Juliana Montani Raimundo

Studies towards the identification of putative bioactive conformation of potent vasodilator arylidene N-acylhydrazone derivatives

In this report we disclose the synthesis, vasodilatory activity, and identification of bioactive conformation of new N-acylhydrazone and N-methyl-N-acylhydrazone derivatives, structurally designed by bioisosteric replacements of previously described cardioactive compounds LASSBio-294 and its N-methyl derivative LASSBio-785. Some of these novel derivatives presented improved vasorelaxant properties, being new cardiovascular drug candidates.

The synergistic interaction between morphine and maprotiline after intrathecal injection in rats.

BACKGROUND: Antidepressant drugs act as potent inhibitors of norepinephrine and/or serotonin reuptake and are widely used with opioids for the treatment of chronic pain. The mechanism of this increased analgesic action is unclear. We compared the antinociceptive effects of the intrathecal administration of morphine with that of a nonselective (amitriptyline) or selective (maprotiline or citalopram) antidepressant drug using the thermal withdrawal test in rats. We also investigated the possible mechanisms involved in the interactions of these drugs. METHODS: Male Wistar rats were anesthetized with sevoflurane and administered morphine and antidepressant drugs, or saline, through intrathecal injection. The antinociceptive effect was evaluated using the thermal withdrawal test before and after drug administration. The time for the withdrawal reaction was expressed as percentage of maximum possible effect (MPE). Animals were also pretreated with yohimbine (a nonselective alpha2-adrenergic antagonist) and naloxone (a nonselective opioid antagonist) for mechanism of action studies. Pharmacologic interaction was evaluated using isobolographic analysis of simultaneous administration of fixed proportions of maprotiline and morphine. RESULTS: Single intrathecal administration of morphine (2 &mgr;g), amitriptiline (125 &mgr;g), citalopram (144 &mgr;g), and maprotiline (1.25 &mgr;g) produced 51.6% ± 8.9%, 10.3% ± 3.2%, 33.8% ± 5.2%, and 48.5% ± 9.2% MPE, respectively. The antinociceptive effect of morphine was increased when combined with amitriptyline (91.3% ± 4.6% MPE) and maprotiline (86.9% ± 9.2% MPE) but not with citalopram (40.6% ± 4.6% MPE). Coadministration of maprotiline increased the antinociceptive duration of morphine by 4-fold (from 120 to 480 min), which was reversed by pretreatment with the α-2 adrenoceptor inhibitor, yohimbine, and the mu-type opioid receptor antagonist, naloxone. Isobolographic analysis demonstrated a synergistic interaction between morphine and maprotiline. CONCLUSIONS: Selective norepinephrine reuptake inhibitors can significantly increase the intensity and duration of morphine antinociceptive activity via both α2-adrenergic and opioid receptors. This interaction was not observed with the selective serotonin inhibitor, citalopram.

Activity of Cecropia lyratiloba extract on contractility of cardiac and smooth muscles in Wistar rats.

1 Brazilian forests show high diversity of medicinal plants and several are used in folk medicine for the treatment of hypertension and asthma. The aim of the present study was to investigate the effects of a methanol extract (ME) of Cecropia lyratiloba and its flavonoid fraction (FF) on the contractility of cardiac, vascular and tracheal smooth muscles. 2 Twitches of rat papillary muscles were obtained with electrical stimulation and were recorded before and after exposure to increasing concentrations of ME and FF. 3 Cardiac depression was induced by FF. At 500 mg/mL FF, the amplitude of twitches was reduced to 56.7 5.1% of control values (P < 0.05). 4 The contractile response to a single concentration of adrenaline (10 mmol/L) was measured before and after exposure to ME and FF in rat aorta rings with intact endothelium. Both ME and FF inhibited adrenaline‐induced contractions of the aorta in a concentration‐dependent manner. Adrenaline‐induced contrations were reduced to 46.4 9.9 and 34.2 6.9% (P < 0.05) of control in the presence of 500 mg/mL ME and FF, respectively. 5 The flavonoids isolated from FF, namely isoorientin and a mixture of orientin and isovitexin, were also tested in the aorta. These flavonoid do not seem to be responsible for the vasorelaxant effects of ME and FF. 6 No changes were observed in acetylcholine‐precontracted trachea when exposed to ME or FF. 7 Endothelium‐dependent vasodilation induced by FF is likely to be mediated by the release of nitric oxide because vascular relaxation was abolished in the presence of Nw‐nitro‐l‐arginine methyl ester, an inhibitor of nitric oxide synthase. 8 In conclusion, vascular relaxation induced by ME and FF could explain the traditional use of the extract of C. lyratiloba for treatment of arterial hypertension.

Sedation and antinociception induced by a new pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivative (LASSBio-873) is modulated by activation of muscarinic receptors.

New substances designed for the treatment of anxiety have previously been synthesized, which resulted in the identification of four new pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivatives structurally designed by using zolpidem as lead compound. Among them, LASSBio-873 was the most potent to produce analgesic, sedative and hypnotic effects. Thus, we investigated the possible mechanisms involved in LASSBio-873-induced sedation, as well as its effects on different models of inflammatory pain. LASSBio-873 (4 mg/kg) reduced locomotor activity of mice in the open field test from 205.2+/-25.6 to 87.6+/-16.2 movements/min. Atropine, a non-selective muscarinic antagonist, prevented the LASSBio-873-induced sedation and increased locomotor activity to 192.9+/-30.2 movements/min. In the formalin test, LASSBio-873 (4 mg/kg) significantly reduced the duration of nociceptive behavior during the inflammatory phase, reducing the control reactivity from 197.6+/-14.5s to 84.4+/-10.3s. Carrageenan reduced the latency for the animal reaction from 5.1+/-0.2s (control) to 2.1+/-0.3s which was completely reverted by LASSBio-873 (6 mg/kg) to 5.6+/-0.6s. Atropine prevented the LASSBio-873-induced antinociceptive and antihyperalgesic activities, indicating the interference of the cholinergic system. LASSBio-873 is a novel prototype of drug that modulates muscarinic activity and could be used for neuropsychiatric and cognitive disorders and other conditions associated to acute and chronic pain.

The lignan eudesmin extracted from Piper truncatum induced vascular relaxation via activation of endothelial histamine H1 receptors.

In Brazilian folk medicine, extracts from Piper species are used to reduce blood pressure. Previously, we demonstrated the vasodilatory activity of crude extracts from leaves of Piper truncatum explaining their possible use in the treatment of hypertension in traditional medicine. In the present study, we investigated the effects of eudesmin, a lignan isolated from hexane extract of leaves from Piper truncatum, on the contractility of rat aortas and the possible mechanisms involved in its vascular action. Eudesmin induced an intense concentration-dependent relaxation of aortic rings precontracted with phenylephrine. The concentration of eudesmin necessary to reduce phenylephrine-induced aortic contraction by 50% (IC(50)) was 10.69+/-0.67 microg/ml. Eudesmin-induced vasodilation required an intact endothelium since vascular relaxation was inhibited by mechanic removal of endothelium, and by pretreatment with nitric oxide synthase inhibitor and soluble guanylate cyclase inhibitor. Relaxation induced by eudesmin was also impaired in the presence of indomethacin and diphenhydramine, a cyclooxygenase inhibitor and an antagonist of type 1 histamine receptor (H(1)), respectively. IC(50) was increased to 18.1+/-1.8 and 18.1+/-2.6 microg/ml (P<0.05; n=6) after exposure to indomethacin and diphenhydramine, respectively. Atropine (muscarinic receptor antagonist), propranolol (beta-adrenoceptor antagonist) and glibenclamide (ATP-sensitive K(+) channel blocker) did not alter the effect of eudesmin. These results indicate that eudesmin-induced vascular relaxation in rat aorta is mediated by release of nitric oxide and prostanoid through the involvement of histamine receptor present in the endothelial cells.

Comparative effects of tramadol on vascular reactivity in normotensive and spontaneously hypertensive rats.

1 The aim of the present study was to determine the effects of tramadol on vascular reactivity in aortic rings from Wistar‐Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). 2 Aortic rings, with or without endothelium, were obtained from male WKY rats and SHR (15–20 weeks old) and prepared for isometric tension recording. Aortic rings were precontracted with phenylephrine (10 µmol/L) or 40 mmol/L KCl and then exposed to cumulative concentrations of tramadol (0.1–1 mmol/L). 3 Tramadol produced a concentration‐dependent relaxation of precontracted aortic rings from WKY rats and SHR, which was not dependent on functional endothelium. Vascular relaxation was significantly greater in rings from SHR than WKY rats. 4 The concentration of tramadol necessary to produce a 50% reduction of the maximal contraction to phenylephrine (IC50) in rings with and without endothelium from SHR was 0.47 ± 0.08 and 0.44 ± 0.03 mmol/L, respectively (P = 0.76). 5 Tramadol attenuated the contracture elicited by Ca2+ in depolarized tissue, suggesting that it may inhibit L‐type Ca2+ channels. However, pretreatment with nicardipine (1 µmol/L) prevented the relaxation induced by tramadol in aortic rings from WKY rats and partially reduced its inhibitory effect in aortic rings from SHR. 6 Pretreatment of endothelium‐denuded aorta with glybenclamide (3 µmol/L), 4‐aminopyridine (3 mmol/L), tetraethylammonium (3 mmol/L) and naloxone (100 µmol/L) did not affect tramadol‐induced vasodilation of aortic rings from either WKY rats or SHR. 7 Intravenous administration of tramadol (10 mg/kg) to conscious SHR significantly reduced both systolic and diastolic blood pressure from 171.4 ± 5.3 to 129.3 ± 5.3 (P = 0.002) and from 125.0 ± 6.5 to 57.8 ± 8.9 mmHg (P = 0.003), respectively.

Could a high-fat diet rich in unsaturated fatty acids impair the cardiovascular system?

BACKGROUND Dyslipidemia results from consumption of a diet rich in saturated fatty acids and is usually associated with cardiovascular disease. A diet rich in unsaturated fatty acids is usually associated with improved cardiovascular condition. OBJECTIVE To investigate whether a high-fat diet rich in unsaturated fatty acids (U-HFD) - in which fatty acid represents approximately 45% of the total calories - impairs the cardiovascular system. METHODS Male, 30-day-old Wistar rats were fed a standard (control) diet or a U-HFD containing 83% unsaturated fatty acid for 19 weeks. The in vivo electrocardiogram, the spectral analysis of heart rate variability, and the vascular reactivity responses to phenylephrine, acetylcholine, noradrenaline and prazosin in aortic ring preparations were analyzed to assess the cardiovascular parameters. RESULTS After 19 weeks, the U-HFD rats had increased total body fat, baseline glucose levels and feed efficiency compared with control rats. However, the final body weight, systolic blood pressure, area under the curve for glucose, calorie intake and heart weight⁄final body weight ratio were similar between the groups. In addition, both groups demonstrated no alteration in the electrocardiogram or cardiac sympathetic parameters. There was no difference in the responses to acetylcholine or the maximal contractile response of the thoracic aorta to phenylephrine between groups, but the concentration necessary to produce 50% of maximal response showed a decrease in the sensitivity to phenylephrine in U-HFD rats. The cumulative concentration- effect curve for noradrenaline in the presence of prazosin was shifted similarly in both groups. CONCLUSIONS The present work shows that U-HFD did not impair the cardiovascular parameters analyzed.

Vasodilatory activity and antihypertensive profile mediated by inhibition of phosphodiesterase type 1 induced by a novel sulfonamide compound

LASSBio‐985 is a sulfonamide compound designed as a simplified structure of a nonselective phosphodiesterase type 4 (PDE‐4) inhibitor that promotes vasodilatory activity in vitro. PDE are enzymes responsible for the hydrolysis of cyclic adenosine 3′,5′‐ monophosphate and cyclic guanosine 3′,5′‐monophosphate. Five different isozymes of PDE are found in vascular smooth muscle (PDE1–PDE5). Aortic rings, with or without endothelium, from male normotensive and spontaneously hypertensive rats (SHR) were prepared for isometric tension recording. Blood pressure was measured in Wistar Kyoto (WKY) rats and SHR during intravenous infusion of LASSBio‐985 (10 mg/kg/min) during 15 min. LASSBio‐985 induced a concentration‐dependent vasodilation in aortic rings from normotensive and SHR, which was almost completely inhibited in endothelium‐denuded vessels. Vasodilatory activity was also reduced in endothelium‐intact aortic rings that had been pretreated with Nω‐nitro‐l‐arginine methyl ester hydrochloride (l‐NAME), a nitric oxide synthase inhibitor and 1H‐[1,2,4]oxadiazolod[4,3‐a]quinoxalin‐1‐one (ODQ), a guanylate cyclase inhibitor. LASSBio‐985‐induced vasodilation was also inhibited by sildenafil (100 μm) and SQ 22536, a PDE5 inhibitor and adenylate cyclase inhibitor, respectively. To evaluate the involvement of some endothelial receptors, atropine, diphenhydramine, HOE 140, naloxone, propranolol, indomethacin, and wortmannin were tested, but none inhibited the effects of LASSBio‐985. The residual effect observed on endothelium‐denuded aortic rings was abolished by nicardipine, a voltage‐sensitive‐Ca2+‐channel blocker. Intravenous infusion of LASSBio‐985 (10 mg/kg/min) significantly reduced systolic and diastolic pressures in both WKY and SHR. LASSBio‐985 is a compound with vasodilatory activity, which could be consequent to PDE1 inhibition and voltage‐sensitive‐Ca2+‐channel blockade.

Inibição da corrente de cálcio tipo L por tramadol e enantiômeros em miócitos cardíacos de ratos

BACKGROUND Tramadol is a centrally acting analgesic, whose mechanism of action involves opioid-receptor activation. Previously, we have shown that tramadol and its enantiomers had a negative inotropic effect on the papillary muscle in which the (+)-enantiomer is more potent than (-)- and (±)-tramadol. OBJECTIVE In this study, we investigated the effects of tramadol and its enantiomers on L-type calcium current (ICa-L). METHODS The experiments were carried out in isolated Wistar rat ventricular myocytes by using the whole cell patch clamp technique. RESULTS Tramadol (200 µM) reduced the peak amplitude of ICa-L at potentials from 0 to +50 mV. At 0 mV, I(Ca-L) was reduced by 33.7 ± 7.2%. (+)- and (-)-tramadol (200 µM) produced a similar inhibition of ICa-L, in which the peak amplitude was reduced by 64.4 ± 2.8% and 68.9 ± 5.8%, respectively at 0 mV (p > 0.05). Tramadol, (+)- and (-)-tramadol shifted the steady-state inactivation of ICa-L to more negative membrane potentials. Also, tramadol and (+)-tramadol markedly shifted the time-dependent recovery curve of I(Ca-L) to the right and slowed down the recovery of I(Ca-L) from inactivation. The time constant was increased from 175.6 ± 18.6 to 305.0 ± 32.9 ms (p < 0.01) for tramadol and from 248.1 ± 28.1 ms to 359.0 ± 23.8 ms (p < 0.05) for (+)-tramadol. The agonist of µ-opioid receptor DAMGO had no effect on the I(Ca-L). CONCLUSION The inhibition of ICa-L induced by tramadol and its enantiomers was unrelated to the activation of opioid receptors and could explain, at least in part, their negative cardiac inotropic effect.

In‐vitro vasodilatory activity of the hexanic extract of leaves and stems from Piper truncatum Vell. in rats

Several plants from the Brazilian Tropical Forest are used in folk medicine for treatment of hypertension and asthma. In this study, we investigated the effects of hexanic extracts of leaves (HLE) and stems (HSE) from Piper truncatum on the contractility of cardiac, vascular and tracheal smooth muscles. Twitches of cardiac muscles obtained with electrical stimulation were recorded before and after exposure to increasing concentrations of hexanic extracts. HLE and HSE respectively reduced significantly the amplitude of twitches to 57.05 ± 11.63 and 61.58 ±5.70% of control in the presence of 100 μg mL−1. Contractile response to a single concentration of adrenaline (epinephrine) was measured before and after exposure of rat aorta rings to HLE and HSE. Both extracts inhibited aorta contraction in a concentration‐dependent manner. The concentration of 50% inhibitory effect (IC50) was 32.3 ± 13.8 and 47.0 ± 23.8 μg mL−1 for HLE and HSE, respectively, in aorta with intact endothelium. HLE and HSE also reduced the acetylcholine‐precontracted trachea in a concentration‐dependent manner with maximal effect observed at 250 and 350 μg mL−1, respectively. Vasodilatation and trachea relaxation induced by HLE and HSE could explain the use of Piper extracts to reduce blood pressure and bronchospasm.