The salicylate metabolite gentisic acid, but not the parent drug, inhibits glucose autoxidation-mediated atherogenic modification of low density lipoprotein

The Puzzle of Aspirin and Iron Deficiency: The Vital Missing Link of the Iron-Chelating Metabolites

Acetylsalicylic acid or aspirin is the most commonly used drug in the world and is taken daily by millions of people. There is increasing evidence that chronic administration of low-dose aspirin of about 75-100 mg/day can cause iron deficiency anaemia (IDA) in the absence of major gastric bleeding; this is found in a large number of about 20% otherwise healthy elderly (>65 years) individuals. The mechanisms of the cause of IDA in this category of individuals are still largely unknown. Evidence is presented suggesting that a likely cause of IDA in this category of aspirin users is the chelation activity and increased excretion of iron caused by aspirin chelating metabolites (ACMs). It is estimated that 90% of oral aspirin is metabolized into about 70% of the ACMs salicyluric acid, salicylic acid, 2,5-dihydroxybenzoic acid, and 2,3-dihydroxybenzoic acid. All ACMs have a high affinity for binding iron and ability to mobilize iron from different iron pools, causing an overall net increase in iron excretion and altering iron balance. Interestingly, 2,3-dihydroxybenzoic acid has been previously tested in iron-loaded thalassaemia patients, leading to substantial increases in iron excretion. The daily administration of low-dose aspirin for long-term periods is likely to enhance the overall iron excretion in small increments each time due to the combined iron mobilization effect of the ACM. In particular, IDA is likely to occur mainly in populations such as elderly vegetarian adults with meals low in iron content. Furthermore, IDA may be exacerbated by the combinations of ACM with other dietary components, which can prevent iron absorption and enhance iron excretion. Overall, aspirin is acting as a chelating pro-drug similar to dexrazoxane, and the ACM as combination chelation therapy. Iron balance, pharmacological, and other studies on the interaction of iron and aspirin, as well as ACM, are likely to shed more light on the mechanism of IDA. Similar mechanisms of iron chelation through ACM may also be implicated in patient improvements observed in cancer, neurodegenerative, and other disease categories when treated long-term with daily aspirin. In particular, the role of aspirin and ACM in iron metabolism and free radical pathology includes ferroptosis, and may identify other missing links in the therapeutic effects of aspirin in many more diseases. It is suggested that aspirin is the first non-chelating drug described to cause IDA through its ACM metabolites. The therapeutic, pharmacological, toxicological and other implications of aspirin are incomplete without taking into consideration the iron binding and other effects of the ACM.

Gentisic acid exerts neuroprotective effects in neurotoxin-induced Parkinson's disease model in zebrafish: Cross-talk between pathways related with neurodegeneration in the gut-brain axis

Given that global prevalence of Parkinson's disease (PD) is expected to rise over the next few decades, understanding the mechanisms and causes of PD is critical. With emphasis on gut-brain axis, we sought to assess the impact of gentisic acid (GA), a diphenolic compound generated from benzoic acid, in rotenone (Rot) induced PD model in zebrafish. For thirty days, adult zebrafish were exposed to GA and rotenone. Tox-Track program was used to analyze locomotor behaviors in the control, GA, Rot, and Rot + GA groups. LC-MS/MS was performed in brain and intestinal tissues. Proteome Discoverer 2.4 was used to analyze raw files, peptide lists were searched against Danio rerio proteins. Protein interactions or annotations were obtained from STRING database. Tyrosine hydroxylase (Th) staining was performed immunohistochemically in the brain. PD-related gene expressions were determined by RT-PCR. Lipid peroxidation, nitric oxide, superoxide dismutase, glutathione S-transferase, and acetylcholinesterase were measured spectrophotometrically. Improved locomotor behaviors were observed by GA treatment in Rot group as evidenced by increased average speed, exploration rate, and total distance. 5214 proteins were identified in intestinal tissues, 4114 proteins were identified in brain by LC-MS/MS. Rotenone exposure altered protein expressions related to oxidative phosphorylation in brain and intestines. Protein expressions involved in ferroptis and actin cytoskeleton changed in brain and intestines. Altered protein expressions were improved by GA. GA ameliorated Th-immunoreactivity in brain, improved park2, park7, pink1, and lrrk2 expressions. Our results show that GA may be a candidate agent to be evaluated for its potential protective effect for PD.

Gentisic acid prevents colorectal cancer metastasis via blocking GPR81-mediated DEPDC5 degradation

BACKGROUND

Metastasis driven by epithelial-mesenchymal transition (EMT) remains a significant contributor to the poor prognosis of colorectal cancer (CRC), and requires more effective interventions. GPR81 signaling has been linked to tumor metastasis, while lacks an efficient specific inhibitor.

PURPOSE

Our study aimed to investigate the effect and mechanism of Gentisic acid on colorectal cancer (CRC) metastasis.

STUDY DESIGN

A lung metastasis mouse model induced by tail vein injection and a subcutaneous graft tumor model were used. Gentisic acid (GA) was administered by an intraperitoneal injection. HCT116 was treated with lactate to establish an in vitro model.

METHODS

MC38 cells with mCherry fluorescent protein were injected into tail vein to investigate lung metastasis ability in vivo. GA was administered by intraperitoneal injection for 3 weeks. The therapeutic effect was evaluated by survival rates, histochemical analysis, RT-qPCR and live imaging. The mechanism was explored using small interfering RNA (siRNA), Western blotting, RT-qPCR and immunofluorescence.

RESULTS

GA had a therapeutic effect on CRC metastasis and improved survival rates and pathological changes in dose-dependent manner. GA emerged as an GPR81 inhibitor, effectively suppressed EMT and mTOR signaling in CRC induced by lactate both in vivo and in vitro. Mechanistically, GA halted lactate-induce degradation of DEPDC5 through impeding the activation of Chaperone-mediated autophagy (CMA).

CONCLUSION

CMA-mediated DEPDC5 degradation is crucial for lactate/GPR81-induced CRC metastasis, and GA may be a promising candidate for metastasis by inhibiting GPR81 signaling.

Hepatoprotective Activity of Gentisic Acid on 5-Fluorouracil-induced Hepatotoxicity in Wistar Rats

Objectives

5-Fluorouracil (5-FU) is a very potent and effective antineoplastic drug that has been widely used for the management of various types of cancer. However, the clinical use of 5-FU is often associated with severe toxicities including hepatotoxicity, which limit its therapeutic use as a potent anticancer agent. The present study aimed to evaluate the hepatoprotective activity of a plant phenolic acid, gentisic acid (GA) (2,5-dihyroxybenzoic acid), against hepatotoxicity induced by 5-FU administration in Wistar rats.

Materials and Methods

The rats were randomly divided into six groups, with six rats per group. Among these, group I and II served as normal control and 5-FU control groups, respectively. The rats in these groups received distilled water (1 mL/kg) for 14 days by oral route. Groups III, IV, V, and VI served as test groups and received GA at doses of 3, 10, 30, and 100 mg/kg body weight, respectively, via oral route for 14 days. From Day 9 onwards, all the groups, except group I, received intraperitoneal dose of 5-FU (20 mg/kg body weight) for five days up to day 14. At the end of the study, the rats were sacrificed, blood was withdrawn for biochemical estimations, and hepatic tissues were excised for histopathological evaluations.

Results

Administration of 5-FU at a dose of 20 mg/kg body weight resulted in a significant increase in the serum levels of hepatic biomarkers, including aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, direct bilirubin, and total bilirubin. In comparison to these, 5-FU treatment resulted in a reduction in total protein content (TPC). This was accompanied by significant histopathological changes in the hepatic tissues of the rats, indicating severe hepatotoxicity. Pre- and co-administration of GA with 5-FU at doses of 30 and 100 mg/kg body weight for 14 days resulted in a dose-dependent amelioration of the 5-FU induced alterations in the biochemical and histopathological parameters.

Conclusion

The results of the study highlighted the potential of GA as a hepatoprotective agent for the prevention of 5-FU-induced hepatotoxicity.

Non-negative Least Squares Approach to Quantification of 1H Nuclear Magnetic Resonance Spectra of Human Urine

Because of its quantitative character and capability for high-throughput screening, ¹H nuclear magnetic resonance (NMR) spectroscopy is used extensively in the profiling of biofluids such as urine and blood plasma. However, the narrow frequency bandwidth of ¹H NMR spectroscopy leads to a severe overlap of the spectra of components present in the complex mixtures such as biofluids. Therefore, ¹H NMR-based metabolomics analysis is focused on targeted studies related to concentrations of the small number of metabolites. Here, we propose a library-based approach to quantify proportions of overlapping metabolites from ¹H NMR mixture spectra. The method boils down to the linear non-negative least squares (NNLS) problem, whereas proportions of the pure components contained in the library stand for the unknowns. The method is validated on an estimation of the proportions of (i) the 78 pure spectra, presumably related to type 2 diabetes mellitus (T2DM), from their synthetic linear mixture; (ii) metabolites present in 62 ¹H NMR spectra of urine of subjects with T2DM and 62 ¹H NMR spectra of urine of control subjects. In both cases, the in-house library of 210 pure component ¹H NMR spectra represented the design matrix in the related NNLS problem. The proposed method pinpoints 63 metabolites that in a statistically significant way discriminate the T2DM group from the control group and 46 metabolites discriminating control from the T2DM group. For several T2DM-discriminative metabolites, we prove their presence by independent analytical determination or by pointing out the corresponding findings in the published literature.

A review on gentisic acid as a plant derived phenolic acid and metabolite of aspirin: Comprehensive pharmacology, toxicology, and some pharmaceutical aspects

Beneficial therapeutic effects of phenolic acids have been proven in various research projects including in vivo and in vitro studies. Gentisic acid (GA) is a phenolic acid that has been associated with useful effects on human health, such as antiinflammatory, antigenotoxic, hepatoprotective, neuroprotective, antimicrobial, and especially antioxidant activities. It is an important metabolite of aspirin and also widely distributed in plants as a secondary plant product such as Gentiana spp., Citrus spp., Vitis vinifera, Pterocarpus santalinus, Helianthus tuberosus, Hibiscus rosa-sinensis, Olea europaea, and Sesamum indicum and in fruits such as avocados, batoko plum, kiwi fruits, apple, bitter melon, black berries, pears, and some mushrooms. This study was undertaken to review the pharmacological effects, pharmacokinetic properties as well as toxicity and pharmaceutical applications of GA.

Gentisic acid prevents the transition from pressure overload-induced cardiac hypertrophy to heart failure

We previously reported that gentisic acid attenuates cardiac hypertrophy and fibrosis in transverse aortic constriction (TAC)-induced cardiac hypertrophy. Here, we examined whether gentisic acid prevents the development of heart failure. Heart failure was induced in mice via chronic TAC. Mice were administered the vehicle, gentisic acid (10 and 100 mg∙kg^-1∙day^-1), or bisoprolol (0.5 mg∙kg^-1∙day^-1) orally for 3 weeks, beginning 3 weeks after TAC. After oral administration of gentisic acid (2000 mg∙kg^-1), no significant differences in organ weight, histology, or analyzed serum and hematological parameters were observed between female mice in the control and gentisic acid-treated groups. Gentisic acid administration inhibited cardiac dysfunction in a dose-dependent manner, and reduced cardiac hypertrophy and fibrosis, as was revealed via western blotting, quantitative real-time PCR, and Masson's trichrome staining. Gentisic acid dose-dependently reduced the expression of fibrosis marker genes, suppressed the renin-angiotensin-aldosterone system, and reduced lung size and pulmonary vascular remodeling. Our data indicate that gentisic acid prevents cardiac hypertrophy, fibrosis, cardiac dysfunction, and pulmonary pathology in TAC-induced heart failure. These findings suggest that supplementation with gentisic acid may provide an advantage in preventing the progression from cardiac hypertrophy to heart failure.

Gentisic acid attenuates pressure overload-induced cardiac hypertrophy and fibrosis in mice through inhibition of the ERK1/2 pathway

We previously reported that gentisic acid (2,5‐dihydroxybenzoic acid) is the third most abundant phenolic component of Dendropanax morbifera branch extracts. Here, we investigated its effects on cardiac hypertrophy and fibrosis in a mouse model of pressure overload and compared them to those of the beta blocker bisoprolol and calcium channel blocker diltiazem. Cardiac hypertrophy was induced in mice by transverse aortic constriction (TAC). Beginning 2 weeks after this procedure, the mice were given daily intraperitoneal injections of gentisic acid (100 mg/kg/d), bisoprolol (5 mg/kg/d) or diltiazem (10 mg/kg/d) for 3 weeks. Cardiac hypertrophy was evaluated by the heart weight‐to‐body weight ratio, the cardiomyocyte cross‐sectional area after haematoxylin and eosin staining, and echocardiography. Markers of cardiac hypertrophy and fibrosis were tested by reverse transcription‐quantitative real‐time polymerase chain reaction, western blotting and Masson's trichrome staining. The suppressive effects of gentisic acid treatment on TAC‐induced cardiac hypertrophy and fibrosis were comparable to those of bisoprolol administration. Cardiac hypertrophy was reversed and left ventricular septum and posterior wall thickness were restored by gentisic acid, bisoprolol and diltiazem treatment. Cardiac hypertrophic marker gene expression and atrial and brain natriuretic peptide levels were decreased by gentisic acid and bisoprolol, as were cardiac (interstitial and perivascular) fibrosis and fibrosis‐related gene expression. Cardiac hypertrophy‐associated upregulation of the transcription factors GATA4 and Sp1 and activation of extracellular signal‐regulated kinase 1/2 were also negated by these drugs. These results suggest that gentisic acid could serve as a therapeutic agent for cardiac hypertrophy and fibrosis.

HPLC study on Fenton-reaction initiated oxidation of salicylic acid. Biological relevance of the reaction in intestinal biotransformation of salicylic acid

Fenton-reaction initiated in vitro oxidation and in vivo oxidative biotransformation of salicylic acid was investigated by HPLC-UV-Vis method. By means of the developed high performance liquid chromatography (HPLC) method salicylic acid, catechol, and all the possible monohydroxylated derivatives of salicylic acid can be separated. Fenton oxidations were performed in acidic medium (pH 3.0) with two reagent molar ratios: (1) salicylic acid: iron: hydrogen peroxide 1:3:1 and (2) 1:0.3:1. The incubation samples were analysed at different time points of the reactions. The biological effect of elevated reactive oxygen species concentration on the intestinal metabolism of salicylic acid was investigated by an experimental diabetic rat model. HPLC-MS analysis of the in vitro samples revealed presence of 2,3- and 2,5-dihydroxybenzoic acids. The results give evidence for nonenzyme catalysed intestinal hydroxylation of xenobiotics.

Cytotoxicity, mutagenicity, and antimutagenicity of the gentisic acid on HTC cells

Gentisic acid (GA) exhibits antioxidant, anti-inflammatory, and antibiotic activities. This substance can be found in citrus fruits, grapes, olive oil, and peas. Considering that there are few studies in the literature on the toxicity of GA, the present work aimed to investigate its cytotoxic, mutagenic, and antimutagenic activities on HTC cells. GA was diluted in culture medium at the final concentration of 0.08, 0.16, 0.8, 1.6, and 8 μg/mL. The cytotoxicity was determined by the MTT assay and Trypan Blue exclusion method, with methyl methanesulfonate and doxorubicin as positive controls, respectively. The cytokinesis-block micronucleus assay determined the mutagenic/antimutagenic activity with benzo[a]pyrene as positive control. Negative control received culture medium only. GA (0.08-8 μg/mL) was not cytotoxic to HTC cells by the MTT assay nor the Trypan Blue exclusion method as no statistical difference was observed when compared to the control. Concentration of 0.08 and 0.8 μg/mL showed no mutagenic or clastogenic effects, as no significant micronuclei inductions were observed, different from 8 μg/mL, that was mutagenic. Furthermore, none of the concentrations presented an antiproliferative activity. The antimutagenic activity of GA (0.08 μg/mL) was observed at the simultaneous treatment, as it reduced the frequency of micronuclei by 76% (24 h) and 79% (48 h). Although pre- and post-treatments were not statistically different from the mutagen, they reduced the induced-damage by 11% and 21%, respectively. The present study indicated the absence of cytotoxicity and antiproliferative activities of GA, in addition to their antimutagenic/protective effects that may contribute to human health.

Urtica dioica leaves modulates muscarinic cholinergic system in the hippocampus of streptozotocin-induced diabetic mice

Diabetes mellitus is a chronic metabolic disorder and has been associated with cognitive dysfunction. In our earlier study, chronic Urtica dioica (UD) treatment significantly ameliorated diabetes induced associative and spatial memory deficit in mice. The present study was designed to explore the effect of UD leaves extract on muscarinic cholinergic system, which has long been known to be involved in cognition. Streptozotocin (STZ) (50 mg/kg, i.p., consecutively for 5 days) was used to induce diabetes followed by treatment with UD extract (50 mg/kg, oral) or rosiglitazone (5 mg/kg, oral) for 8 weeks. STZ-induced diabetic mice showed significant reduction in hippocampal muscarinic acetylcholine receptor-1 and choline acetyltransferase expressions. Chronic diabetes significantly up-regulated the protein expression of acetylcholinesterase associated with oxidative stress in hippocampus. Besides, STZ-induced diabetic mice showed hypolocomotion with up-regulation of muscarinic acetylcholine receptor-4 expression in striatum. Chronic UD treatment significantly attenuated the cholinergic dysfunction and oxidative stress in the hippocampus of diabetic mice. UD had no effect on locomotor activity and muscarinic acetylcholine receptor-4 expression in striatum. In conclusion, UD leaves extract has potential to reverse diabetes mediated alteration in muscarinic cholinergic system in hippocampus and thereby improve memory functions.

Anti-diabetic effect of dietary mango (Mangifera indica L.) peel in streptozotocin-induced diabetic rats

BACKGROUND

In the present study, the composition of mango peel powder (MPP) collected from the mango pulp industry was determined and the effect of MPP on ameliorating diabetes and its associated complications was studied.

RESULTS

Mango peel was rich in polyphenols, carotenoids and dietary fibre. Peel extract contained various bioactive compounds and was found to be rich in soluble dietary fibre. Peel extract exhibited antioxidant properties and protected against DNA damage. Therefore, the effect of peel on ameliorating diabetes was investigated in a rat model of diabetes. A significant increase in urine sugar, urine volume, fasting blood glucose, total cholesterol, triglycerides and low density lipoprotein, and decrease in high density lipoprotein were observed in the rats; however, these parameters were ameliorated in diabetic rats fed with diet supplemented with mango peel at 5% and 10% levels in basal diet. Treatment of diabetic rats with MPP increased antioxidant enzyme activities and decreased lipid peroxidation in plasma, kidney and liver compared to untreated diabetic rats. Glomerular filtration rate and microalbuminuria levels were ameliorated in MPP treated diabetic group.

CONCLUSIONS

Mango peel, a by-product, can be used as an ingredient in functional and therapeutic foods.

Hydroxybenzoic acid isomers and the cardiovascular system

Today we are beginning to understand how phytochemicals can influence metabolism, cellular signaling and gene expression. The hydroxybenzoic acids are related to salicylic acid and salicin, the first compounds isolated that have a pharmacological activity. In this review we examine how a number of hydroxyphenolics have the potential to ameliorate cardiovascular problems related to aging such as hypertension, atherosclerosis and dyslipidemia. The compounds focused upon include 2,3-dihydroxybenzoic acid (Pyrocatechuic acid), 2,5-dihydroxybenzoic acid (Gentisic acid), 3,4-dihydroxybenzoic acid (Protocatechuic acid), 3,5-dihydroxybenzoic acid (α-Resorcylic acid) and 3-monohydroxybenzoic acid. The latter two compounds activate the hydroxycarboxylic acid receptors with a consequence there is a reduction in adipocyte lipolysis with potential improvements of blood lipid profiles. Several of the other compounds can activate the Nrf2 signaling pathway that increases the expression of antioxidant enzymes, thereby decreasing oxidative stress and associated problems such as endothelial dysfunction that leads to hypertension as well as decreasing generalized inflammation that can lead to problems such as atherosclerosis. It has been known for many years that increased consumption of fruits and vegetables promotes health. We are beginning to understand how specific phytochemicals are responsible for such therapeutic effects. Hippocrates’ dictum of ‘Let food be your medicine and medicine your food’ can now be experimentally tested and the results of such experiments will enhance the ability of nutritionists to devise specific health-promoting diets.

Antioxidant activity and free radical scavenging reactions of gentisic acid: in-vitro and pulse radiolysis studies

Abstract Antioxidant activity of gentisic acid has been studied using fast chemical kinetics and two in vitro models, namely the isolated rat liver mitochondria (RLM) and the human erythrocytes. The presence of gentisic acid (GA) during irradiation significantly reduced the levels of gamma radiation induced damages to lipids and proteins in RLM. Further, GA imparted protection to the human erythrocytes against exposure to gamma radiation. Molecular mechanism of free radical scavenging reactions has been evaluated with the help of rate constants and transients obtained from gentisic acid using pulse radiolysis technique. GA efficiently scavenged hydroxyl radical (k = 1.1 × 10(10) dm(3)mol(-1)s(-1)) to produce reducing adduct radical (~76%) and oxidizing phenoxyl radical (~24%). GA has also scavenged organohaloperoxyl radical (k = 9.3 × 10(7) dm(3) mol(-1)s(-1)). Ascorbate has been found to repair phenoxyl radical of GA (k = 1.0 × 10(7) dm(3)mol(-1)s(-1)). Redox potential value of GA(•)/GA couple (0.774 V vs NHE) obtained by cyclic voltammetry is less than those of physiologically important oxidants, which supports the observed antioxidant capacity of GA. We, therefore, propose that the antioxidant and radioprotective properties of GA are exerted by its phenoxyl group.

Aluminum ions stimulate the oxidizability of low density lipoprotein by Fe2+: Implication in hemodialysis mediated atherogenic LDL modification

OBJECTIVE

Al(3+) stimulates Fe(2+) induced lipid oxidation in liposomal and cellular systems. Low-density lipoprotein (LDL) oxidation may render the particle atherogenic. As elevated levels of Al(3+) and increased lipid oxidation of LDL are found in sera of hemodialysis patients, we investigated the influence of Al(3+) on LDL oxidation.

MATERIALS AND METHODS

Using different LDL modifying systems (Fe(2+), Cu(2+), free radical generating compounds, human endothelial cells, hemin/H(2)O(2) and HOCl), the influence of Al(3+) on LDL lipid and apoprotein alteration was investigated by altered electrophoretic mobility, lipid hydroperoxide-, conjugated diene- and TBARS formation.

RESULTS

Al(3+) could stimulate the oxidizability of LDL by Fe(2+), but not in the other systems tested. Al(3+) and Fe(2+) were found to bind to LDL and Al(3+)could compete with Fe(2+) binding to the lipoprotein. Fluorescence polarization data indicated that Al(3+) does not affect the phospholipid compartment of LDL.

CONCLUSIONS

The results indicate that increased LDL oxidation by Fe(2+) in presence of Al(3+) might be due to blockage of Fe(2+) binding sites on LDL making more free Fe(2+) available for lipid oxidation.

One-step sampling, extraction, and storage protocol for peptidomics using dihydroxybenzoic Acid

The isolation and extraction of natively occurring signaling peptides (SPs) from tissue is a critical first step in characterizing these peptides. Recent studies have outlined several approaches designed to preserve and extract SPs from tissue. Here, we demonstrate a surprisingly simple method to extract SPs from tissue samples, ranging from cell clusters to brain punches to intact brain regions, using a matrix often employed in matrix-assisted laser desorption/ionization mass spectrometry-2,5-dihydroxybenzoic acid (DHB). DHB allows for the effective extraction of endogenous peptides from tissue as well as long-term preservation of tissue samples and extracts. Using the mouse pituitary gland as a model, the extraction protocol effectively recovers 24 known and many additional putative peptides from individual samples. Peptide extracts stored in the DHB extraction media are stable for years without freezing. The approach is also effective for other neuronal tissues; the complement of neuropeptides in bag cell neuron clusters from the Aplysia central nervous system, the rat cerebellum, and rat dorsal striatum also have been examined. Advantages of this new extraction procedure are its technical simplicity, reproducibility, ease of remote preparation of samples, and long-term sample preservation without freezing.

Venous thromboembolism prevention in cancer patients: the search for common antecedents

Venous thromboembolism (VTE) is a well-recognized concomitant of cancer. Although treatment with warfarin is often difficult and tedious, the heparins, and particularly the low molecular weight heparins, have afforded improved care of the patient with cancer-associated VTE, but with increased cost and the need for self-injection. Development by the pharmaceutical industry of inhibitors of specific activated coagulation factors and P-selectin holds promise for improved control of thrombosis with reduced toxicity. Increasing understanding of the interplay between the coagulation mechanism and neoplasia has yielded clues to the upstream origins of both, which may lead to experimental intervention potentially capable of preventing both.

Monosaccharide-H2O2 reactions as a source of glycolate and their stimulation by hydroxyl radicals

An analysis of the H(2)O(2)-induced breakdown and transformation of different keto-monosaccharides at physiological concentrations reveals that glycolate and other short-chained carbohydrates and organic acids are produced. Depletion of monosaccharides and glycolate synthesis occurs at increased rates as the length of the carbohydrate chain is decreased, and is significantly increased in the presence of trace amounts of Fe(2+) ions (10 microM). Rates of monosaccharide depletion (initial concentration of 3 mM) observed were up to 1.55 mmol h(-1) in the case of fructose, and 2.59 mmol h(-1) in the case of dihydroxyacetone, depending upon pH, H(2)O(2) concentration, temperature and the presence or absence of catalytic amounts of Fe(2+). Glycolate was produced by dihydroxyacetone cleavage at rates up to 0.45 mmol h(-1) in the absence, and up to 1.88 mmol h(-1) in the presence of Fe(2+) ions (pH 8). Besides glycolate, other sugars (ribose, glyceraldehyde, glucose), glucitol (sorbitol) and organic acids (formic and 2-oxogluconic acid) were produced in such H(2)O(2)-induced reactions with fructose or dihydroxyacetone. EPR measurements demonstrated the participation of the OH radical, especially at higher pH. Presence of metal ions at higher pH values, resulting in increased glycolate synthesis, was accompanied by enhanced hydroxyl radical generation. Observed changes in intensity of DEPMPO-OH signals recorded from dihydroxyacetone and fructose reactions demonstrate a strong correlation with changes in glycolate yield, suggesting that OH radical formation enhances glycolate synthesis. The results presented suggest that different mechanisms are responsible for the cleavage or other reactions (isomerisation, auto- or free-radical-mediated oxidation) of keto-monosaccharides depending of experimental conditions.

Comparison of protective effects of aspirin, d-penicillamine and vitamin E against high glucose-mediated toxicity in cultured endothelial cells

This study compared the protective effects of three different anti-glycation compounds, aspirin, D-penicillamine and vitamin E, against high glucose and advanced glycation endproduct (AGE) mediated toxicity in cultured bovine aortic endothelial cells using two approaches. Their proliferation was assessed in culture in different concentrations of glucose (5.5-100 mmol/l) with and without these inhibitors. A monolayer of cultured endothelial cells was wounded and recovery at the wound site was measured following exposure to different concentrations of glucose with and without inhibitors. The ability of these compounds to protect cultured endothelial cells following exposure to bovine serum albumin-derived advanced glycation endproducts (BSA-AGE) was also studied. Addition of glucose to cultured endothelial cells inhibited their proliferation in a dose dependent manner. All three compounds protected against the anti-proliferative effects of high glucose, with vitamin E being the most effective. The migration of cultured endothelial cells following wounding was inhibited by increasing concentrations of glucose but was maintained in the presence of all three anti-glycation compounds with vitamin E, again giving the greatest protection. Vitamin E was also the most effective at protecting against the anti-proliferative effects of BSA-AGE. D-penicillamine was not as effective as vitamin E whereas aspirin offered no significant protection against AGE-induced cellular toxicity. Our studies suggest that compounds, such as vitamin E, with combined antiglycation and antioxidant properties offer maximum therapeutic potential in protection against high glucose and AGE-mediated cellular toxicity.

Protective effect of protocatechuic acid from Alpinia oxyphylla on hydrogen peroxide-induced oxidative PC12 cell death

The neuroprotective effects of protocatechuic acid (PCA), a phenolic compound isolated from the kernels of Alpinia oxyphylla, on hydrogen peroxide (H(2)O(2))-induced apoptosis and oxidative stress in cultured PC12 cells were investigated. Exposure of PC12 cells to 0.4 mM H(2)O(2) induced a leakage of lactate dehydrogenase (LDH) and decreased cell viability denoted by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. PCA increased PC12 cellular viability and markedly attenuated H(2)O(2)-induced apoptotic cell death in a dose-dependent manner. By flow cytometric analysis, PCA showed its significant effect on protecting PC12 cells against H(2)O(2)-induced apoptosis. In these cells, the levels of glutathione (GSH) and activity of catalase were augmented, while glutathione peroxidase activity remained unchanged. In addition, PCA also protected against cell damage induced by H(2)O(2) and Fe(2+), which generated hydroxyl radicals (OH) by the Fenton reaction. These results suggest that PCA may be a candidate chemical for the treatment of oxidative stress-induced neurodegenerative disease.

Copper- and magnesium protoporphyrin complexes inhibit oxidative modification of LDL induced by hemin, transition metal ions and tyrosyl radicals

The oxidative modification of LDL may play an important role in the early events of atherogenesis. Thus the identification of antioxidative compounds may be of therapeutic and prophylactic importance regarding cardiovascular disease. Copper-chlorophyllin (Cu-CHL), a Cu(2+)-protoporphyrin IX complex, has been reported to inhibit lipid oxidation in biological membranes and liposomes. Hemin (Fe(3+)-protoporphyrin IX) has been shown to bind to LDL thereby inducing lipid peroxidation. As Cu-CHL has a similar structure as hemin, one may assume that Cu-CHL may compete with the hemin action on LDL. Therefore, in the present study Cu-CHL and the related compound magnesium-chlorophyllin (Mg-CHL) were examined in their ability to inhibit LDL oxidation initiated by hemin and other LDL oxidizing systems. LDL oxidation by hemin in presence of H(2)O(2) was strongly inhibited by both CHLs. Both chlorophyllins were also capable of effectively inhibiting LDL oxidation initiated by transition metal ions (Cu(2+)), human umbilical vein endothelial cells (HUVEC) and tyrosyl radicals generated by myeloperoxidase (MPO) in presence of H(2)O(2) and tyrosine. Cu- and Mg-CHL showed radical scavenging ability as demonstrated by the diphenylpicrylhydracylradical (DPPH)-radical assay and estimation of phenoxyl radical generated diphenyl (dityrosine) formation. As assessed by ultracentrifugation the chlorophyllins were found to bind to LDL (and HDL) in serum. The present study shows that copper chlorophyllin (Cu-CHL) and its magnesium analog could act as potent antagonists of atherogenic LDL modification induced by various oxidative stimuli. As inhibitory effects of the CHLs were found at concentrations as low as 1 mumol/l, which can be achieved in humans, the results may be physiologically/therapeutically relevant.

Gentisic acid, an aspirin metabolite, inhibits oxidation of low-density lipoprotein and the formation of cholesterol ester hydroperoxides in human plasma

Gentisic acid, an aspirin metabolite, has an antioxidant effect, although its detailed mechanism remains elusive. The present study was designed to determine whether it inhibits low-density lipoprotein (LDL) oxidation and the formation of lipid hydroperoxides in human plasma. The susceptibility of LDL oxidative modification was investigated by a method using 2,2'-azobis or Cu2+. To study the effect of gentisic acid on free radical-induced damage to plasma lipids, cholesterol ester hydroperoxides generated by incubating human fresh plasma with Cu2+ and gentisic acid was analyzed. Gentisic acid inhibited LDL oxidation in a concentration-dependent manner. It significantly inhibited the formation of cholesterol ester hydroperoxides in plasma, and was consumed after the depletion of ascorbic acid and reduced form of coenzyme Q-10 (CoQH2-10), whereas concentrations of other antioxidants remained unchanged. Gentisic acid had a potent free radical scavenging activity with a minimal chelating effect. The potent antioxidant property of gentisic acid may partly account for the anti-atherogenic effects of aspirin.

Modulatory effect of gentisic acid on the augmentation of biochemical events of tumor promotion stage by benzoyl peroxide and ultraviolet radiation in Swiss albino mice

The present study was carried out to study the effect of gentisic acid (2,5-dihydroxybenzoic acid (2,5-DHBA)) on the tumor promotion related events of carcinogenesis in murine skin. Benzoyl peroxide (BPO) (20 mg/0.2 ml/animal) and ultraviolet radiations (UVR) (0.420 J/m2/s) were used to induce tumor promotion response and oxidative stress and caused significant depletion in the detoxification and antioxidant enzyme armory with concomitant elevation in malondialdehyde (MDA) formation, hydrogen peroxide (H2O2) generation, ornithine decarboxylase (ODC) activity and unscheduled DNA synthesis. However, gentisic acid pretreatment at two different doses restored the levels of the above said parameters (P < 0.05) in a dose-dependent manner except in the case of ODC activity. Therefore, we propose that it might suppress the promotion stage via inhibition of oxidative stress but may not affect the polyamine biosynthetic pathway.

Effect of natural phenolic acids on DNA oxidation in vitro

We examined the antioxidant activity of the following natural phenolic compounds present in food: 3-OH-benzoic acid (3-OH-BA); 4-OH-benzoic acid (4-OH-BA); 2,3-dihydroxybenzoic acid (2,3-diOH-BA); 3,4-dihydroxybenzoic acid (3,4-diOH-BA or protocatechuic acid); ferulic acid; caffeic acid; and 2-coumaric, 3-coumaric and 4-coumaric acids. We measured the inhibitory effect of these compounds on iron-dependent oxidative DNA damage in vitro [incubating herring sperm DNA with Fe(III)/GSH] or using cumene hydroperoxide (CumOOH) as a free-radical generating system; we also studied the interaction of these phenols with Fe(II) or Fe(III) spectrophotometrically. Among the tested compounds, 2,3-diOH-BA, 3,4-diOH-BA and caffeic acid interacted with Fe(II) and showed a potent inhibitory effect on iron-induced oxidative DNA damage. CumOOH-induced DNA oxidation was not modified by these compounds. On the contrary, 2-coumaric, 3-coumaric and 4-coumaric acids did not interact with iron but protected against oxidative DNA damage induced by Fe(III)/GSH and by CumOOH, indicating a direct free-radical scavenging activity of these compounds in both systems. The IC(50)+/-S.E.M. of the three coumaric acids against CumOOH-induced DNA oxidation was 44.2+/-2.0, 54.7+/-2.0 and 33.1+/-1.0 microM, respectively. On the contrary, 3-OH-BA and 4-OH-BA did not have scavenging activity and 3-OH-BA actually enhanced oxidative DNA damage. In conclusion, some natural phenolic acids, commonly present in food, have interesting protective activity against DNA oxidation in vitro and deserve further consideration as effective antioxidants in vivo.