Unravelling the interactions between small molecules and liposomal bilayers via molecular dynamics and thermodynamic modelling.

Lipid-based drug delivery systems hold immense promise in addressing critical medical needs, from cancer and neurodegenerative diseases to infectious diseases. By encapsulating active pharmaceutical ingredients - ranging from small molecule drugs to proteins and nucleic acids - these nanocarriers enhance treatment efficacy and safety. However, their commercial success faces hurdles, such as the lack of a systematic design approach and the issues related to scalability and reproducibility. This work aims to provide insights into the drug-phospholipid interaction by combining molecular dynamic simulations and thermodynamic modelling techniques. In particular, we have made a connection between the structural properties of the drug-phospholipid system and the physicochemical performance of the drug-loaded liposomal nanoformulations. We have considered two prototypical drugs, felodipine (FEL) and naproxen (NPX), and one model hydrogenated soy phosphatidylcholine (HSPC) bilayer membrane. Molecular dynamic simulations revealed which regions within the phospholipid bilayers are most and least favoured by the drug molecules. NPX tends to reside at the water-phospholipid interface and is characterized by a lower free energy barrier for bilayer membrane permeation. Meanwhile, FEL prefers to sit within the hydrophobic tails of the phospholipids and is characterized by a higher free energy barrier for membrane permeation. Flory-Huggins thermodynamic modelling, small angle X-ray scattering, dynamic light scattering, TEM, and drug release studies of these liposomal nanoformulations confirmed this drug-phospholipid structural difference. The naproxen-phospholipid system has a lower free energy barrier for permeation, higher drug miscibility with the bilayer, larger liposomal nanoparticle size, and faster drug release in the aqueous medium than felodipine. We suggest that this combination of molecular dynamics and thermodynamics approach may offer a new tool for designing and developing lipid-based nanocarriers for unmet medical applications.

A role for vessel-associated extracellular matrix proteins in multiple sclerosis pathology.

Multiple sclerosis (MS) is unsurpassed for its clinical and pathological hetherogeneity, but the biological determinants of this variability are unknown. HLA-DRB1*15, the main genetic risk factor for MS, influences the severity and distribution of MS pathology. This study set out to unravel the molecular determinants of the heterogeneity of MS pathology in relation to HLA-DRB1*15 status. Shotgun proteomics from a discovery cohort of MS spinal cord samples segregated by HLA-DRB*15 status revealed overexpression of the extracellular matrix (ECM) proteins, biglycan, decorin, and prolargin in HLA-DRB*15-positive cases, adding to established literature on a role of ECM proteins in MS pathology that has heretofore lacked systematic pathological validation. These findings informed a neuropathological characterisation of these proteins in a large autopsy cohort of 41 MS cases (18 HLA-DRB1*15-positive and 23 HLA-DRB1*15-negative), and seven non-neurological controls on motor cortical, cervical and lumbar spinal cord tissue. Biglycan and decorin demonstrate a striking perivascular expression pattern in controls that is reduced in MS (-36.5%, p = 0.036 and - 24.7%, p = 0.039; respectively) in lesional and non-lesional areas. A concomitant increase in diffuse parenchymal accumulation of biglycan and decorin is seen in MS (p = 0.015 and p = 0.001, respectively), particularly in HLA-DRB1*15-positive cases (p = 0.007 and p = 0.046, respectively). Prolargin shows a faint parenchymal pattern in controls that is markedly increased in MS cases where a perivascular deposition pattern is observed (motor cortex +97.5%, p = 0.001; cervical cord +49.1%, p = 0.016). Our findings point to ECM proteins and the vascular interface playing a central role in MS pathology within and outside the plaque area. As ECM proteins are known potent pro-inflammatory molecules, their parenchymal accumulation may contribute to disease severity. This study brings to light novel factors that may contribute to the heterogeneity of the topographical variation of MS pathology.

Genetic factors associated with age-related macular degeneration modulating plasma inflammatory biomarker levels in patients with AIDS.

INTRODUCTION: Patients with the acquired immunodeficiency syndrome (AIDS) have an increased prevalence and incidence of intermediate-stage age-related macular degeneration (AMD). Several elevated plasma inflammatory biomarkers are associated with increased incidence of intermediate-stage AMD in this population. We evaluated the association between AMD risk alleles and plasma inflammatory biomarker levels in persons with AIDS. MATERIALS AND METHODS: Cryopreserved plasma specimens of 229 non-Hispanic White and 252 non-Hispanic blacks from the Longitudinal Study of the Ocular Complications of AIDS cohort were assayed for plasma levels of soluble tumor necrosis factor receptor (sTNFR) 2, interleukin (IL)-18, C × 3motif chemokine ligand 1 (CX3CL1), C-reactive protein (CRP), and soluble CD14 (sCD14). Genotyping included AMD-associated variants rs10801553 and rs800292 for complement factor H (CFH) rs9332739 and rs547154 for complement factor 2 (C2), rs2230199 for C3, rs2285714 for CFI, and rs3732379 and rs3732378 for C × 3motif chemokine receptor 1 (CX3CR1). RESULTS: In Whites, AMD low-risk CX3CR1 variants (V249I and T280M) were associated with reduced plasma levels of IL-18. In Blacks, AMD low-risk C3 R102G and low-risk CX3CR1 T280M variants were associated with reduced CRP levels. CONCLUSIONS: Genetic variants in AMD-associated immune genes may influence AMD-associated systemic plasma inflammatory biomarker levels in patients with AIDS.

The prevalence and topography of spinal cord demyelination in multiple sclerosis: a retrospective study.

Spinal cord pathology is a major determinant of irreversible disability in progressive multiple sclerosis. The demyelinated lesion is a cardinal feature. The well-characterised anatomy of the spinal cord and new analytic approaches allows the systematic study of lesion topography and its extent of inflammatory activity unveiling new insights into disease pathogenesis. We studied cervical, thoracic, and lumbar spinal cord tissue from 119 pathologically confirmed multiple sclerosis cases. Immunohistochemistry was used to detect demyelination (PLP) and classify lesional inflammatory activity (CD68). Prevalence and distribution of demyelination, staged by lesion activity, was determined and topographical maps were created to identify patterns of lesion prevalence and distribution using mixed models and permutation-based voxelwise analysis. 460 lesions were observed throughout the spinal cord with 76.5% of cases demonstrating at least 1 lesion. The cervical level was preferentially affected by lesions. 58.3% of lesions were inflammatory with 87.9% of cases harbouring at least 1 inflammatory lesion. Topographically, lesions consistently affected the dorsal and lateral columns with relative sparing of subpial areas in a distribution mirroring the vascular network. The presence of spinal cord lesions and the proportion of active lesions related strongly with clinical disease milestones, including time from onset to wheelchair and onset to death. We demonstrate that spinal cord demyelination is common, highly inflammatory, has a predilection for the cervical level, and relates to clinical disability. The topography of lesions in the dorsal and lateral columns and relative sparing of subpial areas points to a role of the vasculature in lesion pathogenesis, suggesting short-range cell infiltration from the blood and signaling molecules circulating in the perivascular space incite lesion development. These findings challenge the notion that end-stage progressive multiple sclerosis is 'burnt out' and an outside-in lesional gradient predominates in the spinal cord. Taken together, this study provides support for long-term targeting of inflammatory demyelination in the spinal cord and nominates vascular dysfunction as a potential target for new therapeutic approaches to limit irreversible disability.

Understanding the impact of ammonium ion substitutions on heterogeneous ice nucleation.

Understanding the mechanisms underpinning heterogeneous ice nucleation in the presence of ionic inclusions is important for fields such as cryopreservation and for improved models of climate and weather prediction. Feldspar and ammonium are both present in significant quantities in the atmosphere, and experimental evidence has shown that feldspar can nucleate ice from ammonium-containing solutions at temperatures warmer than water alone. In recent work, Whale hypothesised that this increase in nucleation temperature is due to an increase in configurational entropy when an ammonium ion is included in the ice hydrogen bond network (T. F. Whale, J. Chem. Phys., 2022, 156, 144503). In this work, we investigate the impact of the inclusion of an ammonium ion on the hydrogen bond network by direct enumeration of the number of structures found using Rick's algorithm. We also determine the energy of these systems and thus compare the effects of enthalpy and entropy to test Whale's hypothesis. We find that the inclusion of an ammonium ion increases the total number of configurations under conditions consistent with a realistic surface charge. We also find that the enthalpic contribution is dominant in determining the location of the ammonium ion within the structure, although we note that this neglects other practicalities of ice nucleation.

Lower Eyelid Blepharoplasty With Volume Preservation Using the Skin Flap.

Lower blepharoplasty is one of the most commonly performed facial plastic surgeries and can be approached through many different techniques to improve perceived aging and fatigue due to prominent eyelid fat pads, deep tear troughs, loose eyelid skin, and global periorbital deflation. The technique discussed herein is a personal approach to lower eyelid rejuvenation surgery by the senior author, focusing on volume preservation with conservative resection and transposition of lower eyelid fat pads, muscle preservation, and microfat grafting. The authors discuss a series of 80 patients with case examples and a technique video.

Regional contribution of vascular dysfunction in white matter dementia: clinical and neuropathological insights.

The maintenance of adequate blood supply and vascular integrity is fundamental to ensure cerebral function. A wide range of studies report vascular dysfunction in white matter dementias, a group of cerebral disorders characterized by substantial white matter damage in the brain leading to cognitive impairment. Despite recent advances in imaging, the contribution of vascular-specific regional alterations in white matter dementia has been not extensively reviewed. First, we present an overview of the main components of the vascular system involved in the maintenance of brain function, modulation of cerebral blood flow and integrity of the blood-brain barrier in the healthy brain and during aging. Second, we review the regional contribution of cerebral blood flow and blood-brain barrier disturbances in the pathogenesis of three distinct conditions: the archetypal white matter predominant neurocognitive dementia that is vascular dementia, a neuroinflammatory predominant disease (multiple sclerosis) and a neurodegenerative predominant disease (Alzheimer's). Finally, we then examine the shared landscape of vascular dysfunction in white matter dementia. By emphasizing the involvement of vascular dysfunction in the white matter, we put forward a hypothetical map of vascular dysfunction during disease-specific progression to guide future research aimed to improve diagnostics and facilitate the development of tailored therapies.

Combining machine learning and molecular simulations to predict the stability of amorphous drugs.

Amorphous drugs represent an intriguing option to bypass the low solubility of many crystalline formulations of pharmaceuticals. The physical stability of the amorphous phase with respect to the crystal is crucial to bring amorphous formulations into the market-however, predicting the timescale involved with the onset of crystallization a priori is a formidably challenging task. Machine learning can help in this context by crafting models capable of predicting the physical stability of any given amorphous drug. In this work, we leverage the outcomes of molecular dynamics simulations to further the state-of-the-art. In particular, we devise, compute, and use "solid state" descriptors that capture the dynamical properties of the amorphous phases, thus complementing the picture offered by the "traditional," "one-molecule" descriptors used in most quantitative structure-activity relationship models. The results in terms of accuracy are very encouraging and demonstrate the added value of using molecular simulations as a tool to enrich the traditional machine learning paradigm for drug design and discovery.

Interplay of multiple clusters and initial interface positioning for forward flux sampling simulations of crystal nucleation.

Forward flux sampling (FFS) is a path sampling technique widely used in computer simulations of crystal nucleation from the melt. In such studies, the order parameter underpinning the progress of the FFS algorithm is often the size of the largest crystalline nucleus. In this work, we investigate the effects of two computational aspects of FFS simulations, using the prototypical Lennard-Jones liquid as our computational test bed. First, we quantify the impact of the positioning of the liquid basin and first interface in the space of the order parameter. In particular, we demonstrate that these choices are key to ensuring the consistency of the FFS results. Second, we focus on the frequently encountered scenario where the population of crystalline nuclei is such that there are multiple clusters of size comparable to the largest one. We demonstrate the contribution of clusters other than the largest cluster to the initial flux; however, we also show that they can be safely ignored for the purposes of converging a full FFS calculation. We also investigate the impact of different clusters merging, a process that appears to be facilitated by substantial spatial correlations-at least at the supercooling considered here. Importantly, all of our results have been obtained as a function of system size, thus contributing to the ongoing discussion on the impact of finite size effects on simulations of crystal nucleation. Overall, this work either provides or justifies several practical guidelines for performing FFS simulations that can also be applied to more complex and/or computationally expensive models.

Posterior circulation ischaemic stroke diagnosis and management.

This narrative review provides an overview of the posterior circulation and the clinical features of common posterior circulation stroke (PCS) syndromes in the posterior arterial territories and how to distinguish them from mimics. We outline the hyperacute management of patients with suspected PCS with emphasis on how to identify those who are likely to benefit from intervention based on imaging findings. Finally, we review advances in treatment options, including developments in endovascular thrombectomy (EVT) and intravenous thrombolysis (IVT), and the principles of medical management and indications for neurosurgery. Observational and randomised clinical trial data have been equivocal regarding EVT in PCS, but more recent studies strongly support its efficacy. There have been concomitant advances in imaging of posterior stroke to guide optimal patient selection for thrombectomy. Recent evidence suggests that clinicians should have a heightened suspicion of posterior circulation events with the resultant implementation of timely, evidence-based management.

The most at-risk regions in the world for high-impact heatwaves.

Heatwaves are becoming more frequent under climate change and can lead to thousands of excess deaths. Adaptation to extreme weather events often occurs in response to an event, with communities learning fast following unexpectedly impactful events. Using extreme value statistics, here we show where regional temperature records are statistically likely to be exceeded, and therefore communities might be more at-risk. In 31% of regions examined, the observed daily maximum temperature record is exceptional. Climate models suggest that similar behaviour can occur in any region. In some regions, such as Afghanistan and parts of Central America, this is a particular problem - not only have they the potential for far more extreme heatwaves than experienced, but their population is growing and increasingly exposed because of limited healthcare and energy resources. We urge policy makers in vulnerable regions to consider if heat action plans are sufficient for what might come.

Tuberous sclerosis complex-1 (TSC1) contributes to selective neuronal vulnerability in Alzheimer's disease.

AIMS: Selective neuronal vulnerability of hippocampal Cornu Ammonis (CA)-1 neurons is a pathological hallmark of Alzheimer's disease (AD) with an unknown underlying mechanism. We interrogated the expression of tuberous sclerosis complex-1 (TSC1; hamartin) and mTOR-related proteins in hippocampal CA1 and CA3 subfields. METHODS: A human post-mortem cohort of mild (n = 7) and severe (n = 10) AD and non-neurological controls (n = 9) was used for quantitative and semi-quantitative analyses. We also developed an in vitro TSC1 knockdown model in rat hippocampal neurons, and transcriptomic analyses of TSC1 knockdown neuronal cultures were performed. RESULTS: We found a selective increase of TSC1 cytoplasmic inclusions in human AD CA1 neurons with hyperactivation of one of TSC1's downstream targets, the mammalian target of rapamycin complex-1 (mTORC1), suggesting that TSC1 is no longer active in AD. TSC1 knockdown experiments showed accelerated cell death independent of amyloid-beta toxicity. Transcriptomic analyses of TSC1 knockdown neuronal cultures revealed signatures that were significantly enriched for AD-related pathways. CONCLUSIONS: Our combined data point to TSC1 dysregulation as a key driver of selective neuronal vulnerability in the AD hippocampus. Future work aimed at identifying targets amenable to therapeutic manipulation is urgently needed to halt selective neurodegeneration, and by extension, debilitating cognitive impairment characteristic of AD.

A potential protective role of the nuclear receptor-related factor 1 (Nurr1) in multiple sclerosis motor cortex: a neuropathological study.

Cerebral cortical inflammation and neurodegeneration are hallmark pathological features of multiple sclerosis that contribute to irreversible neurological disability. While the reason for nerve cell death is unknown, the pathogenic inflammatory role of infiltrating lymphocytes is likely an important contributor. The nuclear receptor-related factor 1 counteracts inflammation in animal models of multiple sclerosis, and protects against neuronal loss in other neurodegenerative disorders, but its expression in post-mortem multiple sclerosis tissue is not known. This study aims to investigate the nuclear receptor-related factor 1 expression in multiple sclerosis motor cortex and evaluate its relationship with motor cortical pathology. To accomplish this, an autopsy cohort of pathologically confirmed multiple sclerosis (n = 46), and control (n = 11) cases was used, where the nuclear receptor-related factor 1 expression was related to neuronal and lymphocytic densities. Motor cortical nuclear receptor-related factor 1 was overexpressed in multiple sclerosis compared to control cases. Increased nuclear receptor-related factor 1 expression positively associated with neuronal densities, especially when present in nucleus of neurons, and associated with decreased CD8+ cytotoxic lymphocyte density. Our findings expand the current knowledge on nuclear receptor-related factor 1 in neurological diseases, and support the hypothesis that nuclear receptor-related factor 1 may play a dual neuroprotective role in multiple sclerosis by influencing inflammatory and neurodegenerative processes. Future studies elucidating the influence of nuclear receptor-related factor 1 on these processes in multiple sclerosis may cast light onto novel targets that may be modulated to alter clinical outcome.

Microglia directly associate with pericytes in the central nervous system.

Cerebral blood flow (CBF) is important for the maintenance of brain function and its dysregulation has been implicated in Alzheimer's disease (AD). Microglia associations with capillaries suggest they may play a role in the regulation of CBF or the blood-brain-barrier (BBB). We explored the relationship between microglia and pericytes, a vessel-resident cell type that has a major role in the control of CBF and maintenance of the BBB, discovering a spatially distinct subset of microglia that closely associate with pericytes. We termed these pericyte-associated microglia (PEM). PEM are present throughout the brain and spinal cord in NG2DsRed × CX3 CR1+/GFP mice, and in the human frontal cortex. Using in vivo two-photon microscopy, we found microglia residing adjacent to pericytes at all levels of the capillary tree and found they can maintain their position for at least 28 days. PEM can associate with pericytes lacking astroglial endfeet coverage and capillary vessel width is increased beneath pericytes with or without an associated PEM, but capillary width decreases if a pericyte loses a PEM. Deletion of the microglia fractalkine receptor (CX3 CR1) did not disrupt the association between pericytes and PEM. Finally, we found the proportion of microglia that are PEM declines in the superior frontal gyrus in AD. In summary, we identify microglia that specifically associate with pericytes and find these are reduced in number in AD, which may be a novel mechanism contributing to vascular dysfunction in neurodegenerative diseases.

Generating Protein Folding Trajectories Using Contact-Map-Driven Directed Walks.

Recent advances in machine learning methods have had a significant impact on protein structure prediction, but accurate generation and characterization of protein-folding pathways remains intractable. Here, we demonstrate how protein folding trajectories can be generated using a directed walk strategy operating in the space defined by the residue-level contact-map. This double-ended strategy views protein folding as a series of discrete transitions between connected minima on the potential energy surface. Subsequent reaction-path analysis for each transition enables thermodynamic and kinetic characterization of each protein-folding path. We validate the protein-folding paths generated by our discretized-walk strategy against direct molecular dynamics simulations for a series of model coarse-grained proteins constructed from hydrophobic and polar residues. This comparison demonstrates that ranking discretized paths based on the intermediate energy barriers provides a convenient route to identifying physically sensible folding ensembles. Importantly, by using directed walks in the protein contact-map space, we circumvent several of the traditional challenges associated with protein-folding studies, namely, long time scales required and the choice of a specific order parameter to drive the folding process. As such, our approach offers a useful new route for studying the protein-folding problem.