Immunolocalization of tight junction proteins in the adult and developing human brain

Abstract

The formation of endothelial tight junctions (TJs) is crucial in blood-brain barrier (BBB) differentiation, and the expression and targeting of TJ-associated proteins mark the beginning of BBB functions. Using confocal microscopy, this study analyzed endothelial TJs in adult human cerebral cortex and the fetal telencephalon and leptomeninges in order to compare the localization of two TJ-associated transmembrane proteins, occludin and claudin-5. In the arterioles and microvessels of adult brain, occludin and claudin-5 form continuous bands of endothelial immunoreactivity. During fetal development, occludin and claudin-5 immunoreactivity is first detected as a diffuse labeling of endothelial cytoplasm. Later, at 14 weeks, the immunosignal for both proteins shifts from the cytoplasm to the interface of adjacent endothelial cells, forming a linear, widely discontinuous pattern of immunoreactivity that achieves an adult-like appearance within a few weeks. These results demonstrate that occludin and claudin-5 expression is an early event in human brain development, followed shortly by assembly of both proteins at the junctional areas. This incremental process suggests more rapid establishment of the human BBB, consistent with its specific function of creating a suitable environment for neuron differentiation and neurite outgrowth during neocortical histogenesis.

Claudin‐5 is Restricted to the Tight Junction Region of Uterine Epithelial Cells in the Uterus of Pregnant/Gravid Squamate Reptiles

“…During the diestrus and proestrus phase in rats, claudin-5 and occludin shifts to the TJ region of the lateral plasma membrane, therefore assembling a strict paracellular barrier (Mendoza-Rodriguez et al, 2005) associated with regulation of the luminal fluid to prepare the uterus for implantation (de Jesus et al, 1972). The redistribution of claudin-5 from the cytosol to the region of the TJ in endothelial cells has also been detected during fetal development of the brain (Virgintino et al, 2004). This finding suggests that, as claudin-5 redistributes to the TJ region of the lateral plasma membrane in the uterine epithelium of skinks, free diffusion of solutes across the paracellular pathway is greatly reduced.…”

“…Claudin-5 was expressed not only in the TJ region of the lateral plasma membrane, but also along the apical, lateral, and basal region of the cytoplasm of uterine epithelial and glandular epithelial cells. In various cells, it has been documented that claudins are distributed not only in the TJs, but also at the lateral membranes without forming TJ strands (Furuse et al, 2002;Li et al, 2004) or it can occur as diffuse labeling in endothelial cell cytoplasm as in the human brain (Virgintino et al, 2004). Similarly, in the estrus phase in rats, claudin-5 is detected in the basolateral region of the plasma membrane and in the cytosol (Mendoza-Rodriguez et al, 2005), and is thus not associated with a TJ seal.…”

Blockade of cathepsin B expression in human glioblastoma cells is associated with suppression of angiogenesis

“…The development of new blood vessels in tumors depends on the production of angiogenic factors released from the tumor cells and/or stromal cells. VEGF and MMP-9 have been shown to be involved in angiogenesis in a variety of experimental models (Vu et al, 1998;Miyoshi and Ohshima, 2001;Hamano et al, 2003;Virgintino et al, 2003). However, the mechanisms that regulate the expression of angiogenic factors in tumor cells are still not well understood.…”

“…Microvessel development was markedly less where the cathepsin B antisense transfectants had been implanted as compared with the controls. PV, pre-existing vessels; TN, tumor vessels Cathepsin B and angiogenesis in glioma N Yanamandra et al correlate with malignant potential (Chaudhry et al, 2001;Virgintino et al, 2003) and administration of anti-VEGF antibodies to mice injected with human glioblastoma cancer cells has been shown to inhibit neovascularization within the tumors (Kim et al, 1993). Moreover, a mere threefold suppression of VEGF expression in GBM xenografts was capable of nearly obliterating the tumorigenic ability and vascularization of these malignant cells (Cheng et al, 1996).…”

Hyperbilirubinemia and Bilirubin Toxicity in the Late Preterm Infant

“…With respect to the anatomy and function of the blood-brain and blood-CSF barriers, there has been considerable controversy regarding their relative maturity in neonates [25]. Although gestational age may be an important variable in modulating blood-brain and blood-CSF permeability to selected substrates in experimental animals (eg, ontogenic decreases in ovine bloodbrain barrier permeability [26]), clinical and morphologic data on people are less convincing, at least from the gestational age of viability onward [25,27]. Similarly, virtually nothing is known about potential developmental differences in human neuronal vulnerability to unconjugated bilirubin (UCB) in vivo.…”