scholarly journals Claudin-12 is not required for blood–brain barrier tight junction function

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Mariana Castro Dias ◽  
◽  
Caroline Coisne ◽  
Pascale Baden ◽  
Gaby Enzmann ◽  
...  
Keyword(s):  
Tight Junction ◽  
Blood Brain Barrier ◽  
Cell Types ◽  
Brain Barrier ◽  
Blood Brain ◽  
Exact Function ◽  
Associated Proteins ◽  
Junctional Complexes ◽  
Paracellular Diffusion ◽  
Cardiovascular Functions

Abstract Background The blood–brain barrier (BBB) ensures central nervous system (CNS) homeostasis by strictly controlling the passage of molecules and solutes from the bloodstream into the CNS. Complex and continuous tight junctions (TJs) between brain endothelial cells block uncontrolled paracellular diffusion of molecules across the BBB, with claudin-5 being its dominant TJs protein. However, claudin-5 deficient mice still display ultrastructurally normal TJs, suggesting the contribution of other claudins or tight-junction associated proteins in establishing BBB junctional complexes. Expression of claudin-12 at the BBB has been reported, however the exact function and subcellular localization of this atypical claudin remains unknown. Methods We created claudin-12-lacZ-knock-in C57BL/6J mice to explore expression of claudin-12 and its role in establishing BBB TJs function during health and neuroinflammation. We furthermore performed a broad standardized phenotypic check-up of the mouse mutant. Results Making use of the lacZ reporter allele, we found claudin-12 to be broadly expressed in numerous organs. In the CNS, expression of claudin-12 was detected in many cell types with very low expression in brain endothelium. Claudin-12lacZ/lacZ C57BL/6J mice lacking claudin-12 expression displayed an intact BBB and did not show any signs of BBB dysfunction or aggravated neuroinflammation in an animal model for multiple sclerosis. Determining the precise localization of claudin-12 at the BBB was prohibited by the fact that available anti-claudin-12 antibodies showed comparable detection and staining patterns in tissues from wild-type and claudin-12lacZ/lacZ C57BL/6J mice. Conclusions Our present study thus shows that claudin-12 is not essential in establishing or maintaining BBB TJs integrity. Claudin-12 is rather expressed in cells that typically lack TJs suggesting that claudin-12 plays a role other than forming classical TJs. At the same time, in depth phenotypic screening of clinically relevant organ functions of claudin-12lacZ/lacZ C57BL/6J mice suggested the involvement of claudin-12 in some neurological but, more prominently, in cardiovascular functions.

scholarly journals Autoregulated paracellular clearance of amyloid-β across the blood-brain barrier

2015 ◽  
Vol 1 (8) ◽  
pp. e1500472 ◽  
Author(s):  
James Keaney ◽  
Dominic M. Walsh ◽  
Tiernan O’Malley ◽  
Natalie Hudson ◽  
Darragh E. Crosbie ◽  
...  
Keyword(s):  
Tight Junction ◽  
Blood Brain Barrier ◽  
Amyloid Β ◽  
Paracellular Pathway ◽  
Brain Barrier ◽  
Blood Brain ◽  
Polar Solutes ◽  
First Time ◽  
Paracellular Diffusion ◽  
Brain Homeostasis

The blood-brain barrier (BBB) is essential for maintaining brain homeostasis and protecting neural tissue from damaging blood-borne agents. The barrier is characterized by endothelial tight junctions that limit passive paracellular diffusion of polar solutes and macromolecules from blood to brain. Decreased brain clearance of the neurotoxic amyloid-β (Aβ) peptide is a central event in the pathogenesis of Alzheimer’s disease (AD). Whereas transport of Aβ across the BBB can occur via transcellular endothelial receptors, the paracellular movement of Aβ has not been described. We show that soluble human Aβ(1–40) monomers can diffuse across the paracellular pathway of the BBB in tandem with a decrease in the tight junction proteins claudin-5 and occludin in the cerebral vascular endothelium. In a murine model of AD (Tg2576), plasma Aβ(1–40) levels were significantly increased, brain Aβ(1–40) levels were decreased, and cognitive function was enhanced when both claudin-5 and occludin were suppressed. Furthermore, Aβ can cause a transient down-regulation of claudin-5 and occludin, allowing for its own paracellular clearance across the BBB. Our results show, for the first time, the involvement of the paracellular pathway in autoregulated Aβ movement across the BBB and identify both claudin-5 and occludin as potential therapeutic targets for AD. These findings also indicate that controlled modulation of tight junction components at the BBB can enhance the clearance of Aβ from the brain.

scholarly journals Lipid polymeric nanoparticles modified with tight junction-modulating peptides promote afatinib delivery across a blood–brain barrier model

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yu-Li Lo ◽  
Hua-Ching Lin ◽  
Shu-Ting Hong ◽  
Chih-Hsien Chang ◽  
Chen-Shen Wang ◽  
...  
Keyword(s):  
Brain Metastases ◽  
Tight Junction ◽  
Blood Brain Barrier ◽  
Polymeric Nanoparticles ◽  
Growth Factor Receptor ◽  
Brain Barrier ◽  
Polymeric Nanoparticle ◽  
Blood Brain ◽  
Blood Brain Barrier Model ◽  
Delivery Platform

Abstract Background Brain metastases from non-small cell lung cancer (NSCLC) remain one of the most challenging malignancies. Afatinib (Afa) is an orally administered irreversible ErbB family blocker approved for epidermal growth factor receptor (EGFR)-mutated NSCLC. However, the incidence of brain metastases in patients with NSCLC and EGFR mutation is high. One of the major obstacles in the treatment of brain metastases is to transport drugs across the blood–brain barrier (BBB). A lipid polymeric nanoparticle (LPN) modified with a tight junction-modulating peptide is a potential formulation to deliver therapeutics across the BBB. FD7 and CCD are short peptides that perturb the tight junctions (TJs) of the BBB. In this study, the use of LPN modified with FD7 or CCD as a delivery platform was explored to enhance Afa delivery across the BBB model of mouse brain-derived endothelial bEnd.3 cells. Results Our findings revealed that Afa/LPN-FD7 and Afa/LPN-CCD exhibited a homogeneous shape, a uniform nano-scaled particle size, and a sustained-release profile. FD7, CCD, Afa/LPN-FD7, and Afa/LPN-CCD did not cause a significant cytotoxic effect on bEnd.3 cells. Afa/LPN-FD7 and Afa/LPN-CCD across the bEnd.3 cells enhanced the cytotoxicity of Afa on human lung adenocarcinoma PC9 cells. FD7 and CCD-modulated TJ proteins, such as claudin 5 and ZO-1, reduced transendothelial electrical resistance, and increased the permeability of paracellular markers across the bEnd.3 cells. Afa/LPN-FD7 and Afa/LPN-CCD were also partially transported through clathrin- and caveolae-mediated transcytosis, revealing the effective activation of paracellular and transcellular pathways to facilitate Afa delivery across the BBB and cytotoxicity of Afa on PC9 cells. Conclusion TJ-modulating peptide-modified LPN could be a prospective platform for the delivery of chemotherapeutics across the BBB to the brain for the potential treatment of the BM of NSCLC.

Abstract TP256: Mouse Model of Uremic Cerebral Microbleeds

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
Wei Ling Lau ◽  
Mary Tarbiat-Boldaji ◽  
Hayley Smalls ◽  
Ane Nunes ◽  
Javad Savoj ◽  
...  
Keyword(s):  
Mouse Model ◽  
Tight Junction ◽  
Blood Brain Barrier ◽  
Cerebral Microbleeds ◽  
Brain Barrier ◽  
Barrier Integrity ◽  
Blood Brain ◽  
Increased Risk ◽  
Junction Protein ◽  
Blood Brain Barrier Integrity

Introduction: Cerebral microbleeds are more common in chronic kidney disease (CKD) and dialysis patients compared to the general population. Diminished kidney function alone appears to be a risk factor for microbleeds, independent of age and hypertension. Microbleed burden in CKD patients is associated with increased risk of future hemorrhagic stroke and with cognitive dysfunction. The mechanisms that drive uremic microbleed formation are unclear. Hypothesis: We hypothesized that CKD mice are predisposed to develop cerebral microhemorrhages (the pathologic substrate of microbleeds), and that a standardized inflammatory stimulus (lipopolysaccharide, LPS) will amplify microhemorrhage burden in CKD mice compared to non-CKD controls (CTL). We also hypothesized that uremia induces depletion of tight junction proteins, altering blood-brain barrier integrity and representing a potential mechanism of microbleed formation. Methods: Animal groups included CTL (n=3), CKD (n=3), CTL+LPS (n=5) and CKD+LPS (n=5). CKD induction in male C57BL/6 mice was achieved via nephrotoxic adenine diet x18 days. Two weeks following CKD induction, CKD and control mice were treated with LPS 1 mg/kg i.p. dosed at 0, 6 and 24 hours. Brains were harvested one week after LPS injections and 40-micron sections were stained using Prussian blue to identify microhemorrhages. Immunohistochemistry was performed for the blood-brain barrier tight junction protein claudin-5. Results: CKD mice had significantly elevated blood urea nitrogen, and tubulointerstitial fibrosis was present on kidney histology. Total number of microhemorrhages per brain was 2.3±1.5 (mean ± standard error of the mean) for CTL mice, 8.3±1.5 for CKD mice, 23.2±4.2 for CTL+LPS mice, and 27.6±6.2 for CKD+LPS mice (p<0.05 for CKD+LPS vs. CTL). Immunostaining showed decreased claudin-5 expression in CKD mice compared to CTL. Conclusions: We have generated a mouse model that will facilitate future mechanistic studies in the field of uremic microbleeds. Our initial findings suggest that CKD alters blood-brain barrier integrity and that inflammation amplifies development of microbleeds in CKD.

Tight Junction Regulation by Morphine and HIV-1 Tat Modulates Blood–Brain Barrier Permeability

2008 ◽  
Vol 28 (5) ◽  
pp. 528-541 ◽  
Author(s):  
Supriya D. Mahajan ◽  
Ravikumar Aalinkeel ◽  
Donald E. Sykes ◽  
Jessica L. Reynolds ◽  
B. Bindukumar ◽  
...  
Keyword(s):  
Tight Junction ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Barrier Permeability ◽  
Blood Brain Barrier Permeability ◽  
Blood Brain ◽  
Brain Barrier Permeability ◽  
Tight Junction Regulation ◽  
Hiv 1
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