Xiao-Yuan Lian

Fructose-1,6-Bisphosphate Has Anticonvulsant Activity in Models of Acute Seizures in Adult Rats

A variety of observations suggest that decreasing glycolysis and increasing levels of reduced glutathione, generated by metabolism of glucose through the pentose phosphate pathway, would have an anticonvulsant effect. Because fructose-1,6-bisphosphate (F1,6BP) shifts the metabolism of glucose from glycolysis to the pentose phosphate pathway, it was hypothesized to have anticonvulsant activity. The anticonvulsant activity of F1,6BP was determined in rat models of acute seizures induced by pilocarpine, kainic acid, or pentylenetetrazole. The efficacy of F1,6BP was compared with that of 2-deoxyglucose (2-DG; an inhibitor of glucose uptake and glycolysis), valproic acid (VPA), and the ketogenic diet. One hour before each convulsant, Sprague Dawley rats received either saline (as seizure controls), F1,6BP (0.25, 0.5 or 1 g/kg), 2-DG (0.25 or 0.5 g/kg), or VPA (0.3 g/kg). Additional animals received the ketogenic diet (starting at 20 or 60 d old). Time to seizure onset, seizure duration, and seizure score were measured in each group. F1,6BP had dose-dependent anticonvulsant activity in all three models, whereas VPA had partial efficacy. 2-DG was only effective in the pilocarpine model. The ketogenic diet had no effect in these models. F1,6BP was also partially effective when given at the first behavioral seizure after pilocarpine. Administration of sodium lactate, which bypasses the block in the glycolytic pathway, abolished the anticonvulsant activity of 2-DG in the pilocarpine model, but only decreased the efficacy of F1,6BP. These data demonstrate that F1,6BP has significant anticonvulsant efficacy.

Astrocytes contribute to regulation of extracellular calcium and potassium in the rat cerebral cortex during spreading depression

This study used spreading depression (SD), which is characterized by redistribution of ions, to examine the role of astrocytes in the regulation of extracellular potassium ([K+]o) and calcium ([Ca2+]o) levels. Recurrent spreading depression episodes were induced by application of 3 M potassium chloride to the cortex of adult anesthetized rats while monitoring the extracellular direct current (DC) potential shifts and changes in [K+]o or [Ca2+]o 6-7 mm away. The reversible glial toxins, fluorocitrate (FC) and fluoroacetate (FA), were injected locally into the cortex at doses that are selective for reducing glial function. The peak changes and area under the curve for [K+]o and [Ca2+]o, recovery rate for [K+]o, and interval between spreading depression episodes were measured before and at various times after administration of the toxins. Both fluorocitrate and fluroacetate slowed the recovery of the [K+]o and altered the recovery of the [Ca2+]o. Local injection of glutamate uptake inhibitors or barium had no effect on the peak changes in [K+]o or the rate of recovery of the [K+]o. The slowing of the recovery rate is consistent with the hypothesis that glial cells play a role in the return of [K+]o to baseline after spreading depression in the cortex in vivo. The change in movement of calcium after administration of FC suggests that astrocytes normally extrude calcium during spreading depression, resulting in rapid recovery of the levels of [Ca2+]o with an overshoot. These findings demonstrate that astrocytes contribute to the regulation of both potassium and calcium during and after a stress to the ionic homeostatic mechanisms.

Anticonvulsant Activity of Ginseng on Seizures Induced by Chemical Convulsants

Summary:u2002 Purpose: To test the anticonvulsant activity of three preparations of American ginseng: whole root extract, whole leaves/stems extract, and a partially purified extract that concentrates the Rb ginsenosides (Rb extract).

Energy failure in astrocytes increases the vulnerability of neurons to spreading depression

A neuroprotective role of astrocytes has been hypothesized, but the mechanism is debated and in vivo evidence is limited. To test this hypothesis, a sublethal stressor (spreading depression) and fluorocitrate (FC), a selective inhibitor of the astrocytic Krebs cycle, were used in urethane‐anaesthetized adult rats. Neuronal damage was assessed 24u2003h after treatment with silver stain and immunoreactivity for a 72‐kDa heat‐shock protein. ATP levels and mitochondrial aconitase activity, a marker indicating exposure to reactive oxygen species, were measured after 4 and 24u2003h. Spreading depression alone did not affect ATP levels, mitochondrial aconitase activity, or induce neuronal injury in the cortex. Local or intraventricular injection of FC significantly decreased ATP levels and mitochondrial aconitase activity, but did not produce neuronal damage. In animals receiving injections of FC and then spreading depression, there was evidence of significant neuronal stress and damage. Isocitrate, which bypasses the metabolic inhibition produced by FC, prevented all of the changes seen after the combination of FC and spreading depression. One‐hour pretreatment with dimethyl sulfoxide (a scavenger of hydroxyl radicals), deferoxamine (an iron chelator) or fructose‐1,6‐bisphosphate also blocked inactivation of mitochondrial aconitase, ATP depletion and the neuronal damage induced by FC and spreading depression. These experiments demonstrate that inhibition of the metabolism of astrocytes, with a decrease in ATP levels, will increase the susceptibility of neurons to the stress induced by spreading depression. The neuroprotective effects of dimethyl sulfoxide, deferoxamine and fructose‐1,6‐bisphosphate suggest that oxidative stress contributes to the neurotoxicity in this situation.

Protective effects of ginseng components in a rodent model of neurodegeneration

To test the proposed neuroprotective activity of whole ginseng extract and its components, we used 3‐nitropropionic acid (3‐NP), an inhibitor of succinate dehydrogenase, to produce neurodegeneration. Treatment with 3‐nitropropionic acid (90mg/kg) over a 5‐day period resulted in severe impairment of movement and loss of neurons in the striatum. Pretreatment with a preparation from the whole root of American ginseng had no protective effects. Pretreatment with a preparation of ground leaves and stems, which contains greater levels of ginsenosides than ground root, improved the behavioral score and reduced the volume of the striatal lesion. A partial purification of American ginseng was performed to concentrate the putative protective components: Rb1, Rb3, and Rd (termed Rb extract). Pretreatment with the Rb extract significantly reduced the 3‐nitropropionic acid–induced motor impairment and cell loss in the striatum, and it completely prevented any mortality. Significant effects on motor function, mortality, and the striatal lesion volume also were measured in animals pretreated with the individual ginsenosides, Rb1, Rb3, or Rd. The results demonstrate that some of the ginsenosides have neuroprotective activity, and that a partial purification of whole ginseng to concentrate the neuroprotective components may have utility as a neuroprotective agent. Ann Neurol 2005;57:642–648

An Overview of Genus Aesculus L.: Ethnobotany, Phytochemistry, and Pharmacological Activities

The genus Aesculus L. (Hippocastanaceae) has 12 species distributed in eastern Asia, eastern and western North America, and Europe. In Europe and the United States, A. hippocastanum has been used for the treatment of chronic venous insufficiency, hemorrhoids, and postoperative edema. In China, A. chinensis var. chinense has been used as a stomachic and analgesic in the treatment of distention and pain in the chest and the abdomen, malaria, dysentery, and heart disease. The objective of this paper is to review the ethnobotany, phytochemistry, and pharmacological properties of the genus Aesculus. To date, more than 210 compounds have been isolated and identified primarily from the fruits or seeds of Aesculus, with polyhydroxylated triterpenoid saponins as the major active principles. Studies have confirmed that Aesculus seed extracts and isolates possess diverse activities, including anti-inflammatory, antitumor, antiviral, antifungal, antiangiogenic (vascular protection), anti-obesity, antioxidative, and antigenotoxic properties. Interestingly, detailed stud- ies of the saponins from more eastern North American species and other uninvestigated Aesculus species are necessary to further confirm the chemotaxonomic value of the novel cytotoxic saponins discovered recently from A. pavia, an eastern North American species, and to fully understand the chemical profile of the genus. Animal investigations of these novel cytotoxic saponins on the potential for the treatment of cancer are also intriguing.

Characterization of chemical ingredients and anticonvulsant activity of American skullcap (Scutellaria lateriflora).

American skullcap (the aerial part of Scutellaria lateriflora L.) has been traditionally used by Native Americans and Europeans as a nerve tonic, sedative, and anticonvulsant. However, despite some previous studies, the quality and safety, the bioactive ingredients, and the pharmacological properties of American skullcap are not fully understood. The aims of this study were to characterize the chemical ingredients of American skullcap and to evaluate its anticonvulsant activity. Twelve phenolic compounds including 10 flavonoids and two phenylethanoid glycosides were isolated and identified from American skullcap and used as marker compounds. An HPLC analytic method for analyzing these marker compounds in commercial American skullcap products from different sources was established and validated. The anticonvulsant activity of American skullcap was determined in rat models of acute seizures induced by pilocarpine and pentylenetetrazol. The results from this study indicate that (1) phenolic compounds, especially flavonoids, are the predominant constituents in American skullcap; (2) American skullcap products have similar constituents, but the content and relative proportions of the individual constituents varies widely; and (3) American skullcap has anticonvulsant activity in rodent models of acute seizures.

Anticonvulsant and neuroprotective effects of ginsenosides in rats

A partially purified extract from American ginseng has been shown to have anticonvulsant activity. To identify the active components in this extract, the activities of the individual ginsenosides (Rb(1), Rb(3) and Rd), mixtures of the purified ginsenosides and a newly prepared Rb fraction were determined. One hour after treatment with vehicle or one of the ginseng products, seizures were induced in adult, Sprague-Dawley rats with kainic acid (KA, 10 mg/kg), pilocarpine (300 mg/kg) or pentylenetetrazole (PTZ, 50mg/kg i.p. or 90 mg/kg s.c.). Time to seizure onset, duration of seizure activity and seizure severity were determined. Weight change and neuronal damage were assessed 24h after administration of KA or pilocarpine. Mixtures of purified Rb(1), Rb(3) with or without Rd had significant anticonvulsant effects in all three models of acutely induced seizures demonstrating that the ginsenosides are the active components in the Rb extract. The individual ginsenosides significantly increased the latency to onset of seizures after administration of kainic acid. Since no one individual ginsenoside accounted for the majority of the activity of the Rb extract, the results suggest that the most effective anticonvulsant product is a combination of ginsenosides. In addition, all of the ginseng products had significant neuroprotective activity beyond the reduction in seizure severity and duration.

New Capoamycin-Type Antibiotics and Polyene Acids from Marine Streptomyces fradiae PTZ0025

Capoamycin-type antibiotics (2–5) and polyene acids (6, 7) were isolated from marine Streptomyces fradiae strain PTZ0025. Their structures were established by extensive nuclear magnetic resonance (NMR) and high resolution electron spray ionization mass spectroscopy (HRESIMS) analyses and chemical degradation. Compounds 3, 4, 6, 7 were found to be new and named as fradimycins A (3) and B (4), and fradic acids A (6) and B (7). Compounds 3–5 showed in vitro antimicrobial activity against Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 2.0 to 6.0 μg/mL. Interestingly, Compounds 3–5 also significantly inhibited cell growth of colon cancer and glioma with IC50 values ranging from 0.13 to 6.46 μM. Fradimycin B (4), the most active compound, was further determined to arrest cell cycle and induce apoptosis in tumor cells. The results indicated that fradimycin B (4) arrested the cell cycle at the G0/G1 phase and induced apoptosis and necrosis in colon cancer and glioma cells. Taken together, the results demonstrated that the marine natural products 3–5, particularly fradimycin B (4), possessed potent antimicrobial and antitumor activities.

Bioactive Sulfated Saponins from Sea Cucumber Holothuria moebii

The bioactive ingredients of sea cucumber Holothuria moebii were investigated, and four sulfated saponins (1-4) and one desulfated saponin (3B) with an unusual 3,4-epoxy xylose were obtained from this study. Compound 2 is a new triterpenoid saponin and 3B is a new artificial compound. On the basis of the extensive NMR and HRESIMS data, their structures were assigned as 3-O-[β-D-quinovopyranosyl-(1u2009→u20092)-4-sodium sulfato-β-D-xylopyranosyl]-25-acetoxy-22-oxo-9(11)-holostene-3β,12α,17α-triol (2) and 3-O-[β-D-quinovopyranosyl-(1u2009→u20092)-3,4-epoxy-β-xylopyranosyl]-22,25-epoxy-9(11)-holostene-3β,12α,17α-triol (3B). Compounds 1-4 showed activity suppressing the proliferation of four different glioma cells with IC50 values ranging from 0.99 to 8.64u2009µM. New saponin 2 significantly induced apoptosis in human glioblastoma U87-MG cells and reduced the expression levels of several glioma metabolic enzymes of glycolysis and glutaminolysis. This study reveals for the first time that selectively targeting multiple glioma metabolic regulators of glycolysis and glutaminolysis might be one of the anti-glioma mechanisms of saponin 2.