Conditioned medium from amniotic mesenchymal tissue cells reduces progression of bleomycin-induced lung fibrosis

Background and aims

We have demonstrated recently that transplantation of placental membrane-derived cells reduces bleomycin-induced lung fibrosis in mice, despite a limited presence of transplanted cells in host lungs. Because placenta-derived cells are known to release factors with potential immunomodulatory and trophic activities, we hypothesized that transplanted cells may promote lung tissue repair via paracrine-acting molecules. To test this hypothesis, we examined whether administration of conditioned medium (CM) generated from human amniotic mesenchymal tissue cells (AMTC) was able to reduce lung fibrosis in this same animal model.

Methods

Bleomycin-challenged mice were either treated with AMTC-CM or control medium, or were left untreated (Bleo group). After 9 and 14 days, the distribution and severity of lung fibrosis were assessed histologically with a scoring system. Collagen deposition was also evaluated by quantitative image analysis.

Results

At day 14, lung fibrosis scores in AMTC-CM-treated mice were significantly lower (P<0.05) compared with mice of the Bleo group, in terms of fibrosis distribution [1.0 (interquartile range, IQR 0.9) versus 3.0 (IQR 1.8)], fibroblast proliferation [0.8 (IQR 0.4) versus 1.6 (IQR 1.0)], collagen deposition [1.4 (IQR 0.5) versus 2.0 (IQR 1.2)] and alveolar obliteration [2.3 (IQR 0.8) versus 3.2 (IQR 0.5)]. No differences were observed between mice of the Bleo group and mice treated with control medium. Quantitative analysis of collagen deposition confirmed these findings. Importantly, AMTC-CM treatment significantly reduced the fibrosis progression between the two observation time-points.

Conclusions

This pilot study supports the notion that AMTC exert anti-fibrotic effects through release of yet unknown soluble factors.

Amniotic membrane application reduces liver fibrosis in a bile duct ligation rat model

Biliary fibrosis and resultant cirrhosis are among the most common outcomes of chronic liver diseases. Currently, liver transplantation remains the only effective treatment. In seeking alternative therapeutic approaches, we focused on the potential use of the human amniotic membrane (AM). Indeed, AM has gained increasing importance for its antiscarring, anti-inflammatory, and wound-healing properties, as well as for the multipotent differentiation ability and immunomodulatory features of AM-derived cells. Intriguingly, we have recently demonstrated that placenta-derived cells reduce lung fibrosis in bleomycin-treated mice, and that AM patches reduce postischemic cardiac injury in rats. Hence, we have now investigated the effects of human AM on biliary fibrosis induced in rats through the bile duct ligation (BDL) procedure. A fragment of human AM was applied onto the liver surface after BDL and the effects on fibrosis establishment and progression were evaluated at different time points in comparison with fibrosis progression in control BDL rats. The degree of liver fibrosis was first assessed by the semiquantitative Knodell scoring system and, thereafter, by digital image morphometric analysis to quantify the area occupied by ductular reaction, activated myofibroblasts, and collagen deposition. We demonstrated a significant reduction in the severity of BDL-induced fibrosis in AM-treated rats. Indeed, while fibrosis progressed rapidly in control BDL rats, leading to cirrhosis within 6 weeks, AM-treated rats showed confined fibrosis at the portal/periportal area with no signs of cirrhosis, and a reduction in collagen deposition to about 50% of levels observed in control BDL rats. In addition, the AM was able to significantly slow the gradual progression of the ductular reaction and reduce, at all time points, the area occupied by activated myofibroblasts. These findings suggest that human AM, when applied as a patch onto the liver surface, might inhibit fibrosis progression in BDL-injured livers, and could protect against hepatic damage associated with fibrotic degeneration.

Transplantation of allogeneic and xenogeneic placenta-derived cells reduces bleomycin-induced lung fibrosis

Fetal membranes (amnion and chorion) have recently raised significant attention as potential sources of stem cells. We have recently demonstrated that cells derived from human term placenta show stem cell phenotype, high plasticity, and display low immunogenicity both in vitro and in vivo. Moreover, placenta-derived cells, after xenotransplantation, are able to engraft in solid organs including the lung. On these bases, we studied the effects of fetal membrane-derived cells on a mouse model of bleomycin-induced lung fibrosis. Fetal membrane-derived cells were infused 15 min after intratracheal bleomycin instillation. Different delivery routes were used: intraperitoneal or intratracheal for both xenogeneic and allogeneic cells, and intravenous for allogeneic cells. The effects of the transplanted cells on bleomycin-induced inflammatory and fibrotic processes were then scored and compared between transplanted and control animals at different time points. By PCR and immunohistochemistry analyses, we demonstrated the presence of transplanted cells 3, 7, 9, and 14 days after transplantation. Concomitantly, we observed a clear decrease in neutrophil infiltration and a significant reduction in the severity of bleomycin-induced lung fibrosis in mice treated with placenta-derived cells, irrespective of the source (allogeneic or xenogeneic) or delivery route. Our findings constitute further evidence in support of the hypothesis that placenta-derived cells could be useful for clinical application, and warrant further studies toward the use of these cells for the repair of tissue damage associated with inflammatory and fibrotic degeneration.

Amniotic membrane patching promotes ischemic rat heart repair

The amniotic membrane has long been applied for wound healing and treatment of ophthalmological disorders, even though the mechanisms underlying its actions remain to be clarified. Recently, cells derived from fetal membranes of human term placenta have raised strong interest in regenerative medicine for their stem cell potential and immunomodulatory features. Our study aimed to investigate the possible utility of amniotic membrane to limit postischemic cardiac injury. A fragment of human amniotic membrane was applied onto the left ventricle of rats that had undergone ischemia through left anterior descending coronary artery ligation. Echocardiographic assessment of morphological and functional cardiac parameters was then performed over a 3-month period. We demonstrated that application of an amniotic membrane fragment onto ischemic rat hearts could significantly reduce postischemic cardiac dysfunction. The amniotic membrane-treated rats showed higher preservation of cardiac dimensions and improved cardiac contractile function in terms of higher left ventricle ejection fraction, fractional shortening, and wall thickening. These improvements were apparent by day 7 after application of the amniotic membrane, persisted for at least 2 months, and occurred independently of cardiac injury severity. No engraftment of amniotic cells was detected into host cardiac tissues. Our results suggest that use of amniotic membrane may constitute a convenient vehicle for supplying cells that produce cardioprotective soluble factors, and reinforce the notion that this tissue constitutes a cell source with clinical potential that has yet to be completely revealed.

Heart rate reduction with ivabradine improves energy metabolism and mechanical function of isolated ischaemic rabbit heart

AIMS

The anti-anginal agent ivabradine slows heart rate (HR) by selectively inhibiting the I(f) current in the sinus node. We report an ex vivo study to evaluate the anti-ischaemic effect of ivabradine in terms of modulation of cardiac energy metabolism.

METHODS AND RESULTS

A Langendorff-perfused rabbit heart model was subjected to low-flow ischaemia and reperfusion. Cardiac metabolism was studied by measuring cardiac high-energy phosphate contents via HPLC, mitochondrial respiration was analysed polarographically, and cardiac redox potentials by HPLC. Cardiac function was determined in terms of the recovery of developed pressure during reperfusion and release of creatine kinase (CK) (spectrophotometrically) and noradrenaline (HPLC) after reperfusion. Four concentrations of ivabradine (0.3, 1, 3, and 6 microM) were tested on aerobically perfused hearts to select the most effective without causing changes in mechanical parameters. This proved to be 3 microM, which was therefore the concentration selected for the ischaemia-reperfusion experiments. Ivabradine concentration-dependently reduced HR with a maximal effect of 41 +/- 4% at 3 microM (P < 0.001 vs. vehicle), without a negative inotropic effect. This concentration protected the heart against ischaemia-reperfusion damage by reducing the rise in diastolic pressure (from 66 +/- 3 with vehicle to 39 +/- 4 mmHg, P < 0.01) and improving developed pressure after 30 min reperfusion (39 +/- 3 vs. 18 +/- 3 mmHg with vehicle, P < 0.01). Ivabradine reduced both CK and noradrenaline release by 47% (both P < 0.05 vs. vehicle) and improved mitochondrial respiratory control index (from 6.9 +/- 0.3 to 11.9 +/- 1.3, P < 0.001). It preserved cardiac energy metabolism (ATP, from 3.7 +/- 0.3 to 11.0 +/- 0.6 microM/g dry weight, P < 0.001) and redox state (NADPH/NADP(+), from 2.5 +/- 0.5 to 4.2 +/- 0.5, P < 0.001). There was a significant correlation between HR reduction in the ivabradine-treated hearts and cardiac creatine phosphate (r = 0.574, P = 0.02) and ATP levels (ATP, r = 0.674, P = 0.0042) at the end of ischaemia. These benefits were no longer detectable during pacing.

CONCLUSION

HR reduction by ivabradine confers a marked anti-ischaemic benefit. It significantly reduces cardiac energy consumption, preserves redox potentials during ischaemia, and enhances recovery at reperfusion.

Percutaneous coronary injection of bone marrow cells in small experimental animals: small is not too small

Intracoronary infusion of bone marrow cells (BMCs) is thought to induce cardiac regeneration in ischemic heart disease and dilated cardiomyopathy. The aim of our study was to develop a new method to inject BMCs into coronary arteries of small experimental animals. Transient atrioventricular block (AVB) was induced in 25 rats and 39 hamsters by intracarotid injection of adenosine 5'-triphosphate (ATP). Contrast echocardiography was obtained. BMCs (0.2-0.5 ml) were collected through femoral puncture, stained with PKH26 and injected into the carotid artery (CA). Animals were immediately sacrificed or followed for 1 month. To evaluate BMCs transfer from CA to myocardium, AVB and BMCs injections were performed in 10 hamsters subjected to coronary ligation for 30 min. Induction of transient AVB was possible in all animals by injecting 20-30 mg of ATP. Animals recovered a basal cardiac activity spontaneously or by dopamine injection. Flash injection of contrast medium through the CA induced staining of aortic root, coronary arteries, and myocardium. BMCs injection was possible in all cases. No immediate or late ECG changes were observed. Immediately after injection in healthy animals, histological examination showed the presence of BMCs in small coronary arteries and, after 1 month, the absence of infarction. In ischemic hearts, the presence of BMCs in the myocardium was observed 24h after ischemia. ATP-induced AVB block allows for percutaneous intracoronary injection of BMCs in small experimental animals with no immediate or late mortality and morbidity. This method offers new perspectives for the investigation of BMCs coronary infusion and engraftment in heart diseases.

Therapeutic modulation of the nitric oxide: all ace inhibitors are not equivalent

The properties of the angiotensin-converting enzyme (ACE) inhibitors have largely been attributed to a class effect. However, this opinion is now increasingly challenged in view of the findings from recent clinical trials, which have demonstrated differential effects of ACE inhibitors, in particular with respect to secondary cardiovascular prevention outcomes. In this experimental study, Sprague-Dawley rats were treated with five different ACE inhibitors (enalapril, perindopril, quinapril, ramipril, and trandolapril) at equihypotensive doses. All ACE inhibitors increased endothelial nitric oxide synthase (eNOS) protein expression and activity in the aorta (both P<0.0001 versus vehicle) and in cardiac myocytes (both P<0.05 versus vehicle). A highly significant effect was observed with perindopril when compared with vehicle in the modulation of eNOS protein expression and activity in aorta (22.52+/-1.09 versus 9.12+/-0.57 AU microg(-1) protein and 1.59+/-0.03 versus 0.77+/-0.02 pmol l(-1) citrulline min(-1)mg protein(-1), respectively) and in cardiac myocytes (17.64+/-0.94 versus 11.30+/-0.59 AU microg(-1) protein and 0.93+/-0.02 versus 0.62+/-0.03 pmol l(-1) citrulline min(-1)mg protein(-1), respectively). On the basis of the eNOS protein expression in the rat aorta, the other ACE inhibitors had similar, but lower effects. Indeed, the rank of potency - based both on eNOS protein expression and activity - was perindopril>trandolapril approximately quinapril approximately ramipril approximately enalapril (P<0.05 perindopril versus trandolapril and ramipril and P<0.01 perindopril versus enalapril, respectively). Levels of circulating nitrite/nitrate, the end-metabolites of nitric oxide, were also significantly affected by ACE inhibition, with the same order of potency. Our findings provide further evidence in favor of differential effects associated with ACE inhibitor therapy and suggest that the clinical benefits associated with these drugs may not solely reflect a class effect extending their benefit beyond blood pressure-lowering effect.

Anti-ischaemic effect of ivabradine

Ivabradine, the first representative of a new class of exclusive heart rate-reducing agents, selectively inhibits the I(f) current in the sinoatrial node. The direct electrophysiological consequence of this inhibition is a reduction in the slope of the diastolic depolarisation curve and a decrease in heart rate. Pharmacological inhibition of the I(f) current with ivabradine has been shown to preserve coronary vasodilatation upon exercise, i.e., myocardial perfusion, with no negative inotropic effects and maintenance of cardiac contractility. Ivabradine protects the myocardium during ischaemia, improves left ventricular function in congestive heart failure, and reduces remodelling subsequent to myocardial infarction. Pure heart rate reduction by specific and selective I(f) inhibition decreases oxygen demand, improves myocardial energetics and improves perfusion of the ischaemic myocardium. We can expect distinct clinical benefits from long-term heart rate reduction in patients with chronic ischaemic disease.

Heart rate reduction by pharmacological If current inhibition

Heart rate reduction is becoming a new strategy to treat coronary patients. The development of heart-rate-lowering drugs, with a more specific activity than Beta-blockers, coincides with the detection of the sinoatrial pacemaker I(f) current. The first selective I(f) inhibitor that has been approved for clinical use is ivabradine. Ivabradine has been shown to reduce heart rate, preserve myocardial contractility, increase diastolic filling and maintain both small and large coronary artery vasodilation, whatever the level of exercise, thus ensuring adequate endocardial blood perfusion during exercise. Furthermore ivabradine decreases myocardial oxygen consumption and improves myocardial energetics, protecting the myocardium during acute ischemic conditions and showing favorable antiremodelling properties in patients with chronic ischemic disease.

Experimental ischemic cardiomyopathy: insights into remodeling, physiological adaptation, and humoral response

Ligation of the left anterior descending coronary artery (LAD) is used to induce experimental myocardial infarction (MI). Most previous studies have focused on the early postoperative period, while data on mid-term follow-up are scanty. This study examined the mid-term effects of LAD ligation in 95 MI rats and 28 controls. The following parameters were evaluated: systemic blood pressure (SBP), heart rate (HR), and plasma brain natriuretic peptide (BNP) level. In addition, M-mode and B-mode echocardiography, histologic examinations, and cardiac hydroxyproline assays were performed. Forty-seven perioperative and 5 late deaths were recorded. Left ventricular dilation, observed 1 mo after MI, did not progress with time. Septal thickening was similar in the 2 groups, while wall thickening was lower in the MI rats at 1 mo only. Stroke volume was diminished in MI rats, while cardiac output was depressed only at 1 and 2 mo, due to increased heart rate. SBP was unchanged and plasma BNP level was similar in the 2 groups. The infarcted area (mean +/- SD) was 35 +/- 10%. The ventricles in MI rats were heavier and had increased hydroxyproline content. In conclusion, these data show that LAD ligation is not only a model of acute MI, but at mid-term it provides a model of chronic ischemic dilated cardiomyopathy.

Oxidative stress in cardiovascular disease: myth or fact?

Oxidative stress is a mechanism with a central role in the pathogenesis of atherosclerosis, cancer, and other chronic diseases. It also plays a major role in the aging process. Ischemic heart disease is perhaps the human condition in which the role of oxidative stress has been investigated in more detail: reactive oxygen species and consequent expression of oxidative damage have been demonstrated during post-ischemic reperfusion in humans and the protective role of antioxidants has been validated in several experimental studies addressing the pathophysiology of acute ischemia. Although an impressive bulk of experimental studies substantiate the role of oxidative stress in the progression of the damage induced by acute ischemia, not a single pathophysiologic achievement has had a significant impact on the treatment of patients and randomized, controlled clinical trials, both in primary and secondary prevention, have failed to prove the efficacy of antioxidants in the treatment of ischemic cardiovascular disease. This dichotomy, between the experimental data and the lack of impact in the clinical setting, needs to be deeply investigated: certainly, the pathophysiologic grounds of oxidative stress do maintain their validity but the concepts of the determinants of oxidative damage should be critically revised. In this regard, the role of intermediate metabolism during myocardial ischemia together with the cellular redox state might represent a promising interpretative key.

Skeletal muscle abnormalities in rats with experimentally induced heart hypertrophy and failure

BACKGROUND

In congestive heart failure (CHF), function and metabolism of skeletal muscles are abnormal.

AIM

To evaluate whether the reduced oxidative capacity of skeletal muscles in CHF is due to impaired O(2) utilisation.

METHODS

CHF was induced in rats by injecting 50 mg/Kg monocrotaline. Several animals received the same dose of monocrotaline but only compensated right ventricular hypertrophy and no sign of congestion resulted. Two age- and diet-matched groups of control animals were also studied. In soleus and extensor digitorum longus (EDL) muscles, we studied skeletal muscle blood flow, oxidative capacity and respiratory function of skinned muscle fibres.

RESULTS

In CHF, we observed a decrease of muscle blood flow (statistically significant in the soleus, p < 0.05 vs. controls). In compensated rats, a similar trend in blood flow was observed. In both soleus and EDL, a significant reduction of high energy phosphate and a shift of the redox potential towards accumulation of reducing equivalents were observed. The reduction of energy charge was not correlated to the decrease of blood flow. In skinned myofibres, the ratio of O(2) utilised in the presence and in absence of ADP (an index of phoshorilating efficiency) was reduced from 8.9 +/- 1.9 to 2.7 +/- 0.2 (p < 0.001) and from 5.7 +/- 1.0 to 2.0 +/- 0.3 (p < 0.01) in soleus and EDL, respectively. Activity of the different complexes of respiratory chain was investigated by means of specific inhibitors, showing major abnormalities at the level of complex I. In fact, inhibition of VO(2) by rotenone was decreased from 83.5 +/- 3.2 to 36.4 +/- 9.6 % (p < 0.005) and from 81.8 +/- 6.1 to 38.2 +/- 7.4 % (p < 0.005) in soleus and EDL, respectively.

CONCLUSIONS

In rats with CHF, abnormalities of oxidative phosphorylation of muscles occur and complex I of the respiratory chain seem to be primarily affected. The metabolic alterations of skeletal muscles in CHF may be explained, at least in part, by an impaired O(2) utilisation.

Preliminary observations on the effects of acute infusion of growth hormone on coronary vasculature and on myocardial function and energetics of an isolated and blood-perfused heart

Recent studies have shown that growth hormone (GH) deficiency may deteriorate post-ischemic myocardial reperfusion damage. Furthermore, GH has been reported to be a promising therapeutic option in the treatment of chronic myocardial dysfunction. However, the exact mechanisms of action of GH on the cardiovascular system, particularly in the acute setting, are still unclear. The aim of our study consisted of monitoring the acute effects of GH infusion on isolated blood-perfused rabbit heart according to dose-response pattern and during ischemic conditions to test its anti-ischemic property. Seven blood-donors perfused isolated hearts were used as experimental model. The mechanical and metabolic data of the isolated organs were continuously monitored. Under aerobic conditions, dose-response curves were initially tested after intracoronary infusion of GH at increasing dosages (1, 2, 3 mg/l). After a stabilization period, the effects of GH infusion (5 mg/kg) administered 30 minutes prior to acute global myocardial ischemia (30 minutes) were also investigated. At the doses tested, GH did not induce any changes either in the developed or in the diastolic pressures of the isolated organ. However, transient reduction of the coronary perfusion pressure was observed at the dosage of 3 mg/l. During the ischemia/reperfusion study, at the dosages used in this study, GH did not modify either the degree of stunning in the early reperfusion or the recovery of the developed pressure at the end of reperfusion. In addition, GH did not prevent either the increase of diastolic pressure during ischemia or the release of lactate and CPK during reperfusion. Tissue content of high-energy phosphates was also not changed by GH infusion. In our experimental model, acute GH infusion did not reduce the ischemic/reperfusion damage of the myocardium. However, GH transiently induced coronary vasodilation without modifying the myocardial contractility. Acute effects of GH appear, therefore, to predominantly relate to vascular dilation suggesting that the effects on myocardial contractility may require long-lasting intake being likely linked to enhancement of specific protein synthesis or gene expression of cardiac myocytes.

Revascularization of hibernating myocardium: rate of metabolic and functional recovery and occurrence of oxidative stress

BACKGROUND

Left ventricular (LV) dysfunction due to coronary artery disease (CAD) may improve after revascularization in patients with hibernating myocardium (HM).

METHODS AND RESULTS

We compared the rate of metabolic (arterial-great cardiac vein differences of lactate, glucose and pyruvate) and functional (intra-operative transesophageal and epicardial echocardiography) recovery and occurrence of oxidative stress (myocardial release of oxidized glutathione (GSSG)) early after surgical revascularization, in patients with CAD, LV dysfunction and HM (n=16) vs those with preserved LV function (n=15). By comparing the two groups, we observed that, after de-clamping, in patients with HM (a) the kinetic of lactate production was converted to extraction (P<0.01 at 1, 5, 10 and 20 min after revascularization), (b) myocardial extraction of pyruvate increased (P<0.01 during the first 5 min after revascularization), (c) GSSG release was less and of shorter duration (P<0.01 at all times), (d) segmental wall motion score improved from 2.4+/-0.3 to 1.7+/-0.5 (P<0.01) as did the thickening of the akinetic territories corresponding to the antero-distal septum and to the distal anterior wall regions (to 36+/-23%, and to 36+/-13%, respectively). There was a correlation between the rate of recovery of metabolic and functional indices.

CONCLUSIONS

The contractile and metabolic recovery of HM is more rapid than that of non-HM, and it is not accompanied by oxidative stress.

Cellular thiols redox status: a switch for NF-kappaB activation during myocardial post-ischaemic reperfusion

Myocardial ischaemia/reperfusion induces NF-kappaB activation, but little is known about the stimuli through which it occurs. Aims of the study were to investigate whether: (a) oxidative stress induced by ischaemia/reperfusion is linked with NF-kappaB activation; (b) counteraction of oxidative stress by N-acetyl cysteine (NAC) reduces NF-kappaB activation. At this purpose, in isolated rat hearts, we induced mild (15 min) and severe (30 min) ischaemia; a group of the hearts submitted to severe ischaemia were treated with NAC. Our data indicate that reperfusion after severe ischaemia activates NF-kappaB: the presence of p65 in the nuclear extracts was 274.5+/-18.6% vs aerobia; (P<0.05) and an induced DNA-binding activity was detected. NF-kappaB translocation occurs in parallel with myocardial decrease in reduced glutathione and protein -SH (from 9.2+/-0.4 to 5.4+/-0.3 nmol/mg prot, P<0.01, and from 350.3+/-16.6 to 296.0+/-9.1 nmol/mg prot, P<0.05) and accumulation of oxidised glutathione-GSSG-(from 0.075+/-0.005 to 0.118+/-0.007 nmol/mg prot, P<0.01). When ischaemia/reperfusion does not result in any oxidative stress (in mild ischaemia or severe ischaemia plus NAC), NF-kappaB does not translocate. A significant correlation was found between the activation of NF-kappaB and the accumulation of GSSG in the myocardium. Our data indicate that an oxidative shift of cellular thiolic pools can modulate the genic transcription of the heart through NF-kappaB activation.

Beta-adrenergic receptors and intracellular signalling pathway in stunned and non-ischemic regions of pig myocardium

The beta-adrenergic pathway may have a role in the pathophysiology of ischemic syndromes characterised by reversible left ventricular dysfunction, such as myocardial stunning and other clinical conditions of unstable angina or coronary spasms, or chronic reversible left ventricular dysfunction, which might be a consequence of repeated events of short-term ischemia ("repetitive stunning"). A partial-to-total occlusion of the left anterior descending coronary artery in pigs was used to induce short periods of ischemia (total ischemic time 12 +/- 2 min). Hypokinesis and dyskinesis of the myocardium were considered signs of myocardial dysfunction. We found a maintained function of the beta-adrenergic signalling system. Density and affinity of beta-adrenergic receptors were not different in stunned and non-ischemic regions, nor were cyclic AMP and cyclic GMP intracellular contents and ratio, nor well as the ratio of stimulatory/inhibitory G protein a subunits. Our findings are in agreement with a maintained beta-adrenergic signalling system in the pathophysiology of chronic reversible left ventricular dysfunction.

Role of bradykinin and eNOS in the anti-ischaemic effect of trandolapril

1. Angiotensin converting enzyme (ACE) inhibitors are under study in ischaemic heart diseases, their mechanism of action being still unknown. 2. The anti-ischaemic effect of trandolapril and the possible involvement of a bradykinin-modulation on endothelial constitutive nitric oxide synthase (eNOS) in exerting this effect, were investigated. 3. Three doses of trandolapril, chronically administered in vivo, were studied in isolated perfused rat hearts subjected to global ischaemia followed by reperfusion. 4. Trandolapril has an anti-ischaemic effect. The dose of 0.3 mg kg(-1) exerted the best effect reducing diastolic pressure increase during ischaemia (from 33.0+/-4.5 to 14.0+/-5.2 mmHg; P<0.05 vs control) and reperfusion (from 86.1+/-9.4 to 22.2+/-4.1 mmHg; P<0.01 vs control), improving functional recovery, counteracting creatine phosphokinase release and ameliorating energy metabolism after reperfusion. 5. Trandolapril down-regulated the baseline developed pressure. 6. Trandolapril increased myocardial bradykinin content (from 31.8+/-6.1 to 54.8+/-7.5 fmol/gww; P<0.05, at baseline) and eNOS expression and activity in aortic endothelium (both P<0.01 vs control) and in cardiac myocytes (from 11.3+/-1.5 to 17.0+/-2.0 mUOD microg protein(-1) and from 0.62+/-0.05 to 0.80+/-0.06 pmol mg prot(-1) min(-1); both P<0.05 vs control). 7. HOE 140 (a bradykinin B(2) receptor antagonist) and NOS inhibitors counteracted the above-reported effects. 8. There was a negative correlation between myocyte's eNOS up-regulation and myocardial contraction down-regulation. 9. Our findings suggest that the down-regulation exerted by trandolapril on baseline cardiac contractility, through a bradykinin-mediated increase in NO production, plays a crucial role in the anti-ischaemic effect of trandolapril by reducing energy breakdown during ischaemia.

Ace-inhibition with quinapril modulates the nitric oxide pathway in normotensive rats

Angiotensin-converting enzyme (ACE) inhibitors exert some cardiovascular benefits by improving endothelial function. We evaluated the effects of chronic treatment with quinapril (Q) on the l -arginine/nitric oxide (NO) pathway in normotensive rats under baseline and inflammatory conditions. The role of bradykinin was also investigated. The animals received for 1 week either the ACE-inhibitor Q (1 and 10 mg/kg/day), the B(2)receptor antagonist HOE 140, Q+HOE 140, or no drug. At the end of chronic treatment, rats underwent either a 6-h placebo or an E. coli endotoxin challenge. The following measurements were made: (i) endothelial and inducible NO synthase (eNOS and iNOS) protein expression; (ii) eNOS/iNOS activity; (iii) serum levels of nitrite/nitrate and tumour necrosis factor (TNF)- alpha; (iv) NO in the expired air (eNO). Q increased baseline aortic eNOS protein expression (up to 99%, P<0.001) and activity (l -citrulline synthesis up to 94%, P<0.01; serum nitrite/nitrate up to 55%, P<0.05). HOE 140 partially reversed Q-induced upregulation of eNOS (P<0.05). Moreover, Q counteracted LPS effects, i.e. increased the impaired eNOS pathway and limited iNOS induction (up to 94 and 24%, respectively), and reduced the increased nitrite/nitrate and TNF- alpha serum levels as well as eNO (up to 25, 38 and 28%, respectively, P<0.01 for all comparisons). HOE 140 did not influence Q effects on iNOS during endotoxaemia. In conclusion, in (patho)physiological conditions in rats, Q up-regulated eNOS with a bradykinin-mediated mechanism, while downregulated iNOS with a possible TNF- alpha -mediated mechanism.

New insights on myocardial pyridine nucleotides and thiol redox state in ischemia and reperfusion damage

OBJECTIVE

to investigate the changes of pyridine nucleotides and thiol redox state in cardiac tissue following ischemia and reperfusion. NADH/NAD and NADPH/NADP redox couples were specifically studied and the influence of NADPH availability on cellular thiol redox was also investigated.

METHODS

isolated rabbit hearts were Langendorff perfused and subjected to a protocol of ischemia and reperfusion. An improved technique for extraction and selective quantitation of pyridine nucleotides was applied.

RESULTS

ischemia and reperfusion induced an increase in diastolic pressure, limited recovery in developed pressure and loss of creatine phosphokinase. Creatine phosphate and ATP were decreased by ischemia and only partially recovered during reperfusion. NADH was increased (from 0. 36+/-0.04 to 1.96+/-0.15 micromol/g dry wt. in ischemia, P<0.001), whereas NADPH decreased during ischemia (from 0.78+/-0.04 to 0. 50+/-0.06 micromol/g dry wt., P<0.01) and reperfusion (0.45+/-0.03 micromol/g dry wt.). Furthermore, we observed: (a) release of reduced (GSH) and oxidised glutathione (GSSG) during reperfusion; (b) decreased content of reduced sulfhydryl groups during ischemia and reperfusion (GSH: from 10.02+/-0.76 to 7.11+/-0.81 nmol/mg protein, P<0.05, and to 5.48+/-0.57 nmol/mg protein; protein-SH: from 280.42+/-12.16 to 135.11+/-17.00 nmol/mg protein, P<0.001, and to 190.21+/-11.98 nmol/mg protein); (c) increased content in GSSG during reperfusion (from 0.17+/-0.02 to 0.36+/-0.02 nmol/mg protein, P<0.001); (d) increased content in mixed disulphides during ischemia (from 6.14+/-0.13 to 8.31+/-0.44 nmol/mg protein, P<0.01) and reperfusion (to 9.87+/-0.82 nmol/mg protein, P<0.01).

CONCLUSIONS

under severe low-flow ischemia, myocardial NADPH levels can decrease despite the accumulation of NADH. The reduced myocardial capacity to maintain NADPH/NADP redox potential can result in thiol redox state changes. These abnormalities may have important consequences on cellular function and viability.

Reduction of oxidative stress by carvedilol: role in maintenance of ischaemic myocardium viability

OBJECTIVES

To differentiate the impact of the beta-blocking and the anti-oxidant activity of carvedilol in maintaining myocardium viability.

METHODS

Isolated rabbit hearts, subjected to aerobic perfusion, or low-flow ischaemia followed by reperfusion, were treated with two doses of carvedilol, one dose (2.0 microM) with marked negative inotropic effect due to beta-blockage and the other (0.1 microM) with no beta-blockage nor negative inotropism. Carvedilol was compared with two doses of propranolol, 1.0 - without - and 5.0 microM - with negative inotropic effect. Anti-oxidant activity was measured as the capacity to counteract the occurrence of oxidative stress and myocardium viability as recovery of left ventricular function on reperfusion, membrane damage and energetic status.

RESULTS

Carvedilol counteracted the ischemia and reperfusion induced oxidative stress: myocardial content of reduced glutathione, protein and non-protein sulfhydryl groups after ischaemia and particularly after reperfusion, was higher in hearts treated with carvedilol, while the myocardial content of oxidised glutathione was significantly reduced (0.30+/-0.03 and 0.21+/-0.02 vs. 0.39+/-0.03 nmol/mg prot, both P<0.01, in 0.1 and 2.0 microM). At the same time, carvedilol improved myocardium viability independently from its beta-blocking effect. On the contrary, propranolol maintained viability only at the higher dose, although to a lesser extent than carvedilol. This suggests that the effects of propranolol are dependent on energy saving due to negative inotropism. The extra-protection observed with carvedilol at both doses is likely due to its anti-oxidant effect.

CONCLUSIONS

Our data show that the anti-oxidant activity of carvedilol is relevant for the maintenance of myocardium viability.