Inhibition of the metabolism of platelet activating factor (PAF-acether) by three specific antagonists from Ginkgo biloba

Ginkgo diterpene lactones inhibit cerebral ischemia/reperfusion induced inflammatory response in astrocytes via TLR4/NF-κB pathway in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. (Ginkgoaceae) is a traditional Chinese medicine known to treating stroke and other cardio-cerebrovascular diseases for thousands of years in China. Ginkgo diterpene lactones (GDL) attracted much attention because of their neuroprotective properties.

AIM OF THE STUDY

To uncover the effects of GDL, which consist of ginkgolide A (GA), ginkgolide B (GB), and ginkgolide K (GK), on ischemic stroke, as well as the underlying molecular mechanisms.

MATERIALS AND METHODS

We used middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models mimicking the process of ischemia/reperfusion in vivo and in vitro, respectively. Anticoagulant effects of GDL were investigated on platelet activating factor (PAF), arachidonic acid (AA) and adenosine diphosphate (ADP)-induced platelet aggregation both in vivo and in vitro. We also evaluated the effects of GDL on lipopolysaccharide (LPS)-induced inflammatory response in primary cultured rats' astrocytes. Infarct size, neurological deficit score, and brain edema were measured at 72 h after MCAO. Immunohistochemistry was utilized to analyze neurons necrosis and astrocytes activation. Expression of pro-inflammatory cytokines, including tumor necrotic factor-α (TNF-α) and interleukin-1β (IL-1β) were detected using enzyme-linked immunosorbent assay (ELISA) and real time PCR. The levels of toll-like receptor 4 (TLR4) and nuclear factor κB (NF-κB) were assessed by real time PCR or Western blot.

RESULTS

Compared with MCAO/R rats, GDL significantly reduced infarct size and brain edema, improved neurological deficit score. Meanwhile, GDL suppressed platelet aggregation, astrocytes activation, pro-inflammatory cytokines releasing, TLR4 mRNA expression and transfer of NF-κB from cytoplasm to nucleus. Furthermore, GDL alleviated OGD/R injury and LPS-induced inflammatory response in primary astrocytes, characterized by promoting cell viability, decreasing lactate dehydrogenase (LDH) activity, and inhibiting IL-1β and TNF-α releasing.

CONCLUSIONS

In summary, GDL attenuate cerebral ischemic injury, inhibit platelet aggregation and astrocytes activation. The anti-inflammatory activity might be associated with the downregulation of TLR4/NF-κB signal pathway. Our present findings provide an innovative insight into the novel treatment of GDL in ischemic stroke therapy.

Ginkgo biloba extracts prevent aortic rupture in angiotensin II-infused hypercholesterolemic mice

Abdominal aortic aneurysms (AAAs) are a chronic vascular disease characterized by pathological luminal dilation. Aortic rupture is the fatal consequence of AAAs. Ginkgo biloba extracts (GBEs), a natural herb extract widely used as food supplements, drugs, and cosmetics, has been reported to suppress development of calcium chloride-induced AAAs in mice. Calcium chloride-induced AAAs do not rupture, while angiotensin II (AngII)-induced AAAs in mice have high rate of aortic rupture, implicating potentially different mechanisms from calcium chloride-induced AAAs. This study aimed to determine whether GBE would improve aortic dilation and rupture rate of AngII-induced AAAs. Male apolipoprotein E (apoE) -/- mice were infused with AngII and administered either GBE or its major active ingredients, flavonoids and ginkgolides, individually or in combination. To determine the effects of GBE in mice with established AAAs, male apoE-/- mice were firstly infused with AngII for 28 days to develop AAAs, and then administered either GBE or vehicle in mice with established AAAs, which were continuously infused with AngII for another 56 days. GBE, but not the two major active components separately or synergistically, prevented aortic rupture, but not aortic dilation. The protection of GBE from aortic rupture was independent of systolic blood pressure, lipid, and inflammation. GBE also did not attenuate either aortic rupture or progressive aortic dilation in mice with established AAAs. GBE did not reduce the atherosclerotic lesion areas, either. In conclusion, GBE prevents aortic rupture in AngII-infused hypercholesterolemic mice, but only in the early phase of the disease development.

Human pharmacokinetics of ginkgo terpene lactones and impact of carboxylation in blood on their platelet-activating factor antagonistic activity

Terpene lactones are a class of bioactive constituents of standardized preparations of Ginkgo biloba leaf extract, extensively used as add-on therapies in patients with ischemic cardiovascular and cerebrovascular diseases. This investigation evaluated human pharmacokinetics of ginkgo terpene lactones and impact of their carboxylation in blood. Human subjects received oral YinXing-TongZhi tablet or intravenous ShuXueNing, two standardized ginkgo preparations. Their plasma protein-binding and platelet-activating factor antagonistic activity were assessed in vitro. Their carboxylation was assessed in phosphate-buffered saline (pH 7.4) and in human plasma. After dosing YinXing-TongZhi tablet, ginkgolides A and B and bilobalide exhibited significantly higher systemic exposure levels than ginkgolides C and J; after dosing ShuXueNing, ginkgolides A, B, C, and J exhibited high exposure levels. The compounds' unbound fractions in plasma were 45-92%. Apparent oral bioavailability of ginkgolides A and B was mostly >100%, while that of ginkgolides C and J was 6-15%. Bilobalide's bioavailability was probably high but lower than that of ginkgolides A/B. Terminal half-lives of ginkgolides A, B, and C (4-7 h) after dosing ShuXueNing were shorter than their respective values (6-13 h) after dosing YinXing-TongZhi tablet. Half-life of bilobalide after dosing the tablet was around 5 h. Terpene lactones were roughly evenly distributed in various body fluids and tissues; glomerular-filtration-based renal excretion was the predominant elimination route for the ginkgolides and a major route for bilobalide. Terpene lactones circulated as trilactones and monocarboxylates. Carboxylation reduced platelet-activating factor antagonistic activity of ginkgolides A, B, and C. Ginkgolide J, bilobalide, and ginkgo flavonoids exhibited no such bioactivity. Collectively, differences in terpene lactones' exposure between the two preparations and influence of their carboxylation in blood should be considered in investigating the relative contributions of terpene lactones to ginkgo preparations' therapeutic effects. The results here will inform rational clinical use of ginkgo preparations.

Ginkgolide K promotes angiogenesis in a middle cerebral artery occlusion mouse model via activating JAK2/STAT3 pathway

Ginkgolide K (GK) is a new compound extracted from the leaves of Ginkgo biloba, which has been recognized to exert anti-oxidative stress and neuroprotective effect on ischemic stroke. While whether it plays an enhanced effect on angiogenesis during ischemic stroke remains unknown. The aim of this study was to investigate the effect of ginkgolide K on promoting angiogenesis as well as the protective mechanism after cerebral ischemia-reperfusion. Using the transient middle cerebral artery occlusion (tMCAO) mouse model, we found that GK (3.5, 7.0, 14.0 mg/kg, i.p., bid., 2 weeks) attenuated neurological impairments, and promoted angiogenesis of injured ipsilateral cortex and striatum after 14 days of cerebral ischemia-reperfusion in mice. Further, GK (3.5 mg/kg in vivo, 10 μM in vitro) significantly up-regulated the expressions of HIF-1α and VEGF in tMCAO mouse brains and in b End3 cells after OGD/R, and GK-induced upregulation of HIF-1α and VEGF in b End3 cells could be abolished by JAK2/STAT3 inhibitor AG490. Our results demonstrate that GK promotes angiogenesis after ischemia stroke through increasing the expression of HIF-1α/VEGF via JAK2/STAT3 pathway, which provide an insight into the novel clinical application of GK and its analogs in ischemic stroke therapy in future.

Ginkgoghrelins, unique acylated flavonoid diglycosides in Folium Ginkgo, stimulate growth hormone secretion via activation of the ghrelin receptor

ETHNOPHARMACOLOGICAL RELEVANCE

Folium Ginkgo, the dried leaf of Ginkgo biloba L. is a traditional Chinese medicine listed in the Pharmacopoeia of the People's Republic of China with several therapeutic effects, including prevention of aging. It is used as herbal medicine for the treatment of several aging-related diseases. The therapeutic effects of Folium Ginkgo on aging-related diseases are suspected to be similar to the anti-aging effects of growth hormone release induced by ghrelin.

MATERIALS AND METHODS

Candidate components responsible for the anti-aging effects via the ghrelin receptor-activated pathway were searched from the known compounds found in Folium Ginkgo. Two acylated flavonoid diglycosides, tentatively named ginkgoghrelins in this study, were selected and isolated from the methanol extract of Folium Ginkgo, and their chemical structures were confirmed by spectroscopic analysis. These two compounds were examined for their capability of stimulating growth hormone release of rat primary anterior pituitary cells via activation of the ghrelin receptor. The major metabolites of ginkgoghrelins in rat bile were detected after intravenous injection and structurally analyzed by mass spectroscopy. Molecular modeling of ginkgoghrelins docking to the ghrelin receptor was exhibited to explore the possible interaction within the binding pocket.

RESULTS

Similar to growth hormone-releasing hormone-6 (GHRP-6), a synthetic analog of ghrelin, ginkgoghrelins were demonstrated to stimulate growth hormone secretion of rat primary anterior pituitary cells in a dose dependent manner, and the stimulation was inhibited by [d-Arg¹, d-Phe⁵, d-Trp^7,9, Leu¹¹]-substance P, an inverse agonist of the ghrelin receptor. Putative metabolites of ginkgoghrelins via glucuronidation and methylation were detected in bile of rats after intravenous injection. Molecular modeling and docking showed that ginkgoghrelins as well as GHRP-6 could fit in and adequately interact with the binding pocket of the ghrelin receptor.

CONCLUSION

The results suggest that ginkgoghrelins are putative components partly accounting for the anti-aging effects of Folium Ginkgo possibly via activation of the ghrelin receptor, and possess great potential to be developed as non-peptidyl analogs of ghrelin.

Ginkgolide B enhances the differentiation of preosteoblastic MC3T3-E1 cells through VEGF: Involvement of the p38 MAPK signaling pathway

Ginkgolide B (GB) is one of the ginkgolides isolated from the leaves of the Ginkgo biloba tree. Our previous study indicated that GB promotes the proliferation, migration and adhesion of endothelial progenitor cells, and the induction of angiogenesis through vascular endothelial factor (VEGF). In the present study, the effects of GB on the differentiation of MC3T3‑E1 cells and the signaling pathway involved were investigated in vitro. The MC3T3‑E1 cell viability activities were assessed using an MTS assay. Measurements of alkaline phosphatase activity and Alizarin Red staining were used to identify osteoblastic differentiation of the MC3T3‑E1 cells. The mRNA and secretion levels of VEGF were detected using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) analysis and enzyme-linked immunosorbent assays, respectively. The protein expression levels of phosphorylation‑associated markers were detected using western blot analysis and associated gene expression was determined using RT‑qPCR analysis. It was found that GB significantly promoted alkaline phosphatase activity and osteoblastic mineralization in the MC3T3‑E1 cells. In addition, the mRNA expression and secretion levels of VEGF in the MC3T3‑E1 cells were significantly increased in MC3T3‑E1 cells treated with GB. SB203580, a specific inhibitor of p38 mitogen‑activated protein (MAP) kinase, markedly suppressed the GB‑induced p38 kinase phosphorylation and GB‑induced synthesis of VEGF. PD98059, an inhibitor of the upstream kinase, which activates p44/p42 MAP kinase, had minimal effect on the GB‑induced phosphorylation of p44/p42 MAP kinase or the GB‑induced synthesis of VEGF. Taken together, these results indicated that GB promoted osteoblastic differentiation of the MC3T3‑E1 cells through VEGF, and that the p38, but not the p44/p42 MAP kinase signaling pathway, was involved in the GB‑induced synthesis of VEGF.

Ginkgolide B increases hydrogen sulfide and protects against endothelial dysfunction in diabetic rats

Aim

To evaluate the effect of ginkgolide B treatment on vascular endothelial function in diabetic rats.

Methods

The study included four groups with 15 male Sprague-Dawley rats: control group; control group treated with ginkgolide B; diabetic group; and diabetic treated with ginkgolide B. The activity of superoxide dismutase (SOD), malondialdehyde content, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, and glutathione peroxidase 1 (GPX1) protein expression were determined in aortic tissues. Vasoconstriction to phenylephrine (PHE) and vasorelaxation to acetylcholine (Ach) and sodium nitroprusside (SNP) were assessed in aortic rings. Nitric oxide (NO) and hydrogen sulfide (H₂S) were measured, as well as cystathionine γ lyase (CSE) and cystathionine β synthetase (CBS) protein expression, and endothelial nitric oxide synthase (eNOS) activity.

Results

Diabetes significantly impaired PHE-induced vasoconstriction and Ach-induced vasorelaxation (P < 0.001), reduced NO bioavailability and H₂S production (P < 0.001), SOD activity, and GPX1 protein expression (P < 0.001), and increased malondialdehyde content and NADPH oxidase subunits, and CSE and CBS protein expression (P < 0.001). Ginkgolide B treatment improved PHE vasoconstriction and Ach vasorelaxation (P < 0.001), restored SOD (P = 0.005) and eNOS (P < 0.001) activities, H₂S production (P = 0.044) and decreased malondialdehyde content (P = 0.014). Vasorelaxation to SNP was not significantly different in control and diabetic rats with or without ginkgolide B treatment. Besides, ginkgolide B increased GPX1 protein expression and reduced NADPH oxidase subunits, CBS and CSE protein expression.

Conclusion

Ginkgolide B alleviates endothelial dysfunction by reducing oxidative stress and elevating NO bioavailability and H₂S production in diabetic rats.

Medicinal herbs and therapeutic drugs interactions

People mistakenly think that all herbs are safe, because of the fact that they are natural, and the use of herbal medication is growing. Aspects of the efficacy, safety, and quality of herbal or natural products are the subjects of on-going debates. Concurrent administration of herbs may interfere with the effect of drugs. Lack of knowledge of the interaction potential together with an underreporting of herbal use poses a challenge for health care providers and a safety concern for patients. A good understanding of the mechanisms of herb-drug interactions is also essential for assessing and minimizing clinical risks. Examples of herbal medicine-pharmaceutical drug interactions of commonly used herbs are presented. The potential pharmacokinetic and pharmacodynamic basis of such interactions is discussed, as well as the challenges associated with the identification and prediction of herb-drug interactions.

Ginkgolide B inhibits platelet release by blocking Syk and p38 MAPK phosphorylation in thrombin-stimulated platelets

INTRODUCTION

Atherosclerosis is a chronic vascular inflammatory disease. Platelets play a critic role in the initiation of vascular inflammation in atherosclerosis. In the present study, we investigated the effects of ginkgolide B on the inhibition of platelet release and the potential mechanisms.

METHODS

Experiments were performed in freshly human platelets. Platelet aggregation and ATP release were measured with a Lumi-aggregometer. Thrombin (0.5 U/ml) was used to induce platelet activation. Protein expression and phosphorylation was examined by Western blotting.

RESULTS

The results showed that ginkgolide B significantly suppressed ATP release by 50.8% in thrombin-activated platelets. Ginkgolide B completely abolished the expression of platelet factor 4 (PF4) and CD40 Ligand (CD40L). Moreover, ginkgolide B fully attenuated the phosphorylation of Syk and p38MAPK. Similarly, R788 (a syk inhibitor) and SB203580 (a p38 MAPK inhibitor) inhibited the expression PF4 and CD40L, respectively. Furthermore, the combination of low concentrations of ginkgolide B and R788 or SB203580 has synergistic inhibition on the expression of PF4 and CD40L. Ginkgolide B partially reduced calcium efflux by 52.7% in thrombin-stimulated platelets.

CONCLUSION

Ginkgolide B potently inhibited the expression of PF4 and CD40L in thrombin-activated platelets. Ginkgolide B partially decreased ATP release and Ca(2+) efflux. The mechanism might be associated with the inhibition of Syk and p38 MAPK phosphorylation. These results demonstrated that ginkgolide B might be a promising drug on inhibiting platelet function and reducing inflammation in atherosclerosis.

Warfarin Interactions with Medicinal Herbs

Recognition of the adverse effects of medicinal herbs is not routine and the reports on such effects are even less frequent in clinical practice. Potential herb-drug interactions are of a major safety concern, especially for drugs with narrow therapeutic indices like warfarin, which can lead to severe adverse reactions that are sometimes life-threatening. The interactions between warfarin and medicinal herbs described in the literature have been summarized in this paper relying on Medline database (via PubMed) using the key words: warfarin, herbal supplements and interactions. The references on the analyzed literature have been investigated in order to collect the existing data. The case reports with severe adverse effects such as spontaneous postoperative bleeding, formation of hematomas, hematemesis, melena, thrombosis, subarachnoid hemorrhage and/or subdural hematomas after concomitant use of warfarin and the medicinal herbs: Panax ginseng, Hypericum perforatum, Salvia milthiorizza, Gingko biloba, Serenoa repens, Angelica sinensis, Vaccinium species, Allium sativum, Zingiber officinale, Tanacetum parthenium, Lucium barbarum, Matricaria chamomilla, Boswellia serrata and Camellia sinensis have been estimated. Some of the interactions between warfarin and medicinal herbs have been well assessed proving that they are closely-dependent.

The interactions between warfarin and medicinal herbs, not generally reported in previous reviews, are presented in our review. The health professionals who are involved in treating the patients are expected to be fully informed about the interactions between warfarin and medicinal herbs in order to minimize the health risks of the patients.

Ginkgolide B reduces atherogenesis and vascular inflammation in ApoE(-/-) mice

Aims

To investigate whether ginkgolide B (a platelet-activating factor inhibitor) affects vascular inflammation in atherosclerosis-prone apolipoprotein E-deficient (ApoE^−/−) mice.

Methods and Results

Human platelets were used to evaluate the effects of ginkgolide B on platelet aggregation and signal transduction. Ginkgolide B attenuated platelet aggregation and inhibited phosphatidylinositol 3 kinase (PI3K) activation and Akt phosphorylation in thrombin- and collagen-activated platelets. ApoE^−/− mice were administered a high-cholesterol diet for 8 weeks. Plasma platelet factor 4 (PF4) and RANTES (regulated upon activation, normal T-cell expressed, and secreted protein) were then measured using an enzyme-linked immunosorbent assay. Scanning electron microscopy and immunohistochemistry were used to determine atherosclerotic lesions. Ginkgolide B decreased plasma PF4 and RANTES levels in ApoE^−/− mice. Scanning electron microscopic examination showed that ginkgolide B reduced aortic plaque in ApoE^−/− mice. Immunohistochemistry analysis demonstrated that ginkgolide B diminished P-selectin, PF4, RANTES, and CD40L expression in aortic plaque in ApoE^−/− mice. Moreover, ginkgolide B suppressed macrophage and vascular cell adhesion protein 1 (VCAM-1) expression in aorta lesions in ApoE^−/− mice. Similar effects were observed in aspirin-treated ApoE^−/− mice.

Conclusion

Ginkgolide B significantly reduced atherosclerotic lesions and P-selectin, PF4, RANTES, and CD40L expression in aortic plaque in ApoE−/− mice. The efficacy of ginkgolide B was similar to aspirin. These results provide direct evidence that ginkgolide B inhibits atherosclerosis, which may be associated with inhibition of the PI3K/Akt pathway in activated platelets.

Ginkgo biloba extract attenuates warfarin-mediated anticoagulation through induction of hepatic cytochrome P450 enzymes by bilobalide in mice

Ginkgo biloba extract (GBE) is a popular herbal ingredient used worldwide, but it is reported to induce bleeding as a serious adverse event. In this study we examined whether GBE induced spontaneous bleeding or accelerated warfarin anticoagulation via herb-drug interaction. Mice were given GBE or various active components of GBE orally for 5 days and blood coagulation parameters and hepatic cytochrome P450 enzymes (CYPs) were measured. Mice also received warfarin (racemate, (S)- or (R)-enantiomer) for the last 3 days of the 5-day regimen to examine GBE-warfarin interactions. Neither GBE (up to 1000 mg/kg) nor ginkgolide B (up to 140 mg/kg), a platelet-activating factor antagonist, influenced blood coagulation parameters. In contrast, GBE attenuated the anticoagulant action of warfarin. Bilobalide, a component of GBE that markedly induced hepatic CYPs including (S)-warfarin hydroxylase, showed similar effects. For (S)-warfarin, the anticoagulation action and the interaction with GBE was clear, while the influence on metabolism was greater for (R)-warfarin than for (S)-warfarin, which corresponded to the CYP types induced by GBE. These results suggest that GBE and ginkgolide B have no influence on blood coagulation in vivo, and that GBE attenuates the anticoagulation action of warfarin via induction of hepatic CYPs by bilobalide.

Ginkgolide B suppresses intercellular adhesion molecule-1 expression via blocking nuclear factor-kappaB activation in human vascular endothelial cells stimulated by oxidized low-density lipoprotein

Atherosclerosis is a complex inflammatory arterial disease. Oxidized low-density lipoprotein (ox-LDL) is directly associated with chronic vascular inflammation. In the current study, we tested the hypothesis that ginkgolide B, a component of traditional Chinese herbal medicine for heart disorder, may affect ox-LDL-induced inflammatory responses in human umbilical vein endothelial cells (HUVECs). The results showed that the ox-LDL treatment caused a significantly increase in the expression of intercellular adhesion molecule-1 (ICAM-1) in HUVECs, which was associated with a dramatic augmentation in phosphorylation of IkappaB and relocation of nuclear factor-kappaB (NF-kappaB) into the nuclei. Interestingly, the ox-LDL-induced ICAM-1 expression and NF-kappaB relocation could be attenuated by addition of ginkgolide B. Moreover, ginkgolide B significantly reduces ox-LDL-induced generation of reactive oxygen species (ROS). In conclusion, ginkgolide B may decrease inflammatory responses induced by ox-LDL via blocking NF-kappaB signaling and inhibiting ROS generation in HUVECs.

Systematic Internet-Based Review of Complementary and Alternative Medicine for Glaucoma

OBJECTIVE

To identify the most popular forms of complementary and alternative medicine (CAM) for glaucoma on the Internet and to assess the quality of the most popular Web sites addressing CAM for glaucoma.

DESIGN

Systematic Internet-based search.

METHODS

Using a predefined search algorithm, Web sites most likely to receive hits from people searching the Internet for information on CAM therapies for glaucoma were identified.

MAIN OUTCOME MEASURES

Web sites were evaluated for quality based on the Sandvik score. Each Web site was also assessed for external validation based on listing on the Health on the Net (HON) Foundation Web site in accordance with their code of approval. Finally, the risk each Web site potentially posed to patients was assessed using a previously described scoring method.

RESULTS

Twenty-one Web sites were included in our study. Forty-four different CAM therapies were encountered; vitamin C supplements, forskolin, and diet and lifestyle modulation were the most common CAMs discussed. The mean Sandvik score for all Web sites was 9.4 (standard deviation, 2.6). Only one Web site was listed in the HON Foundation code of approval. Two of the 21 Web sites received the highest risk scores of 3 of a potential 4 points. None of the Web sites discouraged adhering to a clinician's advice. Fourteen of the 21 Web sites assessed provided commercial details promoting CAM, with the possibility of purchasing remedies or arranging consultations. Thirteen Web sites provided opinions and experiences without factual details.

CONCLUSIONS

Medical information conveyed over the Internet is of variable quality and is not subject to regulation. Many sources of information contain advice on therapies that have no evidence base and may put patients at risk. It is important that researchers and health care providers be aware of the content and quality of this information so as to offer advice to patients about the evidence and potential risks of CAM therapies. This can only be achieved by increasing awareness among ophthalmologists of the range of products and quality of information available for CAM therapies for glaucoma.

Ginkgo biloba extract protects against mercury(II)-induced oxidative tissue damage in rats

Mercury(II) is a highly toxic metal which induces oxidative stress in the body. In this study we aimed to investigate the possible protective effect of Ginkgo biloba (EGb), an antioxidant agent, against experimental mercury toxicity in rat model. Following a single dose of 5mg/kg mercuric chloride (HgCl(2); Hg group) either saline or EGb (150mg/kg) was administered for 5days. After decapitation of the rats trunk blood was obtained and the tissue samples from the brain, lung, liver, and kidney were taken for the determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen contents. Formation of reactive oxygen species in the tissue samples was monitored by chemiluminescence (CL) technique. BUN, creatinin, ALT, and AST levels and tumor necrosis factor-alpha (TNF-alpha) and lactate dehydrogenase (LDH) activity were assayed in serum samples. The results revealed that HgCl(2) induced oxidative damage caused significant decrease in GSH level, significant increase in MDA level, MPO activity and collagen content of the tissues. Treatment of rats with EGb significantly increased the GSH level and decreased the MDA level, MPO activity, and collagen contents. Similarly, serum ALT, AST and BUN levels, as well as LDH and TNF-alpha, were elevated in the Hg group as compared to control group. On the other hand, EGb treatment reversed all these biochemical indices. Our results implicate that mercury-induced oxidative damage in brain, lung, liver, and kidney tissues protected by G. biloba extract, with its antioxidant effects.

Preventive Effects of Ginkgo biloba Extract on Ischemia-Reperfusion Injury in Rat Bladder

AIMS

The aim of this experimental study was to evaluate the effects of Ginkgo biloba (EGb 761) on ischemia-reperfusion (I-R) injury in the rat bladder.

METHODS

A bladder I-R injury was induced by abdominal aorta occlusion by ischemia for 30 min, followed by 45 min reperfusion in rats. The rats were divided into four groups of 7 rats each; the control, I-R, and I-R groups were pretreated intraperitoneally with 50 or 100 mg/kg G. biloba 60 min before ischemia induction. Contractile responses to carbachol through isolated organ bath studies were recorded, histological sections were evaluated by light microscopy, and TUNEL staining was performed for the evaluation of apoptosis.

RESULTS

In the I-R group, the contractile responses of the bladder strips were lower than those of the control group (p < 0.01-0.001) and were restored by pretreatment with 100 mg/kg G. biloba (p < 0.05-0.001). Decreased polymorphonuclear leukocyte infiltration was detected in the G. biloba pretreatment groups when compared to the I-R group during histological evaluation. The ratio of TUNEL-positive nuclei was 1.84% in the I-R group, whereas it was decreased in both of the G. biloba pretreatment groups (p < 0.01, p < 0.01).

CONCLUSION

Our data indicated that G. biloba has a preventive effect on I-R injury in rat urinary bladder.

Effects of Ginkgo biloba extract on cell proliferation, cytokines and extracellular matrix of hepatic stellate cells

BACKGROUND/AIMS

Hepatic fibrosis is the common wound-healing response to chronic liver injury. Ginkgo biloba extract (GbE) has been indicated to reverse hepatic fibrosis and exhibit therapeutic effects both in vitro and in vivo. This study aimed to investigate the underlying mechanism of GbE using HSC-T6 cells, a subline of hepatic stellate cells (HSC) as a model.

METHODS

HSC-T6 cells were seeded into six-well plates and allowed to attach overnight. After exposure to different concentrations of GbE761 for 24 or 48 h, cell cycle analysis, semiquantitative RT-PCR, Western blotting analysis and analysis of ECM secretion were performed.

RESULTS

It was revealed that GbE (1, 10, 100, 500 mg/l) suppressed HSC proliferation and caused G0/G1 phase arrest in a concentration-dependent manner. RT-PCR and Western blot assays were applied to detect the decline of transforming growth factor beta1(TGF-beta1) and connective tissue growth factor (CTGF) in both mRNA and protein levels after GbE treatment in HSC-T6 cells for 24 or 48 h. Meanwhile, GbE inhibited the synthesis of type I and type III collagens. Secretion of some extracellular matrix (ECM) proteins, such as type III procollagen (PC III), type IV collagen (collagen IV), laminin (LN), hyaluronic acid (HA), were all decreased in supernatant of GbE treated HSC cells.

CONCLUSIONS

Our results suggest that GbE confers its anti-fibrosis effects through inhibiting HSC proliferation, reducing TGF-beta1 and CTGF expression and consequently suppressing the collagen production and ECM secretion.

Protective effects of ginkgo biloba against acetaminophen-induced toxicity in mice

BACKGROUND

The analgesic acetaminophen (AAP) causes a potentially fatal, hepatic centrilobular necrosis when taken in overdose. It was reported that these toxic effects of AAP are due to oxidative reactions that take place during its metabolism.

OBJECTIVE

In this study, we aimed to investigate the possible beneficial effect of Ginkgo biloba (EGb), an antioxidant agent, against AAP toxicity in mice.

METHODS

Balb/c mice were injected i.p. with: (1) vehicle, control (C) group; (2) a single dose of 50 mg/kg Ginkgo biloba extract, EGb group; (3) a single dose of 900 mg/kg i.p. acetaminophen, AAP group, and (4) EGb, in a dose of 50 mg/kg after AAP injection, AAP + EGb group. Serum ALT, AST, and tumor necrosis factor-alpha (TNF-alpha) levels in blood and glutathione (GSH), malondialdehyde (MDA) levels, myeloperoxidase (MPO) activity, and collagen contents in liver tissues were measured. Formation of reactive oxygen species in hepatic tissue samples was monitored by using chemiluminescence (CL) technique with luminol and lusigenin probe. Tissues were also examined microscopically.

RESULTS

ALT, AST levels, and TNF-alpha were increased significantly (p < 0.001) after AAP treatment, and reduced with EGb. Acetaminophen caused a significant (p < 0.05-0.001) decrease in GSH levels while MDA levels and MPO activity were increased (p < 0.001) in liver tissues. These changes were reversed by EGb treatment. Furthermore, luminol and lusigenin CL levels in the AAP group increased dramatically compared to control and reduced by EGb treatment (p < 0.01).

CONCLUSION

Our results implicate that AAP causes oxidative damage in hepatic tissues and Ginkgo biloba extract, by its antioxidant effects protects the tissues. Therefore, its therapeutic role as a "tissue injury-limiting agent" must be further elucidated in drug-induced oxidative damage.

Herbal, Prescribed, and Over-the-Counter Drug Use in Older Women: Prevalence of Drug Interactions

Older adults are at particular risk for drug and herbal interactions because they have multiple health problems that require treatment and are generally more susceptible to adverse drug effects. This study used a database containing self-reported herbal, prescription, and over-the-counter (OTC) drugs concurrently taken by a sample of 58 women who were aged 65 years or older. Drug-drug interactions (DDIs) were identified using a Web-based pharmaceutical program. At least 1 moderate or high-risk DDI was identified in 74% of participants, with 136 total DDIs identified. Fifty-two percent (71) of total DDIs were between prescribed and OTC or herbals, with 63% (45) of these involving nonsteroidal antiinflammatory drugs (NSAIDs). It is imperative that health care providers identify all prescribed, OTC, and herbal drugs taken by their patients and assess all interactions in order to avoid the possibility of adverse drug effects.

Ginkgo biloba extract improves oxidative organ damage in a rat model of thermal trauma

This study was designed to determine the possible protective effect of Ginkgo biloba extract (EGb) against oxidative organ damage distant from the original burn wound. Under brief ether anesthesia, the shaved dorsum of the rats was exposed to 90 degrees C (burn group) or 25 degrees C (control group) water bath for 10 seconds. EGb (50 mg/kg/day) or saline was administered intraperitoneally immediately and at 12 hours after the burn injury. Rats were decapitated 24 hours after burn injury and tissue samples from the liver and kidney were taken for the determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity, and collagen contents. Formation of reactive oxygen species in the tissue samples was monitored by the chemiluminescence technique. Tissues also were examined microscopically. Blood urea nitrogen, creatinine, alanine aminotransferase, and aspartate aminotransferase levels and tumor necrosis factor- and lactate dehydrogenase activity were assayed in serum samples. Severe skin scald injury (30% TBSA) caused a significant decrease in GSH levels and significant increases in MDA levels, MPO activity, and collagen content of hepatic and renal tissues. Treatment of rats with EGb significantly increased the GSH level and decreased the MDA level, MPO activity, and collagen contents. Similarly, serum alanine aminotransferase, aspartate aminotransferase, and blood urea nitrogen levels, as well as lactate dehydrogenase and tumor necrosis factor-, were increased in the burn group as compared with the control group. However, treatment with EGb reversed all these biochemical indices, as well as histopathological alterations that were induced by thermal trauma. Our results show that thermal trauma-induced oxidative damage in hepatic and renal tissues is protected by the administration of EGb, with its antioxidant effects. Therefore, its therapeutic role as a "tissue injury-limiting agent" must be further elucidated in oxidant-induced tissue damage.

Evidence for the use of nutritional supplements and herbal medicines in common eye diseases

PURPOSE

To provide a perspective by reviewing the evidence for the role of nutritional supplements and herbal medicines in the common causes of visual impairment.

DESIGN

Retrospective literature review.

METHODS

Published studies and information found in PubMed, International Bibliographic Information of Dietary Supplements, and selected websites were reviewed for the role of nutritional and herbal medicines in the treatment of age-related macular degeneration, cataract, diabetic retinopathy, and glaucoma. The studies were evaluated systematically for their study design, study population, benefits, risks, biases, and criteria for the categorization of the level of evidence.

RESULTS

The available evidence does support the use of certain vitamins and minerals in patients with certain forms of age-related macular degeneration. For cataracts, the available evidence does not support these supplements to prevent or treat cataracts in healthy individuals. For diabetic retinopathy and glaucoma, the available evidence does not support the use of these supplements. In the category of herbal medicines, the available evidence does not support the use of herbal medicines for any of these ocular diseases.

CONCLUSION

Because of the widespread use of nutritional supplements and herbal medicines, ophthalmologists should be aware of their use so that they can inform patients properly when the supplements and herbal medicine are being used for eye disease.

Ginkgo biloba extract reduces naphthalene-induced oxidative damage in mice

This investigation elucidated the role of free radicals in naphthalene-induced toxicity and protection by Ginkgo biloba extract (EGb). BALB-c mice of either sex were administered with naphthalene (100 mg/kg; i.p.) for 30 days, along with either saline or EGb (150 mg/kg, orally). At the end of the experiment, following decapitation, lung, liver and kidney tissue samples were taken for histological examination or determination of malondialdehyde (MDA), glutathione (GSH), myeloperoxidase (MPO) activity and collagen contents. In addition, proinflammatory cytokines (TNF-alpha and IL-beta) and total antioxidant capacity (AOC) were assayed in the plasma, while lactate dehydrogenase (LDH) activity was assayed in serum samples. The results revealed that naphthalene caused a significant decrease in GSH level, and significant increases in MDA level, MPO activity and collagen content of tissues. Similarly, plasma cytokines, as well as serum LDH activity, were elevated while AOC was decreased in the naphthalene group compared with the control group. On the other hand, EGb treatment reversed all these biochemical indices. The results demonstrate that EGb extract, by balancing the oxidant-antioxidant status and inhibiting the generation of proinflammatory cytokines and neutrophil infiltration, protects against naphthalene-induced oxidative organ injury.

Hepatic fibrosis in biliary-obstructed rats is prevented by Ginkgo biloba treatment

AIM: To assess the antioxidant and antifibrotic effects of long-term Ginkgo biloba administration on liver fibrosis induced by biliary obstruction in rats.

METHODS: Liver fibrosis was induced in male Wistar albino rats by bile duct ligation and scission (BDL). Ginkgo biloba extract (EGb 761, 50 mg/kg·per d) or saline was administered for 28 d. At the end of the treatment period, all rats were killed. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) levels were determined to assess liver functions and tissue damage, respectively. Tumor necrosis factor-α (TNF-α) was also assayed in serum samples. Liver tissues were taken for determination of the hepatic malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Production of reactive oxidants was monitored by chemilu-minescence (CL) assay. Serum AST, ALT, LDH, and TNF-α levels were elevated in the BDL group as compared to control group and were significantly decreased by EGb treatment.

RESULTS: Hepatic GSH level, depressed by BDL, was elevated back to control level in EGb-treated BDL group. Increase in tissue MDA level, MPO activity and collagen content due to BDL were also attenuated by EGb treatment. Furthermore, luminol and lucigenin CL values in BDL group increased dramatically compared to control and reduced by EGb treatment.

CONCLUSION: Our results suggest that Ginkgo biloba protects the liver from oxidative damage following BDL in rats. This effect possibly involves the inhibition of neutrophil infiltration and lipid peroxidation; thus, restoration of oxidant and antioxidant status in the tissue.

Effect of ginkgo and ginger on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects

AIM

The aim of this study was to investigate the effect of two common herbal medicines, ginkgo and ginger, on the pharmacokinetics and pharmacodynamics of warfarin and the independent effect of these herbs on clotting status.

METHODS

This was an open label, three-way crossover randomized study in 12 healthy male subjects, who received a single 25 mg dose of warfarin alone or after 7 days pretreatment with recommended doses of ginkgo or ginger from herbal medicine products of known quality. Dosing with ginkgo or ginger was continued for 7 days after administration of the warfarin dose. Platelet aggregation, international normalized ratio (INR) of prothrombin time, warfarin enantiomer protein binding, warfarin enantiomer concentrations in plasma and S-7-hydroxywarfarin concentration in urine were measured. Statistical comparisons were made using anova and the 90% confidence intervals (CIs) of the ratio of log transformed parameters are reported.

RESULTS

INR and platelet aggregation were not affected by administration of ginkgo or ginger alone. The mean (95% CI) apparent clearances of S-warfarin after warfarin alone, with ginkgo or ginger were 189 (167-210) ml h(-1), 200 (173-227) ml h(-1) and 201 (171-231) ml h(-1), respectively. The respective apparent clearances of R-warfarin were 127 (106-149) ml h(-1), 126 (111-141) ml h(-1) and 131 (106-156) ml h(-1). The mean ratio (90% CI) of apparent clearance for S-warfarin was 1.05 (0.98-1.21) and for R-warfarin was 1.00 (0.93-1.08) when coadministered with ginkgo. The mean ratio (90% CI) of AUC(0-168) of INR was 0.93 (0.81-1.05) when coadministered with ginkgo. The mean ratio (90% CI) of apparent clearance for S-warfarin was 1.05 (0.97-1.13) and for R-warfarin was 1.02 (0.95-1.10) when coadministered with ginger. The mean ratio (90% CI) of AUC(0-168) of INR was 1.01 (0.93-1.15) when coadministered with ginger. The mean ratio (90% CI) for S-7-hydroxywarfarin urinary excretion rate was 1.07 (0.85-1.32) for ginkgo treatment, and 1.00 (0.81-1.23) for ginger coadministration suggesting these herbs did not affect CYP2C9 activity. Ginkgo and ginger did not affect the apparent volumes of distribution or protein binding of either S-warfarin or R-warfarin.

CONCLUSIONS

Ginkgo and ginger at recommended doses do not significantly affect clotting status, the pharmacokinetics or pharmacodynamics of warfarin in healthy subjects.

Anti-apoptotic Actions of the Platelet-activating Factor Acetylhydrolase I α2 Catalytic Subunit

Platelet-activating factor (PAF) is an important mediator of cell loss following diverse pathophysiological challenges, but the manner in which PAF transduces death is not clear. Both PAF receptor-dependent and -independent pathways are implicated. In this study, we show that extracellular PAF can be internalized through PAF receptor-independent mechanisms and can initiate caspase-3-dependent apoptosis when cytosolic concentrations are elevated by approximately 15 pM/cell for 60 min. Reducing cytosolic PAF to less than 10 pM/cell terminates apoptotic signaling. By pharmacological inhibition of PAF acetylhydrolase I and II (PAF-AH) activity and down-regulation of PAF-AH I catalytic subunits by RNA interference, we show that the PAF receptor-independent death pathway is regulated by PAF-AH I and, to a lesser extent, by PAF-AH II. Moreover, the anti-apoptotic actions of PAF-AH I are subunit-specific. PAF-AH I alpha1 regulates intracellular PAF concentrations under normal physiological conditions, but expression is not sufficient to reduce an acute rise in intracellular PAF levels. PAF-AH I alpha2 expression is induced when cells are deprived of serum or exposed to apoptogenic PAF concentrations limiting the duration of pathological cytosolic PAF accumulation. To block PAF receptor-independent death pathway, we screened a panel of PAF antagonists (CV-3988, CV-6209, BN 52021, and FR 49175). BN 52021 and FR 49175 accelerated PAF hydrolysis and inhibited PAF-mediated caspase 3 activation. Both antagonists act indirectly to promote PAF-AH I alpha2 homodimer activity by reducing PAF-AH I alpha1 expression. These findings identify PAF-AH I alpha2 as a potent anti-apoptotic protein and describe a new means of pharmacologically targeting PAF-AH I to inhibit PAF-mediated cell death.

Microglial Calcium Responses to Platelet-Activating Factor are Inhibited by Analogue CAS 99103-16-9 and Dihydropyridine PCA 4248 but Not by Ginkgolide A

Calcium signals evoked in N9 microglial cells were monitored using the calcium indicator dye Fluo-4 in a fluorescence imaging plate reader. Platelet activating factor in the range 100 nM to 20 microM elicited graded calcium responses. The analogue CAS 99103-16-9 inhibited the evoked calcium rise with an apparent KB of 1.3 +/- 0.4 microM. The dihydropyridine PCA 4248 inhibited the evoked calcium rise with an apparent KB of 1.2 +/- 0.2 microM. Ginkgolide A at concentrations up to 18 microM had no effect on the evoked calcium rise. While CAS 99103-16-9 and PCA 4248 appear to be simple competitive inhibitors of platelet-activating factor responses, the efficacy of ginkgolide in more complex pharmacological situations may result from an action at a site other than the platelet-activating factor receptor.

Preventive effects of extract of leaves of ginkgo (Ginkgo biloba) and its component bilobalide on azoxymethane-induced colonic aberrant crypt foci in rats

The modifying effects of dietary feeding of extract of leaves of ginkgo (Ginkgo biloba) (EGb) and bilobalide isolated from EGb on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were investigated in male F344 rats. We also assessed the effects of EGb and bilobalide on proliferating cell nuclear antigen (PCNA) index in 'normal-appearing' crypts and activities of detoxifying enzymes of cytochrome P450 (CYP), glutathione S-transferase (GST) and quinine reductase (QR) activity in the liver. To induce ACF, rats were given two weekly subcutaneous injections of AOM (20 mg/kg body wt). They also received the experimental diets containing EGb (50 or 500 ppm) and bilobalide (15 or 150 ppm) for 4 weeks, starting 1 week before the first dosing of AOM. AOM exposure produced a substantial number of ACF (106 +/- 10) at the end of the study (week 4). Dietary administration of EGb and bilobalide caused significant reduction in the frequency of ACF: 50 ppm EGb, 73 +/- 17 (31% reduction, P < 0.001); 500 ppm EGb, 56 +/- 13 (47% reduction, P < 0.001); 15 ppm bilobalide, 79 +/- 17 (25% reduction, P < 0.001); and 150 ppm bilobalide, 71 +/- 30 (33% reduction, P < 0.01). Immunohistochemically, EGb or bilobalide administration significantly lowered PCNA index in normal-appearing crypts. Feeding with EGb or bilobalide increased activities of CYP as well as GST and QR in the liver. These findings might suggest possible chemopreventive ability of EGb or bilobalide, through alterations in cryptal cell proliferation activity and drug metabolizing enzymes' activities, in colon tumorigenesis.

The leaf extract of Ginkgo Biloba L. suppresses oxidized LDL-stimulated fibronectin production through an antioxidant action in rat mesangial cells

1 The leaf extract of Ginkgo Biloba L. exhibits a variety of pharmacological effects through an antioxidant action. We examined the effects of the leaf extract (Ginkgolon-24) on the production of fibronectin induced by oxidized low-density lipoprotein (oxLDL) in rat mesangial cells. 2 Stimulation with oxLDL accelerated the production of fibronectin with the preceding generation of reactive oxygen species (ROS). Pretreatment with Ginkgolon-24 inhibited the oxLDL-induced fibronectin production as well as ROS generation. 3 oxLDL also elicited the activation of SP-1, nuclear factor-kappaB, and cAMP response element-binding protein, which are transcription factors involved in the fibronectin production. Among these activated transcription factors, Ginkgolon-24 inhibited the activation of SP-1 only. 4 Furthermore, 7-ketocholesterol, an oxidized lipid in oxLDL particles, induced the production of fibronectin and the activation of SP-1, which were also suppressed by Ginkgolon-24. 5 These results suggest that the leaf extract of Ginkgo Biloba L. inhibits the oxLDL-induced production of fibronectin probably through inhibitory effects on ROS generation and SP-1 activation in rat mesangial cells.

The effect of EGb-761 on morphologic vasospasm in canine basilar artery after subarachnoid hemorrhage

This study investigated the effects of Ginkgo biloba extract (EGb-76l), an anti-oxidant and platelet-activating factor antagonist, on basilar artery vasospasm in an experimental canine subarachnoid hemorrhage model. Morphometric analyses were performed, and serum and cerebrospinal fluid endothelin-l levels were measured by radioimmunoassay. Comparisons were made between treated and untreated groups. Twenty-four mongrel dogs were randomly assigned to three groups. The animals in group 1 (n = 8) were not subjected to subarachnoid hemorrhage and received no treatment. In this group, serum and cerebrospinal fluid endothelin-l levels were measured daily for 8 days. On day 9, the animals were killed and their basilar arteries were excised for histopathological examination. In group 2 (n = 8), subarachnoid hemorrhage was produced using autologous arterial blood, and daily intravenous boluses of saline were administered for the next 8 days. Assessments of endothelin-l levels and the basilar arteries were performed as described for group 1. In group 3 (n = 8), subarachnoid hemorrhage was produced using autologous arterial blood, and daily intravenous boluses of EGb-761 were administered for 8 days. Endothelin-1 levels and the basilar arteries were assessed as described above. The groups' serum endothelin-1, cerebrospinal fluid endothelin-1, and histopathological findings were compared. In group 1, the serum and cerebrospinal fluid endothelin-1 levels did not change significantly over the 8 days, and histopathological examination of the basilar arteries revealed no abnormalities. In group 2, the serum and cerebrospinal fluid endothelin-1 levels increased abruptly and significantly on day 2, and remained high to the end of the study period (day 8). Histopathological examination revealed marked vasospasm. In group 3, the serum and cerebrospinal fluid endothelin-1 levels followed the same pattern observed in group 2; however, the arteries showed significantly less vasospasm than that observed in group 2. The study findings did not provide information about the mechanism of action of the platelet-activating factor-antagonist EGb-761, but they clearly show that this agent decreases morphologic vasospasm in the dog basilar artery.

Safety evaluation of functional ingredients

Functional ingredients are a diverse group of compounds that are intended to produce a positive effect on the health of the consumer. The term "functional" is not meant to differentiate these ingredients from other ingredients historically consumed as part of the food supply that are indeed biologically active constituents, for example, nutrients. Indeed, all foods should be considered "functional". The term functional ingredient is meant to convey the function of these new ingredients, which is to produce a positive health outcome via physiological activity in the body. Functional ingredients encompass elements of drugs, nutrients and food additives. A framework for evaluation of the safety of functional ingredients utilizes an understanding of both the current regulatory frameworks in place as well as the characteristics that define these particular ingredients. The types of studies conducted and the data generated to support safety of functional ingredients is product-specific and can include compositional analysis, structure/toxicity analysis, evaluation of historical and intended exposure, animal studies, clinical/epidemiologic studies, and evaluation of special considerations such as potential for adverse food or drug interactions.

Receptor-dependent metabolism of platelet-activating factor in murine macrophages

Degradation of platelet-activating factor (PAF) was examined by incubating PAF with macrophages from PAF receptor-deficient mice. The degradation rate was halved as compared with wild-type mice. The reduction of the rate was comparable with the presence of a PAF antagonist WEB 2086 in wild-type cells. PAF was internalized rapidly (t(12) approximately 1 min) into wild-type macrophages. The PAF internalization was inhibited by the treatment of 0.45 m sucrose but was not affected by phorbol 12-myristate 13-acetate, suggesting that PAF internalizes into macrophages with its receptor in a clathrin-dependent manner. Internalized PAF was degraded into lyso-PAF with a half-life of 20 min. Treatment of concanavalin A inhibited the conversion of PAF into lyso-PAF, suggesting that uptake of PAF enhances PAF degradation. Lyso-PAF was subsequently metabolized into 1-alkyl-2-acyl-phosphatidylcholine. In addition, release of PAF acetylhydrolase from macrophages was enhanced when wild-type macrophages were stimulated with PAF but not from macrophages of PAF receptor-deficient mice. Thus, the PAF stimulation of macrophages leads to its degradation through both intracellular and extracellular mechanisms.

Potential role for Ginkgo biloba extract in the treatment of glaucoma

Glaucoma is becoming recognized as a condition for which not only elevated intraocular pressure, but also non-pressure-dependent risk factors are responsible. New avenues of treatment into which investigations are being initiated include agents which could possibly improve blood flow to the eye and neuroprotective drugs. Only calcium channel blockers are presently available for such treatment in glaucoma, and these have not been widely adopted, in contrast to clinical trials involving a number of neuroprotectants in other neurologic disorders. Ginkgo biloba extract is freely available and has several biological actions which combine to make it a potentially important agent in the treatment of glaucoma: improvement of central and peripheral blood flow, reduction of vasospasm, reduction of serum viscosity, antioxidant activity, platelet activating factor inhibitory activity, inhibition of apoptosis, and inhibition of excitotoxicity. The effect of Ginkgo biloba extract as a potential antiglaucoma therapy deserves intensive scrutiny.

Herb-drug interactions

Concurrent use of herbs may mimic, magnify, or oppose the effect of drugs. Plausible cases of herb-drug interactions include: bleeding when warfarin is combined with ginkgo (Ginkgo biloba), garlic (Allium sativum), dong quai (Angelica sinensis), or danshen (Salvia miltiorrhiza); mild serotonin syndrome in patients who mix St John's wort (Hypericum perforatum) with serotonin-reuptake inhibitors; decreased bioavailability of digoxin, theophylline, cyclosporin, and phenprocoumon when these drugs are combined with St John's wort; induction of mania in depressed patients who mix antidepressants and Panax ginseng; exacerbation of extrapyramidal effects with neuroleptic drugs and betel nut (Areca catechu); increased risk of hypertension when tricyclic antidepressants are combined with yohimbine (Pausinystalia yohimbe); potentiation of oral and topical corticosteroids by liquorice (Glycyrrhiza glabra); decreased blood concentrations of prednisolone when taken with the Chinese herbal product xaio chai hu tang (sho-salko-to); and decreased concentrations of phenytoin when combined with the Ayurvedic syrup shankhapushpi. Anthranoid-containing plants (including senna [Cassia senna] and cascara [Rhamnus purshiana]) and soluble fibres (including guar gum and psyllium) can decrease the absorption of drugs. Many reports of herb-drug interactions are sketchy and lack laboratory analysis of suspect preparations. Health-care practitioners should caution patients against mixing herbs and pharmaceutical drugs.

Dietary supplements and natural products as psychotherapeutic agents

Alternative therapies are widely used by consumers. A number of herbs and dietary supplements have demonstrable effects on mood, memory, and insomnia. There is a significant amount of evidence supporting the use of Hypericum perforatum (St. John's wort) for depression and Ginkgo biloba for dementia. Results of randomized, controlled trials also support the use of kava for anxiety and valerian for insomnia. Although evidence for the use of vitamins and amino acids as sole agents for psychiatric symptoms is not strong, there is intriguing preliminary evidence for the use of folate, tryptophan, and phenylalanine as adjuncts to enhance the effectiveness of conventional antidepressants. S-adenosylmethionine seems to have antidepressant effects, and omega-3 polyunsaturated fatty acids, particularly docosahexaenoic acid, may have mood-stabilizing effects. More research should be conducted on these and other natural products for the prevention and treatment of various psychiatric disorders.

The effect of inhibitors of platelet aggregation on the metabolism of platelet-activating factor (PAF) in washed rabbit platelets

The rabbit platelet metabolizes platelet-activating factor (PAF) intracellularly. PAF is deacetylated to produce lysoPAF which, in turn, can be acylated to produce 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine (alkylacyl GPC). Some PAF receptor antagonists have been shown to inhibit this metabolic conversion. In the present study we examined whether the PAF receptor antagonists SRI 63-441 and WEB 2086 would inhibit the metabolism of PAF by intact rabbit platelets. In addition, we examined whether iloprost, a stable analogue of prostaglandin I2 (PGI2), and a potent inhibitor of platelet activation induced by a range of agonists, would also inhibit PAF metabolism. We found that SRI 63-441 and WEB 2086 caused an almost complete inhibition of the conversion of PAF to alkylacyl GPC. Iloprost caused up to a 50% inhibition of PAF metabolism compared to antagonist-free controls. Iloprost (and PGI2) is thought to inhibit platelet response by elevation of cAMP, while receptor antagonists act by blocking PAF binding to its receptor. Since iloprost caused partial inhibition of PAF metabolism, the results of this study suggest that inhibition of PAF metabolism does not occur solely due to competitive inhibition of PAF binding to its receptor.