Vascular effects of neuropeptides and UDP-β-S and alterations after stroke

The aim of this thesis is to investigate the changes in vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide(CGRP) and P2Y6-mediated signaling following experimental subarachnoid hemorrhage (SAH) and transient middle cerebral artery occlusion (tMCAO). VIP and CGRP are among the most powerful vasodilators known to man while P2Y6 mediates strong vasoconstriction in cerebral blood vessels. By describing the potential changes in these receptor/agonist systems, we hope to better describe the balance between vasoconstriction and vasodilation following stroke.Stroke is a common and severe disorder of the central nervous system, where disturbances in blood supply induce ischemic injury. Ischemia and the following cascade of inflammation cause not only neuronal death but also induce changes in blood vessels and surrounding tissue. We have previously demonstrated an increase in the expression of several vasoconstrictive receptor systems following both ischemic and hemorrhagic stroke. These changes are hypothesized to induce a more vasoconstrictive state, which reduce blood flow and may enhance ischemic damage in the near-ischemic zone surrounding the ischemic core. Most previous studies have focused on traditional vasoconstrictors such as endothelin, angiotensin and serotonin, while less focus has been put on more locally acting vasoconstrictors such as purines. Even less effort has been applied to the investigation of vasodilatory receptor systems and their plasticity following ischemia. The first two papers making up the basis for this thesis investigate the physiological function of CGRP, VIP and the closely related pituitary adenylate cyclase-activating polypeptide (PACAP) in rat middle cerebral arteries (MCAs). Wire myography and pressurized arteriography evaluate changes in wall tension and vessel diameter along with measurements of intracellular calcium. Immunohistochemistry is used to determine receptor localization. Based on these experiments we conclude that CGRP and VIP receptors are located on the smooth muscle cells and not on the entothelial cells of the rat MCA. VIP and CGRP both induce a sustained vasorelaxation which correlates with a decrease in intracellular calcium. It was also demonstrated that VPAC1 and VPAC2 receptors are predominant over PAC1 receptors.The last two papers of this thesis investigate changes in receptor expression and agonist effect in rat MCAs following either experimental SAH or transient MCA occlusion. Wire myography was used to determine changes in wall tension and western blot and/or flow cytometry was used to evaluate alterations in receptor expression. We demonstrate an enhanced vasodilatory response to VIP following tMCAO but not after SAH. CRGP-mediated vasodilation is completely unaffected by SAH or tMCAO. An enhanced expression of the P2Y6 receptor following both types of stroke was demonstrated, however contraction was only enhanced after tMCAO

Enhanced external counter pulsation in treatment of refractory angina pectoris: two year outcome and baseline factors associated with treatment failure

<p>Abstract</p> <p>Background</p> <p>Enhanced external counter pulsation (EECP) is a non-invasive treatment option for patients with refractory angina pectoris ineligible to further traditional treatment. The aim of this study was to evaluate the effect of EECP on patients at a Scandinavian medical centre and to investigate if outcome can be predicted by analysing baseline factors.</p> <p>Methods</p> <p>86 consecutive patients (70 male, 16 female) were treated with EECP and followed for two years post treatment. Canadian cardiovascular society (CCS) class was analysed, and medication and adverse clinical events were researched prior to EECP, at the end of the treatment, and at six, 12 and 24 months thereafter. Patients responding to therapy by improving at least one CCS class were compared with those who failed to respond. Any differences in background factors were recorded and analysed.</p> <p>Results</p> <p>79% of the patients responded to therapy by improving at least one CCS class. In general, the CCS class improved by one class after EECP treatment (3.05 before versus 2.14 after treatment). A total of 61.5% of the initial responders showed sustained improvement at the 12 month follow-up while 29% presented sustained improvement after 24 months. Treatment was most effective among patients suffering from CCS class III-IV angina pectoris, while patients suffering from CCS class II angina pectoris improved transiently but failed to show sustained improvement after the 12 month follow-up. Diabetes mellitus and calcium channel antagonists were more common among the non-responders (<it>p </it>< 0.05).</p> <p>Conclusion</p> <p>This study confirms the safety and efficiency of EECP as a treatment option for patients suffering from refractory angina pectoris. The therapy is most beneficial in patients suffering from severe angina (CCS III-IV) while sustained response to therapy could not be verified among patients suffering from CCS class II angina pectoris.</p

Differential inhibitory response to telcagepant on αCGRP induced vasorelaxation and intracellular Ca2+ levels in the perfused and non-perfused isolated rat middle cerebral artery

Abstract Background Calcitonin gene-related peptide (CGRP) is one of the most potent endogenous vasodilators identified to date. The present study elucidates the differential interaction of CGRP, its receptor and the effect of the CGRP-receptor antagonist telcagepant on intracellular Ca2+ -levels and tension in rat middle cerebral arteries (MCA) by pressurized arteriography, FURA-2/wire myography and immunohistochemistry. Methods A pressurized arteriograph system was used to evaluate changes in MCA tension when subjected to CGRP and/or telcagepant. Intracellular calcium levels were evaluated using a FURA-2/wire myograph system. Localization of the CGRP-receptor components was verified using immunohistochemistry. Results Abluminal but not luminal αCGRP (10-12-10-6 M) caused concentration-dependent vasorelaxation in rat MCA. Luminal telcagepant (10-6 M) failed to inhibit this relaxation, while abluminal telcagepant inhibited the relaxation (10-6 M). Using the FURA-2 method in combination with wire myography we observed that αCGRP reduced intracellular calcium levels and in parallel the vascular tone. Telcagepant (10-6 M) inhibited both vasorelaxation and drop in intracellular calcium levels. Both functional components of the CGRP receptor, CLR (calcitonin receptor-like receptor) and RAMP1 (receptor activity modifying peptide 1) were found in the smooth muscle cells but not in the endothelial cells of the cerebral vasculature. Conclusions This study thus demonstrates the relaxant effect of αCGRP on rat MCA. The vasorelaxation is associated with a simultaneous decrease in intracellular calcium levels. Telcagepant reduced relaxation and thwarted the reduction in intracellular calcium levels localized in the vascular smooth muscle cells. In addition, telcagepant may act as a non-competitive antagonist at concentrations greater than 10-8 M

VIP/PACAP receptors in cerebral arteries of rat: Characterization, localization and relation to intracellular calcium.

BACKGROUND: Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide (PACAP)-containing nerves surround cerebral blood vessels. The peptides have potent vasodilator properties via smooth muscle cell receptors and activation of adenylate cyclase. The purpose of this study was to describe the effects of two putative VIP/PACAP receptor antagonists and the distribution of the receptor protein in rat brain vessels. METHODS: The vascular effects of VIP, PACAP-27 and PACAP-38 were investigated in segments of rat middle cerebral artery (MCA) by pressurized arteriography, and in a wire myograph. The antagonistic responses to PACAP6-38 and PG99-465 were evaluated. In addition, the receptor subtypes for VIP and PACAP (VPAC(1), VPAC(2) and PAC(1)) were visualized in the rat middle cerebral artery by immunohistochemistry and Western blotting. RESULTS: In the perfusion model, abluminal but not luminal VIP, PACAP-27 and PACAP-38 caused concentration-dependent relaxations of the MCA (27.1±0.2%, 25.2±0.4% and 0.3±0.1%, respectively). In the wire myograph, there was no significant difference in potency of the peptides in the MCA. In both systems, PACAP6-38 and PG99-465 inhibited the VIP induced relaxation. Western blot showed the presence of the receptor proteins in cerebral vasculature and immunohistochemistry showed that all three receptors are present and located in the cytoplasm of smooth muscle cells. CONCLUSION: In both systems, the two blockers antagonized the relaxant VIP effect; the potency order of agonists and the immunohistochemistry suggest the presence of the dilatory VPAC(1) and VPAC(2) receptors on the smooth muscle cells

Changes in P2Y6 receptor-mediated vasoreactivity following focal and global ischemia

Ischemia, both in the form of focal thromboembolic stroke and following subarachnoid hemorrhage (SAH), causes upregulation of vasoconstrictive receptor systems within the cerebral vasculature. Descriptions regarding changes in purinergic signaling following ischemia are lacking, especially when the importance of purinergic signaling in regulating vascular tone is taken into consideration. This prompted us to evaluate changes in P2Y6-mediated vasomotor reactivity in two different stroke models in rat. We used wire myography to measure changes in cerebral vasoreactivity to the P2Y6 agonist UDP-β-S following either experimental SAH or transient middle cerebral artery occlusion. Changes in receptor localization or receptor expression were evaluated using immunohistochemistry and quantitative flow cytometry. Transient middle cerebral artery occlusion caused an increase in Emax when compared to sham (233.6 [206.1–258.5]% vs. 161.1 [147.1–242.6]%, p = 0.0365). No such change was seen following SAH. Both stroke models were associated with increased levels of P2Y6 receptor expression in the vascular smooth muscle cells (90.94 [86.99–99.15]% and 93.79 [89.96–96.39]% vs. 80.31 [70.80–80.86]%, p = 0.021) and p = 0.039 respectively. There was no change in receptor localization in either of the stroke models. Based on these findings, we conclude that focal ischemic stroke increases vascular sensitivity to UDP-β-S by upregulating P2Y6 receptors on vascular smooth muscle cells while experimental SAH did not induce changes in vasoreactivity in spite of increased P2Y6 receptor expression

Comparison of patients undergoing enhanced external counterpulsation and spinal cord stimulation for refractory angina pectoris.

INTRODUCTION: As more patients survive coronary events, the prevalence of patients with refractory angina pectoris is increasing. The aim was to evaluate the effects of enhanced external counterpulsation (EECP) and spinal cord stimulation (SCS) and compare with optimal medically treated patients with refractory angina. METHODS: 153 patients with refractory angina were treated with either EECP, SCS, or were retained on their pharmacological treatment (control). Glyceryl trinitrate usage and Canadian Cardiovascular Society classification were registered at baseline, 6 and 12 months after therapy. RESULTS: Both EECP and SCS reduced the angina as compared with controls (P<0.001). Patients treated with EECP showed a more effective reduction as compared with SCS patients (P<0.05). Both treatments resulted in significantly decreased glyceryl trinitrate usage at 6 and 12 months follow-up (P<0.001). The nitrate consumed was unaltered in the controls. DISCUSSION: The results from this study show that both EECP and SCS therapy reduce angina in patients with refractory angina pectoris; the response to EECP was slightly more effective than that to SCS. Thus, EECP can be used as an alternative treatment for patients not responding to electrical stimulation. The beneficial effects in the treated groups were maintained during the 12 months follow-up period

Ciclosporin to Protect Renal function In Cardiac Surgery (CiPRICS) : A study protocol for a double-blind, randomised, placebo-controlled, proof-of-concept study

Introduction: Acute kidney injury (AKI) after cardiac surgery is common and results in increased morbidity and mortality. One possible mechanism for AKI is ischaemia-reperfusion injury caused by the extracorporeal circulation (ECC), resulting in an opening of the mitochondrial permeability transition pore (mPTP) in the kidneys, which can lead to cell injury or cell death. Ciclosporin may block the opening of mPTP if administered before the ischaemia- reperfusion injury. We hypothesised that ciclosporin given before the start of ECC in cardiac surgery can decrease the degree of AKI. Methods and analysis: Ciclosporin to Protect Renal function In Cardiac Surgery (CiPRICS) study is an investigator-initiated double-blind, randomised, placebo-controlled, parallel design, single-centre study performed at a tertiary university hospital. The primary objective is to assess the safety and efficacy of ciclosporin to limit the degree of AKI in patients undergoing coronary artery bypass grafting surgery. We aim to evaluate 150 patients with a preoperative estimated glomerular filtration rate of 15-90 mL/min/ 1.73 m2. Study patients are randomised in a 1:1 ratio to receive study drug 2.5 mg/kg ciclosporin or placebo as an intravenous injection after anaesthesia induction but before start of surgery. The primary end point consists of relative P-cystatin C changes from the preoperative day to postoperative day 3. The primary variable will be tested using an analysis of covariance method. Secondary end points include evaluation of P-creatinine and biomarkers of kidney, heart and brain injury. Ethics and dissemination: The trial is conducted in compliance with the current version of the Declaration of Helsinki and the International Council for Harmonisation (ICH) Good Clinical Practice guidelines E6 (R1) and was approved by the Regional Ethical Review Board, Lund and the Swedish Medical Products Agency (MPA). Written and oral informed consent is obtained before enrolment into the study

Effect of Cyclosporine on Cytokine Production in Elective Coronary Artery Bypass Grafting : A Sub-Analysis of the CiPRICS (Cyclosporine to Protect Renal Function in Cardiac Surgery) Study

Objectives: The augmented inflammatory response to cardiac surgery is a recognized cause of postoperative acute kidney injury. The present study aimed to investigate the effects of preoperative cyclosporine treatment on cytokine production and delineate factors associated with postoperative kidney impairment. Design: A randomized, double-blind, placebo-controlled, single-center study. Setting: At a tertiary care, university hospital. Participants: Patients eligible for elective coronary artery bypass grafting surgery; 67 patients were enrolled. Interventions: Patients were randomized to receive 2.5 mg/kg cyclosporine or placebo before surgery. Cytokine levels were measured after the induction of anesthesia and 4 hours after the end of cardiopulmonary bypass. Measurements and Main Results: Tissue-aggressive (interleukin [IL]-1β, macrophage inflammatory protein [MIP]-1β, granulocyte colony-stimulating factor [G-CSF], IL-6, IL-8, IL-17, MCP-1), as well tissue-lenient (IL-4) cytokines, were significantly elevated in response to surgery. Changes in cytokine levels were not affected by cyclosporine pretreatment. Conclusions: Elective coronary artery bypass grafting surgery with cardiopulmonary bypass triggers cytokine activation. This activation was not impacted by preoperative cyclosporine treatment