Jesper Petersson

Vanilloid receptors on sensory nerves mediate the vasodilator action of anandamide

The endogenous cannabinoid receptor agonist anandamide is a powerful vasodilator of isolated vascular preparations, but its mechanism of action is unclear. Here we show that the vasodilator response to anandamide in isolated arteries is capsaicin-sensitive and accompanied by release of calcitonin-gene-related peptide (CGRP). The selective CGRP-receptor antagonist 8-37 CGRP (ref. 5), but not the cannabinoid CB1 receptor blocker SR141716A (ref. 7), inhibited the vasodilator effect of anandamide. Other endogenous (2-arachidonylglycerol, palmitylethanolamide) and synthetic (HU 210, WIN 55,212-2, CP 55,940) CB1 and CB2 receptor agonists could not mimic the action of anandamide. The selective ‘vanilloid receptor’ antagonist capsazepine, inhibited anandamide-induced vasodilation and release of CGRP. In patch-clamp experiments on cells expressing the cloned vanilloid receptor (VR1), anandamide induced a capsazepine-sensitive current in whole cells and isolated membrane patches. Our results indicate that anandamide induces vasodilation by activating vanilloid receptors on perivascular sensory nerves and causing release of CGRP. The vanilloid receptor may thus be another molecular target for endogenous anandamide, besides cannabinoid receptors, in the nervous and cardiovascular systems.

European Stroke Organisation (ESO) guidelines for the management of spontaneous intracerebral hemorrhage

Background Intracerebral hemorrhage (ICH) accounted for 9% to 27% of all strokes worldwide in the last decade, with high early case fatality and poor functional outcome. In view of recent randomized controlled trials (RCTs) of the management of ICH, the European Stroke Organisation (ESO) has updated its evidence-based guidelines for the management of ICH. Method A multidisciplinary writing committee of 24 researchers from 11 European countries identified 20 questions relating to ICH management and created recommendations based on the evidence in RCTs using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Results We found moderate- to high-quality evidence to support strong recommendations for managing patients with acute ICH on an acute stroke unit, avoiding hemostatic therapy for acute ICH not associated with antithrombotic drug use, avoiding graduated compression stockings, using intermittent pneumatic compression in immobile patients, and using blood pressure lowering for secondary prevention. We found moderate-quality evidence to support weak recommendations for intensive lowering of systolic blood pressure to <140 mmHg within six-hours of ICH onset, early surgery for patients with a Glasgow Coma Scale score 9–12, and avoidance of corticosteroids. Conclusion These guidelines inform the management of ICH based on evidence for the effects of treatments in RCTs. Outcome after ICH remains poor, prioritizing further RCTs of interventions to improve outcome.

Mechanical thrombectomy in acute ischemic stroke: Consensus statement by ESO-Karolinska Stroke Update 2014/2015, supported by ESO, ESMINT, ESNR and EAN

The original version of this consensus statement on mechanical thrombectomy was approved at the European Stroke Organisation (ESO)-Karolinska Stroke Update conference in Stockholm, 16–18 November 2014. The statement has later, during 2015, been updated with new clinical trials data in accordance with a decision made at the conference. Revisions have been made at a face-to-face meeting during the ESO Winter School in Berne in February, through email exchanges and the final version has then been approved by each society. The recommendations are identical to the original version with evidence level upgraded by 20 February 2015 and confirmed by 15 May 2015. The purpose of the ESO-Karolinska Stroke Update meetings is to provide updates on recent stroke therapy research and to discuss how the results may be implemented into clinical routine. Selected topics are discussed at consensus sessions, for which a consensus statement is prepared and discussed by the participants at the meeting. The statements are advisory to the ESO guidelines committee. This consensus statement includes recommendations on mechanical thrombectomy after acute stroke. The statement is supported by ESO, European Society of Minimally Invasive Neurological Therapy (ESMINT), European Society of Neuroradiology (ESNR), and European Academy of Neurology (EAN).

Characterization of the potassium channels involved in EDHF‐mediated relaxation in cerebral arteries

In the presence of NG‐nitro‐l‐arginine (l‐NOARG, 0.3 mm) and indomethacin (10 μm), the relaxations induced by acetylcholine and the calcium (Ca) ionophore A23187 are considered to be mediated by endothelium‐derived hyperpolarizing factor (EDHF) in the guinea‐pig basilar artery. Inhibitors of adenosine 5′‐triphosphate (ATP)‐sensitive potassium (K)‐channels (KATP; glibenclamide, 10 μm), voltage‐sensitive K‐channels (KV; dendrotoxin‐I, 0.1 μm or 4‐aminopyridine, 1 mm), small (SKCa; apamin, 0.1 μm) and large (BKCa; iberiotoxin, 0.1 μm) conductance Ca‐sensitive K‐channels did not affect the l‐NOARG/indomethacin‐resistant relaxation induced by acetylcholine. Synthetic charybdotoxin (0.1 μm), an inhibitor of BKCa and KV, caused a rightward shift of the concentration‐response curve for acetylcholine and reduced the maximal relaxation in the presence of l‐NOARG and indomethacin, whereas the relaxation induced by A23187 was not significantly inhibited. A combination of charybdotoxin (0.1 μm) and apamin (0.1 μm) abolished the l‐NOARG/indomethacin‐resistant relaxations induced by acetylcholine and A23187. However, the acetylcholine‐induced relaxation was not affected by a combination of iberiotoxin (0.1 μm) and apamin (0.1 μm). Ciclazindol (10 μm), an inhibitor of KV in rat portal vein smooth muscle, inhibited the l‐NOARG/indomethacin‐resistant relaxations induced by acetylcholine and A23187, and the relaxations were abolished when ciclazindol (10 μm) was combined with apamin (0.1 μm). Human pial arteries from two out of four patients displayed an l‐NOARG/indomethacin‐resistant relaxation in response to substance P. This relaxation was abolished in both cases by pretreatment with the combination of charybdotoxin (0.1 μm) and apamin (0.1 μm), whereas each toxin had little effect alone. The results suggest that KV, but not KATP and BKCa, is involved in the EDHF‐mediated relaxation in the guinea‐pig basilar artery. The synergistic action of apamin and charybdotoxin (or ciclazindol) could indicate that both KV and SKCa are activated by EDHF. However, a single type of K‐channel, which may be structurally related to KV and allosterically regulated by apamin, could also be the target for EDHF.

EuroHYP-1: European multicenter, randomized, phase III clinical trial of therapeutic hypothermia plus best medical treatment vs. best medical treatment alone for acute ischemic stroke

Rationale Cooling reduced infarct size and improved neurological outcomes in animal studies modeling ischemic stroke, and also improved outcome in randomized clinical trials in patients with hypoxic-ischemic brain injury after cardiac arrest. Cooling awake patients with ischemic stroke has been shown feasible in phase II clinical trials. Primary aim To determine whether systemic cooling to a target body temperature between 34·0 and 35·0°C, started within six-hours of symptom onset and maintained for 24 h, improves functional outcome at three-months in patients with acute ischemic stroke. Design International, multicenter, phase III, randomized, open-label clinical trial with blinded outcome assessment in 1500 patients aged 18 years or older with acute ischemic stroke and a National Institutes of Health Stroke Scale score of 6 up to and including 18. In patients randomized to hypothermia, cooling to a target body temperature of 34–35°C will be started within six-hours after symptom onset with rapid intravenous infusion of refrigerated normal saline or a surface cooling technique and maintained for 24 h with a surface or endovascular technique. Patients randomized to hypothermia will receive pethidine and buspirone to prevent shivering and discomfort. Primary outcome Score on the modified Rankin Scale at 91 days, as analyzed with ordinal logistic regression and expressed as a common odds ratio. Discussion With 750 patients per intervention group, this trial has 90% power to detect 7% absolute improvement at the 5% significance level. The full trial protocol is available at http://www.eurohyp1.eu. ClinicalTrials.gov Identifier: NCT01833312.

Risk Factors and Treatment at Recurrent Stroke Onset: Results from the Recurrent Stroke Quality and Epidemiology (RESQUE) Study

Background: Much effort has been made to study first-ever stroke patients. However, recurrent stroke has not been investigated as extensively. It is unclear which risk factors dominate, and whether adequate secondary prevention has been provided to patients who suffer from recurrent stroke. Also, the different types of recurrent stroke need further evaluation. Methods: The study included patients with recurrent stroke admitted to twenty-three Swedish stroke centers. The type of previous and recurrent stroke was determined, as well as evaluation (when applicable) of recurrent ischemic stroke according to the TOAST classification. Presence of vascular risk factors was registered and compared to the type of stroke. Also assessed was ongoing secondary prevention treatment at recurrent stroke onset. Results: A total of 889 patients with recurrent stroke (mean age 77) were included in the study. Of these, 805 (91%) had ischemic stroke, 78 (9%) had intracerebral hemorrhage and 6 (<1%) stroke of unknown origin. The most frequent vascular risk factors were hypertension (75%) and hyperlipidemia (56%). Among the 889 patients, 29% had atrial fibrillation. Of the patients in the ischemic group with cardiac embolism, only 21% were on anticoagulation treatment. The majority of the patients (75%) had their most recent previous stroke >12 months before admission. Conclusions: Few patients had a recurrent stroke shortly after the previous stroke in this study. This indicates that it is meaningful to prevent a second event with an adequate long-term treatment strategy for secondary prevention after first-ever stroke. There also seems to be a clear potential for improving secondary prevention after stroke.

Prediagnostic body fat and risk of death from amyotrophic lateral sclerosis: The EPIC cohort

Objectives: The aim of this study was to investigate for the first time the association between body fat and risk of amyotrophic lateral sclerosis (ALS) with an appropriate prospective study design. Methods: The EPIC (European Prospective Investigation into Cancer and Nutrition) study included 518,108 individuals recruited from the general population across 10 Western European countries. At recruitment, information on lifestyle was collected and anthropometric characteristics were measured. Cox hazard models were fitted to investigate the associations between anthropometric measures and ALS mortality. Results: Two hundred twenty-two ALS deaths (79 men and 143 women) occurred during the follow-up period (mean follow-up = 13 years). There was a statistically significant interaction between categories of body mass index and sex regarding ALS risk (p = 0.009): in men, a significant linear decrease of risk per unit of body mass index was observed (hazard ratio = 0.93, 95% confidence interval 0.86–0.99 per kg/m2); among women, the risk was more than 3-fold increased for underweight compared with normal-weight women. Among women, a significant risk reduction increasing the waist/hip ratio was also evident: women in the top quartile had less than half the risk of ALS compared with those in the bottom quartile (hazard ratio = 0.48, 95% confidence interval 0.25–0.93) with a borderline significant p value for trend across quartiles (p = 0.056). Conclusion: Increased prediagnostic body fat is associated with a decreased risk of ALS mortality.

Substance P-induced relaxation and hyperpolarization in human cerebral arteries.

1 Vascular effects of substance P were studied in human isolated pial arteries removed from 14 patients undergoing cerebral cortical resection. 2 Substance P induced a concentration‐dependent relaxation in the presence of indomethacin. No relaxation was seen in arteries where the endothelium had been removed. 3 Nω–nitro‐L‐arginine (l‐NOARG, 0.3 mM) abolished the relaxation in arteries from six patients. The relaxation was only partially inhibited in the remaining eight patients, the reduction of the maximum relaxation being less than 50% in each patient. 4 The L‐NOARG‐resistant relaxation was abolished when the external K+ concentration was raised above 30 mM. 5 Substance P caused a smooth muscle hyperpolarization (in the presence of L‐NOARG and indomethacin), but only when the artery showed an L‐NOARG‐resistant relaxation. 6 The results indicate that nitric oxide is an important mediator of endothelium‐dependent relaxation in human cerebral arteries. Furthermore, another endothelium‐dependent pathway, causing hyperpolarization and vasodilatation, was identified in arteries from more than half the population of patients.

Changes in Functional Outcome Over the First Year After Stroke: An Observational Study From the Swedish Stroke Register

Background and Purpose— Large longitudinal studies on stroke outcome are scarce. The aim of this study was to analyze predictors and changes in functional outcome during the first year poststroke. Methods— Data on patients who were independent in activities of daily living (ADL) and hospitalized for acute stroke in 2008 to 2010 were obtained from the Swedish Stroke Register. Case fatality was assessed by linkage to the Swedish Population Register. ADL was defined by independence or dependence in dressing, toileting, and indoor mobility and assessed at 3 and 12 months. Predictors of ADL dependency were assessed through multivariate analysis. Results— In total, 64 746 patients were included. Case fatality at 3 months was 13.1% (men 11.6% versus women 14.8%; P<0.0001) and at 12 months 18.2% (men 16.4% versus women 20.3%; P<0,0001). In the 35 064 followed-up survivors, ADL dependency rates at 3 and 12 months were 16.2% (men 15.9% versus women 19.2%; P<0.0001) and 28.3% (men 22.7% versus women 34.9%, P<0.0001), respectively. Factors predicting deterioration to ADL dependency between 3 and 12 months were female sex (relative risk [RR]=1.56; 95% confidence interval [CI], 1.50–1.70), diabetes mellitus (RR=1.50; 95% CI, 1.05–1.60), comatose at admittance (RR=2.34; 95% CI, 1.79–3.05), previous stroke (RR=1.52; 95% CI, 1.43–1.61), hemorrhagic or unspecified stroke (RR=1.14; 95% CI, 1.05–1.25), and atrial fibrillation (RR= 1.11; 95% CI, 1.04–1.17). Conclusions— Transition from ADL independence to dependence was observed in a high proportion of patients between 3 and 12 months, challenging the common belief that functioning after stroke is stable beyond 3 months. Deterioration occurred more commonly in women, among whom 1/6 converted to dependency.

Characterization of Endothelium- Dependent Relaxation in Guinea Pig Basilar Artery – Effect of Hypoxia and Role of Cytochrome P450 Mono-Oxygenase

In the guinea pig basilar artery, acetylcholine and the calcium ionophore A23187 induced endothelium-dependent relaxations, which were not significantly affected by the nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine (L-NOARG; 0.3 mM) or the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one; 1-10 µM), or by these inhibitors combined. However, acetylcholine (10 µM) and A23187 (3 µM) each significantly increased the tissue level of cGMP in the absence but not in the presence of L-NOARG, suggesting that NO is released from the vascular endothelium in this blood vessel. Treatment with the potassium (K) channel inhibitors charybdotoxin (0.1 µM) plus apamin (0.1 µM), a toxin mixture previously shown to inhibit relaxations mediated by endothelium-derived hyperpolarizing factor (EDHF) in this artery, had no effect on the A23187-induced relaxation but slightly inhibited the response to acetylcholine (Emax was reduced by 24%). When the action of EDHF was prevented by these K channel inhibitors, the remaining relaxation was abolished by either ODQ (1 µM) or L-NOARG (0.3 mM), indicating that NO, apart from EDHF, contributes to the endothelium-dependent relaxations. Furthermore, ODQ (10 µM) abolished the relaxation induced by the NO donor S-nitroso-N-acetylpenicillamine. Thus, activation of soluble guanylate cyclase seems to be the only mechanism through which NO causes relaxation in this artery. When vessels were exposed to grave hypoxia (pO2 = 6 mm Hg), the NO-mediated relaxation (induced by acetylcholine in the presence of charybdotoxin plus apamin) disappeared. In contrast, EDHF-mediated responses (elicited by acetylcholine in the presence of L-NOARG) were only marginally affected by hypoxia (Emax was reduced by 16%). 17-Octadecynoic acid (50 µM) and 5,8,11,14-eicosatetraynoic acid (10 µM), inhibitors of cytochrome P450-dependent oxidation of arachidonic acid, failed to inhibit the acetylcholine-induced relaxation in the presence of L-NOARG. The cytochrome P450-dependent arachidonic acid metabolite 11,12-epoxyecosatrienoic acid (0.3–3.0 µM) had no relaxant effect per se. In conclusion, EDHF and NO are both mediators of endothelium-dependent relaxations in the guinea pig basilar artery. However, during grave hypoxia, EDHF alone mediates acetylcholine-induced relaxation. The results further suggest that EDHF is not a metabolite of arachidonic acid formed by cytochrome P450 mono-oxygenase or generated by another oxygen-dependent enzyme in this artery.