Publications by authors named "Carmel M McVicar"

8 Publications

  • Page 1 of 1

Role of the receptor for advanced glycation endproducts (RAGE) in retinal vasodegenerative pathology during diabetes in mice.

Diabetologia 2015 May 17;58(5):1129-37. Epub 2015 Feb 17.

Centre for Experimental Medicine, Queen's University Belfast, Belfast, BT12 6BA, Northern Ireland, UK.

Aims/hypothesis: The receptor for AGEs (RAGE) is linked to proinflammatory pathology in a range of tissues. The objective of this study was to assess the potential modulatory role of RAGE in diabetic retinopathy.

Methods: Diabetes was induced in wild-type (WT) and Rage (-/-) mice (also known as Ager (-/-) mice) using streptozotocin while non-diabetic control mice received saline. For all groups, blood glucose, HbA1c and retinal levels of methylglyoxal (MG) were evaluated up to 24 weeks post diabetes induction. After mice were killed, retinal glia and microglial activation, vasopermeability, leucostasis and degenerative microvasculature changes were determined.

Results: Retinal expression of RAGE in WT diabetic mice was increased after 12 weeks (p < 0.01) but not after 24 weeks. Rage (-/-) mice showed comparable diabetes but accumulated less MG and this corresponded to enhanced activity of the MG-detoxifying enzyme glyoxalase I in their retina when compared with WT mice. Diabetic Rage (-/-) mice showed significantly less vasopermeability, leucostasis and microglial activation (p < 0.05-0.001). Rage (-/-) mice were also protected against diabetes-related retinal acellular capillary formation (p < 0.001) but not against pericyte loss.

Conclusions/interpretation: Rage (-/-) in diabetic mice is protective against many retinopathic lesions, especially those related to innate immune responses. Inhibition of RAGE could be a therapeutic option to prevent diabetic retinopathy.
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May 2015

The gastrointestinal peptide obestatin induces vascular relaxation via specific activation of endothelium-dependent NO signalling.

Br J Pharmacol 2012 May;166(1):327-38

School of Biological Sciences, Queen's University Belfast, Belfast, UK.

Background And Purpose: Obestatin is a recently discovered gastrointestinal peptide with established metabolic actions, which is linked to diabetes and may exert cardiovascular benefits. Here we aimed to investigate the specific effects of obestatin on vascular relaxation.

Experimental Approach: Cumulative relaxation responses to obestatin peptides were assessed in rat isolated aorta and mesenteric artery (n≥ 8) in the presence and absence of selective inhibitors. Complementary studies were performed in cultured bovine aortic endothelial cells (BAEC).

Key Results: Obestatin peptides elicited concentration-dependent relaxation in both aorta and mesenteric artery. Responses to full-length obestatin(1-23) were greater than those to obestatin(1-10) and obestatin(11-23). Obestatin(1-23)-induced relaxation was attenuated by endothelial denudation, l-NAME (NOS inhibitor), high extracellular K(+) , GDP-β-S (G-protein inhibitor), MDL-12,330A (adenylate cyclase inhibitor), wortmannin (PI3K inhibitor), KN-93 (CaMKII inhibitor), ODQ (guanylate cyclase inhibitor) and iberiotoxin (BK(Ca) blocker), suggesting that it is mediated by an endothelium-dependent NO signalling cascade involving an adenylate cyclase-linked GPCR, PI3K/PKB, Ca(2+) -dependent eNOS activation, soluble guanylate cyclase and modulation of vascular smooth muscle K(+) . Supporting data from BAEC indicated that nitrite production, intracellular Ca(2+) and PKB phosphorylation were increased after exposure to obestatin(1-23). Relaxations to obestatin(1-23) were unaltered by inhibitors of candidate endothelium-derived hyperpolarizing factors (EDHFs) and combined SK(Ca) /IK(Ca) blockade, suggesting that EDHF-mediated pathways were not involved.

Conclusions And Implications: Obestatin produces significant vascular relaxation via specific activation of endothelium-dependent NO signalling. These actions may be important in normal regulation of vascular function and are clearly relevant to diabetes, a condition characterized by endothelial dysfunction and cardiovascular complications.
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May 2012

Intervention with an erythropoietin-derived peptide protects against neuroglial and vascular degeneration during diabetic retinopathy.

Diabetes 2011 Nov 12;60(11):2995-3005. Epub 2011 Sep 12.

Centre for Vision and Vascular Science, Queen’s University Belfast, Belfast, Northern Ireland, UK.

Objective: Erythropoietin (EPO) may be protective for early stage diabetic retinopathy, although there are concerns that it could exacerbate retinal angiogenesis and thrombosis. A peptide based on the EPO helix-B domain (helix B-surface peptide [pHBSP]) is nonerythrogenic but retains tissue-protective properties, and this study evaluates its therapeutic potential in diabetic retinopathy.

Research Design And Methods: After 6 months of streptozotocin-induced diabetes, rats (n = 12) and age-matched nondiabetic controls (n = 12) were evenly split into pHBSP and scrambled peptide groups and injected daily (10 μg/kg per day) for 1 month. The retina was investigated for glial dysfunction, microglial activation, and neuronal DNA damage. The vasculature was dual stained with isolectin and collagen IV. Retinal cytokine expression was quantified using real-time RT-PCR. In parallel, oxygen-induced retinopathy (OIR) was used to evaluate the effects of pHBSP on retinal ischemia and neovascularization (1-30 μg/kg pHBSP or control peptide).

Results: pHBSP or scrambled peptide treatment did not alter hematocrit. In the diabetic retina, Müller glial expression of glial fibrillary acidic protein was increased when compared with nondiabetic controls, but pHBSP significantly reduced this stress-related response (P < 0.001). CD11b+ microglia and proinflammatory cytokines were elevated in diabetic retina responses, and some of these responses were attenuated by pHBSP (P < 0.01-0.001). pHBSP significantly reduced diabetes-linked DNA damage as determined by 8-hydroxydeoxyguanosine and transferase-mediated dUTP nick-end labeling positivity and also prevented acellular capillary formation (P < 0.05). In OIR, pHBSP had no effect on preretinal neovascularization at any dose.

Conclusions: Treatment with an EPO-derived peptide after diabetes is fully established can significantly protect against neuroglial and vascular degenerative pathology without altering hematocrit or exacerbating neovascularization. These findings have therapeutic implications for disorders such as diabetic retinopathy.
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November 2011

Differential modulation of angiogenesis by erythropoiesis-stimulating agents in a mouse model of ischaemic retinopathy.

PLoS One 2010 Jul 29;5(7):e11870. Epub 2010 Jul 29.

Centre for Vision and Vascular Science, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom.

Background: Erythropoiesis stimulating agents (ESAs) are widely used to treat anaemia but concerns exist about their potential to promote pathological angiogenesis in some clinical scenarios. In the current study we have assessed the angiogenic potential of three ESAs; epoetin delta, darbepoetin alfa and epoetin beta using in vitro and in vivo models.

Methodology/principal Findings: The epoetins induced angiogenesis in human microvascular endothelial cells at high doses, although darbepoetin alfa was pro-angiogenic at low-doses (1-20 IU/ml). ESA-induced angiogenesis was VEGF-mediated. In a mouse model of ischaemia-induced retinopathy, all ESAs induced generation of reticulocytes but only epoetin beta exacerbated pathological (pre-retinal) neovascularisation in comparison to controls (p<0.05). Only epoetin delta induced a significant revascularisation response which enhanced normality of the vasculature (p<0.05). This was associated with mobilisation of haematopoietic stem cells and their localisation to the retinal vasculature. Darbepoetin alfa also increased the number of active microglia in the ischaemic retina relative to other ESAs (p<0.05). Darbepoetin alfa induced retinal TNFalpha and VEGF mRNA expression which were up to 4 fold higher than with epoetin delta (p<0.001).

Conclusions: This study has implications for treatment of patients as there are clear differences in the angiogenic potential of the different ESAs.
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July 2010

Sildenafil citrate improves sperm motility but causes a premature acrosome reaction in vitro.

Fertil Steril 2007 May 28;87(5):1064-70. Epub 2007 Feb 28.

School of Medicine, Obstetrics and Gynaecology, Queen's University Belfast, Institute of Clinical Science, Belfast, United Kingdom.

Objective: To determine whether sildenafil citrate, a cyclic monophosphate-specific type 5 phosphodiesterase inhibitor, influences sperm motility or the acrosome reaction.

Design: Laboratory analysis of sperm motility after exposure to sildenafil citrate using computer-assisted semen analysis and acrosome reaction by fluorescein isothiocyanate-labeled peanut agglutinin staining.

Setting: An assisted reproductive technology (ART) unit.

Patient(s): Fifty-seven male patients.

Intervention(s): Sperm were divided into 90% (those with the best fertilizing potential used in assisted conception) and 45% (the poorer population) fractions by density centrifugation and incubated with sildenafil citrate (0.67 muM) at 37 degrees C for up to 180 minutes.

Main Outcome Measure(s): Both the number and velocity of progressively motile sperm were significantly increased by sildenafil citrate between 15 and 135 minutes. Furthermore, samples revealed that these effects were consistent in the 90% and 45% populations of sperm. In both populations, sildenafil also caused a significant increase in the proportion of acrosome-reacted sperm-22.1% compared with 11.8% in the control group of the good quality fraction and 16.6% compared with 9.4% in the control group of the poorer quality fraction.

Conclusion(s): The use of sildenafil citrate may adversely affect male fertility.
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May 2007

Reduced sperm yield from testicular biopsies of vasectomized men is due to increased apoptosis.

Fertil Steril 2007 Apr 22;87(4):834-41. Epub 2007 Jan 22.

Obstetrics and Gynaecology, School of Medicine, Queen's University Belfast, Institute of Clinical Science, Belfast, United Kingdom.

Objective: To compare sperm yields, apoptotic indices, and sperm DNA fragmentation from vasectomized men and fertile men undergoing vasectomy.

Design: Testicular biopsies from vasectomized (n = 26) and fertile men (n = 46), were milked to calculate sperm/gram and also formalin-fixed to determine the numbers of developing sperm and incidence and intensities of testicular FasL, Fas, Bax, and Bcl-2. Testicular sperm DNA fragmentation was assessed using the alkaline Comet assay.

Setting: An ART unit.

Patient(s): Twenty-six men attending for intracytoplasmic sperm injection (ICSI) and 46 men attending for vasectomies.

Main Outcome Measure(s): Spermatocyte, spermatid and sperm yields, Fas, FasL, and Bax staining.

Result(s): Sperm yields from men vasectomized >5 years previously were markedly reduced compared to fertile men. Increased intensities of FasL and Bax staining were observed in the seminiferous tubules of vasectomy men. FasL positivity (percentage) also increased in Sertoli cells, and both FasL and Fas positivity (percentage) increased in primary spermatocytes and round spermatids of vasectomized men. Sperm DNA fragmentation, an end point marker of apoptosis, increased significantly in vasectomized men compared to fertile men.

Conclusion(s): Reduced sperm yields after vasectomy are associated with increased apoptosis through the Fas-FasL and Bax pathways. Sperm after vasectomy displayed increased DNA fragmentation.
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April 2007

Effects of short and long incubations on DNA fragmentation of testicular sperm.

Fertil Steril 2004 Nov;82(5):1443-5

DNA fragmentation in testicular sperm from men with obstructive azoospermia is increased by 4-hour and 24-hour incubations and after cryopreservation with the effect is intensified by post-thaw incubation. Testicular sperm for use in intracytoplasmic sperm injection (ICSI) should be injected without delay.
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November 2004

Incidence of Fas positivity and deoxyribonucleic acid double-stranded breaks in human ejaculated sperm.

Fertil Steril 2004 Mar;81 Suppl 1:767-74

Department of Obstetrics and Gynaecology, School of Medicine, Queens University Belfast, Institute of Clinical Science, Grosvenor Road, Belfast BT12 6BJ, N. Ireland, UK.

Objective: To determine the incidence of Fas positivity and DNA double-strand breaks (DSB) as indicators of early- and late-stage apoptosis in ejaculated sperm.

Design: Fas positivity was assessed by flow cytometry and DSB by the neutral Comet assay.

Setting: Andrology Laboratory, Royal Maternity Hospital, Belfast, Northern Ireland, United Kingdom.

Patient(s) And Intervention(s): Forty-five infertile men undergoing infertility investigations and 10 fertile men undergoing vasectomies.

Main Outcome Measure(s): Percentage Fas-positive cells, percentage DNA fragmentation, olive tail moment.

Result(s): The apoptotic marker Fas was detected in ejaculated sperm, with a higher incidence of Fas positivity in teratozoospermic and asthenozoospermic than in normozospermic semen. No Fas positivity was observed in fertile men's sperm. Deoxyribonucleic acid fragmentation (DSB) was greater in infertile than in fertile men's sperm and also greater in sperm in semen than in sperm prepared for assisted conception. There was an inverse relationship between DSB and both sperm concentration and motility. There was no relationship between Fas positivity and DNA damage.

Conclusion(s): Fas was expressed in sperm of infertile men. In contrast, DNA fragmentation was observed in all sperm of fertile and infertile men and correlated with inadequate concentration and motility, which suggests that sperm DSB are ubiquitous and are not solely associated with apoptosis.
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March 2004