting that CNs apparently failed to change GABA synthesis in striatonigral GABAergic neurons. A similar lack of effect of HU-210 on in vitro [3H]GABA release, both basal and K+-evoked, was seen when this CN was added to perifused substantia nigra fragments, also suggesting no changes at the level of GABA release. However, when synaptosome preparations obtained from the substantia nigra were incubated in the presence of WIN-55,212-2, a decrease in [3H]GABA uptake could be measured. This lowering effect was specific of striatonigral GABAergic neurons since it was not observed in synaptosome preparations obtained from the globus pallidus. In summary, the activation of CNRs located on striatonigral GABAergic neurons, which primarily access to GABA-B receptor synapses, was accompanied by a reduction in neurotransmitter uptake, thus prolonging the presence of GABA into the synaptic cleft. This mechanism might underly the CN-induced motor inhibition through the potentiation of the inhibitory effect of GABA on neuronal activity, in particular of nigrostriatal dopaminergic neurons.

Antibodies to GAD and glycemic control in recent-onset IDDM

OBJECTIVE

To analyze the effect of antibodies to glutamic acid decarboxylase (GAD65Ab) and islet cells (ICA512Ab) on glycemic control early in IDDM.

RESEARCH DESIGN AND METHODS

GAD65Ab and ICA512Ab were measured twice in 35 patients (10 male, 25 female; age 10-40 years) initially within 2 years of diagnosis and again 1 year later. The glycosylated hemoglobin was measured one to four times each year, and the average glycosylated hemoglobin for the preceding year was calculated each time the antibodies were measured.

RESULTS

The mean HbA1 at the time of the initial evaluation was 8.04 +/- 0.30 (reference range 4.7-7.3% for nondiabetic patients), the average GAD65Ab index was 0.735 +/- 0.306, and the mean ICA512Ab index was 1.94 +/- 0.65. The GAD65Ab index correlated with HbA1 (r = 0.41, P < 0.025), whereas the ICA512Ab index did not (r = 0.13). One year later, the mean GAD65Ab index was 0.94 +/- 0.34, the mean ICA512Ab index was 1.04 +/- 0.40, and the mean HbA1 was 9.03 +/- 0.30. The GAD65Ab index correlated with HbA1 (r = 0.61 P < 0.001), whereas the ICA512Ab index did not (r = -0.06). Stratification of patients into tertiles according to the average GAD65 index revealed, at the follow-up evaluation, that the better glycemic control in the lowest GAD65Ab tertile was accomplished with significantly less insulin (0.43 +/- 0.08 U/kg for the lowest tertile vs. 0.71 +/- 0.09 and 0.64 +/- 0.09 for the middle and highest tertiles, respectively; P < 0.05).

CONCLUSIONS

In summary, patients with IDDM and low GAD65Ab have better glycemic control even though they require less insulin. The ICA512Ab index, however, fails to correlate with glycemia.

Purification and characterization of glutamate decarboxylase from Lactobacillus brevis IFO 12005

Glutamate decarboxylase (GAD) [EC 4.1.1.15] was purified from a cell-free extract of Lactobacillus brevis IFO 12005 by chromatographies on Sephadex G-100, DEAE-Sepharose CL-6B, and Mono Q. About 9 mg of purified GAD was obtained from 90.2 g of wet cells. The purified preparation showed a single protein band on SDS-PAGE. The molecular weights of purified GAD by SDS-PAGE and gel filtration on Superdex 200 were 60,000 and 120,000, respectively, indicating that GAD from L. brevis exists as a dimer. The N-terminal amino acid sequence of the purified GAD was NH2-Met-Asn-Lys-Asn-Asp-Gln-Glu-Gln-Thr-. The optimum pH and temperature of GAD were at pH 4.2 and at 30 degrees C. The GAD activity was increased by the addition of sulfate ions in a dose-dependent manner. The order of effects was as follows: ammonium sulfate > sodium sulfate > magnesium sulfate, indicating that the increase of hydrophobic interaction between subunits causes the increase of GAD activity. The purified GAD reacted only with L-glutamic acid as a substrate and the K(m), kcat, and kcat/K(m) values were 9.3 mM, 6.5 S-1, and 7 x 10(2) M-1 S-1, respectively.

Inhibition of glutamate decarboxylase activity by 3-mercaptopropionic acid has different time course in the immature and adult rat brains

It has been found that the latency of epileptic seizures caused by glutamate decarboxylase (GAD) inhibitor 3-mercaptopropionate (3-MPA) is markedly longer in immature rats than in the adults. Time course of rat brain GAD inhibition was studied in 12-day-old and adult (90-day-old) animals following 3-MPA (70 mg/kg i.p.). GAD activity was determined by quantification of 14CO2 liberated from [1-(14)C]glutamate by supernatant 20,000 x g of brain homogenate prepared from rats killed at different intervals after 3-MPA administration. In adult rats, the enzyme activity decreased significantly by 14.1% even 1 min after 3-MPA administration and was decreasing gradually till the onset of seizures. In immature rats, GAD activity decrease after 1 min was by 41.4% and further decrease was smaller. Comparison of the time profiles of GAD changes in both groups confirmed our findings that in spite of delayed seizure onset, GAD inhibition in immature rats is more pronounced, probably due to immaturity of the blood-brain barrier.

Repeated injections of dizocilpine maleate (MK-801) do not suppress the effects of nigrostriatal dopamine deafferentation on glutamate decarboxylase (GAD67) mRNA expression in the adult rat striatum

The present study examined the effects of glutamate transmission blockade through N-methyl-D-aspartate (NMDA) receptor subtype by repeated administration of dizocilpine maleate (0.2 mg/kg. i.p., twice a day for eight days) alone or in combination with unilateral 6-hydroxydopamine-induced lesion of the nigrostriatal dopaminergic pathway on GABAergic neurons in the adult rat striatum. For this purpose, the expression of the messenger RNA encoding for the 67 kDa isoform of the GABA synthesizing enzyme, glutamate decarboxylase (GAD67 mRNA), was studied in the various conditions by quantitative in situ hybridization. The dizocilpine maleate treatment alone did not induce significant change of GAD67 mRNA levels in the striatum, indicating that NMDA receptors may not have a major role in the transcriptional regulation of GAD67 in the adult rat striatum. As reported previously, the unilateral dopaminergic lesion resulted in marked increases in GAD67 mRNA levels in the ipsilateral striatum. This up-regulation was not significantly affected by the treatment with dizocilpine maleate started 12 days after the unilateral intranigral 6-hydroxydopamine injection. Therefore, NMDA receptors are unlikely to contribute to the dopamine lesion-induced GAD67 mRNA up-regulation in striatal projection neurons. This result is of major interest in comparison with our previous finding that NMDA receptor activation is necessary to maintain the up-regulation of enkephalin expression in the striatum after dopamine lesion.

Glutamic acid decarboxylase in rat olfactory bulb: effect of ovarian steroids or male pheromones

The effect of ovarian steroids and pheromones on the activity of glutamic acid decarboxylase, the enzyme that synthesizes gamma-aminobutyric acid (GABA), was studied in the rat olfactory bulbs. The enzyme activity was measured in the main and accessory olfactory bulbs at 11:00 h and 17:00 h in ovariectomized rats, and in rats treated with ovarian steroids or exposed to male pheromones. The enzyme activity in both bulbs showed a diurnal fluctuation that was not affected in the accessory bulbs by the exposure to pheromones while the rhythm disappeared in the main bulbs. Estrogen and estrogen-progesterone treatments decreased the enzyme activity in both bulbs either in the morning or in the afternoon. The exposure of ovariectomized estrogen-primed rats to male pheromones reversed the effect of estrogen on the enzyme activity in the morning but not in the afternoon. Ovarian hormones plus pheromones prevented the steroid effect only in the morning. These results support the view that in olfactory bulbs, the GABAergic system can be modulated by endocrine and pheromonal factors.

L-DOPA regulates glutamate decarboxylases mRNA levels in MPTP-treated monkeys

The effect of dopaminergic denervation, alone or followed by chronic intermittent L-DOPA administration, on the levels of mRNAs encoding for the two isoforms of the GABA-synthesizing enzyme, glutamate decarboxylase (GAD65 and GAD67), were measured by in-situ hybridization in the caudate and putamen of macaque monkeys. When compared to control monkeys, the level of GAD67 mRNA was increased in the putamen and caudate of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys. On the other hand, GAD65 mRNA labeling in MPTP-treated monkeys was not significantly different from the controls. In MPTP-treated monkeys that received L-DOPA, a significant increase in both GAD67 and GAD65 mRNA levels was measured in the putamen when compared to control or MPTP-treated monkeys. The results suggest that the dyskinetic effect of L-DOPA is paralleled by an increased GABAergic activity in the striatum.

Calmodulin binding to glutamate decarboxylase is required for regulation of glutamate and GABA metabolism and normal development in plants

Glutamate decarboxylase (GAD) catalyzes the decarboxylation of glutamate to CO2 and gamma-aminobutyrate (GABA). GAD is ubiquitous in prokaryotes and eukaryotes, but only plant GAD has been shown to bind calmodulin (CaM). Here, we assess the role of the GAD CaM-binding domain in vivo. Transgenic tobacco plants expressing a mutant petunia GAD lacking the CaM-binding domain (GADdeltaC plants) exhibit severe morphological abnormalities, such as short stems, in which cortex parenchyma cells fail to elongate, associated with extremely high GABA and low glutamate levels. The morphology of transgenic plants expressing the full-length GAD (GAD plants) is indistinguishable from that of wild-type (WT) plants. In WT and GAD plant extracts, GAD activity is inhibited by EGTA and by the CaM antagonist trifluoperazine, and is associated with a CaM-containing protein complex of approximately 500 kDa. In contrast, GADdeltaC plants lack normal GAD complexes, and GAD activity in their extracts is not affected by EGTA and trifluoperazine. We conclude that CaM binding to GAD is essential for the regulation of GABA and glutamate metabolism, and that regulation of GAD activity is necessary for normal plant development. This study is the first to demonstrate an in vivo function for CaM binding to a target protein in plants.

Glutamic acid decarboxylase activity of the olfactory bulb in male rats is influenced by olfactory stimuli and hormonal status

Changes is glutamate decarboxylase activity (GAD) in the main (MOB) and accessory (AOB) olfactory bulbs were determined at 11:00 hr and 17:00 hr in intact odor deprived (IOD) male rats exposed to female olfactory stimuli, and in castrated odor deprived males (COD) either injected with testosterone (T), exposed to female pheromone or injected with T and exposed to pheromone. Grouping IOD males by female olfactory stimulus and time of the day. MOB and AOB-GAD activity changed in the morning and not in the afternoon. In COD males, T injection induced an increased response in MOB-GAD activity 24 hr later either in the morning or in the afternoon, while no changes were seen at 11:00 or 17:00 hr exposure to female odor. In the AOB of COD males, both T administration or exposure to female pheromone, only induced an increase of enzyme activity in the morning. The association of T and female pheromone, decreased morning GAD activity both in the MOB and in the AOB compared with the values of COD males treated with T. In the afternoon this association had no effect compared with MOB, AOB-GAD activity of COD males injected with testosterone. These results indicate that hormonal and olfactory inputs in IOD and COD males are effective in changing olfactory bulb-GAD activity mainly in the morning.

Onset of diabetes with high titer anti-GAD antibody after IFN therapy for chronic hepatitis

A case of hyperglycemia induced by the injection of interferon-alpha was experienced in our hospital. This patient showed a sustained high titer of anti-GAD antibody after the onset of diabetes, suggesting that the involvement of immunological disturbance by IFN induces the onset of the disease. However, the susceptibility and the response of the immune system differs from patient to patient, and only limited destruction of beta-cells in the islet of Langerhans and normalization of glucose tolerance by CSII was induced in this patient.

Estrogen modulation of mRNA levels for the two forms of glutamic acid decarboxylase (GAD) in female rat brain

Two separate forms of glutamic acid decarboxylase, now termed GAD65 and GAD67, are the rate limiting enzymes for synthesis of gamma-aminobutyric acid (GABA). Because of the significance of GABA to neuroendocrine processes, numerous attempts have been made to determine the impact of gonadal steroids on enzyme functioning with inconclusive results. Therefore, we attempted to determine the impact of estradiol on mRNA levels for each form of GAD by quantitative in situ hybridization histochemistry in various brain regions. Ovariectomized rats were treated with estradiol benzoate or oil vehicle on 2 consecutive days and the brains collected on the third day. DNA probes specific for GAD65 and GAD67 were radiolabeled with CTP32 using asymmetric polymerase chain reaction. Results of in situ hybridizations for each probe on alternate sections from the same animals were analyzed for magnocellular preoptic area (McPOA), dorsal medial nucleus of the hypothalamus (DMN), zona incerta (ZI), and midbrain central gray (MCG). In the McPOA, estradiol exerted opposite effects on the frequency distribution of pixels per cell for two GAD mRNA probes, significantly increasing GAD65 (P < .05) and decreasing GAD67 (P < .01; Kolmogorov-Smirnov). In the DMN, estradiol treatment significantly increased GAD67 by 60% (P < .05; two-way ANOVA) but decreased GAD65 mRNA by 73% (P < .01). Note the direction of effects are opposite between McPOA and DMN. In MCG, analysis showed no estradiol effect on GAD mRNA levels/cells, but the proportion of cells expressing detectable levels of GAD65 or GAD67 increased by 33-40% in estradiol-treated rats (chi 2, P < .001).

Response of glutamic acid decarboxylase to glucose but not arginine in islets

This study examined responses of glutamic acid decarboxylase (GAD65) and gamma-aminobutyric acid (GABA) to glucose in pancreatic islets. Islets isolated from Wistar rats were cultured for the three days under different concentrations of glucose (5.6, 11.1 or 16.7 mM) or arginine (2 x 10(-1)-2 x 10(-4) mM) for different periods of time. The expression of GAD65 increased 3.8- and 4.5-fold with the elevation of glucose concentrations as well as the prolongation of culture periods of time, while it did not increase with arginine. GABA content of islets did not change in a range of 5.6 to 16.7 mM glucose. These results suggest that normalization of hyperglycemia would reduce the expression of the autoantigen in islets, which might prevent islets from further destruction. To the contrary, the persistent hyperglycemia could interfere with insulin synthesis not by change of GABA in islets but by the destruction of islets through GAD65 expression.

The effect of cytokines on expression of glutamic acid decarboxylase-65 in cultured islets

Insulin dependent diabetes mellitus (IDDM) is an autoimmune disease characterized by lymphocytic infiltration of the pancreatic islets (insulitis). Cytokines released as part of the insulitis process have been suggested to play an important role in the beta cell lesion of IDDM. A possible diabetogenic effect of cytokines may be mediated by their inducing abnormal expression of islet cell autoantigens. Since glutamic acid decarboxylase-65 (GAD-65) is a target autoantigen in IDDM, we investigated whether the cytokines IL-1 beta, TNF alpha IFN gamma altered islet cell expression of GAD-65 and whether the effect of cytokines on GAD-65 expression was similar to their effect on insulin secretion. We found that: 1) IL-1 beta at low dose (1 U/ml) which stimulated insulin secretion, had no effect on GAD-65 expression, whereas higher doses of IL-1 beta (10, 100, 1000 U/ml) which inhibited insulin secretion, decreased GAD-65 expression. 2) TNF alpha at doses of 10, 100, 1000 U/ml which stimulated insulin secretion had no effect on GAD-65 expression. 3) IFN gamma at doses of 10, 100, 1000 U/ml had no effect on insulin secretion or on GAD-65 expression. 4) In combination, IL-1 beta plus TNF alpha and IFN gamma showed a similar inhibitory effect on GAD-65 expression as IL-1 beta alone. In summary: 1) IL-1 beta dramatically inhibits GAD-65 expression. 2) TNF alpha and IFN gamma have no effect on GAD-65 expression. Of these three cytokines, IL-1 beta is the primary cytokine affecting GAD-65 expression.

Alterations in mRNA levels of D2 receptors and neuropeptides in striatonigral and striatopallidal neurons of rats with neuroleptic-induced dyskinesias

Chronic neuroleptic treatment in rat produces vacuous chewing movements (VCMs), analogous to TD in humans. We hypothesized that these hyperkinetic movements were due to alterations in striatonigral and striatopallidal GABAergic spiny II neurons. Rats were treated for 36 weeks with haloperidol decanoate and withdrawn for 28 weeks. Striatonigral and striatopallidal neurons were assessed using in situ hybridization histochemistry for mRNA levels of D1 and D2 dopamine receptors, preproenkephalin (ENK), prodynorphin (DYN), protachykinin (substance P), and glutamate decarboxylase (GAD67) in the dorsolateral and ventromedial striatum as well as the nucleus accumbens. Rats that did not develop VCMs (-VCM) had increased D2 receptor and DYN mRNA, and reduced substance P mRNA in the dorsolateral striatum. Rats with persistent VCMs (+VCM) had increased D2 receptor, ENK, and DYN mRNA in both striatal regions, and increased ENK and DYN mRNA in the nucleus accumbens, compared with controls. Relative to -VCM rats, however, +VCM rats only had increased ENK mRNA in the nucleus accumbens. Considering the overall pattern of mRNA changes, the data suggest that alterations in both the D1-mediated striatonigral and the D2-mediated striatopallidal pathways play a role in the expression of the VCM syndrome. To the extent that gene expression parallels changes in neuronal activity, this implies that the VCM syndrome is associated with increased activity in both pathways.

Dopamine receptor blockade increases dopamine D2 receptor and glutamic acid decarboxylase mRNAs in mouse substantia nigra

To study the influence of dopaminergic activity on the expression of dopamine D2 receptors and glutamic acid decarboxylase in substantia nigra, mice were treated daily for several days with an irreversibly acting dopamine D1 and dopamine D2 receptor antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) or with a selective irreversible D2 dopamine receptor antagonist fluphenazine-N-mustard. Mice were killed 24 h after the last injection. Dopamine D1 and dopamine D2 receptors were determined by receptor autoradiography, and dopamine D1 and dopamine D2 receptor mRNA and glutamic acid decarboxylase mRNA were determined by in situ hybridization histochemistry. The results showed that treatment with EEDQ, which blocked 80% to 85% of the dopamine D2 and dopamine D1 receptors in substantia nigra, increased the levels of dopamine D2 receptor mRNA in substantia nigra by about 27%. Treatment with fluphenazine-N-mustard, which blocked about 85% of the dopamine D2 receptors in substantia nigra but had no significant effect on dopamine D1 receptors, increased the levels of dopamine D2 receptor mRNA by about 34%. There were no detectable levels of dopamine D1 receptors, increased the levels of dopamine D2 receptor mRNA by about 34%. There were no detectable levels of dopamine D1 receptor mRNA in substantia nigra either in control animals or in animals treated with the dopamine receptor antagonists. Glutamic acid decarboxylase mRNA was expressed in several regions of the mid-brain but only that expressed in substantia nigra was altered by treatment with dopamine receptor antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of GAD expression in islets of Langerhans occurs both at the mRNA and protein level

The expression of the autoantigen glutamate decarboxylase in islets of Langerhans was investigated under different culture conditions, which affect the functional activity of the beta-cell. Using immunoprecipitations and analyses of enzyme activity, an increase in glutamate decarboxylase was detected in rat islets cultured at a glucose concentration of 11 mmol/l compared with those cultured at 5.6 mmol/l glucose. To determine whether the change was induced at the level of mRNA expression, total RNA was extracted from rat islets cultured at 5.6 or 11 mmol/l glucose, reverse transcribed and amplified by the polymerase chain reaction. Comparative quantitation in a phosphor imager revealed a significantly higher (82%, P < 0.005) content of glutamate decarboxylase mRNA in islets cultured at 11 mmol/l glucose. In parallel, human recombinant interleukin-1 beta, and diazoxide were tested for their effects on the expression of glutamate decarboxylase. Islets cultured at 11 mmol/l glucose in the presence of 40 U/ml of interleukin-1 beta, showed a 63% decrease (P < 0.005) in enzyme activity compared with those cultured at 11 mmol/l glucose alone, and similar decreases were noted on analysis of glutamate decarboxylase biosynthesis and mRNA. Islets cultured at 11 mmol/l glucose in the presence of 22.5 mg/ml diazoxide exhibited a significant reduction in enzyme activity (59%; P < 0.001) compared with those cultured at 11 mmol/l glucose only. This reduction, however, was not accompanied by a decrease in the content of glutamate decarboxylase mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

[The GABA-ergic system parameters of the adrenal cortex in animals with normal and stimulated steroidogenesis]

Activity of glutamate decarboxylase, a GABA synthesis enzyme, and intensity of its reception in the adrenal cortex and hypothalamus of guinea pigs and rats with normal and stimulated steroidogenesis was investigated. It has been shown that in the adrenal cortex there is a metabolic system which provides GABA synthesis from glutamate and mechanisms of GABA reception by plasmatic membranes. Mediator synthesis in the adrenal cortex is subjected to seasonal changes, GABA synthesis and reception selectively vary with administration of ACTH, prolactin and maintenance of animals on a diet with an excess of potassium ions.

Sequential neuropathology of dogs treated with vigabatrin, a GABA-transaminase inhibitor

Vigabatrin (Sabril) is a gamma-aminobutyric acid-transaminase (GABA-T) inhibitor that is effective in the treatment of certain types of drug-resistant or uncontrolled epilepsy but is known to cause microscopic vacuolation (intramyelinic edema) in the brains of treated rats, mice, and dogs. The effects of high oral doses (300 mg/kg/day) of vigabatrin administered orally to Beagle dogs were studied during treatment weeks 1-12 and recovery weeks 13, 14, 16, 20, 24, and 28. Emesis, loose stools, and anorexia and 3 drug-related deaths were observed during the first 4 wk of treatment but were virtually nonexistent thereafter because of adaptation to the drug aided by food supplementation. In more sensitive areas of the brain (columns of the fornix, thalamus, and hypothalamus), microscopic quantitative differences between background vacuolation in controls and drug-related vacuolation in treated dogs could be delineated after 4 wk, generally reached highest levels of severity between 8 and 12 wk, and were reversible upon cessation of dosing. Inhibition of brain GABA-T and elevation of brain GABA were noted after 1 wk of treatment. During the course of treatment vigabatrin ranged between 4-17 nmol/ml (plasma) and 42-1,570 nmol/ml [cerebrospinal fluid (CSF)] while CSF GABA concentrations were 4-32 nmol/ml (treated dogs) and 0.1-0.6 nmol/ml (control dogs). Although the cause of vigabatrin-induced microvacuolation is unknown, the results of the study demonstrated that GABA-T inhibition with subsequent GABA elevation occurred within the first week of treatment and was followed by the onset of detectable microvacuolation several weeks later.

Failure of a protein synthesis inhibitor to modify glutamate receptor-mediated neurotoxicity in vivo

The delayed neuronal death (DND) resulting from brief forebrain ischemia has recently been reported to be markedly attenuated by parenteral administration of the reversible protein synthesis inhibitor, anisomycin. Previous work suggests that ischemia-induced DND is mediated by glutamate acting at one or more glutamate receptors, since glutamate receptor antagonists have been reported to reduce ischemia-induced DND. Consequently, we tested whether anisomycin could modify DND induced by direct intracerebral administration of the excitotoxins, N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methylisoxasole (AMPA) or kainic acid. Anisomycin, administered parenterally, in multiple doses did not alter DND induced by any of these excitotoxins, nor did combined parenteral and direct intracerebral injection of anisomycin protect against DND induced by AMPA. Thus, neurotoxicity induced by direct intracerebral administration of NMDA, AMPA or kainic acid does not appear to require de novo protein synthesis, and, therefore, is not likely to be mediated by the expression of a programmed cell death cascade.

[Effect of pyridoxal phosphate on gamma-aminobutyric acid metabolism in different sections of the brain in irradiated animals]

A study was made of the effect of X-rays (4,5 Gy) and pyridoxal phosphate (3 mg/kg, v/v) on the activity of pyridoxal enzymes of GABA metabolism (e.g. glutamate decarboxylase, E.C. 4.1.1.15) and aminobutyrate aminotransferase (GABA-T, E.C. 2.6.1.19), as well as on GABA and glutamate content of the hemisphere cortex, brain stem and cerebellum of rabbits 6 and 10 days following irradiation and injection of a coenzyme. The height of the radiation sickness in rabbits was characterized by the manifest changes in glutamate decarboxylase and GABA-T activity, as well as in GABA and glutamate content of various brain parts differing in the structural and functional functions. The administration of pyridoxal phosphate produced pronounced activation of glutamate decarboxylase, particularly 6 days after irradiation and administration of the co-enzyme, and, to a lesser extent, influenced GABA-T function. Pyridoxal phosphate favored maintaining the GABA level above the control level in the hemisphere cortex and brain stem 6 and 10 days after exposure. The injection of pyridoxal phosphate did not normalize the glutamate content of the brain parts 6 days after exposure, but favored the normalization of GABA-T activity on day 10.