Aortic coarctation induces oxidative stress in rat tissues.

The purpose of this study was to evaluate the induction of oxidative stress in heart and erythrocytes from rats with abdominal aorta coarctation (Coa) compared with sham-operated normotensive controls (Sham). The group of Coa animals developed myocardial hypertrophy, showing heart homogenates markedly increased levels of reduced glutathione (48%), lipid peroxidation (148%) and activation of superoxide dismutase and glutathione peroxidase (189% and 37%, respectively), compared with controls. Other oxidative stress indicators were also altered in erythrocytes from Coa rats: increased protein carbonyl content (141%) and total glutathione level (349%) were determined. Inactivation of the antioxidant enzymes catalase (27%), superoxide dismutase (58%) and glutathione peroxidase (25%) was observed in erythrocytes from the Coa group. Taken jointly our results provide strong evidence for the production of oxidative stress in heart and erythrocytes from aortic coarcted rats.

Expression of NOX-I, gp91phox, p47phox and P67phox in the aorta segments above and below coarctation.

Aorta coarctation results in hypertension (HTN) in the arterial tree proximal to stenosis and, as such, provides an ideal model to discern the effects of different levels of blood pressure on the vascular tissue in the same animal. Compelling evidence has emerged supporting the role of oxidative stress as a cause of HTN. However, whether or not HTN (independent of the circulating humoral factors) can cause oxidative stress is less certain. NAD(P)H oxidase isoforms are the main source of reactive oxygen species (ROS) in the vascular tissues. We therefore compared the expressions of NOX-I, gp91phox and the regulatory subunits of the enzyme in the aorta segments residing above and below coarctation in rats with abdominal aorta banding. Rats were studied 4 weeks after aorta banding above the renal arteries or sham operation. Subunits of NAD(P)H oxidase and its NOX-I isoform as well as endothelial NO synthase (eNOS) and nitrotyrosine (footprint of NO oxidation by superoxide) were measured in the aorta segments above and below coarctation. The gp91phox, p47phox, and p67phox subunits of NAD(P)H oxidase, NOX-I isoform, eNOS and nitrotyrosine were markedly increased in the aorta segment above coarctation (hypertensive zone), but were virtually unchanged in the segment below coarctation. Since, excepting blood pressure, all other conditions were constant, the upregulation of NAD(P)H oxidase isoforms and the increased NO oxidation in the aorta segment above, but not below, coarctation prove that HTN, per se, independent of circulating mediators can cause oxidative/nitrosative stress in the arterial wall. These observations suggest that HTN control may represent a specific form of antioxidant therapy for hypertensive disorders.

Effects of aortic coarctation on aortic antioxidant enzymes and NADPH oxidase protein expression.

Abdominal aortic coarctation above the renal arteries leads to severe hypertension above the stenotic site and provides a model for simultaneous testing of the effects of increased and decreased pressure and consequently shear stress in the same animal. The effects of increased pressure, per se, on oxidative stress and antioxidant enzyme expression is unknown. We studied the protein expressions of antioxidant enzymes and NADPH oxidase (gp91phox subunit) in the aortic segments above and below the stenosis site in sham-operated control and aortic-banded rats at four weeks postoperatively. Compared with the control group, the banded group showed significant up-regulation of NADPH oxidase, catalase (CAT), Cu/Zn superoxide dismutase (SOD) and Mn SOD protein content in the thoracic aorta. In contrast, Mn SOD, Cu/Zn SOD and NADPH oxidase protein abundance were unchanged in the abdominal aortic segment below the stricture where blood pressure is not elevated, whereas CAT protein abundance was also elevated in the abdominal aorta. No changes were noted for glutathione peroxidase (GPX) protein content either in the thoracic or abdominal aortic segments. Coarctation-induced hypertension is associated with increased aortic CAT, Cu/Zn SOD, Mn SOD and NADPH oxidase protein expression. The up-regulation of NADPH oxidase increases reactive oxygen species (ROS) generation noted in the present study and contributes to inactivation of nitric oxide (NO) as shown previously in this model. Upregulation of antioxidant enzymes may be a compensatory response in the face of elevated pressure and oxidative stress. The normality of protein abundance in the abdominal aorta wherein blood pressure is not elevated points to the role of baromechanical factors, as opposed to circulating humoral factors that were similar in both segments, as a mechanism responsible for increased antioxidant enzyme expression.

Decreased cardiac mitochondrial NADP+-isocitrate dehydrogenase activity and expression: a marker of oxidative stress in hypertrophy development.

Mitochondrial dysfunction subsequent to increased oxidative stress and alterations in energy metabolism is considered to play a role in the development of cardiac hypertrophy and its progression to failure, although the sequence of events remains to be elucidated. This study aimed at characterizing the impact of hypertrophy development on the activity and expression of mitochondrial NADP+-isocitrate dehydrogenase (mNADP+-ICDH), a metabolic enzyme that controls redox and energy status. We expanded on our previous finding of its inactivation through posttranslational modification by the lipid peroxidation product 4-hydroxynonenal (HNE) in 7-wk-old spontaneously hypertensive rat (SHR) hearts before hypertrophy development (Benderdour et al. J Biol Chem 278: 45154-45159, 2003). In this study, we used 7-, 15-, and 30-wk-old SHR and Sprague-Dawley (SD) rats with abdominal aortic coarctation. Compared with age-matched control Wistar-Kyoto (WKY) rats, SHR hearts showed a significant 25% decrease of mNADP+-ICDH activity, which preceded in time 1) the decline in its protein and mRNA expression levels (between 10% and 35%) and 2) the increase in hypertrophy markers. The chronic and persistent loss of mNADP+-ICDH activity in SHR was associated with enhanced tissue accumulation of HNE-mNADP+-ICDH and total HNE-protein adducts at all ages and contrasted with the profile of changes in the activity of other mitochondrial enzymes involved in antioxidant or energy metabolism. Two-way ANOVA of the data also revealed a significant effect of age on most parameters measured in SHR and WKY hearts. The mNADP+-ICDH activity, protein, and mRNA expression were reduced between 25% and 35% in coarctated SD rats and were normalized by treatment of SHR or coarctated SD rats with renin-angiotensin system inhibitors, which prevented or attenuated hypertrophy. Altogether, our data show that cardiac mNADP+-ICDH activity and expression are differentially and sequentially affected in hypertrophy development and, to a lesser extent, with aging. Decreased cardiac mNADP+-ICDH activity, which is attributed at least in part to HNE adduct formation, appears to be a relevant early and persistent marker of mitochondrial oxidative stress-related alterations in hypertrophy development. Potentially, this could also contribute to the aetiology of cardiomyopathy.

Renal cytochrome P-450-related arachidonate metabolism in rabbit aortic coarctation.

Cells of the medullary segment of the thick ascending limb of Henle's loop (TALH) convert arachidonic acid (AA) via the cytochrome P-450 monooxygenase pathway to biologically active metabolites: P1, a vasorelaxant, and P2, an inhibitor of Na+-K+-ATPase activity. These AA metabolites may contribute to the renal vascular and metabolic adjustments in response to renal hypoperfusion and the attendant elevation of blood pressure produced by suprarenal aortic coarctation. On the eighth postoperative day, the blood pressures of hypertensive and sham-operated control rabbits were 105 (90-115) and 63 (60-64) mmHg (medians with semiquartile values), respectively (P less than 0.01). Formation of P1 and P2 was increased twofold in TALH cells obtained from hypertensive rabbits: 2.35 (1.79-4.83) and 1.28 (1.56-4.56) micrograms AA converted.mg protein-1.30 min-1 compared with sham-operated rabbits: 1.27 (1.03-1.53) and 0.64 (0.58-1.10) micrograms AA converted.mg protein-1.30 min-1 (P less than 0.05). The profile of biological activity of AA metabolites contained within P1 and P2 was unaffected by aortic coarctation. The cytochrome P-450 monooxygenase-derived AA metabolites may exert a defensive function to limit the degree of TALH cell injury in response to renal hypoperfusion and associated zonal anoxia by reducing energy-dependent Na+-K+-ATPase activity and affecting local vasodilatation.

[Activity of lipolytic enzymes in rabbit plasma during myocardial injury]. / Aktivnost' lipoliticheskikh fermentov v plazme krovi krolikov pri povrezhdeniiakh miokarda.

Dynamics of lipolytic enzymes activity was studied in pre- and postheparin blood plasma of rabbits with hemodynamic heart overloading, with acute local ischemia of myocardium and with diphtheria intoxication. Development of all these pathological processes, impairing myocardium, was accompanied by appearance of lipolytic activity specific for intralipid and for activated intralipid in preheparin blood plasma, by an increase in activity of lipolytic enzymes in postheparin blood plasma as well as by alteration in the spectrum of blood lipoproteins. These alterations depended on the character of disease, impairing the heart muscle.

Muscle substrate levels, muscle enzyme activities and muscle morphology in the vastus lateralis and deltoideus muscles in normal children and in children with coarctation of the aorta.

Muscle biopsies from the deltoideus dx and vastus lat. dx muscles were taken in 17 children with coarctation of the aorta, aged 5.0 to 13.8 years, prior to surgery. Higher concentrations of glycogen, ATP and CP were found in the vastus lat. muscle compared to the deltoideus muscle. The same differences between these two muscles were also found in healthy controls. No differences were found between the patients with coarctation of the aorta and the control group. Nor were any differences found for the other variables studied; glucose, glucose-6-phosphate, lactate, muscle enzyme activities (SDH, LDH and phosphorylase), muscle fibre composition or fibre sizes. It seems reasonable to assume that the differences in muscle substrate levels found between the vasus lat. and the deltoideus muscles in the two groups were due to a higher degree of activity during daily life for the legs as compared to the arms. Patients with coarctation of the aorta do not seem to be influenced by the altered haemodynamic situation with regard to the studied variables.

Myocardial injury in infants with congenital heart disease: evaluation by creatine kinase MB isoenzyme analysis.

Total creatine kinase (CK) and the myocardial isoenzyme CK MB activity were prospectively determined in 282 children hospitalized for cardiac catheterization and evaluation for suspected congenital cardiac abnormalities and compared with a hospitalized control group of children without such abnormalities. The percent CK MB and CK MB activity were abnormally elevated in symptomatic children with a large left to right shunt due either to a large ventricular septal defect (n = 22; p less than 0.001) or to complete atrioventricular canal (n = 10; p less than 0.001). Serum CK MB activity and percent CK MB were significantly related to the size of the shunt and the age of presentation with clinical symptoms of congestive heart failure in infants with a ventricular septal defect. CK MB activity was abnormally elevated in infants with symptomatic coarctation of the aorta, either with or without a ventricular septal defect (n = 15; p less than 0.001), and in infants with symptomatic aortic stenosis (n = 4; p less than 0.02). In contrast, CK MB activity was normal in asymptomatic children with coarctation of the aorta (n = 14) or aortic stenosis (n = 8) despite comparable systolic pressure gradients. CK MB activity and percent CK MB were abnormally elevated in those children with the cyanotic congenital cardiac abnormalities of either transposition of the great arteries (n = 32; p less than 0.001) or right ventricular outflow tract obstruction (n = 31; p less than 0.001). These results suggest that children with congenital cardiac abnormalities may have significant myocardial cell injury and release of CK MB that may be detected by the determination of serum CK MB activity. Cell injury may be secondary to arterial desaturation or acute pressure-volume overload, or both, as manifested by clinical symptoms of heart failure and measured hemodynamic variables.

[Creatine phosphokinase activity and its isoenzymatic ratio in the myocardium in adaptation of the heart to prolonged loading]. / Aktivnost' kreatinfosfokinazy i sootnoshenie ee izozimov v miokarde pri adaptatsii serdtsa k dlitel'noi nagruzke.

Three isoenzymes of creatine phosphokinase (CPK) were detected in rat heart myocardium after electrophoretic separation of the enzyme in agarose gel: MM-isozyme, MB-isozyme and BB-isozyme. The ratios of their activities were 60 : 30 : 5. Total activity of CPK per unit mass of myocardium was increased as well as transformation of its isoenzyme spectrum occurred at the early step of heart adaptation to the increased loading caused by aorta contraction. Within the third day of the heart hyperfunction the BB-isozyme activity was as high as 15% in the heart, the hybrid MB-isozyme activity was increased up to 40% and relative activity of the main muscle MM-isozyme was decreased down to 45%. The relative increase in the activity of BB-isozyme appears to reflect the preferable accumulation of the most functionally effective short-living isoenzymes, which play the key role in adaptation of tissues and systems to long-term loading.