Effect of an extract of Ginkgo biloba on triethyltin-induced cerebral edema

Pharmacologic treatments in preclinical tinnitus models with special focus on Ginkgo biloba leaf extract EGb 761®

Tinnitus is defined as the perception of sound in the absence of external acoustic stimuli. Frequent comorbidities or associated factors are depression, anxiety, concentration problems, insomnia, resignation, helplessness, headache, bruxism, or social isolation, just to name a few. Although many therapeutic approaches have already been tested with varying success, there still is no cure available for tinnitus. The search for an effective treatment has been hampered by the fact that the mechanisms of tinnitus development are still not fully understood, although several models are available and discussed in this review. Our review will give a brief overview about preclinical models, presenting the heterogeneity of tinnitus sub-types depending on the different inner ear and brain structures involved in tinnitus etiology and pathogenesis. Based on these models we introduce the different target structures and transmitter systems implicated in tinnitus development and provide an extensive overview on preclinical drug-based therapeutic approaches that have been explored in various animal models. As the special extract from Ginkgo biloba leaves EGb 761® has been the most widely tested drug in both non-clinical tinnitus models as well as in clinical trials, a special focus will be given to EGb 761®. The efficacy of terpene lactones, flavone glycosides and proanthocyanidines with their distinct contribution to the overall efficacy profile of the multi-constituent drug EGb 761® will be discussed.

Bilobalide protects against ischemia/reperfusion-induced oxidative stress and inflammatory responses via the MAPK/NF-휅B pathways in rats

Background

Clinically, skeletal muscle ischemia/reperfusion injury is a life-threatening syndrome that is often caused by skeletal muscle damage and is characterized by oxidative stress and inflammatory responses. Bilobalide has been found to have antioxidative and anti-inflammatory effects. However, it is unclear whether bilobalide can protect skeletal muscle from ischemia/reperfusion injury.

Methods

The effects of bilobalide on ischemia/reperfusion-injured skeletal muscle were investigated by performing hematoxylin and eosin staining and assessing the wet weight/dry weight ratio of muscle tissue. Then, we measured lipid peroxidation, antioxidant activity and inflammatory cytokine levels. Moreover, Western blotting was conducted to examine the protein levels of MAPK/NF-휅B pathway members.

Results

Bilobalide treatment could protected hind limb skeletal muscle from ischemia/reperfusion injury by alleviating oxidative stress and inflammatory responses via the MAPK/NF-휅B pathways.

Conclusions

Bilobalide may be a promising drug for I/R-injured muscle tissue. However, the specific mechanisms for the protective effects still need further study.

Protective effects of Ginkgo biloba L. against natural toxins, chemical toxicities, and radiation: A comprehensive review

Nowadays in our developing and industrial world, humans' health or even their life is threatened by exposure to poisons. In this situation, detecting a protective compound could be helpful and interesting. In the present article, we collected and reviewed all studies, which have been conducted so far about the protective effects of Ginkgo biloba L. (GB), one of the most ancient medicinal tree species, against toxicities induced by chemical toxic agents, natural toxins, and also radiation. In overall, investigations showed that GB exerts the antioxidant, antiinflammatory, antiapoptotic, and antigenotoxicity effects in different toxicities. There are also some special mechanisms about its protective effects against some specific toxic agents, such as acetylcholine esterase inhibition in the aluminium neurotoxicity or membrane-bond phosphodiesterase activation in the triethyltin toxicity. Ginkgolide A was the most investigated active ingredient of G. biloba leaf extract as a protective compound against toxicities, which had the similar effects of total extract. A few clinical studies have been conducted in this field, which demonstrated the beneficial effects of GB against toxic agents. However, the promising effects of this valuable herbal extract will practically remain useless without carrying out more clinical studies and proving its effects on human beings.

Neuroprotective effects of bilobalide on cerebral ischemia and reperfusion injury are associated with inhibition of pro-inflammatory mediator production and down-regulation of JNK1/2 and p38 MAPK activation

BACKGROUND

Mitogen-activated protein kinase (MAPK) signaling pathways are implicated in inflammatory and apoptotic processes of cerebral ischemia and reperfusion (I/R) injury. Hence, MAPK pathways represent a promising therapeutic target. Exploring the full potential of inhibitors of MAPK pathways is a useful therapeutic strategy for ischemic stroke. Bilobalide, a predominant sesquiterpene trilactone constituent of Ginkgo biloba leaves, has been shown to exert powerful neuroprotective properties, which are closely related to both anti-inflammatory and anti-apoptotic pathways. We investigated the neuroprotective roles of bilobalide in the models of middle cerebral artery occlusion and reperfusion (MCAO/R) and oxygen-glucose deprivation and reoxygenation (OGD/R) of cerebral I/R injury. Moreover, we attempted to confirm the hypothesis that its protection effect is via modulation of pro-inflammatory mediators and MAPK pathways.

METHODS

Male Sprague-Dawley rats were subjected to MCAO for 2 h followed by reperfusion for 24 h. Bilobalide was administered intraperitoneally 60 min before induction of middle cerebral artery occlusion (MCAO). After reperfusion, neurological deficit scores, infarct volume, infarct weight, and brain edema were assessed. Ischemic penumbrae of the cerebral cortex were harvested to determine superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide, TNF-α, interleukin 1β (IL-1β), p-ERK1/2, p-JNK1/2, and p-p38 MAPK concentration. Similarly, the influence of bilobalide on the expression of nitric oxide, TNF-α, IL-1β, p-ERK1/2, p-JNK1/2, and p-p38 MAPK was also observed in an OGD/R in vitro model of I/R injury.

RESULTS

Pretreatment with bilobalide (5, 10 mg/kg) significantly decreased neurological deficit scores, infarct volume, infarct weight, brain edema, and concentrations of MDA, nitric oxide, TNF-α, IL-1β, and increased SOD activity. Furthermore, bilobalide (5, 10 mg/kg) pretreatment significantly down-regulated both p-JNK1/2 and p-p38 MAPK expression, whereas they had no effect on p-ERK1/2 expression in the ischemic penumbra. Supporting these observations in vivo, pretreatment with bilobalide (50, 100 μM) significantly down-regulated nitric oxide, TNF-α, IL-1β, p-JNK1/2, and p-p38 MAPK expression, but did not change p-ERK1/2 expression in rat cortical neurons after OGD/R injury.

CONCLUSIONS

These data indicate that the neuroprotective effects of bilobalide on cerebral I/R injury are associated with its inhibition of pro-inflammatory mediator production and down-regulation of JNK1/2 and p38 MAPK activation.

Preventive and curative effects of etifoxine in a rat model of brain oedema

1. The aim of the present study was to test the hypothesis that increasing GABAergic neurotransmission is involved in the prevention or treatment of brain oedema. The study was conducted in the well-established rat triethyltin (TET) model of brain oedema and examined the effects of etifoxine, a compound that increases GABAergic neurotransmission through multiple mechanisms, including neurosteroid synthesis. 2. Daily oral administration of 3 mg/kg per day TET for 5 consecutive days strongly perturbed rat behaviour and induced reproducible cerebral oedema. Coadministration of etifoxine (2 x 25 or 2 x 50 mg/kg per day, p.o.) over the 5 days of TET treatment blocked the development of brain oedema and the increase in brain sodium content induced by TET, as well as reducing the increase in brain chloride content. Moreover, etifoxine inhibited the decrease in bodyweight, the neurological deficit and the altered locomotor activity induced by TET. At a lower dose (2 <--> 10 mg/kg per day, p.o.), etifoxine did not have any preventive effects. 3. To examine the curative effects of etifoxine, it was administered from the 4th day of TET treatment for 5 consecutive days, when brain oedema was already established. In these experiments, etifoxine (2 <--> 50 mg/kg per day, p.o.) significantly reduced cerebral oedema and the outcomes induced by TET treatment. Moreover, etifoxine reduced the mortality in response to TET treatment. 4. In conclusion, because etifoxine has a good safety profile as an anxiolytic, the results of the present study suggest that it is worth further clinical investigation as a neuroprotectant.

Bilobalide inhibits 6-OHDA-induced activation of NF-kappaB and loss of dopaminergic neurons in rat substantia nigra

AIM

To investigate the effects of bilobalide on the activation of NF-kappaB, and apoptosis of dopaminergic neurons induced by 6-hydroxydopamine (6-OHDA).

METHODS

A rat model of Parkinson's disease was produced with a unilateral infusion of 6-OHDA (8 mug) into the substantia nigra par compact. Bilobalide was administered 5, 10, and 20 mg/kg (ip) once a day for 7 d, starting 6 d prior to the 6- OHDA infusion. The rats were subjected to locomotor activity and rotational behavior testing 2 or 3 weeks after the 6-OHDA infusion. The expressions of tyrosine hydroxylase (TH) and NF-kappaB p65 were examined by immunofluorescence. The loss of dopaminergic neurons was detected by Nissl's staining. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling was used to identify apoptosis.

RESULTS

The behavioral changes due to 6-OHDA were significantly restored by bilobalide pretreatment. Bilobalide inhibited the 6-OHDA-induced loss of TH-positive neurons, decreased the activation of NF-kappaB, and protected dopaminergic neurons from apoptosis remarkably.

CONCLUSION

NF-kappaB activation contributes to the 6-OHDA-induced loss of dopaminergic neurons, and the inhibition of the NF-kappaB pathway is likely to be involved in the neuroprotective effect of bilobalide.

Efficacy of moclobemide in a rat model of neurotoxicant-induced edema

The potent antidepressant effect of moclobemide, a selective and reversible type A monoamine oxidase (MAO) inhibitor, is clinically established. In view of the ongoing debate on the neuroprotective properties of MAO inhibitors, the present study was undertaken to further define the protective effect of moclobemide in a rat model of neurotoxicant-induced edema. In this model, daily oral triethyltin (TET) administration for 5 consecutive days strongly perturbed the rat behaviour and induced a cerebral edema at the 5th day. Oral coadministration of moclobemide (2 × 100 mg·kg–1·day–1) with TET blocked the development of brain edema and the increase in the cerebral chloride content induced by TET. Moreover, moclobemide reduced the increase in the cerebral sodium content and attenuated the neurological deficit. In conclusion, moclobemide possesses potent protective properties in this rat model of cerebral edema, suggesting potential clinical utility as a neuroprotectant.

Bilobalide prevents ischemia-induced edema formation in vitro and in vivo

EGb761, a standardized extract of Ginkgo biloba, has neuroprotective properties in animal models of ischemia, an activity that is partially attributed to its constituent, bilobalide. EGb761 has also been reported to inhibit edema formation induced by toxins such as triethyltin. The goal of this study was to test the activity of pure bilobalide to prevent edema formation in models of ischemia. Oxygen-glucose deprivation (OGD) in rat hippocampal slices served as a model of in vitro-ischemia. OGD caused cellular edema formation as indicated by an increase of slice water contents in 30 min. Bilobalide (1-10 microM) reduced slice water contents in ischemic slices in a concentration-dependent manner. As a model of in vivo-ischemia, we performed middle cerebral artery occlusion (MCAO) in mice. Permanent MCAO caused cell death and swelling of the ischemic hemisphere within 24 h. Pretreatment of the mice with bilobalide (10 mg/kg i.p.) reduced infarct area by 43% (as judged by 2,3,5-triphenyl-tetrazolium chloride (TTC) staining) and edema formation by 70% (as judged by hemispheric enlargement). In parallel experiments, pretreatment with bilobalide also reduced forebrain water contents in the ischemic hemisphere by 57%. As an alternative model of brain edema formation, we used water intoxication to increase brain water content; bilobalide, was, however, inactive in this model. We conclude that bilobalide strongly and specifically attenuates edema formation in models of brain ischemia in vitro and in vivo. Bilobalide may be therapeutically effective in brain edema which occurs secondarily to large hemispheric stroke and traumatic brain injury in humans.

Water homeostasis in the brain: basic concepts

The mammalian CNS is separated from the blood by tight junctions, collectively termed the blood-brain barrier (BBB). This imposes unique features of solvent and water movement into and out of the CNS. The basic equations for water fluxes driven by osmotic gradients are presented. The anatomy of the BBB and the physiology of the transport processes for cerebrospinal fluid production, extracellular fluid production and intercellular water and solute transport are then described. A quantitative analysis of the need for aquaporin-based water movements to accompany the known rates of CSF production is also presented. Finally, the mechanisms and roles of cellular and vasogenic edema in the CNS, especially in relation to aquaporins, are described.

Effects of mexiletine, ginkgo biloba extract (EGb 761), and their combination on experimental head injury

Lipid peroxidation (LP) and brain edema are important factors that produce tissue damage in head injury. The purpose of this study was to investigate the effect of mexiletine, gingko biloba extract (EGb 761), and their combination on LP and edema after moderate head trauma. Forty rats were randomly and blindly divided into four groups of ten animals each: control group (bolus injection of physiological saline), mexiletine group (50 mg/kg per injection), EGb 761 group (30 mg/kg per injection), and mexiletine plus EGb 761 group (50 mg/kg and 30 mg/kg per injection, respectively). The injections were given intraperitoneally at 1 h, 9 h, and 17 h after trauma. Twenty-four hours after injury, the rats were killed, and malondialdehyde (MDA) levels and brain water content were determined. Rats treated with mexiletine, EGb 761, and mexiletine plus EGb 761 had significantly lower MDA levels than the control group (P<0.01). The lowest MDA levels were measured in the mexiletine plus EGb 761 group. However, there was no significant difference in brain water content between treated groups and the control group (P>0.05). These findings show the usefulness of mexiletine and its combination with EGb 761 as a cerebroprotective agent in this model of experimental head injury.

A pilot trial of piracetam and ginkgo biloba for the treatment of cocaine dependence

BACKGROUND

Chronic cocaine use is associated with cognitive deficits that may reduce the effectiveness of psychosocial treatment and promote relapse in newly abstinent cocaine-dependent patients. Nootropic agents, such as piracetam and ginkgo biloba, may improve cognitive function and reduce the incidence of relapse in these patients.

METHODS

This was a 10-week, double-blind, placebo-controlled pilot trial involving 44 cocaine-dependent subjects. Subjects received either piracetam (4.8 g/day), ginkgo biloba (120 mg/day), or placebo. Subjects were required to attain abstinence from cocaine during a 2-week baseline phase demonstrated by providing at least one benzoylecgonine (BE)-negative urine toxicology screen. Outcome measures included treatment retention, urine toxicology screens, Clinical Global Impression (CGI) scores, and results from the Addiction Severity Index (ASI).

RESULTS

Ginkgo biloba was not superior to placebo in any outcome measure. Piracetam was associated with more cocaine use and lower CGI scores compared to placebo.

CONCLUSIONS

Neither piracetam nor ginkgo biloba appears to be a promising medication for the treatment of cocaine dependence.

A double-blind, placebo-controlled, randomized trial of Ginkgo biloba extract EGb 761 in a sample of cognitively intact older adults: neuropsychological findings

There appears to be an absence of large-scaled clinical trials that have examined the efficacy of Ginkgo biloba extract on the neuropsychological functioning of cognitively intact older adults. The importance of such clinical research appears paramount in light of the plethora of products containing Ginkgo biloba that are currently being widely marketed to predominantly cognitively intact adults with claims of enhanced cognitive performances. The purpose of this research was to conduct the first known, large-scaled clinical trial of the efficacy of Ginkgo biloba extract (EGb 761) on the neuropsychological functioning of cognitively intact older adults. Two hundred and sixty-two community-dwelling volunteers (both male and female) 60 years of age and older, who reported no history of dementia or significant neurocognitive impairments and obtained Mini-Mental State Examination total scores of at least 26, were examined via a 6-week, randomized, double-blind, fixed-dose, placebo-controlled, parallel-group, clinical trial. Participants were randomly assigned to receive either Ginkgo biloba extract EGb 761(n = 131; 180 mg/day) or placebo (n = 131) for 6 weeks. Efficacy measures consisted of participants' raw change in performance scores from pretreatment baseline to those obtained just prior to termination of treatment on the following standardized neuropsychological measures: Selective Reminding Test (SRT), Wechsler Adult Intelligence Scale-III Block Design (WAIS-III BD) and Digit Symbol-Coding (WAIS-III DS) subtests, and the Wechsler Memory Scale-III Faces I (WMS-III FI) and Faces II (WMS-III FII) subtests. A subjective Follow-up Self-report Questionnaire was also administered to participants just prior to termination of the treatment phase. Analyses of covariance indicated that cognitively intact participants who received 180 mg of EGb 761 daily for 6 weeks exhibited significantly more improvement on SRT tasks involving delayed (30 min) free recall (p < 0.04) and recognition (p < 0.01) of noncontextual, auditory-verbal material, compared with the placebo controls. The EGb 761 group also demonstrated significantly greater improvement on the WMS-III FII subtest assessing delayed (30 min) recognition (p < 0.025) of visual material (i.e. human faces), compared with the placebo group. However, based on the significant difference (p < 0.03) found between the two groups' pretreatment baseline scores on the WMS-III FII, this result should be interpreted with caution. An examination of the participants' subjective ratings of their overall abilities to remember by treatment end on the Follow-up Self-report Questionnaire also revealed that significantly more (p = 0.05) older adults in the EGb 761 group rated their overall abilities to remember by treatment end as 'improved' compared with the placebo controls. Overall, the results from both objective, standardized, neuropsychological tests and a subjective, follow-up self-report questionnaire provided complementary evidence of the potential efficacy of Ginkgo biloba EGb 761 in enhancing certain neuropsychological/memory processes of cognitively intact older adults, 60 years of age and over.

Mitochondrial respiratory chain as a new target for anti-ischemic molecules

Vascular diseases like thrombosis, myocardial infarction, cerebral ischemia or chronic venous insufficiency affect a high proportion of the population. They are all associated with more or less pronounced ischemic conditions. We have previously shown that some venotropic drugs display an anti-ischemic activity, i.e. they prevent the hypoxia-induced decrease in ATP content in cultured cells. The effect is due to the fact that these molecules maintain mitochondrial respiratory activity during hypoxia. Among them is bilobalide. Starting from the 3D structure of bilobalide, we designed new molecules presenting the same chemical features. They were synthesized and tested for their biological activity. As the parent compound, two of them, malonic acid dicyclopent-2-enyl ester (MRC2P119) and 2-oxo-3-oxa-bicyclo[3.1.0]hexane-1-carboxylic acid allyl ester (MRC2P57), were able to markedly increase the respiratory control ratio of isolated mitochondria. They are able to prevent the inhibition of complex I by amytal and of complex III by myxothiazol, but not the uncoupling of the respiration by carbonylcyanide m-chlorophenyl hydrazone (m-CCP). Moreover, MRC2P119 and MRCP2P57 inhibit, in a dose-dependent way, the hypoxia-induced decrease in ATP content in endothelial cells as well as the subsequent activation of these cells as evidenced by an inhibition of the increase in neutrophil adherence to the endothelial cells induced by hypoxia. Finally, MRC2P119 prevent the hypoxia- and the hypoxia-reoxygenation-induced decrease in viability of SH-SY5Y neuroblastoma cells. In conclusion, we identified two new molecules, which display anti-ischemic properties when tested in vitro on endothelial and neuronal cell types. This anti-ischemic activity is probably due to a protection of complexes I and III of the mitochondrial respiratory chain.

Protection of mitochondrial respiration activity by bilobalide

Mitochondria alteration is an early event in ischemia-induced damage, and its prevention improves tissue survival upon reperfusion. Adenine translocase and complex I activities are rapidly affected by ischemia. Ginkgo biloba extract demonstrates anti-ischemic properties attributable to the terpenoid fraction, mainly due to the presence of bilobalide. The mechanism of the protection afforded by bilobalide is not yet known. In this work, the effects of bilobalide on mitochondrial respiration were investigated. Mitochondria isolated from rats treated with bilobalide (2 to 8 mg/kg) showed a dose-dependent increase in the respiratory control ratio, due to a lower oxygen consumption during state 4. Bilobalide also decreased the sensitivity of oxygen consumption to inhibition of complex I by Amytal or to inhibition of complex III by antimycin A or myxothiazol. There was no protection of complexes IV and V. It also increased the activity of complex I but not of adenine translocase. Similar effects were also obtained in vitro when control mitochondria were preincubated for 1 hr with 0.8 microg/mL bilobalide. Treatment of the rats with 8 mg/kg bilobalide also prevented the ischemia-induced decrease in state 3 of the mitochondrial respiration and thus the decrease in RCR. The protective effect of bilobalide on cellular ATP content observed under ischemic conditions can be correlated with the above observations. By protecting complex I and III activities, bilobalide allows mitochondria to maintain their respiratory activity under ischemic conditions as long as some oxygen is present, thus delaying the onset of ischemia-induced damage. This mechanism provides a possible explanation for the anti-ischemic properties of bilobalide and of Ginkgo biloba extract in therapeutic interventions.

Glial cells in neurotoxicity development

Neuroglial cells of the central nervous system include the astrocytes, oligodendrocytes, and microglia. Their counterparts in the peripheral nervous system are the Schwann cells. The term neuroglia comes from an erroneous concept originally coined by Virchow (1850), in which he envisioned the neurons to be embedded in a layer of connective tissue. The term, or its shortened form--glia, has persisted as the preferred generic term for these cells. A reciprocal relationship exists between neurons and glia, and this association is vital for mutual differentiation, development, and functioning of these cell types. Therefore, perturbations in glial cell function, as well as glial metabolism of chemicals to active intermediates, can lead to neuronal dysfunction. The purpose of this review is to explore neuroglial sites of neurotoxicant actions, discuss potential mechanisms of glial-induced or glial-mediated central nervous system and peripheral nervous system damage, and review the role of glial cells in neurotoxicity development.

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.

Phospholipid breakdown and choline release under hypoxic conditions: inhibition by bilobalide, a constituent of Ginkgo biloba

A marked increase of choline release from rat hippocampal slices was observed when the slices were superfused with oxygen-free buffer, indicating hypoxia-induced hydrolysis of choline-containing phospholipids. This increase of choline release was suppressed by bilobalide, an ingredient of Ginkgo biloba, but not by a mixture of ginkgolides. The EC50 value for bilobalide was 0.38 microM. In ex vivo experiments, bilobalide also inhibited hypoxia-induced choline release when given p.o. in doses of 2-20 mg/kg 1 h prior to slice preparation. The half-maximum effect was observed with 6 mg/kg bilobalide. A similar effect was noted after p.o. administration of 200 mg/kg EGb 761, a ginkgo extract containing approximately 3% of bilobalide. We conclude that ginkgo extracts can suppress hypoxia-induced membrane breakdown in the brain, and that bilobalide is the active constituent for this effect.

Current concepts of brain edema. Review of laboratory investigations

Klatzo's classification of brain edema into two types, vasogenic and cytotoxic, has been in general use since 1967. The former involves overall brain swelling due to fluid entry from the vasculature because of openings in the blood-brain barrier (BBB), whereas the latter refers to cell swelling without any loss of the normal impermeability of the BBB. This review principally covers new work that identifies the intracellular swelling of astrocytes as a major form of cytotoxic edema seen in many different kinds of brain injury. The term edema should be retained because of its familiarity; however, because such intracellular swelling is usually not a response to toxins, it is suggested that the term cellular edema is preferable to cytotoxic edema. The difficulties involved in measuring cellular edema clinically are discussed, and the belief that a "pure" form of either edema is unlikely to exist. It is emphasized that the mechanisms and direct consequences of vasogenic and cellular edema are so different that the connection is mainly semantic. Studies conducted in vitro have identified several potentially damaging secondary consequences of astrocytic swelling. One of the most important of these seems likely to be the increased release of excitatory amino acids from swollen astrocytes. Potential mechanisms for inhibition of the increased release of amino acids have been identified in vitro and could prove therapeutically useful.

Effects of Ginkgo biloba constituents related to protection against brain damage caused by hypoxia

The purpose of the present study was to approach the compound(s) responsible for the beneficial effects of an extract of Ginkgo biloba leaves (EGB) on animals subjected to hypoxia. In this first approach we compared the effects of the flavone and the non-flavone fraction of EGB with those of the whole extract on mice in lethal hypoxia (3.5% O2), on brain energy metabolism of artificially ventilated rats inspiring 7% O2, and on local cerebral blood flow (LCBF) of normoxic rats. The latter two experimental settings should also extend the knowledge about the underlying mechanisms of the antihypoxidotic actions. EGB as well as its non-flavone fraction considerably prolonged the survival time of mice under lethal hypoxia. EGB retarded the breakdown of brain energy metabolism in the hypoxic artificially ventilated rat. A corresponding effect was exerted by the non-flavone fraction while the flavone fraction even worsened the metabolic state. The non-flavone fraction increased LCBF in the majority of 35 examined brain regions; a similar effect could be seen after EGB-treatment, while the flavone fraction caused only minor alterations of LCBF. We conclude that the non-flavone fraction of EGB carries the antihypoxidotic activity. Metabolic effects are suggested to cause this activity. Further studies are necessary to elucidate the effective compound within this fraction.

Ultrastructural features of a brain injury model in cat. I. Vascular and neuroglial changes and the prevention of astroglial swelling by a fluorenyl (aryloxy) alkanoic acid derivative (L-644,711)

We present qualitative and quantitative ultrastructural observations on the changes induced in neuroglia and blood vessels of gray matter of cat brain by an experimental acceleration-deceleration injury which, when used alone, causes negligible morbidity and mortality, but, when combined with systemic hypoxia, leads to coma and delayed death in approximately 50% of experimental subjects. An increase in the proportion of neuropil occupied by astrocytic cytoplasm is detectable qualitatively in layer Vb of pericruciate cortex 20 min after injury without hypoxia, and is maximal (22%, as measured morphometrically, vs 11.4% in controls) 40 min afterward. Near-normal values (14.1%) are obtained 100 min following the insult. If trauma is succeeded 40 min later by a 60-min period of hypoxia, there is prolongation of astrocytic edema and other neuroglial accompaniments of the traumatic lesion, such as aggregation of nuclear nucleoprotein granules and, in astrocytes, fusion of rosette ribosomes and enlargement of mitochondria. A decrease in luminal area occurs in capillaries 40 min after trauma applied alone. Hypoxia without trauma leads to a significant increase in capillary luminal area, which, however, is abolished when trauma precedes the hypoxic interlude. Intravenous injection of a non-diuretic, fluorenyl derivative (L-644,711) of (aryloxy)alkanoic acid loop diuretics, completely prevents the astrocytic swelling ordinarily present 40 min after acceleration-deceleration injury. Also, L-644,711 improves mortality and morbidity scores in cats subjected to trauma with hypoxia. We suggest that astroglial swelling may be a critical step in the evolving pathology of this head injury model and its prevention, as by L-644,711 administration, may have relevance to the treatment of cerebral edema in human head injury and other clinical disorders accompanied by astrocytic swelling.

Stimulation of astrocytes affects cytotoxic brain edema

Cytotoxic brain edema has been produced in rats by subacute intoxication with triethyltin (TET). Some animals were allowed to recover spontaneously, others were post-treated with an extract of Ginkgo biloba (EGB) for 1 to 4 weeks, beginning 3 days after intoxication was stopped. The time course of the resolution of the edema was studied biochemically and morphologically by light microscopy, histochemistry and electron microscopy (EM). Morphometric evaluation showed that the spontaneous reabsorption of TET-induced edema was very slow: it was evident only 2 weeks after ending TET administration and it required more than 4 weeks to be completed. EGB therapy markedly decreased the vacuolation, as well as the abnormal levels of water and sodium contents, 1 week after beginning the treatment. Less influence of EGB was observed at the later stages. During spontaneous recovery, astroglial cells in the edematous white matter of TET-intoxicated animals showed short and swollen processes containing few organelles, low levels of NADH- and NADPH-tetrazolium reductase activities and glial fibrillary acidic protein (GFAP)-immunofluorescence for about 2 weeks. During EGB therapy the astrocytes regained their cellular processes, containing intense oxidative enzyme activities and GFAP-immunofluorescence as early as after 1 week of treatment. In the EM, astrocytes often appeared hypertrophic, surrounding myelin vacuoles and displaying phagocytosis of myelin debris. We conclude that EGB can accelerate the reabsorption of TET-induced cerebral edema and improve the astroglial reaction.