Protection of primary glial cells by grape seed proanthocyanidin extract against nitrosative/oxidative stress

Tackling the Future Pandemics: Broad-Spectrum Antiviral Agents (BSAAs) Based on A-Type Proanthocyanidins

A-type proanthocyanidins (PAC-As) are plant-derived natural polyphenols that occur as oligomers or polymers of flavan-3-ol monomers, such as (+)-catechin and (-)-epicatechin, connected through an unusual double A linkage. PAC-As are present in leaves, seeds, flowers, bark, and fruits of many plants, and are thought to exert protective natural roles against microbial pathogens, insects, and herbivores. Consequently, when tested in isolation, PAC-As have shown several biological effects, through antioxidant, antibacterial, immunomodulatory, and antiviral activities. PAC-As have been observed in fact to inhibit replication of many different human viruses, and both enveloped and non-enveloped DNA and RNA viruses proved sensible to their inhibitory effect. Mechanistic studies revealed that PAC-As cause reduction of infectivity of viral particles they come in contact with, as a result of their propensity to interact with virion surface capsid proteins or envelope glycoproteins essential for viral attachment and entry. As viral infections and new virus outbreaks are a major public health concern, development of effective Broad-Spectrum Antiviral Agents (BSAAs) that can be rapidly deployable even against future emerging viruses is an urgent priority. This review summarizes the antiviral activities and mechanism of action of PAC-As, and their potential to be deployed as BSAAs against present and future viral infections.

Reactive Oxygen Species Scavenging Functional Hydrogel Delivers Procyanidins for the Treatment of Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) is accompanied by the overload of reactive oxygen species (ROS), which can result in secondary brain injury. Although procyanidins (PCs) have a powerful free radical scavenging capability and have been widely studied in the treatment of TBI, conventional systemic drug therapy cannot make the drug reach the targeted area in the early stage of TBI and will cause systemic side effects because of the presence of the blood-brain barrier (BBB). To address this tissue, we designed and fabricated a ROS-scavenging functional hydrogel loaded PC (GelMA-PPS/PC) to deliver the drug by responding to the traumatic microenvironment. In situ injection of the GelMA-PPS/PC hydrogel effectively avoided the BBB and was directly applied to the surface of brain tissue to target the traumatic area. Hydrophobic poly(propylene sulfide)60 (PPS60), an ROS quencher and H2O2-responsive substance, was covalently bound to GelMA and exposed in response to the trauma microenvironment. At the same time, the H2O2 response of PPS60 further caused the structure of the hydrogel to degrade and release the encapsulated PC. Then PC could regulate the oxidative stress response in the cells and synergistically deplete ROS to play a neurotrophic protective role. This work suggests a novel method for the treatment of secondary brain injury by inhibiting the oxidative stress response after TBI.

Quantitation of spin probe-detectable oxidants in cells using electron paramagnetic resonance spectroscopy: To probe or to trap?

Electron Paramagnetic Resonance (EPR) spectroscopy coupled with spin traps/probes enables quantitative determination of reactive nitrogen and oxygen species (RNOS). Even with numerous studies using spin probes, the methodology has not been rigorously investigated. The autoxidation of spin probes has been commonly overlooked. Using the spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH), the present study has tested the effects of metal chelators, temperature, and oxygen content on the autoxidation of spin probes, where an optimized condition is refined for cell studies. The apparent rate of CMH autoxidation under this condition is 7.01 ± 1.60 nM/min, indicating low sensitivity and great variation of the CMH method and that CMH autoxidation rate should be subtracted from the generation rate of CMH-detectable oxidants (simplified as oxidants below) in samples. Oxidants in RAW264.7 cells are detected at an initial rate of 4.0 ± 0.7 pmol/min/10⁶ cells, which is not considered as the rate of basal oxidants generation because the same method has failed to detect oxidant generation from the stimulation of phorbol-12-mysirate-13-acetate (PMA, 0.1 nmol/10⁶ cells) in cells (2.5 ± 0.9 for PMA vs. 2.1 ± 1.5 pmol/min/10⁶ cells for dimethyl sulfoxide (DMSO)-treated cells). In contrast, the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), which exhibits minimal autoxidation, reveals differences between PMA and DMSO treatment (0.26 ± 0.09 vs. -0.06 ± 0.12 pmol/min/10⁶ cells), which challenges previous claims that spin probes are more sensitive than spin traps. We have also found that low temperature EPR measurements of frozen samples of CMH autoxidation provide lower signal intensity and greater variation compared to RT measurements of fresh samples. The current study establishes an example for method development of RNOS detection, where experimental details are rigorously considered and tested, and raises questions on the applications of spin probes and spin traps.

Grape seed proanthocyanidins and metformin combination attenuate hepatic endoplasmic reticulum stress in rats subjected to nutrition excess

CONTEXT

Endoplasmic reticulum (ER) stress in the liver is a pathological outcome of nutrient excess and is suggested to be one of the hits for progressive liver injury.

OBJECTIVE

This study investigated whether grape seed proanthocyanidins (GSP) and metformin (MET) alone or in combination can relieve hepatic ER stress induced in rats subjected to calorie excess.

MATERIAL AND METHODS

Male albino Wistar rats were given high calorie diet (HCD) for 45 days, while GSP (100 mg/kg body weight) and MET (50 mg/kg body weight) were administered either alone or in combination for last 15 days.

RESULTS

GSP, MET or both had reduced the levels of ER stress markers and chaperons, and suppressed the activation of lipogenic and inflammatory mediators in rat liver.

DISCUSSION

Though GSP and MET had reduced ER stress and inflammation individually, combination treatment with GSP + MET was more effective.

CONCLUSION

We suggest intervention with GSP and MET intake has to be considered for the management of liver disorders.

Protective role of resveratrol on testicular germ cells in mice with testicular toxicity

Objective

The aim of the present study was to investigate the possible beneficial effects of resveratrol in mice subjected to vinyl cyclohexene dieposide (VCD) -induced testicular toxicity.

Material and methods

A total of thirty- six Swiss albino male mice aged 28-days were used in the present study. The study was composed of two stages where mice which received or did not receive VCD (320 mg/kg/day) were administered resveratrol. The animals were assigned into control and resveratrol-treated groups in the first stage and into groups of VCD- and VCD+resveratrol-treated groups in the second stage. At the end of the experiments, relative testicular weight (TW/BW) and dry/wet weight of testis (TDW/TWW) were calculated. Histological analysis by hematoxylin and eosin (H&E) staining and immunohistochemical staining by BAX and Bcl-2 were performed. Serum testosterone, LH and FSH levels were measured by a commercially available ELISA kit.

Results

Resveratrol caused a dose-dependent increase in TW/BW and decrease in TDW/TWW (p<0.05). Resveratrol at a dose of 20 mg/kg resulted in an improvement in testosterone, LH and FSH levels in mice with VCD-induced testicular toxicity (p<0.001). Resveratrol also improved apoptotic index and epithelial cell height of testicular seminipherous tubuli significantly after VCD exposure (p<0.001).

Conclusion

Results of the present study suggest that resveratrol can be used as a protective and/or therapeutic agent particularly for cases with male infertility caused by testicular toxicity.

Phytochemical Constituents, Health Benefits, and Industrial Applications of Grape Seeds: A Mini-Review

Grapes are one of the most widely grown fruits and have been used for winemaking since the ancient Greek and Roman civilizations. Grape seeds are rich in proanthocyanidins which have been shown to possess potent free radical scavenging activity. Grape seeds are a complex matrix containing 40% fiber, 16% oil, 11% proteins, and 7% complex phenols such as tannins. Grape seeds are rich sources of flavonoids and contain monomers, dimers, trimers, oligomers, and polymers. The monomeric compounds includes (+)-catechins, (−)-epicatechin, and (−)-epicatechin-3-O-gallate. Studies have reported that grape seeds exhibit a broad spectrum of pharmacological properties against oxidative stress. Their potential health benefits include protection against oxidative damage, and anti-diabetic, anti-cholesterol, and anti-platelet functions. Recognition of such health benefits of proanthocyanidins has led to the use of grape seeds as a dietary supplement by the consumers. This paper summarizes the studies of the phytochemical compounds, pharmacological properties, and industrial applications of grape seeds.

Bioactive Compounds and Their Neuroprotective Effects in Diabetic Complications

Hyperglycemia, hyperlipidemia and impaired insulin signaling during the development of diabetes can cause diabetic complications, such as diabetic neuropathy, resulting in significant morbidity and mortality. Although various therapeutics are available for the treatment of diabetic neuropathy, no absolute cure exists, and additional research is necessary to comprehensively understand the underlying pathophysiological pathways. A number of studies have demonstrated the potential health benefits of bioactive compounds, i.e., flavonoids and vitamins, which may be effective as supplementary treatments for diabetes and its complications. In this review, we highlight the most recent reports about the mechanisms of action of bioactive compounds (flavonoids and vitamins) possessing potential neuroprotective properties in diabetic conditions. Additional clinical studies are required to determine the appropriate dose and duration of bioactive compound supplementation for neuroprotection in diabetic patients.

Effects of Flavonoids from Food and Dietary Supplements on Glial and Glioblastoma Multiforme Cells

Quercetin, catechins and proanthocyanidins are flavonoids that are prominently featured in foodstuffs and dietary supplements, and may possess anti-carcinogenic activity. Glioblastoma multiforme is the most dangerous form of glioma, a malignancy of the brain connective tissue. This review assesses molecular structures of these flavonoids, their importance as components of diet and dietary supplements, their bioavailability and ability to cross the blood-brain barrier, their reported beneficial health effects, and their effects on non-malignant glial as well as glioblastoma tumor cells. The reviewed flavonoids appear to protect glial cells via reduction of oxidative stress, while some also attenuate glutamate-induced excitotoxicity and reduce neuroinflammation. Most of the reviewed flavonoids inhibit proliferation of glioblastoma cells and induce their death. Moreover, some of them inhibit pro-oncogene signaling pathways and intensify the effect of conventional anti-cancer therapies. However, most of these anti-glioblastoma effects have only been observed in vitro or in animal models. Due to limited ability of the reviewed flavonoids to access the brain, their normal dietary intake is likely insufficient to produce significant anti-cancer effects in this organ, and supplementation is needed.

Amelioration of cisplatin-induced nephrotoxicity by grape seed extract and fish oil is mediated by lowering oxidative stress and DNA damage

Cisplatin (CP) is a chemotherapeutic drug used in treatment of malignancies. However, its clinical utility is limited by nephrotoxicity. The purpose of the present study was to investigate the protective role of grape seed proanthocyanidin extract (GSPE) (100 mg/kg/day) or fish oil (FO) (5 ml/kg/day) against cisplatin induced nephrotoxicity in terms of biochemical parameters, oxidative stress and DNA damage. CP nephrotoxiciy is manifested by increased levels of serum creatinine, urea and uric acid, accompanied by their decrease in urine. Na, K and Ca levels were altered in both serum and urine. In addition, cisplatin caused a decrease in renal GSH, SH-group, SOD, GST, and Na-K-ATPase levels. However the levels of MDA, H2O2 and NO were increased. Also, we assessed the renal genotoxic potential of cisplatin as manifested by an increase in the tail length of DNA, tail intensity (DNA %) and tail moment. On the other hand, administration of GSPE or FO pre-cisplatin treatment ameliorated the current changes in most of the above tested parameters, particularly oxidative stress, endogenous antioxidant defense system and DNA damage indicating their curative effect. Thus, it can be concluded that the consumption of GSPE or FO might be useful for preventing nephrotoxicity caused by cisplatin treatment.

Anthocyanin Extracts from Black Soybean (Glycine max L.) Protect Human Glial Cells Against Oxygen-Glucose Deprivation by Promoting Autophagy

Anthocyanins have received growing attention as dietary antioxidants for the prevention of oxidative damage. Astrocytes, which are specialized glial cells, exert numerous essential, complex functions in both healthy and diseased central nervous system (CNS) through a process known as reactive astrogilosis. Therefore, the maintenance of glial cell viability may be important because of its role as a key modulator of neuropathological events. The aim of this study was to investigate the effect of anthocyanin on the survival of glial cells exposed to oxidative stress. Our results demonstrated that anthocyanin extracts from black soybean increased survival of U87 glioma cells in a dose dependent manner upon oxygen-glucose deprivation (OGD), accompanied by decrease levels of reactive oxygen species (ROS). While treatment cells with anthocyanin extracts or OGD stress individually activated autophagy induction, the effect was significantly augmented by pretreatment cells with anthocyanin extracts prior to OGD. The contribution of autophagy induction to the protective effects of anthocyanin was verified by the observation that silencing the Atg5 expression, an essential regulator of autophagy induction, reversed the cytoprotective effect of anthocyanin extracts against OGD stress. Treatment of U87 cells with rapamycin, an autophagy inducer, increased cell survival upon OGD stress comparable to anthocyanin, indicating that autophagy functions as a survival mechanism against oxidative stress-induced cytotoxicity in glial cells. Our results, therefore, provide a rationale for the use of anthocyanin as a preventive agent for brain dysfunction caused by oxidative damage, such as a stroke.

Oxidative stress and anti-oxidant status in diabetic rat liver: effect of plant polyphenols

Increased evidence in role of oxidative stress and grape seed extract (GSE) in diabetes and its complication led us to investigate the changes of oxidative stress and anti-oxidant defence in liver tissue of diabetic rats and possible effects of GSE. Diabetes was induced by a single intraperitoneal injection of streptozotocin. Seven days after STZ injection four groups were formed: Control, GSE-supplemented control, diabetic and GSE-supplemented diabetic and GSE was given for 6 weeks. Malondialdehyde levels and xanthine oxidase activities were not different among the groups. However, nitric oxide (NO) levels were higher in diabetic and GSE supplemented groups compared with non-diabetic and non-supplemented groups, respectively. Total anti-oxidant activity (TAA) was lower in diabetic groups compared with their non-diabetic controls and it was not affected by GSE. In conclusion, GSE supplementation has limited protective effect in liver tissue of diabetic rats via affecting NO levels and was not affecting TAA.

Botanical flavonoids on coronary heart disease

Ischemic heart disease (IHD) is one of the leading causes of death in Western countries. Prevention rather than treatment of heart disease can significantly improve patients' quality of life and reduce health care costs. Flavonoids are widely distributed in vegetables, fruits and herbal medicines. Regularly consuming botanicals, especially those containing flavonoids, has been associated with a reduction in cardiovascualar disease; thus, it is important to investigate how flavonoids improve cardiac resistance to heart disease and their related mechanisms of action. It has been shown that cardiomyocyte injury and death can result from ischemia-reperfusion, which is pathognomonic of ischemic heart disease. Massive reactive oxygen species (ROS) release at the onset of reperfusion produces cell injury and death. "Programming" the heart to either generate less ROS or to increase strategic ROS removal could reduce reperfusion response. Additionally, profuse nitric oxide (NO) release at reperfusion could be protective in "preconditioning" models. Botanical flavonoids induce preconditioning of the heart, thereby protecting against ischemia-reperfusion injury. In this article, we will discuss two herbs containing potent flavonoids, Scutellaria baicalensis and grape seed proanthocyanidin, which can potentially offer cardiac protection against ischemic heart disease.

Grape seed proanthocyanidin extract inhibits glutamate-induced cell death through inhibition of calcium signals and nitric oxide formation in cultured rat hippocampal neurons

Background

Proanthocyanidin is a polyphenolic bioflavonoid with known antioxidant activity. Some flavonoids have a modulatory effect on [Ca²⁺]_i. Although proanthocyanidin extract from blueberries reportedly affects Ca²⁺ buffering capacity, there are no reports on the effects of proanthocyanidin on glutamate-induced [Ca²⁺]_i or cell death. In the present study, the effects of grape seed proanthocyanidin extract (GSPE) on glutamate-induced excitotoxicity was investigated through calcium signals and nitric oxide (NO) in cultured rat hippocampal neurons.

Results

Pretreatment with GSPE (0.3-10 μg/ml) for 5 min inhibited the [Ca²⁺]_i increase normally induced by treatment with glutamate (100 μM) for 1 min, in a concentration-dependent manner. Pretreatment with GSPE (6 μg/ml) for 5 min significantly decreased the [Ca²⁺]_i increase normally induced by two ionotropic glutamate receptor agonists, N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). GSPE further decreased AMPA-induced response in the presence of 1 μM nimodipine. However, GSPE did not affect the 50 mM K⁺-induced increase in [Ca²⁺]_i. GSPE significantly decreased the metabotropic glutamate receptor agonist (RS)-3,5-Dihydroxyphenylglycine-induced increase in [Ca²⁺]_i, but it did not affect caffeine-induced response. GSPE (0.3-6 μg/ml) significantly inhibited synaptically induced [Ca²⁺]_i spikes by 0.1 mM [Mg²⁺]_o. In addition, pretreatment with GSPE (6 μg/ml) for 5 min inhibited 0.1 mM [Mg²⁺]_o- and glutamate-induced formation of NO. Treatment with GSPE (6 μg/ml) significantly inhibited 0.1 mM [Mg²⁺]_o- and oxygen glucose deprivation-induced neuronal cell death.

Conclusions

All these data suggest that GSPE inhibits 0.1 mM [Mg²⁺]_o- and oxygen glucose deprivation-induced neurotoxicity through inhibition of calcium signals and NO formation in cultured rat hippocampal neurons.

Procyanidin dimer B1 and trimer C1 impair inflammatory response signalling in human monocytes

The way specific procyanidins exert their anti-inflammatory effects is not fully understood. This study has investigated the capacity of different procyanidins to modulate lipopolysaccharide (LPS)-induced reactive oxygen species (ROS) production in THP1 human monocytes and their effects on the redox regulated protein kinases activity: IkB kinase beta (IKKb) and the extracellular signal-regulated kinase (ERK). LPS-triggered increase of ROS was prevented by cell pre-incubation with procyanidins. LPS induced ERK1/2 activation through phosphorylation, which was inhibited by all the compounds tested, the most active being epigallocatechin (EG), followed by epigallocatechin gallate (EGCG) and C1. Procyanidins inhibited IKKb activity in vitro. C1 and procyanidin extract (PE) exerted the maximal IKKb inhibition, followed by EGCG and dimer B1. Catechin exerted a slight but significant IKKb inhibition, in contrast to epicatechin, which was ineffective. In conclusion, procyanidins reduce the LPS-induced production of ROS and they exert their anti-inflammatory effects by inhibiting ERK1/2 and IKKb activity.

Grape seed proanthocyanidins protect cardiomyocytes from ischemia and reperfusion injury via Akt-NOS signaling

Ischemia/reperfusion (I/R) injury in cardiomyocytes is related to excess reactive oxygen species (ROS) generation and can be modulated by nitric oxide (NO). We have previously shown that grape seed proanthocyanidin extract (GSPE), a naturally occurring antioxidant, decreased ROS and may potentially stimulate NO production. In this study, we investigated whether GSPE administration at reperfusion was associated with cardioprotection and enhanced NO production in a cardiomyocyte I/R model. GSPE attenuated I/R-induced cell death [18.0 +/- 1.8% (GSPE, 50 microg/ml) vs. 42.3 +/- 3.0% (I/R control), P < 0.001], restored contractility (6/6 vs. 0/6, respectively), and increased NO release. The NO synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 200 microM) significantly reduced GSPE-induced NO release and its associated cardioprotection [32.7 +/- 2.7% (GSPE + L-NAME) vs. 18.0 +/- 1.8% (GSPE alone), P < 0.01]. To determine whether GSPE induced NO production was mediated by the Akt-eNOS pathway, we utilized the Akt inhibitor API-2. API-2 (10 microM) abrogated GSPE-induced protection [44.3% +/- 2.2% (GSPE + API-2) vs. 27.0% +/- 4.3% (GSPE alone), P < 0.01], attenuated the enhanced phosphorylation of Akt at Ser473 in GSPE-treated cells and attenuated GSPE-induced NO increases. Simultaneously blocking NOS activation (L-NAME) and Akt (API-2) resulted in decreased NO levels similar to using each inhibitor independently. These data suggest that in the context of GSPE stimulation, Akt may help activate eNOS, leading to protective levels of NO. GSPE offers an alternative approach to therapeutic cardioprotection against I/R injury and may offer unique opportunities to improve cardiovascular health by enhancing NO production and increasing Akt-eNOS signaling.

Protective Effects of Proanthocyanidin on Cerulein-induced Acute Pancreatic Inflammation in Rats

Background

The aim of this study was to assess the possible protective effect of proanthocyanidin against cerulein-induced acute pancreatic inflammation (AP) and oxidative injury.

Methods

Sprague-Dawley rats were pretreated with proanthocyanidine (100 mg/kg, orally) or saline 15 min before cerulein was given by 20 µg/kg subcutaneously at 1-h intervals within 4 hours. Six hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1b). Pancreas tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na⁺, K⁺-ATPase and myeloperoxidase (MPO) activities. Formation of reactive oxygen species in pancreatic tissue samples was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes, while the extent of tissue injury was analyzed microscopically.

Results

Acute pancreatitis caused a significant decrease in tissue GSH level and Na⁺, K⁺-ATPase activity, which was accompanied with significant increases in the pancreatic MDA, luminol and lucigenin chemiluminescences (CL) levels and MPO activity. Similarly TNF-α and IL-1β levels were elevated in the pancreatic group as compared to control group. On the other hand, proanthocyanidin treatment reversed all these biochemical indices, as well as histopathological alterations that were induced by cerulein.

Conclusions

Proanthocyanidine can ameliorate pancreatic injury induced by cerulein in rats, this result suggests that proanthocyanidin may have utility in treating acute pancreatititis.

The effect of OPC Factor on energy levels in healthy adults ages 45-65: a phase IIb randomized controlled trial

OBJECTIVE

To determine the efficacy of the food supplement OPC Factor to increase energy levels in healthy adults aged 45 to 65.

DESIGN

Randomized, placebo-controlled, triple-blind crossover study.

SUBJECTS

Twenty-five (25) healthy adults recruited from the University of Pennsylvania Health System.

INTERVENTIONS

OPC Factor,trade mark (AlivenLabs, Lebanon, TN) a food supplement that contains oligomeric proanthocyanidins from grape seeds and pine bark along with other nutrient supplements including vitamins and minerals, was in the form of an effervescent powder. The placebo was similar in appearance and taste.

OUTCOME MEASURES

Five outcome measurements were performed: (1) Energy subscale scores of the Activation-Deactivation Adjective Check List (AD ACL); (2) One (1) global question of percent energy change (Global Energy Percent Change); (3) One (1) global question of energy change measured on a Likert scale (Global Energy Scale Change); 4. One (1) global question of percent overall status change (Global Overall Status Percent Change); and (5) One (1) global question of overall status change measured on a Likert scale (Global Overall Status Scale Change).

RESULTS

There were no carryover/period effects in the groups randomized to Placebo/Active Product sequence versus Active Product/Placebo sequence. Examination of the AD ACL Energy subscale scores for the Active Product versus Placebo comparison revealed no significant difference in the intention-to-treat (IT) analysis and the treatment received (TR) analysis. However, Global Energy Percent Change (p = 0.06) and Global Energy Scale Change (p = 0.09) both closely approached conventional levels of statistical significance for the active product in the IT analysis. Global Energy Percent Change (p = 0.05) and Global Energy Scale Change (p = 0.04) reached statistical significance in the TR analysis. A cumulative percent responders analysis graph indicated greater response rates for the active product.

CONCLUSIONS

OPC Factor may increase energy levels in healthy adults aged 45-65 years. A larger study is recommended. Clinical Trials.gov identifier: NCT03318019.

Effect of grape seed extract on lead induced hypertension and heart rate in rat

The main objective of this study was to evaluate the potential protective effect of red Grape Seed Extract (GSE) on lead induced hypertension (HTN) and Heart Rate (HR) in male Wistar rats. The rats were randomly assigned to one of 4 groups: Each group received lead acetate (100 ppm in drinking water), GSE (100 mg kg(-1), orally) or Lead + GSE for 45 days. Another group assigned as control group provided with tap water and regular pellet food. The Systolic Blood Pressure (SBP) and heart rate were determined by tail plethysmography coupled to a computer system. There was a sustained elevation of SBP in lead exposed rats that significantly increased at day 18 (lead treated, 112.7 +/- 2.7 mmHg, vs. control, 105.6 +/- 2.6 mmHg, n = 10, p < 0.05) and reached a maximum level at day 36 (lead treated, 124.9 +/- 2.3 mmHg, vs. control, 103.6 +/- 3.1 mmHg, n = 10, p < 0.001). However, the other three groups; showed no significant changes in SBP. Furthermore, the heart rate was increased sustainly in lead exposed animals that was statistically significant at days 36 and 45 (lead treated group, 404.5 +/- 9.4 vs. control group, 381.7 +/- 6.7, n = 10, p < 0.05). The blood lead level in both lead and lead + GSE treated groups was increased significantly compared with control and GSE treated groups (p < 0.001). However, GSE administration had no effect on the blood lead level in lead treated group. According to the result of this study, it may be concluded that GSE could have beneficial effect in protecting the cardiovascular system through its antioxidant activity against oxidative stress.

Short-term supplementation with plant extracts rich in flavonoids protect nigrostriatal dopaminergic neurons in a rat model of Parkinson's disease

OBJECTIVE

Antioxidants from plants were known to reduce the oxidative stress by scavenging free radicals, chelating metal ions and reducing inflammation. As increased oxidative stress was implicated in the nigrostriatal dopaminergic neuronal loss in Parkinson's disease (PD), we have assessed whether the plant extracts protects the nigrostriatal dopaminergic neurons in the animal model of PD.

METHODS

Male adult Sprague-Dawley rats were treated orally between 10 am-11 am each day with the extracts from tangerine peel, grape seeds, cocoa and red clover for four days. One hour after the final dosing, the left medial forebrain bundle was lesioned by infusing the dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA; 12 microg) under anaesthesia. Seven days post-lesion, the number of dopaminergic cells in the substantia nigra pars compacta and the levels of dopamine and its metabolites 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striata were quantified and compared with the vehicle-treated groups.

RESULTS

Compared to the unlesioned side, 6-OHDA lesions significantly reduced the number of dopaminergic cells and the levels of dopamine and its metabolites DOPAC and HVA in the vehicle-treated animals. Pretreatment of animals with extracts of tangerine peel (rich in polymethoxylated flavones; 35 mg/kg/day), cocoa-2 (rich in procyanidins; 100 mg/kg/day) and red clover (rich in isoflavones; 200 mg/kg/day) significantly attenuated the 6-OHDA-induced dopaminergic loss. However, no significant protection was seen in animals supplemented with red and white grape seeds (rich in catechins; 100 mg/kg/day), and cocoa-1 (rich in catechins; 100 mg/kg/day).

CONCLUSIONS

Pre-treatment of plant extracts rich in polymethoxylated flavones, procyanidins and isoflavones but not catechins protected the nigrostriatal dopaminergic neurons in the rat model of PD.

Microglial cells in astroglial cultures: a cautionary note

Primary rodent astroglial-enriched cultures are the most popular model to study astroglial biology in vitro. From the original methods described in the 1970's a great number of minor modifications have been incorporated into these protocols by different laboratories. These protocols result in cultures in which the astrocyte is the predominant cell type, but astrocytes are never 100% of cells in these preparations. The aim of this review is to bring attention to the presence of microglia in astroglial cultures because, in my opinion, the proportion of and the role that microglial cells play in astroglial cultures are often underestimated. The main problem with ignoring microglia in these cultures is that relatively minor amounts of microglia can be responsible for effects observed on cultures in which the astrocyte is the most abundant cell type. If the relative contributions of astrocytes and microglia are not properly assessed an observed effect can be erroneously attributed to the astrocytes. In order to illustrate this point the case of NO production in activated astroglial-enriched cultures is examined. Lipopolysaccharide (LPS) induces nitric oxide (NO) production in astroglial-enriched cultures and this effect is very often attributed to astrocytes. However, a careful review of the published data suggests that LPS-induced NO production in rodent astroglial-enriched cultures is likely to be mainly microglial in origin. This review considers cell culture protocol factors that can affect the proportion of microglial cells in astroglial cultures, strategies to minimize the proportion of microglia in these cultures, and specific markers that allow the determination of such microglial proportions.

Cytotoxicity induced by grape seed proanthocyanidins: role of nitric oxide

Grape seed proanthocyanidin extract (GPSE) at high doses has been shown to exhibit cytotoxicity that is associated with increased apoptotic cell death. Nitric oxide (NO), being a regulator of apoptosis, can be increased in production by the administration of GSPE. In a chick cardiomyocyte study, we demonstrated that high-dose (500 microg/ml) GSPE produces a significantly high level of NO that contributes to increased apoptotic cell death detected by propidium iodide and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. It is also associated with the depletion of intracellular glutathione (GSH), probably due to increased consumption by NO with the formation of S-nitrosoglutathione. Co-treatment with L-NAME, a NO synthase inhibitor, results in reduction of NO and apoptotic cell death. The decline in reduced GSH/oxidized GSH (GSSG) ratio is also reversed. N-Acetylcysteine, a thiol compound that reacts directly with NO, can reduce the increased NO generation and reverse the decreased GSH/GSSG ratio, thereby attenuating the cytotoxicity induced by high-dose GSPE. Taken together, these results suggest that endogenous NO synthase (NOS) activation and excessive NO production play a key role in the pathogenesis of high-dose GSPE-induced cytotoxicity.

Proanthocyanidin exposure to B6C3F1 mice significantly attenuates dimethylnitrosamine-induced liver tumor induction and mortality by differentially modulating programmed and unprogrammed cell deaths

Proanthocyanidins are of current interest as chemopreventive agents. The potential of the pre-, post- and co-exposure of proanthocyanidin-rich grape seed extract (GSPE) in preventing, reducing and/or delaying dimethylnitrosamine (N-nitrosodimethylamine, DMN)-induced liver tumorigenesis, carcinogenesis and mortality in male B6C3F1 mice was determined. Animals were divided into six groups: I-control, II-GSPE alone, III-DMN alone, IV-GSPE+DMN, V-DMN exposure (3 months) followed by GSPE diet (9 months) and VI-GSPE diet (3 months)+DMN (3 months)+control diet (6 months). DMN exposure (0-8 weeks: 5mg/kg; 8-12 weeks: 10mg/kg, i.p.) was limited to a total period of 3 months. GSPE was incorporated in laboratory chow (ADI: 100mg/kg b.w.). Animals were sacrificed at 3 month intervals, and serum chemistry, liver histopathology, integrity of hepatic genomic DNA, antioxidant status, and rates of apoptotic and necrotic cell deaths were determined. DMN-induced liver tumor formation (85%) and animal lethality (38%) were powerfully antagonized by co-administration of GSPE+DMN (tumor positive: 45%; death: 11%). More than 75% of the DMN-treated animals had numerous tumors (five or more), which were significantly reduced in the GSPE+DMN group (35%). GSPE also negatively influenced other protocols specifically designed to test initiation and progression phases. Thus, GSPE was instrumental in modulating metabolic cascades and regulated orchestration of cell death processes involved during the multistage tumorigenic process. These results unraveled that long-term exposure to proanthocyanidin-rich grape seed extract may serve as a potent barrier to all three stages of DMN-induced liver carcinogenesis and tumorigenesis by selectively altering oxidative stress, genomic integrity and cell death patterns in vivo.

Grape seed extract prevents H(2)O(2)-induced chromosomal damage in human lymphoblastoid cells

We examined the effects of grape seed extract (GSE) on chromosomal damage in two ways; induction on its own and prevention against treatment of reactive oxygen species (ROS). Chromosomal damage was evaluated by cytokinesis-block micronucleus assay (CBMN) in a human lymphoblastoid cell line, WIL2-NS cells. The GSE was composed of 89% proanthocyanidin with a degree of polymerization ranging from 2 to 15. GSE did not induce chromosomal damage in WIL2-NS cells at GSE concentrations up to 5 mg/l. In contrast, pretreatment with GSE dose-dependently prevented H(2)O(2)-induced chromosomal damage at an effective dose of 0.3 to 1 mg/l. A similar preventive effect of GSE was not detected in tert-butyl hydroperoxide-induced damage even at 5 mg/l. In a cell free system, GSE (<5 mg/l) directly scavenged H(2)O(2), but produced slight amounts of H(2)O(2) at higher concentrations (>50 mg/l). These results suggest that GSE is not genotoxic, but rather has an antigenotoxic effect against H(2)O(2) via direct scavenging action of H(2)O(2).

Neuroprotective effects of grape seed extract on neuronal injury by inhibiting DNA damage in the gerbil hippocampus after transient forebrain ischemia

Grape seed extract (GSE) possess cardioprotective abilities by functioning as in vivo antioxidants and by virtue of their ability to directly scavenge ROS including hydroxyl and peroxyl radicals. In the present study, we investigated the neuroprotective effects of grape seed extract (GSE) in the gerbil hippocampus after 5 min transient forebrain ischemia. Neuronal cell density in GSE-treated ischemic animals was significantly increased as compared with vehicle-treated ischemic animals 4 days after ischemic insult. In the GSE-treated groups, about 60% of pyramidal cells of the sham-operated group were stained with cresyl violet 4 days after ischemic insult. In this study, we found that GSE had neuroprotective effects on neuronal injury by inhibiting DNA damage in the CA1 region after ischemia. In vehicle-treated groups, 8-hydroxy-2'-deoxyguanosine (8-OHdG) immunoreactivity was significantly changed time-dependently, whereas the immunoreactivity in the GSE-treated group was similar to the sham-operated group. In addition, we confirmed that astrocytes and microglia did not show significant activation in the CA1 region 4 days after ischemia-reperfusion, because many CA1 pyramidal cells were not damaged. Therefore, these results suggest that GSE can protect ischemic neuronal damage by inhibiting DNA damage after transient forebrain ischemia.

Oxyresveratrol and resveratrol are potent antioxidants and free radical scavengers: effect on nitrosative and oxidative stress derived from microglial cells

Hydroxystilbenes are naturally occurring polyphenols with protective effects against reactive oxygen and nitrogen species (ROS/RNS). Here, we investigated oxyresveratrol (OXY), which is contained in high amounts in mulberry wood, in comparison to the antioxidant resveratrol (RES). We found that OXY is a more effective scavenger for 2,2-diphenyl-1-picryl-hydrazyl (DPPH, 100 microM) used as a general free radical model, compared to RES or trans-4-hydroxystilbene (IC(50)=28.9, 38.5, and 39.6 microM, respectively). When primary glial cell cultures were loaded with the ROS/RNS-sensitive fluorochrome 2,7-dichlorodihydrofluorescein, the lowest rise in the fluorescence signal after H(2)O(2) exposure was seen when the cells were pretreated with OXY. Using 4,5-diaminofluorescein (DAF-2) to monitor free nitric oxide levels (7.7 microM NO) in a spectrofluorimetric cell-free assay, we found again that OXY (at 5 microM) is a more effective scavenger. Accordingly, cultures of the murine microglial cell line N9 and primary mixed glial cultures were used to test the drug effects of NO production upon expression of the inducible isoform of nitric oxide synthase (iNOS). We found that both compounds considerably diminished NO (nitrite) levels, RES more effectively than OXY (IC(50)=22.36 and 45.31 microM). RES but not OXY down-regulated the expression of iNOS protein, but both did not alter iNOS activity. Furthermore, OXY displayed a generally lower cytotoxicity than RES. The radical and ROS scavenging properties, as well as the lower cytotoxicity towards microglia and the known good water solubility suggest OXY as a potential protectant against ROS/RNS.

Nitric oxide is not involved in the control of vasopressin release during acute forced swimming in rats

Neurons of the hypothalamo-neurohypophyseal system (HNS) are known to contain high amounts of neuronal nitric oxide (NO) synthase (nNOS). NO produced by those neurons is commonly supposed to be involved as modulator in the release of the two nonapeptides vasopressin (AVP) and oxytocin into the blood stream. Previous studies showed that forced swimming fails to increase the release of AVP into the blood stream while its secretion into the hypothalamus is triggered. We investigated here whether hypothalamically acting NO contributes to the control of the AVP release into blood under forced swimming conditions. Intracerebral microdialysis and in situ hybridization were employed to analyze the activity of the nitrergic system within the supraoptic nucleus (SON), the hypothalamic origin of the HNS. A 10-min forced swimming session failed to significantly alter the local NO release as indicated both by nitrite and, the main by-product of NO synthesis, citrulline levels in microdialysis samples collected from the SON. Microdialysis administration of NO directly into the SON increased the concentration of AVP in plasma samples collected during simultaneous forced swimming. In an additional experiment the effect of the defined stressor exposure on the concentration of mRNA coding for nNOS within the SON was investigated by in situ hybridization. Forced swimming increased the expression of nNOS mRNA at two and four hours after onset of the stressor compared to untreated controls. Taken together, our results imply that NO within the SON does not contribute to the regulation of the secretory activity of HNS neurons during acute forced swimming. Increased nNOS mRNA in the SON after forced swimming and the increase in AVP release in the presence of exogenous NO under forced swimming points to a possible role of NO in the regulation of the HNS under repeated stressor exposure.

Cytosolic and mitochondrial glutathione in microglial cells are differentially affected by oxidative/nitrosative stress

Glutathione (GSH), the major cellular protectant against reactive oxygen and nitrogen species, is compartmentalized in a cytosolic (c) and a mitochondrial (mt) pool. We investigated how c-GSH and mt-GSH are differentially affected by endogenously produced nitric oxide (NO). Microglial cell line (N9) cultures were immunostimulated with lipopolysaccharide/interferon-gamma to elicit the inducible isoform of NO synthase (iNOS). Despite a significant reduction in total GSH, the mt-GSH remained nearly unaffected by iNOS-mediated NO production. To investigate possible consequences of GSH depletion on the mitochondrial membrane potential, we used buthionine sulfoximine (BSO) to reduce separately the c-GSH, whereas ethacrynic acid (EA) was applied to deplete both mt-GSH and c-GSH. The mitochondrial membrane potential was more vulnerable to NO exposure in EA-pretreated cultures than in BSO-pretreated cultures, indicated by a potentiated release of tetramethylrhodamine from mitochondria into the cytosol. To relate the EA-mediated decrease in mitochondrial membrane potential to the oxidant buildup after GSH depletion, we loaded the cells with the oxidant-sensitive fluorochrome 2',7'-dihydrodichlorofluorescein (DCF) diacetate. EA treatment caused an increase in DCF fluorescence over time that was potentiated when the iNOS expression was stimulated. Inhibition of NO production abolished this effect. We conclude that endogenous NO production in microglial cells does not compromise the mt-GSH pool which, in turn, might explain the ability of these cells to combat high-output NO production.

Dermal wound healing properties of redox-active grape seed proanthocyanidins

Angiogenesis plays a central role in wound healing. Among many known growth factors, vascular endothelial growth factor (VEGF) is believed to be the most prevalent, efficacious, and long-term signal that is known to stimulate angiogenesis in wounds. The wound site is rich in oxidants, such as hydrogen peroxide, mostly contributed by neutrophils and macrophages. We proposed that oxidants in the wound microenvironment support the repair process. Proanthocyanidins or condensed tannins are a group of biologically active polyphenolic bioflavonoids that are synthesized by many plants. Previously we have reported that a grape seed proanthycyanidin extract containing 5000 ppm resveratrol (GSPE) potently upregulates oxidant and tumor necrosis factor-alpha inducible VEGF expression in human keratinocytes (Free Radic. Biol. Med. 31:38-42, 2001). Our current objective was to follow up on that finding and test whether GSPE influences dermal wound healing in vivo. First, using a VEGF promoter-driven luciferase reporter construct we observed that the potentiating effect of GSPE on inducible VEGF expression is at the transcriptional level. The reporter assay showed that GSPE alone is able to drive VEGF transcription. Next, two dermal excisional wounds were inflicted on the back of mice and the wounds were left to heal by secondary intention. Topical application of GSPE accelerated wound contraction and closure. GSPE treatment was associated with a more well-defined hyperproliferative epithelial region, higher cell density, enhanced deposition of connective tissue, and improved histological architecture. GSPE treatment also increased VEGF and tenascin expression in the wound edge tissue. Tissue glutathione oxidation and 4-hydroxynonenal immunostaining results supported that GSPE application enhanced the oxidizing environment at the wound site. Oxidants are known to promote both VEGF as well as tenascin expression. In summary, our current study provides firm evidence to support that topical application of GSPE represents a feasible and productive approach to support dermal wound healing.

Identification and in vitro biological activities of hop proanthocyanidins: inhibition of nNOS activity and scavenging of reactive nitrogen species

Oligomeric proanthocyanidins constitute a group of water-soluble polyphenolic tannins that are present in the female inflorescences (up to 5% dry wt) of the hop plant (Humulus lupulus). Humans are exposed to hop proanthocyanidins through consumption of beer. Proanthocyanidins from hops were characterized for their chemical structure and their in vitro biological activities. Chemically, they consist mainly of oligomeric catechins ranging from dimers to octamers, with minor amounts of catechin oligomers containing one or two gallocatechin units. The chemical structures of four procyanidin dimers (B1, B2, B3, and B4) and one trimer, epicatechin-(4beta-->8)-catechin-(4alpha-->8)-catechin (TR), were elucidated using mass spectrometry, NMR spectroscopy, and chemical degradation. When tested as a mixture, the hop oligomeric proanthocyanidins (PC) were found to be potent inhibitors of neuronal nitric oxide synthase (nNOS) activity. Among the oligomers tested, procyanidin B2 was most inhibitory against nNOS activity. Procyanidin B3, catechin, and epicatechin were noninhibitory against nNOS activity. PC and the individual oligomers were all strong inhibitors of 3-morpholinosydnonimine (SIN-1)-induced oxidation of LDL, with procyanidin B3 showing the highest antioxidant activity at 0.1 microg/mL. The catechin trimer (TR) exhibited antioxidant activity more than 1 order of magnitude greater than that of alpha-tocopherol or ascorbic acid on a molar basis.

Oxidative stress in glial cultures: detection by DAF-2 fluorescence used as a tool to measure peroxynitrite rather than nitric oxide

4,5-diaminofluorescein diacetate (DAF-2DA) is widely used as a fluorescent probe to detect endogenously produced nitric oxide (NO). Recent reports that refer to the high sensitivity of DAF-2 toward NO prompted us to test its efficiency and specificity in a mixed murine primary glial culture model, in which the NO-synthesizing enzyme inducible nitric oxide synthase (iNOS) is expressed by stimulation with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). Cultures were loaded with DAF-2DA and the fluorescence was measured using confocal microscopy. NO production in the cultures was determined using the ozone/chemiluminescence technique. Due to the extremely high photosensitivity of DAF-2, low laser intensities were used to avoid artifacts. No difference in DAF-2 fluorescence was observed in NO-producing cultures compared to control cultures, whereas the NO/peroxynitrite-sensitive dye 2,7-dihydrodichlorofluorescein (DCF) showed a significant fluorescence increase specifically in microglia cells. A detectable gain in fluorescence was seen when NO-containing buffer was added to the DAF-2DA-loaded cells with a minimum NO concentration at 7.7 microM. An additional gain of DAF-2 fluorescence was obtained when the cells were depleted of glutathione (GSH) with L-buthionine S,R-sulfoximine (BSO). Hence, we monitored the change in DAF-2 fluorescence intensity in the presence of NO and O(-*)(2) in a cell-free solution. The fluorescence due to NO was indeed larger when O(-*)(2) was added, implying a higher sensitivity of DAF-2 for peroxynitrite. Nevertheless, our results also indicate that measurement of DCF fluorescence is a better tool for monitoring intracellular changes in the levels of NO and/or peroxynitrite than DAF-2.

90-day oral toxicity study of a grape seed extract (IH636) in rats

To assess the safety of grape seed extract with less than 5.5% catechin monomers (IH636), 4 groups of male and female Sprague-Dawley rats were provided grape seed extract in the diet at levels of 0 (control), 0.5, 1.0, or 2.0% for a period of 90 days. All animals survived the duration of the study, and no significant changes in clinical signs, hematological parameters, organ weights, ophthalmology evaluations, or histopathological findings were observed. A significant increase in food consumption was observed in male and female rats provided the grape seed extract diets compared to that of the control rats, especially in male rats consuming 2.0% grape seed extract. This effect was not accompanied by increases in body weight gains. Grape seed extract appeared to increase the insoluble fraction of the diet. Male rats in the high-dose group exhibited decreased serum iron levels and decreased serum iron/total iron binding capacity ratio compared to those of the controls, although all values were within historical ranges for Sprague-Dawley rats. In conclusion, administration of the grape seed extract IH636 to male and female Sprague-Dawley rats in the feed at levels of 0.5, 1.0, or 2.0% for 90 days did not induce any significant toxicological effects.