Daniel M. Johnstone

Accurate quantification of amyloid plaque pathology is essential for understanding Alzheimer's disease (AD) progression and evaluating therapeutic interventions. Yet, conventional histology relies on sampling thin tissue sections and therefore incompletely captures three‐dimensional (3D) plaque distributions, introducing bias and limiting scalability. Here, we present a validated and scalable 3D analysis pipeline for whole‐brain quantification of amyloid plaques in cleared mouse brain tissue imaged by light‐sheet microscopy. This pipeline also integrates deep learning‐based segmentation with atlas registration to enable automated, region‐specific quantification across intact brain volumes. Quantitative measurements obtained using this approach showed strong agreement with gold‐standard stereology, while enabling higher throughput and comprehensive volumetric assessment of amyloid plaque burden. As a demonstration of its utility in a preclinical setting, we applied the pipeline to assess the neuroprotective effects of chronic saffron supplementation in APP/PS1 mice, identifying a significant reduction in hippocampal plaque load ( p < 0.01). Together, these findings establish an accessible and validated framework for scalable 3D quantification of amyloid pathology, providing a platform for neuropathological phenotyping and therapeutic evaluation in preclinical AD research.

The ontological categorization of the cellular elements of the brain was proposed over a century ago by Santiago Ramón y Cajal (neurons, astroglia) and Pío del Río-Hortega (oligodendroglia, microglia). It combines histochemical observations of morphology with allied inferences about the specialized functions and origins (ectoderm or mesoderm) of each cellular element. This ontology shapes modern neuroscience, with the main non-neuronal cells—astroglia, oligodendroglia and microglia—viewed as having distinct primary roles relating respectively to the metabolic support, myelination and immunoprotection of neurons, the information signaling cells. Yet contemporary techniques, ranging from electrophysiology to single-cell transcriptomics and ultrahigh resolution spectroscopy, are revealing intersecting molecular profiles and functional capacities of these cell groups, for example metabolic support, neuroimmune and signaling functions in oligodendroglia. Here we identify discrepancies in current glial paradigms, from empirical, evolutionary and pragmatic perspectives. We suggest a subset of small, iron-rich glial cells, usually with few processes, often viewed as oligodendroglia with myelin-related primary functions, instead have iron-related primary functions that are central to all aspects of brain activity. We call these ‘ferriglia’. We discuss implications for pathogenesis across the spectrum of neuropsychiatric and neurological disorders, including neurodegenerative conditions such as Alzheimer’s disease and other less common cognitive, movement and neurobehavioral disorders, stroke and cerebrovascular disease, glioblastoma and other brain cancers and neuroimmune conditions. We also briefly address the question of where ferriglia may reside within existing glial compartments and lineages, implications for the ontological classification of other glial cells, and research challenges that must be overcome going forward.

UK Biobank studies show Parkinson’s disease risk is almost doubled in men homozygous for the homeostatic iron regulator gene HFE p.C282Y polymorphism, associated with the common genetic iron disorder hemochromatosis. Whether this relationship is causal or spurious is unknown. We previously reported a novel Hfe ^-/- xTfr2 ^mut mouse model of hemochromatosis with elevated brain iron (∼1.5-1.8x). We now show these mice have reduced substantia nigra tyrosine hydroxylase expression at 3 months and 9 months age, sometimes exhibit severe hindlimb clasping by 7-8 months, have impaired rotarod and balance beam performance at 9 months and are untestable on the pole test. These parkinsonian features place the model at the forefront of genetic mouse models of PD, which generally do not show both TH loss and motor impairment. This confirms hemochromatosis-related mutations can cause parkinsonian features, substantiating causality of epidemiological relationships. Despite total brain iron elevation, neuronal iron remains low in Hfe ^-/- xTfr2 ^mut mice, consistent with hemochromatosis-related mutations disrupting the normal, iron-responsive regulation of the neuronal iron exporter ferroportin by hepcidin. Parkinsonian features may reflect reduced mitochondrial respiratory complex (MRC) activity due to functional neuronal iron depletion. This may be exacerbated by indiscriminate chelation and could instead respond to drugs targeting the hepcidin-ferroportin axis or MRC activity. This new model of chronic parkinsonism that increases with age provides unprecedented insights into the complex relationships of brain iron regulation and movement impairment. Since parkinsonism of diverse etiologies can exhibit iron dysregulation, the model may facilitate pre-clinical to end-stage studies relevant to both sporadic and genetic PD.

The ontological categorization of the cellular elements of the brain was proposed over a century ago by Santiago Ramón y Cajal (neurons, astroglia) and Pío del Río-Hortega (oligodendroglia, microglia). It combines histochemical observations of morphology with allied inferences about the specialized functions and origins (ectoderm or mesoderm) of each cellular element. This ontology shapes modern neuroscience, with the main non-neuronal cells – astroglia, oligodendroglia and microglia – viewed as having distinct primary roles relating to metabolic support, myelination and protection of neurons, the information signaling cells. Yet contemporary techniques, ranging from electrophysiology to single-cell transcriptomics and ultrahigh resolution spectroscopy, are revealing intersecting molecular profiles and functional capacities of these cell groups, for example metabolic support, neuroimmune and signaling functions in oligodendroglia. Here we identify discrepancies in current glial paradigms from empirical, evolutionary and pragmatic perspectives. We suggest that a subset of cells often viewed as oligodendroglia instead have iron-related primary functions that are central to all aspects of brain activity, rather than myelin-related primary functions. We discuss implications for pathogenesis across the spectrum of neuropsychiatric and neurological disorders, including neurodegenerative conditions such as Alzheimer’s disease and other less common cognitive, movement and neurobehavioral disorders, stroke and cerebrovascular disease, glioblastoma and other brain cancers and neuroimmune conditions. We also briefly address the question of where these cells reside within existing glial compartments and lineages, implications for the ontological classification of other glial cells and research limitations that must be overcome going forward.

This review explores the hypothesis that dementia in several forms, chronic kidney disease and idiopathic pulmonary fibrosis have a common cause in pulse-induced capillary haemorrhage. All three conditions are age-related and characterised by insidious onset, uncertainty about their cause, exacerbation by hypertension, resistance to treatment and the relentlessness of their progression. We argue that the three conditions are the clinical outcomes of damage caused by pulse-induced haemorrhage from capillaries. The damage, first detectable in mid-life, creates first mild and then severe symptoms of cognitive, renal and pulmonary dysfunction. We also review evidence that in all three organs there has developed, by young adulthood, a reserve of tissue that enables them to function well, despite the ‘heartbeat by heartbeat’ damage that accumulates from early mid-life; and that it is when that reserve is exhausted, typically in late age, that symptoms of organ failure emerge and progress. If this common cause can be established, a step will have been taken towards the understanding, treatment and delay of three conditions that have their beginnings in every individual and that, in those who survive other causes of death, become lethal in late age.

Although it is well established that a vegetable-rich (Mediterranean) diet is associated with health benefits in later life, the mechanisms and biological origins of this benefit are not well established. This review seeks to identify the components a healthful diet that reduce the individual’s suffering from non-communicable disease and extend longevity. We note the difference between the claims made for an essential diet (that prevents deficiency syndromes) and those argued for a diet that also prevents or delays non-communicable diseases and ask: what chemicals in our food induce this added resilience, which is effective against cardiovascular and neurodegenerative diseases, diabetes and even cancer? Working in the framework of acquired resilience (tissue resilience induced by a range of stresses), we arguethat the toxins evolved by plants as part of allelopathy (the competition between plant species) are key in making the ‘healthful difference’. We further suggest the recognition of a category of micronutrients additional to the established ‘micro’ categories of vitamins and trace elements and suggest also that the new category be called ‘trace toxins’. Implications of these suggestions are discussed.

Photobiomodulation (PBM)—the irradiation of tissue with low‐intensity light—mitigates neuropathology in rodent models of Parkinson's disease (PD) when targeted at the head (‘transcranial PBM’). In humans, however, attenuation of light energy by the scalp and skull necessitates a different approach. We have reported that targeting PBM at the body also protects the brain by a mechanism that spreads from the irradiated tissue (‘remote PBM’), although the optimal peripheral tissue target for remote PBM is currently unclear. This study compared the neuroprotective efficacy of remote PBM targeting the abdomen or leg with transcranial PBM, in mouse and non‐human primate models of PD. In a pilot study, the neurotoxin MPTP was used to induce PD in non‐human primates; PBM (670 nm, 50 mW/cm², 6 min/day) of the abdomen (n = 1) was associated with fewer clinical signs and more surviving midbrain dopaminergic cells relative to MPTP‐injected non‐human primates not treated with PBM. Validation studies in MPTP‐injected mice (n = 10 per group) revealed a significant rescue of midbrain dopaminergic cells in mice receiving PBM to the abdomen (~80%, p < .0001) or legs (~80%, p < .0001), with comparable rescue of axonal terminals in the striatum. Strikingly, this degree of neuroprotection was at least as, if not more, pronounced than that achieved with transcranial PBM. These findings confirm that remote PBM provides neuroprotection against MPTP‐induced destruction of the key circuitry underlying PD, with both the abdomen and legs serving as viable remote targets. This should provide the impetus for a comprehensive investigation of remote PBM‐induced neuroprotection in other models of PD and, ultimately, human patients.

Maternal iron deficiency occurs in 40–50% of all pregnancies and is associated with an increased risk of respiratory disease and asthma in children. We used murine models to examine the effects of lower iron status during pregnancy on lung function, inflammation and structure, as well as its contribution to increased severity of asthma in the offspring. A low iron diet during pregnancy impairs lung function, increases airway inflammation, and alters lung structure in the absence and presence of experimental asthma. A low iron diet during pregnancy further increases these major disease features in offspring with experimental asthma. Importantly, a low iron diet increases neutrophilic inflammation, which is indicative of more severe disease, in asthma. Together, our data demonstrate that lower dietary iron and systemic deficiency during pregnancy can lead to physiological, immunological and anatomical changes in the lungs and airways of offspring that predispose to greater susceptibility to respiratory disease. These findings suggest that correcting iron deficiency in pregnancy using iron supplements may play an important role in preventing or reducing the severity of respiratory disease in offspring. They also highlight the utility of experimental models for understanding how iron status in pregnancy affects disease outcomes in offspring and provide a means for testing the efficacy of different iron supplements for preventing disease.

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is commonly used to model Parkinson’s disease (PD) as it specifically damages the nigrostriatal dopaminergic pathway. Recent studies in mice have, however, provided evidence that MPTP also compromises the integrity of the brain’s vasculature. Photobiomodulation (PBM), the irradiation of tissue with low-intensity red light, mitigates MPTP-induced loss of dopaminergic neurons in the midbrain, but whether PBM also mitigates MPTP-induced damage to the cerebrovasculature has not been investigated. This study aimed to characterize the time course of cerebrovascular disruption following MPTP exposure and to determine whether PBM can mitigate this disruption. Young adult male C57BL/6 mice were injected with 80 mg/kg MPTP or isotonic saline and perfused with fluorescein isothiocyanate FITC-labelled albumin at various time points post-injection. By 7 days post-injection, there was substantial and significant leakage of FITC-labelled albumin into both the substantia nigra pars compacta (SNc; p < 0.0001) and the caudate-putamen complex (CPu; p ≤ 0.0003); this leakage partly subsided by 14 days post-injection. Mice that were injected with MPTP and treated with daily transcranial PBM (670 nm, 50 mW/cm², 3 min/day), commencing 24 h after MPTP injection, showed significantly less leakage of FITC-labelled albumin in both the SNc (p < 0.0001) and CPu (p = 0.0003) than sham-treated MPTP mice, with levels of leakage that were not significantly different from saline-injected controls. In summary, this study confirms that MPTP damages the brain’s vasculature, delineates the time course of leakage induced by MPTP out to 14 days post-injection, and provides the first direct evidence that PBM can mitigate this leakage. These findings provide new understanding of the use of the MPTP mouse model as an experimental tool and highlight the potential of PBM as a therapeutic tool for reducing vascular dysfunction in neurological conditions.