Stefano Bongrani

Bronchospasm and pressor effects induced in the guinea-pig by leukotriene C4 are probably due to release of cyclooxygenase products

Synthetic leukotriene C4 (LTC4) i.v. to guinea-pigs induced bronchospasm and immediate hypertension followed by marked and lasting hypotension. These effects were inhibited by indomethacin and FPL-55712 but were unaffected by diphenhydramine and phenoxybenzamine; atropine and tiramide partially antagonized LTC4 bronchospasm. Antagonism by indomethacin suggests that the bronchospasmodic and pressor effects of LTC4 may be mediated by the release of cyclooxygenase products.

Comparative efficacy of a DA2/α2 agonist and a β-blocker in reducing adrenergic drive and cardiac fibrosis in an experimental model of left ventricular dysfunction after coronary artery occlusion

Attenuation of neuroendocrine activation may be beneficial in congestive heart failure. Sympathetic nervous system overactivity can be reduced by receptors blockade or by reducing norepinephrine (NE) spillover. This study evaluated and compared the effects of a DA2-dopaminergic receptor/alpha2-adrenoceptor agonist (CHF-1024) and a beta1-adrenoreceptor antagonist in terms of hemodynamics, ventricular remodeling, beta-adrenergic drive, and cardiac fibrosis after myocardial infarction (MI) in rats. MI was induced by left coronary artery ligation in 213 rats, whereas 12 were left unoperated on. After 2 months, the operated-on animals were treated for 1 more month with CHF-1024 at either 0.33 mg/kg/day (low dose) or 1 mg/kg/day (high dose) or with metoprolol (10 mg/kg/day), delivered through implanted osmotic minipumps. Plasma concentration and urinary excretion of NE were measured before the rats were killed. Hemodynamic variables were measured and morphometric analysis was done on the diastole-arrested hearts to quantify left ventricular remodeling and interstitial collagen density. Metoprolol treatment tended to normalize LV end-diastolic pressure (LVEDP). CHF-1024 at either dose, and metoprolol, significantly reduced collagen deposition in LV of infarcted animals (from 8.8 +/- 0.5% LV area in vehicle-treated rats to 6.6 +/- 0.2% or 6.4 +/- 0.2% after the low or high dose of CHF-1024, respectively; p < 0.05). Similarly, CHF-1024 at either dose reduced the plasma concentration of NE (from 224 +/- 53 pg/ml to 60 +/- 7 pg/ml or 87 +/- 13 pg/ml; p < 0.05) and urinary excretion of NE in rats with MI, whereas beta-blockade did not affect these variables. In conclusion, CHF-1024 infused for 1 month to rats with LV dysfunction reduced heart rate, NE spillover, and collagen deposition, without unwanted effects, only appearing at the higher dose. Effective beta-blockade with metoprotol reduced LVEDP with no effects on heart function. Neither DA2/alpha2 stimulation nor beta-blockade altered LV remodeling after coronary artery ligation.

Cardiovascular effects of nicardipine in anesthetized open-chest dogs in the absence and presence of β-adrenergic receptor blockade: a comparison with nifedipine and verapamil

Summary: Nicardipine, a new 1,4-dihydropyridine calcium-entry blocker, was assessed for cardiovascular effects against nifedipine and verapamil in anesthetized open-chest beagle dogs, in the absence and presence of β-adrenoceptor blockade (propranolol 1 mg/kg i.v.). In control conditions, intravenous nicardipine and nifedipine (30 nmol/kg) produced decreases in blood pressure of similar magnitude without evidence of cardiodepression. An equihypotensive dose of verapamil (300 nmol/kg), by contrast, induced long-lasting negative chronotropic and inotropic effects, which, when combined with the effects of propranolol, were so marked as to cause the death of two of five dogs (atrioventricular block). Dihydropyridine derivatives at higher doses (100 nmol/kg) produced different responses: nifedipine depressed cardiac performance significantly more than nicardipine and, in the presence of β-adrenergic blockade, caused the death of three of six dogs due to cardiovascular failure. In the nicardipine group, on the contrary, cardiac function was adequately preserved even in the presence of β-blocker, and no animals died. The results of the present study confirm a previous in vitro observation: nicardipine is a calcium-entry blocker devoid of remarkable cardiodepressant effects and particularly selective for the vascular smooth muscle.

The involvement of the release of nitric oxide in the pharmacological activity of the new furoxan derivative CHF 2363

1 The mechanism of action and the pharmacological effects of the new furoxan derivative, CHF 2363 (4‐ethoxy‐3‐phenylsulphonylfuroxan), were investigated. 2 Pre‐incubation of CHF 2363 with human platelet‐rich plasma produced a concentration‐dependent inhibition of the platelet aggregation induced by collagen, adenosine diphosphate (ADP) and platelet activating factor (PAF). The test compound was about 5 times more potent than sodium nitroprusside. 3‐Isobutyl‐1‐methyl‐xanthine (IBMX) potentiated the antiaggregating effect of CHF 2363. 3 CHF 2363 was a potent inhibitor of rubbed endothelium rabbit aortic ring contraction induced by noradrenaline. Comparison of IC50 values showed that CHF 2363 was as potent as glyceryl trinitrate (GTN). 4 Increasing concentrations of CHF 2363 elevated platelet guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) levels. Adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) levels were unaffected. 5 Oxyhaemoglobin reduced all the pharmacological actions of the test compound. Moreover, CHF 2363 concentration‐dependently released nitric oxide (NO) in platelet‐rich plasma. The NO release was correlated to its ability to increase platelet cyclic GMP levels. 6 After exposure of rat aortic strips to supramaximal concentrations of GTN (550 μm), the vasorelaxant activity of CHF 2363 did not change, although that of GTN decreased about 55 fold. 7 It has been concluded that the new furoxan derivative CHF 2363 exerts a potent antiaggregating and vasorelaxant activity via NO release and increase of cyclic GMP levels. No in vitro cross tolerance between GTN and CHF 2363 was observed.

Effect of long-term treatment with L-deprenyl on the age-dependent microanatomical changes in the rat hippocampus

Chronic treatment with L-deprenyl increases both mean and maximum life span and improves cognitive functions in the aged rat. The present study was designed to evaluate whether long-term treatment with L-deprenyl at a dosage not inhibiting the monoamine oxidase-B (MAO-B) (1.25 mg/kg/day) or inhibiting the enzyme activity (5 mg/kg/day) had any effect on the age-dependent microanatomical changes in the rat hippocampus. The hippocampus was chosen in view of its key role in learning and memory functions. Treatment with L-deprenyl started at 19 months and lasted until the 24th month of age. Age-matched untreated rats were used as a control, whereas 11-month-old rats were used as an adult reference group. The number of nerve cell and glial fibrillary acidic protein-immunoreactive astrocyte profiles in the CA1 and CA3 fields of the hippocampus and in the dentate gyrus was decreased and increased, respectively in aged compared with adult rats. Treatment with 5 mg/kg/day, but not with 1.25 mg/kg/day L-deprenyl increased the number of neuronal profiles and decreased the number of astrocytes in the hippocampus of aged rats. The density of zinc stores in the associative intrahippocampal pathway of mossy fibres, which was decreased in aged animals, was increased after treatment with the two doses of L-deprenyl. Lipofuscin accumulation within the cytoplasm of pyramidal neurons of the hippocampus was reduced dose dependently by L-deprenyl treatment. These results suggest that long-term treatment with L-deprenyl is able to counter the expression of age-dependent microanatomical changes in the rat hippocampus. These effects seem only partially correlated with the MAO-B inhibitory activity of L-deprenyl.

Effects of a DA2/α2 agonist and a β1-blocker in combination with an ACE inhibitor on adrenergic activity and left ventricular remodeling in an experimental model of left ventricular dysfunction after coronary artery occlusion

Renin-angiotensin-aldosterone and sympathetic nervous systems overactivity play a major role in worsening the extent of heart failure. Attenuation of neurohumoral activation with angiotensin-converting enzyme (ACE) inhibitors and beta-blockers has proven beneficial in congestive heart failure. Because ACE inhibition is a recommended treatment for heart failure, this study was designed to test the effects on neurohumoral activation, hemodynamics, and left ventricular (LV) volume of the combination of an ACE inhibitor (delapril) with a DA2-dopaminergic receptor/alpha2-adrenoceptor agonist (CHF-1024) or a beta1-adrenoceptor antagonist (metoprolol) after a moderate to large myocardial infarction (MI) in rats. MI was induced by left coronary artery ligation in 134 rats, and six were not operated on. After 2 months, the animals with ECG evidence of MI were treated for 1 more month with CHF- 1024, 0.33 mg/kg/day or with metoprolol (10 mg/kg/day), delivered through implanted osmotic minipumps, in addition to delapril (6 mg/kg/day) in the drinking water. Daily urinary excretion of norepinephrine (NE) and circulating concentration were measured. Hemodynamic variables were measured, and three-dimensional morphometric analysis was done on the diastole-arrested hearts to quantify infarct size and LV geometry. In conscious animals, delapril alone or with CHF-1024 or metropolol did not modify heart rate or systolic blood pressure. Both combination treatments, however, significantly reduced heart rate in anesthetized animals compared with the group receiving vehicle. Infarct size was not different between treatments, averaging 20-22% of LV volume. The threefold increase of LV chamber volume in infarcted rats was significantly attenuated by delapril alone or with CHF-1024 or metoprolol (-37 to -44%, p<0.05). Treatment with a combination of the ACEi and CHF-1024 tended to normalize the shape of the LV cavity. Urinary NE excretion was unaffected by delapril alone but was reduced by the addition of CHF-1024 or metoprolol. In conclusion, 1 month of treatment with doses of delapril having no hemodynamic effect, reduced LV volume in a model of chronic heart failure. When CHF-1024 or metoprolol was given with delapril, sympathetic activation decreased with no unwanted effects, such as excessive hypotension.

CHF-1024, A DA2/α2 Agonist, Blunts Norepinephrine Excretion and Cardiac Fibrosis in Pressure Overload

We compared the effects of an ACE inhibitor, captopril, with those of a DA2-dopaminergic/α2-adrenergic receptor agonist (CHF-1024) on neuroendocrine activation and cardiac fibrosis in a model of pressure-overload hypertrophy. Interrenal aortic stenosis was performed in 89 rats, treated with CHF-1024 (0.33, 2 or 6 mg kg−1 day−1), or captopril (1 g/L). Hemodynamic variables were recorded. Cardiac and renal weights, plasma aldosterone, renin activity and urinary catecholamine excretion were measured, as well as cardiac collagen. Blood pressure was lower in stenotic animals treated with CHF-1024 compared to vehicle (161 ± 10 vs 219 ± 10 mmHg, p < 0.01), but LV weight was similar. CHF-1024 elicited a marked dose-dependent attenuation of urinary norepinephrine excretion (1.80 ± 0.18 in controls compared to 0.40 ± 0.14 μg/24 h at the highest dose, p < 0.01) and of LV perivascular fibrosis. Captopril provoked a marked hypotension, reduced cardiac and body weights, plasma aldosterone concentration, dopamine excretion and perivascular collagen. The DA2/α2 agonist CHF-1024 effectively blunts adrenergic drive and cardiac fibrosis in a rat model of pressure overload.

β2-Adrenoceptor blockade is the basis of guinea-pig bronchial hyper-responsiveness to leukotriene C4 and other agonists

1 Four β‐adrenoceptor antagonists, namely (−)‐propranolol, (+)‐propranolol, ICI‐118551 and (±)‐practolol, were investigated for their effects on leukotriene C4 (LTC4)‐induced bronchoconstriction in the anaesthetized guinea‐pig. (−)‐Propranolol was also investigated for its effects on acetylcholine and histamine bronchospasm in the anaesthetized guinea‐pig, and on LTC4‐induced contractions of guinea‐pig isolated trachea and lung parenchyma. 2 The various β‐adrenoceptor antagonists potentiated, dose‐dependently, the bronchoconstriction induced by threshold doses of LTC4 and the intensity of the potentiation correlated with the β2‐blocking capacity possessed by the drugs. 3 (−)‐Propranolol potentiated the bronchospasm induced by threshold doses of acetylcholine and histamine but to a lesser degree than the LTC4‐induced bronchospasm. 4 The airway hyper‐responsiveness induced by (−)‐propranolol was unaffected by pretreatment with mepyramine, cyproheptadine, phenoxybenzamine, atropine or indomethacin. 5 The airway hyper‐responsiveness induced by (−)‐propranolol persisted even in adrenalectomized or reserpine‐treated guinea‐pigs, although adrenalectomy induced some increase in airway responsiveness. 6 (−)‐Propranolol had no effect on LTC4, histamine and acetylcholine‐induced contractions of isolated trachea and lung parenchyma. 7 The results show that the airway hyper‐responsiveness induced by β‐adrenoceptor antagonists generally correlates with their β2‐blocking activity. The possibility remains that some other unknown mechanism(s) may also be implicated.

Neuroanatomy of Aging Brain

The present study was designed to assess the influence of long term L-deprenyl treatment on some microanatomical parameters of aging rat frontal cortex and hippocampus. Male Sprague-Dawley rats of 19 months of age were divided into three groups. Rats of the first group received an oral daily dose of 1.25 mg/kg L-deprenyl; animals of the second group were treated with an oral daily dose of 5 mg/kg L-deprenyl, whereas rats of the third group were left untreated and used as control. Treatment lasted for 5 months, and rats were sacrificed at 24 months. At this age they were considered to be old. Another group of 11-month-old rats was used as an adult reference group. The density of nerve cell profiles and of glial fibrillary acidic protein (GFAP) immunoreactive astrocytes was decreased and increased respectively in the frontal cortex and in the different portions of the hippocampus in old in comparison with adult rats. A decrease in the intensity of sulfide silver staining in the mossy fibers of the hippocampus was also observed in old rats. Moreover, a cytoplasmatic accumulation of lipofuscin was noticeable in old rats as well as a significant increase of the monoamine-oxidase (MAO) B reactivity both in the frontal cortex and in the hippocampus. A higher density of nerve cell profiles, of sulfide silver staining, and fewer astrocyte profiles were noticeable in the frontal cortex and in the hippocampus of old rats treated with 5 mg/kg/day of L-deprenyl. This dose of the compound also significantly reduced lipofuscin accumulation and MAO-B reactivity in old rats. However, the lower dose of the compound did not cause any statistically significant effect on the microanatomical parameters investigated with the exception of sulfide silver staining and lipofuscin accumulation, which were increased and decreased respectively after 1.25 mg/kg per day of L-deprenyl. The above results suggest that long-term treatment with L-deprenyl is able to counter some microanatomical changes typical of the aging frontal cortex and hippocampus in the rat. These changes seem to be in part related to the MAO-B inhibitory activity of L-deprenyl.

Positive interaction of the β2-agonist CHF 4226.01 with budesonide in the control of bronchoconstriction induced by acetaldehyde in the guinea-pigs

1 Pretreatment of anaesthetized guinea‐pigs with either CHF 4226.01 (8‐hydroxy‐5‐[(1R)‐1‐hydroxy‐2‐[N‐[(1R)‐2‐(p‐methoxyphenyl)‐1‐methylethyl]amino]ethyl] carbostyril hydrochloride), formoterol or budesonide reduced acetaldehyde (AcCHO)‐evoked responses in the lungs with a rank order of potency CHF 4226.01 (ED50 values, from 1.88 to 3.31 pmol) > formoterol (ED50 values, from 3.03 to 5.51 pmol) ≫ budesonide (ED50 values, from 335 to 458 nmol). The duration of action of CHF 4226.01 in antagonizing the airway obstruction elicited by AcCHO was also substantially longer than formoterol (area under the curve) at 10 pmol, 763±58 and 480±34, respectively; P<0.01). 2 Continuous infusion of a subthreshold dose of AcCHO enhanced the intratracheal pressure (ITP) increases caused by subsequent challenges with substance P (from 9.7±0.8 to 27.5±1.6 cm H2O as a peak, P<0.001). Pretreatment with either CHF 4226.01 or formoterol prevented the sensitizing effect of AcCHO on substance P responses (ED50 values, 2.85 and 6.11 pmol, respectively; P<0.01). 3 The ED50 value of budesonide (396 nmol) in preventing AcCHO‐evoked ITP increase was reduced when this glucocorticoid was combined with 0.1 pmol CHF 4226.01 (ED50 76 nmol; P<0.001). CHF 4226.01/budesonide was two‐fold more effective (P<0.01) than the formoterol/budesonide combination. 4 These results suggest that CHF 4226.01/budesonide, by optimizing each others beneficial potential in the control of pulmonary changes caused by AcCHO in the guinea‐pigs, may represent a new fixed combination in asthma.