CLDN5 affects lncRNAs acting as ceRNA dynamics contributing to regulating blood­brain barrier permeability in tumor brain metastasis.

The blood­brain barrier (BBB) constitutes an efficient organization of tight junctions that limits the delivery of tumor to the brain. The principal tight junction protein in BBB is claudin­5 (CLDN5), but its mechanism of action remains largely unknown. Long non­coding RNAs (lncRNAs) are aberrantly expressed in many cancers, some lncRNAs play key roles in regulating BBB permeability and are involved in tumor brain metastasis. In particular, lncRNAs can function as competing endogenous RNAs (ceRNAs). Herein, we investigated whether ceRNA dysregulation is associated with alterations of the level of CLDN5 in human brain vascular endothelial hCMEC/D3 cells. The Affymetrix Human Transcriptome Array 2.0 and Affymetrix GeneChip miRNA 4.0 Array were used to detect the expression levels of 2,578 miRNAs, 22,829 lncRNAs, and 44,699 mRNAs in pLL3.7­CLDN5­transfected and pLL3.7 control hCMEC/D3 cells. The distinctly expressed miRNAs, lncRNAs, and mRNAs were subjected to construction of miRNA­lncRNA­mRNA interaction network. A total of 41 miRNAs, 954 lncRNAs, and 222 mRNAs were found to be differentially expressed between the CLDN5­overexpressing and control group. 148 lncRNA acting as ceRNAs were identified based on the miRNA­lncRNA­mRNA interaction network. The function of differential mRNA in the network was determined by GO and pathway analysis. The potential roles of the 27 ceRNAs were revealed, the possible biology functions of these regulatory ceRNAs mainly included tight junction, focal adhesion, cell­cell adhesion, cell growth and apoptosis. The identified sets of miRNAs, lncRNAs and mRNAs specific to CLDN5­overexpressing hCMEC/D3 cells were verified by quantitative real­time RT­PCR experiment. Our study predicts the biological functions of a multitude of ceRNAs associated with the alteration of CLDN5 in brain vascular endothelial cells. Our data suggest that these dysregulated ceRNAs, in conjunction with the high CLDN5 levels, could serve as useful targets of prevention of brain metastasis formation. Further studies are warranted to determine the role of these ceRNAs in facilitating the function of CLDN5 in brain­tumor barrier.

Claudin-5 regulates blood-brain barrier permeability by modifying brain microvascular endothelial cell proliferation, migration, and adhesion to prevent lung cancer metastasis.

AIMS: To investigate the roles of Claudin-5 (CLDN5) in regulating the permeability of the blood-brain barrier (BBB) during lung cancer brain metastasis. RESULTS: By silencing and overexpressing the CLDN5 gene in human brain vascular endothelial (hCMEC/D3) cells, we demonstrated the attenuation of cell migration ability and CLDN5's significant positive role in cell proliferation in CLDN5-overexpressing hCMEC/D3 cells and observed the opposite result in the CLDN5 knockdown group. The reinforced CLDN5 expression reduced the paracellular permeability of hCMEC/D3 cells and decreased the invasion of lung adenocarcinoma A549 cells. Overall, 1685 genes were found to be differentially expressed between the CLDN5-overexpressing cells and the control cells using the Affymetrix Human Transcriptome Array 2.0 (HTA 2.0), and the function of these genes was determined by Gene Ontology and pathway analyses. The possible biological functions of the 1685 genes include cell proliferation, adhesion molecules, and the Jak-STAT, PI3K-Akt, Wnt, and Notch signaling pathways. The identified sets of mRNAs that were specific to CLDN5-overexpressing hCMEC/D3 cells were verified by a qRT-PCR experiment. CONCLUSION: CLDN5 regulates the permeability of BBB by regulating the proliferation, migration, and permeability of hCMEC/D3 cells, especially through the cell adhesion molecule signaling pathway, to enhance the function of the tight junctions, which was involved in reducing the formation of lung cancer brain metastasis.