Inhibitory effect of Ginkgo biloba extract on the expression of inducible nitric oxide synthase in endothelial cells

The Role of Food Supplementation in Microcirculation-A Comprehensive Review

(1) Background: Cardiovascular disease (CVD) is a major public health concern worldwide and a key cause of morbidity and mortality in developed countries. Accumulating evidence shows that several CVD forms are characterized by significant microcirculatory dysfunction, which may both cause and be caused by macrovascular disease, often preceding clinical manifestations by several years. Therefore, interest in exploring food supplements to prevent and restore microcirculation has grown. Given the continuous need to expand the available therapeutic arsenal for CVD, the food supplements market has recently grown and is expected to continue growing. (2) Methods: We provide an authoritative up-to-date comprehensive review of the impact of food supplementation on microcirculation by analyzing the European and American legal food supplements framework and the importance of food safety/food quality in this industry. We review the main literature about food bioactive compounds with a focus on microcirculation and some main food supplements with proven benefits. (3) Results: Despite a lack of scientific evidence, diet and microcirculatory function are clearly connected. The main food supplement examples in the literature with potential beneficial effects on microcirculation are: Ruscus aculeatus L., Centella asiatica L., Ginkgo biloba L., Salvia miltiorrhiza Bunge, Crataegus spp., Ginseng, Mangifera indica L., Aesculus hippocastanum L., Hamamelis virginiana L., and Vitis vinifera L. (4) Conclusions: Further clinical trials are necessary to better explore the effects of these food supplements.

Protective Role of Natural Products in Glioblastoma Multiforme: A Focus on Nitric Oxide Pathway

In spite of therapeutic modalities such as surgical resection, chemotherapy, and radiotherapy, Glioblastoma Multiforme (GBM) remains an incurable fatal disease. This necessitates further therapeutic options that could enhance the efficacy of existing modalities. Nitric Oxide (NO), a short-lived small molecule, has been revealed to play a crucial role in the pathophysiology of GBM. Several studies have demonstrated that NO is involved in apoptosis, metastasis, cellular proliferation, angiogenesis, invasion, and many other processes implicated in GBM pathobiology. Herein, we elaborate on the role of NO as a therapeutic target in GBM and discuss some natural products affecting the NO signaling pathway.

Bilobalide Alleviated Dextran Sulfate Sodium-Induced Experimental Colitis by Inhibiting M1 Macrophage Polarization Through the NF-κB Signaling Pathway

Bilobalide, a unique Ginkgo biloba constituent has attracted significant interest as a novel therapeutic option for neuronal protection. However, there is paucity of data on its effect on colitis. This work sought to evaluate the effect of bilobalide on macrophage polarization in vitro and dextran sulfate sodium (DSS) induced colitis in vivo. Through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and annexin V/PI assay, it was shown that bilobalide has no significant toxicity on macrophage. Lipopolysaccharide (LPS) and interferon-gamma (IFN-γ) induced macrophage activation and polarization were significantly suppressed by bilobalide as indicated by reduced expression of cytokine, major histocompatibility complex II (MHC-II), and CD11c. Pertinently, the signaling pathway study showed that the phosphorylation of p65 and its nuclear translocation were decreased while STAT1 was not affected. In DSS-treated mice, administration (i.g) of three doses of bilobalide na\mely 1.25 mg/kg (low dose group), 2.5 mg/kg (medium dose group), and 5 mg/kg (high dose group) was performed daily starting from day 1 to day 10. Medium and high dose bilobalide markedly reduced the inflammation of colitis proved via elevation of bodyweight, decrement in disease activity index (DAI), alleviation of colon damage as well as reduction in activity of colon tissue myeloperoxidase activity. In accordance with the in vitro results, the levels of inflammatory cytokines such as interleukin 6 (IL-6), IL-1β, and tumor necrosis factor (TNF-α) in serum as well as messenger RNA (mRNA) expression in colon were obviously reduced in the bilobalide treated groups. Also, factor nuclear factor kappa B (NF-κB) signaling pathway was decreased significantly by bilobalide treatment. Collectively, these results indicated that administration of bilobalide improved experimental colitis via inhibition of M1 macrophage polarization through the NF-κB signaling pathway. Thus, bilobalide could act as a potential drug for the treatment of inflammatory bowel disease (IBD) in the not-too-distant future.

EGb761 Ameliorates Neuropathic Pain by Scavenging Reactive Oxygen Species

BACKGROUND

Neuropathic pain is a well-known type of chronic pain caused by damage to the nervous system. Until recently, researchers have found that increased generation of reactive oxygen species (ROS) contributes to the development of exaggerated pain hypersensitivity during neuropathic pain.

METHODS

In this study, we investigated the antinociceptive efficacy of Ginkgo biloba extract (EGb761) in chronic constriction injury (CCI) model of neuropathic pain of rats. To explore the underlying mechanisms, the effects of EGb761 on the excitability of dorsal root ganglion (DRG) neurons and activation of JNK in DRG were explored.

RESULTS

We showed that systemic administration of EGb761 inhibited the behavioral responses of neuropathic pain and found that EGb761 treatment could inhibit the H2O2-induced depolarization in the acutely dissociated DRG neurons. In addition, we found that EGb761 treatment could inhibit the expression of p-JNK in DRG.

CONCLUSION

Taken together, our results suggest that administration of EGb761 can ameliorate neuropathic pain, and further indicate that JNK, which is activated by both exogenous and endogenous ROS, might be the mechanism underlying the effects of EGb761 on CCI neuropathic pain.

The Effect ofGinkgo bilobaExtract (EGb 761) Pretreatment on Intestinal Epithelial Apoptosis Induced by Intestinal Ischemia/Reperfusion in Rats: Role of Ceramide

Apoptosis was demonstrated to be a major mode of intestinal epithelial cell death caused by intestinal ischemia/reperfusion ( II / R ). Ceramide has been proposed as a messenger for apoptosis. The present study was aimed to investigate the effect of Ginkgo biloba extract 761 (EGb 761) pretreatment on II / R -induced intestinal mucosal epithelial apoptosis in rats and the mechanism related to ceramide. The rat model of II / R injury was produced by clamping superior mesenteric artery for 60 min followed by reperfusion for 180 min. Twenty four rats were randomly allocated into Sham, II / R and EGb + II / R groups. In EGb + II / R group, EGb 761 (100 mg/kg per day) was administered intragastrically for 7 days before the surgery. Animals in II / R and sham groups were treated with equal volume of normal saline solution. Intestinal mucosal epithelial apoptosis was detected via electron microscopy and TUNEL method. Lipid peroxidation in intestinal mucosa was determined by detecting the malondialdehyde level and the activities of superoxide dismutase and peroxidase glutathione. The ceramide generation and sphingomyelinase (SMase) mRNA expression in intestinal mucosa were determined by high performance, thin layer chromatography, and RT-PCR, respectively. II / R caused intestinal mucosal epithelial apoptosis and over-production of the ceramide accompanied by up-regulation of SMase mRNA expression and increases of lipid peroxidation. EGb 761 pretreatment significantly decreased apoptosis index, and concurrently reduced the ceramide generation accompanied by down-regulation of SMase expression and inhibition of lipid peroxidation. The findings indicate that EGb 761 pretreatment attenuates II / R -induced intestinal epithelial apoptosis, which might be attributable to its antioxidant action of mediating ceramide pathway.

Pycnogenol and Ginkgo biloba extract: effect on peroxynitrite-oxidized sarcoplasmic reticulum Ca-ATPase

The effect of two natural standardized plant extracts, Pycnogenol(®) and EGb 761, on sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) activity and posttranslational modifications induced by peroxynitrite was investigated to assess their possible protective role. EGb 761 was found to have a protective effect on SERCA activity in the concentration range of 5-40 µg/ml. On the other hand, Pycnogenol(®) caused a decrease of SERCA activity at concentrations of 25 µg/ml. EGb 761 did not prevent protein carbonyl formation upon oxidation with peroxynitrite. On the contrary, Pycnogenol(®) at the concentrations of 5 and 10 µg/ml significantly decreased the level of protein carbonyls by 44% and 54%, respectively. Neither Pycnogenol(®) nor EGb 761 exerted a protective effect against thiol group oxidation.The plant extracts studied modulated peroxynitrite-injured SERCA activity by different ways and failed to correlate with posttranslational modifications. Their effect seems to be associated with their ability to change SERCA conformation rather than by their antioxidant capacity.

Gingko biloba extract reduces VEGF and CXCL-8/IL-8 levels in keratinocytes with cumulative effect with epigallocatechin-3-gallate

In skin inflammation, vascular endothelial growth factor (VEGF) and CXCL-8/IL-8 play an important role and are produced by activated keratinocytes. Extracts from Ginkgo biloba leaves (GBE), widely used in phytotherapy, have been reported to exert antioxidant and anti-inflammatory properties in the skin. We therefore evaluated the effects of GBE on the release of VEGF and CXCL8/IL-8 by normal human keratinocytes (NHKs) activated by tumor necrosis factor alpha (TNFalpha). Moreover, as we previously showed that epigallocatechin-3-gallate (EGCG) reduces VEGF and CXCL8/IL-8 secretion in TNFalpha-activated NHKs, we also tested its effect in association with GBE. Our results showed that GBE exerted a potent inhibition on VEGF and CXCL8/IL-8 levels in activated cells. In association with EGCG, GBE down-regulated VEGF and CXCL8/IL-8 levels in a cumulative manner in TNFalpha-stimulated NHKs. These results suggest that GBE, alone or in association with EGCG may contribute to moderate inflammatory processes in skin diseases associated with angiogenesis.

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.

Ginkgo biloba extract (EGb 761) attenuates lung injury induced by intestinal ischemia/reperfusion in rats: Roles of oxidative stress and nitric oxide

AIM: To investigate the effect of ginkgo biloba extract (EGb 761) on lung injury induced by intestinal ischemia/reperfusion (II/R).

METHODS: The rat model of II/R injury was produced by clamping the superior mesenteric artery for 60 min followed by reperfusion for 180 min. The rats were randomly allocated into sham, II/R, and EGb +II/R groups. In EGb +II/R group, EGb 761 (100 mg/kg per day) was given via a gastric tube for 7 consecutive days prior to surgery. Rats in II/R and sham groups were treated with equal volumes of the vehicle of EGb 761. Lung injury was assessed by light microscopy, wet-to-dry lung weight ratio (W/D) and pulmonary permeability index (PPI). The levels of malondialdehyde (MDA) and nitrite/nitrate (NO₂^-/NO₃^-), as well as the activities of superoxide dismutase (SOD) and myeloperoxidase (MPO) were examined. Western blot was used to determine the expression of inducible nitric oxide synthase (iNOS).

RESULTS: EGb 761 markedly improved mean arterial pressure and attenuated lung injury, manifested by the improvement of histological changes and significant decreases of pulmonary W/D and PPI (p < 0.05 or 0.01). Moreover, EGb 761 markedly increased SOD activity, reduced MDA levels and MPO activity, and suppressed NO generation accompanied by down-regulation of iNOS expression (p < 0.05 or 0.01).

CONCLUSION: The results indicate that EGb 761 has a protective effect on lung injury induced by II/R, which may be related to its antioxidant property and suppressions of neutrophil accumulation and iNOS-induced NO generation. EGb 761 seems to be an effective therapeutic agent for critically ill patients with respiratory failure related to II/R.

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.

Effects of Ginkgo biloba on exhaled nasal nitric oxide during normobaric hypoxia in humans

Ginkgo biloba, an extract of the ginkgo tree, may prevent or lessen symptoms of acute mountain sickness in humans. The mechanism of this effect is poorly understood. One hypothesis is that ginkgo alters nitric oxide (NO) metabolism, possibly by scavenging NO or altering nitric oxide synthase expression and thereby lessening the vasodilatory effects of NO. To date, an effect of Ginkgo biloba on NO metabolism has not been demonstrated in humans. We measured exhaled nasal NO output in humans (n = 9) during normoxia and then during acute normobaric hypoxia (goal oxyhemoglobin saturation 75% to 85%) before and after administration of a standardized extract of Ginkgo biloba (120 mg twice daily for 5 days). Oxygen saturation, heart rate, and minute ventilation were similar before and after Ginkgo biloba administration. Exhaled nasal NO output was increased during normoxia following ginkgo (p < 0.02) and reduced during normobaric hypoxia both before (p < 0.02) and following (p < 0.003) ginkgo. Exhaled nasal NO output during normobaric hypoxia was lowest following ginkgo (p < 0.003). We conclude that Ginkgo biloba increases exhaled nasal NO output during normoxia and enhances reduced exhaled nasal NO output during normobaric hypoxia. Our results suggest that Ginkgo biloba may act to reduce AMS through an effect on NO metabolism.

Genotype-dependent expression of endothelial nitric oxide synthase (eNOS) and its regulatory proteins in cultured endothelial cells

DNA polymorphisms in endothelial nitric oxide synthase (eNOS) gene have been shown to be associated with constitutive eNOS expression and coronary artery disease (CAD). In the present study we explored the hypothesis whether genotype-dependent effects can be maintained in vitro during replication, or the effect is conditional on in vivo biological environments. Human umbilical vein endothelial cells (HUVEC) were collected and cultured from 89 normal deliveries of Mexican Americans. The cells were treated with or without cigarette smoking extracts (CSE) and genotypes of eNOS polymorphisms were determined by PCR. We measured the levels of eNOS by ELISA and its binding proteins including heat-shock protein 90 (Hsp-90) and caveolin-1 by Western blotting. The rare C allele for the promoter T786C polymorphism (0.2), and the rare 4 x 27-bp repeat allele in the intron 4 (0.30) were different from those reported in other populations. Yet, the rare T allele in the exon 7 (G894T polymorphism) was similar as others. After four passages in vitro, both the intron 4 and promoter polymorphisms maintained significant effects on eNOS mRNA levels in HUVECs (P < 0.05). However, the effects on eNOS protein and enzyme activity were less consistent. Although primary smokers had significantly lower eNOS protein levels (P < 0.05), the in vitro CSE treatment on cultured HUVECs only resulted in a significant reduction in NO levels as measured by the stable metabolites of nitrite/nitrate (P < 0.001). Neither Hsp-90 nor caveolin-1--important eNOS regulators--appears to mediate the genotypesmoking effects on eNOS expression although HUVECs did produce more Hsp-90 when exposed to CSE. Our study demonstrates that endothelial cells maintain genotype-dependent expression even after the deprivation of in vivo environment. However, the cigarette smoking-genotype interaction may require such in vivo conditions to be manifested.

The effect of Ginkgo biloba extract (EGb 761) on hepatic sinusoidal endothelial cells and hepatic microcirculation in CCl4 rats

It has been shown that Ginkgo biloba Extract (EGb 761) increases peripheral and cerebral blood flow and microcirculation and improves myocardial ischemia reperfusion injury. This study was designed to investigate the effect of EGb 761 on hepatic endothelial cells and hepatic microcirculation. Sixty male Wister rats were divided into normal, carbon tetrachloride (CCl4) and EGb groups, and were given normal saline, CCl4 and CCl4 plus EGb 761, respectively, for 10 weeks. Samples were taken from the medial lobe of the rat livers ten weeks later. Hepatic sinusoidal endothelial cells and other parameters of hepatic microcirculation were observed under transmission electron microscopy (TEM). The amount of malondialdehyde (MDA), endothelin (ET-1), platelet-activating factor (PAF) and nitric oxide (NO) in liver tissue was determined by spectrophotometry and radioimmunoassay, respectively. Compared with the CCl4 group, aggregation of blood cell or micro thrombosis in hepatic sinusoids, deposition of collagen in hepatic sinusoids and space of Disse, injury of endothelial cells and capillization of hepatic sinusoid was significantly reduced in the EGb group. The amount of MDA, ET-1 and PAF was markedly reduced in the EGb group than in the CCl4 group, while no significant difference in the amount of NO was observed between the two groups. The results demonstrate that EGb 761 has protective effect on hepatic endothelial cells and hepatic microcirculation in rats with chronic liver injury induced by CCl4. The mechanisms may involve its inhibition on ET-1, PAF and lipid peroxidation.

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.

Nitric oxide, human diseases and the herbal products that affect the nitric oxide signalling pathway

1. Nitric oxide (NO) is formed enzymatically from l-arginine in the presence of nitric oxide synthase (NOS). Nitric oxide is generated constitutively in endothelial cells via sheer stress and blood-borne substances. Nitric oxide is also generated constitutively in neuronal cells and serves as a neurotransmitter and neuromodulator in non-adrenergic, non-cholinergic nerve endings. Furthermore, NO can also be formed via enzyme induction in many tissues in the presence of cytokines. 2. The ubiquitous presence of NO in the living body suggests that NO plays an important role in the maintenance of health. Being a free radical with vasodilatory properties, NO exerts dual effects on tissues and cells in various biological systems. At low concentrations, NO can dilate the blood vessels and improve the circulation, but at high concentrations it can cause circulatory shock and induce cell death. Thus, diseases can arise in the presence of the extreme ends of the physiological concentrations of NO. 3. The NO signalling pathway has, in recent years, become a target for new drug development. The high level of flavonoids, catechins, tannins and other polyphenolic compounds present in vegetables, fruits, soy, tea and even red wine (from grapes) is believed to contribute to their beneficial health effects. Some of these compounds induce NO formation from the endothelial cells to improve circulation and some suppress the induction of inducible NOS in inflammation and infection. 4. Many botanical medicinal herbs and drugs derived from these herbs have been shown to have effects on the NO signalling pathway. For example, the saponins from ginseng, ginsenosides, have been shown to relax blood vessels (probably contributing to the antifatigue and blood pressure-lowering effects of ginseng) and corpus cavernosum (thus, for the treatment of men suffering from erectile dysfunction; however, the legendary aphrodisiac effect of ginseng may be an overstatement). Many plant extracts or purified drugs derived from Chinese medicinal herbs with proposed actions on NO pathways are also reviewed.

Effects of Ginkgo biloba extract on the proliferation of vascular smooth muscle cells in vitro and on intimal thickening and interleukin-1beta expression after balloon injury in cholesterol-fed rabbits in vivo

Restenosis may develop in response to cytokine activation and smooth muscle cell proliferation. Ginkgo biloba extract (EGb) has been used to treat cardiovascular and cerebrovascular diseases. In the present study, the effects of EGb on the growth of cultured vascular smooth muscle cells (VSMC), as well as on the expression of interleukin-1beta (IL-1beta) and the intimal response in balloon-injured arteries of cholesterol-fed rabbits, were investigated. Using bromodeoxyuridine incorporation as an index of cell proliferation, EGb was found to inhibit serum-induced mitogenesis of cultured rat aorta VSMC in a dose-dependent manner. In vivo, EGb and probucol ( positive control) reduced the atheroma area in thoracic aortas of male New Zealand white rabbits fed a 2% cholesterol diet for 6 weeks with balloon denudation of the abdominal aorta being performed at the end of the third week. Intimal hyperplasia, expressed as the intimal/medial area ratio, in the abdominal aortas was significantly inhibited in the both the EGb group (0.61 +/- 0.06) and the probucol group (0.55 +/- 0.03) compared to the C group (0.87 +/- 0.02). In the balloon-injured abdominal aorta, both EGb and probucol significantly reduced IL-1beta mRNA and protein expression and the percentage of proliferating cells. The inhibitory effects of EGb on the intimal response might be attributed to its antioxidant capacity. EGb may have therapeutic potential for the prevention of restenosis after angioplasty.

Peroxynitrite scavenging activity of herb extracts

Peroxynitrite (ONOO(-)) is a cytotoxicant with strong oxidizing properties toward various cellular constituents, including sulphydryls, lipids, amino acids and nucleotides and can cause cell death, lipid peroxidation, carcinogenesis and aging. The aim of this study was to characterize ONOO(-) scavenging constituents from herbs. Twenty-eight herbs were screened for their ONOO(-) scavenging activities with the use of a fluorometric method. The potency of scavenging activity following the addition of authentic ONOO(-) was in the following order: witch hazel bark > rosemary > jasmine tea > sage > slippery elm > black walnut leaf > Queen Anne's lace > Linden flower. The extracts exhibited dose-dependent ONOO(-) scavenging activities. We found that witch hazel (Hamamelis virginiana L.) bark showed the strongest effect for scavenging ONOO(-) of the 28 herbs. Hamamelitannin, the major active component of witch hazel bark, was shown to have a strong ability to scavenge ONOO(-). It is suggested that hamamelitannin might be developed as an effective peroxynitrite scavenger for the prevention of ONOO(-) involved diseases.

Peroxynitrite scavenging and cytoprotective activity of 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether from the marine alga Symphyocladia latiuscula

Peroxynitrite (ONOO(-)), formed from the reaction of superoxide (O(2)*(-)) and nitric oxide (*NO), is a cytotoxic species that can oxidize several cellular components such as proteins, lipids, and DNA. It has been implicated in diseases such as Alzheimer's disease, rheumatoid arthritis, cancer, and atherosclerosis. Due to the lack of endogenous enzymes responsible for ONOO(-) inactivation, developing a specific ONOO(-) scavenger is of considerable importance. The aim of this study was to evaluate the ability of marine natural products to scavenge ONOO(-) and to protect cells against ONOO(-). Methanolic extracts of 17 marine alga were tested for their ONOO(-) scavenging activity. Among them, Symphyocladia latiuscula showed the potent scavenging activity. CH(2)CH(2) fraction was partitioned with CH(2)CH(2) following n-hexanal extraction from the methanol extract of S. latiuscula. It was highly effective for ONOO(-) scavenging activity. Further analysis of the active fractionated extract identified 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether (TDB) as a potent ONOO(-) scavenger. The data demonstrated that TDB led to decreased ONOO(-)-mediated nitration of tyrosine through electron donation. TDB showed significant inhibition on nitration of bovine serum albumin and low-density lipoprotein by ONOO(-) in a dose-dependent manner. It also provided cytoprotection from cell damage induced by ONOO(-). TDB can be developed as an effective peroxynitrite scavenger for the prevention of the involved diseases.

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

Nitric oxide (NO) is a principal mediator in many physiological and pathological processes. NO produced by constitutive nitric oxide synthase in endothelial cells (eNOS) acts as a vasodilator, whereas excess NO production due to elevated expression of inducible nitric oxide synthase (iNOS) may produce cytotoxic effects to cells in the vascular wall. We demonstrated in our previous work that the extract of Ginkgo biloba leaves (EGb) inhibits iNOS-mediated NO production. The objective of the present study was to investigate the effects of several active EGb components on iNOS-mediated NO production in macrophages derived from a human monocytic cell line (THP-1), as well as on eNOS-mediated NO production in human umbilical vein endothelial cells (HUVEC). Ginkgolide A, ginkgolide B, or bilobalide (0.25 to 1.0 microg/mL) caused a 30-65% reduction in the levels of NO metabolites released by THP-1 macrophages after 4 hr of incubation, with a corresponding decrease in iNOS activity. Western immunoblotting analysis coupled with a nuclease protection assay and reverse transcription-polymerase chain reaction revealed a concomitant reduction in the levels of iNOS protein mass and mRNA in ginkgolide A-, ginkgolide B-, or bilobalide-treated macrophages. On the other hand, these compounds did not affect eNOS-mediated NO production or the expression of eNOS protein and mRNA in HUVEC. Taken together, these results suggest that ginkgolide A, ginkgolide B, and bilobalide may contribute to the selective inhibitory effect of EGb on iNOS expression without affecting eNOS-mediated NO production.