The Significance of Mitophagy in Myocardial Ischaemia/ Reperfusion: the effect of melatonin

Thesis (MSc)--Stellenbosch University, 2018.Introduction: Myocardial ischaemia and concomitant cell damage are caused by a reduction in the blood supply to the heart. To date, the most effective strategy to salvage the myocardium is timely reperfusion which is unfortunately associated with further tissue damage. This phenomenon, termed ischaemia reperfusion injury, is associated with mitochondrial structural damage which could lead to death of cells previously damaged by ischaemia. Damaged and dysfunctional mitochondria play a key role in mediating tissue damage in this setting, thus the swift yet selective removal of these damaged organelles by mitochondrial autophagy – mitophagy could be of importance in cell survival and therefore is a potential therapeutic target. Studies have shown that upregulation of autophagy during ischaemia/reperfusion is cardioprotective, however, very little is known about the role of mitophagy in this setting. Subsequently, the aims of this study were to (i) characterise the effect of ischaemia/reperfusion on functional recovery during reperfusion and to correlate this with mitochondrial oxidative phosphorylation capacity, infarct size and mitophagy in the working heart model using male Wistar rats; (ii) evaluate the effect of mitophagy manipulation on cardioprotection using the parameters listed above. To achieve this, used was made of melatonin, the pineal hormone, which is well-known for its cardioprotective effects. Methods: Male Wistar rat hearts were perfused ex vivo in the working mode using Krebs-Henseleit buffer and glucose (10mM) as substrate. After a stabilization period of 30 min, hearts were subjected to 20min global ischaemia followed by 30min reperfusion during which time functional recovery was monitored. Mitochondria were isolated from hearts at different times during the perfusion protocol: after stabilization for 30min, after 20min global ischaemia and after 30min of reperfusion. The mitochondrial pellets were used for measurement of mitochondrial oxidative phosphorylation using an Oxygraph as well as for western blotting to evaluate a number of indicators of mitophagy. In addition, hearts were subjected to the perfusion protocol as described above and freeze-clamped at the same time intervals for subsequent Western blotting for mitophagy markers in the cytosolic fraction. In a separate series melatonin (0.3, 50M) was added to the perfusate for 10min before and 10 min after ischaemia and the same parameters evaluated as above. For evaluation of infarct size by the tetrazolium method, hearts were stabilized for 30min, followed by 35min of regional ischaemia and 60min reperfusion. Results: Exposure of hearts to either 35min regional ischaemia/ 60min reperfusion or 20min global ischaemia/ 30min reperfusion was associated with impaired recovery of myocardial function during reperfusion, characterized by significant reduction in several haemodynamic endpoints including coronary flow, aortic output and total work performed. Exposure to 20min global ischaemia per se had no effect on mitochondrial oxidative phosphorylation function, but a significant reduction in QO2 States 3 and 4 was observed after reperfusion, with glutamate/malate as substrates. Contrary to expectations, ischaemia/reperfusion did not upregulate mitophagy, as indicated by the reduced expression of PINK1, Parkin and TOM70 as well as markers of the alternative pathway (ULK1, DRP-1 and Rab9). Melatonin at both concentrations studied, significantly reduced the myocardial infarct size (p<0.0001), but did not improve mechanical recovery during reperfusion. In the global ischaemia model, melatonin increased mitochondrial oxphos during reperfusion only. While not having marked effects on the conventional PINK1/Parkin pathway, melatonin caused significant increases in the expression and phosphorylation of ULK1 and DRP-1, suggesting upregulation of the alternative pathway of mitophagy. Conclusion: In this experimental model ischaemia/ reperfusion reduced (i) contractile function and (ii) oxidative phosphorylation during reperfusion. It also subdued both the (iii) conventional and alternative mitophagy pathways suggesting that mitochondrial fission, which is a prerequisite for mitophagy, may be impaired under these conditions. These changes may contribute to the impaired functional recovery during reperfusion. Melatonin’s cardioprotective effects were associated with upregulation of a novel mitophagy signalling pathway, the significance of which in its cardioprotective actions needs to be further elucidated.Miokardiale iskemie en selbeskadiging word deur ‘n vermindering in die bloedvoorsiening aan die hart teweeggebring. Tot op hede, is herperfusie van die iskemiese hart die mees effektiewe strategie om selbeskadiging te voorkom. Ongelukkig gaan herperfusie ook met verdere selbeskadiging gepaard, die sogenaamde verskynsel van herperfusie beskadiging. Herperfusie gaan gepaard met verdere beskadiging van selle wat reeds deur die voorafgaande periode van iskemie affekteer is. Beskadigde en disfunksionele mitochondria speel ‘n belangrike rol in hierdie scenario, gevolglik is die spoedige en selektiewe verwydering van hierdie organelle deur die proses van mitochondriale outofagie/mitofagie van kardinale belang vir oorlewing. Mitofagie mag dus ‘n potensiële terapeutiese teiken wees vir beskerming van die iskemies/herperfuseerde hart. Dit is voorheen getoon dat opregulering van outofagie tydens iskemie/herperfusie die hart teen beskadiging beskerm, maar min of geen inligting is beskikbaar aangaande die rol van mitofagie in hierdie verband nie. Die doelwitte van hierdie studie was dus (i) karakterisering van die effek van iskemie/herperfusie op funksionele herstel tydens herperfusie en die verband met mitochondriale oksidatiewe fosforilasie, infarkt grootte en mitofagie in ‘n model van die geïsoleerde, geperfuseerde rothart; (ii) evaluasie van mitofagie manipulasie op beskerming van die hart deur gebruik te maak van melatonien, ‘n hormoon afgeskei deur die pineaalklier. Metodes Harte van manlike Wistar rotte is ex vivo geperfuseer met Krebs-Henseleit buffer en glukose (10mM) as substraat, volgens die werkhart tegniek. Na ‘n stabilisasie periode van 30min, is harte onderwerp aan 20min globale iskemie gevolg deur 30min herperfusie waartydens funksionele herstel gemonitor is. Mitochondria is op verskillende tye tydens die perfusie protokol geïsoleer naamlik na stabilisasie, na 20min globale iskemie en na 30min herperfusie. Hierdie pellets is gebruik vir die meting van die oksidatiewe fosforilasie proses met behulp van ‘n Oksigraaf sowel as vir western blots vir evaluering van merkers van mitofagie. ‘n Addisionele series van harte is ook geperfuseer volgens bogenoemde protokol en die harte gevriesklamp vir bereiding van sitosoliese fraksies vir daaropvolgende Western blots. Melatonien (0.3, 50mM) is by die perfusaat gevoeg 10min voor en 10min na globale iskemie en dieselfde parameters evalueer soos bo gelys. Vir bepaling van infarkt grootte met die tetrazolium metode, is harte gestabilseer vir 30min, gevolg deur 35min streeks iskemie en 60 min herperfusie. Resultate Blootstelling van die geperfuseerde hart aan of 35min streeks iskemie/60min herperfusie of 20min globale iskemie/30 min herperfusie het funksionele herstel tydens herperfusie beduidend onderdruk, soos aangedui deur die verlaging in koronêre vloei, aorta en kardiale omset. Blootstelling van die hart aan 20min globale iskemie per se het geen effek op mitochondriale oksidatiewe funksie gehad nie, maar ‘n beduidende onderdrukking in QO2 staat 3 en staat 4 is na herperfusie waargeneem, met glutamaat/malaat as substrate. In teenstelling met verwagtinge, het iskemie/herperfusie nie mitofagie opgereguleer nie, maar onderdruk, soos getoon deur die verminderde uitdrukking van mitochondriale PINK1, Parkin en TOM70 sowel as merkers van die alternatiewe pad van mitofagie (ULK1, DRP-1 en Rab9). Beide hoë en lae melatonien konsentrasies het die infarkt grootte beduidend verlaag, maar nie funksionele herstel tydens herperfusie verbeter nie. Melatonien het mitochondriale oksidatiewe fosforilasie slegs tydens herperfusie na 20min globale iskemie verbeter. Melatonien het geen effek op die konvensionele pad van mitofagie gehad nie, maar het die uitdrukking en fosforilering van ULK1 en DRP-1 beduidend verhoog, wat dui op opregulering van die alternatiewe pad van mitofagie. Gevolgtrekking In die eksperimentele model wat gebruik is, het miokardiale iskemie/herperfusie die kontraktiele herstel en oksidatiewe fosforilasie proses onderdruk tydens herperfusie. Dit het ook beide die konvensionele en alternatiewe paaie van mitofagie onderdruk, wat moontlik dui op inhibisie van die mitochondriale fissie proses. Beide hierdie prosesse mag tot die onderdrukking in funksie bydra. Daarenteen was die beskerming deur melatonien verleen, geassosieer met opregulering van die alternatiewe mitofagie proses en dus moontlik mitochondriale fissie. Die belang van hierdie proses in die beskerming teen iskemiese beskadiging deur melatonien moet egter nog verder ondersoek word

Description of vaccine clinical trials in Africa: a narrative review

Clinical research is important in establishing the effects of health-care interventions. Vaccine clinical trials are to examine the effectiveness and safety of vaccines for the prevention of diseases. Africa has a high burden of infectious diseases such as malaria, tuberculosis, HIV/AIDS, and Ebola virus disease. Here we report a database surveillance study of vaccine-related clinical trials conducted in Africa. An objective is to address and profile vaccine clinical trials conducted in Africa. Data were extracted from the WHO International Clinical Trials Registry Platform on 22 July 2018 and updated on 05 September 2019. We found that 61% of the 377 clinical trials were registered prospectively and 35% registered retrospectively. About 72% of the trials were single-country studies and within the country, most trials (86%) were single-center studies. The proportion of trials involving multiple African countries was 11% and that of trials involving countries outside of Africa was 16%. The biggest funder of the vaccine trials (34%) was industry, followed by governments (25%) and universities (21%). The most studied diseases were malaria (20%), HIV/AIDS (15%), tuberculosis (7%), and Ebola virus disease (6%). Most of the vaccine trials were conducted in adults (42%). The trials ranged from phase I to phase IV, with most of the trials being in phase I (18%) and phase III (18%). The conduct of vaccine clinical trials in Africa seeks to address the disease epidemics faced by the continent. There is a need for more investments from governmental bodies toward vaccine research in Africa. Further, African country collaborations are needed in efforts to find African solutions to the current infectious disease threats faced by the continent

South African healthcare workers and COVID-19 : a shared responsibility to protect a precious and limited resource

CITATION: Dramowski, A. et al. 2020. South African healthcare workers and COVID-19 : a shared responsibility to protect a precious and limited resource. South African Medical Journal, doi:10.7196/SAMJ.2020.v110i7.14903.The original publication is available at http://www.samj.org.zaHealthcare workers (HCWs) in African countries face high risks of occupational exposure to many pathogens, including tuberculosis, measles, HIV and Ebola.[1,2] The novel coronavirus SARSCoV- 2 poses an arguably greater threat to African HCWs than any other infectious agent to date. Data from countries with established epidemics show that HCWs experience high rates of COVID-19 infection, morbidity and mortality. In the USA, 19% of COVID-19 cases whose occupational status was known were HCWs (9 282/49 000),[3] and >90 000 HCW COVID-19 infections were documented in 30 countries, with 260 deaths in nurses, by early May 2020.[4] In South Africa (SA), on 6 May, Minister Zweli Mkhize reported that 511 HCWs had tested positive for SARS-CoV-2 (7% of the national total), with nurses accounting for 53% of total HCW cases.[5] The unprecedented risk posed to HCWs by COVID-19 is clearly acknowledged by all levels of the SA government. Nationally there have been commitments, both financially and administratively, to ensure procurement and local production of personal protective equipment (PPE) and transparent reporting of HCW COVID-19 infections. To varying degrees, administrative and engineering interventions to prevent COVID-19 infections and outbreaks have been implemented in SA healthcare facilities (Table 1). Despite the early phase of the pandemic and general availability of PPE, SA is already facing high rates of HCW COVID-19 infections and exposure events. This is a concerning development reflecting both widespread community transmission (with HCW infections) and the need to strengthen ‘universal’ prevention measures in healthcare facilities, e.g. physical distancing, mask-wearing, hand hygiene, and increased cleaning/ disinfection of surfaces and equipment.http://www.samj.org.za/index.php/samj/issue/view/267Publisher's versio

The availability, utilisation and relevance of therapeutic apparatuses in South African occupational therapy clinical practice

CITATION: Duvenage, C. M. E. 2019. The availability, utilisation and relevance of therapeutic apparatuses in South African occupational therapy clinical practice. South African Journal of Occupational Therapy, 49(3):3-5, doi:10.17159/2310-3833/2019/vol49n3a2.The original publication is available at http://www.sajot.co.zaThe World Federation of Occupational Therapists (WFOT) steers the development, use and practice of occupational therapy internationally through numerous operations including policy and research in an effort to homogenise and advance occupational therapy training globally. The Federation has compiled and published the Minimum Standards for the Education of Occupational Therapists that serves as a blueprint to both set the minimum standard for educational programmes in occupational therapy and to foster continuous quality assurance and professional development. In South Africa, the Professional Board for Occupational Therapy, Medical Orthotics and Prosthetics and Arts Therapy has incorporated these standards into the national policies and guidelines for occupational therapy training2,3. Consistent with international standards, one of the key outcomes highlighted in the national policies and guidelines is the graduate’s knowledge of occupation.Publisher's versio

Adverse birth outcome case definitions associated with maternal HIV and antiretroviral drug use in pregnancy: a scoping review protocol

Introduction The global antiretroviral therapy era has led to a decline in the number of children newly acquiring HIV and an increase in the number of children who are HIV-exposed and uninfected (HEU). This shift has prompted extensive research focussing on health and survival outcomes of children who are HEU. Study findings, particularly in relation to adverse birth outcomes, have been disparate, inconclusive and have not always been generalisable. Thus, the objectives of this scoping review are (1) to identify and extract definitions used for the adverse birth outcome terms ‘low birth weight’, ‘small for gestational age’, ‘stillbirth’ and ‘preterm birth’; (2) to compare the characteristics of studies from which birth outcome definitions were extracted by (a) temporal periods and (b) study country setting (high-income vs low-income and middle-income countries); (3) to use content analysis to map and describe the temporal and geographic distribution of the definitions used and construct a logical model of their evolution.Methods and analysis The online databases of PubMed/MEDLINE, Scopus, Web of Science, Cochrane Library and CINHAL/EBSCOhost will be used to identify published and grey literature from 2011 to 2022 to identify definitions for the adverse birth outcome terms ‘low birth weight’, ‘small for gestational age’, ‘stillbirth’ and ‘preterm birth’. A three-step process of (1) duplicate removal, (2) title and abstract screening and (3) full text screening will be used to select included studies. The extracted data will be used to conduct a comparative analysis, content analysis and construct a logic model.Ethics and dissemination This review will be used to inform a consensus process around the development of harmonised definitions for the specified adverse birth outcomes. Our dissemination plan includes presentations, publications as well as the development infographics and a resource hub. The study is approved by the Human Research Ethics Committee of Stellenbosch University

Training for transformation : opportunities and challenges for health workforce sustainability in developing a remote clinical training platform

CITATION: Muller, J. et al. 2021. Training for transformation : opportunities and challenges for health workforce sustainability in developing a remote clinical training platform. Frontiers in Public Health 9:601026, doi:10.3389/fpubh.2021.601026.The original publication is available at https://www.frontiersin.orgBackground: In 2018, Stellenbosch University’s Ukwanda Centre for Rural Health led a faculty initiative to expand undergraduate health professions training to a new site, 9 hours drive from the health sciences campus in the sparsely populated Northern Cape Province of South Africa in the town of Upington. This is part of a faculty strategy to extend undergraduate health sciences training into an under-resourced part of the country, where there is no medical school. During 2019, the first year of implementation, four final year medical students undertook a longitudinal integrated clerkship at this site, while final year students from other programmes undertook short 5-week rotations, with plans for extending rotations and including more disciplines in 2020. The aim of this study was to understand stakeholder perceptions regarding the development of Upington as a rural clinical training site and how this influenced existing services, workforce sustainability and health professions education. Methods: An iterative thematic analysis of qualitative data collected from 55 participants between January and November 2019 was conducted as part of the case study. A constructivist approach to data collection was utilized to explore participants’ perceptions, experiences and understanding of the new training site. Triangulation of data collection and reflexive thematic analysis contributed to the trustworthiness of the data and credibility of the findings. Findings: The perceptions of three key groups of stakeholders are reported: (1) Dr. Harry Surtie Hospital and Academic Programme Managers; (2) Supervising and non-supervising clinical staff and (3) Students from three undergraduate programs of the Faculty. Five themes emerged regarding the development of the site. The themes include the process of development; the influence on the health service; workforce sustainability; a change in perspective and equipping a future workforce. Discussion: This case study provides data to support the value of establishing a rural clinical training platform in a resource constrained environment. The influence of the expansion initiative on the current workforce speaks to the potential for improved capacity and competence in patient management with an impact on encouraging a rural oriented workforce. Using this case study to explore how the establishment of a new rural clinical training site is perceived to influence rural workforce sustainability and pathways, may have relevance to other institutions in similar settings. The degree of sustainability of the clinical training initiative is explored.https://www.frontiersin.org/articles/10.3389/fpubh.2021.601026/fullPublisher's versio