Analysis of the retina and visual pathway by OCT, OCTA and psychophysical tests in asymptomatic subjects at high genetic risk for the development of Alzheimer's disease

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Medicina, leída el 15-07-2022La Enfermedad de Alzheimer (EA) es una enfermedad neurodegenerativa progresiva que se caracteriza: por una atrofia cortical difusa, declive de las funciones cognitivas, así como la agregación anormal de proteínas como la beta amiloide fibrilar (Aß) y tau hiperfosforilada (p-Tau).El factor de riesgo prevalente es la edad avanzada, tras el cual destaca la herencia genética. Elmayor factor de riesgo genético conocido es ser portador de al menos un alelo 4 del gen de la apoliproteina E (ApoE). Otro de los factores que incrementa el riesgo para desarrollar la EA, es la historia familiar de primer grado. Los signos cerebrales de la EA aparecen décadas antes del inicio clínico de la enfermedad. Dado que la relación entre cerebro y retina se establece ya desde la etapa embrionaria, los cambios retinianos detectados con técnicas de diagnóstico oftalmológico en sujetos con alto riesgo genético para el desarrollo de EA posibilitan la identificación de potenciales pacientes de EA en etapas muy tempranas...Alzheimer's disease (AD) is a progressive neurodegenerative disease characterised by: diffuse cortical atrophy, decline in cognitive functions, as well as abnormal aggregation of proteins such as fibrillar amyloid Beta (Aβ) and hyperphosphorylated tau(p-Tau).The prevalent risk factor is older age, after which genetic inheritance is the most important. The major known genetic risk factor is carrying at least one 4 allele of the apoliprotein E (ApoE 4)gene. Another factor that increases the risk of developing AD is a first-degree family history. Brain signs of AD appear decades before clinical onset of the disease. Since the relationship between brain and retina is established as early as the embryonic stage, retinal changes detected with ophthalmological diagnostic techniques in subjects at high genetic risk for developing AD make it possible to identify potential AD patients at very early stages..Fac. de MedicinaTRUEunpu

The Role of Microglia in Retinal Neurodegeneration: Alzheimer's Disease, Parkinson, and Glaucoma

Microglia, the immunocompetent cells of the central nervous system (CNS), act as neuropathology sensors and are neuroprotective under physiological conditions. Microglia react to injury and degeneration with immune-phenotypic and morphological changes, proliferation, migration, and inflammatory cytokine production. An uncontrolled microglial response secondary to sustained CNS damage can put neuronal survival at risk due to excessive inflammation. A neuroinflammatory response is considered among the etiological factors of the major aged-related neurodegenerative diseases of the CNS, and microglial cells are key players in these neurodegenerative lesions. The retina is an extension of the brain and therefore the inflammatory response in the brain can occur in the retina. The brain and retina are affected in several neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and glaucoma. AD is an age-related neurodegeneration of the CNS characterized by neuronal and synaptic loss in the cerebral cortex, resulting in cognitive deficit and dementia. The extracellular deposits of beta-amyloid (Aβ) and intraneuronal accumulations of hyperphosphorylated tau protein (pTau) are the hallmarks of this disease. These deposits are also found in the retina and optic nerve. PD is a neurodegenerative locomotor disorder with the progressive loss of dopaminergic neurons in the substantia nigra. This is accompanied by Lewy body inclusion composed of α-synuclein (α-syn) aggregates. PD also involves retinal dopaminergic cell degeneration. Glaucoma is a multifactorial neurodegenerative disease of the optic nerve, characterized by retinal ganglion cell loss. In this pathology, deposition of Aβ, synuclein, and pTau has also been detected in retina. These neurodegenerative diseases share a common pathogenic mechanism, the neuroinflammation, in which microglia play an important role. Microglial activation has been reported in AD, PD, and glaucoma in relation to protein aggregates and degenerated neurons. The activated microglia can release pro-inflammatory cytokines which can aggravate and propagate neuroinflammation, thereby degenerating neurons and impairing brain as well as retinal function. The aim of the present review is to describe the contribution in retina to microglial-mediated neuroinflammation in AD, PD, and glaucomatous neurodegeneration

Molecular studies of phages-Klebsiella pneumoniae in mucoid environment: innovative use of mucolytic agents prior to the administration of lytic phages

Mucins are important glycoproteins that form a protective layer throughout the gastrointestinal and respiratory tracts. There is scientific evidence of increase in phage-resistance in the presence of mucin for some bacterial pathogens. Manipulation in mucin composition may ultimately influence the effectiveness of phage therapy. In this work, two clinical strains of K. pneumoniae (K3574 and K3325), were exposed to the lytic bacteriophage vB_KpnS-VAC35 in the presence and absence of mucin on a long-term co-evolution assay, in an attempt to mimic in vitro the exposure to mucins that bacteria and their phages face in vivo. Enumerations of the bacterial and phage counts at regular time intervals were conducted, and extraction of the genomic DNA of co-evolved bacteria to the phage, the mucin and both was performed. We determined the frequency of phage-resistant mutants in the presence and absence of mucin and including a mucolytic agent (N-acetyl L-cysteine, NAC), and sequenced them using Nanopore. We phenotypically demonstrated that the presence of mucin induces the emergence of bacterial resistance against lytic phages, effectively decreased in the presence of NAC. In addition, the genomic analysis revealed some of the genes relevant to the development of phage resistance in long-term co-evolution, with a special focus on the mucoid environment. Genes involved in the metabolism of carbohydrates were mutated in the presence of mucin. In conclusion, the use of mucolytic agents prior to the administration of lytic phages could be an interesting therapeutic option when addressing K. pneumoniae infections in environments where mucin is overproduced.The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This study has been funded by Instituto de Salud Carlos III (ISCIII) through the projects PI19/00878 and PI22/00323 and co-funded by the European Union, and by the Study Group on Mechanisms of Action and Resistance to Antimicrobials, GEMARA (SEIMC). (SEIMC, http://www.seimc.org/). This research was also supported by CIBERINFEC (CIBER21/13/00095) and by Personalized and precision medicine grant from the Instituto de Salud Carlos III (MePRAM Project, PMP22/00092). MT was financially supported by the Miguel Servet Research Programme (SERGAS and ISCIII). OP, LF-G, and ML were financially supported by the grants IN606A-2020/035, IN606B-2021/013, and IN606C-2022/002, respectively (GAIN, Xunta de Galicia). IB was financially supported by the pFIS program (ISCIII, FI20/00302). Finally, to thank to PIRASOA laboratory which is the reference laboratory for molecular typing of nosocomial pathogens and detection of mechanisms of resistance to antimicrobials of health interest in Andalusia, Virgen Macarena Hospital, Seville, to send us the clinical isolates. Thanks to Alvaro Pascual and Luis Martínez-Martínez from Virgen Macarena Hospital, Seville and Reina Sofia Hospital, Cordoba.S

Anatomy of the Human Optic Nerve: Structure and Function

The optic nerve (ON) is constituted by the axons of the retinal ganglion cells (RGCs). These axons are distributed in an organized pattern from the soma of the RGC to the lateral geniculated nucleus (where most of the neurons synapse). The key points of the ON are the optic nerve head and chiasm. This chapter will include a detailed and updated review of the ON different parts: RGC axons, glial cells, connective tissue of the lamina cribrosa and the septum and the blood vessels derivate from the central retina artery and from the ciliary system. There will be an up-to-date description about the superficial nerve fibre layer, including their organization, and about prelaminar, laminar and retrolaminar regions, emphasizing the axoplasmic flow, glial barriers, biomechanics of the lamina cribrosa and the role of the macro- and microglia in their working

The Role of Autophagy in Eye Diseases

This research was funded by the Ophthalmological Network OFTARED (Enfermedades oculares: Prevención, detección precoz, tratamiento y rehabilitación de las patologías oculares) (RD16/0008/0005 and RD16/0008/0026) of the Institute of Health of Carlos III of the Spanish Ministry of Economy and by the European programme FEDER; and Network RETiBRAIN (La retina un modelo para investigar Neuroprotección en patologías del Sistema Nervioso Central) (RED2018-102499-T) of Spanish Ministry of Science and Innovation. And J.A.F.-A. is currently funded by a Predoctoral Fellowship (FPU17/01023) from the Spanish Ministry of Science, Innovation, and Universities; and I.L.-C. is currently funded by a Predoctoral Fellowship (CT42/18-CT43/18) from the Complutense University of Madrid.Autophagy is a catabolic process that ensures homeostasis in the cells of our organism. It plays a crucial role in protecting eye cells against oxidative damage and external stress factors. Ocular pathologies of high incidence, such as age-related macular degeneration, cataracts, glaucoma, and diabetic retinopathy are of multifactorial origin and are associated with genetic, environmental factors, age, and oxidative stress, among others; the latter factor is one of the most influential in ocular diseases, directly affecting the processes of autophagy activity. Alteration of the normal functioning of autophagy processes can interrupt organelle turnover, leading to the accumulation of cellular debris and causing physiological dysfunction of the eye. The aim of this study is to review research on the role of autophagy processes in the main ocular pathologies, which have a high incidence and result in high costs for the health system. Considering the role of autophagy processes in cell homeostasis and cell viability, the control and modulation of autophagy processes in ocular pathologies could constitute a new therapeutic approach.Depto. de Inmunología, Oftalmología y ORLFac. de MedicinaTRUEUnión EuropeaMinisterio de Ciencia e Innovación (España)Instituto de Salud Carlos IIIUniversidad Complutense de Madridpu

Characterization of retinal drusen in subjects at high genetic risk of developing sporadic Alzheimer’s disease: An exploratory analysis

Having a family history (FH+) of Alzheimer’s disease (AD) and being a carrier of at least one ε4 allele of the ApoE gene are two of the main risk factors for the development of AD. AD and age-related macular degeneration (AMD) share one of the main risk factors, such as age, and characteristics including the presence of deposits (Aβ plaques in AD and drusen in AMD); however, the role of apolipoprotein E isoforms in both pathologies is controversial. We analyzed and characterized retinal drusen by optical coherence tomography (OCT) in subjects, classifying them by their AD FH (FH-or FH+) and their allelic characterization of ApoE ε4 (ApoE ε4-or ApoE ε4+) and considering cardiovascular risk factors (hypercholesterolemia, hypertension, and diabetes mellitus). In addition, we analyzed the choroidal thickness by OCT and the area of the foveal avascular zone with OCTA. We did not find a relationship between a family history of AD or any of the ApoE isoforms and the presence or absence of drusen. Subjects with drusen show choroidal thinning compared to patients without drusen, and thinning could trigger changes in choroidal perfusion that may give rise to the deposits that generate drusen

Ocular Exploration in the Diagnosis and Follow-Up of the Alzheimer’s Dementia

The retina is part of the central nervous system (CNS), and therefore, in Alzheimer’s disease (AD), retinal and optic nerve degeneration could take place. This degeneration leads to neurofunctional changes that can be detected early and followed up throughout the evolution of the disease. As opposed to other CNS structures, the eye is easily accessible for in vivo observation. Retinal organization allows for the identification of its different neurons, and in consequence, detection of minimal changes taking place during neurodegeneration is possible. Functional vision studies performed on AD patients in recent years have shown how visual acuity, contrast sensitivity, color vision, and visual integration vary with the progression of neurodegeneration. The development of optical coherence tomography in ophthalmology has meant a breakthrough in retinal exploratory techniques, allowing the obtention of high-resolution images using light. This technique enables retinal analysis in the earliest stages of AD, being considered as a biomarker of neuronal damage. Given AD’s high prevalence and its expected increase, it is important to perform easy tests that cause minimal discomfort to the patients at a low cost while offering abundant information on the stage of the disease

Proteomic Study of the Interactions between Phages and the Bacterial Host Klebsiella pneumoniae

Phages and bacteria have acquired resistance mechanisms for protection. In this context, the aims of the present study were to analyze the proteins isolated from 21 novel lytic phages of Klebsiella pneumoniae in search of defense mechanisms against bacteria and also to determine the infective capacity of the phages. A proteomic study was also conducted to investigate the defense mechanisms of two clinical isolates of K. pneumoniae infected by phages. For this purpose, the 21 lytic phages were sequenced and de novo assembled. The host range was determined in a collection of 47 clinical isolates of K. pneumoniae, revealing the variable infective capacity of the phages. Genome sequencing showed that all of the phages were lytic phages belonging to the order Caudovirales. Phage sequence analysis revealed that the proteins were organized in functional modules within the genome. Although most of the proteins have unknown functions, multiple proteins were associated with defense mechanisms against bacteria, including the restriction-modification system, the toxin-antitoxin system, evasion of DNA degradation, blocking of host restriction and modification, the orphan CRISPR-Cas system, and the anti-CRISPR system. Proteomic study of the phage-host interactions (i.e., between isolates K3574 and K3320, which have intact CRISPR-Cas systems, and phages vB_KpnS-VAC35 and vB_KpnM-VAC36, respectively) revealed the presence of several defense mechanisms against phage infection (prophage, defense/virulence/resistance, oxidative stress and plasmid proteins) in the bacteria, and of the Acr candidate (anti-CRISPR protein) in the phages. IMPORTANCE Researchers, including microbiologists and infectious disease specialists, require more knowledge about the interactions between phages and their bacterial hosts and about their defense mechanisms. In this study, we analyzed the molecular mechanisms of viral and bacterial defense in phages infecting clinical isolates of K. pneumoniae. Viral defense mechanisms included restriction-modification system evasion, the toxin-antitoxin (TA) system, DNA degradation evasion, blocking of host restriction and modification, and resistance to the abortive infection system, anti-CRISPR and CRISPR-Cas systems. Regarding bacterial defense mechanisms, proteomic analysis revealed expression of proteins involved in the prophage (FtsH protease modulator), plasmid (cupin phosphomannose isomerase protein), defense/virulence/resistance (porins, efflux pumps, lipopolysaccharide, pilus elements, quorum network proteins, TA systems, and methyltransferases), oxidative stress mechanisms, and Acr candidates (anti-CRISPR protein). The findings reveal some important molecular mechanisms involved in the phage-host bacterial interactions; however, further study in this field is required to improve the efficacy of phage therapy.This study was funded by grant PI19/00878 and PI22/00323 awarded to M.T. within the State Plan for R1D1I 2013-2016 (National Plan for Scientific Research, Technological Development, and Innovation 2008-2011) and cofinanced by the ISCIII-Deputy General Directorate for Evaluation and Promotion of Research/European Regional Development Fund “A Way of Making Europe” and Instituto de Salud Carlos III FEDER, Spanish Network for the Research in Infectious Diseases (REIPI; RD16/0016/0006 and RD16/0016/0008), CIBERINFEC (CIBER21/13/00012, CB21/13/00049, CIBER21/13/00084, and CIBER21/13/00095), and Personalized Medicine Project (MePRAM; PMP/00092) and also by the Study Group on Mechanisms of Action and Resistance to Antimicrobials, GEMARA (SEIMC; http://www.seimc.org/). M.T. was financially supported by the Miguel Servet Research Program (SERGAS and ISCIII). I.B. was financially supported by pFIS program (ISCIII, FI20/00302). O.P., L.F.-G., and M.L. were financially supported by grants IN606A-2020/035, IN606B-2021/013, and IN606C-2022/002, respectively (GAIN; Xunta de Galicia). The authors acknowledge CESGA (www.cesga.es) in Santiago de Compostela, Spain, for providing access to computing facilities and the RIAIDT-USC analytical facilities. Finally, We thank researchers from the Spanish Network of Bacteriophages and Transducer Elements (FAGOMA) for contributing the lytic phages. I.B., L.B., O.P., and L.F.-G. developed the experiments, analyzed the results, and wrote the original manuscript. M.L., C.O.C. and A.B.P. helped to prepare the visual presentation of the results. F.F.C., Á.P., L.M.-M., and J.O.-I. rewrote the manuscript. M.T. financed and directed the experiments and supervised the writing of the originalmanuscript. We declare that there are no conflicts of interest.S

Beneficial effects of saffron (Crocus sativus L.) in ocular pathologies, particularly neurodegenerative retinal diseases

Saffron (Crocus sativus L.) has been traditionally used in food preparation and as a medicinal plant. It currently has numerous therapeutic properties attributed to it, such as protection against ischemia, as well as anticonvulsant, antidepressant, anxiolytic, hypolipidemic, anti-atherogenic, anti-hypertensive, antidiabetic, and anti-cancer properties. In addition, saffron has remarkable beneficial properties, such as anti-apoptotic, anti-inflammatory and antioxidant activities, due to its main metabolites, among which crocin and crocetin stand out. Furthermore, increasing evidence underwrites the possible neuroprotective role of the main bioactive saffron constituents in neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, both in experimental models and in clinical studies in patients. Currently, saffron supplementation is being tested for ocular neurodegenerative pathologies, such as diabetic retinopathy, retinitis pigmentosa, age-related macular degeneration and glaucoma, among others, and shows beneficial effects. The present article provides a comprehensive and up to date report of the investigations on the beneficial effects of saffron extracts on the main neurodegenerative ocular pathologies and other ocular diseases. This review showed that saffron extracts could be considered promising therapeutic agents to help in the treatment of ocular neurodegenerative diseases