Effect of aminoguanidine on lipid peroxidation in streptozotocin-induced diabetic rats

Inhibitory effect of baicalein against glycation in HSA: an in vitro approach

Hyperglycaemia accelerates the aging process significantly. Diabetes problems can be mitigated by inhibiting glycation. To learn more about glycation and antiglycation mediated by methyl glyoxal and baicalein, we studied human serum albumin as a model protein. A Methylglyoxal (MGO) incubation period of seven days at 37 degrees Celsius induced glycation of Human Serum Albumin.s Hyperchromicity, decreased tryptophan and intrinsic fluorescence, increased AGE-specific fluorescence, and reduced mobility were all seen in glycated human serum albumin (MGO-HSA) in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Fourier transform infrared spectroscopy (FT-IR) and then far ultraviolet dichroism were used to detect secondary and tertiary structural perturbations (CD). The Congo red assay (CR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) all verified the presence of amyloid-like clumps. Structure (carbonyl groups on ketoamine moieties) (CO), physiological problems including diabetes mellitus, and cardiovascular disease, etc. are linked to the structural and functional changes in glycated HSA, as proven by these studies.Communicated by Ramaswamy H. Sarma.

Synthesis, Structural Characterization, Cytotoxicity, and Protein/DNA Binding Properties of Pyridoxylidene-Aminoguanidine-Metal (Fe, Co, Zn, Cu) Complexes

Pyridoxylidene-aminoguanidine (PLAG) and its transition metal complexes are biologically active compounds with interesting properties. In this contribution, three new metal-PLAG complexes, Zn(PLAG)(SO4)(H2O)].∙H2O (Zn-PLAG), [Co(PLAG)2]SO4∙2H2O (Co-PLAG), and [Fe(PLAG)2]SO4∙2H2O) (Fe-PLAG), were synthetized and characterized by the X-ray crystallography. The intermolecular interactions governing the stability of crystal structure were compared to those of Cu(PLAG)(NCS)2 (Cu-PLAG) within Hirshfeld surface analysis. The structures were optimized at B3LYP/6-31+G(d,p)(H,C,N,O,S)/LanL2DZ (Fe,Co,Zn,Cu), and stability was assessed through Natural Bond Orbital Theory and Quantum Theory of Atoms in Molecules. Special emphasis was put on investigating the ligand's stability and reactivity. The binding of these compounds to Bovine and Human serum albumin was investigated by spectrofluorometric titration. The importance of complex geometry and various ligands for protein binding was shown. These results were complemented by the molecular docking study to elucidate the most important interactions. The thermodynamic parameters of the binding process were determined. The binding to DNA, as one of the main pathways in the cell death cycle, was analyzed by molecular docking. The cytotoxicity was determined towards HCT116, A375, MCF-7, and A2780 cell lines. The most active compound was Cu-PLAG due to the presence of PLAG and two thiocyanate ligands.

Oxidative stress, inflammation and hormesis: The role of dietary and lifestyle modifications on aging

Oxidative stress (OS) is primarily caused by the formation of free radicals and reactive oxygen species; it is considered as one of the prominent factors in slowing down and degrading cellular machinery of an individual, and it eventually leads to aging and age-related diseases by its continuous higher state. The relation between molecular damage and OS should be particularized to understand the beginning of destruction at the cellular levels, extending outwards to affect tissues, organs, and ultimately to the organism. Several OS biomarkers, which are established at the biomolecular level, are useful in investigating the disease susceptibility during aging. Slowing down the aging process is a matter of reducing the rate of oxidative damage to the cellular machinery over time. The breakdown of homeostasis, the mild overcompensation, the reestablishment of homeostasis, and the adaptive nature of the process are the essential features of hormesis, which incorporates several factors, including calorie restriction, nutrition and lifestyle modifications that play an important role in reducing the OS. In the current review, along with the concept and theories of aging (with emphasis on free radical theory), various manifestations of OS with special attention on mitochondrial dysfunction and age-related diseases have been discussed. To alleviate the OS, hormetic approaches including caloric restriction, exercise, and nutrition have also been discussed.

Hypoglycemic effect and toxicity of the dry extract of Eugenia biflora (L.) DC. leaves

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Eugenia biflora (Myrtaceae) are traditionally used by Amazonian populations for the control of diabetes. However, their chemical composition has not yet been described and pharmacological evidence has not been reported.

OBJECTIVE

This study aimed to identify the chemical constituents and evaluate the hypoglycemic and toxic effect of the dry extract of the E. biflora leaves (DEEB).

MATERIALS AND METHODS

DEEB, obtained by infusion, was analyzed using LC-HRMS and NMR, whose the catechin flavonoid was quantified using NMR. The antidiabetic effect of DEEB was evaluated according to its inhibition of the enzymes α-amylase and α-glucosidase, as well as the content of total phenols, free radical scavengingand antiglycation activities, and its in vitro cell viability. Oral maltose tolerance and chronic multiple dose tests (28 days) in streptozotocin-induced diabetic mice (STZ) were performed. The hypoglycemic effect and toxicity of this extract were evaluated in the multiple dose assay. Biochemical parameters, hemolysis, and levels of the thiobarbituric acid reactive species in the liver were investigated and histopathological analyses of the kidneys and liver were performed.

RESULTS

Eight phenolic compounds were identified, with catechin (15.5 ± 1.7 mg g-1) being the majority compound and a possible chemical marker of DEEB. The extract showed inhibition activity of the enzyme α-glucosidase. Chronic administration of DEEB (50 mg/kg of body weight) reduced glucose levels in diabetic animals, similar to acarbose; however, DEEB (100 and 200 mg/kg bw) caused premature death of mice by D22 of the treatment. Our data indicate that one of the mechanisms of toxicity in DEEB may be related to the aggravation of oxidative stress in the liver. This histopathological study indicated that DEEB failed to minimize the progression of the toxicity of diabetes caused by STZ.

CONCLUSIONS

This study demonstrated the hypoglycemic potential of E. biflora leaves. However, the prolonged use of this tea can be harmful to its users due to its considerable toxicity, which needs to be better investigated.

Aminoguanidine Prevents the Oxidative Stress, Inhibiting Elements of Inflammation, Endothelial Activation, Mesenchymal Markers, and Confers a Renoprotective Effect in Renal Ischemia and Reperfusion Injury

Oxidative stress produces macromolecules dysfunction and cellular damage. Renal ischemia-reperfusion injury (IRI) induces oxidative stress, inflammation, epithelium and endothelium damage, and cessation of renal function. The IRI is an inevitable process during kidney transplantation. Preliminary studies suggest that aminoguanidine (AG) is an antioxidant compound. In this study, we investigated the antioxidant effects of AG (50 mg/kg, intraperitoneal) and its association with molecular pathways activated by IRI (30 min/48 h) in the kidney. The antioxidant effect of AG was studied measuring GSSH/GSSG ratio, GST activity, lipoperoxidation, iNOS, and Hsp27 levels. In addition, we examined the effect of AG on elements associated with cell survival, inflammation, endothelium, and mesenchymal transition during IRI. AG prevented lipid peroxidation, increased GSH levels, and recovered the GST activity impaired by IRI. AG was associated with inhibition of iNOS, Hsp27, endothelial activation (VE-cadherin, PECAM), mesenchymal markers (vimentin, fascin, and HSP47), and inflammation (IL-1β, IL-6, Foxp3, and IL-10) upregulation. In addition, AG reduced kidney injury (NGAL, clusterin, Arg-2, and TFG-β1) and improved kidney function (glomerular filtration rate) during IRI. In conclusion, we found new evidence of the antioxidant properties of AG as a renoprotective compound during IRI. Therefore, AG is a promising compound to treat the deleterious effect of renal IRI.

Topical nerve growth factor attenuates streptozotocin-induced diabetic cataracts via polyol pathway inhibition and Na+/K+-ATPase upregulation

The purpose of this study was to investigate whether and how topical nerve growth factor (NGF) attenuates streptozotocin (STZ)-induced diabetic cataracts in vivo. Rats were randomly divided into three groups, including the normal control rat group, STZ-induced diabetic cataract rat group (DM group), and STZ-induced diabetic cataract rat group treated with 200 μg/mL recombinant rat β-NGF (DM + NGF group). Cataract formation was evaluated by portable slit lamp biomicroscopy following pupil dilation at 8 weeks. The expression levels of NGF, aldose reductase (AR), and Na⁺/K⁺-ATPase in the lens epithelial cells (LECs) of the three groups were measured in the presence or absence of topical NGF. TUNEL-positive LECs were quantified to determine if hyperglycemia caused LEC apoptosis. At 8 weeks, the mean cataract score in the control group was significantly lower than that in DM and DM + NGF groups, and the score in the DM + NGF group was significantly lower than that in the DM group. At the equatorial zone and anterior central zone of lens, NGF and Na⁺/K⁺-ATPase expression levels were significantly decreased in the DM group; however, they were partially restored in the DM + NGF group. At the equatorial zone and anterior central zone of lens, AR expression and TUNEL-positive apoptotic LECs were significantly increased in the DM group compared with the control group, however, they were significantly decreased in the DM + NGF group. In conclusion, topical NGF could delay the progression of diabetic cataracts by attenuating polyol pathway activation and increasing Na⁺/K⁺-ATPase protein levels.

The Role of Lipoxidation in the Pathogenesis of Diabetic Retinopathy

Lipids can undergo modification as a result of interaction with reactive oxygen species (ROS). For example, lipid peroxidation results in the production of a wide variety of highly reactive aldehyde species which can drive a range of disease-relevant responses in cells and tissues. Such lipid aldehydes react with nucleophilic groups on macromolecules including phospholipids, nucleic acids, and proteins which, in turn, leads to the formation of reversible or irreversible adducts known as advanced lipoxidation end products (ALEs). In the setting of diabetes, lipid peroxidation and ALE formation has been implicated in the pathogenesis of macro- and microvascular complications. As the most common diabetic complication, retinopathy is one of the leading causes of vision loss and blindness worldwide. Herein, we discuss diabetic retinopathy (DR) as a disease entity and review the current knowledge and experimental data supporting a role for lipid peroxidation and ALE formation in the onset and development of this condition. Potential therapeutic approaches to prevent lipid peroxidation and lipoxidation reactions in the diabetic retina are also considered, including the use of antioxidants, lipid aldehyde scavenging agents and pharmacological and gene therapy approaches for boosting endogenous aldehyde detoxification systems. It is concluded that further research in this area could lead to new strategies to halt the progression of DR before irreversible retinal damage and sight-threatening complications occur.

Anti-cataract Effect of Resveratrol in High-Glucose-Treated Streptozotocin-Induced Diabetic Rats

Resveratrol, which is a polyphenol found in grapes, peanuts, and other plants, has health benefits for various chronic diseases. The aim of the present study was to examine the effect of resveratrol on cataract formation in diabetic rats. Male Wistar rats (7-week-old) were treated with streptozotocin, and the streptozotocin-treated animals were administered 5% D-glucose in drinking water to promote the formation of cataracts by inducing severe hyperglycemia. Resveratrol supplementation (10 or 30 mg/kg/d) in drinking water was initiated immediately after induction of diabetes was confirmed. The full lens images of the horizontal plane were captured with the digital camera system which we developed. Cataract formation was assessed by an observer-based scoring method and by quantitative analysis of digital images of the lens. Cataracts at the peripheral region of the lens were detected 2 weeks after induction of hyperglycemia and progressed depending on the length of the diabetic period. The majority of them developed severe cataracts after 9 weeks of hyperglycemia. Resveratrol did not prevent the appearance of diabetic cataracts but significantly delayed the progression of cataracts compared with controls. The contents of sorbitol and protein carbonyls in lenses of diabetic rats were higher than those of control rats. Resveratrol suppressed the increase in protein carbonyls, but not of sorbitol, in diabetic lenses. These results suggest that resveratrol delays the progression of diabetic cataracts partially through attenuation of oxidative damage to lens proteins. Resveratrol may be beneficial in preventing the progression of diabetic cataracts.

Inhibition of advanced glycation end products by isoferulic acid and its free radical scavenging capacity: An in vitro and molecular docking study

Non-enzymatic glycation and Oxidation of some essential biological macromolecules are paramount in the pathogenesis of various diseases including diabetes and atherosclerosis. Hyperglycemia plays a key role in the pathological process of diabetic complications by progressive accumulation of advanced glycation end products (AGEs) in body tissues. Formation of AGEs as a result of protein glycation is followed by an increased free radical activity that additionally contributes towards the bio-macromolecular damage. The present study aimed to evaluate the free radical scavenging and antiglycation capacity of isoferulic acid (IFA). The free radical scavenging activity of IFA was measured using DPPH, FRAP, and metal chelating assays. IFA showed effective reducing power, free radical scavenging activity and metal chelation activity in concentration dependent manner. The antiglycation activity of IFA was studied using various spectroscopic techniques. The obtained results were validated with free amino, sulfhydryl group, carbonyl content and AGEs formation. Secondary structural alterations were monitored using circular dichroism, morphology of aggregates was analyzed using transmission electron microscopy. Molecular docking reveals the possible binding location of IFA with in the sub-domain IIA of human serum albumin (HSA).

The effects of aminoguanidine, methylprednisolone, and melatonin on nerve recovery in peripheral facial nerve neurorrhaphy

BACKGROUND

The medications may enhance the recovery after nerve paralysis. We aimed to evaluate the effects of aminoguanidine (AG), melatonin, and methylprednisolone on peripheral facial nerve neurorrhaphy.

METHODS

The buccal branch of the facial nerve was transected and autografted in 32 New Zealand rabbits. Subjects were divided into 4 groups equally (AG, melatonin, methylprednisolone, and control). After the medical treatment latency and amplitude were measured with nerve conduction study at 3, 6, and 10 weeks. Then, coapted segments of nerve were examined microscopically. The groups were compared with each other.

RESULTS

The latent period was shortened, and the amplitudes were increased in the AG group; the latent period was shortened, and the amplitudes did not show significant change in the melatonin group with the time. There were no significant differences between the amplitudes at 3 to 6 and 3 to 10 weeks in the methylprednisolone group, and the latent period was shortened. There was no significant difference between the amplitude values at 3, 6, and 10 weeks in the control group. In the histological examination, AG had the best influence on preventing myelin degeneration and reducing the accumulation of myelin debris. Considering the increase in collagen fibers, the best results were achieved in the melatonin group. The degree of myelin-axonal degeneration was higher in the methylprednisolone group. The degree of collagen fiber increase, axonal degeneration, myelin degeneration, and the accumulation of myelin debris were detected quite high in the control group.

CONCLUSIONS

Aminoguanidine and melatonin alone achieved an increase in regeneration after peripheral facial nerve neurorrhaphy, but methylprednisolone did not. The best healing was determined in the AG group.

Protective Effects of Ferulic Acid on High Glucose-Induced Protein Glycation, Lipid Peroxidation, and Membrane Ion Pump Activity in Human Erythrocytes

Ferulic acid (FA) is the ubiquitous phytochemical phenolic derivative of cinnamic acid. Experimental studies in diabetic models demonstrate that FA possesses multiple mechanisms of action associated with anti-hyperglycemic activity. The mechanism by which FA prevents diabetes-associated vascular damages remains unknown. The aim of study was to investigate the protective effects of FA on protein glycation, lipid peroxidation, membrane ion pump activity, and phosphatidylserine exposure in high glucose-exposed human erythrocytes. Our results demonstrated that FA (10-100 μM) significantly reduced the levels of glycated hemoglobin (HbA1c) whereas 0.1-100 μM concentrations inhibited lipid peroxidation in erythrocytes exposed to 45 mM glucose. This was associated with increased glucose consumption. High glucose treatment also caused a significant reduction in Na⁺/K⁺-ATPase activity in the erythrocyte plasma membrane which could be reversed by FA. Furthermore, we found that FA (0.1-100 μM) prevented high glucose-induced phosphatidylserine exposure. These findings provide insights into a novel mechanism of FA for the prevention of vascular dysfunction associated with diabetes.

The inhibitory effect of selenium nanoparticles on protein glycation in vitro

Selenium nanoparticles (Se NPs) possess well-known excellent biological activities and low toxicity, and have been employed for numerous applications except as inhibitors to protein glycation. Herein, the present study is carried out to investigate the inhibitory effect of Se NPs on protein glycation in a bovine serum albumin (BSA)/glucose system. By measuring the amount of glucose covalently bound onto BSA, the formation of fructosamine and fluorescent products, it is found that Se NPs can hinder the development of protein glycation in a dose-dependent but time-independent manner under the selected reaction conditions (55 °C, 40 h). And after comparing the increase of inhibitory rate in different stages, it is observed that Se NPs show the greatest inhibitory effect in the early stage, then in the advanced stage, but no effect in the intermediate stage. Fourier transform infrared spectroscopy characterization of Se NPs collected after glycation and determination of ·OH influence and glyoxal formation show that the mechanism for the inhibitory efficacy of Se NPs is related to their strong competitive activity against available amino groups in proteins, their great scavenging activity on reactive oxygen species and their inhibitory effect on α-dicarbonyl compounds' formation. In addition, it is proved that Se NPs protect proteins from structural modifications in the system and they do not exhibit significant cytotoxicity towards BV-2 and BRL-3A cells at low concentrations (10 and 50 μg mL(-1)). Consequently, Se NPs may be suitable for further in vivo studies as novel anti-glycation agents.

Aminoguanidine mitigates apoptosis, testicular seminiferous tubules damage, and oxidative stress in streptozotocin-induced diabetic rats

This study aimed to investigate the effect of aminoguanidine (AG) against testicular damage streptozotocin (STZ) induced diabetes. Thirty two rats were separated into four groups: control, AG, STZ and STZ+AG. In the STZ group, 12.5±1.3% of tubules were seen as containing sloughed spermatogenic cells into the lumen, 28.7±1.8% of tubules were atrophic, 46.2±2.1% of tubules were degenerative and 8.5±0.9% of tubules contained giant cells. Statistically, the affected tubule number was significantly lower in the STZ+AG group than in the STZ group. Intensely stained caspase-3 cells showed a statistically significant increase in the STZ group, while it decreased in the STZ+AG group. The enzyme activities of catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) level decreased and the level of malondialdehyde (MDA) and nitric oxide (NO) increased in the STZ group, while AG treated diabetic rats showed an increase of CAT, SOD activity and GSH level and a decrease in MDA and NO levels. This study shows that the oxidative stress, increased NO level and apoptotic cell death play an important role in diabetic rat testicular damage and that AG treatment of diabetic rats results in protection of spermatogenic cells against oxidative stress and apoptotic cell death.

Tocotrienol-rich fraction from palm oil prevents oxidative damage in diabetic rats

OBJECTIVES

This study was carried out to determine the effects of tocotrienol-rich fraction (TRF) (200 mg/Kg) on biomarkers of oxidative stress on erythrocyte membranes and leukocyte deoxyribonucleic acid (DNA) damage in streptozotocin (STZ)-induced diabetic rats.

METHODS

Male rats (n = 40) were divided randomly into four groups of 10: a normal group; a normal group with TRF; a diabetic group, and a diabetic group with TRF. Following four weeks of treatment, fasting blood glucose (FBG) levels, oxidative stress markers and the antioxidant status of the erythrocytes were measured.

RESULTS

FBG levels for the STZ-induced diabetic rats were significantly increased (P <0.001) when compared to the normal group and erythrocyte malondialdehyde levels were also significantly higher (P <0.0001) in this group. Decreased levels of reduced glutathione and increased levels of oxidised glutathione (P <0.001) were observed in STZ-induced diabetic rats when compared to the control group and diabetic group with TRF. The results of the superoxide dismutase and glutathione peroxidase activities were significantly lower in the STZ-induced diabetic rats than in the normal group (P <0.001). The levels of DNA damage, measured by the tail length and tail moment of the leukocyte, were significantly higher in STZ-induced diabetic (P <0.0001). TRF supplementation managed to normalise the level of DNA damage in diabetic rats treated with TRF.

CONCLUSION

Daily supplementation with 200 mg/Kg of TRF for four weeks was found to reduce levels of oxidative stress markers by inhibiting lipid peroxidation and increasing the levels of antioxidant status in a prevention trial for STZ-induced diabetic rats.

Advanced glycation end-products: a common pathway in diabetes and age-related erectile dysfunction

Reactive derivatives of non-enzymatic glucose-protein condensation reactions integrate a heterogeneous group of irreversible adducts called advanced glycation end-products (AGEs). Numerous studies have investigated the role of the AGEs in cardiovascular system; however, its contribution to erectile dysfunction (ED) that is an early manifestation of cardiovascular disease has been less intensively investigated. This review summarizes the most recent advances concerning AGEs effects in the cavernous tissue of the penis and in ED onset, particularly on diabetes and aging, conditions that not only favor AGEs formation, but also increase risk of developing ED. The specific contribution of AGE on intra- and extracellular deposition of insoluble complexes, interference in activity of endothelial nitric oxide (NO) synthase, NO bioavailability, endothelial-dependent vasodilatation, as well as molecular pathways activated by receptor of AGEs are presented. Finally, the interventional actions that prevent AGEs formation, accumulation or activity in the cavernous tissue and that include nutritional pattern modulation, nutraceuticals, exercise, therapeutic strategies (statins, anti-diabetics, inhibitors of phosphodiesterase-5, anti-hypertensive drugs) and inhibitors of AGEs formation and crosslink breakers, are discussed. From this review, we conclude that despite the experiments conducted in animal models pointing to the AGE/RAGE axis as a potential interventional target with respect to ED associated with diabetes and aging, the clinical data have been very disappointing and, until now, did not provide evidence of benefits of treatments directed to AGE inactivation.

Therapeutic potential of targeting lipid aldehydes and lipoxidation end-products in the treatment of ocular disease

Lipoxidation reactions and the subsequent accumulation of advanced lipoxidation end products (ALEs) have been implicated in the pathogenesis of many of the leading causes of visual impairment. Here, we begin by outlining some of the major lipid aldehydes produced through lipoxidation reactions, the ALEs formed upon their reaction with proteins, and the endogenous aldehyde metabolizing enzymes involved in protecting cells against lipoxidation mediated damage. Discussions are subsequently focused on the clinical and experimental evidence supporting the contribution of lipid aldehydes and ALEs in the development of ocular diseases. From these discussions, it is clear that inhibition of lipoxidation reactions and ALE formation could represent a new therapeutic avenue for the treatment of a broad range of ocular disorders. Current and emerging pharmacological strategies to prevent or neutralize the effects of lipid aldehydes and ALEs are therefore considered, with particular emphasis on the potential of these drugs for treatment of diseases of the eye.

Isoferulic acid, a new anti-glycation agent, inhibits fructose- and glucose-mediated protein glycation in vitro

The inhibitory activity of isoferulic acid (IFA) on fructose- and glucose-mediated protein glycation and oxidation of bovine serum albumin (BSA) was investigated. Our data showed that IFA (1.25–5 mM) inhibited the formation of fluorescent advanced glycation end products (AGEs) and non-fluorescent AGE [N^ε-(carboxymethyl) lysine: CML], as well as the level of fructosamine. IFA also prevented protein oxidation of BSA indicated by decreasing protein carbonyl formation and protein thiol modification. Furthermore, IFA suppressed the formation of β-cross amyloid structures of BSA. Therefore, IFA might be a new promising anti-glycation agent for the prevention of diabetic complications via inhibition of AGEs formation and oxidation-dependent protein damage.

GP-1447, an inhibitor of aldose reductase, prevents the progression of diabetic cataract in rats

We examined the effects of GP-1447 (3-[(4,5,7-trifluorobenzothiazol-2-yl)methyl]-5-methylphenyl acetic acid) on existing cataracts and sorbitol content in the lens in rats with streptozotocin-induced diabetes. GP-1447 is an inhibitor of aldose reductase, which is the first enzyme in the polyol pathway. Cataracts in the central region of the lens were observed in 7 of 14 eyes (50%) by the fifth week after induction of diabetes, and development of mature cataracts was observed in most lenses by the ninth week. In diabetic rats that received GP-1447 treatment beginning in the fifth week after induction of diabetes, progression of cataracts was observed for 1 week after initiation of treatment. Thereafter, the severity of cataracts did not change substantially. Sorbitol levels in the lens peaked during the first week of diabetes, and this increase was maintained during the 9-week observation period. Elevated sorbitol levels in the lenses of diabetic rats gradually declined after GP-1447 treatment was started on the fifth week after induction of diabetes. Cataracts and sorbitol elevation were not observed in the lenses of controls or diabetic rats treated with GP-1447 immediately after induction of diabetes. These results suggest that the polyol pathway plays an important role in both the appearance and progression of cataracts in diabetic rats. Inhibition of aldose reductase could significantly prevent progression of existing cataracts.

The relative efficacy of aminoguanidine and pentoxifylline in modulating endotoxin-induced cardiac stress

This study investigates the effect of aminoguanidine (AG), a selective inducible nitric oxide synthase (iNOS) inhibitor, and pentoxifylline (PTX), a tumour necrosis factor-alpha (TNF-α) inhibitor, on lipopolysaccharide (LPS)-induced cardiac stress. Rats were divided into four groups: group I served as a control, group II (LPS) received a single intraperitoneal injection of LPS (10 mg·kg(-1) ), group III (LPS+AG) and group IV (LPS+PTX) were injected with either AG (100 mg·kg(-1) ) or PTX (150 mg·kg(-1) ) intraperitoneally 10 days prior to LPS administration. Normalization of cardiac levels of nitrite/nitrate (NO(X) ), malondialdehyde (MDA), glutathione (GSH), heme oxygenase-1 (HO-1), glutathione peroxidase (GPx) and Na(+) , K(+) -ATPase activities was evident in the AG group. Both AG and PTX decreased the elevated serum TNF-α levels, the activities of lactate dehydrogenase (LDH), creatine kinase (CK) and cardiac myeloperoxidase (MPO). The levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and phosphocreatine (PCr) were enhanced following AG and PTX pretreatments. Calcium (Ca(2+) ) levels were altered, and the histopathological observations supported the described results. Conclusively, the study highlights the cardioprotective potential of AG and PTX with superior results from AG. These findings reveal the relative contribution of nitric oxide and TNF-α to oxidative stress and energy failure during endotoxemia.

Nitric oxide in paraquat-mediated toxicity: A review

Paraquat, a cationic herbicide, produces degenerative lesions in the lung and in the nervous system after systemic administration to man and animals. Many cases of acute poisoning and death have been reported over the past few decades. Although a definitive mechanism of toxicity of paraquat has not been delineated, a cyclic single electron reduction/oxidation is a critical mechanistic event. The redox cycling of paraquat has two potentially important consequences relevant to the development of toxicity: the generation of the superoxide anion, which can lead to the formation of more toxic reactive oxygen species which are highly reactive to cellular macromolecules; and the oxidation of reducing equivalents (e.g., NADPH, reduced glutathione), which results in the disruption of important NADPH-requiring biochemical processes necessary for normal cell function. Nitric oxide is an important signaling molecule that reacts with superoxide derived from the paraquat redox cycle, to form the potent oxidant peroxynitrite, which causes serious cell damage. Although nitric oxide has been involved in the mechanism of paraquat-mediated toxicity, the role of nitric oxide has been controversial as both protective and harmful effects have been described. The present review summarizes recent findings in the field and describes new knowledge on the role of nitric oxide in the paraquat-mediated toxicity.

Overexpression of glyoxalase-I reduces hyperglycemia-induced levels of advanced glycation end products and oxidative stress in diabetic rats

The reactive advanced glycation end product (AGE) precursor methylglyoxal (MGO) and MGO-derived AGEs are associated with diabetic vascular complications and also with an increase in oxidative stress. Glyoxalase-I (GLO-I) transgenic rats were used to explore whether overexpression of this MGO detoxifying enzyme reduces levels of AGEs and oxidative stress in a rat model of diabetes. Rats were made diabetic with streptozotocin, and after 12 weeks, plasma and multiple tissues were isolated for analysis of AGEs, carbonyl stress, and oxidative stress. GLO-I activity was significantly elevated in multiple tissues of all transgenic rats compared with wild-type (WT) littermates. Streptozotocin treatment resulted in a 5-fold increase in blood glucose concentrations irrespective of GLO-I overexpression. Levels of MGO, glyoxal, 3-deoxyglucosone, AGEs, and oxidative stress markers nitrotyrosine, malondialdehyde, and F2-isoprostane were elevated in the diabetic WT rats. In diabetic GLO-I rats, glyoxal and MGO composite scores were significantly decreased by 81%, and plasma AGEs and oxidative stress markers scores were significantly decreased by ∼50%. Hyperglycemia induced a decrease in protein levels of the mitochondrial oxidative phosphorylation complex in the gastrocnemius muscle, which was accompanied by an increase in the lipid peroxidation product 4-hydroxy-2-nonenal, and this was counteracted by GLO-I overexpression. This study shows for the first time in an in vivo model of diabetes that GLO-I overexpression reduces hyperglycemia-induced levels of carbonyl stress, AGEs, and oxidative stress. The reduction of oxidative stress by GLO-I overexpression directly demonstrates the link between glycation and oxidative stress.

[Amelioration effect of Zhenqing Capsule on peripheral neuropathy in type 1 diabetic rats]

OBJECTIVE

To investigate the effects of Zhenqing Capsule (ZQC), a compound traditional Chinese herbal medicine, in treating type 1 diabetic rats with peripheral neuropathy.

METHODS

Type 1 diabetes was induced by caudal vein injection of high-dose streptozotocin in 30 male Wistar rats. The thirty diabetic rats were randomly divided into three groups: ZQC-treated group, untreated group and aminoguanidine-treated group. Another group of 10 rats was taken as normal control. After 10-week treatment, the changes of body weight and fasting plasma glucose level were measured, and the serum MDA level and the changes of neurological electrophysiology were analyzed. The samples of sciatic nerve in diabetic rats were taken for morphological observation.

RESULTS

The MDA level in type 1 diabetic rats was notably reduced in ZQC-treated group as compared with the untreated group (P<0.01). Compared with the untreated group, ZQC could improve the electrophysiology of sciatic nerve including conduction velocity (P<0.05), latency (P<0.01) and wave amplitude (P<0.05). The nerve myelin staining results showed that segmental demyelination of the nerve fibers in ZQC-treated group was not as serious as that in the untreated group.

CONCLUSION

ZQC can obviously ameliorate the neurological electrophysiological function and the pathological changes of peripheral nerve in type 1 diabetic rats through the removal of free radical and resistance of lipid peroxidation.

Antihyperglycemic, antihyperlipidemic and antioxidative potential of Prosopis cineraria bark

Alloxan administration in male Swiss albino mice, induced diabetes by increasing blood glucose concentration and reducing hepatic glycogen content as compared to normal control group. Besides, serum lipid profile parameters such as total-cholesterol, triglyceride, low-density lipoprotein and very low-density lipoprotein-cholesterol were also elevated, whereas, the level of high-density lipoprotein-cholesterol was reduced significantly (P<0.05) in diabetic mice. Treatment of diabetic animals with crude ethanolic extract of bark of Prosopis cineraria (P. cineraria) for 45 days, significantly lowered blood glucose level, elevated hepatic glycogen content and maintained body weight and lipid-profile parameters towards near normal range. Declined activity of antioxidant enzymes and concentration of non-enzymatic antioxidants were also normalized by drug treatment, thereby reducing the oxidative damage in the tissues of diabetic animals and hence indicating the anti-diabetic and antioxidant efficacy of the extract.

Aminoguanidine inhibits aortic hydrogen peroxide production, VSMC NOX activity and hypercontractility in diabetic mice

Background

Dysfunctionally uncoupled endothelial nitric oxide synthase (eNOS) is involved in producing reactive oxygen species (ROS) in the diabetic endothelium. The present study investigated whether anti-diabetes drug Aminoguanidine (AG) has any effect on eNOS function and vascular oxidant stress.

Methods and Results

Blood glucose levels were increased to 452.0 ± 15.1 mg/dl in STZ-treated male C57BL/6J mice (148.4 ± 3.2 mg/dl in untreated controls). Aortic productions of NO^• and O₂^•- were measured specifically and sensitively using electron spin resonance. Diabetic mice had a marked increase in aortic O₂^•- production. Aortic hydrogen peroxide (H₂O₂) production was also increased in diabetic aortas and significantly attenuated by AG. AG however had only a marginal effect in reducing aortic O₂^•- production, which corresponded to a minimal effect in improving aortic nitric oxide (NO^•) bioavailability. The endothelium-dependent vasodilatation however was modestly but significantly improved by AG, likely consequent to AG-induced reduction in hyper-contractility. NAD(P)H oxidase (NOX)-dependent O₂^•- production was completely attenuated by AG in endothelium-denuded diabetic aortas.

Conclusion

In summary, despite that AG is not an effective eNOS recoupling agent presumably consequent to its ineffectiveness in preventing endothelial NOX activation, it is inhibitory of aortic H₂O₂ production, VSMC NOX activity, and hypercontractility in diabetes.

Oxysterols increase in diabetic rats

To address whether diabetes enhances lipid peroxidation and attenuates nitric oxide (NO) generation resulting in tissue complications, we measured oxysterols and NO metabolites (NOx) in the tissues of diabetic Wistar rats. After 4 weeks of streptozotocin injection (STZ, 80 mg/kg, i.p.), we measured 7 alpha- and 7 beta-hydroperoxycholest-5-en-3 beta-ol (7 alpha-OOH and 7 beta-OOH), 7 alpha- and 7 beta-hydroxycholesterol (7 alpha-OH and 7 beta-OH) and 7-ketocholesterol (7-keto) by HPLC in the kidneys, heart, and liver. All the oxysterols were much higher in the diabetic than in sham rats, while the extent of the increase was higher in the order of the kidney, heart, and liver. Together with high blood urea nitrogen, the data indicate that the kidney is the predominant target of early diabetic complications. Plasma NOx were decreased by 20% in the STZ rats. The enhanced oxidative stress in diabetes would increase oxysterols by peroxidation, while superoxide is known to reduce NO by reaction to form another potent oxidant peroxynitrite.

Mass spectrometric quantification of amino acid oxidation products identifies oxidative mechanisms of diabetic end-organ damage

Diabetes mellitus is increasingly prevalent worldwide. Diabetic individuals are at markedly increased risk for premature death due to cardiovascular disease. Furthermore, substantial morbidity results from microvascular complications which include retinopathy, nephropathy, and neuropathy. Clinical studies involving diabetic patients have suggested that degree of diabetic hyperglycemia correlates with risk of complications. Recent evidence implicates a central role for oxidative stress and vascular inflammation in all forms of insulin resistance, obesity, diabetes and its complications. Although, glucose promotes glycoxidation reactions in vitro and products of glycoxidation and lipoxidation are elevated in plasma and tissue in diabetics, the exact relationships among hyperglycemia, the diabetic state, and oxidative stress are not well-understood. Using a combination of in vitro and in vivo experiments, we have identified amino acid oxidation markers that serve as molecular fingerprints of specific oxidative pathways. Quantification of these products utilizing highly sensitive and specific gas chromatography/mass spectrometry in animal models of diabetic complications and in humans has provided insights in oxidative pathways that result in diabetic complications. Our studies strongly support the hypothesis that unique oxidants are generated in the microenvironment of tissues vulnerable to diabetic damage. Potential therapies interrupting these reactive pathways in target tissue are likely to be beneficial in preventing diabetic complications.

Dynamic determination of Ox-LDL-induced oxidative/nitrosative stress in single macrophage by using fluorescent probes

Increased oxidative/nitrosative stress, resulting from generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) appears to play an important role in the inflammatory responses to atherosclerosis. By using MitoTracker Orange CM-H(2)TMRos, CM-H(2)DCFDA (DCF-DA), Dihydrorhodamine 123 (DHR123), DAF-FM, Dihydroethidium (DHE) and JC-1 alone or in all combinations of red and green probes, the present study was designed to monitor the ROS and RNS generation in acute exposure of single monocyte U937-derived macrophage to oxidized low density lipoprotein (Ox-LDL). Acute Ox-LDL (100 microg/ml) treatment increased time-dependently production of intracellular nitric oxide (NO), superoxide (O2*-), hydrogen peroxide (H(2)O(2)) and peroxynitrite (ONOO(-)), and decreased mitochondrial membrane potential (Deltapsi) in single cell. Pretreatment of aminoguanidine (an inhibitor of inducible nitric oxide synthase (iNOS), 10 microM) and vitamin C (an antioxidant agent, 100 microM) for 2h, reduced significantly the Ox-LDL-induced increase of NO and O2*-, and vitamin C completely inhibited increase of intracellular NO and O2*-. In contrast to aminoguanidine, Vitamin C pretreatment significantly prevented Ox-LDL-induced overproduction of NO and O2*- (P<0.01), indicating that antioxidant may be more effective in therapeutic application than iNOS inhibitor in dysfunction of ROS/RNS. By demonstrating a complex imbalance of ROS/RNS via fluorescent probes in acute exposure of single cell to Ox-LDL, oxidative/nitrosative stress might be more detected in the early atherosclerotic lesions.

Effect of nifedipine on severe experimental cataract in diabetic rats

We examined the effects of Ca(2+)-channel blockers on sugar cataract formation in streptozotocin (65 mg/kg, i.v.)-induced diabetic rats that were given 5% D-glucose as drinking water. The diabetic rats were treated with an L-type Ca(2+)-channel blocker, nifedipine or verapamil, for 9 weeks from the 3rd day of streptozotocin injection. Using the full lens images of the horizontal plane captured with the new digital camera system that we developed recently, the cataract formation was quantitatively assessed in parallel with the conventional scaling method. In the animal model of diabetes mellitus, the cataracts at the peripheral region of the lens were detected 2 weeks after induction of hyperglycemia and progressed depending on the length of the diabetic period. The majority of them developed mature cataracts after 9 weeks of hyperglycemia. Nifedipine slowed the progression rate of diabetic cataracts without affecting the period of time required for the onset of this disease, whereas verapamil had no significant inhibitory effect on the diabetic cataract. These findings suggest that nifedipine may be considered as a candidate drug to suppress the progression of diabetic cataracts.

Further studies on antioxidant potential and protection of pancreatic beta-cells by Embelia ribes in experimental diabetes

This study was designed to examine the antioxidant defense by ethanolic extract of Embelia ribes on streptozotocin-(40 mg/kg, intravenously, single-injection) induced diabetes in Wistar rats. Forty days of oral feeding the extract (100 mg/kg and 200 mg/kg) to diabetic rats resulted in significant (P < .01) decrease in blood glucose, blood glycosylated haemoglobin, serum lactate dehydrogenase, creatine kinase, and increase in blood glutathione levels as compared to pathogenic diabetic rats. Further, the extract also significantly (P < .01) decreased the pancreatic thiobarbituric acid-reactive substances (TBARS) levels and significantly (P < .01) increased the superoxide dismutase, catalase, and glutathione levels as compared to above levels in pancreatic tissue of pathogenic diabetic rats. The islets were shrunken in diabetic rats in comparison to normal rats. In the drug-treated diabetic rats, there was expansion of islets. The results of test drug were comparable to gliclazide (25 mg/kg, daily), a standard antihyperglycemic agent. The study concludes that Embelia ribes enhances the antioxidant defense against reactive oxygen species produced under hyperglycemic condition and this protects β-cells against loss, and exhibit antidiabetic property.

Synthesis, spectroscopic and X-ray characterization of a copper(II) complex with the Schiff base derived from pyridoxal and aminoguanidine: NMR spectral studies of the ligand

A copper(II) complex with the pyridoxal-aminoguanidine (PL-AG) Schiff base adduct, as an organic compound of the very potent biological activity and promising pharmacological importance in the treatment of diabetic complications, has been prepared and characterized. The X-ray structural analysis of the [CuCl2(PL-AG)] complex showed that it has a distorted pseudo-square-pyramidal (4+1) structure with the tridentate ONN Schiff base in the equatorial plane, with the Cu-O(1), Cu-N(1) and Cu-N(3) bond lengths of 1.917(2)A, 1.930(2)A and 1.984(2)A, respectively. The bond length of the equatorial Cu-Cl(1) is 2.279(1)A, while that of the apical Cu-Cl(2) is 2.792(1)A. Pyridoxal fragment is coordinated in its zwitterionic form. In addition to the X-ray structural analysis, the complex was characterized by IR spectrometric, conductometric and magnetic techniques, and the ligand itself by IR, 1H and 13C NMR spectra.

Mechanisms for oxidative stress in diabetic cardiovascular disease

Obesity, metabolic syndrome, and diabetes are increasingly prevalent in Western society, and they markedly increase the risk for atherosclerotic vascular disease, the major cause of death in diabetics. Although recent evidence suggests a causal role for oxidative stress in insulin resistance, diabetes, and atherosclerosis, there is considerable controversy regarding its nature, magnitude, and underlying mechanisms. Glucose promotes glycoxidation reactions in vitro, and products of glycoxidation and lipoxidation are elevated in plasma and tissue from humans suffering from diabetes, but the exact relationships between hyperglycemia and oxidative stress are poorly understood. This review focuses on molecular mechanisms of increased oxidative stress in diabetes, the relationship of oxidant production to hyperglycemia, and the potential interaction of reactive carbonyls and lipids in oxidant generation. Using highly sensitive and specific gas chromatography-mass spectrometry, molecular signatures of specific oxidation pathways were identified in tissues of diabetic humans and animals. These studies support the hypothesis that unique reactive intermediates generated in localized microenvironments of vulnerable tissues promote diabetic damage. Therapies interrupting these reactive pathways in vascular tissue might help prevent cardiovascular disease in this high-risk population.

The effect of aminoguanidine against cholestatic liver injury in rats

We investigated the protective role of aminoguanidine (AG) in rat liver injury induced by chronic biliary obstruction. Secondary biliary cirrhosis was induced by bile duct ligation for 14 days. Swiss albino rats were divided into three groups: Common bile duct ligated (CBDL) rats; Group A, CBDL rats treated with AG as Group B and simple laparotomy group known as the Sham group; Group C. Group B received 200 mg/kg of AG intraperitoneally daily throughout 14 days. The present data showed decreased gama glutamyl transferase (GGT), aspartate aminotransferase (AST), bilirubin and alanine aminotransferase (ALT) levels in the AG treated rats, when compared with CBDL rats (p < 0.05). In the AG treated rats, tissue levels of malondialdehyde (MDA) were significantly lower than that in CBDL rats (p < 0.001). Although the levels of glutathione (GSH) in AG treated rats were higher and myeloperoxidase (MPO) were lower than that in CBDL rats, the difference was not statistically significant (p > 0.05). The levels of interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) were significantly lower and although the levels of interleukin-6 (IL-6) were lower in AG treated rats than that in CBDL rats, the difference was not statistically significant. Administration of AG in the rats with biliary obstruction resulted in inhibition of ductular proliferation and portal inflammation. The present study demonstrates that intraperitoneal administration of AG in CBDL rats maintains antioxidant defenses, reduces liver oxidative and cytokine damage and ductular proliferation and portal inflammation. This effect of AG may be useful in the preservation of liver injury in cholestasis.

Protective effect of aminoguanidine against oxidative stress in an experimental peritoneal adhesion model in rats

Postoperative intraperitoneal adhesion formation is a major cause of intestinal obstruction, pain and infertility. This experimental study was designed to evaluate the degree of adhesion formation and peritoneal tissue levels of malondialdehyde (MDA), reduced glutathione (GSH) and total nitrite and nitrate (NO) and the effect of aminoguanidine (AG) on these metabolite values after postoperative intraperitoneal adhesion formation in rats. A total of 21 adult male Wistar albino rats were randomly divided into three groups. Control rats were untreated; the AG group received AG 200 mg kg(-1) i.p. for 10 consecutive days intraperitoneally after surgery. The sham group was given 0.9% NaCl. The rats were killed on postoperative day 10. The peritoneal tissues were harvested to determine the tissue levels of MDA, GSH, and NO activity. For light microscopic evaluation, the cecum was removed. Adhesion formation scores in the AG group were significantly lower than those of the control and sham groups (p < 0.017, p < 0.026 respectively). In the AG-treated rats, tissue levels of MDA and NO were significantly lower than in the control group (p < 0.017). The levels of GSH in aminoguanidine-treated rats were significantly higher than those of the control group (p < 0.01). The severity of the inflammation was more prominent in the control group compared with the AG-injected rats. The results demonstrate that in this experimental model, intraperitoneal administration of aminoguanidine decreases the incidence and extent of peritoneal adhesions and causes a decrease in MDA and NO and an increase in GSH values.

Advanced glycation endproducts (AGEs): pharmacological inhibition in diabetes

AGE inhibitors may act by various mechanisms at different steps of advanced glycation endproduct (AGE) formation (depending on oxidative stress and/or carbonyl stress) and AGE-mediated damage: trapping of reactive dicarbonyl species; antioxidant activity by transition metal chelation; other antioxidant activity including free radical scavenging; AGE cross-link breaking; AGE receptor (RAGE) blocking; RAGE signaling blocking; glycemia reduction by anti-diabetic therapy; aldose reductase inhibition; shunting of trioses-P towards the pentose-P pathway by transketolase activation. Most of the inhibitors have several sites of action. Practically one can distinguish drugs specifically developed as AGE inhibitors or AGE breakers; RAGE and receptor signaling blockers; other therapeutic compounds which were found subsequently to possess also AGE inhibitor activity, including dietary antioxidants. Encouraging results obtained in studies of various AGE inhibitors, conducted in vitro and in diabetic animals, are summarized in this review. However most of the clinical trials have been more or less disappointing, in part because of side effects; the long-term therapeutic interest of the most recently developed AGE inhibitors or breakers remains to be demonstrated in diabetes.

Effects of aminoguanidine against renal ischaemia-reperfusion injury in rats

Aminoguanidine is an inhibitor of nitric oxide synthase (NOS), with high selectivity for the inducible isoform (iNOS). In addition to being an inhibitor of NOS, aminoguanidine also exhibits antioxidant activity. Recent studies suggest that aminoguanidine reduces ischaemia-reperfusion (I/R)-induced damage. However, the role of aminoguanidine, in renal injury associated with I/R remains unknown. This study was designed to investigate the effects of aminoguanidine on renal I/R injury. There were three groups of eight rats each. I/R was induced by occlusion of the left renal vessels for 60 min, followed by 24 h reperfusion in rats. Malondialdehyde (MDA) levels, a stable metabolite of the free radical-mediated lipid peroxidation cascade, were found to be significantly higher in the I/R group (30.3 +/- 0.1 nmol g(-1) tissue) than in the control group (10 +/- 0.05 nmol g(-1)). Aminoguanidine (100 mg kg(-1)) administration to rats significantly reduced the MDA values. We also demonstrated that I/R leads to structural change but aminoguanidine did not reverse this change. Aminoguanidine, according to the biochemical finding is protective but histopathological findings did not reveal protection against I/R injury in kidney. The effects of aminoguanidine on I/R-induced damage remain a subject for future investigations.

Beneficial role of aminoguanidine on acute cardiomyopathy related to doxorubicin-treatment

Doxorubicin (DOX) is a broad-spectrum anthracycline antibiotic that has cardiotoxicity as a major side effect. One mechanism of this toxicity is believed to involve the reactive oxygen radical species (ROS); these agents likely account for the pathophysiology of DOX-induced cardiomyopathy. Aminoguanidine (AG) is an effective antioxidant and free radical scavenger which has long been known to protect against ROS formation. We investigated the effects of AG on DOX-induced changes in thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GSH) content. The rats were divided into four groups:1) Control; 2) DOX group; injected intraperitoneally (i.p.) with DOX 20 mg/kg in a single dose 3) AG-treated group; injected i.p. in single dose of 20 mg/kg DOX plus 100 mg/kg AG 1 h before the DOX for 3 days, 4) AG group; injected i.p. with AG 100 mg/kg for 3 days. DOX administration to control rats increased TBARS and decreased GSH levels. AG administration before DOX injection caused significant decrease in TBARS and increase in GSH levels in the heart tissue when compared with DOX only. Morphological changes, including severe myocardial fibrosis and inflammatory cell infiltration were clearly observed in the DOX-treated heart. AG reversed the DOX-induced heart damage. Therefore AG could protect the heart tissue against free radical injury. The application of AG during cancer chemotherapy may attenuate tissue damage and improve the therapeutic index of DOX.

Antioxidants and an inhibitor of advanced glycation ameliorate death of retinal microvascular cells in diabetic retinopathy

BACKGROUND

Pericyte ghosts and acellular capillaries are well known as early histological changes resulting from diabetic retinopathy. These histological changes mean that the cell death of retinal microvessels has accelerated. It was reported that apoptosis of retinal microvascular cells (RMCs) was increased in diabetic patients. Therefore, we investigated apoptosis of RMCs in Goto-Kakizaki (GK) rats, a type 2 diabetic model, and involvement with antioxidants (a combination of vitamins C and E) or a novel inhibitor of advanced glycation, OPB-9195.

METHODS

GK rats were treated with the antioxidants combination or OPB-9195 for 36 weeks. We obtained isolated preparations of the vascular network from their retinas by trypsin digestion. Apoptosis of retinal vascular cells was detected with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay.

RESULTS

We found that apoptosis of RMCs was increased in the diabetic GK rats. Furthermore, a combination of vitamins C and E and an advanced glycation end-products inhibitor mostly inhibited this increased apoptosis.

CONCLUSIONS

We concluded that apoptosis of RMCs was a good marker that indicates the progression of diabetic retinopathy in GK rats. Both oxidative stress and the accumulation of advanced glycation end-products appears to promote the apoptosis of retinal microvascular cells, and antioxidants or advanced glycation end-products inhibitors might ameliorate diabetic retinopathy.

Effect of aminoguanidine on ischemia-reperfusion induced myocardial injury in rats

Myocardial ischemia-reperfusion (MI/R) has been implicated in the induction of inducible nitric oxide synthase (iNOS) that leads to increase production of nitric oxide (NO). Recently, excessive production of NO has been involved in causing myocardial injury. In our in vivo model, we examined the effects of aminoguanidine (AMG), a known iNOS inhibitor, on percentage infarct size in anaesthetized rats. A total of 14 rats were equally divided into two groups (n = 7 in each group). To produce myocardial necrosis, the left main coronary artery was occluded for 30 min, followed by 120 min of reperfusion, in anesthetized rats. AMG (200 mg kg(-1)) was given intravenously 10 min before occlusion. The volume of infarct size and the risk zone were determined by planimentry of each tracing and multiplying by the slice thickness. Infarct size was normalized by expressing it as a percentage of the area at risk. Hemodynamic parameters were measured via the left carotid artery. Compared to MI/R group, whereas AMG administration elevated mean arterial blood pressure, statistically reduced the myocardial infarct size (21+/- 1 and 14+/- 4%, respectively) and infract size/risk zone (53+/- 3 and 37+/- 5%, respectively) in rat model of ischemia-reperfusion. In conclusion, this study indicates that iNOS inhibitor, AMG, show reduction in NO's side effect in I/R injury.

Prevention of early renal disease, dyslipidaemia and lipid peroxidation in STZ-diabetic rats by LR-9 and LR-74, novel AGE inhibitors

BACKGROUND

Increased formation of advanced glycation/lipoxidation endproducts (AGEs/ALEs) has been implicated in the pathogenesis of various diabetic complications. Several compounds have been developed as inhibitors of AGE/ALE formation. We examined the effects of two new AGE/ALE inhibitors, LR-9 and LR-74, on the development of early renal disease and lipid metabolism in streptozotocin (STZ)-induced diabetic rats.

METHODS

Diabetic Sprague-Dawley rats were treated with either of the LR compounds for 32 weeks. Progression of renal disease was evaluated by measurements of urinary albumin and plasma creatinine concentrations. AGE/ALE and nitrotyrosine levels in kidneys were determined by immunohistochemistry. AGE-induced chemical modification of the tail tendon collagen and levels of Nepsilon-(carboxymethyl) and (carboxyethyl)- lysines (CML and CEL) in skin collagen were measured. Plasma lipids and their lipid hydroperoxide concentrations were also determined. In vitro, both compounds were tested for inhibiting lipid peroxidation reactions.

RESULTS

Treatment of either LR compounds significantly inhibited the increase in albuminuria, creatinaemia, hyperlipidaemia and lipid peroxidation in diabetic rats without any effect on hyperglycaemia. Both compounds also reduced CML-AGE and nitrotyrosine accumulation in kidney glomeruli and tubules, AGE-linked fluorescence and cross-linking of tail collagen, and levels of CML and CEL in skin collagen. In vitro, LR compounds inhibited the oxidation of human low-density lipoprotein (LDL).

CONCLUSION

Both compounds can inhibit the progression of renal disease and also prevent dyslipidaemia in type-1 diabetic animals. These compounds may have an additional beneficial effect as an antioxidant against lipid peroxidation, and thus may provide alternative therapeutic options for the treatment of various diabetic macrovascular complications.

Protective effects of bendazac lysine on early experimental diabetic nephropathy in rats

AIM

To investigate the preventive and protective effects of bendazac lysine (BDL) on experimental early diabetic nephropathy (DN) rats.

METHODS

After an early DN model was induced by streptozotocin, rats were administered BDL at doses of 100, 200, and 400 mg/kg for 8 weeks. Blood glucose, microalbuminuria, kidney index, total antioxidative capacity, laminin, advanced glycation end products (AGE), aldose reductase (AR) activity, and the relative quantity of transforming growth factor beta1 (TGF- beta1) mRNA were measured by different methods. The ultrastructural morphology was observed by transmission electron microscope.

RESULTS

The physical behaviors of early DN rats were hypopraxia, cachexia, and polyuria, while those treated with high doses of BDL were vibrant and vigorous. For BDL-treated DN rats, when compared with vehicle-treated DN rats, the blood glucose level and the intensity of oxidative stress were ameliorated. Also, the microalbuminuria level, AGE either in serum or in renal, and AR activity were significantly reduced. Furthermore, the expression of TGF-beta1 mRNA in the kidney cortex was declined and the thickness of glomerular base membrane was decreased significantly. The ultrastructure of glomerulus and mesangial matrix of BDL-treated DN rats were ameliorated.

CONCLUSION

BDL has protective effects on several pharmacological targets in the progress of DN and is a potential drug for the prevention of early DN.

Effects of aminoguanidine and antioxidant erdosteine on bleomycin-induced lung fibrosis in rats

Reactive oxygen and nitrogen species have been implicated in the pathogenesis of bleomycin-induced lung fibrosis. The effects of aminoguanidine and erdosteine on the bleomycin-induced lung fibrosis were evaluated in rats. The animals were placed into five groups: Vehicle + vehicle, vehicle + bleomycin (2.5 U/kg), bleomycin + aminoguanidine (200 mg/kg), bleomycin + erdosteine (10 mg/kg), and bleomycin + erdosteine + aminoguanidine. Bleomycin administration resulted in prominent lung fibrosis as measured by lung hydroxyproline content and lung histology, which is completely prevented by erdosteine and aminoguanidine. A strong staining for nitro tyrosine antibody in lung tissue and increased levels of lung NO were found in bleomycin group, that were significantly reduced by aminoguanidine and erdosteine. Aminoguanidine and erdosteine significantly prevented depletion of superoxide dismutase and glutathione peroxidase and elevated myeloperoxidase activities, malondialdehyde level in lung tissue produced by bleomycin. Data presented here indicate that aminoguanidine and erdosteine prevented bleomycin-induced lung fibrosis and that nitric oxide mediated tyrosine nitration of proteins plays a significant role in the pathogenesis of bleomycin-induced lung fibrosis. Also our data suggest that antifibrotic affect of antioxidants may be due to their inhibitory effect on nitric oxide generation in this model.