Showing papers by "Richard Lathe published in 2023"
TL;DR: In this article , the electronic tree of life (eToL) was used to comprehensively address the spectrum of microorganisms in control and Alzheimer's disease (AD) brain.
Abstract: Microbes in human brain and their potential contribution to neurodegenerative conditions such as Alzheimer’s disease (AD) have long been debated. We recently developed a new method (the electronic tree of life, eToL) based on small subunit ribosomal RNA (rRNA) probes, further confirmed by large subunit rRNA analysis, to comprehensively address the spectrum of microorganisms in control and AD brain. We report a remarkable diversity of brain microbes in control brain. The most abundant are fungi, bacteria, and chloroplastida, and we report detailed identification of representative microbial species. The pattern is substantially conserved across different bilateran species from Drosophila to human. In terms of diversity, the human brain microbiome appears to be a subset (~20%) of the gut microbiome. Adenovirus type C was the major virus found in human brain; other viruses were not well represented. However, the spectrum of brain microbes differed between individuals as well as between brain regions examined from single individuals (amygdala, cingulate cortex, hippocampus, hypothalamus); of these four regions, the highest microbial burden was in cingulate cortex. There was evidence of spreading of pathogens between brain regions in single individuals. Some microbes are over-represented in AD brain according to two measures: (i) absolute number of microbes normalized to endogenous human transcripts, and (ii) the number of brain specimens showing overabundance versus control. Species over-represented in AD brain according to both measures notably include bacteria (Streptococcus, Staphylococcus/Bacillus, Sphingomonas/Ralstonia) and fungi (Acrocalymma/Altenaria/Aureobasidium of the Aspergillus group; Komagataella of the Candida group, Cortinarius of the Schizophyllum group, and Tausonia of the Cryptococcus group), that are all related to known human pathogens. In addition, an uncharacterized chloroplastida (algae-related) species was more abundant in AD brain samples. Although these findings point to diverse microbial species, indicative of multiple causation, similar absolute levels of bacteria and fungi in AD brain samples could suggest synergy between pathogens. However, it is important to stress that not all AD samples were positive for these microbes, but this could be because the affected brain region(s) was not examined. These findings support the contention that infection, perhaps associated with declining immunity with age, may contribute to AD development.
2 citations
TL;DR: In this article , the authors argue that the location of the pathology is crucial, specifically, lesions to limbic brain are likely to accentuate immunosenescence, and could thus underlie a vicious cycle of accelerated immune decline and microbial proliferation that culminates in AD.
Abstract: The characteristic maximum lifespan varies enormously across animal species from a few hours to hundreds of years. This argues that maximum lifespan, and the ageing process that itself dictates lifespan, are to a large extent genetically determined. Although controversial, this is supported by firm evidence that semelparous species display evolutionarily programmed ageing in response to reproductive and environmental cues. Parabiosis experiments reveal that ageing is orchestrated systemically through the circulation, accompanied by programmed changes in hormone levels across a lifetime. This implies that, like the circadian and circannual clocks, there is a master ‘clock of age’ (circavital clock) located in the limbic brain of mammals that modulates systemic changes in growth factor and hormone secretion over the lifespan, as well as systemic alterations in gene expression as revealed by genomic methylation analysis. Studies on accelerated ageing in mice, as well as human longevity genes, converge on evolutionarily conserved fibroblast growth factors (FGFs) and their receptors, including KLOTHO, as well as insulin‐like growth factors (IGFs) and steroid hormones, as key players mediating the systemic effects of ageing. Age‐related changes in these and multiple other factors are inferred to cause a progressive decline in tissue maintenance through failure of stem cell replenishment. This most severely affects the immune system, which requires constant renewal from bone marrow stem cells. Age‐related immune decline increases risk of infection whereas lifespan can be extended in germfree animals. This and other evidence suggests that infection is the major cause of death in higher organisms. Immune decline is also associated with age‐related diseases. Taking the example of Alzheimer's disease (AD), we assess the evidence that AD is caused by immunosenescence and infection. The signature protein of AD brain, Aβ, is now known to be an antimicrobial peptide, and Aβ deposits in AD brain may be a response to infection rather than a cause of disease. Because some cognitively normal elderly individuals show extensive neuropathology, we argue that the location of the pathology is crucial – specifically, lesions to limbic brain are likely to accentuate immunosenescence, and could thus underlie a vicious cycle of accelerated immune decline and microbial proliferation that culminates in AD. This general model may extend to other age‐related diseases, and we propose a general paradigm of organismal senescence in which declining stem cell proliferation leads to programmed immunosenescence and mortality.
1 citations
TL;DR: Lathe et al. as mentioned in this paper presented an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) for restricted access data in the neurosciences.
Abstract: COPYRIGHT © 2023 Lathe. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Restricted access data in the neurosciences: Are the restrictions always justified?
TL;DR: The Alzheimer's Pathobiome Initiative as discussed by the authors performed comparative molecular analyses of microbes in post mortem brains versus cerebrospinal fluid, blood, olfactory neuroepithelium, oral/nasopharyngeal tissue, bronchoalveolar, urinary, and gut/stool samples.
Abstract: Microbial infections of the brain can lead to dementia, and for many decades microbial infections have been implicated in Alzheimer's disease (AD) pathology. However, a causal role for infection in AD remains contentious, and the lack of standardized detection methodologies has led to inconsistent detection/identification of microbes in AD brains. There is a need for a consensus methodology; the Alzheimer's Pathobiome Initiative aims to perform comparative molecular analyses of microbes in post mortem brains versus cerebrospinal fluid, blood, olfactory neuroepithelium, oral/nasopharyngeal tissue, bronchoalveolar, urinary, and gut/stool samples. Diverse extraction methodologies, polymerase chain reaction and sequencing techniques, and bioinformatic tools will be evaluated, in addition to direct microbial culture and metabolomic techniques. The goal is to provide a roadmap for detecting infectious agents in patients with mild cognitive impairment or AD. Positive findings would then prompt tailoring of antimicrobial treatments that might attenuate or remit mounting clinical deficits in a subset of patients.