Choroid Plexus Research Articles

Choroid plexus as a mediator of CNS inflammation in multiple sclerosis.

The pathophysiology of multiple sclerosis (MS) remains poorly understood despite decades of tremendous research efforts. Advances in neuroradiography coupled with availability of unbiased approaches including spatial transcriptomics, proteomics, metabolomics, and lipidomics that are compatible with brain and fluid specimens from patients raise hope that discovery of novel disease drivers is on the horizon. Once thought to be little more than salty bathwater, our modern understanding of cerebrospinal fluid (CSF) suggests the CSF as a compelling, critical regulator of brain function in health and disease. Recent studies in the field have reinvigorated interest in CSF as a medium to better understand MS and to deliver disease-modifying therapies. In turn, the choroid plexus, an epithelial tissue located within each brain ventricle that regulates CSF and forms a key blood-CSF barrier, is uniquely positioned to orchestrate neuroinflammation associated with MS. In this perspective review, we will discuss what is known about the choroid plexus as a conductor of immune responses and how it may propagate neuroinflammation associated with MS via the CSF.

Novel hypothesis and therapeutic interventions for irritable bowel syndrome: interplay between metal dyshomeostasis, gastrointestinal dysfunction, and neuropsychiatric symptoms.

Irritable bowel syndrome is a gastrointestinal disorder due to multiple pathologies. While patients with this condition experience anxiety and depressed mood more frequently than healthy individuals, it is unclear how gastrointestinal dysfunction interacts with such neuropsychiatric symptoms. Data suggest that irritable bowel syndrome patients predominantly display a lower zinc intake, which presumably impairs enterochromaffin cells producing 5-hydroxytryptamine, gut bacteria fermenting short-chain fatty acids, and barrier system in the intestine, with the accompanying constipation, diarrhea, low-grade mucosal inflammation, and visceral pain. Dyshomeostasis of copper and zinc concentrations as well as elevated pro-inflammatory cytokine levels in the blood can disrupt blood-cerebrospinal fluid barrier function, leading to locus coeruleus neuroinflammation and hyperactivation with resultant amygdalar overactivation and dorsolateral prefrontal cortex hypoactivation as found in neuropsychiatric disorders. The dysregulation between the dorsolateral prefrontal cortex and amygdala is likely responsible for visceral pain-related anxiety, depressed mood caused by anticipatory anxiety, and visceral pain catastrophizing due to catastrophic thinking or cognitive distortion. Collectively, these events can result in a spiral of gastrointestinal symptoms and neuropsychiatric signs, prompting the progression of irritable bowel syndrome. Given that the negative feedback mechanism in regulation of the hypothalamic-pituitary-adrenal axis is preserved in a subset of neuropsychiatric cases, dorsolateral prefrontal cortex abnormality accompanied by neuropsychiatric symptoms may be a more significant contributing factor in brain-gut axis malfunction than activation of the hypothalamic corticotropin-releasing hormone system. The proposed mechanistic model could predict novel therapeutic interventions for comorbid irritable bowel syndrome and neuropsychiatric disorders.

TMEM106B amyloid filaments in the Biondi bodies of ependymal cells

Biondi bodies are filamentous amyloid inclusions of unknown composition in ependymal cells of the choroid plexuses, ependymal cells lining cerebral ventricles and ependymal cells of the central canal of the spinal cord. Their formation is age-dependent and they are commonly associated with a variety of neurodegenerative conditions, including Alzheimer’s disease and Lewy body disorders. Here, we show that Biondi bodies are strongly immunoreactive with TMEM239, an antibody specific for inclusions of transmembrane protein 106B (TMEM106B). Biondi bodies were labelled by both this antibody and the amyloid dye pFTAA. Many Biondi bodies were also labelled for TMEM106B and the lysosomal markers Hexosaminidase A and Cathepsin D. By transmission immuno-electron microscopy, Biondi bodies of choroid plexuses were decorated by TMEM239 and were associated with structures that resembled residual bodies or secondary lysosomes. By electron cryo-microscopy, TMEM106B filaments from Biondi bodies of choroid plexuses were similar (Biondi variant), but not identical, to the fold I that was previously identified in filaments from brain parenchyma.

Enlarged choroid plexus related to atrophy of hippocampal subfield volumes and glymphatic dysfunction in benzodiazepine use disorder.

The aim of this study was to explore the relationship of choroid plexus (CP) volume with hippocampal subregion volume and glymphatic system in patients with benzodiazepine use disorders (BUD). Eighty-four participants were recruited including 23 patients with BUD, 29 patients with chronic insomnia (CI) and 32 healthy controls (HC). The morphological alterations in CP, hippocampal subfield volumes and diffusion tensor image analysis along the perivascular space (DTI-ALPS) index were compared between the three groups and the relationships between CP volume and hippocampal subfield volumes and the glymphatic system were further investigated. Compared with the HC individuals, the CP volumes augmented and hippocampal subfield volumes reduced in patients with BUD (P < .05) but not in patients with CI (P > .05). In patients with BUD, there were extensive relationships between augmented CP volume and decreased hippocampal subfield volumes (P < .05, r = -0.421--0.513). CP volume was negatively related with the DTI-ALPS index (r = -0.582, P = .004) within the BUD group. In patients with BUD, the volume of bilateral cornu ammonis (CA)1 body, molecular layer (ML) body, hippocampal tail, left CA1 head volumes, right dentate gyrus body volumes, and right CA4 body volumes were positively related with the Montreal Cognitive Assessment scores (P < .05, r = 0.422-0.683). Right CA1 and ML body volumes positively related with the Mini-Mental State Examination scores (P < .05, r = 0.503-0.575). The enlarged CP related to atrophy of hippocampal subfield volumes and the glymphatic system dysfunction were shown in BUD patients.

Choroid Plexus Volume in Pediatric-Onset Multiple Sclerosis.

Recent studies suggest that the choroid plexus (CP) may function as a site of access of inflammatory cells into the CNS in multiple sclerosis (MS). Pediatric-onset MS (POMS) is characterized by a high inflammatory burden, as evidenced by a high relapse rate and volume of T2 lesions, making patients with POMS an informative population to evaluate choroid plexus volume (CPV). The objectives of the study were (1) to evaluate CPV at symptom onset in participants with POMS compared with healthy controls (HCs); (2) to evaluate changes in CPV in the first year of disease in participants with POMS; and (3) to evaluate associations between CPV, brain volumes, relapse activity, and disability in participants with POMS. Baseline 1.5T MRI scans were acquired from 23 participants with POMS and 23 age-matched and sex-matched HCs; 18 participants with POMS also had 12-month follow-up MRI scans. The CP of the lateral ventricles was segmented manually. CP and brain structure volumes were normalized for total intracranial volume. The number of relapses, T2 and gadolinium-enhancing T1 lesion counts, and Expanded Disability Status Scale (EDSS) scores at 12 months were also analyzed. Baseline CPVs were compared between groups using the Wilcoxon exact test, and CPV change from baseline to 12 months in participants with POMS was compared using the Wilcoxon signed-rank test. The relationship between CPV and brain volumetric measures, T2 lesion volumes, lesion count, number of relapses, and EDSS scores was assessed through Spearman correlation. The median normalized CPV was 1.51 × 10-3 (interquartile range [IQR]: 1.32-1.76) in POMS baseline scans and 1.21 × 10-3 (IQR: 1.1-1.47) in HC scans (p = 0.001). CPV did not significantly change at 12 months in the 18 participants with POMS with follow-up scans (p = 0.352). CPV in participants with POMS and HCs correlated with lateral ventricular volume (p = 0.012 for both groups) but did not correlate with brain and T2 lesion volumes or lesion count at baseline, nor with relapse activity or EDSS scores at 12 months in participants with POMS. CPV measured at baseline is greater in participants with POMS than in HCs. Baseline CPV did not predict higher disease activity or worse neurologic outcomes over 1 year. While higher CPV may be an early feature of inflammation in MS, its strong correlation with ventricular volumes could also reflect enlargement secondary to the mechanical attachment of CP to the ventricular wall.

Corrigendum to “Abnormal Rhomboid Lip and Choroid Plexus Should be Valued in Microvascular Decompression for Vestibulocochlear Diseases,” [World Neurosurg. 2024 Jan;181:e607-e614]

Corrigendum to “Abnormal Rhomboid Lip and Choroid Plexus Should be Valued in Microvascular Decompression for Vestibulocochlear Diseases,” [World Neurosurg. 2024 Jan;181:e607-e614]

CNS macrophage contributions to myelin health.

Myelin is the membrane surrounding neuronal axons in the central nervous system (CNS), produced by oligodendrocytes to provide insulation for electrical impulse conduction and trophic/metabolic support. CNS dysfunction occurs following poor development of myelin in infancy, myelin damage in neurological diseases, and impaired regeneration of myelin with disease progression in aging. The lack of approved therapies aimed at supporting myelin health highlights the critical need to identify the cellular and molecular influences on oligodendrocytes. CNS macrophages have been shown to influence the development, maintenance, damage and regeneration of myelin, revealing critical interactions with oligodendrocyte lineage cells. CNS macrophages are comprised of distinct populations, including CNS-resident microglia and cells associated with CNS border regions (the meninges, vasculature, and choroid plexus), in addition to macrophages derived from monocytes infiltrating from the blood. Importantly, the distinct contribution of these macrophage populations to oligodendrocyte lineage responses and myelin health are only just beginning to be uncovered, with the advent of new tools to specifically identify, track, and target macrophage subsets. Here, we summarize the current state of knowledge on the roles of CNS macrophages in myelin health, and recent developments in distinguishing the roles of macrophage populations in development, homeostasis, and disease.

Demyelination and impaired oligodendrogenesis in the corpus callosum following lead exposure.

The corpus callosum is an oligodendrocyte-enriched brain region, replenished by newborn oligodendrocytes from oligodendrocyte progenitor cells (OPCs) in subventricular zone (SVZ). Lead (Pb) exposure has been associated with multiple sclerosis, a disease characterized by the loss of oligodendrocytes. This study aimed to investigate the effects of Pb exposure on oligodendrogenesis in SVZ and myelination in the corpus callosum. Adult female mice were used for a disproportionately higher prevalence of multiple sclerosis in females. Acute Pb exposure (one ip-injection of 27 mg Pb/kg as PbAc2 24 hr before sampling) caused mild Pb accumulation in the corpus callosum. Ex vivo assay using isolated SVZ tissues collected from acute Pb-exposed brains showed a diminished oligodendrogenesis in SVZ-derived neurospheres compared with controls. In vivo subchronic Pb exposure (13.5 mg Pb/kg by daily oral gavage 4wk) revealed significantly decreased newborn BrdU+/MBP+ oligodendrocytes in the corpus callosum, suggesting demyelination. Mechanistic investigations indicated decreased Rictor in SVZ OPCs, defective self-defense pathways, and reactive gliosis in the corpus callosum. Given the interwined pathologies between multiple sclerosis and Alzheimer's disease, the effect of Pb on myelination was evaluated in AD-modeled APP/PS1 mice. Myelin MRI on mice following chronic exposure (1,000 ppm Pb in drinking water as PbAc2 for 20wk) revealed a profound demyelination in the corpus callosum compared with controls. Immunostaining of the choroid plexus showed diminished signaling molecule (Klotho, OTX2) expressions in Pb-treated animals. These observations suggest that Pb caused demyelination in the corpus callosum, likely by disrupting oligodendrogenesis from SVZ OPCs. Pb-induced demyelination represents a crucial pathogenic pathway in Pb neurotoxicity, including multiple sclerosis.

Single-nucleus RNA-seq dissection of choroid plexus tumor cell heterogeneity.

The genomic, genetic and cellular events regulating the onset, growth and survival of rare, choroid plexus neoplasms remain poorly understood. Here, we examine the heterogeneity of human choroid plexus tumors by single-nucleus transcriptome analysis of 23,906 cells from four disease-free choroid plexus and eleven choroid plexus tumors. The resulting expression atlas profiles cellular and transcriptional diversity, copy number alterations, and cell-cell interaction networks in normal and cancerous choroid plexus. In choroid plexus tumor epithelial cells, we observe transcriptional changes that correlate with genome-wide methylation profiles. We further characterize tumor type-specific stromal microenvironments that include altered macrophage and mesenchymal cell states, as well as changes in extracellular matrix components. This first single-cell dataset resource from such scarce samples should be valuable for divising therapies against these little-studied neoplasms.

Maternal separation alters peripheral immune responses associated with IFN-γ and OT in mice

The co-evolution of social behavior and the immune system plays a critical role in individuals' adaptation to their environment. However, also need for further research on the key molecules that co-regulate social behavior and immunity. This study focused on neonatal mice that were separated from their mothers for 4 hours per day between the 6th and 16th day after birth. The results showed that these mice had lower plasma levels of IFN-γ and oxytocin, but higher levels of plasma glucocorticoids (GC), then impacting their social abilities. Additionally, maternal separation led to decreased levels of BDNF, IGF2, and CREB mRNAs in the hippocampus, while levels in the prefrontal cortex (PFC) remained unaffected. Maternal separation also resulted in increased levels of oxytocin and CRH mRNA in the hypothalamus, as well as an increase in CD45+ lymphocyte subsets in the meninges and choroid plexus (CP), with CD8+ lymphocytes in meninges and CD4+ lymphocytes in CP showing an increase. In IFN-γ-/- mice, a decrease in social preference was observed alongside lower plasma oxytocin levels. Moreover, IFN-γ-/- mice exhibited reduced numbers of oxytocin neurons in the paraventricular nucleus of the paraventricular nucleus of hypothalamus (PVN), decreased BDNF levels in the PFC and hippocampus, and alterations in CD45+ lymphocytes in CP and meninges, with an increase in CD8+ lymphocytes in meninges and CD4+ lymphocytes in CP. These findings highlight the immunological impact of social stress on IFN-γ regulation, suggesting that the immunomodulatory molecule IFN-γ may influence social behavior by affecting synaptic efficiency in brain regions such as the hippocampus and PFC, which are linked to oxytocin in the PVN.

Free Kappa light chain in a sample of Egyptian multiple sclerosis patients (a pilot study)

BackgroundMultiple sclerosis is a chronic autoimmune-mediated demyelinating disease of the central nervous system that is usually associated with varying degrees of progressive disability. Free Kappa light chain (FKLC) has attracted growing attention as a significant diagnostic marker of MS. Our aim was to study the diagnostic utility of cerebrospinal fluid free Kappa light chain and related indices in a sample of Egyptian MS patients vs. CSF IgG oligoclonal bands. It was a prospective case–control study of MS patients carried in our hospital during the period from January 2021 till January 2022. Our study carried on 30 patients with multiple sclerosis and other inflammatory neurologic diseases and 20 age and sex matched controls. The study measured FKLC in the CSF and serum sample pairs of patients and control group. Indices calculated using FKLC measured in CSF and serum included; FKLC index, FKLC intrathecal fraction and quotient of FKLC. Indices were used to assess intrathecal synthesis of FKLC considering blood–CSF barrier function. Receiver operating characteristic curve analysis was used to determine diagnostic performance of FKLC and related indices in comparison to CSF–OCB testing.ResultsMeasured FKLC levels as well as its calculated indices have shown statistically significant higher values among MS patients against OIND patients and healthy control group. Both FKLC index and FKLC IF were similarly showing 100% diagnostic sensitivity and 100% diagnostic specificity for MS diagnosis.ConclusionsFKLC biomarkers are proposed to be highly sensitive and easy to detect first-line markers of intrathecal immunoglobulin synthesis with accurate performance and low cost that might prove to be promising diagnostic markers of MS.

Region-independent active CNS net uptake of marketed H+/OC antiporter system substrates

The pyrilamine-sensitive proton-coupled organic cation (H+/OC) antiporter system facilitates the active net uptake of several marketed organic cationic drugs across the blood-brain barrier (BBB). This rare phenomenon has garnered interest in the H+/OC antiporter system as a potential target for CNS drug delivery. However, analysis of pharmacovigilance data has uncovered a significant association between substrates of the H+/OC antiporter and neurotoxicity, particularly drug-induced seizures (DIS) and mood- and cognitive-related adverse events (MCAEs). This preclinical study aimed to elucidate the CNS regional disposition of H+/OC antiporter substrates at therapeutically relevant plasma concentrations to uncover potential pharmacokinetic mechanisms underlying DIS and MCAEs. Here, we investigated the neuropharmacokinetics of pyrilamine, diphenhydramine, bupropion, tramadol, oxycodone, and memantine. Using the Combinatory Mapping Approach for Regions of Interest (CMA-ROI), we characterized the transport of unbound drugs across the BBB in specific CNS regions, as well as the blood-spinal cord barrier (BSCB) and the blood-cerebrospinal fluid barrier (BCSFB). Our findings demonstrated active net uptake across the BBB and BSCB, with unbound ROI-to-plasma concentration ratio, Kp,uu,ROI, values consistently exceeding unity in all assessed regions. Despite minor regional differences, no significant distinctions were found when comparing the whole brain to investigated regions of interest, indicating region-independent active transport. Furthermore, we observed intracellular accumulation via lysosomal trapping for all studied drugs. These results provide new insights into the CNS regional neuropharmacokinetics of these drugs, suggesting that while the brain uptake is region-independent, the active transport mechanism enables high extracellular and intracellular drug concentrations, potentially contributing to neurotoxicity. This finding emphasizes the necessity of thorough neuropharmacokinetic evaluation and neurotoxicity profiling in the development of drugs that utilize this transport pathway.

[11C]Metoclopramide PET can detect a seizure-induced up-regulation of cerebral P-glycoprotein in epilepsy patients

BackgroundP-glycoprotein (P-gp) is an efflux transporter which is abundantly expressed at the blood-brain barrier (BBB) and which has been implicated in the pathophysiology of various brain diseases. The radiolabelled antiemetic drug [11C]metoclopramide is a P-gp substrate for positron emission tomography (PET) imaging of P-gp function at the BBB. To assess whether [11C]metoclopramide can detect increased P-gp function in the human brain, we employed drug-resistant temporal lobe epilepsy (TLE) as a model disease with a well characterised, regional P-gp up-regulation at the BBB.MethodsEight patients with drug-resistant (DRE) TLE, 5 seizure-free patients with drug-sensitive (DSE) focal epilepsy, and 15 healthy subjects underwent brain PET imaging with [11C]metoclopramide on a fully-integrated PET/MRI system. Concurrent with PET, arterial blood sampling was performed to generate a metabolite-corrected arterial plasma input function for kinetic modelling. The choroid plexus was outmasked on the PET images to remove signal contamination from the neighbouring hippocampus. Using a brain atlas, 10 temporal lobe sub-regions were defined and analysed with a 1-tissue-2-rate constant compartmental model to estimate the rate constants for radiotracer transfer from plasma to brain (K1) and from brain to plasma (k2), and the total volume of distribution (VT = K1/k2).ResultsDRE patients but not DSE patients showed significantly higher k2 values and a trend towards lower VT values in several temporal lobe sub-regions located ipsilateral to the epileptic focus as compared to healthy subjects (k2: hippocampus: +34%, anterior temporal lobe, medial part: +28%, superior temporal gyrus, posterior part: +21%).Conclusions[11C]Metoclopramide PET can detect a seizure-induced P-gp up-regulation in the epileptic brain. The efflux rate constant k2 seems to be the most sensitive parameter to measure increased P-gp function with [11C]metoclopramide. Our study provides evidence that disease-induced alterations in P-gp expression at the BBB can lead to changes in the distribution of a central nervous system-active drug to the human brain, which could affect the efficacy and/or safety of drugs. [11C]Metoclopramide PET may be used to assess or predict the contribution of increased P-gp function to drug resistance and disease pathophysiology in various brain diseases.Trial registrationEudraCT 2019-003137-42. Registered 28 February 2020.

L-Arginine and asymmetric dimethylarginine (ADMA) transport across the mouse blood-brain and blood-CSF barriers: Evidence of saturable transport at both interfaces and CNS to blood efflux

L-Arginine is the physiological substrate for the nitric oxide synthase (NOS) family, which synthesises nitric oxide (NO) in endothelial and neuronal cells. NO synthesis can be inhibited by endogenous asymmetric dimethylarginine (ADMA). NO has explicit roles in cellular signalling and vasodilation. Impaired NO bioavailability represents the central feature of endothelial dysfunction associated with vascular diseases. Interestingly, dietary supplementation with L-arginine has been shown to alleviate endothelial dysfunctions caused by impaired NO synthesis. In this study the transport kinetics of [3H]-arginine and [3H]-ADMA into the central nervous system (CNS) were investigated using physicochemical assessment and the in situ brain/choroid plexus perfusion technique in anesthetized mice. Results indicated that L-arginine and ADMA are tripolar cationic amino acids and have a gross charge at pH 7.4 of 0.981. L-Arginine (0.00149±0.00016) has a lower lipophilicity than ADMA (0.00226±0.00006) as measured using octanol-saline partition coefficients. The in situ perfusion studies revealed that [3H]-arginine and [3H]-ADMA can cross the blood-brain barrier (BBB) and the blood-CSF barrier. [3H]-Arginine (11.6nM) and [3H]-ADMA (62.5nM) having unidirectional transfer constants (Kin) into the frontal cortex of 5.84±0.86 and 2.49±0.35 μl.min-1.g-1, respectively, and into the CSF of 1.08±0.24 and 2.70±0.90 μl.min-1.g-1, respectively. In addition, multiple-time uptake studies revealed the presence of CNS-to-blood efflux of ADMA. Self- and cross-inhibition studies indicated the presence of transporters at the BBB and the blood-CSF barriers for both amino acids, which were shared to some degree. Importantly, these results are the first to demonstrate: (i) saturable transport of [3H]-ADMA at the blood-CSF barrier (choroid plexus) and (ii) a significant CNS to blood efflux of [3H]-ADMA. Our results suggest that the arginine paradox, in other words the clinical observation that NO-deficient patients respond well to oral supplementation with L-arginine even though the plasma concentration is sufficient to saturate endothelial NOS, could be related to altered ADMA transport (efflux).

Symptomatic Multi-Nodular Fourth Ventricular Choroid Plexus Papillary Fibrosis in the Context of Chiari II Malformation: Case Report and Literature Review

Introduction: Chiari II malformation (CM-II) is a congenital malformation characterized by the caudal displacement of the cerebellar tonsils, inferior cerebellar vermis, and fourth ventricle through the foramen magnum. Although rare, the association between CM-II and the development of a variety of mass lesions within the fourth ventricle and craniocervical junction has been described in the literature. Case Presentation: We present the case of a 9-year-old boy with a history of mid-lumbar myelomeningocele, CM-II, and ventriculoperitoneal shunt-dependent hydrocephalus who was discovered to have a syringomyelia and numerous spherical/ovoid masses within the caudal fourth ventricle and dorsal cervicomedullary subarachnoid space on a surveillance brain MRI. On questioning, the patient endorsed a longstanding history of poor bilateral hand dexterity and grip strength. After further imaging workup, the patient underwent suboccipital craniectomy and C1 laminectomy for resection of the mass lesions arising from the fourth ventricular choroid plexus (CP) and performance of an expansile pericranial duraplasty. The patient tolerated surgery well and had progressive improvement in hand dexterity/strength as well as radiographic improvement in the cervical cord syrinx after surgery. Pathologic analysis of the resected mass lesions demonstrated the lesions to be predominantly characterized by dense nodular fibrosis of the CP stromal cores which we are describing as choroid plexus papillary fibrosis. A minority of the lesional stromal cores were noted to be edematous, imparting a more “reticular” appearance. There were no features to suggest a neoplastic or infectious process. Conclusion: This combination of dysplastic/reactive CP histologic findings has not been previously reported in an extramedullary location. The unique pathology of this patient’s CP lesions will be discussed, and previously reported fourth ventricular mass lesions seen in association with CM-II will be reviewed.

TTF-1 immunohistochemistry in primary CNS tumors: A systematic review.

Thyroid transcription factor-1 (TTF-1) is a nuclear protein primarily recognized for its role in the development and differentiation of thyroid, lung, and certain diencephalic tissues. Although well-established as an immunohistochemical marker in thyroid and lung cancers, recent studies have explored its expression and diagnostic value in primary central nervous system (CNS) tumors. This systematic review aims to consolidate current knowledge on TTF-1 immunohistochemistry in primary CNS tumors, assessing its prevalence, diagnostic utility, and clinical implications. The review encompasses various CNS tumor types, including subependymal giant cell astrocytoma, chordoid glioma, pituicytoma, ependymomas, astrocytomas, glioblastomas, medulloblastomas, and choroid plexus tumors, highlighting the potential role of TTF-1 in differentiating these neoplasms from other CNS and metastatic tumors. By synthesizing findings from multiple studies, this review underscores the diagnostic value of TTF-1 in the neuropathological evaluation of CNS tumors and suggests directions for future research to refine its clinical application.

Active CNS delivery of oxycodone in healthy and endotoxemic pigs

BackgroundThe primary objective of this study was to advance our understanding of active drug uptake at brain barriers in higher species than rodents, by examining oxycodone brain concentrations in pigs.MethodsThis was investigated by a microdialysis study in healthy and endotoxemic conditions to increase the understanding of inter-species translation of putative proton-coupled organic cation (H+/OC) antiporter-mediated central nervous system (CNS) drug delivery in health and pathology, and facilitate the extrapolation to humans for improved CNS drug treatment in patients. Additionally, we sought to evaluate the efficacy of lumbar cerebrospinal fluid (CSF) exposure readout as a proxy for brain unbound interstitial fluid (ISF) concentrations. By simultaneously monitoring unbound concentrations in blood, the frontal cortical area, the lateral ventricle (LV), and the lumbar intrathecal space in healthy and lipopolysaccharide (LPS)-induced inflammation states within the same animal, we achieved exceptional spatiotemporal resolution in mapping oxycodone transport across CNS barriers.ResultsOur findings provide novel evidence of higher unbound oxycodone concentrations in brain ISF compared to blood, yielding an unbound brain-to-plasma concentration ratio (Kp,uu,brain) of 2.5. This supports the hypothesis of the presence of the H+/OC antiporter system at the blood–brain barrier (BBB) in pigs. Despite significant physiological changes, reflected in pig Sequential Organ Failure Assessment, pSOFA scores, oxycodone blood concentrations and its active net uptake across the BBB remained nearly unchanged during three hours of i.v. infusion of 4 µg/kg/h LPS from Escherichia coli (O111:B4). Mean Kp,uu,LV values indicated active uptake also at the blood-CSF barrier in healthy and endotoxemic pigs. Lumbar CSF concentrations showed minimal inter-individual variability during the experiment, with a mean Kp,uu,lumbarCSF of 1.5. LPS challenge caused a slight decrease in Kp,uu,LV, while Kp,uu,lumbarCSF remained unaffected.ConclusionsThis study enhances our understanding of oxycodone pharmacokinetics and CNS drug delivery in both healthy and inflamed conditions, providing crucial insights for translating these findings to clinical settings.

Elevated peripheral inflammation is associated with choroid plexus enlargement in independent sporadic amyotrophic lateral sclerosis cohorts

BackgroundUsing neuroimaging techniques, growing evidence has suggested that the choroid plexus (CP) volume is enlarged in multiple neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Notably, the CP has been suggested to play an important role in inflammation-induced CNS damage under disease conditions. However, to our knowledge, no study has investigated the relationships between peripheral inflammation and CP volume in sporadic ALS patients. Thus, in this study, we aimed to verify CP enlargement and explore its association with peripheral inflammation in vivo in independent ALS cohorts.MethodsBased on structural MRI data, CP volume was measured using Gaussian mixture models and further manually corrected in two independent cohorts of sporadic ALS patients and healthy controls (HCs). Serum inflammatory protein levels were measured using a novel high-sensitivity Olink proximity extension assay (PEA) technique. Xtreme gradient boosting (XGBoost) was used to explore the contribution of peripheral inflammatory factors to CP enlargement. Then, partial correlation analyses were performed.ResultsCP volumes were significantly higher in ALS patients than in HCs in the independent cohorts. Compared with HCs, serum levels of CRP, IL-6, CXCL10, and 35 other inflammatory factors were significantly increased in ALS patients. Using the XGBoost approach, we established a model-based importance of features, and the top three predictors of CP volume in ALS patients were CRP, IL-6, and CXCL10 (with gains of 0.24, 0.18, and 0.15, respectively). Correlation analyses revealed that CRP, IL-6, and CXCL10 were significantly associated with CP volume in ALS patients (r = 0.462 ∼ 0.636, p < 0.001).ConclusionOur study is the first to reveal a consistent and replicable contribution of peripheral inflammation to CP enlargement in vivo in sporadic ALS patients. Given that CP enlargement has been recently detected in other brain diseases, these findings should consider extending to other disease conditions with a peripheral inflammatory component.

NH4Cl-induced metabolic acidosis increases the abundance of HCO3 - transporters in the choroid plexus of mice.

Regulation of cerebrospinal fluid (CSF) pH and brain pH are vital for all brain cells. The acute regulation of CSF pH is dependent on the transport of HCO3 - across the choroid plexus in the brain ventricles. Acute regulation in response to acidosis is dependent on H+ export and HCO3 - import across the plasma membrane. Acute regulation in response to alkalosis is dependent on HCO3 - export across the plasma membrane. The objective of the study was to investigate the contribution of the Na+-dependent HCO3 - transporters, Ncbe, NBCn1, and NBCe2 to CSF pH regulation during chronic metabolic acidosis in mice. To induce metabolic acidosis, mice received 0.28 M ammonium chloride (NH4Cl) in the drinking water for three, five, or seven days. While in vivo, CSF pH measurements did not differ, measurements of CSF [HCO3 -] revealed a significantly lower CSF [HCO3 -] after three days of acid-loading. Immunoblotting of choroid plexus protein samples showed that the abundance of the basolateral Na+/HCO3 - transporter, NBCn1, was significantly increased. This was followed by a significant increase in CSF secretion rate determined by ventriculo-cisternal perfusion. After five days of treatment with NH4Cl, CSF [HCO3 -] levels were normalized. After the normalization of CSF [HCO3 -], CSF secretion was no longer increased but the abundance of the basolateral Na+-dependent HCO3 - transporters Ncbe and NBCn1 increased. The luminal HCO3 - transporter, NBCe2, was unaffected by the treatment. In conclusion, we establish that 1) acidotic conditions increase the abundance of the basolateral Na+-dependent HCO3 - transporters in the choroid plexus, 2) NH4Cl loading in mice lowers CSF [HCO3 -] and 3) leads to increased CSF secretion likely caused by the increased capacity for transepithelial transport of Na+ and HCO3 - in the choroid plexus.

Choroid Plexus Volume in Rural Chinese Older Adults: Distribution and Association With Cardiovascular Risk Factors and Cerebral Small Vessel Disease.

The choroid plexus (CP) is involved in neurodegenerative diseases. However, the association of CP with cardiovascular risk factors and cerebral small vessel disease in older adults remains unclear. This population-based study included 1263 participants (60 years and older) from the MIND-China (Multimodal Interventions to Delay Dementia and Disability in Rural China) substudy (2018-2020), of which 111 individuals completed diffusion tensor imaging examination. CP volume was automatically segmented. White matter hyperintensities (WMHs), enlarged perivascular spaces (EPVS), cerebral microbleeds, and lacunes were assessed following the Standards for Reporting Vascular Changes on Neuroimaging 1. Peak width of skeletonized mean diffusivity and free water were derived from diffusion tensor imaging images. We used linear regression models to evaluate the association between CP volume and cardiovascular risk factors, WMH volumes, and diffusion tensor imaging metrics, and logistic regression models to examine the association between CP volume and EPVS, cerebral microbleeds, and lacunes. The CP volume increased with age (P<0.001). Men (β coefficient=0.47 [95% CI, 0.29-0.64]) and participants with diabetes (β coefficient=0.16 [95% CI, 0.01-0.31]) had larger CP volumes than women and individuals without diabetes, respectively (P<0.05). Greater CP volume was significantly associated with larger total and periventricular WMH volumes and moderate to severe EPVS in basal ganglia (P<0.05) but not with deep WMHs, EPVS in centrum semiovale, lacunes, or cerebral microbleeds. In the diffusion tensor imaging subsample, enlarged CP was significantly associated with higher peak width of skeletonized mean diffusivity and free water of periventricular and deep white matter (P<0.05). An enlarged CP is associated with larger global and periventricular WMH volume and higher likelihoods of EPVS in basal ganglia and impaired white matter integrity, suggesting that an enlarged CP may represent a precursor of cerebral small vessel disease.