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Phospholipase A2s (PLA2s) seem to be involved in the pathophysiology of ischemic brain injury, but their specific role is far from being completely understood. The present study was carried out to ascertain how and to what extent secretory PLA2s (sPLA2s) activity influences outcome after cerebral ischemia–reperfusion, and to correlate this with the inflammatory response. To do this we used the potent and selective sPLA2 inhibitor, 12- epi-scalaradial. Male Wistar rats were separated into three groups: a control group receiving intracerebroventricular vehicle, and two groups receiving intracerebroventricular 0.005 or 0.5 μg/h 12- epi-scalaradial. Every animal was subjected to middle cerebral artery (MCA) occlusion (90 min, intraluminal thread technique) under continuous monitorization of cerebrocortical perfusion (CP, laser-Doppler flowmetry), followed by reperfusion (3 days). Neurological status, infarct volume, and myeloperoxidase (MPO) activity were the main end points. Three days after the 90-min ischemia period, neurological examination did not reveal significant differences between the three groups of rats. Control rats showed a mean infarct volume of 145.9 ± 24.7 mm3 (21 ± 4.1% of the ipsilateral hemisphere volume), while mean infarct volume in rats treated with 0.005 or 0.5 μg/h 12- epi-scalaradial increased to 164.8 ± 86.8 mm3 (22.0 ± 10.9%) and 211.5 ± 12.2 mm3 (28 ± 3%, P < 0.05), respectively. Treatment with the highest dose of 12- epi-scalaradial (0.5 μg/h) increased MPO activity in the ipsilateral hemisphere by about 140% (from 0.59 ± 0.59 to 1.42 ± 1.03 units of activity/g of tissue in comparison with the control ischemic hemisphere, P < 0.05). Overall, our results point to a positive rather than a negative influence of sPLA2 activity during ischemia. This, along with its inability to decrease the inflammatory response, does not allow to propose the use of 12- epi-scalardial as a potential drug for stroke therapy. [ABSTRACT FROM AUTHOR]

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 17β‐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, ERβ 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 ERβ 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. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to assess the role of K+ and Ca2+ fluxes in the cerebroarterial vasoactive effects of the phosphodiesterase-5 inhibitor sildenafil. We used isolated rabbit basilar arteries to assess the effects of extracellular K+ raising on sildenafil-induced vasodilatation, and studied the pharmacological interaction of sildenafil with selective modulators of membrane K+ and Ca2+ channels. Expression of Kv1 subunits of K+ channels was assessed at messenger and protein levels. Parallel experiments were carried out with zaprinast for comparison. Sildenafil (10 nM–0.1 mM) induced concentration-dependent relaxation of endothelin-1 (10 nM)-precontracted arteries, which was partially inhibited by depolarization with KCl (50 mM), 3 mM tetraethylammonium (non-selective K+ channel blocker) or 1 mM aminopyridine (inhibitor of Kv channels), but not by 1 μM glibenclamide (inhibitor of KATP channels) or 50 nM iberiotoxin (inhibitor of KCa channels). Arterial smooth muscle expressed messengers for Kv1.2, Kv1.3, Kv1.4, Kv1.5 and Kv1.6, and proteins of Kv1.1, Kv1.2 and Kv1.4. CaCl2 (10 μM- 10 mM) induced concentration-dependent contraction in Ca2+-free, depolarizing (50 mM KCl) medium. Sildenafil (0.1–100 μM) produced reversible concentration-dependent inhibition of the response to CaCl2, which was completely abolished by the highest sildenafil concentration. By contrast, only 100 μM zaprinast inhibited the response to CaCl2. The L-type Ca2+ channel activator Bay K 8644 (0.1 nM–1 μM) induced concentration-dependent potentiation of the response to CaCl2 inhibited by 100 μM sildenafil. Moreover, Bay K 8644 (0.1 nM–1 μM) induced concentration-dependent contraction in slightly depolarizing (15 mM) medium, which was inhibited to the same extent and in a concentration-dependent way by sildenafil (0.1–100 μM) and zaprinast (1 or 100 μM). These results show that sildenafil relaxes the rabbit basilar artery by increasing K+ efflux through Kv channels, which in turn may affect Ca2+ signalling. Expression of Kv1 subunits involved in this pharmacological effect occurs at the messenger and, in some cases, at the protein level. In addition to this phosphodiesterase-5-related effect, sildenafil and zaprinast inhibit cerebroarterial vasoconstriction at least in part by directly blocking L-type Ca2+ channels, although a decrease in the sensitivity of the contractile apparatus to Ca2+ can not be discarded. [Copyright &y& Elsevier]

Estrogens could play a cardiovascular protective role not only by means of systemic effects but also by means of direct effects on vascular structure and function. We have studied the acute effects and mechanisms of action of 17-beta-estradiol on vascular tone of rabbit isolated carotid artery. 17-Beta-estradiol (10, 30, and 100 microM) elicited concentration-dependent relaxation of 50 mM KCl-induced active tone in male and female rabbit carotid artery. The stereoisomer 17-alpha-estradiol showed lesser relaxant effects in male rabbits. Endothelium removal did not modify relaxation induced by 17-beta-estradiol. The NO synthase inhibitor L-NAME (100 microM) only reduced significantly relaxation produced by 30 microM 17-beta-estradiol. Relaxation was not modified by the estrogen receptor antagonist ICI 182,780 (1 microM), the protein synthesis inhibitor cycloheximide (1 microM), and the selective K(+) channel blockers charybdotoxin (0.1 microM) and glibenclamide (1 microM). CaCl(2) (30 microM -10 mM) induced concentration-dependent contraction in rabbit carotid artery depolarized by 50 mM KCl in Ca(2+) free medium. Preincubation with 17-beta-estradiol (3, 10, 30, or 100 microM) or the L-type Ca(2+) channel blocker nicardipine (0.01, 0.1, 1, or 10 nM) produced concentration-dependent inhibition of CaCl(2)-induced contraction. In conclusion, 17-beta-estradiol induces endothelium-independent relaxation of rabbit carotid artery, which is not mediated by classic estrogen receptor and protein synthesis activation. The relaxant effect is due to inhibition of extracellular Ca(2+) influx to vascular smooth muscle, but activation of K(+) efflux is not involved. Relatively high pharmacological concentrations of estrogen causing relaxation preclude acute vasoactive effects of plasma levels in the carotid circulation.