Cerebroprotective Effect of 17ß-Estradiol Replacement Therapy in Ovariectomy-Induced Post-Menopausal Rats Subjected to Ischemic Stroke: Role of MAPK/ERK1/2 Pathway and PI3K-Independent Akt Activation.

Despite the overwhelming advances in the understanding of the pathogenesis of stroke, a devastating disease affecting millions of people worldwide, currently there are only a limited number of effective treatments available. Preclinical and clinical studies show that stroke is a sexually dimorphic disorder, affecting males and females differently. Strong experimental evidence indicates that estrogen may play a role in this difference and that exogenous 17ß-estradiol (E2) is neuroprotective against stroke in both male and female rodents. However, the molecular mechanisms by which E2 intervenes in ischemia-induced cell death, revealing these sex differences, remain unclear. The present study was aimed to determine, in female rats, the molecular mechanisms of two well-known pro-survival signaling pathways, MAPK/ERK1/2 and PI3K/Akt, that mediate E2 neuroprotection in response to acute ischemic stroke. E2 pretreatment reduced brain damage and attenuated apoptotic cell death in ovariectomized female rats after an ischemic insult. Moreover, E2 decreased phosphorylation of ERK1/2 and prevented ischemia/reperfusion-induced dephosphorylation of both Akt and the pro-apoptotic protein, BAD. However, MAPK/ERK1/2 inhibitor PD98059, but not the PI3K inhibitor LY294002, attenuated E2 neuroprotection. Thus, these results suggested that E2 pretreatment in ovariectomized female rats modulates MAPK/ERK1/2 and activates Akt independently of PI3K to promote cerebroprotection in ischemic stroke. A better understanding of the mechanisms and the influence of E2 in the female sex paves the way for the design of future successful hormone replacement therapies.

The selective oestrogen receptor modulator, bazedoxifene, mimics the neuroprotective effect of 17ß-oestradiol in diabetic ischaemic stroke by modulating oestrogen receptor expression and the MAPK/ERK1/2 signalling pathway.

Because neuroprotection in stroke should be revisited in the era of recanalisation, the present study analysed the potential neuroprotective effect of the selective oestrogen receptor modulator, bazedoxifene acetate (BZA), in an animal model of diabetic ischaemic stroke that mimics thrombectomy combined with adjuvant administration of a putative neuroprotectant. Four weeks after induction of diabetes (40 mg kg-1 streptozotocin, i.p.), male Wistar rats were subjected to transient middle cerebral artery occlusion (intraluminal thread technique, 60 minutes) and assigned to one of three groups treated with either: vehicle, BZA (3 mg kg-1  day-1 , i.p.) or 17ß-oestradiol (E2 ) (100 µg kg-1  day-1 , i.p.). At 24 hours post-ischaemia-reperfusion, brain damage (neurofunctional score, infarct size and apoptosis), expression of oestrogen receptors (ER)α, ERß and G protein-coupled oestrogen receptor), and activity of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK)1/2 and phosphoinositide 3-kinase/Akt pathways were analysed. At 24 hours after the ischaemic insult, both BZA- and E2 -treated animals showed lower brain damage in terms of improved neurofunctional condition, decreased infarct size and decreased apoptotic cell death. Ischaemia-reperfusion induced a significant decrease in ERα and ERß expression without affecting that of G protein-coupled oestrogen receptor, whereas BZA and E2 reversed such a decrease. The ischaemic insult up-regulated the activity of both the MAPK/ERK1/2 and phosphoinositide 3-kinase/Akt pathways; BZA and E2 attenuated the increased activity of the ERK1/2 pathway, without affecting that of the Akt pathway. The results of the present study lend further support to the consideration of BZA as an effective and safer alternative overcoming the drawbacks of E2 with respect to improving diabetic ischaemic stroke outcome after successful reperfusion.

Molecular mechanisms underlying the neuroprotective role of atrial natriuretic peptide in experimental acute ischemic stroke.

Along with its role in regulating blood pressure and fluid homeostasis, the natriuretic peptide system could be also part of an endogenous protective mechanism against brain damage. We aimed to assess the possibility that exogenous atrial natriuretic peptide (ANP) could protect against acute ischemic stroke, as well as the molecular mechanisms involved. Three groups of rats subjected to transient middle cerebral artery occlusion (tMCAO, intraluminal filament technique, 60 min) received intracerebroventricular vehicle, low-dose ANP (0.5 nmol) or high-dose ANP (2.5 nmol), at 30 min reperfusion. Neurofunctional condition, and brain infarct and edema volumes were measured at 24 h after tMCAO. Apoptotic cell death and expression of natriuretic peptide receptors (NPR-A and NPR-C), K+ channels (KATP, KV and BKCa), and PI3K/Akt and MAPK/ERK1/2 signaling pathways were analyzed. Significant improvement in neurofunctional status, associated to reduction in infarct and edema volumes, was shown in the high-dose ANP group. As to the molecular mechanisms analyzed, high-dose ANP: 1) reduced caspase-3-mediated apoptosis; 2) did not modify the expression of NPR-A and NPR-C, which had been downregulated by the ischemic insult; 3) induced a significant reversion of ischemia-downregulated KATP channel expression; and 4) induced a significant reversion of ischemia-upregulated pERK2/ERK2 expression ratio. In conclusion, ANP exerts a significant protective role in terms of both improvement of neurofunctional status and reduction in infarct volume. Modulation of ANP on some molecular mechanisms involved in ischemia-induced apoptotic cell death (KATP channels and MAPK/ERK1/2 signaling pathway) could account, at least in part, for its beneficial effect. Therefore, ANP should be considered as a potential adjunctive neuroprotective agent improving stroke outcome after successful reperfusion interventions.

Diabetes modifies the role of prostanoids and potassium channels which regulate the hypereactivity of the rabbit renal artery to BNP.

Diabetic nephropathy is associated with increased risk of cardiovascular disease. B-type natriuretic peptide (BNP) plays an important role in cardiovascular pathophysiology and therapeutics. The aim of the present study was to investigate the influence of experimental diabetes on the mechanisms that regulate the relaxant response of the rabbit renal artery to BNP. Arterial relaxations to BNP were enhanced in diabetic rabbits. Indomethacin enhanced BNP-induced relaxation in control rabbits but showed no effect in diabetic rabbits. BNP-induced release of thromboxane A2 or prostacyclin was not different in both groups of animals. Iberiotoxin had no effect on relaxations to BNP in both groups of animals. Charybdotoxin displaced to the right the concentration-response curve to BNP in both group of animals, and inhibited BNP-induced relaxation only in diabetic rabbits. Glibenclamide did not modify the BNP-induced relaxations in control rabbits, but inhibited it in diabetic rabbits. These results suggest that diabetes induces hypereactivity of the rabbit renal artery to BNP by mechanisms that at least include (1) a reduced vasoconstrictor influence of arachidonic acid metabolites via cyclooxygenase 2, which is not related with changes in thromboxane A2 and prostacyclin release from the arterial wall and (2) a selectively increased modulatory activity of KATP and endothelial IKCa channels.

Iron-loaded transferrin (Tf) is detrimental whereas iron-free Tf confers protection against brain ischemia by modifying blood Tf saturation and subsequent neuronal damage.

Despite transferrin being the main circulating carrier of iron in body fluids, and iron overload conditions being known to worsen stroke outcome through reactive oxygen species (ROS)-induced damage, the contribution of blood transferrin saturation (TSAT) to stroke brain damage is unknown. The objective of this study was to obtain evidence on whether TSAT determines the impact of experimental ischemic stroke on brain damage and whether iron-free transferrin (apotransferrin, ATf)-induced reduction of TSAT is neuroprotective. We found that experimental ischemic stroke promoted an early extravasation of circulating iron-loaded transferrin (holotransferrin, HTf) to the ischemic brain parenchyma. In vitro, HTf was found to boost ROS production and to be harmful to primary neuronal cultures exposed to oxygen and glucose deprivation. In stroked rats, whereas increasing TSAT with exogenous HTf was detrimental, administration of exogenous ATf and the subsequent reduction of TSAT was neuroprotective. Mechanistically, ATf did not prevent extravasation of HTf to the brain parenchyma in rats exposed to ischemic stroke. However, ATf in vitro reduced NMDA-induced neuronal uptake of HTf and also both the NMDA-mediated lipid peroxidation derived 4-HNE and the resulting neuronal death without altering Ca2+-calcineurin signaling downstream the NMDA receptor. Removal of transferrin from the culture media or blockade of transferrin receptors reduced neuronal death. Together, our data establish that blood TSAT exerts a critical role in experimental stroke-induced brain damage. In addition, our findings suggest that the protective effect of ATf at the neuronal level resides in preventing NMDA-induced HTf uptake and ROS production, which in turn reduces neuronal damage.

Mechanisms involved in the increased sensitivity of the rabbit basilar artery to atrial natriuretic peptide in diabetes.

Atrial natriuretic peptide (ANP) is a vasodilator with significant regional differences and controversial effects in the cerebral circulation, a vascular bed particularly prone to diabetes-induced complications. The present study has investigated how alloxan-induced diabetes modifies the mechanisms involved in the response of the rabbit basilar artery to ANP. ANP (10-12-10-7M) relaxed precontracted basilar arteries, with higher potency in diabetic than in control rabbits. In arteries from both groups of animals, endothelium removal reduced ANP-induced relaxations. Inhibition of NO-synthesis attenuated ANP-induced relaxation but this attenuation was lower in diabetic than in control rabbits. In control rabbits, indomethacin displaced to the left the concentration-response curve to ANP, without significantly modifying the Emax value. In diabetic rabbits, indomethacin significantly enhanced arterial relaxations to ANP. In KCl-depolarised arteries, relaxation to ANP was almost abolished both in control and in diabetic rabbits. Iberiotoxin inhibited relaxations to ANP in both groups of rabbits. Glibenclamide and 4-aminopyridine inhibited the ANP-induced relaxations more in diabetic than in control rabbits. Basilar arteries from diabetic rabbits showed decreased natriuretic peptide receptor C expression and no changes in natriuretic peptide receptor A, large conductance calcium-activated K+ channels (BKCa), ATP-sensitive K+ channels (KATP) and voltage-sensitive K+ channels (KV) expression. These results suggest that diabetes enhances the sensitivity of the rabbit basilar artery to ANP by mechanisms that at least include reduced expression of natriuretic peptide receptor C, and enhanced activity of KATP and KV channels. Furthermore, diabetes reduces endothelial NO and prostacyclin which mediate arterial relaxation to ANP.

Molecular mechanisms mediating the neuroprotective role of the selective estrogen receptor modulator, bazedoxifene, in acute ischemic stroke: A comparative study with 17ß-estradiol.

As the knowledge on the estrogenic system in the brain grows, the possibilities to modulate it in order to afford further neuroprotection in brain damaging disorders so do it. We have previously demonstrated the ability of the selective estrogen receptor modulator, bazedoxifene (BZA), to reduce experimental ischemic brain damage. The present study has been designed to gain insight into the molecular mechanisms involved in such a neuroprotective action by investigating: 1) stroke-induced apoptotic cell death; 2) expression of estrogen receptors (ER) ERα, ERß and the G-protein coupled estrogen receptor (GPER); and 3) modulation of MAPK/ERK1/2 and PI3K/Akt signaling pathways. For comparison, a parallel study was done with 17ß-estradiol (E2)-treated animals. Male Wistar rats subject to transient right middle cerebral artery occlusion (tMCAO, intraluminal thread technique, 60min), were distributed in vehicle-, BZA- (20.7±2.1ng/mL in plasma) and E2- (45.6±7.8pg/mL in plasma) treated groups. At 24h from the onset of tMCAO, RT-PCR, Western blot and histochemical analysis were performed on brain tissue samples. Ischemia-reperfusion per se increased apoptosis as assessed by both caspase-3 activity and TUNEL-positive cell counts, which were reversed by both BZA and E2. ERα and ERß expression, but not that of GPER, was reduced by the ischemic insult. BZA and E2 had different effects: while BZA increased both ERα and ERß expression, E2 increased ERα expression but did not change that of ERß. Both MAPK/ERK1/2 and PI3K/Akt pathways were stimulated under ischemic conditions. While BZA strongly reduced the increased p-ERK1/2 levels, E2 did not. Neither BZA nor E2 modified ischemia-induced increase in p-Akt levels. These results show that modulation of ERα and ERß expression, as well as of the ERK1/2 signaling pathway accounts, at least in part, for the inhibitory effect of BZA on the stroke-induced apoptotic cell death. This lends mechanistic support to the consideration of BZA as a potential neuroprotective drug in acute ischemic stroke treatment.

Relaxant Effects of the Selective Estrogen Receptor Modulator, Bazedoxifene, and Estrogen Receptor Agonists in Isolated Rabbit Basilar Artery.

We have previously shown that the selective estrogen receptor modulator, bazedoxifene, improves the consequences of ischemic stroke. Now we aimed to characterize the effects and mechanisms of action of bazedoxifene in cerebral arteries. Male rabbit isolated basilar arteries were used for isometric tension recording and quantitative polymerase chain reaction. Bazedoxifene relaxed cerebral arteries, as 17-ß-estradiol, 4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol [estrogen receptor (ER) α agonist], and G1 [G protein-coupled ER (GPER) agonist] did it (4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol > bazedoxifene = G1 > 17-ß-estradiol). 2,3-Bis(4-hydroxyphenyl)-propionitrile (ERß agonist) had no effect. Expression profile of genes encoding for ERα (ESR1), ERß (ESR2), and GPER was GPER > ESR1 > ESR2. As to the endothelial mechanisms, endothelium removal, N-nitro-L-arginine methyl ester, and indomethacin, did not modify the relaxant responses to bazedoxifene. As to the K channels, both a high-K medium and the Kv blocker, 4-aminopyridine, inhibited the bazedoxifene-induced relaxations, whereas tetraethylammonium (nonselective K channel blocker), glibenclamide (selective KATP blocker) or iberiotoxin (selective KCa blocker) were without effect. Bazedoxifene also inhibited both Ca- and Bay K8644-elicited contractions. Therefore, bazedoxifene induces endothelium-independent relaxations of cerebral arteries through (1) activation of GPER and ERα receptors; (2) increase of K conductance through Kv channels; and (3) inhibition of Ca entry through L-type Ca channels. Such a profile is compatible with the beneficial effects of estrogenic compounds (eg, SERMs) on vascular function and, specifically, that concerning the brain. Therefore, bazedoxifene could be useful in the treatment of cerebral disorders in which the cerebrovascular function is compromised (eg, stroke).

The selective estrogen receptor modulator, bazedoxifene, reduces ischemic brain damage in male rat.

While the estrogen treatment of stroke is under debate, selective estrogen receptor modulators (SERMs) arise as a promising alternative. We hypothesize that bazedoxifene (acetate, BZA), a third generation SERM approved for the treatment of postmenopausal osteoporosis, reduces ischemic brain damage in a rat model of transient focal cerebral ischemia. For comparative purposes, the neuroprotective effect of 17ß-estradiol (E2) has also been assessed. Male Wistar rats underwent 60min middle cerebral artery occlusion (intraluminal thread technique), and grouped according to treatment: vehicle-, E2- and BZA-treated rats. Optimal plasma concentrations of E2 (45.6±7.8pg/ml) and BZA (20.7±2.1ng/ml) were achieved 4h after onset of ischemia, and maintained until the end of the procedure (24h). Neurofunctional score and volume of the damaged brain regions were the main end points. At 24h after ischemia-reperfusion, neurofunctional examination of the animals did not show significant differences among the three experimental groups. By contrast, both E2- and BZA-treated groups showed significantly lower total infarct volumes, BZA acting mainly in the cortical region and E2 acting mainly at the subcortical level. Our results demonstrate that: (1) E2 at physiological plasma levels in female rats is neuroprotective in male rats when given at the acute stage of the ischemic challenge and (2) BZA at clinically relevant plasma levels mimics the neuroprotective action of E2 and could be, therefore, a candidate in stroke treatment.

Improvement of the circulatory function partially accounts for the neuroprotective action of the phytoestrogen genistein in experimental ischemic stroke.

We tested the hypothesis that the phytoestrogen genistein protects the brain against ischemic stroke by improving the circulatory function in terms of reduced production of thromboxane A2 and leukocyte-platelet aggregates, and of preserved vascular reactivity. Ischemia-reperfusion (90 min-3 days, intraluminal filament) was induced in male Wistar rats, and functional score and cerebral infarct volume were the end points examined. Genistein (10mg/kg/day) or vehicle (ß-cyclodextrin) was administered at 30 min after ischemia or sham-operation. Production of thromboxane A2 and leukocyte-platelet aggregates, as well as reactivity of carotid artery to U-46619 (thromboxane A2 analogue) and to platelet releasate was measured. At 3 days post-ischemia, both improvement in the functional examination and reduction in the total infarct volume were shown in the ischemic genistein-treated group. Genistein significantly reverted both the increased thromboxane A2 concentration and the increased leukocyte-platelet aggregates production found in samples from the ischemic vehicle-treated group. Both U-46619 and platelet releasate elicited contractions of the carotid artery, which were significantly lower in the ischemic vehicle-treated group. Genistein significantly restored both the decreased U-46619- and the decreased platelet releasate-elicited contractile responses. In conclusion, genistein protects the brain against an ischemia-reperfusion challenge, at least in part, by its beneficial effects on the circulatory function.

Involvement of prostacyclin and potassium channels in the diabetes-induced hyporeactivity of the rabbit carotid artery to B-type natriuretic peptide.

The relation between diabetes and stroke is bidirectional: diabetes is an important risk factor for ischemic stroke, and acute stroke frequently induces hyperglycemia. On the other hand, plasma B-type natriuretic peptide (BNP) levels are raised in diabetes and stroke. The purpose was to study how alloxan-induced diabetes might modify the effects of BNP in rabbit carotid arteries and the mechanisms involved in such actions. To do this, isometric tension in isolated rabbit carotid artery was recorded and prostanoids release and plasma NT-proBNP were measured by enzyme immunoassay. BNP induced a relaxation of phenylephrine-precontracted carotid arteries, and this relaxation was lower in diabetic than in control rabbits. Endothelium removal did not modify the relaxation to BNP in control rabbits but increased this relaxation in diabetic rabbits. In control rabbits, indomethacin inhibited the BNP-induced relaxation in the presence and in the absence of endothelium. In diabetic rabbits, indomethacin did not modify the BNP-induced relaxation in arteries with endothelium and inhibited it in arteries without endothelium. In the presence of BNP the carotid artery released thromboxane A2 and prostacyclin, and the release of endothelial prostacyclin was inhibited in diabetic rabbits. Glibenclamide and 4-aminopyridine inhibited the relaxation to BNP, and these inhibitions were lower in diabetic than in control rabbits. In conclusion, our results provide a new understanding concerning the mechanisms of the diabetes-induced hyporeactivity of the carotid artery to BNP, that at least include the loss of endothelial prostacyclin and a reduced participation of ATP-sensitive K(+) channels (KATP) and voltage-sensitive K(+) channels (KV).

Diabetes impairs the atrial natriuretic peptide relaxant action mediated by potassium channels and prostacyclin in the rabbit renal artery.

Diabetes is associated with increased prevalence of hypertension, cardiovascular and renal disease. Atrial natriuretic peptide (ANP) plays an important role in cardiovascular pathophysiology and is claimed to have cardioprotective and renoprotective effect in diabetic patients. The working hypothesis was that alloxan-induced diabetes might modify the vascular effects of ANP in isolated rabbit renal arteries and the mechanisms involved in such actions. Plasma ANP levels were higher in diabetic rabbits than in control rabbits. ANP (10(-12)-10(-7)M) induced a relaxation of precontracted renal arteries, which was lower in diabetic than in control rabbits. In arteries from both groups of animals, endothelium removal decreased the ANP-induced relaxation but inhibition of NO-synthesis did not modify ANP-induced relaxations. In KCl-depolarised arteries, relaxation to ANP was almost abolished both in control and diabetic rabbits. Tetraethylammonium (TEA) partly inhibited the relaxation to ANP in control rabbits but did not modify it in diabetic rabbits. Glibenclamide and 4-aminopyridine inhibited the relaxation to ANP, and these inhibitions were lower in diabetic than in control rabbits. Indomethacin potentiated the relaxation to ANP, more in control than in diabetic rabbits. In the presence of ANP the renal artery released thromboxane A(2) and prostacyclin, and the release of prostacyclin resulted decreased in diabetic rabbits. The present results suggest that diabetes produces hyporeactivity of the rabbit renal artery to ANP by mechanisms that at least include the reduced modulation by prostacyclin and a lower participation of ATP-sensitive K(+) channel (K(ATP)), voltage-sensitive K(+) channels (K(V)) and TEA-sensitive K(+) channels (K(Ca)).

Novel antihypertensive hexa- and heptapeptides with ACE-inhibiting properties: from the in vitro ACE assay to the spontaneously hypertensive rat.

Bioactive ACE inhibiting peptides are gaining interest in hypertension treatment. We have designed and screened six synthetic heptapeptides (PACEI48 to PACEI53) based on two hexapeptide leads (PACEI32 and PACEI34) to improve ACE inhibitory properties and assess their antihypertensive effects. ACE activity was assayed in vitro and ex vivo. Selected peptides were administered to spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats. In vitro cytotoxicity was assessed with the MTT reduction test. The six heptapeptides at low micromolar concentration produced different degrees of in vitro inhibition of ACE activity using the synthetic substrate HHL or the natural substrate angiotensin I; and ex vivo inhibition of ACE-dependent, angiotensin I-induced vasoconstriction, but not angiotensin II-induced vasoconstriction. Oral administration of the hexapeptide PACEI32L, and the heptapeptides PACEI50L and PACEI52L, induced reductions in systolic blood pressure lasting up to 3h in SHRs but not in WKY rats. Intravenous injection of PACEI32L and PACEI50L, but not PACEI52L, induced acute transient reductions in mean blood pressure of SHRs. d-Amino acid peptides showed five-fold less ACE inhibitory potency, no inhibitory effect on angiotensin I-induced vasoconstriction, and antihypertensive effect in SHRs after i.v. injection, but not after oral administration. The toxicity of peptides to reduce the viability of cultured cells was in the millimolar range. In conclusion, we have obtained novel rationally designed heptapeptides with improved ACE inhibitory properties when compared to lead hexapeptides. One selected hexapeptide and two heptapeptides show oral antihypertensive effects in SHRs and appear safe in cytotoxicity assays.

Mechanisms underlying the diabetes-induced hyporeactivity of the rabbit carotid artery to atrial natriuretic peptide.

Atrial natriuretic peptide (ANP) plays an important role in the pathophysiology of the vascular complications in diabetes. The working hypothesis was that diabetes might modify the vascular actions of ANP in isolated rabbit carotid arteries and the mechanisms involved in these actions. ANP (10(-12)-10(-7)M) induced a relaxation of precontracted carotid arteries, which was lower in diabetic than in control rabbits. In arteries from both groups of animals, endothelium removal increased the ANP-induced relaxation. Isatin inhibited the relaxation to ANP both in arteries with and without endothelium. Carotid arteries from diabetic rabbits showed a decreased natriuretic peptide receptor (NPR)-A expression and an enhanced NPR-C expression. Inhibition of NO-synthesis did not modify ANP-induced relaxation in control rabbits but inhibited it in diabetic rabbits. In arteries with endothelium indomethacin enhanced the relaxation to ANP in control rabbits but did not modify it in diabetic rabbits. In endothelium-denuded arteries indomethacin inhibited the relaxation to ANP in both groups of animals. In KCl-depolarised arteries, relaxation to ANP was almost abolished both in control and diabetic rabbits. Tetraethylammonium inhibited the relaxation to ANP, and this inhibition was higher in diabetic than in control rabbits. These results suggest that diabetes produces hyporeactivity of the rabbit carotid artery to ANP by a mechanism that at least includes a reduced expression of NPR-A, an enhanced expression of NPR-C and a reduced participation of K(+)-channels. Furthermore, diabetes enhances endothelial NO release and diminishes the ratio thromboxane A(2)/prostacyclin. This increase of vasodilators could result from compensatory mechanisms counteracting the arterial hyporeactivity to ANP.

Lactoferricin B-derived peptides with inhibitory effects on ECE-dependent vasoconstriction.

Endothelin-converting enzyme (ECE), a key peptidase in the endothelin (ET) system, cleaves inactive big ET-1 to produce active ET-1, which binds to ET(A) receptors to exert its vasoconstrictor and pressor effects. ECE inhibition could be beneficial in the treatment of hypertension. In this study, a set of eight lactoferricin B (LfcinB)-derived peptides, previously characterized in our laboratory as angiotensin-converting enzyme (ACE) inhibitory peptides, was examined for their inhibitory effects on ECE. In vitro inhibitory effects on ECE activity were assessed using both the synthetic fluorogenic peptide substrate V (FPS V) and the natural substrate big ET-1. To study vasoactive effects, an ex vivo functional assay was developed using isolated rabbit carotid artery segments. With FPS V, only four LfcinB-derived peptides induced inhibition of ECE activity, whereas the eight peptides showed ECE inhibitory effects with big ET-1 as substrate. Regarding the ex vivo assays, six LfcinB-derived peptides showed inhibition of big ET-1-induced, ECE-dependent vasoconstriction. A positive correlation between the inhibitory effects of LfcinB-derived peptides on ECE activity when using big ET-1 and the inhibitory effects on ECE-dependent vasoconstriction was shown. ECE-independent vasoconstriction induced by ET-1 was not affected, thus discarding effects of LfcinB-derived peptides on ET(A) receptors or intracellular signal transduction mechanisms. In conclusion, a combined in vitro and ex vivo method to assess the effects of potentially antihypertensive peptides on the ET system has been developed and applied to show the inhibitory effects on ECE-dependent vasoconstriction of six LfcinB-derived peptides, five of which were dual vasopeptidase (ACE/ECE) inhibitors.

Antihypertensive properties of lactoferricin B-derived peptides.

A set of eight lactoferricin B (LfcinB)-derived peptides was examined for inhibitory effects on angiotensin I-converting enzyme (ACE) activity and ACE-dependent vasoconstriction, and their hypotensive effect in spontaneously hypertensive rats (SHR). Peptides were derived from different elongations both at the C-terminal and N-terminal ends of the representative peptide LfcinB(20-25), which is known as the LfcinB antimicrobial core. All of the eight LfcinB-derived peptides showed in vitro inhibitory effects on ACE activity with different IC(50) values. Moreover, seven of them showed ex vivo inhibitory effects on ACE-dependent vasoconstriction. No clear correlation between in vitro and ex vivo inhibitory effects was found. Only LfcinB(20-25) and one of its fragments, F1, generated after a simulated gastrointestinal digestion, showed significant antihypertensive effects in SHR after oral administration. Remarkably, F1 did not show any effect on ACE-dependent vasoconstriction in contrast to the inhibitory effect showed by LfcinB(20-25). In conclusion, two LfcinB-derived peptides lower blood pressure and exhibit potential as orally effective antihypertensive compounds, yet a complete elucidation of the mechanism(s) involved deserves further ongoing research.

Transient focal cerebral ischemia significantly alters not only EAATs but also VGLUTs expression in rats: relevance of changes in reactive astroglia.

The involvement of plasma membrane glutamate transporters (EAATs - excitatory aminoacid transporters) in the pathophysiology of ischemia has been widely studied, but little is known about the role of vesicular glutamate transporters (VGLUTs) in the ischemic process. We analyzed the expression of VGLUT1-3 in the cortex and caudate-putamen of rats subjected to transient middle cerebral artery occlusion. Western blot and immunohistochemistry revealed an increase of VGLUT1 signal in cortex and caudate-putamen until 3 days of reperfusion followed by a reduction 7 days after the ischemic insult. By contrast, VGLUT2 and 3 were drastically reduced. Confocal microscopy revealed an increase in VGLUT2 and 3 immunolabelling in the reactive astrocytes of the ischemic corpus callosum and cortex. Changes in VGLUTs and EAATs expression were differently correlated to neurological deficits. Interestingly, changes in VGLUT1 and EAAT2 expression showed a significant positive correlation in caudate-putamen. Taken together, these results suggest a contribution of VGLUTs to glutamate release in these structures, which could promote neuroblast migration and neurogenesis during ischemic recovery, and a possible interplay with EAATs in the regulation of glutamate levels, at least in the first stages of ischemic recovery.

Perivascular nerve fiber α-synuclein regulates contractility of mouse aorta: a link to autonomic dysfunction in Parkinson's disease.

Parkinson's disease and other neurodegenerative disorders associated to changes in alpha-synuclein often result in autonomic dysfunction, most of the time accompanied by abundant expression of this synaptic protein in peripheral autonomic neurons. Given that expression of alpha-synuclein in vascular elements has been previously reported, the present study was undertaken to determine whether alpha-synuclein directly participates in the regulation of vascular responsiveness. We detected by immunohistochemistry perivascular nerve fibers containing alpha-synuclein in the aorta of mice while aortic endothelial cells and muscular fibers themselves did not exhibit detectable levels of this protein. To assess the effect of alpha-synuclein on vascular reactivity, aortic ring preparations obtained from alpha-synuclein-deficient knockout mice and from transgenic mice overexpressing human wild-type alpha-synuclein under the control of the tyrosine hydroxylase-promoter were mounted and equilibrated in organ baths for isometric tension recording. Lack of alpha-synuclein did not modify the relaxant responses to the endothelium-dependent (acetylcholine) and -independent (sodium nitroprusside) vasodilators, but resulted in a greater than normal norepinephrine-induced vasoconstriction along with a lowered response to dopamine, suggesting potential presynaptic changes in dopamine and norepinephrine releases in knockout mice. Overexpression of alpha-synuclein in TH-positive fibers resulted in complex abnormal responses, characterized by lowered acetylcholine-induced relaxation and lowered norepinephrin-induced contraction. Taken together, our data show for the first time that alpha-synuclein is present in sympathetic fibers supplying the murine aorta and provide evidence that changes in alpha-synuclein levels in perivascular fibers play a physiological role in the regulation of vascular function.

Acute estradiol protects CA1 neurons from ischemia-induced apoptotic cell death via the PI3K/Akt pathway.

Global ischemia arising during cardiac arrest or cardiac surgery causes highly selective, delayed death of hippocampal CA1 neurons. Exogenous estradiol ameliorates global ischemia-induced neuronal death and cognitive impairment in male and female rodents. However, the molecular mechanisms by which a single acute injection of estradiol administered after the ischemic event intervenes in global ischemia-induced apoptotic cell death are unclear. Here we show that acute estradiol acts via the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling cascade to protect CA1 neurons in ovariectomized female rats. We demonstrate that global ischemia promotes early activation of glycogen synthase kinase-3beta (GSK3beta) and forkhead transcription factor of the O class (FOXO)3A, known Akt targets that are related to cell survival, and activation of caspase-3. Estradiol prevents ischemia-induced dephosphorylation and activation of GSK3beta and FOXO3A, and the caspase death cascade. These findings support a model whereby estradiol acts by activation of PI3K/Akt signaling to promote neuronal survival in the face of global ischemia.

Mechanisms involved in the relaxant action of testosterone in the renal artery from male normoglycemic and diabetic rabbits.

Kidney disease is a frequent complication in diabetes, and significant differences have been reported between male and female patients. Our working hypothesis was that diabetes might modify the vascular actions of testosterone in isolated rabbit renal arteries and the mechanisms involved in these actions. Testosterone (10(-8) to 10(-4)M) induced relaxation of precontracted arteries, without significant differences between control and diabetic rabbits. Both in control and diabetic rabbits endothelium removal inhibited testosterone relaxant action. In arteries with endothelium, incubation with indomethacin (10(-5)M), N(G)-nitro-l-arginine (10(-5)M) or tetraethylammonium (10(-5)M) did not modify relaxations to testosterone neither in control nor in diabetic rabbits. In endothelium-denuded arteries indomethacin enhanced the relaxant action of testosterone, both in control and diabetic rabbits. In arteries from diabetic rabbits, eNOS, iNOS and COX-1 expression and testosterone-induced release of thromboxane A(2) and prostacyclin were not significantly different from those observed in control rabbits. However, COX-2 expression was significantly lower in diabetic rabbits that in control rabbits. In nominally Ca(2+)-free medium, cumulative addition of CaCl2 (10(-5) to 3x10(-2)M) contracted previously depolarized arteries. Testosterone (10(-4)M) inhibited CaCl2 contractions of the renal artery both in control and diabetic rabbits. These results show that testosterone relaxes the renal artery both in control and diabetic rabbits. This relaxation is modulated by muscular thromboxane A(2), it is partially mediated by endothelial prostacyclin, and it involves the blocking of extracellular Ca2+ entry. Diabetes does not modify the mechanisms involved in the relaxant action of testosterone in the rabbit renal artery.