Antioxidant action of the hexahydropyridoindole SMe1EC2 in the cellular system of isolated red blood cells in vitro.

OBJECTIVES: The subject of this study was the hexahydropyridoindole compound SMe1EC2 with reported antioxidant and neuroprotective effects and low toxicity. In this study, the antioxidant action of SMe1EC2 was investigated in a greater detail in the system of isolated rat erythrocytes. METHODS: First, the compound was subjected to the DPPH test. Second, the overall antioxidant action of the compound was studied in the cellular system of isolated rat erythrocytes oxidatively stressed by free radicals derived from either the hydrophilic azoinitiator AAPH or the lipophilic t-BuOOH, and compared with reference antioxidants. RESULTS: The DPPH test revealed significant antiradical activity of SMe1EC2 comparable with that of the standard trolox. In the cellular system, SMe1EC2 protected red blood cells against free radical-initiated hemolysis. The overall antioxidant efficacy of SMe1EC2 relative to the reference antioxidant stobadine was strongly affected by the lipophilicity of the initiating free radical species. CONCLUSIONS: The results proved high antiradical efficacy of SMe1EC2. In the system of t-BuOOH/isolated erythrocytes, a model cellular system of endogenously generated peroxyl radicals, SMe1EC2 significantly exceeded the parent stobadine in its antioxidant action. Considering the reported results of preclinical studies of SMe1EC2 showing its profound neuroprotective effects and low toxicity, the compound represents an example of a potential pharmacologically practicable antioxidant drug.

Free-radical degradation of high-molar-mass hyaluronan induced by ascorbate plus cupric ions: testing of stobadine and its two derivatives in function as antioxidants.

Stobadine·2HCl and its two hydrophilic derivatives SM1dM9dM10·2HCl and SME1i-ProC2·HCl were tested in the function of antioxidants on hyaluronan (HA) degradation induced by the Weissberger oxidative system [ascorbate plus Cu(II)]. As a primary method, rotational viscometry was applied, where the substance tested was added before or 1 h after the initiation of HA degradation. The most effective scavengers of •OH and peroxy-type radicals were recorded to be stobadine·2HCl and SME1i-ProC2·HCl, respectively. The most effective scavenger, determined by applying the ABTS assay, was stobadine·2HCl.

(2-Benzyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indol-8-yl)-acetic acid: an aldose reductase inhibitor and antioxidant of zwitterionic nature.

Novel carboxymethylated pyridoindoles, characterized by antioxidant activity combined with the ability to inhibit aldose reductase, represent an example of a multitarget approach to the treatment of diabetic complications - severe diabetes-related health disorders of multifunctional nature. One of the novel carboxymethylated pyridoindoles, (2-benzyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indol-8-yl)-acetic acid (compound 1), was found to inhibit aldose reductase with the IC(50) value 18.2 ± 1.2 µM. Owing to aldose reductase pharmacophore requirements for an acidic proton, most aldose reductase inhibitors contain an acetic acid moiety, ionized at physiological pH, resulting in poor bioavailability of the drugs. The presence of a basicity center at the tertiary nitrogen of the carboxymethylated pyridoindoles, in addition to the acidic carboxylic function, predisposes these compounds to form double-charged zwitterionic species. The zwitterionic nature of compound 1 may remarkably affect its pH-lipophilicity profile allowing for increased membrane penetration in the pH region around its isoelectric point, which lies close to the physiological pH 7.4. In the first part of this study, the presence of zwitterionic species was experimentally proved by the concentration-dependent effect of sodium 1-hexanesulphonate on the distribution profile of compound 1. Then a series of experiments was performed in the cellular system of isolated erythrocytes in vitro. Isolated rat erythrocytes exposed to peroxyl radicals, generated in the solution by decomposition of the hydrophilic azoinitiator AAPH or intracellularly by decay of lipophilic t-BuOOH, underwent progressive hemolysis. The onset of the hemolysis was shifted from the starting zero point by the time interval assigned as a lag period. In the presence of compound 1 the lag period was significantly prolonged. Finally, under conditions of a short-term experiment in STZ-diabetic rats in vivo, increase in sorbitol levels in erythrocytes was recorded. Compound 1 administered in the dose 50mg/kg/day (i.g.) significantly decreased the sorbitol level in the erythrocytes. To conclude, the physico-chemical proof of the zwitterionic nature of compound 1 was established and the results obtained in isolated red blood cells indicated good cellular availability of the compound. In addition, in diabetic rats, sorbitol accumulation in red blood cells was significantly inhibited by compound 1 administered intra-gastrically, suggesting its ready uptake into the central compartment. The zwitterionic principle thus may have significant consequences for increased bioavailability of drugs bearing an acidic function.

The new pyridoindole antioxidant SMe1EC2 and its intervention in hypoxia/hypoglycemia-induced impairment of longterm potentiation in rat hippocampus.

Previously, the pyridoindole SMe1EC2 was proved to inhibit lipoperoxidation and carbonylation of proteins in rat brain cortex in the system Fe(2+)/ascorbate and improvement of resistance of the rat hippocampus was reported against ischemic conditions in vitro (hypoxia/hypoglycemia) expressed by the enhanced neuronal response recovery in reoxygenation. The hippocampus fulfils many of the criteria for a neuronal correlate of learning and memory. Recently, an impairment of hippocampal long-term potentiation (LTP) was reported under oxidative stress. Different therapies, including antioxidants, have been studied intensively concerning the impairment of neuronal plasticity. In this study marked reduction of LTP, elicited by a single burst (100 Hz, 1s) in the CA3-CA1 area of rat hippocampal slices, was shown due to transient hypoxia/hypoglycemia compared to control slices. On the basis of previously reported antioxidant and neuroprotective effects of SMe1EC2, its effect on loss of LTP in the hippocampus due to ischemic conditions was studied in vitro. The pyridoindole tested improved hypoxia/hypoglycemia-induced reduction of LTP compared to untreated hypoxic slices. An opposite effect of SMe1EC2 on LTP induction was found in control slices. The mechanism of SMe1EC2 action on LTP in ischemic conditions has been suggested to differ from the mechanism of its effect in "normoxia" and may be due to different redox status in control and ischemic brain tissue. The manifested LTP-protective effect of SMe1EC2 observed in the rat hippocampus exposed to ischemia in vitro may find exploitation in therapy associated with injured neuronal plasticity in some conditions, including ischemia, trauma and aging in man.

Maternal treatment of rats with the new pyridoindole antioxidant during pregnacy and lactation resulting in improved offspring hippocampal resistance to ischemia in vitro.

OBJECTIVE: Damage to the developing brain may be caused by maternal environment, nutritional deficiencies, failure of protective mechanisms, etc. Further, the developing brain may be damaged by intrauterine ischemia or by ischemia in newborns complicated by perinatal asphyxia. There is an effort to find agents with neuroprotective effect on the developing brain. The aim was to study the effect of the new pyridoindole antioxidant SMe1EC2 on the resistance of offspring hippocampus exposed to ischemia in vitro after treatment of mothers. MATERIALS AND METHODS: The electrically evoked responses were determined by extracellular recording from offspring hippocampal slices. The effect of oral treatment of rats with SMe1EC2 over 18 consecutive days, from day 15 of gestation to day 10 post partum (PP) was analyzed in the model of ischemia in vitro measured on the hippocampus of 21-day-old pups, with focus on neuronal function recovery in reoxygenation. RESULTS: Increased recovery of neuronal response was found at the end of 20-min reoxygenation in offspring hippocampal slices exposed to 10-min hypoxia/hypoglycemia from rats whose mothers were treated with the dose of 50 and 250 mg/kg of SMe1EC2, compared to control offspring slices (mothers received vehicle over the same time). CONCLUSIONS: The increased offspring hippocampus resistance to hypoxia/hypoglycemia due to 18-day maternal treatment with SMe1EC2 might have been obtained via the transplacental way as well as in the neonatal period via breast milk, skin and saliva. The manifested neuroprotective effect of SMe1EC2 on the developing brain might find exploitation during risk pregnancy and delivery.

Reduction of oxidative stress in adjuvant arthritis. Comparison of efficacy of two pyridoindoles: stobadine dipalmitate and SMe1.2HCl.

The aim of this study was to evaluate the therapeutic potential of oxidative stress (OS) reduction by using pyridoindole (PI) antioxidants in adjuvant arthritis (AA). The substances tested were stobadine dipalmitate (STB) and SMe1. AA was used as animal model. The experiments included healthy animals, control arthritic animals and arthritic animals with administration of PI in the oral daily dose of 15 mg/kg b.m during 28 experimental days. The rats were sacrificed on day 28. Clinical and biochemical parameters were determined. The effect of PI administration was evaluated on the basis of the following parameters: (a) arthritis (volume of hind paws - HPW, change of animal body mass - CBM), (b) OS (chemiluminescence of whole blood - CWB, levels of thiobarbituric acid reacting substance - TBARS and of HNE- and MDA-protein adducts in plasma and activity of gamma-glutamyltransferase (GGT) in hind paw joint homogenates). The PI studied significantly increased the CBM of animals and corrected the HPW. STB also significantly decreased the activity of GGT in joint homogenates. SMe1 was more effective in decreasing plasmatic TBARS levels, but STB was more effective in reducing plasmatic HNE- and MDA-protein adducts. The assay for HNE- and MDA-adducts in plasma as a function of time was applied for the first time in AA. STB markedly decreased spontaneous and PMA-stimulated CWB and reduced neutrophil count. In summary, STB was more effective than SMe1 in reducing OS in AA. Our results showed that the reduction of OS in arthritis also corrected the clinical manifestations of the disease.

Effect of carboxymethylated pyridoindoles on free radical-induced haemolysis of rat erythrocytes in vitro.

Recently novel carboxymethylated pyridoindoles, analogues of the efficient chain-breaking antioxidant stobadine, have been designed, synthesised and characterised as bifunctional compounds with joint antioxidant/aldose reductase inhibitory activities with the potential of preventing diabetic complications. The critical property for the efficacy of the novel aldose reductase inhibitors in vivo is their ability to penetrate into target tissues. In this study, the issue was addressed by measuring the antioxidant activity of compounds 1 [(2-benzyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole-8-yl)-acetic acid] and 2 [(+/-)-2-benzyl-(4a,9b)-cis-1,2,3,4,4a,9b-hexahydro-1H-pyrido[4,3-b] indole-8-yl acetic acid] in the cellular system of intact erythrocytes exposed to peroxyl radicals generated by thermal degradation of the azoinitiator 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) in vitro. Isolated washed rat erythrocytes were incubated in the presence of the azoinitiator AAPH and the compounds tested for increasing periods of time up to 4 h at 37 degrees C. The degree of haemolysis was determined by absorbance of the haemoglobin released. The onset of AAPH-induced haemolysis was found to be shifted from the starting zero point by the time interval assigned as a lag period. In the presence of the compounds studied the lag period was prolonged significantly. The free radical-initiated haemolysis was retarded by the compounds studied with decreasing efficiency: stobadine > compound 1 ~ Trolox > compound 2. The results have demonstrated an antioxidant activity of the novel carboxymethylated pyridoindoles developed as potential agents for multitarget pharmacology of diabetic complications.

Oxidative stress induced by the Fe/ascorbic acid system or model ischemia in vitro: effect of carvedilol and pyridoindole antioxidant SMe1EC2 in young and adult rat brain tissue.

New effective strategies and new highly effective neuroprotective agents are being searched for the therapy of human stroke and cerebral ischemia. The compound SMe1EC2 is a new derivative of stobadine, with enhanced antioxidant properties compared to the maternal drug. Carvedilol, a non-selective beta-blocker, possesses besides its cardioprotective and vasculoprotective properties also an antioxidant effect. We compared the effect of carvedilol and SMe1EC2, antioxidants with a similar chemical structure, in two experimental models of oxidative stress in young and adult rat brain tissue. SMe1EC2 was found to improve the resistance of hippocampal neurons to ischemia in vitro in young and even in 18-month-old rats and inhibited formation of protein carbonyl groups induced by the Fe(2+)/ascorbic acid pro-oxidative system in brain cortex homogenates of young rats. Carvedilol exerted a protective effect only in the hippocampus of 2-month-old rats and that at the concentration 10-times higher than did SMe1EC2. The inhibitory effect of carvedilol on protein carbonyl formation induced by the pro-oxidative system was not proved in the cortex of either young or adult rats. An increased baseline level of the content of protein carbonyl groups in the adult versus young rat brain cortex confirmed age-related changes in neuronal tissue and may be due to increased production of reactive oxygen species and low antioxidant defense mechanisms in the adult rat brain. The results revealed the new pyridoindole SMe1EC2 to be more effective than carvedilol in neuroprotection of rat brain tissue in both experimental models involving oxidative stress.

Effect of the new pyridoindole antioxidant SMe1EC2 on functional deficits and oedema formation in rat hippocampus exposed to ischaemia in vitro.

OBJECTIVES: The idea of neuroprotective therapy for ischaemic stroke is based on results from studies on experimental animal models of brain ischaemia demonstrating efficacy of many natural and synthetic agents. Contrary to positive conclusions with antioxidants from animal models, clinical experience failed to find neuroprotectants so efficient in human stroke, infarction, brain trauma, tissue preservation, etc. Thus new highly effective neuroprotective agents need to be discovered. METHODS: Effects of 10-day oral treatment with the new pyridoindole derivative, code SMe1EC2, was analysed in the model of ischaemia in vitro measured five days after oral treatment, with focus on neuronal function recovery. The responses were determined by extracellular recording from rat hippocampal slices. Further, effect of SMe1EC2, applied into the incubation medium before and during ischaemia in vitro, was studied on the oedema extent in neurons of the CA1 area. RESULTS: Ten-day oral treatment of rats with SMe1EC2 at the doses 50 or 250 mg/kg resulted in improved resistance of hippocampal neurons to 6.5-min hypoxia/hypoglycaemia in vitro measured during reoxygenation, compared to untreated rats. Application of the drug tested into the incubation medium 30 min before and during 6-min hypoxia/hypoglycaemia resulted in reduction of oedema formation in the CA1 area compared to untreated slices exposed to ischaemia in vitro. CONCLUSION: The current study confirmed the neuroprotective effect of the pyridoindole antioxidant SMe1EC2 on the level of recovery of neuronal function as well as on affection of morphological changes expressed by reduced oedema extent in the rat hippocampus under ischemic conditions in vitro.

Metabolism-induced oxidative stress is a mediator of glucose toxicity in HT22 neuronal cells.

Oxidative stress has been widely considered as a key player in the adverse effects of hyperglycaemia to various tissues, including neuronal cells. This study examined the participation of oxidative stress in injurious effects of high glucose on HT22 cells along with the activity of proteasome, a proteolytic system responsible for degradation of oxidized proteins. Although 10-fold glucose concentration caused non-significant viability changes, a significant reduction of cell proliferation was found. Moreover, the cell morphology was also altered. These changes were followed by an enhancement of intracellular ROS generation, however without any significant boost of the carbonyl group concentration in proteins. Correspondingly, only a slight decline in the 20S proteasome activity was found in high-glucose-treated cells. On the other hand, substances affecting glucose metabolism or antioxidants partially preserved the oxidative stress in high glucose treated cells. In summary, these results highlight the role of metabolic oxidative stress in hyperglycaemia affecting neurons.

Carboxymethylated tetrahydropyridoindoles as aldose reductase inhibitors: in vitro selectivity study in intact rat erythrocytes in relation to glycolytic pathway.

Oxidative stress and polyol pathway hypotheses are generally accepted in the etiology of diabetic complications. Recently, novel carboxymethylated pyridoindoles, structural analogues of the efficient chain-breaking antioxidant stobadine, were designed, synthesised and characterised as prospective aldose reductase inhibitors endowed with antioxidant activity. Of them (2-benzyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole-8-yl)-acetic acid (compound 1) and (2-phenethyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole-8-yl)-acetic acid (compound 2) were found to be the most efficient inhibitors of aldose reductase with the corresponding IC50 values in a micromolar region. The aim of this work was to study cellular uptake of the novel pyridoindole derivatives and their effect on the complex metabolism of glucose in isolated rat erythrocytes under euglycaemic conditions. Glycolysis was shown to be the sole process responsible for the observed clearance of glucose. The compounds studied were avidly taken up by the cells, yet they did not significantly affect glucose consumption and lactate production nor did they affect osmotic fragility of the erythrocytes. On balance, the present experimental findings indicate that compounds 1 and 2, efficient inhibitors of aldose reductase, are selective in relation to the glycolytic pathway of glucose elimination. This conclusion supports current preclinical development of novel carboxymethylated tetrahydropyridoindoles as promising aldose reductase inhibitors for pharmacological prevention and treatment of diabetic complications.

Prenatal developmental toxicity study of the pyridoindole antioxidant SMe1EC2 in rats.

OBJECTIVE: The 2-ethoxycarbonyl-8-methoxy-2,3,4,4a,5,9b-hexahydro-1H-pyrido-[4,3b] indolinium chloride (SMe1EC2) is a prospective antioxidant and neuroprotectant drug. The aim of the study was to evaluate the effect of SMe1EC2 on embryofetal development of rats. METHODS: The substance tested was administered orally to Wistar/DV rats from day 6 to day 15 of gestation at the doses 5, 50 and 250 mg/kg/day. The animals were killed on day 20 of gestation and uterine content was inspected. Live fetuses were examined for gross, skeletal and visceral anomalies. RESULTS: Administration of SMe1EC2 did not induce any signs of maternal toxicity. No adverse effect of the substance tested was found on reproductive variables. Morphological examination of fetuses revealed no evidence of teratogenesis. CONCLUSION: The prenatal toxicity study showed that the substance SMe1EC2 tested did not have embryotoxic and teratogenic effects on developing rats. Neither were any signs of maternal toxicity found.

Role of inflammatory cytokines and chemoattractants in the rat model of streptozotocin-induced diabetic heart failure.

OBJECTIVE: It is not yet clear how oxidative stress, free radicals, inflammatory cytokines and chemoattractants produced in the heart induce chronic heart failure. The myocardial damage caused by chronic diabetes results either from the persistence of inflammatory signaling directly in the heart or from the dysregulation of anti-inflammatory signaling systems. In the rat model of streptozotocin-induced diabetes (STZD) we investigated 1/ the concentration of free radicals (FR), 2/ reduced glutathione (GSH), 3/ lysozomal enzymes, 4/ inflammatory cytokines (tumor necrosis factor-? (TNF-?) and interleukin-6 (IL-6)), and monocyte chemoattractant protein-1 (mcp-1) in the myocardium. METHODS: Diabetes was induced in 12 male Wistar rats by injection of streptozotocin (STZ). The free radical scavenger and cardiac protectant SMe1EC2 (10 mg/kg/d.) was given orally for 5 days and 5 weeks and these animals were compared with the diabetic and non-diabetic controls. RESULTS: We found reduced heart rate and rate dependent functions of the rat heart, early release of free radicals triggering the release of cytotoxic inflammatory cytokines (like TNF-? and IL-6) and chemoattractants (mcp-1) as an example of this type of pathogens, resulting in the initiation and progression of cardiac pathology. The reduced myocardial contractility after STZD was accompanied with the increased reactive responsiveness of isolated aorta and mesenteric artery to phenylephrine, with increased production of chemoattractive proteins directly in the myocardium, with increased activity of peripheral beta-N-acetyl-glucosaminidase (NAGA), as representative of lysosomal activation processes. The pretreatment of SME1EC2 reduced increase in vascular reactivity, reduced myocardial depression and protected against myocardial toxicity. CONCLUSION: The newly identified and specific cardiac protectant SMe1EC2 could serve as a prospective target in the treatment of increased myocardial cytokine and chemoattractive proteins in diabetic cardiomyopathy.

Carboxymethylated pyridoindole antioxidants as aldose reductase inhibitors: Synthesis, activity, partitioning, and molecular modeling.

Starting from the efficient hexahydropyridoindole antioxidant stobadine, a series of carboxymethylated tetrahydro- and hexahydropyridoindole derivatives was synthesized and tested for the inhibition of aldose reductase, an enzyme involved in the etiology of diabetic complications. In vitro inhibiton of rat lens aldose reductase was determined by a conventional method. Kinetic analysis of (2-benzyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole-8-yl)-acetic acid (5b) and (2-phenethyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole-8-yl)-acetic acid (5c), the most potent compounds in this series with activities in micromolar range, showed uncompetitive inhibition. In addition to the importance of the acidic function, the inhibition efficacy was highly influenced by the steric conformation of the lipophilic aromatic backbone when comparing tetrahydro- and hexahydropyridoindole congeners. Selectivity with respect to the closely related aldehyde reductase was determined by measuring the corresponding inhibitory activities. Antioxidant action of the novel compounds was documented in a DPPH test and in a liposomal membrane model, oxidatively stressed by peroxyl radicals. The presence of a basicity center at the tertiary nitrogen, in addition to the acidic carboxylic function, predisposes these compounds to form double charged zwitterionic species, a characteristic which may remarkably affect their pH-lipophilicity profile. For compounds 5b and 5c, a maximal distribution ratio in a system comprised of 1-octanol/phosphate buffer was recorded near the neutral physiological pH, the region where the isoelectric point lies. Molecular docking simulations into the ALR2 active site performed for the zwitterionic species provided an explanation for the observed structure-activity relationships and the calculated parameters were in agreement with characteristic differences in the stereoelectronic profiles of the tetrahydro- versus hexahydropyridoindoles. 'Drug-likeness' of the novel aldose reductase inhibitors was assessed by applying the criteria of Lipinski's 'rule of five'.

Content of protein carbonyl groups in gerbil brain after reversible bilateral carotid occlusion: effect of 2,3-dihydromelatonin.

OBJECTIVES: To investigate whether a new derivative of melatonin, (2,3-dihydromelatonin (DHM), prevented the oxidative stress induced by ischemia /reperfusion (I/R) in the gerbil brain. To specify the effect on endogenous antioxidant activity and protein modification in the brain cortex, we evaluated the contents of glutathione (total GSx=GSH+GSSG) and protein carbonyl groups (PCG). METHODS: Brain ischemia (I) was induced by (12 min) bilateral carotid occlusion (BCAO) in adult male gerbils (60-70 g b wt.) DHM (10 mg/kg) was administered i.p. 20 min before surgery, at the beginning of reperfusion (R), and then 2 and 6 hours later. Horizontal locomotor activity was recorded using the open-field test over the course of 24 hours. Contents of GSx and PCG were determined after 6h of reperfusion. Glutathione (GSx ) was determined spectrophotometrically using the microplate reader, lactate by the kit Randox, UK. The measurement of protein carbonyl (PCG) groups after their derivatization with 2,4-dinitrophenylhydrazine (DNPH) is the most widely used assessment of protein oxidation. The contents of PCG and malondialdehyde (MDA) were assayed spectrophotometrically. RESULTS: Evaluation of the data obtained from horizontal locomotor activity recorded over the course of 24 hours using the open-field test showed that hyperactivity induced by I/R was returned by DHM almost to its control value during the interval of up to 6 hours (from 18,000 to 5,000 cm distance traveled, p<0.05). I/R decreased the content of GSx by 27.2% (p<0.001). Administration of DHM resulted in maintaining the content of GSx at control values (p<0.05). DHM diminished the I/R-induced increase in PCG in the cortex by 34.2% (p<0.01). CONCLUSIONS: Our data indicate that the effect of DHM on the content of glutathione and protein carbonyl groups occurred during the first 6 hours of reperfusion. In this time interval both the content of GSx and protein carbonyl groups seem to be sensitive indicators of I/R-induced oxidative stress in the gerbil brain.

Participation of reactive oxygen species in diabetes-induced endothelial dysfunction.

OBJECTIVES: In the present study, the relationship between diabetes-induced hyperglycemia, reactive oxygen species production and endothelium-mediated arterial function was examined. The effect of antioxidant on the reactive oxygen species induced damage was tested. METHODS: Diabetes was induced by streptozotocin (STZ), 3 x 30 mg/kg i.p., administered on three consecutive days. After 10 weeks of diabetes, the functional state of the endothelium of the aorta was tested, endothelemia evaluation was performed and systolic blood pressure was measured. Reactive oxygen species (ROS) formation in blood and the aorta was measured using luminol-enhanced chemiluminescence (CL). Levels of reduced glutathione (GSH) were determined in the aorta, kidney, and plasma. To study the involvement of hyperglycemia in functional impairment of the endothelium, aortal rings incubated in solution with high glucose concentration were tested in in vitro experiments. RESULTS: After 10 weeks of diabetes, endothelial injury was observed, exhibited by diminished endothelium-dependent relaxation of the aorta, increased endothelemia and by elevated systolic blood pressure. Using luminol-enhanced CL, a significant increase of ROS production was found in arterial tissue and blood. GSH levels were significantly increased in the kidney, while there were no GSH changes in plasma and the aorta. Incubation of aortic rings in solution with high glucose concentration led to impairment of endothelium-dependent relaxation. The synthetic antioxidant SMe1EC2 was able to restore reduced endothelium-mediated relaxation. CONCLUSIONS: Our results suggest an important role of hyperglycemia-induced ROS production in mediating endothelial dysfunction in experimental diabetes, confirmed by CL and the protective effect of the antioxidant SMe1EC2.

Free radical scavenging and antioxidant activities of substituted hexahydropyridoindoles. Quantitative structure-activity relationships.

New synthetic substituted hexahydropyridoindoles were studied for their radical scavenging ability in a system of an ethanolic solution of alpha,alpha'-diphenyl-beta-picrylhydrazyl and for their lipid peroxidation inhibitory properties in a suspension of unilamellar dioleoylphosphatidylcholine liposomes. The activities in both in vitro systems were correlated with several structural parameters. In the homogeneous system of alpha,alpha'-diphenyl-beta-picrylhydrazyl, the sum of aromatic substitution constants (sigma(+)) and the hydration energy were shown to be effective predictors of the radical scavenging activity of the hexahydropyridoindole derivatives. Moreover, in the heterogeneous system comprising a model liposomal membrane, the overall antioxidant activity of the compounds was affected by their lipid-phase availability governed by the lipophilicity and basicity of the molecules.