Inhibition by ginkgolides and bilobalide of the production of nitric oxide in macrophages (THP-1) but not in endothelial cells (HUVEC)

Impact of targeting the platelet-activating factor and its receptor in cancer treatment

The lipid mediator platelet-activating factor (PAF) and its receptor (PAFR) signaling play critical roles in a wide range of physiological and pathophysiological conditions, including cancer growth and metastasis. The ability of PAFR to interact with other oncogenic signaling cascades makes it a promising target for cancer treatment. Moreover, numerous natural and synthetic compounds, characterized by diverse pharmacological activities such as anti-inflammatory and anti-tumor effects, have been explored for their potential as PAF and PAFR antagonists. In this review, we provide comprehensive evidence regarding the PAF/PAFR signaling pathway, highlighting the effectiveness of various classes of PAF and PAFR inhibitors and antagonists across multiple cancer models. Notably, the synergistic effects of PAF and PAFR antagonists in enhancing the efficacy of chemotherapy and radiation therapy in several experimental cancer models are also discussed. Overall, the synthesis of literature review indicates that targeting the PAF/PAFR axis represents a promising approach for cancer treatment and also exerts synergy with chemotherapy and radiation therapy.

TiO2-Nanowired Delivery of Chinese Extract of Ginkgo biloba EGb-761 and Bilobalide BN-52021 Enhanced Neuroprotective Effects of Cerebrolysin Following Spinal Cord Injury at Cold Environment

Military personnel during combat or peacekeeping operations are exposed to extreme climates of hot or cold environments for longer durations. Spinal cord injury is quite common in military personnel following central nervous system (CNS) trauma indicating a possibility of altered pathophysiological responses at different ambient temperatures. Our previous studies show that the pathophysiology of brain injury is exacerbated in animals acclimated to cold (5 °C) or hot (30 °C) environments. In these diverse ambient temperature zones, trauma exacerbated oxidative stress generation inducing greater blood-brain barrier (BBB) permeability and cell damage. Extracts of Ginkgo biloba EGb-761 and BN-52021 treatment reduces brain pathology following heat stress. This effect is further improved following TiO₂ nanowired delivery in heat stress in animal models. Several studies indicate the role of EGb-761 in attenuating spinal cord induced neuronal damages and improved functional deficit. This is quite likely that these effects are further improved following nanowired delivery of EGb-761 and BN-52021 with cerebrolysin-a balanced composition of several neurotrophic factors and peptide fragments in spinal cord trauma. In this review, TiO₂ nanowired delivery of EGb-761 and BN-52021 with nanowired cerebrolysin is examined in a rat model of spinal cord injury at cold environment. Our results show that spinal cord injury aggravates cord pathology in cold-acclimated rats and nanowired delivery of EGb-761 and BN-52021 with cerebrolysin significantly induced superior neuroprotection, not reported earlier.

CB1 as a novel target for Ginkgo biloba's terpene trilactone for controlling chemotherapy-induced peripheral neuropathy (CIPN)

The application of antineoplastic chemotherapeutic agents causes a common side effect known as chemotherapy-induced peripheral neuropathy (CIPN) that leads to reducing the quality of patient's life. This research involves the performance of molecular docking and molecular dynamic (MD) simulation studies to explore the impact of terpenoids of Ginkgo biloba on the targets (CB-1, TLR4, FAAH-1, COX-1, COX-2) that can significantly affect the controlling of CIPN's symptoms. According to the in-vitro and in-vivo investigations, terpenoids, particularly ginkgolides B, A, and bilobalide, can cause significant effects on neuropathic pain. The molecular docking results disclosed the tendency of our ligands to interact with mainly CB1 and FAAH-1, as well as partly with TLR4, throughout their interactions with targets. Terpene trilactone can exhibit a lower rate of binding energy than CB1's inhibitor (7dy), while being precisely located in the CB1's active site and capable of inducing stable interactions by forming hydrogen bonds. The analyses of MD simulation proved that ginkgolide B was a more suitable activator and inhibitor for CB1 and TLR4, respectively, when compared to bilobalide and ginkgolide A. Moreover, bilobalide is capable of inhibiting FAAH-1 more effectively than the two other ligands. According to the analyses of ADME, every three ligands followed the Lipinski's rule of five. Considering these facts, the exertion of three ligands is recommended for their anti-inflammatory, neuroprotective, and anti-nociception influences caused by primarily activating CB1 and inhibiting FAAH-1 and TLR4; in this regard, these compounds can stand as potential candidates for the control and treatment of CIPN's symptoms.

New Insight into the Mechanisms of Ginkgo Biloba Extract in Vascular Aging Prevention

BACKGROUND

Aging-associated vascular dysfunction promotes cardiovascular diseases. Recently, Ginkgo biloba extract (GBE) has attracted considerable attention in the prevention of aged vasculature.

METHODS

This review discusses the pathophysiological alterations in aged vasculature and the underlying mechanisms of GBE in vascular aging suppression.

RESULTS

Both arterial stiffening and endothelial dysfunction are critical aging-related vascular phenotypes that result in the progression of cardiovascular diseases in the general population. Consistent oxidative stress and inflammatory reaction lead to vascular dysfunction. GBE ameliorates aging-related vascular dysfunction, due to its antioxidant and anti-inflammatory properties. The main effects of GBE in aged vasculature might be associated with the longevity signaling pathways. GBE also attenuates the progression of vascular aging in diabetes mellitus via regulation of glucose and lipid metabolism.

CONCLUSION

GBE plays an important role in the prevention of vascular aging process. It is a promising therapeutic approach to ameliorate aging-related vascular dysfunction and cardiovascular diseases.

Therapeutic promises of ginkgolide A: A literature-based review

Ginkgolide A is a highly active platelet activating factor antagonist cage molecule which was isolated from the leaves of the Ginkgo biloba L. It is known for its inflammatory and immunological potentials. This review aims to sketch a current scenario on its therapeutic activities on the basis of scientific reports in the databases. A total 30 articles included in this review suggests that ginkgolide A has many important biological activities, including anti-inflammatory, anticancer, anxiolytic-like, anti-atherosclerosis and anti-atherombosis, neuro- and hepatoprotective effects. There is a lack of its toxicological (e.g. toxicity, cytotoxicity, genotoxicity and mutagenitcity) profile. In conclusion, ginkgolide A may be one of the potential therapeutic lead compounds, especially for the treatment of cardiovascular, hepatological, and neurological diseases and disorders. More studies are necessary on this hopeful therapeutic agent.

Endothelium-Independent Vasodilatory Effect of Sailuotong (SLT) on Rat Isolated Tail Artery

Background

Sailuotong (SLT) is a standardized three-herb formulation consisting of extracts of Panax ginseng, Ginkgo biloba, and Crocus sativus for the treatment of vascular dementia (VaD). Although SLT has been shown to increase cerebral blood flow, the direct effects of SLT on vascular reactivity have not been explored. This study aims to examine the vasodilatory effects of SLT and the underlying mechanisms in rat isolated tail artery.

Methods

Male (250-300 g) Wistar Kyoto (WKY) rat tail artery was isolated for isometric tension measurement. The effects of SLT on the influx of calcium through the cell membrane calcium channels were determined in Ca²⁺-free solution experiments.

Results

SLT (0.1-5,000 μg/ml) caused a concentration-dependent relaxation in rat isolated tail artery precontracted by phenylephrine. In the contraction experiments, SLT (500, 1,000, and 5,000 μg/mL) significantly inhibited phenylephrine (0.001 to 10 μM)- and KCl (10-80 mM)-induced contraction, in a concentration-dependent manner. In Ca²⁺-free solution, SLT (500, 1,000, and 5,000 μg/mL) markedly suppressed Ca²⁺-induced (0.001-3 mM) vasoconstriction in a concentration-dependent manner in both phenylephrine (10 μM) or KCl (80 mM) stimulated tail arteries. L-type calcium channel blocker nifedipine (10 μM) inhibited PE-induced contraction. Furthermore, SLT significantly reduced phenylephrine-induced transient vasoconstriction in the rat isolated tail artery.

Conclusion

SLT induces relaxation of rat isolated tail artery through endothelium-independent mechanisms. The SLT-induced vasodilatation appeared to be jointly meditated by blockages of extracellular Ca²⁺ influx via receptor-gated and voltage-gated Ca²⁺ channels and inhibition of the release of Ca²⁺ from the sarcoplasmic reticulum.

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.

Ginkgo biloba and ovarian cancer prevention: Epidemiological and biological evidence

There is considerable interest in herbal therapies for cancer prevention but often with little scientific evidence to support their use. In this study, we examined epidemiological data regarding effects of commonly used herbal supplements on risk for ovarian cancer and sought supporting biological evidence. 4.2% of 721 controls compared to 1.6% of 668 cases regularly used Ginkgo biloba for an estimated relative risk (and 95% confidence interval) of 0.41 (0.20,0.84) (p=0.01); and the effect was most apparent in women with non-mucinous types of ovarian cancer, RR=0.33 (0.15,0.74) (p=0.007). In vitro experiments with normal and ovarian cancer cells showed that Ginkgo extract and its components, quercetin and ginkgolide A and B, have significant anti-proliferative effects ( approximately 40%) in serous ovarian cancer cells, but little effect in mucinous (RMUG-L) cells. For the ginkgolides, the inhibitory effect appeared to be cell cycle blockage at G0/G1 to S phase. This combined epidemiological and biological data provide supportive evidence for further studies of the chemopreventive or therapeutic effects of Ginkgo and ginkgolides on ovarian cancer.

In vitro peroxynitrite scavenging activity of 6-hydroxykynurenic acid and other flavonoids fromGingko biloba yellow leaves

As part of our research on phytochemicals that exert protective effects against diseases related to reactive nitrogen species, we have evaluated the scavenging activity of the yellow leaves of Ginkgo biloba on ONOO-. The methanol extract and ethyl acetate fraction obtained from yellow leaves of G. biloba evidenced a marked scavenging activity on authentic ONOO-. Repeated column chromatography of the active ethyl acetate soluble fraction on silica gel, Sephadex LH-20, and RP-18, resulted in the purification of 15 known compounds, including sciadopitysin (1), ginkgolide B (2), bilobalide (3), isoginkgetin (4), kaempferol (5), luteolin (6), protocatechuic acid (7), bilobetin (8), amentoflavone (9), beta-sitosterol glucopyranoside (10), kaempferol 3-O-rhamnopyranoside (11), kaempferol 3-O-glucopyranoside (12), kaempferol 3-O-[6"'-O-p-coumaroyl-beta-D-glucopyranosyl(1 --> 2)-alpha-L-rhamnopyranoside] (13), kaempferol 3-O-rutinoside (14), and 6-hydroxykynurenic acid (15). Among the compounds isolated, flavonoids (5, 6 and 11-14), protocatechuic acid (7), and 6-hydroxykynurenic acid (15) all exhibited marked scavenging activities on authentic ONOO-. The IC50 values of 5-7, 11-14 and 15 were as follows: 2.86 +/- 0.70, 2.30 +/- 0.04, 2.85 +/- 0.10, 5.60 +/- 0.47, 4.16 +/- 1.65, 2.47 +/- 0.15, 3.02 +/- 0.48, and 6.24 +/- 0.27 microM, respectively. DL-Penicillamine (IC50 = 4.98 +/- 0.27 microM) was utilized as a positive control. However, the other compounds (1-4, 8-10) exerted no effects against ONOO-.

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.

Ganoderma lucidum inhibits inducible nitric oxide synthase expression in macrophages

Nitric oxide (NO) is a principal mediator in many physiological and pathological processes. Overproduction of NO via the inducible nitric oxide synthase (iNOS) has cytotoxic effect through the formation of peroxynitrite with superoxide anion. The iNOS is mainly expressed in macrophages and is able to produce large amount of NO. The expression of iNOS is mainly regulated at the transcriptional level. The iNOS-mediated NO production plays a role in the development of atherosclerosis. Ganoderma lucidum (G. lucidum, Linzhi or Reishi) is a traditional herbal medicine which is commonly used as health supplement. Several studies have demonstrated its effectiveness against cancer, immunological disorders and cardiovascular diseases. The objective of the present study was to investigate the effect of G. lucidum on iNOS-mediated NO production in macrophages. Human monocytic cell (THP-1) derived macrophages were incubated with lipopolysaccharide (LPS) for 24 h. Such treatment significantly stimulated NO production (253% versus the control). Such a stimulatory effect was resulted from increased iNOS mRNA expression (270% versus the control) and iNOS activity (169.5% versus the control) in macrophages. The superoxide anion level was also elevated (150% versus the control) in LPS-treated macrophages. Treatment of macrophages with G. lucidum extract (100 microg/ml) completely abolished LPS-induced iNOS mRNA expression and NO production. Such an inhibitory effect of G. lucidum was mediated via its antioxidant action against LPS-induced superoxide anion generation in macrophages. These results suggest that G. lucidum may exert a therapeutic effect against atherosclerosis via ameliorating iNOS-mediated NO overproduction in macrophages.

Emerging issues in traditional Chinese medicine

Traditional Chinese medicine (TCM) has many beneficial effects and has been practiced for several thousand years. It is known to treat the cause of a disease rather than to alleviate its symptoms. Based on a belief that TCM is natural, safe, and of lower cost, consumers worldwide are spending more out-of-pocket money on this form of therapy. This increased spending, and reports of adverse reactions, has drawn the attention of many regulatory agencies. Scientists have called for more evidence-based and scientific research on the risks and benefits of TCM. In Canada, the Natural Health Product Regulations came into effect January 2004. TCM herbal product manufacturers will need to provide products of reputable quality to the market. Many will apply modern technology and good science to support their products. The issues facing producers, scientists, and consumers alike are quality control and assessment, standardization of bioactive components, mechanisms of actions, and integration of the evolved modern Chinese medicine into the healthcare system. Solid science, better regulation of the final product, and better education of consumers are necessary to extract the best of TCM to complement existing conventional medicine to deliver the best healthcare.Key words: bioactive components, chromatographic fingerprinting, integration, mechanisms, Natural Health Product (NHP) Regulations, standardization, traditional Chinese medicine.

Hyperhomocysteinemia activates NF-kappaB and inducible nitric oxide synthase in the kidney

BACKGROUND

Hyperhomocysteinemia is an independent risk factor for cardiovascular disorders. Injury of multiple organs, including the kidney, was observed in hyperhomocysteinemic individuals. Activation of a transcription factor, namely, nuclear factor kappa B (NF-kappaB), plays an important role in inflammatory response and can exacerbate organ injury. The objective of the present study was to investigate the effect of hyperhomocysteinemia on renal NF-kappaB activation and the consequence of such activation.

METHODS

Hyperhomocysteinemia was induced in Sprague-Dawley rats after 4 weeks of a high-methionine diet. Activation of NF-kappaB was determined by electrophoretic mobility shift assay. Role of inhibitor protein IkappaBalpha was examined by Western immunoblotting analysis.

RESULTS

There was a significant increase in the level of phosphorylated IkappaBalpha protein in kidneys of hyperhomocysteinemic rats. This resulted in a decrease in the IkappaBalpha protein level leading to NF-kappaB activation. As a consequence, the expression of inducible nitric oxide synthase (iNOS) mRNA and protein was significantly elevated in kidneys of hyperhomocysteinemic rats. Increased nitric oxide production (150% of the control) resulted in peroxynitrite formation in these kidneys. Pretreatment of rats with a NF-kappaB inhibitor not only abolished NF-kappaB activation, but also reversed hyperhomocysteinemia-induced iNOS expression in the kidney.

CONCLUSION

Hyperhomocysteinemia alone can activate NF-kappaB and hence induce iNOS-mediated nitric oxide production in the kidney leading to increased peroxynitrite formation. This may represent one of the mechanisms for renal dysfunction in hyperhomocysteinemia.

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.

Ginkgo biloba extracts and cancer: a research area in its infancy

Recent studies conducted with various molecular, cellular and whole animal models have revealed that leaf extracts of Ginkgo biloba may have anticancer (chemopreventive) properties that are related to their antioxidant, anti-angiogenic and gene-regulatory actions. The antioxidant and associated anti-lipoperoxidative effects of Ginkgo extracts appear to involve both their flavonoid and terpenoid constituents. The anti-angiogenic activity of the extracts may involve their antioxidant activity and their ability to inhibit both inducible and endothelial forms of nitric oxide synthase. With regard to gene expression, a Ginkgo extract and one of its terpenoid constituents, ginkgolide B, inhibited the proliferation of a highly aggressive human breast cancer cell line and xenografts of this cell line in nude mice. cDNA microarray analyses have shown that exposure of human breast cancer cells to a Ginkgo extract altered the expression of genes that are involved in the regulation of cell proliferation, cell differentiation or apoptosis, and that exposure of human bladder cancer cells to a Ginkgo extract produced an adaptive transcriptional response that augments antioxidant status and inhibits DNA damage. In humans, Ginkgo extracts inhibit the formation of radiation-induced (chromosome-damaging) clastogenic factors and ultraviolet light-induced oxidative stress - effects that may also be associated with anticancer activity. Flavonoid and terpenoid constituents of Ginkgo extracts may act in a complementary manner to inhibit several carcinogenesis-related processes, and therefore the total extracts may be required for producing optimal effects.

Homocysteine stimulates inducible nitric oxide synthase expression in macrophages: antagonizing effect of ginkgolides and bilobalide

Hyperhomocysteinemia is an independent risk factor for atherosclerotic diseases. Inducible nitric oxide synthase (iNOS) is mainly expressed in macrophages upon stimulation. Overproduction of nitric oxide (NO) by iNOS can exacerbate the development of atherosclerosis. Our previous studies demonstrated that the extract of ginkgo biloba leaves (EGb) inhibited the iNOS-mediated NO production in monocyte-derived macrophage. We also reported that homocysteine could stimulate monocyte chemoattractant protein-1 (MCP-1) expression in vascular cells causing enhanced monocyte chemotaxis. The objective of the present study was to investigate the effect of homocysteine on iNOS-mediated NO production in macrophages and the antagonizing effect of EGb. Human monocytic cell (THP-1)-derived macrophages were incubated with homocysteine for various time periods. Homocysteine at concentrations of 0.05-0.1 mM significantly stimulated NO production and iNOS activity in macrophages via increased expression of iNOS mRNA and protein. The increased iNOS expression was associated with activation of nuclear factor-kappa B (NF-kappaB) arising from reduced expression of inhibitor protein (IkappaB alpha) mRNA as well as increased phosphorylation of IkappaB alpha protein in homocysteine-treated cells. EGb and its terpenoids (ginkgolide A, ginkgolide B and bilobalide) could antagonize the homocysteine effect on iNOS expression in macrophages via their antioxidant effect resulting in attenuation of NF-kappaB activation. Taken together, our results have demonstrated that homocysteine, at pathophysiological concentrations, stimulates iNOS-mediated NO production in macrophages. EGb and its terpenoids can antagonize such stimulatory effect via antioxidation and attenuation of NF-kappaB activation.

Bilobalide and neuroprotection

In vivo studies have indicated that systemically administered bilobalide, a sesquiterpene trilactone constituent of Ginkgo biloba leaf extracts, can reduce cerebral edema produced by triethyltin, decrease cortical infarct volume in certain stroke models, and reduce cerebral ischemia. In vitro and ex vivo studies indicate that bilobalide has multiple mechanisms of action that may be associated with neuroprotection, including its preservation of mitochondrial ATP synthesis, its inhibition of apoptotic damage induced by staurosporine or by serum-free medium, its suppression of hypoxia-induced membrane deterioration in the brain, and its actions of increasing the expression of the mitochondrial DNA-encoded COX III subunit of cytochrome c oxidase and the ND1 subunit of NADH dehydrogenase. As multiple modes of action may apply to bilobalide, it could be useful in developing therapy for disorders involving cerebral ischemia and neurodegeneration.