Eyes on glutamate in angiogenesis and barrier formation.

In this issue of Neuron, Biswas et al.1 demonstrate the roles of glutamatergic neuronal activity in the regulation of angiogenesis and retinal vascular endothelial barrier maturation using three different knockout mouse models. Their findings shed light on how aberrant glutamatergic activity can impact neural vascular function and barrier integrity.

Pumilio-1 mediated translational control of claudin-5 at the blood-brain barrier.

Claudin-5 is one of the most essential tight junction proteins at the blood-brain barrier. A single nucleotide polymorphism rs10314 is located in the 3'-untranslated region of claudin-5 and has been shown to be a risk factor for schizophrenia. Here, we show that the pumilio RNA-binding protein, pumilio-1, is responsible for rs10314-mediated claudin-5 regulation. The RNA sequence surrounding rs10314 is highly homologous to the canonical pumilio-binding sequence and claudin-5 mRNA with rs10314 produces 25% less protein due to its inability to bind to pumilio-1. Pumilio-1 formed cytosolic granules under stress conditions and claudin-5 mRNA appeared to preferentially accumulate in these granules. Added to this, we observed granular pumilio-1 in endothelial cells in human brain tissues from patients with psychiatric disorders or epilepsy with increased/accumulated claudin-5 mRNA levels, suggesting translational claudin-5 suppression may occur in a brain-region specific manner. These findings identify a key regulator of claudin-5 translational processing and how its dysregulation may be associated with neurological and neuropsychiatric disorders.

A loss of function mutation in CLDN25 causing Pelizaeus-Merzbacher-like leukodystrophy.

Claudin-25 (CLDN-25), also known as Claudin containing domain 1, is an uncharacterized claudin family member. It has less conserved amino acid sequences when compared to other claudins. It also has a very broad tissue expression profile and there is currently a lack of functional information from murine knockout models. Here, we report a de novo missense heterozygous variant in CLDN25 (c. 745G>C, p. A249P) found in a patient diagnosed with Pelizaeus-Merzbacher-like leukodystrophy and presenting with symptoms such as delayed motor development, several episodes of tonic absent seizures and generalized dystonia. The variant protein does not localize to the cell-cell borders where it would normally be expected to be expressed. Amino acid position 249 is located 4 amino acids from the C-terminal end of the protein where most claudin family members have a conserved binding motif for the key scaffolding protein ZO-1. However, CLDN-25 does not contain this motif. Here, we show that the C-terminal end of CLDN-25 is required for its junctional localization in a ZO-1 independent manner. The A249P mutant protein as well as a deletion mutant lacking its last 5 C-terminal amino acids also failed to localize to the cell-cell border in vitro. Intriguingly, cellular knockout of CLDN25, in vitro, appeared to increase the integrity of the tight junction between 2 contacting cells, while driving highly unusual increased movement of solutes between cells. We propose that the barrier function of CLDN-25 is akin to a decoy claudin, whereby decreasing its expression in "leaky" epithelial cells and endothelial cells will drive dynamic changes in the adhesion and interaction capacity of cell-cell contact points. While it remains unclear how this de novo CLDN-25 mutant induces leukodystrophy, our findings strongly suggest that this mutation induces haploinsufficiency of CLDN-25. Elucidating the function of this uncharacterized claudin protein will lead to a better understanding of the role of claudin proteins in health and disease.

The CLDN5 gene at the blood-brain barrier in health and disease.

The CLDN5 gene encodes claudin-5 (CLDN-5) that is expressed in endothelial cells and forms tight junctions which limit the passive diffusions of ions and solutes. The blood-brain barrier (BBB), composed of brain microvascular endothelial cells and associated pericytes and end-feet of astrocytes, is a physical and biological barrier to maintain the brain microenvironment. The expression of CLDN-5 is tightly regulated in the BBB by other junctional proteins in endothelial cells and by supports from pericytes and astrocytes. The most recent literature clearly shows a compromised BBB with a decline in CLDN-5 expression increasing the risks of developing neuropsychiatric disorders, epilepsy, brain calcification and dementia. The purpose of this review is to summarize the known diseases associated with CLDN-5 expression and function. In the first part of this review, we highlight the recent understanding of how other junctional proteins as well as pericytes and astrocytes maintain CLDN-5 expression in brain endothelial cells. We detail some drugs that can enhance these supports and are being developed or currently in use to treat diseases associated with CLDN-5 decline. We then summarise mutagenesis-based studies which have facilitated a better understanding of the physiological role of the CLDN-5 protein at the BBB and have demonstrated the functional consequences of a recently identified pathogenic CLDN-5 missense mutation from patients with alternating hemiplegia of childhood. This mutation is the first gain-of-function mutation identified in the CLDN gene family with all others representing loss-of-function mutations resulting in mis-localization of CLDN protein and/or attenuated barrier function. Finally, we summarize recent reports about the dosage-dependent effect of CLDN-5 expression on the development of neurological diseases in mice and discuss what cellular supports for CLDN-5 regulation are compromised in the BBB in human diseases.

New aneurysm formation and regrowth associated with rebleeding of residual pediatric ruptured arteriovenous malformation: patient series.

BACKGROUND: If complete obliteration of ruptured pediatric arteriovenous malformation (AVM) cannot be achieved, the appropriate follow-up duration and predictors of rebleeding remain unknown. OBSERVATIONS: Pediatric patients with ruptured AVMs admitted to the authors' hospital within the past 30 years were evaluated. Rebleeding was confirmed in two patients. The first patient was a 5-year-old boy who experienced right thalamic hemorrhage. AVM was found in the bilateral thalamus and treated with stereotactic radiosurgery (SRS). New aneurysm formation and residual AVM regrowth were confirmed 21 years after the SRS. Eight months later, rebleeding occurred. The second patient was a 5-year-old boy who underwent removal of a left cerebellar hemorrhage and AVM. The residual AVM was treated with SRS. Residual AVM regrowth was detected at 6 years 7 months after SRS. Five months later, new aneurysm formation was confirmed. Two additional days later, rebleeding occurred. LESSONS: New aneurysm formation and residual AVM regrowth may predict rebleeding and can occur >20 years after the initial rupture and treatment. If AVM obliteration is not achieved, long-term follow-up is needed, even in adulthood, with attention to new aneurysm formation and residual AVM regrowth. Further treatment is recommended if these findings are confirmed.

A case of laparoscopic distal gastrectomy and median arcuate ligament release for a gastric cancer patient with median arcuate ligament syndrome.

BACKGROUND: The median arcuate ligament syndrome (MALS) is a disease in which the celiac artery is compressed by the arcuate ligament and causes stenosis. If abdominal pain or an aneurysm is observed in the head of the pancreas, it is necessary to release the arcuate ligament, and recently laparoscopic surgery has been reported. However, the indication for treatment in asymptomatic cases is unknown. The treatment for asymptomatic MALS in patients with gastric cancer who are indicated for surgery is also novel. CASE PRESENTATION: A 70-year-old female was found with early gastric cancer in the middle body of the stomach. An enhanced CT scan showed no metastasis, but a gallstone and stenosis of the celiac artery due to the MALS were found. The patient underwent releasing median arcuate ligament after lymph node dissection. A median arcuate ligament was located on the ventral side of the left gastric artery stump, and the celiac artery was exposed when cutting it off. The operation time was 4 h and 59 min, and the bleeding was 6 ml. It took about 5 min to dissect the medial arcuate ligament. The postoperative course was satisfactory, and the patient was discharged 7 days after the operation. CT scan and 3-D CT angiography were performed about 2 months after the operation, and the findings revealed that the celiac artery's stenosis resolved. CONCLUSION: The patient underwent laparoscopic gastrectomy and simultaneously the median arcuate ligament release under an excellent visual field. Therefore, median arcuate ligament release may be considered if MALS is found in a gastrectomy case.

Recurrent de novo mutations in CLDN5 induce an anion-selective blood-brain barrier and alternating hemiplegia.

Claudin-5 is the most enriched tight junction protein at the blood-brain barrier. Perturbations in its levels of expression have been observed across numerous neurological and neuropsychiatric conditions; however, pathogenic variants in the coding sequence of the gene have never been reported previously. Here, we report the identification of a novel de novo mutation (c.178G>A) in the CLDN5 gene in two unrelated cases of alternating hemiplegia with microcephaly. This mutation (G60R) lies within the first extracellular loop of claudin-5 and based on protein modelling and sequence alignment, we predicted it would modify claudin-5 to become an anion-selective junctional component as opposed to a purely barrier-forming protein. Generation of stably transfected cell lines expressing wild-type or G60R claudin-5 showed that the tight junctions could still form in the presence of the G60R mutation but that the barrier against small molecules was clearly attenuated and displayed higher Cl- ion permeability and lower Na+ permeability. While this study strongly suggests that CLDN5 associated alternating hemiplegia is a channelopathy, it is also the first study to identify the conversion of the blood-brain barrier to an anion-selective channel mediated by a dominant acting variant in CLDN5.

Dissipative Kerr soliton microcombs for FEC-free optical communications over 100 channels.

The demand for high-speed and highly efficient optical communication techniques has been rapidly growing due to the ever-increasing volume of data traffic. As well as the digital coherent communication used for core and metro networks, intensity modulation and direct detection (IM-DD) are still promising schemes in intra/inter data centers thanks to their low latency, high reliability, and good cost performance. In this work, we study a microresonator-based frequency comb as a potential light source for future IM-DD optical systems where applications may include replacing individual stabilized lasers with a continuous laser driven microresonator. Regarding comb line powers and spectral intervals, we compare a modulation instability comb and a soliton microcomb and provide a quantitative analysis with regard to telecom applications. Our experimental demonstration achieved a forward error correction (FEC) free operation of bit-error rate (BER) <10-9 with a 1.45 Tbps capacity using a total of 145 lines over the entire C-band and revealed the possibility of soliton microcomb-based ultra-dense wavelength division multiplexing (WDM) with a simple, cost-effective IM-DD scheme, with a view to future practical use in data centers.

The impact of second-hand smoke on ear, nose, and throat diseases and head and neck cancers in Japan: a cross-sectional study using a questionnaire and secondary data from the national health and nutrition survey.

BACKGROUND: The risk of head and neck cancers (HNCs) and ear, nose, and throat (ENT) diseases due to second-hand smoke (SHS) have not been fully assessed. OBJECTIVE: To determine which ENT diseases or HNCs are associated with SHS. MATERIAL AND METHODS: Data from a survey of a cross-sectional sample of ENT patients (n = 1228) on SHS exposure were compared to control-subject data (n = 6598) from a Japan National Health Survey. Multivariate logistic regression and estimated odds ratios (ORs) determined whether SHS-disease associations were related to exposure location and disease occurrence. RESULTS: SHS was significantly associated with acute tonsillitis (OR in workplaces, 2.24 [95% CI, 1.34-3.75]; OR in restaurants, 4.24 [95% CI, 2.50-7.19]; OR in leisure places, 4.72 [95% CI, 2.93-7.62]); recurrent tonsillitis (OR in restaurants, 4.24 [95% CI, 2.52-7.13]; OR in leisure places, 5.29 [95% CI, 3.31-8.46]); facial palsy (OR in home, 2.18 [95% CI, 1.25-3.81]; OR in leisure places, 3.41 [95% CI, 1.97-5.89]); hypopharyngeal cancer (OR in home, 2.51 [95% CI, 1.18-5.36]; OR in workplaces, 2.53 [95% CI, 1.24-5.15]); and laryngeal cancer (OR in home, 2.44 [95% CI, 1.04-5.68]; OR in leisure places, 2.25 [95% CI, 1.00-5.07]). CONCLUSIONS AND SIGNIFICANCE: SHS may contribute to HNCs and ENT diseases, suggesting that merely being in the presence of smokers could increase the risk of head and neck morbidities.

Claudin-5: A Pharmacological Target to Modify the Permeability of the Blood-Brain Barrier.

Claudin-5 is the dominant tight junction protein in brain endothelial cells and exclusively limits the paracellular permeability of molecules larger than 400 Da across the blood-brain barrier (BBB). Its pathological impairment or sustained down-regulation has been shown to lead to the progression of psychiatric and neurological disorders, whereas its expression under physiological conditions prevents the passage of drugs across the BBB. While claudin-5 enhancers could potentially act as vascular stabilizers to treat neurological diseases, claudin-5 inhibitors could function as delivery systems to enhance the brain uptake of hydrophilic small-molecular-weight drugs. Therefore, the effects of claudin-5 manipulation on modulating the BBB in different neurological diseases requires further examination. To manipulate claudin-5 expression levels and function, several claudin-5 modulating molecules have been developed. In this review, we first describe the molecular, cellular and pathological aspects of claudin-5 to highlight the mechanisms of claudin-5 enhancers/inhibitors. We then discuss recently developed claudin-5 enhancers/inhibitors and new methods to discover these molecules.

Safety and efficacy of an anti-claudin-5 monoclonal antibody to increase blood-brain barrier permeability for drug delivery to the brain in a non-human primate.

Claudin-5 (CLDN-5) is an essential component of the tight junction seal in the blood-brain barrier. Previously, we showed that CLDN-5 modulation in vitro via an anti-CLDN-5 monoclonal antibody (mAb) may be useful for increasing the permeability of the blood-brain barrier for drug delivery to the brain. Based on these findings, here we examined the safety and efficacy of the anti-CLDN-5 mAb in a non-human primate. Cynomolgus monkeys were intravenously administered the anti-CLDN-5 mAb followed by fluorescein dye (376 Da), and the concentrations of the dye in the cerebrospinal fluid was examined. When the mAb was administered at 3.0 mg/kg, the concentration of dye in the cerebrospinal fluid was increased, and no behavioral changes or changes in plasma biomarkers for inflammation or liver or kidney injury were observed. However, a monkey that received the mAb at 6 mg/kg experienced convulsions, and subsequent histopathological examination of this animal revealed vasodilation in the liver, lung, and kidney; hemorrhage in the lung; and edema in the brain. Together, our data indicate that CLDN-5 might be a potential target for enhancing drug delivery to the brain, but also that the therapeutic window of the anti-CLDN-5 mAb may be narrow for separating efficacy and toxicity.

On-chip photon-pair generation in a silica microtoroidal cavity.

Microcavities with high Q factor and small mode volume have the potential to be efficient and compact sources of photon pairs. Here, we demonstrate on-chip photon-pair generation by spontaneous four-wave mixing in a silica microtoroidal cavity and obtain a coincidence-to-accidental ratio of 7.4 ± 0.1 with a pump power of 46 µW. The heralded photons also exhibit antibunching characterized by autocorrelation function values of gc(2)(0)=0.57±0.03<1. Comparing with a scaling model, the main noise source is found to be spontaneous Raman scattering in the cavity. This work opens a new possible means for realizing integrated nonclassical photon sources based on silica photonic circuits toward scalable quantum technologies.

Comparison Between Optical Frequency Domain Imaging and Intravascular Ultrasound for Percutaneous Coronary Intervention Guidance in Biolimus A9-Eluting Stent Implantation: A Randomized MISTIC-1 Non-Inferiority Trial.

BACKGROUND: Given the characteristic differences between intravascular ultrasound (IVUS) and optical frequency domain imaging (OFDI), their approach to therapeutic guidance during percutaneous coronary interventions (PCIs) and arterial healing response after stenting may also vary. METHODS: MISTIC-1 (The Multimodality Imaging Study in Cardiology cohort 1) is a multicenter, randomized-controlled, noninferiority trial that compared imaging end points between OFDI- and IVUS-guided PCI. Patients with stable coronary artery disease were randomly assigned to either OFDI- or IVUS-guided PCI using a Biolimus A9-eluting stent according to a prespecified protocol for imaging guidance. Stent sizing was based on external elastic lamina in IVUS-guided PCI while lumen up-size in OFDI-guided PCI. Postprocedural OFDI was investigated regardless of randomization, while operators in IVUS-guided PCI arm were blinded to the images. The primary end point was in-segment minimum lumen area assessed using OFDI at 8 months, while the secondary end point was a composite of cardiovascular mortality, target-vessel myocardial infarction, or target-lesion revascularization (device-oriented composite end point). Patients were followed up to 3 years after the index procedure. RESULTS: A total of 109 patients (mean age 70 years, male 78%) with 126 lesions were enrolled. Postprocedural minimum stent area was 6.31±1.89 and 6.72±2.08 mm2 in OFDI and IVUS group, respectively (P=0.26). At the 8-month follow-up, in-segment minimum lumen area was 4.56±1.94 and 4.13±1.86 mm2 in OFDI and IVUS group, respectively (Pnon-inferiority <0.001). Both groups had comparable neointimal healing score (median 0.16 [interquartile range, 0.00-3.14] versus 0.90 [0.00-3.30], respectively; P=0.43). The incidence rate of device-oriented composite end point at 3 years was 7.4% and 7.3% in OFDI and IVUS group, respectively (hazard ratio, 1.05 [95% CI, 0.26-4.18]; P=0.95). CONCLUSIONS: OFDI-guided PCI was not inferior to IVUS-guided PCI in terms of in-segment minimum lumen area at 8 months. Although a small sample size was acknowledged, OFDI could be an alternative to IVUS when considering intracoronary imaging-guided PCI in selected populations with coronary artery diseases. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT03292081.

Tight junction modulation at the blood-brain barrier: Current and future perspectives.

The blood-brain barrier (BBB) is the one of the most robust physical barriers in the body, comprised of tight junction (TJ) proteins in brain microvascular endothelial cells. The need for drugs to treat central nervous systems diseases is ever increasing, however the presence of the BBB significantly hampers the uptake of drugs into the brain. To overcome or circumvent the barrier, many kinds of techniques are being developed. Modulating the paracellular route by disruption of the TJ complex has been proposed as a potential drug delivery system to treat brain diseases, however, it has several limitations and is still in a developmental stage. However, recent significant advance in medical equipment /tools such as targeted ultra-sound technologies may resolve these limitations. In this review, we introduce recent advances in site- or molecular size-selective BBB disruption/modulation technologies and we include details on pharmacological inhibitory molecules against intercellular TJ proteins to modulate the BBB.

Tight junction modulators for drug delivery to the central nervous system.

Overcoming the blood-brain barrier (BBB) to enable the treatment of central nervous system (CNS) diseases is an active field of research. Modulating or opening the tight junctions (TJs) in brain endothelial cells is one method to enable a range of small-molecular-weight drugs to cross the BBB via the paracellular route. Over the past 2 decades, the molecular understanding of TJ proteins in the BBB has significantly improved, and several agonists and antagonists have been tested for modulation of the TJs. In this review, we discuss the composition of TJ proteins in the BBB and introduce indirect pharmacological TJ modulators, which target regulators of TJ proteins, and direct TJ modulators, which can selectively inhibit functions of TJ proteins.

Phase Locking between Two All-Optical Quantum Memories.

Optical approaches to quantum computation require the creation of multimode photonic quantum states in a controlled fashion. Here we experimentally demonstrate phase locking of two all-optical quantum memories, based on a concatenated cavity system with phase reference beams, for the time-controlled release of two-mode entangled single-photon states. The release time for each mode can be independently determined. The generated states are characterized by two-mode optical homodyne tomography. Entanglement and nonclassicality are preserved for release-time differences up to 400 ns, confirmed by logarithmic negativities and Wigner-function negativities, respectively.

All-Optical Storage of Phase-Sensitive Quantum States of Light.

We experimentally demonstrate storage and on-demand release of phase-sensitive, photon-number superposition states of the form α|0⟩+ße^{iθ}|1⟩ for an optical quantized oscillator mode. For this purpose, we newly developed a phase-probing mechanism compatible with a storage system composed of two concatenated optical cavities, which was previously employed for storage of phase-insensitive single-photon states [Phys. Rev. X 3, 041028 (2013)PRXHAE2160-330810.1103/PhysRevX.3.041028]. This is the first demonstration of all-optically storing highly nonclassical and phase-sensitive quantum states of light. The strong nonclassicality of the states after storage becomes manifest as a negative region in the corresponding Wigner function shifted away from the origin in phase space. This negativity is otherwise, without the phase information of the memory system, unobtainable. While our scheme includes the possibility of optical storage, on-demand release and synchronization of arbitrary single-rail qubit states, it is not limited to such states. In fact, our technique is extendible to more general phase-sensitive states such as multiphoton superposition or entangled states, and thus it represents a significant step toward advanced optical quantum information processing, where highly nonclassical states are utilized as resources.

Potential for Tight Junction Protein-Directed Drug Development Using Claudin Binders and Angubindin-1.

The tight junction (TJ) is an intercellular sealing component found in epithelial and endothelial tissues that regulates the passage of solutes across the paracellular space. Research examining the biology of TJs has revealed that they are complex biochemical structures constructed from a range of proteins including claudins, occludin, tricellulin, angulins and junctional adhesion molecules. The transient disruption of the barrier function of TJs to open the paracellular space is one means of enhancing mucosal and transdermal drug absorption and to deliver drugs across the blood-brain barrier. However, the disruption of TJs can also open the paracellular space to harmful xenobiotics and pathogens. To address this issue, the strategies targeting TJ proteins have been developed to loosen TJs in a size- or tissue-dependent manner rather than to disrupt them. As several TJ proteins are overexpressed in malignant tumors and in the inflamed intestinal tract, and are present in cells and epithelia conjoined with the mucosa-associated lymphoid immune tissue, these TJ-protein-targeted strategies may also provide platforms for the development of novel therapies and vaccines. Here, this paper reviews two TJ-protein-targeted technologies, claudin binders and an angulin binder, and their applications in drug development.