Effect of aminoguanidine on the generation of superoxide anion and nitric oxide by peripheral blood granulocytes of rats with streptozotocin-induced diabetes

Beneficial effects of aminoguanidine on skin flap survival in diabetic rats

Random flaps in DM patients have poor reliability for wound coverage, and flap loss remains a complex challenge. The protective effects of aminoguanidine (AG) administration on the survival of dorsal random flaps and oxidative stress were studied in diabetic rats. Two months after the onset of DM, dorsal McFarlane flaps were raised. Forty rats were divided into four groups: (1) control, (2) AG, (3) DM, and (4) DM + AG groups. Flap viability, determined with the planimetric method, and free-radical measurements were investigated. In addition, HbA1c and blood glucose levels, body weight measurements, and histopathological examinations were evaluated. The mean flap necrotic areas (%) in Groups I to IV were 50.9 ± 13.0, 32.9 ± 12.5, 65.2 ± 11.5, and 43.5 ± 14.7, respectively. The malondialdehyde (MDA) and nitric oxide (NO) levels were higher in the DM group than in the nondiabetic group, while the reduced glutathione (GSH) levels and superoxide dismutase (SOD) activity were reduced as a result of flap injury. In the diabetic and nondiabetic groups, AG administration significantly reduced the MDA and NO levels and significantly increased GSH content and SOD enzyme activity. We concluded that AG plays an important role in preventing random pattern flap necrosis.

Protective effect of aminoguanidine against cyclophosphamide-induced oxidative stress and renal damage in rats

BACKGROUND

Cyclophosphamide (CP) is widely used in the treatment of tumors and B-cell malignant disease, such as lymphoma, myeloma, chronic lymphocytic leukemia, and Waldenstrom's macroglobulinemia. Renal damage is one of the dose-limiting side effects of CP. Oxidative stress is reported to play important roles in CP-induced renal damage.

AIM

To find out whether aminoguanidine (AG) protects against CP-induced oxidative stress and renal damage.

METHOD

Renal damage was induced in the rats by administration of a single injection of CP at a dose of 150 mg/kg body weight intraperitoneally. For the AG pretreatment studies, the rats were injected intraperitoneally with AG at a dose of 200 mg/kg body weight 1 hour before administration of CP. The control rats received AG or saline alone. All the rats were killed 16 hours after the administration of CP or saline. The kidneys were used for histological examination by light microscopy and biochemical assays--malondialdehyde, protein carbonyl content, reduced glutathione (GSH), and the activities of antioxidant enzymes including glutathione peroxidase (GPx), glutathione S transferase (GSTase), catalase, glutathione reductase, and myeloperoxidase (MPO), a marker of neutrophil infiltration.

RESULTS

Pretreatment with AG attenuated CP-induced renal damage histologically. Pretreatment with AG prevented CP-induced lipid peroxidation, protein oxidation, depletion of reduced GSH, and loss of activities of the antioxidant enzymes including GPx, catalase, and GSTase and also MPO activity.

CONCLUSION

The results of the present study reveal that AG can prevent CP-induced renal damage by inhibiting oxidative stress. Thus, AG may be useful for prevention of the nephrotoxicity of CP.

Involvement of nitric oxide in maneb- and paraquat-induced Parkinson's disease phenotype in mouse: is there any link with lipid peroxidation?

The study aimed to investigate the involvement of nitric oxide (NO) in maneb (MB)- and paraquat (PQ)-induced Parkinson's disease (PD) phenotype in mouse and its subsequent contribution to lipid peroxidation. Animals were treated intraperitoneally with or without MB and PQ, twice a week for 3, 6 and 9 weeks. In some sets of experiments (9 weeks treated groups), the animals were treated intraperitoneally with or without inducible nitric oxide synthase (iNOS) inhibitor-aminoguanidine, tyrosine kinase inhibitor-genistein, nuclear factor-kappa B (NF-kB) inhibitor-pyrrolidine dithiocarbamate (PDTC) or p38 mitogen activated protein kinase (MAPK) inhibitor-SB202190. Nitrite content and lipid peroxidation were measured in all treated groups along with respective controls. RNA was isolated from the striatum of control and treated mice and reverse transcribed into cDNA. RT-PCR was performed to amplify iNOS mRNA and western blot analysis was done to check its protein level. MB- and PQ-treatment induced nitrite content, expressions of iNOS mRNA and protein and lipid peroxidation as compared with respective controls. Aminoguanidine resulted in a significant attenuation of iNOS mRNA expression, nitrite content and lipid peroxidation demonstrating the involvement of nitric oxide in MB- and PQ-induced lipid peroxidation. Genistein, SB202190 and PDTC reduced the expression of iNOS mRNA, nitrite content and lipid peroxidation in MB- and PQ-treated mouse striatum. The results obtained demonstrate that nitric oxide contributes to an increase of MB- and PQ-induced lipid peroxidation in mouse striatum and tyrosine kinase, p38 MAPK and NF-kB regulate iNOS expression.

Overexpression of Bcl-2 in vascular endothelium inhibits the microvascular lesions of diabetic retinopathy

Recent studies on the pathogenesis of diabetic retinopathy have focused on correcting adverse biochemical alterations, but there have been fewer efforts to enhance prosurvival pathways. Bcl-2 is the archetypal member of a group of antiapoptotic proteins. In this study, we investigated the ability of overexpressing Bcl-2 in vascular endothelium to protect against early stages of diabetic retinopathy. Transgenic mice overexpressing Bcl-2 regulated by the pre-proendothelin promoter were generated, resulting in increased endothelial Bcl-2. Diabetes was induced with streptozotocin, and mice were sacrificed at 2 months of study to measure superoxide generation, leukostasis, and immunohistochemistry, and at 7 months to assess retinal histopathology. Diabetes of 2 months duration caused a significant decrease in expression of Bcl-2 in retina, upregulation of Bax in whole retina and isolated retinal microvessels, and increased generation of retinal superoxide and leukostasis. Seven months of diabetes caused a significant increase in the number of degenerate (acellular) capillaries in diabetic animals. Furthermore, overexpression of Bcl-2 in the vascular endothelium inhibited the diabetes-induced degeneration of retinal capillaries and aberrant superoxide generation, but had no effect on Bax expression or leukostasis. Therefore, overexpression of Bcl-2 in endothelial cells inhibits the capillary degeneration that is characteristic of the early stages of diabetic retinopathy, and this effect seems likely to involve inhibition of oxidative stress.

Nitric oxide selective electrodes

Since nitric oxide (NO) was identified as the endothelial-derived relaxing factor in the late 1980s, many approaches have attempted to provide an adequate means for measuring physiological levels of NO. Although several techniques have been successful in achieving this aim, the electrochemical method has proved the only technique that can reliably measure physiological levels of NO in vitro, in vivo, and in real time. We describe here the development of electrochemical sensors for NO, including the fabrication of sensors, the detection principle, calibration, detection limits, selectivity, and response time. Furthermore, we look at the many experimental applications where NO selective electrodes have been successfully used.

Evaluation of some biochemical changes in diabetic patients

OBJECTIVE

Hyperglycemia is considered a primary cause of diabetic vascular complications and is associated with oxidative stress, impaired trace element and lipid metabolism as well as pancreatic enzyme abnormalities. The role of trace elements in some of the metabolic dysfunctions and their contributions in the development of vascular complications is not clear. Therefore, the present study investigates the relationship among diabetes mellitus, trace elements status, advanced glycation end products (AGEs), advanced oxidation protein products (AOPP), lipid profiles, antioxidant status, nitric oxide and pancreatic amylase activity in the sera of 55 non-insulin-dependent diabetes mellitus (NIDDM; 35 with microvascular complications and 20 without vascular complications), 40 insulin-dependent diabetes mellitus (IDDM; 25 with microvascular and 15 without microvascular complications), and 20 nondiabetic healthy control subjects. The mean age of the diabetic patients was similar to that of control. The mean duration of the disease was 11.8 +/- 6.8 years (3-27 years) in IDDM and 7.1 +/- 4.7 years (1-15 years) in NIDDM.

METHODS

Plasma Cu, Zn, Mg, Ca, thiobarbituric acid-reactive substance (i.e. malondialdehyde; MDA), nitric oxide (NO), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), ceruloplasmin (Cp) and amylase activities as well as AOPP were assessed spectrophotometrically whereas AGEs were estimated spectrofluorometrically in two types of diabetes mellitus (DM) as well as control subjects of matched sex and ages.

RESULTS

SOD, CAT and Cp activities were decreased whereas serum alpha-amylase activity was increased in two types of DM in comparison to the corresponding activities of the control subjects. The plasma levels of MDA, NO and Cu were increased but GSH, Zn, Mg and Ca levels were significantly diminished in diabetic patients as compared to the controls. The averages of total cholesterol (CHOL), triglyceride (TG) and low-density lipoprotein-cholesterol (LDLc) were higher in both types of diabetes mellitus in comparison to the control subjects. The mean value of high-density lipoprotein-cholesterol (HDLc) was lower in both types of diabetes mellitus. Further, the mean values of AGEs and AOPP were elevated in diabetic patients vs. control. These parameters are significantly higher in NIDDM patients when compared to the IDDM subjects. Slight but not significant differences in these parameters were observed in patients with diabetic complications when compared to that of without diabetic complications.

CONCLUSION

These findings may explain the role of impaired trace element status, defect of antioxidants and increased of AGE and AOPP in the pathogenesis of pancreas and the vascular complications of diabetes mellitus. Oxidative stress is increased in both types of DM, but it is more in NIDDM patients than in IDDM subjects. In addition, oxidative stress also plays an important role in the formation of AGEs and AOPP in DM.

Protective effect of aminoguanidine against paraquat-induced oxidative stress in the lung of mice

The effect of aminoguanidine (AG) against toxicity of paraquat (PQ), an oxidative-stress inducing substance, in mice was investigated. A single dose of PQ (50 mg/kg, i.p.) induced lung-toxicity, manifested by significant decrease of the activity of angiotensin converting enzyme (ACE) in lung tissue indicating pulmonary capillary endothelial cell damage. Lung toxicity was further evidenced by significant decrease of total sulfhydryl (-SH) content and significant increase in lipid peroxidation measured as malondialdehyde (MDA) in lung tissues. Oral pretreatment of mice with AG (50 mg/kg) in drinking water, starting 5 days before PQ injection and continuing during the experimental period, ameliorated the lung toxicity induced by PQ. This was evidenced by a significant increase in the levels of ACE activity, a significant decrease in lung MDA content and a significant increase in the total sulfhydryl content 24 h after PQ administration. Moreover, pretreatment of mice with AG leads to an increase of the LD(50) value of paraquat. These results indicate that AG is an efficient cytoprotective agent against PQ-induced lung toxicity.

Aminoguanidine renders inducible nitric oxide synthase knockout mice more susceptible to Salmonella typhimurium infection

Aminoguanidine (AG), a nitric oxide synthase (NOS) inhibitor, has been widely used to study the role of inducible NOS (iNOS) in host defense against infections caused by various pathogens including Salmonella typhimurium. iNOS has been reported to play an important role in host defense against S. typhimurium infection both in vitro and in vivo. In this report we show those AG treatment lead to weight loss in both wild-type and iNOS knockout mice, and rendered them more susceptible to Salmonella infection. These results suggest that AG may have side effects other than the inhibition of iNOS, and that data obtained from studies using AG should be interpreted with caution.

Effects of aminoguanidine and desferrioxamine on some vascular and biochemical changes associated with streptozotocin-induced hyperglycaemia in rats

The effects of aminoguanidine (AG; 100 mg x kg(-1)) and desferrioxamine (DFO; 50 mg x kg(-1)) on some vascular and biochemical changes associated with streptozotocin (STZ; 65 mg x kg(-1); i.p.)-induced hyperglycaemia were investigated in rats. Both AG and DFO were administered i.p., once daily, for 14 consecutive days to normal and hyperglycaemic animals. The responsiveness of the isolated aortic rings to phenylephrine (PE) was tested. In addition, biochemical markers for oxidative stress such as plasma levels of lipid peroxides and total thiols, as well as the activities of erythrocytic superoxide dismutase (SOD) and whole blood glutathione peroxidase (GSH-Px) were assessed. Results of the present study indicated that induction of hyperglycaemia was associated with increased aortic ring responsiveness to PE, loss in body weight, increase in urine volume, elevation of plasma total thiols and lipid peroxide levels and elevated SOD and GSH-Px enzymatic activities. Treatment of normal rats with AG reduced the response of their aortae to PE. Furthermore, a profound increase in body weight without any significant change in the measured biochemical parameters was observed. In hyperglycaemic animals, AG tended to normalize the enhanced aortic response to PE and modulated STZ-induced biochemical changes without affecting the elevated plasma glucose level. Treatment of normal rats with DFO reduced the response of their aortae to PE and decreased their body weight without altering any of the chosen biochemical parameters. In hyperglycaemic animals, DFO attenuated the responsiveness of their aortae to PE and at the same time, did not affect the loss in body weight and the elevation of plasma glucose level observed in the hyperglycaemic group. Additionally, DFO normalized the elevated plasma level of total thiols and exerted a modulatory influence on the enhanced activities of SOD and GSH-Px as well as on the increased levels of lipid peroxides. Our data lend further credence for the contribution of oxidative stress in the vascular and biochemical changes associated with STZ-induced hyperglycaemia. It is also apparent that advanced glycosylation end products and nitric oxide might be involved. Until clinical studies prove the efficacy and safety of these drugs, specific agents which could scavenge free radicals and block protein glycosylation seem beneficial as a helpful adjunct to the therapy of diabetes.

Enhancement of methylcholanthrene-induced neoplastic transformation in murine C3H 10T1/2 fibroblasts by antisense phosphorothioate oligodeoxynucleotide sequences

Antisense phosphorothioate oligodeoxynucleotides (ODNs) are increasingly used to target specific proteins for inhibition. Previous reports of antisense inhibition of the inducible nitric oxide synthase (iNOS) gene suggested its utility in defining the role of nitric oxide (NO) in carcinogenesis, as NO is mutagenic and chemical inhibitors of iNOS block neoplastic transformation in C3H 10T1/2 fibroblasts. Treatment with ODNs (0.025-25 microM) directed against 15mer sequences in the iNOS coding region decreased NO production consistent with a reduction of iNOS protein and iNOS mRNA, however, control ODNs (2.5 microM) also showed considerable nonspecific inhibition of NO synthesis. Treatment with both iNOS antisense and missense ODNs during the promotional phase of the C3H10T1/2 transformation assay significantly increased the number of neoplastic foci in 3-methylcholanthrene (MCA) treated cells which corresponded with the ability of the ODN to inhibit NO production. Enhanced neoplastic transformation and non-specific inhibition of NO synthesis resulting from exposure to antisense ODNs suggest limitations to their long-term use in humans at higher doses.