Differential regulation of NO availability from macrophages and endothelial cells by the garlic component S-allyl cysteine

Does garlic have a role as an antidiabetic agent?

Diabetes affects a large segment of the population worldwide, and the prevalence of this disease is rapidly increasing. Despite the availability of medication for diabetes, traditional remedies are desirable and are currently being investigated. Garlic (Allium sativum), which is a common cooking spice and has a long history as a folk remedy, has been reported to have antidiabetic activity. However, there is no general agreement on the use of garlic for antidiabetic purposes, primarily because of a lack of scientific evidence from human studies and inconsistent data from animal studies. The validity of data from previous studies of the hypoglycemic effect of garlic in diabetic animals and the preventive effects of garlic on diabetes complications are discussed in this review. The role of garlic as both an insulin secretagogue and as an insulin sensitizer is reviewed. Evidence suggests that garlic's antioxidative, antiinflammatory, and antiglycative properties are responsible for garlic's role in preventing diabetes progression and the development of diabetes-related complications. Large-scale clinical studies with diabetic patients are warranted to confirm the usefulness of garlic in the treatment and prevention of diabetes.

Hypochlorous acid scavenging capacity of garlic

The ability of the following aqueous garlic extracts to scavenge hypochlorous acid (HOCl) was studied: (a) unheated extract of raw garlic (RG), (b) heated extract of raw garlic (HRG), (c) extract of boiled garlic cloves (BG) and (d) extract of microwave-treated garlic cloves (MG). The HOCl scavenging activity was evaluated following changes in the absorption spectrum of catalase (370-450 nm). RG, HRG and BG scavenged HOCl in a concentration-dependent way: the IC(50) (mg/mL) values for RG, HRG and BG were 0.339 +/- 0.028, 0.632 +/- 0.030 and 0.690 +/- 0.031, respectively. The HOCl scavenging ability of garlic was significantly decreased when garlic cloves or the extract of raw garlic were heated (BG and HRG, respectively); this scavenging ability was eliminated when garlic was subjected to microwave heating (MG). The IC(50) value for the reference compound, ascorbic acid, was 0.500 +/- 0.049 mg/mL. In summary, raw garlic concentration-dependently scavenged HOCl; this ability was eliminated in extracts of microwave-treated garlic cloves but not in heated extracts of raw garlic or extracts of boiled garlic cloves.

Cyclo(dehydrohistidyl-l-tryptophyl) inhibits nitric oxide production by preventing the dimerization of inducible nitric oxide synthase

Dimerization of inducible NOS has been known to be a potential therapeutic target for iNOS-mediated pathologies. Cyclic dipeptides are among the simplest peptides commonly found as by-products of food processing or metabolites of microorganisms. In this study, we found that cyclo(dehydrohistidyl-l-tryptophyl) (CDHT), a cyclic dipeptide from an unidentified fungal strain Fb956, prevents iNOS dimerization in activated microglial BV-2 cells. CDHT inhibited NO production with an IC50 of 6.5 microM in LPS-treated BV-2 cells. Western blot analysis and iNOS activity measurement of fractions from size-exclusion chromatography of cell lysates indicated that CDHT inhibits dimerization of iNOS, while it has no effect on iNOS expression or enzyme activity. The CDHT inhibition of iNOS dimerization was confirmed by partially denaturing SDS-PAGE analysis. In contrast, CDHT did not affect cGMP production in endothelial HUVEC cells, which indicates no inhibition of endothelial NOS activity. These results reveal that CDHT, one of the simplest and cyclic dipeptides, selectively inhibits NO production by inhibiting iNOS dimerization, and could be a useful therapeutic agent for inflammation-mediated diseases.

S-allylcysteine scavenges singlet oxygen and hypochlorous acid and protects LLC-PK1 cells of potassium dichromate-induced toxicity

It has been found that S-allylcysteine (SAC), a garlic-derived compound, has in vivo and in vitro antioxidant properties. In addition, it is known that SAC is able to scavenge different reactive oxygen or nitrogen species including superoxide anion (O(2)(-)), hydrogen peroxide (H(2)O(2)), hydroxyl radical (OH()), and peroxynitrite anion (ONOO(-)) although the IC(5O) values for each reactive species has not been calculated and the potential ability of SAC to scavenge singlet oxygen ((1)O(2)) and hypochlorous acid (HOCl) has not been explored. The purposes of this work was (a) to explore the potential ability of SAC to scavenge (1)O(2) and HOCl, (b) to further characterize the O(2)(-), H(2)O(2), OH(), and ONOO(-) scavenging ability of SAC by measuring the IC(50) values using in vitro assays, and (c) to explore the potential ability of SAC to ameliorate the potassium dichromate (K(2)Cr(2)O(7))-induced cytotoxicity in LLC-PK1 cells in which oxidative stress is involved. The scavenging activity was compared against the following reference compounds: N-acetylcysteine for O(2)(-), sodium pyruvate for H(2)O(2), dimethylthiourea for OH(), lipoic acid and glutathione for (1)O(2), lipoic acid for HOCl, and penicillamine for ONOO(-). It was found that SAC was able to scavenge concentration-dependently all the species assayed with the following IC(5O) (mean+/-SEM, mM): O(2)(-) (14.49+/-1.67), H(2)O(2) (68+/-1.92), OH() (0.68+/-0.06), (1)O(2) (1.93+/-0.27), HOCl (2.86+/-0.15), and ONOO(-) (0.80+/-0.05). When the ability of SAC to scavenge these species was compared to those of the reference compounds it was found that the efficacy of SAC (a) to scavenge O(2)(-), H(2)O(2), OH(), and ONOO(-) was lower, (b) to scavenge HOCl was similar, and (c) to scavenge (1)O(2) was higher. In addition, it was found that SAC was able to prevent K(2)Cr(2)O(7)-induced toxicity in LLC-PK1 cells in culture. It was showed for the first time that SAC is able to scavenge (1)O(2) and HOCl and to ameliorate the K(2)Cr(2)O(7)-induced toxicity.

Amelioration of early cognitive deficits by aged garlic extract in Alzheimer's transgenic mice

Subtle accumulation of beta-amyloid peptide (Abeta) oligomers of Abeta42 species in particular, is known to correlate with cognitive deficits independent of Abeta plaque deposition in the brain. Majority of the research showing behavioral improvement after cerebral Abeta reduction has been reported when the animals carried fewer/abundant amyloid plaques in the brain. Very few studies have addressed whether or not behavioral deficits exist even at the pre-plaque stage or in the absence of plaques that would parallel the mild cognitive impairment (MCI) stage of Alzheimer's disease (AD). Current study was undertaken to determine whether there exists any cognitive impairment during the pre-plaque stage which may parallel the MCI stage of AD, and to confirm whether the observed behavioral deficits correlate with Abeta42 predominance. In addition, the study determined whether anti-amyloidogenic effects of dietary aged garlic extract would prevent progressive behavioral impairment. For this purpose we used Tg2576 model showing slow plaque development with a predominance of Abeta40, and the TgCRND8 model showing accelerated plaque development with a predominance of Abeta42. The results show that at 2 months of age Tg2576 mice did not exhibit behavioral impairment in any of the tasks studied. While 2-month-old TgCRND8 mice displayed only a subtle behavioral deficit that matched the behavioral deficits observed in 7-month-old Tg2576 mice which may correlate with the MCI stage of AD. TgCRND8 mice at 7 months of age exhibited advanced deterioration in all behavioral tasks studied, suggesting that accelerated Abeta accumulation and the predominance of Abeta42 species may account for the pronounced cognitive deficits observed in TgCRND8. Feeding of aged garlic extract prevented deterioration of hippocampal based memory tasks in these mice, suggesting that aged garlic extract has a potential for preventing AD progression.

Renoprotective and antihypertensive effects of S-allylcysteine in 5/6 nephrectomized rats

Progressive renal damage and hypertension are associated with oxidative and nitrosative stress. On the other hand, S-allylcysteine (SAC), the most abundant organosulfur compound in aged garlic extract (AG), has antioxidant properties. The effects of SAC and AG on blood pressure, renal damage, and oxidative and nitrosative stress were studied in five-sixths nephrectomized rats treated with SAC (200 mg/kg ip) and AG (1.2 ml/kg ip) every other day for 30 days. Proteinuria and serum creatinine and blood urea nitrogen concentrations were measured on days 0, 5, 10, 15, and 30, and systolic blood pressure was recorded on days 0, 15, and 30. The degree of glomerulosclerosis and tubulointerstitial damage, the immunostaining for inducible nitric oxide synthase, 3-nitrotyrosine, poly(ADP-ribose), and the subunits of NADPH oxidase p22phox and gp91phox, and the activity of SOD were determined on day 30. SAC and AG reduced hypertension, renal damage, and the abundance of inducible nitric oxide synthase, 3-nitrotyrosine, poly(ADP-ribose), p22phox, and gp91phox and increased SOD activity. Our data suggest that the antihypertensive and renoprotective effects of SAC and AG are associated with their antioxidant properties and that they may be used to ameliorate hypertension and delay the progression of renal damage.

S-allyl cysteine prevents CCl(4)-induced acute liver injury in rats

Aged garlic extract (AGE) possesses multiple biological activities. We evaluated the protective effect of S-allyl cysteine (SAC), one of the organosulfur compounds of AGE, against carbon tetrachloride (CCl(4))-induced acute liver injury in rats. SAC was administrated intraperitoneally (50-200 mg/kg). SAC significantly suppressed the increases of plasma ALT and LDH levels. SAC also attenuated histological liver damage. CCl(4) administration induced lipid peroxidation accompanied by increases in the plasma malondialdehyde and hepatic 4-hydroxy-2-nonenal levels, and SAC dose-dependently attenuated these increases. The hepatic total level of hydroxyoctadecadienoic acid (HODE), a new oxidative stress biomarker, was closely correlated with the amount of liver damage. These results suggest that SAC decreased CCl(4)-induced liver injury by attenuation of oxidative stress, and may be a better therapeutic tool for chronic liver disease.

Anti-inflammatory constituents isolated from clerodendron trichotomum tunberg leaves (CTL) inhibits pro-inflammatory gene expression in LPS-stimulated RAW 264.7 macrophages by suppressing NF-κB activation

Clerodendron trichotomum Tunberg Leaves (CTL) have been used for centuries in Chinese folk medicine for their anti-inflammatory properties. To investigate the molecular mechanism of anti-inflammation by CTL, we analyzed the regulation of TNF-alpha expression in RAW 264.7 cells, a key step in inflammation. The effect of CTL on the production and expression of tumor necrosis factor-alpha (TNF-alpha) was determined by enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR). CTL inhibited the production and expression of TNF-alpha in LPS-stimulated RAW 264.7 cells in a dose-dependent manner. In addition, activation of NF-kappaB, which controls TNF-alpha expression, was inhibited in LPS-stimulated RAW 264.7 cells by CTL in a dose-dependent manner, as demonstrated by an electro phoretic mobility shift assay (EMSA). Furthermore, CTL inhibited activation of NF-kappaB through inhibition IkappaB degradation, as demonstrated by an western blot analysis of IkappaB-alpha. These results suggest that CTL inhibits the expression of the pro-inflammation gene through the inhibition of NF-kappaB dependent pathway in RAW 264.7 cells.

Effect of heating on peroxynitrite scavenging capacity of garlic

The ability to scavenge peroxynitrite (ONOO(-)) was studied in the following aqueous garlic extracts: (a) unheated extract of garlic powder (GP), (b) heated extract of garlic powder (HGP), (c) unheated extract of raw garlic (RG), (d) heated extract of raw garlic (HRG), (e) extract of boiled garlic cloves (BG), (f) extract of microwave-treated garlic cloves (MG), and (g) extract of pickled garlic (PG). All the extracts scavenged ONOO(-) in a concentration-dependent way. IC(50) (mg/mL) values for each extract were 0.30+/-0.02 and 0.35+/-0.04 for GP and HGP, respectively; and 0.84+/-0.08, 0.59+/-0.04, 0.76+/-0.09, 1.71+/-0.19, and 1.45+/-0.07 for RG, HRG, BG, MG, and PG, respectively. The ONOO(-) scavenging capacity (IC(50) values) was not decreased in HGP (vs. GP, p>0.05) and in HRG and BG (p>0.05 vs. RG). In contrast, the ONOO(-) scavenging capacity decreased in MG and PG (vs. RG, p<0.001). The IC(50) values for the reference compounds nordihydroguiaretic acid and penicillamine were 1.1 and 4.5mug/mL. The heating before or after garlic cutting was unable to eliminate the capacity of the extracts to scavenge ONOO(-); this capacity was significantly decreased in PG and MG.

Neuronal nitric oxide synthase protects neuroblastoma cells from oxidative stress mediated by garlic derivatives

In this study, we further examined the effects of diallyl disulfide (DADS), one of the major components of oil-soluble garlic extracts (GE) and of raw water GE on SH-SY5Y and NSC34 neuronal cell lines. Both treatments with DADS and GE were able to induce growth arrest and apoptosis, and we observed an increased flux of reactive oxygen and nitrogen species as early signs of cytotoxicity. We demonstrated that the content of neuronal nitric oxide synthase (nNOS) increased as early as 1 h of treatment demonstrating to be a very early sensor of DADS and GE cytotoxicity. Treatments with L-nitropropyl-arginine, an inhibitor of nNOS, increased the rate of apoptosis whereas the overexpression of nNOS significantly reduced cell death by inhibiting DNA damage, protein oxidation, and the activation of the JNK/c-Jun apoptotic signaling cascade. Overall these results demonstrate that garlic derivatives may modulate nNOS and suggest an important contribution of nitric oxide in counteracting their reactive oxygen species-mediated cytotoxicity.

S-Allyl-L-cysteine attenuates cerebral ischemic injury by scavenging peroxynitrite and inhibiting the activity of extracellular signal-regulated kinase

S-Allyl-L-cysteine (SAC) has been shown to reduce ischemic injury due to its antioxidant activity. However, the antioxidant property of SAC has been controversial. The present study investigated the neuroprotective mechanism of SAC in cerebral ischemic insults. SAC decreased the size of infarction after transient or global ischemic insults. While it did not alter the N-methyl-D-aspartate excitotoxicity, SAC significantly scavenged the endogenously or exogenously produced ONOO- and reduced ONOO- cytotoxicity. In contrast, SAC has much lower scavenging activity against H2O2, O2*(-) or NO. Further, SAC inhibited the activity of extracellular signal-regulated kinase (ERK) increased in cultured neurons exposed to oxygen-glucose deprivation or in rat brain tissue after transient middle cerebral artery occlusion. The neuroprotective effect of SAC was mimicked by the ERK inhibitor U0125. The present results indicate that SAC exert its neuroprotective effect by scavenging ONOO- and inhibiting the ERK signaling pathway activated during initial hypoxic/ischemic insults.

Antithrombotic effects of odorless garlic powder both in vitro and in vivo

Antithrombotic activities of odorless garlic powder were demonstrated in blood fibrinolytic and coagulation systems. Though the odorless garlic preparation did not influence tissue-type plasminogen activator (t-PA) or its inhibitor secretions from human umbilical vein endothelial cells, it enhanced plasmin generation by t-PA on fibrin film and in chromogenic assays by 1.8-fold and 8.7-fold respectively. The coagulation system was considerably reduced after the administration of the garlic in a rat in situ loop model, indicating that increased levels of thrombin-antithrombin III (TAT) complex in the control group were significantly reduced to normal (sham) in the garlic group (p<0.05), which was associated with decreasing tendencies towards prolonged or increased values of coagulation parameters in the control group. These findings suggest that odorless garlic not only activates fibrinolytic activity by accelerating t-PA-mediated plasminogen activation, but also suppresses the coagulation system by downregulating thrombin formation, suggesting a beneficial role in preventing pathological thrombus formation in such cardiovascular disorders.

Effect of aged garlic extract on APP processing and tau phosphorylation in Alzheimer's transgenic model Tg2576

Multiple components present in garlic and various garlic preparations are known to exert pleiotropic protective effects as demonstrated in various in vitro and in vivo model systems. However, garlic pleiotropy in relation to Alzheimer's pathophysiology has not been explored extensively. Current study investigated anti-amyloidogenic, anti-inflammatory and anti-tangle effects of dietary aged garlic extract (AGE) (2%) and compared with its prominent constituents, i.e. S-allyl-cysteine (SAC) (20 mg/kg) and di-allyl-disulfide (DADS) (20 mg/kg) in Alzheimer's Swedish double mutant mouse model (Tg2576). Possible cholesterol-dependent and cholesterol-independent mechanisms of actions of AGE, SAC and DADS in exerting anti-amyloidogenic, anti-inflammatory and anti-tangle effects are discussed. Finally, ameliorative effects of dietary interventions were found to be in the order of AGE>SAC>DADS. If validated pre-clinically, dietary intervention with herbal alternative such as AGE having pleiotropic useful properties and least adverse effects may provide greater therapeutic benefit over a single-ingredient synthetic pharmaceutical drug having serious side effects in treating Alzheimer's disease.

Dietary S-allyl-L-cysteine reduces mortality with decreased incidence of stroke and behavioral changes in stroke-prone spontaneously hypertensive rats

S-Allyl-L-cysteine (SAC), an active organosulfur compound derived from garlic, was found to reduce mortality with lesser incidence of stroke and also to lower the overall stroke-related behavioral score in stroke-prone spontaneously hypertensive (SHRSP) rats by dietary administration. Consequently, the anti-stroke effect of dietary SAC was demonstrated in SHRSP rats.

4-O-Methylgallic acid suppresses inflammation-associated gene expression by inhibition of redox-based NF-κB activation

4-O-methylgallic acid (4-OMGA) is an in vivo major metabolite of gallic acid which is abundant in red wine, tea, legumes and fruit. We examined the in vitro and in vivo effects of 4-OMGA on the production and expression of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) as well as the expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta). 4-OMGA inhibited the expression and production of these inflammatory genes and mediators in RAW264.7 cells and primary macrophages stimulated with lipopolysaccharide (LPS). This compound also reduced the serum levels of these inflammatory mediators in endotoxemic mice. 4-OMGA inhibited iNOS promoter activity and NF-kappaB activation in LPS-treated RAW264.7 cells. 4-OMGA inhibited the LPS-mediated increase in reactive oxygen species production and exogenous H(2)O(2)-induced NF-kappaB activation. Moreover, this compound blocked IkappaBalpha phosphorylation and degradation and nuclear translocation of the cytosolic NF-kappaB p65 subunit, which highly correlated with its inhibitory effect on IkappaB kinase activity and inflammatory mediator production. These results suggest that 4-OMGA suppresses inflammation-associated gene expression by blocking NF-kappaB activation through the inhibition of redox-sensitive IkappaB kinase activity, suggesting that this compound may be beneficial for treating endotoxemia.

Use of herbal preparations in the treatment of oxidant-mediated inflammatory disorders

Complementary and alternative medicine (CAM) use has increased in popularity in recent years and herbal therapy alone is now a billion dollar market. For centuries herbs have been used as food and for medicinal purposes. Various herbs have been identified as possessing anti-inflammatory and antioxidative properties, and they are currently being used to treat inflammatory disorders as well as those caused by reactive oxygen species (ROS). Asthma, Alzheimer's disease, inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and atherogenesis are all disorders where inflammation and ROS are involved in their pathogenesis. This review examines the pathogenesis of the above mentioned ROS-mediated inflammatory disorders, as well as discusses the antioxidant and anti-inflammatory mechanisms of various herbs and the clinical trials where herbs have been used to treat these disorders.

S-Allylcysteine prevents the rat from 3-nitropropionic acid-induced hyperactivity, early markers of oxidative stress and mitochondrial dysfunction

We investigated the effects of S-allylcysteine (SAC) on early behavioral alterations, striatal changes in superoxide dismutase (SOD) activity, lipid peroxidation (LP) and mitochondrial dysfunction induced by the systemic infusion of 3-nitropropionic acid (3-NPA) to rats. SAC (300 mg/kg, i.p.), given to animals 30 min before 3-NPA (30 mg/kg, i.p.), prevented the hyperkinetic pattern evoked by the toxin. In addition, 3-NPA alone produced decreased activities of manganese- (Mn-SOD) and copper/zinc-dependent superoxide dismutase (Cu,Zn-SOD), increased LP (evaluated as the formation of lipid fluorescent products) and produced mitochondrial dysfunction in the striatum (measured as decreased 3-(3,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction). In contrast, pretreatment of 3-NPA-injected rats with SAC resulted in a significant prevention of all these markers. Our findings suggest that the protective actions of SAC are related with its antioxidant properties, which in turn may be accounting for the preservation of SOD activity and primary mitochondrial tasks.

Role of fibrillar Abeta25-35 in the inflammation induced rat model with respect to oxidative vulnerability

The major pathological ramification of Alzheimer's disease (AD) is accumulation of beta-Amyloid (Abeta) peptides in the brain. An emerging therapeutic approach for AD is elimination of excessive Ass peptides and preventing its re-accumulation. Immunization is the most effective strategy in removing preexisting cerebral Abetas and improving the cognitive capacity as shown in transgenic mice model of AD. However, active immunization is associated with adverse effect such as encephalitis with perivascular inflammation and hemorrhage. Details about the mechanistic aspects of propagation of these toxic effects are matter of intense enquiry as this knowledge is essential for the understanding of the AD pathophysiology. The present work aimed to study the oxidative vulnerability in the plasma, liver and brain of the inflammation-induced rats subjected to Ass immunization. Induction of inflammation was performed by subcutaneous injection of 0.5?ml of 2% silver nitrate. Our present result shows that the proinflammatory cytokines such as IL1alpha and TNFalpha are increased significantly in the inflammation-induced, Abeta1-42, Abeta25-35 treated groups and inflammation with Abeta25-35 treated group when compared to control, complete Freund's adjuvant and Abeta35-25 treated groups. These increased proinflammatory cytokines concurrently releases significant amount of free radicals in the astrocytes of respected groups. The present result shows that nitric oxide (NO) level was significantly higher (P<0.001) in plasma, liver and brain of the rat subjected to inflammation, Abeta1-42, Abeta25-35 and inflammation with Abeta25-35 injected groups when compared to control. The increased level of lipid peroxides (LPO) (P<0.001) and decreased antioxidant status (P<0.05) were observed in the plasma, liver and brain of inflammation-induced group when compared to control. Our result shows that significant oxidative vulnerability was observed in the inflammation with Ass treated rats when compared to other groups. Based on our results, we suggest that immunization of AD patients with Ass should be done with caution as the increase in Ass could trigger the brain inflammation in uncontrollable level.

Effects of garlic oil and two of its major organosulfur compounds, diallyl disulfide and diallyl trisulfide, on intestinal damage in rats injected with endotoxin

Garlic and its active components are known to possess antioxidant and antiinflammatory effects. The present study investigated the effects of garlic oil and its organosulfur compounds on endotoxin-induced intestinal mucosal damage. Wistar rats received by gavage 50 or 200 mg/kg body weight garlic oil (GO), 0.5 mmol/kg body weight diallyl disulfide or diallyl trisulfide, or the vehicle (corn oil; 2 ml/kg body weight) every other day for 2 weeks before being injected with endotoxin (i.p., 5 mg/kg body weight). Control rats were administered with corn oil and were injected with sterile saline. Samples for the measurement of proinflammatory cytokines were collected 3 h after injection, and all other samples were collected 18 h after injection. The low dose of GO suppressed endotoxin-induced inducible nitric oxide synthase (iNOS) activity, ulceration, and apoptosis in the intestinal mucosa (P < 0.05). The high dose of GO significantly lowered the peripheral level of nitrate/nitrite and endotoxin-induced iNOS activity in the intestinal mucosa (P < 0.05) but worsened intestinal mucosal damage accompanied by elevated peripheral proinflammatory cytokines. Diallyl trisulfide but not diallyl disulfide showed similar toxic effect as that of high-dose GO. These results suggest the preventive effect and possible toxicity of garlic oil and its organosulfur compounds in endotoxin-induced systemic inflammation and intestinal damage.

Aged garlic extract improves homocysteine-induced endothelial dysfunction in macro- and microcirculation

Endothelial dysfunction caused by increases in vascular oxidant stress that decrease bioavailable nitric oxide (NO) plays a critical role in the vascular pathobiology of hyperhomocysteinemia. Boosting cellular glutathione levels or increasing the activity of cellular glutathione peroxidase can compensate for homocysteine's effects on endothelial function. Aged garlic extract (AGE) contains water- and oil-soluble sulfur compounds that modify the intracellular thiol and redox state, minimize intracellular oxidant stress, and stimulate NO generation in endothelial cells and animals. We performed a placebo-controlled, blinded, crossover trial to examine whether AGE reduces macro- and microvascular endothelial dysfunction during acute hyperhomocysteinemia induced by an oral methionine challenge in healthy subjects. Acute hyperhomocysteinemia leads to a significant decrease in flow-mediated vasodilation of the brachial artery as determined by vascular ultrasound, indicative of macrovascular endothelial dysfunction. In addition, acute hyperhomocysteinemia leads to a decrease in acetylcholine-stimulated skin perfusion as measured by laser-Doppler flowmetry. This indicates microvascular endothelial dysfunction, which is presumably a result of impairment of the endothelium-derived hyperpolarizing factor pathway. Pretreatment with AGE for 6 wk significantly diminished the adverse effects of acute hyperhomocysteinemia in both vascular territories. We conclude that AGE may at least partly prevent a decrease in bioavailable NO and endothelium-derived hyperpolarizing factor during acute hyperhomocysteinemia. This pilot study warrants further investigations on the effects of AGE on endothelial dysfunction in patients with other cardiovascular risk factors or established vascular disease and on the clinical outcome of patients with cardiovascular disease.

Nitric oxide mediates the blood-pressure lowering effect of garlic in the rat two-kidney, one-clip model of hypertension

Garlic reduces blood pressure (BP) in two-kidney, one-clip (2K-1C) rats, and enhances nitric oxide (NO) synthesis in in vivo and in vitro experiments. NO is an important modulator of BP in the 2K-1C model. This study investigated the role of NO in the BP-lowering effect of garlic in the 2K-1C model. BP readings (mm Hg) were obtained from 2K-1C rats in 4 groups treated intraperitoneally for 2 wk with either normal saline (NS), garlic, L-nitroarginine-methylester (L-NAME), or L-NAME+garlic (n=4x5). BP was determined using the tail-cuff method and compared with data of 4 similarly treated groups of normal (unclipped) rats (NRs). The BP readings of NR groups were 120+/-3 mm Hg for the NS-treated group, 120+/-2 mm Hg for the garlic-treated group, 167+/-3 mm Hg for the L-NAME treated group (higher than NS or garlic, P<0.001) and 128+/-5 mm Hg for the garlic+L-NAME-treated group (lower than L-NAME, P<0.001). The BP readings of 2K-1C rat groups were: for the NS group, 169+/-6 mm Hg (higher than NRs, P<0.001); for the garlic group, 116+/-7 mm Hg (lower than NS, P<0.001); for the L-NAME group: 184+/-8 mm Hg (higher than garlic, P<0.001), and for the L-NAME+garlic group: 130+/-6 mm Hg (lower than garlic or NS, P<0.001). The data show that L-NAME increases the BP of both NRs and 2K-1C rats, with the rise more evident in the NRs (39 vs. 9%, respectively). Garlic counteracts the hypertensive effect of L-NAME in NRs as well as 2K-1C rats. We conclude that the BP-lowering effect of garlic in the rat 2K-1C model may be partly mediated through the NO pathway.

Aged garlic extract maintains cardiovascular homeostasis in mice and rats

Nitric oxide (NO) plays an important role in controlling the physiological functions of the cardiovascular system. However, toxic peroxynitrite is produced by the reaction of NO with superoxide. We investigated the effect of aged garlic extract (AGE) on NO production, and on oxidative stress induced by peroxynitrite. A single dose of AGE temporarily increased NO production by 30-40% between 15 and 60 min after administration to mice. The time course of the fluctuation in NO levels in the AGE-treated group clearly differed from that in a group treated with an inducible NO synthase (iNOS) inducer. A selective constitutive NOS (cNOS) inhibitor overcame the effect of AGE. These results indicate that AGE increases NO production by activating cNOS, but not iNOS. In another experiment, the addition of AGE to a rat erythrocyte suspension reduced the rate of peroxynitrite-induced hemolysis in a concentration-dependent manner, suggesting that AGE protects erythrocytes from membrane damage induced by peroxinitrite. Because an increase in NO derived from cNOS and protection against peroxynitrite are important factors in the prevention of cardiovascular disease, our data strongly suggest that AGE could be useful in preventing cardiovascular diseases associated with oxidative stress or dysfunctions of NO production.

Reactive oxygen species scavenging capacity of different cooked garlic preparations

It was studied if the ability of aqueous garlic extracts to scavenge superoxide anion (O(2)(*-)), hydrogen peroxide (H(2)O(2)), and hydroxyl radical (OH(*)) is altered in the following aqueous preparations: (a) extracts of boiled garlic cloves (BG), (b) extracts of microwave-treated garlic cloves (MG), and (c) extracts of pickled garlic (PG), and heated extracts of (a) garlic powder (HGP) and (b) raw garlic (HRG). The data were compared with the unheated raw garlic (RG) or with the unheated garlic powder (GP). Extracts of GP and RG scavenged O(2)(*-), H(2)O(2), and OH(*) in a concentration-dependent way. The reactive oxygen species scavenging capacity was not decreased in the aqueous garlic extracts except in MG and HRG (for O(2)(*-)) and in HGP and PG (for H(2)O(2)). The heating before or after garlic cutting was unable to eliminate the capacity of the extracts to scavenge H(2)O(2), O(2)(*-), and OH(*).

S-allyl cysteine attenuated CCl4-induced oxidative stress and pulmonary fibrosis in rats

This study examined effects of S-allyl cysteine (SAC) on carbon tetrachloride (CCl4)-induced interstitial pulmonary fibrosis in Wistar rats. CCl4 (0.5 ml/kg) was intraperitoneally injected into rats twice a week for 8 weeks, and SAC (50, 100, or 200 mg/kg), N-acetyl cysteine (NAC, 200 or 600 mg/kg), or L-cysteine (CYS, 600 mg/kg) were orally administrated to rats everyday for 8 weeks. SAC significantly reduced the increases of transforming growth factor beta, lipid peroxides, AST, and ALT in plasma, induced by CCl4. Although CCl4 is mainly metabolized by hepatic cytochrome P450, CCl4 induced systemic inflammation and some organ fibrosis. SAC dose-dependently and significantly attenuated CCl4-induced systemic inflammation and fibrosis of lung. SAC also inhibited the decrease of thiol levels, the increase of inducible nitric oxide synthase expression, the infiltration of leukocytes, and the generation of reactive oxygen species in lungs. Although NAC and CYS attenuated CCl4-induced pulmonary inflammation and fibrosis, the order of preventive potency was SAC > NAC > CYS according to their applied doses. These results indicate that SAC is more effective than other cysteine compounds in reducing CCl4-induced lung injury, and might be useful in prevention of interstitial pulmonary fibrosis.

Molecular chaperone alpha-crystallin prevents detrimental effects of neuroinflammation

Silver nitrate administration stimulates immune activation, inflammation and deterioration in cell function. It is well established that hippocampal and cortical tissue are susceptible to degeneration in responses to insult such as oxidative stress or infection. This study was designed to investigate the prophylactic effect of alpha-crystallin, a major chaperone lens protein comprising of alpha-A and alpha-B subunits in inflammation induced mice. Mice were divided into three groups (n=6 in each), control, inflammation and alpha-crystallin treated. Our result shows that alpha-crystallin pretreatment effectively diminished systemic inflammation induced glial fibrillary acidic protein (GFAP) and nuclear factor kappa B (NFkappaB) expression in the mice neocortex, reversed elevated intracellular calcium levels, acetylcholine esterase activity and depletion of glucose. Furthermore it also significantly prevented nitric oxide (P<0.05) and lipid peroxide production in the plasma, liver, neocortex and hippocampus of the inflammation-induced mice. In order to demonstrate the direct *OH and nitric oxide radical scavenging ability of alpha-crystallin, an In vitro experiment using primary astrocyte culture subjected to lipopolysaccharide (LPS), a well-known inflammatory stimuli were also carried out. This study reiterates that alpha-crystallin therapy may serve as a potent pharmacological agent in neuroinflammation.

The neuroprotective efficacy of alpha-crystallin against acute inflammation in mice

Acute inflammation activates macrophages or monocytes and subsequently releases several inflammatory cytokines and reactive oxygen and nitrogen species. These proinflammatory cytokines activate astrocytes and trigger neurodegenerative diseases. In this work, we chose to address the mechanistic aspects of alpha-crystallin's protective function in inflammation-triggered neurotoxicity in mice. Alpha-crystallin, a lens structural protein, comprising alpha-A and alpha-B subunits is an ubiquitous molecular chaperone, which have been shown to reduce reactive oxygen species (ROS) production and enhance cellular glutathione level in the acute inflammation-induced mice. Results show that the proinflammatory cytokines such as interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) were significantly high (P<0.05) in the plasma, liver, cortex and hippocampus of inflammation-induced mice when compared to control. Alpha-crystallin pretreatment prevents inflammation-induced cytokines and NO production. In addition, a significant (P<0.05) reduction of dopamine (DA), 5-hydroxytryptamine (5-HT) and norepinephrine (NE) was also observed in the inflammation-induced mice. Nevertheless, their metabolites, such as 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) increased significantly (P<0.05) as compared to control. The results indicate that alpha-crystallin pretreatment controls the inflammation-induced DA, 5-HT and NE catabolism and suggest that alpha-crystallin has the potential to act as an anti-inflammatory agent in the neuroprotective processes.

Protective effect of S-allylcysteine on 3-nitropropionic acid-induced lipid peroxidation and mitochondrial dysfunction in rat brain synaptosomes

3-Nitropropionic acid is a neurotoxin that irreversibly inhibits succinate dehydrogenase, a relevant enzyme constituting the complex II of the respiratory chain during mitochondrial electron transport. 3-Nitropropionic acid is known to produce oxidative/nitrosative stress and evokes an experimental model of Huntington's disease. In this work we evaluated the effects of the antioxidant compound and major organosulfur garlic derivative, S-allylcysteine, on lipid peroxidation and mitochondrial dysfunction induced by 3-nitropropionic acid in synaptosomal fractions from rat brain. 3-Nitropropionic acid, at concentrations ranging 0.75-2.5 mM, produced enhanced levels of lipid peroxidation, while increasing concentrations of S-allylcysteine (0.1-2 mM) decreased the peroxidative action of 3-nitropropionic acid (1 mM) in synaptosomal fractions in a concentration-dependent manner. S-Allylcysteine (0.75 mM) also prevented the 3-nitropropionic acid (1mM)-induced mitochondrial dysfunction. These findings suggest that the protective actions that S-allylcysteine exert on the in vitro neurotoxicity induced by 3-nitropropionic acid are mediated by its antioxidant properties.

Investigating the protective effects of aged garlic extract on cyclosporin-induced nephrotoxicity in rats

Cyclosporin A (CsA) nephrotoxicity has been described in solid organ recipients and in the patients who were treated for autoimmune diseases. Reactive oxygen species-induced oxidative stress and lipid peroxidations are implicated in the pathophysiology of CsA-induced renal injury. Aged garlic extract (AGE) has been reported to exhibit potent antioxidative and free radical scavenging abilities in various disease conditions. The present study was designed to investigate whether AGE could possibly have a protective effect against nephrotoxicity induced by CsA. Male Wistar rats were treated orally with CsA (50 mg/kg/day), CsA + AGE (0.25, 0.5, 1, and 2 g/kg/day started 3 days before the first dose of CsA), or the vehicle of CsA for a period of 10 days. Blood urea nitrogen, serum creatinine, creatinine clearance, and renal histopathological changes were evaluated after 24 h of the last treatment. CsA caused an increase in blood urea nitrogen and serum creatinine by 117 and 100%, respectively, whereas it decreased creatinine clearance by 78% compared with the vehicle-treated rats (all P < 0.001). AGE treatment (0.5, 1 and 2 g/kg) significantly protected animals against CsA-induced biochemical changes, albeit blood urea nitrogen and creatinine clearance in the 0.5 g/kg AGE treated-animals were only partially restored. Kidney sections taken from CsA-treated rats showed severe vacuolations and tubular necrosis. These histopathological changes were markedly improved by pretreatment of rats with AGE at the dose of 0.5--2 g/kg. The results indicate that AGE ameliorates renal dysfunction and morphological changes induced by CsA, and imply that it could be a beneficial remedy for attenuating the CsA nephrotoxicity.

Differential effects of organosulfur compounds from garlic oil on nitric oxide and prostaglandin E2 in stimulated macrophages

OBJECTIVE

We investigated the inhibition of nitric oxide (NO) and prostaglandin E2 (PGE2) production by the garlic oil derivatives, diallyl sulfide (DAS), diallyl disulfide (DADS), and allyl methyl sulfide (AMS), in lipopolysaccharide (LPS)-activated RAW 264.7 cells.

METHODS

Cells were treated with LPS (330 ng/mL) and various concentrations of DAS, DADS, and AMS. NO and PGE2 released into the medium and expressions of inducible NO synthase and cyclooxygenase-2 protein were measured.

RESULTS

All three compounds suppressed stimulated NO production, among which AMS exhibited the least inhibition. Western blot analysis showed that DAS and DADS, but not AMS, inhibited the corresponding inducible NO synthase expression. An in vitro study showed that all three compounds possess NO clearance activity, and that DADS and AMS were more effective than DAS. On the contrary, only DAS inhibited activated PGE2 production and cyclooxygenase-2 protein expression.

CONCLUSIONS

The garlic derivatives, DAS, DADS, and AMS, differentially regulated the production of NO and PGE2 in stimulated macrophages. DAS decreased stimulated NO and PGE2 production by inhibiting inducible NO synthase and cyclooxygenase-2 expressions, and its enzyme inhibiting and NO clearance activity may also partly contribute to the suppression of NO. DADS inhibited activated NO production by decreasing inducible NO synthase expression and by directly clearing NO, whereas AMS suppressed NO mainly through its direct NO clearance activity. Further, neither DADS nor AMS showed any inhibitory effect on stimulated PGE2 production.

Bioactive S-alk(en)yl cysteine sulfoxide metabolites in the genus Allium: the chemistry of potential therapeutic agents

S-Alk(en)yl cysteine sulfoxides are odourless, non-protein sulfur amino acids typically found in members of the family Alliaceae and are the precursors to the lachrymatory and flavour compounds found in the agronomically important genus Allium. Traditionally, Allium species, particularly the onion (Allium cepa) and garlic (A. sativum), have been used for centuries in European, Asian and American folk medicines for the treatment of numerous human pathologies, however it is only recently that any significant progress has been made in determining their mechanisms of action. Indeed, our understanding of the role of Allium species in human health undoubtedly comes from the combination of several academic disciplines including botany, biochemistry and nutrition. During tissue damage, S-alk(en)yl cysteine sulfoxides are converted to their respective thiosulfinates or propanethial-S-oxide by the action of the enzyme alliinase (EC 4.4.1.4). Depending on the Allium species, and under differing conditions, thiosulfinates can decompose to form additional sulfur constituents including diallyl, methyl allyl, and diethyl mono-, di-, tri-, tetra-, penta-, and hexasulfides, the vinyldithiins and (E)- and (Z)-ajoene. Recent reports have shown onion and garlic extracts, along with several principal sulfur constituents, can induce phase II detoxification enzymes like glutathione-S-transferases (EC 2.5.1.18) and quinone reductase (QR) NAD(P)H: (quinine acceptor) oxidoreductase (EC 1.6.99.2) in mammalian tissues, as well as also influencing cell cycle arrest and apoptosis in numerous in vitro cancer cell models. Moreover, studies are also beginning to highlight a role of Allium-derived sulfur compounds in cardiovascular protection. In this review, we discuss the chemical diversity of S-alk(en)yl cysteine sulfoxide metabolites in the context of their biochemical and pharmacological mechanisms.

S-Allylcysteine, a garlic-derived antioxidant, ameliorates quinolinic acid-induced neurotoxicity and oxidative damage in rats

Excitotoxicity elicited by overactivation of N-methyl-D-aspartate receptors is a well-known characteristic of quinolinic acid-induced neurotoxicity. However, since many experimental evidences suggest that the actions of quinolinic acid also involve reactive oxygen species formation and oxidative stress as major features of its pattern of toxicity, the use of antioxidants as experimental tools against the deleterious effects evoked by this neurotoxin becomes more relevant. In this work, we investigated the effect of a garlic-derived compound and well-characterized free radical scavenger, S-allylcysteine, on quinolinic acid-induced striatal neurotoxicity and oxidative damage. For this purpose, rats were administered S-allylcysteine (150, 300 or 450 mg/kg, i.p.) 30 min before a single striatal infusion of 1 microl of quinolinic acid (240 nmol). The lower dose (150 mg/kg) of S-allylcysteine resulted effective to prevent only the quinolinate-induced lipid peroxidation (P < 0.05), whereas the systemic administration of 300 mg/kg of this compound to rats decreased effectively the quinolinic acid-induced oxidative injury measured as striatal reactive oxygen species formation (P < 0.01) and lipid peroxidation (P < 0.05). S-Allylcysteine (300 mg/kg) also prevented the striatal decrease of copper/zinc-superoxide dismutase activity (P < 0.05) produced by quinolinate. In addition, S-allylcysteine, at the same dose tested, was able to reduce the quinolinic acid-induced neurotoxicity evaluated as circling behavior (P < 0.01) and striatal morphologic alterations. In summary, S-allylcysteine ameliorates the in vivo quinolinate striatal toxicity by a mechanism related to its ability to: (a) scavenge free radicals; (b) decrease oxidative stress; and (c) preserve the striatal activity of Cu,Zn-superoxide dismutase (Cu,Zn-SOD). This antioxidant effect seems to be responsible for the preservation of the morphological and functional integrity of the striatum.

Garlic's ability to prevent in vitro Cu2+-induced lipoprotein oxidation in human serum is preserved in heated garlic: effect unrelated to Cu2+-chelation

Background

It has been shown that several extracts and compounds derived from garlic are able to inhibit Cu²⁺-induced low density lipoprotein oxidation. In this work we explored if the ability of aqueous garlic extract to prevent in vitro Cu²⁺-induced lipoprotein oxidation in human serum is affected by heating (a) aqueous garlic extracts or (b) garlic cloves. In the first case, aqueous extract of raw garlic and garlic powder were studied. In the second case, aqueous extract of boiled garlic cloves, microwave-treated garlic cloves, and pickled garlic were studied. It was also studied if the above mentioned preparations were able to chelate Cu²⁺.

Methods

Cu²⁺-induced lipoprotein oxidation in human serum was followed by the formation of conjugated dienes at 234 nm and 37°C by 240 min in a phosphate buffer 20 mM, pH 7.4. Blood serum and CuSO₄ were added to a final concentration of 0.67% and 0.0125 mM, respectively. The lag time and the area under the curve from the oxidation curves were obtained. The Cu²⁺-chelating properties of garlic extracts were assessed using an approach based upon restoring the activity of xanthine oxidase inhibited in the presence of 0.050 mM Cu²⁺. The activity of xanthine oxidase was assessed by monitoring the production of superoxide anion at 560 nm and the formation of uric acid at 295 nm. Data were compared by parametric or non-parametric analysis of variance followed by a post hoc test.

Results

Extracts from garlic powder and raw garlic inhibited in a dose-dependent way Cu²⁺-induced lipoprotein oxidation. The heating of garlic extracts or garlic cloves was unable to alter significantly the increase in lag time and the decrease in the area under the curve observed with the unheated garlic extracts or raw garlic. In addition, it was found that the garlic extracts were unable to chelate Cu²⁺.

Conclusions

(a) the heating of aqueous extracts of raw garlic or garlic powder or the heating of garlic cloves by boiling, microwave or pickling do not affect garlic's ability to inhibit Cu²⁺-induced lipoprotein oxidation in human serum, and (b) this ability is not secondary to Cu²⁺-chelation.

Nitridergic platelet pathway activation by hementerin, a metalloprotease from the leech Haementeria depressa

Hementerin (HT) is an 80 kDa fibrino(geno)lytic metalloprotease, purified from saliva of the leech Haementeria depressa. In the present report, the effect of HT on several functional parameters of human platelets was assessed. HT inhibited platelet aggregation and ATP release induced by different agonists such as ADP, adrenaline, collagen, thrombin, and arachidonic acid. HT did neither modify the expression of platelet glycoproteins (Ib, IIb-IIIa, Ia-IIa, IV) nor intraplatelet fibrinogen levels, whereas it markedly decreased CD62P and CD63 levels after the stimulation with thrombin. HT significantly increased thrombin-induced platelet Ca2+ intracellular levels, cGMP content and nitric oxide synthase (NOS) activity. The effect of HT on platelet aggregation was reversed by two NOS inhibitors, N(omega)-Nitro-L-arginine methyl ester and 2 N(G)-Nitro-L-arginine. In summary, these results indicate that HT is an effective inhibitor of human platelet aggregation, presumably through activation of the platelet's nitridergic pathway.

S-Allylcysteine prevents amyloid-β peptide-induced oxidative stress in rat hippocampus and ameliorates learning deficits

The effects of S-allylcysteine on oxidative damage and spatial learning and memory deficits produced by an intrahippocampal injection of amyloid-beta peptide 25-35 (Abeta(25-35)) in rats were investigated. The formation of reactive oxygen species, lipid peroxidation and the activities of the antioxidant enzymes superoxide dismutase and glutathione peroxidase were all measured in hippocampus 120 min after Abeta(25-35) injection (1 microl of 100 microM solution), while learning and memory skills were evaluated 2 and 35 days after the infusion of Abeta(25-35) to rats, respectively. Abeta(25-35) increased both reactive oxygen species and lipid peroxidation, whereas pretreatment with S-allylcysteine (300 mg/kg, i.p.) 30 min before peptide injection decreased both of these markers. In addition, Abeta(25-35)-induced incorrect learning responses were prevented in most of trials by S-allylcysteine. In contrast, enzyme activities were found unchanged in all groups tested. Findings of this work: (i) support the participation of reactive oxygen species in Abeta(25-35)-induced hippocampal toxicity and learning deficits; and (ii) suggest that the protective effects of S-allylcysteine were related to its ability to scavenge reactive oxygen species.

Membrane dynamics, cholesterol homeostasis, and Alzheimer's disease

Alzheimer's disease (AD) is characterized by the deposition of beta-amyloid (A beta) plaques derived from the amyloidogenic processing; of a transmembrane protein called beta-amyloid precursor protein (APP). In addition to the known genetic/sporadic factors that promote the formation of A beta, the composition and structural dynamics of the membrane are also thought to play a significant role in the amyloidogenic processing of APP that promotes seeding of A beta. This minireview reinforces the roles played by membrane dynamics, membrane microdomains, and cholesterol homeostasis in relation to amyloidogenesis, and reviews current strategies of lowering cholesterol in treating AD.

Aged garlic extract attenuates gentamicin induced renal damage and oxidative stress in rats

Gentamicin (GM) is an antibiotic whose clinical use is limited by its nephrotoxicity. Experimental evidences suggest a role of reactive oxygen species in GM-induced nephrotoxicity. Therefore, we investigated if aged garlic extract (AGE), an antioxidant, has a protective role in this experimental model. Four groups of male Wistar rats were studied: 1) Control (CT), injected subcutaneously (s.c.) and intraperitoneally (i.p.) with saline, 2) GM, treated s.c. with GM (70 mg/kg/12 hours/4 days), 3) AGE, treated i.p with AGE (1.2 mL/kg/12 hours/6 days), and 4) GM + AGE treated with GM and AGE. The treatment with AGE started two days before the first dose of GM (GM + AGE group) or saline (AGE group). Animals were sacrificed on day 5, and blood, urine, and kidneys were obtained. Nephrotoxicity was made evident by: 1) the increase in blood urea nitrogen and plasma creatinine, 2) the decrease in plasma glutathione peroxidase (GPx) activity and the urinary increase in N-acetyl-beta-D-glucosaminidase activity and total protein, and 3) necrosis of proximal tubular cells. These alterations were prevented or ameliorated by AGE treatment. Furthermore, AGE prevented the GM-induced increase in the renal levels of oxidative stress markers: nitrotyrosine and protein carbonyl groups and the decrease in manganese superoxide dismutase (Mn-SOD), GPx, and glutathione reductase (GR) activities. The protective effect of AGE was associated with the decrease in the oxidative stress and the preservation of Mn-SOD, GPx, and GR activities in renal cortex. These data suggest that AGE may be a useful agent for the prevention of GM-nephrotoxicity.

Nafamostat mesilate suppresses NF-kappaB activation and NO overproduction in LPS-treated macrophages

Nafamostat mesilate (NM), a clinically used serine protease inhibitor, suppressed the overproduction of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS) in RAW264.7 murine macrophages treated with lipopolysaccharide (LPS, 100 ng/ml); however, it had little effect on endothelial NOS (eNOS) in human umbilical vein endothelial cells (HUVEC). Electrophoretic mobility shift assay (EMSA) revealed that LPS activated nuclear factor-kappaB (NF-kappaB) in RAW264.7 cells and that this activation was suppressed by nafamostat mesilate. Western blotting showed that nafamostat mesilate suppressed the phosphorylation and degradation of inhibitor kappaB-alpha (IkappaB-alpha), which holds NF-kappaB in the cytoplasm in an inactivated state. Our observations suggest that nafamostat mesilate is a candidate agent for various diseases such as ischemia-reperfusion, graft rejection, inflammatory diseases, and autoimmune diseases, in which iNOS and/or NF-kappaB are upregulated.

Antioxidant S-allylcysteine prevents gentamicin-induced oxidative stress and renal damage

Acute renal failure (ARF) is a major complication of gentamicin (GM) treatment, which is effective against gram-negative infections. Since experimental evidence suggests a role of reactive oxygen species (ROS) in GM-induced ARF, in this work we studied the effect of a garlic-derived compound, S-allylcysteine (SAC), which is a free radical scavenger, on GM-induced nephrotoxicity. In rats treated with GM (70 mg/kg/12 h/4 days/s.c.), ARF was evident by the: (i) decrease in creatinine clearance and increase in blood urea nitrogen, (ii) decrease in blood glutathione peroxidase (GPx) activity and increase in urinary excretion of N-acetyl-beta-D-glucosaminidase and total protein, and (iii) necrosis of proximal tubular cells. These alterations were prevented by SAC treatment (250 mg/kg/i.p. 24 h before the first dose of GM and 125 mg/kg/12 h/4 days along GM-treatment). Furthermore, SAC prevented the GM-induced oxidative stress (protein carbonyl groups) and the decrease in manganese superoxide dismutase (Mn-SOD), GPx, and glutathione reductase (GR) activities in renal cortex. In conclusion, SAC ameliorates the GM-induced ARF by a mechanism related, at least in part, to its ability to decrease oxidative stress and to preserve antioxidant enzymes activity in renal cortex.

Radiation protection of HepG2 cells by Podophyllum hexandrum Royale

Radioprotection by an aqueous extract of Podophyllum hexandrum (RP-1) was investigated in HepG2 cells by evaluating colony forming efficacy (CFE), redox status of mitochondria, reactive oxygen species (ROS), generation of nitric oxide (NO), peroxidation of lipids and intracellular glutathione. Lower concentrations of RP-1 (0.1 and 1 microg/ml) rendered maximum radioprotection when administered 1 or 2 h before irradiation. Higher concentrations (5 and 10 microg/ml) however were less effective when administered 1 or 2 h before irradiation, but were more effective with increased time intervals (4 or 8 h) between RP-1 administration and irradiation. RP-1 pre-treatment also significantly inhibited radiation-induced MTT reduction in a concentration and time-dependent manner by decreasing gamma radiation-induced leakage of electrons from electron transport chain. Pre-irradiation administration of RP-1 significantly reduced both ROS and NO generation and enhanced glutathione levels, thereby inhibiting lipid peroxidation.

Beneficial effect of aqueous garlic extract on the vascular reactivity of streptozotocin-diabetic rats

The present study evaluated the beneficial effect of aqueous extract of garlic (Allium sativum L.; 100mg/kg/day) on the alterations in vascular reactivity of streptozotocin-diabetic rats. After 8 weeks of treatment, thoracic aortic rings of rats were mounted in organ baths and contractile responses to phenylephrine and relaxant responses to acetylcholine and isosorbide dinitrate were assessed. Induction of diabetes significantly increased contractile responses to phenylephrine and impaired endothelium-dependent relaxations to acetylcholine in aortic rings, but did not change endothelium-independent relaxation to isosorbide dinitrate. Garlic administration significantly improved the impaired endothelium-dependent relaxations and decreased the enhanced contractile response to phenylephrine in diabetic rats. It is concluded that intraperitoneal administration of aqueous garlic extract can improve endothelial dysfunction in insulin-dependent model of uncontrolled diabetes.

Garlic as an antioxidant: the good, the bad and the ugly

Garlic has played an important dietary and medicinal role throughout the history of mankind. In some Western countries, the sale of garlic preparations ranks with those of leading prescription drugs. The therapeutic efficacy of garlic encompasses a wide variety of ailments, including cardiovascular, cancer, hepatic and microbial infections to name but a few. However, the elucidation of its mechanism for therapeutic action has proved to be more elusive and a unifying theory, which could account for its reported multifarious activities, is yet to emerge. Reactive oxygen species (ROS) seem to be at the core of many disease processes and it is an attractive and convenient hypothesis that garlic might exert its activities through modulatory effects on ROS. A literature search on garlic and its antioxidant potential churned up a surprisingly large amount of data, some of it good, some bad and some of its definitely ugly. Various preparations of garlic, mainly aged garlic extract (AGE), have been shown to have promising antioxidant potential. However, the presence of more than one compounds in garlic, with apparently opposite biological effects, has added to the complexity of the subject. Raw garlic homogenate has been reported to exert antioxidant potential but higher doses have been shown to be toxic to the heart, liver and kidney. So where do we stand today on this issue of garlic? Is garlic always good for health? How safe is it? Is it necessary to isolate the antioxidant compounds for its medicinal use in a more effective way? These issues are addressed in this review.

Suppressive effects of garlic extract on Helicobacter pylori-induced gastritis in Mongolian gerbils

Helicobacter pylori infection is intimately involved in stomach cancer development and recent epidemiological studies have indicated that the consumption of allium vegetables reduces the risk of gastric neoplasia. Therefore, in the present study, we investigated the effect of a garlic extract on H. pylori-induced gastritis in Mongolian gerbils. Garlic extract was fed to animals at doses of 1, 2 and 4% in the diet from 4 h after H. pylori inoculation until the end of the experiment, at week 6. With the administration of garlic extract, H. pylori-induced gastritis in animals was decreased in a dose-dependent manner, and significantly so at 4%. The numbers of hemorrhagic spots in the glandular stomach and the microscopic score for gastritis were significantly reduced from 19.2+/-15.6 and 5.9+/-0.8 in control gerbils to 8.1+/-11.2 and 4.2+/-1.5, respectively, by 4% garlic extract treatment. The stomach wet weight (1.04+/-0.22 g) of control gerbils was also reduced by 4% garlic extract (0.86+/-0.18 g). However, the number of viable H. pylori was not changed by the garlic extract treatment. The above observations indicated that garlic extract might be useful as an agent for prevention of H. pylori-induced gastritis, leading to reduction in the risk of gastric cancer.