Ex Vivo and In Silico Approaches of Tracheal Relaxation through Calcium Channel Blockade of 6-Aminoflavone and Its Toxicological Studies in Murine Models

Asthma is a condition in which a person's airways become inflamed, narrowed, and produce greater amounts of mucus than normal. It can cause shortness of breath, chest pain, coughing, or wheezing. In some cases, symptoms may be exacerbated. Thus, the current study was designed to determine the mechanism of action of 6-aminoflavone (6-NH₂F) in ex vivo experiments, as well as to determine its toxicity in acute and sub-chronic murine models. Tissues were pre-incubated with 6-NH₂F, and concentration-response curves to carbachol-induced contraction were constructed. Therefore, tracheal rings pre-treated with glibenclamide, 2-aminopyridine, or isoproterenol were contracted with carbachol (1 µM), then 6-NH₂F relaxation curves were obtained. In other sets of experiments, to explore the calcium channel role in the 6-NH₂F relaxant action, tissues were contracted with KCl (80 mM), and 6-NH₂F was cumulatively added to induce relaxation. On the other hand, tissues were pre-incubated with the test sample, and after that, CaCl₂ concentration-response curves were developed. In this context, 6-NH₂F induced significant relaxation in ex vivo assays, and the effect showed a non-competitive antagonism pattern. In addition, 6-NH₂F significantly relaxed the contraction induced by KCl and CaCl₂, suggesting a potential calcium channel blockade, which was corroborated by in silico molecular docking that was used to approximate the mode of interaction with the L-type Ca²⁺ channel, where 6-NH₂F showed lower affinity energy when compared with nifedipine. Finally, toxicological studies revealed that 6-NH₂F possesses pharmacological safety, since it did not produce any toxic effect in both acute and sub-acute murine models. In conclusion, 6-aminoflavone exerted significant relaxation through calcium channel blockade, and the compound seems to be safe.

Morphology and cyclooxygenase-2 and renin expression in the kidney of young spontaneously hypertensive rats

The kidneys play an important role in blood pressure regulation under normal and pathological conditions. We examined the histological changes and expression patterns of cyclooxygenase-2, renin, and (pro)renin receptor (PRR) in the renal cortex of prehypertensive spontaneously hypertensive rats (SHRs) and Wistar Kyoto rats (WKYs). Moreover, blood pressure and plasma urea, creatinine, angiotensin II, and angiotensin (1-7) levels were measured. The results showed that both strains had similar blood pressure and plasma urea and creatinine levels. The glomerular area, basement membrane thickness, collagen fiber content, and arterial wall thickness were greater in SHRs than in WKYs. By immunohistochemistry, cyclooxygenase-2 was localized in the macula densa and renal tubules of both strains. In SHRs, cyclooxygenase-2 was detected in a larger number of tubules, and the cortical expression of cyclooxygenase-2 was also increased. In both strains, PRR and renin were localized in the tubular epithelium and juxtaglomerular cells, respectively. In SHRs, PRR immunolocalization was increased in the glomerulus. The cortical expression of immature renin was markedly increased in SHRs compared to that in WKYs, while renin was significantly decreased. These changes were associated with higher plasma angiotensin II levels and lower plasma angiotensin (1-7) levels in SHRs. The results indicate that the kidneys of SHRs showed morphological changes and variations in cortical expression patterns of PRR, cyclooxygenase-2, and renin before the development of hypertension.

Antihypertensive and vasorelaxant effect of leucodin and achillin isolated from Achillea millefolium through calcium channel blockade and NO production: In vivo, functional ex vivo and in silico studies

ETHNOPHARMACOLOGICAL RELEVANCE

Achillea millefolium L. (Asteraceae), known as yarrow (milenrama), is a plant used in Mexican traditional medicine for the treatment of hypertension, diabetes, and related diseases.

AIM

To determine the vasorelaxant and antihypertensive effect of A. millefollium and to isolate the main bioactive antihypertensive agents.

MATERIALS AND METHODS

Organic (hexane, dichloromethane and methanol) and hydro-alcohol (Ethanol-H2O: 70:30) extracts obtained from flowers, leaves and stems were evaluated on isolated aorta rat rings with and without endothelium to determine their vasorelaxant effect. Hexane extract from flowers (HEAmF) was studied to evaluate its antihypertensive effect on spontaneously hypertensive rats (SHR). From HEAmF, bioactive compounds were obtained by bio-guided phytochemical separation through chromatography.

RESULTS

Organic extracts showed the best vasorelaxant activity. Hexane extract from flowers was the most potent and efficient ex vivo vasorelaxant agent, showing significant decrease of systolic and diastolic blood pressure in SHR (p < 0.05). Phytochemical separation of HEAmF yielded two epimeric sesquiterpene lactones: leucodin (1) and achillin (2), the major components of the extract. Both 1 and 2 showed similar vasorelaxant action ex vivo (p < 0.05), and their effects where modified by L-NAME (10 μM, nitric oxide synthase inhibitor), by ODQ (1 μM, soluble guanylyl cyclase inhibitor), and also relaxed the contraction induced by KCl (80 mM). Finally, 1 and 2 intragastric administration (50 mg/kg) decreased systolic and diastolic blood pressure in SHR.

CONCLUSIONS

Achillea millefolium showed antihypertensive and vasorelaxant effects, due mainly to leucodin and achillin (epimers). Both compounds showed antihypertensive activity by vasorelaxation putatively by endothelium-dependent NO release and cGMP increase, as well as by calcium channels blockade.

Pharmacological characterization of the cardiovascular effect of Nibethione: ex vivo, in vivo and in silico studies

OBJECTIVE

This work describes the vasorelaxant and antihypertensive effects and the mechanism of action on vascular smooth muscle cells of Nibethione, a synthetic thiazolidinedione derivative. Additionally, evidence of its cytotoxicity is assessed.

METHODS

Nibethione (NB) was synthesized, and its vasorelaxant effect and mechanism of action were assessed through ex vivo experiments. Molecular docking studies were used to predict the mode of interaction with L-type Ca²⁺ channel, and in vivo antihypertensive activity was assayed on spontaneously hypertensive rats (SHR). The cytotoxicity potential was evaluated in porcine aortic endothelial cells (PAECs) from primary explants.

KEY FINDINGS

Nibethione vasorelaxant effect was efficient on KCl (80 mm) and NE-contraction. This effect was deleteriously modified in the presence of potassium channel block drugs, while the maximal contraction induced with NE was significantly decreased by NB; the CaCl₂ -induced contraction was abolished entirely. In vivo experiments showed that NB decreased diastolic blood pressure in 20.3 % after its administration on SHR. The molecular docking showed that NB blocks L-type Ca²⁺ channel, and in vitro tests showed that NB did not produce cytotoxic activity on PAECs (IC₅₀ >1000 µm).

CONCLUSIONS

Nibethione showed in vivo antihypertensive and ex vivo vasorelaxant effects with implication of voltage-dependent L-type Ca²⁺ channel blocking, and this may contribute to the research of novel antihypertensive drugs.

Tracheal relaxation through calcium channel blockade of Achillea millefolium hexanic extract and its main bioactive compounds

ETHNOPHARMACOLOGICAL IMPORTANCE

Achillea millefolium L. (Asteraceae) is used for the treatment of respiratory diseases, diabetes, and hypertension.

AIM

to explore its tracheal relaxant properties and clarify its functional mechanism of action on smooth muscle cells, which allow us to propose it as a potential anti-asthmatic drug.

MATERIAL AND METHODS

organic and hydro-alcoholic extracts from A. millefolium were obtained by macerations, then their relaxing effect on ex vivo isolated rat trachea rings was determined. Most active extract (hexanic extract, EHAm) was studied to determine its functional mechanism of action using synergic, antagonist and inhibitor agents related with the contraction/relaxation process of the smooth muscle. Also, EHAm was subjected to bio-guided fractionation by open-column chromatography (on silica gel) using cyclohexane-EtOAc (80:20) in an isocratic way to isolate main bioactive compounds.

RESULTS

organic and hydro-alcoholic extracts showed relaxant effect in a concentration-response dependent manner, being EHAm the most active. The functional mechanism of action indicates that EHAm induced a non-competitive antagonism to the muscarinic receptors ; in addition, the NO/cGMP pathway is involved in the relaxation process of the tracheal smooth muscle. However, the most important mechanism of action showed by EHAm was related with the calcium channel blockade influx into the smooth muscle cells. On the other hand, epimeric sesquiterpene lactones leucodin (1) and achillin (2) were isolated and purified, which are responsible for the observed smooth muscle relaxant activity of the extract.

CONCLUSION

hexanic extract of A. millefollium induced a significant relaxant effect on tracheal rat rings by calcium channel blockade and NO release.

Bioactivity of an antihypertensive peptide expressed in Chlamydomonas reinhardtii

In this study, we developed a transplastomic C. reinhardtii strain that accumulates anti-hypertensive peptides. Tandem repeats of VLPVP peptide were included. PCR analysis confirmed the presence of the transgene in the modified strains. After in vitro digestion of biomass of a recombinant C. reinhardtii strain the VLVPV peptide was identified and quantified by HPLC. The highest expression line produced 0.292mg of recombinant protein per mg of freeze-dried biomass. Intragastric administration of the genetically modified strain to spontaneous hypertensive rats at a dose of 30mg/kg of body weight of recombinant protein significantly reduced systolic blood pressure. At the same dose, the recombinant protein exerts an ACE-inhibitory effect. This is the first study that indicates the potential of this microalga producing an antihypertensive peptide as a dietary supplement for hypertension patients.

Regulación de la liberación de renina durante la hipertensión renovascular

La hipertensión es un síndrome cardiovascular progresivo que surge de etiologías complejas e interrelacionadas. Los marcadores tempranos del síndrome a menudo están presentes antes de que la elevación de la presión sanguínea sea observada. El desarrollo de la hipertensión arterial se asocia con anomalías cardíacas y vasculares funcionales y estructurales que dañan el corazón, los riñones, el cerebro, los vasos, y otros órganos, y conducen a la morbilidad y muerte prematura. El sistema renina angiotensina y los riñones son los principales mecanismos que subyacen para el desarrollo de la hipertensión. La renina es la enzima limitante para la síntesis de la angiotensina II; la liberación de renina está regulada por mecanismos como el barorreceptor intrarrenal, la mácula densa (MD) y el sistema nervioso simpático. Desde la MD son liberadas prostaglandinas vasodilatadoras (PG) como PGI2 y PGE2, generadas por la ciclooxigenasa 2, que inducen la liberación de renina de las células yuxtaglomerulares. En esta revisión, mostramos los mecanismos interrelacionados entre la ciclooxigenasa 2 de la MD y la angiotensina II renal.

Vascular endothelial function is improved by oral glycine treatment in aged rats

Glycine has been used to reduce oxidative stress and proinflammatory mediators in some metabolic disorders; however, its effect on the vasculature has been poorly studied. The aim of this work was to explore the effect of glycine on endothelial dysfunction in aged rats. Aortic rings with intact or denuded endothelium were obtained from untreated or glycine-treated male Sprague-Dawley rats at 5 and 15 months of age. Concentration-response curves to phenylephrine (PHE) were obtained from aortic rings incubated with N(G)-nitro-l-arginine methyl ester (l-NAME), superoxide dismutase (SOD), indomethacin, SC-560, and NS-398. Aortic mRNA expression of endothelial nitric oxide synthase (eNOS), NADPH oxidase 4 (NOX-4), cyclooxygenase 1 (COX-1), cyclooxygenase 2 (COX-2), tumour necrosis factor (TNF)-α, and interleukin-1 β was measured by real time RT-PCR. The endothelial modulation of the contraction by PHE was decreased in aortic rings from aged rats. Glycine treatment improved this modulator effect and increased relaxation to acetylcholine. Glycine augmented the sensitivity for PHE in the presence of l-NAME and SOD. It also reduced the contraction by incubation with indomethacin, SC-560, and NS-398. Glycine increased the mRNA expression of eNOS and decreased the expression of COX-2 and TNF-α. Glycine improved the endothelium function in aged rats possibly by enhancing eNOS expression and reducing the role of superoxide anion and contractile prostanoids that increase the nitric oxide bioavailability.

Early co-expression of cyclooxygenase-2 and renin in the rat kidney cortex contributes to the development of N(G)-nitro-L-arginine methyl ester induced hypertension

We investigated the involvement of cyclooxygenase-2 (COX-2) and the renin-angiotensin system in N(G)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension. Male Wistar rats were treated with L-NAME (75.0 mg·(kg body mass)(-1)·day(-1), in their drinking water) for different durations (1-33 days). COX-2 and renin mRNA were measured using real-time PCR in the renal cortex, and prostanoids were assessed in the renal perfusate, whereas angiotensin II (Ang II) and Ang (1-7) were quantified in plasma. In some rats, nitric oxide synthase inhibition was carried out in conjunction with oral administration of captopril (30.0 mg·kg(-1)·day(-1)) or celecoxib (1.0 mg·kg(-1)·day(-1)) for 2 or 19 days. We found a parallel increase in renocortical COX-2 and renin mRNA starting at day 2 of treatment with L-NAME, and both peaked at 19-25 days. In addition, L-NAME increased renal 6-Keto-PGF(1α) (prostacyclin (PGI2) metabolite) and plasma Ang II from day 2, but reduced plasma Ang (1-7) at day 19. Captopril prevented the increase in blood pressure, which was associated with lower plasma Ang II and increased COX-2-derived 6-Keto-PGF(1α) at day 2 and plasma Ang (1-7) at day 19. Celecoxib partially prevented the increase in blood pressure; this effect was associated with a reduction in plasma Ang II. These findings indicate that renal COX-2 expression increased in parallel with renin expression, renal PGI2 synthesis, and plasma Ang II in L-NAME-induced hypertension.

Semisynthesis, ex vivo evaluation, and SAR studies of coumarin derivatives as potential antiasthmatic drugs

Asthma is a chronic inflammatory disorder that causes contraction in the smooth muscle of the airway and blocking of airflow. Reversal the contractile process is a strategy for the search of new drugs that could be used for the treatment of asthma. This work reports the semisynthesis, ex vivo relaxing evaluation and SAR studies of a series of 18 coumarins. The results pointed that the ether derivatives 1-3, 7-9 and 13-15 showed the best activity (Emax = 100%), where compound 2 (42 μM) was the most potent, being 4-times more active than theophylline (positive control). The ether homologation (methyl, ethyl and propyl) in position 7 or positions 6 and 7 of coumarins lead to relaxing effect, meanwhile formation of esters generated less active compounds than ethers. The SAR analysis showed that it is necessary the presence of two small ether groups and the methyl group at position 4 (site 3) encourage biological activity through soft hydrophobic changes in the molecule, without drastically affecting the cLogP.

Effect of bis-1,4-dihydropyridine in the kidney of diabetic rats

The in vivo effectiveness of 4-dihydropyridine (bis-1,4-DHP), a new calcium-channel blocker, as a nephroprotector in isolated perfused kidney was evaluated by determining its effects on parameters associated with renal injury in diabetic rats. Diabetes in male Wistar rats, control, diabetic, control + bis-1,4-DHP, and diabetic + bis-1,4-DHP, was induced by a single administration of STZ (55 mg·kg(-1), i.p.). In the drug-treated groups, treatment with bis-1,4-DHP (10 mg·kg(-1)·day(-1)) started one week before diabetes induction; bis-1,4-DHP was dissolved in DMSO (0.3%) and suspended in drinking water with carboxymethyl cellulose (3%). Parameters evaluated were body weight, blood glucose, albuminuria, proteinuria, creatinine, urea excretion, kidney's weight / body weight ratio, and kidney perfusion pressure in all rat groups at different times of diabetes (2, 4, 6, and 10 weeks). Kidney weight of diabetic rats significantly increased vs. control, control + bis-1,4-DHP, and diabetic + bis-1,4-DHP rats at different times of diabetes. The ratios % kidney weight / 100 g body weight were different between control, control + bis-1,4-DHP, and diabetic + bis-1,4-DHP rats vs. diabetic rats (P < 0.05). Kidney perfusion pressure was decreased by diabetes, while it was partially recovered by bis-1,4-DHP treatment in response to phenylephrine. Bis-1,4-DHP had a tendency to decrease hyperglycemia vs. diabetic rats, even though glycemia was too high as compared with controls, and it ameliorated albuminuria, creatinine, and urea excretion, suggesting a favorable effect on renal haemodynamics. Bis-1,4-DHP, by inhibiting Ca(2+) entrance, induced vasodilation in renal vascular bed and thus may have a nephroprotective effect against diabetes-induced renal dysfunction, but does not have significant impact on hyperglycemia.

Antihyperglycemic and sub-chronic antidiabetic actions of morolic and moronic acids, in vitro and in silico inhibition of 11β-HSD 1

Morolic (1) and moronic (2) acids are the main constituents of acetonic extract from Phoradendron reichenbachianum (Loranthaceae), a medicinal plant used in Mexico for the treatment of diabetes. The aim of the current study was to establish the sub-acute antidiabetic and antihyperlipidemic effects of compounds 1 and 2 over non insulin-dependent diabetic rat model. Also, to determine the antihyperglycemic action on normoglycemic rats by oral glucose tolerance test. Daily-administered morolic (1) and moronic (2) acids (50 mg/kg) significantly lowered the blood glucose levels at 60% since first day until tenth day after treatment than untreated group (p<0.05). Moreover, analyzed blood samples obtained from diabetic rats indicated that both compounds diminished plasmatic concentration of cholesterol (CHO) and triglycerides (TG), returning them to normal levels (p<0.05). Also, pretreatment with 50 mg/kg of each compound induced significant antihyperglycemic effect after glucose and sucrose loading (2 g/kg) compared with control group (p<0.05). In vitro studies showed that compounds 1 and 2 induced inhibition of 11β-HSD 1 activity at 10 μM. However, in silico analysis of the pentaclyclic triterpenic acids on 11β-HSD 1 revealed that all compounds had high docking scores and important interactions with the catalytic site allowing them to inhibit 11β-HSD 1 enzyme. In conclusion, morolic and moronic acids have shown sustained antidiabetic and antihyperglycemic action possibly mediated by an insulin sensitization with consequent changes of glucose, cholesterol and triglycerides, in part mediated by inhibition of 11β-HSD 1 as indicated by in vitro and in silico studies.

Dose-dependent antihypertensive determination and toxicological studies of tilianin isolated from Agastache mexicana

ETHNOPHARMACOLOGICAL RELEVANCE

Agastache mexicana is used in Mexican traditional medicine for the treatment of hypertension, anxiety and related diseases.

AIM OF THE STUDY

Current work was developed to establish pharmacological/toxicological parameters of tilianin, a flavone extracted from Agastache mexicana in order to propose it for clinical trials.

MATERIALS AND METHODS

Acute and sub-acute toxicology studies in Imprinting Control Region (ICR) mice and median effective dose (ED50) determination in conscious spontaneously hypertensive rats (SHR) were done.

RESULTS

A median lethal dose (LD50) of 6624 mg/kg (6201, 7076) in mice and significant antihypertensive effect (ED50=53.51 mg/kg) in SHR were determined. Moreover, sub-acute oral administration of tilianin did not alter body weight, clinical chemistry parameters (alanine amino-transferase, aspartate amino-transferase, total cholesterol, high density lipoprotein, low density lipoprotein, triglycerides, glucose and insulin), and also did not induce any toxic or adverse effects on kidney, heart, liver, and lung functions.

CONCLUSIONS

We have shown that tilianin, isolated from Agastache mexicana, was not toxic for rodents. Also, its antihypertensive effect was dose-dependent and ED50 (53.51 mg/kg) calculated was lesser than LD50 determined (6624 mg/kg), which suggest a wide range of pharmacology-toxicology patterns. Results support the hypothesis that tilianin must be investigated and developed for clinical trials as antihypertensive drug.

Ex vivo study of the vasorelaxant activity induced by phenanthrene derivatives isolated from Maxillaria densa

The phenanthrenes gymnopusin (1), fimbriol A (2), and erianthridin (3) from Maxillaria densa were found to induce significant relaxant effects in a concentration-dependent and endothelium-independent manner on aortic rings precontracted with norepinephrine (NE, 0.1 μM) and KCl (80 mM). Compound 1 was the most active and also inhibited the cumulative concentration-response contraction of NE or CaCl(2). Contractions induced by FPL 64176, an agonist of L-type voltage-dependent calcium channels, were blocked by 1. The potassium channel blockers glibenclamide and TEA (tetraethylammonium) reduced the relaxations induced by 1. Nevertheless, the effect of 1 was not modified by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a specific soluble guanylate cyclase inhibitor. The functional results obtained suggest that 1 induces relaxation through an endothelium-independent pathway by the control of cationic channels (calcium channel blockade and potassium channel opening) in the myogenic response of rat aortic rings.

Relaxant effects of Artemisia ludoviciana on isolated rat smooth muscle tissues

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia ludoviciana spp. mexicana (Willd. Ex.) Spring D.D. Keck (Asteraceae), known as "estafiate" is employed for the treatment of diarrhea, dysentery, parasites, abdominal pain, vomiting, stomach ache, and also as antispasmodic agent. The aim of the present study was to evaluate the relaxant effect of hexanic (HEAl), dichloromethanic (DEAl) and methanolic (MEAl) extracts on isolated trachea, ileum and aorta rat rings, and to establish the tracheo-relaxant mode of action of DEAl.

MATERIALS AND METHODS

All extracts were investigated based on their capacity of to inhibit the rat ileum spontaneous contraction, to relax contraction induced by noradrenaline (0.1 μM) on endothelium-intact and endothelium-denuded thoracic aorta rat rings, and also to inhibit contraction provoked by carbachol (1 μM) on rat trachea.

RESULTS

Organic extracts had no spasmolytic action on ileum strips compared to positive control (papaverine, p<0.05). On the other hand, all extracts induced a significant concentration- and partial endothelium-dependent vasorelaxant activity. Extracts also showed significant relaxant effect on pre-contracted tracheal tissue in a concentration-dependent manner. In last two experiments, DEAl was the most potent and efficient extract; however, it was less potent than papaverine and theophylline, used as positive controls (p<0.05). In tracheal preparation, DEAl shifted to the right, in a parallel manner, the concentration-response curves induced by carbachol (p<0.05). Also, DEAl induced a significant relaxant effect on the contraction produced by potassium chloride (KCl, 80 mM). Pre-incubation with 1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one (ODQ, 10 μM), indomethacin (10 μM), N(ω)-nitro-L-arginine methyl ester (L-NAME, 10 μM), glibenclamide (10 μM) and 2-aminopyridine (2-AP, 100 μM) did not modify the DEAl-relaxant curves.

CONCLUSIONS

Functional experiments suggest that the most active extract, DEAl, induced its relaxant effect by possible muscarinic receptors antagonism and calcium channel blockade in tracheal rings. On the other hand, significant vasorelaxant activity showed by DEAl is partially endothelium-dependent. Finally, spasmolytic activity induced by the extracts in the rat ileum was not significant, which suggests that the antidiarrheic effect of the plant is related to antimicrobial and antiparasitic properties previously described.

Cochlospermum vitifolium induces vasorelaxant and antihypertensive effects mainly by activation of NO/cGMP signaling pathway

AIM OF THE STUDY

Cochlospermum vitifolium is a medicinal plant used for the treatment of diabetes, hepatobilary and cardiovascular illnesses. The aim of current study was to determine the in vivo antihypertensive and in vitro functional vasorelaxant mechanism of methanol extract of Cochlospermum vitifolium (MECv) and naringenin (NG).

MATERIALS AND METHODS

Test material was assayed on rat isolated aorta rings test with- and without-endothelium to determine their vasorelaxant mechanism. Also, the in vivo antihypertensive effect was evaluated on spontaneously hypertensive rat (SHR) model. In addition, presence of NG into the extract was confirmed by reverse phase high performance liquid chromatography (RP-HPLC) analysis.

RESULTS

MECv (120 mg/kg) and NG (50 and 160 mg/kg) showed acute antihypertensive effects on SHR when systolic and diastolic pressure were decreased at 1 h and 24 h after administration, respectively. Vasorelaxant effect of MECv and NG was shifted to the right when endothelium-intact aortic rings were pre-incubated with L-NAME (10 microM) and ODQ (1 microM). Also, NG relaxant curves were displaced to the right in the presence of tetraethylammonium (TEA, 1 mM) and 2-aminopyridine (2-AP, 100 microM) on endothelium-denuded aortic rings.

CONCLUSION

Experiments described above showed that MECv play an important role in hypertension regulation through NO synthesis and may be PGI(2) production and potassium channel activation on excessive endothelial dysfunction conditions. Unfortunately, presence of NG into the extract is not significant on bioactivity of the extract; however, this compound could be tested and evaluated as structural scaffold for future drug design for development of antihypertensive agents.

Antihypertensive and vasorelaxant effects of tilianin isolated from Agastache mexicana are mediated by NO/cGMP pathway and potassium channel opening

Current investigation was undertaken to elucidate the mode of action of tilianin, isolated from Agastache mexicana, as a vasorelaxant agent on in vitro functional rat thoracic aorta test and to investigate the in vivo antihypertensive effect on spontaneously hypertensive rats (SHR). Tilianin (0.002-933 microM) induced significant relaxation in a concentration- and endothelium-dependent and -independent manners in aortic rings pre-contracted with noradrenaline (NA, 0.1 microM), and serotonin (5-HT, 100 microM). Effect was more significant (p < 0.05) in endothelium-intact (+E) aorta rings than when endothelium was removed(E). Pre-treatment with N-nitro-L-arginine methyl ester (L-NAME; 10 microM) or 1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one (ODQ, 1 microM) produced a significant change of the relaxant response and activity was markedly inhibited, but not by indomethacin (10 microM) or atropine (1 microM). Furthermore, tilianin (130 microM) provoked a significant displacement to the left in the relaxation curve induced by sodium nitroprusside (SNP; 0.32 nM to 0.1 microM). Moreover, tilianin induced significant in vitro NO overproduction (1.49 +/- 0.86 microM of nitrites/g of tissue) in rat aorta compared with vehicle (p < 0.05). In addition, pre-treatment with tetraethylammonium (TEA, 5 mM) and 2-aminopyridine (2-AP, 0.1 microM) shifted to the right the relaxant curve induced by tilianin (p < 0.05). Finally, a single oral administration of tilianin (50 mg/kg) exhibited a significant decrease in systolic and diastolic blood pressures (p < 0.05) in SHR model. Results indicate that tilianin mediates relaxation mainly by an endothelium-dependent manner,probably due to NO release, and also through an endothelium-independent pathway by opening K+ channels, both causing the antihypertensive effect.

Angiotensin II augments renal vasoconstriction via AT1 receptors in L-NAME-induced hypertensive rats

The renal renin angiotensin system modulates blood pressure via the action of angiotensin II at type 1 (AT1) and type 2 (AT2) angiotensin receptors. It has been proposed that there is an increased pressor response to angiotensin II (ANG II) in the hypertensive rat kidney. We determined the role of the AT1 receptor in L-NAME-induced hypertension. Male Wistar rats (250-300 g) were divided into control (tap water) and L-NAME (50 mg/kg/day/2 weeks) treated groups. Concentration-response curves to ANG II were constructed in isolated perfused kidneys and AT1 receptor expression was determined by Western blot in the renal cortex, medulla and papilla. ANG II evoked an increase in perfusion pressure in kidneys of both control and L-NAME-treated rats in a concentration-related manner. In L-NAME-treated rats, a greater maximal effect was observed compared to control rats (160 +/- 13 vs. 138 +/- 8 mmHg; p<0.05, respectively), suggesting that L-NAME promoted ANG II hypersensitivity. In both, control and L-NAME groups, the response to ANG II was blocked by the selective AT1 receptor antagonist losartan (1 x 10(-8) and 3.16 x 10(-8) M). AT1 receptor expression in kidney cortex, medulla and papilla did not show significant differences between groups. Our results demonstrate that AT1 receptor stimulation is related to renal vasculature hypersensitivity in L-NAME-induced hypertension.

Angiotensin II pressor response in the L-NAME-induced hypertensive pithed rat: role of the AT1 receptor

The blockade of renin-angiotensin system by pharmacological interventions with angiotensin converting-enzyme (ACE) inhibitors or AT1 receptor antagonists in the juvenile critical age may attenuate or even prevent the development of hypertension. In this work, we determined the Ang II type 1 (AT1) receptor role in L-NAME-induced hypertension in pithed rats. Male Wistar rats (250-300 g) were used. Rats were divided into the following groups: Control (tap water) and N(omega)-Nitro-L-arginine methyl ester (L-NAME, 60 mg/kg/day/2 weeks). Dose-response curves to Ang II were constructed in the pithed rat. The results show that Ang II evoked blood pressure increase in pithed rats in a dose-related manner. In L-NAME-treated rats a greater maximal effect was observed, indicating that L-NAME promotes Ang II hypersensitivity. In L-NAME-treated rats, Ang II response was blocked by losartan (1 and 3 mg/kg), a selective AT1 receptor antagonist, indicating that AT1 receptor influence L-NAME hypertensive mechanism. Our results suggest that Ang II hypersensitivity in L-NAME-induced hypertension can be due to increased AT1 receptor expression or sensitivity changes.

Antidiabetic activity of N-(6-substituted-1,3-benzothiazol-2-yl)benzenesulfonamides

N-(6-Substituted-1,3-benzothiazol-2-yl)benzenesulfonamide derivatives 1-8 were synthesized and evaluated for their in vivo antidiabetic activity in a non-insulin-dependent diabetes mellitus rat model. Several compounds synthesized showed significant lowering of plasma glucose level in this model. As a possible mode of action, the compounds were in vitro evaluated as 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) inhibitors. The most active compounds (3 and 4) were docked into the crystal structure of 11beta-HSD1. Docking results indicate potential hydrogen bond interactions with catalytic amino acid residues.