Biology subjects

Talwar, P.

Publications and source records attributed to Talwar, P..

18 recordsLinked to original sources

bioRxiv2026

Cognitive Fitness in Ageing (COFITAGE): A Multimodal and Longitudinal Neuroimaging Dataset

Purpose: Brain aging involves interrelated changes in molecular processes, neuroinflammatory mechanisms, brain macro- and microstructure, sleep physiology, and cognition. The 50 to 70 years age range represents a critical transition period, in which these subtle alterations may precede measurable cognitive decline and the onset of clinical neurodegenerative disease. To allow systematic investigation of these early alterations and the subsequent progression in brain aging, we provide an open-access data resource from a multidisciplinary longitudinal study integrating neuroimaging, genetics, sleep, and neuropsychological phenotyping with assessments at baseline and at 2-year follow-up. Acquisition and Validation Methods: The baseline cohort comprises 101 community-dwelling participants (50-69 years old) who underwent magnetic resonance imaging (MRI) using a 3T protocol that included high-resolution structural imaging (T1- and T2-weighted), quantitative multi-parametric acquisitions with B1 mapping, and multi-shell diffusion-weighted imaging. Moreover, positron emission tomography (PET) imaging was performed using [18F]Flutemetamol or [18F]Florbetapir (amyloid-beta tracers) in all participants, with a subset also undergoing [18F]THK-5351 PET (tau-related/neuroinflammation). The dataset was complemented by extensive phenotypic data, including sleep and neuropsychological assessments, and by genotype data through genetic analysis. 66 participants underwent a 2-year cognitive follow-up, enabling longitudinal analyses of cognitive trajectories. Data acquisition and curation were performed using standardized procedures, with systematic quality control to support reliable cross-sectional and longitudinal analyses. Data Format and Usage Notes: All data are distributed in a BIDS-compliant format, and released in open-access (EBRAINS). Potential Applications: This dataset supports multimodal analyses, allowing the identification of interpretable patterns characterizing brain aging from multiple perspectives. It enables the comparison of different models to derive (semi)quantitative MRI parameters, the discovery of imaging biomarkers associated with early cognitive decline, and the monitoring or prediction of brain aging progression. In addition, it offers focused coverage of adults aged 50-70 years, which is often underrepresented in existing healthy subjects public datasets.

neuroscience↗

bioRxiv2026

In vivo modulation of locus coeruleus activity by light

Dysfunction of the Locus coeruleus (LC), a small brainstem nucleus which consists of the brains primary source of norepinephrine, is linked to various neurological and psychiatric disorders. Light exposure influences many non-image-forming (NIF) biological functions including those modulated by LC activity. Yet direct evidence of light-driven modulation of the LC has remained elusive due to the structures small size and deep location. Using ultra-high-field (7 Tesla) functional MRI during an emotional task under varying illuminances, we demonstrate that light modulates LC activity in an emotion-dependent manner. We show that increased illuminance dampens LC responses to negative emotional stimuli while enhancing responses to neutral stimuli. Furthermore, we provide tentative evidence that within an emotional context, light may affect LC activity through the basomedial nucleus of the amygdala as well as through a region of the hypothalamus encompassing the lateral hypothalamus. These findings open avenues for the development of targeted, non-pharmacological treatments leveraging light to modulate norepinephrine tone and/or LC activity in several neuropsychiatric disorders. Significance StatementDysfunction of the Locus Coeruleus (LC), a small nucleus of brain and the main source of norepinephrine, is linked to various brain disorders. Here we provide in vivo evidence that exposure to light can alter the activity of the LC with higher illuminance leading to dampened LC responses to negative emotional stimuli. These findings identify the LC as a key target for the therapeutic effects of light on emotion, offering a biological framework for using light to treat neuropsychiatric disorders.

neuroscience↗

bioRxiv2026

Pooling quantitative MRI data: A multi-protocol study of healthy subcortical ageing

Quantitative MRI (qMRI) measures relaxation rates, exchange rates and proton densities that reflect biophysical properties of tissue and are ideally free from protocol- and scanner-dependence. In practice, qMRI has not yet achieved this level of independence from sequence and hardware choice, and quantitative estimates often differ across sites and acquisition schemes. At the same time pooling data across different sources can be beneficial to statistical power of longitudinal, cross-sectional or case-control studies. Here we investigate how protocol and hardware differences can affect pooling data from different sources in large ultra high field (UHF) qMRI studies in the context of healthy aging. We combine the openly available ageing UHF qMRI MP2RAGEME-based dataset with two different MPM-based sets of qMRI data. We evaluate how pooling affects age dependence of qMRI parameters and investigate protocol-related biases, with a particular focus on subcortical structures. We focus the analysis, first, on replication and expansion of the reference qMRI dataset on normative aging, second, the examination of the protocol influence on the estimated qMRI values, and third, on detecting the protocol effect on the age dependence inferred from the data. We find that the age-related changes for R1 measure around 4-17% of the lifespan mean in different structures. Similarly, age-related R2* variation in different structures constitutes around 6-30%. Subcortical structure volume change is on the order of 5-27%. We further observe larger relative difference between protocols for R1 and volume, while R2* remains more consistent for most regions. We show how pooling the UHF qMRI data from different sites and collected with different quantitative protocols can be both detrimental and beneficial for the analysis outcomes.

neuroscience↗

bioRxiv2026

Regional Hypothalamic Responses to Light Vary Across Developmental Stages but Remain Stable with Time of Day

Background: Light plays a significant role in regulating various non-visual biological processes, such as stimulating alertness and cognition. However, the precise subcortical neural pathways are not fully established, including within the hypothalamus. In particular, how the hypothalamus processes are modulated by time-of-day and developmental stages, remains poorly understood. Methods: In this study, we used 7 Tesla functional magnetic resonance imaging to examine in vivo the impact of different light illuminance (0.16, 37, 92, and 190 melanopic equivalent daylight illuminance: mel-EDI lux) on the activity of the hypothalamus of healthy young adults (N=33; 20 women; 24.3 {+/-}3.2y) and adolescents (N=16; 5 women; 16.8 {+/-}1.1y) while they completed an auditory executive task, in the morning or in the evening. Results: Performance to the task improved with increasing illuminance irrespective of time of day and age group. When focusing on time-of-day differences in young adults, we found that the regional impact of light illuminance on the activity of the hypothalamus was consistent between the morning and the evening, with the posterior and anterior hypothalamus, respectively, showing increased and decreased activity with increasing illuminance. When focusing on developmental stages differences, during the evening session only, we found similar regional patterns in adolescents and young adult. The magnitude of the response at the highest illuminance was, however, larger in adolescents, with a larger deactivation of the superior-anterior and inferior-tubular hypothalamus. Conclusions: These findings reveal a complex and non-uniform impact of light on hypothalamus activity and provide novel insights into how light influences vary with developmental stages.

neuroscience↗

bioRxiv2025

Sleep arousals are associated with the polygenic risk for developing Alzheimer's disease and with cognitive decline in healthy late middle-aged individuals

ObjectiveSleep disturbances are increasingly recognized as early features of Alzheimers disease (AD) neuropathology. In that context, spontaneous arousals during sleep have been associated with the burden of Amyloid beta in the brain of healthy late middle-aged individuals. Whether the heterogeneity of arousals during sleep may be related to the genetic risk of developing AD in young adults is not established. Likewise, whether arousals may be associated with cognitive decline is not known. Here, we evaluated the association between arousals, the genetic risk for developing AD and cognitive performance and cognitive decline in healthy young and late-middle-aged individuals. MethodsWe classified spontaneous arousals using in-lab EEG recordings of sleep in 453 younger individuals (22+/-2.7y; 49 women) and 87 late middle-aged individuals (59.3+/-5.3y; 59 women) based on their association with sleep stage transitions and changes in muscle tone. We examined the associations between arousal types and the polygenic risk scores (PRS) for AD, cognitive performance at baseline and, in late middle-aged individuals, cognitive decline over 2 and 7 years. ResultsThe prevalence of arousals associated with sleep stage transition was higher in late middle-aged vs. younger individuals. Among these arousals, those with and without muscle tone increases were, respectively, associated with lower and higher PRS for AD in late middle-aged but not in younger individuals. In the late middle-aged individuals, transition arousals associated with and without muscle tone increases were, respectively, correlated with better and worse attentional performance at baseline, and lower and larger memory decline over 2 or 7 years. ConclusionThe heterogeneity in spontaneous arousals during sleep may reflect their physiological intensity or underlying neural activation, and may indicate vulnerability to AD in late middle-aged individuals. The findings may contribute to identifying early markers of neurodegenerative risk. Statement of SignificanceSleep arousals are typically regarded as disruptive events, yet their physiological diversity may reveal important insights into brain health. In this study, we report that distinct subtypes of spontaneous sleep arousals are differentially associated with genetic vulnerability to Alzheimers disease (AD) and with future cognitive decline in healthy late middle-aged adults. Specifically, sleep arousals linked to sleep stage transitions but lacking muscle activation were related to higher polygenic risk for AD and greater memory decline, while those accompanied by muscle tone increases showed the opposite pattern. These findings indicate that subtle variations in sleep microstructure can reflect neurobiological vulnerability to AD before clinical symptoms emerge. By identifying electrophysiological markers associated with genetic risk and cognitive trajectories, this work advances the potential for using sleep-based biomarkers to detect and monitor preclinical neurodegenerative processes.

neuroscience↗

bioRxiv2025

The crosstalk between the anterior hypothalamus and the locus coeruleus during wakefulness is associated with low frequency oscillations power during sleep

Study ObjectivesAnimal research has demonstrated that sleep regulation heavily depends on a network of subcortical nuclei. In particular, whether the crosstalk between the Locus Coeruleus (LC) and hypothalamic nuclei influences sleep variability and age-related changes in humans remains unexplored. This study investigated whether the effective connectivity between the LC and subparts of the hypothalamus is associated with the electrophysiology of rapid eye movement sleep (REMS). MethodsThirty-three healthy younger ([~]22y, 27 women) and 18 older ([~]61y, 14 women) individuals underwent 7-Tesla functional magnetic resonance imaging during wakefulness to investigate the effective connectivity between LC and distinct hypothalamus subparts encompassing several nuclei. Additionally, we recorded their sleep electroencephalogram (EEG) to explore relationships between effective connectivity measures and REMS theta energy and sigma power prior to REMS episodes. ResultsThe effective connectivity analysis revealed robust evidence of a mutual positive influence between the LC and the anterior-superior and posterior hypothalamus, supporting the idea that the connectivity patterns observed in animal models are also present in humans. Furthermore, our results suggest that in older adults, stronger effective connectivity from the anterior-superior hypothalamus, including the preoptic area, to the LC is associated with reduced REM theta energy. Specificity analysis showed that this association was not limited to REM theta energy but also extended to specific lower-frequency bands during REMS and NREMS. ConclusionsThese findings highlight the complex age-dependent modulation of the LC circuitry and its role in sleep regulation. Understanding these neural interactions offers valuable insight into the mechanisms driving age-related sleep changes.

neuroscience↗

bioRxiv2025

Light Impact on Thalamo-Cortical Connectivity During an Executive Cognitive Task: Effects of Time of Day and Specificities of Teenagers

BackgroundLight affects not only vision but also attention, alertness, and cognition, primarily through intrinsically photosensitive retinal ganglion cells sensitive to blue-wavelength light. While previous research has shown that light influences brain regional activity, its impact on brain connectivity remains unclear. MethodsUsing 7-Tesla fMRI, this study examined how light illuminance modulates canonical left-lateralized verbal thalamo-prefrontal-parietal network connectivity during an auditory executive task. Fifty-five participants, including young adults (19-30 y, 23 Females: scanned in the morning or evening) and adolescents (15-18 y, 6 Females: scanned only in the evening), were studied. ResultsWe first found that across all the groups, moderate blue-enriched light strengthened parietal-to-frontal connectivity, while low-illuminance orange light enhanced thalamus-to-parietal connectivity. When focusing on time-of-day differences in young adults, we found that higher-illuminance blue-enriched light strengthened thalamus-to-prefrontal connectivity in the morning compared to the evening. When focusing on developmental stages differences, during the evening session only, we observe that moderate blue-enriched light enhanced thalamus-to-parietal connectivity in adolescents compared to young adults. ConclusionThese findings reinforce the view that the thalamus plays a key role in mediating the impact of light on cognition and the impact of light depends on the context of light administration, i.e. with timing and age.

neuroscience↗

bioRxiv2025

Age-related differences in the association between REM sleep and the polygenic risk for Parkinson's disease

ObjectiveParkinsons disease (PD) is one of the rare diseases for which sleep alteration is a true marker of disease outcome. Yet, how the association between sleep and PD emerges over the healthy lifetime is not established. We examined association between the polygenic risk score (PRS) for PD and the variability in the electrophysiology of Rapid Eye Movement (REM) sleep in 433 younger (18-31y) and 85 late-midlife (50-69y) healthy individuals. MethodsIn this prospective cross-sectional study, in-lab EEG recordings of sleep were recorded to extract REM sleep metrics. PRS was computed using SBayesR approach. ResultsGeneralized Additive Model for Location, Scale and Shape (GAMLSS) analysis showed significant association of REM duration (pcorr=0.03) and theta energy in REM (pcorr=0.004) with PRS for PD in interaction with age group. In the younger sub-sample, REM duration and theta energy were positively associated with PD PRS. In contrast, in the late-midlife sub-sample, the same associations were negative (though only qualitatively for REM theta energy) and may differ between men and women. InterpretationREM sleep is associated with the PRS for PD in early adulthood, 2 to 5 decades prior to typical symptoms onset. The association changes from positive in younger individuals, presumably free of alpha-synuclein, to negative in late-midlife individuals, possibly because of the progressive presence of alpha-synuclein aggregates or of the repeated increased oxidative metabolism imposed by REM sleep. Our findings may unravel core associations between PD and sleep and may contribute to novel intervention targets to prevent or delay PD.

neuroscience↗

bioRxiv2024

REM sleep quality is associated with balanced tonic activity of the locus coeruleus during wakefulness

BackgroundAnimal studies established that the locus coeruleus (LC) plays important roles in sleep and wakefulness regulation. Whether it contributes to sleep variability in humans is not yet established. Here, we investigated if the in vivo activity of the LC is related to the variability in the quality of Rapid Eye Movement (REM) sleep. MethodsWe assessed the LC activity of 34 healthy younger ([~]22y) and 18 older ([~]61y) individuals engaged in bottom-up and top-down cognitive tasks using 7-Tesla functional Magnetic Resonance Imaging (fMRI). We further recorded their sleep electroencephalogram (EEG) to evaluate associations between LC fMRI measures and REM sleep EEG metrics. ResultsTheta oscillation energy during REM sleep was positively associated with LC response in the top-down task. In contrast, REM sleep theta energy was negatively associated with LC activity in older individuals during the bottom-up task. Importantly, sigma oscillations power immediately preceding a REM sleep episode was positively associated with LC activity in the top-down task. ConclusionsLC activity during wakefulness was related to REM sleep intensity and to a transient EEG change preceding REM sleep, a feature causally related to LC activity in animal studies. The associations depend on the cognitive task, suggesting that a balanced level of LC tonic activity during wakefulness is required for optimal expression of REM sleep. The findings may have implications for the high prevalence of sleep complaints reported in aging and for disorders such as insomnia, Alzheimers, and Parkinsons disease, for which the LC may play pivotal roles through sleep.

neuroscience↗

bioRxiv2024

Exposure to light supresses the activity of the medial and superior amygdala during emotional processing

The brain mechanisms through which changes in season and light exposure modulate mood may involve different nuclei of the amygdala. We aimed to test this hypothesis using 7 Tesla functional magnetic resonance imaging in 29 healthy young adults. We first considered time-of-year changes in activity that are related to the slow change in photoperiod. We find that the response to emotional stimuli of selected medial and superior nuclei of the amygdala peaked around the start of winter or increased with worse mood status. We further assessed how alternating short exposures to light of different illuminance acutely affected the regional activity of the amygdala. We show that the same areas showed a linear reduction of activity when exposed to increasing light illuminance, specifically when processing emotional stimuli. Importantly, the impact of light on part of these nuclei peaked around the start of summer or decreased with worse mood. These findings provide new evidence that humans show seasonality and that, for mood, it involves parts of the amygdala. The results bring novel insights into the mechanisms that underlie the long-term and acute impact of light on mood and that may contribute to the benefits of light therapy in the treatment of mood disorders.

neuroscience↗

bioRxiv2023

Regional response to light illuminance across the human hypothalamus

Light exerts multiple non-image-forming biological effects on physiology including the stimulation of alertness and cognition. However, the subcortical circuitry underlying the stimulating impact of light is not established in humans. We used 7 Tesla functional magnetic resonance imaging to assess the impact of variations in light illuminance on the regional activity of the hypothalamus while healthy young adults (N=26; 16 women; 24.3 {+/-} 2.9y) were completing two auditory cognitive tasks. We find that, during both the executive and emotional tasks, higher illuminance triggered an activity increase over the posterior part of the hypothalamus, which includes part of the tuberomamillary nucleus and the posterior part of the lateral hypothalamus. In contrast, increasing illuminance evoked a decrease in activity over the anterior and ventral parts of the hypothalamus, encompassing notably the suprachiasmatic nucleus and another part of the tuberomammillary nucleus. Critically, the performance of the executive task was improved under higher illuminance and was negatively correlated with the activity of the posterior hypothalamus area. These findings reveal the distinct local dynamics of different hypothalamus regions that underlie the impact of light on cognition.

neuroscience↗

bioRxiv2023

In vivo marker of brainstem myelin is associated to quantitative sleep parameters in healthy young men

Brain structural integrity has been suggested to contribute to the variability in human sleep quality and composition. The associations between sleep parameters and the regional integrity of subcortical structures implicated in sleep-wake regulation remain, however, largely unexplored. The present study aimed at assessing association between quantitative Magnetic Resonance Imaging (qMRI)-derived marker of the myelin content of the brainstem with the variability in the sleep electrophysiology in a large sample of healthy young men (N=321;[~]22y). Generalized Additive Model for Location, Scale and Shape (GAMLSS) was used to seek associations between sleep metrics and Magnetisation Transfer saturation (MTsat) qMRI values, proxy for myelin content. Separate GAMLSS revealed that sleep onset latency and slow wave sleep intensity were significantly associated with MTsat-derived myelin estimates in the brainstem (pcorrected[≤].03), with overall higher MTsat value associated with values reflecting better sleep quality. The association changed with age, however (MTsat-by-age interaction - pcorrected[≤].03), with higher MTsat value linked to better values in the two sleep metrics in the individuals of our sample aged [~]18 to 20y. Similar associations were detected across different parts of the brainstem (pcorrected[≤].03), suggesting that the overall maturation and integrity of the brainstem was associated with both sleep metrics. Our results suggest that myelination of the many reticular nuclei of the brainstem essential to regulation of sleep is associated with inter-individual differences in sleep characteristics during early adulthood. They may have implications for sleep disorders or neurological diseases related to myelin.

neuroscience↗

bioRxiv2023

Light modulates task-dependent thalamo-cortical connectivity during an auditory attentional task

Exposure to blue wavelength light stimulates alertness and performance by modulating a widespread set of task-dependent cortical and subcortical areas. How light affects the crosstalk between brain areas to trigger this stimulating effect is not established. We recorded the brain activity of 19 healthy young participants (24.05{+/-}2.63; 12 women) while they completed an auditory attentional task in darkness or under an active (blue-enriched) or a control (orange) light, in an ultra-high-field 7 Tesla MRI scanner. We tested if light modulated the effective connectivity between an area of the posterior associative thalamus, encompassing the pulvinar, and the intraparietal sulcus (IPS), key areas in the regulation of attention. We found that only the blue-enriched light strengthened the connection from the posterior thalamus to the IPS. Our results provide the first empirical data supporting that blue wavelength light affects ongoing non-visual cognitive activity by modulating task-dependent information flow from subcortical to cortical areas.

neuroscience↗

bioRxiv2023

Impact of repeated short light exposures on sustained pupil responses in an fMRI environment

Light triggers numerous non-image forming (NIF), or non-visual, biological effects. The brain correlates of these NIF effects have been investigated, notably using Magnetic Resonance Imaging (MRI) and short light exposures varying in irradiance and spectral quality. However, it is not clear whether having light in subsequent blocks may induce carry over effects of one light block onto the next, thus biasing the study. We reasoned that pupil light reflex (PLR) was an easy readout of one of the NIF effects of light that could be used to address this issue. We characterized the sustained PLR in 13 to 16 healthy young individuals under short light exposures during three distinct cognitive processes (executive, emotional and attentional). Light conditions pseudo-randomly alternated between monochromatic orange light [0.16 melanopic Equivalent Daylight Illuminance (mel EDI) lux] and polychromatic blue-enriched white light of three different levels [37, 92, 190 mel EDI lux]. As expected, higher melanopic irradiance was associated with larger sustained PLR in each cognitive domain. This result was stable over the light block sequence under higher melanopic irradiance levels as compared to lower ones. Exploratory frequency-domain analyses further revealed that PLR was more variable within a light block under lower melanopic irradiance levels. Importantly, PLR varied across tasks independently of the light condition pointing to a potential impact of the light history and/or cognitive context on PLR. Together, our results emphasize that the distinct contribution and adaptation of the different retinal photoreceptors influence the NIF effects of light and therefore potentially their brain correlates.

neuroscience↗

bioRxiv2023

In vivo Locus Coeruleus activity while awake is associated with REM sleep quality in healthy older individuals

The locus coeruleus (LC) is the primary source of norepinephrine (NE) in the brain, and the LC-NE system is involved in regulating arousal and sleep. It plays key roles in the transition between sleep and wakefulness, and between slow wave sleep (SWS) and rapid eye movement sleep (REMS). However, it is not clear whether the LC activity during the day predicts sleep quality and sleep properties during the night, and how this varies as a function of age. Here, we used 7 Tesla functional Magnetic Resonance Imaging (7T fMRI), sleep electroencephalography (EEG) and a sleep questionnaire to test whether the LC activity during wakefulness was associated with sleep quality in 52 healthy younger (N=33; ~22y; 28 women) and older (N=19; ~61y; 14 women) individuals. We find that, in older, but not in younger participants, higher LC activity, as probed during an auditory mismatch negativity task, is associated with worse subjective sleep quality and with lower power over the EEG theta band during REMS (4-8Hz), which are two sleep parameters significantly correlated in our sample of older individuals. The results remain robust even when accounting for the age-related changes in the integrity of the LC. These findings suggest that the activity of the LC may contribute to the perception of the sleep quality and to an essential oscillatory mode of REMS, and that the LC may be an important target in the treatment of sleep disorders and age-related diseases.

neuroscience↗

bioRxiv2023

MRI-assessed locus coeruleus contrast and functional response are not associated in young and late middle-aged individuals

The brainstem locus coeruleus (LC) influences a broad range of brain processes, including cognition. The so-called LC contrast is an accepted marker of the integrity of the LC that consists of a local hyperintensity on specific Magnetic Resonance Imaging (MRI) structural images. The small size of the LC has, however, rendered its functional characterization difficult in humans, including in aging. A full characterization of the structural and functional characteristics of the LC in healthy young and late middle-aged individuals is needed to determine to potential roles of the LC in different medical conditions. Here, we wanted to determine whether the activation of the LC in a mismatch negativity task changes in aging and whether the LC functional response was associated to the LC contrast. We used Ultra-High Field (UHF) 7-Tesla functional MRI (fMRI) to record brain response during an auditory oddball task in 53 healthy volunteers, including 34 younger (age: 22.15y {+/-} 3.27; 29 women) and 19 late middle-aged (age: 61.05y {+/-} 5.3; 14 women) individuals. Whole-brain analyses confirmed brain responses in the typical cortical and subcortical regions previously associated with mismatch negativity. When focusing on the brainstem, we found a significant response in the rostral part of the LC probability mask generated based on individual LC images. Although bilateral, the activation was more extensive in the left LC. Individual LC activity was not significantly different between young and late middle-aged individuals. Critically, while the LC contrast was higher in older individuals, the functional response of the LC was not associated with its contrast. These findings show that the age-related alterations of the LC structural integrity may not necessarily be related to changes in its functional response. The results further indicate that LC responses could remain stable in healthy individuals aged 20 to 70.

neuroscience↗

bioRxiv2018

IRE1α is critical for kaempferol induced neuroblastoma differentiation

Neuroblastoma is an embryonic malignancy arises out of the neural crest cells of the sympathetic nervous system. It is the most common childhood tumor and well known for its spontaneous regression via the process of differentiation. The induction of differentiation using small molecule modulators such as all trans retinoic acid is one of the treatment strategies to treat the residual disease. In this study, we have reported the effect of kaempferol, a phytoestrogen in inducing differentiation of neuroblastoma cells in vitro. Treatment of neuroblastoma cells with kaempferol reduced the proliferation and enhanced apoptosis along with the induction of neuritogenesis. Analysis of the expression of neuron specific markers such as {beta} III tubulin, neuron specific enolase and NRDG1 (N-myc down regulated gene 1) revealed the process of differentiation accompanying kaempferol induced apoptosis. Further analysis on understanding the molecular mechanism of action showed that the activity of kaempferol happened through the activation of the endoribonuclease activity of IRE1 (Inositol requiring enzyme 1 alpha), an endoplasmic reticulum (ER) resident transmembrane protein. The in silico docking analysis and biochemical assays using recombinant human IRE1 confirms the binding of kaempferol to the ATP binding site of IRE1 and thereby activating ribonuclease activity. Treatment of cells with the small molecule inhibitor STF083010 which specifically targets and inhibits the endoribonuclease activity of IRE1 showed reduced expression of neuron specific markers and curtailed neuritogenesis. The knock down of IRE1 using plasmid based shRNA lentiviral particles also showed diminished changes in the change in morphology of the cells upon kaempferol treatment. Thus our study suggests that kaempferol induces differentiation of neuroblastoma cells via the IRE1-XBP1 pathway.

molecular biology↗

bioRxiv2018

Identification of FDA-approved drugs as novel allosteric inhibitors of human executioner caspases

The regulation of apoptosis is a tightly-coordinated process and caspases are its chief regulators. Of special importance are the executioner caspases, caspase-3/7, the activation of which irreversibly sets the cell on the path of death. Dysregulation of apoptosis, particularly an increased rate of cell death lies at the root of numerous human diseases. Although several peptide-based inhibitors targeting the homologous active site region of caspases have been developed, owing to their non-specific activity and poor pharmacological properties their use has largely been restricted. Thus, we sought to identify FDA-approved drugs that could be repurposed as novel allosteric inhibitors of caspase-3/7. In this study, we virtually screened a catalog of FDA-approved drugs targeting an allosteric pocket located at the dimerization interface of caspase-3/7. From among the top-scoring hits we short-listed five compounds for experimental validation. Our enzymatic assays using recombinant caspase-3 suggested that four out of the five drugs effectively inhibited caspase-3 enzymatic activity in vitro with IC50 values ranging ~10-55 M. Structural analysis of the docking poses show the four compounds forming specific non-covalent interactions at the allosteric pocket suggesting that these molecules could disrupt the adjacently-located active site. In summary, we report the identification of four novel non-peptide allosteric inhibitors of caspase-3/7 from among FDA-approved drugs.

bioinformatics↗