Aminoguanidine Research Articles

Investigations on synthesis and structure elucidation of novel [1,2,4]triazolo[1,2-a]pyridazine-1-thiones and their inhibitory activity against inducible nitric oxide synthase

The inducible nitric oxide synthase (iNOS) is a target of great research interest due to its importance in a number of diseases, for example, septic shock and inflammatory lung diseases. A variety of 3-substituted [1,2,4]triazolo[1,2-a]pyridazine derivatives was synthesized by ring closure with hexahydropyridazine-1-carbothioamide by using aliphatic and aromatic aldehydes. The activity of the new substances was tested on the insulin-secreting rat insulinoma cell line RINm5F. iNOS was expressed through exposure to interleukin-1β (IL-1β) and interferon-γ (IFN-γ). A number of the investigated compounds were more active than the reference inhibitor aminoguanidine (AG). Structure–activity relationships showed that a phenyl substituent in position 3 is apparently essential for inhibition.

Involvement of inducible nitric oxide synthase in radiation-induced vascular endothelial damage

The use of radiation therapy has been linked to an increased risk of cardiovascular disease. To understand the mechanisms underlying radiation-induced vascular dysfunction, we employed two models. First, we examined the effect of X-ray irradiation on vasodilation in rabbit carotid arteries. Carotid arterial rings were irradiated with 8 or 16 Gy using in vivo and ex vivo methods. We measured the effect of acetylcholine-induced relaxation after phenylephrine-induced contraction on the rings. In irradiated carotid arteries, vasodilation was significantly attenuated by both irradiation methods. The relaxation response was completely blocked by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a potent inhibitor of soluble guanylate cyclase. Residual relaxation persisted after treatment with L-Nω-nitroarginine (L-NA), a non-specific inhibitor of nitric oxide synthase (NOS), but disappeared following the addition of aminoguanidine (AG), a selective inhibitor of inducible NOS (iNOS). The relaxation response was also affected by tetraethylammonium, an inhibitor of endothelium-derived hyperpolarizing factor activity. In the second model, we investigated the biochemical events of nitrosative stress in human umbilical-vein endothelial cells (HUVECs). We measured iNOS and nitrotyrosine expression in HUVECs exposed to a dose of 4 Gy. The expression of iNOS and nitrotyrosine was greater in irradiated HUVECs than in untreated controls. Pretreatment with AG, L-N6-(1-iminoethyl) lysine hydrochloride (a selective inhibitor of iNOS), and L-NA attenuated nitrosative stress. While a selective target of radiation-induced vascular endothelial damage was not definitely determined, these results suggest that NO generated from iNOS could contribute to vasorelaxation. These studies highlight a potential role of iNOS inhibitors in ameliorating radiation-induced vascular endothelial damage.

Nitric oxide mediates the insulin sensitizing effects of β-sitosterol in high fat diet-fed rats

β-Sitosterol has been shown to have antidiabetic and antioxidant effects in animal models. The objective of the study is to investigate the effects of β-sitosterol on insulin sensitivity, oxidative and nitrosative stress and lipid abnormalities in liver of high fat-fed rat model of insulin resistance (IR) and to assess whether nitric oxide (NO) is involved in its action. Adult male albino Wistar rats of body weight 150–180g were fed either control diet (CON) or high fat diet (HFD). Each dietary group was divided into two and treated or untreated with β-sitosterol (10mg/kgb.w.−1day−1) for 4weeks. Inhibition of total nitric oxide synthase (NOS) by administration of nitro-l-arginine methyl ester (L-NAME) and inducible NOS (iNOS) by aminoguanidine (AG) in HFD and HFD+ β-sitosterol groups were accomplished to identify the role of NO. After 28days, assays were performed in plasma and liver. HFD-fed rats showed hyperglycemia, hyperinsulinemia, IR, oxidative damage, nitrosative stress, lipid accumulation and elevated serum aminotransferases. Increased expression of iNOS and decreased expression of endothelial NOS (eNOS) were observed in them. Hepatic fat accumulation was further confirmed by histology. The biochemical and histological abnormalities associated with HFD feeding were significantly reduced by β-sitosterol administration. Administration of L-NAME to HFD-fed rats caused decrease in insulin sensitivity and increase in oxidative stress. Co-administration of L-NAME for the last seven days to β-sitosterol-treated HFD rats abolished the glucose lowering effect of β-sitosterol, but the ability to decrease oxidative stress remained unaltered. On the other hand, administration of AG resulted in improved glucose homeostasis and antioxidant levels but decreased oxidative stress and enhanced antioxidant potential in both HFD and HFD+ β-sitosterol treated groups. Thus, β-sitosterol promotes insulin sensitivity in rats fed HFD possibly by improving NO levels. With additional studies, β-sitosterol might be used as a functional drug or as an adjuvant in the management of IR and associated fatty liver disease.

The Mechanism of the Down-Regulation of Hepatic Transporters in Rats with Indomethacin-Induced Intestinal Injury

Previously, we reported that hepatic transporters were down-regulated consistent with intestinal injury in indomethacin (IDM)-treated rats. The purpose of this study was to characterize this mechanism of the down-regulation of hepatic transporters in IDM-treated rats. Hepatic nuclear receptor expressions, oxidative stress condition and the expression of hepatic transporters were evaluated in rats with IDM-induced intestinal injury with or without the administration of mucosal protectant ornoprostil, a prostaglandin E1 analogue, or aminoguanidine (AG), an iNOS inhibitor. All the nuclear receptors examined in the present study, which regulates hepatic transporters, were decreased by the administration of IDM. Hepatic glutathione, an indicator of oxidative stress, was significantly reduced compared with control. We then determined the expression of hepatic transporters by semi-quantitative real-time RT-PCR and Western blot analysis in IDM-treated rats with or without the administration of ornoprostil or AG. Ornoprostil recovered the gene expression of Oatp1a1, Oatp1b2 and Mrp2 and protein expression of Mrp2 while it had no effect on Oatp1a1 and Oatp1b2 proteins. These results indicated that the gene expression of hepatic transporters was down-regulated in association with the intestinal injury. On the other hand, there is no effect of AG on the reduced gene expression of hepatic Oatp1a1, Oatp1b2 and Mrp2. In protein expression, AG slightly recovered Mrp2 expression accompanied by a partial decrease in portal NO levels. We suggest that the transcriptional process influenced by a dysfunction of hepatic nuclear receptors as well as the effect of NO on the post-transcriptional process due to intestinal injury are partially involved in the down-regulation of hepatic transporters.

Research on thermal decomposition of trinitrophloroglucinol salts by DSC, TG and DVST

Abstract The thermal decomposition of the four nitrogen-rich salts of ammonia (NH4), aminoguanidine (AG), carbohydrazide (CHZ) and 5-aminotetrazo (ATZ) based on trinitrophloroglucinol (H3TNPG) was investigated using the differential scanning calorimetry (DSC), thermogravity (TG), and dynamic vacuum stability test (DVST). DSC and TG methods research the complete decomposition, while DVST method researches the very early reaction stage. The peak temperatures of DSC curves are consistent with the temperatures of maximum mass loss rates of TG curves. The apparent activation energies of these H3TNPG-based salts obtained by DSC and DVST have the same regularity, i.e., (ATZ)(H2TNPG)·2H2O 2O 4(H2TNPG) 2TNPG). The thermal stability order is (ATZ)(H2TNPG)·2H2O 2O 2TNPG) 4(H2TNPG), which was evaluated by DVST according to the evolved gas amount of thermal decomposition. DVST can monitor the real-time temperature and pressure changes caused by thermal decomposition, dehydration, phase transition and secondary reaction, and also evaluate the thermal stability and kinetics.

Chickens treated with a nitric oxide inhibitor became more resistant to Plasmodium gallinaceum infection due to reduced anemia, thrombocytopenia and inflammation

Malaria is a serious infectious disease caused by parasites of the Plasmodium genus that affect different vertebrate hosts. Severe malaria leads to host death and involves different pathophysiological phenomena such as anemia, thrombocytopenia and inflammation. Nitric oxide (NO) is an important effector molecule in this disease, but little is known about its role in avian malaria models. Plasmodium gallinaceum- infected chickens were treated with aminoguanidine (AG), an inhibitor of inducible nitric oxide synthase, to observe the role of NO in the pathogenesis of this avian model. AG increased the survival of chickens, but also induced higher parasitemia. Treated chickens demonstrated reduced anemia and thrombocytopenia. Moreover, erythrocytes at different stages of maturation, heterophils, monocytes and thrombocytes were infected by Plasmodium gallinaceum and animals presented a generalized leucopenia. Activated leukocytes and thrombocytes with elongated double nuclei were observed in chickens with higher parasitemia; however, eosinophils were not involved in the infection. AG reduced levels of hemozoin in the spleen and liver, indicating lower inflammation. Taken together, the results suggest that AG reduced anemia, thrombocytopenia and inflammation, explaining the greater survival rate of the treated chickens.

Effect of Local Application of Aminoguanidine on the Biomechanical Retention of Implants in Rats with Induced Diabetes

To evaluate the effect of surgical placement of an aminoguanidine (AG)-loaded chitosan membrane, which allows slow local release of AG, over an endosseous implant on mechanical retention of the implant in nondiabetic and diabetic rats. Forty-eight male Wistar rats were randomly divided into six groups of eight animals each and subjected to three different treatment modalities: (1) implant placement in the femur, (2) placement of implant + chitosan membrane without AG at the surgical site, or (3) placement of implant + AG-loaded chitosan membrane (AG concentration of 7.35 mmol/kg body weight) at the surgical site. Groups 1, 2, and 3 were nondiabetic (control groups), and groups 4, 5, and 6 had chemically induced type 1 diabetes (test groups). At 4 weeks after implant placement, the animals were sacrificed and the countertorque force (CTF) required to disrupt the bone-implant interface was measured. Analyses of variance were performed, and the mean CTF values were compared between groups by using the Student t test. The mean CTF values were significantly lower in diabetic groups not treated with AG than in the corresponding nondiabetic animals that had received the same treatment modality. In groups that received AG locally, the mean CTF values were not statistically significantly different, regardless of diabetes status. Induced diabetes (type 1) negatively affected the CTF necessary for disrupting the bone-implant interface. Local availability of AG in diabetic animals led to an increase in the CTF values to the same level as that in nondiabetic animals.

Original article Suppression of the lipid peroxidation process in the CNS reduces neurological expression of experimentally induced autoimmune encephalomyelitis

Here we report the influence of malondialdehyde (MDA) as a measure of the lipid peroxidation process (LP), on multiple sclerosis (MS) pathogenesis and its neurological signs, during the treatment with aminoguanidine (AG) - a selective inducible nitric oxide synthase inhibitor and N-Acetyl cysteine (NAC) - an oxidative scavenger, in the experimental autoimmune encephalomyelitis (EAE), an animal model for studying MS. Encephalomyelitis induction by the subcutaneous injection of myelin basic protein of bovine type, dissolved in phosphate buffered saline (PBS) emulsified in equal volume of the complete Freund's adjuvant (CFA), was described in detail in our earlier published papers. Each of animals was randomly assigned to seven groups - control (PBS), EAE, CFA, EAE + AG, AG, EAE + NAC and NAC group. In each animal, the development of neurological signs of EAE was scored, these results were published earlier. MDA was evaluated in the central nervous system (CNS) structure - cerebellums and spinal cords. The obtained results show that the AG and NAC treatment significantly reduces the MDA level in both examined tissues (p < 0.05) ameliorating at the same time EAE clinical signs (p < 0.05). Taking together our present and earlier findings we conclude that LP may provoke and promote MS, while blocking of this process results in amelioration of the clinical onset and disease activity. These results may be useful as a new insight into mechanisms and potential targets for therapeutic strategies in MS.

A novel mechanism for antiglycative action of limonene through stabilization of protein conformation

Inhibition of protein glycation is known to ameliorate secondary complications in diabetes. In the present study antiglycative properties of limonene, a natural product, were evaluated using BSA as a model protein. AMG (aminoguanidine) was used as a positive control. Measurement of total AGEs (Advanced Glycation End-products) and specific AGEs revealed that limonene could inhibit protein glycation to the extent of 56.3% and 75.1% respectively at 50 μM concentration as against 54.4% and 82.2% by AMG at 1 mM. Congo red binding and CD (Circular Dichroism) analysis revealed inhibition of α-helix to β-sheet transition wherein 18.5% β-sheet structures were observed in glycated BSA (bovine serum albumin) as against 4.9% with limonene. Glycation of protein in the presence of urea was enhanced by 18%, while in the presence of limonene it was reduced by 23% revealing the stabilizing effect of limonene. Electrophoretic mobility was similar to the normal control and a zeta potential value of -12.1 mV as against -15.1 mV in diabetic control was observed. Inhibition of glycation in limonene treated samples was confirmed through LC-MS analysis wherein AGEs such as pentosidine, CML (N(ε)-(carboxymethyl)lysine), CEL (N(ε)-(carboxyethyl)lysine), MOLD (methylglyoxal-lysine dimer) and imidazolone observed in glycated samples were absent in limonene treated samples. PatchDock studies revealed that limonene could bind to the major glycation sites IB, IIA and IIB sub domains and AMG to the IIIA sub domain. Thus limonene is a potent protein glycation inhibitor that prevents protein glycation through a novel mechanism of stabilization of protein structure through hydrophobic interactions.

Differential effects of selective and non-selective nitric oxide synthase inhibitors on the blood perfusion of ischemia-reperfused myocardium in dogs

BackgroundNitric oxide (NO) is protective for the cardiovascular system, and excessive NO exerts negative effects on the circulatory system. This study aimed to compare the effects of selective or non-selective NO synthase (NOS) inhibitors on blood flow perfusion of ischemia-reperfused myocardium.Materials/MethodsMale mongrel dogs were randomly assigned to 4 groups: only ischemia-reperfusion (control), ischemia-reperfusion plus Nω-nitro-L-arginine methyl ester (NAME) treatment, ischemia-reperfusion plus aminoguanidine (AMD) treatment, and sham operation group. Myocardial contrast echocardiography (MCE) was performed. Blood samples were taken for measurement of NO. Background-subtracted peak videointensity (PVI) and PVI ratio in myocardium were measured.ResultsIn the NAME-treated group, the PVI at 5 min reperfusion did not significantly differ from pre-LAD-occlusion, but declined to and retained at a level obviously lower than the pre-LAD-occlusion. In the AMD-treated group, the PVI at 5 min reperfusion was significantly higher than at pre-LAD-occlusion, and then restored to and remained at the pre-LAD-occlusion level. The changes of PVI ratios in the 3 groups were similar to PVI values. In the AMD-treated group, the curve width increased in the early reperfusion, but returned to the pre-LAD-occlusion level at 90 min reperfusion. The plasma NO concentration in the NAME-treated group greatly decreased and remained low during the whole period of reperfusion. In the AMD-treated group, there were only slight increases in NO concentrations during reperfusion.ConclusionsNAME totally inhibited NO production and attenuated myocardial blood flow perfusion. Aminoguanidine significantly relieved the increase in NO production and alleviated the congestion of reperfused myocardium. Selective inhibitors of iNOS might be useful in the management of certain diseases associated with ischemia-reperfusion.

Nitro-oxidative stress in a mice model of toluene diisocyanate-induced asthma.

Toluene-2,4-diisocyanate (TDI) induced occupational asthma mechanisms are not completelyknown. The aim of the study was to evaluate the nitro-oxidative stress associated to experimental miceTDI induced asthma. It was used a model of mice experimental exposure to TDI for 10 days. The studygroups (n = 12) were: a negative control group with skin sensitization and intranasal challenge, performedwith saline; group with sensitization and challenge with the solvent; group withsensitization and challenge with TDI; groups with TDI and aminoguanidine (AG) (50 mg/kg/d i.p.) orNG-nitro-L-arginine methyl ester (NAME), (5 mg/kg/d i.p.) or arginine (ARG) (100 mg/kg/d i.p.) ortrolox (20 mg / kg / day ip). On the 11th day blood was collected by cardiac puncture, and nitro-oxidativestress was assessed by total oxidative status (TOS), total antioxidative capacity (TAC), oxidative stressindex (OSI) and serum nitrates and nitrites (NOx). TDI increased TOS, OSI and NOx andreduced TAC. The solvent did not influence any parameter. AG, NAME and Trolox reduced NOx, TOSand OSI. Experimental exposure of mice to TDI caused systemic nitro-oxidative stress, and NOxreduction and Trolox lowered the systemic nitro-oxidative stress.

Pharmacological inhibition of inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, convalesce behavior and biochemistry of hypertension induced vascular dementia in rats

Cognitive disorders are likely to increase over the coming years (5–10). Vascular dementia (VaD) has heterogeneous pathology and is a challenge for clinicians. Current Alzheimer's disease drugs have had limited clinical efficacy in treating VaD and none have been approved by major regulatory authorities specifically for this disease. Role of iNOS and NADPH-oxidase has been reported in various pathological conditions but there role in hypertension (Hypt) induced VaD is still unclear. This research work investigates the salutiferous effect of aminoguanidine (AG), an iNOS inhibitor and 4′-hydroxy-3′-methoxyacetophenone (HMAP), a NADPH oxidase inhibitor in Hypt induced VaD in rats. Deoxycorticosterone acetate-salt (DOCA-S) hypertension has been used for development of VaD in rats. Morris water-maze was used for testing learning and memory. Vascular system assessment was done by testing endothelial function. Mean arterial blood pressure (MABP), oxidative stress [aortic superoxide anion, serum and brain thiobarbituric acid reactive species (TBARS) and brain glutathione (GSH)], nitric oxide levels (serum nitrite/nitrate) and cholinergic activity (brain acetyl cholinesterase activity-AChE) were also measured. DOCA-S treated rats have shown increased MABP with impairment of endothelial function, learning and memory, reduction in serum nitrite/nitrate & brain GSH levels along with increase in serum & brain TBARS, and brain AChE activity. AG as well as HMAP significantly convalesce Hypt induced impairment of learning, memory, endothelial function, and alterations in various biochemical parameters. It may be concluded that AG, an iNOS inhibitor and HMAP, a NADPH-oxidase inhibitor may be considered as potential agents for the management of Hypt induced VaD.

In vivo inhibition of inducible nitric oxide synthase by aminoguanidine influences free radicals production and macrophage activity in Trichinella spiralis infected low responders (C57BL/6) and high responders (BALB/c) mice

Abstract The influence of aminoguanidine (AG) — inhibitor of inducible nitric oxide synthase (iNOS), on macrophage activity and free radicals level was examined during Trichinella spiralis infection in two strains of mice: C57BL/6 and BALB/c. AG was administered either between 1–5 days post infection (dpi) for intestinal phase examinations or between 16–29 dpi for muscle phase examinations. The number of peritoneal macrophages and level of nitric oxide NO) and hydrogen peroxide (H2O2) in biological fluids were determined in both strains after infection or infection together with AG treatment as well as in control uninfected mice. The performed studies have proved, that free radicals play role in host immune response during intestinal and muscle phase of T.spiralis infection in mice. Inflammatory response in peritoneal cavity was delayed during infection in low responders C57BL/6 mice in comparison with high responders BALB/c mice. C57BL/6 mice are Th-1 like strain and react stronger to AG in contrary to BALB/c being Th-2 like strain. It was manifested as changes and fluctuations of free radicals levels and in the number of peritoneal macrophages after AG treatment in C57BL/6 mice. A weak or no reaction on AG injection in BALB/c mice is responsible for more stable and more effective defense response of the host to T. spiralis infection.

The effect of aminoguanidine on the kidney of diabetic albino Balb/c mice

The aim of this study is to find out how activated inducible nitric oxide synthase (iNOS) and nitric oxide (NO) affect kidney tissue in streptozotocin (STZ)-induced diabetic mice and whether its influence can be prevented by aminoguanidine (AG), a specific iNOS inhibitor. Twenty-four male mice were divided into four study groups (n=6) receiving a daily dose of 100 mg.kg-1 AG for 90 days (Group AG), a single dose of 150 mg.kg-1 STZ (Group STZ), a single dose of 150 mg.kg-1 STZ followed by daily administration of 100 mg.kg-1 AG for 90 days (Group STZ-AG), and intraperitoneally injections of saline only (Group Control) for 90 days. Dispersion of NADPH-diaphorase (NADPH-d) was stronger in the kidney sections of STZ-treated animals compared with the controls. STZ treatment caused disruption of continuity of the brush borders in proximal tubules, glomerular endothelial damage, and considerable renin granules in the juxtaglomerular cells. AG administration following STZ treatment partly prevented histological and cytological changes in kidney cortex, and renin dispersion was similar to that in control animals. We found that increased inducible nitric oxide (iNO) caused kidney tissue degeneration that could be prevented to some extent by AG treatment. There is a possible relationship between increased iNOS and dispersion of renin granules in juxtaglomerular cells in diabetes.

Role of Peroxynitrite in Sepsis-Induced Acute Kidney Injury in an Experimental Model of Sepsis in Rats

The mechanisms involved in sepsis-induced acute kidney injury (AKI) are unknown. We investigated the role of nitrosative stress in sepsis-induced AKI by studying the effects of manganese (III) tetrakis-(1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP), a peroxynitrite decomposition catalyst, and aminoguanidine (AG), a selective nitric oxide synthase 2 (NOS2) inhibitor and peroxynitrite scavenger, on kidney function of rats subjected to cecal ligation and puncture (CLP). Sprague-Dawley rats (weighing 350 [SD, 50] g) were treated with MnTMPyP (6 mg/kg i.p.) or AG (50 mg/kg i.p.) at t = 12 and 24 h after CLP or sham procedure. At t = 36 h, mean arterial pressure and aortic blood flow were measured, and blood and urine samples were obtained for biochemical determinations, including creatinine clearance, fractional excretion of sodium, and neutrophil gelatinase-associated lipocalin concentration in the urine. Kidney tissue samples were obtained for (i) light microscopy, (ii) immunofluorescence and Western blot for 3-nitrotyrosine and NOS2, (iii) gene expression (quantitative real-time polymerase chain reaction) studies (NOS1, NOS2, NOS3, and superoxide dismutase 1), and (iv) matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Mean arterial pressure was unchanged and aortic blood flow decreased 25% in CLP animals. The sepsis-induced (i) decreased urine output and creatinine clearance and increased fractional excretion of sodium and urinary neutrophil gelatinase-associated lipocalin concentration, (ii) increased protein nitration and NOS2 protein, and (iii) NOS1 and NOS2 upregulation were all significantly attenuated by treatment with MnTMPyP or AG. Nitrated proteins in renal tissue from CLP animals (matrix-assisted laser desorption ionization time-of-flight mass spectrometry) were glutamate dehydrogenase, methylmalonate-semialdehyde dehydrogenase, and aldehyde dehydrogenase, mitochondrial proteins involved in energy metabolism or antioxidant defense. Nitro-oxidative stress is involved in sepsis-induced AKI, and protein nitration seems to be one mechanism involved.

INOS/NO ACTS AS TRIGGERS AND EFFECTORS IN THE MECHANISMS OF LTA PROTECTION AGAINST MYOCARDIAL ISCHAEMIA/REPERFUSION INJURY IN SPONTANEOUS HYPERTENSIVE RAT

ObjectivesTo explore the effects of lipoteichoic acid (LTA) induced delayed preconditioning on myocardial ischaemia/reperfusion injury (I/R) in spontaneous hypertensive rat (SHR) and whether iNOS/NO were participated the mechanisms.MethodsI/R model was...

Oxidative stress and nitrosative stress are involved in different stages of proteolytic pulmonary emphysema

Our aim was to investigate the role of oxidative stress in elastase-induced pulmonary emphysema. C57BL/6 mice were subjected to pancreatic porcine elastase (PPE) instillation (0.05 or 0.5U per mouse, i.t.) to induce pulmonary emphysema. Lungs were collected on days 7, 14, and 21 after PPE instillation. The control group was sham injected. Also, mice treated with 1% aminoguanidine (AMG) and inducible NO synthase (iNOS) knockout mice received 0.5U PPE (i.t.), and lungs were analyzed 21 days after. We performed bronchoalveolar lavage, biochemical analyses of oxidative stress, and lung stereology and morphometry assays. Emphysema was observed histologically at 21 days after 0.5U PPE treatment; tissues from these mice exhibited increased alveolar linear intercept and air-space volume density in comparison with the control group. TNF-α was elevated at 7 and 14 days after 0.5U PPE treatment, concomitant with a reduction in the IL-10 levels at the same time points. Myeloperoxidase was elevated in all groups treated with 0.5U PPE. Oxidative stress was observed during early stages of emphysema, with increased nitrite levels and malondialdehyde and superoxide dismutase activity at 7 days after 0.5U PPE treatment. Glutathione peroxidase activity was increased in all groups treated with 0.5U PPE. The emphysema was attenuated when iNOS was inhibited using 1% AMG and in iNOS knockout mice. Furthermore, proteolytic stimulation by PPE enhanced the expression of nitrotyrosine and iNOS, whereas the PPE+AMG group showed low expression of iNOS and nitrotyrosine. PPE stimulus also induced endothelial (e) NOS expression, whereas AMG reduced eNOS. Our results suggest that the oxidative and nitrosative stress pathways are triggered by nitric oxide production via iNOS expression in pulmonary emphysema.

Influence of aminoguanidine on retina morphology and expression of nitric oxide and inducible nitric oxide synthase after retina ischemia-reperfusion injury

Background Many eye diseases such as central retinal artery occlusion,glaucoma and ischemic optic neuropathy,etc.lead to retinal ischemia-reperfusion injury (RIRI) and furthmore visual functional damage.It is neeessary to study the treatment of RIRI.Objective This study was to observe and discuss the influence of aminoguanidine on the retina morphological changes and its mechanism after RIRI.Methods Eighty clean healthy male Japanese white rabbits were randomly divided into normal injury group,RIRI group and aminoguanidine (AG)treated group.The model of RIRI was established by infusing saline solution into the anterior chamber to elevate intraocular pressure (IOP) in both RIRI group and AG group.AG was intraperitoneally injected in the models of the AG group,and normal saline solution was used at the same method in tbe normal group and the RIRI group.The fundus photography and fundus fluorescein angiography(FFA) were pertormed on the rabbits at the moment of retina ischemia and 6,24 and 72 hours after reperfusion.The parts of rabbits were sacrificed 1,6,24 and 72 hours after reperfusion,followed by the enucleation of the eyeballs.Retinal section was prepared for TUNEL examination to evaluate the apoptosis of retinal cells.Nitric oxide (NO) concentration in retina was detected with nitrate reductase,and the activity of inducible nitric oxide synthase (iNOS) was measured by colorimetric detection.The use of the animals followed the Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.Results The fundus photography and FFA showed that the retinal edema was more mild,and the percentage of vascular occlusion was lower in the AG treatment group than that in RIRI group and the amount and area of fluorescein leakage were also smaller than the treatment group.The numbers of TUNEL positive cells in the AG treatment group were less than those in the RIRI model group at 1,6,24 and 72 hours after experiment (F分组 =2762.37,P =0.00 ; F时间 =894.24,P =0.00).Numbers of TUNEL positive cells between adjacent time points were significantly different in both RIRI model group and AG treatment group (RIRI group:q =24.475,36.591,-20.37,P＜0.05;AG group:q =20.94,16.79,-6.92,P＜0.05),with the peak value at 24 hours after experiment.NO contents were significantly higher in the RIRI model group compared to AG group at various time points(q =3.84,4.01,8.91,3.75,P＜0.05),and those between adjacent time points showed significant differences (RIRI group:q=4.77,13.403,-10.29,P＜0.05;AG group:q=4.55,9.05,-5.08,P＜0.05).iNOS activity was significantly elevated in the RIRI model group compared with AG group(q=-3.74,-4.94,-6.53,-3.98,P＜0.05),and obvious differences also were seen between the adjacent time points in both two groups(RIRI group:q =8.43,6.71,-6.39,P＜0.05 ;AG group:q =4.16,5.08,-3.93,P＜0.05).Conclusions Aminoguanidine can protect the retinal function and morpbology from oxidative stress damage after RIRI by reducing the NO level and inhibiting the iNOS activity in retina. Key words: Retina ischemia-reperfusion injury; Aminoguanidine; Apoptosis; Nitric oxide; Inducible nitric oxide synthase

Attenuation of acute nitrogen mustard-induced lung injury, inflammation and fibrogenesis by a nitric oxide synthase inhibitor

Nitrogen mustard (NM) is a toxic vesicant known to cause damage to the respiratory tract. Injury is associated with increased expression of inducible nitric oxide synthase (iNOS). In these studies we analyzed the effects of transient inhibition of iNOS using aminoguanidine (AG) on NM-induced pulmonary toxicity. Rats were treated intratracheally with 0.125mg/kg NM or control. Bronchoalveolar lavage fluid (BAL) and lung tissue were collected 1d–28d later and lung injury, oxidative stress and fibrosis assessed. NM exposure resulted in progressive histopathological changes in the lung including multifocal lesions, perivascular and peribronchial edema, inflammatory cell accumulation, alveolar fibrin deposition, bronchiolization of alveolar septal walls, and fibrosis. This was correlated with trichrome staining and expression of proliferating cell nuclear antigen (PCNA). Expression of heme oxygenase (HO)-1 and manganese superoxide dismutase (Mn-SOD) was also increased in the lung following NM exposure, along with levels of protein and inflammatory cells in BAL, consistent with oxidative stress and alveolar-epithelial injury. Both classically activated proinflammatory (iNOS+ and cyclooxygenase-2+) and alternatively activated profibrotic (YM-1+ and galectin-3+) macrophages appeared in the lung following NM administration; this was evident within 1d, and persisted for 28d. AG administration (50mg/kg, 2×/day, 1d–3d) abrogated NM-induced injury, oxidative stress and inflammation at 1d and 3d post exposure, with no effects at 7d or 28d. These findings indicate that nitric oxide generated via iNOS contributes to acute NM-induced lung toxicity, however, transient inhibition of iNOS is not sufficient to protect against pulmonary fibrosis.

Analysis of the Protective Biochemical and Pathologic Effects of Aminoguanidine on an Experimental Aspiration Pneumonitis Model Induced by Bile Acids

BackgroundGastroesophageal reflux (GER) is a common clinical pathology detected in childhood. Bile acids (BAs) are present in reflux and cause various pathologies in the esophagus, the larynx, and the lungs. ObjectiveWe aimed to show if aminoguanidine (AG) contributes to the biochemical and histopathologic treatment of experimental aspiration pneumonitis induced by BAs. MethodsTwenty-eight female Sprague Dawley rats were used. There were 4 groups in the study: (1) group aspirated with 0.9% saline (n = 7), (2) group aspirated with 0.9% saline and treated with AG (n = 7), (3) group aspirated with a solution of 10 mg/kg taurocholic acid and 5 mg/kg taurochenodeoxycholate (n = 7), and (4) group aspirated with BA and treated with AG (n = 7). The saline and BA solutions were administered as 1 mL/kg intratracheally. The AG was administered intraperitoneally twice a day at a 150 mg/kg dose for 7 days. The different histopathologic and biochemical parameters were analyzed. ResultsClara cell protein 16 and malondialdehyde levels were found to be significantly higher in the BA group than in the group where saline was administered; however, they were significantly lower in the BA + AG group than in the BA group. The total superoxide dismutase activity decreased significantly in the BA group compared with the group where saline was administered. A significant increase in superoxide dismutase activity was observed in the BA + AG group when compared with the group where only BA was administered. When the group where BA was administered solely was compared with the group where saline was administered, peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar histiocytes, interstitial fibrosis, and granuloma were significantly higher in the BA group than in the saline group. When the BA + AG group was compared with the BA group, peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar histiocytes, interstitial fibrosis, and granuloma were found to be significantly lower. ConclusionsOxidant stress increases and antioxidant capacity decreases in pneumonitis induced by BAs. AG administration as an antioxidant helps in recovery, both biochemically and histopathologically. Consequently, AG seems to be an alternative that should be considered in a conservative approach to treating aspiration pneumonitis.