Biology subjects

Platt, B.

Publications and source records attributed to Platt, B..

10 recordsLinked to original sources

bioRxiv2026

Genotoxic and metabolic stress drive divergent senescence programs in human microglia

Microglial dysfunction is a hallmark of brain ageing linked to the accumulation of senescent microglial phenotypes that promote chronic neuroinflammation. Both genotoxic and metabolic stress have been implicated in microglial senescence; yet, whether distinct stressors shape senescence programs remain unclear. Here, we investigated the impact of chronic genotoxic and metabolic stress on senescence-associated phenotypes in the human microglia cell line HMC3. Cells were exposed to doxorubicin to induce sustained DNA damage or to chronic high-glucose conditions to model metabolic stress. Both stress paradigms induced characteristic senescence features including cellular and nuclear hypertrophy, increased senescence-associated {beta} galactosidase activity and reduced metabolic viability without significant cell loss. Both conditions activated the p53-p21 pathway and sustained DNA damage signalling, whereas metabolic stress additionally induced p16 expression and peripheral nuclear localisation of p21, suggesting divergence in senescence regulatory pathways. Mitochondrial alterations were evident under both conditions, Dox-induced stress was associated with downregulation of NRF2-TFAM signalling, whereas HG-induced stress induced NRF2-TFAM activation alongside increased KEAP1 expression, suggesting a constrained antioxidant response. This was accompanied by activation of mitochondrial and antioxidant stress responses that did not restore mitochondrial content. Furthermore, both stressors induced robust inflammatory activation, with genotoxic stress promoting a chemokine-rich senescence-associated secretory phenotype, while metabolic stress induced an interferon-associated inflammatory signature. Collectively, these findings demonstrated that chronic genotoxic and metabolic stress drive distinct yet overlapping senescence programs characterised by morphological changes, mitochondrial remodelling and persistent inflammatory activation. These stress-specific responses may differentially contribute to neurodegenerative processes and disease susceptibility.

neuroscience↗

bioRxiv2026

DNA damage-induced senescence reshapes transcriptomic and functional landscape of human neural progenitor cells

Ageing-related decline in hippocampal neurogenesis has been associated with cognitive impairment and neurodegenerative disease, yet experimentally tractable human models to study the underlying cellular and molecular mechanisms remain limited. Cellular senescence has emerged as a candidate driver of age-related tissue dysfunction, but its induction and consequences in human NPCs have not been well characterized. Here, we established a human in vitro model of NPC senescence using induced pluripotent stem cell-derived NPCs exposed to transient low-dose doxorubicin to activate the DNA damage response (DDR) while minimizing acute cytotoxicity. Doxorubicin-treated NPCs developed a stable senescent phenotype characterized by increased senescence-associated {beta}-galactosidase activity, reduced proliferation, persistent DNA damage, and sustained induction of p21 and p16. Transcriptomic profiling revealed widespread senescence-associated remodeling, including activation of p53 and inflammatory programs and repression of cell cycle and DNA repair pathways. Senescent NPCs exhibited apoptosis resistance despite transcriptional priming of apoptotic pathways and underwent mitochondrial remodeling with a shift towards oxidative metabolism. In parallel, they acquired a senescence-associated secretory phenotype enriched in inflammatory, TGF{beta}-related and pro-angiogenic factors, and conditioned media from these cells promoted angiogenesis in vascular organoids. Importantly, key senescence-associated features were recapitulated in human hippocampal organoids, confirming the robustness of this paradigm in a three-dimensional neural context. Together, these findings establish a tractable human model of DDR-driven NPC senescence and identify senescence as a mechanism linking genotoxic stress to impaired progenitor function, metabolic rewiring, and paracrine niche remodeling relevant to hippocampal ageing and neurodegeneration.

neuroscience↗

bioRxiv2026

Reproducible social phenotyping of 5xFAD mice in the Agora maze (Sociobox)

Neuropsychiatric (depression, schizophrenia, etc.) and neurological disorders (Alzheimers disease, AD, Parkinsons disease) are characterized by disruptions in cognition including social interaction and recognition. Developing tools for the assessment of social behaviour in mouse models and its relevance is essential to further advance our understanding of social impairments in these diseases. In the Agora maze for rodents, stranger mice confined into cubicles around the perimeter of the open square mirror the agora (marketplace) in ancient cities. Up to 5 social interaction partners are presented and can be freely selected for interaction (exposure). In the discrimination phase one novel mouse (SNew) is presented while 4 familiar partners remain. Interaction time is recorded via video observation. In Exp 1, we validated the test with different strains of wild-type male mice (C57BL/6J, Balb/c, NMRI) that were able to readily identify SNew and spent significantly more time in zones adjacent to their cubicle; only NMRI mice did not prefer SNew. Exp. 2 explored 5xFAD Alzheimer mice and showed normal exploration and discrimination when aged 6 and 8 months old. Repeat of the experiment in a second cohort confirmed robustness of this phenotype, but also reproducibility of the behavioural paradigm. The Agora task allows semi-automated evaluation of preference for social novelty in a more complex paradigm by expanding the number of social interaction partners from 2 (three-chamber test) to 5 (or more), while still avoiding physical approaches and aggressive episodes. Thus, Agora provides a more physiological behavioural paradigm which is highly robust and reproducible. HighlightsO_LIMore comprehensive behavioural test bed for social recognition C_LIO_LIMale wild-type mice can identify a stranger mouse amongst 5 social interaction partners C_LIO_LINo deficit in amyloid-based Alzheimer model 5xFAD aged 6-8 months. C_LIO_LIRepeat of experiments returned highly robust and reproducible results. C_LI

animal behavior and cognition↗

bioRxiv2025

The Icelandic mutation APPA673T on amyloid-β plaque burden in the 5xFAD Alzheimer model

The protective Icelandic mutation in the amyloid precursor protein (APP) gene, APPA673T, identified in Icelandic and other Nordic populations is associated with a significantly lower risk of developing Alzheimers disease (AD). Conflicting results have been reported for the APPA673T mutation in various knock-in models of AD, but its effect in 5x familial AD (5xFAD) mice has never been investigated. We have crossed C57Bl6/J mice expressing a single point mutation edited into the murine APP gene via CRISPR-Cas gene editing, termed APPA673T, with 5xFAD mice that overexpress human APP carrying the Swedish (K670N/M671L), Florida (I716V), and London (V717I) mutations as well as human presenilin-1 (PS1) with two mutations (M146L and L286V); the resulting mice were termed 5xFADxAPPA673T. We have investigated amyloid beta (A{beta}) pathology in 5xFADxAPPA673T, 5xFAD and their respective controls, APPA673T and C57Bl6/J wild types, at 6-months of age using immunohistochemistry, immunoblotting, and ELISAs. We found a moderate yet significant reduction for A{beta} plaque size in male 5xFADxAPPA673T compared to 5xFAD. No differences were observed for soluble/insoluble A{beta}40 and A{beta}42 levels per se, but lower plaque count/area was found in 5xFADxAPPA673T when A{beta}42/A{beta}40 ratios were low, suggesting a genotype-dependent sensitivity to A{beta} aggregation and accumulation. Therefore, the APPA673T mutation has the potential to modify A{beta} pathology in 5xFAD mice at the age of 6 months.

neuroscience↗

bioRxiv2025

The effect of the Icelandic mutation APPA673T in the line 66 model of tauopathy

The Icelandic mutation in the amyloid precursor protein (APP), APPA673T, has been identified in Icelandic and Scandinavian populations and is associated with a significantly lower risk of developing Alzheimers disease (AD). Although this mutation led to reduction in amyloid {beta}-protein (A{beta}) production, its effect on tau pathology is not well studied. We have crossed line 66 (L66) tau transgenic mice that overexpress the P301S aggregation-prone form of tau with C57Bl6/J mice expressing a single point mutation edited into the murine APP gene via CRISPR-Cas gene editing, termed APPA673T. We have performed ELISA, histopathological and behavioural analyses of heterozygous male/female L66 and L66xAPPA673T crosses at the age of 6 months to investigate the effect of the A673T mutation on tau brain pathology and behavioural deficits in these mice. Using immunohistochemistry, we found only a moderate, yet significant, reduction of mAb 7/51-reactive tau in prefrontal cortex for L66xAPPA673T compared to L66 mice. Quantification of tau in soluble/insoluble brain homogenate fractions by ELISA confirmed the lack of overt differences between genotypes, as did our extensive behavioural phenotyping using six different paradigms accessing motor function, olfaction, depression/apathy-like behaviour, as well as exploration and sociability. Therefore, the APPA673T mutation does not appear to modulate tau pathology or motor and neuropsychiatric behaviour in L66 tau transgenic mice.

neuroscience↗

bioRxiv2024

Mouse Exploratory behaviour in the open field with and without NAT-1 EEG device: Effects of MK801 and scopolamine

AbstractOne aspect of reproducibility in preclinical research that is frequently overlooked is the physical condition in which physiological, pharmacological or behavioural recordings are conducted. In this study, the physical conditions of mice were altered through the attachments of wireless electrophysiological recording devices (Neural Activity Tracker-1, NAT-1). NAT-1 devices are miniaturised multichannel devices with on-board memory for direct high-resolution recording of brain activity for >48 hrs. Such devices may limit the mobility of animals and affect their behavioural performance due to the added weight (total weight of approximately 3.4 g). Mice were additionally treated with saline (control), N-methyl-D-aspartate (NMDA) receptor antagonist MK801 (0.85 mg/kg), or the muscarinic acetylcholine receptor blocker scopolamine (0.65 mg/kg) to allow exploration of the effect of NAT-1 attachments in pharmacologically treated mice. We found only minimal differences in behavioural outcomes with NAT-1 attachments in standard parameters of locomotor activity widely reported for the open field test between drug-treatments. Hypoactivity was globally observed as a consistent outcome in MK801-treated subjects and hyperactivity in scopolamine groups regardless of NAT-1 attachments. These data collectively confirm the reproducibility for combined behavioural, pharmacological and physiological endpoints even in the presence of lightweight wireless data loggers. The NAT-1 therefore constitutes a pertinent tool for investigating brain activity in e.g. drug discovery, models of neuropsychiatric and/or neurodegenerative diseases with minimal effects on pharmacological and behavioural outcomes.

neuroscience↗

bioRxiv2024

Effects of age and dietary methionine restriction on cognitive and behavioural phenotypes in the rTg4510 model of frontotemporal dementia

Metabolic disorders such as diabetes and obesity are linked to neurodegenerative diseases, with evidence of decreased brain glucose metabolism and insulin resistance in patients with dementia. Given the rising prevalence of age-related diseases, lifestyle adjustments and nutritional interventions are gaining interest. Dietary methionine restriction (MR) is a nutritional intervention that enhances insulin sensitivity and delays ageing-associated metabolic alterations. Since the potential impact of MR on neurodegenerative diseases like dementia is not fully understood, we here examined the metabolic and behavioural phenotypes of a murine tauopathy model (rTg4510), which overexpresses human P301L mutated tau, and assessed the impact of an 8-week dietary MR. The rTg4510 mice and wild type (WT) littermates were assessed at 6 and 12 months of age. While rTg4510 mice displayed progressive behavioural and motor impairments at 6 and 12 months of age, MR led to significant benefits in the aged 12-month-old cohort, improving motor coordination and learning, short-term memory, and social recognition. These effects were accompanied by increased glycolysis in the hippocampus and higher FGF21 levels in the cortex. These benefits occurred in the absence of alterations in glucose metabolism/adiposity in this model. Overall, our results support the positive impact of MR on rTg4510 mice, suggesting this as a potential therapeutic intervention to delay and/or improve the progression in tau-related disease.

neuroscience↗

bioRxiv2023

How stra(i)nge are your controls? A comparative analysis of metabolic phenotypes in commonly used C57 substrains

In recent years, the use of insufficiently characterised control subjects has been a contributing factor to increasing irreproducibility in different areas of biomedical research including neuroscience and metabolism. There is now a growing awareness of phenotypic differences between the metabolic profiles of C57BL/6 substrains which are commonly used as control animals. We here investigated baseline metabolic characteristics such as glucose regulation, fasted serum insulin levels and hepatic insulin signalling in five different C57BL/6 sub-strains (N, J, JOla, JRcc) of both sexes, obtained from two commercial vendors Charles River Laboratories (Crl) and Envigo (Env). Our results indicated systematic and tissue-specific differences between substrains, modulated by both vendor and sex in all parameters investigated, not necessarily mediated by the presence of the Nnt mutation. Not only were there differences between 6J and 6N as expected, all three 6J sub-strains exhibited different profiles, even from the same breeder. Two distinct metabolic profiles were identified, one in which low insulin levels resulted in impaired glucose clearance (6JCrl; both sexes) and the other, where sustained elevations in fasted basal insulin levels led to glucose intolerance (male 6JRccEnv). Further, 6JRccEnv displayed sex differences in both glucose clearance and hepatic insulin signalling markers. In comparison, the two 6N substrains of either sex, irrespective of vendor, did not exhibit considerable differences, with 6NCrl animals presenting a good choice as a healthy baseline control for many types of experiments. Overall, our data emphasise the importance of selecting and characterising control subjects regarding background, sex, and supplier to ensure proper experimental outcomes in biomedical research.

physiology↗

bioRxiv2021

Pulsation changes link to impaired glymphatic function in a mouse model of vascular cognitive impairment

Large vessel disease and carotid stenosis are key mechanisms contributing to vascular cognitive impairment (VCI) and dementia. Our previous work, and that of others, using rodent models, demonstrated that bilateral common carotid stenosis (BCAS) leads to cognitive impairment via gradual deterioration of the glial-vascular unit and accumulation of amyloid-{beta} (A{beta}) protein. Since brain-wide drainage pathways (glymphatic) for waste clearance, including A{beta} removal, have been implicated in the pathophysiology of VCI via glial mechanisms, we hypothesized that glymphatic function would be impaired in a BCAS model and exacerbated in the presence of A{beta}. Male wild- type and Tg-SwDI (model of microvascular amyloid) mice were subjected to BCAS or sham surgery which led to a reduction in cerebral perfusion and impaired spatial learning and memory. After 3 months survival, glymphatic function was evaluated by cerebrospinal fluid (CSF) fluorescent tracer influx. We demonstrated that BCAS caused a marked regional reduction of CSF tracer influx in the dorsolateral cortex and CA1-DG molecular layer. In parallel to these changes increased reactive astrogliosis was observed post-BCAS. To further investigate the mechanisms that may lead to these changes, we measured the pulsation of cortical vessels. BCAS impaired vascular pulsation in pial arteries in WT and Tg-SwDI mice. Since our findings show that BCAS may influence VCI by impaired glymphatic drainage and reduced vascular pulsation we propose that these additional targets need to be considered when treating VCI.

neuroscience↗

bioRxiv2021

Sex differences in behaviour and molecular pathology in the 5XFAD model

BackgroundThe prevalence of Alzheimers Disease (AD) is greater in women compared to men, but the reasons for this remain unknown. This sex difference has been widely neglected in experimental studies using transgenic mouse models of AD. ObjectiveHere, we studied behaviour and molecular pathology of 5-month-old 5XFAD mice, which express mutated human amyloid precursor protein and presenilin-1 on a C57BL/6J background, vs. their wild-type littermate controls, to compared both sex- and genotype-dependent differences. MethodsA novel behavioural paradigm was utilised (OF-NO-SI), comprising activity measures (Open Field, OF) arena, followed by Novel Object exploration (NO) and Social Interaction (SI) of a sex-matched conspecific. Each segment consisted of two repeated trials to assess between-trial habituation. Subsequently, brain pathology (amyloid load, stress response and inflammation markers, synaptic integrity, trophic support) was assessed using qPCR and Western blotting. ResultsFemale 5XFAD mice had higher levels of human APP and beta-amyloid (A{beta}) and heightened inflammation vs males. These markers correlated with hyperactivity observed in both sexes, yet only female 5XFAD mice presented with deficits in object and social exploration. Male animals had higher expression of stress markers and neurotrophic factors irrespective of genotype, this correlated with cognitive performance. ConclusionThe impact of sex on AD-relevant phenotypes is in line with human data and emphasises the necessity of appropriate study design and reporting. Differential molecular profiles observed in male vs. female mice offer insights into possible protective mechanisms, and hence treatment strategies.

neuroscience↗