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Hadjilaou A, Brandi J, Riehn M, Friese MA, Jacobs T. Pathogenetic mechanisms and treatment targets in cerebral malaria. Nat Rev Neurol 2023; 19:688-709. [PMID: 37857843 DOI: 10.1038/s41582-023-00881-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2023] [Indexed: 10/21/2023]
Abstract
Malaria, the most prevalent mosquito-borne infectious disease worldwide, has accompanied humanity for millennia and remains an important public health issue despite advances in its prevention and treatment. Most infections are asymptomatic, but a small percentage of individuals with a heavy parasite burden develop severe malaria, a group of clinical syndromes attributable to organ dysfunction. Cerebral malaria is an infrequent but life-threatening complication of severe malaria that presents as an acute cerebrovascular encephalopathy characterized by unarousable coma. Despite effective antiparasite drug treatment, 20% of patients with cerebral malaria die from this disease, and many survivors of cerebral malaria have neurocognitive impairment. Thus, an important unmet clinical need is to rapidly identify people with malaria who are at risk of developing cerebral malaria and to develop preventive, adjunctive and neuroprotective treatments for cerebral malaria. This Review describes important advances in the understanding of cerebral malaria over the past two decades and discusses how these mechanistic insights could be translated into new therapies.
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Affiliation(s)
- Alexandros Hadjilaou
- Protozoen Immunologie, Bernhard-Nocht-Institut für Tropenmedizin (BNITM), Hamburg, Germany.
- Institut für Neuroimmunologie und Multiple Sklerose, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.
| | - Johannes Brandi
- Protozoen Immunologie, Bernhard-Nocht-Institut für Tropenmedizin (BNITM), Hamburg, Germany
| | - Mathias Riehn
- Protozoen Immunologie, Bernhard-Nocht-Institut für Tropenmedizin (BNITM), Hamburg, Germany
| | - Manuel A Friese
- Institut für Neuroimmunologie und Multiple Sklerose, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Thomas Jacobs
- Protozoen Immunologie, Bernhard-Nocht-Institut für Tropenmedizin (BNITM), Hamburg, Germany
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2
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Arteaga GM, Crow S. End organ perfusion and pediatric microcirculation assessment. Front Pediatr 2023; 11:1123405. [PMID: 37842022 PMCID: PMC10576530 DOI: 10.3389/fped.2023.1123405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 09/05/2023] [Indexed: 10/17/2023] Open
Abstract
Cardiovascular instability and reduced oxygenation are regular perioperative critical events associated with anesthesia requiring intervention in neonates and young infants. This review article addresses the current modalities of assessing this population's adequate end-organ perfusion in the perioperative period. Assuring adequate tissue oxygenation in critically ill infants is based on parameters that measure acceptable macrocirculatory hemodynamic parameters such as vital signs (mean arterial blood pressure, heart rate, urinary output) and chemical parameters (lactic acidosis, mixed venous oxygen saturation, base deficit). Microcirculation assessment represents a promising candidate for assessing and improving hemodynamic management strategies in perioperative and critically ill populations. Evaluation of the functional state of the microcirculation can parallel improvement in tissue perfusion, a term coined as "hemodynamic coherence". Less information is available to assess microcirculatory disturbances related to higher mortality risk in critically ill adults and pediatric patients with septic shock. Techniques for measuring microcirculation have substantially improved in the past decade and have evolved from methods that are limited in scope, such as velocity-based laser Doppler and near-infrared spectroscopy, to handheld vital microscopy (HVM), also referred to as videomicroscopy. Available technologies to assess microcirculation include sublingual incident dark field (IDF) and sublingual sidestream dark field (SDF) devices. This chapter addresses (1) the physiological basis of microcirculation and its relevance to the neonatal and pediatric populations, (2) the pathophysiology associated with altered microcirculation and endothelium, and (3) the current literature reviewing modalities to detect and quantify the presence of microcirculatory alterations.
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Affiliation(s)
- Grace M. Arteaga
- Department of Pediatric and Adolescent Medicine, Pediatric Critical Care, Mayo Clinic, Rochester MN, United States
| | - Sheri Crow
- Department of Pediatric and Adolescent Medicine, Pediatric Critical Care, Mayo Clinic, Rochester MN, United States
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Hempel C, Milner D, Seydel K, Taylor T. Specific components associated with the endothelial glycocalyx are lost from brain capillaries in cerebral malaria. J Infect Dis 2022; 226:1470-1479. [PMID: 35556124 DOI: 10.1093/infdis/jiac200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 05/10/2022] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Cerebral malaria (CM) is a rare, but severe and frequently fatal outcome of infections with Plasmodium falciparum. Pathogenetic mechanisms include endothelial activation and sequestration of parasitized erythrocytes in the cerebral microvessels. Increased concentrations of glycosaminoglycans in urine and plasma of malaria patients have been described, suggesting involvement of endothelial glycocalyx. METHODS We used lectin histochemistry on postmortem samples to compare the distribution of multiple sugar epitopes on cerebral capillaries in children who died from CM and from non-malarial comas. RESULTS N-acetyl glucosamine residues detected by tomato lectin are generally reduced in children with CM compared to controls. We used the vascular expression of intercellular adhesion molecule-1 and mannose residues on brain capillaries of CM as evidence of local vascular inflammation, and both were expressed more highly in CM patients than controls. Sialic acid residues were found to be significantly reduced in patients with CM. By contrast, the levels of other sugar epitopes regularly detected on the cerebral vasculature were unchanged, and this suggests specific remodeling of cerebral microvessels in CM patients. CONCLUSIONS Our findings support and expand upon earlier reports of disruptions of the endothelial glycocalyx in children with severe malaria.
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Affiliation(s)
- Casper Hempel
- Department Health Technology, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Dan Milner
- American Society for Clinical Pathology, Chicago, IL, USA.,Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, US
| | - Karl Seydel
- Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, US.,Blantyre Malaria Project, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Terrie Taylor
- Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, US.,Blantyre Malaria Project, Kamuzu University of Health Sciences, Blantyre, Malawi
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Richter RP, Payne GA, Ambalavanan N, Gaggar A, Richter JR. The endothelial glycocalyx in critical illness: A pediatric perspective. Matrix Biol Plus 2022; 14:100106. [PMID: 35392182 PMCID: PMC8981764 DOI: 10.1016/j.mbplus.2022.100106] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 02/28/2022] [Accepted: 03/01/2022] [Indexed: 12/18/2022] Open
Abstract
The endothelial glycocalyx thins with age and cardiovascular comorbidities. Endothelial glycocalyx is affected by and integral to severe pediatric illnesses. Mechanistic insight into cause/effect of endothelial glycocalyx injury is paramount. Vascular glycocalyx damage in pediatric critical illness warrants further study.
The vascular endothelium is the interface between circulating blood and end organs and thus has a critical role in preserving organ function. The endothelium is lined by a glycan-rich glycocalyx that uniquely contributes to endothelial function through its regulation of leukocyte and platelet interactions with the vessel wall, vascular permeability, coagulation, and vasoreactivity. Degradation of the endothelial glycocalyx can thus promote vascular dysfunction, inflammation propagation, and organ injury. The endothelial glycocalyx and its role in vascular pathophysiology has gained increasing attention over the last decade. While studies characterizing vascular glycocalyx injury and its downstream consequences in a host of adult human diseases and in animal models has burgeoned, studies evaluating glycocalyx damage in pediatric diseases are relatively few. As children have unique physiology that differs from adults, significant knowledge gaps remain in our understanding of the causes and effects of endothelial glycocalyx disintegrity in pediatric critical illness. In this narrative literature overview, we offer a unique perspective on the role of the endothelial glycocalyx in pediatric critical illness, drawing from adult and preclinical data in addition to pediatric clinical experience to elucidate how marked derangement of the endothelial surface layer may contribute to aberrant vascular biology in children. By calling attention to this nascent field, we hope to increase research efforts to address important knowledge gaps in pediatric vascular biology that may inform the development of novel therapeutic strategies.
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Affiliation(s)
- Robert P. Richter
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
- Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Center for Injury Science, University of Alabama at Birmingham, Birmingham, AL, USA
- Corresponding author at: Department of Pediatrics, University of Alabama at Birmingham, 1600 5 Avenue South, CPPI Suite 102, Birmingham, Alabama 35233, USA.
| | - Gregory A. Payne
- Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Namasivayam Ambalavanan
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Translational Research in Normal and Disordered Development Program, University of Alabama, Birmingham, AL, USA
| | - Amit Gaggar
- Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jillian R. Richter
- Center for Injury Science, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, USA
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5
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Bush MA, Anstey NM, Yeo TW, Florence SM, Granger DL, Mwaikambo ED, Weinberg JB. Vascular Dysfunction in Malaria: Understanding the Role of the Endothelial Glycocalyx. Front Cell Dev Biol 2021; 9:751251. [PMID: 34858979 PMCID: PMC8631294 DOI: 10.3389/fcell.2021.751251] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 09/27/2021] [Indexed: 01/18/2023] Open
Abstract
Malaria caused by Plasmodium falciparum results in over 400,000 deaths annually, predominantly affecting African children. In addition, non-falciparum species including vivax and knowlesi cause significant morbidity and mortality. Vascular dysfunction is a key feature in malaria pathogenesis leading to impaired blood perfusion, vascular obstruction, and tissue hypoxia. Contributing factors include adhesion of infected RBC to endothelium, endothelial activation, and reduced nitric oxide formation. Endothelial glycocalyx (eGC) protects the vasculature by maintaining vessel integrity and regulating cellular adhesion and nitric oxide signaling pathways. Breakdown of eGC is known to occur in infectious diseases such as bacterial sepsis and dengue and is associated with adverse outcomes. Emerging studies using biochemical markers and in vivo imaging suggest that eGC breakdown occurs during Plasmodium infection and is associated with markers of malaria disease severity, endothelial activation, and vascular function. In this review, we describe characteristics of eGC breakdown in malaria and discuss how these relate to vascular dysfunction and adverse outcomes. Further understanding of this process may lead to adjunctive therapy to preserve or restore damaged eGC and reduce microvascular dysfunction and the morbidity/mortality of malaria.
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Affiliation(s)
- Margaret A Bush
- Duke University School of Nursing and Durham VA Medical Centers, Durham, NC, United States
| | - Nicholas M Anstey
- Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia
| | - Tsin W Yeo
- Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,National Centre for Infectious Diseases, Tan Tock Seng Hospital, Singapore, Singapore
| | | | - Donald L Granger
- School of Medicine, University of Utah and Salt Lake City VA Medical Centers, Salt Lake City, UT, United States
| | | | - J Brice Weinberg
- Duke University School of Medicine and Durham VA Medical Centers, Durham, NC, United States
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Puchwein-Schwepcke A, Genzel-Boroviczény O, Nussbaum C. The Endothelial Glycocalyx: Physiology and Pathology in Neonates, Infants and Children. Front Cell Dev Biol 2021; 9:733557. [PMID: 34540845 PMCID: PMC8440834 DOI: 10.3389/fcell.2021.733557] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/12/2021] [Indexed: 11/13/2022] Open
Abstract
The endothelial glycocalyx (EG) as part of the endothelial surface layer (ESL) is an important regulator of vascular function and homeostasis, including permeability, vascular tone, leukocyte recruitment and coagulation. Located at the interface between the endothelium and the blood stream, this highly fragile structure is prone to many disruptive factors such as inflammation and oxidative stress. Shedding of the EG has been described in various acute and chronic diseases characterized by endothelial dysfunction and angiopathy, such as sepsis, trauma, diabetes and cardiovascular disease. Circulating EG components including syndecan-1, hyaluronan and heparan sulfate are being evaluated in animal and clinical studies as diagnostic and prognostic markers in several pathologies, and advances in microscopic techniques have enabled in vivo assessment of the EG. While research regarding the EG in adult physiology and pathology has greatly advanced throughout the last decades, our knowledge of the development of the glycocalyx and its involvement in pathological conditions in the pediatric population is limited. Current evidence suggests that the EG is present early during fetal development and plays a critical role in vessel formation and maturation. Like in adults, EG shedding has been demonstrated in acute inflammatory conditions in infants and children and chronic diseases with childhood-onset. However, the underlying mechanisms and their contribution to disease manifestation and progression still need to be established. In the future, the glycocalyx might serve as a marker to identify pediatric patients at risk for vascular sequelae and as a potential target for early interventions.
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Affiliation(s)
- Alexandra Puchwein-Schwepcke
- Division of Neonatology, Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, LMU Munich, Munich, Germany.,Department of Pediatric Neurology and Developmental Medicine, University of Basel Children's Hospital, Basel, Switzerland
| | - Orsolya Genzel-Boroviczény
- Division of Neonatology, Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, LMU Munich, Munich, Germany
| | - Claudia Nussbaum
- Division of Neonatology, Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, LMU Munich, Munich, Germany
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Bush MA, Florence SM, Yeo TW, Kalingonji AR, Chen Y, Granger DL, Rubach MP, Anstey NM, Mwaikambo ED, Weinberg JB. Degradation of endothelial glycocalyx in Tanzanian children with falciparum malaria. FASEB J 2021; 35:e21805. [PMID: 34403544 DOI: 10.1096/fj.202100277rr] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 06/25/2021] [Accepted: 07/01/2021] [Indexed: 01/20/2023]
Abstract
A layer of glycocalyx covers the vascular endothelium serving important protective and homeostatic functions. The objective of this study was to determine if breakdown of the endothelial glycocalyx (eGC) occurs during malaria infection in children. Measures of eGC integrity, endothelial activation, and microvascular reactivity were prospectively evaluated in 146 children: 44 with moderately severe malaria (MSM), 42 with severe malaria (SM), and 60 healthy controls (HC). Biochemical measures of eGC integrity included plasma syndecan-1 and total urinary glycosaminoglycans (GAG). Side-stream dark field imaging was used to quantitatively assess integrity of eGC. Plasma angiopoietin-2 (Ang-2) was measured as a marker of endothelial activation and also as a possible mediator of eGC breakdown. Our results show that urinary GAG, syndecan-1, and Ang-2 were elevated in patients with MSM and SM compared with HC. Syndecan-1 and GAG levels correlated significantly with each other and with plasma Ang-2. The eGC breakdown products also inversely correlated significantly with hemoglobin and platelet count. In the MSM group, imaging results provided further evidence for eGC degradation. Although not correlated with markers of eGC degradation, vascular function (assessed by non-invasive near infrared spectroscopy [NIRS]) demonstrated reduced microvascular reactivity, particularly affecting the SM group. Our findings provide further evidence for breakdown of eGC in falciparum malaria that may contribute to endothelial activation and adhesion of parasitized red blood cells, with reduced nitric oxide formation, and vascular dysfunction.
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Affiliation(s)
- Margaret A Bush
- School of Medicine, Duke University and Durham VA Medical Centers, Durham, NC, USA
| | | | - Tsin W Yeo
- Menzies School of Health Research, Charles Darwin University, Darwin, Australia.,Lee Kong Chian School of Medicine, Nanyang Technological University, Republic of Singapore.,National Centre for Infectious Diseases, Tan Tock Seng Hospital, Republic of Singapore
| | | | - Youwei Chen
- School of Medicine, Duke University and Durham VA Medical Centers, Durham, NC, USA
| | - Donald L Granger
- University of Utah and VA Medical Centers, Salt Lake City, UT, USA
| | - Matthew P Rubach
- School of Medicine, Duke University and Durham VA Medical Centers, Durham, NC, USA
| | - Nicholas M Anstey
- Menzies School of Health Research, Charles Darwin University, Darwin, Australia
| | | | - Joe Brice Weinberg
- School of Medicine, Duke University and Durham VA Medical Centers, Durham, NC, USA
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Barber BE, Grigg MJ, Piera KA, Chen Y, William T, Weinberg JB, Yeo TW, Anstey NM. Endothelial glycocalyx degradation and disease severity in Plasmodium vivax and Plasmodium knowlesi malaria. Sci Rep 2021; 11:9741. [PMID: 33963210 PMCID: PMC8105350 DOI: 10.1038/s41598-021-88962-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 04/13/2021] [Indexed: 02/03/2023] Open
Abstract
Degradation of the endothelial glycocalyx is associated with mortality in adult falciparum malaria. However, its role in the pathogenesis of non-falciparum malaria is unknown. In Malaysian patients with knowlesi (n = 200) and vivax (n = 61) malaria, and in healthy controls (n = 50), we measured glycocalyx breakdown products plasma syndecan-1 and urinary glycosaminoglycans, and evaluated correlations with biomarkers of disease severity. Urinary glycosaminoglycans were increased in patients with knowlesi and vivax malaria compared to healthy controls, and in knowlesi malaria were highest in those with severe disease. In knowlesi malaria, plasma syndecan-1 was also highest in those with severe disease, and correlated with markers of endothelial activation (angiopoietin-2, osteoprotegerin, ICAM-1), asymmetric dimethylarginine (ADMA) and impaired microvascular reactivity. Syndecan-1 also correlated with endothelial activation (ICAM-1, angiopoietin-2) and ADMA in vivax malaria. In knowlesi malaria increased syndecan-1 was associated with acute kidney injury, after controlling for age and parasitemia. In knowlesi malaria, the difference in median syndecan-1 between severe and non-severe disease was more marked in females than males. Endothelial glycocalyx degradation is increased in knowlesi and vivax malaria, and associated with disease severity and acute kidney injury in knowlesi malaria. Agents that inhibit glycocalyx breakdown may represent adjunctive therapeutics for severe non-falciparum malaria.
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Affiliation(s)
- Bridget E. Barber
- QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD 4006 Australia ,Menzies School of Health Research and Charles Darwin University, Darwin, Australia ,Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Malaysia
| | - Matthew J. Grigg
- Menzies School of Health Research and Charles Darwin University, Darwin, Australia ,Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Malaysia
| | - Kim A. Piera
- Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Youwei Chen
- Duke University and V.A. Medical Centre, Durham, USA
| | - Timothy William
- Clinical Research Centre, Queen Elizabeth Hospital, Kota Kinabalu, Malaysia ,Gleneagles Hospital, Kota Kinabalu, Malaysia
| | | | - Tsin W. Yeo
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Nicholas M. Anstey
- Menzies School of Health Research and Charles Darwin University, Darwin, Australia ,Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Malaysia
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Singh G, Njamnshi AK, Sander JW. Vector-borne protozoal infections of the CNS: cerebral malaria, sleeping sickness and Chagas disease. Curr Opin Neurol 2021; 34:439-446. [PMID: 33709976 DOI: 10.1097/wco.0000000000000919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Malaria, Chagas Disease and Human African Trypanosomiasis are vector-borne protozoan illnesses, frequently associated with neurological manifestations. Intriguing but ignored, limited mainly to resource-limited, tropical settings, these disorders are now coming to light because of globalisation and improved diagnosis and treatment. Enhanced understanding of these illnesses has prompted this review. RECENT FINDINGS Methods of diagnosis have currently transitioned from blood smear examinations to immunological assays and molecular methods. Tools to assess neurological involvement, such as magnetic resonance imaging, are now increasingly available in regions and countries with high infection loads. Sleep and other electrophysiological technologies (electroencephalography, actigraphy) are also promising diagnostic tools but requiring field-validation. Access to treatments was formerly limited, even as limitations of agents used in the treatment are increasingly recognised. Newer agents are now being developed and trialled, encouraged by improved understanding of the disorders' molecular underpinnings. SUMMARY Prompt diagnosis and treatment are crucial in ensuring cure from the infections. Attention should also be due to the development of globally applicable treatment guidelines, the burden of neurological sequelae and elimination of the zoonoses from currently endemic regions.
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Affiliation(s)
- Gagandeep Singh
- Department of Neurology, Dayanand Medical College, Ludhiana, India.,NIHR University College London Hospitals Biomedical Research Centre, UCL Queen Square Institute of Neurology, London, UK
| | - Alfred K Njamnshi
- Neurology Department, Central Hospital Yaoundé/Neuroscience Lab, Faculty of Medicine and Biomedical Sciences (FMBS), The University of Yaoundé 1, Yaoundé, Cameroon.,Brain Research Africa Initiative (BRAIN), Yaoundé, Cameroon
| | - Josemir W Sander
- NIHR University College London Hospitals Biomedical Research Centre, UCL Queen Square Institute of Neurology, London, UK.,Chalfont Centre for Epilepsy, Chalfont St Peter, Buckinghamshire, UK.,Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, Netherlands
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Hempel C, Kapishnikov S, Perez-Berna AJ, Werner S, Guttmann P, Pereiro E, Qvortrup K, Andresen TL. The need to freeze-Dehydration during specimen preparation for electron microscopy collapses the endothelial glycocalyx regardless of fixation method. Microcirculation 2020; 27:e12643. [PMID: 32542908 DOI: 10.1111/micc.12643] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 05/25/2020] [Accepted: 06/06/2020] [Indexed: 12/31/2022]
Abstract
OBJECTIVE The endothelial glycocalyx covers the luminal surface of the endothelium and plays key roles in vascular function. Despite its biological importance, ideal visualization techniques are lacking. The current study aimed to improve the preservation and subsequent imaging quality of the endothelial glycocalyx. METHODS In mice, the endothelial glycocalyx was contrasted with a mixture of lanthanum and dysprosium (LaDy). Standard chemical fixation was compared with high-pressure frozen specimens processed with freeze substitution. Also, isolated brain microvessels and cultured endothelial cells were high-pressure frozen and by transmission soft x-rays, imaged under cryogenic conditions. RESULTS The endothelial glycocalyx was in some tissues significantly more voluminous from chemically fixed specimens compared with high-pressure frozen specimens. LaDy labeling introduced excessive absorption contrast, which impeded glycocalyx measurements in isolated brain microvessels when using transmission soft x-rays. In non-contrasted vessels, the glycocalyx was not resolved. LaDy-contrasted, cultured brain endothelial cells allowed to assess glycocalyx volume in vitro. CONCLUSIONS Both chemical and cryogenic fixation followed by dehydration lead to substantial collapse of the glycocalyx. Cryogenic fixation without freeze substitution could be a way forward although transmission soft x-ray tomography based solely on amplitude contrast seems unsuitable.
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Affiliation(s)
- Casper Hempel
- Department of Health Technology, Technical University of Denmark, Lyngby, Denmark.,Centre for Medical Parasitology, Department for Clinical Microbiology, Copenhagen University Hospital, Copenhagen, Denmark.,Department for Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Sergey Kapishnikov
- Department X-Ray microscopy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.,Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | | | - Stephan Werner
- Department X-Ray microscopy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | - Peter Guttmann
- Department X-Ray microscopy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | - Eva Pereiro
- MISTRAL Beamline-Experiments Division, ALBA Synchrotron Light Source, Barcelona, Spain
| | - Klaus Qvortrup
- Core Facility for Integrated Microscopy (CFIM), University of Copenhagen, Copenhagen, Denmark
| | - Thomas Lars Andresen
- Department of Health Technology, Technical University of Denmark, Lyngby, Denmark
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Early Endothelial Activation Precedes Glycocalyx Degradation and Microvascular Dysfunction in Experimentally Induced Plasmodium falciparum and Plasmodium vivax Infection. Infect Immun 2020; 88:IAI.00895-19. [PMID: 32122938 DOI: 10.1128/iai.00895-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 02/25/2020] [Indexed: 12/13/2022] Open
Abstract
Endothelial activation and microvascular dysfunction are key pathogenic processes in severe malaria. We evaluated the early role of these processes in experimentally induced Plasmodium falciparum and P. vivax infection. Participants were enrolled in induced blood-stage malaria clinical trials. Plasma osteoprotegerin, angiopoietin-2, and von Willebrand Factor (vWF) levels were measured as biomarkers of endothelial activation. Microvascular function was assessed using peripheral arterial tonometry and near-infrared spectroscopy, and the endothelial glycocalyx was assessed by sublingual videomicroscopy and measurement of biomarkers of degradation. Forty-five healthy, malaria-naive participants were recruited from 5 studies. Osteoprotegerin and vWF levels increased in participants following inoculation with P. vivax (n = 16) or P. falciparum (n = 15), with the angiopoietin-2 level also increasing in participants following inoculation with P. falciparum For both species, the most pronounced increase was seen in osteoprotegerin. This was particularly marked in participants inoculated with P. vivax, where the osteoprotegerin level correlated with the levels of parasitemia and the malaria clinical score. There were no changes in measures of endothelial glycocalyx or microvascular function. Plasma biomarkers of endothelial activation increased in early P. falciparum and P. vivax infection and preceded changes in the endothelial glycocalyx or microvascular function. The more pronounced increase in osteoprotegerin suggests that this biomarker may play a role in disease pathogenesis.
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