L-carnitine added to post-thawed semen acts as an antioxidant and a stimulator of equine sperm metabolism

The objective of this study was to enhance the in vitro sperm quality and in vivo fertility of frozen-thawed equine semen by the addition of l-carnitine (LC) to post-thawed semen. Different concentrations of LC were added to thawed samples to obtain four treatments control and 0.5, 1 and 2 mM LC. In the in vitro experiments, sperm motility and kinematics, membrane integrity and intracellular calcium ion concentration ([Ca²⁺ ]_i ) were investigated, and the antioxidant bioactivity of LC was assessed by measuring hydrogen peroxide and nitrite concentrations (NO₂ ^- ). The fertility rate was assessed via the artificial insemination of mares. The treatment with 1 mM LC increased sperm [Ca²⁺ ]_i (60.6 ± 0.05 AU), reduced nitrite concentration (39.1 ± 14.9 µM/µg protein), increased the sperm straightness percentage (STR: 78.3 ± 5.3%) and increased the pregnancy rate (75%) as compared to the control ([Ca²⁺ ]_i 48.4 ± 0.05 AU, NO₂ ^- concentration 63.1 ± 14.4 µM/µg protein, STR 67.5 ± 7.9%, 12.5% pregnancy rate, p < 0.05). These results suggest that 1 mM LC acts as an antioxidant and stimulator of sperm metabolism in post-thawed equine semen, increasing the fertility rate. Thus, addition of LC might be an alternative to improve the fertility of poor quality post-thawed equine semen.

Addition of caffeine to equine thawed sperm increases motility and decreases nitrite concentration

The aim of this study was to improve the quality of frozen-thawed equine sperm by the addition of caffeine to it. Semen from nine stallions was frozen and different concentrations of caffeine (3, 5 and 7.5 mM) were added to frozen-thawed semen. The sperm kinetic parameters, membrane functionality and integrity, and acrosome integrity and spontaneous acrosome reacted sperm were evaluated with a computer-assisted sperm analysis, a hypoosmotic swelling test and epifluorescent microscopy, respectively. Nitrite and hydroperoxide concentrations of frozen-thawed semen were measured using spectrophotometry. Sperm fertility was evaluated by artificial insemination (AI) of 16 mares with thawed ejaculates (control and 5 mM caffeine-treated groups). Compared to that in the control, the addition of 5 mM caffeine induced an increase in sperm motility (38.9 ± 2.8 versus 32.6 ± 3.4%), and a decrease in nitrite concentration (11.4 ± 2.1 versus 12.8 ± 2.9 µM/µg protein, p < .05). Moreover, the pregnancy rate from AI in the caffeine group was significantly higher (62.5%) than that in the control group (12.5%). These data suggest that caffeine reduced the nitrite concentration and enhanced sperm motility in thawed equine sperm, thus increasing the fertility rate in mares inseminated with caffeine-treated equine semen.

Lactoferrin increases sperm membrane functionality of frozen equine semen

During cryopreservation, sperm was submitted to an increase in reactive oxygen species generation. This work aimed to improve the quality of frozen equine sperm after the addition of antioxidants lactoferrin (Lf) and catalase (Cat) to a freezing extender. Semen from six stallions was frozen with the extenders: F1) control, INRA 82 freezing extender, F2) F1 + 500 μg/ml Lf and F3) F1 + 200 IU/ml Cat. After thawing, sperm motility parameters, membrane functionality and integrity, and acrosome integrity and spontaneous acrosome-reacted sperm were evaluated with a computer-assisted sperm analysis, a hypoosmotic swelling test and epifluorescent microscopy, respectively. Nitrite, hydroperoxide and iron concentrations of frozen semen were measured with spectrophotometry. The percentage of functional membrane sperm treated with Lf was higher (50.7% ± 11.6%) compared to that of the control (37.6% ± 15.6%), while the iron (61.4 ± 11.6 vs 73.3 ± 13.8 mg/dl) and nitrite concentrations (16.3 ± 7.1 vs 25.9 ± 4.2 μM/μg protein) were lower, respectively (p < .05). Thus, it can be suggested that Lf protect stallion spermatozoon during freezing as it has increased the percentage of sperm with functional membrane and decreased the lipid oxidant agents.

Mas receptor overexpression increased Ang-(1-7) relaxation response in renovascular hypertensive rat carotid

Renin-angiotensin system (RAS) is an important factor in the pathophysiology of hypertension. Mas receptor, Angiotensin-(1-7) [Ang-(1-7)]-activated receptor, is an important RAS component and exerts protective effects in the vasculature. Ang-(1-7) vascular effects and Mas receptor expression in carotid from renovascular hypertensive (2K-1C) rats is not clear. In the present study we investigated Mas receptor vasodilator response activated by Ang-(1-7) in the carotid rings from sham and 2K-1C rats. Changes in isometric tension were recorded on organ chamber. Mas receptors expression was investigated in carotid by Western blot. Nitric oxide production was evaluated by 2,3-diaminonaphthalene (DAN) and eNOS expression and activity by immunofluoresce and western blot, respectively. Ang-(1-7) induced concentration-dependent vasodilator effect in carotid rings from sham and 2K-1C, which the hypertension increased vasodilatation response. In the 2K-1C carotid rings, A-779 (Mas receptor antagonist) reduced but not abolish the vasodilator effect of Ang-(1-7). Corroborating, Mas receptor protein expression was significantly increased in the 2K-1C rats. L-NAME and ibuprofen decreased Ang-(1-7) vasodilator response and L-NAME plus ibuprofen practically abolish the remaining vasodilatation response. Nitric oxide production is increased due increased of eNOS expression and pSer(1177) activity. Our results demonstrated that renovascular hypertension increased Mas receptors expression and nitric oxide production in the rats carotid which, consequently increased Ang-(1-7)-vasorelaxant response.

Decreased production of neuronal NOS-derived hydrogen peroxide contributes to endothelial dysfunction in atherosclerosis

BACKGROUND AND PURPOSE

Reduced NO availability has been described as a key mechanism responsible for endothelial dysfunction in atherosclerosis. We previously reported that neuronal NOS (nNOS)-derived H(2)O(2) is an important endothelium-derived relaxant factor in the mouse aorta. The role of H(2)O(2) and nNOS in endothelial dysfunction in atherosclerosis remains undetermined. We hypothesized that a decrease in nNOS-derived H(2)O(2) contributes to the impaired vasodilatation in apolipoprotein E-deficient mice (ApoE(-/-)).

EXPERIMENTAL APPROACH

Changes in isometric tension were recorded on a myograph; simultaneously, NO and H(2)O(2) were measured using carbon microsensors. Antisense oligodeoxynucleotides were used to knockdown eNOS and nNOS in vivo. Western blot and confocal microscopy were used to analyse the expression and localization of NOS isoforms.

KEY RESULTS

Aortas from ApoE(-/-) mice showed impaired vasodilatation paralleled by decreased NO and H(2)O(2) production. Inhibition of nNOS with L-Arg(NO2) -L-Dbu, knockdown of nNOS and catalase, which decomposes H(2)O(2) into oxygen and water, decreased ACh-induced relaxation by half, produced a small diminution of NO production and abolished H(2)O(2) in wild-type animals, but had no effect in ApoE(-/-) mice. Confocal microscopy showed increased nNOS immunostaining in endothelial cells of ApoE(-/-) mice. However, ACh stimulation of vessels resulted in less phosphorylation on Ser852 in ApoE(-/-) mice.

CONCLUSIONS AND IMPLICATIONS

Our data show that endothelial nNOS-derived H(2)O(2) production is impaired and contributes to endothelial dysfunction in ApoE(-/-) aorta. The present study provides a new mechanism for endothelial dysfunction in atherosclerosis and may represent a novel target to elaborate the therapeutic strategy for vascular atherosclerosis.

Hancornia speciosa Gomes induces hypotensive effect through inhibition of ACE and increase on NO

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Hancornia speciosa Gomes are popularly used in Brazil to treat diabetes and hypertension. Cardiovascular diseases are the main cause of death worldwide and their incidences are increasing in Brazilian population. The present study aimed to investigate the hypotensive effect and the mechanism of action of Hancornia speciosa Gomes.

METHODS

A fraction of the ethanolic extract of leaves from Hancornia speciosa (SFH) was obtained and standardized by its content on rutin, bornesitol and quinic acid. Systolic blood pressure (SBP) of normotensive mice was measured by tail plethysmography. SFH was given orally and SBP was monitored for 5h. Angiotensin-converting enzyme (ACE) inhibitor activity of SFH (1mg/kg) or captopril (10mg/kg) was measured by colorimetric methods. Serum nitrite levels were measured by spectrophotometry.

RESULTS

SFH induced a dose-dependent hypotensive effect in normotensive mice. The serum activity of ACE and the level of angiotensin II were significantly reduced by SFH and by captopril. Administration of SFH induced a significant increase on plasmatic level of nitrites and the systemic inhibition of nitric oxide synthase by L-NAME (20mg/kg) reduced the hypotensive effect of SFH.

CONCLUSIONS

The present work demonstrated that Hancornia speciosa has a potent hypotensive effect in normotensive mice. The inhibition of ACE leading to reduction on angiotensin II and increase on NO levels might account for the hypotensive effect. These results support the use of Hancornia speciosa by traditional medicine as antihypertensive.

Phosphatidylinositol 3-kinase-δ up-regulates L-type Ca2+ currents and increases vascular contractility in a mouse model of type 1 diabetes

BACKGROUND AND PURPOSE

Vasculopathies represent the main cause of morbidity and mortality in diabetes. Vascular malfunctioning in diabetes is associated with abnormal vasoconstriction and Ca(2+) handling by smooth muscle cells (SMC). Phosphatidylinositol 3-kinases (PI3K) are key mediators of insulin action and have been shown to modulate the function of voltage-dependent L-type Ca(2+) channels (Ca(V) 1.2). In the present work, we investigated the involvement of PI3K signalling in regulating Ca(2+) current through Ca(V) 1.2 (I(Ca,L) ) and vascular dysfunction in a mouse model of type I diabetes.

EXPERIMENTAL APPROACH

Changes in isometric tension were recorded on myograph. Ca(2+) currents in freshly dissociated mice aortic SMCs were measured using the whole-cell patch-clamp technique. Antisense techniques were used to knock-down the PI3Kδ isoform. KEY RESULTS Contractile responses to phenylephrine and KCl were strongly enhanced in diabetic aorta independent of a functional endothelium. The magnitude of phenylephrine-induced I(Ca,L) was also greatly augmented. PI3Kδ expression, but not PI3Kα, PI3Kβ, PI3Kγ, was increased in diabetic aortas and treatment of vessels with a selective PI3Kδ inhibitor normalized I(Ca,L) and contractile response of diabetic vessels. Moreover, knock-down of PI3Kδin vivo decreased PI3Kδ expression and normalized I(Ca,L) and contractile response of diabetic vessels ex vivo.

CONCLUSIONS AND IMPLICATIONS

Phosphatidylinositol 3-kinase δ was essential to the increased vascular contractile response in our model of type I diabetes. PI3Kδ signalling was up-regulated and most likely accounted for the increased I(Ca,L,) leading to increased vascular contractility. Blockade of PI3Kδ may represent a novel therapeutic approach to treat vascular dysfunction in diabetic patients.

Mechanism of the vasodilator effect of Euxanthone in rat small mesenteric arteries

In the present work we investigated the mechanism involved in the vasodilator effect induced by euxanthone in rat small mesenteric arteries. We observed that euxanthone induced concentration-dependent vasodilatation in arteries by a mechanism independent on the release of endothelial factors, such as nitric oxide (NO) and cyclooxygenase-derived factors. In addition our results also suggest that euxanthone induced its vasodilator effect through inhibition of calcium-sensitive mechanisms activated by protein kinase C, rather than by inhibition of contractions dependent on the release of the intracellular calcium stores or by inhibition of voltage-operated calcium channels.

ACE inhibition by astilbin isolated from Erythroxylum gonocladum (Mart.) O.E. Schulz

Erythroxylum species have several traditional uses in different countries, including the treatment of hypertension. The ethanol extract from E. gonocladum aerial parts, a species endemic to the Brazilian cerrado, elicited a concentration-dependent inhibition of angiotensin converting enzyme (ACE) (pIC(50)=4.53+/-0.05). Extract fractionation led to the isolation of two compounds, whose structures were assigned by spectrometric data as astilbin and beta-sitosterol, along with a mixture of palmitic, stearic and linolenic acids. This is the first report on the occurrence of these compounds on E. gonocladum. Astilbin promoted significant ACE inhibition in vitro (pIC(50)=5.86+/-0.33) and its activity did not differ from captopril, when both compounds were assayed at 10 microM concentration.

Neuronal nitric oxide synthase-derived hydrogen peroxide is a major endothelium-dependent relaxing factor

Endothelium-dependent vasorelaxation in large vessels is mainly attributed to Nomega-nitro-L-arginine methyl ester (L-NAME)-sensitive endothelial nitric oxide (NO) synthase (eNOS)-derived NO production. Endothelium-derived hyperpolarizing factor (EDHF) is the component of endothelium-dependent relaxations that resists full blockade of NO synthases (NOS) and cyclooxygenases. H2O2 has been proposed as an EDHF in resistance vessels. In this work we propose that in mice aorta neuronal (n)NOS-derived H2O2 accounts for a large proportion of endothelium-dependent ACh-induced relaxation. In mice aorta rings, ACh-induced relaxation was inhibited by L-NAME and Nomega-nitro-L-arginine (L-NNA), two nonselective inhibitors of NOS, and attenuated by selective inhibition of nNOS with L-ArgNO2-L-Dbu-NH2 2TFA (L-ArgNO2-L-Dbu) and 1-(2-trifluoromethylphehyl)imidazole (TRIM). The relaxation induced by ACh was associated with enhanced H2O2 production in endothelial cells that was prevented by the addition of L-NAME, L-NNA, L-ArgNO2-L-Dbu, TRIM, and removal of the endothelium. The addition of catalase, an enzyme that degrades H2O2, reduced ACh-dependent relaxation and abolished ACh-induced H2O2 production. RT-PCR experiments showed the presence of mRNA for eNOS and nNOS but not inducible NOS in mice aorta. The constitutive expression of nNOS was confirmed by Western blot analysis in endothelium-containing vessels but not in endothelium-denuded vessels. Immunohistochemistry data confirmed the localization of nNOS in the vascular endothelium. Antisense knockdown of nNOS decreased both ACh-dependent relaxation and ACh-induced H2O2 production. Antisense knockdown of eNOS decreased ACh-induced relaxation but not H2O2 production. Residual relaxation in eNOS knockdown mouse aorta was further inhibited by the selective inhibition of nNOS with L-ArgNO2-L-Dbu. In conclusion, these results show that nNOS is constitutively expressed in the endothelium of mouse aorta and that nNOS-derived H2O2 is a major endothelium-dependent relaxing factor. Hence, in the mouse aorta, the effects of nonselective NOS inhibitors cannot be solely ascribed to NO release and action without considering the coparticipation of H2O2 in mediating vasodilatation.

Tx2-6 toxin of the Phoneutria nigriventer spider potentiates rat erectile function

The venom of the spider Phoneutria nigriventer contains several toxins that have bioactivity in mammals and insects. Accidents involving humans are characterized by various symptoms including penile erection. Here we investigated the action of Tx2-6, a toxin purified from the P. nigriventer spider venom that causes priapism in rats and mice. Erectile function was evaluated through changes in intracavernosal pressure/mean arterial pressure ratio (ICP/MAP) during electrical stimulation of the major pelvic ganglion (MPG) of normotensive and deoxycorticosterone-acetate (DOCA)-salt hypertensive rats. Nitric oxide (NO) release was detected in cavernosum slices with fluorescent dye (DAF-FM) and confocal microscopy. The effect of Tx2-6 was also characterized after intracavernosal injection of a non-selective nitric oxide synthase (NOS) inhibitor, L-NAME. Subcutaneous or intravenous injection of Tx2-6 potentiated the elevation of ICP/MAP induced by ganglionic stimulation. L-NAME inhibited penile erection and treatment with Tx2-6 was unable to reverse this inhibition. Tx2-6 treatment induced a significant increase of NO release in cavernosum tissue. Attenuated erectile function of DOCA-salt hypertensive rats was fully restored after toxin injection. Tx2-6 enhanced erectile function in normotensive and DOCA-salt hypertensive rats, via the NO pathway. Our studies suggest that Tx2-6 could be important for development of new pharmacological agents for treatment of erectile dysfunction.

Endothelium-dependent vasodilation induced by Hancornia speciosa in rat superior mesenteric artery

The vasodilator effect of the ethanolic extract of leaves from Hancornia speciosa Gomes (HSE) was evaluated in superior mesenteric artery rings. HSE produced a concentration-dependent vasodilation (IC50 = 10.8 +/- 4.0 microg/mL) in arterial rings pre-contracted with phenylephrine, which was completely abolished in endothelium-denuded vessels. Endothelium-dependent vasodilation induced by HSE was strongly reduced by L-NAME (100 microM), a nitric oxide (NO) synthase inhibitor, but neither by atropine, a muscarinic receptor antagonist (1 microM), nor by indomethacin (10 microM), a cyclooxygenase inhibitor. In rings pre-contracted with 80 mM KCl, the vasodilator effect of HSE was shifted to the right and was completely abolished in the presence of L-NAME (100 microM). Similar effects were obtained in mesenteric rings pre-contracted with phenylephrine in the presence of KCl 25 mM alone or in addition to 100 microM L-NAME. In addition, BaCl2 (1 mM) dramatically reduced the vasodilation induced by HSE. Together, these findings led us to conclude that HSE induces an endothelium-dependent vasodilation in rat mesenteric artery, by a mechanism dependent on NO, on the activation of potassium channels and endothelium-derived hyperpolarizing factor release. Rutin, identified as a major peak in the HPLC fingerprint obtained for HSE, might contribute for the observed vasodilator effect, since it was able to induce an endothelium-dependent vasodilation in rat superior mesenteric arteries.

Endothelial dysfunction and compromised eNOS/Akt signaling in the thoracic aorta during the progression of Marfan syndrome

BACKGROUND AND PURPOSE

Aortic complications account for the major mortality in Marfan syndrome (MFS), a connective tissue disorder caused by mutations in FBN1 encoding fibrillin-1. We hypothesized that MFS impaired endothelial function and nitric oxide (NO) production in the aorta.

EXPERIMENTAL APPROACH

Mice (at 3, 6, 9 and 12 months of age) heterozygous for the Fbn1 allele encoding a cysteine substitution (Fbn1 (C1039G/+), Marfan mice, n=75), the most common class of mutation in MFS, were compared with age-matched control littermates (n=75). Thoracic and abdominal aortas from the two groups were studied.

KEY RESULTS

Isometric force measurements revealed that relaxation to ACh (but not to sodium nitroprusside) was diminished in the phenylephrine-precontracted Marfan thoracic aorta at 6 months of age (pEC(50)=6.12+/-0.22; maximal response, E(max)=52.7+/-6.8%; control: pEC(50)=7.34+/-0.19; E(max)=84.8+/-2.2%). At one year, both inhibition of NO production with N(omega)-nitro-L-arginine methyl ester, or denudation of endothelium increased the phenylephrine-stimulated contraction in the control thoracic aorta by 35%, but had no effect in the Marfan aorta, indicating a loss of basal NO production in the Marfan vessel. From 6 months, a reduced phosphorylation of endothelial NOS (eNOS)(Ser1177) and Akt(Thr308) detected by Western blotting was observed in the Marfan thoracic aorta, which was accompanied by decreased levels of cGMP. Expressions of Akt and eNOS in the abdominal aorta were not different between the two groups.

CONCLUSIONS AND IMPLICATIONS

MFS impairs endothelial function and signaling of NO production in the thoracic aorta, suggesting the importance of NO in the age-related progression of thoracic aortic manifestations.

Evidence for a new angiotensin-(1-7) receptor subtype in the aorta of Sprague-Dawley rats

We have recently described, in the mouse aorta, the vasodilator effect of angiotensin-(1-7) (Ang-(1-7)) was mediated by activation of the Mas Ang-(1-7) receptor and that A-779 and D-Pro7-Ang-(1-7) act as Mas receptor antagonists. In this work we show pharmacological evidence for the existence of a different Ang-(1-7) receptor subtype mediating the vasodilator effect of Ang-(1-7) in the aorta from Sprague-Dawley (SD) rats. Ang-(1-7) induced an endothelium-dependent vasodilator effect in aortic rings from SD rats which was inhibited by removal of the endothelium and by L-NAME (100 microM) but not by indomethacin (10 microM). The Ang-(1-7) receptor antagonist D-Pro7-Ang-(1-7) (0.1 microM) abolished the vasodilator effect of the peptide. However, the other specific Ang-(1-7) receptor antagonist, A-779 in concentrations up to 10 microM, did not affect vasodilation induced by Ang-(1-7). The Ang II AT1 and AT2 receptors antagonists CV11974 (0.01 microM) and PD123319 (1 microM), respectively, the bradykinin B2 receptor antagonist HOE 140 (1 microM) and the inhibitor of ACE captopril (10 microM) did not change the effect of Ang-(1-7). Our results show that in the aorta of SD rats, the vasodilator effect of Ang-(1-7) is dependent on endothelium-derived nitric oxide. This effect is mediated by the activation of Ang-(1-7) receptors sensitive to D-Pro7-Ang-(1-7), but not to A-779, which suggests the existence of a different Ang-(1-7) receptor subtype.

Vascular effects of 7-epiclusianone, a prenylated benzophenone from Rheedia gardneriana, on the rat aorta

The vascular effects of 7-epiclusianone on the rat aorta were investigated. In the rat aortic rings with functional endothelia, 7-epiclusianone up to 10microM induced a concentration-dependent vasodilatation of the sustained contractions induced by phenylephrine (0.3microM). At concentrations higher than 10microM, 7-epiclusianone induced a concentration-dependent contraction in the aortic rings. The vasodilator effect of 7-epiclusianone was drastically decreased with L-NAME (100microM) as well as in endothelium-denuded aortic rings. Moreover, indomethacin (10microM) induced a significant shift to the left in the vasodilator but did not modify the vasoconstrictor effect of 7-epiclusianone. In arteries without pre-contraction, 7-epiclusianone (3-100microM) induced concentration-dependent contraction only in endothelium-intact and in the presence of L-NAME (100microM). This effect was inhibited by indomethacin (10microM) and ZM230487 (1microM), selective inhibitors of cyclooxygenase and of 5-lipoxygenase, respectively. We can conclude that at low concentrations 7-epiclusianone induces an endothelium-dependent vasodilator effect in rat aortic rings. At higher concentrations and in conditions where NO synthase was inhibited, 7-epiclusianone induces a vasocontractile effect. Nitric oxide seems to participate in the vasodilatation, while endothelial cyclooxygenase- and 5-lipoxygenase-derived products play a role in the vasoconstrictor effect.

Endothelium-independent vasorelaxant effect of dioclein, a new flavonoid isolated from Dioclea grandiflora, in the rat aorta

We have investigated the endothelium-independent vasorelaxant effect of the new flavonoid dioclein (5,2',5'-trihydroxy-6-7-dimethoxyflavanone) in the rat aorta. In endothelium-denuded vessels, dioclein induced a concentration-dependent relaxation of aortic rings precontracted with noradrenaline (IC50 = 3.5+/-0.89 x 10(-4) M and KCl (IC50 = 5.2+/-1.2 x 10(-4) M). In the absence of extracellular calcium, dioclein reduced the contraction induced by noradrenaline (maximal reduction approximately 33%) but not that induced by caffeine. Dioclein also produced a concentration-dependent inhibition of the sustained contractions induced by the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate in normal (IC50 = 4.0+/-0.2 x 10(-4) M) and Ca2+-free solution (IC50 = 4.0+/-0.3 x 10(-4) M). The results indicate that the endothelium-independent vasorelaxant effect of dioclein may be explained by inhibition of contractions dependent on activation of protein kinase C, voltage-dependent Ca2+ influx and on the release of intracellular Ca2+ stores sensitive to noradrenaline.