Biology subjects

Ansar, S.

Publications and source records attributed to Ansar, S..

4 recordsLinked to original sources

bioRxiv2026

Urban PM2.5 at Realistic Environmental Concentrations Impairs Blood-Brain Barrier Integrity and Enhances LOX-1 Expression in Human Brain Endothelial Cells

IntroductionAmbient air pollution, especially fine particulate matter 2.5 (PM2.5) has emerged as a critical environmental risk factor for cerebrovascular diseases, contributing to an estimated 7.9 million premature deaths annually. PM2.5 induces cellular toxicity and is hypothesized to disrupt the blood-brain barrier (BBB), a pathological hallmark in cerebrovascular diseases such as ischemic stroke. Despite epidemiological evidence linking PM2.5 to increased stroke incidence, its underlying cellular mechanism driving this association is poorly understood. It remains unclear how environmentally relevant pollution concentrations affects brain endothelial function or influence stroke-related biomarkers such as the lectin-like oxLDL receptor 1 (LOX-1). MethodPrimary adult male human brain microvascular endothelial cells (HBMEC) were exposed to PM2.5 (5, 15, 75, or 300 g/m3) collected from an urban environment in southern Sweden, or control. Thereafter, exposed to normoxia (21% O2) or hypoxia (1% O2) and glucose deprivation, followed by reperfusion as a model for ischemic stroke. Cell viability, oxidative stress, inflammation, BBB integrity (claudin-5, ZO-1) and LOX-1 protein expression were assessed. ResultsPM2.5 exposure induced cellular dysfunction, oxidative stress and inflammation starting at 75 g/m3 PM2.5. Notably, decreased claudin-5 and ZO-1 protein levels and increased LOX-1 expression at concentrations as low as 15 g/m3 PM2.5, levels commonly encountered in urban environments globally. The cellular effects of PM2.5 closely resembled those induced by ischemic-like injury. ConclusionThese findings demonstrate dose-dependent detrimental effects of PM2.5 on HBMEC. The results suggest that ambient urban PM2.5 may act as a predisposing factor for cerebrovascular disease onset, by causing endothelial and barrier dysregulation. HighlightsO_LIUrban PM2.5 dose-dependently disrupts BBB integrity in human brain endothelial cells C_LIO_LIPM2.5 induces endothelial dysfunction resembling ischemic-like injury C_LIO_LIUrban PM2.5 exposure upregulates cardiovascular disease biomarker LOX-1 C_LIO_LIA majority of the global population are exposed to BBB-disrupting PM2.5 levels C_LIO_LIVascular endothelial- and BBB dysfunction enhances risk for cerebrovascular disease C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/702473v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@42cce6org.highwire.dtl.DTLVardef@19a2ff9org.highwire.dtl.DTLVardef@1c38e7corg.highwire.dtl.DTLVardef@1bfa837_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Cerebrovascular Claudin-5 Isoform Expression Correlates with Worsened Stroke Outcomes Following Thromboembolic Stroke

Background and PurposeClaudin-5 plays a crucial role in the maintenance of the blood-brain barrier (BBB) integrity through its role in endothelial tight junction formation. Alternative splicing of claudin-5 within the microvascular endothelium may modulate BBB structural and functional dynamics, potentially influencing neuronal damage and recovery following ischemic stroke. We hypothesized that ischemic stroke induces temporal changes in claudin-5 protein isoform expression that correlates with worsened neurological outcomes. MethodsMale Wistar rats underwent thromboembolic stroke. Claudin-5 isoform expression was assessed at 3, 6, and 24h post-stroke onset, with additional groups receiving recombinant tissue plasminogen activator (rt-PA) at 4 hours post-stroke. Brain edema, infarct volume, hemorrhage, and cerebral blood flow was evaluated using 9.4T MRI. Ipsilateral and contralateral cerebrovascular claudin-5 expression was quantified via western blotting while neurological function was assessed by 28-point neuroscore. In addition, RNA sequencing analysis was performed to identify novel splice variants. ResultsA time-dependent increase in claudin-5 isoform 1 (35kDa) expression levels in the ipsilateral cerebrovasculature at 6 h was observed. Isoform 2 (25kDa) and fragment (10kDa) isoforms of claudin-5 remain unchanged. Treatment with rt-PA maintained the elevated levels of isoform 1 claudin-5 protein expression within the ipsilateral hemisphere. Increased claudin-5 isoform 1 expression within the ipsilateral hemisphere correlated with increased brain edema, hemorrhage, and worsened neurological function at 24h post-stroke onset. RNA sequencing revealed novel CLDN5 splice isoforms in post-stroke rat brain tissue which resemble structural similarity to known human CLDN5 isoforms. ConclusionThese findings demonstrate that ischemic stroke induces temporal, hemisphere-specific alterations in claudin-5 isoform expression that correlate with BBB dysfunction and poor neurological outcomes. The potential indication of novel alternative splice variants suggests that post-transcriptional regulation of claudin-5 represents a previously unrecognized mechanism contributing to endothelial tight junction dysfunction and stroke pathophysiology. These results highlight claudin-5 isoform expression as a potential therapeutic target for preserving BBB integrity following cerebral ischemia.

neuroscience↗

bioRxiv2023

LOX-1 and MMP-9 inhibition attenuates the detrimental effects of delayed rt-PA therapy and improves outcomes after acute ischemic stroke

BackgroundAcute ischemic stroke triggers endothelial activation that disrupts vascular integrity and increases hemorrhagic transformation leading to worsened stroke outcomes. Recombinant-tissue plasminogen activator (rt-PA) is an effective treatment; however, its use is limited due to a restricted time window and high risk for hemorrhagic transformation, which in part may involve activation of metalloproteinases (MMPs) mediated through lectin-like oxidized LDL receptor 1 (LOX-1). This studys overall aim was to evaluate the therapeutic potential of novel MMP-9 and LOX-1 inhibitors in combination with rt-PA to improve stroke outcomes. MethodsThromboembolic rat stroke model was utilized to investigate the impact of rt-PA delivered 4h post-stroke onset as well as selective LOX-1 (BI-0115) and/or MMP-9 (JNJ0966) inhibitors given prior to rt-PA administration. Infarct size, perfusion, and hemorrhagic transformation were evaluated by MRI. Neurological function was assessed using sensorimotor functioning testing. Using an in vitro, human brain microvascular endothelial cell (HBMEC) model, cells were exposed to hypoxia plus glucose deprivation (3h)/reperfusion (12h) (HGD/R) and treated with rt-PA {+/-} an MMP-9 and LOX-1 inhibition cocktail. MMP-9 activity was determined with zymography, and endothelial barrier marker gene expression and LOX-1 levels were evaluated via qRT-PCR and western blot respectively. ResultsRt-PA treatment increased edema, hemorrhage, and worsened neurological outcomes post stroke. LOX-1 inhibition significantly improved neurological function and reduced edema after delayed rt-PA treatment. Hemorrhagic transformation, edema, and increased MMP-9 activity were attenuated by the MMP-9 inhibitor. Stroke induced increases in cerebrovascular LOX-1 expression correlated with increased MMP-9 activity and elevated activity correlated with increased edema, infarct volume, and decreased neurological function. In cultured HBMECs, LOX-1/MMP-9 inhibition differentially attenuated rt-PA-mediated increases in endothelial derived MMP-9 levels and activity, inflammation, and activation following HGD/R. ConclusionHere, we conclude that MMP-9/LOX-1 inhibition attenuates negative aspects of delayed rt-PA therapy leading to improved neurological function.

neuroscience↗

bioRxiv2021

Arrestin-mediated Desensitization Enables Olfactory Discrimination in C. elegans

In the mammalian olfactory system, crosstalk among diverse olfactory signals is minimized through labelled line coding: individual neurons express one or few olfactory receptors among those encoded in the genome. Labelled line coding allows for separation of stimuli during mammalian olfactory signal transduction, however, in the nematode worm Caenorhabditis elegans, 1,300 olfactory receptors are primarily expressed in only 32 neurons, precluding this strategy. Here we report genetic, pharmacological and behavioural evidence that {beta}-arrestin-mediated desensitization of olfactory receptors, working downstream of the kinase GRK-1, enables discrimination between intra-neuronal olfactory stimuli, but that this discrimination relies on quantitative, rather than qualitative differences in signalling. Our findings suggest that C. elegans exploits {beta}-arrestin desensitization to maximize responsiveness to novel odors, allowing for behaviourally appropriate responses to olfactory stimuli despite the large number of olfactory receptors signalling in single cells. This represents a fundamentally different solution to the problem of olfactory discrimination than that which evolved in mammals, allowing for economical use of an extremely limited number of sensory neurons.

neuroscience↗